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1

Playlist: Sedimentology and Stratigraphy  

NSDL National Science Digital Library

A YouTube playlist created by Dr. Dawn Sumner of the University of California - Davis. This videos include short pieces from her lectures on sedimentology and stratigraphy as well as other videos she has found on YouTube about the subject.

Sumner, Dawn; Youtube

2

Relationships among sedimentology, stratigraphy, and diagenesis in the Proterozoic Thelon Basin, Nunavut, Canada: implications for  

E-print Network

Relationships among sedimentology, stratigraphy, and diagenesis in the Proterozoic Thelon Basin and paragenetic relationships vary systematically with sedimentology and stratigraphy of the Thelon and provide. Keywords: Diagenesis; Sedimentology; Thelon; Sequence stratigraphy; Hydrostratigraphy 0375-6742/03/$ - see

Hiatt, Eric E.

3

The Early Aptian of Aralar (northern Spain): stratigraphy, sedimentology, ammonite biozonation, and OAE1  

E-print Network

The Early Aptian of Aralar (northern Spain): stratigraphy, sedimentology, ammonite biozonation Stratigraphy Ammonite biozonation TOC Oceanic Anoxic Event 1 a b s t r a c t The stratigraphy, sedimentology. The sedimentology indicates general deposition in a shallow marine environment, corresponding to mixed siliciclastic

Gilli, Adrian

4

Sedimentology and sequence stratigraphy of reefs and carbonate platforms  

SciTech Connect

Classical sequence stratigraphy has been developed primarily from siliciclastic systems. Application of the concept to carbonates has not been as straightforward as was originally expected even though the basic tenets of sequence stratigraphy are supposed to be applicable to all depositional systems. Rather than force carbonate platforms into the straightjacket of a concept derived from another sediment family, this course takes a different tack. It starts out from the premise that sequence stratigraphy is a modern and sophisticated version of lithostratigraphy and as such is a sedimentologic concept. More sedimentology into sequence stratigraphy is the motto of the course and the red line that runs through the chapter of this book. The cook sets out with a review of sedimentologic in reference to petroleum deposits principles governing the large-scale anatomy of reefs and platforms. It then looks at sequences an systems tracts from a sedimentologic point of view, assesses the differences between siliciclastics and carbonates in their response to sea level, evaluates processes that compete with sea level for control on carbonate sequences, and finally presents a set of guidelines for application of sequence stratigraphy to reefs and carbonate platforms.

Schlager, W. (Free Univ., Amsterdam (NL))

1992-01-01

5

Reading and Abstracting Journal Articles in Sedimentology and Stratigraphy.  

ERIC Educational Resources Information Center

An assignment centered on reading journal articles and writing abstracts is an effective way to improve student reading and writing skills in sedimentology and stratigraphy laboratories. Each student reads two articles and writes informative abstracts from the author's point of view. (PR)

Conrad, Susan Howes

1991-01-01

6

Sedimentology and sequence stratigraphy of the Sturgeon Lake field, Alberta  

SciTech Connect

This study examines the sedimentology, sequence stratigraphy and reservoir characterization of the Lower Triassic Montney Formation in the Sturgeon Lake field located in west-central Alberta. The Montney Formation is grouped into two facies associations. Facies Association 1 is a siliciclastic upward-coarsening sequence deposited by storm, current and wave processes and is interpreted as a low energy progradational lower shoreface. Facies Association 2 is a carbonate shallowing upward sequence deposited in a wave dominated progradational shoreface. The contact between Facies Association 1 and 2 is marked by a major change in lithology and is erosive. Palynological analyses reveal two missing palynologic subzones between Facies Association 1 and Facies Association 2 suggesting a period of erosion and/or nondeposition. The boundary between the two facies association is defined as a sequence boundary which stratigraphically divides the Montney Formation into two sequences in the study area. The Lower Montney sequence is composed of eight retrogradational, aggradational and progradational parasequences and represent the Transgressive and the High-stand System Tract. The Upper Montney sequence is composed only of one parasequence and represents the Transgressive System Tract. The Sturgeon Lake Field has two types of reservoir with respect to lithology, porosity, permeability and geometry. The best reservoir facies is a brachiopod wackestone-packstone with permeabilities up to 8 Darcys. Siliciclastic reservoirs consist of very fine grained sandstones with permeabilities of 132 md when fractured.

Mederos, S.M. [Maraven, S.A., Caracas (Venezuela); Moslow, T.F. [Univ. of Alberta, Edmonton (Canada)

1996-08-01

7

Integrated Field Project in Structural Geology and Sedimentology/Stratigraphy  

NSDL National Science Digital Library

The field project described in the Big Horn Basin is a capstone experience for our innovative full-year course sequence that combines two geologic disciplines traditionally taught separately (in "silos") sedimentology/stratigraphy and structural geology. We feel that a holistic approach that combines an understanding of the processes involved in both disciplines allows students to more easily develop the geologic history of an area from collected field data. The result is a two-semester course sequence that integrates the concepts of the two disciplines through a full year of study. While we have more than ten different field projects during the year, these are simply "snapshots" that allow the student to only see a piece of the geologic puzzle. These exercises do develop skills that the student will use in the capstone experience the geologic synthesis of a specific region currently the Sheep Mountain region of the Big Horn Basin. The field-mapping project in the Big Horn Basin is followed by five weeks of sequenced work that allows each student to synthesize a complete geologic (sedimetologic and structural) history of the region. This includes the construction of a geologic map and cross-sections, understanding the depositional history (including environments of deposition), the syn- or post-depositional deformation of the region and an attempt to put the local geologic history into the context of regional deformation and tectonics. We believe that by integrating the disciplines into the two-semester sequence capped with the field mapping and synthesis better prepares students to "think like a geologist".

Malinconico, Lawrence

8

The Jurassic of Svalbard, Sedimentology, Stratigraphy and Paleontology  

NASA Astrophysics Data System (ADS)

During the Mesozoic the landmass now known as Svalbard drifted from 45oN to 65oN. The average global temperature was significantly higher, disabling the formation of icecaps at the poles, resulting in a higher sea-level. At the time the location now known as Svalbard was covered by a shallow ocean and mostly marine, organic rich, black shales, interrupted by possibly deltaic sediments were deposited. These sediments are rich in invertebrate fossils. A general description of the Agardhfjellet formation, spanning the middle to upper Jurassic, was made by Dypvik in 1991. Wierzbowski (1989) described some ammonites in detail from the Kimmeridgian. It is not known if the fauna extends further up or down in the formation. Since 2004 the Museum of Natural History of Oslo has been active in Spitsbergen Svalbard. Extensive and detailed sedimentological and stratigraphic research was never conducted as the focus lay on vertebrate fossils. A detailed sedimentological analysis, description and correlation to other Jurassic Formations (such as the Kimmeridge Shales, Hekkingen Formation and draupne Formation) is essential to better understand the circumstances where the black organic-rich shales (a highly potential source rock) were deposited in and to be able to predict their occurrences. Included in this description is taxonomy, taphonomy and the stratigraphic development of invertebrate fauna to pinpoint the age of the sediments.

Koevoets, Maayke; Hammer, Øyvind

2014-05-01

9

Lower Palaeozoic sedimentology and stratigraphy of the Kerman region, East-Central Iran  

Microsoft Academic Search

The Kerman-Tabas region of East-Central Iran contains the thickest and most complete sequence of Early Palaeozoic (Cambrian to Silurian) rocks in Iran and the Middle East, but the stratigraphy is complex.\\u000aDetailed reassessment of stratigraphic relationships between the Early Palaeozoic strata, together with new sedimentological, petrological and palaeontological data, indicate that the Kerman-Tabas region was tectonically active during this period,

Mir Alireza Hamedi

1995-01-01

10

Contribution of logging data to sedimentology and stratigraphy. [Electrofacies  

SciTech Connect

A technique has been developed using multivariate analysis of logging data to give a high-resolution sedimentological description of any sequence of formations. The number of different logs and their range allow determination of many of the physical characteristics of the rock. The definition of a lithofacies has been extended by introducing the concept of an electrofacies, constructed on the basis of all the logging data at any depth interval. Each logging datum is considered a descriptor for purposes of establishing electrofacies in a logged interval. Once established, electrofacies then can be correlated with actual geologic facies, if the logged interval has been cored. 23 refs.

Serra, O.; Abbott, H.T.

1982-02-01

11

Carboniferous clastic-wedge stratigraphy, sedimentology, and foreland basin evolution: Black Warrior basin, Alabama and Mississippi  

SciTech Connect

Carboniferous clastic-wedge stratigraphy and sedimentology in the Black Warrior basin of Alabama and Mississippi indicate deposition in an evolving foreland basin flanking the Appalachian-Ouachita fold-thrust belt. The strata reflect specific responses to foreland basin subsidence, orogenic activity, sediment supply, and dispersal systems. Definition of the regional stratigraphy of the clastic wedge provides for interpretation of the foreland basin subsidence history by enabling quantitative reconstruction of regional compaction and subsidence profiles. Comparison of the interpreted subsidence history with model profiles of foreland basin subsidence (predicted from loading and flexure of continental lithosphere) allows evaluation of mechanical models in terms of observed clastic-wedge sedimentology and stratigraphy. Mechanical modeling of foreland basin subsidence predicts formation of a flexural bulge that migrates cratonward ahead of the subsiding foreland basin during loading. In the Black Warrior basin, local stratigraphic thins, pinch-outs, and areas of marine-reworked sediments suggest migration of the flexural bulge. Comparison of flexural bulge migration with thermal maturation history allows evaluation of timing of stratigraphic trapping mechanisms with respect to onset of hydrocarbon generation.

Hines, R.A.

1986-05-01

12

Stratigraphy and sedimentology of the Upper Cretaceous to Paleogene Kilwa Group, southern coastal Tanzania  

NASA Astrophysics Data System (ADS)

The geology of southern coastal Tanzania has remained poorly understood since the first comments on its stratigraphy were made over 100 years ago. However, new field surveys combined with shallow drilling along the coast between Kilwa and Lindi are beginning to resolve the depositional history and structural evolution of this region over the past 85 Ma. Here we present the first attempt to synthesize the results of these studies to provide a coherent sedimentological, litho- and sequence stratigraphic framework, including new geological maps, for the Upper Cretaceous and Paleogene of the coastal zone. Santonian to Oligocene sediments crop out along a broad coastal belt south of the Rufiji River from the Kilwa peninsula to Lindi Creek in southern Tanzania. During ˜55 Ma, over 1 km of a broadly homogeneous, mid to outer shelf clay-dominated succession was deposited across the passive margin, which we define here as the Kilwa Group. This lies disconformably across the shelf on Albian marls and is itself unconformably overlain by shallow water Miocene clays and more recent limestones, sands and gravels. Four formations can be identified within the Kilwa Group on the basis of characteristic secondary lithologies and facies, described here for the first time; the Nangurukuru, Kivinje, Masoko and Pande Formations. These formations include conformable stratigraphic intervals through both the Paleocene-Eocene and Eocene-Oligocene boundaries. Within the Kilwa Group, 12 sequence stratigraphic cycles can be identified at present, demonstrating relatively uniform and continual subsidence across the margin from Santonian to Early Oligocene time. A further major bounding surface is present between the Upper Cretaceous and Paleogene, but this may become partly conformable in the Lindi area. Although the principal lithology in all formations is clay or claystone, there are more permeable intervals containing pervasive coarser siliciclastic sediments and these have yielded traces of crude oil which is likely to have migrated from lower in the succession. The Kilwa Group thus also provides important new evidence for petroleum play development in the southern coastal zone.

Nicholas, Christopher J.; Pearson, Paul N.; Bown, Paul R.; Jones, Tom Dunkley; Huber, Brian T.; Karega, Amina; Lees, Jackie A.; McMillan, Ian K.; O'Halloran, Aoife; Singano, Joyce M.; Wade, Bridget S.

2006-08-01

13

Stratigraphy, sedimentology and eruptive mechanisms in the tuff cone of El Golfo (Lanzarote, Canary Islands)  

NASA Astrophysics Data System (ADS)

The tuff cone of El Golfo on the western coast of Lanzarote (Canary Islands) is a typical hydrovolcanic edifice. Along with other edifices of the same age, it was constructed along a fracture oriented NEE-SWW that coincides with the main structural trend of recent volcanism in this part of the island. We conducted a detailed stratigraphic study of the succession of deposits present in this tuff cone and here interpret them in light of the depositional processes and eruptive dynamics that we were able to infer. The eruptive sequence is represented by a succession of pyroclastic deposits, most of which were emplaced by flow, plus a number of air-fall deposits and ballistic blocks and bombs. We distinguished five different eruptive/depositional stages on the basis of differences in inferred current flow regimes and fragmentation efficiencies represented by the resulting deposits; the different stages may be related to variations in the explosive energy. Eight lithofacies were identified based on sedimentary discontinuities, grain size, components, variations in primary laminations and bedforms. The volcanic edifice was constructed very rapidly around the vent, and this is inferred to have controlled the amount of water that was able to enter the eruption conduit. The sedimentological characteristics of the deposits and the nature and distribution of palagonitic alteration suggest that most of the pyroclastic succession in El Golfo was deposited in a subaerial environment. This type of hydrovolcanic explosive activity is common in the coastal zones of Lanzarote and the other Canary Islands and is one of the main potential hazards that could threaten the human population of this archipelago. Detailed studies of these hydrovolcanic eruptions such as the one we present here can help volcanologists understand the hazards that this type of eruption can generate and provide essential information for undertaking risk assessment in similar volcanic environments.

Pedrazzi, Dario; Martí, Joan; Geyer, Adelina

2013-07-01

14

Formation of mega-scale glacial lineations on the Dubawnt Lake Ice Stream bed: 2. Sedimentology and stratigraphy  

NASA Astrophysics Data System (ADS)

Mega-scale glacial lineations (MSGLs) are highly elongate, subglacial landforms produced beneath zones of fast-flowing ice. While qualitative data on their morphology have existed for several decades, studies of their composition and sedimentology are comparatively rare. Sediment exposures along the course of the Finnie River in Nunavut, northern Canada, provide a window into the internal stratigraphy and sedimentology of MSGLs formed by the Dubawnt Lake Palaeo-Ice Stream during regional deglaciation of the Laurentide Ice Sheet. Stratigraphic sections record evidence for an initial advance of ice into the study area followed by ice sheet recession and deposition of glacifluvial and glacilacustrine outwash. Subsequently, the Dubawnt Lake Palaeo-Ice Stream overrode and reworked this outwash subglacially forming an ‘MSGL till’. This till comprises a sandy, red diamicton facies, forming the core of the MSGL ridges and containing variably deformed lenses, stringers and rafts of outwash. The sedimentology of this diamicton is consistent with an origin as a glacitectonite and hybrid till formed by a combination of non-pervasive subglacial sediment deformation and lodgement. Facies variations from stratified to massive diamicton reflect, in turn, variations in strain and subglacial transport distance. The occurrence of stratified glacifluvial sediments within these ridges and the well-preserved nature of many of the sandy inclusions within the diamicton imply relatively short transport distances and incomplete mixing. MSGLs under the Dubawnt Lake Palaeo-Ice Stream formed through a combination of subglacial erosion and deposition. This included non-pervasive, subglacial sediment deformation and the reworking of pre-existing sediment depocentres during streaming flow. These results highlight the importance of sediment supply to MSGL formation with the presence of abundant pre-existing sediments which were subsequently overridden being critical to lineation formation.

Ó Cofaigh, C.; Stokes, C. R.; Lian, O. B.; Clark, C. D.; Tulacyzk, S.

2013-10-01

15

Sedimentology and stratigraphy of a tidal sand bank in the southern North Sea  

Microsoft Academic Search

A set of 125 vibrocores collected on the basis of a dense grid of high and very high resolution seismic coverage over a tidal sand bank (the Middelkerke Bank) provides a unique opportunity to reconstruct the stratigraphy and sedimentary facies succession of such a large tidal sand body. Five sedimentary facies are distinguished. They range from clay to pebble and

Alain Trentesaux; Ad Stolk; Serge Berné

1999-01-01

16

Integration of sequence stratigraphy and process sedimentology: Miocene Rincon and Topanga Formations, Santa Barbara basin near Point Mugu, California  

SciTech Connect

The Miocene Rincan and Topanga formations exposed at Point Mugu comprise over 1,200 ft of interbedded sandstones, siltstones, claystones, and clay shales that were deposited in a tectonically active marine basin adjacent to the present Santa Monica Mountains. Integration of sequence stratigraphic interpretation techniques and process sedimentology demonstrates that this section originated as shelfal deposits during sea level rise that were cut by a submarine canyon during subsequent sea level lowstand. The base of the sequence contains a bioturbated silty sandstone indicative of a transgressive deposit within the sequence stratigraphic framework. Upsection, dark clay shales of a condensed section contain fish fragments and sponge progradational highstand shelf sandstones. An erosional surface flooring a deep-water canyon cuts the highstand deposits and marks a sequence boundary. Within the submarine canyon fill, deep-water deposits represent at least two episodes of sediment gravity flows. A predominantly deformed lower section is cut by an erosional surface (another sequence boundary ) overlain by undeformed strata. The deformed section was caused by slumping of a canyon wall within a slope environment and deposition of high-density turbidites and debris flows. The undeformed section contains Bouma sequences, graded beds, dish structures, and biogenic structures. Interstratified bed-thinning and bed-thickening sequences suggest minor progradational events and small feeder channels within the undeformed section. These relationships demonstrate that not all sequences comprising deep-water deposits can be easily assigned to facies, such as channels and lobes, based on vertical and lateral profiles. This integration of sequence stratigraphy and sedimentology has assisted in understanding the vertical and lateral heterogeneities present within exploration and production areas in the adjacent Santa Barbara Channel.

Jordan, D.W.; Marquard, R.S. (ARCO Oil and Gas Co., Plano, TX (USA))

1990-05-01

17

Basin Evolution and Exhumation of the Xigaze Forearc, Southern Tibet: Insight from Sedimentology, Stratigraphy, and Geo-Thermochronology  

NASA Astrophysics Data System (ADS)

Forearc basins are important data archives for understanding continental dynamics because they preserve the tectono-erosional record of continental margins before collision. This study focuses on the Cretaceous-Eocene Xigaze forearc basin in southern Tibet, which is exposed along ~600 km of the Indus-Yarlung Suture Zone between the Indian craton to the south and the Asian Lhasa terrane to the north. From late Cretaceous to early Cenozoic time, subduction of Neo-Tethyan oceanic crust beneath the southern margin of Asia accommodated the northward motion of the Indian craton and formed the Xigaze forearc basin. Following collision with India in the early Cenozoic, the basin transitioned from predominantly marine to non-marine sedimentation and was subsequently uplifted to a mean elevation of 5000 m. How this transition occurred remains unresolved. This study's overall objective is to decipher forearc-basin and Indo-Asia continental-margin development from field sedimentology and stratigraphy, and detrital geo-thermochronology. We present new stratigraphic sections, totaling 8 km thick, from a previously unexplored ~60 km segment of the Xigaze forearc, ~50 km north-northwest of Saga. These sections are quite different from those known farther east. Sedimentary facies of mid-Cretaceous to early Eocene deposits indicate a shoaling-upward trend consistent with other ancient forearc basins (e.g., Great Valley forearc, California). Middle to late Cretaceous deposits indicate a variety of facies and depositional environments along strike in the study area. Facies include distal marine turbidites, shelf limestones, estuarine siliciclastics, and brown paleosols. In contrast, Eocene depositional environments are transitional from nearshore marine to pericontinental. Facies consist of dirty limestones, packstones, and wackestones, interbedded with terrigenous conglomerates and red-green paleosols. Eocene fauna include abundant foraminifera such as Nummulites-Discocyclina and Miscellanea-Daviesina. The along-strike variability of the Cretaceous strata suggests that, prior to collision, the diverse and irregular paleogeography of Asia's southern margin greatly influenced the three-dimensional nature and distribution of time-equivalent facies. In order to determine the timing of exhumation of Xigaze forearc strata, we utilize zircon (U-Th)/He thermochronology coupled with U-Pb geochronology. Preliminary U-Pb detrital geochronology indicates that the primary source of forearc detritus is the Gangdese magmatic arc which was active from ~150 Ma to 50 Ma. Preliminary double-dated (U-Th/He and U-Pb) zircon crystals from eight samples in ~80 Ma deposits suggest basin exhumation from 30 to 10 Ma. This time span corresponds to ages determined independently for movements occurring along the basin-bounding Great Counter Thrust system. Therefore, we postulate that this fault system was responsible for erosional exhumation of the Xigaze forearc.

Orme, D. A.; Carrapa, B.; Abbey, A. L.; Kapp, P. A.; Ding, L.

2012-12-01

18

Sedimentology and Stratigraphy of the Granite Wash: Contact Rapids and Keg River Sandstone (Red Earth Area)  

NASA Astrophysics Data System (ADS)

The Granite Wash is comprised of diachronous, Cambrian to Devonian sandstone deposits, which include the Devonian Contact Rapids and Keg River sandstones of which this study will focus. Prolific oil production from the Granite Wash has fueled exploration since the 1950s and as a result substantial core and wireline data is available. Mapping of the Precambrian subcrop suggests that palaeo-highs, known as inselbergs, strongly influenced sedimentation transport, volume, rate and ultimately preservation after marine transgression. Several distinct surfaces identified from wireline data and cores indicate an overall marine transgression throughout Keg River time. The facies observed represent continental, shallow marine and sabkha environments and a climatic shift from arid to semi-arid to arid. This detailed sedimentological and stratigraphic study provided the depositional framework that allowed for palaeogeographic maps to be constructed.

Balshaw, Kevin Ewart

19

Stratigraphy and sedimentology of the K/T boundary deposit in Haiti  

NASA Technical Reports Server (NTRS)

The K/T boundary sequence is exposed in uplifted carbonate sediments of the southwest peninsula of Haiti. It is found at 15 localities within the Beloc formation, a sequence of limestone and marls interpreted as a monoclinal nappe structure thrust to the north. This tectonic deformation has affected the K/T boundary deposit to varying degrees. In some cases the less competent K/T deposit has acted as a slip plane leading to extensive shearing of the boundary layer, as well as duplication of the section. The presence of glassy tektites, shocked quartz, and an Ir anomaly directly link the deposit to a bolide impact. Stratigraphic and sedimentological features of the tripartite sequence indicate that it was formed by deposition from ballistic fallout of coarse tektites, emplacement of particle gravity flows and fine grained fallout of widely dispersed impact ejecta.

Carey, S.; Sigurdsson, H.; Dhondt, S.; Espindola, J. M.

1993-01-01

20

The Mud Hills, Mojave Desert, California: Structure, stratigraphy and sedimentology of a rapidly extended terrane  

SciTech Connect

The Mud Hills exposes synorogenic breccia (Mud Hills Fm.) deposited during the final stages of crustal extension of the upper plate above the Waterman Hills detachment (20--18 Ma). Previous workers have misinterpreted fault contacts as stratigraphic contacts, and have developed intricate pseudostratigraphy to explain their observations. The authors' detailed mapping, combined with stratigraphic and sedimentologic data, documents that the volcaniclastic Pickhandle Fm. is conformably overlain by the plutoniclastic Mud Hills Fm., with no interfingering. Repetition of these south-dipping lithologic units is due to imbricate, north-dipping listric faults. These relations are demonstrated by the systematic northward v''ing of fault contacts and southward v''ing of stratigraphic contacts. Stratigraphic dip decreases upsection, which is consistent with incremental rotation of basinal strata simultaneously with deposition. Most of the Mud Hills Fm. consists of rock-avalanche breccia and megabreccia derived from granodiorite, which is identical to basement exposed beneath the Pickhandle and Jackhammer Fms. to the north. The Mud Hills Fm. was derived from now-buried granodiorite of a stranded upper-plate block to the south, as demonstrated by northward paleocurrents, facies relations and the presence of fine-grained units close to the presumed master fault (as is typical of half-graben sedimentation). Unconformably overlying the Mud Hills Fm. is the Owl Conglomerate (Barstow Fm.), which has mixed provenance with southward paleocurrents; the Owl Conglomerate was derived from residual highlands after extension ceased. Integration of structural, stratigraphic and sedimentologic information is essential for correct reconstruction of highly extended terranes.

Ingersoll, R.V.; Devaney, K.A.; Geslin, J.K.; Cavazza, W.; Diamond, D.S.; Jagiello, K.J.; Marsaglia, K.M.; Paylor, E.D. II; Short, P.F. (Univ. of California, Los Angeles, CA (United States). Dept. of Earth and Space Sciences)

1993-04-01

21

Stratigraphy, sedimentology and paleontology of lower Eocene San Jose formation, central San Juan basin, New Mexico  

SciTech Connect

The lower Eocene San Jose Formation in the central portion of the San Juan basin (Gobernador-Vigas Canyon area) consists of the Cuba Mesa, Regina, Llaves, and Tapicitos Members. Well log data indicate that, from its 100-m thickness, the Cuba Mesa Member thins toward the basin center and pinches out to the northeast by lat. 36{degree}40'N, long. 107{degree}19'W. The Regina Member has the most extensive outcrops in the central basin, and it decreases in sandstone/mud rock ratio to the north. The Llaves and Tapicitos Members occur only at the highest elevations, are thin due to erosion, and are not mappable as separate units. Well log data and 1,275 m of measured stratigraphic section in the Regina, Llaves, and Tapicitos Members indicate these strata are composed of approximately 35% medium to coarse-grained sandstone and 65% fine-grained sandstone and mud rock. Sedimentology and sediment-dispersal patterns indicate deposition by generally south-flowing streams that had sources to the northwest, northeast, and east. Low-sinuosity, sand-bedded, braided( ) streams shifted laterally across about 1 km-wide channel belts to produce sheet sandstones that are prominent throughout the San Jose Formation. Subtle levees separated channel environments from floodplain and local lacustrine areas. Avulsion relocated channels periodically to areas on the floodplain, resulting in the typically disconnected sheet sandstones within muddy overbank deposits of the Regina Member.

Lucas, S.G.; Smith, L.N. (New Mexico Museum of Natural History, Albuquerque (USA))

1989-09-01

22

Sedimentology and stratigraphy of tidal sand ridges southwest Florida inner shelf  

SciTech Connect

Detailed investigation of linear shelf sand ridges located off the southwest coast of Florida shows them to be tide-dominated sand bodies. These ridges are remarkably similar to the large sand ridges of the North Sea, and they have abundant apparent analogs in the stratigraphic record, many of which are important petroleum producers. The Florida ridges are asymmetric in profile, about 10 km long, 1 km wide, with relief of 3-4 m with the adjacent sea bed. Extensive tidal current monitoring, sediment distribution patterns and side scan sonar surveys permit characterizing their morphodynamics. Tidal currents show distinct bidirectional patterns with speeds up to 70 cm/s. There is slight flood-dominance, and currents show much higher velocities in the troughs as compared to the crests of the ridges. Megaripples and sand waves are widespread and migrate obliquely across the ridges at opposite directions on the gentle and steep side of the ridge. Shallow, high-resolution seismic data and 39 vibracores din the area of the ridges show a consistent sequence characterized by three ascending Holocene lithofacies: (1) muddy quartz sand with limestone clasts; (2) bioturbated muddy shelly quartz sand; and (3) well-sorted, cross-stratified quartz sand that characterizes the sand ridges themselves. Each of the tidal sand ridges displays a coarsening-upward sequence of fine, well-sorted sand. Small-scale, multidirectional, cross stratification dominates the stratigraphy of the cores in this facies, but megaripple cross stratification is also present. All data indicate that these tidal ridges are good modern analogs for many of the shelf sand bodies in the ancient record, especially the Mesozoic of the mid-continent area.

Davis, R.A. Jr.; Klay, J.; Jewell, P. (Univ. of South Florida, Tampa (United States))

1993-01-01

23

Sedimentology, stratigraphy, and micropalaeontology of the Upper Triassic reefal series in Eastern Sulawesi (Indonesia)  

Microsoft Academic Search

An Upper Triassic (Upper Norian-Rhaetian) carbonate complex, composed of open marine to reefal deposits, has been investigated for the first time in Eastern Sulawesi. The age is based on the occurrence of benthic foraminifera, and also of the Upper Sevatian to Rhaetian conodont Misikella posthernsteini Kozur and Mock. Palynological assemblages contain Upper Triassic-Lower Jurassic palynomorphs. The scleractinian coral Retiophyllia seranica

Rossana Martini; Daniel Vachard; Louisette Zaninetti; Simonetta Cirilli; Jean-Jacques Cornée; Bernard Lathuilière; Michel Villeneuve

1997-01-01

24

Stratigraphy, sedimentology and structure of the Numidian Flysch thrust belt in northern Tunisia  

NASA Astrophysics Data System (ADS)

The Oligo-Miocene Numidian Flysch of northern Tunisia has long been divided into three distinct lithostratigraphic units considered as vertically superimposed: the lower unit or the "Zouza member", the middle unit or the "Kroumirie member" and the upper unit or the "Babouch member". According to this reconstruction the two first members are mostly Oligocene in age and only the third member was assigned as early Miocene in age. In this study, we present new biostratigraphic data, based on planktonic foraminiferal analysis, demonstrating that both the Zouza and the Kroumirie members are Oligocene-early Miocene in age and are, therefore, coeval. Four distinct facies associations have been identified within the Numidian Flysch including: (a) massive sandstones; (b) conglomerate; (c) an interbedded mudstone-sandstone association; and (d) a mudstone facies association. Slide-slump units and injectionite sands occur within the more mud-rich associations. The likely depositional setting is a muddy slope-apron system, cut locally by sand-rich channels, which fed channel-terminal lobe deposits. Paleocurrent data support strongly a flow from N and NW. Modal analysis, demonstrates that the Numidian sandstones are quartz-arenite type (QFL, 97.25:1.25:1.5) derived from middle to high grade-metamorphic and granitic rocks. Zircon geochronology, yielding ages of 514 ± 19 Ma from Tunisia and 550 ± 28 Ma from Sicily, would support the basement terrain that crops out along the Algerian coast and forms part of Calabro-Peloritani-Kabylian zone, as the most likely parental source of the Numidian Flysch for both Sicily and Tunisia. Zircon data from the Fortuna Formation yields ages of 1698 ± 67 Ma, which is more compatible with an African craton source ( Fildes et al., 2009). Structural consideration of the basal contact of the Numidian Flysch with the underlying Tellian rocks, as well as newly interpreted seismic data; confirm the allochthounous position of the Numidian complex and its displacement southward. Facies comparison with the equivalent Oligo-Miocene Bejaoua siliciclastic deposits outcropping towards the south shows that the Numidian complex is an "out-of-sequence thrust unit" and that the two Oligo-Miocene sedimentary systems are quite distinct and were sourced from wholly different source regions.

Sami, Riahi; Soussi, Mohamed; Kamel, Boukhalfa; Kmar, Ben Ismail Lattrache; Stow, Dorrik; Sami, Khomsi; Mourad, Bedir

2010-04-01

25

Sedimentology and petroleum geology  

SciTech Connect

This book presents an introduction to sedimentology as well as petroleum geology. It integrates both subjects, which are closely related but mostly treated separately. The author covers the basic aspects of sedimentology, sedimentary geochemistry and diagenesis. Principles of stratigraphy, seismic stratigraphy and basin modelling forms the base for the part on petroleum geology. Subjects discussed include the composition of kerogen and hydrocarbons, theories of migration and trapping of hydrocarbons and properties of reservoir rocks. Introductions to well logging and production geology are given.

Bjorlykke, K.O. (Oslo Univ. (Norway))

1989-01-01

26

Valley fill stratigraphy in the southern Ganga basin : age constraints and forcing mechanisms.  

NASA Astrophysics Data System (ADS)

Although some advances have been made towards understanding the interfluve stratigrahy in the southern Indo-Gangetic plains, the dynamics of valley filling and its forcing mechanisms remain poorly understood. We describe here sedimentological and chronological evolution of the subsurface alluvial stratigraphy developed in a section of river Ganga (width~13km; area:26°30'-27°00'N and 80°00'-80°30'E) The sedimentary succession was studied using litho- and electro-logs from six boreholes up to 33 m deep. These boreholes lie on two parallel transects (separated by 40km), across the valley, and well beyond the influence of the active channel. The sediment cores from these boreholes were used for facies analysis, magnetic susceptibility and optically stimulated luminescence (OSL) dating. These investigations suggest an upper about 13km wide and 12-15m deep continuous sandy channel deposits containing about 3-4 depositional cycles (unit1). The unit 1 is underlain by alternating layers of channel, aeolian and floodplain facies (unit2). The flood plain and aeolian facies show weak to moderate peodogenic alteration, terminating at prominent kankar layers, markers of discontinuity in deposition. About eighteen samples were used for OSL dating of the borehole sediments. A single-aliquot regenerative- dose protocol was applied to quartz obtained from medium to very fine sand and coarse silt. A good agreement between OSL and C-14 ages has been observed in the adjacent interfluve stratigraphy. The OSL chronology from the boreholes suggest that the upper channel filling activity (unit1) started around 10 ka. The base of the channel body in different boreholes gives ages from 10 to 1 ka, thus constraining the rate of progressive movement of the channel across the valley. The quartz derived from unit 2 was in OSL saturation suggesting an age of >40ka for these units. These results indicate a major hiatus in the youngest channel sand filling episodes in the area; this is supported by greater pedogenic alteration in the upper part of unit2. It is possible that unit 2 represents a period of relative fluvial dormancy during OIS 3 and 2, followed by rejuvenation during OIS 1. The details of these investigations and their implications for understanding the role of climate in shaping valley fill architecture will be discussed.

Roy, N.; Sinha, R.; Gibling, M.; Jain, M.; Murray, A. S.

2006-05-01

27

Stratigraphy and sedimentology of pre-late Wisconsin catastrophic glacial flood sediments, western Walla Walla Valley, Washington  

SciTech Connect

The Cummins Bridge site in the western Walla Walla Valley exhibits clear evidence for pre-late Wisconsin catastrophic glacial flooding. The section consists of an unstratified, poorly sorted diamict with angular basaltic clasts in a matrix of sand and silt, and a large number of well-rounded clasts of exotic lithology in the coarse fraction, gradationally overlain by a coarse, angular gravel that is matrix poor and exotic-free; this unit grades upward into a matrix-rich diamict with a well-developed caliche in the upper portion. Above this is a sand and silt unit showing vague cross-stratification, lamination, and graded beds; this unit may represent local temporary ponding of the ancestral drainage. Overlying this on a pronounced erosional surface are rhythmically stratified sand-to-salt beds assigned to the late Wisconsin Toughet Beds. The section is capped by a thin bed of Holocene loess. Stratigraphic and sedimentologic criteria suggest that the lowermost units represent an indirect record of catastrophic glacial flooding. Flood sediments were deposited on an adjacent topographic high and subsequently mass-wasted via mudflow into their present position. Normal fluvial processes alternated with mass-wasting events to concentrate the angular, matrix-poor basaltic gravel. The lower diamict shows characteristics similar to documented pre-late Wisconsin catastrophic flood sediments at a nearby site, including rounded exotic clasts, angular basaltic clasts, lack of stratification, and poor sorting. The two sites may represent the same pre-late Wisconsin flood event.

Robertson, J.L.; Spencer, P.K. (Whitman College, Walla Walla, WA (United States). Geology Dept.)

1993-04-01

28

University of Minnesota: Sedimentology Group  

NSDL National Science Digital Library

The sedimentology group at the University of Minnesota presents its research in earthscape processes at this website. Visitors can find out about the goals, results, and publications of three main research areas: experimental stratigraphy and landscape evolution, theoretical sedimentology and stratigraphy, and river dynamics. The site offers downloads for many of the group's publications. Visitors discover the latest sedimentology-related news. While the links Useful Things and Links do not contain information at this time, users can still learn about the work of sedimentologists at this website.

29

Taconic foreland basin evolution: Sedimentology and cement stratigraphy of the Black River Group limestones in the Champlain Basin  

SciTech Connect

The Black River Group (Middle Ordovician, Mohawkian Series) limestones in the Champlain Basin record the transition between the shallow deposits of the underlying Chazy Group limestones and the shale-limestone couplets of the overlying Trenton Group which record rapid deepening of the foreland basin. The Black River Group was deposited in a subsiding foreland basin during the early stages of the Taconic Orogeny. Syn-depositional block faulting as a result of thrust loading has been demonstrated to affect Chazy and Trenton Group deposition. Abrupt lithofacies changes within the Black River Group record the dynamic bathymetry present in the Champlain Basin during its deposition. The Black River Group helps refine the timing of extensional block faulting during the Taconic Orogeny. The Black River Group in the Champlain Basin is a relatively thin unit, approximately 80 feet thick at Crown Point, New York. Exposures between Crown Point, NY and South Hero Island, VT record deposition of the Black River Group limestones in a protected lagoonal environment, with an evolving fringing pellet shoal barrier complex. Eight lithofacies are defined, grading from a basal sandstone and/or a sandy dolomite, to a micrite to biomicrite, to an intra-pelsparite of a shoal environment. Intraclast horizons and broken, rounded marine allochems suggest the influence of storm activity as a modifier of depositional history. Rapid deepenings into the normal marine subtidal environment, as well as micro-karst textures and fossil beach rock exposures are interpreted to represent sudden bas level changes, possibly from syndepositional block fault movement. Although dynamic bathymetry influences the stratigraphy within the Black River Group, a macro-scale deepening upwards on a formation scale is present, representing subsidence of the foreland basin.

Bechtel, S.C.; Mehrtens, C.J. (Univ. of Vermont, Burlington, VT (United States). Geology Dept.)

1993-03-01

30

Sedimentology and petroleum geology  

SciTech Connect

In this introduction to sedimentology and petroleum geology the subjects, which are closely related but mostly treated separately, are integrated. The first part covers the basic aspects of sedimentology, sedimentary geochemistry and diagenesis, including brief discussions of flow in rivers and channels, types of sediment transport, lake and river deposits, deltas (river-dominated, tide-dominated, and wave-dominated) and the water budget. Principles of stratigraphy, seismic stratigraphy and basin modeling form the basis for the last part on petroleum geology. Here subjects include the composition of kerogen and hydrocarbons, theories of migration and trapping of hydrocarbons and properties of reservoir rocks. Finally, short introductions to well logging and production geology are given.

Bjorlykke, K.

1989-01-01

31

Age calibration of piston core EW9709-07 (equatorial central Pacific) using fish teeth Sr isotope stratigraphy  

Microsoft Academic Search

A high-resolution age-depth profile is presented for a 16-m deep-sea piston core (EW9709-PC07) using three different methods: magnetostratigraphy, fish-teeth strontium isotope stratigraphy, and radiolarian biostratigraphy. Fish teeth are abundant throughout the core, allowing for precise age determinations by Sr isotope stratigraphy. Magnetostratigraphic ages, though not available for this core, were determined by correlation with the drill core record from adjacent

J. D. Gleason; T. C. Moore Jr.; T. M. Johnson; D. K. Rea; R. M. Owen; J. D. Blum; J. Pares; S. A. Hovan

2004-01-01

32

Identifying Fracture Types and Relative Ages Using Fluid Inclusion Stratigraphy  

SciTech Connect

Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Understanding the life cycle of a fracture in a geothermal system is fundamental to the development of techniques for creating fractures. Recognizing the stage of a fracture, whether it is currently open and transmitting fluids; if it recently has closed; or if it is an ancient fracture would assist in targeting areas for further fracture stimulation. Identifying dense fracture areas as well as large open fractures from small fracture systems will also assist in fracture stimulation selection. Geothermal systems are constantly generating fractures, and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. Fluid inclusions trapped in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. Our hypothesis is that fractures over their life cycle have different chemical signatures that we can see in fluid inclusion gas analysis and by using the new method of fluid inclusion stratigraphy (FIS) the different stages of fractures, along with an estimate of fracture size can be identified during the well drilling process. We have shown with this study that it is possible to identify fracture locations using FIS and that different fractures have different chemical signatures however that signature is somewhat dependent upon rock type. Open, active fractures correlate with increase concentrations of CO2, N2, Ar, and to a lesser extent H2O. These fractures would be targets for further enhancement. The usefulness of this method is that it is low cost alternative to current well logging techniques and can be done as a well is being drilled.

Dilley, Lorie M.; Norman, David; Owens, Lara

2008-06-30

33

Lunar impact basins: Stratigraphy, sequence and ages from superposed impact crater populations measured from Lunar Orbiter Laser Altimeter (LOLA) data  

E-print Network

Impact basin formation is a fundamental process in the evolution of the Moon and records the history of impactors in the early solar system. In order to assess the stratigraphy, sequence, and ages of impact basins and the ...

Fassett, C. I.

34

Stratigraphy, sedimentology and diagenetic evolution of the Lapur Sandstone in northern Kenya: Implications for oil exploration of the Meso-Cenozoic Turkana depression  

NASA Astrophysics Data System (ADS)

The northern Turkana region of northwestern Kenya forms the intersection between two major rift systems in Africa, the Cretaceous-Paleogene Central African Rift System (CARS), and the eastern arm of the Paleogene-Present East African Rift System (EARS). The southern Sudanese oil-rich rift basins form part of the CARS, and their extension into the Anza Rift in northeastern Kenya makes the area of northern Turkana an important target for oil exploration. Limited past exploration activity in the area leaves the study of surface outcrops as the main avenue for understanding the reservoir potential of the fluvial deposits of these rift systems. The outcrops of these potential reservoirs, collectively referred to as "Turkana Grits" in the past, are represented on the western side of Lake Turkana by the Lapur Sandstone in the north, and by other grit formations in the central and southern parts of the basin. Isotopic age determinations on the basal parts of the "Turkana Volcanics" that overlie the Lapur Sandstone have enabled the precise dating of the upper parts of the LS at between 35 and 37 Ma, while the lower part of the formation near the contact with the underlying Precambrian basement is estimated as Upper Cretaceous (Turonian-early Campanian), based on the discovery of dinosaur and other reptilian fauna. Detailed lithological logging, coupled with subsequent petrographic and sedimentological studies, have enabled the determination of the depositional environments and the diagenetic evolution of the Lapur Sandstone. The basal and uppermost parts of the formation are interpreted as distal alluvial fan environments possibly connected to the last stages of rifting characterizing the Central African Rift System. The middle part of the Lapur Sandstone corresponds to a wide braided fluvial system that can be compared to fluvial episodes of Late Cretaceous age in the Sudan region, associated to major palaeogeographical changes in northern Africa. The nearly abrupt disappearance of the Lapur upper fan system relates to the deposition of the "Turkana Volcanics" from Late Eocene, possibly as a consequence of the emplacement of the Afar Plume at 45-35 Ma. In terms of diagenesis, the main cement material at the base of the Lapur Sandstone is calcite, whereas at the middle of the formation, hematite becomes the dominant cement, and at the topmost section, kaolin cement dominates. The diagenetic evolution of the sandstones has been favourable to the retention of adequate primary intergranular porosity and the creation of secondary intragranular dissolution porosity, mainly through feldspar dissolution, and thus preserving the reservoir potential of the Lapur Sandstone. The reservoir characteristics, such as the porosity and cementation style, of the Lapur Sandstone are comparable to those of the fluvial sandstone reservoirs of the southern Sudan oil fields and this should positively contribute to the overall petroleum potential of the northern Turkana region. Though the northern Turkana area has remained largely unexplored, it is hoped that the demonstration of the presence of reasonably good reservoir quality sandstones in the Lapur Sandstone will serve to encourage further interest in hydrocarbon exploration in the Turkana area.

Tiercelin, Jean-Jacques; Potdevin, Jean-Luc; Thuo, Peter Kinyua; Abdelfettah, Yassine; Schuster, Mathieu; Bourquin, Sylvie; Bellon, Hervé; Clément, Jean-Philippe; Guillou, Hervé; Nalpas, Thierry; Ruffet, Gilles

2012-08-01

35

The stratigraphy, sedimentology, and fossils of the Haughton formation - A post-impact crater-fill, Devon Island, N.W.T., Canada  

Microsoft Academic Search

After the impact that formed Haughton crater, 22.4 ± 1.4 Ma ago (early Miocene), the cavity filled with water and began to accumulate lacustrine sediments. These preserve detailed evidence of pre-impact stratigraphy and post-impact morphology and development of the crater, as well as of the climatic and biotic regime in which it lay. In this report we formally designate these

Leo J. Hickey; Kirk R. Johnson; Mary R. Dawson

1988-01-01

36

Principles of lake sedimentology  

SciTech Connect

This book presents a comprehensive outline on the basic sedimentological principles for lakes, and focuses on environmental aspects and matters related to lake management and control-on lake ecology rather than lake geology. This is a guide for those who plan, perform and evaluate lake sedimentological investigations. Contents abridged: Lake types and sediment types. Sedimentation in lakes and water dynamics. Lake bottom dynamics. Sediment dynamics and sediment age. Sediments in aquatic pollution control programmes. Subject index.

Janasson, L.

1983-01-01

37

BGS School of Field Geology An introduction to Sequence Stratigraphy  

E-print Network

Stratigraphy in the field.The course also provides the opportunity to gain experience of clastic sedimentology stratigraphic approaches to the division of rock successions, sedimentology of Cretaceous alluvial to marine siliciclastic rocks, sedimentology of Permian to Cretaceous alluvial, red bed successions, including palaeosols

38

Edgar_Answers to student questions 414.pdf Student questions: Lauren Edgar colloquium on "Martian Sedimentology as Revealed by the  

E-print Network

Sedimentology as Revealed by the Curiosity Rover" 3/26/14 Question 1: How are the studies that you've done of the same kinds of instruments to investigate the sedimentology and stratigraphy at each landing site

Rhoads, James

39

Evaporite sedimentology  

SciTech Connect

The purpose of this book is to introduce the sedimentology of evaporites and to demonstrate how sedimentological principles can be applied to ancient evaporites. It includes chapter on: Sabkhas; marine and continental; Shallow water evaporites: lakes, salinas and platforms; and deep water evaporites.

Warren, J.K.

1989-01-01

40

Reservoir sedimentology  

SciTech Connect

Collection of papers focuses on sedimentology of siliclastic sandstone and carbonate reservoirs. Shows how detailed sedimentologic descriptions, when combined with engineering and other subsurface geologic techniques, yield reservoir models useful for reservoir management during field development and secondary and tertiary EOR. Sections cover marine sandstone and carbonate reservoirs; shoreline, deltaic, and fluvial reservoirs; and eolian reservoirs. References follow each paper.

Tillman, R.W.; Weber, K.J.

1987-01-01

41

Till stratigraphy and sedimentology at the margins of terrestrially terminating ice streams: case study of the western Canadian prairies and high plains  

NASA Astrophysics Data System (ADS)

Complex glacigenic sediment sequences arranged in large arcuate assemblages and demarcating the lobate termini of fast ice flow corridors in western Canada represent the terrestrial equivalents of the trough-mouth fans of the marine palaeo-ice stream record. Intensive sedimentological and stratigraphic investigations at a regional scale are employed in the interpretation of thick units or sequences of diamicton and two depositional scenarios are proposed. First, glacier-marginal till thickening and the stacking of till wedges takes place in areas where an ice stream margin was stationary for short periods of time. Stacks of subglacial traction tills potentially record annual sub-marginal incremental thickening at ice stream margins especially in areas where densely spaced recessional push moraines appear to record seasonal climatic forcing. Second, proglacial lake and valley infilling with glacilacustrine rhythmites and mass flow diamictons is associated with the advection of sub-marginal till into preglacial bedrock depressions and records ice stream marginal oscillations and debris influx into discontinuous proglacial lakes, which act as subaqueous sediment sinks for materials that would otherwise have been used to construct sub-marginal till wedges and moraines. Glacial overriding modifies the deposits produced in both scenarios through deformation and the dislocation and entrainment of bedrock and sediment rafts at the margins of bedrock valley walls, resulting in the widespread development of glacitectonites and megablocks. The occurrence of the thickest deposits as preglacial valley fills may be significant in groundwater siphoning away from subglacial deforming layers and the promotion of sticky spots.

Evans, David J. A.; Hiemstra, John F.; Boston, Clare M.; Leighton, Iain; Cofaigh, Colm Ó.; Rea, Brice R.

2012-07-01

42

Sedimentology and Sequence Stratigraphy of the Lower Cretaceous Fortress Mountain and Torok Formations Exposed Along the Siksikpuk River, North-Central Alaska  

USGS Publications Warehouse

An exposure of the Lower Cretaceous Fortress Mountain and Torok Formations along the Siksikpuk River in north-central Alaska provides a rare opportunity to observe the stratigraphic contact between these two formations and to interpret the depositional facies and sequence stratigraphy of the exposed strata. The Fortress Mountain Formation at the base of the measured section includes braided-fluvial and coastal-plain facies deposited in a lowstand-systems tract, and an overlying succession of mostly shallow marine facies deposited in the basal part of a transgressive-systems tract. The overlying Torok Formation includes a thick, upward-deepening succession of marine-shelf to marine-slope facies deposited in the upper part of the transgressive-systems tract. The upper part of the section includes marine-slope and incised-slope-channel turbidite deposits of the Torok Formation, interpreted as a highstand-systems tract. Consideration of the balance between accommodation and sediment flux inferred from the sequence-stratigraphic analysis suggests that both tectonics and eustasy may have influenced deposition of the lowstand-systems and transgressive-systems tracts. In contrast, the highstand-systems tract may have been primarily influenced by progradation of a regional sediment-dispersal system and by subsidence induced by sediment loading.

Houseknecht, David W.; Schenk, Christopher J.; Wartes, Marwan A.

2007-01-01

43

A re-evaluation of the stratigraphy and sedimentology of the Day Point Formation (Chazy Group): A new look at old reefs  

SciTech Connect

The Day Point Formation (Chazy Group, Middle Ordovician) outcrops in the Champlain Valley of New York and Vermont. The stratigraphy of the Day Point Formation is complex, containing lithologic sequences that are unique at different localities around the Champlain Valley. The formation exhibits complex lateral interfingering of seven lithofacies: (1) Highly bioturbated sandstone with symmetrical and bifurcating ripples. (2) Bioturbated, brachiopod rich, wackestone facies. (3) Planar cross-bedded, interlayered sand and sandy packstone. (4) Interlayered sand and shale grading into sand and limestone layers. (5) Grainstone which, at some localities, contains mound-shaped bryozoan reefs, at other localities thin non-reefal sheet-like layers are present. The grainstone also has planar laminated and cross stratified beds. (6) Fine-grained, calcareous sandstone with planar and herringbone cross bedding, which in places contains small bryozoan reefs and thin sheet-reefs. (7) Planar cross bedded packstone containing bryozoan reefs and thin sheet-like non-reefal layers. The thin reefal layers are found where the mound-shaped reefs are absent. The sand units are found only in the lower portion of the Day Point Formation. The bryozoan reefs and non-reefal layers are associated with the sand beds in the lower portion of the Day Point Formation, and either live within the sand or on top of it. The bryozoans that form the non-reefal layers, found in the limestones, are contained within thin layers of sand. In contrast, no sand is found in the upper section of the Day Point Formation, yet the bryozoan reefs flourish.

Falkenberg, J.; Mehrtens, C.J. (Vermont Univ., Burlington, VT (United States). Dept. of Geology)

1993-03-01

44

Stratigraphy and age of the Cappadocia ignimbrites, Turkey: reconciling field constraints with paleontologic,  

E-print Network

with paleontologic, radiochronologic, geochemical and paleomagnetic data J.-L. Le Penneca, , A. Temelb , J Valibaba Tepe ignimbrite. Keywords: ignimbrite; geochronology; paleontology; stratigraphy; rock magnetism

45

Revised stratigraphy of the Trenton Group in its type area, central New York State: sedimentology and tectonics of a Middle Ordovician shelf-to-basin succession  

NASA Astrophysics Data System (ADS)

This paper presents new stratigraphic correlations of the middle and upper parts of the Trenton Group in the type area, near Trenton Falls, New York, based on detailed bed by bed matching, of all outcrop sections. This work, in conjunction with newly revised biostratigraphy and geochemical fingerprinting of K-bentonites, has been used to establish a high resolution chronology for these deposits. Our revised correlations reveal that published stratigraphic-geochronologic schemes are largely in error, resolve several long-standing dilemmas, and have important implications for interpreting sedimentological and tectonic history of the Taconic foreland basin. Key new conclusions/revisions include: (1) The lowermost part of the Trenton type section at Trenton Falls is laterally equivalent to the Rathbun Member of the Sugar River Limestone (lower Shermanian) in the Newport-Herkimer, New York area. (2) The medial Trenton (Denley Formation), dated primarily within the Corynoides americanus graptolite Zone, can be divided in ascending order into two distinctive units, the Poland, Russia members, each of which is further subdivisible into component shallowing-upward cycles and condensed beds. As such, the Poland is completely exposed at Trenton Gorge (contrary to assertions by previous authors) and is about 10.5 m-thick. At its type section, also Trenton Gorge, the overlying Russia Member, comprising four shallowing-upward cycles, extends upward from the Kuyahoora K-bentonites for about 24 m to its sharp upper contact with another distinctive and fingerprinted K-bentonite, the High Falls ash bed. (3) Both the Poland and Russia members thin southeastward from Trenton Falls and become condensed in downslope sections near Middleville. However, the Poland section then thickens and passes eastward into basinal dark gray shales (lower-medial part of the Flat Creek Formation) in central Mohawk Valley sections, whereas the Russia remains thin and relatively carbonate-rich throughout this area. (4) A third unit, the Rust Limestone is elevated to formation status and subdivided into members. The lower part of the Rust Formation (Mill Dam Member) thins dramatically to the southeast from about 12 m at Trenton Falls to 1.5-2 m in the Middleville-Herkimer area before thickening again into basinal black shale facies. (5) The upper Rust and Steuben formations (coarse skeletal pack-to grainstone facies) of the Trenton Falls area apparently thin by condensation into the Newport area before expanding again into turbiditic slope facies of the Dolgeville Formation (essentially corresponding to the Orthograptus ruedemanni graptolite zone) beginning in the Middleville-Herkimer area. The new correlations imply that the lower-middle Rust interval belongs to the Corynoides americanus graptolite Zone, and that the upper Rust-Steuben interval probably belongs in the O. ruedemanni Zone, rather than the Climacograptus spiniferus or even to the lower Geniculograptus pygmaeus Zone, as previously inferred. (6) The Dolgeville carbonate turbidite facies is found to extend eastward to the vicinity of the Hoffmans Fault, east of Amsterdam. (7) Slumped breccia-filled channels in shelf-margin facies of the upper Rust and Steuben limestones may have served as feeder conduits to submarine fans now represented by the Dolgeville Formation. These observations indicate that a sediment-starved east-facing submarine ramp was developed across the study area during Shermanian time. Regional lithospheric flexure coupled with westward retreat of the shelf, explains the distribution of condensed facies and discontinuities. The widespread distribution of many marker beds plus the observation of spectral facies gradations at many levels, suggests that submarine faulting was usually a minor process superimposed on larger-scale diastrophic and eustatic patterns.

Brett, Carlton E.; Baird, Gordon C.

2002-01-01

46

STRATIGRAPHY OF COUNTER-POINT-BAR AND EDDY-ACCRETION DEPOSITS IN LOW-ENERGY MEANDER BELTS OF THE PEACE-ATHABASCA  

E-print Network

Sedimentologic Solutions, 2104 3rd Avenue NW, Calgary, AB, T2N 0K4, Canada DALE A. LECKIE, AND MILOVAN FUSTIC 801 little research attention, and their stratigraphy and sedimentology is poorly understood in modern-point-bar deposits (CPBD) (Smith et al., 2009). Smith et al. (2009) examined the stratigraphy, sedimentology

47

Stratigraphy and sedimentology of radioactive Devonian--Mississippian shales of the central Appalachian Basin. Final report, April 1, 1975December 31, 1976  

Microsoft Academic Search

In eastern Kentucky and nearby, the Ohio Shale--a radioactive, black, organic-rich shale of Late Devonian age--consists of two dominant lithologic types, which occur in a distinctive stratigraphic sequence. These two lithologies are brownish-black, organic-rich shale and greenish-gray, organic-poor shale and mudstone. Five to seven stratigraphic subunits can be recognized easily in both the subsurface and outcrop and are traceable over

Provo

1976-01-01

48

Analytical sedimentology  

SciTech Connect

Both a self instruction manual and a cookbook'' guide to field and laboratory analytical procedures, this book provides an essential reference for non-specialists. With a minimum of mathematics and virtually no theory, it introduces practitioners to easy, inexpensive options for sample collection and preparation, data acquisition, analytic protocols, result interpretation and verification techniques. This step-by-step guide considers the advantages and limitations of different procedures, discusses safety and troubleshooting, and explains support skills like mapping, photography and report writing. It also offers managers, off-site engineers and others using sediments data a quick course in commissioning studies and making the most of the reports. This manual will answer the growing needs of practitioners in the field, either alone or accompanied by Practical Sedimentology, which surveys the science of sedimentology and provides a basic overview of the principles behind the applications.

Lewis, D.W. (Univ. of Canterbury, Christchurch (New Zealand). Dept. of Geology); McConchie, D.M. (Southern Cross Univ., New South Wales (Australia). Centre for Coastal Management)

1994-01-01

49

Initial insights from the Baumkirchen Palaeo-lake Record: Sedimentology, Stratigraphy and Geochemistry of a unique Marine Isotope Stage 3 succession in the Alps  

NASA Astrophysics Data System (ADS)

We present preliminary results from a 150 m-long core through a lacustrine sediment sequence from the Lower Inn Valley in the Eastern Alps. The banded clay sequence of Baumkirchen is the longest (over 220 m) known continuous pre-LGM sediment sequence in the Alps. Radiocarbon dates of wood from the upper section place the sequence in Marine Isotope Stage 3. Therefore the sequence provides a unique opportunity to study the climatic and ecological impacts of Greenland/North Atlantic Dansgaard Oeschger events (high frequency-high amplitude climate fluctuations) on the European Alps in high resolution. Millimetre and micrometre-scale X-ray fluorescence records, X-ray diffraction data, thin-section analysis and visual inspection reveal complexly laminated (mm-cm) sediments mainly of silt grain size, rich in mica with occasional coarse silty to fine sandy turbidites (mm to >10 cm thick). X-ray diffraction in conjunction with X-ray fluorescence reveal high-amplitude variations in both dolomite (dominant) and calcite suggesting a clastic origin of the laminae. No evidence of authigenic calcite forming biogenic varves was found. Rare, short sections (up to 0.5 m) are unlaminated, and along with variations in lamina thickness and frequency of turbidites, show changing sedimentary conditions, giving a relative and qualitative record of environmental and climatic change through the lake's history. Future work will focus on quantitative proxies (e.g. pollen and biomarkers) and establish an age model using optically stimulated luminescence dating. A further coring campaign (summer 2013) will increase the length of the core to cover the entire lacustrine section, possibly covering the entire Marine Isotope Stage 3.

