Karst landforms revealed at various scales using LiDAR and UAV in semi-arid Brazil: Consideration on karstification processes and methodological constraints

NASA Astrophysics Data System (ADS)

Silva, Orildo L.; Bezerra, Francisco H. R.; Maia, Rubson P.; Cazarin, Caroline L.

2017-10-01

This paper analyzes different types of karst landforms and their relationships with fracture systems, sedimentary bedding, and fluvial processes. We mapped karst features in the Cretaceous carbonates of the Jandaíra Formation in the Potiguar Basin, Brazil. We used high-resolution digital elevation models acquired using LiDAR and aerial orthophotographs acquired using an unmanned aerial vehicle (UAV). We grouped and described karst evolution according to scale and degree of karstification. These degrees of karst evolution are coeval. Fractures are opened by dissolution, forming vertical fluid conduits, whereas coeval dissolution occurs along horizontal layers. This conduit system acts as pathways for water flow. The enlargement of conduits contributes to the collapse of blocks in sinkholes and expansion of caves during an intermediate degree of karstification. Propagation of dissolution can cause the coalescence of sinkholes and the capture of small streams. Fluvial processes dominate karst dissolution at an advanced degree of karstification. Comparisons with previously published ground-penetrating radar (GPR), borehole and seismic surveys in sedimentary basins indicate that these structures can be partially preserved during burial.

Subsidence history and tectonic evolution of Campos basin, offshore Brazil

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

Mohriak, W.U.; Karner, G.D.; Dewey, J.F.

1987-05-01

The tectonic component of subsidence in the Campos basin reflects different stages of crustal reequilibration subsequent to the stretching that preceded the breakup of Pangea. Concomitant with rifting in the South Atlantic, Neocomian lacustrine rocks, with associated widespread mafic volcanism, were deposited on a vary rapidly subsiding crust. The proto-oceanic stage (Aptian) is marked by a sequence of evaporitic rocks whose originally greater sedimentary thickness is indicated by residual evaporitic layers with abundant salt flow features. An open marine environment begins with thick Albian/Cenomanian limestones that grade upward and basinward into shales. This section, with halokinetic features and listric detachedmore » faulting sloping out on salt, is characterized by an increased sedimentation rate. The marine Upper Cretaceous to Recent clastic section, associated with the more quiescent phase of thermal subsidence, is characterized by drastic changes in sedimentation rate. Stratigraphic modeling of the sedimentary facies suggests a flexurally controlled loading mechanism (regional compensation) with a temporally and spatially variable rigidity. Locally, the subsidence in the rift-phase fault-bounded blocks shows no correspondence with the overall thermal subsidence, implying that the crust was not effectively thinned by simple, vertically balanced stretching. Deep reflection seismic sections show a general correspondence between sedimentary isopachs and Moho topography, which broadly compensates for the observed subsidence. However, even the Moho is locally affected by crustal-scale master faults that apparently are also controlling the movement mechanisms during the rift-phase faulting.« less

Analysis of ERTS-1 imagery and its application to evaluation of Wyoming's natural resources

NASA Technical Reports Server (NTRS)

Houston, R. S. (Principal Investigator); Marrs, R. W.

1973-01-01

The author has identified the following significant results. Significant results of the Wyoming ERTS-1 investigation during the first six months (July-December 1972) included: (1) successful segregation of Precambrian metasedimentary/metavolcanic rocks from igneous rocks, (2) discovery of iron formation within the metasedimentary sequence, (3) mapping of previously unreported tectonic elements of major significance, (4) successful mapping of large scale fracture systems of the Wind River Mountains, (5) successful distinction of some metamorphic, igneous, and sedimentary lithologies by color additive viewing, (6) mapping of large scale glacial features, and (7) development of techniques for mapping small urban areas.

Asteroid Pond Mineralogy: View from a Cognate Clast in LL3 NWA 8330

NASA Technical Reports Server (NTRS)

Zolensky, M.; Le, L.

2017-01-01

All asteroids surfaces imaged at the cm-scale reveal the presence of pond deposits. These ponds are important because it is likely all asteroid sample return missions will sample them, being the safest (very flat) places to touch down. Therefore, it is essential to understand the differences between the material at the pond surfaces and the host asteroid. Fortunately, some fine-grained cognate lithologies in chondrites show sedimentary features indicating that they sample asteroid ponds.

Digital Aeromagnetic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California

USGS Publications Warehouse

Ponce, David A.

2000-01-01

An aeromagnetic map of the Nevada Test Site area was prepared from publicly available aeromagnetic data described by McCafferty and Grauch (1997). Magnetic surveys were processed using standard techniques. Southwest Nevada is characterized by magnetic anomalies that reflect the distribution of thick sequences of volcanic rocks, magnetic sedimentary rocks, and the occurrence of granitic rocks. In addition, aeromagnetic data reveal the presence of linear features that reflect faulting at both regional and local scales.

Geomorphological and sedimentary processes of the glacially influenced northwestern Iberian continental margin and abyssal plains

NASA Astrophysics Data System (ADS)

Llave, Estefanía; Jané, Gloria; Maestro, Adolfo; López-Martínez, Jerónimo; Hernández-Molina, F. Javier; Mink, Sandra

2018-07-01

The offshore region of northwestern Iberia offers an opportunity to study the impacts of along-slope processes on the morphology of a glacially influenced continental margin, which has traditionally been conceptually characterised by predominant down-slope sedimentary processes. High-resolution multibeam bathymetry, acoustic backscatter and ultrahigh-resolution seismic reflection profile data are integrated and analysed to describe the present-day and recent geomorphological features and to interpret their associated sedimentary processes. Seventeen large-scale seafloor morphologies and sixteen individual echo types, interpreted as structural features (escarpments, marginal platforms and related fluid escape structures) and depositional and erosional bedforms developed either by the influence of bottom currents (moats, abraded surfaces, sediment waves, contourite drifts and ridges) or by gravitational features (gullies, canyons, slides, channel-levee complexes and submarine fans), are identified for the first time in the study area (spanning 90,000 km2 and water depths of 300 m to 5 km). Different types of slope failures and turbidity currents are mainly observed on the upper and lower slopes and along submarine canyons and deep-sea channels. The middle slope morphologies are mostly determined by the actions of bottom currents (North Atlantic Central Water, Mediterranean Outflow Water, Labrador Sea Water and North Atlantic Deep Water), which thereby define the margin morphologies and favour the reworking and deposition of sediments. The abyssal plains (Biscay and Iberian) are characterised by pelagic deposits and channel-lobe systems (the Cantabrian and Charcot), although several contourite features are also observed at the foot of the slope due to the influence of the deepest water masses (i.e., the North Atlantic Deep Water and Lower Deep Water). This work shows that the study area is the result of Mesozoic to present-day tectonics (e.g. the marginal platforms and structural highs). Therefore, tectonism constitutes a long-term controlling factor, whereas the climate, sediment supply and bottom currents play key roles in the recent short-term architecture and dynamics. Moreover, the recent predominant along-slope sedimentary processes observed in the studied northwestern Iberian Margin represent snapshots of the progressive stages and mixed deep-water system developments of the marginal platforms on passive margins and may provide information for a predictive model of the evolution of other similar margins.

Novel patch modelling method for efficient simulation and prediction uncertainty analysis of multi-scale groundwater flow and transport processes

NASA Astrophysics Data System (ADS)

Sreekanth, J.; Moore, Catherine

2018-04-01

The application of global sensitivity and uncertainty analysis techniques to groundwater models of deep sedimentary basins are typically challenged by large computational burdens combined with associated numerical stability issues. The highly parameterized approaches required for exploring the predictive uncertainty associated with the heterogeneous hydraulic characteristics of multiple aquifers and aquitards in these sedimentary basins exacerbate these issues. A novel Patch Modelling Methodology is proposed for improving the computational feasibility of stochastic modelling analysis of large-scale and complex groundwater models. The method incorporates a nested groundwater modelling framework that enables efficient simulation of groundwater flow and transport across multiple spatial and temporal scales. The method also allows different processes to be simulated within different model scales. Existing nested model methodologies are extended by employing 'joining predictions' for extrapolating prediction-salient information from one model scale to the next. This establishes a feedback mechanism supporting the transfer of information from child models to parent models as well as parent models to child models in a computationally efficient manner. This feedback mechanism is simple and flexible and ensures that while the salient small scale features influencing larger scale prediction are transferred back to the larger scale, this does not require the live coupling of models. This method allows the modelling of multiple groundwater flow and transport processes using separate groundwater models that are built for the appropriate spatial and temporal scales, within a stochastic framework, while also removing the computational burden associated with live model coupling. The utility of the method is demonstrated by application to an actual large scale aquifer injection scheme in Australia.

Soft-sediment deformation structures in Cambrian Series 2 tidal deposits (NW Estonia): implications for identifying endogenic triggering mechanisms in ancient sedimentary record

NASA Astrophysics Data System (ADS)

Põldsaar, Kairi

2015-04-01

Soft-sediment deformation structures (SSDS) are documented in several horizons within silt- and sandstones of the Cambrian Series 2 (Dominopolian Stage) Tiskre Formation, and some in the below-deposited argillaceous deposits of the Lükati Formation (northern part of the Baltoscandian Palaeobasin, NW Estonia). The aim of this study was to map, describe, and analyze these deformation features, discuss their deformation mechanism and possible triggers. Load structures (simple load casts, pillows, flame structures, convoluted lamination) with varying shapes and sizes occur in the Tiskre Fm in sedimentary interfaces within medium-bedded peritidal rhythmites (siltstone-argillaceous material) as well as within up to 3 m thick slightly seaward inclined stacked sandstone sequences. Homogenized beds, dish-and-pillar structures, and severely deformed bedding are also found within these stacked units and within a large tidal runoff channel infill. Autoclastic breccias and water-escape channels are rare and occur only in small-scale -- always related to thin, horizontal tidal laminae. Profound sedimentary dykes, sand volcanoes, and thrust faults, which are often related to earthquake triggered soft sediment deformation, were not observed within the studied intervals. Deformation horizon or horizons with large flat-topped pillows often with elongated morphologies occur at or near the boundary between the Tiskre and Lükati formations. Deformation mechanisms identified in this study for the various deformation types are gravitationally unstable reversed density gradient (especially in case of load features that are related to profound sedimentary interfaces) and lateral shear stress due to sediment current drag (in case of deformation structures that not related to loading at any apparent sedimentary interface). Synsedimentary liquefaction was identified as the primary driving force in most of the observed deformation horizons. Clay thixotropy may have contributed in the formation of large sandstone pillows within the Tiskre-Lükati boundary interval at some localities. It is discussed here that the formation of the observed SSDS is genetically related to the restless dynamics of the storm-influenced open marine tidal depositional environment. The most obvious causes of deformation were rapid-deposition, shear and slumping caused by tidal surges, and storm-wave loading.

Primary sedimentary structures and the internal architecture of a Martian sand body in search of evidence for sand transport and deposition

NASA Technical Reports Server (NTRS)

Basu, Abhijit

1988-01-01

Lunar experiences show that unmanned sample return missions, despite limitations on sample size, can produce invaluable data to infer crustal processes, regolith processes, regolith-atmosphere/ionosphere interaction processes, etc. Drill cores provide a record of regolith evolution as well as a more complete sample of the regolith than small scoops and/or rakes. It is proposed that: (1) a hole be drilled in a sand body to obtain continuous oriented cores; a depth of about 10 m would be compatible with what we know of bed form hierarchy of terrestrial stream deposits; (2) two trenches, at right angles to each other and close to the drill-hole, be dug and the walls scraped lightly such that primary/internal sedimentary structures of the sand body become visible; (3) the walls of the trenches be made gravitationally stable by impregnation techniques; (4) acetate or other peels of a strip on each wall be taken; and (5) appropriately scaled photographs of the walls be taken at different sun-angles to ensure maximum ease of interpretation of sedimentary structures; and, to correlate these structural features with those in the core at different depth levels of the core.

Geologic map of Lake Mead and surrounding regions, southern Nevada, southwestern Utah, and northwestern Arizona

USGS Publications Warehouse

Felger, Tracey J.; Beard, Sue

2010-01-01

Regional stratigraphic units and structural features of the Lake Mead region are presented as a 1:250,000 scale map, and as a Geographic Information System database. The map, which was compiled from existing geologic maps of various scales, depicts geologic units, bedding and foliation attitudes, faults and folds. Units and structural features were generalized to highlight the regional stratigraphic and tectonic aspects of the geology of the Lake Mead region. This map was prepared in support of the papers presented in this volume, Special Paper 463, as well as to facilitate future investigations in the region. Stratigraphic units exposed within the area record 1800 million years of geologic history and include Proterozoic crystalline rocks, Paleozoic and Mesozoic sedimentary rocks, Mesozoic plutonic rocks, Cenozoic volcanic and intrusive rocks, sedimentary rocks and surfi cial deposits. Following passive margin sedimentation in the Paleozoic and Mesozoic, late Mesozoic (Sevier) thrusting and Late Cretaceous and early Tertiary compression produced major folding, reverse faulting, and thrust faulting in the Basin and Range, and resulted in regional uplift and monoclinal folding in the Colorado Plateau. Cenozoic extensional deformation, accompanied by sedimentation and volcanism, resulted in large-magnitude high- and low-angle normal faulting and strike-slip faulting in the Basin and Range; on the Colorado Plateau, extension produced north-trending high-angle normal faults. The latest history includes integration of the Colorado River system, dissection, development of alluvial fans, extensive pediment surfaces, and young faulting.

Megatsunami of the World Ocean: Did They Occur in the Recent Past?

NASA Astrophysics Data System (ADS)

Abbott, D.; Bryant, T.; Gusiakov, V.; Masse, W.

2007-05-01

The comprehensive historical tsunami database collected at the Novosibirsk Tsunami Laboratory, contains data on more than 2250 historical tsunamis in the World Ocean from 1628 BC to present. Even if the historical data set is incomplete for many areas, especially for older times, the world catalog contains enough data to estimate average run-up heights for the largest seismically-induced tsunamis that caused wide-spread damage and many fatalities (1755 Lisbon, 1868 and 1877 Chile, 1952 Kamchatka, 1957 Aleutians, 1960 Chile, 1964 Alaska, 2005 Sumatra). This average run-up does not exceed 30-35 meters on the nearest coast with 10-12 meters at the distances of more than 5000 km. Somewhat larger waves (up to 40-45 m) can be generated by volcanic explosions followed by volcanic cone collapse (Santorini 1628 BC, Kuwae 1453, Unzen 1792, Tambora 1815, Krakatau 1883). Landslide-generated tsunamis have the largest recorded heights (up to 525 m) but normally these events are very local with a width of inundated area from hundreds of meters to several kilometers (1958, 1936, 1853 Lituya Bay, 1936 Norway, 2000 Greenland). Meanwhile, many parts of the World Ocean coastline contain prominent features of catastrophic impact of water currents and waves that came from the ocean. They are large boulders, weighing well above one hundred tons, lying on the top of vertical cliffs at the height up to 60 m and large vortexes cut-down in rather resistive coastal rocks. On a smaller scale, these features include sculptured bedrocks, grooves, canyons, cavettos and flutes, found in areas where hurricanes and severe tropical storms are not common. Sedimentary features of water impacts include mega-ripples found in the north-western Australia and so-called chevrons (parabolic and blade- like sand dunes) that are common along many parts of the Indian Ocean coast. In southern Madagascar, chevrons reach an altitude of 205 m with 30-45 km of in-land penetration. A high energy water flux of that scale could be generated by Storegga-class submarine landslides or Santorini-class volcanic explosions, but for this area does not have nearby active volcanoes or large sedimentary basins with the potential for large-volume submarine sliding. Not widely acknowledged presently, but still a real possibility is the creation of these coastal features by catastrophic oceanic waves generated by deep-water impacts of large comets or asteroids. In the Indian Ocean, several crater candidates (Burckle, Mahuika, Kukla, Christie) have been found recently by geomorphological analysis of detailed bathymetric maps. They are geologically young and analysis of nearby deep-sea cores shows the presence of some elements and minerals typical of oceanic impact structures. This paper discusses the consistency of these data with spatial and azimuthal distribution of the large-scale erosional and sedimentary features found at the Australian and Madagascar coast.

Seismic reflection images of the accretionary wedge of Costa Rica

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

Shipley, T.H.; Stoffa, P.L.; McIntosh, K.

The large-scale structure of modern accretionary wedges is known almost entirely from seismic reflection investigations using single or grids of two-dimensional profiles. The authors will report on the first three-dimensional seismic reflection data volume collected of a wedge. This data set covers a 9-km-wide {times} 22-km-long {times} 6-km-thick volume of the accretionary wedge just arcward of the Middle America Trench off Costa Rica. The three-dimensional processing has improved the imaging ability of the multichannel data, and the data volume allows mapping of structures from a few hundred meters to kilometers in size. These data illustrate the relationships between the basement,more » the wedge shape, and overlying slope sedimentary deposits. Reflections from within the wedge define the gross structural features and tectonic processes active along this particular convergent margin. So far, the analysis shows that the subdued basement relief (horst and graben structures seldom have relief of more than a few hundred meters off Costa Rica) does affect the larger scale through going structural features within the wedge. The distribution of mud volcanoes and amplitude anomalies associated with the large-scale wedge structures suggests that efficient fluid migration paths may extend from the top of the downgoing slab at the shelf edge out into the lower and middle slope region at a distance of 50-100 km. Offscraping of the uppermost (about 45 m) sediment occurs within 4 km of the trench, creating a small pile of sediments near the trench lower slope. Underplating of parts of the 400-m-thick subducted sedimentary section begins at a very shallow structural level, 4-10 km arcward of the trench. Volumetrically, the most important accretionary process is underplating.« less

Clay, Water, and Salt: Controls on the Permeability of Fine-Grained Sedimentary Rocks.

PubMed

Bourg, Ian C; Ajo-Franklin, Jonathan B

2017-09-19

The ability to predict the permeability of fine-grained soils, sediments, and sedimentary rocks is a fundamental challenge in the geosciences with potentially transformative implications in subsurface hydrology. In particular, fine-grained sedimentary rocks (shale, mudstone) constitute about two-thirds of the sedimentary rock mass and play important roles in three energy technologies: petroleum geology, geologic carbon sequestration, and radioactive waste management. The problem is a challenging one that requires understanding the properties of complex natural porous media on several length scales. One inherent length scale, referred to hereafter as the mesoscale, is associated with the assemblages of large grains of quartz, feldspar, and carbonates over distances of tens of micrometers. Its importance is highlighted by the existence of a threshold in the core scale mechanical properties and regional scale energy uses of shale formations at a clay content X clay ≈ 1/3, as predicted by an ideal packing model where a fine-grained clay matrix fills the gaps between the larger grains. A second important length scale, referred to hereafter as the nanoscale, is associated with the aggregation and swelling of clay particles (in particular, smectite clay minerals) over distances of tens of nanometers. Mesoscale phenomena that influence permeability are primarily mechanical and include, for example, the ability of contacts between large grains to prevent the compaction of the clay matrix. Nanoscale phenomena that influence permeability tend to be chemomechanical in nature, because they involve strong impacts of aqueous chemistry on clay swelling. The second length scale remains much less well characterized than the first, because of the inherent challenges associated with the study of strongly coupled nanoscale phenomena. Advanced models of the nanoscale properties of fine-grained media rely predominantly on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, a mean field theory of colloidal interactions that accurately predicts clay swelling in a narrow range of conditions (low salinity, low compaction, Na + counterion). An important feature of clay swelling that is not predicted by these models is the coexistence, in most conditions of aqueous chemistry and dry bulk density, of two types of pores between parallel smectite particles: mesopores with a pore width of >3 nm that are controlled by long-range interactions (the osmotic swelling regime) and nanopores with a pore width <1 nm that are controlled by short-range interactions (the crystalline swelling regime). Nanogeochemical characterization and simulation techniques, including coarse-grained and all-atom molecular dynamics simulations, hold significant promise for the development of advanced constitutive relations that predict this coexistence and its dependence on aqueous chemistry.

Sedimentary architecture of the Shaler outcrop, Gale Crater, Mars: paleoenvironmental and sediment transport implications

NASA Astrophysics Data System (ADS)

Gupta, S.; Edgar, L. A.; Rubin, D. M.; Lewis, K. W.; Kocurek, G.; Anderson, R. B.; Bell, J. F.; Dromart, G.; Edgett, K. S.; Grotzinger, J. P.; Hardgrove, C. J.; Kah, L. C.; Leveille, R. J.; Malin, M.; Mangold, N.; Milliken, R.; Minitti, M. E.; Muller, J.; Rice, M. S.; Rowland, S. K.; Schieber, J.; Stack, K.; Sumner, D. Y.; Team, M.

2013-12-01

Sedimentary rocks are archives of ancient depositional processes and environments on planetary surfaces. Reconstructing such processes and environments requires observations of sedimentary structures and architecture (the large-scale geometry and organisation of sedimentary bedsets). We report the analysis of the distinct Shaler outcrop, a prominent stratified unit located between the Bathurst Inlet outcrop and the floor of Yellowknife bay. The Shaler outcrop is an ~1 m thick stratal unit that spans approximately 30 m outcrop in length, and was examined by Curiosity on sols 120-121 and more recently on sols 309-324. Detailed stereo observations of the outcrop across most of its entire lateral extent were made using Navigation and Mast Cameras. These data permit detailed analysis of stratal geometries, distribution of sedimentary structures, and broad grain size trends. Overall the Shaler outcrop comprises a heterogeneous assemblage of interstratified platy sandstones separated by recessive, likely finer-grained beds. Coarser-grained beds are characterised by decimeter-scale trough cross-bedding. The north-eastern section of the outcrop shows greater abundance of interstratified sandstones and finer-grained beds. The southwestern section is characterised by darker bedsets that are likely coarser grained interstratified with finer-grained sandstones. The darker bedsets appear to comprise stacked trough-cross stratified bedsets. Finer-grained recessive intervals are not apparent in this section. The presence and scale of trough cross-stratification indicates that sediment was transported by the migration of sinuous crested dunes. Bedding geometries indicate sub-critical angles of climb. We examine the large-scale bedset architecture to evaluate the original depositional geometry of the Shaler sedimentary system, and consider its plausible depositional processes and paleoenvironmental setting. Finally, we consider its relationship to the sedimentary succession exposed in the Yellowknife bay region.

Centimeter to Decimeter Size Spherical and Cylindrical Features in Gale Crater Sediments

NASA Technical Reports Server (NTRS)

Wiens, R. C.; Maurice, S.; Gasnault, O.; Clegg, S.; Fabre, C.; Nachon, M.; Rubin, D.; Goetz, W.; Mangold, N.; Schroeder, S.;

Multi-scale mass movements: example of the Nile deep-sea fan (NDSF)

NASA Astrophysics Data System (ADS)

Loncke, L.; Droz, L.; Bellaiche, G.; Gaullier, V.; Mascle, J.; Migeon, S.

2003-04-01

The almost 90 000 km2 NDSF, fed by one of the major river in the world, has been nearly entirely surveyed by swath bathymetry and back-scatter imagery during the last four years. Seismic-reflection and 3-5 kHz profiles, and in some places, high resolution data were collected. Some profiles have been provided by BP-Egypt. Using this set of data, we have conducted a multi-scale regional synthesis which stresses the importance of gravity processes in the edification and evolution of this major deep turbidite system. Gravity processes range from regional gravity-driven spreading and gliding of the Plio-Pleistocene sediments above the Messinian mobile evaporites, to huge collapses of large areas of the upper continental slope as well as very localized levee destabilizations and related avulsion mechanisms. The Eastern - tectonized - area of the NDSF is characterized by lens-shaped transparent bodies, likely indicating debris-flow deposits, settled at crestal graben flanks, themselves generated by reactive diapir rise. Debris flows are probably triggered by local readjustments of salt-related tectonic features destabilizing their sedimentary cover. In contrast, within the poorly deformed Western part of the NDSF, we mainly observe recent slumping and gliding phenomenons, incising the upper slope where salt layers are absent. These slumps and glidings evolved downslope to large debris flows. Some of them exhibit volumes up to 1900 km3 and are covered by recent stacked channel-levees units. Smaller scale debris-flows are inter-fingered within these constructional units and led to numerous channel migrations and avulsions, characterized by typical HARP's seismic facies. Recent sedimentary destabilizations seem to be associated with gas seeping or under-compacted mud ascents: in the Central NDSF, the association between pock-marks (or mounds) and destabilizated masses suggest the existence of gas hydrates. Given the variety of processes (either triggered by tectonics, sedimentary overloading, sea-level fluctations, or fluids) and scales of the identified destabilizations, the NDSF appears as an excellent natural laboratory to study mass movement processes.

Fold-structure analysis of paleozoic rocks in the Variscan Harz Mountains (Lautenthal, Central Germany) based on laserscanning and 3D modelling

NASA Astrophysics Data System (ADS)

Wagner, Bianca; Leiss, Bernd; Stöpler, Ralf; Zahnow, Fabian

2017-04-01

Folded paleozoic sedimentary rocks of Upper Devonian to Lower Carboniferous age are very well exposed in the abandoned chert quarry of Lautenthal in the western Harz Mountains. The outcrop represents typical structures of the Rhenohercynian thrust and fold belt of the Variscan orogen and therefore allows quantitative studies for the understanding of e.g. fold mechanisms and the amount of shortening. The sequence is composed of alternating beds of cherts, shales and tuffites, which show varying thicknesses, undulating and thinning out of certain layers. Irregularly occurring lenses of greywackes are interpreted as sedimentary intrusions. The compressive deformation style is expressed by different similar and parallel fold structures at varying scales as well as small-scale reverse faults and triangle structures. An accurate mapping of the outcrop in the classical way is very challenging due to distant and unconnected outcrop parts with differing elevations and orientations. Furthermore, the visibility is limited because of nearby trees, diffuse vegetation cover and no available total view. Therefore, we used a FARO 120 3D laserscanner and Trimble GNSS device to generate a referenced and drawn to scale point cloud of the complete quarry. Based on the point cloud a geometric 3D model of prominent horizons and structural features of various sizes was constructed. Thereafter, we analyzed the structures in matters of orientation and deformation mechanisms. Finally, we applied a retrodeformation algorithm on the model to restore the original sedimentary sequence and to calculate shortening including the amount of pressure solution. Only digital mapping allows such a time-saving, accurate and especially complete 3D survey of this excellent study object. We demonstrated that such 3D-models enable spatial correlations with other complex structures cropping out in the area. Moreover, we confirmed that a structural upscaling to the 100 to 1000 m scale is much easier and much more instructive than it could have been done in the classical way.

Sea-floor morphology and sedimentary environments in southern Narragansett Bay, Rhode Island

USGS Publications Warehouse

McMullen, Katherine Y.; Poppe, Lawrence J.; Blackwood, Dann S.; Nardi, Matthew J.; Andring, Matthew A.

2015-09-09

Multibeam echosounder data collected by the National Oceanic and Atmospheric Administration along with sediment samples and still and video photography of the sea floor collected by the U.S. Geological Survey were used to interpret sea-floor features and sedimentary environments in southern Narragansett Bay, Rhode Island, as part of a long-term effort to map the sea floor along the northeastern coast of the United States. Sea-floor features include rocky areas and scour depressions in high-energy environments characterized by erosion or nondeposition, and sand waves and megaripples in environments characterized by coarse-grained bedload transport. Two shipwrecks are also located in the study area. Much of the sea floor is relatively featureless within the resolution of the multibeam data; sedimentary environments in these areas are characterized by processes associated with sorting and reworking. This report releases bathymetric data from the multibeam echosounder, grain-size analyses of sediment samples, and photographs of the sea floor and interpretations of the sea-floor features and sedimentary environments. It provides base maps that can be used for resource management and studies of topics such as benthic ecology, contaminant inventories, and sediment transport.

Mapping epibenthic assemblages and their relations to sedimentary features in shallow-water, high-energy environments

NASA Astrophysics Data System (ADS)

Sisson, John D.; Shimeta, Jeff; Zimmer, Cheryl Ann; Traykovski, Peter

2002-03-01

Knowledge of spatial relationships among benthic biota and sedimentary features in shallow-water (<30 m) high-energy environments has been severely limited by sampling technology. We describe and report tests of a SCUBA-diving mapping method specifically for this region. Underwater acoustic location is used to achieve meter-scale resolution over kilometer-scale regions of the sea floor. A triad of acoustic transponders is bottom-mounted at known positions, 300-500 m apart. Transported by underwater personal vehicles, SCUBA-divers map the bed using hand-held acoustic receivers that record ranges to the transponders. The mean error of acoustic fixes was 2.4±1.2 m in a 0.5 km×1.0 km test area. Dense assemblages of epibenthic animals were mapped relative to sediment texture and bedforms off the exposed south coast of Martha's Vineyard Island, Massachusetts, USA. Surveys one month apart within a 0.6 km×0.6 km area (8-12 m depth) revealed 100-m-scale patches of the tube worm Spiophanes bombyx (⩽30,000 m -2) in fine sand and of the sand dollar Echinarachnius parma (⩽55 m -2) in coarse sand. Raised mud patches that, together with fine sand, occurred in two shore-perpendicular belts are likely exposed, ancient marsh deposits. Depth gradients of sand-ripple geometry indicated that ripples in deeper areas were not in equilibrium with wave conditions monitored during surveys; i.e., they were relict ripples. Thus, sand dollars in some areas may have had >1 month to rework surficial sands since their transformation by physical processes. Linear regressions of ripple characteristics against sand dollar or tube worm densities were not significant, although such relationships would be highly dependent on temporal scale. The survey method described here can be used at more frequent intervals to explore such interactions between epibenthic animals and sediment-transport dynamics.

Magnetotelluric and aeromagnetic investigations for assessment of groundwater resources in Parnaiba basin in Piaui State of North-East Brazil

NASA Astrophysics Data System (ADS)

Chandrasekhar, E.; Fontes, Sergio L.; Flexor, Jean M.; Rajaram, Mita; Anand, S. P.

2009-06-01

In an attempt to locate the presence of possible groundwater resource regions in the semi-arid North-East Brazil, an integrated survey including aeromagnetic and magnetotelluric (MT) studies have been undertaken in the Guaribas region and only MT survey in the Caracol region. In the Guaribas region the aeromagnetic data, its analytic signal and Euler solutions reveal several subsurface small-scale faults and intrusives that are conducive to be potential groundwater resource regions. A total of about 22 broad-band magnetotelluric (MT) soundings in the period range of 0.006-300 s along two profiles on the marginal arcs of the intra-cratonic sedimentary Parnaíba basin in North-East Brazil have been made across the regional geological strike, the Senador Pompeu Lineament (SPL). SPL trends N40°E and marks a basement high reflecting an irregularity in the original basin geometry. While one of the MT profiles traverses across the SPL, the other lies only in the aeromagnetically surveyed sedimentary region. Two-dimensional inversion of MT data of both profiles shows that the sedimentary basin is conductive (100-150 Ω m) and shows as a thin graben with an average thickness of about 2-3 km beneath both profiles. The basin is located to be at shallow depths (from surface to about 500 m). Based on the facts that the study region falls on sedimentary region having low-to-very low permeability and also in accordance with the subsurface lithology around the study region, the mapped sedimentary basin largely manifests the zone of potential sedimentary aquifer having moderate resistivity of 50-250 Ω m and is located at relatively shallow depths. The identified aquifer zone is believed to have links with the Parnaiba River flowing at a distance of about 300 km NW from the study region. We discuss interpretation of our results of MT and aeromagnetic data sets in the light of hydrological features of the study region.

Experimental Investigation of the Influence of Small Scale Geological Heterogeneity on Capillary Trapping of CO2 Using Engineered Beadpacks

NASA Astrophysics Data System (ADS)

Ganesan Krishnamurthy, P.; Trevisan, L.; Meckel, T. A.

2017-12-01

During geologic CO2 sequestration, most of the storage domain far from the injection sites is likely to be dominated by buoyancy and capillary forces. Under such flow regimes, small scale geological heterogeneities have been shown to dampen plume migration rates and cause trapping beneath capillary barriers. To understand the impact of such heterogeneities on CO2 trapping processes experimentally, many core-scale and lab scale flow studies have been conducted. Reservoir cores are limited by the scale of investigation possible and most lab experiments are conducted in macroheterogeneous media constructed by arranging homogeneous units to represent heterogeneity. However, most natural sedimentary facies display heterogeneity at a hierarchy of scales, and heterogeneity at the mesoscale (mm to decimeters) goes unrepresented in laboratory experiments due to the difficulty in reproducibility. This work presents results from buoyancy driven migration experiments conducted at the meter scale using glass beads packed in a quasi 2D glass cell and complementary reduced physics simulations. We demonstrate a novel automated technique to build beadpacks with 2D heterogeneous sedimentary features in a reproducible manner. A fluid pair that mimics the phase density and viscosity contrasts, and interfacial tension of CO2-Brine at reservoir pressures and temperatures is employed for the flow experiments. Light transmission technique is used for visualization, and to calibrate and quantify saturation of the trapped non-wetting fluid during the experiments. Invasion Percolation is used to simulate the buoyancy driven flow. With the ability to generate different types of heterogeneous structures in a reproducible manner, and by comparing experiments and simulations, a systematic investigation of the effect of heterogeneity on capillary trapping becomes possible.

Mechanisms Of Saucer-Shaped Sill Emplacement: Insight From Experimental Modeling

NASA Astrophysics Data System (ADS)

Galland, O.; Planke, S.; Malthe-Sørenssen, A.; Polteau, S.; Svensen, H.; Podladchikov, Y. Y.

2006-12-01

It has been recently demonstrated that magma intrusions in sedimentary basins had a strong impact on petroleum systems. Most of these intrusions are sills, and especially saucer-shaped sills. These features can be observed in many sedimentary basins (i.e. the Karoo basin, South Africa; the Norwegian and North Sea; the Tunguska basin, Siberia; the Neuquén basin in Argentina). The occurrence of such features in so various settings suggests that their emplacement results from fundamental processes. However, the mechanisms that govern their formation remain poorly constrained. Experiments were conducted to simulate the emplacement of saucer-shaped magma intrusions in sedimentary basins. The model rock and magma were fine-grained silica flour and molten vegetable oil, respectively. This modeling technique allows simultaneous simulation of magma emplacement and brittle deformation at a basin scale. For our purpose, we performed our experiments without external deformation. During the experiments, the oil was injected horizontally at constant flow rate within the silica flour. Then the oil initially emplaced in a sill, whereas the surface of the model inflated into a smooth dome. Subsequently, the oil propagated upwards along inclined sheets, finally reaching the surface at the edge of the dome. The resulting geometries of the intrusions were saucer-shaped sills. Then the oil solidified, and the model was cut in serial cross-sections through which the structures of the intrusive body and of the overburden can be observed. In order to constraint the processes governing the emplacement of such features, we performed a parametric study based on a set of experiments in which we systematically varied parameters such as the depth of emplacement and the injection flow rate of the oil. Our results showed that saucer diameters are larger at deeper level of emplacement. Opposite trend was obtained with varying injection flow rates. Based on our results, we conducted a detailed physical analysis that resulted in the definition of a dimensionless parameter that governs the emplacement of saucers.

Geological timing and duration of methane seepage in different sedimentary and tectonic settings in the Lower Congo Basin

NASA Astrophysics Data System (ADS)

Wenau, S.; Spiess, V.

2016-12-01

Methane seepage sites have been investigated in the Lower Congo Basin using seismo-acoustic methods in combination with geological and geochemical sampling. Pockmarks were observed in different areas of the Lower Congo Basin that are affected by different styles of salt-tectonic deformation and sedimentary input. At the salt front in the southern part of the basin, methane seepage shifts continuously westwards as previously undeformed sediments are affected by westward moving salt. Older seepage sites to the East are cut off from methane supply in the process of continuing salt-tectonic deformation. The initiation of gas accumulation and seepage directly at the deformation front is expected in the late Miocene due to salt-induced uplift. In the northern part of the basin on the lower slope, methane seepage is focused along salt-tectonic faults connecting Pliocene fan deposits to the seafloor, breaching the hemipelagic seal. These sites show indications for continuing seepage for the last 640 kyrs. Such long term seepage activity may be due to the lack of polygonal faults in the hemipelagic seal, focusing gas migration on fewer, salt-tectonic faults. Westward of the salt front, seepage features include the Regab pockmark where a potential reservoir in an Early Pleistocene channel flank is connected to the seafloor feature via a seismic chimney. Seepage activity in this area is also documented to be continuous over geologic time scales by seafloor and sub-seafloor seepage indications such as chimneys, pockmarks and buried seepage features. The Lower Congo Basin thus documents the longevity of seepage processes in the context of various tectonic and sedimentary regimes on a passive continental margin. Indications of the duration of seepage activity at individual sites may be used for methane budgeting in combination with emission rates estimated for typical seepage sites.

Aeromagnetic maps of the Uinta and Piceance Basins and vicinity, Utah and Colorado

USGS Publications Warehouse

Grauch, V.J.S.; Plesha, Joseph L.

1989-01-01

In order to understand the evolution of sedimentary basins, it is important to understand their tectonic setting. In a U.S. Geological Survey (USGS) study of the Uinta and Piceance basins in Utah and Colorado, this understanding is approached through characterization of subsurface structure and lithology of a large region encompassing the basins. An important tool for interpreting these subsurface features is aeromagnetic data. Aeromagnetic anomalies represent variations in the strength and direction of the Earth's magnetic field that are produced by rocks containing a significant number of magnetic minerals (commonly magnetite). The shape and magnitude of an anomaly produced by one body of rock are complexly related to the amount of magnetic minerals present, the magnetic properties of those minerals (determined by a number of factors, including the history of the rock), and the shape of the rock body. In the study area, only crystalline basement rocks and volcanic rocks are likely to contain enough magnetic minerals to produce anomalies; sedimentary rocks and metasediments are generally so poor in magnetic minerals that their magnetic effects cannot be detected by the types of surveys presented in this report. Patterns of anomalies on aeromagnetic maps can reveal not only lithologic differences related to magnetite content, but structural features as well, such as faults that have juxtaposed crystalline rocks against sedimentary rocks, and upwarps of crystalline basement underlying sedimentary sequences. Tectonic features of regional extent may not become apparent until a number of aeromagnetic surveys have been compiled and plotted at the same scale. Commonly the compilation involves piecing together data from surveys that were flown at different times and have widely disparate flight specifications and data reduction procedures. The data may be compiled into a composite map, where all the pieces are plotted onto one map without regard to the differences in flight elevation and datum, or they may be compiled into a merged map, where all survey data are analytically reduced to a common flight elevation and datum, and then digitally merged at the survey boundaries. The composite map retains the original resolution of all survey data, but computer methods to enhance or model regional features crossing the survey boundaries cannot be applied. On the other hand, these computer methods can be applied to the merged data, but the resolution of the data may be somewhat diminished. This report presents both composite and merged aeromagnetic maps for a large region that includes the Uinta Basin in Utah and the Piceance basin in Colorado (fig. 1).

Sedimentary rock-hosted Au deposits of the Dian-Qian-Gui area, Guizhou, and Yunnan Provinces, and Guangxi District, China

USGS Publications Warehouse

Peters, S.G.; Jiazhan, H.; Zhiping, L.; Chenggui, J.

2007-01-01

Sedimentary rock-hosted Au deposits in the Dian-Qian-Gui area in southwest China are hosted in Paleozoic and early Mesozoic sedimentary rocks along the southwest margin of the Yangtze (South China) Precambrian craton. Most deposits have characteristics similar to Carlin-type Au deposits and are spatially associated, on a regional scale, with deposits of coal, Sb, barite, As, Tl, and Hg. Sedimentary rock-hosted Au deposits are disseminated stratabound and(or) structurally controlled. The deposits have many similar characteristics, particularly mineralogy, geochemistry, host rock, and structural control. Most deposits are associated with structural domes, stratabound breccia bodies, unconformity surfaces or intense brittle-ductile deformation zones, such as the Youjiang fault system. Typical characteristics include impure carbonate rock or calcareous and carbonaceous host rock that contains disseminated pyrite, marcasite, and arsenopyrite-usually with ??m-sized Au, commonly in As-rich rims of pyrite and in disseminations. Late realgar, orpiment, stibnite, and Hg minerals are spatially associated with earlier forming sulfide minerals. Minor base-metal sulfides, such as galena, sphalerite, chalcopyrite, and Pb-Sb-As-sulphosalts also are present. The rocks locally are silicified and altered to sericite-clay (illite). Rocks and(or) stream-sediment geochemical signatures typically include elevated concentrations of As, Sb, Hg, Tl, and Ba. A general lack of igneous rocks in the Dian-Qian-Gui area implies non-pluton-related, ore forming processes. Some deposits contain evidence that sources of the metal may have originated in carbonaceous parts of the sedimentary pile or other sedimentary or volcanic horizons. This genetic process may be associated with formation and mobilization of petroleum and Hg in the region and may also be related to As-, Au-, and Tl-bearing coal horizons. Many deposits also contain textures and features indicative of strong structural control by tectonic domes or shear zones and also suggest syndeformational ore deposition, possibly related to the Youjiang fault system. Several sedimentary rock-hosted Au deposits in the Dian-Qian-Gui area also are of the red earth-type and Au grades have been concentrated and enhanced during episodes of deep weathering. ?? 2006 Elsevier B.V. All rights reserved.

Variety of Sedimentary Process and Distribution of Tsunami Deposits in Laboratory Experiments

NASA Astrophysics Data System (ADS)

Yamaguchi, N.; Sekiguchi, T.

2017-12-01

As an indicator of the history and magnitude of paleotsunami events, tsunami deposits have received considerable attention. To improve the identification and interpretation of paleotsunami deposits, an understanding of sedimentary process and distribution of tsunami deposits is crucial. Recent detailed surveys of onshore tsunami deposits including the 2004 Indian Ocean tsunami and the 2011 Tohoku-oki tsunami have revealed that terrestrial topography causes a variety of their features and distributions. Therefore, a better understanding of possible sedimentary process and distribution on such influential topographies is required. Flume experiments, in which sedimentary conditions can be easily controlled, can provide insights into the effects of terrestrial topography as well as tsunami magnitude on the feature of tsunami deposits. In this presentation, we report laboratory experiments that focused on terrestrial topography including a water body (e.g. coastal lake) on a coastal lowland and a cliff. In both cases, the results suggested relationship between the distribution of tsunami deposits and the hydraulic condition of the tsunami flow associated with the terrestrial topography. These experiments suggest that influential topography would enhance the variability in thickness of tsunami deposits, and thus, in reconstructions of paleotsunami events using sedimentary records, we should take into account such anomalous distribution of tsunami deposits. Further examination of the temporal sequence of sedimentary process in laboratory tsunamis may improve interpretation and estimation of paleotsunami events.

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.

A Martian analog in Kansas: Comparing Martian strata with Permian acid saline lake deposits

NASA Astrophysics Data System (ADS)

Benison, Kathleen C.

2006-05-01

An important result of the Mars Exploration Rover's (MER) mission has been the images of sedimentary structures and diagenetic features in the Burns Formation at Meridiani Planum. Bedding, cross-bedding, ripple marks, mud cracks, displacive evaporite crystal molds, and hematite concretions are contained in these Martian strata. Together, these features are evidence of past saline groundwater and ephemeral shallow surface waters on Mars. Geochemical analyses of these Martian outcrops have established the presence of sulfates, iron oxides, and jarosite, which strongly suggests that these waters were also acidic. The same assemblage of sedimentary structures and diagenetic features is found in the salt-bearing terrestrial red sandstones and shales of the middle Permian (ca. 270 Ma) Nippewalla Group of Kansas, which were deposited in and around acid saline ephemeral lakes. These striking sedimentological and mineralogical similarities make these Permian red beds and evaporites the best-known terrestrial analog for the Martian sedimentary rocks at Meridiani Planum.

Pore network properties of sandstones in a fault damage zone

NASA Astrophysics Data System (ADS)

Bossennec, Claire; Géraud, Yves; Moretti, Isabelle; Mattioni, Luca; Stemmelen, Didier

2018-05-01

The understanding of fluid flow in faulted sandstones is based on a wide range of techniques. These depend on the multi-method determination of petrological and structural features, porous network properties and both spatial and temporal variations and interactions of these features. The question of the multi-parameter analysis on fluid flow controlling properties is addressed for an outcrop damage zone in the hanging wall of a normal fault zone on the western border of the Upper Rhine Graben, affecting the Buntsandstein Group (Early Triassic). Diagenetic processes may alter the original pore type and geometry in fractured and faulted sandstones. Therefore, these may control the ultimate porosity and permeability of the damage zone. The classical model of evolution of hydraulic properties with distance from the major fault core is nuanced here. The hydraulic behavior of the rock media is better described by a pluri-scale model including: 1) The grain scale, where the hydraulic properties are controlled by sedimentary features, the distance from the fracture, and the impact of diagenetic processes. These result in the ultimate porous network characteristics observed. 2) A larger scale, where the structural position and characteristics (density, connectivity) of the fracture corridors are strongly correlated with both geo-mechanical and hydraulic properties within the damage zone.

Indicators and Methods to Understand Past Environments from ExoMars Rover Drills

NASA Astrophysics Data System (ADS)

Kereszturi, A.; Bradak, B.; Chatzitheodoridis, E.; Ujvari, G.

2016-11-01

Great advances are expected during the analysis of drilled material acquired from 2 m depth by ExoMars rover, supported by the comparison to local context, and the joint use of different instruments. Textural information might be less detailed relatively to what is usually obtained at outcrops during classical geological field work on the Earth, partly because of the lack of optical imaging of the borehole wall and also because the collected samples are crushed. However sub-mm scale layering and some other sedimentary features might be identified in the borehole wall observations, or in the collected sample prior to crushing, and also at nearby outcrops. The candidate landing sites provide different targets and focus for research: Oxia Planum requires analysis of phyllosilicates and OH content, at Mawrth Vallis the layering of various phyllosilicates and the role of shallow-subsurface leaching should be emphasized. At Aram Dorsum the particle size and fluvial sedimentary features will be interesting. Hydrated perchlorates and sulphates are ideal targets possibly at every landing sites because of OH retention, especially if they are mixed with smectites, thus could point to even ancient wet periods. Extensive use of information from the infrared wall scanning will be complemented for geological context by orbital and rover imaging of nearby outcrops. Information from the context is especially useful to infer the possible action of past H2O. Separation of the ice and liquid water effects will be supported by cation abundance and sedimentary context. Shape of grains also helps here, and composition of transported grains points to the weathering potential of the environment in general. The work on Mars during the drilling and sample analysis will provide brand new experience and knowledge for future missions.

The depositional environment and petrology of the White Rim Sandstone Member of the Permian Cutler Formation, Canyonlands National Park, Utah

USGS Publications Warehouse

Steele-Mallory, B. A.

1982-01-01

The White Rim Sandstone Member of the Cutler Formation of Permian age in Canyonlands National Park, Utah, was deposited in coastal eolian and associated interdune environments. This conclusion is based on stratigraphic relationships primary sedimentary structures, and petrologic features. The White Rim consists of two major genetic units. The first represents a coastal dune field and the second represents related interdune ponds. Distinctive sedimentary structures of the coastal dune unit include large- to medium-scale, unidirectional, tabular-planar cross-bedding; high-index ripples oriented parallel to dip direction of the foresets; coarse-grained lag layers; avalanche or slump marks; and raindrop impressions. Cross-bedding measurements suggest the dunes were deposited as transverse ridges by a dominantly northwest to southeast wind. Distinctive sedimentary structures of the interdune pond unit include wavy, horizontally laminated bedding, adhesion ripples, and desiccation polygons. These features may have been produced by alternate wetting and drying of sediment during water-table fluctuations. Evidence of bioturbation is also present in this unit. Petrologic characteristics of the White Rim helped to define the depositional environment as coastal. A crinoid fragment was identified at one location; both units are enriched in heavy minerals, and small amounts of well rounded, reworked glauconite were found in the White Rim throughout the study area. Earlier work indicates that the White Rim sandstone is late Wolfcampian to early Leonardian in age. During this time, the Canyonlands area was located in a depositional area alternately dominated by marine and nonmarine environments. Results of this study suggest the White Rim represents a coastal dune field that was deposited by predominantly on-shore winds during a period of marine transgression.

Indicators and Methods to Understand Past Environments from ExoMars Rover Drills.

PubMed

Kereszturi, A; Bradak, B; Chatzitheodoridis, E; Ujvari, G

2016-11-01

Great advances are expected during the analysis of drilled material acquired from 2 m depth by ExoMars rover, supported by the comparison to local context, and the joint use of different instruments. Textural information might be less detailed relatively to what is usually obtained at outcrops during classical geological field work on the Earth, partly because of the lack of optical imaging of the borehole wall and also because the collected samples are crushed. However sub-mm scale layering and some other sedimentary features might be identified in the borehole wall observations, or in the collected sample prior to crushing, and also at nearby outcrops. The candidate landing sites provide different targets and focus for research: Oxia Planum requires analysis of phyllosilicates and OH content, at Mawrth Vallis the layering of various phyllosilicates and the role of shallow-subsurface leaching should be emphasized. At Aram Dorsum the particle size and fluvial sedimentary features will be interesting. Hydrated perchlorates and sulphates are ideal targets possibly at every landing sites because of OH retention, especially if they are mixed with smectites, thus could point to even ancient wet periods. Extensive use of information from the infrared wall scanning will be complemented for geological context by orbital and rover imaging of nearby outcrops. Information from the context is especially useful to infer the possible action of past H 2 O. Separation of the ice and liquid water effects will be supported by cation abundance and sedimentary context. Shape of grains also helps here, and composition of transported grains points to the weathering potential of the environment in general. The work on Mars during the drilling and sample analysis will provide brand new experience and knowledge for future missions.

New insights into the geodiversity of the southeast Indian Ocean seafloor revealed by Malaysia Airlines flight MH370 search data

NASA Astrophysics Data System (ADS)

Picard, K.; Brooke, B. B.; Harris, P. T.; Siwabessy, J. P. W.; Coffin, M. F.; Tran, M.; Spinoccia, M.; Weales, J.; Macmillan-Lawler, M.; Sullivan, J.

2017-12-01

A large multibeam echo sounder (MBES) dataset (710, 000 km2, inclusive of transit data) was acquired in the SE Indian Ocean to assist the search for Malaysia Airlines Flight 370 (MH370). Here, we present the results of a geomorphic analysis of this new data and compare with the Global Seafloor Geomorphic Features Map (GSFM) that is based on coarser resolution satellite-derived bathymetry data. The analyses show that abyssal plains and basins are significantly more rugged than their representation in the GSFM, with a 20% increase in the extent of hills and mountains. The new model also reveals four times more seamounts than presented in the GSFM, suggesting a greater number of these features than previously estimated for the broader region and indeed globally. This is important considering the potential ecological significance of these high-relief structures. Analyses of the new data also enabled knolls, fans, valleys, canyons, troughs and holes to be identified, doubling the number of discrete features mapped and revealing the true geodiversity of the deep ocean in this area. This high-resolution mapping of the seafloor also provides new insights into the geological evolution of the region, both in terms of structural, tectonic, and sedimentary processes. For example, sub-parallel ridges extend over approximately 20% of the area mapped and their form and alignment provide valuable insight into Southeast Indian Ridge seafloor spreading processes. Rifting is recorded along the Broken Ridge - Diamantina Escarpment, with rift blocks and well-bedded sedimentary bedrock exposures discernible down to 2,400 m water depth. Ocean floor sedimentary processes are represented in sediment mass transport features, especially along and north of Broken Ridge, and pockmarks (the finest-scale features mapped) south of Diamantina Trench. The new MBES data highlight the complexity of the search area and serve to demonstrate how little we know about the 85-90% of the ocean floor that has not been mapped with this technology. The availability of high-resolution and accurate maps of the ocean floor can clearly provide new insights into the Earth's geological evolution, modern ocean floor processes, and the location of sites that are likely to have relatively high biodiversity.

Determining the saliency of feature measurements obtained from images of sedimentary organic matter for use in its classification

NASA Astrophysics Data System (ADS)

Weller, Andrew F.; Harris, Anthony J.; Ware, J. Andrew; Jarvis, Paul S.

2006-11-01

The classification of sedimentary organic matter (OM) images can be improved by determining the saliency of image analysis (IA) features measured from them. Knowing the saliency of IA feature measurements means that only the most significant discriminating features need be used in the classification process. This is an important consideration for classification techniques such as artificial neural networks (ANNs), where too many features can lead to the 'curse of dimensionality'. The classification scheme adopted in this work is a hybrid of morphologically and texturally descriptive features from previous manual classification schemes. Some of these descriptive features are assigned to IA features, along with several others built into the IA software (Halcon) to ensure that a valid cross-section is available. After an image is captured and segmented, a total of 194 features are measured for each particle. To reduce this number to a more manageable magnitude, the SPSS AnswerTree Exhaustive CHAID (χ 2 automatic interaction detector) classification tree algorithm is used to establish each measurement's saliency as a classification discriminator. In the case of continuous data as used here, the F-test is used as opposed to the published algorithm. The F-test checks various statistical hypotheses about the variance of groups of IA feature measurements obtained from the particles to be classified. The aim is to reduce the number of features required to perform the classification without reducing its accuracy. In the best-case scenario, 194 inputs are reduced to 8, with a subsequent multi-layer back-propagation ANN recognition rate of 98.65%. This paper demonstrates the ability of the algorithm to reduce noise, help overcome the curse of dimensionality, and facilitate an understanding of the saliency of IA features as discriminators for sedimentary OM classification.

Geomorphological and sedimentological analysis of flash-flood deposits: The case of the 1997 Rivillas flood (Spain)

NASA Astrophysics Data System (ADS)

Ortega, Jose A.; Garzón Heydt, Guillermina

2009-11-01

On the basis of the description of the 1997 Rivillas flood deposits, a morphosedimentary feature classification is proposed. Mapping of the main morphosedimentary deposits in seven reaches along the basin has provided abundant data for each defined typology and for a better adjustment of their stability fields. Because of their unstable preservation environment, immediate post-flood field surveys with descriptions of erosive and depositional features were undertaken. Up to 18 features were classified as either sedimentary or erosive and mapped according to their genetic environments. Anthropic interference such as land use changes produce modification of sediment supply and in channel and floodplain erosive processes causing flash-floods to be more catastrophic. Erosive features are dominant over sedimentary ones, as the sedimentary budget in the river is negative. By means of HEC-RAS (Hydrologic Engineering Center) modelling, we were able to obtain mean values of the main variables limiting feature stability (velocity, depth, stream powers and shear stress). These provide information regarding maximum stability threshold and peak flood discharge. The ephemeral nature of riverine flash-flood deposits in this type of setting does not mean that they are not significant, and their interpretation after recent floods can significantly improve interpretation of the event dynamics and its flood hydrology and also be useful for flood risk mapping.

Highly Shocked Low Density Sedimentary Rocks from the Haughton Impact Structure, Devon Island, Nunavut, Canada

NASA Technical Reports Server (NTRS)

Osinski, G. R.; Spray, J. G.

2001-01-01

We present the preliminary results of a detailed investigation of the shock effects in highly shocked, low density sedimentary rocks from the Haughton impact structure. We suggest that some textural features can be explained by carbonate-silicate immiscibility. Additional information is contained in the original extended abstract.

Sedimentary Geology Context and Challenges for Cyberinfrastructure Data Management

NASA Astrophysics Data System (ADS)

Chan, M. A.; Budd, D. A.

2014-12-01

A cyberinfrastructure data management system for sedimentary geology is crucial to multiple facets of interdisciplinary Earth science research, as sedimentary systems form the deep-time framework for many geoscience communities. The breadth and depth of the sedimentary field spans research on the processes that form, shape and affect the Earth's sedimentary crust and distribute resources such as hydrocarbons, coal, and water. The sedimentary record is used by Earth scientists to explore questions such as the continental crust evolution, dynamics of Earth's past climates and oceans, evolution of the biosphere, and the human interface with Earth surface processes. Major challenges to a data management system for sedimentary geology are the volume and diversity of field, analytical, and experimental data, along with many types of physical objects. Objects include rock samples, biological specimens, cores, and photographs. Field data runs the gamut from discrete location and spatial orientation to vertical records of bed thickness, textures, color, sedimentary structures, and grain types. Ex situ information can include geochemistry, mineralogy, petrophysics, chronologic, and paleobiologic data. All data types cover multiple order-of-magnitude scales, often requiring correlation of the multiple scales with varying degrees of resolution. The stratigraphic framework needs dimensional context with locality, time, space, and depth relationships. A significant challenge is that physical objects represent discrete values at specific points, but measured stratigraphic sections are continuous. In many cases, field data is not easily quantified, and determining uncertainty can be difficult. Despite many possible hurdles, the sedimentary community is anxious to embrace geoinformatic resources that can provide better tools to integrate the many data types, create better search capabilities, and equip our communities to conduct high-impact science at unprecedented levels.

Limestones: the love of my life - sun, sea and cycles (Jean Baptiste Lamarck Medal Lecture)

NASA Astrophysics Data System (ADS)

Tucker, M. E.

2009-04-01

In studies of sedimentary rocks we are striving to understand the short and long-term controls on deposition that lead to the variety of facies we see in the geological record. With the development and application of sequence stratigraphy has come the realisation that in most cases the stratigraphic record is not random, but there are patterns and trends in the nature (composition, facies, diagenesis) and thickness of sedimentary units. In addition, sedimentary cycles are widely, if not ubiquitously, developed through stratigraphic successions, and do themselves vary in thickness and facies through a formation and through time. In many cases, orbital forcing is clearly a major control, in addition to longer term tectonic and tectono-eustatic processes. Understanding the major controls on the stratigraphic record and the processes involved in deposition enables us to develop a degree of prediction for the occurrence of particular facies and rock-types. This is especially significant in terms of hydrocarbon potential in frontier basins, notably in the search for source and reservoir rocks. In the case of carbonate and carbonate-evaporite successions, recent work is showing that even at the higher-frequency scale of individual beds and bed-sets, there are regular patterns and changes in thickness. These show that controls on deposition are not random but well organised. Studies of Carboniferous shelf/mid-ramp bioclastic limestones and Jurassic shallow-marine oolites from England reveal systematic variations in bed thickness, as well as oxygen isotopes, Sr and org C values. Permian lower slope carbonates from NE England show thinning-thickening-upward patterns in turbidite bed thickness on several orders of scale. Turbidity current frequency of 1 per ~200 years can be deduced from thicknesses of interbedded laminated facies, which provide the timescale. Beds in ancient shelf and slope carbonates of many geological periods are on a millennial-scale and their features and patterns clearly indicate that millennial-scale changes in climate, most likely driven by fluctuations in solar output, analogous to the D-O cycles of the Quaternary, were responsible, and that these were then modulated by orbital forcing. Solar forcing rules in carbonates, even at the highest frequency.

Sedimentary basins reconnaissance using the magnetic Tilt-Depth method

USGS Publications Warehouse

Salem, A.; Williams, S.; Samson, E.; Fairhead, D.; Ravat, D.; Blakely, R.J.

2010-01-01

We compute the depth to the top of magnetic basement using the Tilt-Depth method from the best available magnetic anomaly grids covering the continental USA and Australia. For the USA, the Tilt-Depth estimates were compared with sediment thicknesses based on drilling data and show a correlation of 0.86 between the datasets. If random data were used then the correlation value goes to virtually zero. There is little to no lateral offset of the depth of basinal features although there is a tendency for the Tilt-Depth results to be slightly shallower than the drill depths. We also applied the Tilt-Depth method to a local-scale, relatively high-resolution aeromagnetic survey over the Olympic Peninsula of Washington State. The Tilt-Depth method successfully identified a variety of important tectonic elements known from geological mapping. Of particular interest, the Tilt-Depth method illuminated deep (3km) contacts within the non-magnetic sedimentary core of the Olympic Mountains, where magnetic anomalies are subdued and low in amplitude. For Australia, the Tilt-Depth estimates also give a good correlation with known areas of shallow basement and sedimentary basins. Our estimates of basement depth are not restricted to regional analysis but work equally well at the micro scale (basin scale) with depth estimates agreeing well with drill hole and seismic data. We focus on the eastern Officer Basin as an example of basin scale studies and find a good level of agreement between previously-derived basin models. However, our study potentially reveals depocentres not previously mapped due to the sparse distribution of well data. This example thus shows the potential additional advantage of the method in geological interpretation. The success of this study suggests that the Tilt-Depth method is useful in estimating the depth to crystalline basement when appropriate quality aeromagnetic anomaly data are used (i.e. line spacing on the order of or less than the expected depth to basement). The method is especially valuable as a reconnaissance tool in regions where drillhole or seismic information are either scarce, lacking, or ambiguous.

A high-resolution, 60 kyr record of the relative geomagnetic field intensity from Lake Towuti, Indonesia

NASA Astrophysics Data System (ADS)

Kirana, Kartika Hajar; Bijaksana, Satria; King, John; Tamuntuan, Gerald Hendrik; Russell, James; Ngkoimani, La Ode; Dahrin, Darharta; Fajar, Silvia Jannatul

2018-02-01

Past changes in the Earth's magnetic field can be highlighted through reconstructions of magnetic paleointensity. Many magnetic field variation features are global, and can be used for the detailed correlation and dating of sedimentary records. On the other hand, sedimentary magnetic records also exhibit features on a regional, rather than a global scale. Therefore, the development of regional scale magnetic field reconstructions is necessary to optimize magnetic paleointensity dating. In this paper, a 60 thousand year (kyr) paleointensity record is presented, using the core TOW10-9B of Lake Towuti, located in the island of Sulawesi, Indonesia, as a part of the ongoing research towards understanding the Indonesian environmental history, and reconstructing a high-resolution regional magnetic record from dating the sediments. Located in the East Sulawesi Ophiolite Belt, the bedrock surrounding Lake Towuti consists of ultramafic rocks that render the lake sediments magnetically strong, creating challenges in the reconstruction of the paleointensity record. These sediment samples were subject to a series of magnetic measurements, followed by testing the obtained paleointensity records resulting from normalizing natural remanent magnetization (NRM) against different normalizing parameters. These paleointensity records were then compared to other regional, as well as global, records of magnetic paleointensity. The results show that for the magnetically strong Lake Towuti sediments, an anhysteretic remanent magnetization (ARM) is the best normalizer. A series of magnetic paleointensity excursions are observed during the last 60 kyr, including the Laschamp excursion at 40 kyr BP, that provide new information about the magnetic history and stratigraphy of the western tropical Pacific region. We conclude that the paleointensity record of Lake Towuti is reliable and in accordance with the high-quality regional and global trends.

A refined model of sedimentary rock cover in the southeastern part of the Congo basin from GOCE gravity and vertical gravity gradient observations

NASA Astrophysics Data System (ADS)

Martinec, Zdeněk; Fullea, Javier

2015-03-01

We aim to interpret the vertical gravity and vertical gravity gradient of the GOCE-GRACE combined gravity model over the southeastern part of the Congo basin to refine the published model of sedimentary rock cover. We use the GOCO03S gravity model and evaluate its spherical harmonic representation at or near the Earth's surface. In this case, the gradiometry signals are enhanced as compared to the original measured GOCE gradients at satellite height and better emphasize the spatial pattern of sedimentary geology. To avoid aliasing, the omission error of the modelled gravity induced by the sedimentary rocks is adjusted to that of the GOCO03S gravity model. The mass-density Green's functions derived for the a priori structure of the sediments show a slightly greater sensitivity to the GOCO03S vertical gravity gradient than to the vertical gravity. Hence, the refinement of the sedimentary model is carried out for the vertical gravity gradient over the basin, such that a few anomalous values of the GOCO03S-derived vertical gravity gradient are adjusted by refining the model. We apply the 5-parameter Helmert's transformation, defined by 2 translations, 1 rotation and 2 scale parameters that are searched for by the steepest descent method. The refined sedimentary model is only slightly changed with respect to the original map, but it significantly improves the fit of the vertical gravity and vertical gravity gradient over the basin. However, there are still spatial features in the gravity and gradiometric data that remain unfitted by the refined model. These may be due to lateral density variation that is not contained in the model, a density contrast at the Moho discontinuity, lithospheric density stratifications or mantle convection. In a second step, the refined sedimentary model is used to find the vertical density stratification of sedimentary rocks. Although the gravity data can be interpreted by a constant sedimentary density, such a model does not correspond to the gravitational compaction of sedimentary rocks. Therefore, the density model is extended by including a linear increase in density with depth. Subsequent L2 and L∞ norm minimization procedures are applied to find the density parameters by adjusting both the vertical gravity and the vertical gravity gradient. We found that including the vertical gravity gradient in the interpretation of the GOCO03S-derived data reduces the non-uniqueness of the inverse gradiometric problem for density determination. The density structure of the sedimentary formations that provide the optimum predictions of the GOCO03S-derived gravity and vertical gradient of gravity consists of a surface density contrast with respect to surrounding rocks of 0.24-0.28 g/cm3 and its decrease with depth of 0.05-0.25 g/cm3 per 10 km. Moreover, the case where the sedimentary rocks are gravitationally completely compacted in the deepest parts of the basin is supported by L∞ norm minimization. However, this minimization also allows a remaining density contrast at the deepest parts of the sedimentary basin of about 0.1 g/cm3.

Late Hesperian plains formation and degradation in a low sedimentation zone of the northern lowlands of Mars

USGS Publications Warehouse

Rodriguez, J.A.P.; Tanaka, K.L.; Berman, D.C.; Kargel, J.S.

2010-01-01

The plains materials that form the martian northern lowlands suggest large-scale sedimentation in this part of the planet. The general view is that these sedimentary materials were transported from zones of highland erosion via outflow channels and other fluvial systems. The study region, the northern circum-polar plains south of Gemini Scopuli on Planum Boreum, comprises the only extensive zone in the martian northern lowlands that does not include sub-basin floors nor is downstream from outflow channel systems. Therefore, within this zone, the ponding of fluids and fluidized sediments associated with outflow channel discharges is less likely to have taken place relative to sub-basin areas that form the other northern circum-polar plains surrounding Planum Boreum. Our findings indicate that during the Late Hesperian sedimentary deposits produced by the erosion of an ancient cratered landscape, as well as via sedimentary volcanism, were regionally emplaced to form extensive plains materials within the study region. The distribution and magnitude of surface degradation suggest that groundwater emergence from an aquifer that extended from the Arabia Terra cratered highlands to the northern lowlands took place non-catastrophically and regionally within the study region through faulted upper crustal materials. In our model the margin of the Utopia basin adjacent to the study region may have acted as a boundary to this aquifer. Partial destruction and dehydration of these Late Hesperian plains, perhaps induced by high thermal anomalies resulting from the low thermal conductivity of these materials, led to the formation of extensive knobby fields and pedestal craters. During the Early Amazonian, the rates of regional resurfacing within the study region decreased significantly; perhaps because the knobby ridges forming the eroded impact crater rims and contractional ridges consisted of thermally conductive indurated materials, thereby inducing freezing of the tectonically controlled waterways associated with these features. This hypothesis would explain why these features were not completely destroyed. During the Late Amazonian, high-obliquity conditions may have led to the removal of large volumes of volatiles and sediments being eroded from Planum Boreum, which then may have been re-deposited as thick, circum-polar plains. Transition into low obliquity ~5. myr ago may have led to progressive destabilization of these materials leading to collapse and pedestal crater formation. Our model does not contraindicate possible large-scale ponding of fluids in the northern lowlands, such as for example the formation of water and/or mud oceans. In fact, it provides a complementary mechanism involving large-scale groundwater discharges within the northern lowlands for the emplacement of fluids and sediments, which could have potentially contributed to the formation of these bodies. Nevertheless, our model would spatially restrict to surrounding parts of the northern plain either the distribution of the oceans or the zones within these where significant sedimentary accumulation would have taken place. ?? 2010 Elsevier Inc.

Modeling the Sedimentary Infill of Lakes in the East African Rift: A Case Study of Multiple versus Single Rift Basin Segments

NASA Astrophysics Data System (ADS)

Zhang, C.; Scholz, C. A.

2016-12-01

The sedimentary basins in the East African Rift are considered excellent modern examples for investigating sedimentary infilling and evolution of extensional systems. Some lakes in the western branch of the rift have formed within single-segment systems, and include Lake Albert and Lake Edward. The largest and oldest lakes developed within multi-segment systems, and these include Lake Tanganyika and Lake Malawi. This research aims to explore processes of erosion and sedimentary infilling of the catchment area in single-segment rift (SSR) and multi-segment rift (MSR) systems. We consider different conditions of regional precipitation and evaporation, and assess the resulting facies architecture through forward modeling, using state-of-the-art commercial basin modeling software. Dionisos is a three-dimensional numerical stratigraphic forward modeling software program, which simulates basin-scale sediment transport based on empirical water- and gravity-driven diffusion equations. It was classically used to quantify the sedimentary architecture and basin infilling of both marine siliciclastic and carbonate environments. However, we apply this approach to continental rift basin environments. In this research, two scenarios are developed, one for a MSR and the other for a SSR. The modeled systems simulate the ratio of drainage area and lake surface area observed in modern Lake Tanganyika and Lake Albert, which are examples of MSRs and SSRs, respectively. The main parameters, such as maximum subsidence rate, water- and gravity-driven diffusion coefficients, rainfall, and evaporation, are approximated using these real-world examples. The results of 5 million year model runs with 50,000 year time steps show that MSRs are characterized by a deep water lake with relatively modest sediment accumulation, while the SSRs are characterized by a nearly overfilled lake with shallow water depths and thick sediment accumulation. The preliminary modeling results conform to the features of sedimentary infills revealed by seismic reflection data acquired in Lake Tanganyika and Lake Albert. Future models will refine the parameters of rainfall and evaporation in these two scenarios to better evaluate detailed basin facies architecture.

Preferential pathways in complex fracture systems and their influence on large scale transport

NASA Astrophysics Data System (ADS)

Willmann, M.; Mañé, R.; Tyukhova, A.

2017-12-01

Many subsurface applications in complex fracture systems require large-scale predictions. Precise predictions are difficult because of the existence of preferential pathways at different scales. The intrinsic complexity of fracture systems increases within fractured sedimentary formations, because also the coupling of fractures and matrix has to be taken into account. This interplay of fracture system and the sedimentary matrix is strongly controlled by the actual fracture aperture of an individual fracture. And an effective aperture cannot be easily be determined because of the preferential pathways along the fracture plane. We investigate the influence of these preferential pathways on large scale solute transport and upscale the aperture. By explicitly modeling flow and particle tracking in individual fractures, we develop a new effective transport aperture, which is weighted by the aperture along the preferential paths, a Lagrangian aperture. We show that this new aperture is consistently larger than existing definitions of effective flow and transport apertures. Finally, we apply our results to a fractured sedimentary formation in Northern Switzerland.

Development of lower Triassic wrinkle structures: implications for the search for life on other planets.

PubMed

Mata, Scott A; Bottjer, David J

2009-11-01

Wrinkle structures are microbially mediated sedimentary structures that are a common feature of Proterozoic and earliest Phanerozoic siliciclastic seafloors on Earth and occur only rarely in post-Cambrian strata. These macroscopic microbially induced sedimentary structures are readily identifiable at the outcrop scale, and their recognition on other planetary bodies by landed missions may suggest the presence of past microbial life. Wrinkle structures of the Lower Triassic (Spathian) Virgin Limestone Member of the Moenkopi Formation in the western United States record an occurrence of widespread microbialite formation in the wake of the end-Permian mass extinction, the largest biotic crisis of the Phanerozoic. Wrinkle structures occur on proximal sandy tempestites deposited within the offshore transition. Storm layers appear to have been rapidly colonized by microbial mats and were subsequently buried by mud during fair-weather conditions. Wrinkle structures exhibit flat-topped crests and sinuous troughs, with associated mica grains oriented parallel to bedding, suggestive of trapping and binding activity. Although Lower Triassic wrinkle structures postdate the widespread occurrence of these features during the Proterozoic and Cambrian, they exhibit many of the same characteristics and environmental trends, which suggests a conservation of microbial formational and preservational processes in subtidal siliciclastic settings on Earth from the Precambrian into the Phanerozoic. In the search for extraterrestrial life, it may be these conservative characteristics that prove to be the most useful and robust for recognizing microbial features on other planetary bodies, and may add to an ever-growing foundation of knowledge for directing future explorations aimed at seeking out macroscopic microbial signatures.

Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

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

Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

1988-02-01

Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.« less

Seismic scattering attribute for sedimentary classification of nearshore marine quarries for a major beach nourishment project: Case study of Adriatic coastline, Regione Abruzzo (Italy)

NASA Astrophysics Data System (ADS)

Orlando, Luciana; Contini, Paolo; De Girolamo, Paolo

2017-06-01

Of fundamental importance for any major beach nourishment project using marine quarries is a correct sedimentary classification. The main purpose of such a classification is to identify sand with the appropriate features for beach nourishment. This task is more onerous when quarry sediments are heterogeneous and mixed with silt. This is typical of nearshore marine quarries. The presence of excess silt compromises the use of marine quarries because of the water turbidity that may be induced in the nourished beaches, especially when the beaches are protected by defense structures. Here we discuss the use of scattering amplitude of seismic data, acquired with a pinger source (2-10 kHz), to detect and classify the unconsolidated sediment of a marine quarry. A robust correlation was found between this seismic attribute and the silt content in the sediment. The scattering amplitude was numerically calculated from the seismic data and used to map slices of silt content at different depths. The results have been validated with sedimentary analysis of vibra- and rotary cores, and by the dredged material used for the beach nourishment. The marine quarry produced about 1.200.000 m3 of sand used to nourish eight different beach sites along the Adriatic coasts of the Regione Abruzzo (Italy). The large-scale sedimentary assessment of the area was based on seismic boomer data and the evaluation of the volume of dredged sediments on multibeam data surveyed before and after the exploitation of the quarry. The study shows that this approach is effective in sites with high lateral and vertical variations in the percentage of sand in the sediments.

Utilization of digital LANDSAT imagery for the study of granitoid bodies in Rondonia: Case example of the Pedra Branca massif

NASA Technical Reports Server (NTRS)

Parada, N. D. J. (Principal Investigator); Almeidafilho, R.; Payolla, B. L.; Depinho, O. G.; Bettencourt, J. S.

1984-01-01

Analysis of digital multispectral MSS-LANDSAT images enhanced through computer techniques and enlarged to a video scale of 1:100.000, show the main geological and structura features of the Pedra Branca granitic massif in Rondonia. These are not observed in aerial photographs or adar images. Field work shows that LANDSAT photogeological units correspond to different facies of granitic rocks in the Pedra Branca massif. Even under the particular characteristics of Amazonia (Tropical Forest, deep weathering, and Quaternary sedimentary covers), an adequate utilization of orbital remote sensing images can be important tools for the orientation of field works.

Analysis of ERTS-1 imagery of Wyoming and its application to evaluation of Wyoming's natural resources

NASA Technical Reports Server (NTRS)

Marrs, R. W.

1973-01-01

The author has identified the following significant results. Significant results of the Wyoming investigation during the first six months include: (1) successful segregation of Precambrian metasedimentary/metavolcanic rocks from igneous rocks; (2) discovery of iron formation within the metasedimentary sequence; (3) mapping of previously unreported tectonic elements of major significance; (4) successful mapping of large scale fractures of the Wind River Mountains; (5) sucessful distinction of some metamorphic, igneous, and sedimentary lithologies by color-additive viewing of ERTS images; (6) mapping and interpretation of glacial features in western Wyoming; and (7) development of techniques for mapping small urban areas.

SIR-A imagery in geologic studies of the Sierra Madre Oriental, northeastern Mexico. Part 1 (Regional stratigraphy): The use of morphostratigraphic units in remote sensing mapping

NASA Technical Reports Server (NTRS)

Longoria, J. F.; Jimenez, O. H.

1985-01-01

SIR-A imaging was used in geological studies of sedimentary terrains in the Sierra Madre Oriental, northeastern Mexico. Geological features such as regional strike and dip, bedding, folding and faulting were readily detected on the image. The recognition of morphostructural units in the imagery, coupled with field verification, enabled geological mapping of the region at the scale of 1:250 000. Structural profiling lead to the elaboration of a morphostructural map allowing the recognition of an echelon folds and field trends which were used to postulate the ectonic setting of the region.

Improved estimation of hydraulic conductivity by combining stochastically simulated hydrofacies with geophysical data.

PubMed

Zhu, Lin; Gong, Huili; Chen, Yun; Li, Xiaojuan; Chang, Xiang; Cui, Yijiao

2016-03-01

Hydraulic conductivity is a major parameter affecting the output accuracy of groundwater flow and transport models. The most commonly used semi-empirical formula for estimating conductivity is Kozeny-Carman equation. However, this method alone does not work well with heterogeneous strata. Two important parameters, grain size and porosity, often show spatial variations at different scales. This study proposes a method for estimating conductivity distributions by combining a stochastic hydrofacies model with geophysical methods. The Markov chain model with transition probability matrix was adopted to re-construct structures of hydrofacies for deriving spatial deposit information. The geophysical and hydro-chemical data were used to estimate the porosity distribution through the Archie's law. Results show that the stochastic simulated hydrofacies model reflects the sedimentary features with an average model accuracy of 78% in comparison with borehole log data in the Chaobai alluvial fan. The estimated conductivity is reasonable and of the same order of magnitude of the outcomes of the pumping tests. The conductivity distribution is consistent with the sedimentary distributions. This study provides more reliable spatial distributions of the hydraulic parameters for further numerical modeling.

Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

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

Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

1988-01-01

Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet.« less

3D mechanical stratigraphy of a deformed multi-layer: Linking sedimentary architecture and strain partitioning

NASA Astrophysics Data System (ADS)

Cawood, Adam J.; Bond, Clare E.

2018-01-01

Stratigraphic influence on structural style and strain distribution in deformed sedimentary sequences is well established, in models of 2D mechanical stratigraphy. In this study we attempt to refine existing models of stratigraphic-structure interaction by examining outcrop scale 3D variations in sedimentary architecture and the effects on subsequent deformation. At Monkstone Point, Pembrokeshire, SW Wales, digital mapping and virtual scanline data from a high resolution virtual outcrop have been combined with field observations, sedimentary logs and thin section analysis. Results show that significant variation in strain partitioning is controlled by changes, at a scale of tens of metres, in sedimentary architecture within Upper Carboniferous fluvio-deltaic deposits. Coupled vs uncoupled deformation of the sequence is defined by the composition and lateral continuity of mechanical units and unit interfaces. Where the sedimentary sequence is characterized by gradational changes in composition and grain size, we find that deformation structures are best characterized by patterns of distributed strain. In contrast, distinct compositional changes vertically and in laterally equivalent deposits results in highly partitioned deformation and strain. The mechanical stratigraphy of the study area is inherently 3D in nature, due to lateral and vertical compositional variability. Consideration should be given to 3D variations in mechanical stratigraphy, such as those outlined here, when predicting subsurface deformation in multi-layers.

3D geometries of normal faults in a brittle-ductile sedimentary cover: Analogue modelling

NASA Astrophysics Data System (ADS)

Vasquez, Lina; Nalpas, Thierry; Ballard, Jean-François; Le Carlier De Veslud, Christian; Simon, Brendan; Dauteuil, Olivier; Bernard, Xavier Du

2018-07-01

It is well known that ductile layers play a major role in the style and location of deformation. However, at the scale of a single normal fault, the impact of rheological layering is poorly constrained and badly understood, and there is a lack of information regarding the influence of several décollement levels within a sedimentary cover on the single fault geometry under purely extensive deformation. We present small-scale experiments that were built with interbedded layers of brittle and ductile materials and with minimum initial constraints (only a velocity discontinuity at the base of the experiment) on the normal fault geometry in order to investigate the influence of controlled parameters such as extension velocity, rate of extension, ductile thickness and varying stratigraphy on the 3D fault geometry. These experiments showed a broad-spectrum of tectonic features such as grabens, ramp-flat-ramp normal faults and reverse faults. Forced folds are associated with fault flats that develop in the décollement levels (refraction of the fault angle). One of the key points is that the normal fault geometry displays large variations in both direction and dip, despite the imposed homogeneous extension. This result is exclusively related to the presence of décollement levels, and is not associated with any global/regional variation in extension direction and/or inversion.

Sedimentary textures formed by aqueous processes, Erebus crater Meridiani Planum, Mars

USGS Publications Warehouse

Grotzinger, J.; Bell, J.; Herkenhoff, K.; Johnson, J.; Knoll, A.; McCartney, E.; McLennan, S.; Metz, J.; Moore, J.; Squyres, S.; Sullivan, R.; Ahronson, O.; Arvidson, R.; Joliff, B.; Golombek, M.; Lewis, K.; Parker, T.; Soderblom, J.

2006-01-01

New observations at Erebus crater (Olympia outcrop) by the Mars Exploration Rover Opportunity between sols 671 and 735 (a sol is a martian day) indicate that a diverse suite of primary and penecontemporaneous sedimentary structures is preserved in sulfate-rich bedrock. Centimeter-scale trough (festoon) cross-lamination is abundant, and is better expressed and thicker than previously described examples. Postdepositional shrinkage cracks in the same outcrop are interpreted to have formed in response to desiccation. Considered collectively, this suite of sedimentary structures provides strong support for the involvement of liquid water during accumulation of sedimentary rocks at Meridiani Planum. ?? 2006 Geological Society of America.

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.

ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

NASA Astrophysics Data System (ADS)

Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.

2014-12-01

The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as those recognized in the Cretaceous Arctic and Marca Shale of California.

On contemporary sedimentation at the titanic survey area

NASA Astrophysics Data System (ADS)

Lukashin, V. N.

2009-12-01

The basic parameters of the sedimentation environment are considered: the Western Boundary Deep Current that transports sedimentary material and distributes it on the survey area; the nepheloid layer, its features, and the distribution of the concentrations and particulate standing crop in it; the distribution of the horizontal and vertical fluxes of the sedimentary material; and the bottom sediments and their absolute masses. The comparison of the vertical fluxes of the particulate matter and the absolute masses of the sediments showed that the contemporary fluxes of sedimentary material to the bottom provided the distribution of the absolute masses of the sediments in the survey area during the Holocene.

The location and nature of the Telemzan High Ghadames basin boundary in southern Tunisia based on gravity and magnetic anomalies

NASA Astrophysics Data System (ADS)

Gabtni, H.; Jallouli, C.; Mickus, K. L.; Zouari, H.; Turki, M. M.

2006-03-01

Gravity and magnetic data were analyzed to add constraints on the location and nature of the Telemzan-Ghadames boundary (TGB) and structure of the Ghadames basin in southern Tunisia. TGB is the boundary between the thick sedimentary cover of the intracratonic Ghadames basin to the south and the thin sedimentary cover of the Saharan platform to the north. The upward continuation of the Bouguer gravity anomalies showed that the TGB is a regional geophysical feature that may have controlled the amount of sediment being deposited both north and south of the boundary and the tectonic environment in the region since Paleozoic time. To emphasize the shorter wavelength gravity and magnetic anomalies, a series of gray scale images of the directional horizontal gradients were constructed that determined a series of previously unknown east-west-trending gravity and magnetic anomalies south of 31.6°N that correspond to lineaments seen on a Landsat 7 image and the location of the TGB. Also, an edge-enhancement analysis illustrated the same linear gravity anomalies and showed the subbasins and uplifts within the Ghadames basin had source depths of between 0.5 and 3.4 km. A north-south trending gravity model showed that the TGB is a relatively gradual feature (possibly basement stepped down by relatively low-displacement faulting) controlling the subsidence of the main Ghadames basin and confirms the edge-enhancement analysis that subbasin S3 and uplift U1 are the main structural features within the Ghadames basin. The knowledge of basement architecture of the Ghadames basin is important for future petroleum exploration within this intracratonic basin.

Oceanographic Mower Cruise

NASA Astrophysics Data System (ADS)

Valencia, J.; Ercilla, G.; Hernández-Molina, F. J.; Casas, D.

2015-04-01

The MOWER Cruise has executed a geophysics and geologic expedition in the Gulf of Cádiz (sector adjacent to the Strait of Gibraltar) and west off Portugal, in the framework of the coordinate research project MOWER "Erosive features and associated sandy deposits generated by the Mediterranean Outflow Water (MOW) around Iberia: paleoceanographic, sedimentary & economic implications" (CTM 2012-39599-C03). The main aim of this project is to identify and study the erosional features (terraces and channels) and associated sedimentary deposits (sandy contourites) generated by the Mediterranean Water Masses around the middle continental slope of Iberia (The Mediterranean Outflow Water - MOW - in the Atlantic margins), their Pliocene and Quaternary evolution and their paleoceanographic, sedimentary and economic implications. This objective directly involves the study of alongslope (contourite) processes associated with the MOW and across-slope (turbiditic flows, debris flows, etc.) processes in the sedimentary stacking pattern and evolution of the Iberian margins. The MOWER project and cruise are related to the Integrated Ocean Drilling Program (IODP) Expedition 339 (Mediterranean Outflow). It is also linked and coordinated with CONDRIBER Project "Contourite drifts and associated mass-transport deposits along the SW Iberia margin - implications to slope stability and tsunami hazard assessment" (2013-2015) funded by the Fundação para a Ciência e Tecnologia, Portugal (PTDC/GEO-GEO/4430/2012).

Late Pleistocene dune-sourced alluvial fans in coastal settings: Sedimentary facies and related processes (Mallorca, Western Mediterranean)

NASA Astrophysics Data System (ADS)

Pomar, F.; del Valle, L.; Fornós, J. J.; Gómez-Pujol, L.

2018-05-01

Aeolian-alluvial sedimentary interaction results in the formation of deposits characterized by typical alluvial sedimentary structures, but is composed of conspicuous amounts of aeolian sediments. The literature on this topic is limited and most works relate more with continental aeolian dunes or fluvial dune interference with fan bodies. Furthermore, there is a lack of examples of aeolian-alluvial sedimentary interference in coastal settings. In the western Mediterranean, there are many Pleistocene alluvial fan deposits built up partly by sediment originating from coastal dunes dismantled by alluvial streams. Very often, these deposits show a continuous sedimentary sequence through which we can derive the contribution and predominance of coastal, alluvial-colluvial and aeolian processes and their controls on landscape formation. This is an outstanding feature within coastal systems since it shows marine sediments reworked and integrated within coastal dune fields by aeolian transport, and the latter built up into alluvial fan bodies. In this sense, aeolian-alluvial interaction is the geomorphic-sedimentary expression of the coexistence and overlapping of alluvial and aeolian environments resulting in deposits sharing sedimentary features from both environments. The aim of this paper is to unravel the contribution of coastal dunes in the construction of alluvial fans bodies and identify the main sedimentary facies that constitute these deposits, as well as their climatic controls. For this reason, Es Caló fan (northern Mallorca) has been selected due to its well-exposed deposits exhibiting the alternation of aeolian, alluvial and colluvial deposits. Sedimentological and stratigraphic analyses based on 33 logs and complementary analyses demonstrate that most of the facies constituting the fan body are made up completely of marine bioclastic sands. These deposits record an alluvial fan sedimentary environment characterized by sediments inputs that do not proceed from non-alluvial/fluvial/colluvial systems. In fact they relate with a marine source. Chronologies on aeolianites of northern Mallorca indicate that up to four periods of aeolian deposition took place during cooling stages and marine regressions over the last 100 kyr. Moreover, the alternation of short warming-cooling fluctuations between the cooling stages may have provided the conditions necessary to generate stormy weather in the western Mediterranean, resulting in aeolian-alluvial interactions. Additionally, the dynamics of this sedimentary environment were only possible because during the Last Glacial Maximum, the sea level remained low enough to allow for the formation of coastal dune fields and fans.

Evolution of fore-arc and back-arc sedimentary basins with focus on the Japan subduction system and its analogues

NASA Astrophysics Data System (ADS)

Sato, Hiroshi; Ishiyama, Tatsuya; Matenco, Liviu; Nader, Fadi Henri

2017-07-01

The International Lithosphere Program (ILP) seeks to elucidate the nature, dynamics, origin and evolution of the lithosphere through international, multidisciplinary geoscience research projects and coordinating committees (Cloetingh and Negendank, 2010). The focus of the Task Force VI Sedimentary Basins activities is to foster collaborations between academia, research institutes and industry in all domains relevant for the understanding of sedimentary basins, from regional to nano-scale, from the deep earth to near surface processes (e.g., Roure et al., 2010, 2013). In this activity, it is important to develop and validate novel concepts of sedimentary basin evolution and topography building by incorporating geological/geophysical datasets and methodologies applied to worldwide natural laboratories (Cloetingh et al., 2011; Cloetingh and Willett, 2013; Matenco and Andriessen, 2013). The Task Force aims to understand and predict the processes that control the formation and evolution of the coupled orogens and sedimentary basins system through integration of field studies, analytical techniques and numerical/analogue modelling. At the same time, the Task Force aims to promote research in the domain of sedimentary basins evolution and quantitative tectonics for the study of mountain building and the subsequent extensional collapse, and their quantitative implications for vertical motions on different temporal and spatial scales (Gibson et al., 2015; Matenco et al., 2016; Roure, 2008; Seranne et al., 2015). The implications of tectonics on basin fluids (fluid-flow and rock-fluid interactions) are important to understand and predict geo-resources (e.g., Nader, 2016). Important is to initiate innovative research lines in linking the evolution of sedimentary systems by integrating cross-disciplinary expertise with a focus on integrated sedimentary basins and orogenic evolution. The key is to strengthen the synergy between academic research and applied industry in large (inter)national interdisciplinary research networks able to tackle complex problems at integrated system level.

Paleoclimatic signature in terrestrial flood deposits.

PubMed

Koltermann, C E; Gorelick, S M

1992-06-26

Large-scale process simulation was used to reconstruct the geologic evolution during the past 600,000 years of an alluvial fan in northern California. In order to reproduce the sedimentary record, the simulation accounted for the dynamics of river flooding, sedimentation, subsidence, land movement that resulted from faulting, and sea level changes. Paleoclimatic trends induced fluctuations in stream flows and dominated the development of the sedimentary deposits. The process simulation approach serves as a quantitative means to explore the genesis of sedimentary architecture and its link to past climatic conditions and fault motion.

Supercomputer analysis of sedimentary basins.

PubMed

Bethke, C M; Altaner, S P; Harrison, W J; Upson, C

1988-01-15

Geological processes of fluid transport and chemical reaction in sedimentary basins have formed many of the earth's energy and mineral resources. These processes can be analyzed on natural time and distance scales with the use of supercomputers. Numerical experiments are presented that give insights to the factors controlling subsurface pressures, temperatures, and reactions; the origin of ores; and the distribution and quality of hydrocarbon reservoirs. The results show that numerical analysis combined with stratigraphic, sea level, and plate tectonic histories provides a powerful tool for studying the evolution of sedimentary basins over geologic time.

Geologic map of the Callville Bay Quadrangle, Clark County, Nevada, and Mohave County, Arizona

USGS Publications Warehouse

Anderson, R. Ernest

2003-01-01

Report: 139 Map Scale: 1:24,000 Map Type: colored geologic map A 1:24,000-scale, full-color geologic map and four cross sections of the Callville Bay 7-minute quadrangle in Clark County, Nevada and Mohave County, Arizona. An accompanying text describes 21 stratigraphic units of Paleozoic and Mesozoic sedimentary rocks and 40 units of Cenozoic sedimentary, volcanic, and intrusive rocks. It also discusses the structural setting, framework, and history of the quadrangle and presents a model for its tectonic development.

Lithofacies control in detrital zircon provenance studies: Insights from the Cretaceous Methow basin, southern Canadian Cordillera

USGS Publications Warehouse

DeGraaff-Surpless, K.; Mahoney, J.B.; Wooden, J.L.; McWilliams, M.O.

2003-01-01

High-frequency sampling for detrital zircon analysis can provide a detailed record of fine-scale basin evolution by revealing the temporal and spatial variability of detrital zircon ages within clastic sedimentary successions. This investigation employed detailed sampling of two sedimentary successions in the Methow/Methow-Tyaughton basin of the southern Canadian Cordillera to characterize the heterogeneity of detrital zircon signatures within single lithofacies and assess the applicability of detrital zircon analysis in distinguishing fine-scale provenance changes not apparent in lithologic analysis of the strata. The Methow/Methow-Tyaughton basin contains two distinct stratigraphic sequences of middle Albian to Santonian clastic sedimentary rocks: submarine-fan deposits of the Harts Pass Formation/Jackass Mountain Group and fluvial deposits of the Winthrop Formation. Although both stratigraphic sequences displayed consistent ranges in detrital zircon ages on a broad scale, detailed sampling within each succession revealed heterogeneity in the detrital zircon age distributions that was systematic and predictable in the turbidite succession but unpredictable in the fluvial succession. These results suggest that a high-density sampling approach permits interpretation of finescale changes within a lithologically uniform turbiditic sedimentary succession, but heterogeneity within fluvial systems may be too large and unpredictable to permit accurate fine-scale characterization of the evolution of source regions. The robust composite detrital zircon age signature developed for these two successions permits comparison of the Methow/Methow-Tyaughton basin age signature with known plutonic source-rock ages from major plutonic belts throughout the Cretaceous North American margin. The Methow/Methow-Tyaughton basin detrital zircon age signature matches best with source regions in the southern Canadian Cordillera, requiring that the basin developed in close proximity to the southern Canadian Cordillera and providing evidence against large-scale dextral translation of the Methow terrane.

