The discovery and character of Pleistocene calcrete uranium deposits in the Southern High Plains of west Texas, United States

USGS Publications Warehouse

Van Gosen, Bradley S.; Hall, Susan M.

2017-12-18

This report describes the discovery and geology of two near-surface uranium deposits within calcareous lacustrine strata of Pleistocene age in west Texas, United States. Calcrete uranium deposits have not been previously reported in the United States. The west Texas uranium deposits share characteristics with some calcrete uranium deposits in Western Australia—uranium-vanadium minerals hosted by nonpedogenic calcretes deposited in saline lacustrine environments.In the mid-1970s, Kerr-McGee Corporation conducted a regional uranium exploration program in the Southern High Plains province of the United States, which led to the discovery of two shallow uranium deposits (that were not publicly reported). With extensive drilling, Kerr-McGee delineated one deposit of about 2.1 million metric tons of ore with an average grade of 0.037 percent U3O8 and another deposit of about 0.93 million metric tons of ore averaging 0.047 percent U3O8.The west-Texas calcrete uranium-vanadium deposits occur in calcareous, fine-grained sediments interpreted to be deposited in saline lakes formed during dry interglacial periods of the Pleistocene. The lakes were associated with drainages upstream of a large Pleistocene lake. Age determinations of tephra in strata adjacent to one deposit indicate the host strata is middle Pleistocene in age.Examination of the uranium-vanadium mineralization by scanning-electron microscopy indicated at least two generations of uranium-vanadium deposition in the lacustrine strata identified as carnotite and a strontium-uranium-vanadium mineral. Preliminary uranium-series results indicate a two-component system in the host calcrete, with early lacustrine carbonate that was deposited (or recrystallized) about 190 kilo-annum, followed much later by carnotite-rich crusts and strontium-uranium-vanadium mineralization in the Holocene (about 5 kilo-annum). Differences in initial 234U/238U activity ratios indicate two separate, distinct fluid sources.

Prehistoric earthquake history revealed by lacustrine slump deposits

NASA Astrophysics Data System (ADS)

Schnellmann, Michael; Anselmetti, Flavio S.; Giardini, Domenico; McKenzie, Judith A.; Ward, Steven N.

2002-12-01

Five strong paleoseismic events were recorded in the past 15 k.y. in a series of slump deposits in the subsurface of Lake Lucerne, central Switzerland, revealing for the first time the paleoseismic history of one of the most seismically active areas in central Europe. Although many slump deposits in marine and lacustrine environments were previously attributed to historic earthquakes, the lack of detailed three-dimensional stratigraphic correlation in combination with accurate dating hampered the use of multiple slump deposits as paleoseismic indicators. This study investigated the fingerprint of the well-described A.D. 1601 earthquake (I = VII VIII, Mw ˜ 6.2) in the sediments of Lake Lucerne. The earthquake triggered numerous synchronous slumps and megaturbidites within different subbasins of the lake, producing a characteristic pattern that can be used to assign a seismic triggering mechanism to prehistoric slump events. For each seismic event horizon, the slump synchronicity was established by seismic-stratigraphic correlation between individual slump deposits through a quasi-three-dimensional high-resolution seismic survey grid. Four prehistoric events, dated by accelerator mass spectrometry, 14C measurements, and tephrochronology on a series of long gravity cores, occurred at 2420, 9770, 13,910, and 14,560 calendar yr ago. These recurrence times are essential factors for assessing seismic hazard in the area. The seismic hazard for lakeshore communities is additionally amplified by slump-induced tsunami and seiche waves. Numerical modeling of such tsunami waves revealed wave heights to 3 m, indicating tsunami risk in lacustrine environments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cregg, A.K.

Kenya basins have evolved primarily through extension related to episodic continental rifting. In eastern Kenya, thick accumulations of sediments formed within grabens during the prerift phase (Precambrian to Carboniferous) of the Gondwana breakup. Synrift sedimentation (Late Carboniferous to Middle Jurassic) occurred within a north-south rift system, which included the Mandera basin, South Anza basin, and Lamu embayment. During the Early Jurassic, a marine transgression invaded the margins of the eastern Kenya rift basins, resulting in the deposition of platform carbonates and shales. A Callovian-aged salt basin formed in the offshore regions of the Lamu embayment. Intermittent tectonic activity and eustaticmore » sea-level changes controlled sedimentation, which produced marine shales, carbonates or evaporites, and fluvio-deltaic to lacustrine sandstones. From the Early Cretaceous to recent, continental sediments were deposited within the North Anza and Turkana basins. These fluvial-lacustrine sediments are similar to the Lower Cretaceous sequences that have produced oil in the Mesozoic Sudanese Abu Gabra rift. Although exploration activities began in the early 1950s, significant occurrences of potential reservoir, source, and seal lithologies as well as trapping configurations remain in many areas. Favorable structures and sequences of reservoir sandstones and carbonates overlain by potentially sealing lacustrine or marine shales, evaporites, or volcanics have been noted. Potential source beds are believed to be present within shales of the lacustrine or marine depositional environments.« less

Paleontological analysis of a lacustrine carbonaceous uranium deposit at the Anderson mine, Date Creek basin, west-central Arizona (U.S.A.)

USGS Publications Warehouse

Otton, J.K.; Bradbury, J.P.; Forester, R.M.; Hanley, J.H.

1990-01-01

The Tertiary sedimentary sequence of the Date Creek basin area of Arizona is composed principally of intertonguing alluvial-fan and lacustrine deposits. The lacustrine rocks contain large intermediate- to, locally, high-grade uranium deposits that form one of the largest uranium resources in the United States (an estimated 670,000 tons of U3O8 at an average grade of 0.023% is indicated by drilling to date). At the Anderson mine, about 50,000 tons of U3O8 occurs in lacustrine carbonaceous siltstones and mudstones (using a cutoff grade of 0.01%). The Anderson mine constitutes a new class of ore deposit, a lacustrine carbonaceous uranium deposit. Floral and faunal remains at the Anderson mine played a critical role in creating and documenting conditions necessary for uranium mineralization. Organic-rich, uraniferous rocks at the Anderson mine contain plant remains and ostracodes having remarkably detailed preservation of internal features because of infilling by opaline silica. This preservation suggests that the alkaline lake waters in the mine area contained high concentrations of dissolved silica and that silicification occurred rapidly, before compaction or cementation of the enclosing sediment. Uranium coprecipitated with the silica. Thinly laminated, dark-colored, siliceous beds contain centric diatoms preserved with carbonaceous material suggesting that lake waters at the mine were locally deep and anoxic. These alkaline, silica-charged waters and a stagnant, anoxic environment in parts of the lake were necessary conditions for the precipitation of large amounts of uranium in the lake-bottom sediments. Sediments at the Anderson mine contain plant remains and pollen that were derived from diverse vegetative zones suggesting about 1500 m of relief in the area at the time of deposition. The pollen suggests that the valley floor was semiarid and subtropical, whereas nearby mountains supported temperate deciduous forests. ?? 1990.

Hydraulic properties of three types of glacial deposits in Ohio

USGS Publications Warehouse

Strobel, M.L.

1993-01-01

The effects of thickness, grain size, fractures, weathering, and atmosphericconditions on vertical ground-water flow in glacial deposits were studied at three sites that represent ground moraine, end moraine, and lacustrine depositional environments. Vertical hydraulic conductivities computed from pumped-well tests were 3.24 x 10-1 to 6.47 x 10-1 ft/d (feet per day) at the site representing end moraine and 1.17 ft/d at the site representing lacustrine deposits. Analysis of test data for the ground moraine site did not yield estimates of hydraulic conductivities, but did indicate that ground water flows through the total thickness of deposits in response to discharge from a lower gravel unit. Vertical hydraulic conductivities computed from pumped-well tests of nested wells and data from drill-core analyses indicate that fractures affect the migration of ground water downward through the glacial deposits at these sites. Flow through glacial deposits is complex; it is controlled by fractures, gram-size distribution, clay content, thickness, and degree of weathering, and atmospheric conditions.

Fine-grained sediment gravity flow deposits induced by flood and lake slope failure events: examples of lacustrine varved sediments in Japan

NASA Astrophysics Data System (ADS)

Ishihara, Yoshiro; Sasaki, Yasunori; Sasaki, Hana; Onishi, Yuri

2016-04-01

Fine-grained sediment gravity flow deposits induced by flood and lake slope failure events are frequently intercalated in lacustrine successions. When sediment gravity flow deposits are present in varved sediments, it is suggested that they provide valuable information about sediment gravity flows, because they can easily trace laterally and can give the magnitude of erosion and recurrence interval of events. In addition, because large sedimentary bodies of stacked sediment gravity flow deposits in varved sediments of a calm lake are not suggested, a relatively simple depositional environment is expected. In the present study, we analysed sedimentary facies of sediment gravity flow deposits in varved lacustrine diatomites in the Middle Pleistocene Hiruzenbara and Miyajima formations in Japan, and concluded a depositional model of the lacustrine sediment gravity flow deposits. Varved diatomites: The Hiruzenbara Fm., a dammed lake fill as foots of Hiruzen Volcanos, is deposited during an interglacial period during MIS12 to 15. Varves of ca. 8000 yr were measured in a 20 m intercalating flood and lake slope failure-induced sediment gravity flow deposits. The Miyajima Fm., distributed in a paleo-caldera lake in NE Japan, includes many sediment gravity flow deposits possibly originated from fandeltas around the lake. These formations have differences in their depositional setting; the Hiruzebara Fm. was deposited in a large lake basin, whereas the Miyajima Fm. was deposited in a relatively small basin. Because of the depositional setting, intercalation of volcaniclastics is dominant in the Miyajima Fm. Lacustrine sediment gravity flow deposits: Sediment gravity flow deposits in both formations can be classified into flood- and lake slope failure-induced types based on the sedimentary facies. Composites of the both types are also found. Flood-induced types comprise fine-grained silts dominated by carbonaceous fragments, whereas lake slope failure-induced types are dominated by rip-up clasts of diatomite. The former is well continued in outcrops; however, the thickness of the latter is changeable and the lower contact is erosive. In the Hirzenbara Fm., flood-induced type includes epiphytic diatom valves as river inflows, whereas slope failure-induced type is composed of diatom valves of varved diatomite. Flood-induced types are suggested to be classified into hyperpycnal flow and hypopycnal flow types with regard to the presence of basal erosion. On the other hand, slope failure-induced types can be interpreted as debris flow deposits occurred in the lakes. Differences in the two types are also shown as bed-thickness frequency distributions indicating event magnitude.

The Upper Jurassic Stanleyville Group of the eastern Congo Basin: An example of perennial lacustrine system

NASA Astrophysics Data System (ADS)

Caillaud, Alexis; Blanpied, Christian; Delvaux, Damien

2017-08-01

The intracratonic Congo Basin, located in the Democratic Republic of Congo (DRC), is the largest sedimentary basin of Africa. The Jurassic strata outcrop along its eastern margin, south of Kisangani (formerly Stanleyville). In the last century, the Upper Jurassic Stanleyville Group was described as a lacustrine series containing a thin basal marine limestone designed as the ;Lime Fine; beds. Since the proposal of this early model, the depositional environment of the Stanleyville Group, and especially the possible marine incursion, has been debated, but without re-examining the existing cores, outcrop samples and historical fossils from the type location near Kisangani that are available at the Royal Museum for Central Africa (MRAC/KMMA, Tervuren, Belgium). In order to refine the former sedimentology, a series of nine exploration cores drilled in the Kisangani sub-basin have been described. This study aims at integrating sedimentary facies in existing sedimentary models and to discuss the hypothesis of the presence of Kimmeridgian marine deposits along the Congo River near Kisangani, a region which lies in the middle of the African continent. Eight facies have been identified, which permit a reinterpretation of the depositional environment and paleogeography of the Stanleyville Group. The base of the Stanleyville Group is interpreted to represent a conglomeratic fluvial succession, which filled an inherited Triassic paleotopography. Above these conglomerates, a transition to a typically lacustrine system is interpreted, which includes: (1) a basal profundal, sublittoral (brown to dark fine-grained siltstones with microbial carbonates, i.e., the ;Lime Fine; beds) and littoral lacustrine series; covered by (2) a sublittoral to profundal interval (brown to dark organic-rich, fine-grained siltstones), which corresponds to the maximum extent of the paleo-lake; and, finally (3) a shallow lacustrine series (greenish calcareous siltstones and sandstones with red siltstones). Unlike what has been proposed, the ;Lime Fine; beds are interpreted herein to be of lacustrine origin, rather than representing a Kimmeridgian marine transgression. We conclude that a Jurassic marine transgression did not, in fact, occur in the eastern region of the Congo Basin.

The ichnologic record of the continental invertebrate invasion: evolutionary trends in environmental expansion, ecospace utilization, and behavioral complexity

USGS Publications Warehouse

Buatois, L.A.; Mangano, M.G.; Genise, Jorge F.; Taylor, T.N.

1998-01-01

The combined study of continental trace fossils and associated sedimentary facies provides valuable evidence of colonization trends and events throughout the Phanerozoic. Colonization of continental environments was linked to the exploitation of empty or under-utilized ecospace. Although the nonmarine trace fossil record probably begins during the Late Ordovician, significant invasion of nonmarine biotopes began close to the Silurian-Devonian transition with the establishment of a mobile arthropod epifauna (Diplichnites ichnoguild) in coastal marine to alluvial plain settings. Additionally, the presence of vertical burrows in Devonian high-energy fluvial deposits reflects the establishment of a stationary, deep suspension-feeding infauna of the Skolithos ichnoguild. The earliest evidence of plant-arthropod interaction occurred close to the Silurian-Devonian boundary, but widespread and varied feeding patterns are known from the Carboniferous. During the Carboniferous, permanent subaqueous lacustrine settings were colonized by a diverse, mobile detritus-feeding epifauna of the Mermia ichnoguild, which reflects a significant palaeoenvironmental expansion of trace fossils. Paleozoic ichnologic evidence supports direct routes to the land from marginal marine environments, and migration to lakes from land settings. All nonmarine sedimentary environments were colonized by the Carboniferous, and subsequent patterns indicate an increase in ecospace utilization within already colonized depositional settings. During the Permian, back-filled traces of the Scoyenia ichnoguild record the establishment of a mobile, intermediate-depth, deposit-feeding in-fauna in alluvial and transitional alluvial-lacustrine sediment. Diversification of land plants and the establishment of ecologically diverse plant communities through time provided new niches to be exploited by arthropods. Nevertheless, most ot the evolutionary feeding innovations took place relatively early, during the Late Palaeozoic or early Mesozoic. A stationary deep unfauna, the Camborygma ichnoguild, was developed in Triassic transitional alluvial-lacustrinbe deposits. Terrestrial environments hosted the rise of complex social behavioral patterns, as suggested by the probable presence of hymenopteran and isopteran nests in Triassic paleosols. An increase in diversity of trace fossils is detected in Triassic-Jurassic eolian deposits, where the ichnofauna displays more varied behavioral patterns than their Paleozoic counterparts. Also, a mobile, intermediate-depth, deposit-feeding infauna, the Vagorichnus ichnoguild, was established in deep lake environments during the Jurassic. In contrast to Paleozoic permanent subaqueous assemblages typified by surface trails, Jurassic ichnocoenoses are dominated by infaunal burrows. High density of infaunal deposit-feeding traces of the Planolites ichnoguild caused major disruption of lacustrine sedimentary fabrics during the Cretaceous. Most insect mouthpart classes, functional feeding groups, and dietary guilds were established by the end of the Cretaceous. Diversification of modern insects is recorded by the abundance and complexity of structures produced by wasps, bees, dung-beetles, and termites in Cretaceous-Tertiary paleosols. The increase in bioturbation migrated from fluvial and lake-margin settings to permanent subaqueous lacustrine environments through time.

Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA

USGS Publications Warehouse

Dunagan, S.P.; Turner, C.E.

2004-01-01

During deposition of the Upper Jurassic Morrison Formation, water that originated as precipitation in uplands to the west of the Western Interior depositional basin infiltrated regional aquifers that underlay the basin. This regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland/lacustrine successions. A freshwater carbonate wetland/lacustrine succession formed in the distal reaches of the basin, where regional groundwater discharged into the Denver-Julesburg Basin, which was a smaller structural basin within the more extensive Western Interior depositional basin. An alkaline-saline wetland/lacustrine complex (Lake T'oo'dichi') formed farther upstream, where shallower aquifers discharged into the San Juan/Paradox Basin, which was another small structural basin in the Western Interior depositional basin. These were both wetlands in the sense that groundwater was the major source of water. Input from surface and meteoric water was limited. In both basins, lacustrine conditions developed during episodes of increased input of surface water. Inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology. The distal carbonate wetland/lacustrine deposits are well developed in the Morrison Formation of east-central Colorado, occupying a stratigraphic interval that is equivalent to the "lower" Morrison but extends into the "upper" Morrison Formation. Sedimentologic, paleontologic, and isotopic evidence indicate that regional groundwater discharge maintained shallow, hydrologically open, well oxygenated, perennial carbonate wetlands and lakes despite the semi-arid climate. Wetland deposits include charophyte-rich wackestone and green mudstone. Lacustrine episodes, in which surface water input was significant, were times of carbonate and siliciclastic deposition in scarce deltaic and shoreline deposits. Marginal lacustrine deposits include ooid and skeletal packstone-grainstone, siltstone, and sandstone. Distal lacustrine units are skeletal mudstone-wackestone, microbialites, and laminated (siliciclastic) mudstone. Differentiation between wetlands and distal lacustrine units is not always possible. Palustrine features, Magadi-type chert (MTC), and evaporites record episodes of increased aridity and exposure. Farther upstream, during deposition of the upper part of the Brushy Basin Member, the ancestral Uncompahgre Uplift imposed a barrier to shallow, eastward-flowing groundwater that discharged into the San Juan/Paradox Basin on the upstream side of the uplift. This created the closed hydrologic setting necessary for development of an alkaline-saline wetland/lacustrine complex ("Lake" T'oo'dichi'). Silicic volcanic ash, delivered by prevailing winds from calderas west and southwest of the basin, contributed to the pore-water evolution in the sediments. A distinctive lateral hydrogeochemical gradient, reflecting increasing salinity and alkalinity in the pore waters, altered the ash to a variety of authigenic minerals that define concentric zones within the basin. The basinward progression of diagenetic mineral zones is smectite???clinoptilolite???analcime ??potassium feldspar???albite. The groundwater-fed wetlands were shallow and frequently evaporated to dryness. Scarce laminated gray mudstone beds record distinct episodes of freshwater lacustrine deposition that resulted from intermittent streams that carried detritus well out into the basin. ?? 2004 Elsevier B.V. All rights reserved.

Evidence for an 800 km Diameter Impact Structure in Meridiani Planum and Associated Channels and Basins: A Connection with the Origin of the Hematite Deposits?

NASA Technical Reports Server (NTRS)

Newsom, H. E.; Barber, C. A.; Schelble, R. T.; Hare, T. M.; Feldman, W. C.; Sutherland, V.; Gordon, H.; Thorsos, I. E.; Livingston, A.; Lewis, K.

2003-01-01

Topographic evidence for the existence of an early 800 km diameter multi-ringed impact structure, and evidence for fluvial and lacustrine environments in Meridiani Planum suggests a connection with the origin of the hematite deposits present in the region.

Deposition of Boron in Possible Evaporite Deposits in Gale Crate

NASA Astrophysics Data System (ADS)

Gasda, P. J.; Peets, E.; Lamm, S. N.; Rapin, W.; Lanza, N.; Frydenvang, J.; Clark, B. C.; Herkenhoff, K. E.; Bridges, J.; Schwenzer, S. P.; Haldeman, E. B.; Wiens, R. C.; Maurice, S.; Clegg, S. M.; Delapp, D.; Sanford, V.; Bodine, M. R.; McInroy, R.

2017-12-01

Boron has been previously detected in Gale crater using the ChemCam instrument on board the NASA Curiosity rover within calcium sulfate fracture fill hosted by lacustrine mudstone and eolian sandstone units. Recent results show that up to 300 ppm B is present in the upper sections of the lacustrine unit. Boron has been detected in both the groundwater-emplaced calcium sulfate fracture fill materials and bedding-parallel calcium sulfate layers. The widespread bedding-parallel calcium sulfate layers within the upper strata of the lacustrine bedrock that Curiosity has encountered recently could be interpreted as primary evaporite deposits. We have two hypotheses for the history of boron in Gale crater. In both hypotheses, borates were first deposited as lake water evaporated, depositing primary evaporates that were later re-dissolved by groundwater, which redistributed the boron into secondary evaporitic calcium sulfate fracture fill deposits. In the first scenario, Gale crater may have undergone a period of perennial lake formation during a drier period of martian history, depositing layers of evaporitic minerals (including borates) among lacustrine mudstone layers. In the second scenario, lake margins could have become periodically exposed during cyclic drops in lake level and subsequently desiccated. Evaporites were deposited and desiccation features were formed in lowstand deposits. Either hypothetical scenario of evaporite deposition would promote prebiotic chemical reactions via wet-dry cycles. Boron may be an important prebiotic element, and as such, its presence in ancient martian surface and groundwater provides evidence that important prebiotic chemical reactions could occur on Mars if organics were present. The presence of boron in ancient Gale crater groundwater also provides additional evidence that a habitable environment existed in the martian subsurface well after the expected disappearance of liquid water on the surface of Mars. We will report on the most recent results for boron in relation to these bedding-parallel calcium sulfate layers and lowstand deposits. If a connection between observations of boron and lowstand lake features is found, this would suggest the existence of boron-bearing lake-deposited evaporites in Gale.

Sediment characteristics and configuration within the Otsego City Dam impoundment on the Kalamazoo River, Michigan, 2001-02

USGS Publications Warehouse

Rheaume, S.J.; Hubbell, D.L.; Rachol, C.M.; Simard, A.; Fuller, L.M.

2004-01-01

The removal of the Otsego City Dam on the Kalamazoo River at Otsego, Mich., is under consideration by the Michigan Department of Environmental Quality and the city of Otsego. The historical discharge of papermill waste containing polychlorinated biphenyls from sources upstream from the dam has led the U.S. Environmental Protection Agency to designate the Kalamazoo River from Morrow Dam near Comstock to its mouth near Saugatuck as a Federal Superfund site. The papermill waste is concentrated in organic sediment and kaolinite clay, with the sediment containing as much as 94 milligrams per kilogram polychlorinated biphenyls. This contaminated sediment could move if the dam is removed; therefore, it is necessary to estimate the characteristics and configuration of the sediment before removal plans begin. Data from augered sections and sediment cores show that the current Otsego City impoundment sediments were deposited in two distinctly different sedimentary environments: (1) lacustrine sediments consisting of organic-rich silt and clay, fine to medium sand, and some gravel deposited in a repetitive, cyclic fashion related to former stream velocities when the Otsego City impoundment water levels were 2-4 feet higher (1880s-1960s), and from downstream movement of lacustrine sediments during the removal of the upstream Plainwell Dam superstructure in the 1980s; and (2) more recent (1980s-2002) coarse-grained alluvium deposited on top of the lacustrine sediments. The volume of instream sediment contained within the Otsego City impoundment is estimated to be about 457,270 cubic yards. This estimate is based on the composite thicknesses of the lacustrine deposits and overlying alluvium, which were determined to contain PCBs, and does not include bank or flood-plain deposits.

Seeking Signs of Life on Mars: The Importance of Sedimentary Suites as Part of Mars Sample Return

NASA Astrophysics Data System (ADS)

iMOST Team; Mangold, N.; McLennan, S. M.; Czaja, A. D.; Ori, G. G.; Tosca, N. J.; Altieri, F.; Amelin, Y.; Ammannito, E.; Anand, M.; Beaty, D. W.; Benning, L. G.; Bishop, J. L.; Borg, L. E.; Boucher, D.; Brucato, J. R.; Busemann, H.; Campbell, K. A.; Carrier, B. L.; Debaille, V.; Des Marais, D. J.; Dixon, M.; Ehlmann, B. L.; Farmer, J. D.; Fernandez-Remolar, D. C.; Fogarty, J.; Glavin, D. P.; Goreva, Y. S.; Grady, M. M.; Hallis, L. J.; Harrington, A. D.; Hausrath, E. M.; Herd, C. D. K.; Horgan, B.; Humayun, M.; Kleine, T.; Kleinhenz, J.; Mackelprang, R.; Mayhew, L. E.; McCubbin, F. M.; McCoy, J. T.; McSween, H. Y.; Moser, D. E.; Moynier, F.; Mustard, J. F.; Niles, P. B.; Raulin, F.; Rettberg, P.; Rucker, M. A.; Schmitz, N.; Sefton-Nash, E.; Sephton, M. A.; Shaheen, R.; Shuster, D. L.; Siljestrom, S.; Smith, C. L.; Spry, J. A.; Steele, A.; Swindle, T. D.; ten Kate, I. L.; Usui, T.; Van Kranendonk, M. J.; Wadhwa, M.; Weiss, B. P.; Werner, S. C.; Westall, F.; Wheeler, R. M.; Zipfel, J.; Zorzano, M. P.

2018-04-01

Sedimentary, and especially lacustrine, depositional environments are high-priority geological/astrobiological settings for Mars Sample Return. We review the detailed investigations, measurements, and sample types required to evaluate such settings.

Fluvial to Lacustrine Facies Transitions in Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Sumner, Dawn Y.; Williams, Rebecca M. E.; Schieber, Juergen; Palucis, Marisa C.; Oehler, Dorothy Z.; Mangold, Nicolas; Kah, Linda C.; Gupta, Sanjeev; Grotzinger, John P.; Grant, John A., III;

Reconnaissance geochronology of tuffs in the Miocene Barstow Formation: implications for basin evolution and tectonics in the central Mojave Desert

USGS Publications Warehouse

Miller, David M.; Leslie, Shannon R.; Hillhouse, John W.; Wooden, Joseph L.; Vazquez, Jorge A.; Reynolds, R.E.

2010-01-01

Early to middle Miocene lacustrine strata of the Barstow Formation are well dated in just a few places, limiting our ability to infer basin evolution and regional tectonics. At the type section in the Mud Hills, previous studies have shown that the lacustrine interval of the Barstow Formation is between ~16.3 Ma and ~13.4 Ma. Elsewhere, lake beds of the Barstow Formation have yielded vertebrate fossils showing the Hemingfordian/Barstovian transition at ~16 Ma but are otherwise poorly dated. In an attempt to clarify the age and depositional environments of the lake deposits, we are mapping the Barstow Formation and dating zircons from interbedded tuffs, as well as testing ash-flow tuffs for the distinctive remanent magnetization direction of the widespread Peach Spring Tuff. Thus far, our new U-Pb zircon ages indicate that the Barstow lake beds contain tuff beds as old as 19.1 Ma and as young as 15.3 Ma. At Harvard Hill, Barstow lake beds contain a thick tuff dated at 18.7 Ma. On the basis of zircon ages, mineralogy, zircon chemistry, and paleomagnetic results, we consider the thick tuff to be a lacustrine facies of the Peach Spring Tuff. We have identified the Peach Spring Tuff by similar methods at eight localities over a broad area, providing a timeline for several fluvial and lacustrine sections. The new dates indicate that long-lived lacustrine systems originated before 19 Ma and persisted to at least 15 Ma. The onset of lacustrine conditions predates the Peach Spring Tuff in most Barstow Formation sections and may be older than 19.5 Ma in some places. The new data indicate that the central Mojave Desert contained narrow to broad lake basins during and after extension, and that Barstow lacustrine deposits did not exclusively postdate extensional tectonics. At present, it is unclear whether several separate, small lake basins coexisted during the early to middle Miocene, or if instead several small early Miocene basins gradually coalesced over about 6 million years to form one or two large middle Miocene lake basins.

Reconnaissance geochronology of tuffs in the Miocene Barstow Formation: implications for basin evolution and tectonics in the central Mojave Desert

USGS Publications Warehouse

Miller, D.M.; Leslie, S.R.; Hillhouse, J.W.; Wooden, J.L.; Vazquez, J.A.; Reynolds, R.E.

2010-01-01

Early to middle Miocene lacustrine strata of the Barstow Formation are well dated in just a few places, limiting our ability to infer basin evolution and regional tectonics. At the type section in the Mud Hills, previous studies have shown that the lacustrine interval of the Barstow Formation is between ~16.3 Ma and ~13.4 Ma. Elsewhere, lake beds of the Barstow Formation have yielded vertebrate fossils showing the Hemingfordian/Bartovian transition at ~16 Ma but are otherwise poorly dated. In an attempt to clarify the age and depositional environments of the lake deposits, we are mapping the Barstow Formation and dating zircons from interbedded tuffs, as well as testing ash-flow tuffs for the distinctive remanent magnetization direction of the widespread Peach Spring Tuff. Thus far, our new U-Pb zircon ages inficate that the Barstow lake beds contain tuff beds as old as 19.1 Ma and as young as 15.3 Ma. At Harvard Hill, Barstow lake beds contain a thick tuff dated at 18.7 Ma. On the basis of zircon ages, mineralogy, zircon chemistry, and paleomagnetic results, we consider the thick tuff to be a lacustrine facies of the Peach Spring Tuff. We have identified the Peach Spring Tuff by similar methods at eight localities over a broad area, providing a timeline for several fluvial and lacustrine sections. The new dates indicate that long-lived lacustrine systems originated before 19 Ma and persisted to at least 15 Ma. The onset of lacustrine conditions predates the Peach Spring Tuff in most Barstow Formation sections and may be older than 19.5 Ma in some places. The new data indicate that the central Mojave Desert contained narrow to broad lake basins during and after extension, and that Barstow lacustrine deposits did not exclusively postdate extensional tectonics. At present, it is unclear whether several separate, small lake basins coexisted during the early to middle Miocene, or if instead several small early Miocene basins gradually coalesced over about 6 millions years to form one or two large middle Miocene lake basins.

MX Siting Investigation. Geotechnical Evaluation of Luke Bombing and Gunnery Range. Geotechnical Report, Lechuguilla Desert, Arizona. Volume I.

DTIC Science & Technology

1978-01-20

8217-5000 -150 C KILOETERS , 1 2 V i asagerat- EXPLANATION i SURFICIAL BASIN FILL; Alluvial tans and playa lacustrine deposits; average seismic velocity...Undetermined e Velocity zone I represents alluvial fan deposits and possible playa /lacustrine materials underlying the unconsolidated, thin 1younger...alluvial fan unit (A5y, A5yf). Velocity zone 2 seems to represert older, playa /lacustrine deposits overlying Veloc- ity zone 3, which may be the well

Late Holocene Environmental Reconstruction and Flood Records of Lake Bafa, Western Turkey

NASA Astrophysics Data System (ADS)

Yalamaz, Burak; Bulkan, Özlem; Namık Çaǧatay, M.; Acar, Dursun

2016-04-01

Lake Bafa is a significant inland lake located in the Büyük Menderes River Basin near the Aegean Sea in the horst and graben system of western Turkey. Lake Bafa was part of the ancient Gulf of Latmos that was gradually filled by the prograding sediments of Büyük Menderes River during the Holocene transgression, and resulted in the creation of the Lake in the southern part. The lake is presently located 15 km from the shoreline, 2 m above sea level. It has a maximum depth of 21 m and surface area of 60 km2. We used multi-proxy analyses of a 4.17 m-long core extending back to ca. 2300 years from the central depo centre of the lake. The objectives are to reconstruct the environmental evolution of the Lake Bafa as it changed from a marginal marine to a lacustrine environment, and to investigate the flood records during the past 2300 yrs. The core is composed of three units: an uppermost lacustrine unit, a unit representing marine to lacustrine conditions and a lowermost marine unit. The uppermost lacustrine unit is 1 m-thick, homogenous clayey silt mud layer with relatively high total organic carbon (TOC= 2.5 - 4.5 %), high total inorganic carbon (TIC = 1.8 -4.5 %) and low detrital input (Si, K, Zr, Ti). According to AMS radiocarbon dating, it was deposited over the last 600 yrs under brackish lacustrine conditions. The underlying unit is 2 m-thick, and consists of banded mud layers with relatively low TOC (1.2-4 %) and TIC (1.2-3.5) contents and high detrital input. Its fossil content, with scarce Cardium sp. and Ammonia sp., indicates that it was deposited under brackish water conditions and represents a transition from marine to lacustrine environments. The unit was deposited between ca. 600 and 1750 yrs BP, and includes frequent flood units ranging up to 10 cm-thick fine sand- to clay-bearing coarse silt. The lowermost unit is characterized by relatively high TOC (2-5.5 %), TIC (1.5-3.5 %) contents and high detrital input. With its abundant Cardium sp. and foraminiferal content, the unit was deposited under marine conditions prior to 1750 years. The marine unit also includes records of flood events. The coarse flood sediments in both marine and transitional units are characterized by high magnetic susceptibility and high density, low TOC and TIC. The core sequence suggests that the the prograding alluvial sediments during the late Holocene gradually closed the western mouth the intermontane Bafa Basin in the south of the ancient Gulf of Latmos, gradually converting it into a closed limnic environment. The frequent flood records during marine and transitional period supports the continuing connection with Büyük Menderes River until ca. 800 yrs BP. Keywords: Lake Bafa, Büyük Menderes River, environmental changes, flood.

Sedimentology and geochemistry of lacustrine sequences of the upper Pleistocene and holocene in intertropical area (Lake Magadi and Green crater lake): paleoclimatic implications

NASA Astrophysics Data System (ADS)

Damnati, B.

1993-05-01

Sedimentological and geochemical analyses have been carried out on lacustrine deposits of East Africa, at Lake Magadi (2°S, 36°E, Kenya) and at Green Crater Lake (0°S, 36°E, Kenya), to determine the parameters controlling climatic and environmental dynamics during late Pleistocene and Holocene. These sedimentary sequences were collected with a stationary piston corer. At Lake Magadi (Fig. 1), sedimentary and geochemical control show three phases of lake level variation which corresponds to climatic change occurring during the last 40 thousand years. These phases were defined by three lithostratigraphic units. Laminated deposits of Lake Magadi were formed during a wet period. Analysis of these laminae define two microfacies: a dark lamina, characterised by lacustrine organic matter and a light lamina enriched in detritus, carbonates (CaCO 3) and magadiite (NaSi 7O 13(OH) 3, 3H 2O). The formation and preservation of each couplet was favoured by climatic contrast, lake stratification and various origin of the sediments (autochthon and allochthon) in the drainage basin. Therefore a relative chronology can be derived from laminae counting and the duration of deposition of each couplet. Spectral analysis applied on variation of the laminae thickness, shows the existence of three main periods, 4-7 years, 8-14 years and 18-30 years, respectively (Fig. 2). These cyclicites of the lacustrine environment precise former determinations established on more recent lacustrine sequences from East Africa. They are related to the global climatic cycle (quasi-biannual oscillations, El Nino Southern Oscillations and the sun spot cycles). At Green Crater Lake, the study of the sedimentary sequence was completed by physico-chemical analysis of the waters and interface sediments which demonstrate the carbonate, sodium, bicarbonate composition and the thermal and chemical stratification of the modern lake. The sedimentary sequence is characterized by volcanic deposits overlain by physico-chemical analysis of the lake waters and interface sediments which demonstrate the carbonate, sodium, bicarbonate composition and the thermal and chemical stratification of the modern lake. The sedimentary sequence is characterized by volcanic deposits overlain by silt and clays deposited before 7400 years B.P., followed by loweing of the lake level at 3000 years B. P. Results from lake Magadi document the occurrence of a wet period starting at about 12,000 years B. P. The methodology applied on modern Green Crater lake provides base of interpretative models for other Holocene sequence lacustrine systems of intertropical zones.

Sedimentation rates in eastern North America reveal strong links between regional climate, depositional environments, and sediment accumulation

NASA Astrophysics Data System (ADS)

Goring, S. J.; McLachlan, J. S.; Jackson, S. T.; Blaauw, M.; Christen, J.; Marlon, J.; Blois, J.; Williams, J. W.

2011-12-01

PalEON is a multidisciplinary project that combines paleo and modern ecological data with state-of-the-art statistical and modelling tools to examine the interactions between climate, fire and vegetation during the past two millennia in the northeastern United States. A fundamental challenge for PalEON (and paleo research more broadly) is to improve age modelling to yield more accurate sediment-core chronologies. To address this challenge, we assessed sedimentation rates and their controls for 218 lakes and mires in the northeastern U.S. Sedimentation rates (yr/cm) were calculated from age-depth models, which were obtained from the Neotoma database (www.neotomadb.org) and other contributed pollen records. The age models were recalibrated to IntCal09 and augmented in some cases using biostratigraphic markers (Picea decline, 16 kcal BP - 10.5 kcal BP; Quercus rise, 12 - 9.1 kcal BP; and Alnus decline, 11.5 - 10.6 kcal BP) as described in Blois et al. (2011). Relationships between sedimentation rates and sediment age, site longitude, and depositional environment (lacustrine or mire) are significant but weak. There are clear and significant links between variations in the NGRIP record of δ18O and sedimentation in mires across the PalEON region, but no links to lacustrine sedimentation rates. This result indicates that super-regional climatic control of primary productivity, and thus autochthonic sediment deposition, dominates in mires while deposition in lacustrine basins may be driven primarily by local and regional factors including watershed size, surficial materials,and regional vegetation. The shape of the gamma probability functions that best describe sedimentation rate distributions are calculated and presented here for use as priors in Bayesian age modelling applications such as BACON (Blaauw and Christen, in press). Future applications of this research are also discussed.

Characterization of petroleum reservoirs in the Eocene Green River Formation, Central Uinta Basin, Utah

USGS Publications Warehouse

Morgan, C.D.; Bereskin, S.R.

2003-01-01

The oil-productive Eocene Green River Formation in the central Uinta Basin of northeastern Utah is divided into five distinct intervals. In stratigraphically ascending order these are: 1) Uteland Butte, 2) Castle Peak, 3) Travis, 4) Monument Butte, and 5) Beluga. The reservoir in the Uteland Butte interval is mainly lacustrine limestone with rare bar sandstone beds, whereas the reservoirs in the other four intervals are mainly channel and lacustrine sandstone beds. The changing depositional environments of Paleocene-Eocene Lake Uinta controlled the characteristics of each interval and the reservoir rock contained within. The Uteland Butte consists of carbonate and rare, thin, shallow-lacustrine sandstone bars deposited during the initial rise of the lake. The Castle Peak interval was deposited during a time of numerous and rapid lake-level fluctuations, which developed a simple drainage pattern across the exposed shallow and gentle shelf with each fall and rise cycle. The Travis interval records a time of active tectonism that created a steeper slope and a pronounced shelf break where thick cut-and-fill valleys developed during lake-level falls and rises. The Monument Butte interval represents a return to a gentle, shallow shelf where channel deposits are stacked in a lowstand delta plain and amalgamated into the most extensive reservoir in the central Uinta Basin. The Beluga interval represents a time of major lake expansion with fewer, less pronounced lake-level falls, resulting in isolated single-storied channel and shallow-bar sandstone deposits.

Multiple-scale hydraulic characterization of a surficial clayey aquitard overlying a regional aquifer in Louisiana

NASA Astrophysics Data System (ADS)

Chapman, Steven W.; Cherry, John A.; Parker, Beth L.

2018-03-01

The vertical hydraulic conductivity (Kv) of a 30-m thick surficial clayey aquitard overlying a regional aquifer at an industrial site in the Mississippi River Valley in Louisiana was investigated via intensive hydraulic characterization using high resolution vertical hydraulic head profiles with temporal monitoring and laboratory tests. A study area was instrumented with a semi-circular array of piezometers at many depths in the aquitard at equal distance from a large capacity pumping well including replicate piezometers. Profiles showed negligible head differential to 20 m bgs, below which there was an abrupt change in vertical gradients over the lower 8-10 m of the aquitard. Hydraulic characteristics are strongly associated with depositional environment; the upper zone of minimal head differentials with depth and minimal variation over time correlates with Paleo-Mississippi River backswamp deposits, while the lower zone with large head differentials and slow but moderate head changes correlates with lacustrine deposits. The lower zone restricts groundwater flow between the surface and underlying regional aquifer, which is hydraulically connected to the Mississippi River. Lab tests on lacustrine samples show low Kv (8 × 10-11-4 × 10-9 m/s) bracketing field estimates (6 × 10-10 m/s) from 1-D model fits to piezometric data in response to large aquifer head changes. The slow response indicates absence of through-going open fractures in the lacustrine unit, consistent with geotechnical properties (high plasticity, normal consolidation), suggesting high integrity that protects the underlying aquifer from surficial contamination. The lack of vertical gradients in the overlying backswamp unit indicates abundant secondary permeability features (e.g. fractures, rootholes) consistent with depositional and weathering conditions. 2-D stylized transient flow simulations including both units supports this interpretation. Other published reports on surficial aquitards in the Gulf Coast Region pertain to Pleistocene deposits that lack laterally extensive lacustrine units and where Kv is enhanced by secondary permeability features, resulting in clayey aquitards with poor integrity.

A Major Eocene Lake System in the Hinterland of the North American Cordillera Comes into Geochronologic Focus

NASA Astrophysics Data System (ADS)

Smith, M. E.; Cassel, E. J.; Canada, A.; Jicha, B.; Singer, B. S.

2015-12-01

Eastern Nevada lay east of the Cordilleran continental divide and experienced continental drainage ponding during the Eocene Epoch. Though recognized for nearly a century, lake deposits of the Elko Formation have yet to be placed in a regional chronostratigraphic context, due primarily to Neogene extension and a paucity of radioisotopic ages. New geochronology is essential for creating robust reconstructions of paleogeography and paloeohydrology from scattered surviving outcrops, and for assessing competing tectonic interpretations for lake basin formation and evolution. New single crystal sanidine 40Ar/39Ar ages for 21 ash beds collected from the Elko Formation and contemporaneous fluvial deposits indicate that lacustrine deposition occurred locally as early as ca. 48.7 Ma, coeval with deposition of the Bridgerian portion of the lacustrine Sheep Pass Formation to the south. Lake Elko's most expansive phase occurred between ca. 44.0 and 40.5 Ma, resulting in regional overlap of lacustrine strata atop fluvial strata. Based on lithofacies and lithofacies stacking patterns, an up-section transition from overfilled to balanced-fill conditions occurred at ca. 41.3 Ma. This transition led to increasing salinity and lake level variations that formed a prominent 1-4 meter-scale depositional cyclicity characteristic of partly closed lakes that periodically dropped below their sill elevation. The stromatolitic uppermost Elko Formation records proximal volcanism, including several welded ignimbrites, and is overlain by an unconformity of >10 m.y. duration. Initial ponding, the shift to balanced fill conditions, voluminous siliceous volcanism, and subsequent unconformity are interpreted to reflect the progressive NE to SW advance of 500-900 m of topographic uplift and volcanism resulting from rollback of the Farallon slab. 40Ar/39Ar ages for ash beds at five individual locations suggest that a single ignimbrite, likely the Tuff of Nelson Creek, was deposited across a ~10,000 km2 area of NE NV at 40.45 ± 0.08 Ma, near the end of Elko Formation accumulation. Within this bed, the hydrogen isotope composition of glass hydration waters vary systematically according to paleo-landscape position, recording a 102 ± 20‰ increase in δD values for glasses deposited in lacustrine versus fluvial environments.

Sedimentation and tectonics in the southern Bida Basin, Nigeria: depositional response to varying tectonic context

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braide, S.P.

1990-05-01

The Upper Cretaceous Bida basin of central Nigeria is sandwiched between the Precambrian schist belts of the Northern Nigerian massif and the West African craton. Of interest is the southern part of the basin, which developed in continental settings, because the facies architecture of the sedimentary fill suggests a close relation between sedimentation dynamics and basin margin tectonics. This relationship is significant to an understanding of the basin's origin, which has been controversial. A simple sag and rift origin has been suggested, and consequently dominated the negative thinking on the hydrocarbon prospects of the basin which were considered poor. Thismore » detailed study of the facies indicates rapid basin-wide changes from various alluvial fan facies through flood-basin and deltaic facies to lacustrine facies. Paleogeographic reconstruction suggests lacustrine environments were widespread and elongate. Lacustrine environments occurred at the basin's axis and close to the margins. This suggests the depocenter must have migrated during the basin's depositional history and subsided rapidly to accommodate the 3.5-km-thick sedimentary fill. Although distinguishing pull-apart basins from rift basins, based solely on sedimentologic grounds, may be difficult, the temporal migration of the depocenter, as well as the basin architecture of upward coarsening cyclicity, show a strong tectonic and structural overprint that suggests a tectonic framework for the Southern Bida basin similar in origin to a pull-apart basin.« less

Diagenetic Crystal Growth in the Murray Formation, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Kah, L. C.; Kronyak, R. E.; Ming, D. W.; Grotzinger, J. P.; Schieber, J.; Sumner, D. Y.; Edgett, K. S.

2015-01-01

The Pahrump region (Gale Crater, Mars) marks a critical transition between sedimentary environments dominated by alluvial-to-fluvial materials associated with the Gale crater rim, and depositional environments fundamentally linked to the crater's central mound, Mount Sharp. At Pahrump, the Murray formation consists of an approximately 14-meter thick succession dominated by massive to finely laminated mudstone with occasional interbeds of cross-bedded sandstone, and is best interpreted as a dominantly lacustrine environment containing tongues of prograding fluvial material. Murray formation mudstones contain abundant evidence for early diagenetic mineral precipitation and its subsequent removal by later diagenetic processes. Lenticular mineral growth is particularly common within lacustrine mudstone deposits at the Pahrump locality. High-resolution MAHLI images taken by the Curiosity rover permit detailed morphological and spatial analysis of these features. Millimeter-scale lenticular features occur in massive to well-laminated mudstone lithologies and are interpreted as pseudomorphs after calcium sulfate. The distribution and orientation of lenticular features suggests deposition at or near the sediment-water (or sediment-air) interface. Retention of chemical signals similar to host rock suggests that original precipitation was likely poikilotopic, incorporating substantial amounts of the primary matrix. Although poikilotopic crystal growth is common in burial environments, it also occurs during early diagenetic crystal growth within unlithified sediment where high rates of crystal growth are common. Loss of original calcium sulfate mineralogy suggests dissolution by mildly acidic, later-diagenetic fluids. As with lenticular voids observed at Meridiani by the Opportunity Rover, these features indicate that calcium sulfate deposition may have been widespread on early Mars; dissolution of depositional and early diagenetic minerals is a likely source for both calcium and sulfate ion-enrichment in burial fluids that precipitated in ubiquitous late-stage hydrofracture veins

Palaeoenvironmental implications of a Holocene sequence of lacustrine-peat sediments from the desert-loess transitional zone in Northern China

NASA Astrophysics Data System (ADS)

Jia, Feifei; Lu, Ruijie; Liu, Xiaokang; Zhao, Chao; Lv, Zhiqiang; Gao, Shangyu

2018-05-01

A high-resolution lacustrine-peat record from the desert-loess transitional zone in Northern China was obtained to reconstruct Holocene environmental change in the region. AMS 14C dates are used to provide a chronology. The results indicate that the site was a desert environment before 12.2 cal kyr BP, and was then occupied by a paleolake which started to shrink, with a wetland occurring from 6.2 to 3.0 cal kyr BP. Subsequently, the site became a seasonally water-filled depression. Based on the lithology and measurements of grain size and total organic carbon content, the climate changed from arid to humid at 12.2 cal kyr BP, and became more humid after 8.3 cal kyr BP. From 6.2 to 3.0 cal kyr BP, precipitation decreased but the climate remained at an optimum. After 3.0 cal kyr BP, the climate was dry overall but with several humid intervals. A comparison of paleoclimatic records from lacustrine and aeolian deposits from the region reveals a discrepancy about the nature of the early Holocene climate, and we conclude that this is because lacustrine sediments responded more sensitively to precipitation than aeolian deposits when the temperature was low. The environmental evolution of the region was synchronous with changes in the Asian summer monsoon (ASM), but temperature also played a key role in the early Holocene.

Re–Os geochronology of the lacustrine Green River Formation: Insights into direct depositional dating of lacustrine successions, Re–Os systematics and paleocontinental weathering

USGS Publications Warehouse

Cumming, Vivien M.; Selby, David; Lillis, Paul G.

2012-01-01

Lacustrine sedimentary successions provide exceptionally high-resolution records of continental geological processes, responding to tectonic, climatic and magmatic influences. These successions are therefore essential for correlating geological and climatic phenomena across continents and furthermore the globe. Producing accurate geochronological frameworks within lacustrine strata is challenging because the stratigraphy is often bereft of biostratigraphy and directly dateable tuff horizons. The rhenium–osmium (Re–Os) geochronometer is a well-established tool for determining precise and accurate depositional ages of marine organic-rich rocks. Lake systems with stratified water columns are predisposed to the preservation of organic-rich rocks and thus should permit direct Re–Os geochronology of lacustrine strata. We present Re–Os systematics from one of the world's best documented lacustrine systems, the Eocene Green River Formation, providing accurate Re–Os depositional dates that are supported by Ar–Ar and U–Pb ages of intercalated tuff horizons. Precision of the Green River Formation Re–Os dates is controlled by the variation in initial 187Os/188Os and the range of 187Re/188Os ratios, as also documented in marine systems. Controls on uptake and fractionation of Re and Os are considered to relate mainly to depositional setting and the type of organic matter deposited, with the need to further understand the chelating precursors of Re and Os in organic matter highlighted. In addition to geochronology, the Re–Os data records the 187Os/188Os composition of lake water (1.41–1.54) at the time of deposition, giving an insight into continental runoff derived from weathering of the geological hinterland of the Green River Formation. Such insights enable us to evaluate fluctuations in continental climatic, tectonic and magmatic processes and provide the ability for chemostratigraphic correlation combined with direct depositional dates. Furthermore, initial 187Os/188Os values can be used as a diagnostic tool to distinguish between lacustrine and marine depositional settings when compared to known oceanic 187Os/188Os values.

Depositional environments of the Cache, Lower Lake, and Kelseyville Formations, Lake County, California

USGS Publications Warehouse

Rymer, Michael J.; Roth, Barry; Bradbury, J. Platt; Forester, Richard M.

1988-01-01

We describe the depositional environments of the Cache, Lower Lake, and Kelseyville Formations in light of habitat preferences of recovered mollusks, ostracodes, and diatoms. Our reconstruction of paleoenvironments for these late Cenozoic deposits provides a framework for an understanding of basin evolution and deposition in the Clear Lake region. The Pliocene and Pleistocene Cache Formation was deposited primarily in stream and debris flow environments; fossils from fine-grained deposits indicate shallow, fresh-water environments with locally abundant aquatic vegetation. The fine-grained sediments (mudstone and siltstone) were probably deposited in ponds in abandoned channels or shallow basins behind natural levees. The abandoned channels and shallow basins were associated with the fluvial systems responsible for deposition of the bulk of the technically controlled Cache Formation. The Pleistocene Lower Lake Formation was deposited in a water mass large enough to contain a variety of local environments and current regimes. The recovered fossils imply a lake with water depths of 1 to 5 m. However, there is strong support from habitat preferences of the recovered fossils for inferring a wide range of water depths during deposition of the Lower Lake Formation; they indicate a progressively shallowing system and the culmination of a desiccating lacustrine system. The Pleistocene Kelseyville Formation represents primarily lacustrine deposition with only minor fluvial deposits around the margins of the basin. Local conglomerate beds and fossil tree stumps in growth position within the basin indicate occasional widespread fluvial incursions and depositional hiatuses. The Kelseyville strata represent a large water mass with a muddy and especially fluid substrate having permanent or sporadic periods of anoxia. Central-lake anoxia, whether permanent or at irregular intervals, is the simplest way to account for the low numbers of benthic organisms recovered from the Kelseyville Formation. Similar low-oxygen conditions for benthic life are represented throughout the sedimentary history of Clear Lake. Water depths for the Kelseyville Formation of 10 to 30 m and 12 m near the margins of the basin are inferred both before and after fluvial incursions. These water-depth fluctuations cannot be correlated with major climatic changes as indicated by pollen and fossil leaves and cones; they may be due to faulting in this technically active region.

Early Triassic wrinkle structures on land: stressed environments and oases for life

NASA Astrophysics Data System (ADS)

Chu, Daoliang; Tong, Jinnan; Song, Haijun; Benton, Michael J.; Bottjer, David J.; Song, Huyue; Tian, Li

2015-06-01

Wrinkle structures in rocks younger than the Permian-Triassic (P-Tr) extinction have been reported repeatedly in marine strata, but rarely mentioned in rocks recording land. Here, three newly studied terrestrial P-Tr boundary rock succession in North China have yielded diverse wrinkle structures. All of these wrinkles are preserved in barely bioturbated shore-shallow lacustrine siliciclastic deposits of the Liujiagou Formation. Conversely, both the lacustrine siliciclastic deposits of the underlying Sunjiagou Formation and the overlying Heshanggou Formation show rich bioturbation, but no wrinkle structures or other microbial-related structures. The occurrence of terrestrial wrinkle structures in the studied sections reflects abnormal hydrochemical and physical environments, presumably associated with the extinction of terrestrial organisms. Only very rare trace fossils occurred in the aftermath of the P-Tr extinction, but most of them were preserved together with the microbial mats. This suggests that microbial mats acted as potential oases for the surviving aquatic animals, as a source of food and oxygen. The new finds suggests that extreme environmental stresses were prevalent both in the sea and on land through most of the Early Triassic.

Hydrothermal activity and its paleoecological implications in the latest Miocene to Middle Pleistocene lacustrine environments of the Baza Basin (Betic Cordillera, SE Spain)

NASA Astrophysics Data System (ADS)

García-Aguilar, José Manuel; Guerra-Merchán, Antonio; Serrano, Francisco; Palmqvist, Paul; Flores-Moya, Antonio; Martínez-Navarro, Bienvenido

2014-07-01

The continental sedimentary record of the Baza Basin (Guadix-Baza Depression, Betic Cordillera, SE Spain) shows six sedimentary units of lacustrine origin deposited from the latest Miocene to the Middle Pleistocene. Depending on the interval considered, the lacustrine deposits are mainly composed of marls, carbonates or gypsiferous evaporites, showing lithological, mineralogical and geochemical features (i.e., magnesium, strontium and sulfur contents, celestine deposits and travertine growths) that are evidence of intense, tectonically-induced hydrothermal activity. According to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays, the supply of hot waters was greater during the Zanclean, the Gelasian and the Calabrian, as a result of tectonic activity. Hydrothermal activity has continued until the present time and is responsible of the hot springs that are nowadays active in the Guadix-Baza Depression. The paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table, not subject to periodic desiccations in the dry season, and warmer temperatures throughout the year. This resulted in a high level of organic productivity, especially for the Calabrian, which allowed the development of a rich and well diversified mammalian community, similar to those of modern African savannas with tree patches. In this mild environment, the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo Hippopotamus antiquus. The high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins, which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings.

Evaluating Late Cretaceous OAEs and the influence of marine incursions on organic carbon burial in an expansive East Asian paleo-lake

NASA Astrophysics Data System (ADS)

Jones, Matthew M.; Ibarra, Daniel E.; Gao, Yuan; Sageman, Bradley B.; Selby, David; Chamberlain, C. Page; Graham, Stephan A.

2018-02-01

Expansive Late Cretaceous lacustrine deposits of East Asia offer unique stratigraphic records to better understand regional responses to global climate events, such as oceanic anoxic events (OAEs), and terrestrial organic carbon burial dynamics. This study presents bulk organic carbon isotopes (δ13Corg), elemental concentrations (XRF), and initial osmium ratios (187Os/188Os, Osi) from the Turonian-Coniacian Qingshankou Formation, a ∼5 Ma lacustrine mudstone succession in the Songliao Basin of northeast China. A notable δ13Corg excursion (∼ + 2.5‰) in organic carbon-lean Qingshankou Members 2-3 correlates to OAE3 in the Western Interior Basin (WIB) of North America within temporal uncertainty of high-precision age models. Decreases in carbon isotopic fractionation (Δ13C) through OAE3 in the WIB and Songliao Basin, suggest that significantly elevated global rates of organic carbon burial drew down pCO2, likely cooling climate. Despite this, Osi chemostratigraphy demonstrates no major changes in global volcanism or weathering trends through OAE3. Identification of OAE3 in a lake system is consistent with lacustrine records of other OAEs (e.g., Toarcian OAE), and underscores that terrestrial environments were sensitive to climate perturbations associated with OAEs. Additionally, the relatively radiogenic Osi chemostratigraphy and XRF data confirm that the Qingshankou Formation was deposited in a non-marine setting. Organic carbon-rich intervals preserve no compelling Osi evidence for marine incursions, an existing hypothesis for generating Member 1's prolific petroleum source rocks. Based on our results, we present a model for water column stratification and source rock deposition independent of marine incursions, detailing dominant biogeochemical cycles and lacustrine organic carbon burial mechanisms.

Comparison of formation mechanism of fresh-water and salt-water lacustrine organic-rich shale

NASA Astrophysics Data System (ADS)

Lin, Senhu

2017-04-01

Based on the core and thin section observation, major, trace and rare earth elements test, carbon and oxygen isotopes content analysis and other geochemical methods, a detailed study was performed on formation mechanism of lacustrine organic-rich shale by taking the middle Permian salt-water shale in Zhungaer Basin and upper Triassic fresh-water shale in Ordos Basin as the research target. The results show that, the middle Permian salt-water shale was overall deposited in hot and dry climate. Long-term reductive environment and high biological abundance due to elevated temperature provides favorable conditions for formation and preservation of organic-rich shale. Within certain limits, the hotter climate, the organic-richer shale formed. These organic-rich shale was typically distributed in the area where palaeosalinity is relatively high. However, during the upper Triassic at Ordos Basin, organic-rich shale was formed in warm and moist environment. What's more, if the temperature, salinity or water depth rises, the TOC in shale decreases. In other words, relatively low temperature and salinity, stable lake level and strong reducing conditions benefits organic-rich shale deposits in fresh water. In this sense, looking for high-TOC shale in lacustrine basin needs to follow different rules depends on the palaeoclimate and palaeoenvironment during sedimentary period. There is reason to believe that the some other factors can also have significant impact on formation mechanism of organic-rich shale, which increases the complexity of shale oil and gas prediction.

Fluvial and Lacustrine Processes in Meridiani Planum and the Origin of the Hematite by Aqueous Alteration

NASA Technical Reports Server (NTRS)

Newsom, H. E.; Barber, C. A.; Schelble, R. T.; Hare, T. M.; Feldman, W. C.; Sutherland, V.; Livingston, A.; Lewis, K.

2003-01-01

The prime MER landing site in Meridiani Planum is located on layered materials, including hematite, whose origin as lacustrine or aeolian sediments, or volcanic materials is uncertain. Our detailed mapping of the region provides important constraints on the history of the region. Our mapping of the location of fluvial and lacustrine land forms in the region relative to the layered deposits provides new evidence of a long history of erosion and deposition as has long been noted . In addition, our detailed mapping of the southern boundary of the hematite deposit strongly supports an association between longlived fluvial channels and lacustrine basins and the strongest hematite signatures. This evidence supports an origin of the hematite deposits by interaction with water under ambient conditions in contrast to suggestions of hydrothermal processes due to volcanic or impact crater processes. An important part of the story is the evidence for the localization of the layered deposits due to topographic control induce by the presence of a large early basin we have identified that extends to the north-east of the landing site. Distribution of current channel networks, drainages,

Fluvial Volumes, Timescales, and Intermittency in Milna Crater, Mars

NASA Technical Reports Server (NTRS)

Buhler, P.; Fassett, C. I.; Head, J. W.; Lamb, M. P.

2017-01-01

Ancient lake deposits and valley networks on Mars provide strong evidence that its surface was once modified by liquid water, but the extent of that modification is still debated. Ancient lacustrine deposits in Milna Crater provide insight into the timescale and fluid volume required to construct fluvially derived sedimentary deposits near the Noachian-Hesperian boundary. Placing the lacustrine deposits their regional context in Paraná Valles provides a quantitative measurement of the intermittency of large, water-mediated sediment transport events in that region.

Diagenetic contrast of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK, USA)

NASA Astrophysics Data System (ADS)

Wolela, A.

2014-11-01

Diagenetic studied in hydrocarbon-prospective Mesozoic rift basins were carried out in the Blue Nile Basin (Ethiopia), Ulster Basin (United Kingdom) and Hartford Basin (United States of America). Alluvial fan, single and amalgamated multistorey meandering and braided river, deep and shallow perennial lake, shallow ephemeral lake, aeolian and playa mud-flat are the prominent depositional environments. The studied sandstones exhibit red bed diagenesis. Source area geology, depositional environments, pore-water chemistry and circulation, tectonic setting and burial history controlled the diagenetic evolution. The diagenetic minerals include: facies-related minerals (calcrete and dolocrete), grain-coating clay minerals and/or hematite, quartz and feldspar overgrowths, carbonate cements, hematite, kaolinite, illite-smectite, smectite, illite, chlorite, actinolite, laumontite, pyrite and apatite. Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment and burial history of the basins. Variation in infiltrated clays, carbonate cements and clay minerals observed in the studied sandstones. The alluvial fan and fluviatile sandstones are dominated by kaolinite, illite calcite and ferroan calcite, whereas the playa and lacustrine sandstones are dominated by illite-smectite, smectite-chlorite, smectite, chlorite, dolomite ferroan dolomite and ankerite. Albite, pyrite and apatite are predominantly precipitated in lacustrine sandstones. Basaltic eruption in the basins modified mechanically infiltrated clays to authigenic clays. In all the studied sandstones, secondary porosity predominates over primary porosity. The oil emplacement inhabited clay authigenesis and generation of secondary porosity, whereas authigenesis of quartz, pyrite and apatite continued after oil emplacement.

Sedimentology and Reservoir Characteristics of Early Cretaceous Fluvio-Deltaic and Lacustrine Deposits, Upper Abu Gabra Formation, Sufyan Sub-basin, Muglad Rift Basin, Sudan

NASA Astrophysics Data System (ADS)

Yassin, Mohamed; Abdullatif, Osman; Hariri, Mustafa

2017-04-01

Sufyan Sub-basin is an East-West trending Sub-basin located in the northwestern part of the Muglad Basin (Sudan), in the eastern extension of the West and Central Africa Rift System (WCARS). The Early Cretaceous Abu Gabra Formation considered as the main source rock in the Muglad Basin. In Sufyan Sub-basin the Early Cretaceous Upper Abu Gabra Formation is the main oil-producing reservoir. It is dominated by sandstone and shales deposited in fluvio-deltaic and lacustrine environment during the first rift cycle in the basin. Depositional and post-depositional processes highly influenced the reservoir quality and architecture. This study investigates different scales of reservoir heterogeneities from macro to micro scale. Subsurface facies analysis was analyzed based on the description of six conventional cores from two wells. Approaches include well log analysis, thin sections and scanning electron microscope (SEM) investigations, grain-size, and X-ray diffraction (XRD) analysis of the Abu Gabra sandstone. The cores and well logs analyses revealed six lithofacies representing fluvio-deltaic and lacustrine depositional environment. The sandstone is medium to coarse-grained, poorly to moderately sorted and sub-angular to subrounded, Sub-feldspathic arenite to quartz arenite. On macro-scale, reservoir quality varies within Abu Gabra reservoir where it shows progressive coarsening upward tendencies with different degrees of connectivity. The upper part of the reservoir showed well connected and amalgamated sandstone bodies, the middle to lower parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenesis.The XRD and SEM analyses show that kaolinite and chlorite clay are the common clay minerals in the studied samples. Clay matrix and quartz overgrowth have significantly reduced the reservoir porosity and permeability, while the dissolution of feldspars during the diagenetic process increase it. The estimated porosity in Abu Gabra Formation ranges from 10 to 21% with an average of 15%; while permeability varies from 200 to 400 md. The results of this study might contribute to better understanding of reservoir heterogeneities and help in reservoir quality prediction, therefore enhancing the hydrocarbon productivity.

Taphonomy and paleoecology of nonmarine mollusca: indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation ( Paleocene), Northern Powder River Basin, Wyoming and Montana ( USA).

USGS Publications Warehouse

Hanley, J.H.; Flores, R.M.

1987-01-01

The composition, species abundances, and spatial and temporal distributions of mollusc assemblages were controlled by the environments in which they lived and the depositional processes that affected the molluscs after death and before final burial. Post-mortem transport, reworking and concentration of shells, and mixing of faunal elements from discrete habitats produced a taphonomic 'overprint' on assemblage characteristics that directly reflects the processes of alluvial plain and floodbasin lacustrine sedimentation. The 'overprint' can be interpreted from outcrop analysis of molluscan biofabric, which consists of: 1) orientation, fragmentation, size-sorting, abrasion, density, and dispersion of shells, 2) the nature and extent of shell-infilling, and 3) ratio of articulated to disarticulated bivalves. Taphonomic characteristics were used with sedimentological properties to differentiate in-place, reworked, transported, and ecologically mixed mollusc assemblages. This study also defines the paleoecology of habitat preferences of mollusc species as a basis for recognition of the environments in which these assemblages were deposited: 1) large floodbasin lakes, 2) small floodbasin lakes, and 3) crevasse deltas and splays. Integration of sedimentology and paleoecology provides an interdisciplinary approach to the interpretation of alluvial environments through time in the Tongue River Member. -Authors

Surficial Geologic Map of the West Franklin Quadrangle, Vanderburgh and Posey Counties, Indiana, and Henderson County, Kentucky

USGS Publications Warehouse

Moore, David W.; Newell, Wayne L.; Counts, Ronald C.; Fraser, Gordon S.; Fishbaugh, David A.; Brandt, Theodore R.

2007-01-01

The valley of the Ohio River is filled with alluvium and outwash (unit Qal), which total 33-39 m thick under the land surface in the southeast part of the West Franklin quadrangle in Indiana, and 30.5-35 m thick under Diamond Island in the southwest corner of the quadrangle. The deposits are chiefly fine- to medium-grained, lithic quartzose sand, interbedded by lenses of clay, clayey silt, silt, coarse sand, granules, and gravel. Although grain size of the river alluvium varies widely, in general it fines upward-being gravelly sand to sandy gravel in the lower part, mainly sand in the middle part, and silty and clayey in the upper part (Holocene). The middle and lower parts probably accumulated during the Wisconsin Episode (late Pleistocene). The sandy middle part contains interbeds of clay, silt, and minor gravel. At the base is highly consolidated mud (silt and clay), sand, and gravel 2-10 m thick. This unit may be valley train that predates the Wisconsin Episode. Creek alluvium (unit Qa) is silt, clayey silt, and subordinate intercalated fine sand, granules, and pebbles; the coarser grains are generally concentrated in the basal 1-2 m of the deposit. Lenses and beds of clay are present locally. Fossil wood collected from an auger hole in the alluvial deposits of Little Creek, at depths of 10.6 m and 6.4 m, were dated 16,650?50 and 11,120?40 radiocarbon years, respectively. Probable lacustrine terrace silt and clay (Qlt), so-called slackwater-lake or backwater deposits, form deposits 12-22 m thick in the lowest reaches of tributary creeks to the Ohio River. The surfaces of the lacustrine deposits are terraces a few meters higher than the modern creek flood plains. Covering the bedrock upland is loess (Ql) 3-7.5 m thick, deposited about 18,000-12,000 years before present. Most surficial deposits in the quadrangle are probably no older than about 35,000 yrs. Lithologic logs, shear-wave velocities, and other cone penetrometer data are used to interpret depositional environments and geologic history of the alluvium and lacustrine deposits.

Sedimentological reservoir characteristics of the Paleocene fluvial/lacustrine Yabus Sandstone, Melut Basin, Sudan

NASA Astrophysics Data System (ADS)

Mahgoub, M. I.; Padmanabhan, E.; Abdullatif, O. M.

2016-11-01

Melut Basin in Sudan is regionally linked to the Mesozoic-Cenozoic Central and Western African Rift System (CWARS). The Paleocene Yabus Formation is the main oil producing reservoir in the basin. It is dominated by channel sandstone and shales deposited in fluvial/lacustrine environment during the third phase of rifting in the basin. Different scales of sedimentological heterogeneities influenced reservoir quality and architecture. The cores and well logs analyses revealed seven lithofacies representing fluvial, deltaic and lacustrine depositional environments. The sandstone is medium to coarse-grained, poorly to moderately-sorted and sub-angular to sub-rounded, arkosic-subarkosic to sublitharenite. On the basin scale, the Yabus Formation showed variation in sandstone bodies, thickness, geometry and architecture. On macro-scale, reservoir quality varies vertically and laterally within Yabus Sandstone where it shows progressive fining upward tendencies with different degrees of connectivity. The lower part of the reservoir showed well-connected and amalgamated sandstone bodies, the middle to the upper parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenetic changes such as compaction, cementation, alteration, dissolution and kaolinite clays pore fill and coat all have significantly reduced the reservoir porosity and permeability. The estimated porosity in Yabus Formation ranges from 2 to 20% with an average of 12%; while permeability varies from 200 to 500 mD and up to 1 Darcy. The understanding of different scales of sedimentological reservoir heterogeneities might contribute to better reservoir quality prediction, architecture, consequently enhancing development and productivity.

Sediment characteristics and configuration within three dam impoundments on the Kalamazoo River, Michigan, 2000

USGS Publications Warehouse

Rheaume, S.J.; Rachol, C.M.; Hubbell, D.L.; Simard, Andreanne

2002-01-01

The removal of the remnants of three hydroelectric dams on the Kalamazoo River near Plainwell, Otsego, and Allegan, Michigan, has been proposed. The benefits of this removal include returning the Kalamazoo River to its pre-dam flow, increasing recreational use and safety on the river, and improving aquatic habitat. The U.S. Environmental Protection Agency has designated this reach of the Kalamazoo River as a Federal Superfund site because of the historical discharge of papermill waste containing polychlorinated biphenyls. Much of this waste material remains concentrated in organic sediment and kaolinite clay deposited upstream from the three dam foundations. Sediment containing up to 150 milligrams per kilogram polychlorinated biphenyls could move if dam foundations are removed; therefore, it is necessary to estimate the characteristic and configuration of the sediment before work begins. Data collected from augered sections and sediment cores show that impoundment sediments were deposited in two distinctly different sedimentary environments. Interbedded lacustrine sediments that overlie the pre-dam channel surface consist of organic-rich silt and clay, fine to medium sand, and some gravel. These materials were deposited in a repetitive, cyclic fashion related to former stream velocities when the impoundment water levels were 5-10 feet higher. Lowering of these water levels and demolition of the superstructures of these dams resulted in erosion of much of these instream lacustrine sediments and subsequent deposition of coarse-grained alluvium in the impounded channel behind the remaining dam foundations. The composite thicknesses of the lacustrine deposits and overlying alluvium was determined from sediment cores collected from each impoundment. The volume of instream sediment contained in each impoundment is estimated to be about 77,600 cubic yards at the Plainwell impoundment; 268,900 cubic yards at the Otsego impoundment; and 1,192,600 cubic yards at the Trowbridge impoundment. Estimates do not include bank or flood-plain deposits.

Hinterland drainage closure and lake formation in response to middle Eocene Farallon slab removal, Nevada, U.S.A.

NASA Astrophysics Data System (ADS)

Smith, M. Elliot; Cassel, Elizabeth J.; Jicha, Brian R.; Singer, Brad S.; Canada, Andrew S.

2017-12-01

Hinterland basins can accumulate high resolution archives of orogenic processes and continental climate, but are challenging to reconstruct due to tectonic overprinting and the inherent complexity of their lithofacies assemblages. The Cordilleran hinterland of northeast Nevada has been interpreted to have overlain a flattened Farallon slab from the Late Cretaceous to Eocene. Slab removal and advection of asthenospheric mantle beneath Nevada have been invoked to explain a southwestward migrating wave of Eocene to Oligocene volcanism and proposed as a driver for topographic uplift. However, the timing of slab removal and possible subsequent delamination of North American lithospheric mantle can only ambiguously be related to the surface record. Subsequent Neogene extension and basin filling has complicated the correlation and interpretation of strata that record these events. Here we apply single crystal sanidine 40Ar/39Ar geochronology to 26 ash beds in northeast Nevada to reconstruct Paleogene geographic and hydrologic evolution. We use these ages and legacy geochronology to compare lithofacies and isotope proxy records of meteoric waters to regional tectonics and global climate, and assess competing tectonic interpretations for lake basin formation. Lakes formed locally prior to ca. 48.7 Ma in northeast Nevada, coeval with foreland lakes of the Green River Formation. The most expansive phase of lacustrine deposition resulted in onlap onto locally derived fluvial deposits and folded Paleozoic bedrock, and occurred between ca. 43.4 and ca. 40.8 Ma. Elko Formation strata exhibit a basin-wide transition from fluvial-lacustrine to fluctuating profundal lithofacies at ca. 42.7 Ma, suggesting a shift towards regional hydrologic closure. The stromatolitic upper Elko Formation is intercalated with ash fall tuffs and several partially welded to unwelded ignimbrites from increasingly proximal volcanism. Elko Formation deposition ended by ca. 40.4 Ma. 40Ar/39Ar ages for seven ash beds in the Dead Horse Formation at Copper Basin in northern Elko County indicate intermittent ash bed deposition between 45.2 Ma and 38.6 Ma, and an episode of lacustrine deposition between 39.8 Ma and 38.6 Ma that post-dates the main phase of Lake Elko. δD values of volcanic glass sampled from dated ash beds reflect changes in the hydrogen isotope compositions of local Eocene waters, and systematically vary by 80-102‰ according to their depositional environment. The Elko Formation and overlying volcanic strata are overlain regionally by a pronounced unconformity of ∼20 m.y. In the Copper Basin area, deposition continued locally into the Oligocene in the hanging wall of a ductile detachment. The geochronologic and isotopic framework presented here permits reanalysis of the Piñon Range carbonate proxy record that was previously interpreted to record both regional uplift and the middle Eocene climatic optimum. New data suggest instead that isotope values of hydration waters within the Elko Formation were strongly influenced by evaporation, and a change from lacustrine to non-lacustrine conditions can account for the δ18O shift that was interpreted to reflect regional uplift. Moreover, the end of Elko Formation deposition predated the middle Eocene climatic optimum. We interpret the overall record of drainage ponding and paleovalley inundation, progressively more evaporative lacustrine conditions, increasingly proximal volcanism, and subsequent prolonged unconformity to reflect the surface effects of progressive NE to SW removal of the Farallon slab.

High resolution HH-XRF scanning and XRD modelling as a tool in sedimentological analysis - A case study from the Enreca-3 core, Bach Long Vi Island, Vietnam

NASA Astrophysics Data System (ADS)

Rizzi, Malgorzata; Hemmingsen Schovsbo, Niels; Korte, Christoph; Bryld Wessel Fyhn, Michael

2017-04-01

To improve the understanding and interpretation of the depositional environment of a late Oligocene lacustrine organic rich oil-prone source rock succession, 2464 hand held (HH)-XRF measurements were made systematically on the 500 m long, continuous core from the fully cored Enreca-3 well. This core, drilled on the remote Bach Long Vi Island, northern Gulf of Tonkin, offshore Vietnam, represents a deep lake succession alternating between lacustrine pelagic dominated sediments interrupted by hyperpycnal turbidites, high density turbidites and debris flows [1, 2]. From a combined HH-XRF-XRD data set, multivariate data analysis and regression models are used to type the rock and to predict the XRD mineral composition based on HH-XRF composition. The rock types and the modelled mineral composition highlight the geochemical variations of the sediment and allows for direct comparison with sedimentological processes and facies changes. The modeling also depicts the cyclic alteration of rock types that are present on many different scales ranging from centimeters to hundreds of meters [1, 2]. The sedimentological and geochemical variations observed throughout the cored section reflects fluctuating paleoclimate, tectonism and hinterland condition controlling the depositional setting, which may provide a deeper understanding of the deposition of this and similar Paleogene syn-rift succession in the South China Sea region. It allows furthermore the development of a more generalized depositional model relevant for other deep-lacustrine syn-rift basins. [1] Petersen et al. (2014) Journal of Petroleum Geology, 37: 373-389. [2] Hovikoski et al. (2016) Journal of Sedimentary Research, 86(8): 982-1007.

Evidence for persistent flow and aqueous sedimentation on early Mars.

PubMed

Malin, Michael C; Edgett, Kenneth S

2003-12-12

Landforms representative of sedimentary processes and environments that occurred early in martian history have been recognized in Mars Global Surveyor Mars Orbiter Camera and Mars Odyssey Thermal Emission Imaging System images. Evidence of distributary, channelized flow (in particular, flow that lasted long enough to foster meandering) and the resulting deposition of a fan-shaped apron of debris indicate persistent flow conditions and formation of at least some large intracrater layered sedimentary sequences within fluvial, and potentially lacustrine, environments.

Deformation of ``Villafranchian'' lacustrine sediments in the Chisone Valley (Western Alps, Italy)

NASA Astrophysics Data System (ADS)

Collo, Giovanni; Giardino, Marco

1997-09-01

The Chisone Valley is located in the internal NW Alps, in the Pinerolese District, an area characterized by present low to medium seismicity. Fine-grained sediments (sand, silt and clay with interbedded gravel) crop out in the lower Chisone Valley: they were first interpreted as glaciolacustrine deposits, and then as a lacustrine infilling of the valley floor probably due to differential uplifting of the valley mouth. Review of this data, together with new field and palynological observations, lead us to refer the lacustrine deposits to approximately the Lower Pleistocene (Villafranchian). In many outcrops, the lacustrine deposits show strong soft-sediment deformation such as convolute laminations, water-escape structures and disrupted beds, some of them associated with folds and faults (cm to dm in size); only two sites show metric to decametric folds and faults trending E-W and N-S. Detailed structural analysis conducted along a recently exposed section (Rio Gran Dubbione site) shows several soft-sediment deformation features on the limbs of mesoscale folds. Because of their intimate structural association, the origin of these minor structures seems to be connected to synsedimentary activity on reverse and normal faults (m to dm in size) affecting the lacustrine deposits in the same locality. Soft-sediment deformation features can be interpreted as possible paleoseismites. If so, the present seismicity of the Pinerolese District, which is the major area of such activity in NW Italy, cannot be considered an isolated episode in the geological evolution of the region; even if there is no supporting evidence for continuous seismicity, the deformations in the lacustrine sediments of the Chisone Valley testify to Early Pleistocene seismic activity, probably related to the recent tectonic evolution of the internal side of the NW Alps.

The Lacustrine Upper Brushy Basin Member of the Morrison Formation, Four Corners Region, Usa: a Lithological and Mineralogical Terrestrial Analog for Gale Crater, Mars

NASA Astrophysics Data System (ADS)

Potter-McIntyre, S. L.; Chan, M. A.; McPherson, B. J.

2013-12-01

The upper part of the Jurassic Brushy Basin Member of the Morrison Formation is an iron- and clay-rich volcaniclastic shale deposited in an ephemeral alkaline saline lake system. Sedimentary rocks exposed in Gale Crater consist of similar non-acidic clays, possibly of lacustrine origin. Three primary clastic lithofacies are present in both the Brushy Basin Member and at Gale Crater: silt-/claystone, sandstone, and conglomerate. Both the terrestrial and martian silt-/claystone lithofacies are interpreted as lacustrine depositional environments due to features such as parallel laminated and massive sedimentary structures. Vugs are present in the siltstone/claystone facies on both the Colorado Plateau and at Gale Crater. Fluvial features are also observed in both examples such as cross-bedded sandstones and imbricated conglomerates. Concretions are present in both the Colorado Plateau and Gale Crater units. The vugs in the Brushy Basin Member preserve algal forms with cellular elaboration and are interpreted as charophyte molds. Two distinct suites of elements (1. C, Fe, As, P and, 2. C, S, Se, P) are associated with the microbial fossils and may be potential markers for biosignatures. Vugs at Gale Crater are a potential target to investigate the possibility of preserved microbial (algal) life where early analyses show the presence of the elements capable of supporting life. The Brushy Basin Member is composed predominately of quartz, feldspars, zeolites and altered volcanic ash. The abundant clay minerals in both the terrestrial and martian examples are hypothesized to have formed due to partial alteration of volcanic minerals in alkaline fluid. Similarly, concretions present in the terrestrial unit exhibit a diverse range of mineralogies likely due to alkaline fluid chemistries interacting with reactive volcaniclastic sediments. Terrestrial concretion mineralogy is diverse even within an outcrop or stratigraphic horizon which suggests reactants to precipitate concretions are being sourced from diagenetic micorenvironments. Similar diagenetic microenvironments may be preserved at Gale Crater due to the fine-grained, volcaniclastic (reactive) rocks. The Brushy Basin Member is a valuable analog because comparative iron-and clay-rich compositions help to: 1) understand diagenetic processes in a non-acidic, saline lacustrine environment, 2) document specific sedimentary structures and lithofacies associations to interpret depositional environment, 3) document specific biomediated features (e.g., textures, morphologies, chemistries), and 4) demonstrate how these features might persist or respond to diagenesis over time.

Sedimentary architecture of a sub-lacustrine debris fan: Eocene Dongying Depression, Bohai Bay Basin, east China

NASA Astrophysics Data System (ADS)

Liu, Jianping; Xian, Benzhong; Wang, Junhui; Ji, Youliang; Lu, Zhiyong; Liu, Saijun

2017-12-01

The sedimentary architectures of submarine/sublacustrine fans are controlled by sedimentary processes, geomorphology and sediment composition in sediment gravity flows. To advance understanding of sedimentary architecture of debris fans formed predominantly by debris flows in deep-water environments, a sub-lacustrine fan (Y11 fan) within a lacustrine succession has been identified and studied through the integration of core data, well logging data and 3D seismic data in the Eocene Dongying Depression, Bohai Bay Basin, east China. Six types of resedimented lithofacies can be recognized, which are further grouped into five broad lithofacies associations. Quantification of gravity flow processes on the Y11 fan is suggested by quantitative lithofacies analysis, which demonstrates that the fan is dominated by debris flows, while turbidity currents and sandy slumps are less important. The distribution, geometry and sedimentary architecture are documented using well data and 3D seismic data. A well-developed depositional lobe with a high aspect ratio is identified based on a sandstone isopach map. Canyons and/or channels are absent, which is probably due to the unsteady sediment supply from delta-front collapse. Distributary tongue-shaped debris flow deposits can be observed at different stages of fan growth, suggesting a lobe constructed by debrite tongue complexes. Within each stage of the tongue complexes, architectural elements are interpreted by wireline log motifs showing amalgamated debrite tongues, which constitute the primary fan elements. Based on lateral lithofacies distribution and vertical sequence analysis, it is proposed that lakefloor erosion, entrainment and dilution in the flow direction lead to an organized distribution of sandy debrites, muddy debrites and turbidites on individual debrite tongues. Plastic rheology of debris flows combined with fault-related topography are considered the major factors that control sediment distribution and fan architecture. An important implication of this study is that a deep-water depositional model for debrite-dominated systems was proposed, which may be applicable to other similar deep-water environments.

Diagenetic silica enrichment and late-stage groundwater activity in Gale crater, Mars

USGS Publications Warehouse

Frydenvang, Jens; Gasda, Patrick J.; Hurowitz, Joel A.; Grotzinger, John P.; Wiens, Roger C.; Newsom, Horton E.; Edgett, Ken S.; Watkins, Jessica; Bridges, John C.; Maurice, Sylvestre; Fisk, Martin R.; Johnson, Jeffrey R.; Rapin, William; Stein, Nathan; Clegg, Sam M.; Schwenzer, S. P.; Bedford, C.; Edwards, P.; Mangold, Nicolas; Cousin, Agnes; Anderson, Ryan; Payre, Valerie; Vaniman, David; Blake, David; Lanza, Nina L.; Gupta, Sanjeev; Van Beek, Jason; Sautter, Violaine; Meslin, Pierre-Yves; Rice, Melissa; Milliken, Ralf; Gellert, Ralf; Thompson, Lucy; Clark, Ben C.; Sumner, Dawn Y.; Fraeman, Abigail A.; Kinch, Kjartan M; Madsen, Morten B.; Mitofranov, Igor; Jun, Insoo; Calef, Fred J.; Vasavada, Ashwin R.

2017-01-01

Diagenetic silica enrichment in fracture-associated halos that crosscut lacustrine and unconformably overlying aeolian sedimentary bedrock is observed on the lower north slope of Aeolis Mons in Gale crater, Mars. The diagenetic silica enrichment is colocated with detrital silica enrichment observed in the lacustrine bedrock yet extends into a considerably younger, unconformably draping aeolian sandstone, implying that diagenetic silica enrichment postdates the detrital silica enrichment. A causal connection between the detrital and diagenetic silica enrichment implies that water was present in the subsurface of Gale crater long after deposition of the lacustrine sediments and that it mobilized detrital amorphous silica and precipitated it along fractures in the overlying bedrock. Although absolute timing is uncertain, the observed diagenesis likely represents some of the most recent groundwater activity in Gale crater and suggests that the timescale of potential habitability extended considerably beyond the time that the lacustrine sediments of Aeolis Mons were deposited.

Facies analysis, palaeoenvironmental reconstruction and stratigraphic development of the Early Cretaceous sediments (Lower Bima Member) in the Yola Sub-basin, Northern Benue Trough, NE Nigeria

NASA Astrophysics Data System (ADS)

Sarki Yandoka, Babangida M.; Abubakar, M. B.; Abdullah, Wan Hasiah; Amir Hassan, M. H.; Adamu, Bappah U.; Jitong, John S.; Aliyu, Abdulkarim H.; Adegoke, Adebanji Kayode

2014-08-01

The Benue Trough of Nigeria is a major rift basin formed from the tension generated by the separation of African and South American plates in the Early Cretaceous. It is geographically sub-divided into Southern, Central and Northern Benue portions. The Northern Benue Trough comprises two sub-basins; the N-S trending Gongola Sub-basin and the E-W trending Yola Sub-basin. The Bima Formation is the oldest lithogenetic unit occupying the base of the Cretaceous successions in the Northern Benue Trough. It is differentiated into three members; the Lower Bima (B1), the Middle Bima (B2) and the Upper Bima (B3). Facies and their stratigraphical distribution analyses were conducted on the Lower Bima Member exposed mainly at the core of the NE-SW axially trending Lamurde Anticline in the Yola Sub-basin, with an objective to interpret the paleodepositional environments, and to reconstruct the depositional model and the stratigraphical architecture. Ten (10) lithofacies were identified on the basis of lithology, grain size, sedimentary structures and paleocurrent analysis. The facies constitute three (3) major facies associations; the gravelly dominated, the sandy dominated and the fine grain dominated. These facies and facies associations were interpreted and three facies successions were recognized; the alluvial-proximal braided river, the braided river and the lacustrine-marginal lacustrine. The stratigraphic architecture indicates a rifted (?pull-apart) origin as the facies distribution shows a progradational succession from a shallow lacustrine/marginal lacustrine (at the axial part of the basin) to alluvial fan (sediment gravity flow)-proximal braided river (gravel bed braided river) and braided river (channel and overbank) depositional systems. The facies stacking patterns depict sedimentation mainly controlled by allogenic factors of climate and tectonism.

Effects of the Laramide Structures on the Regional Distribution of Tight-Gas Sandstone in the Upper Mesaverde Group, Uinta Basin, Utah

NASA Astrophysics Data System (ADS)

Sitaula, R. P.; Aschoff, J.

2013-12-01

Regional-scale sequence stratigraphic correlation, well log analysis, syntectonic unconformity mapping, isopach maps, and depositional environment maps of the upper Mesaverde Group (UMG) in Uinta basin, Utah suggest higher accommodation in northeastern part (Natural Buttes area) and local development of lacustrine facies due to increased subsidence caused by uplift of San Rafael Swell (SRS) in southern and Uinta Uplift in northern parts. Recently discovered lacustrine facies in Natural Buttes area are completely different than the dominant fluvial facies in outcrops along Book Cliffs and could have implications for significant amount of tight-gas sand production from this area. Data used for sequence stratigraphic correlation, isopach maps and depositional environmental maps include > 100 well logs, 20 stratigraphic profiles, 35 sandstone thin sections and 10 outcrop-based gamma ray profiles. Seven 4th order depositional sequences (~0.5 my duration) are identified and correlated within UMG. Correlation was constructed using a combination of fluvial facies and stacking patterns in outcrops, chert-pebble conglomerates and tidally influenced strata. These surfaces were extrapolated into subsurface by matching GR profiles. GR well logs and core log of Natural Buttes area show intervals of coarsening upward patterns suggesting possible lacustrine intervals that might contain high TOC. Locally, younger sequences are completely truncated across SRS whereas older sequences are truncated and thinned toward SRS. The cycles of truncation and thinning represent phases of SRS uplift. Thinning possibly related with the Uinta Uplift is also observed in northwestern part. Paleocurrents are consistent with interpretation of periodic segmentation and deflection of sedimentation. Regional paleocurrents are generally E-NE-directed in Sequences 1-4, and N-directed in Sequences 5-7. From isopach maps and paleocurrent direction it can be interpreted that uplift of SRS changed route of sediment supply from west to southwest. Locally, paleocurrents are highly variable near SRS further suggesting UMG basin-fill was partitioned by uplift of SRS. Sandstone composition analysis also suggests the uplift of SRS causing the variation of source rocks in upper sequences than the lower sequences. In conclusion, we suggest that Uinta basin was episodically partitioned during the deposition of UMG due to uplift of Laramide structures in the basin and accommodation was localized in northeastern part. Understanding of structural controls on accommodation, sedimentation patterns and depositional environments will aid prediction of the best-producing gas reservoirs.

Estimation of the tectonic slip-rate from Quaternary lacustrine facies within the intraplate Albacete province (SE of Spain)

USGS Publications Warehouse

Rodriguez-Pascua, M. A.; Bischoff, J.; Garduno-Monroy, Victor H.; Pérez-López, R.; Giner-Robles, J.L.; Israde-Alcántara, I.; Calvo, J.P.; Williams, Ross W.

2009-01-01

The Quaternary lacustrine basin of Cordovilla (CB) represents one of the most active tectonic areas of the Prebetic Zone (Albacete, SE of Spain). The Quaternary sedimentary deposits of this basin are mainly endoreic lacustrine carbonate and alluvial deposits, developed in a semi-arid climate (Pleistocene-present). The basin is a NW-SE-elongated graben bounded by a major right-lateral oblique-fault, the Pozohondo Fault. This fault trends NW-SE, with an approximate trace of 55 km, and is composed of various segments which are identified by fault scarps. In order to establish the slip-rate of the most active segment of the Pozohondo Fault, called the Cordovilla segment, we carried out a detailed study of the affected Quaternary lacustrine deposits. We found that the lacustrine facies could be related to episodic moderate paleoearthquakes. The slip-rate is calculated to be 0.05 and 0.09 mm/yr, using radiometric dating for the vertical offsets of the lacustrine facies. A trenching study at the northern part of the Cordovilla segment revealed two events caused by paleoearthquakes, with the most recent expressed as an oblique-fault off-setting a poorly-developed soil. The magnitude of the last event was greater than 6, using various empirical relationships for the fault displacement and the surface-length rupture. We estimate episodic activity across the Cordovilla segment, to be characterized by moderate-sized paleoearthquakes (M6), which is in agreement with the tectonic context of an intraplate zone of the Iberian plate. ?? 2009 Elsevier B.V.

Oil Shale

USGS Publications Warehouse

Birdwell, Justin E.

2017-01-01

Oil shales are fine-grained sedimentary rocks formed in many different depositional environments (terrestrial, lacustrine, marine) containing large quantities of thermally immature organic matter in the forms of kerogen and bitumen. If defined from an economic standpoint, a rock containing a sufficient concentration of oil-prone kerogen to generate economic quantities of synthetic crude oil upon heating to high temperatures (350–600 °C) in the absence of oxygen (pyrolysis) can be considered an oil shale.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mello, M.R.; Soldan, A.L.; Maxwell, J.R.

A geochemical and biological marker investigation of a variety of oils from offshore Brazil and west Africa, ranging in age from Lower Cretaceous to Tertiary, has been done, with the following aims: (1) assessing the depositional environment of source rocks, (2) correlating the reservoired oils, (3) comparing the Brazilian oils with their west African counterparts. The approach was based in stable isotope data; bulk, elemental, and hydrous pyrolysis results; and molecular studies involving quantitative geological marker investigations of alkanes using GC-MS and GC-MS-MS. The results reveal similarities between groups of oils from each side of the Atlantic and suggest anmore » origin from source rocks deposited in five types of depositional environment: lacustrine fresh water, lacustrine saline water, marine evaporitic/carbonate, restricted marine anoxic, and marine deltaic. In west Africa, the Upper Cretaceous marine anoxic succession (Cenomanian-Santonian) appears to be a major oil producer, but in Brazil it is generally immature. The Brazilian offshore oils have arisen mainly from the pre-salt sequence, whereas the African oils show a balance between origins from the pre-salt and marine sequences. The integration of the geochemical and geological data indicate that new frontiers of hydrocarbon exploration in the west African basins must consider the Tertiary reservoirs in the offshore area of Niger Delta, the reservoirs of the rift sequences in the shallow-water areas of south Gabon, Congo, and Cuanza basins, and the reservoirs from the drift sequences (post-salt) in the deep-water areas of Gabon, Congo Cabinda, and Cuanza basins.« less

Organic geochemical characteristics and paleoclimate conditions of the Miocene coals at the Çan-Durali (Çanakkale)

NASA Astrophysics Data System (ADS)

Hoş-Çebi, Fatma

2017-05-01

In this study, n-alkane and isoprenoid, saturated and aromatic biomarker distributions of Miocene coals in the Çan (Çanakkale) region, were studied to investigate organic geochemical characteristics, depositional environment, and hydrocarbon potential of these coals. Çan formation (Middle Miocene) unconformably overlies the basement Çan volcanites (Upper Oligocene-Lower Miocene). This formation is composed of lignite, clayey lignite, and ligniferous clayey levels of various thicknesses interlayering with clay and tuffite. The formation represents sediments of small lacustrine basins that are isolated by faults that are formed contemporaneously with Early-Middle Eocene volcanism. Coaliferous units are overlain by lower agglomerate levels. The Rock Eval analyses show that the average TOC (Total Organic Carbon) content of the coal is 53.71% and the average HI (Hydrogen Index) value is 180.5 mgHC/gTOC. OI (Oxygen Index) values (avg. 22.33 mgCO2/gTOC) show that the depositional environment of peat deposits is suboxic. According to HI-Tmax, S2-TOC classification diagrams and Pr/n-C17vs. Ph/n-C18 diagram, the organic matter is composed of Type II and Type III kerogen mixing and represents a transitional environment. In gas chromatograms, n-alkanes with high, mostly odd-numbered carbons are dominant and they are associated with a slight algal contribution. CPI22-30 (Carbon Preference Index) and TARHC (Terrigenous/Aquatic Ratio) values indicate a dominance of high-carbon numbered n-alkanes, indicating the presence of terrestrial organic matter. Paq (aquatic plant n-alkane proxy) values (0.2; 0.3) indicate a climate with relatively wet conditions or low precipitation, the presence of emergent macrophyteses, and the scarcity of hydrophilic plants. Pwax (vascular plant n-alkane proxy) ratio (0.8; 0.7) shows moderately wet conditions and a relatively low water level. The TOC, ACL (n-alkane average chain length), Qwood/grass, Qwood/plant, and Qgrass/plant values indicate the presence of woody plants in a peat bog and relatively wet and moderately warm climate conditions. Based on DBT/P (dibenzothiophene/phenanthrene) ratio, sample Ç-2 points to the character of marine shale and other lacustrines whereas sample Ç-6 indicates fluvial/deltaic depositional environment. Overall, 20S/(20R + 20S), ββ/(αα+ββ) sterane, 22S/(22R + 22S) homohopane, and moretane/hopane ratios that reflect the maturity of organic matter are indicative of immature organic matter. MA(I)/MA(I + II), TA(I)/TA(I + II) and C28TA/(C29MA + C28TA) steroid, MPI, MPR, and MDR ratios calculated from aromatic biomarkers are quite low, which indicate an immature nature. The n-alkane, saturated and aromatic biomarker data on the Çan coals reveal that deposition should have taken place in a terrestrial environment changing from lacustrine to fluvial under predominately suboxic-oxic and acidic conditions.

The depositional setting of the Late Quaternary sedimentary fill in southern Bannu basin, Northwest Himalayan fold and thrust belt, Pakistan.

PubMed

Farid, Asam; Khalid, Perveiz; Jadoon, Khan Zaib; Jouini, Mohammed Soufiane

2014-10-01

Geostatistical variogram and inversion techniques combined with modern visualization tools have made it possible to re-model one-dimensional electrical resistivity data into two-dimensional (2D) models of the near subsurface. The resultant models are capable of extending the original interpretation of the data to depict alluvium layers as individual lithological units within the 2D space. By tuning the variogram parameters used in this approach, it is then possible to visualize individual lithofacies and geomorphological features for these lithologic units. The study re-examines an electrical resistivity dataset collected as part of a groundwater study in an area of the Bannu basin in Pakistan. Additional lithological logs from boreholes throughout the area have been combined with the existing resistivity data for calibration. Tectonic activity during the Himalayan orogeny uplifted and generated significant faulting in the rocks resulting in the formation of a depression which subsequently has been filled with clay-silt and dirty sand facies typical of lacustrine and flood plain environments. Streams arising from adjacent mountains have reworked these facies which have been eroded and replaced by gravel-sand facies along channels. It is concluded that the sediments have been deposited as prograding fan shaped bodies, flood plain, and lacustrine deposits. Clay-silt facies mark the locations of paleo depressions or lake environments, which have changed position over time due to local tectonic activity and sedimentation. The Lakki plain alluvial system has thus formed as a result of local tectonic activity with fluvial erosion and deposition characterized by coarse sediments with high electrical resistivities near the mountain ranges and fine sediments with medium to low electrical resistivities towards the basin center.

Review of taxonomy, geographic distribution, and paleoenvironments of Azhdarchidae (Pterosauria)

PubMed Central

Averianov, Alexander

2014-01-01

Abstract The taxonomy, geographic distribution, and paleoenvironmental context of azhdarchid pterosaurs are reviewed. All purported pteranodontid, tapejarid, and azhdarchid specimens from the Cenomanian Kem Kem beds of Morocco are referred to a single azhdarchid taxon, Alanqa saharica. The four proposed autapomorphies of Eurazhdarcho langendorfensis from the lower Maastrichtian Sebeş Formation of Romania are based on misinterpretations of material and this taxon is likely a subjective junior synonym of Hatzegopteryx thambema. Among 54 currently reported azhdarchid occurrences (51 skeletal remains and 3 tracks) 13% are from lacustrine deposits, 17% from fluvial plain deposits, 17% from coastal plain deposits, 18% from estuarine and lagoonal deposits, and 35% from costal marine deposits. Azhdarchids likely inhabited a variety of environments, but were abundant near large lakes and rivers and most common in nearshore marine paleoenvironments. PMID:25152671

Sedimentology and palaeontology of the Upper Jurassic Puesto Almada Member (Cañadón Asfalto Formation, Fossati sub-basin), Patagonia Argentina: Palaeoenvironmental and climatic significance

NASA Astrophysics Data System (ADS)

Cabaleri, Nora G.; Benavente, Cecilia A.; Monferran, Mateo D.; Narváez, Paula L.; Volkheimer, Wolfgang; Gallego, Oscar F.; Do Campo, Margarita D.

2013-10-01

Six facies associations are described for the Puesto Almada Member at the Cerro Bandera locality (Fossati sub-basin). They correspond to lacustrine, palustrine, and pedogenic deposits (limestones); and subordinated alluvial fan, fluvial, aeolian, and pyroclastic deposits. The lacustrine-palustrine depositional setting consisted of carbonate alkaline shallow lakes surrounded by flooded areas in a low-lying topography. The facies associations constitute four shallowing upward successions defined by local exposure surfaces: 1) a Lacustrine-Palustrine-pedogenic facies association with a 'conchostracan'-ostracod association; 2) a Palustrine facies association representing a wetland subenvironment, and yielding 'conchostracans', body remains of insects, fish scales, ichnofossils, and palynomorphs (cheirolepidiacean species and ferns growing around water bodies, and other gymnosperms in more elevated areas); 3) an Alluvial fan facies association indicating the source of sediment supply; and 4) a Lacustrine facies association representing a second wetland episode, and yielding 'conchostracans', insect ichnofossils, and a palynoflora mainly consisting of planktonic green algae associated with hygrophile elements. The invertebrate fossil assemblage found contains the first record of fossil insect bodies (Insecta-Hemiptera and Coleoptera) for the Cañadón Asfalto Formation. The succession reflects a mainly climatic control over sedimentation. The sedimentary features of the Puesto Almada Member are in accordance with an arid climatic scenario across the Upper Jurassic, and they reflect a strong seasonality with periods of higher humidity represented by wetlands and lacustrine sediments.

High-resolution δ13C record of fossil wood and bulk organic matter from a deep Oligocene lacustrine succession, Bach Long Vi Island, Vietnam

NASA Astrophysics Data System (ADS)

Rizzi, M.; Schovsbo, N. H.; Fyhn, M. B. W.; Korte, C.

2017-12-01

We present a high-resolution stable isotope record based on bulk organic matter (δ13Corg) and fossil wood (δ13Cwood) originating from Oligocene deep lacustrine sediments cored on the Bach Long Vi Island, northern Gulf of Tonkin, offshore Vietnam. The sediments are exceptionally well preserved. They are thus excellently suited for a detailed stratigraphical analysis of the stable isotope record and as proxy for environmental and climatic changes within this period. The sediments were deposited in rapid subsiding, narrow and elongated fault-bound graben (Fyhn and Phach, 2015) and are represented by deep pelagic lacustrine organic-rich mud interrupted by numerous density-flow deposits (Hovikoski et al., 2016). The density-flow deposits contain abundant fragments of fossil wood. Therefore it was possible to obtain 262 coalified wood fragments together with 1063 bulk organic samples throughout the span of the core. This allowed to establish a high resolution stable C isotope record (δ13Corg and δ13Cwood). In addition 2464 handheld XRF determinations were carried out to further characterize the depositional environment (Rizzi et al., 2017). The organic carbon isotope trend from the 500 m core succession provides insight into the palaeoenvironmental changes of the lake during the Oligocene. Both, global and local factors control the δ13C variations. The aim of the study is to obtain pure global δ13Corg and δ13Cwood signals that would allow comparison of the studied sediments with coeval syn-rift successions in the South China Sea region and other parts of the world. [1] Fyhn and Phach (2015) Tectonics, 34(2): 290-312. [2] Hovikoski et al. (2016) Journal of Sedimentary Research, 86(8): 982-1007. [3] Rizzi et al. (2017) EGU General Assembly Abstract EGU 2017-17584.

Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record

NASA Astrophysics Data System (ADS)

Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Vander Auwera, Jacqueline; Obrochta, Stephen; Boes, Evelien; Nakamura, Atsunori; Fujiwara, Osamu; Shishikura, Masanobu; Schmidt, Sabine; Siani, Giuseppe; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.; QuakeRecNankai Team

2018-01-01

Lacustrine sediments are particularly sensitive to modifications within the lake catchment. In a volcanic area, sedimentation rates are directly affected by the history of the volcano and its eruptions. Here, we investigate the impact of Mt. Fuji Volcano (Japan) on Lake Motosu and its watershed. The lacustrine infill is studied by combining seismic reflection profiles and sediment cores. We show evidence of changes in sedimentation patterns during the depositional history of Lake Motosu. The frequency of large mass-transport deposits recorded within the lake decreases over the Holocene. Before 8000 cal yr BP, large sublacustrine landslides and turbidites were filling the lacustrine depression. After 8000 cal yr BP, only one large sublacustrine landslide was recorded. The change in sedimentation pattern coincides with a change in sediment accumulation rate. Over the last 8000 cal yr BP, the sediment accumulation rate was not sufficient enough to produce large sublacustrine slope failures. Consequently, the frequency of large mass-transport deposits decreased and only turbidites resulting from surficial slope reworking occurred. These constitute the main sedimentary infill of the deep basin. We link the change in sediment accumulation rate with (i) climate and vegetation changes; and (ii) the Mt. Fuji eruptions which affected the Lake Motosu watershed by reducing its size and strongly modified its topography. Moreover, this study highlights that the deposition of turbidites in the deep basin of Lake Motosu is mainly controlled by the paleobathymetry of the lakefloor. Two large mass-transport deposits, occurring around 8000 cal yr BP and 2000 cal yr BP respectively, modified the paleobathymetry of the lakefloor and therefore changed the turbidite depositional pattern of Lake Motosu.

Reconstruction of a saline, lacustrine carbonate system (Priabonian, St-Chaptes Basin, SE France): Depositional models, paleogeographic and paleoclimatic implications

NASA Astrophysics Data System (ADS)

Lettéron, Alexandre; Hamon, Youri; Fournier, François; Séranne, Michel; Pellenard, Pierre; Joseph, Philippe

2018-05-01

A 220-m thick carbonate-dominated succession has been deposited in shallow-water, saline lake environments during the early to middle Priabonian (MP17A-MP18 mammal zones) in the Saint-Chaptes Basin (south-east France). The palaeoenvironmental, paleoclimatic and palaeogeographic significance of such saline lake carbonates has been deciphered on the basis of a multi-proxy analyses including: 1) depositional and diagenetic features; 2) biological components (molluscs, benthic foraminifera, characean gyrogonites, spores and pollens); 3) carbon and oxygen stable isotopes; 4) trace elements; and 5) clay mineralogy. Five stages of lacustrine system evolution have been identified: 1) fresh-water closed lake under dry climate (unit U1); 2) fresh to brackish water lacustrine deltaic system with a mixed carbonate-siliciclastic sedimentation under relatively wet climatic conditions (unit U2); 3) salt-water lacustrine carbonate system under humid climatic setting (unit U3); 4) evaporitic lake (unit U4); and 5) closed lake with shallow-water carbonate sedimentation under subtropical to Mediterranean climate with dry seasons (unit U5). Upper Eocene aridification is evidenced to have started as early as the earliest Priabonian (unit U1: MP17A mammal zone). A change from humid to dryer climatic conditions is recorded between units U3 and U4. The early to middle Priabonian saline lake is interpreted as an athalassic (inland) lake that have been transiently connected with neighboring salt lakes influenced by seawater and/or fed with sulfates deriving from recycling of evaporites. Maximum of connection with neighboring saline lakes (Mormoiron Basin, Camargue and Central grabens, Hérault Basin) likely occurred during unit U3 and at the base of unit U5. The most likely sources of salts of these adjacent basins are: 1) Triassic evaporites derived from salt-diapirs (Rhône valley) or from paleo-outcrops located east of the Durance fault or offshore in the Gulf of Lion; or 2) marine incursions from the south, through Paleogene grabens in the Gulf of Lion.

Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars

USGS Publications Warehouse

Grotzinger, J.P.; Gupta, S.; Malin, M.C.; Rubin, D.M.; Schieber, J.; Siebach, K.; Sumner, D.Y.; Stack, K.M.; Vasavada, A.R.; Arvidson, R.E.; Calef, F.; Edgar, Lauren; Fischer, W.F.; Grant, J.A.; Griffes, J.L.; Kah, L.C.; Lamb, M.P.; Lewis, K.W.; Mangold, N.; Minitti, M.E.; Palucis, M.C.; Rice, M.; Williams, R.M.E.; Yingst, R.A.; Blake, D.; Blaney, D.; Conrad, P.; Crisp, J.A.; Dietrich, W.E.; Dromart, G.; Edgett, K.S.; Ewing, R.C.; Gellert, R.; Hurowitz, J.A.; Kocurek, G.; Mahaffy, P.G.; McBride, M.J.; McLennan, S.M.; Mischna, M.A.; Ming, D.; Milliken, R.E.; Newsom, H.; Oehler, D.; Parker, T.J.; Vaniman, D.; Wiens, R.C.; Wilson, S.A.

2015-01-01

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp).

Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

USGS Publications Warehouse

Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

2015-01-01

This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser inorganic sediment from less dense OM and allows terrestrial OM to preferentially be transported farther offshore. The conclusion is that for the organic carbon content in these regions to be elevated a mixed terrestrial-lacustrine origin is required. The hydrodynamic separation of mineral and organic constituents is most pronounced in regions with shallow bathymetric gradients, consistent with previous findings from Lake Tanganyika.

Sedimentary record of seismic events in the Eocene Green River Formation and its implications for regional tectonics on lake evolution (Bridger Basin, Wyoming)

NASA Astrophysics Data System (ADS)

Törő, Balázs; Pratt, Brian R.

2016-10-01

Outcrops and cores from the top of the lacustrine Tipton Member and the base of the Wilkins Peak Member ( 51.5 Ma) of the Eocene Green River Formation, Bridger Basin in southwestern Wyoming yield a wide variety of sedimentary deformation features many of which are laterally extensive for more than 50 km. They include various types of folds, load structures, pinch-and-swell structures, microfaults, breccias and sedimentary dikes. In most cases deformation is represented by hybrid brittle-ductile structures exhibiting lateral variation in deformation style. These occur in low-energy, profundal organic-rich carbonate mudstones (oil shales), trona beds, tuffs, and profundal to sublittoral silty carbonate deposited in paleolake Gosiute. The deformation is not specific to the depositional environment because sedimentary units stratigraphically higher with similar facies show no deformation. The studied interval lacks any evidence for possible trigger mechanisms intrinsic to the depositional environment, such as strong wave action, rapid sediment loading, evaporite dissolution and collapse, or desiccation, so 'endogenic' causes are ruled out. Thus, the deformation features are interpreted as seismites, and change in deformation style and inferred increase in intensity towards the south suggest that the earthquakes were sourced from the nearby Uinta Fault System. The 22 levels exhibiting seismites recognized in cores indicate earthquakes with minimum magnitudes between 6 and 7, minimum epicentral intensity (MCS) of 9, and varying recurrence intervals in the seismic history of the Uinta Fault System, with a mean apparent recurrence period of 8.1 k.y. using average sedimentation rates and dated tuffs; in detail, however, there are two noticeably active periods followed by relative quiescence. The stratigraphic position of these deformed intervals also marks the transition between two distinct stages in lake evolution, from the balanced-filled Tipton Member to the overlying, underfilled Wilkins Peak Member. Thus, these seismites are evidence for regional-scale changes in lacustrine sedimentation of Eocene Lake Gosiute in response to syndepositional tectonic activity. Analysis of synsedimentary deformation features is, therefore, a promising yet under-utilized tool to trace the tectonic evolution of lacustrine deposits of the Green River Formation and other tectonically active marine and non-marine basins.

Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America

USGS Publications Warehouse

Smoot, J.P.

1991-01-01

The early Mesozoic Newark Supergroup consists of continental sedimentary rocks and basalt flows that occupy a NE-trending belt of elongate basins exposed in eastern North America. The basins were filled over a period of 30-40 m.y. spanning the Late Triassic to Early Jurassic, prior to the opening of the north Atlantic Ocean. The sedimentary rocks are here divided into four principal lithofacies. The alluvial-fan facies includes deposits dominated by: (1) debris flows; (2) shallow braided streams; (3) deeper braided streams (with trough crossbeds); or (4) intense bioturbation or hyperconcentrated flows (tabular, unstratified muddy sandstone). The fluvial facies include deposits of: (1) shallow, ephemeral braided streams; (2) deeper, flashflooding, braided streams (with poor sorting and crossbeds); (3) perennial braided rivers; (4) meandering rivers; (5) meandering streams (with high suspended loads); (6) overbank areas or local flood-plain lakes; or (7) local streams and/or colluvium. The lacustrine facies includes deposits of: (1) deep perennial lakes; (2) shallow perennial lakes; (3) shallow ephemeral lakes; (4) playa dry mudflats; (5) salt-encrusted saline mudflats; or (6) vegetated mudflats. The lake margin clastic facies includes deposits of: (1) birdfoot deltas; (2) stacked Gilbert-type deltas; (3) sheet deltas; (4) wave-reworked alluvial fans; or (5) wave-sorted sand sheets. Coal deposits are present in the lake margin clastic and the lacustrine facies of Carnian age (Late Triassic) only in basins of south-central Virginia and North and South Carolina. Eolian deposits are known only from the basins in Nova Scotia and Connecticut. Evaporites (and their pseudomorphs) occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes, and some evaporite and alkaline minerals present in the Mesozoic rocks may be a result of later diagenesis. These relationships suggest climatic variations across paleolatitudes, more humid to the south where coal beds are preserved, and more arid in the north where evaporites and eolian deposits are common. Fluctuations in paleoclimate that caused lake levels to rise and fall in hydrologically closed basins are preserved as lacustrine cycles of various scales, including major shifts in the Late Triassic from a wet Carnian to an arid Norian. In contrast, fluvial deposits were mainly formed in response to the tectonic evolution of the basins, but to some extent also reflect climatic changes. The Newark Supergroup illustrates the complexity of rift-basin sedimentation and the problems that may arise from using a single modern analog for sedimentary deposition spanning millions of years. It also shows that a tremendous wealth of depositional, climatic, and tectonic information is preserved in ancient rift-basin deposits which can be recovered if the depositional processes of modern rift-basin deposits are understood. ?? 1991.

Random field theory to interpret the spatial variability of lacustrine soils

NASA Astrophysics Data System (ADS)

Russo, Savino; Vessia, Giovanna

2015-04-01

The lacustrine soils are quaternary soils, dated from Pleistocene to Holocene periods, generated in low-energy depositional environments and characterized by soil mixture of clays, sands and silts with alternations of finer and coarser grain size layers. They are often met at shallow depth filling several tens of meters of tectonic or erosive basins typically placed in internal Appenine areas. The lacustrine deposits are often locally interbedded by detritic soils resulting from the failure of surrounding reliefs. Their heterogeneous lithology is associated with high spatial variability of physical and mechanical properties both along horizontal and vertical directions. The deterministic approach is still commonly adopted to accomplish the mechanical characterization of these heterogeneous soils where undisturbed sampling is practically not feasible (if the incoherent fraction is prevalent) or not spatially representative (if the cohesive fraction prevails). The deterministic approach consists on performing in situ tests, like Standard Penetration Tests (SPT) or Cone Penetration Tests (CPT) and deriving design parameters through "expert judgment" interpretation of the measure profiles. These readings of tip and lateral resistances (Rp and RL respectively) are almost continuous but highly variable in soil classification according to Schmertmann (1978). Thus, neglecting the spatial variability cannot be the best strategy to estimated spatial representative values of physical and mechanical parameters of lacustrine soils to be used for engineering applications. Hereafter, a method to draw the spatial variability structure of the aforementioned measure profiles is presented. It is based on the theory of the Random Fields (Vanmarcke 1984) applied to vertical readings of Rp measures from mechanical CPTs. The proposed method relies on the application of the regression analysis, by which the spatial mean trend and fluctuations about this trend are derived. Moreover, the scale of fluctuation is calculated to measure the maximum length beyond which profiles of measures are independent. The spatial mean trend can be used to identify "quasi-homogeneous" soil layers where the standard deviation and the scale of fluctuation can be calculated. In this study, five Rp profiles performed in the lacustrine deposits of the high River Pescara Valley have been analyzed. There, silty clay deposits with thickness ranging from a few meters to about 60m, and locally rich in sands and peats, are investigated. In this study, vertical trends of Rp profiles have been derived to be converted into design parameter mean trends. Furthermore, the variability structure derived from Rp readings can be propagated to design parameters to calculate the "characteristic values" requested by the European building codes. References Schmertmann J.H. 1978. Guidelines for Cone Penetration Test, Performance and Design. Report No. FHWA-TS-78-209, U.S. Department of Transportation, Washington, D.C., pp. 145. Vanmarcke E.H. 1984. Random Fields, analysis and synthesis. Cambridge (USA): MIT Press.

Permian paleogeography of west-central Pangea: Reconstruction using sabkha-type gypsum-bearing deposits of Parnaíba Basin, Northern Brazil

NASA Astrophysics Data System (ADS)

Abrantes, Francisco R.; Nogueira, Afonso C. R.; Soares, Joelson L.

2016-07-01

Extreme aridity during Late Permian - Early Triassic period was the main factor for resetting the entire paleoclimate of the planet. Permian evaporite basins and lacustrine red beds were widely distributed along the supercontinent of Pangea. Sulphate deposits in Western Pangea, particularly in Northern Brazil, accumulated in an extensive playa lake system. Outcrop-based facies and stratigraphic analysis of up to 20 m thick evaporite-siliciclastic deposits reveal the predominance of laminated reddish mudstone with subordinate limestone, marl and lenses of gypsum. The succession was deposited in shallow lacustrine and inland sabkha environments associated with saline pans and mudflats. Gypsum deposits comprise six lithofacies: 1) bottom-growth gypsum, 2) nodular/micronodular gypsum, 3) mosaic gypsum, 4) fibrous/prismatic gypsum, 5) alabastrine gypsum, and 6) rosettes of gypsum. Gypsum types 1 and 2 are interpreted as primary deposition in saline pans. Bottom-growth gypsum forms grass-like crusts while nodular/micronodular gypsum indicates displacive precipitation of the crust in shallow water and the groundwater capillary zone. Types 3 and 4 are early diagenetic precipitates. Abundant inclusions of tiny lath-like anhydrite crystals suggest a primary origin of anhydrite. Alabastrine gypsum, fibrous gypsum (satinspar) and rosettes of gypsum probably derived from near-surface hydration of anhydrite. The gypsum-bearing deposits in the Parnaíba Basin contribute towards understanding paleogeographic changes in Western Pangea. A progressive uplift of East Pangea, culminated in the forced regression and retreat of epicontinental seas to the West. Restricted seas or large lakes were formed before the definitive onset of desert conditions in Pangea, leading to the development of extensive ergs.

Sedimentary and tectonic evolution of Plio Pleistocene alluvial and lacustrine deposits of Fucino Basin (central Italy)

NASA Astrophysics Data System (ADS)

Cavinato, Gian Paolo; Carusi, Claudio; Dall'Asta, Massimo; Miccadei, Enrico; Piacentini, Tommaso

2002-04-01

The Fucino Basin was the greatest lake of the central Italy, which was completely drained at the end of 19th century. The basin is an intramontane half-graben filled by Plio-Quaternary alluvial and lacustrine deposits located in the central part of the Apennines chain, which was formed in Upper Pliocene and in Quaternary time by the extensional tectonic activity. The analysis of the geological surface data allows the definition of several stratigraphic units grouped in Lower Units and Upper Units. The Lower Units (Upper Pliocene) are exposed along the northern and north-eastern basin margins. They consist of open to marginal lacustrine deposits, breccia deposits and fluvial deposits. The Upper Units (Lower Pliocene-Holocene) consist of interbedded marginal lacustrine deposits and fluvial deposits; thick coarse-grained fan-delta deposits are interfingered at the foot of the main relief with fluvial-lacustrine deposits. Most of the thickness of the lacustrine sequences (more than 1000-m thick) is buried below the central part of the Fucino Plain. The basin is bounded by E-W, WSW-ENE and NW-SE fault systems: Velino-Magnola Fault (E-W) and Tremonti-Celano-Aielli Fault (WSW-ENE) and S. Potito-Celano Fault (NW-SE) in the north; the Trasacco Fault, the Pescina-Celano Fault and the Serrone Fault (NW-SE) in the south-east. The geometry and kinematic indicators of these faults indicate normal or oblique movements. The study of industrial seismic profiles across the Fucino Basin gives a clear picture of the subsurface basin geometry; the basin shows triangular-shaped basin-fill geometry, with the maximum deposits thickness toward the main east boundary fault zones that dip south-westward (Serrone Fault, Trasacco Fault, Pescina-Celano Fault). On the basis of geological surface data, borehole stratigraphy and seismic data analysis, it is possible to recognize and to correlate sedimentary and seismic facies. The bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of Meso-Cenozoic carbonate rocks. The shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the NW-SE boundary faults. In fact, the continental deposits are frequently in on-lap contact over the carbonate substratum; several disconformable contacts occurred during the sedimentary evolution of the basin. The main faults (with antithetic and synthetic fault planes) displace the whole sedimentary sequence up to the surface indicating a recent faults' activity (1915 Avezzano earthquake, Ms=7.0). The stratigraphic and tectonic setting of the Fucino Basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural-sedimentary evolution of the Plio-Quaternary deposits. The geometry of the depositional bodies, of the fault planes and their relationships indicate that the Fucino Basin was formed as a half-graben type structure during Plio-Quaternary extensional events. Some internal complexities are probably related to the fold-and-thrust structures of the Apenninic orogeny formed in Messinian time, in this area, and to a different activity timing of the E-W and WSW-ENE fault systems and the NW-SE fault systems. We believe, based on the similarity of the surface characteristics, that the structural setting of the Fucino Basin can be extrapolated to the other great intramontane basins in Central Italy (e.g. Rieti, L'Aquila, Sulmona, Sora, Isernia basins).

Plio-Pleistocene facies environments from the KBS Member, Koobi Fora Formation: implications for climate controls on the development of lake-margin hominin habitats in the northeast Turkana Basin (northwest Kenya).

PubMed

Lepre, Christopher J; Quinn, Rhonda L; Joordens, Josephine C A; Swisher, Carl C; Feibel, Craig S

2007-11-01

Climate change is hypothesized as a cause of major events of Plio-Pleistocene East African hominin evolution, but the vertically discontinuous and laterally confined nature of the relevant geological records has led to difficulties with assessing probable links between the two. High-resolution sedimentary sequences from lacustrine settings can provide comprehensive data of environmental changes and detailed correlations with well-established orbital and marine records of climate. Hominin-bearing deposits from Koobi Fora Ridge localities in the northeast Turkana Basin of Kenya are an archive of Plio-Pleistocene lake-margin sedimentation though significant developmental junctures of northern African climates, East African environments, and hominin evolution. This study examines alluvial channel and floodplain, nearshore lacustrine, and offshore lacustrine facies environments for the approximately 136-m-thick KBS Member (Koobi Fora Formation) exposed at the Koobi Fora Ridge. Aspects of the facies environments record information on the changing hydrosedimentary dynamics of the lake margin and give insights into potential climatic controls. Seasonal/yearly climate changes are represented by the varve-like laminations in offshore mudstones and the slickensides, dish-shaped fractures, and other paleosol features overprinted on floodplain strata. Vertical shifts between facies environments, however, are interpreted to indicate lake-level fluctuations deriving from longer-term, dry-wet periods in monsoonal rainfall. Recurrence periods for the inferred lake-level changes range from about 10,000 to 50,000 years, and several are consistent with the average estimated timescales of orbital precession ( approximately 20,000 years) and obliquity ( approximately 40,000 years). KBS Member facies environments from the Koobi Fora Ridge document the development of lake-margin hominin habitats in the northeast Turkana Basin. Environmental changes in these habitats may be a result of monsoonal rainfall variations that derive from orbital insolation and/or glacial forcing.

Earthquake-induced soft-sediment deformation structures in Late Pleistocene lacustrine deposits of Issyk-Kul lake (Kyrgyzstan)

NASA Astrophysics Data System (ADS)

Gladkov, A. S.; Lobova, E. U.; Deev, E. V.; Korzhenkov, A. M.; Mazeika, J. V.; Abdieva, S. V.; Rogozhin, E. A.; Rodkin, M. V.; Fortuna, A. B.; Charimov, T. A.; Yudakhin, A. S.

2016-10-01

This paper discusses the composition and distribution of soft-sediment deformation structures induced by liquefaction in Late Pleistocene lacustrine terrace deposits on the southern shore of Issyk-Kul Lake in the northern Tien Shan mountains of Kyrgyzstan. The section contains seven deformed beds grouped in two intervals. Five deformed beds in the upper interval contain load structures (load casts and flame structures), convolute lamination, ball-and-pillow structures, folds and slumps. Deformation patterns indicate that a seismic trigger generated a multiple slump on a gentle slope. The dating of overlying subaerial deposits suggests correlation between the deformation features and strong earthquakes in the Late Pleistocene.

Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars.

PubMed

Grotzinger, J P; Gupta, S; Malin, M C; Rubin, D M; Schieber, J; Siebach, K; Sumner, D Y; Stack, K M; Vasavada, A R; Arvidson, R E; Calef, F; Edgar, L; Fischer, W F; Grant, J A; Griffes, J; Kah, L C; Lamb, M P; Lewis, K W; Mangold, N; Minitti, M E; Palucis, M; Rice, M; Williams, R M E; Yingst, R A; Blake, D; Blaney, D; Conrad, P; Crisp, J; Dietrich, W E; Dromart, G; Edgett, K S; Ewing, R C; Gellert, R; Hurowitz, J A; Kocurek, G; Mahaffy, P; McBride, M J; McLennan, S M; Mischna, M; Ming, D; Milliken, R; Newsom, H; Oehler, D; Parker, T J; Vaniman, D; Wiens, R C; Wilson, S A

2015-10-09

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp). Copyright © 2015, American Association for the Advancement of Science.

A multi-proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA

USGS Publications Warehouse

Grimley, D.A.; Daniel, L.; Kaplan, S.W.; Yansa, C.H.; Curry, B. Brandon; Oches, E.A.

2009-01-01

The Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1km continuous exposure (~20m vertically) of Quaternary fluvial and lacustrine deposits, inset within Eocene sediments and buried by thick loess. Fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations, with deposition between ca. 190-140 ka and 24-1814C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 24-22 14C ka BP), a relatively permanent shallow lake environment is indicated by ostracods, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier ??18O compositions suggest marsh-like conditions in a periodically drying lake. The surrounding uplands consisted of Picea-Pinus woodlands mixed with cool-temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14C ka BP, with loess and slopewash gradually infilling the former lake by 18 14C ka BP. Modern analogue analyses of ostracods and palaeontological evidence imply a full glacial climate similar to today's mixed-boreal zone in central Minnesota, USA, about 98C cooler in mean annual temperature than present-day western Tennessee. Copyright ?? 2009 John Wiley & Sons, Ltd.

Stratigraphic evidence for the role of lake spillover in the inception of the lower Colorado River in southern Nevada and western Arizona

USGS Publications Warehouse

House, P.K.; Pearthree, P.A.; Perkins, M.E.

2008-01-01

Late Miocene and early Pliocene sediments exposed along the lower Colorado River near Laughlin, Nevada, contain evidence that establishment of this reach of the river after 5.6 Ma involved flooding from lake spillover through a bedrock divide between Cottonwood Valley to the north and Mohave Valley to the south. Lacustrine marls interfingered with and conformably overlying a sequence of post-5.6 Ma finegrained valley-fill deposits record an early phase of intermittent lacustrine inundation restricted to Cottonwood Valley. Limestone, mud, sand, and minor gravel of the Bouse Formation were subsequently deposited above an unconformity. At the north end of Mohave Valley, a coarse-grained, lithologically distinct fluvial conglomerate separates subaerial, locally derived fan deposits from subaqueous deposits of the Bouse Formation. We interpret this key unit as evidence for overtopping and catastrophic breaching of the paleodivide immediately before deep lacustrine inundation of both valleys. Exposures in both valleys reveal a substantial erosional unconformity that records drainage of the lake and predates the arrival of sediment of the through-going Colorado River. Subsequent river aggradation culminated in the Pliocene between 4.1 and 3.3 Ma. The stratigraphic associations and timing of this drainage transition are consistent with geochemical evidence linking lacustrine conditions to the early Colorado River, the timings of drainage integration and canyon incision on the Colorado Plateau, the arrival of Colorado River sand at its terminus in the Salton Trough, and a downstream-directed mode of river integration common in areas of crustal extension. ?? 2008 The Geological Society of America.

Subsurface geology of the late Tertiary and Quaternary water-bearing deposits of the southern part of the San Joaquin Valley, California

USGS Publications Warehouse

Croft, M.G.

1972-01-01

The study area, which includes about 5,000 square miles of the southern part of the San Joaquin Valley, is a broad structural trough of mostly interior drainage. The Sierra Nevada on the east is composed of consolidated igneous and metamorphic rocks of pre-Tertiary age. The surface of these rocks slopes 4?-6? southwestward from the foothills and underlies the valley. The Coast Ranges on the west consist mostly of complexly folded and faulted consolidated marine and nonmarine sedimentary rocks of Jurassic, Cretaceous, and Tertiary age, which dip eastward and overlie the basement complex. Unconsolidated deposits, of late Pliocene to Holocene age, blanket the underlying consolidated rocks in the valley and are the source of most of the fresh ground water. The unconsolidated deposits, the subject of this report, are divided into informal stratigraphic units on the basis of source of sediment, environment of deposition, and texture. Flood-basin, lacustrine, and marsh deposits are fine grained and underlie the valley trough. They range in age from late Pliocene to Holocene. These deposits, consisting of nearly impermeable gypsiferous fine sand, silt, and clay, are more than 3,000 feet thick beneath parts of Tulare Lake bed. In other parts of the trough, flood-basin, lacustrine, and marsh deposits branch into clayey or silty clay tongues designated by the letter symbols A to F. Three of these tongues, the E, C, and A clays, lie beneath large areas of the southern part of the valley. The E clay includes the Corcoran Clay Member of the Tulare Formation, the most extensive hydrologic confining layer in the valley. The E clay underlies about 3,500 square miles of bottom land and western slopes. The beds generally are dark-greenish-gray mostly diatomaceous silty clay of Pleistocene age. Marginally, the unit bifurcates into an upper and a lower stratum that contains thin beds of moderately yellowish-brown silt and sand. The E clay is warped into broad, gentle northwesterly trending anticlines and synclines. The C clay, of Pleistocene age, is a fine-grained lacustrine or paludal deposit occurring 220-300 feet beneath Tulare Lake bed and parts of Fresno Slough. The beds consist of bluish-gray silty clay. Structural contours indicate that the C clay has been extensively warped and folded. The A clay of Pleistocene and Holocene (?) age is a fine-grained lacustrine or paludal deposit occurring 10-60 feet beneath Buena Vista, Kern, and Tulare Lake beds, and parts of Fresno Slough. The clay is mainly blue or dark greenish gray, plastic, and highly organic. In some areas the unit is separated into an upper and a lower stratum by several feet of sand. A radiocarbon date of 26,780 ? 600 years was obtained from wood cored 3 feet beneath the clay. Continental deposits are arkosic beds of late Pliocene and Pleistocene (?) age and were derived from the Sierra Nevada, Tehachapi, and San Emigdio Mountains. In places, a reduced-oxidized contact transgresses the deposits derived from the Sierra Nevada. The reduced deposits consist of moderately permeable bluish-green or bluish-gray fine to medium sand, silt, and clay. The oxidized deposits consist mainly of poorly permeable yellowish-brown silt and fine sand. Deposits derived from the Tehachapi and the San Emigdio Mountains consist of poorly to moderately permeable yellowish-brown sand and silt. Continental and alluvial deposits of Tertiary and Quaternary age that were derived from the Coast Ranges consist mainly of poorly to moderately permeable yellowish-brown gravel, sand, silt, and clay. They include the Tulare Formation and overlying alluvial deposits. Alluvium is composed of coarse arkosic deposits derived from the Sierra Nevada, Tehachapi, and San Emigdio Mountains. A reduced-oxidized contact also transgresses the alluvial deposits derived from the Sierra Nevada. The oxidized deposits consist of poorly to highly permeable yellowish-brown gravel, sand, silt, and clay. The reduc

Hydrocarbon potential of Early Cretaceous lacustrine sediments from Bima Formation, Yola Sub-basin, Northern Benue Trough, NE Nigeria: Insight from organic geochemistry and petrology

NASA Astrophysics Data System (ADS)

Sarki Yandoka, Babangida M.; Abdullah, Wan Hasiah; Abubakar, M. B.; Adegoke, Adebanji Kayode; Maigari, A. S.; Haruna, A. I.; Yaro, Usman Y.

2017-05-01

The Early Cretaceous lacustrine sediments from Bima Formation in the Yola Sub-basin, Northern Benue Trough, northeastern Nigeria were studied based on organic geochemistry and petrology. This is in other to provide information on hydrocarbon generation potential; organic matter type (quality), richness (quantity), origin/source inputs, redox conditions (preservation) and thermal maturation in relation to thermal effect of Tertiary volcanics. The total organic carbon (TOC) contents ranges from 0.38 to 0.86 wt % with extractable organic matter (EOM) below 1000 ppm and pyrolysis S2 yield values from 0.16 to 0.68 mg/g, suggesting poor to fair source rock richness. Based on kerogen pyrolysis and microscopy coupled with biomarker parameters, the organic matters contain Type I (lacustrine algae), Type III (terrestrially derived land-plants) and Type IV kerogens deposited in a mixed lacustrine-terrestrial environment under suboxic to relatively anoxic conditions. This suggest potential occurrence of Early Cretaceous lacustrine sediments (perhaps Lower Cretaceous petroleum system) in Yola Sub-basin of the Northern Benue Trough as present in the neighbouring basins of Chad, Niger and Sudan Republics that have both oil and gas generation potential within the same rift trend (WCARS). Vitrinite reflectance (%Ro) and Tmax values of the lacustrine shales ranges from 1.12 to 2.32 VRo% and 448-501 °C, respectively, indicating peak-late to post-maturity stage. This is supported by the presence of dark brown palynomorphs, amorphous organic matter and phytoclasts as well as inertinite macerals. Consequently, the organic matters in the lacustrine shales of Bima Formation in the Yola Sub-basin appeared as a source of oil (most likely even waxy) and gas prone at a relatively deeper part of the basin. However, the high thermal maturity enhanced the organic matters and most of the hydrocarbons that formed in the course of thermal maturation were likely expelled to the reservoir rock units and further cracked into secondary or major gas probably due to thermal effects of Tertiary volcanic intrusion known to be present in the basin.

40Ar/39Ar Temporal Constraints on Eocene Uplift, Subsidence, and Paleohydrology in the Laramide Foreland, Western U. S.

NASA Astrophysics Data System (ADS)

Smith, M. E.; Carroll, A. R.; Singer, B. S.

2004-12-01

Due to their sensitivity to relatively subtle changes in regional drainage patterns, Eocene lake deposits of the Green River Formation offer a unique and richly detailed record of landscape modification caused by orogenic processes in the broken foreland of the western U. S. Recently obtained 40Ar/39Ar age determinations for 22 interbedded tephras provide excellent temporal resolution of this record, and enable inter-basin correlations at an unprecedented level of precision (approaching 2σ uncertainties of ± k.y.). Green River Formation strata span an interval of ~8 m.y., beginning and ending with freshwater fluvial-lacustrine deposits. Two episodes of regional basin closure and evaporite deposition, each lasting ˜1-2 m.y., coincide with evidence for active Laramide faulting at basin margins and increased rates of sediment accumulation. Evaporite deposition therefore appears to have been principally caused by enhanced uplift of basin sills rather than increased aridity. Regional stratigraphic relations, facies types, and 40Ar/39Ar geochronology permit deduction of the following paleodrainage history: 1) > ˜51.3 Ma: Fluvial-lacustrine deposition occurred in greater Green River, Piceance Creek and Uinta basins. The onset of lacustrine deposition is not well-dated due to a paucity of tephras. 2) ˜51.3-49.7 Ma: The greater Green River and Piceance Creek basins both became terminal sinks that received overflow from neighboring freshwater basins. Coarse clastic basin-marginal alluvial strata, cross-cutting fault relations, and pronounced differential subsidence in both basins indicate active uplift of the Uinta Mountains and surrounding ranges. 3) ˜49.7-49.1 Ma: Lake Gosiute expanded in extent, coincident with an influx of water and sediment derived from volcanic centers to the north. Episodic overflow over the eastern Uinta uplift flushed dissolved solutes southward, freshening Lake Gosiute while evaporite deposition continued in Lake Uinta. 4) ˜49.1-48.4 Ma: Fresh water spilled consistently from Lake Gosiute into an expanding Lake Uinta. The saline, organic-rich Mahoghany zone of the Parachute Creek Member was deposited over an interval of 0.6 ± 0.3 m.y. coincident with deposition of the freshwater upper LaClede bed of the Laney Member and alluvial Bridger Formation in the greater Green River Basin. 5) ˜48.4-46.3: Fluvial volcaniclastic sediments progressively filled the greater Green River and Piceance Creek basins. Alluvial and freshwater lacustrine deposition dominated both basins. Saline lake deposition continued unabated in the Uinta Basin. 6) ˜46.3-45.0 Ma: Lake Uinta, limited to the western Uinta Basin, became hydrologic closed as evidenced by bedded evaporite deposition. The change to evaporite deposition coincided with an increase in differential subsidence, reflecting a renewal of tectonic deformation. The up-section disappearance of west-directed volcaniclastic input into the eastern Uinta Basin at ˜46.3 Ma suggests that drainage diversion may also have contributed to hydrologic closure. 7) Following ˜45.0 Ma, Lake Uinta returned to fluvial-lacustrine deposition and was subsequently filled with alluvial deposits.

Microbial lime-mud production and its relation to climate change

USGS Publications Warehouse

Yates, K.K.; Robbins, L.L.; Gerhard, L.C.; Harrison, W.E.; Hanson, B.M.B.

2001-01-01

Microbial calcification has been identified as a significant source of carbonate sediment production in modern marine and lacustrine environments around the globe. This process has been linked to the production of modern whitings and large, micritic carbonate deposits throughout the geologic record. Furthermore, carbonate deposits believed to be the result of cyanobacterial and microalgal calcification suggest that the potential exists for long-term preservation of microbial precipitates and storage of carbon dioxide (CO2). Recent research has advanced our understanding of the microbial-calcification mechanism as a photosynthetically driven process. However, little is known of the effects of this process on inorganic carbon cycling or of the effects of changing climate on microbial-calcification mechanisms.Laboratory experiments on microbial cellular physiology demonstrate that cyanobacteria and green algae can utilize different carbon species for metabolism and calcification. Cyanobacterial calcification relies on bicarbonate (HCO3–)utilization while green algae use primarily CO2. Therefore, depending on which carbonate species (HCO3– or CO2) dominates in the ocean or lacustrine environments (a condition ultimately linked to atmospheric partial pressure PCO2), the origin of lime-mud production by cyanobacteria and/or algae may fluctuate through geologic time. Trends of cyanobacteria versus algal dominance in the rock record corroborate this conclusion. These results suggest that relative species abundances of calcareous cyanobacteria and algae in the Phanerozoic may serve as potential proxies for assessing paleoclimatic conditions, including fluctuations in atmospheric PCO2.

The formation of lacustrine dolomites: an example from the Tortonian-Messinian sequence at the East Mediterranean margins (northern Israel)

NASA Astrophysics Data System (ADS)

Shaked Gelband, Dotan; Starinsky, Abraham; Stein, Mordechai

2017-04-01

Lacustrine water bodies that filled the tectonic depressions in the Lower Galilee area of Israel during the Tortonian-Messinian periods deposited Bira and Gesher Formations, which comprise marly limestones and dolomites, basalts, and varying amounts of mollusc fossils. Most fossils are gastropods of fresh to brackish water origin, while marine representation is minor and comprise monospecific assemblages of euryhaline bivalves. During the deposition of the Tortonian Bira formation the lakes were mostly influenced by meteoric waters while during the deposition of the Messinian Gesher Formation they became more swampy. Here, we set to establish the deposition conditions of the dolomites in the lacustrine formations. The following petrographic characteristics indicate dolomitization of precursor carbonate sediment during early diagenesis stage: (1) Dolomitized fossils with similar texture as the surrounding dolomite matrix; (2) Common euhedral inner zone crystals, representing original growth in solution or plastic environment; (3) Subhedral outer shape derived from neighboring crystals collisions. More information is given by the δ18O and δ13C values of the dolomites. The δ18O of the inter-layered limestones and dolomites fluctuates between -3‰ to -4‰ (VPDB) in the limestones and +5‰ to -1.5‰ (VPDB) in the adjacent dolomites. These fluctuations are prominent in the Bira formation and become smaller along the sequence with the decrease in the dolomite values. δ13C values of both limestones and dolomites gradually decrease along the stratigraphic section, from -3.5‰ to -10‰ (VPDB) in the limestones, and from 0‰ to -8‰ (VPDB) in the dolomites. The data suggest a dolomitization process controlled by the following events: 1. Evaporation of fresh lake waters originated from the surrounding environment as runoff. It should be emphasized that significant evaporation could take place only in terminal lakes, during periods of relatively dry climate with low precipitations. 2. Calcite minerals precipitated due to evaporation, forming carbonate sediment at the bottom of the lake. 3. Precipitation of calcite raised the Mg/Ca ratio in the lake's waters. 4. High Mg/Ca ratio initiated dolomitization. The process terminated when replacement of the original carbonate sediments was complete. Thus, dolomites of the studied sequence are climate indicators. The alternate appearance of limestones and dolomites indicates climate changes through time. An additional dolomitization mechanism is suggested for the upper part of the sequence. This part is synchronous to the Messinian Salinity Crisis (MSC), in which evaporate sediments were deposited in the Mediterranean basin as a result of the sea desiccation. As mentioned above, there is a decrease of δ13C in both dolomites and limestones, explained by organic activity in a swampy environment (Bacterial Sulfate Reduction (BSR): 2CH2O + SO4 → 2HCO3- + H2S). During BSR, biogenic HCO3- ions are supplied and SO42- ions, which considered as inhibitores for dolomite growth, are consumes, enabling dolomite precipitatation.

The occurrence and transformation of lacustrine sediment gravity flow related to depositional variation and paleoclimate in the Lower Cretaceous Prosopis Formation of the Bongor Basin, Chad

NASA Astrophysics Data System (ADS)

Tan, Mingxuan; Zhu, Xiaomin; Geng, Mingyang; Zhu, Shifa; Liu, Wei

2017-10-01

Bed variability of sediment-gravity-flow deposits is quite prevalent in deep-marine settings, but it has not been well investigated in lacustrine settings. The depositional characteristics of various event beds are characterized in the North Slope Belt of the Bongor Basin (Chad), using detailed sedimentological, petrographic, geochemical as well as palynological analysis. Four bed types including classical turbidite bed, debrite bed, hybrid event bed, and hyperpycnite bed were distinguished based on their interpreted depositional processes. Variable mud contents of debrite beds and classic turbidite beds show distinct genetic characteristics in four core wells, whilst the high mud content of cohesive debrite interval and the low mud content of turbidite interval in hybrid event bed demonstrate the existence of flow transformation. Generally, several trace element and rare earth element proxy parameters show that these gravity-flow deposits of BS1-1 and D-3 cores are formed in more distal depositional settings than them of BN8 and BNE3 cores, which is also well consistent with sedimentological understandings achieved by seismic facies analysis. Although palynological results show a general hot arid climate during the deposition of the Prosopis Formation, but the climate-sensitive Sr/Cu ratio demonstrates that most sampled turbidite beds are postulated to be formed within a short humid pulse. The multi-approach analysis has illustrated that two potential forming mechanisms (delta-front-failure and flood-related origin) can be derived in different cored wells of such a small lacustrine rift basin. Differentiated flow transformation plays a significant role in the depositional characteristics and heterogenetic distribution of these event deposits.

Highly Seasonal and Perennial Fluvial Facies: Implications for Climatic Control on the Douglas Creek and Parachute Creek Members, Green River Formation, Southeastern Uinta Basin, Utah

NASA Astrophysics Data System (ADS)

Gall, Ryan D.

The early to middle Eocene Green River Formation consists of continental strata deposited in Laramide ponded basins in Utah, Colorado, and Wyoming. This study (1) documents fluvial and lacustrine strata from the Douglas Creek and Parachute Creek Members of the middle Green River Formation, southeastern Uinta Basin, Utah, and (2) uses new interpretations of the link between climate and fluvial sedimentary expression to interpret the terrestrial evolution of early Eocene climate. The stratigraphy was analyzed via outcrops along a 10 km transect in Main Canyon on the Tavaputs Plateau, and is divided into three distinct, stratigraphically separated depositional settings: (1) the lowermost Interval 1 is dominated by amalgamated sandstone channels that contain 70-100% upper flow regime sedimentary structures. The channels are interpreted to represent fluvial deposits controlled by a highly seasonal climate, where most deposition was limited to seasonal flooding events. (2) Interval 2 is dominated by alternating siliciclastic and carbonate lacustrine deposits, interpreted as local pulsed fluvial siliciclastic input into shallow Lake Uinta, and periods of fluvial quiescence represented by littoral carbonate deposition. (3) The uppermost Interval 3 is dominated by erosively-based, trough cross bedded sandstone channels interbedded with littoral lacustrine and deltaic deposits. The Interval 3 sandstone channels are interpreted as perennial fluvial deposits with relatively little variation in annual discharge, akin to modern humid-temperate fluvial systems. The stratigraphic transition from seasonally-controlled (Interval 1) to perennial (Interval 3) fluvial deposits is interpreted to represent a fundamental shift in Eocene climate, from the peak hyperthermal regime of the Early Eocene Climatic Optimum (EECO) to a more stable post-EECO climate.

Volcano-ice interaction as a microbial habitat on Earth and Mars.

PubMed

Cousins, Claire R; Crawford, Ian A

2011-09-01

Volcano-ice interaction has been a widespread geological process on Earth that continues to occur to the present day. The interaction between volcanic activity and ice can generate substantial quantities of liquid water, together with steep thermal and geochemical gradients typical of hydrothermal systems. Environments available for microbial colonization within glaciovolcanic systems are wide-ranging and include the basaltic lava edifice, subglacial caldera meltwater lakes, glacier caves, and subsurface hydrothermal systems. There is widespread evidence of putative volcano-ice interaction on Mars throughout its history and at a range of latitudes. Therefore, it is possible that life on Mars may have exploited these habitats, much in the same way as has been observed on Earth. The sedimentary and mineralogical deposits resulting from volcano-ice interaction have the potential to preserve evidence of any indigenous microbial populations. These include jökulhlaup (subglacial outflow) sedimentary deposits, hydrothermal mineral deposits, basaltic lava flows, and subglacial lacustrine deposits. Here, we briefly review the evidence for volcano-ice interactions on Mars and discuss the geomicrobiology of volcano-ice habitats on Earth. In addition, we explore the potential for the detection of these environments on Mars and any biosignatures these deposits may contain.

Soft-sediment deformation structures in the late Miocene Şelmo Formation around Adıyaman area, Southeastern Turkey

NASA Astrophysics Data System (ADS)

Koç Taşgın, Calibe; Orhan, Hükmü; Türkmen, İbrahim; Aksoy, Ercan

2011-04-01

The Şelmo Formation was deposited in the basins associated with the Southeastern Anatolian Thrust Belt and East Anatolian Fault Zone in SE Turkey. These structures developed as a result of compressional stresses created by the movement of the Arabian plate to the north and the Eurasian plate to the west from early Miocene to late Pliocene. The outcrops of the Şelmo Formation in the Adýyaman area (SE Turkey) comprise braided river deposits (lower alluvial unit) at the base, lacustrine and deltaic deposits in the middle (lacustrine unit) and low sinuousity river and alluvial deposits at the top (upper alluvial unit). Soft-sediment deformation structures were developed in sandstone, siltstone and marl of the deltaic and lacustrine unit of the Şelmo Formation. These are slumps, recumbent folds, load casts, ball-and-pillow structures, flame structures, neptunian dykes, chaotically associated structures and synsedimentary faults. The tectonic setting of the basin, the lateral extent of the soft-sediment deformation structures over tens of kilometers, their similarities to deformation structures interpreted as being induced seismically in other regions worldwide or in a laboratory setting, and being confined by undeformed layers suggest that the main trigger system was related to seismic activity in the area.

Geochemical characteristics of The Emet (Espey-Hisarcik) borate deposits, Kütahya, Turkey

NASA Astrophysics Data System (ADS)

Koçak, İ.; Koç, Ş.

2018-06-01

Nearly 72% world's borate reserves are in western part of Turkey. The Emet (Kütahya) deposit is one of these deposits. The Emet borate deposit, like other deposits in western Anatolia, was deposited in Miocene lacustrine environment whose formation coincides with volcanic activity started in Paleogene and lasted to the beginning of Quaternary. The borate ore displaying lenticular structure is alternated with claystone, marl, tuff and thin bedded limestone. The mineral paragenesis is composed of colemanite, hydroboracite, Veatchite, dolomite, calcite, montmorillonite and illite. The Emet borate deposit has been the subject of various geologic and mineralogical studies. In the present study major and trace element contents of 60 borate samples from this deposit are discussed. Among the trace elements, significant enrichment was found in As, Se, Sr, Cs, Sb and Li. Element correlations indicate volcanic source for boron (exhalations and hydrothermal solutions) whilst other elements are found to be derived from a terrestrial source. According to REE data, high Ce concentrations and anomalies are generally indicative of oxygenated depositional environment whilst low Ce contents facilitated the lake waters to be low oxygenated as a result of H2S-rich hydrothermal solutions. The weak negative anomaly detected only in the Hisarcık region is attributed to lacking of Eu contribution to the lake due to insufficient alteration on the continent.

Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

NASA Astrophysics Data System (ADS)

Baiyegunhi, Christopher; Liu, Kuiwu; Gwavava, Oswald

2017-11-01

Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.

Evidences of melting of terrestrial sediments and paleoenvironment changes during the Younger Dryas in tectonic lacustrine basins of Transmexican Volcanic Belt, Mexico.

NASA Astrophysics Data System (ADS)

Israde-Alcantara, I.

2017-12-01

It is well known in the sedimentary record of several parts of the world that during the Younger Dryas interval (YD) ocurred an abrupt environmental change between 12,900 and 11,700 cal yr BP (10,900 to 10,000 14C BP). In the lacustrine basins this changes are often preserved and in some Mexican lakes this is a distinctive stratigraphic marker for the YD. We analized the proxies of this event in cores of two lakes (Chapala, Cuitzeo) and three trenches of ex-lakes (Acambay,Texcoco and El Cedral). Deposits consist of fine detrital material with often Pleistocene fossil vertebrate assemblages. At the Chapala, Cuitzeo, Acambay, and Tocuila lacustrine environments are found in association with a distinctive dark organic layer showing sharp changes in the diatom, pollen, mineralogical and geochemical record. Includes also microscopic magnetic, Fe-rich spherules, silica melted droplets with aerodynamic shapes (tektites), followed by large amounts of charcoal, and sometimes nanodiamonds (Cuitzeo), that were deposited at the onset of the YD or in the limit Pleistocene-Holocene. These unusual materials are buried more than 2.50 meters and were not observed above or below the Younger Dryas sediments at these sites. The geochemistry of the microspherules indicates that they are not volcanic, anthropogenic or authigenic origin. A very distinctive feature is the shape of the spherules, ovoid, polygonal, filigreed or dendritic indicating melting and quenching infering that are product of an impact event. Their morphologies includes hollow shells caused by de-gassing of elements at very high temperatures causing a flattened side with a "skirt" structure by a high-velocity collision.Our results are consistent with the Firestone hypothesis.

Geochemical characteristics of Kırka (Sarıkaya) borate deposit, northwestern Anatolia, Turkey

NASA Astrophysics Data System (ADS)

Koçak, İ.; Koç, Ş.

2016-02-01

The Kırka borate deposit was deposited in a Miocene lacustrine basin which is closely associated with volcanic activity which lasted from Paleogene to the beginning of Quaternary. Borate mineralization alternates with claystone, mudstone, tuff and fine-layered limestone and mostly shows a lenticular structure. The mineral paragenesis is composed of borax, tincalconite, ulexite, kurnakovite, probertite, tunellite, colemanite, dolomite, smectite group minerals, illite and some firstly reported minerals for the Kırka deposit including hydrochloroborite, brianroulstonite, hilgardite-4M and searlesite minerals. In comparison to average values of earth crust, concentrations of Cs, Sr, Li, As and Se were significantly enriched with respective rates of 21, 15, 14, 3 and 188 folds. Regarding KY, KS1 and KS2 locations, there are differences in both element abundances and their geochemical tendencies which are attributed to variations in discharge regime and physico-chemical conditions of the depositional environment. Independent behaviour of B2O3 might indicate that boron is not associated with clays and carbonates and, therefore, most part of boron must be derived from volcanic activity (hydrothermal solutions, gases). REE data indicate that the Kırka borate deposit was formed in a sedimentary environment where highly alkaline (high pH) hydrothermal solutions also took part in borate precipitation process.

From lakes to sand seas: a record of early Mars climate change explored in northern Gale crater, Mars

NASA Astrophysics Data System (ADS)

Gupta, S.; Banham, S.; Rubin, D. M.; Watkins, J. A.; Edgett, K. S.; Sumner, D. Y.; Grotzinger, J. P.; Lewis, K. W.; Edgar, L. A.; Stack, K.; Day, M.; Lapôtre, M. G. A.; Bell, J. F., III; Ewing, R. C.; Stein, N.; Rivera-Hernandez, F.; Vasavada, A. R.

2017-12-01

While traversing the northern flank of Aeolis Mons, Gale crater, Mars Science Laboratory rover Curiosity encountered a decametre-thick sandstone unit unconformably overlying the lacustrine Murray formation. This sandstone contains cross-bed sets on the order of 1 m thick, composed of uniform mm-thick laminations of uniform thickness, and lacks silt- or mud-grade sediments. Cross sets are separated by sub-horizontal bounding surfaces which extend for tens of metres across outcrops. Dip-azimuths of cross-laminations are predominantly toward the north-east, which is oblique to the north-west slope of the unconformity on which the sandstone accumulated. This sandstone was designated the Stimson formation after Mt. Stimson, where it was delineated from the Murray formation. Textural analysis of this sandstone revealed a bi-modal sorting with well-rounded grains, typical of particles transported by aeolian processes. Stacked cross-bedded sets, representing the migration of aeolian dune-scale bedforms, combined with the absence of finer-grained facies characteristic of interdune deposits, suggest that the Stimson accumulated by aerodynamic processes and that the depositional surface was devoid of moisture which could have attracted dust to form interdune deposits. Reconstruction of this "dry" dune-field based on architectural measurements suggest that cross sets were emplaced by the migration of dunes with minimum heights of 10m, that were spaced 160 m apart. The dune field covered an area of 30-45 km2, and was confined to the break-in-slope at the base of Aeolis Mons. Cross-set dips suggest that the palaeowind drove these dunes toward the north east, oblique to the slope of the unconformity on which these sandstones accumulated. Construction of a dry dune field in Gale crater required an environment of extreme aridity with absence of water at the surface and within the shallow sub-surface. This is in stark contrast to the lacustrine environment in which the underlying Murray formation accumulated. The contrast in depositional environments between these units suggest that the prevailing climate in Gale crater changed, at least temporarily, from a humid environment with surface water that had potential for sustaining life, to a barren desert with reduced potential for habitability at the surface.

Enigmatic Sedimentary Deposits Within Partially Exhumed Impact Craters in the Aeolis Dorsa Region, Mars: Evidence for Past Crater Lakes

NASA Astrophysics Data System (ADS)

Peel, S. E.; Burr, D. M.

2018-06-01

We mapped enigmatic sedimentary deposits within five partially exhumed impact craters within the Aeolis Dorsa Region of Mars. Ten units have been identified and are found to be consistent with deposition within and adjacent to lacustrine systems.

Tectono-sedimentary analysis using the anisotropy of magnetic susceptibility: a study of the terrestrial and freshwater Neogene of the Orava Basin

NASA Astrophysics Data System (ADS)

Łoziński, Maciej; Ziółkowski, Piotr; Wysocka, Anna

2017-10-01

The Orava Basin is an intramontane depression filled with presumably fine-grained sediments deposited in river, floodplain, swamp and lake settings. The basin infilling constitutes a crucial record of the neoalpine evolution of the Inner/Outer Carpathian boundary area since the Neogene, when the Jurassic-Paleogene basement became consolidated, uplifted and eroded. The combination of sedimentological and structural studies with anisotropy of magnetic susceptibility (AMS) measurements provided an effective tool for recognition of terrestrial environments and deformations of the basin infilling. The lithofacies-oriented sampling and statistical approach to the large dataset of AMS specimens were utilized to define 12 AMS facies based on anisotropy degree (P) and shape (T). The AMS facies allowed a distinction of sedimentary facies ambiguous for classical methods, especially floodplain and lacustrine sediments, as well as revealing their various vulnerabilities to tectonic modification of AMS. A spatial analysis of facies showed that tuffites along with lacustrine and swamp deposits were generally restricted to marginal and southern parts of the basin. Significant deformations were noticed at basin margins and within two intrabasinal tectonic zones, which indicated the tectonic activity of the Pieniny Klippen Belt after the Middle Miocene. The large southern area of the basin recorded consistent N-NE trending compression during basin inversion. This regional tectonic rearrangement resulted in a partial removal of the southernmost basin deposits and shaped the basin's present-day extent.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winn, R.D. Jr.; Steinmetz, J.C.; Kerekgyarto, W.L.

Lithological and compositional relationships, thicknesses, and palynological data from drilling cuttings from five wells in the Anza rift, Kenya, indicate active rifting during the Late Cretaceous and Eocene-Oligocene. The earlier rifting possibly started in the Santonian-Coniacian, primarily occurred in the Campanian, and probably extended into the Maastrichtian. Anza rift sedimentation was in lacustrine, lacustrine-deltaic, fluvial, and flood-basin environments. Inferred synrift intervals in wells are shalier, thicker, more compositionally immature, and more poorly sorted than Lower Cretaceous ( )-lower Upper Cretaceous and upper Oligocene( )-Miocene interrift deposits. Synrift sandstone is mostly feldspathic or arkosic wacke. Sandstone deposited in the Anza basinmore » during nonrift periods is mostly quartz arenite, and is coarser and has a high proportion of probable fluvial deposits relative to other facies. Volcanic debris is absent in sedimentary strata older than Pliocene-Holocene, although small Cretaceous intrusions are present in the basin. Cretaceous sandstone is cemented in places by laumontite, possibly recording Campanian extension. Early Cretaceous history of the Anza basin is poorly known because of the limited strata sampled; Jurassic units were not reached. Cretaceous rifting in the Anza basin was synchronous with rifting in Sudan and with the breakup and separation of South America and Africa; these events likely were related. Eocene-Oligocene extension in the Anza basin reflects different stresses. The transition from active rifting to passive subsidence in the Anza basin at the end of the Neogene, in turn, records a reconfigured response of east African plates to stresses and is correlated with formation of the East Africa rift.« less

Storm and tide influenced depositional architecture of the Pliocene-Pleistocene Chad Formation, Chad Basin (Bornu Sub-basin) NE Nigeria: A mixed fluvial, deltaic, shoreface and lacustrine complex

NASA Astrophysics Data System (ADS)

Shettima, Bukar; Kyari, Aji Maina; Aji, Mallam Musa; Adams, Fatimoh Dupe

2018-07-01

Lithofacies analyses of the upper part of the Chad Formation (Bama Ridge Complex) in the Bornu Sub-basin of the Chad Basin indicated four facies associations; fluvial, deltaic, shoreface and lacustrine sequences. The fluvial sequences are composed of fining upward cycles with successive occurrence of planar crossbedded sandstone facies displaying unimodal paleocurrent system and rare mudstone facies typical of braided river system. The deltaic succession consists of both fining and coarsening upwards cycles with the former depicting fluvial setting of an upper delta plain while the later suggestive of mouth-bar sequences. The setting displays a polymodal current system of fluvial, waves, storms and tides that were primarily induced by complex interactions of seiches and lunar tides. Similar current systems devoid of fluvial patterns were reflected in the coarsening upward packages of the shoreface sequences. Lacustrine succession composed of thick bioturbated mudstone facies generally defines the base of these coarsening upward profiles, giving a fluvio-lacustrine geomorphic relief where complex interaction developed the deltaic and shoreface facies along its shorelines. Clay mineral fractions of the formation are dominantly kaolinitic, indicating a predominantly humid tropical-subtropical climatic condition during their deposition. This climatic regime falls within the African humid period of the early-mid Holocene that led to the third lacustrine transgression of the Lake Mega-Chad, whereas the subordinate smectite mineralization points to aridification that characterizes most of the post humid period to recent.

Late Holocene stratigraphy of the Tetimpa archaeological sites, northeast flank of Popocatepetl volcano, central Mexico

USGS Publications Warehouse

Panfil, M.S.; Gardner, T.W.; Hirth, K.G.

1999-01-01

Late Holocene (240 km2 on the east side of the volcano with >25 cm of tephra. Lavas from eruptive sequence I dammed drainage in the lowland area near the town of San Nicolas and caused local upstream deposition of as much as 30 m of lacustrine silts, clays, and sands. These lacustrine deposits record an eruptive hiatus for the Tetimpa area of about 750 14C yr: between ca. 2100 and ca. 1350 yr B.P., no major tephras were deposited in the Tetimpa area. In upland areas, this time period is represented by an unconformity and by Entisols formed in the top of pumice deposits and lavas from eruptive sequence I. Artifacts, agricultural furrows, and dwellings record human reoccupation of this surface. At the end of this hiatus, several lahars were deposited above the lacustrine sequence and locally above the Entisol in upland positions adjacent to streams. Between ca. 1350 and ca. 1200 yr B.P., tephras from eruptive sequence II buried these paleosols, occupation sites, lacustrine sediments, and lahars. Andesitic (~62% SiO2) pumice lapilli deposits in the Tetimpa area record three pumice-fall eruptions directed northeast and east of the crater. The first and smallest of these (maximum Tetimpa area thickness = 12 cm; >52 km2 covered by >25 cm) took place at ca. 1350 yr B.P. and was accompanied by pyroclastic surge events preserved in the Tetimpa area by charcoal, sand waves, and cross-stratified sand-sized tephra. At ca. 1200 yr B.P., the products of two Plinian-style events and additional pyroclastic surges reached the Tetimpa area. The largest of these tephra-fall events covered the Tetimpa area with 0.5-1 m of tephra and blanketed an area of >230 km2 with a thickness of >25 cm. The Tetimpa record confirms two of the four periods of explosive volcanism recognized by studies conducted around Popocatepetl in the past 30 yr. Eruptive sequence I corresponds to the explosive period between 2100 and 2500 yr B.P., and eruptive sequence II corresponds to the period between 900 and 1400 yr B.P. The archaeology and lacustrine stratigraphy of the Tetimpa area help constrain the timing of the Plinian phase of eruptive sequence I to ca. 2100 yr B.P. and suggest that the pumice-fall eruptions of eruptive sequence II took place in at least two intervals between ca. 1350 and ca. 1200 yr B.P.

Interstratified arkosic and volcanic rocks of the Miocene Spanish Canyon Formation, Alvord Mountain area, California: descriptions and interpretations

USGS Publications Warehouse

Buesch, David C.

2014-01-01

The Spanish Canyon Foundation in the Alvord Mountain area, California, varies from about 50 to 120 m thick and records the interstratification of arkosic sandstone and conglomerate with tuffaceous deposits and lava flows. In the lower third of the formation, arkosic sandstone and conglomerate are interstratified with tuffaceous deposits. Some tuffs might have been deposited as primary, nonwelded to partially welded ignimbrites or fallout tephra. Many of the tuffaceous deposits represent redeposited material that formed tuffaceous sandstone, and many of these deposits contain arkosic grains that represent mixing of different source matieral. Arkosic sandstone, and especially conglomerate (some with maximum clast lengths up to 1 m), represent intermittent incursions of coarser plutoniclastic fan deposits into other finer grained and mostly volcaniclastic basin deposits. After deposition of the 18.78 Ma Peach Spring Tuff, the amount of tuffaceous material decreased. The upper two-thirds of the formation has arkosic sandstone and conglomerate interstratified with two olivine basalt lave flows. locally, conglomerate clasts in this part of the section have maximum lengths up to 1 m. Many tuffaceous and arkosic sandstone beds of the Spanish Canyon Formation have tabular to broad (low-relief) lenticular geometry, and locally, some arkosic conglomerate fills channels as much as 1.5 m deep. These bedforms are consistent with deposition in medial to distal alluvial-fan or fluvial environments; some finer-grained deposits might have formed in lacustrine environments.

An isotopic study of a fluvial-lacustrine sequence: The Plio-Pleistocene koobi fora sequence, East Africa

USGS Publications Warehouse

Cerling, T.E.; Bowman, J.R.; O'Neil, J.R.

1988-01-01

Stable isotopic analyses of Plio-Pleistocene and modern sediments in the fluvial-lacustrine system occupying the Turkana Basin, East Africa provide constraints on the paleoenvironmental and diagenetic histories of the Pliocene through the Recent sediments in the basin. The ??13C values for carbonates in lacustrine sediments range from -15 to +22??? relative to PDB, depending on the varying proportions of CO2 from the atmospheric reservoir and from various metabolic sources. The ??18O values of carbonates in lacustrine sediments indicate that the isotopic composition of paleolake water varied by over 10??? from the Pliocene to the present. The ??13C values for pedogenic carbonates record paleoccologic variations and suggest that C4 plants did not become well established in the preserved depositional parts of the basin until about 1.8 myr ago. The ??18O values pedogenic carbonates suggest a range of over 10??? for the isotopic composition of soil water during this interval. They also suggest a period of major climatic instability from about 3.4 to 3.1 myr and at about 1.8 myr. Together, the ??13C and ??18O values of pedogenic carbonates indicate that the present conditions are as arid and hot as any that had prevailed during deposition of these Plio-Pleistocene sediments. ?? 1988.

Terrestrial responses of low-latitude Asia to the Eocene-Oligocene climate transition revealed by integrated chronostratigraphy

NASA Astrophysics Data System (ADS)

Li, Y. X.; Jiao, W. J.; Liu, Z. H.; Jin, J. H.; Wang, D. H.; He, Y. X.; Quan, C.

2016-02-01

The Paleogene sedimentary records from southern China hold important clues to the impacts of the Cenozoic climate changes on low latitudes. However, although there are extensive Paleogene terrestrial archives and some contain abundant fossils in this region, few are accurately dated or have a temporal resolution adequate to decipher climate changes. Here, we present a detailed stratigraphic and paleomagnetic study of a fossiliferous late Paleogene succession in the Maoming Basin, Guangdong Province. The succession consists of oil shale of the Youganwo Formation (Fm) in the lower part and the overlying sandstone-dominated Huangniuling Fm in the upper part. Fossil records indicate that the age of the succession possibly spans the late Eocene to the Oligocene. Both the Youganwo Fm and the overlying Huangniuling Fm exhibit striking sedimentary rhythms, and spectral analysis of the depth series of magnetic susceptibility of the Youganwo Fm reveals dominant sedimentary cycles at orbital frequency bands. The transition from the Youganwo oil shale to the overlying Huangniuling sandstones is conformable and represents a major depositional environmental change from a lacustrine to a deltaic environment. Integrating the magnetostratigraphic, lithologic, and fossil data allows establishing a substantially refined chronostratigraphic framework that places the major depositional environmental change at 33.88 Ma, coinciding with the Eocene-Oligocene climate transition (EOT) at ˜ 33.7 to ˜ 33.9 Ma. We suggest that the transition from a lacustrine to deltaic environment in the Maoming Basin represents terrestrial responses to the EOT and indicates prevailing drying conditions in low-latitude regions during the global cooling at EOT.

Mesozoic lacustrine system in the Parnaíba Basin, northeastern Brazil: Paleogeographic implications for west Gondwana

NASA Astrophysics Data System (ADS)

Cardoso, Alexandre Ribeiro; Nogueira, Afonso César Rodrigues; Abrantes, Francisco Romério; Rabelo, Cleber Eduardo Neri

2017-03-01

The fragmentation of the West Gondwana during Early Triassic to Cretaceous was marked by intense climatic changes, concomitant with the establishment of extensive desertic/lacustrine systems. These deposits succeeded the emplacement and extrusion of lava flows, related to the pre-rift phase and initial opening of the Equatorial Atlantic Ocean. The thermal phase is recorded in the Upper Jurassic-Lower Cretaceous Pastos Bons Formation, exposed mainly in southeast parts of the Parnaíba Basin, Northeastern Brazil. The sedimentary facies of this unit were grouped in two facies associations (FA), representative of a shallow lacustrine system, influenced by episodic hyperpycnal and oscillatory flows. Central lake facies association (FA1) is composed by laminated mudstone (Ml), sandstone/mudstone rhythmite (S/Mr) and sandstone with even-parallel lamination (Sel). Flysch-like delta front (FA2) consists in sandstones with wave structures (Sw), sandstones with even-parallel stratification (Ses), massive sandstones (Sm), sandstones with soft-sediment deformation structures (Sd) and laminated mudstones (Ml). FA1 was deposited in the deepest portions of the lake, characterized by low energy, episodically disturbed by siliciclastic influx. FA2 presents sandy deposits generated by unconfined flow, probably fed by ephemeral stream flows that generated thickening upward of tabular sandstone beds. The progressive filling of the lake resulted in recurrent shoaling up of the water level and reworking by wave action. The installation of Pastos Bons lakes was controlled by thermal subsidence, mainly in restricted depocenters. The siliciclastic fluvial inflow can be related to the adjacent humid desertic facies, formed under climatic attenuation, typical of post-Triassic period, with reduced biological activity. Smectite and abundant feldspars, in lacustrine facies, corroborate an arid climate, with incipient chemical weathering. The new facies and stratigraphic data present in this paper provide an explanation about the implantation of a huge lacustrine system in the southern of Parnaiba Basin, with strong paleogeographic implications for the West-Central Gondwana during Late Jurassic to Early Cretaceous.

Palynology and age of some Cretaceous nonmarine deposits in Mongolia and China

USGS Publications Warehouse

Nichols, D.J.; Matsukawa, M.; Ito, M.

2006-01-01

To provide biostratigraphic and paleoecologic data for a major international project studying dinosaur trackways in eastern Asia, samples were collected for palynological analysis from the Choyr Basin of southeastern Mongolia and the Yanji Basin, Jilin Province, northeastern China. Palynologically productive samples from the Choyr Basin are from strata previously identified as either the Shinekhudag Formation or the Zuunbayan Formation but recently renamed the Khuren Dukh Formation; productive samples from the Yanji Basin are from the Tongfosi Formation. The biostratigraphically most important palynomorphs from both units are angiosperm pollen. The Khuren Dukh Formation is determined to be middle to late Albian in age. The Tongfosi Formation is determined to be early Cenomanian in age. These results conflict with some previously published interpretations of the ages of these units. Lacustrine depositional environments are indicated for both units by the presence of freshwater algae in both deposits. ?? 2006 Elsevier Ltd. All rights reserved.

Mass-movement deposits in the lacustrine Eocene Green River Formation, Piceance Basin, western Colorado

USGS Publications Warehouse

Johnson, Ronald C.; Birdwell, Justin E.; Brownfield, Michael E.; Mercier, Tracey J.

2015-01-01

The Eocene Green River Formation was deposited in two large Eocene saline lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. Here we will discuss mass-movement deposits in just the Piceance Basin part of Lake Uinta.

Mineral Trends in Early Hesperian Lacustrine Mudstone at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Ming, D. W.; Grotzinger, J. P.; Morris, R. V.; Blake, D. F.; Vaniman, D. T.; Bristow, T. F.; Morrison, S. M.; Yen, A. S.; Chipera, S. J.;

The Alleret Maar lacustrine sequence (French Massif Central): a 150 ka long early-middle Pleistocene continental paleoenvironmental record.

NASA Astrophysics Data System (ADS)

Nomade, S.; Pastre, J.; Guillou, H.; Gauthier, A.; Scaillet, S.

2008-12-01

Lacustrine maar sequences of the French Massif Central are of great interest for paleoclimatic and paleoenvironmental reconstructions of mid-latitudes Quaternary continental environments. In particular, the western Velay region yields exceptional sequences spanning the last 450 ka (Reille et al., J. Quat. Sci. 2000). However, older sequences remain largely unknown despite the presence of interbedded alkaline tephras allowing precise absolute radiochronological control of many lacustrine squences. The Alleret maar is a 1500 m wide phreatomagmatic crater that provides a long lacustrine sequence (41 m). The upper part of this sequence (AL2 core, 14.6 m) was studied between 2005 and 2006 (Pastre et al., C. R. Acad Sci, 2007). A 39Ar/40Ar date (557 ± 5ka) obtained from an interbedded tephra layer located at 7m as well as the associated pollen data attribute the beginning of this sequence to the MIS 15. Thanks to the AL3 core recovered in 2005 (40.6 m, CNRS Meudon) several new tephra layers were discovered in the bottom part of this lacustrine sequence. Three new 39Ar/40Ar ages (single crystal analyses) from trachytic tephra layers were obtained at the LSCE Argon Laboratory (France). These layers are located at -30.2, -36.2 and -39.2m. Ages obtained relative to the ACR-2 flux standard (1,201Ma, Kuiper et al., Science, 2008) range from 692 ± 6 ka (MSWD: 2.3, n=18) for the youngest (-30.2m) to 726 ± 9Ka Ka (MSWD: 2.2, n=12) for the lowest tephra located at -39.2m. These new dates indicate a relatively homogeneous deposition rate of 3.5cm/ka and that the last 10 meters cover the MIS 17-MIS18 period. According to these current radiochronological data the complete lacustrine sequence last more than 150ka. Ongoing sedimentary and pollen studies will allow to extend the paleoenvironmental and paleoclimatic records of the French Massif Central towards the beginning of the early middle Pleistocene.

Glaciolacustrine deposits formed in an ice-dammed tributary valley in the south-central Pyrenees: New evidence for late Pleistocene climate

NASA Astrophysics Data System (ADS)

Sancho, Carlos; Arenas, Concha; Pardo, Gonzalo; Peña-Monné, José Luis; Rhodes, Edward J.; Bartolomé, Miguel; García-Ruiz, José M.; Martí-Bono, Carlos

2018-04-01

Combined geomorphic features, stratigraphic characteristics and sedimentologic interpretation, coupled with optically stimulated luminescence (OSL) dates, of a glacio-fluvio-lacustrine sequence (Linás de Broto, northern Spain) provide new information to understand the palaeoenvironmental significance of dynamics of glacier systems in the south-central Pyrenees during the Last Glacial Cycle (≈130 ka to 14 ka). The Linás de Broto depositional system consisted of a proglacial lake fed primarily by meltwater streams emanating from the small Sorrosal glacier and dammed by a lateral moraine of the Ara trunk glacier. The resulting glacio-fluvio-lacustrine sequence, around 55 m thick, is divided into five lithological units consisting of braided fluvial (gravel deposits), lake margin (gravel and sand deltaic deposits) and distal lake (silt and clay laminites) facies associations. Evolution of the depositional environment reflects three phases of progradation of a high-energy braided fluvial system separated by two phases of rapid expansion of the lake. Fluvial progradation occurred during short periods of ice melting. Lake expansion concurred with ice-dam growth of the trunk glacier. The first lake expansion occurred over a time range between 55 ± 9 ka and 49 ± 11 ka, and is consistent with the age of the Viu lateral moraine (49 ± 8 ka), which marks the maximum areal extent of the Ara glacier during the Last Glacial Cycle. These dates confirm that the maximum areal extent of the glacier occurred during Marine Isotope Stages 4 and 3 in the south-central Pyrenees, thus before the Last Glacial Maximum. The evolution of the Linás de Broto depositional system during this maximum glacier extent was modulated by climate oscillations in the northern Iberian Peninsula, probably related to latitudinal shifts of the atmospheric circulation in the southern North-Atlantic Ocean, and variations in summer insolation intensity.

Paleogeography and Depositional Systems of Cretaceous-Oligocene Strata: Eastern Precordillera, Argentina

NASA Astrophysics Data System (ADS)

Reat, Ellen J.; Fosdick, Julie C.

2016-04-01

New data from the Argentine Precordillera in the southern Central Andes document changes in depositional environment and sediment accumulation rates during Upper Cretaceous through Oligocene basin evolution, prior to the onset Miocene foredeep sedimentation. This work presents new sedimentology, detrital geochronology, and geologic mapping from a series of continental strata within this interval to resolve the timing of sedimentation, nature of depositional environments, and basin paleogeography at the nascent phase of Andean orogenic events, prior to the uplift and deformation of the Precordillera to the west. Five stratigraphic sections were measured across both limbs of the Huaco Anticline, detailing sedimentology of the terrestrial siliciclastic upper Patquía, Ciénaga del Río Huaco (CRH), Puesto la Flecha, Vallecito, and lower Cerro Morado formations. Paleocurrent data indicate a flow direction change from predominantly NE-SW in the upper Patquía and the lower CRH to SW-NE directed flow in the upper CRH, consistent with a large meandering river system and a potential rise in topography towards the west. This interpretation is further supported by pebble lag intervals and 1-3 meter scale trough cross-bedding in the CRH. The thinly laminated gypsum deposits and siltstones of the younger Puesto la Flecha Formation indicate an upsection transition into overbank and lacustrine sedimentation during semi-arid climatic conditions, before the onset of aeolian dune formation. New maximum depositional age results from detrital zircon U-Pb analysis indicate that the Puesto la Flecha Formation spans ~57 Myr (~92 to ~35 Ma) across a ~48 m thick interval without evidence for major erosion, indicating very low sedimentation rates. This time interval may represent distal foredeep or forebulge migration resultant from western lithospheric loading due to the onset of Andean deformation at this latitude. Detrital zircon U-Pb age spectra also indicate shifts in sediment routing pathways over time, consistent with a transition from local basement-sourced quartz-rich sediments during the Triassic-Cretaceous to increased volcanic and sedimentary lithics from the rising Andes in the west during Paleocene-Eocene time. We therefore interpret these changes in depositional character as representing a transition from a large fluvial system with craton-sourced sediments during the Triassic-Cretaceous CRH to low energy lacustrine and ephemeral playa environments with an increase in westerly derived sediments during the Paleocene-Eocene Puesto la Flecha, prior to the reported Oligocene onset of the Andean continental foredeep represented by the Vallecito Formation.

A contribution to regional stratigraphic correlations of the Afro-Brazilian depression - The Dom João Stage (Brotas Group and equivalent units - Late Jurassic) in Northeastern Brazilian sedimentary basins

NASA Astrophysics Data System (ADS)

Kuchle, Juliano; Scherer, Claiton Marlon dos Santos; Born, Christian Correa; Alvarenga, Renata dos Santos; Adegas, Felipe

2011-04-01

The Dom João Stage comprises an interval with variable thickness between 100 and 1200 m, composed of fluvial, eolian and lacustrine deposits of Late Jurassic age, based mainly on the lacustrine ostracod fauna (although the top deposits may extend into the Early Cretaceous). These deposits comprise the so-called Afro-Brazilian Depression, initially characterized as containing the Brotas Group of the Recôncavo Basin (which includes the Aliança and the Sergi Formations) and subsequently extended into the Tucano, Jatobá, Camamu, Almada, Sergipe, Alagoas and Araripe Basins in northeastern Brazil, encompassing the study area of this paper. The large occurrence area of the Dom João Stage gives rise to discussions about the depositional connectivity between the basins, and the real extension of sedimentation. In the first studies of this stratigraphic interval, the Dom João Stage was strictly associated with the rift phase, as an initial stage (decades of 1960-70), but subsequent analyses considered the Dom João as an intracratonic basin or pre-rift phase - without any relation to the active mechanics of a tectonic syn-rift phase (decades of 1980-2000). The present work developed an evolutionary stratigraphic and tectonic model, based on the characterization of depositional sequences, internal flooding surfaces, depositional systems arrangement and paleoflow directions. Several outcrops on the onshore basins were used to build composite sections of each basin, comprising facies, architectural elements, depositional systems, stratigraphic and lithostratigraphic frameworks, and paleocurrents. In addition to that, over a hundred onshore and offshore exploration wells were used (only 21 of which are showed) to map the depositional sequences and generate correlation sections. These show the characteristics and relations of the Dom João Stage in each studied basin, and they were also extended to the Gabon Basin. The results indicate that there were two main phases during the Dom João Stage, in which distinctive sedimentary environments were developed, reflecting depositional system arrangements, paleoflow directions were diverse, and continuous or compartmented basins were developed.

Flashy Water and Sediment Delivery to Fluvial Megafan andFan Delta Systems on Opposing Shorelines of an Early Eocene Lake

NASA Astrophysics Data System (ADS)

Jones, E. R.; Plink-Bjorklund, P.

2015-12-01

Flashy delivery of water and sediment had distinct effects on the process of deposition in coeval fluvial megafan and fan delta deposits on opposing shorelines of a paleolake that occupied the Uinta Basin throughout the Eocene. The Tertiary Uinta Basin was an asymmetric continental interior basin with a steep northern margin, adjacent to the block uplift controlling basin subsidence, and a low gradient southern margin. A ~140 km wide fluvial megafan with catchments as far as ~750 km away occupied the southern margin of the lacustrine basin. Within this megafan system, fluvial deposits contain within-channel continental bioturbation and paleosol development on bar accretion surfaces that are evidence of prolonged periods of groundwater flow or channel abandonment. These are punctuated by channel fills exhibiting a suite of both high-deposition rate and upper flow regime sedimentary structures that were deposited by very rapid suspension-fallout during seasonal to episodic river flooding events. A series of small (~8 km wide) and proximally sourced fan deltas fed sediment into the steeper northern margin of the lacustrine basin. 35-50% of the deposits in the delta plain environment of these fan deltas are very sandy debris flows with as low as 5% clay and silt sized material. Detrital zircon geochronology shows that these fan deltas were tapping catchments where mostly unconsolidated Cretaceous sedimentary cover and thick Jurassic eolianites were being eroded. A combination of flashy precipitation, arid climate, catchments mantled by abundant loose sand-sized colluvium, and steep depositional gradients promoted generation of abundant very sandy (5-10% clay and silt sized material) debris flows. In this way, the Wasatch and Green River Formations in the Uinta Basin, Utah, U.S.A. gives us two very different examples of how routing flashy water and sediment delivery (associated with pulses of hyperthermal climate change during the Early Eocene) through different depositional systems produced unique processes of deposition, and also gives us an opportunity to isolate the effects of other variables (e.g. sediment caliber, system gradient, catchment size) that can modulate the flashy precipitation signal in stratigraphy.

Lacustrine fan delta deposition alongside intrabasinal structural highs in rift basins: an example from the Early Cretaceous Jiuquan Basin, Northwestern China

NASA Astrophysics Data System (ADS)

Zhang, Chengcheng; Muirhead, James D.; Wang, Hua; Chen, Si; Liao, Yuantao; Lu, Zongsheng; Wei, Jun

2018-01-01

Development of fan deltas alongside intrabasinal structural highs has been overlooked compared to those forming on basin margins. However, these fan deltas may provide important clues regarding the tectonic and climatic controls on deposition during rift development. This paper documents fan delta deposition alongside an intrabasinal structural high within the Early Cretaceous Xiagou Formation of the Jiuquan Basin, China, using subsurface geological and geophysical data. Deposits observed in drill core support fan delta deposition occurring almost exclusively through subaerial and subaqueous gravity flows. Subsurface mapping reveals a consistent decrease in the areal extent of fan deltas from lowstand to highstand system tracts, suggesting that deposition alongside the structural high is sensitive to lake-level changes. The temporal and spatial distribution of the fan deltas display retrogradational stacking patterns, where fan deltas exhibit a decreasing lateral extent up-sequence until fan delta deposition terminated and was replaced by deposition of fine-grained lacustrine deposits. The retrogradational stacking patterns observed alongside the intrabasinal structural high are not observed in fan deltas along the basin margin in the lower parts of the Xiagou Formation. Subsidence profiles also show differential subsidence across the basin during the earliest stages of this formation, likely resulting from border fault movements. These data suggest that non-uniform stacking patterns in the lower parts of the Xiagou Formation reflect basin-scale tectonic movements as the dominant control on synrift deposition patterns. However, later stages of Xiagou Formation deposition were characterized by uniform subsidence across the basin, and uniform retrogradational stacking patterns for fan deltas alongside the intrabasinal structural high and border fault. These observations suggest that basin-scale tectonic movements played a relatively limited role in controlling sediment deposition, and imply a potential change to regional-scale processes affecting fan delta deposition during later synrift stages. Climate change is favored here as the region-scale control on the uniform retrogradational fan delta stacking patterns. This assertion is supported by pollen assemblages, isotope signatures, and organic geochemical analyses, which collectively suggest a change from a humid to semi-arid environment during later synrift stages. We suggest that variations in stacking patterns between different fan delta systems can provide insights into the basin- and regional-scale processes that control rift basin deposition.

An overview of the Permian (Karoo) coal deposits of southern Africa

NASA Astrophysics Data System (ADS)

Cairncross, B.

2001-08-01

The coal deposits of southern Africa (Botswana, Malawi, Mozambique, Namibia, South Africa, Swaziland, Tanzania, Zambia and Zimbabwe) are reviewed. The coal seams formed during two periods, the Early Permian (Artinskian-Kungurian) and the Late Permian (Ufimian-Kazanian). The coals are associated with non-marine terrestrial clastic sedimentary sequences, most commonly mudrock and sandstones, assigned to the Karoo Supergroup. The Early Permian coals are most commonly sandstone-hosted while the younger coals typically occur interbedded with mudstones. The sediments were deposited in varying tectono-sedimentary basins such as foreland, intracratonic rifts and intercratonic grabens and half-grabens. The depositional environments that produced the coal-bearing successions were primarily deltaic and fluvial, with some minor shoreline and lacustrine settings. Coals vary in rank from high-volatile bituminous to anthracite and characteristically have a relatively high inertinite component, and medium- to high-ash content. In countries where coal is mined, it is used for power generation, coking coal, synfuel generation, gasification and for (local) domestic household consumption.

Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China

PubMed Central

Wang, Min; Yang, Jinxiu; Wang, Zhiwei; Lu, Shuangfang

2015-01-01

In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions) play a major role in the shale oil occurrence (free or absorbed state), amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope) observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1) Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2) There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3) Pores in lacustrine shale are well developed when the organic matter maturity (Ro) is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon) content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable. PMID:26285123

Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China.

PubMed

Wang, Min; Yang, Jinxiu; Wang, Zhiwei; Lu, Shuangfang

2015-01-01

In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions) play a major role in the shale oil occurrence (free or absorbed state), amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope) observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1) Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2) There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3) Pores in lacustrine shale are well developed when the organic matter maturity (Ro) is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon) content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable.

Organic Geochemical Characteristics and Depositional Environment of Aǧaçbaşi Plateau Peat, Köprübaşi/Trabzon, NE Turkey

NASA Astrophysics Data System (ADS)

Hoş Çebi, Fatma; Korkmaz, Sadettin

2013-04-01

Young peat deposits crop out in the southern part of the Aǧaçbaşı region of Trabzon city, Northern Turkey. In this study, chemical, organic geochemical, petrographic and palynological features of the peat occurrences are investigated and results obtained evaluated. According to palynological investigations, it is determined that peats were occured in terrestrial or lacustrine environments, which is containing average of 80% woody, 15% herbaceous and 5% amorphous organic matter. Age of peats has been determined as Miocene or younger, by the palynological age determinations. It is understood from the obtained SCI (Sport Color Index) analysis results that constituting organic material of peat is immature. Total organic carbon content of the peat is average 41.69% by pyrolysis analysis. HI values were calculated as average 315.46 mgHC/gTOC, which is very high for the coal occurrences. The high OI values (avg. 134 mgCO2/gTOC) show that the environments of peat deposits were oxic or suboxic. TAR (Terrigenous/Aquatic Ratio) and CPI (Carbon Preference Index) index value, is found to be 2.4 and 3.4 respectively. These values that resulted from dominance of high-numbered n-alkanes, indicate terrestrial organic matter input. According to the m/z 191 and m/z 217 mass peaks of GC chromatogram data which is obtained by biomarker analysis, sterane/hopane ratio suggests algal organic matter. Moreover, the lack of C34 and C35 homohopans show that organic matter deposited under oxic or suboxic conditions. Moretane/hopane, Tm/Ts and Tm/C30 hopane ratios were calculated in order of 0.15, 3.25 and 0.33, respectively. These values imply acidic and oxic conditions during the formation of peat. Due to the absence of 17α(H)-28.30-bisnorhopan in the m/z 191 chromatograms, it is concluded that Aǧaçbaşı plateau peat might be deposited in a terrestrial or lacustrine environments under oxic or suboxic conditions. Dominant sterane content of C29 suggests terrestrial organic matter input. In the sterane triangle diagram, the extract of the peat sample was plotted in the area of high plant and brown and green alga inputs. Also C30 sterane, which is implication of marine environment, has not been recorded on chromatogram. 22S/(22S+22R) homohopan index, Ts/(Ts+Tm), moretan/hopane, 20S/(20S+20R) sterane and ββ/(ββ+αα) sterane ratios suggest immature level of the organic matter. Key Words: peat, biomarker, sterane, terpane

Paleogeographic implications of Late Miocene lacustrine and nonmarine evaporite deposits in the Lake Mead region: Immediate precursors to the Colorado River

USGS Publications Warehouse

Faulds, James E.; Schreiber, Charlotte; Langenheim, Victoria; Hinz, Nicholas H.; Shaw, Tom; Heizler, Matthew T.; Perkins, Michael E; El Tabakh, Mohammed; Kunk, Michael J.

2016-01-01

Thick late Miocene nonmarine evaporite (mainly halite and gypsum) and related lacustrine limestone deposits compose the upper basin fill in half grabens within the Lake Mead region of the Basin and Range Province directly west of the Colorado Plateau in southern Nevada and northwestern Arizona. Regional relations and geochronologic data indicate that these deposits are late synextensional to postextensional (ca. 12–5 Ma), with major extension bracketed between ca. 16 and 9 Ma and the abrupt western margin of the Colorado Plateau established by ca. 9 Ma. Significant accommodation space in the half grabens allowed for deposition of late Miocene lacustrine and evaporite sediments. Concurrently, waning extension promoted integration of initially isolated basins, progressive enlargement of drainage nets, and development of broad, low gradient plains and shallow water bodies with extensive clastic, carbonate, and/or evaporite sedimentation. The continued subsidence of basins under restricted conditions also allowed for the preservation of particularly thick, localized evaporite sequences prior to development of the through-going Colorado River.The spatial and temporal patterns of deposition indicate increasing amounts of freshwater input during the late Miocene (ca. 12–6 Ma) immediately preceding arrival of the Colorado River between ca. 5.6 and 4.9 Ma. In axial basins along and proximal to the present course of the Colorado River, evaporite deposition (mainly gypsum) transitioned to lacustrine limestone progressively from east to west, beginning ca. 12–11 Ma in the Grand Wash Trough in the east and shortly after ca. 5.6 Ma in the western Lake Mead region. In several satellite basins to both the north and south of the axial basins, evaporite deposition was more extensive, with thick halite (>200 m to 2.5 km thick) accumulating in the Hualapai, Overton Arm, and northern Detrital basins. Gravity and magnetic lows suggest that thick halite may also lie within the northern Grand Wash, Mesquite, southern Detrital, and northeastern Las Vegas basins. New tephrochronologic data indicate that the upper part of the halite in the Hualapai basin is ca. 5.6 Ma, with rates of deposition of ∼190–450 m/m.y., assuming that deposition ceased approximately coincidental with the arrival of the Colorado River. A 2.5-km-thick halite sequence in the Hualapai basin may have accumulated in ∼5–7 m.y. or ca. 12–5 Ma, which coincides with lacustrine limestone deposition near the present course of the Colorado River in the region.The distribution and similar age of the limestone and evaporite deposits in the region suggest a system of late Miocene axial lakes and extensive continental playas and salt pans. The playas and salt pans were probably fed by both groundwater discharge and evaporation from shallow lakes, as evidenced by sedimentary textures. The elevated terrain of the Colorado Plateau was likely a major source of water that fed the lakes and playas. The physical relationships in the Lake Mead region suggest that thick nonmarine evaporites are more likely to be late synextensional and accumulate in basins with relatively large catchments proximal to developing river systems or broad elevated terranes. Other basins adjacent to the lower Colorado River downstream of Lake Mead, such as the Dutch Flat, Blythe-McCoy, and Yuma basins, may also contain thick halite deposits.

Chapter F: Preliminary Bibliography of Lacustrine Diatomite Deposits in the Western United States and Related Topics

USGS Publications Warehouse

Bolm, Karen S.; Wallace, Alan R.; Moyle, Phillip R.; Bliss, James D.; Orris, Greta J.

2003-01-01

Introduction As part of the assessment of lacustrine diatomite resources in the Western United States (fig. 1), U.S. Geological Survey (USGS) project members conducted a review of literature relating to the formation, location, and nature of deposits in the study area. This preliminary bibliography consists of selected publications to identify, locate, and describe the deposits to be studied, to characterize common geologic factors about the deposits, and to better understand the factors that control their formation, preservation, or destruction. The bibliography also serves as a resource for other workers to research the topic. References included in the preliminary bibliography were gathered by searching existing bibliographic data bases and library collections. Project researchers also contributed references that they found during the course of their work. This bibliography should be considered a working document that will grow as research and literature searches continue. Clearly, many significant publications may be missing from this preliminary list; therefore, USGS staff members intend to issue a revised bibliography as project work progresses. To assure completeness, input from other researchers and industry is welcome. Although the focus of this bibliography is lacustrine diatomite deposits of the Western United States, additional references that provide a foundation of knowledge for the study of diatomites, diatoms, and diatom-related processes (ecology, geology, geochemistry) and for the uses and behavior of diatomite have also been included. An index of keywords has been added to this bibliography, designed to help the user locate reports by topic or by geographic location. The letter 'A' following a number indicates that the report referenced is an abstract.

Middle Jurassic continental biota and paleolandscape in the Dubinino locality (Sharypovo area, Krasnoyarsk krai)

NASA Astrophysics Data System (ADS)

Ivantsov, S. V.; Bystritskaya, L. I.; Krasnolutskii, S. A.; Lyalyuk, K. P.; Frolov, A. O.; Alekseev, A. S.

2016-09-01

On the basis of the lithological-facies analysis, it was established that deposits of the Upper Itat Subformation, comprising the Dubinino locality of the Middle Jurassic flora and insects (Sharypovo district, Krasnoyarsk krai), accumulated in alluvial and lacustrine and, to a lesser extent, floodplain environments (floodplain and alluvial fan facies). The occurrence of remains of insects, macroremains of flora, spores, and pollen allowed us to make a paleoreconstruction of an area with a strongly dissected relief: continental fresh-water reservoir (lake) with varying degree of overflow, surrounded by hills covered with gymnospermous and ginkgo forests.

Use of surface and borehole geophysics to delineate the glacial-drift stratigraphy of northeastern St. Joseph County, Indiana

USGS Publications Warehouse

Bayless, E. Randall; Westjohn, David B.; Watson, Lee R.

1995-01-01

Inverse models of direct current electrical- resistivity sounding data and normal-resistivity and natural-gamma logs were used to assist delineation of the glacial-drift stratigraphy in a 580-square- kilometer area of northeastern St. Joseph County, Indiana. Unconsolidated deposits in the study area are composed of glacial-drift, including outwash, till, and lacustrine sediments; thicknesses range from about 15 to more than 70 meters. The glacial outwash deposits are mostly composed of sand and gravel and are the primary source of drinking water to northeastern St. Joseph County. The glacial till and glacio-lacustrine deposits contain a larger fraction of clay than the outwash deposits and may retard ground-water flow between shallow and deeper sand and gravel aquifers. Results of the geophysical measurements collected during this study indicate that glacial-drift deposits in the area north and east of the St. Joseph River are mostly composed of sand and gravel with inter-layered clay-rich deposits that are laterally discontinuous. In the area south of the St. Joseph River, the thickness of sand and gravel deposits diminishes, and clay-rich deposits dominate the stratigraphy. The presence of an electrically conductive bedrock, the Ellsworth Shale, beneath the glacial-drift deposits is identified in inverse models of direct current electrical-resistivity sounding data.

Depositional environments and cyclo- and chronostratigraphy of uppermost Carboniferous-Lower Triassic -lacustrine deposits, southern Bogda Mountains, NW China - A terrestrfluvialial paleoclimatic record of mid-latitude NE Pangea

USGS Publications Warehouse

Yang, W.; Feng, Q.; Liu, Yajing; Tabor, N.; Miggins, D.; Crowley, J.L.; Lin, J.; Thomas, S.

2010-01-01

Two uppermost Carboniferous–Lower Triassic fluvial–lacustrine sections in the Tarlong–Taodonggou half-graben, southern Bogda Mountains, NW China, comprise a 1834 m-thick, relatively complete sedimentary and paleoclimatic record of the east coast of mid-latitude NE Pangea. Depositional environmental interpretations identified three orders (high, intermediate, and low) of sedimentary cycles. High-order cycles (HCs) have five basic types, including fluvial cycles recording repetitive changes of erosion and deposition and lacustrine cycles recording repetitive environmental changes associated with lake expansion and contraction. HCs are grouped into intermediate-order cycles (ICs) on the basis of systematic changes of thickness, type, and component lithofacies of HCs. Nine low-order cycles (LCs) are demarcated by graben-wide surfaces across which significant long-term environmental changes occurred. A preliminary cyclostratigraphic framework provides a foundation for future studies of terrestrial climate, tectonics, and paleontology in mid-latitude NE Pangea.Climate variabilities at the intra-HC, HC, IC, and LC scales were interpreted from sedimentary and paleosol evidence. Four prominent climatic shifts are present: 1) from the humid–subhumid to highly-variable subhumid–semiarid conditions at the beginning of Sakamarian; 2) from highly-variable subhumid–semiarid to humid–subhumid conditions across the Artinskian-Capitanian unconformity; 3) from humid–subhumid to highly-variable subhumid–semiarid conditions at early Induan; and 4) from the highly-variable subhumid–semiarid to humid–subhumid conditions across the Olenekian-Anisian unconformity. The stable humid–subhumid condition from Lopingian to early Induan implies that paleoclimate change may not have been the cause of the end-Permian terrestrial mass extinction. A close documentation of the pace and timing of the extinction and exploration of other causes are needed. In addition, the semiarid–subhumid conditions from Sakamarian to Artinskian–Kungurian (?) and from middle Induan to end of Olenekian are in conflict with modern mid-latitude east coast meso- and macrothermal humid climate. Extreme continentality, regional orographic effect, and/or abnormal circulation of Paleo-Tethys maybe are possible causes. Our work serves as a rare data point at mid-latitude NE Pangea for climate modeling to seek explanations on the origin(s) of climate variability in NE Pangea from latest Carboniferous to Early Triassic.

The relationship between carbonate facies, volcanic rocks and plant remains in a late Palaeozoic lacustrine system (San Ignacio Fm, Frontal Cordillera, San Juan province, Argentina)

NASA Astrophysics Data System (ADS)

Busquets, P.; Méndez-Bedia, I.; Gallastegui, G.; Colombo, F.; Cardó, R.; Limarino, O.; Heredia, N.; Césari, S. N.

2013-07-01

The San Ignacio Fm, a late Palaeozoic foreland basin succession that crops out in the Frontal Cordillera (Argentinean Andes), contains lacustrine microbial carbonates and volcanic rocks. Modification by extensive pedogenic processes contributed to the massive aspect of the calcareous beds. Most of the volcanic deposits in the San Ignacio Fm consist of pyroclastic rocks and resedimented volcaniclastic deposits. Less frequent lava flows produced during effusive eruptions led to the generation of tabular layers of fine-grained, greenish or grey andesites, trachytes and dacites. Pyroclastic flow deposits correspond mainly to welded ignimbrites made up of former glassy pyroclasts devitrified to microcrystalline groundmass, scarce crystals of euhedral plagioclase, quartz and K-feldspar, opaque minerals, aggregates of fine-grained phyllosilicates and fiammes defining a bedding-parallel foliation generated by welding or diagenetic compaction. Widespread silicified and silica-permineralized plant remains and carbonate mud clasts are found, usually embedded within the ignimbrites. The carbonate sequences are underlain and overlain by volcanic rocks. The carbonate sequence bottoms are mostly gradational, while their tops are usually sharp. The lower part of the carbonate sequences is made up of mud which appear progressively, filling interstices in the top of the underlying volcanic rocks. They gradually become more abundant until they form the whole of the rock fabric. Carbonate on volcanic sandstones and pyroclastic deposits occur, with the nucleation of micritic carbonate and associated production of pyrite. Cyanobacteria, which formed the locus of mineral precipitation, were related with this nucleation. The growth of some of the algal mounds was halted by the progressive accumulation of volcanic ash particles, but in most cases the upper boundary is sharp and suddenly truncated by pyroclastic flows or volcanic avalanches. These pyroclastic flows partially destroyed the carbonate beds and palaeosols. Microbial carbonate clasts, silicified and silica-permineralized tree trunks, log stumps and other plant remains such as small branches and small roots inside pieces of wood (interpreted as fragments of nurse logs) are commonly found embedded within the ignimbrites. The study of the carbonate and volcanic rocks of the San Ignacio Fm allows the authors to propose a facies model that increases our understanding of lacustrine environments that developed in volcanic settings.

Tectonic and climatic controls on continental depositional facies in the Karoo Basin of northern Natal, South Africa

NASA Astrophysics Data System (ADS)

Turner, Brian R.

1986-02-01

The eastern Karoo Basin, South Africa, contains a thick sequence of terrigenous clastic sediments comprising a meanderbelt facies, braided channel facies divided into coarse and fine subfacies, fluviolacustrine facies and aeolian facies. Depositional trends and changes in fluvial style reflect a progressive increase in aridity of the climate under stable tectonic conditions, interrupted by two phases of source area tectonism and the development of fine and coarse clastic wedges of the braided channel subfacies; the latter signifying a short interlude of cool, wet conditions. The fine braided channel subfacies occurs in the upper part of the meanderbelt facies, which was deposited by ephemeral, meandering mixed-load streams of variable discharge and sinuosity, under dry, semi-arid climatic conditions. These deposited complex, internally discordant channel sands and well-developed levee deposits. Following deposition of the coarse braided channel subfacies semi-arid conditions returned and fluvial deposition was dominated by ephemeral, straight to slightly sinuous mixed load streams characterised by simple channel sand bodies. As the aridity of the climate increased, the streams became more localised and carried an increasing proportion of fines. Interbedded with and overlying the fluvial deposits is a mudstone-dominated lacustrine sequence grading up into aeolian sands suggesting a playa lake-type situation. The general absence of evaporites from these sediments is attributed to the fresh nature of the lake waters, as evidenced by the freshwater aquatic organisms and clay-mineral suite, the lack of adequate inflow for solute accumulation and the removal of dust impregnated by salts from the surface of the dry lake bed during the dry season by superheated, upward-spiralling columns of air. Broadly similar environments to the fluvio-lacustrine and aeolian facies sequence are to be found in the Lake Eyre Basin of central Australia and the Okavango "delta" of northern Botswana. The Okavango "delta" model has an important bearing on patterns of fluvial sedimentation in arid regions since it shows many characteristics of temperate, well-vegetated anastomosed fluvial systems despite its location in the Kalahari Desert.

Neogene vegetation and past climate change in the Thakkhola-Mustang Graben (central Nepal).

NASA Astrophysics Data System (ADS)

Adhikari, Basanta Raj; Wagreich, Michael; Draxler, Ilse; Paudayal, Khum N.

2010-05-01

The Thakkhola-Mustang Graben, which reflects Neogene extensional tectonics in the Tibetan Plateau and Himalaya, lies north of the Dhaulagiri-Annapurna ranges and south of the Yarlung-Tsangpo Suture Zone. The basement of Thakkhola-Mustang Graben is made up of Tibetan-Tethyan sedimentary rocks of Paleozoic and Mesozoic ages, which are unconformably overlain by continental debris (more than 850 m) of Neogene to Quaternary age. Stratigraphically, the Thakkhola-Mustang Graben sediments have been divided into five formations namely the Tetang Formation, the Thakkhola Formation, the Sammargaon Formation, the Marpha Formation and the Kaligandaki Formation. Different approaches have been made to study the Neogene sediments in this graben. In this study, we mainly focused on sedimentological and palynological studies of the Thakkhola-Mustang Graben, which provides a basis for discussing the paleo-environmental evolution of the southern continental margin of the Tibetan Plateau towards the end of the Miocene. Field mapping, profile logging, stable carbon and oxygen isotope analysis, and palynological studies were carried out to understand the depositional environment and the paleoclimate. The methodology developed by Zetter (1989) was followed for the pollen extraction. Pollen samples were processed in the laboratory and were studied under the light microscope (LM), which were later transferred to the scanning electron microscope (SEM). A variety of sedimentary environments are recognized including alluvial fan, lacustrine, braided river and glacio-fluvial. Neogene sediments are composed of braided fluvial deposits with lacustrine deposits in different level of the succession. Most of the pollens were found in the lacustrine layers of the Tetang and Thakkhola formations. Pollen analysis shows that the sediments contain dominant alpine trees like Abies, Pinus, Keteleeria, Picea Tsuga and Quercus with some steppe elements like Artemisia, Compositae, Chenopodiaceae, Plantago and Poaceae. The results show that during this period, the southern part of Tibet was covered mainly by steppe vegetation, indicating dry climate. Organic plant material from the Thakkhola and Tetang formations yielded stable carbon isotope (d13C) values between -21.87 to -26.64 permil, indicating the presence of C3 vegetation. However, the d13C values from the carbonates range between -0.62 to 11.08 permil, which shows the mix vegetation of C3 and C4 plants. It is presumed that the paleoclimate during the sediment deposition time of the Thakkhola-Mustang Graben was significantly warmer than the present-day climate. Further study of pollen with LM and SEM is necessary. Reference: Zetter, R., 1989, Methodik und Bedeutung einer routinemäßig kombinierten lichtmikroskopischen und rasterelektronenmikroskopischen Untersuchung fossiler Mikrofloren. Cour. Forsch.-Inst. Senckenberg, Frankfurt am Main, 109, 41-50.

Sedimentology of the lower Karoo Supergroup fluvial strata in the Tuli Basin, South Africa

NASA Astrophysics Data System (ADS)

Bordy, Emese M.; Catuneanu, Octavian

2002-11-01

The Karoo Supergroup in the Tuli Basin (South Africa) consists of a sedimentary sequence (˜450-500 m) composed of four stratigraphic units, namely the informal Basal, Middle and Upper Units, and the formal Clarens Formation. The units were deposited in continental settings from approximately Late Carboniferous to Middle Jurassic. This paper focuses on the ˜60-m-thick Basal Unit, which was examined in terms of sedimentary facies and palaeo-environments based on evidence provided by primary sedimentary structures, palaeo-flow measurements, palaeontological findings, borehole data (59 core descriptions) and stratigraphic relations. Three main facies associations have been identified: (i) gravelstone (breccias and conglomerate-breccias), (ii) sandstone and (iii) fine-grained sedimentary rocks. The coarser facies are interpreted as colluvial fan deposits, possibly associated with glaciogenic diamictites. The sandstone facies association is mainly attributed to channel fills of low sinuosity, braided fluvial systems. The coal-bearing finer-grained facies are interpreted as overbank and thaw-lake deposits, and represent the lower energy correlatives of the sandy channel fills. Sediment aggradation in this fluvio-lacustrine system took place under cold climatic conditions, with floating lake ice likely associated with lacustrine environments. Palaeo-current indicators suggest that the highly weathered, quartz-vein-rich metamorphic rock source of the Basal Unit was situated east-northeast of the study area. The accumulation of the Basal Unit took place within the back-bulge depozone of the Karoo foreland system. In addition to flexural subsidence, the amount of accommodation in this tectonic setting was also possibly modified by extensional tectonism in the later stages of the basin development. Based on sedimentological and biostratigraphic evidence, the coal-bearing fine-grained facies association displays strong similarities with the Vryheid Formation of the main Karoo Basin to the south. The lowermost non-fossiliferous breccias have been correlated before with the Dwyka Group in the main Karoo, and hence the Basal Unit may be regarded as the distal equivalent of the Dwyka and Ecca groups to the south.

Age and isotopic constraints on pleistocene pluvial episodes in the Western Desert, Egypt.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crombie, M. K.; Arvidson, R. E.; Sturchio, N. C.

1997-01-01

North Africa has undergone drastic climatic changes over the past several hundred thousand years. The timing of humid intervals called pluvials was investigated by uranium-series disequilibrium dating of travertines from the Kurkur Oasis, Western Desert, Egypt. The youngest and best dated travertines (70-160 ka) are found in Wadi Kurkur and include spring and lacustrine units exposed as 2 to 3 m high terraces. Travertines having an age of approximately 191-220 ka are exposed by differential erosion as linear mounds produced by spring systems over fracture zones in ancient wadis. The oldest travertines, having ages >260 ka, are extensive, cap limestonemore » units above the oasis, and were deposited in paludal and lacustrine environments. Oxygen isotope ratios were measured for the wadi travertines ({delta}{sup 18}O values ranging from 16.7 to 19.1{per_thousand} SMOW) and for spring mound travertines (18.5-20.5{per_thousand}). Equilibrium oxygen isotope fractionation calculations indicate that the Kurkur travertines were deposited from waters having {delta}{sup 18}O values similar to ancient Western Desert groundwaters ({approx} -11{per_thousand}). The ages of the travertines correspond to times of monsoonal maxima, eustatic sea level high stands and interglacial maxima. Rainfall producing these groundwaters (and travertines) was significantly fractionated during atmospheric transport, in contrast to modern meteoric waters (-2.09{per_thousand}), implying a distant source for the pluvial waters. Increased precipitation, recharge of Western Desert groundwaters, and resultant travertine deposition are interpreted to be consequences of Milankovitch insolation cycle forcing, through enhanced Atlantic and Indian Ocean monsoons during interglacial time periods.« less

Deposition and deformation of stratified rocks in the northern Nia Mensa region of Valles Marineris, Mars

NASA Astrophysics Data System (ADS)

Okubo, C. H.

2016-12-01

Large-scale structural and geologic mapping based on HiRISE (High Resolution Imaging Science Experiment) digital elevation models reveals new details of the depositional environment for the stratified rocks in the northern Nia Mensa region of eastern Candor Chasma, Valles Marineris, Mars. The map area encompasses the contact between massive sedimentary rocks that comprise most of Nia Mensa and the stratified sedimentary and mass-wasting deposits exposed between Nia Mensa and the north wall of eastern Candor Chasma. The area contains a stratified fan-like deposit on the lower slopes of Nia Mensa. The strata within this deposit dip outward at < 10°, away from its morphologic apex, consistent with an origin as a depositional fan (rather than being carved into a fan shape by erosion). Whether this fan has a subaerial or submarine origin has not yet been determined. Additionally, the fan and surrounding stratified rocks exhibit evidence of soft-sediment deformation in the form of clastic dikes and contorted bedding, indicating that these deposits were water-saturated at the time of deformation. Finally, the northern section of the map area encompasses part of a fractured rise, and deposits interpreted as mud flows mantle the top of this rise. Inferred flow directions suggest that the mud erupted out of these fractures. These findings place constraints on the depositional environment of the local stratified bedrock. The presence of the fan deposit indicates that lateral transport was a component in the depositional history of these sediments. Therefore the sediments did not form entirely as a mantling deposit, such as air fall ash or sediments settled out of a water column. The soft-sediment deformation and subsurface mobilized sediments indicate that groundwater was present in the area after emplacement of the stratified deposits, but before its lithification. These findings point to a wet-playa to lacustrine depositional environment.

Riparian landscapes and human habitat preferences during the Hoxnian (MIS 11) Interglacial

NASA Astrophysics Data System (ADS)

Ashton, Nick; Lewis, Simon G.; Parfitt, Simon; White, Mark

2006-07-01

The archaeological, environmental and geological data from Hoxnian Interglacial (Marine Isotope Stage (MIS) 11) sites from Britain are examined to elucidate the type of habitats that humans preferred during this temperate episode. The conclusion is that humans avoided lacustrine situations, but did make use of the full range of resources that fluvial environments provide. This model is strengthened by the examination of other non-archaeological Hoxnian sites. The problem of archaeological visibility in lacustrine sediment sequences is also discussed and methods of identifying other evidence of human presence are suggested that may offset the deficiencies in the lithic record. These include presence of cut-marked bone, micro-debitage and possibly charcoal in fine-grained sediments deposited in distal settings. The reasons for human selection of fluvial situations are discussed. It is concluded that these environments provide a greater diversity of animal, plant and lithic resources, but also are major route-ways through the landscape. Patterns of human site use are identified, which seem to be triggered by local changes in hydrology and drainage, themselves possibly caused by regional changes in climate. Finally, Lower Palaeolithic sites on the interfluves are discussed. Although they lack environmental or dating evidence, it is tentatively suggested that they were used during cooler episodes, when more open conditions prevailed. Copyright

Radiocarbon ages of lacustrine deposits in volcanic sequences of the Lomas Coloradas area, Socorro Island, Mexico

NASA Technical Reports Server (NTRS)

Farmer, J. D.; Farmer, M. C.; Berger, R.

1993-01-01

Extensive eruptions of alkalic basalt from low-elevation fissures and vents on the southern flank of the dormant volcano, Cerro Evermann, accompanied the most recent phase of volcanic activity on Socorro Island, and created the Lomas Coloradas, a broad, gently sloping terrain comprising the southern part of the island. We obtained 14C ages of 4690 +/- 270 BP (5000-5700 cal BP) and 5040 +/- 460 BP (5300-6300 cal BP) from lacustrine deposits that occur within volcanic sequences of the lower Lomas Coloradas. Apparently, the sediments accumulated within a topographic depression between two scoria cones shortly after they formed. The lacrustine environment was destroyed when the cones were breached by headward erosion of adjacent stream drainages. This was followed by the eruption of a thin basaltic flow from fissures near the base of the northernmost cone. The flow moved downslope for a short distance and into the drainages that presently bound the study area on the east and west. The flow postdates development of the present drainage system and may be very recent. Our 14C data, along with historical accounts of volcanic activity over the last century, including submarine eruptions that occurred a few km west of Socorro in early 1993, underscore the high risk for explosive volcanism in this region and the need for a detailed volcanic hazards plan and seismic monitoring.

Diagenesis Along Fractures in an Eolian Sandstone, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Yen, A. S.; Rampe, E. B.; Grotzinger, J. P.; Blake, D. F.; Bristow, T. F.; Chipera, S. J.; Downs, R.; Morris, R. V.; Morrison, S. M.;

Grazing trails formed by soldier fly larvae (Diptera: Stratiomyidae) and their paleoenvironmental and paleoecological implications for the fossil record

USGS Publications Warehouse

Mángano, M. Gabriela; Buatois, Luis A.; Claps, Guillermo L.