Barrett, Samuel; Spötl, Christoph; Brauer, Achim; Dulski, Peter

2013-04-01

50

AGE AND ORIGIN OF THE CHICXULUB IMPACTAND SANDSTONE COMPLEX, BRAZOS RIVER, TEXAS: EVIDENCE FROM LITHOSTRATIGRAPHY AND  

E-print Network

LITHOSTRATIGRAPHY AND SEDIMENTOLOGY THIERRY ADATTE Geological and Paleontological Institute, Anthropole, CH-1015 on the lithology, sedimentology, mineralogy, and biostratigraphy of upper Maastrichtian to lower Danian boundary, sedimentology, sequence stratigraphy, mineralogy, organic matter, sea level, depositional environment, incised

Keller, Gerta

51

Stratigraphy and sedimentology of the Niger Delta  

NASA Astrophysics Data System (ADS)

During the Cenozoic, until the Middle Miocene, the Niger Delta grew through pulses of sedimentation over an oceanward-dipping continental basement into the Gulf of Guinea; thereafter progradation took place over a landward-dipping oceanic basement. A 12,000 m thick succession of overall regressive, offlapping sediments resulted that is composed of three diachronous siliciclastic units: the deep-marine pro-delta Akata Group, the shallow-marine delta-front Agbada Group and the continental, delta-top Benin Group. Regionally, sediment dispersal was controlled by marine transgressive/regressive cycles related to eustatic sea-level changes with varying duration. Differential subsidence locally influenced sediment accumulation. Collectively, these controls resulted in eleven chronostratigraphically confined delta-wide mega-sequences with considerable internal lithological variation. The various sea-level cycles were in or out of phase with each other and with local subsidence, and interfered with each other and thus influenced the depositional processes. At the high inflection points of the long-term eustatic sea-level curve, floodings took place that resulted in delta-wide shale markers. At the low inflection points, erosional channels were formed that are often associated, downdip, with turbidites in low-stand sediments (LSTs). The megasequences contain regional transgressive claystone units (TST) followed by a range of heterogeneous fine-to-coarse progradational or aggradational siliciclastic (para)sequence sets formed during sea-level high-stand (HST). An updated biostratigraphic scheme for the Niger Delta is presented. It also updates a sedimentation model that takes into consideration local and delta-wide effects of sea-level cyclicity and delta tectonics. Megasequences were formed over time intervals of ~5 Ma within individual accurate megastructures that laterally linked into depobelts. The megasequences form the time-stratigraphic frame of the delta and are the backbone for the new delta-wide lithostratigraphy proposed here. Such a new lithostratigraphy is badly needed, in particular because of the vigorous new activity in the offshore part of the Niger Delta (not covered in this contribution). There, as well as in the onshore part of the delta, the traditional lithostratigraphic subdivision of the Cenozoic Niger Delta section into three formations is insufficient for optimum stratigraphic application; moreover, the various informal subdivisions that have been proposed over time are inconsistent.

Reijers, T. J. A.

2011-09-01

52

Kandik basin stratigraphy, sedimentology, and structure  

SciTech Connect

East-central Alaska's Kandik basin is a structural remnant of a larger Permian to Cretaceous basin. Permian shallow-water Tahkandit Limestone and Step Conglomerate at the base of the sequence rest unconformably on Paleozoic chert-pebble conglomerate, siliceous shale, and limestone. These Permian rocks are overlain by Triassic to Lower Cretaceous open-ocean Glenn Shale, which grades upward into Lower Cretaceous (Valanginian) hummocky cross-bedded (outer shelf to upper slope) Keenan Quartzite. The quartzite grades upward into fine-grained north-northeast-flowing turbidites of the Biederman Argillite (undated). East-northeast-flowing pebbly turbidites of the Kathul Graywacke (undated) overlie Biederman strata. Locally, Cretaceous (Albian and younger) through Paleogene nonmarine rocks unconformably overlie the Kandik basin sequence. The Mesozoic part of the sequence is similar to that of Manley basin, northwest Yukon Territory, and much of the North Slope. East-directed flow for Kandik basin strata may require paleogeographic reconstructions involving local to large-scale palinspastic rotations or a western source of chert detritus. Deformation of the Mesozoic sequence in Kandik basin west of the US-Canada border shows northwest-southeast shortening. Shaly units are tightly folded with well-developed cleavage striking northeast. Strikes of beds swing from northeast to east in the extreme southwestern part of the basin, suggesting clockwise rotation. Thrust faults, reverse faults, and fold axes trend east to northeast; normal faults trend northwest. These relations are all consistent with, and probably are closely related to, right slip on the west-northwest-trending Tintina fault.

Wiley, T.J.; Howell, D.G.; Kauffman-Linam, L.; Boundy-Sanders, S.; Murray, R.W.; Jones, D.L.

1987-05-01

53

The Cambrian to Devonian odyssey of the Brabant Massif within Avalonia: A review with new zircon ages, geochemistry, Sm-Nd isotopes, stratigraphy and palaeogeography  

NASA Astrophysics Data System (ADS)

This study provides an up-to-date and comprehensive review of the Early Palaeozoic evolution of the Brabant Massif belonging to the Anglo-Brabant Deformation Belt. Situated at the southeastern side of Avalonia microplate, it is the only well-known part of the northern passive margin of the Rheic Ocean. The Cambrian-Silurian sedimentary pile is > 13 km thick, with > 9 km for the Cambrian only. The unraveling of this continuous registration reflects the successive rifting and drifting of Avalonia from the Gondwana mainland, followed by soft-collisional processes with Baltica and finally the formation of Laurussia. Based on recently established detailed stratigraphy, sedimentology and basin development, on U-Pb LA-ICP-MS analyses of igneous and detrital zircon grains along with geochemical data including Sm-Nd isotopes, a new geodynamic and palaeogeographic evolution is proposed. Brabant Megasequence 1 (lower Cambrian to lowermost Ordovician, > 9 km thick) represents an embayment of the peri-Gondwanan rift from which the Rheic Ocean has evolved. Detrital zircon ages demonstrate that the Brabant is a typical peri-Gondwanan terrane with a major Pan-African (Neoproterozoic age) and a mixed West African and Amazonian source (Palaeoproterozoic, Archaean and some Mesoproterozoic age). The transition towards the Avalonia drifting is marked by an unconformity and a short volcanic episode. The northward drift of Avalonia towards Baltica is recorded by the Megasequence 2 (Middle to Upper Ordovician, 1.3 km thick). The source for Mesoproterozoic zircons vanished, as the result of the Rheic Ocean opening and the isolation from Amazonian sources. The transition to Megasequence 3 is marked by a drastic change in palaeobathymetry and an important (sub)volcanic episode during a tectonic instability period (460-430 Ma), reflecting the Avalonia-Baltica soft docking as also shown by the reappearance of Mesoproterozoic detrital zircons, typical of Baltica. Unradiogenic Nd isotope signature (?Nd - 4/- 5) and TDM model ages (1.3-1.7 Ga) for Brabant magmatic rocks indicate an old recycled component. Megasequence 3 (uppermost Ordovician to lowermost Devonian; > 3.5 km thick) includes the onset of a Silurian foreland basin that reflects the tectonic inversion of the core of the massif (Brabantian orogeny) in response to the Baltica-Avalonia-Laurentia collision. Finally, the comparison with the strikingly similar Cambrian successions of the Harlech Dome (Wales, Avalonia) and the Meguma terrane (Nova Scotia, peri-Gondwana) allows the construction of a new Early Cambrian palaeogeographic model for the whole Avalonia microplate, in which the Meguma terrane is included.

Linnemann, Ulf; Herbosch, Alain; Liégeois, Jean-Paul; Pin, Christian; Gärtner, Andreas; Hofmann, Mandy

2012-05-01

54

Sedimentology, paleontology and age of the Ayacara and Lago Ranco formations (south-central Chile, 40°- 42°S). Tectonic implications.  

NASA Astrophysics Data System (ADS)

Deep-marine, Mio-Pliocene strata correlative with the Navidad Formation crop out in different areas along the forearc of south-central Chile (~34°-41°) and have also been recognized in boreholes drilles on the continental shelf. However, at Lago Ranco (40°S) and Ayacara (42°) there are outcrops of marine strata whose age and correlation with these units remain uncertain. These deposits consist of rhythmic successions of sandstone and siltstone representing facies similar to those of the Navidad and correlative formations. These marine successions are known ase the Estratos de Lago Ranco and Ayacara formations. They both crop out in the western Andean Cordillera near the limit with the Intermediate Depression at Lago Ranco and the submerged equivalent of this physiographic unit at Ayacara. There are very few studies carried out on these units and most of them consist on internal reports and unpublished theses.In order to unravel the sedimentary enviroment, age and tectonic history of this area during the Neogene we carried out sedimentological, ichnological and micropaleontological studies. In addition, we carried out U-Pb dating in detrital zircons (LAICPMS and SHRIMP). Our studies show the presence of sedimentary features and ichnofacies typical of deposition in a deep-marine environment for these units..In agreement, benthic foraminifers (Ciclamina incisa and Siphonodosaria sangrinensis) indicate lower bathial depths (1500 m). U-Pb (LAICPMS and SHRIMP) indicate a maximum depositional age of around 20 Ma for these units. In agreement, the occurrence of the planktic foraminifer species Globorotalia siakensis (P22-N14), Globigerinoides quadrilobatus (N6-Recent) and Globigerinoides sikanus (N8-N9) in strata of the Ayacara Formation suggest an early-middle Miocene age for this unit. These data indicate that the area corresponding to the western Main Andean Cordillera in south central Chile, was subjeted to major subsidence during the early-middle Miocene. Major subsidence of the margin has been attributed to an important event of subduction erosion that would have removed the underside of the upper continental plate and caused its thinning.

Encinas, Alfonso; Zambrano, Patricio; Bernabe, Pablo; Finger, Kenneth; Buatois, Luis; Duhart, Paul; Valencia, Victor; Fanning, M.; Herve, Francisco

2010-05-01

55

Mars Stratigraphy Mission  

NASA Technical Reports Server (NTRS)

The Mars Stratigraphy Mission lands a rover on the surface of Mars which descends down a cliff in Valles Marineris to study the stratigraphy. The rover carries a unique complement of instruments to analyze and age-date materials encountered during descent past 2 km of strata. The science objective for the Mars Stratigraphy Mission is to identify the geologic history of the layered deposits in the Valles Marineris region of Mars. This includes constraining the time interval for formation of these deposits by measuring the ages of various layers and determining the origin of the deposits (volcanic or sedimentary) by measuring their composition and imaging their morphology.

Budney, C. J.; Miller, S. L.; Cutts, J. A.

2000-01-01

56

Ninth international congress on Carboniferous stratigraphy and geology. Proceedings, volume 3. Neuvieme congres international de stratigraphie et de geologie du Carbonifere. Compte rendu, volume 3  

SciTech Connect

Papers were presented on the Carboniferous stratigraphy of the Atlantic Coast basins, on paleogeography and paleotectonics and on sedimentology and geochemistry. A total of 14 papers concerning coal have been abstracted separately. Papers are in English or in French.

Geldsetzer, H.H.J.; Nassichuk, W.W.; Belt, E.S.; Macqueen, R.W.

1984-01-01

57

Cambrian Stratigraphy  

NSDL National Science Digital Library

This site describes in detail the stratigraphy of the Cambrian period, starting approximately 545 million years ago and ending about 490 million years ago. It was one of the most important and dramatic periods because the lower boundary of the Cambrian is not only the beginning of a new system, but also the start of the Paleozoic and the Phanerozoic. Also the Early Cambrian saw the extremely rapid diversification of multicellular animals, the Cambrian Explosion, which determined the animal evolution and is indirectly responsible for present-day life. The site defines both the bottom and the top of the Cambrian layers and also provides a list of type sections with corresponding dates. Two charts are provided. One shows the changes in age assignments from 1982 to 1998 and another shows a time line for the Vendian and the Cambrian. The site also includes a section on isotopic studies and paleomagnetism of Cambrian strata.

58

Carbon isotope stratigraphy, magnetostratigraphy, and 40Ar/39Ar age of the Cretaceous South Atlantic coast, Namibe Basin, Angola  

NASA Astrophysics Data System (ADS)

We present the ?13C and paleomagnetic stratigraphy for marine strata at the coast of southern Angola, anchored by an intercalated basalt with a whole rock 40Ar/39Ar radiometric age of 84.6 ± 1.5 Ma, being consistent with both invertebrate and vertebrate biostratigraphy. This is the first African stable carbon isotope record correlated to significant events in the global carbon record spanning the Late Cenomanian to Early Maastrichtian. A positive ?3‰ excursion seen in bivalve shells below the basalt indicates the Cenomanian-Turonian Boundary Event at 93.9 Ma, during Oceanic Anoxic Event 2. Additional excursions above the basalt are correlated to patterns globally, including a negative ?3‰ excursion near the top of the section interpreted as part of the Campanian-Maastrichtian Boundary Events. The age of the basalt ties the studied Bentiaba section to a pulse of Late Cretaceous magmatic activity around the South Atlantic and significant tectonic activity, including rotation, of the African continent.

Strganac, Christopher; Salminen, Johanna; Jacobs, Louis L.; Polcyn, Michael J.; Ferguson, Kurt M.; Mateus, Octávio; Schulp, Anne S.; Morais, Maria Luísa; Tavares, Tatiana da Silva; Gonçalves, António Olímpio

2014-11-01

59

Sedimentology, weathering, age and geomorphological significance of Tertiary sediments on the far south coast of New South Wales  

Microsoft Academic Search

The age of the NSW coastal lowland from Tuross to the Victorian border can now be shown to be at least mid?Tertiary. By this time the coastal plain had twice been partially blanketed by terrestrial sediments. Palaeomagnetic determinations on the more recent of these sedimentary accumulations, the Long Beach Formation, reveal a minimum depositional age of Early Miocene. Eustatic influences

J. F. Nott; R. W. Young; M. Idnurm

1991-01-01

60

Late Quaternary sedimentological and climate changes at Lake Bosumtwi Ghana: new constraints from laminae analysis and radiocarbon age modeling  

USGS Publications Warehouse

The Lake Bosumtwi sediment record represents one of the longest and highest-resolution terrestrial records of paleoclimate change available from sub-Saharan Africa. Here we report a new sediment age model framework for the last ~ 45 cal kyr of sedimentation using a combination of high-resolution radiocarbon dating, Bayesian age-depth modeling and lamination counting. Our results highlight the practical limits of these methods for reducing age model uncertainties and suggest that even with very high sampling densities, radiocarbon uncertainties of at least a few hundred years are unavoidable. Age model uncertainties are smallest during the Holocene (205 yr) and the glacial (360 yr) but are large at the base of the record (1660 yr), due to a combination of decreasing sample density, larger calibration uncertainties and increases in radiocarbon age scatter. For portions of the chronology older than ~ 35 cal kyr, additional considerations, such as the use of a low-blank graphitization system and more rigorous sample pretreatment were necessary to generate a reliable age depth model because of the incorporation of small amounts of younger carbon. A comparison of radiocarbon age model results and lamination counts over the time interval ~ 15–30 cal kyr agree with an overall discrepancy of ~ 10% and display similar changes in sedimentation rate, supporting the annual nature of sediment laminations in the early part of the record. Changes in sedimentation rates reconstructed from the age-depth model indicate that intervals of enhanced sediment delivery occurred at 16–19, 24 and 29–31 cal kyr, broadly synchronous with reconstructed drought episodes elsewhere in northern West Africa and potentially, with changes in Atlantic meridional heat transport during North Atlantic Heinrich events. These data suggest that millennial-scale drought events in the West African monsoon region were latitudinally extensive, reaching within several hundred kilometers of the Guinea coast. This is inconsistent with a simple southward shift in the mean position of the monsoon rainbelt, and requires changes in moisture convergence as a result of either a reduction in the moisture content of the tropical rainbelt, decreased convection, or both.

Shanahan, Timothy M.; Beck, J. Warren; Overpeck, Jonathan T.; McKay, Nicholas P.; Pigati, Jeffrey S.; Peck, John A.; Scholz, Christopher A.; Heil, Clifford W., Jr.; King, John

2012-01-01

61

Whither stratigraphy?  

NASA Astrophysics Data System (ADS)

There have been three revolutions in sedimentary geology. The first two began in the 1960s, consisting of the development of process-response sedimentary models and the application of plate-tectonic concepts to large-scale aspects of basin analysis. The third revolution, that of sequence stratigraphy, began in the late 1970s and helped to draw together the main results of the first two: the knowledge of autogenic processes learned through facies analysis, and the understanding of tectonism implicit in the unravelling of regional plate kinematics. Developments in the use of seismic-reflection data and the evaluation of a hypothesis of global eustasy provided considerable stimulation for stratigraphic research. Current developments in the field of sequence stratigraphy are focusing on three areas. (1) Elaboration of the sequence-architecture models for various configurations of depositional environment and sea-level history. (2) Exploration of various mechanisms for sequence generation, especially tectonism and orbital forcing. (3) Attempts to improve the level of precision in stratigraphic correlation and to refine the geological time scale, as a means to test the model of global eustasy. The growth in the power of computers and our knowledge of physical and chemical processes has led to the evolution of an entirely new way of evaluating earth history, termed quantitative dynamic stratigraphy. Mathematical modelling and numerical simulation of complex earth processes are now possible, and require the collection and integration of a wide array of quantitative and qualitative data sets. Applications include the study of the geodynamic evolution of sedimentary basins, modelling of stratigraphic sequences and global climates, studies of Milankovitch cycles (cyclostratigraphy) and simulation of fluid flow through porous media. The Global Sedimentary Geology Program has brought many of these areas of study together in multidisciplinary, global-scale studies of the sedimentary history of the earth. The results of these studies have wide application to many problems of importance to the human condition, including the past history of global climate change and other environmental concerns. The study of stratigraphy is at the centre of the new view of the earth, termed earth-systems science, which views earth as an 'organic' interaction between the lithosphere, biosphere, hydrosphere, and atmosphere.

Miall, Andrew D.

1995-12-01

62

Practical sedimentology, Second edition  

SciTech Connect

This book is for technical professionals in mineral exploration, environmental management, agriculture or forestry, this new edition takes an interdisciplinary approach to provide a lively and detailed overview of practical sedimentology. Emphasizing application over theory, the text is streamlined for comprehension, and it features many summary tables and graphs. The ideal companion to Analytical Sedimentology, this volume updates both methodology and applications, incorporates software information and extensively covers new technical developments. Specifically designed for students and cross-functional practitioners, it requires minimal geological background.

Lewis, D.W. (Univ. of Canterbury, Christchurch (New Zealand). Dept. of Geology); McConchie, D.M. (Southern Cross Univ., New South Wales (Australia). Centre for Coastal Management)

1994-01-01

63

Sedimentology of the Pennsylvanian and Permian Strathearn Formation, Northern Carlin Trend, Nevada; with a section on microfossil controls on the age of the Strathearn Formation  

USGS Publications Warehouse

Two framework-supported, poorly bedded conglomerate units of the middle Upper Pennsylvanian and middle Lower Permian Strathearn Formation belonging to the overlap assemblage of the Antler orogen are prominent in the northern Carlin trend. These horizons stratigraphically and temporally bracket thrust emplacement of a major allochthonous thrust plate of mainly quartzarenite of the Ordovician Vinini Formation. Lithologic and shape-ratio data from approximately 4,200 pebbles and cobbles at 17 sites as well as biostratigraphic data in the Strathearn, and their geologic implications, are included in this report. Conodont biofacies throughout the Strathearn Formation are normal marine and suggest middle shelf or deeper depositional environments. The conglomerate units roughly are similar in that they contain only chert and quartzarenite pebbles, but they differ in compositional proportions of the two lithologies. The relative proportion of quartzarenite pebbles increases sixfold in the middle Lower Permian upper conglomerate unit versus its content in the middle Upper Pennsylvanian lower unit, whereas chert pebbles predominate in both units. Various roundness categories of chert pebbles in both conglomerate units of the Strathearn show that the equant pebble class (B/A) = 1 clearly is represented strongly even in the subangular category, the lowest roundness categories for the pebbles. Thus, development of equant pebbles cannot be ascribed totally to a rounding process during predeposition transport. The equant character of many pebbles might, in part, be an original feature inherited from pre-erosion rock fractures and (or) bedding that control overall form of the fragments prior to their release to the transport environment. The allochthon of the Coyote thrust has been thrust above the lower conglomerate unit of the Strathearn during a regionally extensive contractional event in the late Paleozoic. The middle Lower Permian upper conglomerate unit, highest unit recognized in the Strathearn Formation, as well as similarly-aged dolomitic siltstone, onlap directly onto quartzarenite that comprises the allochthon of the Coyote thrust. The conglomerate units thus represent submarine fanglomerates whose quartz grains and quartzarenite fragments of variable roundness and shape were derived from a sedimentologically restored largely southeastward advancing late Paleozoic allochthonous lobe of mostly quartzarenite of the Ordovician Vinini Formation. Chert fragments in the conglomerates probably were derived mostly from Devonian Slaven Chert, including a widespread thick melange unit of the Slaven in the footwall of the Coyote thrust. Some chert pebbles may have been derived from the Ordovician Vinini Formation.

Berger, Vladimir I.; Singer, Donald A.; Theodore, Ted G.; Harris, Anita G.; Stevens, Calvin H.

2001-01-01

64

JOHN W. SNEDDEN RESEARCH INTERESTS: Sequence Stratigraphy, sedimentology, reservoir development  

E-print Network

, Shale Gas, Light Tight Oil). CERTIFIED PETROLEUM GEOLOGIST #5279 AWARDS AND KEY PROFESSIONAL SOCIETY. 32, p. 497-514. Snedden, J.W., 1984, Validity of the use of the spontaneous potential curve shape, in Barwis, J.H., McPherson, J.G., and Studlick, J.R.J., eds., Sandstone Petroleum Reservoirs: Casebooks

Yang, Zong-Liang

65

First Clarkforkian Equivalent Land Mammal Age in the Latest Paleocene Basal Sparnacian Facies of Europe: Fauna, Flora, Paleoenvironment and (Bio)stratigraphy  

PubMed Central

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a “miacid” carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America. PMID:24489703

Smith, Thierry; Quesnel, Florence; De Ploeg, Gael; De Franceschi, Dario; Metais, Gregoire; De Bast, Eric; Sole, Floreal; Folie, Annelise; Boura, Anais; Claude, Julien; Dupuis, Christian; Gagnaison, Cyril; Iakovleva, Alina; Martin, Jeremy; Maubert, Francois; Prieur, Judicael; Roche, Emile; Storme, Jean-Yves; Thomas, Romain; Tong, Haiyan; Yans, Johan; Buffetaut, Eric

2014-01-01

66

First Clarkforkian equivalent Land Mammal Age in the latest Paleocene basal Sparnacian facies of Europe: fauna, flora, paleoenvironment and (bio)stratigraphy.  

PubMed

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a "miacid" carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America. PMID:24489703

Smith, Thierry; Quesnel, Florence; De Plöeg, Gaël; De Franceschi, Dario; Métais, Grégoire; De Bast, Eric; Solé, Floréal; Folie, Annelise; Boura, Anaïs; Claude, Julien; Dupuis, Christian; Gagnaison, Cyril; Iakovleva, Alina; Martin, Jeremy; Maubert, François; Prieur, Judicaël; Roche, Emile; Storme, Jean-Yves; Thomas, Romain; Tong, Haiyan; Yans, Johan; Buffetaut, Eric

2014-01-01

67

Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy  

Microsoft Academic Search

The approach of ‘dynamic stratigraphy’ aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales. This approach was used to investigate Quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties. Facies analysis within 62 gravel pits, laboratory permeability measurements

Jürgen Heinz; Thomas Aigner

2003-01-01

68

Sedimentology and depositional environments of part of the Walden Creek Group, central east Tennessee  

SciTech Connect

Recent questions concerning the age of the Walden Creek Group (WCG), Ocoee Supergroup have increased interest in the depositional history of these rocks. This study focuses on the sedimentology and local stratigraphy of rocks in exposures of the lithologically diverse late Precambrian and/or lower Paleozoic WCG occurring within the Kinzel Springs and Wear Cove quadrangles. Units exposed in the structurally complex Alleghenian thrust setting include the Licklog, Shields, and Wilhite formations. These rocks are divided into twelve lithofacies composed of shale, siltstone, sandstone, conglomerate and carbonate rock. The lithofacies are grouped into seven facies associations indicating deposition below storm wave base in a deep-water, probably marine, environment. Within the study area, rocks of the Wilhite Formation represent deposition in basin plain, lower slope, slope, base of slope, and sandy channel environments. Rocks of the Shields Formation are coarse channel and related overbank deposits of the inner to middle parts of a deep water fan environment. The Licklog Formation contains rocks deposited as lobe and outer-fan or fan-fringe deposits in a middle- to lower-fan environment. These formations can be placed within a single depositional system composed of a submarine slope transitional with a basin plain, and of proximal channels and distal lobes in a sand-rich submarine fan system. Inferred depositional components (associations) compare well with general models of deep-water deposits associated with high gradient fan-delta-fed margins. The basin was bounded by an uplifted, most likely block faulted, margin composed of crystalline basement located to the northwest. Local sedimentologic and stratigraphic relationships suggest an overall progradational sequence during the deposition of these rocks.

Lewis, R.F. III (Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Geology and Geophysics); Miller, J.M.G. (Vanderbilt Univ., Nashville, TN (United States). Dept. of Geology)

1993-03-01

69

Precambrian sequence stratigraphy  

NASA Astrophysics Data System (ADS)

Sequence stratigraphy studies the change in depositional trends in response to the interplay of accommodation and sediment supply, from the scale of individual depositional systems to entire sedimentary basin-fills. As accommodation is controlled by allogenic mechanisms that operate at basinal to global scales, the change in depositional trends is commonly synchronized among all environments established within a basin, thus providing the basis for the definition of systems tracts and the development of models of facies predictability. All classical sequence stratigraphic models assume the presence of an interior seaway within the basin under analysis and are centered around the direction and types of shoreline shifts, which control the timing of all systems tracts and sequence stratigraphic surfaces. In overfilled basins, dominated by nonmarine sedimentation, the definition of systems tracts is based on changes in fluvial accommodation, as inferred from the shifting balance between the various fluvial architectural elements. The method of sequence stratigraphy requires the application of the same set of core principles irrespective of the age of strata under analysis, from Precambrian to Phanerozoic. The study of Precambrian basins is often hampered by poorer stratal preservation and by a general lack of time control. However, where sedimentary facies are well preserved, the lack of time control may be partially compensated by a good knowledge of facies architecture and relationships, as well as by paleocurrent data. The latter are particularly important to understand the stratigraphic record of tectonically active basins, where abrupt shifts in paleoflow directions allow one to infer tectonic events and map the corresponding sequence-bounding unconformities. Arguably the most important contribution of Precambrian research to sequence stratigraphy is the better understanding of the mechanisms controlling stratigraphic cyclicity in the rock record, and hence of the criteria that should be employed in a system of sequence stratigraphic hierarchy. There is increasing evidence that the tectonic regimes which controlled the formation and evolution of sedimentary basins in the more distant geological past were much more erratic in terms of origin and rates than formerly inferred solely from the study of the Phanerozoic record. In this context, time is largely irrelevant as a parameter in the classification of stratigraphic sequences, and it is rather the stratigraphic record of changes in the tectonic setting that provides the key criteria for the basic subdivision of the rock record into basin-fill successions separated by first-order sequence boundaries. These first-order basin-fill successions are in turn subdivided into second- and lower-order sequences that result from shifts in the balance between accommodation and sedimentation at various scales of observation, irrespective of the time span between two same-order consecutive events. Sequences identified in any particular basin are not expected to correlate to other first- and lower-order sequences of other basins that may be similar in age but may have different timing and duration.

Catuneanu, O.; Martins-Neto, M. A.; Eriksson, P. G.

2005-04-01

70

Cretaceous Tethyan Stratigraphy  

NSDL National Science Digital Library

The objective of this site is to construct a database for Cretaceous Tethyan stratigraphy. Stratigraphic information, photos and charts are arranged by geologic stage in a vertical menu. The types of information found in this site include basin reference sections, basin or platform control sections, biostratigraphic and sequence stratigraphic data, as well as other data that support and refine correlations. Access to scientific forums about Tethyan stratigraphy and a list of relevant links are also provided.

Bruno, Granier

71

The USGS Bedform Sedimentology Site  

NSDL National Science Digital Library

The USGS Bedform Sedimentology Site offers materials that are companions to the book: Cross-Bedding, Bedforms, and Paleocurrents, by D. M. Rubin of the USGS Pacific Science Center. Visitors can read an online version of the book, read about bedform initiation, view QuickTime and MPEG movies of bedforms and cross-bedding, download bedform simulation software, and find out how to identify low-dimensional deterministic systems (chaos) in time series or spatial patterns.

1999-01-01

72

International Commission on Stratigraphy  

NSDL National Science Digital Library

This site provides information about the International Commission on Stratigraphy, a collection of downloadable stratigraphic charts and columns, an abridged version of the International Stratigraphic Guide, links to industry journals and publications, and links to a collection of other stratigraphy-related websites. It also features a detailed chart of global boundary stratotype sections and points, as well as the Time Scale Creator, software that lets users create customized downloadable charts of any portion of the geologic time scale and correlated earth history events. The site also links to the GeoWhen Database, a collection of detailed time-scale representations and classifications.

Stratigraphy, International C.

73

Workshop on the Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution  

NASA Technical Reports Server (NTRS)

Papers that have been accepted for presentation at the Workshop on the Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution, on 12-14 Aug. 1993 in Fairbanks, Alaska are included. Topics covered include: hydrological consequences of ponded water on Mars; morphological and morphometric studies of impact craters in the Northern Plains of Mars; a wet-geology and cold-climate Mars model: punctuation of a slow dynamics approach to equilibrium; the distribution of ground ice on Mars; and stratigraphy of the Martian Northern Plains.

Kargel, Jeffrey S. (editor); Moore, Jeffrey (editor); Parker, Timothy (editor)

1993-01-01

74

Tectonic sequence stratigraphy, Early Permian Dry Mountain trough, east-central Nevada  

SciTech Connect

The Early Permian Dry Mountain trough (DMT) of east-central Nevada is one of several tectonic basins and associated uplifts that developed along the continenetal margin during the latest Pennsylvanian-Early Permian Dry Mountain tectonic phase. The sequence stratigraphy reflects a combination of eustatic sea level changes and tectonic uplift or subsidence. Fewer than one to only a few million years separate the development of sequence boundaries within the DMT. At this scale, differences among published eustasy curves preclude their use as definitive tools to identify eustatically controlled sequence boundaries. Nevertheless, available data indicate several pulses of tectonism affected sedimentation within the DMT. The authors are attempting to develop criteria to distinguish tectonic from eustatic sequence boundaries. Detailed biostratigraphic data are required to provide an independent check on the correlation of sequence boundaries between measured sections. For example, the same age boundary may reflect tectonic uplift in one part of the basin and subsidence in another. The uplift may or may not result in subaerial exposure and erosion. For those boundaries that do not result from subaerial exposure, lithofacies and biofacies analyses are required to infer relative uplift (water depth decrease) or subsidence (water depth increase). There are inherent resolution limitations in both the paleontologic and sedimentologic methodologies. These limitations, combined with those of eustasy curves, dictate the preliminary nature of their results.

Snyder, W.S.; Gallegos, D.M.; Spinosa, C. (Boise State Univ., ID (United States)); Schwarz, D.L. (Univ. of Iowa, Iowa City (United States))

1991-06-01

75

A luminescence dating study of the sediment stratigraphy of the Lajia Ruins in the upper Yellow River valley, China  

NASA Astrophysics Data System (ADS)

Pedo-sedimentological fieldwork were carried out in the Lajia Ruins within the Guanting Basin along the upper Yellow River valley. In the eolian loess-soil sections on the second river terrace in the Lajia Ruins, we find that the land of the Qijia Culture (4.20-3.95 ka BP) are fractured by several sets of earthquake fissures. A conglomerated red clay covers the ground of the Qijia Culture and also fills in the earthquake fissures. The clay was deposited by enormous mudflows in association with catastrophic earthquakes and rainstorms. The aim of this study is to provide a luminescence chronology of the sediment stratigraphy of the Lajia Ruins. Eight samples were taken from an eolian loess-soil section (Xialajia section) in the ruins for optically stimulated luminescence (OSL) dating. The OSL ages are in stratigraphic order and range from (31.94 ± 1.99) ka to (0.76 ± 0.02) ka. Combined OSL and 14C ages with additional stratigraphic correlations, a chronological framework is established. We conclude that: (1) the second terrace of the upper part of Yellow River formed 35.00 ka ago, which was followed by the accumulation of the eolian loess-soil section; and (2) the eolian loess-soil section is composed of the Malan Loess of the late last glacial (MIS-2) and Holocene loess-soil sequences.

Zhang, Yuzhu; Huang, Chun Chang; Pang, Jiangli; Zhou, Yali; Zha, Xiaochun; Wang, Longsheng; Zhou, Liang; Guo, Yongqiang; Wang, Leibin

2014-06-01

76

Snow Pit Stratigraphy  

NSDL National Science Digital Library

The student understands that snow leads to avalanches, but is often very inexperienced in the observation of the snow pack. This exercise provides the opportunity to learn about snow stratigraphy, observation, and measurement from a detailed observational perspective. The students work in small groups in 3-6 pits (depends on the class size). By working on a transect from the trees out into the opening, they discover (usually) that the snow depth is different and that the descriptions in the pits differ as one proceeds out from the trees into the opening. (Different stratigraphic units, different thickness, different temperature, different density, different crystals.)

Custer, Stephan

77

Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution  

Microsoft Academic Search

The latest Neoproterozoic through Phanerozoic stratigraphy of the Zagros fold-thrust belt of Iran has been revised in the light of recent investigations. The revised stratigraphy consists of four groups of rocks, each composed of a number of unconformity-bounded megasequences representing various tectonosedimentary settings. In the lowest group, ranging in age from latest Precambrian to Devonian(?), the uppermost Neoproterozoic to middle

MEHDI ALAVI

2004-01-01

78

Sedimentological Evidence of the 1812 Santa Barbara Tsunami in Carpinteria Marsh, CA  

NASA Astrophysics Data System (ADS)

The Santa Barbara coast is at risk for tsunamis generated from tectonic movement in areas of compression and extension associated with the San Andreas Fault, as well as from submarine landslide movement in the Santa Barbara channel. Historical documents and other records indicate Santa Barbara has experienced approximately sixteen historical tsunamis, the largest of which may have occurred on Dec 21, 1812, following a magnitude ~7.1 earthquake. We propose that an anomalous sand deposit, Sand Facies One (SF1), which is found within the first meter of sediment throughout Carpinteria Marsh in Carpinteria, CA, may represent deposition related to this event. We have collected 23 vibracores, up to 4.1 m in length, and three Geoprobe cores to ~14 m depth in Carpinteria Marsh. SF1 occurs in 20 of the 23 vibracores and exhibits sedimentological characteristics associated with a tsunami genesis such as: fining upward grain size, sharp or erosional basal contact, and thinning of the deposit landward. Mineralogy, deposit geometry, and X-Ray Florescence (XRF) data are used to determine a marine versus terrestrial origin for the layer. It is difficult, however, to differentiate between storm and tsunami deposits based purely on the sedimentary characteristics of a deposit. We show that an improved age chronology which includes exotic pollen stratigraphy and radiocarbon data indicates an age range appropriate for the 1812 event but does not exclude regional flooding events documented in the 1860s. We use the characteristics of SF1 to determine if similar layers occur at other depths in the Geoprobe cores. Preliminary core descriptions indicate that there is at least one layer which exhibits characteristics similar to SF1and may indicate the occurrence of a similar inundation event. We conclude that tsunami deposition related to the 1812 event is a possible explanation for SF1, but additional analyses are needed to rule out other flooding events. Whether storm or tsunami, the deposit's characteristics imply inundation at a scale and intensity that would be detrimental to the low lying areas of the Santa Barbara coast--the presence of similar layers at greater depths imply this degree of inundation has recurred over time and is an important process to understand for risk assessment for the Santa Barbara coast.

Reynolds, L.; Simms, A.; King, B. L.; Rockwell, T. K.; Ejarque, A.; Anderson, R.; Peters, R. B.

2013-12-01

79

Long-Term Sedimentology Projects Using Local Geological and Environmental Problems  

NSDL National Science Digital Library

The goal of long-term laboratory projects is to allow students to apply newly learned concepts and methods to real-world problems and thereby add value to the laboratory learning experience. Effective projects are those that are carefully planned, have clearly defined learning objectives and reasonable workload and final product expectations. Exercises vary in length and content depending upon learning goals, class size, available resources, methodology and scheduling concerns (e.g. beginning or end of course, available class time or time of year). Each project begins with an introduction in which a geological question is posed and students are presented with background information, published reference material and guidelines for effective scientific writing. The introductory presentations are followed by group discussions to formulate the hypothesis(es) to be tested and determine the experimental design, with due consideration to the constraints listed above. It is important that students understand their individual responsibilities and their role in the larger group effort. In the following weeks, students are provided with the materials and methods they need to conduct each phase of the project. Students collect and process their own data whenever possible. Preferably this phase involves field description and collection of samples for later lab analysis but previously collected sediment or rock cores or samples may also be used. Data analysis is a class-wide effort with each student or student team contributing a component to a larger class-wide database. Workload expectations must be clearly defined and students must conform to a tight timeframe during the analysis portion of the exercise so that the final database is complete and available on schedule. Interim deadlines for data components generally help students stay on schedule during this phase. Data synthesis and final report preparation are individual efforts. Students are encouraged to be creative in the interpretation and presentation of their results but are warned not to draw conclusions that cannot be supported by their data. Examples of long-term projects that have been used for sedimentology at SUNY Plattsburgh include: Particle shape analysis of beach and fluvial gravel in the Champlain Valley Provenance of glacial till in the Champlain Valley and northeastern Adirondack Mountain region Sedimentology, stratigraphy and landslide susceptibility of proglacial lake and marine deposits on the Lake Champlain lakeshore in Plattsburgh, NY Sedimentology and stratigraphy of the Potsdam Sandstone in the Champlain Valley Sedimentological evidence for breakout floods in proglacial lake and marine deposits in the Champlain Valley

Franzi, David

80

Proceedings, 1983 symposium on surface mining, hydrology, sedimentology, and reclamation  

SciTech Connect

Papers were presented on the following topics: mining technology; hydrology; sedimentology; reclamation; surface mining technology and policy; poster presentations; phosphate and arid land reclamation; reclamation special applications; and hydrology-sedimentology special applications. 45 papers have been abstracted separately.

Graves, D.H. (ed.)

1983-12-01

81

New high precision U-Pb ages for the Vinchina Formation: Implications for the stratigraphy of the Bermejo Andean foreland basin (La Rioja province, western Argentina)  

NASA Astrophysics Data System (ADS)

The Vinchina Formation is one of the thickest Cenozoic units related to the Andean orogeny in Argentina totaling more than 5100 m in thickness. Different ages, from Eocene to latest Miocene, have been postulated for this red-bed succession based on fission track, magnetostratigraphy and whole rock isotopic analyses. Two new high precision U-Pb zircon ages are reported herein for this unit. A maximum U-Pb age of 15.6 ± 0.4 Ma was obtained from detritic zircons collected from a thick tuffaceous interval of the Lower Member of the Vinchina Formation at La Cueva (Precordillera), while a depositional U-Pb age of 9.24 ± 0.034 Ma was derived from volcanic zircons collected from a thin tuff bed in the Upper Member at Quebrada de Los Pozuelos (Northwestern Sierras Pampeanas). At La Cueva, the Vinchina Formation unconformably overlies eolian sandstones of the Vallecito Formation and was divided into four units representing 1) deposits of high-sinuosity ephemeral rivers associated with 2) a playa-lake passing upwards to 3) low-sinuosity sandy ephemeral rivers and finally, 4) a gravelly-sandy braided plain. The tuffaceous level corresponding to unit 1 is located 280 m above the base of the formation. At Quebrada de Los Pozuelos, the Vinchina Formation unconformably overlies the Vallecito Formation and is covered by a deeply incised surface at the base of the Toro Negro Formation. We divided the Vinchina Formation into four units. Unit 1 represents sedimentation in shallow fluvial channels with sandy to muddy floodplains. Units 2 and 3 record sedimentation in braided, meandering and anastomosing rivers. Finally unit 4 represents deposition in braided and wandering fluvial systems. The sampled tuff is located within unit 4 at ?3470 m above the base of the formation. The new ages indicate that the bulk of the Vinchina Formation is Miocene in age but they do not preclude a longer time span for the sedimentation of the whole unit. Ages of the sampled volcanic zircons match an important episode of volcanism recorded in the Cerro Las Tórtolas Formation, located ?90 km to the west in the Andean Cordillera, but also the upper tuff could be related to the late Miocene Puna volcanism. Comparison of the new ages with previous chronological data suggests coetaneous sedimentation along different depocenters of the Bermejo basin (e.g., Vinchina and Talampaya depocenters in Western Sierras Pampeanas and La Troya depocenter and Huaco-Mogna sections in Precordillera) and strenghten the need for correlation among them. In addition the age of 15.6 ± 0.4 Ma constrains the end of the severe arid conditions recorded in the Sierras Pampeanas and Precordillera region.

Ciccioli, P. L.; Limarino, C. O.; Friedman, R.; Marenssi, S. A.

2014-12-01

82

Sedimentology of gas-bearing Devonian shales of the Appalachian Basin  

SciTech Connect

The Eastern Gas Shales Project (1976-1981) of the US DOE has generated a large amount of information on Devonian shale, especially in the western and central parts of the Appalachian Basin (Morgantown Energy Technology Center, 1980). This report summarizes this information, emphasizing the sedimentology of the shales and how it is related to gas, oil, and uranium. This information is reported in a series of statements each followed by a brief summary of supporting evidence or discussion and, where interpretations differ from our own, we include them. We believe this format is the most efficient way to learn about the gas-bearing Devonian shales of the Appalachian Basin and have organized our statements as follows: paleogeography and basin analysis; lithology and internal stratigraphy; paleontology; mineralogy, petrology, and chemistry; and gas, oil, and uranium.

Potter, P.E.; Maynard, J.B.; Pryor, W.A.

1981-01-01

83

Late quarternary glacioeustatic sea-level fluctuations: What are the sedimentologic processes and stratigraphic responses on continental margins  

SciTech Connect

Published stable isotope data from deep-sea sediments clearly show that the earth's climatic cycles have oscillated through at least 10 major glacial and interglacial episodes during the last million years. These high-frequency, orbitally-forced events should have resulted in major glacioeustatic sea-level fluctuations on the continental margins with dramatic sedimentologic effects and stratigraphic responses. However, such high-frequency events have proven difficult to resolve. Are they too short-lived to be recorded, to complex to decipher, or have traditional stratigraphic tools not been adequate to recognize them in continental margin sequences A detailed, multidisciplinary study of various continental margins is necessary to test the sensitivity of sedimentologic systems and response in stratigraphic records. This study must utilize (1) high-resolution event stratigraphy to define the depositional and erosional sediment sequences; (2) sediment analyses to delineate depositional environments and characterize lithofacies of specific system tracts; and (3) biostratigraphic and geochronologic analyses to place the depositional sequences in time. Integration of these data sets will (4) determine the resolving power of sequence stratigraphy; (5) develop working stratal models for recognizing short-pulsed, glacioeustatic sea-level events within the stratigraphic record; and (6) define a chronostratigraphy of changing paleoclimatic and paleoceanographic events operating on continental margin systems during the late Quaternary.

Riggs, S.R. (East Carolina Univ., Greenville, NC (United States)); Snyder, S.W. (North Carolina Univ., Raleigh (United States)); Hine, A.C. (Univ. of South Florida, St. Petersburg (United States))

1990-01-09

84

6 The morphology and sedimentology of landforms  

E-print Network

6 The morphology and sedimentology of landforms created by subglacial megafloods MANDY J. MUNRO, CLAIRE L. BEANEY and BRUCE B. RAINS Summary Subglacial landforms across various scales preserve of many of these landforms is, however, contentious. In this chapter these forms are described both

Brennand, Tracy

85

Stratigraphy, Sedimentology, Volcanology and Development of the Archean Manitou Group, Northwestern Ontario, Canada  

Microsoft Academic Search

The Archean Manitou Group occurs as a northeast-southwest trending arcuate belt in the central part of the Wabigoon greenstone belt, northwestern Ontario. The Manitou Group is mainly conglomerate, sandstone, tuff, tuff-breccia, and argillite, with minor lavas (somewhat alkaline), and iron formation. Mapping has established four formations: the Cane Lake, Sunshine Lake, Uphill Lake, and Mosher Bay. The Uphill Lake includes

Philip Rae Teal

1979-01-01

86

The sequence stratigraphy, sedimentology, and economic importance of evaporite carbonate transitions: a review  

NASA Astrophysics Data System (ADS)

World-class hydrocarbon accumulations occur in many ancient evaporite-related basins. Seals and traps of such accumulations are, in many cases, controlled by the stratigraphic distribution of carbonate-evaporite facies transitions. Evaporites may occur in each of the systems tracts within depositional sequences. Thick evaporite successions are best developed during sea level lowstands due to evaporative drawdown. Type 1 lowstand evaporite systems are characterized by thick wedges that fill basin centers, and onlap basin margins. Very thick successions (i.e. saline giants) represent 2nd-order supersequence set (20-50 m.y.) lowstand systems that cap basin fills, and provide the ultimate top seals for the hydrocarbons contained within such basins. Where slope carbonate buildups occur, lowstand evaporites that onlap and overlap these buildups show a lateral facies mosaic directly related to the paleo-relief of the buildups. This facies mosaic, as exemplified in the Silurian of the Michigan basin, ranges from nodular mosaic anhydrite of supratidal sabkha origin deposited over the crests of the buildups, to downslope subaqueous facies of bedded massive/mosaic anhydrite and allochthonous dolomite-anhydrite breccias. Facies transitions near the updip onlap edges of evaporite wedges can provide lateral seals to hydrocarbons. Porous dolomites at the updip edges of lowstand evaporites will trap hydrocarbons where they onlap nonporous platform slope deposits. The Desert Creek Member of the Paradox Formation illustrates this transition. On the margins of the giant Aneth oil field in southeastern Utah, separate downdip oil pools have accumulated where dolomudstones and dolowackestones with microcrystalline porosity onlap the underlying highstand platform slope. Where lowstand carbonate units exist in arid basins, the updip facies change from carbonates to evaporite-rich facies can also provide traps for hydrocarbons. The change from porous dolomites composed of high-energy, shallow water grainstones and packstones to nonporous evaporitic lagoonal dolomite and sabkha anhydrite occurs in the Upper Permian San Andres/Grayburg sequences of the Permian basin. This facies change provides the trap for secondary oil pools on the basinward flanks of fields that are productive from highstand facies identical to the lowstand dolograinstones. Type 2 lowstand systems, like the Smackover Limestone of the Gulf of Mexico, show a similar relationship. Commonly, these evaporite systems are a facies mosaic of salina and sabkha evaporites admixed with wadi siliciclastics. They overlie and seal highstand carbonate platforms containing reservoir facies of shoalwater nonskeletal and skeletal grainstones. Further basinward these evaporites change facies into similar porous platform facies, and contain separate hydrocarbon traps. Transgressions in arid settings over underfilled platforms (e.g. Zechstein (Permian) of Europe; Ferry Lake Anhydrite (Cretaceous), Gulf of Mexico) can result in deposition of alternating cyclic carbonates and evaporites in broad, shallow subaqueous hypersaline environments. Evaporites include bedded and palmate gypsum layers. Mudstones and wackestones are deposited in mesosaline, shallow subtidal to low intertidal environments during periodic flooding of the platform interior. Highstand systems tracts are characterized by thick successions of m-scale, brining upward parasequences in platform interior settings. The Seven Rivers Formation (Guadalupian) of the Permian basin typifies this transition. An intertonguing of carbonate and sulfates is interpreted to occur in a broad, shallow subaqueous hypersaline shelf lagoon behind the main restricting shelf-edge carbonate complex. Underlying paleodepositional highs appear to control the position of the initial facies transition. Periodic flooding of the shelf interior results in widespread carbonate deposition comprised of mesosaline, skeletal-poor peloid dolowackestones/mudstones. Progressive restriction due to active carbonate deposition and/or an environment of net evaporation causes bri

Sarg, J. F.

2001-04-01

87

Sedimentology and sequence stratigraphy of upper Pleistocene carbonates of southeastern Barbardos, West Indies  

SciTech Connect

Upper Pleistocene reef-associated carbonates of southeastern Barbados have been studied in outcrop and core. Reef terraces, formed during glacio-eustatic sea level highstands and subsequently uplifted, are characterized by thick and areally extensive sequences of allochthonous and autochthonous fore-reef calcarenites. Depositional textures are primarily packstones, and grainstones, wackestones, and coral floatstones are volumetrically less significant. Sediments are coarse- to fine-grained reef-derived allochems and micrite, and autochthonous benthic foraminifera and coralline red algae. Rates of sediment accumulation of fore-reef calcarenites range from about 1 to 4 m/1,000 yr. Although of relatively small scale, the carbonate terraces of southeastern Barbados provide excellent analogs for sequence stratigraphic concepts in carbonate settings. The terraces are primarily highstand systems tract deposits separated by type 1 unconformities. These highstand deposits are characterized by reef development and the progradation of fore-reef calcarenites. Extensive fore-reef deposits resulted from mechanical erosion of the reef framework on this high-energy, windward coastline. Type 1 unconformities are characterized by thin caliche layers developed during lowstand subaerial exposure. Thin basal transgressive systems tract deposits are characterized by incorporation of extraformational clasts derived from the underlying sequence during sea level rise. Slope-front erosion, vertical shift in the position of freshwater lens, and shift in the position of coastal onlap are all consequences of the interplay between eustasy and tectonics. These effects and the development of facies geometries on Barbados are primarily controlled by the glacio-eustatic component, inasmuch as rates of eustatic changes of sea level are at least two orders of magnitude greater than the maximum average rates of tectonic uplift. 12 figs.

Humphrey, J.D.; Kimbell, T.N. (Univ. of Texas, Richardson (USA))

1990-11-01

88

Oligocene Hackberry Formation of southwest Louisiana: Sequence stratigraphy, sedimentology, and hydrocarbon potential  

SciTech Connect

The Oligocene Hackberry sequence was deposited in a slope environment consisting of an irregular, updip slide scar, a rotational slide zone up to 4 mi (6.5 km) wide, and a downdip region more than 20 mi (32 km) wide where meandering submarine channels deposited thick turbiditic sands. The shelf margin slides probably began during the late stage of a relative fall in sea level and prior to a maximum flood event in the middle Oligocene. The slides probably were caused by a combination of salt withdrawal and an unstable shelf edge. The play has produced more than 374 million bbl of oil equivalent (BOE) up to December 1988. The first fields were discovered in structural/stratigraphic traps on the updip flanks of the salt domes, where channels were forced to meander around paleobathymetric highs. Other fields are located in the paleobathymetric lows many miles downdip of the salt domes. Statistical analysis of field data shows that 41 fields with more than 1 million BOE each and with a total estimated ultimate recovery of 117 million BOE remain to be discovered in the play. Interpretation in southwestern Louisiana has shown that new reserves could be discovered in three potential reservoir sands: (1) lower Frio shelf-edge sands preserved in large slide blocks, (2) onlapping, sandy 'fill sequences' restricted to the lows between slide blocks, and (3) meandering, dip-oriented, sandy channel complexes less than 4,500 ft (1,400 m) wide. These three sandstones cannot be distinguished unless dipmeter, seismic, and paleontologic data are used in combination.

Cossey, S.P.J.; Jacobs, R.E. (BP Exploration, Houston, TX (United States))

1992-05-01

89

Neogene stratigraphy and sedimentology in eastern Azerbaijan: Outcrop observations and subsurface implications  

SciTech Connect

The largely Pliocene Productive Series of eastern Azerbaijan contains about 26 billion barrels oil equivalent. It is well exposed in outcrops on the Apsheron Peninsula which a joint team from the GIA and the BP and Statoil Alliance have described. Detailed biostratigraphic and petrographic studies have subsequently been carried out. Productive Series deposition was initiated by a dramatic relative sea-level fall which left the South Caspian an isolated basin fed by deeply incised precursors to the modern Volga, Amu Darya, and Kura rivers. Five facies associations have been recognised within the Productive Series at outcrop, encompassing a range of palaeoenvironments from alluvial braided river sandstones and conglomerates to delta-front siltstones and mudstones. The facies associations suggest a river-dominated, braid delta. Four idealised reservoir models can be recognised: fluvial, delta-plain, proximal delta-front and distal delta-front. Each has distinct grain-size and shale distributions. Studies of nearby oilfields suggest that these models form useful subsurface analogues. Flow simulation models suggest that each reservoir type has dramatically different performance. Productive Series sediments are typically loosely cemented and smectite rich, which may result in clay swelling and sand control problems. Localised reduction in reservoir quality is caused by fault-associated calcite cements. Proximal facies of the upper Productive Series contain porosity occluding gypsum cements. Palynology and nannopalaeontology have been applied to the Neogene sediments of Azerbaijan for almost the first time, and have given encouraging results, at least in terms of a broad biozonation. Micropaleontological analyses have also provided useful palaeoenvironmental data.

Ali-zade, A.A.; Guliyev, I.S.; Ateava, E.Z. [GIA, Baku (Azerbaijan)] [and others

1995-08-01

90

Sequence stratigraphy, sedimentology, and hydrocarbon potential in the North-Eastern part of the Pannonian Basin  

SciTech Connect

The Pannonian basin lies within the Alpine mountain belts of east-central Europe. Deformation of the Pannonian region occurred during the final stage of thrusting and folding in the outer part of the Carpathians. The result was a system of several smaller individual basins separated by relatively shallow basement blocks. The {open_quotes}North-eastern part of the Pannonian basin{close_quotes} represents one of these individual basins. Over the basement, the Neogene sedimentation started with continental or marine transgressive beds followed by shallow-marine shales and marls with sandy intercalations. Several stratigraphic sequences were separated within the succession of sedimentary deposits using the seismic, paleontologic, and well-log data. These sequences with their hydrocarbon significance are largely described in the paper.

Lazar, O.R.; Corbeanu, R.; Vasiliu, G. [Institute for Research and Technology, Prahova (Romania)] [and others

1995-08-01

91

Stratigraphy and sedimentology of a dry to wet eolian depositional system, Burns formation, Meridiani Planum, Mars  

Microsoft Academic Search

Outcrop exposures of sedimentary rocks at the Opportunity landing site (Meridiani Planum) form a set of genetically related strata defined here informally as the Burns formation. This formation can be subdivided into lower, middle, and upper units which, respectively, represent eolian dune, eolian sand sheet, and mixed eolian sand sheet and interdune facies associations. Collectively, these three units are at

J. P. Grotzinger; R. E. Arvidson; J. F. Bell III; W. Calvin; B. C. Clark; D. A. Fike; M. Golombek; R. Greeley; A. Haldemann; K. E. Herkenhoff; B. L. Jolliff; A. H. Knoll; M. Malin; S. M. McLennan; T. Parker; L. Soderblom; J. N. Sohl-Dickstein; S. W. Squyres; N. J. Tosca; W. A. Watters

2005-01-01

92

Sedimentology and stratigraphy of the Kanayut Conglomerate, central Brooks Range, Alaska; report of 1980 field season  

USGS Publications Warehouse

The Upper Devonian Kanayut Conglomerate crops out along the crest of the Brooks Range of northern Alaska for a distance of almost 1000 km. It ranges in thickness from 2600 m in the Atigun River area to 700 m south of Anaktuvuk Pass and has been subdivided into four regionally persistent members: (a) the basal sandstone member, consisting of marine sandstone and shale with some conglomerate; (b) the lower shale member, consisting of nonmarine quartzite, conglomerate and shale; (c) the middle conglomerate member, consisting of nonmarine pebble and cobble conglomerate and quartzite; and (d) the Stuver Member, consisting of nonmarine sandstone and shale. The Kanayut conformably overlies the Upper Devonian marine Hunt Fork Shale and is conformably overlain by the Mississippian marine Kayak Shale. The Kanayut is wholly allochthonous and has probably been transported northward on a series of thrust plates. The basal sandstone member of the Kanayut Conglomerate, which overlies prodelta turbidites of the Hunt Fork Shale, contains marginal-marine coarsening-upward channel-mouth bar sequences. It is conformably overlain by the lower shale member. Measured sections of the nonmarine members of the Kanayut show that the lower shale member ranges in thickness from 120 m to 1115 m and consists of fining-upward cycles interpreted to have been deposited by meandering streams on a broad floodplain. These cycles contain, in ascending order, channelized basal conglomerate, trough cross-stratified sandstone, and ripple-marked siltstone. The cycles are interpreted to be channel and point-bar deposits. Individual cycles average about 10 m in thickness and are separated by intervals of black, brown or maroon floodplain shale deposits. These typically contain thin coarsening-upward units that probably represent prograding levee sequences and irregular and ungraded sandstone bodies interpreted to be crevasse-splay deposits. In the Okokmilaga River area, the lower shale member contains a distinctive coarse-grained unit which is burrowed and interpreted to represent a widespread marine incursion. The middle conglomerate member, which ranges in thickness from 155 m to 525 m, consists of braidplain deposits. It contains fining-upward couplets of conglomerate and parallel-stratified or cross-stratified sandstone that average 2-7 m in thickness. The couplets record deposition in channels and on bars of braided streams. The middle conglomerate member contains the largest clasts, little or no shale, and represents the maximum progradation of nonmarine sedimentation in the Kanayut depositional system. The Stuver Member consists of fining-upward cycles that resemble those of the lower shale member. It ranges in thickness from 160 m to 1400 m and grades upward into tidal and marginal-marine deposits of the Kayak Shale. Conglomerate in the Kanayut is compositionally very mature, averaging 82 percent white, gray, black or red chert clasts, 14 percent vein quartz clasts, 3 percent quartzite clasts, and less than I percent other lithologies, mainly argillite. Although red chert is locally abundant in the Shainin Lake-Galbraith Lake area, there is little variation in conglomerate composition in the Kanayut, suggesting derivation from a single major source terrane.

Nilsen, T.H.; Moore, T.E.; Balin, D.F.; Johnson, S.Y.

1982-01-01

93

Stratigraphy and sedimentology of ledge sandstone in Arctic National Wildlife Refuge northeastern Alaska  

SciTech Connect

Data collected from four measured sections of the Ledge Sandstone member of the Ivishak Formation are presented. These sections are located in the Arctic National Wildlife Refuge (ANWR) in northeastern Alaska. The Ledge Sandstone is the time equivalent of the Ivishak sandstones that form the reservoir in the Prudhoe Bay field, east of the study area. The ANWR region is of interest for oil and gas exploration owing to the numerous oil seeps on the coastal plain and surficial expression of possible subsurface antiforms. The Ledge Sandstone in ANWR consists primarily of a massive, thickly bedded, very fine to fine-grained, well-sorted quartz sandstone. The thick sandstones are separated by thin siltstone intervals ranging from less than an inch to several feet in thickness. Although the thicker siltstones appear laterally continuous, the thinner beds generally are lenticular over short distances (10 to 20 ft; 3 to 6 m). Cementation of the siltstone appears sporadic, varying laterally and vertically within the unit. Burrowing is extensive in the siltstone intervals. Typically, burrowing cannot be detected in the sandstones because of the obliteration by lithification and diagenetic processes. Fossils are sparse throughout the unit, even in the poorly lithified silts. These data are consistent with a shallow marine environment, within wave base. This contrasts with the nonmarine conglomerates and sandstones of Prudhoe Bay. Time-equivalent units to the south and west consist primarily of cherts and shales of probable deep marine origin, with some arkosic sandstones dolomites occuring in NPRA. Thus a paloshoreline is probably located somewha north of the measured sections.

Cloft, H.S.

1983-03-01

94

Stratigraphy and sedimentology of ledge sandstone in Arctic National Wildlife Refuge northeastern Alaska  

Microsoft Academic Search

Data collected from four measured sections of the Ledge Sandstone member of the Ivishak Formation are presented. These sections are located in the Arctic National Wildlife Refuge (ANWR) in northeastern Alaska. The Ledge Sandstone is the time equivalent of the Ivishak sandstones that form the reservoir in the Prudhoe Bay field, east of the study area. The ANWR region is

Harriet S. Cloft

1983-01-01

95

Sedimentology and Holocene stratigraphy of a carbonate mangrove buildup, Twin Cays, Belize, Central America  

E-print Network

used in this study . Pusey delineated eight depositional shelf environments, one of which contains a Halimeda facies characterized by an abundance of algal skeletal plates. In a recent amplification of the work of both Pussy and Purdy, Jordon et al... used in this study . Pusey delineated eight depositional shelf environments, one of which contains a Halimeda facies characterized by an abundance of algal skeletal plates. In a recent amplification of the work of both Pussy and Purdy, Jordon et al...

Bond, Gregor Benton

2012-06-07

96

Stratigraphy and sedimentology of a dry to wet eolian depositional system, Burns formation, Meridiani Planum, Mars  

E-print Network

, Meridiani Planum, Mars J.P. Grotzinger a,*, R.E. Arvidson b , J.F. Bell III c , W. Calvin d , B.C. Clark e: +1 626 568 0935. E-mail address: grotz@gps.caltech.edu (J.P. Grotzinger). Earth and Planetary Science

Grotzinger, John P.