Improved estimation of hydraulic conductivity by combining stochastically simulated hydrofacies with geophysical data

PubMed Central

Zhu, Lin; Gong, Huili; Chen, Yun; Li, Xiaojuan; Chang, Xiang; Cui, Yijiao

2016-01-01

Hydraulic conductivity is a major parameter affecting the output accuracy of groundwater flow and transport models. The most commonly used semi-empirical formula for estimating conductivity is Kozeny-Carman equation. However, this method alone does not work well with heterogeneous strata. Two important parameters, grain size and porosity, often show spatial variations at different scales. This study proposes a method for estimating conductivity distributions by combining a stochastic hydrofacies model with geophysical methods. The Markov chain model with transition probability matrix was adopted to re-construct structures of hydrofacies for deriving spatial deposit information. The geophysical and hydro-chemical data were used to estimate the porosity distribution through the Archie’s law. Results show that the stochastic simulated hydrofacies model reflects the sedimentary features with an average model accuracy of 78% in comparison with borehole log data in the Chaobai alluvial fan. The estimated conductivity is reasonable and of the same order of magnitude of the outcomes of the pumping tests. The conductivity distribution is consistent with the sedimentary distributions. This study provides more reliable spatial distributions of the hydraulic parameters for further numerical modeling. PMID:26927886

Advanced GPR imaging of sedimentary features: integrated attribute analysis applied to sand dunes

NASA Astrophysics Data System (ADS)

Zhao, Wenke; Forte, Emanuele; Fontolan, Giorgio; Pipan, Michele

2018-04-01

We evaluate the applicability and the effectiveness of integrated GPR attribute analysis to image the internal sedimentary features of the Piscinas Dunes, SW Sardinia, Italy. The main objective is to explore the limits of GPR techniques to study sediment-bodies geometry and to provide a non-invasive high-resolution characterization of the different subsurface domains of dune architecture. On such purpose, we exploit the high-quality Piscinas data-set to extract and test different attributes of the GPR trace. Composite displays of multi-attributes related to amplitude, frequency, similarity and textural features are displayed with overlays and RGB mixed models. A multi-attribute comparative analysis is used to characterize different radar facies to better understand the characteristics of internal reflection patterns. The results demonstrate that the proposed integrated GPR attribute analysis can provide enhanced information about the spatial distribution of sediment bodies, allowing an enhanced and more constrained data interpretation.

Aeolian sedimentary processes at the Bagnold Dunes, Mars: Implications for modern dune dynamics and sedimentary structures in the aeolian stratigraphic record of Mars

NASA Astrophysics Data System (ADS)

Ewing, Ryan C.; Bridges, Nathan T.; Sullivan, Rob; Lapotre, Mathieu G. A.; Fischer, Woodward W.; Lamb, Mike P.; Rubin, David M.; Lewis, Kevin W.; Gupta, Sanjeev

2016-04-01

Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under Martian conditions. In-situ observations of sand dunes (informally called the Bagnold Dunes) by Curiosity Rover in Gale Crater, Mars provide the first opportunity to make observations of dunes from the grain-to-dune scale thereby filling the gap in knowledge between theory and orbital observations and refining our understanding of the martian aeolian stratigraphic record. We use the suite of cameras on Curiosity, including Navigation Camera (Navcam), Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI), to make observations of the Bagnold Dunes. Measurements of sedimentary structures are made where stereo images are available. Observations indicate that structures generated by gravity-driven processes on the dune lee slopes, such as grainflow and grainfall, are similar to the suite of aeolian sedimentary structures observed on Earth and should be present and recognizable in Mars' aeolian stratigraphic record. Structures formed by traction-driven processes deviate significantly from those found on Earth. The dune hosts centimeter-scale wind ripples and large, meter-scale ripples, which are not found on Earth. The large ripples migrate across the depositional, lee slopes of the dune, which implies that these structures should be present in Mars' stratigraphic record and may appear similar to compound-dune stratification.The Mars Science Laboratory Curiosity Rover Team is acknowledged for their support of this work.

Recent crustal movements and seismicity in the western coastal region of peninsular India

NASA Astrophysics Data System (ADS)

Kailasam, L. N.

1983-09-01

Recent crustal movements, tectonics and seismicity of the western coastal region of peninsular India have been studied in detail in the very recent past. Prominent geomorphic features and large-scale manifestation of Holocene deformation and crustal movements have been noticed and studied over this coastal region from the Gulf of Cambay to the southernmost parts of Kerala, evidence for which is afforded in the form of Recent and sub-Recent raised beaches, sandbars, raised old terraces, pebble beds, etc. The sedimentary formations in this narrow coastal belt include Neogene and Quaternary sediments. The Bouguer gravity map of the western coastal tract shows some prominent gravity features extending into the offshore regions, suggestive of some significant tectonic and structural features. The seismic data in the offshore regions bring out some prominent roughly northwest-southeast as well as east-west faults and shears, in addition to prominent structural "highs" off the Bombay and Ratnagiri coast which have proved oil. The seismicity in this coastal tract as well as the faulted western margin of the western continental shelf in the Arabian Sea is generally of magnitude 3-6.

Intracontinental rift comparisons: Baikal and Rio Grande Rift Systems

NASA Astrophysics Data System (ADS)

Lipman, P. W.; Logatchev, N. A.; Zorin, Y. A.; Chapman, C. E.; Kovalenko, V.; Morgan, P.

Both the Baikal rift in Siberia and the Rio Grande rift in New Mexico, Colorado and Texas are major intracontinental extensional structures of Cenozoic age that affect regions about 1500 km long and several hundred km wide (Figures 1, 2). In the summer of 1988 these rifts were visited by study groups of U.S. and Soviet geoscientists during cooperative field workshops sponsored by the Soviet Academy of Sciences, U.S. National Academy of Sciences, and U.S. Geological Survey.In the Rio Grande region, we spent 2 weeks examining rift features between El Paso, Tex., and Denver, Colo. Particular emphasis was on the sedimentary record of rift evolution, widespread volcanic activity from inception of rifting to the present, geophysical expression of rift features, and relations between rifting and the larger-scale evolution of the North American Cordillera. In the Baikal region, which presents formidable logistic problems for a workshop, we travelled by bus, truck, helicopter, and ship to examine young seismotectonic features, rift-related basalt, and bounding structures of the Siberian craton that influenced rift development (Figure 3).

Regionalization of local geomorphometric derivations for geological mapping in the sedimentary domain of central Amazônia

NASA Astrophysics Data System (ADS)

Valeriano, Márcio de Morisson; Rossetti, Dilce de Fátima

2017-03-01

This paper reports procedures to prepare locally derived geomorphometric data for geological mapping at regional scale in central Amazônia. The size of the study area, approximately 1.5 million km2, and the prevailing flat topography of the targeted environment were the constraints motivating the aims, at spatial and numerical synthesis of the detailed geomorphometric information derived from SRTM DEM. The developed approach consisted in assigning single (average) values to terrain patches, to represent the regional distribution of pixel-based geomorphometric information (slope, profile curvature and relative relief). In analogy to the nature of sedimentary packs, patches were established as contiguous elevation strata, constructed through a procedure combining segmentation, filterings and range compressions. For slope only, pre-processing of locally derived data with median filtering effectively avoided the typical flattening of the regionalized results due to input distribution characteristics. Profile curvature was transformed into absolute values and thus a different meaning from the original (pixel) variable was considered in the interpretation, also avoiding the compensation of original values (positive and negative) tending to zero value when averaged through a regionally flat extension. Examinations near major river valleys showed patched elevation to depict alluvial terraces. In the interfluves and floodplains, contrasting patterns in the averaged variables among patches of similar elevations allowed the recognition of important relief features. In addition to the reduction of the distribution ranges, the correlation between regionalized geomorphometric variables was higher than observed in the originally local data, due to the thematic synthesis following regionalization. Depth of dissection, claimed to be related to the relative age of sedimentary units, was the main factor to explain the overall variations of the geomorphometric results. The developed regionalization process improved the potential of local geomorphometric data for updating and revision of geological maps and for guiding future surveys in the sedimentary domain of Amazônia.

Sedimentary Framework of an Inner Continental Shelf Sand-Ridge System, West-Central Florida

NASA Astrophysics Data System (ADS)

Locker, S. D.; Hine, A. C.; Wright, A. K.; Duncan, D. S.

2002-12-01

The west-central Florida inner continental shelf is a dynamic environment subject to current flows on a variety of temporal and spatial scales. A site survey program, undertaken in support of the Office of Naval Research's Mine Burial prediction program, is focused on the sedimentary framework and sediment accumulation patterns in 10-18 meters water depth. Our specific goals are to image the shallow subsurface and to monitor changes in bedform distribution patterns that coincide with physical processes studies ongoing in the area. Methods of study include side-scan sonar imaging, boomer and chirp subbottom profiling, and sedimentary facies analysis using surface sediment sampling and vibracoring. A well-defined sand-ridge system was imaged, trending oblique to the west-Florida coastline. The side-scan clearly shows that there is extensive three-dimensional structure within these large-scale NW-SE trending sedimentary bedforms. The sand ridges commonly are approximately 1 km wide and 4-8 km in length. The characteristics of these ridges are distinctly different than the sand ridges in < 8 m water that we have previously studied. Ridges in the offshore area tend to be thicker, have a flatter morphology, and exhibit fewer smaller-scale sand waves. Sand-ridge thickness ranges 2-3 meters, and typically consists of fining upward medium to fine quartz sand facies with occasional centimeter-scale coarser-grained carbonate-rich intervals. Time series investigations tracking the shift in position of the sand ridge margins have found undetectable net annual movement. However significant resuspension and bedform development accompanies high-energy events such as winter cold front passage. Thus the large-scale bedforms (sand ridges) are in a state of dynamic equilibrium with the average annual hydrodynamic regime. Repeated field surveys will focus on monitoring small-scale sedimentological and stratal framework changes that will be integrated with the quantitative process studies.

Imaging the Subsurface of the Thuringian Basin (Germany) on Different Spatial Scales

NASA Astrophysics Data System (ADS)

Goepel, A.; Krause, M.; Methe, P.; Kukowski, N.

2014-12-01

Understanding the coupled dynamics of near surface and deep fluid flow patterns is essential to characterize the properties of sedimentary basins, to identify the processes of compaction, diagenesis, and transport of mass and energy. The multidisciplinary project INFLUINS (Integrated FLUid dynamics IN Sedimentary basins) aims for investigating the behavior of fluids in the Thuringian Basin, a small intra-continental sedimentary basin in Germany, at different spatial scales, ranging from the pore scale to the extent of the entire basin. As hydraulic properties often significantly vary with spatial scales, e.g. seismic data using different frequencies are required to gain information about the spatial variability of elastic and hydraulic subsurface properties. For the Thuringian Basin, we use seismic and borehole data acquired in the framework of INFLUINS. Basin-wide structural imaging data are available from 2D reflection seismic profiles as well as 2.5D and 3D seismic travel time tomography. Further, core material from a 1,179 m deep drill hole completed in 2013 is available for laboratory seismic experiments on mm- to cm-scale. The data are complemented with logging data along the entire drill hole. This campaign yielded e.g. sonic and density logs allowing the estimation of in-situ P-velocity and acoustic impedance with a spatial resolution on the cm-scale and provides improved information about petrologic and stratigraphic variability at different scales. Joint interpretation of basin scale structural and elastic properties data with laboratory scale data from ultrasound experiments using core samples enables a detailed and realistic imaging of the subsurface properties on different spatial scales. Combining seismic travel time tomography with stratigraphic interpretation provides useful information of variations in the elastic properties for certain geological units and therefore gives indications for changes in hydraulic properties.

Fluidized muds: a novel setting for the generation of biosphere diversity through geologic time.

PubMed

Aller, J Y; Aller, R C; Kemp, P F; Chistoserdov, A Y; Madrid, V M

2010-06-01

Reworked and fluidized fine-grained deposits in energetic settings are a major modern-day feature of river deltas and estuaries. Similar environments were probably settings for microbial evolution on the early Earth. These sedimentary systems act as efficient biogeochemical reactors with high bacterial phylogenetic diversity and functional redundancy. They are temporally rather than spatially structured, with repeated cycling of redox conditions and successive stages of microbial metabolic processes. Intense reworking of the fluidized bed entrains bacteria from varied habitats providing new, diverse genetic materials to contribute to horizontal gene transfer events and the creation of new bacterial ecotypes. These vast mud environments may act as exporters and promoters of biosphere diversity and novel adaptations, potentially on a globally important scale.

Numerical modelling of the role of salt in continental collision: An application to the southeast Zagros fold-and-thrust belt

NASA Astrophysics Data System (ADS)

Ghazian, Reza Khabbaz; Buiter, Susanne J. H.

2014-09-01

The Zagros fold-and-thrust belt formed in the collision of Arabia with Central Iran. Its sedimentary sequence is characterised by the presence of several weak layers that may control the style of folding and thrusting. We use 2-D thermo-mechanical models to investigate the role of salt in the southeast Zagros fold-and-thrust belt. We constrain the crustal and lithospheric thickness, sedimentary stratification, convergence velocity, and thermal structure of the models from available geological and geophysical data. We find that the thick basal layer of Hormuz salt in models on the scale of the upper-mantle decouples the overlying sediments from the basement and localises deformation in the sediments by trench-verging shear bands. In the collision stage of the models, basement dips with + 1° towards the trench. Including the basal Hormuz salt improves the fit of predicted topography to observed topography. We use the kinematic results and thermal structure of this large-scale model as the initial conditions of a series of upper-crustal-scale models. These models aim to investigate the effects of basal and intervening weak layers, salt strength, basal dip, and lateral salt distribution on deformation style of the simply folded Zagros. Our results show that in addition to the Hormuz salt at the base of the sedimentary cover, at least one intervening weak layer is required to initiate fold-dominated deformation in the southeast Zagros. We find that an upper-crustal-scale model, with a basal and three internal weak layers with viscosities between 5 × 1018 and 1019 Pa s, and a basement that dips + 1° towards the trench, best reproduces present-day topography and the regular folding of the sedimentary layers of the simply folded Zagros.

Submarine landslide identified in DLW3102 core of the northern continental slope, South China Sea

NASA Astrophysics Data System (ADS)

Xu, Yuanqin; Liu, Lejun; Zhou, Hang; Huang, Baoqi; Li, Ping; Ma, Xiudong; Dong, Feiyin

2018-02-01

In this paper, we take DLW3101 core obtained at the top of the canyon (no landslide area) and DLW3102 core obtained at the bottom of the canyon (landslide area) on the northern continental slope of the South China Sea as research objects. The chronostratigraphic framework of the DLW3101 core and elemental strata of the DLW3101 core and the DLW3102 core since MIS5 are established by analyzing oxygen isotope, calcium carbonate content, and X-Ray Fluorescence (XRF) scanning elements. On the basis of the information obtained by analyzing the sedimentary structure and chemical elements in the landslide deposition, we found that the DLW3102 core shows four layers of submarine landslides, and each landslide layer is characterized by high Si, K, Ti, and Fe contents, thereby indicating terrigenous clastic sources. L1 (2.15-2.44 m) occurred in MIS2, which is a slump sedimentary layer with a small sliding distance and scale. L2 (15.48-16.00 m) occurred in MIS5 and is a debris flow-deposited layer with a scale and sliding distance that are greater than those of L1. L3 (19.00-20.90 m) occurred in MIS5; its upper part (19.00-20.00 m) is a debris flow-deposited layer, and its lower part (20.00-20.90 m) is a sliding deposition layer. The landslide scale of L3 is large. L4 (22.93-24.27 m) occurred in MIS5; its upper part (22.93-23.50 m) is a turbid sedimentary layer, and its lower part (23.50-24.27 m) is a slump sedimentary layer. The landslide scale of L4 is large.

Sedimentary processes associated with sand and boulder deposits formed by the 2011 Tohoku-oki tsunami at Sabusawa Island, Japan

NASA Astrophysics Data System (ADS)

Goto, Kazuhisa; Sugawara, Daisuke; Ikema, Satoko; Miyagi, Toyohiko

2012-12-01

This paper reports on the sedimentary processes of sand and boulder deposition at Sabusawa Island, Japan as a result of the 2011 Tohoku-oki tsunami. Boulders were composed of tuffaceous rocks and sourced from an earthquake-triggered slope failure as well as concrete fragments of seawall. They were scattered over the ground surface and did not form boulder ridges, although there was some local imbrication. The boulders were deposited on top of a sand layer indicating that the latter, possibly deposited from bed load, covered the ground surface first. This sand layer probably reduced friction allowing boulders to be transported more easily than might be expected across a hard ground with a high bottom friction. Sand deposits showed landward thinning and fining features, while the boulders showed a landward coarsening (tuffaceous boulders) or a landward fining (concrete boulders), indicating that large clasts were not necessarily scattered randomly but rather might have a clast size gradient with distance inland. These features are explained by the local topographic setting that constrained the directions of incoming and returning tsunami flows. Some clasts at the inland extent of the boulder field were covered by an upward fining sand layer. This feature suggests that the boulders were deposited prior to the suspended sands, with the latter subsequently laid down before the water level dropped below the top of the boulders. Such modern investigations of the sedimentary features of various sizes of grains and clasts immediately after a tsunami provide invaluable data for the reconstruction of inundation processes.

Alluvial Fans on Dunes in Kaiser Crater Suggest Niveo-Aeolian and Denivation Processes on Mars

NASA Technical Reports Server (NTRS)

Bourke, M. C.

2005-01-01

On Earth, cold region sand dunes often contain inter-bedded sand, snow, and ice. These mixed deposits of wind-driven snow, sand, silt, vegetal debris, or other detritus have been termed Niveo-aeolian deposits. These deposits are often coupled with features that are due to melting or sublimation of snow, called denivation features. Snow and ice may be incorporated into dunes on Mars in three ways. Diffusion of water vapour into pore spaces is the widely accepted mechanism for the accretion of premafrost ice. Additional mechanisms may include the burial by sand of snow that has fallen on the dune surface or the synchronous transportation and deposition of snow, sand and ice. Both of these mechanisms have been reported for polar dunes on Earth. Niveo-aeolian deposits in polar deserts on Earth have unique morphologies and sedimentary structures that are generally not found in warm desert dunes. Recent analysis of MOC-scale data have found evidence for potential niveo-aeolian and denivation deposits in sand dunes on Mars.

Silica deposits on Mars with features resembling hot spring biosignatures at El Tatio in Chile

PubMed Central

Ruff, Steven W.; Farmer, Jack D.

2016-01-01

The Mars rover Spirit encountered outcrops and regolith composed of opaline silica (amorphous SiO2·nH2O) in an ancient volcanic hydrothermal setting in Gusev crater. An origin via either fumarole-related acid-sulfate leaching or precipitation from hot spring fluids was suggested previously. However, the potential significance of the characteristic nodular and mm-scale digitate opaline silica structures was not recognized. Here we report remarkably similar features within active hot spring/geyser discharge channels at El Tatio in northern Chile, where halite-encrusted silica yields infrared spectra that are the best match yet to spectra from Spirit. Furthermore, we show that the nodular and digitate silica structures at El Tatio that most closely resemble those on Mars include complex sedimentary structures produced by a combination of biotic and abiotic processes. Although fully abiotic processes are not ruled out for the Martian silica structures, they satisfy an a priori definition of potential biosignatures. PMID:27853166

The hydrocarbon cycle and its role in hyperthermals, ocean anoxic events and mass extinctions

NASA Astrophysics Data System (ADS)

Dahlgren, Torbjørn

2016-04-01

Release of light isotopic carbon, ocean oxygen deficiency and extinction characterizes the Paleocene-Eocene Thermal Maximum (PETM). The PETM carbon isotope excursion (CIE) has been linked to gas hydrate decomposition and/or methane release due to igneous intrusions in sedimentary basins. In reviewing the published geological and geochemical data it became apparent that the majority of observations are in fact compatible with a different source(s) of the light isotopic carbon, namely, that of fluids trapped in sedimentary basins. Here I make a connection between the drilled paleo-accumulations of oil and gas in the Barents Sea, their burial and tectonic history, and published data of the PETM that may be reinterpreted as to reflect large scale leakage of oil and gas accumulations. I focus on oil, as leaked oil has a preservation potential in the sedimentary record. In contrast, gas from either leaked gas accumulations or exsolution from pore waters has little preservation potential other than contributing to the CIE. Sedimentary records compatible with leaked oil is present in the Arctic Ocean and Spitsbergen as fluorescent bitumen/amorphous organic matter (AOM) with carbon isotope ratios and biomarker signatures similar to those recorded in Barents Sea oil samples. Bitumen/AOM-rich immature sediments are also found in the North Sea and unresolved complex organic matter compatible with highly weathered oil has been found as far south as Walvis Ridge, offshore Namibia. Large scale fluid leakage from sedimentary basins can also explain the increase in radiogenic Osmium and Rhenium that mimic the CIE. Also biological evidence such as the extinction of North Atlantic benthic foraminifera lineages, the A. Augustum bloom and the occurrence of malformed micro/nanno-fossils may be linked to large scale leakage of oil and diagenetically altered porewaters. The leaked oil and gas was partially re-cycled into an organic rich shale (source rock) suggesting a 'hydrocarbon cycle' exists. Based on previously noted similarities between the PETM, the Toarcian OAE and the Triassic-Jurassic and Permian-Triassic events, it is inferred that also these may have been associated with catastrophic leakage of hydrocarbons trapped in sedimentary basins.

Earth observations during STS-58

NASA Image and Video Library

1993-10-22

STS058-88-017 (18 Oct-1 Nov 1993) --- The eye-catching "bullseye" of the Richat Structure adds interest to the barren Gres de Chinguetti Plateau in central Mauretania, northwest Africa. It represents domally uplifted, layered (sedimentary) rocks that have been eroded by water and wind into the present shape. Desert sands have invaded the feature from the south. The origin of the structure is unknown. It is not an impact structure, because field work showed that strata are undisturbed and flat-lying in the middle of the feature, and no shock-altered rock could be found. There is no evidence for a salt dome or shale diapir, nor is there any geophysical evidence for an underlying dome of dense igneous rock having about the same density as the sedimentary layers.

Sedimentary Processes on Earth, Mars, Titan, and Venus

NASA Astrophysics Data System (ADS)

Grotzinger, J. P.; Hayes, A. G.; Lamb, M. P.; McLennan, S. M.

The production, transport and deposition of sediment occur to varying degrees on Earth, Mars, Venus, and Titan. These sedimentary processes are significantly influenced by climate that affects production of sediment in source regions (weathering), and the mode by which that sediment is transported (wind vs. water). Other, more geological, factors determine where sediments are deposited (topography and tectonics). Fluvial and marine processes dominate Earth both today and in its geologic past, aeolian processes dominate modern Mars although in its past fluvial processes also were important, Venus knows only aeolian processes, and Titan shows evidence of both fluvial and aeolian processes. Earth and Mars also feature vast deposits of sedimentary rocks, spanning billions of years of planetary history. These ancient rocks preserve the long-term record of the evolution of surface environments, including variations in climate state. On Mars, sedimentary rocks record the transition from wetter, neutral-pH weathering, to brine-dominated low-pH weathering, to its dry current state.

Structural investigations in the Massif-Central, France

NASA Technical Reports Server (NTRS)

Scanvic, J. Y.

1974-01-01

This survey covered the French Massif-Central (where crystalline and volcanic rocks outcrop) and its surrounding sedimentaries, Bassin de Paris, Bassin d'Aquitaine and Rhodanian valley. One objective was the mapping of fracturing and the surveying of its relationship with known ore deposits. During this survey it was found that ERTS imagery outlines lithology in some sedimentary basins. On the other hand, in a basement area, under temperature climate conditions, lithology is rarely expressed. These observations can be related to the fact that band 5 gives excellent results above sedimentary basins in France and generally band 7 is the most useful in a basement area. Several examples show clearly the value of ERTS imagery for mapping linear features and circular structures. All the main fractures are identified with the exception of new ones found both in sedimentaries and basement areas. Other interesting findings concern sun elevation which, stereoscopic effect not being possible, simulates relief in a better way under certain conditions.

Storm deposits as graves in Early Life: the Fezouata Lagerstätte case (Lower Ordovician, Morocco)

NASA Astrophysics Data System (ADS)

Vaucher, Romain; Pittet, Bernard; Hormière, Hélène; Martin, Emmanuel L. O.; Lefebvre, Bertrand

2016-04-01

The Fezouata Shale (Early Ordovician, Morocco) is renowned in the palaeontological community for its Konservat-Lagerstätte (Tremadocian in age) that yielded thousands of exceptionally well-preserved fossils (EPF) from the Great Ordovician Biodiversification Event. Lower Ordovician deposits in the central Anti-Atlas Mountain (Zagora area) are expressed by the Fezouata Shale and the Zini Formation. They consist in ca. 900m of siltstones and sandstones deposited in an epicontinental sea at the periphery of the Gondwanaland. Sedimentologic field analysis and sequence analysis were achieved on ten stratigraphic sections in order to constrain the palaeoenvironmental context of the Fezouata Biota and to predict the location (geographically and stratigraphically) of new Lagerstätten. Sedimentary structures (cm- to m-scale symmetrical ripples) and geometries (lobe, lobe-channel) point to storm dominance on the sedimentation but peculiar sedimentary features suggest a tide modulation. Thus, a wave-dominated tide-modulated model of deposition recording proximal offshore to shoreface environments for the Fezouata Shale and shoreface to foreshore environments for the overlying Zini Fm is proposed. Layers yielding EPF are argillaceous siltstones (with wave ripples of cm-scale wavelength) always overlain by fine-grained sandstones (distal storm deposits, few cm-thick, several m-long, with cm- to dm-scale hummocky cross-stratifications). Fast burying by storm deposits appear to be of prime importance to initiate the exceptional preservation of the soft tissues of animals in the fossil record. According to the model of deposition it correspond to environments close to the storm weather wave base. Lower Ordovician succession was deposited during a 2nd order cycle, although 3rd and 4th order cycles were also identified. Encoding these different orders of sea level fluctuations giving a value of "1" for the deepest part of sequences (for each order) and a value of "0" for the shallowest, a reconstruction of the sea level fluctuation is then proposed. This reconstruction clearly highlights the stratigraphic position of the today discovered Lagerstätte. It also suggests that a second, younger (Floian in age) stratigraphic interval has very comparable sedimentary conditions in terms of facies and sea level, and has the potential for being a new Lagerstätte in the Fezouata Shale.

Polar continental margins: Studies off East Greenland

NASA Astrophysics Data System (ADS)

Mienert, J.; Thiede, J.; Kenyon, N. H.; Hollender, F.-J.

The passive continental margin off east Greenland has been shaped by tectonic and sedimentary processes, and typical physiographic patterns have evolved over the past few million years under the influence of the late Cenozoic Northern Hemisphere glaciations. The Greenland ice shield has been particularly affected.GLORIA (Geological Long Range Inclined Asdic), the Institute of Oceanographic Sciences' (IOS) long-range, side-scan sonar, was used on a 1992 RV Livonia cruise to map large-scale changes in sedimentary patterns along the east Greenland continental margin. The overall objective of this research program was to determine the variety of large-scale seafloor processes to improve our understanding of the interaction between ice sheets, current regimes, and sedimentary processes. In cooperation with IOS and the RV Livonia, a high-quality set of seafloor data has been produced. GLORIA'S first survey of east Greenland's continental margin covered several 1000- × 50-km-wide swaths (Figure 1) and yielded an impressive sidescan sonar image of the complete Greenland Basin and margin (about 250,000 km2). A mosaic of the data was made at a scale of 1:375,000. The base map was prepared with a polar stereographic projection having a standard parallel of 71°.

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

Soltanian, Mohamad Reza; Sun, Alexander; Dai, Zhenxue

Yucca Mountain, Nevada, had been extensively investigated as a potential deep geologic repository for storing high-level nuclear wastes. Previous field investigations of stratified alluvial aquifer downstream of the site revealed that there is a hierarchy of sedimentary facies types. There is a corresponding log conductivity and reactive surface area subpopulations within each facies at each scale of sedimentary architecture. Here in this paper, we use a Lagrangian-based transport model in order to analyze radionuclide dispersion in the saturated alluvium of Fortymile Wash, Nevada. First, we validate the Lagrangian model using high-resolution flow and reactive transport simulations. Then, we used themore » validated model to investigate how each scale of sedimentary architecture may affect long-term radionuclide transport at Yucca Mountain. Results show that the reactive solute dispersion developed by the Lagrangian model matches the ensemble average of numerical simulations well. The link between the alluvium spatial variability and reactive solute dispersion at different spatiotemporal scales is demonstrated using the Lagrangian model. Finally, the longitudinal dispersivity of the reactive plume can be on the order of hundreds to thousands of meters, and it may not reach its asymptotic value even after 10,000 years of travel time and 2–3 km of travel distance.« less

Sedimentary structures and stratal geometries at the foothills of Mount Sharp: their role in paleoenvironmental interpretation

NASA Astrophysics Data System (ADS)

Gupta, S.; Rubin, D. M.; Sumner, D. Y.; Grotzinger, J. P.; Lewis, K. W.; Stack, K.; Kah, L. C.; Banham, S.; Edgett, K. S.

2015-12-01

The Mars Science Laboratory Curiosity rover has been exploring sedimentary rocks at the foothills of Mount Sharp since August 2014. Robust interpretation of the paleoenvironmental contexts requires detailed facies analysis of these rocks including analysis and interpretation of sedimentary structures and sediment body geometries. Here, we describe some of the detailed sedimentary structures and sedimentary geometries observed by Curiosity between the Pahrump_Hills field site and its current location at Marias Pass. The Pahrump Hills sedimentary section comprises a succession dominated by finely laminated mudstones of the Murray formation that are interpreted to have been deposited in an ancient lake within Gale crater. Toward the top of the Pahump Hills succession, we observe the appearance of coarser-grained sandstones that are interstratified within the lacustrine mudstones. These sandstones that include Whale Rock and Newspaper Rock show lenticular geometries, and are pervasively cross-stratified. These features indicate that currents eroded shallow scours in the lake beds that were then infilled by deposition from migrating subaqueous dunes. The paleoenvironmental setting may represent either a gullied delta front setting or one in which lake level fall caused fluvial erosion and infilling of the shallow scours. Since leaving Pahrump_Hills, Curiosity has imaged extensive exposures of strata that are partly correlative with and stratigraphically overlie the uppermost part of the Pahrump section. Isolated cross-bedded sandstones and possible interstratified conglomerates beds occur within Murray formation mudstones. Capping sandstones with a likely variety of environmental contexts overlie mudstones. Where imaged in detail, sedimentary structures, such as trough-cross bedding and possible eolian pinstriping, provide constraints on plausible sedimentary processes and bounds on depositional setting.

Relationships between heat flow, thermal and pressure fields in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Husson, L.; Henry, P.; Le Pichon, X.

2004-12-01

The thermal field of the Gulf of Mexico (GoM) is restored from a comprehensive temperature-depth database. A striking feature is the systematic sharp gradient increase between 2500 and 4000 m. The analysis of the pressure (fracturation tests and mud weights) indicates a systematic correlation between the pressure and temperature fields, as well as with the thickness of Plio-Pleistocene sedimentary layer, and is interpreted as the fact of cooling from fluid flow in the upper, almost hydrostatically pressured layer. The Nusselt number, that we characterize by the ratio between the near high-P gradient over low-P gradient varies spatially and is correlated to the structural pattern of the GoM; this observation outlines the complex relationships between heat and fluid flows, structure and sedimentation. The deep thermal signal is restored in terms of gradient and heat flow density from a statistical analysis of the thermal data combined to the thermal modelling of about 175 wells. At a regional scale, although the sedimentary cover is warmer in Texas than in Louisiana in terms of temperature, the steady state basal heat flow is higher in Louisiana. In addition, beneath the Corsair Fault, which lay offshore parallel to the Texan coast, the high heat flow suggests a zone of Tertiary lithospheric thinning.

Three-dimensional Magnetotelluric Inversion and Model Validation with Potential Field Data and Seismics for the Central Portion of Parana Sedimentary Basin in Brazil

NASA Astrophysics Data System (ADS)

La Terra, E. F.; Fontes, S. L.; Taveira, D. T.; Miquelutti, L. G.

2015-12-01

The Paraná basin, on the central-south region of the South American Plate, is one of the biggest South American intracratonic basins. It is composed by Paleozoic and Mesozoic sediments, which were covered by the enormous Cretaceous flood basalts, associated with the rifting of Gondwana and the opening of the South Atlantic Ocean. Its depocenter region, with a maximum estimated depth of just over 7000 m, was crossed by three magnetotelluric - MT profiles proposed by the Brazilian Petroleum Agency (ANP) aimed at better characterizing its geological structure, as the seismic images are very poor. The data include about 350 MT broadband soundings spanning from 1000 Hz down to 2,000 s. The MT data were processed using robust techniques and remote reference. Static shift observed in some stations were corrected based on Transient Electromagnetic - TEM measurements at each site. These models were integrated to existent gravity, magnetic and seismic data for a more comprehensive interpretation of the region. A pilot 3D model has also been constructed on a crustal scale covering the study area using four frequencies per decade in the 3D inversion scheme proposed by Siripunvaraporn et al. (2005). The inversion scheme produced a reliable model and the observations were adequately reproduced, with observed fitting particularly better for the deeper structures related to basement compared to the 2D results. The main features in the conductivity model correspond to known geological features. These included the conductivity structures obtained for the upper crust, i.e. the sedimentary sequences, underlain by more resistive material, assumed to be basement. Local resistive features in the near-surface are associated to volcanic basalts covering the sediments. Some highly resistivity horizontal and vertical bodies were associated to volcanic intrusion like dikes and sills. We observed depressions on basement consistent with half-graben structures possibly filled with sandstones.

Barrier island morphodynamic classification based on lidar metrics for north Assateague Island, Maryland

USGS Publications Warehouse

Brock, John C.; Krabill, William; Sallenger, Asbury H.

2004-01-01

In order to reap the potential of airborne lidar surveys to provide geological information useful in understanding coastal sedimentary processes acting on various time scales, a new set of analysis methods are needed. This paper presents a multi-temporal lidar analysis of north Assateague Island, Maryland, and demonstrates the calculation of lidar metrics that condense barrier island morphology and morphological change into attributed linear features that may be used to analyze trends in coastal evolution. The new methods proposed in this paper are also of significant practical value, because lidar metric analysis reduces large volumes of point elevations into linear features attributed with essential morphological variables that are ideally suited for inclusion in Geographic Information Systems. A morphodynamic classification of north Assategue Island for a recent 10 month time period that is based on the recognition of simple patterns described by lidar change metrics is presented. Such morphodynamic classification reveals the relative magnitude and the fine scale alongshore variation in the importance of coastal changes over the study area during a defined time period. More generally, through the presentation of this morphodynamic classification of north Assateague Island, the value of lidar metrics in both examining large lidar data sets for coherent trends and in building hypotheses regarding processes driving barrier evolution is demonstrated

Sedimentary response to ice stream advance and retreat on the Storfjorden Trough Mouth Fan (NW Barents Sea), during Late Weichselian

NASA Astrophysics Data System (ADS)

Pedrosa, Mayte; Camerlengui, Angelo; de Mol, Ben; Lucchi, Renata. G.; Úrgeles, Roger; Rebesco, Michele; Winsborrow, Monica; Laberg, Jan. S.; Andreassen, Karin; Accettella, Daniela

2010-05-01

This seafloor morphological study of the Storfjorden Trough Mouth Fan (TMF) (offshore Svalbard, NW Barents Sea) is based on new multibeam bathymetry and chirp sub-bottom profiler data acquired in 2007 during the BIO Hespérides cruise SVAIS that provides an unprecedented image of the sedimentary processes that accompanied the last advance and retreat of the Storfjorden Ice Stream. Compared to other glacial-marine sedimentary systems (such as the adjacent Bjørnøyrenna TMF), the Storfjorden TMF system is small and associated to a relatively small terrestrial ice sheet, approximately 40.000 km2, with local provenance from Svalbard and the Spitsbergen Bank. Due to this short distance from the ice source to the calving areas and the resulting short residence time of ice in the ice sheet, therefore the glacio -marine system of the Storfjorden reacts rapidly to climatic changes. The Storfjorden continental slope is characterized by three depositional lobes, produced by focused sedimentation at the terminus of ice streams that have changed their location with time. The superficial morphology features associated to the two northernmost lobes are straight gullies in the upper slope, and debris lobes starting from the midslope onwards. The seafloor expression of the southernmost lobe, adjacent to the much smaller Kveithola TMF, demonstrate almost no gully incisions and is dominated by the widespread occurrence of small-scale submarine landslides. The subbottom profiles illustrate that sediment failures occurred throughout the Late Neogene evolution of the southern Storfjorden and Kveithola margin, including large-scale mass transport deposits of up to 200 m thick. Seismic facies of the Neogene sequence shows an alternation of glacigenic debris flows and laminated sediment drape inferred to be plumites. Gullies incising glacigenic debris flows at the surface and subsurface and are filled by an interglacial drape sequence. The gullies are formed during each deglaciation phase, most likely by the erosive action of short-lived high density currents originated by sediment-loaded subglacial melt water discharge.At the outer continental shelf of the southernmost lobe a striking fresh linear straight, which has a width of 1, 5 kilometres and cut the morainal deposits. These features are interpreted as mega-scale glacial lineations, which are tentatively attributed to mega-iceberg scours. These lineations are witness the latest advances of the Storfjorden ice streams before the final retreat which was located at the southernmost lobe. One of the main pre-conditioning factors to slope instability on the southern part of the Storfjorden TMF is identified as high sedimentation rate plumites deposited on the middle-upper continental slope by glacial melt water plumes. This study is part of the SVAIS project (funded by the Spanish IPY), that has a main objective to improve the understanding and the relationship between sedimentation and ice sheet dynamics under natural climatic changes.

Quantification of CO2 generation in sedimentary basins through carbonate/clays reactions with uncertain thermodynamic parameters

NASA Astrophysics Data System (ADS)

Ceriotti, G.; Porta, G. M.; Geloni, C.; Dalla Rosa, M.; Guadagnini, A.

2017-09-01

We develop a methodological framework and mathematical formulation which yields estimates of the uncertainty associated with the amounts of CO2 generated by Carbonate-Clays Reactions (CCR) in large-scale subsurface systems to assist characterization of the main features of this geochemical process. Our approach couples a one-dimensional compaction model, providing the dynamics of the evolution of porosity, temperature and pressure along the vertical direction, with a chemical model able to quantify the partial pressure of CO2 resulting from minerals and pore water interaction. The modeling framework we propose allows (i) estimating the depth at which the source of gases is located and (ii) quantifying the amount of CO2 generated, based on the mineralogy of the sediments involved in the basin formation process. A distinctive objective of the study is the quantification of the way the uncertainty affecting chemical equilibrium constants propagates to model outputs, i.e., the flux of CO2. These parameters are considered as key sources of uncertainty in our modeling approach because temperature and pressure distributions associated with deep burial depths typically fall outside the range of validity of commonly employed geochemical databases and typically used geochemical software. We also analyze the impact of the relative abundancy of primary phases in the sediments on the activation of CCR processes. As a test bed, we consider a computational study where pressure and temperature conditions are representative of those observed in real sedimentary formation. Our results are conducive to the probabilistic assessment of (i) the characteristic pressure and temperature at which CCR leads to generation of CO2 in sedimentary systems, (ii) the order of magnitude of the CO2 generation rate that can be associated with CCR processes.

Reconstructing Magmatic-Hydrothermal Systems via Geologic Mapping of the Tilted, Cross-sectional Exposures of the Yerington District, Nevada

NASA Astrophysics Data System (ADS)

Dilles, J. H.; Proffett, J. M.

2011-12-01

The Jurassic Yerington batholith was cut by Miocene to recent normal faults and tilted ~90° west (Proffett, 1977). Exposures range from the volcanic environment to ~6 km depth in the batholith. Magmatic-hydrothermal fluids derived from the Luhr Hill granite and associated porphyry dikes produced characteristic porphyry copper mineralization and rock alteration (K-silicate, sericitic, and advanced argillic) in near-vertical columnar zones above cupolas on the deep granite. In addition, saline brines derived from the early Mesozoic volcanic and sedimentary section intruded by the batholith were heated and circulated through the batholith producing voluminous sodic-calcic and propylitic alteration. The magnetite-copper ore body at Pumpkin Hollow is hosted in early Mesozoic sedimentary rocks in the contact aureole of the batholith, and appears to be an IOCG type deposit produced where the sedimentary brines exited the batholith. Although many advances in understanding of Yerington have been made by lab-based geochronology and geochemistry studies, the first order igneous and hydrothermal features were recognized first in the 1960s and 1970s and are best documented by geological mapping at a variety of scales ranging from 1:500 to 1:24,000. The Anaconda technique of mapping mine benches, trenches, and drill cores was perfected here (Einaudi, 1997), and other techniques were used for surface exposures. The geologic and hydrothermal alteration maps establish that hydrothermal alteration accompanied each of several porphyry dike intrusions, and affected more than 100 km3 of rock. Both zonation in alteration mineralogy and vein orientations allow reconstruction of source areas and >5 km-long flow-paths of hydrothermal fluids through the batholith and contact aureole.

Linking slope stability and climate change: the Nordfjord region, western Norway, case study

NASA Astrophysics Data System (ADS)

Vasskog, K.; Waldmann, N.; Ariztegui, D.; Simpson, G.; Støren, E.; Chapron, E.; Nesje, A.

2009-12-01

Valleys, lakes and fjords are spectacular features of the Norwegian landscape and their sedimentary record recall past climatic, environmental and glacio-isostatic changes since the late glacial. A high resolution multi-proxy study is being performed on three lakes in western Norway combining different geophysical methods and sediment coring with the aim of reconstructing paleoclimate and to investigate how the frequency of hazardous events in this area has changed through time. A very high resolution reflection seismic profiling revealed a series of mass-wasting deposits. These events, which have also been studied in radiocarbon-dated cores, suggest a changing impact of slope instability on lake sedimentation since the late glacial. A specially tailored physically-based mathematical model allowed a numerical simulation of one of these mass wasting events and related tsunami, which occurred during a devastating rock avalanche in 1936 killing 74 persons. The outcome has been further validated against historical, marine and terrestrial information, providing a model that can be applied to comparable basins at various temporal and geographical scales. Detailed sedimentological and geochemical studies of selected cores allows characterizing the sedimentary record and to disentangle each mass wasting event. This combination of seismic, sedimentary and geophysical data permits to extend the record of mass wasting events beyond historical times. The geophysical and coring data retrieved from these lakes is a unique trace of paleo-slope stability generated by isostatic rebound and climate change, thus providing a continuous archive of slope stability beyond the historical record. The results of this study provide valuable information about the impact of climate change on slope stability and source-to-sink processes.

Water storage in marine sediment and implications for inferences of past global ice volume

NASA Astrophysics Data System (ADS)

Ferrier, K.; Li, Q.; Pico, T.; Austermann, J.

2017-12-01

Changes in past sea level are of wide interest because they provide information on the sensitivity of ice sheets to climate change, and thus inform predictions of future sea-level change. Sea level changes are influenced by many processes, including the storage of water in sedimentary pore space. Here we use a recent extension of gravitationally self-consistent sea-level models to explore the effects of marine sedimentary water storage on the global seawater balance and inferences of past global ice volume. Our analysis suggests that sedimentary water storage can be a significant component of the global seawater budget over the 105-year timescales associated with glacial-interglacial cycles, and an even larger component over longer timescales. Estimates of global sediment fluxes to the oceans suggest that neglecting marine sedimentary water storage may produce meter-scale errors in estimates of peak global mean sea level equivalent (GMSL) during the Last Interglacial (LIG). These calculations show that marine sedimentary water storage can be a significant contributor to the overall effects of sediment redistribution on sea-level change, and that neglecting sedimentary water storage can lead to substantial errors in inferences of global ice volume at past interglacials. This highlights the importance of accounting for the influences of sediment fluxes and sedimentary water storage on sea-level change over glacial-interglacial timescales.

Sedimentary processes of the Bagnold Dunes: Implications for the eolian rock record of Mars

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Lapotre, M. G. A.; Lewis, K. W.; Day, M.; Stein, N.; Rubin, D. M.; Sullivan, R.; Banham, S.; Lamb, M. P.; Bridges, N. T.; Gupta, S.; Fischer, W. W.

2017-12-01

The Mars Science Laboratory rover Curiosity visited two active wind-blown sand dunes within Gale crater, Mars, which provided the first ground-based opportunity to compare Martian and terrestrial eolian dune sedimentary processes and study a modern analog for the Martian eolian rock record. Orbital and rover images of these dunes reveal terrestrial-like and uniquely Martian processes. The presence of grainfall, grainflow, and impact ripples resembled terrestrial dunes. Impact ripples were present on all dune slopes and had a size and shape similar to their terrestrial counterpart. Grainfall and grainflow occurred on dune and large-ripple lee slopes. Lee slopes were 29° where grainflows were present and 33° where grainfall was present. These slopes are interpreted as the dynamic and static angles of repose, respectively. Grain size measured on an undisturbed impact ripple ranges between 50 μm and 350 μm with an intermediate axis mean size of 113 μm (median: 103 μm). Dissimilar to dune eolian processes on Earth, large, meter-scale ripples were present on all dune slopes. Large ripples had nearly symmetric to strongly asymmetric topographic profiles and heights ranging between 12 cm and 28 cm. The composite observations of the modern sedimentary processes highlight that the Martian eolian rock record is likely different from its terrestrial counterpart because of the large ripples, which are expected to engender a unique scale of cross stratification. More broadly, however, in the Bagnold Dune Field as on Earth, dune-field pattern dynamics and basin-scale boundary conditions will dictate the style and distribution of sedimentary processes.

3-D visualisation of palaeoseismic trench stratigraphy and trench logging using terrestrial remote sensing and GPR - a multiparametric interpretation

NASA Astrophysics Data System (ADS)

Schneiderwind, Sascha; Mason, Jack; Wiatr, Thomas; Papanikolaou, Ioannis; Reicherter, Klaus

2016-03-01

Two normal faults on the island of Crete and mainland Greece were studied to test an innovative workflow with the goal of obtaining a more objective palaeoseismic trench log, and a 3-D view of the sedimentary architecture within the trench walls. Sedimentary feature geometries in palaeoseismic trenches are related to palaeoearthquake magnitudes which are used in seismic hazard assessments. If the geometry of these sedimentary features can be more representatively measured, seismic hazard assessments can be improved. In this study more representative measurements of sedimentary features are achieved by combining classical palaeoseismic trenching techniques with multispectral approaches. A conventional trench log was firstly compared to results of ISO (iterative self-organising) cluster analysis of a true colour photomosaic representing the spectrum of visible light. Photomosaic acquisition disadvantages (e.g. illumination) were addressed by complementing the data set with active near-infrared backscatter signal image from t-LiDAR measurements. The multispectral analysis shows that distinct layers can be identified and it compares well with the conventional trench log. According to this, a distinction of adjacent stratigraphic units was enabled by their particular multispectral composition signature. Based on the trench log, a 3-D interpretation of attached 2-D ground-penetrating radar (GPR) profiles collected on the vertical trench wall was then possible. This is highly beneficial for measuring representative layer thicknesses, displacements, and geometries at depth within the trench wall. Thus, misinterpretation due to cutting effects is minimised. This manuscript combines multiparametric approaches and shows (i) how a 3-D visualisation of palaeoseismic trench stratigraphy and logging can be accomplished by combining t-LiDAR and GPR techniques, and (ii) how a multispectral digital analysis can offer additional advantages to interpret palaeoseismic and stratigraphic data. The multispectral data sets are stored allowing unbiased input for future (re)investigations.

Sedimentary exhalative (sedex) zinc-lead-silver deposit model

USGS Publications Warehouse

Emsbo, Poul; Seal, Robert R.; Breit, George N.; Diehl, Sharon F.; Shah, Anjana K.

2016-10-28

This report draws on previous syntheses and basic research studies of sedimentary exhalative (sedex) deposits to arrive at the defining criteria, both descriptive and genetic, for sedex-type deposits. Studies of the tectonic, sedimentary, and fluid evolution of modern and ancient sedimentary basins have also been used to select defining criteria. The focus here is on the geologic characteristics of sedex deposit-hosting basins that contain greater than 10 million metric tons of zinc and lead. The enormous size of sedex deposits strongly suggests that basin-scale geologic processes are involved in their formation. It follows that mass balance constraints of basinal processes can provide a conceptual underpinning for the evaluation of potential ore-forming mechanisms and the identification of geologic indicators for ore potential in specific sedimentary basins. Empirical data and a genetic understanding of the physicochemical, geologic, and mass balance conditions required for each of these elements are used to establish a hierarchy of quantifiable geologic criteria that can be used in U.S. Geological Survey national assessments.  In addition, this report also provides a comprehensive evaluation of environmental considerations associated with the mining of sedex deposits.

The First Radiocarbon-Constrained Full-Vector Holocene Paleomagnetic Secular Variation Reconstruction for Eastern Canada

NASA Astrophysics Data System (ADS)

Barletta, F.; St-Onge, G.; Stoner, J.; Lajeunesse, P.

2009-05-01

Here we present the first high-resolution Holocene paleomagnetic secular variation (PSV) master curve and relative paleointensity stack constrained by radiocarbon dates for Eastern Canada. This reconstruction is based on seven sedimentary sequences collected from the St. Lawrence Estuary and Gulf from the head to the mouth of the Laurentian Channel. The natural remanent magnetization (NRM), the anhysteretic remanent magnetization (ARM) and the isothermal remanent magnetization (IRM) were measured on u-channel samples at the Paleomagnetism Laboratory of ISMER using a 2G Enterprises cryogenic magnetometer. Magnetic mineralogy was additionally assessed using a recently installed alternative gradient force magnetometer (AGM). The magnetic mineralogy of the Holocene postglacial sediments is mainly carried by low-coercivity ferrimagnetic minerals (most likely magnetite) in the pseudo-single domain size range. The characteristic remanent magnetization (ChRM), assessed by principal component analysis, reveals the presence of a stable and well-defined magnetization characterized by maximum angular deviation (MAD) values generally lower than 5°. Furthermore, ChRM inclinations fluctuate around the expected geocentric axial dipole (GAD) magnetic inclination for the latitude of the coring sites (from 63° to 66°). The similarity of these records on their own independent timescales implies that all of the individual sedimentary sequences record a reliable Holocene PSV record for Eastern Canada. Relative paleointensity (RPI) was estimated by normalizing the NRM by the ARM which provided the best coercivity match. Lastly, the paleomagnetic directional and RPI records were stacked on a common time scale spanning the last ~10 000 cal BP. The smoothed PSV stack reveal centennial- to millennial-scale geomagnetic features concordant with the CALS7K.2 time-varying spherical harmonic model, as well as with the US eastern stack (King and Peck, 2001). Comparisons further a field with the Fish Lake record from Oregon (Verosub et al., 1996), the Icelandic and E. Greenland continental margin records (Stoner et al., 2007) and the Fennoscandia stack (Snowball et al., 2007) suggest large scale coherence of geomagnetic features. These and other comparisons will be made. In conclusion, the full-vector Holocene PSV and RPI master curves from Eastern Canada provide a new high-resolution regional chronostratigraphic tool as well as new insights into the Holocene geomagnetic field behaviour.

Quantifying Channelized Submarine Depositional Systems From Bed to Basin Scale

DTIC Science & Technology

2004-09-01

Union of South Africa and South West Africa . Memoirs of the Geological Survey of South Africa , 39:177, 1944. C.D. Winker and J.R. Booth. Sedimentary ...overbank locations. Sedimentary structures, textures and facies preserved in core recovered from the Late Pliocene section of Fisk Basin are consistent...France or Tanqua, Karoo Basin, South Africa in Pickering et al. (1995)) falling well short of the desirable continuous regional exposure. As a result of

Framework for the assessment of interaction between CO2 geological storage and other sedimentary basin resources.

PubMed

Michael, K; Whittaker, S; Varma, S; Bekele, E; Langhi, L; Hodgkinson, J; Harris, B

2016-02-01

Sedimentary basins around the world considered suitable for carbon storage usually contain other natural resources such as petroleum, coal, geothermal energy and groundwater. Storing carbon dioxide in geological formations in the basins adds to the competition for access to the subsurface and the use of pore space where other resource-based industries also operate. Managing potential impacts that industrial-scale injection of carbon dioxide may have on other resource development must be focused to prevent potential conflicts and enhance synergies where possible. Such a sustainable coexistence of various resource developments can be accomplished by implementing a Framework for Basin Resource Management strategy (FBRM). The FBRM strategy utilizes the concept of an Area of Review (AOR) for guiding development and regulation of CO2 geological storage projects and for assessing their potential impact on other resources. The AOR is determined by the expected physical distribution of the CO2 plume in the subsurface and the modelled extent of reservoir pressure increase resulting from the injection of the CO2. This information is used to define the region to be characterised and monitored for a CO2 injection project. The geological characterisation and risk- and performance-based monitoring will be most comprehensive within the region of the reservoir containing the carbon dioxide plume and should consider geological features and wells continuously above the plume through to its surface projection; this region defines where increases in reservoir pressure will be greatest and where potential for unplanned migration of carbon dioxide is highest. Beyond the expanse of the carbon dioxide plume, geological characterisation and monitoring should focus only on identified features that could be a potential migration conduit for either formation water or carbon dioxide.

Is There any Relationship Between the Santa Elena Depression and Chicxulub Impact Crater, Northwestern Yucatan Peninsula, Mexico?

NASA Astrophysics Data System (ADS)

Lefticariu, L.

2005-05-01

The Terminal Cretaceous Chicxulub Impact Crater had a strong control on the depositional and diagenetic history of the northern Yucatan Platform during most of the Cenozoic Era. The Chicxulub Sedimentary Basin (henceforth Basin), which approximately coincides with the impact crater, is circumscribed by a concentration of karstic sinkholes known as the Ring of Cenotes. Santa Elena Depression (henceforth Depression) is the name proposed for the bowl-shaped buried feature, first contoured by geophysical studies, immediately south of the Basin, in the area where the Ticul 1 and UNAM 5 wells were drilled. Lithologic, petrographic, and biostratigraphic data on PEMEX, UNAM, and ICDP cores show that: 1) Cenozoic deposits are much thicker inside the Basin than inside the Depression, 2) in general, the Cenozoic formations from inside the Depression are the thickest among those outside the Basin, 3) variably dolomitized pelagic or outer-platform wackestone or mudstone occur both inside the Basin and Depression, 4) the age of the deeper-water sedimentary carbonate rocks is Paleocene-Eocene inside the Basin and Paleocene?-Early Eocene inside the Depression, 5) the oldest formations that crop out are of Middle Eocene age at the edge of the Basin and Early-Middle Eocene age inside the Depression, 6) saline lake deposits, that consist chiefly of anhydrite, gypsum, and fine carbonate, and also contain quartz, chert, clay, zeolite, potassium feldspar, pyrite, and fragments of wood, are present in the Cenozoic section of the UNAM 5 core between 282 and 198 m below the present land surface, 7) the dolomite, subaerial exposure features (subaerial crusts, vugs, karst, dedolomite), and vug-filling cement from the Eocene formations are more abundant inside the Depression than inside the Basin. The depositional environments that are proposed for explaining the Cenozoic facies succession within the Santa Elena Depression are: 1) deeper marine water (Paleocene?-Early Eocene), 2) relatively isolated saline lake (Middle Eocene), and 3) shallow marine water (Middle-Late Eocene?). In places, the deeper-water facies are similar to those within the Chicxulub Sedimentary Basin. The shallow-water facies is similar to those occurring outside the Basin. In general, quartz and silicates are rare in the Cenozoic sedimentary carbonate of the northwestern Yucatan Peninsula. Therefore, their presence in the UNAM 5 core could be attributed to either impact breccia reworking or silicic volcanic processes. Quartz, chert, zeolite, and clay also are common in the suevite breccia of both Yax-1 and UNAM 5 cores. The fact that the Santa Elena Depression was a distinct sedimentary basin during much of the Paleogene could be explained by any or a combination of the following hypotheses: 1) In spite of being located outside the cenote ring, the Depression is a sub-basin of the larger and deeper Chicxulub Sedimentary Basin and is therefore located within the Chicxulub Impact Crater, 2) the Depression coincides with an impact crater distinct from the Chicxulub Impact Crater, 3) the Depression formed after the Chicxulub bolide impact due to slumping, crater wall failure, or larger-scale tectonic processes. The lack of conclusive evidence for multiple impact breccia layers in the northwestern Yucatan Peninsula, corroborated with the presence on top of the impact breccia from UNAM 5 core of deeper-water limestone similar to that of Late Paleocene-Early Eocene age from Yax-1 core, would be more consistent with either the first or third hypothesis.

Contribution of Anisotropy of Magnetic Susceptibility (AMS) to reconstruct flooding characteristics of a 4220 BP tsunami from a thick unconsolidated structureless deposit (Banda Aceh, Sumatra)

NASA Astrophysics Data System (ADS)

Wassmer, Patrick; Gomez, Christopher; Iskandasyah, T. Yan W. M.; Lavigne, Franck; Sartohadi, Junun

2015-07-01

One of the main concerns of deciphering tsunami sedimentary records along seashore is to link the emplaced layers with marine high energy events. Based on a combination of morphologic features, sedimentary figures, grain size characteristics, fossils content, microfossils assemblages, geochemical elements, heavy minerals presence; it is, in principle, possible to relate the sedimentary record to a tsunami event. However, experience shows that sometimes, in reason of a lack of any visible sedimentary features, it is hard to decide between a storm and a tsunami origin. To solve this issue, the authors have used the Anisotropy of Magnetic Susceptibility (AMS) to evidence the sediment fabric. The validity of the method for reconstructing flow direction has been proved when applied on sediments in the aftermath of a tsunami event, for which the behaviour was well documented (2004 IOT). We present herein an application of this method for a 56 cm thick paleo-deposit dated 4220 BP laying under the soil covered by the 2004 IOT, SE of Banda Aceh, North Sumatra. We analysed this homogenous deposit, lacking of any visible structure, using methods of classic sedimentology to confirm the occurrence of a high energy event. We then applied AMS technique that allowed the reconstruction of flow characteristics during sediment emplacement. We show that all the sequence was emplaced by uprush phases and that the local topography played a role on the re-orientation of a part of the uprush flow, creating strong reverse current. This particular behaviour was reported by eyewitnesses during the 2004 IOT event.

PRo3D®: A Tool for High Resolution Rendering and Geological Analysis of Martian Rover-Derived Digital Outcrop Models.

NASA Astrophysics Data System (ADS)

Gupta, S.; Barnes, R.; Ortner, T.; Huber, B.; Paar, G.; Muller, J. P.; Giordano, M.; Willner, K.; Traxler, C.; Juhart, K.; Fritz, L.; Hesina, G.; Tasdelen, E.

2015-12-01

NASA's Mars Exploration Rovers (MER) and Mars Science Laboratory Curiosity Rover (MSL) are proxies for field geologists on Mars, taking high resolution imagery of rock formations and landscapes which is analysed in detail on Earth. Panoramic digital cameras (PanCam on MER and MastCam on MSL) are used for characterising the geology of rock outcrops along rover traverses. A key focus is on sedimentary rocks that have the potential to contain evidence for ancient life on Mars. Clues to determine ancient sedimentary environments are preserved in layer geometries, sedimentary structures and grain size distribution. The panoramic camera systems take stereo images which are co-registered to create 3D point clouds of rock outcrops to be quantitatively analysed much like geologists would do on Earth. The EU FP7 PRoViDE project is compiling all Mars rover vision data into a database accessible through a web-GIS (PRoGIS) and 3D viewer (PRo3D). Stereo-imagery selected in PRoGIS can be rendered in PRo3D, enabling the user to zoom, rotate and translate the 3D outcrop model. Interpretations can be digitised directly onto the 3D surface, and simple measurements can be taken of the dimensions of the outcrop and sedimentary features. Dip and strike is calculated within PRo3D from mapped bedding contacts and fracture traces. Results from multiple outcrops can be integrated in PRoGIS to gain a detailed understanding of the geological features within an area. These tools have been tested on three case studies; Victoria Crater, Yellowknife Bay and Shaler. Victoria Crater, in the Meridiani Planum region of Mars, was visited by the MER-B Opportunity Rover. Erosional widening of the crater produced <15 m high outcrops which expose ancient Martian eolian bedforms. Yellowknife Bay and Shaler were visited in the early stages of the MSL mission, and provide excellent opportunities to characterise Martian fluvio-lacustrine sedimentary features. Development of these tools is crucial to exploitation of vision data from future missions, such as the 2018 ExoMars Rover and the NASA 2020 mission. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 312377 PRoViDE.

Geologic constraints on the macroevolutionary history of marine animals

PubMed Central

Peters, Shanan E.

2005-01-01

The causes of mass extinctions and the nature of taxonomic radiations are central questions in paleobiology. Several episodes of taxonomic turnover in the fossil record, particularly the major mass extinctions, are generally thought to transcend known biases in the geologic record and are widely interpreted as distinct macroevolutionary phenomena that require unique forcing mechanisms. Here, by using a previously undescribed compilation of the durations of sedimentary rock sequences, I compare the rates of expansion and truncation of preserved marine sedimentary basins to rates of origination and extinction among Phanerozoic marine animal genera. Many features of the highly variable record of taxonomic first and last occurrences in the marine animal fossil record, including the major mass extinctions, the frequency distribution of genus longevities, and short- and long-term patterns of genus diversity, can be predicted on the basis of the temporal continuity and quantity of preserved sedimentary rock. Although these results suggest that geologically mediated sampling biases have distorted macroevolutionary patterns in the fossil record, preservation biases alone cannot easily explain the extent to which the sedimentary record duplicates paleobiological patterns. Instead, these results suggest that the processes responsible for producing variability in the sedimentary rock record, such as plate tectonics and sea-level change, may have been dominant and consistent macroevolutionary forces throughout the Phanerozoic. PMID:16105949

Geoengineering Research for a Deep Underground Science and Engineering Laboratory in Sedimentary Rock

NASA Astrophysics Data System (ADS)

Mauldon, M.

2004-12-01

A process to identify world-class research for a Deep Underground Science and Engineering Laboratory (DUSEL) in the USA has been initiated by NSF. While allowing physicists to study, inter alia, dark matter and dark energy, this laboratory will create unprecedented opportunities for biologists to study deep life, geoscientists to study crustal processes and geoengineers to study the behavior of rock, fluids and underground cavities at depth, on time scales of decades. A substantial portion of the nation's future infrastructure is likely to be sited underground because of energy costs, urban crowding and vulnerability of critical surface facilities. Economic and safe development of subsurface space will require an improved ability to engineer the geologic environment. Because of the prevalence of sedimentary rock in the upper continental crust, much of this subterranean infrastructure will be hosted in sedimentary rock. Sedimentary rocks are fundamentally anisotropic due to lithology and bedding, and to discontinuities ranging from microcracks to faults. Fractures, faults and bedding planes create structural defects and hydraulic pathways over a wide range of scales. Through experimentation, observation and monitoring in a sedimentary rock DUSEL, in conjunction with high performance computational models and visualization tools, we will explore the mechanical and hydraulic characteristics of layered rock. DUSEL will permit long-term experiments on 100 m blocks of rock in situ, accessed via peripheral tunnels. Rock volumes will be loaded to failure and monitored for post-peak behavior. The response of large rock bodies to stress relief-driven, time-dependent strain will be monitored over decades. Large block experiments will be aimed at measurement of fluid flow and particle/colloid transport, in situ mining (incl. mining with microbes), remediation technologies, fracture enhancement for resource extraction and large scale long-term rock mass response to induced stresses - with parallel geophysical imaging of the rock mass (and subsequent verification) flow and transport processes, and time-dependent stress and strain. An experimental advantage of sedimentary rock is the presence of pervasive mechanical interfaces (bedding planes), which suggest a host of experimental designs on large rock blocks and slabs (induced flexure, shear strength of interfaces, etc). Thus DUSEL will enable fundamental research about the behavior of a layered rock mass - the dominant structural architecture in near-surface environments worldwide. A further benefit is the natural suitability of sedimentary rocks for experiments related to oil and gas production, or to CO2 sequestration. For example, fluid-induced fracturing of sedimentary rock has long been used by the hydrocarbon industry to improve oil and coal bed methane recovery. Since some fracturing agents are potential contaminants, a major concern and legal responsibility in the US is ensuring the integrity of nearby aquifers. Hydraulic fracturing from a sedimentary rock DUSEL will be followed by injection of low viscosity grout. The rock mass will then be mined back to expose network characteristics of the induced hydraulic fractures. Key questions related to hydrocarbon extraction, CO2 sequestration, waste isolation, and remediation of subsurface contaminants depend critically on the connectivity and architecture of fractures and on coupled thermal, hydrological, mechanical and chemical processes. Fluid flow, particle transport and reaction transport processes are coupled to the stress across fractures, and to thermal, chemical and hydraulic gradients. All can best be studied via large block tests in a subterranean laboratory, ideally in a sedimentary environment.

Tectonic evolution of the Neoproterozoic Tandilia sedimentary cover, Argentina: New evidence of contraction and extensional events in the southwest Gondwana margin

NASA Astrophysics Data System (ADS)

Hernández, Mariano; Arrouy, María Julia; Scivetti, Nicolás; Franzese, Juan R.; Canalicchio, José M.; Poiré, Daniel G.

2017-11-01

At the northwestern portion of the Tandilia System, a detailed structural analysis on the Precambrian sedimentary units exposed in the quarries of the Olavarría-Sierras Bayas area was carried out. These units exhibit deformational structures of several scales, from centimeters to hundreds of meters. The hundreds of meters scale involves E-W- and NW-SE-trending normal faults and NW-SE- and NE-SW-trending contractional folds. The centimeters to meters scale involves veins, joints, normal faults, shear fractures and stylolites, with a prevailing ∼ E-W to NW-SE trend. All these structures were formed by two major tectonic events. The first was the folding event at ∼580 Ma, with NNE-SSW to NE-SW and NW-SE direction of contraction. The second was the extensional faulting event, given by the widespread NNE-SSW-directed extension event during the Atlantic Ocean opening (Jurassic-Cretaceous). Both major events would have been controlled by the reactivation of basement anisotropies. These major tectonic events controlled the deformation of the Precambrian sedimentary cover of the Tandilia system, leading to an economically important aspect in the mining development of the Olavarría-Sierras Bayas area.

Reactive transport in the complex heterogeneous alluvial aquifer of Fortymile Wash, Nevada

DOE PAGES

Soltanian, Mohamad Reza; Sun, Alexander; Dai, Zhenxue

2017-04-02

Yucca Mountain, Nevada, had been extensively investigated as a potential deep geologic repository for storing high-level nuclear wastes. Previous field investigations of stratified alluvial aquifer downstream of the site revealed that there is a hierarchy of sedimentary facies types. There is a corresponding log conductivity and reactive surface area subpopulations within each facies at each scale of sedimentary architecture. Here in this paper, we use a Lagrangian-based transport model in order to analyze radionuclide dispersion in the saturated alluvium of Fortymile Wash, Nevada. First, we validate the Lagrangian model using high-resolution flow and reactive transport simulations. Then, we used themore » validated model to investigate how each scale of sedimentary architecture may affect long-term radionuclide transport at Yucca Mountain. Results show that the reactive solute dispersion developed by the Lagrangian model matches the ensemble average of numerical simulations well. The link between the alluvium spatial variability and reactive solute dispersion at different spatiotemporal scales is demonstrated using the Lagrangian model. Finally, the longitudinal dispersivity of the reactive plume can be on the order of hundreds to thousands of meters, and it may not reach its asymptotic value even after 10,000 years of travel time and 2–3 km of travel distance.« less

Shock metamorphism and impact melting in small impact craters on Earth: Evidence from Kamil crater, Egypt

NASA Astrophysics Data System (ADS)

Fazio, Agnese; Folco, Luigi; D'Orazio, Massimo; Frezzotti, Maria Luce; Cordier, Carole

2014-12-01

Kamil is a 45 m diameter impact crater identified in 2008 in southern Egypt. It was generated by the hypervelocity impact of the Gebel Kamil iron meteorite on a sedimentary target, namely layered sandstones with subhorizontal bedding. We have carried out a petrographic study of samples from the crater wall and ejecta deposits collected during our first geophysical campaign (February 2010) in order to investigate shock effects recorded in these rocks. Ejecta samples reveal a wide range of shock features common in quartz-rich target rocks. They have been divided into two categories, as a function of their abundance at thin section scale: (1) pervasive shock features (the most abundant), including fracturing, planar deformation features, and impact melt lapilli and bombs, and (2) localized shock features (the least abundant) including high-pressure phases and localized impact melting in the form of intergranular melt, melt veins, and melt films in shatter cones. In particular, Kamil crater is the smallest impact crater where shatter cones, coesite, stishovite, diamond, and melt veins have been reported. Based on experimental calibrations reported in the literature, pervasive shock features suggest that the maximum shock pressure was between 30 and 60 GPa. Using the planar impact approximation, we calculate a vertical component of the impact velocity of at least 3.5 km s-1. The wide range of shock features and their freshness make Kamil a natural laboratory for studying impact cratering and shock deformation processes in small impact structures.

The Origin of the Terra Meridiani Sediments: Volatile Transport and the Formation of Sulfate Bearing Layered Deposits on Mars

NASA Technical Reports Server (NTRS)

Niles, P.B.

2008-01-01

The chemistry, sedimentology, and geology of the Meridiani sedimentary deposits are best explained by eolian reworking of the sublimation residue of a large scale ice/dust deposit. This large ice deposit was located in close proximity to Terra Meridiani and incorporated large amounts of dust, sand, and SO2 aerosols generated by impacts and volcanism during early martian history. Sulfate formation and chemical weathering of the initial igneous material is hypothesized to have occurred inside of the ice when the darker mineral grains were heated by solar radiant energy. This created conditions in which small films of liquid water were created in and around the mineral grains. This water dissolved the SO2 and reacted with the mineral grains forming an acidic environment under low water/rock conditions. Subsequent sublimation of this ice deposit left behind large amounts of weathered sublimation residue which became the source material for the eolian process that deposited the Terra Meridiani deposit. The following features of the Meridiani sediments are best explained by this model: The large scale of the deposit, its mineralogic similarity across large distances, the cation-conservative nature of the weathering processes, the presence of acidic groundwaters on a basaltic planet, the accumulation of a thick sedimentary sequence outside of a topographic basin, and the low water/rock ratio needed to explain the presence of very soluble minerals and elements in the deposit. Remote sensing studies have linked the Meridiani deposits to a number of other martian surface features through mineralogic similarities, geomorphic similarities, and regional associations. These include layered deposits in Arabia Terra, interior layered deposits in the Valles Marineris system, southern Elysium/Aeolis, Amazonis Planitia, and the Hellas basin, Aram Chaos, Aureum Chaos, and Ioni Chaos. The common properties shared by these deposits suggest that all of these deposits share a common formation process which must have acted over a large area of Mars. The results of this study suggest a mechanism for volatile transport on Mars without invoking an early greenhouse. They also imply a common formation mechanism for most of the sulfate minerals and layered deposits on Mars, which explains their common occurrence.

Stratigraphic Correlation via Opportunity's Pancam of the Burns Formation, Meridiani Planum, Mars

NASA Astrophysics Data System (ADS)

Thompson, S. D.; Calvin, W. M.; Farrand, W. H.

2006-12-01

Spectral properties of Meridiani Planum hematite-rich Burns formation observed by Opportunity's Pancam have been described previously but not at minimum spatial scales. This study is of the fine scale visible and near- infrared spectral features within the sedimentary structures over the entire lateral extent explored by Opportunity across an 8 km traverse from Endurance to Victoria craters. Investigation of the bedrock has shown sub-centimeter thinly laminated evaporite deposits with few occurrences of festoon cross-bedding, massive bedding, and subtle differences in color and texture. Pancam data analyses of rock targets where sufficient spatial resolution (<10 mm) is achieved (within 10 m) constrain spectral parameters of laminar, erosional, and possible secondary diagenetic features. Results show differences of statistical significance in iron mineral varieties and phases in both vertical section and lateral extent of the Burns formation. Spectra exhibit a steep positive slope in the visible (432-753 nm) region and subtle changes in the near infrared (753-1009 nm) region ranging from flat, concave, to convex profiles. Maxima are typically in the 750-850 nm region but can occur as low as 673 nm and as high as 1009 nm with the latter usually from the lower albedo materials (i.e., spherules and basaltic sands). Positive slopes from 934-1009 nm in this region are consistent with the presence of hematite, commonly associated with the spherules. The higher albedo surfaces tend to have greatest negative slope in the longer wavelengths. This could result from intrinsic characteristics of the outcrop material or a significantly thick (i.e. >100 micron) dust deposit. Band depth images centered at 535 nm and 904 nm provide statistics on the relative occurrences of crystalline ferric oxide minerals. Rarely iron-rich signatures are present in individual laminations and not in the adjacent layers. Such occurrences could result from multiple iron-rich sedimentary events, secondary diagenetic products such as cementation or recrystallization, or an invasive fracture fill material. Comparisons of geomorphologic and spectroscopic mapping will be presented to show overall relationships of the Meridiani plains materials.

Archean sedimentation and tectonics in southern Africa

NASA Technical Reports Server (NTRS)

Kidd, W. S. F.

1984-01-01

Sequences in the Barberton Mountain Land greenstone belt (southern Africa) were examined to determine the nature of the sedimentary rocks, their tectonic implications, and their bearing on the present large-scale structural condition of the belt. Also assessed was whether there was evidence for a significant component of shallow-water-deposited sedimentary rocks in the parent materials of the Limpopo belt. The nature of a largehigh strain zone on the southern margin of the central Limpopo belt was examined.

A Hydrothermal-Sedimentary Context for the Origin of Life

PubMed Central

Hickman-Lewis, K.; Hinman, N.; Gautret, P.; Campbell, K.A.; Bréhéret, J.G.; Foucher, F.; Hubert, A.; Sorieul, S.; Dass, A.V.; Kee, T.P.; Georgelin, T.; Brack, A.

2018-01-01

Abstract Critical to the origin of life are the ingredients of life, of course, but also the physical and chemical conditions in which prebiotic chemical reactions can take place. These factors place constraints on the types of Hadean environment in which life could have emerged. Many locations, ranging from hydrothermal vents and pumice rafts, through volcanic-hosted splash pools to continental springs and rivers, have been proposed for the emergence of life on Earth, each with respective advantages and certain disadvantages. However, there is another, hitherto unrecognized environment that, on the Hadean Earth (4.5–4.0 Ga), would have been more important than any other in terms of spatial and temporal scale: the sedimentary layer between oceanic crust and seawater. Using as an example sediments from the 3.5–3.33 Ga Barberton Greenstone Belt, South Africa, analogous at least on a local scale to those of the Hadean eon, we document constant permeation of the porous, carbonaceous, and reactive sedimentary layer by hydrothermal fluids emanating from the crust. This partially UV-protected, subaqueous sedimentary environment, characterized by physical and chemical gradients, represented a widespread system of miniature chemical reactors in which the production and complexification of prebiotic molecules could have led to the origin of life. Key Words: Origin of life—Hadean environment—Mineral surface reactions—Hydrothermal fluids—Archean volcanic sediments. Astrobiology 18, 259–293. PMID:29489386

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;

Tectonic Evolution of the Çayirhan Neogene Basin (Ankara), Central Turkey

NASA Astrophysics Data System (ADS)

Behzad, Bezhan; Koral, Hayrettin; İşb&idot; l, Duygu; Karaaǧa; ç, Serdal

2016-04-01

Çayırhan (Ankara) is located at crossroads of the Western Anatolian extensional region, analogous to the Basin and Range Province, and suture zone of the Neotethys-Ocean, which is locus of the North Anatolian Transform since the Late Miocene. To the north of Çayırhan (Ankara), a Neogene sedimentary basin comprises Lower-Middle Miocene and Upper Miocene age formations, characterized by swamp, fluvial and lacustrine settings respectively. This sequence is folded and transected by neotectonic faults. The Sekli thrust fault is older than the Lower-Middle Miocene age formations. The Davutoǧlan fault is younger than the Lower-Middle Miocene formations and is contemporaneous to the Upper Miocene formation. The Çatalkaya fault is younger than the Upper Miocene formation. The sedimentary and tectonic features provide information on mode, timing and evolution of this Neogene age sedimentary basin in Central Turkey. It is concluded that the region underwent a period of uplift and erosion under the influence of contractional tectonics prior to the Early-Middle Miocene, before becoming a semi-closed basin under influence of transtensional tectonics during the Early-Middle Miocene and under influence of predominantly extensional tectonics during the post-Late Miocene times. Keywords: Tectonics, Extension, Transtension, Stratigraphy, Neotectonic features.

Sedimentary processes of the Bagnold Dunes: Implications for the eolian rock record of Mars.

PubMed

Ewing, R C; Lapotre, M G A; Lewis, K W; Day, M; Stein, N; Rubin, D M; Sullivan, R; Banham, S; Lamb, M P; Bridges, N T; Gupta, S; Fischer, W W

2017-12-01

The Mars Science Laboratory rover Curiosity visited two active wind-blown sand dunes within Gale crater, Mars, which provided the first ground-based opportunity to compare Martian and terrestrial eolian dune sedimentary processes and study a modern analog for the Martian eolian rock record. Orbital and rover images of these dunes reveal terrestrial-like and uniquely Martian processes. The presence of grainfall, grainflow, and impact ripples resembled terrestrial dunes. Impact ripples were present on all dune slopes and had a size and shape similar to their terrestrial counterpart. Grainfall and grainflow occurred on dune and large-ripple lee slopes. Lee slopes were ~29° where grainflows were present and ~33° where grainfall was present. These slopes are interpreted as the dynamic and static angles of repose, respectively. Grain size measured on an undisturbed impact ripple ranges between 50 μm and 350 μm with an intermediate axis mean size of 113 μm (median: 103 μm). Dissimilar to dune eolian processes on Earth, large, meter-scale ripples were present on all dune slopes. Large ripples had nearly symmetric to strongly asymmetric topographic profiles and heights ranging between 12 cm and 28 cm. The composite observations of the modern sedimentary processes highlight that the Martian eolian rock record is likely different from its terrestrial counterpart because of the large ripples, which are expected to engender a unique scale of cross stratification. More broadly, however, in the Bagnold Dune Field as on Earth, dune-field pattern dynamics and basin-scale boundary conditions will dictate the style and distribution of sedimentary processes.

Sedimentary processes of the Bagnold Dunes: Implications for the eolian rock record of Mars

PubMed Central

Lapotre, M. G. A.; Lewis, K. W.; Day, M.; Stein, N.; Rubin, D. M.; Sullivan, R.; Banham, S.; Lamb, M. P.; Bridges, N. T.; Gupta, S.; Fischer, W. W.

2017-01-01

Abstract The Mars Science Laboratory rover Curiosity visited two active wind‐blown sand dunes within Gale crater, Mars, which provided the first ground‐based opportunity to compare Martian and terrestrial eolian dune sedimentary processes and study a modern analog for the Martian eolian rock record. Orbital and rover images of these dunes reveal terrestrial‐like and uniquely Martian processes. The presence of grainfall, grainflow, and impact ripples resembled terrestrial dunes. Impact ripples were present on all dune slopes and had a size and shape similar to their terrestrial counterpart. Grainfall and grainflow occurred on dune and large‐ripple lee slopes. Lee slopes were ~29° where grainflows were present and ~33° where grainfall was present. These slopes are interpreted as the dynamic and static angles of repose, respectively. Grain size measured on an undisturbed impact ripple ranges between 50 μm and 350 μm with an intermediate axis mean size of 113 μm (median: 103 μm). Dissimilar to dune eolian processes on Earth, large, meter‐scale ripples were present on all dune slopes. Large ripples had nearly symmetric to strongly asymmetric topographic profiles and heights ranging between 12 cm and 28 cm. The composite observations of the modern sedimentary processes highlight that the Martian eolian rock record is likely different from its terrestrial counterpart because of the large ripples, which are expected to engender a unique scale of cross stratification. More broadly, however, in the Bagnold Dune Field as on Earth, dune‐field pattern dynamics and basin‐scale boundary conditions will dictate the style and distribution of sedimentary processes. PMID:29497590

Geomorphic characterization of the U.S. Atlantic continental margin

USGS Publications Warehouse

Brothers, Daniel S.; ten Brink, Uri S.; Andrews, Brian D.; Chaytor, Jason D.

2013-01-01

The increasing volume of multibeam bathymetry data collected along continental margins is providing new opportunities to study the feedbacks between sedimentary and oceanographic processes and seafloor morphology. Attempts to develop simple guidelines that describe the relationships between form and process often overlook the importance of inherited physiography in slope depositional systems. Here, we use multibeam bathymetry data and seismic reflection profiles spanning the U.S. Atlantic outer continental shelf, slope and rise from Cape Hatteras to New England to quantify the broad-scale, across-margin morphological variation. Morphometric analyses suggest the margin can be divided into four basic categories that roughly align with Quaternary sedimentary provinces. Within each category, Quaternary sedimentary processes exerted heavy modification of submarine canyons, landslide complexes and the broad-scale morphology of the continental rise, but they appear to have preserved much of the pre-Quaternary, across-margin shape of the continental slope. Without detailed constraints on the substrate structure, first-order morphological categorization the U.S. Atlantic margin does not provide a reliable framework for predicting relationships between form and process.

Reducing Risk in Horizontal Directional Drilling (HDD) in Soft Sedimentary Environments

NASA Astrophysics Data System (ADS)

Yarbrough, L. D.; Skonberg, E.

2017-12-01

This is a focus on the applied outcome of geologic reports and the scale of near surface geologic process which affect the success of horizontal directional drilling (HDD) operations. Often there is too little data to fully characterize the subsurface along the drilled hole. Adding uncertainty is the exploration borehole is typically vertical while the drill path orientation of the HDD is not. The stratigraphic principle of original horizontality is heavily relied upon when interpreting the geology of the drill path and for good reason because of the depositional processes involved. However, the scale of secondary sedimentary processes, specifically zones of induration and their potential effects on the HDD can be at a scale or frequency that is not properly sampled during the geotechnical investigation. This lack of direct evidence could lead geologists and designers not to include these low-frequency phenomena in their risk analysis. For HDD planning and design, the industry routinely generalizes the earth materials to be encountered as soft or hard. This use of inexact, colloquial phrasing paints a picture of the a nearly homogeneous drilling site. Even though a majority of the site can be characterized as a low-strength or high-strength material, the diagenesis of sediments can include zones with wide-ranging strengths that can negatively impact the rate of penetration, the ability to steer and bore hole stability. In this generalization, soft is a majority of low strength or unconsolidated material (sands, silts, and clays). This does not preclude concretions and other indurated lenticular features that are widespread in the Gulf Coast states. This investigation reviews several formations commonly encountered during medium to large diameter (>10 inches) HDD operations. The Bashi formation with surface exposures in Mississippi and Alabama; the Wilcox Group in southern Mississippi and central Louisiana; the Cook Mountain Formation; the Hatchetigbee formation and Catahoula Formation of Louisiana and Mississippi were reviewed and potential HDD drilling and pull back complications are discussed.

Magnesium-to-calcium ratio in tap water, and its relationship to geological features and the incidence of calcium-containing urinary stones.

PubMed

Kohri, K; Kodama, M; Ishikawa, Y; Katayama, Y; Takada, M; Katoh, Y; Kataoka, K; Iguchi, M; Kurita, T

1989-11-01

We examined the relationship among magnesium and calcium content in tap water, the geological features and urinary stone incidence in Japan. The magnesium-to-calcium ratio in tap water correlated negatively with the incidence of urolithiasis. There was no correlation between calcium and magnesium concentration in tap water and urinary stone incidence. Geological features in Japan were classified into 5 groups. The magnesium-to-calcium ratio in the basalt areas was higher than in the other areas, while ratio in the granite areas was low. In the sedimentary rock areas calcium and magnesium concentrations were high; the magnesium-to-calcium ratio in these areas was between those of the basalt and granite areas. The limestone areas had a much higher calcium concentration. The incidence of urinary stones in the sedimentary rock and basalt areas was lower than that of the granite areas, while that in the limestone areas was the highest. Thus, the incidence of urinary stone is related to the magnesium-to-calcium ratio in tap water and the geological area.

Multi-physics and multi-scale characterization of shale anisotropy

NASA Astrophysics Data System (ADS)

Sarout, J.; Nadri, D.; Delle Piane, C.; Esteban, L.; Dewhurst, D.; Clennell, M. B.

2012-12-01

Shales are the most abundant sedimentary rock type in the Earth's shallow crust. In the past decade or so, they have attracted increased attention from the petroleum industry as reservoirs, as well as more traditionally for their sealing capacity for hydrocarbon/CO2 traps or underground waste repositories. The effectiveness of both fundamental and applied shale research is currently limited by (i) the extreme variability of physical, mechanical and chemical properties observed for these rocks, and by (ii) the scarce data currently available. The variability in observed properties is poorly understood due to many factors that are often irrelevant for other sedimentary rocks. The relationships between these properties and the petrophysical measurements performed at the field and laboratory scales are not straightforward, translating to a scale dependency typical of shale behaviour. In addition, the complex and often anisotropic micro-/meso-structures of shales give rise to a directional dependency of some of the measured physical properties that are tensorial by nature such as permeability or elastic stiffness. Currently, fundamental understanding of the parameters controlling the directional and scale dependency of shale properties is far from complete. Selected results of a multi-physics laboratory investigation of the directional and scale dependency of some critical shale properties are reported. In particular, anisotropic features of shale micro-/meso-structures are related to the directional-dependency of elastic and fluid transport properties: - Micro-/meso-structure (μm to cm scale) characterization by electron microscopy and X-ray tomography; - Estimation of elastic anisotropy parameters on a single specimen using elastic wave propagation (cm scale); - Estimation of the permeability tensor using the steady-state method on orthogonal specimens (cm scale); - Estimation of the low-frequency diffusivity tensor using NMR method on orthogonal specimens (<μm scale). For each of the above properties, leading-edge experimental techniques have been associated with novel interpretation tools. In this contribution, these experimental and interpretation methods are described. Relationships between the measured properties and the corresponding micro-/meso-structural features are discussed. For example, P-wave velocity was measured along 100 different propagation paths on a single cylindrical shale specimen using miniature ultrasonic transducers. Assuming that (i) the elastic tensor of this shale is transversely isotropic; and (i) the sample has been cored perfectly perpendicular to the bedding plane (symmetry plane is horizontal), Thomsen's anisotropy parameters inverted from the measured velocities are: - P-wave velocity along the symmetry axis (perpendicular to the bedding plane) αo=3.45km/s; - P-wave anisotropy ɛ=0.12; - Parameter controlling the wave front geometry δ=0.058. A novel inversion algorithm allows for recovering these parameters without assuming a priori a horizontal bedding (symmetry) plane. The inversion of the same data set using this algorithm yields (i) αo=3.23km/s, ɛ=0.25 and δ=0.18, and (ii) the elastic symmetry axis is inclined of ω=30° with respect to the specimen's axis. Such difference can have strong impact on field applications (AVO, ray tracing, tomography).

Dynamics of Braided Channels, Bars, and Associated Deposits Under Experimental Density Currents

NASA Astrophysics Data System (ADS)

Limaye, A. B. S.; Jean-Louis, G.; Paola, C.

2015-12-01

Turbidity currents are the principal agents that transfer clastic sediment from continental margins to the deep ocean. The extensive sedimentary deposits that result can record influences from fluvial transport, ocean currents, and seafloor bathymetry; decoding these controls is key to understanding long-term continental denudation and the formation of hydrocarbon reservoirs. Experimental turbidity currents often use pre-formed, single-thread channels, but more recent experiments and seafloor observations suggest that braided channels also develop in submarine environments. Yet controls on the formation of submarine braided channels and relationships between these channels and stratigraphic evolution remain largely untested. We have conducted a series of experiments to determine the conditions conducive to forming braided submarine channels, and to relate channel geometry and kinematics to deposit architecture. Dissolved salt supplies the excess density of the experimental turbidity currents, which transport plastic, sand-sized sediment as bedload across a test section two meters long and one meter wide. Our experiments indicate that braided channels can form as constructional features without prior erosion for a range of input water and sediment fluxes. Channel migration, avulsion, and aggradation construct sedimentary deposits with bars at a variety of scales. Bar geometry and channel kinematics are qualitatively similar under subaerial and subaqueous experiments with other parameters fixed. We will present quantitative analyses of the relationships between channel geometry and mobility and deposit architecture, at scales from individual bars to the entire deposit, and compare these results to control experiments with subaerial braiding. These experimental results suggest parallels between subaerial and subaqueous braiding, and help to constrain forward models for stratigraphic evolution and inverse methods for estimating flow conditions from turbidites.

Geologic influence on induced seismicity: Constraints from potential field data in Oklahoma

USGS Publications Warehouse

Shah, Anjana K.; Keller, G. Randy

2017-01-01

Recent Oklahoma seismicity shows a regional correlation with increased wastewater injection activity, but local variations suggest that some areas are more likely to exhibit induced seismicity than others. We combine geophysical and drill hole data to map subsurface geologic features in the crystalline basement, where most earthquakes are occurring, and examine probable contributing factors. We find that most earthquakes are located where the crystalline basement is likely composed of fractured intrusive or metamorphic rock. Areas with extrusive rock or thick (>4 km) sedimentary cover exhibit little seismicity, even in high injection rate areas, similar to deep sedimentary basins in Michigan and western North Dakota. These differences in seismicity may be due to variations in permeability structure: within intrusive rocks, fluids can become narrowly focused in fractures and faults, causing an increase in local pore fluid pressure, whereas more distributed pore space in sedimentary and extrusive rocks may relax pore fluid pressure.

Surficial Geologic Map of the Ashby-Lowell-Sterling-Billerica 11-Quadrangle Area in Northeast-Central Massachusetts

USGS Publications Warehouse

Stone, Byron D.; Stone, Janet R.

2007-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of eleven 7.5-minute quadrangles (total 505 mi2) in northeast-central Massachusetts. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for water resources, construction aggregate resources, earth-surface hazards assessments, and land-use decisions. This compilation of surficial geologic materials is an interim product that defines the areas of exposed bedrock, and the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), a regional map at 1:50,000 scale (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Surficial Geologic Map of the Salem Depot-Newburyport East-Wilmington-Rockport 16-Quadrangle Area in Northeast Massachusetts

USGS Publications Warehouse

Stone, Byron D.; Stone, Janet Radway; DiGiacomo-Cohen, Mary L.

2006-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of 16 7.5-minute quadrangles (total 658 mi2) in northeast Massachusetts. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (grain size, sedimentary structures, mineral and rock-particle composition), constructional geomorphic features, stratigraphic relationships, and age. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for water resources, construction aggregate resources, earth-surface hazards assessments, and land-use decisions. This compilation of surficial geologic materials is an interim product that defines the areas of exposed bedrock, and the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), a regional map at 1:50,000 scale (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Structural and Sequence Stratigraphic Analysis of the Onshore Nile Delta, Egypt.

