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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

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

3

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

4

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

5

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

6

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

7

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

8

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

9

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

10

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

11

Sedimentology and stratigraphy of a transgressive, muddy gravel beach: Waterside Beach, Bay of Fundy, Canada  

Microsoft Academic Search

Sediments exposed at low tide on the transgressive, hypertidal (>6 m tidal range) Waterside Beach, New Brunswick, Canada permit the scrutiny of sedimentary structures and textures that develop at water depths equivalent to the upper and lower shoreface. Waterside Beach sediments are grouped into eleven sedimentologically distinct deposits that represent three depositional environments: (1) sandy foreshore and shoreface; (2) tidal-creek

SHAHIN E. DASHTGARD; MURRAY K. GINGRAS; KARL E. BUTLER

2006-01-01

12

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

13

Stratigraphy, sedimentology, chronology and palaeohydrology of Quaternary lacustrine deposits at Madigan Gulf, Lake Eyre, south Australia  

Microsoft Academic Search

Madigan Gulf is a large bay at the southern end of Lake Eyre North, a major ephemerally flooded playa in arid central Australia at the southwestern margin of a vast (1,300,000 km2) internal drainage basin. The stratigraphy and chronology of the Quaternary sequence in the gulf is described from 8 cores and a cliff exposure at the gulf margin. A

J. W. Magee; J. M. Bowler; G. H. Miller; D. L. G. Williams

1995-01-01

14

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

15

Sedimentology, stratigraphy, and extinctions during the Cretaceous-Paleogene transition at Bug Creek, Montana  

SciTech Connect

Bug Creek Valley, the source of an unusual and controversial Cretaceous-Paleogene coincidence of mammals, dinosaurs, pollen, and iridium, exemplifies the importance of depositional process in the reconstruction of evolutionary events. Five sedimentary facies are recognized at Bug Creek: a cross-stratified sandstone, a green and purple siltstone, a lateral accretionary sandstone, a coal, and a variegated siltstone. Repeated fluvial channeling restricts the accuracy of lateral correlations, and the relationship of the fossil assemblage to the presumed Cretaceous-Paleogene boundary cannot be established. Sedimentologically, the Cretaceous-Paleogene transition is represented here by Cretaceous meandering channels that gave way initially to Paleogene swamp deposition. 13 references, 4 figures.

Fastovsky, D.E.; Dott, R.H. Jr.

1986-04-01

16

Physical stratigraphy and sedimentology of an alluvial fan delta complex (south Pyrenean basin, Spain)  

SciTech Connect

The Santa Liestra is comprised of four main stratigraphic units with a major stratigraphic unconformity separating unit 2 from unit 3. This unconformity is expressed by an abrupt facies change and large-scale shelf instability features, and it probably represents a depositional sequence boundary related to a phase of thrust movement within the Santa Liestra sequence. Field correlations on transverse cross sections through the basin show a typical foreland asymmetrical clastic wedge; these correlations also illustrate the sheet-like geometry of the fan delta-front deposits. This study of a large fan delta-front system furnishes insight into the complex interactions governing the geometry and sedimentological characteristics of potential petroleum reservoirs in foreland basin settings.

Crumeyrolle, P.

1988-08-01

17

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

18

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

19

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

20

Stratigraphy, sedimentology and tectonic evolution of the Upper Cretaceous/Paleogene succession in north Eastern Desert, Egypt  

NASA Astrophysics Data System (ADS)

The stratigraphy, sedimentology and syn-depositional tectonic events (SdTEs) of the Upper Cretaceous/Paleogene (K-P) succession at four localities in north Eastern Desert (NED) of Egypt have been studied. These localities are distributed from south-southwest to north-northeast at Gebel Millaha, at North Wadi Qena, at Wadi El Dakhal, and at Saint Paul Monastery. Lithostratigraphically, four rock units have been recorded: Sudr Formation (Campanian-Maastrichtian); Dakhla Formation (Danian-Selandian); Tarawan Formation (Selandian-Thanetian) and Esna Formation (Thanetian-Ypresian). These rock units are not completely represented all over the study area because some of them are absent at certain sites and others have variable thicknesses. Biostratigrapgically, 18 planktonic foraminiferal zones have been recorded. These are in stratigraphic order: Globotruncana ventricosa Zone (Campanian); Gansserina gansseri, Contusotruncana contusa, Recimguembelina fructicosa, Pseudohastigerina hariaensis, Pseudohastigerina palpebra and Plummerita hantkenenoides zones (Maastrichtian); Praemurica incostans, Praemurica uncinata, Morozovella angulata and Praemurica carinata/Igorina albeari zones (Danian); Igorina albeari, Globanomanlina pseudomenradii/Parasubbotina variospira, Acarinina subsphaerica, Acarinina soldadoensis/Globanomanlina pseudomenardii and Morozovella velascoensis zones (Selandian/Thantian); and Acarinina sibaiyaensis, Pseudohastigerina wilcoxensis/Morozovella velascoensis zones (earliest Ypresian). Sedimentologically, four sedimentary facies belts forming southwest gently-dipping slope to basin transect have been detected. They include tidal flats, outer shelf, slumped continental slope and open marine hemipelagic facies. This transect can be subdivided into a stable basin plain plus outer shelf in the extreme southwestern parts; and an unstable slope shelf platform in the northeastern parts. The unstable slope shelf platform is characterized by open marine hemipelagic, fine-grained limestones and fine siliciclastic shales (Sudr, Dakhla, Tarawan and Esna formations). The northeastern parts are marked by little contents of planktonic foraminifera and dolomitized, slumped carbonates, intercalated with basinal facies. Tectonically, four remarkable syn-depositional tectonic events (SdTEs) controlled the evolution of the studied succession. These events took place strongly within the Campanian-Ypresian time interval and were still active till Late Eocene. These events took place at: the Santonian/Campanian (S/C) boundary; the Campanian/Maastrichtian (C/M) boundary; the Cretaceous/Paleogene (K/P) boundary; and the Middle Paleocene-Early Eocene interval. These tectonic events are four pronounced phases in the tectonic history of the Syrian Arc System (SAS), the collision of the Afro-Arabian and Eurasian plates as well as the closure of the Tethys Sea.

El Ayyat, Abdalla M.; Obaidalla, Nageh A.

2013-05-01

21

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

22

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

23

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

24

Stratigraphy, sedimentology and eruptive mechanism of the El Golfo phreatomagmatic edifice (Lanzarote, Canary Islands)  

NASA Astrophysics Data System (ADS)

The El Golfo tuff cone is an example of phreatomagmatic edifice, developed in the western coast of Lanzarote (Canary Islands). El Golfo, together with other edifices of the same age, is aligned along a fracture oriented NEE-SWW coinciding with the main lineation of the historic volcanism in this part of the island. In this contribution we present a detailed stratigraphic study of the succession of deposits and we interpret them in terms of depositional processes and eruptive dynamics. The eruptive sequence is exclusively represented by a succession of pyroclastic deposits, and we infer it according to variations in flow regime and the magma-water interaction. Several pyroclastic units were identified according to facies variations based on sedimentary discontinuities, grain size, components, variations in primary laminations and bedforms following the facies model proposed by Chough and Sohn (1990). The growth of the El Golfo tuff cone involved several stages based on variations in depositional processes. The edifice was constructed very rapidly around the vent controlling the amount of water that got access to the eruption conduit. Although the invariable phreatomagmatic character of most of the pyroclastic sequence, it is possible to deduce variations in the explosive energy, with a general increment upwards, according to the increase in the degree of fragmentation of pyroclasts, The absence of hyaloclastites, the nature of the palagonite alteration and the observed sedimentary structures, demonstrate the subaereal character of most of the deposits

Pedrazzi, D.; Marti, J.; Geyer, A.

2012-04-01

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

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

27

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.

28

Sedimentology and Stratigraphy Architecture of the late Pleistocene-Holocene Succession of the Gargaresh Formation, Subratah Basin, NW Libya  

NASA Astrophysics Data System (ADS)

Gargaresh Formation outcrops is comprises the outcrops between the Misurata (N32o22'18'' E15o12'03'') to the Tripoli(N32o 51'10'' E13o 03'22'') areas is represented by prominent carbonate aeolianite exposed in extensive outcrops along the NW Libyan shoreline. Gargaresh Formation outcrops comprises two Members an upper Kaam Member of Aeolian origin and a lower Karrot Member of marine origin. The study of the Gargaresh Formation can provide useful information on reconstructions of Late Pleistocene-Holocene history of NW Libya and new insights on palaeogeography. It is forming low ridges and cliffs along the coastline of NW Libya and occurs as cliffs continuously attached to the sea tide, and occasionally interrupted by broad wadis or deep-cut embayment. The Gargaresh Formation sediments are dominated by calcarenites with skeletal marine fauna and non-skeletal grains of lithoclasts, aggregate, with oolites. In addition, these rocks are characterized by very well aeolian controlling factors represented by wind blown sediments such as large scale cross lamination (aeolianite) . The majority of palaeocurrent direction was to SE, on the other hand the dune migration was SE also. The sediments of Gargaresh Formation outcrops from Misurata to Tripoli NW Libya mostly allochthonous except the paleosols red-brown unit. Most of its fossils are thanatoconoses. Gargaresh Formation sediments shows that the original aragonite composition of pelecypoda and gastropods fragments are mostly preserved, but partly transformed into granular calcite as pendulous (meniscus) cement texture in response to meteoric fresh-water. Keywords: Sedimentology; Stratigraphic architecture; Aeolian origin; marine origin; Calcarenites; Late Pleistocene-Holocene

Hlal, Osama; Bennur, Sami

2014-05-01

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

Stratigraphy and Isotope Ages of Lunar Geologic Units: Chronological Standard for the Inner Solar System  

Microsoft Academic Search

The absolute ages of cratered surfaces in the inner solar system, including Mars, are derived by extrapolation from the impact flux curve for the Moon which has been calibrated on the basis of absolute ages of lunar samples. We reevaluate the lunar flux curve using isotope ages of lunar samples and the latest views on the lunar stratigraphy and the

D. Stöffler; G. Ryder

2001-01-01

31

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

32

Sedimentology and stratigraphy of the middle Eocene Guara carbonate platform near Arguis, South-West Pyrenean foreland: Implications for basin physiography  

NASA Astrophysics Data System (ADS)

The Pyrenees results from the collision between Spain and Europe and developed between the upper Cretaceous (Santonian) and the Miocene. Its foreland basins are characterised by a thick fill of detrital and carbonate sediments. The diversity of Eocene deposits in the southern Pyrenean foreland basin is of particular use in facies sedimentology due to their exceptional outcropping quality and well established stratigraphic framework and has been taken as type examples of many different sedimentary environments. Most studies have concerned facies sedimentology of detrital series in turbiditic environments, meandering and braided rivers, alluvial fans, and deltas. In contrast, the Eocene carbonate series have attracted less attention. The marine Guara limestones are a formation of lower to middle Eocene age deposited on the southern border of the western Pyrenean foreland basin (Jaca basin). They were deposited as a retrogradational carbonate platform dominated by large benthic foraminifers near or at the flexural forebulge of the foreland basin as the Pyrenean orogen developed. This formation represents the last episode of carbonate platform in the Pyrenees and remains poorly studied. In the present work our aim is to provide a detailed facies analysis and physiographic reconstructions of the Guara carbonate platform. This is crucial to unravel the respective influences of tectonics, climate and rheology of the lithosphere on the foreland basin tectonic and stratigraphic development, and it brings new constraints on the paleoenvironments and paleogeography during the Lutetian, i.e. at the beginning of the major phase of activity of the Pyrenean orogenesis. Two outcrops were studied in the Sierras Marginales at the localities of Arguis and Lusera. The Lusera section once restored in its initial position is located to the North of the Arguis section in a basinward direction such that comparing time-equivalent facies between these two sections helps us reconstructing the paleobathymetric gradient on this side of the foreland basin. The sedimentological and paleontological content show that the Guara formation was deposited in shallow water environments (less than 80 m) and can be classified as a carbonate ramp. The evolution of paleobathymetries with time on these two sections allows us to identify three complete progradational - retrogradational cycles. Those cycles do not match global eustatic variations, perhaps indicating the dominating influence of tectonics in this area. The precise study of foraminifera allowed us to date our sections with respect to the SBZ time scale of Serra-Kiel et al. (1). The bottom of the Guara formation, in the Arguis section is dated from the lower Lutetian (SBZ 13) and the top corresponds to the upper Lutetian (SBZ 16). An important hiatus is recorded between the base of the carbonates and the lower Paleocene subjacent continental deposits. Moreover, the base of the formation is older at Lusera i.e. to the centre of the basin. This hiatus could thus represent the foreland flexural forebulge unconformity (2). By restoring the relative position of the two sections during the Lutetian, we have calculated the possible slope of the Guara ramp during this period for each MFS, with values always lower than 0.5°. Extrapolating this slope to the centre of the basin allows us to estimate the paleodepth of the coeval Eocene turbidites and address the important issue of the depth of deposition of submarine fan systems in foreland settings. Within the limits of our approach we propose that these clastic fan systems have been deposited under water depths of 400 to 200 metres. This is partly in agreement with the upper bound of other estimations based on foraminiferal assemblages and trace fossils, and thus favours a relatively "shallow" view of the Middle Eocene Ainsa-Jaca deep marine basin. 1. J. Serra-Kiel et al., Bulletin De La Societe Geologique De France 169, 281 (March 1, 1998, 1998). 2. S. L. Crampton, P. A. Allen, Aapg Bulletin 79, 1495 (October 1, 1995, 1995).

Huyghe, D.; Castelltort, S.; Serra-Kiel, J.; Filleaudeau, P.-Y.; Emmanuel, L.; Mouthereau, F.; Renard, M.

2009-04-01

33

Mars north polar deposits: stratigraphy, age, and geodynamical response  

USGS Publications Warehouse

The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed ???100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements.

Phillips, R. J.; Zuber, M. T.; Smrekar, S. E.; Mellon, M. T.; Head, J. W.; Tanaka, K. L.; Putzig, N. E.; Milkovich, S. M.; Campbell, B. A.; Plaut, J. J.; Safaeinili, A.; Seu, R.; Biccari, D.; Carter, L. M.; Picardi, G.; Orosei, R.; Surdas, Mohit, P.; Heggy, E.; Zurek, R. W.; Egan, A. F.; Giacomoni, E.; Russo, F.; Cutigni, M.; Pettinelli, E.; Holt, J. W.; Leuschen, C. J.; Marinangeli, L.

2008-01-01

34

Late Eocene impact microspherules - Stratigraphy, age and geochemistry  

NASA Astrophysics Data System (ADS)

The stratigraphy, faunal changes, and geochemistry of deep-sea sediments associated with late Eocene microtektite and microspherule layers are reported. Microprobe analyses of major element compositions of microspherules show that, although there is some compositional overlap in all three late Eocene layers as well as with the Pleistocene Australasian and Ivory Coast microtektites, each microspherule population has characteristic compositional features. All three microspherule layers are associated with decreased carbonate, possibly due to a sudden productivity change, increased dissolution as a result of sea-level and climate fluctuations, or impact events. A discovery of microtektites in the Gl. cerroazulensis Zone off the New Jersey coast extends the North American strewn field from the Caribbean to the northwest Atlantic.

Keller, G.; D'Hondt, S. L.; Orth, C. J.; Gilmore, J. S.; Oliver, P. Q.; Shoemaker, E. M.; Molina, E.

1987-03-01

35

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

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

Radiocarbon ages of bones from Vistulian (Weichselian) cave deposits in Poland and their stratigraphy  

NASA Astrophysics Data System (ADS)

Twenty-six bone samples from cave sediments mainly of Vistulian (Weichselian) age were radiocarbon (AMS) dated. The material comes from seven localities in the Krakow-Cz?stochowa Upland and in Podhale (southern Poland). These are: the Komarowa Cave, the Deszczowa Cave, the Upper Rock Shelter of the Deszczowa Cave, the cave in Dziadowa Ska?a, the S?spowska Zachodnia Cave, the Mamutowa Cave and the Ob?azowa Cave. The obtained radiocarbon ages of most of the samples differs from their stratigraphy as formerly proposed. The reasons for this discrepancy are discussed. Also examined were the radiocarbon ages of bones from other caves in the study area. Most of the dated bones are shown to have come from relatively short time periods. The existing data on radiocarbon age of bones from Vistulian cave deposits of the Krakow-Cz?stochowa Upland and Podhale are summarized.

Lorenc, Micha?

2013-09-01

38

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

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

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

41

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

42

Stratigraphy and Sedimentology of Radioactive Devonian--Mississippian Shales of the Central Appalachian Basin. Final Report, April 1, 1975--December 31, 1976.  

National Technical Information Service (NTIS)

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, organi...

L. J. Provo

1976-01-01

43

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

44

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

45

Sedimentological and micromorphological investigation on the fill of the Bronze age wooden pool at Noceto La Torretta (northern Italy)  

NASA Astrophysics Data System (ADS)

A recent excavation at Noceto La Torretta (Parma, northern Italy) revealed an exceptional archaeological structure, composed of a wooden pool, quadrangular in shape, about 12 x 6 m, up to 4 m deep. Since the beginning the pool appears as an unicum in the Prehistory of Europe (Bernabò Brea and Cremaschi, 2009); furthermore, it represents an important naturalistic and environmental archive and the sedimentary infilling undergone to sedimentological and micromorphological analyses. The Noceto La Torretta site is placed on the hydrographic left side of the Taro river, on the northernmost fringe of the Pleistocene Apennine terraces. On the basis of pottery type it is possible to attribute the structure to the Terramare culture (beginning of the advanced phase of the Middle Bronze Age, second half of XV century a.C.). Six radiocarbon dates are available up to now, and, once calibrated, they put the building and activity of the wooden pool between 1420 and 1320 cal. years BP. On the basis of sedimentological and micromorphological analyses (Cremaschi et al., 2009) the stratigraphic sequence could be divided into four groups of units. A) Upper deposits, silty and sandy sediments deposited by colluviation in shallow water, interlayered by charcoal and diatom rich layers. B) Organic deposits, formed in deeper and anoxic water. C) Gyttja in a sandy-silty matrix; three main facies are present: pair of organic and inorganic laminae (O/I), poorly laminated gyttja, anoxic and clastic layers. D) basal deposits. Considering the short time of the deposition inside the pool and the recurrent sedimentary facies, a seasonal control in sedimentation should be inferred. The gyttja-rich laminae should indicate the summer season, with intense biological activity inside and outside the pool, promoting a strong production of organics, while the anoxic and clastic layers are possibly related to the winter season (without production of organic matter). Finally, the O/I laminae represent the rain seasons (spring/autumn), marked by intense sheet-erosion of the banks of the pool. References Bernabò Brea, M., Cremaschi, M., 2009. La vasca di Noceto La Torretta. Acqua e civiltà nell'età del Bronzo. Università degli Studi di Milano e Skirà, Milano. Cremaschi, M., Ferrari, P., Salvioni, M., Zerboni, A., 2009. Il riempimento della vasca e della fossa. In: Bernabò Brea M., Cremaschi M. (Eds.), La vasca di Noceto La Torretta. Acqua e civiltà nell'età del Bronzo. Università degli Studi di Milano e Skirà, Milano, pp. 112-120.

Zerboni, Andrea; Cremaschi, Mauro

2010-05-01

46

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

47

Sedimentology and Age Control of Late Quaternary New Jersey Shelf Deposits  

NASA Astrophysics Data System (ADS)

High-resolution Chirp geophysical profiles have delineated a complex network of shallowly buried stratigraphic features within the New Jersey shelf. These features have been interpreted as fluvial channel incisions ("channels" horizon) and associated infill and regional erosional unconformities (e.g., "R" horizon) related to sea-level fluctuations during the late Quaternary. Age control on these features has been difficult to obtain, hindering geologic interpretations and stratigraphic model development. In addition, the ONR Geoclutter Initiative, also carried out on the New Jersey margin, is seeking to understand and model the interaction of these and similar buried structures with incident acoustic energy from tactical sonars. To address both these needs, drill cores were collected at 3 sites with the DOSECC AHC-800 from the RV KNORR in Sept-Oct 2002. Sites were selected from Chirp profiles to target prominent geologic features and cores were analyzed for texture, AMS C-14 age control and physical properties. These results will be integrated with complementary geophysical studies to provide a better understanding of the Quaternary geologic history of the New Jersey margin. Site 1 (129 m water depth) penetrated the outer shelf wedge, which has been interpreted as predominantly a submarine deltaic deposit. Sediments are sandy from 0-1.0 mbsf, and exhibit ages of ~7-10 kyr BP, whereas deeper than ~1.0 mbsf, sediments are clays interlaminated with silts and are much older, ~32 Kyr BP. This transition from sand to silty clay and a hiatus of 20 kyrs suggests transgression-related nearshore storage of coarser terrigenous material and outer shelf sediment starvation and/or erosion. Site 2 (80 m water depth) penetrated the axis of a large, infilled channel beneath the mid-shelf. These dominantly sandy channel-fill sediments have been previously interpreted as the infill of a fluvial/estuarine(?) system. Below the surficial sand sheet, from ~0.8-3.3 mbsf, ages fall between 12.8 and 12.3 kyr BP, whereas from ~4.0-10.8 mbsf, ages fall between 13.5 and 13.4 kyr BP. The boundary between these two units with distinct age ranges corresponds to a downcore change in dominant sediment type from sand to mud, suggesting a transition from estuarine to nearshore/open marine shelf conditions ~13 kyr BP. Site 3 (76 m water depth) penetrated through both the surficial sand sheet and the "R" erosional unconformity. Although sediments are similarly sandy throughout, ages above "R" are younger than ~10 kyr BP, whereas ages below "R" vary between ~40 and 35 ky BP, confirming previous interpretations of "R" as a lowstand erosional unconformity and/or a transgression-related hiatus.

Alexander, C.; Sommerfield, C.; Austin, J.; Christensen, B.; Fulthorpe, C.; Goff, J.; Gulick, S.; Nordfjord, S.; Nielson, D.; Schock, S.

2003-12-01

48

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

49

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

50

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

51

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

52

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.

53

Stratigraphy and wiggle-matching-based age-depth model of late Holocene marine sediments in Beppu Bay, southwest Japan  

NASA Astrophysics Data System (ADS)

We analyzed the lithology, magnetic susceptibility, bulk density, and X-ray radiographs of 14 sediment cores (1-9 m long) from Beppu Bay in the western Seto Inland Sea, Japan, to establish the late Holocene stratigraphy in the deepest part of the bay and to develop an age-depth model for the sediments there. The cores contained 18 thick (major event) high-density layers (16 turbidites and two volcanic ash; >1 cm thick), and both lithological observations and density variations in the hemipelagic mud that is dominant in the cores revealed a further 55 thin (minor event) high-density layers (<1 cm thick). Analyses of color properties and opal and sand contents of the hemipelagic mud defined nine lithological units. After stratigraphic correlation of the event layers among cores, we projected 14C dates onto a single composite core. Forty-two AMS 14C dates from bivalve mollusk shells were used to construct a wiggle-matching-based age-depth model for the late Holocene sequence and to determine the local reservoir effect (?R). The age-depth model showed a sedimentation rate of 0.23-0.30 cm/yr for a 7.8 m-long composite core and an age of ˜2800 cal yr BP at the base. Wiggle-matching provided ?R values of 115-155 yr for late Holocene bivalve samples from Beppu Bay, which is consistent with previous estimates reported from coastal areas near the Kuroshio Front. Comparison of wiggle-matching-derived ages of thick turbidites with the ages of historical earthquakes showed differences within ±25 yr. Our study demonstrated that wiggle matching with optimal fitting based on either the weighted least-squares or maximum likelihood method can minimize the effect of scatter of age data due to reworking and burrowing of bivalves and thus improve the accuracy of age-depth models.

Kuwae, Michinobu; Yamamoto, Masanobu; Ikehara, Ken; Irino, Tomohisa; Takemura, Keiji; Sagawa, Takuya; Sakamoto, Tatsuhiko; Ikehara, Minoru; Takeoka, Hidetaka

2013-06-01

54

Problems in the interpretation of lunar mare stratigraphy and relative ages indicated by ejecta from small impact craters  

NASA Technical Reports Server (NTRS)

The numbers of large ejecta blocks in excess of several meters in diameter ('blockiness') around the rims of small craters in southeastern Mare Serenitatis exceed those around similar craters in southern Mare Imbrium (and some other regions) at all but the final stages of crater degradation. Terrestrial explosion crater analogs, studies of impact processes, and a layered mare model suggest that the nature of the layering in the subsurface, including lavas, ejecta and buried regolith horizons, could account for the variable blockiness of crater ejecta and, possibly, for some variation in crater size-frequency distributions. Such effects would limit the reliability and utility of counting postmare craters for the purpose of estimating the relative ages of mare surfaces. Similarly, comparisons of the effects of progressive degradation on small impact craters to determine relative or absolute ages of individual craters may be limited by the influence of stratigraphy on ejecta fragment size distributions, which would in turn affect micrometeorite erosion rates and regolith production models.

Young, R. A.; Brennan, W. J.; Nichols, D. J.

1974-01-01

55

Lunar Impact Basins: Stratigraphy, Sequence and Ages from Superposed Impact Crater Populations Measured from Lunar Orbiter Laser Altimeter (LOLA) Data  

NASA Technical Reports Server (NTRS)

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 impactor population as a function of time, we have used topography from the Lunar Orbiter Laser Altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) to measure the superposed impact crater size-frequency distributions for 30 lunar basins (D = 300 km). These data generally support the widely used Wilhelms sequence of lunar basins, although we find significantly higher densities of superposed craters on many lunar basins than derived by Wilhelms (50% higher densities). Our data also provide new insight into the timing of the transition between distinct crater populations characteristic of ancient and young lunar terrains. The transition from a lunar impact flux dominated by Population 1 to Population 2 occurred before the mid-Nectarian. This is before the end of the period of rapid cratering, and potentially before the end of the hypothesized Late Heavy Bombardment. LOLA-derived crater densities also suggest that many Pre-Nectarian basins, such as South Pole-Aitken, have been cratered to saturation equilibrium. Finally, both crater counts and stratigraphic observations based on LOLA data are applicable to specific basin stratigraphic problems of interest; for example, using these data, we suggest that Serenitatis is older than Nectaris, and Humboldtianum is younger than Crisium. Sample return missions to specific basins can anchor these measurements to a Pre-Imbrian absolute chronology.