1996-01-01

Recent trails formed by soldier fly larvae (Díptera: Stratiomyidae) were examined in a shallow pond in the floodplain of a braided river in Jujuy Province, northwestern Argentina. Collected specimens were identified as Stratiomys convexa van der Wulp. Simple, irregularly meandering trails were produced across the surface of a muddy‐silty substrate. Since soldier fly larvae extend their caudal respiratory tube to the water‐air interface, they are restricted to extremely shallow water. The presence of benthic algal remains within the mouthparts of the larvae suggests a feeding habit of algal grazing. If preserved, these trails would be included in the ichno‐genus Helminthopsis, a common element in ancient freshwater ichno‐faunas. Helminthopsis preserved in pond and lacustrine margin deposits younger than Late Jurassic is regarded as one possible trace fossil analogue of the trails documented herein. Additionally, it is suggested that larvae of many aquatic Diptera with similar ecologic restrictions are potential tracemakers of Helminthopsis and other simple trails in these environments, particularly in post‐Paleozoic deposits. Studies of modern shallow aquatic habitats and reex‐amination of the ichnologic record stress the importance of fly larvae as tracemakers in lake margin and pond ecosystems. Ecologic requirements of soldier fly larvae make them inappropriate analogues of Helminthopsis tracemakers in deeper water, lacustrine settings.

Understanding the History of a Diverse Inverted Landscape: Summary and Plan for Finishing the 1:500k Geologic Map of Aeolis Dorsa, Mars

NASA Astrophysics Data System (ADS)

Jacobsen, R. E.; Burr, D. M.; Peel, S. E.; Borden, R. M.; Boyd, A. S.

2018-06-01

The Aeolis Dorsa region, Mars, consists of highlands and transitional units of the late Noachian, and aeolian/volcaniclastic deposits interleaved with fluvial and lacustrine deposits formed during the Hesperian and Amazonian periods.

Diatoms as Proxies for a Fluctuating Ice Cap Margin, Hvitarvatn, Iceland

NASA Astrophysics Data System (ADS)

Black, J. L.; Miller, G. H.; Geirsdottir, A.

2005-12-01

There are no complete records of terrestrial environmental change for the Holocene (11,000yrs) in Iceland and the status of Icelandic glaciers in the early Holocene remains unclear. It is not even known whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. Icelandic lakes are particularly well suited to address these uncertainties as: 1) Glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) Diagnostic tephras aid the geochronology, 3) Iceland's sensitivity to changes in North Atlantic circulation should produce clear signals in key environmental proxies (diatoms) preserved in lacustrine sequences, and 4) Ice-cap profiles are relatively flat so small changes in the equilibrium line altitude result in large changes in accumulation area. Hence, large changes in ice-sheet margins during the Holocene will impact sedimentation in glacier-dominated lakes and the diatom assemblages at those times. Hvitarvatn is a glacier dominated lake located on the eastern margin of Langjokull Ice Cap in central-western Iceland. The uppermost Hvitarvatn sediments reflect a glacially dominated system with planktonic, silica-demanding diatom taxa that suggest a high dissolved silica and turbid water environment consistent with high fluxes of glacial flour. Below this are Neoglacial sediments deposited when Langjokull was active, but outlet glaciers were not in contact with Hvitarvatn. The diatom assemblage here shows a small increase in abundance, but is still dominated by planktic, silica-demanding taxa. A distinct shift in lake conditions is reflected in the lowermost sediments, composed of predominantly benthic diatoms and deposited in clear water conditions with long growing seasons likely found in an environment with warmer summers than present and with no glacial erosion. Langjokull must have disappeared in the early Holocene for such a diverse, benthic dominated diatom assemblage to flourish.

Depositional environments and paleogeography of the Upper Miocene Wassuk Group, west-central Nevada

USGS Publications Warehouse

Golia, R.T.; Stewart, John H.

1984-01-01

Fluvial and lacustrine deposits of the Miocene Wassuk Group, exposed in Coal Valley, west-central Nevada, are divided into five lithofacies: (1) diatomite, claystone, siltstone, and carbonaceous siltstone deposited in a lake with paludal conditions at the margin; (2) upward-coarsening sequences of sandstone deposited on a delta and fan-delta; (3) channel-form sandstone deposited on a distal braided alluvial plain; (4) clast-supported conglomerate deposited on a proxial braided alluvial plain or distal alluvial fan; and (5) matrix-supported conglomerate deposited on a distal to middle alluvial fan. Petrographic analysis records an upsection change from a predominantly andesitic to a predominantly plutonic provenance. This change, combined with the overall upward-coarsening of the Wassuk Group and the great thickness (2400 m) of the sequence, suggests active uplift and rapid subsidence during deposition of the group. Facies relationships and paleocurrent directions indicate source areas to the south, southeast and west of Coal Valley. The Miocene Wassuk Group was deposited in an intra-arc basin with penecontemporaneous volcanism and tectonic activity. Syndepositional faulting at the southern margin of Coal Valley between 13 and 11 m.y. ago suggests an early episode of northeast-southwest extension prior to the onset of east-west basin and range extension. ?? 1984.

Evidence of orbital forcing in lake-level fluctuations in the Middle Eocene oil shale-bearing lacustrine successions in the Mudurnu-Göynük Basin, NW Anatolia (Turkey)

NASA Astrophysics Data System (ADS)

Ocakoğlu, F.; Açıkalın, S.; Yılmaz, İ. Ö.; Şafak, Ü.; Gökçeoğlu, C.

2012-08-01

Mudurnu-Göynük basin of the Sakarya Zone in NW Anatolia comprises ca. 1500 m thick Paleocene-Eocene terrestrial to shallow marine succession overlying the Late Cretaceous deeper marine progradational fore-arc sediments. Formed in a foreland setting in relation to southerly situated İzmir-Ankara suture zone, this terrestrial succession (regionally known as Kızılçay group) comprises a thin (<200 m) oil shale-bearing lacustrine section with very good cyclic patterns that potentially serves the quantification of stratigraphy and enlightening the origin of cyclicities of various hierarchy. Our detailed facies analysis on three correlative measured sections showed that mudstone, oil shale and thinner limestone alternations characterize the relatively deeper part of the Eocene lake with probable marine intervention, while thicker limestone, coal, marl and occasional oil shale alternations typify the southern relatively freshwater shoal areas. These facies are frequently organized as meter-scale symmetric to asymmetric transgressive-regressive cycles. Spectral analysis of the mudstone beds and the cycles within the lacustrine succession strongly indicates the occurrence of full bands of Milankovitch with the shortest precession cycle (19 ka) at ca. 2.30 m. Our observations further revealed quite rhythmic thin couplets with estimated durations of 365-730 yr that might represent abrupt climatic changes during deposition. On the other hand, longer duration (ca. 1 Ma) of shoaling and deepening trends in the studied sections were attributed basically to varying subsidence due to tectonic loading in the southerly suture zone. Lastly, regarding the distribution of depositional environments we propose that the oil shale exploration activities should be carried out within a 20 km wide E-W running belt while the southern limits of this belt is more prolific for coal resources.

Zooplankton fecal pellets link fossil fuel and phosphate deposits

USGS Publications Warehouse

Porter, K.G.; Robbins, E.I.

1981-01-01

Fossil zooplankton fecal pellets found in thinly bedded marine and lacustrine black shales associated with phosphate, oil, and coal deposits, link the deposition of organic matter and biologically associated minerals with planktonic ecosystems. The black shales were probably formed in the anoxic basins of coastal marine waters, inland seas, and rift valley lakes where high productivity was supported by runoff, upwelling, and outwelling. Copyright ?? 1981 AAAS.

Diverse microbially induced sedimentary structures from 1 Ga lakes of the Diabaig Formation, Torridon Group, northwest Scotland

NASA Astrophysics Data System (ADS)

Callow, Richard H. T.; Battison, Leila; Brasier, Martin D.

2011-08-01

The siliciclastic lacustrine rocks of the ~ 1000 Ma Diabaig Formation, northwest Scotland, contain a remarkable diversity of macroscopic structures on bedding planes that can be compared with various kinds of microbially induced sedimentary structures (MISS). Field sedimentological investigations, combined with laboratory analysis of bedding planes and petrographic study of thin sections have allowed us to characterise a range of depositional environments and document the spectrum of biological structures. MISS are reported from frequently subaerial environments, through commonly submerged facies, and down to permanently sub-wavebase settings. Palaeoenvironmental conditions (water depth, exposure, hydrodynamic energy) control the distribution of MISS within these facies. This demonstrates that mat-forming microbial communities were arguably well adapted to low light levels or periodic exposure. Some MISS from the Diabaig Formation are typical of Precambrian microbial mats, including reticulate fabrics and 'old elephant skin' textures. In addition to these, a number of new and unusual fabrics of putative microbial origin are described, including linear arrays of ridges and grooves (cf. 'Arumberia') and discoidal structures that are comparable with younger Ediacaran fossils such as Beltanelliformis. These observations indicate that benthic microbial ecosystems were thriving in freshwater lake systems ~ 1000 Ma, and indicate how microbially induced sedimentary structures may be applied as facies indicators for Proterozoic lacustrine environments. The discovery of structures closely resembling Ediacaran fossils (cf. Beltanelliformis) also serves to highlight the difficulty of interpreting simple discoidal bedding plane structures as metazoan fossils.

The paleomagnetism of clastic and precipitate deposits in limestone and dolomite caves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Latham, A.G.; Ford, D.C.

1991-03-01

Clastic sediments and calcite precipitates (stalagmites, flowstones, etc.) are abundant in modern limestone caves and normally are the dominant infillings in buried (paleokarst) caves. Clastic sediment fillings are chiefly of fluviatile or local breakdown origin, but lacustrine, colluvial, eolian, and glacial deposits are known. Paleomagnetism has been studied in the fluviatile and lacustrine types: (1) reversal stratigraphy aids dating of geomorphic and paleoclimatic events in the late Pliocene/Pleistocene; (2) fine magnetostratigraphy has yielded estimates of the westward drift. Calcite precipitates (speleothems) may display natural remanent magnetism of either depositional (DRM) or chemical (CRM) origin. NRMs of modern speleothems are primary,more » not diagenetic; CRMs are invariably associated with the degradation of surface organic matter. (1) Coarse reversal stratigraphy dates geomorphic, etc., events and erosion rates. (2) Fine stratigraphy combined with {sup 230}Th:{sup 234}U dating gives high precision estimates of secular variation, westward drift, and rate of change of geomagnetic anomalies in upper Pleistocene and Holocene deposits. Magnetostratigraphy of paleokarst speleothem fillings associated with hydrocarbons in Ordovician limestones suggest a Permian age for the karstification. Potential applications of magnetostratigraphy to paleokarst deposits of many different scales are considerable.« less

Impacts of shore expansion and catchment characteristics on lacustrine thermokarst records in permafrost lowlands, Alaska Arctic Coastal Plain

USGS Publications Warehouse

Lenz, Josefine; Jones, Benjamin M.; Wetterich, Sebastian; Tjallingii, Rik; Fritz, Michael; Arp, Christopher D.; Rudaya, Natalia; Grosse, Guido

2016-01-01

Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation, and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological, and geochemical proxies. Radiocarbon and 210Pb/137Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~1400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the “alder high” that occurred in the region ~4000 cal yr BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were, therefore, archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes.

Marine intervals in Neogene fluvial deposits of western Amazonia

NASA Astrophysics Data System (ADS)

Boonstra, Melanie; Troelstra, Simon; Lammertsma, Emmy; Hoorn, Carina

2014-05-01

Amazonia is one of the most species rich areas on Earth, but this high diversity is not homogeneous over the entire region. Highest mammal and tree-alpha diversity is found in the fluvio-lacustrine Pebas system, a Neogene wetland associated with rapid radiation of species. The estuarine to marine origin of various modern Amazonian fish, plants, and invertebrates has been associated with past marine ingressions into this freshwater Pebas system. The exact nature and age of these invasions is, however, debated. Here we present new evidence from fluvial and fluvio-lacustrine deposits of Neogene age in southeast Colombia, that point to periods of widespread marine conditions in western Amazonia. Our evidence is based on an analysis of marine palynomorphs, such as organic linings of foraminifera and dinoflagellate cysts, present in dark sandy clay sediments that outcrop along the Caqueta and Amazon rivers. Characteristically, the foraminiferal linings can be assigned to three benthic morphotypes only, e.g. Ammonia, Elphidium and Trochammina. This low diversity assemblage is associated with estuarine/marginal marine conditions. No distinct marine elements such as shelf or planktonic species were encountered. The observed foraminiferal linings and dinocyst assemblages are typical for a (eutrophic) shallow marine environment, suggesting that the Pebas freshwater wetland system occasionally changed to (marginal) marine. Although some reworked elements are found, a typical Neogene dinocyst taxon is commonly found supporting in situ deposition. Sedimentological features typical for tidal conditions that are reported for sites in Peru and northeastern Brazil likely relate to these marine ingressions. Sea level changes as well as foreland basin development related to Andes formation may have facilitated the entry of marine water during the Neogene.

Synchronisation of sedimentary records using tephra: A postglacial tephrochronological model for the Chilean Lake District

NASA Astrophysics Data System (ADS)

Fontijn, Karen; Rawson, Harriet; Van Daele, Maarten; Moernaut, Jasper; Abarzúa, Ana M.; Heirman, Katrien; Bertrand, Sébastien; Pyle, David M.; Mather, Tamsin A.; De Batist, Marc; Naranjo, Jose-Antonio; Moreno, Hugo

2016-04-01

Well-characterised tephra horizons deposited in various sedimentary environments provide a means of synchronising sedimentary archives. The use of tephra as a chronological tool is however still widely underutilised in southern Chile and Argentina. In this study we develop a postglacial tephrochronological model for the Chilean Lake District (ca. 38 to 42°S) by integrating terrestrial and lacustrine records. Tephra deposits preserved in lake sediments record discrete events even if they do not correspond to primary fallout. By combining terrestrial with lacustrine records we obtain the most complete tephrostratigraphic record for the area to date. We present glass geochemical and chronological data for key marker horizons that may be used to synchronise sedimentary archives used for palaeoenvironmental, palaeoclimatological and palaeoseismological purposes. Most volcanoes in the studied segment of the Southern Volcanic Zone, between Llaima and Calbuco, have produced at least one regional marker deposit resulting from a large explosive eruption (magnitude ≥ 4), some of which now have a significantly improved age estimate (e.g., the 10.5 ka Llaima Pumice eruption from Llaima volcano). Others, including several units from Puyehue-Cordón Caulle, are newly described here. We also find tephra related to the Cha1 eruption from Chaitén volcano in lake sediments up to 400 km north from source. Several clear marker horizons are now identified that should help refine age model reconstructions for various sedimentary archives. Our chronological model suggests three distinct phases of eruptive activity impacting the area, with an early-to-mid-Holocene period of relative quiescence. Extending our tephrochronological framework further south into Patagonia will allow a more detailed evaluation of the controls on the occurrence and magnitude of explosive eruptions throughout the postglacial.

Paleoweathering features in the Sergi Formation (Jurassic-Cretaceous), northeastern Brazil, and implications for hydrocarbon exploration

NASA Astrophysics Data System (ADS)

Pierini, Cristina; Mizusaki, Ana M.; Pimentel, Nuno; Faccini, Ubiratan F.; Scherer, Claiton M. S.

2010-03-01

Paleoweathering in the Sergi Formation has been classified and analyzed to ascertain its origin and relationship with stratigraphic evolution. The Sergi Formation belongs to the pre-rift sequence of the Recôncavo Basin (northeastern Brazil) and comprises a complex association of eolian and fluvial sandstones and lacustrine mudstones. This formation can be subdivided into three depositional sequences bounded by regional unconformities. Four paleoweathering types, each one related to a distinct origin, have been described in the Sergi Formation: (1) textural mottling, which is distinguished by alternating rock colors as a result of the iron oxide mobilization within mineral phases that evolved under alternating oxidation (yellowish, brownish and reddish shades) and reduction (grayish or greenish hues) conditions; (2) non-textural mottling, which displays a discoloration pattern that is independent of the original rock texture; (3) carbonate concentrations, usually related to carbonate nodule formation, which display a massive internal structure that reveals their origin through continuous growth or crystallization; and (4) banded carbonates (silicified), associated with the beginning of regular surface formation due to the chemical precipitation of carbonates within lacustrine environments. Both mottling color motifs and carbonate accumulation usually represent groundwater oscillation rather than pedogenesis. Only carbonate intraclasts and banded carbonate (silicified) have their origin ascribed to pedogenesis sensu stricto, although the carbonate intraclasts do not represent soil deposits in situ, but calcretes eroded from areas close to channels, and the banded carbonates (silicified) have strong diagenetic modifications. Therefore, it is reasonable to assume that fluvial and meteoric water have controlled paleoweathering evolution as well as deposition, yet both aspects are ruled by the same mechanisms (relief, sedimentation rate and, above all, climate).

Dust deposits on Mars: The 'parna' analog

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Williams, Steven H.

1994-01-01

Parna is an Autralian aboriginal word meaning 'sandy dust'. It has been applied to deposits of clay, silt, and sand which were initially transported by the wind as aggregates, or pellets, of sand size. Parna is distinguished by its silt and clay content, which in some cases exceeds 85% of the total volume of the deposit. Much of the fine-grained playa silt and clay is incorporated into the parna as sand-sized aggregates, which greatly facilitate their transportation and reworking by the wind. Rain following aggregate emplacement can cause their disintegration, rendering the parna immobile by the wind, yet some pellets can survive several wetting/drying episodes. Parna deposits on Earth occur both as dune forms and as sheet deposits which mantle older terrains. In both cases the deposits are typically derived from lacustrine (lake) beds, such as playas. There is substantial evidence to suggest that bodies of water existed on Mars in the past. Thus, the potential is high for lacustrine deposits and the formation of parna on Mars. Although no parna dunes have been identified, it is suggested that the deposits derived from White Rock (-8 deg, 335 deg W), near Mamers Valles (34 deg, 343 deg W), and elsewhere on Mars may represent sheet parna. Data obtained from Mars-94/96 missions and potential landed spacecraft may provide additional evidence for the existence of parna on Mars.

Soft sediment deformation structures in a lacustrine sedimentary succession induced by volcano-tectonic activities: An example from the Cretaceous Beolgeumri Formation, Wido Volcanics, Korea

NASA Astrophysics Data System (ADS)

Ko, Kyoungtae; Kim, Sung Won; Lee, Hong-Jin; Hwang, In Gul; Kim, Bok Chul; Kee, Won-Seo; Kim, Young-Seog; Gihm, Yong Sik

2017-08-01

The Cretaceous Beolgeumri Formation is composed of laminated mudstones intercalated with sandstones, chert, and a bed of lapilli tuff that were deposited in a lacustrine environment at the terminal part of a regional strike-slip fault systems on the southwestern Korean Peninsula. The Beolgeumri Formation contains various types of soft sediment deformation (SSD) structures that are characterized by a wide extent (< 4 km), lateral continuity (< 200 m), and vertical repetition. The SSD structures can be classified into six categories based on their morphological features and deformation styles: 1) fold structures, 2) load structures, 3) water-escape structures, 4) rip-down structures, 5) boudin structures, and 6) synsedimentary fault structures. Field examination of SSD structures together with an analysis of the sedimentological records of the Beolgeumri Formation indicate that the SSD structures formed largely by liquefaction and/or fluidization triggered by ground shaking during earthquakes. To constrain the timing of the development of SSD structures in the Beolgeumri Formation, we conducted sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon age dating of block sized lithic clasts bearing volcaniclastic deposits that conformably underlie (the Mangryeongbong Tuff) and overlie (the Ttandallae Tuff) the Beolgeumri Formation. The Mangryeongbong and Ttandallae Tuffs have ages of 86.63 ± 0.83 Ma and 87.24 ± 0.36 Ma, respectively, indicating that the Beolgeumri Formation was deposited during a short interval between major volcanic eruptions. The large lithic clasts of volcaniclastic deposits suggest that the Beolgeumri Formation was deposited adjacent to an active volcanic edifice(s). Syndepositional magmatic activities are suggested by the occurrence of a lapilli tuff bed in the Beolgeumri Formation and an igneous intrusion (intermediate sill) that is crosscut by a sand dike, as well as the similar age results of the underlying and overlying volcaniclastic deposits. Thus, we infer that the earthquakes that caused the development of SSD structures in the study area were closely related to syndepositional magmatic activities, as is the case for modern tectonic earthquakes around active volcanoes.

Orbital radar studies of paleodrainages in the central Namib Desert

USGS Publications Warehouse

Lancaster, N.; Schaber, G.G.; Teller, J.T.

2000-01-01

Orbital radar images of the central Namib Desert show clearly the extent of relict fluvial deposits associated with former courses of the Tsondab and Kuiseb rivers. South of the Kuiseb River, radar data show the existence of a drainage network developed in calcrete-cemented late Tertiary fluvial deposits. The sand-filled paleovalleys are imaged as radar-dark tones in contrast to the radar-bright interfluves where the calcreted gravels occur. The drainage network developed as a result of local runoff from indurated gravels and channeled surface and subsurface flow to the sites of the many interdune lacustrine deposits found in the area. (C) Elsevier Science Inc., 2000.Orbital radar images of the central Namib Desert show clearly the extent of relict fluvial deposits associated with former courses of the Tsondab and Kuiseb rivers. South of the Kuiseb River, radar data show the existence of a drainage network developed in calcrete-cemented late Tertiary fluvial deposits. The sand-filled paleovalleys are imaged as radar-dark tones in contrast to the radar-bright interfluves where the calcreted gravels occur. The drainage network developed as a result of local runoff from indurated gravels and channeled surface and subsurface flow to the sites of the many interdune lacustrine deposits found in the area.

Late Miocene sedimentary environments in south-western Amazonia (Solimões Formation; Brazil)

PubMed Central

Gross, Martin; Piller, Werner E.; Ramos, Maria Ines; Douglas da Silva Paz, Jackson

2011-01-01

In Miocene times a vast wetland existed in Western Amazonia. Whereas the general development of this amazing ecosystem is well established, many questions remain open on sedimentary environments, stratigraphical correlations as well as its palaeogeographical configuration. Several outcrops located in a barely studied region around Eirunepé (SW Amazonas state, Brazil) were investigated to obtain basic sedimentological data. The observed deposits belong to the upper part of the Solimões Formation and are biostratigraphically dated to the Late Miocene. Vertically as well as laterally highly variable fine-grained clastic successions were recorded. Based on the lithofacies assemblages, these sediments represent fluvial deposits, possibly of an anastomosing river system. Sand bodies formed within active channels and dominant overbank fines are described (levees, crevasse splays/channels/deltas, abandoned channels, backswamps, floodplain paleosols). Lacustrine environments are restricted to local floodplain ponds/lakes. The mollusc and ostracod content as well as very light δ18O and δ13C values, measured on ostracod valves, refer to exclusively freshwater conditions. Based on palaeontological and geological results the existence of a long-lived lake (“Lake Pebas”) or any influx of marine waters can be excluded for that region during the Late Miocene. PMID:26523089

Late Miocene sedimentary environments in south-western Amazonia (Solimões Formation; Brazil).

PubMed

Gross, Martin; Piller, Werner E; Ramos, Maria Ines; Douglas da Silva Paz, Jackson

2011-08-01

In Miocene times a vast wetland existed in Western Amazonia. Whereas the general development of this amazing ecosystem is well established, many questions remain open on sedimentary environments, stratigraphical correlations as well as its palaeogeographical configuration. Several outcrops located in a barely studied region around Eirunepé (SW Amazonas state, Brazil) were investigated to obtain basic sedimentological data. The observed deposits belong to the upper part of the Solimões Formation and are biostratigraphically dated to the Late Miocene. Vertically as well as laterally highly variable fine-grained clastic successions were recorded. Based on the lithofacies assemblages, these sediments represent fluvial deposits, possibly of an anastomosing river system. Sand bodies formed within active channels and dominant overbank fines are described (levees, crevasse splays/channels/deltas, abandoned channels, backswamps, floodplain paleosols). Lacustrine environments are restricted to local floodplain ponds/lakes. The mollusc and ostracod content as well as very light δ 18 O and δ 13 C values, measured on ostracod valves, refer to exclusively freshwater conditions. Based on palaeontological and geological results the existence of a long-lived lake ("Lake Pebas") or any influx of marine waters can be excluded for that region during the Late Miocene.

Early Cretaceous stratigraphy, paleontology, and sedimentary tectonics in Paris overthrust foredeep (western Wyoming and southeastern Idaho) compared with Quaternary features of indo-gangetic plain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorr, J.A. Jr.

1983-08-01

Fluviatile clastics of the nonmarine, early Cretaceous Gannett and Wayan groups were deposited on wet alluvial megafans and on intervening interfan piedmont slopes which declined eastward into more poorly drained lowlands from a western highland source area uplifted episodically by movements of the Paris overthrust. Lacustrine episodes of deposition intercalated Peterson and Draney limestones with Gannett fluvial clastics. Westward marine transgressions (Skull Creek, Mowry) intercalated mixed lacustrine and brackish facies (Smiths and Cokedale formations) into Wayan fluviatile clastics. Newly discovered fossil vertebrate and invertebrate materials (all fragmentary but identifiable) include: Gannett Group - large reptiles including turtles; Thomas Fork Formationmore » - freshwater gastropods and unionid pelecypods, gastroliths, two types of turtles, large reptilian fragments (dinosaur), and abundant dinosaur eggshell fragments; Wayan Formation - perennially aquatic snails, turtles, unidentifiable large reptiles, two types of crocodilians, an iguanodontid dinosaur (Tenontosaurus), an ankylosaurian dinosaur, a large ornithopod dinosaur, gastroliths, abundant and ubiquitous dinosaur eggshell fragments (numerous types and sizes), and miscellaneous unidentifiable small vertebrate bone fragments. A census of analogous modern reptile reproductive behaviors supports the conclusion that the Wayan, and probably also the Gannett, alluvial fan environments were used as upland breeding grounds by dinosaurs and perhaps other reptiles. Comparison of these Early Cretaceous data with observations on the tectonic setting, sedimentology, and biology of the Quaternary indo-gangetic plain suggests many close analogies between the two sedimentary tectonic settings.« less

Engineering geology considerations for park planning, Antelope Island State Park, Davis County, Utah

USGS Publications Warehouse

Hecker, Suzanne; Case, William F.; King, Jon K.; Willis, Grant C.

2000-01-01

Report: 00-1 In the mid-1980s, historically high levels of Great Salt Lake caused damage to park facilities on Antelope Island and destroyed the causeway linking the park to the mainland. Information on the engineering geology of Antelope Islandcan be used to improve park facilities and reduce the risk from geologic hazards and poor construction conditions. Certain characteristics of the geologic environment need to be considered in park planning. During wet cycles, Great Salt Lake may reach static levels of 4,217 feet (1,285.3 m), and wave- and wind-elevated levels locally may reach 6.5 feet (2 m) higher. A probabilistic assessment of the earthquake ground-shaking hazard along the Wasatch Front indicates that peak ground accelerations of approximately 0.20 to 0.30 g have a one-in-ten chance of being exceeded in 50 years on the island. A slope-failure hazard exists locally in colluvial and Lake Bonneville deposits, along the modern shore, and beneath cliffs. Flash-flood and debris-flow hazards exist on alluvial fans. Areas in the southern two-thirds of the island may have a relatively high potential for radon emission. Particular soil types on the island may be expansive, compressible, erodible, impermeable, or susceptible to liquefaction or hydrocompaction. The distribution of most geologic hazards can be defined, and many locations on the island have conditions suitable for construction. Lacustrine sand and gravel deposits are wide-spread and have engineering characteristics that are generally favorable for foundations. However, facilities and roads built close to the modern shoreline may be susceptible to lake flooding and erosion, slope failures, shallow ground water, and burial by active sand dunes. Well-graded (poorly sorted) alluvial-fan deposits are generally most suitable for wastewater disposal, although they may be subject to flooding or be underlain by low-permeability, fine-grained lacustrine deposits.

The Mintom Formation (new): Sedimentology and geochemistry of a Neoproterozoic, Paralic succession in south-east Cameroon

NASA Astrophysics Data System (ADS)

Caron, V.; Ekomane, E.; Mahieux, G.; Moussango, P.; Ndjeng, E.

2010-06-01

This paper presents a lithologic and stratigraphic description of the Neoproterozoic (ante- or syn- Pan-African orogeny) Mintom Formation (new) of southeastern Cameroon, and provides a new facies and geochemical analysis of the sedimentary succession, formerly referred to as the upper Dja series. The Mintom Formation can be subdivided from base to top into four members that record a general increase in carbonate content. The members (all new) from lower to upper are: Kol Member (diamictite and pelite), Metou Member (dolostone), Momibolé Member (calcareous pelite), and Atog Adjap Member (limestone). Although the lithostratigraphic architecture looks very similar to that of well-documented syn- and post-glacial Neoproterozoic deposits, physical evidence of glacial influence is absent. By contrast with other Central African Neoproterozoic carbonates deposited in ramp settings, the succession does not contain open marine facies. Limestones consist of monotonous subhedral microsparitic calcite mosaics and display occasional microbial laminae. These observations force reevaluation of both previous paleoenvironmental interpretations of the deposits and their comparison with neighboring Ediacaran carbonates. We assume that the graded basal succession from diamictite to laminated pelitic facies is compatible with emplacement of mass flow deposits in toe-of-slope setting during regional uplift. Interpretation of the overlying Métou dolostone is uncertain though sedimentological and geochemical properties point to a likely quiet depositional setting. The upper part of the Formation, including the Momibolé and Atog Adjap Members, is conspicuously laminated, in places rhythmically and ripple-bedded, suggesting shallow subaqueous and calm depositional conditions only interrupted by occasional slumps indicative of a locally steepened bottom topography. Evaporitic fabrics and fenestral pores further indicate shallow water, possibly peritidal, environmental conditions. In spite of indications of shale and post-depositional contamination, rare earth elements (REE) plus yttrium (Y) patterns obtained from carbonate samples point to a non-marine origin for the Atog Adjap limestone, but instead deposition in lacustrine or lagoonal settings under freshwater influence. This interpretation suggests that the Mintom Formation formed in a small-scale palaeodepression, isolated from the open marine environment, where confined lagoonal or lacustrine sedimentation developed. The final Neoproterozoic evolution of the Mintom Formation was dominated by erosional features, including striations and stair-cased groove structures reported for the first time here, and revealing the passage of glaciers of likely Ediacaran age.

Grain-Scale Analyses of Curiosity Data at Marias Pass, Gale Crater, Mars: Methods Comparison and Depositional Interpretation

NASA Astrophysics Data System (ADS)

Sacks, L. E.; Edgar, L. A.; Edwards, C. S.; Anderson, R. B.

2016-12-01

Images acquired by the Mars Hand Lens Imager (MAHLI) and the ChemCam Remote Micro Imager (RMI) onboard the Mars Science Laboratory (MSL) Curiosity rover provide grain-scale data that are critical for interpreting sedimentary deposits. At the location informally known as Marias Pass, Curiosity used both cameras to image the nine rock targets used in this study. We used manual point-counts to measure grain size distributions from those images to compare the abilities of the two cameras. The manually derived results were compared to automated grain size data obtained using pyDGS (Digital Grain Size), an open-source python program. Grain size analyses were used to test the lacustrine and aeolian depositional hypotheses for the Murray and Stimson formations at Marias Pass. Results indicate that the MAHLI and RMI instruments, despite their different fields of view and properties, provide comparable grain size measurements. Additionally, pyDGS does not account for grains smaller than a few pixels and thus does not report representative grain size data and should not be used on images with a large fraction of unresolved grains. Finally, the data collected at Marias Pass are consistent with the existing interpretations of the Murray and Stimson formations. The fine-grained results of the Murray formation analyses support lacustrine deposition, while the mean grain size of the Stimson formation is fine to medium sized sand, consistent with aeolian deposition. However, directly above the contact with the Murray formation, larger rip-up clasts of the Murray formation are present in the Stimson formation. It is possible that water was involved at this stage of erosion and re-deposition, prior to aeolian deposition. Additionally, the grain-scale analyses conducted in this study show that the Dust Removal Tool on Curiosity should be used prior to capturing images for grain-scale analysis. Two images of the target informally named Ronan, taken before and after brushing, resulted in dramatically different grain size results, suggesting that the common, thin layer of dust obscured the true grain size distribution. These grain-scale analyses at Marias Pass have important implications for the collection and processing of image data, as well as the depositional environments recorded in Gale crater. Funded by NSF Grant AST-1461200

Overview of DAN/MSL water and chlorine measurements acquired in Gale area for four years of surface observations

NASA Astrophysics Data System (ADS)

Litvak, Maxim

2017-04-01

During more than 4 years MSL Curiosity rover (landed in Gale crater in August 2012) is traveling toward sedimentary layered mound deposited with phyllosilicates and hematite hydrated minerals. Curiosity already traversed more than 14 km and identified lacustrine deposits left from ancient lakes filled Gale area in early history of Mars. Along the traverse the Curiosity rover discovered unique signatures regarding how the Mars environment changed from ancient warm and wet conditions and probably habitable environment to the modern cold and dry climate. We have summarized numerous measurements from the Dynamic Albedo of Neutron (DAN) instrument on Curiosity rover to overview variations of subsurface bound water distribution from the wet to the dry locations, compared it with other MSL measurements and with possible distribution of hydrated minerals and sequence of geological units travelled by Curiosity. We have also performed joint analysis of water and chlorine distributions and compared bulk (down to 0.5 m depth) equivalent chlorine concentrations measured by DAN throughout the Gale area and APXS observations of corresponding local surface targets and drill fines.

Architecture and reservoir quality of low-permeable Eocene lacustrine turbidite sandstone from the Dongying Depression, East China

NASA Astrophysics Data System (ADS)

Munawar, Muhammad Jawad; Lin, Chengyan; Chunmei, Dong; Zhang, Xianguo; Zhao, Haiyan; Xiao, Shuming; Azeem, Tahir; Zahid, Muhammad Aleem; Ma, Cunfei

2018-05-01

The architecture and quality of lacustrine turbidites that act as petroleum reservoirs are less well documented. Reservoir architecture and multiscale heterogeneity in turbidites represent serious challenges to production performance. Additionally, establishing a hierarchy profile to delineate heterogeneity is a challenging task in lacustrine turbidite deposits. Here, we report on the turbidites in the middle third member of the Eocene Shahejie Formation (Es3), which was deposited during extensive Middle to Late Eocene rifting in the Dongying Depression. Seismic records, wireline log responses, and core observations were integrated to describe the reservoir heterogeneity by delineating the architectural elements, sequence stratigraphic framework and lithofacies assemblage. A petrographic approach was adopted to constrain microscopic heterogeneity using an optical microscope, routine core analyses and X-ray diffraction (XRD) analyses. The Es3m member is interpreted as a sequence set composed of four composite sequences: CS1, CS2, CS3 and CS4. A total of forty-five sequences were identified within these four composite sequences. Sand bodies were mainly deposited as channels, levees, overbank splays, lobes and lobe fringes. The combination of fining-upward and coarsening-upward lithofacies patterns in the architectural elements produces highly complex composite flow units. Microscopic heterogeneity is produced by diagenetic alteration processes (i.e., feldspar dissolution, authigenic clay formation and quartz cementation). The widespread kaolinization of feldspar and mobilization of materials enhanced the quality of the reservoir by producing secondary enlarged pores. In contrast, the formation of pore-filling authigenic illite and illite/smectite clays reduced its permeability. Recovery rates are higher in the axial areas and smaller in the marginal areas of architectural elements. This study represents a significant insight into the reservoir architecture and heterogeneity of lacustrine turbidites, and the understanding of compartmentalization and distribution of high-quality sand reservoirs can be applied to improve primary and secondary production in these fields.

Deposition and deformation of fluvial-lacustrine sediments of the Upper Triassic-Lower Jurassic Whitmore Point Member, Moenave Formation, northern Arizona

NASA Astrophysics Data System (ADS)

Tanner, Lawrence H.; Lucas, Spencer G.

2010-01-01

The stratigraphic section of the Upper Triassic-Lower Jurassic Whitmore Point Member of the Moenave Formation at Potter Canyon, Arizona, comprises c. 26 m of gray to black shales and red mudstones interbedded with mainly sheet-like siltstones and sandstones. These strata represent deposition from suspension and sheetflow processes in shallow, perennial meromictic to ephemeral lakes, and on dry mudflats of the terminal floodout of the northward-flowing Moenave stream system. The lakes were small, as indicated by the lack of shoreline features and limited evidence for deltas. Changes in base level, likely forced by climate change, drove the variations between mudflat and perennial lacustrine conditions. Lenticular sandstones that occur across the outcrop face in the same stratigraphic interval in the lower part of the sequence represent the bedload fill of channels incised into a coarsening-upward lacustrine sequence following a fall in base level. These sandstones are distinctive for the common presence of over-steepened bedding, dewatering structures, and less commonly, folding. Deformation of these sandstones is interpreted as aseismic due to the lack of features typically associated with seismicity, such as fault-graded bedding, diapirs, brecciated fabrics and clastic dikes. Rapid deposition of the sands on a fluid-rich substrate produced a reverse density gradient that destabilized, and potentially fluidized the underlying, finer-grained sediments. This destabilization allowed synsedimentary subsidence of most of the channel sands, accompanied by longitudinal rotation and/or ductile deformation of the sand bodies.

Stratigraphic architecture of a fluvial-lacustrine basin-fill succession at Desolation Canyon, Uinta Basin, Utah: Reference to Walthers’ Law and implications for the petroleum industry

USGS Publications Warehouse

Ford, Grace L.; David R. Pyles,; Dechesne, Marieke

2016-01-01

Two large-scale (member-scale) upward patterns are noted: Waltherian, and non-Waltherian. The upward successions in Waltherian progressions record progradation or retrogradation of a linked fluvial-lacustrine system across the area; whereas the upward successions in non-Waltherian progressions record large-scale changes in the depositional system that are not related to progradation or retrogradation of the ancient lacustrine shoreline. Four Waltherian progressions are noted: 1) the Flagstaff Limestone to lower Wasatch Formation member records the upward transition from lacustrine to fluvial—or shallowing-upward succession; 2) the upper Wasatch to Uteland Butte records the upward transition from fluvial to lacustrine—or a deepening upward succession; 3) the Uteland Butte to Renegade Tongue records the upward transition from lacustrine to fluvial—a shallowing-upward succession; and 4) the Renegade Tongue to Mahogany oil shale interval records the upward transition from fluvial to lacustrine—a deepening upward succession. The two non-Waltherian progressions in the study area are: 1) the lower to middle Wasatch, which records the abrupt shift from low to high net-sand content fluvial system, and 2) the middle to upper Wasatch, which records the abrupt shift from high to intermediate net-sand content fluvial system.

A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Grotzinger, J. P.; Sumner, D. Y.; Kah, L. C.; Stack, K.; Gupta, S.; Edgar, L.; Rubin, D.; Lewis, K.; Schieber, J.; Mangold, N.;

A habitable fluvio-lacustrine environment at Yellowknife Bay, Gale crater, Mars.

PubMed

Grotzinger, J P; Sumner, D Y; Kah, L C; Stack, K; Gupta, S; Edgar, L; Rubin, D; Lewis, K; Schieber, J; Mangold, N; Milliken, R; Conrad, P G; DesMarais, D; Farmer, J; Siebach, K; Calef, F; Hurowitz, J; McLennan, S M; Ming, D; Vaniman, D; Crisp, J; Vasavada, A; Edgett, K S; Malin, M; Blake, D; Gellert, R; Mahaffy, P; Wiens, R C; Maurice, S; Grant, J A; Wilson, S; Anderson, R C; Beegle, L; Arvidson, R; Hallet, B; Sletten, R S; Rice, M; Bell, J; Griffes, J; Ehlmann, B; Anderson, R B; Bristow, T F; Dietrich, W E; Dromart, G; Eigenbrode, J; Fraeman, A; Hardgrove, C; Herkenhoff, K; Jandura, L; Kocurek, G; Lee, S; Leshin, L A; Leveille, R; Limonadi, D; Maki, J; McCloskey, S; Meyer, M; Minitti, M; Newsom, H; Oehler, D; Okon, A; Palucis, M; Parker, T; Rowland, S; Schmidt, M; Squyres, S; Steele, A; Stolper, E; Summons, R; Treiman, A; Williams, R; Yingst, A

2014-01-24

The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.

Prokaryotic Community in Lacustrine Sediments of Byers Peninsula (Livingston Island, Maritime Antarctica).

PubMed

Gugliandolo, Concetta; Michaud, Luigi; Lo Giudice, Angelina; Lentini, Valeria; Rochera, Carlos; Camacho, Antonio; Maugeri, Teresa Luciana

2016-02-01

Byers Peninsula (Livingston Island, Antarctica), the largest seasonally ice-free region of the Maritime Antarctica, holds a large number of lakes, ponds, and streams. The prokaryotic structure and bacterial diversity in sediment samples collected during the 2008-2009 austral summer from five inland lakes, two coastal lakes, and an estuarine site were analyzed by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) and 16S rRNA 454 tag pyrosequencing techniques, respectively. Differently from inland lakes, which range around the oligotrophic status, coastal lakes are eutrophic environments, enriched by nutrient inputs from marine animals. Although the prokaryotic abundances (estimated as DAPI stained cells) in sediment samples were quite similar among inland and coastal lakes, Bacteria always far dominated over Archaea. Despite the phylogenetic analysis indicated that most of sequences were affiliated to a few taxonomic groups, mainly referred to Proteobacteria, Bacteroidetes, and Actinobacteria, their relative abundances greatly differed from each site. Differences in bacterial composition showed that lacustrine sediments were more phyla rich than the estuarine sediment. Proteobacterial classes in lacustrine samples were dominated by Betaproteobacteria (followed by Alphaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria), while in the estuarine sample, they were mainly related to Gammaproteobacteria (followed by Deltaproteobacteria, Epsilonproteobacteria, Alphaproteobacteria, and Betaproteobacteria). Higher number of sequences of Alphaproteobacteria, Cyanobacteria, Verrucomicrobia, and Planctomycetes were observed in sediments of inland lakes compared to those of coastal lakes, whereas Chloroflexi were relatively more abundant in the sediments of coastal eutrophic lakes. As demonstrated by the great number of dominant bacterial genera, bacterial diversity was higher in the sediments of inland lakes than that in coastal lakes. Ilumatobacter (Actinobacteria), Gp16 (Acidobacteria), and Gemmatimonas (Gemmatimonadetes) were recovered as dominant genera in both inland and coastal lakes, but not in the estuarine sample, indicating that they may be useful markers of Antarctic lakes. The proximity to the sea, the different lake depths and the external or internal origin of the nutrient sources shape the bacterial communities composition in lacustrine sediments of Byers Peninsula.

Stratigraphic and microfossil evidence for hydroclimate changes over the middle to late Holocene in the northern Bahamas from an inland saline lake

NASA Astrophysics Data System (ADS)

van Hengstum, P. J.; Maale, G. E.; Donnelly, J. P.; Onac, B. P.; Sullivan, R.; Winkler, T. S.; Albury, N. A.

2016-12-01

No Man's Land is one of the largest inland lakes on the Little Bahama Bank in the northern Bahamas, so its paleoenvironmental history may provide insight into how the regional hydroclimate developed over the Holocene. In its modern state, the site is shallow (<3 m), brackish (20.6 psu), 170 m in diameter, and located 700 m from the coastline. Prior to 6400 Cal yrs BP, the accumulation of peat deposits and no aquatic invertebrates (e.g., ostracodes, foraminifera, aquatic mollusks) indicate that the site was a terrestrial ecosystem. However, the site transitioned into a subaqueous freshwater environment at 6400 Cal yrs BP, and the site became a palustrine-lacustrine setting thereafter until 4200 Cal yrs BP. During this time, widespread palustrine-lacustrine carbonate deposition and the appearance of freshwater to low mesohaline microfossils indicates that the lake's salinity was likely oligohaline (charophytes, ostracodes: Candona annae, Cypridopsis vidua, foraminifera: Helenina davescottensis, mollusks: Planorbis, Hydrobia). A salinity increase at 4200 Cal yrs BP is inferred from the appearance of the ostracode Cyprideis americana that typically prefers salinities exceeding 10 psu, and deposition of laminated microbial mats. Thereafter, an organic- rich, algal sapropel unit accumulated that was devoid of any microfossils or mollusks. This unit suggests that the lake hosted a stratified water column, where surface waters supported phytoplankton primary productivity and corrosive or anoxic bottom water conditions either hampered microfossil growth or precluded their preservation. The transition to the modern environment ( 20 psu) at 2600 cal yrs BP is characterized by diversification of brackish ostracodes (Aurila floridana, Dolerocypria inopinata, and Hemicyprideis setipunctata), foraminifera (Elphidium spp., Ammonia beccarii, Triloculina oblonga) and mollusks (Anomalocardia, Cerithidea). Over the middle to late Holocene, it appears that the stratigraphic development and salinity changes in No Man's Land has been driven by groundwater-level rise in response to Holocene sea-level rise, the regional delivery of fresh water from hurricanes, and the meridional position of the Intertropical Convergence Zone.

Wetland evolution in the Qinghai Lake area, China, in response to hydrodynamic and eolian processes during the past 1100 years

NASA Astrophysics Data System (ADS)

Yan, Dada; Wünnemann, Bernd; Hu, Yanbo; Frenzel, Peter; Zhang, Yongzhan; Chen, Kelong

2017-04-01

The Daotanghe riverine wetland in close proximity to the Qinghai Lake was investigated to demonstrate the interrelationships between Qinghai Lake hydrodynamic processes, eolian mobility and ecological conditions during the past 1100 years in response to climate change. We used ostracod assemblages from various sites east of Qinghai Lake and from the sediment core QW15 of Daotanghe Pond and combined them with grain size and geochemical data from the same core. The statistical extraction of grain size endmembers (EM) revealed three different transportation processes responsible for pond-related fluvio-lacustrine, pure fluvial and eolian deposits. Identified seasonal effects (eolian mobility phase) and timing of ice cover are possible tracers for the competing influence between the Asian summer monsoon and the Westerlies in the Daotanghe Wetland and surrounding area. Our results show that ostracod associations and sediment properties are evidence of a fluvio-lacustrine fresh water environment without ingression of Qinghai Lake into the wetland. Hydrodynamic variations coupled with phases of eolian input indicate highly variable water budgets in response to climate-induced effective moisture supply. The Medieval Warm Period (MWP) until about 1270 CE displays generally moist and warm climate conditions with minor fluctuations, likely in response to variations in summer monsoon intensity. The three-partite period of the Little Ice Age (LIA), shows hydrologically unstable conditions between 1350 and 1530 CE with remarkably colder periods, assigned to a prolonged seasonal ice cover. Pond desiccation and replacement by fluvial deposits occurred between 1530 and 1750 CE, superimposed by eolian deposits. The phase 1730-1900 CE is recorded by the re-occurrence of a pond environment with reduced eolian input. Principal Component Analysis (PCA) on ostracod abundances shows similar trends. All three phases of the LIA developed during a weak summer monsoon influence, favoring westerly-derived climate conditions until ca. 1850 CE, in accordance with records from the adjacent regions. Seasonal freezing periods in excess of the average time of frozen water bodies also occurred in periods of the well-known grand solar minima and indicate stronger seasonality, possibly independent from variations in summer monsoon strength but with links to global northern hemispheric climate.

Late Cenozoic lacustrine and climatic environments at Tule Lake, northern Great Basin, USA

USGS Publications Warehouse

Platt, Bradbury J.

1992-01-01

Cores of lake sediment to a depth of 334 m in the town of Tulelake, Siskiyou County, northern California, document the late Cenozoic paleolimnologic and paleoclimatic history of the northwestern edge of the Great Basin. The cores have been dated by radiometric, tephrochronologic and paleomagnetic analyses. Lacustrine diatoms are abundant throughout the record and document a nearly continuous paleolimnologic history of the Tule Lake basin for the last 3 Myr. During most of this time, this basin (Tule Lake) was a relatively deep, extensive lake. Except for a drier (and cooler?) interval recorded by Fragilaria species about 2.4 Ma, the Pliocene is characterized by a dominance of planktonic Aulacoseira solida implying a warm monomictic lake under a climatic regime of low seasonality. Much of the Pleistocene is dominated by Stephanodiscus and Fragilaria species suggesting a cooler, often drier, and highly variable climate. Benthic diatoms typical of alkaline-enriched saline waters commonly appear after 1.0 Ma, and tephrochronology indicates slow deposition and possible hiatuses between about 0.6 and 0.2 Ma. The chronology of even-numbered oxygen isotope stages approximately matches fluctuations in the abundance of Fragilaria since 800 ka indicating that glacial periods were expressed as drier environments at Tule Lake. Glacial and interglacial environments since 150 ka were distinct from, and more variable than, those occurring earlier. The last full glacial period was very dry, but shortly thereafter Tule Lake became a deep, cool lacustrine system indicating a substantial increase in precipitation. Aulacoseira ambigua characterized the latest glacial and Holocene record of Tule Lake. Its distribution indicates that warmer and wetter climates began about 15 ka in this part of the Great Basin. Diatom concentration fluctuates at 41 000 year intervals between 3.0 and 2.5 Ma and at approximately 100 000 year intervals after 1.0 Ma. In the late Pliocene and early Pleistocene, Aulacoseira solida percentages wax and wane in an approximately 400 000 year cycle. The possible response of Tule Lake diatom communities to orbitally-induced insolation cycles underscores the importance of this record for the study of late Cenozoic paleoclimate change. ?? 1992 Springer-Verlag.

Buried Mesozoic rift basins of Moroccan Atlantic continental margin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, N.; Jabour, H.; El Mostaine, M.

1995-08-01

The Atlantic continental margin is the largest frontier area for oil and gas exploration in Morocco. Most of the activity has been concentrated where Upper Jurassic carbonate rocks have been the drilling objectives, with only one significant but non commercial oil discovery. Recent exploration activities have focused on early Mesozoic Rift basins buried beneath the post-rift sediments of the Middle Atlantic coastal plain. Many of these basins are of interest because they contain fine-grained lacustrine rocks that have sufficient organic richness to be classified as efficient oil prone source rock. Location of inferred rift basins beneath the Atlantic coastal plainmore » were determined by analysis of drilled-hole data in combination with gravity anomaly and aeromagnetic maps. These rift basins are characterized by several half graben filled by synrift sediments of Triassic age probably deposited in lacustrine environment. Coeval rift basins are known to be present in the U.S. Atlantic continental margin. Basin modeling suggested that many of the less deeply bored rift basins beneath the coastal plain are still within the oil window and present the most attractive exploration targets in the area.« less

Infill and mire evolution of a typical kettle hole: young ages at great depths (Jackenmoos, Austria)

NASA Astrophysics Data System (ADS)

Götz, Joachim; Salcher, Bernhard

2015-04-01

Kettle holes are very common features in proglacial environments. Myriads of small, often circular shaped lakes are indicative of dead ice slowly melting out after the collapse of glaciers and subsequent burial of glaciofluvial sediments. Many of these lakes transformed into mires during the Postglacial and the Holocene. Still, little is known about the mechanisms leading to mire formation in such environments. We aim to analyse the shape and the postglacial history of infilling and peat accumulation of a typical dead ice kettle using 2D resistivity surveying, core-drilling, 14C dating and palynologic analyses. The kettle hole mire is located within a small kame delta deposit just south of the LGM extend of the Salzach Piedmont glacier (Austria/Germany). Today, the mire is a spot of exceptional high biodiversity and under protection. Sediment core samples extracted in the deepest (c. 10-14 m) and central part of the kettle directly overly lacustrine fine sediments and yielded young ages covering the subatlantic period only. Young ages are in agreement with palynologic results comprising e.g. pollen of secale (rye) and juglans (walnut). However, these deposits are situated beneath a massive water body (10 m), only covered by a thin floating mat. A second, more distally situated drill core indicates the thinning of this water body at the expense of peat deposits covering the Late Glacial to Middle Holocene. Multiple 2D resistivity data support drilling information and enabled us to reconstruct the shape of the basin. The transition from lacustrine sediments to the water body above is characterised by a sharp increase in resistivity. Furthermore, the resistivity pattern within the entire kettle indicates an increase towards the centre, most probably as a result of the changing nutrient content. The postglacial evolution of the mire is in agreement with the concept of "floating mat terrestrialisation", representing a horizontal growth of the floating mat from the edges toward the lake centre. This concept further includes the deposition of strongly hydrated and loose debris peat formations under the floating mat. The process leads to decreasing basal ages from the edge towards the centre and therefore well explains the age distribution in the studied kettle hole.

Stratigraphic distribution of veins in the Murray and Stimson formations, Gale crater, Mars: Implications for ancient groundwater circulation

NASA Astrophysics Data System (ADS)

Nachon, M.; Sumner, D. Y.; Borges, S. R.; Stack, K.; Stein, N.; Watkins, J. A.; Banham, S.; Rivera-Hernandez, F.; Wiens, R. C.; l'Haridon, J.; Rapin, W.; Kronyak, R. E.

2017-12-01

Since landing at Gale crater, Mars, in August 2012, the Curiosity rover has driven through more than 300m of stratigraphy. From the first to the most recent sedimentary rocks explored, light-toned veins have been observed cutting the host-rock and were interpreted as diagenetic features emplaced by hydraulic fracturing. Chemical and mineralogical analyses show they consist of Ca-sulfate. Here we report on the veins' distribution within two geological formations explored more recently by the rover: (a) the Murray Formation that consists mainly of fine-grained laminated rocks that have been interpreted as having been deposited in a former lacustrine environment [1], and (b) the Stimson Formation, which lies unconformably above the Murray, and consists of cross bedded sandstones interpreted as being deposited in a aeolian environment [2]. We have performed a systematic observation of the veins within the MastCam images, from the base of the Murray (Sol 750) up to Sol 1515 [3], described their main geometrical characteristics (e.g. orientation to laminae, relative density, branching). Five veins facies were defined based on veins' geometrical properties, abundance, and host-rock grain size. The distribution of veins facies was placed within the broader stratigraphic context. The distribution of veins within the Murray and Stimson Formations shows strong rheological controls. In the Murray, light-toned veins are present from the basal part of the section up to the most recently explored exposures. Several dense vein outcrops are associated with local variations in host-rock type, suggesting rheological control of fluid circulation. In Stimson sandstones, light-toned veins are also present though much rarer, again possibly due to rheological properties. The light-toned veins represent post depositional fluid circulation, occurring after accumulation of the lacustrine Murray rocks; at least some veins formed after Murray's burial, erosion, and the deposition and lithification of the overlying Stimson aeolian rocks. Given the distribution of veins, ground water was likely present during an extended time interval, spanning a duration of at least millions of years. [1]Grotzinger et al., 2015, DOI: 10.1126/science.aac7575 [2]Banham et al., 2017, this meeting [3]Nachon et al., 2017, AbSciCon #3667

The use of hydroxyacids as geochemical indicators

NASA Technical Reports Server (NTRS)

Cardoso, J. N.; Eglinton, G.

1983-01-01

The distributions of hydroxyacids in a variety of recent and ancient sediments have been determined by gas chromatography-mass spectrometry. A lacustrine sediment (Rostherne Mere, U.K.) and two marine situations (Cariaco Trench, Black Sea) were analyzed as examples of recent depositional environments. Beta-hydroxyacids occurred in all of the recent sediments, consistent with their presumed microbial origin, whereas di- and trihydroxyacids were present in the sediments with a significant higher plant input (Black Sea and Rostherne Mere sediments). The two ancient (Eocene) sediments examined, viz, the Greene River (U.S.) and Messel (Germany) oil shales, contained only trace amounts of hydroxyacids. These results provide evidence that hydroxyacids are in general not well preserved over geological time.

Classification and sedimentary characteristics of lacustrine hyperpycnal channels: Triassic outcrops in the south Ordos Basin, central China

NASA Astrophysics Data System (ADS)

Xian, Benzhong; Wang, Junhui; Gong, Chenglin; Yin, Yu; Chao, Chuzhi; Liu, Jianping; Zhang, Guodong; Yan, Qi

2018-06-01

Subaquatic channels are known as active conduits for the delivery of terrigenous sediments into related marine and lacustrine basins, as well as important targets for hydrocarbon exploration. Compared to submarine channels, lacustrine subaqueous channels created by hyperpycnal flows are understudied. Using well-exposed outcrops collected from three different locations in the southern Ordos Basin, central China, morphologies and architecture of a channelized hyperpycnal system were studied and classified. Six facies associations represent sedimentary processes from strong erosion by bedload dominated hyperpycnal flows, to transitional deposition jointly controlled by bedload and suspended-load dominated hyperpycnal flows, finally to deposition from suspended-load dominated hyperpycnal flows. On the basis of channel morphologies, infilling sediments and sedimentary processes, the documented channels can be classified into four main categories, which are erosional, bedload dominated, suspended-load dominated, and depositional channels. In very proximal and very distal locations, erosional channels and depositional channels serve as two end-members, while in middle areas, bedload-dominated channels and suspended-load dominated channels are transitional types. Erosional channels, as a response to strong erosion from bedload dominated hyperpycnal flows on upper slope, were mainly filled by mud interbedded with thin sand beds. As flow energy decreases, bedload dominated channels develop on middle slopes, which are characterized mainly by under- to balanced sediment infillings with cross-bedded sandstones and/or minor massive sandstones. Compared to bedload dominated channels, suspended-load dominated channels mainly develop in deeper water, and were filled mainly by massive or planar-laminated sandstones. Depositional channels, as a response to suspended-load dominated hyperpycnal flows in deep-water areas, are characterized by thin-medium bed classical turbidites with Bouma sequences and thin- to thick massive sandstones. Such evolution patterns of hyperpycnal channel systems are ascribed to the progressive decrease in flow capacity of hyperpycnal flows, and provide an adequate explanation for the basinward channelization behavior of hyperpycnal systems.

Microbial Fossilization in Mineralizing Environments: Relevance for Mars "EXOPALEONTOLOGY"

NASA Technical Reports Server (NTRS)

Farmer, Jack D.; DesMarais, David J.; Morrison, David (Technical Monitor)

1994-01-01

The goals of post-Viking exobiology include the search for a Martian fossil record. How can we optimize future exploration efforts to search for fossils on Mars? The Precambrian fossil record indicates that key factors for the long-term preservation of microbial fossils include: 1) the rapid entombment and/or replacement of organisms and organic matter by fine-grained, stable mineral phases (e.g. silica, phosphate, and to a lesser extent, carbonate), 2) low-permeability host sediments (maintaining a closed chemical system during early diagenesis), and 3) shallow burial (maintaining post-depositional temperatures and pressures within the stability range for complex organic molecules). Modem terrestrial environments where early mineralization commonly occurs in association with microbial organisms include: subaerial thermal springs and shallow hydrothermal systems, sub-lacustrine springs and evaporites of alkaline lakes, and subsoil environments where hardpans (e.g. calcretes, silcretes) and duricrusts form. Studies of microbial fossilization in such environments provide important insights preservation patterns in Precambrian rocks, while also playing a role in the development of strategies for Mars exopaleontology. The refinement of site priorities for Mars exopaleontology is expected to benefit greatly from high resolution imaging and altimetry acquired during upcoming orbital missions, and especially infrared and gamma ray spectral data needed for determining surface composition. In anticipation of future orbital missions, constraints for identifying high priority mineral deposits on Mars are being developed through analog remote sensing studies of key mineralizing environments on Earth.

The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons

NASA Astrophysics Data System (ADS)

Enzel, Yehouda; Kushnir, Yochanan; Quade, Jay

2015-06-01

A dramatic increase in regional summer rainfall amount has been proposed for the Arabian Peninsula during the middle Holocene (ca. 9-5 ka BP) based on lacustrine sediments, inferred lake levels, speleothems, and pollen. This rainfall increase is considered primarily the result of an intensified Indian summer monsoon as part of the insolation-driven, northward shift of the boreal summer position of the Inter-Tropical Convergence Zone (ITCZ) to over the deserts of North Africa, Arabia, and northwest India. We examine the basis for the proposed drastic climate change in Arabia and the shifts in the summer monsoon rains, by reviewing paleohydrologic lacustrine records from Arabia. We evaluate and reinterpret individual lake-basin status regarding their lacustrine-like deposits, physiography, shorelines, fauna and flora, and conclude that these basins were not occupied by lakes, but by shallow marsh environments. Rainfall increase required to support such restricted wetlands is much smaller than needed to form and maintain highly evaporating lakes and we suggest that rainfall changes occurred primarily at the elevated edges of southwestern, southern, and southeastern Arabian Peninsula. These relatively small changes in rainfall amounts and local are also supported by pollen and speleothems from the region. The changes do not require a northward shift of the Northern Hemisphere summer ITCZ and intensification of the Indian monsoon rainfall. We propose that (a) latitudinal and slight inland expansion of the North African summer monsoon rains across the Red Sea, and (b) uplifted moist air of this monsoon to southwestern Arabia highlands, rather than rains associated with intensification of Indian summer monsoon, as proposed before, increased rains in that region; these African monsoon rains produced the modest paleo-wetlands in downstream hyperarid basins. Furthermore, we postulate that as in present-day, the ITCZ in the Indian Ocean remained at or near the equator all year round, and the Indian summer monsoon, through dynamically induced air subsidence, can reduce rather than enhance summer rainfall in the Levant and neighboring deserts, including Arabia. Our summary suggests a widening to the north of the latitudinal range of the rainfall associated with the North African summer monsoon moisture crossing the Red Sea to the east. We discuss other mechanisms that could have potentially contributed to the formation and maintaining of the modest paleo-wetlands.

Mesozoic non-marine petroleum source rocks determined by palynomorphs in the Tarim Basin, Xinjiang, northwestern China

USGS Publications Warehouse

Jiang, D.-X.; Wang, Y.-D.; Robbins, E.I.; Wei, J.; Tian, N.

2008-01-01

The Tarim Basin in Northwest China hosts petroleum reservoirs of Cambrian, Ordovician, Carboniferous, Triassic, Jurassic, Cretaceous and Tertiary ages. The sedimentary thickness in the basin reaches about 15 km and with an area of 560000 km2, the basin is expected to contain giant oil and gas fields. It is therefore important to determine the ages and depositional environments of the petroleum source rocks. For prospective evaluation and exploration of petroleum, palynological investigations were carried out on 38 crude oil samples collected from 22 petroleum reservoirs in the Tarim Basin and on additionally 56 potential source rock samples from the same basin. In total, 173 species of spores and pollen referred to 80 genera, and 27 species of algae and fungi referred to 16 genera were identified from the non-marine Mesozoic sources. By correlating the palynormorph assemblages in the crude oil samples with those in the potential source rocks, the Triassic and Jurassic petroleum source rocks were identified. Furthermore, the palynofloras in the petroleum provide evidence for interpretation of the depositional environments of the petroleum source rocks. The affinity of the miospores indicates that the petroleum source rocks were formed in swamps in brackish to lacustrine depositional environments under warm and humid climatic conditions. The palynomorphs in the crude oils provide further information about passage and route of petroleum migration, which is significant for interpreting petroleum migration mechanisms. Additionally, the thermal alternation index (TAI) based on miospores indicates that the Triassic and Jurassic deposits in the Tarim Basin are mature petroleum source rocks. ?? Cambridge University Press 2008.

Spectral and chemical characterization of jarosite in a palaeolacustrine depositional environment in Warkalli Formation in Kerala, South India and its implications

NASA Astrophysics Data System (ADS)

Singh, Mahima; Rajesh, V. J.; Sajinkumar, K. S.; Sajeev, K.; Kumar, S. N.

2016-11-01

Coastal cliffs fringing the Arabian Sea near Varkala exhibits the Warkalli Formation of the Tertiary sequence of Kerala, South India, with well-marked occurrence of jarosite associated with other hydrous mineral phases of phyllosilicate family in a palaeo-lacustrine depositional environment. Sandy phyllosilicates dominate the mineral assemblage, but jarosite occurs as a prominent secondary phase formed during acid-sulphate alteration of iron sulphide in this area. Here, we discuss about the potentiality of spectroscopic techniques to identify the possible mineral phases in the collected samples. The samples from the coastal cliffs have been characterized by hyperspectral analysis (VIS-NIR-SWIR), X-ray Diffraction (XRD), Fourier Transform Infra-red Reflectance (FTIR), Electron Probe Microanalysis (EPMA) and Laser Raman spectroscopy. The spectral and chemical analyses have confirmed the jarosite as natrojarosite and phyllosilicate as kaolinite. Other accessory phases have also been identified through XRD. FTIR spectroscopy has played a major role in identifying the major hydrous bonds between the minerals. VIS-NIR-SWIR spectra show several optimum spectral features at 910 nm, 1470 nm, 1849-1864 nm (in the form of a doublet), 1940 nm and 2270 nm, which could be utilised to locate jarosite in the remotely-sensed data. X-ray diffraction peaks helped in the identification of maximum number of minerals (kaolinite, smectite, quartz, feldspar, pyrite, marcasite and hematite) and the variation in jarosite content in the samples. We propose the formation of jarosite in the region by a seasonal, local and temporary development of acidic conditions. Abundance of organic matter in a fluvio-lacustrine environment has developed anaerobic conditions by removing available oxygen through decomposition of organic matter containing sulphur compounds. The sulphur thus liberated combines with hydrogen from water to develop acidic conditions and resulted in the formation of jarosite. The occurrence of jarosite in Warkalli Formation suggests on and off supply of water during diagenesis. Jarosite has been detected as a prominent deposit in several regions on Mars by Mars Exploration rover Opportunity and Mars Reconnaissance Orbiter-Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). This study of jarosite formation in terrestrial environment will influence our understanding on the mineral precipitation, diagenesis and hydration processes on Mars. Additionally, it also shows the importance of spectroscopic techniques like Raman spectrometry to be used in future missions to Mars to further validate the results of orbital spectroscopy.

Hollow Nodules Gas Escape Sedimentary Structures in Lacustrine Deposits on Earth and Gale Crater

NASA Astrophysics Data System (ADS)

Bonaccorsi, R.; Willson, D.; Fairen, A. G.; Baker, L.; McKay, C.; Zent, A.; Mahaffy, P. R.

2015-12-01

Curiosity's Mastcam and MAHLI instruments in Gale Crater (GC) imaged mm-sized circular rimmed hollow nodules (HNs) (Figure 1A), pitting the Sheepbed mudstone of Yellowknife Bay Formation [1,2]. HNs are significantly smaller than the solid nodules within the outcrop, with an external mean diameter of 1.2 mm and an interior one of 0.7 mm [2] Several formation mechanisms of HNs have been discussed, such as: (1) Diagenetic dissolution of soluble mineral phases; or, (2) Gas bubbles released shortly after sediment deposition [1-3]. In an ephemeral pond in Ubehebe Crater (Death Valley, CA) we observed the formation of hollow nodule sedimentary structures produced by gas bubbles (Figure 1C) preserved in smectite-rich mud that are strikingly similar to those imaged in GC (Figure 1A). This finding supports the gas bubble hypothesis [2]. Ubehebe Crater (UC) surface sediment hollow nodules were sampled, imaged, and their internal diameter measured (200 hollow structures) showing similar shape, distribution, and composition to those imaged by Curiosity in GC. UC in-situ observations suggest the gas bubbles were generated within the slightly reducing ephemerally submerged mud. These intra-crater deposits remain otherwise extremely dry year round, i.e., Air_rH ~2-5%; ground H2O wt%: 1-2%; Summer air/ground T: 45-48ºC/67-70ºC [4-5]. Data from the Sample Analysis at Mars (SAM), CheMin, and ChemCam instruments onboard the rover revealed that HNs-bearing mudstone are rich in smectite clay e.g., ~18-20% [6,7] deposited in a neutral to mildly alkaline environment, capturing a period when the surface was potentially habitable [1]. The UC HNs-hosting deposits are also rich in smectite clays (~30%) and occur in an ephemeral shallow freshwater setting [4-5]. If present, surface hollow nodules are easy to find in dry clay-rich mud in lacustrine sediments, so they could represent a new indicator of ephemeral but habitable/inhabited environments on both Earth and early Mars. References: [1] Grotzinger J.P. et al. (2014), Science 343, 124277. [2] Stack et al. (2014) JGR,Planets 119343. [4] Bonaccorsi R. et al. (2012) AGU Fall Meeting, Abstract #P11B-1839. [5] Bonaccorsi, R. et al. (2014) AGU Fall Meeting, Paper #EP53A-3632. [6] McLennan, S.M. et al. (2014) Science 343, 1244734. [7] Ming D.W. et al. (2014) Science, 343, 1245267.

Classification of gravity-flow deposits and their significance for unconventional petroleum exploration, with a case study from the Triassic Yanchang Formation (southern Ordos Basin, China)

NASA Astrophysics Data System (ADS)

Fan, Aiping; Yang, Renchao; (Tom) van Loon, A. J.; Yin, Wei; Han, Zuozhen; Zavala, Carlos

2018-08-01

The ongoing exploration for shale oil and gas has focused sedimentological research on the transport and deposition mechanisms of fine-grained sediments, and more specifically on fine-grained mass-flow deposits. It appears, however, that no easily applicable classification scheme for gravity-flow deposits exists, and that such classifications almost exclusively deal with sandy and coarser sediments. Since the lack of a good classification system for fine-grained gravity flow deposits hampers scientific communication and understanding, we propose a classification scheme on the basis of the mud content in combination with the presumed transport mechanism. This results in twelve types of gravity-flow deposits. In order to show the practical applicability of this classification system, we apply it to the Triassic lacustrine Yanchang Formation in the southern Ordos Basin (China), which contains numerous slumps, debris-flows deposits, turbidites and hyperpycnites. The slumps and debrites occur mostly close to a delta front, and the turbidites and hyperpycnites extend over large areas from the delta slopes into the basin plain. The case study shows that (1) mud cannot only be transported but also deposited under active hydrodynamic conditions; (2) fine-grained gravity-flow constitute a significant part of the lacustrine mudstones and shales; (3) muddy gravity flows are important for the transport and deposition of clastic particles, clay minerals and organic matter, and thus are important mechanisms involved in the generation of hydrocarbons, also largely determining the reservoir capability for unconventional petroleum.

The Mount Edgecumbe tephra deposits, a marker horizon in southeastern Alaska near the Pleistocene-Holocene boundary

USGS Publications Warehouse

Riehle, J.R.; Mann, D.H.; Peteet, D.M.; Engstrom, D.R.; Brew, D.A.; Meyer, C.E.

1992-01-01

Late Pleistocene tephra deposits found from Sitka to Juneau and Lituya Bay are assigned to a source at the Mount Edgecumbe volcanic field, based on similarity of glass compositions to nearvent deposits and on thinning away from Kruzof Island. The sequence of near-vent layers is basaltic andesite and andesite at the base, rhyolite, and mixed dacite and rhyolite on top. The only breaks in the tephra sequence are two 1-mm-thick silt partings in a lake-sediment core, indicating a depositional interval from basaltic andesite to dacite of no more than about a millennium. Tephra deposits at sites >30 km from the vent are solely dacite and rhyolite and are 10,600 to 11,400 14C yr old based on interpretation of 18 radiocarbon ages, including 5 by accelerator mass spectrometry (AMS). Basaltic andesite and andesite deposits nearer the vent are as much as 12,000 yr old. Discrepancy among radiocarbon ages of upland tephra deposits provisionally correlated as the same grainfall is resolvable within ??2 ?? of analytical uncertainty. Comparison of bulk and AMS ages in one sediment core indicates a systematic bias of +600 to +1100 yr for the bulk ages; correlation of tephra deposits among upland and lacustrine sites implies an additional discrepancy of 200-400 yr between upland (relatively too young) and lacustrine ages. In any case, the Mount Edgecumbe tephra deposits are a widespread, latest Pleistocene stratigraphic marker that serves to emphasize the uncertainty in dating biogenic material from southeastern Alaska. ?? 1992.

South Sumatra Basin Province, Indonesia; the Lahat/Talang Akar-Cenozoic total petroleum system

USGS Publications Warehouse

Bishop, Michele G.

2000-01-01

Oil and gas are produced from the onshore South Sumatra Basin Province. The province consists of Tertiary half-graben basins infilled with carbonate and clastic sedimentary rocks unconformably overlying pre-Tertiary metamorphic and igneous rocks. Eocene through lower Oligocene lacustrine shales and Oligocene through lower Miocene lacustrine and deltaic coaly shales are the mature source rocks. Reserves of 4.3 billion barrels of oil equivalent have been discovered in reservoirs that range from pre-Tertiary basement through upper Miocene sandstones and carbonates deposited as synrift strata and as marine shoreline, deltaic-fluvial, and deep-water strata. Carbonate and sandstone reservoirs produce oil and gas primarily from anticlinal traps of Plio-Pleistocene age. Stratigraphic trapping and faulting are important locally. Production is compartmentalized due to numerous intraformational seals. The regional marine shale seal, deposited by a maximum sea level highstand in early middle Miocene time, was faulted during post-depositional folding allowing migration of hydrocarbons to reservoirs above the seal. The province contains the Lahat/Talang Akar-Cenozoic total petroleum system with one assessment unit, South Sumatra.

Features caused by ground ice growth and decay in Late Pleistocene fluvial deposits, Paris Basin, France

NASA Astrophysics Data System (ADS)

Bertran, Pascal; Andrieux, Eric; Bateman, Mark; Font, Marianne; Manchuel, Kevin; Sicilia, Deborah

2018-06-01

Last Glacial fluvial sequences in the Paris Basin show laminated lacustrine deposits OSL and radiocarbon dated to between 24.6 and 16.6 ka in one site and overlying alluvial sandy gravel. A thermokarst origin of the lakes is supported by abundant traces of ground ice, particularly ice wedge pseudomorphs beneath the lacustrine layers and synsedimentary deformation caused by thaw settlement. The features include brittle deformation (normal and reverse faults) resulting from ground subsidence owing to ice melting and ductile deformations caused by slumping of the sediments heaved by the growth of ice-cored mounds. These correspond to lithalsas (or lithalsa plateaus) and/or to open system pingos. At least two generations of thermokarst are recorded and may reflect the millennial climate variability typical of the Last Glacial. The structures studied in quarries are associated with an undulating topography visible in 5-m DEMs and a spotted pattern in aerial photographs. The search for similar patterns in the Paris Basin indicates that many other potential thermokarst sites exist in the Last Glacial terrace (Fy) of rivers located north of 48°N when they cross the lower Cretaceous sands and marls. In some sites, the presence of organic-poor, fine-grained deposits presumably of lacustrine origin was confirmed by borehole data. The site distribution coincides broadly with that already known for ice wedge pseudomorphs. This study provides new evidence of permafrost-induced ground deformations in France and strongly suggests that thermokarst played a significant and probably largely underestimated role in the genesis of Late Pleistocene landscapes.

Tree-Ring Investigation of Holocene Flood-Deposited Wood From the Oneida Lake Watershed, New York State

Treesearch

Irina P. Panyushkina; Steven W. Leavitt; Eugene W. Domack; Alex C. Wiedenhoeft

2015-01-01

Glacial deposition and fluvial/lacustrine sedimentation interact over terrains in central New York State to preserve a history of geological and hydrological events as well as hydroclimatic transitions. The lower reach of Fish Creek draining the eastern watershed of Oneida Lake, NY, is an area with prominent wood remains. This study explores a collection of 52 logs...

Paleotopographic control of landslides in lacustrine deposits (Trièves plateau, French western Alps)

NASA Astrophysics Data System (ADS)

Bièvre, Grégory; Kniess, Ulrich; Jongmans, Denis; Pathier, Erwan; Schwartz, Stéphane; van Westen, Cees J.; Villemin, Thierry; Zumbo, Vilma

2011-01-01

Paleotopography in Quaternary sedimentary environments can be an important factor that controls landslide movement. This study investigates the relation between paleotopography and landslide activity in two adjacent landslides in glaciolacustrine sediments located in the Trièves area (French western Alps). Although both are in slopes underlain by the same lacustrine deposits, the Avignonet and Harmalière landslides exhibit major differences in morphology and displacement rates. Through a combination of geological mapping, airborne light detection and ranging (LiDAR) data, aerial photographs, global positioning system (GPS), and seismic noise measurements, a three-dimensional impression was made of both landslides. The analysis reveals that the difference in kinematics between the two mass movements can be traced back to at least 50 years ago. The results show that the Harmalière slide, which failed catastrophically in 1981, is still much more active than the Avignonet landslide. The fear was that the Avignonet landslide might develop in a similar catastrophic manner, threatening a number of houses constructed on the landslide. A geophysical survey based on ambient noise measurements allowed us to map the base of the lacustrine clays, and the results indicate the presence of a N-S ridge of hard sediments (Jurassic bedrock and/or compact alluvial layers) on the eastern side of the Avignonet landslide. This ridge disappears when approaching the Harmalière landslide and makes a place to what can be interpreted as a NW-SE oriented paleovalley of the river Drac. We proposed that the ridge acts as a buttress that could mechanically prevent the Avignonet landslide from evolving as fast as the Harmalière. Furthermore, the NW-SE paleovalley located under the Harmalière landslide corresponds to the motion direction of the slide. Therefore, the different behaviour of the two landslides is partly controlled by the paleotopographic setting of Lake Trièves during the last Glacial Maximum extension. These results suggest a major influence of the bedrock paleotopography on the kinematics of the landslides.

Coal depositional models in some Tertiary and Cretaceous coal fields in the U.S. Western Interior

USGS Publications Warehouse

Flores, R.M.

1979-01-01

Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal thickness, lateral continuity, potential minability, and type of floor and roof rocks. The potentially minable, thick coal beds of the Tongue River Member were primarily formed in long-lived floodbasin backswamps of upper alluvial plain environment. Avulsion of meandering fluvial channels contributed to the erratic lateral extent of coals in this environment. Laterally extensive coals formed in floodbasin backswamps of a lower alluvial plain environment; however, interruption by overbank and crevasse-splay sedimentation produced highly split and merging coal beds. Lacustrine sedimentation common to the lower alluvial plain, similar to the lake-covered lower alluvial valley of the Atchafalaya River Basin, is related to a high-constructive delta. In contrast to these alluvial coals are the deltaic coal deposits of the Blackhawk Formation. The formation consists of three coal populations: upper delta plain, lower delta plain, and 'back-barrier'. Coals of the lower delta plain are thick and laterally extensive, in contrast to those of the upper delta plain and 'back-barrier', which contain abundant, very thin and laterally discontinuous carbonaceous shale partings. The reworking of the delta-front sediments of the Star Point Sandstone suggests that the Blackhawk-Star Point delta was a high-destructive system. ?? 1979.

Dating lacustrine episodes in the eastern Sahara by the epimerization of isoleucine in ostrich eggshells

USGS Publications Warehouse

Miller, G.H.; Wendorf, F.; Ernst, R.; Schild, R.; Close, A.E.; Friedman, I.; Schwarcz, H.P.

1991-01-01

The eggshell of the African ostrich, Struthio camelus, closely approximates a closed system for the retention of indigenous proteinaceous residues. Epimerization of the protein amino acid isoleucine follows linear first-order kinetics in laboratory simulations nearly to racemic equilibrium, and the variation in D/L ratio within a single fragment, or between fragments of the same age, is significantly less than in other carbonate systems. These observations suggest that the extent of isoleucine epimerization (aIle/Ile ratio) in ostrich eggshell offers the potential for high-resolution geochronology of Quaternary deposits. From the simulation experiments, and dated early Holocene samples for which we have in situ mean annual sediment temperature measurements, Arrhenius parameters have been calculated; the activation energy is 30.33 kcal mol-1, similar to that of other carbonate systems. We have measured the aIle/Ile ratio in ostrich eggshell associated with lacustrine episodes at Bir Tarfawi and Bir Sahara East, two depressions in what is currently the hyperarid eastern Sahara. The ratios can be used directly to indicate qualitatively the time represented by each series of lake sediment, and to correlate disjunct lacustrine deposits within and between the basins. Uranium-series disequilibrium dating of algal mats contained within some of the lake beds indicate that a major wet interval occurred about 130 ka ago. Using the U-series date for calibration, the amino acid ratios are used to date the most recent lacustrine interval to about 100 ka B.P., and two older intervals, one about 200 ?? 25 ka B.P., and an older interval that occurred prior to 250 ka ago. ?? 1991.

Deposition and evolution of the Sivas basin evaporites (Turkey)

NASA Astrophysics Data System (ADS)

Pichat, Alexandre; Hoareau, Guilhem; Rouchy, Jean-Marie; Ribes, Charlotte; Kergaravat, Charlie; Callot, Jean-Paul; Ringenbach, Jean-Claude

2015-04-01

The Oligo-Miocene Sivas basin (Turkey) is strongly affected by salt tectonics, best expressed in its central part. Halokinesis initiated from the Upper Eocene Hafik formation, composed of thick evaporite layers. Salt tectonics induced the formation of numerous mini basins filled with continental to marine deposits, and nowadays separated by diapiric gypsum walls or welds. Continental deposits filling minibasins developed in arid conditions. Minibasin sandstones are frequently interlayered with evaporitic deposits (gypsum and anhydrite). Two types of depositional evaporites can be distinguished: (i) evaporites precipitated in lacustrine to sebkhaic environment, (ii) gypsarenites resulting from clastic gypsum remobilization. Field observations suggest that both types of depositional evaporites were likely sourced from the recycling of adjacent salt structures. Precipitation of lacustro-sebkhaic evaporites may have been triggered by meteoric waters enriched in dissolved sulfate after the chemical dissolution of outcropping evaporites. Gypsarenite deposits can be explained by mechanical dismantling of nearby evaporite structures. Evaporitic deposits were subsequently involved in active salt tectonics. During periods of quiescent diapirism, thick sebkhaic deposits were also deposited in secondary minibasins located on former salt domes. During periods of diapiric growth, linked to regional compressive tectonics, these deposits were then locally deformed and can show strong flowage textures. When rising diapiric evaporites reached the surface, it was also able to mechanically spread out within the minibasins, forming salt glaciers. In this case, if depositional evaporites were overlying the extruded diapir, both diapiric and depositional evaporites were incorporated in salt tectonic structures. Ongoing chemical analysis should help us to precise more accurately the different sources and the dynamics of these multigeneration evaporites.

A 3400 year paleolimnological record of prehispanic human–environment interactions in the Holmul region of the southern Maya lowlands

USGS Publications Warehouse

Wahl, David B.; Estrada-Belli, Francisco; Anderson, Lysanna

2015-01-01

The timing, magnitude and drivers of late Holocene environmental change in the Holmul region of the southern Maya lowlands are examined by combining paleoenvironmental and archeological data. Environmental proxy analyses on a ~ 3350 cal yr lacustrine sediment record include pollen, charcoal, loss on ignition, magnetic suscep- tibility, and elemental geochemistry. Archeological evidence is derived from extensive settlement surveys conducted near the study site. Results indicate nearby settlement and agricultural activity taking place in an environment characterized by open forest from around 3350 to 950 cal yr BP. The fire history shows a dramatic increase in burning during the Classic period, possibly reflecting changing agricultural strategies. A distinct band of carbonate deposited from 1270 to 1040 cal yr BP suggests decreased hydrologic input associated with drier conditions. Abrupt changes in proxy data around 940 cal yr BP indicate a cessation of human disturbance and local abandonment of the area.

Palaeoenvironmental evolution at Plio-Pleistocene Hominin sites in Western Kenya: Preliminary results

NASA Astrophysics Data System (ADS)

Vincent, Thomas; Whitfield, Elizabeth; Bishop, Laura; Plummer, Thomas; Ditchfield, Peter; Blumenthal, Scott; Finestone, Emma; Kiriakoulakis, Kostas

2017-04-01

This research uses a multiproxy approach to create detailed reconstructions of Plio-Pleistocene hominin landscapes and environments on the Homa Peninsula, western Kenya. Sedimentary sequences associated with this time period, containing hominin archaeological traces and faunal remains, are studied using analyses of particle size, phytoliths and lipid biomarkers. Reconstructing the palaeoenvironmental substrate here is critical in developing an understanding of the activity and behaviour of previous hominin inhabitants. Three archaeological sites exist in the region that form the bases of this research; these include Kanjera South, Nyayanga and Sare River. Research at Kanjera began in the early 20th century, but systematic investigation of the artefact and faunal assemblages of the southern exposures (Kanjera South), dating to ca. 2 Ma, did not begin until 1995. Field investigations and isotopic analyses of palaeosol carbonate nodules and fauna suggested that Kanjera South sediments were deposited in alluvial and lake marginal environments, on a grassy plain between wooded slopes and a permanent water body. Nyayanga and Sare River are new sites which have been little studied until present. Sediments at Nyayanga are thought to be ca. 2.6 Ma, whilst those at Sare River are ca. 1.77 Ma in age. This research refines previous reconstructions of the depositional environment at Kanjera South using analyses of particle size and end member mixing. These suggest that deposition occurred mainly through low-energy, ephemeral flows in a marginal lacustrine environment, with high energy, hyper-concentrated and viscous flows occurring intermittently. In contrast, these same techniques and field investigations at Nyayanga suggest there was a more consistent energy regime here than at Kanjera South, with sediments being deposited under low-energy conditions. Sediment samples at Sare River are undergoing similar analyses. Through detailed analyses of sediments at three archaeological sites, insights into the depositional dynamics of the ca. 2 Ma palaeoenvironments inhabited by hominins have been made accessible.

Carbonate Formation And Diagenesis In Pastos Grandes Laguna (Bolivia): Modern Analog For The South Atlantic Cretaceous Presalt Travertinoid Deposits

NASA Astrophysics Data System (ADS)

Muller, E.; Ader, M.; Gérard, E.; Virgone, A.; Gaucher, E.; Bougeault, C.; Durlet, C.; Moreira, M. A.; Virgile, R.; Vennin, E.; Agogué, H.; Hugoni, M.

2017-12-01

The Cretaceous Presalt travertinoid deposits of the South Atlantic are usually considered as "strange deposits" having poor equivalents in modern environments. Pastos Grandes Laguna, which is located in a 2.9 Ma caldera on the andean-bolivian Altiplano (at 4450 m), is intersected by active faults with hydrothermal fluids and presents a spherulitic plateform with similar sedimentological facies to the Presalt: halite and bedded evaporites, shrub-shaped calcites, ooids, pisolites and various stromatolites. Pastos Grandes Laguna is certainly one of the best modern analog of the Presalt for investigating the on going processes of carbonate deposition and diagenesis and the influence of biology. During two expeditions, we recovered samples of gas, water and microbial mats from the hydrothermal sources to the evaporating zones on the spherulitic plateform. These samples are being analyzed to determine 1) the influence of the gases emitted at the hydrothermal sources (chemical and isotopic composition) on the chemistry of the Laguna and the mineralogy of its sediments and 2) the role of ecosystems that develop in this environment on carbonate formation. Preliminary results on gas composition, corrected for the atmospheric contribution, indicates a magmatic source of CO2 partly mantellic associated with a small crustal contribution. Other initial results have so far indicated that CO2 gas emissions, evaporation, as well as photosynthesis and respiration play a role on water chemistry and carbonate precipitation. This study will contribute to the overall understanding of the role of organisms in sedimentation and the predictive diagenetic evolution of hydrothermal and lacustrine deposits.

Sedimentology and uranium potential of the Inyan Kara Group, near Buffalo Gap, South Dakota. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dandavati, K.S.; Fox, J.E.

1980-04-01

Sedimentary structures, along with textural and compositional evidence gathered from two stratigraphic sections of the Lower Cretaceous Inyan Kara Group in Calico and Fuson Canyons on the southeastern flank of the Black Hills, suggest the following depositional framework: the basal, Chilson Member of the Lakota Formation consists of a series of upward fining sequences deposited in point-bar and flood-plain environments of a northeasterly flowing, meandering river system. Fluvial sandstones in the Chilson include channel-fill, channel margin, crevasse microdelta and levee facies. The Minnewaste Limestone Member and the lower part of the overlying Fuson Member of the Lakota Formation were depositedmore » in low-energy, lacustrine environments. Flood oriented tidal-delta facies overlain by tidal flat deposits in the upper part of the Fuson Member suggest an earlier incursion of the initial Cretaceous seaway, at least locally, than previously documented in the region. Lower Fall River deposits represent northeast-trending barrier bar and northwest-trending deltaic distributary mouth bar facies, reflecting an increase in sediment supply. Upper Fall River sandstones include distributary mouth bar and lower foreshore deposits. Altered sandstones of the basal Chilson Member and the lower part of the Fuson Member in Calico Canyon contain anomalous values of U/sub 3/O/sub 8/. Fossil wood and bone samples are also enriched in trace elements of U, V, and Mo, suggesting that uranium-bearing solutions might have passed through porous and permeable sandstones of the study area, possibly flowing toward the northeast along Chilson paleochannels.« less

Mixed fluvial systems of Messak Sandstone, a deposit of Nubian lithofacies, southwestern Libya

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorenz, J.C.

1987-05-01

The Messak Sandstone is a coarse to pebbly, tabular cross-bedded, Lower Cretaceous deposit of the widespread Nubian lithofacies. It was deposited at the northern edge of the Murzuq basin in southwestern Libya. Although the sedimentary record is predominantly one of braided fluvial systems, a common subfacies within the formation is interpreted to record the passage of straight-crested sand waves across laterally migrating point bars in sinuous rivers, similar to the pattern documented by Singh and Kumar on the modern Ganga and Yamuna Rivers. Because the sand waves were larger on the lower parts of the point bars, lateral migration createdmore » diagnostic thinning-upward, unidirectional cosets of tabular cross-beds as well as fining-upward, grain-size trends. Common, thick, interbedded claystones, deposited in associated paludal and lacustrine environments, and high variance in cross-bed dispersion patterns also suggest the local presence of sinuous fluvial systems within the overall braided regime. The Messak Sandstone contains some of the features that led Harms et al to propose an unconventional low-sinuosity fluvial environment for the Nubian lithofacies in Egypt, and the continuously high water levels of this model may explain channel-scale clay drapes and overturned cross-beds in the Messak. However, most of the Messak characteristics are incompatible with the low-sinuosity model, suggesting instead that the fluvial channels in the Murzuq basin alternated between braided and high-sinuosity patterns.« less

Lithostratigraphie, sédimentologie et évolution de deux bassins molassiques intramontagneux de la chaine Pan-Africaine: la Série pourprée de l'Ahnet, Nord-Ouest du Hoggar, Algérie

NASA Astrophysics Data System (ADS)

Ait-Kaci Ahmed, Ali; Moussine-Pouchkine, Alexis

The study of two of the intermontane molassic basins of the 'Série pourprée de l'Ahnet' shows that they developed independently both in time and space. The characteristics of their thick sedimentary infillings are quite different. The Ouallen basin is filled by essentially fine-grained sediments which were deposited in continental then marine or lacustrine environments; these sediments thicen from east to west. The In Semmen basin is characterised by coarser sediments which were deposited from south to north, in alluvial fan, fluvial, deltaic and slope environments. This basin is also characterised by an episode of carbonate sedimentation leading to the formation of a remarkable thin layer of carbonate, covering the entire sedimentary area, and perhaps related to a volcanic rhyolitic event. The history of the two basins is also marked by obvious tectonic events simultaneous with the sedimentation and related to the recurrent faulting of major Pan-African faults. These led to the formation of very coarse fanglomerates located near the fault scarps, and are probably responsible for the shape and the evolution of the basins.

The diatom genus Actinocyclus in the Western United States

USGS Publications Warehouse

Bradbury, J. Platt; Krebs, William N.; Bradbury, J. Platt; Krebs, William N.

1995-01-01

Ten new and four known taxa of the diatom genus Actinocyclus are described, illustrated, and (or) noted from middle Miocene lake deposits in the Western United States. A key is presented to help separate the taxa based on morphological criteria visible in the light microscope. The geologic ranges of Actinocyclus species in the Western United States are discussed based on examination of over 100 localities of diatomaceous lacustrine deposits.

Lakes or wetlands? A comment on 'The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons' by Enzel et al.

NASA Astrophysics Data System (ADS)

Engel, Max; Matter, Albert; Parker, Adrian G.; Parton, Ash; Petraglia, Michael D.; Preston, Gareth W.; Preusser, Frank

2017-01-01

Enzel et al. (2015) reassess sedimentary records of Early to Mid-Holocene lake sites in Arabia based on a reinterpretation of published multiproxy data and a qualitative analysis of satellite imagery. The authors conclude that these sites represent palaeo-wetland environments rather than palaeolakes and that the majority of the Arabian Peninsula experienced no or, if at all, only a very minor increase of rainfall at that time mainly due to eastward expansion of the East African Summer Monsoon. We disagree with their reassessment and identify several cases where unequivocal evidence for early Late Pleistocene and Early to Mid-Holocene perennial lake environments in Arabia, lasting for centuries to millennia, was neglected by Enzel et al. (2015). Here we summarize findings which indicate the presence of lakes from the sites of Jubbah, Tayma, Mundafan (all Saudi Arabia), Wahalah, Awafi (both UAE), and the Wahiba Sands (Oman), supported by evidence including occurrence of barnacle colonies in living position, remnant bioclastic shoreline deposits, undisturbed varve formation, shallowing-up lacustrine sequences, various aquatic freshwater, brackish and saline micro- and macrofossils, such as ichnofaunal remains, which are the result of prolonged field-based research. While the precise depth, hydrology and ecology of these water bodies is still not entirely resolved, their perennial nature is indicative of a markedly increased precipitation regime, which, in combination with more abundant groundwater and increased spring outflow in terminal basins fed by charged aquifers, was sufficient to overcome evaporative losses. The palaeolakes' influence on sustaining prehistoric populations is corroborated by the presence of rich archaeological evidence.

Chapter 5: Geologic Assessment of Undiscovered Petroleum Resources in the Waltman Shale Total Petroleum System,Wind River Basin Province, Wyoming

USGS Publications Warehouse

Roberts, Steve B.; Roberts, Laura N.R.; Cook, Troy

2007-01-01

The Waltman Shale Total Petroleum System encompasses about 3,400 square miles in the Wind River Basin Province, Wyoming, and includes accumulations of oil and associated gas that were generated and expelled from oil-prone, lacustrine shale source rocks in the Waltman Shale Member of the Paleocene Fort Union Formation. Much of the petroleum migrated and accumulated in marginal lacustrine (deltaic) and fluvial sandstone reservoirs in the Shotgun Member of the Fort Union, which overlies and intertongues with the Waltman Shale Member. Additional petroleum accumulations derived from Waltman source rocks are present in fluvial deposits in the Eocene Wind River Formation overlying the Shotgun Member, and also might be present within fan-delta deposits included in the Waltman Shale Member, and in fluvial sandstone reservoirs in the uppermost part of the lower member of the Fort Union Formation immediately underlying the Waltman. To date, cumulative production from 53 wells producing Waltman-sourced petroleum exceeds 2.8 million barrels of oil and 5.8 billion cubic feet of gas. Productive horizons range from about 1,770 feet to 5,800 feet in depth, and average about 3,400 to 3,500 feet in depth. Formations in the Waltman Shale Total Petroleum System (Fort Union and Wind River Formations) reflect synorogenic deposition closely related to Laramide structural development of the Wind River Basin. In much of the basin, the Fort Union Formation is divided into three members (ascending order): the lower unnamed member, the Waltman Shale Member, and the Shotgun Member. These members record the transition from deposition in dominantly fluvial, floodplain, and mire environments in the early Paleocene (lower member) to a depositional setting characterized by substantial lacustrine development (Waltman Shale Member) and contemporaneous fluvial, and marginal lacustrine (deltaic) deposition (Shotgun Member) during the middle and late Paleocene. Waltman Shale Member source rocks have total organic carbon values ranging from 0.93 to 6.21 weight percent, averaging about 2.71 weight percent. The hydrocarbon generative potential of the source rocks typically exceeds 2.5 milligrams of hydrocarbon per gram of rock and numerous samples had generative potentials exceeding 6.0 milligrams of hydrocarbon per gram of rock. Waltman source rocks are oil prone, and contain a mix of Type-II and Type-III kerogen, indicating organic input from a mix of algal and terrestrial plant matter, or a mix of algal and reworked or recycled material. Thermal maturity at the base of the Waltman Shale Member ranges from a vitrinite reflectance value of less than 0.60 percent along the south basin margin to projected values exceeding 1.10 percent in the deep basin west of Madden anticline. Burial history reconstructions for three wells in the northern part of the Wind River Basin indicate that the Waltman Shale Member was well within the oil window (Ro equal to or greater than 0.65 percent) by the time of maximum burial about 15 million years ago; maximum burial depths exceeded 10,000 feet. Onset of oil generation calculated for the base of the Waltman Shale member took place from about 49 million years ago to about 20 million years ago. Peak oil generation occurred from about 31 million years ago to 26 million years ago in the deep basin west of Madden anticline. Two assessment units were defined in the Waltman Shale Total Petroleum System: the Upper Fort Union Sandstones Conventional Oil and Gas Assessment Unit (50350301) and the Waltman Fractured Shale Continuous Oil Assessment Unit (50350361). The conventional assessment unit primarily relates to the potential for undiscovered petroleum accumulations that are derived from source rocks in the Waltman Shale Member and trapped within sandstone reservoirs in the Shotgun Member (Fort Union Formation) and in the lower part of the overlying Wind River Formation. The potential for Waltman-sourced oil accumulations in fan-delta depos

Magnetic and gravity studies of Mono Lake, east-central, California

USGS Publications Warehouse

Athens, Noah D.; Ponce, David A.; Jayko, Angela S.; Miller, Matt; McEvoy, Bobby; Marcaida, Mae; Mangan, Margaret T.; Wilkinson, Stuart K.; McClain, James S.; Chuchel, Bruce A.; Denton, Kevin M.

2014-01-01

From August 26 to September 5, 2011, the U.S. Geological Survey (USGS) collected more than 600 line-kilometers of shipborne magnetic data on Mono Lake, 20 line-kilometers of ground magnetic data on Paoha Island, 50 gravity stations on Paoha and Negit Islands, and 28 rock samples on Paoha and Negit Islands, in east-central California. Magnetic and gravity investigations were undertaken in Mono Lake to study regional crustal structures and to aid in understanding the geologic framework, in particular regarding potential geothermal resources and volcanic hazards throughout Mono Basin. Furthermore, shipborne magnetic data illuminate local structures in the upper crust beneath Mono Lake where geologic exposure is absent. Magnetic and gravity methods, which sense contrasting physical properties of the subsurface, are ideal for studying Mono Lake. Exposed rock units surrounding Mono Lake consist mainly of Quaternary alluvium, lacustrine sediment, aeolian deposits, basalt, and Paleozoic granitic and metasedimentary rocks (Bailey, 1989). At Black Point, on the northwest shore of Mono Lake, there is a mafic cinder cone that was produced by a subaqueous eruption around 13.3 ka. Within Mono Lake there are several small dacite cinder cones and flows, forming Negit Island and part of Paoha Island, which also host deposits of Quaternary lacustrine sediments. The typical density and magnetic properties of young volcanic rocks contrast with those of the lacustrine sediment, enabling us to map their subsurface extent.

Age and extent of a giant glacial-dammed lake at Yarlung Tsangpo gorge in the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Liu, Weiming; Lai, Zhongping; Hu, Kaiheng; Ge, Yonggang; Cui, Peng; Zhang, Xiaogang; Liu, Feng

2015-10-01

Many glacier dams on major rivers at the southeastern edge of the Tibetan Plateau had been previously determined through remote sensing and glacier terminal position calculation. It was hypothesized that such damming substantially impeded river incision into the plateau interior. Investigation on the large glacial-dammed lake at the entrance of Tsangpo gorge is critical for understanding this hypothesis. So far, the issues, such as age, lake surface elevation, and stages of this dammed lake, are still in debate. Our field survey of lacustrine deposits and loess distribution along the middle Yarlung Tsangpo River and its tributary, Nyang River, suggested that the lake surface elevation was at about 3180 m asl. The 23 quartz optically stimulated luminescence (OSL) and 4 organic AMS 14C ages all fall into the Last Glacial period ( 41-13 ka). The OSL and 14C ages are in general agreement with each other where applicable. There might be only one long damming event because the ages of lacustrine deposits from 2970 to 3100 m asl are similar, and every lacustrine section is sustained for a long time. The estimated lake surface area was 1089 km2, and the volume was 170 km3, which differ from previous estimations which suggested two-stage (about early Holocene and 1.5 ka) lakes, and the largest lake surface elevation reached 3500 m.

The influence of authigenic clay formation on the mineralogy and stable isotopic record of lacustrine carbonates

NASA Astrophysics Data System (ADS)

Bristow, Thomas F.; Kennedy, Martin J.; Morrison, Keith D.; Mrofka, David D.

2012-08-01

The mineralogical, compositional and stable isotopic variability of lacustrine carbonates are frequently used as proxies for ancient paleoenvironmental change in continental settings, under the assumption that precipitated carbonates reflect conditions and chemistry of ancient lake waters. In some saline and alkaline lake systems, however, authigenic clay minerals, forming at or near the sediment water interface, are a major sedimentary component. Often these clays are rich in Mg, influencing the geochemical budget of lake waters, and are therefore expected to influence the properties of contemporaneous authigenic carbonate precipitates (which may also contain Mg). This paper documents evidence for a systematic feedback between clay mineral and carbonate authigenesis through multiple precessionally driven, m-scale sedimentary cycles in lacustrine oil-shale deposits of the Eocene Green River Formation from the Uinta Basin (NE Utah). In the studied section, authigenic, Mg-rich, trioctahedral smectite content varies cyclically between 9 and 39 wt.%. The highest concentrations occur in oil-shales and calcareous mudstones deposited during high lake level intervals that favored sedimentary condensation, lengthening the time available for clay diagenesis and reducing dilution by other siliciclastic phases. An inverse relation between dolomite percentage of carbonate and trioctahedral smectite abundance suggests the Mg uptake during clay authigenesis provides a first order control on carbonate mineralogy that better explains carbonate mineralogical trends than the possible alternative controls of (1) variable Mg/Ca ratios in lake water and (2) degree of microbial activity in sediments. We also observe that cyclical change in carbonate mineralogy, believed to be induced by clay authigenesis, also causes isotopic covariation between δ13CPDB and δ18OPDB of bulk sediments because of differences in the equilibrium fractionation factors of dolomite and calcite (˜2‰ and ˜2.6%, respectively). This provides an alternative mechanism for the common pattern of isotopic covariation, which is typically attributed to the effect of simultaneous changes in water balance and biological activity on the carbon and oxygen isotopic composition of lake waters. These findings may help improve paleoenvironmental reconstructions based on lacustrine carbonate records by adding to the factors known to influence the mineralogical, compositional and stable isotopic signals recorded by lacustrine carbonates.

Investigations of young (< 2.94 Ma) Hadar Formation deposits and their implication for basin development in southern Afar, Ethiopia

NASA Astrophysics Data System (ADS)

DiMaggio, E.; Arrowsmith, R.; Campisano, C. J.; Johnson, R. A.; Deino, A. L.; Warren, M.; Fisseha, S.; Cohen, A. S.

2014-12-01

Sedimentary deposits in Pliocene extensional rift basins in the Afar Depression, Ethiopia chronicle the evolution and paleoenvironmental context of early humans. In the lower Awash Valley, the long-studied Hadar Basin still lacks constraints on basin development during the onset and termination of Hadar Formation (~3.8 - 2.94 Ma) sedimentation. Here we present new mapping and analysis of tephra deposits from a 26 meter-thick section of sediments exposed in the central Ledi-Geraru project area at Gulfaytu, including 20 m of sediments and tephras conformably overlying a 2.94 Ma tephra marker bed (BKT-2U) that previously served as the uppermost dated tephra of the Hadar Formation. Within the overlying 20 meters of primarily lacustrine strata, we identified eight post-BKT-2U tuffs; four were suitable for geochemical characterization, and one yielded an 40Ar/39Ar age of 2.931 ± 0.034 Ma. Based on regional sedimentation rates and the tephra 40Ar/39Ar age, we infer that the newly mapped Hadar Formation at Gulfaytu represents ca. 20 kyr of post-BKT-2 sedimentation. An erosional surface marked by a conglomerate truncates the strata at Gulfaytu, and shows similarities to the well-documented Busidima unconformity surface to the southwest, suggesting that structural changes after 2.93 Ma also affected basin conditions in central Ledi-Geraru. Furthermore, subsurface geophysical investigations support a model whereby deposition rates and the stratigraphic thickness of paleo-Lake Hadar sediments are greatest in the central Ledi-Geraru, ~20 km northeast of the well-exposed lacustrine-dominated sediments of the Hadar Formation. In addition to preserving a record of post-BKT-2 strata, the central Ledi Geraru hosts the thickest subsurface lacustrine sedimentary record within the Hadar Basin hitherto described, making central Ledi-Geraru an ideal location for collecting a continuous core by the Hominin Sites and Paleolakes Drilling Project (HSPDP).

Searching for Ancient Lakebeds in Ladon Basin, Mars and Implications for Future Exploration

NASA Astrophysics Data System (ADS)

Colón, A. M.; Miranda, C.; Milliken, R.

2017-12-01

It is well known from terrestrial studies that clay-rich rocks, and lacustrine mudstones in particular, are efficient at trapping, binding, and preserving organic matter through geologic time. This has also been demonstrated on Mars, where the Curiosity rover has detected organics in ancient mudstones in Gale crater. A number of other potential ancient lake sites have been proposed as landing sties for the Mars 2020 rover, including regions within the Ladon Basin and Valles system. In this study we map of the distribution of clay deposits in the Uzboi-Morava-Ladon (ULM) System, a system thought to have been a series of lakes interconnected by channels, and assess how these hydrous minerals relate to topography, adjacent fluvial networks, and the overall stratigraphy of basin deposits. We use CTX images and near-IR spectral reflectance data from the Mars Reconnaissance Orbiter CRISM instrument to independently map morphological and mineralogical features within Ladon. We find a number of occurrences of stratified, light-toned outcrops within the basin, but individual outcrops are small even at the scale of CTX images and are concentrated in several locations in the basin. Some light-toned outcrops are associated with clay minerals, but in general the light-toned appearance appears to be a poor proxy for clay distribution. CRISM data reveal that some clay-bearing regions are visually indistinct from adjacent clay-poor terrains. Some of the best examples of stratified, clay-bearing rocks are found in Ladon Valles, where they occur in terraces. In general, the stratigraphic, topographic, and morphologic evidence do not preclude a lacustrine origin, but there is no diagnostic evidence to support this interpretation either. The clay-bearing and light-toned deposits within Ladon basin may instead reflect deposition in an alluvial/fluvial system that post-dates the peak period of inferred lacustrine activity in the ULM system.