NASA Astrophysics Data System (ADS)

Barakat, Moataz; Dominik, Wilhelm

2010-05-01

The Nile Delta is considered the earliest known delta in the world. It was already described by Herodotus in the 5th Century AC. Nowadays; the Nile Delta is an emerging giant gas province in the Middle East with proven gas reserves which have more than doubled in size in the last years. The Nile Delta basin contains a thick sedimentary sequence inferred to extend from Jurassic to recent time. Structural styles and depositional environments varied during this period. Facies architecture and sequence stratigraphy of the Nile Delta are resolved using seismic stratigraphy based on (2D seismic lines) including synthetic seismograms and tying in well log data. Synthetic seismograms were constructed using sonic and density logs. The combination of structural interpretation and sequence stratigraphy of the development of the basin was resolved. Seven chrono-stratigraphic boundaries have been identified and correlated on seismic and well log data. Several unconformity boundaries also identified on seismic lines range from angular to disconformity type. Furthermore, time structure maps, velocity maps, depth structure maps as well as Isopach maps were constructed using seismic lines and log data. Several structural features were identified: normal faults, growth faults, listric faults, secondary antithetic faults and large rotated fault blocks of manly Miocene age. In some cases minor rollover structures could be identified. Sedimentary features such as paleo-channels were distinctively recognized. Typical Sequence stratigraphic features such as incised valley, clinoforms, topsets, offlaps and onlaps are identified and traced on the seismic lines allowing a good insight into sequence stratigraphic history of the Nile Delta most especially in the Miocene to Pliocene clastic sedimentary succession.

Development of multiple source data processing for structural analysis at a regional scale. [digital remote sensing in geology

NASA Technical Reports Server (NTRS)

Carrere, Veronique

1990-01-01

Various image processing techniques developed for enhancement and extraction of linear features, of interest to the structural geologist, from digital remote sensing, geologic, and gravity data, are presented. These techniques include: (1) automatic detection of linear features and construction of rose diagrams from Landsat MSS data; (2) enhancement of principal structural directions using selective filters on Landsat MSS, Spacelab panchromatic, and HCMM NIR data; (3) directional filtering of Spacelab panchromatic data using Fast Fourier Transform; (4) detection of linear/elongated zones of high thermal gradient from thermal infrared data; and (5) extraction of strong gravimetric gradients from digitized Bouguer anomaly maps. Processing results can be compared to each other through the use of a geocoded database to evaluate the structural importance of each lineament according to its depth: superficial structures in the sedimentary cover, or deeper ones affecting the basement. These image processing techniques were successfully applied to achieve a better understanding of the transition between Provence and the Pyrenees structural blocks, in southeastern France, for an improved structural interpretation of the Mediterranean region.

Review of Paleomagnetic Age Constraints of Mid-Continent Rift Strata, Upper Midwestern United States

NASA Astrophysics Data System (ADS)

Houlihan, E.; Runkel, A.; Feinberg, J. M.; Cowan, C. A.; Titus, S.

2016-12-01

The Keweenawan Supergroup consists of 1.1 Ga volcanic units and overlying km-thick sedimentary succession that are associated with the Midcontinent Rift (MR), one of the most prominent geologic features in the Precambrian basement rocks of the North American craton (Morey and Green, 1982; Ojakangas et al., 2001; Ojakangas and Dickas, 2002). Recent studies targeting the sedimentary sequences of the rift highlight a longstanding problem that limits the impact of their results. The studies are based on data collected from a sedimentary package of the Keweenawan Supergroup that is very poorly constrained in age. Sedimentary strata low in the succession are constrained by dated intercalated volcanics, or mineralization ages, that indicate syn-rift filling commenced at about 1087 Ma as volcanism was waning (Davis and Paces, 1990). However, km-thick younger strata within the rift are constrained in maximum age only by virtue of overlying Cambrian fossil-bearing units (Morey and Ojakangas, 1982). Thus, the bulk of the MR sedimentary succession has a range in possible age of about 500 Ma, and potentially is in places as young as Middle Cambrian. Paleomagnetic methods may hold the most promise to date the MR sedimentary succession. Widespread paleomagnetic studies have been conducted on the igneous rocks of the rift, and several previous studies have used paleomagnetic techniques to date the sedimentary units as well (Dubois, 1962; Henry et al., 1976; Elmore and Van der Voo, 1978; Roy and Robertson, 1978; Halls and Palmer, 1981; Palmer et al., 1981; Watts, 1981; McCabe and Van der Voo, 1982; Diehl and Haig, 1994; Kulakov et al., 2013 and others). These authors generally considered the paleomagnetic signatures to be consistent with a Mesoproterozoic age for both the igneous and sedimentary rocks of the rift. Recently, however, authors have suggested that the uppermost sedimentary units are much younger in age, based on a combination of zircon and paleomagnetic analysis (Malone et al., 2016). Here, we present new paleomagnetic data collected in 2015, and combine it with previous paleomagnetic studies to synthesize all paleomagnetic data on the Mid-Continent Rift strata and provide suggestions for future studies to determine the age and correlation of the units.

Sedimentology and sequence stratigraphy of the Lower Jurassic Kayenta Formation, Colorado Plateau, United States

NASA Astrophysics Data System (ADS)

Sanabria, Diego Ignacio

2001-07-01

Detailed outcrop analysis of the Lower Jurassic Kayenta Formation provides the basis for the formulation of a new sequence stratigraphic model for arid to semi-arid continental deposits and the generation of a comprehensive set of sedimentologic criteria for the recognition of ephemeral stream deposits. Criteria for the recognition of ephemeral deposits in the ancient record were divided into three categories according to the scale of the feature being considered. The first category takes into account sedimentary structures commonly found in the record of ephemeral stream deposits including hyperconcentrated and debris flow deposits, planar parallel bedding, sigmoidal cross-bedding, hummocky cross-bedding, climbing ripple lamination, scour-and-fill structures, convolute bedding, overturned cross-bedding, ball-and-pillow structures, pocket structures, pillars, mud curls, flaser lamination, algal lamination, termite nests, and vertebrate tracks. The second category is concerned with the mesoscale facies architecture of ephemeral stream deposits and includes waning flow successions, bedform climb, downstream accretion, terminal wadi splays, and channel-fill successions indicating catastrophic flooding. At the large-scale facies architecture level, the third category, ephemeral stream deposits are commonly arranged in depositional units characterized by a downstream decrease in grain size and scale of sedimentary structures resulting from deposition in terminal fan systems. Outcrops of the Kayenta Formation and its transition to the Navajo Sandstone along the Vermilion and Echo Cliffs of Northern Arizona indicate that wet/dry climatic cyclicity exerted a major control on regional facies architecture. Two scales of wet/dry climatic cyclicity can be recognized in northern Arizona. Three sequence sets composed of rocks accumulated under predominantly dry or wet conditions are the expression of long-term climatic cyclicity. Short-term climatic cyclicity, on the other hand, is represented by high-frequency sequences composed of eolian or ephemeral fluvial deposits overlain by perennial fluvial sediments. Increased evapotranspiration rates, depressed water tables, and accumulation of eolian or ephemeral fluvial deposits characterize the dry portion of these cycles. The wet part of the cycles is marked by an increase in precipitation and the establishment of perennial fluvial systems and lacustrine basins. This depositional model constitutes a valuable tool for correlation of similar deposits in the subsurface.

Microbial shaping of wrinkle structures in siliciclastic deposits

NASA Astrophysics Data System (ADS)

Bosak, T.; Mariotti, G.; Pruss, S. B.; Perron, J.; O'Grady, M.

2013-12-01

Wrinkle structures are millimeter- to centimeter-scale elongated or reticulate sedimentary structures that resemble symmetric ripples. Sharp-crested and flat-topped wrinkle structures up to 1 cm wide occur on numerous bedding planes in the Neoproterozoic and Cambrian, as well as in some Archean and Phanerozoic siliciclastic deposits. Because similar, but unlithified structures occur in some modern, microbially-colonized sands, wrinkle structures are typically interpreted as microbially induced sedimentary structures. However, it is unclear if physical processes, such as the motion of suspended sand grains, can produce similar features in sand even before microbial colonization. We introduced mat fragments to the surface of silica sand in wave tanks and generated sharp-crested, flat-topped and pitted wrinkle structures. The abrasion of the sandy surface by rolling, low density, millimeter-size fragments of microbial mats produces wrinkle structures at extremely weak orbital velocities that cannot move sand grains in the absence of light particles. Wrinkle structures form in a few hours and can become colonized by microbial mats within weeks. Thus, wrinkle structures are patterns formed by microbially mediated sand motion at low orbital velocities in the absence of bioturbation. Once formed, wrinkle structures can be colonized and stabilized by microbial mats, but the shape of these mats does not dictate the shape of wrinkle structures. These experiments bolster the interpretation of wrinkle structures as morphological signatures of organic particles and early life in Archean and Proterozoic siliciclastic deposits.

Pore Effect on the Occurrence and Formation of Gas Hydrate in Permafrost of Qilian Mountain, Qinghai-Tibet Plateau, China

NASA Astrophysics Data System (ADS)

Gao, H.; Lu, H.; Lu, Z.

2014-12-01

Gas hydrates were found in the permafrost of Qilian Mountain, Qinghai- Tibet Plateau, China in 2008. It has been found that gas hydrates occur in Jurassic sedimentary rocks, and the hydrated gases are mainly thermogenic. Different from the gas hydrates existing in loose sands in Mallik, Mackenzie Delta, Canada and North Slope, Alaska, USA, the gas hydrates in Qilian Mountain occurred in hard rocks. For understanding the occurrence and formation mechanism of gas hydrate in hard rcok, extensive experimental investigations have been conducted to study the pore features and hydrate formation in the rocks recovered from the hydrate layers in Qilian Mountain. The structures of sedimentary rock were observed by high-resolution X-ray CT, and pore size distribution of a rock specimen was measured with the mercury-injection method. Methane hydrate was synthesized in water-saturated rocks, and the saturations of hydrate in sedimentary rocks of various types were estimated from the amount of gas released from certain volume of rock. X-ray CT observation revealed that fractures were developed in the rocks associated with faults, while those away from faults were generally with massive structure. The mercury-injection analysis of pore features found that the porosities of the hydrate-existing rocks were generally less than 3%, and the pore sizes were generally smaller than 100 nm. The synthesizing experiments found that the saturation of methane hydrate were generally lower than 6% of pore space in rocks, but up to 16% when fractures developed. The low hydrate saturation in Qilian sedimentary rocks has been found mainly due to the small pore size of rock. The low hydrate saturation in the rocks might be the reason for the failure of regional seismic and logging detections of gas hydrates in Qilian Mountain.

Sonograph mosaic of northern California and southern Oregon Exclusive Economic Zone

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

Cacchione, D.A.; Drake, D.E.; Clarke, S.H.

1985-02-01

During June 15 to July 9, 1984, the third leg of the cooperative US Geological Survey-Institute of Oceanographic Sciences GLORIA survey of the conterminous US Exclusive Economic Zone (EEZ) collected digital acoustic data off northern California and southern Oregon. The region covered during leg 3 extends from the 200-m isobath westward to the 375-km (200-nmi) EEZ boundary and from about 39/sup 0/ to 43/sup 0/N. The survey used the IOS GLORIA long-range side-scan sonar, a 2-channel airgun seismic reflection system, and 3.5 kHz and 10 kHz high-resolution seismic systems. The GLORIA data were collected in a pattern that permitted overlappingmore » coverage so that a mosaic of the sonographs could be constructed. These sonographs were slant-range and anamorphically corrected aboard ship, and a mosaic was constructed at a scale of 1:375,000. Among the most striking geomorphic features revealed in this segment of the EEZ is the Mendocino transform fault, which extends for more than 120 nmi along the northern base of the Mendocino fracture zone and delineates the southern boundary of the Gorda plate. Other features clearly revealed are the complex geometry of the Gorda rift valley, and the subparallel flanking ridges and dramatically deformed base of the continental slope at the eastern boundary of the Gorda plate. The data are presently being processed by image analytical techniques to enhance the fine-scale features such as sediment waves, slumps, and areas of differing sedimentary facies.« less

An ecohydraulic view on stream resilience and ecosystem functioning - what can science teach management?

NASA Astrophysics Data System (ADS)

Battin, Tom J.; Dzubakova, Katharina; Boodoo, Kyle; Ulseth, Amber

2017-04-01

Streams and rivers are increasingly exposed to environmental change across various spatial and temporal scales. Consequently, ecosystem health and integrity are becoming compromised. Most management strategies designed to recover and maintain stream ecosystem health involve engineering measures of geomorphology. The success of such engineering measures relies on a thorough understanding of the underlying physical, chemical and biological process coupling across scales. First, we present results from experimental work unraveling the relevance of streambed heterogeneity for the resilience of phototrophic biofilms. This is critical as phototrophic biofilms are key for nutrient removal and hence for keeping the water clean. These biofilms are also the machinery of primary production and related carbon fluxes in stream ecosystems. Next, we show how climate change may affect primary production, including CO2, in streams and the networks they form. In fact, streams are now recognized as major sources of CO2 to the atmosphere and contributors to the global carbon cycle. Despite this, we do not yet understand how geomorphological features, themselves continuously reworked by hydrology and sedimentary dynamics, affect CO2 fluxes in streams. We show that gravel bars, clearly conspicuous geomorphological features, are hotspots of CO2 fluxes compared to the streamwater itself. This has major implications for carbon cycling and stream ecosystem functioning. Finally, we discuss what stream management could learn from ecohydraulic insights from young scientists doing excellent basic research.

Procedures for Identifying Rocks with Similar Features.

ERIC Educational Resources Information Center

Powell, William E.

1984-01-01

The purpose of this article is to provide college level physical geography and geology teachers with practical and simple techniques to help students classify and understand igneous, sedimentary, and metamorphic rocks. Essential equipment is also discussed, and recommended readings are listed. (RM)

Polygon/Cracked Sedimentary Rock

NASA Technical Reports Server (NTRS)

2004-01-01

4 December 2004 Exposures of sedimentary rock are quite common on the surface of Mars. Less common, but found in many craters in the regions north and northwest of the giant basin, Hellas, are sedimentary rocks with distinct polygonal cracks in them. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example from the floor of an unnamed crater near 21.0oS, 311.9oW. Such cracks might have formed by desiccation as an ancient lake dried up, or they might be related to ground ice freeze/thaw cycles or some other stresses placed on the original sediment or the rock after it became lithified. The 300 meter scale bar is about 328 yards long. The scene is illuminated by sunlight from the upper left.

Hammersley Range, northern Western Australia

NASA Image and Video Library

1990-04-29

The oval shaped basin of the sedimentary rocks of the Hammersley Range, northern Western Australia (23.0S, 119.0E) dominates the center of this near nadir view. The Fortescue River is the remarkably straight, fault controlled feature bordering the Hammersley on the north. Sand dunes are the main surface features in the northeast and southwest. Many dry lakebeds can be seen to the east as light grey colored patches along the watercourses.

Karst in the United States: a digital map compilation and database

USGS Publications Warehouse

Weary, David J.; Doctor, Daniel H.

2014-01-01

This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst. These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rocks with potential for karst development, and about 18 percent of their area is underlain by soluble rocks having karst or the potential for development of karst features. The areas of soluble rocks shown are based primarily on selection from State geologic maps of rock units containing significant amounts of carbonate or evaporite minerals. Areas underlain by soluble rocks are further classified by general climate setting, degree of induration, and degree of exposure. Areas having potential for volcanic pseudokarst are those underlain chiefly by basaltic-flow rocks no older than Miocene in age. Areas with potential for pseudokarst features in sedimentary rocks are in relatively unconsolidated rocks from which pseudokarst features, such as piping caves, have been reported. Areas having potential for development of thermokarst features, mapped exclusively in Alaska, contain permafrost in relatively thick surficial deposits containing ground ice. This report includes a GIS database with links from the map unit polygons to online geologic unit descriptions.

Potential Cement Phases in Sedimentary Rocks Drilled by Curiosity at Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Morris, R. V.; Bish, D. L.; Chipera, S. J.; Ming, D. W.; Blake, D. F.; Vaniman, D. T.; Bristow, T. F.; Cavanagh, P.; Farmer, J. D.;

Questioning the Sedimentary Paradigm for Granites

NASA Astrophysics Data System (ADS)

Glazner, A. F.; Bartley, J. M.; Coleman, D. S.; Boudreau, A.; Walker, J. D.

2007-12-01

A critical question regarding volcano-pluton links is whether plutons are samples of magma that passed through on its way to eruption, or residues left behind after volcanic rocks were extracted. A persistent theme of recent work on granites sensu lato is that many are sedimentary accumulations of crystals that lost significant volumes of magmatic liquid. This view is based on observations of structures that clearly seem to reflect deposition on a magma chamber floor (e.g., flows of chilled mafic magma into silicic magma) and on the inference that many other structures, such as modal layering, truncated layering, and crystal accumulations, reflect crystal sedimentation on such chamber floors. There are significant physical and geochemical reasons to question this view, based on observations in the Sierra Nevada of California and similar results from other batholiths. First, few granites show the enrichments in Ba, Sr, and relative Eu that feldspar accumulation should produce. Second, sedimentary features such as graded bedding and cross-bedding form in highly turbulent flows, but turbulence is unachievable in viscous silicic liquids, where velocities on the order of 104 m/s would be required to induce turbulence in a liquid with η=104 Pa s. Third, tabular modally layered domains commonly cut surrounding modal layering on both sides, and orientations of modal layering and of the troughs of "ladder dikes" commonly scatter widely within hectare-sized areas; it is difficult to reconcile these features with gravity-driven settling. Fourth, accumulations of K-feldspar megacrysts are typically inferred to be depositional, but this is precluded by crystallization of most K- feldspar after rheologic lock-up occurs. Finally, accumulations of K-feldspar and hornblende are typically packed too tightly to be depositional. With analogy to layered mafic intrusions, many features attributed to crystal sedimentation in granites may be better explained by crystal aging and other in situ chemical processes. In particular, many of these features may record pore-melt flow paths rather than depositional processes.

Linking Environmental Forcing and Trophic Supply to Benthic Communities in the Vercelli Seamount Area (Tyrrhenian Sea)

PubMed Central

Covazzi Harriague, Anabella; Bavestrello, Giorgio; Bo, Marzia; Borghini, Mireno; Castellano, Michela; Majorana, Margherita; Massa, Francesco; Montella, Alessandro; Povero, Paolo; Misic, Cristina

2014-01-01

Seamounts and their influence on the surrounding environment are currently being extensively debated but, surprisingly, scant information is available for the Mediterranean area. Furthermore, although the deep Tyrrhenian Sea is characterised by a complex bottom morphology and peculiar hydrodynamic features, which would suggest a variable influence on the benthic domain, few studies have been carried out there, especially for soft-bottom macrofaunal assemblages. In order to fill this gap, the structure of the meio-and macrofaunal assemblages of the Vercelli Seamount and the surrounding deep area (northern Tyrrhenian Sea – western Mediterranean) were studied in relation to environmental features. Sediment was collected with a box-corer from the seamount summit and flanks and at two far-field sites in spring 2009, in order to analyse the metazoan communities, the sediment texture and the sedimentary organic matter. At the summit station, the heterogeneity of the habitat, the shallowness of the site and the higher trophic supply (water column phytopigments and macroalgal detritus, for instance) supported a very rich macrofaunal community, with high abundance, biomass and diversity. In fact, its trophic features resembled those observed in coastal environments next to seagrass meadows. At the flank and far-field stations, sediment heterogeneity and depth especially influenced the meiofaunal distribution. From a trophic point of view, the low content of the valuable sedimentary proteins that was found confirmed the general oligotrophy of the Tyrrhenian Sea, and exerted a limiting influence on the abundance and biomass of the assemblages. In this scenario, the rather refractory sedimentary carbohydrates became a food source for metazoans, which increased their abundance and biomass at the stations where the hydrolytic-enzyme-mediated turnover of carbohydrates was faster, highlighting high lability. PMID:25343621

Genesis and sedimentary record of blind channel and islands of the anabranching river: An evolution model

NASA Astrophysics Data System (ADS)

Leli, Isabel T.; Stevaux, José C.; Assine, Mário L.

2018-02-01

Blind channel (BC) is a fluvial feature formed by attachment of a lateral sand bar to an island or riverbank. It consists of a 10- to 20-m wide and hundreds to thousands meters long channel, parallel to the island or bank, closed at its upstream end by accretion to the island. It is an important feature in anabranching rivers that plays an important role in both the island formation and river ecology. This paper discusses the formation processes, functioning, evolution, and the sedimentary record of a blind channel, related landforms, and its context on island development in the Upper Paraná River. The evolution of this morphologic feature involves (1) formation of a lateral or attachment bar beside an island with the development of a channel in between; (2) vertical accretion of mud deposits during the flood and vegetal development on the bar; (3) the upstream channel closure that generates the blind channel; and (4) annexation of the blind channel to the island. A blind channel is semilotic to lentic, that is not totally integrated to the dynamics of the main active channel and that acts as a nursery for fingerlings and macrophytes. The sedimentary facies succession of BCs are relatively simple and characterized by cross-stratified sand covered by organic muddy sediments. Based on facies analysis of 12 cores, we identified a succession of environments that contribute to the formation of islands: channel bar, blind channel, pond, and swamp. Blind channel formation and its related bar-island attachment are relevant processes associated with the growing of large island evolution in some anabranching rivers.

Sea-floor morphology and sedimentary environments of western Block Island Sound, northeast of Gardiners Island, New York

USGS Publications Warehouse

McMullen, Katherine Y.; Poppe, Lawrence J.; Danforth, William W.; Blackwood, Dann S.; Clos, Andrew R.; Parker, Castle E.

2014-01-01

Multibeam-echosounder data, collected during survey H12299 by the National Oceanic and Atmospheric Administration in a 162-square-kilometer area of Block Island Sound, northeast of Gardiners Island, New York, are used along with sediment samples and bottom photography, collected at 37 stations in this area by the U.S. Geological Survey during cruise 2013-005-FA, to interpret sea-floor features and sedimentary environments. These data and interpretations provide important base maps for future studies of the sea floor, focused, for example, on benthic ecology and resource management. The features and sedimentary environments on the sea floor are products of the glacial history and modern tidal regime. Features include bedforms such as sand waves and megaripples, boulders, a large current-scoured depression, exposed glaciolacustrine sediments, and areas of modern marine sediment. Sand covers much of the study area and is often in the form of sand waves and megaripples, which indicate environments characterized by coarse-grained bedload transport. Boulders and gravelly lag deposits, which indicate environments of erosion or nondeposition, are found off the coast of Gardiners Island and on bathymetric highs, probably marking areas where deposits associated with recessional ice-front positions, the northern flank of the terminal moraine, or coastal-plain sediments covered with basal till are exposed. Bottom photographs and video of boulders show that they are commonly covered with sessile fauna. Strong tidal currents have produced the deep scour depression along the northwestern edge of the study area. The eastern side of this depression is armored with a gravel lag. Sea-floor areas characterized by modern marine sediments appear featureless at the 2-meter resolution of the bathymetry and flat to current rippled in the photography. These modern environments are indicative of sediment sorting and reworking.

Structure and Filling Characteristics of Paleokarst Reservoirs in the Northern Tarim Basin, Revealed by Outcrop, Core and Borehole Images

NASA Astrophysics Data System (ADS)

Tian, Fei; Lu, Xinbian; Zheng, Songqing; Zhang, Hongfang; Rong, Yuanshuai; Yang, Debin; Liu, Naigui

2017-06-01

The Ordovician paleokarst reservoirs in the Tahe oilfield, with burial depths of over 5300 m, experienced multiple phases of geologic processes and exhibit strong heterogeneity. Core testing can be used to analyse the characteristics of typical points at the centimetre scale, and seismic datasets can reveal the macroscopic outlines of reservoirs at the >10-m scale. However, neither method can identify caves, cave fills and fractures at the meter scale. Guided by outcrop investigations and calibrations based on core sample observations, this paper describes the interpretation of high longitudinal resolution borehole images, the identification of the characteristics of caves, cave fills (sedimentary, breccia and chemical fills) and fractures in single wells, and the identification of structures and fill characteristics at the meter scale in the strongly heterogeneous paleokarst reservoirs. The paleogeomorphology, a major controlling factor in the distribution of paleokarst reservoirs, was also analysed. The results show that one well can penetrate multiple cave layers of various sizes and that the caves are filled with multiple types of fill. The paleogeomorphology can be divided into highlands, slopes and depressions, which controlled the structure and fill characteristics of the paleokarst reservoirs. The results of this study can provide fundamental meter-scale datasets for interpreting detailed geologic features of deeply buried paleocaves, can be used to connect core- and seismic-scale interpretations, and can provide support for the recognition and development of these strongly heterogeneous reservoirs.

From coastal barriers to mountain belts - commonalities in fundamental geomorphic scaling laws

NASA Astrophysics Data System (ADS)

Lazarus, E.

2016-12-01

Overwash is a sediment-transport process essential to the form and resilience of coastal barrier landscapes. Driven by storm events, overwash leaves behind distinctive sedimentary features that, although intensively studied, have lacked unifying quantitative descriptions with which to compare their morphological attributes across documented examples or relate them to other morphodynamic phenomena. Geomorphic scaling laws quantify how measures of shape and size change with respect to another - information that helps to constrain predictions of future change and reconstructions of past environmental conditions. Here, a physical model of erosional and depositional overwash morphology yields intrinsic, allometric scaling laws involving length, width, area, volume, and alongshore spacing. Corroborative comparisons with natural washover morphology indicate scale invariance spanning several orders of magnitude. Several observers of the physical model remarked that the overwashed barrier resembled a dissected linear mountain front with an alluvial apron - an intriguing reimagining of the intended analog. Indeed, that resemblance is reflected quantitatively in these new scaling relationships, which align with canonical scaling laws for terrestrial and marine drainage basins and alluvial fans on Earth and Mars. This finding suggests disparate geomorphic systems that share common allometric properties may be related dynamically, perhaps by an influence more fundamental than characteristic erosion and deposition processes. Such an influence could come from emergent behavior at the intersection of advection and diffusion. Geomorphic behaviors at advection-diffusion transitions (and vice versa), specifically, could be the key to disentangling mechanistic causality from acausality in physical landscape patterns.

New insights on late stage volcanism in the Pigafetta basin, western Pacific

NASA Astrophysics Data System (ADS)

Stadler, T.; Tominaga, M.

2014-12-01

We document observations of late stage volcanism in the western Pacific Pigafetta Basin by integrating previously published and new multichannel seismic (MCS) reflection profiles, Ocean Drilling Program (ODP) drill core, and well log data. We examine data from three seismic experiments (FM35-12, MESOPAC II, and MTr5) conducted in the Pigafetta Basin, one of the oldest, deepest abyssal basins in the world, where crustal age is suggested to range from M29 (~157 Ma) to M44 (~169.8 Ma) based on Japanese Mesozoic magnetic lineations. We use a total of ~2150 km of MCS lines along with core and wire-line logging data from ODP Hole 801C. As a basis for our interpretation, we use previously defined seismic stratigraphy for the Pigafetta Basin, including Horizon B (basement) and lower transparent unit (volcaniclastic turbidites) terminology. We build synthetic seismograms from density and p-wave velocity logs using OpendTect v 4.6.0 tie well to seismic feature. We then incorporate energy and similarity attributes of the MCS profiles with the modeled seismogram to correlate reflectors to ODP Hole 801C lithostratigraphy. From this correlation, to be consistent with previous studies, we assign lithology and age to prominent sedimentary and basement reflectors throughout all survey lines. We characterize widely distributed deformation of Horizon B and lower sedimentary unit reflectors based on coherency of wiggle traces, lateral and vertical energy attenuation, and dip of reflectors over a range of scales (>10 km to <1 km). Our findings provide new evidence of late stage volcanism occurring in the Pigafetta Basin during the mid-Cretaceous (110 - 90 Ma). We classify late stage volcanism into 3 types of volcanic related features: (1) seamounts, (2) sills, and (3) vertical seismic disturbance zones (<<1 km wide) characterized by bilateral upward drag of reflectors (indicating a thin, vertical volcanic intrusion). The distribution of these features provide new insights into Cretaceous volcanism in the Pigafetta Basin: (i) late stage volcanism is more widely distributed and younger than previously reported, (ii) findings indicate a local source of magma, and (iii) the modes of volcanism differ from previously documented flood basalts and massive flows.

Visible and Near-Infrared Spectroscopy of Hephaestus Fossae Cratered Cones, Mars

NASA Astrophysics Data System (ADS)

Dapremont, A.; Wray, J. J.

2017-12-01

Hephaestus Fossae are a system of sub-parallel fractures on Mars (> 500 km long) interpreted as near-surface tensional cracks [1]. Images of the Martian surface from the High Resolution Imaging Science Experiment have revealed cratered cones within the Hephaestus Fossae region. A volcanic origin (cinder/tuff cones) has been proposed for these features based on morphometric measurements and fine-scale surface characteristics [2]. In an effort to further constrain the origin of these cones as the products of igneous or sedimentary volcanism, we use data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). We take advantage of CRISM's S (0.4 - 1.0 microns) and L (1.0 - 3.9 microns) detector wavelength ranges to investigate the presence or absence of spectral signatures consistent with previous identifications of igneous and mud volcanism products on Mars [3,4]. Hephaestus Fossae cratered cone rims exhibit a consistent nanophase ferric oxide signature. We also identify ferrous phases and 3-micron absorptions (attributed to fundamental vibrational stretch frequencies in H2O) on the crater rims of several cones. Mafic signatures on cratered cone rims support an igneous provenance for these features. The 3-micron absorptions are consistent with the presence of structurally bound or adsorbed water. Our CRISM observations are similar to those of small edifice features in Chryse Planitia, which were interpreted as mud volcanism products based on their enrichment of nanophase ferric minerals and 3-micron absorptions on summit crater rims [3]. Hydrothermal activity was invoked for a Coprates Chasma pitted cone (scoria/tuff cone) based on CRISM identification of partially dehydrated opaline silica, which we do not observe in Hephaestus Fossae [4]. Our spectral observations are more consistent with mud volcanism, but we do not definitively rule out an igneous volcanic origin for the cones in our study region. We demonstrate that VNIR spectroscopy is a valuable tool in developing criteria to determine the origin (igneous/sedimentary/periglacial) of cone features on Mars. [1] Skinner and Tanaka (2007) Icarus 186: 41-59. [2] Dundas et al (2007) LPSC XXXVIII Abs #2116. [3] Komatsu et al (2016) Icarus 268: 56-75. [4] Brož et al (2017) Earth and Planetary Sci Letters 473: 122-130.

Seismic responses and controlling factors of Miocene deepwater gravity-flow deposits in Block A, Lower Congo Basin

NASA Astrophysics Data System (ADS)

Wang, Linlin; Wang, Zhenqi; Yu, Shui; Ngia, Ngong Roger

2016-08-01

The Miocene deepwater gravity-flow sedimentary system in Block A of the southwestern part of the Lower Congo Basin was identified and interpreted using high-resolution 3-D seismic, drilling and logging data to reveal development characteristics and main controlling factors. Five types of deepwater gravity-flow sedimentary units have been identified in the Miocene section of Block A, including mass transport, deepwater channel, levee, abandoned channel and sedimentary lobe deposits. Each type of sedimentary unit has distinct external features, internal structures and lateral characteristics in seismic profiles. Mass transport deposits (MTDs) in particular correspond to chaotic low-amplitude reflections in contact with mutants on both sides. The cross section of deepwater channel deposits in the seismic profile is in U- or V-shape. The channel deposits change in ascending order from low-amplitude, poor-continuity, chaotic filling reflections at the bottom, to high-amplitude, moderate to poor continuity, chaotic or sub-parallel reflections in the middle section and to moderate-weak amplitude, good continuity, parallel or sub-parallel reflections in the upper section. The sedimentary lobes are laterally lobate, which corresponds to high-amplitude, good-continuity, moundy reflection signatures in the seismic profile. Due to sediment flux, faults, and inherited terrain, few mass transport deposits occur in the northeastern part of the study area. The front of MTDs is mainly composed of channel-levee complex deposits, while abandoned-channel and lobe-deposits are usually developed in high-curvature channel sections and the channel terminals, respectively. The distribution of deepwater channel, levee, abandoned channel and sedimentary lobe deposits is predominantly controlled by relative sea level fluctuations and to a lesser extent by tectonism and inherited terrain.

The Role of the Sedimentary Regime in Shaping the Distribution of Subtidal Sandbank Environments and the Associated Meiofaunal Nematode Communities: An Example from the Southern North Sea

PubMed Central

Schratzberger, Michaela; Larcombe, Piers

2014-01-01

We combined sediment and faunal data to explore the role of the sedimentary regime in shaping the distribution of subtidal sandbank environments and the associated meiofaunal nematode communities at Broken Bank and Swarte Bank, in the southern North Sea. A variety of sediment transport processes occur in the area, differing in the frequency and magnitude of sediment mobility, and the continuum between erosion, translation and sediment accumulation. The seabed contained a variety of bedforms, including longitudinal furrows, and small to very large sandwaves. The bed sediments were dominated by fine and medium sands, with admixtures of silt and gravel. Based on sedimentary bedforms and grain size analysis, a total of 11 sedimentary facies were delineated, of which 8 were analysed in detail for their relationships with the meiofauna. The sedimentary facies fell clearly into groups of facies, respectively representing high, high-moderate and moderate, and episodic sediment mobility. For those sedimentary facies where daily movement of sediments and bedforms occurred (‘high’ sediment mobility), the resulting spatially homogeneous environments were dominated by an impoverished nematode community comprising small deposit feeders and large predators. Resistance to sediment movement and the ability to exploit alternative food sources were prominent functional features of the successful colonisers. Those facies characterised by relatively infrequent sediment mobility (‘episodic’ and ‘high-moderate and moderate’ sediment mobility) comprised a heterogeneous suite of benthic habitats, containing taxonomically and functionally diverse assemblages of nematodes of various sizes, feeding types and reproductive potential. Faunal distribution patterns here indicated trade-offs between the resistance to sediment movement, environmental tolerance and competitive abilities. Our focus on diverse assemblages of organisms with high turnover times, inhabiting highly dynamic sedimentary environments, has revealed new animal-sediment relationships of relevance to pure and applied science. PMID:25296029

Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2011-12-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), CaCO3, benthic foraminiferal δ18O and the coarse grain size fraction from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on oxygen stratigraphy, radiocarbon dating and lithological constraints suggests that the piston core records paleoenvironmental changes of the last 155 kyr. TOC shows orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC might correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 45 ka before present (BP) indicating a possible response to abrupt northern hemispheric temperature changes. Between 70 and 45 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC variability. CaCO3 content tends to anti-correlate with TOC on both orbital and millennial time scales, which we interpret in terms of enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

Sedimentary organic matter variations in the Chukchi Borderland over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2011-03-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), C/N and CaCO3 from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on correlation of our CaCO3 record with the benthic δ18O stack, supplemented by lithological constraints, suggests that the piston core records paleoenvironmental changes of the last 155 kyr. According to this age model, TOC and C/N show orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC and C/N appear to correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 40 ka before present (BP) and thus seem to respond to abrupt northern hemispheric temperature changes. Between 65 and 40 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC and C/N variability. CaCO3 content tends to anti-correlate with TOC and C/N on both orbital and millennial time scales, which we interpret as enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased terrestrial organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

Geomorphological features in the southern Canary Island Volcanic Province: The importance of volcanic processes and massive slope instabilities associated with seamounts

NASA Astrophysics Data System (ADS)

Palomino, Desirée; Vázquez, Juan-Tomás; Somoza, Luis; León, Ricardo; López-González, Nieves; Medialdea, Teresa; Fernández-Salas, Luis-Miguel; González, Francisco-Javier; Rengel, Juan Antonio

2016-02-01

The margin of the continental slope of the Volcanic Province of Canary Islands is characterised by seamounts, submarine hills and large landslides. The seabed morphology including detailed morphology of the seamounts and hills was analysed using multibeam bathymetry and backscatter data, and very high resolution seismic profiles. Some of the elevation data are reported here for the first time. The shape and distribution of characteristics features such as volcanic cones, ridges, slides scars, gullies and channels indicate evolutionary differences. Special attention was paid to recent geological processes that influenced the seamounts. We defined various morpho-sedimentary units, which are mainly due to massive slope instability that disrupt the pelagic sedimentary cover. We also studied other processes such as the role of deep bottom currents in determining sediment distribution. The sediments are interpreted as the result of a complex mixture of material derived from a) slope failures on seamounts and submarine hills; and b) slides and slumps on the continental slope.

Chad Basin: Paleoenvironments of the Sahara since the Late Miocene

NASA Astrophysics Data System (ADS)

Schuster, Mathieu; Duringer, Philippe; Ghienne, Jean-François; Roquin, Claude; Sepulchre, Pierre; Moussa, Abderamane; Lebatard, Anne-Elisabeth; Mackaye, Hassan Taisso; Likius, Andossa; Vignaud, Patrick; Brunet, Michel

2009-08-01

Since the mid 1990s, the Mission paléoanthropologique francotchadienne (MPFT) conducts yearly paleontological field investigations of the Miocene-Pliocene of the Chad Basin. This article synthesizes some of the results of the MPFT, with focus on the Chad Basin development during the Neogene. We propose an overview of the depositional paleoenvironments of this part of Africa at different scales of time and space, based on a multidisciplinary approach (sedimentary geology, geomorphology, geophysic, numerical simulations and geochronology). The Miocene-Pliocene paleoenvironments are examined through the sedimentary archives of the early hominids levels and the Holocene Lake Mega-Chad episode illustrates the last major paleoenvironmental change in this area. The sedimentary record of the Chad Basin since the Late Miocene can be schematized as the result of recurrent interactions from lake to desert environments.

Outwash plains and thermokarst on Mars

USGS Publications Warehouse

Costard, F.M.; Kargel, J.S.

1995-01-01

The spatial distribution of different types of rampart craters on Mars suggests a hemispheric asymmetry in the distribution of ground ice. The northern plains, especially major topographic depressions near the terminations of outflow channels, have high percentages of rampart craters. Two of these basins, Acidalia and Utopia Planitiae, received extraordinarily large amounts of water and sediment from the Chryse and Elysium outflow channels. In both regions, the analysis of high-resolution Viking pictures (12 m/pixel) indicates a concentration of kilometer-scale depressions that are similar in size and form to thermokarstic features in Yakutia (Siberia) and parts of the arctic coastal plain of North America. Accordingly, we infer that (1) Utopia Planitia and Acidalia Planitia may contain thick, laterally continuous, ice-rich sedimentary deposits related to outflow channel-forming floods, and (2) these areas of Mars may have experienced thermokarstic processes similar to modern thermokarstic processes in some periglacial regions of Earth.

Evaluating a 2D image-based computerized approach for measuring riverine pebble roundness

NASA Astrophysics Data System (ADS)

Cassel, Mathieu; Piégay, Hervé; Lavé, Jérôme; Vaudor, Lise; Hadmoko Sri, Danang; Wibiwo Budi, Sandy; Lavigne, Franck

2018-06-01

The geometrical characteristics of pebbles are important features to study transport pathways, sedimentary history, depositional environments, abrasion processes or to target sediment sources. Both the shape and roundness of pebbles can be described by a still growing number of metrics in 2D and 3D or by visual charts. Despite new developments, existing tools remain proprietary and no pebble roundness toolbox has been available widely within the scientific community. The toolbox developed by Roussillon et al. (2009) automatically computes the size, shape and roundness indexes of pebbles from their 2D maximal projection plans. Using a digital camera, this toolbox operates using 2D pictures taken of pebbles placed on a one square meter red board, allowing data collection to be quickly and efficiently acquired at a large scale. Now that the toolbox is freely available for download,

Mountain glaciation drives rapid oxidation of rock-bound organic carbon

PubMed Central

Horan, Kate; Hilton, Robert G.; Selby, David; Ottley, Chris J.; Gröcke, Darren R.; Hicks, Murray; Burton, Kevin W.

2017-01-01

Over millions of years, the oxidation of organic carbon contained within sedimentary rocks is one of the main sources of carbon dioxide to the atmosphere, yet the controls on this emission remain poorly constrained. We use rhenium to track the oxidation of rock-bound organic carbon in the mountain watersheds of New Zealand, where high rates of physical erosion expose rocks to chemical weathering. Oxidative weathering fluxes are two to three times higher in watersheds dominated by valley glaciers and exposed to frost shattering processes, compared to those with less glacial cover; a feature that we also observe in mountain watersheds globally. Consequently, we show that mountain glaciation can result in an atmospheric carbon dioxide source during weathering and erosion, as fresh minerals are exposed for weathering in an environment with high oxygen availability. This provides a counter mechanism against global cooling over geological time scales. PMID:28983510

Evaluation of EREP techniques for geological mapping. [southern Pyrenees and Ebro basin in Spain

NASA Technical Reports Server (NTRS)

Vandermeermohr, H. E. C.; Srivastava, G. S. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Skylab photographs may be successfully utilized for preparing a reconnaissance geological map in the areas where no maps or semi-detailed maps exist. Large coverage of area and regional perspective from Skylab photographs can help better coordination in regional mapping. It is possible to delineate major structural trends and other features like mega-lineaments, geofractures, and faults, which have evaded their detection by conventional methods. The photointerpretability is better in areas dominated by sedimentary rocks. Rock units of smaller extent and having poor geomorphic expressions are difficult to map. Demarcation of quaternary river alluvium can be made with better precision and ease with the Skylab photographs. Stereoscopic viewing greatly helps in interpretation of area structures. Skylab photographs are not good for preparing geological maps larger than 1:270,000 scale.

3D coupled heat and mass transfer processes at the scale of sedimentary basisn

NASA Astrophysics Data System (ADS)

Cacace, M.; Scheck-Wenderoth, M.; Kaiser, B. O.

2014-12-01

We use coupled 3D simulations of fluid, heat, and transport based on a 3D structural model of a complex geological setting, the Northeast German Basin (NEGB). The geological structure of the NEGB is characterized by a relatively thick layer of Permian Zechstein salt, structured in differnet diapirs (up to 5000 m thick) and pillows locally reaching nearly the surface. Salt is thermally more conductive than other sediments, hydraulically impervious but highly solvable. Thus salt structures have first order influence on the temperature distribution, the deep flow regime and the salinity of groundawater bearing aquifers. In addition, the post-Permian sedimentary sequence is vertically subdivided into several aquifers and aquitards. The shallow Quaternary to late Tertiary freshwater aquifer is separated from the underlying Mesozoic saline aquifers by an embedded Tertiary clay enriched aquitard (Rupelian Aquitard). An important feature of this aquitard is that hydraulic connections between the upper and lower aquifers exist in areas where the Rupelian Aquitard is missing (hydrogeological windows). By means of 3D numerical simulations we explore the role of heat conduction, pressure, and density driven groundwater flow as well as fluid viscosity-related and salinity-dependent effects on the resulting flow and temperature fields. Our results suggest that the regional temperature distribution within the basin results from interactions between regional pressure forces and thermal diffusion locally enhanced by thermal conductivity contrasts between the different sedimentary rocks with the highly conductive salt. Buoyancy forces triggered by temperature-dependent fluid density variations affect only locally the internal thermal configuration. Locations, geometry, and wavelengths of convective thermal anomalies are mainly controlled by the permeability field and thickness values of the respective geological layers. Numerical results from 3D thermo-haline numerical simulations suggest that hydrogeological windows act as preferential domains of hydraulic interconnectivity between the different aquifers at depth, and enable vigorous heat and mass transport which causes a mixing of warm and saline groundwater with cold and less saline groundwater within both aquifers.

Investigations of the petrogeneration zones western Bering sea by airborne geophysical data

NASA Astrophysics Data System (ADS)

Litvinova, T.; Petrova, A.

2012-04-01

In 2011, work continued on the interpretation of geophysical data in western Bering Sea. Bering Sea oil-and-gas bearing province occupies a single sedimentary megabasin of the Bering Sea, the formation of which is caused by stage of the Alpine geodynamic development cycle of the Pacific mobile belt. At present, the geological-geophysical exploration maturity of the Bering Sea with respect to oil-gasbearing prognosis is at the level of regional study stage. In 2003, an additional study of oil-gas prospective zones of the Kamchatka Shelf of the Bering Sea was carried out. In the course of works, profile seismic studies and airborne gravity-magnetic survey at 1:200,000 scale were made at three territories: Ilpinsky, Olyutorsky I, and Olyutorsky II. Average survey elevation for the whole area is 300 meters. Geological modeling of sedimentary basin systems was made for this area. Geomagnetic sections it possible to compare the location of the magnetic and weakly magnetic structures with seismic and geological boundaries marker and conducting layers of geoelectric sections. This makes it possible to trace the features of placing magnetic differences in the geologic rock section, to identify their stratigraphic association, select the layers flyuidstubborn, adumbrate reservoir heterogeneity and establish the heterogeneity of internal structure oil-gasbearing zones. Age correlation, thickness estimation and formational characteristics of litho-stratigraphic complexes building up sections are carried out. Geomagnetic deep sections transecting main zones of prospective oil-gas accumulation to airborne magnetic data. Distribution of magnetization in the development interval of potentially productive sandy strata at depths from 1 to 5 km is obtained. The most prospective zones of possible oil-gas accumulation are distinguished in the Olyutorsky and Ilpinsky sedimentary basins. At height of 400 km this minimum keeps the form that speaks about stability of a condition of the permeable zones supervising oil-gas-bearing.

Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

NASA Astrophysics Data System (ADS)

Abrantes, Fatima; Cermeno, Pedro; Lopes, Cristina; Romero, Oscar; Matos, Lélia; Van Iperen, Jolanda; Rufino, Marta; Magalhães, Vitor

2016-07-01

Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

Basin-scale hydrogeologic modeling

NASA Astrophysics Data System (ADS)

Person, Mark; Raffensperger, Jeff P.; Ge, Shemin; Garven, Grant

1996-02-01

Mathematical modeling of coupled groundwater flow, heat transfer, and chemical mass transport at the sedimentary basin scale has been increasingly used by Earth scientists studying a wide range of geologic processes including the formation of excess pore pressures, infiltration-driven metamorphism, heat flow anomalies, nuclear waste isolation, hydrothermal ore genesis, sediment diagenesis, basin tectonics, and petroleum generation and migration. These models have provided important insights into the rates and pathways of groundwater migration through basins, the relative importance of different driving mechanisms for fluid flow, and the nature of coupling between the hydraulic, thermal, chemical, and stress regimes. The mathematical descriptions of basin transport processes, the analytical and numerical solution methods employed, and the application of modeling to sedimentary basins around the world are the subject of this review paper. The special considerations made to represent coupled transport processes at the basin scale are emphasized. Future modeling efforts will probably utilize three-dimensional descriptions of transport processes, incorporate greater information regarding natural geological heterogeneity, further explore coupled processes, and involve greater field applications.

Aptian-Albian boundary in Central Southern Atlas of Tunisia: New tectono-sedimentary facts

NASA Astrophysics Data System (ADS)

Ghanmi, Mohamed Abdelhamid; Barhoumi, Amine; Ghanmi, Mohamed; Zargouni, Fouad

2017-08-01

The Aptian-Albian boundary preserves one of the most important events in Central-Southern Atlas of Tunisia, which belongs to the Southern Tethyan margin. A major sedimentary break was recorded between Early Aptian and Albian series in Bouhedma-Boudouaou Mountains. This major hiatus probably linked to the ''Austrian phase'' and to the Aptian and Albian ''Crisis'' testify a period of major tectonic events. In this paper, field observations on the Mid-Cretaceous stratigraphy combined with seismic profile interpretation were used for the first time to characterize the Aptian-Albian boundary in Central-Southern Atlas of Tunisia. Our new results reveal that Aptian-Albian boundary marks a critical interval not only in Maknassy-Mezzouna orogenic system but also in the Tunisian Atlas. Furthermore, Aptian-Albian series outcrop is marked by the important sedimentary gaps as well as a dramatic thickness change from West to East and predominately from North to South. This is linked to the extensional tectonic features which characterize all the Central-Southern Atlas of Tunisia.

Characteristics of depositional environment and evolution of Upper Cretaceous Mishrif Formation, Halfaya Oil field, Iraq based on sedimentary microfacies analysis

NASA Astrophysics Data System (ADS)

Zhong, Yuan; Zhou, Lu; Tan, Xiucheng; Guo, Rui; Zhao, Limin; Li, Fei; Jin, Zhimin; Chen, Yantao

2018-04-01

As one of the most important carbonate targets in the Middle East, Upper Cretaceous Mishrif Formation has been highlighted for a long time. Although consensus has been reached on the overall sedimentary background, disputes still exist in understanding the sedimentary environment changes among sub-regions due to relatively limited research, rare outcrop, and incomplete drilled core, which hinders the analysis on sedimentary environment and thus the horizontal and vertical correlation. In this study, taking the Halfaya Oil Field as an example, the sedimentary microfacies analysis method was introduced to comprehensively characterize the cored interval of Mishrif Formation, including Single Layers MC1-1 to MA2. A total of 11 sedimentary microfacies are identified through system identification of sedimentary microfacies and environmental analysis, with reference to the standard microfacies classification in the rimmed carbonate platform. Then three kinds of environments are identified through microfacies assemblage analysis, namely restricted platform, open platform, and platform margin. Systematic analyses indicate that the deposits are mainly developed in the open platform and platform margin. Meanwhile, rock-electricity interpretation model is established according to the electricity response to cored intervals, and is then employed to interpret the uncored intervals, which finally helps build the sedimentary evolution pattern through horizontal and vertical correlation. It is proposed that the Single Layers MC1-1 to MB2-3 were deposited in the open platform featured by low water level, including sub-environments of low-energy shoal within platform and inter-shoal sea; Single Layers MB2-2 to MB1-2B were deposited in the open platform and platform margin, including sub-environments of high-energy shoal on the platform margin, low-energy shoal within platform, inter-shoal sea, and open sea; and Single Layers MB1-2A to MA2 were again deposited in the open platform with high water level, and the circumstance of open sea was dominant. The deposition of Single Layers MC1-1 to MA2 actually corresponded to a retrogradation-progradation process. Results of this study will not only provide significant guidance to the exploration and development of Mishrif Formation, Halfaya Oil Field, but also support that the theory of sedimentary environment correlation with adjacent areas is reliable.

Flexure and faulting of sedimentary host rocks during growth of igneous domes, Henry Mountains, Utah

USGS Publications Warehouse

Jackson, M.D.; Pollard, D.D.

1990-01-01

A sequence of sedimentary rocks about 4 km thick was bent, stretched and uplifted during the growth of three igneous domes in the southern Henry Mountains. Mount Holmes, Mount Ellsworth and Mount Hillers are all about 12 km in diameter, but the amplitudes of their domes are about 1.2, 1.85 and 3.0 km, respectively. These mountains record successive stages in the inflation of near-surface diorite intrusions that are probably laccolithic in origin. The host rocks deformed along networks of outcrop-scale faults, or deformation bands, marked by crushed grains, consolidation of the porous sandstone and small displacements of sedimentary beds. Zones of deformation bands oriented parallel to the beds and formation contacts subdivided the overburden into thin mechanical layers that slipped over one another during doming. Measurements of outcrop-scale fault populations at the three mountains reveal a network of faults that strikes at high angles to sedimentary beds which themselves strike tangentially about the domes. These faults have normal and reverse components of slip that accommodated bending and stretching strains within the strata. An early stage of this deformation is displayed at Mount Holmes, where states of stress computed from three fault samples correlate with the theoretical distribution of stresses resulting from bending of thin, circular, elastic plates. Field observations and analysis of frictional driving stresses acting on horizontal planes above an opening-mode dislocation, as well as the paleostress analysis of faulting, indicate that bedding-plane slip and layer flexure were important components of the early deformation. As the amplitude of doming increased, radial and circumferential stretching of the strata and rotation of the older faults in the steepening limbs of the domes increased the complexity of the fault patterns. Steeply-dipping, map-scale faults with dip-slip displacements indicate a late-stage jostling of major blocks over the central magma chamber. Radial dikes pierced the dome and accommodated some of the circumferential stretching. ?? 1990.

Late Cretaceous-Cenozoic subduction-collision history of the Southern Neotethys: new evidence from the Çağlayancerit area, SE Turkey

NASA Astrophysics Data System (ADS)

Akıncı, Ahmet Can; Robertson, Alastair H. F.; Ünlügenç, Ulvi Can

2016-01-01

Evidence of the subduction-collision history of the S Neotethys is well exposed in the frontal part of the SE Anatolian thrust belt and the adjacent Arabian continental margin. The foreland succession in the study area begins with Eocene shelf carbonates, ranging from shallow marine to deeper marine, without sedimentary input from the Tauride continent to the north. After a regional hiatus (Oligocene), sedimentation resumed during the Early Miocene with terrigenous gravity-flow deposition in the north (Lice Formation) and shallow-marine carbonates further south. Clastic detritus was derived from the Tauride continent and oceanic accretionary material. The base of the overriding Tauride allochthon comprises ophiolite-derived debris flows, ophiolite-related mélange and dismembered ophiolitic rocks. Above this, the regional-scale Bulgurkaya sedimentary mélange (an olistostrome) includes blocks and dismembered thrust sheets of metamorphic rocks, limestone and sandstone, which include Late Cretaceous and Eocene foraminifera. The matrix is mainly strongly deformed Eocene-Oligocene mudrocks, hemipelagic marl and sandstone turbidites. The thrust stack is topped by a regionally extensive thrust sheet (Malatya metamorphic unit), which includes greenschist facies marble, calcschist, schist and phyllite, representing Tauride continental crust. Beginning during the Late Mesozoic, the S Neotethys subducted northwards beneath a backstop represented by the Tauride microcontinent (Malatya metamorphic unit). Ophiolites formed within the S Neotethys and accreted to the Tauride active margin. Large-scale sedimentary mélange developed along the Tauride active margin during Eocene-Oligocene. On the Arabian margin, a sedimentary hiatus and tilting (Oligocene) is interpreted to record initial continental collision. The Early Miocene terrigenous gravity flows represent a collision-related flexural foreland basin. Southward overthrusting of the Tauride allochthon took place during Early-Middle Miocene. Associated regional uplift triggered large-scale alluvial deposition. The foreland folded and faulted in response to suture zone tightening (Late Miocene). Left-lateral strike slip characterised the Plio-Pleistocene.

Characteristics of sedimentary structures in coarse-grained alluvial rivers

NASA Astrophysics Data System (ADS)

Ackerley, David; Powell, Mark

2013-04-01

The characteristics of coarse-grained alluvial surfaces have important implications for the estimation of flow resistance, entrainment thresholds and sediment transport rates in gravel-bed rivers. This area of research has, thus, demanded attention from geomorphologists, sedimentologists, and river engineers. The majority of research has focused towards understanding the characteristics and adjustments in surface grain size. Bed stability, however, is not ultimately defined by particle size but how grains are arranged within the bed surface. For example, by the organisation of particles into a variety of grain and form scale sedimentary structures and bedforms (e.g. imbrication; pebble clusters, stone nets, transverse ribs). While it is widely acknowledged sedimentary structuring must be considered within estimates of flow resistance and sediment transport, relatively little is known about the structural properties of water-worked river gravels. As a consequence, we remain woefully ignorant of this important aspect of gravel-bed river sedimentology. The aim of this poster is to present some preliminary results of a study designed to characterise the morphodynamics of sedimentary structures in coarse-grained alluvial rivers and their implications upon entrainment thresholds and sediment transport rates. The poster focuses on investigating the variability in grain and form scale sedimentary structuring across a number of field sites. Representative patches of three gravel bars on the Rivers Wharfe, Manifold and Afon Elan, UK, have been surveyed using a Leica HDS 3000 Terrestrial Laser Scanner. The resultant raw point-cloud data, recorded at a 4mm resolution, has been registered, filtered, and interpolated to produce highly detailed 2½D digital elevation models of gravel-bed surface topography. These surfaces have been analysed using a number of structural parameters including bed elevation probability distribution function statistics (standard deviation, skewness, kurtosis), semivariograms, and inclination indices. This research enhances our understanding of alluvial bed surface structures and lays the foundations for developing a more detailed understanding of their morphodynamics.

A conceptual review of regional-scale controls on the composition of clastic sediment and the co-evolution of continental blocks and their sedimentary cover.

PubMed

Cox, R; Lowe, D R

1995-01-02

Both sediment recycling and first-cycle input influence the composition of clastic material in sedimentary systems. This paper examines conceptually the roles played by these processes in governing the composition of clastic sediment on a regional scale by outlining the expected effects on sediment composition of protracted sediment recycling and of continuous first-cycle input on a maturing continental block. Generally speaking, long-term recycling tends to enrich sediments in the most chemically and mechanically stable components: quartz in the sand and silt size fractions, and illite among the clay minerals. Sandstones trend towards pure quartz arenites, and mudrocks become more potassic and aluminous. The average grain size of clastic sediment decreases by a combination of progressive attrition of sand grains and ongoing breakdown of primary silicate minerals to finer-grained clay minerals and oxides. Sandstones derived by continuous first-cycle input from an evolving continental crustal source also become increasingly rich in quartz, but in addition become more feldspathic as the proportion of granitic material in the upper continental crust increases during crustal stabilization. Associated mudrocks also become richer in potassium and aluminum, but will have higher K2O/Al2O3 ratios than recycled muds. The average grain size of the sediment may increase with time as the proportion of sand-prone granitic source rocks increases at the expense of more mud-prone volcanic sources. In general, except in instances where chemical weathering is extreme, first-cycle sediments lack the compositional maturity of recycled detritus, and are characterized by the presence of a variety of primary silicate minerals. Sedimentary systems are not usually completely dominated by either recycling or first-cycle detritus. Generally, however, sedimentary systems associated with the earliest phases of formation and accretion of continental crust are characterized by first-cycle input from igneous and metamorphic rocks, whereas those associated with more mature cratons tend to be dominated by recycled sedimentary material.

Giant polygons and mounds in the lowlands of Mars: signatures of an ancient ocean?

PubMed

Oehler, Dorothy Z; Allen, Carlton C

2012-06-01

This paper presents the hypothesis that the well-known giant polygons and bright mounds of the martian lowlands may be related to a common process-a process of fluid expulsion that results from burial of fine-grained sediments beneath a body of water. Specifically, we hypothesize that giant polygons and mounds in Chryse and Acidalia Planitiae are analogous to kilometer-scale polygons and mud volcanoes in terrestrial, marine basins and that the co-occurrence of masses of these features in Chryse and Acidalia may be the signature of sedimentary processes in an ancient martian ocean. We base this hypothesis on recent data from both Earth and Mars. On Earth, 3-D seismic data illustrate kilometer-scale polygons that may be analogous to the giant polygons on Mars. The terrestrial polygons form in fine-grained sediments that have been deposited and buried in passive-margin, marine settings. These polygons are thought to result from compaction/dewatering, and they are commonly associated with fluid expulsion features, such as mud volcanoes. On Mars, in Chryse and Acidalia Planitiae, orbital data demonstrate that giant polygons and mounds have overlapping spatial distributions. There, each set of features occurs within a geological setting that is seemingly analogous to that of the terrestrial, kilometer-scale polygons (broad basin of deposition, predicted fine-grained sediments, and lack of significant horizontal stress). Regionally, the martian polygons and mounds both show a correlation to elevation, as if their formation were related to past water levels. Although these observations are based on older data with incomplete coverage, a similar correlation to elevation has been established in one local area studied in detail with newer higher-resolution data. Further mapping with the latest data sets should more clearly elucidate the relationship(s) of the polygons and mounds to elevation over the entire Chryse-Acidalia region and thereby provide more insight into this hypothesis.

Methane on the Move: natural greenhouse gas emissions over geological time

NASA Astrophysics Data System (ADS)

Horsfield, B.; di Primio, R.; Kroeger, K. F.; Schicks, J. M.

2008-12-01

The mass of organic carbon in sedimentary basins amounts to a staggering 1016 tons, dwarfing the mass contained in coal, oil, gas and all living systems by ten thousand-fold. The changing fate of this giant mass during subsidence and uplift, via chemical, physical and biological processes, is known to ultimately control fossil energy resource occurrence worldwide. But what has been overlooked and/or ignored until now is its enormous capacity for driving global climate: only a tiny degree of leakage, particularly when focussed through the clathrate cycle, can result in high greenhouse gas emissions. Understanding the workings of sedimentary basins in time and space is fundamental to gaining insights into Earth's climate. Here we shall present an integrated framework based on petroleum system modelling that will ultimately quantify methane migration and emission from one hundred of the world's most prolific petroliferous sedimentary basins. Timing of hydrocarbon generation from globally occurring prolific Jurassic and Cretaceous source rocks is regarded to be the key factor in quantifying gas release. Combined thermogenic and biogenic methane fluxes are the base for prediction of gas hydrate formation through time and space, by application of kinetics developed in the laboratory to geological scenarios. Results are calibrated in basin scale by emission structure evaluation (mud volcanoes, carbonate mounds, pockmarks) and on a global scale by proxy data from sedimentary archives and local atmospheric data. Identifying potential climate feedback processes over a geological time line that spans the Cenozoic requires a comprehensive understanding of source-sink relationships by coupling these feedstock fluxes with gas hydrate stability considerations, deep biosphere activity, ocean and atmosphere modelling

Mercury species and other selected constituent concentrations in water, sediment, and biota of Sinclair Inlet, Kitsap County, Washington, 2007-10

USGS Publications Warehouse

Huffman, R.L.; Wagner, R.J.; Toft, J.; Cordell, J.; DeWild, J.F.; Dinicola, R.S.; Aiken, G.R.; Krabbenhoft, D.P.; Marvin-DiPasquale, M.; Stewart, A.R.; Moran, P.W.; Paulson, A.J.

2012-01-01

The Methylation and Bioaccumulation Project included a comprehensive field study of mercury biogeochemistry in marine sediment, water, and zooplankton in Sinclair Inlet. Mercury, iron, and sulfur species in sediment porewater from six sites within and three sites outside of Sinclair Inlet were measured to provide insight into the processes that produce methylmercury in the sediments. Total mercury, methylmercury, dissolved organic carbon, and redox-sensitive species were measured in porewaters in the top 2 centimeters of sediment, and these data were paired with sedimentary flux measurements from core incubation experiments to connect sedimentary processes to the water column. A broad-scale study of mercury methylation potential and mercury species at 20-plus stations in Sinclair Inlet was conducted in February 2009 and 2010, June 2009, and August 2009. Sedimentary flux measurements and analysis of mercury and biogeochemicals in sediment porewater and bottom water were made at six of the broad-scale stations. Bioaccumulation processes in the water column in the context of the sedimentary flux of methylmercury were examined using monthly survey data collected between August 2008 and August 2009. The survey data included concentrations of methylmercury and isotope ratios of carbon and nitrogen in bulk zooplankton measured at four stations in Sinclair Inlet in the context of the population of bulk zooplankton ascertained by taxonomical identification. The analysis of filtered total mercury, total particulate mercury, filtered methylmercury, particulate methylmercury, chlorophyll a, isotopes of carbon and nitrogen in suspended matter, and other biogeochemical data will facilitate the examination of the biogeochemistry of mercury in Sinclair Inlet.

The Middle Miocene of the Fore-Carpathian Basin (Poland, Ukraine and Moldova)

NASA Astrophysics Data System (ADS)

Wysocka, Anna; Radwański, Andrzej; Górka, Marcin; Bąbel, Maciej; Radwańska, Urszula; Złotnik, Michał

2016-09-01

Studies of Miocene sediments in the Fore-Carpathian Basin, conducted by geologists from the University of Warsaw have provided new insights on the distribution of the facies infilling the basin, particularly in the forebulge and back-bulge zones. The origin of the large-scale sand bodies, evaporitic deposits and large-scale organic buildups is discussed, described and verified. These deposits originated in variable, shallow marine settings, differing in their water chemistry and the dynamics of sedimentary processes, and are unique with regard to the fossil assemblages they yield. Many years of taxonomic, biostratigraphic, palaeoecologic and ecotaphonomic investigations have resulted in the identification of the fossil assemblages of these sediments, their age, sedimentary settings and post-mortem conditions. Detailed studies were focused on corals, polychaetes, most classes of molluscs, crustaceans, echinoderms, and fishes.

Multiscale Geoarchaeological Approaches from the Laurentine Shore, Castelporziano, Lazio, Italy

NASA Astrophysics Data System (ADS)

Bicket, A. R.; Rendell, H. M.; Claridge, A.; Rose, P.; Brown, F. S. J.

2009-04-01

The relationship between the meso-scale record of human activity during the Roman period and the larger-scale coastal development of the Tiber Delta (ca. 20 ka) is investigated using the archaeological and sedimentary record from a large aquaculture pond and its wider meso- to macro-scale geomorphological setting. The position of the pond is adjacent to the Roman period shoreline, known as the Laurentine Shore on the southern, distal flank of the Tiber delta, Lazio Italy, within what is now the Castelporziano Estate. The pond is thought to have been constructed in the wet dune slack behind the active coastal foredune. Magnetometer survey and excavation of the archaeological structures around this pond have shown them to be substantial features ca. 80m in length with high-status Imperial Roman architecture and with evidence for water management. Sedimentological analysis of sediment cores from within the ponds are supplemented with diatom analysis to assess the period of pre-construction, use and abandonment of this aquaculture pond. Diatom analysis suggests a relatively short period of use and it is argued that abandonment of the aquaculture structures may be linked to both alkali groundwater conditions and the dynamism of the coastal zone preventing effective management. Optical luminescence dating of the archaeological sediments and the post-abandonment dunes that bury part of the site suggest that the aquaculture pond was abandoned ca. 100 years prior to final abandonment of the Roman settlement. This case-study also highlights the implications for meso-scale investigations of human/environment relationships utilising relatively low-sensitivity sedimentary records without high-resolution proxy records. D-GPS survey in conjunction with a high-quality DEM has permitted important archaeological remains to be understood relative to sea level; a key variable for examining the formation and development of the dune ridge record. These surveys have also permitted the effective mapping of dune ridges, from aerial photography, under the extremely dense vegetation that hinders easy access across much of the site. The D-GPS georeferenced DEM has been linked to the diatom analysis of a cored salt marsh to peat sediment transition providing valuable biostratigraphic information for deriving an accurate measurement of the Roman period sea level (Lambeck et al., 2004a). This measurement is in line with published literature from nearby coastal sites, ca. - 1.3m RSL (Lambeck et al., 2004b). Understanding the sites geomorphological development in the context of eustatic sea level is a key consideration for issues of sand supply driving dune formation, linked ultimately to the development of the Tiber Delta since the Last Glacial Maximum and throughout the Holocene. On this larger spatial scale, the archaeological sites described within the Laurentine Shore, built upon the Roman period coastline, are now preserved several hundred metres inland of the contemporary shoreline. The development of the shoreline can now be investigated within the macro-scale progradation of the Tiber delta relative to eustatic sea level rise. Archaeological excavations since the 1980's have provided a rich record of high status villas, and also the supporting infrastructure of a village settlement (vicus), roads, aqueduct and the large aquaculture ponds. The dominant geomorphological features on the site are preserved coastal dune ridges. Sampling was undertaken along an alongshore transect and three inland transects. This sampling regime focuses upon the contemporary deposition of sands on the beach and the phases of dune formation, preservation and alteration recorded by the relict dune crests in relation to the archaeological record. A campaign of optical dating of the relict dune crests has provided a Late Pleistocene and Holocene record of sandsheet and dune formation linked to delta progradation that permits the larger spatial- and temporal-scale context of the archaeological record to be discussed. Sedimentary petrology techniques allow the provenance and transportation dynamics of both the sand-sized and dust-sized sediments to be assessed. Furthermore this approach also enables an investigation of carbonate and iron oxide diagenetic cements, which are an important product of the long-term in situ weathering of the dune ridges' mineralogical assemblages, but is also a feature of short-term weathering of archaeological contexts. This work has implications for locations of interest to geoarchaeological surveys. There are also important implications for the mineralogy, provenance and preservation of luminescent minerals; and some form mineralogical/provenance analysis is recommended for all optical dating studies as a result. In summary, the geoarchaeological approach undertaken at Castelporziano allows the meso-scale human/environment interactions to be considered within the broader temporal scales of the late Quaternary. It also permits consideration within the macro-spatial scales of the Tiber Delta's development during the last 15-20ka within the context of eustatic sea level rise. REFERENCES LAMBECK, K., ANTONIOLI, F., PURCELL, A. & SILENZI, S. (2004a) Sea-level change along the Italian coast for the past 10,000 yr. Quaternary Science Reviews, 23, 1567-1598. LAMBECK, K., ANZIDEI, M., ANTONIOLI, F., BENINI, A. & ESPOSITO, A. (2004b) Sea level in Roman time in the Central Mediterranean and implications for recent change. Earth and Planetary Science Letters, 224, 563-575.

Surficial Geologic Map of the Clinton-Concord-Grafton-Medfield 12-Quadrangle Area in East Central Massachusetts

USGS Publications Warehouse

Stone, Janet R.; Stone, Byron D.

2006-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of twelve 7.5-minute quadrangles (total 660 square miles) in east-central Massachusetts. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (grain size, sedimentary structures, mineral and rock-particle composition), constructional geomorphic features, stratigraphic relationships, and age. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for water resources, construction aggregate resources, earth-surface hazards assessments, and land-use decisions. This compilation of surficial geologic materials is an interim product that defines the areas of exposed bedrock, and the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), a regional map at 1:50,000 scale (PDF), quadrangle maps at 1:24,000 scale (12 PDF files), GIS data layers (ArcGIS shapefiles), scanned topographic base maps (TIF), metadata for the GIS layers, and a readme.txt file.

Capability of ERTS-1 imagery to investigate geological and structural features in a sedimentary basin (Bassin Parisien, France)

NASA Technical Reports Server (NTRS)

Cavelier, C.; Scanvic, J. Y.; Weecksteen, G.; Zizerman, A.

1973-01-01

A preliminary study of the MSS imagery of a sedimentary basin whose structure is regular is reported. Crops and natural vegetation are distributed all over the site located under temperate climate. Ground data available concern plant species geology and tectonic and are correlated with results from ERTS 1 imagery. This comparison shows a good correlation. The main geological units are detected or enhanced by way of agricultural land use and/or natural vegetation. Alluvial deposits are outlined by vegetation grass land and poplar trees. Some spatial relationship of geostructures, suspected until now, are identified or extended in associating results from different spectral bands.

How the structural architecture of the Eurasian continental margin affects the structure, seismicity, and topography of the south central Taiwan fold-and-thrust belt

NASA Astrophysics Data System (ADS)

Brown, Dennis; Alvarez-Marron, Joaquina; Biete, Cristina; Kuo-Chen, Hao; Camanni, Giovanni; Ho, Chun-Wei

2017-07-01

Studies of mountain belts worldwide show that along-strike changes are common in their foreland fold-and-thrust belts. These are typically caused by processes related to fault reactivation and/or fault focusing along changes in sedimentary sequences. The study of active orogens, like Taiwan, can also provide insights into how these processes influence transient features such as seismicity and topography. In this paper, we trace regional-scale features from the Eurasian continental margin in the Taiwan Strait into the south central Taiwan fold-and-thrust belt. We then present newly mapped surface geology, P wave velocity maps and sections, seismicity, and topography data to test the hypothesis of whether or not these regional-scale features of the margin are contributing to along-strike changes in structural style, and the distribution of seismicity and topography in this part of the Taiwan fold-and-thrust belt. These data show that the most important along-strike change takes place at the eastward prolongation of the upper part of the margin necking zone, where there is a causal link between fault reactivation, involvement of basement in the thrusting, concentration of seismicity, and the formation of high topography. On the area correlated with the necking zone, the strike-slip reactivation of east northeast striking extensional faults is causing sigmoidal offset of structures and topography along two main zones. Here basement is not involved in the thrusting; there is weak focusing of seismicity and localized development of topography. We also show that there are important differences in structure, seismicity, and topography between the margin shelf and its necking zone.

Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr

NASA Astrophysics Data System (ADS)

Rella, S. F.; Uchida, M.

2012-12-01

Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), CaCO3, benthic foraminiferal δ18O and the coarse grain size fraction from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean. TOC shows orbital-scale increases and decreases during the past ~155 kyr that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold periods. At millennial scales, increases in TOC might correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 45 ka BP indicating a possible response to abrupt northern hemispheric temperature changes. Between 70 and 45 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC variability. CaCO3 contents tend to anti-correlate with TOC on both orbital and millennial time scales, which we interpret in terms of enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods and increased organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.

Dynamics of particulate organic matter composition in coastal systems: Forcing of spatio-temporal variability at multi-systems scale

NASA Astrophysics Data System (ADS)

Liénart, Camilla; Savoye, Nicolas; David, Valérie; Ramond, Pierre; Rodriguez Tress, Paco; Hanquiez, Vincent; Marieu, Vincent; Aubert, Fabien; Aubin, Sébastien; Bichon, Sabrina; Boinet, Christophe; Bourasseau, Line; Bozec, Yann; Bréret, Martine; Breton, Elsa; Caparros, Jocelyne; Cariou, Thierry; Claquin, Pascal; Conan, Pascal; Corre, Anne-Marie; Costes, Laurence; Crouvoisier, Muriel; Del Amo, Yolanda; Derriennic, Hervé; Dindinaud, François; Duran, Robert; Durozier, Maïa; Devesa, Jérémy; Ferreira, Sophie; Feunteun, Eric; Garcia, Nicole; Geslin, Sandrine; Grossteffan, Emilie; Gueux, Aurore; Guillaudeau, Julien; Guillou, Gaël; Jolly, Orianne; Lachaussée, Nicolas; Lafont, Michel; Lagadec, Véronique; Lamoureux, Jézabel; Lauga, Béatrice; Lebreton, Benoît; Lecuyer, Eric; Lehodey, Jean-Paul; Leroux, Cédric; L'Helguen, Stéphane; Macé, Eric; Maria, Eric; Mousseau, Laure; Nowaczyk, Antoine; Pineau, Philippe; Petit, Franck; Pujo-Pay, Mireille; Raimbault, Patrick; Rimmelin-Maury, Peggy; Rouaud, Vanessa; Sauriau, Pierre-Guy; Sultan, Emmanuelle; Susperregui, Nicolas

2018-03-01

In costal systems, particulate organic matter (POM) results from a multiplicity of sources having their respective dynamics in terms of production, decomposition, transport and burial. The POM pool experiences thus considerable spatial and temporal variability. In order to better understand this variability, the present study employs statistical multivariate analyses to investigate links between POM composition and environmental forcings for a panel of twelve coastal systems distributed along the three maritime regions of France and monitored weekly to monthly for 1 to 8 years. At multi-system scale, two main gradients of POC composition have been identified: a 'Continent-Ocean' gradient associated with hydrodynamics, sedimentary dynamics and depth of the water column, and a gradient of trophic status related to nutrient availability. At local scale, seasonality of POC composition appears to be station-specific but still related to part of the above-mentioned forcings. A typology of systems was established by coupling spatial and temporal variability of POC composition. Four groups were highlighted: (1) the estuarine stations where POC composition is dominated by terrestrial POM and driven by hydrodynamics and sedimentary processes, (2) the oligotrophic systems, characterized by the contribution of diazotrophs due to low nutrient availability, and the marine meso/eutroph systems whose POC composition is (3) either deeply dominated by phytoplankton or (4) dominated by phytoplankton but where the contribution of continental and benthic POC is not negligible and is driven by hydrodynamics, sedimentary processes and the height of the water column. Finally, the present study provides several insights into the different forcings to POM composition and dynamics in temperate coastal systems at local and multi-system scales. This work also presents a methodological approach that establishes statistical links between forcings and POM composition, helping to gain more objectively insight of forcings.

Updating the Geologic Barcodes for South China: Discovery of Late Archean Banded Iron Formations in the Yangtze Craton.

PubMed

Ye, Hui; Wu, Chang-Zhi; Yang, Tao; Santosh, M; Yao, Xi-Zhu; Gao, Bing-Fei; Wang, Xiao-Lei; Li, Weiqiang

2017-11-08

Banded iron formations (BIFs) in Archean cratons provide important "geologic barcodes" for the global correlation of Precambrian sedimentary records. Here we report the first finding of late Archean BIFs from the Yangtze Craton, one of largest Precambrian blocks in East Asia with an evolutionary history of over 3.3 Ga. The Yingshan iron deposit at the northeastern margin of the Yangtze Craton, displays typical features of BIF, including: (i) alternating Si-rich and Fe-rich bands at sub-mm to meter scales; (ii) high SiO 2  + Fe 2 O 3total contents (average 90.6 wt.%) and Fe/Ti ratios (average 489); (iii) relative enrichment of heavy rare earth elements and positive Eu anomalies (average 1.42); (iv) and sedimentary Fe isotope compositions (δ 56 Fe IRMM-014 as low as -0.36‰). The depositional age of the BIF is constrained at ~2464 ± 24 Ma based on U-Pb dating of zircon grains from a migmatite sample of a volcanic protolith that conformably overlied the Yingshan BIF. The BIF was intruded by Neoproterozoic (805.9 ± 4.7 Ma) granitoids that are unique in the Yangtze Craton but absent in the North China Craton to the north. The discovery of the Yingshan BIF provides new constraints for the tectonic evolution of the Yangtze Craton and has important implications in the reconstruction of Pre-Nuna/Columbia supercontinent configurations.

Examining Reservoir Influences on Fluvial Sediment Supply to Estuaries and Coastal Oceans with Sediment Geochronologies: Example from Conowingo Reservoir (Upper Chesapeake Bay, USA)

NASA Astrophysics Data System (ADS)

Palinkas, C. M.; Russ, E.

2016-12-01

The flux of fluvial sediment to estuaries and coastal oceans is often interrupted by natural and anthropogenic influences. Here, we focus on river dams, which alter the connection between rivers and their receiving basins via sediment sequestration in their reservoirs. Sediments are effectively trapped until river discharge is high enough to create flow velocities capable of resuspending sediment. Sediment resuspension often varies within the reservoir, driven by morphological features such as channels and islands. Thus, sediment residence times in the reservoir are often highly variable in space and time. This study focuses on reading the sedimentary record in one such system - the reservoir upstream of Conowingo Dam, built in the late 1920s and the last and largest dam on the Susquehanna River (Maryland, USA) before it enters Chesapeake Bay. This study establishes geochronologies of reservoir sedimentation on seasonal to decadal time scales with a variety of techniques (e.g., natural and anthropogenic radioisotopes (7Be, 210Pb, 137Cs), coal from mining in the watershed) to interpret observed down-core sedimentary structures and characteristics (grain size, organic content). These observations reveal spatial and temporal patterns of sediment deposition and/or erosion. Placed within the broader context of reservoir geomorphology, these results can improve predictions of sediment supply to downstream environments, in this case Chesapeake Bay, where it can impact water quality and/or benthic organisms.

What controls diffuse fractures in platform carbonates? Insights from Provence (France) and Apulia (Italy)

NASA Astrophysics Data System (ADS)

Lavenu, Arthur P. C.; Lamarche, Juliette

2018-03-01

Fractures are widespread in rocks and regional opening-mode arrays are commonly ascribed to major tectonic events. However, fractures occur in otherwise undeformed rocks. Some of these are early-developed features independent of tectonics and forming a background network at regional scale. To overcome this lack of understanding, two hydrocarbon reservoir analogues from platform carbonates have been targeted: the Provence (SE France), and the Apulian platform (SE Italy). In both areas, an early fracturing stage has been observed, made of high-angle-to-bedding opening-mode fractures, and bed-parallel stylolites. These features developed synchronously during the first burial stages and prior to major tectonic events. The fracture sets are not genetically related to the present-day layering. Contrarily, fractures developed in a brittle media where facies transitions were not sharp and did not act as mechanical discontinuities. Carbonate facies distribution and early diagenetic imprint constrained the mechanical stratigraphy when fractures occurred. In addition, we observed that fractures related to late tectonic inversion were partly inhibited. Indeed, rock mechanical properties change through time. Characterizing the temporal evolution of carbonate rocks has revealed that diagenesis and sedimentary facies are the prime actors for brittleness and mechanical layering in carbonates.

Soil archives of a Fluvisol: Subsurface analysis and soil history of the medieval city centre of Vlaardingen, the Netherlands - an integral approach

NASA Astrophysics Data System (ADS)

Kluiving, Sjoerd; De Ridder, Tim; Van Dasselaar, Marcel; Roozen, Stan; Prins, Maarten; Van Mourik, Jan

2016-04-01

In Medieval times the city of Vlaardingen (the Netherlands) was strategically located on the confluence of three rivers, the Meuse, the Merwede and the Vlaarding. A church of early 8th century was already located here. In a short period of time Vlaardingen developed into an international trading place, the most important place in the former county of Holland. Starting from the 11th century the river Meuse threatened to flood the settlement. These floods have been registered in the archives of the fluvisol and were recognised in a multidisciplinary sedimentary analysis of these archives. To secure the future of this vulnerable soil archive currently an extensive interdisciplinary research (76 mechanical drill holes, grain size analysis (GSA), thermo-gravimetric analysis (TGA), archaeological remains, soil analysis, dating methods, micromorphology, and microfauna has started in 2011 to gain knowledge on the sedimentological and pedological subsurface of the mound as well as on the well-preserved nature of the archaeological evidence. Pedogenic features are recorded with soil descriptive, micromorphological and geochemical (XRF) analysis. The soil sequence of 5 meters thickness exhibits a complex mix of 'natural' as well as 'anthropogenic layering' and initial soil formation that enables to make a distinction for relatively stable periods between periods with active sedimentation. In this paper the results of this large-scale project are demonstrated in a number of cross-sections with interrelated geological, pedological and archaeological stratification. Distinction between natural and anthropogenic layering is made on the occurrence of chemical elements phosphor and potassium. A series of four stratigraphic / sedimentary units record the period before and after the flooding disaster. Given the many archaeological remnants and features present in the lower units, we assume that the medieval landscape was drowned while it was inhabited in the 12th century AD. After a final drowning phase in the 13th century, as a reaction to it, inhabitants started to raise the surface.

Mechanical Stability of Stratified Sediments along the upper continental Slope off Vesterålen, northern Norway - Insights from in situ CPTU Tests

NASA Astrophysics Data System (ADS)

Voelker, D.; Stegmann, S.; Kreiter, S.; L'Heureux, J. S.; Vanneste, M. W. B.; Baeten, N. J.; Knudsen, S.; Rise, L.; Longva, O.; Brendryen, J.; Haflidason, H.; Chand, S.; Mörz, T.; Kopf, A.

2015-12-01

High-resolution single channel-seismic data (3.5 kHz) reveal small-scale submarine landslide structures and superficial deformation features (e.g. tension cracks) along the gently dipping (3°) upper continental slope west of the Vesterålen Archipelago off northern Norway. Previous laboratory-based geotechnical studies attest that the slope is per sestable and that seismic events in an order of magnitude M5.7 may have triggered the slope sediments to fail. Here we present geotechnical in situ data (sedimentary strength, pore pressure), which were obtained with RV Poseidon in summer 2014 using the static CPTU system GOST. The CPTU system provided high-resolution geotechnical profiles of the uppermost sediments to a maximum penetration depth of ~ 20 m at six sites within the landslide features and beside them in undisturbed slope sediments as reference. The CPTU data reveal the occurrence of mechanically weaker zones (MWZ) by the drop of sedimentary strength. These zones are interbedded by coarser, more competent layers. The occurrence of sensitive fine-grained material may be responsible for the loss of strength in the deeper portion (appx. 12 to 18 m below seafloor). An 1D infinite pseudo-static stability analysis attests that the mechanically weaker zones (MWZ) correlate well with portions, where the Factor of Safety (FoS) ≤ 1 (meta-stable to unstable) indicates permanent deformation or failure in case additional dynamic load is induced by an earthquake. Thus, the mechanically weak layers can be considered as one important pre-condition for landslide activity. In conclusion, the integration of in situ CPTU data with geophysical data improves soil characterization and hence foster a better understanding of the pre-conditioning factors for slope instability at the upper continental slope off Vesterålen. Risk assessment for the present-day slope off Vesterålen is particularly crucial, because the opening of the region for offshore oil and gas exploration is controversially debated.

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

NASA Astrophysics Data System (ADS)

Smeaton, Craig; Austin, William E. N.; Davies, Althea L.; Baltzer, Agnes; Howe, John A.; Baxter, John M.

2017-12-01

Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.

Evidence of the Zanclean megaflood in the eastern Mediterranean Basin.

PubMed

Micallef, Aaron; Camerlenghi, Angelo; Garcia-Castellanos, Daniel; Cunarro Otero, Daniel; Gutscher, Marc-André; Barreca, Giovanni; Spatola, Daniele; Facchin, Lorenzo; Geletti, Riccardo; Krastel, Sebastian; Gross, Felix; Urlaub, Morelia

2018-01-18

The Messinian salinity crisis (MSC) - the most abrupt, global-scale environmental change since the end of the Cretaceous - is widely associated with partial desiccation of the Mediterranean Sea. A major open question is the way normal marine conditions were abruptly restored at the end of the MSC. Here we use geological and geophysical data to identify an extensive, buried and chaotic sedimentary body deposited in the western Ionian Basin after the massive Messinian salts and before the Plio-Quaternary open-marine sedimentary sequence. We show that this body is consistent with the passage of a megaflood from the western to the eastern Mediterranean Sea via a south-eastern Sicilian gateway. Our findings provide evidence for a large amplitude drawdown in the Ionian Basin during the MSC, support the scenario of a Mediterranean-wide catastrophic flood at the end of the MSC, and suggest that the identified sedimentary body is the largest known megaflood deposit on Earth.

Lower Cretaceous paleo-Vertisols and sedimentary interrelationships in stacked alluvial sequences, Utah, USA

NASA Astrophysics Data System (ADS)

Joeckel, R. M.; Ludvigson, G. A.; Kirkland, J. I.

2017-11-01

The Yellow Cat Member of the Cedar Mountain Formation in Poison Strip, Utah, USA, consists of stacked, erosionally bounded alluvial sequences dominated by massive mudstones (lithofacies Fm) with paleo-Vertisols. Sediment bodies within these sequences grade vertically and laterally into each other at pedogenic boundaries, across which color, texture, and structures (sedimentary vs. pedogenic) change. Slickensides, unfilled (sealed) cracks, carbonate-filled cracks, and deeper cracks filled with sandstone; the latter features suggest thorough desiccation during aridification. Thin sandstones (Sms) in some sequences, typically as well as laminated to massive mudstones (Flm) with which they are interbedded in some cases, are interpreted as avulsion deposits. The termini of many beds of these lithofacies curve upward, parallel to nearby pedogenic slickensides, as the features we call ;turnups.; Turnups are overlain or surrounded by paleosols, but strata sheltered underneath beds with turnups retain primary sedimentary fabrics. Turnups were produced by movement along slickensides during pedogenesis, by differential compaction alongside pre-existing gilgai microhighs, or by a combination of both. Palustrine carbonates (lithofacies C) appear only in the highest or next-highest alluvial sequences, along with a deep paleo-Vertisol that exhibits partially preserved microrelief at the base of the overlying Poison Strip Member. The attributes of the Yellow Cat Member suggest comparatively low accommodation, slow accumulation, long hiatuses in clastic sedimentation, and substantial time intervals of subaerial exposure and pedogenesis; it appears to be distinct among the members of the Cedar Mountain Formation in these respects.

Salix alba and Populus nigra seedlings resistance to physical hydro-sedimentary stresses: nursery experimental approach compared to in situ measurements

NASA Astrophysics Data System (ADS)

Wintenberger, Coraline; Rodrigues, Stephane; Breheret, Jean-Gabriel; Jugé, Philippe; Villar, Marc

2014-05-01

In Europe, riparian Salicaceae is declining following the loss of potential germination areas associated with river management. Nevertheless, as an exception for lowland rivers, the Loire River (France) shows in its middle reaches an efficient sexual regeneration of Populus nigra and Salix alba species on bare sediments deposited during flood events. The study focuses on the influence of flow, sediment dynamics and fluvial maintenance operations on the establishment and survival of black poplar and white willow seedlings during the first year of development in a lowland sandy-gravel river, the Middle Loire. Main questions are: what is the influence of morphological and sedimentary features on seedlings recruitment and how do they withstand the hydro-sedimentary stresses occurring during high flow periods? How fluvial management works, and induced morphology and sedimentary features, modify the sediment dynamics and subsequent establishment and maintenance of seedlings? To answer these questions, we developed an ex-situ approach which allowed, under controlled conditions, to determine the influence of the sedimentological characteristics of the substrate on the development and maintenance of seedlings with a specific focus on the root system. Three experiments were carried out for three sedimentary mixtures from the river (sand, sand-gravel and 0.2 m of sand superimposed on sand-gravel mixture) that correspond to grain size and stratigraphy conditions often observed on bars and secondary channels in the Loire. The experimental design includes 108 plots of 1 m3, with 400 seeds per plot (corresponding to the Loire density measurements) and combining seeds from two species, three sedimentary mixtures, four replicates and three experiments. Experiment 1 (control) is based on the architecture of root systems using the WinRHIZO image analysis software. Experiment 2 is relative to the evaluation of constraints leading to "uprooting" of seedlings. Experiment 3 provides data on the seedlings survival once buried during a flood event. Genetic diversity of the seed lots will be investigated via biomass and shoot / root ratio. Results reveal that willow seedlings have a higher density of roots compared to poplar. In sand mixture, poplar has a taproot system; in sand-gravel mixture, taproot is divided into several roots which leads to a branched root system. The required forces to uprooting are twice much important for sand-gravel mixture. In situ measurements detail the sediment dynamics and morphological evolution during and after floods (topography, scour/fill processes, grain size surveys, flow velocity, sediment transport rates) on a managed alluvial bar. Results associated with floods occurring after fluvial management works highlight the rapid regeneration of bedforms associated with sedimentary and hydraulics constraints. This leads to the development of new morphological and sedimentological units, suitable for seedlings recruitment. Thirty plots measurements of seedlings (densities and species) established were associated with these news physical conditions over the bar. Black poplar and white willow appeared for a wide range of grain sizes and on specific morphological units. Seedlings survival will be analyzed with regard to physical constraints determined for each plot from measurements of hydro-sedimentary dynamics and then compared to ex situ results.

Late Miocene/Pliocene Ostracod Biostratigraphy from South Carpathian Foredeep, Romania (Badislava-Topolog Area)

NASA Astrophysics Data System (ADS)

Floroiu, Alina; Stoica, Marius; Vasiliev, Iuliana; Krijgsman, Wout

2016-04-01

The Paratethys epicontinental sea has been an essential paleogeographic feature defining the Eurasian interior since Oligocene. By the end of the Miocene, ongoing tectonic activity in the region determined severe restrictions of the connection of the large former Paratethys sea resulting in the formation of several smaller subbasins: the Pannonian basin, the Dacian basin, the Black Sea and the Caspian Sea. In the western part of the Dacian Basin, the thick and continuous Mio-Pliocene sedimentary successions of the Getic Depression of Romania provide an exceptional opportunity to study the paleoecological changes in the Eastern Paratethys during the time when the Mediterranean and Black Sea experienced important sea level changes related to the Messinian Salinity Crisis. These sedimentary successions were the basis of high-resolution magnetobiostratigraphic studies that allow a detailed correlation to the Geological Time Scale. Here, we present the main characteristics of the ostracod assemblages of the Late Miocene/Pliocene sedimentary succession from Badislava-Topolog section covering the Eastern Paratethys regional Maeotian and Pontian, stages that are, at moment, under ongoing formal stratigraphic definition process. The Mio-Pliocene is exposed in the central part of the Getic Depression, especially Topolog-Arges area, where it riches up to 500 m in thickness being incorporated into a large monocline structure with 15o-20o plungeto the south. The Upper Maeotian deposits from the area have developed mainly in fluviatile-deltaic facies with frequent continental intercalations. The ostracod assemblage is represented by rare fresh water ostracods of Candona, Pseudocandona and Ilyocypris genera, capable to populate unstable environments like flood-plains, lakes and rivers with temporary existence. The scarce Maeotian ostracod fauna from this marginal section differs essentially from the more diversified one of the same age recorded in areas that evolved in basinal conditions. The top of the Maeotian sequence is marked by an erosional surface. The overlaying Pontian has a transgressive character being represented only by the Late Pontian (Bosphorian) fining-upward sedimentary sequence that starts with coarse to medium-grained pebbles and sands in the lower part, passing to predominant pelitic deposits to the upper part. These Bosphorian, fine-grained sedimentary rocks provided a rich ostracods fauna represented mainly by species of Pontoniella, Camptocypria, Caspiocypris, Cypria, Amplocypris, Bakunella Tyrrhneocythere, Amnicythere, Loxoconcha and Amnicythere. There are no indications for the presence of the Lower and Middle Pontian (Odessian and Portaferrian) substages in the investigated area, the Upper Pontian deposits discordantly overlying the Upper Maeotian sediments. The transition to the Dacian stage (Lower Pliocene) is more gradual, some of Pontian species passing to the Lower Dacian (Getian) where they are in association with typical Dacian ostracods.

Predicting S2S in Deep Time Sedimentary Systems and Implications for Petroleum Systems

NASA Astrophysics Data System (ADS)

Bhattacharya, J.