Fassett, C. I.; Head, J. W.; Kadish, S. J.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

2012-01-01

56

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

57

New Age-Constraints on Syn-Tectonic Stratigraphy and Basin Evolution in the Southwestern Chinese Tian Shan Foreland  

NASA Astrophysics Data System (ADS)

The Kashi foreland basin in NW China contains >8 km of syn-tectonic sediments related to uplift and deformation along the southern margin of the Tian Shan during late Tertiary time. Foreland deposits consist of fine-grained, gypsiferous, lacustine beds (Wuqia Group) near the base that grade up-section into fluvial sandstone and siltstone (Atushi Fm.), with the fluvial Xiyu Conglomerates capping the basin sequence. The distinctive Xiyu Conglomerates form a wedge that thins and interfingers with silt and sand ubiquitously towards the south (distal basin) and locally east-west. The Xiyu Formation is widely distributed around the margin of the Tian Shan, and has been inferred to represent Plio-Pleistocene initiation of deformation of the Tian Shan (e.g. Huang et al., 1980), or a change in either climate (e.g. Burchfiel et al., 1999; Molnar et al., 1994) or a climate-affected erosion rate (Zhang et al, 2001). In contrast, our data show that the Xiyu conglomerates are a time-transgressive formation that has continuously prograded south since at least ~16 Ma, and likely does not represent a distinct climatic or tectonic event from one time period. Eight magnetostratigraphic sections totaling 10,000 m of vertical section through the entire basin sequence, and correlated with the Geomagnetic Polarity Timescale of Cande and Kent (1995), indicate continuous deposition between 0 and ~18 Ma. Paleocurrent data from throughout the basin are consistent with longitudinal drainages moving south as transverse (north-to-south), braided, fluvial systems encroach on the foreland. Clast size, sorting, and composition are consistent with initial unroofing of Paleozoic source rocks to the north, and subsequent re-working and erosion of this conglomerate during progradation into the foreland in concert with a migrating deformation front. Deposition rates increase from <200m/Myr in the early to middle Miocene to ~800 m/My during the Pliocene. These sedimentary data, combined with an 18+/-3 Ma fission track age from the hanging wall of the basin-bounding thrust fault (KBT), indicate that deposition in the Kashi basin began at ~18 Ma. The basin age of 18 Ma is younger than fission-track ages (ca. 25 Ma) from the major range bounding faults ~ 20 km north of the KBT. Thus, the stratigraphy and thermochronolgy support continuous and generally accelerating deposition in the Kashi foreland basin since 18 Ma related to uplift on the KBT, and a syn-tectonic origin for the time-transgressive Xiyu conglomerate. Prior to 18 Ma, the flexural foreland may have lain farther to the north.

Heermance, R. V.; Chen, J.; Burbank, D. W.; Sobel, E. R.

2005-12-01

58

Statistical Models in Sedimentology.  

National Technical Information Service (NTIS)

Three stages of statistical development can be recognized in sedimentology. The first is descriptive statistics, in which the sample is the object of interest, and the second is analytical statistics, in which the population assumes major importance. The ...

W. C. Krumbein

1967-01-01

59

Characterizing avulsion stratigraphy in ancient alluvial deposits  

NASA Astrophysics Data System (ADS)

Guidelines for identifying ancient avulsion deposits were set forth by Kraus and Wells [Kraus, M.J., Wells, T.M., 1999. Recognizing avulsion deposits in the ancient stratigraphical record. In: Smith, N.D., Rogers, J. (Eds.), Fluvial Sedimentology VI, Special Publication of the International Association of Sedimentologists, vol. 28, pp. 251-268], building on the study by Smith et al. [Smith, N.D., Cross, T.A., Dufficy, J.P., Clough, S.R., 1989. Anatomy of an avulsion. Sedimentology 36, 1-23] of the modern Saskatchewan River system (Cumberland Marshes, central Canada), and serve to characterize avulsion depositional sequences in the ancient Willwood and Fort Union Formations (Paleogene, Bighorn Basin, NW Wyoming, USA). We recognize, however, that the model is not universally applicable to avulsion-dominated successions, specifically systems which lack defining "heterolithic avulsion deposits", set forth by Kraus and Wells [Kraus, M.J., Wells, T.M., 1999. Recognizing avulsion deposits in the ancient stratigraphical record. In: Smith, N.D., Rogers, J. (Eds.), Fluvial Sedimentology VI, Special Publication of the International Association of Sedimentologists, vol. 28, pp. 251-268]. Observations in several fluvial intervals suggest that the avulsion stratigraphy outlined by Kraus and Wells [Kraus, M.J., Wells, T.M., 1999. Recognizing avulsion deposits in the ancient stratigraphical record. In: Smith, N.D., Rogers, J. (Eds.), Fluvial Sedimentology VI, Special Publication of the International Association of Sedimentologists, vol. 28, pp. 251-268] represents one category of avulsion stratigraphy found in the rock record, but does not capture the nature of avulsion deposits everywhere. Based on observations (using measured sections, outcrop photo-panels, and aerial photographs) in the Willwood Formation (Eocene, Wyoming) and Ferris Formation (Cretaceous/Paleogene, Wyoming), we present two end-member categories of avulsion stratigraphy in ancient deposits; stratigraphically abrupt, when a main paleochannel is stratigraphically juxtaposed directly atop floodplain/overbank deposits, and stratigraphically transitional, where crevasse splays and other non-floodplain/-overbank deposits stratigraphically precede a main paleochannel. This characterization provides a broader, more inclusive way to recognize and describe avulsion stratigraphy in ancient deposits and may be an important factor to consider when modeling connectivity in fluvial reservoirs. Furthermore, our observations show that one type of avulsion channel stratigraphy may prevail over another within an ancient basin, suggesting that system-wide factors such as splay-proneness or avulsion style (i.e. aggradational, incisional, etc.; [Slingerland, R., Smith, N.D., 2004. River avulsions and their deposits. Annual Review of Earth and Planetary Sciences 32, 257-285]) may be primary controls on the type of avulsion stratigraphy deposited and preserved in ancient basin-fills.

Jones, H. L.; Hajek, E. A.

2007-11-01

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

Age constraints, sedimentology, and tectonics from a well bedded sequence of Feuerstätter Sandstein south of Balderschwang, Allgäu Alps, Bavaria  

NASA Astrophysics Data System (ADS)

The majority of the outcrops of the alpine Feuerstätter Sandstein in southwestern Bavaria and Vorarlberg (Austria) suggests rather massive, homogeneous, more or less glauconite-containing sandstone bodies than well bedded sequences. Normally, the up to 50 m thick Feuerstätter Sandstein formation is characterized by the absence of datable material, massive brittle tectonic deformation and recent mass movements. In contrast, an unusually well bedded sequence of Feuerstätter Sandstein is exposed in the Lappach valley south of the village of Balderschwang, lining the border between Bavaria and Vorarlberg. This specific sandstone succession contains several thin marly intercalations from which samples have been collected recently. Calcareous nannoplancton dating of these marl samples provides an upper Middle-Eocene depositional age which is the youngest age reported for the Feuerstätter Sandstein. The sequence of the quartz sandstone of the Lappach succession including the marly layers is tectonically undisturbed. The beds dip northwards, steeply inclined at the bottom (85°) and moderately in the uppermost part (40°) of the sequence. The sandstone beds of the main part of the complex reveal mostly layers which are 0.1 to 0.7 m thick. In contrast, the uppermost beds exposed within the sequence show an increasing thickness of 2.5 to 4.5 m. A variety of different sedimentary structures occur in individual beds of the lower part: graded bedding, varying grain sizes, different amounts of glauconite, local occurrence of feldspar clasts, fine lamination and N-S striking channel structures at the bottom of certain sandstone layers. Within the uppermost exposed particularly thick and poorly to unsorted deposits of the sequence coarser grain sizes occur, containing even small quartz pebbles. The continuous development from the well bedded and fine grained basal layers towards the massive and coarser grained sandstone deposits at the top suggests sedimentation from a distal to a proximal position in a submarine fan, reflecting an increase of energy within the deposits. Sedimentary structures and northwards inclined beds suggest sediment transport from south to north. Additionally, a syn-sedimentary northward tilting of the base of the sedimentary succession during deposition cannot be excluded. Origin of the deposited sands is most likely a diversified coastal realm providing sand material of various stages of maturity and composition. Among instabilities of sand masses near the coast, frequent seismic activities can be assumed to have triggered the individual events of deposition observed in the Lappach valley sandstone succession, most likely driven by actively prograding tectonic nappes in the south.

Blaha, Ulrich; Scholz, Herbert; Rochow, Henning v.; Lebsanft, Frans

2014-05-01

62

Lithofacies, Age, and Sequence Stratigraphy of the Carboniferous Lisburne Group in the Skimo Creek Area, Central Brooks Range  

USGS Publications Warehouse

The Lisburne Group, a mainly Carboniferous carbonate succession that is widely distributed across northern Alaska, contains notable amounts of oil and gas at Prudhoe Bay. Detailed studies of the Lisburne in the Skimo Creek area, central Brooks Range, delineate its lithofacies, age, conodont biofacies, depositional environments, and sequence stratigraphy and provide new data on its hydrocarbon source-rock and reservoir potential, as well as its thermal history, in this area. We have studied the Lisburne Group in two thrust sheets of the Endicott Mountains allochthon, herein called the Skimo and Tiglukpuk thrust sheets. The southern, Skimo Creek section, which is >900 m thick, is composed largely of even-bedded to nodular lime mudstone and wackestone intercalated with intervals of thin- to thick-bedded bioclastic packstone and grainstone. Some parts of the section are partially to completely dolomitized and (or) replaced by chert. A distinctive, 30-m-thick zone of black, organic-rich shale, lime mudstone, and phosphorite is exposed 170 m below the top of the Lisburne. The uppermost 40 m of section is also distinctive and made up of dark shale, lime mudstone, spiculite, and glauconitic grainstone. The northern, Tiglukpuk Creek section, which is similar to the Skimo Creek section but only ~760 m thick, includes more packstone and grainstone and less organic-rich shale. Analyses of conodonts and foraminifers indicate that both sections range in age from late Early Mississippian (Osagean) through Early Pennsylvanian (early Morrowan) and document a hiatus of at least 15 m.y. at the contact between the Lisburne and the overlying Siksikpuk Formation. No evidence of subaerial exposure was observed along this contact, which may represent a submarine erosional surface. Lithofacies and biofacies imply that the Lisburne Group in the study area was deposited mainly in midramp to outer-ramp settings. Deepest water strata are mud rich and formed below storm or fair-weather wave base on the outer ramp to outer midramp; shallowest facies are storm, sand-wave, and shoal deposits of the inner midramp to inner ramp. A relatively diverse, open-marine fauna occurs throughout much of the Lisburne in the study area, but some beds also contain clasts typical of more restricted, shallow-water environments that were likely transported seaward by storms and currents. Radiolarians are abundant in the shale and phosphorite unit at Skimo Creek and also occur in equivalent strata at Tiglukpuk Creek; high gamma-ray response and elevated total organic-carbon contents (max 5?8 weight percent) also characterize this unit at Skimo Creek. Lithologic, faunal, and geochemical data all suggest that these rocks formed mainly in an outer-ramp to basinal setting with low sedimentation rates, high productivity, and poorly oxygenated bottom water. Shale and mudstone at the top of the Lisburne Group accumulated in a similarly sediment starved, mainly outer ramp environment but lack comparable evidence for high nutrient and low oxygen levels during deposition. Vertical shifts in rock types and faunas delineate numerous parasequences and six probable third-order sequences in the study area; the same sequences are also recognized in the Lisburne Group to the east. Transgressive-system tracts in these sequences generally fine upward, whereas highstand-system tracts coarsen upward. Sequences in the Tiglukpuk Creek section are mostly thinner, contain thinner and more numerous parasequences, and accumulated in somewhat shallower settings than those in the Skimo Creek section. These differences reflect the more seaward position and, thus, increased accommodation space of the Skimo Creek section relative to the Tiglukpuk Creek section during deposition. Organic-rich calcareous shale in the shale and phosphorite unit has a cumulative thickness of at least 15 m and a lateral extent of >50 km; this lithology is the best potential hydrocarbon source rock in the Lisburne Group

Dumoulin, Julie A.; Whalen, Michael T.; Harris, Anita G.

2008-01-01

63

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

64

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

65

Stratigraphy and structure of coalbed methane reservoirs in the United States: an overview  

USGS Publications Warehouse

Stratigraphy and geologic structure determine the shape, continuity and permeability of coal and are therefore critical considerations for designing exploration and production strategies for coalbed methane. Coal in the United states is dominantly of Pennsylvanian, Cretaceous and Tertiary age, and to date, more than 90% of the coalbed methane produced is from Pennsylvanian and cretaceous strata of the Black Warrior and San Juan Basins. Investigations of these basins establish that sequence stratigraphy is a promising approach for regional characterization of coalbed methane reservoirs. Local stratigraphic variation within these strata is the product of sedimentologic and tectonic processes and is a consideration for selecting completion zones. Coalbed methane production in the United States is mainly from foreland and intermontane basins containing diverse compression and extensional structures. Balanced structural models can be used to construct and validate cross sections as well as to quantify layer-parallel strain and predict the distribution of fractures. Folds and faults influence gas and water production in diverse ways. However, interwell heterogeneity related to fractures and shear structures makes the performance of individual wells difficult to predict.Stratigraphy and geologic structure determine the shape, continuity and permeability of coal and are therefore critical considerations for designing exploration and production strategies for coalbed methane. Coal in the United States is dominantly of Pennsylvanian, Cretaceous and Tertiary age, and to date, more than 90% of the coalbed methane produced is from Pennsylvanian and Cretaceous strata of the Black Warrior and San Juan Basins. Investigations of these basins establish that sequence stratigraphy is a promising approach for regional characterization of coalbed methane reservoirs. Local stratigraphic variation within these strata is the product of sedimentologic and tectonic processes and is a consideration for selecting completion zones. Coalbed methane production in the United States is mainly from foreland and intermontane basins containing diverse compressional and extensional structures. Balanced structural models can be used to construct and validate cross sections as well as to quantify layer-parallel strain and predict the distribution of fractures. Folds and faults influence gas and water production in diverse ways. However, interwell heterogeneity related to fractures and shear structures makes the performance of individual wells difficult to predict.

Pashin, J. C.

1998-01-01

66

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

PubMed 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.

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

67

Recent Trends and Advances in Sedimentology.  

ERIC Educational Resources Information Center

Briefly surveys recent trends and developments in sedimentology. Includes Clastic sedimentary petrology, petrology of argillaceous rocks, terrigenous depositional environments, and chemical sedimentology. (MA)

Suttner, Lee J.

1979-01-01

68

Stratigraphy of the Anthropocene  

NASA Astrophysics Data System (ADS)

The Anthropocene is an informal unit that has recently been introduced to refer to the current interval of anthropogenic global environmental change. It is being increasingly adopted in the scientific literature, and has also attracted widespread public interest in emphasizing the scale of contemporary environmental perturbation. An argument may therefore be put forward for its eventual formalization. Such formalization would be the responsibility of the International Commission on Stratigraphy (ICS) and would be preceded by formation of an Anthropocene Working Group, best attached to the Subcommission on Quaternary Stratigraphy. Consideration of evidence for and against formalization would take several years, and would enter novel territory for such discussions. This might include assessment of ongoing environmental change in the context of the near-present and earlier stratigraphic record, and likely also forward-modelling (of sea level, ocean/atmospheric chemistry, biotic composition and so on). Consideration of an effective boundary needs also be made, including whether it should be linked to a Global Stratigraphic Section and Point (GSSP) or Global Stratigraphic Standard Age (GSSA), and also of the hierarchical scale of the unit. We here ask the ICS to establish an Anthropocene Working Group, without prejudice to the eventual outcome. As in past determinations of formal chronostratigraphic boundaries, focussing scientific debate on this question would provide valuable data and insights to both the geological and wider scientific communities

Zalasiewicz, J.; Williams, M.; Haywood, A.; Kerr, A. C.; Pearson, P.; Smith, A.; Barry, T. L.; Coe, A.; Bown, P. R.; Brenchley, P.; Gale, A.; Gibbard, P.; Gregory, F. J.; Hounslow, M.; Knox, R.; Powell, J.; Waters, C.; Marshall, J.; Oates, M.; Rawson, P.; Stone, P.

2008-12-01

69

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

70

Age modelling of late Quaternary marine sequences in the Adriatic: Towards improved precision and accuracy using volcanic event stratigraphy  

Microsoft Academic Search

The first part of this paper presents a review of the problems that constrain the reliability of radiocarbon-based age models with particular focus on those used to underpin marine records. The reasons why radiocarbon data-sets need to be much more comprehensive than has been the norm hitherto, and why age models should be based on calibrated data only, are outlined.

J. J. Lowe; S. Blockley; F. Trincardi; A. Asioli; A. Cattaneo; I. P. Matthews; M. Pollard; S. Wulf

2007-01-01

71

Age modelling of late Quaternary marine sequences in the Adriatic: Towards improved precision and accuracy using volcanic event stratigraphy  

NASA Astrophysics Data System (ADS)

The first part of this paper presents a review of the problems that constrain the reliability of radiocarbon-based age models with particular focus on those used to underpin marine records. The reasons why radiocarbon data-sets need to be much more comprehensive than has been the norm hitherto, and why age models should be based on calibrated data only, are outlined. The complexity of the probability structure of calibrated radiocarbon data and the advantages of a Bayesian statistical approach for constructing calibrated age models are illustrated. The second part of the paper tests the potential for reducing the uncertainties that constrain radiocarbon-based age models using tephrostratigraphy. Fine (distal) ash layers of Holocene age preserved in Adriatic prodelta sediments are analysed geochemically and compared to tephras preserved in the Lago Grande di Monticchio site in southern Italy. The Monticchio tephras have been dated both by radiocarbon and varve chronology. The importance of basing such comparisons on standardised geochemical and robust statistical procedures is stressed. In this instance, both the Adriatic and Monticchio geochemical measurements are based on wavelength dispersive spectrometry, while discriminant function analysis is employed for statistical comparisons. Using this approach, the ages of some of the Adriatic marine ash layers could be estimated in Monticchio varve years, circumventing some of the uncertainty of radiocarbon-based age models introduced by marine reservoir effects. Fine (distal) ash layers are more widespread and better preserved in Mediterranean marine sequences than realised hitherto and may offer much wider potential for refining the dating and correlation of Mediterranean marine sequences as well as marine-land correlations.

Lowe, J. J.; Blockley, S.; Trincardi, F.; Asioli, A.; Cattaneo, A.; Matthews, I. P.; Pollard, M.; Wulf, S.

2007-02-01

72

Holocene evolution of seasonal stratification in the Celtic Sea: refined age model, mixing depths and foraminiferal stratigraphy  

Microsoft Academic Search

Published stable isotopic (oxygen, carbon) and preliminary foraminiferal data from a Holocene vibrocore from the Celtic Sea (Northwest European continental shelf) have been interpreted in terms of the progressive replacement of tidally mixed by seasonally stratified water, the first study of the long-term dynamics of seasonal stratification. This study was hampered by poor age control and the foraminiferal data were

J. D. Scourse; W. E. N. Austin; B. T. Long; D. J. Assinder; D. Huws

2002-01-01

73

Sequence stratigraphy, structural style, and age of deformation of the Malaita accretionary prism (Solomon arc-Ontong Java Plateau convergent zone)  

NASA Astrophysics Data System (ADS)

Possibilities for the fate of oceanic plateaus at subduction zones range from complete subduction of the plateau beneath the arc to complete plateau-arc accretion and resulting collisional orogenesis. Deep penetration, multi-channel seismic reflection (MCS) data from the northern flank of the Solomon Islands reveal the sequence stratigraphy, structural style, and age of deformation of an accretionary prism formed during late Neogene (5-0 Ma) convergence between the ˜33-km-thick crust of the Ontong Java oceanic plateau and the ˜15-km-thick Solomon island arc. Correlation of MCS data with the satellite-derived, free-air gravity field defines the tectonic boundaries and internal structure of the 800-km-long, 140-km-wide accretionary prism. We name this prism the "Malaita accretionary prism" or "MAP" after Malaita, the largest and best-studied island exposure of the accretionary prism in the Solomon Islands. MCS data, gravity data, and stratigraphic correlations to islands and ODP sites on the Ontong Java Plateau (OJP) reveal that the offshore MAP is composed of folded and thrust faulted sedimentary rocks and upper crystalline crust offscraped from the Solomon the subducting Ontong Java Plateau (Pacific plate) and transferred to the Solomon arc. With the exception of an upper, sequence of Quaternary? island-derived terrigenous sediments, the deformed stratigraphy of the MAP is identical to that of the incoming Ontong Java Plateau in the North Solomon trench. We divide the MAP into four distinct, folded and thrust fault-bounded structural domains interpreted to have formed by diachronous, southeast-to-northwest, and highly oblique entry of the Ontong Java Plateau into a former trench now marked by the Kia-Kaipito-Korigole (KKK) left-lateral strike-slip fault zone along the suture between the Solomon arc and the MAP. The structural style within each of the four structural domains consists of a parallel series of three to four fault propagation folds formed by the seaward propagation of thrust faults roughly parallel to sub-horizontal layering in the upper crystalline part of the OJP. Thrust fault offsets, spacing between thrusts, and the amplitude of related fault propagation folds progressively decrease to the west in the youngest zone of active MAP accretion (Choiseul structural domain). Surficial faulting and folding in the most recently deformed, northwestern domain show active accretion of greater than 1 km of sedimentary rock and 6 km, or about 20%, of the upper crystalline part of the OJP. The eastern MAP (Malaita and Ulawa domains) underwent an earlier, similar style of partial plateau accretion. A pre-late Pliocene age of accretion (˜3.4 Ma) is constrained by an onshore and offshore major angular unconformity separating Pliocene reefal limestone and conglomerate from folded and faulted pelagic limestone of Cretaceous to Miocene age. The lower 80% of the Ontong Java Plateau crust beneath the MAP thrust decollement appears unfaulted and unfolded and is continuous with a southwestward-dipping subducted slab of presumably denser plateau material beneath most of the MAP, and is traceable to depths >200 km in the mantle beneath the Solomon Islands.

Phinney, Eric J.; Mann, Paul; Coffin, Millard F.; Shipley, Thomas H.

2004-10-01

74

Lunar highland stratigraphy and radiometric dating  

Microsoft Academic Search

The relevance of lunar highland rock ages to highland and basin stratigraphy is discussed. It is found that radiometric age data for highland rocks do not in any simple way reflect the time of excavation of the major circular basins from which they are believed to originate. Instead, many rocks are of a more local origin and, moreover, radiometric clocks

P. Horn; T. Kirsten

1977-01-01

75

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

76

Messinian events: new constraints from sedimentological investigations and new 40Ar\\/ 39Ar ages in the Melilla–Nador Basin (Morocco)  

Microsoft Academic Search

New 40Ar\\/39Ar ages obtained both from within a platform and from the adjacent basin allow, through the extension of a previous argon dataset, the establishment of a chronological framework for the Messinian carbonate complex of Melilla (Morocco). In the platform, prograding bioclastic deposits began around 6.87±0.02 Ma, whereas the youngest preserved deposits are 5.77±0.04 Ma old. The southern part of

J. J Cornée; S Roger; P Münch; J. P Saint Martin; G Féraud; G Conesa; S Pestrea-Saint Martin

2002-01-01

77

Missoula flood dynamics and magnitudes inferred from sedimentology of slack-water deposits on the Columbia Plateau, Washington  

SciTech Connect

Sedimentological study of late Wisconsin, Missoula-flood slack-water sediments deposited along the Columbia and Tucannon Rivers in southern Washington reveals important aspects of flood dynamics. Most flood facies were deposited by energetic flood surges (velocities>6 m/sec) entering protected areas along the flood tract, or flowing up and then directly out of tributary valleys. True still-water facies are less voluminous and restricted to elevations below 230 m. High flood stages attended the initial arrival of the flood wave and were not associated with subsequent hydraulic ponding upslope from channel constrictions. Among 186 flood beds studied in 12 sections, 57% have bioturbated tops, and about half of these bioturbated beds are separated from overlying flood beds by nonflood sediments. A single graded flood bed was deposited at most sites during most floods. Sequences in which 2-9 graded beds were deposited during a single flood are restricted to low elevations. These sequences imply complex, multi-peaked hydrographs in which the first flood surge was generally the largest, and subsequent surges were attenuated by water already present in slack-water areas. Slack-water - sediment stratigraphy suggests a wide range of flood discharges and volumes. Of >40 documented late Wisconsin floods that inundated the Pasco Basin, only about 20 crossed the Palouse-Snake divide. Floods younger than the set-S tephras from Mount St.Helens were generally smaller than earlier floods of late Wisconsin age, although most still crossed the Palouse-Snake divide. These late floods primarily traversed the Cheney-Palouse scabland because stratigraphy of slack-water sediment along the Columbia River implies that the largest flood volumes did not enter the Pasco Basin by way of the Columbia River. 47 refs., 17 figs., 2 tabs.

Smith, G.A. (Univ. of New Mexico, Albuquerque (United States))

1993-01-01

78

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

79

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

80

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

81

Sub-Ice Shelf Stratigraphy as Documented From Beneath the Larsen B Ice Shelf, Antarctica  

NASA Astrophysics Data System (ADS)

The final disintegration of the Larsen B Ice shelf (March 2002) was a significant event in the history of glaciology. During NBP01-07, the Larsen B Ice shelf area was surveyed as a continuation of a multi-year investigation of the sediment processes and paleohistory of the Larsen B. Six kasten cores (KC1-KC6) were recovered from the Larsen B inlet at depths ranging from 438 m to 676 m. These cores were sampled at 2 cm intervals for grain size analysis and water content. Ice rafted debris (IRD) content was obtained by observing x-rays and counting at 2.5 cm intervals. Magnetic susceptibility was measured every 2.5 cm using the Bartington MS2C 44 mm sensor. 14C-calcite dates were obtained from the top 20 cm in KC2 and KC5. Results from the data allowed for the construction of a general litho-stratigraphy of the Larsen B Ice shelf depositional environments prior to its collapse. KC1-KC6 consist of three main units (from top to bottom): (1) sandy silty clay, (2) stratified sandy mud and muddy sand with granules, and (3) structureless muddy-diamicton. Three different depositional environments are suggested based on the sedimentological features of these units: open-marine, transitional, and glacial. The gravel pavement (0-1 cm) on top of KC5 was deposited as a product of the Larsen B Ice Shelf calving event in 1999. This is significant to our interpretation of the Larsen B­_s sedimentary processes and paleohistory because the stratigraphy of the Larsen A (Pudsey et al. 1998) does not show these angular pebbles and cobbles on top of unit 1, but rather biosiliceous ooze in its silty clay unit . Furthermore, 14C-calcite dates from KC5 (2,300 +/-35 at 2 cm, 2,760+/-35 at 5 cm, and 9,210+/-45 at 20 cm) and KC2 (3,710+/-40 at 2cm, 9,760+/-45 at 15cm, and 10,600+/-55) help confirm that the Larsen B has not experienced a history of recession and reformation since the end of the last Ice Age. Instead the ice shelf seems to have been in place for some time while embayments to the north were experiencing open marine conditions (Domack et al., 2001 & Pudsey et al., 2001). Thus, our investigation illustrates that the disintegration of the Larsen B Ice Shelf was an unprecedented event in which its litho-stratigraphy indicates a sub-ice shelf environment formed during the entire Holocene.

Duran, D. M.; Domack, E.; McMullen, K.; Leventer, A.