Anatomy of major coal successions: Facies analysis and sequence architecture of a brown coal-bearing valley fill to lacustrine tract (Upper Valdarno Basin, Northern Apennines, Italy)

NASA Astrophysics Data System (ADS)

Ielpi, Alessandro

2012-07-01

A late Pliocene incised valley fill to lacustrine succession, which contains an interbedded brown coal seam (< 20 m thick), is examined in terms of facies analysis, physical stratigraphy and sequence architecture. The succession (< 50 m thick) constitutes the first depositional event of the Castelnuovo Synthem, which is the oldest unconformity bounded stratigraphic unit of the nonmarine Upper Valdarno Basin, Northern Apennines (Italy). The integration of field surveys and borehole logs identified the following event sequence: first valley filling stages by coarse alluvial fan and channelised streams; the progressive setting of low gradient floodbasins with shallow floodplain lakes; subsequent major waterlogging and extensive peat mire development; and system drowning and establishment of permanent lacustrine conditions. The deposits are grouped in a set of nested valley fills and are arranged as high-frequency depositional sequences. The sequences are bounded by minor erosive truncations and have distinctive upward trends: lowstand system tract thinning; transgressive system tract thickening; highstand system tract thinning and eventual non-deposition; and the smoothing of along-sequence boundary sub-aerial incisions. Such features fit in with the notion of an idealised model where second-order (high-frequency) fluctuations, modulated by first-order (low-frequency) base-level rising, have short-lived standing + falling phases and prolonged transgressions, respectively. Furthermore, the general sequence architecture reveals how a mixed palustrine-siliciclastic system differs substantially from a purely siliciclastic one. In the transgressive phases, terrigenous starvation induces prevailing peat accumulation, generating abnormally thick transgressive system tracts that eventually come to occupy much of the same transgression-generated accommodation space. In the highstand phases, the development of thick highstand system tracts is then prevented by sediment upstream trapping due to retrogressive fluvial aggradations, probably coupled with low-accommodation settings inherited from the transgressive phases.

Discriminating between tectonism and climate signatures in palustrine deposits: Lessons from the Miocene of the Teruel Graben, NE Spain

NASA Astrophysics Data System (ADS)

Alonso-Zarza, Ana M.; Meléndez, Alfonso; Martín-García, Rebeca; Herrero, Mª Josefa; Martín-Pérez, Andrea

2012-07-01

The Upper Miocene (Vallesian-Turolian) Unit II of the Teruel Graben comprises at its top a 25 m-thick sequence of palustrine deposits. Deposition of the entire unit commenced some 9 to 7 Ma ago in a half-graben basin. Here, via a recent quarry, we examine in detail the lateral and vertical distribution of Unit II's palustrine facies and their features to determine the palaeogeography and main controls on deposit formation. Our findings suggest the deposits formed at a low-gradient lake margin with different energy levels. These energy levels controlled the type of primary deposit within the lake; wackestone to packstone sediments formed in low-energy conditions, whereas cross-bedded rudstones to floatstones formed under higher energy conditions, by erosion and redeposition of prior lacustrine deposits. Pedogenic and diagenetic modifications of the primary sediments took place during sedimentary discontinuities (SD) when the lacustrine sediments were subaerially exposed. These processes serve to explain the formation of eight different palustrine limestones: limestones with root traces, mottled limestones, brecciated limestones, flat pebble breccias, granular limestones, micro-karstified limestones with laminar calcretes, carbonate mounds and clayey limestones with laminar calcretes. Based on the features and thicknesses of the modified sediments five different morphological stages (I to V) of palustrine carbonates are defined. Stage I is characterized by incipient mottling and brecciation. Stage II shows mottling and strong brecciation that lead to the formation of intraclast breccias, in which the fragments are mostly "in situ". In Stage III, the primary fabric is totally changed; intraclasts have moved and may have lost their initial morphology. This Stage III may also be characterized by the formation of micro-karst. Stage IV is typified by the presence of coated grains and thin root mats. The chronological data available suggest that the formation of Stage III (lacustrine deposition + palustrine modification) would require about 40,000 yr. Facies and the SD record changes across short horizontal distances, and thus reflect the topography of prior sedimentation/modification events. Small (50 cm) highs with micro-karst have their SD counterparts in lower areas of the lake, in which the SD is indicated by desiccation and mottling. The topographic differences of the micro-karst were filled by intraclastic rudstones sourced by the adjacent carbonate flats. The example examined not only clearly sketches the morphology of ancient palustrine systems or wetlands, it also provides evidence that recycling of previous carbonate deposits played an important role as a sediment source, apart from biogenic or physical-chemical production processes. Our geochemical data indicate LMC (Low Magnesian Calcite) as the main component and Fe contents lower than 1%, except for the mottled areas that are richer in FeO. Stable isotope compositions provide δ18O values close to - 6.5‰ VPDB, and more varied δ13C (- 3.39 to - 6.97‰ PDB). Oxygen and carbon values reveal no covariation and clear trends are lacking. The homogeneity of δ18O values reflects the intense effects of meteoric waters. The deposition of these palustrine limestones took place under suitable semi-arid to sub-humid climates. Climate could also have a role in determining subaerial exposure periods. However, its imprint is not easy to detect neither in the geochemical signals nor in the vertical arrangement of the facies. This could be attributed to climate changes probably occurring over shorter periods than those that can be recorded in this type of sediment, such as the astronomical precession cycles, and suggests the unsuitability of palustrine carbonates for detailed palaeoclimate analyses. Tectonism controlled the location of the main lacustrine depocentre close to the basin's main fault. The activity of this normal fault during the sedimentation of Unit II determined long- and short-term sedimentary sequences. Such sequences are the response to small-scale subsidence pulses followed by the infill of the created accommodation space by shallow lacustrine deposits, which underwent early pedogenic and diagenetic processes after subaerial exposure.

Formation of lacustrine plains in west-central Alaska as a result of permafrost degradation and aggradation

NASA Astrophysics Data System (ADS)

Kanevskiy, M. Z.; Jorgenson, M. T.; Shur, Y.; O'Donnell, J.; Harden, J. W.; Fortier, D.

2012-12-01

Perennially frozen lacustrine sediments containing a large amount of ground ice comprise a significant part of the upper permafrost of the lowlands of west-central Alaska, including Koyukuk Flats and Innoko Flats. Study sites are located in the discontinuous permafrost zone, where permafrost was encountered mainly within uplifted peat plateaus. The upper part of studied sections is formed by frozen peat up to 3 m thick underlain by lacustrine silt, which is mostly ice-rich. Cryogenic structure of lacustrine sediments at different sites has common features: (1) prevalence of layered, braided, and reticulate cryostructures; (2) high variability in the ice content of sediments; (3) high density and low water content of soil aggregates separated by ice lenses. Volume of visible ice in silt reaches at places 40% and more. The thickness of ice lenses generally varies from 1 to 5 cm and occasionally reaches 10 cm. Remnants of peat plateaus are surrounded by unfrozen bogs and fens, formed as a result of thawing and settling of ice-rich lacustrine silt. Modern thermokarst scars initially form at places where ice-rich silt is not protected by a thick layer of organic material. Further development of thermokarst bogs includes lateral enlargement of thaw bulbs and collapsing of the margins of peat plateaus. Lacustrine silt within taliks is covered by woody peat accumulated under forests during the stage of permafrost plateau formation and then by aquatic sphagnum peat accumulated in taliks after collapse. We relate the formation of ice-rich lacustrine sediments to development of lake thermokarst, which affected ice-rich silty yedoma deposits during the transition from Pleistocene to Holocene. Terrain development in lacustrine lowlands of west-central Alaska includes five stages related to permafrost aggradation and degradation from the late Pleistocene to the present time: 1) formation of the ice-rich syngenetic permafrost (yedoma) during the late Pleistocene; 2) yedoma degradation in the yearly Holocene and formation of thaw lakes; 3) complete yedoma degradation under thaw lakes and refreezing of thawed sediments at elevated areas; 4) peat accumulation and freezing of sediments in thaw lake basins; and 5) new cycle of thermokarst and formation of taliks under thaw lakes, bogs and fens. Stages of terrain development of lacustrine lowlands since the Late Pleistocene

Hydrogeology of the Waverly-Sayre area in Tioga and Chemung ounties, New York and Bradford County, Pennsylvania

USGS Publications Warehouse

Reynolds, Richard J.

2002-01-01

The hydrogeology of a 135-square-mile area centered at Waverly, N.Y. and Sayre, Pa. is summarized in a set of five maps and a sheet of geologic sections, all at 1:24,000 scale, that depict locations of wells and test holes (sheet 1), surficial geology (sheet 2), altitude of the water table (sheet 3), saturated thickness of the surficial aquifer (sheet 4), thickness of the lacustrine confining unit (sheet 5), and geologic sections (sheet 6). The valley-fill deposits that form the aquifer system in the Waverly-Sayre area occupy an area of approximately 30 square miles, within the valleys of the Susquehanna River, Chemung River, and Cayuta Creek.The saturated thickness of the surficial aquifer, which consists of alluvium, valley-train outwash, and underlying ice-contact deposits, ranges from zero to 90 feet and is greatest in areas where (1) the outwash is underlain by ice-contact sand and gravel or (2) the outwash is overlain by alluvium and alluvial fans. Estimated transmissivity of the surficial aquifer ranges from 5,600 to 100,270 feet squared per day, and estimated hydraulic conductivity ranges from 50 feet per day for ice-contact deposits to 1,300 feet per day for well-sorted, valley-train outwash.The surficial aquifer is underlain by deposits of lacustrine sand, silt, and clay in the main valleys; these deposits reach thicknesses of as much as 150 ft and form a thick confining unit. Beneath the lacustrine silt and clay confining unit is a thin, discontinuous sand and gravel aquifer whose thickness averages 5 feet but may be as much as 30 feet locally. This confined aquifer supplies many domestic well in the area; yields average about 22 gallons per minute for 6-inch-diameter, open-ended wells. Average annual recharge to the aquifer system is estimated to be approximately 52.5 Mgal/d (million gallons per day), of which 29.7 Mgal/d is from direct precipitation, 7.6 Mgal/d is from unchanneled upland runoff that infiltrates the stratified drift along the valley wall, and 15.2 Mgal/d is from infiltration from tributary streams on the valley floor.

Small-scale lacustrine drifts in Lake Champlain, Vermont

USGS Publications Warehouse

Manley, Patricia L.; Manley, T.O.; Hayo, Kathryn; Cronin, Thomas

2012-01-01

High resolution CHIRP (Compressed High Intensity Radar Pulse) seismic profiles reveal the presence of two lacustrine sediment drifts located in Lake Champlain's Juniper Deep. Both drifts are positive features composed of highly laminated sediments. Drift B sits on a basement high while Drift A is built on a trough-filling acoustically-transparent sediment unit inferred to be a mass-transport event. These drifts are oriented approximately north–south and are parallel to a steep ridge along the eastern shore of the basin. Drift A, located at the bottom of a structural trough, is classified as a confined, elongate drift that transitions northward to become a system of upslope asymmetric mudwaves. Drift B is perched atop a structural high to the west of Drift A and is classified as a detached elongate drift. Bottom current depositional control was investigated using Acoustic Doppler Current Profilers (ADCPs) located across Drift A. Sediment cores were taken at the crest and at the edges of the Drift A and were dated. Drift source, deposition, and evolution show that these drifts are formed by a water column shear with the highest deposition occurring along its crest and western flank and began developing circa 8700–8800 year BP.

High-resolution seismic stratigraphy of an Holocene lacustrine delta in western Lake Geneva (Switzerland)

USGS Publications Warehouse

Baster, I.; Girardclos, S.; Pugin, A.; Wildi, W.

2003-01-01

A high-resolution seismic survey was conducted in western Lake Geneva on a small delta formed by the Promenthouse, the Asse and the Boiron rivers. This dataset provides information on changes in the geometry and sedimentation patterns of this delta from Late-glacial to Present. The geometry of the deposits of the lacustrine delta has been mapped using 300-m spaced grid lines acquired with a 12 kHz Echosounder subbottom profiler. A complete three dimensional image of the sediment architecture was reconstructed through seismic stratigraphic analysis. Six different delta lobes have been recognized in the prodelta area. Depositional centers and lateral extension of the delta have changed through time, indicating migration and fluctuation of river input as well as changes in lake currents and wind regime from the time of glacier retreat to the Present. The delta slope is characterized by a high instability causing stumps developing and by the accumulation of biogenic gas that prevents seismic penetration.

Authigenesis/Diagenesis of the Murray Formation Mudstone in Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Rampe, E. B.; Grotzinger, J. P.; Hurowitz, J. A.; Morris, R. V.; Yen, A. S.; Blake, D. B.; Geller, R.; Sutter, B.

2016-01-01

The Mars Science Laboratory rover Curiosity has been exploring sedimentary deposits in Gale crater since August, 2012. The rover has traversed up section through approximately 150 m of sedimentary rocks deposited in fluvial, deltaic, and lacustrine environments (Bradbury group and overlying Mount Sharp group). The Murray formation lies at the base of the Mt. Sharp group and has been interpreted to be a finely laminated mudstone likely deposited in a subaqueous lacustrine environment. Four drill samples from several elevations in the Murray fm have been acquired by the rover's sampling system and delivered to the CheMin XRD instrument. The lower section of the Murray fm contains 2:1 phyllosilicate(s), hematite, jarosite, XRD amorphous materials, and primary basaltic minerals. Further up section, the Murray fm contains magnetite, cristobalite, tridymite, abundant Si-rich XRD amorphous materials along with plagioclase and K-feldspars. Murray formation materials appear to have been altered under an open hydrologic system based on the bulk chemistry of these materials measured by the Alpha Particle X-ray Spectrometer (APXS). The 2:1 phyllosilicate only occurs in the lowermost section of the Murray fm and may be detrital or formed during authigenesis of Murray fm materials, similar to the Fe-saponite and magnetite detected in a mudstone in the Yellowknife Bay fm near Curiosity's landing site (stratigraphically at the base of the Bradbury group). The occurrence of jarosite and hematite in the lower section indicates an acidic diagenetic event. These phases may have formed via several acidic alteration mechanisms, including (1) oxidative weathering of mafic igneous rocks containing sulfides; (2) sulfuric acid weathering of Fe-bearing phases; and (3) near-neutral pH subsurface solutions rich in Fe2(+) that were rapidly oxidized to Fe3(+), which produced excess acidity. The transition from abundant hematite in the lowermost Murray fm to magnetite moving up section may indicate changes in lake chemistry, i.e., variable redox conditions, possibly during authigenesis or subsequent diagenetic events. Tridymite, a high temperature mineral, (and possibly cristobalite) is detrital, potentially deposited in a lake from a distal silicic volcanic rock source or from crustal materials present prior to the Gale Crater impact event. Abundant Si-rich XRD amorphous materials in the upper sections of the Murray fm may be detrital or an aqueous alteration product of primary igneous phases and phyllosilicates. Curiosity's science team is still deciphering the authigenesis and diagenetic events that formed the Murray fm. The mineralogy and geochemistry of the formation suggest a complicated history with several (many?) episodes of aqueous alteration under a variety of environmental conditions.

Ground-water resources of the Clifton Park area, Saratoga County, New York

USGS Publications Warehouse

Heisig, Paul M.

2002-01-01

Ground water is the sole source of public water supply for Clifton Park, a growing suburban community north of Albany, New York. Increasing water demand, coupled with concerns over ground-water quantity and quality, led the Clifton Park Water Authority in 1995 to initiate a cooperative study with the U.S. Geological Survey to update and refine the understanding of ground-water resources in the area.Ground-water resources are largely associated with three aquifers in the eastern half of the area. These aquifers overlie or encompass the Colonie Channel, a north-south-oriented bedrock channel that is filled primarily with lacustrine glacial deposits. The three aquifers are: (1) an unconfined lacustrine sand aquifer, (2) the Colonie Channel aquifer, which is confined within the deepest parts of the channel and variably confined and unconfined within the shallower, peripheral channel areas, and (3) an unconfined alluvial aquifer beneath the Mohawk River flood plain, which represents the southern limit of the study area. The lacustrine sand aquifer has little potential for large-scale withdrawals because it is predominantly fine grained and is susceptible to contamination from human activities at land surface. Water from this aquifer can, however, recharge the underlying peripheral parts of the Colonie Channel aquifer where hydraulic connections are present. The Colonie Channel aquifer consists of thin sand and gravel and (or) shallow, fractured bedrock over much of the channel area; discontinuous deposits of thicker (more than 20 feet) sand and gravel are common in the peripheral channel areas. The deepest, or central, channel area of this aquifer is isolated from the overlying lacustrine sand aquifer by a continuous lacustrine silt and clay unit, which is the primary channel-fill deposit. The most productive areas of the Colonie Channel aquifer are typically the shallow peripheral areas, where conditions range from unconfined to confined. The most productive aquifer within the area is the alluvial aquifer, which is sustained to an unknown extent by induced infiltration of Mohawk River water.The chemical composition of ground water within the Clifton Park area varies widely in response to hydrogeologic setting, pumpage, and contamination from human activities. These chemical differences can be used to deduce ground-water flow paths within and between the unconfined and confined areas of the aquifer system. Six water types are defined; three are naturally occurring and three are the result of human activities.Precipitation that infiltrates the land surface is the sole source of recharge to the lacustrine sand aquifer; precipitation also recharges the alluvial aquifer and unconfined parts of the Colonie Channel aquifer. Ground-water withdrawals from confined or unconfined peripheral areas of the Colonie Channel aquifer induce flow from recharge areas, from the underlying bedrock, or from other confined aquifer areas.The rate of recharge to the confined central area of the Colonie Channel aquifer appears to be low. Potentiometric levels as much as 100 feet below water-table levels in the overlying lacustrine sand aquifer indicate two large depressions in the potentiometric surface; these depressions indicate that withdrawals from this aquifer have cumulatively exceeded the recharge rates. Localized recharge of the central channel area apparently occurs from two peripheral channel areas that are characterized by zones of elevated water levels and (or) by water chemistry that differs from those within the central channel area. Recharge from, or hydraulic connection with, adjoining segments of the Colonie Channel aquifer to the north and south is likely, but the potential for significant recharge is low because the aquifer is thin and poorly permeable.

Radial ooids from Great Salt Lake (Utah) as paleoenvironmental archives: Insights from radiocarbon chronology and stable isotopes

NASA Astrophysics Data System (ADS)

Paradis, O. P.; Corsetti, F. A.; Bardsley, A.; Hammond, D. E.; Xu, X.; Walker, J. C.

2017-12-01

Ooids (laminated, carbonate coated grains) are ubiquitous in the geologic record in marine and lacustrine settings, and thus remain a common target for geochemical analysis to understand modern and ancient aqueous environments. However, the processes governing ooid formation remain unclear. Recently, radiocarbon dating has revealed that modern marine ooids grow slowly (Beaupre et al. 2015), and laboratory experiments have highlighted the importance of sediment transport and abrasion on net growth rates and ooid size (Trower et al. 2017). Ooid cortex structure includes micritic, tangential and/or radially oriented fabrics. Most modern marine ooids have tangential or micritic cortices, whereas many ancient ooids have radial cortices—thus, there is a need to understand how radial ooids in ancient rocks might inform us about their depositional environment. The Great Salt Lake (GSL), Utah, provides a unique environment to assess the growth rate of primary radial aragonitic ooids. Ooids collected near Antelope Island in the south arm of GSL were sieved, the 355-500 µm fraction was sequentially leached, and 14C of the evolved gas was analyzed to provide a time series of growth. The oldest inorganic carbon of this size fraction has an apparent 14C age of 6600 yr BP, with subsequent growth spanning over 6,000 years. Closed-basin lakes are particularly susceptible to a "reservoir effect" which results in anomalously old apparent radiocarbon ages. The 14C age of the modern dissolved inorganic carbon (DIC) of the south arm was measured to be 295 yr BP, a reservoir age comparable to estimates from lacustrine cave carbonates (McGee et al. 2012). Net growth rate of south arm ooids ranges between 0.01-0.025 µm per year. The δ13C of the outermost cortex suggests that the ooids resemble the modern DIC in the south arm water, suggesting ooids precipitate in equilibrium with lake water. Finer-scale structure in the δ13C of the ooid cortex through time suggests lake level changed in a relative sense, with evidence for a higher lake altitude around 2700 yr BP. We conclude that 1) 14C-dating using sequential leaching methods indicates ooids began forming in Great Salt Lake over 6,000 yr BP and have continued to the present; and 2) lacustrine ooids are robust high-resolution paleoenvironmental archives when paired with radiochronology.

Oligocene-Miocene burial and exhumation of the southernmost Gangdese mountains from sedimentary and thermochronological evidence

NASA Astrophysics Data System (ADS)

Ge, Yukui; Li, Yalin; Wang, Xiaonan; Qian, Xinyu; Zhang, Jiawei; Zhou, Aorigele; Liu-Zeng, Jing

2018-01-01

The Kailas conglomerates crop out ubiquitously along the southernmost boundary of the Gangdese batholith. They unconformably overlie the Gangdese batholith and are displaced by the Great Counter thrust (GCT) fault, forming a fault contact with the Xigaze forearc basin, the associated subduction complex and the Tethyan Himalayan sequence. These strata furnish a record of uplift and paleoenvironmental change in the Indus-Yarlung suture zone during the Oligocene-Miocene. Our new and previously published low-temperature thermochronometric data from the Gangdese batholith and the Kailas conglomerates indicate a period of rapid exhumation beginning approximately 17-15 Ma centered on the southern margin of the Gangdese batholith, whereas regional uplift commenced significantly earlier during the deposition of the Kailas conglomerates, based on the presence of an abrupt facies transition from deep-water lacustrine deposits to red alluvial fan or fluvial deposits. The period of rapid exhumation probably lagged behind the initiation of faster uplift, while the related changes in the depositional environment were most likely recorded immediately in the basin stratigraphy. Subsequently, the Kailas conglomerates were buried in association with the development of the north-directed Great Counter thrust, while rapid exhumation was facilitated by efficient incision by the paleo-Yarlung river at approximately 17-15 Ma.

Waulsortian-type buildups in the lower carboniferous of the Bechar basin, northwestern Sahara of Algeria, North Africa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Setra, A.

1994-03-01

The carboniferous strata in the Bechar basin can be subdivided into three major groups. The lower group is composed of bioclastic and perireefal carbonates. The middle group is exemplified by carbonate platform deposits that were eroded during episodes of emergence by channels of continental derived sediments. The upper group is represented by terrigenous deposits composed mainly of deltaic, fluvial, and lacustrine deposits, with the sporadic presence of coal seams. The carboniferous Waulsortian-type buildups within the Bechar basin occur in the lower group. They are exposed above the desert floor along a south to north-northwest-trending axis, with the younger buildups locatedmore » to the south and the older ones to the north. These bioherms are apparently younger than those recognized in Europe and North America. These Algerian bioherms were initiated and persisted during the time interval represented by the conodont gnathodus bilineatus zone (lower Visean-upper Visean boundary). Although they are younger than their European and North American counterparts that are of Tournaisian-lower Visean age, these mounds appear to have formed in similar environmental and tectono-sedimentary conditions. Their areal extent, geometry, and facies relationships suggest that they were limited to a shelf edge. Their deposition environments range from shallow marine to deep sea.« less

Sedimentological characteristics and depositional processes of sediment gravity flows in rift basins: The Palaeogene Dongying and Shahejie formations, Bohai Bay Basin, China

NASA Astrophysics Data System (ADS)

Liu, Lei; Chen, Hongde; Zhong, Yijiang; Wang, Jun; Xu, Changgui; Chen, Anqing; Du, Xiaofeng

2017-10-01

Sediment gravity flow deposits are common, particularly in sandy formations, but their origin has been a matter of debate and there is no consensus about the classification of such deposits. However, sediment gravity flow sandstones are economically important and have the potential to meet a growing demand in oil and gas exploration, so there is a drive to better understand them. This study focuses on sediment gravity flow deposits identified from well cores in Palaeogene deposits from the Liaodong Bay Depression in Bohai Bay Basin, China. We classify the sediment gravity flow deposits into eight lithofacies using lithological characteristics, grain size, and sedimentary structures, and interpret the associated depositional processes. Based on the scale, spatial distribution, and contact relationships of sediment gravity flow deposits, we defined six types of lithofacies associations (LAs) that reflect transformation processes and depositional morphology: LA1 (unconfined proximal breccia deposits), LA2 (confined channel deposits), LA3 (braided-channel lobe deposits), LA4 (unconfined lobe deposits), LA5 (distal sheet deposits), and LA6 (non-channelized sheet deposits). Finally, we established three depositional models that reflect the sedimentological characteristics and depositional processes of sediment gravity flow deposits: (1) slope-apron gravel-rich depositional model, which involves cohesive debris flows deposited as LA1 and dilute turbidity currents deposited as LA5; (2) non-channelized surge-like turbidity current depositional model, which mainly comprises sandy slumping, suspended load dominated turbidity currents, and dilute turbidity currents deposited as LA5 and LA6; and (3) channelized subaqueous-fan depositional model, which consists of non-cohesive bedload dominated turbidity currents, suspended load dominated turbidity currents, and dilute turbidity currents deposited as LA2-LA5, originating from sustained extrabasinal turbidity currents (hyperpycnal flow). The depositional models may be applicable to oil and gas exploration and production from sediment gravity flow systems in similar lacustrine depositional environments elsewhere.

Surficial geology and stratigraphy of Pleistocene Lake Manix, San Bernardino County, California

USGS Publications Warehouse

Reheis, Marith C.; Redwine, Joanna R.; Wan, Elmira; McGeehin, John P.; VanSistine, D. Paco

2014-01-01

Pluvial Lake Manix and its surrounding drainage basin, in the central Mojave Desert of California, has been a focus of paleoclimate, surficial processes, and neotectonic studies by the U.S. Geological Survey (USGS) since about 2004. The USGS initiated studies of Lake Manix deposits to improve understanding of the paleoclimatic record and the shifts in atmospheric circulation that controlled precipitation in the Mojave Desert. Until approximately 25,000 years ago, Lake Manix was the terminus of the Mojave River, which drains northeasterly from the San Bernardino Mountains; the river currently terminates in the Soda Lake and Silver Lake playas. Pleistocene Lake Manix occupied several subbasins at its maximum extent. This map focuses on the extensive exposures created by incision of the Mojave River and its tributaries into the interbedded lacustrine and alluvial deposits within the central (Cady) and northeastern (Afton) subbasins of Lake Manix, and extends from the head of Afton Canyon to Manix Wash. The map illuminates the geomorphic development and depositional history of the lake and alluvial fans within the active tectonic setting of the eastern California shear zone, especially interactions with the left-lateral Manix fault. Lake Manix left an extraordinarily detailed but complex record of numerous transgressive-regressive sequences separated by desiccation and deposition of fan, eolian, and fluvial deposits, and punctuated by tectonic movements and a catastrophic flood that reconfigured the lake basin. Through careful observation of the intercalated lacustrine and fan sequences and by determining the precise elevations of unit contacts, this record was decoded to understand the response of the lake and river system to the interplay of climatic, geomorphic, and tectonic forces. These deposits are exposed in steep badland topography. Mapping was carried out mostly at scales of 1:12,000, although the map is presented at 1:24,000 scale, and employs custom unit nomenclature, with multiple subdivided lacustrine and alluvial fan units. In addition, many important units are very thin and cannot be mapped separately, or are covered by thin eolian sand, so these are commonly portrayed as stacks of units or combined units. These details are more accurately portrayed in the measured sections that accompany the map. Altitudes of many contacts were obtained using differentially corrected Global Positioning System (GPS) or, in some cases, lidar (light detection and ranging) data.

The depositional environments of Schöningen 13 II-4 and their archaeological implications.

PubMed

Stahlschmidt, Mareike C; Miller, Christopher E; Ligouis, Bertrand; Goldberg, Paul; Berna, Francesco; Urban, Brigitte; Conard, Nicholas J

2015-12-01

Geoarchaeological research at the Middle Pleistocene site of Schöningen 13 II-4, often referred to as the Speerhorizont, has focused on describing and evaluating the depositional contexts of the well-known wooden spears, butchered horses, and stone tools. These finds were recovered from the transitional contact between a lacustrine marl and an overlying organic mud, originally thought to be a peat that accumulated in place under variable moisture conditions. The original excavators proposed that hominin activity, including hunting and butchery, occurred on a dry lake shore and was followed by a rapid sedimentation of organic deposits that embedded and preserved the artifacts. Our geoarchaeological analysis challenges this model. Here, we present evidence that the sediments of Schöningen 13 II-4 were deposited in a constantly submerged area of a paleolake. Although we cannot exclude the possibility that the artifacts were deposited during a short, extreme drying event, there are no sedimentary features indicative of surface exposure in the sediments. Accordingly, this paper explores three main alternative models of site formation: anthropogenic disposal of materials into the lake, a geological relocation of the artifacts, and hunting or caching on lake-ice. These models have different behavioral ramifications concerning hominin knowledge and exploitation of the landscape and their subsistence strategies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Alluvial to lacustrine sedimentation in an endorheic basin during the Mio-Pliocene: The Toro Negro Formation, Central Andes of Argentina

NASA Astrophysics Data System (ADS)

Ciccioli, Patricia L.; Marenssi, Sergio A.; Amidon, William H.; Limarino, Carlos O.; Kylander-Clark, Andrew

2018-07-01

A 2400 m-thick sedimentary column belonging to the Toro Negro Formation was recorded along the Quebrada del Yeso, Sierra de Los Colorados (Vinchina Basin), La Rioja province, NW Argentina. The Vinchina basin is a good example of a closed basin surrounded by the Precordillera fold and thrust belt to the west and basement-cored blocks to the north, south (Western Sierras Pampeanas) and east (Sierra de Famatina). Seven facies associations (FA) are described and interpreted to represent fluvial, lacustrine and alluvial environments developed in the southern part of the Vinchina basin from the Late Miocene until the earliest Pleistocene. The depositional evolution of the formation was divided in four phases. Phase I (∼7-6.6 Ma) represents sedimentation in medial (FA I) to distal (FA II) parts of a southward directed distributive fluvial system with a retrogradational pattern. During phase II (6.6-6.1Ma), the distributive fluvial system was replaced by a mixed clastic-evaporitic shallow lake (FA III) in a high aggradational basin. In phase III (∼6.1-5 Ma) the eastward progradation of a fluvial system (FA IV) was recorded as a distal clastic wedge. Finally, phase IV (∼5-2.4Ma) records two depositional cycles of proximal clastic wedge progradation of fluvial-dominated piedmonts (FAV, FAVII) from the southwest (Sierra de Umango) and/or the west (Precordillera) with an intervening playa lake (FA VI). Two new U-Pb ages obtained from zircons in volcanic ash layers confirm the Late Miocene age of the lower member of the Toro Negro Formation and permit a tight correlation with the central part of the basin (Quebrada de La Troya section). The sedimentation rate calculated for the dated lacustrine-fluvial interval is higher than the corresponding one in La Troya area suggesting a higher subsidence in the southern part of the basin. During the Late Miocene (∼7-6.6Ma) the ephemeral drainage was controlled by an arid to semiarid climate and initially dissipated mostly internally as terminal fan/distributive fluvial systems descending from the north. A thick lacustrine interval developed in the southern part of the basin between ∼6.6 and 6.1 Ma during a period of high subsidence and closed drainage. Besides, this interval coincides with increased aridity recorded in other basins in the Northwest of Argentina. By ∼6.1 Ma the area started to receive the first coarse-grained sediments heralding the progradation of a clastic wedge from the southwest-west (Sierra de Umango and Precordillera) which fully developed during the rest of the Pliocene to the earliest Pleistocene (∼5-2.4 Ma). The 6.1-2.4 Ma interval records ameliorating climate conditions.

Quaternary geologic map of the Shelby 1° x 2° quadrangle, Montana

USGS Publications Warehouse

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2013-01-01

The Shelby quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Sweet Grass Hills. The primary river is the Marias River. The ancestral Missouri River was diverted south of the Bearpaw Mountains by a Laurentide ice sheet. The fill in the buried ancestral valleys of the Missouri River and Marias River in the southeast quarter of the quadrangle contains a complex stratigraphy of fluvial, glaciofluvial, ice-contact, glacial, lacustrine, and eolian deposits. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 21 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy. Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. On the glaciated plains, the surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits. In the Sweet Grass Hills, beyond the limit of Quaternary glaciation they are fluvial, colluvial, and mass-movement deposits. Till of late Wisconsin age is represented by three map units. Tills of Illinoian and pre-Illinoian glaciations are not mapped, but are widespread in the subsurface. Linear ice-molded landforms (primarily drumlins) indicate directions of ice flow during late Wisconsin glaciation.

Hydrogeology of an ancient arid closed basin: implications for tabular sandstone-hosted uranium deposits

USGS Publications Warehouse

Sanford, R.F.

1990-01-01

Hydrogeologic modeling shows that tabular-type uranium deposits in the Grants uranium region of the San Juan basin, New Mexico, formed in zones of ascending and discharging regional ground-water flow. The association of either lacustrine mudstone or actively subsiding structures and uranium deposits can best be explained by the occurrence of lakes at topographic depressions where ground water having different sources and compositions is likely to converge, mix, and discharge. Ascending and discharging flow also explains the association of uranium deposits with underlying evaporites and suggests a brine interface. The simulations contradict previous suggestions that ground water moved downward in the mudflat. -Author

Evaluating the Effect of Autogenic Sedimentation on the Preservation of Climate Proxy Records: Modeling and Examples from the Paleocene Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Trampush, S. M.; Hajek, E. A.

2016-12-01

The stratigraphic record provides a vital opportunity to investigate how changes in climate can impact many different landscapes and seascapes. However, the inherent variability in sedimentation within many depositional environments may mask or remove the signature of climate change. A common solution is to use geochemical proxies - usually collected at regular stratigraphic intervals - to independently identify climate events. This approach doesn't account for the potentially significant variability in deposition and erosion time series resulting from autogenic landscape dynamics. In order to explore how geochemical proxy records could be overprinted by landscape dynamics, we use a 1D stochastic sedimentation model where we mimic fluvial, lacustrine, shallow marine, and deep marine environmental dynamics by varying the frequency-magnitude distributions of sedimentation rates. We find that even conservative estimates of the frequency and magnitude of stochastic sedimentation variability can heavily modify proxy records in characteristic ways by alternately removing, compressing, and expanding portions of the record, regardless of the magnitude or duration of the climatic event. Our model results are consistent with observations of the carbon isotope excursions of the Paleocene Eocene Thermal Maximum (PETM) preserved within both fluvial (e.g. the Bighorn Basin, Wyoming and the Piceance Basin, Colorado) and shallow marine (e.g. the New Jersey shelf) deposits. Our results suggest that we may be able to use existing geochemical proxy records within well studied, global climate events, such as the PETM, to constrain the variability in sedimentation present within different depositional environments.

Tertiary fission-track ages from the Bagua syncline (northern Peru): Stratigraphic and tectonic implications

NASA Astrophysics Data System (ADS)

Naeser, C. W.; Crochet, J.-Y.; Jaillard, E.; Laubacher, G.; Mourier, T.; Sigé, B.

The results of five zircon fission-track ages of volcanic tuffs intercalated within the continental deposits of the Bagua syncline (northern Peru) are reported. These 2500-meter-thick deposits overlie mid-Campanian to lower Maastrichtian fine-grained red beds (Fundo El Triunfo Formation). The disconformable fluvial conglomerates of the Rentema Formation are associated with a 54 Ma tuff (upper Paleocene-lower Eocene?) and would reflect the Inca-1 tectonic phase. The Sambimera Formation (Eocene to mid-Miocene) is a coarsening-upward sequence (from lacustrine to fluvial) that contains three volcanic tuffs of 31, 29, and 12 Ma, respectively. A probable stratigraphic gap, upper Eocene-lower Oligocene, would be related to the late Eocene Inca-2 phase. Neither deformation nor sedimentary discontinuity has been recognized so far. However, the lacustrine to fluvial transition could relate to the late Oligocene Aymara tectonic phase. The unconformable fanglomerates and fluvial deposits of the San Antonio Formation contain in their upper part a 9 Ma tuff (mid-to upper Miocene), and thier base records a major tectonic event (Quechua-2 phase?). The unconformable fanglomerates of the Tambopara Formation date the folding of the Bagua syncline, which could be ascribed to the latest Miocene Quechua-3 tectonics. These formations are correlative with comparable deposits in the sub-Andean basins, suggesting that these eastern areas underwent strong tectonic subsidence of the foreland basin type since mid-Miocene times.

Tertiary fission-track ages from the Bagua syncline (northern Peru): Stratigraphic and tectonic implications

USGS Publications Warehouse

Naeser, C.W.; Crochet, J.-Y.; Jaillard, E.; Laubacher, G.; Mourier, T.; Sige, B.

1991-01-01

The results of five zircon fission-track ages of volcanic tuffs intercalated within the continental deposits of the Bagua syncline (northern Peru) are reported. These 2500-meter-thick deposits overlie mid-Campanian to lower Maastrichtian fine-grained red beds (Fundo El Triunfo Formation). The disconformable fluvial conglomerates of the Rentema Formation are associated with a 54 Ma tuff (upper Paleocene-lower Eocene?) and would reflect the Inca-1 tectonic phase. The Sambimera Formation (Eocene to mid-Miocene) is a coarsening-upward sequence (from lacustrine to fluvial) that contains three volcanic tuffs of 31, 29, and 12 Ma, respectively. A probable stratigraphic gap, upper Eocene-lower Oligocene, would be related to the late Eocene Inca-2 phase. Neither deformation nor sedimentary discontinuity has been recognized so far. However, the lacustrine to fluvial transition could relate to the late Oligocene Aymara tectonic phase. The unconformable fanglomerates and fluvial deposits of the San Antonio Formation contain in their upper part a 9 Ma tuff (mid-to upper Miocene), and thier base records a major tectonic event (Quechua-2 phase?). The unconformable fanglomerates of the Tambopara Formation date the folding of the Bagua syncline, which could be ascribed to the latest Miocene Quechua-3 tectonics. These formations are correlative with comparable deposits in the sub-Andean basins, suggesting that these eastern areas underwent strong tectonic subsidence of the foreland basin type since mid-Miocene times. ?? 1991.

In-situ monitoring of deformation of clayey and volcanic sequences in the lacustrine plain of Iztapalapa, Mexico City

NASA Astrophysics Data System (ADS)

Carreon-Freyre, D.; Cerca, M.; Barrientos, B.; Gutierrez, R.; Blancas, D.

2012-12-01

Major cities of Central Mexico with lowering of land elevation problems are located in inter-volcanic and fault bounded basins within the central Trans-Mexican Volcanic Belt (TMVB). The most representative and studied case of ground deformation is Mexico City, where the Iztapalapa Municipality presents the highest population density. This area is located over the geological contact between the "Sierra de Santa Catarina" volcanic range and a lacustrine plain. Filling of lacustrine basins includes silty and clayey sediments as well as pyroclastic deposits (coarse and fine grained) and volcanic rocks layers. We used Ground Penetrating Radar (GPR) and MASW prospection to evaluate contrasts in the physical properties of fine grained soils and identify geometry of the deformational features and implemented a mechanical system for in situ monitoring in fractured sites. Deformational features in this basin reflect an interplay between the geological history (depositional conditions), load history, seismic activity, and faulting. Plastic mechanical behaviour predominates in these clayey sediments and differential deformation locally triggers brittle fracturing and/or subsidence of the surface. In this work we present the results of monitoring and characterization of ground deformation and fracturing in different sequences, our results show a dynamic interplay between the mechanisms of ground fracturing and the stress history of sedimentary sequences. Relating the mechanical behaviour of the studied sequences with variations of physical and geological properties should be taken into account to estimate land level lowering and risk of fracturing for urban development planning.

Coastal lake sediments reveal 5500 years of tsunami history in south central Chile

NASA Astrophysics Data System (ADS)

Kempf, Philipp; Moernaut, Jasper; Van Daele, Maarten; Vandoorne, Willem; Pino, Mario; Urrutia, Roberto; De Batist, Marc

2017-04-01

We present an exceptionally long and continuous coastal lacustrine record of ∼5500 years from Lake Huelde on the west coast of Chiloé Island in south central Chile. The study area is located within the rupture zone of the giant 1960 CE Great Chilean Earthquake (MW 9.5). The subsequent earthquake-induced tsunami inundated Lake Huelde and deposited mud rip-up clasts, massive sand and a mud cap in the lake. Long sediment cores from 8 core sites within Lake Huelde reveal 16 additional sandy layers in the 5500 year long record. The sandy layers share sedimentological similarities with the deposit of the 1960 CE tsunami and other coastal lake tsunami deposits elsewhere. On the basis of general and site-specific criteria we interpret the sandy layers as tsunami deposits. Age-control is provided by four different methods, 1) 210Pb-dating, 2) the identification of the 137Cs-peak, 3) an infrared stimulated luminescence (IRSL) date and 4) 22 radiocarbon dates. The ages of each tsunami deposit are modelled using the Bayesian statistic tools of OxCal and Bacon. The record from Lake Huelde matches the 8 regionally known tsunami deposits from documented history and geological evidence from the last ∼2000 years without over- or underrepresentation. We extend the existing tsunami history by 9 tsunami deposits. We discuss the advantages and disadvantages of various sedimentary environments for tsunami deposition and preservation, e.g. we find that Lake Huelde is 2-3 times less sensitive to relative sea-level change in comparison to coastal marshes in the same region.

Carbonate replacement of lacustrine gypsum deposits in two Neogene continental basins, eastern Spain

NASA Astrophysics Data System (ADS)

Anadón, P.; Rosell, L.; Talbot, M. R.

1992-07-01

Bedded nonmarine gypsum deposits in the Miocene Teruel and Cabriel basins, eastern Spain, are partly replaced by carbonate. The Libros gypsum (Teruel Graben) is associated with fossiliferous carbonate wackestones and finely laminated, organic matter-rich mudstones which accumulated under anoxic conditions in a meromictic, permanent lake. The gypsum is locally pseudomorphed by aragonite or, less commonly, replaced by calcite. Low δ 13C values indicate that sulphate replacement resulted from bacterial sulphate reduction processes that were favoured by anacrobic conditions and abundant labile organic matter in the sediments. Petrographic evidence and oxygen isotopic composition suggest that gypsum replacement by aragonite occurred soon after deposition. A subsequent return to oxidising conditions caused some aragonite to be replaced by diagenetic gypsum. Native sulphur is associated with some of these secondary gypsum occurrences. The Los Ruices sulphate deposits (Cabriel Basin) contain beds of clastic and selenitic gypsum which are associated with limestones and red beds indicating accumulation in a shallow lake. Calcite is the principal replacement mineral. Bacterial sulphate reduction was insignificant in this basin because of a scarcity of organic matter. Stable isotope composition of diagenetic carbonate indicates that gypsum replacement occurred at shallow burial depths due to contact with dilute groundwaters of meteoric origin. Depositional environment evidently has a major influence upon the diagenetic history of primary sulphate deposits. The quantity of preserved organic matter degradable by sulphate-reducing bacteria is of particular importance and, along with groundwater composition, is the main factor controlling the mechanism of gypsum replacement by carbonate.

Sedimentary Record of the Back-Arc Basins of South-Central Mexico: an Evolution from Extensional Basin to Carbonate Platform.

NASA Astrophysics Data System (ADS)

Sierra-Rojas, M. I.; Molina-Garza, R. S.; Lawton, T. F.

2015-12-01

The Lower Cretaceous depositional systems of southwestern Oaxaquia, in south-central Mexico, were controlled by tectonic processes related to the instauration of a continental arc and the accretion of the Guerrero arc to mainland Mexico. The Atzompa Formation refers to a succession of conglomerate, sandstone, siltstone, and limestone that crop out in southwestern Mexico with Early Cretaceous fauna and detrital zircon maximum depositional ages. The sedimentary record shows a transition from early fluvial/alluvial to shallow marine depositional environments. The first stage corresponds to juvenile fluvial/alluvial setting followed by a deep lacustrine depositional environment, suggesting the early stages of an extensional basin. The second stage is characterized by anabranched deposits of axial fluvial systems flowing to the NE-SE, showing deposition during a period of rapid subsidence. The third and final stage is made of tidal deposits followed, in turn, by abrupt marine flooding of the basin and development of a Barremian-Aptian carbonate ramp. We interpret the Tentzo basin as a response to crustal extension in a back-arc setting, with high rates of sedimentation in the early stages of the basin (3-4 mm/m.y), slower rates during the development of starved fluvial to tidal systems and carbonate ramps, and at the top of the Atzompa Formation an abrupt deepening of the basin due to flexural subsidence related to terrane docking and attendant thrusting to the west. These events were recorded in the back-arc region of a continental convergent margin (Zicapa arc) where syn-sedimentary magmatism is indicated by Early Cretaceous detrital and volcanic clasts from alluvial fan facies west of the basin. Finally, and as a response to the accretion of the Guerrero superterrane to Oaxaquia during the Aptian, a carbonate platform facing toward the Gulf of Mexico was established in central to eastern Oaxaquia.

Sedimentology, sequence-stratigraphy, and geochemical variations in the Mesoproterozoic Nonesuch Formation, northern Wisconsin, USA

USGS Publications Warehouse

Kingsbury Stewart, Esther; Mauk, Jeffrey L.

2017-01-01

We use core descriptions and portable X-ray fluorescence analyses to identify lithofacies and stratigraphic surfaces for the Mesoproterozoic Nonesuch Formation within the Ashland syncline, Wisconsin. We group lithofacies into facies associations and construct a sequence stratigraphic framework based on lithofacies stacking and stratigraphic surfaces. The fluvial-alluvial facies association (upper Copper Harbor Conglomerate) is overlain across a transgressive surface by the fluctuating-profundal facies association (lower Nonesuch Formation). The fluctuating-profundal facies association comprises a retrogradational sequence set overlain across a maximum flooding surface by an aggradational-progradational sequence set comprising fluctuating-profundal, fluvial-lacustrine, and fluvial-alluvial facies associations (middle Nonesuch through lower Freda Formations). Lithogeochemistry supports sedimentologic and stratigraphic interpretations. Fe/S molar ratios reflect the oxidation state of the lithofacies; values are most depleted above the maximum flooding surface where lithofacies are chemically reduced and are greatest in the chemically oxidized lithofacies. Si/Al and Zr/Al molar ratios reflect the relative abundance of detrital heavy minerals vs. clay minerals; greater values correlate with larger grain size. Vertical facies association stacking records depositional environments that evolved from fluvial and alluvial, to balanced-fill lake, to overfilled lake, and returning to fluvial and alluvial. Elsewhere in the basin, where accommodation was greatest, some volume of fluvial-lacustrine facies is likely present below the transgressive stratigraphic surface. This succession of continental and lake-basin types indicates a predominant tectonic driver of basin evolution. Lithofacies distribution and geochemistry indicate deposition within an asymmetric half-graben bounded on the east by a west-dipping growth fault. While facies assemblages are lacustrine and continental, periodic marine incursions are probable, especially across maximum transgressive surfaces.We demonstrate a sequence-stratigraphic approach may be applied to fine-grained Precambrian sediments using traditional rock description and supporting lithogeochemistry. Identification of a characteristic lithofacies succession in Mesoproterozoic sediments demonstrates fundamental controls commonly interpreted for Phanerozoic lake systems may be extended into the Precambrian. These controls result in a predictable association of lithofacies, with distinct physical, biological, and geochemical properties. This has regional significance for carbon sequestration and the distribution of mineral and hydrocarbon resources and broader significance for addressing Mesoproterozoic paleogeographic reconstructions and questions related to the evolution of terrestrial life.

Depositional environments and sedimentology of Vinita Beds, Richmond basin, Virginia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kornfeld, I.E.

The Carnian (middle to late Middle Triassic Age) Richmond basin of northeast Virginia is the oldest of the exposed Newark rift basins of the eastern seaboard. These basins formed during the Mesozoic divergence of the continents. As presently defined, the Richmond basin is a large synclinal feature measuring 32 mi (53 km) long by 8 mi (13 km) wide, and is located west of Richmond, Virginia, and east of Amelia, Virginia. Sediments of the Richmond basin have been assigned to the Richmond Group and have been stratigraphically subdivided into the following informal units, oldest to youngest: coarse boulder breccias, coalmore » measures, Vinita Beds, and Otterdale Sandstone. The Vinita Beds are composed of arkosic sandstones, shales, siltstones, and minor amounts of coal, and are mineralogically immature. They are composed to angular to subrounded rock fragments, quartz, and feldspars, and are high micaceous and kaolinitic. In places, feldspars make up as much as 50% of the rock. Sandstones and conglomerates are cross-bedded and channeled, and shales and siltstones are thinly laminated. The Vinita Beds are rich in fossil fish, branchiopods, and plant fragments. These rocks were deposited in braided streams as well as in paludal and possible lacustrine environments in a humid and heavily vegetated setting.« less

First Fossil Record of Alphonsea Hk. f. & T. (Annonaceae) from the Late Oligocene Sediments of Assam, India and Comments on Its Phytogeography

PubMed Central

Srivastava, Gaurav; Mehrotra, Rakesh C.

2013-01-01

A new fossil leaf impression of Alphonsea Hk. f. & T. of the family Annonaceae is described from the Late Oligocene sediments of Makum Coalfield, Assam, India. This is the first authentic record of the fossil of Alphonsea from the Tertiary rocks of South Asia. The Late Oligocene was the time of the last significant globally warm climate and the fossil locality was at 10°–15°N palaeolatitude. The known palaeoflora and sedimentological studies indicate a fluvio-marine deltaic environment with a mosaic of mangrove, fluvial, mire and lacustrine depositional environments. During the depositional period the suturing between the Indian and Eurasian plates was not complete to facilitate the plant migration. The suturing was over by the end of the Late Oligocene/beginning of Early Miocene resulting in the migration of the genus to Southeast Asia where it is growing profusely at present. The present study is in congruence with the earlier published palaeofloral and molecular phylogenetic data. The study also suggests that the Indian plate was not only a biotic ferry during its northward voyage from Gondwana to Asia but also a place for the origin of several plant taxa. PMID:23349701

To what extent can intracrater layered deposits that lack clear sedimentary textures be used to infer depositional environments?

NASA Astrophysics Data System (ADS)

Cadieux, Sarah B.; Kah, Linda C.

2015-03-01

Craters within Arabia Terra, Mars, contain hundreds of meters of layered strata showing systematic alternation between slope- and cliff-forming units, suggesting either rhythmic deposition of distinct lithologies or similar lithologies that experienced differential cementation. On Earth, rhythmically deposited strata can be examined in terms of stratal packaging, wherein the interplay of tectonics, sediment deposition, and base level (i.e., the position above which sediment accumulation is expected to be temporary) result in changes in the amount of space available for sediment accumulation. These predictable patterns of sediment deposition can be used to infer changes in basin accommodation regardless of the mechanism of deposition (e.g. fluvial, lacustrine, or aeolian). Here, we analyze sedimentary deposits from three craters (Becquerel Crater, Danielson Crater, Crater A) in Arabia Terra. Each crater contains layered deposits that are clearly observed in orbital images. Although orbital images are insufficient to specifically determine the origin of sedimentary deposits, depositional couplets can be interpreted in terms of potential accommodation space available for deposition, and changes in the distribution of couplet thickness through stratigraphy can be interpreted in terms of changing base level and the production of new accommodation space. Differences in stratal packaging in these three craters suggest varying relationships between sedimentary influx, sedimentary base level, and concomitant changes in accommodation space. Previous groundwater upwelling models hypothesize that layered sedimentary deposits were deposited under warm climate conditions of early Mars. Here, we use observed stacking patterns to propose a model for deposition under cold climate conditions, wherein episodic melting of ground ice could raise local base level, stabilize sediment deposition, and result in differential cementation of accumulated strata. Such analysis demonstrates that a first-order understanding of sedimentary deposition and accumulation-despite a lack of textural information that inhibits interpretation of depositional mechanism-can provide insight into potentially changeable depositional conditions of early Mars.

Potential 2001 Landing Sites in Melas Chasma, Mars

NASA Technical Reports Server (NTRS)

Weitz, C. M.; Lucchitta, B. K.; Chapman, M. G.

1999-01-01

We have selected four areas in Valles Marineris as potential landing sites for the 2001 mission. After 20 years of analyses, the formation of the Valles Marineris system of troughs and its associated deposits still has not been sufficiently explained. They could have formed by collapse, as tectonic grabens, or in two stages involving ancestral collapse basins later cut by grabens. Understanding all aspects of the Valles Marineris, in particular the interior layered deposits, would significantly contribute to deciphering the internal and external history of Mars. The deposits have been postulated to be remnants of wall rock, lacustrine deposits, mass wasting deposits, eolian deposits, carbonate deposits, or volcanic deposits. Because an understanding of the formation of Valles Marineris and its interior deposits is so important to deciphering the history of Mars, we have proposed landing sites for the 2001 mission on flat shelves of interior deposits in Melas Chasma.

Woolly erionite from the Reese River zeolite deposit, Lander County, Nevada, and its relationship to other erionites

USGS Publications Warehouse

Gude, Arthur J.; Sheppard, Richard A.

1981-01-01

Woolly erionite from the Reese River deposit, Nevada, is identical in appearance to that at the type locality, near Durkee, Oregon. Both of these erionites differ in appearance from all other erionite reported in the past 20 years from diverse rocks throughout the world which are described as prismatic or acicular in habit. The non-woolly erionites are especially common as microscopic crystals in diagenetically altered vitroclastic lacustrine deposits of Cenozoic age. The Reese River woolly erionite fills joints in gray to brownish-gray lacustrine mudstone of probably Pliocene age, in a zone about 1 m thick beneath a conspicuous gray vitric tuff. Compact masses of long, curly, woolly erionite fibers are in the plane of the joint and locally are associated with opal. Indices of refraction are ω = 1.468 and ε = 1.472; hexagonal unit-cell parameters are a = 13.186(2) Å, c = 15.055(1) Å, and V = 2267.1(0.9) Å3. A chemical analysis of woolly erionite yields a unit-cell composition of: Na1.01K2.84Mg0.3Ca1.69Al8.18Si27.84O72 · 28.51H2O.

Analysis of soft-sediment deformation structures in Neogene fluvio-lacustrine deposits of Çaybağı Formation, Eastern Turkey

NASA Astrophysics Data System (ADS)

Koç Taşgin, Calibe; Türkmen, İbrahim

2009-06-01

During the Neogene, both strike-slip and extensional regimes coexisted in eastern Turkey and, a number of fault-bounded basins associated with the East Anatolian Fault System developed. The Çaybağı Formation (Late Miocene-Early Pliocene) deposited in one of these basins consists of fluvio-lacustrine deposits. Numerous soft-sediment deformation structures are encountered in this formation, particularly in conglomerates, medium- to coarse-grained tuffaceous sandstones and claystones: folded structures (slumps, convolute laminations, and simple recumbent folds), water-escape structures (intruded sands, internal cusps, interpenetrative cusps and sand volcanoes), and load structures (load casts, pseudonodules, flame structures, and pillow structures). These structures are produced by liquefaction and/or fluidization of the unconsolidated sediments during a seismic shock. Consequently, the existence of seismically-induced deformation structures in the Çaybağı Formation and the association with a Neogene intraformational unconformity, growth faults, and reverse faults in the Çaybağı basin attest to the tectonic activity in this area during the Late Miocene and Early Pliocene. The East Anatolian Fault System, in particular the Uluova fault zone, is the most probable seismogenic source. Earthquakes with a magnitude of over 5 in the Richter scale can be postulated.

Palaeoenvironments during MIS 3 and MIS 2 inferred from lacustrine intercalations in the loess-palaeosol sequence at Bobingen (southern Germany)

NASA Astrophysics Data System (ADS)

Mayr, Christoph; Matzke-Karasz, Renate; Stojakowits, Philipp; Lowick, Sally E.; Zolitschka, Bernd; Heigl, Tanja; Mollath, Richard; Theuerkauf, Marian; Weckend, Marc-Oliver; Bäumler, Rupert; Gregor, Hans-Joachim

2017-12-01

Recently exposed loess-palaeosol sequences in the northern Alpine foreland close to Bobingen (southern Germany) were investigated with a multi-proxy approach combining isotopic, geochemical, lithological, and micropalaeontological methods. Luminescence ages date the sections into the Middle and Upper Würmian periods corresponding to Marine Isotope Stages 3 and 2. A gleyic soil horizon at the base was dated to 45 ka and provided a palynoflora dominated by Poaceae, Cyperaceae, and Pinus, as well as frequent aquatic taxa. Lacustrine conditions prevailed after the gley formation until 30 ka, providing a comparatively diverse lacustrine fauna dominated by aquatic gastropods and the ostracod species Candona candida. At the transition to the Upper Würm, climatic conditions became harsh, indicated by accelerated deposition of more coarse-grained loess, organic geochemical indicators, and scarceness of biotic remains. Two tundra-gley horizons in the Upper Würm point to short phases of climatic amelioration with higher humidity also evidenced by reoccurrence of ostracod and aquatic gastropod remains. We propose that these climatic ameliorations were coincident with the Greenland interstadials 4 and 2.

The Messinian erosional surface and early Pliocene reflooding in the Alboran Sea: New insights from the Boudinar basin, Morocco

NASA Astrophysics Data System (ADS)

Cornée, Jean-Jacques; Münch, Philippe; Achalhi, Mohammed; Merzeraud, Gilles; Azdimousa, Ali; Quillévéré, Frédéric; Melinte-Dobrinescu, Mihaela; Chaix, Christian; Moussa, Abdelkhalak Ben; Lofi, Johanna; Séranne, Michel; Moissette, Pierre

2016-03-01

New investigations in the Neogene Boudinar basin (Morocco) provide new information about the Messinian Salinity Crisis (MSC) and Zanclean reflooding in the southern part of the Alboran realm (westernmost Mediterranean). Based on a new field, sedimentological and palaeontological analyses, the age and the geometry of both the Messinian erosional surface (MES) and the overlying deposits have been determined. The MES is of late Messinian age and was emplaced in subaerial settings. In the Boudinar basin, a maximum of 200 m of Miocene sediments was eroded, including late Messinian gypsum blocks. The original geometry of the MES is preserved only when it is overlain by late Messinian continental deposits, conglomeratic alluvial fans or lacustrine marly sediments. These sediments are interpreted as indicators of the sea-level fall during the MSC. Elsewhere in the basin, the contact between late Messinian and early Pliocene deposits is a low-angle dipping, smooth surface that corresponds to the early Pliocene transgression surface that subsequently re-shaped the regressive MES. The early Pliocene deposits are characterized by: (i) their onlap onto either the basement of the Rif chain or the late Miocene deposits; (ii) lagoonal deposits at the base to offshore marls and sands at the top (earliest Pliocene; 5.33-5.04 Ma interval; foraminifer zone PL1); (iii) marine recovery occurring in the 5.32-5.26 Ma interval; and (iv) the change from lagoonal to offshore environments occurring within deposits tens of metres thick. This information indicates that at least the end of the reflooding period was progressive, not catastrophic as previously thought.

Microbial community composition along a 50 000-year lacustrine sediment sequence

PubMed Central

Ariztegui, Daniel; Horn, Fabian; Kallmeyer, Jens; Orsi, William D

2018-01-01

Abstract For decades, microbial community composition in subseafloor sediments has been the focus of extensive studies. In deep lacustrine sediments, however, the taxonomic composition of microbial communities remains undercharacterized. Greater knowledge on microbial diversity in lacustrine sediments would improve our understanding of how environmental factors, and resulting selective pressures, shape subsurface biospheres in marine and freshwater sediments. Using high-throughput sequencing of 16S rRNA genes across high-resolution climate intervals covering the last 50 000 years in Laguna Potrok Aike, Argentina, we identified changes in microbial populations in response to both past environmental conditions and geochemical changes of the sediment during burial. Microbial communities in Holocene sediments were most diverse, reflecting a layering of taxa linked to electron acceptors availability. In deeper intervals, the data show that salinity, organic matter and the depositional conditions over the Last Glacial-interglacial cycle were all selective pressures in the deep lacustrine assemblage resulting in a genetically distinct biosphere from the surface dominated primarily by Bathyarchaeota and Atribacteria groups. However, similar to marine sediments, some dominant taxa in the shallow subsurface persisted into the subsurface as minor fraction of the community. The subsequent establishment of a deep subsurface community likely results from a combination of paleoenvironmental factors that have shaped the pool of available substrates, together with substrate depletion and/or reworking of organic matter with depth. PMID:29471361

Chapter B: Regional Geologic Setting of Late Cenozoic Lacustrine Diatomite Deposits, Great Basin and Surrounding Region: Overview and Plans for Investigation

USGS Publications Warehouse

Wallace, Alan R.

2003-01-01

Freshwater diatomite deposits are present in all of the Western United States, including the Great Basin and surrounding regions. These deposits are important domestic sources of diatomite, and a better understanding of their formation and geologic settings may aid diatomite exploration and land-use management. Diatomite deposits in the Great Basin are the products of two stages: (1) formation in Late Cenozoic lacustrine basins and (2) preservation after formation. Processes that favored long-lived diatom activity and diatomite formation range in decreasing scale from global to local. The most important global process was climate, which became increasingly cool and dry from 15 Ma to the present. Regional processes included tectonic setting and volcanism, which varied considerably both spatially and temporally in the Great Basin region. Local processes included basin formation, sedimentation, hydrology, and rates of processes, including diatom growth and accumulation; basin morphology and nutrient and silica sources were important for robust activity of different diatom genera. Only optimum combinations of these processes led to the formation of large diatomite deposits, and less than optimum combinations resulted in lakebeds that contained little to no diatomite. Postdepositional processes can destroy, conceal, or preserve a diatomite deposit. These processes, which most commonly are local in scale, include uplift, with related erosion and changes in hydrology; burial beneath sedimentary deposits or volcanic flows and tuffs; and alteration during diagenesis and hydrothermal activity. Some sedimentary basins that may have contained diatomite deposits have largely been destroyed or significantly modified, whereas others, such as those in western Nevada, have been sufficiently preserved along with their contained diatomite deposits. Future research on freshwater diatomite deposits in the Western United States and Great Basin region should concentrate on the regional and local processes that led to the formation and preservation of the deposits. Major questions that need to be answered include (1) why were some basins favorable for diatomite formation, whereas others were not; (2) what post-depositional conditions are needed for diatomite preservation; and (3) what were the optimum process combinations that led to the formation and preservation of economic diatomite deposits?

Geology of tight oil and potential tight oil reservoirs in the lower part of the Green River Formation, Uinta, Piceance, and Greater Green River Basins, Utah, Colorado, and Wyoming

USGS Publications Warehouse

Johnson, Ronald C.; Birdwell, Justin E.; Mercier, Tracey J.; Brownfield, Michael E.

2016-05-02

The recent successful development of a tight oil play in the Eocene-age informal Uteland Butte member of the lacustrine Green River Formation in the Uinta Basin, Utah, using modern horizontal drilling and hydraulic fracturing techniques has spurred a renewed interest in the tight oil potential of lacustrine rocks. The Green River Formation was deposited by two large lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. These three basins contain the world’s largest in-place oil shale resources with recent estimates of 1.53 trillion, 1.33 trillion, and 1.44 trillion barrels of oil in place in the Piceance, Uinta, and Greater Green River Basins, respectively. The Uteland Butte member was deposited during an early freshwater stage of the lake in the Uinta Basin prior to deposition of the assessed oil shale intervals. This report only presents information on the early freshwater interval and overlying brackish-water interval in all three basins because these intervals are most likely to have tight oil potential. Burial histories of the three basins were reconstructed to study (1) variations in subsidence and lake development, and (2) post deposition burial that led to the development of a petroleum system in only the Uinta Basin. The Uteland Butte member is a successful tight oil play because it is thermally mature for hydrocarbon generation and contains organic-rich shale, brittle carbonate, and porous dolomite. Abnormally high pressure in parts of the Uteland Butte is also important to production. Variations in organic richness of the Uteland Butte were studied using Fischer assay analysis from oil shale assessments, and pressures were studied using drill-stem tests. Freshwater lacustrine intervals in the Piceance and Greater Green River Basins are immature for hydrocarbon generation and contain much less carbonate than the Uteland Butte member. The brackish-water interval in the Uinta Basin is thermally mature for hydrocarbon generation but is clay-rich and contains little carbonate, and thus is a poor prospect for tight oil development.

Isotopic identification of the source of methane in subsurface sediments of an area surrounded by waste disposal facilities

USGS Publications Warehouse

Hackley, Keith C.; Liu, Chao-Li; Trainor, D.

1999-01-01

The major source of methane (CH4) in subsurface sediments on the property of a former hazardous waste treatment facility was determined using isotopic analyses measured on CH4 and associated groundwater. The site, located on an earthen pier built into a shallow wetland lake, has had a history of waste disposal practices and is surrounded by landfills and other waste management facilities. Concentrations of CH4 up to 70% were found in the headspace gases of several piezometers screened at 3 different depths (ranging from 8 to 17 m) in lacustrine and glacial till deposits. Possible sources of the CH4 included a nearby landfill, organic wastes from previous impoundments and microbial gas derived from natural organic matter in the sediments. Isotopic analyses included ??13C, ??D, 14C, and 3H on select CH4 samples and ??D and ??18O on groundwater samples. Methane from the deepest glacial till and intermediate lacustrine deposits had ??13C values from -79 to -82???, typical of natural 'drift gas' generated by microbial CO2-reduction. The CH4 from the shallow lacustrine deposits had ??13C values from -63 to -76???, interpreted as a mixture between CH4 generated by microbial fermentation and the CO2-reduction processes within the subsurface sediments. The ??D values of all the CH4 samples were quite negative ranging from -272 to -299???. Groundwater sampled from the deeper zones also showed quite negative ??D values that explained the light ??D observed for the CH4. Radiocarbon analyses of the CH4 showed decreasing 14C activity with depth, from a high of 58 pMC in the shallow sediments to 2 pMC in the deeper glacial till. The isotopic data indicated the majority of CH4 detected in the fill deposits of this site was microbial CH4 generated from naturally buried organic matter within the subsurface sediments. However, the isotopic data of CH4 from the shallow piezometers was more variable and the possibility of some mixing with oxidized landfill CH4 could not be completely ruled out.

Brief communication: beyond the South African cave paradigm--Australopithecus africanus from Plio-Pleistocene paleosol deposits at Taung.

PubMed

Hopley, Philip J; Herries, Andy I R; Baker, Stephanie Edwards; Kuhn, Brian F; Menter, Colin G

2013-06-01

Following the discovery of the "Taung Child" (Australopithecus africanus) in 1924 in the Buxton-Norlim Limeworks near Taung, the fossil-bearing deposits associated with the Dart and Hrdlička pinnacles have been interpreted as the mined remnants of cave sediments that formed within the Plio-Pleistocene Thabaseek Tufa: either as a younger cave-fill or as contemporaneous carapace caves. When combined with the Plio-Pleistocene dolomitic cave deposits from the "Cradle of Humankind," a rather restricted view emerges that South African early hominins derived from cave deposits, whereas those of east and central Africa are derived from fluvio-lacustrine and paleosol deposits. We undertook a sedimentological and paleomagnetic analysis of the pink-colored deposit (PCS) from which the "Taung Child" is purported to have derived and demonstrate that it is a calcrete, a carbonate-rich pedogenic sediment, which formed on the paleo-land surface. The deposit extends 100 s of meters laterally beyond the Dart and Hrdlička Pinnacles where it is interbedded with the Thabaseek Tufa, indicating multiple episodes of calcrete development and tufa growth. The presence of in situ rhizoconcretions and insect trace fossils (Celliforma sp. and Coprinisphaera sp.) and the distinctive carbonate microfabric confirm that the pink deposit is a pedogenic calcrete, not a calcified cave sediment. Paleomagnetic and stratigraphic evidence indicates that a second, reversed polarity, fossil-bearing deposit (YRSS) is a younger fissure-fill formed within a solutional cavity of the normal polarity tufa and pink calcrete (PCS). These observations have implications for the dating, environment, and taphonomy of the site, and increase the likelihood of future fossil discoveries within the Buxton-Norlim Limeworks. Copyright © 2013 Wiley Periodicals, Inc.

Luminescence dating of paleolake deltas and glacial deposits in Garwood Valley, Antarctica: Implications for climate, Ross ice sheet dynamics, and paleolake duration

USGS Publications Warehouse

Levy, Joseph S.; Rittenour, Tammy M.; Fountain, Andrew G.; O'Connor, Jim E.

2017-01-01

The formation of perched deltas and other lacustrine deposits in the McMurdo Dry Valleys of Antarctica is widely considered to be evidence of valley-filling lakes dammed by the grounded Ross Sea ice sheet during the local Last Glacial Maximum, with lake drainage interpreted as a record of grounding line retreat. We used luminescence dating to determine the age of paleolake deltas and glacial tills in Garwood Valley, a coastal dry valley that opens to the Ross Sea. Luminescence ages are stratigraphically consistent with radiocarbon results from algal mats within the same delta deposits but suggest radiocarbon dates from lacustrine carbonates may overestimate deposit ages by thousands of years. Results suggest that late Holocene delta deposition into paleolake Howard in Garwood Valley persisted until ca. 3.5 ka. This is significantly younger than the date when grounded ice is thought to have retreated from the Ross Sea. Our evidence suggests that the local, stranded ice-cored till topography in Garwood Valley, rather than regional ice-sheet dynamics, may have controlled lake levels for some McMurdo Dry Valleys paleolakes. Age control from the supraglacial Ross Sea drift suggests grounding and up-valley advance of the Ross Sea ice sheet into Garwood valley during marine oxygen isotope stage (MIS) 4 (71–78 ka) and the local Last Glacial Maximum (9–10 ka). This work demonstrates the power of combining luminescence dating with existing radiocarbon data sets to improve understanding of the relationships among paleolake formation, glacial position, and stream discharge in response to climate change.

Spatial and Temporal Patterns of Mercury Accumulation in Lacustrine Sediments Across the Laurentian Great Lakes Region

EPA Science Inventory

Data from 103 sediment cores from the Great Lakes and inland lakes of the Great Lakes airshed were compiled to examine and provide a synthesis of patterns of historical and recent changes in mercury (Hg) deposition. Limited data from the lower Laurentian Great Lakes shows a lega...

Surficial Geologic Map of the Evansville, Indiana, and Henderson, Kentucky, Area

USGS Publications Warehouse

Moore, David W.; Lundstrom, Scott C.; Counts, Ronald C.; Martin, Steven L.; Andrews, William M.; Newell, Wayne L.; Murphy, Michael L.; Thompson, Mark F.; Taylor, Emily M.; Kvale, Erik P.; Brandt, Theodore R.

2009-01-01

The geologic map of the Evansville, Indiana, and Henderson, Kentucky, area depicts and describes surficial deposits according to their origin and age. Unconsolidated alluvium and outwash fill the Ohio River bedrock valley and attain maximum thickness of 33-39 m under Diamond Island, Kentucky, and Griffith Slough, south of Newburgh, Indiana. The fill is chiefly unconsolidated, fine- to medium-grained, lithic quartz sand, interbedded with clay, clayey silt, silt, coarse sand, granules, and gravel. Generally, the valley fill fines upward from the buried bedrock surface: a lower part being gravelly sand to sandy gravel, a middle part mostly of sand, and a surficial veneer of silt and clay interspersed with sandy, natural levee deposits at river's edge. Beneath the unconsolidated fill are buried and discontinuous, lesser amounts of consolidated fill unconformably overlying the buried bedrock surface. Most of the glaciofluvial valley fill accumulated during the Wisconsin Episode (late Pleistocene). Other units depicted on the map include creek alluvium, slackwater lake (lacustrine) deposits, colluvium, dune sand, loess, and sparse bedrock outcrops. Creek alluvium underlies creek floodplains and consists of silt, clayey silt, and subordinate interbedded fine sand, granules, and pebbles. Lenses and beds of clay are present locally. Silty and clayey slackwater lake (lacustrine) deposits extensively underlie broad flats northeast of Evansville and around Henderson and are as thick as 28 m. Fossil wood collected from an auger hole in the lake and alluvial deposits of Little Creek, at depths of 10.6 m and 6.4 m, are dated 16,650+-50 and 11,120+-40 radiocarbon years, respectively. Fossil wood collected from lake sediment 16 m below the surface in lake sediment was dated 33,100+-590 radiocarbon years. Covering the hilly bedrock upland is loess (Qel), 3-7.5 m thick in Indiana and 9-15 m thick in Kentucky, deposited about 22,000-12,000 years before present. Most mapped surficial deposits in the quadrangle are probably no older than about 55,000 years. Lithologic logs, shear-wave velocities, and other cone penetrometer data are used to interpret depositional environments and geologic history of the surficial deposits. This map, which includes an area of slightly more than seven 7.5-minute quadrangles, serves several purposes. It is a tool for assessing seismic and flood hazards of a major urban area; aids urban planning; conveys geologic history; and locates aggregate resources. The map was produced concurrently with research by seismologists to determine places where the surficial deposits may tend to liquefy and (or) to amplify ground motions during strong earthquakes. Such hazardous responses to shaking are related to the characteristics of the geologic materials and topographic position, which the geologic map depicts. The geologic map is an element in the cooperative seismic hazard assessment program among the States of Indiana, Kentucky, and Illinois and the U.S. Geological Survey, funded by the National Earthquake Hazards Reduction Program and National Cooperative Geologic Mapping Program of the U.S. Geological Survey.

Pollen preservation and Quaternary environmental history in the southeastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delcourt, P.A.; Delcourt, H.R.

Reconstructions of Quaternary environmental history based upon modern pollen/vegetation/climate calibrations are more tenable if the factors responsible for variation in pollen assemblages are evaluated. Examination of the state of preservation of Quaternary palynomorphs provides quantitative data concerning the degree of information loss due to alteration of pollen assemblages by syndepositional and post-depositional deterioration. The percentage, concentration, and influx values for total indeterminable pollen are useful criteria in providing an objective and quantitative basis for evaluating the comparability of pollen spectra within and between sites. Supporting data concerning sediment particle-size distribution, organic matter content, and concentration, influx, and taxonomic composition ofmore » both determinable pollen and plant macrofossils aid in reconstructing past depositional environments. The potential is high for deterioration of pollen in sediments from the southeastern United States, although considerable variation is found in both kind and degree of deterioration between lacustrine and alluvial sites of different ages and in different latitudes. Modern analogs are a basis for late Quaternary environmental reconstructions when pollen deterioration has not significantly biased the information content of fossil pollen assemblages.« less

Diagenesis in the Murray Formation, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Ming, D. W.; Morris, R. V.; Blake, D. F.; Bristow, T. F.; Chipera. S. J.; Vaniman, D. T.; Yen, A. S.; Grotzinger, J. P.; Downs, R. T.;

Origin and character of loesslike silt in unglaciated south-central Yakutia, Siberia, U.S.S.R.

USGS Publications Warehouse

Pewe, Troy Lewis; Journaux, Andre

1983-01-01

Loesslike silt mantles upland terraces and low plateaus throughout unglaciated south-central Yakutia but is thickest along the south side of the lower Aldan River valley and the east side of the Lena River valley. The silt is probably loess deposited during glacial advances by winds blowing southward from the Verkhoyansk Range and eastward across the broad vegetation-free flood plain of the braided Lena River. The well-sorted uniform tan silt is well displayed along the Aldan and Lena Rivers; the thickest exposure measured, more than 60 m, is on the Tyungyulyu Terrace on the east side of the Lena River. On the west side of the valley, it is 10-25 m thick but thins rapidly to a featheredge west of Yakutsk. Almost all scarps along the south side of the Aldan River are capped by 10-35 m of silt. The texture and mineral composition of the loess like silt are uniform throughout south-central Yakutia, whether it overlies limestone, poorly consolidated sandstone, alluvium, and glacial outwash. All silt samples examined contained a high percentage of quartz and feldspar. The silt stands in sheer cliffs and is massive, with little or no stratification. The origin of the loesslike silt has been ascribed to disintegration in place of country rock by a marine, estuarine, lacustrine, fluvial, residual, or eolian source, or to a combination of these processes. The marine and estuarine hypotheses have never had strong support, but the lacustrine, fluvial, and residual hypotheses have been advanced by many Soviet workers. The most widely accepted explanation of the origin of the upland silt is that it is a combination of lacustrine and alluvial deposits formed on great flood plains and marshy plains. This origin is unlikely, however, because there are no shorelines, wave-cut beaches, deltas, mudcracks, or ripple marks. Neither distinct stratification nor an appreciable amount of clay exists in the silt. Moreover, there is no definite upper boundary to the deposits, as would be expected of lacustrine deposits. The loesslike silt has also been described as a residual deposit formed by the breakdown, by freezing and thawing, of the underlying rocks. The silt bears no chemical, mineralogic, or textural relation to the underlying strata, however, and it is too thick to represent only breakdown of rocks in place. The widespread mantle of uniform loesslike silt is here considered to be windblown, derived from glacial outwash in braided streams and on broad plains, because: (1) it occurs as a surficial mantle; (2) it is lithologically independent of the underlying material; (3) it is stratified indistinctly or not at all, except in retransported material; (4) it is associated with sand dunes; (5) it contains fossils of land animals; (6) its sorting and texture are similar to that of loess and windblown dust from many places elsewhere in the world; (7) its grains are angular and relatively unweathered.

A multi-proxy approach to identifying short-lived marine incursions in the Early Carboniferous

NASA Astrophysics Data System (ADS)

Bennett, Carys; Davies, Sarah; Leng, Melanie; Snelling, Andrea; Millward, David; Kearsey, Timothy; Marshall, John; Reves, Emma

2015-04-01

This study is a contribution to the TW:eed Project (Tetrapod World: early evolution and diversification), which examines the rebuilding of Carboniferous ecosystems following a mass extinction at the end of the Devonian. The project focuses on the Tournaisian Ballagan Formation of Scotland and the Borders, which contains rare fish and tetrapod material. The Ballagan Formation is characterised by sandstones, dolomitic cementstones, paleosols, siltstones and gypsum deposits. The depositional environment ranges from fluvial, alluvial-plain to marginal-marine environments, with fluvial, floodplain and lacustrine deposition dominant. A multi-proxy approach combining sedimentology, palaeontology, micropalaeontology, palynology and geochemistry is used to identify short-lived marine transgressions onto the floodplain environment. Rare marginal marine fossils are: Chondrites-Phycosiphon, Spirorbis, Serpula, certain ostracod species, rare orthocones, brachiopods and putative marine sharks. More common non-marine fauna include Leiocopida and Podocopida ostracods, Mytilida and Myalinida bivalves, plants, eurypterids, gastropods and fish. Thin carbonate-bearing dolomitic cementstones and siltstone contain are the sedimentary deposits of marine incursions and occur throughout the formation. Over 600 bulk carbon isotope samples were taken from the 500 metre thick Norham Core (located near Berwick-Upon-Tweed), encompassing a time interval of around 13 million years. The results range from -26o to -19 δ13Corg, with an average of -19o much lighter than the average value for Early Carboniferous marine bulk organic matter (δ13C of -28 to -30). The isotope results correspond to broad-scale changes in the depositional setting, with more positive δ13C in pedogenic sediments and more negative δ13C in un-altered grey siltstones. They may also relate to cryptic (short-lived) marine incursions. A comparison of δ13C values from specific plant/wood fragments, palynology and bulk sedimentary organic matter from the core is used to identify further changes in environment and vegetation. From the base to the top of the formation, there is a gradual increase in relatively drier conditions, with more developed palaeosols and deep desiccation cracks. However, the main character of the formation is that of rapidly changing deposition between silts, sands and carbonates with many periods of pedogenesis and/or desiccation suggesting frequent switching from alluvial-plain to coastal environments. Marine incursions were short-lived, but important and caused a significant increase in the macro and microfaunal diversity. This temporal variability in the environments may have been an important factor in the evolution of tetrapods in the Early Carboniferous.

Deposition modes in the paleo-lake Colônia (São Paulo, SE / Brazil): detrital input and bio-geochemical processes

NASA Astrophysics Data System (ADS)

Roeser, Patricia; Ledru, Marie-Pierre; Thouveny, Nicolas; Tachikawa, Kazuyo; Rostek, Frauke; Garcia, Marta; Struck, Ulrich; Sawakuchi, André; Favier, Charly; Bard, Edouard

2017-04-01

Colônia, a geomorphological circular structure in southeast Brazil, probably originated from an meteor impact with still unknown age. The structure, situated 40 km south of the center of the mega city São Paulo, has ca. 3.6 km in diameter and a surrounding rim elevated by ca. 120 meters. At present, the inner part of the structure contains a swampy alluvial plain. Sediment columns recovered in September 2014 have shown that below a circa 8 meter thick peat deposit, sediments are lacustrine and characterized by light-gray bands (cm scale). According to a preliminary age-depth model, based on radiocarbon ages, luminescence ages and paleomagnetism, the transition between lake to peat deposition seems to relate to climate boundary conditions from glacial towards interglacial conditions. In the lacustrine fine-grained sediments, the banded gray layers have distinct grain size, as macroscopically observed from mica grains/plates. Correlated to high-resolution geochemical data, lighter colored bands hold increased amounts of K and Si [XRF counts], originating from detrital input from the basin, e.g. flood events during tropical storms. Potassium is mainly contained in the crystalline structure of muscovite, whereas silica is additionally contained in kaolinite and quartz, thereby completing the minerals that make out the major mineral assemblage found in the sediments. Pyrite is found as an accessory mineral with average concentrations between 1 and 2%, peaking at 5% up to 10% in covariance to Fe/Ti [XRF count ratio]. Overall a covariance pattern, with or without phase lag, between pyrite, ∂13C (of TOC) and the concentrations of the biomarker hopane is observed in the lacustrine sediments. These relationships likely originate from stratification conditions in the paleo-lake, such that a more stable stratification eventually led to anoxic lake bottom conditions, favoring authigenic/microbial pyrite precipitation, better preservation of organic matter and affecting gas exchange between the water and the atmosphere.

Stratigraphy of the Sarkisla area, Sivas basin, eastern central Anatolia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilgic, T.; Sumengen, M.; Terlemez, I.

1988-08-01

The stratigraphy of the Sarkisla area, southeastern Central Anatolian Massif, is characterized by a succession of rock units ranging from late Paleocene to Pliocene in age. The Caldag group mostly consists of deep-water units and forms the base of the Tertiary rocks. However, its relation to the basement rocks is not observed in the area. This group is represented by late Paleocene-Lutetian-age turbiditic pyroclastics and limestones, andesitic lavas and pyroclastics topped with reefal limestones, and turbiditic limestones and pyroclastics alternating with limestone blocks. During Lutetian to early Priabonian time, shallow marine clastics were deposited along the southern margin of themore » basin, while continental clastics and platform limestones accumulated along the northern margin. Late Priabonian to early Oligocene time is represented by gypsiferous deposits followed by late Oligocene-age fluvial clastics. The gypsiferous deposits conformably overlie the shallow marine formations but rest on the Caldag group unconformably. During early to middle Miocene time, alternating lacustrine limestones, gypsum, and basalts formed on the fluvial clastics; to the north, basalts formed on the platform limestones. The uppermost sequence of the basin, composed of Tortonian-early Pliocene-age fluvial clastics, lacustrine limestones, and fan deposits, unconformably overlies the older formations. The stratigraphy of the study area is similar to the Ulukisla basin, southwestern Central Anatolian Massif. Therefore, this basin can be considered to be the prolongation of the Ulukisla basin offset by the Ecemis fault.« less

Fluvial/lacustrine diagenesis: Significance for hydrocarbon production and entrapment in the carboniferous Albert Fm, Moncton basin, NB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noble, J.P.A.; Chowdhury, A.H.; Yu, H.

1996-12-31

The Carboniferous Horton Group Albert Formation sediments include lacustrine source-rock oil shales and fluvial porous reservoir sandstones. The petrography, stable isotopes, fluid inclusions, cathodoluminescence and mirror/trace element chemistry of these sandstones are used to establish the diagenetic history and controlling factors. Early diagenetic calcite, quartz and albite cements with minor chlorite and kaolinite are variably present and related to depositional mineralogy and lake levels winch controlled the porewater chemistry. Antitaxial veins occurring preferentially in shales are shown, from heavy {delta}C{sup 13} values and fluid inclusions, to be related to methanogenesis in overpressured zones at shallow depths. Later burial calcite andmore » extensive albitisation are related to mineral reactions during the phase of rapid subsidence at temperatures of 80{degrees} to 150{degrees} in the deepest segment of the basin, together with significant dissolution of carbonates and feldspars related mainly to organic acids generated by organic maturation processes. Mass balance calculations indicate that not enough organic matter was present to account for all the estimated secondary porosity and some evidence suggests that reactions between kaolinite and calcite/ankerite to produce chlorite, and mixed layer illite-smectite ordering reactions, produced significant secondary porosity. Burial history reconstructions and thermal modelling of the Albert Fm. sediments using Arrhenius type maturity models and reflectance and rock-eval data suggest locally variable maturation and reservoir production related to the locally different fault tectonic histories characteristic of strike-slip lacustrine segmented basins. The Horton depositional cycle was followed by major dextral transpression with local faulting and inversion and vein cementation.« less

Fluvial/lacustrine diagenesis: Significance for hydrocarbon production and entrapment in the carboniferous Albert Fm, Moncton basin, NB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noble, J.P.A.; Chowdhury, A.H.; Yu, H.

1996-01-01

The Carboniferous Horton Group Albert Formation sediments include lacustrine source-rock oil shales and fluvial porous reservoir sandstones. The petrography, stable isotopes, fluid inclusions, cathodoluminescence and mirror/trace element chemistry of these sandstones are used to establish the diagenetic history and controlling factors. Early diagenetic calcite, quartz and albite cements with minor chlorite and kaolinite are variably present and related to depositional mineralogy and lake levels winch controlled the porewater chemistry. Antitaxial veins occurring preferentially in shales are shown, from heavy [delta]C[sup 13] values and fluid inclusions, to be related to methanogenesis in overpressured zones at shallow depths. Later burial calcite andmore » extensive albitisation are related to mineral reactions during the phase of rapid subsidence at temperatures of 80[degrees] to 150[degrees] in the deepest segment of the basin, together with significant dissolution of carbonates and feldspars related mainly to organic acids generated by organic maturation processes. Mass balance calculations indicate that not enough organic matter was present to account for all the estimated secondary porosity and some evidence suggests that reactions between kaolinite and calcite/ankerite to produce chlorite, and mixed layer illite-smectite ordering reactions, produced significant secondary porosity. Burial history reconstructions and thermal modelling of the Albert Fm. sediments using Arrhenius type maturity models and reflectance and rock-eval data suggest locally variable maturation and reservoir production related to the locally different fault tectonic histories characteristic of strike-slip lacustrine segmented basins. The Horton depositional cycle was followed by major dextral transpression with local faulting and inversion and vein cementation.« less

Oasis deposits in the southern margin of the Taklimakan Desert and abrupt environmental changes during the last 30 ka

NASA Astrophysics Data System (ADS)

Shu, P.; Li, B.; Wang, H.; Cheng, P.; An, Z.; Zhou, W.; Zhang, D. D.

2017-12-01

Taklimakan Desert, the largest arid landform in the Eurasia, is one of the most important dust sources in the world. Growing evidences shows that millennial-scale abrupt climate changes during the last glacial period in the region. However, records on millennial-scale climate and environmental changes remain poorly understood because dating eolian, lacustrine, and fluvial sediments and establishing the reliable environmental proxies from these records are always challenging. Here, we present 32 AMS 14C dates of bulk sediments, grain size, and Rb/Sr ratio parameters from the oasis sequence and dates of bulk loess and charcoal from the upstream source regions to examine the significance of oasis sediments on millennial-scale environmental changes in the Taklimakan Desert. We found that substantial reversal of radiocarbon dates on total organic carbon (TOC) was controlled by source region organic carbon input. Loess hills, alpine meadow north of the study region provided fluvial deposits along drainage system and deflation in the river valleys further provide eolain materials. We argue that early oasis deposits experienced deflation and re-deposition less severe than the younger oasis deposits. After refining radiocarbon age-depth relationships for an age model by Bacon package, proxy records show substantial abrupt fluctuations in climate and environments during the last glacial period, among which three wet intervals, two dry periods are identified. The wetter and warmer conditions during the Holocene facilitated human to occupy the oasis.

Greigite formed in early Pleistocene lacustrine sediments from the Heqing Basin, southwest China, and its paleoenvironmental implications

NASA Astrophysics Data System (ADS)

Qiang, Xiaoke; Xu, Xinwen; Zhao, Hui; Fu, Chaofeng

2018-05-01

The ferrimagnetic iron sulfide greigite (Fe3S4) occurs widely in sulfidic lacustrine and marine sedimentary environments. Knowledge of its formation and persistence is important for both magnetostratigraphic and paleoenvironmental studies. Although the formation mechanism of greigite has been widely demonstrated, the sedimentary environments associated with greigite formation in lakes, especially on relatively long timescales, are poorly understood. A long and continuous sequence of Pleistocene lacustrine sediments was recovered in the Heqing drill core from southwestern China, which provides an outstanding record of continental climate and environment. Integrated magnetic, geochemical, and paleoclimatic analysis of the lacustrine sequence provides an opportunity to improve our understanding of the environmental controls on greigite formation. Rock magnetic and scanning electron microscope analyses of selected samples from the core reveal that greigite is present in the lower part of the core (part 1, 665.8-372.5 m). Greigite occurs throughout this interval and is the dominant magnetic mineral, irrespective of the climatic state. The magnetic susceptibility (χ) record, which is mainly controlled by the concentration of greigite, matches well with variations in the Indian Summer Monsoon (ISM) index and total organic carbon (TOC) content, with no significant time lag. This indicates that the greigite formed during early diagenesis. In greigite-bearing intervals, with the χ increase, Bc value increase and tends to be stable at about 50 mT. Therefore, we suggest that χ values could estimate the variation of greigite concentration approximately in the Heqing core. Greigite favored more abundant in terrigenous-rich and organic-poor layers associated with weak summer monsoon which are characterized by high χ values, high Fe content, high Rb/Sr ratio and low TOC content. Greigite enhancement can be explained by variations in terrigenous inputs. Our studies demonstrate that, not only the greigite formation, but also its concentration changes could be useful for studying climatic and environmental variability in sulfidic environments.

Depositional environment and sedimentary of the basinal sediments in the Eibiswalder Bucht (Radl Formation and Lower Eibiswald Beds), Miocene Western Styrian Basin, Austria

NASA Astrophysics Data System (ADS)

Stingl, K.

1994-12-01

The Eibiswald Bucht is a small subbasin of the Western Styrian Basin exposing sediments of Lower Miocene age. In the past the entire sequence exposed in the Eibiswalder Bucht has been interpreted as being of fluvial/lacustrine origin; here, results are presented of detailed sedimentological investigations that lead to a revision of this concept. The lowermost siliciclastic sedimentary unit of the Eibiswalder Bucht sequence is the Radl Formation. It is overlain by the Eibiswald Beds, which are subdivided into the Lower, Middle and Upper Eibiswald Beds. The Radl Formation and the Lower Eibiswald Beds are interpreted as a fan delta complex deposited along NNW-SSE striking faults. Based on the sedimentary facies this fan delta can be subdivided into a subaerial alluvial fan facies group, a proximal delta facies group and a distal delta/prodelta facies group. The Radl Formation comprises the alluvial fan and proximal delta facies groups, the Lower Eibiswald Beds the distal delta/prodelta facies group. The alluvial fan and the proximal delta consist of diverse deposits of gravelly flows. The distal delta/prodelta consists of wave-reworked, bioturbated, low density turbidites intercalated with minor gravelly mass flows. The prodelta can be regarded as as the basin facies of the small and shallow Eibiswalder Bucht, where marine conditions prevailed. The basin was probably in part connected with the Eastern Styrian Basin, the contemporary depositional environment of the Styrian Schlier (mainly turbiditic marine offshore sediments in the Eastern Styrian Basin). Analysis of the clast composition, in conjunction with the paleotransport direction of the coarse delta mass flows of the Radl Formation, shows that the source rocks were exclusively crystalline rocks ranging from greenschists to eclogites.

Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel)

NASA Astrophysics Data System (ADS)

Lisker, Sorin; Porat, Roi; Davidovich, Uri; Eshel, Hanan; Lauritzen, Stein-Erik; Frumkin, Amos

2007-09-01

The Moringa Cave within Pleistocene sediments in the En Gedi area of the Dead Sea Fault Escarpment contains a sequence of various Pleistocene lacustrine deposits associated with higher-than-today lake levels at the Dead Sea basin. In addition it contains Chalcolithic remains and 5th century BC burials attributed to the Persian period, cemented and covered by Late Holocene travertine flowstone. These deposits represent a chain of Late Pleistocene and Holocene interconnected environmental and human events, echoing broader scale regional and global climate events. A major shift between depositional environments is associated with the rapid fall of Lake Lisan level during the latest Pleistocene. This exposed the sediments, providing for cave formation processes sometime between the latest Pleistocene (ca. 15 ka) and the Middle Holocene (ca. 4500 BC), eventually leading to human use of the cave. The Chalcolithic use of the cave can be related to a relatively moist desert environment, probably related to a shift in the location of the northern boundary of the Saharo-Arabian desert belt. The travertine layer was U-Th dated 2.46 ± 0.10 to 2.10 ± 0.04 ka, in agreement with the archaeological finds from the Persian period. Together with the inner consistency of the dating results, this strongly supports the reliability of the radiometric ages. The 2.46-2.10 ka travertine deposition within the presently dry cave suggests a higher recharge of the Judean Desert aquifer, correlative to a rising Dead Sea towards the end of the 1st millennium BC. This suggests a relatively moist local and regional climate facilitating human habitation of the desert.

The magnesium isotope (δ26Mg) signature of dolomites

NASA Astrophysics Data System (ADS)

Geske, A.; Goldstein, R. H.; Mavromatis, V.; Richter, D. K.; Buhl, D.; Kluge, T.; John, C. M.; Immenhauser, A.

2015-01-01

Dolomite precipitation models and kinetics are debated and complicated due to the complex and temporally fluctuating fluid chemistry and different diagenetic environments. Using well-established isotope systems (δ18O, δ13C, 87Sr/86Sr), fluid inclusions and elemental data, as well as a detailed sedimentological and petrographic data set, we established the precipitation environment and subsequent diagenetic pathways of a series of Proterozoic to Pleistocene syn-depositional marine evaporative (sabkha) dolomites, syn-depositional non-marine evaporative (lacustrine and palustrine) dolomites, altered marine ("mixing zone") dolomites and late diagenetic hydrothermal dolomites. These data form the prerequisite for a systematic investigation of dolomite magnesium isotope ratios (δ26Mgdol). Dolomite δ26Mg ratios documented here range, from -2.49‰ to -0.45‰ (δ26Mgmean = -1.75 ± 1.08‰, n = 42). The isotopically most depleted end member is represented by earliest diagenetic marine evaporative sabkha dolomites (-2.11 ± 0.54‰ 2σ, n = 14). In comparing ancient compositions to modern ones, some of the variation is probably due to alteration. Altered marine (-1.41 ± 0.64‰ 2σ, n = 4), and earliest diagenetic lacustrine and palustrine dolomites (-1.25 ± 0.86‰ 2σ, n = 14) are less negative than sabkha dolomites but not distinct in composition. Various hydrothermal dolomites are characterized by a comparatively wide range of δ26Mg ratios, with values of -1.44 ± 1.33‰ (2σ, n = 10). By using fluid inclusion data and clumped isotope thermometry (Δ47) to represent temperature of precipitation for hydrothermal dolomites, there is no correlation between fluid temperature (∼100 to 180 °C) and dolomite Mg isotope signature (R2 = 0.14); nor is there a correlation between δ26Mgdol and δ18Odol. Magnesium-isotope values of different dolomite types are affected by a complex array of different Mg sources and sinks, dissolution/precipitation and non-equilibrium fractionation processes and overprinted during diagenetic resetting. Further progress on the use of δ26Mgdol as a proxy will require new theoretical and experimental data for Δ26Mgfluid-dol that includes dehydration effects of the free Mg aquo ion versus fluid temperature. In ancient diagenetic systems, complex variables must be considered. These include fluid chemistry and physical properties, Mg sources and sinks, temporal changes during precipitation and post-precipitation processes including open and closed system geochemical exchange with ambient fluids. All of these factors complicate the application of δ26Mgdol as proxy for their depositional or diagenetic environments. Nevertheless, the data shown here also indicate that δ26Mgdol can in principle be interpreted within a detailed framework of understanding.

Silicate melt inclusion evidence for extreme pre-eruptive enrichment and post-eruptive depletion of lithium in silicic volcanic rocks of the western United States: implications for the origin of lithium-rich brines

USGS Publications Warehouse

Hofstra, Albert H.; Todorov, T.I.; Mercer, C.N.; Adams, D.T.; Marsh, E.E.

2013-01-01

To evaluate whether anatectic and/or highly fractionated lithophile element-enriched rhyolite tuffs deposited in arid lacustrine basins lose enough lithium during eruption, lithification, and weathering to generate significant Li brine resources, pre-eruptive melt compositions, preserved in inclusions, and the magnitude of post-eruptive Li depletions, evident in host rhyolites, were documented at six sites in the western United States. Each rhyolite is a member of the bimodal basalt-rhyolite assemblage associated with extensional tectonics that produced the Basin and Range province and Rio Grande rift, an evolving pattern of closed drainage basins, and geothermal energy or mineral resources. Results from the 0.8 Ma Bishop tuff (geothermal) in California, 1.3 to 1.6 Ma Cerro Toledo and Upper Bandelier tephra (geothermal) and 27.9 Ma Taylor Creek rhyolite (Sn) in New Mexico, 21.7 Ma Spor Mountain tuff (Be, U, F) and 24.6 Ma Pine Grove tuff (Mo) in Utah, and 27.6 Ma Hideaway Park tuff (Mo) in Colorado support the following conclusions. Melt inclusions in quartz phenocrysts from rhyolite tuffs associated with hydrothermal deposits of Sn, Mo, and Be are extremely enriched in Li (1,000s of ppm); those from Spor Mountain have the highest Li abundance yet recorded (max 5,200 ppm, median 3,750 ppm). Forty-five to 98% of the Li present in pre-eruptive magma was lost to the environment from these rhyolite tuffs. The amount of Li lost from the small volumes (1–10 km3) of Li-enriched rhyolite deposited in closed basins is sufficient to produce world-class Li brine resources. After each eruption, meteoric water leaches Li from tuff, which drains into playas, where it is concentrated by evaporation. The localized occurrence of Li-enriched rhyolites may explain why brines in arid lacustrine basins seldom have economic concentrations of Li. Considering that hydrothermal deposits of Sn, Mo, Be, U, and F may indicate potential for Li brines in nearby basins, we surmise that the world’s largest Li brine resource in the Salar de Uyuni (10 Mt) received Li from nearby rhyolite tuffs in the Bolivian tin belt.

Cenozoic sedimentary dynamics of the Ouarzazate foreland basin (Central High Atlas Mountains, Morocco)

NASA Astrophysics Data System (ADS)

El Harfi, A.; Lang, J.; Salomon, J.; Chellai, E. H.

2001-06-01

Cenozoic continental sedimentary deposits of the Southern Atlas named "Imerhane Group" crop out (a) in the Ouarzazate foreland basin between the Precambrian basement of the Anti Atlas and the uplifted limestone dominated High Atlas, and (b) in the Aït Kandoula and Aït Seddrat nappes where Jurassic strata detached from the basement have been thrust southwards over the Ouarzazate Basin. New biostratigraphic and geochronological data constraining the final Eocene marine regression, the characterization of the new "Aït Ouglif Detrital Formation" presumed to be of Oligocene age, and the new stratigraphic division proposed for the Continental Imerhane Group clarify the major tectonogenetic alpidic movements of the Central High Atlas Range. Four continental formations are identified at regional scale. Their emplacement was governed principally by tectonic but also by eustatic controls. The Hadida and Aït Arbi formations (Upper Eocene) record the major Paleogene regression. They are composed of margino-littoral facies (coastal sabkhas and fluviatile systems) and reflect incipient erosion of the underlying strata and renewed fluvial drainage. The Aït Ouglif Formation (presumed Oligocene) had not been characterized before. It frequently overlies all earlier formations with an angular unconformity. It includes siliciclastic alluvial deposits and is composed predominantly of numerous thin fining-upward cycles. The Aït Kandoula Formation (Miocene-Pliocene) is discordant, extensive, and represents a thick coarsening-upward megasequence. It is composed of palustro-lacustrine deposits in a context of alluvial plain with localized sabkhas, giving way to alluvial fans and fluviatile environments. The Upper Conglomeratic Formation (Quaternary) is the trace of a vast conglomeratic pediment, forming an alluvial plain and terraces. The second and third formations correspond to two megasequences engendered by the uplift of the Central High Atlas in two major compressive phases during late Oligocene and Miocene-Pliocene times. These two geodynamic events were separated by a tectonically calm phase, materialized by palustro-lacustrine sedimentation (Görler et al. 1988). Tectono-sedimentary analysis of the two megasequences shows that the basin structure and depositional processes were controlled by the compressive tectonic context generated by the collision of North Africa and Iberia in Tertiary times (Jacobshagen et al. 1988). The Quaternary Formation was apparently controlled by a tectonic continuum and by climatic variations.

Sedimentation, volcanism, and ancestral lakes in the Valles Marineris: Clues from topography

NASA Technical Reports Server (NTRS)

Lucchitta, B. K.; Isbell, N. K.; Howington-Kraus, A.

1993-01-01

Compilation of a simplified geologic/geomorphic map onto a digital terrain model of Valles Marineris has permitted quantitative evaluations of topographic parameters. The study showed that, if their interior layered deposits are lacustrine, the ancestral Valles Marineris must have consisted of isolated basins. If, on the other hand, the troughs were interconnected as they are today, the deposits are most likely to volcanic origin, and the mesas in the peripheral troughs may be table mountains. The material eroded from the trough walls was probably not sufficient to form all of the interior layered deposits, but it may have contributed significantly to their formation.

Ancient hydrothermal ecosystems on earth: a new palaeobiological frontier.

PubMed

Walter, M R

1996-01-01

Thermal springs are common in the oceans and on land. Early in the history of the Earth they would have been even more abundant, because of a higher heat flow. A thermophilic lifestyle has been proposed for the common ancestor of extant life, and hydrothermal ecosystems can be expected to have existed on Earth since life arose. Though there has been a great deal of recent research on this topic by biologists, palaeobiologists have done little to explore ancient high temperature environments. Exploration geologists and miners have long known the importance of hydrothermal systems, as they are sources for much of our gold, silver, copper, lead and zinc. Such systems are particularly abundant in Archaean and Proterozoic successions. Despite the rarity of systematic searches of these by palaeobiologists, already 12 fossiliferous Phanerozoic deposits are known. Five are 'black smoker' type submarine deposits that formed in the deep ocean and preserve a vent fauna like that in the modern oceans; the oldest is Devonian. Three are from shallow marine deposits of Carboniferous age. As well as 'worm tubes', several of these contain morphological or isotopic evidence of microbial life. The oldest well established fossiliferous submarine thermal spring deposit is Cambro-Ordovician; microorganisms of at least three or four types are preserved in this. One example each of Carboniferous and Jurassic sub-lacustrine fossiliferous thermal springs are known. There are two convincing examples of fossiliferous subaerial hydrothermal deposits. Both are Devonian. Several known Proterozoic and Archaean deposits are likely to preserve a substantial palaeobiological record, and all the indications are that there must be numerous deposits suitable for study. Already it is demonstrable that in ancient thermal spring deposits there is a record of microbial communities preserved as stromatolites, microfossils, isotope distribution patterns and hydrocarbon biomarkers.

Limnogeological evidence of tropical floodplain responses to environmental change on a distal fluvial megafan, Pantanal, Brazil

NASA Astrophysics Data System (ADS)

Lo, E. L.; McGlue, M. M.; Silva, A.; Bergier, I.; Yeager, K. M.; Macedo, H. D. A.; O'Dell, M. L.

2016-12-01

Floodplains and their wetlands are host to major components of tropical biogeochemical and nutrient cycles, but these environments are changing in response to increasingly variable climate patterns. As the world's largest freshwater tropical wetland, the Pantanal (South America) is an ideal study site due to its largely pristine state and sensitivity to variability in climate stemming from linkages with Paraguay River flooding. Because of the ability to record aspects of climate, tectonics, and landscape, lakes and their sediments can help with understanding environmental change in tropical floodplain systems. This initial study examined sedimentary indicators of change in Lake Uberaba, which is located at the distal Paraguay megafan along the border of Brazil and Bolivia. Bathymetry measurements, surface sediments, and water samples were collected from the lake in 2015 and 2016, to characterize the contemporary limnogeological system. During the surveys, the lake was 230 km2 with a maximum depth of 3.5 m in the southern part of the lake. Eight short cores (< 1m) were obtained to assess spatial variability in facies, and temporal changes to fluvio-lacustrine environments. Sediment samples were evaluated for elemental composition, clastic grain size, organic carbon, carbonate, radionuclides (137Cs, 210Pb) and biogenic silica. Initial results showed that surface sediment in the lake is primarily silty, with sand concentrated in the center of the lake. Prograding sediments of the Paraguay megafan are filling the lake from north to south, aided by aquatic macrophytes, which stabilize the sediment as woody vegetation becomes more common. Several of the cores contained a pronounced transition from dense, oxidized silty clay to organic-rich clayey silt, which suggested a shift in depositional setting from distal floodplain to an open lacustrine environment. Future work will use radiocarbon (14C) and optically stimulated luminescence (OSL) to constrain the timing of initial lake transgression over the distal megafan, and place this event in the context of regional environmental change in the Pantanal.

A 600-year-long stratigraphic record of tsunamis in south-central Chile

USGS Publications Warehouse

Hong, Isabel; Dura, Tina; Ely, Lisa L.; Horton, Benajamin P.; Nelson, Alan R.; Cisternas, Marco; Nikitina, Daria; Wesson, Robert L.

2017-01-01

The stratigraphy within coastal river valleys in south-central Chile clarifies and extends the region’s history of large, earthquakes and accompanying tsunamis. Our site at Quidico (38.1°S, 73.3°W) is located in an overlap zone between ruptures of magnitude 8–9 earthquakes in 1960 and 2010, and, therefore, records tsunamis originating from subduction-zone ruptures north and south of the city of Concepción. Hand-dug pits and cores in a 3-m-thick sequence of freshwater peat in an abandoned meander (a little-examined depositional environment for tsunami deposits) and exposures along the Quidico River show five sand beds that extend as much as 1.2 km inland. Evidence for deposition of the beds by tsunamis includes tabular sand beds that are laterally extensive (>100 m), well sorted, fine upward, have sharp lower contacts, and contain diatom assemblages dominated by brackish and marine taxa. Using eyewitness accounts of tsunami inundation, 137Cs analyses, and 14C dating, we matched the upper four sand beds with historical tsunamis in 2010, 1960, 1835, and 1751. The oldest prehistoric bed dates to 1445–1490 CE and correlates with lacustrine and coastal records of similar-aged earthquakes and tsunamis in south-central Chile.