97

Sedimentology, stratigraphy, and depositional environment of the Crystal Geyser Dinosaur Quarry, east-central Utah  

USGS Publications Warehouse

The Crystal Geyser Dinosaur Quarry, near Green River, Utah, is located at the base of the Lower Cretaceous (Barremian) Yellow Cat Member of the Cedar Mountain Formation. The quarry preserves a nearly monospecific accumulation of a new basal therizinosauroid, Falcarius utahensis. We used field descriptions and petrographic analysis to determine the depositional environment and development of the quarry strata. Results of these analyses suggest that the quarry represents multiple episodes of bone accumulation buried by spring and overbank flood deposits. Evidence for these previously undescribed spring deposits includes calcite macroscopic structures within the quarry strata - such as pisolites and travertine fragments - and calcite micromorphologies - including radial-fibrous, feather, and scandulitic dendrite morphologies and tufa clasts. At least two episodes of bone incorporation are preserved in the quarry based on their stratigraphic position and lithologic associations. The unique depositional setting in and around the Crystal Geyser Dinosaur Quarry appears to have been favorable for the preservation of vertebrate fossils and provides insight into early Cretaceous environments in North America. Copyright ?? 2007, SEPM (Society for Sedimentary Geology).

Suarez, M.B.; Suarez, C.A.; Kirkland, J.I.; Gonzalez, L.A.; Grandstaff, D.E.; Terry, D.O., Jr.

2007-01-01

98

From BIF to red beds: Sedimentology and sequence stratigraphy of the Paleoproterozoic Koegas Subgroup (South Africa)  

NASA Astrophysics Data System (ADS)

The ~ 2.4 Ga old Koegas Subgroup of the Transvaal Supergroup contains siliciclastics and iron formations. It occupies a transitional stratigraphic position between the major iron formations on the Kaapvaal craton, and strata with evidence for oxygenation of the environment. Koegas siliciclastics reflect a new phase of uplift and erosion on the craton after a period of chemical deposition. Paleocurrent data indicate transport to the west and northwest, away from the craton; however, no precise source area can as yet be defined. Rocks were deposited in foreshore to offshore environments of a prograding delta or submarine fan system. Immature arkosic wackes and subarkoses occur in proximal parts and pass to terrigenous mudstones and chemical iron formations in offshore environments with low detrital input. Lateral facies transitions and the hierarchical stratigraphic stacking pattern of the Koegas Subgroup allow a sequence stratigraphic interpretation in which regressive coarse siliciclastics prograded repeatedly over transgressive units of chemical iron formations. Metals in the transgressive units have an intrabasinal (hydrothermal) source, similar to underlying iron formations. Localized iron-stained detrital units resemble red beds. They reflect additional diagenetic Fe remobilization from deeper-water iron formations, or possibly a continental Fe source. The second possibility would imply the presence of some free oxygen in the environment.

Schröder, S.; Bedorf, D.; Beukes, N. J.; Gutzmer, J.

2011-05-01

99

Sedimentology and Stratigraphy of the Upper Pennsylvanian – Lower Permian Systems of Western Nebraska, USA.  

E-print Network

??Depositional patterns and regional stratigraphic relationships in the carbonate-dominated Pennsylvanian and Permian deposits in western Nebraska are not well established due to poor surface exposure.… (more)

Gilleland, Chesney L

2011-01-01

100

Sedimentology and stratigraphy of the Queen Formation, Millard Field, Pecos County, Texas  

E-print Network

of this project, through him I have learned to research a problem and strive for excellence. Dr. Berg was especially helpful in the early stages of the study and by his example of research techniques. Or. S. J. Mazzullo provided valuable criticism, suggestions..., to establish a model of deposit1on, subsequent cementation, and diagenesis. The Millard Field in Pecos County, Texas produces from the queen Format1on and provides such an area to study the format1on. GEOLOGIC SETTING Structure The Permian Basin reg1on...

Williams, Matt Brian

2012-06-07

101

The Heidelberg Basin Drilling Project - Sedimentology and Stratigraphy of the Quaternary succession  

NASA Astrophysics Data System (ADS)

Within the context of the Heidelberg Basin Drilling Project (Gabriel et al. 2008), a detailed sediment succession is presented here based upon deep drillings taken at Heidelberg UniNord and Mannheim Käfertal. Sediment structures, and micromorphological and pollen analyses were conducted and used to reconsider some of the climate transitions within the lower Pleistocene. A new and novel scenario is postulated regarding the preservation of Quaternary sediment packages within the Cenozoic Graben environment of the Heidelberg basin. The palynological evidence comprises the periods of warm climate of the Holsteinian (mainly Abies (fir), some Fagus (beech), Pterocarya & Azolla); the Cromerian (Pinus-Picea-QM (pine-spruce-QM)); the Bavelian (Abies, Tsuga (hemlock fir), QM & phases of increased NAP including Pinus); the Waalian (Abies, Tsuga, QM); and the Tiglian (Fagus & early Pleistocene taxa especially Sciadopytis, downward increasing Tertiary taxa). The sediment package was studied both macroscopically and microscopically. Both techniques provide evidence of fluvial, lacustrine and mass movement sedimentary processes. Some include evidence of periglacial processes (silt droplets within fine grained sands indicative of frozen ground conditions). The periglacial structures are often, not always, accompanied by pollen spectra dominated by pine and NAP. E.g. the Tiglian part of the succession shows periglacial sediment structures at its base and top but not in its middle sections. I.e. it appears not as a series of warm and cold phases but rather as a constant warm period with warm-cold-alternations at its bottom and top. All results illustrate sediment preservation in the Heidelberg basin almost throughout the Quaternary. This may be due to tectonic subsidence, but also to compaction by sediment loading of underlying fine sediments (Oligocene to Quaternary) leading to incomplete but virtually continuous sediment preservation (Tanner et al. 2009). References Gabriel, G., Ellwanger, D., Hoselmann, C. & Weidenfeller, M. (2008): The Heidelberg Basin Drilling Project. - Eiszeitalter u. Gegenwart (Quaternary Science Journal), 57, 3-4, 253-260, Hannover. Tanner, D.C., Martini, N., Buness, H. & Krawczyk, C.M. (2009): The 3D Geometry of the Quaternary and Tertiary strata in the Heidelberg Basin, as defined by reflection seismics. - DGG Tagung, Dresden, 30.9-02.10.09, Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, 63, 58.

Ellwanger, Dietrich; Gabriel, Gerald; Hahne, Jürgen; Hoselmann, Christian; Menzies, John; Simon, Theo; Weidenfeller, Michael; Wielandt-Schuster, Ulrike

2010-05-01

102

The Mt. Moio eruption (Etna): Stratigraphy, petrochemistry and 40Ar/39Ar age determination with inferences on the relationship between structural setting and magma intrusion  

NASA Astrophysics Data System (ADS)

Mt. Moio is the most peripheral scoria cone of Etna volcano and rises above the Peloritani Mountains sedimentary basement, 18 km north of the volcano summit. Geological and tephrostratigraphic studies and 40Ar/39Ar age determinations were used to characterize the eruption and constrain its occurrence to ~ 29 ka ago, during the activity of the Ellittico volcano, the volcanic edifice active before the actual one, the Mongibello volcano. The Mt. Moio eruption formed a large scoria cone and a widespread tephra fallout deposit, indicating that vigorous explosive activity produced an eruptive plume; minor effusive activity produced a small lava flow at the end of the eruption. Geochemical data indicate that the composition of erupted magma became less evolved during the eruption (mugearite ? basalt-hawaiite); thus Mt. Moio deposits have been divided into Lower and Upper Sequences characterized by similar depositional facies. Based on the classification of Etna flank eruptions available in the literature, Mt. Moio can be classed as an eccentric (sensu Rittmann) and Class B eruption. Historic flank eruptions (e.g. 1669, 1763, 2001, 2002-03) formed deposits that are petrochemically and stratigraphically similar to those of Mt. Moio. The general trend of the Mt. Moio eruptive fissure corresponds to that of extensional neotectonic lineaments in the Apenninic-Maghrebian Chain, indicating that the structure of the basement played a role in controlling the ascent of the volatile-rich magma during Ellittico volcano activity.

Del Carlo, Paola; Branca, Stefano; De Beni, Emanuela; Castro, Maria Deborah Lo; Wijbrans, Jan R.

2012-10-01

103

Lithostratigraphy, petrography, biostratigraphy, and strontium-isotope stratigraphy of the surficial aquifer system of western Collier County, Florida  

USGS Publications Warehouse

In 1996, seven cores were recovered in western Collier County, southwestern Florida, to acquire subsurface geologic and hydrologic data to support ground-water modeling efforts. This report presents the lithostratigraphy, X-ray diffraction analyses, petrography, biostratigraphy, and strontium-isotope stratigraphy of these cores. The oldest unit encountered in the study cores is an unnamed formation that is late Miocene. At least four depositional sequences are present within this formation. Calculated age of the formation, based on strontium-isotope stratigraphy, ranges from 9.5 to 5.7 Ma (million years ago). An unconformity within this formation that represents a hiatus of at least 2 million years is indicated in the Old Pump Road core. In two cores, Collier-Seminole and Old Pump Road, the uppermost sediments of the unnamed formation are not dated by strontium isotopes, and, based on the fossils present, these sediments could be as young as Pliocene. In another core (Fakahatchee Strand-Ranger Station), the upper part of the unnamed formation is dated by mollusks as Pliocene. The Tamiami Formation overlies the unnamed formation throughout the study area and is represented by the Ochopee Limestone Member. The unit is Pliocene and probably includes the interval of time near the early/late Pliocene boundary. Strontium-isotope analysis indicates an early Pliocene age (calculated ages range from 5.1 to 3.5 Ma), but the margin of error includes the latest Miocene and the late Pliocene. The dinocyst assemblages in the Ochopee typically are not age-diagnostic, but, near the base of the unit in the Collier-Seminole, Jones Grade, and Fakahatchee Strand State Forest cores, they indicate an age of late Miocene or Pliocene. The molluscan assemblages indicate a Pliocene age for the Ochopee, and a distinctive assemblage of Carditimera arata and Chione cortinaria in several of the cores specifically indicates an age near the early/late Pliocene boundary. Undifferentiated sands overlie the Pliocene limestones in two cores in the southern part of the study area. Artificial fill occurs at the top of most of the cores. The hydrologic confining units penetrated by these cores are different in different parts of the study area. To the west, a hard tightly cemented dolostone forms the first major confining unit below the water table. In the eastern part of the study area, confinement is more difficult to determine. A tightly cemented sandstone, much younger than the dolostones to the west and probably not laterally connected to them, forms a slight confining unit in one core. Thick zones of poorly sorted muddy unconsolidated sands form a slight confining unit in other cores; these probably are not correlative to either the sandstone or the dolostones to the west. The age and sedimentologic observations suggest a complex compartmentalization of the surficial aquifer system in southwestern Florida. The calibrations of dinocyst and molluscan occurrences with strontium-isotope stratigraphy allows us to expand and document the reported ranges of many taxa. This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Edwards, L. E.; Weedman, S. D.; Simmons, R.; Scott, T. M.; Brewster-Wingard, G. L.; Ishman, S. E.; Carlin, N. M.

1998-01-01

104

Stratigraphy of the crater Copernicus  

NASA Technical Reports Server (NTRS)

The stratigraphy of copernicus based on its olivine absorption bands is presented. Earth based spectral data are used to develop models that also employ cratering mechanics to devise theories for Copernican geomorphology. General geologic information, spectral information, upper and lower stratigraphic units and a chart for model comparison are included in the stratigraphic analysis.

Paquette, R.

1984-01-01

105

Sedimentology: Recent developments and applied aspects  

SciTech Connect

This book reflects some of the developments which have occurred in sedimentology during the last two decades. It identifies problems of concern to sedimentologists. Topics covered include the following: loose-boundary hydraulics and fluid mechanics: selected advances since 1961; clastic facies models and facies analysis; recent shelf clastic sediments; deep-sea clastics; deep-sea pelagic sediments and palaeo-oceanography; facies analysis of volcaniclastic sediments; shallow-marine carbonate facies and facies models; diagenesis of shallow-marine carbonates; clastic diagenesis; sedimentary ore deposits; role of clastic sedimentology in the exploration and production of oil and gas in the North Sea; and carbonate facies analysis in the exploration for hydrocarbons: a case-study from the Cretaceous in the Middle East.

Brenchley, P.J.

1985-01-01

106

Linking sedimentological, stratigraphic and diagenetic processes to understand unconventional reservoirs: the Upper Jurassic Vaca  

E-print Network

Linking sedimentological, stratigraphic and diagenetic processes to understand unconventional as to the scale of sedimentological variability within mudstone successions, and how related diagenetic alteration by Profs Taylor and Flint, to document the scale of sedimentological and diagenetic variability

Henderson, Gideon

107

Combining sedimentological, trace metal (Mn, Mo) and molecular evidence for reconstructing past water-column  

E-print Network

Combining sedimentological, trace metal (Mn, Mo) and molecular evidence for reconstructing past online 22 June 2013 Abstract Here, we present sedimentological, trace metal, and molecular evidence underscores the value of combining sedimentological, geochemical, and microbiological approaches

Wehrli, Bernhard

108

First Year Sedimentological Characteristics and Morphological Evolution of an Artificial Berm at Fort Myers Beach, Florida  

E-print Network

First Year Sedimentological Characteristics and Morphological Evolution of an Artificial Berm Methods and Data Analysis 29 Results and Discussion 34 Sedimentological Characteristics of the Artificial Project Area 45 Control Area Northwest of Berm 47 Discussion of Sedimentological Characteristics 49

US Army Corps of Engineers

109

Amino acid racemization analysis (AAR) as a successful tool for dating Holocene coastal sediments: Stratigraphy of a barrier island spit (Southern Sylt/North Sea)  

NASA Astrophysics Data System (ADS)

Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about 400 years. Amino acid racemization dating (AAR) is a viable alternative for dating young sediments. The method is based on the determination of ratios of D and L amino acid enantiomers in organic matrices of biogenic carbonates. In this study we use AAR as a tool for dating Holocene barrier islands sediments. Based on an AAR derived chronological framework we develop a model of barrier spit accretion which describes the interaction between extreme events, fair weather coastal processes and sedimentary development that constrains the major episodes of barrier island evolution. The stratigraphy was defined using ground-penetrating radar (GPR) surveys complemented by sedimentological coring data. The stratigraphy is then conceptualised in a AAR chronostratigraphic framework to define a chronological order and allow the development of a stratigraphic model of the evolution of Southern Sylt. The AAR data provide high temporal resolution and have been used for dating stages of barrier spit accretion. The time lines are marked as storm surge generated erosion unconformities in the stratigraphic profile. Individual shells and shell fragments of Cerastoderma edule, Mya arenaria, Mytilus edulis and Scrobicularia plana have been accumulated by short-term storm events as shell layers associated with the erosion unconformities and have been dated by AAR. Time lines reveal that the barrier spit accretion occurred episodically, and is dependant on the provided rate of sand delivery. The general trend is that sequences young to the. South. The AAR derived time lines have been verified and correlated by historic maps and sea charts. It is apparent that spit enlargement at this site increased significantly during the Middle Ages (1593 - 1794) and was coupled with several intensive storm surges in this period. The findings indicate that when combined with GRR stratigraphy AAR provides useful results of high accuracy for dating stages of barrier spit progradation.

Tillmann, Tanja; Ziehe, Daniel

2014-05-01

110

Stratigraphy and Chronology  

NSDL National Science Digital Library

This PDF from the National Academy of Sciences discusses the importance of determining and understanding the long and complex geologic history of Mars. The paper describes the major geologic units along with their relative ages as derived from stratigraphic analysis and organizes them into a table. Recommendations for future exploration are also included.

Academies, The N.

111

Les ongulés d'Atapuerca. Stratigraphie et biogéographie  

Microsoft Academic Search

The Ungulates from Atapuerca: Stratigraphy and Biogeography. The Sierra de Atapuerca, near Burgos (Spain), has various fissure fillings that yielded fossil animals, including fossil man, and archaeological remains, of late Early Pleistocene to Holocene age.Level TD6 in the locality Gran Dolina, which contained the type material of Homo antecessor as well as archaeological objects, and levels TDW4 and TDE5 yielded

Jan van der Made

2001-01-01

112

Lithostratigraphy, geophysics, biostratigraphy, and strontium-isotope stratigraphy of the surficial aquifer system of eastern Collier County and northern Monroe County, Florida  

USGS Publications Warehouse

In 1997, ten cores were drilled in eastern Collier County and northern Monroe County, within the limits of the Big Cypress National Preserve. These cores represent a continuation of the study of seven cores in western Collier County begun in 1996 and reported in Weedman and others (1997) and Edwards and others (1998). This joint U.S. Geological Survey and Florida Geological Survey project is designed to acquire subsurface geologic and hydrologic data in southwest Florida to extend current ground-water models, thereby expanding the utility of these models for land and water management. In this report we describe the lithostratigraphy, geophysical logging, sedimentological analysis, dinocyst biostratigraphy, and strontium-isotope stratigraphy of these ten cores. The three geophysical logs (natural gamma-ray, induction conductivity, and neutron porosity) assumed to be related to formation lithology and water quality show that a number of clay-rich zones are present in all of the boreholes, and that pore-water conductivity increases with depth. The clay-rich zones are confirmed by visual examination of core material and sedimentological analysis. The relative transmissivity calculated at 10-foot-thick intervals shows that in six of the boreholes, high values are associated with the shallow aquifer in the 0-40 ft interval. Two of the boreholes (the most northerly and the most easterly) showed relatively higher values of transmissivity in permeable zones at or somewhat below 100 ft in depth. Core geology and logs indicate that the deeper aquifers are not more permeable than similar deeper zones in the other boreholes, but rather that the shallow aquifer appears to be less permeable in these two coreholes. The Arcadia (?) Formation was only penetrated in the deepest core where it is late Miocene in age. The Peace River Formation was penetrated in all but the two westernmost cores. It yields a late Miocene age, based on both dinocysts and strontium-isotope stratigraphy. The top is an irregular surface. Age and stratigraphic relations suggest that the upper part of the Peace River and lower part of the unnamed formation are at least partially equivalent laterally. The unnamed formation was recovered in every core. It is thinnest in the northernmost core and thickest to the west. Ages calculated from strontium isotopes range from 6.9 to 4.6 million years ago (late Miocene to early Pliocene). The top of the unnamed formation is deepest to the north and it becomes shallower to the southwest. The Tamiami Formation also was recovered in every core and consistently yields early Pliocene ages; it yields late Pliocene ages near the top in two cores. The age and lateral relations strongly suggest that the lower part of the Tamiami Formation and the upper part of the unnamed formation are lateral facies of each other. The Fort Thompson (?) Formation, Miami Limestone, and undifferentiated siliciclastic sediments and limestone at the very top of the cores were not dated.

Weedman, S. D; Paillet, F. L.; Edwards, L. E.; Simmons, K. R.; Scott, T. M.; Wardlaw, B. R.; Reese, R. S.; Blair, J. L.

1999-01-01

113

Palynology, sedimentology and palaeoecology of the late Holocene Dead Sea  

NASA Astrophysics Data System (ADS)

Palynological and sedimentological studies were performed at two Holocene profiles in erosion gullies (Ze'elim and Ein Feshkha) which dissect the retreating western shore of the Dead Sea. The aim of the project was to analyse possible links between climate, lithology, and vegetation development. The section in Ze'elim shows both lacustrine and fluvial sediments, whereas sedimentation at Ein Feshkha is predominantly lacustrine. The Ze'elim profile, previously used for paleo-lake reconstruction provides an opportunity to compare climate triggered lake levels as paleo-hydrological indicators and vegetation history by use of palynology. The vegetation development in Ze'elim and Ein Feshkha is influenced by both climate and human impact. The pollen record of Ze'elim begins in the Pottery Neolithic, the section of Ein Feshkha in the Late Bronze Age, both records end in the Middle Ages. The Ze'elim section is characterized by sedimentary hiati between the beginning of the Chalcolithic Period until the Middle Bronze Age and within the Late Bronze Age. Settlement periods during the Middle Bronze Age, Iron Age and Hellenistic-Roman-Byzantine Period are indicated by high values of anthropogenic indicators and/or Mediterranean trees. Collapses of agriculture, which can be related to climate effects, are evident during the Late Bronze Age, during the Iron Age and at the end of the Byzantine Period when the lake level curve indicates arid conditions. A comparison of the two pollen records, from different environments, illustrates a more prominent influence of Mediterranean vegetation and cultivated plants in the pollen diagram of Ein Feshkha. The southern Dead Sea region (at the desert fringe) is more vulnerable to regional climate change.

Neumann, Frank Harald; Kagan, Elisa J.; Schwab, Markus J.; Stein, Mordechai

2007-06-01

114

Mesozoic-Cenozoic sequence stratigraphy of European basins  

SciTech Connect

The preliminary results of the project, [open quotes]Mesozoic-Cenozoic Sequence Stratigraphy of European Basins[close quotes] (introduced at a seminar in Dijon, France, on May 18-20, 1992), show that the Mesozoic-Cenozoic stratigraphic succession of western Europe can be subdivided into a series of transgressive-regressive facies cycles (second order, 3-50 m.y.) and related to tectonic events by subsidence analysis and regional geology. The distribution of the second-order cycles are shown on a series of transects that extend from the Mediterranean to the North Sea. Where possible, each transgressive-regressive phase has been subdivided into a series of higher frequency sequence cycles (third order, 0.5-3 m.y.). These sequence cycles are identified in regions with good outcrops and biostratigraphic control. The sequence stratigraphy interpretation of these outcrop sections provides documentation for the age and distribution of the second- and third-order stratigraphic cycles of western Europe. Subsurface seismic and well data from the North Sea Basin, Paris basin, and the Mediterranean area are interpreted in terms of sequence stratigraphy and correlated to the outcrop reference sections. Chronobiostratigraphy and numerical ages are based on a series of new charts made especially for this project that show the latest correlation of the biostratigraphic zones for both microfossils and macrofossils across Europe. The charts also include a numerical time scale that reconciles the differences between existing time scales.

Vail, P.R. (Rice Univ., Houston, TX (United States)); Jacquin, T. (Ecole des Mines de Paris, Paris (France))

1993-09-01

115

Sedimentological analysis using geophysical well logs  

SciTech Connect

The application of geophysical well logs in sedimentology and stratigraphic prospecting holds great promise in solving a number of geological problems. A suite of logs provides data on a wide range of rock properties: vertical and lateral variation of resistivity, natural polarization, natural and induced radioactivity, shear strength, and acoustic properties. Each of these properties is controlled by the depositional environment of the sediments and their later diagenesis. The attention of geologists and geophysicists is drawn to new techniques in the interpretation of geophysical well logs for exploration, appraisal, and development of oil and gas fields. The relationship between geophysical logs and depositional environments is explored. Bulk composition, rock structure, and texture and facies variation can be quantified by electric log parameters. Also, the possibility of using logs to demonstrate long- and short-period sedimentary cycles is demonstrated. Methods of sedimentological analysis using geophysical well logs are demonstrated. The importance of a genetic approach in the interpretation of geological sequences and paleogeological reconstructions is emphasized using examples taken from oil and gas prospecting operations in the Ukraine.

Izotova, T.S. (Ukrainian State Geological Research Institute, Kiev (Ukraine))

1993-09-01

116

CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF NORTHERN ARIZONA AND SOUTHERN NEVADA  

E-print Network

#12;CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF NORTHERN ARIZONA AND SOUTHERN NEVADA THE 16TH FIELD. A., and Foster, J. R., (editors), 2011, Cambrian Stratigraphy and Paleontology of Northern Arizona Stratigraphy and Paleontology of Northern Arizona and Southern Nevada REGIONAL SETTING AND GENERAL STRATIGRAPHY

Mateo, Jill M.

117

Applications of sequence stratigraphy to Pennsylvanian strata in the Illinois Basin  

USGS Publications Warehouse

Sequence stratigraphy concepts have been applied previously to the interpretation of Pennsylvanian strata in the Illinois Basin with the use of the 'cycle' by J.A. Udden in 1912 and the cyclothem by H. Wanless and J. Weller in 1932. The unconformity-bounded cyclothem was recognized in Pennsylvanian strata throughout the basin and is a small-scale version of the cratonic sequence of L.L. Sloss. Recent applications indicate that the transgressive-regressive unit, a genetic succession bounded by marine-flooding surfaces, is a more practical stratigraphic unit that has applications for stratigraphic control, structural control, sedimentology, and hydrostratigraphy. Transgressive-regressive units conveniently fit within a sequence stratigraphic framework.

Weibel, C. P.

1996-01-01

118

Updated glacial chronology of the South Fork Hoh River valley, Olympic Peninsula, Washington through detailed stratigraphy and OSL dating  

NASA Astrophysics Data System (ADS)

The Olympic Peninsula lies within a maritime climatic zone under the direct influence of westerly atmospheric flow and Pacific Ocean sea surface temperature variations (i.e. ENSO and PDO). During the last glaciation, large valley glaciers extended radially from the Mt. Olympus area and carved deep valleys, which preserve glacial diamicton, outwash, and lacustrine sediment emplaced during ice advance and retreat. Previous work by Thackray (1996) mapped glacial deposits through several key drainages in the western Olympic Mountains and used exposures along the South Fork Hoh River to reconstruct MIS 2 glaciation and determine the relative extent of the LGM ice margin in the region. Findings suggest that the extent of mountain glaciers in the western Olympics were much reduced during MIS 2 in comparison to MIS 3/4, with glacier mass balance primarily controlled by moisture delivery. Here we discuss new data constraining the style and timing of deglaciation in the South Fork Hoh River valley of the western Olympic Mountains, Washington, USA. Previous research in the South Fork Hoh River used radiocarbon ages, geomorphic mapping, and general stratigraphic relationships to establish a chronostratigraphic framework (Thackray, 1996). To further that understanding and provide new insight on the style and timing of MIS 2 glaciation, we examine the sedimentology and stratigraphic architecture of glacial landforms, which contain invaluable information about glacial processes and style. Optically stimulated luminescence (OSL) dating, commonly regarded as problematic in glacial sediments, constrains the ages of proximal glacial outwash and glaciolacustrine deposits that were traditionally difficult to date due to the lack of organic matter for radiocarbon dating. OSL ages are internally coherent and stratigraphically consistent with previous radiocarbon ages. Results from this research in the South Fork Hoh River valley and associated work in the Queets River valley, the next major drainage to the south, provide an update on the style and timing of local ice advance during MIS 2 and the LGM. Glacial advances represented in the stratigraphy of these exposures, with ages constrained by radiocarbon dating, OSL dating, or both, include the Hoh Oxbow II (>23 ka), Twin Creeks I (~19 ka), and Twin Creeks II (<17 ka) advances. Weakly to moderately stratified diamicton mark ice advances and are overlain by one or more distinct packages of outwash. Glaciolacustrine sediments, probably impounded by ice in the Hoh River valley, mark the retreat from the Hoh Oxbow II advance.

Wyshnytzky, C.; Rittenour, T. M.; Thackray, G. D.

2012-12-01

119

Architectural element analysis within the Kayenta Formation (Lower Jurassic) using ground-probing radar and sedimentological profiling, southwestern Colorado  

NASA Astrophysics Data System (ADS)

A well exposed outcrop in the Kayenta Formation (Lower Jurassic) in southwestern Colorado was examined in order to delineate the stratigraphy in the subsurface and test the usefulness of ground-probing radar (GPR) in three-dimensional architectural studies. Two fluvial styles are present within the Kayenta Formation. Sandbodies within the lower third of the outcrop are characterized by parallel laminations that can be followed in the cliff-face for well over 300 m. These sandbodies are sheet-like in appearance, and represent high-energy flood deposits that most likely resulted from episodic floods. The remainder of the outcrop is characterized by concave-up channel deposits with bank-attached and mid-channel macroforms. Their presence suggests a multiple channel river system. The GPR data collected on the cliff-top, together with sedimentological data, provided a partial three-dimensional picture of the paleo-river system within the Kayenta Formation. The 3-D picture consists of stacked channel-bar lenses approximately 50 m in diameter. The GPR technique offers a very effective means of delineating the subsurface stratigraphy. Its high resolution capabilities, easy mobility, and rapid rate of data collection make it a useful tool. Its shallow penetration depth and limitation to low-conductivity environments are its only drawbacks.

Stephens, Mark

1994-05-01

120

Sedimentology of coarse-clastic beach-ridge deposits, Essex, southeast England  

NASA Astrophysics Data System (ADS)

The distinction of cheniers from other types of beach ridge can often be problematic. The stratigraphy, sedimentology and geomorphological development of sand- and gravel-rich beach ridges at three sites on the northern Essex coast, England were determined using ground-penetrating radar (GPR), ground-truthing trenches and auger holes, and historical-aerial photograph analysis. The 900 MHz GPR system used achieved a maximum vertical resolution between 0.02 and 0.06 m. There was good correspondence between the radar stratigraphy obtained from time-migrated radar reflection profiles and the nature and form of bounding surfaces, sets of lamination, beds and bedsets observed in trenches. Data for one of the study sites (Colne Point) illustrate a complex beach-ridge stratigraphy and sequence of development that confirms they are not true cheniers. Instead, the ridges form part of both retrogradational and progradational barrier-spit sequences. Chenier designation at the other two study sites (Foulton Hall and Stone Point) is more straightforward, as the beach ridges lie at the junction between actively eroding mudflat and saltmarsh. However, despite the distinction between the barrier-spit beach ridges and the cheniers, the same types of deposit are recognised in both, indicating similar formative processes. Washover-sheet deposits consist of low-angle (<5°), sub-parallel, landward-dipping stratification, which is concordant with bounding surfaces above and below. Washover sheets develop when high-wave energy/storm-related overwash moves landward onto unflooded marsh or lagoonal surfaces. Washover-delta deposits are characterised by high-angle cross-stratification (up to 28°) that downlaps onto the underlying marsh or lagoonal surface. Washover deltas develop when overwash enters a significant body of standing water to landward, such as a flooded marsh or lagoon. Alternations between washover-sheet and washover-delta development are seen in many instances, but their time scale is unclear due to paucity of detailed information regarding overwash sedimentation rates, or chenier and berm-ridge migration rates. Similarity of the internal structure in both the cheniers and barrier-spit beach ridges confirms that this criterion alone cannot be used to distinguish different types of beach-ridge deposit. Detailed stratigraphic data, preferably complemented by direct evidence for the geomorphological context in which the ridge developed, are also required.

Neal, Adrian; Richards, Julie; Pye, Ken

2003-12-01

121

Stratigraphy, artefact industries and hominid associations for Sterkfontein, member 5.  

PubMed

A revised stratigraphy for the early hominid site of Sterkfontein (Gauteng Province, South Africa) reveals a complex distribution of infills in the main excavation area between 2.8 and 1.4 m.y.a, as well as deposits dating to the mid to late Pleistocene. New research now shows that the Member 4 australopithecine breccia (2.8-2.6 Ma) extends further west than was previously thought, while a late phase of Member 4 is recognized in a southern area. The artefact-bearing breccias were defined sedimentologically as Member 5, but one supposed part of these younger breccias, the StW 53 infill, lacks in situ stone tools, although it does appear to post-date 2.6 Ma when artefacts first appear in the archaeological record. The StW 53 hominid, previously referred to Homo habilis, is here argued to be Australopithecus. The first artefact-bearing breccia of Member 5 is the Oldowan Infill, estimated at 2-1.7 Ma. It occupies a restricted distribution in Member 5 east and contains an expedient, flake-based tool industry associated with a few fossils of Paranthropos robustus. An enlarged cave opening subsequently admitted one or more Early Acheulean infills associated in Member 5 west with Homo ergaster. The artefacts attest to a larger site accumulation between ca. 1.7 and 1.4 Ma, with more intensive use of quartzite over quartz and a subtle but important shift to large flakes and heavier-duty tools. The available information on palaeoenvironments is summarized, showing an overall change from tropical to sub-tropical gallery forest, forest fringe and woodland conditions in Member 4 to more open woodland and grassland habitats in the later units, but with suggestions of a wet localized topography in the Paranthropus -bearing Oldowan Infill. PMID:10835264

Kuman, K; Clarke, R J

2000-06-01

122

Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone  

USGS Publications Warehouse

East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

Anderson, P.B.; Chidsey, T.C., Jr.; Ryer, T.A.

1997-01-01

123

Sedimentology by satellite: Space age approach to the coastal zone  

SciTech Connect

Satellites such as LANDSAT (EOSAT) and SPOT, with a variety of spectral configurations, combined with computer interpretive systems will allow us to synoptically evaluate coastal systems at relatively short intervals. Resolution of satellite images measured in meters dictates concentration on large-scale changes and fluxes. In areas of relatively clear water, such as the Mediterranean Sea or the eastern Gulf of Mexico, some satellite spectra will allow us to map below the sea surface and hence determine how the innermost shelf changes with time. To illustrate these points, we studied the barrier island system of the central west Florida coastline (USA) before and after the 1985 hurricane season. Two major storms impacted this region during that period. By computer overlaying before and after images, we were able to map changes in the barrier islands and to quantify acreage gained and lost. We were also able to detect and map changes in the submarine portions of the system, especially in the ebb and flood tidal deltas associated with inlets. The third dimension can be added by surveying the submarine features with high-resolution geophysics. Applications of this kind hold the promise of a new era in investigating beach/barrier islands and their relationship with the inner continental shelf.

Doyle, L.J.; McGarry, G.

1988-08-01

124

SEQUENCE STRATIGRAPHY AT THE TURN OF THE CENTURY: E.O. ULRICH'S OZARKIAN SYSTEM IN WISCONSIN  

Microsoft Academic Search

Edward Oscar Ulrich (1857-1944) was a major force in North American paleontology and stratigraphy, especially of the Paleozoic Era. Ulrich was immersed in correlation problems for many years; he came to believe that although fossils could tell the age of given strata, they were unsuitable for defining boundaries in the stratigraphic record. Instead, he advocated the use of erosional breaks—subaerial

Charles W. Byers

125

Large-scale River Channel Shifts on the Western Indo-Gangetic Plains and their implications for the Bronze-age Harappan Civilisation Settlement Patterns  

NASA Astrophysics Data System (ADS)

The distribution of settlements in ancient societies is commonly linked to the courses of large river systems. The Bronze Age Harappan civilisation (4800-3500BP) is no exception with the major sites of Harappa and Mohenjo-Daro located along the Indus river system. However, the largest collection of Harappan archaeological sites are associated with the postulated surface trace of a large palaeo-river channel in the drainage divide tract between the Ganges and Indus river systems, where no major river currently flows. It has been proposed that this palaeo-channel was occupied by a major river sourced in the Himalaya, and that this river provided water resources to sustain the extensive Harappan sites located along its ancient course. The abrupt abandonment of urban centres here at ~3500 BP has been explained as a consequence of river diversion, although alternative explanations for cultural decline have also been entertained. These hypotheses have remained untested because the stratigraphy and chronology of the postulated palaeochannel has never been determined. We use a combination of satellite image analysis, subsurface geophysical analysis and sediment coring to analyse the large-scale planform geometry, and detailed sedimentary and stratigraphic nature of the postulated palaeochannel in NW India. In particular we focus our analysis on a tract of the proposed channel adjacent to the major Harappan urban centre of Kalibangan in Rajastan State. We find that the surface trace of a postulated palaeochannel on satellite imagery is confirmed by subsurface geophysical investigation and detailed coring. In this presentation we will describe the remotely sensed character of the palaeochannel on satellite imagery, and the detailed stratigraphy and sedimentology based on resistivity investigations and sedimentological analysis of the cores. We will consider how changes in the course of the palaeochannel may have influenced settlement patterns of the Harappan civilisation in present day NW India.

Gupta, S.; Sinha, R.; Mason, P.; Yadav, G.; Singh, A.; Carter, A.; Murrey, A.

2009-12-01

126

Near coast sedimentary stratigraphy as a proxy for climatic instability  

NASA Astrophysics Data System (ADS)

Several studies have indicated a link between climatic deterioration and dune stability (Wilson 2002, Issar 2003, Dawson et al 2004). The frequency and magnitude of storms have been cited as a key variable in the stability of large dune systems. For the stratigraphy of dune systems to act as a regional climatic proxy there must be a good regional relationship between known climatic events and regionally correlated stratigraphic changes. Dunnet Bay in Caithness, Northern Scotland was chosen as a study site to look at the relationship between dune stability and climatic change during the late Holocene in Northern Scotland. Dunnet Bay was chosen for its physical attributes which make it an excellent natural sediment trap. Tucked in between headlands which act as barriers to long-shore transport the predominant movement of sediment there is straight onshore, with only minor amounts being lost to the sea. The immediate back-dune stratigraphy, colloquially known as "links", provided evidence of peat formation and dune stability. Stratigraphy was mapped using traditional field techniques and ground penetrating radar. The cores consisted mostly of massive layers of sand interleaved with peat. Sand layers were dated with optically stimulated luminescence (OSL) and interpreted as reflecting high wind energy regimes transporting sand inland. Peat layers were C14 dated and taken as representing climatic stability. Stratigraphy was mapped using hand auguring, percussion coring, and open sections. Ground penetrating radar was also used to look at the continuity of key layers. OSL dating in two open sections showed dates obtained from the first section (1790 AD ±70, 53 BC ± 100, 300 BC ± 100, 400 BC ± 100) mapped to the top of the second section (1800 AD ± 100, 1500 BC ± 200, 2900 BC ± 300) which was consistent with stratigraphy increasing sediment thickness towards the centre of the bay. The results were consistent with acquired C14 dates from selected peat layers. Taken collectively the results are consistent with some known episodes of climatic instability which occurred during the mid Holocene with instability phases occurring in Dunnet from approximately 6300- 4250 yrs BP, associated with climatic deterioration between 6000 - 5,200 Yrs BP (Lamb 1995) and dune instability between 2560 - 3900 Yrs BP, associated with an abrupt change of climate (Anderson 1995) In addition to the luminescence dates, 31 luminescence profiling dates were acquired in order to look at the continuity of the age vs. depth profile. Luminescence profile dates are small samples that require less preparation prior to luminescence measurement than full luminescence dating. Although larger errors are associated with luminescence profiling, it offered means of identifying at lesser cost the possible occurrence of mixing between eroded layers. The stratigraphic chronology was compared to other local and regional dune studies and periods of climatic deterioration found in other proxies. The GISP2 ice core (Greenland Ice Sheet Project) was found to provide chemical proxies for North Atlantic storminess which partially explained our observed stratigraphy (O`brien et al 1995). It is concluded that changes in dune stability at a regional scale are also influenced by local variables, so that one should be careful when attempting to draw stratigraphy to climate change. Key References: Issar, A. (2003) Climate changes during the Holocene and their impact on hydrological systems. Published by the Cambridge University Press 2003. Wilson, P. (2002) Holocene coastal dune development on the South Erridale peninsula, Wester Ross, Scotland. Scottish Journal of Geology, 38, 1, 5-13. Dawson, S., smith, D., Jordan, J., and Dawson D. G. (2004) Late Holocene coastal sand movements in the outer Hebrides N. W. Scotland. Marine Geology 210, 281-306 O`Brien, S. M. Mayewski, P.A. Meeker, L. D., Meese, D. A., Twickler, M. S. & Whitlow, S. I. (1995) Complexity of the Holocene Climate as reconstructed from a Greenland ice core. Science 270, pp 1962-1964 Lamb, H. (1995) Cl

McLivenny, J.

2009-04-01

127

Sequence stratigraphy - a historical perspective  

SciTech Connect

Sequence stratigraphy was originally defined by Sloss as the study of genetically related strata that are bounded by unconformities. A sequence was regarded as a lithostratigraphic unit. The definition has been expanded to [open quotes]bounded by unconformities of their correlative conformities[close quotes] and a sequence was changes to a chronostratigraphic unit. In petroleum exploration within shelf areas of foreland and continental margin basins and cratonic basins, two types of unconformities are particularly important, both related to sea level changes. The first type of unconformity, a subaerially exposed lowstand surface of erosion (LSE, sequence boundary), is caused by relative sea level lowering. The boundary is recognized by incised paleovalleys, paleosols, and missing facies. The second type of unconformity is a transgressive surface of erosion (TSE, sometimes called a ravinement surface), and occurs where shoreface erosion moves over coastal plain deposits during a relative sea level rise. Examples of subtle stratigraphic traps in siliciclastic rocks associated with unconformities are discussed for the Lower Pennsylvanian strata of the mid-continent region. Also reviewed are the problems of applying the new sequence stratigraphic terminology in relation to established terminology.

Weimer, R.J. (Colorado School of Mines, Golden, CO (United States))

1993-09-01

128

Magnetic stratigraphy procedures at Etna  

NASA Astrophysics Data System (ADS)

Different procedures in terms of sampling techniques and data analyses for the magnetic stratigraphy studies carried out at Etna over the past twenty three years, are presented and discussed. Mean directions of magnetization of lava flows have been derived from Fisher statistics on the data obtained by three different methods: NRM measurements and remanence measurements of partial PAFD of uncut samples; remanence measurements of cores subjected to complete PAFD; primary components defined by very strict PCA from cores subjected to complete PTD or PAFD. Comparison of the directions of magnetizations from Vesuvius and Arso in Ischia Island west of Vesuvius lava flows (about 350 km from Etna), geomagnetic measurements in Paris and Rome (about 1500 and 500 km from Etna respectively) and archaeomagnetic directions from France, all relocated to Etna via the inclined geocentric dipole, indicates that the third procedure produces a coherent time sequence of geomagnetic;remanence direction variations. Guidelines in terms of complete demagnetization, information on the magnetic carriers, very constricted data analysis procedure and relocation of directions of magnetizations are suggested.

Incoronato, Alberto; Del Negro, Ciro

129

Paleozoic cratonal/miogeoclinal stratigraphy in the western Mojave Desert  

SciTech Connect

Detailed mapping of metasedimentary rocks by many workers in the western Mojave Desert, California, has revealed Paleozoic lithologies of cratonal/miogeoclinal affinity. These exposures are metamorphosed, highly strained, and dismembered, and sit as roof pendants to Mesozoic and Tertiary intrusive rocks. In most outcrops no diagnosis fossils are preserved. Age correlation of these units is based, therefore, solely on similarities to lithologic packages outside the region. Despite the complex tectonic history this area has suffered since the late Paleozoic paleogeographic elements trend southwest into the region from where they are last clearly defined near the California-Nevada border. Dolomitic and calcitic marbles, quartzites, and biotite schists make up a major part of the stratigraphy in many areas. The stratigraphy and lithology of these units strongly suggest that they are correlative with late Precambrian-Cambrian units in the Death Valley region. Possible Ordovician and Devonian marbles also are present within some sections; at least one locality contains stromatoporoids of probable Devonian age. Calcite marbles tentatively correlated with lithologically similar Permian units in the Death Valley area are also represented and appear to be depositionally overlain by Mesozoic( ) shallow-marine and are-derived clastic rocks. Although the western Mojave Desert region has experienced compressional, transcurrent, and extensional deformation since late Paleozoic, our current understanding and restoration of this deformation history does not significantly alter the general southwest Paleozoic paleogeographic trends known to exist farther east.

Martin, M.W.; Walker, J.D. (Univ. of Kansas, Lawrence (United States))

1991-02-01

130

CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF NORTHERN ARIZONA AND SOUTHERN NEVADA  

E-print Network

#12;CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF NORTHERN ARIZONA AND SOUTHERN NEVADA THE 16TH FIELD. A., and Foster, J. R., (editors), 2011, Cambrian Stratigraphy and Paleontology of Northern Arizona and Southern Nevada: Museum of Northern Arizona Bulletin 67, 321 p. #12;Cambrian Stratigraphy and Paleontology

Mateo, Jill M.

131

Author's personal copy Reverse engineering mother nature --Shale sedimentology from an  

E-print Network

Author's personal copy Review Reverse engineering mother nature -- Shale sedimentology from of the sedimentology of shales can take a variety of forms. At its simplest one can experiment with suspensions conducted by hydraulic engineers, the transfer of that knowledge to sedimentology is hampered by the fact

Polly, David

132

The Cretaceous/ Tertiary boundary: sedimentology and micropalaeontology at El Mulato section, NE Mexico  

E-print Network

The Cretaceous/ Tertiary boundary: sedimentology and micropalaeontology at El Mulato section, NE and sedimentological analysis of this transition at the El Mulato section (NE Mexico), in order to infer the little Palaeogene Velasco Formation, there is a 2-m-thick Clastic Unit. Strati- graphical and sedimentological ana

Royer, Dana

133

David A. Katz $ Comparative Sedimen-tology Laboratory, University of Miami, 4600  

E-print Network

Sedimentology Laboratory. His research investigates the earliest diagenesis and geochemistry of modern Sedimentology Laboratory. He received his Ph.D. from the Swiss Institute of Technology (Eidgeno¨ssische Technische Hochschule) in Zurich, Switzerland. His field research focuses on sedimentology and se- quence

Swart, Peter K.

134

Mid-Holocene strengthening of the Southern Westerlies in South America --Sedimentological evidences from  

E-print Network

Mid-Holocene strengthening of the Southern Westerlies in South America -- Sedimentological layers, a composite sedimentological record of almost 25 m was established covering the last ~16,000 cal yr. Sedimentological and petrophysical analysis of the cores revealed the establishment of a dominant

Gilli, Adrian

135

Rudist formations in mixed siliciclastic-carbonate depositional environments, Upper Cretaceous, Austria: stratigraphy, sedimentology, and models of development  

Microsoft Academic Search

The upper Turonian to lower Campanian succession (Lower Gosau Subgroup) of the Northern Calcareous Alps, Austria, provides a model for the development of rudist formations on wave-dominated, mixed siliciclastic-carbonate shelves that were situated on top of an accretionary wedge. The rudist formations are present either within parasequences or in non-cyclic transgressive successions, and include (a) skeletal mounds up to about

Diethard Sanders; Josep Maria Pons

1999-01-01

136

Sedimentology and stratigraphy of the Miocene to Pliocene Mona Reef Complex and its relation with relative sea-level fluctuations  

E-print Network

, subaerial exposure and uplift. Data from the visual porosity survey revealed porosity ranging between 2% and 35% in limestone and 7% and 25% in dolomites. The porosity in the platform commonly occurs as moldic, interparticle and intercrystalline porosity...

Rodriguez Delgado, Alejandra Maria

2012-05-31

137

Taconic foreland basin evolution: Sedimentology and cement stratigraphy of the Black River Group limestones in the Champlain Basin  

Microsoft Academic Search

The Black River Group (Middle Ordovician, Mohawkian Series) limestones in the Champlain Basin record the transition between the shallow deposits of the underlying Chazy Group limestones and the shale-limestone couplets of the overlying Trenton Group which record rapid deepening of the foreland basin. The Black River Group was deposited in a subsiding foreland basin during the early stages of the

S. C. Bechtel; C. J. Mehrtens

1993-01-01

138

Magnetic stratigraphy and sedimentology of Holocene glacial marine deposits in the Palmer Deep, Bellingshausen Sea, Antarctica: implications for climate change?  

Microsoft Academic Search

The Palmer Deep is a closed bathymetric depression on the Antarctic Peninsula continental shelf. It contains three separate sub-basins. These basins lie along a northeast–southwest axis with water depths ranging from >1400 m to the southwest (Basins II and III) to just over 1000 m to the northeast (Basin I). Six sediment piston cores were collected from the study region;

Matthew E. Kirby; Eugene W. Domackb; Charles E. McClennen

1998-01-01

139

Stratigraphy and Sedimentology of the Late Cretaceous (Coniacian) Muskiki and Marshybank Members, Southern Alberta and Northwestern Montana.  

E-print Network

??A high-resolution allostratigraphic study of the Coniacian Muskiki and Marshybank members of the Wapiabi Formation in southern Alberta revealed a southwest thickening wedge of mudstone-dominated… (more)

Grifi, Meriem

2012-01-01

140

Sedimentology of coal and coal-bearing sequences  

SciTech Connect

Papers on all aspects of coal sedimentology are presented. The emphasis of the book is on coal depositional environments and facies models, and the main topics covered are coal environments, composition and geochemistry, facies models of associated clastic rocks, applications of facies models to coal mining, and sedimentary tectonics of coal basins.

Rahmani, R.A.; Flores, R.M.

1985-01-01

141

1981 symposium on surface-mining hydrology, sedimentology, and reclamation  

SciTech Connect

Papers presented at the symposium are included in this volume. Discussions are presented under the following headings: reclamation; special applications; hydrology; sewage sludge application; sedimentology; and wildlife and recreation. The proceedings contains 80 papers, 74 of which are abstracted separately for inclusion in the Energy Data Base. (DMC)

Graves, D.H. (ed.)

1981-01-01

142

Sedimentology and geochemistry of saline lakes of the Great Plains  

Microsoft Academic Search

Southern Saskatchewan and portions of adjacent Alberta, North Dakota and Montana are occupied by hundreds of saline and hypersaline lakes ranging in size from small prairie potholes (less than 1 km2) to relatively large bodies of water (greater than 300 km2). From a sedimentological perspective, distinction must be made between two basic types of saline lakes: playas and perennial lakes.

W. M. Last; T. H. Schweyen

1983-01-01

143

Floodplain deposits, channel changes and riverbank stratigraphy of the Mekong River area at the 14th-Century city of Chiang Saen, Northern Thailand  

Microsoft Academic Search

Riverbank stratigraphy and paleochannel patterns of the Mekong River at Chiang Saen provide a geoarchaeological framework to explore for evidence of Neolithic, Bronze-age, AD 5th Century Yonok and AD 14–16th Century Lan Na Cultures. Typical bank stratigraphy charted on the Thailand side is imbricate cobble gravel overlain by 5–10 m of reddish-brown sandy silt. The silt section is composed chiefly of

Spencer H. Wood; Alan D. Ziegler; Tharaporn Bundarnsin

2008-01-01

144

Sedimentology of mega-scale glacial lineations on the Dubawnt Lake Palaeo-Ice Stream bed, Canada and implications for lineation genesis  

NASA Astrophysics Data System (ADS)

Mega-scale glacial lineations (MSGLs) are highly elongate, subglacial landforms produced beneath zones of fast-flowing ice. While qualitative data on their morphology have existed for several decades, studies of their composition and sedimentology are comparatively rare. Sediment exposures along the course of the Finnie River in Nunavut, northern Canada, provide a window into the internal stratigraphy and sedimentology of MSGLs formed by the Dubawnt Lake Palaeo-Ice Stream during regional deglaciation of the Laurentide Ice Sheet. Stratigraphic sections record evidence for an initial advance of ice into the study area followed by ice sheet recession and deposition of glacifluvial and glacilacustrine outwash. Subsequently, the Dubawnt Lake Palaeo-Ice Stream overrode and reworked this outwash subglacially forming an 'MSGL till'. This till comprises a sandy, red diamicton facies, forming the core of the MSGL ridges and containing variably deformed lenses, stringers and rafts of outwash. The sedimentology of this diamicton is consistent with an origin as a glacitectonite and hybrid till formed by a combination of non-pervasive subglacial sediment deformation and lodgement. Facies variations from stratified to massive diamicton reflect, in turn, variations in strain and subglacial transport distance. The occurrence of stratified glacifluvial sediments within these ridges and the well-preserved nature of many of the sandy inclusions within the diamicton imply relatively short transport distances and incomplete mixing. MSGLs under the Dubawnt Lake Palaeo-Ice Stream formed through a combination of subglacial erosion and deposition. This included non-pervasive, subglacial sediment deformation and the reworking of pre-existing sediment depocentres during streaming flow. These results highlight the importance of sediment supply to MSGL formation with the presence of abundant pre-existing sediments which were subsequently overridden being critical to lineation formation.

O'Cofaigh, Colm; Stokes, Chris R.; Lian, Olav B.; Clark, Chris D.; Tulaczyk, Slawek

2014-05-01

145

Sedimentological study of sandy and shaly deposits (Beglia Formation) in Cap Bon area  

SciTech Connect

Sedimentological study of sandy and shaly deposits of the Beglia formation has been made in Cap Bon (northeast of Tunisia) to define a sedimentological and paleogeographical model which could be extrapolated into the Gulf of Hammamet. The main results follow. (1) The Beglia formation is serravalian in age and has a migratory deltaic complex facies which includes river and marine affinities (flood plain and tidal). (2) Three intervals within the Beglia have been studied in detail and indicate a northwest-southeast depositional trend which the authors consider the main direction of the middle Miocene detrital deposits in northeastern Tunisia. (3) The fine and well-sorted sandstones which extend up to hectometric and kilometric size, observed in outcrop, are the distal zones of the migratory fans and bars. (4) These sandstone bodies, because of their relative small size within their deltaic model, do not extend to the Gulf of Hammamet. The sandstones offshore have produced hydrocarbons in several areas. They are the distal equivalent of the poorly sorted and coarse channel deposits studied in the outcrops.

Mahjoub, M.N.; Khessibi, M.

1988-08-01

146

SEQUENCE STRATIGRAPHY AND CHEMOSTRATIGRAPHY OF AN INCISED VALLEY FILL WITHIN THE CRETACEOUS BLACKHAWK FORMATION, BOOK CLIFFS, UTAH  

E-print Network

was divided into nine stages of fill using the parasequence stratigraphy and chemostratigraphy. Stages of valley fill are defined by changes in base level. A minimum-average-age was determined for five stages (numbers 3, 4, 5, 6, and 8) based on paleosol...

Cornwell, Christine Frasca

2012-12-31

147

Sedimentology: general introduction and definitions : fluvial sediment and channel morphology  

USGS Publications Warehouse

Sedimentology, the study of sedimentary rocks and the processes by which they are formed, includes and is related to a large number of phenomena. Sedimentology includes the five fundamental processes defined by the term sediaentation --weathering, erosion, transportation, deposition and diagenesis. Sedimentology shares with geomorphology the study of the surface features of the earth. Sedimentology also shares with hydrology the study of river.--channels. River channels are formed in part or in total as a result of flowing water and sediment transport, commonly called the "work of the rivers." This survey of published literature was made to aid in arriving at definitions which would be acceptable to, and representative of, a majority of professional personnel actively engaged in laboratory and field investigations related to the "work of the river." The definitions in this list are intended to explain the terms used in studies of fluvial sediment and channel morphology. No set of definitions can expect universal acceptance, however, i t is hoped that this compilation will be considered a summary and synthesis of present and past usage and that it will serve as a starting point for future usage. Multiple references are cited from textbooks, glossaries and dictionaries, scientific journals and u.s. Government publications. To obtain a mutual understanding and enhance precision, many of the proposed definitions are a composite of those selected from papers or reports covering research studies and field investigations. A draft of this glossary has been reviewed by a group of interested personnel. The results of this review have been carefully considered and the originally-suggested definitions have been revised accordingly, resulting in the present compilation. R. G. Wolff, with the help of Mrs. v. Blatcher, carried out the literature search and compilation of terms and the review results. Paul c. Benedict approved or composed the definitions as presented in this report.

Wolff, Roger G.; Benedict, Paul C.

1964-01-01

148

Process-sedimentological challenges in distinguishing paleo-tsunami deposits  

Microsoft Academic Search

There has been a lively debate since the 1980s on distinguishing between paleo-tsunami deposits and paleo-cyclone deposits\\u000a using sedimentological criteria. Tsunami waves not only cause erosion and deposition during inundation of coastlines in subaerial\\u000a environments, but also trigger backwash flows in submarine environments. These incoming waves and outgoing flows emplace sediment\\u000a in a wide range of environments, which include coastal

G. Shanmugam

149

Jurassic sequence stratigraphy of the eastern Gulf Coastal Plain: Applications to hydrocarbon exploration  

SciTech Connect

Based on regional stratigraphic and sedimentologic data, three unconformity-bounded depositional sequences associated with cycles of relative sea-level change and coastal onlap are recognized for Jurassic strata in the eastern Gulf Coastal Plain area. These sequences are designated, in ascending order, the LZAGC (Lower Zuni A Gulf Coast)-3.1, the LZAGC-4.1, and the LZAGC-4.2 sequences and include Callovian through Kimmeridgian Stage strata. An understanding of the relationship of Jurassic reservoirs to sequence stratigraphy can serve as an aid to hydrocarbon exploration in the eastern gulf area. The most extensive and productive Jurassic hydrocarbon reservoirs in the study area occur within the progradational, regressive highstand deposits of the LZAGC-3.1 and LZAGC-4.1 depositional sequences. For example, the majority of Norphlet sandstone reservoirs in the onshore and offshore Alabama area are interpreted to have accumulated in eolian dune, interdune, and wadi (fluvial) depositional environments, which occurred in association with the highstand regressive system of the LZAGC-3.1 sequence. The most important Smackover reservoirs generally consist of partially to completely dolomitized ooid and peloid packstones and grainstones in the upper portion of the unit. These reservoirs occur in subtidal to supratidal, shoaling-upward carbonate mudstone to grainstone cycles in the highstand regressive system of the LZAGC-4.1 sequence. In addition, minor reservoirs that are discontinuous and not well developed are associated with the shelf margin and transgressive systems of the LZAGC-4.1.

Tew, B.H.; Mancini, E.A.; Mink, R.M. (Geological Survey of Alabama, Tuscaloosa (United States))

1991-03-01

150

Sedimentological and geophysical properties of a ca. 4000 year old tsunami deposit in southern Spain  

NASA Astrophysics Data System (ADS)

The coastlines around the Gulf of Cádiz were affected by numerous tsunami events damaging infrastructure and causing countless human losses. A tsunami deposit at Barbate-Zahara de los Atunes, Spain, is located at various heights above mean sea level and shows several characteristics indicative of high-energy event deposition. This study uses sedimentology, foraminifera assemblage, magnetic susceptibility, X-ray fluorescence analysis, ground penetrating radar (GPR) to support an interpretation of high-energy deposition and determine the deposit's transport mechanisms and sediment source. Radiocarbon and optically stimulated luminescence dating of the tsunami deposit reveals ages of ~ 4000 BP and does not support the AD 1755 Lisbon event as suggested in former publications.

Koster, Benjamin; Reicherter, Klaus

2014-12-01

151

Analysis of Subglacial Deposits and Landforms in Southern Ontario Using Sedimentology and Geomatics.  

E-print Network

?? This research utilizes sedimentology and geomatics to investigate relationships between sediment types, landforms and former glacial movement in southern Ontario, Canada. The research integrates… (more)

Maclachlan, John C

2011-01-01

152

Microfacies sedimentology of the Lower-Middle Kindblade Formation, Slick Hills, Southwestern Oklahoma.  

E-print Network

??MICROFACIES SEDIMENTOLOGY OF THE LOWER-MIDDLE KINDBLADE FORMATION (ORDOVICIAN), SLICK HILLS, SOUTHWESTERN OKLAHOMA In the late Cambrian (Franconian), a marine transgression took place on the Laurentian… (more)

Blair, Charles Grant

2013-01-01

153

Improved Osisotope stratigraphy of the Arctic Ocean Andr Poirier1  

E-print Network

Improved Osisotope stratigraphy of the Arctic Ocean André Poirier1 and Claude HillaireMarcel1 of the Arctic Ocean remained poorly known until the 2004 IODP coring of Lomonosov Ridge sediments. Early studies. Citation: Poirier,A., and C. HillaireMarcel (2011), Improved Osisotope stratigraphy of the Arctic Ocean

Long, Bernard

154

CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF NORTHERN ARIZONA AND SOUTHERN NEVADA  

E-print Network

#12;CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF NORTHERN ARIZONA AND SOUTHERN NEVADA THE 16TH FIELD. A., and Foster, J. R., (editors), 2011, Cambrian Stratigraphy and Paleontology of Northern Arizona will examine upper Dyeran strata in the Split Mountain area that record the history of the carbonate bank

Mateo, Jill M.