2003-12-01

82

USC Sequence Stratigraphy Web  

NSDL National Science Digital Library

Sequence stratigraphy is a technique used to subdivide the sedimentary section into packages that are defined by bounding unconformities and internal surfaces, and are the products of changes in relative sea level and rates of sedimentation. Sequence stratigraphic analyses are made from seismic cross-sections, well logs, and outcrop studies of sedimentary rocks to infer changes of relative sea level and rates of sedimentation, and predict the continuity and extent of their lithology. This University of South Carolina website provides: animated cartoons demonstrating how gross sedimentary geometric relationships develop in response to varying rates of change of sedimentation, eustasy, and tectonic movement; movies of sedimentary simulations; video narration; films on location; 3D perspectives; simple interactive exercises on chronostratigraphy; fact sheets on world petroleum; historical perspectives about stratigraphy; the potential to simulate the development of geometric relationships on-line; links; references; and on-line papers.

Kendall, Christopher

83

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

84

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

85

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

86

Early Bronze Age settlement system and village life in the Jenin Region\\/ Palestine: a study of Tell Jenin stratigraphy and pottery traditions  

Microsoft Academic Search

The dissertation investigates the settlement system development of the Jenin region during the transitional period from the Late Chalcolithic to the Early Bronze Age. It is based on three components.\\u000a\\u000a1) The first is the investigation of the settlement systems of the Jenin region during the Chalcolithic to the Early Bronze Age. It is an attempt to develop the principles

Hamed J. Salem

2006-01-01

87

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

88

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

89

Ground-penetrating radar and its use in sedimentology: principles, problems and progress  

NASA Astrophysics Data System (ADS)

Ground-penetrating radar (GPR, also referred to as ground-probing radar, surface-penetrating radar, subsurface radar, georadar or impulse radar) is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface (<50 m). It does this by generation, transmission, propagation, reflection and reception of discrete pulses of high-frequency (MHz) electromagnetic energy. During the 1980s radar systems became commercially available, but it was not until the mid-1990s that sedimentary geologists and others began to widely exploit the technique. During the last decade numerous sedimentological studies have used GPR to reconstruct past depositional environments and the nature of sedimentary processes in a variety of environmental settings; to aid hydrogeological investigations, including groundwater reservoir characterisation, and to assist in hydrocarbon reservoir analogue studies. This is because in correctly processed radar profiles, and at the resolution of a survey, primary reflections usually parallel primary depositional structure. Despite the wide use of GPR, a number of fundamental problems remain in its application to sedimentary research. In particular, there are a wide range of approaches to the processing of radar data and interpretation techniques used on the final subsurface images vary widely, with little consensus over a common methodology. This review attempts to illustrate that methods for the collection, processing and interpretation of radar data are intimately linked and that thorough understanding of the nature, limitations and implications of each step is required if realistic sedimentological data are to be generated. In order to extract the maximum amount of meaningful information, the user must understand the scientific principles that underlie the technique, the effects of the data collection regime employed, the implications of the technique's finite resolution and depth of penetration, the nature and causes of reflections unrelated to primary sedimentary structure, and the appropriateness of each processing step with respect to the overall aim of the study. Following suitable processing, a radar stratigraphy approach to reflection profile interpretation should be adopted. New or modified terminologies and techniques to define a radar stratigraphy are also recommended, in order to make the interpretation process more transparent and to avoid confusion with related methodologies such as seismic stratigraphy and sequence stratigraphy. The full potential of GPR in sedimentary research will only be realised if more thorough and systematic approaches to data collection, processing and interpretation are adopted.

Neal, Adrian

2004-08-01

90

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

91

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

92

The morphology, stratigraphy and sedimentology of the Carstairs esker, Scotland, U.K  

Microsoft Academic Search

The series of ridges, mounds and basins around Carstairs have been variously interpreted as recessional moraines, kames, sub- or en-glacial eskers or as landforms developed in response to supraglacial outwash fan sediments deposited on stagnant ice. This paper argues that the ridges are eskers. They formed in an interlobate sediment sink between the uncoupling margins of Highland and Southern Upland

G. S. P. Thomas; E. Montague

1997-01-01

93

The morphology, stratigraphy and sedimentology of the Carstairs esker, Scotland, U.K.  

NASA Astrophysics Data System (ADS)

The series of ridges, mounds and basins around Carstairs have been variously interpreted as recessional moraines, kames, sub- or en-glacial eskers or as landforms developed in response to supraglacial outwash fan sediments deposited on stagnant ice. This paper argues that the ridges are eskers. They formed in an interlobate sediment sink between the uncoupling margins of Highland and Southern Upland ice during Devensian deglaciation. This conclusion is based on geomorphological mapping, lithofacies and palaeocurrent analysis, and borehole interpretation. An extensive lake system developed between the two ice margins and was fed by a major sub-glacial conduit flowing towards the NE. This conduit initially exited into the lake subaqueously to form a prominent single esker ridge across the lake floor. On downwasting, the feeding conduit emerged onto the surface of the ice to form a complex supraglacial outwash sandur. During periods of catastrophic flow, large channels cut through the sandur surface into underlying ice. These channels filled with coarse gravel which, on abandonment and further downwasting, were topographically inverted to form a series of sub-parallel, slightly sinuous ridges giving the appearance of braiding. During lower flow extensive finer-grained supraglacial sandur sedimentation took place on the periphery of these ridges and this passed down-current across the ice margin into fan-deltas feeding into the expanding ice-front lake.

Thomas, G. S. P.; Montague, E.

94

Seismic stratigraphy, sedimentology, and reservoir potential of a late pleistocene shelf-edge delta  

SciTech Connect

Evaluation of a 92-m continuous boring through a shelf-edge delta sequence in Main Pass lease area, Block 303 (MP303), and 4500 line-km of high-resolution seismic profiles on the outer Mississippi-Alabama shelf have led to a better understanding of the internal architecture of fluvio-deltaic systems during falling to low sea level periods. The resulting stratigraphic mapping supplies valuable knowledge about the lithologic character, stratigraphic position, distribution, and compartmentalization of reservoir facies in an outer shelf setting. The clinoforms of the landward-thinning delta wedge have prograded onto a shelf-wide, high-amplitude reflector. The deltaic clinoform wedge appears to be sand rich. Steep clinoforms at the boring site correspond to the top half of the deltaic sequence, consisting of silty to clean, upper delta front fine sands. Mapping of steep clinoforms indicate that delta sands are volumetrically the most significant reservoir facies on the outer shelf. The broad evacuation created by fluvial scour is a northeast to southwest trending feature, which is filled with mainly medium to coarse sands and gravel, and minor estuarine sand silts at the boring site. The clean fluvial sands form the best quality reservoir facies. Delta reservoir facies have been removed where overridden by widespread fluvial scour on the middle shelf. Fluvial reworking during sea level lowering thus results in poor preservation potential of preceding highstand-delta deposits on the middle and inner shelf. This reworking provides remobilized sand-rich sediment for shelf-edge delta construction. The fluvial deposits in the boring are capped by the bayline flooding surface, which is in turn overlain by estuarine deposits, the transgressive ravinement surface, and finally, submarine shoal and thin sheet deposits. Submarine shoals are sandy, but contain abundant shell material. Shoals are of the poorest quality and volumetrically least important reservoir facies.

Roberts, H.H. (Coastal Studies Institute, Baton Rouge, LA (United States)); Sydow, J.; Bouma, A.H. (Louisiana State Univ., Baton Rouge, LA (United States))

1993-09-01

95

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, Jr. , D. O.

2007-01-01

96

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

97

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

98

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

99

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

100

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

101

Sedimentology, stratigraphy and tectonics of evolving wedge-top depozone: Ariano Basin, southern Apennines, Italy  

NASA Astrophysics Data System (ADS)

The late Zanclean wedge-top Ariano Basin, located in the external sector of the southern Apennines, was initially characterized by alluvial and fan-delta environments and successively, southward of the Benevento-Buonalbergo fault, by a gradual drowning with coastal and alluvial plains evolving to shelf and marine coastal settings, respectively. Basin evolution continued with a synsedimentary uplift of different sectors resulting in variations in the drainage pattern and basin shape, and ultimately leading to complete basin closure and transition to continental depositional environments. Early Pliocene paleogeography, prior to the Ariano Basin activity, is due to regional subsidence and subsequent differential uplifts that resulted from geodynamic processes related to both the downgoing Apulian slab and the allochthonous orogenic wedge. Slab break off and the migration of a tear in the southeastward Apulian slab occurred, producing a strong subsidence in the external sectors of the southern Apennines recorded by the development of the Ariano Basin. Subsequently out-of-sequence synsedimentary thrusting, related to thin-skinned tectonics, occurred in the allochthonous units and unconformably overlying wedge-top basin deposits, producing northeastward migration of the main depocenters in the Ariano Basin. Finally renewed thrusting, related to the inversion of pre-existing normal faults located in the buried Apulian Platform and enhanced by regional uplift, affected the whole tectonic and sedimentary pile, as recorded by deformation of the overlying Pliocene deposits.

Ciarcia, Sabatino; Vitale, Stefano

2013-05-01

102

Stratigraphy and sedimentology of the Caples terrane of the Thomson Mountains, northern Southland, New Zealand  

Microsoft Academic Search

The Thomson Mountains west of Lake Wakatipu are underlain by sediments of the volcaniclastic Caples terrane, lying east of the Dun Mountain Ophiolite Belt and gradational into the western margin of the Haast Schist Zone. Although traditional formation-mapping methods are difficult to apply in the area, five formations have been differentiated. The Caples sediments can be divided into eight subordinate

I. M. Turnbull

1979-01-01

103

Geophysical logs in British stratigraphy  

SciTech Connect

This Special Report outlines the stratigraphic applications of the main geophysical logging tools. It characterises the British geological succession by means of the geophysical log signatures of its principle constituent formations. A large amount of previously unpublished data is provided on a geographical area long known for its importance in the development of the science of stratigraphy. The book in units modern developments of petroleum industry geophysical techniques with long-established stratigraphical discovery/research. Contents include: Introduction; Types of logs commonly used; Some geological uses of geophysical logs; Log signatures in British Stratigraphy; References.

Whittaker, A.; Holliday, D.W.; Penn, I.E.

1985-01-01

104

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

Microsoft Academic Search

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

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

2010-01-01

105

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

106

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

107

Cretaceous strontium isotope stratigraphy using marine barite  

NASA Astrophysics Data System (ADS)

The strontium isotope ratios (87Sr/86Sr) of marine barite microcrystals separated from Cretaceous sedimentary deposits from Ocean Drilling Program and Deep Sea Drilling Project sites from the Pacific and Indian Oceans have been compared to the composite Sr isotope curve of McArthur et al. The barite in these cores accurately recorded the seawater 87Sr/86Sr ratio, thereby reaffirming the composite Cretaceous strontium curve. Moreover, marine barite is a more reliable recorder of 87Sr/86Sr than is carbonate in sedimentary deposits with high clay content, thereby providing an opportunity for Sr isotope stratigraphy and dating in carbonate-poor or diagenetically altered sections. We have used the barite-derived Sr isotope record to refine the biostratigraphic age models of the sites investigated.

Mearon, Sarah; Paytan, Adina; Bralower, Timothy J.

2003-01-01

108

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

109

Time, Space and Structure on the Korea Cretaceous Dinosaur Coast: Cretaceous Stratigraphy, Geochronology, and Paleoenvironments  

Microsoft Academic Search

The stratigraphy, geological ages, and paleoenvironments of the Korea Cretaceous Dinosaur Coast (KCDC) are reviewed and synthesized in order to understand the occurrence and diversity of the vertebrate fossils and track remains in time and space. Various absolute age measurements obtained during the last decade yield new age data to correlate with the dinosaur fossil-bearing Cretaceous deposits in Korea. The

In Sung Paik; Yong Il Lee; Hyun Joo Kim; Min Huh

2012-01-01

110

Geological Interpretation of the Structure and Stratigraphy of the A/M Area, Savannah River Site, South Carolina  

SciTech Connect

The geological interpretation of the structure and stratigraphy of the A/M Area was undertaken in order to evaluate the effects of deeper Cretaceous aged geological strata and structure on shallower Tertiary horizons.

Wyatt, D. [Westinghouse Savannah River Company, AIKEN, SC (United States); Aadland, R.K.; Cumbest, R.J.; Stephenson, D.E.; Syms, F.H.

1997-12-01

111

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

112

U–Pb SHRIMP ages of volcanic zircons from the Merrions and Turondale Formations, New South Wales, and the Early Devonian time?scale: A biostratigraphic and sedimentological assessment  

Microsoft Academic Search

U–Pb ages for volcanic zircons from the Lower Devonian Turondale and Merrions Formations initially dated by Jagodzinski and Black (1999) have been recalculated by Compston (2000, 2001). The Turondale, Waterbeach and Merrions Formations are, in ascending stratigraphic order, three of the Lower Devonian deep?water formations of the Hill End Trough. The recent discovery of a Lochkovian conodont fauna of the

G. H. Packham

2003-01-01

113

Sedimentologic relevance of convulsive geologic events  

SciTech Connect

Convulsive (or catastrophic) geologic events undeniably have been part of the history of our planet throughout geologic time. Convulsive events are violent disturbances of regional or even global extent. Some types, such as giant storms or explosive volcanic eruptions, are commonplace in the geologic record; others, such as major bolide impact, are exceedingly rare. The sedimentologic record of convulsive geologic events differs in preservation potential depending largely on whether the effect occurs within an active depositional basin. In some settings, such as deep sea fans, a significant part of the deposit may result from large and violent events. The record within the sediment of a convulsive event may be either dramatic or subtle; the degree of distinctiveness therein may not be an accurate guide to the overall consequence of the event on a accurate guide to the overall consequence of the event on a planetary scale. Because convulsive events typically produce a brief, but significant, disturbance over a broad area, their sedimentologic consequences provide excellent chronologic markers in the stratigraphic record, in some cases on a global scale. Perhaps most importantly, the recognition of the results of convulsive events in the geologic record forces one to consider processes operating at a scale that may be inconceivable in the context of our present-day world.

Clifton, H.E.

1985-01-01

114

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

115

Beach ridge sedimentology: field observation and palaeoenvironmental interpretation for Anegada Island, British Virgin Islands.  

NASA Astrophysics Data System (ADS)

Beach ridge landforms have been observed in different environments and in settings that range from polar to tropical. Their stratigraphy and sedimentology has received a limited amount of discussion in the literature (Tamura, 2012). In coastal geomorphology a beach ridge can be seen as a transitional deposit between onshore and offshore environments. They are regarded as representing high level wave action along a coastline. In the Caribbean the origin of beach ridges has been variously attributed to one of three extreme wave events: extreme swell, extreme storm or tsunami waves. Beach ridges are arranged in beach ridge plains where there is succession of the landforms and can be several kilometres long. Beach ridge accumulation is not continuous and the coast shows alternating accretion and erosion periods. The use of beach ridges as palaeostorm archives is therefore not straightforward. The temporal continuity of beach ridge formation is being assessed on the beach ridge plains of Anegada, British Virgin Islands (Lesser Antilles). This carbonate platform surrounded by a fringing reef contains two beach ridge plains. There are more than 30 ridges in the Atlantic facing- coast and around 10 in the south, Caribbean- facing coast. The sediments of the modern beaches are dominated by the sand fraction and are 100% biogenic origin due to the isolation of Anegada from terrestrial sediment sources. The beach ridge sections have been studied in different area of Anegada beach ridge plains and present low angle seaward-dipping bedding. The sand fraction is dominant in the stratigraphy with a few intact shells. At only one site were coral pebbles deposited in association with the sand fraction. Aeolian deposits represent the upper part of the beach ridges and reflect the stabilization of the beach ridges with ongoing accretion. The sedimentology of the contemporary beach and dunes will be discussed in terms of their implications for understanding beach ridge genesis and its relationship to extreme wave events. Tamura, T., 2012. Beach ridges and prograded beach deposits as palaeoenvironment records. Earth-Science Reviews, 114, pp. 279-297.

Cescon, Anna Lisa; Cooper, J. Andrew G.; Jackson, Derek W. T.

2014-05-01

116

Seismic stratigraphy in high resolution shallow marine seismic data of the Gemlik Gulf  

SciTech Connect

Seismic stratigraphy and sedimentological studies of the Gemlik Gulf in the Sea of Marmara, Turkey, have been carried out. For this purpose, 19 lines totaling 189 km of excellent quality, high-resolution seismic data were recorded. Four major acoustic units were identified in the seismic profiles. Three were sedimentary units: irregular layered, cross-layered and well-layered; and the fourth was an acoustic basement which is probably composed of crystalline volcanic rocks. Some local areas in the Neogene formation contain gas accumulations. The formation of faults in E--W and N--S directions can be explained by the existence of shear stresses in the Gulf. The bathymetric map shows good accommodation with the shore line as does the tectonic map.

Kurtulus, C. (Yildiz Univ., Izmit (Turkey). Dept. of Geophysical Engineering)

1993-10-01

117

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

118

Seismic stratigraphy of the offshore Nile delta  

SciTech Connect

The seismic stratigraphy of the offshore Nile delta has been established using a 10,000-km Merlin reprocessed regional seismic database. This paper focuses on the Neogene interval in which three major seismic super sequences have been recognized. The oldest (super sequence A) is a thick sheet unit of middle Miocene age composed of marine shales and sandstones, affected in places by shale diapirism. The upper super sequence, of Pliocene age (C), is characterized by progradation complicated by both slumping and faulting. These sediments represent deposits from the present Nile delta system, a relatively recent event. Between super sequences A and C lies a thin upper Miocene - lowermost Pliocene unit (super sequence B). This unit can be divided into three sequences, the upper and lower of which (Abu Madi and Oawasim Formations, respectively) are characterized by widespread channeling. The intermediate Messinian sequence, commonly evaporitic, may also be associated with channeling episodes. Potential hydrocarbon plays exist in all three super sequences, and varied trapping mechanisms may be invoked. Dip closures are associated with both rollover on listric normal faults and shale diapirism. Stratigraphic trap potential involves both truncation of C beneath B, occasionally associated with severe angular unconformity, and super sequence B channeling. The Abu Madi channel-fill sand bodies form the primary exploration target. Despite only 12 offshore wells drilled, there have already been gas discoveries (Abu Qir field, Naf-1 well) which, together with recent changes in Egyptian hydrocarbon legislation, make this region an attractive exploration province.

Kilenyi, T.; Trayner, P.; Doherty, M.; Jamieson, G.

1988-08-01

119

Sedimentology and taphonomy of the upper Karoo-equivalent Mpandi Formation in the Tuli Basin of Zimbabwe, with a new 40Ar/ 39Ar age for the Tuli basalts  

NASA Astrophysics Data System (ADS)

Karoo-equivalent rocks in the Tuli Basin of Zimbabwe are described, with a focus on the dinosaur-bearing Mpandi Formation, which correlates with the Elliot Formation (Late Triassic-Early Jurassic) in the main Karoo Basin. Isolated exposures of the Mpandi Formation along the banks of the Limpopo River consist of red silty claystones and siltstones that preserve root traces, small carbonate nodules, and hematite-coated prosauropod bones. These fine-grained facies accumulated on an ancient semi-arid floodplain. Widespread exposures of quartz-rich sandstone and siltstone representing the upper Mpandi Formation crop out on Sentinel Ranch. These strata preserve carbonate concretions and silicified root casts, and exhibit cross-bedding indicative of deposition via traction currents, presumably in stream channels. Prosauropod fossils are also preserved in the Sentinel Ranch exposures, with one particularly noteworthy site characterized by a nearly complete and articulated Massospondylus individual. An unconformity caps the Mpandi Formation in the study area, and this stratigraphically significant surface rests on a laterally-continuous zone of pervasive silicification interpreted as a silcrete. Morphologic, petrographic, and geochemical data indicate that the Mpandi silcrete formed by intensive leaching near the ground surface during prolonged hiatus. Chert clasts eroded from the silcrete are intercalated at the base of the overlying Samkoto Formation (equivalent to the Clarens Formation in the main Karoo Basin), which in turn is overlain by the Tuli basalts. These basalts, which are part of the Karoo Igneous Province, yield a new 40Ar/ 39Ar plateau age of 186.3 ± 1.2 Ma.

Rogers, Raymond R.; Rogers, Kristina Curry; Munyikwa, Darlington; Terry, Rebecca C.; Singer, Bradley S.

2004-10-01

120

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

121

Sequence stratigraphy, paleoclimate, and tectonics of coal-bearing strata  

SciTech Connect

The origin of coal-bearing strata has been debated vigorously for more than a century, and with the emergence of coalbed methane as a major energy resource and the possibility of sequestering greenhouse gas in coal, this debate has never been more relevant. This volume contains 10 chapters on coal-bearing strata of Carboniferous through Tertiary age and is based on a special session that was held at an AAPG Annual Meeting in New Orleans. Contributors have employed a multitude of approaches ranging from basin analysis to plant taphonomy to support a variety of views on the sequence stratigraphy, paleoclimate, and tectonics of coal-bearing strata.

Jack C. Pashin; Robert A. Gastaldo (eds.)

2004-07-15

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, Jr. , T. C.; Ryer, T. A.

1997-01-01

123

Seismic stratigraphy and sedimentation history of the East Mariana Basin, western Pacific  

Microsoft Academic Search

An interpretation of the seismic stratigraphy and sedimentation history of the East Mariana Basin has been made using recently collected seismic reflection and refraction data. This Mesozoic(?) age basin, between the Marshall Islands and the Mariana Trench, is subdivided into three regions. The central region with about 1000 m of sediment probably records Jurassic to Late Cretaceous sedimentation of a

Thomas H. Shipley; Jill M. Whitman; Frederick K. Duennebier; Lisa D. Petersen

1983-01-01

124

Sequence stratigraphy, basin dynamics, and petroleum geology of the Miocene from eastern Tunisia  

Microsoft Academic Search

On the eastern margin of Tunisia, Miocene limestones, marl, and siliciclastic deposits crop out poorly and are lacking in age-diagnostic faunal content. The biostratigraphic and lithostratigraphic subdivisions of these series are not clearly defined. A regional study of subsurface sequences of this margin (Cap Bon, Gulf of Hammamet, and Sahel) by means of sequence stratigraphy and subsurface structural analyses permits

M. Bedir; S. Tlig; C. Bobier

1996-01-01

125

Elevated marine terraces from Eleuthera (Bahamas) and Bermuda: sedimentological, petrographic and geochronological evidence for important deglaciation events during the middle Pleistocene  

Microsoft Academic Search

Sedimentological, petrographic and geochronological (uranium series and amino acid racemization dating) study of middle Pleistocene deposits from the archipelagos of Bermuda and The Bahamas revealed the occurrence of marine terraces of possible stage 11 age at +2, +7 and over 20 m above mean sea level. Considering the tectonic stability of the investigated regions, these elevated deposits likely correspond to

Pascal Kindler; Paul J. Hearty

2000-01-01

126

The orbital record in stratigraphy  

NASA Technical Reports Server (NTRS)

Orbital signals are being discovered in pre-Pleistocene sediments. Due to their hierarchical nature these cycle patterns are complex, and the imprecision of geochronology generally makes the assignment of stratigraphic cycles to specific orbital cycles uncertain, but in sequences such as the limnic Newark Group under study by Olsen and pelagic Cretaceous sequence worked on by our Italo-American group the relative frequencies yield a definitive match to the Milankovitch hierarchy. Due to the multiple ways in which climate impinges on depositional systems, the orbital signals are recorded in a multiplicity of parameters, and affect different sedimentary facies in different ways. In platform carbonates, for example, the chief effect is via sea-level variations (possibly tied to fluctuating ice volume), resulting in cycles of emergence and submergence. In limnic systems it finds its most dramatic expression in alternations of lake and playa conditions. Biogenic pelagic oozes such as chalks and the limestones derived from them display variations in the carbonate supplied by planktonic organisms such as coccolithophores and foraminifera, and also record variations in the aeration of bottom waters. Whereas early studies of stratigraphic cyclicity relied mainly on bedding variations visible in the field, present studies are supplementing these with instrumental scans of geochemical, paleontological, and geophysical parameters which yield quantitative curves amenable to time-series analysis; such analysis is, however, limited by problems of distorted time-scales. My own work has been largely concentrated on pelagic systems. In these, the sensitivity of pelagic organisms to climatic-oceanic changes, combined with the sensitivity of botton life to changes in oxygen availability (commonly much more restricted in the Past than now) has left cyclic patterns related to orbital forcing. These systems are further attractive because (1) they tend to offer depositional continuity, and (2) presence of abundant microfossils yields close ties to geochronology. A tantalizing possibility that stratigraphy may yield a record of orbital signals unrelated to climate has turned up in magnetic studies of our Cretaceous core. Magnetic secular variations here carry a strong 39 ka periodicity, corresponding to the theoretical obliquity period of that time - Does the obliquity cycle perhaps have some direct influence on the magnetic field?

Fischer, Alfred G.

1992-01-01

127

Potentiality of the ground-penetrating radar for the analysis of the stratigraphy and sedimentology of Mars  

NASA Astrophysics Data System (ADS)

The ground-penetrating radar (GPR) is a good candidate for the exploration of the Martian subsurface because it is smaller and lighter than seismic instruments, and, due to the lack of water in the Martian rocks, has great penetration capability. The modelling of the GPR signal response has been performed by computing the dielectric properties of each simulated layer as a linear function of porosity, known values of the solids, and the nature of the material filling the voids (ice water, carbou dioxide ice, gas, liquid water). The synthetic response was computed by reflecting ray-tracing at various peak frequencies. The complex results show that reflections are due to variations in mineralogy, porosity and porc-filling material. The reflectors produced by the reflection of the electromagnetic waves provide a picture of the geometries of the layers of the subsurface and give elues on the nature of rocks. Permafrost and liquid water can be investigated, chiefly their seasonal changes can be analysed by means of repeated profiles. The use of the GPR would be a major breakthrough in the reconstruction of the past geological history of the planet.

Ori, G. G.; Ogliani, F.

1996-11-01

128

The Sinemurian carbonate mud-mounds from central High Atlas (Morocco): stratigraphy, geometry, sedimentology and geodynamic patterns  

NASA Astrophysics Data System (ADS)

The Moroccan Central High Atlasic mud-mounds correspond to carbonate sponge-algal buildups developed in open marine conditions towards the Lower-Upper Sinemurian boundary. The structures gradually increase in size through time, from the small-sized lenses included in the Idikel coarse-bedded Lower Sinemurian grainstones to the high domes observed in the succeeding Aberdouz and Ouchbis Upper Sinemurian thin-bedded mudstones. The biological communities (mainly algae, sponges, thrombolites, stromatolites, annelids, bryozoans, brachiopods, pelecypods, gastropods, echinoderms, corals and scarce foraminifera) comprise common, well conserved remains in the rising core frameworks and small reworked bioclasts in the surrounding sedimentary depressions. These buildups are closely linked to tectonic processes as they grew on the normal synsedimentary faults which affected the central Atlasic area during the Lower Liassic period, leading to the breakup of the Early Sinemurian carbonate platform and the resultant initiation of the Upper Sinemurian subsiding basin. Silting conditions under hernipelagic sedimentation led to their death. Similar palaeogeographic changes and geodynamic evolution have been described recently from different structures in North Africa, Western Europe and North America.