The Hei River Basin in northwestern China - tectonics, sedimentary processes and pathways

NASA Astrophysics Data System (ADS)

Rudersdorf, Andreas; Nottebaum, Veit; Schimpf, Stefan; Yu, Kaifeng; Hartmann, Kai; Stauch, Georg; Wünnemann, Bernd; Reicherter, Klaus; Diekmann, Bernhard; Lehmkuhl, Frank

2014-05-01

The Hei River Basin (catchment area of c. 130,000 km²) is situated at the transition between the northern margin of the Tibetan Plateau and the southern slopes of Gobi-Tien-Shan. As part of the northwestern Chinese deserts, the Ejina Basin (Gaxun Nur Basin) constitutes the endorheic erosion base of the drainage system. The basin - hosting the second largest continental alluvial fans in the world, is tectonically strongly shaped by the Gobi belt of left-lateral transpression. The tectonic setting in combination with competing climatic driving forces (Westerlies and summer/winter monsoon currents) has supported the formation of a valuable long-time sediment archive comprises at least the last 250,000 yrs. of deposition. It is composed by the interplay of eolian, fluvial and lacustrine sedimentation cycles and today is dominated by widespread (gravel) gobi surfaces, insular dune fields and shallow evaporitic playa areas. Thus, it provides excellent conditions to investigate tectonic evolution and Quaternary environmental changes. Recently, geomorphological, geophysical, neotectonic and mineralogical studies have enhanced the understanding of the environmental history and the modern depositional environment. Moreover, the role of the Hei River Basin as an important source area of silt particles which were later deposited on the Chinese Loess Plateau is evaluated. Therefore, a 230 m long drill core, sediment sections and ca. 700 surface samples throughout the whole catchment and basin were analyzed. Instrumental and historical seismicity are very low, but the proximity to active fault zones and dating irregularities in earlier publications indicate evidence for deformation in the study area. Despite flat topography, indications of active tectonics such as fault-related large-scale lineations can be observed. Seismically deformed unconsolidated lacustrine deposits (seismites), presumably of Holocene age, are evident and must be related to the nearby faults. The upper catchment is represented by the Qilian Shan mountain range and its immediate foreland. Here, a tripartite altitudinal distribution of terrestrial sediment archives is evident, which is representative of catchment-wide sedimentological processes. Insights into their formation mechanisms, therefore, add valuable perspective regarding the reconstruction of sedimentological and paleoenvironmental conditions in the depositional area of the Hei River Basin. For the characterization of provenance and dispersal of Quaternary sediments in relation to the modern depositional environment, over 200 surface samples from the whole catchment were analyzed using XRD and XRF measurements on the clay fractions, heavy minerals and bulk sediments. The clay mineral results in-particular show that it is possible to discriminate between the chlorite rich metamorphic sediments originating from greenschist bearing rocks in the Qilian Shan Mountain Range in the south, and the more intrusive rocks from the Bei Shan Mountain Range west of the Hei River Basin. Additionally, these two main sources reflect different transportation processes; the Qilian Shan sediments are mainly transported by the rivers Heihe and Beida He, and the deposition of the Bei Shan sediments is mainly driven by wind or local runoff. Grain size results of primary loess deposits indicate different eolian transport pathways, i.e., far-travelled dust input (medium silty) vs. local deflation from active fluvial channels (fine sandy). Along the altitudinal transect, the varying geomorphological settings exert a significant influence on the grain size composition showing an increased contribution of far-travelled dust at higher altitudes.

Unique phenomenon of the accumulation of terrestrial metal iron particles in lacustrine deposits: Zhombolok volcanic region, East Sayan

NASA Astrophysics Data System (ADS)

Pechersky, D. M.; Kazanskii, A. Yu.; Markov, G. P.; Tselmovich, V. A.; Shchetnikov, A. A.

2018-01-01

The native iron particles that were previously detected by thermomagnetic and microprobe analyses in the sediments of different age in many regions of the world are of extraterrestrial origin. The similarity in the compositions, grain shapes, and sizes observed in the extraterrestrial and terrestrial particles of native iron testifies to the common production conditions of iron particles during the formation of planets. In this paper, the single finding of terrestrial iron in the lacustrine sediments of the Zhombolok volcanic region, East Sayan, is discussed. The uniqueness of the results indicates that the spatial distribution of the particles of native iron is limited to a fairly narrow area around their source—volcanic eruption or/and the fall of a large meteorite.

The Main Factors of Uranium Accumulation in the Ishim Plain Saline Lakes (Western Siberia)

NASA Astrophysics Data System (ADS)

Vladimirov, A. G.; Krivonogov, S. K.; Karpov, A. V.; Nikolaeva, I. V.; Razvorotneva, L. I.; Kolpakova, M. N.; Moroz, E. N.

2018-04-01

Hydrochemical analysis of the high-salinity lakes in the Ishim Plain (>250-300 g/L) located at the border with the Northern Kazakhstan uranium ore province is performed. The studies have shown that the main factor of concentration and redistribution of uranium in the lake basins of the Ishim Plain are the processes of intense salt deflation causing sanding of lakes and uranium depletion in the near-surface layer of the bottom deposits. The correlation between the hydroxide forms of uranium binding in the bottom lacustrine deposits of the Ishim Plain and the coffinite composition of the Semizbai deposit makes it possible to consider this province to be promising for the discovery of hydromineral uranium deposits.

MX Siting Investigation. Geotechnical Evaluation. Verification Study - Ralston Valley, Nevada. Volume II. Geotechnical Data.

DTIC Science & Technology

1980-06-15

A3d). A4 Playa and Lacustrine Deposits - Deposits occurring in modern, active playas (A4) or in either inactive playas or older lake beds and abandoned...some f ine gravel 2 1 3403 3 4 vertical Smedium usal 2 10 de tnse GRAVELLY SAND,* brown *f ins to coarse, mell graded ,slightly moist ,sub- 12 o... lima 11𔄀-1 5 of ? - nRm NATIONAL, INS. 47 AFV-O1 -3 FN-TR-27-RV PERCENT FINER BY WEIGHT SAMPLE INTERVAL STANDARD SIEVE OPENING U S STAIIOA

Complex patterns of glacier advances during the Lateglacial in the Chagan-Uzun Valley, Russian Altai

NASA Astrophysics Data System (ADS)

Gribenski, Natacha; Lukas, Sven; Jansson, Krister N.; Stroeven, Arjen P.; Preusser, Frank; Harbor, Jonathan M.; Blomdin, Robin; Ivanov, Mikhail N.; Heyman, Jakob; Petrakov, Dmitry; Rudoy, Alexei; Clifton, Tom; Lifton, Nathaniel A.; Caffee, Marc W.

2016-04-01

Over the last decades, numerous paleoglacial reconstructions have been carried out in Central Asian mountain ranges because glaciers in this region are sensitive to climate change, and thus their associated glacial deposits can be used as proxies for paleoclimate inference. However, non-climatic factors can complicate the relationship between glacier fluctuation and climate change. Careful investigations of the geomorphological and sedimentological context are therefore required to understand the mechanisms behind glacier retreat and expansion. In this study we present the first detailed paleoglacial reconstruction of the Chagan Uzun valley, located in the Russian Altai. This reconstruction is based on detailed geomorphological mapping, sedimentological logging, in situ cosmogenic 10Be and 26Al surface exposure dating of glacially transported boulders, and Optically Stimulated Luminescence (OSL) dating. The Chagan Uzun valley includes extensive lobate moraine belts (>100 km2) deposited in the intramontane Chuja basin, reflecting a series of pronounced former glacial advances. Observation of "hillside-scale" folding and extensive faulting of pre-existing soft sediments within the outer moraine belts, together with the geomorphology, indicate that these moraine belts were formed during glacier-surge like events. In contrast, the inner (up-valley) glacial landforms of the Chagan Uzun valley indicate that they were deposited by retreat of temperate valley glaciers and do not include features indicative of surging. Cosmogenic ages associated with the outermost, innermost and intermediary stages, all indicate deposition times clustered around 19.5 ka, although the 10Be ages of the outermost margin are likely slightly underestimated due to brief episode of glacial lake water coverage. Such close deposition timings are consistent with periods of fast or surge advances, followed by active glacier retreat. OSL dating yields significantly older ages of thick lacustrine accumulation along the Chagan Uzun River, which confirms the presence of lacustrine sediments in the Chagan Uzun glacier foreland before the glacier advances. Such sediments could have acted as a soft bed over which fast or unstable glacier flow occurred. This is the first study reporting surge-like behaviour of former glaciers in the Altai mountain range, supported by detailed geomorphological and sedimentological evidences. Such findings are crucial for paleoclimate inference, as the surge-related features cannot be attributed to a glacier system in equilibrium with the contemporary climate, and cannot be interpreted with traditional ELA reconstructions. This study also highlights the complexity of establishing robust paleoglacial chronologies in highly dynamic environments, with interactions between glacial events and the formation and drainage of lakes.

Late Cenozoic geology and lacustrine history of Searles Valley, Inyo and San Bernardino Counties, California

USGS Publications Warehouse

Smith, George I.

2009-01-01

Searles Valley is an arid, closed basin lying 70 km east of the south end of the Sierra Nevada, California. It is bounded on the east and northeast by the Slate Range, on the west by the Argus Range and Spangler Hills, and on the south by the Lava Mountains; Searles (dry) Lake occupies the north-central part of the valley. During those parts of late Pliocene and Pleistocene time when precipitation and runoff from the east side of the Sierra Nevada into the Owens River were much greater than at present, a chain of as many as five large lakes was created, of which Searles Lake was third. The stratigraphic record left in Searles Valley when that lake expanded, contracted, or desiccated, is fully revealed by cores from beneath the surface of Searles (dry) Lake and partly recorded by sediments cropping out around the edge of the valley. The subsurface record is described elsewhere. This volume includes six geologic maps (scales: 1:50,000 and 1:10,000) and a text that describes the outcrop record, most of which represents sedimentation since 150 ka. Although this outcrop record is discontinuous, it provides evidence indicating the lake's water depths during each expansion, which the subsurface record does not. Maximum-depth lakes rose to the 2,280-ft (695 m) contour, the level of the spillway that led overflowing waters to Panamint Valley; that spillway is about 660 ft (200 m) above the present dry-lake surface. Several rock units of Tertiary and early Quaternary ages crop out in Searles Valley. Siltstone and sandstone of Tertiary age, mostly lacustrine in nature and locally deformed to near-vertical dips, are exposed in the southern part of the valley, as is the younger(?) upper Miocene Bedrock Spring Formation. Unnamed, mostly mafic volcanic rocks of probable Miocene or Pliocene age are exposed along the north and south edges of the basin. Slightly deformed lacustrine sandstones are mapped in the central-southwestern and southern parts of the study area. The Christmas Canyon Formation and deposits mapped as older gravel and older tufa are extensively exposed over much of the basin floor. The older gravel unit and the gravel facies of the Christmas Canyon Formation are boulder alluvial gravels; parts of these units are probably correlative. The lacustrine facies of the Christmas Canyon Formation includes the Lava Creek ash, which is dated at 0.64 Ma; the older tufa deposits may be equivalent in age to those sediments. Most of this study concerns sediments of the newly described Searles Lake Formation, whose deposition spanned the period between about 150 ka and 2 ka. Most of this formation is lacustrine in origin, but it includes interbedded alluvium. To extract as much geologic detail as possible, criteria were developed that permitted (1) intrabasin correlation of some thin outcrop units representative of only a few thousand years (or less), (2) identification of unconformities produced by subaerial erosion, (3) identification of unconformities produced by sublacustrine erosion, and (4) correlation of outcrop units with subsurface units. The Searles Lake Formation is divided into seven main units, many of which are subdivided on the five larger scale geologic maps. Units A (oldest), B, C, and D are dominantly lacustrine in origin. The Pleistocene-Holocene boundary is placed at the top of unit C. In areas that were a kilometer or more from shore at the time of deposition, deposits of units A,B, and C consist of fine, highly calcareous sand, silt, or clay; nearer to shore they consist of well-sorted coarse sand and gravel. Unit A has been locally subdivided into as many as four subunits, unit B into six subunits, and unit C into six subunits. The finer facies of units A, B, and C contain such high percentages of Caco3 that they are best described as marl. Sediments of unit C, and to a lesser extent those of unit B, are laminated with light- to white-colored layers of aragonite, calcite, or dolomite(?) that may repre

Lipid-based palaeotemperature reconstruction in lakes: New insights on the applicability of branched GDGTs in lacustrine sedimentary archives

NASA Astrophysics Data System (ADS)

Weber, Yuki; De Jonge, Cindy; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S.; Gilli, Adrian; Lehmann, Moritz F.; Niemann, Helge

2014-05-01

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids that occur ubiquitously in soils worldwide. The relative abundances of nine structurally related brGDGTs (used in the MBT and CBT indices) have been shown to correlate with mean annual air temperature (MAAT) and soil pH, making them potential proxies in sediments that receive soil organic matter from terrestrial environments. The brGDGT distributions in lake deposits, however, mostly follow a different correlation with air temperature and (to a minor extent) lake water pH. This points to a substantial contribution of brGDGTs from in situ production within the lake water column and/or -sediments. It is also quite likely that the fractions of soil- and lake-derived brGDGTs vary considerably between sampling sites and with time, due to spatial and temporal changes in sediment input rates. Paleoclimate reconstructions using lacustrine brGDGT records thus remain challenging, especially because little is known about the environmental variables that control bacterial brGDGT production within aquatic environments. In order to decipher the impact of in situ production, we compared the brGDGT composition of surface sediments and corresponding catchment soils of 35 lakes from the Swiss alpine region, spanning an altitudinal gradient from 200 - 2000 m above mean sea level. We used an improved HPLC method to additionally quantify six recently discovered isomers, which vary in the position of their methyl branches. These 6-methyl compounds previously co-eluted with those brGDGTs used to calculate the MBT and CBT indices, obscuring any paleoenvironmental information they potentially yield. A principal component analysis suggests that the fractional abundances of the 6-methyl brGDGTs are primarily controlled by the surface water pH of the lakes. Notably, and in contrast to soils, the fractional abundance of the 5-methyl pentamethylated brGDGT in lake sediments does not show a correlation with MAAT (derived from the lapse rate model), possibly pointing to different source organisms in soils and lakes. Our results imply that in situ production of brGDGTs plays a mayor role. By further constraining the environmental controls on lake-derived brGDGTs, we aim to improve the future applicability of brGDGT-based proxies in lacustrine climate archives.

Geomorphic investigation of the Late-Quaternary landforms in the southern Zanskar Valley, NW Himalaya

NASA Astrophysics Data System (ADS)

Sharma, Shubhra; Hussain, Aadil; Mishra, Amit K.; Lone, Aasif; Solanki, Tarun; Khan, Mohammad Khatib

2018-02-01

The Suru, Doda and Zanskar river valleys in the semi-arid region of Southern Zanskar Ranges (SZR) preserve a rich repository of the glacial and fluvial landforms, alluvial fans, and lacustrine deposits. Based on detailed field observations, geomorphic mapping and limited optical ages, we suggest four glaciations of decreasing magnitude in the SZR. The oldest Southern Zanskar Glaciation Stage (SZS-4) is inferred from glacially polished bedrock and tillite pinnacles. The SZS-4 is ascribed to the Marine Isotopic Stage (MIS)-4/3. The subsequent SZS-3 is represented by obliterated and dissected moraines, and is assigned to MIS-2/Last Glacial Maximum. The multiple recessional moraines of SZS-2 glaciation are assigned the early to mid Holocene age whereas, the youngest SZS-1 moraines were deposited during the Little Ice Age. We suggest that during the SZS-2 glaciation, the Drang-Drung glacier shifted its course from Suru Valley (west) to the Doda Valley (east). The study area has preserved three generations of outwash gravel terraces, which broadly correlate with the phases of deglaciation associated with SZS-3, 2, and 1. The alluvial fan aggradation, lacustrine sedimentation, and loess deposition occurred during the mid-to-late Holocene. We suggest that glaciation was driven by a combination of the mid-latitude westerlies and the Indian Summer Monsoon during periods of cooler temperature, while phases of deglaciation occurred during enhanced temperature.

Late Paleogene terrestrial fauna and paleoenvironments in Eastern Anatolia: New insights from the Kağızman-Tuzluca Basin

NASA Astrophysics Data System (ADS)

Métais, Grégoire; Sen, Sevket; Sözeri, Koray; Peigné, Stéphane; Varol, Baki

2015-08-01

In Eastern Turkey, relatively little work has been undertaken to characterize the sedimentologic and stratigraphical context of the Kağızman-Tuzluca Basin until now. Extending across the Turkey-Armenian border, this basin documents the syn- and post-collisional evolution of Eastern Anatolia, resulting from the closure of the Neotethyan Seaways and the final collision of the Afro-Arabian and Eurasian plates. From detailed sedimentological and paleontological studies, we propose an interpretation of the lithology and depositional environment of the Late Paleogene Alhan Formation located on the western bank of the Aras River. This sequence of terrestrial clastics rests directly and unconformably onto the ophiolitic mélange, and it documents several depositional sequences deposited in alluvial plain and lacustrine environments. At this stage, the age of the Alhan Formation can only be calibrated by fossil evidence. Several stratigraphic levels yielding fossil data along the section have been identified, but these poor assemblages of fauna and flora hamper extensive comparisons with roughly contemporaneous localities of Central and Southern Asia. Carnivorous and ruminant mammal remains are reported for the first time from the supposed Late Oligocene Güngörmez Formation. The identified fossil mammal taxa reveal biogeographic affinities between Central Anatolia and southern Asia, thus suggesting dispersal between these areas during the Oligocene or earlier. Further studies of the fossil assemblages from the Kağızman-Tuzluca Basin and other basins of Eastern Anatolia and lesser Caucasus regions are needed to better constrain the paleobiogeographic models.

Paleohydrologic regimes in the southwestern Great Basin, 0-3.2 my ago, compared with other long records of "gobal" climate

USGS Publications Warehouse

Smith, G.I.

1984-01-01

Nine distinct paleohydrologic regimes in the southwestern Great Basin over the last 3.2 my are recorded by the lacustrine deposits in KM-3, a 930-m core from Searles Lake, California. These are characterized as being "wet," "intermediate," or "dry" (like today). Excepting the present incomplete regime, each lasted 0.12 to 0.76 my. Major regime changes 0.01, 0.13, 0.6, and 2.5 my ago appear to coincide with recognized changes in global ice-sheet histories as represented by 18O and other records from marine sediments, but comparable changes 0.3, 1.0, 1.3, and 2.0 my ago do not appear to coincide closely with comparable perturbations in ice-sheet histories. However, all regime boundaries (during the last 1.75 my) coincide closely in time with changes in sea-surface temperatures in the tropical Atlantic, and many coincide with other deep-sea and continental paleoclimatic boundaries.The average duration of these paleohydrologic regimes was about 0.4 my (standard deviation, 0.2 my or less, depending on assumptions), and it is suggested that the regime boundaries reflect times of change in global(?) sea-surface temperatures, possibly controlled in part by the Earth's 413,000-yr orbital eccentricity cycle. During the wettest and driest regimes in the Searles Lake area, lake levels were not sufficiently affected by the 23,000-, to 42,000-, or 100,000-yr climate cycles related to high-latitude ice-sheet fluctuations to produce changes in the lacustrine sediment character. During intermediate regimes, however, when lacustrine sedimentation in this area was more sensitive to climate, the sediments, in KM-3, record lake fluctuations with average frequencies near those of the ice sheets. This seems to indicate that the high-latitude ice-sheet fluctuations caused local climatic perturbations but did not dominate the hydrologic component of climate in this area. Other lacustrine deposits in the southwestern Great Basin of California and Nevada have ages comparable in part to those of the wet to intermediate regimes indicated by KM-3, and they may all be products of finite periods when lake expansion, alluvial fan growth, increased spring discharge, and fluvial deposition were promoted in this area by widespread wet climates. Glacier expansion in the Sierra Nevada may also have been primarily an expression of, and in phase with, these wet regimes. ?? 1984.

Sedimentology and paleoenvironments of the Las Chacritas carbonate paleolake, Cañadón Asfalto Formation (Jurassic), Patagonia, Argentina

NASA Astrophysics Data System (ADS)

Cabaleri, Nora G.; Benavente, Cecilia A.

2013-02-01

The Las Chacritas Member is the lower part of the Cañadón Asfalto Formation (Jurassic). The unit is a completely continental limestone succession with volcanic contributions that were deposited during the development of the Cañadón Asfalto Rift Basin (Chubut province, Patagonia, Argentina). A detailed sedimentological analysis was performed in the Fossati depocenter to determine the paleoenvironments that developed in the context of this rift. The Las Chacritas Member represents a carbonate paleolake system with ramp-shaped margins associated with wetlands that were eventually affected by subaerial exposure and pedogenesis. This process is represented by three main subenvironments: a) a lacustrine setting sensu stricto (lacustrine limestone facies association), represented by Mudstones/Wackestones containing porifera spicules (F1), Intraclastic packstones (F6) and Tabular stromatolites (F10) in which deposition and diagenesis were entirely subaqueous; b) a palustrine setting (palustrine limestone facies association) containing Microbial Mudstones (F2), Intraclastic sandy packstone with ostracode remains (F3), Oncolitic packstone (F5), Brecciated limestone (F7) and Nodular-Mottled limestone (F8) representing shallow marginal areas affected by groundwater fluctuations and minor subaerial exposure; and c) a pedogenic paleoenvironment (pedogenic limestone facies association) including Intraclastic limestone (F4) and Packstones containing Microcodium (F9) facies displaying the major features of subaerial exposure, pedogenic diagenesis and the development of paleosols. The fluvial-palustrine-lacustrine succession shows a general shallow upward trend in which contraction-expansion cycles are represented (delimited by exposure and surface erosion). The variations in the successive formations reflect the responses to fluctuations in a combination of two major controls, the tectonic and local climatic variables. The predominance of the palustrine facies associations was determined by its accommodation space as well as the local climate conditions. The variations in the lacustrine limestone facies associations reflect differential patterns of subsidence within the sub-basin. The diagnostic features of the palustrine limestone facies associations (organic matter (OM) content, microinvertebrate fauna, abundant mud cracks, brecciation, presence of evaporitic minerals) frame the sub-basin in a climatic context intermediate between arid and subhumid conditions.

Tephras in lacustrine sediments of the Sarliève marsh (French Massif Central): age and preservation

NASA Astrophysics Data System (ADS)

Fourmont, Agathe; Macaire, Jean-Jacques; Bréhéret, Jean-Gabriel; Argant, Jacqueline; Prat, Béatrice; Vernet, Gérard

2006-12-01

The Sarliève marsh sediments (Massif Central, France) contain two tephras. The first tephra [ 13.7±0.4ka(2δ), ca. 12 000 BP], regionally well known, enables to date the beginning of lacustrine infill to the Lateglacial. The second tephra, the 'tephra de Sarliève', the emitting volcano of which is unknown, would be dated to around the Early Subboreal from pollen data. This occurrence, after the discovery of the 'tephra de Beaunit', emphasizes that volcanic eruption(s) occurred in the 'Chaîne des Puys' or in the volcanic Cézallier more than 1000 years after the last known eruption (Pavin) in the 'Chaîne des Puys' at around 6.6/6.7 ka (5800/5900 BP). In the Sarliève piles, these tephras, well preserved in thick and more silicated deposits of deltas, were not observed in carbonated basin sediments where they were altered. The abundance of authigenic zeolites formed during the Lateglacial in restricted depocentre lacustrine waters allows us to detect initial CF1 tephra occurrence. To cite this article: A. Fourmont et al., C. R. Geoscience 338 (2006).

Chronological framework for the deglaciation of the Lake Michigan lobe of the Laurentide ice sheet from ice-walled lake deposits

USGS Publications Warehouse

Curry, B.; Petras, J.

2011-01-01

A revised chronological framework for the deglaciation of the Lake Michigan lobe of the south-central Laurentide Ice Sheet is presented based on radiocarbon ages of plant macrofossils archived in the sediments of low-relief ice-walled lakes. We analyze the precision and accuracy of 15 AMS 14C ages of plant macrofossils obtained from a single ice-walled lake deposit. The semi-circular basin is about 0.72km wide and formed of a 4- to 16-m-thick succession of loess and lacustrine sediment inset into till. The assayed material was leaves, buds and stems of Salix herbacea (snowbed willow). The pooled mean of three ages from the basal lag facies was 18 270??50 14C a BP (21 810cal. a BP), an age that approximates the switch from active ice to stagnating conditions. The pooled mean of four ages for the youngest fossil-bearing horizon was 17 770??40 14C a BP (21 180cal. a BP). Material yielding the oldest and youngest ages may be obtained from sediment cores located at any place within the landform. Based on the estimated settling times of overlying barren, rhythmically bedded sand and silt, the lacustrine environment persisted for about 50 more years. At a 67% confidence level, the dated part of the ice-walled lake succession persisted for between 210 and 860cal. a (modal value: 610cal. a). The deglacial age of five moraines or morainal complexes formed by the fluctuating margin of the Lake Michigan lobe have been assessed using this method. There is no overlap of time intervals documenting when ice-walled lakes persisted on these landforms. The rapid readvances of the lobe during deglaciation after the last glacial maximum probably occurred at some point between the periods of ice-walled lake sedimentation. ?? 2011 John Wiley & Sons, Ltd.

A Quaternary paleolake in a sinkhole at Cassis (SE France) : a geomorphology and geophysical study

NASA Astrophysics Data System (ADS)

Romey, C.; Rochette, P.; Vella, C.; Arfib, B.; Champollion, C.; Dussouillez, P.; Hermitte, D.; Parisot, J.-C.

2012-04-01

The Lower Provence and the Massif des Calanques, near Marseille, are a key area in understanding the mechanisms of evolution of the Mediterranean climate and the study of human impact on the local environment during the Quaternary. However, a continuous continental record of paleoenvironment in coastal Provence was not previously available. Looking for such a record, we discovered in a coastal alluvial plain a small paleolake filling a sinkhole that occurred in a marl sequence topping pure limestones at an altitude of 80 m, and a distance to the sea of 2 km. The sinkhole is close to the outlet of a small catchment area of about 8 km2. Limestone is massive but much fractured and therefore suitable for the development of karst. The drilling sedimentary sequence of 50 meters is mainly resulting from the weathering of Cretaceous marls. It consists of 5 meters of oxidized brown clay deposit which covers 45 meters of laminated lacustrine gray clay with sandy past. Cretaceous marls are at the base of the sequence. The presence of marls pebbles in the last meters of the sequence reflects the collapse of the sinkhole. The lacustrine clay was probably deposed during stages isotope 2 to 4 (48 ± 3 ka C14 date at 23 meters depth), whereas brown clay deposit was interpreted as Holocene paleosol. Combination of surface observation, drilling and geophysical studies (gravimetry and Electrical Resistivity Tomography) allows to constraint the geometry of the paleo-polje that formed during glacial period. Lake diameter was likely of the order of 200 m. It evolved from a deep lake to a swamp (probably Holocene, dating in progress) and it was drained in roman times for agriculture. Locally, this discovery has implications for the understanding of karst processes and water resources. The relationship between the sinkhole, rooted at circa 100 m below surface according to gravimetric modeling and the underground karstic river of Bestouan is strongly suggested by underwater exploration and hydrogeologic investigations.

Impact Crater Deposits in the Martian Highlands

NASA Technical Reports Server (NTRS)

Mest, S. C.; Crown, D. a.

2005-01-01

The martian highlands of Noachis Terra (20-30 deg S, 20-50 deg E), Tyrrhena Terra (0-30 deg S, 50- 100 deg E) and Terra Cimmeria (0-60 deg S, 120-170 deg E) preserve long and complex histories of degradation, but the relative effects of such factors as fluvial, eolian, and mass wasting processes have not been well constrained. The effects of this degradation are best observed on large (D greater than 10 km) impact craters that characterize the ancient highlands. Some craters exhibit distinct interior deposits, but precise origins of these deposits are enigmatic; infilling may occur by sedimentary (e.g., fluvial, lacustrine, eolian), mass wasting and (or) volcanic processes.

A tale of two rare wild buckwheats (Eriogonum subgenus Eucycla (Polygonaceae)) from Southeastern Arizona

Treesearch

John L. Anderson

2007-01-01

Unusual soils, compared to surrounding common soils, act as edaphic habitat islands and often harbor rare plants. These edaphic elements can be disjuncts or endemics. Two rare wild buckwheats from southeastern Arizona that grow on Tertiary lacustrine lakebed deposits have been found to be a disjunct, and an endemic. Eriogonum apachense from the Bylas...

Introduction to special section: China shale gas and shale oil plays

USGS Publications Warehouse

Jiang, Shu; Zeng, Hongliu; Zhang, Jinchuan; Fishman, Neil; Bai, Baojun; Xiao, Xianming; Zhang, Tongwei; Ellis, Geoffrey S.; Li, Xinjing; Richards-McClung, Bryony; Cai, Dongsheng; Ma, Yongsheng

2015-01-01

Even though China shale gas and shale oil exploration is still in an early stage, limited data are already available. We are pleased to have selected eight high-quality papers from fifteen submitted manuscripts for this timely section on the topic of China shale gas and shale oil plays. These selected papers discuss various subject areas including regional geology, resource potentials, integrated and multidisciplinary characterization of China shale reservoirs (geology, geophysics, geochemistry, and petrophysics) China shale property measurement using new techniques, case studies for marine, lacustrine, and transitional shale deposits in China, and hydraulic fracturing. One paper summarizes the regional geology and different tectonic and depositional settings of the major prospective shale oil and gas plays in China. Four papers concentrate on the geology, geochemistry, reservoir characterization, lithologic heterogeneity, and sweet spot identification in the Silurian Longmaxi marine shale in the Sichuan Basin in southwest China, which is currently the primary focus of shale gas exploration in China. One paper discusses the Ordovician Salgan Shale in the Tarim Basin in northwest China, and two papers focus on the reservoir characterization and hydraulic fracturing of Triassic lacustrine shale in the Ordos Basin in northern China. Each paper discusses a specific area.

Glacial Refugium of Pinus pumila (Pall.) Regel in Northeastern Siberia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shilo, N A; Lozhkin, A V; Anderson, P M

One of the most glowing representatives of the Kolyma flora [1], ''Pinus pumila'' (Pall.) Regel (Japanese stone pine), is a typical shrub in larch forests of the northern Okhotsk region, basins of the Kolyma and Indigirka rivers, and high-shrub tundra of the Chukchi Peninsula. It also forms a pine belt in mountains above the forest boundary, which gives way to the grass-underbrush mountain tundra and bald mountains. In the southern Chukchi Peninsula, ''Pinus pumila'' along with ''Duschekia fruticosa'' (Rupr.) Pouzar and ''Betula middendorffii'' Trautv. et C. A. Mey form trailing forests transitional between tundra and taiga [2]. Pinus pumila pollen,more » usually predominating in subfossil spore-and-pollen spectra of northeastern Siberia, is found as single grains or a subordinate component (up 2-3%, rarely 10%) in spectra of lacustrine deposits formed during the last glacial stage (isotope stage 2) in the Preboreal and Boreal times of the Holocene. Sometimes, its content increases to 15-22% in spectra of lacustrine deposits synchronous to the last glacial stage near the northern coast of the Sea of Okhotsk [3], evidently indicating the proximity of Japanese stone pine thickets.« less

Palaeoenvironmental reconstruction of Hüsamlar coal seam, SW Turkey

NASA Astrophysics Data System (ADS)

Büçkün, Zeynep; İnaner, Hülya; Oskay, Riza Görkem; Christanis, Kimon

2015-06-01

The Ören and Yatağan Basins in SW Turkey host several Miocene coal deposits currently under exploitation for power generation. The present study aims to provide insight into the palaeoenvironmental conditions, which controlled the formation of the Hüsamlar coal seam located in Ören Basin. The coal seam displays many sharp alternations of matrix lignite beds and inorganic, lacustrine sediment layers. The coal is a medium-to-high ash lignite (10.47-31.16 wt%, on dry basis) with high total sulphur content (up to 10 wt%, on dry, ash-free basis), which makes it prone to self-combustion. The maceral composition indicates that the peat-forming vegetation consisted of both arboreal and herbaceous plants, with the latter being predominant in the upper part of the seam. Mica and feldspars contribute to the low part of the seam; carbonates are dominant in the upper part, whereas quartz and pyrite are present along the entire coal profile. The sudden transitions of the telmatic to the lacustrine regime and reverse is attributed to tectonic movements that controlled water table levels in the palaeomire, which affected surface runoff and hence, clastic deposition.

Paleolimnology of Lake Tubutulik, an iron-meromictic Eocene Lake, eastern Seward Peninsula, Alaska

USGS Publications Warehouse

Dickinson, K.A.

1988-01-01

Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual "iron-meromictic" Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a structural graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Late Cretaceous Darby Pluton, on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the river valley of the ancestral Tubutulik River in early Eocene time. Lake Tubutulik contained a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital layers containing mostly quartz and clay minerals. Both lacustrine facies contain turbidities. The lacustrine sediments graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake apparently occupied a small deep basin in a tectonically active area of high relief. Meromixus was probably stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixus decreased as the lake became shallower from sediment filling. The source of the iron, abundant in the monimolimnion of Lake Tubutulik, was probably the Eocene basalt. Based on carbon isotope analysis of the siderite, the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature (??13C = +16.9) consistent with residual carbon formed during methanogenic fermentation. ?? 1988.

Controls on the distribution of productivity and organic resources in Antarctic Dry Valley soils.

PubMed

Hopkins, D W; Sparrow, A D; Novis, P M; Gregorich, E G; Elberling, B; Greenfield, L G

2006-11-07

The Antarctic Dry Valleys are regarded as one of the harshest terrestrial habitats on Earth because of the extremely cold and dry conditions. Despite the extreme environment and scarcity of conspicuous primary producers, the soils contain organic carbon and heterotrophic micro-organisms and invertebrates. Potential sources of organic compounds to sustain soil organisms include in situ primary production by micro-organisms and mosses, spatial subsidies from lacustrine and marine-derived detritus, and temporal subsidies ('legacies') from ancient lake deposits. The contributions from these sources at different sites are likely to be influenced by local environmental conditions, especially soil moisture content, position in the landscape in relation to lake level oscillations and legacies from previous geomorphic processes. Here we review the abiotic factors that influence biological activity in Dry Valley soils and present a conceptual model that summarizes mechanisms leading to organic resources therein.

Geochemistry of Precambrian carbonates. IV - Early Paleoproterozoic (2.25 +/- 0.25 Ga) seawater

NASA Technical Reports Server (NTRS)

Veizer, Jan; Clayton, R. N.; Hinton, R. W.

1992-01-01

The mineralogy, chemistry, and isotopic composition of the Malmani Dolomite, Duck Creek Dolomite, and Bruce 'Limestone' Member of the Espanola Formation are studied in an effort to restrict the first- and second-order variations in isotopic composition of Early Paleoproterozoic seawater. The diagenetic rank is found to increase in the order Duck Creek less than Bruce less than Malmani. The interpolation of alteration trends to 'best' value yields an estimate of 0.70550 for Sr-87/Sr-86. For delta C-13, the measured range of 0 +/- 1.5 percent PDB is similar to that observed for Phanerozoic marine carbonates, while the 'best' delta O-18 value for dolostones is -5 percent PDB, depleted in O-18 relative to Phanerozoic counterparts but comparable to estimates obtained for Archean facies. The isotope geochemistry and mineralogy of Bruce 'Limestone' Member is consistent with the proposition that the sequence was deposited in a lacustrine environment.

New evidence suggests pyroclastic flows are responsible for the remarkable preservation of the Jehol biota

NASA Astrophysics Data System (ADS)

Jiang, Baoyu; Harlow, George E.; Wohletz, Kenneth; Zhou, Zhonghe; Meng, Jin

2014-02-01

The lower Cretaceous Yixian and Jiufotang formations contain numerous exceptionally well-preserved invertebrate, vertebrate and plant fossils that comprise the Jehol Biota. Freshwater and terrestrial fossils of the biota usually occur together within some horizons and have been interpreted as deposits of mass mortality events. The nature of the events and the mechanisms behind the exceptional preservation of the fossils, however, are poorly understood. Here, after examining and analysing sediments and residual fossils from several key horizons, we postulate that the causal events were mainly phreatomagmatic eruptions. Pyroclastic density currents were probably responsible for the major causalities and for transporting the bulk of the terrestrial vertebrates from different habitats, such as lizards, birds, non-avian dinosaurs and mammals, into lacustrine environments for burial. Terrestrial vertebrate carcasses transported by and sealed within the pyroclastic flows were clearly preserved as exceptional fossils through this process.

Sedimentology and paleoecology of an Eocene Oligocene alluvial lacustrine arid system, Southern Mexico

NASA Astrophysics Data System (ADS)

Beraldi-Campesi, Hugo; Cevallos-Ferriz, Sergio R. S.; Centeno-García, Elena; Arenas-Abad, Concepción; Fernández, Luis Pedro

2006-10-01

A depositional model of the Eocene-Oligocene Coatzingo Formation in Tepexi de Rodríguez (Puebla, Mexico) is proposed, based on facies analysis of one of the best-preserved sections, the Axamilpa Section. The sedimentary evolution is interpreted as the retrogradation of an alluvial system, followed by the progressive expansion of an alkaline lake system, with deltaic, palustrine, and evaporitic environments. The analysis suggests a change towards more arid conditions with time. Fossils from this region, such as fossil tracks of artiodactyls, aquatic birds and cat-like mammals, suggest that these animals traversed the area, ostracods populated the lake waters, and plants grew on incipient soils and riparian environments many times throughout the history of the basin. The inferred habitat for some fossil plants coincides with the sedimentological interpretation of an arid to semiarid climate for that epoch. This combined sedimentological-paleontological study of the Axamilpa Section provides an environmental context in which fossils can be placed and brings into attention important biotic episodes, like bird and camelid migrations or the origin of endemic but extinct plants in this area.

Geology and mineral deposits of Churchill County, Nevada

USGS Publications Warehouse

Willden, Ronald; Speed, Robert C.

1974-01-01

Churchill County, in west-central Nevada, is an area of varied topography and geology that has had a rather small total mineral production. The western part of the county is dominated by the broad low valley of the Carson Sink, which is underlain by deposits of Lake Lahontan. The bordering mountain ranges to the west and south are of low relief and underlain largely by Tertiary volcanic and sedimentary units. Pre-Tertiary rocks are extensively exposed east of the Carson Sink in the Stillwater Range, Clan Alpine Mountains, Augusta Mountains, and New Pass Mountains. The eastern valleys are underlain by Quaternary alluvial and lacustrine deposits contemporaneous with the western deposits of Lake Lahontan. The eastern mountain ranges are more rugged than the western ranges and have higher relief; the eastern valleys are generally narrower.

Genesis and continuity of quaternary sand and gravel in glacigenic sediment at a proposed low-level radioactive waste disposal site in east-central Illinois

USGS Publications Warehouse

Troost, K.G.; Curry, B. Brandon

1991-01-01

The Illinois Department of Nuclear Safety has characterized the Martinsville Alternative Site (MAS) for a proposed low-level radioactive waste disposal facility. The MAS is located in east-central Illinois approximately 1.6 km (1 mi) north of the city of Martinsville. Geologic investigation of the 5.5-km2 (1380-acre) site revealed a sequence of chiefly Illinoian glacigenic sediments from 6 to 60 m (20-200 ft) thick overlying two major bedrock valleys carved in Pennsylvanian strata. Relatively permeable buried units include basal, preglacial alluvium; a complex of intraglacial and subglacial sediment; englacial deposits; and supraglacial fluvial deposits. Postglacial alluvium underlies stream valleys on and adjacent to the site. In most areas, the buried sand units are confined by low-permeability till, lacustrine sediment, colluvium, and loess. The distribution and thickness of the most extensive and continuous buried sand units have been modified considerably by subglacial erosion, and their distributions have been influenced by the buried bedrock valleys. The most continuous of the various sand units were deposited as preglacial and postglacial alluvium and are the uppermost and lowermost stratigraphic units at the alternative site. Sand units that were deposited in englacial or ice-marginal environments are less continuous. Aquifer pumping tests, potentiometric head data, and groundwater geochemistry analyses indicate minimal interaction of groundwater across localized interconnections of the permeable units. ?? 1991 Springer-Verlag New York Inc.

Surveying Clay Mineral Diversity in the Murray Formation, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Bristow, T. F.; Blake, D. F.; Vaniman, D. T.; Chipera, S. J.; Rampe, E. B.; Grotzinger, J. P.; McAdam, A. C.; Ming, D. W.; Morrison, S. M.; Yen, A. S.;

Sedimentary Basin Structure of the Hadar Formation's Lacustrine-Dominated Depocenter (Ledi-Geraru, Afar, Ethiopia) and its Relevance for Investigating Hominin Paleoenvironments

NASA Astrophysics Data System (ADS)

Dimaggio, E. N.; Campisano, C. J.; Arrowsmith, J. R.; Dupont-Nivet, G.; Johnson, R. A.; Warren, M. B.

2008-12-01

Sedimentary sequences preserved in East African rift basins record the long-term response of past depositional environments to climatic and tectonic forcing. Motivations for recent field investigations at the Ledi-Geraru site, part of the greater Hadar sedimentary basin in the Afar region of Ethiopia, stem from a need to characterize local basin structure and expand and refine interpretations of the complex mid-late Pliocene history of local and regional-scale landscape change during a time of critical importance for understanding hominin evolution. Detailed geologic mapping (1:7,000), measured stratigraphic sections, and seismic reflection surveys provide the datasets necessary for basin evaluation. The Ledi-Geraru sedimentary sequence (>250m thick) exposes nearly the entirety of the hominin-bearing Hadar Formation of west- central Afar. Both primary unmodified lake deposits and intervals modified by subsequent subaerial exposure and pedogenesis are well-exposed. The lacustrine-dominated signature is indicated by the prevalence of laminated silty clays that contain leaf impressions, fish scales, and gastropod shells, undisturbed laminated diatomite and clays, and pedogenically modified diatomaceous silts. The sequence is generally flat lying, with low bedding dips ranging from 0-2° NNW to <1° NNE and minor NNW trending faults with <5 m vertical offset. Whereas coeval fluvio-lacustrine sediments associated with hominin and archaeological sites west of Ledi-Geraru (e.g., Hadar and Gona) are marked by comparatively slow and episodic sedimentation, sedimentation rates in the Ledi-Geraru sequence are extremely high and consistent, on the order of ~0.9-1.0mm/yr. Laterally extensive tephra marker beds and paleomagnetic records provide excellent age control for sedimentation rate estimates and correlation to nearby fossil-rich sequences. As the Hadar basin sediments preserve a rich paleoanthropologic and archaeological record, this work provides the geologic framework necessary for a proposed (2011) continental drilling effort to obtain a near-continuous, ultra-high resolution terrestrial record of past climate variability from multiple paleo-lake basins in East Africa, including the Ledi-Geraru. A seismic reflection survey was completed there in spring 2008, below the planned drilling site. Gently east-dipping coherent reflections interpreted to be from the Ledi-Geraru sedimentary sequence are imaged in the seismic data to at least 0.2 to 0.3 s (two-way travel time). Preliminary average velocities of about 2000 m/s suggest a sequence thickness of 200-300 m. Furthermore, there is no indication of large-offset faults or of buried basalt ridges that would disrupt or reduce the stratigraphic column available for coring. The anticipated cores from Ledi-Geraru should yield a high-resolution chronostratigraphic framework and paleoenvironmental record from >3.5 to 2.9Ma. Combined geologic and seismic evaluations of depositional sequences are central for evaluating the geometry, tectonic evolution, and stratigraphic history of basins and facilitate interpretations of the space-time progression of evolving paleosurfaces.

Multidisciplinary distinction of mass-movement and flood-induced deposits in lacustrine environments: implications for Holocene palaeohydrology and natural hazards (Lake Ledro, Southern Alps, Italy)

NASA Astrophysics Data System (ADS)

Simonneau, A.; Chapron, E.; Vannière, B.; Wirth, S. B.; Gilli, A.; Di Giovanni, C.; Anselmetti, F. S.; Desmet, M.; Magny, M.

2012-08-01

High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and river-bed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events) in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic profiles in Lake Ledro. Lake sediments are finely laminated in the basin since 9000 cal. yr BP and frequently interrupted by two types of sedimentary events: light-coloured massive layers and dark-coloured graded beds. Optical analysis (quantitative organic petrography) of the organic matter occurring in soils, river beds and lacustrine samples together with lake-sediment bulk density and grain-size analysis illustrate that light-coloured layers consist of a mixture of lacustrine sediments and mainly contain algal particles similar to the ones observed in background sediments. Light-coloured layers thicker than 1.5 cm in the main basin of Lake Ledro are dense and synchronous to numerous coeval mass-wasting deposits remoulding the slopes of the basin. They are interpreted as subaquatic mass movements triggered by historical and pre-historical regional earthquakes dated to 2005 AD, 1891 AD, 1045 AD and 1260, 2545, 2595, 3350, 3815, 4740, 7190, 9185 and 11495 cal. yr BP. Dark-coloured sedimentary event are dense and develop high-amplitude reflections in front of the deltas and in the deep central basin. These beds are mainly made of terrestrial organic matter (soils and ligno-cellulosic debris) and are interpreted as resulting from intense hyperpycnal flood events. Mapping and quantifying the amount of soil material accumulated in the Holocene hyperpycnal flood deposits of the sequence and applying the De Ploey erosion model allow estimating that the equivalent soil thickness eroded over the catchment area reached up to 4 mm during the largest Holocene flood events. Such significant soil erosion is interpreted as resulting from the combination of heavy rainfall and snowmelt. The recurrence of flash-flood events during the Holocene was however not high enough to affect pedogenesis processes and highlight several wet regional periods during the Holocene. The Holocene period is divided into four phases of environmental evolution. Over the first half of the Holocene, a progressive stabilization of the soils present through the catchment of Lake Ledro was associated with a progressive reforestation of the area and only interrupted during the wetter 8.2 event when the soil destabilization was particularly important. Lower soil erosion was recorded during the Mid-Holocene climatic optimum (8000-4200 cal. yr BP) and associated with higher algal production. Between 4200 and 3100 cal. yr BP, both wetter climate and human activities within the drainage basin drastically increased soil erosion rates. Finally, from 3100 cal. yr BP to the present-day, results suggest increasing and changing human land-use.

The Kramer deposit of southern California--Preliminary insights on the origins of zoned lacustrine evaporite borate deposits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swihart, G.H.; McBay, E.H.; Smith, D.H.

1992-01-01

Lacustrine evaporite borate deposits span the range from mineralogically unzoned or poorly zoned to concentrically or complexly zoned types. Deposits often contain an inner ulexite or probertite (Na-Ca borates) zone and an outer colemanite (Ca borate) zone. A few deposits contain an innermost borax (Na borate) zone. Boron isotopic analyses of core material from the zoned borax-ulexite-colemanite Kramer deposit have been made with the aim of providing a better understanding of the processes of zone formation. Samples from 6 depths over a 63 foot interval in the borax zone yield a [delta] B-11 range of +0.1 to +2.3 permil. Twomore » samples in the portion of the ulexite zone below the borax zone, vertically separated from one another by 20 feet, yield identical results of [delta]B-11 = [minus]2.1 permit. Three ulexite samples from a 10 foot interval above the borax zone produced results in the range [delta]B-11 = [minus]4.6 to [minus]5.5 permil. A number of possible origins for ulexite at Kramer have been proposed: (1) primary precipitation from the lake brines; (2) postdepositional alteration of the borax zone margin by Ca-rich groundwater; (3) mixing of seeping lake brines and Ca-rich groundwater in muds around the lake. Given the small variation in B isotopic composition exhibited in the borax zone, mechanisms 1 and 2 would produce upper and lower portions of the ulexite zone with similar isotopic compositions. In the third scenario, the difference in composition of the upper and lower ulexites could be due to distance from the lake and relative proportions of seeped lake brine (B-11-rich) and clay adsorbed B (B-10-rich). Furthermore, the cotton ball form of the ulexite in this core is identical to that of ulexite forming today just beneath the surface of dry lakes in NV and CA.« less

Geology of McLaughlin Crater, Mars: A Unique Lacustrine Setting with Implications for Astrobiology

NASA Technical Reports Server (NTRS)

Michalski, J. R.; Niles, P. B.; Rogers, A. D.; Johnson, S. S.; Ashley, J. W.; Golombek, M. P.

2016-01-01

McLaughlin crater is a 92-kmdiameter Martian impact crater that contained an ancient carbonate- and clay mineral-bearing lake in the Late Noachian. Detailed analysis of the geology within this crater reveals a complex history with important implications for astrobiology [1]. The basin contains evidence for, among other deposits, hydrothermally altered rocks, delta deposits, deep water (>400 m) sediments, and potentially turbidites. The geology of this basin stands in stark contrast to that of some ancient basins that contain evidence for transient aqueous processes and airfall sediments (e.g. Gale Crater [2-3]).

Relationship of fluviodeltaic facies to coal deposition in the lower Fort Union formation (Palaeocene), south-western North Dakota

USGS Publications Warehouse

Belt, Edward S.; Flores, Romeo M.; Warwick, Peter D.; Conway, Kevin M.; Johnson, Kirk R.; Waskowitz, Robert S.; Rahmani, R.A.; Flores, Romeo M.

1984-01-01

Facies analysis of the Ludlow and Tongue River Members of the Palaeocene Fort Union Formation provides an understanding of the relationship between fluviodeltaic environments and associated coal deposition in the south-western Williston Basin. The Ludlow Member consists of high-constructive delta facies that interfinger with brackish-water tongues of the Cannonball Member of the Fort Union Formation. The lower part of the Ludlow Member was deposited on a lower delta plain that consisted of interdistributary crevasse and subdelta lobes. The upper part of the Ludlow Member was deposited in meander belts of the upper delta plain. The delta plain facies of the Ludlow Member is overlain by alluvial plain facies consisting of swamp, crevasse-lobe, lacustrine, and trunk meander belt deposits of the Tongue River Member. The Ludlow delta is believed to have been fed by fluvial systems that probably flowed from the Powder River Basin to the Williston Basin undeterred by the Cedar Creek Anticline. However, the evidence indicates that the Cedar Creek Anticline was prominent enough, during early Tongue River Member deposition, to cause the obstruction of the regional fluvial system flowing from the SW, and the formation of local drainage.The Ludlow Member contains 18 coal beds in the area studied, of which the T-Cross and Yule coals are as thick as 4 m (12 ft). Abandoned delta lobes served as platforms where coals formed, which in turn, were drowned by mainly fresh water and subordinate brackish water. Repetition of deltaic sedimentation, abandonment, and occupation by swamp led to preservation of the T-Cross and Oyster coals in areas as extensive as 260 km2 (< 100 miles2).

210Pb dating

USGS Publications Warehouse

Swarzenski, Peter W.

2014-01-01

Roughly fifty years ago, a small group of scientists from Belgium and the United States, trying to better constrain ice sheet accumulation rates, attempted to apply what was then know about environmental lead as a potential geochronometer. Thus Goldberg (1963) developed the first principles of the 210Pb dating method, which was soon followed by a paper by Crozaz et al. (1964), who examined accumulation history of Antarctic snow using 210Pb. Shortly thereafter, Koide et al. (1972, 1973) adapted this technique to unravel sediment deposition and accumulation records in deep-sea environments. Serendipitously, they chose to work in a deep basin off California, where an independent and robust age model had already been developed. Krishanswami et al. (1971) extended the use of this technique to lacustrine deposits to reconstruct depositional histories of lake sediment, and maybe more importantly, contaminant inputs and burial. Thus, the powerful tool for dating recent (up to about one century old) sediment deposits was established and soon widely adopted. Today almost all oceanographic or limnologic studies that address recent depositional reconstructions employ 210Pb as one of several possible geochronometers (Andrews et al., 2009; Gale, 2009; Baskaran, 2011; Persson and Helms, 2011). This paper presents a short overview of the principles of 210Pb dating and provides a few examples that illustrate the utility of this tracer in contrasting depositional systems. Potential caveats and uncertainties (Appleby et al., 1986; Binford, 1990; Binford et al., 1993; Smith, 2001; Hancock et al., 2002) inherent to the use and interpretation of 210Pb-derived age-models are also introduced. Recommendations as to best practices for most reliable uses and reporting are presented in the summary.

Reactive transport and mass balance modeling of the Stimson sedimentary formation and altered fracture zones constrain diagenetic conditions at Gale crater, Mars

NASA Astrophysics Data System (ADS)

Hausrath, E. M.; Ming, D. W.; Peretyazhko, T. S.; Rampe, E. B.

2018-06-01

On a planet as cold and dry as present-day Mars, evidence of multiple aqueous episodes offers an intriguing view into very different past environments. Fluvial, lacustrine, and eolian depositional environments are being investigated by the Mars Science Laboratory Curiosity in Gale crater, Mars. Geochemical and mineralogical observations of these sedimentary rocks suggest diagenetic processes affected the sediments. Here, we analyze diagenesis of the Stimson formation eolian parent material, which caused loss of olivine and formation of magnetite. Additional, later alteration in fracture zones resulted in preferential dissolution of pyroxene and precipitation of secondary amorphous silica and Ca sulfate. The ability to compare the unaltered parent material with the reacted material allows constraints to be placed on the characteristics of the altering solutions. In this work we use a combination of a mass balance approach calculating the fraction of a mobile element lost or gained, τ, with fundamental geochemical kinetics and thermodynamics in the reactive transport code CrunchFlow to examine the characteristics of multiple stages of aqueous alteration at Gale crater, Mars. Our model results indicate that early diagenesis of the Stimson sedimentary formation is consistent with leaching of an eolian deposit by a near-neutral solution, and that formation of the altered fracture zones is consistent with a very acidic, high sulfate solution containing Ca, P and Si. These results indicate a range of past aqueous conditions occurring at Gale crater, Mars, with important implications for past martian climate and environments.

Were lakes on early Mars perennially were ice-covered?

NASA Astrophysics Data System (ADS)

Sumner, D. Y.; Rivera-Hernandez, F.; Mackey, T. J.

2016-12-01

Paleo-lake deposits indicate that Mars once sustained liquid water, supporting the idea of an early "wet and warm" Mars. However, liquid water can be sustained under ice in cold conditions as demonstrated by perennially ice-covered lakes (PICLs) in Antarctica. If martian lakes were ice-covered, the global climate on early Mars could have been much colder and dryer than if the atmosphere was in equilibrium with long-lived open water lakes. Modern PICLs on Earth have diagnostic sedimentary features. Unlike open water lakes that are dominated by mud, and drop stones or tills if icebergs are present, previous studies determined that deposits in PICLs can include coarser grains that are transported onto the ice cover, where they absorb solar radiation, melt through the ice and are deposited with lacustrine muds. In Lake Hoare, Antarctica, these coarse grains form conical sand mounds and ridges. Our observations of ice-covered lakes Joyce, Fryxell, Vanda and Hoare, Antarctica suggest that the distributions of grains depend significantly on ice characteristics. Deposits in these lakes contain moderately well to moderately sorted medium to very coarse sand grains, which preferentially melt through the ice whereas granules and larger grains remain on the ice surface. Similarly, high albedo grains are concentrated on the ice surface, whereas low albedo grains melt deeper into the ice, demonstrating a segregation of grains due to ice-sediment interactions. In addition, ice cover thickness may determine the spatial distribution of sand deposited in PICLs. Localized sand mounds and ridges composed of moderately sorted sand are common in PICLs with rough ice covers greater than 3 m thick. In contrast, lakes with smooth and thinner ice have disseminated sand grains and laterally extensive sand layers but may not have sand mounds. At Gale Crater, Mars, the Murray formation consists of sandy lacustrine mudstones, but the depositional process for the sand is unknown. The presence of a perennial ice-cover could explain the sand, but no definitive ice-related deposits have been identified to date. The Murray formation is an ideal target to start analyzing for evidence of ancient PICL deposits on Mars.

Equatorial Layered Deposits in Arabia Terra, Mars: Facies and Process Variability

NASA Astrophysics Data System (ADS)

Pondrelli, M.; Rossi, A.; van Gasselt, S.; Le Deit, L.; Glamoclija, M.; Cavalazzi, B.; Franchi, F.; Fueten, F.; Hauber, E.; Zegers, T.

2012-12-01

Genetic mechanisms proposed to explain Equatorial Layered Deposits (ELDs) formation include subglacial volcanism, aeolian/airfall, lacustrine, lacustrine/volcanic and spring-fed deposition. ELDs have been frequently shown to consist of sulfates (e.g. Gendrin et al., 2005) that might form as a response to evaporation in a playa environment (Hoefen et al., 2003) or during spring precipitation (e.g. Allen and Oehler, 2008; Rossi et al., 2008). The importance of groundwater-dominated hydrological systems was proposed to explain the formation of light-toned deposits in Meridiani Planum and Arabia Terra (e.g. Andrews-Hanna et al. 2007). Additionally, fluid expulsion processes have been invoked to explain the formation of mounds within the light-toned deposits in Arabia Terra (Allen and Oehler, 2008; Rossi et al., 2008; Pondrelli et al., 2011). Potential for habitable conditions of both playa and spring-related settings (Cavalazzi et al., 2007; Glamoclija et al., 2011) coupled with the high preservation potential within sulfates (Panieri et al., 2010), make these deposits a good candidate to understand the potential past habitability of the planet. In order to investigate ELDs genesis, an area in the vicinity of Firsoff crater, where ELDs are present within and outside the craters, was selected for geological mapping and analysis of the landforms and their association using the available dataset, including CRISM in order to infer ELDs composition. Within Firsoff crater, ELDs form a bulge that can be estimated to be at least a few hundred meters thick, while, outside the craters, ELDs form flat-lying deposits. Although heavily eroded by wind and carved by yardangs, several morphologies within the ELDs in the craters seem to be depositional, which would exclude that the entire Firsoff basin had been originally filled by ELDs. Within craters, ELDs consist of roughly meter thick layers draping and onlapping the substratum. They appear affected by polygonal patterns with no evidence of sedimentary structures. Polyhydrated sulfates have been detected. At places, ELDs appear to be linked to and possibly sourced from tectonically controlled lineaments. Large cone-shaped mounds (100 to 500 m) are situated locally on top of ELDs. They consist of boulders embedded in a matrix, and about one-third of them display an orifice at their top. Outside of the craters, ELDs show large-scale cross stratification associated to duneforms, which suggests an aeolian origin possibly associated to playa deposits. We distinguish between fluid expulsion ELDs forming within the crater and aeolian ELDs outside and possibly inside the craters. Fluid expulsion ELDs would result from groundwater upwelling and following evaporitic precipitation, whereas aeolian ELDs would result from reworking and redeposition of the spring ELDs. References Allen and Oehler (2008), Astrobiology, 8, 1093-1112. Andrews-Hanna et al. (2007), Nature, 446, 163-166. Cavalazzi et al. (2007), Sed. Geol., 200, 73-88. Gendrin et al. (2005), Science, 307, 1587. Glamoclija et al. (2011), Geomicrob. J., 29, 733-751. Hoefen et al. (2003), Science, 302, 627-630. Panieri et al. (2010), Geobiology, 8, 101-111. Pondrelli et al. (2011), EPSL, 304, 511-519. Rossi et al. (2008), JGR, 113(8).

Geomorphic Drainage Capture Recorded by Oxygen Isotopes of Green River Formation Lacustrine Mudstone, Eocene, Wyoming

NASA Astrophysics Data System (ADS)

Doebbert, A. C.; Booth, A. L.; Carroll, A.; Chamberlain, C.; Rhodes, M.

2005-12-01

The isotopic composition of cement and other meteoric precipitates are increasingly being used to interpret orogenic uplift histories, based on the relationship between altitude and rainwater δ18O. However, other variables such as changing regional drainage patterns may also affect the downstream composition of surface waters, especially when multiple drainages commingle in a lake. The Green River Formation contains some of the best documented lacustrine deposits in the world, making it ideal for examining such issues. Carbonate mudstone in balanced-fill facies of the lower LaClede Bed averages 3.41‰ (PDB), and records a deep, saline to brackish lake that fluctuated near its sill. In contrast, overfilled facies of the upper LaClede Bed record a freshwater lake, and δ18O reaches values as low as -9.72‰. This transition occurred shortly after deposition of the Analcite Tuff at 48.94 ± 0.12 Ma (Smith et al., 2003), and was geologically abrupt. Based on 40Ar/39Ar-calibrated sediment accumulation rates it required no more than 200-300 ky. An almost identical transition occurs in two cores separated by about 30 km, making local diagenesis an unlikely cause. The magnitude of δ18O change is similar to that in some uplift studies, but its rapidity virtually excludes uplift as a controlling mechanism. Instead, we propose that both the change in sedimentation and the sharp decrease in δ18O are the result of a drainage capture event. The addition of a new drainage to the basin may have adjusted isotopic values in two ways: by introducing runoff with relatively low δ18O, and by decreasing residence time (and therefore evaporation) of lake water. Decreasing 87Sr/86Sr across the same transition suggests that the newly added waters may have been sourced from rising volcanic topography to the north in the Absaroka province. Although this rising topography allows for the possibility of some uplift component, the rate of change in lacustrine δ18O is consistent with geomorphic processes rather than uplift. These results indicate the need for considerable caution when examining uplift records from other ancient lake deposits.

Quaternary geologic map of the Havre 1° x 2° quadrangle

USGS Publications Warehouse

Compilations by Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2012-01-01

The Havre quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes parts of the Bearpaw Mountains, the Little Rocky Mountains, and the Boundary Plateau. The primary river is the Milk River. The ancestral Missouri River was diverted south of the Bearpaw Mountains by a Laurentide ice sheet. The fill in the buried ancestral valley at and southwest of Havre contains a complex stratigraphy of fluvial, glaciofluvial, ice-contact, glacial, lacustrine, and eolian deposits. The old valley east of Havre now is occupied by the Milk River. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (e.g., ground-moraine deposits, end-moraine deposits, stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 24 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. On the glaciated plains and on the Boundary Plateau the surficial deposits are glacial, ice-contact, glaciofluvial, catastrophic flood, alluvial, lacustrine, eolian, and colluvial deposits. In the Bearpaw Mountains and Little Rocky Mountains beyond the limit of Quaternary glaciation they are fluvial, colluvial, and mass-wasting deposits and residual materials. Tills of late Wisconsin and Illinoian ages are represented by map units. Tills of two pre-Illinoian glaciations are not mapped but are widespread in the subsurface and are identified in stratigraphic sections. Thirteen stratigraphic sections document a complex glacial and interglacial history in the quadrangle. Pliocene continental glaciation possibly is represented by erratic blocks of garnet gneiss and pegmatite from the Canadian Shield, perched high on drainage divides in the western Bearpaw Mountains. Glacial striations on bedrock, two boulder trains, and linear ice-molded landforms (primarily drumlins) indicate the possible presence of an east-southeast flowing ice stream in the Havre glacial lobe during late Wisconsin glaciation.

Variations in eruptive style and depositional processes of Neoproterozoic terrestrial volcano-sedimentary successions in the Hamid area, North Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Khalaf, Ezz El Din Abdel Hakim

2013-07-01

Two contrasting Neoproterozoic volcano-sedimentary successions of ca. 600 m thickness were recognized in the Hamid area, Northeastern Desert, Egypt. A lower Hamid succession consists of alluvial sediments, coherent lava flows, pyroclastic fall and flow deposits. An upper Hamid succession includes deposits from pyroclastic density currents, sills, and dykes. Sedimentological studies at different scales in the Hamid area show a very complex interaction of fluvial, eruptive, and gravitational processes in time and space and thus provided meaningful insights into the evolution of the rift sedimentary environments and the identification of different stages of effusive activity, explosive activity, and relative quiescence, determining syn-eruptive and inter-eruptive rock units. The volcano-sedimentary deposits of the study area can be ascribed to 14 facies and 7 facies associations: (1) basin-border alluvial fan, (2) mixed sandy fluvial braid plain, (3) bed-load-dominated ephemeral lake, (4) lava flows and volcaniclastics, (5) pyroclastic fall deposits, (6) phreatomagmatic volcanic deposits, and (7) pyroclastic density current deposits. These systems are in part coeval and in part succeed each other, forming five phases of basin evolution: (i) an opening phase including alluvial fan and valley flooding together with a lacustrine period, (ii) a phase of effusive and explosive volcanism (pulsatory phase), (iii) a phase of predominant explosive and deposition from base surges (collapsing phase), and (iv) a phase of caldera eruption and ignimbrite-forming processes (climactic phase). The facies architectures record a change in volcanic activity from mainly phreatomagmatic eruptions, producing large volumes of lava flows and pyroclastics (pulsatory and collapsing phase), to highly explosive, pumice-rich plinian-type pyroclastic density current deposits (climactic phase). Hamid area is a small-volume volcano, however, its magma compositions, eruption styles, and inter-eruptive breaks suggest, that it closely resembles a volcanic architecture commonly associated with large, composite volcanoes.

Regional stratigraphy and subsurface geology of Cenozoic deposits, Gulf Coastal Plain, south-central United States

USGS Publications Warehouse

Hosman, R.L.

1991-01-01

Although Cenozoic deposits are not uniformly differentiated, interstate correlations of major Paleocene and Eocene units are generally established throughout the area. Younger deposits are not as well differentiated. Some stratigraphic designations made at surface exposures cannot be extended into the sub-surface, and the scarcity of distinct geologic horizons has hampered differentiation on a regional scale. The complexities of facies development in Oligocene and younger coastal deposits preclude the development of extensive recognizable horizons needed for stratigraphic applications. Coastal deposits are a heterogeneous assemblage of deltaic, lagoonal, lacustrine, palustrine, eolian, and fluvial clastic facies and local calcareous reef facies. Even major time boundaries, as between geologic series, are not fully resolved. Surficial Quaternary deposits overlie the truncated subcrops of Tertiary strata and generally are distinguishable, although some contacts between Pleistocene and underlying Pliocene deposits have been a ?lstoncal source of controversy. Glacially related terraces are characteristic of the Pleistocene Epoch, and alluvium of aggrading streams typifies the Holocene. 

Searching for Biosignatures in Martian Sedimentary Systems

NASA Astrophysics Data System (ADS)

Stevens, A. H.; McDonald, A.; Cockell, C. S.

2018-04-01

We present experiments designed to simulate an inhabited martian lacustrine system analogous to Gale Crater. We describe the microbes found to thrive in this simulated environment and identify issues detecting biomarkers in this context.

Use of cover habitat by bull trout Salvelinus confluentus and lake trout Salvelinus namaycush in a laboratory environment

USGS Publications Warehouse

Meeuwig, Michael H.; Guy, Christopher S.; Fredenberg, Wade A.

2011-01-01

Lacustrine-adfluvial bull trout, Salvelinus confluentus, migrate from spawning and rearing streams to lacustrine environments as early as age 0. Within lacustrine environments, cover habitat pro- vides refuge from potential predators and is a resource that is competed for if limiting. Competitive inter- actions between bull trout and other species could result in bull trout being displaced from cover habitat, and bull trout may lack evolutionary adaptations to compete with introduced species, such as lake trout, Salvelinus namaycush. A laboratory experiment was performed to examine habitat use and interactions for cover by juvenile (i.e., <80 mm total length) bull trout and lake trout. Differences were observed between bull trout and lake trout in the proportion of time using cover (F1,22.6=20.08, P<0.001) and bottom (F1,23.7 = 37.01, P < 0.001) habitat, with bull trout using cover and bottom habitats more than lake trout. Habitat selection ratios indicated that bull trout avoided water column habitat in the presence of lake trout and that lake trout avoided bottom habitat. Intraspecific and interspecific agonistic interactions were infrequent, but approximately 10 times greater for intraspecific inter- actions between lake trout. Results from this study provide little evidence that juvenile bull trout and lake trout compete for cover, and that species-specific differences in habitat use and selection likely result in habitat partitioning between these species.

A review of the sedimentology of the Early Proterozoic Pretoria Group, Transvaal Sequence, South Africa: implications for tectonic setting

NASA Astrophysics Data System (ADS)

Eriksson, P. G.; Schreiber, U. M.; van der Neut, M.

The sedimentary rocks of the Early Proterozoic Pretoria Group form the floor rocks to teh 2050 M.a. Bushveld Complex. An overall alluvial fan-fan-delta - lacustrine palaeoenvironmental model is postulated for the Pretoria Group. This model is compatible with a continental half-graben tectonic setting, with steep footwall scarps on the southern margin and a lower gradient hanging wall developed to the north. The latter provided much of the basin-fill detritus. It is envisaged that the southern boundary fault system migrated southwards by footwall collapse as sedimentation continued. Synsedimentary mechanical rifting, associated with alluvial and deltaic sedimentation (Rooihoogte-Strubenkop Formations) was followed by thermal subsidence, with concomitant transgressive lacustrine deposition (Daspoort-Magaliesberg Formations). The proposed half-graben basin was probably related to the long-lived Thabazimbi-Murchison and Sugarbush-Barberton lineaments, which bound the preserved outcrops of the Pretoria Group.

The microbial nature of laminated limestones: Lessons from the Upper Aptian, Araripe Basin, Brazil

NASA Astrophysics Data System (ADS)

Catto, Bruno; Jahnert, Ricardo Jorge; Warren, Lucas Verissimo; Varejao, Filipe Giovanini; Assine, Mario Luis

2016-07-01

The Araripe Basin, located in northeastern Brazil, originated during the Gondwana continental break-up responsible for the opening of the South Atlantic during the Early Cretaceous. In the Araripe Basin, the post-rift Aptian sequence corresponds to the Santana Group, which is composed, in upward succession, of mostly clastic continental and rare carbonate layers of the Barbalha, Crato, Ipubi and Romualdo Formations. The laminated limestones of the Crato Formation were deposited in a lacustrine environment preceding the deposition of the Ipubi Formation evaporites. They are age-equivalent to the limestones of the pre-salt interval of the east coast of Brazil, which contains large petroleum reserves. The excellent preservation of its macrofossils has made the Crato Formation known worldwide as a Fossil Lagerstätte. The limestones are macroscopically homogeneous, and their deposition has been previously attributed to chemical precipitation. Although the carbonate laminites are macroscopically undifferentiated, mineralogical variations, microscopic texture and distinctive biotic aspects supported the characterization of four microfacies: planar laminated, crustiform, nodular and rhythmic. The microfacies analysis indicated a strong and pervasive biological activity in the Crato limestone morphogenesis. Organominerals precipitated by the metabolic action of cyanobacteria and/or sulfate-reducing bacteria and methanogenic-oxidizing archea are represented by calcite and pyrite. Calcified coccoid and filaments are common, furthermore, the presence of calcified biofilms composed of exopolymeric substances (EPS) is ubiquitous. The presence of amorphous organic matter (AOM) and gypsum, particularly in the rhythmic microfacies, indicates anoxic/dysoxic conditions and stressful environments during periods of drought and low lake levels which favored the development and preservation of microbial biofilms. Phytoclasts and miospores when present in the succession indicate an extrabasinal contribution during wetter periods, although the environment remained of very low energy. The evidence of microbial influence in the formation of the laminated limestones of the Crato Formation is of great importance for understanding the excellent preservation of the unit's fossils and for modeling the evolution of the Aptian carbonate sequences in Brazil.

A modern plant-climate research dataset for modelling eastern North American plant taxa.

NASA Astrophysics Data System (ADS)

Gonzales, L. M.; Grimm, E. C.; Williams, J. W.; Nordheim, E. V.

2008-12-01

Continental-scale modern pollen-climate data repositories are a primary data source for paleoclimate reconstructions. However, these repositories can contain artifacts, such as records from different depositional environment and replicate records, that can influence the observed pollen-climate relationships as well as the paleoclimate reconstructions derived from these relationships. In this paper, we address the issues related to these artifacts as we define the methods used to create a research dataset from the North American Modern Pollen Database (Whitmore et al., 2005). Additionally, we define the methods used to select the environmental variables that are best for modeling regional pollen-climate relationships from the research dataset. Because the depositional environment determines the relative strengths of the local and regional pollen signals, combining data from different depositional environments results in pollen abundances that can be influenced by the local pollen signal. Replicate records in pollen-climate datasets can skew pollen-climate relationships by causing an over- or under- representation of pollen abundances in climate space. When these two artifacts are combined, the errors introduced into pollen-climate relationship modeling are compounded. The research dataset we present consists of 2,613 records in eastern North America, of which 70.9% are lacustrine sites. We demonstrate that this new research database improves upon the modeling of regional pollen-climate relationships for eastern North American taxa. The research dataset encompasses the majority of the temperature and mean summer precipitation ranges of the NAMPD's climatic range and 40% of its mean winter precipitation range. NAMPD sites with higher winter precipitation are located along the northwestern coast of North America where a rainshadow effect produces abundant winter precipitation. We present our analysis of the research dataset for use in paleoclimate reconstructions, and recommend that mean winter and summer temperature and precipitation variables be used for pollen-climate relationship modeling.

Branched GDGT distributions in lakes from Mexico and Central America

NASA Astrophysics Data System (ADS)

Lei, A.; Werne, J. P.; Correa-Metrio, A.; Pérez, L.; Caballero, M.

2017-12-01

The potential to use bacterial derived branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct mean annual air temperatures from soils sparked significant interest in the terrestrial paleoclimate community, where a high-fidelity paleotemperature proxy is desperately needed. While the source of brGDGTs remains unknown (but are potentially attributed to the highly diverse phylum Acidobacteria), much evidence points to the potential for these bacteria to live not only in the terrestrial environment but also in lake water and sediments as well. Though the application of brGDGTs to lacustrine reconstructions is promising, the initial applications of soil-based MBT/CBT proxy to lacustrine sediments typically resulted in lower temperatures than were reasonable, likely due to additions from lacustrine bacterial brGDGTs. Here, we present data from a suite of >100 lakes in Mexico and Central America, producing a regional core-top calibration different from those developed in other regions. Results indicate a significant role for regional differences in controlling the brGDGTs distribution, likely due to different brGDGT-producing microbial communities thriving under varying environmental conditions. Rigorous development of brGDGT based proxies will improve our understanding of the source and applicability of these biomarkers, and increase confidence in the accuracy of paleotemperature reconstructions to numerous lacustrine records in the region.

Late Quaternary distal tephra-fall deposits in lacustrine sediments, Kenai Peninsula, Alaska

USGS Publications Warehouse

de Fontaine, C.S.; Kaufman, D.S.; Scott, Anderson R.; Werner, A.; Waythomas, C.F.; Brown, T.A.

2007-01-01

Tephra-fall deposits from Cook Inlet volcanoes were detected in sediment cores from Tustumena and Paradox Lakes, Kenai Peninsula, Alaska, using magnetic susceptibility and petrography. The ages of tephra layers were estimated using 21 14C ages on macrofossils. Tephras layers are typically fine, gray ash, 1-5??mm thick, and composed of varying proportions of glass shards, pumice, and glass-coated phenocrysts. Of the two lakes, Paradox Lake contained a higher frequency of tephra (0.8 tephra/100 yr; 109 over the 13,200-yr record). The unusually large number of tephra in this lake relative to others previously studied in the area is attributed to the lake's physiography, sedimentology, and limnology. The frequency of ash fall was not constant through the Holocene. In Paradox Lake, tephra layers are absent between ca. 800-2200, 3800-4800, and 9000-10,300??cal yr BP, despite continuously layered lacustrine sediment. In contrast, between 5000 and 9000??cal yr BP, an average of 1.7 tephra layers are present per 100 yr. The peak period of tephra fall (7000-9000??cal yr BP; 2.6 tephra/100 yr) in Paradox Lake is consistent with the increase in volcanism between 7000 and 9000 yr ago recorded in the Greenland ice cores. ?? 2007 Elsevier Inc. All rights reserved.

Field pilot test of surfactant-enhanced remediation of trichloroethane DNAPL in a sand aquifer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, R.E.; Butler, G.W.; Londergan, J.T.

The sequence of lacustrine and outwash deposits beneath a vapor degreasing operation at the Paducah Gaseous Division Plant, Kentucky, is contaminated with trichloroethane due to leakage from a sewer/sump line. A plume of dissolved trichloroethane (TCE) extends throughout an area of approximately 3 km[sup 2] in the Regional Gravel Aquifer (RGA) which is located between 20 and 30 meters below ground surface. It is suspected that some 40,000 liters of TCE might have escaped into the subsurface at Paducah, most of which is still present in the lacustrine deposits and the underlying RGA as DNAPL. A field test to confirmmore » the presence of TCE DNAPL in the sandy, upper portion of the RGA around a monitoring well and to test the efficiency of the surfactant for TCE solubilization is described. The aqueous concentrations of TCE in this well have consistently been measured at 300--550 mg TCE/L over a period of three years. The use of Capillary and Bond numbers to estimate the improbability of mobilization of DNAPL due to the lowering of the interfacial tension is described. The multiphase, multicomponent simulator UTCHEM was used to simulate both the injection and extraction of the surfactant solution and the solubilization of the TCE by the surfactant micelles.« less

First Observations of Boron on Mars and Implications for Gale Crater Geochemistry

NASA Astrophysics Data System (ADS)

Gasda, P. J.; Haldeman, E. B.; Wiens, R. C.; Rapin, W.; Frydenvang, J.; Maurice, S.; Clegg, S. M.; Delapp, D.; Sanford, V.; McInroy, R.

2016-12-01

Borates are potentially important precursor materials for the origin of life on Earth. It has been shown that borates are required to stabilize ribose, a component of RNA, when produced by the formose reaction, a prebiotically plausible mechanism to produce ribose from formaldehyde. Evaporites, including borates, also shed light on the history of aqueous activity on Mars. The ChemCam instrument onboard the NASA Curiosity rover provides quantitative elemental compositions of targets in Gale Crater, Mars, using laser-induced breakdown spectroscopy (LIBS). Laboratory observations of Fe-free targets indicate that a LIBS emission line is visible with as little as 10 ppm B. We have observed B lines in 23 calcium sulfate veins in Gale Crater: 3 in Yellowknife Bay and 20 in the Murray lacustrine mudstone and the Stimson eolian sandstone units since sol 727, as Curiosity arrived at the base of Mt. Sharp, a 5 km sedimentary mound in the center of Gale Crater. To calibrate these observations, samples composed of borates diluted with Hawaiian basalt have been analyzed using the LANL ChemCam engineering model. Preliminary results show that the Gale Crater veins have between 10-100 ppm B. One possible explanation for borates in veins is that Gale Lake evaporated, depositing evaporites, including borates. Later, Gale Crater was partially buried and its lacustrine and overlying eolian units were lithified and fractured. Water flowed through the evaporite-rich layers, partially dissolving them. Fluid moved through the fractures, re-precipitating the borates and sulfates as veins. ChemCam cannot directly determine mineralogy, but B is likely present as borax as the dominate borate phase in these veins, based on previous estimates of vein fluid temperature. Borates forming in this environment tend to precipitate from mildly alkaline fluids. The fluid temperature and pH implies these veins were potentially habitable environments.

Lake Qinghai sediment geochemistry linked to hydroclimate variability since the last glacial

NASA Astrophysics Data System (ADS)

Jin, Zhangdong; An, Zhisheng; Yu, Jimin; Li, Fuchun; Zhang, Fei

2015-08-01

Geochemistry of basin sediments from semi-arid regions is valuable to understand past hydroclimatic changes. Here, we investigate the links of sedimentary geochemistry (Rb, Sr, Ca/Zr, TOC, and %CaCO3), carbonate mineralogy and ostracod shell δ18O of Lake Qinghai, a basin proximal to major dust production centers at mid-latitudes of the Northern Hemisphere, to changes in depositional conditions and hydroclimate during the past 32 ka. Surface lacustrine sediments are characterized by low-Rb, high-Sr, low-Rb/Sr, high-%CaCO3 and high-Ca/Zr values, in contrast to the chemical compositions of eolian loess (high-Rb, low-Sr, high-Rb/Sr, low-%CaCO3, and low-Ca/Zr). A direct comparison of soluble Ca and Sr in two short cores with instrumental water discharge data suggests that lacustrine precipitates in Lake Qinghai are dominated by authigenic aragonite formed under Ca2+-limited water conditions, and that the accumulation rate of aragonite dominantly depends on solute fluxes into the lake during the rainy seasons (late May to September). Our high-resolution down-core records show that sediments during the last glacial (∼32-19.8 ka) had high-Rb, low-Sr, low-%CaCO3, and low-Ca/Zr, indicating eolian dust (loess) accumulation in a desiccated basin under dry glacial conditions, further supported by grain size and pollen results. This type of sedimentation was maintained during the last deglacial (∼19.8-11.5 ka), but interrupted by episodic lacustrine precipitates with high-Sr, high-%CaCO3, high-Ca/Zr, and low-Rb. At ∼11.5 ka, sedimentary Rb/Sr, Ca/Zr, %CaCO3 and TOC show dramatic and permanent changes, implying an abrupt shift in the atmospheric circulation at the onset of the Holocene in the Lake Qinghai region. Lacustrine precipitates have persisted throughout the Holocene with a maximum during the early to mid-Holocene (∼10.5-8.0 ka). Since ∼8.0 ka, the gradual and significant decreases in aragonite and Sr accumulations in tandem with increasing dust deposit and more positive ostracod δ18O may be linked to a weakening of Asian summer monsoons during the mid-to-late Holocene. Overall, our records appear to show a high sensitivity of sediment development and geochemistry in Lake Qinghai to the regional hydroclimate changes since the last glacial.

Recently Deglaciated High-Altitude Soils of the Himalaya: Diverse Environments, Heterogenous Bacterial Communities and Long-Range Dust Inputs from the Upper Troposphere

PubMed Central

Stres, Blaz; Sul, Woo Jun; Murovec, Bostjan; Tiedje, James M.

2013-01-01

Background The Himalaya with its altitude and geographical position forms a barrier to atmospheric transport, which produces much aqueous-particle monsoon precipitation and makes it the largest continuous ice-covered area outside polar regions. There is a paucity of data on high-altitude microbial communities, their native environments and responses to environmental-spatial variables relative to seasonal and deglaciation events. Methodology/Principal Findings Soils were sampled along altitude transects from 5000 m to 6000 m to determine environmental, spatial and seasonal factors structuring bacterial communities characterized by 16 S rRNA gene deep sequencing. Dust traps and fresh-snow samples were used to assess dust abundance and viability, community structure and abundance of dust associated microbial communities. Significantly different habitats among the altitude-transect samples corresponded to both phylogenetically distant and closely-related communities at distances as short as 50 m showing high community spatial divergence. High within-group variability that was related to an order of magnitude higher dust deposition obscured seasonal and temporal rearrangements in microbial communities. Although dust particle and associated cell deposition rates were highly correlated, seasonal dust communities of bacteria were distinct and differed significantly from recipient soil communities. Analysis of closest relatives to dust OTUs, HYSPLIT back-calculation of airmass trajectories and small dust particle size (4–12 µm) suggested that the deposited dust and microbes came from distant continental, lacustrine and marine sources, e.g. Sahara, India, Caspian Sea and Tibetan plateau. Cyanobacteria represented less than 0.5% of microbial communities suggesting that the microbial communities benefitted from (co)deposited carbon which was reflected in the psychrotolerant nature of dust-particle associated bacteria. Conclusions/Significance The spatial, environmental and temporal complexity of the high-altitude soils of the Himalaya generates ongoing disturbance and colonization events that subject heterogeneous microniches to stochastic colonization by far away dust associated microbes and result in the observed spatially divergent bacterial communities. PMID:24086740

Jezero Crater, Mars, as a Compelling Site for Future In Situ Exploration

NASA Technical Reports Server (NTRS)

Goudge, T. A.; Ehlmann, B. L.; Fassett, C. I.; Head, J. W.; Mustard, J. F.; Mangold, N.; Gupta, S.; Milliken, R. E.; Brown, A. J.

2017-01-01

Jezero is a approximately 45 km diameter impact crater located in the Nili Fossae region of Mars. Jezero is an outstanding site to address key questions of ancient Mars climate, habitability, and volcanic history because: (a) It hosted an open-basin lake during the era of valley network formation [1,2], which ceased at approximately the Noachian-Hesperian boundary [3]. (b) It contains two delta deposits [1,4] with Fe/Mg-smectite and Mg-carbonate sediment [4-7] (the only exposure of lacus-trine shoreline carbonates seen so far on Mars). (c) The depositional environment and mineral assemblage of the delta are promising for the concentration and preservation of organic matter [5,8]. (d) The diverse geologic units in Jezero are in clear stratigraphic context [7]. The Jezero paleolake system has been thoroughly investigated at a variety of scales, including work on: the mineralogy of the delta deposits [4-6] and watershed [7], as well as the morphology and sedimentology of the basin [9] and delta deposits [1,4]. The geologic context of Jezero is also well-studied given the broad suite of alteration minerals exposed in the ancient stratigraphies of the Nili Fossae region [e.g., 6,10-13]. Here we present an overview of the units accessible for exploration in the Jezero basin, including questions and hypotheses that can be tested through analysis in situ and of returned samples. This is particularly timely given the upcoming Mars 2020 mission, for which Jezero is one of the final eight landing sites [14]. Primary science objectives for Mars 2020 are to: (1) characterize the geologic history of a site with "evidence of an astrobiologically-relevant ancient environment and geologic diversity"; (2) assess the habitability and "potential evidence of past life" in units with "high biosignature preservation potential"; and (3) cache scientifically compelling samples for potential return to Earth [15].

Geologic map of the Winslow 30’ × 60’ quadrangle, Coconino and Navajo Counties, northern Arizona

USGS Publications Warehouse

Billingsley, George H.; Block, Debra L.; Redsteer, Margaret Hiza

2013-01-01

The Winslow 30’ × 60’ quadrangle encompasses approximately 5,018 km2 (1,960 mi2) within Coconino and Navajo Counties of northern Arizona. It is characterized by gently dipping Paleozoic and Mesozoic strata that dip 1° to 2° northeastward in the southwestern part of the quadrangle and become nearly flat-lying in the northeastern part of the quadrangle. In the northeastern part, a shallow Cenozoic erosional basin developed about 20 million years ago, which subsequently was filled with flat-lying Miocene and Pliocene lacustrine sediments of the Bidahochi Formation, as well as associated volcanic rocks of the Hopi Buttes Volcanic Field. The lacustrine sediments and volcanic rocks unconformably overlie Triassic, Jurassic, and Cretaceous strata. Beginning about early Pliocene time, the Little Colorado River and its tributaries began to remove large volumes of Paleozoic and Mesozoic bedrock from the map area. This erosional development has continued through Pleistocene and Holocene time. Fluvial sediments accumulated episodically throughout this erosional cycle, as indicated by isolated Pliocene(?) and Pleistocene Little Colorado River terrace-gravel deposits on Tucker Mesa and Toltec Divide west of Winslow and younger terrace-gravel deposits along the margins of the Little Colorado River Valley. These gravel deposits suggest that the ancestral Little Colorado River and its valley has eroded and migrated northeastward toward its present location and largely parallels the strike of the Chinle Formation. Today, the Little Colorado River meanders within a 5-km (3-mi) wide valley between Winslow and Leupp, where soft strata of the Chinle Formation is mostly covered by an unknown thickness of Holocene flood-plain deposits. In modern times, the Little Colorado River channel has changed its position as much as a 1.5 km (1 mi) during flood events, but for much of the year the channel is a dry river bed. Surficial alluvial and eolian deposits cover extensive parts of the bedrock outcrops over the entire Winslow quadrangle.

Giving perspective to cliff exposures with ground penetrating radar: Devonian lacustrine shore zone architecture

NASA Astrophysics Data System (ADS)

Andrews, Steven; Moreau, Julien; Archer, Stuart

2015-04-01

The orbitally-controlled cyclic lacustrine successions of the Middle Devonian in Northern Scotland contains repeated developments of shore zone sandstones. However, due to the cliff-forming nature of the succession and the attitude of the sections through these sandstones, interpretation of this facies has been problematic. To better understand the shore zone systems, we carried out very high resolution sedimentary logging and constructed photo-panels which were combined with high resolution GPR profiling (250 MHz). To ensure close ties between the sedimentary logs and the GPR data, the cliffs were accessed using rope access techniques while GPR grids were shot directly above. The profiles were shot mainly in the strike direction of what was thought to be the shore elongation every 5-10 m and every 20-30 m in the dip direction. Shore zone systems of 3 different sequences have been imaged for a total of 1155 m of GPR profile collected. This configuration has allowed 3D visualisation of the architecture of the shore zone systems and, in combination with detailed sedimentology, provided insights into the generation of the dynamic shore zone environments. The coastal cliffs of northern Scotland expose sedimentary cycles on average 16-m-thick which record deep lake, perennial lake and playa environments. The shore zone deposits reach 2 to 3.5 m in thickness. Loading and discrete channel forms are recognised in both the GPR data and sedimentary logs through the lower portion of the lake shore zone successions. Up-section the sandstone beds appear to become amalgamated forming subtle low angle accretionary bar complexes which although visible in outcrop, after careful investigation, can be fully visualised and examined in the GPR data. The 3D visualisation allowed mapping the architecture and distribution of the bars . The orientation of these features, recognised from the survey, is consistent with extensive palaeocurrent measurements from oscillation ripples. Further loaded sandstone beds and sand-filled shallow channel features overlie the bar forms. The channels are well imaged in the radargrams where their wider context can be gained. Through the combination of high resolution GPR data and detailed sedimentological analysis determination of the processes through which the previously enigmatic lake shore zone sandstones has been possible. The shore zone sandstones overlie playa facies which contain abundant desiccation horizons, reflecting the most arid phase in the climatically-controlled lacustrine cycle. As climatic conditions ameliorated the rejuvenation of fluvial systems resulted in the transport of sand out into the basin. Initial deposition was limited to intermittent events where sediment was laid down on a water saturated substrate. Some of these may have occurred subaqueously as small scale turbidity flows. High resolution fluctuations in lake level resulted in periodic short-lived reworking events along the lake margin which produced amalgamated sands, forming low relief bars. Shore zone reworking is likely to have occurred over a wide area as the lake margin migrated back and forth, and gradually transgressed. Continued transgression forced fluvial systems back towards the basin margin.

Geomorphological map and preliminary analysis of Quaternary sediments in the Planica-Tamar valley (Julian Alps, NW Slovenia)

NASA Astrophysics Data System (ADS)

Novak, Andrej; Šmuc, Andrej

2016-04-01

The Planica-Tamar valley is located in the Julian Alps in north-west Slovenia. The Planica-Tamar valley represents typical mountain glacial valley bounded by steep, mainly carbonate cliffs with some glacial deposits still preserved. The valley is currently being filled with numerous Holocene sediments deposited by rock falls, landslides, mass gravity flows and fluvial flows. These deposits are forming active or inactive interfingering talus slopes, alluvial and debris-flow fans, all of them with a complex history of sedimentation and erosion forming unconformity bounded sedimentary units. In order to make a thorough analysis of these deposits a detailed geomorphological map in a scale of 1:10 000 has been made. Six different types of sedimentary deposits were defined and mapped. These are moraines, lacustrine sediments, fluvio-glacial deposits, talus slopes, debris fans and alluvial fans. Other mapped features also include shape of ravines, their depths, ridges and direction of sedimentary flow. Additionally areas of active, semi-active and inactive sedimentation were marked. Moraines forms a ridge in the bottom of the valleys and are composed of unconsolidated, poorly sorted, subangular grains ranging from clay size to a few cubic meters big blocks. Lacustrine sediments are represented by laminated well sorted sand and silt, while fluvio-glacial deposits are composed of washed out subrounded sands and gravels. Talus slope deposits are characterised by clast-supported poorly sorted very angular gravel. Debris flow fans are represented by extremely poorly sorted matrix-supported gravels with grain size ranging from clay to few cubic meters big blocks. Alluvial fans are composed by variety of sedimentary textures. Sediments at the fan apex are clast-supported poorly sorted very angular gravels with up to a few cubic meters big block. In the middle part of the fan the sieve deposits are common, while in the distal parts a few centimeters thick layers of sand and moderately sorted clast or sandy matrix-supported angular gravels occur. In cross-sections of alluvial fans distinct palaeosoil horizons are present indicating longer inactivity of that part of the fan. The geomorphological map forms a base for further research and thorough analysis of Quaternary deposits in order to reconstruct the Holocene dynamic of triggering and sedimentation of different types of slope deposits and relate them to base rock geology, tectonic and local/regional climate events. Key words: geomorphological mapping, Holocene slope deposits, alluvial fans, debris fans, Alpine geomorphology.

Volcanic recycling of carbonates on Mars

NASA Technical Reports Server (NTRS)

Schaefer, M. W.

1993-01-01

Thermal erosion of carbonate deposits by turbulently-flowing lava is investigated as a means of recycling carbon dioxide back into the atmosphere of Mars. Erosion rates of several meters/day are found, implying that up to hundreds of meters of carbonate could be removed over the lifetime of a flow. A large fraction of the northern plains and other parts of Mars were covered by lava during the Hesperian, and may have released the carbon dioxide trapped in carbonate deposits. This period of time, several times 10 exp 8 yrs, is comparable to that for the redeposition of such carbonate deposits. Therefore, there could have existed a relatively dense atmosphere, and enhanced weathering and erosion, after the Noachian era. This may help explain the apparent observational evidence for late fluvial and lacustrine activity on Mars.

Changing fluvial styles in volcaniclastic successions: A cretaceous example from the Cerro Barcino Formation, Patagonia

NASA Astrophysics Data System (ADS)

Umazano, A. Martín; Krause, J. Marcelo; Bellosi, Eduardo S.; Perez, Mariano; Visconti, Graciela; Melchor, Ricardo N.

2017-08-01

The Cretaceous Puesto La Paloma (PLPM) and Cerro Castaño (CCM) members (Cerro Barcino Formation, Chubut Group) are pyroclastic-rich, alluvial successions deposited in the Somuncurá-Cañadón Asfalto Basin during sag and endorheic conditions. The PLPM comprises sheet-like tuffaceous sandstone strata, whereas the overlying CCM includes sheet-to ribbon-channel sandstone bodies intercalated within tuffaceous and fine-grained sediments. In this context, the goals of this contribution were: i) to make a detailed documentation of the contrasting sedimentary palaeonvironments; and ii) to infer the allocyclic controls that governed the sedimentation of both units. The study area is located in the western sector of the basin, where six localities, which were studied. Six facies associations were defined including ash-falls, sheet-floods, shallow lakes, aeolian, fluvial channel-belts, and reworked debris-flows. We defined four stratigraphic intervals for the studied sections, denominated 1 to 4 in chronological order of deposition, which increase their thicknesses toward the Puesto Mesa-Cerro León site. The interval 1 (18-42 m thick) corresponds to the PLPM and includes numerous pedogenized sheet-flood deposits, carbonate-rich lacustrine, aeolian sandy facies, and ash-fall beds. The interval 1 is interpreted as an ephemeral and unconfined alluvial system that interacted with aeolian dunes and dry interdune zones. The interval 2 (20-47 m thick) represents the lower part of the CCM. It shows an alternation of fluvial channel-belt deposits and vegetated floodplain facies with sediments originated from sheet-floods, lakes, and few ash-falls and debris-flows. The mean palaeoflow was toward E-SE, except in the northernmost locality where the drainage was towards SW. Proportion of channel-belt bodies ranges from 10 to 36%, reaching higher values in the northern part of the study area, where they are also thicker. The interval 2 represents a permanent, meandering or locally low-sinuosity, fluvial system, and displays both an increase of lacustrine facies and a decrease of ash-fall deposits. The interval 3 (7.5-27 m thick) corresponds to the middle part of the CCM, and lacks channel-belt bodies. It has the highest participation of sheet-flood and ash-fall deposits. This interval entirely records a pedogenized floodplain setting. In relation to the interval 2, participation of debris-flow deposits remains constant and lacustrine facies subtly increases. The interval 4 (18-148 m thick) represents the upper part of the CCM. It comprises an alternation of channel-belt bodies and pedogenized floodplain facies, the last characterized by sheet-flood, lake, debris-flow, and volcanic ash rain deposits. The mean palaeoflow was toward E-SE, except in the two localities positioned further north where the drainage was towards NE and SSE. Proportion of channel-belt deposits ranges from 6 to 32%. It represents channelized and perennial fluvial systems with meandering and locally low-sinuosity styles. Increase in channel proportion and thicker channel bodies are in the northern part of the study area. Particularly, in Puesto Mesa-Cerro León locality this interval is the thickest and has the highest proportion of thicker channel-belt bodies. We interpret these changes in facies architecture as the response to alternated periods of high (intervals 1 and 3) and low (intervals 2 and 4) primary pyroclastic sediment supply. Moreover, there was a climatic change to wetter conditions (intervals 1 to 2-4); as well as intrabasinal tectonic activity in northern area for intervals 2 and 4 inferred from palaeocurrent data.

Geophysical imaging of the lacustrine sediments deposited in the La Calderilla Volcanic Caldera (Gran Canaria Island, Spain) for paleoclimate research

NASA Astrophysics Data System (ADS)

Himi, Mahjoub; Rodríguez-González, Alejandro; Criado, Constantino; Tapias, Josefina C.; Ravazzi, Cesare; Pérez-Torrado, Francisco; Casas, Albert

2016-04-01

The discovery of well-preserved maar structures is important not only for studying the eruptive activity and formation of volcanoes, but also for paleoclimate research, since laminated maar lake sediments may contain very detailed archives of climate and environmental history. Maars are a singular type of volcanic structure generated by explosive phreatomagmatic eruptions as a result of interaction between rising magma and groundwater. This kind of structures are characterised by circular craters, often filled with water and/or lacustrine sediments and surrounded by a ring of pyroclastic deposits.Recently a borehole was drilled at the bottom of La Calderilla volcanic complex which penetrated about 8.7 m in its sedimentary sequence and paleobotanical study has supplied the first evidence of paleoenvironmental evolution during the Holocene on the Gran Canaria Island. This survey, however, did not penetrate into the substrate because the total thickness of the sedimentary fill was unknown. Since the age of formation of La Calderilla volcanic complex based on K/Ar dating is about 85,000 years (Upper Pleistocene), the possibility of its sedimentary fill extends beyond of the Holocene is extremely attractive, since, for example, there are few paleoenvironmental data regarding how much the last glaciation that affected the Canary Islands. In these circumstances, the knowledge of the total thickness of the lacustrine sediments is crucial to design a deeper borehole in the next future. Therefore, the subsurface characterisation provided by geophysics is essential for determining thickness and geometry of the sedimentary filling. Multielectrode ERT method was used to obtain five 2-D resistivity cross-sections into La Calderilla volcanic caldera. An Iris Syscal Pro resistivity system with 48 electrodes connected to a 94 m long cable (2m electrode spacing) in Wenner-Schlumberger configuration for an investigation depth of about 20 m. Data quality (q <2 %).was assessed by averaging or stacking several measurements. Also, very low contact resistances were found because of the high moisture of the soils and the special design of the stainless steel electrodes directly in contact with the multicore cable (R values <3 kΩ). Current injected was automatically adjusted by the system to optimize the input voltage and to ensure the best signal-to-noise ratio. All inverted ERT cross-sections show typical three layer models with very high resistivity contrast. The upper layer with intermediate to high resistivity values (1000 Ω.m to 2500 Ω.m) thin and quit heterogeneous can be correlated with the recent coarse deposits. An intermediate low resistivity layer (200 Ω.m to 400 Ω.m) with a thickness increasing to the NW where reach more than 14 meters and that can be associated to the laminated lacustrine sediments. A lower layer of very high resistivity (> 8000 Ω.m) that can be associated with be volcanic rocks that were the basement of the lake. Sedimentation rate is certainly not homogeneous. A very high rate has been obtained from the first four meters, giving all ages around 2,200 years. Nevertheless, for the rest of the geological log the sedimentation rate is lower and in our opinion more realistic: about 0.5 m for 1,000 years. Extrapolating this rate up to 14 m, the oldest age of lacustrine sedimentary record should be about 19,000 years, far away from the 85,000 years of the formation of La Calderilla volcanic complex following K/Ar dating.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamlin, H.S.; Dutton, S.P.; Tyler, N.

The Tirrawarra Sandstone contains 146 million bbl of oil in Tirrawarra field in the Cooper basin of South Australia. We used core, well logs, and petro-physical data to construct a depositional-facies-based flow-unit model of the reservoir, which describes rock properties and hydrocarbon saturations in three dimensions. Using the model to calculate volumes and residency of original and remaining oil in place, we identified an additional 36 million bbl of oil in place and improved understanding of past production patterns. The Tirrawarra Sandstone reservoir was deposited in a Carboniferous-Permian proglacial intracratonic setting and is composed of lacustrine and fluvial facies assemblages.more » The stratigraphic framework of these nonmarine facies is defined by distinctive stacking patterns and erosional unconformities. Mudstone dominated zones that are analogous to marine maximum flooding surfaces bound the reservoir. At its base a progradational lacustrine-delta system, composed of lenticular mud-clast-rich sandstones enclosed in mudstone, is truncated by an unconformity. Sandstones in these lower deltaic facies lost most of their porosity by mechanical compaction of ductile grains. Sediment reworking by channel migration and locally shore-zone processes created by quartz-rich, multilateral sandstones, which retained the highest porosity and permeability of all the reservoir facies and contained most of the original oil in place. Braided-channel sandstones, however, are overlain by lenticular meandering-channel sandstones, which in turn grade upward into widespread mudstones and coals. Thus, this uppermost part of the reservoir displays a retrogradational stacking pattern and upward-decreasing reservoir quality. Our results demonstrate that depositional variables are the primary controls on reservoir quality and productivity in the Tirrawarra Sandstone.« less

Aqueous history of Mars as inferred from landed mission measurements of rocks, soils, and water ice

NASA Astrophysics Data System (ADS)

Arvidson, Raymond E.

2016-09-01

The missions that have operated on the surface of Mars acquired data that complement observations acquired from orbit and provide information that would not have been acquired without surface measurements. Data from the Viking Landers demonstrated that soils have basaltic compositions, containing minor amounts of salts and one or more strong oxidants. Pathfinder with its rover confirmed that the distal portion of Ares Vallis is the site of flood-deposited boulders. Spirit found evidence for hydrothermal deposits surrounding the Home Plate volcanoclastic feature. Opportunity discovered that the hematite signature on Meridiani Planum as seen from orbit is due to hematitic concretions concentrated on the surface as winds eroded sulfate-rich sandstones that dominate the Burns formation. The sandstones originated as playa muds that were subsequently reworked by wind and rising groundwater. Opportunity also found evidence on the rim of the Noachian Endurance Crater for smectites, with extensive leaching along fractures. Curiosity acquired data at the base of Mount Sharp in Gale Crater that allows reconstruction of a sustained fluvial-deltaic-lacustrine system prograding into the crater. Smectites and low concentrations of chlorinated hydrocarbons have been identified in the lacustrine deposits. Phoenix, landing above the Arctic Circle, found icy soils, along with low concentrations of perchlorate salt. Perchlorate is considered to be a strong candidate for the oxidant found by the Viking Landers. It is also a freezing point depressant and may play a role in allowing brines to exist at and beneath the surface in more modern periods of time on Mars.

MX Siting Investigation Geotechnical Siting Status Report. Volume I.

DTIC Science & Technology

1978-06-21

and have moderate shear strength. GNU. HAl SUNAL, INC ENGINEERING AND GEOPHYSICAL PROPERTIES Int rrniatd.an. ungur . Aluvial Lacustrine /oNan gdotlS t...an unvarnished, active surface of sediment transport gra A53 stream channel and floodplain deposits. A52 - Unconsolidated to poorly consolidated sand...silt, and sandy gravel, with va c.0 A52 surface gravels forming isolated areas of desert pavement. This fan is in vario Cc surface of sediment

Luminescence dating of the lacustrine record of Vršac (Carpathian Basin, Serbia) - implications for a palaeoenvironmetal reconstruction

NASA Astrophysics Data System (ADS)

Klasen, N.; Zeeden, C.; Markovic, S.; Fischer, P.; Lehmkuhl, F.; Schulte, P.; Bösken, J.; Hambach, U.; Vött, A.

2017-12-01

The Carpathian Basin is one of the key areas to investigate the influence of the continental, Mediterranean and Atlantic climate interaction over Europe. The available Upper Pleistocene and Holocene geoarchives in the region are mainly loess-paleosol records. Long lacustrine records are sparse and do not always span the whole last glacial cycle. In the area around Vršac, we drilled a 10 m core to contribute to the palaeoenvironmental reconstruction of the Carpathian Basin. Electrical Resistivity Tomography (ERT) was used to find the best-suited drilling location. We applied luminescence and radiocarbon dating, because a robust chronology is important for the interpretation of the sedimentary record. Pulsed OSL measurements were carried out to identify the best sampling positions. We expect runoff from the catchment being the main source of the lacustrine sediments, because coarse fluvial input is absent. Knowledge about the depositional conditions is important in luminescence dating to evaluate partial bleaching prior to deposition, which may cause age overestimation. Therefore, we compared infrared stimulated luminescence (IRSL) signals with post infrared infrared stimulated luminescence (pIRIR) signals, which bleach at different rates. Estimation of a representative water content has major influence on the age estimate, but remains challenging in luminescence dating. We measured the present day water content as well as the saturation water content, to account for variations over time. Luminescence and radiocarbon ages differ greatly from each other. According to the laboratory experiments, luminescence dating was reliable and we conclude that radiocarbon ages were underestimated because of an intrusion of younger organic material. The initial results demonstrated the potential of the drill core. Integrating more proxy data will be useful to enhance the importance of the geoarchive at Vršac for a better understanding of the last glacial cycle in the Carpathian Basin.

Late Quaternary stratigraphy and luminescence geochronology of the northeastern Mojave Desert

USGS Publications Warehouse

Mahan, S.A.; Miller, D.M.; Menges, C.M.; Yount, J.C.

2007-01-01

The chronology of the Holocene and late Pleistocene deposits of the northeastern Mojave Desert have been largely obtained using radiocarbon ages. Our study refines and extends this framework using optically stimulated luminescence (OSL) to date deposits from Valjean Valley, Silurian Lake Playa, Red Pass, and California Valley. Of particular interest are eolian fine silts incorporated in ground-water discharge (GWD) deposits bracketed at 185-140 and 20-50 ka. Alluvial fan deposits proved amenable for OSL by dating both eolian sand lenses and reworked eolian sand in a matrix of gravel that occurs within the fan stratigraphy. Lacustrine sand in spits and bars also yielded acceptable OSL ages. These OSL ages fill gaps in the geochronology of desert deposits, which can provide data relevant to understanding the responses of several depositional systems to regional changes in climate. This study identifies the most promising deposits for future luminescence dating and suggests that for several regions of the Mojave Desert, sediments from previously undated landforms can be more accurately placed within correct geologic map units.

Shell We Date? ESR Dating Sangamon Interglacial Episode Deposits at Hopwood Farm, IL.

PubMed

Blackwell, Bonnie A B; Kim, Danny M K; Curry, B Brandon; Grimley, David A; Blickstein, Joel I B; Skinner, Anne R

2016-12-01

During the Sangamon Episode, North America occasionally experienced warm climates. At Hopwood Farm, IL, a small kettle lake filled with sediment after the Illinois Episode glaciers retreated from southern Illinois. To date those deposits, 14 mollusc samples newly collected with associated sediment from three depths at Hopwood Farm were dated by standard electron spin resonance (ESR) dating. ESR can date molluscs from ~0.5 ka to >2 Ma in age with 5-10% precision, by comparing the accumulated radiation dose with the total radiation dose rate from the mollusc and its environment. Because all molluscs contained ≤0.6 ppm U, their ages do not depend on the assumed U uptake model. Using five different species, ESR analyses for 14 mollusc subsamples from Hopwood Farm showed that Unit 3, a layer rich in lacustrine molluscs, dates at 102 ± 7 ka to 90 ± 6 ka, which correlates with Marine (Oxygen) Isotope Stage 5c-b. Thus, the period with the highest non-arboreal pollen at Hopwood also correlates with the European Brørup, Dansgaard-Oeschger Event DO 23, a time period when climates were cooling and drying somewhat over the same period. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Evidence for stagnation of the Harvard sublobe (Lake Michigan lobe) in Northeastern Illinois, U.S.A., from 24 000 to 17 600 BP and subsequent tundra-like ice-marginal paleoenvironments from 17 600 to 15 700 BP

USGS Publications Warehouse

Curry, B. Brandon; Yansa, C.H.