155

The applicability of OSL as a sedimentological proxy: new avenues to distinguish extreme events  

NASA Astrophysics Data System (ADS)

Signature underwater tsunami deposits have been relatively recently found in the upper Mediterranean shelf offshore Israel. They have been attributed as a potential cause for the demise of the ancient Roman city of Caesarea Maritima and its artificial Herodian harbour of Sebastos. Present annual large winter storm activity (2010-2011; waves heights up to 14 m) has severely impacted the area, showing increased coastal erosion and rigorous movement of nearshore sands, complicating the stratigraphical histories of the near offshore record. Recent sedimentological and geoarchaeological studies conducted in and around the harbour have been aimed to investigate extreme event characterization by different means, using Optically Stimulated Luminescence (OSL). A comparative study of modern and palaeo-storm sediments was launched in order to obtain physical correlation between offshore sediments, enabling further comparison with historical tsunami deposits, as well as modern and ancient sands emplaced during normal marine conditions. A suite of previously collected and identified sediment samples was selected from the same area where the modern storm analogues were collected. The palaeo-samples came from long-vertical hydraulic percussion cores (14-30 m depths) and small horizontal tubes pushed into excavated underwater sediment walls (2-12 m depths). The uniqueness of OSL relays on its capacity to date the last time a mineral grain was effectively exposed to sunlight, just prior to its burial. It is intrinsically related to final depositional process, which should reflect the completeness of the OSL signal resetting (zeroing process), evidenced by the normality and modality of the Equivalent Dose (DE) distribution. In Optical Dating, DE over-dispersion values have been used as a measure of inhomogeneitiy in the natural palaeo-dose of sediments. Such heterogeneity can be due to an array of causes, including insufficient zeroing during transport and deposition, or turbation processes after burial. Environments where sediments are well exposed to daylight at deposition (e.g. aeolian and some coastal) do not show extreme over-dispersion values but rather well clustered DE's as noted by probability-distribution plots. The degrees of variance and skewness of Gaussian or relative-probability distributions are intrinsically related to the scatter factor. Hence, the latter could be used to differentiate between depositional mechanisms and/or environmental settings. In this study, the single-aliquot regenerative-dose (SAR) protocol was used to measure the OSL signals from single grains of quartz from tsunami, storm and normal marine conditions deposits. Over-dispersion analyses were conducted on all samples. Preliminary results suggest the possibility of differentiating between all three types of deposits based on pre-established over-dispersion values and representative single-dose population distributions. Further comparative OSL experiments are currently being carried out on other known tsunamigenic analogues to further evaluate OSL signal behaviours and constrain the findings (2011 Tohoku Tsunami; 1979 night Petatlán Tsunami). Rather than a dating tool, OSL was used to identify signal patterns exclusive to known depositional conditions, in hope of applying it as sedimentological proxy in event stratigraphy and palaeoseismic tsunami research.

Lopez, G. I.

2012-12-01

156

GEOBULLETIN GeoBulletin is distributed weekly, by E-mail. Contributions are requested!  

E-print Network

in sedimentology and stratigraphy, and geological mapping. Currently I am studying geology for the academic year interested in sedimentology and stratigraphy at Miami and have since taken additional courses at Trinity including sedimentology and stratigraphy, sedimentary petrology, and paleontology, paleoecology

Carlson, Anders

157

Sedimentary development of the Pearl River Estuary based on seismic stratigraphy  

Microsoft Academic Search

The Pearl River Estuary in the Southern China was studied both by applying concepts of seismic stratigraphy to the interpretation of high resolution seismic profiles and by correlating with borehole records. The correlation between seismic facies and borehole stratigraphy of the estuary enables to propose a seismic stratigraphy model of the estuarine infill. The stratigraphy and evolution of the Holocene

Cheng Tang; Di Zhou; Rudolf Endler; Jinqing Lin; Jan Harff

2010-01-01

158

Late-Quaternary morpho-sedimentology and submarine mass movements of the Betsiamites area, Lower St. Lawrence Estuary, Quebec, Canada  

E-print Network

Late-Quaternary morpho-sedimentology and submarine mass movements of the Betsiamites area, Lower St 2008 Accepted 4 March 2008 Keywords: submarine mass movements morpho-sedimentology multibeam bathymetry the submarine morpho-sedimentology of an area of 500 km2 with focus on the consequences of four mass movement

St-Ong, Guillaume

159

Part II of manuscript submitted to Sedimentology, May, 2006 Unraveling the conundrum of river response to rising sea level from  

E-print Network

Part II of manuscript submitted to Sedimentology, May, 2006 1 Unraveling the conundrum of river to Sedimentology, May, 2006 2 deltas is adapted to describe the response of the Fly-Strickland River system, Papua of manuscript submitted to Sedimentology, May, 2006 3 Pleistocene-Holocene eustatic sea level rise of some 120 m

Parker, Gary

160

Part I of Manuscript submitted to Sedimentology, May, 2006 Unraveling the conundrum of river response to rising sea level  

E-print Network

Part I of Manuscript submitted to Sedimentology, May, 2006 1 Unraveling the conundrum of river of Manuscript submitted to Sedimentology, May, 2006 2 Fly-Strickland River system, Papua New Guinea to Holocene of Manuscript submitted to Sedimentology, May, 2006 3 Mississippi River was able to resist drowning due to sea

Parker, Gary

161

Probable age of Autolycus and calibration of lunar stratigraphy  

SciTech Connect

{sup 39}Ar-{sup 40}Ar analyses of three petrographically distinct, shocked Apollo 15 KREEP (i.e., high K, rare earth element, P, and other trace element contents) basalt samples demonstrate that a major impact event affected all three samples at about 2.1 Ga. The Copernican System craters Aristillus and Autolycus are to the north; a ray from one of them crosses the landing site and had been suggested prior to the Apollo 15 mission as a source of material that could be used to date these craters. Autolycus, the older of the two, is in a particularly appropriate terrain and is the most likely source of the 2.1 Ga heating and delivery event. With this calibration point, and if Autolycus really is a Copernican crater, the Copernican System lasted twice as long as has previously been suggested. Furthermore, the Moon was not subjected to a constant cratering rate over the past 3 b.y.; the average rate in the preceding Eratosthenian must have been twice that in the Copernican.

Ryder, G. (Lunar and Planetary Institute, Houston, TX (USA)); Bogard, D. (NASA-Johnson Space Center, Houston, TX (USA)); Garrison, D. (Lockheed ESC, Houston, TX (USA))

1991-02-01

162

Sequence stratigraphy buoys W. Indonesia basins  

SciTech Connect

Since oil exploration began in Indonesia in 1870 more than 3,000 exploratory wells have been drilled in Western Indonesia, which means a significant data base exists; however, many of the published technical papers describing Indonesian petroleum geology are based on lithostratigraphy. This article presents a correlative framework based on the application of sequence stratigraphy, which has been established for the hydrocarbon productive basins. Part 1 illustrates this correlative framework with an example each from areas in Sumatra, Java, and Kalimantan. These examples review the hydrocarbon system in each area from the perspective of source, reservoir, seal, and timing of structure. In Part 2 the ideas developed are expanded and integrated into an examination of the future hydrocarbon potential for western Indonesia, which is refreshingly different and perhaps more encouraging than those made using the traditional tools of lithostratigraphy and biostratigraphy.

Courteney, S. [Wairarapa Geological Services (New Zealand)

1996-05-20

163

Late Quaternary geotechnical stratigraphy of North Texas continental shelf  

E-print Network

LATE QUATERNARY GEOTECHNICAL STRATIGRAPHY OF NORTH TEXAS CONTINENTAL SHELF A Thesis by JOHN SAL MUNSEY Submitted to the Graduate College of Texas Algi University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... December 1985 Major Subject: Geology LATE QUATERNARY GEOTECHNICAL STRATIGRAPHY OF NORTH TEXAS CONTINENTAL SHELF A Thesis by JOHN SAL MUNSEY Approved as to style and content by: br' sto er . Mathewson (Cha&r of Committee) Norman R . ' ord (Memb...

Munsey, John Sal

2012-06-07

164

Osmium isotope stratigraphy of a marine ferromanganese crust  

USGS Publications Warehouse

Ferromanganese crusts provide records of long term change in ocean circulation and continental weathering. However, calibrating their age prior to 10 Ma has been entirely based on empirical growth rate models using Co concentrations, which have inherently large uncertainties and fail to detect hiatuses and erosional events. We present a new method for dating these crusts by measuring their osmium (Os) isotope record and matching it to the well-known marine Os isotope evolution of the past 80 Ma. The well-characterised crust CD29-2 from the central Pacific, was believed to define a record of paleooceanographic change from 50 Ma. Previous growth rate estimates based on the Co method are consistent with the new Os isotope stratigraphy but the dating was grossly inaccurate due to long hiatuses that are now detectable. The new chronology shows that it in fact started growing prior to 70 Ma in the late Cretaceous and stopped growing or was eroded between 13.5 and 47 Ma. With this new technique it is now possible to exploit the full potential of the oceanographic and climatic records stored in Fe-Mn crusts. ?? 2005 Elsevier B.V. All rights reserved.

Klemm, V.; Levasseur, S.; Frank, M.; Hein, J.R.; Halliday, A.N.

2005-01-01

165

Mesozoic stratigraphy of northwestern Australian and northern Himalayan margins  

SciTech Connect

The Mesozoic stratigraphies of the Himalayan margin, the Argo abyssal plain, and the Exmouth Plateau exhibit marked contrasts in their sedimentation histories. The sedimentary sequence on the northeastern Exmouth Plateau off Australia includes a Carnian to Rhaetian sequence of fluviodeltaic and marine clastics and carbonates, capped by a shallowing-upward sequence of platform carbonates overlain, with a major unconformity, by marine Aptian sediments deposited during rapid subsidence of the plateau. Argo abyssal plain basement is overlain by red-brown, bioturbated, inoceramid-rich quartzose claystones, bentonites, and quartz siltstones, dated by radiolarians and benthic foraminifera as lowest Cretaceous. This is overlain by red and green claystones and nannofossil chalks. The basal age indicates that sea-floor spreading began in the earliest Cretaceous, not Oxfordian as had been thought. In the Thakkola region of Nepal, uppermost Triassic through Lower Jurassic shelf and carbonate platform facies are capped by a ferruginous oolite deposit of latest Bathonian to earliest Callovian age. Sedimentation resumed in the middle Oxfordian with deposition of Berriasian( ) deep-water black organic-rich mud. Following a valanginian regression and progradation of terrigenous clastics, Aptian black shales were deposited. In geological studies of the northwestern Australian margin, the ubiquitous hiatus within the Callovian-Oxfordian has been termed the breakup unconformity. Existence of a similar-aged hiatus in the Himalayas on a margin which formed during the late Paleozoic, absence of any Jurassic on the Exmouth Plateau, and the apparent initiation of spreading in the Argo basin during the earliest Cretaceous suggest that this widespread unconformity is not associated with a continental breakup in these regions.

Ogg, J.; Kopaskamerkel, D.C.

1989-03-01

166

Upper Jurassic of east Texas, a stratigraphic sedimentologic reevaluation  

SciTech Connect

The Smackover-Haynesville of east Texas has long been modeled as a simple progradational carbonate-evaporite ramp. Recent data indicate that the conventional ramp model for this sequence should be abandoned in favor of an evolving rimmed shelf to platform model, forming in response to changes in rate of relative sea level rise during the Late Jurassic. Evidence for Smackover-Haynesville shelves include: (1) thick high-energy carbonates along the basin margin in the Smackover and throughout the Haynesville, (2) low-energy pellet-dominated lagoonal carbonates, evaporites, and evaporitic siliciclastics occurring landward of, and interfingering with, the Smackover and Haynesville basin-margin carbonate barriers, (3) deeper water, open-marine low-energy limestones with black shales seaward of the basin-margin barriers (Smackover-Gilmer undifferentiated), and (4) the Gilmer shale forms a siliciclastic wedge seaward of the Haynesville basin margin and its zero isopach defines the Kimmeridgian shelf margin. The Smackover and Haynesville seem to represent 2 distinct sedimentologic cycles, with each cycle reflecting an initial relative sea level rise during which a rimmed shelf and lagoon are developed, and a terminal sea level standstill during which the shelf evolved into a high-energy platform. Although these sedimentologic patterns seem compatible with accepted Jurassic sea level curves, they may also reflect differential basin-margin subsidence combined with variable carbonate production rates. Finally, the shelf-platform model more clearly defines future exploration strategies for Smackover-Haynesville targets in east Texas and perhaps across the Gulf of Mexico, if eustatic sea level changes were the dominant causative factor for shelf development in the Late Jurassic.

Moore, C.H.; McGillis, K.; Stewart, S.; Wilkinson, S.; Harwood, G.

1985-02-01

167

Sedimentology, Detrital Zircon Geochronology, and Stable Isotope Paleoaltimetry of the Early Eocene Wind River Basin, Wyoming  

NASA Astrophysics Data System (ADS)

Large sedimentary basins in Wyoming archive information about tectonic setting and paleotopography during Laramide deformation. In the northwestern corner of the Wind River Basin, the early Eocene Indian Meadows Formation and overlying Wind River Formation are well exposed. Previous studies of fossil assemblages in the two formations place the depositional age in the Wasatchian Land Mammal Age (51-55 Ma). We present results of a multidisciplinary study of sedimentology, detrital geochronology, and isotope paleoaltimetry. Lithostratigraphic data from four measured sections show that the sedimentary environment changed from alluvial fan-debris flow to anastomosing river systems, with paleocurrent directions mostly southward. Clast counts and sandstone modal framework point counts show that the proportions of Precambrian granite clasts, feldspar and lithic fragments increase upsection, indicating the sediment source terrane experienced rapid unroofing during early Eocene. Detrital zircon U-Pb age spectra show that the majority of the sediment was recycled from Paleozoic-Mesozoic sedimentary rocks in the Sevier thrust belt. One sample from the top of the Indians Meadow Formation mainly contains zircons from Grenville-age basement, which were most likely recycled from Cambrian sandstone. Surprisingly, very few Archean zircons were found as the proportion of basement granite clasts is high. Late Cretaceous-early Paleocene zircons were derived from the magmatic arc, but no depositional age zircons were recovered. The ?18O values of unaltered paleosol carbonate range between -8.5 and -9.8 (VPDB), similar to ?18O values of paleosol carbonate in the Bighorn Basin during early Eocene. Correcting for warmer Eocene global temperature and lower ?18O values of seawater, the inferred ?18O value of early Eocene precipitation is -6.9± 0.7 (VSMOW). The inferred precipitation ?18O value is comparable to that of the modern summer precipitation of the same latitude in the Great Plains, suggesting that the paleoelevation of the early Eocene Wind River Basin and Bighorn Basin was on the order of 500 meters.

Fan, M.; Decelles, P. G.; Gehrels, G. E.; Dettman, D. L.; Peyton, S. L.

2008-12-01

168

Fluvial responses to climate and sea-level change: a review and look forward  

E-print Network

stratigraphic, sedimentological and geochronological frameworks in a variety of continental interior sedimentology, Quaternary geology, sea-level change, sequence stratigraphy. Sedimentology (2000), 47 (Suppl. 1

Törnqvist, Torbjörn E.

169

An organodiagenetic model for Marinoan-age cap carbonates  

NASA Astrophysics Data System (ADS)

The Nuccaleena Formation cap carbonate is the global stratotype for the Marinoan glaciation and Ediacaran GSSP, a designation that emphasises the importance of cap carbonates to our current understanding of global Neoproterozoic biogeochemistry, sedimentology and stratigraphy. However, to date there is no agreed depositional model for cap carbonates, and there remains minimal detailed paragenetic data for developing process based depositional models. Here an early diagenetic "organodiagenetic" dolomite cementation model for Marinoan cap carbonate formation is hypothesised and explored. It is demonstrated how this process-based model can explain the three main atypical sedimentary structures that are the basis for correlation of Marinoan-age cap carbonates; giant tepee-like structures, sheet veins and tubestones. These features are interpreted to be products of fluid overpressure deformation induced by organodiagenetic expansive cementation. Giant tepee-like structures, the hallmark of Marinoan cap carbonates, conform to a simple structural analysis that is consistent with the predicted stress field induced by expansive cementation-driven fluid overpressure. The undeformed to highly deformed gradient of deformation features in cap carbonates is consistent with the range of rheologies in a shallowly buried cementing carbonate. Modification of matrix textures and bedding surfaces also conforms to the range of expected textures within this model. Overall, it is hypothesised that the aggradational, condensed section architecture of cap carbonates was the primary control over the generation of these atypical sedimentary features. The available paragenetic analysis suggests that the geochemical data, particularly the C-isotopic data, can be reinterpreted as supportive of the organodiagenetic model, and that the Neoproterozoic ocean was perhaps similar to that of today. The proposed model indicates that the current criteria for the placement of the Ediacaran GSSP are non-unique and potentially non-isochronous. Perhaps the most important aspect of this model is that it is testable, and is a call for focused research on the much-overlooked paragenesis of cap carbonates.

Gammon, P. R.

2012-01-01

170

Acquisition, 3-D display and interpretation of GPR data in fluvial sedimentology.  

E-print Network

??Alluvial architecture has an inherently three-dimensional character; however, standard methods used within fluvial sedimentology, including ground penetrating radar (GPR) surveys, generally provide only 1-D or… (more)

Zuk, Tomasz

2011-01-01

171

Sequential stratigraphy of Jurassic and Cretaceous in the central Saudi Arabian platform  

SciTech Connect

Depositional sequences and system tracts in the Jurassic and Cretaceous sedimentary rocks of the Central Saudi Arabian platform have been established on the basis of precise lithofacies analysis, detailed sedimentologic interpretation, and accurate age determination by ammonites, nautoli, brachipods, echinoids, and nannoflora. A eustatic depositional model integrated with accepted worldwide sequential stratigraphic data is proposed, and appears to correlate fairly well with the 1988 global sea level chart by Haq and others, particularly for the Lower and Middle Jurassic and the Middle and Upper Cretaceous. Ages determined by accurate biostratigraphic data enable time correlations to be made with third-order eustatic cycles from Vail's 1988 global chart. Eustatic changes therefore appear to be the main factors of sedimentary control during the Jurassic and Cretaceous on the Arabian platform.

Le Nindre, Y.M.; Manivit, J.; Vaslet, D. (Bureau de Recherches Geologiques et Minieres, Orleans (France)); Manivit, H. (Bureau de Recherches Geologiques et Minieres, Orleans (France) Univ. Pierre et Marie Curie, Paris (France))

1991-08-01

172

Late quaternary sequence stratigraphy, South Florida margin  

SciTech Connect

Late Quaternary sea-level change and the Florida Current have combined to produce a progradational shelf-slope margin along the western portion of the south Florida Platform facing the Straits of Florida. Analysis of high resolution seismic reflection profiles suggest at least eight 5th order late Quaternary sequences downlap onto the Pourtales Terrace at 250 m water depth. Along most of the south Florida margin, this Late Quaternary section is very thin, and only where significant accumulations occur can the stratigraphic patterns produced by sea-level change be clearly observed. Recognition of systems tracts and their boundaries from high-resolution seismic data is important for prediction of sedimentary facies and stratigraphic development of margins. Many south Florida seismic boundaries can be fit to the Exxon sequence stratigraphy model. Others appear to reflect the added effect of bottom-current erosion that complicates the signal produced by sea-level change. Overall, the sea-level signal appears to dominate the stratigraphic record, especially from the 2-dimensional perspective of dip-oriented seismic profiles. However, the 3-dimensional geometry of deposits are strongly influenced by along slope accumulation patterns controlled by the Florida Current. This study provides new insight on the importance of both geostrophic boundary currents and sea-level change in controlling stratigraphic development of a carbonate platform margin. Similar anomalously thick slope deposits in ancient sequences may indicate similar controls on accumulation and could lend to predictions of related paleo-platform configurations.

Locker, S.D.; Hine, A.C. [Univ. of South Florida, St. Petersburg, FL (United States). Dept. of Marine Science

1995-12-01

173

Jurassic stratigraphy of the Wiggins Arch, Mississippi  

SciTech Connect

Mobil and Shell jointly explored the Wiggins arch area in southern Mississippi from 1985 to 1991. The effort concentrated on the Jurassic Norphlet and Smackover formations. Two wells were drilled into Paleozoic crystalline rocks and one well into the Pine Hill formation. Two of these wells were located on the southern side of the Wiggins arch and provide significant data for interpreting Jurassic stratigraphy. The Mobil No. 1 U.S.A. well encountered a complete Jurassic section, but with some significantly different facies than those encountered by wells to the north. A granite wash section is the equivalent to the Frisco City formation previously only found 100 mi to the north-northeast. All 300 ft of Smackover is crystalline dolomite. The Norphlet section is entirely granite wash. The Pine Hill anhydrite is unusually thick and interpreted to be equivalent to the Louann Salt. Correlations to other wells on the Wiggins arch, particularly the Conoco No. 1 Higgins, indicate that the Jurassic can be divided into three transgressive events separated by the Norphlet/Pine Hill and Frisco City/Buckner regressive events.

Rhodes, J.A.; Maxwell, G.B. (Mobil Oil Company, Houston, TX (United States))

1993-09-01

174

Sediment transport processes and their resulting stratigraphy: informing science and society  

NASA Astrophysics Data System (ADS)

Sediment transport physically shapes planetary surfaces by producing patterns of erosion and deposition, with the relative magnitudes of geomorphic actions varying according to environmental conditions. Where sediment fills accommodation space and generates accumulation, a stratigraphic archive develops that potentially harbors a trove of information documenting dynamic conditions during the periods of sediment production, transport and deposition. By investigating the stratigraphic record, it is possible to describe changes in surface environments, as well as hypothesize about the development of regional tectonic and climate regimes. Ultimately, information contained within the stratigraphic record is critical for evaluating the geological history of terrestrial planets. The enigma of stratigraphy, however, is that sediment deposition is finicky, there is no uninterrupted record, and while deposits may reflect only a brief temporal window, they may still be used to infer about conditions that encompass much longer periods of time. Consider a case where meter-scale dune foresets, deposited in a matter of minutes to hours, are in contact with sediments above and below that reflect entirely different depositional circumstances and are separated in time by a hiatus of thousands or perhaps millions of years. To effectively unlock the scientific trove bound in stratigraphy, it is first necessary to identify where such unconformities exist and the conditions that lead to their development. This challenge is made much simpler through scientific advances in understanding sediment transport processes -- the examination of how fluid and solids interact under modern conditions -- because this is precisely where sediment patterns first emerge to produce accumulation that builds a stratigraphic record. By advancing an understanding of process-based sedimentology, it is possible to enhance diagnostic evaluations of the stratigraphic record. Fortunately, over the past several decades, there have been numerous scientific advances pertaining to the coupling of sediment transport and hydrodynamics. This research has produced new theory about how sediments accumulating in many unique environments shape the stratigraphic record. Recent studies have taken advantage of novel methods for acquiring observational data, which in turn have been used to advance numerical modeling schemes as well as experimental designs. As an example, consider fluvial deltas: here, hydrodynamics are constantly evolving over space and time. Patterns of sediment deposition and erosion (from dune to delta-lobe scales), resolved using high-resolution 3-D acoustic data, are used as input data to construct models that further show how channel dynamics (e.g., avulsions) and kinematics (e.g., lateral migration) evolve due to sediment and hydrodynamic coupling. This information is used to propose new theories of delta stratigraphy, which are then tested by examining ancient fluvial-delta systems. Finally, research efforts evaluating modern sediment-transport and depositional processes offer significant benefits to society. For example, fluvial deltas are heavily relied upon for societal welfare and yet are among the most dynamic landscapes on Earth's surface. Therefore, research examining the evolution of these landscapes not only advances basic science, but also doubles as an exercise in applied geomorphology.

Nittrouer, J. A.

2013-12-01

175

Interpretation of seismic stratigraphy on the Amazon continental shelf  

SciTech Connect

The stratigraphy of the Amazon subaqueous delta has been examined using high-resolution reflection profiles. 15 piston cores from the Amazon Shelf were used to interpret the significance of the reflectors evident in the seismic profiles. Acoustic reflectors correlate with changes in grain size within cores, and generally represent coarser layers within the muddy deposits of the delta. Measurement of compressional-wave seismic velocity and saturated bulk density demonstrate that the correlation results from changes in acoustic impedance, caused by the grain-size variations. The reflectors reveal two predominant types of seismic stratigraphy: depositional and erosional. The depositional stratigraphy contains reflectors formed by relatively subtle change in grain size. Gently dipping topset and steeply dipping foreset demonstrate upward and seaward progradation of the subaqueous delta. This stratigraphy is truncated by erosional reflectors, which are significantly coarser layers. The erosional reflectors divide the depositional stratigraphy into distinct sets. The prevalence of erosional reflectors is greatest in the topset region near the river mouth, suggesting that sediment in this region, which is rapidly accumulating on 100-year time scales, has been eroded over longer time scales within the Holocene.

Alexander, C.R. Jr.; Nittrouer, C.A.; Demaster, D.J.

1985-01-01

176

Sedimentology and origin of source rocks in the Tertiary Niger delta  

SciTech Connect

Organic matter in Tertiary strata of the Niger delta is mainly a mixture of types II and III, has a high pristane/phytane ratio (> 1.0), and is composed of the macerals vitrinite and minor liptinite. The main palynofacies are structured woody material, cuticles, pollen, spores, and opaque and minor amorphous organic matter. The distribution and abundance of the organic matter reflects the age and sedimentology of the strata. There is a progressive decline in mean total organic carbon (TOC) content from upper Eocene (2.2% TOC) to Pliocene strata (0.90% TOC) and an associated general decrease in hydrogen index (HI) and pristane/phytane ratio. The decrease in TOC and HI in younger strata mainly reflects increased dilution of a nearly constant supply of terrestrial organic matter associated with the generally higher sedimentation rates of younger strata. The low pristane/phytane ratio of younger strata may reflect less oxidizing depositional conditions. No rich source rocks occur in the Niger delta and, as conventionally measured, the strata have little or no oil generating potential. The poor quality of the source rocks has been compensated for by their greater volume and excellent migration routes. The Niger delta type of source rock - although an end member in terms of general source rock composition - appears to be relatively typical of Tertiary deltas.

Bustin, R.M.

1988-08-01

177

Stratigraphy and Leonardian F'usulinid Paleontology in Central Pequop Mountains,  

E-print Network

Stratigraphy and Leonardian F'usulinid Paleontology in Central Pequop Mountains, Elko County ......................Systematic paleontology 110 General statement ............................ 110 ..............Genus

Seamons, Kent E.

178

Geomorphology, facies architecture, and high-resolution, non-marine sequence stratigraphy in avulsion deposits, Cumberland Marshes, Saskatchewan  

USGS Publications Warehouse

This paper demonstrates field relationships between landforms, facies, and high-resolution sequences in avulsion deposits. It defines the building blocks of a prograding avulsion sequence from a high-resolution sequence stratigraphy perspective, proposes concepts in non-marine sequence stratigraphy and flood basin evolution, and defines the continental equivalent to a parasequence. The geomorphic features investigated include a distributary channel and its levee, the Stage I crevasse splay of Smith et al. (Sedimentology, vol. 36 (1989) 1), and the local backswamp. Levees and splays have been poorly studied in the past, and three-dimensional (3D) studies are rare. In this study, stratigraphy is defined from the finest scale upward and facies are mapped in 3D. Genetically related successions are identified by defining a hierarchy of bounding surfaces. The genesis, architecture, geometry, and connectivity of facies are explored in 3D. The approach used here reveals that avulsion deposits are comparable in process, landform, facies, bounding surfaces, and scale to interdistributary bayfill, i.e. delta lobe deposits. Even a simple Stage I splay is a complex landform, composed of several geomorphic components, several facies and many depositional events. As in bayfill, an alluvial ridge forms as the feeder crevasse and its levees advance basinward through their own distributary mouth bar deposits to form a Stage I splay. This produces a shoestring-shaped concentration of disconnected sandbodies that is flanked by wings of heterolithic strata, that join beneath the terminal mouth bar. The proposed results challenge current paradigms. Defining a crevasse splay as a discrete sandbody potentially ignores 70% of the landform's volume. An individual sandbody is likely only a small part of a crevasse splay complex. The thickest sandbody is a terminal, channel associated feature, not a sheet that thins in the direction of propagation. The three stage model of splay evolution proposed by Smith et al. (Sedimentology, vol. 36 (1989) 1) is revised to include facies and geometries consistent with a bayfill model. By analogy with delta lobes, the avulsion sequence is a parasequence, provided that its definition is modified to be independent from sea level. In non-marine settings, facies contacts at the tops of regional peats, coals, and paleosols are analogous to marine flooding surfaces. A parasequence is redefined here as a relatively conformable succession of genetically related strata or landforms that is bounded by regional flooding surfaces or their correlative surfaces. This broader definition incorporates the concept of landscape evolution between regional flooding surfaces in a variety of depositional settings. With respect to landscape evolution, accommodation space has three spatial dimensions - vertical (x), lateral (y), and down-the-basin (z). A flood basin fills in as landforms vertically (x) and laterally accrete (y), and prograde down-the-basin (z). Vertical aggradation is limited by the elevation of maximum flood stage (local base level). Differential tectonism and geomorphology control the slope of the flood basin floor and the direction of landscape evolution. These processes produce parasequences that include inclined stratal surfaces and oriented, stacked macroforms (clinoforms) that show the magnitude and direction of landscape evolution. ?? 2001 Elsevier Science B.V. All rights reserved.

Farrell, K.M.

2001-01-01

179

Venus Stratigraphy: Results from the Mapping of Six Quadrangles (Invited)  

NASA Astrophysics Data System (ADS)

Two views about the way Venus has evolved have been generated from studies of Magellan data. Venus has been suggested to have had a history in which there was a series of epochs each represented by a different volcanic or tectonic process on a global scale (e.g., Basilevsky et al. 1997). However, there is evidence to suggest that coronae, rifts, wrinkle ridges, small and large edifices, and large flow fields have each formed throughout the portion of Venus' history revealed by presently exposed rock units (Guest and Stofan, 1999). We propose that the plains have been built up by lavas erupted in a number of different styles, each occurring throughout the history represented by the exposed stratigraphy of the planet. The low number and apparent randomness of the impact crater population has left us with an inability to date individual terrains on Venus. Dates derived from crater counts accumulated from the combined area of specific types of feature such as coronae (e.g., Price et al. 1996), must be interpreted with care as the method is based upon the assumption that features of like morphology have the same age. Additional problems arise with features such as corona and large volcanoes, where late-stage volcanic flows mask evidence of the timing of the initiation of the feature with respect to surrounding units. Our detailed studies indicate that Venus has had a complex history in which most geologic processes have operated in a non-directional fashion to a greater or lesser extent throughout the planet's history.

Stofan, E. R.; Guest, J. E.

1999-09-01

180

Quaternary high-resolution stratigraphy and its application in studies of the Canary basin  

SciTech Connect

The Quaternary nannofossil stratigraphy has three zones based on the last appearance datum of Pseudoemillania lacunosa and the first appearance datum of Emiliania buxleyi. Other first and last occurrences can be added to this to give a conventional stratigraphy with zones a few hundred thousand years long. The calcareous nannofossil flora however is frequently dominated by a single species which allows acme zones to be identified giving a resolution of a few tens of thousands of years (individual oxygen isotope stages). The acmes are not controlled by climate since they span both cold and warm stages through a range of latitude. This high-resolution stratigraphy has been used in two ways to study sedimentation in the Canary basin off West Africa. First, it has been combined with the lithostratigraphy to identify particular oxygen isotope stages in sediments from the Madeira Abyssal Plain. Second, it has been used to identify the age range of material included in each turbidite by comparing coccolith mixtures in each turbidite with calculated synthetic mixtures based on the proportions of particular species in each oxygen isotope stage. The results show that each turbidite contains a mixture of sediment representing a few hundred thousand years. Since the author knows the volume of each turbidite and the rate of sediment accumulation in the source areas, he can calculate the depth and area of erosion of each flow. The calculated values tie in with the knowledge of recent erosion in the area off West Africa and suggest that areas of the margin have periodically failed removing 50-100 m thick units. The focus of this erosion has varied with time.

Weaver, P.P.E. (Inst. of Oceanographic Sciences Deacon Lab., Surrey (United Kingdom))

1991-08-01

181

Stratigraphy of the Santa Cruz area. Export trade information  

SciTech Connect

The report documents the results of a feasibility study which addressed the viability of developing petroleum areas in Bolivia. The objective of the report, volume 3 of 4, was to use both geologic modeling and seismic analysis to study the structures and stratigraphy of the specified oil fields to develop a regional picture to be used with sufficient certainty to drill stepout wells and explore for additional hydrocarbon producing structures. Along with the Introduction, Summary, Conclusions, and Recommendations, the report discusses the Scope of Work, Objective, Geologic Setting, and the Seismic Stratigraphy for the following fields: Montecristo, La Pena, Rio Grande Norte, and Santa Cruz.

Not Available

1991-05-01

182

Middle Jurassic stratigraphy in the southwestern part of the Republic of Tatarstan  

NASA Astrophysics Data System (ADS)

Data on the structure of the Middle Jurassic marine deposits in the vicinity of Ulyanovsk (sections of the Tarkhanovskaya Pristan-Dolinovka profile) are generalized with due regard for ammonites, bivalves, and microfossils occurring in sediments. Outcrops of the Tarkhanovskaya Pristan site represent the northernmost Bajocian section of the Russian Platform, where ammonites of Tethyan origin are identified. As is established, the pre-Callovian sand-clay sequence formerly attributed to the Bathonian includes the Garantiana beds of the upper Bajocian in its middle part. The multidisciplinary biostratigraphic-sedimentological research showed that downwarping of the Ulyanovsk-Saratov basin and origin of the Simbirsk Bay of the Tethyan marginal sea commenced in the Bajocian Age. The identified fossils of the upper Bajocian and lower and upper Callovian are cited in paleontological plates of this work.

Mitta, V. V.; Kostyleva, V. V.; Glinskikh, L. A.; Shurygin, B. N.; Starodubtseva, I. A.

2014-01-01

183

Sedimentological processes in lahars: Insights from optically stimulated luminescence analysis  

NASA Astrophysics Data System (ADS)

A lahar is a sediment-laden flow capable of major destructive impacts on infrastructure and human life. How lahars transport sediment is thus a key issue for understanding lahar sedimentology and behavior, especially in terms of the lahar's hydraulic and rheological properties, which can be substantially altered as the lahar gains or loses material during its travel. In this research, we analyze lahar entrainment processes by evaluating luminescence signals (total photon counts) from lahar sediments using blue luminescence signals (BLSL). A portable OSL reader that analyzes several grams of polymineral and polygrain-size samples was applied. We use data from three lahars in the Tenenepanco and Huiloac gorges on Popocatépetl volcano (Mexico) to elucidate the ways in which lahars may gain, lose and transport sediment during flow. Sediment samples for luminescence analysis were taken through the full thickness of the lahar deposits at eight different sites for two lahars (1997 and 2001) and at one site for a lahar that occurred > 500 yrs ago. Mean luminescence values obtained for the 1997 lahar help to evaluate the relationship between the lahar entrainment processes and the drainage at the different sites. For the 2001 lahar this relationship was also established taking into account the channel slope. The main conclusion is that luminescence signals (total photon counts) can be used to detect entrained material in the flow because the bulked materials modify the final OSL signals. The application of this type of luminescence analysis thus has the potential to provide a better understanding of sediment entrainment in these sediment-laden flows.

Muñoz-Salinas, Esperanza; Bishop, Paul; Zamorano, Jose-Juan; Sanderson, David

2012-01-01

184

Paleosols and carbonate sequence stratigraphy, Carboniferous, S. Kazakstan  

Microsoft Academic Search

Carbonate platform facies in the Karatau Mountains of S. Kazakhstan are analogs for coeval oil and gas fields in the N. Caspian Basin, W. Kazakhstan. Understanding the sequence stratigraphy of these analogs is enhanced by the recognition and interpretation of paleosols. Thirty four paleosols subdivide 620 in of Visean-Bashkirian carbonates that span [approx] 30 my. M. and U. Visean strata

P. J. Lehmann; H. E. Cook; W. G. Zempolich

1996-01-01

185

Near coast sedimentary stratigraphy as a proxy for climatic instability  

Microsoft Academic Search

Several studies have indicated a link between climatic deterioration and dune stability (Wilson 2002, Issar 2003, Dawson et al 2004). The frequency and magnitude of storms have been cited as a key variable in the stability of large dune systems. For the stratigraphy of dune systems to act as a regional climatic proxy there must be a good regional relationship

J. McLivenny

2009-01-01

186

Geochemical stratigraphy and magmatic evolution at Arenal Volcano, Costa Rica  

E-print Network

Geochemical stratigraphy and magmatic evolution at Arenal Volcano, Costa Rica Louise L. Bolge a Miravalles (OSIVAM), Instituto Costarricense de, Electricidad (ICE), Apdo. 10032-1000, Costa Rica Received 13; tephrostratigraphy; Central American arc 1. Introduction Arenal is a small strato volcano located in Costa Rica (10

187

Stratigraphy of Late Pleistocene formations of the Mezen river valley  

NASA Astrophysics Data System (ADS)

Stratigraphy of Late Pleistocene formations of the Mezen river valley A.V. Maksimov, L.R. Semenova A.P. Karpinski All-Russian Geological Research Institute (VSEGEI), St.-Petersburg, Russia In recent years received extensive and contradictory evidence on the genesis, age and area of spreading of quaternary formations in NW Russia. The reason for this - the heterogeneity of investigated objects and methods of research. Within a valley of the river Mezen quaternary sediments are distributed everywhere. In outcrops opened sediments relating to the fifth and sixth stages of Middle Pleistocene, Upper Pleistocene and Holocene. Thickness of the quaternary sediments varies over a wide range, generally increasing from west to east. The authors have studied quaternary formations, opened in outcrops in valley of river Mezen (downstream) and its right tributary Peza, as well as in marine coastal cliffs. The aim of the study was to demonstrate specific features of the lithological composition of quaternary sediments from various (in age and origin) moraine complexes of the Russian NW and to reconstruction of paleogeographic sedimentary environments in the Late Pleistocene. Such attention to glacial sediments was dictated by the fact that they bear the most valuable information pertaining to the type and composition of provenances and to the geodynamic settings of feeding and sedimentation zones. To achieve these goals following tasks were set: 1. Lithostratigraphic subdivision of the section of Quaternary sediments. 2. Correlation of local stratigraphic units with stratigraphic scheme adjacent areas using the geochronological, paleontological and paleoclimatic data. 3. Reconstruction of the main geological events Late Pleistocene NW European part of Russia. First for glacial sediments in valley of the river Mezen applied lithological method, for determining the origin of formations. Was studied lithological composition of the sediments and were correlated geological sections. Also was conducted geochronological research. Based on these results, it was found that: - the glaciers of the Baltic Shield and the Czech lip penetrated into the valley of the river Mezen in Valdai time, forming moraines of different lithology; - sea waters penetrated to the valley of the river Mezen in Leningrad and Mikulino time. In Mikulino time the basin was deeper.

Maksimov, Anton; Semenova, Ljudmila

2014-05-01

188

Aragats stratovolcano in Armenia - volcano-stratigraphy and petrology  

NASA Astrophysics Data System (ADS)

In this contribution we discuss the geological structure and volcano-stratigraphy of the Quaternary Aragats stratovolcano in Armenia based on recent age determinations as well as petrological and geochemical features of magma generation processes specific for collision zones. Armenia is situated in the NE part of the Anatolian-Armenian-Iranian plateau, an intensely deformed segment of the Alpine-Himalayan belt. The complex geological structure of the region is represented by a mosaic of tectonic blocks comprising fragments of volcanic arcs, continental crust and exhumed oceanic crust. Collision of the Arabian plate with the Eurasian margin in early Miocene resulted in orogenic uplift associated with intense volcanism. Aragats (4090m) is one the largest volcanoes in the entire region and produced central vent (inc. Plinian VEI>4) and monogenetic type flank eruptions and periphery plateaus within a total area greater than 5000 km2, known as Aragats volcanic province (AVP). The Aragats volcanic province (AVP) comprises the composite cone of Aragats volcano, the peak of which is built on a summit plateau, ~45 km in diameter shield structure with dozens of flank vents, scattered monogenetic cinder cones on the adjacent volcanic plateaus as well as the neighboring stratovolcano Arailer. New K-Ar and 40Ar/39Ar age determinations of groundmass and separated plagioclase samples indicate that volcanism at AVP began ~2.5 Ma, while most recent volcanic activity is 0.49 Ma for Plinian eruption of dacites from Irind flank vent and basaltic trachyandesite lava flows from Tirinkatar (0.48-0.61 Ma), Kakavasar, (0.52-0.54 Ma) and Ashtarak (0.58 Ma) monogenetic flank centers, as well as trachyandesites of Jrbazhan volcano on the summit plateau of Aragats (0.52 Ma). Based on bulk rock geochemical data (major, minor and low abundance trace elements, Sr and Nd isotopes) and mineral chemistry, we conclude that volcanic rocks of AVP are largely recording a complex mixing between deep asthenospheric mantle and remnants of subduction-modified and metasomatically enriched mantle sources, followed by fractionation in large magma chamber(s). Mineral-melt equilibria studies reveal dry (<1%H2O) and very hot source, fluid inclusions study reveal pronounced enrichment with CO2 over H2O in fluid phase. Noteworthy are high eruption temperatures compared to global volcanic arcs, explaining the very long (up to 25 km) and thick (>200m) trachydacitic lava flows.

Meliksetian, Khachatur; Savov, Ivan; Connor, Charles; Halama, Ralf; Jrbashyan, Ruben; Navasardyan, Gevorg; Ghukasyan, Yura; Gevorgyan, Hripsime; Manucharyan, Davit; Ishizuka, Osamu; Quidelleur, Xavier; Germa, Aurélie

2014-05-01

189

Quaternary magnetic and isotope stratigraphy at IODP Sites U1306 and U1305 (Eirik Drift, SW Greenland)  

NASA Astrophysics Data System (ADS)

Quaternary stratigraphies for IODP Sites U1305 and U1306 (Eirik Drift, off SW Greenland) are facilitated by combined use of planktic oxygen isotopes, relative paleointensity (RPI), and the magnetic polarity record, back to ~1.5 Ma. RPI is now a well-tested stratigraphic tool for the Quaternary of the North Atlantic, and the Eirik Drift records can be matched to calibrated RPI stacks such as PISO. Benthic foraminifers are too scarce, at both sites, to permit benthic isotope records. A stratigraphy based on correlation of RPI to PISO can be used to access perturbations in the planktic isotope record due to meltwater affects at glacial terminations. The combined oxygen-isotope/RPI stratigraphy indicates contrasting sedimentation-rate patterns at Site U1305 (3460 m water depth) and Site U1306 (2272 m water depth). According to the resolved stratigraphies, meltwater signals in the planktic isotope record are manifest by premature (age-shifted) apparent glacial "terminations" particularly well resolved at Site U1305. At Site U1306, sedimentation rates are elevated during glacial isotopic stages (up to 40 cm/kyr) and reduced during interglacials to about 10 cm/kyr. At Site U1305, the sedimentation-rate pattern is converse, with interglacial sedimentation rates reaching 50 cm/kyr and glacial sedimentation rates often less than 10 cm/kyr. At Site U1306, volume susceptibility and magnetic grain size are elevated during peak glacials whereas these same parameters are elevated during interglacials at Site U1305. We attribute these contrasts to the vigor and location of the Western Boundary UnderCurrent (WBUC), the interaction of bathymetry with the WBUC, and variations in sediment supply from east Greenland.

Channell, J. E.; Wright, J. D.; Mazaud, A.; Stoner, J. S.; Hillaire-Marcel, C.

2012-12-01

190

Influence of barrier island stratigraphy and bathymetry on shoreline change  

SciTech Connect

The barrier island chain off the Atlantic coast of Virginia exhibits anomalous rates of shoreline change, from [minus]40 m/year to +20 m/year. To determine the causes of these anomalous rates the relationships between stratigraphy, bathymetry, orientation of the islands, and rate of shoreline change were investigated. The stratigraphy of the islands if variable along their length and from island to island. Areas of the islands that contain more cohesive materials, such as mud and buried marsh, may be more resistant to erosion than areas of less cohesive material such as fine sand. Vibracoring was conducted at sites exhibiting extremely high rates of shoreline change to see if there is a relation between stratigraphy and rates of shoreline change. Variations in offshore slope and along the islands may affect wave approach so that their energy is unevenly dispersed along island strike. When the offshore slope is steep the waves may dissipate more of their energy on the shore and cause significant erosion. Where a more gradual slope induces wave dissipation farther offshore and diminishes the energy which may cause less erosions. Ebb tidal deltas appear to play a major role in distributing wave energy along the barrier shoreline. Island segments to the south of ebb tidal delta platforms are sheltered from large northeasterly storm waves by the ebb tidal deltas. Results show that neither stratigraphy nor bathymetry alone appear to exhibit a dominating influence on shoreline change of the Virginia Barrier Islands. However, in combination with other factors, such as beach cusp periodicity and inlet migration, stratigraphy and bathymetry may cause a strong influence on shoreline changes.

Kowalski, K.A. (Bucknell Univ., Lewisburg, PA (United States). Dept. of Geology)

1993-03-01

191

Implications of sedimentological studies for environmental pollution assessment and management: Examples from fluvial systems in North Queensland and Western Australia  

Microsoft Academic Search

Sedimentology is of increasing importance in environmental research, particularly environmental pollution studies, where past trends in environmental processes need to be combined with data on present conditions to predict likely future changes—the past and present as a key to the future. Two examples are used to illustrate the role of sedimentology in assessing the influence of major processes on the

Bradley D Eyre; David M McConchie

1993-01-01

192

Sedimentology of Seismo-Turbidites off the Cascadia and Northern California Active Tectonic Continental Margins, Northwest Pacific Ocean  

E-print Network

of the Cascadia Subduction Zone (offshore Vancouver Island to Mendocino Triple Junction) and the northern SanÃ?Ã? Ã? Ã?Ã?Ã? Ã? Ã?Ã? Sedimentology of Seismo-Turbidites off the Cascadia and Northern California Active, Goldfinger, Chris, Escutia, Carlota, Sedimentology of Seismo-Turbidites off the Cascadia and Northern Cal

Goldfinger, Chris

193

The Black Reef Quartzite Formation in the western Transvaal: sedimentological and economic aspects, and significance for basin evolution  

Microsoft Academic Search

A sedimentological study of the early Proterozoic Black Reef Quartzite Formation in the south-western parts of the Transvaal province of South Africa was undertaken with the primary aim of examining the sedimentological controls of gold mineralization in the Black Reef placer, which occurs at the base of this Formation. A second aim of the study was to investigate the early

B. G. Els; W. A. van den Berg; J. J. Mayer

1995-01-01

194

GARY KOCUREK Department of Geological Sciences, Jackson School, University of Texas, 1 University Station  

E-print Network

.D., Geology, University of Wisconsin, 1980 RESEARCH AREAS: Sedimentology, stratigraphy, geomorphology, aeolian ­ Sedimentary Geology, Sedimentology, Summer Field Camp, Field Methods, Geology of the National Parks, Earth Committee, First International Conference on Mars Sedimentology & Stratigraphy, 2009 - 2010, El Paso Field

Yang, Zong-Liang

195

Mechanical stratigraphy of deep-water sandstones: insights from a multisciplinary field and laboratory study  

NASA Astrophysics Data System (ADS)

Turbidite sandstones found in deep-water fold-and-thrust belts are increasingly exploited as hydrocarbon reservoirs. Within these rocks, the fluid flow is profoundly affected by the complex interaction between primary sedimentological and stratigraphic attributes (i.e, facies, layering, reservoir quality, stacking patterns, bed connectivity and lateral extent) and fracture characteristics (i.e., length, spacing, distribution, orientation, connectivity). Unfortunately, most of these features are at, or below, the resolution of conventional seismic datasets and, for this reason, their identification and localization represent one of the fundamental challenges facing exploration, appraisal and production of the sandstone reservoirs. In this respect, whereas considerable effort has been afforded to a characterization of the sedimentological and stratigraphic aspects of sandstones, detailed analysis of fractures in this type of successions has received significantly less attention. In this work, we combine field and laboratory analyses to assess the possible mechanical control exerted by the rock properties (grain size, intergranualr porosity, and Young modulus), as well as the influence of bed thickness, on joint density in turbidite sandstones. Joints are mode-I fractures occurring parallel to the greatest principle stress axis, which solve opening displacement and do not show evidence of shearing and enhance the values of total porosity forming preferential hydraulic conduits for fluid flow. Within layered rocks, commonly, joints form perpendicular to bedding due to overburden or exhumation. The empirical relation between joint spacing and bed thickness, documented in the field by many authors, has been mechanically related to the stress perturbation taking place around joints during their formation. Furthermore, close correlations between joint density and rock properties have been already established. In this present contribution, we focus on the bed-perpendicular joint spacing/bed thickness (S/T) relationships on sandstone bodies that experienced similar diagenetic and tectonic histories. The field area is located in the Periadriatic foreland basin, eastern central Italy, which show late Pliocene slope turbidites in excellent 3d views. The Periadriatic foreland basin is an elongated, roughly N-S oriented trough located immediately east of the Apennines fold-thrust belt. The basin fill mostly consists of deepwater Plio-Pleistocene sediments partially incorporated into the frontal part of the orogenic wedge. During the late Pliocene, gravel and sand originated from the uplifting Apennines were abundantly supplied to the deep-water basin through a series of erosional conduits that, in the rock record, appear as a series of N-S oriented slope submarine canyon systems deeply incised into the hemipelagic mudstones of the adjacent slope. The studied exposure allows direct observation of spatial and temporal relationships among the various depositional elements comprising the canyon system and related lithofacies, as well as the bed-perpendicular joint density within each lithofacies. We performed a multidisciplinary work involving the following tasks: (i) 3D stratigraphic model of the depositional architecture of the Castignano and Ascensione canyon systems (Marche region, Italy); (ii) 2D scanline survey of several outcrops displaying bed-perpendicular joints; (iii) digital image analysis of selected thin-section obtained from oriented hand samples to characterize the 3D intergranualr porosity; (iv) Stiffness analysis of representative sandstone bodies by mean of Schmidt hammer tests. The first results of this ongoing study on the mechanical stratigraphy of the two Late Pliocene canyon systems are consistent with the joint density being effected by both geometrical (i.e., bed thickness) and mechanical properties. This data set will help field and experimental geologists to better define common strategies to assess the controlling factors on joint distribution within layered media. Furthermore, this knowledge can be very import

Agosta, Fabrizio; di Celma, Claudio; Tondi, Emanuele; Corradetti, Amerigo; Cantalamessa, Gino

2010-05-01

196

Autocyclic progradation and allocyclic ravinement of a shoreface: Sedimentology and sequence stratigraphy of the Panther Sandstone Tongue (Upper Cretaceous, Campanian), Wasatch plateau, Utah, U. S. A  

SciTech Connect

The Panther Sandstone Tongue of the Star Point Formation exposed in the vicinity of Helper, Utah reflects a coarse-grained, clastic wedge that penetrated the Mancos Shale basin in Early Campanian (Late Cretaceous) time. Panther Sandstone rocks may be grouped into six lithofacies: (1) thin-bedded, bioturbated and rippled, mudstone and very fine-grained sandstone; (2) thin- to medium-bedded, bioturbated, rippled and parallel laminated, mudstone and very fine-grained sandstone; (3) thick- to very thick-bedded HCS and parallel-laminated, mudstone and fine- to medium-grained sandstone; (4) medium- to thick-bedded, Ophiomorpha bioturbated, medium- to coarse-grained sandstone; (5) medium- to very-thick bedded, current bedded and hydroplasticly deformed sandstone, and (6) medium- to thick-bedded, trough cross-stratified and bundle-laminated, fine grained sandstone. Lithofacies are arranged in definable vertical and lateral successions. L. 1, 2 and 3 are upward coarsening and shoaling and are common in the Helper area. L. 5 and 6 are common to the west. L. 4 is a transgressive and ravinement lag that rests on all other lithofacies. Interpreted environments reflect a storm modified, microtidal, strandplain system. Rocks, except L. 4, are contained in a parasequence system that built into the basin during relative sea-level fall. This system prograded episodically suggesting varying sediment supply and event-controlled sediment reworking -- responses associated with autocyclic forcing. In contrast, ravinement decapitated the parasequence intersecting progressively shallower lithofacies. These responses suggest that ravinement was driven by allocyclic forcing, perhaps in response to tectonism in the foreland.

Krause, F.F.; Aitken, S.A.; Braunberger, W.F.; Chung, P.; Macrae, A.; Meyer, R.O.; Nunez-Betelu, L.; Williams, C.A.; Hol, H.M. (Univ. of Calgary, Alberta (Canada))

1993-04-01

197

Sedimentology and sequence stratigraphy of a pronounced Early Ordovician sea-level fall on Baltica — The Bjørkåsholmen Formation in Norway and Sweden  

NASA Astrophysics Data System (ADS)

The Bjørkåsholmen Formation consists of interbedded carbonates, shales, and glauconitic beds and is characterized by heavy bioturbation and few preserved sedimentary structures. The unit shows five facies shale, glauconitic packstone, and three predominantly mud-dominated carbonate facies. Carbonates and shales are arranged in small-scale deepening-upward cycles. A minimum of fourteen of these small-scale cycles are recognized in the Bjørkåsholmen Formation. They are arranged in stacks of 3 to 5, forming a total of four medium-scale cycles separated by decimeter-thick shale units. Based on the predominance of mud-rich facies the succession is interpreted to have been deposited in an overall tranquil setting during one mayor sea-level fall and subsequent initial rise of third order. Time-estimates suggest that the 14 small-scale cycles fall into the Milankovitch band of precessional forcing, and the overriding medium-scale cycles likely represent short eccentricity. The sequence stratigraphic interpretation shows that the Bjørkåsholmen Formation is characterized by falling stage, lowstand and initial transgressive systems tracts. Consequently, the contact between the Bjørkåsholmen and the underlying Alum Shale Formation represents the basal surface of forced regression. The maximum regressive surface is defined by a hiatus in the Öland sections and by shallow-marine packstones within mud-rich distal ramp carbonates in Norway. The top of the Bjørkåsholmen Formation represents a flooding surface at the base of the transgressive systems tract. A comparison of time-equivalent successions worldwide suggests that the Bjørkåsholmen Formation represents a tectonically-enhanced lowstand with two overriding short-term Milankovitch eustatic signals. Although deposition of the Bjørkåsholmen Formation coincides with the initiation of a foreland basin in the Caledonides of Norway it remains unclear how these tectonic movements may have lead to the widespread Bjørkåsholmen lowstand during the Early Ordovician. It is suggested in this study that a combination of compressional forces from Avalonia and the Caledonian margin may have acted in concert to produce an uplift of larger parts of the Baltica plate for a time-span of approximately 0.5 Myr.

Egenhoff, Sven; Cassle, Chris; Maletz, Jörg; Frisk, Åsa M.; Ebbestad, Jan Ove R.; Stübner, Konstanze

2010-03-01

198

Summary of the stratigraphy, sedimentology, and mineralogy of Pennsylvanian and permian rocks of Oklahoma in relation to uranium-resource potential  

Microsoft Academic Search

Pennsylvanian-Permian strata in Oklahoma were deposited in environments which ranged from deep marine to alluvial fan. The former was most common in the Ouachita geosyncline during Early Pennsylvanian, but parts of the Anadarko basin were also relatively deep water during Middle and Late Pennsylvanian. Alluvial-fan deposits in Oklahoma are related primarily to the Amarillo-Wichita-Criner, Arbuckle, and Ouachita uplifts. As a

R. W. Olmsted; R. E. Hanson; R. T. May; R. T. Owens

1976-01-01

199

Revised stratigraphy of the Trenton Group in its type area, central New York State: sedimentology and tectonics of a Middle Ordovician shelf-to-basin succession  

Microsoft Academic Search

This paper presents new stratigraphic correlations of the middle and upper parts of the Trenton Group in the type area, near Trenton Falls, New York, based on detailed bed by bed matching, of all outcrop sections. This work, in conjunction with newly revised biostratigraphy and geochemical fingerprinting of K-bentonites, has been used to establish a high resolution chronology for these

Carlton E Brett; Gordon C Baird

2002-01-01

200

Sedimentologic and structural controls of floodplain development in the Sprague River, Oregon, USA  

NASA Astrophysics Data System (ADS)

The Sprague River in the Klamath basin of south-central Oregon is currently the focus of a multi-year, multi- agency restoration effort involving both active and passive restoration approaches. As part of our project on understanding geomorphological processes as a science basis for restoration, we constructed a GIS map of the floodplain boundary using soils, elevation and surface morphology criteria. The wide valley floor consists of a thin veneer of alluvial deposits (fans, terraces and floodplain) underlain at shallow depth by Pliocene fine- grained ashy and diatomite sedimentary rocks and Miocene tuff. We delineated a distinct belt of abandoned meanders, mid- to late-Holocene in age, as the modern floodplain within the wide valley floor. This floodplain post-dates the ca 6700 yr BP Mount Mazama eruption. Sedimentology, soil formation and fluvial processes of this floodplain were influenced by the tremendous volume of sand-size Mazama pumice added to an otherwise sand-poor drainage basin. The channel has shifted by lateral migration and meander cut-off (including both chute and neck cut-offs), for at least the last 3500 years, including several historic meander cut-offs. No appreciable incision has occurred during this period. The width of the floodplain varies irregularly from 100 to 1700 m, as a function of geologic controls, and structural influences on river gradient. Our results will contribute to channel and wetland restoration design by 1) identifying differences between and the distribution of the modern floodplain and adjacent low terraces, and 2) identifying the processes and causes of meander cut-off.

McDowell, P. F.; O'Connor, J. E.; Lind, P.

2006-12-01

201

Sedimentologic and biostratigraphic implications for early Eocene lacustrine systems, eastern Great Basin, Nevada  

SciTech Connect

A multidisciplinary study integrating sedimentology, molluscan paleontology and paleoecology, structural and geologic mapping, and [sup 40]Ar/[sup 39]Ar dating of volcanic flows indicates the White Sage Formation north of the Deep Creek Range on the NV-UT border was deposited during the early Eocene in marginal-lacustrine, lacustrine, freshwater-marsh, and minor terrestrial settings. Sedimentary facies include wave-reworked, locally derived Paleozoic carbonate-clast basal conglomerates in contact with bedrock; carbonate tufa mounds; organic-rich mudstones; and laminated to medium-bedded carbonates. The wave-reworked conglomerate implies a broad lake with considerable fetch to generate large waves, but one with only small drainage basins with sharp relief to supply the locally-derived clasts. There is a striking lack of any fluvial, deltaic, or alluvial-fan deposits that would indicate development of substantial drainage areas. The large tufa mounds indicate a high-wave-energy shoaling environment with stable substrate and topography. The profusion of lacustrine carbonates indicates dominantly chemical- or biochemical-induced deposition in a carbonate-saturated lake. The aquatic molluscan fauna indicates shallow, quiet lacustrine conditions with emergent vegetation. The limpets inhabited areas of rooted aquatic vegetation, and the terrestrial gastropods indicate marshes adjacent to the lacustrine system. The molluscan assemblage constrains the age of the White Sage as early Eocene, indicating a lacustrine system equivalent to the Sheep Pass Formation and to outcrops near Illipah, NV that have similar facies and molluscan faunas and that also lack significant fluvial, deltaic, or alluvial fan deposits. The data are consistent with a model wherein the White Sage, Sheep Pass, and Illipah carbonates were deposited in a large lake superimposed on preexisting topography with low relief and little or no syndepositional extension.