Chafiki, Driss; Canérot, Joseph; Souhel, Abdellatif; el Hariri, Khadija; Eddine, Kamal Taj

2004-06-01

129

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

130

Sedimentology and sequence stratigraphy of paralic and shallow marine Upper Jurassic sandstones in the northern Danish Central Graben  

Microsoft Academic Search

Paralic and shallow marine sandstones were deposited in the Danish Central Graben during Late Jurassic rifting when half-grabens were developed and the overall eustatic sea level rose. During the Kimmeridgian, an extensive plateau area consisting of the Heno Plateau and the Gertrud Plateau was situated between two highs, the Mandal High to the north, and the combined Inge and Mads

Peter N. Johannessen

131

Sedimentology, petrology, and geotechnical properties of Athabasca oil sands, Alberta  

Microsoft Academic Search

The Athabasca oil sands deposit is not only one of the largest petroleum reservoirs in the world (870 billion bbl of oil in place), it is virtually the only supergiant oil accumulation that can be examined at outcrop. Sedimentologic and petrographic knowledge, gleaned both from the outcrop and from many subsurface cores, has direct and immediate implication for surface mining

M. B. Dusseault; G. D. Mossop

1979-01-01

132

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

133

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

134

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

135

Characterizing avulsion stratigraphy in ancient alluvial deposits  

Microsoft Academic Search

Guidelines for identifying ancient avulsion deposits were set forth by Kraus and Wells [Kraus, M.J., Wells, T.M., 1999. Recognizing avulsion deposits in the ancient stratigraphical record. In: Smith, N.D., Rogers, J. (Eds.), Fluvial Sedimentology VI, Special Publication of the International Association of Sedimentologists, vol. 28, pp. 251–268], building on the study by Smith et al. [Smith, N.D., Cross, T.A., Dufficy,

H. L. Jones; E. A. Hajek

2007-01-01

136

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

137

Stratigraphy of the Caloris basin, Mercury  

NASA Astrophysics Data System (ADS)

A formal rock stratigraphic nomenclature in proposed for the ejecta units of the 1300-km diameter Caloris impact basin of Mercury. The ejecta units can be recognized for more than 1000 km radially outward from the basin edge, and are collectively called the Caloris Group. The formations recognized within the Caloris Group include: (1) the Caloris Montes; (2) the Nervo; (3) the Odin; and (4) two Van Eyck Formations, one with lineated facies and the other with secondary crater facies. It is shown that of the craters in the 30-100-km size range superposed on the Caloris ejecta assemblage, most are of the c(4) and c(5) type. The youngest craters are assigned the highest subscript numbers. If other basins and craters can be tied into the Caloris basin over the rest of Mercury using data from Mariner 10, the stratigraphy described may help establish a time stratigraphy consisting of formal systems and periods in the history of Mercury.

McCauley, J. F.; Guest, J. E.; Schaber, G. G.; Trask, N. J.; Greeley, R.

1981-08-01

138

Solute Transport Modeling In An Experimental Stratigraphy  

Microsoft Academic Search

A high-resolution, multiscale hydraulic conductivity map is created based on an experimental stratigraphy. A heterogeneous model is created, incorporating the complete conductivity variation. A 14-unit hydrostratigraphic model (HSM) is also created for which an equivalent conductivity is estimated for each unit via a novel upscaling method. Under a lateral hydraulic gradient, steady-state, incompressible flow experiment is conducted in both models.

Y. Zhang

2006-01-01

139

Calibration of upper Pliocene-lower Pleistocene nannofossil events with oxygen isotope stratigraphy  

Microsoft Academic Search

Twelve upper Pliocene-lower Pleistocene nannofossil events are calibrated with oxygen isotope stratigraphy at eight DSDP\\/ODP sites ranging from 53°N to 41°S latitudes in different oceans in order to determine their ages and to reveal their synchrony or diachrony within a significantly higher-resolution time scale than the geomagnetic polarity time scale allows. Six nannofossil vents appear to be synchronous from low

Wuchang Wei

1993-01-01

140

Calibration of Upper Pliocene-Lower Pleistocene Nannofossil Events with Oxygen Isotope Stratigraphy  

Microsoft Academic Search

Twelve upper Pliocene-lower Pleistocene calcareous nannofossil events are calibrated with oxygen isotope stratigraphy at eight DSDP\\/ODP sites ranging from 53°N to 41°S latitudes in different oceans in order to determine their ages and to reveal their synchrony or diachrony within a significantly higher-resolution time scale than the geomagnetic polarity time scale allows. Six nannofossil events appear to be synchronous from

Wuchang Wei

1993-01-01

141

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

142

Reverse engineering mother nature — Shale sedimentology from an experimental perspective  

NASA Astrophysics Data System (ADS)

Experimental study of the sedimentology of shales can take a variety of forms. At its simplest one can experiment with suspensions in a glass jar and try to understand their settling behavior, or one can manipulate mud in a tank or bucket to gain insights into its rheology. This approach was championed over a century ago by Sorby, and the insights gained can be quite profound. More recently, tank and settling tube experiments of animal-sediment interactions, compaction behavior, and sediment unmixing via re-suspension have proven to be highly informative in spite of their simplicity. Flumes can be used to obtain quantitative information about depositional and erosional parameters and to generate fundamental bedforms. In flume experiments, however, it is of critical importance that the flume be designed in a way that flocculated materials move under shear stress conditions that would be reasonable in natural environments. Although much flume work on muds has been conducted by hydraulic engineers, the transfer of that knowledge to sedimentology is hampered by the fact that engineers and sedimentologists are interested in different (though not mutually exclusive) products from such experiments. Engineers and hydrologists are commonly concerned with quantifying fluid flow properties, whereas sedimentogists are particularly interested in the sedimentary products that result from a variety of flow conditions. Recent sedimentologically oriented flume studies have shown that muds can form deposits at flow velocities and shear stresses that would suffice to transport and deposit medium grained sand. Mud suspensions are prone to flocculation and the resulting floccules travel in bedload and form ripples that accrete into beds. The latter finding suggests that many laminated shales were deposited from currents rather than by settling from slow moving or still water. There are many other sedimentary features in shales that can potentially be reproduced in flume studies and in the future serve to provide a quantitative basis for shale sedimentology.

Schieber, Juergen

2011-06-01

143

Sequence Stratigraphy and Frequency Analysis of the Zhada Basin, SW Tibet  

NASA Astrophysics Data System (ADS)

Zhada basin is a large late Miocene - Pleistocene extensional sag basin in the Tethyan Himalaya of southwestern Tibet. Sequence stratigraphy in the basin reveals a long-term tectonic signal in the formation and filling of Zhada basin. The sedimentological record of the Zhada Formation also archives higher frequency cyclical expansion and contraction of a large paleolake. Expansion and contraction of lakes and wetlands has been linked to variability in the strength of the Asian monsoon and thought to be modulated by orbital cyclicity. In order to determine the forcing mechanism for Zhada paleolake expansion and contraction we created a wave form by assigning numerical values to the various depositional environments and applied spectral analysis to this record. Depositional environments in the South Zhada measured section were identified at 0.5 m increments or where the depositional environment changed. The result is a clipped waveform with uneven sample spacing and temporal resolution better than 4,000 yrs. In addition to a peak at 91.7 kyr (95% confidence level), spectral analysis reveals a peak at 22 kyr (85% confidence level). These are within 1/2 bandwidth (6 dB bandwidth = 2.4) of the eccentricity and precession frequencies. The record of Milankovitch cycles in Zhada basin implies that global climate drove lake and wetland expansion and contraction in the southern Tibetan Plateau from the late Miocene to the Pleistocene.

Saylor, J. E.; Decelles, P. G.; Quade, J.

2008-12-01

144

Geomorphological and sedimentological evidence for variations in Holocene flooding in Welsh river catchments  

NASA Astrophysics Data System (ADS)

Valley floor geomorphology, sedimentology and radiocarbon dating have been used to reconstruct variations in flooding during the Holocene at six sites within the upper Severn, Teifi and Dee catchments in Wales, UK. High-magnitude palaeoflood deposits, for which ages were estimated, were identified at three floodbasin sites in the upper Severn and Teifi catchments. At the remaining sites fluvial discontinuities, indicative of episodes of increased flooding, were identified. Data from these six sites, and six additional sites studied previously, indicate that seven probably centennial length episodes of major flooding have occurred in Wales since c. 7000 cal BP. These flooding episodes occur at similar times to peaks in flood frequency within Great Britain as a whole.

Jones, A. F.; Brewer, P. A.; Macklin, M. G.

2010-02-01

145

Stratigraphie relations of australites in the Port Campbell Embayment, Victoria  

USGS Publications Warehouse

In the Port Campbell Embayment of Victoria, australites have been found in situ in channel deposits of the Hanson Plain Sand of Pliocene and Pleistocene age. The large majority of the australites, however, occur as a lag deposit at the basal contact of the Sturgess Sand of late Pleistocene and Holocene age and are spatially correlated with ferruginous sandstone clasts that are derived from the Hanson Plain Sand. Some of the tektites are imbedded in or bonded to the ferruginous sandstone clasts, but most are found as individual tektite fragments. A few percent of the tektites have nearly perfectly preserved, complete aerodynamically shaped forms. The sandstone clasts and associated tektites have been reworked from the much older underlying Hanson Plain and have been locally concentrated in the lag deposit. Some tektites also occur at higher levels in the Sturgess Sand, almost invariably in association with stone flakes, exotic stones transported by the aborigines and, locally, with middens of mollusc shells. Circumstantial evidence indicates that the aborigines transported the tektites found in the upper part of the Sturgess, particularly at Stanhope Bay. As Port Campbell australites unequivocally occur in strata much older than the late Pleistocene and Holocene Sturgess, there is no longer any conflict between the apparent stratigraphie age of the tektites and the middle Pleistocene ages obtained by various Chronometrie methods. ?? Meteoritical Society, 1999.

Shoemakeri, E. M.; Ralph, Uhlherr, H.

1999-01-01

146

Latest Carboniferous–earliest Permian transgressive deposits in the Paganzo Basin of western Argentina: Lithofacies and sequence stratigraphy of a coastal-plain to bay succession  

Microsoft Academic Search

The upper Paleozoic rocks of Gondwana record a complex paleoclimatic history related to the migration of the supercontinent over high latitudes. Changes in climate and relative sea level can be traced through detailed sedimentologic and sequence-stratigraphic analysis. Our study focuses on transgressive deposits of Stephanian–Early Permian age in the lower member of the Tupe Formation with the objective of characterizing

Patricio R. Desjardins; Luis A. Buatois; Carlos O. Limarino; Gabriela A. Cisterna

2009-01-01

147

Stratigraphic and sedimentologic considerations in vapor extraction system design  

Microsoft Academic Search

Vapor extraction (VE) is a commonly used remediation technique for vadose zone sediments that contain volatile and semivolatile organic compounds with vapor pressures greater than 0.1 mm Hg at 20C. Proper design of an effective VE system requires complete site-specific evaluation of (1) stratigraphy; (2) distribution, volume, and phase of organic compounds; and (3) the subsurface airflow dynamics when vacuum

T. P. Garvey; J. M. Jr. Evensen; R. J. Jr. Menzie

1991-01-01

148

Alaskan Peninsula Cenozoic stratigraphy: stratigraphic sequences and current research  

SciTech Connect

Geology of the Alaska Peninsula-Island Arc and Continental Margin, by C.A. Burk, is the principal reference for stratigraphic studies on the Alaska Peninsula. Burk mapped the Phanerozoic stratigraphy and provided a geologic history and structural interpretation of the area between Wide Bay and Unimak Island. Cenozoic rocks were mapped as three unconformity-bounded sequences. Recognition of specific formations was difficult due to similarity of lithofacies, isolated outcrops, rapid facies changes, and alteration and burial by young volcanics. Consequently, megafossil assemblages were relied upon to facilitate correlations between study areas. The three unconformity-bounded Cenozoic sequences are: (1) the Paleogene Beaver Bay Group consisting of three formations: the dominantly nonmarine Tolstoi Formation, the dominantly marine Stepovak Formation, and the volcanic Meshik Formation. Current work suggests these units are at least in part coeval facies of late Paleocene through Oligocene age. (2) The Neogene Bear Lake Formation consisting of the lower Unga Conglomerate Member and an unnamed upper member. Rapid facies changes and incorrect reports of fossil occurrence have resulted in confusion of stratigraphic relationships within this sequence of middle to late Miocene age. (3) A late Neogene informally defined upper sequence consisting of interbedded marginal marine, coastal-plain, and volcanic facies. Current work suggests this sequence is Pliocene through Pleistocene in age.

Allison, R.C.; Armentrout, J.M.

1985-04-01

149

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

150

Seismic stratigraphy of East Greenland  

SciTech Connect

The Neogene has two climatic signatures, based on the climate patterns of the Quaternary. The late Pleistocene, the last 800,000 years, contains 100,000-year-long glacial cycles with sea level drops from 90 to 160 m during glacial maximas. The middle Pleistocene, from approximately 2 Ma to 0.9 Ma, is composed of glacial cycles of 20,000 and of 40,000 years duration with sea level drops from 50 to 70 m. In the former case, deposition was restricted to the lower half of the shelf down to the shelfbreak and, in the latter case, to the upper and middle shelf. This climatic model has been applied to the interpretation of a multichannel seismic line collected by the Bundesanstalt fuer Geowissenschaften und Rohstoffe on the East Greenland continental margin near 71/sup 0/N. From seismic facies analysis, sigmoid reflection patterns indicate low-energy depositional along the shelfbreak; tangential oblique and complex sigmoid-oblique reflectors both indicate high-energy deposition. Sigmoid and tangential oblique reflectors suggest deposition onto the outer neritic, shelfbreak, and upper slope areas. Complex sigmoid-oblique reflectors suggest alternating prograding and aggrading on the upper and middle shelf. Thus, these various seismic facies are indicative of long-term climatic conditions. Sigmoid and tangential oblique reflectors suggest deposition during a glacial epoch, and complex sigmoid-oblique reflectors suggest deposition during an interglacial epoch. Tentative dates for the various glacial and interglacial epochs are given here. Thus, ages and energies of deposition may be assigned to the several interpreted glacial epochal seismic sequences.

Lowrie, A.; Hinz, K.

1986-05-01

151

Structural geology and sedimentology of the Heiligenhafen till section, Northern Germany  

NASA Astrophysics Data System (ADS)

Three Pleistocene tills can be distinguished in a coastal cliff section near Heiligenhafen, northern Germany, on the basis of structural and petrographic characteristics. The Lower and Middle Tills had previously been ascribed to the Saalian, and the Upper Till to the Late Weichselian. The former two tills are folded, and unconformably overlain by the Upper Till. In this paper, structural and sedimentological observations are used to investigate whether the Lower and Middle Tills belong to one glacial advance, or two separate (Saalian) advances, as was suggested in earlier studies based on fine gravel stratigraphy. From the contact with local rocks to the top of the MT there is a steady increase in allochtonous components (Scandinavian rocks) and decrease in parautochtonous (chalk and flint) and autochtonous components (local Eocene siltstone and meltwater sediments). This is paralleled by a trend towards increasing deformation (finite strain) from the bedrock to the top of the section. The most obvious aspect of this latter trend is the massive appearance of the MT which can be interpreted as the result of homogenization by repeated folding and attenuation of sediment lenses which have been incorporated into the till. This interpretation is supported by macroscopic and microscopic observations of structures in both tills. The structural analysis of the tills is based on the marked contrast in symmetry between sections parallel and perpendicular to the shear direction. Structures on all scales in the LT as well as in the MT indicate E-W (dextral) shearing, except in the western part of the section, where this is overprinted by W-E (sinistral) shearing. The sediment inclusions in the chalk-rich LT are mainly fragments of one or more strongly extended glaciofluvial delta bodies with a depositional direction towards WSW. Locally these delta sediments rest on Eocene siltstone and contain numerous angular fragments of this local bedrock. Boudins and lenses of sorted sediments are incorporated into the till and occur as "islands of low strain" in a high strain homogeneous matrix. It is concluded that the LT and MT do not belong to two stratigraphically separate Saalian advances. The section is alternatively interpreted as one subglacial shear zone (deformation till) with upward increasing strain and allochtonous component content. It probably formed during the Younger Saalian (Warthe) westward advance from the Baltic region. Folding of the two diamicts occurred due to lateral compression near the Late Saalian ice margin. The section was finally overridden by the Late Weichselian Young Baltic advance, eroding the folded LT and MT and depositing the UT.

Van der Wateren, Frederik M.

1999-12-01

152

Sedimentology of a lacustrine barrier system at Wasaga Beach, Ontario, Canada  

Microsoft Academic Search

Martini, I.P, 1975. Sedimentology of a lacustrine barrier system at Wasaga Beach, Onta- rm, Canada. Sediment. Geol., 14. 169--190 In an area of 4 by 15 miles (6.5 x 24 km) at Wasaga Beach, Ontario, a Holocene system is exposed that can be considered sedimentologically to be a lacustrine \\

I. P. MARTINI

1975-01-01

153

Aging.  

PubMed

Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction. PMID:24653904

Park, Dong Choon; Yeo, Seung Geun

2013-09-01

154

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

155

Ichnological analysis in high-resolution sequence stratigraphy: The Glossifungites ichnofacies in Triassic successions from the Betic Cordillera (southern Spain)  

NASA Astrophysics Data System (ADS)

This study integrates ichnological and sedimentological data in order to refine sequence stratigraphy and interpretations of sea-level dynamics for the Ladinian (Middle Triassic), Muschelkalk succession (Siles Formation) in the Betic Cordillera (southern Spain). Facies analysis was integrated with a detailed ichnological study, focused on the middle part of the lower member of the Muschelkalk succession (transgressive systems tract), which is characterized by an abundant and conspicuous trace fossil assemblage. Seven lithofacies were recognized, recording sediment accumulation in tidal flat, and inner to outer marine carbonate ramp, depositional environments. Thin-bedded marly limestones with bioclastic shelly beds (Facies E: middle ramp, with storm influence), are characterized by Diplocraterion and Rhizocorallium. Diplocraterion is protrusive, usually eroded on top, and mainly recorded in the marly limestone intervals. Rhizocorallium preserves well defined scratch-marks, and is commonly emplaced in bioclastic, shelly beds. The assemblage represents the Glossifungites ichnofacies. Sedimentological and ichnological data are interpreted to record a complex transgressive context, associated with high-frequency sea-level dynamics that allowed formation of transgressive surfaces of erosion (TSE, i.e., ravinement surfaces) of different orders. Major TSE, associated with continuous bioclastic shelly beds, delimit parasequences; the absence of the Glossifungites suite reveals that there was little time between erosion and deposition. Intermediate TSE, associated with discontinuous shell beds, are related to comparatively less significant sea-level rises and occur within parasequences. The Glossifungites suite reveals colonization of firmgrounds during relatively prolonged times between erosion and deposition related to intermediate TSE. Minor order TSE, recorded between the intermediate TSE, are related to punctuated, highest frequency sea-level changes; phases of colonization by the Diplocraterion tracemaker and protrusive, capped structures reveal more or less stillstand phases (TSE/stillstand phases), and minor order erosional phases.

Rodríguez-Tovar, Francisco J.; Pérez-Valera, Fernando; Pérez-López, Alberto

2007-06-01

156

Valleys, facies, and sequence stratigraphy of the Ferron Notom Delta, Capital Reef, Utah  

NASA Astrophysics Data System (ADS)

The Turonian-Coniacian Ferron Sandstone is the first significant elastic tongue prograding from the thin-skinned Sevier Orogenic belts into the western interior foreland basin after the Greenhorn sea-level maxima. The Ferron Notom Delta, one of the Ferron wedges, is exposed three dimensionally in the Henry Mountains region, Utah. This dissertation attempts to: (1) subdivide the complex in a sequence stratigraphic perspective, and (2) evaluate the existing nonmarine sequence stratigraphic and delta asymmetry models. A large amount of integrated sedimentological and ichnological data shows that the 100-160 m thick complex consists of 6 sequences, 18 parasequence sets, and 43 parasequences. Without this extensive data control, this stratal complexity could not be resolved, resulting in huge correlations uncertainties. Incised valleys are developed in the younger two sequences. The youngest valley system within SQ1 is a compound incised valley, containing two nested valleys, each of which consists of amalgamated fluvial sandstones in the lower part, grading upward into heterolithic tidal/tidal-fluvial facies, and finally capped by more fluvial facies. There is a change in fluvial style from meandering into braided across the boundary of these two valleys. These observations support the existing nonmarine sequence stratigraphy models. Facies within the fluvial-deltaic complex are diverse, ranging from river-dominated to storm/wave-dominated. Sedimentological analysis within parasequence 6 recognized a clear along-strike facies transition from sandy shoreface in the north, into heterolithic river-dominated delta-front facies southeastward, and into wave/storm-reworked facies further southeastward. Ichnogenera correspondingly show distinct along-strike changes from a robust and healthy archetypal Cruziana to Skolithos ichnofacies in the north into a suite characterized by horizontal, morphologically simple, facies-crossing structures of the suppressed Skolithos and Cruziana ichnofacies to the SE. Further southeastward, suites show higher abundance and diversity, and in some cases reflect the archetypal ichnofacies. The overall facies types and their distribution within the parasequence suggest delta asymmetry, with net longshore transport from north to south. However, unlike the recent delta asymmetry models, paralic, lagoonal, and bay-fill facies are largely absent in the studied asymmetric delta. This presumably reflects lack of paralic accommodation, because of negative shoreline trajectory, as well as post-depositional erosion during subsequent transgression.

Li, Weiguo

157

Time-stratigraphic reconstruction and integration of paleopedologic, sedimentologic, and biotic events (Willwood Formation, lower Eocene, northwest Wyoming, USA)  

SciTech Connect

Relative paleosol maturities are inversely proportional to the accumulation rates of the sediment upon which they formed, and are therefore excellent relative indicators of how much geologic time elapsed between any two horizons. An empirically-based model is advanced using paleosol maturities to estimate the relative geologic time separating any stratigraphic levels within the lower Eocene Willwood Formation. The revised Willwood time stratigraphy from this analysis helps evaluate the nature, tempo, and possible causes of three major episodes of mammalian appearance and disappearance. These faunal events are directly correlated with certain aspects of paleosol evolution in the Willwood Formation. That evolution is tied directly to climatic changes and to varying sediment accumulation rates in response to tectonism. The first faunal turnover occurs at the base of the Willwood Formation. It coincides with a major increase in pedogenic maturity, reflecting a major decrease in sediment accumulation rate, and accompanying general climatic warming at about the time of the Paleocene-Eocene boundary. Throughout the remainder of Willwood time, there was a gradual, yet continual, decrease in paleosol maturity and degree of hydromorphy, probably related to the progressive structural elevation of the Owl Creek antiform bounding the south and southeast margins of the Bighorn Basin. This gradual decrease was punctuated by two intervals of more significant decline in paleosol maturity and in the incidence of hydromorphic soils. Both intervals are also marked by faunal turnovers. These sedimentologic and biologic events may reflect tectonic, periods when the rate of basin subsidence increased more rapidly. 58 refs., 7 figs., 2 tabs.

Brown, T.M. (Geological Survey, Denver, CO (United States)); Kraus, M.J. (Univ. of Colorado, Boulder (United States))

1993-02-01

158

High-Resolution Subsurface Imaging and Stratigraphy of Quaternary Deposits, Marapanim Estuary, Northern Brazil  

NASA Astrophysics Data System (ADS)

The Marapanim estuary is situated in the Para Coastal Plain, North Brazil. It is characterized by an embayed coastline developed on Neogene and Quaternary sediments of the Barreiras and Pos-Barreiras Group. This system is strongly influenced by macrotidal regimes with semidiurnal tides and by humid tropical climate conditions. The interpretation of GPR-reflections presented in this paper is based on correlation of the GPR signal with stratigraphic data acquired on the coastal plain through five cores that were taken along GPR survey lines from the recent deposits and outcrops observed along to the coastal area. The profiles were obtained using a Geophysical Survey Systems Inc., Model YR-2 GPR, with monostatic 700 MHz antenna that permitted to get records of subsurface deposits at 20m depth. Were collected 54 radar sections completing a total of 4.360m. The field data were analyzed using a RADAN software and applying different filters. The interpretation of radar facies following the principles of seismic stratigraphy that permitted analyze the sedimentary facies and facies architecture in order to understand the lithology, depositional environments and stratigraphic evolution of this sedimentary succession as well as to leading to a more precise stratigraphic framework for the Neogene to Quaternary deposits at Marapanim coastal plain. Facies characteristics and sedimentologic analysis (i.e., texture, composition and structure aspects) were investigated from five cores collected through a Rammkernsonde system. The locations were determined using a Global Positioning System. Remote sensing images (Landsat-7 ETM+ and RADARSAT-1 Wide) and SRTM elevation data were used to identify and define the distribution of the different morphologic units. The Coastal Plain extends west-east of the mouth of the Marapanim River, where were identified six morphologic units: paleodune, strand plain, recent coastal dune, macrotidal sandy beach, mangrove and salt marsh. The integration of GPR profiles and stratigraphy data allowed for the recognition of paleochannel geometry, with width of 150m and depth of 20m, developed on Barreiras Group, two discontinuity surfaces and three facies associations organized into sedimentary facies: (i) Tidal channel with mottled sand, Conglomerate with clay pebble and Ophiomorpha/linear Skolithos, channel-fill and tabular cross-bedding sand and sand/mud interlayer facies. (ii) Dune/interdune with wavy bedding and cross-bedding sand and planar bedding and tabular cross-bedding sand facies. (iii) infilled tidal channel with mottled sand, planar/flaser bedding sand, lenticular bedding clay and sand/mud interlayer facies. The present study demonstrates that some facies associations occur restricts to tidal paleochannels and shows features well preserved that are very important to reconstruction of the relative sea-level history in the Marapanim Estuary.

Silva, C. A.; Souza Filho, P. M.; Gouvea Luiz, J.

2007-05-01

159

Carbon isotope stratigraphy of an ancient (Ordovician) Bahamian-type carbonate platform: Implications for preservation of global seawater trends  

NASA Astrophysics Data System (ADS)

Carbon isotope stratigraphy has a unique role in the interpretation of Earth history as one of the few geochemical proxies that have been widely applied throughout the geologic time scale, from the Precambrian to the Recent, as both a global correlation tool and proxy for the carbon cycle. However, in addition to consideration of the role of diagenesis, numerous studies have raised awareness of the fact that C-isotope trends derived from ancient carbonate platforms may not be representative of dissolved inorganic carbon from a well-mixed global ocean reservoir. Furthermore, the larger carbon isotopic fractionation in the formation of aragonite versus calcite from seawater must be taken into account. All three of these variables (diagenesis, water mass residence time, % aragonite) may change in response to sea level, producing trends in C-isotopes on ancient carbonate platforms that are unrelated to the global carbon cycle. Global carbon cycle fluxes may also have a cause-effect relationship with sea level changes, further complicating interpretations of stratigraphic trends in carbon isotopes from ancient platform environments. Studies of C-isotopes in modern carbonate platform settings such as the Great Bahama Bank (GBB) provide important analogues in addressing whether or not ancient platforms are likely to preserve a record of carbon cycling in the global ocean. Swart et al. (2009) found that waters of the GBB had generally the same or elevated values (ranging from +0.5‰ to +2.5‰) compared to the global oceans, interpreted as reflecting differential photosynthetic fractionation and precipitation of calcium carbonate (which lowers pH and converts bicarbonate into 12-C enriched carbon dioxide, leaving residual bicarbonate heavier). Carbonate sediments of the GBB have elevated C-isotopes, not only because of the high C-isotope composition of the overlying waters, but also due to the greater fractionation associated with precipitation of aragonite versus calcite. Few studies of ancient carbonates have attempted to explicitly compare C-isotope trends in both restricted platform settings and open marine settings (e.g., Immenhauser et al. 2002). We studied a restricted Bahamian-type carbonate platform of Middle-Late Ordovician (Darriwilian-early Sandbian) age included in the St. Paul Group of Maryland, notable for sedimentologic evidence of severe restriction and a general lack of open marine macrofauna. We are able to correlate the C-isotope curve from the St. Paul Group to other sections globally by using a combination of conodont microfossils and measurement of Sr isotopes on conodont apatite. Coeval C-isotope trends from open marine settings in the western United States and Estonia are comparable to the restricted platform in Maryland. In our Ordovician example, local factors appear to have modified the magnitude of the global trends, but not the timing and direction. A remaining question is whether magnitude differences are a function of sedimentation rate and completeness. We continue to test hypotheses of global correlations of C-isotope trends in the Middle-Late Ordovician by utilizing the rapidly changing Sr isotope curve at that time.