2004-01-01

Glacial deposits of the last glaciation associated with the Harvard sublobe (Lake Michigan lobe) in northeastern Illinois, U.S.A., occur between sediment with dateable organics. The lower organics include fragments of Picea sp. as young as 24 000 ?? 270 BP. The supraglacial organics occur sparsely in laminated silt and fine sand in landforms that are positioned relatively high on the landscape, such as deposits from ice-walled lakes. These terrestrial organics yield ages that are 2500 to 1300 14C years older than organics at the base of sediment successions in nearby kettle basins. Basal 14C ages from four upland sites range from 17 610 ?? 270 to 16 120 ?? 80 BP. Our revised time-distance diagram of the Harvard sublobe now reflects a period of stagnation from 24 000 to about 17 600 BP. The supraglacial lacustrine silt yielded plant macrofossil assemblages of primarily tundra plants, including Salix herbacea and Dryas integrifolia. These plants likely grew in supraglacial and ice-marginal environments. The ostracode fauna include Cytherissa lacustris and Limnocythere friabilis. Geomorphic relations and ostracode ecology indicate that more than 17 m of ice buttressed some of the supraglacial lakes.

Rifting by continental rotation, mantle flow and hotspot volcanism in the salt-depositing South Atlantic

NASA Astrophysics Data System (ADS)

Szatmari, P.

2012-04-01

Rabinowitz & LaBrecque (1979) proposed that Africa and South America separated between 130 Ma and 107 Ma by 11.1° rigid plate rotation about an Euler pole in NE Brazil. According to those authors, the two continents remained contiguous in the north as the wedge-shaped South Atlantic opened up between them and deposited salt mostly over oceanic crust. Subsequent seismic profiling and drilling showed that salt, restricted to north of the volcanic proto-Walvis Ridge, deposited over rift sediments and stretched-thinned continental crust. Increasingly accurate restorations by Nürnberg & Müller (1991), Aslanian et al. (2009), Torsvik et al. (2009), and Moulin et al. (2010) differentiated in both continents several rigid plates separated by active deformation zones. Still, tectonic analysis of the rifted margins indicates that the main Early Cretaceous event was the clockwise rotation of South America about an Euler pole in its northeast. Both rifting and volcanism, including the Paraná-Etendeka large igneous province, where most flood basalts erupted at 134.6 ± 0.6 Ma (Thiede & Vasconcelos, 2010), were controlled by distance and orientation of rift segments relative to that pole in NE Brazil. Rifting was active from latest Jurassic to early Albian time (Magnavita et al., 2011) over inherited late Proterozoic fold-thrust belts. By Aptian time a long, dry wedge-shaped basin formed north of the volcanic barrier of the proto-Walvis Ridge, widening southward to 700 km and subsiding deep below sea level in the Santos Basin. The basin was filled with oil-rich lacustrine limestone and marine salt, each more than 2 km thick, deposited in often desiccating shallow water over the partially hyperextended continental crust of the São Paulo Plateau (Zalán et al., 2010; Magnavita et al., 2011; Szatmari, 2011). Further south marine sediments deposited over oceanic crust. Surface subsidence of the long, deep sediment-starved rift wedge was shaped, prior to the deposition of the lacustrine limestones and marine evaporites, by South America's continental rotation and by hotspot activity; asthenosphere inflow was limited by the bordering two old continents.

Hydrogeology of the Susquehanna River valley-fill aquifer system and adjacent areas in eastern Broome and southeastern Chenango Counties, New York

USGS Publications Warehouse

Heisig, Paul M.

2012-01-01

The hydrogeology of the valley-fill aquifer system along a 32-mile reach of the Susquehanna River valley and adjacent areas was evaluated in eastern Broome and southeastern Chenango Counties, New York. The surficial geology, inferred ice-marginal positions, and distribution of stratified-drift aquifers were mapped from existing data. Ice-marginal positions, which represent pauses in the retreat of glacial ice from the region, favored the accumulation of coarse-grained deposits whereas more steady or rapid ice retreat between these positions favored deposition of fine-grained lacustrine deposits with limited coarse-grained deposits at depth. Unconfined aquifers with thick saturated coarse-grained deposits are the most favorable settings for water-resource development, and three several-mile-long sections of valley were identified (mostly in Broome County) as potentially favorable: (1) the southernmost valley section, which extends from the New York–Pennsylvania border to about 1 mile north of South Windsor, (2) the valley section that rounds the west side of the umlaufberg (an isolated bedrock hill within a valley) north of Windsor, and (3) the east–west valley section at the Broome County–Chenango County border from Nineveh to East of Bettsburg (including the lower reach of the Cornell Brook valley). Fine-grained lacustrine deposits form extensive confining units between the unconfined areas, and the water-resource potential of confined aquifers is largely untested. Recharge, or replenishment, of these aquifers is dependent not only on infiltration of precipitation directly on unconfined aquifers, but perhaps more so from precipitation that falls in adjacent upland areas. Surface runoff and shallow groundwater from the valley walls flow downslope and recharge valley aquifers. Tributary streams that drain upland areas lose flow as they enter main valleys on permeable alluvial fans. This infiltrating water also recharges valley aquifers. Current (2012) use of water resources in the area is primarily through domestic wells, most of which are completed in fractured bedrock in upland areas. A few villages in the Susquehanna River valley have supply wells that draw water from beneath alluvial fans and near the Susquehanna River, which is a large potential source of water from induced infiltration.

Proglacial Hydrogeology of the Cordillera Blanca (Peru): Integrating Field Observations with Hydrogeophysical Inversions to Inform Groundwater Flow Simulations and Conceptual Models

NASA Astrophysics Data System (ADS)

Glas, R. L.; Lautz, L.; McKenzie, J. M.; Moucha, R.; Mark, B. G.

2017-12-01

Geological and depositional conditions of the glaciated Cordillera Blanca in Peru have given way to proglacial aquifer systems that contribute substantially to regional streams and rivers, particularly during the dry season. As glacial retreat accelerates, the dry season water budget will be increasingly dominated by groundwater inputs, although predictions of future groundwater quantities require estimations of groundwater storage capacity, aquifer extents, and groundwater residence time. We present a characterization of the sediment structure in a prototypical proglacial valley in the central portion of the range, the Quilcayhuanca Valley. Northern and Central valleys of the Cordillera Blanca feature ubiquitous talus deposits that line the steep granite walls, and have become partially buried beneath lacustrine sediments deposited in proglacial lake beds. The portion of the talus still exposed near the valley walls provides recharge to deeper portions of the valley aquifers that underlie lacustrine clay, resulting in a confined aquifer system that is connected to the surface via perennial springs. Seismic refraction surveys reveal an interface separating relatively slow ( 400-800 m/s) and fast ( 2500 m/s) p-wave velocities. The depth of this refractor coincides with the depth to buried talus observed in drilling records. Electrical resistivity tomography profiles of the same transect show depths near the buried talus to be relatively conductive (10-100 Ωm). At these depths, we hypothesize that electrical conductance is elevated by saturated clay particles in the sediment matrix of the talus deposit. The resistivity models all show a more resistive ( 700 Ω m) region at depth, likely corresponding to a more hydraulically conductive material. The resistive zone is interpreted to be a deeper portion of a buried talus deposit that did not accumulate clay in the matrix. Other possibilities include a thick deposit of gravelly glacial outwash, or a relatively clay-poor glacial till. We present a groundwater modeling framework to resolve the nature of the sediments in deeper layers, where geophysical data become less certain. Sediment permeability estimates will allow for more refined predictions of groundwater storage volume in buried talus aquifers, which are likely prevalent throughout the range.

Paleoenvironmental change in the southern Kenya Rift System: A case study based on the Pleistocene Olorgesailie and Oltulelei Formations

NASA Astrophysics Data System (ADS)

Behrensmeyer, A. K.; Potts, R.; Deino, A. L.

2017-12-01

The Pleistocene paleoenvironmental history of the East African Rift in southern Kenya is recorded by the Olorgesailie Fm. (1.2 - 0.5 ma) and the overlying Oltulelei Fm. ( 320 ka - 50 ka), which occur in a depositional basin north of Mt. Olorgesailie that extends into the northern end of the Koora Graben west of the mountain. The two formations preserve abundant archeological sites and fossil remains that document hominin behavior and paleoecology during the time in Africa when Homo erectus evolved into Homo sapiens. Geochronological calibration, based primarily on Ar-Ar dates of interbedded tephras, shows shifts in the physical landscape on time scales of 104 - 105 yrs, with a prolonged period of primarily lacustrine deposition (Olorgesailie Fm.) followed by tectonically driven changes in base level leading to accelerating cycles of erosion and deposition (Oltulelei Fm.). Following major erosion of the Olorgesailie Fm. between 500 and 320 ka, the Oltulelei Fm. was deposited during three cycles of aggradation and erosion, with fluvial, lacustrine and wetlands deposits preserved in fault-controlled areas or temporarily blocked drainage valleys. Deposition occurred in three sub-basins with varying degrees of linkage, reflecting a changing balance of sediment input and accommodation space controlled by climate, volcanism, and periodic movement of faults in the volcanic basement. Large volumes of sediment were removed during erosive phases, requiring increased precipitation and through-flowing drainage into Koora Graben southwest and south of Mt. Olorgesailie. The southern Kenya rift provided a shifting array of habitats and environmental challenges for hominins, which were driven both by the dynamic tectonic setting and climate cycles. Portions of both the Olorgesailie and Oltulelei Fms. correlate geochronologically with a drill core record 20 km to the south (ODP-OLO12-1A), which will provide paleoclimate information for times when erosion and subaerial landscapes prevailed in the Olorgesailie Basin to the north. This sets the stage for paleoenvironmental reconstructions that relate closely in time and space to documented changes in the archeology and faunas, which record critical transitions in technology and mammalian communities over the past 1.2 ma.

Ancient Martian aeolian processes and palaeomorphology reconstructed from the Stimson formation on the lower slope of Aeolis Mons, Gale crater, Mars

USGS Publications Warehouse

Banham, Steve G.; Gupta, Sanjeev; Rubin, David M.; Watkins, Jessica A.; Sumner, Dawn Y.; Edgett, Kenneth S.; Grotzinger, John P.; Lewis, Kevin W.; Edgar, Lauren; Stack, Kathryn M.; Barnes, Robert; Bell, Jame F. III; Day, Mackenzie D.; Ewing, Ryan C.; Lapotre, Mathieu G.A.; Stein, Nathan T.; Rivera-Hernandez, Frances; Vasavada, Ashwin R.

2018-01-01

Reconstruction of the palaeoenvironmental context of Martian sedimentary rocks is central to studies of ancient Martian habitability and regional palaeoclimate history. This paper reports the analysis of a distinct aeolian deposit preserved in Gale crater, Mars, and evaluates its palaeomorphology, the processes responsible for its deposition, and its implications for Gale crater geological history and regional palaeoclimate. Whilst exploring the sedimentary succession cropping out on the northern flank of Aeolis Mons, Gale crater, the Mars Science Laboratory rover Curiosity encountered a decametre‐thick sandstone succession, named the Stimson formation, unconformably overlying lacustrine deposits of the Murray formation. The sandstone contains sand grains characterized by high roundness and sphericity, and cross‐bedding on the order of 1 m in thickness, separated by sub‐horizontal bounding surfaces traceable for tens of metres across outcrops. The cross‐beds are composed of uniform thickness cross‐laminations interpreted as wind‐ripple strata. Cross‐sets are separated by sub‐horizontal bounding surfaces traceable for tens of metres across outcrops that are interpreted as dune migration surfaces. Grain characteristics and presence of wind‐ripple strata indicate deposition of the Stimson formation by aeolian processes. The absence of features characteristic of damp or wet aeolian sediment accumulation indicate deposition in a dry aeolian system. Reconstruction of the palaeogeomorphology suggests that the Stimson dune field was composed largely of simple sinuous crescentic dunes with a height of ca10 m, and wavelengths of ca 150 m, with local development of complex dunes. Analysis of cross‐strata dip‐azimuths indicates that the general dune migration direction and hence net sediment transport was towards the north‐east. The juxtaposition of a dry aeolian system unconformably above the lacustrine Murray formation represents starkly contrasting palaeoenvironmental and palaeoclimatic conditions. Stratigraphic relationships indicate that this transition records a significant break in time, with the Stimson formation being deposited after the Murray formation and stratigraphically higher Mount Sharp group rocks had been buried, lithified and subsequently eroded.

Climate and tectonic evolution of the Descanso-Yauri basin in the northernmost Altiplano: Archetype example of a 'lithospheric drip' basin

NASA Astrophysics Data System (ADS)

Kar, N.; Garzione, C. N.

2015-12-01

We present a new multiproxy Miocene-Pliocene paleoelevation record of the northernmost Altiplano plateau reconstructed from pollen, clumped isotope (TΔ47) and δ18Oc of sedimentary carbonates and leaf wax n-alkane δD signatures. The ~18Ma to ~9Ma deposits of our study area, Descanso-Yauri basin in southern Peru show 11 to 16ºC warmer than modern mean annual air temperature, low elevation vegetation pollen assemblage (dominated by Podocarpus), and an average precipitation δ18Omw (VSMOW) value of -8.3±2.0‰ (2σ). The ~5 to 4 Ma deposits in the Descanso-Yauri basin are characterized by herb and shrub vegetation and an average δ18O mw (VSMOW) value of -14.6±3.0‰ (2σ), indicative of an elevation and/or climate similar to modern conditions. Based on the multiproxy paleoclimate record, we interpret that there was a 2±1 km surface uplift between 9 and 5 Ma in the northernmost Altiplano plateau. Deformation history analysis through map scale structural investigation combined with provenance analysis from conglomerate clast composition and paleocurrents show that the thrusts bounding the NE side of the Descanso-Yauri basin were active until ˜9Ma. Deformation waned afterwards, and switched to an extensional deformation regime, coincident with decrease in subsidence rate from ˜0.2mm/year to ˜0.03mm/year. Depositional history reconstructed by facies analysis and stratigraphic correlation reveal that deposition in the basin began with transverse braided river systems that formed along the thrust front and gave way to a larger fluvial-lacustrine system until ˜4 Ma. The basin deposits show an overall fining upward trend from coarse clastic dominated, in the lower most parts of the basin fill to fluvial overbank and lacustrine mudstone and diatomite deposits in the middle-upper parts. The thickest deposits formed in the central part of the basin. Based on these depositional and deformational patterns, we infer that the Descanso-Yauri basin formed in response to a growing eclogite and mantle root in the lower lithosphere. Removal of this root, possibly combined with lower crustal flow, led to the rapid 9-5 Ma surface uplift of the northernmost part of the Central Andean Plateau.

Sediment records of Yellow River channel migration and Holocene environmental evolution of the Hetao Plain, northern China

NASA Astrophysics Data System (ADS)

Wang, Jingzhong; Wu, Jinglu; Pan, Baotian; Jia, Hongjuan; Li, Xiao; Wei, Hao

2018-05-01

The origin and evolution of lakes in the Hetao Plain, northern China, were influenced by climate variation, channel migration, and human activity. We analyzed a suite of sediment cores from the region to investigate Yellow River channel migration and environmental change in this region over the Holocene. Short sediment cores show that environmental indicators changed markedly around CE 1850, a time that corresponds to flood events, when large amounts of river water accumulated in the western part of the Hetao Plain, giving rise to abundant small lakes. Multiple sediment variables (environmental proxies) from two long cores collected in the Tushenze Paleolake area show that sediments deposited between 12.0 and 9.0 cal ka BP were yellow clay, indicative of fluvial deposition and channel migration. From 9.0 to 7.5 cal ka BP, sand was deposited, reflecting a desert environment. From 7.5 to 2.2 cal ka BP, however, the sediments were blue-gray clay that represents lacustrine facies of Lake Tushenze, which owes its origin to an increase in strength of the East Asian monsoon. At about 2.2 cal ka BP, the north branch of the Yellow River was flooded, and the Tushenze Paleolake developed further. Around 2.0 cal ka BP, the paleolake shrank and eolian sedimentation was recorded. The analyzed sediment records are consistent with the written history from the region, which documents channel migration and environmental changes in the Hetao Plain over the Holocene.

Brazilian continental cretaceous

NASA Astrophysics Data System (ADS)

Petri, Setembrino; Campanha, Vilma A.

1981-04-01

Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

Thermokarst lake dynamics and its influence on biogeochemical sediment characteristics: A case study from the discontinuous permafrost zone in Interior Alaska

NASA Astrophysics Data System (ADS)

Lenz, J.; Walter Anthony, K. M.; Maio, C. V.; Matuszewski, F.; Grosse, G.

2017-12-01

Under currently projected scenarios of climate warming, discontinuous warm permafrost in Interior Alaska is expected to experience widespread disappearance. Thermokarst ponds and lakes are evidence for rapid permafrost thaw and amplify deep thaw by talik development. During the thawing process, previously preserved organic matter is made available for decomposition and former permafrost carbon is potentially released as greenhouse gases carbon dioxide and methane. In the course of lake development and shoreline expansion, both, younger near-surface and older organic matter from slumping shores are potentially deposited in the lake basin. Lake internal bioproductivity is complementing carbon accumulation in lacustrine deposits and provides an additional source of young carbon. This study presents results of two intersecting, limnolithological transects of 5 sediment cores from Goldstream Lake, a typical small, boreal thermokarst lake in Interior Alaska. We here distinguish external terrestrial and internal aquatic carbon contributions to sediments based on sediment samples that were analyzed for the total organic carbon/total nitrogen ratio (C/N) as well as stable carbon isotopes. The littoral zone with actively eroding shorelines is characterized by methane seeps produced from anaerobic microbial decomposition; however, near-shore sediments have surprisingly low total organic carbon contents with a mean of 1.5 wt%; the low C/N ratio of 8.7 indicate a dominance of lacustrine plant material. Very similar results were found for sediments in the central basin, but here a clear shift to a terrestrial carbon signal (C/N of 22) with total organic carbon content of almost 30 wt% is presumably indicating the presence of a trash layer featuring largely terrestrial plants submerged during the initial lake phase. The talik sediments have carbon storage similar to the lake sediments but in contrast are not layered. Subarctic aquatic environments such as Goldstream Lake demonstrate a high aquatic productivity as well as a high biogeochemical turn-over over short periods of time. In addition, the ongoing decomposition of organic matter in talik sediments proves to be crucial to assess the contribution of thermokarst lakes to future climate change by mobilizing soil carbon previously frozen in permafrost.

Detailed north-south cross section showing environments of deposition, organic richness, and thermal maturities of lower Tertiary rocks in the Uinta Basin, Utah

USGS Publications Warehouse

Johnson, Ronald C.

2014-01-01

The Uinta Basin of northeast Utah has produced large amounts of hydrocarbons from lower Tertiary strata since the 1960s. Recent advances in drilling technologies, in particular the development of efficient methods to drill and hydraulically fracture horizontal wells, has spurred renewed interest in producing hydrocarbons from unconventional low-permeability dolomite and shale reservoirs in the lacustrine, Eocene Green River Formation. The Eocene Green River Formation was deposited in Lake Uinta, a long-lived saline lake that occupied the Uinta Basin, the Piceance Basin to the east, and the intervening Douglas Creek arch. The focus of recent drilling activity has been the informal Uteland Butte member of the Green River Formation and to a much lesser extent the overlying R-0 oil shale zone of the Green River Formation. Initial production rates ranging from 500 to 1,500 barrels of oil equivalent per day have been reported from the Uteland Butte member from horizontal well logs that are as long as 4,000 feet (ft);. The cross section presented here extends northward from outcrop on the southern margin of the basin into the basin’s deep trough, located just south of the Uinta Mountains, and transects the area where this unconventional oil play is developing. The Monument Butte field, which is one of the fields located along this line of section, has produced hydrocarbons from conventional sandstone reservoirs in the lower part of the Green River Formation and underlying Wasatch Formation since 1981. A major fluvial-deltaic system entered Lake Uinta from the south, and this new line of section is ideal for studying the effect of the sediments delivered by this drainage on hydrocarbon reservoirs in the Green River Formation. The cross section also transects the Greater Altamont-Bluebell field in the deepest part of the basin, where hydrocarbons have been produced from fractured, highly overpressured marginal lacustrine and fluvial reservoirs in the Green River, Wasatch, and North Horn Formations since 1970. Datum for the cross section is sea level so that hydrocarbon source rocks and reservoir rocks could be integrated into the structural framework of the basin.

Seismic Triggers of Lacustrine Subaqueous Landslides in Lake Champlain, USA

NASA Astrophysics Data System (ADS)

Manley, P.; Manley, T.; Ghosh, S. J.; Rosales-Underbrink, P.; Silverhart, P.

2017-12-01

Lacustrine slumps and debris flows (landslides) have been identified in Lake Champlain via Multibeam and CHIRP (compressed high intensity radar pulse) seismic profile data. Numerous large landslides studied by Ghosh (2012), Rosales-Underbrink (2015), and Silverhart (2016) have shown that many of these landslides are coeval. All landslides failed on a specific interface between marine Champlain Sea and modern lacustrine Lake Champlain sediments. Utilizing radionuclide dating on sediment from the unfailed slopes or undisturbed sediment above failed deposits, sedimentation rates were determined and used to calculate the approximate failure ages for each of the landslides studied. The northernmost failure, south of the Bouquet River, occurred about 950-1200 cal yr BP and is the first mass wasting event of this age to be recorded on Lake Champlain. The remaining landslides failed about 4500-5200 cal yr BP and agree with nearby Western Quebec Seismic Zone (WQSZ) with clusters of terrestrial landslides occurring at 1000 and 5000 cal yr BP triggered by large earthquakes (Brooks, 2015) along the same interface. The 5000 cal yr BP event has been attributed to a M 6.4 or greater earthquake within the WQSZ. The coeval landslides observed in Lake Champlain were likely triggered by this same earthquake. Lake tsunami models show that these simultaneous landslide failures can generate surface waves wave that can impact the Lake Champlain shoreline within 3-10 minutes after the earthquake.

I-15 reconstruction long-term embankment monitoring study : final report.

DOT National Transportation Integrated Search

2012-05-01

The I-15 Reconstruction Project in Salt Lake City, Utah required rapid embankment construction in an urban environment atop soft lacustrine soils. These soils are thick, highly compressible, have low shear strength and require significant time to com...

Sulfur Geochemistry of a Lacustrine Record from Taiwan Reveals Enhanced Marine Aerosol Input during the Early Holocene

PubMed Central

Ding, Xiaodong; Li, Dawei; Zheng, Liwei; Bao, Hongyan; Chen, Huei-Fen; Kao, Shuh-Ji

2016-01-01

Lacustrine record of marine aerosol input has rarely been documented. Here, we present the sulfur geochemistry during the last deglaciation and early Holocene of a sediment core retrieved from the Dongyuan Lake in southern Taiwan. An unusually high sulfur peak accompanying pyrite presence is observed at 10.5 ka BP. Such high sulfur content in lacustrine record is unusual. The δ34S of sulfur varied from +9.5 to + 17.1‰ with two significant positive shifts at 10.5 and 9.4 ka BP. The sources of sulfur and potential processes involving the sulfur isotope variation including bacterial sulfate reduction, volcanic emissions, in-catchment sulfide oxidation and marine aerosol input are discussed. Enhanced marine aerosol input is the most likely explanation for such sulfur peaks and δ34S shifts. The positive δ34S shifts appeared concurrently with the maximum landslide events over Taiwan resulted from enhanced typhoon activities. The synchronicity among records suggests that increased typhoon activities promoted sea spray, and consequently enhanced the marine aerosol input with 34S-enriched sulfate. Our sulfur geochemistry data revealed sea spray history and marine influence onto terrestrial environment at coastal regions. Wider coverage of spatial-temporal lacustrine sulfur geochemistry record is needed to validate the applicability of sulfur proxy in paleoenvironmental research. PMID:27941864

Liquefaction features interpreted as seismites in the Pleistocene fluvio-lacustrine deposits of the Neuquén Basin (Northern Patagonia)

NASA Astrophysics Data System (ADS)

Moretti, M.; Ronchi, A.

2011-04-01

Superbly exposed soft-sediment deformation structures in Pleistocene fluvio-lacustrine deposits along the southern border of the depression area called Bajo de Añelo (Departamento de Añelo, Neuquén Basin) have been analysed. In the study area, five stratigraphic sections were measured in detail: facies distributions and stacking patterns show that these sediments result from the interaction between fluvial and lacustrine systems, represented by cross-bedded and rippled strata, and varved deposits. The lateral extent of the deformation is some hundred metres and the deformed bed involves the lower-mid part of the 30-metre-thick succession. Deformation affects about 1.5 m of coarse-grained sand, fine-grained sand and rare gravel alternations. The base and top of the deformed layer are defined by planar surfaces: undeformed beds of similar thickness, lithology and facies to the deformed layer occur above and below. Deformation is represented by a complex vertical succession of disturbed layers: each layer shows a general load-structure morphology. It can be described as a multilayered unstable density gradient system: in each bed a partial gravitational re-adjustment occurred after liquefaction. Unequal loading related to lateral variation of both bed thickness and grain packing and porosity is a probable additional driving force that can be described in the undeformed beds. Trigger mechanism recognition for the observed liquefaction features can be based on the study of the geometry of deformed beds and on facies analysis results. Two key factors drive our interpretation: (1) the occurrence of undeformed beds below and above the deformed bed; (2) deformed and undeformed beds showing the same sedimentological features. These field data allow us to exclude the action of internal erosive and/or sedimentary processes (such as overloading, wave action, etc.) as possible trigger agents for liquefaction since deformation is totally absent in beds with similar sedimentary features. Furthermore, each internal erosive and/or sedimentary process can be discussed and easily excluded by analysing its specific signature in the geological record. Having excluded every possible internal trigger (autokinetic processes), the observed liquefaction effects can reasonably be interpreted as seismically induced (allokinetic trigger). From this point of view, this deformed bed is an important record of seismic activity in this sector of the Neuquén Basin during the Pleistocene.

The Role of (Delta)C-13 in the Search for Reduced Organics on the Surface of Mars

NASA Technical Reports Server (NTRS)

Stern, J. C.; McAdam, A. C.

2012-01-01

The capabilities of the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) to detect trace amounts of organic carbon compounds are unprecedented, and MSL may be the first mission to reveal the presence of organic carbon on Mars. The search for reduced organic carbon on Mars is inextricably tied to: a) the preservation potential of the environment from which we take a solid sample, and b) the evolved gas analysis (EGA) techniques used by SAM to release volatiles from this solid sample. Several prospective targets have been identified for sample analysis at Gale Crater. Stratigraphic sequences of phyllosilicates and sulfates at Gale are thought to represent a period of global climate transition from a moderate pH lacustrine environment to an evaporitic environment, both of which could sequester organic carbon (Thomson et al. 2011). The sediment mound in Gale Crater contains a range of lithologies suggesting changes in redox conditions, and evidence of both lacustrine and fluvial depositional processes, which may have transported organic carbon from the layer in which it formed and resulted in its preservation elsewhere within the crater (Anderson and Bell, 2010). Inverted channel fills suggest erosion resistant material that could serve to preserve organics originally deposited in a low energy aqueous environment. The lithology sampled will affect not only the preservation of organics, but also our ability to detect organics during our evolved gas analysis, based on the sample matrix. For example, reduced organics may be trapped in the mineral structure, and thermal evolution of these organics will occur during thermal decomposition of the host mineral. If organics are occluded in minerals that have very high thermal decomposition temperatures, they may be, in effect, "too well preserved," and difficult to detect during EGA. Alternatively, the possible presence of perchlorate, or other strong oxidants in surface regolith, may result in destruction of structural information identifying organic molecules before reaching the QMS on SAM via oxidation to C02 during heating. If this is the case, the stable carbon isotopic composition (delta 13C) of the C02 evolved and measured by the Tunable Laser Spectrometer (TLS) on SAM may help identify the presence of organics. On Earth, biological activity can cause large fractionations of 13C/12C, which can preserved in sedimentary deposits and distinguish the organic products of biotic processes from inorganic atmospheric and geological reservoirs. It is plausible that similar fractionations could occur on Mars and be preserved in reduced organic matter in sediments. Bulk delta 13C measurements alone may not reveal a signature of trace organic carbon that may be present along with inorganic carbon. If both organic and inorganic carbon compounds are present, it may be possible to detect the organic carbon by comparing the 013C of pyrolysis and combustion experiments. The TLS on SAM is capable of obtaining high precision measurements of delta13C from C02 evolved during pyrolysis and combustion of solid regolith samples. Because carbonates are expected to be present at abundances of 0.1-1 % in Martian soil, and organics in the ppb range (Webster and Mahaffy, 2011), analog samples must represent this mix of reduced organic carbon and carbonate. The work presented here will examine the use of delta13C of C02 produced during combustion of bulk Mars analog samples as a proxy for detection of reduced organic carbon.

Depositional setting and diagenetic evolution of some Tertiary unconventional reservoir rocks, Uinta Basin, Utah.

USGS Publications Warehouse

Pitman, Janet K.; Fouch, T.D.; Goldhaber, M.B.

1982-01-01

The Douglas Creek Member of the Tertiary Green River Formation underlies much of the Uinta basin, Utah, and contains large volumes of oil and gas trapped in a complex of fractured low-permeability sandstone reservoirs. In the SE part of the basin at Pariette Bench, the Eocene Douglas Creek Member is a thick sequence of fine- grained alluvial sandstone complexly intercalated with lacustrine claystone and carbonate rock. Sediments were deposited in a subsiding intermontane basin along the shallow fluctuating margin of ancient Lake Uinta. Although the Uinta basin has undergone postdepositional uplift and erosion, the deepest cored rocks at Pariette Bench have never been buried more than 3000m.-from Authors

Preliminary paleohydrological interpretation of an Amazon floodplain system based on seismic stratigraphy: Varzea do Lago Grande do Curuai, Pará, Brazil.

NASA Astrophysics Data System (ADS)

Amorim, M. A.; Moreira-Turcq, P.; Turcq, B.

2009-04-01

The aquatic lacustrine ecosystems are depositional environments that register in yours sediments the process that occurs on the own site and in the all drainage basin. The Amazonas River and its tributaries are followed along your upward and downward course by several floodplains that cover a large area of environs 300.000 km2. These sites are dynamic and complexes systems. Floodplains affect the erosion the transport and the sedimentation flux in the system and it has a special importance for carbon cycle due yours high productivity. In the floodplains systems the sediment deposition occurs in a different scale of time period. In these work, we study the "Varzea Grande do Curuai" which size varies from 1340km2 during the dry season, to 3600 km2 during the wet season, according to the level of the river. This floodplain is located on the southern margin of the Amazonas River, close to the city of Óbidos, Pará-Brazil, in the Lower Amazonas. The floodplain contains several white water lakes such as Grande, Poção, Santa Ninha and Salé Lakes, and black water lakes such as the Curumucuri and Açaí Lakes. These lakes are connected to each other and to the Amazonas River by small channels, some of which are permanently connected to the river and others not, depending on the variations of the water level. The purpose of this work is to reconstruct past sedimentary processes using seismic stratigraphy profiles realized all along the floodplain lakes and sediment cores collected at strategic sites. The sedimentary patterns observed in the seismic profiles are horizontal layers, highly reflective unpenetrated levels and paleochannels that could have been formed during the Holocene. The larger quantity of paleochannels along the lakes has been observed in the Grande and Salé lakes. The paleochannels in the Grande Lake would indicate a migration of actual depositional ridge that separates the floodplain from the river. In the Salé Lake, the paleochannels indicate that the region has suffered hydrological alterations. A comparison between the images of the floodplain in two different seasons (flooded and dry) with the stratigraphy profile, indicate that at sites that are emerged in the dry season there is no penetration of acoustic waves, the bottom of the lakes forming then a strong reflector.These sediments are hard due to a lower water content. The typical layers found in almost all the lakes were planar strata, characteristic of lacustrine sedimentation. These strata are covering the paleochannel structures and a second lower horizontal strong reflector. It should indicate a past environment where the water level was lower; the sediment surface was exposed during low water periods and eroded by channels draining the water to a lowered river during the lowering water season. This lower river and floodplain levels must be related to a lower sea level and/or to a dryer or more contrasted climate during the Holocene.

Petroleum systems of the Malay Basin Province, Malaysia

USGS Publications Warehouse

Bishop, Michele G.

2002-01-01

The offshore Malay Basin province is a Tertiary oil and gas province composed of a complex of half grabens that were filled by lacustrine shales and continental clastics.These deposits were overlain by clastics of a large delta system that covered the basin.Delta progradation was interupted by transgressions of the South China Sea to the southeast, which finally flooded the basin to form the Gulf of Thailand.Oil and gas from the Oligocene to Miocene lacustrine shales and Miocene deltaic coals is trapped primarily in anticlines formed by inversion of the half grabens during the late Miocene.Hydrocarbon reserves that have been discovered amount to 12 billion barrels of oil equivalent.The U.S. Geological Survey assessment of the estimated quantities of conventional oil, gas and condensate that have the potential to be added to reserves by the year 2025 for this province is 6.3 billion barrels of oil equivalent (BBOE) (U. S. Geological Survey World Energy Assessment Team, 2000).

Origins of carbonate spherulites: Implications for Brazilian Aptian pre-salt reservoir

NASA Astrophysics Data System (ADS)

Chafetz, Henry; Barth, Jennifer; Cook, Megan; Guo, Xuan; Zhou, Jie

2018-03-01

Spherulites, spherical to elliptical allochems composed of crystals radiating from a common core, investigated from a variety of depositional settings, e.g., hot springs, ambient water temperature geyser, tufa, and caliche, are all composed of a fine-grained nucleus made-up of carbonate encrusted bacterial bodies, biofilms, and/or EPS and surrounded by a cortex of radiating crystals of either aragonite or calcite. The microbes and their by-products in the nucleus induced the precipitation of carbonate, overcoming the inhibition to initiate crystal formation. The enveloping radiating crystals comprising aragonitic cortices tended to grow abiotically producing well-formed euhedral crystals with a paucity of included bacterial fossils. Whereas those cortical crystals made-up of calcite commonly contained bacterial fossils, indicating that the bacterial colonies contributed to the calcitic cortical crystal precipitation. Similar spherulites form a thick, widespread accumulation in the Aptian Pre-Salt lacustrine deposits in the Campos Basin, offshore Brazil. As with the travertine, tufa, and caliche spherulites, the Pre-Salt spherulites most likely initiated carbonate precipitation around bacterial colonies and/or their bioproducts, probably while afloat in a lacustrine water column before settling to the water-sediment interface. Absence of inter-spherulite sediment and the spherulite-to-spherulite compaction indicate that cortical crystal growth continued while the spherulites were at the sediment-water interface rather than displacively within a sediment.

Miocene transgression in the central and eastern parts of the Sivas Basin (Central Anatolia, Turkey) and the Cenozoic palaeogeographical evolution

NASA Astrophysics Data System (ADS)

Poisson, André; Vrielynck, Bruno; Wernli, Roland; Negri, Alessandra; Bassetti, Maria-Angela; Büyükmeriç, Yesim; Özer, Sacit; Guillou, Hervé; Kavak, Kaan S.; Temiz, Haluk; Orszag-Sperber, Fabienne

2016-01-01

We present here a reappraisal of the tectonic setting, stratigraphy and palaeogeography of the central part of the Sivas Basin from Palaeocene to late Miocene. The Sivas Basin is located in the collision zone between the Pontides (southern Eurasia) and Anatolia (a continental block rifted from Gondwana). The basin overlies ophiolites that were obducted onto Anatolia from Tethys to the north. The Central Anatolian Crystalline Complex (CACC) experienced similar ophiolite obduction during Campanian time, followed by exhumation and thrusting onto previously emplaced units during Maastrichtian time. To the east, crustal extension related to exhumation of the CACC created grabens during the early Tertiary, including the Sivas Basin. The Sivas Basin underwent several tectonic events during Paleogene-Neogene. The basin fill varies, with several sub-basins, each being characterised by a distinctive sequence, especially during Oligocene and Miocene. Evaporite deposition in the central part of the basin during early Oligocene was followed by mid-late Oligocene fluvio-lacustrine deposition. The weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation. Lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late Oligocene age. Emergent areas including the pre-existing Sivas Basin and neighbouring areas were then flooded from the east by a shallow sea, giving rise to a range of open-marine sub-basins, coralgal reef barriers and subsiding, restricted-marine sub-basins. Utilising new data from foraminifera, molluscs, corals and nannoplankton, the age of the marine transgression is reassessed as Aquitanian. Specifically, age-diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence. However, classical stratigraphic markers have not been found within the planktic foraminiferal assemblages, even in the open-marine settings. In the restricted-marine sediments, there are rich planktic foraminiferal assemblages of classical type but these are of little use in stratigraphy. In contrast, the gastropod fauna indicate a Burdigalian age. Sediment reworking in the restricted-marine environments precludes stratigraphic determination. In such environments, micro- and nano-organisms experienced atypical developmental conditions. The small benthic foraminifera and associated ostracod assemblages are good indicators of salinity which varied considerably within the restricted-marine sub-basins. Some of the corals within the coralgal reefs barriers are also dated as Aquitanian. A combination of the salt tectonics and the late Miocene north-westward-verging thrusting created the present basin complexity.

Characterization of phyllosilicates observed in the central Mawrth Vallis region, Mars, their potential formational processes, and implications for past climate

USGS Publications Warehouse

McKeown, N.K.; Bishop, J.L.; Noe Dobrea, E.Z.; Ehlmann, B.L.; Parente, M.; Mustard, J.F.; Murchie, S.L.; Swayze, G.A.; Bibring, J.-P.; Silver, E.A.

2009-01-01

Mawrth Vallis contains one of the largest exposures of phyllosilicates on Mars. Nontronite, montmorillonite, kaolinite, and hydrated silica have been identified throughout the region using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). In addition, saponite has been identified in one observation within a crater. These individual minerals are identified and distinguished by features at 1.38-1.42, ???1.91, and 2.17-2.41 ??m. There are two main phyllosilicate units in the Mawrth Vallis region. The lowermost unit is nontronite bearing, unconformably overlain by an Al-phyllosilicate unit containing montmorillonite plus hydrated silica, with a thin layer of kaolinite plus hydrated silica at the top of the unit. These two units are draped by a spectrally unremarkable capping unit. Smectites generally form in neutral to alkaline environments, while kaolinite and hydrated silica typically form in slightly acidic conditions; thus, the observed phyllosilicates may reflect a change in aqueous chemistry. Spectra retrieved near the boundary between the nontronite and Al-phyllosilicate units exhibit a strong positive slope from 1 to 2 ??m, likely from a ferrous component within the rock. This ferrous component indicates either rapid deposition in an oxidizing environment or reducing conditions. Formation of each of the phyllosilicate minerals identified requires liquid water, thus indicating a regional wet period in the Noachian when these units formed. The two main phyllosilicate units may be extensive layers of altered volcanic ash. Other potential formational processes include sediment deposition into a marine or lacustrine basin or pedogenesis. Copyright 2009 by the American Geophysical Union.

Extracting paleo-climate signals from sediment laminae: A new, automated image processing method

NASA Astrophysics Data System (ADS)

Gan, S. Q.; Scholz, C. A.

2010-12-01

Lake sediment laminations commonly represent depositional seasonality in lacustrine environments. Their occurrence and quantitative attributes contain various signals of their depositional environment, limnological conditions and climate. However, the identification and measurement of laminae remains a mainly manual process that is not only tedious and labor intensive, but also subjective and error prone. We present a batch method to identify laminae and extract lamina properties automatically and accurately from sediment core images. Our algorithm is focused on image enhancement that improves the signal-to-noise ratio and maximizes and normalizes image contrast. The unique feature of these algorithms is that they are all direction-sensitive, i.e., the algorithms treat images in the horizontal direction and vertical direction differently and independently. The core process of lamina identification is to use a one-dimensional (1-D) lamina identification algorithm to produce a lamina map, and to use image blob analyses and lamina connectivity analyses to aggregate and smash two-dimensional (2-D) lamina data for the best representation of fine-scale stratigraphy in the sediment profile. The primary output datasets of the system are definitions of laminae and primary color values for each pixel and each lamina in the depth direction; other derived datasets can be retrieved at users’ discretion. Sediment core images from Lake Hitchcock , USA and Lake Bosumtwi, Ghana, were used for algorithm development and testing. As a demonstration of the utility of the software, we processed sediment core images from the top of 50 meters of drill core (representing the past ~100 ky) from Lake Bosumtwi, Ghana.

High-resolution multi-proxy reconstruction of Lake Ighiel (Western Carpathians, Romania): processes and controlling factors of lacustrine dynamics during the mid and late Holocene

NASA Astrophysics Data System (ADS)

Haliuc, Aritina; Veres, Daniel; Hubay, Katalin; Begy, Robert; Brauer, Achim; Hutchinson, Simon; Braun, Mihaly

2016-04-01

Concerns about current and prospective environmental change have increased the interest in past climate variability and its impact on the bio-hydro-atmosphere and human society. Acting as high-resolution terrestrial archives, lacustrine sediments are the result of the complex interaction between internal and external forcing and an important tool in efforts to resolve questions related to the palaeoclimatic and palaeoenvironmental conditions of the recent past. Here we discuss a new, high-resolution sedimentary record from the Romanian Carpathians (central-eastern Europe). Lake Ighiel (46° 10'50"N, 23° 22'00"E) is a small lake located in a mid-altitude mountain belt (Trascau Mountains) at an altitude of 924 m ( lake maximum depth 9 m; catchment area 487 ha). We employ detailed 210Pb and 14C dating coupled with high-resolution X-ray fluorescence scanning (μ-XRF) measurements, long-core sedimentary logging, environmental magnetic proxies (susceptibility, natural and induced remanences) in an attempt to trace the 6000 years evolution of lake-catchment system. More specifically, we discuss: i) the temporal evolution of the main sedimentation phases of the lake based on sedimentological, geochemical and magnetic proxies; ii) the amplitude and interplay of processes (natural and/or anthropogenic) controlling the depositional environment through time; iii) assess the contribution of each controlling factors and reconstruct the evolution of lacustrine system and palaeoclimate forcing using multivariate statistics. The sedimentary record can be divided into six phases based on alternating high and low detrital fluxes, oscillating lacustrine productivity and redox conditions. A series of detrital events (5200; 4800; 5400; 5250; 4500; 4050; 3800; 3500; 3250; 3050; 2650; 2350; 2250; 1400; 1100; 500; 100 cal yr BP) were identified by microfacies analyses and X-ray fluorescence scanning (μ-XRF) analysis. These events are reflected in most of the parameters and appear synchronous with climatically induced forcing such as increased regional precipitation and decreased total solar radiation. These changes are superimposed on clear anthropogenic derived contributions reflecting natural and mineral resource exploitation during the early metal ages, the Roman and Medieval periods, as well as during the recent period. The comparison of the our proxies with similarly resolved records from central-eastern Europe highlight the potential of Lake Ighiel as a record of palaeoclimatic and palaeohydrological conditions in a region still lacking high-resolution multi-proxy palaeoenvironmental archives. The authors acknowledge financial support from project PN-II-ID-PCE-2012-4-0530 "Millennial-scale geochemical records of anthropogenic impact and natural climate change in the Romanian Carpathians", contract nr. 15/02.09.2013.

Lithostratigraphy and physical properties of lacustrine sediments of the last ca. 150 kyr from Chalco basin, central México

NASA Astrophysics Data System (ADS)

Ortega-Guerrero, Beatriz; Lozano-García, Socorro; Herrera-Hernández, Dimitris; Caballero, Margarita; Beramendi-Orosco, Laura; Bernal, Juan Pablo; Torres-Rodríguez, Esperanza; Avendaño-Villeda, Diana

2017-11-01

The recognition of past climatic fluctuations in sedimentary sequences in central Mexico is relevant for understanding the forcing mechanisms and responses of climatic system in the northern American tropic. Moreover, in this active volcanic setting the sedimentary record preserves the history of past volcanic activity. Climatic and environmental variability has been documented for the last tenths of thousands of years from the upper lacustrine sediments in Chalco basin. A series of cores drilled down to 122 m depth in this basin offer a long, continuous and high resolution record of past climatic changes of the last ca. 150 kyr in this region. Here we present the detailed lithostratigraphy and some physical properties (magnetic susceptibility and density) of the master sequence. Sedimentary components and their abundance were identified and quantified in smear slides and direct core observations. Age model is based on 13 14C and one 230Th/U dates. Based on their facies association seven lithostratigraphic units were defined, which reflect the main stages of lake Chalco evolution. These phases closely match the marine isotopic stages. The data reveal that at the end of MIS6 Chalco was a relatively deep and stratified freshwater lake. During MIS5 the depositional environment fluctuated between low lake stands to marshy and marginal playa settings with sporadic flooding events, and severe arid periods resulted in aerial exposure of lake sediments. Low lake stands persisted during MIS4 and MIS3, with minor fluctuations towards slightly deeper phases. The Last Glacial Maximum (LGM) and the deglacial period (21-13 kyr) are characterized by intense volcanism. The early and mid-Holocene high calcareous content and alkaline-subsaline lake suggest dry conditions. The fluctuations of lake levels inferred provide the basis for future paleoclimatic works.

Impacts of the Central Atlantic Magmatic Province on the Terrestrial Carbon Cycle in Western Pangea

NASA Astrophysics Data System (ADS)

Knobbe, T.; Suarez, C. A.

2014-12-01

Carbon isotope analysis of bulk organic and inorganic carbon preserved in the lacustrine deposits of the late Triassic to Jurassic Moenave Formation were analyzed to construct a carbon isotope chemostratigraphic profile of western Pangea. Negative carbon isotope excursions (NCIE) are characteristic of the Late Triassic and are attributed to the effects of the Central Atlantic Magmatic Province (CAMP) on climate and the global C-cycle. The aerial extent of the CAMP basalts is the largest in Earth's history spanning four continents with an area of ~ 7 x 106 km2 and a volume of 3 to 11 x 106 km3. Carbon isotope and paleontological evidence has shown that the end Triassic extinction is near synchronous to the CAMP and likely spurred on the extinction event as well as an increase in global temperatures of 2 - 2.5°C. Global correlations of NCIEs between marine and terrestrial strata provide a connection between the CAMP basalts and the end-Triassic extinction. Preliminary data collected at Potter Canyon, Arizona reveal a 5.5 ‰ decrease in δ13Corganic and a 2.75‰ decrease in δ13Ccarbonate in the lower portion of the Whitmore Point Member. These NCIEs indicate the global carbon cycle perturbation caused by the CAMP is recorded in lacustrine sediments of the Whitmore Point Member in southern Utah and northern Arizona. Additional samples collected at high sampling frequencies at other locations in the Whitmore Point Member will corroborate the terrestrial impacts of the CAMP perturbation at these locations across the region. Correlation of NCIES associated with the CAMP and any identified microfossils of the Whitmore Point Member will also illustrate the global effects of increased atmospheric CO2 on the terrestrial environment and biota.

Elemental Gains/Losses Associated with Alteration Fractures in an Eolian Sandstone, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Ming, D. W.; Yen, A. S.; Gellert, R.; Sutter, B.; Berger, J. A.; Thompson, L. M.; Schmidt, M. E.; Morris, R. V.; Treiman, A. H.

2016-01-01

The Mars Science Laboratory rover Curiosity has traversed up section through approximately 100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation unconformably overlies a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Unaltered Stimson sandstone has a basaltic composition similar to the average Mars crustal composition, but is more variable and ranges to lower K and higher Al. Fluids passing through alteration "halos" adjacent to fractures have altered the chemistry and mineralogy of the sandstone. Elemental mass gains and losses in the alteration halos were quantified using immobile element concentrations, i.e., Ti (taus). Alteration halos have elemental gains in Si, Ca, S, and P and large losses in Al, Fe, Mn, Mg, Na, K, Ni, and Zn. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes. The igneous phases were less abundant in the altered sandstone with a lower pyroxene/plagioclase feldspar. Large elemental losses suggest acidic fluids initially removed these elements (Al mobile under acid conditions). Enrichments in Si, Ca, and S suggest secondary fluids (possibly alkaline) passed through these fractures leaving behind X-ray amorphous Si and Ca-sulfates. The mechanism for the large elemental gains in P is unclear. The geochemistry and mineralogy of the altered sandstone suggests a complicated diagenetic history with multiple episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).

Sources and proxy potential of long chain alkyl diols in lacustrine environments

NASA Astrophysics Data System (ADS)

Rampen, Sebastiaan W.; Datema, Mariska; Rodrigo-Gámiz, Marta; Schouten, Stefan; Reichart, Gert-Jan; Sinninghe Damsté, Jaap S.

2014-11-01

Long chain 1,13- and 1,15-alkyl diols form the base of a number of recently proposed proxies used for climate reconstruction. However, the sources of these lipids and environmental controls on their distribution are still poorly constrained. We have analyzed the long chain alkyl diol (LCD) composition of cultures of ten eustigmatophyte species, with three species from different families grown at various temperatures, to identify the effect of species composition and growth temperature on the LCD distribution. The results were compared with the LCD distribution of sixty-two lake surface sediments, and with previously reported LCD distributions from marine environments. The different families within the Eustigmatophyceae show distinct LCD patterns, with the freshwater family Eustigmataceae most closely resembling LCD distributions in both marine and lake environments. Unlike the other two eustigmatophyte families analyzed (Monodopsidaceae and Goniochloridaceae), C28 and C30 1,13-alkyl diols and C30 and C32 1,15-alkyl diols are all relatively abundant in the family Eustigmataceae, while the mono-unsaturated C32 1,15-alkyl diol was below detection limit. In contrast to the marine environment, LCD distributions in lakes did not show a clear relationship with temperature. The Long chain Diol Index (LDI), a proxy previously proposed for sea surface temperature reconstruction, showed a relatively weak correlation (R2 = 0.33) with mean annual air temperature used as an approximation for annual mean surface temperature of the lakes. A much-improved correlation (R2 = 0.74, p-value <0.001) was observed applying a multiple linear regression analysis between LCD distributions and lake temperatures reconstructed using branched tetraether lipid distributions. The obtained regression model provides good estimates of temperatures for cultures of the family Eustigmataceae, suggesting that algae belonging to this family have an important role as a source for LCDs in lacustrine environments, or, alternatively, that the main sources of LCDs are similarly affected by temperature as the Eustigmataceae. The results suggest that LCDs may have the potential to be applicable as a palaeotemperature proxy for lacustrine environments, although further calibration work is still required.

Bluebell Field, Uinta Basin: reservoir characterization for improved well completion and oil recovery

USGS Publications Warehouse

Montgomery, S.L.; Morgan, C.D.

1998-01-01

Bluefield Field is the largest oil-producing area in the Unita basin of northern Utah. The field inclucdes over 300 wells and has produced 137 Mbbl oil and 177 bcf gas from fractured Paleocene-Eocene lacustrine and fluvial deposits of the Green River and Wasatch (Colton) formations. Oil and gas are produced at depths of 10 500-13 000 ft (3330-3940 m), with the most prolific reservoirs existing in over-pressured sandstones of the Colton Formation and the underlying Flagstaff Member of the lower Green River Formation. Despite a number of high-recovery wells (1-3 MMbbl), overall field recovery remains low, less than 10% original oil in place. This low recovery rate is interpreted to be at least partly a result of completion practices. Typically, 40-120 beds are perforated and stimulated with acid (no proppant) over intervals of up to 3000 ft (900 m). Little or no evaluation of individual beds is performed, preventing identification of good-quality reservoir zones, water-producing zones, and thief zones. As a result, detailed understanding of Bluebell reservoirs historically has been poor, inhibiting any improvements in recovery strategies. A recent project undertaken in Bluebell field as part of the U.S. Department of Energy's Class 1 (fluvial-deltaic reservoir) Oil Demonstration program has focused considerable effort on reservoir characterization. This effort has involved interdisciplinary analysis of core, log, fracture, geostatistical, production, and other data. Much valuable new information on reservoir character has resulted, with important implications for completion techniques and recovery expectations. Such data should have excellent applicability to other producing areas in the Uinta Basin withi reservoirs in similar lacustrine and related deposits.Bluebell field is the largest oil-producing area in the Uinta basin of northern Utah. The field includes over 300 wells and has produced 137 MMbbl oil and 177 bcf gas from fractured Paleocene-Eocene lacustrine and fluvial deposits of the Green River and Wasatch (Colton) formations. Oil and gas are produced at depths of 10,500-13,000 ft (3330-3940 m), with the most prolific reservoirs existing in over-pressured sandstones of the Colton Formation and the underlying Flagstaff Member of the lower Green River Formation. Despite a number of high-recovery wells (1-3 MMbbl), overall field recovery remains low, less than 10% original oil in place. This low recovery rate is interpreted to be at least partly a result of completion practices. Typically, 40-120 beds are perforated and stimulated with acid (no proppant) over intervals of up to 3000 ft (900 m). Little or no evaluation of individual beds is performed, preventing identification of good-quality reservoir zones, water-producing zones, and thief zones. As a result, detailed understanding of Bluebell reservoirs historically has been poor, inhibiting any improvements in recovery strategies. A recent project undertaken in Bluebell field as part of the U.S. Department of Energy's Class 1 (fluvial-deltaic reservoir) Oil Demonstration program has focused considerable effort on reservoir characterization. This effort has involved interdisciplinary analysis of core, log, fracture, geostatistical, production, and other data. Much valuable new information on reservoir character has resulted, with important implications for completion techniques and recovery expectations. Such data should have excellent applicability to other producing areas in the Uinta basin with reservoirs in similar lacustrine and related deposits.

Diversity of Microfossils and Preservation of Thermally Altered Stromatolites from Anomalous Precambrian Paleoenvironments

NASA Astrophysics Data System (ADS)

Osterhout, Jeffrey Thomas

Studies of Precambrian life on Earth have been dominated by those of shallow marine deposits, and in order to gain a more complete picture of life's early evolution it is important to consider a wider range of inhabited environments, including deep marine and terrestrial ecosystems. Evidence for early microbial life comes primarily from fossil microorganisms (microfossils), microbial sedimentary structures (e.g., stromatolites), and sedimentary organic matter (e.g., kerogen). The diversity and preservation of these different forms of fossil evidence introduces several challenges to their interpretation, requiring thorough analysis for accurately determining their biological origins. Investigating the paleobiology, organic geochemistry, and thermal maturity of such deposits provides a holistic approach to exploring the Precambrian biosphere in unfamiliar paleoenvironments. This thesis presents two studies of unique Precambrian ecosystems: a diverse microfossil assemblage from a 2.52-billion-year-old (Ga) deep marine deposit, and thermally altered stromatolites from a 1.4-billion-year-old evaporitic lacustrine deposit. Black cherts from the upper Gamohaan Formation (2.52 Ga) contain a consortium of organic-walled large and small coccoids, tubular filaments, and mat-like biofilm structures. Geochemical analyses of stromatolitic chert-carbonate from the Middlebrun Bay Member (1.4 Ga) in contact with a mafic sill show a trend in organic carbon isotopes relative to thermal maturity that is contrary to theoretical predictions. Findings from these studies reveal, for the first time, microfossil evidence of a diverse microbial community in the open Archean ocean prior to the Great Oxidation Event (GOE) 2.4 billion years ago, and provide insight on the relationship between thermal maturity and organic carbon isotopes within a set of terrestrial stromatolites. Together, these studies help capture the enigmatic nature of the Precambrian fossil record and expand our full understanding of Earth's early biosphere.

High-coercivity minerals from North African Humid Period soil material deposited in Lake Yoa (Chad)

NASA Astrophysics Data System (ADS)

Just, J.; Kroepelin, S.; Wennrich, V.; Viehberg, F. A.; Wagner, B.; Rethemeyer, J.; Karls, J.; Melles, M.

2015-12-01

The Holocene is a period of fundamental climatic change in North Africa. Humid conditions during the so-called African Humid Period (AHP) have favored the formation of big lake systems. Only very few of these lakes persist until today. One of them is Lake Yoa (19°03'N/20°31'E) in the Ounianga Basin, Chad, which maintains its water level by ground water inflow. Here we present the magnetic characteristics together with proxies for lacustrine productivity and biota of a sediment core (Co1240) from Lake Yoa, retrieved in 2010 within the framework of the Collaborative Research Centre 806 - Our Way to Europe (Deutsche Forschungsgemeinschaft). Magnetic properties of AHP sediments show strong indications for reductive diagenesis. An up to ~ 80 m higher lake level is documented by lacustrine deposits in the Ounianga Basin, dating to the early phase of the AHP. The higher lake level and less strong seasonality restricted deep mixing of the lake. Development of anoxic conditions consequently lead to the dissolution of iron oxides. An exception is an interval with high concentration of high-coercivity magnetic minerals, deposited between 7800 - 8120 cal yr BP. This interval post-dates the 8.2 event, which was dry in Northern Africa and probably caused a reduced vegetation cover. We propose that the latter resulted in the destabilization of soils around Lake Yoa. After the re-establishment of humid conditions, these soil materials were eroded and deposited in the lake. Magnetic minerals appear well preserved in the varved Late Holocene sequence, indicating (sub-) oxic conditions in the lake. This is surprising, because the occurrence of varves is often interpreted as an indicator for anoxic conditions of the lake water. However, the salinity of lake water rose strongly after the AHP. We therefore hypothesize that the conservation of varves and absence of benthic organisms rather relates to the high salinity than to anoxic conditions.

Mercury in soils, lakes, and fish in Voyageurs National Park (Minnesota): Importance of atmospheric deposition and ecosystem factors

USGS Publications Warehouse

Wiener, J.G.; Knights, B.C.; Sandheinrich, M.B.; Jeremiason, Jeffrey D.; Brigham, M.E.; Engstrom, D.R.; Woodruff, L.G.; Cannon, W.F.; Balogh, S.J.

2006-01-01

Concentrations of methylmercury in game fish from many interior lakes in Voyageurs National Park (MN, U.S.A.) substantially exceed criteria for the protection of human health. We assessed the importance of atmospheric and geologic sources of mercury to interior lakes and watersheds within the Park and identified ecosystem factors associated with variation in methylmercury contamination of lacustrine food webs. Geologic sources of mercury were small, based on analyses of underlying bedrock and C-horizon soils, and nearly all mercury in the O- and A-horizon soils was derived from atmospheric deposition. Analyses of dated sediment cores from five lakes showed that most (63% ?? 13%) of the mercury accumulated in lake sediments during the 1900s was from anthropogenic sources. Contamination of food webs was assessed by analysis of whole, 1-year-old yellow perch (Perca flavescens), a regionally important prey fish. The concentrations of total mercury in yellow perch and of methylmercury in lake water varied substantially among lakes, reflecting the influence of ecosystem processes and variables that affect the microbial production and abundance of methylmercury. Models developed with the information-theoretic approach (Akaike Information Criteria) identified lake water pH, dissolved sulfate, and total organic carbon (an indicator of wetland influence) as factors influencing methylmercury concentrations in lake water and fish. We conclude that nearly all of the mercury in fish in this seemingly pristine landscape was derived from atmospheric deposition, that most of this bioaccumulated mercury was from anthropogenic sources, and that both watershed and lacustrine factors exert important controls on the bioaccumulation of methylmercury. ?? 2006 American Chemical Society.

Vegetation changes and human impact inferred from an oxbow lake in southwestern Amazonia, Brazil since the 19th century

NASA Astrophysics Data System (ADS)

Rodríguez-Zorro, Paula A.; Enters, Dirk; Hermanowski, Barbara; da Costa, Marcondes Lima; Behling, Hermann

2015-10-01

Pollen and X-ray fluorescence spectrometry (XRF) analyses from a 272 cm-long sediment core of Lago Amapá, an oxbow lake in western Amazonia, reveal the first palaeoecological investigation of late Holocene sediments in Acre state, Brazil. Radiocarbon dating of older sediments failed due to re-deposition of organic material but a historical map suggests that lacustrine deposition started at 1900 AD. We detected two periods of changes in sediment and vegetation, dominated by pioneer taxa especially Cecropia. The first period around 1900 AD is documenting an initial oxbow lake, with regular fluvial input (high Ti) and low accumulation of organic matter (low inc/coh ratio). During that period Andean pollen taxa originating from Peruvian Andean headwaters were deposited. A fully lacustrine phase started about 1950 AD and is characterized by prolonged periods of stagnant water (low Fe/Mn ratio). The increase of pioneer taxa, sedimentation rates and a reduction of most of the XRF element counts point to a period during which Lago Amapá was a more isolated lake which was flooded only during exceptional severe flood events and is catching mainly anthropogenic disturbances. The extensive human influence during this period was assumed by 1) the high occurrence of pioneer taxa and the absence of charcoal which could indicate changes in vegetation possibly as a result of logging, 2) the Ca and Ti/K ratio which reflect changes to a local sediment source, and 3) comparison of Landsat images from the last 30 years which shows broad changes in vegetation cover and land transformation in the peripheral areas of the oxbow lake.

Tetrapod localities from the Triassic of the SE of European Russia

NASA Astrophysics Data System (ADS)

Tverdokhlebov, Valentin P.; Tverdokhlebova, Galina I.; Surkov, Mikhail V.; Benton, Michael J.

2003-01-01

Fossil tetrapods (amphibians and reptiles) have been discovered at 206 localities in the Lower and Middle Triassic of the southern Urals area of European Russia. The first sites were found in the 1940s, and subsequent surveys, from the 1960s to the present day, have revealed many more. Broad-scale stratigraphic schemes have been published, but full documentation of the rich tetrapod faunas has not been presented before. The area of richest deposits covers some 900,000 km 2 of territory between Samara on the River Volga in the NW, and Orenburg and Sakmara in the SW. Continental sedimentary deposits, consisting of mudstones, siltstones, sandstones, and conglomerates deposited by rivers flowing off the Ural Mountain chain, span much of the Lower and Middle Triassic (Induan, Olenekian, Anisian, Ladinian). The succession is divided into seven successive svitas, or assemblages: Kopanskaya (Induan), Staritskaya, Kzylsaiskaya, Gostevskaya, and Petropavlovskaya (all Olenekian), Donguz (Anisian), and Bukobay (Ladinian). This succession, comprising up to 3.5 km of fluvial and lacustrine sediments, documents major climatic changes. At the beginning of the Early Triassic, arid-zone facies were widely developed, aeolian, piedmont and proluvium. These were replaced by fluvial facies, with some features indicating aridity. At the end of the Middle Triassic, deltaic and lacustrine-marsh formations were dominant, indicating more humid conditions. The succession of Early to Mid Triassic tetrapod faunas documents the recovery of life after the end-Permian mass extinction. The earliest faunas consist only of small, aquatic tetrapods, in low-diversity, low-abundance assemblages. Climbing the succession through the Early Triassic, more terrestrially adapted tetrapods appear, and larger herbivorous and carnivorous reptiles come to dominate in the Mid Triassic as ecosystems were rebuilt.

Origin of intraformational folds in the Jurassic Todilto Limestone, Ambrosia Lake uranium mining district, McKinley and Valencia counties, New Mexico

USGS Publications Warehouse

Green, M.W.

1982-01-01

The Todilto Limestone of Middle Jurassic age in the Ambrosia Lake uranium mining district of McKinley and Valencia Counties, New Mexico, is the host formation for numerous small- to medium-sized uranium deposits in joints, shear zones, and fractures within small- to large-scale intraformational folds. The folds probably were formed as a result of differential sediment loading when eolian sand dunes of the overlying Summerville Formation of Middle Jurassic age migrated over soft, chemically precipitated, lime muds of the Todilto shortly after their deposition in a regressive, mixed fresh and saline lacustrine or marine environment of deposition. Encroachment of Summerville eolian dunes over soft Todilto lime muds was apparently a local phenomenon and was restricted to postulated beltlike zones which trended radially across the Todilto coastline toward the receding body of water. Intraformational folding is believed to be confined to the pathways of individual eolian dunes or clusters of dunes within the dune belts. During the process of sediment loading by migrating sand dunes, layers of Todilto lime mud were differentially compacted, contorted, and dewatered, producing both small- and large-scale plastic deformation structures, including convolute laminations, mounds, rolls, folds, and small anticlines and synclines. With continued compaction and dewatering, the mud, in localized areas, reached a point of desaturation at which sediment plasticity was lost. Prolonged loading by overlying dune sands thus caused faulting, shearing, fracturing, and jointing of contorted limestone beds. These areas or zones of deformation within the limestone became the preferred sites of epigenetic uranium mineralization because of the induced transmissivity created by sediment rupture. Along most of the prograding Todilto coastline, adjacent to the eolian dune belts, both interdune and coastal sabkha environments dominated during Todilto-Summerville time. Sediments in coastal areas consisted mainly of clay, silt, sandy silt, and very fine-grained sand, which was apparently derived from the winnowing of the finer grained fraction of sediment from adjacent dune fields during periods of eolian activity. Most of the sabkha sediments were probably carried in airborne suspension to the low-lying, ground-water-saturated coastal areas, where they were deposited as relatively uniform blanket-like layers. Deposition of sabkha deposits was apparently slow and uniform over most of the Todilto coastal areas and crested only small-scale deformation features in underlying Todilto rocks. Large-scale deformation features and uranium deposits are both notably absent in the Todilto where it is overlain by finer textured sabkha deposits in the Summerville.

Facies analysis, depositional environments and paleoclimate of the Cretaceous Bima Formation in the Gongola Sub - Basin, Northern Benue Trough, NE Nigeria

NASA Astrophysics Data System (ADS)

Shettima, B.; Abubakar, M. B.; Kuku, A.; Haruna, A. I.

2018-01-01

Facies analysis of the Cretaceous Bima Formation in the Gongola Sub -basin of the Northern Benue Trough northeastern Nigeria indicated that the Lower Bima Member is composed of alluvial fan and braided river facies associations. The alluvial fan depositional environment dominantly consists of debris flow facies that commonly occur as matrix supported conglomerate. This facies is locally associated with grain supported conglomerate and mudstone facies, representing sieve channel and mud flow deposits respectively, and these deposits may account for the proximal alluvial fan region of the Lower Bima Member. The distal fan facies were represented by gravel-bed braided river system of probably Scot - type model. This grade into sandy braided river systems with well developed floodplains facies, forming probably at the lowermost portion of the alluvial fan depositional gradient, where it inter-fingers with basinal facies. In the Middle Bima Member, the facies architecture is dominantly suggestive of deep perennial sand-bed braided river system with thickly developed amalgamated trough crossbedded sandstone facies fining to mudstone. Couplets of shallow channels are also locally common, attesting to the varying topography of the basin. The Upper Bima Member is characterized by shallow perennial sand-bed braided river system composed of successive succession of planar and trough crossbedded sandstone facies associations, and shallower channels of the flashy ephemeral sheetflood sand - bed river systems defined by interbedded succession of small scale trough crossbedded sandstone facies and parallel laminated sandstone facies. The overall stacking pattern of the facies succession of the Bima Formation in the Gongola Sub - basin is generally thinning and fining upwards cycles, indicating scarp retreat and deposition in a relatively passive margin setting. Dominance of kaolinite in the clay mineral fraction of the Bima Formation points to predominance of humid sub - tropical to tropical climatic conditions. This favors pedogenic activities which are manifested in the several occurrences of paleosols. Pronounced periods of arid climatic conditions are also notable from the subordinate smectite mineralization. Chlorite mineralization at some localities is indicative of elevation of the provenance area, and this is synonymous with deposition of the Bima Formation, because of its syn - depositional tectonics. The absences of lacustrine shales in the syn - rift stratigraphic architecture of the Bima Formation indicates that the lower Cretaceous petroleum system that are common in the West and Central African Rift basins are generally barren in the Gongola Sub - basin of the Northern Benue Trough.

Geology of the Okanogan Lobe Does Not Support Subglacial Catastrophic Flooding from Beneath the Cordilleran Ice Sheet

NASA Astrophysics Data System (ADS)

Dawes, Ralph

2017-04-01

The Okanogan lobe (OL) of the Cordilleran ice sheet (CIS) extended south from interior British Columbia in Canada to the subaerial, megaflood-scoured channeled scablands of Bretz (1923) in eastern Washington state. The drumlins and large, overdeepened valleys of the OL have been attributed to glaciofluvial processes that include at least one catastrophic megaflood, or underburst (e.g. Shaw et al., 1999; Lesemann and Brennand, 2009). If correct, the underburst hypothesis would have the OL provide another source, besides glacial Lake Missoula (GLM), for channeled scablands megaflooding. However, the geomorphology and sedimentology of the OL and the channeled scablands to its south appear to rule out megaflood-scale (≥106 m^3/s) underbursts. Underburst theory posits large subglacial lakes in the deepest valleys of the OL, overlain by relatively thin ice shelves. The largest, the Okanogan Valley, runs north-south 250 km across the US-Canada border, has bedrock-floored basins eroded to up to 650 m below sea level (Eyles et al., 1991), and sediment fill to terrace surfaces 380-420 m above sea level. Advance outwash overlain by till is exposed locally in valley walls, marking the arrival of the ice sheet. Glacial striations on bedrock at or near lowest current exposure elevations show thick glacial ice in the valleys. The last stage of the OL consisted of thick ice in the main valleys. A set of kame terraces deposited between ice and valley walls forms a composite "Great Terrace" 200 km along the sides of the Okanogan and Columbia River valleys, pocked by kettles, with local ice-contact-disturbed bedding. Ice-marginal, side-stream channels were eroded into bedrock adjacent to the Okanogan, Methow, and Columbia River valleys while the main valleys remained choked with last-stage glacial ice. Lacustrine beds in the Great Terrace, deposited in short-lived proglacial lakes, are interbedded with outwash and alluvial fans. A particularly thick, extensive sequence of lacustrine beds, including probable varves, extends for over 100 km along the British Columbia Okanagan Valley and was deposited in a large proglacial lake. In sum, the evidence supports the earlier model (e.g. Clague and Eyles, 1993) that the ice sheet was thickest along the main valley axes and the lacustrine beds in the region formed in proglacial lakes. In contrast to the channeled scablands to the south, in the OL region there are no major features that can be uniquely attributed to turbulent megafloods - no pendant bars, boulder lags strewn at high levels on outer channel walls, fosses, or potholes, as others have pointed out (e.g. Waitt, 2016). Underbursts from the interior CIS, passing beneath and discharging from the OL, would deposit large volumes of sediment. However, studies of sediment provenance in megaflood deposits of the channeled scablands have found no significant volume of sediment from the OL; instead, the major source of megaflood sediments in the channeled scablands was GLM, which was surrounded by uniquely identifiable Proterozoic metasedimentary lithologies. Glacial Lake Columbia was a large proglacial lake along the southeastern margin of the OL, into which large volumes of sediment were deposited. A recent provenance, sedimentary facies, and current-direction analysis (Nelson & Clague, 2016) finds that sediment within glacial Lake Columbia was deposited by megafloods from GLM, not from the OL, confirming the most detailed preceding study (Atwater, 1986). If the evidence across the area covered by the OL and adjacent channeled scablands rules out megaflood-scale underbursts, the subglacial landforms of the CIS, including the drumlins and the overdeepened valleys, must have other causes. Smaller-scale than whole-valley volumes of subglacial water trapped beneath the ice sheet in the overdeepened valleys, and smaller than megaflood-scale glaciofluvial discharges, may have been involved in eroding the largest valleys, including the Okanogan Valley. As for the origin of the drumlins, which have cores that vary from till, to outwash ± lacustrine beds (commonly topped by till), to bedrock, the evidence outlined here suggests they formed beneath the ice sheet, with water in the interface important in the process, but not in the form of subglacial megafloods.

Sulphur isotope constraints on formation conditions of the Luiswishi ore deposit, Democratic Republic of Congo (DRC)

NASA Astrophysics Data System (ADS)

Lerouge, C.; Cailteux, J.; Kampunzu, A. B.; Milesi, J. P.; Fléhoc, C.

2005-07-01

Luiswishi is a Congo-type Neoproterozoic sediment-hosted stratiform Cu-Co ore deposit of the Central Africa Copperbelt, located northwest of Lubumbashi (DRC). The ores form two main Cu-Co orebodies hosted by the Mines Subgroup, one in the lower part of the Kamoto Formation and the other at the base of the Dolomitic Shales Formation. Sulphides occur essentially as early parallel layers of chalcopyrite and carrolite, and secondarily as late stockwork sulphides cross-cutting the bedding and the early sulphide generation. Both types of stratiform and stockwork chalcopyrite and carrolite were systematically analyzed for sulphur isotopes, along the lithostratigraphic succession of the Mine Series. The quite similar δ 34S values of stratiform sulphides and late stockwork sulphides suggest an in situ recrystallization or a slight remobilization of stockwork sulphides without attainment of isotopic equilibrium between different sulphide phases (chalcopyrite and carrolite). The distribution of δ 34S values (-14.4‰ to +17.5‰) combined with the lithology indicates a strong stratigraphic control of the sulphur isotope signature, supporting bacterial sulphate reduction during early diagenesis of the host sediments, in a shallow marine to lacustrine environment. Petrological features combined with sulphur isotopic data of sulphides at Luiswishi and previous results on nodules of anhydrite in the Mine Series indicate a dominant seawater/lacustrine origin for sulphates, precluding a possible hydrothermal participation. The high positive δ 34S values of sulphides in the lower orebody at Luiswishi, hosted in massive chloritic-dolomitic siltite (known as Grey R.A.T.), fine-grained stratified dolostone (D.Strat.) and silicified-stromatolitic dolomites alternating with chloritic-dolomitic silty beds (R.S.F.), suggest that they were probably deposited during a period of regression in a basin cut off from seawater. The variations of δ 34S values (i.e. the decrease of δ 34S values from the Kamoto Formation to the overlying Dolomitic Shales and then the slight increase from S.D.2d to S.D.3a and S.D.3b members) are in perfect agreement with the inferred lithological and transgressive-regressive evolution of the ore-hosting sedimentary rocks [Cailteux, J., 1994. Lithostratigraphy of the Neoproterozoic Shaba-type (Zaire) Roan Supergroup and metallogenesis of associated stratiform mineralization. In: Kampunzu A.B., Lubala, R.T. (Eds.), Neoproterozoic Belts of Zambia, Zaire and Namibia. Journal of African Earth Sciences 19, 279-301].

Sample descriptions and geophysical logs for cored well BP-3-USGS, Great Sand Dunes National Park and Preserve, Alamosa County, Colorado

USGS Publications Warehouse

Grauch, V.J.S.; Skipp, Gary L.; Thomas, Jonathan V.; Davis, Joshua K.; Benson, Mary Ellen

2015-01-01

BP-3-USGS was sited to test hypotheses developed from geophysical studies and to answer questions about the history and evolution of Pliocene and Pleistocene Lake Alamosa, which is represented by lacustrine deposits sampled by the well. The findings reported here represent a basis from which future studies can answer these questions and address other important scientific questions in the San Luis Valley regarding geologic history and climate change, groundwater hydrology, and geophysical interpretation.

Cenomanian-? early Turonian minimum age of the Chubut Group, Argentina: SHRIMP U-Pb geochronology

NASA Astrophysics Data System (ADS)

Suárez, Manuel; Márquez, Marcelo; De La Cruz, Rita; Navarrete, César; Fanning, Mark

2014-03-01

Four new SHRIMP U-Pb zircon ages older than 93 Ma from samples of the two uppermost formations accumulated in two different depocenters (Golfo de San Jorge and Cañadón Asfalto basins) of the Chubut Group in central Argentinean Patagonia, establish a pre-late Cenomanian-? early Turonian age for the group. It also confirms a coeval and comparable evolution of the two depocenters, where distal pyroclastic material was deposited together with fluvial and lacustrine facies.

Monitoring tropical environments with Space Shuttle photography

NASA Technical Reports Server (NTRS)

Helfert, Michael R.; Lulla, Kamlesh P.

1989-01-01

Orbital photography from the Space Shuttle missions (1981-88) and earlier manned spaceflight programs (1962-1975) allows remote sensing time series to be constructed for observations of environmental change in selected portions of the global tropics. Particular topics and regions include deforestation, soil erosion, supersedimentation in streams, lacustrine, and estuarine environments, and desertification in the greater Amazon, tropical Africa and Madagascar, South and Southeast Asia, and the Indo-Pacific archipelagoes.

Layered, massive and thin sediments on Mars: Possible Late Noachian to Late Amazonian tephra?

USGS Publications Warehouse

Chapman, M.G.

2002-01-01

Data from instruments on the currently orbiting Mars Global Surveyor (MGS) suggest that as an alternative interpretation to lacustrine deposits, widespread sediments on Mars may be tephra deposits of variable age, formed in part by volcano-ice interactions. The materials are often associated with outcrops of mapped geological units that have each been previously interpreted as volcanic ash deposits with identified, but unconfirmed possible volcanic vents. Spectral investigation indicates that although some outcrops are basaltic, many show moderate to high concentrations of andesite, a composition at which large explosive eruptions may be possible. In addition, many outcrops are in areas suspected to be water/ice rich. On Earth, magma and groundwater can react to create violent explosive eruptions. Observations from MGS support a pyroclastic mechanism of deposition and show some morphologies consistent with volcano-ice interactions, including subaqueous eruptions. Perhaps MGS data are finally producing more definitive evidence of the widespread tephra that were predicted to be likely in the reduced atmospheric pressure of Mars.

The Evolution of Juventae Chasma, Valles Marineris, Mars: Progressive Collapse and Sedimentation

NASA Astrophysics Data System (ADS)

Fueten, F.; Novakovic, N.; Stesky, R.; Flahaut, J.; Hauber, E.; Rossi, A. P.

2017-11-01

Juventae Chasma is an isolated chasm located north of the interconnected chasms within Valles Marineris. It contains four separate interior layered deposit (ILD) mounds. We have combined layer measurements, as well as mineralogical data of the mounds with topographic data of the remaining chasm and the surrounding plateau. Our observations indicate that the chasm underwent a complex geological history. We suggest that individual ILD mounds are not contemporaneous with each other and a series of progressive collapses enlarged an initially smaller chasm to its current shape. ILDs were deposited in a lacustrine setting, and the time of ILD deposition was limited. Basin collapse and chasm enlargement continued beyond the time of ILD deposition and thus were not driven by sediment load. Glacial processes appear to have played a role in the late, postlacustrine history of the chasm. We present a simplified model that highlights some of the complexity of the chasm evolution, but acknowledge that the true history is undoubtedly more complicated.

Radiocarbon dates for lava flows and pyroclastic deposits on Sao Miguel, Azores

USGS Publications Warehouse

Moore, R.B.; Rubin, M.

1991-01-01

We report 63 new radiocarbon analyses of samples from Sao Miguel, the largest island in the Azores archipelago. The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall and lacustrine deposits and lava flows. One calcite date is reported. These dates establish ages for 48 previously undated lava flows and pyroclastic deposits, and revise three ages previously reported. These data are critical to deciphering the Holocene and late Pleistocene eruptive history of Sao Miguel and evaluating its potential volcanic hazards. Average dormant intervals during the past 3000 years are about 400 years for Sete Cidades volcano, 145 years for volcanic Zone 2, 1150 years for Agua de Pau volcano and 320 years for Furnas volcano. No known eruptions have occurred in volcanic Zone 4 during the past 3000 years. -from Authors

Developing Regional Tephrostratigraphic Frameworks: Applications and Challenges.

NASA Astrophysics Data System (ADS)

Fontijn, K.; Pyle, D. M.; Smith, V.; Mather, T. A.

2017-12-01

Detailed stratigraphic studies of pyroclastic deposits form arguably the best tool to estimate the frequency and magnitude of explosive eruptions at volcanoes where limited or no historical records exist. As such tephrostratigraphy forms a first-order assessment of potential future eruptive behavior at poorly known volcanoes. Alternations of soils and pyroclastic deposits at proximal to medial distances of the volcano however typically only allow reconstructing eruptive behavior within the Holocene. Moreover, they only tend to preserve relatively large explosive eruptions, of magnitude 3-4 and above, and therefore almost invariably form a biased view of the frequency-magnitude relationships at a particular volcano. Long lacustrine records in medial to distal regions offer significant potential to obtain a more complete view of the explosive eruptive record as they often preserve thin fine-grained tephra deposits representing either small-scale explosive eruptions not preserved on land, or distal ash deposits from large explosive eruptions. Furthermore, these sedimentary records often contain material that can be dated to establish a detailed age-depth model that can be used to date the eruptions and estimate the tempo of activity. In settings where volcanoes and lakes closely co-exist, integrating terrestrial and lacustrine data therefore allows the development of regional-scale tephrostratigraphic frameworks. Such frameworks provide a view of temporal trends in volcanic activity and mid/long-term eruptive rates on a regional scale rather than at the level of an individual volcano, i.e. in interaction with regional tectonic stress regimes. They also highlight the spatial distribution of deposits from large explosive eruptions, allowing improved estimates of magnitudes of individual eruptions as well as of frequency of impact by volcanic ash in specific regions. Provided such tephra horizons are well characterized and dated they can be used as age marker horizons and help fine-tune age models for palaeoenvironmental studies. In this presentation we will highlight a few key examples of both local and regional-scale tephrostratigraphic frameworks in East Africa, Chile and South-East Asia, and discuss the multidisciplinary applications as well as challenges posed by data acquisition.

Siphateles (Gila) sp. and Catostomus sp. from the Pleistocene OIS-6 Lake Gale, Panamint Valley, Owens River system, California

NASA Astrophysics Data System (ADS)

Jayko, A. S.; Forester, R. M.; Smith, G. R.

2014-12-01

Panamint Valley lies within the Owens River system which linked southeastern Sierra Nevada basins between Mono Lake and Death Valley during glacial-pluvial times. Previous work indicates that late Pleistocene glacial-pluvial Lake Gale, Panamint Valley was an open system during OIS-6, a closed ground water supported shallow lake during OIS-4, and the terminal lake basin for the Owens River system during OIS-2. We here report the first occurrence of fossil fish from the Plio-Pleistocene Panamint basin. Fish remains are present in late Pleistocene OIS-6 nearshore deposits associated with a highstand that was spillway limited at Wingate Wash. The deposits contain small minnow-sized remains from both Siphateles or Gila sp. (chubs) and Catostomus sp. (suckers) from at least four locations widely dispersed in the basin. Siphateles or Gila sp. and Catostomus are indigenous to the Pleistocene and modern Owens River system, in particular to the historic Owens Lake area. Cyprinodon (pupfish) and Rhinichthys (dace) are known from the modern Amargosa River and from Plio-Pleistocene deposits in Death Valley to the east. The late Pleistocene OIS-6 to OIS-2 lacustrine and paleohydrologic record in Panamint basin is interpreted from ostracod assemblages, relative abundance of Artemia sp. pellets, shallow water indicators including tufa fragments, ruppia sp. fragments and the relative abundance of charophyte gyrogonites obtained from archived core, as well as faunal assemblages from paleoshoreline and nearshore deposits. The OIS-4 groundwater supported shallow saline lake had sufficiently low ratios of alkalinity to calcium (alk/Ca) to support the occurrence of exotic Elphidium sp. (?) foraminfera which are not observed in either OIS-2 or OIS-6 lacustrine deposits. The arrival of Owens River surface water into Panamint Basin during OIS-2 is recorded by the first appearance of the ostracod Limnocythere sappaensis at ~27 m depth in an ~100 m archived core (Smith and Pratt, 1957) which extends between OIS-5 and post OIS-2 based on based on proxy correlation with the marine oxygen isotope record.

The ichthyofauna of limnic systems in Quaternary deposits of extreme southern Brazil

PubMed Central

Assumpção, Cindy M.; Quintela, Fernando M.; Corrêa, Fabiano; Loebmann, Daniel

2016-01-01

Abstract The Quaternary in the state of Rio Grande do Sul (RS), southern Brazil, is geologically represented by the coastal plain and was originated by successive events of Pleistocene-Holocene marine transgressions and the occurrence of alluvial deposits. This paper aimed to characterize the fish assemblage occurring in a swampy Quaternary area adjacent to Lagoa Pequena, a lacustrine system connected to the west margin of the Laguna dos Patos estuary. A checklist is also provided of the ichthyofauna so far recorded in limnic systems of Quaternary deposits in the state of Rio Grande do Sul. A total of 42 species was recorded, distributed in nine orders, 18 families and 31 genera. Characidae and Cichlidae were the most representative families, comprising 15 and 4 species respectively. A bibliographic revision associated to our sample data revealed the occurrence of 156 species in limnic systems inserted in RS Quaternary deposits (114 limnic, 15 marine/estuarine/limnic, ten marine/estuarine, nine estuarine/limnic and eight marine). Characiformes and Siluriformes are the most diverse orders, corroborating the Neotropical pattern. Seven species can be considered endemic to RS Quaternary deposits. PMID:28174498

Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments

NASA Astrophysics Data System (ADS)

Drevnick, Paul E.; Yang, Handong; Lamborg, Carl H.; Rose, Neil L.

2012-11-01

In this study we used lake sediments, which faithfully record Hg inputs, to derive estimates of net atmospheric Hg deposition to Svalbard, Norwegian Arctic. With the exception of one site affected by local pollution, the study lakes show twofold to fivefold increases in sedimentary Hg accumulation since 1850, likely due to long-range atmospheric transport and deposition of anthropogenic Hg. Sedimentary Hg accumulation in these lakes is a linear function of the ratio of catchment area to lake area, and we used this relationship to model net atmospheric Hg flux: preindustrial and modern estimates are 2.5 ± 3.3 μg m-2 y-1 and 7.0 ± 3.0 μg m-2 y-1, respectively. The modern estimate, by comparison with data for Hg wet deposition, indicates that atmospheric mercury depletion events (AMDEs) or other dry deposition processes contribute approximately half (range 0-70%) of the net flux. Hg from AMDEs may be moving in significant quantities into aquatic ecosystems, where it is a concern because of contamination of aquatic food webs.

Vanadium accumulation in carbonaceous rocks: A review of geochemical controls during deposition and diagenesis

USGS Publications Warehouse

Breit, G.N.; Wanty, R.B.

1991-01-01

Published data relevant to the geochemistry of vanadium were used to evaluate processes and conditions that control vanadium accumulation in carbonaceous rocks. Reduction, adsorption, and complexation of dissolved vanadium favor addition of vanadium to sediments rich in organic carbon. Dissolved vanadate (V(V)) species predominate in oxic seawater and are reduced to vanadyl ion (V(IV)) by organic compounds or H2S. Vanadyl ion readily adsorbs to particle surfaces and is added to the sediment as the particles settle. The large vanadium concentrations of rocks deposited in marine as compared to lacustrine environments are the result of the relatively large amount of vanadium provided by circulating ocean water compared to terrestrial runoff. Vanadium-rich carbonaceous rocks typically have high contents of organically bound sulfur and are stratigraphically associated with phosphate-rich units. A correspondence between vanadium content and organically bound sulfur is consistent with high activities of H2S during sediment deposition. Excess H2S exited the sediment into bottom waters and favored reduction of dissolved V(V) to V(IV) or possibly V(III). The stratigraphic association of vanadiferous and phosphatic rocks reflects temporal and spatial shifts in bottom water chemistry from suboxic (phosphate concentrated) to more reducing (euxinic?) conditions that favor vanadium accumulation. During diagenesis some vanadium-organic complexes migrate with petroleum out of carbonaceous rocks, but significant amounts of vanadium are retained in refractory organic matter or clay minerals. As carbon in the rock evolves toward graphite during metamorphism, vanadium is incorporated into silicate minerals. ?? 1991.

Compound-Specific Radiocarbon Dating Reveals the Age Distribution of Plant-Wax Biomarkers Exported to the Bengal Fan

NASA Astrophysics Data System (ADS)

Galy, V.; French, K. L.; Hein, C. J.; Haghipour, N.; Wacker, L.; Kudrass, H.; Eglinton, T. I.

2017-12-01

The stable isotope composition of leaf-wax compounds preserved in lacustrine and marine sediments has been widely used to reconstruct terrestrial paleo-environments. However, the timescales of plant-wax storage in continental reservoirs before riverine export are not well known, representing a key uncertainty in paleo-environment studies. We couple numerical models with bulk and leaf-wax fatty acid organic 13C and 14C signatures hosted in a high-deposition-rate sediment core from the Bengal shelf canyon in order to estimate storage timescales within the Ganges-Brahmaputra catchment area. The fatty acid 14C record reveals a muted nuclear weapons bomb spike, requiring that the Ganges-Brahmaputra river system exports a mixture of young and old (pre-aged) leaf-wax compounds. According to numerical simulations, 79-83% of the leaf-wax fatty acids in this core are sourced from continental reservoirs that store organic carbon on an average of 1000-1200 calendar years, while the remainder has an average age of 15 years. These results demonstrate that a majority of the leaf-wax compounds produced in the Ganges-Brahmaputra river basin was stored in soils, floodplains, and wetlands prior to its export to the Bengal Fan. We will discuss the implications of these findings for plant-wax based paleoenvironmental records.

Sedimentology of the Essaouira Basin (Meskala Field) in context of regional sediment distribution patterns during upper Triassic pluvial events

NASA Astrophysics Data System (ADS)

Mader, Nadine K.; Redfern, Jonathan; El Ouataoui, Majid

2017-06-01

Upper Triassic continental clastics (TAGI: Trias Argilo-Greseux Inferieur) in the Essaouira Basin are largely restricted to the subsurface, which has limited analysis of the depositional environments and led to speculation on potential provenance of the fluvial systems. Facies analysis of core from the Meskala Field onshore Essaouira Basin is compared with tentatively time-equivalent deposits exposed in extensive outcrops in the Argana Valley, to propose a process orientated model for local versus regional sediment distribution patterns in the continuously evolving Moroccan Atlantic rift during Carnian to Norian times. The study aims to unravel the climatic overprint and improve the understanding of paleo-climatic variations along the Moroccan Atlantic margin to previously recognised Upper Triassic pluvial events. In the Essaouira Basin, four facies associations representing a progressive evolution from proximal to distal facies belts in a continental rift were established. Early ephemeral braided river systems are succeeded by a wet aeolian sandflat environment with a strong arid climatic overprint (FA1). This is followed by the onset of perennial fluvial deposits with extensive floodplain fines (FA2), accompanied by a distinct shift in fluvial style, suggesting increase in discharge and related humidity, either locally or in the catchment area. The fluvial facies transitions to a shallow lacustrine or playa lake delta environment (FA3), which exhibits cyclical abandonment. The delta is progressively overlain by a terminal playa with extensive, mottled mudstones (FA4), interpreted to present a return from cyclical humid-arid conditions to prevailing aridity in the basin. In terms of regional distribution and sediment source provenance, paleocurrent data from Carnian to Norian deposits (T5 to T8 member) in the Argana Valley suggest paleoflow focused towards the S and SW, not directed towards the Meskala area in the NW as previously suggested. A major depo-centre for fluvial sediments is instead located in the southern Argana Valley, possibly the Souss Basin. To effectively source the reservoir sandstones found in the Meskala Field, a more local provenance area has hence to be envisaged. Despite this, the direct comparison of the genetic evolution of sedimentary sequences in the Argana Valley and Essaouira Basin shows a similar progression from dominantly arid ephemeral depositional environments to humid perennial sedimentation, returning to prominent arid conditions. This suggests climatic control in both regions, where an enhanced humid signal drives perennial fluvial flow in otherwise arid dominated sequences. On a regional scale, this is suggested to record the impact of strong Triassic pluvial events previously recognised in other basins along the Central Atlantic margin during the Carnian to Norian periods.

Reconnaissance Borehole Geophysical, Geological, and Hydrological Data from the Proposed Hydrodynamic Compartments of the Culpeper Basin in Loudoun, Prince William, Culpeper, Orange, and Fairfax Counties, Virginia (Version 1.0)

USGS Publications Warehouse

Ryan, Michael P.; Pierce, Herbert A.; Johnson, Carole D.; Sutphin, David M.; Daniels, David L.; Smoot, Joseph P.; Costain, John K.; Coruh, Cahit; Harlow, George E.

2006-01-01

The Culpeper basin is part of a much larger system of ancient depressions or troughs, that lie inboard of the Atlantic Coastal Plain, and largely within the Applachian Piedmont Geologic Province of eastern North America, and the transition region with the neighboring Blue Ridge Geologic Province. This basin system formed during an abortive attempt to make a great ocean basin during the Late Triassic and Early Jurassic, and the eroded remnants of the basins record major episodes of sedimentation, igneous intrusion and eruption, and pervasive contact metamorphism. Altogether, some twenty nine basins formed between what is now Nova Scotia and Georgia. Many of these basins are discontinuous along their strike, and have therefore recorded isolated environments for fluvial and lacustrine sedimentation. Several basins (including the Culpeper, Gettysburg, and Newark basins) are fault-bounded on the west, and Mesozoic crustal stretching has produced assymetrical patterns of basin subsidence resulting in a progressive basin deepening to the west, and a virtual onlap relationship with the pre-basin Proterozoic rocks to the east. A result of such a pattern of basin deepening is the development of sequences of sandstones and siltstones that systemmatically increase in dip towards the accomodating western border faults. A second major structural theme in several of the major Mesozoic basins (including the Culpeper) concerns the geometry of igneous intrusion, as discussed below. Froelich (1982, 1985) and Lee and Froelich (1989) discuss the general geology of the Culpeper basin, and Smoot (1989) discusses the sedimentation environments and sedimentary facies of the Mesozoic with respect to fluvial and shallow lacustrine deposition in the Culpeper basin. Ryan and others, 2007a, b, discuss the role of diabase-induced compartmentalization in the Culpeper basin (and other Mesozoic basins), and illustrate (using alteration mineral suites within the diabase and adjacent hornfels, among other evidence) how this process has played a role in organizing the paleo- and contemporary-flow of crustal fluids at local and regional scales. Within this report, the Newark Supergroup nomenclature of Weems and Olsen (1997) is adopted.

Cenozoic record of aeolian sediment accumulation and aridification from Lanzhou, China, driven by Tibetan Plateau uplift and global climate

NASA Astrophysics Data System (ADS)

Zhang, Yuebao; Sun, Donghuai; Li, Zaijun; Wang, Fei; Wang, Xin; Li, Baofeng; Guo, Feng; Wu, Sheng

2014-09-01

Previous work has shown that aeolian Red Clay first appears at around 8 Ma in the main Chinese Loess Plateau and at 25-22 Ma in the western Loess Plateau; however, records of aeolian deposition in the North Pacific suggest that aeolian accumulation occurred throughout the Cenozoic, and that changes in aeolian flux occurred in distinct stages. Tracing the Cenozoic aeolian history of the interior of the Asian continent may help us to understand the history of Asian aridification and its driving forces. In the Lanzhou area on the western margin of the Loess Plateau and the northeastern edge of the Tibetan Plateau, the Cenozoic stratigraphic sequence consists of fluvial-lacustrine sediments in the lower part, aeolian Red Clay with intercalated fluvial layers in the middle part, and predominantly aeolian loess in the upper part. We use high resolution paleomagnetic measurements of this sequence to construct a time scale, and measurements of sediment rock magnetic properties, grain-size, and color reflectance and sedimentary facies analysis to reconstruct the paleoenvironment. The results show that prior to 33 Ma the area was dominantly a fluvial-lacustrine environment, and that subsequently an aridification trend commenced, as indicated by the appearance of aeolian sediment. This change coincided with, and is thus explained as the environmental response to global cooling. A significant increase in aeolian sediments occurred at ~ 26 Ma, suggesting that a large scale arid environment had formed in the Asian interior since the late Oligocene. Stepwise increases of aeolian sediment, and decreases in sediments of hydraulic origin, occurred at ~ 22, ~ 14, ~ 8 and 2.6 Ma and represent important stages in the aridification process. This long-term trend was interrupted by intervals dominated by fluvial sedimentation at 23.6-22 Ma and 17.1-14.1 Ma and which were probably associated with warming of the global climate and the tectonic uplift of the northeastern Tibetan Plateau. Tectonic events occurring in Lanzhou at ~ 9-8 Ma and ~ 3.5 Ma indicate strong uplift of the northeastern Tibetan Plateau.

Noachian Climate of Mars: Insights from Noachian Stratigraphy and Valley Networks System Formation Times

NASA Astrophysics Data System (ADS)

Head, J. W., III

2017-12-01

Noachian climate models have been proposed in order to account for 1) observed fluvial and lacustrine activity, 2) weathering processes producing phyllosilicates, and 3) an unusual impact record including three major impact basins and unusual degradation processes. We adopt a stratigraphic approach in order place these observations in a temporal context. Formation of the major impact basins Hellas, Isidis and Argyre in earlier Noachian profoundly influenced the uplands geology and appears to have occurred concurrently with major phyllosilicate and related surface occurrences/deposits; the immediate aftermath of these basins appears to have created a temporary hot and wet surface environment with significant effect on surface morphology and alteration processes. Formation of Late Noachian-Early Hesperian valley network systems (VNS) signaled the presence of warm/wet conditions generating several hypotheses for climates permissive of these conditions. We examined estimates for the time required to carve channels/deltas and total duration implied by plausible intermittencies. Synthesis of required timescales show that the total time to carve the VN does not exceed 106 years, < 0.25% of the total Noachian. What climate models can account for the VNS? 1) Warm and wet/semiarid/arid climate: Sustained background MAT >273 K, hydrological system vertically integrated, and rainfall occurs to recharge the aquifer. 2) Cold and Icy climate warmed by greenhouse gases or episodic stochastic events: Climate is sustained cold/icy, but greenhouse gases of unspecified nature/amount/duration elevate MAT by several tens of Kelvins, bringing the annual temperature range into the realm where peak seasonal temperatures (PST) exceed 273 K. In this climate environment, analogous to the Antarctic Dry Valleys, seasonal summer temperatures above 273 K are sufficient to melt snow/ice and form fluvial and lacustrine features, but MAT is well below 273 K (253 K); punctuated warming alternatives include impacts or volcanic eruptions. We conclude that a cold and icy background climate with modest greenhouse warming or punctuated warming and melting events for the VNs origin is consistent with: 1) the estimated durations of continuous VN formation (<105 years) and 2) VN system estimated recurrence rates (106-107 years).

Geologic report on the San Rafael Swell Drilling Project, San Rafael Swell, Utah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bluhm, C.T.; Rundle, J.G.

1981-08-01

Twenty-two holes totaling 34,874 feet (10,629.6 meters) were rotary and core drilled on the northern and western flanks of the San Rafael Swell to test fluvial-lacustrine sequences of the Morrison Formation and the lower part of the Chinle Formation. The objective of the project was to obtain subsurface data so that improved uranium resource estimates could be determined for the area. Although the Brushy Basin and the Salt Wash Members of the Morrison Formation are not considered favorable in this area for the occurrence of significant uranium deposits, uranium minerals were encountered in several of the holes. Some spotty ormore » very low-grade mineralization was also encountered in the White Star Trunk area. The lower part of the Chinle Formation is considered to be favorable for potentially significant uranium deposits along the west flank of the San Rafael Swell. One hole (SR-202) east of Ferron, Utah, intersected uranium, silver, molybdenum, and copper mineralization. More exploratory drilling in the vicinity of this hole is recommended. As a result of the study of many geochemical analyses and a careful determination of the lithology shown by drilling, a sabkha environment is suggested for the concentration of uranium, zinc, iron, lead, copper, silver, and perhaps other elements in parts of the Moody Canyon Member of the Moenkopi Formation.« less

Origin of mounds in the Pantanal wetlands: An integrated approach between geomorphology, pedogenesis, ecology and soil micromorphology.

PubMed

de Oliveira Junior, Jairo Calderari; Beirigo, Raphael Moreira; Chiapini, Mariane; do Nascimento, Alexandre Ferreira; Couto, Eduardo Guimarães; Vidal-Torrado, Pablo

2017-01-01

Vegetated mounds are an important geomorphological feature of the Pantanal, where the influence of floods dictates not only hydropedological processes, but also the distribution and ecology of the flora and fauna. This work aimed to identify factors and processes that influence the formation and spatial distribution of the mounds, which are commonly associated with termite activity. In order to characterize pedological processes, macro and micro morphological descriptions, satellite image interpretation, dating of the sandy sedimentary material using OSL and carbon dating using 14C AMS were carried out. This dating of the materials indicates that the sediments in which the soils were formed were deposited during the Pleistocene, while the carbonates are from the Holocene. The basin-like format of the laminar structures suggests that part of the more clayey material was deposited in lacustrine environments. The more humid climate in the Holocene intensified argilluviation, which at an advanced stage, led to a more pronounced textural gradient, reducing drainage and leading to ferrolysis and thickening of the E horizon. Besides pedogenic processes, more erosive flooding during the Holocene began reducing and rounding the landscape's more elevated structures (paleolevees). In the final stage, these structures were occupied by termites to shelter from flooding. Thereafter, the bio-cementation action of the termite nests has increased the resistance of the vegetated mounds to processes of erosion.

Origin of mounds in the Pantanal wetlands: An integrated approach between geomorphology, pedogenesis, ecology and soil micromorphology

PubMed Central

de Oliveira Junior, Jairo Calderari; Beirigo, Raphael Moreira; Chiapini, Mariane; do Nascimento, Alexandre Ferreira; Couto, Eduardo Guimarães

2017-01-01

Vegetated mounds are an important geomorphological feature of the Pantanal, where the influence of floods dictates not only hydropedological processes, but also the distribution and ecology of the flora and fauna. This work aimed to identify factors and processes that influence the formation and spatial distribution of the mounds, which are commonly associated with termite activity. In order to characterize pedological processes, macro and micro morphological descriptions, satellite image interpretation, dating of the sandy sedimentary material using OSL and carbon dating using 14C AMS were carried out. This dating of the materials indicates that the sediments in which the soils were formed were deposited during the Pleistocene, while the carbonates are from the Holocene. The basin-like format of the laminar structures suggests that part of the more clayey material was deposited in lacustrine environments. The more humid climate in the Holocene intensified argilluviation, which at an advanced stage, led to a more pronounced textural gradient, reducing drainage and leading to ferrolysis and thickening of the E horizon. Besides pedogenic processes, more erosive flooding during the Holocene began reducing and rounding the landscape’s more elevated structures (paleolevees). In the final stage, these structures were occupied by termites to shelter from flooding. Thereafter, the bio-cementation action of the termite nests has increased the resistance of the vegetated mounds to processes of erosion. PMID:28700595

Two examples of subaqueously welded ash-flow tuffs: the Visean of southern Vosges (France) and the Upper Cretaceous of northern Anatolia (Turkey)

NASA Astrophysics Data System (ADS)

Schneider, Jean-Luc; Fourquin, Claude; Paicheler, Jean-Claude

1992-02-01

Pyroclastic deposits interpreted as subaqueous ash-flow tuff have been recognized within Archean to Recent marine and lacustrine sequences. Several authors proposed a high-temperature emplacement for some of these tuffs. However, the subaqueous welding of pyroclastic deposits remains controversial. The Visean marine volcaniclastic formations of southern Vosges (France) contain several layers of rhyolitic and rhyodacitic ash-flow tuff. These deposits include, from proximal to distal settings, breccia, lapilli and fine-ash tuff. The breccia and lapilli tuff are partly welded, as indicated by the presence of fiamme, fluidal and axiolitic structures. The lapilli tuff form idealized sections with a lower, coarse and welded unit and an upper, bedded and unwelded fine-ash tuff. Sedimentary structures suggest that the fine-ash tuff units were deposited by turbidity currents. Welded breccias, interbedded in a thick submarine volcanic complex, indicate the close proximity of the volcanic source. The lapilli and fine-ash tuff are interbedded in a thick marine sequence composed of alternating sandstones and shales. Presence of a marine stenohaline fauna and sedimentary structures attest to a marine depositional environment below storm-wave base. In northern Anatolia, thick massive sequences of rhyodacitic crystal tuff are interbedded with the Upper Cretaceous marine turbidites of the Mudurnu basin. Some of these tuffs are welded. As in southern Vosges, partial welding is attested by the presence of fiamme and fluidal structures. The latter are frequent in the fresh vitric matrix. These tuff units contain a high proportion of vitroclasis, and were emplaced by ash flows. Welded tuff units are associated with non-welded crystal tuff, and contain abundant bioclasts which indicate mixing with water during flowage. At the base, basaltic breccia beds are associated with micritic beds containing a marine fauna. The welded and non-welded tuff sequences are interbedded in an alternation of limestones and marls. These limestones are rich in pelagic microfossils. The evidence above strongly suggest that in both examples, tuff beds are partly welded and were emplaced at high temperature by subaqueous ash flows in a permanent marine environment. The sources of the pyroclastic material are unknown in both cases. We propose that the ash flows were produced during submarine fissure eruptions. Such eruptions could produce non-turbulent flows which were insulated by a steam carapace before deposition and welding. The welded ash-flow tuff deposits of southern Vosges and northern Anatolia give strong evidence for existence of subaqueous welding.

Stratigraphy, sedimentology, and geothermal reservoir potential of the volcaniclastic Cura-Mallín succession at Lonquimay, Chile

NASA Astrophysics Data System (ADS)

Pedroza, Viviana; Le Roux, Jacobus P.; Gutiérrez, Néstor M.; Vicencio, Vladimir E.

2017-08-01

The Tolhuaca Volcano near Lonquimay in south-central Chile has been the subject of several studies due to its geothermal manifestations, but little is known about the stratigraphy and reservoir potential of the Cura-Mallín Formation forming its basement. Field work and U-Pb dating of detrital zircons allow us to redefine this succession as the Cura-Mallín Group, consisting of the volcano-sedimentary Guapitrío Formation, sedimentary Río Pedregoso Formation, and volcano-sedimentary Mitrauquén Formation. The Río Pedregoso Formation can be subdivided into three formal units, namely the Quilmahue Member, Rucañanco Member, and Bío-Bío Member. The base of the Quilmahue Member interfingers laterally with the base of the Guapitrío Formation, for which a previous K/Ar date of 22.0 ± 0.9 Ma was apparently discarded by the original authors. However, this date is consistent with the stratigraphic position of the Quilmahue Member and new zircon dates from the overlying units, also coinciding with the initiation of an extensional phase in the Bíobío-Aluminé Basin. Deposition of the Quilmahue Member continued throughout the early Miocene, as confirmed by dates of 17.5 Ma reported by previous authors and 16.5 Ma obtained in this study. The Rucañanco Member was deposited during the Serravalian around 12.6 Ma, whereas the Bío-Bío Member was dated at the Serravalian-Tortonian limit (11.6 Ma). Although all three members were deposited in a fluvio-lacustrine environment, they were dominated respectively by flood plains with crevasse splays, lake margins with distributary mouth bars and Gilbert-type deltas, and distal braided and meandering rivers. Whereas the Quilmahue Member was deposited during basin extension, the Rucañanco Member was formed during a period of basin inversion and compression. Temporary tectonic quiescence during deposition of the Bío-Bío Member allowed denudation of the landscape, but around 9.5 Ma tectonism was renewed again during deposition of the Mitrauquén Formation. From a geothermal point of view, the Guapitrío Formation has a low potential to host significant reservoirs due to extensive hydrothermal alteration that produced secondary minerals clogging pore spaces and fractures. In the Río Pedregoso Formation, on the other hand, the Rucañanco Member seems to have the best reservoir potential, as it has relatively thick, semi-permeable sandstones and conglomerates deposited in a lake-margin environment.