Dubiel, R.F.; Potter, C.J.; Snee, L.W. (Geological Survey, Denver, CO (United States)); Good, S.C. (State Univ. Coll., Cortland, NY (United States))

1993-04-01

202

Geometric and sedimentologic characteristic of Mid-Miocene lowstand reservoir sandstones, offshore northwest Java, Indonesia  

SciTech Connect

Numerous reservoirs in the Upper Cibulakan Formation (Mid-Miocene) of the Offshore Northwest Java shelf occur in sharp-based sandbodies that range from less than 1 m up to 10 m in thickness. Well-log derived net-sand isopach and seismic amplitude maps of these sandbodies depict elongate features, that are 1-2 km wide and 5-8 km long. The orientation of the longest axis of these sandbodies is predominantly north-south. Conventional cores reveal that these sandbodies are burrowed to completely bioturbated sandstones. Common trace fossils associated with these sandbodies include Ophiomorpha, Teichichnus and Thalassinoides. The lower contact of these sands is typically sharp and is commonly associated with a Glossifungites surface and siderite mud clasts. Overlying and underlying mudstones are relatively devoid of burrowing. Benthonic foraminifera assemblages within these mudstones indicate inner to outer neritic conditions in a relatively restricted marine setting. The upper contact of these sandstones is gradational over a 0.5 to 1m interval. Sandbodies of the same age and similar facies were observed in outcrops in onshore west Java. Here, they can be observed to pinch out over a distance of 500 m. The lower bounding contact appears discordant with underlying interbedded sandstones and mudstones. Several of the sandstones contain abundant accumulations of the large, open marine, benthonic foraminifera Cycloclypeus and Lepidocyclina. Occasionally the concentration of these large foraminifera form limestones within the sharp-based sandbodies. These bioclastic deposits commonly exhibit planar-tabular and trough cross-stratification. The sandbodies are interpreted as having been emplaced during relative falls in sea-level within a large Mid-Miocene embayment. Our understanding of their geometry and sedimentologic characteristics is leading to a more effective exploitation strategy for these sandbodies in the Offshore Northwest Java area.

Lowry, P.; Kusumanegara, Y.; Warman, S. [ARCO Indonesia, Jakarta (Indonesia)

1996-12-31

203

Geometric and sedimentologic characteristic of Mid-Miocene lowstand reservoir sandstones, offshore northwest Java, Indonesia  

SciTech Connect

Numerous reservoirs in the Upper Cibulakan Formation (Mid-Miocene) of the Offshore Northwest Java shelf occur in sharp-based sandbodies that range from less than 1 m up to 10 m in thickness. Well-log derived net-sand isopach and seismic amplitude maps of these sandbodies depict elongate features, that are 1-2 km wide and 5-8 km long. The orientation of the longest axis of these sandbodies is predominantly north-south. Conventional cores reveal that these sandbodies are burrowed to completely bioturbated sandstones. Common trace fossils associated with these sandbodies include Ophiomorpha, Teichichnus and Thalassinoides. The lower contact of these sands is typically sharp and is commonly associated with a Glossifungites surface and siderite mud clasts. Overlying and underlying mudstones are relatively devoid of burrowing. Benthonic foraminifera assemblages within these mudstones indicate inner to outer neritic conditions in a relatively restricted marine setting. The upper contact of these sandstones is gradational over a 0.5 to 1m interval. Sandbodies of the same age and similar facies were observed in outcrops in onshore west Java. Here, they can be observed to pinch out over a distance of 500 m. The lower bounding contact appears discordant with underlying interbedded sandstones and mudstones. Several of the sandstones contain abundant accumulations of the large, open marine, benthonic foraminifera Cycloclypeus and Lepidocyclina. Occasionally the concentration of these large foraminifera form limestones within the sharp-based sandbodies. These bioclastic deposits commonly exhibit planar-tabular and trough cross-stratification. The sandbodies are interpreted as having been emplaced during relative falls in sea-level within a large Mid-Miocene embayment. Our understanding of their geometry and sedimentologic characteristics is leading to a more effective exploitation strategy for these sandbodies in the Offshore Northwest Java area.

Lowry, P.; Kusumanegara, Y.; Warman, S. (ARCO Indonesia, Jakarta (Indonesia))

1996-01-01

204

New considerations on the stratigraphy and environmental context of the oldest (2.34 Ma) Lokalalei archaeological site complex of the Nachukui Formation, West Turkana, northern Kenya Rift  

NASA Astrophysics Data System (ADS)

At the northwest end of the Lake Turkana Basin (northern Kenya Rift), intensive fieldwork conducted on the Plio-Pleistocene fluvio-lacustrine Nachukui Formation by the National Museums of Kenya and the West Turkana Archaeological Project (WTAP), led to the discovery of more than 50 archaeological sites aged between 2.4 and 0.7 Ma. Among them is the Lokalalei archaeological site complex, which includes the two oldest archaeological sites (2.34 Ma) found in the Kenyan segment of the East African Rift System. The environmental background of the two sites was described as a succession of ephemeral streams with floodplain palaeosols in which the archaeological sites are situated, bordering the western bank of a large axial meandering river flowing southward. The Lokalalei 1 (LA1) and Lokalalei 2C (LA2C) archaeological sites are of extreme importance in terms of knowledge of hominins' knapping activities. The stratigraphic position of the LA1 and LA2C sites as well as implications on the technical differences between the two sites have been successively discussed by Roche et al. (1999), Brown and Gathogo (2002), and Delagnes and Roche (2005). In terms of stratigraphic position, Lokalalei 2C was estimated to be slightly higher in the section (i.e. younger) than Lokalalei 1. An alternative stratigraphic correlation was proposed by Brown and Gathogo (2002), who suggested that LA2C site should have been approximately 100,000 years younger than LA1. New considerations on the stratigraphy and environmental context of the Lokalalei sites have been developed following controversy on the stratigraphic position and time interval between the LA1 and LA2C sites. High-resolution lithostratigraphic work based on bed-to-bed field correlations, facies sedimentology and tephra geochemistry confirms that the LA2C site is slightly higher in the section than the LA1 site by about 11.20 m. This represents a time interval of ˜74,000 years based on an assumed sedimentation rate of 152 mm/ka. Sedimentary facies analysis indicates that the hominin occupation sites were situated in the vicinity of a lagoon/embayment environment close to the shoreline of an open lake. This lake was part of the broad lake development described across East Africa during the 2.7-2.4 Ma period. Palaeontological data associated with the sites suggest at the LA1 site a lake margin habitat, and at the LA2 sites an habitat with poor and sparse vegetation along channels of an alluvial fan system landward of the lake margin. They also confirm the aridity trend mentioned at the global scale for this period, which is demonstrated in the upper Lokalalei sediment sequence by progradation of an alluvial fan environment over the lake shoreline. Associated conglomeratic deposits could have been the source from which the knappers collected their raw materials. In addition, rapid variations from humid to arid episodes in a unique environment such as the East African Rift may have had a major influence in controlling hominin evolution.

Tiercelin, Jean-Jacques; Schuster, Mathieu; Roche, Hélène; Brugal, Jean-Philippe; Thuo, Peter; Prat, Sandrine; Harmand, Sonia; Davtian, Gourguen; Barrat, Jean-Alix; Bohn, Marcel

2010-09-01

205

Acoustic stratigraphy and hydrothermal activity within Epi Submarine Caldera, Vanuatu, New Hebrides Arc  

USGS Publications Warehouse

Geological and geophysical surveys of active submarine volcanoes offshore and southeast of Epi Island, Vanuatu, New Hebrides Arc, have delineated details of the structure and acoustic stratigraphy of three volcanic cones. These submarine cones, named Epia, Epib, and Epic, are aligned east-west and spaced 3.5 km apart on the rim of a submerged caldera. At least three acoustic sequences, of presumed Quaternary age, can be identified on single-channel seismic-reflection profiles. Rocks dredged from these cones include basalt, dacite, and cognate gabbroic inclusions with magmatic affinities similar to those of the Karua (an active submarine volcano off the southeastern tip of Epi) lavas. ?? 1988 Springer-Verlag New York Inc.

Greene, H. Gary; Exon, N.F.

1988-01-01

206

Basalt stratigraphy of southern Mare Serenitatis. [based on Apollo 17 photographs  

NASA Technical Reports Server (NTRS)

The major features of the stratigraphic and structural sequence are summarized for Mare Serenitatis. The dark oldest basalts include flows coextensive with Mare Tranquillitatis and also flows and pyroclastic deposits (dark mantles) that erupted from the edge of the Serenitatis basin. The basin sagged, possibly isostatically, as basalts of intermediate age were emplaced. Sagging had nearly ceased by the time the youngest flows were deposited. Compressive movements including thrusting followed, and small extensional fissures formed in late Copernican time. The revised stratigraphic sequence that was elaborated has implications for lunar stratigraphy that transcend the boundaries of Mare Serenitatis. Dark mantle deposits and the darkest maria have commonly been assumed in geologic mapping to be relatively youthful. These assumptions must now be reevaluated and perhaps discarded.

Howard, K. A.; Carr, M. H.; Muehlberger, W. R.

1973-01-01

207

Lake Level Controlled Sedimentological I Heterogenity of Oil Shale, Upper Green River  

E-print Network

Chapter 3 Lake Level Controlled Sedimentological 1:'_i 'I I Heterogenity of Oil Shale, Upper Green email: mgani@uno.edu t",. The Green River Formation comprises the world's largest deposit of oil-shale characterization of these lacustrine oil-shale deposits in the subsurface is lacking. This study analyzed ~300 m

Gani, M. Royhan

208

Morphological and sedimentological responses of streams to human impact in the southern Blue Ridge Mountains, USA  

Microsoft Academic Search

Morphological and sedimentological responses of streams to basin-scale impact have been well documented for intensively agricultural or urban areas. Sensitivity thresholds of streams to modest levels of disturbance, however, are not well understood. This study addresses the influence of forest conversion on streams of the southern Blue Ridge Mountains, a region that has received little attention with respect to human

Katie Price; David S. Leigh

2006-01-01

209

Limnology, sedimentology, and hydrology of a jökulhlaup into a meromictic High Arctic lake1  

Microsoft Academic Search

A large ice-dammed lake drained catastrophically into Lake Tuborg, Ellesmere Island, beginning on 25 July 2003. Limnological, sedimentological, and hydrological parameters were recorded before, during, and after this event. For several weeks prior to the jökulhlaup, water overtopped the ice-dammed lake and flowed into Lake Tuborg's fresh- water basin. A shallow sill separates the freshwater basin from a larger, deeper

Ted Lewis; Pierre Francus; Raymond S. Bradley

210

Upper Permian vertebrates and their sedimentological context in the South Urals, Russia  

E-print Network

some 900,000 km2 of territory between Samara on the River Volga in the NW, and Orenburg and Sakmara­Triassic successions, especially in the zone from the River Volga to the plain south Upper Permian vertebrates and their sedimentological context in the South Urals, Russia Valentin P

Benton, Michael

211

Stratigraphy and Tectonics of Southeastern Serenitatis. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

Results of investigations of returned Apollo 17 samples, and Apollo 15 and 17 photographs have provided a broad data base on which to interpret the southeastern Serenitatis region of the moon. Although many of the pre-Apollo 17 mission interpretations remain valid, detailed mapping of this region and correlation with earth-based and orbital remote-sensing data have resulted in a revision of the local mare stratigraphy.

Maxwell, T. A.

1976-01-01

212

Summary of Quaternary Stratigraphy and history, Eastern Canada  

NASA Astrophysics Data System (ADS)

Deposits of three Wisconsinan substages, Sangamonian Stage, and older Quaternary stratigraphic units are recognized in Eastern Canada. The age assignment of these units is based on radiocarbon dating and correlation of events. Quaternary deposits older than Sangamonian are recognized locally in Eastern Canada. In southern Ontario glacial deposits directly underlie Sangamonian sediments and are referred to as Illinoian in age. In other areas the ages of older sediments are largely unknown. Offshore core stratigraphy suggests that a major glaciation took place about 436 ka and that the Illinoian (oxygen isotope stage 6) was also a time of extensive glaciation. In this report Sangamonian is used as the name for the chronostratigraphic stage that includes all of deep-sea oxygen isotope stage 5 and consequently, on a regional basis, it includes warm interglacial deposits, glacial deposits and cool interglacial deposits. In southern Ontario the warm interglacial deposits are represented by the Don Formation, the stadial deposits by the Scarborough Formation and the cool interglacial deposits by the Pottery Road Formation. Warm interglacial deposits have not been recognized in Quebec (unless they are part of the pre-Johnville Sediments); the Bécancour Till is included as glacial Sangamonian sediments, and the St. Pierre Sediments are recognized as cool interglacial sediments. The Early Wisconsinan appears to have been the time of maximum Wisconsinan glaciation in Eastern Canada with ice moving south of the International Boundary and well out onto the continental shelf. The Middle Wisconsinan was primarily a nonglacial period in southern Ontario and a glacial stade elsewhere in Eastern Canada. In southern Ontario the Middle Wisconsinan record has been subdivided into two interstades (Port Talbot and Plum Point), separated by a stade (Cherrytree). The Port Talbot Interstade began before the limit of radiocarbon dating (before 48 ka) and ended about 40 ka; glacial or near glacial conditions of the Cherrytree Stage lasted from about 40 to 35 ka ago, and the Plum Point Interstade was from about 35 to 23 ka ago. Central St. Lawrence Lowland was occupied by ice throughout the Middle Wisconsinan, but southeastern Quebec and the Montreal area were briefly deglaciated. Scattered evidence in Atlantic Canada suggests local deglaciation of coastal areas during Middle Wisconsinan but extensive ice remained on the continental shelf and ice from centres located on the shelf flowed onto land in at least two areas. Glacial conditions predominated throughout Eastern Canada during the Late Wisconsinan. At the Late Wisconsinan maximum, through-moving ice deposited the Catfish Creek Drift in southern Ontario but ice lobes, which developed in the basins of the Great Lakes after 15.5 ka, controlled ice flow during a period of ice margin oscillation and retreat. A calving bay developed in lower St. Lawrence valley, after the Late Wisconsinan maximum, causing a reversal of flow on the south shore of the St. Lawrence and replacing ice in the valley with the Champlain Sea about 12 ka. Late Wisconsinan glaciers were largely limited to land areas in Atlantic Canada. Local ice caps dominated with complicated patterns of flow and retreat developing as centres of accumulation shifted and competing ice centres achieved dominance. The period of Late Wisconsinan retreat in Atlantic Canada appears to have lasted from about 14 to 10 ka.

Fulton, R. J.; Karrow, P. F.; LaSalle, P.; Grant, D. R.

213

Volcaniclastic stratigraphy of Gede volcano in West Java  

NASA Astrophysics Data System (ADS)

Gede volcano (2958 m a.s.l.) and the adjacent Pangrango volcano (3019 m a.s.l.) form large (base diameter 35 km) volcanic massif 60 km south of Jakarta. While Pangrango has no recorded eruptions, Gede is one of the most active volcanoes in Indonesia: eruptions were reported 26 times starting from 1747 (Petroeschevsky 1943; van Bemmelen 1949). Historic eruptions were mildly explosive (Vulcanian) with at least one lava flow. Modern activity of the volcano includes persistent solfataric activity in the summit crater and periodic seismic swarms - in 1990, 1991, 1992, 1995, 1996, 1997, 2000, 2010, and 2012 (CVGHM). Lands around the Gede-Pangrango massif are densely populated with villages up to 1500-2000 m a.s.l. Higher, the volcano is covered by rain forest of the Gede-Pangrango Natural Park, which is visited every day by numerous tourists who camp in the summit area. We report the results of the detailed reinvestigation of volcaniclastic stratigraphy of Gede volcano. This work has allowed us to obtain 24 new radiocarbon dates for the area. As a result the timing and character of activity of Gede in Holocene has been revealed. The edifice of Gede volcano consists of main stratocone (Gumuruh) with 1.8 km-wide summit caldera; intra-caldera lava cone (Gede proper) with a 900 m wide summit crater, having 2 breaches toward N-NE; and intra-crater infill (lava dome/flow capped with 3 small craters surrounded by pyroclastic aprons). The Gumuruh edifice, composed mostly of lava flows, comprises more than 90% of the total volume of the volcano. Deep weathering of rocks and thick (2-4 m) red laterite soil covering Gumuruh indicates its very old age. Attempts to get 14C dates in 4 different locations of Gumuruh (including a large debris avalanche deposit on its SE foot) provided ages older than 45,000 years - beyond the limit for 14C dating. Outside the summit caldera, notable volumes of fresh, 14C datable volcaniclastic deposits were found only in the NNE sector of the volcano where they form a fan below the breached summit crater. The fan is composed of pyroclastic flows (PFs) and lahars of Holocene age that were deposited in 4 major stages: ~ 10 000 BP - voluminous PF of black scoria; ~ 4000 BP - two PFs of mingled grey/black scoria; ~ 1200 BP - multiple voluminous PFs strongly enriched by accidental material; ~ 1000 BP - a small scale debris avalanche (breaching of the crater wall) followed by small scale PFs of black scoria. The intra-crater lava dome/flow was erupted in 1840 (Petroeschevsky, 1943). Three small craters on the top of the lava dome were formed by multiple post-1840 small-scale phreatomagmatic eruptions. Ejected pyroclasts are lithic hydrothermally altered material containing a few breadcrust bombs. The Holocene eruptive history of Gede indicates that the volcano can produce moderately strong (VEI 3-4) explosive eruptions and send PFs and lahars onto the NE foot of the volcano.

Belousov, A.; Belousova, M.; Zaennudin, A.; Prambada, O.

2012-12-01

214

Cenozoic stratigraphy of the northern Sakhalin shelf  

NASA Astrophysics Data System (ADS)

The analysis of diatom, palynofloral, and benthic foraminiferal assemblages made it possible to substantiate the age of Cenozoic sections recovered by wells on the northern and northeastern Sakhalin shelf. Biostratigraphic materials, lithological properties of stratigraphic units, and standard logs served as the basis for developing the first stratigraphic correlation scale of Cenozoic sequences on the Sakhalin shelf.

Zharov, A. E.; Mitrofanova, L. I.; Tuzov, V. P.

2013-09-01

215

Large-scale River Channel Shifts on the Western Indo-Gangetic Plains and their implications for the Bronze-age Harappan Civilisation Settlement Patterns  

NASA Astrophysics Data System (ADS)

The distribution of settlements in ancient societies is commonly linked to the courses of large river systems. The Bronze Age Harappan civilisation (4800-3500BP) is no exception with the major sites of Harappa and Mohenjo-Daro located along the Indus river system. However, the largest collection of Harappan archaeological sites are associated with the postulated surface trace of a large paleo-river channel in the drainage divide tract between the Ganges and Indus river systems, where no major river currently flows. It has been proposed that this paleo-channel was occupied by a major river sourced in the Himalaya, and that this river provided water resources to sustain the extensive Harappan sites located along its ancient course. The abrupt abandonment of urban centres here at ~3500 BP has been explained as a consequence of river diversion, although alternative explanations for cultural decline have also been entertained. These hypotheses have remained untested because the stratigraphy and chronology of the postulated paleochannel has never been determined. Here we investigate the evolution of these paleodrainage systems using a combination of satellite image analysis, subsurface geophysical analysis and sediment coring to analyse the large-scale planform geometry, and detailed sedimentary and stratigraphic nature of the postulated paleochannel in NW India. We focus our analysis on tracts of the proposed channel that lie adjacent to major Harappan urban centres in NW India, such as the site of Kalibngan in Rajastan. We find that the postulated surface trace of the paleochannel on satellite imagery is is confirmed by subsurface geophysical investigation and detailed coring. The sedimentology and stratigraphy of multiple cores taken at several transects along the trace of the paleochannel shows the evolution of the fluvial system. We determine the provenance of the fluvial channels using U-Pb dating of detrital zircons and Ar-Ar dating of detrital muscovites. These detrital minerals can be fingerprinted with potential source areas in the Himalaya using modern river sands and bedrock ages to constrain sediment sources. We use optically stimulated luminescence dating to develop age models for the cores. These data are combined to reconstruct the spatial and temporal evolution of this paleo-river and consider its influence on settlement patterns of the Harappan civilization in NW India.

Gupta, S.; Singh, A.; Sinha, R.; Thomsen, K.; Murray, A. S.; Carter, A.; Mark, D. F.; Buylaert, J.; Mason, P.; Ferrat, M.

2011-12-01

216

Stratigraphie et paléontologie (plantes, vertébrés) de la série paralique Albien terminal–Cénomanien basal de Tonnay-Charente (Charente-Maritime, France)  

Microsoft Academic Search

Stratigraphy and palaeontology (plants, vertebrates) of the paralic deposits from the Uppermost Albian–Lower Cenomanian of Tonnay-Charente (Charente-Maritime, France). The Tonnay-Charente area (Charente-Maritime, southwestern France) contains several sand and clay exploitations of Uppermost Albian and Lower Cenomanian ages. These sediments have been deposited in a coastal area where plant remains, amber, and aquatic or terrestrial vertebrates were trapped. The two last

Didier Néraudeau; Romain Vullo; Bernard Gomez; Vincent Perrichot; Blaise Videt

2005-01-01

217

Archaeological recording and chemical stratigraphy applied to contaminated land studies.  

PubMed

The method used by archaeologists for excavation and recording of the stratigraphic evidence, within trenches with or without archaeological remains, can potentially be useful to contaminated land consultants (CLCs). The implementation of archaeological practice in contaminated land assessments (CLAs) is not meant to be an exercise in data overkill; neither should it increase costs. Rather, we suggest, that if the excavation and recording, by a trained archaeologist, of the stratigraphy is followed by in-situ chemical characterisation then it is possible that much uncertainty associated with current field sampling practices, may be removed. This is because built into the chemical stratigraphy is the temporal and spatial relationship between different parts of the site reflecting the logic behind the distribution of contamination. An archaeological recording with chemical stratigraphy approach to sampling may possibly provide 'one method fits all' for potentially contaminated land sites (CLSs), just as archaeological characterisation of the stratigraphic record provides 'one method fits all' for all archaeological sites irrespective of period (prehistoric to modern) or type (rural, urban or industrial). We also suggest that there may be practical and financial benefits to be gained by pulling together expertise and resources stemming from different disciplines, not simply at the assessment phase, but also subsequent phases, in contaminated land improvement. PMID:21962595

Photos-Jones, Effie; Hall, Allan J

2011-11-15

218

PermophilesInternational Commission on Stratigraphy International Union of Geological Sciences  

E-print Network

PermophilesInternational Commission on Stratigraphy International Union of Geological Sciences of conodonts (p. 17). Sweetognathus merrillicf. 54 m at Apillapampa, Bolivia (p. 19) #12;Table of Contents

219

Integrating radar stratigraphy with high resolution visible stratigraphy of the north polar layered deposits, Mars  

NASA Astrophysics Data System (ADS)

Shallow Radar (SHARAD) on board NASA’s Mars Reconnaissance Orbiter has successfully detected tens of reflectors in the subsurface of the north polar layered deposits (NPLD) of Mars. Radar reflections are hypothesized to originate from the same material interfaces that result in visible layering. As a first step towards verifying this assumption, this study uses signal analyses and geometric comparisons to quantitatively examine the relationship between reflectors and visible layers exposed in an NPLD outcrop. To understand subsurface structures and reflector geometry, reflector surfaces have been gridded in three dimensions, taking into account the influence of surface slopes to obtain accurate subsurface geometries. These geometries reveal reflector dips that are consistent with optical layer slopes. Distance-elevation profiling of subsurface reflectors and visible layer boundaries reveals that reflectors and layers demonstrate similar topography, verifying that reflectors represent paleosurfaces of the deposit. Statistical and frequency-domain analyses of the separation distances between successive layers and successive reflectors confirms the agreement of radar reflector spacing with characteristic spacing of certain visible layers. Direct elevation comparisons between individual reflectors and discrete optical layers, while necessary for a one-to-one correlation, are complicated by variations in subsurface structure that exist between the outcrop and the SHARAD observations, as inferred from subsurface mapping. Although these complications have prevented a unique correlation, a genetic link between radar reflectors and visible layers has been confirmed, validating the assumption that radar reflectors can be used as geometric proxies for visible stratigraphy. Furthermore, the techniques for conducting a stratigraphic integration have been generalized and improved so that the integration can be undertaken at additional locations.

Christian, S.; Holt, J. W.; Byrne, S.; Fishbaugh, K. E.

2013-11-01

220

The deglaciation in Picos de Europa (area of Enol Glacier) based on geomorphological and sedimentological studies  

NASA Astrophysics Data System (ADS)

The chronology for the deglaciation in the Cantabrian Range is still poorly understood. Several papers have proposed a maximum advance well before the LGM (Jiménez and Farias, 2002; Moreno et al. 2010; Serrano et al. 2012). The Western massif of Picos de Europa held a ice field of 50 km2. In this communication we present two cores collected in two glacial depressions in the frontal area of Enol Glacier that allow reconstructing the environment since the deglaciation of the massif. The first core (5.6 m long) was collected in the kame terrace of Belbin. This terrace was dammed by a lateral moraine corresponding to the phase of maximum expansion of Enol Glacier. Three clear layers are observed: the basal 2.5 m consists of grey clay with small gravel limestones; the second is 2 m thick and is composed of grey clays; the upper 1.1 m shows several paleosoils with abundant organic matter and charcoals. The based was dated at 14,810 ± 70 yr BP. This age represents a minimum age for the maximum expansion of Enol Glacier. The second core was collected in the glaciokarst depression of Vega del Bricial, located within a moraine complex corresponding to LGM. The core is 8 m long and looks very homogeneous. It consists of a succession of organic layers and slope deposits. Two radiocarbon dates were performed on the sediments at 8 and 2.8 m depth, resulting in 9,690 ± 260 and 3,420 ± 95 yr BP, respectively. Based on sedimentological and geomorphological evidences, we propose a chronology for the environmental changes occurred in this massif since the last glacial period. References Jiménez, M. and Farias, P., 2002. New radiometric and geomorphologic evidences of a Last Glacial Maximum older than 18 ka in SW European mountains: the example of Redes Natural Park (Cantabrian Mountains, NW Spain). Geodinamica Acta, 15, 93-101. Moreno, A., Valero, B. L., Jiménez, M., Domínguez, M. J., Mata, M. P., Navas, A., González, P., Stoll, H., Farias, P., Morellón, M., Corella, J. P. and Rico, M., 2010. The last deglaciation in the Picos de Europa National Park (Cantabrian Mountains, Northern Spain). Journal of Quaternary Science, 25 (7), 1076-1091. Serrano, E., González-Trueba, J. J. and González-García, M., 2012. Mountain glaciation and paleoclimate reconstruction in the Picos de Europa (Iberian Peninsula, SW Europe). Quaternary Research, 78, 303-314.

Ruiz-Fernández, Jesus; Oliva, Marc; García, Cristina

2013-04-01

221

The Late Pleistocene Duoi U'Oi cave in northern Vietnam: palaeontology, sedimentology, taphonomy and palaeoenvironments  

NASA Astrophysics Data System (ADS)

This paper describes new fossil materials recovered at the Duoi U'Oi site, in December 2003, by a Vietnamese-French-Japanese team. The Duoi U'Oi cave is located in Man Duc village, 25 km of Hoà Binh city in northern Vietnam. It belongs to a karstic network developed in a dark grey micritic marine limestone dated from the Lower to the Middle Triassic. The sedimentary fill produced a rich mammalian fauna, essentially composed of isolated teeth of middle- to large-sized mammals (Artiodactyla, Perissodactyla, Proboscidea, Carnivora, Rodentia, Primates), and characteristic of Late Pleistocene. The results of the Duoi U'Oi fieldwork are of great interest for the following reasons: (1) the biochronological age of the fauna is consistent with 230Th/ 234U/ 238U dating from the calcitic floors (66±3 ka). The Duoi U'Oi fauna is thus the oldest well-dated modern fauna known for the Southeast Asian mainland; (2) in terms of sedimentology, the analysis of the formation of the fossiliferous breccia and that of the processes of deposits shows a close relation between the karstic deposits inside the cave and the deposits in the alluvial terraces. The observation of three levels of alluvial terraces associated with three caves situated at 62, 10 and 3 m above the present alluvial plain suggests that exokarstic and endokarstic sediments evolved together; (3) in terms of palaeobiogeography, Duoi U'Oi is the continental fauna showing the strongest resemblance with the Late Pleistocene faunas from Indonesian islands (Punung, Gunung Dawung, Lida Ajer, Sibrambang and Djambu caves); this implies that, at the time of Duoi U'Oi, ca 70 ka, the Sundaland was mainly characterised by faunas of modern aspect; (4) the analysis of major taphonomic factors that led to the mammal assemblage reveals a combination of selective agents (selective role of predators and porcupines, selective destruction of age classes for some species, selective preservation of fossils due to the deposition processes in the karstic network), which contribute to the poor representation of the diversity of the fauna; no arguments show that humans, present at Duoi U'Oi, might have a possible role in the taphonomic process; (5) the palaeoenvironmental reconstruction based on the composition of the faunal assemblage suggests a forested area and some open habitats, under warm and humid conditions.

Bacon, Anne-Marie; Demeter, F.; Duringer, P.; Helm, C.; Bano, M.; Vu, The Long; Kim Thuy, Nguyen Thi; Antoine, P.-O.; Thi Mai, Bui; Huong, Nguyen Thi Mai; Dodo, Y.; Chabaux, F.; Rihs, S.

2008-08-01

222

Stratigraphy and optically stimulated luminescence (OSL) dating of a Quaternary sequence along the Dong Nai River, southern Vietnam  

NASA Astrophysics Data System (ADS)

The pre-Holocene Cenozoic sequence outcrops in the terrestrial part of the eastern margin of the Mekong Basin. However, the stratigraphy of the sequence is still unclear. Its detailed stratigraphy and chronology were therefore studied along the Dong Nai River, southern Vietnam, and the lithofacies and the relations among the formations were investigated from the outcrops. The ages of the deposits were determined by using optically stimulated luminescence (OSL) dating. The Ba Mieu Formation was deposited about 176±52 ka during marine isotope stage (MIS) 7-6. The Thu Duc Formation was deposited about 97±27 ka during MIS 5. Both the Ba Mieu and Thu Duc formations are composed of fluvial and tidally influenced coastal deposits. The newly proposed Nhon Trach Formation was originally an eolian (blanket) deposit, but it has been partly reworked by fluvial processes. The Nhon Trach Formation was deposited about 10.9±4.7 ka, in the last part of the Pleistocene to the beginning of the Holocene. The OSL ages for the Ba Mieu, Thu Duc, and Nhon Trach formations are younger than the ages previously assigned to these formations.

Kitazawa, Toshiyuki; Nakagawa, Takahiro; Hashimoto, Tetsuo; Tateishi, Masaaki

2006-10-01

223

Changes in Colorado Subalpine Fen Peat Stratigraphy and Humification During the Holocene  

NASA Astrophysics Data System (ADS)

This project focuses on the record of peat stratigraphy and decomposition preserved in cores taken from minerotrophic peatlands in Colorado. Subalpine peatlands in the Colorado Rocky Mountains and in the Colorado Plateau cover only about 2% of the state's land area, yet these wetlands provide important wildlife habitat and ecosystem services. The peatlands in Colorado are fens, and, while summer precipitation contributes to the local hydrology, the fens are only found in locations where winter snowpack persists long enough into the summers to maintain sufficiently high water tables to preserve the peat. We hypothesized that changes in summer precipitation and winter snowpack through the Holocene would be evident in the degree of peat humification and stratigraphy. We were interested in determining how warmer summer conditions early in the Holocene influenced precipitation, particularly summer monsoons, and thus, groundwater. In addition, our research using lake sediment cores in the region indicates that sediment organic content may fluctuate with paleotemperature. We sought to determine whether fens likewise preserve evidence of relatively low magnitude temperature changes, including those associated with the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). Since fens persist in the region only under marginal conditions, they are very sensitive to fluctuations in climate and consequent hydrological responses. Nine fens were sampled in the study. Fen stratigraphy was studied at all of the sites. Humification analysis and bulk density and organic content determinations were conducted at one-centimeter intervals on cores from four of the fens. Core chronology was established using radiocarbon dating. Our results suggest that warmer summers in the early Holocene led to earlier snowmelt at lower elevations. Fens located near the lower margins of the subalpine zone (<3100 m elevation) ceased to accumulate peat during this period, changing to alluvial depositional environments, only returning to peat accumulation when cooler/moister conditions reestablished. This stratigraphic change is similar to that found by other researchers working in the Sierra Nevada, California. Higher elevation fens in Colorado persisted as peatlands throughout the Holocene, but warmer periods produced higher rates of peat accumulation and greater humification during these intervals. Peat humifiation and stratigraphic analyses indicate that the subalpine fens in Colorado preserve a sensitive record of Holocene climate change and ecohydrological conditions. Our results suggest that warmer summers over the next century will likely result in earlier snowmelt and the potential loss of lower elevation fens, and changes in peat accumulation in higher elevation fens in the subalpine zone. These changes will have significant impacts on water quality and hydrology in Colorado.

Sullivan, D. G.

2013-12-01

224

Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy  

USGS Publications Warehouse

Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

McLaughlin, P. I.; Brett, C. E.; Wilson, M. A.

2008-01-01

225

Geochronology and subsurface stratigraphy of Pukapuka and Rakahanga atolls, Cook Islands: Late Quaternary reef growth and sea level history  

USGS Publications Warehouse

Eustatic sea-level cycles superposed on thermal subsidence of an atoll produce layers of high sea-level reefs separated by erosional unconformities. Coral samples from these reefs from cores drilled to 50 m beneath the lagoons of Pukapuka and Rakahanga atolls, northern Cook Islands give electron spin resonance (ESR) and U-series ages ranging from the Holocene to 600,000 yr B.P. Subgroups of these ages and the stratigraphic position of their bounding unconformities define at least 5 periods of reef growth and high sea-level (0-9000 yr B.P., 125,000-180,000 yr B.P., 180,000-230,000 yr B.P., 300,000-460,000 yr B.P., 460,000-650,000 yr B.P.). Only two ages fall within error of the last interglacial high sea-level stand (???125,000-135,000 yr B.P.). This paucity of ages may result from extensive erosion of the last intergracial reef. In addition, post-depositional isotope exchange may have altered the time ages of three coral samples to apparent ages that fall within glacial stage 6. For the record to be preserved, vertical accretion during rising sea-level must compensate for surface lowering from erosion during sea-level lowstands and subsidence of the atoll; erosion rates (6-63 cm/1000 yr) can therefore be calculated from reef accretion rates (100-400 cm/1000 yr), subsidence rates (2-6 cm/1000 yr), and the duration of island submergence (8-15% of the last 600,000 yr). The stratigraphy of coral ages indicates island subsidence rates of 4.5 ?? 2.8 cm/1000 yr for both islands. A model of reef growth and erosion based on the stratigraphy of the Cook Islands atolls suggests average subsidence and erosion rates of between 3-6 and 15-20 cm/1000 yr, respectively. ?? 1992.

Gray, S. C.; Hein, J. R.; Hausmann, R.; Radtke, U.

1992-01-01

226

Late-Quaternary morpho-sedimentology and submarine mass movements of the Betsiamites area, Lower St. Lawrence Estuary, Quebec, Canada  

E-print Network

-sedimentology multibeam bathymetry seismic reflection earthquakes St. Lawrence Estuary Betsiamites River A complex submarine geomorphology was revealed from multibeam bathymetry and seismic reflection surveys conducted between 2001 and 2007 in the Lower St. Lawrence Estuary offshore Betsiamites River, Quebec, Canada

Long, Bernard

227

The "Continental Intercalaire" of southern Tunisia: Stratigraphy, paleontology, and paleoecology  

NASA Astrophysics Data System (ADS)

The "Continental Intercalaire" deposits of southern Tunisia preserve one of the most diverse Early Cretaceous vertebrate fauna from Africa, consisting of elasmobranchs, actinopterygians, sarcopterygians, turtles, crocodyliforms, pterosaurs, and non-avian dinosaurs. Vertebrate remains representative of both marine and fluvial environments have been historically referred to a specific bonebed within the Chenini Member, which crops out extensively in the Tataouine region. A stratigraphic revision of the mainly siliciclastic deposits of the Douiret and the Aïn El Guettar formations in the area based on new sedimentological and paleontological data is presented. Data collected indicate the presence of multiple fossil-bearing strata encompassing the stratigraphic interval from the Berriasian to the Albian and document faunal variation through time as well as major environmental and climatic changes. Detailed sedimentological analysis combined with biostratigraphic correlation performed at a basin scale indicate lateral facies variability within each formation as a result of tectonically and climatically driven zonations within the Tataouine Basin in the Early Cretaceous. Furthermore, proposed stratigraphic correlations indicate that vertebrate remains previously referred to the fluvial Chenini Member (and in particular theropod and sauropod dinosaurs) are instead representative of a transgressive deposit which mark the base of the overlying Oum ed Diab Member.

Fanti, Federico; Contessi, Michela; Franchi, Fulvio

2012-09-01

228

Clear Lake sediments: anthropogenic changes in physical sedimentology and magnetic response.  

PubMed

We analyzed the sedimentological characteristics and magnetic properties of cores from the three basins of Clear Lake, California, USA, to assess the depositional response to a series of land use changes that occurred in the watershed over the 20th century. Results indicate that distinct and abrupt shifts in particle size, magnetic concentration/mineralogy, and redox conditions occur concurrently with a variety of ecological and chemical changes in lake bed sediments. This coincidence of events occurred around 1927, a datum determined by an abrupt increase in total mercury (Hg) in Clear Lake cores and the known initiation of open-pit Hg mining at the Sulphur Bank Mercury Mine, confirmed by 210Pb dating. Ages below the 1927 horizon were determined by accelerator mass spectrometry on 14C of coarse organic debris. Calculated sedimentation rates below the 1927 datum are approximately 1 mm/yr, whereas rates from 1927 to 2000 are up to an order of magnitude higher, with averages of approximately 3.5-19 mm/yr. In both the Oaks and Upper Arms, the post-1927 co-occurrence of abrupt shifts in magnetic signatures with color differences indicative of changing redox conditions is interpreted to reflect a more oxygenated diagenetic regime and rapid burial of sediment below the depth of sulfate diffusion. Post-1927 in the Oaks Arm, grain size exhibits a gradual coarsening-upward pattern that we attribute to the input of mechanically deposited waste rock related to open-pit mining activities at the mine. In contrast, grain size in the Upper Arm exhibits a gradational fining-upward after 1927 that we interpret as human-induced erosion of fine-grained soils and chemically weathered rocks of the Franciscan Assemblage by heavy earthmoving equipment associated with a road- and home-building boom, exacerbated by stream channel mining and wetlands destruction. The flux of fine-grained sediment into the Upper Arm increased the nutrient load to the lake, and that in turn catalyzed profuse cyanobacterial blooms through the 20th century. The resulting organic biomass, in combination with the increased inorganic sediment supply, contributed to the abrupt increase in sedimentation rate after 1927. PMID:19475928

Osleger, David A; Zierenberg, Robert A; Suchanek, Thomas H; Stoner, Joseph S; Morgan, Sally; Adam, David P

2008-12-01

229

Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments  

NASA Astrophysics Data System (ADS)

An interdisciplinary study was conducted to evaluate the relationship between geological and paleoenvironmental parameters and the bacterial and archaeal community structure of two contrasting subseafloor sites in the Western Mediterranean Sea (Ligurian Sea and Gulf of Lion). Both depositional environments in this area are well-documented from paleoclimatic and paleooceanographic point of views. Available data sets allowed us to calibrate the investigated cores with reference and dated cores previously collected in the same area, and notably correlated to Quaternary climate variations. DNA-based fingerprints showed that the archaeal diversity was composed by one group, Miscellaneous Crenarchaeotic Group (MCG), within the Gulf of Lion sediments and of nine different lineages (dominated by MCG, South African Gold Mine Euryarchaeotal Group (SAGMEG) and Halobacteria) within the Ligurian Sea sediments. Bacterial molecular diversity at both sites revealed mostly the presence of the classes Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria within Proteobacteria phylum, and also members of Bacteroidetes phylum. The second most abundant lineages were Actinobacteria and Firmicutes at the Gulf of Lion site and Chloroflexi at the Ligurian Sea site. Various substrates and cultivation conditions allowed us to isolate 75 strains belonging to four lineages: Alpha-, Gammaproteobacteria, Firmicutes and Actinobacteria. In molecular surveys, the Betaproteobacteria group was consistently detected in the Ligurian Sea sediments, characterized by a heterolithic facies with numerous turbidites from a deep-sea levee. Analysis of relative betaproteobacterial abundances and turbidite frequency suggested that the microbial diversity was a result of main climatic changes occurring during the last 20 ka. Statistical direct multivariate canonical correspondence analyses (CCA) showed that the availability of electron acceptors and the quality of electron donors (indicated by age) strongly influenced the community structure. In contrast, within the Gulf of Lion core, characterized by a homogeneous lithological structure of upper-slope environment, most detected groups were Bacteroidetes and, to a lesser extent, Betaproteobacteria. At both site, the detection of Betaproteobacteria coincided with increased terrestrial inputs, as confirmed by the geochemical measurements (Si, Sr, Ti and Ca). In the Gulf of Lion, geochemical parameters were also found to drive microbial community composition. Taken together, our data suggest that the palaeoenvironmental history of erosion and deposition recorded in the Western Mediterranean Sea sediments has left its imprint on the sedimentological context for microbial habitability, and then indirectly on structure and composition of the microbial communities during the late Quaternary.

Ciobanu, M.-C.; Rabineau, M.; Droz, L.; Révillon, S.; Ghiglione, J.-F.; Dennielou, B.; Jorry, S.-J.; Kallmeyer, J.; Etoubleau, J.; Pignet, P.; Crassous, P.; Vandenabeele-Trambouze, O.; Laugier, J.; Guégan, M.; Godfroy, A.; Alain, K.

2012-09-01

230

Three-dimensional sedimentary architecture of Quaternary deposits; a case study of environmental sedimentology (Bam, Iran)  

Microsoft Academic Search

Detailed 3-D analysis of the sedimentary structure and stratigraphy of these deposits allows for an accurate understand of sedimentary model of basin. This paper presents a case study in Bam (SE Iran) reconstructing the 3-D distribution of fluvial sediments based on a high resolution, process-orientated sedimentary facies classification and lithostratigraphy. We investigated the mean grain size with vertical and horizontal

K. Rezaei; B. Guest; A. Friedrich; F. Fayazi; M. Nakhaei; H. Bakhtiari; L. Nouri

2009-01-01

231

Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean Leonid Polyak a,  

E-print Network

Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean Leonid Polyak a Article history: Accepted 17 March 2009 Available online xxxx Keywords: Arctic Ocean sediment stratigraphy sedimentary environments Late Quaternary glaciations Sediment cores from the western Arctic Ocean obtained

Howat, Ian M.

232

Snow stratigraphy measurements with high-frequency FMCW radar: Comparison with snow micro-penetrometer  

Microsoft Academic Search

The stratigraphy of an alpine snowpack is very important for avalanche danger assessment, as well as interpretation of remote sensing measurements for hydrological purposes. Since spatial variability is often widespread, due mainly to wind, micro-climatic and topographic effects, extrapolating point measurements can be difficult. Tools which can quickly characterize snowpack stratigraphy, such as high frequency radar and mechanical probes, will

Hans-Peter Marshall; Martin Schneebeli; Gary Koh

2007-01-01

233

Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology  

SciTech Connect

The purpose of our research has been to develop and demonstrate a seismic technology that will provide the oil and gas industry a better methodology for understanding reservoir and seal architectures and for improving interpretations of hydrocarbon systems. Our research goal was to expand the valuable science of seismic stratigraphy beyond the constraints of compressional (P-P) seismic data by using all modes (P-P, P-SV, SH-SH, SV-SV, SV-P) of a seismic elastic wavefield to define depositional sequences and facies. Our objective was to demonstrate that one or more modes of an elastic wavefield may image stratal surfaces across some stratigraphic intervals that are not seen by companion wave modes and thus provide different, but equally valid, information regarding depositional sequences and sedimentary facies within that interval. We use the term elastic wavefield stratigraphy to describe the methodology we use to integrate seismic sequences and seismic facies from all modes of an elastic wavefield into a seismic interpretation. We interpreted both onshore and marine multicomponent seismic surveys to select the data examples that we use to document the principles of elastic wavefield stratigraphy. We have also used examples from published papers that illustrate some concepts better than did the multicomponent seismic data that were available for our analysis. In each interpretation study, we used rock physics modeling to explain how and why certain geological conditions caused differences in P and S reflectivities that resulted in P-wave seismic sequences and facies being different from depth-equivalent S-wave sequences and facies across the targets we studied.

Bob A. Hardage; Milo M. Backus; Michael V. DeAngelo; Sergey Fomel; Khaled Fouad; Robert J. Graebner; Paul E. Murray; Randy Remington; Diana Sava

2006-07-31

234

Sequence stratigraphy: Fact, fantasy, or work in progress  

SciTech Connect

Sequence stratigraphy has been hailed as a magic elixir to cure exploration problems in mature and frontier basins. Yet, like most cure-alls, analyses of modern depositional systems show that critical assumptions regarding sequence stratigraphy merit further review. An example from the modern Canterbury Plains, New Zealand, demonstrates some of the potential pit- falls of sequence stratigraphy and its application to hydrocarbon exploration. The Canterbury Plains, New Zealand, bounded by the Southern Alps and Pacific Ocean, are 60 km wide and 185 km long, and traversed by four large gravel rivers. The Canterbury basin is up to 750 m deep, filled primarily with gravel. The coastline is wave dominated and microtidal, with high rates of north-directed longshore drift. The southern coast is transgressive with 22 in wave-cut cliffs in Pleistocene gravel. Beaches are gravel and sand. Coastal erosion at approximately 1 m/yr steepens the fluvial gradient, causing the rivers to incise 1.5-4.2 mm/yr during the present highstand. River headwaters in the Southern Alps are uplifting, tectonically causing incision, which decreases seaward. Thus, fluvial incision takes place in the west due to mountain uplift and in the east due to the transgressing shoreline. A zone of null valley incision occurs 8-15 km from the coast. Existing sequence stratigraphic models suggest that downcutting should occur during falling sea level, not during transgression. The southern coastline is separated from the northern coast-line by Banks Peninsula, a resistant volcanic complex that acts as a large groyne to southerly waves. The northern coastline progrades approximately I m/yr and is largely sandy. Thus, the coastline within the same basin during the present sea level highstand is at one locale progradational and elsewhere transgressive. Gravel reaches the transgressive coast, where a steep gradient is maintained by downcutting.

Leckie, D.A. [Geological survey of Canada, Calgary, Alberta (Canada)

1995-11-01

235

Stratigraphy of Atlantic coastal margin of United States north of Cape Hatteras; brief survey  

USGS Publications Warehouse

A synthesis of studies of sea-floor outcrops of the sedimentary wedge beneath the northeastern United States continental shelf and slope and a reassessment of coastal plain Mesozoic stratigraphy, particularly of the coastal margin, provide insight for estimating the oil and gas potential and provide geologic control for marine seismic investigations of the Atlantic continental margin. The oldest strata known to crop out on the continental slope are late Campanian in age. The Cretaceous-Tertiary contact along the slope ranges from a water depth of 0.6 to 1.5 km south of Georges Bank to 1.8 km in Hudson Canyon. Few samples are available from Tertiary and Late Cretaceous outcrops along the slope. Sediments of the Potomac Group, chiefly of Early Cretaceous age, constitute a major deltaic sequence in the emerged coastal plain. This thick sequence lies under coastal Virginia, Maryland, Delaware, southeastern New Jersey, and the adjacent continental shelf. Marine sands associated with this deltaic sequence may be present seaward under the outer continental shelf. South of the Norfolk arch, under coastal North Carolina, carbonate rocks interfinger with Lower Cretaceous clastic strata. From all available data, Mesozoic correlations in coastal wells between coastal Virginia and Long Island have been revised. The Upper-Lower Cretaceous boundary is placed at the transition between Albian and Cenomanian floras. Potential hydrocarbon source beds are present along the coast in the subsurface sediments of Cretaceous age. Potential reservoir sandstones are abundant in this sequence.

Perry, W. J.; Minard, J. P.; Weed, E. G. A.; Robbins, E. I.; Rhodehamel, E. C.

1975-01-01

236

Sequence stratigraphy applied to the hydrocarbon productive basins of Western Indonesia  

SciTech Connect

Oil exploration began in Indonesia in 1870, and the first commercial discovery was made in 1885 in the North Sumatra basin. Since then, over 3000 exploratory wells have been drilled in western Indonesia, with about 750 discoveries reported. By the end of 1992, over 300 fields in eleven geological basins were producing in western Indonesia, and 100 more fields were either shut in or had been abandoned. However, despite the fact that western Indonesia is a mature hydrocarbon province, all published work of a regional nature, and indeed most internal company reports, use lithostratigraphy and, to a lesser extent, biostratigraphy. Lithostratigraphy is based, often unwittingly, on pre-1960s work, when only relatively shallow wells and limited seismic data were available. Additional difficulties arise from companies using alternative names for a rock unit and the same formation name for different rock units. Biostratigraphy is handicapped by the lack of age diagnostic fossils in the early Miocene and older sediments in most of Sumatra and Natuna. In Java and Kalimantan, where the older section tends to be more marine and age diagnostic fossils are present, significant errors in age determination occur due to reworking of sediments. As a consequence, the [open quotes]hydrocarbon system[close quotes] in western Indonesia is inadequately understood, and exploration efforts are often poorly applied. This paper proposes a correlative framework using sequence stratigraphy for the hydrocarbon productive basins of western Indonesia, which should contribute to a better understanding of the hydrocarbon system and significantly reduce exploration risk in western Indonesia.

Courteney, S.

1994-07-01

237

Late Quaternary stratigraphy and luminescence geochronology of the northeastern Mojave Desert  

USGS Publications Warehouse

The chronology of the Holocene and late Pleistocene deposits of the northeastern Mojave Desert have been largely obtained using radiocarbon ages. Our study refines and extends this framework using optically stimulated luminescence (OSL) to date deposits from Valjean Valley, Silurian Lake Playa, Red Pass, and California Valley. Of particular interest are eolian fine silts incorporated in ground-water discharge (GWD) deposits bracketed at 185-140 and 20-50 ka. Alluvial fan deposits proved amenable for OSL by dating both eolian sand lenses and reworked eolian sand in a matrix of gravel that occurs within the fan stratigraphy. Lacustrine sand in spits and bars also yielded acceptable OSL ages. These OSL ages fill gaps in the geochronology of desert deposits, which can provide data relevant to understanding the responses of several depositional systems to regional changes in climate. This study identifies the most promising deposits for future luminescence dating and suggests that for several regions of the Mojave Desert, sediments from previously undated landforms can be more accurately placed within correct geologic map units.

Mahan, S. A.; Miller, D. M.; Menges, C. M.; Yount, J. C.

2007-01-01

238

Stratigraphy and Observations of Nepthys Mons Quadrangle (V54), Venus  

NASA Technical Reports Server (NTRS)

Initial mapping has begun in Venus' Nepthys Mons Quadrangle (V54, 300-330 deg. E, 25-50 deg. S). Major research areas addressed are how the styles of volcanism and tectonism have changed with time, the evolution of shield volcanoes, the evolution of coronae, the characteristics of plains volcanism, and what these observations tell us about the general geologic history of Venus. Reported here is a preliminary general stratigraphy and several intriguing findings. Additional information is contained in the original extended abstract.

Bridges, N. T.

2001-01-01

239

Sedimentological evolution in an UASB treating SYNTHES, a new representative synthetic sewage, at low loading rates.  

PubMed

The changes in the sedimentological attributes of the sludge bed in an upflow anaerobic sludge blanket (UASB) reactor fed with a low-strength wastewater mimicking raw domestic sewage were assessed in this study. The reactor was inoculated with 250 ml of granular sludge from a full-scale UASB reactor. The organic loading rate (OLR) varied from 1 to 2 g COD/ld. During the half-year long study, the reactor was operated at hydraulic retention times (HRTs) of 4.8 and 10 h, at 33 degrees C. Sludge sedimentology showed that the original granular sludge experienced serious instability and disintegration, leading to a much finer final grain assemblage, mainly due to substrate transfer limitation and cell starvation at the interior of larger granules. With time, the size uniformity tended to decrease, sphericity tended to increase, the skewness of the granule size distribution became negative, and the kurtosis became peaked and leptokurtic. In spite of the observed size reduction, reactor efficiency increased to a CODtotal removal of 96%. Biomass (sludge) yield was 0.012 g VS/g COD removed. The CH4 content of the biogas was high (up to 96%). This study thus highlights the treatment of a new type of wastewater with the deployment of the UASB reactor. It also reports the evolutionary trend of the biomass particle size distribution, making reference to a classic sedimentological appraisal. PMID:15062822

Aiyuk, Sunny; Verstraete, Willy

2004-07-01

240

A martian case study of segmenting images automatically for granulometry and sedimentology, Part 2: Assessment  

NASA Astrophysics Data System (ADS)

In a companion work, we bridge the gap between mature segmentation software used in terrestrial sedimentology and emergent planetary segmentation with an original algorithm optimized to segment whole images from the Microscopic Imager (MI) of the Mars Exploration Rovers (MER). In this work, we compare its semi-automated outcome with manual photoanalyses using unconsolidated sediment at Gusev and Meridiani Planum sites for geologic context. On average, our code and manual segmentation converge to within ?10% in the number and total area of identified grains in a pseudo-random, single blind comparison of 50 samples. Unlike manual segmentation, it also locates finer grains in an image with internal consistency, enabling robust comparisons across geologic contexts. When implemented in Mathematica-8, the algorithm segments an entire MI image within minutes, surpassing the extent and speed possible with manual segmentation by about a factor of ten. These results indicate that our algorithm enables not only new sedimentological insight from the MER MI data, but also detailed sedimentology with the Mars Science Laboratory’s Mars Hand Lens Instrument.

Karunatillake, Suniti; McLennan, Scott M.; Herkenhoff, Kenneth E.; Husch, Jonathan M.; Hardgrove, Craig; Skok, J. R.

2014-02-01

241

Petroacoustic Modelling of Heterolithic Sandstone Reservoirs: A Novel Approach to Gassmann Modelling Incorporating Sedimentological Constraints and NMR Porosity data  

NASA Astrophysics Data System (ADS)

Heterolithic or 'shaly' sandstone reservoirs constitute a significant proportion of hydrocarbon resources. Petroacoustic models (a combination of petrophysics and rock physics) enhance the ability to extract reservoir properties from seismic data, providing a connection between seismic and fine-scale rock properties. By incorporating sedimentological observations these models can be better constrained and improved. Petroacoustic modelling is complicated by the unpredictable effects of clay minerals and clay-sized particles on geophysical properties. Such effects are responsible for erroneous results when models developed for "clean" reservoirs - such as Gassmann's equation (Gassmann, 1951) - are applied to heterolithic sandstone reservoirs. Gassmann's equation is arguably the most popular petroacoustic modelling technique in the hydrocarbon industry and is used to model elastic effects of changing reservoir fluid saturations. Successful implementation of Gassmann's equation requires well-constrained drained rock frame properties, which in heterolithic sandstones are heavily influenced by reservoir sedimentology, particularly clay distribution. The prevalent approach to categorising clay distribution is based on the Thomas - Stieber model (Thomas & Stieber, 1975), this approach is inconsistent with current understanding of 'shaly sand' sedimentology and omits properties such as sorting and grain size. The novel approach presented here demonstrates that characterising reservoir sedimentology constitutes an important modelling phase. As well as incorporating sedimentological constraints, this novel approach also aims to improve drained frame moduli estimates through more careful consideration of Gassmann's model assumptions and limitations. A key assumption of Gassmann's equation is a pore space in total communication with movable fluids. This assumption is often violated by conventional applications in heterolithic sandstone reservoirs where effective porosity, which includes a capillary bound water porosity component, is used. The novel approach attempts to better address this assumption through incorporation of NMR porosity data which distinguishes between bound water and free (movable) fluid components of porosity. The simplistic approach to heterolithic sandstone sedimentology, with poor linkage between petrophysical and sedimentological analyses and ignorance of model caveats, compounds petroacoustic modelling issues. This research uses a single well dataset comprising a log suite including NMR and OBMI data, together with extensive core data including core-NMR, SEM images and detailed sedimentological analysis. Integration of log and core data enables better insight to the key sedimentological properties influencing reservoir elastic properties. This approach improves understanding of key sedimentological properties affecting acoustic propagation in heterolithic sandstones and in turn provides better models for describing these important reservoirs. This contributes to enhanced seismic data interpretation of reservoir properties, including fluid saturations, during exploration and development phases.

Matthews, S.; Lovell, M.; Davies, S. J.; Pritchard, T.; Sirju, C.; Abdelkarim, A.

2012-12-01

242

Fluctuating Mesozoic and Cenozoic sea levels and implications for stratigraphy  

SciTech Connect

Sequence stratigraphy encompasses depositional models of genetically related packages of sediments deposited during various phases of cycle of sea level change, i.e., from a lowstand to highstand to the subsequent lowstand. The application of these models to marine outcrops around the world and to subsurface data led to the construction of Mesozoic-Cenozoic sea level curves with greater event resolution than the earlier curves based on seismic data alone. Construction of these better resolution curves begins with an outline of the principles of sequence-stratigraphic analysis and the reconstruction of the history of sea level change from outcrop and subsurface data for the past 250 Ma. Examples of marine sections from North America, Europe, and Asia can be used to illustrate sequence analysis of outcrop data and the integration of chronostratigraphy with sea level history. Also important are the implications of sequence-stratigraphic methodology and the new cycle charts to various disciplines of stratigraphy, environmental reconstruction, and basin analysis. The relationship of unconformities along the continental margins to hiatuses and dissolution surfaces in the deep basins must also be explored, as well as the relevance of sequence-stratigraphic methodology to biofacies and source rock prediction.

Haq, B.U. (National Science Foundation, Washington, DC (USA))

1988-12-01

243

Sedimentological, geochemical and paleontological insights applied to continental omission surfaces: A new approach for reconstructing an eocene foreland basin in NW Argentina  

NASA Astrophysics Data System (ADS)

An Eocene foreland basin linked to the Andean uplift in northwestern Argentina has recently been proposed. The basin is divided and partially eroded due to subsequent Neogene orogenic phases, so that a simple reconstruction is insufficient to describe complex field relationships. This presents a new challenge in understanding the initial phases of Central Andean evolution. We propose a multidisciplinary approach in key locations and/or at key geological features as a way to reconstruct the Paleogene basin. In this contribution, we report on sedimentological and geochemical evidence of a conspicuous weathering surface in the continental Eocene Lumbrera Formation and provide an age estimate based on vertebrate mammalian biostratigraphy and an absolute U/Pb zircon age of 39.9 Ma. Weathering surfaces become evident when diagnostic features like paleosols, karsts, and trace fossils are distinctive but, in our case, these characteristics only emerge through detailed sedimentological and geochemical surveys. The Lumbrera paleosurface is represented by a hardened level (20-30 cm thick) characterized by moderately developed reddish paleosols. Moreover, major and trace element profiles show inflections at the top and/or base of the weathered horizon delineating it. A modified form of the chemical index of alteration shows that chemical leaching was moderate and not extensive. In addition, mammalian fossil records substantially differ below and above the weathered paleosol-bearing surface. We conclude that this horizon represents a Middle Eocene omission surface and represents a key level marking a major basin change in northwest Argentina, adding a new constraints for Eocene foreland reconstruction.

del Papa, C.; Kirschbaum, A.; Powell, J.; Brod, A.; Hongn, F.; Pimentel, M.

2010-03-01

244

Pleistocene pollen stratigraphy from borehole 81/34, devil's hole area, central north sea  

NASA Astrophysics Data System (ADS)

Twelve pollen assemblage zones are identified in a 229 m deep borehole (BH 81/34) from the Devil's Hole area in the central North Sea (British sector). The sediment from this borehole is Early to Late Pleistocene in age and the observation of massulae from Azolla filiculoides in sediment with reversed polarity indicates an age younger than the Olduvai geomagnetic event for the entire sequence. The Early Pleistocene sediments were at least partly deposited in the vicinity of a river outlet and can be correlated either with the Eburonian or the Menapian cold stage and with the Bavel interglacial and the Linge glacial within the Bavelian stage in the Dutch stratigraphy. The Middle Pleistocene sequence contains an interval rich in Abies, Picea and Pinus, probably deposited during the end of either Cromerian Complex interglacial IV (Noordbergum) or possibly the Holsteinian. The uppermost 80 m of the core contains high frequencies of pre-Quaternary and deteriorated palynomorphs indicating extensive glacial or glaciofluvially reworked sediment.

Ekman, Sten R.