Saltzman, M.; Leslie, S. A.; Edwards, C. T.; Diamond, C. W.; Trigg, C. R.; Sedlacek, A. R.

2013-12-01

160

Principles of pleistocene stratigraphy, applied to the Gulf of Mexico  

SciTech Connect

This study of one of the world's major oil provinces is an examination of advances made in the past decade in high resolution stratigraphy of Pleistocene marine sediments. Topics covered include magnetostratigraphy, planktonic foraminiferal biostratigraphy, oxygen isotope stratigraphy, tephrochronology and a review and updating of terrestrial-marine correlations during the Pleistocene. The emphasis is on the Gulf of Mexico, but the techniques described can be applied to other marine sedimentary basins.

Fillon, R.H.; Healy-Williams, N.; Ledbetter, M.T.; Thunell, R.C.; Williams, D.F.

1984-01-01

161

Seismic sequence stratigraphy of the East China Sea  

SciTech Connect

Interpretation of the relationships of the second- and third-order depositional sequences, their sequence boundaries, maximum flooding surfaces, low stand and high stand systems tracts, and their surfaces were made on three wells in the East China sea. The age of the sediments is based on the integration of calcareous nannofossils, planktonic, benthic and large forams, and palynomorphs. The maximum flooding surfaces, sequence, and systems tract boundaries were identified and annotated on well logs and on a sequence stratigraphy analysis chart. These surfaces and boundaries on well logs were correlated with a series of seismic reflection profiles. The lacustrine-fluvial sediments in the Shi Men Tan 1 well were correlated to similar sediments in the Ming Yue Feng 1 well. Lowstand systems track slope fan complexes, that were deposited at the same time as the Andrews and Forties fans in the North Sea, were found in the Shi Men Tan 1 and Ming Yue Feng 1 wells. The slope-fan complexes were deposited in upper bathyal water depths (200-500 m) based on benthic foraminifers. Coastal swamp lagoonal sediments identified in the three wells could be the source rocks for hydrocarbon accumulations in the channels or channel overbank deposits in the slope-fan complexes and the lowstand prograding complexes. Stratigraphically above these deposits, nummulite carbonate banks were identified in the Shi Men Tan 1 and the Ling Feng 1 wells. Several significant angular unconformities were recognized at various intervals in the three wells.

Wornardt, W.W.; Zhang, J.Z. (MICRO-STRAT Inc., Houston, TX (United States)); Vail, P.R. (Rice Univ., Houston, TX (United States)); Li Peilian (Shanghai Bureau of Marine Geological Survey (China)); Baie, L.F. (SETSCO Inc., Houston, TX (United States))

1994-07-01

162

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

163

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

164

Upper Triassic reef facies in the Asher-Atlit-1 borehole, Northern Israel: Microfacies, cement stratigraphy and paleogeographic implications  

Microsoft Academic Search

Summary  The late Triassic succession of the Asher-Atlit 1 borehole is over 1000 m thick, and is composed of reefal and associated\\u000a facies interbedded with volcanics of Norian age. Only borehole cuttings are available. Microfacies classification and cement\\u000a stratigraphy determined by optical and CL microscopy, allowed discrimination of six episodes of reef establishment, progradation,\\u000a shallowing, and termination. Organic buildups are constructed

Dorit Korngreen; Chaim Benjamini

2001-01-01

165

Annotated Definitions of Selected Geomorphic Terms and Related Terms of Hydrology, Sedimentology, Soil Science and Ecology.  

National Technical Information Service (NTIS)

Terminology used in fluvial geomorphology, hydrology, sedimentology, soil science, climatology, and ecology is often inconsistent among the disciplines and within a discipline. The terms defined and described herein were compiled to: 1. recognize the over...

W. R. Osterkamp

2008-01-01

166

Ageing  

NASA Astrophysics Data System (ADS)

By 2020, the number of the world’s older population is expected to exceed one billion, and maintaining a high quality of life for these people has become an important issue throughout the world. The Web has been shown to have a positive experience on the quality of life and well-being of older persons, by assisting them to maintain an independent living. However, many older people seem to shy away from the Web due to various problems they experience when interacting with the Web. To understand the nature of these problems, this chapter presents the functional impairments and the attitudes that might contribute to older persons’ hesitation of utilising the Web. This chapter discusses the changes that happen with age, their effects on Web interaction and how they can be mediated through the accessible Web.

Kurniawan, Sri H.

167

Sedimentological study of the Chernobyl NPP site to schematise radionuclide migration conditions  

Microsoft Academic Search

The approach, methods and results of a sedimentological study of a near-surface stratum of Late Pleistocene-Holocene deposits in the near-zone (5–10 km radius) of the Chernobyl Nuclear Power Plant are presented. Sedimentological analyses are carried out at three levels of detail: regional-, local- and object-scale. The unsaturated zone and unconfined aquifer at the site are composed of two main genetic types

Andrei Matoshko; Dmitry Bugai; Lionel Dewiere; Alexander Skalskyy

2004-01-01

168

Hauptdolomit (Norian) — stratigraphy, paleogeography and diagenesis  

NASA Astrophysics Data System (ADS)

Geochemical and carbonate petrographical methods were coordinated in facies investigations and environmental reevaluations, related to the Hauptdolomit (Hd.) = main doimite formation (±Norian) of the Northern Calcareous Alps. It is practical to distinguish eight, environmentally controlled, facies units (1-8) and three geochemical groups (I-III). Superimposed upon the environment pattern (tidal complex, lagoonal complex, barrier bar and shoal complex) is a predictable (geochemical) dolomitization and non-carbonate distribution. The vertical and lateral facies associations, their waxing and waning in the geologic columns, allow paleogeographic reconstructions. Especially important are clayey, ±bituminous facies, commonly known as "Seefeld facies", which are interpreted to be of mainly intertidal to very shallow near-shore, rather than of deep-water, origin. Threefold stratigraphy can be substantiated and is found to be practicable for the Hd. formation in a large part of the Northern Calcareous Alps. In an attempt to explain some of the phenomena associated with dolomitization in the Hd. formation, a model of anaerobic dolomitization has been considered, outlining steps of early diagenetic dolomitization.

Fruth, I.; Scherreiks, R.

1982-06-01

169

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

170

Sequence stratigraphy of the Jurassic of the Danish Central Graben  

Microsoft Academic Search

A sequence stratigraphic framework is established for the Jurassic of the Danish Central Graben based primarily on petrophysical log data, core sedimentology and biostratigraphic data from about 50 wells. Regional seismic lines are used to assist in the correlation of some wells and in the con- struction of isochore maps. In the Lower Jurassic (Hettangian-Pliensbachian) succession, five sequences have been

Jan Andsbjerg; Karen Dybkjær

171

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

172

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

173

Sequence stratigraphy interpretation of the central shelf area, offshore Louisiana  

SciTech Connect

Sequence stratigraphy methods are demonstrated on a Halliburton regional seismic line and several well logs near the Eugene Island-Ship Shoal border off the central Louisiana shelf area of the Gulf of Mexico. The example shows five sequences of Pliocene-Pleistocene age interpreted by synthesizing log character, biostratigraphy and seismic character. These sequences show the complete range of shallow water to deeper water systems tracts, demonstrating a significant presence of lowstand wedge sediments high onto the present-day shelf. The study area shows exceptional development of the transgressive systems tract between the 2.4 and 3.0-m.y. sequence boundaries. This is evidenced by apparent truncation on seismic and corresponds to an overall shaly unit which contains several parasequences identified in well logs. The individual sands of the parasequences are easily correlated from well to well. The Lenticulina 1 paleo picks fluctuate between the 1.6 and 2.4-m.y. sequences but generally occur near the top of the 2.4- m.y. transgression. The 2.4-m.y. sequence boundary is deeply incised and filled with lowstand wedge prograding sands and shales. The 3.0, 3.8, and 4.2-m.y. sequences show an increasing thickness of lowstand wedge sediments and mounded slope fan seismic character with some channelized gull wing development. Several sands with blocky log character are interpreted as channelized portions of the slope fan. Updip along the sequence boundary, the proximal slope fan seismic facies character becomes dominant, i.e., much more laterally continuous seismic reflectors with few mounds.

Radovich, B.; Powell, T.; Lovell, M. (Pennzoil Exploration and Production Co., Houston, TX (USA)); Mitchum, R. Jr. (Sangree, Sneider, and Mitchum Consultants, Houston, TX (USA))

1990-05-01

174

Hydrated mineral stratigraphy of Ius Chasma, Valles Marineris  

NASA Astrophysics Data System (ADS)

New high-resolution spectral and morphologic imaging of deposits on walls and floor of Ius Chasma extend previous geomorphic mapping, and permit a new interpretation of aqueous processes that occurred during the development of Valles Marineris. We identify hydrated mineralogy based on visible-near infrared (VNIR) absorptions. We map the extents of these units with CRISM spectral data as well as morphologies in CTX and HiRISE imagery. Three cross-sections across Ius Chasma illustrate the interpreted mineral stratigraphy. Multiple episodes formed and transported hydrated minerals within Ius Chasma. Polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma. They may have been precipitates in a closed basin or diagenetically altered after deposition. Fluvial or aeolian processes then deposited layered Fe/Mg smectite and hydrated silicate on the chasma floor, postdating the sulfates. The smectite apparently was weathered out of Noachian-age wallrock and transported to the depositional sites. The overlying hydrated silicate is interpreted to be an acid-leached phyllosilicate transformed from the underlying smectite unit, or a smectite/jarosite mixture. The finely layered smectite and massive hydrated silicate units have an erosional unconformity between them, that marks a change in surface water chemistry. Landslides transported large blocks of wallrock, some altered to contain Fe/Mg smectite, to the chasma floor. After the last episode of normal faulting and subsequent landslides, opal was transported short distances into the chasma from a few m-thick light-toned layer near the top of the wallrock, by sapping channels in Louros Valles. Alternatively, the material was transported into the chasma and then altered to opal. The superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential, distinct aqueous environments, characterized by alkaline, then circum-neutral, and finally very acidic surface or groundwater chemistry.

Roach, Leah H.; Mustard, John F.; Swayze, Gregg; Milliken, Ralph E.; Bishop, Janice L.; Murchie, Scott L.; Lichtenberg, Kim

2010-03-01

175

Hydrated mineral stratigraphy of Ius Chasma, Valles Marineris  

USGS Publications Warehouse

New high-resolution spectral and morphologic imaging of deposits on walls and floor of Ius Chasma extend previous geomorphic mapping, and permit a new interpretation of aqueous processes that occurred during the development of Valles Marineris. We identify hydrated mineralogy based on visible-near infrared (VNIR) absorptions. We map the extents of these units with CRISM spectral data as well as morphologies in CTX and HiRISE imagery. Three cross-sections across Ius Chasma illustrate the interpreted mineral stratigraphy. Multiple episodes formed and transported hydrated minerals within Ius Chasma. Polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma. They may have been precipitates in a closed basin or diagenetically altered after deposition. Fluvial or aeolian processes then deposited layered Fe/Mg smectite and hydrated silicate on the chasma floor, postdating the sulfates. The smectite apparently was weathered out of Noachian-age wallrock and transported to the depositional sites. The overlying hydrated silicate is interpreted to be an acid-leached phyllosilicate transformed from the underlying smectite unit, or a smectite/jarosite mixture. The finely layered smectite and massive hydrated silicate units have an erosional unconformity between them, that marks a change in surface water chemistry. Landslides transported large blocks of wallrock, some altered to contain Fe/Mg smectite, to the chasma floor. After the last episode of normal faulting and subsequent landslides, opal was transported short distances into the chasma from a few m-thick light-toned layer near the top of the wallrock, by sapping channels in Louros Valles. Alternatively, the material was transported into the chasma and then altered to opal. The superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential, distinct aqueous environments, characterized by alkaline, then circum-neutral, and finally very acidic surface or groundwater chemistry. ?? 2009 Elsevier Inc. All rights reserved.

Roach, L. H.; Mustard, J. F.; Swayze, G.; Milliken, R. E.; Bishop, J. L.; Murchie, S. L.; Lichtenberg, K.

2010-01-01

176

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

177

Le bassin sédimentaire a phosphates du Togo (Maastrichtien-Eocène): stratigraphie, environnements et évolutionThe phosphate sedimentary basin of Togo [Maastrichtian-Eocène): stratigraphy, environments and evolution)  

NASA Astrophysics Data System (ADS)

Studies carried out in the quarries at Tabligbo (klinker feed materials) Hahotoé and Kpogamé (phosphate extraction), coupled with core sample analyses of five boreholes, have led to a more precise stratigraphy of the Togo coastal basin and a younger age for the Tabligbo Limestones (Upper Palaeocene) and the palygorskite fissile-laminated Clays (Early Eocene). An outline of the depositional environment of the phosphate deposits is proposed through the sedimentary and dynamic evolution of the basin: transgression on to the continental margin, followed by a progressive deepening of the basin with deposition and preservation of organic matter; phosphates at the start of the regression; differential displacements of faulted blocks make a structural trap for the phosphates; accumulation and alteration of the phospharenite.

Johnson, Ampah Kodjo; Rat, Pierre; Lang, Jacques

2000-01-01

178

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

179

Strontium-isotope stratigraphy of Upper Cretaceous platform carbonates of the island of Bra? (Adriatic Sea, Croatia): implications for global correlation of platform evolution and biostratigraphy  

Microsoft Academic Search

The chronostratigraphy of Coniacian–Maastrichtian platform carbonates exposed on the island of Bra? and the adjacent mainland has been revised, based on numerical ages derived from strontium-isotope stratigraphy (SIS) of low-Mg calcite of rudist shells. The Dol intra-platform basin formed during the mid-Coniacian–early Santonian. The base of the prograding Pu?iš?a Formation is of mid-Santonian age (84.9Ma) in the southeast, and late

Thomas Steuber; Tvrtko Korbar; Vladimir Jelaska; Ivan Guši?

2005-01-01

180

Yucatán subsurface stratigraphy based on the Yaxcopoil-1 drillhole  

NASA Astrophysics Data System (ADS)

The Yaxcopoil-1 CSDP hole was drilled on the southern inner flank of the Chicxulub impact crater, approximately 60 km from its center. Lithological, sedimentological and stratigraphic investigations of this core between a depth of 775m and 1511m identified 10 major bio-and lithostratigraphic units. The lower part of the core up to 894m contains a sequence of limestones, dolomites and anhydrites of late early to late Cretaceous ages. These lithologies indicate deposition in various carbonate platform (e.g. sabkha, lagoons) and open marine shelf environments. Anhydrites make up for approximately 25% of the section (157m of >615m), less than expected from published records. A 100m thick suevitic breccia is present between 794-894m, with the top 15m reworked by ocean water. Dolomitic limestones and limestones overlie the suevite. At 25cm above the breccia/dolomite contact the first early Danian P. eugubina Zone planktic foraminifers are present and indicate deposition in a quiet open marine shelf environment. Upsection, the limestones of planktic foraminiferal Zone P1c indicate more proximal conditions with debris flows from nearby shallow carbonate platform environments.These data suggest that the Cretaceous sediment sequence is largely autochthonous, with a stratigraphical sequence comparable to Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan. Our investigation revealed no evidence for major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, or major mechanical fragmentation, shock alteration or ductile deformation. Breccia units intercalated in the carbonate platform sequence show conformable and sometimes gradational contacts to under- and overlying non-brecciated sediments and appear to be of intraformational origin (e.g. dissolution of evaporites), rather than a consequence of instant shaking, shearing and sliding of impact megablocks. No glass spherules or altered glass shards are present in any of these layers and no basement rocks or other exotic clasts were detected. Only a single dyke was recognized at a depth of 1399m, in addition to two dykes of suevitic breccia (at 915m and 909m) close to the contact between Cretaceous sediments and overlying suevite. The contact between suevite and overlying hemipelagic carbonates is abrupt. The absence of a gradational contact and transitional lithologies is surprising, considering the enormeous amount of compaction, mass sliding and subsequent shaking which is expected to have accompanied the post-impact period in and around the Chicxulub crater.

Stinnesbeck, W.; Keller, G.; Adatte, T.; Harting, M.; Kramar, U.; Stüben, D.

2003-04-01

181

Cone-penetrometer exploration of sinkholes: Stratigraphy and soil properties  

SciTech Connect

Four sinkholes with varying surficial expressions were subjected to detailed stratigraphic and soil analysis by means of Standard Penetration Tests (SPT) and Electric Friction Cone Penetration Tests (CPT) in order to evaluate applications of CPT to sinkhole investigations. Although widely used, SPT data are of limited value and difficult to apply to sinkhole mapping. CPT is sensitive to minor lithologic variability and is superior to SPT as a cost-effective technique for determining geotechnical properties of sinkholes. The effectiveness of CPT data results from the force measurements made along the sleeve of the cone. The friction ratio (ratio of sleeve to tip resistance) is a good indicator of soil stratigraphy and properties. By smoothing the friction-ratio data, general stratigraphy and changes in soil properties are easily identified. Stratigraphy of the sinks has been complicated by intense weathering, karstification and marine transgressions. The resulting deposits include five stratigraphic units. 1 and 2 represent Plio-Pleistocene marine sediments with Unit 2 being the zone of soil clay accumulation. 3 and 4 are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units 1 and 2. CPT provides sufficient information for recognition of sinkhole stratigraphy and geotechnical properties. When coupled with laboratory soil analysis, CPT provides unique information about sinkhole geometry and dynamics. In contrast, SPT indicates general, inconclusive trends.

Bloomberg, D.; Upchurch, S.B.; Hayden, M.L. (Univ. of South Florida, Tampa (United States)); Williams, R.C. (Williams and Associates, Inc., Clearwater, FL (United States))

1988-10-01

182

Yucatán subsurface stratigraphy: Implications and constraints for the Chicxulub impact  

Microsoft Academic Search

Much of the discussion about the effects of an end-of-Cretaceous impact by a large extraterrestrial body in northwestern Yucatán has been done in the context of limited and partly erroneous published data on the Mesozoic stratigraphy of that area. Reexamination of cores and geophysical logs taken in several Pemex wells has produced improved lithologic and biostratigraphic correlation of the Jurassic

W. C. Ward; G. Keller; W. Stinnesbeck; T. Adatte

1995-01-01

183

Sequence stratigraphy in Neogene expanded sections, Gulf of Mexico  

Microsoft Academic Search

Recent developments in sequence stratigraphy offer an approach to the stratigraphic interpretation of the thick, highly structured Neogene sediments of the Gulf of Mexico Basin. The general sequence-stratigraphic model consists of a depositional sequence with lowstand basin floor fan, slope fan, and prograding wedge, transgressive systems tract, and highstand systems tract. Each systems tract is deposited at a predictable position

R. M. Mitchum; J. B. Sangree; P. R. Vail

1990-01-01

184

Stratigraphy and sedimentation in the Mediterranean Ridge diapiric belt  

Microsoft Academic Search

Two basic sediment types are recorded in the Mediterranean Ridge diapiric belt: the host sediment and the mud breccia. The host sediment consists of hemipelagic marl as dominant lithology, associated with sapropels and tephras as minor isochronous lithologies. A high resolution stratigraphy, which allows much more detailed and precise correlations than those based on biostratigraphy (essentially calcareous nannofossils) is applicable

M. B. Cita; E. Erba; R. Lucchi; M. Pott; R. van der Meer; L. Nieto

1996-01-01

185

Investigating peatland stratigraphy and hydrogeology using integrated electrical geophysics  

Microsoft Academic Search

Hydrology has been suggested as the mechanism controlling vegetation and related surficial pore-water chemistry in large peatlands. Peatland hydrology influences the carbon dynamics within these large carbon reservoirs and will influence their response to global warming. A geophysical survey was completed in Caribou Bog, a large peatland in Maine, to evaluate peatland stratigraphy and hydrology. Geophysical measurements were integrated with

Lee D. Slater; Andrew S. Reeve

2002-01-01

186

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

187

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

188

Yucatán subsurface stratigraphy based on the Yaxcopoil-1 drillhole  

Microsoft Academic Search

The Yaxcopoil-1 CSDP hole was drilled on the southern inner flank of the Chicxulub impact crater, approximately 60 km from its center. Lithological, sedimentological and stratigraphic investigations of this core between a depth of 775m and 1511m identified 10 major bio-and lithostratigraphic units. The lower part of the core up to 894m contains a sequence of limestones, dolomites and anhydrites

W. Stinnesbeck; G. Keller; T. Adatte; M. Harting; U. Kramar; D. Stüben

2003-01-01

189

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

190

Morphologic and sedimentologic characteristics of continental slope box slides offshore Fraser Island, Queensland, Australia  

NASA Astrophysics Data System (ADS)

The Fraser Island Slide complex is located on eastern Australia's continental slope offshore Fraser Island in southern Queensland. Morphologic, sedimentologic and geomechanical properties data for two submarine landslides, the 'North Fraser Island Upper Slope Slide' (upper slope slide) and the 'Fraser Island Middle Slope Slide' (middle slope slide) are described. Both of these features are box-shaped, slide scars from which rectangular slabs of material have been shed. The upper slope slide is situated at a water depth of approximately 750 m at the northern end of the Fraser Canyon. The head of this slide has apparently detached from a structural surface comprised of a Miocene reef complex located beneath the continental shelf edge; this slide is estimated to be 25 square kilometres in area and an average of 100m thick. The middle slope slide is situated in 1500 m of water at the southern end of the Fraser Canyon. It estimated to be 12 square kilometres in area and 50 m thick. Cores taken in the continental slope within both slides are long (upper slope 5.65 m, middle slope 3.64 m) and are dominantly comprised of hemipelagic mud. Cores taken adjacent to both slides are short (upper slope 1.33m, middle slope 0.43m) and terminate in stiff muds of suspected Miocene or Pliocene age. Additionally, the 1.33 m core on the slope adjacent to the upper slide presents a near surface layer of upper-fining of coarse to fine shelly sand which we interpret to be a turbidite deposit, this layer was deposited within hemipelagic muds which are ubiquitously present on the upper eastern Australian Continental Slope in New South Wales and Southern Queensland.

Fletcher, Melissa; Hubble, Thomas; Clarke, Samantha; Airey, David; Yu, Phyllis; Southern Surveyor V01-2013, Scientific Party RV

2014-05-01

191

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

192

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  

Microsoft Academic Search

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

F. F. Krause; S. A. Aitken; W. F. Braunberger; P. Chung; A. Macrae; R. O. Meyer; L. Nunez-Betelu; C. A. Williams; H. M. Hol

1993-01-01

193

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

194

Stratigraphy, sedimentology, and ichnology of the Late Pennsylvanian Glenshaw Formation (Lower Conemaugh Group), southern Dunkard basin, Ohio-Kentucky-West Virginia  

SciTech Connect

Facies analysis of outcrops of the Glenshaw Formation was carried out at 45 localities over a 761 sq. km area. The glenshaw Formation is 61--76 m thick in the study area. Four marine units (Lower Brush Creek, Upper Brush Creek, Cambridge , and Ames) occur which contain invertebrate body fossils and/or trace fossils including Teichichnus, Rhizocorallium, Aulichnites, Paleophycus, Lockeia, and Curvolithus. Alluvial channel-fills contain internal features that reflect deposition in high sinuosity suspended or mixed load rivers. Paleocurrent data (N = 77) are broadly dispersed with a mean azimuth of 335 degrees. Overbank facies have yielded trackways from giant arthropods and Eryopoid amphibians (Limnopus). There are fewer marine units in the glenshaw than toward the north and west which has made direct detailed correlation of much of the formation problematic. The coal beds and marine units used previous stratigraphic studies may be extended through the recognition of non-coal-bearing paleosols and marine-influenced intervals distinguished by facies relations, and sedimentary and biogenic structures. Nine laterally persistent, paleosol-bounded packages occur which are comparable to allocyclic T-R units reported by Busch and Rollins (1984) from Pennsylvania and Ohio. Alternating episodes of soil formation and alluvial aggradation may reflect updip coastal plain responses to low stand incision of drainage lines and sediment bypassing followed by aggradation of alluvial systems in response to rising sea level. Climate changes may also have played a role in sediment flux.

Martino, R.L. (Marshall Univ., Huntington, WV (United States). Dept. of Geology)

1994-03-01

195

Integrated stratigraphy of the Cenomanian-Turonian boundary interval: improving understanding of Oceanic Anoxic Events  

NASA Astrophysics Data System (ADS)

The Cenomanian-Turonian boundary (CTB) interval ~ 94 Ma represented a period of major global palaeoenvironmental change. Increasingly detailed multidisciplinary studies integrating sedimentological, palaeontological and geochemical data from multiple basins, are enabling the development of refined but complex models that aid understanding of the mechanisms driving changes in ocean productivity and climate. This paper reviews some of the exciting new developments in this field. Facies change characterizes the CTB interval in most areas. In the Chalk seas of northern Europe, a widespead hiatus was followed by the deposition of clay-rich organic-lean beds of the Plenus Marl and its equivalents, and then nodular chalks. In the North Sea basin and its onshore extension in eastern England and northern Germany, black shales of the Black Band (Blodøks Formation, Hasseltal Formation) occur. Similarly, in northern Tethys, a brief interval of black shale accumulation within a predominantly carbonate succession, is exemplified by the Niveau Thomel in the Vocontian Basin (SE France), and the Livello Bonarelli in Italy. Widespread deposition of organic-rich marine sediments during CTB times led to 12C depletion in surface carbon reservoirs (oceans, atmosphere, biosphere), and a large positive global ?13C excursion preserved in marine carbonates and both marine and terrestrial organic matter (Oceanic Anoxic Event 2). Significant biotic turnover characterises the boundary interval, and inter-regional correlation may be achieved at high resolution using integrated biostratigraphy employing macrofossils (ammonites, inoceramid bivalves), microfossils (planktonic foraminifera, dinoflagellate cysts) and calcareous nannofossils. Correlations can be tested against those based on comparison of ?13C profiles - carbon isotope chemostratigraphy, supplemented by oxygen isotope and elemental data. Interpretation of paired carbonate - organic matter ?13C data from multiple CTB sections implicates rising atmospheric pCO2 linked to volcanic outgassing as a major forcing mechanism for palaeoclimate warming and palaeoceanographic change accompanying OAE2. New marine 187Os/188Os isotope stratigraphy further reveals the interaction of volcanism and ocean circulation during OAE2, and provides a further chemostratigraphic tool. Li isotope (? 7Li) data may be interpreted as evidence that increased silicate weathering promoted by rising pCO2 acted as both a forcing and negative feedback mechanism driving OAE2 history. Neodymium and sulphur isotopes offer further insights into interactions between global biogeochemical cycles and ocean circulation changes.