Mohawk Lake or Mohawk meadow Sedimentary facies and stratigraphy of Quaternary deposits in Mohawk Valley, upper Middle Fork of the Feather River, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yount, J.C.; Harwood, D.S.; Bradbury, J.P.

1993-04-01

Mohawk Valley (MV) contain thick, well-exposed sections of Quaternary basin-fill sediments, with abundant interbedded tephra and a diverse assemblage of sedimentary facies. The eastern arm of MV, extending from Clio to Portola, contains as much as 100 m of trough cross-bedded cobble to pebble gravel and planar and trough cross-bedded coarse and medium sand, interpreted as braided stream deposits. Sections exposed in the western arm of MV consist in their lower parts of massive organic-rich silt and clay interbedded with blocky to fissile peat beds up to 1 m thick. Diatom assemblages are dominated by benthic species indicating fresh marshmore » environments with very shallow water depths of one meter or less. Proglacial lacustrine deposits of limited lateral extent are present within the outwash complexes as evidenced by varved fine sand and silt couplets, poorly sorted quartz-rich silt beds containing dropstones, and contorted beds of diamict grading laterally into slump blocks surrounded by wood-bearing silt and silty sand. The Rockland Ash (400 ka) is a prominent marker in the middle or lower part of many sections throughout MV, indicating that at least half of the basin-fill sequence is Late Quaternary in age. A log buried in diamict slumped into a proglacial lake lying approximately 3 km downstream from the Tioga Stage ice termini in Jamison and Gray Eagle Creeks yields an age of 18,715 [+-]235 C[sup 14] years BP. Previous interpretations of MV deposits originating in a large, deep lake with water depths in excess of 150 m are untenable given the sedimentary facies and diatom floras that dominate the valley. Unexhumed valleys such as Sierra Valley to the east and Long Valley to the northwest which contain large meadows traversed by braided streams are probably good analogs for the conditions that existed during the accumulation of the Mohawk Valley deposits.« less

Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records

NASA Astrophysics Data System (ADS)

Douglas, Peter M. J.; Pagani, Mark; Eglinton, Timothy I.; Brenner, Mark; Hodell, David A.; Curtis, Jason H.; Ma, Keith F.; Breckenridge, Andy

2014-09-01

Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350-1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (<200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules.

Trench Logs and Scarp Data from an Investigation of the Steens Fault Zone, Bog Hot Valley and Pueblo Valley, Humboldt County, Nevada

USGS Publications Warehouse

Personius, Stephen F.; Crone, Anthony J.; Machette, Michael N.; Kyung, Jai Bok; Cisneros, Hector; Lidke, David J.; Mahan, Shannon

2006-01-01

Introduction: This report contains field and laboratory data from a study of the Steens fault zone near Denio, Nev. The 200-km-long Steens fault zone forms the longest, most topographically prominent fault-bounded escarpment in the Basin and Range of southern Oregon and northern Nevada. The down-to-the-east normal fault is marked by Holocene fault scarps along nearly half its length, including the southern one-third of the fault from the vicinity of Pueblo Mountain in southern Oregon to the southern margin of Bog Hot Valley (BHV) southwest of Denio, Nev. We studied this section of the fault to better constrain late Quaternary slip rates, which we hope to compare to deformation rates derived from a recently established geodetic network in the region (Hammond and Thatcher, 2005). We excavated a trench in May 2003 across one of a series of right-stepping fault scarps that extend south from the southern end of the Pueblo Mountains and traverse the floor of Bog Hot Valley, about 4 km south of Nevada State Highway 140. This site was chosen because of the presence of well-preserved fault scarps, their development on lacustrine deposits thought to be suitable for luminescence dating, and the proximity of two geodetic stations that straddle the fault zone. We excavated a second trench in the southern BHV, but the fault zone in this trench collapsed during excavation and thus no information about fault history was documented from this site. We also excavated a soil pit on a lacustrine barrier bar in the southern Pueblo Valley (PV) to better constrain the age of lacustrine deposits exposed in the trench. The purpose of this report is to present photomosaics and trench logs, scarp profiles and slip data, soils data, luminescence and radiocarbon ages, and unit descriptions obtained during this investigation. We do not attempt to use the data presented herein to construct a paleoseismic history of this part of the Steens fault zone; that history will be the subject of a future report.

Quaternary geologic map of the Winnipeg 4 degrees x 6 degrees quadrangle, United States and Canada

USGS Publications Warehouse

Fullerton, D. S.; Ringrose, S.M.; Clayton, Lee; Schreiner, B.T.; Goebel, J.E.

2000-01-01

The Quaternary Geologic Map of the Winnipeg 4? ? 6? Quadrangle, United States and Canada, is a component of the U.S. Geological Survey Quaternary Geologic Atlas of the United States map series (Miscellaneous Investigations Series I-1420), an effort to produce 4? ? 6? Quaternary geologic maps, at 1:1 million scale, of the entire conterminous United States and adjacent Canada. The map and the accompanying text and supplemental illustrations provide a regional overview of the areal distributions and characteristics of surficial deposits and materials of Quaternary age (~1.8 Ma to present) in parts of North Dakota, Minnesota, Manitoba, and Saskatchewan. The map is not a map of soils as soils are recognized in agriculture. Rather, it is a map of soils as recognized in engineering geology, or of substrata or parent materials in which agricultural soils are formed. The map units are distinguished chiefly on the basis of (1)genesis (processes of origin) or environments of deposition: for example, sediments deposited primarily by glacial ice (glacial deposits or till), sediments deposited in lakes (lacustrine deposits), or sediments deposited by wind (eolian deposits); (2) age: for example, how long ago the deposits accumulated; (3) texture (grain size)of the deposits or materials; (4) composition (particle lithology) of the deposits or materials; (5) thickness; and (6) other physical, chemical, and engineering properties. Supplemental illustrations show (1) temporal correlation of the map units, (2) the areal relationships of late Wisconsin glacial ice lobes and sublobes, (3) temporal and spatial correlation of late Wisconsin glacial phases, readvance limits, and ice margin stillstands, (4) temporal and stratigraphic correlation of surface and subsurface glacial deposits in the Winnipeg quadrangle and in adjacent 4? ? 6? quadrangles, and (5) responsibility for state and province compilations. The database provides information related to geologic hazards (for example, materials that are characterized by expansive clay minerals; landslide deposits or landslide-prone deposits), natural resources (for example, sources of aggregate, peat, and clay; potential shallow sources of groundwater), and areas of environmental concern (for example, areas that are potentially suitable for specific ecosystem habitats; areas of potential soil and groundwater contamination). All of these aspects of the database relate directly to land use, management, and policy. The map, text, and accompanying illustrations provide a database of regional scope related to geologic history, climatic changes, the stratigraphic and chronologic frameworks of surface and subsurface deposits and materials of Quaternary age, and other problems and concerns.

Discovery of silicified lacustrine micro-fossils and stromatolites: Triassic-Jurassic Fundy Group, Nova Scotia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cameron, B.

A unique assemblage of silicified invertebrate and algal fresh-water lake fossils has been discovered in the Scots Bay Formation at the top of the Triassic-Jurassic Fundy Group of the Fundy Basin in Nova Scotia. This is important because the basins of the eastern North American Triassic-Jurassic rift system have not yielded many invertebrate and algal fossils. These new finds will contribute significantly to evolutionary, paleoecological and biostratigraphic studies of fresh-water Mesozoic deposits. Silicified fossils have been extracted from chert-bearing, mixed carbonate and siliciclastic lithologies. They include ostracodes, gastropods, rare bivalves, charaphytes (algae), stromatolites, and chert nodules cored with well-preserved woodymore » tissues of tree trunks. Possible algal filaments occur in the silicified stromatolites. This association of charaphytes, ostracodes, microscopic gastropods and stromatolites is found in carbonate lakes today. The Scots Bay Formation is probably a near-shore carbonate facies of the more widespread silicilastic lacustrine McCoy Brook Formation. The gastropods and ostracodes, studied by SEM, indicate a Jurassic age for the Scots bay Formation, confirming speculations based on other data.« less

South Atlantic sag basins: new petroleum system components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henry, S.G.; Mello, M.R.

Newly discovered pre-salt source rocks, reservoirs and seals need to be included as components to the petroleum systems of both sides of the South Atlantic. These new components lie between the pre-salt rift strata and the Aptian salt layers, forming large, post-rift, thermal subsidence sag basins. These are differentiated from the older rift basins by the lack of syn-rift faulting and a reflector geometry that is parallel to the base salt regional unconformity rather than to the Precambrian basement. These basins are observed in deep water regions overlying areas where both the mantle and the crust have been involved inmore » the extension. This mantle involvement creates post-rift subsiding depocenters in which deposition is continuous while proximal rift-phase troughs with little or no mantle involvement are bypassed and failed to accumulate potential source rocks during anoxic times. These features have been recognized in both West African Kwanza Basin and in the East Brasil Rift systems. The pre-salt source rocks that are in the West African sag basins were deposited in lacustrine brackish to saline water environment and are geochemically distinct from the older, syn-rift fresh to brackish water lakes, as well as from younger, post-salt marine anoxic environments of the drift phase. Geochemical analyses of the source rocks and their oils have shown a developing source rock system evolving from isolated deep rift lakes to shallow saline lakes, and culminating with the infill of the sag basin by large saline lakes to a marginally marine restricted gulf. Sag basin source rocks may be important in the South Atlantic petroleum system by charging deep-water prospects where syn-rift source rocks are overmature and the post-salt sequences are immature.« less

Sedimentology and sequence stratigraphy from outcrops of the Kribi-Campo sub-basin: Lower Mundeck Formation (Lower Cretaceous, southern Cameroon)

NASA Astrophysics Data System (ADS)

Ntamak-Nida, Marie Joseph; Bourquin, Sylvie; Makong, Jean-Claude; Baudin, François; Mpesse, Jean Engelbert; Ngouem, Christophe Itjoko; Komguem, Paul Bertrand; Abolo, Guy Martin

2010-08-01

The Kribi-Campo sub-basin is composed of an Early to Mid Cretaceous series from West Africa's Atlantic coast and is located in southern Cameroon in the Central African equatorial rain forest. It is the smallest coastal basin in Cameroon and forms the southern part of the Douala/Kribi-Campo basin known as Douala basin ( s.l.). Until now, no detailed sedimentological studies have been carried out on the outcrops of this basin located in the Campo area. The aim of this study was to characterise the depositional environments, vertical evolution and tectonic context of these Lower Cretaceous series in order to make a comparison with adjacent basins and replace them in the geodynamic context. Facies analysis of the Lower Mundeck Formation (Lower Cretaceous) indicates the presence of four major, interfigered facies associations, that are inferred to represent elements of an alluvial to lacustrine-fan delta system. The clast lithologies suggest proximity of relief supplying coarse-grained sediment during the deposition of the Lower Mundeck Formation at Campo. The general dip and direction of the bedding is approximately 10°-12°NW, which also corresponds to the orientation of the foliations in the underlying metamorphic basement. The main sedimentary succession is characterised by a major retrogradational/progradational cycle of Late Aptian age, evaluated at about 3 Ma, with a well-developed progradational trend characterised by fluctuations of the recognised depositional environments. Fluctuations in lake level and sediment supply were possibly controlled by active faults at the basin margin, although climatic changes may have also played a role. The consistently W-WNW palaeoflow of sediments suggests that the palaeorelief was located to the east and could be oriented in a NNE-SSW direction, downthrown to the west. Local outcrops dated as Albian, both north and south of the main outcrop, display some marine influence. These deposits are cut by 040-060 faults parallel to the oceanic transform. Similarly, the Lower Mundeck Formation of the Campo outcrops is considered to be associated mainly with the early drift period of Late Aptian-Albian age. This study is also the first step of knowledge of these African margin deposits, to realise in the future the correlations between outcrops and offshore data.

Geochemistry of Precambrian carbonates: 3-shelf seas and non-marine environments of the Archean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veizer, J.; Clayton, R.N.; Hinton, R.W.

1990-10-01

A comprehensive whole-rock study of mineralogical, chemical, and isotopic attributes of Archean carbonates suggests that their lithologies and facies have been controlled by tectonic setting. In the first two papers of this series they have shown that the dominant lithology of sedimentary carbonates in greenstone belt settings is limestone. In this paper the authors suggest that the Archean shelf sequences are mostly dolostone, and the contemporaneous lacustrine playa lakes are characterized by limestone facies. The present study is of the shelf environments of the Archean, represented by the Pongola Supergroup of South Africa and the Hamersley Group of Australia. Themore » lacustrine playa examples have been sampled from the Ventersdorp Supergroup of South Africa and the Fortescue Group of Australia. Geological, trace element, and oxygen isotope considerations of the shelf carbonates suggest that their original mineralogy may have been aragonite and that the Pongola dolostones probably represent a direct dolomitization product of this precursor. In contrast, the stabilization of the Hamersley carbonates may have involved an additional step of transformation of a metastable precursor into limestone prior to dolomitization.« less

Distinguishing megathrust from intraplate earthquakes using lacustrine turbidites (Laguna Lo Encañado, Central Chile)

NASA Astrophysics Data System (ADS)

Van Daele, Maarten; Araya-Cornejo, Cristian; Pille, Thomas; Meyer, Inka; Kempf, Philipp; Moernaut, Jasper; Cisternas, Marco

2017-04-01

One of the main challenges in seismically active regions is differentiating paleo-earthquakes resulting from different fault systems, such as the megathrust versus intraplate faults in subductions settings. Such differentiation is, however, key for hazard assessments based on paleoseismic records. Laguna Lo Encañado (33.7°S; 70.3°W; 2492 m a.s.l.) is located in the Central Chilean Andes, 50 km east of Santiago de Chile, a metropole with about 7,000,000 inhabitants. During the last century the study area experienced 3 large megathrust earthquakes (1906, 1985 and 2010) and 2 intraplate earthquakes (1945 and 1958) (Lomnitz, 1960). While the megathrust earthquakes cause Modified Mercalli Intensities (MMIs) of VI to VII at the lake (Van Daele et al., 2015), the intraplate earthquakes cause peak MMIs up to IX (Sepúlveda et al., 2008). Here we present a turbidite record of Laguna Lo Encañado going back to 1900 AD. While geophysical data (3.5 kHz subbottom seismic profiles and side-scan sonar data) provides a bathymetry and an overview of the sedimentary environment, we study 15 short cores in order to understand the depositional processes resulting in the encountered lacustrine turbidites. All mentioned earthquakes triggered turbidites in the lake, which are all linked to slumps in proximal areas, and are thus resulting from mass wasting of the subaquatic slopes. However, turbidites linked to the intraplate earthquakes are additionally covered by turbidites of a finer-grained, more clastic nature. We link the latter to post-seismic erosion of onshore landslides, which need higher MMIs to be triggered than subaquatic mass movements (Howarth et al., 2014). While intraplate earthquakes can cause MMIs up to IX and higher, megathrust earthquakes do not cause sufficiently high MMIs at the lake to trigger voluminous onshore landslides. Hence, the presence of these post-seismic turbidites allows to distinguish turbidites triggered by intraplate earthquakes from those triggered by megathrust earthquakes. These findings are an important step forward in the interpretation of lacustrine turbidites in subduction settings, and will eventually improve hazard assessments based on such paleoseismic records in the study area, and in other subduction zones. References Howarth et al., 2014. Lake sediments record high intensity shaking that provides insight into the location and rupture length of large earthquakes on the Alpine Fault, New Zealand. Earth and Planetary Science Letters 403, 340-351. Lomnitz, 1960. A study of the Maipo Valley earthquakes of September 4, 1958, Second World Conference on Earthquake Engineering, Tokyo and Kyoto, Japan, pp. 501-520. Sepulveda et al., 2008. New Findings on the 1958 Las Melosas Earthquake Sequence, Central Chile: Implications for Seismic Hazard Related to Shallow Crustal Earthquakes in Subduction Zones. Journal of Earthquake Engineering 12, 432-455. Van Daele et al., 2015. A comparison of the sedimentary records of the 1960 and 2010 great Chilean earthquakes in 17 lakes: Implications for quantitative lacustrine palaeoseismology. Sedimentology 62, 1466-1496.

Shallow lacustrine system of the Permian Pedra de Fogo Formation, Western Gondwana, Parnaíba Basin, Brazil

NASA Astrophysics Data System (ADS)

Araújo, Raphael Neto; Nogueira, Afonso César Rodrigues; Bandeira, José; Angélica, Rômulo Simões

2016-04-01

The Permian Period of the Parnaíba Basin, northern Brazil, represented here by deposits from the Pedra de Fogo Formation, records important events that occurred in Western Gondwana near its boundary with the Mesozoic Era. The analysis of outcrop based facies from the Permian Pedra de Fogo Formation, which is 100 m thick, carried out along the eastern and western borders of the Parnaiba Basin, allowed the identification of eleven sedimentary facies, which were grouped into three distinct facies associations (FA), representative of a shallow lacustrine system associated with mudflats and ephemeral rivers. Bioturbation, desiccation cracks, silcretes and various siliceous concretions characterize the Pedra de Fogo deposits. The FA1 mudflat deposits occur predominantly at the base of the Pedra de Fogo Formation and consist of laminated claystone/mudstone, mudcrack-bearing sandstones/mudstones and sandstones exhibiting cross-lamination, massive and megaripple bedding. Popcorn-like silicified nodules and casts indicate evaporite deposits. Other common features are silica concretions, silicified tepees and silcretes. FA2 represents nearshore deposits and consists of fine-grained sandstones with evenly parallel lamination, climbing ripple cross-lamination, massive and megaripple bedding and mudstone/siltstone showing evenly parallel lamination. FA3 refers to wadi/inundite deposits, generally organized as fining-upward cycles of metric size, composed of conglomerates and medium-grained pebbly sandstones showing massive bedding and cross-stratification, as well as claystone/siltstone showing evenly parallel to undulate lamination. Scour-and-fill features are isolated in predominantly tabular deposits composed of mudstones interbedded with fine to medium-grained sandstones showing planar to slightly undulate lamination. Silicified plant remains previously classified as belonging to the Psaronius genus found in the uppermost levels of the Pedra de Fogo Formation, near the contact with the Motuca Formation, are considered here as excellent biostratigraphic markers. Fish remains, ostracods, bryozoans and scolecodonts represent other fossils that are present in the succession. Mudflat deposits developed in an arid and hot climate probably in the Early Permian. Semi-arid conditions prevailed in the Middle Permian allowing the proliferation of fauna and flora in adjacent humid regions and onto the lake margin. The climate variation was responsible for the contraction and expansion phases of the lake, fed by sporadic sheet floods carrying plant remains. The reestablishment of the arid climate, at the end of Permian, marks the final sedimentation of the Pedra de Fogo Formation, linked to the consolidation of the Pangaea Supercontinent. This last event was concomitant with the deposition of the Motuca Formation red beds and the development of extensive ergs related to the Triassic Sambaíba Formation in Western Gondwana.

On the origin of saline soils at Blackspring Ridge, Alberta, Canada

NASA Astrophysics Data System (ADS)

Stein, Richard; Schwartz, Franklin W.

1990-09-01

Problems of soil salinity occur at Blackspring Ridge, Alberta, in four different settings. The most seriously affected area is at the base of the ridge where salinity appears as severe salt crusting on the surface, salt-tolerant vegetation, and areas of poor or no crop production. Blackspring Ridge is a structural bedrock high that is underlain by Upper Cretaceous sediment of the Horseshoe Canyon Formation. Bedrock is overlain by fluvial, glacial, lacustrine, and aeolian sediment. Piezometric data indicate that groundwater is recharged on and along the upper flanks of Blackspring Ridge and discharges in southern parts of a lacustrine plain that surrounds the ridge. Hydraulic conductivity data, water-level fluctuations, stable isotopes, and hydrochemical data indicate that the fractured near-surface bedrock and overlying thin-drift sediment constitute a zone of active groundwater flow within which salts are generated and transported. Water discharging from this shallow system evaporates and forms saline areas at the base of the ridge. The most seriously affected areas on the lacustrine plain coincide with places where the water table is less than 1.5m from the ground surface. A high water table occurs locally because of the changing topology of geologic units, and lows in the topographic surface that focus groundwater and surface water flows. Some proportion of the shallow groundwater salinized by evaporation is also transported down the flow system where it mixes with unevaporated water. Surface water, from snowmelt and precipitation events, dissolves salt that was deposited at the surface by evaporating groundwater and redistributes the salt to areas of lower elevation.

Preliminary study of favorability for uranium resources in Juab County, Utah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leedom, S.H.; Mitchell, T.P.

1978-02-01

The best potential for large, low-grade uranium deposits in Juab County is in the hydrothermally altered vitric tuffs of Pliocene age. The lateral extent of the altered tuffs may be determined by subsurface studies around the perimeter of the volcanic centers in the Thomas Range and the Honeycomb Hills. Because the ring-fracture zone associated with collapse of the Thomas caldera was a major control for hydrothermal uranium deposits, delineation of the northern and eastern positions of the ring-fracture zone is critical in defining favorable areas for uranium deposits. A small, medium-grade ore deposit in tuffaceous sand of Pliocene age atmore » the Yellow Chief mine in Dugway Dell is unique in origin, and the probability of discovering another deposit of this type is low. A deposit of this type may be present under alluvial cover in the northwestern Drum Mountains along the southern extension of the ring-fracture zone of the Thomas caldera. Festoonlike iron oxide structures and uranium deposition within permeable sandstone horizons indicate that the Yellow Chief deposit was formed by recent ground-water circulation. Granitic intrusive rocks in the Deep Creek Range and in Desert Mountain contain isolated epigenetic vein-type deposits. These rocks could be a source of arkosic sediments buried in adjacent valleys. The Pleistocene lacustrine sediments and playa lake brines may contain concentrations of uranium leached from uranium-rich rocks.« less

From the North American Great Basin to the planet Mars: Taking Lacustrine Geomorphology into the 21st Century

NASA Astrophysics Data System (ADS)

Edgett, Kenneth S.; Parker, Timothy J.

1997-09-01

Introduction. The entire planet Mars is presently a desert more arid than any on Earth. The planet appears to have had more water in the past, and some of this water affected the surface geology and geomorphology by carving a variety of channels. Despite the evidence for running water in the martian past, the presence of sanding bodies of water (lakes, oceans) has been a topic of considerable controversy in the past two decades. The issue is still not settled, but evidence has mounted to suggest that lakes and oceans were indeed a major factor in shaping the present geomorphology of the martian surface. Although there remains uncertainty as to whether lakes were present on Mars, major efforts to seek evidence for fossil martian organisms are focused on the search for lake sediments and tufa deposits [1]. In 2001 and 2003, the NASA Mars Surveyor Program will launch mobile rovers designed to explore the surface and collect samples for return to Earth. The first set of samples will reach Earth in 2008. The types of landing sites being considered for the '01 and '03 missions include areas interpreted as ancient lacustrine deposits. Knowledge and experience with the geomorphology of lacustrine features in the North American Great Basin is crucial for identifying lake features on Mars. Martian Lakes and Oceans: Prior to spacecraft exploration of Mars, many early astronomers though that the low-albedo surfaces of Mars could be seas or lakes, others considered these to be vast tracts of vegetation [2]. The low-albedo surfaces are now known to be the result of aeolian action on the distribution of sand and dust. The Mariner 4, 6, and 7 spacecraft in 1965 and 1969 stunned the world by showing a cratered, lunar-like martian surface. In 1972, Mariner 9 showed a more Earth-like surface - indeed, there were numerous channels, some carved by massive floods, others perhaps by fluvial run-off or sapping. The Viking orbiters (1976-1980) provided additional images; these formed the basis of study for the past two decades. In the mid-1980s some investigators began to speak of Mars as having a more "wet" history than was discussed earlier [3, 4]. Parker et al. [5-7] showed similarities between landforms along the margins of the great northern plains of Mars and landforms along the margins of Great Basin Lakes Bonneville and Lahontan; this work has stimulated much additional research [e.g., 8] and controversy [e.g., 9]. Others began to identify smaller basins that seem to contain sediments deposited by various channels. Among the earliest convincing arguments were presented by De Hon [10], who simply noted the occurrence of places where water had ponded along the course of some of the giant martian outflow channels. Evidence Mounts: The most commonly-cited place on Mars that may have been an ancient lake is within a 175 km-diameter crater, Gusev, located at 5°S, 184.5°W. A channel, Ma'adim Vallis, flowed into this crater; and an eroded, delta-like deposit is found at the site where the channel contacts the basin. This particular site has been repeatedly described in recent years as a place worthy of future Mars landers and sample returns, largely because it is one of the few possible lake features that most of the Mars science community can agree upon. Many more possible ancient lakebeds have been identified and summarized by Goldspiel and Squyres [11], Scott et al. [12], De Hon [13], Wharton et al. [14], and Parker and Currey [15]. Most of the proposed lakebeds are areas of low elevation where one or more channels appear to terminate at the location of a smooth, flat-lying deposit. In some cases, the smooth deposit has been eroded to form buttes and mesas. Other lake features are identified on the basis of thick, layered deposits [16]; or high-albedo deposits on crater floors, interpreted to be possible evaporates [17]. Parker [18, 19] has continued the approach of looking for Bonneville-like paleoshore features, but has moved from looking at the margins of great northern plans to the large (100s to 1000s of km) impact basins. Edgett and Parker [20] recently proposed that a vast portion of ancient cratered highlands terrain in the martian region of western Arabia was once part of a vast, northern hemisphere ocean that was bigger than previously envisioned by anyone. Upcoming Missions: NASA's decade-long Mars Surveyor Program is focused on the theme of "water." The program's emphasis recently shifted toward the search for evidence of martian life. One of the main types of sites desired for exobiologic investigation is "sublacustrine spring deposits and evaporates/lacustrine shales" [1]. New high resolution images (1.5 m/pixel) and thermal infrared mineral spectra will be obtained by Mars Global Surveyor instruments during its primary mission (March 1998-January 2000) - these are both expected to contribute greatly toward the identification of lacustrine features. In addition, the Mars Global Surveyor laser altimeter may confirm topographic continuity of shore features identified by Parker et al. [6,7]. Additional orbiters with complimentary capabilities will launch in 1998 and 2001. Rovers designed to cache samples for return to Earth will land in 2002 and 2004, and at least one of these is expected to be a lacustrine site. Knowledge of North America's Great Basin lacustrine geomorphology will contribute greatly to the exploration of this new frontier in the 21st Century. References: [1] An Exobiological Strategy for Mars Exploration (1995) NASA SP-530, 56 p. [2] Lowell, P. (1896) Pop. Astron., 4, 289-296. [3] Clifford, S. M., et al. (1988) Eos, Trans. AGU, 69, 1585, 1595-1596. [4] McEwen, A. S. (1991) Rev. Geophys. Suppl., 29, 290-296. [5] Parker, T. J. et al. (1987) pp. 96-98 in Mars: Evolution of its Climate and Atmosphere, LPI Tech. Rept. 87-01, Houston, TX. [6] Parker, T. J. et al. (1989) Icarus, 82, 111-145. [7] Parker, T. J. et al. (1993) J. Geophys. Res., 98, 11061-11078. [8] Baker, V. R., et al. (1991) Nature, 352, 589-594. [9] Carr, M. H. (1991) Bull. Amer. Astron. Soc., 23, 1206. [10] De Hon, R. A. (1987) Lunar Planet. Sci. XIX, 261-262. [11] Goldspiel, J. M. and S. W. Squyres (1991) Icarus, 89, 392-410. [12] Scott, D. H. et al. (1991) Origins Life Evol. Biosph., 21, 189-198. [13] De Hon, R. A. (1992) Earth, Moon, Planets, 56, 95-112. [14] Wharton, R. A. et al. (1995) J. Paleolimn., 13, 267-283. [15] Parker, T. J. and D. R. Currey (in press) Extraterrestrial coastal geomorphology, Geomorphology. [16] Nedell, S. S., et al. (1987) Icarus, 70, 409-441. [17] Wiliams, S. H., and J. R. Zimbelman (1994) Geology, 22, 107-110. [18] Parker, T. J. (1996) Lunar Planet. Sci. XXVII, 1003-1004. [19] Parker, T. J. (1997) pp. 65-66 in Conference on Early Mars, Lunar Planet. Inst., Houston, TX. [20] Edgett, K. S., and T. J. Parker (1997) pp. 27-28 in Conference on Early Mars, Lunar Planet. Inst., Houston, TX.

Bouse Formation in the Bristol basin near Amboy, California, USA

USGS Publications Warehouse

Miller, David M.; Reynolds, Robert E.; Bright, Jordan E.; Starratt, Scott W.

2014-01-01

Limestone beds underlain and overlain by alluvial fan conglomerate near Amboy, California, are very similar in many respects to parts of the Bouse Formation, suggesting that an arm of the Pliocene Bouse water body extended across a wide part of the southern Mojave Desert. The deposits are north of the town of Amboy at and below an elevation of 290 m, along the northern piedmont of the Bristol “dry” Lake basin. The Amboy outcrops contain the Lawlor Tuff (4.83 Ma), which is also found in an outcrop of the Bouse Formation in the Blythe basin near Buzzards Peak in the Chocolate Mountains, 180 km southeast of Amboy. Bouse exposures near Amboy are ∼3.4 m thick, white, distinctly bedded, with limestone and calcareous sandstone as well as stromatolite mounds; we interpret these as nearshore deposits. The Bouse at Amboy contains ostracodes, diatoms, and mollusks that indicate saline lake or estuarine environments with an admixture of fresh-water forms. Along with wading bird tracks and a spine from a marine fish, these fossils suggest that the deposits formed in saline waters near a fresh-water source such as a perennial stream. Beds of the outcrop dip southward and are 113 m above the surface of Bristol Playa, where similar age sediments are buried 270+ m deep, indicating significant faulting and vertical tectonics in this part of the Eastern California Shear Zone during the past 5 m.y. Confirmation of the Bouse Formation at Amboy strengthens previous assignments to the Bouse Formation for mudstones in driller logs at Danby “dry” Lake, California, and suggests that areally extensive arms of the Bouse water body were west of the Blythe basin. The Bristol basin arm of the lower Bouse basin probably was restricted from the main water body by narrow passages, but Bouse sediment there is similar to that in the Blythe basin, suggesting generally similar water chemistry and environmental conditions. Examining the degree to which Bouse deposits in the western arms differed from Bouse deposits in the Blythe basin offers an approach to test whether the southernmost Bouse water body was deposited in an estuarine or lacustrine setting.

The Relationship between Litho-Sequential Stratigraphy, Chemostratigraphy of Khuff Carbonates: Implication for Facies and Paleoenvironmental Recognition and Correlation, Central Saudi Arabia

NASA Astrophysics Data System (ADS)

Abdullatif, Osman; Abdlmutalib, Ammar; Ahmed, Jarrah; Abdelgadir, Mohamed; Adam, Ammar

2017-04-01

The Permian-Triassic Khuff Formation carbonate reservoirs (and equivalents) in the Middle East are estimated to contain about 15-20 % of the world's gas reserves. Excellently exposed outcropping Khuff strata in central Saudi Arabia provide good outcrop equivalents to the Khuff Formation in the subsurface. The Khuff Formation is composed of five members and from bottom to top are Ash Shiqqah, Huqayl, Duhaysan, Midnab and Khartam members. The Carbonates lithofacies dominate with minor terrestrial clastics, and the paleoenvironments vary from terrestrial, sabkha, tidal-intertidal and open marine environments. This study investigates the relationship between lithostratigraphy, sequence stratigraphy and chemostratigraphy by integration of both field and laboratory sedimentological and chemical elements data. The vertical chemical elements profiles along the Khuff members show variations in their chemical elements content with the variation in lithofacies types, staking pattern, depositional and stratigraphic pattern. The chemostratigraphic distribution of the chemical elements also showed variation within and between the Khuff members. There is a general agreement between chemostratigraphic analyses based on vertical profiles and binary cross plots. The Khuff members and their stratigraphic boundaries can be differentiated based on their chemostratigraphic signatures. Moreover, the lithofacies and depositional paleoenvironmental of different Khuff members can be identified based on their chemical element contents. Chemostratigraphic zones or clusters are markedly established indicating different lithofacies and depositional paleoenvironments. Terrestrial, channel, lacustrine, shoreline to open marine carbonate lithofacies, as building blocks of sequence stratigraphy, all may be distinguished based on their chemical signatures. These outcrop analog results might be of significance to lithofacies, paleoenvironmental, stratigraphic identification, classification and correlation of Khuff Formation in the subsurface. The results might also provide guides and application to reservoir Khuff Formation identification, layering and zonation in the subsurface.

Environmental Transitions Recorded by Fluvial Fan Stratigraphy at Dingo Gap and Moonlight Valley, Gale Crater, Mars

NASA Astrophysics Data System (ADS)

Edgar, L. A.; Gupta, S.; Rubin, D. M.; Schieber, J.; Stack, K.; Lewis, K. W.

2016-12-01

The Mars Science Laboratory (MSL) Curiosity rover investigated a number of sedimentary outcrops across Aeolis Palus. Observations of conglomerates, cross-bedded sandstones, and mudstones suggest that fluvial and lacustrine environments were common. Outcrops that expose cross-sections are particularly helpful for identifying stratigraphic relationships and changes through time. In the vicinity of an outcrop informally named Dingo Gap, the drive strategy shifted from driving on the topographic high areas to the topographic low areas, which resulted in a unique vantage point to observe stratigraphy in cross-section. During Sols 513-541, Curiosity investigated 4 m of stratigraphy exposed at Dingo Gap and Moonlight Valley. The valley walls reveal five distinct sedimentary facies, including 1) a fine-grained evenly laminated facies interpreted as upper plane bed stratification, 2) ripple and dune cross-stratified sandstone facies, interpreted to represent the southward migration of subaqueous bedforms, 3) fully preserved bedform sandstone facies, formed during high rates of deposition, 4) planar-bedded granule-rich sandstone facies, interpreted as sheet flood deposits, and 5) a weakly stratified, poorly-sorted conglomerate facies, interpreted to represent rapid deposition from a high-energy fluvial flow. The conglomerate facies is unlike other conglomerates observed thus far in the mission, on the basis of both texture and chemistry. Analysis of conglomerates reveal that they occur as distinct channel bodies, incised into cross-stratified sandstones. This coarsening upward signature is interpreted to record a prograding fan succession. Channel bodies appear to be time-equivalent, which suggests a major change in the system, likely associated with a drop in base level. The unique viewing geometry offered by Dingo Gap and Moonlight Valley makes it possible to observe these environmental changes.

Record of a Statherian rift-sag basin in the Central Espinhaço Range: Facies characterization and geochronology

NASA Astrophysics Data System (ADS)

Costa, Alice Fernanda de Oliveira; Danderfer, André; Bersan, Samuel Moreira

2018-03-01

Several rift-related sequences and volcanic-plutonic associations of Statherian age occur within the São Francisco block. One succession within the sedimentary record, the Terra Vermelha Group, defines one of the evolutionary stages of the Espinhaço basin in the Central Espinhaço Range. As a result of stratigraphic analyses and supported by U-Pb zircon geochronological data, the evolution of this unit has been characterized. To more effectively delimit its upper depositional interval, the sequence of this unit, which is represented by the Pau d'Arco Formation, was also studied. The sedimentary signature of the Terra Vermelha Group suggests the infilling of an intracontinental rift associated with alluvial fans as well as lacustrine and eolian environments with associated volcanism. The basal succession represented by the Cavoada do Buraco Formation mainly consists of conglomerates with interlayered sandstones and subordinate banded iron formations. Detrital zircon obtained from this unit reveals ages of 1710 ± 21 Ma. The upper succession, represented by the Espigão Formation, records aeolian sandstones with volcanic activity at the top. A volcanic rock dated at 1758 ± 4 Ma was interpreted as the timing of volcanism in this basin. The eolian deposits recorded within the Pau d'Arco Formation were caused by a renewal of the sequence, which represent a stage of post-rift thermal subsidence. The maximum age of sedimentation for this unit is 1675 ± 22 Ma. The basin-infill patterns and Statherian ages suggest a direct link with the first rifting event within the São Francisco block, which was responsible for the deposition of the Espinhaço Supergroup.

Influence of near-surface stratigraphy on coastal landslides at Sleeping Bear Dunes National Lakeshore, Lake Michigan, USA

USGS Publications Warehouse

Barnhardt, W.A.; Jaffe, B.E.; Kayen, R.E.; Cochrane, G.R.

2004-01-01

Lake-level change and landslides are primary controls on the development of coastal environments along the coast of northeastern Lake Michigan. The late Quaternary geology of Sleeping Bear Dunes National Lakeshore was examined with high-resolution seismic reflection profiles, ground-penetrating radar (GPR), and boreholes. Based on sequence-stratigraphic principles, this study recognizes ten stratigraphic units and three major unconformities that were formed by late Pleistocene glaciation and postglacial lake-level changes. Locally high sediment supply, and reworking by two regressions and a transgression have produced a complex stratigraphy that is prone to episodic failure. In 1995, a large landslide deposited approximately 1 million m3 of sediment on the lake floor. The highly deformed landslide deposits, up to 18 m thick, extend 3-4 km offshore and unconformably overlie well-stratified glacial and lacustrine sediment. The landslide-prone bluff is underlain by channel-fill deposits that are oriented nearly perpendicular to the shoreline. The paleochannels are at least 10 m deep and 400 m wide and probably represent stream incision during a lake-level lowstand about 10.3 ka B.P. The channels filled with sediment during the subsequent transgression and lake-level highstand, which climaxed about 4.5 ka B.P. As lake level fell from the highstand, the formation of beach ridges and sand dunes sealed off the channel and isolated a small inland lake (Glen Lake), which lies 5 m above the level of Lake Michigan and may be a source of piped groundwater. Our hypothesis is that the paleochannels act as conduits for pore water flow, and thereby locally reduce soil strength and promote slope failure.

Phylogenomics reveals habitat-associated body shape divergence in Oryzias woworae species group (Teleostei: Adrianichthyidae).

PubMed

Mokodongan, Daniel F; Montenegro, Javier; Mochida, Koji; Fujimoto, Shingo; Ishikawa, Asano; Kakioka, Ryo; Yong, Lengxob; Mulis; Hadiaty, Renny K; Mandagi, Ixchel F; Masengi, Kawilarang W A; Wachi, Nakatada; Hashiguchi, Yasuyuki; Kitano, Jun; Yamahira, Kazunori

2018-01-01

The Oryzias woworae species group, composed of O. asinua, O. wolasi, and O. woworae, is widely distributed in southeastern Sulawesi, an island in the Indo-Australian Archipelago. Deep-elongated body shape divergence is evident among these three species to the extent that it is used as a species-diagnostic character. These fishes inhabit a variety of habitats, ranging from upper streams to ponds, suggesting that the body shape divergence among the three species may reflect adaptation to local environments. First, our geometric morphometrics among eight local populations of this species group revealed that the three species cannot be separated by body shape and that riverine populations had more elongated bodies and longer caudal parts than lacustrine populations. Second, their phylogenetic relationships did not support the presence of three species; phylogenies using mitochondrial DNA and genomic data obtained from RNA-Seq revealed that the eight populations could not be sorted into three different clades representing three described species. Third, phylogenetic corrections of body shape variations and ancestral state reconstruction of body shapes demonstrated that body shape divergence between riverine and lacustrine populations persisted even if the phylogenies were considered and that body shape evolved rapidly irrespective of phylogeny. Sexual dimorphism in body shape was also evident, but the degree of dimorphism did not significantly differ between riverine and lacustrine populations after phylogenetic corrections, suggesting that sexual selection may not substantially contribute to geographical variations in body shape. Overall, these results indicate that the deep-elongated body shape divergence of the O. woworae species group evolved locally in response to habitat environments, such as water currents, and that a thorough taxonomic reexamination of the O. woworae species group may be necessary. Copyright © 2017 Elsevier Inc. All rights reserved.

Paleohydrology of China Lake basin and the context of early human occupation in the northwestern Mojave Desert, USA

NASA Astrophysics Data System (ADS)

Rosenthal, Jeffrey S.; Meyer, Jack; Palacios-Fest, Manuel R.; Young, D. Craig; Ugan, Andrew; Byrd, Brian F.; Gobalet, Ken; Giacomo, Jason

2017-07-01

Considerable prior research has focused on the interconnected pluvial basins of Owens Lake and Searles Lake, resulting in a long record of paleohydrological change in the lower Owens River system. However, the published record is poorly resolved or contradictory for the period encompassing the terminal Pleistocene (22,000 to 11,600 cal BP) and early Holocene (11,600-8200 cal BP). This has resulted in conflicting interpretations about the timing of lacustrine high stands within the intermediate basin of China Lake, which harbors one of the most extensive records of early human occupation in the western Great Basin and California. Here, we report a broad range of radiocarbon-dated paleoenvironmental evidence, including lacustrine deposits and shoreline features, tufa outcrops, and mollusk, ostracode, and fish bone assemblages, as well as spring and other groundwater-related deposits (a.k.a. "black mats") from throughout China Lake basin, its outlet, and inflow drainages. Based on 98 radiocarbon dates, we develop independent evidence for five significant lake-level oscillations between 18,000 and 13,000 cal BP, and document the persistence of groundwater-fed wetlands from the beginning of the Younger Dryas through the early Holocene (12,900-8200 cal BP); including the transition from ground-water fed lake to freshwater marsh between about 13,000 and 12,600 cal BP. Results of this study support and refine existing evidence that shows rapid, high-amplitude oscillations in the water balance of the Owens River system during the terminal Pleistocene, and suggest widespread human use of China Lake basin began during the Younger Dryas.

Climate Change and Drought Events in the Geochemical Records of the Lacustrine Deposits in the Southeastern Tibetan Plateau

PubMed Central

Shi, Zhengtao; Niu, Jie; Su, Huai

2016-01-01

Lacustrine deposits at the margin of the southeastern Tibetan Plateau (SETP) are sensitive indicators for the evolution of the southwest Asian monsoon (SWAM) during the Quaternary. Thus, they can provide insight into the Quaternary climatic history and their relationship with global climatic changes. The results of the geochemical analysis of the Xiaozhongdian Basin section at the SETP suggest that SiO2 had the highest content of the major elements followed by Al2O3. The order of the abundance of the major elements was generally as follows: SiO2>Al2O3>Fe2O3>CaO>MgO>K2O>TiO2>Na2O>MnO2. The geochemical proxies, such as chemical index of alteration (CIA), the index of compositional variability (ICV) and (CaO+K2O+Na2O)/Al2O3, indicate the weak chemical weathering and the aridification of the margin of the SETP during the Heinrich events. In addition, the aridification of the SETP during the Heinrich events may be closely related to the cold signals transmitted from the high latitudes of the North Atlantic to the TP, and the effect caused the cooling effect to be very strong on the TP as a result of the upper-level westerly jet stream and then reduced the suction action associated with the SWAM, thus accelerating the drying rate of Xiaozhongdian Basin, which was amplifying the degree of drought in Heinrich events. PMID:28033377

Biotic association and palaeoenvironmental reconstruction of the "Loma del Pterodaustro" fossil site (Early Cretaceous, Argentina)

USGS Publications Warehouse

Chiappe, L.; Rivarola, D.; Cione, A.; Fregenal-Martinez, M.; Sozzi, H.; Buatois, L.; Gallego, O.; Laza, J.; Romero, E.; Lopez-Arbarello, A.; Buscalioni, A.; Marsicano, C.; Adamonis, S.; Ortega, F.; McGehee, S.; Di, Iorio O.

1998-01-01

A sedimentological analysis of the basal section of the Early Cretaceous, lacustrine Lagarcito Formation at "Loma del Pterodaustro" (San Luis, Argentina) and a summary of its biological components are presented. Three sedimentological facies can be recognized in the basal sequence of the Lagarcito Formation. Fossil remains are particularly abundant in laminated claystones of a facies interpreted as deposits formed in offshore areas of the lake. The preservation of delicate structures allows recognition of these deposits as a Konservat Lagersta??tte. Up to now, rocks at "Loma del Pterodaustro" have yielded plants, conchostracans, semionotid and pleuropholid fishes, pterodactyloid pterosaurs, and a variety of invertebrate traces. The chronology of the Lagarcito Formation is discussed and it is concluded that this unit is of Albian age. The palaeoenvironment of deposition of the basal sequence of the Lagarcito Formation at "Loma del Pterodaustro" is interpreted as a perennial, shallow lake developed within an alluvial plain, under semiarid climatic conditions.

Influence of Fault-Controlled Topography on Fluvio-Deltaic Sedimentary Systems in Eberswalde Crater, Mars

NASA Technical Reports Server (NTRS)

Rice, Melissa S.; Gupta, Sanjeev; Bell, James F., III; Warner, Nicholas H.

2011-01-01

Eberswalde crater was selected as a candidate landing site for the Mars Science Laboratory (MSL) mission based on the presence of a fan-shaped sedimentary deposit interpreted as a delta. We have identified and mapped five other candidate fluvio -deltaic systems in the crater, using images and digital terrain models (DTMs) derived from the Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX). All of these systems consist of the same three stratigraphic units: (1) an upper layered unit, conformable with (2) a subpolygonally fractured unit, unconformably overlying (3) a pitted unit. We have also mapped a system of NNE-trending scarps interpreted as dip-slip faults that pre-date the fluvial -lacustrine deposits. The post-impact regional faulting may have generated the large-scale topography within the crater, which consists of a Western Basin, an Eastern Basin, and a central high. This topography subsequently provided depositional sinks for sediment entering the crater and controlled the geomorphic pattern of delta development.

Hydrogeology and water quality of the Clinton Street-Ballpark Aquifer near Johnson City, New York

USGS Publications Warehouse

Coon, William F.; Yager, Richard M.; Surface, Jan M.; Randall, Allan D.; Eckhardt, David A.

1998-01-01

The Clinton Street-Ballpark aquifer, in the Susquehanna River valley in southern Broome County, N.Y., supplies drinking water to the Village of Johnson City near Binghamton. The hydrogeology and water quality of the aquifer were studied in 1994-95 to identify the source area of 1,1,1-trichloroethane, which was detected at the Johnson City Camden Street wellfield in 1991.The aquifer is generally 100 to 150 ft thick and consists primarily of ice-contact deposits of silty sand and gravel that are overlain by outwash deposits of sand and gravel. These two types of deposits are separated by lacustrine silt and clay of variable thickness into an upper and a lower layer of the aquifer. The coarse deposits form a single aquifer in areas where the lacustrine deposits are absent.Synoptic water-level surveys indicated that ground water moves from upgradient areas flanking the aquifer boundaries toward two major pumping centers?the Anitec wellfield in Binghamton and the Camden Street wellfield in Johnson City. Areas contributing recharge to municipal and industrial wells in the aquifer were delineated by a previously developed groundwater- flow model. The residence time of ground water within the area contributing recharge to Johnson City well no. 2 in the Camden Street wellfield was estimated to be less than 6 years.1,1,1-Trichloroethane, trichloroethene, and their metabolites were detected in ground water at several locations in and near Johnson City. Relatively high concentrations of 1,1,1-trichloroethane were found in ground water about 3,000 ft north of the Camden Street wellfield. The suspected source is an area bordered on the south by Field Street, on the north by Harry L. Drive, on the east by New York State Route 201, and on the west by Marie Street. A trichloroethene metabolite, cis-1,2-dichloroethene, appears to be migrating westward from U.S. Air Force Plant 59 toward the Camden Street well-field, 1,000 ft southwest of the plant, although this compound has not been detected in water pumped by municipal wells, possibly because it has become diluted by ground water from other locations within the contributing area to the wells.

Sedimentary facies and environmental ichnology of a ?Permian playa-lake complex in western Argentina

USGS Publications Warehouse

Zhang, G.; Buatois, L.A.; Mangano, M.G.; Acenolaza, F.G.

1998-01-01

A moderately diverse arthropod icnofauna occurs in ?Permian ephemeral lacustrine deposits of the Paganzo Basin that crop out at Bordo Atravesado, Cuesta de Miranda, western Argentina. Sedimentary successions are interpreted as having accumulated in a playa-lake complex. Deposits include three sedimentary facies: (A) laminated siltstone and mudstone: (B) current-rippled cross-laminated very fine grained sandstone: and (C) climbing and wave-rippled cross-laminated fine-grained sandstone deposited by sheet floods under wave influence in the playa-lake complex. Analysis of facies sequences suggests that repeated vertical facies associations result from transgressive regressive episodes of variable time spans. The Bordo Atravesado ichnofauna includes Cruziana problematica, Diplocraterion isp., cf. Diplopadichnus biformis, Kouphichnium? isp., Merostomichnites aicunai, Mirandaichnium famatinense, Monomorphichnus lineatus, Palaeophyeus tubularis, Umfolozia sinuosa and Umfolozia ef. U. longula. The assemblage is largely dominated by arthropod trackways and represents an example of the Scoyenia ichnofacies. Trace fossils are mostly preserved as hypichnial ridges on the soles of facies C beds, being comparatively rare in facies A and B. Ichnofossil preservation was linked to rapid influx of sand via sheet floods entering into the lake. Four taphonomic variants (types 1-4) are recognized, each determined by substrate consistency and time averaging. Type 1 is recorded by the presence of low density assemblages consisting of poorly defined trackways, which suggests that arthropods crawled in soft, probably slightly subaqueous substrates. Type 2 is represented by low to moderate density suites that include sharply defined trackways commonly associated with mud cracks, suggesting that the tracemakers inhabited a firm, desiccated lacustrine substrate. Type 3 displays features of types 1 and 2 and represents palimpsestic bedding surfaces, resulting from the overprint of terrestrial ichnocoenoses over previously formed softground suites. Type 4 differs from type 2 only in that assemblages display a high density of traces, recorded by numerous superimposed trackways, which suggests a major time gap of subaerial exposure before sheet flood entrance. Therefore, type 4 surfaces are mostly interpreted as track imprinted omission surfaces.

Soft-sediment deformation in a tectonically active area: The Plio-Pleistocene Zarzal Formation in the Cauca Valley (Western Colombia)

NASA Astrophysics Data System (ADS)

Neuwerth, Ralph; Suter, Fiore; Guzman, Carlos A.; Gorin, Georges E.

2006-04-01

The Plio-Pleistocene Zarzal Formation corresponds to fluvio-lacustrine sediments deposited in an intramontane depression within the Colombian Andes, associated with the Cauca-Romeral Fault System. It crops out mainly in the Cauca Valley where numerous field sections have permitted the mapping of the vertical and lateral lithological variations. Lacustrine deposits of sands, silts, clays and diatomites are interbedded with fluvial sand and gravel beds and fluvio-volcanic mass flows derived from the volcanic Central Cordillera. Numerous soft-sediment deformation structures are encountered in this formation, particularly in fine- to medium-grained sands, silts and clays: load structures (load casts, flame structures, pseudonodules), water escape structures (water escape cusps, dish-and-pillar and pocket-and-pillar structures), soft-sediment intrusions (clastic sills and dykes), disturbed laminites, convolute laminations, slumps and synsedimentary faulting. Deformation mechanisms and driving forces are related essentially to gravitational instabilities, dewatering, liquidization and brittle deformations. Field and regional geological data show that most of these deformations are related to seismicity and can be interpreted as seismites. This area has a geological and recent seismic history and outcrops show both syn- and post-depositional faulting related to the transpressional regime of this part of the Colombian Andes, which generates strike-slip faults and associated local normal faults. The drainage pattern within the Zarzal Formation shows the signature of neotectonics. Moreover, the fine to coarse-grained sands of the Zarzal Formation are lithologies prone to liquefaction when affected by seismic waves. The intercalation of the deformed intervals within undisturbed strata confirms the catastrophic nature of the events. Finally, the large areal extent of the deformations and the type of structures are compatible with seismites. Consequently, the existence of seismites in the Zarzal Formation represents corroboration of tectonic activity in this area during the Pleistocene. Earthquakes with a magnitude higher than 5 can be postulated, based upon the proximity of active faults and the types of deformations.

Late Holocene evolution of playa lakes in the central Ebro depression based on geophysical surveys and morpho-stratigraphic analysis of lacustrine terraces

NASA Astrophysics Data System (ADS)

Gutiérrez, F.; Valero-Garcés, B.; Desir, G.; González-Sampériz, P.; Gutiérrez, M.; Linares, R.; Zarroca, M.; Moreno, A.; Guerrero, J.; Roqué, C.; Arnold, L. J.; Demuro, M.

2013-08-01

The origin and morpho-stratigraphic evolution of the largest playa-lake system (La Playa-El Pueyo) in the Bujaraloz-Sástago endorheic area, located in the semiarid central sector of the Ebro Depression, are analysed. The enclosed depressions are developed on gypsiferous Tertiary bedrock and show a prevalent WNW-ESE orientation parallel to the direction of the prevalent strong local wind (Cierzo). Yardangs have been carved in bedrock and unconsolidated terrace deposits in the leeward sector of the largest lake basins. A sequence of three lacustrine terrace levels has been identified by detailed geomorphological mapping. The treads of the upper, middle and lower terrace levels are situated at + 9 m, + 6 m and + 0.5 m above the playa-lake floors, respectively. Seismic refraction and electrical resistivity profiles acquired in La Playa reveal a thin basin fill (~ 2 m) with a planar base. These data allow ruling out the genetic hypothesis for the depressions involving the collapse of large bedrock cavities and support a mixed genesis of combined widespread dissolution and subsidence by groundwater discharge and eolian deflation during dry periods. The 5 m thick deposit of the middle terrace was investigated in hand-dug and backhoe trenches. Six AMS radiocarbon ages from this terrace indicate an aggradation phase between 3.9 ka and ca. 2 ka. These numerical ages yield a maximum average aggradation rate of 2.6 mm/yr and a minimum excavation rate by wind deflation of 3 mm/yr subsequent to the accumulation of the middle terrace. The latter figure compares well with those calculated in several arid regions of the world using yardangs carved in palaeolake deposits. The aggradation phase between 4 and 2 ka is coherent with other Iberian and Mediterranean records showing relatively more humid conditions after 4 ka, including the Iron Ages and the Iberian-Roman Period.

Paleocurrents of the Middle-Upper Jurassic strata in the Paradox Basin, Colorado, inferred from anisotropy of magnetic susceptibility (AMS)

NASA Astrophysics Data System (ADS)

Ejembi, J. I.; Ferre, E. C.; Potter-McIntyre, S. L.

2017-12-01

The Middle-Upper Jurassic sedimentary strata in the southwestern Colorado Plateau recorded pervasive eolian to fluvio-lacustrine deposition in the Paradox Basin. While paleocurrents preserved in the Entrada Sandstone, an eolian deposition in the Middle Jurassic, has been well constrained and show a northwesterly to northeasterly migration of ergs from the south onto the Colorado Plateau, there is yet no clear resolution of the paleocurrents preserved in the Wanakah Formation and Tidwell Member of the Morrison Formation, both of which are important sedimentary sequences in the paleogeographic framework of the Colorado Plateau. New U-Pb detrital zircon geochronology of sandstones from these sequences suggests that an abrupt change in provenance occurred in the early Late Jurassic, with sediments largely sourced from eroding highlands in central Colorado. We measured the anisotropy of magnetic susceptibility (AMS) of sediments in oriented sandstone samples from these three successive sequences; first, to determine the paleocurrents from the orientations of the AMS fabrics in order to delineate the source area and sediments dispersal pattern and second, to determine the depositional mechanisms of the sediments. Preliminary AMS data from two study sites show consistency and clustering of the AMS axes in all the sedimentary sequences. The orientations of the Kmin - Kint planes in the Entrada Sandstone sample point to a NNE-NNW paleocurrent directions, which is in agreement with earlier studies. The orientations of the Kmin - Kint planes in the Wanakah Formation and Tidwell Member samples show W-SW trending paleocurrent directions, corroborating our hypothesis of a shift in provenance to the eroding Ancestral Front Range Mountain, located northeast of the Paradox Basin, during the Late Jurassic. Isothermal remanence magnetization (IRM) of the samples indicate that the primary AMS carriers are detrital, syndepositional ferromagnetic minerals. Thus, we contend that AMS can be successfully deployed in constraining paleocurrents in lacustrine sedimentary strata, which lacks traditional sedimentary structures for paleocurrent analyses.

Quaternary geology of the DFDP-2 drill holes, Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Upton, P.; Cox, S.; Howarth, J. D.; Sutherland, R.; Langridge, R.; Barth, N. C.; Atkins, C.

2015-12-01

A 240 m-thick Quaternary sediment sequence in Whataroa Valley was much thicker than predicted before drilling. DFDP-2A and DFDP-2B were mostly drilled through the sequence by dual-rotary method using air or water circulation, returning cuttings bagged at 1 or 2 m sample intervals. Some sorting/bias and contamination occurred. Core was retrieved in DFDP-2A from 125-160 m, with highly variable recovery (0-100%) and mixed preservation/quality. The sequence is interpreted to comprise: fluvial-glacial gravels (0-58 m); grading downward into sandy lake delta sediments (59-77 m); overlying a monotonous sequence of lake mud and silts, with rare pebble-cobble diamictite (77-206 m); with a basal unit (206-240 m) containing coarse cobbles and boulders that may represent a distinct till/diamictite. Evidence has yet to be found for any marine influence in lowermost sediments, despite deposition at least 120 m below present day sea level, and potentially 200 m bsl if uplift has occurred on the Alpine Fault. When corrected for uplift the lacustrine sequence broadly correlates to those in present Lakes Rotokina and Wahapo, suggesting a substantial (~100 km2) pro-glacial lake once covered the area. Radiocarbon dating of plant fragments indicate 70 m of upper lacustrine and deltaic sediments (129-59 m) were deposited rapidly between 16350-15800 Cal BP. Overlying alluvial gravels are much younger (<1 ka), but potentially also involved pulses of rapid aggradation. The sequence provides a record of sedimentation on the Alpine Fault hanging wall following late-glacial ice retreat up Whataroa Valley, with uplift and erosion followed by Holocene alluvial gravel deposition. Future work will address: (1) the nature and history of sedimentation, including the lithology and origin of sediments; (2) what, if any, geological record of tectonics (movement) or Alpine Fault earthquakes (shaking) the sediments contain.

Trace fossils from Jurassic lacustrine turbidites of the Anyao Formation (Central China) and their environmental and evolutionary significance

USGS Publications Warehouse

Buatois, Luis A.; Mángano, M. Gabriela; Wu, Xiantao; Zhang, Guocheng

1996-01-01

The Lower Jurassic Anyao Formation crops out near Jiyuan city, western Henan Province, central China. It is part of the infill of the nonmarine early Mesozoic Jiyuan‐Yima Basin. In the Jiyuan section, this unit is about 100 m thick and consists of laterally persistent, thin and thick‐bedded turbidite sandstones and mudstones displaying complete and base‐or top‐absent Bouma sequences, and thick‐bedded massive sandstones. The Anyao Formation records sedimentation within a lacustrine turbidite system developed in a pull‐apart basin. Processes involved include high and low density turbidity currents, sometimes affected by liquefaction or fluidization. Facies analysis suggests that this succession is formed by stacked aggradational turbidite lobes. The absence of thick mudstone packages indicates that background sedimentation was subordinate to high frequency turbidite deposition.The Anyao Formation hosts a moderately diverse ichnofauna preserved as hypichnial casts on the soles of thin‐bedded turbidite sandstones. The ichnofauna consists of Cochlichnus anguineus, Hel‐minthoidichnites tenuis, Helminthopsis abeli, H. hieroglyphica, Mono‐morphichnus lineatus, Paracanthorhaphe togwunia, Tuberculichnus vagans, Vagorichnus anyao, tiny grazing trails, and irregularly branching burrows. Vagorichnus anyao occurs not only as a discrete trace, but also as a compound ichnotaxon intergrading with Gordia marina and Tuberculichnus vagans. Both predepositional and post‐depositional traces are present on the soles of turbidites.This ichnofauna comprises both feeding and grazing traces produced by a deposit‐feeding lacustrine benthic biota. Crawling traces are rare. Although certain ichnofossils (e.g. V. anyao, P. togwunia) show overall similarities with deep‐sea agrichnia, they differ in reflecting remarkably less specialized feeding strategies, displaying overcrossing between specimens (and to a lesser extent, self‐crossing), and in the case of V’ anyaorecording post‐turbidite burrowing activity. The development of less specialized strategies than those displayed by deep‐marine ichnofaunas may be related to less stable conditions, typical of lake settings. Oxyenation, energy, sedimentation rate (both event and background), food supply, soft‐sediment deformation and erosion rate have mainly influenced trace‐fossil distribution. Turbidity currents would have ensured oxygen (as well as food) supply to deep lake settings, thus allowing the establishment of a moderately diverse biota. Biogenic structures were mostly confined to the outer, low energy areas. High sedimentation rates and strong erosion precluded preservation of ichnofossils in inner lobe settings.The Anyao ichnofauna is of significance in furthering knowledge of the colonization of deep lakes throughout the stratigraphie record and in identification of additional nonmarine ichnofacies. The ana‐lyzed ichnofauna resembles late Paleozoic lacustrine assemblages described from different localities around the world and is regarded as a Mesozoic example of the Mermia ichnofacies. However, when compared with Paleozoic assemblages, the Anyao ichnofauna shows a clear dominance of burrows over surface trails, deeper burrowing penetration, larger size, and presence of relatively more complex structures. The high burrow/surface trail ratio may be indicative of lower preservation potential in the latter, thus reflecting a tap‐honomic overprint. In contrast to the Paleozoic examples, the establishment of a relatively well‐developed lacustrine infauna may have precluded preservation of surface trails. Burrower activity probably obliterated biogenic structures formed close to the sediment‐water interface.

Marine and Lacustrine Organic-rich Sedimentary Unit Time Markers: Implications from Rhenium-Osmium Geochronology

NASA Astrophysics Data System (ADS)

Selby, D.

2011-12-01

Geochronology is fundamental to understand the age, rates and durations of Earth processes. This concerned Arthur Holmes who, for much of his career, attempted to define a geological time scale. This is a topic still important to Earth Scientists today, specifically the chronostratigraphy of sedimentary rocks. Here I explore the Re-Os geochronology of marine and lacustrine sedimentary rocks and its application to yield absolute time constraints for stratigraphy. The past decade has seen the pioneering research of Re-Os organic-rich sedimentary rock geochronology blossom into a tool that can now to be used to accurately and precisely determine depositional ages of organic-rich rock units that have experienced up to low grade greenschist metamorphism. This direct dating of sedimentary rocks is critical where volcanic horizons are absent. As a result, this tool has been applied to timescale calibration, basin correlation, formation duration and the timing of key Earth events (e.g., Neoproterozoic glaciations). The application of Re-Os chronometer to the Devonian-Mississippian boundary contained within the Exshaw Formation, Canada, determined an age of 361.3 ± 2.4 Ma. This age is in accord with U-Pb dates of interbedded tuff horizons and also U-Pb zircon date for the type Devonian-Mississippian Hasselbachtal section, Germany. The agreement of the biostratigraphic and U-Pb constraints of the Exshaw Formation with the Re-Os date illustrated the potential of the Re-Os chronometer to yield age determinations for sedimentary packages, especially in the absence of interbedd tuff horizons and biozones. A Re-Os date for the proposed type section of the Oxfordian-Kimmeridgian boundary, Staffin Bay, Isle of Skye, U.K., gave an age of 154.1 ± 2.2 Ma. This Re-Os age presents a 45 % (1.8 Ma) improvement in precision for the basal Kimmeridgian. It also demonstrated that the duration of the Kimmeridgian is nominally 3.3 Ma and thus is 1.6 Ma shorter than previously indicated. In addition to these examples, several studies have presented precise dates for Phanerozoic marine organic-rich units that are in excellent agreement with biostratigraphic determinations. A recent Re-Os study of the Woodford Shale (that was deposited throughout the Frasnian and Famennian) has provided important time markers as well as suggesting that the sedimentation rate of the Formation was relatively constant for ~20 Ma. To date only marine organic-rich sedimentary rocks have been utilized for Re-Os geochronology. However, lacustrine sedimentary rocks provide an invaluable archive of continental geological processes responding to tectonic, climatic and magmatic influences. Correlating these rocks to global geological phenomena requires accurate geochronological frameworks. The organic-rich lacustrine sedimentary units of the Eocene Green River Formation are enriched is Re and Os comparable to that of marine units. The Re-Os dates for the Green River Formation from the Uinta basin are 48.5 ± 0.6 Ma and 49.2 ± 1.0 Ma. These dates are in excellent agreement with Ar/Ar and U/Pb dates of interbedded tuffs in the GRF, therefore demonstrating that lacustrine units can be used for Re-Os geochronology in addition to marine organic-rich units.

Hot-spring sinter deposits in the Alvord-Pueblo Valley, Harney County, Oregon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cummings, M.L.; St. John, A.M.

1993-04-01

Silica sinter deposits occur at Borax Lake, Alvord Hot Springs, and Mickey Springs in the Alvord-Pueblo Valley. Although the sinter deposits occur in areas of active hot springs, sinter is not being deposited. Hot springs are localized along faults that have been active since the Pleistocene. The sinter deposits formed after the drying of glacial Lake Alvord, but before and during extensive wind deflation of glacial-lacustrine sediments. At Mickey Springs, sinter rests directly on unaltered, unconsolidated lithic-rich sand. At Borax Lake, sinter overlies unaltered diatomite, but some armoring, presumably by silica, of the 30 m vent has developed. Field relationsmore » suggest rapid dumping of silica from solution without alteration of the country rock at the vent. Discharge of thermal fluids and cold groundwater along the same structure may have produced colloidal silica carried in a solution stripped of dissolved silica. Sinter is composed of opal-a, traces of detrital feldspar and quartz, and evaporation-related boracite. The concentration of Sb is similar among the three sinter deposits (20 to 70 ppm); however, As, Cs, and Br are highest at Borax Lake (5 to 560 ppm; 26 to 118 ppm; 5 to 1,040 ppm) while Hg is highest at Mickey Springs (1.0 to 5.2 ppm).« less

Abiotically-formed, primary dolomite in the mid-Eocene lacustrine succession at Gebel El-Goza El-Hamra, NE Egypt: An approach to the role of smectitic clays

NASA Astrophysics Data System (ADS)

Wanas, H. A.; Sallam, E.

2016-08-01

This study discusses the role of smectitic clays in the formation of an abiotic (physio-chemical) primary dolomite within an evaporative alkaline-saline marginal lake system, in the absence of carbonate precursor and microbes. The present work has been achieved in terms of textural, mineralogical, and geochemical characteristics of dolostones in the Mid-Eocene (Bartonian) lacustrine succession cropping out at Gebel El-Goza El-Hamra (Shabrawet area, NE Egypt). This lacustrine succession is 15-16 m thick, and made up of alternating horizontal beds of dolostone, marlstone and mudrock that show some pedogenic and subaerial exposure features. The dolostones are composed mainly of dolomite (60-90%), smectite (20-30%) and quartz grains (5-10%). The dolomite comprises fine-crystalline rhombs to micro-spherical crystals with no obvious relics of microbial activity and/or carbonate precursor. It is, ordered, nearly stoichiometric (with 46-50% mole of MgCO3) and has δ18O and δ13C values ranging from + 0.44 to + 2.96 VPDB ‰, and 0.93 to - 8.95 VPDB ‰, respectively. The smectite occurs as thin mats that are commonly intergrown and associated with dolomite. Mineralogical, textural and stable isotopic results of the dolomite indicated that the dolomite was formed as an abiotic primary precipitate in alkaline saline lacustrine systems. In this respect, the gel-like highly viscous smectitic medium plus progressive CO2 degassing, elevated evaporation, low sedimentation rate, low sulphates level and alkaline soil solution lowered the kinetic barriers of dolomite precipitation from solution and promoted the incorporation of Mg2 + in the structure of dolomite. Consequently, the presence of smectitic clays in evaporative saline lakes is significant for dolomite formation because they can generate a gel-like highly viscous medium and provide Mg2 + that can facilitate the physcio-chemical precipitation of primary dolomite from solution at ambient temperatures. However, more work is needed to better characterize the role of clays during dolomite formation in alkaline lacustrine environments at ambient temperatures.

Palaeoecological aspects of some invertebrate trace fossils from the mid- to Upper Permian Middleton Formation (Adelaide Subgroup, Beaufort Group, Karoo Supergroup), Eastern Cape, South Africa

NASA Astrophysics Data System (ADS)

Bordy, Emese M.; Linkermann, Sean; Prevec, Rose

2011-10-01

Ichnological and sedimentological analyses in the Eastern Cape allowed the first description of a Cochlichnus-dominated ichnofossil site from the mid- to Upper Permian Middleton Formation (Karoo Supergroup) in South Africa. The locality is within the uppermost Pristerognathus Assemblage Zone, a biostratigraphic interval characterized by a low vertebrate biodiversity at the turn of the mid- to Late Permian. Our field data indicates that the surficial bioturbation of very fine to fine-grained sand layers resulted from life activities of shallow infaunal and epifaunal invertebrates (possibly annelids, aquatic oligochaetes, nematodes, insect larvae) and fish. The morphology of the trails, their relationship to the substrate and the behaviour inferred from them indicate that the tracemakers developed a strategy that facilitated the optimization of low food resources in a permanently submerged freshwater setting. Combined ichnological and sedimentological evidence suggests a low-energy, freshwater lacustrine depositional environment, where occasional higher energy currents brought nutrients. Data also imply that colonization of these erratic event beds by opportunistic sediment-feeders was short-lived and followed by longer intervals of lower energy deposition under possibly poorly oxygenated conditions. We propose that these event beds as well as the sporadic red mudstones of the Middleton Formation may have formed during short-term, higher storm-frequency and dryer periods, signalling changes in the otherwise humid climate in this part of the main Karoo Basin during the mid- to Late Permian.

Characteristics of Impact Craters and Interior Deposits: Analysis of the Spatial and Temporal Distribution of Volatiles in the Highlands of Mars

NASA Technical Reports Server (NTRS)

Mest, S. C.

2005-01-01

The martian southern highlands contain impact craters that display pristine to degraded morphologies, and preserve a record of degradation that can be attributed to fluvial, eolian, mass wasting, volcanic and impact-related processes. However, the relative degree of modification by these processes and the amounts of material contributed to crater interiors are not well constrained. Impact craters (D>10 km) within Terra Cimmeria (0deg-60degS, 190deg-240degW), Terra Tyrrhena (0deg-30degS, 260deg-310degW) and Noachis Terra (20deg-50degS, 310deg-340degW) are being examined to better understand the degradational history and evolution of highland terrains. The following scientific objectives will be accomplished. 1) Determine the geologic processes that modified impact craters (and surrounding highland terrains). 2) Determine the sources (e.g. fluvial, lacustrine, eolian, mass wasting, volcanic, impact melt) and relative amounts of material composing crater interior deposits. 3) Document the relationships between impact crater degradation and highland fluvial systems. 4) Determine the spatial and temporal relationships between degradational processes on local and regional scales. And 5) develop models of impact crater (and highland) degradation that can be applied to these and other areas of the martian highlands. The results of this study will be used to constrain the geologic, hydrologic and climatic evolution of Mars and identify environments in which subsurface water might be present or evidence for biologic activity might be preserved.

Periodic jökulhlaups from Pleistocene glacial Lake Missoula-New evidence from varved sediment in northern Idaho and Washington

USGS Publications Warehouse

Waitt, Richard B.

1984-01-01

Newly examined exposures in northern Idaho and Washington show that catastrophic floods from glacial Lake Missoula during late Wisconsin time were repeated, brief jökulhlaups separated by decades of quiet glaciolacustrine and subaerial conditions. Glacial Priest Lake, dammed in the Priest River valley by a tongue of the Purcell trench lobe of the Cordilleran ice sheet, generally accumulated varved mud; the varved mud is sharply interrupted by 14 sand beds deposited by upvalley-running currents. The sand beds are texturally and structurally similar to slackwater sediment in valleys in southern Washington that were backflooded by outbursts from glacial Lake Missoula. Beds of varved mud also accumulated in glacial Lake Spokane (or Columbia?) in Latah Creek valley and elsewhere in northeastern Washington; the mud beds were disrupted, in places violently, during emplacement of each of 16 or more thick flood-gravel beds. This history corroborates evidence from southern Washington that only one graded bed is deposited per flood, refuting a conventional idea that many beds accumulated per flood. The total number of such floodlaid beds in stratigraphic succession near Spokane is at least 28. The mud beds between most of the floodlaid beds in these valleys each consist of between 20 and 55 silt-to-clay varves. Lacustrine environments in northern Idaho and Washington therefore persisted for two to six decades between regularly recurring, colossal floods from glacial Lake Missoula.

The Impact of Elevated Temperatures on Continental Carbon Cycling in the Paleogene

NASA Astrophysics Data System (ADS)

Pancost, R. D.; Handley, L.; Taylor, K. W.; Collinson, M. E.; Weijers, J.; Talbot, H. M.; Hollis, C. J.; Grogan, D. S.; Whiteside, J. H.

2010-12-01

Recent climate and biogeochemical modelling suggests that methane flux from wetlands and soils was greater during past greenhouse climates, due to a combination of higher continental temperatures, an enhanced hydrological cycle, and elevated primary production. Here, we examine continental environments in the Paleogene using a range of biomarker proxies (complemented by palaeobotanical approaches), including air temperatures derived from the distribution of soil bacterial glycerol dialkyl glycerol tetraethers (the MBT/CBT proxy), as well as evidence from wetland and lacustrine settings for enhanced methane cycling. Previously published and new MBT/CBT records parallel sea surface temperature records, suggesting elevated continental temperatures during the Eocene even at mid- to high latitudes (New Zealand, 20-28°C; the Arctic, 17°C; across the Sierra Nevada, 15-25°C; and SE England, 20-30°C). Such temperatures are broadly consistent with paleobotanical records and would have directly led to increased methane production via the metabolic impact of temperature on rates of methanogenesis. To test this, we have determined the distributions and carbon isotopic compositions of archaeal ether lipids and bacterial hopanoids in thermally immature Eocene lignites. In particular, the Cobham lignite, deposited in SE England and spanning the PETM, is characterised by markedly higher concentrations of both methanogen and methanotroph biomarkers compared to modern and Holocene temperate peats. Elevated temperatures, by fostering either stratification and/or decreased oxygen solubility, could have also led to enhanced methane production in Paleogene lakes. Both the Messel Shale (Germany) and Green River Formation, specifically the Parachute Creek oil shale horizons (Utah and Wyoming), are characterised by strongly reducing conditions (including euxinic conditions in the latter), as well as abundant methanogen and methanotroph biomarkers. Such results confirm model predictions of elevated Eocene methane levels relative to the Holocene (x10), but suggest that even these could be underestimates as they do not take into account lacustrine production and are generally characterised by lower high latitude temperatures than proxies suggest.

Multiple Magma Batches Recorded in Tephra Deposits from the Toba Complex, Sumatra.

NASA Astrophysics Data System (ADS)

Pearce, N. J. G.; Westgate, J.; Gatti, E.

2015-12-01

The Toba Caldera Complex is the largest Quaternary caldera on Earth, and has generated three voluminous and compositionally similar rhyolitic tuffs, viz. the Oldest (OTT, 800 ka), Middle (MTT, ~500 ka) and Youngest Toba Tuffs (YTT, 75 ka). These tephra deposits are widespread across Indonesia, Malaysia, South China Sea, Sea of Bengal, India and Indian Ocean and provide useful stratigraphic markers in oceanic, lacustrine and terrestrial environments. Single shard trace element analysis of these deposits reveals the changing availability of different batches of magma through time, with Sr, Ba and Y contents defining 5 discrete magma populations in YTT, 4 populations in MTT and only a single, low Ba population in OTT. Within an individual eruption these populations are clearly distinct, but between eruptions (e.g. MTT and YTT) some of these populations overlap while others do not, indicating both the longevity (and/or continuous supply of fresh material) and evolution of these magma batches in the Toba Complex. Major element compositions of the different groups show equilibration at different pressures (based on Q'-Ab'-Or'), with the equilibration of low Ba populations at ~160 MPa, increasing to depths of ~210 MPa for the highest Ba population. The proportions of different populations of glass in distal YTT shows that relatively little of the high Ba population makes it into the distal record across India, and that this population appears to be over-represented in the proximal free glass and pumice from the caldera walls. This data may shed light on magma availability and tephra dispersal during the YTT eruption. Similarly, the glass composition of individual pumices from proximal deposits record regional, compositional and temporal differences in the erupted products. These show, for example, the apparent mingling of some of the magma batches and also that the high Ba population appears early (i.e. stratigraphically lower) in the northern caldera wall.

Styles and timing of volatile-driven activity in the eastern Hellas region of Mars

NASA Astrophysics Data System (ADS)

Crown, David A.; Bleamaster, Leslie F.; Mest, Scott C.

2005-12-01

Recent analyses of Mars Global Surveyor and Mars Odyssey data sets provide new insights into the geologic evolution of the eastern Hellas region of Mars, in particular, the role of volatiles. Here, we present results of our recent work and integrate these with previous studies by various investigators to provide a synthesis of the history of volatile-driven activity of the region. We utilize high-resolution images from the Mars Orbiter Camera and Thermal Emission Imaging System combined with Mars Orbiter Laser Altimeter digital elevation models and profiles to examine fluvial systems that dissect the circum-Hellas highlands, to characterize stages in the development of the Dao, Niger, Harmakhis, and Reull Valles canyon systems, and to evaluate evidence for ancient lakes in Hellas Planitia. The occurrence of valley networks, dissected highland crater rims, and crater interior deposits such as layered plateaus suggests widespread ancient degradation of the circum-Hellas highlands. Canyon development, which represents subsequent more localized activity, may have included an early fluvial phase followed by the collapse and sapping dominated stages that, along with recent wall erosion and floor resurfacing, produced the currently observed morphologies. The prominent role of collapse and sapping along the east rim of Hellas, along with the presence of numerous channels extending toward the basin and sequences of finely layered deposits along the basin rim, suggests a volatile-rich substrate across a broad depositional shelf. The east rim of the basin was an accumulation zone for atmospheric volatiles and/or the edge of volatile-rich deposits associated with the basin floor. This evidence combined with topographic data and cratered terrain preservation around the basin is consistent with a lacustrine period or periods in early Martian history. The style, magnitude, and spatial extent of volatile-driven activity in eastern Hellas have varied considerably with time, and these variations may represent a transition from a water- to an ice-dominated surface environment.

Holocene intramontane lake development: A new model in the Jáchal River Valley, Andean Precordillera, San Juan, Argentina

NASA Astrophysics Data System (ADS)

Colombo, Ferran; Busquets, Pere; Sole de Porta, Nuria; Limarino, Carlos Oscar; Heredia, Nemesio; Rodriguez-Fernandez, Luis Roberto; Alvarez-Marron, Joaquina

2009-10-01

The Jáchal River Valley displays a number of significant Holocene sedimentary accumulations made up of fine-grained materials. These deposits are interpreted as the sedimentary infill of shallow temporary lakes that were generated by slow growing episodes of alluvial fans that obstructed the Jáchal River Valley. The association of fossil remains through the Holocene sedimentary sequence suggests that the accumulation of lacustrine sediments was affected by climate variations. The predominant aridity was punctuated by very few humid episodes characterised by fresh-water gastropoda and the intercalations of muddy sediments. The high proportion of charcoal particles in some samples indicates periodic forest fires. Abundant non-pollen forest remains suggest that an open zone dominated by several types of grasses underwent a dry season during part of the year. The palynomorph associations found in the Jáchal River Valley Holocene lacustrine sediments suggest that the humid conditions were less intense than those in the San Juan River Valley located more than one hundred kilometres southwards. Our study suggests that lake formation could have been controlled by climate oscillation probably related to the ENSO variation at 30° south latitude.

Zeolitization of intracaldera sediments and rhyolitic rocks in the 1.25 Ma lake of Valles caldera, New Mexico, USA

NASA Astrophysics Data System (ADS)

Chipera, Steve J.; Goff, Fraser; Goff, Cathy J.; Fittipaldo, Melissa

2008-12-01

Quantitative X-ray diffraction analysis of about 80 rhyolite and associated lacustrine rocks has characterized previously unrecognized zeolitic alteration throughout the Valles caldera resurgent dome. The alteration assemblage consists primarily of smectite-clinoptilolite-mordenite-silica, which replaces groundmass and fills voids, especially in the tuffs and lacustrine rocks. Original rock textures are routinely preserved. Mineralization typically extends to depths of only a few tens of meters and resembles shallow "caldera-type zeolitization" as defined by Utada et al. [Utada, M., Shimizu, M., Ito, T., Inoue, A., 1999. Alteration of caldera-forming rocks related to the Sanzugawa volcanotectonic depression, northeast Honshu, Japan — with special reference to "caldera-type zeolitization." Resource Geol. Spec. Issue No. 20, 129-140]. Geology and 40Ar/ 39Ar dates limit the period of extensive zeolite growth to roughly the first 30 kyr after the current caldera formed (ca. 1.25 to 1.22 Ma). Zeolitic alteration was promoted by saturation of shallow rocks with alkaline lake water (a mixture of meteoric waters and degassed hydrothermal fluids) and by high thermal gradients caused by cooling of the underlying magma body and earliest post-caldera rhyolite eruptions. Zeolitic alteration of this type is not found in the later volcanic and lacustrine rocks of the caldera moat (≤ 0.8 Ma) suggesting that later lake waters were cooler and less alkaline. The shallow zeolitic alteration does not have characteristics resembling classic, alkaline lake zeolite deposits (no analcime, erionite, or chabazite) nor does it contain zeolites common in high-temperature hydrothermal systems (laumontite or wairakite). Although aerially extensive, the early zeolitic alteration does not form laterally continuous beds and are consequently, not of economic significance.

Miocene to recent history of the western Altiplano in northern Chile revealed by lacustrine sediments of the Lauca basin (18°15' 18°40' S/69°30' 69°05'W)

NASA Astrophysics Data System (ADS)

Kött, A.; Gaupp, R.; Wörner, G.

1995-12-01

The intramontane Lauca Basin at the western margin of the northern Chilean Altiplano lies to the west of and is topographically isolated from the well-known Plio-Pleistocene lake system of fluvio-lacustrine origin that covers the Bolivian Altiplano from Lake Titicaca to the north for more than 800 km to the Salar de Uyuni in the south. The Lauca Basin is filled by a sequence of some 120 m of mainly upper Miocene to Pliocene elastic and volcaniclastic sediments of lacustrine and alluvial origin. Volcanic rocks, partly pyroelastic, provide useful marker horizons. In the first period (6 4 Ma) of its evolution, the ‘Lago Lauca’ was a shallow ephemeral lake. Evaporites indicate temporarily closed conditions. After 4 Ma the lake changed to a perennial water body surrounded by alluvial plains. In the late Pleistocene and Holocene (2-0 Ma) there was only marginal deposition of alluvial and glacial sediments. The basin formed as a half-graben or by pull-apart between 10 and 15 Ma (tectonic displacement of the basal ignimbrite sequence during the ‘Quechua Phase’) and 6.2 Ma (maximum K/Ar ages of biotites of tuff horizons in the deepest part of the basin). Apart from this early basin formation, there has been surprisingly little displacement during the past 6 Ma close to the Western Cordillera of the Altiplano. Also, climate indicators (pollen, evaporites, sedimentary facies) suggest that an arid climate has existed for the past 6 Ma on the Altiplano. Together, these pieces of evidence indicate the absence of large scale block-faulting, tilt and major uplift during the past 5 6 Ma in this area.

Miocene to Recent history of the western Altiplano in northern Chile revealed by lacustrine sediments of the Lauca Basin (18°15'-18°40'S/69°30'-69°05'W)

NASA Astrophysics Data System (ADS)

Kött, A.; Gaupp, R.; Wörner, G.

The intramontane Lauca Basin at the western margin of the northern Chilean Altiplano lies to the west of and is topographically isolated from the well-known Plio-Pleistocene lake system of fluvio-lacustrine origin that covers the Bolivian Altiplano from Lake Titicaca to the north for more than 800km to the Salar de Uyuni in the south. The Lauca Basin is filled by a sequence of some 120m of mainly upper Miocene to Pliocene clastic and volcaniclastic sediments of lacustrine and alluvial origin. Volcanic rocks, partly pyroclastic, provide useful marker horizons. In the first period (6-4Ma) of its evolution, the 'Lago Lauca' was a shallow ephemeral lake. Evaporites indicate temporarily closed conditions. After 4Ma the lake changed to a perennial water body surrounded by alluvial plains. In the late Pleistocene and Holocene (2-0Ma) there was only marginal deposition of alluvial and glacial sediments. The basin formed as a half-graben or by pull-apart between 10 and 15Ma (tectonic displacement of the basal ignimbrite sequence during the 'Quechua Phase') and 6.2Ma (maximum K/Ar ages of biotites of tuff horizons in the deepest part of the basin). Apart from this early basin formation, there has been surprisingly little displacement during the past 6Ma close to the Western Cordillera of the Altiplano. Also, climate indicators (pollen, evaporites, sedimentary facies) suggest that an arid climate has existed for the past 6Ma on the Altiplano. Together, these pieces of evidence indicate the absence of large scale block-faulting, tilt and major uplift during the past 5-6Ma in this area.

Late Glacial and Holocene Climate Change in the subantarctic Auckland Islands

NASA Astrophysics Data System (ADS)

Gilmer, G.; Moy, C. M.; Vandergoes, M.; Gadd, P.; Riesselman, C. R.; Jacobsen, G. E.; Wilson, G. S.; Visinand, C.

2017-12-01

Situated within the core of the Southern Hemisphere westerly winds, and between the subtropical and subantarctic fronts, the New Zealand subantarctic islands are uniquely positioned to evaluate past ocean and atmospheric change in the middle to high southern latitudes. We collected a series of sediment cores from Auckland Island fjords to produce a high-resolution record of climate change following the Last Glacial Maximum. Physical property and organic geochemical data, Itrax XRF, and visual core descriptions indicate the cores capture several phases of sedimentation. From these studies, we identify four primary sedimentary facies: 1) a deglacial facies exhibiting mm-scale laminae defined by magnetic susceptibility and density contrasts and high counts of elements associated with terrigenous sources; 2) a lacustrine facies defined by very low density, high organic carbon concentrations and low counts of lithophilic elements; 3) a marine transgression facies with moderate density, moderate bioturbation and alternating marine and lacustrine sedimentary components; 4) a marine facies that contains biogenic carbonate. Radiocarbon results indicate deglacial sedimentation was underway in the basin by approximately 19,000 cal yr BP. Lacustrine deposition in ice-free conditions began around 15,600 cal yr BP and continued until marine transgression at approximately 9,500 cal yr BP. During the early Holocene between 11 and 9.5 ka, we observe elevated n-alkane δD values and an overall increase in redox-sensitive elements that signal a combination of warmer atmospheric temperatures and reduced westerly wind strength that drives fjord stratification. Poleward-shifted westerlies south of the Auckland Islands could accommodate these results, but there are few records to corroborate this interpretation. We will discuss these results within the context of developing New Zealand and subantarctic paleoclimate records in order to provide a more comprehensive record of past change.

Unraveling the mineralogy of delta deposits on Mars

NASA Astrophysics Data System (ADS)

Osterloo, Mikki; Kierein-Young, Kathryn

2017-04-01

Detailed geologic characterizations of three of 50+ fan deltas on Mars have yielded important information on their mineralogy as well as formation processes. Data returned from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) have been used to identify spectroscopic signatures consistent with phyllosilicates in fans or deltas within paleolake basins (i.e., Eberswalde, Holden, and Jezero) that indicate sustained subaqueous sediment deposition. Based on these results, two periods of martian history have been identified when the surface or near surface may have been habitable: (1) during the formation of the iron-magnesium smectite clays, likely in the Early Noachian and (2) during the Late Noachian to Early Hesperian fluvial surface activity that led to the formation of Jezero lake. On Earth, rapid deposition of deltaic sediments can preserve organic materials; hence Martian fan deltas may be ideal environments to investigate the past habitability of the planet. Rapid burial coupled with the identification of phyllosilicates within at least some of the martian deltas makes an even more intriguing argument for further investigation of the remainder of deltas. This is because phyllosilicates, and specifically smectite clays, have the ability to trap organic matter in the interlayer sites of their mineral structures and in terrestrial settings are commonly associated with the most organic rich units. Organic materials that were transported into paleolakes would likely have been buried relatively quickly. Hence, the organics would have been protected within the clay-rich deltaic and lacustrine deposits from oxidation and photochemical dissociation. We will present the initial results of a comprehensive study designed to investigate the compositional and mineralogical variability of the remainder of dust-free, previously un-characterized deltas on Mars (of which, there are 33). Our study aims to provide key information regarding differences in formation and preservation processes between the fan delta deposits. Our initial survey of the deltas indicates that almost all sites contain minor phyllosilicate detections, however only nine sites have significant abundances (i.e., spatially cohesive mapped deposits). Most of the phyllosilicate deposits consist of Fe/Mg clays such as nontronite and saponite, with a few sites showing detections of minor amounts of Al clays. Geologic observations indicate that most of the clays outcrop along the bottom edge of the deltas with a few sites showing a larger band of clays located just beyond the base of the delta. HiRISE images provide additional small-scale geologic context and indicate that most of the clay deposits are exposed as thin erosional layers. When clay deposits are located beyond the base of the delta they are typically more massive in outcrop. Our ongoing morphological, watershed, and catchment basin investigations will provide additional constraints on the style and extent of hydrologic activity. Coupling our detailed spectroscopic characterization with our ongoing work will provide key information on the geologic processes that produced the mineralogical diversity of martian deltas and will likely provide important clues regarding the past habitability of these environments.

Coastal geomorphology of the Martian northern plains

NASA Technical Reports Server (NTRS)

Parker, Timothy J.; Gorsline, Donn S.; Saunders, Stephen R.; Pieri, David C.; Schneeberger, Dale M.

1993-01-01

The paper considers the question of the formation of the outflow channels and valley networks discovered on the Martian northern plains during the Mariner 9 mission. Parker and Saunders (1987) and Parker et al. (1987, 1989) data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains. It is suggested, that of the geological processes capable of producing similar morphologies on earth, lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on Mars.

First Pleistocene faunas from the Arabian Peninsula: An Nafud desert, Saudi Arabia

NASA Astrophysics Data System (ADS)

Thomas, Herbert; Geraads, Denis; Vaslet, Denis; Memesh, Abdallah; Billiou, Daniel; Bocherens, Hervé; Dobigny, Gauthier; Eisenmann, Véra; Gayet, Mireille; France de Lapparent de Broin; Petter, Germaine; Halawani, Mohammed

1998-01-01

Three Pleistocene vertebrate localities in lacustrine deposits which accumulated in interdune depressions were discovered in the south-western part of the An Nafud sand sea (northern Saudi Arabia). Although the fossil vertebrate fauna is restricted in diversity, its composition and stage of evolution suggest an Early Pleistocene age in contrast with the recent Pleistocene or Holocene lake beds occurring in several other interdune depressions in central and southern An Nafud. The Nafud fauna has clear African affinities whereas faunas from the Levant, dating from the Middle Pleistocene onwards, contain typically European elements.

Petrographic and geochemical evidence for the formation of primary, bacterially induced lacustrine dolomite: La Roda 'white earth' (Pliocene, Central Spain)

USGS Publications Warehouse

Garcia, Del; Cura, M.A.; Calvo, J.P.; Ordonez, S.; Jones, B.F.; Canaveras, J.C.

2001-01-01

Upper Pliocene dolomites ('white earth') from La Roda, Spain, offer a good opportunity to evaluate the process of dolomite formation in lakes. The relatively young nature of the deposits could allow a link between dolomites precipitated in modern lake systems and those present in older lacustrine formations. The La Roda Mg-carbonates (dolomite unit) occur as a 3??5- to 4-m- thick package of poorly indurated, white, massive dolomite beds with interbedded thin deposits of porous carbonate displaying root and desiccation traces as well as local lenticular gypsum moulds. The massive dolomite beds consist mainly of loosely packed 1- to 2-??m-sized aggregates of dolomite crystals exhibiting poorly developed faces, which usually results in a subrounded morphology of the crystals. Minute rhombs of dolomite are sparse within the aggregates. Both knobbly textures and clumps of spherical bodies covering the crystal surfaces indicate that bacteria were involved in the formation of the dolomites. In addition, aggregates of euhedral dolomite crystals are usually present in some more clayey (sepiolite) interbeds. The thin porous carbonate (mostly dolomite) beds exhibit both euhedral and subrounded, bacterially induced dolomite crystals. The carbonate is mainly Ca-dolomite (51-54 mol% CaCO3), showing a low degree of ordering (degree of ordering ranges from 0??27 to 0??48). Calcite is present as a subordinate mineral in some samples. Sr, Mn and Fe contents show very low correlation coefficients with Mg/Ca ratios, whereas SiO2 and K contents are highly correlated. ??18O- and ??13C-values in dolomites range from -3??07??? to 5??40??? PDB (mean = 0??06, ?? = 1??75) and from -6??34??? to -0??39??? PDB (mean = -3??55, ?? = 1??33) respectively. Samples containing significant amounts of both dolomite and calcite do not in general show significant enrichment or depletion in 18O and 13C between the two minerals. The correlation coefficient between ??18O and ??13C for dolomite is extremely low and negative (r = -0??05), whereas it is higher and positive (r = 0??47) for calcite. The lacustrine dolomite deposit from La Roda is interpreted mainly as a result of primary precipitation of dolomite in a shallow, hydrologically closed perennial lake. The lake was supplied by highly saturated HCO3-/CO32- groundwater that leached dolomitic Mesozoic formations. Precipitation of dolomite from alkaline lake waters took place under a semi-arid to arid climate. However, according to our isotopic data, strong evaporative conditions were not required for the formation of the La Roda dolomite. A significant contribution by bacteria to the formation of the dolomites is assumed in view of both petrographic and geochemical evidence.

Uplift sequence of the Andes at 30°S: Insights from sedimentology and U/Pb dating of synorogenic deposits

NASA Astrophysics Data System (ADS)

Suriano, J.; Mardonez, D.; Mahoney, J. B.; Mescua, J. F.; Giambiagi, L. B.; Kimbrough, D.; Lossada, A.

2017-04-01

The South Central Andes at 30°S represent a key area to understand the Andes geodynamics as it is in the middle of the flat slab segment and all the morphotectonic units of the Central Andes are well developed. This work is focused in the proximal synorogenic deposits of the Western Precordillera, in the La Tranca valley, in order to unravel the uplift sequence of this belt. Nine facies associations were recognized; most of them represent piedmont facies with local provenance from Precordillera and were deposited in the wedge-top depozone, as is expected for proximal sinorogenic deposits. However there are intercalations of transference fluvial systems, which show mixed provenance indicating that Permo-Triassic igneous rocks were already exposed to the west (Frontal Cordillera). There are also lacustrine deposits which are interpreted as the result of damming by fault activity at east of the studied basin. Finally, two maximum depositional ages at ca. 11 Ma and 8 Ma of these deposits indicate that the onset of uplift of the Precordillera at 30°S is little older than 11 Ma. These data change two previous ideas about the evolution of the Precordillera: its uplift at 30° S is younger than proposed by previous works and it is nearly synchronous along strike.

Stepped fans and facies-equivalent phyllosilicates in Coprates Catena, Mars

NASA Astrophysics Data System (ADS)

Grindrod, P. M.; Warner, N. H.; Hobley, D. E. J.; Schwartz, C.; Gupta, S.

2018-06-01

Stepped fan deposits and phyllosilicate mineralogies are relatively common features on Mars but have not previously been found in association with each other. Both of these features are widely accepted to be the result of aqueous processes, but the assumed role and nature of any water varies. In this study we have investigated two stepped fan deposits in Coprates Catena, Mars, which have a genetic link to light-toned material that is rich in Fe-Mg phyllosilicate phases. Although of different sizes and in separate, but adjacent, trough-like depressions, we identify similar features at these stepped fans and phyllosilicates that are indicative of similar formation conditions and processes. Our observations of the overall geomorphology, mineralogy and chronology of these features are consistent with a two stage formation process, whereby deposition in the troughs first occurs into shallow standing water or playas, forming fluvial or alluvial fans that terminate in delta deposits and interfinger with interpreted lacustrine facies, with a later period of deposition under sub-aerial conditions, forming alluvial fan deposits. We suggest that the distinctive stepped appearance of these fans is the result of aeolian erosion, and is not a primary depositional feature. This combined formation framework for stepped fans and phyllosilicates can also explain other similar features on Mars, and adds to the growing evidence of fluvial activity in the equatorial region of Mars during the Hesperian and Amazonian.

Improving age-depth models using sedimentary proxies for accumulation rates in fluvio-lacustrine deposits

NASA Astrophysics Data System (ADS)

Minderhoud, Philip S. J.; Cohen, Kim M.; Toonen, Willem. H. J.; Erkens, Gilles; Hoek, Wim Z.

2017-04-01

Lacustrine fills, including those of oxbow lakes in river floodplains, often hold valuable sedimentary and biological proxy records of palaeo-environmental change. Precise dating of accumulated sediments at levels throughout these records is crucial for interpretation and correlation of (proxy) data existing within the fills. Typically, dates are gathered from multiple sampled levels and their results are combined in age-depth models to estimate the ages of events identified between the datings. In this paper, a method of age-depth modelling is presented that varies the vertical accumulation rate of the lake fill based on continuous sedimentary data. In between Bayesian calibrated radiocarbon dates, this produces a modified non-linear age-depth relation based on sedimentology rather than linear or spline interpolation. The method is showcased on a core of an infilled palaeomeander at the floodplain edge of the river Rhine near Rheinberg (Germany). The sequence spans from 4.7 to 2.9 ka cal BP and consists of 5.5 meters of laminated lacustrine, organo-clastic mud, covered by 1 meter of peaty clay. Four radiocarbon dates provide direct dating control, mapping and dating in the wider surroundings provide additional control. The laminated, organo-clastic facies of the oxbow fill contains a record of nearby fluvial-geomorphological activity, including meander reconfiguration events and passage of rare large floods, recognized as fluctuations in coarseness and amount of allochthonous clastic sediment input. Continuous along-core sampling and measurement of loss-on-ignition (LOI) provided a fast way of expressing the variation in clastic sedimentation influx from the nearby river versus autochthonous organic deposition derived from biogenic production in the lake itself. This low-cost sedimentary proxy data feeds into the age-depth modelling. The sedimentology-modelled age-depth relation (re)produces the distinct lithological boundaries in the fill as marked changes in sedimentation rate. Especially the organo-clastic muddy facies subdivides in centennial intervals of relative faster and slower accumulation. For such intervals, sedimentation rates are produced that deviate 10 to 20% from that in simpler stepped linear age-models. For irregularly laminated muddy intervals of the oxbow fill - from which meaningful sampling for radiocarbon dating is more difficult than from peaty or slowly accumulating organic lake sediments - supplementing spotty radiocarbon sampling with continuous sedimentary proxy data creates more realistic age-depth modelling results.

Palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest Permian- late Triassic Solway basin (U.K.)

NASA Astrophysics Data System (ADS)

Brookfield, Michael E.

2008-10-01

The late Permian to late Triassic sediments of the Solway Basin consist of an originally flat-lying, laterally persistent and consistent succession of mature, dominantly fine-grained red clastics laid down in part of a very large intracontinental basin. The complete absence of body or trace fossils or palaeosols indicates a very arid (hyperarid) depositional environment for most of the sediments. At the base of the succession, thin regolith breccias and sandstones rest unconformably on basement and early Permian rift clastics. Overlying gypsiferous red silty mudstones, very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary, and their margins. These pass upwards into thick-bedded, multi-storied, fine- to very fine-grained red quartzo-felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter. Above, thick trough cross-bedded and parallel laminated fine-grained aeolian sandstones (deposited in extensive barchanoid dune complexes) pass up into very thick, multicoloured mudstones, and gypsum deposited in marginal marine or lacustrine sabkha environments. The latter pass up into marine Lower Jurassic shales and limestones. Thirteen non-marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures. The five associations can be compared with the desert pavement, arid ephemeral stream, sabkha, saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as Lake Eyre and Lake Chad. The accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent (caused by climatic change and local variation) and this promotes a large-scale layer-cake stratigraphy as exemplified in the Solway basin. Here, the dominant fine-grained mature sandstones above the local basal reg breccias suggest water-reworking of wind-transported sediment, as in the northern part of the Lake Chad basin. Growth faulting occurs in places in the Solway basin, caused by underlying evaporite movement, but these faults did not significantly affect pre-late Triassic sedimentation and did not expose pre-Permian units above the basal breccias. There is no evidence of post-early Permian rifting anywhere during deposition of the late Permian to middle Triassic British succession although the succession is often interpreted with a rift-basin model. The arid to hyperarid palaeoclimate changed little during deposition of the Solway basin succession, in contrast to Lakes Eyre and Chad: and this is attributed to tectonic and palaeolatitude stability. Unlike the later Mesozoic- Cenozoic, only limited plate movements took place during the Triassic in western Europe, palaeolatitude changed little, and the Solway Basin remained in the northern latitudinal desert belt from early to mid-Triassic times. However, the influence of the early Triassic impoverished biota on environmental interpretations needs further study.

Sedimentology and paleoenvironments of a new fossiliferous late Miocene-Pliocene sedimentary succession in the Rukwa Rift Basin, Tanzania

NASA Astrophysics Data System (ADS)

Mtelela, Cassy; Roberts, Eric M.; Hilbert-Wolf, Hannah L.; Downie, Robert; Hendrix, Marc S.; O'Connor, Patrick M.; Stevens, Nancy J.

2017-05-01

This paper presents a detailed sedimentologic investigation of a newly identified, fossiliferous Late Neogene sedimentary succession in the Rukwa Rift Basin, southwestern Tanzania. This synrift deposit is a rare and significant new example of a fossiliferous succession of this age in the Western Branch of East Africa Rift System. The unit, informally termed the lower Lake Beds succession, is late Miocene to Pliocene in age based on cross-cutting relationships, preliminary biostratigraphy, and U-Pb geochronology. An angular unconformity separates the lower Lake Beds from underlying Cretaceous and Oligocene strata. Deposition was controlled by rapid generation of accommodation space and increased sediment supply associated with late Cenozoic tectonic reactivation of the Rukwa Rift and synchronous initiation of the Rungwe Volcanic Centre. The lower Lake Beds, which have thus far only been identified in three localities throughout the Rukwa Rift Basin, are characterized by two discrete lithologic members (herein A and B). The lower Member A is a volcanic-rich succession composed mostly of devitrified volcanic tuffs, and volcaniclastic mudstones and sandstones with minor conglomerates. The upper Member B is a siliciclastic-dominated succession of conglomerates, sandstones, mudstones and minor volcanic tuffs. Detailed facies analysis of the lower Lake Beds reveals various distinctive depositional environments that can be grouped into three categories: 1) alluvial fan; 2) fluvial channel; and 3) flood basin environments, characterized by volcanoclastic-filled lakes and ponds, abandoned channel-fills and pedogenically modified floodplains. Member A represents a shallow lacustrine setting filled by tuffaceous sediments, which grade up into a system of alluvial fans and high-energy, proximal gravel-bed braided rivers. An unconformity marks the contact between the two members. Member B shows an upward transition from a high-energy, gravel-bed braided river system to a sandy braided river system with increasingly abundant floodplain deposits and well-developed paleosols. Vertebrate fossils are sparse in member A, but common in member B, preserved both within pedogenic soil horizons and as isolated elements and microsites within fluvial channel facies associations. Faunal remains include fishes, turtles and crocodylians, along with well-preserved mammal cranial and post-cranial remains. In addition, freshwater gastropod shells are locally present in member A and continental trace fossils, including abundant fossilized termite nests, are present in both members.

Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults

USGS Publications Warehouse

Miller, David; Haddon, Elizabeth; Langenheim, Victoria; Cyr, Andrew J.; Wan, Elmira; Walkup, Laura; Starratt, Scott W.

2018-01-01

Hinkley Valley in the Mojave Desert, near Barstow about 140 km northeast of Los Angeles and midway between Victorville Valley and the Lake Manix basin, contains a thick sedimentary sequence delivered by the Mojave River. Our study of sediment cores drilled in the valley indicates that Hinkley Valley was probably a closed playa basin with stream inflow from four directions prior to Mojave River inflow. The Mojave River deposited thick and laterally extensive clastic wedges originating from the southern valley that rapidly filled much of Hinkley Valley. Sedimentary facies representing braided stream, wetland, delta, and lacustrine depositional environments all are found in the basin fill; in some places, the sequence is greater than 74 m (245 ft) thick. The sediment is dated in part by the presence of the ~631 ka Lava Creek B ash bed low in the section, and thus represents sediment deposition after Victorville basin was overtopped by sediment and before the Manix basin began to be filled. Evidently, upstream Victorville basin filled with sediment by about 650 ka, causing the ancestral Mojave River to spill to the Harper and Hinkley basins, and later to Manix basin.Initial river sediment overran wetland deposits in many places in southern Hinkley Valley, indicating a rapidly encroaching river system. These sediments were succeeded by a widespread lake (“blue” clay) that includes the Lava Creek B ash bed. Above the lake sediment lies a thick section of interlayered stream sediment, delta and nearshore lake sediment, mudflat and/or playa sediment, and minor lake sediment. This stratigraphic architecture is found throughout the valley, and positions of lake sediment layers indicate a successive northward progression in the closed basin. A thin overlapping sequence at the north end of the valley contains evidence for a younger late Pleistocene lake episode. This late lake episode, and bracketing braided stream deposits of the Mojave River, indicate that the river avulsed through the valley, rather than continuing toward Lake Manix, during the late Pleistocene. Two dextral strike-slip fault zones, the Lockhart and the Mt. General, fold and displace the distinctive stratigraphic units, as well as surficial late Pleistocene and Holocene deposits. The sedimentary architecture and the two fault zones provide a framework for evaluating groundwater flow in Hinkley Valley.

Evolution of the Creede Caldera and its relation to mineralization in the Creede mining district, Colorado

USGS Publications Warehouse

Barton, Paul B.; Rye, Robert O.; Bethke, Philip M.