1998-09-01

245

Cover sequence stratigraphy and structure: Salem Church basement culmination, Georgia Blue Ridge  

SciTech Connect

The Salem Church anticline SW of Jasper, Georgia in the western Blue Ridge is roughly an oval shaped structural dome with its long axis trending NE-SW. The anticline is cored by the Grenville age Corbin Gneiss which represents allochthonous North American basement. In debate for decades has been the age and origin of several kilometers of poly-deformed cover sequence rocks which were metamorphosed to greenschist facies and were probably transported over a long distance inland after their deposition. The stratigraphy of the cover sequence exhibits rapid lithofacies changes. At most localities, the basement is overlain by a 500--600 m thick coarse clastic unit sourced from the basement rocks, composed mainly of metaconglomerate, metasandstone and metadiamictite. A thin unit less than 20 m thick of sericite phyllite occurs between the basement and the coarse clastic unit along the SE limb of the anticline but pinches out to the MW. A relatively sharp stratigraphic contact occurs between quartzite unit and overlying dark colored metagreywackes and metadiamictites containing distinctive cobbles and boulders of granitic and gneissic basement rocks up to 1 meter in length. This unit is about 100 m thick in the SW but thins rapidly towards the NE. It grades up into a geographically widespread graphitic phyllite which encircles most of the anticline. Unlike the cover sequence above the corbin basement west of Waleska, Georgia, no carbonate is found in this area.

Li, L.; Tull, J.F. (Florida State Univ., Tallahassee, FL (United States). Dept. of Geology)

1994-03-01

246

Relationships between fracture patterns, geodynamics and mechanical stratigraphy in Carbonates (South-East Basin, France)  

NASA Astrophysics Data System (ADS)

This study aims at improving the understanding of fracture genesis in layered carbonate sedimentary sequences, focusing on field analysis of Jurassic to Maastrichtian age carbonates of Provence (France). Fracture patterns of 9 outcrops were characterized in 3D: 6 of Urgonian, 1 of Tithonian and 2 of Campanian-Late Maastrichtian ages. Seven sites are located in relatively weakly deformed areas away from larges fault and fold zones where strain partitioning and stress localization effects may take place. Two sites are located in fold flanks for the purpose of relative dating and for comparison with the sites in the weakly deformed areas. Patterns and detailed fracture attributes were compared to host rock sedimentary facies, porosity and P-wave velocities. Fracture chronology was determined with cross-cutting relationships and compared to burial/uplift history reconstructed from subsidence curves and from a regional structural analysis. Our results show that fractures are clustered in two perpendicular joint sets whatever the host rock age. We observe an average spacing of 20 cm and no control of strike, age, facies, or bed thickness on fracture size. There is no mechanical stratigraphy. The fracture sequence compared to subsidence curves indicates that fractures occurred before tectonic inversion, during early and rapid burial, whatever the host rock age and facies. The abundance of burial stylolites does not correlate with maximum burial depth but with fracture frequency, host rock porosity and P-wave velocity. We conclude that the studied carbonates had early brittle properties controlled by their geographic position rather than by depositional facies types and undergone early diagenesis. The porosity loss/gain and the mechanical differentiation in carbonates of Provence could have been acquired during very early burial and diagenesis and have preserved through time. This study also demonstrates that regional fracturing is not necessarily driven by large scale structural events as it is often assumed in fractured reservoir modelling.

Lamarche, Juliette; Lavenu, Arthur P. C.; Gauthier, Bertrand D. M.; Guglielmi, Yves; Jayet, Océane

2012-12-01

247

Geoacoustic character, sedimentology and chronology of a cross-shelf Holocene sediment deposit off Cabo Frio, Brazil (southwest Atlantic Ocean)  

NASA Astrophysics Data System (ADS)

The Cabo Frio region in the state of Rio de Janeiro, southeast coast of Brazil, is characterized by a local coastal upwelling system and converging littoral sediment transport systems that are deflected offshore at Cabo Frio, as a consequence of which a thick cross-shelf sediment deposit has developed over time. To investigate the evolution of this muddy deposit, geophysical, sedimentological and geochemical data from four sediment cores (3.8-4.1 m in length) recovered in water depths between 88 and 141 m were analyzed. The high-resolution seismic data show variable sediment thicknesses ranging from 1 to 20 m, comprising two sedimentary units separated by a high-impedance layer at a depth of about 10 m below the seafloor at the coring sites. According to the available age datings, the upper sedimentary unit is late Pleistocene to Holocene in age, whereas the lower unit (not dated) must, by implication, be entirely Pleistocene in age. The boomer-seismic reflection signal can be divided into three echo-types, namely transparent (inner shelf), stratified (middle shelf) and reflective (outer shelf), each type seemingly related to the local sediment composition. The upper 4 m of the upper sedimentary unit is dominated by silty sediment on the middle shelf, and by upward-fining sediments (silty sand to sandy silt) on the inner and outer shelf. The downcore trends of P-wave velocity, gamma-ray density and acoustic impedance are largely similar, but generally reversed to those of water and organic carbon contents. Total organic carbon contents increase with decreasing mean grain size, periodic fluctuations suggesting temporal changes in the regional hydrodynamics and primary productivity fuelled by the local upwelling system. The reconstruction of sedimentation rates in the course of the Holocene is based on 35 AMS age datings of organic material recovered from variable downcore depths. These range from a maximum of 13.3 cm/decade near the base of the inner shelf core (7.73-7.70 ka BP) to generally very low values (<0.11 cm/century) over the last thousand years in all cores. Over the last 6 ka there appear to have been three distinct sedimentation peaks, one between 6 and 5 ka BP, another between 4 and 3 ka PB, and one around 1 ka BP. Due to different time intervals between dates, not every peak is equally well resolved in all four cores. Based on the similar sedimentology of the inner and outer shelf cores, an essentially identical sedimentation model is proposed to have been active in both cases, albeit at different times. Thus, already during the last glacial maximum, alongshore sediment transport was deflected offshore by a change in shoreline orientation caused by the Cabo Frio structural high. The source of terrigenous material was probably a barrier-island complex that was subsequently displaced landward in the course of sea-level rise until it stabilized some 6.5 ka BP along the modern coast.

Mendoza, Ursula; Ayres Neto, Arthur; C. Abuchacra, Rodrigo; Fernandes Barbosa, Cátia; G. Figueiredo, Alberto; C. Gomes, Manoela; Belem, Andre L.; Capilla, Ramsés; S. Albuquerque, Ana Luiza

2014-08-01

248

Imaging Structure, Stratigraphy and Groundwater with Ground-Penetrating Radar on the Big Island, Hawaii  

NASA Astrophysics Data System (ADS)

A series of exploratory ground-penetrating radar (GPR) surveys were carried out on the Big Island, Hawaii in March of 2004 to evaluate the efficacy of using GPR to address hydrological, volcanological, and tectonic issues in extrusive basaltic materials. Target sites included beach sands, nearshore lava flows, well-developed soil covers, lava tubes, and major fault zones. Surveys were carried out with a Sensors and Software T Pulse Ekko 100, which was equipped with 50, 100, and 200 MHz antennae. Both reflection profiles and CMP expanding spreads were collected at most sites to provide both structural detail and in situ velocity estimation. In general, the volcanic rocks exhibited propagation velocities of ca 0.09-0.10 m/ns, a value which we interpret to reflect the large air-filled porosity of the media. Penetration in the nearshore area was expectedly small (less than 1 m), which we attribute to seawater infiltration. However, surveys in the volcanics away from the coast routinely probed to depths of 10 m or greater, even at 100 MHz. While internal layering and lava tubes could be identified from individual profiles, the complexity of returns suggests that 3D imaging is required before detailed stratigraphy can be usefully interpreted. A pilot 3D survey over a lava tube complex supports this conclusion, although it was prematurely terminated by bad weather. Although analysis of the CMP data does not show a clear systematic variation in radar velocity with age of flow, the dataset is too limited to support any firm conclusions on this point. Unusually distinct, subhorizontal reflectors on several profiles seem to mark groundwater. In one case, the water seems to lie within a lava tube with an air-filled roof zone. Surveys over part of the controversial Hilana fault zone clearly image the fault as a steeply dipping feature in the subsurface, albeit only to depths of a few meters. The results suggest, however, that deeper extensions of the faults could be mapped by more aggressive surveying techniques (e.g. lower frequencies or high levels of signal stacking). In summary, GPR has proven to be a very effective technique in mapping stratigraphy, structure, and hydrology in the volcanic rocks of Hawaii. Future work is planned to evaluate more fully the merits of 3D imaging, the systematics of propagation velocity with composition and age of extrusion, the internal morphology of successive flows, and whether GPR can discriminate aa from pahoehoe flows at depth.

Shapiro, S. R.; Tchakirides, T. F.; Brown, L. D.

2004-12-01

249

Sedimentology of mid Permian strata of the Sublett Range, South-Central Idaho  

E-print Network

STRATIGRAPHY Park City Group The Park City Group was originally named by Hose and Repenning (1959) for a th1ck early to mid Permian carbonate sequence in the Confusion Range, western Utah. The Park City Group extends from northeastern Nevada...). 22 Kaibab Limestone Formation From its type area in the Confusion Range (Hose and Repenning, 1959), the homogeneous Kaibab Limestone extends north to the Leach Mountains (Fig. 7) and Gerster Gulch before grading into the heterogeneous Grandeur...

Duree, Dana Kay

2012-06-07

250

DESCRIPTIONS/STRATEGIES What can I do with this degree?  

E-print Network

Sedimentology StructuralGeology Geophysics EconomicGeology Geomorphology Paleontology Fossil Energy Geologists. Minerals MiningGeology Mineralogy Geochemistry EconomicGeology Paleontology Stratigraphy Sedimentology

Kaminsky, Werner

251

The Department of Geology at Wayne State University consists of five full-time faculty and five  

E-print Network

(Geochemistry and Geophysics), Jeffrey Howard (Sedimentology), Larry Lemke (Hydrogeology), and Ed van Hees faculty are conducting research in the general areas of Sedimentology, Stratigraphy, Soil Science

Baskaran, Mark

252

Relation of sequence stratigraphy to modern sedimentary environments  

SciTech Connect

One method of testing the concept of sequence stratigraphy is to compare it to Quaternary sediments in which chronology, stratigraphic relations, and facies geometry are more clearly understood than in older rocks. Rapid deposition rates during Quaternary glacial-eustatic cycles in large deltaic depocenters generate sequences comparable to those in the ancient stratigraphic record. In the northern Gulf of Mexico, the late Wisconsinan-Holocene Mississippi River has deposited a Type 1 sequence that includes lowstand, transgressive, and high-stand systems tracts. Characteristics of modern Mississippi River sedimentary environments support the methodology used in sequence analysis, but the short time taken for sequence generation here raises important questions about sequence time scales, correlation, and driving mechanisms.

Boyd, R. (Dalhousie Univ., Halifax, Nova Scotia (Canada)); Suter, J.; Penland, S. (Louisiana Geological Survey, Baton Rouge (USA))

1989-10-01

253

Postglacial transgressive stratigraphy of the Durban continental shelf, South Africa  

NASA Astrophysics Data System (ADS)

This paper examines the geomorphology and seismic stratigraphy of the high-energy KwaZulu-Natal shelf offshore Durban, South Africa. Particular attention is paid to a laterally persistent (30 km) Holocene submerged shoreline located at 60 m water depth. Five major seismic units are identified (Units 1-5). Unit 1 comprises a series of infilled incised valleys that formed during the sea level lowering towards the Last Glacial Maximum. Unit 2 comprises a calcarenite core that forms the -60 m postglacial barrier complex. Unit 3 comprises lake-lagoon depressions in the back-barrier that formed simultaneously with the barrier system. These are backed to landward by several relict parabolic dunes preserved in Unit 2. Several relict weathering features (Unit 4) are associated with the barrier and reflect similar processes observed in contemporary aeolianite/beachrock outcrops on the adjacent coastline. These are draped by a thin veneer of post-transgressive Holocene sediment that caps the shelf stratigraphy (Unit 5). The development of the barrier and associated features occurred during a period of stillstand or slowstand associated with the Younger Dryas Cold Period (~12.7-11.6 Ka BP). Shoreline preservation in such a high-energy environment is considered unlikely as a result of the intense ravinement processes experienced during shoreline translation, coupled with the relatively low gradient setting of the KwaZulu-Natal shelf. The preservation of both the 100 m and 60 m shorelines was fostered by overstepping of the paleo-landscape, whereby preservation was promoted by a particularly rapid phase of relative sea-level rise associated with meltwater pulse 1B. This was further aided by early subtropical diagenesis during stillstand.

Green, Andrew; Salzmann, Leslee; Cooper, Andrew

2014-05-01

254

Phaneorozoic sequence stratigraphy of Bolivia and adjacent regions  

SciTech Connect

Phaneorozoic sequence stratigraphy of the Pacific margin of western South America, particularly the Bolivian section, has been completed and new interpretations and hypotheses have been proposed as a result of data analyses of this information. The Paleozoic margin was initially passive (late Cambrian-Llanvirn, [open quotes]Puna aulacogen[close quotes]), but became active during a middle Ordovician compressional episode. Most of late Cambrian to early Triassic Bolivian rocks are of marine origin, with dark shale units recording sea level rises, whereas middle Triassic to Recent rocks were mainly deposited in continental environments (except six restricted-marine ingressions in the late Cretaceous-Danian, and one in the late Miocene, all with hydrocarbon potential). A noteworthy similarity exists between the Devonian to Jurassic stratigraphies of Bolivia and the Parana basin, suggesting that Bolivia behaved as part of the Brazilian craton from late Cambrian to late Jurassic, when it was captured into the Pacific margin geotectonic system. Organic-rich units correlate with Paleozoic highstand deposits and younger ingressions. The Bolivian Phanerozoic strata is characterized by thick layers, partly due to middle Ordovician-Carboniferous and late Cretaceous-Cenozoic foreland basins. Paleozoic foreland geometries include northeastern onlaps and, potentially, stratigraphic traps. Hydrocarbon generation, migration and trapping mainly depended on Cenozoic structural loading and burial and on propagation of Andean deformation which are comprised of Paleozoic shale decollements. Precise knowledge of the evolution of the Phanerozoic geodynamic contexts and basin geometries through sedimentation and subsequent deformations is crucial for hydrocarbon exploration strategies in these regions.

Sempere, T. (Convenio YPFB-Orstom, Santa Cruz (Bolivia))

1993-02-01

255

Sedimentology of cores recovered from the Canada Basin of the Arctic Ocean  

NASA Astrophysics Data System (ADS)

Researchers from the United States and Canada are collaborating to understand the tectonic and sedimentary history of the Arctic Ocean between Canada and Alaska. As part of this on-going study, a joint US-Canadian ice breaker expedition operated in parts of the Canada Basin during August 2010. Occasional interruptions of the seismic data acquisition provided the ship time to collect gravity and piston cores at five sites-of-opportunity throughout the basin. High-resolution multibeam bathymetry and chirp sub-bottom profiler data collected immediately prior to coring reveal the fine-scale morphology of each site. Core photographs, X-ray radiographs, and physical property data support the following descriptions. Two piston cores were collected from the Beaufort Sea continental margin in a region of known bottom simulating reflectors (BSRs). Site 1 (2538 m water depth): This core recovered 5.72 m of gas-charged, gray sticky clay and silty-clay from an approximately 1100 m diameter, 130 m high conical mound overlying the crest of a buried anticline. Gas hydrate recovered in the core catcher combined with cracks and voids, methane and other hydrocarbon gasses, pyrite concretions, chemosynthetic clams, carbonate nodules, and soft carbonate masses indicate the likely upward migration of deep-seated fluids. Site 2 (1157 m water depth): This core, positioned 40 km upslope from the gas hydrate core, recovered 3 m of gray sticky silty clay and clayey silt near the base of an erosional scarp. Some voids and fracturing are apparent but carbonate masses and pyrite concretions are absent. Site 3 (3070 m water depth): This core from the top of a seamount discovered in 2009 in the north-central part of the Canada Basin recovered 4.94 m of sediment. More than 3 m of dark brown to yellowish brown, massive interbedded silty clays with sands and matrix-supported gravels (ice rafted debris [IRD]) occur in abrupt contact with underlying reddish yellow to brownish yellow silty clay and gravelly sandy clay interpreted to be altered hydrothermally. Successions of IRD layers create a thinly- to medium-bedded sequence throughout the lower section. Site 4 (3700 m water depth; central Canada Basin): This core recovered 3.4 m of sediment typified by decimeter-thick sequences of stacked graded beds with erosional basal contacts (Bouma sequences) characteristic of turbidite deposition. Site 5 (2081 m water depth; continental slope west of the Canadian archipelago): This core recovered 4.96 m of sediment of which the upper 2 m is silty clay to clayey silt with dispersed sand and granules. This upper section has an irregular, sharp basal contact with an underlying 16-cm-thick clast-supported massive gravel. The gravel has a scoured basal contact and overlies a monotonous gray clayey silt containing dispersed granules of IRD. Sparse and poorly preserved fauna throughout all the cores make age determination difficult; however, given the paucity of sediment cores in the Arctic Ocean, these samples provide vital geophysical groundtruth and sedimentological information about the basin.

Edwards, B. D.; Saint-Ange, F.; Pohlman, J.; Higgins, J.; Mosher, D. C.; Lorenson, T. D.; Hart, P.

2011-12-01

256

Sedimentologic and stratigraphic constraints on emplacement of the Star Kimberlite, east-central Saskatchewan  

NASA Astrophysics Data System (ADS)

Diamond-bearing kimberlites in the Fort à la Corne region, east-central Saskatchewan, consist primarily of extra-crater pyroclastic deposits which are interstratified with Lower Cretaceous (Albian and Cenomanian) marine, marginal marine and continental sediments. Approximately 70 individual kimberlite occurrences have been documented. The Star Kimberlite, occurring at the southeastern end of the main Fort à la Corne trend, has been identified as being of economic interest, and is characterized by an excellent drill core database. Integration of multi-disciplinary data-sets has helped to refine and resolve models for emplacement of the Star Kimberlite. Detailed core logging has provided the foundation for sedimentological and volcanological studies and for construction of a regionally consistent stratigraphic and architectural framework for the kimberlite complex. Micropaleontologic and biostratigraphic analysis of selected sedimentary rocks, and U-Pb perovskite geochronology on kimberlite samples have been integrated to define periods of kimberlite emplacement. Radiometric age determination and micropaleontologic evidence support the hypothesis that multiple kimberlite eruptive phases occurred at Star. The oldest kimberlite in the Star body erupted during deposition of the predominantly continental strata of the lower Mannville Group (Cantuar Formation). Kimberlites within the Cantuar Formation include terrestrial airfall deposits as well as fluvially transported kimberlitic sandstone and conglomerate. Successive eruptive events occurred contemporaneous with deposition of the marginal marine upper Mannville Group (Pense Formation). Kimberlites within the Pense Formation consist primarily of terrestrial airfall deposits. Fine- to medium-grained cross-stratified kimberlitic (olivine-dominated) sandstone in this interval reflects reworking of airfall deposits during a regional marine transgression. The location of the source feeder vents of the Cantuar and Pense kimberlite deposits has not been identified. The youngest and volumetrically most significant eruptive events associated with the Star Kimberlite occur within the predominantly marine Lower Colorado Group (Joli Fou and Viking Formations). Kimberlite beds, which occur at several horizons within these units, consist of subaerial and marine fall deposits, the latter commonly exhibiting evidence of wave-reworking. Black shale-encased resedimented kimberlite beds, likely deposited as subaqueous debris flows and turbidites, are particularly common in the Lower Colorado Group. During its multi-eruptive history, the Star Kimberlite body is interpreted to have evolved from a feeder vent and overlying positive-relief tephra ring, into a tephra cone. Initial early Joli Fou volcanism resulted in formation of a feeder vent (˜200 m diameter) and tephra ring. Subsequent eruptions, dominated by subaerial deposits, partly infilled the crater and constructed a tephra cone. A late Joli Fou eruption formed a small (˜70 m diameter) feeder pipe slightly offset to the NW of the early Joli Fou feeder vent. Deposits from this event further infilled the crater, and were deposited on top of early Joli Fou kimberlite (proximal to the vent) and sediments of the Joli Fou Formation (distal to the vent). The shape of the tephra cone was modified during multiple marine transgression and regression cycles coeval with deposition of the Lower Colorado Group, resulting in wave-reworked kimberlite sand along the fringes of the cone and kimberlitic event deposits (tempestites, turbidites, debris flows) in more distal settings.

Zonneveld, John-Paul; Kjarsgaard, Bruce A.; Harvey, Shawn E.; Heaman, Larry M.; McNeil, David H.; Marcia, Kirsten Y.

2004-09-01

257

Intrusive origin of the Sudbury Igneous Complex: Structural and sedimentological evidence  

NASA Technical Reports Server (NTRS)

In recent years, many geoscientists have come to believe that the Sudbury event was exogenic rather than endogenic. Critical to a recent exogenic hypothesis is the impact melt origin of the Sudbury Igneous Complex (SIC). Such origin implies that the SIC was emplaced before deposition of the Whitewater Group, in contrast to origins in which the SIC postdates the lithification of the Onaping Formation. Structural and sedimentological evidence is summarized herein that supports an intrusion of the SIC after lithification of all Whitewater Group strata, and conflicts with the hypothesis advanced by other researchers.

Cowan, E. J.; Schwerdtner, W. M.

1992-01-01

258

Application of sedimentological studies in the reservoir geological modeling of the Al Huwaisah Field, Oman  

SciTech Connect

A reservoir-geological review has been carried out on the Al Huwaisah oil field (North Oman) and a geological model has been developed. Mainly based on sedimentological studies of core material, the distribution of the different lithofacies types of the reservoir formation has been reconstructed and the depositional environment interpreted. The resulting geological model shows analogies with the sedimentation pattern on Recent carbonate shoals in the Arabian Gulf. This, in combination with the good correlation between lithofacies types and reservoir properties, allows prediction of the different reservoir units and hence optimisation of the future development of the field.

Baumann, A.

1983-03-01

259

Use of ground-penetrating radar for 3-D sedimentological characterization of clastic reservoir analogs  

SciTech Connect

Clastic reservoir analogs based on 2-D outcrop studies provide valuable definitions of geometric and petrophysical heterogeneities at interwell scales. Integration of 3-D ground-penetrating radar (GPR) surveys with sedimentological and stratigraphic data provides information on the internal heterogeneities of sedimentary sequences at scales that allow dissection of the 3-D anatomy of clastic depositional systems. Two 3-D GPR data volumes were acquired in the Ferron sandstone of east-central Utah. The data show prominent lenticular features, a variety of lithologies, and structural elements such as channels and shale drapes that match well with those seen at the same stratigraphic levels in adjacent cliff faces.

McMechan, G.A.; Szerbiak, R.B. [Univ. of Texas, Richardson, TX (United States). Center for Lithospheric Studies] [Univ. of Texas, Richardson, TX (United States). Center for Lithospheric Studies; Gaynor, G.C. [Reservoir Geosystems, Inc., Dallas, TX (United States)] [Reservoir Geosystems, Inc., Dallas, TX (United States)

1997-05-01

260

Carbon isotope (13 Ccarb) stratigraphy of the LowerMiddle Ordovician  

E-print Network

Ordovician Biodiversification Event (GOBE) New stable carbon isotope data (13 Ccarb) from LowerCarbon isotope (13 Ccarb) stratigraphy of the Lower­Middle Ordovician (Tremadocian February 2014 Keywords: Carbon isotopes Ordovician Chemostratigraphy Carbon cycling Great Basin Great

Saltzman, Matthew R.

261

CARBON ISOTOPE STRATIGRAPHY AND DIAGENESIS OF PENNSYLVANIAN (DESMOINESIAN-MISSOURIAN) CARBONATES IN EAST-CENTRAL IDAHO  

E-print Network

Carbon isotope stratigraphy of carbonate sediments is instrumental in examining major perturbations in the global carbon cycle and in correlating strata. However, the primary isotopic signal recorded in these sediments can vary with depositional...

Wood, Stephanie

2011-05-10

262

Deep Wilcox structure and stratigraphy in Fandango field area, Zapata County, Texas  

Microsoft Academic Search

The Fandango field in Zapata County, Texas, is a new deep Wilcox trend extension. The deep Wilcox sands are commonly found at depths of 15,000 to 20,000 ft (4,500 to 6,100 m). Enough well log and seismic control now exists to make an accurate integrated interpretation of regional deep Wilcox structure and stratigraphy. Deep Wilcox structure and stratigraphy are controlled

1983-01-01

263

Deep Wilcox structure and stratigraphy in Fandango field area, Zapata County, Texas  

Microsoft Academic Search

The Fandango field in Zapata County, Texas, is a new deep Wilcox trend extension. The deep Wilcox sands are commonly found at depths of 15,000-20,000 ft (4500-6100 m). Enough well log and seismic control exists to make an accurate integrated interpretation of regional deep Wilcox structure and stratigraphy. Deep Wilcox structure and stratigraphy are controlled by regionally extensive shale anticlines.

1984-01-01

264

Late Cenozoic seismic stratigraphy and structure of the northern Gulf of Alaska  

E-print Network

LATE CENOZOIC SEISMIC STRATIGRAPHY AND STRUCTURE OF THE NORTHERN GULF OF ALASKA A Thesis ROCKY RAY RODEN Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... August 1980 Major Subject: Oceanography I ATE CENOZOIC SEISIIIC STRATIGRAPHY AND STRUCTURE OF THE NORTHERN GULF OF ALASKA A Thesis by ROCKY RAY RODEN Approved as to style and content by: ~lle~mbe r (He ot Departne~nt August 1980 ABSTRACT Late...

Roden, Rocky Ray

2012-06-07

265

Knob fields in the Terra Cimmeria/Terra Sirenum region of Mars: Stratigraphy, mineralogy and morphology  

NASA Astrophysics Data System (ADS)

We investigate the stratigraphy, morphology and mineralogy of five major knob fields in the region between Terra Cimmeria and Terra Sirenum on Mars based on HRSC, CTX, MOC and HiRISE imagery together with hyperspectral data from CRISM. The knob fields comprise Ariadnes Colles, Atlantis Chaos and Gorgonum Chaos and further, unnamed fields of mounds. They have been mapped in previous studies as Hesperian or Amazonian units and are located within the shoreline of the proposed "Eridania lake", the putative source of Ma'adim Vallis. The mounds contain Mg/Fe-bearing phyllosilicates and locally Al-rich phyllosilicates. Our geological mapping shows that the knob fields have a late Noachian age, which indicates later phyllosilicate formation than typically observed on Mars. The knob fields formed by alteration of the "Electris deposit", an airfall deposit possibly rich in basaltic glass (Grant, J.A., Schultz, P.H. [1990]. Icarus 84, 166-195), in local depressions, possibly in the Eridania lake. The spectroscopic detection of phyllosilicates here may indicate that liquid water persisted longer in this region than elsewhere on Mars. The knob fields are embayed by the Hesperian ridged plains. Numerous valleys carve into the ridged plains and document that the aqueous history of this region continued into the Hesperian and Amazonian. The study area is traversed by the Sirenum Fossae. These graben appear to post-date the aqueous activity in the study area except in the Gorgonum basin, where a lake developed after their formation.

Wendt, Lorenz; Bishop, Janice L.; Neukum, Gerhard

2013-07-01

266

Stratigraphy and paleontology of Lower Permian rocks north of Cananea, northern Sonora, Mexico  

NASA Astrophysics Data System (ADS)

Lower Permian carbonate and overlying red bed clastic rocks are present in a 2 km 2 stratigraphic window in the vicinity of Rancho La Cueva, Santa Cruz sheet (scale 1:50,000), northern Sonora, Mexico. This exposure lies unconformably beneath predominantly intermediate Upper Cretaceous volcanics yielding 40Ar/ 39Ar ages of 73.4±0.18 and 71.1±0.35 Ma. The lower part of the Permian succession consists of light- to medium-gray colored limestones of the Colina Limestone, with a minimum thickness of 235 m. Sedimentary features suggest shallow water, slightly restricted depositional environments. Although lacking observable fossils for the most part, two intervals of richly fossiliferous, silicified shell beds are present near the base and top of the Colina Limestone. The lower fauna consist mostly of gastropods and bivalves. The presence of a new microdomatid gastropod species, Glyptospira sonorensis n. sp., close to Glytospira arelela Plas, suggests a late Wolfcampian age for this horizon. The upper fauna are predominantly molluscan dominated (gastropods and bivalves), but some brachiopods (productids and the rhynchonellid genus Pontisia) are also present. Gastropod genera include Bellerophon, Warthia, Euomphalus (represented by the species, Euomphalus kaibabensis Chronic), Baylea, Worthenia, Naticopsis, Goniasma, Kinishbia, Cibecuia, and Glyptospira. The gastropods suggest a Leonardian (late Early Permian) age for this horizon, and many of the species have previously been recorded from the Supai Group and Kaibab Formation of northern and central Arizona. The Colina Limestone is conformably overlain by 11.2 m of light-gray lime mudstone and dolostone, assigned here to the Epitaph Dolomite, which in turn is succeeded by 58.8 m of red-colored sandstone and gray lime mudstone, assigned here to the Scherrer Formation. This Lower Permian succession is significant because it further strengthens the stratigraphic ties of southeastern Arizona rocks with those of northern Sonora and confirms the presence of North American cratonal stratigraphy in the northern part of the state of Sonora, Mexico.

Blodgett, Robert B.; Moore, Thomas E.; Gray, Floyd

2002-09-01

267

Sedimentology and diagenesis of windward-facing fore-reef calcarenites, Late Pleistocene of Barbados, West Indies  

SciTech Connect

Late Pleistocene reef terraces in southeastern Barbardos developed extensive fore-reef sand facies during deposition in response to high-energy windward-facing conditions. Sedimentology and diagenesis of these deposits illustrate significant contrasts with previous studies from the leeward west coast. These calcarenites are dominantly skeletal packstones with less common grainstones and wackestones present. The fore-reef sand facies occurs within progradational reef sequences, being conformably overlain by deep-water head coral facies. Medium-bedded, laterally continuous sand sheets retain original depositional slopes, dipping seaward at 10/degrees/-15/degrees/. These fore-reef deposits, in places, are over 30 m thick (average 20 m) and developed rapidly during late Pleistocene glacio-eustatic sea level highstands. Sedimentation rate ranges from 2 to 5 m/1000 years. Areal extent of fore-reef calcarenites in southeastern Barbados is estimated to be 8-10 km/sup 2/. Lithologically, the packstones are composed of an abundance of coralline red algae and the benthic foraminifer Amphistegina sp. Other volumetrically significant allochems include echinoids, mollusks, rhodoliths, peloids, and micritized grains. Micrite in the wackestone and packstone lithologies is likely derived from intense physical/mechanical abrasion of shoal-water reef facies. Diagenesis of these lithologies reflects a complex interplay of meteoric, mixing zone, and marine environments as a result of glacio-eustasy. Differences in diagenetic character are derived from differences in terrace ages, terrace geometry, a paleotopographic control on meteoric ground-water distribution, and high-energy coastal conditions. Diagenetic fabrics include equant, blocky meteoric phreatic calcite; limpid dolomite of mixing zone origin: and peloidal and isopachous fibrous cements from marine precipitation.

Humphrey, J.D.; Kimbell, T.N.

1989-03-01

268

Proposition curve: A tool for reservoir modeling and for improvement of sedimentological interpretations  

SciTech Connect

The IFP and Center of Geostatistics of Paris School of Mines have been working on reservoir characterization modeling since 1986. Emphasis has been placed upon the acquisition of geological data from outcrops and definition of the pertinent parameters that can be quantified which will constrain the simulations. It has been demonstrated that detailed sequence and cyclostratigraphy studies are necessary in order to provide the boundaries of the reservoir units, horizontal reference level used for computations, and a sequential ordering of lithofacies. Mathematical tools have also been created. Two quantitative parameters of primary importance for modeling are proportion curves of lithofacies and variograms. In the development of an accurate reservoir model, two points should be emphasized. (1) The quality of the preliminary sedimentological study is often inadequate for a quantitative modeling and limited data creates correlation problems. (2) Proportion curves are very powerful for refining the sedimentological interpretation and/or testing different hypotheses of correlation. These points will be illustrated with proportion curves computed mainly in fluvial or fluvial to deltaic environment from both outcrop analogs and subsurface field data.

Ravenne, C. (Institut Francais du Petrole, Rueil-Malmaison (France)); Galli, A.

1993-02-01

269

Integrated sequence stratigraphy of the postimpact sediments from the Eyreville core holes, Chesapeake Bay impact structure inner basin  

USGS Publications Warehouse

The Eyreville core holes provide the first continuously cored record of postimpact sequences from within the deepest part of the central Chesapeake Bay impact crater. We analyzed the upper Eocene to Pliocene postimpact sediments from the Eyreville A and C core holes for lithology (semiquantitative measurements of grain size and composition), sequence stratigraphy, and chronostratigraphy. Age is based primarily on Sr isotope stratigraphy supplemented by biostratigraphy (dinocysts, nannofossils, and planktonic foraminifers); age resolution is approximately ??0.5 Ma for early Miocene sequences and approximately ??1.0 Ma for younger and older sequences. Eocene-lower Miocene sequences are subtle, upper middle to lower upper Miocene sequences are more clearly distinguished, and upper Miocene- Pliocene sequences display a distinct facies pattern within sequences. We recognize two upper Eocene, two Oligocene, nine Miocene, three Pliocene, and one Pleistocene sequence and correlate them with those in New Jersey and Delaware. The upper Eocene through Pleistocene strata at Eyreville record changes from: (1) rapidly deposited, extremely fi ne-grained Eocene strata that probably represent two sequences deposited in a deep (>200 m) basin; to (2) highly dissected Oligocene (two very thin sequences) to lower Miocene (three thin sequences) with a long hiatus; to (3) a thick, rapidly deposited (43-73 m/Ma), very fi ne-grained, biosiliceous middle Miocene (16.5-14 Ma) section divided into three sequences (V5-V3) deposited in middle neritic paleoenvironments; to (4) a 4.5-Ma-long hiatus (12.8-8.3 Ma); to (5) sandy, shelly upper Miocene to Pliocene strata (8.3-2.0 Ma) divided into six sequences deposited in shelf and shoreface environments; and, last, to (6) a sandy middle Pleistocene paralic sequence (~400 ka). The Eyreville cores thus record the fi lling of a deep impact-generated basin where the timing of sequence boundaries is heavily infl uenced by eustasy. ?? 2009 The Geological Society of America.

Browning, J. V.; Miller, K. G.; McLaughlin, Jr. , P. P.; Edwards, L. E.; Kulpecz, A. A.; Powars, D. S.; Wade, B. S.; Feigenson, M. D.; Wright, J. D.

2009-01-01

270

Extended stratigraphy, palynology and depositional environments record the initiation of the Himalayan Gyirong Basin (Neogene China)  

NASA Astrophysics Data System (ADS)

Here we report new sedimentological and paleontological data from a 603.5 m thick Neogene sequence (Woma section) in the Gyirong Basin, a basin induced by east-west extension in the Himalayas of southern Tibet. We document the conglomeratic Danzengzhukang Formation, at the base of the section, and the overlying finer grained Woma Formation that includes a Hipparion fauna. Based on stratigraphic correlations and earlier thermochronology and magnetostratigraphic results, we bracket the depositional age of this section between 10.8 Ma and 1.7 Ma. Lithology, paleo-current directions and provenance analysis, together with palynological and paleontological data, have revealed three depositional environments for the deposition of the studied section. (1) Alluvial-fan to braided river environments with ESE transport directions (Danzengzhukang Formation, <10.8 to ˜7.2 Ma) were associated with a warm and humid coniferous- and broad-leaved mixed forest. (2) Lacustrine dominated conditions (Lower Woma Formation, ˜7.2 to 3.2 Ma) with WSW transport directions were associated with locally warm and humid environments in the low-lying areas while input from a new source area suggests the presence of a high-altitude, cold and arid deciduous coniferous-leaved forests. (3) A fan delta dominated environment (Upper Woma Formation, 3.2 to >1.7 Ma) with increased denudation and WSW paleo-currents was associated with a deciduous coniferous and broad-leaved mixed forest that suggests an increase in climate variability. Our data indicate that the Gyirong Basin was under overall warm and humid conditions throughout most of its history, in agreement with high-resolution oxygen and carbon isotope data collected from the same section (this issue). We interpret our warm climate in the Gyirong Basin to reflect the prevalence of the monsoonal influence and the distal pollen sources to result from orographic effects.

Xu, Ya-Dong; Zhang, Ke-Xin; Wang, Guo-Can; Jiang, Shang-Song; Chen, Fen-Ning; Xiang, Shu-Yuan; Dupont-Nivet, Guillaume; Hoorn, Carina

2012-01-01

271

The INTIMATE event stratigraphy and recommendations for its use  

NASA Astrophysics Data System (ADS)

The North Atlantic INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) group has previously recommended an Event Stratigraphy approach for the synchronisation of records of the Last Termination using the Greenland ice core records as the regional stratotypes. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. In addition to presenting the updated event stratigraphy, we make a series of recommendations on how to refer to these periods in a way that promotes unambiguous comparison and correlation between different proxy records, providing a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is a part of a manuscript under review for publication in Quaternary Science Reviews. Author team: S.O. Rasmussen, M. Bigler, S.P.E. Blockley, T. Blunier, S.L. Buchardt, H.B. Clausen, I. Cvijanovic, D. Dahl-Jensen, S.J. Johnsen, H. Fischer, V. Gkinis, M. Guillevic, W.Z. Hoek, J.J. Lowe, J. Pedro, T. Popp, I.K. Seierstad, J.P. Steffensen, A.M. Svensson, P. Vallelonga, B.M. Vinther, M.J.C. Walker, J.J. Wheatley, and M. Winstrup (deceased).

Rasmussen, Sune O.

2014-05-01

272

Stratigraphy of Phyllosilicates and Sulfates in Northern Meridiani Planum, Mars  

NASA Astrophysics Data System (ADS)

The Meridiani Planum region on Mars is currently being explored by the Mars Exploration Rover Opportunity, and multiple landing sites for the upcoming Mars Science Laboratory (MSL) have been proposed in the region. Northern Meridiani is characterized in part by expanses of exposed light-toned layered rock (formerly known as "etched terrain"). We have generated new regional mosaics of Meridiani Planum data from the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) near-IR imaging spectrometer on the Mars Express orbiter and have used them to map spectral parameters that are indicative of hydrated minerals, sulfates, and phyllosilicates. Our maps are consistent with though not identical to previous OMEGA maps of this region. They reveal widespread (thousands of km2) evidence for hydration in the Meridiani light-toned layered rock (indicated by an absorption band at 1.9 microns). Sulfates, indicated by a decrease in reflectivity at 2.4 microns, are also apparent in our OMEGA mosaics, and are most clearly detected in a specific ~130 km × 30 km valley in the light-toned layered rock, near 2°N, 0.4°W. We also detect phyllosilicates in small (several km2) isolated patches of the light-toned layered rock. Of particular interest is a phyllosilicate detection in the light-toned layered rock roughly 60 km southwest of the sulfate-bearing valley. This phyllosilicate detection has not been reported in previous OMEGA maps of the region. The phyllosilicates occur ~300 m higher in elevation than the floor of the sulfate-bearing valley. If both the phyllosilicates and sulfate detections are representative of bulk bedrock, this may indicate that the phyllosilicates are stratigraphically younger than the sulfates. Alternatively, it is possible that the sulfates and/or the phyllosilicates were not deposited with the bedrock but are the result of subsequent alteration, or have been transported to their current location by aeolian or fluvial processes. Finally, it is possible that in the Meridiani region, phyllosilicates and sulfates were forming concurrently at some points in the past. To test the hypothesis that the phyllosilicates are stratigraphically younger than the sulfates in this region, we are examining high resolution images from the Mars Orbital Camera (MOC), the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) and determining the tilt and stratigraphy of the sulfate- bearing valley, the phyllosilicate-bearing regions, and the surrounding terrain. This investigation will be supplemented by Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) observations of the same region. Wherever possible, we will correlate composition with morphology to develop a more complete understanding of the stratigraphy in Northern Meridiani Planum.

Anderson, R. B.; Bell, J. F.

2008-12-01

273

Late Quaternary Provenance and Flow Regime Reconstruction through Sedimentologic and Geochemical Evidence from the Bering/Chukchi Seas  

NASA Astrophysics Data System (ADS)

The last 20 kyr have been marked by great changes in the Arctic, as the Laurentide Ice Sheet melted and led to the submergence of the Bering Land Bridge and the re-opening of the Bering Strait (BS). The BS is a narrow connection (about 85 km wide) between the Arctic and Pacific Oceans averaging less than 50 m in depth, with present-day flow of seawater northward through the BS, from the Pacific to the Arctic. This flow is of vital importance to global ocean circulation through its role in formation and stability of North Atlantic Deep Water (NADW). An open BS is believed to speed dispersal of North Atlantic freshwater anomalies, both by keeping thermohaline circulation strong, and through reversals of flow through the BS when the North Atlantic is hosed with freshwater. When the BS is closed, these anomalies cannot efficiently dissipate and thermohaline circulation is weakened, which is considered a factor in climate perturbations outside of orbital forcing. Given the period of flux and transition in the Arctic following the Last Glacial Maximum (LGM), the paleoceanographic history of the Bering and Chukchi Seas post-LGM, is important to an understanding of Arctic Ocean circulation, and consequent climate impacts. Today the Arctic is in a period of rapid change, multi-year sea ice is disappearing, and the continuation of climatic stability of the Holocene appears to be at an end. Comprehension of the functioning of the Arctic as a dynamic system is essential to predict future response of the system to change, such as seawater salinity-density changes, lowered sea and land albedo, and rising temperatures. Changes in BS throughflow intensity and direction during deglaciation and submergence of the Bering Land Bridge are proposed and supported in modeling simulations, and are thought to occur during millennial-scale climate changes. We have conducted a coupled sedimentological and geochemical investigation of a suite of marine sediment cores from the Bering and Chukchi Seas. Elemental, isotopic, and grain size shifts correspond to changes in sediment routing, identifying changes in the magnitude and direction of throughflow in the BS. Major and trace element geochemistry spanning the past ~30 kyr was derived using an ITRAX XRF core scanner. Age control is well established by previous studies for a majority of the cores, primarily radiocarbon dates on diatoms. Elemental XRF data indicate significant change during the Bølling-Allerød warming around 15 kyr, and the opening of the BS at 11 kyr. During both of these periods there is a drop in Ti, Fe, K, and Ba with a corresponding rise in Cl, Ca, and Br. These data, in concert with the other sedimentologic data, infer shifts in paleo-flow conditions and sediment provenance during this time period. A key goal is the identification of how variations in geochemical properties correspond to bulk biogeochemical or biomarker variability, in comparison to sea ice proxies. The data being collected will add to a growing understanding of the Arctic as a dynamic system and answer questions concerning the post-glacial and Holocene evolution of changes that took place across the marine portion of the Bering Land Bridge.

Pelto, B. M.; Brigham-Grette, J.; Kocis, J. J.; Petsch, S.

2013-12-01

274

INSIDE: SEDIMENTATION ACROSS THE TIDAL-FLUVIAL TRANSITION IN THE LOWER FRASER RIVER,  

E-print Network

documents this evidence based on paleontology, sedimentology, sequence stratigraphy, mineralogy, isotope Sedimentology and Stratigraphy, held in El Paso, Texas in April of 2010. The papers presented in this volume

Venditti, Jeremy G.

275

Sedimentology, dating and palaeoclimatic interpretation of A 76.3 ka record from Lago Grande di Monticchio, southern Italy  

Microsoft Academic Search

Detailed sedimentological and microstratigraphical investigations of lacustrine sediments from Lago Grande di Monticchio (southern Italy) provide a time scale based on rates of sedimentation obtained from annual laminations. Although not annually laminated throughout, a time scale covering the last 76.3 ka is available by interpolation of sedimentation rates. Results of this chronology agree with radiocarbon dates, and with ArAr dates

Bernd Zolitschka; Jörg F. W. Negendank

1996-01-01

276

Geotechnical and sedimentological investigations of deep-sea sediments from a manganese nodule field of the Peru Basin  

Microsoft Academic Search

Deep-sea mining of manganese nodules will significantly modify the surface layer of deep sea. Surface sediments are mechanically disturbed, and a cloud of sediment particles suspended and re-deposited. Assessment of sedimentological and soil mechanical characteristics of undisturbed top layer sediments from a manganese nodule field of the Peru Basin are necessary to provide baseline data for soil mechanical estimations and

Bernd Grupe; Hermann J Becker; Horst U Oebius

2001-01-01

277

Implications of sedimentological studies for environmental pollution assessment and management: Examples from fluvial systems in North Queensland and Western Australia  

NASA Astrophysics Data System (ADS)

Sedimentology is of increasing importance in environmental research, particularly environmental pollution studies, where past trends in environmental processes need to be combined with data on present conditions to predict likely future changes—the past and present as a key to the future. Two examples are used to illustrate the role of sedimentology in assessing the influence of major processes on the transport, accumulation, deposition and modification of contaminants in fluvial/estuarine systems and in developing environmental management plans. Example 1 shows that when assessing nutrient behaviour in fluvial/estuarine depositional settings, it is important to examine the partitioning of phosphorus between grain size fractions to evaluate the sedimentological processes which control the dispersion and trapping of these contaminants. Example 2 shows that in studies of anthropogenic metal inputs to modern depositional settings, lateral and stratigraphic trends in sediment texture and mineralogy should be examined, in addition to trends in metal loads and evaluation of the prevailing physical, chemical and biological processes that may influence metal mobility and dispersion. Clearly, basic sedimentological data should form part of any assessment of potentially contaminated sites and part of investigations into the dispersion and trapping of contaminants in fluvial systems. These data are also required for rational environmental management to ensure that planning decisions are compatible with natural environmental constraints.

Eyre, Bradley; McConchie, David

1993-05-01

278

Assessing the interplay of tectonics, sedimentology and lithology in coastline development of Puerto Rico using a GIS  

Microsoft Academic Search

The authors used a GIS to characterize the coastline morphology of Puerto Rico at different length scales as a function of lithology, sedimentology, and tectonics in order to assess the contribution of each to coastline development. Independent variables considered include orientation and density of mapped onshore faults and geology. Puerto Rico was divided into four coastline segments: north, south, east,

D. Torres-Pulliza; Pamela E. Jansma; Glen S. Mattioli

2000-01-01

279

Geology and Hydrogeology of Carbonate Islands. Developments in Sedimentology 54 edited by H.L. Vacher and T. Quinn  

E-print Network

Geology and Hydrogeology of Carbonate Islands. Developments in Sedimentology 54 edited by H, with a mean annual temperature of ~26°C. Tectonic and geologic setting The northeastern margin that the present tectonic regime of the region reflects a change in Caribbean Plate motion from a northerly

González, Luis A.

280

The Absolute Dating Potential of Proximal-Distal Tephra Correlations in an Aegean Marine Stratigraphy (Core LC21).  

NASA Astrophysics Data System (ADS)

Quaternary marine stratigraphies frequently suffer from poor absolute age control. Radiocarbon dating is intuitively the most appropriate technique for most marine stratigraphies, but its application is limited to the last 50ka or so by the decay rate of carbon. There are also uncertainties related to reservoir effects and the calibration of radiocarbon time to real time. However, precise dating and correlation of marine cores is essential to understand the timing and spatial relationships of the valuable environmental records they preserve. Here we demonstrate the potential of both visible and "invisible" micro-tephra layers to precisely date an important marine environmental record (Core LC21 from the Southern Aegean Sea). This is done by geochemically correlating the distal marine tephra layers to proximal volcanic deposits from Italy, Greece and Turkey. We use both Major Element (EPMA- Oxford Archaeology) and Trace Element (LA-ICP-MS, Royal Holloway Earth Sciences) analyses on individual tephra shards to determine the source of the tephra, and to make the correlations to explosive eruptive events. The most precise date (14C, 39Ar:40Ar or U-Th) from the event's proximal deposit is then imported into the equivalent distal tephra found in the marine core. Many of these distal "micro-tephras" were previously undetected by standard core logging techniques such as visual stratigraphy or scanning XRF. The extent and potential application of these tephras is now being realised. This study will provide the first direct (same core) and independent, absolute chronological markers for sapropels S3, S4 and S5, three major anoxic events found in the Eastern Mediterranean. In addition, the major and trace element geochemistry will be used to robustly correlate three marine cores spanning the Mediterranean. This work forms the Marine Tephrostratigraphy component (Work Package 5) of the UK Natural Environment Research Council (NERC) consortium project "RESET" (Response of Humans to Abrupt Environmental Transitions). In collaboration with a number of European research teams, the programme aims to construct a secure chronological framework for assessing the timing and effects of rapid environmental changes during the late Quaternary. See http://c14.arch.ox.ac.uk/reset/embed.php?File=index.html

Satow, Christopher; Lowe, John; Rohling, Eelco; Blockley, Simon; Menzies, Martin; Grant, Katharine; Smith, Vicki; Tomlinson, Emma

2010-05-01

281

Influence of mechanical stratigraphy and kinematics on fault scaling relations  

NASA Astrophysics Data System (ADS)

In order to document effects of mechanical anisotropy, fault geometry, and structural style on displacement-length ( D-L) scaling relations, we investigated fault dimensions in the lithologically heterogeneous Monterey Formation exposed along Arroyo Burro Beach, California. The faults, which range in length from several centimeters to several meters, group into two populations: small faults confined to individual mudstone beds, and larger faults that displace multiple beds and often merge into bedding plane detachments. Whereas a linear correlation exists between displacement and length for small faults, displacement across large faults is independent of length. We attribute this deviation from scale-invariance to a combination of geologic factors that influence fault growth once faults extend beyond the confines of mudstone beds. Propagation of large faults across higher moduli opal-CT porcellanite leads to a reduction in DL, as does the development of drag folds. Further scatter in DL occurs when fault tips splay as they approach detachments. Large faults eventually merge into bedding plane detachments, which originally formed due to flexural slip folding. Extremely high DL ratios are recorded for these merged faults as they accommodate block rotation within a simple shear zone. Thus, both mechanical stratigraphy and the temporal evolution of fault systems can lead to a breakdown in fault scaling relations thought to characterize isolated fault growth in a homogeneous medium.

Gross, Michael R.; G´rrez-Alonso, Gabriel; Bai, Taixu; Wacker, Michael A.; Collinsworth, Kevin B.; Behl, Richard J.

1997-02-01

282

SHARAD radar stratigraphy of the Martian North Pole  

NASA Astrophysics Data System (ADS)

SHARAD (SHAllow RADar) is a nadir looking synthetic aperture subsurface sounding radar and altimeter provided by the Italian Space Agency (ASI) to NASA's Mars Reconnaissance Orbiter (MRO). The primary objective of SHARAD is the investigation of the subsurface at shallow depth to detect geological signatures for water reservoirs. The Mars polar regions and their ice caps are among the highest priority targets for SHARAD. In its first several months of data acquisition, SHARAD made many successful observations of the Martian north pole, detecting the diverse stratification of the polar layer deposits (NPLD) down to hundreds of meters. Some spacecraft-rolled observations resulted in increased performance, allowing identification of even more complex stratigraphy in the NPLD and variable depth of the basal unit. One major north polar campaign of SHARAD observations targeted the Gemina Lingula region of Mars. In addition to establishing the context for these observations, this paper presents a detailed reconstruction of the subsurface layers as a function of location and geometrical setting based on several crossing groundtracks above Gemina Lingula. This allows a three dimensional view of the sequences revealed by the radar to be compared with surface information. Moreover, these orbit crossovers permit the systematic removal of clutter and noise, yielding more precise measurements of the subsurface layer depths.

Biccari, D.; Marinangeli, L.; Cutigni, M.; Giacomoni, E.; Fuga, O.; Russo, F.; Pettinelli, E.; Seu, R.; Putzig, N.; Holt, J.; Phillips, R.; Flamini, E.

2007-12-01

283

Relationships between sediment caliber and delta shoreline geometry and stratigraphy  

NASA Astrophysics Data System (ADS)

Recent morphodynamic modeling of non-uniform turbulent transport and deposition of sediment in a standing body of water devoid of tides and waves shows that sediment caliber plays a major role in determining the shapes, cumulative number of distributaries, and wetland areas of river-dominated deltas. In this study we introduce metrics for quantifying delta shoreline rugosity and foreset dip (clinoform) variability, and explore their variation with sediment caliber. Delta shoreline rugosity is calculated using the isoperimetric quotient, IP = 4 pi A / P2, where a circle has a value of one. Clinoform complexity is calculated using the uniformity test in circular statistics wherein clinoform dip direction uniformity is the sum of the deviations of dip azimuths from a theoretical uniform distribution. Analysis of fifteen simulated deltas shows that IP increases from 0.1 to 0.5 as the normalized shear stress for re-erosion of cohesive sediment, ?n, increases from 0.65 to 1. Clinoform dip azimuth uniformity decreases from 300 to 130 with increasing ?n. Preliminary analysis of data from outcrops of the Cretaceous Ferron Delta and ground penetrating radar data of the Pleistocene Weber and Brigham City Deltas are consistent with these trends. These results imply that changes in sediment caliber delivered to a deltaic coastal system will profoundly change its wetland area, bathymetric hypsometry, ecological function, and interior stratigraphy.

Burpee, A. P.; Slingerland, R. L.; Edmonds, D.

2011-12-01

284

Stratigraphy of the Jurassic system in northern Egypt  

SciTech Connect

A regional synthesis is presented of the stratigraphy of Jurassic strata in Egypt north of 30/degree/N, based on the study of about 80 wells and outcrops from northeastern Egypt. Almost all fossil groups have been investigated for biostratigraphic control. Published work on ammonite faunas from Gebel el Maghara (north Sinai) is integrated with extensive original work on palynofloras (and, to a lesser extent, ostracod/foraminiferal faunas) recovered from marine rocks in the subsurface. The recovery of rich dinocyst assemblages enables the recognition of a ten-fold zonation scheme, largely within the Middle-Late Jurassic sedimentary package. The upper limit of this package is marked by the Cimmerian erosional event; strata younger than Oxfordian are rarely preserved. Only east of 30/degree/E is significant sedimentation known to have occurred immediately prior to the major early Bajocian transgressive event. Thereafter mean sea level rose steadily. The Lower Triassic-Lower Jurassic sedimentary package is poorly understood, largely the result of scanty and ambiguous stratigraphic evidence. However, regional correlations suggest that only very thin earliest Jurassic (Hettangian ) clastic deposition succeeded a sequence of Upper Triassic carbonates and evaporites (Wadi en Natrun Formation) in the north. Arising from these studies is a standard lithostratigraphical scheme. The upper sedimentary package, the Gebel el Maghara Group, comprises three formations (Masajid, Khatatba, and Inmar) and seven members; new units are defined and old units redefined.

Keeley, M.L.; Shaw, D.; Forbes, G.A.

1988-08-01

285

Relationships between the internal stratigraphy and ice flow of the Greenland ice sheet  

NASA Astrophysics Data System (ADS)

Several studies of the Antarctic ice sheet have found correlations between the continuity of its internal stratigraphy and ice flow, leading to an improved understanding of the instability of fast-flowing regions. Here we use airborne radar data acquired across the whole of the Greenland ice sheet by CReSIS and NASA's Operation IceBridge campaigns to perform similar analyses, aiming to extend previous work exploring its northeastern sector. These data possess extensive internal stratigraphy throughout large sectors of the ice sheet. We examine the continuity of this stratigraphy using the recently developed "continuity index", which quantifies horizontal variability in the vertical gradient of the internally reflected power for each radar waveform. The continuity index is calculated using minimally processed radar data and can distinguish regions of continuous, discontinuous and absent stratigraphy. Our Greenland-wide continuity index is compared with modern ice-flow speeds to understand the long-term spatiotemporal variability in fast-flow conditions. We find correlations between areas of disrupted stratigraphy (low continuity index), fast ice flow, and apparent basal freeze-on.

Mabrey, A. N.; Catania, G. A.; MacGregor, J. A.; Young, S. K.; Rybarski, S. C.

2012-12-01

286

Sedimentological data indicate greater range of water depths for Costistricklandia lirata in the Southern Appalachians  

SciTech Connect

Two distinct horizons of the pentamerid brachiopod Costistricklandia lirata occur in the upper part of the Red Mountain Formation (Lower Silurian) in northern Alabama. Stratigraphic and sedimentologic characteristics of the rocks associated with the brachiopods suggest water depths of 15-150 m during times of low rates of terrigenous influx. Costistricklandid assemblages from the lower horizon are composed of extremely large individuals in association with a diverse population of large corals. They are interpreted to have lived in a protected environment. In an overlying horizon, costistricklandids occur in growth position at the base of a thick siliciclastic interval. These brachiopods lived in a storm-dominated environment and were buried in situ by the rapid influx of sediment associated with a passing storm.

Bolton, J.C. (Univ. of Tennessee, Knoxville (USA))

1990-08-01

287

Sedimentology of the Sbaa oil reservoir in the Timimoun basin (S. Algeria)  

SciTech Connect

In 1980 oil was discovered in the Timimoun portion of the Sbaa depression in Southern Algeria. Until that time this basin had produced only dry gas. Since the 1980 oil discovery, several wells have been drilled. Data acquired from these wells were analyzed and are presented in this study. The oil reservoir is located within a sandstone interval of the Sbaa formation which has an average thickness of 75 m. The Sbaa lies between the Tournaisian (Lower Carboniferous) silts and the Strunian (uppermost Devonian) shales and sandstones. The sedimentological study reveals that the Sbaa formation contains bimodal facies consisting of coarse siltstones and fine sandstones. The sequence has been attributed to a deltaic environment developed in the central part of the Ahnet basin. The sources of the associated fluvial system are from the surrounding In-Semmen, Tinessourine, and Arak-Foum-Belrem paleohighs. Thermoluminescence indicates the provenance for the Sbaa sands was the crystalline basement Cambrian and Ordovician sections.

Mehadi, Z. (Institute des Hydrocarbures et de la Chimique, Boumerdes (Algeria))

1990-05-01

288

Sedimentology models from activity concentration measurements: application to the "Bay of Cadiz" Natural Park (SW Spain).  

PubMed

A previous study on seabed sediments of the Bay of Cadiz (SW of Spain) enabled us to identify several relations between sedimentological variables and activity concentrations of environmental radionuclides such as (137)Cs, (226)Ra, (232)Th and (40)K. In this paper the study has been extended to a large neighbouring inter-tidal area in order to establish if the above mentioned models can be generalized. As a result we have determined that the measured activity concentrations are closely to the values predicted by the theoretical models (correlation coefficient range=0.85-0.93). Furthermore, the proposal model for granulometric facies as a function of activity concentrations of the abovementioned radionuclides provides for the sediments distribution a representation which agrees with the values of the tidal energy distribution obtained using numeric models calibrated with experimental data from current meters and water level recorders. PMID:19136180

Ligero, R A; Vidal, J; Meléndez, M J; Hamani, M; Casas-Ruiz, M

2009-03-01

289

First ERTS-1 results in southeastern France: Geology, sedimentology, pollution at sea  

NASA Technical Reports Server (NTRS)

Results obtained by four ERTS projects in southeastern France are summarized. With regard to geology, ERTS photos of Western Alps are very useful for tectonic interpretation because large features are clearly visible on these photographs even though they are often hidden by small complicated structures if studied on large scale documents. The 18-day repetition coverage was not obtained, and time-varying sedimentological surveys were impossible. Nevertheless, it was possible to delineate the variations of the shorelines in the Rhone Delta for a period covering the least 8,000 years. Some instances of industries discharging pollutant products at sea were detected, as well as very large anomalies of unknown origin. Some examples of coherent optical processing have been made in order to bring out tectonic features in the Alps mountains.

Fontanel, A.; Guillemot, J.; Guy, M.

1973-01-01

290

A martian case study of segmenting images automatically for granulometry and sedimentology, Part 1: Algorithm  

NASA Astrophysics Data System (ADS)

In planetary exploration, delineating individual grains in images via segmentation is a key path to sedimentological comparisons with the extensive terrestrial literature. Samples that contain a substantial fine grain component, common at Meridiani and Gusev at Mars, would involve prohibitive effort if attempted manually. Unavailability of physical samples also precludes standard terrestrial methods such as sieving. Furthermore, planetary scientists have been thwarted by the dearth of segmentation algorithms customized for planetary applications, including Mars, and often rely on sub-optimal solutions adapted from medical software. We address this with an original algorithm optimized to segment whole images from the Microscopic Imager of the Mars Exploration Rovers. While our code operates with minimal human guidance, its default parameters can be modified easily for different geologic settings and imagers on Earth and other planets, such as the Curiosity Rover’s Mars Hand Lens Instrument. We assess the algorithm’s robustness in a companion work.