2013-12-01

The source to sink concept is focused on quantification of the various components of siliciclastic sedimentary systems from initial source areas, through the dispersal system, and deposition within a number of potential ultimate sedimentary sinks. Sequence stratigraphy shows that depositional system are linked through time and show distinctively predictable 3D stratigraphic organization, which can be related to cycles of relative changes in accommodation and sediment supply. For example, erosion and formation of incised fluvial valleys generally occur during periods of falling base level with lowstand reservoir deposits favored in more basin distal settings (e.g. deepwater fans), whereas during highstands of sea level, significantly more sediment may be sequestered in the non-marine realm and more distal environments may favor deposition of slowly-deposited condensed sections, which may make excellent hydrocarbon source rocks. Only more recently have attempts been made to quantify the size and scaling relationships of the ultimate source areas on the basis of analysis of ancient depositional systems, and the use of these scaling relationships to predict the sixe of linked depositional systems along the S2S tract. The maximum size of depositional systems, such as rivers, deltas, and submarine fans, is significantly controlled by the area, relief, and climate regime of the source area, which in turn may linked to the plate tectonic and paleogeographic setting. Classic provenance studies, and more recent use of detrital zircons, provide critical information about source-areas, and may help place limits on the size and relief of a drainage basin. Provenance studies may also provide key information about rates of exhumation of source areas and the link to the tectonic setting, Examination of ancient river systems in the rock record, and especially the largest trunk rivers, which are typically within incised valleys, can also be used to estimate paleodischarge, which in turn can be linked to the drainage basin to make estimates about the size and sale of the source area. The best estimates can be made in basins with well-constrained data that allow details of cross-sectional or plan-view channel-architecture to be determined, such as extensive outcrops, or abundant subsurface data, and especially where higher resolution 3D seismic data are available. Paleodischarge estimates of lowstand Quaternary-age continental-scale ancient rivers from passive continental margins, using seismic data, are orders-of-magnitude higher (1000's of cumecs) than smaller-scale Cretaceous lowstand systems that drained into the Western-Interior Seaway of North America (100s of cumecs). Paleodischarge of rivers can also be estimated independently by integrating estimates of drainage basin area and paleoclimate. These can be compared with paleodischarge estimates based on the river deposits themselves. The integration of paleodischarge estimates with more sophisticated provenance analysis should enable improved use of the sedimentary record to make estimates about the entire S2S system, as opposed to primarily the depositional component. A more quantitative approach to estimating the scale of sedimentary systems, and especially in the context of source areas, also puts constraints on the size and scale of potential hydrocarbon reservoirs and thus has economic value.

Reinterpretation of the Quaternary sedimentary infill of the Ría de Vigo, NW Iberian Peninsula, as a compound incised valley

NASA Astrophysics Data System (ADS)

Martínez-Carreño, N.; García-Gil, S.

2017-10-01

Seismic data have been used to investigate the stratigraphy of the Galician rias for more than two decades. Here, we present a new interpretation of the sedimentary infill of an incised valley (Ría de Vigo, NW Iberian Peninsula), based on high-resolution seismic profiles, core sediment analysis, and radiocarbon 14C data. The new data indicate that the stratigraphic architecture of the Galician rias result from multiple incision/infill phases and, therefore, they are reclassified as compound rather than simple incised valleys. Seven seismic units were identified: one of Tertiary age (U1), four of Pleistocene age (U2-U5) which are interpreted as 4th-order sequences deposited between MIS 11 and MIS 2, and Late Pleistocene (U6) and Holocene (U7) units corresponding with post-glacial sedimentation. The sedimentary infill overlies a highly faulted irregular granitic and metamorphic basement; the inherited morphology is shown to be important for controlling the pathway and evolution of the fluvial network as well as preservation of the sedimentary deposits during several glacial/interglacial cycles. The presence of a rocky barrier at the mouth of the ria is a distinctive feature that conditions sedimentation and exchange of sediment between the ria and the adjacent shelf. For the first time, faults and tilted blocks affecting Late Pleistocene (MIS 3) deposits have been identified. The new data presented here provide the opportunity to reconstruct the evolution of the sedimentary infill of a ria, with especially high-resolution during the last post-glacial transgression.

Using Crater Counts to Constrain Erosion Rates on Mars: Implications for the Global Dust Cycle, Sedimentary Rock Erosion and Organic Matter Preservation

NASA Astrophysics Data System (ADS)

Mayer, D. P.; Kite, E. S.

2016-12-01

Sandblasting, aeolian infilling, and wind deflation all obliterate impact craters on Mars, complicating the use of crater counts for chronology, particularly on sedimentary rock surfaces. However, crater counts on sedimentary rocks can be exploited to constrain wind erosion rates. Relatively small, shallow craters are preferentially obliterated as a landscape undergoes erosion, so the size-frequency distribution of impact craters in a landscape undergoing steady exhumation will develop a shallower power-law slope than a simple production function. Estimating erosion rates is important for several reasons: (1) Wind erosion is a source of mass for the global dust cycle, so the global dust reservoir will disproportionately sample fast-eroding regions; (2) The pace and pattern of recent wind erosion is a sorely-needed constraint on models of the sculpting of Mars' sedimentary-rock mounds; (3) Near-surface complex organic matter on Mars is destroyed by radiation in <108 years, so high rates of surface exhumation are required for preservation of near-surface organic matter. We use crater counts from 18 HiRISE images over sedimentary rock deposits as the basis for estimating erosion rates. Each image was counted by ≥3 analysts and only features agreed on by ≥2 analysts were included in the erosion rate estimation. Erosion rates range from 0.1-0.2 {μ }m/yr across all images. These rates represent an upper limit on surface erosion by landscape lowering. At the conference we will discuss the within and between-image variability of erosion rates and their implications for recent geological processes on Mars.

Interpreting Biosignatures in the Context of Marine Evaporitic Environments

NASA Astrophysics Data System (ADS)

Des Marais, D. J.; Vogel, M. B.

2008-12-01

A biosignature is an object, substance and/or pattern whose origin specifically requires a biological agent. The usefulness of a biosignature is determined, not only by the probability of life creating it, but also by the improbability of nonbiological processes producing it. So what sets life apart from the rest? Life as we know it is the harnessing of free energy to sustain and perpetuate, by molecular replication and evolution, a high density of information in the form of functional complex molecules and functionally-related larger structures. Accordingly, biosignatures can arise from key attributes such as converting solar to chemical energy, exploiting the versatility of organic chemistry to sustain metabolic processes and preserve information, and maintaining microenvironments that enhance these functions. The external environment affects such functions and so it must be defined in order to interpret effectively the biosignatures that emerge from them. Hypersaline benthic cyanobacterial communities at Guerrero Negro, Baja California Sur, Mexico provide illustrative examples of biosignatures research that is relevant to our early biosphere and to Mars. Where brines are undersaturated with respect to gypsum, filamentous cyanobacteria dominate over unicellular cyanobacteria and can trap and bind sedimentary grains more effectively, thus altering their response to sedimentary processes and creating laminated fabrics. Biofilms in gypsiferrous sediments also can alter the response of the clastic or crystal matrix to chemical and physical sedimentary processes such as erosion or precipitate accumulation. Gypsum precipitating within biofilms offers compelling evidence of biological influences on crystal textures and habits. Such gypsum exhibits dissolution textures, accessory mineral precipitation and unique crystal form aspect ratios. Irregular textures include conchoidal and globular features associated with both dissolution and nucleation that are likely affected by biofilm pore water compositions. The accessory phases forming in association with gypsum-hosted biofilms (Sº, Ca-carbonate, and Sr/Ca-sulfate) are known byproducts of bacterially mediated sulfate reduction. Light penetrates the relatively transparent gypsum to sustain discretely layered successions of orange-, green-, purple-, pink-, and black-pigmented endoevaporitic biofilms. Lipid biosignatures include carotenoids, tricyclic terpenoids, benzothiophenes, thiacycloalkanes and methylhopanoids. These represent the aggregate effects of light regimes and hypersaline conditions. Features that could be preserved over geological timescales therefore include sedimentary textures, minerals, crystal forms, and lipids. Collectively these features can serve both as biosignatures and paleoenvironmental indicators on early Earth and on Mars.

Evidence for and implications of sedimentary diapirism and mud volcanism in the southern Utopia highland-lowland boundary plain, Mars

USGS Publications Warehouse

Skinner, J.A.; Tanaka, K.L.

2007-01-01

Several types of spatially associated landforms in the southern Utopia Planitia highland-lowland boundary (HLB) plain appear to have resulted from localized geologic activity, including (1) fractured rises, (2) elliptical mounds, (3) pitted cones with emanating lobate materials, and (4) isolated and coalesced cavi (depressions). Stratigraphic analysis indicates these features are Hesperian or younger and may be associated with resurfacing that preferentially destroyed smaller (< 8 ?? km diameter) impact craters. Based on landform geomorphologies and spatial distributions, the documented features do not appear to be specifically related to igneous or periglacial processes or the back-wasting and erosion of the HLB scarp. We propose that these features are genetically related to and formed by sedimentary (mud) diapirs that ascended from zones of regionally confined, poorly consolidated, and mechanically weak material. We note morphologic similarities between the mounds and pitted cones of the southern Utopia boundary plain and terrestrial mud volcanoes in the Absheron Peninsula, Azerbaijan. These analogs provide a context for understanding the geological environments and processes that supported mud diapir-related modification of the HLB. In southern Utopia, mud diapirs near the Elysium volcanic edifice may have resulted in laccolith-like intrusions that produced the fractured rises, while in the central boundary plain mud diapirs could have extruded to form pitted cones, mounds, and lobate flows, perhaps related to compressional stresses that account for wrinkle ridges. The removal of material a few kilometers deep by diapiric processes may have resulted in subsidence and deformation of surface materials to form widespread cavi. Collectively, these inferences suggest that sedimentary diapirism and mud volcanism as well as related surface deformations could have been the dominant Hesperian mechanisms that altered the regional boundary plain. We discuss a model in which detritus would have accumulated thickly in the annular spaces between impact-generated structural rings of Utopia basin. We envision that these materials, and perhaps buried ejecta of Utopia basin, contained volatile-rich, low-density material that could provide the source material for the postulated sedimentary diapirs. Thick, water-rich, low-density sediments buried elsewhere along the HLB and within the lowland plains may account for similar landforms and resurfacing histories. ?? 2006 Elsevier Inc. All rights reserved.

Mars sedimentary rock erosion rates constrained using crater counts, with applications to organic-matter preservation and to the global dust cycle

NASA Astrophysics Data System (ADS)

Kite, Edwin S.; Mayer, David P.

2017-04-01

Small-crater counts on Mars light-toned sedimentary rock are often inconsistent with any isochron; these data are usually plotted then ignored. We show (using an 18-HiRISE-image, > 104-crater dataset) that these non-isochron crater counts are often well-fit by a model where crater production is balanced by crater obliteration via steady exhumation. For these regions, we fit erosion rates. We infer that Mars light-toned sedimentary rocks typically erode at ∼102 nm/yr, when averaged over 10 km2 scales and 107-108 yr timescales. Crater-based erosion-rate determination is consistent with independent techniques, but can be applied to nearly all light-toned sedimentary rocks on Mars. Erosion is swift enough that radiolysis cannot destroy complex organic matter at some locations (e.g. paleolake deposits at SW Melas), but radiolysis is a severe problem at other locations (e.g. Oxia Planum). The data suggest that the relief of the Valles Marineris mounds is currently being reduced by wind erosion, and that dust production on Mars < 3 Gya greatly exceeds the modern reservoir of mobile dust.

Trace Elemental Imaging of Rare Earth Elements Discriminates Tissues at Microscale in Flat Fossils

PubMed Central

Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B.; Cohen, Serge X.; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

2014-01-01

The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies. PMID:24489809

Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.

PubMed

Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B; Cohen, Serge X; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

2014-01-01

The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies.

An Aquatic Journey toward Aeolis Mons (Mount Sharp): Sedimentary Rock Evidence observed by Mars Science Laboratory

NASA Astrophysics Data System (ADS)

Gupta, Sanjeev; Edgar, Lauren; Williams, Rebecca; Rubin, David; Yingst, Aileen; Lewis, Kevin; Kocurek, Gary; Anderson, Ryan; Dromart, Gilles; Edgett, Ken; Hardgrove, Craig; Kah, Linda; Mangold, Nicolas; Milliken, Ralph; Minitti, Michelle; Palucis, Marisa; Rice, Melissa; Stack, Katie; Sumner, Dawn; Williford, Ken

2014-05-01

Since leaving Yellowknife Bay (summer 2013), Mars Science Laboratory Curiosity has investigated a number of key outcrops as it traverses along the Rapid Transit Route toward the entry point to begin its investigations of the extensive rock outcrops at the base of Mount Sharp. Rover observations are characterizing the variability of lithologies and sedimentary facies along the traverse and establishing stratigraphic relationships with the aim of reconstructing depositional processes and palaeoenvironments. Here, we report on sedimentological and stratigraphic observations based on images from the Mastcam and MAHLI instruments at Shaler and the Darwin waypoint. The informally named Shaler outcrop, which forms part of the Glenelg member of the Yellowknife Bay formation [1] is remarkable for the preservation of a rich suite of sedimentary structures and architecture, and was investigated on sols 120-121 and 309-324. The outcrop forms a pebbly sandstone body that is ~0.7 m thick and extends for up to 20 m. Shaler is largely characterized by pebbly sandstone facies showing well-developed decimeter-scale trough cross-stratification. Bedding geometries indicate sub-critical angles of climb, resulting in preservation of only the lee slope deposits. The grain size, and the presence and scale of cross-stratification imply sediment transport and deposition by unidirectional currents in a fluvial sedimentary environment. Curiosity investigated the informally named Darwin waypoint between sols 390 and 401, making detailed Mastcam and MAHLI observations at two separate locations. The Darwin outcrop comprises light-toned sandstone beds separated by darker pebbly sandstones. MAHLI observations permit differentiation of distinct sedimentary facies. The Altar Mountain facies is a poorly sorted pebbly sandstone that is rich in fine pebbles. Pebbles are sub-angular to sub-rounded in shape and show no preferred orientation or fabric. Pebbles and sand grains show clast-to-clast contacts. The clast-supported nature of the facies, the presence of coarse sand grains to fine pebbles, and the occurrence of some rounding of clasts indicates that these are sedimentary clasts that have been transported by aqueous flows. However, the absence of a well-sorted fabric, size grading of clast, and major rounding of grains suggests that these pebbly sandstones were rapidly deposited rather than built up from sustained fluvial reworking, implying that the deposits may be the result of more ephemeral river flows rather than sustained flow discharges. The Bardin Bluffs facies overlies the Altar Mountain facies and shows a more sand-dominated fabric with a smaller proportion of floating fine pebbles. This facies is also clast-supported but contains fewer pebbles and shows an overall fining-up trend. This facies is also interpreted to represent fluvial deposition albeit with a different grain size distribution than the Altar Mountains facies. We will compare and contrast the varying sedimentary fabrics and facies to develop models for the variety of aqueous fluvial transport processes that have led to the deposition of sedimentary rocks en route to Mount Sharp. The origin of these sedimentary rocks with relation to fluvial fan processes in Gale Crater will be discussed. References: [1] Grotzinger, J.P. et al Science 2013, doi: 10.1126/science.1242777.

Sedimentary and structural evolution of a Pleistocene small-scale push moraine in eastern Poland: New insight into paleoenvironmental conditions at the margin of an advancing ice lobe

NASA Astrophysics Data System (ADS)

Włodarski, Wojciech; Godlewska, Anna

2016-08-01

Recent studies of push moraines have focused on the interplay between the dynamics of ice margins and the environmental variables of the foreland into which they advance. These studies showed that the spatial distribution, geometry and style of the glaciotectonic deformation of push moraines are controlled by ice-induced stresses, the strain rate, the rheology of the deposits and hydraulic conductivity. In this work, we provide new insight into this interplay at a small spatio-temporal scale, specifically, the ancient glacial system of the Liwiec ice lobe within the younger Saalian ice sheet in eastern Poland. The paleoenvironmental variables that are analysed here refer to the dynamics of the hydrological processes that affected the patterns and sediment deposition rate on the terminoglacial fan and the resulting mechanical stratigraphy and hydraulic conductivity of the foreland. We document the progradational sequence of the fan deposits that developed as a result of the ice lobe thickening and the steepening of its stationary front. The sedimentary features of the fan, the lithology of its basement and the hydraulic conductivity of the foreland strongly influenced the geometry and kinematics of fold growth during the advance of the ice lobe. The predominance of flexural slip and the development of fractures, including fold-accommodation faults, were interpreted to be an effect of buckle folding due to horizontal shortening induced by ice advance. The partial overriding of the push moraine by the ice lobe and, thus, the submarginal conditions for deformation were inferred from the significant hinge migration and internal deformation of the strata under undrained conditions in one of the folds. The synfolding deposition pattern of the fan growth strata allowed us to suggest that the push moraine was probably formed by a sustained advance rather than surge.

Aram and Iani Chaos

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-344, 28 April 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image mosaic was constructed from data acquired by the MOC red wide angle camera. The large, circular feature in the upper left is Aram Chaos, an ancient impact crater filled with layered sedimentary rock that was later disrupted and eroded to form a blocky, 'chaotic' appearance. To the southeast of Aram Chaos, in the lower right of this picture, is Iani Chaos. The light-toned patches amid the large blocks of Iani Chaos are known from higher-resolution MOC images to be layered, sedimentary rock outcrops. The picture center is near 0.5oN, 20oW. Sunlight illuminates the scene from the left/upper left.

Modeling the interaction between sedimentary organic carbon and infaunal macrobenthos and their temporal (1980-2000) variation in the southern North Sea

NASA Astrophysics Data System (ADS)

Zhang, Wenyan; Daewel, Ute; Schrum, Corinna; Wirtz, Kai

2017-04-01

The mutual dependency between sedimentary total organic carbon (TOC) and benthic macrofauna is here for the first time quantified by a mechanistic model. The model describes (i) the vertical distribution of infaunal biomass resulting from a trade-off between nutritional benefit (quantity and quality of TOC) and the costs of burial (respiration), and (ii) the variable distribution of TOC being in turn shaped by bioturbation of local macrobenthos. In contrast to state-of-the-art diagenetic models, our approach resolves variations of bioturbation both in space and time, which depend on the macrobenthic community structure and biomass. Our implementation of the dynamic interaction between sedimentary organic carbon and infaunal macrobenthos is able to capture a real-time benthic response to both depositional and erosional events and provides improved estimates of the material exchange flux at the sediment-water interface. Applications to literature data for the North Sea demonstrate the robustness and accuracy of the model and its potential as an analysis tool for the status of TOC as well as benthic infauna in marine sediments. The model was coupled to two different 3D hydrodynamic-ecological models (ECOSMO and MOSSCO for 10 x 10 and 1 x 1 km setups, respectively) to evaluate the robustness of the estimates with respect to variable forcings on different spatial scales. Hindcast simulations of the benthic status in the southern North Sea from 1980 to 2000 indicate a relatively stable pattern at large temporal and spatial scales but significant variations at small scales.

Extensional deformation of the Guadalquivir Basin: rate of WSW-ward tectonic displacement from Upper Tortonian sedimentary rocks

NASA Astrophysics Data System (ADS)

Roldán, Francisco J.; Azañón, Jose Miguel; Rodríguez-Fernández, Jose; María Mateos, Rosa

2016-04-01

The Guadalquivir Basin (Upper Tortonian-Quaternary sedimentary infilling) has been considered the foreland basin of the Betic Orogen built up during its collision with the Sudiberian margin. The basin is currently restricted to its westernmost sector, in the Cadiz Gulf, because the Neogene-Quaternary uplift of the Betic Cordillera has produced the emersion of their central and eastern parts. The upper Tortonian chronostratigraphic unit is the oldest one and it was indistinctly deposited on the South Iberian paleomargin and the External units from the Betic Cordillera. However, these rocks are undeformed on the Sudiberian paleomargin while they are deeply affected by brittle deformation on the External Betic Zone. Outcrops of Upper Tortonian sedimentary rocks on External Betic Zone are severely fragmented showing allocthonous characters with regard to those located on the Sudiberian paleomargin. This post- Upper Tortonian deformation is not well known in the External Zones of the Cordillera where the most prominent feature is the ubiquity of a highly deformed tecto-sedimentary unit outcropping at the basement of the Guadalquivir sedimentary infilling. This tecto-sedimentary unit belongs to the Mass Wasting Extensional Complex (Rodríguez-Fernández, 2014) formed during the collision and westward migration of the Internal Zone of the Betic Cordillera (15-8,5 Ma). In the present work, we show an ensemble of tectonic, geophysical and cartographic data in order to characterize the post-Upper Tortonian deformation. For this, seismic reflection profiles have been interpreted with the help of hidrocarbon boreholes to define the thickness of the Upper Tortonian sedimentary sequence. All these data provide an estimation of the geometrical and kinematic characteristics of the extensional faults, direction of movement and rate of displacement of these rocks during Messinian/Pliocene times. References Rodríguez-Fernández, J., Roldan, F. J., J.M. Azañón y Garcia-Cortes, A. 2013. EL colapso gravitacional del frente orogénico alpino en el Dominio Subbético durante el Mioceno medio-superior: El Complejo Extensional Subbético. Boletín Geológico y Minero, 124 (3): 477-504

Exhumation and stress history in the sedimentary cover during Laramide thick-skinned tectonics assessed by stylolite roughness analysis.

NASA Astrophysics Data System (ADS)

Beaudoin, Nicolas; Lacombe, Olivier; David, Marie-Eléonore; Koehn, Daniel; Coltier, Robin

2017-04-01

Basement-involvement in shortening in forelands has a strong impact on the overlying sedimentary cover. The basement influences namely the geometry of folds and structures, the stress evolution and the nature and pathways for fluid migrations. However, these influences are poorly documented in context where the basement/cover interface is shallow (<6 km). This contribution presents the reconstruction of paleostress and vertical burial history of the Palaeozoic sedimentary strata affected by the Sevier-Laramide deformation at the front of the Rocky Mountains, in the Bighorn Basin (Wyoming, USA). Stylolite populations have been considered as part of an extensive microstructure investigation including also fractures, striated microfaults and calcite twins in key major structures such as the Sheep Mountain Anticline, the Rattlesnake Mountain Anticline, and the Bighorn Mountains Arch. Stylolite recognized in the field are clearly related to successive stages of deformation of the sedimentary cover, including fold development. We further apply a newly developed roughness analysis of pressure-solution stylolites which grant access (1) to the magnitude of the vertical principal stress, hence the maximum burial depth of the strata based on sedimentary stylolites, (2) to the principal stress orientations and regimes based on tectonic stylolites and (3) ultimately to the complete stress tensor when sedimentary and tectonic stylolites can be considered coeval. This approach was then coupled to mechanical properties of main competent formations exposed in the basin. Results of stylolite paleopiezometry, compared and combined to existing paleostress estimates from calcite twins and to exhumation reconstruction from low-temperature thermochronology, unravel the potential of the method to refine the structural history at the structure- and basin-scale. On top of the advances this case study adds to the methodology, the quantified reconstruction of stress-exhumation evolution in such a broken-foreland context offers a unique opportunity to discuss how thick-skinned tectonics impacts stress distribution in the sedimentary cover.

Geology, Geochemistry and Geophysics of Sedimentary Rock-Hosted Au Deposits in P.R. China

USGS Publications Warehouse

Peters, Stephen G.

2002-01-01

This is the second report concerning results of a joint project between the U.S. Geological Survey and the Tianjin Geological Academy to study sedimentary rock-hosted Au deposits in P.R. China. Since the 1980s, Chinese geologists have devoted a large-scale exploration and research effort to the deposits. As a result, there are more than 20 million oz of proven Au reserves in sedimentary rock-hosted Au deposits in P.R. China. Additional estimated and inferred resources are present in over 160 deposits and occurrences, which are undergoing exploration. This makes China second to Nevada in contained ounces of Au in Carlin-type deposits. It is likely that many of the Carlin-type Au ore districts in China, when fully developed, could have resource potential comparable to the multi-1,000-tonne Au resource in northern Nevada. The six chapters of this report describe sedimentary rock-hosted Au deposits that were visited during the project. Chapters 1 and 2 provide an overview of sedimentary rock-hosted Au deposits and Carlin-type Au deposits and also provide a working classification for the sedimentary rock-hosted Au deposits. Chapters 3, 4, and 5 provide descriptions that were compiled from the literature in China in three main areas: the Dian-Qian-Gui, the Qinling fold belt, and Middle-Lower Yangtze River areas. Chapter 6 contains a weights-of-evidence (WofE), GIS-based mineral assessment of sedimentary rock-hosted Au deposits in the Qinling fold belt and Dian-Qian-Gui areas. Appendices contain scanned aeromagnetic (Appendix I) and gravity (Appendix II) geophysical maps of south and central China. Data tables of the deposits (Appendix III) also are available in the first report as an interactive database at http://geopubs.wr.usgs.gov/open-file/of98-466/. Geochemical analysis of ore samples from the deposits visited are contained in Appendix IV.

Relationship Between Sea Surface Salinity from L-Band Radiometer and Optical Features in the East China Sea

DTIC Science & Technology

2014-01-01

7330-14-2132. REFERENCE [1] Guo, Z., Lin, T., Zhang, G., et al., "The sedimentary fluxes of polycyclic aromatic hydrocarbons in the Yangtze ...Total Light Absorption in Optically Complex Waters, a Case Study in Yangtze Estuary and Adjacent Coast," Advances in Computational Environment

Changes of scaling relationships in an evolving population: The example of "sedimentary" stylolites

NASA Astrophysics Data System (ADS)

Peacock, D. C. P.; Korneva, I.; Nixon, C. W.; Rotevatn, A.

2017-03-01

Bed-parallel (;sedimentary;) stylolites are used as an example of a population that evolves by the addition of new components, their growth and their merger. It is shown that this style of growth controls the changes in the scaling relationships of the population. Stylolites tend to evolve in carbonate rocks through time, for example by compaction during progressive burial. The evolution of a population of stylolites, and their likely effects on porosity, are demonstrated using simple numerical models. Starting with a power-law distribution, the adding of new stylolites, the increase in their amplitudes and their merger decrease the slope of magnitude versus cumulative frequency of the population. The population changes to a non-power-law distribution as smaller stylolites merge to form larger stylolites. The results suggest that other populations can be forward- or backward-modelled, such as fault lengths, which also evolve by the addition of components, their growth and merger. Consideration of the ways in which populations change improves understanding of scaling relationships and vice versa, and would assist in the management of geofluid reservoirs.

Atmospheric methane from organic carbon mobilization in sedimentary basins — The sleeping giant?

NASA Astrophysics Data System (ADS)

Kroeger, K. F.; di Primio, R.; Horsfield, B.

2011-08-01

The mass of organic carbon in sedimentary basins amounts to a staggering 10 16 t, dwarfing the mass contained in coal, oil, gas and all living systems by ten thousand-fold. The evolution of this giant mass during subsidence and uplift, via chemical, physical and biological processes, not only controls fossil energy resource occurrence worldwide, but also has the capacity for driving global climate: only a tiny change in the degree of leakage, particularly if focused through the hydrate cycle, can result in globally significant greenhouse gas emissions. To date, neither climate models nor atmospheric CO 2 budget estimates have quantitatively included methane from thermal or microbial cracking of sedimentary organic matter deep in sedimentary basins. Recent estimates of average low latitude Eocene surface temperatures beyond 30 °C require extreme levels of atmospheric CO 2. Methane degassing from sedimentary basins may be a mechanism to explain increases of atmospheric CO 2 to values as much as 20 times higher than pre-industrial values. Increased natural gas emission could have been set in motion either by global tectonic processes such as pulses of activity in the global alpine fold belt, leading to increased basin subsidence and maturation rates in the prolific Jurassic and Cretaceous organic-rich sediments, or by increased magmatic activity such as observed in the northern Atlantic around the Paleocene-Eocene boundary. Increased natural gas emission would have led to global warming that was accentuated by long lasting positive feedback effects through temperature transfer from the surface into sedimentary basins. Massive gas hydrate dissociation may have been an additional positive feedback factor during hyperthermals superimposed on long term warming, such as the Paleocene-Eocene Thermal Maximum (PETM). As geologic sources may have contributed over one third of global atmospheric methane in pre-industrial time, variability in methane flux from sedimentary basins may have driven global climate not only at time scales of millions of years, but also over geologically short periods of time. Earth system models linking atmospheric, ocean and earth surface processes at different timescales with the sedimentary organic carbon cycle are the tools that need to be developed in order to investigate the role of methane from sedimentary basins in earth's climate.

Estimating tectonic history through basin simulation-enhanced seismic inversion: Geoinformatics for sedimentary basins

USGS Publications Warehouse

Tandon, K.; Tuncay, K.; Hubbard, K.; Comer, J.; Ortoleva, P.

2004-01-01

A data assimilation approach is demonstrated whereby seismic inversion is both automated and enhanced using a comprehensive numerical sedimentary basin simulator to study the physics and chemistry of sedimentary basin processes in response to geothermal gradient in much greater detail than previously attempted. The approach not only reduces costs by integrating the basin analysis and seismic inversion activities to understand the sedimentary basin evolution with respect to geodynamic parameters-but the technique also has the potential for serving as a geoinfomatics platform for understanding various physical and chemical processes operating at different scales within a sedimentary basin. Tectonic history has a first-order effect on the physical and chemical processes that govern the evolution of sedimentary basins. We demonstrate how such tectonic parameters may be estimated by minimizing the difference between observed seismic reflection data and synthetic ones constructed from the output of a reaction, transport, mechanical (RTM) basin model. We demonstrate the method by reconstructing the geothermal gradient. As thermal history strongly affects the rate of RTM processes operating in a sedimentary basin, variations in geothermal gradient history alter the present-day fluid pressure, effective stress, porosity, fracture statistics and hydrocarbon distribution. All these properties, in turn, affect the mechanical wave velocity and sediment density profiles for a sedimentary basin. The present-day state of the sedimentary basin is imaged by reflection seismology data to a high degree of resolution, but it does not give any indication of the processes that contributed to the evolution of the basin or causes for heterogeneities within the basin that are being imaged. Using texture and fluid properties predicted by our Basin RTM simulator, we generate synthetic seismograms. Linear correlation using power spectra as an error measure and an efficient quadratic optimization technique are found to be most effective in determining the optimal value of the tectonic parameters. Preliminary 1-D studies indicate that one can determine the geothermal gradient even in the presence of observation and numerical uncertainties. The algorithm succeeds even when the synthetic data has detailed information only in a limited depth interval and has a different dominant frequency in the synthetic and observed seismograms. The methodology presented here even works when the basin input data contains only 75 per cent of the stratigraphic layering information compared with the actual basin in a limited depth interval.

Identification of Photosynthetic Plankton Communities Using Sedimentary Ancient DNA and Their Response to late-Holocene Climate Change on the Tibetan Plateau

PubMed Central

Hou, Weiguo; Dong, Hailiang; Li, Gaoyuan; Yang, Jian; Coolen, Marco J. L.; Liu, Xingqi; Wang, Shang; Jiang, Hongchen; Wu, Xia; Xiao, Haiyi; Lian, Bin; Wan, Yunyang

2014-01-01

Sediments from Tibetan lakes in NW China are potentially sensitive recorders of climate change and its impact on ecosystem function. However, the important plankton members in many Tibetan Lakes do not make and leave microscopically diagnostic features in the sedimentary record. Here we established a taxon-specific molecular approach to specifically identify and quantify sedimentary ancient DNA (sedaDNA) of non-fossilized planktonic organisms preserved in a 5-m sediment core from Kusai Lake spanning the last 3100 years. The reliability of the approach was validated with multiple independent genetic markers. Parallel analyses of the geochemistry of the core and paleo-climate proxies revealed that Monsoon strength-driven changes in nutrient availability, temperature, and salinity as well as orbitally-driven changes in light intensity were all responsible for the observed temporal changes in the abundance of two dominant phytoplankton groups in the lake, Synechococcus (cyanobacteria) and Isochrysis (haptophyte algae). Collectively our data show that global and regional climatic events exhibited a strong influence on the paleoecology of phototrophic plankton in Kusai Lake. PMID:25323386

Geology and geochemistry of three sedimentary-rock-hosted disseminated gold deposits in Guizhou Province, People's Republic of China

USGS Publications Warehouse

Ashley, R.P.; Cunningham, C.G.; Bostick, N.H.; Dean, W.E.; Chou, I.-Ming

1991-01-01

Five sedimentary-rock-hosted disseminated gold deposits have been discovered since 1980 in southwestern Guizhou Province (PRC). Submicron-sized gold is disseminated in silty carbonate and carbonaceous shale host rocks of Permian and Triassic age. Arsenic, antimony, mercury, and thallium accompany the gold. Associated hydrothermal alteration resulted in decarbonatization of limestone, silicification, and argillization, and depletion of base metals, barium, and many other elements. Organic material occurs in most host rocks and ores. It was apparently devolatilized during a regional heating event that preceded hydrothermal activity, and thus was not mobilized during mineralization, and did not affect gold deposition. The geologic setting of the Guizhou deposits includes many features that are similar to those of sedimentary-rock-hosted deposits of the Great Basin, western United States. The heavy-element suite that accompanies gold is the same, but base metals are even scarcer in the Guizhou deposits than they are in U.S. deposits. The Guizhou deposits discovered to date are smaller than most U.S. deposits and have no known spatially associated igneous rocks. ?? 1991.

Summary of the geology and resources of uranium in the San Juan Basin and adjacent region, New Mexico, Arizona, Utah, and Colorado

USGS Publications Warehouse

Ridgley, Jennie L.; Green, M.W.; Pierson, C.T.; Finch, W.I.; Lupe, R.D.

1978-01-01

The San Juan Basin and adjacent region lie predominantly in the southeastern part of the uranium-rich Colorado Plateau of New Mexico, Arizona, Utah, and Colorado. Underlying the province are rocks of the Precambrian basement complex composed mainly of igneous and metamorphic rocks; a thickness of about 3,600 meters of generally horizontal Paleozoic, Mesozoic, and Cenozoic sedimentary rocks; and a variety of Upper Cretaceous and Cenozoic igneous rocks. Sedimentary rocks of the sequence are commonly eroded and well exposed near the present basin margins where Tertiary tectonic activity has uplifted, folded, and faulted the sequence into its present geologic configuration of basins, platforms, monoclines, and other related structural features. Sedimentary rocks of Jurassic age in the southern part of the San Juan Basin contain the largest uranium deposits in the United States, and offer the promise of additional uranium deposits. Elsewhere in the basin and the adjacent Colorado Plateau, reserves and resources of uranium are known primarily in Triassic, Jurassic, and Cretaceous strata. Only scattered occurrences of uranium are known in Paleozoic

Records of Triassic volcanism in Pangean Great Lakes, and implications for reconstructing the distal effects of Large Igneous Provinces

NASA Astrophysics Data System (ADS)

Whiteside, J. H.; Percival, L.; Kinney, S.; Olsen, P. E.; Mather, T. A.; Philpotts, A.

2017-12-01

Documentation of the precise timing of volcanic eruptions in sedimentary records is key for linking volcanic activity to both historical and geological episodes of environmental change. Deposition of tuffs in sediments, and sedimentary enrichment of trace metals linked to igneous processes, are both commonly used for such correlations. In particular, sedimentary mercury (Hg) enrichments have been used as a marker for volcanic activity from Large Igneous Provinces (LIPs) to support their link to episodes of major climate change and mass extinction in the geological record. However, linking such enrichments to a specific eruption or eruption products is often challenging or impossible. In this study, the mercury records from two exactly contemporaneous latest Triassic-earliest Jurassic rift lakes are presented. Both sedimentary records feature igneous units proposed to be related to the later (Early Jurassic) stages of volcanism of the Central Atlantic Magmatic Province (CAMP). These CAMP units include a small tuff unit identified by thin-section petrology and identified at 10 localities over a distance of over 200 km, and a major CAMP basalt flow overlying this tuff (and dated at 200.916±0.064 Ma) which is also known across multiple sedimentary basins in both North America and Morocco and is thought to have been emplaced about 120 kyr after the tuff. A potential stratigraphic correlation between Hg enrichments and the igneous units is considered, and compared to the established records of mercury enrichments from the latest Triassic that are thought to be coeval with the earlier stages of CAMP volcanism. Investigating the Hg records of sedimentary successions containing tuffs and basalt units is an important step for demonstrating whether the mercury emissions from specific individual volcanic eruptions in the deep past can be identified in the geological record, and are thus important tools for interpreting the causes of associated past geological events, such as mass extinctions.

The Rock Elm meteorite impact structure, Wisconsin: Geology and shock-metamorphic effects in quartz

USGS Publications Warehouse

French, B.M.; Cordua, W.S.; Plescia, J.B.

2004-01-01

The Rock Elm structure in southwest Wisconsin is an anomalous circular area of highly deformed rocks, ???6.5 km in diameter, located in a region of virtually horizontal undeformed sedimentary rocks. Shock-produced planar microstructures (PMs) have been identified in quartz grains in several lithologies associated with the structure: sandstones, quartzite pebbles, and breccia. Two distinct types of PMs are present: P1 features, which appear identical to planar fractures (PFs or cleavage), and P2 features, which are interpreted as possible incipient planar deformation features (PDFs). The latter are uniquely produced by the shock waves associated with meteorite impact events. Both types of PMs are oriented parallel to specific crystallographic planes in the quartz, most commonly to c(0001), ??112??2, and r/z101??1. The association of unusual, structurally deformed strata with distinct shock-produced microdeformation features in their quartz-bearing rocks establishes Rock Elm as a meteorite impact structure and supports the view that the presence of multiple parallel cleavages in quartz may be used independently as a criterion for meteorite impact. Preliminary paleontological studies indicate a minimum age of Middle Ordovician for the Rock Elm structure. A similar age estimate (450-400 Ma) is obtained independently by combining the results of studies of the general morphology of complex impact structures with estimated rates of sedimentation for the region. Such methods may be applicable to dating other old and deeply eroded impact structures formed in sedimentary target rocks.

Corrected Late Triassic latitudes for continents adjacent to the North Atlantic.

PubMed

Kent, Dennis V; Tauxe, Lisa

2005-01-14

We use a method based on a statistical geomagnetic field model to recognize and correct for inclination error in sedimentary rocks from early Mesozoic rift basins in North America, Greenland, and Europe. The congruence of the corrected sedimentary results and independent data from igneous rocks on a regional scale indicates that a geocentric axial dipole field operated in the Late Triassic. The corrected paleolatitudes indicate a faster poleward drift of approximately 0.6 degrees per million years for this part of Pangea and suggest that the equatorial humid belt in the Late Triassic was about as wide as it is today.

Up-Scaling Geochemical Reaction Rates for Carbon Dioxide (CO2) in Deep Saline Aquifers

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

Peters, Catherine A

2013-02-28

Geochemical reactions in deep subsurface environments are complicated by the consolidated nature and mineralogical complexity of sedimentary rocks. Understanding the kinetics of these reactions is critical to our ability to make long-term predictions about subsurface processes such as pH buffering, alteration in rock structure, permeability changes, and formation of secondary precipitates. In this project, we used a combination of experiments and numerical simulation to bridge the gap between our knowledge of these reactions at the lab scale and rates that are meaningful for modeling reactive transport at core scales. The focus is on acid-driven mineral dissolution, which is specifically relevantmore » in the context of CO2-water-rock interactions in geological sequestration of carbon dioxide. The project led to major findings in three areas. First, we modeled reactive transport in pore-network systems to investigate scaling effects in geochemical reaction rates. We found significant scaling effects when CO2 concentrations are high and reaction rates are fast. These findings indicate that the increased acidity associated with geological sequestration can generate conditions for which proper scaling tools are yet to be developed. Second, we used mathematical modeling to investigate the extent to which SO2, if co-injected with CO2, would acidify formation brines. We found that there exist realistic conditions in which the impact on brine acidity will be limited due to diffusion rate-limited SO2 dissolution from the CO2 phase, and the subsequent pH shift may also be limited by the lack of availability of oxidants to produce sulfuric acid. Third, for three Viking sandstones (Alberta sedimentary basin, Canada), we employed backscattered electron microscopy and energy dispersive X-ray spectroscopy to statistically characterize mineral contact with pore space. We determined that for reactive minerals in sedimentary consolidated rocks, abundance alone is not a good predictor of mineral accessible surface area, and should not be used in reactive transport modeling. Our work showed that reaction rates would be overestimated by three to five times.« less

Sedimentation, bioturbation, and sedimentary fabric evolution on a modern mesotidal mudflat: A multi-tracer study of processes, rates, and scales

NASA Astrophysics Data System (ADS)

Bentley, Samuel J.; Swales, Andrew; Pyenson, Benjamin; Dawe, Justin

2014-03-01

A study of muddy tidal-flat sedimentation and bioturbation was undertaken in the Waitetuna Arm of Raglan Harbor, New Zealand, to evaluate the physical and biological processes that control cycling of sediment between the intertidal seabed and sediment-water interface, and also the formation of tidal flat sedimentary fabric and fine-scale stratigraphy. Cores were collected along an intertidal transect, and analyzed for sedimentary fabric, 210Pb and 7Be radiochemical distributions, and grain size. At the same locations, a new approach for time-series core-X-radiography study was undertaken (spanning 191 days), using magnetite-rich sand as a tracer for sedimentation and bioturbation processes in shallow tidal flat sediments. Sedimentary fabric consists of a shallow stratified layer overlying a deeper zone of intensely bioturbated shelly mud. Bioadvection mixes the deeper zone and contributes fine sediment to the surface stratified layer, via biodeposition. Physical resuspension and deposition of surface muds by wave and tidal flow are also likely contributors to formation of the surficial stratified layer, but physical stratification is not observed below this depth. The deliberate tracer study allowed calculation of bioadvection rates that control strata formation, and can be used to model diagenetic processes. Results suggest that the upper ˜15 cm of seabed can be fully mixed over timescales <1.75 y. Such mixing will erase pre-existing sedimentary fabric and transport buried sediment and chemical compounds back to the tidal-flat surface. Shallow biodiffusion also exists, but produces much slower and shallower mass transport. Best fits for 210Pb profiles using a diagenetic bioadvection/sedimentation model and independently measured tiered bioadvection rates suggest that sediment accumulation rates (SARs) on the tidal flat are ˜0.25 cm/y, near the low end of contemporary New Zealand muddy intertidal SARs. Frequent deposition and erosion of the surface layer demonstrates that long-term sediment accumulation captures only a small fraction of sediment deposited at any one time. Model results also suggest that our magnetite tracer method may slightly underestimate short-term shallow mixing rates (demonstrated by 7Be profiles), and slightly overestimate longer-term, deeper bioturbation rates (demonstrated by 210Pb profiles).

Hyper-spectral imaging: A promising tool for quantitative pigment analysis of varved lake sediments

NASA Astrophysics Data System (ADS)

Butz, Christoph; Grosjean, Martin; Tylmann, Wojciech

2015-04-01

Varved lake sediments are good archives for past environmental and climate conditions from annual to multi-millennial scales. Among other proxies, concentrations of sedimentary photopigments have been used for temperature reconstructions. However, obtaining well calibrated annually resolved records from sediments still remains challenging. Most laboratory methods used to analyse lake sediments require physical subsampling and are destructive in the process. Hence, temporal resolution and number of data are limited by the amount of material available in the core. Furthermore, for very low sediment accumulation rates annual subsampling is often very difficult or even impossible. To address these problems we explore hyper-spectral imaging as a non-destructive method to analyse lake sediments based on their reflectance spectra in the visible and near infrared spectrum. In contrast to other scanning methods like X-ray fluorescence, VIS/NIR reflectance spectrometry distinguishes between biogeochemical substances rather than single elements. Among others Rein (2003) has shown that VIS-RS can be used to detect relative concentrations of sedimentary photopigments (e.g. chlorins, carotenoids) and clay minerals. In this study hyper-spectral imaging is used to infer ecological proxy data from reflectance spectra of varved lake sediments. Hyper-spectral imaging permits the measurement of an entire sediment core in a single run at high spatial (30x30µm/pixel) and spectral resolutions (~2.8nm) within the visual to near infrared spectrum (400-1000nm). This allows the analysis of data time series and spatial mapping of sedimentary substances (e.g. chlorophylls/bacterio-chlorophylls and diagenetic products) at sub-varve scales. The method is demonstrated on two varved lake sediments from northern Poland showing the distributions of relative concentrations of two types of sedimentary pigments (Chlorophyll-a + derivatives and Bacterio-pheophytin-a) within individual varve years. The relative concentrations from the spectral data set have then been calibrated with absolute concentrations derived by High-Performance-Liquid-Chromatography (HPLC). This results in very high-resolution data sets of absolute sedimentary pigment concentrations suitable for the analysis of seasonal pigment variations.

A Lithology Based Map Unit Schema For Onegeology Regional Geologic Map Integration

NASA Astrophysics Data System (ADS)

Moosdorf, N.; Richard, S. M.

2012-12-01

A system of lithogenetic categories for a global lithological map (GLiM, http://www.ifbm.zmaw.de/index.php?id=6460&L=3) has been compiled based on analysis of lithology/genesis categories for regional geologic maps for the entire globe. The scheme is presented for discussion and comment. Analysis of units on a variety of regional geologic maps indicates that units are defined based on assemblages of rock types, as well as their genetic type. In this compilation of continental geology, outcropping surface materials are dominantly sediment/sedimentary rock; major subdivisions of the sedimentary category include clastic sediment, carbonate sedimentary rocks, clastic sedimentary rocks, mixed carbonate and clastic sedimentary rock, colluvium and residuum. Significant areas of mixed igneous and metamorphic rock are also present. A system of global categories to characterize the lithology of regional geologic units is important for Earth System models of matter fluxes to soils, ecosystems, rivers and oceans, and for regional analysis of Earth surface processes at global scale. Because different applications of the classification scheme will focus on different lithologic constituents in mixed units, an ontology-type representation of the scheme that assigns properties to the units in an analyzable manner will be pursued. The OneGeology project is promoting deployment of geologic map services at million scale for all nations. Although initial efforts are commonly simple scanned map WMS services, the intention is to move towards data-based map services that categorize map units with standard vocabularies to allow use of a common map legend for better visual integration of the maps (e.g. see OneGeology Europe, http://onegeology-europe.brgm.fr/ geoportal/ viewer.jsp). Current categorization of regional units with a single lithology from the CGI SimpleLithology (http://resource.geosciml.org/201202/ Vocab2012html/ SimpleLithology201012.html) vocabulary poorly captures the lithologic character of such units in a meaningful way. A lithogenetic unit category scheme accessible as a GeoSciML-portrayal-based OGC Styled Layer Description resource is key to enabling OneGeology (http://oneGeology.org) geologic map services to achieve a high degree of visual harmonization.

GEOCHEMICAL FACTORS GOVERNING METHYL MERCURY PRODUCTION IN MERCURY CONTAMINATED SEDIMENTS

EPA Science Inventory

Bench scale experiments were conducted to improve our understanding of aquatic mercury transformation processes (biotic and abiotic), specifically those factors which govern the production of methyl mercury (MeHg) in sedimentary environments. The greatest cause for concern regar...

Complex Rayleigh Waves Produced by Shallow Sedimentary Basins and their Potential Effects on Mid-Rise Buildings

NASA Astrophysics Data System (ADS)

Kohler, M. D.; Castillo, J.; Massari, A.; Clayton, R. W.

2017-12-01

Earthquake-induced motions recorded by spatially dense seismic arrays in buildings located in the northern Los Angeles basin suggest the presence of complex, amplified surface wave effects on the seismic demand of mid-rise buildings. Several moderate earthquakes produced large-amplitude, seismic energy with slow shear-wave velocities that cannot be explained or accurately modeled by any published 3D seismic velocity models or by Vs30 values. Numerical experiments are conducted to determine if sedimentary basin features are responsible for these rarely modeled and poorly documented contributions to seismic demand computations. This is accomplished through a physics-based wave propagation examination of the effects of different sedimentary basin geometries on the nonlinear response of a mid-rise structural model based on an existing, instrumented building. Using two-dimensional finite-difference predictive modeling, we show that when an earthquake focal depth is near the vertical edge of an elongated and relatively shallow sedimentary basin, dramatically amplified and complex surface waves are generated as a result of the waveguide effect introduced by this velocity structure. In addition, for certain source-receiver distances and basin geometries, body waves convert to secondary Rayleigh waves that propagate both at the free-surface interface and along the depth interface of the basin that show up as multiple large-amplitude arrivals. This study is motivated by observations from the spatially dense, high-sample-rate acceleration data recorded by the Community Seismic Network, a community-hosted strong-motion network, currently consisting of hundreds of sensors located in the southern California area. The results provide quantitative insight into the causative relationship between a sedimentary basin shape and the generation of Rayleigh waves at depth, surface waves at the free surface, scattered seismic energy, and the sensitivity of building responses to each of these.

Benthic foraminiferal response to sedimentary disturbance in the Capbreton canyon (Bay of Biscay, NE Atlantic)

NASA Astrophysics Data System (ADS)

Duros, P.; Silva Jacinto, R.; Dennielou, B.; Schmidt, S.; Martinez Lamas, R.; Gautier, E.; Roubi, A.; Gayet, N.

2017-02-01

Living (Rose Bengal stained) and dead benthic foraminifera were investigated at 6 deep-sea sites sampled in the Capbreton canyon area (Bay of Biscay, France). Three sites were located along the canyon axis at 301 m, 983 m and 1478 m and 3 stations were positioned on adjacent terraces at 251 m, 894 m and 1454 m. Sedimentary features indicate that frequent sedimentary disturbances of different magnitudes occur along the Capbreton canyon axis and adjacent terraces. Such environmental conditions cause the presence of very particular benthic environments. Along the 6 studied sites, different foraminiferal responses to various sedimentary patterns are observed revealing the complexity of this canyon environment. Some sites (Gitan 3 (canyon axis), Gitan 5 (canyon axis) and Gitan 6 (terrace)) are characterized by moderate to low standing stocks and low diversity and are mainly dominated by pioneer taxa such as Fursenkoina brady, Reophax dentaliniformis and Technitella melo suggesting a recent response to turbidite deposits recorded at these sites. Others sites (Gitan 1 and Gitan 2) show extremely high standing stocks and are mainly dominated by the opportunistic Bolivina subaenariensis and Bulimina marginata. Such faunal characteristics belonging to a more advanced stage of ecosystem colonization indicates strongly food-enriched sediment but extremely unstable conditions. Moderate standing stocks and diverse assemblage composed of species such as Uvigerina mediterranea and U. peregrina has only been observed at the terrace site Gitan 4. More stable sedimentary conditions recorded at this terrace seem to be suitable to the development of a dense and diverse foraminiferal community. Numerous neritic allochtonous species were observed in the dead foraminiferal fauna. These allochthonous species mainly originate from shelf areas (<60 m).

Change in Sediment Provenance Near the Current Estuary of Yellow River Since the Holocene Transgression

NASA Astrophysics Data System (ADS)

Song, Sheng; Feng, Xiuli; Li, Guogang; Liu, Xiao; Xiao, Xiao; Feng, Li

2018-06-01

Sedimentary sequence and sediment provenance are important factors when it comes to the studies on marine sedimentation. This paper studies grain size distribution, lithological characteristics, major and rare earth elemental compositions, micropaleontological features and 14C ages in order to examine sedimentary sequence and sediment provenance of the core BH6 drilled at the mouth of the Yellow River in Bohai Sea. According to the grain size and the micropaleontological compositions, 4 sedimentary units have been identified. Unit 1 (0-8.08 mbsf) is of the delta sedimentary facies, Unit 2 (8.08-12.08 mbsf) is of the neritic shelf facies, Unit 3 (12.08-23.85 mbsf) is of near-estuary beach-tidal facies, and Unit 4 (23.85 mbsf-) is of the continental lake facies. The deposits from Unit 1 to Unit 3 have been found to be marine strata formed after the Holocene transgression at about 10 ka BP, while Unit 4 is continental lacustrine deposit formed before 10 ka BP. The provenances of core BH6 sediments show properties of the continental crust and vary in different sedimentary periods. For Unit 4 sediments, the source regions are dispersed while the main provenance is not clear, although the parent rock characteristics of a few samples are similar to the Luanhe River sediments. For Unit 3, sediments at 21.1-23.85 mbsf have been mainly transported from the Liaohe River, while sediments above 21.1 mbsf are mainly from the Yellow River and partially from the Liaohe River. For Unit 2, the sediments have been mainly transported from the Yellow River, with a small amount from other rivers. For Unit 1, the provenance is mainly the Yellow River catchment. These results help in better understanding the evolution of the Yellow River Delta.

Sedimentary Facies Mapping Based on Tidal Channel Network and Topographic Features

NASA Astrophysics Data System (ADS)

Ryu, J. H.; Lee, Y. K.; Kim, K.; Kim, B.

2015-12-01

Tidal flats on the west coast of Korea suffer intensive changes in their surface sedimentary facies as a result of the influence of natural and artificial changes. Spatial relationships between surface sedimentary facies distribution and benthic environments were estimated for the open-type Ganghwa tidal flat and semi closed-type Hwangdo tidal flat, Korea. In this study, we standardized the surface sedimentary facies and tidal channel index of the channel density, distance, thickness and order. To extract tidal channel information, we used remotely sensed data, such as those from the Korea Multi-Purpose Satellite (KOMPSAT)-2, KOMPSAT-3, and aerial photographs. Surface sedimentary facies maps were generated based on field data using an interpolation method.The tidal channels in each sediment facies had relatively constant meandering patterns, but the density and complexity were distinguishable. The second fractal dimension was 1.7-1.8 in the mud flat, about 1.4 in the mixed flat, and about 1.3 in the sand flat. The channel density was 0.03-0.06 m/m2 in the mud flat and less than 0.02 m/m2 in the mixed and sand flat areas of the two test areas. Low values of the tidal channel index, which indicated a simple pattern of tidal channel distribution, were identified at areas having low elevation and coarse-grained sediments. By contrast, high values of the tidal channel index, which indicated a dendritic pattern of tidal channel distribution, were identified at areas having high elevation and fine-grained sediments. Surface sediment classification based on remotely sensed data must circumspectly consider an effective critical grain size, water content, local topography, and intertidal structures.

Integrated characterization of the geologic framework of a contaminated site in West Trenton, New Jersey

USGS Publications Warehouse

Ellefsen, Karl J.; Burton, William C.; Lacombe, Pierre J.

2012-01-01

Fractured sedimentary bedrock and groundwater at the former Naval Air Warfare Center in West Trenton, New Jersey (United States of America) are contaminated with chlorinated solvents. Predicting contaminant migration or removing the contaminants requires an understanding of the geology. Consequently, the geologic framework near the site was characterized with four different methods having different spatial scales: geologic field mapping, analyses of bedrock drill core, analyses of soil and regolith, and S-wave refraction surveys. A fault zone is in the southeast corner of the site and separates two distinct sedimentary formations; the fault zone dips (steeply) southeasterly, strikes northeasterly, and extends at least 550 m along its strike direction. Drill core from the fault zone is extensively brecciated and includes evidence of tectonic contraction. Approximately 300 m east of this fault zone is another fault zone, which offsets the contact between the two sedimentary formations. The S-wave refraction surveys identified both fault zones beneath soil and regolith and thereby provided constraints on their lateral extent and location.

Dune-Yardang Interactions in Becquerel Crater, Mars.

PubMed

Urso, Anna; Chojnacki, Matthew; Vaz, David A

2018-01-01

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind-driven activity. Resultantly, Martian landscapes often exhibit large-scale aeolian features, including yardang landforms carved from sedimentary-layered deposits. High-resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune-yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16-40 μm yr -1 ) would yield a formation time of 1.8-4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size-frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian-driven landscape evolution on Mars.

Dune-Yardang Interactions in Becquerel Crater, Mars

PubMed Central

Urso, Anna; Chojnacki, Matthew; Vaz, David A.

2018-01-01

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars’ recent history has been dominated by wind-driven activity. Resultantly, Martian landscapes often exhibit large-scale aeolian features, including yardang landforms carved from sedimentary-layered deposits. High-resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune-yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16–40 μm yr−1) would yield a formation time of 1.8–4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size-frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian-driven landscape evolution on Mars. PMID:29564199

Dune-Yardang Interactions in Becquerel Crater, Mars

NASA Astrophysics Data System (ADS)

Urso, Anna; Chojnacki, Matthew; Vaz, David A.

2018-02-01

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind-driven activity. Resultantly, Martian landscapes often exhibit large-scale aeolian features, including yardang landforms carved from sedimentary-layered deposits. High-resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune-yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16-40 μm yr-1) would yield a formation time of 1.8-4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size-frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian-driven landscape evolution on Mars.

The European Alps as an interrupter of the Earth's conductivity structures

NASA Astrophysics Data System (ADS)

Al-Halbouni, D.

2013-07-01

Joint interpretation of magnetotelluric and geomagnetic depth sounding results in the period range of 10-105 s in the Western European Alps offer new insights into the conductivity structure of the Earth's crust and mantle. This first large scale electromagnetic study in the Alps covers a cross-section from Germany to northern Italy and shows the importance of the alpine mountain chain as an interrupter of continuous conductors. Poor data quality due to the highly crystalline underground is overcome by Remote Reference and Robust Processing techniques and the combination of both electromagnetic methods. 3-D forward modeling reveals on the one hand interrupted dipping crustal conductors with maximum conductances of 4960 S and on the other hand a lithosphere thickening up to 208 km beneath the central Western Alps. Graphite networks arising from Palaeozoic sedimentary deposits are considered to be accountable for the occurrence of high conductivity and the distribution pattern of crustal conductors. The influence of huge sedimentary Molasse basins on the electromagnetic data is suggested to be minor compared with the influence of crustal conductors. Dipping direction (S-SE) and maximum angle (10.1°) of the northern crustal conductor reveal the main thrusting conditions beneath the Helvetic Alps whereas the existence of a crustal conductor in the Briançonnais supports theses about its belonging to the Iberian Peninsula. In conclusion the proposed model arisen from combined 3-D modeling of noise corrected electromagnetic data is able to explain the geophysical influence of various structural features in and around the Western European Alps and serves as a background for further upcoming studies.

Mapping the mineralogy and lithology of Canyonlands, Utah with imaging spectrometer data and the multiple spectral feature mapping algorithm

NASA Technical Reports Server (NTRS)

Clark, Roger N.; Swayze, Gregg A.; Gallagher, Andrea

1992-01-01

The sedimentary sections exposed in the Canyonlands and Arches National Parks region of Utah (generally referred to as 'Canyonlands') consist of sandstones, shales, limestones, and conglomerates. Reflectance spectra of weathered surfaces of rocks from these areas show two components: (1) variations in spectrally detectable mineralogy, and (2) variations in the relative ratios of the absorption bands between minerals. Both types of information can be used together to map each major lithology and the Clark spectral features mapping algorithm is applied to do the job.

Scale dependant compensational stacking of channelized sedimentary deposits

NASA Astrophysics Data System (ADS)

Wang, Y.; Straub, K. M.; Hajek, E. A.

2010-12-01

Compensational stacking, the tendency for sediment transport system to preferentially fill topographic lows, thus smoothing out topographic relief is a concept used in the interpretation of the stratigraphic record. Recently, a metric was developed to quantify the strength of compensation in sedimentary basins by comparing observed stacking patterns to what would be expected from simple, uncorrelated stacking. This method uses the rate of decay of spatial variability in sedimentation between picked depositional horizons with increasing vertical stratigraphic averaging distance. We explore how this metric varies as a function of stratigraphic scale using data from physical experiments, stratigraphy exposed in outcrops and numerical models. In an experiment conducted at Tulane University’s Sediment Dynamics Laboratory, the topography of a channelized delta formed by weakly cohesive sediment was monitored along flow-perpendicular transects at a high temporal resolution relative to channel kinematics. Over the course of this experiment a uniform relative subsidence pattern, designed to isolate autogenic processes, resulted in the construction of a stratigraphic package that is 25 times as thick as the depth of the experimental channels. We observe a scale-dependence on the compensational stacking of deposits set by the system’s avulsion time-scale. Above the avulsion time-scale deposits stack purely compensationally, but below this time-scale deposits stack somewhere between randomly and deterministically. The well-exposed Ferris Formation (Cretaceous/Paleogene, Hanna Basin, Wyoming, USA) also shows scale-dependant stratigraphic organization which appears to be set by an avulsion time-scale. Finally, we utilize simple object-based models to illustrate how channel avulsions influence compensation in alluvial basins.

Eifel maars: Quantitative shape characterization of juvenile ash particles (Eifel Volcanic Field, Germany)

NASA Astrophysics Data System (ADS)

Rausch, Juanita; Grobéty, Bernard; Vonlanthen, Pierre

2015-01-01

The Eifel region in western central Germany is the type locality for maar volcanism, which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water (i.e. phreatomagmatic eruptions). Sedimentary structures, deposit features and particle morphology found in many maar deposits of the West Eifel Volcanic Field (WEVF), in contrast to deposits in the East Eifel Volcanic Field (EEVF), lack the diagnostic criteria of typical phreatomagmatic deposits. The aim of this study was to determine quantitatively the shape of WEVF and EEVF maar ash particles in order to infer the governing eruption style in Eifel maar volcanoes. The quantitative shape characterization was done by analyzing fractal dimensions of particle contours (125-250 μm sieve fraction) obtained from Scanning electron microscopy (SEM) and SEM micro-computed tomography (SEM micro-CT) images. The fractal analysis (dilation method) and the fractal spectrum technique confirmed that the WEVF and EEVF maar particles have contrasting multifractal shapes. Whereas the low small-scale dimensions of EEVF particles (Eppelsberg Green Unit) coincide with previously published values for phreatomagmatic particles, the WEVF particles (Meerfelder Maar, Pulvermaar and Ulmener Maar) have larger values indicating more complex small-scale features, which are characteristic for magmatic particles. These quantitative results are strengthening the qualitative microscopic observations, that the studied WEVF maar eruptions are rather dominated by magmatic processes. The different eruption styles in the two volcanic fields can be explained by the different geological and hydrological settings found in both regions and the different chemical compositions of the magmas.

Crater Mound Formation by Wind Erosion on Mars

NASA Astrophysics Data System (ADS)

Steele, L. J.; Kite, E. S.; Michaels, T. I.

2018-01-01

Most of Mars' ancient sedimentary rocks by volume are in wind-eroded sedimentary mounds within impact craters and canyons, but the connections between mound form and wind erosion are unclear. We perform mesoscale simulations of different crater and mound morphologies to understand the formation of sedimentary mounds. As crater depth increases, slope winds produce increased erosion near the base of the crater wall, forming mounds. Peak erosion rates occur when the crater depth is ˜2 km. Mound evolution depends on the size of the host crater. In smaller craters mounds preferentially erode at the top, becoming more squat, while in larger craters mounds become steeper sided. This agrees with observations where smaller craters tend to have proportionally shorter mounds and larger craters have mounds encircled by moats. If a large-scale sedimentary layer blankets a crater, then as the layer recedes across the crater it will erode more toward the edges of the crater, resulting in a crescent-shaped moat. When a 160 km diameter mound-hosting crater is subject to a prevailing wind, the surface wind stress is stronger on the leeward side than on the windward side. This results in the center of the mound appearing to "march upwind" over time and forming a "bat-wing" shape, as is observed for Mount Sharp in Gale crater.

Géodynamique et évolution thermique de la matière organique: exemple du bassin de Qasbat-Tadla, Maroc centralBasin geodynamics and thermal evolution of organic material: example from the Qasbat-Tadla Basin, central Morocco

NASA Astrophysics Data System (ADS)

Er-Raïoui, H.; Bouabdelli, M.; Bélayouni, H.; Chellai, H.

2001-05-01

Seismic data analysis of the Qasbat-Tadla Basin allows the deciphering of the main tectonic and sedimentary events that characterised the Hercynian orogen and its role in the basin's structural development. The global tectono-sedimentary framework involves structural evolution of an orogenic foreland basin and was the source of rising geotherms in an epizonal metamorphic environment. The complementary effects of these parameters has led to different source rock maturity levels, ranging from oil producing to graphite domains. Different maturity levels result from three distinct structural domains within the basin, each of which exhibit characteristic geodynamic features (tectonic contraints, rate of subsidence, etc.).

Micro-imager View: Layers in 'Vera Rubin Ridge,' Mars

NASA Image and Video Library

2017-09-13

This view of "Vera Rubin Ridge" from the Chemistry and Camera (ChemCam) instrument on NASA's Curiosity Mars rover shows multiple sedimentary layers and fracture-filling deposits of minerals. Buried layers of what is now a ridge became fractured, and the fractures were filled with mineral deposits precipitated from underground fluids that moved through the fractures. ChemCam's telescopic Remote Micro-Imager took the 10 component images of this mosaic on July 3, 2017, during the 1,745th Martian day, or sol, of Curiosity's work on Mars. The camera was about 377 feet (115 meters) away from the pictured portion of the ridge. The rover's location at the time, shown in a Sol 1741 traverse map, was west of the place where it began its ascent up the ridge about two months later. The scale bar at lower right indicates how wide a feature 9 inches (22.8 centimeters) in width would look in the middle portion of the scene. https://photojournal.jpl.nasa.gov/catalog/PIA21852

Geologic map of the Ponca quadrangle, Newton, Boone, and Carroll Counties, Arkansas

USGS Publications Warehouse

Hudson, Mark R.; Murray, Kyle E.

2003-01-01

This digital geologic map compilation presents new polygon (i.e., geologic map unit contacts), line (i.e., fault, fold axis, and structure contour), and point (i.e., structural attitude, contact elevations) vector data for the Ponca 7 1/2' quadrangle in northern Arkansas. The map database, which is at 1:24,000-scale resolution, provides geologic coverage of an area of current hydrogeologic, tectonic, and stratigraphic interest. The Ponca quadrangle is located in Newton, Boone, and Carroll Counties about 20 km southwest of the town of Harrison. The map area is underlain by sedimentary rocks of Ordovician, Mississippian, and Pennsylvanian age that were mildly deformed by a series of normal and strike-slip faults and folds. The area is representative of the stratigraphic and structural setting of the southern Ozark Dome. The Ponca quadrangle map provides new geologic information for better understanding groundwater flow paths and development of karst features in and adjacent to the Buffalo River watershed.

In situ, spatially resolved biosignature detection at the microbial scale

NASA Astrophysics Data System (ADS)

Williford, K. H.; Eigenbrode, J. L.; Hallmann, C.; Kitajima, K.; Kozdon, R.; Summons, R. E.; Kudryavstev, A.; Lepot, K.; Schopf, J.; Spicuzza, M.; Sugitani, K.; Ushikubo, T.; van Kranendonk, M.; Valley, J. W.

2013-12-01

Whether life has ever existed beyond Earth is one of the great human questions. The Science Definition Team (SDT) for the proposed NASA Mars 2020 rover mission recently announced a suggested approach for NASA to 'demonstrate significant technical progress towards the future return of scientifically selected, well-documented samples to Earth' in part 'to investigate whether Mars was ever inhabited by microbial life.' The SDT further recommended a per-sample volume of 8 cm3 [1] (e.g., a core with a diameter of 1 cm and length of 10 cm). Such samples would be the first available for scientific inquiry with the potential to definitively answer the fundamental question of astrobiology, and their small volume would necessitate analysis with non- or minimally destructive techniques. Potential biosignatures include 'chemical, isotopic, mineralogical, and morphological features that can be created by life and also appear to be inconsistent with nonbiological processes'[1]. Guidelines for biosignature detection in extraterrestrial samples derive in part from the search for evidence of life in the most ancient sedimentary rocks on Earth, wherein the most compelling case for biogenicity is made when these 'chemical, isotopic, mineralogical, and morphological features' occur in association. Sedimentary rocks deposited on Earth prior to ~3.5 billion years ago (i.e., when persistent surface water [e.g., 2] likely supported habitable environments on Mars) have only very rarely escaped severe alteration by metamorphism and metasomatism. Understanding how these processes have operated on Earth through strategic interrogation of biosignature alteration records in (meta)sedimentary rocks is thus a critical task in the search for extraterrestrial life. Here we present techniques for and results of in situ, spatially resolved, non- or minimally destructive detection of morphological, elemental, molecular, and light stable isotopic biosignatures, as well as records of alteration, in Precambrian sedimentary rocks from Earth in the context of the eventual analysis of samples returned from Mars. Sample acquisition and preparation, morphological analysis by conventional light, confocal laser, and electron microscopy, elemental analysis by energy and wavelength dispersive spectroscopy, molecular analysis by laser Raman microscopy, carbon isotope analysis of organic matter and carbonate minerals, and multiple sulfur isotope analysis of pyrite with secondary ion mass spectrometry will be discussed. New and recently published [3-5] results from the application of these methods towards detection of the signatures of life, environment, and alteration history in rocks containing putative and bona fide microfossils ranging in age from 0.6 to 3.5 billion years, and in rocks of similar age lacking morphological biosignatures, as well as our current understanding of key challenges and opportunities for future research will be reviewed. [1] Mustard, J.F. et al. 2013. Report of the Mars 2020 Science Definition Team, 154 pp., posted by MEPAG at http://mepag.jpl.nasa.gov/reports/MEP/Mars_2020_SDT_Report_Final.pdf. [2] Williams, R.M.E. et al. 2013. Science 340: 1068-1072. [3] Williford, K.H. et al. 2011. GCA 75: 5686-5705. [4] Williford, K.H. et al. 2013. GCA 104: 165-182. [5] Lepot, K. et al. 2013. GCA 112: 66-86.

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.

Millennial-scale climate variability during the Last Glacial period in the tropical Andes

NASA Astrophysics Data System (ADS)

Fritz, S. C.; Baker, P. A.; Ekdahl, E.; Seltzer, G. O.; Stevens, L. R.

2010-04-01

Millennial-scale climate variation during the Last Glacial period is evident in many locations worldwide, but it is unclear if such variation occurred in the interior of tropical South America, and, if so, how the low-latitude variation was related to its high-latitude counterpart. A high-resolution record, derived from the deep drilling of sediments on the floor of Lake Titicaca in the southern tropical Andes, is presented that shows clear evidence of millennial-scale climate variation between ˜60 and 20 ka BP. This variation is manifested by alternations of two interbedded sedimentary units. The two units have distinctive sedimentary, geochemical, and paleobiotic properties that are controlled by the relative abundance of terrigenous or nearshore components versus pelagic components. The sediments of more terrigenous or nearshore nature likely were deposited during regionally wetter climates when river transport of water and sediment was higher, whereas the sediments of more pelagic character were deposited during somewhat drier climates regionally. The majority of the wet periods inferred from the Lake Titicaca sediment record are correlated with the cold events in the Greenland ice cores and North Atlantic sediment cores, indicating that increased intensity of the South American summer monsoon was part of near-global scale climate excursions.

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.

Biosignatures in modern sulfates: texture, composition and depositional environments of gypsum deposits at Guerrero Negro, Baja, Mexico

NASA Astrophysics Data System (ADS)

Vogel, M. B.; Des Marais, D. J.; Jahnke, L. L.; Turk, K.; Kubo, M.

2007-12-01

Gypsum (CaSO4·H2O) is an important phase in biogeochemistry and sedimentology as a mineral sink for sulfur, a paleoclimatic indicator, and an endolithic niche for phototrophic and chemotrophic bacteria. Sulfate deposits are also important targets of exploration for evidence of habitable environments and life on Mars. Gypsum deposits from a range of sedimentary environments at the Guerrero Negro crystallizer ponds and sabkha settings were investigated for microscale structure and composition to differentiate fabrics formed under microbial influence from those formed under abiogenic conditions. Sub-sedimentary gypsum forms in sabkha environments as mm to cm scale selenite discs (termed bird beak gypsum; Warren, 2006) and selenite disc aggregates. Selenite discs and other sub-sedimentary gypsum are characterized by a sinuous axial microtexture and poikilitically enclosed detrital particles. Sub-aqueous gypsum forms as cements, granules (termed gypsooids), and massive botryoidal crusts that line the sediment water interface and margins of managed crystallizer ponds and natural anchialine pools. Sub-aqueous gypsum exhibits a wide range of textures and mineral/biofilm associations that include amorphous to euhedral, tabular, needle and lensoidal morphologies. Elemental sulfur forms rinds on prismatic, growth aligned gypsum twins and reticulate magnesian carbonate is interspersed with both twinned crystals and rosette aggregates in stratified sub-aqueous environments. Intracrystalline biofilms and cell material was observed in association with nearly all sub-aqueous morphologies but only scarce evidence has been found for intercrystalline microbial communities. Columnar microbial communities living in anchialine pools were found to host precipitation of mm scale gypsum granules in their EPS matrix. Fine scale gypsum textures are unlikely to persist through diagenetic alteration, but understanding their primary associations with sulfur and carbonates is necessary for interpreting sulfates or their replacement phases in the ancient record.

Precipitation variability within the West Pacific Warm Pool over the past 120 ka: Evidence from the Davao Gulf, southern Philippines

NASA Astrophysics Data System (ADS)

Fraser, Nicholas; Kuhnt, Wolfgang; Holbourn, Ann; Bolliet, Timothé; Andersen, Nils; Blanz, Thomas; Beaufort, Luc

2014-11-01

Proxy records of hydrologic variability in the West Pacific Warm Pool (WPWP) have revealed wide-scale changes in past convective activity in response to orbital and suborbital climate forcings. However, attributing proxy responses to regional changes in WPWP hydrology versus local variations in precipitation requires independent records linking the terrestrial and marine realms. We present high-resolution stable isotope, UK'37 sea surface temperature, X-ray fluorescence (XRF) core scanning, and coccolithophore-derived paleoproductivity records covering the past 120 ka from International Marine Global Change (IMAGES) Program Core MD06-3075 (6°29'N, 125°50'E, water depth 1878 m), situated in the Davao Gulf on the southern side of Mindanao. XRF-derived log(Fe/Ca) records provide a robust proxy for runoff-driven sedimentary discharge from Mindanao, while past changes in local productivity are associated with variable freshwater runoff and stratification of the surface layer. Significant precessional-scale variability in sedimentary discharge occurred during marine isotope stage (MIS) 5, with peaks in discharge contemporaneous with Northern Hemisphere summer insolation minima. We attribute these changes to the latitudinal migration of the Intertropical Convergence Zone (ITCZ) over the WPWP together with variability in the strength of the Walker circulation acting on precessional timescales. Between 60 and 15 ka sedimentary discharge at Mindanao was muted, displaying little orbital- or millennial-scale variability, likely in response to weakened precessional insolation forcing and lower sea level driving increased subsidence of air masses over the exposed Sunda Shelf. These results highlight the high degree of local variability in the precipitation response to past climate changes in the WPWP.

Sidescan-Sonar Imagery and Surficial Geologic Interpretations of the Sea Floor in Western Rhode Island Sound

USGS Publications Warehouse

McMullen, K.Y.; Poppe, L.J.; Haupt, T.A.; Crocker, J.M.

2009-01-01

The U.S. Geological Survey (USGS) and National Oceanic and Atmospheric Administration (NOAA) have been working together to interpret sea-floor geology along the northeastern coast of the United States. In 2004, the NOAA Ship RUDE completed survey H11322, a sidescan-sonar and bathymetric survey that covers about 60 square kilometers of the sea floor in western Rhode Island Sound. This report interprets sidescan-sonar and bathymetric data from NOAA survey H11322 to delineate sea-floor features and sedimentary environments in the study area. Paleozoic bedrock and Cretaceous Coastal Plain sediments in Rhode Island Sound underlie Pleistocene glacial drift that affects the distribution of surficial Holocene marine and transgressional sediments. The study area has three bathymetric highs separated by a channel system. Features and patterns in the sidescan-sonar imagery include low, moderate, and high backscatter; sand waves; scarps; erosional outliers; boulders; trawl marks; and dredge spoils. Four sedimentary environments in the study area, based on backscatter and bathymetric features, include those characterized by erosion or nondeposition, coarse-grained bedload transport, sorting and reworking, and deposition. Environments characterized by erosion or nondeposition and coarse-grained bedload transport are located in shallower areas and environments characterized by deposition are located in deeper areas; environments characterized by sorting and reworking processes are generally located at moderate depths.

Use of structural geology in exploration for and mining of sedimentary rock-hosted Au deposits

USGS Publications Warehouse

Peters, Stephen G.

2001-01-01

Structural geology is an important component in regional-, district- and orebody-scale exploration and development of sedimentary rock-hosted Au deposits.Identification of timing of important structural events in an ore district allows analysis and classification of fluid conduits and construction of genetic models for ore formation.The most practical uses of structural geology deal with measurement and definition of various elements that comprise orebodies, which can then be directly applied to ore-reserve estimation,ground control,grade control, safety issues,and mine planning.District- and regional-scale structural studies are directly applicable to long-term strategic planning,economic analysis,and land ownership. Orebodies in sedimentary rock-hosted Au deposits are discrete, hypogene, epigenetic masses usually hosted in a fault zone,breccia mass, or lithologic bed or unit. These attributes allow structural geology to be directly applied to the mining and exploration of sedimentary rock-hosted Au deposits. Internal constituents in orebodies reflect unique episodes relating to ore formation.The main internal constituents in orebodies are ore minerals, gangue, and alteration minerals that usually are mixed with one another in complex patterns, the relations among which may be used to interpret the processes of orebody formation and control.Controls of orebody location and shape usually are due to structural dilatant zones caused by changes in attitude, splays, lithologic contacts,and intersections of the host conduit or unit.In addition,conceptual parameters such as district fabric,predictable distances, and stacking also are used to understand the geometry of orebodies.Controls in ore districts and location and geometry of orebodies in ore districts can be predicted to various degrees by using a number of qualitative concepts such as internal and external orebody plunges,district plunge, district stacking, conduit classification, geochemical, geobarometric and geothermal gradients, and tectonic warps. These concepts have practical and empirical application in most mining districts where they are of use in the exploration for ore, but are of such broad and general application that they may not represent known or inferred ore formation processes. Close spatial relation among some sedimentary rock- hosted Au deposits and their host structures suggests that the structures and the orebodies are genetically linked because they may have shared the same developmental history. Examples of probable syn-deformational genesis and structural control of sedimentary rock-hosted Au deposits are in the large Betze deposit in the Carlin trend, Nevada and in the Lannigou, Jinlongshan, and Maanqiao Au deposits, China.

Mud Volcanoes - Analogs to Martian Cones and Domes (by the Thousands!)

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Oehler, Dorothy

2010-01-01

Mud volcanoes are mounds formed by low temperature slurries of gas, liquid, sediments and rock that erupt to the surface from depths of meters to kilometers. They are common on Earth, with estimates of thousands onshore and tens of thousands offshore. Mud volcanoes occur in basins with rapidly-deposited accumulations of fine-grained sediments. Such settings are ideal for concentration and preservation of organic materials, and mud volcanoes typically occur in sedimentary basins that are rich in organic biosignatures. Domes and cones, cited as possible mud volcanoes by previous authors, are common on the northern plains of Mars. Our analysis of selected regions in southern Acidalia Planitia has revealed over 18,000 such features, and we estimate that more than 40,000 occur across the area. These domes and cones strongly resemble terrestrial mud volcanoes in size, shape, morphology, associated flow structures and geologic setting. Geologic and mineralogic arguments rule out alternative formation mechanisms involving lava, ice and impacts. We are studying terrestrial mud volcanoes from onshore and submarine locations. The largest concentration of onshore features is in Azerbaijan, near the western edge of the Caspian Sea. These features are typically hundreds of meters to several kilometers in diameter, and tens to hundreds of meters in height. Satellite images show spatial densities of 20 to 40 eruptive centers per 1000 square km. Many of the features remain active, and fresh mud flows as long as several kilometers are common. A large field of submarine mud volcanoes is located in the Gulf of Cadiz, off the Atlantic coasts of Morocco and Spain. High-resolution sonar bathymetry reveals numerous km-scale mud volcanoes, hundreds of meters in height. Seismic profiles demonstrate that the mud erupts from depths of several hundred meters. These submarine mud volcanoes are the closest morphologic analogs yet found to the features in Acidalia Planitia. We are also conducting laboratory analyses of surface samples collected from mud volcanoes in Azerbaijan, Taiwan and Japan. X-ray diffraction, visible / near infrared reflectance spectroscopy and Raman spectroscopy show that the samples are dominated by mixed-layer smectite clays, along with quartz, calcite and pyrite. Thin section analysis by optical and scanning electron microscopy confirms the mineral identifications. These samples also contain chemical and morphological biosignatures, including common microfossils, with evidence of partial replacement by pyrite. The bulk samples contain approximately 1 wt% total organic carbon and 0.4 mg / gm volatile hydrocarbons. The thousands of features in Acidalia Planitia cited as analogous to terrestrial mud volcanoes clearly represent an important element in the sedimentary record of Mars. Their location, in the distal depocenter for massive Hesperian-age floods, suggests that they contain fine-grained sediments from a large catchment area in the martian highlands. We have proposed these features as a new class of exploration target that can provide access to minimally-altered material from significant depth. By analogy to terrestrial mud volcanoes, these features may also be excellent sites for the sampling martian organics and subsurface microbial life, if such exist or ever existed.

Roughness of stylolites: implications of 3D high resolution topography measurements.

PubMed

Schmittbuhl, J; Renard, F; Gratier, J P; Toussaint, R

2004-12-03

Stylolites are natural pressure-dissolution surfaces in sedimentary rocks. We present 3D high resolution measurements at laboratory scales of their complex roughness. The topography is shown to be described by a self-affine scaling invariance. At large scales, the Hurst exponent is zeta(1) approximately 0.5 and very different from that at small scales where zeta(2) approximately 1.2. A crossover length scale at around L(c)=1 mm is well characterized. Measurements are consistent with a Langevin equation that describes the growth of a stylolitic interface as a competition between stabilizing long range elastic interactions at large scales or local surface tension effects at small scales and a destabilizing quenched material disorder.

NGH: A Dynamic Factor in Deep Water Sediments & the Geological Record

NASA Astrophysics Data System (ADS)

Max, M. D.; Johnson, A. H.

2012-12-01

Prior to identification of natural gas hydrate (NGH) in marine sediments, gravity and tectonic forces were the recognized dynamic forces that could cause disruption in deep marine sediments. NGH introduces a new dynamic factor into continental slope and rise sediments as well as sediments in the deeper parts of some continental shelves. Two critical elements interplay to provide for a slow acting, long-term NGH-dynamic cyclical system. First, NGH forms spontaneously from dissolved natural gas generally in a passive manner without causing any other than very subtle alterations to the megascopic sediment structure. When NGH forms in either dispersed form in muddy sediments or in concentrated form in veins or nodules or in porosity in sandy sediments, it increases overall mechanical strength. Second, when it dissociates, mechanical strength weakens to the point where shear strengths can approach zero. Because the chemical reaction of NGH is highly reversible, changes in sea level that affect pressure, and changes in seafloor temperature can alter rapidly the tendency of NGH to either crystallize or dissociate, with consequent structural and morphological effects. The cyclicity of the Earth's climate introduces a mechanism for periodically injecting overpressured gas into marine sediments as the gas hydrate stability zones (GHSZ) undergoes changes to its thickness and depth. Natural climate change has the potential to produce overpressured natural gas converted from NGH in marine sediments periodically. In-place disruption would consist of disrupted sandy beds, chaotic textures on all scales, intrusion effects, limited mass flow features, dramatic sediment mixing not related to large scale movement and sediment redeposition from fluidized beds. Mobilization would involve larger scale sediment mass flow effects that would be indistinguishable from olistostromic melanges postulated to be initiated by tectonic or gravitational forces. The earliest interpretation of this fluidization type of large scale sediment disruption in the later part of the 1900s identified them as tectonic in origin. Subsequently, in the 1970s, it was recognized that the features were more likely a product of soft sediment deformation whose initiator might be gravity or tectonic forces, of 'tectonosedimentary' origin. The action of the NGH cycle to initiate sedimentary disruption may more readily explain many of these features in the geological record. Drill core taken across seismic reflection sediment redeposition features that otherwise show no tectonic activity related movement in abandoned GHSZ could provide important evidence for the long-term geological action of the NGH cycle.

Dunes on Titan: A major landform revealing atmospheric and surface processes

NASA Astrophysics Data System (ADS)

Radebaugh, Jani; Lorenz, Ralph; Arnold, Karl; Savage, Christopher; Williams, Brigitte

The surface of Saturn’s moon Titan is covered in features that herald an active atmosphere and perhaps interior, such as dunes, rivers, lakes, mountain chains, and possible cryovolcanoes. Examining the geomorphology of these features helps us approach an understanding of the processes that are occurring or have occurred in the atmosphere and subsurface. A major landform on Titan is dunes, composed of organic sands ultimately derived from upper atmospheric processing of methane, subsequently perhaps eroded from organic sedimentary layers by methane rainfall and fluvial flow. Dunes fill vast fields, termed sand seas, similar to those observed in the Sahara, Namibia, and the Arabian peninsula. The equatorial region of Titan contains five separate sand seas as observed by the Cassini Synthetic Aperture Radar (SAR), Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) instruments. Together these sand seas cover 14 percent of the surface, totaling 12 million km2, and each have areas on the scale of the Saharan Great Sand Sea. They adjoin each other through sediment pathways around landmasses, and these large-scale connections as well as individual dune interactions with topography indicate a general transport of sediment from west to east. Measurements of dune height, width and spacing in Cassini SAR images reveal all of Titan’s thousands of linear dunes are of the same population. This indicates there was general uniformity in the wind and sediment supply conditions that led to the current dune forms. Variations in the parametric values result from deviations from these conditions, in some locations where elevated terrains have deflected winds. Dunes and sand seas are among the stratigraphically youngest features on Titan, showing little evidence of being affected by impact cratering or fluvial flow. However, individual dunes may be relatively stable, as the reorganization time scale for these features on Earth can be tens to hundreds of thousands of years. Recent field studies of large, linear dunes in Namibia reveal a complex reworking of the dune interior, overprinted on the main duneform, as a result of changing regional conditions. These field studies, which can be undertaken at a level of detail not yet possible to obtain on Titan, help us better understand the history of similar landforms on a distant solar system body.

SMALL-SCALE HETEROGENEITY IN THE GEOCHEMISTRY OF SEAGRASS VEGETATED AND NON-VEGETATIVE SEDIMENTS: CAUSES AND CONSEQUENCES

EPA Science Inventory

In addition to nutrient and light availability, sedimentary biogeochemical processes can play an essential role in seagrass productivity. Previous investigations of the interactions between seagrasses and their underlying sediments have failed to clearly identify the spatio-tempo...

Comparison of CO2 trapping in highly heterogeneous reservoirs with Brooks-Corey and van Genuchten capillary pressure curves

NASA Astrophysics Data System (ADS)

Gershenzon, Naum; Soltanian, Mohamadreza; Ritzi, Robert, Jr.; Dominic, David

2015-04-01

Geological heterogeneities essentially affect the dynamics of a CO2 plume in subsurface environments. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to the performance of some deep saline reservoirs [1, 2]. Previously we showed how the dynamics of a CO2 plume, during and after injection, is influenced by the hierarchical and multi-scale stratal architecture in such reservoirs [3]. The results strongly suggest that representing these small scales (few cm in vertical direction and few meters in horizontal direction) features and representing how they are organized within a hierarchy of larger-scale features, is critical to understanding capillary trapping processes. The results also demonstrated the importance of using separate capillary pressure and relative permeability relationships for different textural facies types. Here we present the result of simulation of CO2 trapping in deep saline aquifers using two different conventional approaches, i.e. Brooks-Corey and van Genuchten, to capillary pressure. We showed that capillary trapping as well as dissolution rates are very different for the Brooks-Corey and van Genuchten approaches if reservoir consists from various species with different capillary pressure and relative permeability curves. We also found a dramatic difference in simulation time; using the van Genuchten approach improves convergence and thus reduces calculation time by one-two orders of magnitude. [1] Bridge, J.S. (2006), Fluvial facies models: Recent developments, in Facies Models Revisited, SEPM Spec. Publ., 84, edited by H. W. Posamentier and R. G. Walker, pp. 85-170, Soc. for Sediment. Geol. (SEPM), Tulsa, Okla [2] Ramanathan, R., A. Guin, R.W. Ritzi, D.F. Dominic, V.L. Freedman, T.D. Scheibe, and I.A. Lunt (2010), Simulating the heterogeneity in channel belt deposits: Part 1. A geometric-based methodology and code, Water Resources Research, v. 46, W04515. [3] Gershenzon N.I., M. Soltanian, R.W. Ritzi Jr., and D.F. Dominic (2014) Influence of small scale heterogeneity on CO2 trapping processes in deep saline aquifers, Energy Procedia, 59, 166 - 173.

Derivation of S and Pb in phanerozoic intrusion-related metal deposits from neoproterozoic sedimentary pyrite, Great Basin, United States

USGS Publications Warehouse

Vikre, Peter G.; Poulson, S.R.; Koenig, Alan E.

2011-01-01

The thick (≤8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high δ34S values (−11.6 to 40.8‰, >70% exceed 10‰; 51 analyses) derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes (207Pb/204Pb >19.2; 15 analyses) acquired from clastic detritus eroded from Precambrian cratonal rocks to the east-southeast. In the overlying Paleozoic section, Pb-Zn-Cu-Ag-Au deposits associated with Jurassic, Cretaceous, and Tertiary granitic intrusions (intrusion-related metal deposits) contain galena and other sulfide minerals with S and Pb isotope compositions similar to those of TDS sedimentary pyrite, consistent with derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits.Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb from sedimentary pyrite, and volatiles acquired from deeper crustal or mantle sources.In the central and eastern Great Basin, the wide distribution and high density of small to mid-sized vein, replacement, and skarn intrusion-related metal deposits in lower Paleozoic rocks that contain TDS sedimentary pyrite S and Pb reflect (1) prolific Jurassic, Cretaceous, and Tertiary magmatism, (2) a regional, substrate reservoir of S and Pb in permeable and homogeneous siliciclastic strata, and (3) relatively small scale concentration of substrate and magmatic components. Large intrusion-related metal deposits in the central and eastern Great Basin acquired S and most Pb from thicker lithospheric sections.

Determination of Cenozoic sedimentary structures using integrated geophysical surveys: A case study in the Barkol Basin, Xinjiang, China

NASA Astrophysics Data System (ADS)

Sun, Kai; Chen, Chao; Du, Jinsong; Wang, Limin; Lei, Binhua

2018-01-01

Thickness estimation of sedimentary basin is a complex geological problem, especially in an orogenic environment. Intense and multiple tectonic movements and climate changes result in inhomogeneity of sedimentary layers and basement configurations, which making sedimentary structure modelling difficult. In this study, integrated geophysical methods, including gravity, magnetotelluric (MT) sounding and electrical resistivity tomography (ERT), were used to estimate basement relief to understand the geological structure and evolution of the eastern Barkol Basin in China. This basin formed with the uplift of the eastern Tianshan during the Cenozoic. Gravity anomaly map revealed the framework of the entire area, and ERT as well as MT sections reflected the geoelectric features of the Cenozoic two-layer distribution. Therefore, gravity data, constrained by MT, ERT and boreholes, were utilized to estimate the spatial distribution of the Quaternary layer. The gravity effect of the Quaternary layer related to the Tertiary layer was later subtracted to obtain the residual anomaly for inversion. For the Tertiary layer, the study area was divided into several parts because of lateral difference of density contrasts. Gravity data were interpreted to determine the density contrast constrained by the MT results. The basement relief can be verified by geological investigation, including the uplift process and regional tectonic setting. The agreement between geophysical survey and prior information from geology emphasizes the importance of integrated geophysical survey as a complementary means of geological studies in this region.

Evidence of synsedimentary microbial activity and iron deposition in ferruginous crusts of the Late Cenomanian Utrillas Formation (Iberian Basin, central Spain)

NASA Astrophysics Data System (ADS)

García-Hidalgo, José F.; Elorza, Javier; Gil-Gil, Javier; Herrero, José M.; Segura, Manuel

2018-02-01

Ferruginous sandstones and crusts are prominent sedimentary features throughout the continental (braided)-coastal siliciclastic (estuarine-tidal) wedges of the Late Cenomanian Utrillas Formation in the Iberian Basin. Crust types recognized are: Ferruginous sandy crusts (Fsc) with oxides-oxyhydroxides (hematite and goethite) concentrated on sandstone tops presenting a fibro-radial internal structure reminding organic structures that penetrate different mineral phases, suggesting the existence of bacterial activity in crust development; Ferruginous muddy crusts (Fmc) consisting of wavy, laminated, microbial mats, being composed mainly of hematite. On the other hand, a more dispersed and broader mineralization included as Ferruginous sandstones with iron oxides and oxyhydroxides (hematite and goethite) representing a limited cement phase on these sediments. The presence of microbial remains, ferruginous minerals, Microbially-induced sedimentary structures, microbial laminites and vertebrate tracks preserved due to the presence of biofilms suggest firstly a direct evidence of syn-depositional microbial activity in these sediments; and, secondly, that iron accumulation and ferruginous crusts development occurred immediately after deposition of the host, still soft sediments. Ferruginous crusts cap sedimentary cycles and they represent the gradual development of hard substrate conditions, and the development of a discontinuity surface at the top of the parasequence sets, related to very low sedimentary rates; the overlying sediments record subsequent flooding of underlying shallower environments; crusts are, consequently, interpreted as boundaries for these higher-order cycles in the Iberian Basin.