Jarvis, Ian

2014-05-01

196

The stratigraphy and palaeoenvironment of the Bathonian "Great Oolite Group" of Woodeaton Quarry, Oxfordshire.  

NASA Astrophysics Data System (ADS)

Woodeaton Quarry, Oxfordshire, represents the most continuously exposed section of the Upper Bathonian 'Great Oolite Group' in the United Kingdom. Like most of the British Bathonian, it is lacking in reliable ammonite zonation from which to define a chronostratigraphy. The sedimentology of the succession can be broken up into two broad facies types: A clay rich, brackish lagoonal environment with intermixed freshwater-influenced flora and fauna; A marginal marine calcareous succession of an oolitic nature with periodic mud-drape intervals. The marginal marine depositional setting, the completeness of the Upper Bathonian stratigraphy and lack of biostratigraphically important macrofauna has motivated this study into the micropalaeontology of Woodeaton. The primary aims of this study are to use foraminifera and ostracods to reconstruct the palaeoenvironments and to refine the biostratigraphy of the Upper Bathonian. The studied succession commences at the top of the Taynton Limestone Formation, which fines upwards into the clay-rich Rutland Formation. Several species of marine ostracods known from the Mid-Upper Bathonian are recovered from the base of the Rutland Formation, such as Praeschuleridea confossa and Angliaecytherldea calvata, as well as fragments of fish scales and elasmobranch teeth. Freshwater influence is evident further up the Rutland Formation where freshwater charophytes, nested bivalves and ostracods of the genus Bisulcocypris have been found. The progression from the Rutland Formation's marine base into the freshwater influenced clays is clear from the varied micropalaeontological fauna. A return to marine conditions in the overlying White Limestone Formation can be observed through the increasing number of benthic foraminiferal taxa - with Spirillina and Lenticulina the most abundant - compared to the Rutland Formation. Within the Shipton and Ardley Members there are also indicative marine ostracod taxa present (including Acanthocythere spiniscutulata and Terquemula robusta). The upper part of the section exposes the Bladon Member that displays a relative shallowing within the fimbriatus-waltoni beds preserving a number of in situ rootlets and exogenous carbonised logs. This unit contains a mixed assemblage of marine species of ostracods (e.g. Fossaterquemula blakeana) and foraminifera (e.g. Lenticulina tricarinella) in association with freshwater ostracod taxa such as Timiriasevia sp. The succession at Woodeaton Quarry of Upper Bathonian carbonates exhibits microfaunal assemblages that can be viewed as direct proxies to the palaeoenvironment. The assemblages of ostracods and foraminifera indicate marine conditions prevailed in the basal Rutland Formation before the evolution of a freshwater environment. A return to a marine dominated environment with freshwater fluctuations occurs throughout the White Limestone Formation. It is through the high-resolution micropalaeontological study that palaeoenvironmental analysis can be refined in the marginal marine settings of the Upper Bathonian in Oxfordshire.

Guthrie, Ronald; Stukins, Stephen; Raub, Tim

2014-05-01

197

Aptian Carbon Isotope Stratigraphy in Sierra del Rosario, Northeastern Mexico  

NASA Astrophysics Data System (ADS)

In most recent years Aptian carbon isotope stratigraphy has been widely studied in Europe where isotopic stages have been developed to correlate global events. Two negative excursions have been recorded in the Lower Aptian, the older is OAE 1a in the middle part, and a younger negative excursion labeled "Aparein level", which occurs in the uppermost part of the Lower Aptian. In Mexico previous works reported a carbon isotope negative excursion in the lowermost part of the La Peña Formation that was assigned to the onset of Oceanic Anoxic Event 1a (=OAE 1a). In this work we study the isotopic record of the ?13Ccarb of 32 bulk rock samples of limestone from the uppermost part of the Cupido Formation and the lower part of the La Peña Formation at the Francisco Zarco Dam Section (=FZD), Durango State, northeastern Mexico. The isotopic data are calibrated using the latest ammonite biostratigraphic biozonation of the Aptian. This age calibration allows us to make a precise correlation between the carbon isotopic record of Mexico and several European sections (e.g. Spain and France). In the studied Francisco Zarco Dam section we recognize a negative carbon isotopic excursion in the Dufrenoyia justinae ammonite Zone that corresponds to the "Aparein level", which we correlate using the ammonite zonation of others European sections (Figure 1). This correlation allows us to see how the negative excursion that characterizes the "Aparein level" is consistent with the C7 segment. Thus, our recent stratigraphic study allows us to conclude that the ammonite record in the lowermost part of the La Peña Formation is regionally isochronous, and correlates with the Dufrenoyia justinae Zone and Lower Aptian isotope interval C7. In agreement to these biostratigraphic data, the supposed record of the OAE 1a in the lowermost part of the La Peña Formation is not correct, and the carbon isotope negative excursion must be assigned to the younger event "Aparein level". Taking this into account, other Lower Aptian negative excursions reported in the literature and assigned to the OAE 1a, perhaps, must be reconsidered to distinguish among the two Lower Aptian negative excursions.; Figure 1: Isotopic curve of the FZD section compared with one section of Spain. The sharp negative peak in the Mexican section is compared with the Spanish section (see the arrow).

Barragan-Manzo, R.; Moreno-Bedmar, J.; Nuñez, F.; Company, M.

2013-05-01

198

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

199

Propagation of the thrust system and erosion in the Lesser Himalaya: Geochemical and sedimentological evidence  

Microsoft Academic Search

Sedimentological and Nd isotope data of two sections of the sub-Himalaya of western Nepal are used as new constraints for understanding the erosion history of the Himalaya. Throughout the deposition of the middle and upper members of the Siwalik Group, the Lesser Himalaya contribution to the total detrital input progressively increased from less than 20% to 40%. The increasing proportion

Pascale Huyghe; Albert Galy; Jean-Louis Mugnier; Christian France-Lanord

2001-01-01

200

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

201

Sedimentology and Uranium Mineralization of the Klipbankskraal Deposit North of Merweville, C.P.  

National Technical Information Service (NTIS)

A sedimentological study was conducted on the farm Klipbankskraal, north-west of Merweville. The orebody is located in the Poortjie Member at the base of the Teekloof Formation. The mineralised sandstone, S1, is a tabular lithosome deposited in an ephemer...

J. P. Le Roux

1982-01-01

202

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. G.; Exon, N. F.

1988-01-01

203

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

204

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

205

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

206

Process-response modelling of fluvio-deltaic stratigraphy  

Microsoft Academic Search

Numerical modelling is a tool to investigate the controls on the formation of the stratigraphic record on geological timescales. The model presented in this paper (DELTASIM) uses a process-response approach that simulates the stratigraphy of fluvial-dominated deltaic systems in two dimensions, based on simplified diffusion rules of cross-shore sedimentation. Net sedimentation is calculated for individual grain-size classes as the sum

Robert M. Hoogendoorn; Irina Overeem; Joep E. A. Storms

2008-01-01

207

New constraints on the limits of the Barents-Kara ice sheet during the Last Glacial Maximum based on borehole stratigraphy from the Pechora Sea  

Microsoft Academic Search

A new, 14C-verified borehole stratigraphy provides the first age-controlled reconstruction of the late Quaternary glacial history of the Pechora Sea (southeasternmost Barents Sea). A complete glaciation of the Pechora Sea is confirmed for middle Weichselian time, prior to ca. 35 40 ka. Composition of glacial erratics indicates that ice was moving from or across southernmost Novaya Zemlya and Vaygach Island.

Leonid Polyak; Valery Gataullin; Ol'ga Okuneva; Vilnis Stelle

2000-01-01

208

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

209

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

210

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

211

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

212

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

213

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

214

The story of landscape evolution in Lower Austria told by sedimentological analysis and luminescence dating  

NASA Astrophysics Data System (ADS)

Loess/palaeosol sequences contain detailed information about palaeoenvironmental changes during the Quaternary. Furthermore, because of its long distance aeolian transport, which resets the luminescence signal to zero prior to deposition, loess is highly suitable for luminescence dating. This allows the determination of geodynamic processes with time. The loess deposits in the Kremser Feld (Lower Austria) are up to 30 m thick. The loess/paleosol sequence of Stratzing is situated at the eastern margin of the west-east elongated hill of the ‘Galgenberg'; this location is famous for its archaeological finds, e.g. the sculpture "Fanny", one of the oldest identifiable representations of the human figure (Neugebauer-Maresch, 1993). The loess profile examined here has a total depth of 7.5 m and is subdivided into 19 prominent horizons. For each horizon the grain size distribution, pH-value, total carbonate content, total organic content and sulphur content was derived in order to reconstruct the environmental conditions leading to sedimentation and soil formation. To set up a geochronological framework for the loess deposition and the subsequent soil formation, nine samples were dated by means of elevated temperature post-IR IRSL (Thiel et al., submitted). Besides a general discussion about the sedimentological data we will discuss horizon 18 in more detail; this is a paleosol rich in clay and poor in mineralic carbonate. The sulphur content is relatively high and indicates higher humidity and warmer climate, all making the unexpectedly low organic carbon content of particular interest. The luminescence ages reveal an important hiatus above this well-developed palaeosol (from ~ 100 to ~ at least 200 ka) clearly showing that this loess/palaeosol sequence is not a continuous record. This implies either significant erosion or lack of loess deposition in this area. Neugebauer-Maresch, C., 1993. Kunst und geistige Welt. - In: Neugebauer-Maresch, C., (ed): Altsteinzeit im Osten Österreichs. Wissenschaftliche Schriftenreihe Niederösterreich 95/96/97 (St. Pölten). Thiel, C., Buylaert, J. P., Terhorst, B., Murray, A. S., Hofer, I., Tsukamoto, S., Frechen, M., submitted. Luminescence dating of the Stratzing loess profile (Austria) - Testing the potential of an elevated temperature post-IR IRSL protocol. Quaternary International.

Hofer, Ingo; Thiel, Christine; Terhorst, Birgit; Jaburova, Iva; Buylaert, Jan-Pieter; Murray, Andrew; Frechen, Manfred

2010-05-01

215

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

216

Sedimentology and cyclicity in the Lower Permian De Chelly Sandstone on the Defiance Plateau: eastern Arizona  

USGS Publications Warehouse

The Lower Permian (Leonardian) De Chelly Sandstone crops out along a north-south trend on the Defiance Plateau of eastern Arizona. It is divided into lower and upper members separated by a tongue of the Supai Formation that pinches out to the north. Stratigraphy, and lateral and vertical facies relations within the lower and upper members, are discussed. -from Author

Stanesco, J. D.

1991-01-01

217

Capitan reef complex (Permian), Guadalupe Mountains, southwestern United States: a classic sedimentologic model in flux  

SciTech Connect

The Capitan reef complex of west Texas and New Mexico has been an important sedimentologic model since a reef origin was proposed for the Capitan Limestone in 1929. The Capitan's magnificent exposures in the Guadalupe Mountain area; its large scale; its variety of carbonate, sandstone, and evaporite facies; and its relationship to major petroleum resources of the Permian basin have made it a justly famous sedimentary geologic model for academic and industrial geologists alike. Since 1950, extensive research has yielded markedly contrasting sedimentologic interpretations of key features, such as the nature and origin of the Capital massive (reef wall); the back-reef pisolite, sandstone, and evaporite facies; the depositional profile of the shelf and shelf edge; the importance and magnitude of sea level fluctuations; and the role of submarine, vadose, and phreatic diagenesis.

Pray, L.C.

1987-11-01

218

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

219

Radiogenic isotopes: systematics and applications to earth surface processes and chemical stratigraphy  

Microsoft Academic Search

Radiogenic isotopes have wide application to chemical stratigraphy, geochronology, provenance studies, and studies of temporal changes in Earth surface processes. This paper briefly reviews the principles of radiogenic isotope geochemistry and the distribution of a number of elements of interest in the environment, and then uses this information to explore the range of applications to chemical stratigraphy and other fundamental

Jay L. Banner

2004-01-01

220

Strontium isotopic, chemical, and sedimentological evidence for the evolution of Lake Lisan and the Dead Sea  

Microsoft Academic Search

Precise strontium isotope ratios, combined with chemical analyses and sedimentological information, are used to monitor the water sources and the evolution of the Dead Sea and its late Pleistocene precursor, Lake Lisan (70-18 kyr B.P.). The materials analyzed include bulk aragonite, water-leached soluble salts, and residual aragonite and gypsum from the Lisan Formation in the Perazim Valley (near the SW

M. Stein; A. Starinsky; A. Katz; S. L. Goldstein; M. Machlus; A. Schramm

1997-01-01

221

Sedimentology and diagenesis of Tertiary carbonates on the Mangkalihat Peninsula, Borneo: implications for subsurface reservoir quality  

Microsoft Academic Search

Combined field and laboratory studies of surface exposures on the Mangkalihat Peninsula, Borneo, provide new constraints on the chronostratigraphy, sedimentology and diagenesis of Tertiary carbonate deposits. The reservoir characteristics of carbonate facies are described, providing an analogue model for carbonate reservoirs in the subsurface of this region.A mixed carbonate-siliciclastic shelf with intervening, probably fault-bounded, deeper water areas developed on the

Moyra E. J Wilson; Martin J Evans

2002-01-01

222

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

Microsoft Academic Search

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

George A. McMechan; R. B. Szerbiak; G. C. Gaynor

1997-01-01

223

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

224

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

225

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

226

A consistent magnetic polarity stratigraphy of Plio-Pleistocene fluvial sediments from the Heidelberg Basin (Germany)  

NASA Astrophysics Data System (ADS)

Deep drillings in the Heidelberg Basins provide access to one of the thickest and most complete successions of Quaternary and Upper Pliocene continental sediments in Central-Europe [1]. In absence of any comprehensive chronostratigraphic model, these sediments are so far classified by lithological and hydrogeological criteria. Therefore the age of this sequence is still controversially discussed ([1], [2]). In spite of the fact that fluvial sediments are a fundamental challenge for the application of magnetic polarity stratigraphy we performed a thorough study on four drilling cores (from Heidelberg, Ludwigshafen and nearby Viernheim). Here, we present the results from the analyses of these cores, which yield to a consistent chronostratigraphic framework. The components of natural remanent magnetisation (NRM) were separated by alternating field and thermal demagnetisation techniques and the characteristic remanent magnetisations (ChRM) were isolated by principle component analysis [3]. Due to the coring technique solely inclination data of the ChRM is used for the determination of the magnetic polarity stratigraphy. Rock magnetic proxies were applied to identify the carriers of the remanent magnetisation. The investigations prove the NRM as a stable, largely primary magnetisation acquired shortly after deposition (PDRM). The Matuyama-Gauss boundary is clearly defined by a polarity change in each core, as suggested in previous work [4]. These findings are in good agreement with the biostratigraphic definition of the base of the Quaternary ([5], [6], [7]). The Brunhes-Matuyama boundary could be identified in core Heidelberg UniNord 1 and 2 only. Consequently, the position of the Jaramillo and Olduvai subchron can be inferred from the lithostratigraphy and the development of fluvial facies architecture in the Rhine system. The continuation of the magnetic polarity stratigraphy into the Gilbert chron (Upper Pliocene) allows alternative correlation schemes for the cores Viernheim and Heidelberg. All things considered, the application of magnetic polarity stratigraphy on Pliocene and Pleistocene fluvial sediments from the Heidelberg Basin provides a consistent and independent chronology and opens the perspective for global correlations where other approaches hardly come to results. [1] GABRIEL, G., ELLWANGER, D., HOSELMANN, C. & WEIDENFELLER, M. 2008. Preface: The HeidelbergBasin Drilling Project. E & G (Quaternary Science Journal), 57, 253-260. [2] ELLWANGER, D. & WIELAND-SCHUSTER, U. 2012. Fotodokumentation und Schichtenverzeichnis der Forschungsbohrungen Heidelberg UniNord I und II. LGRB-Informationen, 26, 25-86. [3] KIRSCHVINK, J. L. 1980. The least-squares line and plane and the analysis of palaeomagnetic data. Geophysical Journal, Royal Astronomical Society, 62, 699-718. [4] ROLF, C., HAMBACH, U. & WEIDENFELLER, M. 2008. Rock and palaeomagnetic evidence for the Plio-/Pleistocene palaeoclimatic change recorded in Upper Rhine Graben sediments (Core Ludwigshafen-Parkinsel), Neth. J. Geosci., 87 (1), 41-50. [5] KNIPPING, M. 2008. Early and Middle Pleistocene pollen assemblages of deep core drillings in the northern Upper Rhine Graben, Germany, Neth. J. Geosci., 87(1), 51-65. [6] HEUMANN, G., pers. Comm. [7] HAHNE, J., pers. Comm.

Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

2014-05-01

227

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

228

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

229

Sedimentological and Geostatistical Characterization of the Paleozoic Wajid Sandstone Aquifer, Saudi Arabia  

NASA Astrophysics Data System (ADS)

Paleozoic siliciclastic successions form important primary groundwater aquifers in different parts of Saudi Arabia. Determination of aquifer sedimentological heterogeneity is important for realistic aquifer evaluation, development and management. This study aims to establish, from outcrop aquifer analog description, a geological and petrophysical model for the Paleozoic Wajid Sandstone aquifer in southwest Saudi Arabia. This study examined and studied several outcrop analogs for Wajid Sandstone. The methods of study included field and laboratory sedimentological investigations including facies, petrographic, porosity, permeability and statistical and geostatistical analysis techniques. The sedimentological field study revealed that the Wajid Sandstone vary facies, grain size, texture, composition and deposition environments. All these aspects appear to have impacted the porosity and permeability patterns at outcrop scale. The sedimentary facies vary in type, abundances and their vertical and lateral stacking patterns. Depositional environments also vary from fluvial braided stream to shallow marine environments. Grain size of sandstone varies from very fine to very coarse and from moderately sorted to well sorted. Sandstone composition varies from quartz arenite to subarkose. Both depositional and post depositional controls appear to have affected aquifer heterogeneity and porosity and permeability distribution. In general 2D geostatistical porosity and permeability models show agreement at outcrop scale, especially at high values; however, some variability is encountered among Wajid members. The 2D permeability models also reflect depositional factors including depositional environment and sub environment change layering, stratigraphic hierarchy, vertical and lateral facies changes and the superimposition of post depositional changes expresses in matrix and cement content, and cement type and styles.

Abdullatif, Osman; Makkawi, Mohamed

2010-05-01

230

The Georgia Embayment continental shelf: stratigraphy of a submergence.  

USGS Publications Warehouse

The Holocene-Pleistocene sediment veneer is thin, generally less than 4m thick. Lagoon sediments deposited during the last regression or the Holocene transgression occur in patches on the inner and central shelf. During each transgression or submergence, the surficial sand sheet is recharged with a new biogenic carbonate fraction along with the addition of small amounts of clastic sediments derived from 'overrun' estuaries and erosion of underlying Tertiary sediments. The stratigraphy based on the vibracores supports the concept of cross-shelf migration of the shore face-barrier island systems in response to rising sea level. -from Authors

Pilkey, O. H.; Blackwelder, B. W.; Knebel, H. J.; Ayers, M. W.

1981-01-01

231

Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology  

SciTech Connect

We have developed a numerical technique that will adjust 3-D S-wave seismic images so that they are depth equivalent to 3-D P-wave seismic images. The ability to make this type of P-SV to P-P depth registration is critical to our elastic wavefield seismic stratigraphy research because we now have higher confidence that depth-equivalent data windows are being used in the P-SV to P-P comparisons that we are making.

Bob A. Hardage

2005-07-31

232

Contributions to the stratigraphy of southwestern Colorado  

USGS Publications Warehouse

In the course of field work of the United States Geological Survey in the San Juan region of Colorado observations have been made in the last three seasons that considerably extend our knowledge of the great stratigraphic break below the La Plata sandstone, which is currently assumed to be of Jurassic age. The new data pertain partly to the relations existing in the Gunnison Valley, north of the San Juan Mountains, where the unconformity marking this break was already known at certain places, and partly to the conditions in the Piedra Valley, on the south side of the mountains, where the unconformity had not before been noted. The Piedra Valley is of special interest, and it seems well to call attention to the relations observed even though they were examined only in a reconnaissance. The first part of this paper is devoted to the evidence of the overlap of the La Plata sandstone; the second to the stratigraphic relations in the Piedra Valley. The section of sedimentary formations in Piedra Canyon is of much interest because none of the pre-La Plata formations are known east of this locality on the south side of the San Juan Mountains. Most of these formations exhibit a notably different facies where they reappear from beneath the overlying beds at their nearest exposures in New Mexico, southeast of the Piedra Valley. It is believed that the character of the formations in the Piedra section should be recorded for the benefit of geologists who may be studying the Paleozoic and Mesozoic rocks of New Mexico, and accordingly the second part of the paper presents details of the structure and the stratigraphic section of Piedra Valley.

Cross, Whitman; Larsen, E. S., Jr.

1915-01-01

233

Cenozoic stratigraphy of the Sahara, Northern Africa  

USGS Publications Warehouse

This paper presents an overview of the Cenozoic stratigraphic record in the Sahara, and shows that the strata display some remarkably similar characteristics across much of the region. In fact, some lithologies of certain ages are exceptionally widespread and persistent, and many of the changes from one lithology to another appear to have been relatively synchronous across the Sahara. The general stratigraphic succession is that of a transition from early Cenozoic carbonate strata to late Cenozoic siliciclastic strata. This transition in lithology coincides with a long-term eustatic fall in sea level since the middle Cretaceous and with a global climate transition from a Late Cretaceous–Early Eocene “warm mode” to a Late Eocene–Quaternary “cool mode”. Much of the shorter-term stratigraphic variability in the Sahara (and even the regional unconformities) also can be correlated with specific changes in sea level, climate, and tectonic activity during the Cenozoic. Specifically, Paleocene and Eocene carbonate strata and phosphate are suggestive of a warm and humid climate, whereas latest Eocene evaporitic strata (and an end-Eocene regional unconformity) are correlated with a eustatic fall in sea level, the build-up of ice in Antarctica, and the appearance of relatively arid climates in the Sahara. The absence of Oligocene strata throughout much of the Sahara is attributed to the effects of generally low eustatic sea level during the Oligocene and tectonic uplift in certain areas during the Late Eocene and Oligocene. Miocene sandstone and conglomerate are attributed to the effects of continued tectonic uplift around the Sahara, generally low eustatic sea level, and enough rainfall to support the development of extensive fluvial systems. Middle–Upper Miocene carbonate strata accumulated in northern Libya in response to a eustatic rise in sea level, whereas Upper Miocene mudstone accumulated along the south side of the Atlas Mountains because uplift of the mountains blocked fluvial access to the Mediterranean Sea. Uppermost Miocene evaporites (and an end-Miocene regional unconformity) in the northern Sahara are correlated with the Messinian desiccation of the Mediterranean Sea. Abundant and widespread Pliocene paleosols are attributed to the onset of relatively arid climate conditions and (or) greater variability of climate conditions, and the appearance of persistent and widespread eolian sediments in the Sahara is coincident with the major glaciation in the northern hemisphere during the Pliocene.

Swezey, Christopher S.

2009-01-01

234

Plio-Pleistocene cliff-bound, wedge-shaped, warm-temperate carbonate deposits from Rhodes (Greece): Sedimentology and facies  

NASA Astrophysics Data System (ADS)

The Pliocene to Pleistocene temperate carbonates of Rhodes were deposited in a tectonically active region, strongly influenced by a complicated and rapidly changing topography, provided by the highly tectonised late Cretaceous Lindos Limestone as basement rock. Deposition on this basement took place in accommodation loci restricted to micrograbens and their downslope extension, to the foot of steep submarine cliffs, to basement neptunian dykes and depressions in the basement rock. Consequently the sediments comprise a high degree of facies variability, and are typically thin and laterally discontinuous. The integration of several outcrops is necessary for the reconstruction of the stratigraphy and the relative sea-level changes. The sediments were deposited during a large-scale, tectonically driven transgressive-regressive cycle in water depths changing from zero to several hundreds of metres. At the studied Lindos-Pefkos Road cutting the Kolymbia Limestone, bound to the foot of Lindos Limestone cliffs, marks the onset of the marine deposition in the late Pliocene. Its fabric is a rudstone consisting of unsorted angular Lindos Limestone clasts (up to boulder-size) with a matrix dominated by molluscs and coralline algae. The overlying Plio-Pleistocene St. Paul's Bay Limestone consists of deep-water float- and rudstones containing the 'white coral community' dominated by the coral Lophelia pertusa. Its matrix shows a complex fabric of up to five sediment zones separated by differing states of lithification. In this maximum flooding phase, mineralised hardgrounds indicate depositional hiati. The subsequent shallowing phase is represented by the Cape Arkhangelos Calcarenite, a series of distinctive facies of very patchy distribution. They are characterised by the Bryozoan-Brachiopod Facies, overlain by a facies heavily dominated by the bivalve Mytilaster sp. ( Mytilaster Facies). Conspicuous for the Mytilaster Facies is the inverse, concave-up, stacking pattern of shelly material. This facies is followed by a serpulid framestone and associated serpulid rudstone. Neptunian dykes cut through the first two facies and are filled with an intraformational breccia grading into a breccia with abundant Mytilaster Facies clasts (Neptunian Dyke Facies). The sedimentology and interpretation of each facies include a description of the ichnology, in particular the bioerosion peculiar to each facies. The separation of different gravity transport processes in steep submarine environments is rarely described and most of the literature concentrates on siliciclastic-dominated coarse-grained, sandy or gravely sand delta environments. For a classification of the transport processes of the examined deposits, the following criteria were evaluated: sediment body symmetry, inclination of the palaeorelief, sediment constituents, fabric complexity, sedimentary structures and availability of fine matrix. Sedimentary structures and grading can be camouflaged in carbonates due to density differences of bioclasts; however bioclast-orientations such as bivalve stacking patterns can give information about the sedimentary process. We suggest the inverse, concave-up, stacking pattern of bivalve shells to be a texture potentially indicative for debris falls. Because of the above-mentioned criteria we classified the Kolymbia Limestone as rock-fall deposits and the St. Paul's Bay Limestone as well as the Mytilaster Facies of the Cape Arkhangelos Calcarenite as debris-fall deposits. The Bryozoan-Brachiopod Facies could not be classified with certainty because of the lack of sedimentary structures and bioclast-orientation. However, a grain-flow or most likely a debris-fall transport process seems probable.