2000-01-01

At 25 Ma a major epithermal silver and base metal deposit formed in rhyolitic welded tuff near Creede, Colorado. Nearly 24000 metric tons of silver, appreciable lead, and small amounts of zinc, copper, and gold, have been produced from large, crustified veins under Bachelor and Bulldog Mountains north and northwest of Creede. Prior geologic, hydrologic, and stable-isotope studies showed that ore deposition was associated with the mixing and boiling of waters from diverse sources and suggester that a critical part of the ore-forming fluid may have originated within the ancient lake and sediments of the lacustrine Creede Formation that filled the Creede caldera. Two drill holes that sampled the heretofore hidden lower half of the Creede Formation are the focus of this book. The Creede caldera formed at 26.9 Ma within a high constructional plateau of silicic ashflows that covered and were sporadically interlayed with, intermediate lavas and lahars from large stratovolcanoes. The Creede caldera lake had an inflow evaporation balance that did not permit rapid filling to create a brim-full deep lake. Thus salts were evaporatively concentrated; but, with the exception of possible gypsum, no evaporite minerals preserved. Cool springs deposited travertine as mounds and contributed to limestone interlaminations within the sediment. The lake bottom was anoxic, and bacterial reduction of sulfate led to extreme sulfur isotopic fractionation in diagenetic pyrite. The caldera gradually resurged, converting the initial equant lake into an arcuate moat. Resurgent doming, alluvial fans, lacustrine sediments, ashfalls, and lava domes displaced water, lifted the lake so that it overlapped what later became the southern edge of the mineralized are, and eventually filled the basin. At 25.1 Ma an unseen pluton intruded beneath the northen part of the Creede district and created a convecting olume that drew in brine from the Creede caldera fill, meteotic water from highlands to the north, and possibly a fluid carrying radiogenic lead. These waters mixed and boiled as they approached the surface and moved southward, deposited a zoned epithermal deposit a few hundred meters below the paleosurface, and finally discharged into the top of the Creede Formation. The sulfide in the ores was the igneous derivation, but the sulfate was a mixture of biogenic sulfur from the Creede Formation, oxidized igneous sulfide, and thermochemically reduced and partially oxygen exchanged sulfate. The studies of the Creede caldera provide key observational and conceptual elements for the generalized model of the Creede ore deposit. The relation of the Creed ore deposit to a brine reservoir has broad significance because other brine accumulations (as in the Great Basin, the Green River Basin, or the playas of the Altiplano offer similar setting and exploration opportunities.

The origin, type and hydrocarbon generation potential of organic matter in a marine-continental transitional facies shale succession (Qaidam Basin, China).

PubMed

Wang, Guo-Cang; Sun, Min-Zhuo; Gao, Shu-Fang; Tang, Li

2018-04-26

This organic-rich shale was analyzed to determine the type, origin, maturity and depositional environment of the organic matter and to evaluate the hydrocarbon generation potential of the shale. This study is based on geochemical (total carbon content, Rock-Eval pyrolysis and the molecular composition of hydrocarbons) and whole-rock petrographic (maceral composition) analyses. The petrographic analyses show that the shale penetrated by the Chaiye 2 well contains large amounts of vitrinite and sapropelinite and that the organic matter within these rocks is type III and highly mature. The geochemical analyses show that these rocks are characterized by high total organic carbon contents and that the organic matter is derived from a mix of terrestrial and marine sources and highly mature. These geochemical characteristics are consistent with the results of the petrographic analyses. The large amounts of organic matter in the Carboniferous shale succession penetrated by the Chaiye 2 well may be due to good preservation under hypersaline lacustrine and anoxic marine conditions. Consequently, the studied shale possesses very good hydrocarbon generation potential because of the presence of large amounts of highly mature type III organic matter.

Increased terrestrial methane cycling at the Palaeocene-Eocene thermal maximum.

PubMed

Pancost, Richard D; Steart, David S; Handley, Luke; Collinson, Margaret E; Hooker, Jerry J; Scott, Andrew C; Grassineau, Nathalie V; Glasspool, Ian J

2007-09-20

The Palaeocene-Eocene thermal maximum (PETM), a period of intense, global warming about 55 million years ago, has been attributed to a rapid rise in greenhouse gas levels, with dissociation of methane hydrates being the most commonly invoked explanation. It has been suggested previously that high-latitude methane emissions from terrestrial environments could have enhanced the warming effect, but direct evidence for an increased methane flux from wetlands is lacking. The Cobham Lignite, a recently characterized expanded lacustrine/mire deposit in England, spans the onset of the PETM and therefore provides an opportunity to examine the biogeochemical response of wetland-type ecosystems at that time. Here we report the occurrence of hopanoids, biomarkers derived from bacteria, in the mire sediments from Cobham. We measure a decrease in the carbon isotope values of the hopanoids at the onset of the PETM interval, which suggests an increase in the methanotroph population. We propose that this reflects an increase in methane production potentially driven by changes to a warmer and wetter climate. Our data suggest that the release of methane from the terrestrial biosphere increased and possibly acted as a positive feedback mechanism to global warming.

Facies development in the Lower Freeport coal bed, west-central Pennsylvania, U.S.A.

USGS Publications Warehouse

Pierce, B.S.; Stanton, R.W.; Eble, C.F.

1991-01-01

The Lower Freeport coal bed in west-central Pennsylvania is interpreted to have formed within a lacustrine-mire environment. Conditions of peat formation, caused by the changing chemical and physical environments, produced five coal facies and two mineral-rich parting facies within the coal bed. The coal bed facies are compositionally unique, having developed under varying conditions, and are manifested by megascopic, petrographic, palynologic and quality characteristics. The initial environment of the Lower Freeport peat resulted in a coal facies that is relatively high in ash yield and contains large amounts of lycopod miospores and moderate abundances of cryptotelinite, crypto-gelocollinite, inertinite and tree fern miospores. This initial Lower Freeport peat is interpreted to have been a topogenous body that was low lying, relatively nutrient rich (mesotrophic to eutrophic), and susceptible to ground water and to sediment influx from surface water. The next facies to form was a ubiquitous, clay-rich durain parting which is attributed to a general rise in the water table accompanied by widespread flooding. Following formation of the parting, peat accumulation resumed within an environment that inhibited clastic input. Development of doming in this facies restricted deposition of the upper shale parting to the margins of the mire and allowed low-ash peat to form in the interior of the mire. Because this environment was conducive to preservation of cellular tissue, this coal facies also contains large amounts of crypto-telinite. This facies development is interpreted to have been a transitional phase from topogenous, planar peat formation to slightly domed, oligotrophic (nutrient-poor) peat formation. As domed peat formation continued, fluctuations in the water table enabled oxidation of the peat surface and produced high inertinite concentrations toward the top of the coal bed. Tree ferns became an increasingly important peat contributor in the e upper facies, based on the palynoflora. This floral change is interpreted to have resulted from the peat surface becoming less wet or better drained, a condition that inhibited proliferation of lycopod trees. Accumulation of the peat continued until rising water levels formed a freshwater lake within which clays and silts were deposited. The development of the Lower Freeport peat from a planar mire through transitional phases toward domed peat formation may be an example of the type of peat formation of other upper Middle and Upper Pennsylvanian coal beds. ?? 1991.

Drivers of pluvial lake distributions in western North America

NASA Astrophysics Data System (ADS)

Ibarra, D. E.; Oster, J. L.; Winnick, M.; Caves, J. K.; Ritch, A. J.; Chamberlain, C. P.; Maher, K.

2016-12-01

The distribution of large inland lakes in western North America during the Plio-Pleistocene is intimately linked to the regional hydroclimate and moisture delivery dynamics. We investigate the climatological conditions driving terminal basin lakes in western North America during the mid-Pliocene warm period and the latest Pleistocene glacial maximum. Lacustrine deposits and geologic proxies suggest that lakes and wet conditions persisted during both warm and cold periods in the southwest, despite dramatically different global climate, ice sheet configuration and pCO2 levels. We use two complementary methods to quantify the hydroclimate drivers of terminal basin lake levels. First, a quantitative proxy-model comparison is conducted using compilations of geologic proxies and an ensemble of climate models. We utilize archived climate model simulations of the Last Glacial Maximum (21 ka, LGM) and mid-Pliocene (3.3 Ma) produced by the Paleoclimate Modelling Intercomparison Project (PMIP and PlioMIP). Our proxy network is made up of stable isotope records from caves, soils and paleosols, lake deposits and shorelines, glacier chronologies, and packrat middens. Second, we forward model the spatial distribution of lakes in the region using a Budyko framework to constrain the water balance for terminally draining watersheds, and make quantitative comparisons to mapped lacustrine shorelines and outcrops. Cumulatively these two approaches suggest that reduced evaporation and moderate increases in precipitation, relative to modern, drove moderate to large pluvial lakes during the LGM in the Great Basin. In contrast, larger precipitation increases appear to be the primary driver of lake levels during the mid-Pliocene in the southwest, with this spatial difference suggesting a role for El Niño teleconnections. These results demonstrate that during past periods of global change patterns of `dry-gets-drier, wet-gets-wetter' do not hold true for western North America.

Diatremes of the Hopi Buttes, Arizona; chemical and statistical analyses

USGS Publications Warehouse

Wenrich, K.J.; Mascarenas, J.F.

1982-01-01

Lacustrine sediments deposited in maar lakes of the Hopi Buttes diatremes are hosts for uranium mineralization of as much as 1500 ppm. The monchiquites and limburgite turfs erupted from the diatremes are distinguished from normal alkalic basalts of the Colorado Plateau by their extreme silica undersaturation and high water, TiO2, and P2O5 contents. Many trace elements are also unusually abundant, including Ag, As, Ba, Be, Ce, Dy, Eu, F, Gd, Hf, La, Nd, Pb, Rb, Se, Sm, Sn, Sr, Ta, Tb, Th, U, V, Zn, and Zr. The lacustrine sediments, which consist predominantly of travertine and clastic rocks, are the hosts for syngenetic and epigenetic uranium mineralization of as much as 1500 ppm uranium. Fission track maps show the uranium to be disseminated within the travertine and clastic rocks, and although microprobe analyses have not, as yet, revealed discrete uranium-bearing phases, the clastic rocks show a correlation of high Fe, Ti, and P with areas of high U. Correlation coefficients show that for the travertines, clastics, and limburgite ruffs, Mo, As, Sr, Co, and V appear to have the most consistent and strongest correlations with uranium. Many elements, including many of the rare-earth elements, that are high in these three rocks are also high in the monchiquites, as compared to the average crustal abundance for the respective rock type. This similar suite of anomalous elements, which includes such immobile elements as the rare earths, suggests that Fluids which deposited the travertines were related to the monchiquitic magma. The similar age of about 5 m.y. for both the lake beds and the monchiquites also appears to support this source for the mineralizing fluids.

Quaternary landscape evolution of tectonically active intermontane basins: the case of the Middle Aterno River Valley (Abruzzo, Central Italy)

NASA Astrophysics Data System (ADS)

Falcucci, Emanuela; Gori, Stefano; Della Seta, Marta; Fubelli, Giandomenico; Fredi, Paola

2014-05-01

The Middle Aterno River Valley is characterised by different Quaternary tectonic depressions localised along the present course of the Aterno River (Central Apennine) .This valley includes the L'Aquila and Paganica-Castelnuovo-San Demetrio tectonic basins, to the North, the Middle Aterno Valley and the Subequana tectonic basin, to the South. The aim of this contribution is to improve the knowledge about the Quaternary geomorphological and tectonic evolution of this portion of the Apennine chain. A synchronous lacustrine depositional phase is recognized in all these basins and attributed to the Early Pleistocene by Falcucci et al. (2012). At that time, this sector of the chain showed four distinct closed basins, hydrologically separated from each other and from the Sulmona depression. This depression, actually a tectonic basin too, was localized South of the Middle Aterno River Valley and it was drained by an endorheic hydrographic network. The formation of these basins was due to the activity of different fault systems, namely the Upper Aterno River Valley-Paganica system and San Pio delle Camere fault, to the North, and the Middle Aterno River Valley-Subequana Valley fault system to the South. These tectonic structures were responsible for the origin of local depocentres inside the depressions which hosted the lacustrine basins. Ongoing surveys in the uppermost sectors of the Middle Aterno River Valley revealed the presence of sub-horizontal erosional surfaces that are carved onto the carbonate bedrock and suspended several hundreds of metres over the present thalweg. Gently dipping slope breccias referred to the Early Pleistocene rest on these surfaces, thus suggesting the presence of an ancient low-gradient landscape adjusting to the local base level.. Subsequently, this ancient low relief landscape underwent a strong erosional phase during the Middle Pleistocene. This erosional phase is testified by the occurrence of valley entrenchment and of coeval fluvial deposition within the Middle Aterno River Valley. These fluvial deposits are deeply embedded into the lacustrine sequence, thus suggesting the happening of a hydrographic connection among the originally separated tectonic depressions. This was probably due to the headward erosion by streams draining the Sulmona depression that progressively captured the hydrological networks of the Subequana basin, the Middle Aterno Valley, the L'Aquila and Paganica-Castelnuovo-San Demetrio basins to the North. Stream piracy was probably helped by an increase of the regional uplift rate, occurred between the Lower and the Middle Pleistocene. To reconstruct the paleo-landscape that characterised the early stages of these basins formation we sampled the remnants of the Quaternary erosinal/depositional surfaces and reconstructed the ancient topographic surfaces using the Topo to Raster tool of ArcGIS 10.0 package. Finally we have cross-checked the geological and geomorphological data with the model of the Middle Aterno River paleo-drainage basin obtained through the GIS based method. References Falcucci E., Scardia G., Nomade S., Gori S., Giaccio B., Guillou H., Fredi P. (2012). Geomorphological and Quaternary tectonic evolution of the Subequana basin and the Middle Aterno Valley (central Apennines).16th Joint Geomorphological Meeting Morphoevolution of Tectonically Active Belts Rome, July 1-5, 2012

Photomosaics and Logs of Trenches on the San Andreas Fault near Coachella, California

USGS Publications Warehouse

Philibosian, Belle; Fumal, Thomas E.; Weldon, Ray J.; Kendrick, Katherine J.; Scharer, Katherine M.; Bemis, Sean P.; Burgette, Reed J.; Wisely, Beth A.

2009-01-01

Valley in southern California east of Dillon Road and south of Avenue 44. Three benched trenches, a total of more than 950 m, were excavated across the fault zone as part of an Alquist-Priolo fault investigation study. These trenches exposed a thick section of latest Holocene lacustrine, fluvial, and shoreline deposits. Only the central and eastern trenches exposed faulting so we confined our investigations to those two trenches. In the central trench, we photographed and logged in detail both walls of about 70 m of the trench where it spanned several zones of complex faulting which form a 15-m-wide depression. After carefully cleaning the trench walls, we put up a 1- by 0.5-m string- and nail-grid. We photographed each 1- by 0.5-m panel individually and then photologged features directly on these unrectified photos. The photos were digitally rectified later to remove distortion caused by irregularities in the trench walls and to correct the slight distortion introduced by the camera lens. The rectified photos were spliced together to make photomosaics of the trench walls. Most of the field linework and descriptions were then transferred to the rectified photomosaics. For the eastern trench, we took a set of overview photographs of the full length (about 200 m) of each wall. These photographs were taken from the top of the trench towards the opposite wall. Because the photographs were taken at a downward angle, there is significant distortion. We logged directly on these photos in the field, recording significant contacts, primarily between lacustrine and subaerial deposits, along with descriptions. For this report, we spliced together these unrectified overview photos and transfered field linework and some descriptions. For both trenches, contacts and lithologhic descriptions of stratigraphic units, faults and carbon sample locations are indicated on the photomosaics. Lacustrine deposits are tinted to better show deformation across the fault zones. Evidence for six paleoearthquakes rated as 'probable' is indicated with red stars that contain the sequential event number (1 is most recent event). Evidence for two additional 'possible' paleoearthquakes is indicated with blue stars. The sedimentary deposits contain abundant dateable material which includes detrital charcoal, lenses of organic material formed in-situ, and shells. Two organic fractions, humic acids and acid-alkali-acid-pretreated (AAA), were dated for 13 of 15 samples taken from organic layers and both dates are shown for these samples on the photomosaics and tables 1 and 2. All radiocarbon dates are in 14C years B.P. (considered to be A.D. 1950). Horizontal distance is measured along the trenches from the southwest ends of the logged exposures (marked as 0 m), and depth is measured from the highest points on the ground surface within the logged exposures. Bench locations are indicated by white lines and gaps in the photomosaics. Note that faults and contacts that are somewhat oblique to the trench walls occasionally appear disconnected owing to the approximately 1 m width of the benches.

Digital Database of Selected Aggregate and Related Resources in Ada, Boise, Canyon, Elmore, Gem, and Owyhee Counties, Southwestern Idaho

USGS Publications Warehouse

Moyle, Phillip R.; Wallis, John C.; Bliss, James D.; Bolm, Karen D.

2004-01-01

The U.S. Geological Survey (USGS) compiled a database of aggregate sites and geotechnical sample data for six counties - Ada, Boise, Canyon, Elmore, Gem, and Owyhee - in southwest Idaho as part of a series of studies in support of the Bureau of Land Management (BLM) planning process. Emphasis is placed on sand and gravel sites in deposits of the Boise River, Snake River, and other fluvial systems and in Neogene lacustrine deposits. Data were collected primarily from unpublished Idaho Transportation Department (ITD) records and BLM site descriptions, published Army Corps of Engineers (ACE) records, and USGS sampling data. The results of this study provides important information needed by land-use planners and resource managers, particularly in the BLM, to anticipate and plan for demand and development of sand and gravel and other mineral material resources on public lands in response to the urban growth in southwestern Idaho.

Archaeogeophysical tests in water saturated and under water scenarios at the Hydrogeosite Laboratory

NASA Astrophysics Data System (ADS)

Capozzoli, Luigi; De Martino, Gregory; Giampaolo, Valeria; Perciante, Felice; Rizzo, Enzo

2016-04-01

The growing interest in underwater archaeology as witnessed by numerous archaeological campaigns carried out in the Mediterranean region in marine and lacustrine environments involves a challenge of great importance for archaeogeophysical discipline. Through a careful use of geophysical techniques it is possible support archaeological research to identify and analyse the undiscovered cultural heritage placed under water located near rivers and sea. Over the past decades, geophysical methods were applied successfully in the field of archaeology: an integrated approach based on the use of electric, electromagnetic and magnetic techniques have showed the ability to individuate and reconstruct the presence of archaeological remains in the subsoil allowing to define their distribution in the space limiting the excavation activities. Moreover the capability of geophysics could be limited cause the low geophysical contrasts occurring between archaeological structures and surrounding environment; in particular problems of resolution, depth of investigation and sensitivity related to each adopted technique can result in a distorted reading of the subsurface behaviour preventing the identification of archaeological remains. This problem is amplified when geophysical approach is applied in very humid environments such as in lacustrine and marine scenarios, or in soils characterized by high clay content that make more difficult the propagation of geophysical signals. In order to improve our geophysical knowledge in lacustrine and coastal scenarios a complex and innovative research project was realized at the CNR laboratory of Hydrogeosite which permitted to perform an archaeogeophysical experiment in controlled conditions. The designed archaeological context was focused on the Roman age and various elements characterized by different shapes and materials were placed at different depths in the sub-soil. The preliminary project activities with some scenarios were presented last year, now we would like to show the final results of the project where different scenarios were set up for GPR and ERT investigations. Severale phases were performed: buried objects were covered by different thickness of sediments and different soil water contents were defined. Moreover, geophysical measurements were acquired on an underwater scenario. The 2D and 3D acquisitions have allowed to identify the limits and the abilities of the GPR and resistivity measurements.

Rain shadow development and paleoenvironmental change in the southern Central Anatolian Plateau

NASA Astrophysics Data System (ADS)

Meijers, Maud J. M.; Mulch, Andreas; Brocard, Gilles Y.; Whitney, Donna L.

2015-04-01

Ongoing Arabia-Eurasia convergence in the eastern Mediterranean region has led to the westward escape of the Anatolian microplate and the formation of the Central Anatolian Plateau (CAP). The US-NSF CD-CAT (Continental Dynamics-Central Anatolian Tectonics) project aims at understanding the surface-to-mantle coupling during the transition from collision to escape tectonics and plateau formation in Anatolia. Within the CD-CAT project, this study aims at determining the paleoenvironmental conditions and the age of plateau (margin) uplift by integrating stable isotope geochemistry and absolute dating techniques (40Ar/39Ar geochronology and magnetostratigraphy) on middle Miocene to Pliocene lacustrine sedimentary rocks. The low-relief CAP (~1.5 km average elevation) is characterized by high-relief mountain ranges at its southern and northern margins. The Tauride mountain belt forms the southern plateau margin of the CAP with a relief of up to 3 km. Uplift of Tortonian marine sediments in the central Taurides to modern elevations of up to 2 km constrain the onset of surface uplift of the southern plateau margin to ~8 Ma (Schildgen et al. 2012a,b). Proxy records of oxygen isotopes (δ18O) in precipitation allow to reconstruct the development of the present-day Tauride rain shadow and hence the surface elevation history of the southern plateau margin. Here we evaluate δ18O and δ13C records of seven lacustrine basins situated along a SW-NE swath in the lee of the modern Tauride mountains in order to track the development of a Tauride rain shadow and changes in open to closed lake conditions through the late Miocene to Pliocene. We focus on lacustrine sections with available mammal ages and integrate these with 40Ar/39Ar geochronology of widespread volcanics of the Central Anatolian Volcanic Province and magnetostratigraphy where possible. Our results from seven sections of ~12-4 Ma in lacustrine deposits and pedogenic soil carbonates of ~3-2.5 Ma show a decrease of δ18O values between ~12 and ~6 Ma of ca. 3o followed by a period of remarkably stable δ18O values around 21.5o until about 2.5 Ma. The latter coincides with modern δ18O values of the least-evaporative rinds of modern pedogenic carbonate. The observed 3o decrease in δ18O of lacustrine carbonate accounts for about 50 % of the present-day effect of orographic rainout on δ18O of precipitation (Schemmel et al. 2013) along the southern plateau margin. This might indicate the presence of a ~1000m high plateau prior to the formation of the Tauride chain. Schildgen et al., EPSL 317-118, 2012a; Schildgen et al., Tectonics 31, 2012b; Schemmel et al., AJS 313, 2013

Tectonics, basin analysis and organic geochemical attributes of Permian through Mesozoic deposits and their derivative oils of the Turpan-Hami basin, northwestern China

NASA Astrophysics Data System (ADS)

Greene, Todd Jeremy

The Turpan-Hami basin is a major physiographic and geologic feature of northwest China, yet considerable uncertainty exists as to the timing of its inception, its late Paleozoic and Mesozoic tectonic history, and the relationship of its petroleum systems to those of the nearby Junggar basin. Mesozoic sedimentary fades, regional unconformities, sediment dispersal patterns, and sediment compositions within the Turpan-Hami and southern Junggar basins suggest that these basins were initially separated between Early Triassic and Early Jurassic time. Prior to separation, Upper Permian profundal lacustrine and fan-delta fades and Triassic coarse-grained braided-fluvial/alluvial fades were deposited across a contiguous Junggar-Turpan-Hami basin. Permian through Triassic fades were derived mainly from the Tian Shan to the south as indicated by northward-directed paleocurrent directions and geochemical provenance of granitoid cobbles. Lower through Middle Jurassic strata begin to reflect ponded coal-forming, lake-plain environments within the Turpan-Hami basin. A sharp change in sedimentary-lithic-rich Lower Jurassic sandstone followed by a return to lithic volcanic-rich Middle Jurassic sandstone points to the initial uplift and unroofing of the largely andesitic Bogda Shan range, which first shed its sedimentary cover as it emerged to become the partition between the Turpan-Hami and southern Junggar basins. In Turpan-Hami, source rock age is one of three major statistically significant discriminators of effective source rocks in the basin. A newly developed biomarker parameter appears to track conifer evolution and can distinguish Permian rocks and their correlative oils from Jurassic coals and mudrocks, and their derivative oils. Source fades is a second key control on petroleum occurrence and character. By erecting rock-to-oil correlation models, the biomarker parameters separate oil families into end-member groups: Group 1 oils---Lower/Middle Jurassic peatland/swamp fades, Group 2 oils---Lower/Middle Jurassic marginal lacustrine fades, and Group 3 oils---Upper Permian lacusbine fades. Burial history exercises a third major control on petroleum in the Turpan-Hami basin. While relatively uninterrupted deep burial in the Tabei Depression exhausted Upper Permian source rocks and brought Lower/Middle Jurassic rocks well into the oil generative window, Late Jurassic uplift in the Tainan Depression eroded much of the Lower/Middle Jurassic section and preserved Upper Permian sourced oils as biodegraded, relict, heavy oils.* *This dissertation includes a CD that is multimedia (contains text and other applications that are not available in a printed format). The CD requires the following applications: Adobe Acrobat, UNIX.

Geomorphic evidence for an eolian contribution to the formation of the Martian northern plains

NASA Technical Reports Server (NTRS)

Zimbelman, J. R.

1993-01-01

The northern plains of Mars have many morphologic characteristics that are uncommon or absent on the rest of the planet. Mariner 9 and Viking images obtained north of latitude 30 deg N revealed 'smooth' and 'mottled' plains of an uncertain origin. Some or all of the northern plains were interpreted to consist of lava plains intermixed with eolian and volcanic materials thick eolian mantles that buried portions of the mid latitudes periglacial deposits resulting from the presence of ground ice and as water-transported sediments derived from fluvial runoff, lacustrine deposition in standing bodies of water, or glacial runoff. The highest-resolution Viking images show many intriguing details that may provide clues to the origin of this complex and distinctive terrain. Some of the informative features present in the best Viking images, comparing the observations to what may be expected from various hypotheses of formation, are reviewed. While the results are not conclusive for any single hypothesis, eolian processes have played a major role in the erosion (and possibly deposition) of the materials that make up the surface exposures in the Martian northern plains.

Composition of aeolian dust in natural traps on isolated surfaces of the central Mojave Desert - Insights to mixing, sources, and nutrient inputs

USGS Publications Warehouse

Reynolds, R.L.; Reheis, M.; Yount, J.; Lamothe, P.

2006-01-01

The recognition and characterization of aeolian dust in soil contribute to a better understanding of landscape and ecosystem dynamics of drylands. Results of this study show that recently deposited dust, sampled in isolated, mostly high-ground settings, is chemically and mineralogically similar on varied geologic substrates over a large area (15 000 km2) in the Mojave Desert. The silt-plus-clay fraction (fines) on these isolated surfaces is closely alike in magnetic-mineral composition, in contrast to greatly dissimilar magnetic compositions of rock surfaces of vastly different lithologies, on which the fines have accumulated. The fines, thus, are predominantly deposited dust. The amounts of potential nutrients in the sampled dust are much more uniform than might be provided by direct, local weathering of bedrock or by dust locally derived from nearby weathered products. The compositional similarity of the dust on these surfaces is interpreted to result from mixing of fines in the atmosphere as well as in fluvial, alluvial, and lacustrine depositional settings prior to dust emission.

Lacustrine responses to decreasing wet mercury deposition rates: results from a case study in northern Minnesota

USGS Publications Warehouse

Brigham, Mark E.; Sandheinrich, Mark B.; Gay, David A.; Maki, Ryan P.; Krabbenhoft, David P.; Wiener, James G.

2014-01-01

We present a case study comparing metrics of methylmercury (MeHg) contamination for four undeveloped lakes in Voyageurs National Park to wet atmospheric deposition of mercury (Hg), sulfate (SO4–2), and hydrogen ion (H+) in northern Minnesota. Annual wet Hg, SO4–2, and H+ deposition rates at two nearby precipitation monitoring sites indicate considerable decreases from 1998 to 2012 (mean decreases of 32, 48, and 66%, respectively). Consistent with decreases in the atmospheric pollutants, epilimnetic aqueous methylmercury (MeHgaq) and mercury in small yellow perch (Hgfish) decreased in two of four lakes (mean decreases of 46.5% and 34.5%, respectively, between 2001 and 2012). Counter to decreases in the atmospheric pollutants, MeHgaq increased by 85% in a third lake, whereas Hgfish increased by 80%. The fourth lake had two disturbances in its watershed during the study period (forest fire; changes in shoreline inundation due to beaver activity); this lake lacked overall trends in MeHgaq and Hgfish. The diverging responses among the study lakes exemplify the complexity of ecosystem responses to decreased loads of atmospheric pollutants.

Quaternary deposits in southwestern Afghanistan

USGS Publications Warehouse

Smith, G.I.

1974-01-01

Geologic evidence in the closed Seistan Basin of southwestern Afghanistan and adjacent parts of Iran and Pakistan indicates that a lake as much as 65,000 sq km in size occupied this closed depression during Pleistocene time. The deposits consist mostly of lacustrine silt and clay and have a maximum observed thickness of about 250 m. A layer of alluvial gravels overlies the sequence. The deposits are probably early or middle Pleistocene in age; they are old enough to have sustained nearly 300 m of erosion over large areas but are not faulted or detectably folded in the central part of the basin although they are upwarped along the west edge of the basin. Sand dunes cover extensive areas of the basin. Dune orientation shows that the strong surface winds enter the basin blowing toward the south-southeast and then are deflected to the east, apparently as a response to mountains bordering the basin on its south side. The Gawdezereh, a large deflation depression, may be a result of an augmented excavation ability of winds that oc urs where turbulence is created along a zone of deflection. ?? 1974.

Znaczenie analizy minerałów ciężkich w badaniach osadów czwartorzędowych Polski

NASA Astrophysics Data System (ADS)

Racinowski, Roman

2008-01-01

In most regions of Poland the composition of heavy minerals assemblage permits to distinguish the Quaternary deposits from the older ones. The pre-Quaternary deposits are characterized by high content of glauconite, carbonate-ferruginous-manganese concretions, muscovite and chlorites. In their transparent heavy minerals spectrum the following minerals predominate: zircon, tourmaline, rutile, staurolite, disthene. However, the Tertiary deposits in the Carpathians and their foreland contain a significant amount of garnet, and sometimes also amphiboles, pyroxenes and biotite. Pyroxenes and sillimanite are found in the Sudetes foreland. In many Tertiary deposits of the northwestern and western Poland there are rather high contents of amphiboles, biotite, pyroxenes, garnets, rutile. In all Quaternary deposits in Poland the qualitative composition of heavy minerals assemblage is similar but the contents of particular minerals are different depending on the examined grain fraction. In tills (Table 1) and glaciofluvial deposits (Table 2), with the decreasing grain diameter the contents of zircon, rutile, and partly epidote increase, and those of amphiboles and garnets decrease. In rubble of coastal zone in the Polish Baltic Sea, with the decreasing grain diameter the contents of zircon, rutile and epidote increase, and those of amphibole, biotite and pyroxenes decrease (Tables 3-7). In Poland, glacial, glaciofluvial and glaciolacustrine deposits are characterized by quantitatively similar composition of heavy minerals assemblage. Amphiboles, biotite, epidotes, garnets and pyroxenes are typical transparent minerals (Tables 8 and 9). Young Pleistocene and Holocene sands of river terraces and dune fields in the upland zone of Poland differ from glacial deposits in low contents of amphiboles, biotite and pyroxenes, and higher contents of garnets and epidotes (Tables 8 and 9). Fossil river and lacustrine deposits of Polish Lowlands have very similar assemblage of heavy minerals to that found in glacial deposits. Both glacial and glaciofluvial deposits have similar composition of heavy minerals assemblage irrespective of their age (Tables 10, 11 and 12). This principle concerns also loesses (Table 13a, b) but the youngest ones are characterized by higher contents of amphiboles and epidotes. The composition of heavy minerals assemblage is useful for determining the source of material forming the Quaternary deposits. In the case of glacial deposits, the enrichment in glauconite, chlorites, and even zircon, rutile, tourmaline, staurolite indicates that material from local older substratum was supplied to the Quaternary deposits. Heavy minerals spectrum of non-glacial deposits can directly indicate the source material that formed a deposit. Conversely, it is difficult to draw the conclusions about fossil and modern weathering-soil horizons in loesses from the composition of heavy minerals assemblage (Tables 14 and 15). The results of heavy minerals analysis are useful for lithodynamic and lithofacial interpretation of flowing water environments, e.g. river (Table 16), glaciofluvial (Table 17) and sea coastal (Table 18).

Deposits of the Peruvian Pisco Formation compared to layered deposits on Mars

NASA Astrophysics Data System (ADS)

Sowe, M.; Bishop, J. L.; Gross, C.; Walter, S.

2013-09-01

Deposits of the Peruvian Pisco Formation are morphologically similar to the mounds of Juventae Chasma at the equatorial region on Mars (Fig. 1). By analyzing these deposits, we hope to gain information about the environmental conditions that prevailed during sediment deposition and erosion, hence conditions that might be applicable to the Martian layered and hydrated deposits. Mariner 9 data of the Martian mid-latitudes have already shown evidence of the wind-sculptured landforms that display the powerful prevailing eolian regime [1]. In addition, [2] reported on similarities between Martian erosional landforms and those of the rainless coastal desert of central Peru from the Paracas peninsula to the Rio Ica. As indicated by similar erosional patterns, hyper-arid conditions and unidirectional winds must have dominated at least after deposition of the sediments, which are intermixed volcaniclastic materials and evaporate minerals at both locations. Likewise, variations in composition are displayed by alternating layers of different competence. The Pisco formation bears yardangs on siltstones, sandstones and clays with volcaniclastic admixtures [3] whereas the presence of sulphate minerals and the omnipresent mafic mineralogy has been reported for the layered mounds of Juventae Chasma equally [4]. Likewise, a volcanic airfall deposition and lacustrine formation have been proposed for the sulphate-rich deposits of Juventae Chasma [5,6]. In order to find out about potential spectral similarities, we performed a detailed spectral analysis of the surface by using LANDSAT and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) VNIR/ SWIR data (visible to near-infrared and shortwave infrared region).

Eocene lake basins in Wyoming and Nevada record rollback of the Farallon flat-slab beneath western North America

NASA Astrophysics Data System (ADS)

Smith, M. E.; Cassel, E. J.; Jicha, B. R.; Singer, B. S.; Carroll, A.

2014-12-01

Numerical and conceptual models of flat-slab rollback predict broad initial dynamic subsidence above the slab hinge then uplift and volcanism triggered by the advection of asthenosphere beneath the overriding plate. These predicted surface effects provide a viable but largely untested explanation for lake basin formation in Cordilleran-type orogenies. We argue that the hydrologic closure of both the foreland (early Eocene) and hinterland (late Eocene) of the North American Cordillera were caused by a trenchward-migrating wave of dynamic and thermal topography resulting from progressive removal of the Farallon flat-slab. Two major episodes of hydrologic drainage closure are recorded by Eocene terrestrial strata in the western United States. The first occurred in the retroarc foreland during the early Eocene, and resulted in the deposition of the Green River Fm. The second occurred in the hinterland during the late Eocene and resulted in accumulation of the Elko Fm. In both regions, lake strata overlie fluvial strata and become progressively more evaporative up-section, and are overlain by volcaniclastic strata. Both successions were then truncated by regional unconformities that extend until the Oligocene. We interpret these stratigraphic successions to record trenchward propagation of a regional topographic wave, caused by slab rollback. Migration of the slab-hinge initially caused dynamic subsidence and initiation of lacustrine deposition. Regional surface uplift followed, and was associated with scattered volcanism. Uplift promoted formation of endorheic basins and ultimately the development of regional unconformities. The height of the uplift can be roughly approximated by the preserved thickness of lacustrine and other nonmarine deposits at both locations (0.2-1.0 km). The 40Ar/39Ar and U-Pb geochronology of Green River Fm ash beds indicate that this surface topographic wave migrated trenchward (SW) across the foreland from 53 to 47 Ma at a velocity of ~6 cm/yr. Single crystal sanidine 40Ar/39Ar ages for ash beds within the Elko Fm indicate hydrologic ponding from 43 to 38 Ma. The 4 myr gap between Green River and Elko Fm deposition may represent the time required for the rollback wave to transit the steep eastern slope of the Sevier fold-thrust belt.

Paleoseismic potential of sublacustrine landslide records in a high-seismicity setting (south-central Alaska)

USGS Publications Warehouse

Praet, Nore; Moernaut, Jasper; Van Daele, Maarten; Boes, Evelien; Haeussler, Peter J.; Strupler, Michael; Schmidt, Sabine; Loso, Michael G.; De Batist, Marc

2017-01-01

Sublacustrine landslide stratigraphy is considered useful for quantitative paleoseismology in low-seismicity settings. However, as the recharging of underwater slopes with sediments is one of the factors that governs the recurrence of slope failures, it is not clear if landslide deposits can provide continuous paleoseismic records in settings of frequent strong shaking. To test this, we selected three lakes in south-central Alaska that experienced a strong historical megathrust earthquake (the 1964 Mw9.2 Great Alaska Earthquake) and exhibit high sedimentation rates in their main basins (0.2 cm yr-1 -1.0 cm yr-1). We present high-resolution reflection seismic data (3.5 kHz) and radionuclide data from sediment cores in order to investigate factors that control the establishment of a reliable landslide record. Seismic stratigraphy analysis reveals the presence of several landslide deposits in the lacustrine sedimentary infill. Most of these landslide deposits can be attributed to specific landslide events, as multiple landslide deposits sourced from different lacustrine slopes occur on a single stratigraphic horizon. We identify numerous events in the lakes: Eklutna Lake proximal basin (14 events), Eklutna Lake distal basin (8 events), Skilak Lake (7 events) and Kenai Lake (7 events). The most recent event in each basin corresponds to the historic 1964 megathrust earthquake. All events are characterized by multiple landslide deposits, which hints at a regional trigger mechanism, such as an earthquake (the synchronicity criterion). This means that the landslide record in each basin represents a record of past seismic events. Based on extrapolation of sedimentation rates derived from radionuclide dating, we roughly estimate a mean recurrence interval in the Eklutna Lake proximal basin, Eklutna Lake distal basin, Skilak Lake and Kenai Lake, at ~ 250 yrs, ~ 450 yrs, ~ 900 yrs and ~ 450 yrs, respectively. This distinct difference in recording can be explained by variations in preconditioning factors like slope angle, slope recharging (sedimentation rate) and the sediment source area: faster slope recharging and a predominance of delta and alluvial fan failures, increase the sensitivity and lower the intensity threshold for slope instability. Also, the seismotectonic setting of the lakes has to be taken into account. This study demonstrates that sublacustrine landslides in several Alaskan lakes can be used as reliable recorders of strong earthquake shaking, when a multi-lake approach is used, and can enhance the temporal and spatial resolution of the paleoseismic record of south-central Alaska.

Gold deposition by sulfidation of ferrous Fe in the lacustrine sediments of the Pueblo Viejo district (Dominican Republic): The effect of Fe-C-S diagenesis on later hydrothermal mineralization in a Maar-Diatreme complex

USGS Publications Warehouse

Kettler, R.M.; Rye, R.O.; Kesler, S.E.; Meyers, P.A.; Polanco, J.; Russell, N.

1992-01-01

The Pueblo Viejo district, located in the Cordillera Central of the Dominican Republic, contains large Au-Ag deposits associated with acid-sulfate alteration within spilites, conglomerates and carbonaceous sedimentary rocks that were deposited in a maar-diatreme complex. Much of the Au mineralization occurs in pyritic, carbonaceous siltstones of the Pueblo Viejo Maar-Diatreme Member of the Cretaceous Los Ranchos Formation. Pyrite is the only Fe-bearing phase in mineralized rock, whereas siderite is the dominant Fe-bearing phase in siltstones distal to mineralization. Disseminated pyrite occurs as framboids, cubes, pyritohedra, concretions and cement. Early framboids occur throughout the district. Au occurs as inclusions in later non-framboid disseminated pyrite (NFDP); an occurrence that is interpreted to be indicative of contemporaneous deposition. Pyrite framboids exhibit a wide range of ??34Scdt-values (-17.5 to +4.8???) and are interpreted to have formed during biogenic reduction of pore-water sulfate. The NFDP yield restricted ??34Scdt-values ( x ?? = -5.2???, s = ??2.4???, n = 43) similar to those obtained from later vein pyrite ( x ?? = -6.4???, s = ??1.5???, n = 12). Alunite and barite have ??34S-values ranging from +18.8 to +21.6???. The interpretation that the NFDP, vein pyrite, alunite and barite, and possibly even the framboidal pyrite share a common source of igneous sulfur is supported by the ??34S data. Siderite occurs as concretions and cement, contains abundant Mg (Fe0.75Mg0.19Mn0.03Ca0.02CO3) and has ??13Cpdb- and ??18Osmow-values ranging from -2.5 to +1.1%. and +14.6 to +19.5???, respectively. These data are consistent with the interpretation that the siderite formed in lacustrine sediments and that the carbonate in the siderite is probably methanogenic, although contributions from oxidation of organic matter during biogenic sulfate reduction, thermal decarboxylation of organic matter, or magmatic vapor cannot be ruled out. Disseminated Au mineralization in the sedimentary rocks formed when a hydrothermal fluid encountered reactive Fe2+ in diagenetic siderite. The ensuing pyrite deposition consumed H2S and destabilized the Au (HS)-2 complex, leading to precipitation of Au. The capacity of the sedimentary rocks to consume H2S and precipitate Au was controlled by the amount of non-pyrite Fe present as siderite. The abundance of siderite was controlled by the extent of pyrite formation during diagenesis. ?? 1992.

Lakes, Lagerstaetten, and Evolution

NASA Astrophysics Data System (ADS)

Kordesch, E. G.; Park, L. E.

2001-12-01

The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method for determining species diversity changes in the terrestrial environment because of their faunal completeness. Important Konservat Lagerstaetten, such as the Green River Formation (US) and Messel (Germany), both Eocene in age, are found in lake sediments and show a remarkable faunal diversity for both vertebrates and invertebrates. To date information from nearly 25 lake lagerstaetten derived from different types of lake basins from the Carboniferous to the Miocene have been collected and described. Carboniferous sites derive from the cyclothems of Midcontinent of the US while many Cenozoic sites have been described from North and South America as well as Europe and Australia. Asian sites contain fossils from the Mesozoic and Cenozoic. With this data, insight into the evolutionary processes associated with lake systems can be examined. Do lakes act as unique evolutionary crucibles in contrast to marine systems? The speciation of cichlid fishes in present-day African lakes appears to be very high and is attributed to the diversity of environments found in large rift lakes. Is this true of all ancient lakes or just large rift lakes? The longevity of a lake system may be an important factor in allowing speciation and evolutionary processes to occur; marine systems are limited only in the existence of environments as controlled by tectonics and sea level changes, on the order of tens of millions of years. Rift lakes are normally the longest lived in the millions of years. Perhaps there are only certain types of lakes in which speciation of nonmarine organisms, and thus the evolution of freshwater organisms, can occur in a short geologic timespan. Because of their unique and varied conditions, the evolution of nonmarine organisms may be linked to lake basin type as well as lake longevity.

Chrysophyte cysts as potential environmental indicators.

USGS Publications Warehouse

Adam, D.P.; Mahood, A.D.

1981-01-01

Many chrysophyte algae produce morphologically distinctive, siliceous, microscopic cysts during a resting stage of their life cycles; these cysts are often preserved in sediments. Scanning electron microscopy and Nomarski optics permit much more detailed observation of these cysts than was heretofore possible. Many cyst types are found only in specific habitats, such as montane lakes, wet meadows, ephemeral ponds, and Sphagnum bogs. In the samples studied, cysts seem to be most common in fluctuating fresh-water habitats of low to moderate pH and some winter freezing. Chrysophyte cysts have the potential to be a useful tool for modern environmental assessments and paleoecological studies of Cenozoic fresh-water lacustrine deposits. -from Authors

Fluidized-sediment pipes in Gale crater, Mars, and possible Earth analogs

USGS Publications Warehouse

Rubin, David M.; Fairen, A.G.; Frydenvang, J.; Gasnault, O.; Gelfenbaum, Guy R.; Goetz, W.; Grotzinger, J.P.; Le Mouélic, S.; Mangold, N.; Newsom, H.; Oehler, D. Z.; Rapin, W.; Schieber, J.; Wiens, R.C.

2017-01-01

Since landing in Gale crater, the Mars Science Laboratory rover Curiosity has traversed fluvial, lacustrine, and eolian sedimentary rocks that were deposited within the crater ∼3.6 to 3.2 b.y. ago. Here we describe structures interpreted to be pipes formed by vertical movement of fluidized sediment. Like many pipes on Earth, those in Gale crater are more resistant to erosion than the host rock; they form near other pipes, dikes, or deformed sediment; and some contain internal concentric or eccentric layering. These structures provide new evidence of the importance of subsurface aqueous processes in shaping the near-surface geology of Mars.

Distal alluvial fan sediments in early Proterozoic red beds of the Wilgerivier formation, Waterberg Group, South Africa

NASA Astrophysics Data System (ADS)

Van Der Neut, M.; Eriksson, P. G.; Callaghan, C. C.

The 1900 - 1700 M.a. Waterberg Group belongs to a series of southern African cratonic cover sequences of roughly equivalent age. Red beds of the Wilgerivier Formation comprise sandstones, interbedded with subordinate conglomerates and minor mudrocks. These immature sedimentary rocks exhibit lenticular bedding, radial palaeocurrent patterns and features indicative of both streamflow and gravity-flow deposition. A distal wet alluvial fan palaeoenvironmental setting is envisaged, with fan-deltas forming where alluvial lobes prograded into a lacustrine basin. Intrastratal, diagenetic alteration of ferromagnesian detrital grains and ferruginous grain coatings led to the red colouration of the Wilgerivier sediments.

Microbial and biogeochernical processes Soda Lake, Nevada

USGS Publications Warehouse

Oremland, R.S.; Cloern, J.E.; Sofer, Z.; Smith, R.L.; Culbertson, C.W.; Zehr, J.; Miller, L.; Cole, B.; Harvey, R.; Iversen, N.; Klug, M.; Des Marais, D J; Rau, G.

1988-01-01

Meromictic, alkaline lakes represent modern-day analogues of lacustrine source rock depositional environments. In order to further our understanding of how these lakes function in terms of limnological and biogeochemical processes, we have conducted an interdisciplinary study of Big Soda Lake. Annual mixolimnion productivity (ca. 500 g m-2) is dominated by a winter diatom bloom (60% of annual) caused by upward transport of ammonia to the epilimnion. The remainder of productivity is attributable to chemoautotrophs (30%) and photosynthetic bacteria (10%) present at the oxic -anoxic interface from May to November. Studies of bacterial heterotrophy and particulate fluxes in the water column indicate that about 90% of annual productivity is remineralized in the mixolimnion, primarily by fermentative bacteria. However, high rates of sulphate reduction (9-29 mmol m-2 yr-1) occur in the monimolimnion waters, which could remineralize most (if not all) of the primary productivity. This discrepancy has not as yet been fully explained. Low rates of methanogenesis also occur in the monimolimnion waters and sediments. Most of the methane is consumed by anaerobic methane oxidation occurring in the monimolimnion water column. Other bacterial processes occurring in the lake are also discussed. Preliminary studies have been made on the organic geochemistry of the monimolimnion sediments. Carbon-14-dating indicates a lower depositional rate prior to meromixis and a downcore enrichment in 13C of organic carbon and chlorophyll derivatives. Hydrous pyrolysis experiments indicate that the sediment organic matter is almost entirely derived from the water column with little or no contribution from terrestrial sources. The significance of the organics released by hydrous pyrolysis is discussed.

Zeolite-clay mineral zonation of volcaniclastic sediments within the McDermitt caldera complex of Nevada and Oregon

USGS Publications Warehouse

Glanzman, Richard K.; Rytuba, James J.

1979-01-01

Volcaniclastic sediments deposited in the moat of the collapsed McDermitt caldera complex have been altered chiefly to zeolites and potassium feldspar. The original rhyolitic and peralkaline ash-flow tuffs are included in conglomerates at the caldera rims and grade into a lacustrine series near the center of the collapse. The tuffs show a lateral zeolitic alteration from almost fresh glass to clinoptilolite, clinoptilolite-mordenite, and erionite; to analcime-potassium feldspar; and finally to potassium feldspar. Vertical zonation is in approximately the same order. Clay minerals in associated mudstones, on the other hand, show little lateral variation but a distinct vertical zonation, having a basal dioctahedral smectite, a medial trioctahedral smectite, and an upper dioctahedral smectite. The medial trioctahedral smectite is enriched in lithium (as much as 6,800 ppm Li). Hydrothermal alteration of the volcaniclastic sediments, forming both mercury and uranium deposits, caused a distinct zeolite and clay-mineral zonation within the general lateral zonation. The center of alteration is generally potassium feldspar, commonly associated with alunite. Potassium feldspar grades laterally and vertically to either clinoptilolite or clinoptilolite-mordenite, generally associated with gypsum. This zone then grades vertically and laterally into fresh glass. The clay minerals are a dioctahedral smectite, a mixed-layer clay mineral, and a 7-A clay mineral. The mixed-layer and 7-A clay minerals are associated with the potassium feldspar-alunite zone of alteration, and the dioctahedral smectite is associated with clinoptilolite. This mineralogical zonation may be an exploration guide for mercury and uranium mineralization in the caldera complex environment.

Paleo-environmental Setting of the Murray Formation of Aeolis Mons, Gale Crater, Mars, as Explored by the Curiosity Rover

NASA Astrophysics Data System (ADS)

Lewis, K. W.; Fedo, C.; Grotzinger, J. P.; Gupta, S.; Stein, N.; Rivera-Hernandez, F.; Watkins, J. A.; Banham, S.; Edgett, K. S.; Minitti, M. E.; Schieber, J.; Edgar, L. A.; Siebach, K. L.; Stack, K.; Newsom, H. E.; House, C. H.; Sumner, D. Y.; Vasavada, A. R.

2017-12-01

Since landing, the Mars Science Laboratory Curiosity rover climbed 300 meters in elevation from the floor of north Gale crater up the lower northwest flank of Aeolis Mons ("Mount Sharp"). Nearly 200 meters of this ascent was accomplished in the 1.5 years alone, as the rover was driven up-section through the sedimentary rocks of the informally designated "Murray" formation. This unit comprises a large fraction of the lower strata of Mt. Sharp along the rover traverse. Our exploration of the Murray formation reveals a diverse suite of fine-grained facies. Grain sizes range from finer grains than can be resolved by the MAHLI imager (particles <62.5 microns) up to medium sand; the finer fraction comprises the bulk of the stratigraphy. Layering occurs at a range of scales; the majority is expressed as parallel laminae of mm-scale. Some sandy stratigraphic intervals exhibit cross-stratification at ripple (cm) and dune (m and larger) scales; the inferred bedforms are consistent with a range of subaqueous and aeolian depositional settings. Diagenetic features include locally variable occurrences of concretions and near-ubiquitous Ca-sulfate veins; these attest to extended interaction of the sediment with aqueous fluids in the subsurface. As a whole, the sedimentary facies of the Murray formation have been interpreted to record a predominately lacustrine paleo-environment, with likely subaerial aeolian and fluvial intervals. Further exploration, including the campaign at the hematite-bearing Vera Rubin Ridge, continues to reveal the complex and long-lived depositional history of the Gale crater basin.

Paleoenvironmental reconstruction and evolution of an Upper Cretaceous lacustrine-fluvial-deltaic sequence in the Parecis Basin, Brazil

NASA Astrophysics Data System (ADS)

Rubert, Rogerio R.; Mizusaki, Ana Maria Pimentel; Martinelli, Agustín G.; Urban, Camile

2017-12-01

The Cretaceous in the Brazilian Platform records events of magmatism, tectonism and sedimentation coupled to the Gondwana breakup. Some of these events are registered as sedimentary sequences in interior basins, such as in the Cretaceous sequence of the Alto Xingu Sub-basin, Parecis Basin, Central Brazil. This article proposes the faciologic characterization and paleoenvironmental reconstruction of the Cretaceous sequence of the eastern portion of the Parecis Basin and its relation with some reactivated structures as, for instance, the Serra Formosa Arch. Based on both data from outcrops and core drillings a paleoenvironmental and evolutionary reconstruction of the sequence is herein presented. The base of the studied section is characterized by chemical and low energy clastic sedimentation of Lake Bottom and Shoreline, in a context of fast initial subsidence and low sedimentation rate. As the subsidence process decreased, a deltaic progradation became dominant with deposition in a prodelta environment, followed by a deltaic front and deltaic plain interbedded with fluvial plain, and aeolian deposition completing the sequence. The inferred Coniacian-Santonian age is based on vertebrate (fishes and notosuchians) and ostracod fossils with regional chrono-correlates in the Adamantina (Bauru Group), Capacete (Sanfranciscana Basin), and Bajo de la Carpa (Neuquén Group, in Argentina) formations. The formation of a Coniacian depocenter in the Alto Xingu Sub-basin is associated to the Turonian-Coniacian reactivation event in the Peruvian Orogenic Phase of the Andean Orogeny, with the transference of stresses to interplate setting, reactivating Proterozoic structures of the basement.

Geochemical study of crude oils from the Xifeng oilfield of the Ordos basin, China

NASA Astrophysics Data System (ADS)

Duan, Y.; Wang, C. Y.; Zheng, C. Y.; Wu, B. X.; Zheng, G. D.

2008-01-01

The Xifeng oilfield is the largest newly-discovered oilfield in the Ordos basin. In order to determine the possible source, crude oils collected systematically from the oilfield and an adjacent oilfield have been examined isotopically and molecularly. The predominance of long-chain n-alkanes, high abundance of C 29 sterane, lower ratios of C 25/C 26 tricyclic terpane and C 25 tricyclic terpane/C 24 tetracyclic terpane and high C 24 tetracyclic terpane/(C 24 tetracyclic terpane + C 26 tricyclic terpanes ratio in the studied oils suggest generation from a source with mixed terrigenous and algal-bacterial organic matter. The presence of diterpenoid hydrocarbon with abietane skeletons is characteristic of the main contribution of higher land plants to the oils. The biomarker distributions in the oils show that they were formed under a weakly reducing freshwater environment. Molecular maturity parameters indicate that the crude oils are mature. The oil-source rock correlation and oil migration investigation suggest that the oils in the Xifeng oilfield originated from the source rocks of the Yanchang formation deposited in a shallow to deep freshwater lacustrine environment, especially Chang-7 source rocks. The data from the distribution of pyrrolic nitrogen compounds indicate that the charging direction of the Chang-8 crude oils is mainly from the Zhuang 12 well northeast of the oilfield toward the southwest. This direction of oil migration is consistent with that indicated by regional geological data.

Ancient glaciations and hydrocarbon accumulations in North Africa and the Middle East

NASA Astrophysics Data System (ADS)

Le Heron, Daniel Paul; Craig, Jonathan; Etienne, James L.

2009-04-01

At least six glaciations are purported to have affected North Africa and the Middle East region over the last one billion years, including two in the Cryogenian (Neoproterozoic), Hirnantian (Late Ordovician), Silurian, Carboniferous and Early Permian events. The sedimentary record associated with these glaciations, together with the intensity to which each has been investigated, is highly variable. As hydrocarbon exploration proceeds aggressively across the North Africa and Middle East regions, we review the relationship between glaciation and hydrocarbon accumulations. With the exception of Oman, and locally Egypt, which were tectonically active both during the Neoproterozoic and Early Palaeozoic all glaciations took place along an essentially stable passive continental margin. During the Neoproterozoic, two glaciations are recognised, referred to as older and younger Cryogenian glaciations respectively. Both of these Cryogenian events are preserved in Oman; only the younger Cryogenian has been reported in North Africa in Mauritania and Mali at the flanks of the Taoudenni Basin. The process of initial deglaciation in younger Cryogenian glaciations resulted in incision, at least locally producing large-bedrock palaeovalleys in Oman, and the deposition of glacial diamictites, gravels, sandstones and mudstones. As deglaciation progressed "cap carbonates" were deposited, passing vertically into shale with evidence for deposition in an anoxic environment. Hence, younger Cryogenian deglaciation may be associated with hydrocarbon source rock deposits. Hirnantian (Late Ordovician) glaciation was short lived (< 0.5 Myr) and affected intracratonic basins of Mauritania, Morocco, Algeria, Libya, Egypt and Saudi Arabia. The organisation of the glacial sedimentary record is considered to be controlled at the basin-scale by the location of fast-flowing ice streams active during glacial maxima, and by the processes of meltwater release during glacial recession. In these latter phases, subglacial tunnel valley networks were cut at or near the ice margin. These tunnel valleys were filled in two main phases. The initial phase was characterised by debris flow release, whereas during later phases of ice retreat a range of glaciofluvial, shallow glaciomarine to shelf deposits were laid down, depending on the water depth at the ice front. Production of linear accumulations of sediment, parallel to the ice front, also occurred between tunnel valleys at the grounding line. In Arabia, the geometry of these features may have been influenced by local tectonic uplift. As glaciogenic reservoirs, Hirnantian deposits are already of great economic significance across central North Africa. Therefore, an appreciation of the processes of ice sheet growth and decay provides significant insights into the controls on large-scale heterogeneities within these sediments, and in analogue deposits produced by glaciations of different ages. Deglacial, Early Silurian black shale represents the most important Palaeozoic source rock across the region. Existing models do not adequately explain the temporal and spatial development of anoxia, and hence of black shale/deglacial source rocks. The origins of a palaeotopography previously invoked as the primary driver for this anoxia is allied to a complex configuration of palaeo-ice stream pathways, "underfilled" tunnel valley incisions, glaciotectonic deformation structures and re-activation of older crustal structures during rebound. A putative link with the development of Silurian glaciation in northern Chad is suggested. Silurian glaciation appears to have been restricted to the southern Al Kufrah Basin in the eastern part of North Africa, and was associated with the deposition of boulder beds. Equivalent deposits are lacking in shallow marine deposits in neighbouring outcrop belts. Evidence for Carboniferous-Permian glaciation is tentative in the eastern Sahara (SW Egypt) but well established on the Arabian Peninsula in Oman and more recently in Saudi Arabia. Pennsylvanian-Sakmarian times saw repeated glaciation-deglaciation cycles affecting the region, over a timeframe of about 20 Myr. Repeated phases of deglaciation produced a complex stratigraphy consisting, in part, of structureless sandstone intervals up to 50 m thick. Some of these sandstone intervals are major hydrocarbon intervals in the Omani salt basins. Whilst studies of the Hirnantian glaciation can provide lessons on the causes of large-scale variability within Carboniferous-Permian glaciogenic reservoirs, additional factors also influenced their geometry. These include the effects of topography produced during Hercynian orogenesis and the mobilisation and dissolution of the Precambrian Ara Salt. Deglacial or interglacial lacustrine shale, with abundant palynomorphs, is also important. Whilst both Cryogenian intervals and the Hirnantian-Rhuddanian deglaciation resulted in the deposition of glaciomarine deposits, Carboniferous-Permian deglaciation likely occurred within a lacustrine setting. Hence, compared to shales of other glacial epochs, the source rock potential of Carboniferous-Permian deglacial deposits is minimal.

Hydrology and land use in Grand Traverse County, Michigan

USGS Publications Warehouse

Cummings, T.R.; Gillespie, J.L.; Grannemann, N.G.

1990-01-01

Glacial deposits are the sole source of ground-water supplies in Grand Traverse County. These deposits range in thickness from 100 to 900 feet and consist of till, outwash, and materials of lacustrine and eolian origin. In some areas, the deposits fill buried valleys that are 500 feet deep. Sedimentary rocks of Paleozoic age, which underlie the glacial deposits, are mostly shale and are not used for water supply. Of the glacial deposits, outwash and lacustrine sand are the most productive aquifers. Most domestic wells obtain water from sand and gravel at depths ranging from 50 to 150 feet and yield at least 20 gallons per minute. Irrigation, municipal, and industrial wells capable of yielding 250 gallons per minute or more are generally greater than 150 feet deep. At places in the county where moranial deposits contain large amounts of interbedded silt and clay, wells are generally deeper and yields are much lower. Areal variations in the chemical and physical characteristics of ground and surface water are related to land use and chemical inputs to the hydrologic system. Information on fertilizer application, septic-tank discharges, animal wastes, and precipitation indicate that 40 percent of nitrogen input is from precipitation, 6 percent from septic tanks, 14 percent from animal wastes, and 40 percent from fertilizers. Streams and lakes generally have a calcium bicarbonate-type water. The dissolved-solids concentration of streams ranged from 116 to 380 milligrams per liter, and that of lakes, from 47 to 170 milligrams per liter. Water of streams is hard to very hard; water of lakes ranges from soft to hard. The maximum total nitrogen concentration found in streams was 4.4 milligrams per liter. Water of lakes have low nitrogen concentrations; the median nitrate concentration is less than 0.01 milligrams per liter. Pesticides (Parathion and Simazine) were detected in low concentrations at six stream sites; 2,4-D was detected in low concentrations in water of two lakes. Relationships between land use and the yield of dissolved and suspended substances could not be established for most stream basins. Calcium and bicarbonate are the principal dissolved substances in ground water. Dissolved-solids concentrations ranged from 70 to 700 milligrams per liter; the countywide mean concentration is 230 milligrams per liter. The mean nitrate concentration is 1.3 milligrams per liter; about 1.6 percent of the county's ground water has nitrate concentrations that exceed the U.S. Environmental Protection Agency's maximum drinking water level of 10 milligrams per liter. An effect of fertilizer applications on ground-water quality is evident in some parts of the county.

The Location of Lake Titicaca's Coastal Area During the Tiwanaku and Inca Periods: Methodology and Strategies of Underwater Archaeology

NASA Astrophysics Data System (ADS)

Delaere, Christophe

2017-12-01

For more than 30 years, numerous research projects have revealed the dense and complex human settlement of the lacustrine basin of Lake Titicaca in Bolivia and Peru. Physical evidence of such establishments has been discovered in plains, valleys, and highlands connected to the lake. These remains confirm human occupation and development in this environment, particularly during the Tiwanaku (AD 500-1150) and Inca (AD 1400-1532) Periods. The research project discussed in this paper includes consideration of submerged areas through underwater archaeology. This investigation involves analysis of two areas that have evidence of ancient human occupation but are poorly documented: the coastal and lacustrine regions. Due to its dominance in the landscape, Lake Titicaca has always been a major feature in the life and identity of populations of this vicinity. These inhabitants have developed socio-economic and ritual behaviours directly associated with the lake that have left cultural and material prints that are the foci of the present study.

From submarine to lacustrine groundwater discharge

USGS Publications Warehouse

Lewandowski, Jörg; Meinikmann, Karin; Pöschke, Franziska; Nützmann, Gunnar; Rosenberry, Donald O.

2017-01-01

Submarine groundwater discharge (SGD) and its role in marine nutrient cycling are well known since the last decade. The freshwater equivalent, lacustrine groundwater discharge (LGD), is often still disregarded, although first reports of LGD are more than 50 years old. We identify nine different reasons why groundwater has long been disregarded in both freshwater and marine environments such as invisibility of groundwater discharge, the size of the interface and its difficult accessibility. Although there are some fundamental differences in the hydrology of SGD and LGD, caused primarily by seawater recirculation that occurs only in cases of SGD, there are also a lot of similarities such as a focusing of discharge to near-shore areas. Nutrient concentrations in groundwater near the groundwater–surface water interface might be anthropogenically enriched. Due to spatial heterogeneity of aquifer characteristics and biogeochemical processes, the quantification of groundwater-borne nutrient loads is challenging. Both nitrogen and phosphorus might be mobile in near-shore aquifers and in a lot of case studies large groundwater-borne nutrient loads have been reported.

A multi-proxy record of MIS 11-12 deglaciation and glacial MIS 12 instability from the Sulmona basin (central Italy)

NASA Astrophysics Data System (ADS)

Regattieri, Eleonora; Giaccio, Biagio; Galli, Paolo; Nomade, Sebastien; Peronace, Edoardo; Messina, Paolo; Sposato, Andrea; Boschi, Chiara; Gemelli, Maurizio

2016-01-01

A multi-proxy record (lithology, XRF, CaCO3 content, carbonate δ18O and δ13C) was acquired from a sediment core drilled in the intermountain Sulmona basin (central Italy). Tephrostratigraphic analyses of three volcanic ash layers ascribe the investigated succession to the MIS 12-MIS 11 period, spanning the interval ca. 500-410 ka. Litho-pedo facies assemblage indicates predominant lacustrine deposition, interrupted by a minor sub-aerial and lake low stand episode. Variations in major and minor elements concentrations are related to changes in the clastic input to the lake. The oxygen isotopic composition of carbonate (δ18Oc) intervals is interpreted mainly as a proxy for the amount of precipitation in the high-altitude catchment of the karst recharge system. The record shows pronounced hydrological variability at orbital and millennial time-scales, which appears closely related to the Northern Hemisphere summer insolation pattern and replicates North Atlantic and west Mediterranean Sea Surface Temperature (SST) fluctuations. The MIS 12 glacial inception is marked by an abrupt reduction of precipitation, lowering of the lake level and enhanced catchment erosion. A well-defined and isotopically prominent interstadial with increased precipitation maybe related to insolation maxima-precession minima at ca. 465 ka. This interstadial ends abruptly at ca. 457 ka and it is followed by a phase of strong short-term instability. Drastic lake-level lowering and enhanced clastic flux characterized the MIS 12 glacial maximum. Lacustrine deposition restarted about 440 ka ago. The MIS 12-MIS 11 transition is characterized by a rapid increase in the precipitation, lake-level rise and reduction in the clastic input, interrupted by a short and abrupt return to drier conditions. Comparison with marine records from the Iberian margin and western Mediterranean suggests that major events of ice rafted debris deposition, related to southward migrations of the polar front, match the harshest periods in central Italy. This indicates strong teleconnections between Northern hemisphere ice sheet dynamics, North Atlantic oceanic conditions and Mediterranean continental hydrology.

Stratigraphy and tephra of the Kibish Formation, southwestern Ethiopia.

PubMed

Brown, Francis H; Fuller, Chad R

2008-09-01

The Kibish Formation in southwestern Ethiopia, with an aggregate thickness of approximately 105 m, consists of lacustrine, marginal lacustrine, and deltaic deposits. It is divided into four members numbered I to IV on the basis of erosion surfaces (disconformities) between the strata of each member. It overlies the Mursi and Nkalabong formations, the latter of which is here shown to correlate with the Shungura Formation. Tephra layers in each member allow for secure correlation between geographically separated sections on the basis of the composition of their volcanic glass. Members I, III, and IV of the Kibish Formation appear to have been deposited at the same times as sapropels S7 (197 ka), S4 (104 ka), and S1 (8 ka) in the eastern Mediterranean Sea, respectively. We correlate the KHS Tuff of the Kibish Formation with a >154-kyr-old unnamed tuff in the Konso Formation. Tephra in Member IV may derive from Mount Wenchi, a volcano situated on the divide between the Omo and Blue Nile drainage basins. Thin-bedded sedimentary layers probably represent annual deposition reflecting rapid sedimentation (approximately 30 m/kyr) of parts of the formation. This conclusion is supported by variation in paleomagnetic inclination through a sequence of these layers at KHS. Two fossils of early Homo sapiens (Omo I and Omo II) derive from Member I. Their stratigraphic placement is confirmed by analysis of the KHS Tuff in the lower part of Member II at both fossil sites. The KHS Tuff lies above a disconformity, which itself lies above the fossils at both sites. (40)Ar/(39)Ar dates provide an estimated age of approximately 195 kyr for these fossils. Omo III, a third fossil H. sapiens, probably also derives from Member I of the Kibish Formation and is of similar age. Hominin fossils from AHS, a new site, also derive from Member I. Hominin fossils from CHS can only be placed between 104 ka and 10 ka, the H. sapiens specimen from JHS is most likely 9-13 kyr in age, and a partial skeleton of H. sapiens from Pelvic Corner is most likely approximately 6.6 kyr in age.

Geology and stratigraphy of the San Lorenzo Tezonco deep well and its correlation to surrounding ranges, Mexico Basin

NASA Astrophysics Data System (ADS)

Arce, J. L.; Layer, P. W.; Morales-Casique, E.; Benowitz, J.

2014-12-01

The San Lorenzo Tezonco deep well stratigraphy records intense episodic volcanic activity in the Mexico Basin and surroundings during the past 20 Ma. The 2008-m deep lithological column is dominated by volcanic material, either as lava flows or pyroclastic deposits (97%), and only the upper most 70 m are composed of lacustrine deposits (3%). Based on geochronology and geochemistry, the lower part of the drill core is represented by rocks correlating to the Tepoztlán Formation (876-2008 m deep) that vary in composition from basaltic-andesite to rhyolite, and ages ranging from 13 to 21.2 Ma. On the surface this formation outcrops near the towns of Malinalco and Tepoztlán, ~43 km south of the deep well. Between depths of 581 and 875 m, volcanic rocks were recovered and are interpreted as lavas from the Sierra de las Cruces that vary in composition from andesite to dacite and range in age from 0.9 Ma to 5 Ma. Additionally, we documented rocks belonging to the Xochitepec Formation, outcropping around Xochimilco, in the Mexico City, with ages ranging from 1.2 and 1.7 Ma, in contrast with the Oligocene age proposed in previous works for these rocks. These new ages plus the chemical composition data, allow us to correlate the Xochitepec rocks with Sierra de las Cruces. Upward in the drill core (510-580 m) there are andesitic rocks that correlate with the 0.25 Ma Cerro de la Estrella volcanic center. The last volcanic package found in the well is correlated to the Santa Catarina basaltic andesites (70-120 m) that are younger than 0.25 Ma, and probably Holocene. Lacustrine deposits crown the stratigraphic column of the drill core with ages probably younger than 34 ka. The San Lorenzo Tezonco well is in a graben-like structure that was filled with more than 1900 m of volcanic products, suggesting that volcanism were intense in the Miocene to the Recent, and the south drainage of the Mexico Basin was closed probably in the early Pleistocene.

Martian paleolakes and waterways - Exobiological implications

NASA Technical Reports Server (NTRS)

Scott, David H.; Rice, James W., Jr.; Dohm, James M.

1991-01-01

Mars may have had an early environment similar to earth's that was conductive to the emergence of life. In addition, increasing geologic evidence indicates that water, upon which terrestrial life depends, has been present on Mars throughout its history. This evidence suggests that life could have developed not only on early Mars but also over longer periods of time in longer lasting, more element local environments. It is suggested that paleolakes may have provided such environments. Unlike the case on earth, this record of the origin and evolution of life has probably not been erased by extensive deformation of the Martian surface. The work reported in this paper has identified eleven prospective areas where large lacustrine basins may once have existed.

The Hydrological Evolution of Mars as Recorded at Gale Crater

NASA Astrophysics Data System (ADS)

Andrews-Hanna, J. C.; Horvath, D. G.

2017-12-01

The sedimentary deposits making up the Aeolis Mons sedimentary mound within Gale Crater preserve a record of the evolving hydrology and climate of Mars during the Late Noachian and Hesperian epochs. Aqueous sedimentary deposits including mudstones, deltaic deposits, and sulfate-cemented sediments indicate the past presence of liquid water on the surface. However, these observations alone do not strictly constrain the nature of the hydrology and climate at the time of deposition. We use models of the subsurface and surface hydrology to shed light on the conditions required to reproduce the observed deposits. Changes in the nature and composition of the deposits reflect changes in the balance between the surface and subsurface components of the hydrological cycle, driven by climate changes. Mudstones observed by the MSL rover at the base of the crater reflect lacustrine deposition under semi-arid conditions, with substantial fluid supply from both the surface (overland flow and direct precipitation) and subsurface. A transition at higher stratigraphic levels to sulfate-cemented sandstones required a change to a more arid climate, with the hydrology dominated by long-distance subsurface transport. Near the top of the mound, unaltered deposits indicate deposition under dry conditions, though this transition coincides with the natural limit on the rise of the water table imposed by the surrounding topography and does not require a change in climate. Erosion of the crater-filling sedimentary deposits to their present mound shape required a dramatic drop in the water table under hyper-arid conditions. Evidence for later lake stands in the Hesperian indicates transient returns to semi-arid conditions similar to those that prevailed during the Late Noachian. By coupling surface and orbital observations with hydrological modeling, we are able to make more specific constraints on the evolving climate and aridity of early Mars.

Sedimentary processes in High Arctic lakes (Cape Bounty, Melville Island, Canada): What do sediments really record?

NASA Astrophysics Data System (ADS)

Normandeau, Alexandre; Lamoureux, Scott; Lajeunesse, Patrick; Francus, Pierre

2016-04-01

Lacustrine sedimentary sequences can hold a substantial amount of information regarding paleoenvironments, hydroclimate variability and extreme events, providing critical insights into past climate change. The study of lacustrine sediments is often limited to the analysis of sediment cores from which past changes are inferred. However, studies have provided evidence that the accumulation of sediments in lacustrine basins and their distribution can be affected by a wide range of internal and external forcing mechanisms. It is therefore crucial to have a good knowledge of the factors controlling the transport and distribution of sediments in lakes prior to investigating paleoenvironmental archives. To address this knowledge gap, the Cape Bounty Arctic Watershed Observatory (CBAWO), located on southern Melville Island in the Canadian High Arctic, was initiated in 2003 as a long term monitoring site with the aim of understanding the controls over sediment transport within similar paired watersheds and lakes. The East and West lakes have been monitored each year since 2003 to document the role of hydro-climate variability on water column processes and sediment deposition. Moorings recording water electrical conductivity, temperature, density, dissolved oxygen and turbidity, as well as sediment traps were deployed during the active hydrological period (generally May-July). These data were analyzed in combination with hydrological and climatic data from the watersheds. Additionally, a high-resolution bathymetric and sub-bottom survey was completed in 2015 and allowed imaging the lake floor and sub-surface in great detail. This combination of process and lake morphological data are unique in the Arctic. The morphostratigraphic analysis reveals two highly disturbed lake floors, being widely affected by subaqueous mass movements that were triggered during the last 2000 years. Backscatter intensity maps and the presence of bedforms on each delta foresets indicate that underflows (turbidity currents) generated at the river mouths are frequent and deliver coarse-grained sediments to the deeper waters. According to the 2003-2014 mooring data, no single hydroclimatic process can explain this underflow activity. Spring snowmelt is often responsible for delivering a substantial amount of sediment to the lakes in the form of underflows, while the contribution of summer rainfalls has also been important in some years. However, one of the largest rainfall recorded (100 mm over four days in August 2013) did not trigger a corresponding underflow event in West Lake, confirming that antecedent soil conditions can significantly reduce runoff and suspended sediment concentrations in the rivers. Moreover, high peaks of turbidity were recorded below ice cover, during the winter, a season thought to be inactive in terms of sedimentary processes. Hence, reconciling the range of processes responsible for sediment deposition and that generate both bedforms and subaqueous mass movements are important to developing consistent records and interpretations of sediment deposition in High Arctic lakes.

Marine-to-lacustrine transition, mud volcanism, and slope instability in an active tectonic setting: the MIS 5 to 4 transition in the Sea of Marmara, Turkey

NASA Astrophysics Data System (ADS)

Grall, Céline; Henry, Pierre; Kendé, Julia; Namık Çaǧatay, M.; Kadir Eriş, K.; Paillès, Christine; Sorlien, Christopher; Shillington, Donna; McHugh, Cecilia; Steckler, Michael; Çifçi, Günay; Géli, Louis

2016-04-01

In the Sea of Marmara, glacio-eustatic cycles set the tempo of a complex history of disconnection and reconnection with the Black Sea and with the global ocean through the Mediterranean Sea. As a result, the sedimentary record consists of alternating high stand marine sediments and lowstand sea or lake sediments. The Sea of Marmara is also an active transtensional basin along the Northern branch of the North Anatolian Fault (NNAF), which accommodates most (~3/4) of the 21-27 mm/a dextral slip between Eurasia and Anatolia. This peculiar setting makes the Sea of Marmara an exceptional site to study the interplay of paleo-environmental factors and seismotectonic processes. Notably, Mass Transport Deposits (MTDs) crossing the faults provide offset markers although their age remains uncertain. A high resolution seismic stratigraphic model has been proposed for 100 ka glacial cycles, based on onlap sequences within basins, and paleo-deltas at shorelines. The sedimentation rate in basins decreases during episodes of sea-level rise and reach maximum values during low stands. Remarkably, seismic reflector sequences display nearly identical character for locations with similar sedimentation rate. The uppermost sequence boundary reflector (Red-H1) has been recently cored at several locations during MARSITECRUISE (Ifremer R/V Pourquoi Pas?, Oct-Nov. 2014), enabled us to correlate high resolution seismic data with core data. The Red-H1 reflector is regionally characterized by a high amplitude and a reverse polarity. Correlations between seismic data and piston core logs indicate that the reverse polarity of this reflector may be explained by a negative density contrast between lacustrine sediments above and a greenish sapropellic layer of several meters thickness below. On shelves, Red-H1 is on top of the low stand wedge. On slopes and topographic highs, Red-H1 appears as an erosional surface laterally correlative with an onlapping unit in basins and is frequently overlain by MTDs. At the transition from Marine Isotope Stage (MIS) 5 to 4, sea-level fell from 25 to 85 m below the modern sea-level resulting in the disconnection of the Sea of Marmara. Sapropels deposited on the shelf before the disconnection and are attributed to MIS-5 (Cagatay et al. 2009). Grall et al, (2014) proposed that MTDs found above the Red-H1 were deposited at the beginning of MIS-4 at ~70 ka and that MTD complexes found during earlier glacial cycles also accumulated after marine to lacustrine-disconnections, possibly in relation with hydrate dissociation and/or clay swelling. Buried mud volcanoes located within the NNAF damage zone pierce the Red-H1 reflector but not the reflector above, suggesting that the last main eruption may also happens at the beginning of MIS-4. We will present preliminary assessment of the paleoenvironmental changes across the MIS-5 to 4 transition from bio-indicators and geochemistry.

Wind influence on the course of sedimentation processes of the laminated lacustrine sediments of Lake Czechowskie

NASA Astrophysics Data System (ADS)

Wiśniewska, Daria; Kramkowski, Mateusz; Tyszkowski, Sebastian

2016-04-01

The studies of the laminated lacustrine sediments play a very important role in the analysis of climate change. They provide valuable information related to the response of the ecosystem to changes in the environment. The condition for the development of the annual lamination is calm sedimentation, which can be compromised by the movement of water caused by waving. The depth to which this movement affects depends on the shape of the lake basin as well as the velocity and direction of the wind. During the study of sedimentary processes of laminated deposits in Lake Czechowskie (Tuchola Forest, North Poland, 53°52'N, 18°14' E, 108 m asl), the following question arose: How strong was the influence of the wind on the processes of lacustrine sedimentation? The key in getting the answers was the use of GIS techniques. Lake Czechowskie has an area of 76.6 hectares; it has two deeps separated by a threshold: a deeper one of 33 m (maximum depth of the basin) in the central-eastern part, and a shallower of 13 m in the western part. The speed of movement of water that is able to move sediment from the bottom of the lake, called the orbital wave velocity, is the basis for the designation of areas where re-suspension takes place. To calculate the wave parameters, the process of mixing, as well as the designation of re-suspension zones, the tool-script Wave Model (Rohweder et al. 2008) in the program ArsGIS 10.1 was used. The input data were wind direction and velocity from the meteorological station of Wirty about 15 km away, bathymetric data from acoustic profiling, and the Maximum Orbital Wave Velocity. The elements taken into account include maximum wind velocity of the multi-year 1996-2013, with particular emphasis on hurricanes Ksawery (December 2013) and Yoda (November 2011), during which wind velocity exceeded 120 km/h. In addition, maximum wind velocity ever recorded in the Polish Lowlands was considered. On the basis of the modelling, the authors delimited the areas where re-suspension takes place in medium and extreme conditions, and those in which wind waving does not affect the mixing of the sediment. The areas particularly predisposed to accumulation and preservation of laminated sediments have been identified. The analysis results allow a better understanding of the re-suspension processes, especially in the littoral zone of the lake. This analysis is also helpful in research of the laminated sediments, and is essential for determining locations for their sampling. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis -ICLEA- of the Helmholtz Association; grant number VH-VI-415.

Late Pleistocene and Holocene aeolian sedimentation in Gonghe Basin, northeastern Qinghai-Tibetan Plateau: Variability, processes, and climatic implications

NASA Astrophysics Data System (ADS)

Qiang, Mingrui; Jin, Yanxiang; Liu, Xingxing; Song, Lei; Li, Hao; Li, Fengshan; Chen, Fahu

2016-01-01

Although stratigraphic sequences of aeolian deposits in dryland areas have long been recognized as providing information about past environments, the exact nature of the environmental processes they reflect remains unclear. Here, we report the results of a detailed investigation of eight outcrop sections in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau. Measurements of sediment grain-size and chemical composition indicate that the deposits are primarily of aeolian origin, consisting of interbedded, well-sorted sand, silty sand, loess and/or palaeosol; however, their occurrence varies from site to site. Fossil dune sands mainly occur in or close to the currently stabilized or semi-stabilized dune fields, whereas loess is distributed along the downwind marginal areas. This pattern of basin-scale differentiation was controlled mainly by spatial variability of sediment supply due to the antecedent sedimentary patterns within the basin. Together with previously-published optically stimulated luminescence (OSL) ages, 24 new OSL dates are used to elucidate the history of aeolian activity and its relationship to climatic changes. There is no apparent relationship between past dune activity and downwind loess deposits. Deposition of silty sand probably occurred during past phases of windy, dry and cold climate in the Late Pleistocene. However, climatic factors alone cannot explain the occurrence of silty sand deposition. This is because the deposition of silty sand was always preceded by episodes of fluvial deposition prior to river incision, thereby indicating the importance of an 'activated' sediment supply associated with fluvial processes. Deposition of well-sorted sand occurred episodically, not only during the Late Pleistocene, but also during the early- to mid-Holocene. Vegetation conditions, controlled either by the occurrence of intervals of moisture deficit during the Late Pleistocene or by changes in the balance between precipitation and evapotranspiration at a local scale, played an important role in sand mobility and deposition. The effect of vegetation on sand mobility is also suggested by independent evidence of aeolian activity from Genggahai Lake in the Gonghe Basin. Here, the deposition of aeolian sand in the basin during the early- to mid-Holocene indicates a low level of effective moisture caused by high evaporation induced by higher summer insolation, despite the coeval increased regional precipitation recorded by lacustrine sediments. In contrast, late Holocene palaeosols represent a high level of effective moisture, and their formation did not necessarily require increased regional precipitation. Overall, our results suggest that the relationship between aeolian activity and regional climate change is complex, and that sand accumulations do not represent the consistent action of surface processes that are related to climatic changes.

Surface ages and rates of erosion at the Calico Archaeological Site in the Mojave Desert, Southern California

NASA Astrophysics Data System (ADS)

Owen, Lewis A.; Davis, Teresa; Caffee, Marc W.; Budinger, Fred; Nash, David

2011-01-01

Erosion rates and surface exposure ages were determined at the Calico Archaeological Site in the Calico Hills of the Mojave Desert, California, using 10Be terrestrial cosmogenic nuclides (TCN) methods. The Calico Hills are composed of Miocene lacustrine deposits of the Barstow Formation and fanglomerates/debris flows of the Pleistocene Yermo Deposits. These deposits are highly denuded and dissected by arroyos that have surfaces armored with chert. Surface erosion rates based on cosmogenic 10Be concentrations in stream sediments range from 19 to 39 m/Ma, with an average of 30.5 ± 6.2 m/Ma. Surface boulders have 10Be TCN ages that range from 27 ka to 198 ka, reflecting significant erosion of the Calico Hills. The oldest boulder age (197 ± 20 ka) places a minimum limit on the age of Yermo deposits. Depth profile ages at four locations within the study area have minimum ages that range from 31 to 84 ka and erosion rate-corrected surface exposure ages ranging from 43 to 139 ka. These surface exposure ages support the view that the surfaces in Yermo deposits formed during the Late Pleistocene to latest Middle Pleistocene. This chronology has important implications for interpreting the context of possible artifacts/geofacts at the site that might provide evidence for early human occupation of North America, and for reconstructing paleoenvironment change and landscape evolution in the region.

Geologic map of the Bodie Hills, California and Nevada

USGS Publications Warehouse

John, David A.; du Bray, Edward A.; Box, Stephen E.; Vikre, Peter G.; Rytuba, James J.; Fleck, Robert J.; Moring, Barry C.

2015-01-01

The Bodie Hills covers about 1,200 km2 straddling the California-Nevada state boundary just north of Mono Lake in the western part of the Basin and Range Province, about 20 km east of the central Sierra Nevada. The area is mostly underlain by the partly overlapping, middle to late Miocene Bodie Hills volcanic field and Pliocene to late Pleistocene Aurora volcanic field (John and others, 2012). Upper Miocene to Pliocene sedimentary deposits, mostly basin-filling sediments, gravel deposits, and fanglomerates, lap onto the west, north, and east sides of the Bodie Hills, where they cover older Miocene volcanic rocks. Quaternary surficial deposits, including extensive colluvial, fluvial, glacial, and lacustrine deposits, locally cover all older rocks. Miocene and younger rocks are tilted ≤30° in variable directions. These rocks are cut by several sets of high-angle faults that exhibit a temporal change from conjugate northeast-striking left-lateral and north-striking right-lateral oblique-slip faults in rocks older than about 9 Ma to north- and northwest-striking dip-slip faults in late Miocene rocks. The youngest faults are north-striking normal and northeast-striking left-lateral oblique-slip faults that cut Pliocene-Pleistocene rocks. Numerous hydrothermal systems were active during Miocene magmatism and formed extensive zones of hydrothermally altered rocks and several large mineral deposits, including gold- and silver-rich veins in the Bodie and Aurora mining districts (Vikre and others, in press).

Quaternary Geologic Map of the Regina 4 Degrees x 6 Degrees Quadrangle, United States and Canada

USGS Publications Warehouse

Fullerton, David S.; Christiansen, Earl A.; Schreiner, Bryan T.; Colton, Roger B.; Clayton, Lee; Bush, Charles A.; Fullerton, David S.

2007-01-01

For scientific purposes, the map differentiates Quaternary surficial deposits and materials on the basis of clast lithology or composition, matrix texture or particle size, structure, genesis, stratigraphic relations, engineering geologic properties, and relative age, as shown on the correlation diagram and indicated in the 'Description of Map Units'. Deposits of some constructional landforms, such as end moraines, are distinguished as map units. Deposits of erosional landforms, such as outwash terraces, are not distinguished, although glaciofluvial, ice-contact, fluvial, and lacustrine deposits that are mapped may be terraced. Differentiation of sequences of fluvial and glaciofluvial deposits at this scale is not possible. For practical purposes, the map is a surficial materials map. Materials are distinguished on the basis of lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized and classified in pedology or agronomy. Rather, it is a generalized map of soils as recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. As a materials map, it serves as a base from which a variety of maps for use in planning engineering, land-use planning, or land-management projects can be derived and from which a variety of maps relating to earth surface processes and Quaternary geologic history can be derived.

Hydrological responses of the Chihuahua Desert of Mexico to possible Heinrich Stadials: A study inferred from geochemistry and stable isotopes of lacustrine sediments

NASA Astrophysics Data System (ADS)

Quiroz-Jiménez, J. D.; Roy, P. D.; Lozano-SantaCruz, R.; López Balbiaux, N.; Girón-García, P.

2016-12-01

The Heinrich Stadials (H6-H1) were cooler intervals of different duration characterized by massive discharge of icebergs from the Laurentide Ice Sheet mainly through the Hudson Straight into the Atlantic Ocean. In this paper, we present a proxy record to infer hydrological responses of the Chihuahua Desert of Mexico to all the Heinrich Stadials (HS) from element ratios, CO3 abundance, and oxygen and carbon isotope compositions of lacustrine calcite of the sediments deposited between depths of 560-78 cm ( 66-8 ka) of a new core collected from the Santiaguillo Basin. Sediments deposited during different HS were identified by radiocarbon dating up to 27.3 ka, extrapolation of an average sediment rate and tuning the CO3 abundance record with insolation in rest of the sequence, and oxygen isotope composition of authigenic CO3. Proxies suggest that hydroclimate of the Chihuahua Desert of Mexico responded differently to different HS. The overall runoff and hence precipitation remained below average during H6, H4, H2 and H1. Both of them were above average during H5 and H3. Similarly, runoff during H4 showed the least variability and it was the most variable during H5. Except for H2, negative excursions in δ18O values suggest cooler conditions during all other HS. In general, dissolved HCO3- was mainly sourced from the atmospheric CO2 during arid intervals. Both the lake productivity and atmospheric CO2 influenced the carbon isotope composition of dissolved HCO3- during humid intervals. During the H2, δ13C values indicate dominant influence of lacustrine productivity. Similar to Chihuahua Desert of Mexico, speleothem records from Fort Stanton and Cave of the Bells (Asmerom et al., 2010; Wagner et al., 2010) showed that hydroclimate of southwest USA also experienced millennial-scale variability and some intervals were more homogeneous compared to others. We did not observe concurrency in proxy records of the Chihuahua Desert of Mexico and southwest USA. Instead, we observed a possible hemispheric link between hydroclimate of the Chihuahua Desert of Mexico and the East Asian Monsoon. Characterized by millennial-scale fluctuations, tendencies of runoff into the Santiaguillo Basin and intensity of the East Asian Monsoon inferred from speleothems from the Hulu Cave of China (Wang et al., 2001) across the six HS were similar.

The Mineralogical and Chemical Case for Habitability at Yellowknife Bay, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Blake, David Frederick; Vaniman, David; Grotzinger, John P.; Conrad, Pamela Gales; Ming, Douglas W.; Bish, David L.; Farmer, Jack D.; Bristow, Thomas

2013-01-01

Sediments of the Yellowknife Bay formation (Gale crater) include the Sheepbed member, a mudstone cut by light-toned veins. Two drill samples, John Klein and Cumberland, were collected and analyzed by the CheMin XRD/XRF instrument and the Sample Analysis at Mars (SAM) evolved gas and isotopic analysis suite of instruments. Drill cuttings were also analyzed by the Alpha Particle X-ray Spectrometer (APXS) for bulk composition. The CheMin XRD analysis shows that the mudstone contains basaltic minerals (Fe-forsterite, augite, pigeonite, plagioclase), as well as Fe-oxide/hydroxides, Fe-sulfides, amorphous materials, and trioctahedral phyllosilicates. SAM evolved gas analysis of higher-temperature OH matches the CheMin XRD estimate of 20% clay minerals in the mudstone. The light-toned veins contain Ca-sulfates; anhydrite and bassanite are detected by XRD but gypsum is also indicated from Mastcam spectral mapping. These sulfates appear to be almost entirely restricted to late-diagenetic veins. The sulfate content of the mudstone matrix itself is lower than other sediments analyzed on Mars. The presence of phyllosilicates indicates that the activity of water was high during their formation and/or transport and deposition (should they have been detrital). Lack of chlorite places limits on the maximum temperature of alteration (likely <100 C). The presence of Ca-sulfates rather than Mg- or Fe-sulfates suggests that the pore water pH was near-neutral and of relatively low ionic strength (although x-ray amorphous Mg-and Fe- sulfates could be present and undetectable by CheMin). The presence of Fe and S in both reduced and oxidized states represents chemical disequilibria that could have been utilized by chemolithoautotrophic biota, if present. When compared to the nearby Rocknest sand shadow mineralogy or the normative mineralogy of Martian soil, both John Klein and Cumberland exhibit a near-absence of olivine and a surplus of magnetite (7-9% of the crystalline component). The magnetite is interpreted as an authigenic product formed when olivine was altered to phyllosilicate. Saponitization of olivine (a process analogous to serpentinization) could have produced H2 in situ. Indeed, early diagenetic hollow nodules ("minibowls") present in the Cumberland mudstone are interpreted by some as forming when gas bubbles accumulated in the unconsolidated mudstone. Lastly, all of these early diagenetic features appear to have been preserved with minimal alteration since their formation, as indicated by the ease of drilling (weak lithification, lack of cementing phases), the presence of 20-30% amorphous material, and the late-stage fracturing with emplacement of calcium sulfate veins and minibowl infills, where they were intersected by veins. A rough estimate of the minimum duration of the lacustrine environment is provided by the minimum thickness of the Sheepbed member. Given 1.5 meters, and applying a mean sediment accumulation rate for lacustrine strata of 1 m/1000 yrs yields a duration of 1,500 years. If the aqueous environments represented by overlying strata are considered, such as Gillespie Lake and Shaler, then this duration increases. The Sheepbed mudstone meets all the requirements of a habitable environment: Aqueous deposition at clement conditions of P, T, pH, Eh and ionic strength, plus the availability of sources of chemical energy.

Nitrate-Dependent Iron Oxidation: A Potential Mars Metabolism

PubMed Central

Price, Alex; Pearson, Victoria K.; Schwenzer, Susanne P.; Miot, Jennyfer; Olsson-Francis, Karen

2018-01-01

This work considers the hypothetical viability of microbial nitrate-dependent Fe2+ oxidation (NDFO) for supporting simple life in the context of the early Mars environment. This draws on knowledge built up over several decades of remote and in situ observation, as well as recent discoveries that have shaped current understanding of early Mars. Our current understanding is that certain early martian environments fulfill several of the key requirements for microbes with NDFO metabolism. First, abundant Fe2+ has been identified on Mars and provides evidence of an accessible electron donor; evidence of anoxia suggests that abiotic Fe2+ oxidation by molecular oxygen would not have interfered and competed with microbial iron metabolism in these environments. Second, nitrate, which can be used by some iron oxidizing microorganisms as an electron acceptor, has also been confirmed in modern aeolian and ancient sediment deposits on Mars. In addition to redox substrates, reservoirs of both organic and inorganic carbon are available for biosynthesis, and geochemical evidence suggests that lacustrine systems during the hydrologically active Noachian period (4.1–3.7 Ga) match the circumneutral pH requirements of nitrate-dependent iron-oxidizing microorganisms. As well as potentially acting as a primary producer in early martian lakes and fluvial systems, the light-independent nature of NDFO suggests that such microbes could have persisted in sub-surface aquifers long after the desiccation of the surface, provided that adequate carbon and nitrates sources were prevalent. Traces of NDFO microorganisms may be preserved in the rock record by biomineralization and cellular encrustation in zones of high Fe2+ concentrations. These processes could produce morphological biosignatures, preserve distinctive Fe-isotope variation patterns, and enhance preservation of biological organic compounds. Such biosignatures could be detectable by future missions to Mars with appropriate instrumentation. PMID:29616015

Nitrate-Dependent Iron Oxidation: A Potential Mars Metabolism.

PubMed

Price, Alex; Pearson, Victoria K; Schwenzer, Susanne P; Miot, Jennyfer; Olsson-Francis, Karen

2018-01-01

This work considers the hypothetical viability of microbial nitrate-dependent Fe 2+ oxidation (NDFO) for supporting simple life in the context of the early Mars environment. This draws on knowledge built up over several decades of remote and in situ observation, as well as recent discoveries that have shaped current understanding of early Mars. Our current understanding is that certain early martian environments fulfill several of the key requirements for microbes with NDFO metabolism. First, abundant Fe 2+ has been identified on Mars and provides evidence of an accessible electron donor; evidence of anoxia suggests that abiotic Fe 2+ oxidation by molecular oxygen would not have interfered and competed with microbial iron metabolism in these environments. Second, nitrate, which can be used by some iron oxidizing microorganisms as an electron acceptor, has also been confirmed in modern aeolian and ancient sediment deposits on Mars. In addition to redox substrates, reservoirs of both organic and inorganic carbon are available for biosynthesis, and geochemical evidence suggests that lacustrine systems during the hydrologically active Noachian period (4.1-3.7 Ga) match the circumneutral pH requirements of nitrate-dependent iron-oxidizing microorganisms. As well as potentially acting as a primary producer in early martian lakes and fluvial systems, the light-independent nature of NDFO suggests that such microbes could have persisted in sub-surface aquifers long after the desiccation of the surface, provided that adequate carbon and nitrates sources were prevalent. Traces of NDFO microorganisms may be preserved in the rock record by biomineralization and cellular encrustation in zones of high Fe 2+ concentrations. These processes could produce morphological biosignatures, preserve distinctive Fe-isotope variation patterns, and enhance preservation of biological organic compounds. Such biosignatures could be detectable by future missions to Mars with appropriate instrumentation.

An Archeological Overview and Management Plan for the Dugway Proving Ground.

DTIC Science & Technology

1984-03-29

niches, particulary the lacustrine environment of the Great Basin (Baumhoff and Heizer 1965, Butler 1978, Heizer and Krieger 1956, Heizer and Harper...power that would capture the animals souls, rendering them docile and stupid (Steward 1970:34). Other large game was present, but were not numerous...uni versity. Baum, Bernard. 1947. Dugway Proving Ground. Aberdeen: U.S. Army Chemical Corps.* Bailmhoff, W.A. and R.F. Heizer . 1965. Postglacial

Geologic map of the Puye Quadrangle, Los Alamos, Rio Arriba, Sandoval, and Santa Fe Counties, New Mexico

USGS Publications Warehouse

Dethier, David P.

2003-01-01

The Puye quadrangle covers an area on the eastern flank of the Jemez Mountains, north of Los Alamos and west of Espanola, New Mexico. Most of the quadrangle consists of a dissected plateau that was formed on the resistant caprock of the Bandelier Tuff, which was erupted from the Valles caldera approximately 1 to 2 million years ago. Within the canyons of the east-flowing streams that eroded this volcanic tableland, Miocene and Pliocene fluvial deposits of the Puye Formation and Santa Fe Group are exposed beneath the Bandelier Tuff. These older units preserve sand and gravel that were deposited by streams and debris flows flowing from source areas located mostly north and northeast of the Puye quadrangle. The landscape of the southeastern part of the quadrangle is dominated by the valley of the modern Rio Grande, and by remnants of piedmont-slope and river-terrace deposits that formed during various stages of incision of the Rio Grande drainage on the landscape. Landslide deposits are common along the steep canyon walls where broad tracts of the massive caprock units have slumped toward the canyons on zones of weakness in underlying strata, particularly on silt/clay-rich lacustrine beds within the Puye Formation.

Investigating the potential of floating mires as record of palaeoenvironmental changes

NASA Astrophysics Data System (ADS)

Zaccone, C.; Adamo, P.; Giordano, S.; Miano, T. M.

2012-04-01

Peat-forming floating mires could provide an exceptional resource for palaeoenvironmental and environmental monitoring studies, as much of their own history, as well as the history of their surrounds, is recorded in their peat deposits. In his Naturalis historia (AD 77-79), Pliny the Elder described floating islands on Lake Vadimonis (now Posta Fibreno Lake, Italy). Actually, a small floating island (ca. 35 m of diameter and 3 m of submerged thickness) still occurs on this calcareous lake fed by karstic springs at the base of the Apennine Mountains. Here the southernmost Italian populations of Sphagnum palustre occur on the small surface of this floating mire known as "La Rota", i.e., a cup-formed core of Sphagnum peat and rhizomes of Helophytes, erratically floating on the water-body of a submerged doline, annexed to the easternmost edge of the lake, characterised by the extension of a large reed bed. Geological evidence point out the existence in the area of a large lacustrine basin since Late Pleistocene. The progressive filling of the lake caused by changing in climatic conditions and neotectonic events, brought about the formation of peat deposits in the area, following different depositional cycles in a swampy environment. Then, a round-shaped portion of fen, originated around lake margins in waterlogged areas, was somehow isolated from the bank and started to float. Coupling data about concentrations and fluxes of several major and trace elements of different origin (i.e., dust particles, volcanic emissions, cosmogenic dusts and marine aerosols), with climate records (plant micro- and macrofossils, pollens, isotopic ratios), biomolecular records (e.g., lipids), detailed age-depth modelling (i.e., 210Pb, 137Cs, 14C), and humification indexes, the present work is hoped to identify and better understand the reliability of this particular "archive", and thus possible relationships between biogeochemical processes occurring in this floating bog and environmental changes.

Evidence for a Neoproterozoic carbonate ramp on the northern edge of the Central African craton: relations with late Proterozoic intracratonic troughs

NASA Astrophysics Data System (ADS)

Alvarez, Philippe

1995-09-01

During Late Proterozoic times, the Archaean Central African craton was affected by trough faulting which led to the formation of grabens, the Sangha aulacogen being the main structure of this type in the studied area. This transverse basin connects with other basins on the northern and south-western borders of the craton. During the Cryogenian, this network of basins was filled with fluvio-deltaic and lacustrine periglacial deposits. The glacio-eustatic transgression in Neoproterozoic III (end-Proterozoic) times flooded extensive areas of shelf on the northern edge of the craton, leading to the development of carbonate sedimentation in a broad outer shelf environment associated with nearshore barriers and evaporitic lagoons. These facies are similar to those developed in the West Congolian Schisto-calcaire (shale-limestone) ramp succession. The North-Central African ramp succession (sediment slope) contains an example of tidal rhythmites in vertical accretion, which occurs beneath the barrier deposits on the subtidal outer shelf. Mathematical analysis of the bedding pattern yields a period of 29 30 days for the lunar month, a result which is in agreement with astrophysical evidence for this epoch (i.e. 650 Ma ago). Major subsidence and seismic activity on this gently sloping platform, associated with the proximity of the Sangha aulacogen, caused the triggering of carbonate turbidites and mass flow deposits. The proliferation of microbial mats under euphotic conditions on an extensive shelf led to the build-up of a carbonate platform. During early Neoproterozoic III times, the West Congolian and North-Central African ramps prograded northwards and southwards, respectively, into the Sangha aulacogen. The sea at that time was restricted to a long graben-like basin, while a remaining area of marine sedimentation persisted into the Palaeozoic. Thus the pattern of end-Proterozoic carbonate sedimentation on the borders of the Central African craton can be interpreted in terms of an overall gently sloping ramp model with progradation converging towards the Sangha aulacogen.

Evidence for a Neoproterozoic carbonate ramp on the northern edge of the Central African craton: relations with Late Proterozoic intracratonic troughs

NASA Astrophysics Data System (ADS)

Alvarez, Philippe

During Late Proterozoic times, the Archaean Central African craton was affected by trough faulting which led to the formation of grabens, the Sangha aulacogen being the main structure of this type in the studied area. This transverse basin connects with other basins on the northern and south-western borders of the craton. During the Cryogenian, this network of basins was filled with fluvio-deltaic and lacustrine periglacial deposits. The glacio-eustatic transgression in Neoproterozoic III (end-Proterozoic) times flooded extensive areas of shelf on the northern edge of the craton, leading to the development of carbonate sedimentation in a broad outer shelf environment associated with nearshore barriers and evaporitic lagoons. These facies are similar to those developed in the West Congolian Schisto-calcaire (shale-limestone) ramp succession.The North-Central African ramp succession (sediment slope) contains an example of tidal rhythmites in vertical accretion, which occurs beneath the barrier deposits on the subtidal outer shelf. Mathematical analysis of the bedding pattern yields a period of 29-30 days for the lunar month, a result which is in agreement with astrophysical evidence for this epoch (i.e. 650Ma ago). Major subsidence and seismic activity on this gently sloping platform, associated with the proximity of the Sangha aulacogen, caused the triggering of carbonate turbidites and mass flow deposits. The proliferation of microbial mats under euphotic conditions on an extensive shelf led to the build-up of a carbonate platform. During early Neoproterozoic III times, the West Congolian and North-Central African ramps prograded northwards and southwards, respectively, into the Sangha aulacogen. The sea at that time was restricted to a long graben-like basin, while a remaining area of marine sedimentation persisted into the Palaeozoic. Thus the pattern of end-Proterozoic carbonate sedimentation on the borders of the Central African craton can be interpreted in terms of an overall gently sloping ramp model with progradation converging towards the Sangha aulacogen.

Distribution and significance of long-chain alkenones as salinity and temperature indicators in Spanish saline lake sediments

NASA Astrophysics Data System (ADS)

Pearson, Emma J.; Juggins, Steve; Farrimond, Paul

2008-08-01

We investigated relationships between sedimentary solvent-extractable long-chain alkenone (LCA) concentration and composition and environmental factors in a suite of endorheic lakes from inland Spain. LCAs were found in 14 of the 54 lakes examined, with concentrations comparable with those from previously published lacustrine settings. The composition of LCAs in our sites, however, contrast from the majority of those previously reported from lake environments; in our study the tri-unsaturated component is the most abundant component at most sites where LCAs are detected, and C 38:3 is the most abundant LCA in the majority of sites. LCA occurrence appears to be restricted to brackish-hypersaline sites and C 37 LCAs are absent above a salinity of ˜40 g L -1 suggesting a salinity control on LCA-producing organisms in these sites. Low concentrations of C 37 LCA components means U37k and U37k temperature indices are generally not applicable. Instead we find good relationships between C 38 components and (in particular mean autumn) temperature and the strongest LCA-temperature relationships are found when using a combination of all C 37 and C 38 compounds. We propose a new alkenone temperature index for lakes with elevated salinity and where the C 38 components dominate the LCA distributions. This is expressed as U3738k=0.0464×MAutAT-0.867 ( r2 = 0.80, n = 13). In this paper, we provide the first account of sedimentary LCA distributions from lakes in inland Spain, extending the range of environments within which these compounds have been found and highlighting their significance as indicators of both salinity and temperature in saline, endorheic lake environments. This has important implications for extending the potential role of LCAs as palaeoclimatic indicators in lacustrine environments.

Quaternary geologic map of the Glasgow 1° x 2° quadrangle, Montana

USGS Publications Warehouse

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2012-01-01

The Glasgow quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Boundary Plateau, Peerless Plateau, and Larb Hills. The primary river is the Milk River. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, and stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 23 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy. Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. The surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits. Residuum, a surficial material, also is mapped. Till of late Wisconsin age is represented by three map units. Till of Illinoian age is also represented locally but is widespread in the subsurface. This map was prepared to serve as a database for compilation of a Quaternary geologic map of the United States and Canada (scale 1:1,000,000). Letter symbols for the map units are those used for the same units in the Quaternary Geologic Atlas of the United States map series.

Geology and oil and gas assessment of the Todilto Total Petroleum System, San Juan Basin Province, New Mexico and Colorado: Chapter 3 in Total petroleum systems and geologic assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado

USGS Publications Warehouse

Ridgley, J.L.; Hatch, J.R.

2013-01-01

Organic-rich, shaly limestone beds, which contain hydrocarbon source beds in the lower part of the Jurassic Todilto Limestone Member of the Wanakah Formation, and sandstone reservoirs in the overlying Jurassic Entrada Sandstone, compose the Todilto Total Petroleum System (TPS). Source rock facies of the Todilto Limestone were deposited in a combined marine-lacustrine depositional setting. Sandstone reservoirs in the Entrada Sandstone were deposited in eolian depositional environments. Oil in Todilto source beds was generated beginning in the middle Paleocene, about 63 million years ago, and maximum generation of oil occurred in the middle Eocene. In the northern part of the San Juan Basin, possible gas and condensate were generated in Todilto Limestone Member source beds until the middle Miocene. The migration distance of oil from the Todilto source beds into the underlying Entrada Sandstone reservoirs was short, probably within the dimensions of a single dune crest. Traps in the Entrada are mainly stratigraphic and diagenetic. Regional tilt of the strata to the northeast has influenced structural trapping of oil, but also allowed for later introduction of water. Subsequent hydrodynamic forces have influenced the repositioning of the oil in some reservoirs and flushing in others. Seals are mostly the anhydrite and limestone facies of the Todilto, which thin to as little as 10 ft over the crests of the dunes. The TPS contains only one assessment unit, the Entrada Sandstone Conventional Oil Assessment Unit (AU) (50220401). Only four of the eight oil fields producing from the Entrada met the 0.5 million barrels of oil minimum size used for this assessment. The AU was estimated at the mean to have potential additions to reserves of 2.32 million barrels of oil (MMBO), 5.56 billion cubic feet of natural gas (BCFG), and 0.22 million barrels of natural gas liquids (MMBNGL).