Provenance and depositional environment of epi-shelf lake sediment from Schirmacher Oasis, East Antarctica, vis-à-vis scanning electron microscopy of quartz grain, size distribution and chemical parameters

NASA Astrophysics Data System (ADS)

Shrivastava, Prakash K.; Asthana, Rajesh; Roy, Sandip K.; Swain, Ashit K.; Dharwadkar, Amit

2012-07-01

The scientific study of quartz grains is a powerful tool in deciphering the depositional environment and mode of transportation of sediments, and ultimately the origin and classification of sediments. Surface microfeatures, angularity, chemical features, and grain-size analysis of quartz grains, collectively reveal the sedimentary and physicochemical processes that acted on the grains during different stages of their geological history. Here, we apply scanning electron microscopic (SEM) analysis to evaluating the sedimentary provenance, modes of transport, weathering characteristics, alteration, and sedimentary environment of selected detrital quartz grains from the peripheral part of two epi-shelf lakes (ESL-1 and ESL-2) of the Schirmacher Oasis of East Antarctica. Our study reveals that different styles of physical weathering, erosive signatures, and chemical precipitation variably affected these quartz grains before final deposition as lake sediments. Statistical analysis (central tendencies, sorting, skewness, and kurtosis) indicates that these quartz-bearing sediments are poorly sorted glaciofluvial sediments. Saltation and suspension seem to have been the two dominant modes of transportation, and chemical analysis of these sediments indicates a gneissic provenance.

Combined Rock Magnetic and Dielectric studies applied to stratigraphic and archeological problems in Venezuela

NASA Astrophysics Data System (ADS)

Costanzo-Alvarez, V.; Aldana, M.; Suarez, N.

2007-05-01

In the last few years the paleomagnetism research group, at the Universidad Simon Bolivar in Caracas (Venezuela), has undertaken combined studies of rock magnetism (e.g. natural magnetic remanence, magnetic susceptibility, hysteresis parameters etc.) and dielectric properties (maximum current depolarization temperatures and average activation energies) in Cretaceous and Paleogene sedimentary sequences from eastern and western Venezuela. Our main goal has been to find new ways of defining physical markers, in fossil- poor sedimentary rocks, for stratigraphic correlations. Magneto/dielectric characterizations of these rocks have proved also useful identifying lithological discontinuities and paleoenvironmental changes. More recently these two-fold technique have been extended to archeological materials (potsherds) from a series of Venezuelan islands, in order to track down clay sources and find out about different stages of pottery craftsmanship. Magneto/Dielectric characterization of archeological potsherds seems to allow the tracing of their provenance from various mainland prehistoric settlements of distinct Venezuelan amerindian groups. In this paper we present a comprehensive review of this research applied to a contact between two sedimentary formations in eastern Venezuela (Cretaceous Chimana/Querecual) and a number of pottery samples with diverse stylistic features excavated in a single archeological site from Los Roques islands.

A Guide for Selecting Remedies for Subsurface Releases of Chlorinated Solvents

DTIC Science & Technology

2011-03-01

exception of secondary permeability features (e.g., fractures , root holes, animal burrows), high displacement pressures typically preclude DNAPL from...1 to 40 percent. Fractured media with high matrix porosity are commonly encountered in sedimentary rock (e.g., limestone, dolomite , shale, and...Low Permeability .......... 21 Type III – Granular Media with Moderate to High Heterogeneity ........................ 21 Type IV - Fractured Media

Facies architecture of a Triassic rift-related Silicic Volcano-Sedimentary succession in the Tethyan realm, Peonias subzone, Vardar (Axios) Zone, northern Greece; Regional implications

NASA Astrophysics Data System (ADS)

Asvesta, Argyro; Dimitriadis, Sarantis

2010-06-01

In northern Greece, along the western edge of the Paleozoic Vertiscos terrane (Serbomacedonian massif) and within the Peonias subzone - the eastern part of the Vardar (Axios) Zone - a Silicic Volcano-Sedimentary (SVS) succession of Permo(?)-Skythian to Mid Triassic age records the development of a faulted continental margin and the formation of rhyolitic volcanoes along a continental shelf fringed by neritic carbonate accumulations. It represents the early rifting extensional stages that eventually led to the opening of the main oceanic basin in the western part of the Vardar (Axios) Zone (the Almopias Oceanic Basin). Even though the SVS succession is deformed, altered, extensively silicified and metamorphosed in the low greenschist facies, primary textures, original contacts and facies relationships are recognized in some places allowing clues for the facies architecture and the depositional environment. Volcanic and sedimentary facies analysis has been carried out at Nea Santa and Kolchida rhyolitic volcanic centres. Pyroclastic facies, mostly composed of gas-supported lapilli tuffs and locally intercalated accretionary lapilli tuffs, built the early cones which were then overridden by rhyolitic aphyric and minor K-feldspar-phyric lava flows. The characteristics of facies, especially the presence of accretionary lapilli, imply subaerial to coastal emplacement at this early stage. The mature and final stages of volcanism are mostly represented by quartz-feldspar porphyry intrusions that probably occupied the vents. At Nea Santa area, the presence of resedimented hyaloclastite facies indicates subaqueous emplacement of rhyolitic lavas and/or lobes. Moreover, quartz-feldspar-phyric sills and a partly extrusive dome featuring peperites at their margins are inferred to have intruded unconsolidated, wet carbonate sediments of the overlying Triassic Neritic Carbonate Formation, in a shallow submarine environment. The dome had probably reached above wave-base as is indicated by the presence of reworked rhyolitic clasts in the younger mixed rhyolite-carbonate epiclastic sedimentary facies. This facies is interpreted as mass- and debris-flow of mixed provenance, deposited below wave-base. The facies architecture of the SVS succession records a change in volcanic activity from explosive to effusive and then to intrusive. The depositional environment changed from subaerial-coastal to shallow submarine as the silicic volcanism evolved and carbonate sedimentation was progressively taking over, probably compensating for the gradual subsidence of the corresponding basin. Silicic magmatism and carbonate sedimentation were contemporaneous and spatially related. The timing of the rifting, the continental crustal elements involved and the accompanying tectonic, magmatic and sedimentary processes are features of the spatially and temporally evolving western peri-Tethyan region.

Tertiary sedimentary history and structure of the Valencia trough (western Mediterranean)

NASA Astrophysics Data System (ADS)

Maillard, A.; Mauffret, A.; Watts, A. B.; Torné, M.; Pascal, G.; Buhl, P.; Pinet, B.

1992-03-01

We present here main results of the Common Depth Point (CDP) data acquired during the Valsis 2 Cruise in 1988 in the Valencia trough. The profiles are tied in with industrial well data and this correlation allows the sedimentary and structural history of the region to be deduced. The Valsis Cruise seismic profiles have been supplemented by a very dense grid of industrial seismic lines and these data permit us to establish an accurate depth to basement map. The formation of the initial grabens, coeval with those of the Gulf of Lions, is related to the Early Miocene opening of the northwestern Mediterranean basin and the Barcelona graben is filled by the same sedimentary layers, including evaporites, as that of the Provençal region. Nevertheless, the Valencia-Catalan grabens have been reactivated by young extensional tectonics which could be a consequence of the convergence of Africa relative to Europe. The Valencia trough is segmented by transfer faults which trend NW-SE. These faults, which have a more accentuated structural expression than the Valencia and Catalonia grabens, may act as transform faults separating the individual Balearic Islands. The transfer faults are in strike with volcanic ridges which have been sampled during the DSDP Leg 13. The dense seismic grid allows us to delineate several widespread volcanic features in the Valencia trough which have been active from the Early Miocene to the Pleistocene. However, we note that the volcanic features are mainly Miocene in age whereas the recent volcanism is restricted to a narrow zone (Columbretes Islands). The compressional tectonics which deformed the Balearic Islands does not appear to extend far towards the North. We delineate the compressional front north of Ibiza, but we failed to determine any thrust or fold north of Mallorca, whereas an extensional tectonics is evident.

CONCORDANCE OF TAXONOMIC COMPOSITION PATTERNS ACROSS MULTIPLE LAKE ASSEMBLAGES: EFFECTS OF SCALE, BODY SIZE, AND LAND USE

EPA Science Inventory

We assessed environmental gradients and the extent to which they induced concordant patterns of taxonomic composition among benthic macroinvertebrate, riparian bird, sedimentary diatom, fish, and pelagic zooplankton assemblages in 186 northeastern U.S.A. lakes. Human population ...

About the geologic map in the National Atlas of the United States of America

USGS Publications Warehouse

Reed, John C.; Bush, Charles A.

2007-01-01

Introduction The geologic map in the National Atlas of the United States of America shows the age, distribution, and general character of the rocks that underlie the Nation, including Alaska, Hawaii, Puerto Rico, and the Virgin Islands (but excluding other small island possessions). (The National Atlas of the United States can be accessed at URL http://nationalatlas.gov/natlas/Natlasstart.asp.) The map depicts the bedrock that lies immediately beneath soils or surficial deposits except where these deposits are so thick and extensive that the type of bedrock beneath them can only be inferred by deep drilling or geophysical methods, or both. Thus, it does not show the extensive glacial deposits of the North Central and Northeastern States, the deep residuum of the Southeastern and South Central States, the relatively thin alluvium along many major rivers and basins, and extensive eolian deposits on the high plains. However, it does show, in a general way, the thick alluvial deposits along the lower Mississippi River and on the Atlantic and Gulf Coastal Plains, and in the deep basins of the western cordillera. The rocks are classified as either sedimentary, volcanic, plutonic, or metamorphic, and their geologic ages are given in terms using a simplified version of the 1999 Geological Society of America geologic time scale. In some places rocks depicted as sedimentary are interlayered with volcanic rocks, including tuff, volcanic breccia, and volcanic flows. Conversely, many of the rocks shown as volcanic include interlayered sedimentary rocks. Plutonic rocks are classified by age and as granitic, intermediate, mafic, or ultramafic, but no similar classification has been attempted for the volcanic rocks in this version of the map. Where sedimentary or volcanic rocks have been metamorphosed but still retain clear evidence of their depositional age and origin, the extent of the metamorphism is shown by a pattern. Where the metamorphism has been so intense that the rocks bear little resemblance to the rocks from which they were derived, they are mapped as gneiss, but the age given is generally the age of the original rocks. The map in the National Atlas is a generalization of a new geologic map of North America that has recently been published by the Geological Society of America. The original compilation was prepared at a scale of 1:2,500,000 for publication at a scale of 1:5,000,000. This generalized version is intended for viewing at scales between about 1:10,000,000 and 1:7,500,000.

Ancient sedimentary structures in the <3.7 Ga Gillespie Lake Member, Mars, that resemble macroscopic morphology, spatial associations, and temporal succession in terrestrial microbialites.

PubMed

Noffke, Nora

2015-02-01

Sandstone beds of the <3.7 Ga Gillespie Lake Member on Mars have been interpreted as evidence of an ancient playa lake environment. On Earth, such environments have been sites of colonization by microbial mats from the early Archean to the present time. Terrestrial microbial mats in playa lake environments form microbialites known as microbially induced sedimentary structures (MISS). On Mars, three lithofacies of the Gillespie Lake Member sandstone display centimeter- to meter-scale structures similar in macroscopic morphology to terrestrial MISS that include "erosional remnants and pockets," "mat chips," "roll-ups," "desiccation cracks," and "gas domes." The microbially induced sedimentary-like structures identified in Curiosity rover mission images do not have a random distribution. Rather, they were found to be arranged in spatial associations and temporal successions that indicate they changed over time. On Earth, if such MISS occurred with this type of spatial association and temporal succession, they would be interpreted as having recorded the growth of a microbially dominated ecosystem that thrived in pools that later dried completely: erosional pockets, mat chips, and roll-ups resulted from water eroding an ancient microbial mat-covered sedimentary surface; during the course of subsequent water recess, channels would have cut deep into the microbial mats, leaving erosional remnants behind; desiccation cracks and gas domes would have occurred during a final period of subaerial exposure of the microbial mats. In this paper, the similarities of the macroscopic morphologies, spatial associations, and temporal succession of sedimentary structures on Mars to MISS preserved on Earth has led to the following hypothesis: The sedimentary structures in the <3.7 Ga Gillespie Lake Member on Mars are ancient MISS produced by interactions between microbial mats and their environment. Proposed here is a strategy for detecting, identifying, confirming, and differentiating possible MISS during current and future Mars missions.

Flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone of the Three Gorges Reservoir, China.

PubMed

Tang, Qiang; Bao, Yuhai; He, Xiubin; Fu, Bojie; Collins, Adrian L; Zhang, Xinbao

2016-04-01

Since the launch of the Three Gorges Dam on the Yangtze River, a distinctive reservoir fluctuation zone has been created and significantly modified by regular dam operations. Sediment redistribution within this artificial landscape differs substantially from that in natural fluvial riparian zones, due to a specific hydrological regime comprising steps of water impoundment with increasing magnitudes and seasonal water level fluctuation holding a range of sediment fluxes. This study reinterpreted post-dam sedimentary dynamics in the reservoir fluctuation zone by stratigraphy determination of a 345-cm long sediment core, and related it to impact of the hydrological regime. Seasonality in absolute grain-size composition of suspended sediment was applied as a methodological basis for stratigraphic differentiation. Sedimentary laminations with relatively higher proportions of sandy fractions were ascribed to sedimentation during the dry season when proximal subsurface bank erosion dominates source contributions, while stratigraphy with a lower proportion of sandy fractions is possibly contributed by sedimentation during the wet season when distal upstream surface erosion prevails. Chronology determination revealed non-linear and high annual sedimentation rates ranging from 21.7 to 152.1cm/yr. Although channel geomorphology may primarily determine the spatial extent of sedimentation, seasonal sedimentary dynamics was predominantly governed by the frequency, magnitude, and duration of flooding. Summer inundation by natural floods with enhanced sediment loads produced from upstream basins induced higher sedimentation rates than water impoundment during the dry season when distal sediment supply was limited. We thus conclude that flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone, though little impact on total sediment retention rate was detected. Ongoing reductions in flow and sediment supply under human disturbance may have profound implications in affecting sedimentary equilibrium in the reservoir fluctuation zone. The results herein provide insights of how big dams have disrupted the sediment conveyance processes of large scale fluvial systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantitative topographic analysis as a guide to rover-based research on Mars

NASA Astrophysics Data System (ADS)

Palucis, M. C.; Dietrich, W. E.; Parker, T. J.; Sumner, D. Y.; Williams, R. M. E.; Hayes, A.; Mangold, N.; Lewis, K. W.

2014-12-01

Satellite imagery of Mars now provides remarkable topographic data, often better than that on Earth in many countries. For decades, researchers have identified landforms on Mars that indicated the presence of gullies, rivers, deltas, fans, and lakes, pointing to the presence of surface waters, and the apparent necessity of an active hydrologic cycle involving rain or snow. Quantitative topographic analysis has provided a means to estimate volumes of runoff, sediment transport rates, and peak flow discharges, first using orbital imagery alone and then using laser altimetery coverage and higher resolution HiRISE (1 m/px), CTX (20 m/px) and HRSC (50 m/px) topography. Our detailed topographic analysis of the Peace Vallis fan near the Curiosity rover landing site in Gale Crater (Mars) suggested that the fan entered into a pre-existing enclosed basin that would likely contain lake sediments; sedimentary, mineralogical, and chemical analysis of this region, now named Yellowknife Bay, later found this to be the case, though debate remains on the exact origin and history of the deposit. The rover is currently heading to a 5 km high sedimentary mound (Aeolis Mons) with mineral signatures hypothesized to be the result of planet-wide changes in climate. Topographic features on the mound, which correspond in elevation with other large depositional features around the crater, suggest that a succession of lakes developed post-Noachian. Within Gale, we are in a unique position to determine the extent at which topography can tell us the evolutionary history of a place on another planet, since our hypotheses can actually be tested as the Curiosity rover makes its ascent up Aeolis Mons. Along the rover's traverse, we propose based on the geomorphic record that the sediments being examined were water soaked, perhaps several times under deep lakes, and that the rover will cross shorelines that may not be well-preserved, but are worth searching for. A quantitative topographic analysis of the fan and delta features and their source areas on the crater wall and Aeolis Mons suggest that mass is conserved, hence these features have experienced little modification since emplacement, but this also presents challenges for explaining the origin of the coarse sedimentary deposits Curiosity has recently encountered.

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.

Sedimentology of new fluvial deposits on the Elwha River, Washington, USA, formed during large-scale dam removal

USGS Publications Warehouse

Draut, Amy; Ritchie, Andrew C.

2015-01-01

Removal of two dams 32 m and 64 m high on the Elwha River, Washington, USA, provided the first opportunity to examine river response to a dam removal and controlled sediment influx on such a large scale. Although many recent river-restoration efforts have included dam removal, large dam removals have been rare enough that their physical and ecological effects remain poorly understood. New sedimentary deposits that formed during this multi-stage dam removal result from a unique, artificially created imbalance between fluvial sediment supply and transport capacity. River flows during dam removal were essentially natural and included no large floods in the first two years, while draining of the two reservoirs greatly increased the sediment supply available for fluvial transport. The resulting sedimentary deposits exhibited substantial spatial heterogeneity in thickness, stratal-formation patterns, grain size and organic content. Initial mud deposition in the first year of dam removal filled pore spaces in the pre-dam-removal cobble bed, potentially causing ecological disturbance but not aggrading the bed substantially at first. During the second winter of dam removal, thicker and in some cases coarser deposits replaced the early mud deposits. By 18 months into dam removal, channel-margin and floodplain deposits were commonly >0.5 m thick and, contrary to pre-dam-removal predictions that silt and clay would bypass the river system, included average mud content around 20%. Large wood and lenses of smaller organic particles were common in the new deposits, presumably contributing additional carbon and nutrients to the ecosystem downstream of the dam sites. Understanding initial sedimentary response to the Elwha River dam removals will inform subsequent analyses of longer-term sedimentary, geomorphic and ecosystem changes in this fluvial and coastal system, and will provide important lessons for other river-restoration efforts where large dam removal is planned or proposed.

Relating sedimentary processes in the Bagnold Dunes to the development of crater basin aeolian stratification

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Lapotre, M. G. A.; Lewis, K. W.; Day, M. D.; Stein, N.; Rubin, D. M.; Sullivan, R. J., Jr.; Banham, S.; Thomas, N. M.; Lamb, M. P.; Gupta, S.; Fischer, W. W.

2017-12-01

Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under martian conditions. Exploration of the Bagnold Dunes by the Curiosity Rover in Gale Crater, Mars provided the first opportunity to make in situ observations of martian dunes from the grain-to-dune scale. We used the suite of cameras on Curiosity, including Navigation Camera, Mast Camera, and Mars Hand Lens Imager. We measured grainsize and identified sedimentary processes similar to processes on terrestrial dunes, such as grainfall, grainflow, and impact ripples. Impact ripple grainsize had a median of 0.103 mm. Measurements of grainflow slopes indicate a relaxation angle of 29° and grainfall slopes indicate critical angles of at least 32°. Dissimilar to terrestrial dunes, large, meter-scale ripples form on all slopes of the dunes. The ripples form both sinuous and linear crestlines, have symmetric and asymmetric profiles, range in height between 12cm and 28cm, and host grainfall, grainflow, and impact ripples. The largest ripples are interpreted to integrate the annual wind cycle within the crater, whereas smaller large ripples and impact ripples form or reorient to shorter term wind cycling. Assessment of sedimentary processes in combination with dune type across the Bagnold Dunes shows that dune-field pattern development in response to a complex crater-basin wind regime dictates the distribution of geomorphic processes. From a stratigraphic perspective, zones of highest potential accumulation correlate with zones of wind convergence, which produce complex winds and dune field patterns thereby limiting the potential distribution of types of aeolian stratification preserved within crater basins.

Surficial Geologic Map of the Pocasset-Provincetown-Cuttyhunk-Nantucket 24-Quadrangle Area of Cape Cod and Islands, Southeast Massachusetts

USGS Publications Warehouse

Stone, Byron D.; DiGiacomo-Cohen, Mary L.

2006-01-01

The surficial geologic map layer shows the distribution of nonlithified earth materials at land surface in an area of 24 7.5-minute quadrangles (555 mi2 total) in southeast Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. On Cape Cod and adjacent islands, these materials completely cover the bedrock surface. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relations, and age. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Layers and Fractures in Ophir Chasma

NASA Image and Video Library

2015-11-05

Ophir Chasma forms the northern portion of Valles Marineris, and this image from NASA Mars Reconnaissance Orbiter spacecraft features a small part of its wall and floor. The wall rock shows many sedimentary layers and the floor is covered with wind-blown ridges, which are intermediate in size between sand ripples and sand dunes. Rocks protruding on the floor could be volcanic intrusions of once-molten magma that have pushed aside the surrounding sedimentary layers and "froze" in place. Images like this can help geologists study the formation mechanisms of large tectonic systems like Valles Marineris. (The word "tectonics" does not mean the same thing as "plate tectonics." Tectonics simply refers to large stresses and strains in a planet's crust. Plate tectonics is the main type of tectonics that Earth has; Mars does not have plate tectonics.) http://photojournal.jpl.nasa.gov/catalog/PIA20044

Early dolomitization in the Lower Cretaceous shallow-water carbonates of Southern Apennines (Italy): Clues about palaeoclimatic fluctuations in western Tethys

NASA Astrophysics Data System (ADS)

Vinci, Francesco; Iannace, Alessandro; Parente, Mariano; Pirmez, Carlos; Torrieri, Stefano; Giorgioni, Maurizio

2017-12-01

A multidisciplinary study of the dolomitized bodies present in the Lower Cretaceous platform carbonates of Mt. Faito (Southern Apennines - Italy) was carried out in order to explore the connection between early dolomite formation and fluctuating climate conditions. The Berriasian-Aptian investigated succession is 466 m thick and mainly consists of shallow-water lagoonal limestones with frequent dolomite caps. The dolomitization intensity varies along the succession and reaches its peak in the upper Hauterivian-lower Barremian interval, where it is present a completely dolomitized interval about 100-m-thick. Field relations, petrography, mineralogy, and geochemistry of the analyzed dolomite bodies allowed identifying two populations of early dolomites, a fine-medium crystalline (FMdol) and a coarse crystalline dolomite (Cdol), both interpreted as the product of mesohaline water reflux. According to our interpretation, FMdol precipitated from concentrated brines in the very early stage of the reflux process, producing typical sedimentary features as dolomite caps. In the successive step of the process, the basin-ward 'latent' reflux precipitated Cdol from less concentrated brines. A peculiar feature of the studied succession is the great consistency between stratigraphic distribution of dolomite bodies and their geochemical signature. The completely dolomitized Hauterivian-Barremian interval, in fact, is characterized by geochemical values suggesting an origin from distinctly saltier brines. Considering that the observed near-surface dolomitization process is controlled by physical and chemical parameters reflecting the paleoenvironmental and paleoclimatic conditions during dolomite formation, we propose that the stratigraphically controlled dolomitization intensity reflects periodic fluctuations in the salinity of dolomitizing fluid, in turn controlled by long-term climate oscillations. The present work highlights that the stratigraphic distribution of early diagenetic dolomite may be used as proxy to define the climatic fluctuations that have influenced the sedimentary dynamics in the Early Cretaceous. Moreover, considering that a comparable early dolomite distribution is present also in the Dinaric Platform, we suggest that a regional scale climate control acted on early dolomite formation and distribution. Refining the knowledge of such a key control may have a significative impact on hydrocarbon reservoir characterization and exploration in the Periadriatic area.

Regional implications of heat flow of the Snake River Plain, Northwestern United States

NASA Astrophysics Data System (ADS)

Blackwell, D. D.

1989-08-01

The Snake River Plain is a major topographic feature of the Northwestern United States. It marks the track of an upper mantle and crustal melting event that propagated across the area from southwest to northeast at a velocity of about 3.5 cm/yr. The melting event has the same energetics as a large oceanic hotspot or plume and so the area is the continental analog of an oceanic hotspot track such as the Hawaiian Island-Emperor Seamount chain. Thus, the unique features of the area reflect the response of a continental lithosphere to a very energetic hotspot. The crust is extensively modified by basalt magma emplacement into the crust and by the resulting massive rhyolite volcanism from melted crustal material, presently occurring at Yellowstone National Park. The volcanism is associated with little crustal extension. Heat flow values are high along the margins of the Eastern and Western Snake River Plains and there is abundant evidence for low-grade geothermal resources associated with regional groundwater systems. The regional heat flow pattern in the Western Snake River Plains reflects the influence of crustal-scale thermal refraction associated with the large sedimentary basin that has formed there. Heat flow values in shallow holes in the Eastern Snake River Plains are low due to the Snake River Plains aquifer, an extensive basalt aquifer where water flow rates approach 1 km/yr. Below the aquifer, conductive heat flow values are about 100 mW m -2. Deep holes in the region suggest a systematic eastward increase in heat flow in the Snake River Plains from about 75-90 mW m -2 to 90-110 mW m -2. Temperatures in the upper crust do not behave similarly because the thermal conductivity of the Plio-Pleistocene sedimentary rocks in the west is lower than that in the volcanic rocks characteristic of the Eastern Snake River Plains. Extremely high heat loss values (averaging 2500 mW m -2) and upper crustal temperatures are characteristic of the Yellowstone caldera.

Geologic Map of the Nulato Quadrangle, West-Central Alaska

USGS Publications Warehouse

Patton, W.W.; Moll-Stalcup, E. J.

2000-01-01

Introduction The Nulato quadrangle encompasses approximately 17,000 km2 (6,500 mi2) of west-central Alaska within the Yukon River drainage basin. The quadrangle straddles two major geologic features-the Yukon-Koyukuk sedimentary basin, a huge triangle-shaped Cretaceous depression that stretches across western Alaska from the Brooks Range to the Yukon delta; and the Ruby geanticline,a broad uplift of pre-Cretaceous rocks that borders the Yukon-Koyukuk basin on the southeast. The Kaltag Fault crosses the quadrangle diagonally from northeast to southwest and dextrally offsets all major geologic features as much as 130 km.

Bacterial diversity and community composition from seasurface to subseafloor.

PubMed

Walsh, Emily A; Kirkpatrick, John B; Rutherford, Scott D; Smith, David C; Sogin, Mitchell; D'Hondt, Steven

2016-04-01

We investigated compositional relationships between bacterial communities in the water column and those in deep-sea sediment at three environmentally distinct Pacific sites (two in the Equatorial Pacific and one in the North Pacific Gyre). Through pyrosequencing of the v4-v6 hypervariable regions of the 16S ribosomal RNA gene, we characterized 450,104 pyrotags representing 29,814 operational taxonomic units (OTUs, 97% similarity). Hierarchical clustering and non-metric multidimensional scaling partition the samples into four broad groups, regardless of geographic location: a photic-zone community, a subphotic community, a shallow sedimentary community and a subseafloor sedimentary community (⩾1.5 meters below seafloor). Abundance-weighted community compositions of water-column samples exhibit a similar trend with depth at all sites, with successive epipelagic, mesopelagic, bathypelagic and abyssopelagic communities. Taxonomic richness is generally highest in the water-column O2 minimum zone and lowest in the subseafloor sediment. OTUs represented by abundant tags in the subseafloor sediment are often present but represented by few tags in the water column, and represented by moderately abundant tags in the shallow sediment. In contrast, OTUs represented by abundant tags in the water are generally absent from the subseafloor sediment. These results are consistent with (i) dispersal of marine sedimentary bacteria via the ocean, and (ii) selection of the subseafloor sedimentary community from within the community present in shallow sediment.

Contact zone permeability at intrusion boundaries: New results from hydraulic testing and geophysical logging in the Newark Rift Basin, New York, USA

USGS Publications Warehouse

Matter, J.M.; Goldberg, D.S.; Morin, R.H.; Stute, M.

2006-01-01

Hydraulic tests and geophysical logging performed in the Palisades sill and the underlying sedimentary rocks in the NE part of the Newark Rift Basin, New York, USA, confirm that the particular transmissive zones are localized within the dolerite-sedimentary rock contact zone and within a narrow interval below this contact zone that is characterized by the occurrence of small layers of chilled dolerite. Transmissivity values determined from fluid injection, aquifer testing, and flowmeter measurements generally fall in the range of 8.1E-08 to 9.95E-06 m2/s and correspond to various scales of investigation. The analysis of acoustic and optical BHTV images reveals two primary fracture sets within the dolerite and the sedimentary rocks - subhorizontal fractures, intersected by subvertical ones. Despite being highly fractured either with subhorizontal, subvertical or both fracture populations, the dolerite above and the sedimentary rocks below the contact zone and the zone with the layers of chilled dolerite are significantly less conductive. The distribution of the particular conductive intervals is not a function of the two dominant fracture populations or their density but rather of the intrusion path of the sill. The intrusion caused thermal fracturing and cracking of both formations, resulting in higher permeability along the contact zone. ?? Springer-Verlag 2005.

The Western River--An Offscale Teaching and Experimental Tool.

ERIC Educational Resources Information Center

Chapman, John J.; Wilcox, John T.

1983-01-01

Sedimentary patterns and hydraulic effects can be studies in model streams which are not to scale. The "Western River" is such a model which is being used effectively at Western Carolina College. Construction of the model, student exercises, and observations made when using the model are discussed. (Author/JN)

Drilling the centre of the Thuringian Basin, Germany, to decipher potential interrelation between shallow and deep fluid systems

NASA Astrophysics Data System (ADS)

Kukowski, Nina; Totsche, Kai Uwe; Abratis, Michael; Habisreuther, Annett; Ward, Timothy; Influins Drilling-Team

2014-05-01

To shed light on the coupled dynamics of near surface and deep fluids in a sedimentary basin on various scales, ranging from the pore scale to the extent of an entire basin, is of paramount importance to understand the functioning of sedimentary basins fluid systems and therefore e.g. drinking water supply. It is also the fundamental goal of INFLUINS (INtegrated FLuid dynamics IN Sedimentary basins), a research initiative of several groups from Friedrich-Schiller University of Jena and their partners. This research association is focusing on the nearby Thuringian basin, a well confined, small intra-continental sedimentary basin in Germany, as a natural geo laboratory. In a multidisciplinary approach, embracing different fields of geophysics like seismic reflection profiling or airborne geomagnetics, structural geology, sedimentology, hydrogeology, hydrochemistry and hydrology, remote sensing, microbiology and mineralogy, among others, and including both, field-based, laboratory-based and computer-based research, an integral INFLUINS topic is the potential interaction of aquifers within the basin and at its rims. The Thuringian basin, which is composed of sedimentary rocks from the latest Paleozoic and mainly Triassic, is particularly suited to undertake such research as it is of relative small size, about 50 to 100 km, easily accessible, and quite well known from previous studies, and therefore also a perfect candidate for deep drilling. After the acquisition of 76 km seismic reflection data in spring 2011, to get as much relevant data as possible from a deep drilling at the cross point between two seismic profiles with a limited financial budget, an optimated core sampling and measuring strategy including partial coring, borehole geophysics and pump tests as well as a drill hole design, which enables for later continuation of drilling down to the basement, had been developed. Drilling Triassic rocks from Keuper to lower Buntsandstein was successfully realised down to a final depth of 1179 m from late June to mid-September 2013. Here, we give an introduction into the layout of INFLUINS deep drilling together with a summary of preliminary results, e.g. on the nature of the boundaries between Muschelkalk and Buntsandstein, and between upper and middle Buntsandstein, a complete core recovery of upper Buntsandstein saliniferous formations as well as unexpectedly low porosity and permeability of potential aquifers.

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

General Approach for Rock Classification Based on Digital Image Analysis of Electrical Borehole Wall Images

NASA Astrophysics Data System (ADS)

Linek, M.; Jungmann, M.; Berlage, T.; Clauser, C.

2005-12-01

Within the Ocean Drilling Program (ODP), image logging tools have been routinely deployed such as the Formation MicroScanner (FMS) or the Resistivity-At-Bit (RAB) tools. Both logging methods are based on resistivity measurements at the borehole wall and therefore are sensitive to conductivity contrasts, which are mapped in color scale images. These images are commonly used to study the structure of the sedimentary rocks and the oceanic crust (petrologic fabric, fractures, veins, etc.). So far, mapping of lithology from electrical images is purely based on visual inspection and subjective interpretation. We apply digital image analysis on electrical borehole wall images in order to develop a method, which augments objective rock identification. We focus on supervised textural pattern recognition which studies the spatial gray level distribution with respect to certain rock types. FMS image intervals of rock classes known from core data are taken in order to train textural characteristics for each class. A so-called gray level co-occurrence matrix is computed by counting the occurrence of a pair of gray levels that are a certain distant apart. Once the matrix for an image interval is computed, we calculate the image contrast, homogeneity, energy, and entropy. We assign characteristic textural features to different rock types by reducing the image information into a small set of descriptive features. Once a discriminating set of texture features for each rock type is found, we are able to discriminate the entire FMS images regarding the trained rock type classification. A rock classification based on texture features enables quantitative lithology mapping and is characterized by a high repeatability, in contrast to a purely visual subjective image interpretation. We show examples for the rock classification between breccias, pillows, massive units, and horizontally bedded tuffs based on ODP image data.

Analyzing sources to sedimentary organic carbon in the Gulf of Urabá, southern Caribbean, using carbon stable isotopes

NASA Astrophysics Data System (ADS)

Rúa, Alex; Liebezeit, Gerd; Grajales, Heazel; Palacio, Jaime

2017-10-01

Carbon stable isotopes analysis serve reconstruction of the origin of organic matter (OM) deposited onto sediments. They also allow tracing vegetation change at different time scales. This study weighs the contribution of both marine and terrestrial sources to sedimentary organic carbon (OC) from a southwestern Caribbean Gulf partly surrounded by large Musa acuminata (banana) croplands. The δ13C values in three sediment cores from the gulf have slightly decreased over 1000 yrs BP, indicating enhanced terrestrial input of detrital carbon owing to river discharge. A two-end mixing model fed with these δ13C values showed that averaged terrestrial contribution of OC to sediment was 52.0% at prodelta, 76.4% at delta front, and 64.2% at Colombia Bay. This agrees well with sediment dynamics. The main source of sedimentary OC within the gulf was terrestrial instead of marine. In fact, a distorted trend in δ13C values for one of the coring sites could be the result of banana crop expansion through the 20th century.

The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change

PubMed Central

Keeling, Charles D.; Whorf, Timothy P.

2000-01-01

Variations in solar irradiance are widely believed to explain climatic change on 20,000- to 100,000-year time-scales in accordance with the Milankovitch theory of the ice ages, but there is no conclusive evidence that variable irradiance can be the cause of abrupt fluctuations in climate on time-scales as short as 1,000 years. We propose that such abrupt millennial changes, seen in ice and sedimentary core records, were produced in part by well characterized, almost periodic variations in the strength of the global oceanic tide-raising forces caused by resonances in the periodic motions of the earth and moon. A well defined 1,800-year tidal cycle is associated with gradually shifting lunar declination from one episode of maximum tidal forcing on the centennial time-scale to the next. An amplitude modulation of this cycle occurs with an average period of about 5,000 years, associated with gradually shifting separation-intervals between perihelion and syzygy at maxima of the 1,800-year cycle. We propose that strong tidal forcing causes cooling at the sea surface by increasing vertical mixing in the oceans. On the millennial time-scale, this tidal hypothesis is supported by findings, from sedimentary records of ice-rafting debris, that ocean waters cooled close to the times predicted for strong tidal forcing. PMID:10725399

The transitional depositional environment and sequence stratigraphy of Chasma Boreale

NASA Astrophysics Data System (ADS)

Brothers, S. C.; Kocurek, G.

2018-07-01

The depositional system within Chasma Boreale is unique in that it contains active aeolian environments, expressed as dune fields, and active cryosphere environments, present as layered ice deposits, as well as environments that transition between these. This work presents a new analysis of the Chasma Boreale sediment system that creates an interpretative framework addressing: (a) controls on the balance between aeolian and cryospheric processes in the modern depositional system, (b) the stratigraphic architecture of related sedimentary deposits, and (c) processes of sediment accumulation and preservation. Images from Context Camera (CTX; 6 m/pixel) are used to classify and map sedimentary environments, surfaces, and deposits on the reentrant floor, to refine the established geologic map of the reentrant, and to infer the stratigraphic record of the accumulation from Chasma Boreale's depositional system. A spectrum of sedimentary environments occurring between those dominated by aeolian and by cryospheric processes are identified. Through time, the boundaries of these sedimentary environments have shifted, resulting in complex lateral changes in the configuration of sedimentary environments on the reentrant's floor. Vertically, the stratigraphic record is characterized by the punctuation of sandy aeolian deposits by icy surfaces that indicate episodes of ice growth that preserve underlying deposits, resulting in accumulation. Stabilized icy surfaces occur at multiple vertical (temporal) scales and lateral extents, suggesting the influence of both regional climate change due to allogenic forcing, as well as autogenic dynamics within the transitional system. These observations demonstrate that the Chasma Boreale accumulation can be interpreted in an aeolian sequence stratigraphic framework. This work contributes the first detailed description of the processes forming polar aeolian sequences, with an emphasis on the competing and complementary dynamics between aeolian and cryospheric systems.

SDAR 1.0 a New Quantitative Toolkit for Analyze Stratigraphic Data

NASA Astrophysics Data System (ADS)

Ortiz, John; Moreno, Carlos; Cardenas, Andres; Jaramillo, Carlos

2015-04-01

Since the foundation of stratigraphy geoscientists have recognized that data obtained from stratigraphic columns (SC), two dimensional schemes recording descriptions of both geological and paleontological features (e.g., thickness of rock packages, grain size, fossil and lithological components, and sedimentary structures), are key elements for establishing reliable hypotheses about the distribution in space and time of rock sequences, and ancient sedimentary environmental and paleobiological dynamics. Despite the tremendous advances on the way geoscientists store, plot, and quantitatively analyze sedimentological and paleontological data (e.g., Macrostrat [http://www.macrostrat.org/], Paleobiology Database [http://www.paleodb.org/], respectively), there is still a lack of computational methodologies designed to quantitatively examine data from a highly detailed SCs. Moreover, frequently the stratigraphic information is plotted "manually" using vector graphics editors (e.g., Corel Draw, Illustrator), however, this information although store on a digital format, cannot be used readily for any quantitative analysis. Therefore, any attempt to examine the stratigraphic data in an analytical fashion necessarily takes further steps. Given these issues, we have developed the sofware 'Stratigraphic Data Analysis in R' (SDAR), which stores in a database all sedimentological, stratigraphic, and paleontological information collected from a SC, allowing users to generate high-quality graphic plots (including one or multiple features stored in the database). SDAR also encompasses quantitative analyses helping users to quantify stratigraphic information (e.g. grain size, sorting and rounding, proportion of sand/shale). Finally, given that the SDAR analysis module, has been written in the open-source high-level computer language "R graphics/statistics language" [R Development Core Team, 2014], it is already loaded with many of the crucial features required to accomplish basic and complex tasks of statistical analysis (i.e., R language provide more than hundred spatial libraries that allow users to explore various Geostatistics and spatial analysis). Consequently, SDAR allows a deeper exploration of the stratigraphic data collected in the field, it will allow the geoscientific community in the near future to develop complex analyses related with the distribution in space and time of rock sequences, such as lithofacial correlations, by a multivariate comparison between empirical SCs with quantitative lithofacial models established from modern sedimentary environments.

Near-shore Evaluation of Holocene Faulting and Earthquake Hazard in the New York City Metropolitan Region

NASA Astrophysics Data System (ADS)

Cormier, M. H.; King, J. W.; Seeber, L.; Heil, C. W., Jr.; Caccioppoli, B.

2016-12-01

During its relatively short historic period, the Atlantic Seaboard of North America has experienced a few M6+ earthquakes. These events raise the specter of a similar earthquake occurring anywhere along the eastern seaboard, including in the greater New York City (NYC) metropolitan area. Indeed, the NYC Seismic Zone is one of several concentrations of earthquake activity that stand out in the field of epicenters over eastern North America. Various lines of evidence point to a maximum magnitude in the M7 range for metropolitan NYC - a dramatic scenario that is counterbalanced by the low probability of such an event. Several faults mapped near NYC strike NW, sub-normal to the NE-striking structural trends of the Appalachians, and all earthquake sequences with well-established fault sources in the NYC seismic zone originate from NW-striking faults. With funding from the USGS Earthquake Hazard Program, we recently (July 2016) collected 85 km of high-resolution sub-bottom (CHIRP) profiles along the north shore of western Long Island Sound, immediately adjacent to metropolitan NYC. This survey area is characterized by a smooth, 15.5 kyr-old erosional surface and overlying strata with small original relief. CHIRP sonar profiles of these reflectors are expected to resolve fault or fold-related vertical relief (if present) greater than 50 cm. They would also resolve horizontal fault displacements with similar resolution, as may be expressed by offsets of either sedimentary or geomorphic features. No sedimentary cover on the land portion of the metro area offers such ideal reference surfaces, which are continuous in both time and space. Seismic profiles have a spacing of 200 m and have been acquired mostly perpendicular to the NW-striking faults mapped on land. These new data will be analyzed systematically for all resolvable features and then interpreted, distinguishing sedimentary, geomorphic, and tectonic features. The absence of evidence of post-glacial tectonic deformation would be a reliable negative result with implications regarding the lateral dimensions and southeastward continuity of the brittle faults mapped on land, and their potential for generation of large earthquakes with surface ruptures.

Rifting and reactivation of a Cretaceous structural belt at the northern margin of the South China Sea

NASA Astrophysics Data System (ADS)

Nanni, Ugo; Pubellier, Manuel; Chan, Lung Sang; Sewell, Roderick J.

2017-04-01

The Tiu Tang Lung Fault, Hong Kong Special Administrative Region - China, is located on the northern stretched continental margin of the South China Sea. Along this fault, Middle Jurassic volcanic rocks of the Tai Mo Shan Formation are tectonically juxtaposed on Lower Cretaceous sedimentary rocks of the Pat Sin Leng Formation. Both extensional detachments and compressional features are observed and various genetic strain configurations are proposed for the Tiu Tang Lung Fault with implications for understanding the dynamics of the pre-South China Sea rifting during the Cretaceous. We have identified tilted bedding planes in the continental deposits of the Pat Sin Leng Formation which can be related to Early Cretaceous syn-extensional deposition. A mid-Cretaceous penetrative top-to-the-south to top-to-the-west shear fabric is also observed and serves as an indicator of the strain pattern. This deformation is expressed by cleavages, schistosity, S/C fabrics, kink-folds, phacoids and stretched pebbles at both a macroscopic and microscopic scale. Cleavages and bedding are generally sub-parallel to the local shear orientation. The whole sedimentary pile is crosscut by Cenozoic N70 and N150 normal faults. These constraints, together with previous fission track, seismic and structural data, allow us to reinterpret the kinematics of this domain during syn-orogenic to syn-extensional periods. The observed top-to-the-south thrusting event is coeval with NE-SW strike-slip sinistral fault movement. Subsequent N-S extension can be correlated with South China Sea rifting from Eocene to Oligocene. These observations reveal a polyphase history associated with continental margin inversion which witnessed localized extension on previous compressional structures.

Morphology, sedimentary features and evolution of a large palaeo submarine canyon in Qiongdongnan basin, Northern South China Sea

NASA Astrophysics Data System (ADS)

Li, Xiangquan; Fairweather, Luke; Wu, Shiguo; Ren, Jianye; Zhang, Hongjie; Quan, Xiayun; Jiang, Tao; Zhang, Cheng; Su, Ming; He, Yunlong; Wang, Dawei

2013-01-01

The large Miocene-aged palaeo canyon that extents through the Qiongdongnan basin (QDNB) and Yinggehai basin (YGHB) of Northern South China Sea has been of considerable interest both economically and scientifically over the past decade. Stemmed from this, significant research has been employed into understanding the mechanism for its existence, incision, and sedimentary fill, yet debate remains. In the first case the canyon itself is actually quite anomalous. Alone from the size (over 570 km in length and more than 8 km in width (Yuan et al., 2009)), which is considerably more than most ancient deep-water channels (REFS), the canyon's sedimentary fill is also distinctly different. Some explanations have been given to explain the canyon's origin and existence, these include increased sediment supply from the Red River which is genetically linked to uplift of the Tibetan Plateau, lowstand turbidite and mass-transport activity, reactivation and dextral displacement of the Red River Fault zone inducing erosive gravity-flows, regional tilt of the QDNB and YGHB, paleo-seafloor morphology and seal-level fluctuations. With the application of new data obtained from interpretations of a large number of 2D seismic profiles, core and well log data, and tectonic and sedimentary analysis this contribution aims to: (1) Present models to explain the Canyon's sedimentary fill and basin plain deposits, which provided significant understanding of processes pre-, syn- and post-incision and; (2) review the plausibility and likelihood of each of the controlling mechanisms, hoping to shed light on this controversial aspect. We conclude that the final erosive event that shaped the canyon is dated at 5.5 Ma. The Canyon's unusual fill is a product of variation in the interaction between turbidity currents and MTD that blocked the canyon's axis, and the reduction in gravity flow energy through time; and therefore the complete succession represents one major erosive and cut event at 5.5 Ma and thereafter multi-gravity currents fills unlike in most slope channel-fills.

Rock-avalanche and ocean-resurge deposits in the late Eocene Chesapeake Bay impact structure: Evidence from the ICDP-USGS Eyreville cores, Virginia, USA

USGS Publications Warehouse

Gohn, G.S.; Powars, D.S.; Dypvik, H.; Edwards, L.E.

2009-01-01

An unusually thick section of sedimentary breccias dominated by target-sediment clasts is a distinctive feature of the late Eocene Chesapeake Bay impact structure. A cored 1766-m-deep section recovered from the central part of this marine-target structure by the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) drilling project contains 678 m of these breccias and associated sediments and an intervening 275-m-thick granite slab. Two sedimentary breccia units consist almost entirely of Cretaceous nonmarine sediments derived from the lower part of the target sediment layer. These sediments are present as coherent clasts and as autoclastic matrix between the clasts. Primary (Cretaceous) sedimentary structures are well preserved in some clasts, and liquefaction and fluidization structures produced at the site of deposition occur in the clasts and matrix. These sedimentary breccias are interpreted as one or more rock avalanches from the upper part of the transient-cavity wall. The little-deformed, unshocked granite slab probably was transported as part of an extremely large slide or avalanche. Water-saturated Cretaceous quartz sand below the slab was transported into the seafloor crater prior to, or concurrently with, the granite slab. Two sedimentary breccia units consist of polymict diamictons that contain cobbles, boulders, and blocks of Cretaceous nonmarine target sediments and less common shocked-rock and melt ejecta in an unsorted, unstratified, muddy, fossiliferous, glauconitic quartz matrix. Much of the matrix material was derived from Upper Cretaceous and Paleogene marine target sediments. These units are interpreted as the deposits of debris flows initiated by the resurge of ocean water into the seafloor crater. Interlayering of avalanche and debris-flow units indicates a partial temporal overlap of the earlier avalanche and later resurge processes. A thin unit of stratified turbidite deposits and overlying laminated fine-grained deposits at the top of the section represents the transition to normal shelf sedimentation. ?? 2009 The Geological Society of America.

Millennial-scale variability in Holocene aquatic productivity from Burial Lake, Arctic Alaska

NASA Astrophysics Data System (ADS)

Finkenbinder, Matthew S.; Abbott, Mark B.; Stoner, Joseph S.; Ortiz, Joseph D.; Finney, Bruce P.; Dorfman, Jason M.; Stansell, Nathan D.

2018-05-01

Holocene records of lacustrine primary production are commonly used to reconstruct past changes in environmental and climatic conditions. While several methods exist to infer paleoproductivity trends, few studies to date have applied multiple geochemical indices in the same core sequence from Arctic lakes to evaluate their fidelity and sensitivity to specific climate variables over long (Holocene length) timescales. In this study, we evaluate sub-century to millennial-scale fluctuations in paleoproductivity over the Holocene using geochemical (biogenic opal and sedimentary chlorin) analyses of sediments from Burial Lake in the western Brooks Range, Alaska. Large fluctuations in opal and related proxies occur at millennial timescales over the last 10,000 years. We interpret the changes in opal to result from variability in diatom productivity, which is indirectly mediated by climate primarily through changes in the duration of the ice-free growing season and the availability of limiting nutrients at this oligotrophic, tundra lake. Comparison of the opal and sedimentary chlorin record, which is correlated with TOC, shows contrasting patterns on both short (century to multi-century) and relatively long (millennial) time scales. The concentration of opal far exceeds that of TOC and variations in sediment dry bulk density, driven by changes in the accumulation of opal, are likely responsible in part for the variations in sedimentary chlorin. Further, C/N ratio values indicate a mixed algal-terrestrial source of sedimentary organic matter. This result highlights the complexity in the climatic interpretation of sedimentary chlorin as an index of whole lake production, because the signal is prone to dilution/concentration from opal and also reflects a combination of aquatic and terrestrial production. Time series analysis of the productivity records indicates the presence of a significant ∼1500-yr oscillation in opal concentration, which has been found in North Atlantic Ocean proxy records and numerous other marine and terrestrial paleorecords. Comparison of diatom productivity against a sea-ice inferred reconstruction of the Arctic Oscillation (AO) from the Beaufort Sea (Darby et al., 2012) shows that periods of reduced productivity at Burial Lake coincide with inferred positive phases of the AO (AO+). Combined with modern observations of sea ice extent and meteorological data, we hypothesize that AO + conditions and a strengthened polar jet correspond with a shortened ice-free growing season, a decrease in the availability of limiting nutrients, and lower levels of diatom production at Burial Lake. Comparison of the spectral properties between opal and the AO reconstruction reveal similar millennial scale variations with ∼1500-yr variability during the middle Holocene that transition to ∼1000-yr variability during the late Holocene. In light of these findings, we suggest the possibility that millennial variations in diatom productivity observed in the Burial Lake record are related to millennial variability in high-latitude atmospheric circulation similar to the AO. These results shed light on the sensitivity of aquatic ecosystems in northern Alaska to changes in the duration of the ice-free growing season, the availability of limiting nutrients for phytoplankton growth, and Arctic-wide atmospheric circulation dynamics over the Holocene on millennial timescales.

Microstructural evolution of gas hydrates in sedimentary matrices observed with synchrotron X-ray computed tomographic microscopy

NASA Astrophysics Data System (ADS)

Chaouachi, Marwen; Falenty, Andrzej; Sell, Kathleen; Enzmann, Frieder; Kersten, Michael; Haberthür, David; Kuhs, Werner F.

2015-06-01

The formation process of gas hydrates in sedimentary matrices is of crucial importance for the physical and transport properties of the resulting aggregates. This process has never been observed in situ at submicron resolution. Here we report on synchrotron-based microtomographic studies by which the nucleation and growth processes of gas hydrate were observed at 276 K in various sedimentary matrices such as natural quartz (with and without admixtures of montmorillonite type clay) or glass beads with different surface properties, at varying water saturation. Both juvenile water and metastably gas-enriched water obtained from gas hydrate decomposition was used. Xenon gas was employed to enhance the density contrast between gas hydrate and the fluid phases involved. The nucleation sites can be easily identified and the various growth patterns are clearly established. In sediments under-saturated with juvenile water, nucleation starts at the water-gas interface resulting in an initially several micrometer thick gas hydrate film; further growth proceeds to form isometric single crystals of 10-20 µm size. The growth of gas hydrate from gas-enriched water follows a different pattern, via the nucleation in the bulk of liquid producing polyhedral single crystals. A striking feature in both cases is the systematic appearance of a fluid phase film of up to several micron thickness between gas hydrates and the surface of the quartz grains. These microstructural findings are relevant for future efforts of quantitative rock physics modeling of gas hydrates in sedimentary matrices and explain the anomalous attenuation of seismic/sonic waves.

Geologic map of the Dillon quadrangle, Summit and Grand Counties, Colorado

USGS Publications Warehouse

Kellogg, Karl S.

2002-01-01

New 1:24,000-scale geologic mapping along the Interstate-70 urban corridor in western Colorado, in support of the USGS Central Region State/USGS Cooperative Geologic Mapping Project, is contributing to a more complete understanding of the stratigraphy, structure, tectonic evolution, and hazard potential of this rapidly developing region. The 1:24,000-scale Dillon quadrangle is near the headwaters of the Blue River and straddles features of the Blue River graben (Kellogg, 1999), part of the northernmost reaches of the Rio Grande rift, a major late Oligocene to recent zone of extension that extends from Colorado to Mexico. The Williams Range thrust fault, the western structural margin of the Colorado Front Range, cuts through the center of the quadrangle, although is mostly covered by surficial deposits. The oldest rocks in the quadrangle underlie the Williams Fork Mountains and the ridge immediately east of South Fork Middle Fork River, and include biotite-sillimanite schist and gneiss, amphibolite, and migmatite that are intruded by granite inferred to be part of the 1,667-1,750 Ma Routt Plutonic Suite (Tweto, 1987). The oldest exposed sedimentary unit is the Upper Jurassic Morrison Formation, but Pennsylvanian Maroon Formation, a sequence of red sandstone, conglomerate, and interbedded shale, underlies the southern part of the quadrangle. The thickest sequence of sedimentary rocks is Cretaceous in age and includes at least 500 m of the Upper Cretaceous Pierre Shale. Surficial deposits include (1) an old, deeply dissected landslide deposit, possibly as old as Pliocene, on the west flank of the Williams Fork Mountains, (2) deeply weathered, very coarse gravel deposits underlying a mesa in the southwest part of the quadrangle (the Mesa Cortina subdivision. The gravels are gold bearing and were mined by hydraulic methods in the 1800s), (3) moderately to deeply weathered, widespread, bouldery material that is a combination of till of the Bull Lake glaciation, debris-flow deposits, landslide deposits, and possibly pre-Bull Lake till, (4) glacial deposits of both Bull Lake (middle Pleistocene) and Pinedale (late Pleistocene)glaciations, (5) recent landslide deposits, and (6)extensive colluvial and alluvial deposits.

Geologic map of the Dillon quadrangle, Summit and Grand Counties, Colorado

USGS Publications Warehouse

Kellogg, Karl S.

1997-01-01

New 1:24,000-scale geologic mapping along the Interstate-70 urban corridor in western Colorado, in support of the USGS Central Region State/USGS Cooperative Geologic Mapping Project, is contributing to a more complete understanding of the stratigraphy, structure, tectonic evolution, and hazard potential of this rapidly developing region. The 1:24,000-scale Dillon quadrangle is near the headwaters of the Blue River and straddles features of the Blue River graben (Kellogg, 1999), part of the northernmost reaches of the Rio Grande rift, a major late Oligocene to recent zone of extension that extends from Colorado to Mexico. The Williams Range thrust fault, the western structural margin of the Colorado Front Range, cuts through the center of the quadrangle, although is mostly covered by surficial deposits. The oldest rocks in the quadrangle underlie the Williams Fork Mountains and the ridge immediately east of South Fork Middle Fork River, and include biotite-sillimanite schist and gneiss, amphibolite, and migmatite that are intruded by granite inferred to be part of the 1,667-1,750 Ma Routt Plutonic Suite (Tweto, 1987). The oldest exposed sedimentary unit is the Upper Jurassic Morrison Formation, but Pennsylvanian Maroon Formation, a sequence of red sandstone, conglomerate, and interbedded shale, underlies the southern part of the quadrangle. The thickest sequence of sedimentary rocks is Cretaceous in age and includes at least 500 m of the Upper Cretaceous Pierre Shale. Surficial deposits include (1) an old, deeply dissected landslide deposit, possibly as old as Pliocene, on the west flank of the Williams Fork Mountains, (2) deeply weathered, very coarse gravel deposits underlying a mesa in the southwest part of the quadrangle (the Mesa Cortina subdivision. The gravels are gold bearing and were mined by hydraulic methods in the 1800s), (3) moderately to deeply weathered, widespread, bouldery material that is a combination of till of the Bull Lake glaciation, debris-flow deposits, landslide deposits, and possibly pre-Bull Lake till, (4) glacial deposits of both Bull Lake (middle Pleistocene) and Pinedale (late Pleistocene)glaciations, (5) recent landslide deposits, and (6)extensive colluvial and alluvial deposits.

Migration Reversals in Grain-size Transitions to Shoreline

NASA Astrophysics Data System (ADS)

Baumanis, C.; Kim, W.

2015-12-01

The migration of the lithofacies boundary recorded in the sedimentary record is key to interpreting changes in depositional environments. Change in grain size in the stratigraphic record is one of the most recognizable physical lithological features. Advance and retreat of the lithofacies boundary (gravel-sand transition) is attributed to external control variation, e.g., climate variation, sea-level change, and tectonic subsidence. While most models focus on predicting the response of the fluviodeltaic shoreline to these forcings, none have thoroughly incorporated the migration of grain-size transitions (GST) that coevolve within the fluviodeltaic system. We present a delta evolution model that treats the shoreline and GST as moving boundaries to provide quantitative understanding of the dynamic interaction between the external boundary (shoreline) and the internal lithofacies boundaries (GSTs) under relative sea-level rise. We tested a range of relative sea-level rise rates in the model. The shoreline and GST gradually reduced their progradation rates and eventually retreated landward as the fluviodeltaic topset and foreset elongated. However, their timings of retreats were different, resulting in a counterintuitive case for a quicker retreat of GST while the shoreline still continued to advance. A series of scaled flume experiments with a sand and crushed walnut sediment mixture captured the same behaviors of these two moving boundaries. We found that GST experienced higher relative sea-level rise rates that scale with the downstream river slope and the shoreline progradation rate, which caused earlier GST retreat timing in comparison to the shoreline. Time series data from the experiments show higher natural variability in migration rate of GST compared to that of the shoreline. Therefore, final recorded stratigraphy displayed a GST trajectory as a shazam line that shows zigzag fluctuations. This study investigates autogenic processes acting on the fluviodeltaic surface and tests their stratigraphic architecture recorded in the trajectories. The fundamental understanding of migration of both the lithofacies transition and shoreline in fluviodeltaic systems from this study will aid in accurately assessing the trajectories of GST in sedimentary strata as a proxy for environmental change.

Trace fossils, sedimentary facies and parasequence architecture from the Lower Cretaceous Mulichinco Formation of Argentina: The role of fair-weather waves in shoreface deposits

NASA Astrophysics Data System (ADS)

Wesolowski, Lindsey J. N.; Buatois, Luis A.; Mángano, M. Gabriela; Ponce, Juan José; Carmona, Noelia B.

2018-05-01

Shorefaces can display strong facies variability and integration of sedimentology and ichnology provides a high-resolution model to identify variations among strongly storm-dominated (high energy), moderately storm-affected (intermediate energy), and weakly storm-affected (low energy) shoreface deposits. In addition, ichnology has proved to be of help to delineate parasequences as trace-fossil associations are excellent indicators of environmental conditions which typically change along the depositional profile. Shallow-marine deposits and associated ichnofaunas from the Mulichinco Formation (Valanginian, Lower Cretaceous) in Puerta Curaco, Neuquén Basin, western Argentina, were analyzed to evaluate stress factors on shoreface benthos and parasequence architecture. During storm-dominated conditions, the Skolithos Ichnofacies prevails within the offshore transition and lower shoreface represented by assemblages dominated by Thalassinoides isp. and Ophiomorpha irregulaire. Under weakly storm-affected conditions, the Cruziana Ichnofacies is recognized, characterized by assemblages dominated by Thalassinoides isp. and Gyrochorte comosa in the offshore transition, and by Gyrochorte comosa within the lower shoreface. Storm-influenced conditions yield wider ichnologic variability, showing elements of both ichnofacies. Storm influence on sedimentation is affected by both allogenic (e.g. tectonic subsidence, sea-level, and sediment influx) and autogenic (e.g. hydrodynamic) controls at both parasequence and intra-parasequence scales. Four distinct types of parasequences were recognized, strongly storm-dominated, moderately storm-affected, moderately storm-affected - strongly fair-weather reworked, and weakly storm-affected, categorized based on parasequence architectural variability derived from varying degrees of storm and fair-weather wave influence. The new type of shoreface described here, the moderately storm-affected - strongly fair-weather reworked shoreface, features storm deposits reworked thoroughly by fair-weather waves. During fair-weather wave reworking, elements of the Cruziana Ichnofacies are overprinted upon relict elements of the Skolithos Ichnofacies from previous storm induced deposition. This type of shoreface, commonly overlooked in past literature, expands our understanding of the sedimentary dynamics and stratigraphic architecture in a shoreface susceptible to various parasequence and intra-parasequence scale degrees of storm and fair-weather wave influence.

Geology of parts of the Johnny Gulch quadrangle, Montana

USGS Publications Warehouse

Freeman, Val L.

1954-01-01

An area of about 35 square miles, situated about 30 miles southeast of Helena, Montana, was mapped during the summer of 1952 at a scale of l:24, 000. The area includes a part of the eastern foothills of the Elkhorn Mountains, and is underlain by sedimentary mad volcanic rocks of Cretaceous age that were intruded during late Cretaceous or early Tertiary time by several types of igneous rocks. The oldest rocks in the map area are the nonmarine sandstone, shale, and limestone of the Kootenai formation. These are overlain disconformably by the black shale siltstone, sandstone, and siliceous mudstone of the Colorado group that is subdivided into three map units; a lower black shale unit composed of black shale and silty shale with a basal clean sandstone, all of probable marine origin; a middle siliceous unit composed of sandstone, siltstone, and siliceous mudstone of both marine and nonmarine origin; and an upper black unit composed of black shale of marine origin. Conformably above the Colorado group are crystal lithic turfs of the Slim Sam formation; in places theme grade into and in other places are unconformably overlain by the Elkhorn Mountains volcanics composed of crystal tuff, breccia, flows, and bedded tuff of andesitic composition. The rocks of the Elkhorn Mountains volcanics and older formations have been intruded by diorite porphyry and related rocks and by hornblende quartz monzonite. The diorite porphyry and related rocks include hornblende diorite porphyry, hornblende augite diorite porphyry, augite diorite porphyry, and basalt. Resting with marked unconformity upon older rocks are volcanic sedimentary rocks of early Tertiary age that are locally overlain by thin rhyolite flows. Late Tertiary and Quaternary fans overlie the rhyolite flows. Alluvium, talus, and other mantle are present in small amounts in many parts of the area. The sedimentary rocks of the area mapped form a part of the east flank of a major anticline. A major north-south syncline to the north of map area is believed to have been deflected to the east of the area because of the rigidity of large irregular plutons of diorite porphyry. The location of the plutons may have been controlled by the initiation of the major syncline, by a postulated pre-intrusive fault, or by both. Most of the small-scale structural features are related to the emplacement of the plutons. During emplacement the intruded sediments yielded either by faulting or by folding; the deeper rocks failed by faulting and the shallower rocks failed by folding. The area contains deposits of gold, silver, copper, lead, and zinc, none of which are currently being mined; and a deposit of magnetite which is being mined for use in cement.

Bottom currents and sediment transport in Long Island Sound: A modeling study

USGS Publications Warehouse

Signell, R.P.; List, J.H.; Farris, A.S.

2000-01-01

A high resolution (300-400 m grid spacing), process oriented modeling study was undertaken to elucidate the physical processes affecting the characteristics and distribution of sea-floor sedimentary environments in Long Island Sound. Simulations using idealized forcing and high-resolution bathymetry were performed using a three-dimensional circulation model ECOM (Blumberg and Mellor, 1987) and a stationary shallow water wave model HISWA (Holthuijsen et al., 1989). The relative contributions of tide-, density-, wind- and wave-driven bottom currents are assessed and related to observed characteristics of the sea-floor environments, and simple bedload sediment transport simulations are performed. The fine grid spacing allows features with scales of several kilometers to be resolved. The simulations clearly show physical processes that affect the observed sea-floor characteristics at both regional and local scales. Simulations of near-bottom tidal currents reveal a strong gradient in the funnel-shaped eastern part of the Sound, which parallels an observed gradient in sedimentary environments from erosion or nondeposition, through bedload transport and sediment sorting, to fine-grained deposition. A simulation of estuarine flow driven by the along-axis gradient in salinity shows generally westward bottom currents of 2-4 cm/s that are locally enhanced to 6-8 cm/s along the axial depression of the Sound. Bottom wind-driven currents flow downwind along the shallow margins of the basin, but flow against the wind in the deeper regions. These bottom flows (in opposition to the wind) are strongest in the axial depression and add to the estuarine flow when winds are from the west. The combination of enhanced bottom currents due to both estuarine circulation and the prevailing westerly winds provide an explanation for the relatively coarse sediments found along parts of the axial depression. Climatological simulations of wave-driven bottom currents show that frequent high-energy events occur along the shallow margins of the Sound, explaining the occurrence of relatively coarse sediments in these regions. Bedload sediment transport calculations show that the estuarine circulation coupled with the oscillatory tidal currents result in a net westward transport of sand in much of the eastern Sound. Local departures from this regional westward trend occur around topographic and shoreline irregularities, and there is strong predicted convergence of bedload transport over most of the large, linear sand ridges in the eastern Sound, providing a mechanism which prevents their decay. The strong correlation between the near-bottom current intensity based on the model results and the sediment response, as indicated by the distribution of sedimentary environments, provides a framework for predicting the long-term effects of anthropogenic activities.

Liquification and soft-sediment deformation in a limestone megabreccia: The Ayabacas giant collapse, Cretaceous, southern Peru

NASA Astrophysics Data System (ADS)

Callot, Pierre; Odonne, Francis; Sempere, Thierry

2008-12-01

In the back-arc basin of southern Peru, the bulk of the mid-Cretaceous carbonate platform collapsed near the Turonian-Coniacian boundary (~ 90-89 Ma), due to slope creation and resulting oversteepening. The resulting mass-wasting deposits, namely the Ayabacas Formation, consist of a megabreccia which is organised from NE to SW in relation with two major fault systems. Facies of sediment reworking (such as brecciation, liquification, sedimentary dykes and soft-sediment deformation) are described and four types of resedimentation facies are define. In the northeastern part of the study area, deposits mainly consist of a mixture of very heterometric clasts and blocks (millimetric to kilometric in size), mainly carbonate but also sandy-marly in nature, floating in sandy-marly matrix that exhibits features of liquification (sedimentary dykes and flows) and plastic deformation. Here, resedimentation facies are characterized by deformations and a brecciated facies at each observation scale (from aerial photographs to thin sections) and are therefore defined as fractal or multi-scale breccias. Some clasts and large amounts of the matrix were derived from the underlying clay-rich sandstones of the Murco Formation. These materials were prone to liquification and plastic deformation, allowing them to act as a sliding sole that facilitated the slides and the downslope movement of large limestone rafts. In the southwestern part of the study area, only limestone breccias are observed, in alternation with well-stratified levels. The sliding sole of plastically deformable siliciclastic sediments that previously acted as a lubricating layer was not present here, as materials were more deeply buried. Variations in the degree of sediment lithification from northeast to southwest are inferred to have existed before the collapse and also within the sedimentary succession in the northeastern part. In particular, limestones were well-cemented at the base of the carbonate succession and formed a cap that prevented water to escape from the underlying siliciclastic materials. Such a succession allowed the formation of limestone clasts and of a slide sole constituted by water-saturated siliciclastic materials. In the southern part of the study area, the slide surface was located within the Murco Formation in the upper part of the collapse and just above the Murco Formation downslope. The collapse was frontally confined as it was blocked downslope by a topographic high that folded the whole limestone succession. In the northern part of the study area, the slide surface was also within the Murco Formation in the upper part, but occurs within the limestone succession downslope, due to higher subsidence that buried the sediments more deeply. The compressional structures affecting the limestone succession in the south are not observed there, suggesting that the toe of the collapse was not blocked here.

The immature thrust belt of the northern front of the Tianshan

NASA Astrophysics Data System (ADS)

Chen, Ke; Gumiaux, Charles; Augier, Romain; Chen, Yan; Wang, Qingchen

2010-05-01

The modern Tianshan (central Asia), which extends east-west on about 2500 km long with an average of more than 2000 m in altitude, is considered as a direct consequence of the reactivation of a Paleozoic belt due to the India - Asia collision. At first order, the finite structure of this range obviously displays a significant uprising of Paleozoic "basement" rocks - as a crustal-scale ‘pop-up' - surrounded by two Cenozoic foreland basins. In order to characterize the coupling history of this Cenozoic orogeny with its northern foreland basin (Junggar basin), a detailed structural field work has been carried out on the northern piedmont of Tianshan. From Wusu to Urumqi, on about 250 km long, the thrusting of the Paleozoic basement on the Mesozoic or Cenozoic sedimentary series of the basin is remarkably exposed along several river valleys. In contrast, in other sections, the Triassic to Jurassic sedimentary series can be followed from the basin to the range where they unconformably overlie on the Carboniferous basement. These series are only gently folded along the "range front". These features imply that, at regional-scale, the Cenozoic reactivation of the Tianshan has not produced important deformation along its contact with the juxtaposed Junggar basin. The shortening ascribed to the Cenozoic intra-continental collision would either be localized in the range, mostly accommodated by reactivated Paleozoic structures or faults in the basement units, or in the distal parts of the Junggar basin, by folds and faults within the Cenozoic sedimentary series. Alternative hypothesis would be that the Tianshan uplift and the movements associated with along its northern front structures, which are traditionally assigned to its Cenozoic reactivation, might be reduced. Such characteristic significantly differs from other well-known orogenic ranges, such as the Canadian Rocky Mountains, the Appalachians, the Pyrenees which display highly folded foreland basins and thrust belts with rather well developed range front structures. This suggests that the Tianshan intra-continental range is rather "young" and still at a primary stage of its orogenic evolution. In other words, its front may be considered as an immature thrust belt. If considering the available tomographic data across the Tianshan, its actual uplift may probably be produced by an asymmetric intracontinental deformation mechanism, i.e. a deeper subduction of the Tarim plate below the Tianshan (to the south), with respect to the one of Junggar plate to the north of the range. Consequently, the Tianshan range offers an excellent natural laboratory to study the processes of the on-going orogeny-foreland basin coupling, ancient structures reactivation as well as initiation and development of range front structures.

Late Mesozoic tectonics of the Southern-Thai Peninsula: from transpression to basins opening

NASA Astrophysics Data System (ADS)

Sautter, Benjamin; Pubellier, Manuel; Menier, David

2015-04-01

The petroleum basins of the Southern Thailand Peninsula are poorly known and their final geometry is controlled by the Tertiary stress variations applied on pre-existing Paleozoic and Mesozoic basement structures. From the end of Mesozoic times, the arrival of Indian plate was accomodated by transpressionnal deformation along the Western Margin of Sunda Plate. Evidences of this strain are the motions along several regional strike Slip Faults (Sagaing, Three Pagodas, Mae Ping, Red River, Ranong and Klong Marui Faults) as well as compressional features (folds and thrusts) evidenced onshore. Due to changes in the boundary forces, these structures were reactivated during the Tertiary, leading to the opening of basins in this part of Sundaland. We present a structural analysis based on geomorphology, fieldwork and seismic interpretation of the Southern Thai Peninsula with emphasis on the deformation's style onshore from Ranong to Satun and offshore from Eastern Mergui to Songhkla. By analyzing morphostructures and drainage anomalies from Digital Elevation Model (SRTM and ASTER), we highlight a predominance of N-S structures in the Southern Thai Peninsula: both in the granitic belt and in the sedimentary cover. The Triassic-Jurassic (Indosinian) post-collision granitic belt is intensely fractured, with 2 penetrative directions: N140 and N50. On both sides, the sedimentary units appear folded at a large wavelength (~20km). On most of the studied outcrops, Triassic to Early Cretaceous series are gently tilted and weakly fractured whereas the Paleozoic ones shows intense fracturation and steep dipping beds. Moreover, all the Paleozoic stratas display a constant N-S S1 which does not appear in the Mezosoic sediments. Althought most of the post-Mesozoic sediments do not crop out due to thick vegetal cover, several Tertiary basins can be easily seen from seismic data both onshore and offshore. These data suggest that rifting started in the Eocene and was accommodated by large crust-scale Low Angle Normal Faults reactivating basement fabrics including intrusive edges and folds hinges. We propose a tectonic scenario for the southern Thai Peninsula according to which the northward motion of giant morphostructures (the Wharton Ridge followed by the Indian Plate) induced first right-lateral transpressionnal tectonics at the End of the Mesozoics. This system is illustrated by the 2 sets of fractures of the Indosinian Belt, the large-scale folds of Early Cretaceous Strata and the strike slip motions of the Ranong and Klong Marui Faults. Following the path of Indian Plate, a collapse of this hot and thin crust occurred accommodated via LANF's along the granitic belts and the sedimentary basement morpho-structures.

Sedimentological processes in a scarp-controlled rocky shoreline to upper continental slope environment, as revealed by unusual sedimentary features in the Neogene Coquimbo Formation, north-central Chile

NASA Astrophysics Data System (ADS)

Le Roux, J. P.; Gómez, Carolina; Fenner, Juliane; Middleton, Heather

2004-03-01

Exceptionally good outcrops of Miocene to Pliocene deposits in the vicinity of submarine Paleozoic basement scarps at Carrizalillo, north of La Serena, reveal a wealth of sedimentary features not commonly observed. The most proximal facies consist of rock fall and coarse-grained debris flow deposits directly abutting the basement wall from which they originated. Angular basement clasts are mixed with well-rounded cobbles, which probably formed as a basal gravel on a wave-cut platform at the beginning of marine flooding, subsequently accumulated at the scarp edge and were incorporated into the debris when the latter collapsed. The poor sorting, inverse grading, and protruding cobbles and boulders are classical debris flow features, with good clast imbrication indicating a laminar shearing action. A medial facies is represented by secondary channels running parallel to the major scarp about 1 km downslope of the first locality. In the largest channel, megaflutes at the base indicate the passage of highly turbulent, nondepositing flows eroding the soft, silty substrate. In the deepest, central part of the channel, a pebbly coquina shows horizontal and trough cross-stratification, with most of the bivalves oriented convex side up. Meter-scale rip-up clasts of the underlying siltstone are also present, indicating turbulent flow with a density sufficiently high to retard settling. The coquina is interpreted as a detachment deposit resulting from a hydroplaning debris flow along the central part of the channel, where the velocity and rate of pore pressure decay were highest. This deposit is overlain by fining upward, massive to horizontally stratified sandstone very similar in texture and composition to the matrix of the debris flow, suggesting its formation by surface transformation and elutriation of the latter. Along the channel margin, a basal centimeter-scale sandstone layer is virtually unaffected by the megaflute topography and clearly represents a subsequent event. It is interpreted as a basal shear carpet driven by the overlying debris flow. Within the shear carpet, a basal friction zone and an overlying collision zone containing a higher concentration of shell hash can be distinguished. The overlying debris flow deposit is represented by massive coquina with scattered, angular to rounded basement clasts. It contains disarticulated bivalves oriented with their concave side up, indicating large-scale upward fluid escape during deposition. A smaller secondary channel shows large rip-up rafts of the underlying substrate. Some rafts appear to have been plucked from the substrate by a process of sand injection from an overriding high-density sandy debris flow, which probably originated during a tsunami. Such clasts can climb upward into a laminar flow by down-current tilting and tumbling. The most distal facies occurs below a second scarp oriented more or less parallel to the present coastline, where finer-grained turbidites onlap and backlap onto the stoss and lee sides of an obstacle formed by eroded boulder conglomerates. The onlap deposits resemble inclined sandy macroforms recently described in submarine canyon settings. They are interbedded with diatom-containing, volcanic ash beds with cross-stratification dipping eastwards and containing deepwater microflora typical of continental upwelling zones.

Brine Flow Up a Borehole Caused by Pressure Perturbation From CO2 Storage: Static and Dynamic Evaluations

EPA Science Inventory

Industrial-scale storage of CO2 in saline sedimentary basins will cause zones of elevated pressure, larger than the CO2 plume itself. If permeable conduits (e.g., leaking wells) exist between the injection reservoir and overlying shallow aquifers, brine could be pushed upwards al...

Multiscale roughness characterization from multiresolution remote sensing data acquired over the Asal-Ghoubbet rift, Republic of Djibouti

NASA Astrophysics Data System (ADS)

Labarre, Sébastien; Jacquemoud, Stéphane; Ferrari, Cécile; Delorme, Arthur; Rupnik, Ewelina; Derrien, Allan; Pierrot-Deseilligny, Marc; Grandin, Raphaël; Jalludin, Mohamed

2017-04-01

Surface roughness is a key parameter in soil physics which controls many surface processes at a wide range of scales: microscopic and mesoscopic scales from 10 μm to 1 cm (soil particles or regolith), macroscopic scale from 1 cm to 1 m (clods, aggregates of rock or ice, micro-fractures or lava flows), and topographic scale from 1 m to several kilometers (faults, hills, craters or mountains). While it is recognized that surface roughness is strongly scale-dependent, it is often expressed as an integrated parameter (root-mean-square height, correlation length, tortuosity index), which does not address the full range of spatial features present on the surface. In particular, the Hapke roughness parameter is defined as the mean slope angle of the facets composing the surface, integrated over all scales from the microscopic to the macroscopic scales. Yet its physical meaning is still a question at issue, as the scale at which it occurs is undefined in the model. Photogrammetry has been shown to be an inexpensive and powerful method for topography reconstruction from optical data. We took advantage of a series of 21 Pléiades-1B images (video acquisition mode) to build a global digital elevation model (DEM) over the Asal-Ghoubbet rift, Republic of Djibouti. Additionally, we acquired close range data with a quadcopter equipped with a HD camera. Topography at four scales is available: 1 m with the satellite images (694 km), 1 cm with the drone flying at medium altitude ( 100 m), 1 mm with the drone flying at low altitude ( 10 m), and <1 mm with the handheld camera ( 1.5 m). We have defined twenty-two sites, 20 × 30 m in dimension, corresponding to a wide range of volcanic and sedimentary terrains, from regolith-like structures to very rough lava flows, over which DEMs have been generated at two or more resolutions. In order to investigate the contribution of each scale to the integrated roughness and to test the ability of the Hapke model to retrieve a roughness parameter that depicts well the ground truth, we applied two multiscale methods: fractal analysis and wavelet transform. The latter allows splitting the frequency band of a signal in several sub-bands, each of which corresponding to a spatial scale. By analyzing data acquired at Piton de la Fournaise Volcano, Réunion island, we showed that wavelet transform is a very powerful tool for characterizing roughness regimes over scales and that sub-centimeter surface features mostly explain the integrated roughness for meter-sized surfaces (Labarre et al., 2017, Icarus). This has to be confirmed on Djibouti terrains, for which we have a broader range of resolutions and larger areas.

Facies-related fracturing in turbidites: insights from the Marnoso-Arenacea Fm. (Northern Apennines, Italy)

NASA Astrophysics Data System (ADS)

Ogata, Kei; Storti, Fabrizio; Balsamo, Fabrizio; Bedogni, Enrico; Tinterri, Roberto; Fetter, Marcos; Gomes, Leonardo; Hatushika, Raphael

2016-04-01

Natural fractures deeply influence subsurface fluid flow, exerting a primary control on resources like aquifers, hydrocarbons and geothermal reservoirs, and on environmental issues like CO2 storage and nuclear waste disposal. In layered sedimentary rocks, depositional processes-imprinted rock rheology favours the development of both mechanical anisotropy and heterogeneity on a wide range of scales, and are thus expected to strongly influence location and frequency of fractures. To better constrain the contribution of stratigraphic, sedimentological and petrophysical attributes, we performed a high-resolution, multidisciplinary study on a selected stratigraphic interval of jointed foredeep turbidites in the Miocene Marnoso-arenacea Formation (Northern Apennines, Italy), which are characterised by a great lateral and vertical variability of grain-size and depositional structures. Statistical relationships among field and laboratory data significantly improve when the single facies scale is considered, and, for similar facies recording different evolutionary stages of the parent turbidity currents, we observed a direct correlation between the three-dimensional anisotropies of rock hardness tensors and the normalized fracture frequencies, testifying for the primary sedimentary flow-related control on fracture distributions.

Evidence of repeated wildfires prior to human occupation on San Nicolas Island, California

USGS Publications Warehouse

Pigati, Jeffrey S.; McGeehin, John P.; Skipp, Gary L.; Muhs, Daniel R.

2014-01-01

Understanding how early humans on the California Channel Islands might have changed local fire regimes requires a baseline knowledge of the frequency of natural wildfires on the islands prior to human occupation. A sedimentary sequence that was recently discovered in a small canyon on San Nicolas Island contains evidence of at least 24 burn events that date to between ~37 and 25 ka (thousands of calibrated 14C years before present), well before humans entered North America. The evidence includes abundant macroscopic charcoal, blackened sediments, and discrete packages of oxidized, reddish-brown sediments that are similar in appearance to sedimentary features called “fire areas” on Santa Rosa Island and elsewhere. Massive fine-grained sediments that contain the burn evidence are interpreted as sheetwash deposits and are interbedded with coarse-grained, clast-supported alluvial sediments and matrix supported sands, pebbles, and cobbles that represent localized debris flows. These sedimentary sequences suggest that the catchment area above our study site underwent multiple cycles of relative quiescence that were interrupted by fire and followed by slope instability and mass wasting events. Our 14C-based chronology dates these cycles to well before the arrival of humans on the Channel Islands and shows that natural wildfires occurred here, at a minimum, every 300–500 years prior to human occupation.

Thin-skinned deformation of sedimentary rocks in Valles Marineris, Mars

USGS Publications Warehouse

Metz, Joannah; Grotzinger, John P.; Okubo, Chris; Milliken, Ralph

2010-01-01

Deformation of sedimentary rocks is widespread within Valles Marineris, characterized by both plastic and brittle deformation identified in Candor, Melas, and Ius Chasmata. We identified four deformation styles using HiRISE and CTX images: kilometer-scale convolute folds, detached slabs, folded strata, and pull-apart structures. Convolute folds are detached rounded slabs of material with alternating dark- and light-toned strata and a fold wavelength of about 1 km. The detached slabs are isolated rounded blocks of material, but they exhibit only highly localized evidence of stratification. Folded strata are composed of continuously folded layers that are not detached. Pull-apart structures are composed of stratified rock that has broken off into small irregularly shaped pieces showing evidence of brittle deformation. Some areas exhibit multiple styles of deformation and grade from one type of deformation into another. The deformed rocks are observed over thousands of kilometers, are limited to discrete stratigraphic intervals, and occur over a wide range in elevations. All deformation styles appear to be of likely thin-skinned origin. CRISM reflectance spectra show that some of the deformed sediments contain a component of monohydrated and polyhydrated sulfates. Several mechanisms could be responsible for the deformation of sedimentary rocks in Valles Marineris, such as subaerial or subaqueous gravitational slumping or sliding and soft sediment deformation, where the latter could include impact-induced or seismically induced liquefaction. These mechanisms are evaluated based on their expected pattern, scale, and areal extent of deformation. Deformation produced from slow subaerial or subaqueous landsliding and liquefaction is consistent with the deformation observed in Valles Marineris.

Arsinoes Chaos Landforms

NASA Technical Reports Server (NTRS)

2004-01-01

23 October 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned rock outcrops, possibly sedimentary rocks, in the Arsinoes Chaos region east of the Valles Marineris trough system. These rocky materials were once below the martian surface. These features are located near 7.2oS, 27.9oW. The image covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the upper left.

The geological heritage of the Kurkur-Dungul area in southern Egypt

NASA Astrophysics Data System (ADS)

Sallam, Emad S.; Ponedelnik, Alena A.; Tiess, Günter; Yashalova, Natalia N.; Ruban, Dmitry A.

2018-01-01

The inventory of the geological heritage of Egypt is important for its efficient conservation and usage for the purposes of science, education, and tourism. The field investigations in the Kurkur-Dungul area in southern Egypt have permitted to identify several unique geological features. Their type, rank, relative abundance, and intrinsic diversity, as well as importance of the entire geological heritage of the study area are investigated. Seven geological heritage types are distinguished, namely stratigraphical, sedimentary, palaeogeographical, mineralogical, structural, geomorphological, and economical types. The rank of the features belonging to the listed types ranges from local to global, and the relative abundance and the intrinsic diversity range from low to high. The global rank is established for the sedimentary type, which is determined by the wide distribution of palaeospring tufa deposits. The high relative abundance and intrinsic diversity are established for the geomorphological type. The entire geological heritage of the Kurkur-Dungul area can be employed for diversification of the existing tourism programs offered at the tourist destination of Aswan, as well as for geotourism development. A geopark can be created in the Kurkur-Dungul area for the better exploitation of its geological heritage. The combined development of geological and industrial tourism seems to be possible.

Discussion on final rifting evolution and breakup : insights from the Mid Norwegian - North East Greenland rifted system

NASA Astrophysics Data System (ADS)

Peron-Pinvidic, Gwenn; Terje Osmundsen, Per

2016-04-01

In terms of rifted margin studies, the characteristics of the distal and outer domains are among the today's most debated questions. The architecture and composition of deep margins are rarely well constrained and hence little understood. Except from in a handful number of cases (eg. Iberia-Newfoundland, Southern Australia, Red Sea), basement samples are not available to decipher between the various interpretations allowed by geophysical models. No consensus has been reached on the basement composition, tectonic structures, sedimentary geometries or magmatic content. The result is that non-unique end-member interpretations and models are still proposed in the literature. So, although these domains mark the connection between continents and oceans, and thus correspond to unique stages in the Earth's lithospheric life cycle, their spatial and temporal evolution are still unresolved. The Norwegian-Greenland Sea rift system represents an exceptional laboratory to work on questions related to rifting, rifted margin formation and sedimentary basin evolution. It has been extensively studied for decades by both the academic and the industry communities. The proven and expected oil and gas potentials led to the methodical acquisition of world-class geophysical datasets, which permit the detailed research and thorough testing of concepts at local and regional scales. This contribution is issued from a three years project funded by ExxonMobil aiming at better understanding the crustal-scale nature and evolution of the Norwegian-Greenland Sea. The idea was to take advantage of the data availability on this specific rift system to investigate further the full crustal conjugate scale history of rifting, confronting the various available datasets. In this contribution, we will review the possible structural and sedimentary geometries of the distal margin, and their connection to the oceanic domain. We will discuss the definition of 'breakup' and introduce a first order conceptual model that proposes a combined influence of tectonic and magmatic processes on the outbuilding of the distal, outer and oceanic domains.

Estimation of Hydraulic Properties Influencing Recharge and Contaminant Transport through Complex Vadose Zones by Analyzing Perched Water Data from the 1994 Large-Scale Infiltration Test at the Idaho National Laboratory

NASA Astrophysics Data System (ADS)

Creasey, K. M.; Nimmo, J. R.

2014-12-01

Layers of strong geologic contrast within the vadose zone can control recharge and contaminant transport to underlying aquifers. Above the eastern Snake River Plain Aquifer, multiple sedimentary interbeds are interspersed between fractured basalt. These interbeds have a variety of thicknesses and hydraulic properties, and can impede water flow, which allows perched water to collect on the interbeds. The Large-Scale Infiltration Test (LSIT) of 1994 at the Idaho National Laboratory (INL) maintained a circular pond, 200 meters in diameter, at a constant head for 20 days. Monitoring wells were arranged in circles of different radii around and within the pond, and perched water levels on a major sedimentary interbed, 55 meters below ground surface, were measured over time. Data showed that water formed a mound on the interbed before seeping through the interbed. Such behavior is consistent with a hypothesis of rapid flow through the fractured basalt being impeded by the sedimentary interbed. In 2014, the USGS, in cooperation with the U.S. Department of Energy, used a modified version of a Hantush (1967) equation to model the time-dependent perched water table heights from the LSIT as a function of radial distance from the pond center. The modeled volume change between time-steps and the known inflows to the pond were used in a mass balance to estimate the time-varying volume of water seeping through the interbed. This volume of water, the height of perched water, and the interbed thickness were used in Darcy's Law to estimate the effective saturated hydraulic conductivity of the impeding interbed. Results indicate a slightly higher effective conductivity than laboratory measurements of small core samples taken from the interbed, reflecting the presence of fractures or other heterogeneities that facilitate field-scale flow through the interbed. Applied to other locations, this method can improve estimates of recharge and contaminant transport to underlying aquifers.

Seafloor character and sedimentary processes in eastern Long Island Sound and western Block Island Sound

USGS Publications Warehouse

Poppe, Lawrence J.; Cohen-DiGiacomo, M. L.; Smith, S.M.; Stewart, H.F.; Forfinski, N.A.

2006-01-01

Multibeam bathymetric data and seismic-reflection profiles collected in eastern Long Island Sound and western Block Island Sound reveal previously unrecognized glacial features and modern bedforms. Glacial features include an ice-sculptured bedrock surface, a newly identified recessional moraine, exposed glaciolacustrine sediments, and remnants of stagnant-ice-contact deposits. Modern bedforms include fields of transverse sand waves, barchanoid waves, giant scour depressions, and pockmarks. Bedform asymmetry and scour around obstructions indicate that net sediment transport is westward across the northern part of the study area near Fishers Island, and eastward across the southern part near Great Gull Island.

Horizontal stress in planetary lithospheres from vertical processes

NASA Technical Reports Server (NTRS)

Banerdt, W. B.

1991-01-01

Understanding the stress states in a lithosphere is of fundamental importance for planetary geophysics. It is closely linked to the processes which form and modify tectonic features on the surface and reflects the behavior of the planet's interior, providing a constraint for the difficult problem of determining interior structure and processes. The tectonics on many extraterrestrial bodies (Moon, Mars, and most of the outer planet satellites) appears to be mostly vertical, and the horizontal stresses induced by vertical motions and loads are expected to dominate the deformation of their lithospheres. Herein, only changes are examined in the state of stress induced by processes such as sedimentary and volcanic deposition, erosional denudation, and changes in the thermal gradient that induce uplift or subsidence. This analysis is important both for evaluating stresses for specific regions in which the vertical stress history can be estimated, as well as for applying the proper loading conditions to global stress models. All references to lithosphere herein should be understood to refer to the elastic lithosphere, that layer which deforms elastically or brittlely when subjected to geologically scaled stresses.

Frustules to fragments, diatoms to dust: How degradation of microfossil shape and microstructures can teach us how ice sheets work

USGS Publications Warehouse

Scherer, R.P.; Sjunneskog, C.M.; Iverson, M.R.; Hooyer, T.S.

2005-01-01

In a laboratory experiment we investigated micro- and nanoscale changes in fossil diatom valves and in the texture of diatomaceous sediments that result from ice sheet overburden and subglacial shearing. Our experiment included compression and shearing of Antarctic diatom-rich sediments in a ring shear device and comparison of experimental samples with natural glacial sediments from the Antarctic continental shelf. The purpose of the experiment is to establish objective criteria for analyzing subglacial processes and interpreting the origin of glacial-geologic features on the Antarctic continental shelf. We find distinct changes resulting from different glacial settings, with respect to whole diatom frustules, diatom micromorphology, and microtextural properties of sedimentary units. By providing constraints on subglacial shearing, these observations of genetically controlled micro- and nanoscale diatom structures and architecture are contributing to the understanding of large-scale glacial processes, aiding the development of models of modern ice sheet processes, and guiding interpretation of past ice sheet configurations. Copyright ?? 2005 American Scientific Publishers. All rights reserved.