Titschack, Jürgen; Bromley, Richard G.; Freiwald, André

2005-10-01

235

New perspectives on Beringian Quaternary paleogeography, stratigraphy, and glacial history  

NASA Astrophysics Data System (ADS)

Aspects of the paleogeography, stratigraphy, and glacial history of Beringia have been greatly revised over the past 15-20 yr. Access to North East Russia, in particular, has provided the opportunity to evaluate the Beringia landscape as a contiguous subcontinent during the Quaternary. For the first time, new research has made clearer the connection between tectonic forces and the submergence of the Bering Strait during the middle Pliocene. Revisions in the regional stratigraphy of glacial and interglacial deposits in northwest Alaska and northeast Russia provide a new foundation for assessing the causes for differences in glacial ice extent through time. The consensus of all field workers verifies that glacial ice throughout most of Beringia was of very limited extent during the last glacial maximum. The onset of regional glaciation during the waning stages of the last interglaciation is clearly out of phase with glaciation at lower latitudes. Despite the lack of much glacial activity during the early Holocene, Alaska contains a rich record of late Holocene glacial response to Neoglacial cooling. Changes in the Holocene environment of Beringia likely had a profound affect on early inhabitants. The curiosity-driven vision and spirit of both David Hopkins and the late Troy Pewe have had a profound influence on Arctic paleoenvironmental research.

Brigham-Grette, Julie

2001-01-01

236

Perspective on the sequence stratigraphy of continental strata  

SciTech Connect

This report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 NUNA conference in Banff, Canada. To data, sequence stratigraphic concepts have been applied mainly to the marine realm, but unconformity-bounded units have long been recognized in nonmarine strata. Successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply. As with shallow marine environments, relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings. Farther inland, stratigraphic base level, which determines accomodation space, is more complex and takes various forms, such as the graded profile for fluvial strata, groundwater tables for some eolian strata, and lake level for some intermontane sediments. Sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area. The influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments. Although in its infancy, sequence stratigraphy concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture. Future advances in this field promise tools for more precise correlation of nonmarine strata and better prediction of the location and geometry of facies from a limited knowledge of the stratigraphic relationships within a basin. This would be useful in the exploration for fluvial and eolian sandstone reservoirs and coalbeds. 135 refs., 13 figs.

Shanley, K.W. (Shell Development Company, Houston, TX (United States)); McCabe, P.J. (Geological Survey, Denver, CO (United States))

1994-04-01

237

Quantitative stratigraphy of snow resolved by high-resolution penetrometry  

NASA Astrophysics Data System (ADS)

Precise measurements of snow structural parameters are essential to understand and model snow physical processes. Snow metamorphism, mass and energy balance of snow, radiative properties or the snowpack stability with respect to avalanche formation, all these processes depend on the snow structural parameters and the stratigraphy of the snowpack. However, most snow measurements are limited in spatial and temporal resolution and by extensive measurement times. For this reason, we developed a statistical model to derive three major snow structural parameters, density, correlation length and specific surface area (SSA) solely from a portable, high-resolution penetrometer. We demonstrate the potential of the method by a transect through Alpine snow in the Wannengrat study site, Davos, Switzerland. The two-dimensional plot of the transect reveals the depositional and metamorphic events. The results for the density are compared to independent density measurements from snow profiles. Based on these data, we are able to give a more complete interpretation of the snow stratigraphy and the underlying physical processes.

Proksch, Martin; Reuter, Benjamin; Schneebeli, Martin; Löwe, Henning

2014-05-01

238

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

2014-04-01

239

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

240

Sequence stratigraphy, basin dynamics, and petroleum geology of the Miocene from eastern Tunisia  

SciTech Connect

On the eastern margin of Tunisia, Miocene limestones, marl, and siliciclastic deposits crop out poorly and are lacking in age-diagnostic faunal content. The biostratigraphic and lithostratigraphic subdivisions of these series are not clearly defined. A regional study of subsurface sequences of this margin (Cap Bon, Gulf of Hammamet, and Sahel) by means of sequence stratigraphy and subsurface structural analyses permits the identification of seven third-order sedimentary sequences of inferred Langhian to Messinian age, the boundaries of which are characterized by downlap and onlap/toplap relationships. These sequences include turbidites, sands, and sandstones deposited in connection with eustatic sea level changes and tectonic movements of east-west and south-north deep-seated faults due to the Alpine and Atlassic paroxysm. Stratal sequences are organized around Miocene syndepositional grabens, half-grabens, platforms, and folds occurring inside and outside of regional tectonic corridors. The geodynamic evolution of Miocene basins has led to the deposition of turbiditic black argillaceous source rocks, and sandstone and carbonate reservoirs that present new Miocene petroleum targets. The basin subsidence in response to the Alpine/Atlassic orogeny has permitted the maturation of Miocene source rocks, oil generation, and the formation of oil traps, stratigraphic pinch-outs, and structural enclosures on the flanks of folds and on the borders of grabens.

Bedir, M. [Campus Universitaire, Tunis (Tunisia)]|[Unite des Ressources Naturelles et Environnement, Hammam-Lif (Tunisia); Tlig, S. [Campus Universitaire, Tunis (Tunisia); Bobier, C. [Universite Bordeaux, Talence (France)] [and others

1996-01-01

241

Seismic stratigraphy and sedimentation history of the East Mariana Basin, western Pacific  

NASA Astrophysics Data System (ADS)

An interpretation of the seismic stratigraphy and sedimentation history of the East Mariana Basin has been made using recently collected seismic reflection and refraction data. This Mesozoic(?) age basin, between the Marshall Islands and the Mariana Trench, is subdivided into three regions. The central region with about 1000 m of sediment probably records Jurassic to Late Cretaceous sedimentation of a pelagic biogenic and clay-rich section overlain by a thick section of mainly Cenozoic carbonates shed from nearby volcanic platforms. A western region is characterized by a thinner sediment cover and a shallower acoustic basement with a similar sedimentation history except that the upper section is thinner as a consequence of fewer nearby volcanic highs. Extensive Late Cretaceous mid-plate volcanics apparently masks the lower section and forms acoustic basement. The shallower eastern region (east of 157.5°E) contains WNW-trending ridges which may be either fracture zones or high-amplitude abyssal hills. The sedimentation appears controlled by the same factors as in the other regions but the area was bypassed by most Cenozoic basin-filling turbidites because of its elevation. The isostatistically corrected basement depths between the three regions suggest that the crust in the east may be substantially younger than in the rest of the East Mariana Basin, perhaps Cretaceous in age. This requires the existence of a tectonic boundary within the basin.

Shipley, Thomas H.; Whitman, Jill M.; Duennebier, Frederick K.; Petersen, Lisa D.

1983-08-01

242

North polar region of Mars: Advances in stratigraphy, structure, and erosional modification  

NASA Astrophysics Data System (ADS)

We have remapped the geology of the north polar plateau on Mars, Planum Boreum, and the surrounding plains of Vastitas Borealis using altimetry and image data along with thematic maps resulting from observations made by the Mars Global Surveyor, Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter spacecraft. New and revised geographic and geologic terminologies assist with effectively discussing the various features of this region. We identify 7 geologic units making up Planum Boreum and at least 3 for the circumpolar plains, which collectively span the entire Amazonian Period. The Planum Boreum units resolve at least 6 distinct depositional and 5 erosional episodes. The first major stage of activity includes the Early Amazonian (˜3 to 1 Ga) deposition (and subsequent erosion) of the thick (locally exceeding 1000 m) and evenly-layered Rupes Tenuis unit (A Brt), which ultimately formed approximately half of the base of Planum Boreum. As previously suggested, this unit may be sourced by materials derived from the nearby Scandia region, and we interpret that it may correlate with the deposits that regionally underlie pedestal craters in the surrounding lowland plains. The second major episode of activity during the Middle to Late Amazonian ( ˜<1 Ga) began with a section of dark, sand-rich and light-toned ice-rich irregularly-bedded sequences (Planum Boreum cavi unit, A Bb c) along with deposition of evenly-bedded light-toned ice- and moderate-toned dust-rich layers (Planum Boreum 1 unit, A Bb 1). These units have transgressive and gradational stratigraphic relationships. Materials in Olympia Planum underlying the dunes of Olympia Undae are interpreted to consist mostly of the Planum Boreum cavi unit (A Bb c). Planum Boreum materials were then deeply eroded to form spiral troughs, Chasma Boreale, and marginal scarps that define the major aspects of the polar plateau's current regional topography. Locally- to regionally-extensive (though vertically minor) episodes of deposition of evenly-bedded, light- and dark-toned layered materials and subsequent erosion of these materials persisted throughout the Late Amazonian. Sand saltation, including dune migration, is likely to account for much of the erosion of Planum Boreum, particularly at its margin, alluding to the lengthy sedimentological history of the circum-polar dune fields. Such erosion has been controlled largely by topographic effects on wind patterns and the variable resistance to erosion of materials (fresh and altered) and physiographic features. Some present-day dune fields may be hundreds of kilometers removed from possible sources along the margins of Planum Boreum, and dark materials, comprised of sand sheets, extend even farther downwind. These deposits also attest to the lengthy period of erosion following emplacement of the Planum Boreum 1 unit. We find no evidence for extensive glacial flow, topographic relaxation, or basal melting of Planum Boreum materials. However, minor development of normal faults and wrinkle ridges may suggest differential compaction of materials across buried scarps. Timing relations are poorly-defined mostly because resurfacing and other uncertainties prohibit precise determinations of surface impact crater densities. The majority of the stratigraphic record may predate the recent (<20 Ma) part of the orbitally-driven climate record that can be reliably calculated. Given the strong stratigraphic but loose temporal constraints of the north polar geologic record, a comparison of north and south polar stratigraphy permits a speculative scenario in which major Amazonian depositional and erosional episodes driven by global climate activity is plausible.

Tanaka, Kenneth L.; Rodriguez, J. Alexis P.; Skinner, James A.; Bourke, Mary C.; Fortezzo, Corey M.; Herkenhoff, Kenneth E.; Kolb, Eric J.; Okubo, Chris H.

2008-08-01

243

Pleistocene calcretes from eastern Tunisia: The stratigraphy, the microstructure and the environmental significance  

NASA Astrophysics Data System (ADS)

This paper is meant to study the stratigraphy, the mineralogy, the microstructure and the geochemistry of Pleistocene calcretes from eastern Tunisia in order to infer the environmental factors intervening in their formation. Samples of eight profiles of Pleistocene calcretes from eastern Tunisia were examined on the basis of a variety of techniques including Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), chemical analysis and Atomic Absorption Spectrophotometer (AAS) techniques. Then, the obtained data underwent a statistical analysis on the basis of Factor Analysis (FA) and Principal Component Analysis (PCA). On the basis of field missions, five different horizons have been differentiated from bottom to top of all profiles: nodular, powdery, massive Brecciated and laminar horizon. The mineralogical study shows two minerals categories inversely proportional: calcite and (quartz and the clay). It shows also shows that Palygorskite is the dominant clay mineral. The escarpment edge is capped by a limestone containing fibrous palygorskite. Finally, superficial calcrete are described: a brecciated horizon which occurs in pockets on the plateau surface. This study about eastern Tunisia revealed the occurrence of successive cycles of calcretisation. Pedogenesis, water table oscillation, sedimentogenesis and stromatogenesis are the intervening factors in the calcretisation process. During the Pleistocene, they interfered with each other according to the climatic pulsations. From the studied case, it may be noticed that the formation of each calcrete horizon is the result of a dominating process that takes place during a distinguishable stage. In the first stage, the pedogenic process is developed by palygorskite formation including authigenic replacement or formation from a precursor mineral, neoformation from the breakdown products of such minerals or neoformation from suitable solutions. In the second stage, the powdery horizon is formed in the slope of the distal zone which presents a drained environment. In the third stage, several diagenetic processes (cementing, compaction, dissolution...) contribute to the formation of the laminar and massive horizon. Since it is exposed to dryness for a long period, the massive horizon is harder and more compact. In the fourth stage, the banding of light-dark in the laminar horizons reflects a dry-wet season alternation seasons. Dark beds are formed by the stromatolitic cover were developed during the wet season, whereas light beds were developed in an extremely arid climate argued by the presence of the detrital grains. In the fifth stage, the brecciated horizon, which occupies the channels, is formed by well rolled concretions, which present a dismantling material of Early and Middle Pleistocene calcretes after the Post-Villafranchian compressive phase. Thus, calcretisation seems to have been controlled by periods of uplift and stability of the slope, given that calcrete formation might be inhibited by the activation of the sedimentation of colluvial materials as a consequence of the tectonic activity. We also suggest that groundwater and biological activity may play a significant role in the development of pedogenic, sedimentological and polygenetic calcrete cycles within the same sedimentary basin. The alternation of dry and wet climatic periods may be responsible for the calcrete genesis.

Gallala, Wissem; Gaied, Mohamed Essghaïer; Essefi, Elhoucine; Montacer, Mabrouk

2010-10-01

244

Magnetic polarity stratigraphy of the Permian and Carboniferous: The extension of the magnetic reversal record into the Paleozoic  

SciTech Connect

Magnetic polarity stratigraphy has revolutionized stratigraphic studies in Jurassic to Pleistocene sediments. These studies have been greatly facilitated by the reversal record that is recorded in rocks of the ocean floor. For times prior to the Jurassic, the reversal history of the magnetic field must be determined and eventually related through the type section concept. The magnetic reversal history of the late Paleozoic is dominated by the Permo-Carboniferous reversed superchron (PCRS), which extends from the late Permian to the Carboniferous (Westphalian). Recent studies by the author and his students in Middle Carboniferous sediments of eastern Canada, Pennsylvania, Arizona, and Nevada reveal that the magnetic field has reversed frequently in late Mississippian and early Pennsylvanian times (Meramecian through late Morrowan). The polarity of the magnetic field over this interval is approximately 50% normal and 50% reversed. The frequency of reversal appears to be about one reversal per m.y. The possibility, therefore, exists that this pattern may be used for continental and intercontinental correlation. Attempts are currently underway to correlate this magnetic stratigraphy to fossiliferous marine sections. The base of the PCRS is probably of Atokan age.

Opdyke, N.D. (Univ. of Florida, Gainesville (United States))

1991-03-01

245

Integration of sedimentological, paleontological, petrophysical, paleomagnetic, and 3-D seismic data to construct a 3-D geological model of the C sands reservoir, Maui field, offshore New Zealand  

SciTech Connect

Integration of core descriptions with paleontological data and a core-derived paleomagnetic reversal stratigraphy has been used to interpret a conceptual depositional model for the Eocene C sands reservoir of the Maui gas-condensate field. The C1 sands were deposited as highstand, regressive shoreline sands that are partitioned by thin, tight transgressive deposits. Lowstand valleys were incised into these sediments in the eastern part of the field. On the basis of the paleomagnetic reversal stratigraphy, the fill of these valleys is demonstrably of a different age to laterally equivalent shoreline sediments. Dipmeter data indicate that the early fill of these valleys predominantly comprises flood-tidal sediments, deposited as relative sea level began to rise. This model has been extended from the cored wells by careful calibration and correlation of wireline logs from all wells. Both the landward and seaward pinch-out of the shoreline sands have been traced from amplitude displays of the three-dimensional (3-D) seismic data. The lateral extent of the lowstand valley fills is also defined by the 3-D seismic data. The well and seismic data have been combined within a sequence stratigraphic framework to construct 3-D geological models of the field that are consistent with the dynamic performance of the reservoir and will be used to construct a 3-D reservoir simulation model.

Bryant, I.D.; Voggenreiter, W.R.; Greenstreet, C.W. (Shell Todd Oil Services Limited, New Plymouth (New Zealand))

1993-09-01

246

Stratigraphy of the Odessa shelf, Ukrainian Black Sea: existing problems and their solution  

NASA Astrophysics Data System (ADS)

The stratification of sedimentary cover within the Odessa Shelf of the Black Sea is traditionally based on biostratigraphy. Data of microfauna began to collect 37 years ago since drilling first wells within the shelf. More than 80 wells have been drilled up to nowadays. The detailed stratigraphy with the determination of biozones developed for adjoining Crimea Peninsula that had been studied in well exposed outcrops was extrapolated on sedimentary sections penetrated by offshore wells. However, there are substantial errors, which are usually caused by limited core data describing only 4-5 percents of well depths and consequently by limited microfaunal variety in core samples. Moreover, the core distribution along boreholes is not regular, and core samples were not taken at all in upper parts of boreholes (< 500-700 m). More complete and continuous information on well sections is given by well-logging records. However, there is a wide well spacing only and thus, correlation of the records does not allow substantially improve a determination of even-aged sedimentary layers. Objective ambiguity of geological and geophysical data obtained from wells has resulted in multichoice stratification over the same subcrops. It has accordingly generated difficulties to interpret seismic data in a crosswell extent as well as it makes problems for oil and gas exploration. Integrated interpretation of a new dense set of regional seismic reflection profiles, microfauna data and well-logging records has allowed us to eliminate some existing uncertainties in stratigraphy of Odessa Shelf as well as to trace the main even-aged sedimentary units from the shelf to the deep water part of the Ukrainian Black Sea, where no well has been drilled up to nowadays. The main sedimentary units are determined through the tracking of regional lithological marker beds, angular unconformities, sedimentation gaps, changes of lithology. Our results demonstrate that the following stratigraphical units are fixed confidently: 1) Middle Miocene - Quaternary; 2) Lower Miocene - Oligocene; 3) Upper Eocene; 4) Middle Eocene; 5) Lower Eocene; 6) Paleocene; 7) Upper Cretaceous; 8) Cenomanian - Albian; 9) Lower Cretaceous; 10) pre-Cretaceous. The units are well distinguished by microfaunal data, well-logging records and seismic data. They serve as a reliable basis for reconstructions of tectonics and evolution of the Black Sea region.

Khriachtchevskaia, O.; Stovba, S.

2009-04-01

247

Sedimentologic and tectonic aspects of the Archean Limpopo belt  

SciTech Connect

There are marked lithic differences between the central Limpopo belt and other well-studied Archean high-grade and greenstone-granitoid terranes, in particular the presence, in thick sections of supracrustals including approx. 15% of each of 1) carbonate and calc-silicate rocks and 2) pure metaquartzite, often fuchsite-bearing, with the lithic character of quartz arenite, not metachert. Isotopic ages suggest these sediments are 3.3-3.5 Ga old. The sequence and distribution of lithic, plutonic, metamorphic, and structural events in the Limpopo belt resembles that in younger orogens where there has been rifting of continental lithosphere, deposition of sediments at an Atlantic-type margin, then convergence and collision with another continental block. The southern margin of the central Limpopo belt is a wide (20 km) zone of vertically-dipping, horizontally-lineated mylonites, clearly representing the deeper ductile levels of a major strike-slip fault. This fault resembles large strike-slip systems that allow tectonic escape during collision in young orogenic belts. The authors conclude that continental fragments large enough to provide a substrate for significant platform arenite and carbonate sedimentation existed by 3.3-3.5 Ga, and that Tibetan-Himalayan style collisional tectonics greater than or equal to 2.6 Ga ago accounts for the large-scale relationships between the Limpopo belt and the adjacent Archean greenstone-granitoid terrane cratons. By inference, other more fragmentary Archean gneissic terranes may have once been part of such collisional zones.

Erikkson, K.A.; Kidd, W.S.F.

1985-01-01

248

Compositional stratigraphy of crustal material from near-infrared spectra  

NASA Technical Reports Server (NTRS)

An Earth-based telescopic program to acquire near-infrared spectra of freshly exposed lunar material now contains data for 17 large impact craters with central peaks. Noritic, gabbroic, anorthositic and troctolitic rock types can be distinguished for areas within these large craters from characteristic absorptions in individual spectra of their walls and central peaks. Norites dominate the upper lunar crust while the deeper crustal zones also contain significant amounts of gabbros and anorthosites. Data for material associated with large craters indicate that not only is the lunar crust highly heterogeneous across the nearside, but that the compositional stratigraphy of the lunar crust is nonuniform. Crustal complexity should be expected for other planetary bodies, which should be studied using high spatial and spectral resolution data in and around large impact craters.

Pieters, Carle M.

1987-01-01

249

GPS Subsidence Rate of Tahiti: Comparison with Coral Reef Stratigraphy  

NASA Astrophysics Data System (ADS)

A decade of GPS observations from 20 IGS stations located in and around the Pacific Plate including two co-located IGS stations (thti, tah1) is analyzed at the Geodetic Observatory of Tahiti, using the precise point positioning mode of the GIPSY-OASIS II (GOA) software followed by Ambizap algorithm. The data processing was repeated using GAMIT and GLOBK (GG) package. GOA and GG velocity fields of thti and tah1 are consistent (see table 1) and yield an average subsidence rate of -0.37 mm/yr of Tahiti Island in good agreement with the lower range of coral reef stratigraphy rate (-0.25 mm/yr).Vertical velocity and one sigma error of the two co-located IGS stations thti and tah1 using GIPSY-OASIS and GAMIT-GLOBK

Fadil, A.; Barriot, J.; Sichoix, L.; Ortega, P.

2009-12-01

250

Regional stratigraphy and geologic history of Mare Crisium  

NASA Technical Reports Server (NTRS)

Remote sensing and Luna 24 sample data are used to develop a summary of the regional stratigraphy and geologic history of Mare Crisium. Laboratory spectra of Luna 24 samples, telescopic reflectance spectra in the 0.3 to 1.1 micron range and orbital X-ray data have identified three major basalt groups in the region. Group I soil is derived from iron- and magnesium-rich titaniferous basalts and was apparently emplaced over the majority of the basin, however is presently exposed as a shelf in the southwest part. Group II soils, derived from very low titanium ferrobasalts, were emplaced in two stages subsequent to Group I emplacement and now appear as part of the outer shelf and topographic annulus. Subsidence of the basin interior preceded and continued after the emplacement of the third basalt group, a soil derived from a low titanium ferrobasalt. The Luna 24 site is found to be within a patch of Group II material.

Head, J. W., III; Adams, J. B.; Mccord, T. B.; Pieters, C.; Zisk, S.

1978-01-01

251

Sedimentological Investigations of the Martian Surface using the Mars 2001 Robotic Arm Camera and MECA Optical Microscope  

NASA Technical Reports Server (NTRS)

The first microscopic sedimentological studies of the Martian surface will commence with the landing of the Mars Polar Lander (MPL) December 3, 1999. The Robotic Arm Camera (RAC) has a resolution of 25 um/p which will permit detailed micromorphological analysis of surface and subsurface materials. The Robotic Ann will be able to dig up to 50 cm below the surface. The walls of the trench will also be inspected by RAC to look for evidence of stratigraphic and / or sedimentological relationships. The 2001 Mars Lander will build upon and expand the sedimentological research begun by the RAC on MPL. This will be accomplished by: (1) Macroscopic (dm to cm): Descent Imager, Pancam, RAC; (2) Microscopic (mm to um RAC, MECA Optical Microscope (Figure 2), AFM This paper will focus on investigations that can be conducted by the RAC and MECA Optical Microscope.

Rice, J. W., Jr.; Smith, P. H.; Marshall, J. R.

1999-01-01

252

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

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

Process-response modelling of fluvio-deltaic stratigraphy  

NASA Astrophysics Data System (ADS)

Numerical modelling is a tool to investigate the controls on the formation of the stratigraphic record on geological timescales. The model presented in this paper (DELTASIM) uses a process-response approach that simulates the stratigraphy of fluvial-dominated deltaic systems in two dimensions, based on simplified diffusion rules of cross-shore sedimentation. Net sedimentation is calculated for individual grain-size classes as the sum of independent erosion and deposition functions, enabling simulations of fluvio-deltaic stratigraphy besides clinoform evolution. Critical sediment transport parameters are validated using synthetic data from a process-based morphodynamic model, DELFT3D. Generic experiments show the effect of changes in sea level, sediment supply, offshore gradient and sediment size distribution. These experiments show that the model is fully capable of reproducing classic concepts of delta development on geological timescale. Such experiments allow students a possibility to evaluate the controls on the formation of the stratigraphic record. DELTASIM has been successfully applied to improve the understanding of the sedimentary evolution of a real-world fluvial-dominated delta in the Caspian Sea. Additional functionality encompasses a stochastic discharge model that can be used as input to simulate series of scenarios of delta development using the model's rapid run time to our advantage. This functionality enables us to present probabilistic output of longitudinal stratigraphic sections as an alternative to the deterministic predictions often made by stratigraphic models. The characteristics of the model; simplicity, speed and compatibility of the output to conceptual sequence stratigraphic models make DELTASIM suitable as a teaching tool.

Hoogendoorn, Robert M.; Overeem, Irina; Storms, Joep E. A.

2008-10-01

255

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

256

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

257

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

258

Stratigraphy and environmental reconstruction at the middle Wisconsinan Gilman Canyon formation type locality, Buzzard's Roost, southwestern Nebraska, USA  

NASA Astrophysics Data System (ADS)

The middle Wisconsinan Gilman Canyon Formation at the Buzzard's Roost type locality in southwestern Nebraska was investigated to document the stratigraphy and to reconstruct the environmental and climate record. The Gilman Canyon Formation was subdivided into three loess units and three soils, with radiocarbon ages constraining it between about 40 ka and 25 ka. Stable carbon isotope ratios, magnetic susceptibility, and carbon content were used to define and characterize soils within both the Gilman Canyon Formation and underlying Illinoian Loveland Loess. At the height of soil development within the Gilman Canyon Formation, climate was supporting C 4-dominated grassland, with July temperatures equal to or exceeding those of today. Soil-forming intervals within the Loveland Loess, including the Sangamon Soil, also exhibited relative increases in C 4 biomass. Climate, as recorded in the Gilman Canyon Formation, is corroborated by regional proxy data. The formation accumulated during MIS 3, and concurrent soil formation coincided with a summer insolation maximum.

Johnson, William C.; Willey, Karen L.; Mason, Joseph A.; May, David W.

2007-05-01

259

Sedimentology of resedimented carbonates: Facies and geometrical characterisation of an upper Cretaceous calciturbidite system in Albania  

NASA Astrophysics Data System (ADS)

Carbonate turbidite systems are not as well studied as their siliciclastic counterparts, resulting in a lack of knowledge on their vertical and lateral organisation. Thus, a preliminary detailed sedimentological study was undertaken in the upper Cretaceous limestones of Albania, which have been described as brecciated limestones and, more recently, as calciturbidites. The sedimentological study of three outcrops (Piluri, Vanister and Muzina) allows the definition of different lithologies grading from fine- to coarse-grained sequences representing the calciturbidites, intercalated with debris flow deposits and thick slumped levels. The thin-section examination of several facies defined in the field shows a dominance of mud-rich microfacies with variable granulometry, texture (mainly wackestone to packstone and floatstone), and the mixing of bioclastic and lithoclastic grains from both shallow-water (intertidal/infratidal) and deep-water settings (slope/basin). The microfacies description and fauna determination support the gravity origin of these calciclastic limestones. According to previous studies of the Ionian Basin and the surrounding platforms, the upper Cretaceous calciturbidite system could be reasonably linked to regional tectonic instabilities in relation to the beginning of the convergence between the Africa and Eurasian plates. The lateral and vertical organisation of these carbonate gravity deposits favours a depositional model over the apron model and that these deposits were fed by material derived from either the Apulian or the Kruja platform, through faulted shelf breaks.