Karunatillake, Suniti; McLennan, Scott M.; Herkenhoff, Kenneth E.; Husch, Jonathan M.; Hardgrove, Craig; Skok, J. R.

2014-02-01

291

Morpho-dynamics and sedimentology of confluences in gravelly braided rivers  

NASA Astrophysics Data System (ADS)

Confluences are important elements in braided rivers because they are points of channel convergence where sediment transport rates and bed scouring are maximized. Confluences control the formation of downstream bars and therefore may determine the overall morphology of braided rivers. Confluence migration and significant bed scour, confluences have a substantial influence on the geometry of braided river deposits. Prior research on confluences has focused on their equilibrium morphology and flow structure and has not assessed the amount of geometric change at a confluence nor addressed the link between confluence morpho-dynamics and sedimentology. The purpose of the thesis is to further our understanding of confluence behaviour in braided rivers and to link this directly to the geometry and sediment sorting of braided river deposits. This is done by focusing on the morpho-dynamic development and sediment sorting at 24 confluences observed in a physical-scale model of a gravelly braided river. The analysis uses high resolution, photogrammetrically-derived ortho-images, Digital Elevation Models (DEMs) and surface grain size maps using techniques developed and tested as part of the thesis. The analysis of a time series of DEMs, combined with overlays of grain size is a novel aspect of the research and allows direct, quantitative analysis of both confluence morpho-dynamics and the resulting deposits. While the static area of confluences in a river is instantaneously small (approximately 3%), their spatial influence is much greater as a result of confluence migration, accounting for approximately 20% of the active river area. Confluences tend to migrate about the same distance as the typical confluence-bifurcation spacing in braided rivers along a flow-parallel direction. Confluence mobility is strongly correlated with confluence depth, area, and length, though not with confluence width, suggesting that deeper and longer confluences may migrate further than small, shallow confluences. The shape of confluence deposits indicates that their static dimensions are roughly equivalent to those dimensions reported in the sedimentology literature. However, migration tends to increase the spatial area of confluence deposits by greater than 2 times their static area and therefore their depositional aspect ratios are similar to gravel sheets and bars. Most confluences erode to the minimum surface of the deposit, and the thickness of the deposit is defined by multiple migrating confluences. The incidence of confluence deposits is approximately 15% of the total river deposit. The sedimentology of the boundary surfaces of a braided river and at confluences suggests there is little difference in grain size populations between the lower and upper boundary surfaces. This finding challenges the conventional view of braided river deposits where a coarse lag is often deemed diagnostic of the basal scour surface of braided river deposits. Grain sorting patterns at a confluence are highly variable with no strong trend evident, indicating that current models of diagnostic grain sorting patterns at confluences are too simplified to fit reality. Keywords. braided rivers, morpho-dynamics, sedimentology, confluences, sediment sorting, photogrammetry, digital elevation models.

Gardner, James Tobias

292

Morphological and sedimentological characters of the East Sea (Japan Sea) continental margin  

NASA Astrophysics Data System (ADS)

Consecutive geophysical and geological surveys were conducted in the southwestern margin of the East Sea (Japan Sea) in Korea in order to investigate the complex patterns of morphological and sedimentological characters as well as to understand their relationship with various oceanographic agents. A total of 4,200 line-km seismic records and 172 samples were analyzed so that a series of maps could be made and compared. Based on the results it is revealed that the study area could be divided into five unique subenvironments according to slope changes and surface sediments; flat monotonous shelf (inner and outer), steep and irregular slope (upper and lower) and gentle basin plain. Tectonic movement, sea level change, earthquake, and regional current system are seemingly the major controlling factors to formulate the regional scale morphology and sediment distribution pattern.

Kim, Seong-Pil; Koo, Bon Young; Kong, Gee Soo; Um, Inkwon; Lee, Gwang Soo; Chung, Gong Soo; Choi, Jin-Yong

2014-05-01

293

Lithofacies, depositional environments, and regional stratigraphy of the lower Eocene Ghazij Formation, Balochistan, Pakistan  

USGS Publications Warehouse

A regional stratigraphic investigation of one of the most important coal-bearing lithostratigraphic units in Pakistan, the report includes sedimentologic observations taken from outcrops and measured sections, information derived from petrographic and paleontologic analyses, depositional interpretations, and descriptions of regional trends.

Johnson, Edward A.; Warwick, P.D.; Roberts, S.B.; Khan, I.H.

1999-01-01

294

Sedimentological and geochemical characterization of the Cretaceous strata of Calabar Flank, southeastern Nigeria  

NASA Astrophysics Data System (ADS)

An integrated sedimentological and geochemical evaluation has been carried out on the Cretaceous sediments of the Calabar Flank. This study is to characterize the provenance, depositional environments and hydrocarbon potentials. The techniques involved field descriptions, textural parameters, petrographic analysis and biostratigraphic studies using standard sedimentological methods. The geochemical studies involved the determination of major oxides and trace elements using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS); Total Organic Carbon (TOC) and Rock Eval Pyrolysis. Results show that sandstone from Awi Formation have elongation ratio ranging from 0.4b to 0.9, oblate-prolate index and maximum sphericity index range from 9.6 to 9.7 and 0.5 to 0.9 respectively. The sandstone units are arkosic and mineralogically immature (MI = 3); ZTR indexes range from 54.6% to 82.5%, with tourmaline, zircon, staurolite, garnet, apatite, augite and rutile grains being angular-sub-angular. This suggests nearness to source, and that Awi Formation was deposited in a fluvial environment. The limestone deposit of Mfamosing Formation is predominantly bioclastic consisting of algal stromatolites, oolitic and pelloidal grainstones/packstones with high carbonate content. The dark grey fissile shales of Nkporo and Ekenkpon Formations indicate deposition in quiet oxic and/or anoxic conditions. Average TOC suggests good source rocks. Predominance of Type III kerogen, Tmax and hydrocarbon source potential of Mfamosing, Ekenkpon, New Netim Marl and Nkporo Formations suggest marginal mature to mature source rocks deposited in shallow continental to open marine setting that some gas may have been generated. The sediments are derived from passive continental margin in plutonic humid palaeoclimatic setting of continental block province.

Boboye, O. A.; Okon, E. E.

2014-11-01

295

High-resolution seismic stratigraphy of the Galicia Bank Region and neighbouring abyssal plains (NW Iberian continental margin)  

Microsoft Academic Search

The high-resolution seismic stratigraphy of the Galicia Bank Region and adjacent deposits of the neighbouring Iberian and Biscay Abyssal Plains was included as part of the geological studies conducted in the area where the oil-tanker Prestige wreck is located. This seismic stratigraphy is characterized by five seismic units (5 to 1, from oldest to youngest) lying above an irregular acoustic

G. Ercilla; S. García-Gil; F. Estrada; E. Gràcia; A. Vizcaino; J. T. Váquez; S. Díaz; F. Vilas; D. Casas; B. Alonso; J. Dañobeitia; M. Farran

2008-01-01

296

Geoscience Curriculum Environmental Geoscience track Directed Electives: take one from each category  

E-print Network

Introduction to Geologic Structures (Fall) 4 GEOSCI 430 Sedimentology and Stratigraphy 3 GEOSCI 204 Geologic 3 GEOSCI 375 Principles of Geochemistry 3 GEOSCI 430 Sedimentology and Stratigraphy 3 Geobiology: GEOSCI 411 Energy Resources 3 GEOSCI 431 Sedimentology and Stratigraphy Lab 1 GEOSCI 455 Structural

Carlson, Anders

297

Geological Sciences 330 Fall 2007 Sedimentary Geology  

E-print Network

. Principles of sedimentology and stratigraphy. 4th edition. Prentice Hall, Upper Saddle River, NJ. 662 pp: Principles of Stratigraphy and Sedimentology (1) Week 2 10 Sept Sedimentary Particles: Weathering (13, 15 & 16) 28 Nov Integrated Stratigraphy and Sedimentology Lab 10: Well-log Interpretation Week 14

298

New Geoscience Curriculum Environmental Geoscience track Directed Electives: take one from each category  

E-print Network

GEOSCI 430 Sedimentology and Stratigraphy 3 GEOSCI 204 Geologic Evolution of the Earth 4 GEOSCI 627 Sedimentology and Stratigraphy 3 Geobiology GEOSCI 455 Structural Geology 4 GEOSCI 304 Geobiology 3 Geoscience as a Public Problem 3 Required: GEOSCI 411 Energy Resources 3 GEOSCI 431 Sedimentology and Stratigraphy Lab 1

Sheridan, Jennifer

299

Merguerian, Charles, 1984, Revised stratigraphy of the Manhattan Schist, New York City. Field and petrographic data indicate that the "type" Manhattan Schist of Manhattan Island  

E-print Network

Merguerian, Charles, 1984, Revised stratigraphy of the Manhattan Schist, New York City. Field of the stratigraphy is in progress. Merguerian, Charles, 1984, Revised stratigraphy of the Manhattan Schist, New York City (abs.): Empire State Geogram, v. 20, p. 28-29. Filename: CM1984.doc #12;

Merguerian, Charles

300

DESCRIPTIONS/STRATEGIES What can I do with this major?  

E-print Network

Sedimentology StructuralGeology Geophysics EconomicGeology Geomorphology Paleontology Fossil Energy Geologists. Minerals MiningGeology Mineralogy Geochemistry EconomicGeology Paleontology Stratigraphy Sedimentology) LANDSCAPE EnvironmentalGeology Sedimentology Hydrology Geomagnetism Earth Surface Dynamics Coastal & Marine

New Hampshire, University of

301

Acoustic stratigraphy of Bear Lake, Utah-Idaho: late Quaternary sedimentation patterns in a simple half-graben  

USGS Publications Warehouse

A 277-km network of high-resolution seismic-reflection profiles, supplemented with a sidescan-sonar mosaic of the lake floor, was collected in Bear Lake, Utah–Idaho, in order to explore the sedimentary framework of the lake's paleoclimate record. The acoustic stratigraphy is tied to a 120 m deep, continuously cored drill hole in the lake. Based on the age model for the drill core, the oldest continuously mapped acoustic reflector in the data set has an age of about 100 ka, although older sediments were locally imaged. The acoustic stratigraphy of the sediments below the lake indicates that the basin developed primarily as a simple half-graben, with a steep normal-fault margin on the east and a flexural margin on the west. As expected for a basin controlled by a listric master fault, seismic reflections steepen and diverge toward the fault, bounding eastward-thickening sediment wedges. Secondary normal faults west of the master fault were imaged beneath the lake and many of these faults show progressively increasing offset with depth and age. Several faults cut the youngest sediments in the lake as well as the modern lake floor. The relative simplicity of the sedimentary sequence is interrupted in the northwestern part of the basin by a unit that is interpreted as a large (4 × 10 km) paleodelta of the Bear River. The delta overlies a horizon with an age of about 97 ka, outcrops at the lake floor and is onlapped by much of the uppermost sequence of lake sediments. A feature interpreted as a wave-cut bench occurs in many places on the western side of the lake. The base of this bench occurs at a depth (22–24 m) similar to that (20–25 m) of the distal surface of the paleodelta. Pinch-outs of sedimentary units are common in relatively shallow water on the gentle western margin of the basin and little Holocene sediment has accumulated in water depths of less than 30 m. On the steep eastern margin of the basin, sediments commonly onlap the hanging wall of the East Bear Lake Fault. However, no major erosional or depositional features suggestive of shoreline processes were observed on acoustic profiles in water deeper than about 20–25 m.

Colman, S.M.

2006-01-01

302

Characterising and modelling regolith stratigraphy using multiple geophysical techniques  

NASA Astrophysics Data System (ADS)

Regolith is the weathered, typically mineral-rich layer from fresh bedrock to land surface. It encompasses soil (A, E and B horizons) that has undergone pedogenesis. Below is the weathered C horizon that retains at least some of the original rocky fabric and structure. At the base of this is the lower regolith boundary of continuous hard bedrock (the R horizon). Regolith may be absent, e.g. at rocky outcrops, or may be many 10's of metres deep. Comparatively little is known about regolith, and critical questions remain regarding composition and characteristics - especially deeper where the challenge of collecting reliable data increases with depth. In Australia research is underway to characterise and map regolith using consistent methods at scales ranging from local (e.g. hillslope) to continental scales. These efforts are driven by many research needs, including Critical Zone modelling and simulation. Pilot research in South Australia using digitally-based environmental correlation techniques modelled the depth to bedrock to 9 m for an upland area of 128 000 ha. One finding was the inability to reliably model local scale depth variations over horizontal distances of 2 - 3 m and vertical distances of 1 - 2 m. The need to better characterise variations in regolith to strengthen models at these fine scales was discussed. Addressing this need, we describe high intensity, ground-based multi-sensor geophysical profiling of three hillslope transects in different regolith-landscape settings to characterise fine resolution (i.e. < 1 m) regolith stratigraphy. The geophysics included: ground penetrating radar collected at a number of frequencies; multiple frequency, multiple coil electromagnetic induction; and high resolution resistivity. These were accompanied by georeferenced, closely spaced deep cores to 9 m - or to core refusal. The intact cores were sub-sampled to standard depths and analysed for regolith properties to compile core datasets consisting of: water content; texture; electrical conductivity; and weathered state. After preprocessing (filtering, geo-registration, depth correction, etc.) each geophysical profile was evaluated by matching the core data. Applying traditional geophysical techniques, the best profiles were inverted using the core data creating two-dimensional (2-D) stratigraphic regolith models for each transect, and evaluated using independent validation. Next, in a test of an alternative method borrowed from digital soil mapping, the best preprocessed geophysical profiles were co-registered and stratigraphic models for each property created using multivariate environmental correlation. After independent validation, the qualities of the latest models were compared to the traditionally derived 2-D inverted models. Finally, the best overall stratigraphic models were used in conjunction with local environmental data (e.g. geology, geochemistry, terrain, soils) to create conceptual regolith hillslope models for each transect highlighting important features and processes, e.g. morphology, hydropedology and weathering characteristics. Results are presented with recommendations regarding the use of geophysics in modelling regolith stratigraphy at fine scales.

Thomas, M.; Cremasco, D.; Fotheringham, T.; Hatch, M. A.; Triantifillis, J.; Wilford, J.

2013-12-01

303

Post-glacial stratigraphy for the Malin Basin (NW Ireland)  

NASA Astrophysics Data System (ADS)

The Irish National Seabed Survey mapped the Malin Shelf (NW Ireland) between 2003 and 2005 using multibeam and shallow seismic techniques. A total of 5 shallow cores limited to 6m length were taken between 2006 and 2008 in the deepest part of the Malin Basin. The region's bathymetry exhibits a strong glacial imprint from the last British-Irish Ice Sheet characterised by a variety of glacial morphologies. The shallow stratigraphy shows a pronounced LGM ice erosional surface cutting out the Stanton Formation, ranging from several meters around the basin's edges up to 50 m in the central part. Two distinct pre-LGM units are present in the records: the Jura and the Barra formations. The Barra Formation lies unconformably just above the LGM erosional surface thinning towards the west. The Jura Formation lies conformably above the Barra FM. Paleogene Igneous intrusions are present throughout the region influencing the basin geometry. Radiocarbon dating was performed on foraminifera assemblages extracted from one of the 3 m long cores. Dating indicates that the entire length consists of Holocene record. The sand on the surface of the core (0.1 mbsf) is 3 ka cal BP years old and the entire sandy unit (0.55 mbsf) accumulated over 4.6 ka cal BP. Change of lithology is coupled with drastic change in sedimentation rates. Nearly 40 cm of sediment accumulated over a period of only 300 years (4.9 ka cal BP at 1.0 mbsf). However, high sedimentation rates in this part of the shelf are not uncommon. The dating of 71/9 BGS borehole west of the Malin Shelf showed sedimentation rates of 0.75 m/ky in the first 6 meters (10 ky) followed by 3.5 m/ky in the next 30 m.

Monteys, Xavier; Kelleher, Brian; Szpak, Michal; Garcia-Gil, Soledad

2014-05-01

304

Stratigraphy, structure and mineralisation of the Akjoujt area, Mauritania  

NASA Astrophysics Data System (ADS)

The stratigraphy of the highly deformed and overthrust supracrustal rocks of the Akjoujt area consists of two sequences separated by an angular unconformity. A new stratigraphic framework has been proposed that is virtually the reverse of previously published schemes. The oldest recognisable supracrustal sequence consists of metabasalts overlain by banded iron formations and semipelitic and quartz-rich metasedimentary schists, for which the name Eizzene group has been proposed. This is overlain with angular unconformity by orthoquartzite followed by a suite of siliciclastic rocks, mafic to felsic volcaniclastic rocks, flows and banded iron formations. This well-layered sequence is overlain by poorly layered monotonous submarine metabasalts and coeval dolerites. All the rocks above the unconformity have been assigned to the newly created Oumachoue??ma group. The supracrustal rocks of the Akjoujt area are preserved as a complex system of overlapping thrust sheets, representing the disjointed limbs of a large-scale recumbent syncline. Igneous and metamorphic basement, with basal Oumachoue??ma group metasedimentary rocks attached, has been overthrust and is preserved in synformal remnants within the supracrustal domain. These are the erosional remnants of refolding by later, upright events. The main tectonic episodes consisted essentially of two periods of thrusting and recumbent folding followed by two episodes of thin-skinned upright folding above the sole thrust. Overthrusting of the suite onto the Archaean Amsaga basement to the northeast along the sole thrust is believed to be a late-stage event. The idiosyncratic Fe-Cu-Au-Mg carbonate mineralisation style of the Akjoujt area shows evidence of having been generated more than once during the evolution of the host rocks. Starting with pre to syn-early thrusting events, the carbonate-rich mineralisation recurred at least until the upright folding. There is strong field evidence for a genetic link to carbonate-rich iron formations by remobilisation, but no evidence of a synvolcanic or synsedimentary mineralising event.

Martyn, John; Strickland, Colin

2004-04-01

305

Sequence stratigraphy of the Koonap and Middleton fluvial formations in the Karoo foredeep South Africa  

NASA Astrophysics Data System (ADS)

The Koonap and Middleton formations build a fully fluvial succession of late Permian age which accumulated in the foredeep of the Karoo Basin during the overfilled phase of the foreland system. Fluvial aggradation took place after the final retreat of the Ecca seaway from the limits of the Karoo foredeep, which is why this paper provides a case study for accommodation and sequence development controlled by tectonic mechanisms. The Koonap-Middleton stratigraphy consists of a succession of eight third-order fluvial sequences separated by subaerial unconformities. They formed in isolation from eustatic influences, with a timing controlled by orogenic cycles of loading and unloading. Sediment accumulation took place during stages of flexural subsidence, whereas the bounding surfaces are related to stages of isostatic uplift. The vertical profile of all sequences displays an overall fining-upward trend related to the gradual decrease in topographic slope during orogenic loading. At the same time, an upward change in fluvial styles can be observed within each sequence, from initial higher to final lower-energy systems. The actual fluvial styles in each location depend on paleoslope gradients and the position of the stratigraphic section relative to the orogenic front. Proximal sequences show transitions from braided to meandering systems, whereas more distal sequences show changes from sand-bed to fine-grained meandering systems. The average duration of the stratigraphic cycles is 0.6 My, i.e., eight cycles during 5 My. No climatic fluctuations are recorded during this time, with the long-term climatic background represented by temperate to humid conditions.

Catuneanu, Octavian; Bowker, Duncan

2001-08-01

306

Sedimentological and Stratigraphic Study of a Falling-Stage Delta Complex in the Upper Cretaceous (Turonian) Ferron Sandstone Member of the Mancos Shale, South-Central Utah, USA.  

E-print Network

??The character and distribution of lithofacies in falling-stage deltas are incompletely documented. This paper presents a sedimentological and stratigraphic evaluation of a superbly-exposed interval of… (more)

Alaboud, Fares

2014-01-01

307

Stratigraphy, Structure, and Ore Deposits of the Southern Limb of the Midcontinent Rift System  

NSDL National Science Digital Library

This site features an overview of the Midcontinent Rift system of North America, an area that extends for more than 2000 km northeasterly from Kansas, through the Lake Superior region, and then southeasterly through lower Michigan. This summary of the stratigraphy, structure, and mineralization of rift rocks provides an overview of the geologic history in northern Wisconsin and upper Michigan. Separate sections describe the tectonic history and structural features of the area, the stratigraphy of volcanic and sedimentary deposits, and the mineralization that produced rich copper and silver deposits. Information is supported by numerous citations while maps and diagrams help illustrate the concepts.

Bornhorst, T.; Woodruff, L.; Nicholson, S.; University, Michigan T.

308

Preliminary Investigation of Linkages Between Arctic Pingos and Subsurface Stratigraphy  

NASA Astrophysics Data System (ADS)

This NASA-SETI supported study investigates the distribution of pingos (elliptically-shaped ice-rich topographic mounds) across 2300 square kilometers of the central coastal plain of Arctic Alaska in relation to the shallow geological framework that exists immediately beneath them. Pingos in the central North Slope of Alaska are classified as being of the closed or hydrostatic type. Their genesis is often assigned to freezing and cryogenic uplift of near-surface saturated thaw lake sediments that are exposed as lakes are drained and/or become choked with sediments. Although thaw lakes appear rather ubiquitous across the study area, pingos do not. Pingo distributions can be categorized as either clusters of elements or as relatively dispersed. Spatial statistical analysis reveals that pingo distribution is non-random and clustered. The analysis also took into account that pingo distribution is a function of preferential preservation between modern rivers channels that cross the study area. Pingo distributions and frequency were tested in relation to the location and type of stratigraphic and sedimentological features that characterized the shallow subsurface across the study area. Subsurface interpretation was derived mostly from oil well wireline logs. Gamma ray logs for more than 160 wells were used to define, correlate and assess the connectivity and conductivity of shallow and near-surface stratigraphic units between wells. Assessed also were major facies changes and the type and locations of subsurface structures such as major basement-to-surface faults and folds. The surface and near-surface truncation and subcropping of tilted, alternating units of permeable coarse-grained and confining fine- grained units were also mapped in relation to pingo locations. Preliminary and intriguing findings will be presented which contribute to the hypothesis that pingo genesis, location, and variations in morphology could be, in part, linked to a well-documented and active subsurface geohydrologic system. This system is characterized by multiple stacked hydrocarbon-, saline- and freshwater-rich reservoirs. Processes include fault reactivation and basin subsidence that drive episodic basin expulsion, and upward migration and mixing of deep basin and phreatic fluids along basin margins. Endpoints of the system include demonstrable gas hydrates deposits that occur below and within the permafrost, and documented seepage of hydrocarbons and groundwater at the surface. Our hypothesis entertains the idea that closed pingos might also be endpoints of the petroluem system as basin and phreatic fluids migrate vertically within a thick and leaky permafrost interval along faults and tilted reservoir sand-rich units, which intersect and differentially charge frozen near-surface sedimentary units. Future field-based sampling and geophysical studies may shed additional light on this model's application for pingo genesis and resource exploration on Mars.

Casavant, R.; Skirvin, S.; Patel, C.; Burr, D.

2008-12-01

309

Stratigraphy of till and lake beds of late Wisconsinan age in Iroquois and neighboring counties, Illinois  

NASA Astrophysics Data System (ADS)

Three surficial rock-stratigraphic till units and six textural units within glacial lake beds were recognized in Wisconsinan till plains 130 km south of Chicago. These deposits record fluctuations in the northward-retreating Woodfordian glacier between 17,000 and 14,500 yrs. BP., intially Lake Michigan Lobe, followed by Erie-Huron Lobe. Early in the period the Lake Michigan Lobe covered the entire area depositing the Snider Till Member of the Wedron Formation (till 2) in three successively younger and overlapping sheets and building the corresponding Chatsworth, Gilman and Marseilles Moraines.

Moore, D. W.

310

Little ice age as recorded in the stratigraphy of the tropical quelccaya ice cap  

Microsoft Academic Search

The analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent. Annual variations in visible dust layers, oxygen isotopes, microparticle concentrations, conductivity, and identification of the historical (A.D. 1600) Huaynaputina ash permit accurate dating and time-scale verification. The fact that

L. G. Thompson; E. Mosley-Thompson; P. M. Grootes

1986-01-01

311

Lunar impact basins: Stratigraphy, sequence and ages from superposed impact crater populations measured  

E-print Network

measured from Lunar Orbiter Laser Altimeter (LOLA) data C. I. Fassett,1,2 J. W. Head,2 S. J. Kadish,2 E to a Pre-Imbrian absolute chronology. Citation: Fassett, C. I., J. W. Head, S. J. Kadish, E. Mazarico, G. A

Zuber, Maria

312

Glacial Ordovician new evidence in the Pakhuis Formation, South Africa : sedimentological investigation and palaeo-environnemental reconstruction  

Microsoft Academic Search

During the Late Ordovician (Hirnantian) an ice sheet covered a great part of the Gondwana. In Africa, several studies present the stratigraphy and the complexity of these glacial records. The different glacial landsystems correspond to several glacial cycles, related to rapid ice front oscillations and are grouped into two major ice-sheet advances, separated by a major ice sheet recession. The

E. Portier; Jf. Buoncristiani; Jf. Deronzier

2009-01-01

313

Reconstruction of Holocene coastal depositional environments based on sedimentological and palaeontological analyses, Zakynthos Island, Western Greece Mediterranean Sea  

NASA Astrophysics Data System (ADS)

Zakynthos Island is one of the most seismically active regions in Europe and the Holocene coastal depositional environments were influenced both by tectonic activity and sea level rise. In the present study detailed sedimentological, palaeontological and 14C dating analyses were used in order to reconstruct the Holocene coastal depositional environments as well as the different rates of sedimentation, based on data from three cores up to 30 m deep. The results of the analyses indicate changes in depositional environments from marine to brackish lagoonal and lagoon / barrier systems with temporary intrusions of marine water via storms or tsunamigenic events. High sedimentation rates in coastal areas of Zakynthos Island correspond well to the most widespread Holocene warm and humid phases. The interpretation of the sedimentological environments reveals that Zakynthos Island before 8300 BP was constituted by two islands, where the present southern part of the island was separated from the northern one by a shallow and narrow sea channel.

Avramidis, Pavlos; Iliopoulos, George; Papadopoulou, Penelope; Nikolaou, Konstantinos; Kontopoulos, Nikolaos; Wijngaarden, Gert

2014-05-01

314

Holocene erosion, sedimentation, and stratigraphy at Raven Fork, Southern Blue Ridge Mountains, USA  

NASA Astrophysics Data System (ADS)

Holocene colluvial and alluvial stratigraphy and a radiocarbon chronology are presented for the valley of the lower three kilometers of Raven Fork, a mountain stream draining 194 km 2 of high relief (1.3 km) terrain of the Southern Blue Ridge Mountains in western North Carolina, USA, which is in a region that lacks good chronological data. Lower hillslopes, alluvial/colluvial fans, alluvial bottomlands (first terrace and floodplain), and the modern stream channel are landforms described with respect to soils, stratigraphy, and sedimentary structures. Standard methods for subsurface investigations (core holes, excavation units, exposures) are used in conjunction with extensive archeological excavations and cultural chronologies. Radiocarbon ages from each landform are used to calculate long-term-average rates of sedimentation. Results indicate that the first half of the Holocene experienced somewhat more rapid rates of hillslope sedimentation (0.3 to 1.1 mm/yr) than the last half of the Holocene (0.1-0.2 mm/yr) on footslopes, toeslopes, and alluvial/colluvial fans prior to historic time. We suggest that these subtle differences in the rates of sedimentation were driven by changes in global paleoclimate that favored a high frequency of heavy rainfall, including tropical storms and/or severe thunderstorms and more (and possibly larger) floods during the first half of the Holocene. Prehistoric rates of vertical accretion on the first terrace (T1) ranged from 0.1 to 0.8 mm/yr between about 10,000 and 3000 calendar years ago, and incision below T1 formed the late Holocene floodplain beginning at about 6000 years ago. We suggest that this incision is linked to a reduction in the supply of sediment and a reduction in the magnitude of floods. Historical rates of sedimentation on all parts of the depositional landscape (2.0-2.7 mm/yr on hillslopes and fans and 5.8-6.5 mm/yr on floodplains) were about an order of magnitude greater than prehistoric rates. We attribute these rates to human impacts, such as timber harvest and land clearing, which caused accelerated erosion. We attribute the abundance of fine-grained sediment in streams of the Southern Blue Ridge province, which is atypical in many mountain streams around the world, to the regionally widespread mantle of saprolite as a source of sediment to the fluvial system. Holocene sedimentation on all depositional landforms in the valley led to sedimentary burial of archeological materials, which highlights the need to consider site burial on lower hillslopes and terraces for evaluation of the cultural resources in the Southern Blue Ridge Mountains. These findings show that the entrenched condition of the Raven Fork channel was inherited from the middle Holocene and can be considered a "natural" state for this mountain stream, casting doubt on the negative connotation that is often assigned to entrenched channels.

Leigh, David S.; Webb, Paul A.

2006-08-01

315

Sedimentological and geochemical records of past trophic state and hypolimnetic anoxia in large, hard-water Lake Bourget, French Alps  

Microsoft Academic Search

Sedimentological, geochemical and particle-size analyses were used to reconstruct the evolution of both trophic state and\\u000a hypolimnetic anoxia in Lake Bourget (French Alps) during the last century. Radionuclide dating (210Pb, 137Cs and 241Am) confirmed the annual rhythm of laminations in the upper sediment profile. In Lake Bourget, biochemical varves are triplets\\u000a composed of a diatom layer (spring lamina), a bio-precipitated

Charline Giguet-Covex; Fabien Arnaud; Jérôme Poulenard; Dirk Enters; Jean-Louis Reyss; Laurent Millet; Jérome Lazzaroto; Olivier Vidal

2010-01-01

316

Magma chamber dynamics constrained by crystal isotope stratigraphy  

NASA Astrophysics Data System (ADS)

The architecture of subvolcanic magma plumbing systems controls the thermal regime transited by magmas in the lithosphere, and consequently influences the rates and processes by which magmas evolve. The resolution of current geophysical methods is unable to accurately define the shapes, sizes and crystallinity of small magma bodies. Exhumed fossil magma chambers may provide terminal or cumulative plumbing system assemblies but cannot provide snapshots of the system at a given time, and fail to identify ephemeral components such as dikes, which may open and close to transport magma. Petrographically-constrained in situ analysis of the components of volcanic rocks, including crystal isotope stratigraphy, has recently proved an important new approach to constraining the dynamics of magma storage systems. Core-to-rim decreases in 87Sr/86Sr accompanied by increases in Sr concentration for single plagioclase crystals seen at volcanoes such as El Chichon, Mexico, are explained by frequent recharge of a storage reservoir(s). The fact that high 87Sr/86Sr values are restricted to cores suggests that contamination occurs at the initial stages of injection and contact between magma and the crust. This in turn suggests that crystallization occurs at the margins of the magma body where the thermal gradient is strongest, volatiles are concentrated and epitaxial crystallization is promoted. The crystallized boundary zone then isolates the magma and prevents subsequent recharge magma from interacting directly with the crust. In cases such as Ngauruhoe volcano, New Zealand, 87Sr/86Sr increases from core-to-rim of plagioclase crystals suggest that the magma was not completely isolated from a crustal contaminant. In either case, changes in Sr isotope ratio are correlated with punctuated textural evidence for disequilibrium events, underscoring the importance of recharge. Recharge disaggregates and remobilizes much of the material crystallized from earlier events. Petrographic and geochemical observations from many volcanic systems suggest that the crystalline components are mechanical aggregates of crystals grown in different places and times in the magma storage and delivery system. Indeed the occurrence of true phenocrysts in volcanic rocks is arguably rare. Repeated remobilization of crystalline material by recharge magma indicates that the solids exist in a sufficiently weak state (as a crystal mush or framework) such that an injection of magma can cause disaggregation. This in turn limits the cooling time available for solidification between recharge episodes. The potential now exists for diffusional treatment of trace element and isotopic profiles from mineral phases to constrain effective residence times, and thereby determine crystallization and differentiation rates.

Davidson, J. P.; Tepley, F. J., III; Hora, J. M.

2003-04-01

317

Sorting out meandering and braiding: discriminating formative conditions and stratigraphy  

NASA Astrophysics Data System (ADS)

For various river channel patterns, the necessary formative conditions differ, but how is not entirely understood. Furthermore, not only the morphology and dynamics differ, but also the resulting stratigraphy differs, of which understanding is required to infer past environmental conditions and predict reservoir behaviour. Our objective is to identify the necessary and sufficient conditions for forming dynamic meandering and braided rivers. We reproduced both patterns experimentally and with a physics-based numerical model, and produced synthetic stratification from bed elevation maps and control lacquer peels for the experiments. Experimental meandering was produced using a mixture of poorly sorted sediment and silt-sized silica flour and a transversely moving inflow boundary. Braiding was produced in exactly the same conditions but without the silica flour. These experiments represent gravel-bed rivers in nature, where both experimental meandering and braiding channels were close to the transition between the types. Onset meandering was also produced in the numerical model (Delft3D) with a similar transversely moving inflow boundary, whilst braided rivers formed with fixed inflow or some noise on the transverse discharge distribution at the inflow boundary. The silica flour deposited on crevasse splays and in chute channels, forming new floodplain. This caused much less chute cutoffs and stronger banks. The resulting meandering river formed multiple sets of scroll bars forming pointbars, overlain by splays and floodplain. The braided river, in contrast, showed mid-channel bars and multiple active channels, faster and more haphazard bar and channel migration, and frequent chute cutoffs. Apart from the floodplain, stratification in meandering rivers consisted of sigmoidally stratified units formed by scroll bars and channel fills, usually formed after chute cutoff. Braided rivers had similar units but much smaller and more. In both cases the highest preservation potential is in the deepest channels. We conclude that some floodplain-filling sediment or vegetation is required for meandering to prevent chute cutoffs to lead to weak braiding, but, more importantly, that some dynamics are required at the upstream boundary, where periodic perturbation causes meandering whilst stochastic perturbation causes braiding. Furthermore, morphology and stratification in braided gravel-bed rivers have much smaller morphological and stratigraphic units relative to average channel width than the meandering rivers, even though active bar dimensions are comparable.

Kleinhans, M. G.; van de Lageweg, W. I.; Schuurman, F.; Van Dijk, W. M.

2011-12-01

318

Sedimentology and diagenesis of misoa C-2 reservoir, VLE-305/326 area, block V, Lamar Field, Maracaibe Lake, Venezuela  

SciTech Connect

The main purpose of this study was to characterize the Upper Eocene C-2 reservoir using sedimentological, petrophysical and biostratigraphic parameters. The reservoir quality was evaluated by defining its physical attributes, geometry, areal distribution and orientation, from facies analysis of sedimentary units identified in core samples. In evaluating the sedimentary features of the Misoa C-2 reservoir in VLE 305/326 area, Block V, Lamar Field, Maracaibo Lake, 2,000' of cores from five wells (named VLe-339, VLE-720, VLE -723, VLe-754, LPG-1211) were analyzed. The sedimentary sequence studied represents upper-middle deltaic plain deposits with no marine influence. These deposits were identified as interdistributary channels, crevasse splays and interdistributary bays deposited in a northward prograding system. Seven sedimentary facies were defined from the physical, chemical and biological features observed in all cores. These facies were petrophysically and petrographically characterized then grouped in six sedimentary units which were then correlated over the entire area. One hundred well logs were correlated using sedimentological criteria. Finally, four flow units were identified in the reservoir using the sedimentological parameters, petrophysical data and production behavior. A surface trend analysis program utilizing thickness values resulted in contours, trends, residuals and isometry maps of each unit with a generalized southwest-northeast trend orientation. It was determined that facies distribution in the units controls the reservoir quality. These results are the main input into reservoir simulation. An accurate reservoir modeling is needed to prepare for optimizing secondary oil recovery.

Cabrera de Casas, L.; Chacartegui, F. (Maraven S.A., Caracas (Venezuela))

1993-02-01

319

Early Triassic magnetic polarity time scale—integration of magnetostratigraphy, ammonite zonation and sequence stratigraphy from stratotype sections (Canadian Arctic Archipelago)  

NASA Astrophysics Data System (ADS)

Stratotypes defining the stages of the Early Triassic (Griesbachian, Dienerian, Smithian and Spathian) are located on Ellesmere and Axel Heiberg islands in the northern Canadian Arctic. Ammonite-rich horizons are within a clastic outer shelf-to-slope facies of thick progradational wedges of mudstones and siltstones. Three sections were sampled for magnetostratigraphy and interpreted for transgressive and regressive pulses of sedimentation. Using the ammonite zonation as a guide, the transgressive-regressive cycles and magnetostratigraphies have been correlated among the sections and to the published Triassic sequence stratigraphy time scale, thus enabling definition of the magnetic polarity pattern for the upper Griesbachian to Smithian stages in multiple sections. The magnetic polarity and associated sequence stratigraphy pattern for the lower Griesbachian and for the Spathian were derived from single sections. The Griesbachian and Dienerian stages each have two pairs of normal- and reversed-polarity chrons; the Smithian is predominantly of normal polarity, and the Spathian is predominantly of reversed polarity. This magnetic polarity time scale may help to resolve age correlations of North American redbed facies and to define the Permian-Triassic boundary. After correction for variable structural orientations, the mean directions of magnetization from the three sites converge at 296° declination, 57° inclination ( k = 60, ? 95 = 16.5° ; equivalent pole = 41°N, 161°E; paleolatitude = 38°N), which is consistent with the pole derived from nearby Early Permian volcanics and supports a postulated post-Early Triassic, pre-Tertiary counterclockwise rotation of this region with respect to cratonic North America.

Ogg, James G.; Steiner, Maureen B.

1991-10-01

320

Late Wisconsin history north of the Giants Range, northern Minnesota, inferred from complex stratigraphy*1  

NASA Astrophysics Data System (ADS)

In an area north of the Giants Range in northeastern Minnesota the late Wisconsin glacial and extraglacial lithostratigraphy shows that, apart from one occurrence of red clayey till, the deposits can be related to the deglaciation of the Rainy Lobe, the margin of which retreated northward, leaving debris-rich ice behind. By a combination of pollen stratigraphy, lithostratigraphy, and chronostratigraphy of lake sediments in this area, together with multivariate numerical analyses of the data set, a "hiatus" stratigraphy was set up. Combined with the glacial and extraglacial stratigraphy, it shows that the area of Glacial Lake Norwood was possibly later filled with sediments, between masses of stagnant ice, following a damming of drainge in the south by the St. Louis Sublobe. The area was drained through the Embarrass channel when the St. Louis Sublobe retreated. Then followed the drainage of Lake Koochiching through the Embarrass channel. At ca. 10,200 14C yr B.P. the area apparently became free of stagnant ice as normal lake sedimentation began in all lakes studied. A lake-level rise is indicated ca. 1000 yr later. Apart from a long-lasting phase of birch tundra parkland between ca. 12,000 (or 11,500?) and 10,600 14C yr B.P., the general pollen stratigraphy fits into the regional picture with a more or less undisturbed and gradual plant immigration from the time of the culmination of the St. Louis Sublobe.

Björck, Svante

1990-01-01

321

Tectono-stratigraphy of late Archaean greenstone terranes in the southern Eastern Goldfields, Western Australia  

Microsoft Academic Search

Late Archaean greenstone terranes in the southern part of the Eastern Goldfields are regionally extensive, faultbounded entities defined on the basis of small but distinct differences in stratigraphy and structure. The greenstones comprise volcano-sedimentary successions that were all deposited at the same time (c. 2720-2675 Ma) on sialic crust. Hence, the terranes are interpreted to represent contemporaneous, probably adjacent, basins.

C. P. Swager

1997-01-01

322

Long-period orbital control on middle Miocene global cooling: Integrated stratigraphy and astronomical tuning  

E-print Network

Long-period orbital control on middle Miocene global cooling: Integrated stratigraphy in the middle Miocene global cooling (13.82 Ma ± 0.03) coincides with minimum eccentricity values associated with the major step in middle Miocene global cooling and provides a level suitable for placing the physical

Utrecht, Universiteit

323

Upward-looking ground-penetrating radar for monitoring snowpack stratigraphy  

Microsoft Academic Search

Operational remote monitoring of snowpack stratigraphy, melt water intrusions and their evolution with time for forecasting snowpack stability is not possible to date. Determination of the spatial variability of snowpack conditions on various scales requires a number of point measurements with various methods. These methods are either destructive or do not provide information about the internal structure of the snowpack.

Achim Heilig; Martin Schneebeli; Olaf Eisen

2009-01-01

324

Contaminant Stratigraphy of the Ballville Reservoir, Sandusky River, NW Ohio: Implications for Dam Removal  

E-print Network

Contaminant Stratigraphy of the Ballville Reservoir, Sandusky River, NW Ohio: Implications for Dam in the Lake Erie water- shed, impounding 1.7 million m3 of water and sediment. Removal of the dam would open sediment in the reservoir. In cooperation with the Ohio EPA, sediment cores were evaluated for 18 metals

Gottgens, Hans

325

Stratigraphy of small shield volcanoes on Venus: Criteria for determining stratigraphic relationships and assessment of relative  

E-print Network

Stratigraphy of small shield volcanoes on Venus: Criteria for determining stratigraphic than about 20 km, are common and sometimes very abundant features on the plains of Venus. Typically plains of Venus. Did the eruption style of small shields occur repeatedly throughout the visible part

Head III, James William

326

Equivalent hydraulic conductivity of an experimental stratigraphy: Implications for basin-scale flow  

E-print Network

Equivalent hydraulic conductivity of an experimental stratigraphy: Implications for basin-scale groundwater flow models are the estimation of representative hydraulic conductivity for the model units. In this study, high-resolution, fully heterogeneous basin-scale hydraulic conductivity map is generated

Gable, Carl W.

327

C-Isotope stratigraphy, a monitor of paleoenvironmental change: A case study from the early cretaceous  

Microsoft Academic Search

Today's disturbance of the global carbon cycle induced by anthropogenic processes has raised new interest in the history of the global carbon cycle and its relationship to climate and other geochemical cycles. Carbon-isotope stratigraphy proves to be most useful as a monitor of the history of the carbon-cycle during the last 200 million years. In the introductory paragraphs of this

Helmut Weissert

1989-01-01

328

Oil and Gas CDT Mesozoic Biosequence Stratigraphy of the Wessex Basin, UK  

E-print Network

expert academics from across the CDT and also experienced oil and gas industry professionalsOil and Gas CDT Mesozoic Biosequence Stratigraphy of the Wessex Basin, UK University of Birmingham of a CDT cohort, you will receive 20 weeks bespoke, residential training of broad relevance to the oil

Henderson, Gideon

329

Precise Dating of FloodPlain Stratigraphy Using Changes in Tree-Ring Anatomy Following Burial  

Microsoft Academic Search

Determination of sediment deposition rates from stratigraphy is typically limited by a scarcity of chronological information. We present a method for precise dating of sedimentary beds based on the change in anatomy of tree rings upon burial. When stems of tamarisk (Tamarix ramosissima)and sandbar willow (Salix exigua) are buried, subsequent annual rings in the buried portions become narrower and vessels

J. M. Friedman; P. B. Shafroth; K. R. Vincent; M. L. Scott; G. T. Auble

2001-01-01

330

High-resolution stratigraphy reveals repeated earthquake faulting in the Masada Fault Zone, Dead Sea Transform  

E-print Network

High-resolution stratigraphy reveals repeated earthquake faulting in the Masada Fault Zone, Dead lacustrine laminites in the Dead Sea Basin near Masada. The Masada Fault Zone offers a unique opportunity of the syndepositional Masada Fault Zone (MFZ) provides an example for fundamental characteristics of earthquakes

Marco, Shmuel "Shmulik"

331

Snow stratigraphy measured by snow hardness and compared to surface section images  

Microsoft Academic Search

Abstract: Snow hardness is one of the most important parameters in the study of snow. Hand, ram and micro penetrometer hardness measurements,were taken in seven snow pits. The snow profiles are analysed in terms of the three hardness tests and surface section images are used as an objective reference. From the images we established the stratigraphy in terms of layers

Christine Pielmeier; Martin Schneebeli

332

Magnetic Polarity Stratigraphy: Stochastic Properties of Data, Sampling Problems, and the Evaluation of Interpretations  

Microsoft Academic Search

A statistical model has been derived which can be used either to test the interpretation of a given magnetic stratigraphy or to make time estimates from the paleomagnetic data. The model is based on the presently accepted statistical properties of the earth's magnetic field and the stochastic nature of the paleomagnetic sampling process. Given knowledge of the number of paleomagnetic

Noye M. Johnson; Victor E. McGee

1983-01-01

333

Magnetic polarity stratigraphy: Stochastic properties of data, sampling problems, and the evaluation of interpretations  

Microsoft Academic Search

A statistical model has been derived which can be used either to test the interpretation of a given magnetic stratigraphy or to make time estimates from the paleomagnetic data. The model is based on the presently accepted statistical properties of the earth's magnetic field and the stochastic nature of the paleomagnetic sampling process. Given knowledge of the number of paleomagnetic

Noye M. Johnson; Victor E. McGee

1983-01-01

334

M.R. Saltzman and E. Thomas Chapter 11 Carbon Isotope Stratigraphy  

E-print Network

derived from pelagic carbonates, and exhibit low amplitude d13 Ccarb variability (from �1 to þ4&) relative OF CARBON ISOTOPE STRATIGRAPHY The potential of marine carbonate d13 C trends and excursions to date.g., Shackleton and Hall, 1984; Berner, 1990; Kump and Arthur, 1999; Falkowski, 2003; Sundquist and Visser, 2004

Saltzman, Matthew R.

335

Lithospheric Stratigraphy beneath the Southern Rocky Mountains, USA Brian Zurek and Ken Dueker  

E-print Network

Lithospheric Stratigraphy beneath the Southern Rocky Mountains, USA Brian Zurek and Ken Dueker of the continental lithosphere of the southern Rocky Mountains. In this paper, we present the detailed results of images constructed using broadband teleseismic receiver functions of the continental lithosphere

Dueker, Ken

336

Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation in the Fundy basin  

E-print Network

Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation] characterized the Triassic as perhaps the most arid period of the Phanerozoic, citing evidence for widespread,5] and the apparent expan- sion of deserts in the Triassic and Early Jurassic to an extent not since repeated [6

Olsen, Paul E.

337

Extended stratigraphy, palynology and depositional environments record the initiation of the Himalayan Gyirong Basin (Neogene China)  

E-print Network

Extended stratigraphy, palynology and depositional environments record the initiation, a basin induced by east­west extension in the Himalayas of south- ern Tibet. We document the conglomeratic, have revealed three depositional environ- ments for the deposition of the studied section. (1) Alluvial

Utrecht, Universiteit

338

Quaternary stratigraphy and sea-level history of the U.S. Middle Atlantic Coastal Plain  

NASA Astrophysics Data System (ADS)

Middle-Atlantic, inner continental shelf stratigraphic studies document a regional, Late Pleistocene, fossiliferous mud deposit, from northern New Jersey to Cape Lookout, North Carolina. Seismic reconnaissance and detailed stratigraphic analyses reveal the nature of the mud, termed unit Q2, on the Maryland inner continental shelf. Extensive amino acid relative age determinations (from the single genus Mulinia), combined with additional amino acid analyses from onshore deposits having radiometric dates for calibration, indicate an age range for unit Q2 corresponding to Oxygen Isotope Stage 5. Ostracode assemblages delineate four distinct climatic episodes in unit Q2, enabling correlation of the zones in Q2 to the deep sea isotopic record of climatic fluctuations (substages) in Stage 5. Late Stage 5 is represented, on the Maryland shelf, by the 6 meter-thick mud of unit Q2, deposited in an open-shelf environment at slightly depressed sea levels relative to Substage 5e. Late Stage 5 sea levels (including sea-level minima) can be estimated for the mid-Atlantic Coastal Plain by direct measurement of the altitudes of ostracode zone boundaries offshore, and from peak transgressive facies in correlative deposits onshore. Late Stage 5 sea levels determined from the inner shelf and adjacent nearshore facies on the Atlantic coast comprise the most complete sea-level history for Stage 5 yet proposed. Some recent revisions of glacioeustatic sea-level models advocate slightly higher sea levels during late Stage 5 (Substage 5c in particular) than originally estimated from uplifting reef tracts, and support sea levels higher than estimates from deep-sea isotopic records. The sea-level record from the Maryland inner continental shelf confirms these recent estimates in an area of minimal tectonism, and adds sea-level minima estimates for Substages 5d and 5b. Offshore, a more complete record of Stage 5 is preserved than in onshore deposits, which are limited to peak transgressive facies. Discrepancies in correlation among emerged coastal plain facies therefore become resolvable within the context provided by the shelf stratigraphy.

Toscano, Marguerite A.; York, Linda L.

339

Stanley, G.D., Jr., McRoberts, C.A., and Whalen, M.T., 2008, Stratigraphy of the Triassic Martin Bridge Formation, Wallowa terrane: Stratigraphy and depositional setting, in Blodgett, R.B., and Stanley, G.D., eds., The terrane puzzle: New perspectives on  

E-print Network

Martin Bridge Formation, Wallowa terrane: Stratigraphy and depositional setting, in Blodgett, R.B., and Stanley, G.D., eds., The terrane puzzle: New perspectives on paleontology and stratigraphy from the North Bridge Formation, Wallowa terrane: Stratigraphy and depositional setting George D. Stanley* Jr

McRoberts, Christopher A.

340

Sedimentology and petroleum occurrence, Schoolhouse Member, Maroon Formation (Lower Permian), northwestern Colorado  

SciTech Connect

The Lower Permian Schoolhouse Member of the Maroon Formation (formerly considered the Schoolhouse Tongue of the Weber Sandstone) forms a partly exhumed petroleum reservoir in the Eagle basin of northwestern Colorado. The Schoolhouse consists mainly of yellowish gray to gray, low-angle to parallel bedded, very fine to fine-grained sandstone of eolian sand-sheet origin; interbedded fluvial deposits are present in most sections. The sand-sheet deposits of the Schoolhouse Member are sedimentologically and petrologically similar to those in the underlying red beds of the main body of the Maroon Formation, and the Schoolhouse is considered the uppermost sand sheet in the Maroon depositional sequence. The bleached and oil-stained Schoolhouse member is distinguished from the underlying Maroon red beds on the basis of its diagenetic history, which is related to regional hydrocarbon migration and development of secondary porosity. Geological and geochemical data suggest that Schoolhouse Member oils have upper Paleozoic sources, including the intrabasinal Belden Formation. 13 figs., 1 tab.

Johnson, S.Y.; Schenk, C.J.; Anders, D.L.; Tuttle, M.L. (Geological Survey, Denver, CO (USA))

1990-02-01

341

Variation in sedimentology and architecture of Eocene alluvial strata, Wind River and Washakie basins, Wyoming  

SciTech Connect

Eocene continental, alluvial strata of the Wind River Formation (Wind River Basin) and the Cathedral Bluffs Member of the Wasatch Formation (Washakie basin) provide two examples of Laramide intermontane basin aggradation. These alluvial sediments primarily represent overbank flood deposits marginal to channel complexes. Their sedimentology and architecture, although grossly similar, appear to vary somewhat with proximity to Laramide uplifts. In both cases, repetitive sedimentation on the floodplain produced a succession of depositional couplets, each composed of a light-gray sand overlain by a red clay-rich silt or sand. The lower sands are tabular bodies that, near their distal margins, taper discernibly. They commonly display planar and ripple-drift laminations. Upper clay-rich layers, which are laminated, are also generally tabular. Those floodplain strata depositional proximal to Laramide uplifts show little evidence of scouring prior to deposition of the next, overlying couplet. Most of these sedimentary layers, therefore, are laterally continuous (up to 2 km). This alluvial architecture results in relatively uniform porosity laterally within depositional units but variable porosity stratigraphically through the sequence. In contrast, alluvial sediments deposited farther from the Laramide uplifts have undergone sporadic incision (either during rising flood stage or subsequently) followed by aggradation. As a result, many of these floodplain couplets are discontinuous laterally and, hence, exhibit large-scale lateral variability in porosity. Both alluvial sequences have undergone similar types and extents of burial diagenesis.

Patterson, P.E.; Larson, E.E. (Univ. of Colorado, Boulder (United States))

1991-03-01

342

Sedimentology and diagenesis of a rift basin lacustrine sandstone: Pematang group, central Sumatra, Indonesia  

SciTech Connect

The Central Sumatra basin is a back-arc basin that formed during the Paleocene as a series of half-graben structures. These early formed half-graben structures were filled with nonmarine clastics and lacustrine sediments of the Pematang Group, sourced from local highland areas. The Pematang Group consists of the Lower Red Beds, Brown Shale, Coal Zone Member, and Lake Fill Formation (in ascending order). The Pematang Group sedimentology is intimately related to the regional and basinal tectonic development and history. Sandstones of the Pematang Group are predominantly sublitharenites and litharenites; feldspars are rare. Sandstone diagenesis is relatively uniform regardless of the depositional environment. Diagenetic modifications include compaction, early calcite and dolomite cementation, quartz overgrowth formation, unstable rock-fragment dissolution, kaolinite precipitation, siderite formation, and local illite formation. Secondary porosity accounts for up to 50% of the effective porosity and was created by rock-fragment dissolution. This dissolution is probably caused by the organic acids released during kerogen maturation. Stable isotope data from diagenetic siderite are presented.

Janks, J.S.; Kelley, P.A.; Williams, H.H.

1986-05-01

343

Workshop on the Martian Northern Plains: Sedimentological, periglacial, and paleoclimatic evolution  

NASA Technical Reports Server (NTRS)

The penultimate meeting in the Mars Surface and Atmosphere Through Time (MSATT) series of workshops was held on the campus of the University of Alaska in Fairbanks, Alaska, 12-13 Aug. 1993. This meeting, entitled 'The Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution,' hosted by the Geophysical Institute at the University of Alaska, was designed to help foster an exchange of ideas among researchers of the Mars science community and the terrestrial glacial and periglacial science community. The technical sessions of the workshop were complemented by field trips to the Alaska Range and to the Fairbanks area and a low-altitude chartered overflight to the Arctic Costal Plain, so that, including these trips, the meeting lasted from 9-14 Aug. 1993. The meeting, field trips, and overflight were organized and partially funded by the Lunar and Planetary Institute and the MSATT Study Group. The major share of logistical support was provided by the Publications and Program Services Department of the Lunar and Planetary Institute. The workshop site was selected to allow easy access to field exposures of active glaciers and glacial and periglacial landforms. In all, 25 scientists attended the workshop, 24 scientists (plus 4 guests and the meeting coordinator) participated in the field trips, and 18 took part in the overflight. This meeting reaffirmed the value of expertly led geologic field trips conducted in association with topical workshops.

Kargel, J. S. (editor); Parker, T. J. (editor); Moore, J. M. (editor)

1993-01-01

344

Sedimentological control on saturation distribution in Arctic gas-hydrate-bearing sands  

NASA Astrophysics Data System (ADS)

A mechanistic model is proposed to predict/explain hydrate saturation distribution in “converted free gas” hydrate reservoirs in sub-permafrost formations in the Arctic. This 1-D model assumes that a gas column accumulates and subsequently is converted to hydrate. The processes considered are the volume change during hydrate formation and consequent fluid phase transport within the column, the descent of the base of gas hydrate stability zone through the column, and sedimentological variations with depth. Crucially, the latter enable disconnection of the gas column during hydrate formation, which leads to substantial variation in hydrate saturation distribution. One form of variation observed in Arctic hydrate reservoirs is that zones of very low hydrate saturations are interspersed abruptly between zones of large hydrate saturations. The model was applied to data from Mount Elbert well, a gas hydrate stratigraphic test well drilled in the Milne Point area of the Alaska North Slope. The model is consistent with observations from the well log and interpretations of seismic anomalies in the area. The model also predicts that a considerable amount of fluid (of order one pore volume of gaseous and/or aqueous phases) must migrate within or into the gas column during hydrate formation. This paper offers the first explanatory model of its kind that addresses “converted free gas reservoirs” from a new angle: the effect of volume change during hydrate formation combined with capillary entry pressure variation versus depth.

Behseresht, Javad; Bryant, Steven L.

2012-08-01

345

High-resolution sedimentological and subsidence analysis of the Late Neogene, Pannonian Basin, Hungary  

USGS Publications Warehouse

Detailed sedimentological and paleontological analyses were carried out on more than 13,000 m of core from ten boreholes in the Late Neogene sediments of the Pannonian Basin, Hungary. These data provide the basis for determining the character of high-order depositional cycles and their stacking patterns. In the Late Neogene sediments of the Pannonian Basin there are two third-order sequences: the Late Miocene and the Pliocene ones. The Miocene sequence shows a regressive, upward-coarsening trend. There are four distinguishable sedimentary units in this sequence: the basal transgressive, the lower aggradational, the progradational and the upper aggradational units. The Pliocene sequence is also of aggradational character. The progradation does not coincide in time in the wells within the basin. The character of the relative water-level curves is similar throughout the basin but shows only very faint similarity to the sea-level curve. Therefore, it is unlikely that eustasy played any significant role in the pattern of basin filling. Rather, the dominant controls were the rapidly changing basin subsidence and high sedimentation rates, together with possible climatic factors.

Juhasz, E.; Muller, P.; Toth-Makk, A.; Hamor, T.; Farkas-Bulla, J.; Suto-Szentai, M.; Phillips, R.L.; Ricketts, B.

1996-01-01

346

Glacial Ordovician new evidence in the Pakhuis Formation, South Africa : sedimentological investigation and palaeo-environnemental reconstruction  

NASA Astrophysics Data System (ADS)

During the Late Ordovician (Hirnantian) an ice sheet covered a great part of the Gondwana. In Africa, several studies present the stratigraphy and the complexity of these glacial records. The different glacial landsystems correspond to several glacial cycles, related to rapid ice front oscillations and are grouped into two major ice-sheet advances, separated by a major ice sheet recession. The study was performed on three well outcropping Late Ordovician sections in South Africa. The Ordovician IV is described as the Pakhuis Rm, and is divided into three different lithological members (known as Sneekop, Oskop and Sternbras Mb) that could be related to two major glacial cycles. In the first cycle (pool the two first Mb), facies association indicate continental environment, with : massive sandy tillites with facetted and striated erratics, subaerial outwash plain to glaciolacustrine cross bedded sands and laminated silts. Near Clanwilliam, the outcrops exhibit a high lateral variability in facies and thickness, ranging from a few meters to several tens of meters. The second cycle is dominated by clear marine sedimentation and may be interpreted as a transgressive sequence, quite different from what occurred in North Gondwana. Typical facies define shoreface environment, and periglacial evidence such as dropstones at base are encountered, passing progressively to a clear offshore environment at top of the series, likely Silurian aged, and known as Cederberg fm. Two glacial pavements were also described. The most spectacular one was firstly described by Visser et al. 1974 and should be interpreted as an intra-formational glacial pavement, with striae indicating a flow from East to West. This pavement is overlying a newly discovered glacial floor which exhibits grooves, crescents marks, en echelon fractures, with the same E-W general orientation, and shaped as ‘roches moutonnées', which are typical evidences of glacial erosion on indurated substratum. Reconstructing paleoenvironment suggests a clear structural paleo-topography controlling the erosion and distribution of paelo-valleys, lakes and glacial lobes. The glaciogenic Ordovician deposits constitute a proven oil and gas bearing reservoir on the North Gondwana margin, also known for their sharp and rapid facies changes. Also, such a study provides an excellent opportunity to understand and appraise the complex architecture and geometries of the sands bodies, the structural control of the glacial erosion and infill of this promising play. Visser, 1974 J.N.J. Visser, The Table Mountain Group: a study in the deposition of quartz arenites on a stable shelf, Trans. Geol. Soc. S. Afr. 77 (1974), pp. 229-237.

Portier, E.; Buoncristiani, Jf.; Deronzier, Jf.