Recent sedimentological studies of the Murray and Stimson formations and their implications for Gale crater evolution, Mars

NASA Astrophysics Data System (ADS)

Gupta, Sanjeev; Fedo, Chris; Grotzinger, John; Edgett, Ken; Vasavada, Ashwin

2017-04-01

The Mars Science Laboratory (MSL) Curiosity rover has been exploring sedimentary rocks on the lower north slope of Aeolis Mons since August 2014. Previous work has demonstrated a succession of sedimentary rock types deposited dominantly in river-delta settings (Bradbury group), and interfingering/overlying contemporaneous/younger lake settings (Murray formation, Mt. Sharp group). The Murray formation is unconformably overlain by the Stimson formation, an ancient aeolian sand lithology. Here, we describe the MSL team's most recent sedimentological findings regarding the Murray and Stimson formations. The Murray formation is of the order of 200 meters thick and formed dominantly of mudstones. The mudstone facies, originally identified at the Pahrump Hills field site, show abundant fine-scale planar laminations throughout the Murray formation succession and is interpreted to record deposition in an ancient lake system in Gale crater. Since leaving the Naukluft Plateau (Stimson formation rocks) and driving south-southeastwards and progressive stratigraphically upwards through the Murray succession, we have recognised a variety of additional facies have been recognized that indicate variability in the overall palaeoenvironmental setting. These facies include (1) cross-bedded siltstones to very fine-grained sandstones with metre-scale troughs that might represent aeolian sedimentation; (2) a heterolithic mudstone-sandstone facies with laminated fine-grained strata, cm-scale ripple cross-laminations in siltstone or very fine sandstone, and dm-scale cross-stratified siltstone and very fine grained sandstone. The palaeoenvironmental setting for the second facies remains under discussion. Our results show that Gale crater hosted lakes systems for millions to tens of millions of years, perhaps punctuated by drier intervals. Murray strata are unconformably overlain by the Stimson formation. Stimson outcrops are typically characterized by cross-bedded sandstones with cross-sets ranging between 40-80 cm thick (Fig. 2). Within the sets, cross-strata comprise repetitive laminations that are a few millimeters thick and typically sub-parallel. Cross-laminations downlap onto the underlying bounding surface with an asymptotic profile and are truncated at their top by an overlying bounding surface. Palaeocurrent analysis based on measurements of 117 foreset azimuths indicate a wind regime that drove dune migration towards the northeast. Cross sets are separated by erosional bounding surfaces, which are interpreted to represent interdune surfaces, which were formed by migrating dunes as they climbed over the stoss slope of a preceding dune, eroding its stoss and upper part of the lee slope. From analysis of the sedimentary architecture, and comparison with terrestrial aeolian strata, we interpret the Stimson formation to represent sands deposited in a dry-aeolian dune system. In summary, sedimentary observations by the Curiosity rover record a diverse range of palaeoenvironments and a rich geological history in strata preserved in lower Aeolis Mons.

A model of tephra dispersal from an early Palaeogene shallow submarine Surtseyan-style eruption(s), the Red Bluff Tuff Formation, Chatham Island, New Zealand

NASA Astrophysics Data System (ADS)

Sorrentino, Leonor; Stilwell, Jeffrey D.; Mays, Chris

2014-03-01

The Red Bluff Tuff Formation, an early Palaeogene volcano-sedimentary shallow marine succession from the Chatham Islands (New Zealand), provides a unique framework, in eastern 'Zealandia', to explore tephra dispersal processes associated with ancient small phreatomagmatic explosions (i.e. Surtseyan-style eruptions). Detailed sedimentological mapping, logging and sampling integrated with the results of extensive laboratory analyses (i.e. grain-size, componentry and applied palaeontological methods) elucidated the complex mechanisms of transport and deposition of nine identified resedimented fossiliferous volcaniclastic facies. These facies record the subaqueous reworking and deposition of tephra from the erosion and degradation of a proximal, entirely submerged ancient Surtseyan volcanic edifice (Cone II). South of this volcanic cone, the lowermost distal facies provides significant evidence of deposition as water-supported volcanic- or storm-driven mass flows (e.g. turbidity currents and mud/debris flows) of volcaniclastic and bioclastic debris, whereas the uppermost distal facies exhibit features of tractional sedimentary processes caused by shallow subaqueous currents. Further north, within the proximity of the volcanic edifice, the uppermost facies are represented by an abundant, diverse, large, and well preserved in situ fauna of shallow marine sessile invertebrates (e.g. corals and sponges) that reflect the protracted biotic stabiliszation and rebound following pulsed volcanic events. Over a period of time, these stable and wave-eroded volcanic platforms were inhabited by a flourishing and diversifying marine community of benthic and sessile pioneers (corals, bryozoans, molluscs, brachiopods, barnacles, sponges, foraminifera, etc.). This succession exhibits a vertical progression of sedimentary structures (i.e. density, cohesive and mass flows, and cross-bedding) and our interpretations indicate a shallowing upwards succession. This study reports for the first time mechanisms of degradation of a Surtseyan volcano on Chatham Islands and contributes to a better understanding of complex ancient volcano-sedimentary subaqueous terrains. This model of deposition (i.e. onlapping/overlapping features onto the remains of volcanic edifice(s), a vertical transition of structures from deeper- to shallower-marine environments, disaster faunas and subsequent preferential colonisation of diverse biota, including large in situ sessile invertebrates, on the summit), characterises an extraordinary example to be applied to other ancient subaqueous volcanic environments.

The tsunami phenomenon

NASA Astrophysics Data System (ADS)

Röbke, B. R.; Vött, A.

2017-12-01

With human activity increasingly concentrating on coasts, tsunamis (from Japanese tsu = harbour, nami = wave) are a major natural hazard to today's society. Stimulated by disastrous tsunami impacts in recent years, for instance in south-east Asia (2004) or in Japan (2011), tsunami science has significantly flourished, which has brought great advances in hazard assessment and mitigation plans. Based on tsunami research of the last decades, this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view. Starting with the wave features, tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss. At the coast, tsunamis typically show wave shoaling, funnelling and resonance effects as well as a significant run-up and backflow. Tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms. Such are earthquakes as the main trigger, submarine and subaerial mass wastings, volcanic activity, atmospheric disturbances (meteotsunamis) and cosmic impacts, as is demonstrated by giving corresponding examples from the past. Tsunamis are known to have a significant sedimentary and geomorphological off- and onshore response. So-called tsunamites form allochthonous high-energy deposits that are left at the coast during tsunami landfall. Tsunami deposits show typical sedimentary features, as basal erosional unconformities, fining-upward and -landward, a high content of marine fossils, rip-up clasts from underlying units and mud caps, all reflecting the hydrodynamic processes during inundation. The on- and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro- and morphodynamic numerical models. The paper provides an overview of the basic tsunami modelling techniques, including discretisation, guidelines for appropriate temporal and spatial resolution as well as the nesting method. Furthermore, the Boussinesq approximation-a simplification of the three-dimensional Navier-Stokes equations-is presented as a basic theory behind numerical tsunami models, which adequately reflects the non-linear, dispersive wave behaviour of tsunamis. The fully non-linear Boussinesq equations allow the simulation of tsunamis e.g. in the form of N-waves. Based on the various subtopics presented, recommendations for future multidisciplinary tsunami research are made. It is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre-/history and physiogeographical setting of a specific region.

High severity fires, positive fire feedbacks and alternative stable states in Athrotaxis rainforest ecosystems in western Tasmania.

NASA Astrophysics Data System (ADS)

Holz, A.; Wood, S.; Fletcher, M. S.; Ward, C.; Hopf, F.; Veblen, T. T.; Bowman, D. M. J. S.

2016-12-01

Recurrent landscape fires present a powerful selective force on plant regeneration strategies that form a continuum between vegetative resprouters and obligate seeders. In the latter case, reduction of the interval between fires, combined with factors that affect plant traits and regeneration dynamics can drive plant population to local extinction. Here we use Athrotaxis selaginoides, a relict fire-sensitive Gondwanan tree species that occurs in western Tasmania, as model system to investigate the putative impacts of climate change and variability and human management of fire. We integrate landscape ecology (island-wide scale), with field survey and dendrochronology (stand-scale) and sedimentary records (watershed and landscape-scales) to garner a better understanding of the timing and impact of landscape fire on the vegetation dynamics of Athrotaxis at multiple scales. Across the species range sedimentary charcoal and pollen concentrations indicate that the recovery time since the last fire has consistently lengthened over the last 10,000 yrs. Stand-scale tree-age and fire-scar reconstructions suggest that populations of the Athrotxis have survive very infrequent landscape fires over the last 4-6 centuries, but that fire severity has increased following European colonization causing population collapse of Athrotaxis and an associate shift in stand structure and composition that favor resprouter species over obligate seeders. Overall our findings suggest that the resistance to fires and postfire recovery of populations of A. selaginoides have gradually declined throughout the Holocene and rapidly declined after Europeans altered fire regimes, a trend that matches the fate other Gondwanan conifers in temperate rainforests elsewhere in the southern Hemisphere.

Mapping Mars' northern plains: origins, evolution and response to climate change - a new overview of recent ice-related landforms in Acidalia Planitia.

NASA Astrophysics Data System (ADS)

Hauber, Ernst; Orgel, Csilla; van Gasselt, Stephan; Reiss, Dennis; Johnsson, Andreas; Ramsdale, Jason; Balme, Matthew; Conway, Susan; Costard, Francois; Gallagher, Colman; Kereszturi, Akos; Platz, Thomas; Séjourné, Antoine; Skinner, James; Swirad, Zuzanna; Łosiak, Anna

2015-04-01

An International Space Science Institute (ISSI) team project has been convened to study the northern plains of Mars. It uses a geomorphological grid-mapping approach to compare ice-related landforms across N-S traverses in the three main basins of the northern plains: Acidalia, Arcadia, and Utopia Planitiae. The main science questions are (i) the distribution of ice-related landforms in the northern plains and their relation to distinct latitude bands or different geological units, (ii) the relationship between the latitude dependent mantle (LDM) and landforms indicative of ground ice, and (iii) the distributions and associations of recent landforms indicative of thaw of ice or snow. We mapped individual landforms across the Acidalia Planitia that may have been formed in association with ice or water in an attempt to determine their extent and identify possible spatial relationships and genetic links between them. Our list includes mantling deposits, small-scale polygons, gullies, viscous flow features, thumbprint terrain (TPT), giant polygons and large pitted mounds (LPM). Our resulting maps show the distribution of specific landforms (no data - absence - presence - dominance) in grid cells with a size of ~20 × 20 km, but allows also for some ambiguity (possible). Preliminary results show that the mantling deposits are ubiquitous and occur basically everywhere between ~43°N and almost the margin of the north polar cap. As their surface may appear smooth if intact, their texture can be difficult to detect at CTX scale. Gullies were observed within a limited latitude range between ~32°N and ~54°N. They predominantly occur in Acidalia and Acidalia Colles, although gullies were found in several impact craters. Small-scale polygons occur between ~60°N to ~70°N in agreement with previous studies. They are predominantly oriented in orthogonal networks in crater interiors, depressions and on plains. Viscous flow features are present only in higher-relief areas of the Acidalia Mensae and Colles. Their morphology is not well pronounced, partially subdued and covered, and most features are restricted to debris aprons distributed circumferentially around small knobs. TPT appears north of about 30°N in the most distal parts of the Chryse outflow channels and shows a transition zone with LPM at around 36°N and it is not observed north of ~39N°. The giant polygons with the LPM have been considered analogous to fluid expulsion features in terrestrial sedimentary basins. They characterize the study area from to 35 N° until 61 N° and completely disappear in the Acidalia Colles region. Grid mapping proved to be an efficient way to map small-scale landforms over wide areas. The distribution of possible ice- and water-related features in Acidalia is clearly latitude- and topography-dependent

Multivariate geostatistical modeling of the spatial sediment distribution in a large scale drainage basin, Upper Rhone, Switzerland

NASA Astrophysics Data System (ADS)

Schoch, Anna; Blöthe, Jan Henrik; Hoffmann, Thomas; Schrott, Lothar

2018-02-01

There is a notable discrepancy between detailed sediment budget studies in small headwater catchments (< 102 km2) focusing on the identification of sedimentary landforms in the field (e.g. talus cones, moraine deposits, fans) and large scale studies (> 103 km2) in higher order catchments applying modeling and/or remote sensing based approaches for major sediment storage delineation. To bridge the gap between these scales, we compiled an inventory of sediment and bedrock coverage from field mapping, remote sensing analysis and published data for five key sites in the Upper Rhone Basin (Val d'Illiez, Val de la Liène, Turtmanntal, Lötschental, Goms; 360.3 km2, equivalent to 6.7% of the Upper Rhone Basin). This inventory was used as training and testing data for the classification of sediment and bedrock cover. From a digital elevation model (2 × 2 m ground resolution) and Landsat imagery we derived 22 parameters characterizing local morphometry, topography and position, contributing area, and climatic and biotic factors on different spatial scales, which were used as inputs for different statistical models (logistic regression, principal component logistic regression, generalized additive model). Best prediction results with an excellent performance (mean AUROC: 0.8721 ± 0.0012) and both a high spatial and non-spatial transferability were achieved applying a generalized additive model. Since the model has a high thematic consistency, the independent input variables chosen based on their geomorphic relevance are suitable to model the spatial distribution of sediment. Our high-resolution classification shows that 53.5 ± 21.7% of the Upper Rhone Basin are covered with sediment. These are by no means evenly distributed: small headwaters (< 5 km2) feature a very strong variability in sediment coverage, with watersheds drowning in sediments juxtaposed to watersheds devoid of sediment cover. In contrast, larger watersheds predominantly show a bimodal distribution, with highest densities for bedrock (30-40%) being consistently lower than for sediment cover (60-65%). Earlier studies quantifying sedimentary cover and volume focus on the broad glacially overdeepened Rhone Valley that accounts for c. 9% of our study area. While our data support its importance, we conservatively estimate that the remaining 90% of sediment cover, mainly located outside trunk valleys, account for a volume of 2.6-13 km3, i.e. 2-16% of the estimated sediment volume stored in the Rhone Valley between Brig and Lake Geneva. Furthermore, our data reveal increased relative sediment cover in areas deglaciated since the Little Ice Age, as compared to headwater regions without this recent glacial imprint. We therefore conclude that sediment storage in low-order valleys, often neglected in large scale studies, constitutes a significant component of large scale sediment budgets that needs to be better included into future analysis.

General geology and geomorphology of the Mars Pathfinder landing site

USGS Publications Warehouse

Ward, A.W.; Gaddis, L.R.; Kirk, R.L.; Soderblom, L.A.; Tanaka, K.L.; Golombek, M.P.; Parker, T.J.; Greeley, Ronald; Kuzmin, R.O.

1999-01-01

The Mars Pathfinder (MPF) spacecraft landed on relatively young (late Hesperian-early Amazonian; 3.1-0.7 Ga) plains in Chryse Planitia near the mouth of Ares Vallis. Images returned from the spacecraft reveal a complex landscape of ridges and troughs, large hills and crater rims, rocks and boulders of various sizes and shapes, and surficial deposits, indicating a complex, multistage geologic history of the landing site. After the deposition of one or more bedrock units, depositional and erosional fluvial processes shaped much of the present landscape. Multiple erosional events are inferred on the basis of observations of numerous channels, different orientations of many streamlined tails from their associated knobs and hills, and superposition of lineations and streamlines. Medium- and small-scale features, interpreted to be related to late-stage drainage of floodwaters, are recognized in several areas at the landing site. Streamlined knobs and hills seen in Viking orbiter images support this inference, as they seem to be complex forms, partly erosional and partly depositional, and may also indicate a series of scouring and depositional events that, in some cases, further eroded or partially buried these landforms. Although features such as these are cited as evidence for catastrophic flooding at Ares Vallis, some of these features may also be ascribed to alternative primary or secondary depositional processes, such as glacial or mass-wasting processes. Close inspection of the landing site reveals rocks that are interpreted to be volcanic in origin and others that may be conglomeratic. If such sedimentary rocks are confirmed, fluvial processes have had a greater significance on Mars than previously thought. For the last several hundred million to few billion years, eolian processes have been dominant. Dunes and dune-like features, ventifacts, and deflation and exhumation features around several rocks probably are the most recent landforms. The relatively pristine nature of the overall landscape at the MPF site suggests weathering and erosion processes on Mars are exceptionally slow.

Integrated Potential-field Studies in Support of Energy Resource Assessment in Frontier Areas of Alaska

NASA Astrophysics Data System (ADS)

Phillips, J. D.; Saltus, R. W.; Potter, C. J.; Stanley, R. G.; Till, A. B.

2008-05-01

In frontier areas of Alaska, potential-field studies play an important role in characterizing the geologic structure of sedimentary basins having potential for undiscovered oil and gas resources. Two such areas are the Yukon Flats basin in the east-central interior of Alaska, and the coastal plain of the Arctic National Wildlife Refuge (ANWR) in northeastern Alaska. The Yukon Flats basin is a potential source of hydrocarbon resources for local consumption and possible export. Knowledge of the subsurface configuration of the basin is restricted to a few seismic reflection profiles covering a limited area and one well. The seismic profiles were reprocessed and reinterpreted in preparation for an assessment of the oil and gas resources of the basin. The assessment effort required knowledge of the basin configuration away from the seismic profiles, as well as an understanding of the nature of the underlying basement. To extend the interpretation of the basin thickness across the entire area of the basin, an iterative Jachens-Moring gravity inversion was performed on gridded quasi-isostatic residual gravity anomaly data. The inversion was constrained to agree with the interpreted basement surface along the seismic profiles. In addition to the main sedimentary depocenter interpreted from the seismic data as having over 8 km of fill, the gravity inversion indicated a depocenter with over 7 km of fill in the Crooked Creek sub-basin. Results for the Crooked Creek sub-basin are consistent with magnetic and magnetotelluric modeling, but they await confirmation by drilling or seismic profiling. Whether hydrocarbon source rocks are present in the pre-Cenozoic basement beneath Yukon Flats is difficult to determine because extensive surficial deposits obscure the bedrock geology, and no deep boreholes penetrate basement. The color and texture patterns in a red-green-blue composite image consisting of reduced-to-the-pole aeromagnetic data (red), magnetic potential (blue), and basement gravity (green) highlight domains with common geophysical characteristics and, by inference, lithology. The observed patterns suggest that much of the basin is underlain by Devonian to Jurassic oceanic rocks that probably have little or no potential for hydrocarbon generation. The coastal plain surficial deposits in the northern part of ANWR conceal another frontier basin with hydrocarbon potential. Proprietary aeromagnetic and gravity data were used, along with seismic reflection profiles, to construct a structural and stratigraphic model of this highly deformed sedimentary basin for use in an energy resource assessment. Matched-filtering techniques were used to separate short-wavelength magnetic and gravity anomalies attributed to sources near the top of the sedimentary section from longer-wavelength anomalies attributed to deeper basin and basement sources. Models along the seismic reflection lines indicate that the primary sources of the short-wavelength anomalies are folded and faulted sedimentary beds truncated at the Pleistocene erosion surface. In map view, the aeromagnetic and gravity anomalies produced by the sedimentary units were used to identify possible structural trapping features and geometries, but they also indicated that these features may be significantly disrupted by faulting.

Analysis of marine multi-channel seismic data using a 2D continuous wavelet transform

NASA Astrophysics Data System (ADS)

Vuong, A. K.; Zhang, J.; Gibson, R. L.; Sager, W. W.

2011-12-01

Marine multi-channel seismic (MCS) profiles provide important constraints on crustal structure beneath the sea floor. MCS data usually provide good images of the upper part of the oceanic crust, especially in sedimentary layers. In contrast, it is often difficult to interpret deeper layers, especially those within the igneous basement, which is often nearly seismically transparent. That difference in interpretability occurs because sediments typically have continuous, well-layered and easily-traced structural features, whereas volcanic materials are characterized by smaller features with poorer lateral continuity and often with weak impedance contrasts. Since the basement tends to create weaker reflections, the signal-to-noise ratio decreases, creating additional difficulties that can be exacerbated by the presence of multiples generated by the sea floor and other sources of noise. However, it is still important to characterize the basement accurately to better understand oceanic crust formation and associated basaltic volcanism. We analyzed marine MCS data collected by R/V Marcus G. Langseth across the TAMU Massif of Shatsky Rise in the Northwest Pacific. The seismic data from this experiment display the typical problems in imaging basement features. Therefore, we seek to facilitate interpretation by applying 2-D continuous wavelet transforms to the data. Conventional Fourier methods transform 2-D seismic data from space and time domains to wavenumber and frequency, but the results are global in that there is no knowledge of temporal or spatial variations in frequency or wavenumber content. In contrast, wavelet transforms provide estimates of the local frequency and wavenumber content of the seismic image. The transform achieves this result by utilizing a localized, 2D wavelet function instead of the infinite sines and cosines applied in Fourier transforms. We utilize an anisotropic Mexican hat wavelet, where the horizontal and vertical scales are related to wavelength and period of the data, respectively. When analyzing the Shatsky Rise data set, we find, for example, that much of the noise in the seismic image of the basement is at small wavelengths corresponding to several traces, about 25 m. Using the wavelet transforms, we can extract reflection events at longer wavelengths corresponding to expected features in the subsurface. Observing reflections at a certain wavelength provides an estimate of the size scale of the associated geologic structures. The results at a frequency of 31.25 Hz, near the dominant frequency of the data, provide images of reflectors in the deep part of oceanic crust with scales from 200 m to 2000 m that are much easier to interpret than in the original seismic image. In particular, at scales from 200 m to 1000 m, we can see many reflectors with consistent with sizes and locations for localized magma intrusions into the oceanic crust. However, for spatial scales of about 2000 m, only a few reflectors are observed, suggesting there are fewer intrusions of this dimension. These features can also be examined at a range of frequencies to provide additional insights, and the wavelet transform can also be generalized to estimate dips of reflectors.

Geological survey of Maryland using EREP flight data. [mining, mapping, Chesapeake Bay islands, coastal water features

NASA Technical Reports Server (NTRS)

Weaver, K. N. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Underflight photography has been used in the Baltimore County mined land inventory to determine areas of disturbed land where surface mining of sand and ground clay, or stone has taken place. Both active and abandoned pits and quarries were located. Aircraft data has been used to update cultural features of Calvert, Caroline, St. Mary's, Somerset, Talbot, and Wicomico Counties. Islands have been located and catalogued for comparison with older film and map data for erosion data. Strip mined areas are being mapped to obtain total area disturbed to aid in future mining and reclamation problems. Coastal estuarine and Atlantic Coast features are being studied to determine nearshore bedforms, sedimentary, and erosional patterns, and manmade influence on natural systems.

Rind-Like Features at a Meridiani Outcrop

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Annotated image of PIA04189 Rind-Like Features at a Meridiani Outcrop

After months spent crossing a sea of rippled sands, Opportunity reached an outcrop in August 2005 and began investigating exposures of sedimentary rocks, intriguing rind-like features that appear to cap the rocks, and cobbles that dot the martian surface locally. Opportunity spent several martian days, or sols, analyzing a feature called 'Lemon Rind,' a thin surface layer covering portions of outcrop rocks poking through the sand north of 'Erebus Crater.' In images from the panoramic camera, Lemon Rind appears slightly different in color than surrounding rocks. It also appears to be slightly more resistant to wind erosion than the outcrop's interior. This is an approximately true-color composite produced from frames taken during Opportunity's 552nd martian day, or sol (Aug. 13, 2005).

Quantitative lithologic mapping in spectral ratio feature space - Volcanic, sedimentary and metamorphic terrains

NASA Technical Reports Server (NTRS)

Campos-Marquetti, Raul, Jr.; Rockwell, Barnaby

1990-01-01

The nature of spectral lithologic mapping is studied utilizing ratios centered around the wavelength means of TM imagery. Laboratory-derived spectra are analyzed to determine the two-dimensional relationships and distributions visible in spectral ratio feature space. The spectral distributions of various rocks and minerals in ratio feature space are found to be controlled by several spectrally dominant molecules. Three study areas were examined: Rawhide Mining District, Nevada; Manzano Mountains, New Mexico; and the Sevilleta Long Term Ecological Research site in New Mexico. It is shown that, in the comparison of two ratio plots of laboratory reflectance spectra, i.e., 0.66/0.485 micron versus 1.65/2.22 microns with those derived from TM data, several molecules spectrally dominate the reflectance characteristic of surface lithologic units. Utilizing the above ratio combination, two areas are successfully mapped based on their distribution in spectral ratio feature space.

Determining the Accuracy of Paleomagnetic Remanence and High-Resolution Chronostratigraphy for Sedimentary Rocks using Rock Magnetics

NASA Astrophysics Data System (ADS)

Kodama, K. P.

2017-12-01

The talk will consider two broad topics in rock magnetism and paleomagnetism: the accuracy of paleomagnetic remanence and the use of rock magnetics to measure geologic time in sedimentary sequences. The accuracy of the inclination recorded by sedimentary rocks is crucial to paleogeographic reconstructions. Laboratory compaction experiments show that inclination shallows on the order of 10˚-15˚. Corrections to the inclination can be made using the effects of compaction on the directional distribution of secular variation recorded by sediments or the anisotropy of the magnetic grains carrying the ancient remanence. A summary of all the compaction correction studies as of 2012 shows that 85% of sedimentary rocks studied have enjoyed some amount of inclination shallowing. Future work should also consider the effect of grain-scale strain on paleomagnetic remanence. High resolution chronostratigraphy can be assigned to a sedimentary sequence using rock magnetics to detect astronomically-forced climate cycles. The power of the technique is relatively quick, non-destructive measurements, the objective identification of the cycles compared to facies interpretations, and the sensitivity of rock magnetics to subtle changes in sedimentary source. An example of this technique comes from using rock magnetics to identify astronomically-forced climate cycles in three globally distributed occurrences of the Shuram carbon isotope excursion. The Shuram excursion may record the oxidation of the world ocean in the Ediacaran, just before the Cambrian explosion of metazoans. Using rock magnetic cyclostratigraphy, the excursion is shown to have the same duration (8-9 Myr) in southern California, south China and south Australia. Magnetostratigraphy of the rocks carrying the excursion in California and Australia shows a reversed to normal geomagnetic field polarity transition at the excursion's nadir, thus supporting the synchroneity of the excursion globally. Both results point to a primary depositional origin for the excursion, and strengthens the argument for oxidation of the world ocean in the Ediacaran. Future work must learn how global climate is encoded by rock magnetics, but our work to date suggests that variations in continental run-off are detected by rock magnetics.

Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia) and their provenance

NASA Astrophysics Data System (ADS)

Gawlick, Hans-Jürgen; Djerić, Nevenka; Missoni, Sigrid; Bragin, Nikita Yu.; Lein, Richard; Sudar, Milan; Jovanović, Divna

2017-08-01

Oceanic radiolarite components from the Middle Jurassic ophiolitic mélange between Trnava and Rožanstvo in the Zlatibor Mountains (Dinaridic Ophiolite Belt) west of the Drina-Ivanjica unit yield Late Triassic radiolarian ages. The microfacies characteristics of the radiolarites show pure ribbon radiolarites without crinoids or thin-shelled bivalves. Beside their age and the preservation of the radiolarians this points to a deposition of the radiolarites on top of the oceanic crust of the Neo-Tethys, which started to open in the Late Anisian. South of the study area the ophiolitic mélange (Gostilje-Ljubiš-Visoka-Radoševo mélange) contains a mixture of blocks of 1) oceanic crust, 2) Middle and Upper Triassic ribbon radiolarites, and 3) open marine limestones from the continental slope. On the basis of this composition we can conclude that the Upper Triassic radiolarite clasts derive either from 1) the younger parts of the sedimentary succession above the oceanic crust near the continental slope or, more convincingly 2) the sedimentary cover of ophiolites in a higher nappe position, because Upper Triassic ribbon radiolarites are only expected in more distal oceanic areas. The ophiolitic mélange in the study area overlies different carbonate blocks of an underlying carbonate-clastic mélange (Sirogojno mélange). We date and describe three localities with different Upper Triassic radiolarite clasts in a mélange, which occurs A) on top of Upper Triassic fore-reef to reefal limestones (Dachstein reef), B) between an Upper Triassic reefal limestone block and a Lower Carnian reef limestone (Wetterstein reef), and C) in fissures of an Upper Triassic lagoonal to back-reef limestone (Dachstein lagoon). The sedimentary features point to a sedimentary and not to a tectonic emplacement of the ophiolitic mélange (= sedimentary mélange) filling the rough topography of the topmost carbonate-clastic mélange below. The block spectrum of the underlying and slightly older carbonate-clastic mélange points to a deposition of the sedimentary ophiolitic mélange east of or on top of the Drina-Ivanjica unit.

Centimeter-scale characterization of biogeochemical gradients at a wetland-aquifer interface using capillary electrophoresis

USGS Publications Warehouse

Baez-Cazull, S.; McGuire, J.T.; Cozzarelli, I.M.; Raymond, A.; Welsh, L.

2007-01-01

Steep biogeochemical gradients were measured at mixing interfaces in a wetland-aquifer system impacted by landfill leachate in Norman, Oklahoma. The system lies within a reworked alluvial plain and is characterized by layered low hydraulic conductivity wetland sediments interbedded with sandy aquifer material. Using cm-scale passive diffusion samplers, "peepers", water samples were collected in a depth profile to span interfaces between surface water and a sequence of deeper sedimentary layers. Geochemical indicators including electron acceptors, low-molecular-weight organic acids, base cations, and NH4+ were analyzed by capillary electrophoresis (CE) and field techniques to maximize the small sample volumes available from the centimeter-scale peepers. Steep concentration gradients of biogeochemical indicators were observed at various interfaces including those created at sedimentary boundaries and boundaries created by heterogeneities in organic C and available electron acceptors. At the sediment-water interface, chemical profiles with depth suggest that SO42 - and Fe reduction dominate driven by inputs of organic C from the wetland and availability of electron acceptors. Deeper in the sediments (not associated with a lithologic boundary), a steep gradient of organic acids (acetate maximum 8.8 mM) and NH4+ (maximum 36 mM) is observed due to a localized source of organic matter coupled with the lack of electron acceptor inputs. These findings highlight the importance of quantifying the redox reactions occurring in small interface zones and assessing their role on biogeochemical cycling at the system scale. ?? 2007 Elsevier Ltd. All rights reserved.

Quantification of Reflection Patterns in Ground-Penetrating Radar Data

NASA Astrophysics Data System (ADS)

Moysey, S.; Knight, R. J.; Jol, H. M.; Allen-King, R. M.; Gaylord, D. R.

2005-12-01

Radar facies analysis provides a way of interpreting the large-scale structure of the subsurface from ground-penetrating radar (GPR) data. Radar facies are often distinguished from each other by the presence of patterns, such as flat-lying, dipping, or chaotic reflections, in different regions of a radar image. When these patterns can be associated with radar facies in a repeated and predictable manner we refer to them as `radar textures'. While it is often possible to qualitatively differentiate between radar textures visually, pattern recognition tools, like neural networks, require a quantitative measure to discriminate between them. We investigate whether currently available tools, such as instantaneous attributes or metrics adapted from standard texture analysis techniques, can be used to improve the classification of radar facies. To this end, we use a neural network to perform cross-validation tests that assess the efficacy of different textural measures for classifying radar facies in GPR data collected from the William River delta, Saskatchewan, Canada. We found that the highest classification accuracies (>93%) were obtained for measures of texture that preserve information about the spatial arrangement of reflections in the radar image, e.g., spatial covariance. Lower accuracy (87%) was obtained for classifications based directly on windows of amplitude data extracted from the radar image. Measures that did not account for the spatial arrangement of reflections in the image, e.g., instantaneous attributes and amplitude variance, yielded classification accuracies of less than 65%. Optimal classifications were obtained for textural measures that extracted sufficient information from the radar data to discriminate between radar facies but were insensitive to other facies specific characteristics. For example, the rotationally invariant Fourier-Mellin transform delivered better classification results than the spatial covariance because dip angle of the reflections, but not dip direction, was an important discriminator between radar facies at the William River delta. To extend the use of radar texture beyond the identification of radar facies to sedimentary facies we are investigating how sedimentary features are encoded in GPR data at Borden, Ontario, Canada. At this site, we have collected extensive sedimentary and hydrologic data over the area imaged by GPR. Analysis of this data coupled with synthetic modeling of the radar signal has allowed us to develop insight into the generation of radar texture in complex geologic environments.

Diversity of Rock Compositions at Gale Crater Observed by ChemCam and APXS on Curiosity, and Comparison to Meteorite and Orbital Observations

NASA Astrophysics Data System (ADS)

Wiens, R. C.; Maurice, S.; Grotzinger, J. P.; Gellert, R.; Mangold, N.; Sautter, V.; Ollila, A.; Dyar, M. D.; Le Mouelic, S.; Ehlmann, B. L.; Clegg, S. M.; Lanza, N.; Cousin, A.; Forni, O.; Gasnault, O.; Lasue, J.; Blaney, D. L.; Newsom, H. E.; Herkenhoff, K. E.; Anderson, R. B.; D'Uston, L.; Bridges, N. T.; Fabre, C.; Meslin, P.; Johnson, J.; Vaniman, D.; Bridges, J.; Dromart, G.; Schmidt, M. E.; Team, M.

2013-12-01

Gale crater was selected as the Curiosity landing site because of the apparent sedimentary spectral signatures seen from orbit. Sedimentary materials on Mars have to this point showed very little expression of major element mobility, so compositions of precursor igneous minerals play a strong role in the compositions of sediments. In addition, pebbles and float rocks on Bradbury Rise (sols 0-50, > 324) appear to be mostly igneous in origin, and are assumed to have been carried down from the crater rim. Overall in the first year on Mars ChemCam obtained >75,000 LIBS spectra on > 2,000 observation points, supported by > 1,000 RMI images, and APXS obtained a significant number of observations. These show surprisingly variable compositions. The mean ChemCam compositions for Bradbury Rise dust-free rocks and pebbles (62 locations) give SiO2 = 56%, FeOT = 16% and show high alkalis consistent with Jake Matijevic (sol ~47) APXS Na2O ~6.6 wt%. ChemCam observations on the conglomerate Link (sol 27) gave Rb > 150 ppm and Sr > 1500 ppm. These compositions imply the presence of abundant alkali feldspars in the material infilling the lower parts of Gale crater. They are generally consistent with the more feldspar-rich SNC meteorites but show a radical departure from larger scale orbital observations, e.g., GRS, raising the question of how widespread these compositions are outside of Gale crater. Sedimentary materials at Yellowknife Bay encompassing the Sheepbed (sols 125-300) and Shaler (sols 121, 311-324) units, potentially including Point Lake (sols 301-310) and Rocknest (sols 57-97), appear to have incorporated varying amounts of igneous source materials. Seven rocks investigated at Rocknest show significant additions of Fe, with mean FeOT = 25% (154 locations), suggesting that FeO was a cementing agent. ChemCam observations at Shaler show varying amounts of alkali feldspar (i.e., related to Bradbury Rise), Fe-rich material (Rocknest-like), and potassium-rich material (related potentially to Bathurst, apparent bedrock observed sols 54-55, located stratigraphically between Bradbury and Rocknest). ChemCam observations in Yellowknife Bay formation rocks identified calcium-sulfate veins with varying amounts of hydration, as suggested by Mastcam multispectral observations. ChemCam also discovered Mg-rich raised ridges as a diagenetic feature occurring in the upper part of the Sheepbed member.

Potentiometric surface of the Minnekahta Aquifer in the Black Hills area, South Dakota

USGS Publications Warehouse

Strobel, Michael L.; Galloway, Joel M.; Hamade, Ghaith R.; Jarrell, Gregory J.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and springs that originate from the confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the potentiometric surface of the Minnekahta aquifer within the study area. The map provides a tool for evaluating ground-water flow directions and hydraulic gradients in the Minnekahta aquifer.

Potentiometric surface of the Inyan Kara Aquifer in the Black Hills area, South Dakota

USGS Publications Warehouse

Strobel, Michael L.; Galloway, Joel M.; Hamade, Ghaith R.; Jarrell, Gregory J.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and springs that originate from the confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the potentiometric surface of the Inyan Kara aquifer within the study area. The map provides a tool for evaluating ground-water flow directions and hydraulic gradients in the Inyan Kara aquifer.

Potentiometric surface of the Deadwood Aquifer in the Black Hills area, South Dakota

USGS Publications Warehouse

Strobel, Michael L.; Galloway, Joel M.; Hamade, Ghaith R.; Jarrell, Gregory J.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and springs that originate from the confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the potentiometric surface of the Deadwood aquifer within the study area. The map provides a tool for evaluating ground-water flow directions and hydraulic gradients in the Deadwood aquifer.

Potentiometric surface of the Minnelusa Aquifer in the Black Hills area, South Dakota

USGS Publications Warehouse

Strobel, Michael L.; Galloway, Joel M.; Hamade, Ghaith R.; Jarrell, Gregory J.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and springs that originate from the confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the potentiometric surface of the Minnelusa aquifer within the study area. The map provides a tool for evaluating ground-water flow directions and hydraulic gradients in the Minnelusa aquifer.

Potentiometric surface of the Madison Aquifer in the Black Hills area, South Dakota

USGS Publications Warehouse

Strobel, Michael L.; Galloway, Joel M.; Hamade, Ghaith R.; Jarrell, Gregory L.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and springs that originate from the confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the potentiometric surface of the Madison aquifer within the study area. The map provides a tool for evaluating ground-water flow directions and hydraulic gradients in the Madison aquifer.

Sedimentological constraints on the initial uplift of the West Bogda Mountains in Mid-Permian.

PubMed

Wang, Jian; Cao, Ying-Chang; Wang, Xin-Tong; Liu, Ke-Yu; Wang, Zhu-Kun; Xu, Qi-Song

2018-01-23

The Late Paleozoic is considered to be an important stage in the evolution of the Central Asian Orogenic Belt (CAOB). The Bogda Mountains, a northeastern branch of the Tianshan Mountains, record the complete Paleozoic history of the Tianshan orogenic belt. The tectonic and sedimentary evolution of the west Bogda area and the timing of initial uplift of the West Bogda Mountains were investigated based on detailed sedimentological study of outcrops, including lithology, sedimentary structures, rock and isotopic compositions and paleocurrent directions. At the end of the Early Permian, the West Bogda Trough was closed and an island arc was formed. The sedimentary and subsidence center of the Middle Permian inherited that of the Early Permian. The west Bogda area became an inherited catchment area, and developed a widespread shallow, deep and then shallow lacustrine succession during the Mid-Permian. At the end of the Mid-Permian, strong intracontinental collision caused the initial uplift of the West Bogda Mountains. Sedimentological evidence further confirmed that the West Bogda Mountains was a rift basin in the Carboniferous-Early Permian, and subsequently entered the Late Paleozoic large-scale intracontinental orogeny in the region.

Structural geology of Amazonian-aged layered sedimentary deposits in southwest Candor Chasma, Mars

USGS Publications Warehouse

Okubo, C.H.

2010-01-01

The structural geology of an outcropping of layered sedimentary deposits in southwest Candor Chasma is mapped using two adjacent high-resolution (1 m/pixel) HiRISE digital elevation models and orthoimagery. Analysis of these structural data yields new insight into the depositional and deformational history of these deposits. Bedding in non-deformed areas generally dips toward the center of west Candor Chasma, suggesting that these deposits are basin-filling sediments. Numerous kilometer-scale faults and folds characterize the deformation here. Normal faults of the requisite orientation and length for chasma-related faulting are not observed, indicating that the local sediments accumulated after chasma formation had largely ceased in this area. The cause of the observed deformation is attributed to landsliding within these sedimentary deposits. Observed crosscutting relationships indicate that a population of sub-vertical joints are the youngest deformational structures in the area. The distribution of strain amongst these joints, and an apparently youthful infill of sediment, suggests that these fractures have been active in the recent past. The source of the driving stress acting on these joints has yet to be fully constrained, but the joint orientations are consistent with minor subsidence within west Candor Chasma.

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.

Stratigraphy, petrography, and provenance of Archean sedimentary rocks of the Nsuze Group, Pongola Supergroup, in the Wit M'folozi Inlier, South Africa

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

Gamero de Villarroel, H.; Lowe, D.R.

1993-02-01

The Upper Archean Pongola Supergroup is a succession of clastic and volcanic rocks that represents the oldest relatively unmetamorphosed sedimentary sequence deposited on the basement of the 3.5-3.2 Ga-old Kaapvaal Craton. The Pongola Supergroup includes two subdivisions, the Nsuze and the Mozaan Groups. The Nsuze Group is composed of clastic rocks, minor carbonate units, and basalt. Nsuze sandstones are dominated by granite-derived sediments, and minor basaltic-derived detritus. Most Nsuze sedimentary rocks are sandstones that include both quartz-fieldspar and lithic-rich varieties. The mineralogy of Nsuze sandstones reflects the mixing of debris derived from two distinctive sources: (1) a sialic plutonic sourcemore » yielding quartz and microcline and (2) a basaltic source yielding basaltic lithic detritus and plagioclase. The most likely source rocks for the Nsuze sandstones in the Wit M'folozi Inlier were Archean granitic basement, represented by the Mpuluzi batholith, and Nsuze basaltic volcanic rocks. Both continental arc and rift settings have been proposed for the Pongola Supergroup. Nsuze sandstones show similarities to continental arc sandstone suites. However, there is no report of the existence of high standing stratovolcanoes, calc-alkaline plutonism, or contact and regional metamorphism of the intruded volcanic-sedimentary and basement rocks in the Pongola basin, features that are typically associated with continental arcs. The dominance of continent-derived detritus in the Nsuze Group argues that volcanic rocks made up a minor part of the exposed source area and that volcanism was largely restricted to the basin of deposition. Collectively, available evidence favors an intracratonic rift for the depositional setting of the Nsuze Group.« less

The inner filter effects and their correction in fluorescence spectra of salt marsh humic matter.

PubMed

Mendonça, Ana; Rocha, Ana C; Duarte, Armando C; Santos, Eduarda B H

2013-07-25

The inner filter effects in synchronous fluorescence spectra (Δλ=60 nm) of sedimentary humic substances from a salt marsh were studied. Accordingly to their type and the influence of plant colonization, these humic substances have different spectral features and the inner filter effects act in a different manner. The fluorescence spectra of the humic substances from sediments with colonizing plants have a protein like band (λexc=280 nm) which is strongly affected by primary and secondary inner filter effects. These effects were also observed for the bands situated at longer wavelengths, i.e., at λexc=350 nm and λex=454 nm for the fulvic acids (FA) and humic acids (HA), respectively. However, they are more important for the band at 280 nm, causing spectral distortions which can be clearly seen when the spectra of solutions 40 mg L(-1) of different samples (Dissolved Organic Carbon - DOC~20 mg L(-1)) are compared with and without correction of the inner filter effects. The importance of the spectral distortions caused by inner filter effects has been demonstrated in solutions containing a mixture of model compounds which represent the fluorophores detected in the spectra of sedimentary humic samples. The effectiveness of the mathematical correction of the inner filter effects in the spectra of those solutions and of solutions of sedimentary humic substances was studied. It was observed that inner filter effects in the sedimentary humic substances spectra can be mathematically corrected, allowing to obtain a linear relationship between the fluorescence intensity and humic substances concentration and preventing distortions at concentrations as high as 50 mg L(-1) which otherwise would obscure the protein like band. Copyright © 2013 Elsevier B.V. All rights reserved.

Geomorphic and shallow-acoustic investigation of an Antarctic Peninsula fjord system using high-resolution ROV and shipboard geophysical observations: Ice dynamics and behaviour since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

García, Marga; Dowdeswell, J. A.; Noormets, R.; Hogan, K. A.; Evans, J.; Ó Cofaigh, C.; Larter, R. D.

2016-12-01

Detailed bathymetric and sub-bottom acoustic observations in Bourgeois Fjord (Marguerite Bay, Antarctic Peninsula) provide evidence on sedimentary processes and glacier dynamics during the last glacial cycle. Submarine landforms observed in the 50 km-long fjord, from the margins of modern tidewater glaciers to the now ice-distal Marguerite Bay, are described and interpreted. The landforms are grouped into four morpho-sedimentary systems: (i) glacial advance and full-glacial; (ii) subglacial and ice-marginal meltwater; (iii) glacial retreat and neoglaciation; and (iv) Holocene mass-wasting. These morpho-sedimentary systems have been integrated with morphological studies of the Marguerite Bay continental shelf and analysed in terms of the specific sedimentary processes and/or stages of the glacial cycle. They demonstrate the action of an ice-sheet outlet glacier that produced drumlins and crag-and-tail features in the main and outer fjord. Meltwater processes eroded bedrock channels and ponds infilled by fine-grained sediments. Following the last deglaciation of the fjord at about 9000 yr BP, subsequent Holocene neoglacial activity involved minor readvances of a tidewater glacier terminus in Blind Bay. Recent stillstands and/or minor readvances are inferred from the presence of a major transverse moraine that indicates grounded ice stabilization, probably during the Little Ice Age, and a series of smaller landforms that reveal intermittent minor readvances. Mass-wasting processes also affected the walls of the fjord and produced scars and fan-shaped deposits during the Holocene. Glacier-terminus changes during the last six decades, derived from satellite images and aerial photographs, reveal variable behaviour of adjacent tidewater glaciers. The smaller glaciers show the most marked recent retreat, influenced by regional physiography and catchment-area size.

Sedimentary rhythms in coastal dunes as a record of intra-annual changes in wind climate (Łeba, Poland)

NASA Astrophysics Data System (ADS)

Ludwig, J.; Lindhorst, S.; Betzler, C.; Bierstedt, S. E.; Borówka, R. K.

2017-08-01

It is shown that coastal dunes bear a so far unread archive of annual wind intensity. Active dunes at the Polish coast near Łeba consist of two genetic units: primary dunes with up to 18 m high eastward-dipping foresets, temporarily superimposed by smaller secondary dunes. Ground-penetrating radar (GPR) data reveal that the foresets of the primary dunes are bundled into alternating packages imaged as either low- or high-amplitude reflections. High-amplitude packages are composed of quartz sand with intercalated heavy-minerals layers. Low-amplitude packages lack these heavy-mineral concentrations. Dune net-progradation is towards the east, reflecting the prevalence of westerly winds. Winds blowing parallel to the dune crest winnow the lee slope, leaving layers enriched in heavy minerals. Sediment transport to the slip face of the dunes is enhanced during the winter months, whereas winnowing predominantly takes place during the spring to autumn months, when the wind field is bi-directional. As a consequence of this seasonal shift, the sedimentary record of one year comprises one low- and one high-amplitude GPR reflection interval. This sedimentary pattern is a persistent feature of the Łeba dunes and recognized to resemble a sedimentary "bar code". To overcome hiatuses in the bar code of individual dunes and dune-to-dune variations in bar-code quality, dendrochronological methods were adopted to compile a composite bar code from several dunes. The resulting data series shows annual variations in west-wind intensity at the southern Baltic coast for the time period 1987 to 2012. Proxy-based wind data are validated against instrumental based weather observations.

Early rifting deposition: examples from carbonate sequences of Sardinia (Cambrian) and Tuscany (Triassic-Jurassic), Italy: an analogous tectono-sedimentary and climatic context

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

Cocozza, T.; Gandin, A.

Lower Cambrian Ceroide Limestone (Sardinia) and Lower Jurassic Massiccio Limestone (Tuscany) belong to sequences deposited in analogous tectono-sedimentary context: the former linked to the Caledonian Sardic Phase, the latter to the Alpine Orogeny. Both units consist of massive pure limestone characterized by marginal and lagoonal sequences repeatedly interfingering in the same geological structure. This distribution indicates a morphology of the platforms composed of banks (marginal facies) and shallow basins (lagoonal facies) comparable with a Bahamian complex. Dolomitization affects patchily the massive limestone bodies, and karstic features, breccias, and sedimentary dikes occur at their upper boundary. Both units overlie early dolomitemore » and evaporites (sabkha facies) containing siliciclastic intercalations in their lower and/or upper part and are unconformably covered by open-shelf red (hematitic), nodular limestone Ammonitico Rosso facies). The sedimentary evolution of the two sequences appears to have been controlled by synsedimentary tectonics whose major effects are the end of the terrigenous input, the bank-and-basin morphology of the platform, the irregular distribution of the dolomitization, and the nodular fabric of the overlying facies. The end of the Bahamian-type system is marked by the karstification of the emerged blocks and is followed by their differential sinking and burial under red-nodular facies. From a geodynamic viewpoint, sequences composed of Bahamian-like platform carbonates followed by Ammonitico Rosso facies imply deposition along continental margins subjected to block-faulting during an extensional regime connected with the beginning of continental rifting. Moreover, the variation from sabkha to Bahamian conditions suggests the drifting of the continent from arid to humid, tropical areas.« less

Response of megabenthic assemblages to different scales of habitat heterogeneity on the Mauritanian slope

NASA Astrophysics Data System (ADS)

Jones, Daniel O. B.; Brewer, Michael E.

2012-09-01

The topographically complex deep seabed on the Mauritanian slope, from 990 to 1460 m water depth, was imaged with video in an extensive quantitative survey of 17,199 m2 of seafloor using a Remote Operated Vehicle (ROV). This study investigated the influence of habitat heterogeneity at two scales on the megafaunal assemblages observed by ROV. Changes in megafaunal assemblages on the Mauritanian slope were assessed at a broad scale, within depth zones, and at a finer scale, in response to changes in local geomorphology associated with submarine landslides. Geomorphology was determined by classification of habitat parameters (slope, aspect, bathymetric position, curvature, fractal dimension and ruggedness) derived from an autonomous underwater vehicle-based multibeam bathymetry survey. Habitat parameters were classified by Iterative Self Organizing Clustering into six major geomorphological groups, four of which were assessed in the ROV video survey. A total of 29 megafaunal taxa were observed along the entire survey, with an overall average faunal density of 0.344 ind m-2. Megafaunal assemblage density, species richness and evenness varied significantly across the depth range of the survey in the most common geomorphological zone (sedimentary plains of low slope and complexity). Characteristic species inhabited the shallow areas (asteroid, ophiuroid, anemone, small macrourid), intermediate areas (Benthothuria funabris, black cerianthid, squat lobster) and deeper areas (the holothurians Enypniastes eximia and Elipidia echinata). Megafaunal density, species richness and evenness were not significantly different between geomorphogical groups within one depth zone (1300-1400 m). However, the steepest zone, on the edge of a major headwall feature, had four unique taxa (Parapagurus pilosimanus, a comatulid crinoid, a gorgonian and its associated ophiuroid).

Marine geological and geophysical records of the last British-Irish Ice Sheet on the continental shelf west of Ireland

NASA Astrophysics Data System (ADS)

O'Cofaigh, Colm; Callard, S. Louise; Benetti, Sara; Chiverell, Richard C.; Saher, Margot; van Landeghem, Katrien; Livingstone, Stephen J.; Scourse, James; Clark, Chris D.

2015-04-01

The record of glaciation on the continental shelf west of Ireland has, until recently, been relatively poorly studied. The UK NERC funded project BRITICE-CHRONO collected marine geophysical data in the form of multibeam swath bathymetry and sub-bottom profiles supplemented by over 50 vibro- and piston cores across the continental shelf west of Ireland during cruise JC106 of the RRS James Cook in 2014. Across the western Irish shelf, offshore of counties Galway and Clare, a series of large arcuate moraines record the former presence of a grounded ice sheet on the shelf. However, geophysical data from further to the west across the Porcupine Bank show a series of ridges and wedge-shaped sedimentary features whose form is consistent with an origin as moraines and/or grounding-zone wedges. Sediment cores from several of these landforms recovered stiff, massive diamictons containing reworked shells that are interpreted as subglacial tills. Cores from the eastern Porcupine Bank recovered laminated muds with cold-water glacimarine foraminifera, in some cases overlying till. Collectively the geophysical and sedimentary data imply the presence of grounded ice across the northern Porcupine Bank and thus much further west on the Irish margin than has previously been considered. This ice underwent retreat in a glacimarine setting. The large 'Olex Moraine' on the western Irish shelf is thus interpreted as recessional feature. Work is currently underway to dates these features and to obtain a retreat chronology for this sector of the last British-Irish Ice Sheet.

Aeolian Abrasion at the Curiosity Landing Site: Clues to the Role of Wind in Landscape Modification

NASA Astrophysics Data System (ADS)

Bridges, N. T.; Le Mouélic, S.; Hallet, B.; Newman, C. E.; Rice, M. S.; Blaney, D. L.; Calef, F. J.; Herkenhoff, K. E.; Langevin, Y.; Lewis, K. W.; Maurice, S.; Pinet, P. C.; Wiens, R. C.; de Pablo, M.; Renno, N. O.

2013-12-01

The broad scale geomorphology of Gale Crater reflects diverse aeolian processes, from airfall settling that likely deposited much of the upper and some of the lower units of Mt. Sharp, to evidence of extensive wind exhumation and removal of material exterior to the mound, to active dunes on the crater floor. The integrated effect of aeolian sand transport can also be examined on a much smaller scale by the study of ventifacts, rocks that have been abraded by windborne particles. A diversity of ventifacts are found along Curiosity's traverse through the upper 'hummocky' (HY) geomorphic unit and the lower Yellowknife Bay (YKB) sedimentary rocks. The textures are analogous to abrasion features found on Earth and include cm-scale facets, keels, elongated pits, grooves, flutes, and basal sills. High-resolution images from ChemCam's Remote Micro-Imager also show mm-scale lineations. Evidence of differential erosion is common, with HY conglomerates (e.g., Hottah, Link) and the YKB Sheepbed mudstone unit containing distinct wind tails in the lee of resistant pebbles, and bedding features within Rocknest 3, the YKB Shaler sandstone unit, and other layered rocks displaying prominent ridge-groove topography. ChemCam LIBS depth profile data so far show no strong evidence for chemical differences in the elemental composition between abraded and non-abraded surfaces (as determined from qualitative assessment), as might be expected if there were rock coatings or weathering rinds undergoing active abrasion. Preliminary measurements of ventifact texture and wind tail orientations indicate sandblasting in HY and YKB from predominantly southwesterly and northerly directions, respectively. Based on meso-scale models of current winds and REMS results, SW flow is uncommon whereas N winds are frequent. Compositional and textural information from the suite of MSL instruments indicate that HY rocks are dominated by various types of basalt (either as whole rocks or the resistant clasts in conglomerates), whereas YKB are basaltic clastic rocks, with the lower members impregnated with sulfate veins, and were easily drilled. The HY rocks are therefore likely more resistant to abrasion than those of YKB. Combined, these results indicate that ventifacts so far investigated by MSL record two wind regimes, one a long-term integrated record of rare, yet strong winds and the other more reflective of typical conditions.

Microstructural controls on the viscoplasticity of Carbopol, and possible applications to shale deformation studies

NASA Astrophysics Data System (ADS)

Hayman, N. W.; Shafiei, M.; Balhoff, M.; Daigle, H.

2017-12-01

To a first order, sedimentary materials behave in an elastic-plastic manner for most experimental and natural conditions at short time scales. However, long-term patterns of leakage from carbon-capture and storage efforts, and reduced efficiency during unconventional hydrocarbon production, point to a broader range of subsurface behaviors. Our analyses of microstructural and porosity responses to experimental deformation of shale suggest that sedimentary rock deformation is not strictly elastic-plastic. For example, organic matter (OM) in mudrocks can fracture during failure, but elsewhere may be more viscous in the same rock volume. The fracture of OM can be accompanied by some combination of frictional and poroelastic deformation in the surrounding clay aggregates, potentially described by critical-state-line soil mechanics. What is less clear is the possible role of viscoplasticity in sedimentary rock deformation. Though not a good analog material for all rock deformation, the cross-linked polymer Carbopol provides an excellent opportunity to explore controls on viscoplasticity. Above the yield stress, carbopol plastic deformation follows a Herschel-Bulkley model wherein shear stress varies as function of strain rate to a power that is generally <1; i.e. it is a shear-thinning material. The rheology can then be tuned by changing the pH of the gel. Using images obtained from scanning electron microscopy, including using a cryogenic system, we found that a structural transition from a dilute neutralized dispersion to an aggregate of closely packed particulates occurs as the pH of the polymer solution increases. This closely packed microstructure thus controls the yield strength which in turn follows approximately a non-linear relationship with porosity. This "analog material" thus has allowed us to quantify the microstructural length-scales that govern viscoplasticity in this material. Future experiments and numerical modeling can evaluate if a viscoplastic component to sedimentary rock deformation is important during engineering efforts. Such an exploration might focus on porosity-yield stress relationships and the monitoring fracture propagation for a wide range of stress conditions, including those which enhance ductility.

Exploring the potential of hyper-spectral imaging for the biogeochemical analysis of varved lake sediments

NASA Astrophysics Data System (ADS)

Butz, Christoph; Grosjean, Martin; Enters, Dirk; Tylmann, Wojciech

2014-05-01

Varved lake sediments have successfully been used to make inferences about past environmental and climate conditions from annual to multi-millennial scales. Among other proxies, concentrations of sedimentary photopigments have been used for temperature reconstructions. However, obtaining well calibrated annually resolved records from sediments still remains challenging. Most laboratory methods used to analyse lake sediments require physical subsampling and are destructive in the process. Hence, temporal resolution and number of data are limited by the amount of material available in the core. Furthermore, for very low sediment accumulation rates annual subsampling is often very difficult or even impossible. To address these problems we explore hyper-spectral imaging as a new method to analyse lake sediments based on their reflectance spectra in the visible and near infrared spectrum. In contrast to other fast and non-destructive methods like X-ray fluorescence, VIS/NIR reflectance spectrometry distinguishes between biogeochemical substances rather than single elements. Rein (2003) has shown that VIS-RS can be used to detect relative concentrations of sedimentary photopigments (e.g. chlorins, carotenoids) and clay minerals. This study presents an advanced approach using a hyper-spectral camera and remote sensing techniques to infer climate proxy data from reflectance spectra of varved lake sediments. Hyper-spectral imaging allows analysing an entire sediment core in a single measurement, producing a spectral dataset with very high spatial (30x30µm/pixel) and spectral resolutions (~1nm) and a higher spectral range (400-1000nm) compared to previously used spectrophotometers. This allows the analysis of data time series at sub-varve scales or spatial mapping of sedimentary substances (e.g. chlorophyll-a and diagenetic products) at very high resolution. The method is demonstrated on varved lake sediments from northern Poland showing the change of the relative concentrations of chlorin pigments within individual varve years. In a next step absolute concentrations of chlorins derived from HPLC measurements have been calibrated to the spectral data using a linear regression model. This results in a very high-resolution dataset of absolute sedimentary pigment concentrations. In a second example µXRF measurements are used to validate a spectral index for clay mineral detection.

The influences of the AMO and NAO on the sedimentary infill in an Azores Archipelago lake since ca. 1350 CE

NASA Astrophysics Data System (ADS)

Hernández, Armand; Sáez, Alberto; Bao, Roberto; Raposeiro, Pedro M.; Trigo, Ricardo M.; Doolittle, Sara; Masqué, Pere; Rull, Valentí; Gonçalves, Vítor; Vázquez-Loureiro, David; Rubio-Inglés, María J.; Sánchez-López, Guiomar; Giralt, Santiago

2017-07-01

The location of the Azores Archipelago in the North Atlantic makes this group of islands an excellent setting to study the long-term behavior of large oceanic and atmospheric climate dynamic patterns, such as the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO). Here, we present the impacts of these patterns on Lake Empadadas (Azores Archipelago) from the Medieval Climate Anomaly (MCA) - Little Ice Age (LIA) transition to the present based on sedimentological, geochemical and biological characterizations of the sedimentary record. Multivariate analyses of a number of proxies including X-ray fluorescence (XRF), X-ray diffraction (XRD), total organic and inorganic carbon (TOC and TIC) and diatom life forms abundance reveal that the sedimentary infill evolution has been controlled by (i) fluctuations in the lake level and (ii) variations in organic matter accumulation. Both processes are governed by climate variability and modulated by anthropogenic activities associated with changes on the lake catchment. Changes in these two sedimentary processes have been used to infer five stages: (i) the MCA-LIA transition (ca. 1350-1450 CE) was characterized by a predominantly positive AMO phase, which led to intermediate lake levels and high organic matter concentration; (ii) the first half of the LIA (ca. 1450-1600 CE) was characterized by predominant lowstand conditions and intermediate organic matter deposition mainly related to negative AMO phases; (iii) the second half of the LIA (ca. 1600-1850 CE) was characterized by negative AMO and NAO phases, implying intermediate lake levels and high organic matter deposition; (iv) the Industrial era (ca. 1850-1980 CE) was characterized by the lowest lake level and organic matter accumulation associated with negative AMO phases; and (v) the period spanning between 1980 CE and the present reveals the highest lake levels and low organic matter deposition, being associated with very positive AMO conditions. At decadal-to-centennial scales, the influence of the AMO on Azorean climate plays a larger role than previously thought. In fact, the AMO appears to exert a stronger influence compared to the NAO, which is the main mode of climate variability at shorter time scales.

Recirculation System for Geothermal Energy Recovery in Sedimentary Formations: Laboratory Experiments and Numerical Simulations

NASA Astrophysics Data System (ADS)

Elkhoury, J. E.; Detwiler, R. L.; Serajian, V.; Bruno, M. S.

2012-12-01

Geothermal energy resources are more widespread than previously thought and have the potential for providing a significant amount of sustainable clean energy worldwide. In particular, hot permeable sedimentary formations provide many advantages over traditional geothermal recovery and enhanced geothermal systems in low permeability crystalline formations. These include: (1) eliminating the need for hydraulic fracturing, (2) significant reduction in risk for induced seismicity, (3) reducing the need for surface wastewater disposal, (4) contributing to decreases in greenhouse gases, and (5) potential use for CO2 sequestration. Advances in horizontal drilling, completion, and production technology from the oil and gas industry can now be applied to unlock these geothermal resources. Here, we present experimental results from a laboratory scale circulation system and numerical simulations aimed at quantifying the heat transfer capacity of sedimentary rocks. Our experiments consist of fluid flow through a saturated and pressurized sedimentary disc of 23-cm diameter and 3.8-cm thickness heated along its circumference at a constant temperature. Injection and production ports are 7.6-cm apart in the center of the disc. We used DI de-aired water and mineral oil as working fluids and explored temperatures from 20 to 150 oC and flow rates from 2 to 30 ml/min. We performed experiments on sandstone samples (Castlegate and Kirby) with different porosity, permeability and thermal conductivity to evaluate the effect of hydraulic and thermal properties on the heat transfer capacity of sediments. The producing fluid temperature followed an exponential form with time scale transients between 15 and 45 min. Steady state outflow temperatures varied between 60% and 95% of the set boundary temperature, higher percentages were observed for lower temperatures and flow rates. We used the flow and heat transport simulator TOUGH2 to develop a numerical model of our laboratory setting. Given the remarkable match between our observations and numerical results, we extended our model to explore a wider range of thermal and hydrological parameters beyond the experimental conditions. Our results prove the capability of heat transfer in sedimentary formations for geothermal energy production.) Sandstone sample with two thermally insulating Teflon caps (white discs). In and out arrows indicate the flow direction while the sample is heated along its circumference (heater not shown). B) Example of a 2D temperature distribution during injection. White x shows the location of the flow ports, inlet (left) and outlet (right). Red is the set boundary temperature and blue is the fluid temperature at the inlet.

Early Archaean collapse basins, a habitat for early bacterial life.

NASA Astrophysics Data System (ADS)

Nijman, W.

For a better definition of the sedimentary environment in which early life may have flourished during the early Archaean, understanding of the basin geometry in terms of shape, depth, and fill is a prerequisite. The basin fill is the easiest to approach, namely from the well exposed, low-grade metamorphic 3.4 - 3.5 Ga rock successions in the greenstone belts of the east Pilbara (Coppin Gap Greenstone Belt and North Pole Dome) in West Australia and of the Barberton Greenstone Belt (Buck Ridge volcano-sedimentary complex) in South Africa. They consist of mafic to ultramafic volcanic rocks, largely pillow basalts, with distinct intercalations of intermediate to felsic intrusive and volcanic rocks and of silicious sediments. The, partly volcaniclastic, silicious sediments of the Buck Ridge and North Pole volcano-sedimentary complexes form a regressive-transgressive sequence. They were deposited close to base level, and experienced occasional emersion. Both North Pole Chert and the chert of the Kittys Gap volcano-sedimentary complex in the Coppin Gap Greenstone Belt preserve the flat-and-channel architecture of a shallow tidal environment. Thickness and facies distribution appear to be genetically linked to systems, i.e. arrays, of syn-depositionally active, extensional faults. Structures at the rear, front and bottoms of these fault arrays, and the fault vergence from the basin margin towards the centre characterize the basins as due to surficial crustal collapse. Observations in the Pilbara craton point to a non-linear plan view and persistence for the basin-defining fault patterns over up to 50 Ma, during which several of these fault arrays became superposed. The faults linked high-crustal level felsic intrusions within the overall mafic rock suite via porphyry pipes, black chert veins and inferred hydrothermal circulations with the overlying felsic lavas, and more importantly, with the cherty sediments. Where such veins surfaced, high-energy breccias, and in the case of the North Pole Chert huge barite growths, are juxtaposed with the otherwise generally low-energy sediments. Such localities are interpreted as sites of hydrothermal vents. Within this large-scale geological context, many environments on the micro-scale were habitable for life, such as hydrothermal vents and their vicinities, volcanic rock surfaces, subsurface sediments and sediment surfaces. These early collapse basins, hosting this bacterial life, are only partially comparable to Earthly analogues. A resemblance with Venus' coronae and the chaos terranes on Mars is suggested. This study forms part of an international project on Earth's Earliest Sedimentary Basins, supported by the Dutch Foundation Dr. Schürmannfonds. 2

Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

USGS Publications Warehouse

Martinez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

2011-01-01

Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region.Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

Habitat heterogeneity of hadal trenches: Considerations and implications for future studies

NASA Astrophysics Data System (ADS)

Stewart, Heather A.; Jamieson, Alan J.

2018-02-01

The hadal zone largely comprises a series of subduction trenches that do not form part of the continental shelf-slope rise to abyssal plain continuum. Instead they form geographically isolated clusters of deep-sea (6000-11,000 m water depth) environments. There is a growing realization in hadal science that ecological patterns and processes are not driven solely by responses to hydrostatic pressure, with comparable levels of habitat heterogeneity as observed in other marine biozones. Furthermore, this heterogeneity can be expressed at multiple scales from inter-trench levels (degrees of geographical isolation, and biochemical province), to intra-trench levels (variation between trench flanks and axis), topographical features within the trench interior (sedimentary basins, ridges, escarpments, 'deeps', seamounts) to the substrate of the trench floor (seabed-sediment composition, mass movement deposits, bedrock outcrop). Using best available bathymetry data combined with the largest lander-derived imaging dataset that spans the full depth range of three hadal trenches (including adjacent slopes); the Mariana, Kermadec and New Hebrides trenches, the topographic variability, fine-scale habitat heterogeneity and distribution of seabed sediments of these three trenches have been assessed for the first time. As well as serving as the first descriptive study of habitat heterogeneity at hadal depths, this study also provides guidance for future hadal sampling campaigns taking into account geographic isolation, total trench particulate organic matter flux, maximum water depth and area.

The role of bedrock in creating habitat in temperate watercourses

NASA Astrophysics Data System (ADS)

Entwistle, N. S.; Heritage, G. L.; Milan, D. J.

2016-12-01

Bedrock influenced rivers are a relatively common yet little studied river type across temperate regions, occurring predominantly in upland areas and in areas where isostatic rebound has promoted rapid watercourse downcutting through resistant bedrock. The presence of bedrock in the bed and banks exerts a major influence on channel development, controlling local flow hydraulics and subsequently influencing in-channel and valley bottom sedimentary feature development. This paper summarises extensive field audit evidence of bedrock influenced features on watercourses in the UK to characterise the diverse morphology of bedrock influenced channels and reviews the bedrock induced hydraulic influences on their development and maintenance. Such features include bedrock waterfalls, steps, rapids and cascades and associated alluvial deposits forming lee bars, bedrock obstruction bars, plunge pool bars and fine sediment drapes and veneers. Bedrock influence on valley bottom features is also reviewed and a functional typology is developed for this river type based on the feature assemblage and degree of bedrock/alluvial influence.

Dome Structures Above Sills and Saucer-Shaped Sills: Insights From Experimental Modeling

NASA Astrophysics Data System (ADS)

Planke, S.; Galland, O.; Malthe-Sørenssen, A.

2007-12-01

Saucer-shaped magma and sand intrusions are common features in sedimentary basins. They result from fundamental processes for the emplacement of fluids in shallow sedimentary basins. Seismic data show that the overburden above saucer-shaped intrusions is usually deformed and exhibits a dome-like structure. The formation of such structures, and the associated deformation, are of primary importance in the evolution of petroleum systems. In this presentation, we report on experimental investigation of the deformation processes associated with the intrusion of saucer-shaped intrusions into sedimentary basins. The experimental setup consists of molten low-viscosity oil injected into fine-grained silica flour (see Galland et al., this session). It properly simulates the emplacement of saucer-shaped intrusions and the deformation of the country rock. During experiments, the surface of the model is digitalized through a structured light technique based on moiré projection principle. Such a tool provides topographic maps of the model and allows a periodic (every 1.5 s) monitoring of the model surface. When the model magma starts intruding, a symetrical dome rises above the inlet. As injection proceeds, the dome inflates and widens. Subsequently, the dome evolves to a plateau-like feature, with nearly flat surface and steep edges. The plateau keeps lifting up, but nearly stoppes widening. At the end of the experiments, the intruding liquid erupts at the edge of the plateau. The intrusion formed in the experiment is a typical saucer-shaped sill. The evolution of the deforming surface reflects the evolution of the intrusion. We infer that the first doming phase corresponds to the emplacement of a horizontal basal sill by open fracturing. The dome-to-plateau transition corresponds to a transition of the liquid emplacement mechanism from basal sill to inclined sheet. We suggest that the emplacement of the inclined sheets results from shear fracturing at the dome edge.

Length scale hierarchy and spatiotemporal change of alluvial morphologies over the Selenga River delta, Russia

NASA Astrophysics Data System (ADS)

Dong, T. Y.; Nittrouer, J.; McElroy, B. J.; Ma, H.; Czapiga, M. J.; Il'icheva, E.; Pavlov, M.; Parker, G.

2017-12-01

The movement of water and sediment in natural channels creates various types of alluvial morphologies that span length scales from dunes to deltas. The behavior of these morphologies is controlled microscopically by hydrodynamic conditions and bed material size, and macroscopically by hydrologic and geological settings. Alluvial morphologies can be modeled as either diffusive or kinematic waves, in accordance with their respective boundary conditions. Recently, it has been shown that the difference between these two dynamic behaviors of alluvial morphologies can be characterized by the backwater number, which is a dimensionless value normalizing the length scale of a morphological feature to its local hydrodynamic condition. Application of the backwater number has proven useful for evaluating the size of morphologies, including deltas (e.g., by assessing the preferential avulsion location of a lobe), and for comparing bedform types across different fluvial systems. Yet two critical questions emerge when applying the backwater number: First, how do different types of alluvial morphologies compare within a single deltaic system, where there is a hydrodynamic transition from uniform to non-uniform flow? Second, how do different types of morphologies evolve temporally within a system as a function of changing water discharge? This study addresses these questions by compiling and analyzing field data from the Selenga River delta, Russia, which include measurements of flow velocity, channel geometry, bed material grain size, and channel slope, as well as length scales of various morphologies, including dunes, island bars, meanders, bifurcations, and delta lobes. Data analyses reveal that the length scale of morphologies decrease and the backwater number increases as flow transitions from uniform to non-uniform conditions progressing downstream. It is shown that the evaluated length scale hierarchy and planform distribution of different morphologies can be used to estimate slope, shear velocity and sediment flux within this depositional system. The findings from this research can be applied to evaluate spatially and temporally varying morphodynamic conditions, based on structures measured from both modern systems and ancient sedimentary records.

Structural and stratigraphic framework and spatial distribution of permeability of the Atlantic coastal plain, North Carolina to New York

USGS Publications Warehouse

Brown, Philip Monroe; Miller, James A.; Swain, Frederick Morrill

1972-01-01

This report describes and interprets the results of a detailed subsurface mapping program undertaken in that part of the Atlantic Coastal Plain which extends from the South Carolina and North Carolina border through Long Island, N.Y. Data obtained from more than 2,200 wells are analyzed. Seventeen chronostratigraphic units are mapped in the subsurface. They range in age from Jurassic(?) to post-Miocene. The purpose of the mapping program was to determine the external and internal geometry of mappable chronostratigraphic units and to derive and construct a permeability-distribution network for each unit based upon contrasts in the textures and compositions of its contained sediments. The report contains a structure map and a combined isopach, lithofacies, and permeability-distribution map for each of the chronostratigraphic units delineated in the subsurface. In addition, it contains a map of the top of the basement surface. These maps, together with 36 stratigraphic cross sections, present a three-dimensional view of the regional subsurface hydrogeology. They provide focal points of reference for a discussion of regional tectonics, structure, stratigraphy, and permeability distribution. Taken together and in chronologic sequence, the maps constitute a detailed sedimentary model, the first such model to be constructed for the middle Atlantic Coastal Plain. The chronostratigraphic units mapped record a structural history dominated by lateral and vertical movement along a system of intersecting hinge zones. Taphrogeny, related to transcurrent faulting, is the dominant type of deformation that controlled the geometry of the sedimentary model. Twelve of the seventeen chronostratigraphic units mapped have depositional alinements and thickening trends that are independent of the present-day configuration of the underlying basement surface. These 12 units, classified as genetically unrooted units, are assigned to a first-order tectonic stage. A structural model is proposed whose alinements of positive and negative structural features are accordant with the depositional geometry of the chronostratigraphic units assigned to this tectonic stage. The dominant features of the structural model are northeast-plunging half grabens arranged en echelon and bordered by northeast-plunging fault-block anticlines. Tension-type hinge zones that strike north lie athwart the half grabens. Five of the seventeen chronostratigraphic units mapped have depositional alinements and thickening trends that are accordant with the present-day configuration of the underlying basement surface. These five units, classified as genetically rooted units, are assigned to a second-order tectonic stage. A structural model is proposed whose alinements of positive and negative features are accordant with the depositional geometry of the chronostratigraphic units assigned to this tectonic stage. The dominant feature of this model is a graben that stands tangential to southeast-plunging asymmetrical anticlines. Tension-type hinge zones that strike northeast lie athwart the graben. To account for the semiperiodic realinement of structural features that has characterized the history of the region and as a working hypothesis, we propose that the dominant tectonic element, which is present in the area between north Florida and Long Island, N.Y., is a unit-structural block, a ?basement? block, bounded by wrench-fault zones. We propose that forces derived principally from the rotation and precession of the earth act on the unit-structural block and deform it. Two tectonic models are proposed. One model is compatible with the structural and sedimentary geometries that are associated with chronostratigraphic units assigned to a first-order tectonic stage. It features tension-type hinge zones that strike north and shear-type hinge zones that strike northeast. The other model is compatible with the structural and sedimentary geometries associated with chronostratigraphi

Detection of crystalline hematite mineralization on Mars by the Thermal Emission Spectrometer: evidence for near-surface water

USGS Publications Warehouse

Christensen, P.R.; Bandfield, J.L.; Clark, R.N.; Edgett, K.S.; Hamilton, V.E.; Hoefen, T.; Kieffer, H.H.; Kuzmin, R.O.; Lane, M.D.; Malin, M.C.; Morris, R.V.; Pearl, J.C.; Pearson, R.; Roush, T.L.; Ruff, S.W.; Smith, M.D.

2000-01-01

The Thermal Emission Spectrometer (TES) instrument on the Mars Global Surveyor (MGS) mission has discovered a remarkable accumulation of crystalline hematite (α-Fe2O3) that covers an area with very sharp boundaries approximately 350 by 350–750 km in size centered near 2°S latitude between 0° and 5°W longitude (Sinus Meridiani). Crystalline hematite is uniquely identified by the presence of fundamental vibrational absorption features centered near 300, 450, and >525 cm−1 and by the absence of silicate fundamentals in the 1000 cm−1 region. Spectral features resulting from atmospheric CO2, dust, and water ice were removed using a radiative transfer model. The spectral properties unique to Sinus Meridiani were emphasized by removing the average spectrum of the surrounding region. The depth and shape of the hematite fundamental bands show that the hematite is crystalline and relatively coarse grained (>5–10 μm). Diameters up to and greater than hundreds of micrometers are permitted within the instrumental noise and natural variability of hematite spectra. Hematite particles 30 μm diameter) to 40–60% (10 μm diameter). The hematite in Sinus Meridiani is thus distinct from the fine-grained (diameter <5–10 μm), red, crystalline hematite considered, on the basis of visible, near-IR data, to be a minor spectral component in Martian bright regions like Olympus-Amazonis. Sinus Meridiani hematite is closely associated with a smooth, layered, friable surface that is interpreted to be sedimentary in origin. This material may be the uppermost surface in the region, indicating that it might be a late stage sedimentary unit or a layered portion of the heavily cratered plains units. We consider five possible mechanisms for the formation of coarse-grained, crystalline hematite. These processes fall into two classes depending on whether they require a significant amount of near-surface water: the first is chemical precipitation that includes origin by (1) precipitation from standing, oxygenated, Fe-rich water (oxide iron formations), (2) precipitation from Fe-rich hydrothermal fluids, (3) low-temperature dissolution and precipitation through mobile ground water leaching, and (4) formation of surface coatings, and the second is thermal oxidation of magnetite-rich lavas. Weathering and alteration processes, which produce nanophase and red hematite, are not consistent with the coarse, crystalline hematite observed in Sinus Meridiani. We prefer chemical precipitation models and favor precipitation from Fe-rich water on the basis of the probable association with sedimentary materials, large geographic size, distance from a regional heat source, and lack of evidence for extensive groundwater processes elsewhere on Mars. The TES results thus provide mineralogic evidence for probable large-scale water interactions. The Sinus Meridiani region may be an ideal candidate for future landed missions searching for biotic and prebiotic environments, and the physical characteristics of this site satisfy all of the engineering requirements for the missions currently planned.

Evaluating order in vertical successions of deltaic Holocene sediments on the Ganges-Brahmaputra-Meghna delta

NASA Astrophysics Data System (ADS)

Sincavage, R.; Goodbred, S. L., Jr.

2017-12-01

Most stratigraphic models are predicated on the presence of cyclicity or some form of order in vertical successions of strata. In spite of this a priori assumption of ordered stratigraphy, rarely are statistical metrics employed to quantify cyclicity in sedimentary packages. The presence or absence of preserved order in vertical sedimentary successions has important implications for the nature of environmental signals that are transmitted into the rock record. We interrogate the Holocene sedimentary archive of the Ganges-Brahmaputra-Meghna delta (GBMD) in an effort to explore to what extent fluvio-deltaic deposits exhibit recognizable order. Specifically, we focus on grain size data to evaluate 1.) if stratigraphic order in vertical sedimentary successions can be identified and quantified, and 2.) if there are spatial patterns of stratigraphic order across the GBMD. A runs order metric r is used to identify sequences of coarsening and fining within an extensive borehole network. Observed grain size data are shuffled enough times to generate synthetic "random" stratigraphy, and a Monte Carlo simulation generates 5000 realizations. The distribution of r values from the Monte Carlo are compared to the r metric calculated from observed data to determine how likely the observed metric could be generated by chance. The spatial distribution of order metrics indicates a relationship between areas of enhanced mass extraction and preservation of fluvial successions that scale with modern bar deposits on the Jamuna River. Similarly, probability metrics indicate that vertical successions of grain size data unlikely to have been generated by chance are more likely to be found on distal areas of the delta where 60% of the input mass has been extracted. Combining a mass balance framework with simple statistical metrics has the potential of improving predictions of the stratigraphic architecture and the preservation of ordered vs. disordered signals in the sedimentary record.

Warm Eocene climate enhanced petroleum generation from Cretaceous source rocks - a potential climate feedback mechanism?

NASA Astrophysics Data System (ADS)

Kroeger, K. F.; Funnell, R. H.

2012-04-01

Surface and deep sea temperatures from late Paleocene to early Eocene until the Early Eocene climatic Optimum increased by 5 - 10° C. This change was associated with a negative δ13C trend which implies major changes in global carbon cycling and enrichment of surface systems in isotopically light carbon. The degree of change in sedimentary δ13C requires emission of >10,000 gigatonnes of isotopically light carbon into the ocean. We reveal a relationship between global warming and increased petroleum generation in sedimentary basins operating on 100 kyr to Myr time scales that may explain the observed isotope shift. We use TEX86-based surface temperature data1 to predict how change in surface temperature influences the temperature evolution and resultant petroleum generation in four southwest Pacific sedimentary basins. Models predict an up to 50% increase in oil and gas expulsion rates in response to the increase in temperatures from late Paleocene to early Eocene in the region. Such an increase in petroleum generation would have significantly increased leakage of light hydrocarbons and oil degeneration products into surface systems. We propose that our modelling results are representative of a large number of sedimentary basins world-wide and that early Eocene warming has led to a synchronization of periods of maximum petroleum generation and enhanced generation in otherwise unproductive basins through extension of the volume of source rock within the oil and gas window. Extrapolating our modelling results to hundreds of sedimentary basins worldwide suggests that globally increased leakage could have led to the release of an amount of CH4, CO2 and light petroleum components into surface systems compatible with the observed changes in δ13C. We further suggest that this is a significant feedback effect, enhancing early Eocene climate warming. 1Bijl, P. K., S. Schouten, A. Sluijs, G.-J. Reichart, J. C. Zachos, and H. Brinkhuis (2009), Early Palaeogene temperature evolution of the southwest Pacific Ocean, Nature, 461, 776-779.

Sedimentary fabrics of the macrotidal, mud-dominated, inner estuary to fluvio-tidal transition zone, Petitcodiac River estuary, New Brunswick, Canada

NASA Astrophysics Data System (ADS)

Shchepetkina, Alina; Gingras, Murray K.; Zonneveld, John-Paul; Pemberton, S. George

2016-03-01

The study provides a detailed description of mud-dominated sedimentary fabrics and their application for the rock record within the inner estuary to the fluvial zone of the Petitcodiac River estuary, New Brunswick, Canada. Sedimentological characteristics and facies distributions of the clay- and silt-rich deposits are reported. The inner estuary is characterized by thick accumulations of interbedded silt and silty clay on intertidal banks that flank the tidally influenced channel. The most common sedimentary structures observed are parallel and wavy lamination, small-scale soft-sediment deformation with microfaults, and clay and silt current ripples. The tidal channel contains sandy silt and clayey silt with planar lamination, massive and convolute bedding. The fluvio-tidal transition zone is represented by interbedded trough cross-stratified sand and gravel beds with planar laminated to massive silty mud. The riverine, non-tidal reach of the estuary is characterized by massive, planar tabular and trough cross-stratified gravel-bed deposits. The absence of bioturbation within the inner estuary to the fluvio-tidal transition zone can be explained by the following factors: low water salinities (0-5 ppt), amplified tide and current speeds, and high concentrations of flocculated material in the water body. Notably, downstream in the middle and outer estuary, bioturbation is seasonally pervasive: in those locales the sedimentary conditions are similar, but salinity is higher. In this study, the sedimentological (i.e., grain size, bedding characters, sedimentary structures) differences between the tidal estuary and the fluvial setting are substantial, and those changes occur over only a few hundred meters. This suggests that the widely used concept of an extensive fluvio-tidal transition zone and its depositional character may not be a geographically significant component of fluvial or estuary deposits, which can go unnoticed in the study of the ancient rocks.

Extensional Tectonics and Sedimentary Architecture Using 3-D Seismic Data: An Example from Hydrocarbon-Bearing Mumbai Offshore Basin, West Coast of India

NASA Astrophysics Data System (ADS)

Mukhopadhyay, D. K.; Bhowmick, P. K.; Mishra, P.

2016-12-01

In offshore sedimentary basins, analysis of 3-D seismic data tied with well log data can be used to deduce robust isopach and structure contour maps of different stratigraphic formations. The isopach maps give depocenters whereas structure contour maps give structural relief at a specific time. Combination of these two types of data helps us decipher horst-graben structures, sedimentary basin architecture and tectono-stratigraphic relations through Tertiary time. Restoration of structural cross sections with back-stripping of successively older stratigraphic layers leads to better understand tectono-sedimentary evolution of a basin. The Mumbai (or Bombay) Offshore Basin is the largest basin off the west coast of India and includes Bombay High giant oil/gas field. Although this field was discovered in 1974 and still producing, the basin architecture vis-à-vis structural evolution are not well documented. We take the approach briefly outlined above to study in detail three large hydrocarbon-bearing structures located within the offshore basin. The Cretaceous Deccan basalt forms the basement and hosts prodigal thickness (> 8 km at some localities) of Tertiary sedimentary formations.A two stage deformation is envisaged. At the first stage horst and graben structures formed due to approximately E-W extensional tectonics. This is most spectacularly seen at the basement top level. The faults associated with this extension strike NNW. At the second stage of deformation a set of ENE-striking cross faults have developed leading to the formation of transpressional structures at places. High rate of early sedimentation obliterated horst-graben architecture to large extent. An interesting aspect emerges is that the all the large-scale structures have rather low structural relief. However, the areal extent of such structures are very large. Consequently, these structures hold commercial quantities of oil/gas.

Multiscale Multiphysics Caprock Seal Analysis: A Case Study of the Farnsworth Unit, Texas, USA

NASA Astrophysics Data System (ADS)

Heath, J. E.; Dewers, T. A.; Mozley, P.

2015-12-01

Caprock sealing behavior depends on coupled processes that operate over a variety of length and time scales. Capillary sealing behavior depends on nanoscale pore throats and interfacial fluid properties. Larger-scale sedimentary architecture, fractures, and faults may govern properties of potential "seal-bypass" systems. We present the multiscale multiphysics investigation of sealing integrity of the caprock system that overlies the Morrow Sandstone reservoir, Farnsworth Unit, Texas. The Morrow Sandstone is the target injection unit for an on-going combined enhanced oil recovery-CO2 storage project by the Southwest Regional Partnership on Carbon Sequestration (SWP). Methods include small-to-large scale measurement techniques, including: focused ion beam-scanning electron microscopy; laser scanning confocal microscopy; electron and optical petrography; core examinations of sedimentary architecture and fractures; geomechanical testing; and a noble gas profile through sealing lithologies into the reservoir, as preserved from fresh core. The combined data set is used as part of a performance assessment methodology. The authors gratefully acknowledge the U.S. Department of Energy's (DOE) National Energy Technology Laboratory for sponsoring this project through the SWP under Award No. DE-FC26-05NT42591. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Geologic map of outcrop areas of sedimentary units in the eastern part of the Hailey 1 degree x 2 degrees quadrangle and part of the southern part of the Challis 1 degree x 2 degrees quadrangle, south-central Idaho

USGS Publications Warehouse

Link, P.K.; Mahoney, J.B.; Bruner, D.J.; Batatian, L.D.; Wilson, Eric; Williams, F.J.C.

1995-01-01

The paper version of the Geologic map of outcrop areas of sedimentary units in the eastern part of the Hailey 1x2 Quadrangle and part of the southern part of the Challis 1x2 Quadrangle, south-central Idaho was compiled by Paul Link and others in 1995. The plate was compiled on a 1:100,000 scale topographic base map. TechniGraphic System, Inc. of Fort Collins Colorado digitized this map under contract for N.Shock. G.Green edited and prepared the digital version for publication as a GIS database. The digital geologic map database can be queried in many ways to produce a variety of geologic maps.

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

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

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

USGS Publications Warehouse

Edgar, Lauren; Gupta, Sanjeev; Rubin, David M.; Lewis, Kevin W.; Kocurek, Gary A.; Anderson, Ryan; Bell, James F.; Dromart, Gilles; Edgett, Kenneth S.; Grotzinger, John P.; Hardgrove, Craig; Kah, Linda C.; LeVeille, Richard A.; Malin, Michael C.; Mangold, Nicholas; Milliken, Ralph E.; Minitti, Michelle; Palucis, Marisa C.; Rice, Melissa; Rowland, Scott K.; Schieber, Juergen; Stack, Kathryn M.; Sumner, Dawn Y.; Wiens, Roger C.; Williams, Rebecca M.E.; Williams, Amy J.

2018-01-01

This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time, and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture, and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution, and bedform migration direction, this study concludes that the Shaler outcrop likely records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the northeast, across the surface of a bar that migrated southeast. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggests that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry, and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

DOE PAGES

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.; ...

2017-03-09

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less

Large-scale environmental influences on the benthic macroinfauna of the southern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Hernández-Arana, Hector A.; Rowden, Ashley A.; Attrill, Martin J.; Warwick, Richard M.; Gold-Bouchot, Gerardo

2003-12-01

The influence of large-scale natural disturbance from winter storms ('northers') and river runoff on the macrobenthic community structure of the southern Gulf of Mexico was investigated in both carbonate and transitional carbonate-terrigenous sedimentary environments. Samples of the infauna were obtained in three seasons from 13 stations from two 250 km transects along 80-170 and 20-50 m water depth. Samples after the northers season had the lowest total number of families and individuals, 114 and 2940, respectively, compared to the dry and rainy seasons with 129 and 132 families and 11580 and 15266 individuals, respectively. Spatial patterns of macroinfauna composition varied across and along the shelf as a response to sedimentary environments and depth. Coarser sediments from the carbonate area harboured the highest mean densities per station with 500-24,000 individuals m -2 and 108-122 families in total, compared to the transitional sediment with 500-8200 individuals m -2 and 56-74 families across the three seasons. Univariate and multivariate statistical techniques demonstrated that low densities and number of taxa were associated with winter storms, but storm influence was dependent on depth and sediment type. Multiple linear regression analysis and BIOENV analysis indicated that sediment mean grain size, percentage of clay and organic matter best explained the macroinfauna spatial patterns, although BIOENV indicated that depth has an overriding role. An increase in densities of opportunistic taxa (numerous polychaetes of small sizes) was observed four months after the 'northers' and this was more evident in the area of carbonate sediment. Additionally a combined disturbance from northers and river runoff is suspected to be responsible for a naturally impoverished macroinfauna community in the transitional sedimentary environment.

New evidence for long-distance fluid migration within the Earth's crust

NASA Astrophysics Data System (ADS)

Person, M.; Baumgartner, L.

1995-07-01

During the past decade, geologists have come to appreciate the interconnectedness of hydrologic, tectonic, thermal, and geochemical processes operating within the Earth's continental crust [Oliver, 1992]. This has led to a new geologically-based conceptual model of hydrology which is crustal-scale and is centered in plate tectonics theory (Fig. 1). From a geological perspective, the tectonic and thermal processes which drive plate motion are also responsible, either directly or indirectly, for inducing fluid motion across and through the continents. Supporting evidence for this emerging paradigm is based on observations of pervasive rock-water interactions associated with geologic processes as diverse as the chemical alteration of crustal rocks [Shelton et al, 1992; Elliott and Aronson, 1993; McManus and Hanor, 1993; Ague, 1991, 1994], devolatilization of minerals during burial and consequent metamorphism [Cox and Etheridge, 1989], the formation of energy and mineral deposits [Garven et al, 1993; and Cathles et al, 1993], remagnitization of ancient sedimentary rocks [McCabe and Elmore, 1989], the tectonic deformation of sedimentary basins [Oliver 1992, Ge and Garven, 1992], and the regulation of global climate [Caldeira et al, 1993, Kerrick and Caldeira, 1993, 1994]. This paper summarizes the many recent lines of theoretical, laboratory, and field evidence from diverse disciplines within the Earth Sciences supporting this emerging view of crustal-scale hydrology. Evidence for two types of long-distance fluid migration are highlighted: vertical pore water movement through crystalline rocks to depths greater than six km and lateral groundwater movement through sedimentary basins over hundereds of km. Also emphasized are the many driving mechanisms on fluid motion which are not typically considered in water quality and water supply investigations. Some geologic terms used in this paper, which may be unfamiliar to the reader, are defined in geologic dictionaries [American Geologic Institute, 1976].

PUMa - modelling the groundwater flow in Baltic Sedimentary Basin

NASA Astrophysics Data System (ADS)

Kalvane, G.; Marnica, A.; Bethers, U.