2009-04-01

347

Stratigraphy of the Arriaga Palaeolithic sites. Implications for the geomorphological evolution recorded by thickened fluvial sequences within the Manzanares River valley (Madrid Neogene Basin, Central Spain)  

NASA Astrophysics Data System (ADS)

The Arriaga Palaeolithic sites, located within the Middle-Late Pleistocene thickened terrace (TCMZ: + 18-22 m) of the Manzanares River valley (Madrid, Central Spain), were subject to intensive archaeological and palaeontological prospecting during the 1980s. Compilation of documents from these old excavations, together with new geoarchaeological, sedimentological, pedological and geophysical data, allow us to locate the morpho-stratigraphic position of the analysed sites within the overall stratigraphy of the TCMZ. This thickened terrace comprises two main fluvial sequences (Lower and Upper) topped by a thick (2.5-5 m) alluvial-colluvial formation. The fluvial sequences are stacked in the study site located in the lowermost reach of the valley, but display complex inset relationships upstream, where they are individualized in two different terrace levels at + 18-22 and + 12-15 m. Terrace thickening was primarily controlled by synsedimentary subsidence caused by dissolution of the evaporitic substratum and locally influenced and backfed by tectonic activity. The regional analysis of the dated (TL and OSL) fluvial sequences containing Palaeolithic sites within the TCMZ, together with new TL dates provided in this study, indicate that the three sedimentary sequences in the TCMZ are time-transgressive valley-fill bodies. Terrace thickening started before the Last Interglacial Period (MIS 6 or older) and continued during whole MIS 5 (lower fluvial sequence) and MIS 4 (upper fluvial sequence) reaching the MIS 3 (top alluvial formation), the latter characterized by the accumulation of alluvial-colluvial sequences derived from the main tributaries and valley slopes. The TCMZ records the Middle-Late Pleistocene boundary, but also the transition between the Lower and Middle Palaeolithic periods during the Late MIS 5 (ca. 96 to 74 ka). The studied Arriaga sites contain evolved Lower Palaeolithic industry (evolved Acheulean techno-complexes) and warm faunal assemblages located within the Lower fluvial sequence, but apparently well constrained Middle Palaeolithic sites are placed within the Upper fluvial sequence at other upstream locations. Deposition of the thickened alluvium was mainly controlled by the upstream advance of dissolution-induced subsidence phenomena, blurring the impact of Late Pleistocene climatic cycles and producing time-transgressive longitudinal valley-fill bodies (i.e. sedimentary sequences). Late Quaternary climatic changes only seem to control the incision/aggradation cycles after the termination of the TCMZ from the Late MIS 3. Dates related to the development of younger inset terraces indicate that they are apparently linked with cold Heinrich events H4 to H1. These younger inset terraces yield cold faunal assemblages and abundant Middle Palaeolithic "Mousterian" assemblages.

Silva, P. G.; López-Recio, M.; Tapias, F.; Roquero, E.; Morín, J.; Rus, I.; Carrasco-García, P.; Giner-Robles, J. L.; Rodríguez-Pascua, M. A.; Pérez-López, R.

2013-08-01

348

Sequence stratigraphy of Niger Delta, Delta field, offshore Nigeria  

E-print Network

to middle Miocene age formed canyons which filled with shale; these fills provide top seals on the flanks of the delta for some important offshore fields (Doust and Omatsola, 1990). 18 LOCATION AND METHODOLOGY Location Delta field is located... to middle Miocene age formed canyons which filled with shale; these fills provide top seals on the flanks of the delta for some important offshore fields (Doust and Omatsola, 1990). 18 LOCATION AND METHODOLOGY Location Delta field is located...

Owoyemi, Ajibola Olaoluwa

2005-11-01

349

Deciphering the Geochronological Framework of Serbian Loess Using Amino Acid Stratigraphy  

NASA Astrophysics Data System (ADS)

Serbian loess deposits preserve the most widespread, semi-continuous terrestrial records of glacial-interglacial climate variability in Europe. The sedimentary deposition, distribution, and thickness of loess in SE Europe are closely linked with major fluvial systems draining the continental interior. During glacial periods, under predominantly cold, semiarid climatic conditions, the extensive floodplain of the middle and lower Danube River was exposed to aeolian deflation, resulting in the accumulation of loess deposits up to 50 m thickness on adjacent fluvial terraces. The geomorphic setting of these loess formations, however, made them vulnerable to fluvial erosion and reworking, resulting in unconformities that may not be visually recognized in sedimentary sequences. Such unconformities, often of unknown duration and spatial extent, confound regional chronostratigraphic and paleoclimatic interpretations. Amino acid racemisation (AAR) geochronology, although primarily a relative dating method, offers an independent assessment of numerical age estimates when results are at or near their methodological limits and can assist in the chronostratigraphic evaluation of loess units beyond the applicable range of numerical dating methods. In this study we present the first comprehensive aminostratigraphic results measured on fossil gastropod shells of the genera Pupilla, Helicopsis, and Vallonia from the loess series at Stari Slankamen and Mosorin/Dukatar (Titel Plateau) in Vojvodina, Serbia, in order to verify the chronostratigraphic position of the upper stratigraphic units and to establish a reliable correlation between older loess-paleosol couplets. Given the interpreted stratigraphic continuity and the high sedimentation rates at Mosorin/Dukatar, we established this site as a chronostratigraphic reference for correlation with the long-studied loess profile Stari Slankamen, where at least two unconformities have led to ambiguous paleoclimatic and stratigraphic interpretation in previous studies. AAR analyses allow us to establish an independent chronostratigraphic framework for Serbian loess sequences correlated with marine oxygen-isotope stages 16-2. The results demonstrate the vast potential of amino acid stratigraphy to identify and constrain the extent, continuity, and duration of erosional discontinuities in long sedimentary sequences, such as those at Stari Slankamen. Ultimately, these results contribute to the development of a robust regional chronostratigraphic framework in support of paleoclimate reconstructions from high-resolution proxies, such as grain-size data, toward an improved understanding of the paleoenvironmental dynamics of SE Europe in an intra-hemispheric context.

Oches, E. A.; Machalett, B.; McCoy, W. D.; Markovic, S.

2010-12-01

350

Ground-Water Salinity and Isotope Stratigraphy of North Carolina's Outer Banks  

NASA Astrophysics Data System (ADS)

As part of a larger investigation of the geologic framework of the North Carolina coast, ground-water and sediment samples were collected and analyzed for salinity and ?13C of total organic carbon (TOC). Salinity was measured on samples from eight borings (depths up to 56 m), located between Kitty Hawk and Nags Head, to determine the thickness of the barrier island's fresh-water lens, and to examine stratigraphic control on freshwater-saltwater boundaries. ?13C was measured to establish the origin of organic matter (OM) preserved in the sediments. Results indicate that ground-water salinity is strongly correlated with stratigraphy based on core descriptions and downhole gamma logs. The subsurface fresh-water lens is 3-30 m thick across the study region (20 km). The thickness of the fresh-saline transition at depth is also highly variable (<2 m to 15 m). At three of four deep coring locations (\\>38 m), a zone of fresher water exists beneath an intermediate saline zone. The maximum salinity of water in the saline zone is typically around 27 ppt, but in one location a brine (45 ppt) is present. Based on preliminary ?13C-TOC data, most OM in the cores appears to be derived from mixed terrestrial (?13C \\approx -26 permil VPDB) and marine (?13C \\approx -20 permil) sources. Two cores show a clear trend from more terrestrial OM at depth toward more marine OM with a component of salt-marsh material (?13C \\approx -13 to -15 permil) near the surface. Sharp upcore transitions from terrestrial to mixed, or mixed to salt-marsh OM may indicate either unconformities, marine incursions associated with rapid sea-level rise events, or opening of inlets. Such transitions are present in one core at a depth of 20 m (14C age = 23.7 cal ka), and in two other cores at 33 to 36 m (10.6 cal ka). The study showed that filled paleo-valleys and paleo-tidal inlets under the modern barrier are serving as conduits for both salt-water migration and sub-estuarine transport of fresh water from the mainland. Channel fills contain OM from a variety of distinct coastal paleoenvironments.

Bratton, J. F.; Thieler, E. R.; Hoffman, C. W.; Brooks, R. W.

2002-12-01

351

Using NIR Photography to Document Snow Stratigraphy Quickly: Lessons from Three Field Campaigns  

NASA Astrophysics Data System (ADS)

We began using near-infrared (NIR) photography as a quick way to document snow stratigraphy in 2006 as part a snow validation campaign in Barrow, Alaska. Seventeen snow pits (30 to 80 cm deep) were photographed using a Sony DSC-P200 Cybershot 7.2-megapixel digital camera supported on a mini-tripod and equipped with a NIR filter (850 nm). Standard layer measurements of thickness, density, grain size, hardness, and grain type were also made in each pit. During the 2007 SnowSTAR traverse across Alaska and Canada, 43 snow pits were photographed and measured in the same fashion. During the CLPX-Alaska campaign of 2008, three trenches each about 10 m long were photographed in their entirety as well as documented in a traditional manner, this time using a Fuji S9100 9 mega-pixel digital camera with an 850 nm filter. For the trenches, the camera was supported on a sliding rail system. NIR photographs were processed using Image-J software and a simple algorithm that enhanced contrast based on grain size. Our goal is to develop a method of documenting stratigraphy that is faster than recording the results in a field book. For a 50 cm deep pit prior methods of recording stratigraphy would have required about 30 minutes. We succeeded in reducing the average time to acquire a pit photograph to less than 15 minutes. However, pit face preparation time increased by about 15 minutes because of the need to produce a smooth, divot-free snow surface. Required protocols to compute grain size from the photos added a further 20 minutes or more if used, so frequently these were omitted. While at present there is no real net reduction in the time to record stratigraphy using NIR photography vs. older methods, the result is superior in all ways to our best previous efforts to "map" the stratigraphy though hand-recorded data. A combination of older traditional methods and NIR photography is strongly recommended as the best method to document the snow stratigraphy.

Sturm, M.; Tape, K.; Liston, G. E.; Rutter, N.

2008-12-01

352

Stochastic inverse method for estimation of geostatistical representation of hydrogeologic stratigraphy using borehole logs and pressure observations  

Microsoft Academic Search

An approach is presented for identifying statistical characteristics of stratigraphies from borehole and hydraulic data. The\\u000a approach employs a Markov-chain based geostatistical framework in a stochastic inversion. Borehole data provide information\\u000a on the stratigraphy while pressure and flux data provide information on the hydraulic performance of the medium. The use of\\u000a Markov-chain geostatistics as opposed to covariance-based geostatistics can provide

Dylan R. HarpVelimir; Velimir V. Vesselinov

2010-01-01

353

A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan  

NASA Astrophysics Data System (ADS)

Hayakawa, T., Hirano, H. 2013. A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan. Acta Geologica Polonica, 63 (2), 239-263. Warszawa. Biostratigraphic correlations of inoceramid bivalves between the North Pacific and Euramerican provinces have been difficult because the inoceramid biostratigraphy of the Japanese strata has been based on endemic species of the northwest Pacific. In this study, carbon stable isotope fluctuations of terrestrial organic matter are assembled for the Upper Cretaceous Yezo Group in the Haboro and Obira areas, Hokkaido, Japan, in order to revise the chronology of the inoceramid biozonation in Japan. The carbon isotope curves are correlated with those of marine carbonates in English and German sections with the aid of age-diagnostic taxa. According to the correlations of the carbon isotope curves, 11 isotope events are recognised in the sections studied. As a result of these correlations, the chronology of the inoceramid biozones of the Northwest Pacific has been considerably revised. The revised inoceramid biozones suggest that the timing of the origination and extinction of the inoceramids in the North Pacific biotic province is different from the stage/substage boundaries defined by inoceramids, as used in Europe and North America.

Hayakawa, Tatsuya; Hirano, Hiromichi

2013-06-01

354

The Monterey Formation of the Santa Ynez Unit, Part 1: Stratigraphy, outcrop gamma-rays, and cyclicity  

SciTech Connect

Monterey reservoirs challenge conventional analytical techniques because of their widely varying, thinly-bedded lithotypes and dependence on fractures for economic production. Our studies employ a multi-faceted approach linking outcrops, cores, well logs, borehole images, and production data. Excellent outcrops of reservoir facies at Shell Beach and Mussel Rock have been correlated to subsurface stratigraphy using spectral gamma-ray surveys. Gamma-ray components vary with rock composition. Uranium correlates with organic matter (r[sup 2]=0.80), potassium and thorium are generally reliable detritus indicators (r[sup 2]=0.75), and thorium is concentrated in many volcanic ash beds. Gamma-ray signatures also reveal key stratigraphic surfaces. We project chronostratigraphy established at the outcrops into the subsurface using the gamma-ray logs, guiding regional and field correlations. Chronostratigraphy is critical for establishing facies distribution and depositional models because lithofacies are time-transgressive. Mineralogic data derived from strip samples of continuous cores calibrate the well-log models that portray lithotype variation. The lithotypes depend on the relative abundance of the three main sediment components in these deep-basin environments (fine-grained detritus, carbonate, and biogenic silica), and reflect Miocene paleoceanography. Monterey strata stack in repetitive packages at various scales. Understanding the controls on the cyclic packages facilitates the prediction of rock properties away from the wells. Independent age control allows us to test the approximate frequency of these cycles versus projected orbital parameters.

Schwalbach, J.R.; Lockman, D.F. (Exxon, USA, Thousand Oaks, CA (United States)); Bohacs, K.M. (Exxon Production Research, Houston, TX (United States))

1996-01-01

355

The Ardross reservoir gridblock analogue: Sedimentology, statistical representivity, and flow upscaling  

SciTech Connect

We have used a reservoir gridblock-sized outcrop (10m by 100m) of fluvio-deltaic sandstones to evaluate the importance of internal heterogeneity for a hypothetical waterflood displacement process. Using a dataset based on probe permeameter measurements taken from two vertical transacts representing {open_quotes}wells{close_quotes} (5cm sampling) and one {open_quotes}core{close_quotes} sample (exhaustive 1mm-spaced sampling), we evaluate the permeability variability at different lengthscales, the correlation characteristics (structure of the variogram, function), and larger-scale trends. We then relate these statistical measures to the sedimentology. We show how the sediment architecture influences the effective tensor permeability at the lamina and bed scale, and then calculate the effective relative permeability functions for a waterflood. We compare the degree of oil recovery from the formation: (a) using averaged borehole data and no geological structure, and (b) modelling the sediment architecture of the interwell volume using mixed stochastic/deterministic methods. We find that the sediment architecture has an important effect on flow performance, mainly due to bedscale capillary trapping and a consequent reduction in the effective oil mobility. The predicted oil recovery differs by 18% when these small-scale effects are included in the model. Traditional reservoir engineering methods, using averages permeability values, only prove acceptable in high-permeability and low-heterogeneity zones. The main outstanding challenge, represented by this illustration of sub-gridblock scale heterogeneity, is how to capture the relevant geological structure along with the inherent geo-statistical variability. An approach to this problem is proposed.

Ringrose, P.; Pickup, G.; Jensen, J. [Heriot-Watt Univ., Edinburgh (United Kingdom)] [and others

1997-08-01

356

Sedimentology and paleogeography of the Natih carbonate platform in the Oman mountains  

SciTech Connect

Field study of the Natih Formation in the Jebel Akhdar and the Oman foothills allows us to establish a new stratigraphical and sedimentological model of this important hydrocarbon reservoir unit. Thanks to the study of rudists and the discovery of ammonites, a new precisions can be given to the chronostratigraphy of the Natih Formation. It was especially demonstrated by the presence of Hippuritids (rudists) that the top of the Natih Formation matches the Cenomanian/Turonian boundary and corresponds to either rudist-rich layers or hard grounds and condensed levels. The stratigraphical correlations between several outcrop section allow one to establish a conceptual sequence stratigraphic model which can be compared to the subsurface by using the Natih subdivisions [open quotes]A to G.[close quotes] The recognition of sequence boundaries, maximum flooding surfaces, and system tracts might help to understand the seismo-stratigraphic expression of the Natih interval in the subsurface. Furthermore, this sequence stratigraphic model clearly illustrates the interfingering of the carbonate reservoir intervals and the organic-rich units (Fitri Mb) at the top of the Natih Formation. We also have identified a clear zonation from deeper marine to shallow-marine carbonate deposits, the most significant of which are the rudistid facies. They form banks, thickets, and biostroms and do not constitute anomalous build ups such as bioherms. Good leaching potentials generally are related to these rudistid facies, especially when they are very rich in skeletal aragonite from the Caprinids shells. Significant primary porosity may be related also to the Hippuritid skeletal cavities at the top of the Natih. Reservoir potentials can be enhanced if these Caprinid-rich intervals are related to exposure surfaces such as the top Natih E and the top Natih A.

Philip, J.M. (Univ. Aix-Marseille I, Marseille (France)); Borgomano, J.R.; Al Maskiry, S. (Petroleum Development Oman, Muscat (Oman))

1993-09-01

357

Morphology and sedimentology of a central Brazos River point bar, Boxley Bend, Brazos County, Texas  

SciTech Connect

A reconnaissance of Brazos River point bars reveals great variety in their morphology and sedimentology, owing to the complex interaction of climate, local hydrography, and local sediment sources. This paper presents the first in a series of studies of point bars of the Brazos River and concentrates on the Boxley Bend point bar near Snook, Texas. The summer morphology of the point bar is complex, consisting of an upper and lower tier separated by a scarp but connected by a central ramp. The surfaces of the lower tier and ramp display numerous large gravel bars and shallow scour pools as well as low-amplitude sand waves, ripples, and current lineations. In cross section, the lower tier and ramp are characterized by (1) trough cross-bedded, medium to fine sand produced by megaripple migration during floods; (2) massive gravel beds, the product of formation and migration of gravel bars during floods; and (3) fine rippled sand and clay drapes formed during falling flood. The surface of the upper tier displays ripple-laminated eolian sand and deflation deposits of mud clasts. In cross section, the upper tier is characterized by thick beds of horizontally stratified fine sand. During the winter, the entire surface of the point bar is covered by large (2 m high) transverse bars separated by deep scour troughs. Transverse bars migrate into the troughs to produce a sequence of fine sand with backflow ripple cross-stratification overlain by thick beds of tabular cross-bedded medium sand. The transverse bars appear to be transitory features with little net effect on sedimentation, because they are removed from the surface of the point bar by summertime.

Connolly, W.M.; Mazzullo, J.

1986-09-01

358

Sedimentology, diagenesis, and oil habitat of Lower Cretaceous Qamchuqa Group, Northern Iraq  

SciTech Connect

The Zagros basin (Iraq) constitutes a rich petroleum province. The Lower Cretaceous Qamchuqa Group comprises on of its major reservoirs. Data from about 30 wells, drilled in a limited sector corresponding to a northwest-southeast anticlinal structure situated in the Kirkuk region, permit analysis of serveral sedimentological and diagenetic events that led to the formation of this reservoir. Facies changes took place and divided the structure into three parts: the northwestern part in which neritic facies dominate, the central part in which basinal influence is considerable, and the southeastern part that shows basinal mudstone type facies. The Lower Cretaceous carbonate platform in the northwestern part of the study area displays good primary porosity. During the course of burial, high secondary porosity related to dolomitization appeared. However, a major part of the porosity was produced when the reservoir was fractured during the Priabonian after the collision between the Arabian and Eurasian plates. Lopatin`s method suggests that organic matter maturation started during the Turonian (around 90 MA), whereas most of the maturation developed during the Miocene due to the rapid accumulation of foreland basin sediments containing evaporite facies (lower Fars Formation) followed by the accumulation of thick upper molasse-type sediments from the erosion of the Zagros Mountains. The accumulation of sediments enhanced the total tectonic subsidence. During this period, the relatively brief time spent by the source rock in a given temperature interval was compensated for by a rapid rise in temperature. This late thermal maturation period controlled most of the transformation of the organic matter into hydrocarbons.

Al Shdidi, S.; Thomas, G.; Delfaud, J. [Avenue de l`Universite, Pau (France)

1995-05-01

359

Sedimentological control on Mn, and other trace elements, in groundwater of the Bengal delta.  

PubMed

To reveal what controls the concentration and distribution of possibly hazardous (Mn, U, Se, Cd, Bi, Pb) and nonhazardous (Fe, V, Mo, PO(4)) trace elements in groundwater of the Bengal delta, we mapped their concentrations in shallow groundwater (<60 mbgl) across 102 km(2) of West Bengal. Only Mn is a potential threat to health, with 55% of well water exceeding 0.3 mg/L, the current Indian limit for drinking water in the absence of an alternate source, and 75% exceeding the desirable limit of 0.1 mg/L. Concentrations of V are <3 ?g/L. Concentrations of U, Se, Pb, Ni, Bi, and Cd, are below WHO guideline values. The distributions of Fe, Mn, As, V, Mo, U, PO(4), and ?(18)O in groundwater reflect subsurface sedimentology and sources of water. Areas of less negative ?(18)O reveal recharge by sources of evaporated water. Concentrations of Fe, As, Mo, and PO(4) are high in palaeo-channel groundwaters and low in palaeo-interfluvial groundwaters. Concentrations of U, V, and Mn, are low in palaeo-channel groundwaters and high in palaeo-interfluvial groundwaters. Concentrations of Fe and Mn are highest (18 and 6 mg/L respectively) at dual reduction-fronts that form strip interfaces at depth around the edges of palaeo-interfluvial aquifers. The fronts form as focused recharge carries dissolved organic carbon into the aquifer margins, which comprise brown, iron-oxide bearing, sand. At the Mn-reduction front, concentrations of V and Mo reach peak concentrations of 3 ?g/L. At the Fe-reduction front, concentrations of PO(4) and As reach concentrations 3 mg/L and 150 ?g/L respectively. Many groundwaters contain >10 mg/L of Cl, showing that they are contaminated by Cl of anthropogenic origin and that organic matter from in situ sanitation may contribute to driving reduction. PMID:22148466

McArthur, J M; Sikdar, P K; Nath, B; Grassineau, N; Marshall, J D; Banerjee, D M

2012-01-17

360

Sedimentological, biogeochemical and mineralogical facies of Northern and Central Western Adriatic Sea  

NASA Astrophysics Data System (ADS)

The aim of this work was to identify sedimentary facies, i.e. facies having similar biogeochemical, mineralogical and sedimentological properties, in present and recent fine sediments of the Northern and Central Adriatic Sea with their spatial and temporal variations. Further aims were to identify the transportation, dispersion and sedimentation processes and provenance areas of sediments belonging to the facies. A Q-mode factor analysis of mineralogical, granulometric, geochemical (major and trace elements) and biochemical (organic carbon and total nitrogen) properties of surficial and sub-surficial sediments sampled in the PRISMA 1 Project has been used to identify the sedimentary facies. On the whole, four facies were identified: 1) Padanic Facies, made up of fine siliciclastic sediments which reach the Adriatic Sea mainly from the Po River and are distributed by the Adriatic hydrodynamic in a parallel belt off the Italian coast. Southward, this facies gradually mixes with sediments from the Apennine rivers and with biogenic autochthonous particulate; 2) Dolomitic Facies, made up of dolomitic sediments coming from the eastern Alps. This facies is predominant north of the Po River outfalls and it mixes with Padanic Facies sediments in front of the Po River delta; 3) Mn-carbonate Facies, made up of very fine sediments, rich in coccolithophores and secondary Mn-oxy-hydroxides resulting from the reworking of surficial fine sediments in shallow areas and subsequent deposition in deeper areas; 4) Residual Facies, made up of coarse siliciclastic sediments and heavy minerals resulting from the action of waves and coastal currents; this facies is present mainly in inshore areas. The zoning of the facies, resulting from this study, will make possible the identification, through further investigation, on a greater scale, of more accurate facies borders and the recognition of sub-facies, resulting from secondary or weaker biogeochemical processes.

Spagnoli, Federico; Dinelli, Enrico; Giordano, Patrizia; Marcaccio, Marco; Zaffagnini, Fabio; Frascari, Franca

2014-11-01

361

Effect of explicit representation of detailed stratigraphy on brine and gas flow at the Waste Isolation Pilot Plant  

SciTech Connect

Stratigraphic units of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) disposal room horizon includes various layers of halite, polyhalitic halite, argillaceous halite, clay, and anhydrite. Current models, including those used in the WIPP Performance Assessment calculations, employ a ``composite stratigraphy`` approach in modeling. This study was initiated to evaluate the impact that an explicit representation of detailed stratigraphy around the repository may have on fluid flow compared to the simplified ``composite stratigraphy`` models currently employed. Sensitivity of model results to intrinsic permeability anisotropy, interbed fracturing, two-phase characteristic curves, and gas-generation rates were studied. The results of this study indicate that explicit representation of the stratigraphy maintains higher pressures and does not allow as much fluid to leave the disposal room as compared to the ``composite stratigraphy`` approach. However, the differences are relatively small. Gas migration distances are also different between the two approaches. However, for the two cases in which explicit layering results were considerably different than the composite model (anisotropic and vapor-limited), the gas-migration distances for both models were negligible. For the cases in which gas migration distances were considerable, van Genuchten/Parker and interbed fracture, the differences between the two models were fairly insignificant. Overall, this study suggests that explicit representation of the stratigraphy in the WIPP PA models is not required for the parameter variations modeled if ``global quantities`` (e.g., disposal room pressures, net brine and gas flux into and out of disposal rooms) are the only concern.

Christian-Frear, T.L.; Webb, S.W. [Sandia National Labs., Albuquerque, NM (United States). Geohydrology Dept.

1996-04-01

362

Improved method for correlating late Pleistocene/Holocene records from the Bering Sea: application of a biosiliceous/geochemical stratigraphy  

USGS Publications Warehouse

The combination of high-resolution siliceous biostratigraphy and radiocarbon dating provides a mechanism for detailed assessment of the depositional history in late Pleistocene sediments from the Bering Sea where average accumulation rates are uncharacteristically high compared to rates calculated for most other ocean basins. Vital to the development of this stratigraphy was the recognition that the abundance pattern of the radiolarian species Cycladophora davisiana in Bering Sea cores is quite similar to this species' previously correlated abundance curve in a late Pleistocene/Holocene record from the northwest Pacific. Comparison of this high-resolution stratigraphy with other recently developed floral and lithologic stratigraphies for late Pleistocene Bering Sea sediments shows that the various stratigraphies do not always yield identical results when applied to a particular sediment sequence. With this new stratigraphy based upon a combination of siliceous microfaunal abundance patterns and radiocarbon dating, one can identify reworking, discontinuities and other interruptions in the depositional sequence more precisely than with previously devised stratigraphies, thereby improving the correlation techniques for comparison of late Pleistocene/Holocene records from this marginal sea. ?? 1986.

Morley, J. J.; Robinson, S. W.

1986-01-01

363

Sedimentology and sequence stratigraphy of a Tithonian-Valanginian carbonate ramp (Vaca Muerta Formation): A misunderstood exceptional source rock in the Southern Mendoza area of the Neuquén Basin, Argentina  

NASA Astrophysics Data System (ADS)

The Vaca Muerta Formation (early Tithonian-early Valanginian) is a rhythmic succession of marls and limestones, cropping out in the Neuquén Basin, west-central Argentina. This lithostratigraphic unit was traditionally interpreted as basinal to slope deposits. Detailed facies analysis allows to differentiate seven facies associations, representing basinal to middle ramp facies of a homoclinal ramp system prograding westward from the eastern margin, and slope facies attributed to a distally steepened ramp system that progrades eastward from the Andean volcanic arc in the west. Two sequence hierarchies are recognized: five third order depositional sequences, and fifteen fourth order high-frequency sequences. Fluctuations in organic matter content within the Vaca Muerta Formation suggest relationship with depositional sequences, finding the highest values associated with transgressive system tracts. This work represents an important advance in the understanding of the sedimentary and stratigraphic evolution of this exceptional unconventional reservoir. Our sequence stratigraphic approach contributes to the understanding of the relationship between organic matter, facies, and sea-level changes.

Kietzmann, Diego A.; Palma, Ricardo M.; Riccardi, Alberto C.; Martín-Chivelet, Javier; López-Gómez, José

2014-04-01

364

A review of Arbuckle Group strata in Kansas from a sedimentologic perspective: Insights for future research from past and recent studies  

USGS Publications Warehouse

Arbuckle Group and equivalent-age rocks (Cambrian and Lower Ordovician) represent an important record of sediment deposition in the history of the North American continent and they contain important accumulations of hydrocarbons (oil and gas) and base metal deposits. This is true for Kansas as well where Arbuckle strata account for approximately 40% of the volume of produced petroleum and known reserves. However, in comparison to their counterparts in other areas, such as the Ellenburger and Knox, Arbuckle rocks in Kansas remain relatively understudied, especially with respect to sedimentology and diagenesis. The Arbuckle is present in the subsurface in most of Kansas and is absent only in areas of northeastern and northwestern Kansas, and over ancient uplifts and buried Precambrian highs. Arbuckle rocks thicken from north to south and are up to 1,390 feet in the southeastern corner of Kansas. Arbuckle Group and equivalent-age rocks from Kansas and surrounding areas are similar, consisting of platform deposits dominated by ramp-type subtidal to peritidal carbonates (mostly dolomitized) which can be subdivided into cycles, less than 0.5 m to 40 m thick, based on facies type and depositional patterns. Recent studies from central Kansas show that major depositional facies consist of coarse-grained packstones/ grainstones, fine-grained packstones/wackestones/mudstones, stromatolites-thrombolites, intraclastic conglomerate and breccia, and shale. In addition, secondary features include dolomitization, breccia, fracture, and conglomerate related to early subaerial exposure and later karst, burial or structural processes, silicification, and local mineralization. Arbuckle and equivalent strata in the Midcontinent were affected by prolonged subaerial exposure that began immediately after Arbuckle deposition, forming the sub-Tippecanoe to sub-Absaroka unconformity. Favorable reservoir qualities generally are thought to be related directly to basement structural elements and karstic features from the post-Arbuckle subaerial exposure event. Although most production in Kansas is from the top of the Arbuckle, some early and recent studies indicate that the Arbuckle is not a simple homogeneous reservoir, that complex vertical and lateral heterogeneities exist including both nonporous and porous horizons in the formation, and that high probability exist of locating additional oil with improved reservoir characterization. Although fracture and vuggy porosity contribute importantly to the production of Arbuckle strata, recent observations indicate a significant amount of porosity (about 50%) in many cores is controlled by depositional facies and dolomitization. Studies of Arbuckle and equivalent-age strata from other areas indicate that Arbuckle strata and diagenetic processes are complex and that porosity/permeability patterns are related to a number of processes. These studies underscore the importance of continued study of Arbuckle rocks in Kansas for improved reservoir characterization. Ongoing and future geologic studies of Arbuckle rocks in Kansas are being directed toward: (1) Continued sedimentologic, stratigraphic, and sequence stratigraphic analyses incorporating core, well log, and seismic data; (2) petrophysical studies. Initial studies indicate that core plug petrophysical properties are controlled by matrix grain size and that upscalling from plug to whole-core and drill-stem test data can identify and quantify the relative contribution of karstic, fracture and matrix porosity and permeability: (3) Regional and local structural analyses and mapping of the upper Arbuckle surface to provide more details on the contribution of structural features and karst paleogeomorphology to reservoir character; and (4) diagenetic and geochemical studies focusing especially on the timing of, and processes associated with, dolomitization and karstification events and their contributions to creating or occluding porosity.

Franseen, E.K.

2000-01-01

365

Bayesian Uncertainty of Thwaites Glacier Catchment Radar Stratigraphy  

NASA Astrophysics Data System (ADS)

Information about the history and dynamics of ice sheets is contained in basin-scale radar sounding surveys. Englacial, isochronous radar horizons traced throughout the sampled domain of these basins can give a three-dimensional picture of past ice flow by revealing significant details of deformation within the ice column. We focus our efforts in the Thwaites Glacier catchment, West Antarctica, which previous studies have shown to be a bellwether in future WAIS deglaciation scenarios. Here we present a Bayesian determination of the age-depth profile at the Byrd ice core, Antarctica, based on robust uncertainty estimates in ice core ages and radar sounding depths. A simple ice flow model is used to determine the age-depth relationship in ice near the core and a Markov Chain Monte Carlo technique is used to sample a posterior distribution of age as a function of depth to within uncertainty. We propagate the age-depth information, including uncertainty, for several prominent radar reflectors from the Byrd ice-coring site in the Interior Ross Embayment across the ice divide and throughout the Thwaites Glacier catchment using airborne ice-penetrating radar data collected and processed by the University of Texas Institute for Geophysics.

Gutowski, G.; Jackson, C. S.; Blankenship, D. D.; Young, D. A.; Cavitte, M. G.

2013-12-01

366

The Late Holocene Stratigraphy of an Inlet-Dominated Barrier Island, Pea Island, North Carolina.  

NASA Astrophysics Data System (ADS)

Sedimentological, foraminiferal, geochemical, and geophysical data sets as well as aerial photographs have been used to investigate the natural processes (inlet dynamics, ocean/estuarine washover, and sea-level change) responsible for the late Holocene units preserved in the barrier island subsurface at Pea Island National Wildlife Refuge. Historic nautical charts indicate that three inlets characterized Pea Island between early European exploration (1590) and the late 19th century; aerial photographs show New Inlet open in 1932 and 1940. Vibracores (up to 5.5 m) collected along three transects across Pea Island extend our knowledge of the geological evolution of this region to pre-historic times. The section in the longest core (PI01S6) consists of four fining-upwards depositional sequences. The basal unit of each sequence is a bedded, medium to fine, clean quartz sand with increasing concentrations of organic matter (3-4 % detrital and 5-7 % in situ Spartina alterniflora roots) or irregular mud clasts (2-5 cm) to spherical mud balls (1-2 cm) up core. The clean sand units have so far proven to be barren of foraminifera except for a shelly unit at ca. 220 cm below MSL. The foraminiferal assemblage in this unit is of open shelf character (Elphidium excavatum, Hanzawaia strattoni, and Buccella inusitata). A 14C age on a disarticulated Chione cancellata valve from this unit is cal. 930+/-60 BP. The sand grades into a gray, tight mud in the first two sequences and into an inter-laminated mud and in situ peat in the third sequence. The peat contains leaf fragments and rhizomes of the marsh plants Juncus roemarianus, Spartina cynosuroides, and/or Phragmites spp. The peat and muddy sand units contain marsh foraminifera (Trochammina spp., Miliammina fusca, Arenoparrella mexicana), which are also found in modern marsh deposits. A peat sample from the third fining upward sequence (the only one to grade into a true peat) has a 14C age of cal. 395+/-35 BP, cal. 295+/-35 BP, or cal 180+/-40 BP. The four fining-upwards sequences have sharp erosional basal contacts. These deposits appear to reflect back-barrier processes including sequential deposition of flood-tide delta sands and/or sound sands adjacent to marshes. The shelly sands, containing open shelf foraminiferal assemblages, represent oceanic overwash, inlet deposits, or open embayment sands deposited behind a laterally extensive breach in the barrier island. The sequences are capped by the deposits of modern environments that include algal flats, tidal creeks, high and low marshes, back-barrier berms, overwash fans, and aeolian dunes. Several of the modern environments became covered with marsh vegetation after the construction of barrier dune ridges in the late 1930?s.

Smith, C. G.; Ames, D.; Corbett, D. R.; Culver, S.; Mallinson, D.; Riggs, S. R.; Vance, D.

2002-12-01

367

Site characterization using a portable optically stimulated luminescence reader: delineating disrupted stratigraphy in Holocene eolian deposits on the Canadian Great Plains  

NASA Astrophysics Data System (ADS)

The use of portable optically stimulated luminescence (POSL) readers to elucidate on complex depositional sequences has been demonstrated in a number of recent studies. POSL readers are robust versions of the traditional lab-bound luminescence readers and they can be used in the field, allowing for rapid decisions to be made when collecting samples for dating. Furthermore, in contrast with lab-bound readers, POSL readers can perform measurements on bulk samples, negating the need to carry out time-intensive mineralogical separations. The POSL reader is equipped with both infra-red and blue light (OSL) stimulating sources such that signal separation during measurement can be carried out by selectively exciting feldspar using the IR source (IRSL) after which a quartz dominant signal is obtained from the same sample using post-IR blue OSL. The signals obtained are then plotted to give luminescence profiles that depict the variation of the luminescence signal with depth. Signal intensities depend on mineralogical concentrations, grain luminescence sensitivities, dose rates as well as on burial ages of the grains. Where all these variables, apart from the burial age, are held constant up the depositional sequence the luminescence profile serves as a proxy for the chronostratigraphy. As a contribution to a growing archive of studies that have employed POSL readers to unravel complex depositional sequences, this study uses a POSL system developed by the Scottish Universities Environmental Research Centre to characterize the stratigraphy at an archaeological site that lies next to an oilfield plant located on a Holocene fossil dune landscape in southern Alberta, Canada. Oilfield activity was initiated at the site several decades ago and it involved the laying of pipelines below ground which disturbed considerable archaeological deposits. Subsequent work led to the discovery of the archeological site which was previously occupied by ancestral indigenous peoples at various times during the mid to late Holocene. Ongoing maintenance of the original pipelines is now carefully monitored to maximize the protection of the site's archaeological resources, and a critical part of this process is the ability to distinguish between previously disturbed deposits from areas of the site that have intact stratigraphy. The POSL reader was incorporated in this study to address this aspect. As a preliminary test, excavations were made at selected sites and samples collected at 5 cm intervals from four separate profiles. These were then analyzed with the POSL reader using both IRSL and post IR blue OSL stimulation. A portable gamma ray spectrometer was used to determine concentrations of elements responsible for environmental radiation. Constructed luminescence profiles show that areas with disrupted stratigraphy are identifiable by the fluctuating signals, a result of the mixing of strata of varying age. Conversely, zones that have undisturbed stratigraphy display luminescence profiles that have stable signals or show an increase with depth. The luminescence profiling also allows the approximation of relative ages of the undisturbed strata. The approach used in this study has potential for a broad range of applications within the earth sciences.

Munyikwa, K.; Gilliland, K.; Gibson, T.; Plumb, E.

2012-12-01

368

Stratigraphy and erosional landforms of layered deposits in Valles Marineris, Mars  

NASA Astrophysics Data System (ADS)

Satellite imagery is used to identify stratigraphy and erosional landforms of 13 layered deposits in the Valles Marineris region of Mars (occurring, specifically, in Gangis, Juventae, Hebes, Ophir-Candor, Melas, and Capri-Eos Chasmata), based on albedo and erosional styles. Results of stratigraphic correlations show that the stratigraphy of layered deposits in the Hebes, Juventae, and Gangis Chasmata are not well correlated, indicating that at least these chasmata had isolated depositional environments resulting in different stratigraphic sequences. On the other hand, the layered deposits in Ophir-Candor and Melas Chasmata appear to have been connected in each chasma. Some of the layered deposits display complexities which indicate changes in space and time in the dominant source materials.

Komatsu, G.; Geissler, P. E.; Strom, R. G.; Singer, R. B.

1993-06-01

369

Sequence Stratigraphy—Concepts and Applications: Norwegian Petroleum Society, Special Publication No. 8  

NASA Astrophysics Data System (ADS)

As prefaced by the authors, this special publication of the Norwegian Petroleum Society (NPF) stems from a conference, titled “Predictive High Resolution Sequence Stratigraphy,” sponsored by the society. The first half of the book consists of six studies dedicated to a conceptual overview of sequence stratigraphy and stratigraphic simulation applications and philosophies, while the second half focuses on 12 studies covering high-resolution sequence descriptions relating to the distribution and modeling of hydrocarbon reservoirs in the North Sea basin.While the high-resolution theme is beautifully developed and illustrated in regards to conveying the characteristics of reservoir sands, the supporting modeling studies are somewhat limited, showing a strong emphasis on two-dimensional geometric formulations. Simulations are presented for depositional stratigraphic systems in locales such as the United States, North and Barents Sea basins, and Bangladesh.

Karner, Garry D.

370

Neogene carbonate exploration play concepts for Northern New Guinea: New iteration from field work and seismic stratigraphy along the Northern New Guinea Fault Zone  

SciTech Connect

Recent field reconnaissance, petrography, nanno and foraminifera age determinations, and seismic stratigraphy of the Sepik and Piore subbasins of northern New Guinea reveal the existence of an extensive, tectonically unstable, Miocene-Pliocene carbonate shelf system. These findings represent the first recorded evidence of northern Papuan limestones coeval in age to those of the hydrocarbon productive Salawati Basin of Irian Jaya. Moreover, these observations also demonstrate the significance of episodic activities of the northern New Guinea fault zone upon the changes in carbonate sedimentation and diagenesis. During the Neogene, algal biosparites to foraminiferal biomicrites defined the clean portion of a mixed clastic-carbonate shelf system of the northern New Guinea basin, which began at the central New Guinea cordillera and deepened northward. This shelf was interrupted by coral-coralline algal boundstone fringing- to patch-reef buildups with associated skeletal grainstones. Clean carbonates were spatially and temporally restricted to basement blocks, which episodically underwent uplift while terrigenous dilutes carbonates were more common in adjacently subsiding basement block bathymetric lows. These tectonic expressions were caused by the spatially transient nature of constraining bends of the evolving north New Guinea faults. As shown by seismic stratigraphy, by the late Miocene to the early Pliocene the uplift of the Bewani-Torricelli Mountains sagittally divided the shelf of the northern New Guinea basin into the Ramu-Sepik and the Piore basins. Continued regional sinistral transpression between the Pacific and the New Guinea leading edge of the Indo-Australian plates led to the reverse tilting of the Piore basin, the shallowing of the former distal shelf with concomitant extensive biolithite development (e.g., on subsiding volcanic islands) eventual uplifting of the Oenake Range, and en echelon faulting of the Bewani-Torricelli Mountains.

Pigott, J.D.; Geiger, C. (Univ. of Oklahoma, Norman, OK (United States))

1994-07-01

371

Deglacial and Holocene evolution of the Vietnam shelf: stratigraphy, sediments and sea-level change  

Microsoft Academic Search

On the Vietnam Shelf more than 1000 miles of shallow high-resolution seismics were analyzed to unravel post-glacial evolution in a tropical, siliciclastic environment together with 25 sediment cores from water depths between 21 and 169 m to determine stratigraphy, distribution and style of sedimentation. Fourty-seven samples were dated with the AMS-14C technique.The shelf was grouped into three regions: a southern

A. Schimanski; K. Stattegger

2005-01-01

372

Holocene erosion, sedimentation, and stratigraphy at Raven Fork, Southern Blue Ridge Mountains, USA  

Microsoft Academic Search

Holocene colluvial and alluvial stratigraphy and a radiocarbon chronology are presented for the valley of the lower three kilometers of Raven Fork, a mountain stream draining 194 km2 of high relief (1.3 km) terrain of the Southern Blue Ridge Mountains in western North Carolina, USA, which is in a region that lacks good chronological data. Lower hillslopes, alluvial\\/colluvial fans, alluvial

David S. Leigh; Paul A. Webb

2006-01-01

373

Image analysis for measuring stratigraphy in sand-gravel laboratory experiments  

NASA Astrophysics Data System (ADS)

Measurements of spatial and temporal changes in the grain size distribution are crucial to improving the modelling of sediment transport and associated grain size-selective processes. We present three complementary techniques to determine such variations in the grain size distribution in sand-gravel laboratory experiments, as well as the resulting stratigraphy: (1) particle colouring, (2) removal of sediment layers, and (3) image analysis. The resulting stratigraphy measurement method has been evaluated in two sets of experiments. In both sets three grain size fractions within the range of coarse sand to fine gravel were painted in different colours. Sediment layers are removed using a wet vacuum cleaner. Subsequently areal images are taken of the surface of each layer. The areal fraction content, i.e. the relative presence of each size fraction over the bed surface, is determined using a colour segmentation algorithm which provides the areal fraction content of a specific colour (i.e., grain size) covering the bed surface. Particle colouring is not only beneficial to this type of image analysis but also observing and understanding grain size-selective processes. The stratigraphy based on areal fractions is measured with sufficient accuracy. Other advantages of the proposed stratigraphy measurement technique are: (a) rapid collection and processing of a large amount of data, (b) very high spatial density of information on the grain size distribution (so far unequalled in other methods), (c) the lack of disturbances to the bed surface, (d) only minor disturbances to the substrate due to the removal of sediment layers, and (e) the possibility to return a sediment layer at its original elevation and continue the flume experiment. The areal fractions can be converted into volumetric fractions using a conversion model. The proposed empirical conversion model is based on a comparison between the photogrammetry results and dry sieve analysis.

Orrú, C.; Chavarrías, V.; Uijttewaal, W. S. J.; Blom, A.

2013-11-01

374

A revised stratigraphy and petrogenetic interpretation of the Cordilleran basement in the Mazatlan, Sinaloa region (NW Mexico): Evidence from new geochemical and geochronological data  

NASA Astrophysics Data System (ADS)

The age, composition, and thermal history of the cordilleran basement in NW Mexico are still poorly known. We focus here on the Mazatlan, Sinaloa region where previous works identified the following sequences: 158 Ma orthogneisses(U-Pb) are covered by metamorphosed clastic sediments of supposed Jurassic age which are intruded by a mafic complex mainly represented by 134-139 Ma gabbros (K-Ar hornblende ages). Both rock series are considered as parts of the basement in this region. The remaining stratigraphy is characterized by a batholitic complex formed by two major magmatic events. The first one, around 100 Ma (U-Pb and K-Ar), is tonalitic in composition with some signs of regional deformation associated to a syntectonic emplacement. The second one, between 46 and 83 Ma (K-Ar), varies from diorite to granodiorite. The latter is the most widely distributed event, hosts the important ore deposits in the region and is interpreted to be emplaced postectonically, and. Our new U-Pb geochronological data include the identification of two additional plutonic events. The first occurred at 136 Ma and was obtained from the Concordia granodiorite 30 km E of Mazatlan. This unit was formerly dated at 54 Ma (hornblend, biotite; K-Ar). A fourth plutonic unit (Copala granodiorite) was dated at 28 Ma and can be correlated to the Upper Sierra Madre Supergroup. Additionally we obtained detrital zircon ages from a paragneiss covering the 158 Ma orthogneisses with peaks at 256 Ma, 492 Ma, and 1014 Ma. Our field observations indicate a reset of the 134-139 Ma gabbro ages by the close Concordia granodiorite, whose biotites were in turn rehomogenized by the 46 to 83 Ma plutonic event. Until now very few geochemical and Sr-Nd isotopic studies with petrogenetic interpretation of the units mentioned above are published. The results of our new investigations will be presented at the meeting as well as a new dataset for the coastal Quaternary Piaxtla basalt and its peridotitic xenoliths. These rocks are related to the opening of the Gulf of California and give evidence for the local upper mantle composition. In the light of the new geochronological information an updated stratigraphy and chronology of the magmatic and thermal events in the area is under work. The discrepancy between some of the previously reported ages and our new data can be explained by a complex thermal history which resetted some of the earlier published K-Ar hornblende and mica ages.

Arrieta, G. F.; Schaaf, P. E.; Maldonado, R.; Solis, G.; Weber, B.; Rodriguez, L.

2013-12-01

375

Postglacial eruptive history of Laguna del Maule volcanic field in Chile, from fallout stratigraphy in Argentina  

NASA Astrophysics Data System (ADS)

The Laguna del Maule (LdM) volcanic field, which surrounds the 54-km2 lake of that name, covers ~500 km2 of rugged glaciated terrain with Quaternary lavas and tuffs that extend for 40 km westward from the Argentine frontier and 30 km N-S from the Rio Campanario to Laguna Fea in the Southern Volcanic Zone of Chile. Geologic mapping (Hildreth et al., 2010) shows that at least 130 separate vents are part of the LdM field, from which >350 km3 of products have erupted since 1.5 Ma. These include a ring of 36 postglacial rhyolite and rhyodacite coulees and domes that erupted from 24 separate vents and encircle the lake, suggesting a continued large magma reservoir. Because the units are young, glassy, and do not overlap, only a few ages had been determined and the sequence of most of the postglacial eruptions had not previously been established. However, most of these postglacial silicic eruptions were accompanied by explosive eruptions of pumice and ash. Recent investigations downwind in Argentina are combining stratigraphy, grain-size analysis, chemistry, and radiocarbon dating to correlate the tephra with eruptive units mapped in Chile, assess fallout distribution, and establish a time-stratigraphic framework for the postglacial eruptions at Laguna del Maule. Two austral summer field seasons with a tri-country collaboration among the geological surveys of the U.S., Chile, and Argentina, have now established that a wide area east of the volcanic field was blanketed by at least 3 large explosive eruptions from LdM sources, and by at least 3 more modest, but still significant, eruptions. In addition, an ignimbrite from the LdM Barrancas vent complex on the border in the SE corner of the lake traveled at least 15 km from source and now makes up a pyroclastic mesa that is at least 40 m thick. This ignimbrite (72-75% SiO2) preceded a series of fall deposits that are correlated with eruption of several lava flows that built the Barrancas complex. Recent 14C dates suggest that most of the preserved LdM fallout eruptions were between 7 ka and 2 ka. However, the oldest and perhaps largest fall unit yet recognized is correlated with the Los Espejos rhyolite lava flow that dammed the lake and yields a 40Ar/39Ar age of 23 ka. Pumice clasts as large as 8.5 cm and lithics to 4 cm were measured 32 km ENE of source. It is the only high-silica rhyolite (75.5-76% SiO2) fall layer yet found, correlates chemically with the Los Espejos rhyolite lava flow, and includes distinctive olivine-bearing lithics that are correlated with mafic lavas which underlie the Espejos vent. Extremely frothy pumice found near the vent is also consistent with the bubble-wall shards and reticulite pumice distinctive of the correlative fall deposit. Another large rhyolite fall deposit (74.5% SiO2), 4 m thick 22 km E of source, has pumice clasts to 9.5 cm and includes ubiquitous coherent clasts of fine, dense soil that suggests it erupted through wet ground; 14C dates (uncalibrated) yield ages ~7 ka. Stratigraphic details suggest that pulses of fallout were accompanied by small pyroclastic flows. Ongoing field and lab work continues to build the LdM postglacial eruptive story. The numerous postglacial explosive eruptions from the LdM field are of significant concern because of ongoing 33 cm/year uplift along the western lakeshore, as measured by InSAR and verified by GPS.

Fierstein, J.; Sruoga, P.; Amigo, A.; Elissondo, M.; Rosas, M.

2012-12-01

376

Sedimentology of the Neoproterozoic (c. 580 Ma) Squantum 'Tillite', Boston Basin, USA: Mass flow deposition in a deep-water arc basin lacking direct glacial influence  

NASA Astrophysics Data System (ADS)

The Squantum 'Tillite' (c. 593-570 Ma) consists of thick (up to 215 m) massive and crudely-stratified diamictites conformably interbedded with subaqueously-deposited conglomerates and sandstones within a thick (~ 7 km) Boston Basin fill which is dominated by argillite turbidites. The Squantum Tillite was first interpreted as being glacigenic in origin in 1914 because of the presence of diamictites; argillites were interpreted as glaciolacustrine 'varves' with rare ice-rafted debris, and conglomerates as glaciofluvial outwash. More recently these have been shown to be the product of deep marine mass flow processes with no glacial influence, yet because of its age equivalence with the deep marine, glacially-influenced Gaskiers Formation, the Squantum Tillite is still seen by some as supporting evidence for a widespread 'Snowball Earth' event at c. 580 Ma. New sedimentological work confirms that conglomerate and sandstone facies are deep marine sediment gravity flows genetically related to massive (homogeneous) and crudely-stratified (heterogeneous) diamictites produced subaqueously by downslope mixing of gravel and cobbles with muddy facies. Rare horizons of 'ice rafted debris' in thin-bedded and laminated turbidite facies interbedded with thick debrites show a weak but positive correlation of lamina thickness with grain size, suggesting these facies are non-glacial co-genetic 'debrite-turbidite' couplets. A significant volcanic influence on sedimentation is identified from reworked lapilli tuff beds and reworked ash in turbidites. The depositional setting of the Squantum 'Tillite' appears to be that of a submarine slope/fan setting in an open marine volcanic arc basin receiving large volumes of poorly-sorted sediment on the mid-latitude active margin of Gondwana. No direct glacial influence is apparent.

Carto, Shannon L.; Eyles, Nick

2012-08-01

377

Mars - Stratigraphy and gravimetry of Olympus Mons and its aureole  

NASA Technical Reports Server (NTRS)

The relative ages of the major geologic units on and around Olympus Mons are considered, together with an interpretation of the gravity anomaly found for this area. The crater data for this investigation have been acquired and interpreted according to the method outlined by Neukum and Hiller (1981). After careful geological mapping, craters clearly identified as impacts are measured and counted. Crater frequency values per sq km for craters greater than or equal to 1 km ('crater retention ages') are read from the individual counts by fitting the Martian cumulative crater production size-frequency distribution to the individual counts. In addition to age dating, the problem of the origin and nature of the aureole materials using gravity data is addressed. This is done by determining whether the line-of-sight gravity extending from Olympus Mons to the northwestern part of the aureole can be explained by the aureole masses alone or whether additional high-density intrusive masses must be assumed in the aureola area.

Hiller, K. H.; Neukum, G. P. O.; Janle, P.; Guest, J. E.; Lopes, R. M. C.

1982-01-01

378

Sedimentology and geomorphology of a relict lacustrine system in Tingri, Tibet, China  

NASA Astrophysics Data System (ADS)

A patchy sequence of near horizontal sedimentary deposits composed of consolidated carbonate-rich laminated gravelly sand and silt are exposed on the hill slopes near Tingri, Tibet, China. They are classified as mid- to late-Pleistocene and Holocene lacustrine deposits in Chinese geological maps, but the style and nature of lacustrine deposition and the facies associations in the sequence have never been reported. This study presents a number of sections in the locality showing the varied sedimentology of the deposits. The deposits are interpreted as relict sandy or gravelly dune ridges and plains, salt pans, prograded deltas, and lacustrine sediments. Interpretation was primarily based on a comparison with modern inland lakes in the Tibetan Plateau as analogues of processes in arid mountain lake systems. Relict dune ridges appear on the margins of many Tibetan inland lakes where the highly erosive regime allowed an abundant supply of gravels and sand to deposit along lake shorelines. The strong winds in Tibet have also allowed high to medium energy shoreline systems to develop in exposed areas. The high gravel and carbonate content in the gravelly ridges provided ample resistance to erosion and they often remain a topographically pronounced feature after lake drainage. Salt pans and gravelly or sandy ridge fields are also left after lake regression along with rare lacustrine deltas represented by the lakeward prograding beds. Laminated shelly sand or silt preserved in pockets near the valley floor characterise deposition at deeper lacustrine regimes. At Tingri the exposures of the palaeoshoreline deposits can reach 20 m in thickness and are identified at an elevation ranging from 4286 to 4404 masl. Although patchy in occurrence the sequence suggests a relatively long lived relict lake system. The timing of lake phases is poorly constrained by optically stimulated luminescence mid-to-late Pleistocene and Holocene. A number of incised channels are observed in various deposits in Tingri, indicating high energy drainage during lake regression. The final drainage history leading to the disappearance of this large compound lake system is uncertain, but this rapid, high volume drainage of lake water downstream may provide a partial explanation for the rapid incision of the Arun Gorge located at the southeastern boundary of the reconstructed lake of Tingri.

Chiu, H.; Switzer, A. D.; Aitchison, J.

2010-12-01

379

Biogeomorphological influence of slope processes and sedimentology on vascular talus vegetation in the southern Cascades, California  

NASA Astrophysics Data System (ADS)

The vascular vegetation of alpine talus slopes between 2035 and 3095 m altitude was studied at Lassen Volcanic National Park (California) in the Cascade Range. Taluses show a diverse flora, with 79 plant species; growth forms include coniferous trees, shrubs, suffrutices, herbs, graminoids, and ferns. Spatial patterns of plant distribution were studied along 40 point-intercept transects. Plant cover was low (0-32.7%) on all slopes, spatially variable, and showed no consistent trends. Sedimentological characteristics were determined by photosieving next to 1500 plants; this census indicated preferential plant growth on blocks and cobbles, with 43.2% and 23.3% of the plants growing on these stones, respectively; fewer specimens were rooted on pebbles (13%) or on stone-free gravel areas (20.5%). Growth forms displayed different substrate preferences: 92.5% of the shrubs and 83% of the suffrutices colonized blocks or cobbles, but only 57.2% of the herbs and 59.8% of the graminoids grew on large stones. Plants are associated with large clasts because (1) coarse talus is more stable than fine sediment areas, which are more frequently disturbed by various geomorphic processes, and (2) large stones help conserve substrate water beneath them while moisture quickly evaporates from fine debris. Root patterns were studied for 30 plant species; 10 specimens for each species were excavated and inspected, and several root growth ratios calculated. All species exhibited pronounced root asymmetry, as roots for most plants grew upslope from their shoot base. For 23 species, all specimens had 100% of their roots growing upslope; for the other 7 species, 92.2-99.3% of below-ground biomass extended uphill. This uneven root distribution is ascribed to continual substrate instability and resulting talus shift; as cascading debris progressively buries roots and stems, plants are gradually pushed and/or stretched downhill. Various disturbance events affect root development. Slope erosion following rubble removal often exposes plant roots. Debris deposition can completely bury plants; some may survive sedimentation, producing new shoots that grow through accumulated debris. Shrubs may propagate by layering, as adventitious roots develop along buried stems; or produce new clones along their roots. Slope processes may damage and transport plant pieces downhill; some species can sprout from severed, displaced root or stem fragments. Vegetation interacts with several geomorphic processes, including debris flows, grain flows, rockfall, snow avalanches, frost creep, and runoff. Larger plants may alter local patterns of debris movement and deposition, damming cascading debris on their upslope side and deflecting sediments laterally to plant margins, where they form narrow elongated stone stripes.

Pérez, Francisco L.

2012-02-01

380

Sedimentological, Mineralogical and Geochemical Characterization of Sand Dunes in Saudi Arabia  

NASA Astrophysics Data System (ADS)

Sedimentological, mineralogical, morphological and geochemical studies of sand dunes from ten locations in Saudi Arabia were conducted in order to determine the differences between them and to find out the provenance and tectonic setting of these sand dunes. Sixty seven samples were collected from different sand dunes types ranging in morphology from linear, barchans, parabolic to stars dunes. In overall, the sand dunes are fine to coarse grained mean grain size, moderately sorted, near symmetrical skewness with mesokurtic distribution characterized sand dunes in most locations. The sand dunes grains are subrounded in all locations except in the Red sea, Qassim, central Arabia and the eastern province which showed sub-angular grains. The main mineral compositions of studied aeolian sand dunes are quartz, feldspar, calcite, and mica. Quartz is the dominant mineral in locations with significant amount of feldspars and mica in Najran, Red sea and Central Arabia locations. Moreover, calcite is present in Sakaka and NW Empty Quarter (Jafurah). Basement related sand dunes in Najran, Central Arabia and Red sea locations are sub-mature in terms of their mineralogical maturity. Whereas, sand dunes in other locations are texturally mature except those from the Red sea which showed sub-mature sand. The sands are classified as quartz arenite, except in the basement related sand dunes in Najran, central Arabia and the Red sea are ranging from sub-arkose, sub-litharenite and lithraenite. Morphologically, parallel to sub-parallel sand ridges with NE-SW orientation occurred in east and north parts of Empty Quarter (Najran and Jafurah) and NW-SE orientation in Dahna and Nafud deserts in central and north regions of Saudi Arabia. Parabolic sand dunes characterized the Nafud desert (Hail, Sakaka, Tayma locations). Barchans and star sand dunes characterize the Empty Quarter (Jafurah). Major, trace, and rare earth elements studies were carried out to determine the composition, provenance and tectonic history of the sand dunes. Geochemical analysis indicated that most of sand dunes are quartz arenite type, except in the Red sea, basement related central Saudi Arabia and Najran areas, the sand dunes are sub-arkoses, sub-litharenite and litharenite. The concentration of major,trace and rare elements showed active continental margins as a tectonic setting of Red sea, basement related Najran and central Arabia sand dune. In contrast, passive continental margins for the other locations. The distribution of major, trace and rare earth elements showed similarity in chemical composition between basement related sand dunes in Red sea, Najran and central Arabia.

Benaafi, Mohammed; Abdullatif, Osman

2014-05-01