2012-04-01

In 2009-2012 at University of Latvia and Latvia University of Agriculture project "Establishment of interdisciplinary scientist group and modelling system for groundwater research" is implemented financed by the European Social Fund. The aim of the project is to develop groundwater research in Latvia by establishing interdisciplinary research group and modelling system covering groundwater flow in the Baltic Sedimentary Basin. Researchers from fields like geology, chemistry, mathematical modelling, physics and environmental engineering are involved in the project. The modelling system is used as a platform for addressing scientific problems such as: (1) large-scale groundwater flow in Baltic Sedimentary Basin and impact of human activities on it; (2) the evolution of groundwater flow since the last glaciation and subglacial groundwater recharge; (3) the effects of climate changes on shallow groundwater and interaction of hydrographical network and groundwater; (4) new programming approaches for groundwater modelling. Within the frame of the project most accessible geological information such as description of geological wells, geological maps and results of seismic profiling in Latvia as well as Estonia and Lithuania are collected and integrated into modelling system. For example data form more then 40 thousands wells are directly used to automatically generate the geological structure of the model. Additionally a groundwater sampling campaign is undertaken. Contents of CFC, stabile isotopes of O and H and radiocarbon are the most significant parameters of groundwater that are established in unprecedented scale for Latvia. The most important modelling results will be published in web as a data set. Project number: 2009/0212/1DP/1.1.1.2.0/09/APIA/VIAA/060. Project web-site: www.puma.lu.lv

Fluvial-aeolian interactions in sediment routing and sedimentary signal buffering: an example from the Indus Basin and Thar Desert

USGS Publications Warehouse

East, Amy E.; Clift, Peter D.; Carter, Andrew; Alizai, Anwar; VanLaningham, Sam

2015-01-01

Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the Late Holocene–Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1–10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.

Characterizing flow pathways in a sandstone aquifer at multiple depths

NASA Astrophysics Data System (ADS)

Medici, Giacomo; West, Jared; Mountney, Nigel

2017-04-01

Sandstone aquifers are commonly assumed to represent porous media characterized by a permeable matrix. However, such aquifers may be heavily fractured where rock properties and timing of deformation favour brittle failure and crack opening. In many aquifer types, fractures associated with faults, bedding planes and stratabound joints represent preferential pathways for fluids and contaminants. This presentation reports well-test results and outcrop-scale studies that reveal how strongly lithified siliciclastic rocks may be entirely dominated by fracture flow at shallow depths (≤ 150 m), similar to limestone and crystalline aquifers. The Triassic St Bees Sandstone Formation of the UK East Irish Sea Basin represents an optimum succession for study of the influence of both sedimentary and tectonic aquifer heterogeneities in a strongly lithified sandstone aquifer-type. This sedimentary succession of fluvial origin accumulated in rapidly subsiding basins, which typically favour preservation of complete depositional cycles, including fine-grained mudstone and silty sandstone layers of floodplain origin interbedded with sandstone-dominated fluvial channel deposits. Vertical joints in the St Bees Sandstone Formation form a pervasive stratabound system whereby joints terminate at bedding-parallel discontinuities. Additionally, normal faults are present through the succession and record development of open-fractures in their damage zones. Here, the shallow aquifer (depth ≤150 m BGL) was characterized in outcrop and well tests. Fluid temperature, conductivity and flow-velocity logs record inflows and outflows from normal faults, as well as from pervasive bed-parallel fractures. Quantitative flow logging analyses in boreholes that cut fault planes indicate that zones of fault-related open fractures typically represent ˜ 50% of well transmissivity. The remaining flow component is dominated by bed-parallel fractures. However, such sub-horizontal fractures become the principal flow conduits in wells that penetrate the exterior parts of fault damage zones, as well as in non-faulted areas. Optical televiewer logs show development of karst-like conduits in correspondence of bedding fractures and faults up to 150 m below the ground surface, where recharge water containing dissolved carbonic acid enlarges fractures; these features may be responsible for the relatively high field-scale permeability (K˜0.1-1 m/day) of the phreatic zone at these depths. Below this 'karstifed' zone, field-scale permeability progressively decreases from K˜10-2 to 10-4 m/day from 150 m to 1100 m depth. Notably, differences between plug and field-scale permeability, and frequency of well in-flows seen in temperature and conductivity logs, also decrease between intermediate (150 to 450 m) and elevated (450 to 1100 m) depths. This confirms how fracture closure leads to a progressively more important matrix contribution to flow with increasing lithostatic stress, leading to intergranular flow dominance at ˜ 1 km depth.

Distribution, input pathway and mass inventory of black carbon in sediments of the Gulf of Thailand, SE Asia

NASA Astrophysics Data System (ADS)

Hu, Limin; Shi, Xuefa; Bai, Yazhi; Fang, Yin; Chen, Yingjun; Qiao, Shuqing; Liu, Shengfa; Yang, Gang; Kornkanitnan, Narumol; Khokiattiwong, Somkiat

2016-03-01

The coastal margins around Southeast Asia (SE Asia) may serve as an ideal location to study the source-sink process of sedimentary black carbon (BC) because SE Asia has been identified as one of the major BC emission source regions in the world. This study provides an extensive picture of recent regional-scale sedimentary BC sequestration in the Gulf of Thailand (GOT), a tropical marine system in SE Asia. Generally, the sedimentary BC concentrations (0.07-3.99 mg/g) were in the low to moderate ranges of those obtained in other coastal sediments around the world. Regional variability of the BC and its correlation with the sediment grain size and total organic carbon (TOC) content indicated a general hydrodynamic constraint on BC occurrence in the lower Gulf in contrast to the upper Gulf with a more source dependence due to the direct land-based input. BC/TOC% values and the varied BC components (char and soot), as well as their correlations suggested that char was the predominant constituents of sedimentary BC both in the upper and lower Gulf, which could be mainly derived from biomass burning and entered into the nearshore region through direct fluvial transport and surface run-off. The estimated BC burial flux (∼212 μg/cm2/y) and mass inventory (∼200 Gg/y) in the GOT on the hundred-year timescale were of the same order of magnitude compared with other oceanic margins, and thus the tropical shelf sediments from SE Asia could serve as an important sink of land-emitted BC.

Recent organic carbon sequestration in the shelf sediments of the Bohai Sea and Yellow Sea, China

NASA Astrophysics Data System (ADS)

Hu, Limin; Shi, Xuefa; Bai, Yazhi; Qiao, Shuqing; Li, Li; Yu, Yonggui; Yang, Gang; Ma, Deyi; Guo, Zhigang

2016-03-01

This study provides an extensive depiction of regional scale sedimentary total organic carbon (TOC) sequestration in the Bohai Sea (BS) and Yellow Sea (YS), marginal system of the western Pacific Ocean. The spatial pattern of the sediment mass accumulation rate (MAR) in the BS and YS was summarized based on a 100-year timescale. The relatively higher MAR (3 - 7 g/cm2/y) in the Yellow River estuary, compared to the adjacent areas, indicate a predominant impact of river discharge on the modern sedimentation process in the BS. Relatively stable sedimentary environment in the offshore mud deposits of the BS and YS was also identified based on the along-core sediment composition and radionuclides profiles. The corresponding spatial pattern of grain size and TOC content suggest a hydrodynamic constraint on the sedimentary TOC accumulation. Moreover, in spite of the various TOC sources revealed by the bulk organic matter (OM) proxies (C/N ratio and δ13C), the restriction of these bulk parameters with potential masking of the signature of terrigenous OM was also identified. The average burial flux of TOC (15.3 g C/m2/y) was finally obtained with a total sequestration of 5.6 × 106 t C/y, suggesting that the BS and YS serve as a significant repository of sedimentary TOC. The overall organic carbon storage capacity of the BS and YS is mainly sustained by the fluvial/land-based OM input, high phytoplankton primary productivity, convergent hydrodynamic and stable depositional settings.

Next-generation seismic experiments: wide-angle, multi-azimuth, three-dimensional, full-waveform inversion

NASA Astrophysics Data System (ADS)

Bell, Rebecca; Morgan, Joanna; Warner, Michael

2016-04-01

There are many outstanding plate-tectonic scale questions that require us to know information about sub-surface physical properties, for example ascertaining the geometry and location of magma chambers and estimating the effective stress along plate boundary faults. These important scientific targets are often too deep, impractical and expensive for extensive academic drilling. Full-waveform inversion (FWI) is an advanced seismic imaging technique that has recently become feasible in three dimensions, and has been widely adopted by the oil and gas industry to image reservoir-scale targets at shallow-to-moderate depths. In this presentation we explore the potential for 3-D FWI, when combined with appropriate marine seismic acquisition, to recover high-resolution high-fidelity P-wave velocity models for sub-sedimentary targets within the crystalline crust and uppermost mantle. Using existing geological and geophysical models, we construct P-wave velocity models over three potential sub-sedimentary targets: the Soufrière Hills Volcano on Montserrat and its associated crustal magmatic system, the downgoing oceanic plate beneath the Nankai subduction margin, and the oceanic crust-uppermost mantle beneath the East Pacific Rise mid-ocean ridge. We use these models to generate realistic multi-azimuth 3-D synthetic seismic data, and attempt to invert these data to recover the original models. We explore the resolution and accuracy, sensitivity to noise and acquisition geometry, ability to invert elastic data using acoustic inversion codes, and the trade-off between low frequencies and starting velocity model accuracy. We will show that FWI applied to multi-azimuth, refracted, wide-angle, low-frequency data can resolve features in the deep crust and uppermost mantle on scales that are significantly better than can be achieved by any other geophysical technique, and that these results can be obtained using relatively small numbers (60-90) of ocean-bottom receivers combined with large numbers of air-gun shots. We demonstrate that multi-azimuth 3-D FWI is robust in the presence of noise, that acoustic FWI can invert elastic data successfully, and that the typical errors to be expected in starting models derived using travel times will not be problematic for FWI given appropriately designed acquisition. In this presentation we will also discuss a recent field-example of the use of FWI to image the Endeavour spreading centre in the northeastern Pacific. FWI is a rapidly maturing technology; its transfer from the petroleum sector to tackle a broader range of targets now appears entirely achievable.

Spatial association analysis between hydrocarbon fields and sedimentary residual magnetic anomalies using Weights of Evidence: An example from the Triassic Province of Algeria

NASA Astrophysics Data System (ADS)

Allek, Karim; Boubaya, Djamel; Bouguern, Abderrahmane; Hamoudi, Mohamed

2016-12-01

The presence of near-surface magnetic anomalies over oil and gas accumulations and their contribution to exploration remain somewhat controversial despite encouraging results and an improved understanding of genetic links between hydrocarbon seepage-induced alterations and near-surface magnetic minerals. This controversy is likely to remain since the cause of shallow-sourced sedimentary magnetic anomalies may well be microseepage related, but could also result from other sources such as cultural features and detrital magnetite. The definite way of discriminating between them remains a challenge. In this paper we examine means to deal with this particular purpose using a Bayesian technique known as 'Weights-of-Evidence'. The technique is implemented in GIS to explore spatial associations between known hydrocarbon fields within the central Triassic province of Algeria and sedimentary residual magnetic anomalies. We use the results to show possible application of the method to the recognition of some characteristics (amplitude and width) of anomalies assumed to be induced by hydrocarbon microseepages. Our results reveal strong spatial association with certain typical class of anomalies, confirming therefore hypothesis that hydrocarbon microseepages may result in detectable magnetic anomalies. It is possible to use the anomalies occurring outside the known gas and oil fields to make informed decisions in the selection of new targets for more detailed hydrocarbon exploration.

Hydrological and sedimentary controls over fluvial thermal erosion, the Lena River, central Yakutia

NASA Astrophysics Data System (ADS)

Tananaev, Nikita I.

2016-01-01

Water regime and sedimentary features of the middle Lena River reach near Yakutsk, central Yakutia, were studied to assess their control over fluvial thermal erosion. The Lena River floodplain in the studied reach has complex structure and embodies multiple levels varying in height and origin. Two key sites, corresponding to high and medium floodplain levels, were surveyed in 2008 to describe major sedimentary units and properties of bank material. Three units are present in both profiles, corresponding to topsoil, overbank (cohesive), and channel fill (noncohesive) deposits. Thermoerosional activity is mostly confined to a basal layer of frozen channel fill deposits and in general occurs within a certain water level interval. Magnitude-frequency analysis of water level data from Tabaga gauging station shows that a single interval can be deemed responsible for the initiation of thermal action and development of thermoerosional notches. This interval corresponds to the discharges between 21,000 and 31,000 m3 s- 1, observed normally during spring meltwater peak and summer floods. Competence of fluvial thermal erosion depends on the height of floodplain level being eroded, as it acts preferentially in high floodplain banks. In medium floodplain banks, thermal erosion during spring flood is constrained by insufficient bank height, and erosion is essentially mechanical during summer flood season. Bank retreat rate is argued to be positively linked with bank height under periglacial conditions.

Geomorphological and sedimentary record from Poseidi, N. Greece and relationship with Late Bronze and Iron age settlements

NASA Astrophysics Data System (ADS)

Psomiadis, David; Parashou, Theodoros; Albanakis, Konstantinos; Dotsika, Elissavet; Zisi, Nikoleta

2010-05-01

Coastal geomorphological features from Poseidi, Chalkidiki, N. Greece have been studied in order to classify the Late Pleistocene and Holocene formations that prevail across the coastal zone of Cape Poseidi. Carbonate cementation in the littoral shelf (beachrocks) indicates phases of coastal instability. The adjacent conglomerate formation and the stratigraphical characteristics of the backshore sedimentary sequence define the geomorphological setting of the human occupation in the area that dates back to 3500 BP. Eretrians settled the area (Pallini peninsula) during the Iron age, while Poseidi was already used for ritual ceremonies of god Neptune. Although ancient Mendi was built on an approximately 100m-high hill, its so-called "Suburb" by Thucydides was reaching the shoreline, and its cemetery was excavated in the beach sediments. Palaeo-shorelines have been reconstructed using bathymetry data and submerged fossil coastlines. The submerged beachrock horizons are spotted northwards at 1m, 1.7m, 2.4m and 3.6m depth as well as the formation occupies the swashzone at two subsequent separated beaches southwards near ancient Mendi. Tectonic movements were also evaluated and reconsidered in relation to coastal archaeological sites for the reconstruction of the geomorphological setting. The dynamic wave regime at Cape Poseidi and the sedimentary characteristics seem to have played a prominent role during stages of relatively stable sea level and influenced the human occupation in the area.

Provenance and tectonic setting of the supra-crustal succession of the Qinling Complex: Implications for the tectonic affinity of the North Qinling Belt, Central China

NASA Astrophysics Data System (ADS)

Shi, Yu; Huang, Qianwen; Liu, Xijun; Krapež, Bryan; Yu, Jinhai; Bai, Zhian

2018-06-01

The Qinling Complex lies in the Qinling orogenic belt of Central China and holds the key to understanding the evolution of this feature. The Qinling Complex comprises a basement complex composed of amphibolite and ecologite, overlain by a supra-crustal succession that has been metamorphosed to the upper greenschist facies at approximately 516-509 Ma. The protoliths of the meta-sedimentary rocks are graywackes, which are divided into lower, middle and upper units. Detrital zircons from nine samples of the supra-crustal succession have ages ranging from 1182 to 1158 Ma for the lower unit, 957 to 955 Ma for the middle unit and 917 to 840 Ma for the upper unit. The lower unit is intruded by a ca. 960 Ma pluton. The bulk compositions of these meta-sedimentary rocks and their detrital zircon ages clearly indicate derivation from Meso- and Neo-proterozoic granites. Thus, we suggest that the sedimentary succession was derived from an arc-related tectonic setting and that none of the detritus was sourced from the southern margin of the North China Block or from the northern and western margins of the South China Block. We conclude that the North Qinling Belt was an independent micro-continental block during the Meso- to Neo-proterozoic.

Spatio-temporal variations of organic matter along the Seine estuary (France)

NASA Astrophysics Data System (ADS)

Thibault, Alexandre; Huguet, Arnaud; Parlanti, Edith; Derenne, Sylvie

2017-04-01

Organic matter (OM) in aquatic systems plays an important role in water quality and biogeochemical processes. It is thus essential to characterize OM, especially in estuaries which are the place of the transport and the reactivity of natural and anthropogenic compounds. However, the characterization of OM in estuaries is complex due to its heterogeneity and variability in addition to specific features of these environments (salinity, turbidity…). Two types of aquatic OM, namely particulate (POM) and dissolved (DOM) are commonly distinguished by filtration. Due to its low concentration in estuaries (few mg/L), DOM has to be concentrated prior to its molecular (or structural) analysis. However, this step also induces the concentration of salts which are predominant (several g/L) in coastal environments. To overcome this issue, DOM has been isolated by a combination of reverse osmosis and electrodialysis. This method is more efficient than classical ones (ultrafiltration, solid phase techniques) in the isolation of representative DOM material. As a result, DOM can be characterized just as POM and sedimentary OM. The aim of this study is to characterize the spatiotemporal variability of DOM, POM and sedimentary OM along the Seine estuary (France) so as to understand its role in the functioning of this ecosystem. To this end, 5 sampling campaigns were performed in the Seine estuary between January 2015 and April 2016, during which large water samples (100 L) and sediment cores (10 cm) were collected. These campaigns covered the whole estuary. The three OM pools were analyzed through (i) elemental and isotopic analyses (Elemental Analysis-isotope ratio Mass Spectrometry, 14C ages) and (ii) structural analyses (13C solid state nuclear magnetic resonance, pyrolysis coupled with gas chromatography and mass spectrometry and ultrahigh resolution mass spectrometry), allowing to obtain both bulk and molecular information. The combination of these chemical characterization and statistical analyses shows that the 2 main factors driving the composition of OM in the Seine estuary are the OM pool (DOM, POM or sedimentary) and its origin (marine vs freshwater) whereas seasonal variations appear less pronounced. Indeed, OM exhibits higher C/N ratio and is richer in aliphatic and alkoxyl carbons than POM and sedimentary OM. The latter share the same elemental and isotopic composition but POM is enriched in aliphatic carbons with respect to sedimentary OM. These results confirm the higher hydrophilic nature of DOM when compared to POM and that the sedimentary OM in the Seine estuary is close to POM. Moreover, the dating of OM shows that DOM and POM are recent (> 1950 AD) contrary to sedimentary OM. When going downstream along the estuary, DOM is depleted in aliphatic carbons and enriched in alkoxyl carbons, the reverse trend being observed for POM. Both are enriched in δ13C.

The Salzach Valley overdeeping: A most precise bedrock model of a major alpine glacial basin

NASA Astrophysics Data System (ADS)

Pomper, Johannes; Salcher, Bernhard; Eichkitz, Christoph

2016-04-01

Overdeepenings are impressive phenomena related to the erosion in the ablation zone of major glaciers. They are common features in glaciated and deglaciated regions worldwide and their sedimentary fillings may act as important archives for regional environmental change and glaciation history. Sedimentary fillings are also important targets of geotechnical exploration and construction including groundwater resource management, shallow geothermal exploitation, tunneling and the foundation of buildings. This is especially true in densely populated areas such as the European Alps and their foreland areas, regions which have been multiply glaciated during the last million years. However, due depths often exceeding some hundreds of meters, the overall knowledge on their geometry, formation and sedimentary content is still poor and commonly tied to some local spots. Here we present a bedrock model of the overall lower Salzach Valley, one of the largest glacial overdeepings in the European Alps. We utilized seismic sections from hydrocarbon exploration surveys and deep drillings together with topographic and modelling data to construct a 3D bedrock model. Through the existence of seismic inline and crossline valley sections, multiple drillings reaching the bedrock surface, log and abundant outcrop data we were, as far to our knowledge, able to create the most accurate digital bedrock topography of an alpine major overdeepening. We furthermore analyzed the sedimentary content of the valley as recorded by driller's lithologic logs. Our results suggest that the valley is far from being a regular U-shaped trough with constant depth, rather highlighting highs and lows of different magnitude and underground valley widths of variable extent. Data also indicates that the largest overdeepening of bedrock, reaching around 450 m below the alluvial fill, is not situated after a major glacial confluence following a prominent bedrock gorge but shifted several km down the valley. The sedimentary succession, representing multiple cycles of massive gravels and lacustrine fines, indicate that the valley was not fully excavated during the last glacial coverage at the LGM. Through its model accuracy related to a comprehensive geodatabase and a relatively homogenous rock erodibility, the Salzach Valley overdeepening might be a highly suitable testing site for future numerical simulations.

Evaluation of conditions along the grounding line of temperate marine glaciers: An example from Muir Inlet, Glacier Bay, Alaska

USGS Publications Warehouse

Seramur, K.C.; Powell, R.D.; Carlson, P.R.

1997-01-01

In the marine environment, stability of the glacier terminus and the location of subglacial streams are the dominant controls on the distribution of grounding-line deposits within morainal banks. A morainal bank complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a model of terminus stability and location of subglacial streams along the grounding line of temperate marine glaciers. This model can be used to interpret former grounding-line conditions in other glacimarine settings from the facies architecture within morainal bank deposits. The Muir Inlet morainal bank complex was deposited between 1860 A.D. and 1899 A.D., and historical observations provide a record of terminus positions, glacial retreat rates and sedimentary sources. These data are used to reconstruct the depositional environment and to develop a correlation between sedimentary facies and conditions along the grounding line. Four seismic facies identified on the high-resolution seismic-reflection profiles are used to interpret sedimentary facies within the morainal bank complex. Terminus stability is interpreted from the distribution of sedimentary facies within three distinct submarine geomorphic features, a grounding-line fan; stratified ridges, and a field of push ridges. The grounding-line fan was deposited along a stable terminus and is represented on seismic-reflection profiles by two distinct seismic facies, a proximal and a distal fan facies. The proximal fan facies was deposited at the efflux of subglacial streams and indicates the location of former glacifluvial discharges into the sea. Stratified ridges formed as a result of the influence of a quasi-stable terminus on the distribution of sedimentary facies along the grounding line. A field of push ridges formed along the grounding line of an unstable terminus that completely reworked the grounding-line deposits through glacitectonic deformation. Between 1860 A.D. and 1899 A.D. (39 years), 8.96 x 108 m3 of sediment were deposited within the Muir Inlet morainal bank complex at an average annual sediment accumulation rate of 2.3 x 107 m3/a. This rate represents the annual sediment production capacity of the glacier when the Muir Inlet drainage basin is filled with glacial ice.

Venus analogues on the Earth's ocean floor(?): Volcanic terrains seen by SeaMARC 2 side scan sonar

NASA Technical Reports Server (NTRS)

Mouginis-Mark, P. J.; Fryer, P.; Hussong, D.; Zisk, S. H.

1984-01-01

The geology of Venus is discussed. The approximate age of the surface and the relative importance of large scale volcanic, tectonic and sedimentary processes are not known. Venus holds a very important role in comparative planetology. The investigation of comparable environments to Venus to test ideas of landform development on that planet are proposed.

Mola Topography Supports Drape-Folding Models for Polygonal Terrain of Utopia Planitia, Mars

NASA Technical Reports Server (NTRS)

McGill, George E.; Buczkowski, D. L.

2002-01-01

One of the most important questions we ask about Mars is whether or not there have ever been large bodies of standing water on the surface. The polygonal terrains of Utopia and Acidalia Planitiae are located in the lowest parts of the northern lowlands, the most logical places for water to pond and sediments to accumulate. Showing that polygonal terrain is sedimentary in origin would represent strong evidence in favor of a northern ocean. A number of hypotheses for the origin of the giant martian polygons have been proposed, from the cooling of lava to frost wedging to the desiccation of wet sediments, but Pechman showed that none of these familiar processes could be scaled up to martian dimensions. Two models for polygon origin attempt to explain the scale of the martian polygons by postulating drape folding of a cover material, either sedimentary or volcanic, over an uneven, buried surface. The drape folding would produce bending stresses in the surface layers that increase the probability of Fracturing over drape anticlines and suppress the probability of fracturing over drape synclines. However, both models require an additional source of extensional strain to produce the total strain needed to produce the observed troughs.

Predictive modelling of flow in a two-dimensional intermediate-scale, heterogeneous porous media

USGS Publications Warehouse

Barth, Gilbert R.; Hill, M.C.; Illangasekare, T.H.; Rajaram, H.

2000-01-01

To better understand the role of sedimentary structures in flow through porous media, and to determine how small-scale laboratory-measured values of hydraulic conductivity relate to in situ values this work deterministically examines flow through simple, artificial structures constructed for a series of intermediate-scale (10 m long), two-dimensional, heterogeneous, laboratory experiments. Nonlinear regression was used to determine optimal values of in situ hydraulic conductivity, which were compared to laboratory-measured values. Despite explicit numerical representation of the heterogeneity, the optimized values were generally greater than the laboratory-measured values. Discrepancies between measured and optimal values varied depending on the sand sieve size, but their contribution to error in the predicted flow was fairly consistent for all sands. Results indicate that, even under these controlled circumstances, laboratory-measured values of hydraulic conductivity need to be applied to models cautiously.To better understand the role of sedimentary structures in flow through porous media, and to determine how small-scale laboratory-measured values of hydraulic conductivity relate to in situ values this work deterministically examines flow through simple, artificial structures constructed for a series of intermediate-scale (10 m long), two-dimensional, heterogeneous, laboratory experiments. Nonlinear regression was used to determine optimal values of in situ hydraulic conductivity, which were compared to laboratory-measured values. Despite explicit numerical representation of the heterogeneity, the optimized values were generally greater than the laboratory-measured values. Discrepancies between measured and optimal values varied depending on the sand sieve size, but their contribution to error in the predicted flow was fairly consistent for all sands. Results indicate that, even under these controlled circumstances, laboratory-measured values of hydraulic conductivity need to be applied to models cautiously.

Millennial-scale Climate Variations Recorded As Far Back As The Early Pliocene

NASA Astrophysics Data System (ADS)

Steenbrink, J.; Hilgen, F. J.; Lourens, L. J.

Quaternary climate proxy records show compelling evidence for climate variability on time scales of a few thousand years. The causes for these millennial-scale or sub- Milankovitch cycles are yet poorly understood, not in the least due to the complex feedback mechanisms of large ice-sheets during the Quaternary. We present evidence of millennial-scale climate variability in Early Pliocene lacustrine sediments from the intramontane Ptolemais Basin in northwestern Greece. The sediments are well ex- posed in a series of open-pit lignite mines and exhibit a distinct m-scale sedimentary cyclicity of alternating lignites and lacustrine marl beds that result from precession- induced variations in climate. A higher-frequency cyclicity is particular prominent within the marl segment of individual cycles. A stratigraphic interval of~115 kyr, cov- ering five precession-induced sedimentary cycles, was studied in nine parallel sections from two quarries located several km apart. Colour reflectance records were used to quantify the within-cycle variability and to determine its lateral continuity. Much of the within-cycle variability could be correlated between the parallel sections, even in fine detail, which suggests that these changes reflect basin-wide variations in environ- mental conditions related to (regional) climate fluctuations. Interbedded volcanic ash beds demonstrate the synchronicity of these fluctuations and spectral analysis of the reflectance time series shows a significant concentration of variability at periods of ~11,~5.5 and~2 kyr. Their occurrence at times before the intensification of the North- ern Hemisphere glaciation suggests that they cannot solely have resulted from internal ice-sheet dynamics. Possible candidates include harmonics or combination tones of the main orbital cycles, variations in solar output or periodic motions of the Earth and moon.

Late Mesozoic and Cenozoic thermotectonic evolution of the central Brooks Range and adjacent North Slope foreland basin, Alaska: Including fission track results from the Trans-Alaska Crustal Transect (TACT)

USGS Publications Warehouse

O'Sullivan, P. B.; Murphy, J.M.; Blythe, A.E.

1997-01-01

Apatite fission track data are used to evaluate the thermal and tectonic history of the central Brooks Range and the North Slope foreland basin in northern Alaska along the northern leg of the Trans-Alaska Crustal Transect (TACT). Fission track analyses of the detrital apatite grains in most sedimentary units resolve the timing of structures and denudation within the Brooks Range, ranging in scale from the entire mountain range to relatively small-scale folds and faults. Interpretation of the results indicates that rocks exposed within the central Brooks Range cooled rapidly from paleotemperatures 110?? to 50??C during discrete episodes at ???100??5 Ma, ???60??4 Ma, and ???24??3 Ma, probably in response to kilometer-scale denudation. North of the mountain front, rocks in the southern half of the foreland basin were exposed to maximum paleotemperatures 110??C in the Late Cretaceous to early Paleocene as a result of burial by Upper Jurassic and Cretaceous sedimentary rocks. Rapid cooling from these elevated paleotemperatures also occurred due to distinct episodes of kilometer-scale denudation at ???60??4 Ma, 46??3 Ma, 35??2 Ma, and ???24??3 Ma. Combined, the apatite analyses indicate that rocks exposed along the TACT line through the central Brooks Range and foreland basin experienced episodic rapid cooling throughout the Late Cretaceous and Cenozoic in response to at least three distinct kilometer-scale denudation events. Future models explaining orogenic events in northern Alaska must consider these new constraints from fission track thermochronology. Copyright 1997 by the American Geophysical Union.

A ground penetrating radar investigation of a glacial-marine ice- contact delta, Pineo Ridge, eastern coastal Maine

USGS Publications Warehouse

Tary, A.K.; Duncan, M. FitzGerald; Weddle, T.K.

2007-01-01

In eastern coastal Maine, many flat-topped landforms, often identified as glacial-marine deltas, are cultivated for blueberry production. These agriculturally valuable features are not exploited for aggregate resources, severely limiting stratigraphic exposure. Coring is often forbidden; where permissible, coarse-grained surficial sediments make coring and sediment retrieval difficult. Ground penetrating radar (GPR) has become an invaluable tool in an ongoing study of the otherwise inaccessible subsurface morphology in this region and provides a means of detailing the large-scale sedimentary structures comprising these features. GPR studies allow us to reassess previous depositional interpretations and to develop alternative developmental models. The work presented here focuses on Pineo Ridge, a large, flat-topped ice-marginal glacial-marine delta complex with a strong linear trend and two distinct landform zones, informally termed East Pineo and West Pineo. Previous workers have described each zone separately due to local morphological variation. Our GPR work further substantiates this geomorphic differentiation. East Pineo developed as a series of deltaic lobes prograding southward from an ice-contact margin during the local marine highstand. GPR data do not suggest postdepositional modification by ice-margin re-advance. We suggest that West Pineo has a more complex, two-stage depositional history. The southern section of the feature consists of southward-prograding deltaic lobes deposited during retreat of the Laurentide ice margin, with later erosional modification during marine regression. The northern section of West Pineo formed as a series of northward-prograd- ing deltaic lobes as sediment-laden meltwater may have been diverted by the existing deposits of the southern section of West Pineo. ?? 2007 The Geological Society of America. All rights reserved.

High-resolution characterization of chemical heterogeneity in an alluvial aquifer

USGS Publications Warehouse

Schulmeister, M.K.; Healey, J.M.; McCall, G.W.; Birk, S.; Butler, J.J.

2002-01-01

The high-resolution capabilities of direct-push technology were exploited to develop new insights into the hydrochemistry at the margin of an alluvial aquifer. Hydrostratigraphic controls on groundwater flow and contaminant loading were revealed through the combined use of direct-push electrical conductivity (EC) logging and geochemical profiling. Vertical and lateral variations in groundwater chemistry were consistent with sedimentary features indicated by EC logs, and supported a conceptual model of recharge along the floodplain margin.

Geologic map of the Alley Spring quadrangle, Shannon County, Missouri

USGS Publications Warehouse

Weary, David J.; Orndorff, Randall C.

2012-01-01

The Alley Spring 7.5-minute quadrangle is located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 1,990 feet (ft) of flat-lying to gently dipping Lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic volcanic rocks. A small exposure of the volcanic rocks exists near the eastern edge of the quadrangle. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Karst features, such as sinkholes, caves, and springs, have formed in the carbonate rocks. Many streams are spring fed. Alley Spring, the largest karst spring in the quadrangle, has an average discharge of 81 million gallons per day. The topography is a dissected karst plain with elevation ranging from 630 ft where the Jacks Fork River exits the quadrangle to more than 1,140 ft at numerous places in the northern half of the quadrangle. The most prominent physiographic feature is the valley of the Jacks Fork River. Most of the land in the quadrangle is privately owned and used primarily for grazing cattle and horses and growing timber. A large minority of the land within the quadrangle is publicly owned, either by the Missouri State Forests or by the Ozark National Scenic Riverways of the National Park Service. Geologic mapping for this investigation was conducted in 2003 and 2004.

Lateral variations in lithospheric and landscape evolution at both ends of the Himalaya-Tibet orogen

NASA Astrophysics Data System (ADS)

Zeitler, P. K.; Schmidt, J. L.; Meltzer, A.

2015-12-01

At the broadest scale, like many orogens the Himalaya encompass a range of orogenic features that are remarkably similar along much of the length of the mountain belt and its neighboring terranes. At one scale of consideration, these similarities appear to be a signal that fundamental processes associated with lithospheric collision have been active. However, the vast size of the Himalaya and Tibet, the different climate regimes experienced by the orogen across time and space, and the along-strike variations in the continental and arc margins that faced one another before collision, make it at once remarkable that any similarities exist, and important to more critically evaluate their nature. The eastern and western Himalayan syntaxes confound any attempt to generalize too much about the Himalaya-Tibet orogen. By area these features occupy at least 25% of the orogenic belt, and compared to the "main" portions of the arc they show clear differences in their lithospheric structures, landscapes, and evolution. The boundary and initial conditions that shaped the eastern and western indentor corners were and are different, as is the nature and timing of erosional exhumation. Some of the most active geologic processes on Earth have recently been in play within the syntaxes, and the evolution of landscapes and fluvial systems, important in developing the sedimentary record of the Himalaya-Tibet system, has been complex and variable in space and time. Southeasternmost Tibet and the Lhasa Block in particular exemplify this complexity both in its complex topographic evolution linked to surface processes and climate, and in lateral variability in lithospheric structure. Taking a system viewpoint, an important question to debate is the degree to which there are features in the Himalaya-Tibet system that are robustly emergent, given the broad boundary conditions of the continental collision plus the suite of local and regional geodynamical processes that have operated during orogenesis. A related question is the degree to which the variability seen within the orogen represents important information about process that is exportable to other orogens, or is in effect tectonic noise contingent on local geologic details and secular changes.

Millennial-scale climate variations recorded in Early Pliocene colour reflectance time series from the lacustrine Ptolemais Basin (NW Greece)

NASA Astrophysics Data System (ADS)

Steenbrink, J.; Kloosterboer-van Hoeve, M. L.; Hilgen, F. J.

2003-03-01

Quaternary climate proxy records show compelling evidence for climate variability on time scales of a few thousand years. The causes for these millennial-scale or sub-Milankovitch cycles are still poorly understood, not least due to the complex feedback mechanisms of large ice sheets during the Quaternary. We present evidence of millennial-scale climate variability in Early Pliocene lacustrine sediments from the intramontane Ptolemais Basin in northwestern Greece. The sediments are well exposed in a series of open-pit lignite mines and exhibit a distinct millennial-scale sedimentary cyclicity of alternating lignites and lacustrine marl beds that resulted from precession-induced variations in climate. The higher-frequency, millennial-scale cyclicity is particularly prominent within the grey-coloured marl segment of individual cycles. A stratigraphic interval of ˜115 ka, covering five precession-induced sedimentary cycles, was studied in nine parallel sections from two open-pit lignite mines located several km apart. High-resolution colour reflectance records were used to quantify the within-cycle variability and to determine its lateral continuity. Much of the within-cycle variability could be correlated between the parallel sections, even in fine detail, which suggests that these changes reflect basin-wide variations in environmental conditions related to (regional) climate fluctuations. Interbedded volcanic ash beds demonstrate the synchronicity of these fluctuations and spectral analysis of the reflectance time series shows a significant concentration of within-cycle variability at periods of ˜11, ˜5.5 and ˜2 ka. The occurrence of variability at such time scales at times before the intensification of the Northern Hemisphere glaciation suggests that they cannot solely have resulted from internal ice-sheet dynamics. Possible candidates include harmonics or combination tones of the main orbital cycles, variations in solar output or periodic motions of the Earth and Moon.

Cordilleran hingeline: Late Precambrian rifted margin of the North American craton and its impact on the depositional and structural history, Utah and Nevada

NASA Astrophysics Data System (ADS)

Picha, Frank; Gibson, Richard I.

1985-07-01

The structural pattern set by late Precambrian rifting and fragmentation of the North American continent is apparent in both sedimentary and tectonic trends in western Utah and eastern Nevada. The late Precambrian cratonic margin (Cordilleran hingeline) displays several prominent structural features, such as the Wasatch and Ancient Ephraim faults, Fillmore arch and northeast-trending lineaments, which were repeatedly reactivated as structural uplifts, ramps, strike-slip faults, and extensional detachments. The renewed activity affected, among others, the geometry of the late Paleozoic Ancestral Rocky Mountain uplifts and basins, the extent of the Jurassic Arapien basin, the sedimentary pattern of the Cretaceous foreland basin, the geometry of the Sevier orogenic belt, and the extent and type of Basin-and-Range extensional tectonics. The rifted cratonic margin has thus remained a major influence on regional structures long after rifting has ceased. *Present address: Everest Geotech, 10101 Southwest Freeway, Houston, Texas 77074

The origin and fate of 4-methyl steroid hydrocarbons. I. Diagenesis of 4-methyl sterenes

NASA Astrophysics Data System (ADS)

Wolff, George A.; Lamb, Neil A.; Maxwell, James R.

1986-03-01

Treatment of 4-methylcholest-4-ene under mild acid conditions at low temperatures gives chemical evidence for certain features seen in the distributions of sedimentary 4-methyl steroid hydrocarbons, and further indicates that many low temperature diagenetic reactions of steroids are explicable in terms of acid catalysed rearrangements. Specifically, the results provide: (i) Indirect evidence that the 4-ene skeleton is a key intermediate in the dehydration of 4-methyl stanols in sediments. (ii) An explanation for the distribution of 4-methyl sterenes and A-nor sterenes in the lacustrine Messel shale (Eocene). (iii) An explanation for the presence of 4β-methyl steranes in relatively immature sedimentary rocks, despite the precursor stanols having the 4α-methyl configuration. With increasing maturity in the Paris Basin shales (Lower Toarcian), the less stable 4β-methyl steranes decrease gradually in abundance relative to their 4α-methyl counterparts, at a rate fairly similar to the change in pristane stereochemistry.

Relationship between the incidence infection stones and the magnesium-calcium ratio of tap water.

PubMed

Kohri, K; Ishikawa, Y; Iguchi, M; Kurita, T; Okada, Y; Yoshida, O

1993-01-01

In a previous study we showed that the magnesium-calcium ratio of tap water is negatively correlated with the incidence of calcium-containing urinary stones. In this study we examined the relationship between the incidence of struvite stones, water hardness and the regional geological features on the basis of our previous study and an epidemiological study of urolithiasis performed in Japan. The magnesium-calcium ratio of tap water was found to correlate positively with the incidence of struvite stones. The tap water magnesium-calcium ratio was high in regions of basalt and sedimentary rock and was low in granite and limestone areas. The incidence of struvite stones in the regions of basalt and sedimentary rock was higher than that in the granite and limestone areas. Thus, this study suggested that the incidence of struvite stones is related to the magnesium-calcium ratio of tap water and to the regional geology, as is the case for calcium-containing stones.

Vast geologic basins attract Indonesian oil exploration. Pt. 3

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

Soeparjadi, R.A.; Slocum, R.C.

1973-10-01

This concluding article of a 3-part series describes key geologic features that make Indonesia's S. and E. Kalimantan, Irian Jaya, and S. China Sea areas prime targets for continuing oil and gas exploration. Thick sedimentary basins in E. Kalimantan contain Indonesia'a largest offshore oilfield and other important developments. New reef discoveries in Irian Jaya highlight an extensive exploration effort. Continued drilling in the huge S. China Sea is assured by near commercial shows in recent wildcats. While many thousands of square miles still do not claim a significant discovery, proven successes such as Kalimantan's Attaka field (Indonesia's largest offshore producer)more » and Irian Jaya's new 23,600 bopd Kasim 3 well provide ample incentive for intensive oil searches. Near commercial recoveries of both gas and oil in Indonesia's huge S. China Sea and the recent testing of a 6,000 bopd oil well in nearby Malaysian waters spur interest in the area's W. Natuna and Miri-Seria sedimentary basins.« less

Sedimentary and Enhanced Geothermal Systems | Geothermal Technologies |

Science.gov Websites

NREL Sedimentary and Enhanced Geothermal Systems Sedimentary and Enhanced Geothermal Systems To innovative technologies, such as sedimentary and enhanced geothermal systems (EGS). Photo of a geothermal power plant in Imperial California. Capabilities To advance EGS and sedimentary geothermal systems, NREL

Crustal structure of the Alps as seen by attenuation tomography

NASA Astrophysics Data System (ADS)

Mayor, Jessie; Calvet, Marie; Margerin, Ludovic; Vanderhaeghe, Olivier; Traversa, Paola

2016-04-01

We develop a simple tomographic approach exploiting the decay rate of coda waves to map the absorption properties of the crust in a region delimited approximately by the Rhine Graben to the North, the Apennines to the South, the Massif Central to the West and the Dinarides to the East. Our dataset comprises 40 000 coda records of about 2000 weak to moderate crustal earthquakes, with magnitude ranging from 2.8 to 6 and recorded by broad-band, accelerometric and short-period stations. After proper choice of a coda window minimizing the effects of variable epicentral distances, we measure the coda quality factor Qc in five non-overlapping frequency windows covering the 1-32 Hz band for all available source station pairs. These measurements are subsequently converted into maps of absorption quality factor (Qi) using a linearized, approximate relation between Qc and Qi. In practice the following procedure is applied in each frequency band: (1) we divide the target region into 40 × 40 km cells; (2) for each source-station pair, we assign the measured Qc value to each pixel intercepted by the direct ray path; (3) the results are averaged over all paths and subsequently smoothed with a 3 × 3 pixels moving window. Our approach is consistent with the high sensitivity of Qc to the value of Qi between source and station. Our tomographic approach reveals strong lateral variations of absorption with length scales ranging from 100 km to 1000 km. At low frequency (∼ 1 Hz), the correlation with the surface geology is clear, Cenozoic and Mesozoic sedimentary basins (resp. crystalline massifs) being recognized as high (resp. low)-absorption regions. Furthermore the Qi map delineates finer geological features such as the Ivrea Body, the Rhône Valley, or felsic intrusions in the central Alps. At high-frequency (>16 Hz), only the thickest Cenozoic sedimentary deposits show up as high-attenuation regions and a north/south dichotomy is apparent in the absorption structure. The limit between low-attenuation regions to the North and high-attenuation region to the South correlates geographically with the location of the Periadriatic Lineament (PL), a major late-alpine crustal- to lithospheric-scale structure. Furthermore, the attenuation structure seems to prolong the PL to the West along a line marked by large historical earthquakes. The Apennines orogenic belts exhibit a distinct frequency behavior, with high attenuation at low-frequency and low-attenuation at high-frequency. Low-frequency absorption may likely be explained by the relatively thick cover of Cenozoic sedimentary materials, as well as by shallow geothermal activity. We hypothesize that the frequency dependence of the attenuation structure, in particular in the Apennines, is caused by a change of the wavefield composition which accentuates the sensitivity of the coda to the deeper parts of the medium as the frequency increases.

Geologic map of the Frisco quadrangle, Summit County, Colorado

USGS Publications Warehouse

Kellogg, Karl S.; Bartos, Paul J.; Williams, Cindy L.

2002-01-01

New 1:24,000-scale geologic mapping along the Interstate-70 urban corridor in western Colorado, in support of the USGS Central Region State/USGS Cooperative Geologic Mapping Project, is contributing to a more complete understanding of the stratigraphy, structure, tectonic evolution, and hazard potential of this rapidly developing region. The 1:24,000-scale Frisco quadrangle is near the headwaters of the Blue River and straddles features of the Blue River graben (Kellogg, K.S., 1999, Neogene basins of the northern Rio Grande rift?partitioning and asymmetry inherited from Laramide and older uplifts: Tectonophysics, v. 305, p. 141-152.), part of the northernmost reaches of the Rio Grande rift, a major late Oligocene to recent zone of extension that extends from Colorado to Mexico. The Williams Range thrust fault, the western structural margin of the Colorado Front Range, cuts the northeastern corner of the quadrangle. The oldest rocks in the quadrangle underlie the Tenmile Range and include biotite-sillimanite schist and gneiss, amphibolite, and migmatite that are intruded by granite inferred to be part of the 1,667-1,750 Ma Routt Plutonic Suite (Tweto, Ogden, 1987, Rock units of the Precambrian- basement in Colorado: U.S. Geological Survey Professional Paper 1321-A, 54 p.). The oldest sedimentary unit is the Pennsylvanian Maroon Formation, a sequence of red sandstone, conglomerate, and interbedded shale. The thickest sequence of sedimentary rocks is Cretaceous in age and includes at least 500 m of the Upper Cretaceous Pierre Shale. The sedimentary rocks are intruded by sills and dikes of dacite porphyry sills of Swan Mountain, dated at 44 Ma (Marvin, R.F., Mehnert, H.H., Naeser, C.W., and Zartman, R.E., 1989, U.S. Geological Survey radiometric ages, compilation ?C??Part five?Colorado, Montana, Utah, and Wyoming: Isochron/West, no. 53, p. 14-19. Simmons, E.C., and Hedge, C.E., 1978, Minor-element and Sr-isotope geochemistry of Tertiary stocks, Colorado mineral belt: Contributions to Mineralogy and Petrology, v. 67, p. 379-396.). Surficial deposits include (1) an old, deeply dissected landslide deposit, possibly as old as Tertiary, on the south flank of Tenderfoot Mountain, (2) deeply weathered, very coarse gravel deposits, mostly along Gold Run and underlying Mesa Cortina; the gravels are gold bearing and were mined by hydraulic methods in the 1800's, (3) glacial deposits of both Bull Lake (middle Pleistocene) and Pinedale (late Pleistocene) that were derived from large valley glaciers that flowed down Tenmile and North Tenmile Creeks; the town of Frisco is underlain mostly by Pinedale-age glacial outwash, (4) recent landslide deposits, including one large (about 1 square kilometer) area just downslope from Lilly Pad Lake, west of I-70, and (5)extensive colluvial and alluvial deposits. The latest seismic events appear to be middle Pliestocene in age and are associated with small scarps that cut Bull Lake till but do not cut Pinedale till.

Ecosystem disturbances in Central European spruce forests: a multi-proxy integration of dendroecology and sedimentary records

NASA Astrophysics Data System (ADS)

Clear, Jennifer; Chiverrell, Richard; Kunes, Petr; Svoboda, Miroslav; Boyle, John

2016-04-01

Disturbance dynamics in forest ecosystems shows signs of perturbation in the light of changing climate regimes with the frequency and intensity of events (e.g. pathogens in North America and Central Europe) amplified, becoming more frequent and severe. The montane Norway spruce (Picea abies) dominated forests of Central Europe are a niche habitat and environment; situated outside their natural boreal distribution (e.g. Fenno-Scandinavia). These communities are at or near their ecological limits and are vulnerable to both short term disturbances (e.g. fire, windstorm and pathogens) and longer-term environmental change (e.g. climate induced stress and changing disturbance patterns). Researches have linked negative impacts on spruce forest with both wind disturbance (wind-throw) and outbreaks of spruce bark beetle (Ips typographus), and there is growing evidence for co-association with wind damage enhancing pathogenic outbreaks. Examples include: in the Bohemian Forest (Czech Republic) the mid-1990s spruce bark beetle outbreak and the 2007 windstorm and subsequent bark beetle outbreak. In the High Tatra Mountains (Slovakia) there is a further co-association of forest disturbance with windstorms (2004 and 2014) and an ongoing bark beetle outbreak. The scale and severity of these recent outbreaks of spruce bark beetle are unprecedented in the historical forest records. Here, findings from ongoing research developing and integrating data from dendroecological, sedimentary palaeoecological and geochemical time series to develop a longer-term perspective on forest dynamics in these regions. Tree-ring series from plots or forest stands (>500) are used alongside lake (5) and forest hollow (3) sediments from the Czech and Slovak Republics to explore the local, regional and biogeographical scale of forest disturbances. Dendroecological data showing tree-ring gap recruitment and post-suppression growth release highlight frequent disturbance events focused on tree or forest stand spatial scales, but are patchy in terms of reoccurrence. However they highlight levels of disturbance in the late 19th Century. Sediment records from lakes and forest hollows record variable pollen influx (beetle host / non-host ratios) and a stratigraphy that includes mineral in-wash events. μXRF scanning of lakes in the region with varying catchments and catchment-to-lake area ratios show spikes in K, Zr, Ti concentrations reflecting frequent erosive episodes throughout the Holocene. Linking across the temporal scales inherent in dendroecological (0 to 250 years) and sedimentary (0 to 11,500 years) is enhancing our understanding of disturbance dynamics. The identified recent and ongoing forest disturbances coupled with well-evidenced events in the 19th century highlight the need for the longer sedimentary perspective to assess whether contemporary climate warming has and continues to stretch the resilience of these fragile ecosystems. Our data are informative to the ongoing land-management conflict between active forest management (harvesting valuable timber and salvage logging) and forest conservation agenda encouraging forest dynamics and disturbance recovery.

The Plumbing System Feeding the Lusi Eruption Revealed by Ambient Noise Tomography

NASA Astrophysics Data System (ADS)

Fallahi, Mohammad Javad; Obermann, Anne; Lupi, Matteo; Karyono, Karyono; Mazzini, Adriano

2017-10-01

Lusi is a sediment-hosted hydrothermal system featuring clastic-dominated geyser-like eruption behavior in East Java, Indonesia. We use 10 months of ambient seismic noise cross correlations from 30 temporary seismic stations to obtain a 3-D model of shear wave velocity anomalies beneath Lusi, the neighboring Arjuno-Welirang volcanic complex, and the Watukosek fault system connecting the two. Our work reveals a hydrothermal plume, rooted at a minimum 6 km depth that reaches the surface at the Lusi site. Furthermore, the inversion shows that this vertical anomaly is connected to the adjacent volcanic complex through a narrow ( 3 km wide) low velocity corridor slicing the survey area at a depth of 4-6 km. The NE-SW direction of this elongated zone matches the strike of the Watukosek fault system. Distinct magmatic chambers are also inferred below the active volcanoes. The large-scale tomography features an exceptional example of a subsurface connection between a volcanic complex and a solitary erupting hydrothermal system hosted in a hydrocarbon-rich back-arc sedimentary basin. These results are consistent with a scenario where deep-seated fluids (e.g., magmas and released hydrothermal fluids) flow along a region of enhanced transmissivity (i.e., the Watukosek fault system damage zone) from the volcanic arc toward the back arc basin where Lusi resides. The triggered metamorphic reactions occurring at depth in the organic-rich sediments generated significant overpressure and fluid upwelling that is today released at the spectacular Lusi eruption site.

High-performance coupled poro-hydro-mechanical models to resolve fluid escape pipes

NASA Astrophysics Data System (ADS)

Räss, Ludovic; Makhnenko, Roman; Podladchikov, Yury

2017-04-01

Field observations and laboratory experiments exhibit inelastic deformation features arising in many coupled settings relevant to geo-applications. These irreversible deformations and their specific patterns suggest a rather ductile or brittle mechanism, such as viscous creep or micro cracks, taking place on both geological (long) and human (short) timescales. In order to understand the underlying mechanisms responsible for these deformation features, there is a current need to accurately resolve the non-linearities inherent to strongly coupled physical processes. Among the large variety of modelling tools and softwares available nowadays in the community, very few are capable to efficiently solve coupled systems with high accuracy in both space and time and run efficiently on modern hardware. Here, we propose a robust framework to solve coupled multi-physics hydro-mechanical processes on very high spatial and temporal resolution in both two and three dimensions. Our software relies on the Finite-Difference Method and a pseudo-transient scheme is used to converge to the implicit solution of the system of poro-visco-elasto-plastic equations at each physical time step. The rheology including viscosity estimates for major reservoir rock types is inferred from novel lab experiments and confirms the ease of flow of sedimentary rocks. Our results propose a physical mechanism responsible for the generation of high permeability pathways in fluid saturated porous media and predict their propagation in rates observable on operational timescales. Finally, our software scales linearly on more than 5000 GPUs.

Restoration of original 3D sedimentary geometries in deformed basin fill supporting reservoir characterization

NASA Astrophysics Data System (ADS)

Back, S.

2009-04-01

A large progradational clastic system centred on Brunei Darussalam has been present on the NW Borneo margin since the early middle Miocene. This system has many sedimentary and structural similarities with major deltaic provinces such as the Niger and Nile. It differs from these systems by being affected in the hinterland by contemporaneous compressional tectonics. Uplift partially forced strong progradation of the clastic system, but also folded older deltaic units. Erosion and the exhumation of folded strata in the area of the Jerudong Anticline resulted in the exposure of large-scale prograding clinoforms and syn-sedimentary deltaic faults of middle Miocene age along a natural cross-section of several tens of kilometres in extent. Westward of the key outcrop sites on the Jerudong Anticline, the middle Miocene deltaic units are overlain by late Miocene, Pliocene and Quaternary clastics up to 3 kilometres thick. Both, the middle Miocene target units of this study as well as the late Miocene to recent overburden are recorded in the subsurface of the Belait Syncline on regional 2D seismic lines (total line length around 1400 km) and at 7 well locations. In this study, we integrate the available geophysical subsurface information with existing structural, sedimentological and geomorphological field data of the "classic" Jerudong Anticline exposures (e.g., Back et al. 2001, Morley et al. 2003, Back et al. 2005) into a static 3D surface-subsurface model that provides quantitative constraints on the structural and stratigraphic architecture of the Miocene Belait delta and the overlying units in three dimensions, supporting basin-scale as well as reservoir-scale analysis of the subsurface rock volume. Additionally, we use the static surface-subsurface model as input for a tectonic retro-deformation of the study area, in which the 3D paleo-relief of the middle Miocene Belait delta is restored by unfolding and fault balancing (Back et al. 2008). This kinematic reconstruction ultimately provides a detailed view into the stratal architecture of middle Miocene delta clinoforms, indicating a close relationship between delta-lobe activity, clinoform morphology, and the generation of slumps and turbidites. Literature BACK, S., MORLEY, C.K., SIMMONS, M.D. & LAMBIASE, J.J. (2001): Depositional environment and sequence stratigraphy of Miocene deltaic cycles exposed along the Jerudong anticline, Brunei Darussalam. - Journal of Sedimentary Research, 71: 915-923. BACK, S., TIOE HAK JING, TRAN XUAN THANG & MORLEY, C.K. (2005): Stratigraphic development of synkinematic deposits in a large growth-fault system, onshore Brunei Darussalam. - Journal of the Geological Society, London, 162: 243-258. BACK, S., STROZYK, F., KUKLA, P.A. & LAMBIASE, J.J. (2008): 3D restoration of original sedimentary geometries in deformed basin fill, onshore Brunei Darussalam, NW Borneo. Basin Research, 20: 99-117. MORLEY, C.K., BACK, S., VANRENSBERGEN, P., CREVELLO, P. & LAMBIASE, J.J. (2003): Characteristics of repeated, detached, Miocene -Pliocene tectonic inversion events, in a large delta province on an active margin, Brunei Darussalam, Borneo. - Journal of Structural Geology, 25: 1147-1169.

Techniques of remote sensing applied to the environmental analysis of part of an aquifer located in the São José dos Campos Region sp, Brazil.

PubMed

Bressan, Mariana Affonseca; Dos Anjos, Célio Eustáquio

2003-05-01

The anthropogenic activity on the surface can modify and introduce new mechanisms of recharging the groundwater system, modifying the tax, the frequency and the quality of recharge of underground waters. The understanding of these mechanisms and the correct evaluation of such modifications are fundamental in determining the vulnerability of groundwater contamination. The groundwater flow of the South Paraíba Compartment, in the region of São José dos Campos, São Paulo, is directly related to structural features of the Taubaté Basin and, therefore, the analysis of its behaviour enhances the understanding of tectonic structure. The methodology adopted for this work consists in pre-processing and processing of the satellite images, visual interpretation of HSI products, field work and data integration. The derivation of the main structural features was based on visual analysis of the texture elements of drainage, and the relief in sedimentary and crystalline rocks. Statistical analysis of the feature densities and the metric-geometric relations between the analysed elements have been conducted. The crystalline rocks, on which the sediments were laying, conditions and controls the structural arrangement of sedimentary formations. The formation of the South Paraíba Grabén is associated with Cenozoic distensive movement which reactivated old features of crust weakness and generated previous cycles with normal characteristics. The environmental analysis is based on the integration of the existing methodology to characterise vulnerability of an universal pollutant and density fracture zone. The digital integration was processed using GIS (Geographic Information System) to delineate five defined vulnerability classes. The hydrogeological settings were analysed in each thematic map and, using fuzzy logic, an index for each different vulnerability class was compiled. Evidence maps could be combined in a series of steps using map algebra.

Sorted bed forms as self-organized patterns: 2. complex forcing scenarios

USGS Publications Warehouse

Coco, Giovanni; Murray, A. Brad; Green, Malcom O.; Thieler, E. Robert; Hume, T.M.

2007-01-01

We employ a numerical model to study the development of sorted bed forms under a variety of hydrodynamic and sedimentary conditions. Results indicate that increased variability in wave height decreases the growth rate of the features and can potentially give rise to complicated, a priori unpredictable, behavior. This happens because the system responds to a change in wave characteristics by attempting to self-organize into a patterned seabed of different geometry and spacing. The new wavelength might not have enough time to emerge before a new change in wave characteristics occurs, leading to less regular seabed configurations. The new seabed configuration is also highly dependent on the preexisting morphology, which further limits the possibility of predicting future behavior. For the same reasons, variability in the mean current magnitude and direction slows down the growth of features and causes patterns to develop that differ from classical sorted bed forms. Spatial variability in grain size distribution and different types of net sediment aggradation/degradation can also result in the development of sorted bed forms characterized by a less regular shape. Numerical simulations qualitatively agree with observed geometry (spacing and height) of sorted bed forms. Also in agreement with observations is that at shallower depths, sorted bed forms are more likely to be affected by changes in the forcing conditions, which might also explain why, in shallow waters, sorted bed forms are described as ephemeral features. Finally, simulations indicate that the different sorted bed form shapes and patterns observed in the field might not necessarily be related to diverse physical mechanisms. Instead, variations in sorted bed form characteristics may result from variations in local hydrodynamic and/or sedimentary conditions.

Rind-Like Features at a Meridiani Outcrop

NASA Technical Reports Server (NTRS)

2005-01-01

After months spent roving across a sea of rippled sands, Opportunity reached an outcrop in August 2005 and began investigating exposures of sedimentary rocks, intriguing rind-like features that appear to cap the rocks, and cobbles that dot the martian surface locally. Opportunity spent several sols analyzing a feature called 'Lemon Rind,' a thin surface layer covering portions of outcrop rocks poking through the sand north of 'Erebus Crater.' In images from the panoramic camera, Lemon Rind appears slightly different in color than surrounding rocks. It also appears to be slightly more resistant to wind erosion than the outcrop's interior. To obtain information on how this surface layer (or weathering rind) may have formed and how it compares to previously analyzed outcrops, Opportunity is using the microscopic imager, alpha particle X-ray spectrometer and Moessbauer spectrometer to analyze surfaces that have been brushed and ground with the rock abrasion tool. Scientists will compare these measurements with similar measurements made on the underlying rock material.

This is a false-color composite generated by draping enhanced red-green-blue color from the panoramic camera's 753-nanometer, 535-nanometer and 482-nanometer filters over a high-fidelity violet, 432-nanometer-filter image. The image was acquired on martian day, or sol 552 (Aug. 13, 2005) around 11:55 a.m. local true solar time. In this representation, bright sulfur-bearing sedimentary rocks appear light tan to brown, depending on their degree of dust contamination, and small dark 'blueberries' and other much less dusty rock fragments appear as different shades of blue. Draping the color derived from the blue to near-infrared filters over the violet filter image results in a false color view with the sharpest color and morphology contrasts.

Discriminating between natural and anthropogenic features of the sedimentary record in the coastal Beaufort Sea

NASA Astrophysics Data System (ADS)

Trefry, J. H.; Trocine, R. P.; Fox, A. L.; Fox, S. L.; Durell, G.; Kasper, J.

2016-02-01

The coastal Beaufort Sea is at a crossroads with respect to the impacts of human activities. Accurate discrimination of regional and global anthropogenic impacts, versus those due to natural physical and biogeochemical processes, is an important tool for managing environmental issues in the Arctic. We have investigated several natural and anthropogenic features in age-dated sediment cores from the coastal Beaufort Sea. For example, Hg enrichment (by 20 to >50% or +20 to 40 ng/g) was identified in some surface sediments using Hg/Al ratios in cores from nearshore, outer shelf and slope environments. Nearshore Hg anomalies, although quite limited in number, have been linked to drilling fluids deposited during oil and gas exploration in the 1980s. In contrast, similar offshore Hg anomalies are likely due to natural sediment diagenesis as previously noted by others in the deeper Arctic Ocean. We also found Ba enrichment in surface sediments that can be best explained by the deposition of natural, Ba-rich suspended particles from the Colville River; yet, Ba enrichment can sometimes be explained by the presence of drilling fluids in sediments near historic drilling sites. Human induced diagenetic changes are likely to follow current increases in river runoff and coastal erosion. Higher deposition rates for sediment and organic carbon in the coastal Beaufort Sea may create future anomalies for As, Cd and other metals. For example, metal anomalies can presently be found in older subsurface sediments where a layer of carbon-rich sediment was previously deposited. Correct identification of natural versus anthropogenic forcing factors that lead to distinct diagenetic features in the sedimentary record will help us to identify problem areas and make informed regulatory decisions.

Geologic Stratigraphy, Delta Morphology, and Regional History of Hypanis Delta, Mars

NASA Astrophysics Data System (ADS)

Adler, J.; Bell, J. F., III; Warner, N. H.; Fawdon, P.; Gupta, S.; Sefton-Nash, E.; Grindrod, P. M.; Davis, J.

2016-12-01

Hypanis is a large Noachian aged fan-shaped deposit that has been interpreted by many as being a delta in Xanthe Terra along the dichotomy boundary. The position of the putative delta at the edge of an open basin and its preserved morphology including potential access to bottomset beds had made Hypanis a compelling candidate future landing site for Mars 2020 and ExoMars. Its topographic location, without a clear local closed basin, may even imply a large northern sea. We further previous studies of Hypanis delta by 1) analyzing the stratigraphy of floor plains materials surrounding ancient deltaic deposits 2) conducting a survey of sedimentary bed strike and dip distribution, and 3) presenting a regional history model that includes a diversity of volcanic, sedimentary, tectonic, and impact processes identified. Hypanis delta has previously been dated at 3.8 Ga based on crater counts in the Hypanis Valles catchment and previous fluvial system analysis estimates 150 km3 of sediment deposited. We utilize 17 HiRISE and 8 CTX DTMs to measure fluvial and stratigraphic quantities, a CTX 5 m/pixel mosaic basemap (USGS), and THEMIS day/night IR images. We determine map unit stratigraphy (relative ages) from superposition and cross cutting relationships supported in our 3D models. We discuss periods of subaqueous sedimentation, fluvial migration, volcanic resurfacing, and multiple periods of erosion throughout the study region to explain the observed morphologies and inferred geologic timeline. Additional work focuses on newly discovered tectonic features prevalent in the low-lying plains unit. These 2 m wide linear features suggest orthogonal jointing and relatively recent faulting. We assess whether these features could be related to the cooling of Hesperian lava plains or isostatic uplift from a removed glacier or eroded landmass.

A Comparison of Resistivity Imaging Techniques Using 1D, 2D and 3D MT Inversions in the Middle Rio Grande Rift, NM

NASA Astrophysics Data System (ADS)

Folsom, M.; Pepin, J.; Person, M. A.; Kelley, S.; Peacock, J.

2016-12-01

Twelve magnetotelluric (MT) soundings were collected along a 40 km profile crossing the Rio Grande rift and a portion of the Socorro Magma Body (SMB). A comparison of 1D, 2D and 3D inverse models highlight the strengths and weaknesses of the respective methods. 2D inversion results are distorted by the 3D nature of the data at longer periods, producing conductive artifacts at depths greater than 3 km. We demonstrate through a 3D forward modelling exercise how it is possible to recreate this effect by placing large resistive and conductive features off of an otherwise perfectly 2D resistivity model. Investigators that image deep conductors using 2D inversion codes should consider the influence of off-axis 3D features. Interpretation of the models currently show no indication of the SMB, but outlines the geometry of syn-rift and pre-rift sediments at the "Socorro Constriction", the southern terminus of the Albuquerque Basin. A strong, northward trending conductor 2-3 km deep and less than 2 ohm-m is coincident with the rift, creating a reversal of induction arrow direction at this point. This is interpreted as deep basin brines, perhaps influenced by evaporates hosted in the Permian Abo and Yeso formations. It has been noted that Rio Grande salinity increases in a stepwise manner, coincident with the terminal ends of sedimentary basins. Our geophysical models suggest a possible connection between rift-bounding faults and deep sedimentary brines, which likely impact the water quality of the Rio Grande. Future work includes adding additional MT stations to better constrain off-axis features and their relationship to the Rio Grande.

AMT measurements compared with gravimetry and magnetometry for structural study of a sedimentary basin: Letlhakeng-Botlhapatlou groundwater project, Botswana

NASA Astrophysics Data System (ADS)

Bourgeois, B.; Mathieu, F.; Vachette, C.; Vaubourg, P.

1994-02-01

Within the framework of hydrogeological studies for additional water supply to the main towns of Botswana, the BRGM company has carried out a multimethod geophysical survey of a large sedimentary basin in the Kalahari desert, for the purpose of assessing its water resources. On a regional scale, gravimetry, magnetometry and audio-magnetotellurics (AMT) were used to determine the structure of the basin, which is intensely faulted into horsts and grabens. Next, a number of favourable areas were selected for detailed profiling with horizontal portable loop EM (HLEM) and DC electrical arrays to locate accurately the fractured zones at the edges of grabens, the targets for exploratory drillholes. The AMT method proved to be the most effective for mapping the basement of the basin, thanks to the good resistivity contrast between the resistive basement and its conductive cover, and to the regional constancy of sedimentary organisation of the cover. The presence of the uniformly resistive Kalahari Sands at the top of the cover was also very favourable, protecting AMT data from troublesome "static" effects. These good conditions enabled a fast and innovative quantitative interpretation of AMT soundings, determined by borehole calibration and based on the reading of the apparent resistivity at a single frequency (10 Hz).

Measurement of Sedimentary Interbed Hydraulic Properties and Their Hydrologic Influence near the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory

USGS Publications Warehouse

Perkins, Kim S.

2003-01-01

Disposal of wastewater to unlined infiltration ponds near the Idaho Nuclear Technology and Engineering Center (INTEC), formerly known as the Idaho Chemical Processing Plant, at the Idaho National Engineering and Environmental Laboratory (INEEL) has resulted in the formation of perched water bodies in the unsaturated zone (Cecil and others, 1991). The unsaturated zone at INEEL comprises numerous basalt flows interbedded with thinner layers of coarse- to fine-grained sediments and perched ground-water zones exist at various depths associated with massive basalts, basalt-flow contacts, sedimentary interbeds, and sediment-basalt contacts. Perched ground water is believed to result from large infiltration events such as seasonal flow in the Big Lost River and wastewater discharge to infiltration ponds. Evidence from a large-scale tracer experiment conducted in 1999 near the Radioactive Waste Management Complex (RWMC), approximately 13 km from the INTEC, indicates that rapid lateral flow of perched water in the unsaturated zone may be an important factor in contaminant transport at the INEEL (Nimmo and others, 2002b). Because sedimentary interbeds, and possibly baked-zone alterations at sediment-basalt contacts (Cecil and other, 1991) play an important role in the generation of perched water it is important to assess the hydraulic properties of these units.

Sedimentology and palaeontology of upper Karoo aeolian strata (Early Jurassic) in the Tuli Basin, South Africa

NASA Astrophysics Data System (ADS)

Bordy, Emese M.; Catuneanu, Octavian

2002-08-01

The Karoo Supergroup in the Tuli Basin (South Africa) consists of a sedimentary sequence composed of four stratigraphic units, namely the Basal, Middle and Upper units, and Clarens Formation. The units were deposited in continental settings from approximately Late Carboniferous to Middle Jurassic. This paper focuses on the Clarens Formation, which was examined in terms of sedimentary facies and palaeo-environments based on evidence provided by primary sedimentary structures, palaeo-flow measurements and palaeontological findings. Two main facies associations have been identified: (i) massive and large-scale planar cross-bedded sandstones of aeolian origin; and (ii) horizontally and cross-stratified sandstones of fluvial origin. Most of the sandstone lithofacies of the Clarens Formation were generated as transverse aeolian dunes produced by northwesterly winds in a relatively wet erg milieu. Direct evidence of aquatic subenvironments comes from local small ephemeral stream deposits, whereas palaeontological data provide indirect evidence. Fossils of the Clarens Formation include petrified logs of Agathoxylon sp. wood type and several trace fossils which were produced by insects and vertebrates. The upper part of the Clarens Formation lacks both direct and indirect evidence of aquatic conditions, and this suggests aridification that led to the dominance of dry sand sea conditions.

Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Plain Aquifer Sediments at the Idaho National Laboratory, Idaho

USGS Publications Warehouse

Perkins, Kim S.

2008-01-01

Sediments are believed to comprise as much as 50 percent of the Snake River Plain aquifer thickness in some locations within the Idaho National Laboratory. However, the hydraulic properties of these deep sediments have not been well characterized and they are not represented explicitly in the current conceptual model of subregional scale ground-water flow. The purpose of this study is to evaluate the nature of the sedimentary material within the aquifer and to test the applicability of a site-specific property-transfer model developed for the sedimentary interbeds of the unsaturated zone. Saturated hydraulic conductivity (Ksat) was measured for 10 core samples from sedimentary interbeds within the Snake River Plain aquifer and also estimated using the property-transfer model. The property-transfer model for predicting Ksat was previously developed using a multiple linear-regression technique with bulk physical-property measurements (bulk density [pbulk], the median particle diameter, and the uniformity coefficient) as the explanatory variables. The model systematically underestimates Ksat,typically by about a factor of 10, which likely is due to higher bulk-density values for the aquifer samples compared to the samples from the unsaturated zone upon which the model was developed. Linear relations between the logarithm of Ksat and pbulk also were explored for comparison.

Linking microbial assemblages to paleoenvironmental conditions from the Holocene and Last Glacial Maximum times in Laguna Potrok Aike sediments, Argentina

NASA Astrophysics Data System (ADS)

Vuillemin, Aurele; Ariztegui, Daniel; Leavitt, Peter R.; Bunting, Lynda

2014-05-01

Laguna Potrok Aike is a closed basin located in the southern hemisphere's mid-latitudes (52°S) where paleoenvironmental conditions were recorded as temporal sedimentary sequences resulting from variations in the regional hydrological regime and geology of the catchment. The interpretation of the limnogeological multiproxy record developed during the ICDP-PASADO project allowed the identification of contrasting time windows associated with the fluctuations of Southern Westerly Winds. In the framework of this project, a 100-m-long core was also dedicated to a detailed geomicrobiological study which aimed at a thorough investigation of the lacustrine subsurface biosphere. Indeed, aquatic sediments do not only record past climatic conditions, but also provide a wide range of ecological niches for microbes. In this context, the influence of environmental features upon microbial development and survival remained still unexplored for the deep lacustrine realm. Therefore, we investigated living microbes throughout the sedimentary sequence using in situ ATP assays and DAPI cell count. These results, compiled with pore water analysis, SEM microscopy of authigenic concretions and methane and fatty acid biogeochemistry, provided evidence for a sustained microbial activity in deep sediments and pinpointed the substantial role of microbial processes in modifying initial organic and mineral fractions. Finally, because the genetic material associated with microorganisms can be preserved in sediments over millennia, we extracted environmental DNA from Laguna Potrok Aike sediments and established 16S rRNA bacterial and archaeal clone libraries to better define the use of DNA-based techniques in reconstructing past environments. We focused on two sedimentary horizons both displaying in situ microbial activity, respectively corresponding to the Holocene and Last Glacial Maximum periods. Sequences recovered from the productive Holocene record revealed a microbial community adapted to subsaline conditions producing methane with a high potential of organic matter degradation. In contrast, sediments rich in volcanic detritus from the Last Glacial Maximum showed a substantial presence of lithotrophic microorganisms and sulphate-reducing bacteria mediating authigenic minerals. Together, these features suggested that microbial communities developed in response to climatic control of lake and catchment productivity at the time of sediment deposition. Prevailing climatic conditions exerted a hierarchical control on the microbial composition of lake sediments by regulating the influx of organic and inorganic material to the lake basin, which in turn determined water column chemistry, production and sedimentation of particulate material, resulting in the different niches sheltering these microbial assemblages. Moreover, it demonstrated that environmental DNA can constitute sedimentary archives of phylogenetic diversity and diagenetic processes over tens of millennia.

Sedimentary noise and sea levels linked to land-ocean water exchange and obliquity forcing.

PubMed

Li, Mingsong; Hinnov, Linda A; Huang, Chunju; Ogg, James G

2018-03-08

In ancient hothouses lacking ice sheets, the origins of large, million-year (myr)-scale sea-level oscillations remain a mystery, challenging current models of sea-level change. To address this mystery, we develop a sedimentary noise model for sea-level changes that simultaneously estimates geologic time and sea level from astronomically forced marginal marine stratigraphy. The noise model involves two complementary approaches: dynamic noise after orbital tuning (DYNOT) and lag-1 autocorrelation coefficient (ρ 1 ). Noise modeling of Lower Triassic marine slope stratigraphy in South China reveal evidence for global sea-level variations in the Early Triassic hothouse that are anti-phased with continental water storage variations in the Germanic Basin. This supports the hypothesis that long-period (1-2 myr) astronomically forced water mass exchange between land and ocean reservoirs is a missing link for reconciling geological records and models for sea-level change during non-glacial periods.

The Geomechanics of CO 2 Storage in Deep Sedimentary Formations

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

Rutqvist, Jonny

2012-01-12

This study provides a review of the geomechanics and modeling of geomechanics associated with geologic carbon storage (GCS), focusing on storage in deep sedimentary formations, in particular saline aquifers. The paper first introduces the concept of storage in deep sedimentary formations, the geomechanical processes and issues related with such an operation, and the relevant geomechanical modeling tools. This is followed by a more detailed review of geomechanical aspects, including reservoir stress-strain and microseismicity, well integrity, caprock sealing performance, and the potential for fault reactivation and notable (felt) seismic events. Geomechanical observations at current GCS field deployments, mainly at the Inmore » Salah CO 2 storage project in Algeria, are also integrated into the review. The In Salah project, with its injection into a relatively thin, low-permeability sandstone is an excellent analogue to the saline aquifers that might be used for large scale GCS in parts of Northwest Europe, the U.S. Midwest, and China. Some of the lessons learned at In Salah related to geomechanics are discussed, including how monitoring of geomechanical responses is used for detecting subsurface geomechanical changes and tracking fluid movements, and how such monitoring and geomechanical analyses have led to preventative changes in the injection parameters. Recently, the importance of geomechanics has become more widely recognized among GCS stakeholders, especially with respect to the potential for triggering notable (felt) seismic events and how such events could impact the long-term integrity of a CO 2 repository (as well as how it could impact the public perception of GCS). As described in the paper, to date, no notable seismic event has been reported from any of the current CO 2 storage projects, although some unfelt microseismic activities have been detected by geophones. However, potential future commercial GCS operations from large power plants will require injection at a much larger scale. In conclusion, for such large-scale injections, a staged, learn-as-you-go approach is recommended, involving a gradual increase of injection rates combined with continuous monitoring of geomechanical changes, as well as siting beneath a multiple layered overburden for multiple flow barrier protection, should an unexpected deep fault reactivation occur.« less

Imaging the Moho beneath Sedimentary Basins: A Comparative Study of Virtual Deep Seismic Sounding (VDSS) and P Wave Receiver Functions (PRF)

NASA Astrophysics Data System (ADS)

Liu, T.; Klemperer, S. L.; Yu, C.; Ning, J.

2017-12-01

In the past decades, P wave receiver functions (PRF) have been routinely used to image the Moho, although it is well known that PRFs are susceptible to contamination from sedimentary multiples. Recently, Virtual Deep Seismic Sounding (VDSS) emerged as a novel method to image the Moho. However, despite successful applications of VDSS on multiple datasets from different areas, how sedimentary basins affect the waveforms of post-critical SsPmp, the Moho reflection phase used in VDSS, is not widely understood. Here, motivated by a dataset collected in the Ordos plateau, which shows distinct effects of sedimentary basins on SsPmp and Pms waveforms, we use synthetic seismograms to study the effects of sedimentary basins on SsPmp and Pms, the phases used in VDSS and PRF respectively. The results show that when the sedimentary thickness is on the same order of magnitude as the dominant wavelength of the incident S wave, SsPmp amplitude decreases significantly with S velocity of the sedimentary layer, whereas increasing sedimentary thickness has little effect in SsPmp amplitude. Our explanation is that the low S velocity layer at the virtual source reduces the incident angle of S wave at the free surface, thus decreases the S-to-P reflection coefficient at the virtual source. In addition, transmission loss associated with the bottom of sedimentary basins also contributes to reducing SsPmp amplitude. This explains not only our observations from the Ordos plateau, but also observations from other areas where post-critical SsPmp is expected to be observable, but instead is too weak to be identified. As for Pms, we observe that increasing sedimentary thickness and decreasing sedimentary velocities both can cause interference between sedimentary multiples and Pms, rendering the Moho depths inferred from Pms arrival times unreliable. The reason is that although Pms amplitude does not vary with sedimentary thickness or velocities, as sedimentary velocities decrease and thickness grows, the sedimentary multiples will become stronger and arrive later, and will eventually interfere with Pms. In summary, although both VDSS and PRF are subject to sedimentary effects, when the sedimentary velocity is relatively high, we can still expect VDSS to give reasonable estimations of Moho depths, whereas PRF in such cases might be too noisy to use.

High-resolution characterization of chemical heterogeneity in an alluvial aquifer

USGS Publications Warehouse

Schulmeister, M.K.; Healey, J.M.; Butler, J.J.; McCall, G.W.; Birk, S.

2002-01-01

The high-resolution capabilities of direct push technology were exploited to develop new insights into the hydrochemistry at the margin of an alluvial aquifer. Hydrostratigraphic controls on groundwater flow and contaminant loading were revealed through the combined use of direct push electrical conductivity (EC) logging and geochemical profiling. Vertical and lateral variations in groundwater chemistry were consistent with sedimentary features indicated by EC logs, and were supported by a conceptual model of recharge along the flood plain margin.

Geological and hydrogeological investigation in West Malaysia

NASA Technical Reports Server (NTRS)

Ahmad, J. B. (Principal Investigator)

1976-01-01

The author has identified the following significant results. The broad synoptic view of the images allowed easy identification of circular features and major fault traces in low lying areas. Sedimentary units were delineated in accordance with the prevailing rock types and where applicable the folding characteristics. Igneous units could easily be differentiated by tone, degree of fracturing, texture, and drainage pattern. The larger fold structures, anticlinoriums and synclinoriums, of the younger sediments on the eastern edge of the central belt could also be easily delineated.

The group of Macha craters in western Yakutia

NASA Astrophysics Data System (ADS)

Gurov, E. P.; Gurova, E. P.

1998-02-01

The group of Macha impact craters in western Yakutia is represented by five crateriform structures from 60 to 300 m in diameter. The craters were formed in sandy strata of the Quaternary period and in underlying sedimentary rocks of Late Proterozoic ages. Shock metamorphic effects including planar features in quartz were established in the rocks from the craters. The age of the craters is 7315 ± 80 yr. The nature of the projectiles is not totally clear, although they might be iron meteoritic.

Features in Aureum Chaos

NASA Technical Reports Server (NTRS)

2004-01-01

12 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, sedimentary rock outcrops in the Aureum Chaos region of Mars. On the brightest and steepest slope in this scene, dry talus shed from the outcrop has formed a series of dark fans along its base. These outcrops are located near 3.4oS, 27.5oW. The image covers an area approximately 3 km (1.9 mi) across and sunlight illuminates the scene from the upper left.

Windblown Sand in Ganges Chasma

NASA Image and Video Library

2017-04-25

Dark, windblown sand covers intricate sedimentary rock layers in this image captured by NASA's Mars Reconnaissance Orbiter (MRO) from Ganges Chasma, a canyon in the Valles Marineris system. These features are at once familiar and unusual to those familiar with Earth's beaches and deserts. Most sand dunes on Earth are made of silica-rich sand, giving them a light color; these Martian dunes owe their dark color to the iron and magnesium-rich sand found in the region. https://photojournal.jpl.nasa.gov/catalog/PIA21600

Earth Observations taken by the Expedition 15 Crew

NASA Image and Video Library

2007-06-26

ISS015-E-14584 (26 June 2007) --- The "bull's-eye" of the Richat Structure in the barren Gres de Chinguetti Plateau, central Mauritania in northwest Africa is featured in this image photographed by an Expedition 15 crewmember on the International Space Station. It represents domally uplifted, layered (sedimentary) rocks that have been eroded by water and wind into the present shape. The 25-mile-wide structure is a 300-foot-deep landmark that has caught the eye of many an astronaut in Earth orbit.

Geology of Badlands National Park: a preliminary report

USGS Publications Warehouse

Stoffer, Philip W.

2003-01-01

Badlands National Park is host to perhaps the most scenic geology and landscape features in the Western Interior region of the United States. Ongoing erosion that forms the "badlands" exposes ancient sedimentary strata of Late Cretaceous through Oligocene age. Quaternary erosional and depositional processes are responsible for most of the modern landscape features in the park and surrounding region. This report provides a basic overview of the park geology The discussions presented within include both well-established concepts and theories and new, preliminary data and interpretations. Much emphasis is placed on presenting information about the oldest and least studied rocks in the park (particularly the Late Cretaceous and earliest Tertiary deposits that underlie the White River beds throughout the park region). Rock formations and selected fossils they contain are described. Faults, folds, unconformities, and other geologic structures in the North Unit of the park are illustrated, including features associated with the Sage Creek anticline and fault system.

An evaluation of the suitability of ERTS data for the purposes of petroleum exploration

NASA Technical Reports Server (NTRS)

Collins, R. J., Jr. (Principal Investigator); Mccown, F. P.; Stonis, L. P.; Petzel, G.

1973-01-01

The author has identified the following significant results. ERTS-1 imagery seems to be good to excellent for reconnaissance level investigations of large sedimentary basins such as the Anadarko Basin. Many lithologic boundaries, and geomorphic features, and linear features inferred to be indicative of geologic structure are visible in the imagery. This imagery in conjunction with high altitude photography seems to be useful as a tool for intermediate level geologic exploration. Several types of crudely circular anomalous features, such as geomorphic/structural anomalies, hazy areas and tonal anomalies, are identifiable in the imagery. There seems to be a strong correlation between the geomorphic/structural and hazy anomalies and known structurally controlled oil and gas fields. The features recognizable on ERTS-1 imagery and their ease of recognition vary from area to area even in imagery acquired at the same time under essentially uniform atmospheric conditions. Repeated coverage is exceedingly valuable in geologic applications. One time complete coverage even for the various seasons does not reveal all the features that ERTS-1 can reveal.

Preliminary results from an investigation of AIS-1 data over an area of epithermal alteration: Plateau, Northern Queensland, Australia

NASA Technical Reports Server (NTRS)

Mackin, Steve; Munday, Tim; Hook, Simon

1987-01-01

Airborne Imaging Spectrometer-1 (AIS-1) data were flown over undifferentiated sequences of acid to intermediate volcanics and intrusives; meta-sediments; and a series of partially lateritized sedimentary rocks. The area exhibits a considerable spectral variability, after the suppression of striping effects. Log residual, and Internal Average Relative Reflectance (IARR) analytical techniques were used to enhance mineralogically related spectral features. Both methods produce similar results, but did not visually highlight mineral absorption features due to processing artifacts in areas of significant vegetation cover. The enhancement of mineral related absorption features was achieved using a hybrid processing approach based on the relative reflectance differences between vegetated and non-vegetated surfaces at 1.2 and 2.1 micron. The result is an image with little overall contrast, but which enhances the more subtle spectral features believed to be associated with clays and epidote. The AIS data was subject to interactive analysis using SPAM. Clear separation of clay and epidote related absorption features was apparent, and the identification of kaolinite was possible despite detrimental spectral effects.

Nd Isotopic Provenance of Sedimentary Rocks Along Margins of North America: ten Years of Study

NASA Astrophysics Data System (ADS)

Patchett, J.; Ross, G. M.

2001-12-01

Ten years of effort, principally employing Nd isotopes, have resulted in substantial advances in understanding of the movements of sedimentary material around North America from Cambrian to Cretaceous time. This synthesis has depended upon work of current and former students S. Samson, J. Gleason, N. Boghossian, C. Garzione, M. Roth, B. Canale and E. Rosenberg, as well as collaborators W. Dickinson and A. Embry, among others. Nd isotopes are particularly good at documenting movements of sedimentary material on the largest (continental) scale and over extended times. What has emerged is a picture of a largely exposed North America-Greenland craton from Neoproterozoic to Ordovician time, a partial to complete burial by detritus from Caledonian-Appalachian mountains starting in the Ordovician, a gradual exhumation during Late Paleozoic and Mesozoic time, followed by a partial burial with Cordilleran detritus during Late Jurassic to Tertiary time. One current question is the nature of the Mesozoic and Tertiary sedimentary material eroded from the North American Cordillera, and its relevance for Cordilleran orogenesis. Another current question is the extent to which Caledonian-Appalachian detritus covered the craton in Devonian-Carboniferous time, and the timing and manner of its removal during Mesozoic time. At first glance, available Nd isotopic data appear to suggest that the Canada-Greenland Shield was largely covered during most of Mesozoic time, a conclusion that would have profound effects on models of dynamic topography. However, this conclusion is also very dependent on the relationship between topography and erosion, because in certain situations a geographically-restricted cover sequence could dominate over low-relief cratonic terrain as a sediment source.

a New Approach for Sediment Balance Quantification and Wind Erosion Monitoring

NASA Astrophysics Data System (ADS)

Ouerchefani, Dalel; Callot, Yann; Delaitre, Eric; Abdeljaouad, Saadi

2014-05-01

Studies on spatio-temporal heterogeneity of land surface in arid and semi-arid regions in relation to wind erosion are very few. These are ad hoc and instantaneous measurements of physical parameters, taking little account of aeolian landforms as markers of a changing environment. This is a handicap in the analysis of these spaces, in particular their sedimentary dynamic. Design methods for understanding the specific organization of aeolian landforms and their spatio-temporal monitoring is therefore essential. This allows quantifying the annual and seasonal sedimentary budgets of bad-instrumented sites which have not automatic recordings of meteorological variables In this work, we propose a method for multi-temporal quantification of sediment balance across a transect. This method were applied and validated in the Oglet Merteba study site. It has the advantage of linking the amount of sand deposited / eroded with changing surface conditions. It is to delineate and compare apparently accumulation and deflation areas with those having real positive and negative sedimentary budget. To do this, linear analysis techniques 'point quadrat' and 'profile leveling' were applied to a 500 m length transect. Measurements of variables related to aeolian landforms, soil and vegetation characteristics were undertaken during 2 years. The results show that the overall balance of Oglet Merteba is positive but with important seasonal fluctuations. Accumulation areas may actually be deflation zones, despite the presence of indicators showing the contrary. Conversely areas mapped as deflation zones can correspond really to zones of accumulation. This work is a contribution for the quantification of sedimentary budgets at the site level. It allows, when integrated in an Observatory approach, to harmonize the methods of data collection/analysis to regularly produce a synthesis of the situation of the local environment in a format that enables comparisons to that space as well time scales.

Alteration of immature sedimentary rocks on Earth and Mars. Recording Aqueous and Surface-atmosphere Processes

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

Cannon, Kenneth M.; Mustard, John F.; Salvatore, Mark R.

The rock alteration and rind formation in analog environments like Antarctica may provide clues to rock alteration and therefore paleoclimates on Mars. Clastic sedimentary rocks derived from basaltic sources have been studied in situ by martian rovers and are likely abundant on the surface of Mars. Moreover, how such rock types undergo alteration when exposed to different environmental conditions is poorly understood compared with alteration of intact basaltic flows. Here we characterize alteration in the chemically immature Carapace Sandstone from Antarctica, a terrestrial analog for martian sedimentary rocks. We employ a variety of measurements similar to those used on previousmore » and current Mars missions. Laboratory techniques included bulk chemistry, powder X-ray diffraction (XRD), hyperspectral imaging and X-ray absorption spectroscopy. Through these methods we find that primary basaltic material in the Carapace Sandstone is pervasively altered to hydrated clay minerals and palagonite as a result of water–rock interaction. A thick orange rind is forming in current Antarctic conditions, superimposing this previous aqueous alteration signature. The rind exhibits a higher reflectance at visible-near infrared wavelengths than the rock interior, with an enhanced ferric absorption edge likely due to an increase in Fe 3+ of existing phases or the formation of minor iron (oxy)hydroxides. This alteration sequence in the Carapace Sandstone results from decreased water–rock interaction over time, and weathering in a cold, dry environment, mimicking a similar transition early in martian history. This transition may be recorded in sedimentary rocks on Mars through a similar superimposition mechanism, capturing past climate changes at the hand sample scale. These results also suggest that basalt-derived sediments could have sourced significant volumes of hydrated minerals on early Mars due to their greater permeability compared with intact igneous rocks.« less

Preliminary correlations of MAGSAT anomalies with tectonic features of Africa

USGS Publications Warehouse

Hastings, David A.

1982-01-01

An overview of the MAGSAT scalar anomaly map for Africa has suggested a correlation of MAGSAT anomalies with major crustal blocks of uplift or depression and different degrees of regional metamorphism. The strongest MAGSAT anomalies in Africa are closely correlated spatially with major tectonic features. Although a magnetic anomaly caused by a rectangular crustal block would be offset from the block's center by the effects of magnetic inclination, an anomaly caused by real crustal blocks of varying uplift, depression, and degree of regional metamorphism would be located nearer to the locus of greatest vertical movement and highest grade of metamorphism. Thus, the Bangui anomaly may be caused by a central old Precambrian shield, flanked to the north and south by two relatively young sedimentary basins.

Hydrothermal and Diagenetic Mineralization on Mars

NASA Astrophysics Data System (ADS)

Ehlmann, B. L.; Quinn, D. P.

2015-12-01

Predicted by geophysical modeling, the mineraolgic record of early Mars groundwater has only recently been discovered. First, rover exploration in sedimentary basins reveals diagenesis. At Meridiani, sandstone porosity is occluded by precipitation of secondary sulfates, hematite, and silica. Multiple alteration episodes are indicated by crystal vugs, disruption of preexisting textures by hematite concretions, and grain coatings (e.g. McLennan et al., 2005). At Gale crater, raised ridges in mudstones, interpreted to be early diagenetic features, are crossed by later-emplaced hydrated calcium sulfate veins (e.g. Grotzinger et al., 2014). Waters in Gale were likely circumneutral while jarosite mineralogy at Meridiani implies acidic waters. Second, systems of raised ridges at 100-m scale are observed from orbit in multiple Martian sedimentary rock units. An outstanding example is sulfate-bearing sediments exhumed at the northern margin of the Syrtis Major lavas (e.g. Quinn & Ehlmann, 2015). Polygonal and with no clearly preferred orientation, the ridges rise 5-30 m above the surrounding terrain. Parallel light-toned grooves with dark interiors (indicative of isopachous fills) and jarosite in ridge mineralogy point to mineralization by acidic waters. Third, some mineral assemblages observed from orbit represent the products of subsurface aqueous alteration at elevated temperatures (Ehlmann et al., 2011). These are globally distributed, exposed in scarps and by impact cratering. Mineral assemblages variously include (a) serpentine and carbonate; (b) prehnite and chlorite, and (c) zeolites. Collectively, these datasets indicate that groundwaters were spatially widespread on ancient Mars, contributing to the sustenance of lakes and to the alteration of bedrock to >1 km depths. While the Martian surface may have always been relatively inhospitable, a warmer, wetter subsurface provided a long-term potentially habitable environment. Key outstanding questions remaining include groundwater sources, their composition and compositional variability, and subsurface transport distances. Continued exploration of Mars, combined with studies of analogous bedrock mineralization on Earth, will advance understanding of environments with liquid water during Mars' first billion years.

Last century seabed morphodynamics of the Magra River estuary (Western Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Pratellesi, Marta; Ivaldi, Roberta; Ciavola, Paolo; Sinapi, Luigi

2016-04-01

The estimation of morphological and volumetric changes of the delta system at the mouth of the Magra River is presented in this paper using bathymetric and sedimentological data. The data series were collected during several hydro-oceanographic surveys carried out from 1882 to 2014, processed following the hydrographic international standards and stored in the Italian Navy Hydrographic Institute database. In particular, bathymetric data characterized by the same standard and accuracy were collected using different devices such as sounding lines, single-beam and multi-beam acoustic system. This research compares Digital Terrain Models (DTMs), derived from highly accurate bathymetric data and covering different time scales (secular, half-century and decade) in order to assess and quantify the seabed morphodynamics in relation with the river sedimentary budget. The methodology and data exploitation consist mainly in the production of DTMs to study the elevation change, two-dimensional and three dimensional maps, cross-sections of the seabed, difference surfaces and computation of net volumes as well as an historical sedimentological map. These products are also an useful contribution to the aim of EU RISC-KIT Project. The results of the analysis highlight changes in the geometry of the Magra River mouth, of the coastal profile and bottom features primarily due to variations of the sedimentary budget and secondarily to wave dynamics. This behaviour is characterized by evident river mouth and coastal retreat, beach erosion and sediment bars decay and net accretion under periods of high river sediment discharge and elongate bar formation during relatively fair conditions. In the last century the main change is constituted by the disappearance of the typical constructive seabed delta morphology and the transformation into the current small estuary, with microtidal condition. This small estuary has an upper sector where river processes, sediments and bedforms dominate, a lower sector near the mouth, where wave and tidal processes and marine sediments dominate, and a middle sector, where tidal currents dominate and both river and marine sediments are present.

Investigating the Geomorphic Behavior of the Cape Canaveral Coast Through High-Resolution Beach Monitoring, Sediment Analysis, Oceanographic Observations, and Numerical Modeling

NASA Astrophysics Data System (ADS)

Adams, P. N.; Jaeger, J. M.; MacKenzie, R. A.; Kline, S. W.; Maibauer, B. J.; Plant, N. G.; Gravens, M. B.; Pierro, T. P.; Shaffer, J.

2011-12-01

The salient of Cape Canaveral interrupts a relatively straight, sandy, passive margin coastline that extends nearly 400 km from the St. Johns River mouth to the St. Lucie Inlet along the Florida Atlantic coast. OSL dating indicates that the modern cape has been prograding rapidly since the LGM and subtle topographic features, inland from the modern cape, suggest that this salient has persisted over several sea level cycles since the early Pleistocene. Dynamic shoreline change over the past decade at the Kennedy Space Center (KSC) is threatening critical NASA infrastructure and has prompted officials to develop a mitigation strategy through a partnership among researchers from the U.S. Geological Survey, the U.S. Army Corps of Engineers, private coastal engineering firms, and the University of Florida. Since May 2009, the research team has assembled data on decadal to event-scale shoreline change (dGPS), beach and nearshore morphodynamics (dGPS and Argus), beach sedimentary character (grain size analysis), wave climate and transformation (ADCP), and inner shelf bathymetry (Echo Sounding) in an effort to assess dune vulnerability and flooding risk. In addition, SWAN numerical modeling simulations offer insight into the influence of irregular bathymetry (cape-associated shoals) on the alteration of spatial patterns of wave energy flux during a decadal shift in deep-water wave climate. Beach-fx, modeling of cross-shore profile evolution is being applied to evaluate the performance of alternative protective measures, estimate project costs, and examine ecological influences of the proposed alternative protective measures. By combining contemporaneous data of coastal geomorphic and sedimentary response to wave forcing with numerical model results that explore a range of climate scenarios, we aim to develop a useful understanding of the coastal geomorphic behavior at KSC that can be used to make a mitigation recommendation.

Using Receiver Functions to Image the Montana Crust and Upper Mantle

NASA Astrophysics Data System (ADS)

Sirianni, R. T.; Russo, R. M.

2008-12-01

We determined receiver functions (RFs) at six permanent Advanced National Seismic System (ANSS) stations to examine crust and upper mantle structure of the Wyoming craton (WC) and Medicine Hat block (MHB). The Deep Probe & SAREX projects (Henstock et al., 1998; Clowes et al., 2002; Gorman et al., 2002) used active source seismics to model a high velocity crustal layer (the so-called 7x layer) beneath the WC. This layer exhibits P wave velocities that are high for lower continental crust (~7+ km/s) and extends from 30-55 km below the surface. Interpretations of the active source data indicate that this layer may represent wide scale crustal underplating of the WC, implying post-Archean craton modification with implications for Laurentia assembly. We used 43 earthquakes from a wide azimuthal distribution recorded at the Montana ANSS stations; high signal-to-noise ratios of 25 of these RFs were acceptable for further analysis. Receiver functions constrain crustal velocity structure beneath a seismometer by using P-to-S wave conversions at sharp velocity contrast boundaries. Preliminary results for seismic stations DGMT, EGMT, and LAO, located to the east of the Deep Probe and SAREX seismic line on the Wyoming craton/Medicine Hat block show the influence of sedimentary cover and a strong Ps phase at approximately four seconds after P. At BOZ and MSO, located in the Rocky mountains, the sedimentary cover signal previously noted is absent, and instead we observe a sharp Ps phase at about four and a half seconds after P. RFs at station RLMT (on the WC) are highly anomalous, probably reflecting complex conversions from two differently oriented dipping layers. We will use the RFs to produce suites of acceptable structural models to test for the presence and lateral extent of the 7x layer and other structural features of the Rocky Mountains-craton transition.

Deformational sequence of a portion of the Michipicoten greenstone belt, Chabanel Township, Ontario

NASA Technical Reports Server (NTRS)

Shrady, C. H.; Mcgill, G. E.

1986-01-01

Detailed mapping at a scale of one inch = 400 feet is being carried out within a fume kill, having excellent exposure, located in the southwestern portion of the Michipicoten Greenstone Belt near Wawa, Ontario. The rocks are metasediments and metavolcanics of lower greenschist facies. U-Pb geochronology indicates that they are at least 2698 + or - 11 Ma old. The lithologic packages strike northeast to northwest, but the dominant strike is approximately east-west. Sedimentary structures and graded bedding are well preserved, aiding in the structural interpretation of this multiply deformed area. At least six phases of deformation within a relatively small area of the Michipicoten Greenstone Belt have been tentatively identified. These include the following structural features in approximate order of occurrence: (0) soft-sediment structures; (1) regionally overturned rocks, flattened pebbles, bedding parallel cleavage, and early, approximately bedding parallel faults; (2) northwest to north striking cleavage; (3) northeast striking cleavage and associated folds, and at least some late movement on approximately bedding parallel faults; (4) north-northwest and northeast trending faults; and (5) diabase dikes and associated fracture cleavages. Minor displacement of the diabase dikes occurs on faults that appear to be reactivated older structures.

Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid-Atlantic continental margin

USGS Publications Warehouse

Obelcz, Jeffrey; Brothers, Daniel S.; Chaytor, Jason D.; ten Brink, Uri S.; Ross, Steve W.; Brooke, Sandra

2013-01-01

Shelf-sourced submarine canyons are common features of continental margins and are fundamental to deep-sea sedimentary systems. Despite their geomorphic and geologic significance, relatively few passive margin shelf-breaching canyons worldwide have been mapped using modern geophysical methods. Between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the US Mid-Atlantic margin: Wilmington, Baltimore, Washington, and Norfolk canyons. More than 5700 km2 of high-resolution multibeam bathymetry and 890 line-km of sub-bottom CHIRP profiles were collected along the outer shelf and uppermost slope (depths of 80-1200 m). The data allowed us to compare and contrast the fine-scale morphology of each canyon system. The canyons have marked differences in the morphology and orientation of canyon heads, steepness and density of sidewall gullies, and the character of the continental shelf surrounding canyon rims. Down-canyon axial profiles for Washington, Baltimore and Wilmington canyons have linear shapes, and each canyon thalweg exhibits morphological evidence for recent, relatively small-scale sediment transport. For example, Washington Canyon displays extremely steep wall gradients and contains ~100 m wide, 5–10 m deep, v-shaped incisions down the canyon axis, suggesting modern or recent sediment transport. In contrast, the convex axial thalweg profile, the absence of thalweg incision, and evidence for sediment infilling at the canyon head, suggest that depositional processes strongly influence Norfolk Canyon during the current sea-level high-stand. The north walls of Wilmington, Washington and Norfolk canyons are steeper than the south walls due to differential erosion, though the underlying cause for this asymmetry is not clear. Furthermore, we speculate that most of the geomorphic features observed within the canyons (e.g., terraces, tributary canyons, gullies, and hanging valleys) were formed during the Pleistocene, and show only subtle modification by Holocene processes active during the present sea-level high-stand.

Large Grooves in the South Polar Layered Deposits: Insights from Spacecraft Data and Terrestrial Analogs

NASA Technical Reports Server (NTRS)

Bridges, N. T.; Herkenhoff, K. E.

2000-01-01

The Martian polar layered deposits (PLD) are probably the best source of information about the recent climate history of Mars, but their origin and the mechanisms of accumulation are still a mystery. The polar layers are sedimentary deposits that most planetary scientists believe are composed of water ice and varying amounts of wind-blown dust, although their composition is poorly constrained. Interpretation of the observed polar stratigraphy in terms of global climate changes is complicated by the significant difference in surface ages between the north and south PLD inferred from crater statistics. The study reported here was undertaken as part of the landing site selection effort for the Mars Polar Lander (MPL) and Deep Space 2 (DS2) missions that made use of all available data. We used Mariner 9, Viking, and Mars Global Surveyor images of the south PLD in the area accessible to MPL and DS2 to evaluate the topography and morphology of grooves, terraced layers, and other features. Here we report on results from grooves that appear to have been carved by strong winds. Because these features are found throughout the interior of the PLD, where MPL and DS2 were targeted to land, their topographic characteristics were judged as important input for landing site safety assessment. The characteristics of the grooves also provide constraints and insights into aeolian processes in the polar regions and the effects these have on PLD ablation. Our results indicate that these grooves do not represent landing hazards at the scale of the images (approx. 80 m/pixel). Their topography and shape do not seem correlated with south PLD layering. No Earth analog of suitable scale exists, although the grooves bear some resemblance to smaller terrestrial deflation hollows found in soft sediment and ice. Additional information is contained in original extended abstract.

Mass movement and storms in the drainage basin of Redwood Creek, Humboldt County, California: a progress report

USGS Publications Warehouse

Harden, Deborah Reid; Janda, Richard J.; Nolan, K. Michael

1978-01-01

Numerous active landslides are clearly significant contributors to high sediment loads in the Redwood Creek basin. Field and aerial-photograph inspections indicate that large mass-movement features, such as earthflows and massive streamside debris slides, occur primarily in terrain underlain by unmetamorphosed or slightly metamorphosed sedimentary rocks. These features cannot account for stream sediment derived from schist. Observed lithologic heterogeneity of stream sediment therefore suggests that large-scale mass movement is only one part of a complex suite of processes supplying sediment to streams in this basin. Other significant sediment contributors include various forms of fluvial erosion and small-scale discrete mass failures, particularly on oversteepened hillslopes adjacent to perennial streams. Photo-interpretive studies of landslide and timber-harvest history adjacent to Redwood Creek, together with analysis of regional precipitation and runoff records for six flood-producing storms between 1953 and 1975, indicate that loci and times of significant streamside landsliding are influenced by both local storm intensity and streamside logging. Analysis of rainfall records and historic accounts indicates that the individual storms comprising a late-19th-century series of storms in northwestern California were similar in magnitude and spacing to those of the past 25 years. The recent storms apparently initiated more streamside landslides than comparable earlier storms, which occurred prior to extensive road construction and timber harvest. Field observations and repeated surveys of stake arrays at 10 sites in the basin indicate that earthflows are especially active during prolonged periods of moderate rainfall; but that during brief intense storms, fluvial processes are the dominant erosion mechanism. Stake movement occurs mostly during wet winter months. Spring and summer movement was detected at some moist streamside sites. Surveys of stake arrays in two recently logged areas did not indicate exceptionally rapid rates of movement in three years following timber harvest.

Meso-Cenozoic morphological evolution of NW Africa, the case of the Tuareg swell.

NASA Astrophysics Data System (ADS)

Rougier, S.; Gautheron, C.; Barbarand, J.; Missenard, Y.; Zeyen, H.; Pinna, R.; Bonin, B.; Liégeois, J.-P.; Ouabadi, A.; Frizon de Lamotte, D.

2012-04-01

The continental crust of Africa, largely built during the Pan-African orogeny (late Neoproterozoic) has acquired in its northern part, during Paleozoic times, an arch and basin morphology. Meso-Cenozoic large scale topographic anomalies, associated to Cenozoic intraplate volcanism, such as Hoggar, Tibesti or Darfur domes, are superimposed to these structures. Precise ages of swells, as well as their relations with Paleozoic arch and basin morphology of the area, remain controversial. The aim of this study, focussed on the Hoggar dome, in southern Algeria, is to produce new constraints on the Post-Paleozoic evolution of this region. The Tuareg shield, from which Hoggar is the main central part and Aïr a SE extension, forms a topographic high reaching an altitude >2900m (Mt Tahat, Atakor district), exposing Precambrian rocks over 500000km2. While presumed Cretaceous sedimentary remnants suggest a possible stage of slightly positive topography during the Mesozoic, current high topography is emphasized by Cenozoic volcanic formations, mostly basaltic in composition. We present new low-temperature thermochronology data, with apatite fission track and (U-Th)/He ages on Hoggar and Aïr substratum. We combine these results with thermal, gravimetric and isostatic two-dimensional lithosphere-scale geophysical models, following the method of Zeyen & Fernandez (1994). Preliminary thermochronological results present ages from 99+-6 to 166+-10 Myr for AFT, and AHe from 10 to 300 Myr. Thermal simulations of these data suggest that currently outcropping Precambrian Hoggar basement could have experienced temperatures of approximately 80°C between Upper Cretaceous and Eocene. We propose that these elevated temperatures are related to burial beneath a 1 to 3 km thick sedimentary cover, depending on thermal gradient. The base of this sedimentary cover could correspond to the poorly described Upper Cretaceous remnants, currently uplifted up to 1450 m. These results are in agreement with geophysical calculations showing that, when eliminating the topographical effect of lithosphere heating related to recent volcanism and assuming an Upper Cretaceous to Late Eocene thermally unperturbed lithosphere, a sedimentary basin may have existed. Up to 2 km of Cretaceous sediments could have been deposited on the Hoggar, confirming the thermochronological results. Ref: Zeyen, H. and M. Fernàndez (1994): Integrated lithospheric modeling combining thermal, gravity and local isostasy analysis: application to the NE Spanish Geotransect. J. Geophys. Res. 99: 18089-18102.

Reconstruction of anthropogenic eutrophication in the region off the Changjiang Estuary and central Yellow Sea: From decades to centuries

NASA Astrophysics Data System (ADS)

Zhu, Zhuo-Yi; Wu, Ying; Zhang, Jing; Du, Jin-Zhou; Zhang, Guo-Sen

2014-01-01

Anthropogenic activities are known to induce estuarine and coastal eutrophication. However, the eutrophication history over a longer time scale (e.g., over hundreds of years) is often missing, and this perspective is important for an objective assessment of recent-decades anthropogenic activities. To reconstruct eutrophication history in this region, two sediment cores were taken, core E4 in the region off the Changjiang Estuary in the coast of East China Sea, and core E2 in the central Yellow Sea. High sedimentation rate (3.8 cm/yr) of core E4 enabled us to reconstruct a detailed anthropogenic eutrophication history for the past 70 years, while the history at least back to 1855 was further revealed via core E2. Sedimentary nitrogen isotopes (δ15N) in core E4 showed a gradually depleting trend from 5‰ (1930s) to 3.8‰ in the top, which is consistent with the increasing riverine nitrogen flux over the past few decades. A negative relationship was found between total sedimentary Chla (=preserved chlorophyll a+its degradation products) and δ15N (r2=0.68), suggesting the promotion of estuarine productivity by chemical fertilizer-N. Preserved diagnostic pigments ratio (peridinin/fucoxanthin) further suggests that after 1995, the influence of dinoflagellates has been increasing compared to diatoms. At a longer time scale (i.e., core E2), sedimentary δ15N also decreased from 5.1‰ (before 1855) to 4.4‰ (at top layer). As normalized fossil cyanobacterial pigment (zeaxanthin) showed a decreasing trend from before 1855 to the top of the core, we propose that the decreasing sedimentary δ15N after 1855 was not due to assimilation of atmospheric nitrogen, but due to excess nutrients input to the central Yellow Sea, which promoted primary production. This is further proved by preserved pheopigments, which continuously increased from 41.7 nmol g OC-1 (before 1855) to 251 nmol g OC-1 (at top layer) in core E2. Besides revealing the eutrophication history, big history events were also recorded, including the 1998 flood of the Changjiang River (core E4) and the shift of the Yellow River mouth in 1855 (core E2).

Global perspectives on oxidative weathering of organic carbon in sedimentary rocks

NASA Astrophysics Data System (ADS)

Dellinger, M.; Hilton, R. G.; West, A. J.; Horan, K.; Gaillardet, J.

2016-12-01

Over geological timescales, the oxidation of organic carbon in sedimentary rocks is major source of carbon dioxide (CO2) to the atmosphere. The global magnitude of this flux remains poorly constrained, but it is likely to be between 40-100 x 1012 g C yr-1, similar to the CO2 emissions from volcanism. The rates of CO2 emission ultimately set the rate of silicate weathering by carbonic acid and new organic carbon burial, which act together to stabilise the climate system. To constrain how the geological carbon cycle operates and modifies Earth's climate over millions of years, we must better understand the controls on the oxidation of sedimentary rock-derived organic carbon (`petrogenic' OC, OCpetro). Here we examine new and published constraints on OCpetro oxidation flux, which come from indirect measurements (e.g. trace element proxies such as rhenium) and direct measurements (e.g. CO2 trapping and 14C). Existing datasets track the gaseous and dissolved products of weathering as well as the solid residues over a range of spatial scales, from soil profiles to large river catchments. Although the datasets are still sparse, they indicate that physical denudation plays a major role in setting OCpetro oxidation flux. These measurements are interrogated in the framework of a catchment-scale numerical model of OCpetro oxidation. By harnessing approaches developed to examine and quantify acid-hydrolysis reactions (i.e. silicate mineral weathering by carbonic acid) the model considers realistic geochemical processes and the links between erosion and weathering. Key parameters emerge, such as the `weathering thickness' which describes a depth to which oxidative waters penetrate. The reaction kinetics of OCpetro remain poorly constrained, but nevertheless, the model predicts that the kinetic limitation of OCpetro oxidation is not reached until physical erosion rates exceed 2 mm yr-1, which is much higher than for CO2 consumption by silicate weathering. These findings mirror data on sulphide oxidation, demonstrating that physical erosion can drive an important CO2 release to the atmosphere both from inorganic and organic reduced phases in sedimentary rocks. The degree to which this release is compensated by CO2 drawdown associated with the erosion and transfer of biospheric OC will also be considered.

The Mesozoic palaeo-relief and immature front belt of northern Tianshan

NASA Astrophysics Data System (ADS)

Chen, K.; Gumiaux, C.; Augier, R.; Chen, Y.; Wang, Q.

2012-04-01

The modern Tianshan (central Asia) extends east-west on about 2500 km long with an average of more than 2000 m in altitude. At first order, the finite structure of this range obviously displays a crust-scale 'pop-up' of Palaeozoic rocks surrounded by two Cenozoic foreland basins. Up to now, this range is regarded as a direct consequence of the Neogene to recent reactivation of a Palaeozoic belt due to the India - Asia collision. This study focuses on the structure of the northern front area of Tianshan and is mainly based on field structural works. In particular, relationships in between sedimentary cover and basement units allow discussing the tectonic and morphological evolution of the northern Tianshan during Mesozoic and Cenozoic times. The study area is about 250 km long, from Wusu to Urumqi, along the northern piedmont of the Tianshan. Continental sedimentary series of the basin as well as structure of the cover/basement interface can well be observed along several incised valleys. Sedimentological observations argue for a limited transport distance for Lower and Uppermost Jurassic deposits that are preserved within intra-mountainous basins or within the foreland basin, along the range front. Moreover, some of the studied geological sections show that Triassic to Jurassic sedimentary series can be continuously followed from the basin to the range where they unconformably overlie the Carboniferous basement. Such onlap type structures of the Jurassic series, on top of the Palaeozoic rock units, can also be observed at more local-scale (~a few 100 m). At different scales, our observations thus clearly evidence i) the existence of a substantial relief during Mesozoic times and ii) very limited deformation, after Mesozoic, along some segments of the northern range front. Yet, thrusting of the Palaeozoic basement on the Mesozoic or Cenozoic sedimentary series of the basin is also well exposed along some other river valleys. As a consequence, the northern front of Tianshan displays as very uncylindrical with rapid lateral transitions from one type to the other. This study shows that the Cenozoic reactivation of the Tianshan range has not yielded important deformation along its contact with the juxtaposed Junggar basin, into the studied segment. Besides, the topography of the current northern Tianshan area can not be considered as the unique consequence of Cenozoic reactivation. Finally, from a compilation of structural field observations with available seismic geophysical data, regional cross sections show only moderate shortening in the deformed belt of the northern piedmont of Tianshan. Structure of the fold-and-thrust belt looks controlled by several basement thrusts faults separating rigid blocks. This study suggests that the northern front of the intra-continental Tianshan range may be considered as an immature thrust belt and is still at an early developing stage of its orogenic evolution.

Surficial geologic map of the Heath-Northfield-Southwick-Hampden 24-quadrangle area in the Connecticut Valley region, west-central Massachusetts

USGS Publications Warehouse

Stone, Janet R.; DiGiacomo-Cohen, Mary L.

2010-01-01

The surficial geologic map layer shows the distribution of nonlithified earth materials at land surface in an area of 24 7.5-minute quadrangles (1,238 mi2 total) in west-central Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, and organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text, quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Surficial geologic map of the Norton-Manomet-Westport-Sconticut Neck 23-quadrangle area in southeast Massachusetts

USGS Publications Warehouse

Stone, Byron D.; Stone, Janet R.; DiGiacomo-Cohen, Mary L.; Kincare, Kevin A.

2012-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of 23 7.5-minute quadrangles (919 mi2 total) in southeastern Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, and organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Surficial geologic map of the Mount Grace-Ashburnham-Monson-Webster 24-quadrangle area in central Massachusetts

USGS Publications Warehouse

Stone, Janet R.

2013-01-01

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of 24 7.5-minute quadrangles (1,238 mi2 total) in central Massachusetts. Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and as resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, and organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for assessing water resources, construction-aggregate resources, and earth-surface hazards, and for making land-use decisions. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This report includes explanatory text (PDF), quadrangle maps at 1:24,000 scale (PDF files), GIS data layers (ArcGIS shapefiles), metadata for the GIS layers, scanned topographic base maps (TIF), and a readme.txt file.

Three-dimensional hydrogeologic framework model of the Rio Grande transboundary region of New Mexico and Texas, USA, and northern Chihuahua, Mexico

USGS Publications Warehouse

Sweetkind, Donald S.

2017-09-08

As part of a U.S. Geological Survey study in cooperation with the Bureau of Reclamation, a digital three-dimensional hydrogeologic framework model was constructed for the Rio Grande transboundary region of New Mexico and Texas, USA, and northern Chihuahua, Mexico. This model was constructed to define the aquifer system geometry and subsurface lithologic characteristics and distribution for use in a regional numerical hydrologic model. The model includes five hydrostratigraphic units: river channel alluvium, three informal subdivisions of Santa Fe Group basin fill, and an undivided pre-Santa Fe Group bedrock unit. Model input data were compiled from published cross sections, well data, structure contour maps, selected geophysical data, and contiguous compilations of surficial geology and structural features in the study area. These data were used to construct faulted surfaces that represent the upper and lower subsurface hydrostratigraphic unit boundaries. The digital three-dimensional hydrogeologic framework model is constructed through combining faults, the elevation of the tops of each hydrostratigraphic unit, and boundary lines depicting the subsurface extent of each hydrostratigraphic unit. The framework also compiles a digital representation of the distribution of sedimentary facies within each hydrostratigraphic unit. The digital three-dimensional hydrogeologic model reproduces with reasonable accuracy the previously published subsurface hydrogeologic conceptualization of the aquifer system and represents the large-scale geometry of the subsurface aquifers. The model is at a scale and resolution appropriate for use as the foundation for a numerical hydrologic model of the study area.

Comparison of geoelectrical/tectonic models for suture zones in the western U.S.A. and eastern Europe: are black shales a possible source of high conductivities?

USGS Publications Warehouse

Stanley, W.D.

1989-01-01

Large-scale geoelectrical anomalies have been mapped with geomagnetic depth sounding (GDS) and magnetotelluric (MT) surveys in the Carpathian Mountains region. These anomalies are associated with the zone of closure between stable Europe and a complex of microplates in front of the converging African plate. The zone of closure, or suture zone, is largely occupied by an extensive deformed flysch belt. The models derived to fit the observed geoelectrical data are useful in the study of other suture zones, and Carpathian structures have been compared with areas currently being studied in the western Cordillera of the U.S.A. Models derived for a smaller-scale suture zone mapped in western Washington State have features that are similar to the Carpathian models. The geoelectrical models for both the Carpathian and Washington anomalies require dipping conductive slabs of 1-5 ?? m material that extends to depths > 20 km. In both instances there is evidence that these materials may merge with lower crustal-mantle conductors along the down-dip margins of the slab. The main conductive units are interpreted to be sedimentary rocks that have been partially subducted due to collisional processes. Heat flow is low in both regions and it is difficult to explain fully the deep conduction mechanisms; however, evidence suggests that the conduction at depth may include electronic conduction in sulfide mineral or carbon films as well as ionic conduction in fluids or partial melt. ?? 1989.

Satellite images survey for the identification of the coastal sedimentary system changes and associated vulnerability along the western bay of the Gulf of Tunis (northern Africa)

NASA Astrophysics Data System (ADS)

Hzami, Abderraouf; Amrouni, Oula; Romanescu, Gheorghe; Constantin Stoleriu, Cristian; Mihu-Pintilie, Alin; Saâdi, Abdeljaouad

2018-04-01

The aim of this study consists in testing the effectiveness of satellite data in order to monitoring shoreline and sedimentary features changes, especially the rapidly changing of Gulf of Tunis coast. The study area is located in the Gulf of Tunis western bay (Southern Mediterranean Sea) which is characterized by sandy beaches of Ghar Melah and Raoued (Medjerda Delta area). The aerial photographs and satellite imageries were used for mapping the evolution of shoreline. Diachronic data (satellite imagery, aerial photography and topographic maps) were used to monitor and to quantify, the evolution of the coastal areas. These thematic data were digitally overlaid and vectorised for highlighting the shoreline changes between 1936 and 2016, in order to map the rate of erosion and accretion along the shoreline. Results show that the accretion and degradation are related to the Medjerda: change of outlet in 1973 and impoundment of the Sidi Salem dam in 1982. We found that the general trend of the coastal geomorphic processes can be monitored with satellite imageries (such as Sentinel A2, Spots 4 and 5), due to its repetitive coverage along the time and their high quality concerning the spectral contrast between land and sea areas. Improved satellite imageries with high resolution should be a valuable tool for complementing traditional methods for mapping and assessing the sedimentary structures (such as shoreline, delta, marine bars), and monitoring especially the lowlands coastal areas (slightly eroded).

The volcano-sedimentary succession of Upper Permian in Wuli area, central Qinghai-Tibetan Plateau: Sedimentology, geochemistry and paleogeography

NASA Astrophysics Data System (ADS)

Liu, Shengqian; Jiang, Zaixing; Gao, Yi

2017-04-01

Detailed observations on cores and thin sections well documented a volcano-sedimentary succession from Well TK2, which is located in Wuli area, central Qinghai-Tibetan Plateau. The TK2 volcano-sedimentary succession reflects an active sedimentary-tectonic setting in the north margin of North Qiangtang-Chamdo terrane in the late Permian epoch. Based on the observation and recognition on lithology and mineralogy, the components of TK2 succession are mainly volcanic and volcaniclastic rocks and four main lithofacies are recognized, including massive volcanic lithofacies (LF1), pyroclastic tuff lithofacies (LF2), tuffaceous sandstone lithofacies (LF3) and mudstone lithofacies (LF4). LF1 is characterized by felsic components, massive structure and porphyrotopic structure with local flow structure, which indicates submarine intrusive domes or extrusion-fed lavas that formed by magma ascents via faults or dykes. Meanwhile, its eruption style may reflect a relative high pressure compensation level (PCL) that mainly determined by water depth, which implies a deep-water environment. LF2 is composed of volcanic lapilli or ash and featured with massive structure, parallel bedding and various deformed laminations including convolve structure, slide deformation, ball-and-pillow structure, etc.. LF2 indicates the sedimentation of initial or reworked explosive products not far away from volcano centers, reflecting the proximal accumulation of volcano eruption-fed clasts or their resedimentation as debris flows. In addition, the submarine volcano eruptions may induced earthquakes that facilitate the resedimentation of unconsolidated sediments. LF3 contains abundant pyroclastic components and is commonly massive with rip-up mudstone clasts or usually interbedded with LF4. In addition, typical flute casts, scour structures and graded beddings in thin-interbedded layers of sandstone and mudstone are commonly observed, which also represents the sedimentation of debris flows or turbidity flows in a relative deep-water environment. LF4 indicates suspension deposits of distal turbidity sediments in deeper-water setting, which is mainly tuffaceous and ordinary mudstone, commonly interbedded with thin pyroclastic layers. Geochemically, the felsic volcanic rocks belong to tholeiitic to calc-alkaline series, exhibiting characteristics of right-leaning rare earth element (REE) patterns with conspicuous Eu negative anomalies, enrichments in large ion lithophile elements (LILEs) and depletions in high field-strength elements (HFSEs), which reflect an island arc environment that corresponds to the late-Permian subduction of slabs. The TK2 volcanic-sedimentary succession reveals a submarine volcano-dominated depositional model and proves the existence of a deeper water environment, at least in a restricted zone of Wuli area. However, the traditional sedimentary and paleogeographic knowledges are mostly about coal-forming transitional facies in stable environment. Therefore, the proposing of a deep-water volcano-sedimentary model will provide a further comprehension of paleogeography in southern Qinghai at late-Permian, which will also supplement the previous cognition of stable ocean-land transitional environments and provide a new sight to the paleogeographic framework of late-Permian in North Qiangtang-Chamdo terrane.

Incorporating the International Polar Year Into Introductory Geology Laboratories at Ohio State University

NASA Astrophysics Data System (ADS)

Judge, S. A.; Wilson, T. J.

2005-12-01

The International Polar Year (IPY) provides an excellent opportunity for highlighting polar research in education. The ultimate goal of our outreach and education program is to develop a series of modules that are focused on societally-relevant topics being investigated in Antarctic earth science, while teaching basic geologic concepts that are standard elements of school curricula. For example, we envision a university-level, undergraduate, introductory earth science class with the entire semester/quarter laboratory program focused on polar earth science research during the period of the International Polar Year. To attain this goal, a series of modules will be developed, including inquiry-based exercises founded on imagery (video, digital photos, digital core scans), GIS data layers, maps, and data sets available from OSU research groups. Modules that highlight polar research are also suitable for the K-12 audience. Scaleable/grade appropriate modules that use some of the same data sets as the undergraduate modules can be outlined for elementary through high school earth science classes. An initial module is being developed that focuses on paleoclimate data. The module provides a hands-on investigation of the climate history archived in both ice cores and sedimentary rock cores in order to understand time scales, drivers, and processes of global climate change. The paleoclimate module also demonstrates the types of polar research that are ongoing at OSU, allowing students to observe what research the faculty are undertaking in their respective fields. This will link faculty research with student education in the classroom, enhancing learning outcomes. Finally, this module will provide a direct link to U.S. Antarctic Program research related to the International Polar Year, when new ice and sedimentary rock cores will be obtained and analyzed. As a result of this laboratory exercise, the students will be able to: (1) Define an ice core and a sedimentary rock core. (Knowledge) (2) Identify climate indicators in each type of core by using digital core images. These include layers of particulate material (such as volcanic tephra) in ice cores and layers of larger grains (such as ice-rafted debris) in sedimentary rock cores. (Knowledge) (3) Describe how cores are taken in extreme environments, such as Antarctica. (Comprehension) (4) Use actual data from proxies in the ice and sedimentary records to graph changes through time in the cores. (Application) (5) Recognize variances in data sets that might illustrate periods of climate change. (Analysis) (6) Integrate data results from several proxies in order to construct a climate record for both ice cores and sedimentary rock cores. (Synthesis) (7) Interpret both the ice core and sedimentary rock core records to ascertain the effectiveness of both of these tools in archiving climate records. (Evaluation)

'Cape capture': Geologic data and modeling results suggest the holocene loss of a Carolina Cape

USGS Publications Warehouse

Thieler, E.R.; Ashton, A.D.

2011-01-01

For more than a century, the origin and evolution of the set of cuspate forelands known as the Carolina Capes-Hatteras, Lookout, Fear, and Romain-off the eastern coast of the United States have been discussed and debated. The consensus conceptual model is not only that these capes existed through much or all of the Holocene transgression, but also that their number has not changed. Here we describe bathymetric, lithologic, seismic, and chronologic data that suggest another cape may have existed between Capes Hatteras and Lookout during the early to middle Holocene. This cape likely formed at the distal end of the Neuse-Tar-Pamlico fiuvial system during the early Holocene transgression, when this portion of the shelf was fiooded ca. 9 cal (calibrated) kyr B.P., and was probably abandoned by ca. 4 cal kyr B.P., when the shoreline attained its present general configuration. Previously proposed mechanisms for cape formation suggest that the large-scale, rhythmic pattern of the Carolina Capes arose from a hydrodynamic template or the preexisting geologic framework. Numerical modeling, however, suggests that the number and spacing of capes can be dynamic, and that a coast can self-organize in response to a high-angle-wave instability in shoreline shape. In shoreline evolution model simulations, smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of 'cape capture.' The suggested former cape in Raleigh Bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self-organization hypothesis. Cape capture may be a widespread process in coastal environments with large-scale rhythmic shoreline features; its preservation in the sedimentary record will vary according to geologic setting, physical processes, and sea-level history. ?? 2011 Geological Society of America.

‘Cape capture’: Geologic data and modeling results suggest the Holocene loss of a Carolina Cape

USGS Publications Warehouse

Thieler, E. Robert; Ashton, Andrew D.

2011-01-01

For more than a century, the origin and evolution of the set of cuspate forelands known as the Carolina Capes—Hatteras, Lookout, Fear, and Romain—off the eastern coast of the United States have been discussed and debated. The consensus conceptual model is not only that these capes existed through much or all of the Holocene transgression, but also that their number has not changed. Here we describe bathymetric, lithologic, seismic, and chronologic data that suggest another cape may have existed between Capes Hatteras and Lookout during the early to middle Holocene. This cape likely formed at the distal end of the Neuse-Tar-Pamlico fluvial system during the early Holocene transgression, when this portion of the shelf was flooded ca. 9 cal (calibrated) kyr B.P., and was probably abandoned by ca. 4 cal kyr B.P., when the shoreline attained its present general configuration. Previously proposed mechanisms for cape formation suggest that the large-scale, rhythmic pattern of the Carolina Capes arose from a hydrodynamic template or the preexisting geologic framework. Numerical modeling, however, suggests that the number and spacing of capes can be dynamic, and that a coast can self-organize in response to a high-angle-wave instability in shoreline shape. In shoreline evolution model simulations, smaller cuspate forelands are subsumed by larger neighbors over millennial time scales through a process of ‘cape capture.’ The suggested former cape in Raleigh Bay represents the first interpreted geological evidence of dynamic abandonment suggested by the self-organization hypothesis. Cape capture may be a widespread process in coastal environments with large-scale rhythmic shoreline features; its preservation in the sedimentary record will vary according to geologic setting, physical processes, and sea-level history.

Tectono-sedimentary features in the Yap subduction zone, Western Pacific: constraints from latest integrated geophysical survey

NASA Astrophysics Data System (ADS)

Dong, D.; Zhang, G.; Bai, Y.; Fan, J.; Zhang, Z.

2017-12-01

The Yap subduction zone, western Pacific, is a typical structure related to the ridge subduction, but comparative shortage of the geophysical data makes the structural details unknown in this area. In this study, we present the latest and high-quality multi-beam swath bathymetry and multi-channel seismic data acquired synchronously in the year 2015 across the Yap subduction zone. Multichannel seismic and multi-beam data are mainly applied to investigate the topography of major tectonic units and stratigraphic structure in the Yap subduction zone and discuss the tectonic characteristics controlled by ridge subduction. It suggests that, Parece Vela Basin, as the regional sedimentary center, developed sedimentary layers nearly 800 meters thick. On the contrast, the horizontal sedimentary layers were not obviously identified in the Yap trench, where subduction erosion occurred. Caroline ridge changed the tectonic characteristics of subduction zone, and influenced magmatism of the Yap arc because of the special topography. The seismic profile clearly reveals landslide deposits at the upper slope break of the forearc, north of the Yap Island, which was identified as the fault notch denoting a lithological boundary in previous work. Detailed topography and geological structure of horst and graben in the north of Yap are depicted, and topographic high of Caroline ridge is supposed to bring greater bending and tension and the subsequent horst and graben belt. Multichannel seismic evidence has been provided for interpreting the expansion of Sorol Trough and its inferred age. A modified model for the Yap subduction zone evolution is proposed, incorporating three major tectonic events: proto-Yap Arc rupture in the Oligocene, collision of the Caroline Ridge and the Yap Trench in the Late Oligocene or Middle Miocene, and onset of the Sorol Trough rifting in the Late Miocene. Acknowledge: This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA11030102), the National Natural Science Foundation of China (No. 41476042, 41506055 )

The Chicxulub crater - impact metamorphism of sulfate and carbonate lithologies

NASA Astrophysics Data System (ADS)

Deutsch, A.; Langenhorst, F.; Hornemann, U.; Ivanov, B. A.

2003-04-01

It is discussed whether in the aftermath of the Chicxulub event, impact-released CO_2 and SO_x have changed the Earth's climate, acting also as lethal thread for life. Undoubtedly, vaporization of carbonates and sulfates, which are major target lithologies at the Chicxulub impact site, occurred in the footprint of the projectile. What happened to these lithologies outside this very restricted zone was so far unconstrained. Petrologic observations on PEMEX and UNAM as well as on the CSDP cores allow to set up a general classification for shock-related pro-grade effects on sulfate and carbonate sedimentary rocks. Shock effects in lithic breccias are restricted to brecciation and formation of twins in calcite. Suevites mostly lack melted carbonate clasts; annealing effects in anhydrite fragments are absent. The underlying melt breccias contain anhydrite fragments still displaying a sedimentary texture, and limestone clasts, whose texture reflect crystallization from melt. Impact melt breccias from deeper levels frequently contain partially resorbed anhydrite clasts and a melt matrix with the Ca-rich mineral assemblage quartz + plagioclase + clinopyroxene; this mineral assemblage provides evidence for partial dissociation of CaSO_4. Large clasts of anhydrite consist of equant crystals with 120^o triple junctions, a feature indicative for re-crystallization in the solid state. Tagamites (impact melt rocks) are virtually free of clasts from sedimentary lithologies. These rocks have an extremely high formation temperature, which caused total dissociation of CaSO_4 and CaCO_3. Finally, up to 100 μm wide veins of anhydrite + calcite + quartz cut the matrix of all lithologies except the tagamites. They probably represent "degassing vents". The given scheme is in qualitative accordance with data of shock recovery and annealing experiments as well as with modeling results. In addition, it substantiates that annealing plays a fundamental role in the impact metamorphism of sedimentary rocks.

Pore water colloid properties in argillaceous sedimentary rocks.

PubMed

Degueldre, Claude; Cloet, Veerle

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay colloid concentration is expected to be very low (<1ppb, for 10-100nm) which restricts their relevance for radionuclide transport. Copyright © 2016. Published by Elsevier B.V.

Metal accumulation in soils derived from volcano-sedimentary rocks, Rio Itapicuru Greenstone Belt, northeastern Brazil.

PubMed

Dos Santos, Laíse Milena Ribeiro; Gloaguen, Thomas Vincent; Fadigas, Francisco de Souza; Chaves, Joselisa Maria; Martins, Tamires Moraes Oliveira

2017-12-01

Many countries and some Brazilian regions have defined the guideline values for metals in soils. However, the local geological features may be so heterogeneous that global or even regional guideline values cannot be applied. The Greenstone Belts are worldwide geological formations of vast extension, containing mineralization of various metals (e.g., Au, Cr, Ni, and Ag). Natural concentrations of soils must be known to correctly assess the impact of mining. We studied the soils of the Rio Itapicuru Greenstone Belt (RIGB), of Paleoproterozoic age, sampling at 24 sites (0-0.20m) in the areas not or minimally human impacted, equally distributed in the three units of the RIGB: Volcanic Mafic Unit (VMU), Volcanic Felsic Unit (VFU), and Volcano-clastic Sedimentary Unit (SU). The natural pseudo-total concentrations of Cr, Ni, Cu, Zn, Pb, Fe, and Mn were obtained by acid digestion (EPA3050b) both in the soil and the particle-size fractions (sand and clay+silt). The concentrations of metals in RIGB soils, especially Cr and Ni, are generally higher than those reported for other regions of Brazil or other countries. Even the sedimentary soils have relatively high metal values, naturally contaminated by the VMU of the RIGB; a potential impact on Mesozoic and Cenozoic sedimentary rocks located near the study region is highly expected. Metals are concentrated (80%) in the fine particle-size fraction, implying an easy availability through surface transport (wind and runoff). We introduced a new index, called the Fe-independent accumulation factor - AF -Fe , which reveals that 90-98% of the dynamics of the trace metals is associated with the iron geochemical cycle. We primarily conclude that determining the guideline values for different soil classes in variable geological/geochemical environment and under semiarid climate is meaningless: the concentration of metals in soils is clearly more related to the source material than to the pedogenesis processes. Copyright © 2017 Elsevier B.V. All rights reserved.

Contaminant behavior in fractured sedimentary rocks: Seeing the fractures that matter

NASA Astrophysics Data System (ADS)

Parker, B. L.

2017-12-01

High resolution spatial sampling of continuous cores from sites contaminated with chlorinated solvents over many decades was used as a strategy to quantify mass stored in low permeability blocks of rock between hydraulically active fractures. Given that core and geophysical logging methods cannot distinguish between hydraulically active fractures and those that do not transmit water, these samples were informed by careful logging of visible fracture features in the core with sample spacing determined by modelled diffusion transport distances given rock matrix properties and expected ages of contamination. These high resolution contaminant concentration profiles from long term contaminated sites in sedimentary rock showed evidence of many more hydraulically active fractures than indicated by the most sophisticated open-hole logging methods. Fracture density is an important attribute affecting fracture connectivity and influencing contaminant plume evolution in fractured porous sedimentary rock. These contaminant profile findings were motivation to find new borehole methods to directly measure hydraulically active fracture occurrence and flux to corroborate the long term "DNAPL tracer experiment" results. Improved sensitivity is obtained when boreholes are sealed using flexible fabric liners (FLUTeTM technology) and various sensor options are deployed in the static water columns used to inflate these liners or in contact with the borehole wall behind the liners. Several methods rely on high resolution temperature measurements of ambient or induced temperature variability such as temperature vector probes (TVP), fiber optic cables for distributed temperature sensing (DTS), both using active heat; packer testing, point dilution testing and groundwater flux measurements between multiple straddle packers to account for leakage. In all cases, numerous hydraulically active fractures are identified over 100 to 300 meters depth, with a large range in transmissivities and hydraulic apertures to inform discrete fracture flow and transport models. 3-D field mapping of decades-old contaminant plumes in sedimentary aquifers shows that numerous hydraulically active fractures are needed to reproduce observed plume concentration distributions and allow targeted monitoring and remediation.

Geomorphic origin of Merritt Island-Cape Canaveral, Florida, USA: A paleodelta of the reversed St. Johns River?

NASA Astrophysics Data System (ADS)

Adams, Peter N.

2018-04-01

The Merritt Island-Cape Canaveral (MICCSC) sedimentary complex consists of a series of adjacent, non-conformable, beach ridge sets that suggest a multi-phase constructional history, but the feature's geomorphic and sedimentary origins are not well-understood. In spite of its notable sedimentary volume (surface area = 1200 km2), the MICCSC lacks a clear sediment source, or supply mechanism, to explain its presence today. Previously published U/Th, radiocarbon and OSL dates indicate that beach ridge deposition was active during MIS 5 (130-80 ka) on Merritt Island, but has occurred over a shorter, younger time interval on Cape Canaveral proper (6 ka to present). In this paper, it is proposed that the MICCSC is an abandoned paleodelta whose fluvial source provided a sediment supply sufficient for coastal progradation. Although the MICCSC, today, does not receive an appreciable sediment supply, the nearly 23,000 km2 drainage basin of the St. Johns River may well have provided such a sediment supply during MIS 5 times. This low-gradient fluvial system currently empties to the Atlantic Ocean some 200 km north of the MICCSC (near Jacksonville, Florida) but may have flowed southward during the time of MICCSC sedimentary construction, then experienced flow reversal since MIS 5 times. Three possible uplift mechanisms are proposed to explain the northward down-tilting that may have reversed the flow direction of the St. Johns, abandoning deltaic construction of the MICCSC: (1) karst-driven, flexural isostatic uplift in response to carbonate rock dissolution in central Florida, (2) glacio-hydro-isostatic tilting/back-tilting cycles during loading and unloading of the Laurentide ice sheet during the Pleistocene, and (3) mantle convection-driven dynamic topography operating within southeastern North America since the Pliocene. This example testifies to the sensitivity of low-gradient, low-relief landscapes to various sources of uplift, be they isostatic or otherwise.

3D depth-to-basement and density contrast estimates using gravity and borehole data

NASA Astrophysics Data System (ADS)

Barbosa, V. C.; Martins, C. M.; Silva, J. B.

2009-05-01

We present a gravity inversion method for simultaneously estimating the 3D basement relief of a sedimentary basin and the parameters defining the parabolic decay of the density contrast with depth in a sedimentary pack assuming the prior knowledge about the basement depth at a few points. The sedimentary pack is approximated by a grid of 3D vertical prisms juxtaposed in both horizontal directions, x and y, of a right-handed coordinate system. The prisms' thicknesses represent the depths to the basement and are the parameters to be estimated from the gravity data. To produce stable depth-to-basement estimates we impose smoothness on the basement depths through minimization of the spatial derivatives of the parameters in the x and y directions. To estimate the parameters defining the parabolic decay of the density contrast with depth we mapped a functional containing prior information about the basement depths at a few points. We apply our method to synthetic data from a simulated complex 3D basement relief with two sedimentary sections having distinct parabolic laws describing the density contrast variation with depth. Our method retrieves the true parameters of the parabolic law of density contrast decay with depth and produces good estimates of the basement relief if the number and the distribution of boreholes are sufficient. We also applied our method to real gravity data from the onshore and part of the shallow offshore Almada Basin, on Brazil's northeastern coast. The estimated 3D Almada's basement shows geologic structures that cannot be easily inferred just from the inspection of the gravity anomaly. The estimated Almada relief presents steep borders evidencing the presence of gravity faults. Also, we note the existence of three terraces separating two local subbasins. These geologic features are consistent with Almada's geodynamic origin (the Mesozoic breakup of Gondwana and the opening of the South Atlantic Ocean) and they are important in understanding the basin evolution and in detecting structural oil traps.

Permo-Carboniferous sedimentary basins related to the distribution of planetary cryptoblemes

USGS Publications Warehouse

Windolph, J.F.

1997-01-01

Massive/high velocity solar, galactic, and cosmic debris impacting the Earths surface may account for the enormous energy required for the formation of Permo-Carboniferous sedimentary basins and related mountain building orogenies. Analysis of satellite immagry, sea floor sonar, geophysical data, and geotectonic fabrics show a strong correlation throughout geologic time between sedimentary basin origin and planetary cryptoblemes. Cryptoblemes are subtile, multi-ringed, radial centric impact shock signatures covering the entire terrestrial surface and ocean floors, having a geometry and distribution strikingly similar to the surfaces of the lunar planetary bodies in the solar system. Investigations of Permo-Carboniferous basins show an intensely overprinted pattern of cryptoblemes coinciding with partial obliteration and elliptical compression of pre-existing basins and accompanying shock patterns. Large distorted cryptoblemes may incorporate thin skin deformation, localized sediment diagenesis, regional metamorphism, and juxtaposed exotic terrains. These data, related to basin morphogenic symmetry, suggest that large episodic impact events are the primary cause of tectonogenic features, geologic boundary formation and mass extinction episodes on the planet Earth. Plate tectonics may be only a slow moving, low energy secondary effect defined and set in motion by megacosmic accretion events. Permo-Carboniferous sediments of note are preserved or accumulated in relatively small rectangular to arcuate rift valleys and synclinal down warps, such as the Narraganset basin of Massachusetts, USA, and Paganzo basin in Argentina, S.A. These deposits and depocenters may originate from dynamic reinforcement/cancellation impact effects, as can be seen in the Basin Range of Nevada and Utah, USA. Large circular to oval sedimentary basins commonly include internal ring structures indicating post depositional subsidence and rebound adjustments with growth faulting, notable in the Illinois basin USA and Ordos basin in China. Recent impact events on the planet Jupiter, July 1994, lend increasing support towards an impact orogenic geologic paradigm on the planet Earth.

Do river channels decrease in width downstream on Distributive Fluvial Systems? An evaluation of modern mega-fans

NASA Astrophysics Data System (ADS)

Espinoza, T. N.; Scuderi, L. A.; Weissmann, G. S.; Hartley, A. J.

2014-12-01

Recent studies on aggradational continental sedimentary basins globally show that fluvial deposits in most modern sedimentary basins are dominated Distributive Fluvial Systems (DFS). DFS's are identified by: (1) pattern of channels and floodplain deposits that radiate outward from an apex located where the river enters the sedimentary basin, (2) deposition where an alluvial system becomes unconfined upon entering the sedimentary basin, (3) broadly fan shaped deposit that is convex upward across the DFS and concave upward down-fan, and (4) if the DFS is incised, an intersection point above which the alluvial system is held in an incised valley and below which it distributes sediment across an active depositional lobe. Several papers about DFS hypothesized that rivers on DFS decrease in size down-fan. We are testing this hypothesis through evaluation of LANDSAT and STRM data from large DFS described by Hartley et al (2010). We use ArcGIS to: (1) open the images and merge them together if there are more than one image corresponding to the DFS being studied, (2) use a Maximum Likelihood Analysis in six classes to segment different features on the DFS (e.g. exposed sands, water, vegetation, and other fan environments), (3) isolate the classes that correspond to the active channel belt (e.g., exposed sand bars and water), (4) divide the active channel belt into 1000 m long sections, (5) determine the area of active channel belt in each section, and (6) calculate the average width of the river in each section (e.g., W = area/1000m). We present our result for each DFS river on a graph that shows the change in width downstream. Our final product will be a dataset that contains width versus distance down-fan from the apex for as many of the large DFS from Hartley et al (2010) as possible. If the hypothesis is supported, the decrease in width could have a substantial predictive significance on sandstone geometry in fluvial successions.

Circum-North Pacific tectonostratigraphic terrane map

USGS Publications Warehouse

Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Baranov, Boris B.; Byalobzhesky, Stanislav G.; Bundtzen, Thomas K.; Feeney, Tracey D.; Fujita, Kazuya; Gordey, Steven P.; Grantz, Arthur; Khanchuk, Alexander I.; Natal'in, Boris A.; Natapov, Lev M.; Norton, Ian O.; Patton, William W.; Plafker, George; Scholl, David W.; Sokolov, Sergei D.; Sosunov, Gleb M.; Stone, David B.; Tabor, Rowland W.; Tsukanov, Nickolai V.; Vallier, Tracy L.; Wakita, Koji

1994-01-01

after accretion of most terranes in the region; (2) Cenozoic and Mesozoic basinal deposits that occur within a terrane or on the craton; (3) plutonic rocks. The postaccretion igneous units are identified by age-lithologic abbreviations and by name. These overlap assemblages and basinal deposits formed mainly during sedimentation and magmatism that occurred after accretion of terranes to each other or to a continental margin. Overlap assemblages provide minimum ages on the timing of accretion of terranes. Some Cenozoic and Mesozoic overlap assemblages and basinal deposits, as well as fragments of terranes, are extensively offset by movement along postaccretion faults. In addition, in onshore areas, the map depicts major preaccretion plutonic rocks that are limited to individual terranes. and in offshore areas. the map depicts major oceanic plates,-ocean floor magnetic lineations. oceanic spreading ridges, and seamounts. The map consists of five sheets. Sheets I and 2 depict, at a scale of I :5.000.000. the tectonostratigraphic terranes. preaccretion plutonic rocks, and postaccretion Cenozoic and Mesozoic overlap sedimentary, volcanic. and plutonic assemblages, and basinal deposits for the Circum- orth Pacific including the Russian Far East, northern Hokkaido Island of Japan, Alaska. the Canadian Cordillera, part of the U.S.A. Pacific Northwest. and adjacent offshore areas. Sheet 3 provides the list of map units for Sheets I and 2. Sheet 4 is a index map showing generalized onshore terranes and overlap assemblages for onshore parts of the Circum-North Pacific at a scale of I: I 0,000,000. Sheet 4 is a guide to the more complicated onshore features depicted on Sheets I and 2. Sheet 5 is an index map showing the major geographic regions for the Circum-North Pacific. Significant differences exist between the representation of onshore and offshore geology on Sheets I and 2. These are: (I) compared to the onshore part of the map, the offshore part is depicted in a more schematic fashion because of more limited data and because the offshore terranes and early Cenozoic and older overlap assemblages generally are obscured by extensive late Cenozoic sedimentary cover that is not shown unless thicker than two kilometers; (2) marginal contacts of offshore Cenozoic and Cretaceous sedimentary basins do not match contacts of onshore Cenozoic and Cretaceous sedimentary units because offshore basins are limited to those regions with sediment thicknesses greater than two kilometers; (3) stratigraphic columns, included at the end of this explanation. are provided only for onshore terranes because the geology of offshore terranes is generally less well-known; and (4) for simplicity, the major onshore Cenozoic sedimentary basins are generally not defined and described separately because the onshore part of the map is designed to emphasize terranes and overlap volcanic assemblages that are crucial for both for tectonic and metallogenic analyses published elsewhere (Nokleberg and others, 1993, 1994a). Several key geologic sources were used in the compilation of the map. For Alaska. the basic outcrop pattern for the map is from Beikman (1980), Gehrels and Berg (1992, 1994). Barker and others ( 1994). Brew (1994), and Moli-Stalcup and others ( 1994b). The distribution of terranes is from Jones and others (1987) and Monger and Berg (1987), with modification by Grantz and other (1991 ). Worall (199 1 ), okleberg and others (1993, 1994a), the cited references, and the Alaskan co-authors of this report. For the Canadian Cordillera. the basic outcrop pattern is from Monger and Berg ( 1987), Wheeler and other (1988). and Wheeler and McFeeley ( 1991) with modifications by the Canadian authors. For the northern part of the Russian Far East. the basic outcrop pattern is from So unov (1985) with modifications by the Russian authors. For the outhern part of the Russian Far East, the basic outcrop pattern is from Krasny (1991) and Bazhanov and Oleinik ( 1986) with modification by the Russian authors. The Russian Far East part of the map is the first attempt to define and delineate terranes in that region. In their compilation. the Russian authors utilized the methodology of U.S.A. and Canadian geologists. Because this map is the first attempt to display the terranes. Cenozoic and Mesozoic overlap assemblages. basinal deposit , and plutonic belts of the Russian Far East. the Russian author will appreciate constructive sugge tions for improving the map.

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.

Detailed structure and tectonics of the Ninetyeast Ridge near Site ODP 758 (on new geophysical data from KNOX06RR cruise of R/V Roger Revelle)

NASA Astrophysics Data System (ADS)

Levchenko, O.; Eisin, A. E.; Ivanenko, A. N.; Marinova, J. G.; Paul, C. F.; Sborshchikov, I. M.; Sager, W. W.

2008-12-01

Detailed geophysical survey was carried out during the NSF-funded KNOX06RR cruise of R/V Roger Revelle in July 2007 over the ~70×70 km area near ODP Site 758, the northern Ninetyeast Ridge (NER). In addition to multibeam echo-sounder bathymetry, 3.5 kHz echo-sounder profiles, magnetic, and gravity data, high-resolution multichannel seismic reflection data were collected on eight orthogonal profiles of total length ~270 km. Large NE-trending depressions with complicated horst and graben morphology dominate the whole detailed survey area. The numerous basement faults extend upward into overlying sediments filling out these depressions. Thickness of the sedimentary fill is highly variable due to very rough basement topography, and is up to 800 m maximum. This fill is divided in two clear sedimentary layers: transparent pelagic sediments above and stratified shallow-water ones below. Two high ~400-450 m isometric seamounts extend from the surrounding NER seafloor. High-resolution seismic records show that these igneous basement highs are covered by thin transparent pelagic sediments which hamper the dredging of volcanic rocks. Seismic stratigraphy analyses for sedimentary cover over the seamounts buried slopes suggest that they seem to be recent volcanoes superimposed on the main NER edifice. Both volcanoes are clearly delineated in the constructed map of total anomaly magnetic field. Since water depths are ~2.5 km above these seamounts, the lower edge of the magnetic body in these volcanoes is situated deep at ~7 km under sea level. That appears to represent deep roots of the volcanoes. Preliminary magnetic modeling shows that they were generated during negative chron of the geomagnetic scale rather not long ago and not far from their present location, seeming to confirm the inference that these volcanoes are recent in origin. In general, one may assume a secondary phase of magmatic activity on the NER. It is important to reveal, any recent phase of tectonic and magnetic activity occurred over the northern NER during the same time of well-known intense intraplate deformation in the Central Indian Basin which was initiated ~8 Ma in response to growing regional compression due to continental collision Hindustan and Eurasia. It appears to be nonrandom that this NER segment is located in an anomalous zone of high oceanic intraplate seismicity. Seismic stratigraphy analyses of high-resolution seismic records over the fault features simultaneously with careful study of reflectors on the buried slopes of the recent volcanoes will allow us to examine this problem.

Characterization of Sedimentary Deposits Using usSEABED for Large-scale Mapping, Modeling and Research of U.S.Continental Margins

NASA Astrophysics Data System (ADS)

Williams, S. J.; Reid, J. A.; Arsenault, M. A.; Jenkins, C.

2006-12-01

Geologic maps of offshore areas containing detailed morphologic features and sediment character can serve many scientific and operational purposes. Such maps have been lacking, but recent computer technology and software to capture diverse marine data are offering promise. Continental margins, products of complex geologic history and dynamic oceanographic processes, dominated by the Holocene marine transgression, contain landforms which provide a variety of important functions: critical habitats for fish, ship navigation, national defense, and engineering activities (i.e., oil and gas platforms, pipeline and cable routes, wind-energy sites) and contain important sedimentary records. Some shelf areas also contain sedimentary deposits such as sand and gravel, regarded as potential aggregate resources for mitigating coastal erosion, reducing vulnerability to hazards, and restoring ecosystems. Because coastal and offshore areas are increasingly important, knowledge of the framework geology and marine processes is useful to many. Especially valuable are comprehensive and integrated digital databases based on data from original sources in the marine community. Products of interest are GIS maps containing thematic information such as seafloor physiography, geology, sediment character and texture, seafloor roughness, and geotechnical engineering properties. These map products are useful to scientists modeling nearshore and shelf processes as well as planners and managers. The USGS with partners is leading a Nation-wide program to gather a wide variety of extant marine geologic data into the usSEABED system (http://walrus.wr.usgs/usseabed). This provides a centralized, fully integrated digital database of marine geologic data collected over the past 50 years by USGS, other federal and state agencies, universities and private companies. To date, approximately 325,000 data points from the U.S. EEZ reside in usSEABED. The usSEABED, which combines a broad array of physical data and information (both analytical and descriptive) about the sea floor, including sediment textural, statistical, geochemical, geophysical, and compositional information, is available to the marine community through USGS Data Series publications. Three DS reports for the Atlantic (DS-118), Gulf of Mexico (DS-146) and Pacific(DS-182) were published in 2006 and reports for HI and AK are forthcoming. The use of usSEABED and derivative map products are part of ongoing USGS efforts to conduct regional assessments of potential marine sand and gravel resources, map benthic habitats, and support research in understanding seafloor character and mobility, transport processes and natural resources.

Altitude of the Top of the Madison Limestone in the Black Hills area, South Dakota, 1999

USGS Publications Warehouse

Carter, Janet M.; Redden, Jack A.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and groundwater in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study arca arc Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and artesian springs that originate from confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the altitude of the top (structure contours) of the Madison Limestone within the area of the Black Hills Hydrology Study. The depth to the top of the Madison Limestone can be estimated at a specific site by subtracting the altitude of the top of the formation from the topographic elevation. However, caution is urged in determining the depth to the top of the formation in areas on the map where the contours are approximately located.

Altitude of the Top of the Deadwood Formation in the Black Hills area, South Dakota, 1999

USGS Publications Warehouse

Carter, Janet M.; Redden, Jack A.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and artesian springs that originate from confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the altitude of the top (structure contours) of the Deadwood Formation within the area of the Black Hills Hydrology Study. The depth to the top of the Deadwood Formation can be estimated at a specific site by subtracting the altitude of the top of the formation from the topographic elevation, However, caution is urged in determining the depth to the top of the formation in areas on the map where the contours are approximately located.

Altitude of the Top of the Minnelusa Formation in the Black Hills area, South Dakota, 1999

USGS Publications Warehouse

Carter, Janet M.; Redden, Jack A.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and ground water in the Black Hills area of South Dakota (Driscoll, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara, Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and artesian springs that originate from confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the altitude of the top (structure contours) of the Minnelusa Formation within the area of the Black Hills Hydrology Study. The depth to the top of the Minnelusa Formation can be estimated at a specific site by subtracting the altitude of the top of the formation from the topographic elevation. However, caution is urged in determining the depth to the top of the formation in areas on the map where the contours are approximately located.

Altitude of the Top of the Minnekahta Limestone in the Black Hills area, South Dakota, 1999

USGS Publications Warehouse

Carter, Janet M.; Redden, Jack A.

2000-01-01

This map is a product of the Black Hills Hydrology Study, which was initiated in 1990 to assess the quantity, quality, and distribution of surface water and groundwater in the Black Hills area of South Dakota (Driscoli, 1992). This long-term study is a cooperative effort between the U.S. Geological Survey (USGS), the South Dakota Department of environment and Natural Resources, and the West Dakota Water development District, which represents various local and county cooperators. This map is part of a series of 1:100,000-scale maps for the study. The maps include a hydrogeologic map, structure-contour maps (altitudes of the tops of formations) for five formations that contain major aquifers in the study area, and potentiometric maps for these five major aquifers (the Inyan Kara. Minnekahta, Minnelusa, Madison, and Deadwood aquifers).The study area consists of the topographically defined Black Hills and adjacent areas located in western South Dakota. The Black Hills area is an elongated, dome-shaped feature, about 125 miles long and 60 miles wide, which was uplifted during the Laramide orogeny (Feldman and Heimlich, 1980). The oldest geologic units in the study area are Precambrian metamorphic and igneous rocks, which are exposed in the central core of the Black Hills. Surrounding the Precambrian core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly concentric rings around the uplifted flanks of the Black Hills. The bedrock sedimentary units typically dip away from the uplifted Black Hills at angles that approach or exceed 10 degrees near the outcrops, and decrease with distance from the uplift. Many of the sedimentary units contain aquifers, both within and beyond the study area. Recharge to these aquifers occurs from infiltration of precipitation upon the outcrops and, in some cases, from infiltration of streamflow (Hortness and Driscoll, 1998). Artesian conditions generally exist within these aquifers where an upper confining layer is present. Flowing wells and artesian springs that originate from confined aquifers are common around the periphery of the Black Hills.The purpose of this map is to show the altitude of the top(structure contours) of the Minnekahta limestone within the area of the Black Hills Hydrology Study. The depth to the top of the Minnekahta Limestone can be estimated at a specific site by subtracting the altitude of the top of the formation from the topographic elevation. However, caution is urged in determining the depth to the top of the formation in areas on the map where the contours are approximately located.

Crustal structure and evolution of the Mawson Sea, western Wilkes Land margin, East Antarctica

USGS Publications Warehouse

Leitchenkov, G.L.; Gandyukhin, V.V.; Guseva, Yu. B.; Kazankov, A. Yu

2007-01-01

3 to 11 mm/yr. Three major unconformities are identified in the sedimentary cover of the Mawson Sea and are interpreted to be caused by break-up between Australia and Antarctica at about 81 Ma ago (WL1), the first arrival of the ice sheet to the Mawson Sea (WL3) and continental scale glaciation at about 34 Ma ago (WL4).

Diverse Deposits in Melas Chasma

NASA Image and Video Library

2015-07-29

This scene captured by NASA Mars Reconnaissance Orbiter includes chaotic deposits with a wide range of colors. The deposits are distinctive with both unique colors and small-scale textures such as fracture patterns. These are probably sedimentary rocks, transported and deposited in water or air. The original layers may have been jumbled in a landslide. Dark or reddish sand dunes cover some of the bedrock. http://photojournal.jpl.nasa.gov/catalog/PIA19860

Chitin Lengthens Power Production in a Sedimentary Microbial Fuel Cell

DTIC Science & Technology

2014-01-01

sulfate-reducing bacteria; marine I. INTRODUCTION Ocean-based energy recovery devices are often based on kinetic or solar energy harvesting . In...enhancement would scale with an increase in system size. More work is also planned on improving energy harvesting efficiency and understanding the...utilization by marine bacteria. Degradation and catabolism of chitin oligosaccharides by Vibrio furnissii,” J Biol Chem, 1991. vol 266, pp. 24276-24286

Large short-term deviations from dipolar field during the Levantine Iron Age Geomagnetic Anomaly ca. 1050-700 BCE

NASA Astrophysics Data System (ADS)

Shaar, R.; Tauxe, L.; Ebert, Y.

2017-12-01

Continuous decadal-resolution paleomagnetic data from archaeological and sedimentary sources in the Levant revealed the existence a local high-field anomaly, which spanned the first 350 years of the first millennium BCE. This so-called "the Levantine Iron Age geomagnetic Anomaly" (LIAA) was characterized by a high averaged geomagnetic field (virtual axial dipole moments, VADM > 140 Z Am2, nearly twice of today's field), short decadal-scale geomagnetic spikes (VADM of 160-185 Z Am2), fast directional and intensity variations, and substantial deviation (20°-25°) from dipole field direction. Similar high field values in the time frame of LIAA have been observed north, and northeast to the Levant: Eastern Anatolia, Turkmenistan, and Georgia. West of the Levant, in the Balkans, field values in the same time are moderate to low. The overall data suggest that the LIAA is a manifestation of a local positive geomagnetic field anomaly similar in magnitude and scale to the presently active negative South Atlantic Anomaly. In this presentation we review the overall archaeomagnetic and sedimentary evidences supporting the local anomaly hypothesis, and compare these observations with today's IGRF field. We analyze the global data during the first two millennia BCE, which suggest some unexpected large deviations from a simple dipolar geomagnetic structure.

Magma-driven antiform structures in the Afar rift: The Ali Sabieh range, Djibouti

NASA Astrophysics Data System (ADS)

Le Gall, Bernard; Daoud, Mohamed Ahmed; Maury, René C.; Rolet, Joël; Guillou, Hervé; Sue, Christian

2010-06-01

The Ali Sabieh Range, SE Afar, is an antiform involving Mesozoic sedimentary rocks and synrift volcanics. Previous studies have postulated a tectonic origin for this structure, in either a contractional or extensional regime. New stratigraphic, mapping and structural data demonstrate that large-scale doming took place at an early stage of rifting, in response to a mafic laccolithic intrusion dated between 28 and 20 Ma from new K-Ar age determinations. Our 'laccolith' model is chiefly supported by: (i) the geometry of the intrusion roof, (ii) the recognition of roof pendants in its axial part, and (iii) the mapping relationships between the intrusion, the associated dyke-sill network, and the upper volcanic/volcaniclastic sequences. The laccolith is assumed to have inflated with time, and to have upwardly bent its sedimentary roof rocks. From the architecture of the ˜1 km-thick Mesozoic overburden sequences, ca. 2 km of roof lifting are assumed to have occurred, probably in association with reactivated transverse discontinuities. Computed paleostress tensors indicate that the minimum principal stress axis is consistently horizontal and oriented E-W, with a dominance of extensional versus strike-slip regimes. The Ali Sabieh laccolith is the first regional-scale magma-driven antiform structure reported so far in the Afro-Arabian rift system.

Aptian sedimentation in the Recôncavo-Tucano-Jatobá Rift System and its tectonic and paleogeographic significance

NASA Astrophysics Data System (ADS)

Freitas, Bernardo T.; Almeida, Renato P.; Carrera, Simone C.; Figueiredo, Felipe T.; Turra, Bruno B.; Varejão, Filipe G.; Assine, Mario L.

2017-12-01

This study, based on detailed sedimentologic and stratigraphic analysis of the Aptian succession preserved in the Recôncavo-Tucano-Jatobá Rift System (RTJ), present new elements for biostratigraphic correlation and paleogeographic reconstruction in the mid-Cretaceous South Atlantic realm, supporting novel interpretations on the tectonic and sedimentary evolution related to the W-Gondwana breakup. The Aptian sedimentary succession in the RTJ has been referred to as Marizal Formation, and interpreted as post-rift deposits. Detailed sedimentologic and stratigraphic studies of these deposits enabled the recognition and individualization of two distinctive sedimentary units that can be traced in the entire RTJ. These units are here described and named Banzaê and Cícero Dantas members of the Marizal Formation. Their contact is locally marked by the fossiliferous successions of the here proposed Amargosa Bed, lying at the top of the Banzaê Member. Both members of the Marizal Formation record large river systems captured by the Tucano Basin with the local development of eolian dune fields and fault-bounded alluvial fans. The Amargosa Bed represents a regional-scale base level change preserved between the Aptian fluvial successions along the RTJ. Hence, the studied sedimentary record presents important implications for the timing and direction of marine ingressions affecting NE-Brazil interior basins during the Aptian. A remarkable contrast in preserved fluvial architecture between the Banzaê Member, characterized by connected channel bodies, and the Cícero Dantas Member, characterized by isolated channel bodies within overbank fines, is here reported. The main interpreted control for the observed contrast in fluvial stratigraphy is sedimentary yield variation. The interval is also subject to the interpretation of a regional shift in the mechanism responsible for the subsidence of the basins formed during the Cretaceous break-up of the Central South Atlantic. This view is challenged by our results which reveal that basin forming extension continued throughout the Aptian. As a conclusion, the detailed stratigraphy of the Marizal Formation forward alternative geodynamic interpretations for the Aptian successions in northeastern Brazil, bringing new elements to the mid-Cretaceous biogeographical, paleogeographical and tectonic reconstructions of western Gondwana.

A multi-factor approach for process-based seabed characterization: example from the northeastern continental margin of the Korean peninsula (East Sea)

NASA Astrophysics Data System (ADS)

Cukur, Deniz; Um, In-Kwon; Chun, Jong-Hwa; Kim, So-Ra; Lee, Gwang-Soo; Kim, Yuri; Kong, Gee-Soo; Horozal, Senay; Kim, Seong-Pil

2018-04-01

This study investigates sediment transport and depositional processes from a newly collected dataset comprising sub-bottom chirp profiles, multibeam bathymetry, and sediment cores from the northeastern continental margin of Korea in the East Sea (Japan Sea). Twelve echo-types and eleven sedimentary facies have been defined and interpreted as deposits formed by shallow-marine, hemipelagic sedimentation, bottom current, and mass-movement processes. Hemipelagic sedimentation, which is acoustically characterized by undisturbed layered sediments, appears to have been the primary sedimentary process throughout the study area. The inner and outer continental shelf (<150 m water depth) have been influenced by shallow-marine sedimentary processes. Two slope-parallel canyons, 0.2-2 km wide and up to 30 km long, appear to have acted as possible conduits for turbidity currents from the shallower shelf into the deep basins. Bottom current deposits, expressed as erosional moats immediately below topographic highs, are prevalent on the southern lower slope at water depths of 400-450 m. Mass-movements (i.e., slides/slumps, debris flow deposits) consisting of chaotic facies characterize the lower slope and represent one of the most important sedimentary processes in the study area. Piston cores confirm the presence of mass-transport deposits (MTDs) that are characterized by mud clasts of variable size, shape, and color. Multibeam bathymetry shows that large-scale MTDs are chiefly initiated on the lower slope (400-600 m) with gradients up to 3° and where they produce scarps on the order of 100 m in height. Sandy MTDs also occur on the upper continental slope adjacent to the seaward edge of the shelf terrace. Earthquakes associated with tectonic activity and the development of fluid overpressure is considered as the main conditioning factor for destabilizing the slope sediments. Overall, the sedimentary processes show typical characteristics of a fine-grained clastic slope apron and change down-slope and differ within each physiographic province. Furthermore, the influence of geological inheritance (i.e., structural folds and faults) on geomorphology and sediment facies development is an important additional factor on the lower slopes. Together, these factors provide a rational basis for continental margin seabed characterization.

Sediment Transport and Landscape Evolution on Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Birch, S.; Umurhan, O. M.; Hayes, A.; Tang, Y.; Moore, J. M.; White, O. L.

2017-12-01

New observations from ESA's Rosetta orbiter of comet 67P/Churyumov-Gerasimenko (67P) have revolutionized our understanding of these primitive bodies and the processes that act to modify their surfaces. Centimeter to meter scale images of the surface of 67P have revealed a diverse sedimentary world, where the dominant landforms consist of vertical, consolidated cliffs and pits interspersed, and in the northern hemisphere buried, by smooth, decameter thick sedimentary deposits. Sublimation erosion, in the form of jets, from exposed cliff faces acts to break off parts of the weakened bedrock material, which then accumulate as mass wasting deposits at the cliff bases. The large boulders within these deposits may also contribute to the jets, as volatiles in exposed faces of the boulders, previously hidden from the Sun, can sublimate away. During a jet event, the less volatile material that does not escape the comet falls back and drapes the rocky surface as smooth deposits. This is particularly evident in the northern hemisphere of 67P and within gravitational lows, where the underlying consolidated material appears to outcrop from underneath a vast cover of sedimentary deposits. These sedimentary materials, having a low thermal inertia, counteracts the erosive process, and allows for the surface of 67P to retain a relatively primitive form to the current day. To understand this process quantitatively, and constrain over what timescale(s) the surface of 67P evolves, we utilized high-resolution photoclinometry digital terrain models ( 14 cm/pixel), and the MARSSIM landscape evolution model, adapted for a low, and variable gravity environment. Perfectly suited to model sublimation erosion and mass-wasting, MARSSIM also allows us to track the re-condensation of non-volatile materials to accurately account for the important feedback played by the sedimentary deposits. These simulations will allow for us to constrain the rates of landscape evolution on 67P, to compare directly to observations of dynamic changes on the nucleus. Through this work, we will also be able to assess the question of whether 67P is primitive or not, using reasonable assumptions as to the volatility and strength of the bedrock materials.

The magnetic and mineralogical signature of the Deccan volcanism in the sedimentary record: a review

NASA Astrophysics Data System (ADS)

Font, Eric

2016-04-01

The contribution of the Deccan Traps volcanism in the Cretaceous-Palaeogene (KPg) crisis is still a matter of debate. The main limitation is the lack of mass extinction proxies within the Deccan lava flows, making hard the correlation of the onset of Deccan volcanism in India with the mass extinction recorded in the global marine record. An alternative is to investigate the magnetic and mineral assemblages of remote marine section. Iron oxides are very sensitive to changes in redox conditions, and thus can be possibly used as markers of paleoenvironmental changes driven by Deccan volcanism. This is the case in the Basque-Cantabric basin (Bidart, Zumaya) and the western margin of the Tethys (Gubbio), where an interval of low magnetic susceptibility (MS) containing akaganeite features in the last 50 cm just below the KPg boundary. The low MS interval originated from the loss of detrital and biogenic magnetites, features consistent with reductive iron oxide dissolution possibly linked to environmental acidification (acid rain and acidification of surficial waters). These insights provide new and promising benchmarks of the sedimentary imprint of the Deccan-induced paleoclimatic and paleoenvironmental changes. More importantly, the fact that the hypothesised Deccan perturbations occurred some 50 cm (~30,000 y.r.) before the KPg boundary suggest that Deccan volcanism may have contribute significantly to the KPg mass extinction. Keywords: Deccan, reductive iron oxide dissolution, akaganeite, KPg boundary, mass extinction Funded by IDL (FCT UID/GEO/50019/2013)

Recent carbonate firm- to hardgrounds in the Abu Dhabi lagoon: Environmental controls and petrography

NASA Astrophysics Data System (ADS)

Immenhauser, Adrian; Lokier, Stephen W.; Kwiecien, Ola; Riechelmann, Sylvia; Buhl, Dieter

2017-04-01

Marine carbonate firm- and hardgrounds have been described from the Precambrian to the recent sedimentary archive. In comparison to the numerous publications dealing with fossil case examples, well-constrained studies of shoalwater hardground formation from modern (sub)tropical seas are comparably scarce. This comes as a surprise as only modern depositional environments offer direct insight into the plethora of environmental, geochemical, kinetic, and biological parameters that affect these features at formation and during diagenetic pathways. Here, we present the first results of a combined field and laboratory study with focus on firm- to hardgrounds (also termed "discontinuity" in the sense of a catch-it-all term) forming both in the shallow inner lagoon and the outer lagoon ooid shoals of the Abu Dhabi barrier-island complex. Essentially, the discontinuities found represent sub-grounds in the sense that they form a few centimetres beneath the sediment surface. Sub-grounds in the outer lagoon ooid shoals are cemented by characteristic needle-shaped aragonite crystals and essentially represent lithified crab burrows. In contrast, sub-grounds in the inner lagoon of Abu Dhabi form brittle intervals, perhaps 5 cm in thickness, that are cemented by platy aragonitic crystals that show uncommon morphologies. Botryoids are abundant and generally seem to affect crystal morphologies. First evidence suggests that these features form below the uppermost oxic layer of pore fluids in the shallow sedimentary column. These findings are placed in context with temporally-resolved data on sea and porewater chemistry.

Earth Observations taken during Expedition 16/STS-120 Joint Operations

NASA Image and Video Library

2007-10-26

ISS016-E-008436 (26 Oct. 2007) --- Beirut Metropolitan Area, Lebanon is featured in this image photographed by an Expedition 16 crewmember on the International Space Station. The capital of Lebanon, Beirut is located along the southeastern shoreline of the Mediterranean Sea. According to geologists, the metropolitan area is built on a small peninsula composed mainly of sedimentary rock deposited over the past 100 million years or so. The growth of the city eastwards is bounded by foothills of the more mountainous interior of Lebanon (sparsely settled greenish brown region visible at upper right). While this sedimentary platform is stable, the country of Lebanon is located along a major transform fault zone, or region where the African and Arabian tectonic plates are moving laterally in relation to (and against) each other. This active tectonism creates an earthquake hazard for the country. The Roum Fault, one of the fault strands that is part of the transform boundary, is located directly to the south of the Beirut metropolitan area. Other distinctive features visible in this image include the Rafic Hariri Airport at lower right, the city sports arena at center, and several areas of green and open space (such a large golf course at center). Also visible in the image are several plumes of sediment along the coastline -- the most striking of which are located near the airport. The general lack of vegetation in the airport may promote higher degrees of soil transport by surface water runoff or wind.

Early Jurassic extensional inheritance in the Lurestan region of the Zagros fold-and-thrust belt, Iran.

NASA Astrophysics Data System (ADS)

Tavani, Stefano; Parente, Mariano; Vitale, Stefano; Puzone, Francesco; Erba, Elisabetta; Bottini, Cinzia; Morsalnejad, Davoud; Mazzoli, Stefano

2017-04-01

It has long been recognized that the tectonic architecture of the Zagros mountain belt was strongly controlled by inherited structures previously formed within the Arabian plate. These preexisting features span in age from the pre-Cambrian to the Mesozoic, showing different trends and deformation styles. Yet, these structures are currently not fully understood. This uncertainty is partly related with the paucity of exposures, which rarely allows a direct observation of these important deformation features. The Lurestan Province of Iran provides a remarkable exception, since it is one of the few places of the Zagros mountain belt where exposures of Triassic and Jurassic rocks are widespread. In this area we carried out structural observations on Mesozoic extensional structures developed at the southern margin of the Neo-Tethyan basin. Syn-sedimentary extensional faults are hosted within the Triassic-Cretaceous succession, being particularly abundant in the Jurassic portion of the stratigraphy. Early to Middle Jurassic syn-sedimentary faults are observed in different paleogeographic domains of the area, and their occurrence is coherent with the subsequent transition from shallow-water to deep-sea basin environments, observed in a wide portion of the area. Most of the thrusts exposed in the area may indeed be interpreted as reactivated Jurassic extensional faults, or as reverse faults whose nucleation was controlled by the location of preexisting normal faults, as a result of positive inversion during crustal shortening and mountain building.

A Late Pleistocene-Holocene wetland megafan in the Brazilian Amazonia

NASA Astrophysics Data System (ADS)

Rossetti, D. F.; Zani, H.; Cohen, M. C. L.; Cremon, É. H.

2012-12-01

Despite the growing interest in megafans, definitions provided for this type of environmental setting have not yet been widely agreed upon. A record of sedimentary facies distribution in both space and time including a larger number of analogs is particularly needed for improving megafan facies models. This work focuses on a large fan-like feature from an Amazonian wetland in northern Brazil. Morphological data based on remote sensing, as well as sedimentary facies and radiocarbon analyses, were integrated to propose that this feature is related to a megafan system active during the Late Pleistocene to Holocene. The megafan displays a divergent drainage network, gently-dipping slope, and concave-up and convex-up longitudinal and transverse profiles, respectively. Near surface deposits correspond to fining and coarsening upward sands related to active channels and overbank sand sheets/terminal fan lobes. Sediments are interbedded with abandoned channel/floodplain and lake/pond muds. Morphostructural analyses and drainage anomalies revealed a geological setting affected by reactivation of pre-existing faults contemporaneous with sediment accumulation. Establishment of a megafan system in this wetland most likely occurred within a slightly tectonically subsiding basin under favorable climatic conditions. During wet seasons, high water discharge would have favored sediment transport from highlands into this depositional site. High summer temperatures and drought under a monsoonal regime kept the water levels low. The described megafan could serve as an analog for contemporary tropical wetland megafans formed under a monsoonal climate regime.

Geologic map of the Jam Up Cave and Pine Crest quadrangles, Shannon, Texas, and Howell Counties, Missouri

USGS Publications Warehouse

Weary, David J.; Orndorff, Randall C.; Repetski, John E.

2013-01-01

The Jam Up Cave and Pine Crest 7.5-minute quadrangles are located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 2,400 to 3,100 feet (ft) of flat-lying to gently dipping Lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic igneous basement rocks. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Numerous karst features, such as sinkholes, caves, and springs, have formed in the carbonate rocks. Many streams are spring fed. The topography is a dissected karst plain with elevations ranging from about 690 ft where the Jacks Fork River exits the northeastern corner of the Jam Up Cave quadrangle to about 1,350 ft in upland areas along the north-central edge and southwestern corner of the Pine Crest quadrangle. The most prominent physiographic feature is the valley of the Jacks Fork River. This reach of the upper Jacks Fork, with its clean, swiftly-flowing water confined by low cliffs and bluffs, provides one of the most beautiful canoe float trips in the nation. Most of the land in the quadrangles is privately owned and used primarily for grazing cattle and horses and growing timber. A large minority of the land within the quadrangles is publicly owned by the Ozark National Scenic Riverways of the National Park Service. Geologic mapping for this investigation was conducted in 2005 and 2006.

Research core drilling in the Manson impact structure, Iowa

NASA Technical Reports Server (NTRS)

Anderson, R. R.; Hartung, J. B.; Roddy, D. J.; Shoemaker, E. M.

1992-01-01

The Manson impact structure (MIS) has a diameter of 35 km and is the largest confirmed impact structure in the United States. The MIS has yielded a Ar-40/Ar-39 age of 65.7 Ma on microcline from its central peak, an age that is indistinguishable from the age of the Cretaceous-Tertiary boundary. In the summer of 1991 the Iowa Geological Survey Bureau and U.S. Geological Survey initiated a research core drilling project on the MIS. The first core was beneath 55 m of glacial drift. The core penetrated a 6-m layered sequence of shale and siltstone and 42 m of Cretaceous shale-dominated sedimentary clast breccia. Below this breccia, the core encountered two crystalline rock clast breccia units. The upper unit is 53 m thick, with a glassy matrix displaying various degrees of devitrification. The upper half of this unit is dominated by the glassy matrix, with shock-deformed mineral grains (especially quartz) the most common clast. The glassy-matrix unit grades downward into the basal unit in the core, a crystalline rock breccia with a sandy matrix, the matrix dominated by igneous and metamorphic rock fragments or disaggregated grains from those rocks. The unit is about 45 m thick, and grains display abundant shock deformation features. Preliminary interpretations suggest that the crystalline rock breccias are the transient crater floor, lifted up with the central peak. The sedimentary clast breccia probably represents a postimpact debris flow from the crater rim, and the uppermost layered unit probably represents a large block associated with the flow. The second core (M-2) was drilled near the center of the crater moat in an area where an early crater model suggested the presence of postimpact lake sediments. The core encountered 39 m of sedimentary clast breccia, similar to that in the M-1 core. Beneath the breccia, 120 m of poorly consolidated, mildly deformed, and sheared siltstone, shale, and sandstone was encountered. The basal unit in the core was another sequence of sedimentary clast breccia. The two sedimentary clast units, like the lithologically similar unit in the M-1 core, probably formed as debris flows from the crater rim. The middle, nonbrecciated interval is probably a large, intact block of Upper Cretaceous strata transported from the crater rim with the debris flow. Alternatively, the sequence may represent the elusive postimpact lake sequence.

Provenance of Carboniferous sedimentary rocks in the northern margin of Dabie Mountains, central China and the tectonic significance: constraints from trace elements, mineral chemistry and SHRIMP dating of zircons

NASA Astrophysics Data System (ADS)

Li, Renwei; Li, Shuangying; Jin, Fuquan; Wan, Yusheng; Zhang, Shukun

2004-04-01

A suite of slightly metamorphosed Carboniferous sedimentary strata occurs in the northern margin of the Dabie Mountains, central China. It consists, in ascending order, of the upper Huayuanqiang Formation (C 1), the Yangshan Formation (C 1), the Daorenchong Formation (C 1-2), the most widely distributed Huyoufang Formation (C 2) and the Yangxiaozhuang Formation (C 2). The provenance of the Carboniferous sedimentary rocks is constrained by the integration of trace elements, detrital mineral chemistry and sensitive high resolution ion microprobe (SHRIMP) dating of detrital zircons, which can help to understand the connection between the provenance and the Paleozoic tectonic evolution of the Qinling-Dabie Orogen. The trace element compositions indicate that the source terrain was probably a continental island arc. Detrital tourmalines were mainly derived from aluminous and Al-poor metapelites and metapsammites, and some are sourced from Li-poor granitoids, pegmatites and aplites. Detrital garnets, found only in the uppermost Huyoufang Formation, are almandine and Mn-almandine garnets, indicating probable sources mainly from garnetiferous schists, and partly from granitoid rocks. The detrital white K-micas are muscovitic in the Huayuanqiang, Daorenchong and Huyoufang Formations, and phengitic with Si contents (p.f.u.) from 3.20 up to max. 3.47-3.53 in the uppermost Huyoufang and the Yangxiaozhuang Formations, a meta-sedimentary source. Major components in the detrital zircon age structure for the Huyoufang Formation range from 506 to 363 Ma, centering on ˜400 and ˜480 Ma, which is characteristic of the Qinling and Erlangping Groups in the Qinling and Tongbai Mountains, central China. Evidently, the major source of the Carboniferous sedimentary rocks in the northern margin of Dabie Mountains was from the southern margin of the Sino-Korean Craton represented by the Qinling and Erlangping Groups. The source area was an island-arc system during the Early Paleozoic that collided with the Sino-Korea plate towards the end of the Early Paleozoic or during the Devonian. A prominent feature in the detrital zircon age structure of the Huyoufang Formation is the Neoproterozoic detritus, which could be derived only from the Yangtze Craton. Reasonable interpretation of the two distinct source materials for the Huyoufang Formation is that the two plates were juxtaposed through collision before the late Carboniferous.

Cosmogenic Nuclides 10Be-21Ne Burial Dating of Middle Miocene Sedimentary Formation of the Hongliu Valley in Southern Ningxia Basin: A Case of Isotopic Geochronology Study for the Cenozoic Sedimentary Strata

NASA Astrophysics Data System (ADS)

Ma, Y.; Zhang, H.; Wang, W.; Wu, Y.; Pang, J.; Zheng, D.; Li, D.

2015-12-01

Chronology studies for the Cenozoic sedimentary strata based on the magnetostratigraphy cannot afford the unique chronological sequences in the absence of absolute ages from biostratigraphy or volcanic ash chronology. In situ-produced cosmogenic nuclides provide a powerful tool for the sediment dating based on the time-dependent concentration ratio of two nuclides, which are produced in the same mineral but with different half-lives. Thereinto, 10Be-26Al is the most widely used nuclide pairs, of which the available dating range spans the Plio-Pleistocene. But the coupling of 10Be with the stable nuclide 21Ne would significantly improve the burial dating range up to the middle Miocene, which is promising in revolutionizing the chronology study for the Late Cenozoic terrestrial sedimentary sequences. We have applied 10Be-21Ne pair for dating the middle Miocene sediments of the Hongliu Valley in southern Ningxia basin. Two major features of the sediments are involved in our study: (1) sediments originated from the steady erosion of the source area, and (2) the burial depth of our sample after deposition is time dependent due to the gradual accumulation of sediments into basin. The post-burial nuclide production is estimated to be less than 3%, including the contribution by muon interactions, of the total nuclide concentrations measured in our sample. Our 10Be-21Ne analysis demonstrates the age of the burial sample is 12.4(+0.6/-0.4) Ma, and the erosion rate at the source area is 0.26±0.01 cm ka-1. The sample's burial age is consistent with the age constraint set by the Hongliugou Formation (16.7-5.4 Ma) which we collected the sample in. Vertebrate fossils of Platybelodon tongxinensis with an age between 12 and 15 Ma exhumated along with our sample further verifies the reliability of our dating results for the middle Miocene sediments.This study has shown the improved age range of cosmogenic-nuclide burial dating method by incorporating the stable nuclide 21Ne, and has established the feasibility of 10Be-21Ne pair in chronology studies for the Cenozoic sedimentary strata.

Rates and cycles of microbial sulfate reduction in the hyper-saline Dead Sea over the last 200 kyrs from sedimentary d34S and d18O(SO4)

NASA Astrophysics Data System (ADS)

Torfstein, Adi; Turchyn, Alexandra V.

2017-08-01

We report the d34S and d18O(SO4) values measured in gypsum, pyrite, and elemental sulfur through a 456-m thick sediment core from the center of the Dead Sea, representing the last 200 kyrs, as well as from the exposed glacial outcrops of the Masada M1 section located on the margins of the modern Dead Sea. The results are used to explore and quantify the evolution of sulfur microbial metabolism in the Dead Sea and to reconstruct the lake’s water column configuration during the late Quaternary. Layers and laminae of primary gypsum, the main sulfur-bearing mineral in the sedimentary column, display the highest d34S and d18O(SO4) in the range of 13-28‰ and 13-30‰, respectively. Within this group, gypsum layers deposited during interglacials have lower d34S and d18O(SO4) relative to those associated with glacial or deglacial stages. The reduced sulfur phases, including chromium reducible sulfur, and secondary gypsum crystals are characterized by extremely low d34S in the range of -27 to +7‰. The d18O(SO4) of the secondary gypsum in the M1 outcrop ranges from 8 to 14‰. The relationship between d34S and d18O(SO4) of primary gypsum suggests that the rate of microbial sulfate reduction was lower during glacial relative to interglacial times. This suggests that the freshening of the lake during glacial wet intervals, and the subsequent rise in sulfate concentrations, slowed the rate of microbial metabolism. Alternatively, this could imply that sulfate-driven anaerobic methane oxidation, the dominant sulfur microbial metabolism today, is a feature of the hypersalinity in the modern Dead Sea. Sedimentary sulfides are quantitatively oxidized during epigenetic exposure, retaining the lower d34S signature; the d18O(SO4) of this secondary gypsum is controlled by oxygen atoms derived equally from atmospheric oxygen and from water, which is likely a unique feature in this hyperarid environment.