Rubert, Yolaine; Jati, Mohamed; Loisy, Corinne; Cerepi, Adrian; Foto, Gjergji; Muska, Kristaq

2012-06-01

260

The Paleogene pre-rift to syn-rift succession in the Dhofar margin (northeastern Gulf of Aden): Stratigraphy and depositional environments  

NASA Astrophysics Data System (ADS)

The Paleogene deposits on the northern passive margin of the Gulf of Aden record the transition from the pre-rift to the syn-rift stages of the southern Arabian plate margin. In southern Oman (Dhofar Region), the relative continuity of the sedimentary record offers the possibility to investigate the early deformation phases of the Aden rift system. A new detailed sedimentological and biostratigraphic analysis of the Cuisian to Rupelian deposits of the Dhofar region allows to define a second-order transgressive-regressive cycle, that can be further subdivided into four third-order sequences between the Late Cuisian and the Early Rupelian time. The sequence stratigraphy established in this study has major implications for the understanding of the time equivalent deposits described in the eastern Arabian plate and illustrates the polyphased history of the initiation of the Aden Gulf rift system. The first two depositional sequences are controlled by a phase of deformation that only affects the eastern Oman margin, in relation with the tectonic activity at the Arabian-Indian plate boundary, during the Late Cuisian-Middle Lutetian. The last two depositional sequences record a westward migration of the deformation within the eastern realm of the proto-Gulf of Aden from the Bartonian. Priabonian uplift resulted in the basinward shift of the depositional system followed by a phase of tectonic subsidence that is recorded by the aggradation of lacustrine deposits in localized fault bounded basins. A subsequent major regional relative sea level fall related to domal uplift is recorded by terrigenous deposits (lower part of the Ashawq Formation) prior to the main phase of syn-rift tectonic subsidence (upper part of the Ashawq and Mughsayl formations) in Rupelian-Chattian times.

Robinet, J.; Razin, P.; Serra-Kiel, J.; Gallardo-Garcia, A.; Leroy, S.; Roger, J.; Grelaud, C.

2013-11-01

261

Sequence stratigraphy of the Maturin sub-basin (Eastern Venezuela)  

SciTech Connect

The prolific Eastern Venezuela Basin has an area of about 160,000 km{sup 2} and is bounded by the Pilar Fault to the North, the Guayana Shield to the South, the Baul Arch to the West and beyond the Orinoco Delta to the East. Sequence analysis of three N-S and one W-E regional transects covered by over one thousand km of seismic lines and sedimentological, biostratigraphic and electrofacies studies of 80 wells allowed the definition of the sequence stratigraphic column of the basin. Seven major unconformity bounded depositional sequences were defined from Barremian to Recent, three in the Cretaceous and four in the Tertiary. Twenty-one third-order cycles were recognized in the Tejas B supercycle (Upper Oligocene-Recent). This cycle correlates very well with the Gulf of Mexico and Global chronostratigraphic charts. In the proximal, southern area, each sequence shows transgressive sandstones in its lower section and regressive ones in the upper part, separated by claystones that include a maximum flooding surface. In the distal area, fine marine sediments predominate with local turbidities. Some electrical markers and planktonic fossils are traceable over long distances. Regional transacts show two distinct structural zones: tensional to the South and compressional to the North. The best petroleum reservoirs occur in Tertiary and to a lesser extent in Cretaceous sequences. In this basin occurs the largest oil accumulation of the world (Orinoco), as well as several giant oil fields.

Gonzales, G.; Mata, S.; Santiago, N. [Departamento de Geologia, Lagoven, S.A., Caracas (Venezuela)

1996-08-01

262

The origin of 17O-depleted barite in Neoproterozoic cap carbonates in South China: A sedimentological perspective  

NASA Astrophysics Data System (ADS)

Barite deposits are known from the Marinoan cap carbonate sequence in NW Africa, NW Canada, and many other localities worldwide, including South China, where the barite has been found to have distinct, non-mass-dependent depletion in 17O. It has been proposed that the negative anomalies most likely reflect an extremely high pCO2 atmosphere at the initiation of a global glacial meltdown. While widespread in occurrence and distinct in isotopic composition, the barite’s origin remains elusive. Field observation shows that the 17O-anomalous barite occurs only at one specific horizon/surface of the cap dolostone. A satisfying formation model based on geochemical data for the barite must corroborate evidence from geological, tectonic, sedimentological, and petrographic contexts. The Nantuo glacial deposit (Marinoan in age) and its cap carbonate occur widely on the Yangtze Block of South China. The thickness of the Nantuo tillites increases evidently from the shallow platform to basinal settings. The overlying cap carbonates, consisting mainly of dolostone, however, are generally around 3~4 meters thick and remain relatively stable on the Yangtze Block. There is a widespread occurrence of voids and cavities in the lower part of cap dolostones, in both shallow platform facies and transitional zones of the Yangtze Block. Barite deposits occur as fans or coatings on pre-existing surfaces or on walls of voids and fractures, probably marking a synchronous event affecting the entire Yangtze Block. Void and cavity fills generally start with aragonite crystal fans and barite fans, followed by opal (silica) or quartz, or calcite. The remaining space was finally filled with large blocky calcite crystals in shallower settings or pyrite crystals in deeper settings. We propose that the voids and cavities are the result of carbonate dissolution after the initial deposition of cap dolostones. The dissolution may imply a regional or even a global sedimentation hiatus during the deposition of Marinoan cap carbonates. One possibility is that the initially deposited cap carbonate may have been uplifted into a zone influenced by meteoric water due to glacioeustasy and lithospheric rebound as a result of a quick unloading of a massive continental ice cap on the Yangtze Block. Karstic dissolution has also been recognized in cap dolostones in NW Africa and NW Canada. While the voids and cavities in South China may be of a similar karst origin as those in NM Africa, sedimentological evidence, together with multiple sulfur and oxygen isotope data, suggests that the precipitation of the barite in South China may be related to an episode of free Ba2+ supply from deep, anoxic water, in association with a transgression (instead of an sea-level fall) after a karst dissolution. Thus, we suggest that SO42- was present in seawater prior to the beginning of Marinoan meltdown. It was the Ba2+ supply that limited the occurrence of barite to specific stratigraphic horizons in the cap carbonates. If the above inference is true, the 17O-depleted barite has recorded an atmospheric/hydrological condition well after the initial meltdown of the Marinoan "snowball" Earth.

Zhou, C.; Bao, H.; Yuan, X.

2009-12-01

263

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

264

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

265

From Grains to Basin: An Example of a Project-Based Sedimentology Exercise  

NSDL National Science Digital Library

To prepare for this project, students have gained familiarity with thin-section preparation and the use of analytical equipment such as the XRD. The students have also learnt how to measure and interpret paleocurrent data. They have read background articles on the basin of study. In the field, students learn how to measure a stratigraphic section and the application of Walther's Law. The goal is to combine the skills acquired earlier in the class to interpret the stratigraphy, facies, depositional history and paleogeography of an outcrop in the field. This exercise also links sedimentation and tectonics.

Harmsen, Frederika

266

Ostracods and fore?reef sedimentology of the Frasnian-Famennian boundary beds in Kielce (Holy Cross Mountains, Poland)  

Microsoft Academic Search

Four major microfacies have been recognized in the Psie Górki section and the bioclastic content indicates an open ma? rine environment in the photic zone close to an algal shole. Sedimentological studies point to a regressive episode starting close to the Frasnian-Famennian boundary. The regressive microfacies pattern is revealed by the presence of semi? restricted algal microbreccias that compose all

GEORGES CASIER; XAVIER DEVLEESCHOUWER; FRANCIS LETHIERS; GRZEGORZ RACKI

267

Improved reservoir description of the Heidrun Field, Norway, using a combination of sedimentological, geochemical and pressure data  

Microsoft Academic Search

The Tilje Fm. on the Heidrun Field was deposited in a shallow marine to parallic setting dominated by tidal processes. The resulting, often heterolithic, sedimentary sequences can potentially act as barriers to fluid flow due to lack of lateral continuity of sand bodies, and restricted vertical permeability due to clay drapes and tentacular bedding. Based on the sedimentological model and

G. W. Van Graas; W. Odden; E. Svela

1996-01-01

268

CORE-BASED INTEGRATED SEDIMENTOLOGIC, STRATIGRAPHIC, AND GEOCHEMICAL ANALYSIS OF THE OIL SHALE BEARING GREEN RIVER FORMATION, UINTA BASIN, UTAH  

Microsoft Academic Search

An integrated detailed sedimentologic, stratigraphic, and geochemical study of Utah's Green River Formation has found that Lake Uinta evolved in three phases (1) a freshwater rising lake phase below the Mahogany zone, (2) an anoxic deep lake phase above the base of the Mahogany zone and (3) a hypersaline lake phase within the middle and upper R-8. This long term

Lauren P. Birgenheier; Michael D. Vanden Berg

2011-01-01

269

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

270

Geostatistical modeling of sedimentological parameters using multi-scale terrain variables: application along the Belgian Part of the North Sea  

Microsoft Academic Search

In the nowadays highly pressurized marine environment, a science?based approach to management becomes increasingly important. In many cases, the sediment nature and processes are the key to the understanding of the marine ecosystem, and can explain particularly the presence of soft?substrata habitats. For predictions of the occurrence of species and habitats, detailed sedimentological information is required. This paper presents a

E. Verfaillie; I. Du Four; M. Van Meirvenne; V. Van Lancker

2009-01-01

271

Carbonate fracture stratigraphy: An integrated outcrop and 2D discrete element modelling study  

NASA Astrophysics Data System (ADS)

Constraining fracture stratigraphy is important as natural fractures control primary fluid flow in low matrix permeability naturally fractured carbonate hydrocarbon reservoirs. Away from the influence of folds and faults, stratigraphic controls are known to be the major control on fracture networks. The fracture stratigraphy of carbonate nodular-chert rhythmite successions are investigated using a Discrete Element Modelling (DEM) technique and validated against observations from outcrops. Comparisons are made to the naturally fractured carbonates of the Eocene Thebes Formation exposed in the west central Sinai of Egypt, which form reservoir rocks in the nearby East Ras Budran Field. DEM allows mechanical stratigraphy to be defined as the starting conditions from which forward numerical modelling can generate fracture stratigraphy. DEM can incorporate both stratigraphic and lateral heterogeneity, and enable mechanical and fracture stratigraphy to be characterised separately. Stratally bound stratified chert nodules below bedding surfaces generate closely spaced lateral heterogeneity in physical properties at stratigraphic mechanical interfaces. This generates extra complexity in natural fracture networks in addition to that caused by bed thickness and lithological physical properties. A series of representative geologically appropriate synthetic mechanical stratigraphic models were tested. Fracture networks generated in 15 DEM experiments designed to isolate and constrain the effects of nodular chert rhythmites on carbonate fracture stratigraphy are presented. The discrete element media used to model the elastic strengths of rocks contain 72,866 individual elements. Mechanical stratigraphies and the fracture networks generated are placed in a sequence stratigraphic framework. Nodular chert rhythmite successions are shown to be a distinct type of naturally fractured carbonate reservoir. Qualitative stratigraphic rules for predicting the distribution, lengths, spacing, tortuosity, apertures and quantitative fracture indices (P21, P22 and fractal dimension) of natural fractures in the subsurface are generated from DEM fracture networks. The results of this study have widespread significance for characterising naturally fractured carbonate nodular-chert rhythmite reservoirs.

Spence, Guy; Finch, Emma

2013-04-01

272

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

273

Preliminary Sequence stratigraphy framework of the SW part of the Actopan Platform, Lower Cretaceous, Hidalgo, Mexico  

NASA Astrophysics Data System (ADS)

The oldest sedimentary rocks in what is known as the Actopan Platform, in the State of Hidalgo, Mexico, are superbly exposed toward the southwestern part of such platform. A detailed stratigraphic/sedimentologic study was carried out to a 623 m-thick section; this study was focused to establish a sequence stratigraphic framework. The base of the section consists of a Lower Cretaceous 6223-m thick, mixed siliciclastic-carbonate sedimentary succession that has been named Santuario Formation. The terrigenous facies of this unit correspond to red beds that consist of shales, sandstones y few conglomerates deposited under continental conditions (fluvial). White and yellowish sandstones, possibly deposited by deltaic systems, occur in minor amounts. A tuff layer is found in its lower part. The carbonate facies of the Santuario Formation consist mainly of skeletal mudstones/wackestones de bioclastos-peloides and subordinate quantities of sandy dolostones, skeletal packstones/grainstones and rudist (requeniids) boundstones. The middle and upper parts of the studied stratigraphic section correspond to an essentially carbonate succession that in known as El Abra Formation. This unit is comprised of the following facies: skeletal mudstones/wackestones, skeletal packstones/grainstone, and minor rudist (requeniid and Chondrodonta) boundstones and cryptalgal laminites deposited in shallow subtidal lagoon to tidal flat conditions. At this location, a "Middle" Cretaceous age (Albian-Cenomanian) has been assigned to the El Abra Formation. However, the common presence of the benthic foraminifer Chofatella decipiens Schlumberger in these facies indicates that their age extends, at least, to the Lower Cretaceous (Barremian). This age was confirmed with the dating of zircons in tuff deposited in the base section. The carbonate facies of the Santuario Formation stack forming fifth-order subtidal cycles or parasequences. While the carbonate facies of the El Abra Formation also stack forming subtidal and peritidal cycles. In turn, the fifth order cycles also stack forming fourth-order high frequency sequences. These sequences in the Santuario Formation are distinguished by the presence in their bases of the red beds interpreted as their lowstand systems tracts.

Abascal, G.; Murillo-Muñeton, G.

2013-05-01

274

Modeling the stratigraphy and preservation potential of meandering stream deposits  

NASA Astrophysics Data System (ADS)

Both natural and human-induced modes of river and floodplain behavior have the potential to obscure, expose, or even destroy portions of the archaeological record. In valley systems with actively meandering channels much material can be lost to lateral bank erosion. Conversely, floodplain aggradation can bury and therefore obscure sites. In this study we aim to quantify the preservation potential of fluvial units containing archaeological sites as a function of the natural process of meandering, climate change and increased land-use during the Holocene. We used the CHILD simulation model of landscape evolution to explore alternative scenarios in which these three factors are both varied independently and combined. Boundary and initial conditions for the model scenarios are based on the Holocene evolution of the archaeologically-rich Upper Thames Valley, which is known to have witnessed variations in flood frequency, land-clearance, episodic alluviation and river entrenchment. The CHILD model is set up to combine four components that simulate the development of valley and floodplain system: hillslope and channel erosion, lateral stream meandering, overbank deposition, and the accumulation of a 3D stratigraphy. The landscape is represented by an adaptable triangular mesh of nodes, especially suited for simulating the gradual shifting of meander bends. The new stratigraphic layering routine recently added to the model in improves the resolution of the stratigraphic record accumulated by the model. Simulation results reveal systematic controls on preservation potential, and suggest potential sources of bias in the archaeological record.

Tucker, G. E.; Clevis, Q.; Lock, G.; Lancaster, S.; Desitter, A.

2003-12-01

275

The magnetic polarity stratigraphy of the Mauch Chunk Formation, Pennsylvania  

PubMed Central

Three sections of Chesterian Mauch Chunk Formation in Pennsylvania have been studied paleomagnetically to determine a Late Mississippian magnetic polarity stratigraphy. The upper section at Lavelle includes a conglomerate with abundant red siltstone rip-up clasts that yielded a positive conglomerate test. All samples were subjected to progressive thermal demagnetization to temperatures as high as 700°C. Two components of magnetization were isolated: a synfolding “B” component and the prefolding “C” component. The conglomerate test is positive, indicating that the C component was acquired very early in the history of the sediment. A coherent pattern of magnetic polarity reversals was identified. Five magnetozones were identified in the upper Lavelle section, which yields a pattern that is an excellent match with the pattern of reversals obtained from the upper Mauch Chunk at the original type section of the Mississippian/Pennsylvanian boundary at Pottsville, PA. The frequency of reversals in the upper Mississippian, as identified in the Mauch Chunk Formation, is approximately one to two per million years, which is an average for field reversal through time.

Opdyke, Neil D.; DiVenere, Victor J.

2004-01-01

276

Sediment mixing in the tropical Pacific and radiolarian stratigraphy  

NASA Astrophysics Data System (ADS)

The reworking of older radiolarian microfossils into near-surface sediments of the tropical Pacific has long been the source of confusion for the development of radiolarian stratigraphy and of puzzlement over the mechanism(s) that could effect such pervasive reworking. Widespread dissolution "pits" in the sediments of the tropical Pacific are believed to be associated with hydrothermal circulation cells in the older oceanic crust and are here linked to processes which expose older sections and inject older non-carbonate material into near-bottom waters. Discharging waters of these circulation cells tend to dissolve carbonate in near-surface sediments; thus, only the non-carbonate material (including radiolarians) is preserved and reworked into younger sediments. Results from the study of two sites in the tropical Pacific indicate that reworked older, stratigraphically important radiolarians are less than 2% of the total radiolarian assemblage. This constitutes a minimum estimate of the amount of reworked, non-carbonate material in the younger sediments. The oldest reworked radiolarians are no more than 10 m.y. younger than the underlying basement, and radiolarians from the entire older section above that level can be found in the reworked material. A time series of the flux of reworked material at one site is not constant but instead has varied by a factor of 3 to 4 over the past 2.5 m.y. During times when the flux of reworked material is particularly low, the proportion of older, more robust radiolarians is larger.

Moore, Ted C., Jr.; Mayer, Larry A.; Lyle, Mitchell

2012-08-01

277

Large-scale cement stratigraphy in cavern porosity, Mallorca, Spain  

SciTech Connect

Rapid precipitation of carbonate cements occurs at the air-water interface in the zone of mixed fresh and marine waters in karstic caverns near the coast of Mallorca, Spain,. These cements, which have been precipitating at least since the middle Pleistocene, occur as fibrous calcite, rhombic calcite, and fibrous aragonite, which have accumulated in superimposed bands reaching total thicknesses of a few centimeters to a few meters. Calcite overgrown on aragonite without evidence of aragonite dissolution is common, although in some places the calcite shows later dissolution. Recent fibrous calcite with rapid rates of growth is precipitated in the few-decimenters-thick zone of tidal fluctuation (atmospheric pressure tides). Carbon-14 dating of these cements gives growth rates of 72.5 mm/1000 years. Extensive coatings of these cements extend 55 m vertically, from 40 m above to 15 m below the water table. Uranium-thorium and SER dating of some of the coatings shows that the cycles of precipitation recorded in the cements over the least 700,000 years are on the order of 100,000 years (Milankovich cyclicity). Precipitation of these cements occurred in the upper phreatic zone, whose position was tied to sea level changes during the Pleistocene-Holocene. The stratigraphy of these cements therefore provides an excellent record of late Quaternary sea level history in the western Mediterranean.

Pomar, L.

1989-03-01

278

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

279

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

280

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

281

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

282

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

283

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

284

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

285

Late Pleistocene-Holocene Chemical Stratigraphy and Paleolimnology of the Rift Valley Lakes of Central Africa.  

National Technical Information Service (NTIS)

The interaction of climate and geology in Central Africa during Late Pleistocene and Holocene is examined. The study is based on sedimentological and limnological work on the main lakes of the Western Branch of the East African Rift Valley, particularly L...

R. E. Hecky E. T. Degens

1973-01-01

286

Carbonate platform evolution and conodont stratigraphy during the middle Silurian Mulde Event, Gotland, Sweden  

Microsoft Academic Search

E vidence from sedimentology and conodont biostratigraphy is used to reinterpret the mid-Homerian (Late Wenlock) succession on Gotland, Sweden. A new conodont zonation includes from below: the Ozarkodina bohemica longa Zone (including five subzones), the Kockelella ortus absidata Zone and the Ctenognathodus murchisoni Zone (two taxa are named, Ozarkodina bohemica longa and Pseudooneotodus linguicornis). These new zones are integrated with

MIKAEL C ALNER; L ENNART J EPPSSON

2003-01-01

287

Evidence for a dynamic 'Snowball Earth' in Neoproterozoic Svalbard through magnetic, structural and sedimentological analysis  

NASA Astrophysics Data System (ADS)

In recent years, our understanding of glacial sedimentation has improved through observations of current glacial environments,aided by the development of new techniques. Anisotropy of magnetic susceptibility (AMS) has been shown to provide insights into till formation and deformation. This technique, along with field, structural and sedimentological analysis has been applied to the Neoproterozoic Wilsonbreen Formation in Svalbard. Fabrics within sediments normally result from processes acting on the sediment either during or shortly after deposition. Fabrics can therefore be used to provide information on genetic environment, palaeo-ice flow directions in subglacially generated or deformed sediments and palaeo-slope in mass flow units. Primary fabrics (not subsequent tectonic fabrics) are confirmed through comparison of AMS with pebble. Both sets of data reveal almost identical fabric orientations suggesting that AMS does indeed record primary fabrics and that these fabrics indicate flow initially north-south but switching to northwest - southeast upwards in the succession. Through analysis of AMS, sedimentology and structures at both macro and microscopic scales, a range of glacial-depositional environments (subglacial, glaciomarine and proglacial) as well as non-glacial (terrestrial, lacustrine and fluvial) are recognised, which are highly variable both spatially and temporally. Glacial cycles are observed, some which appear analogous to processes occurring in modern glacial environments. The range of facies seen and the possible cyclicity in some of the deposition reveal that in contrast to a single advance meltback cycle, the Wilsonbreen is composed of a series of oscillations where glaciers advanced and retreated. This variability could possible provide challenges to the classic 'Snowball Earth' model.

Fleming, Edward; Benn, Doug; Hambrey, Mike; Stevenson, Carl; Petronis, Mike; Fairchild, Ian

2013-04-01

288

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

289

Tracing time in the ocean: a brief review of chronological constraints (60-8 kyr) on North Atlantic marine event-based stratigraphies  

NASA Astrophysics Data System (ADS)

Well-resolved event-based stratigraphies in marine sediments spanning a significant portion of the last glacial period (60-8 kyr) provide a unique opportunity for time-stratigraphic correlation in the North Atlantic region. Here, we review the current methods available to chronologically constrain these event-based stratigraphies, highlighting, in particular, the value of tephrochronology as an independent tool to validate correlations between records. While the INTIMATE protocols (Lowe et al., 2008; Blockley et al., 2011) are equally applicable to marine and terrestrial records, spatially and temporally variable marine radiocarbon reservoir age effects (MREs) provide a challenge to using marine radiocarbon in the former as an independent chronostratigraphic tool. Despite the inherent uncertainties associated with 'tuning', we conclude that the mid-points of the common abrupt warming transitions associated with the well-defined, millennial-scale climate oscillations (the Dansgaard-Oeschger (D/O) cycles) observed in the oxygen isotopes of the Greenland ice cores and North Atlantic sea surface temperature (SST) records currently provide the most robust correlation tie-points from which to derive age control. In this invited INTIMATE special issue article we propose a new protocol for establishing marine event-based chronostratigraphies in the North Atlantic region and focus on areas of chronological potential in palaeoceanographic research.

Austin, William E. N.; Hibbert, Fiona D.

2012-03-01

290

Carbonate sequence stratigraphy on the development geology scale: Outcrop and subsurface examples from the Permian Grayburg Formation, Permian basin  

Microsoft Academic Search

Grayburg outcrop studies in the Guadalupe Mountains, combined with subsurface reservoir studies in the Permian basin, have helped define updip, downdip, and strike-view variations in reservoir architecture in a carbonate ramp setting. The hierarchy of sequence stratigraphy was identified within the Grayburg sequence, identifying simple sequences, parasequence sets, parasequences, beds, and laminae. Sequence stratigraphy slices the reservoir horizontally, becoming more

1993-01-01

291

Predicting fracture localization in folded strata from mechanical stratigraphy and fold shape: Case study of east Kaibab Monocline, Utah  

Microsoft Academic Search

Joints within folds are often localized within zones. These joint clusters may influence the flow of fluids in the subsurface but are often undetectable on conventional seismic lines. Joints develop in folded strata in response to fold shape and mechanical stratigraphy. Mechanical stratigraphy describes the distribution of layers (layer thicknesses) and the nature of the layer contacts. Within folded strata,

M. L. Cooke

1997-01-01

292

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

293

Shallow sub-surface stratigraphy of interfluves inferred from vertical electric soundings in western Ganga plains, India  

Microsoft Academic Search

The application of geophysical surveys such as Vertical Electric Sounding (VES) for inferring shallow sub-surface stratigraphy in the vast alluvial tract of India has been under-utilized. This paper is aimed at demonstrating the potential of resistivity methods for mapping alluvial stratigraphy in parts of the Ganga plains where the availability of exposed sections is scarce and bore logs are very

G. S. Yadav; A. S. Dasgupta; R. Sinha; T. Lal; K. M. Srivastava; S. K. Singh

2010-01-01

294

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. ?? 2005 Elsevier B.V. All rights reserved.

Colman, S. M.

2006-01-01

295

Bathymetry and seismic stratigraphy in St. Jonsfjorden, Spitsbergen  

NASA Astrophysics Data System (ADS)

St. Jonsfjorden is an approx. 21 km long and maximum ~5 km wide fjord on west Spitsbergen where modern sediment supply is glacifluvial and from tidewater glaciers. Its large-scale bathymetry is characterised by shoals and ridges as shallow as <30 m, as well as an outer and inner basin with up to 160 and 110 m water depths, respectively. Several large N-S oriented 'steps' of up to 50 m and slopes exceeding 30 degrees are most probably related to vertical movements along tectonic lineaments within the West Spitsbergen Fold-and-Thrust Belt. More detailed bathymetry reveals fjord-parallel linear features, most probably drumlinoid landforms providing evidence of fast ice flow through the fjord during the last glacial. Transverse, discontinuous, sinuous ridges are interpreted to be moraines deposited during temporal halts and/or re-advances of the ice front during the last deglaciation. A landform assemblage typical for most inner fjords on Svalbard has formed close to the fjord head. This includes large transverse ridges (terminal moraines) that were most probably deposited during relatively recent advances of one or several tidewater glaciers at the fjord head. Multiple sediment lobes, the largest being more than 4.5 km long and up to >20 m thick, were deposited beyond the outermost terminal moraine. Fjord parallel linear features overlain by multiple small transverse ridges characterise the seafloor between the innermost terminal moraine and the present glacier fronts. Whereas the linear features are interpreted to be glacial lineations providing evidence of one or several relatively rapid glacier advances, the small ridges are suggested to be 'annual retreat moraines' that were formed during halts and/or small re-advances during the retreat of the ice front(s) after its/their maximum extent(s). The heights of these ridges exceed rarely 2 meters and the distances between their crests indicate that the annual retreat rate of the ice front(s) was mainly in the order of 30-40 m. Apart from local variations, the general seismo-stratigraphy of the sub-seafloor in St. Jonsfjorden is similar to stratigraphies observed in other Spitsbergen fjords. It includes 1) a lowermost acoustically transparent to semi-transparent unit of glacigenic landforms and deposits above bedrock/acoustic basement, 2) acoustically stratified deposits reflecting frequently changing physical conditions in a glacier-proximal glacimarine environment during the last deglaciation, 3) an acoustically more transparent sequence with rare and discontinuous reflections that was deposited in a glacimarine environment with more stable physical conditions due to reduced glacial activity, and 4) an uppermost interval with strong and continuous reflections deposited during a time of increased glacial activity during the late Holocene. Crater-like features (pockmarks) of maximum 5 m depth and 110 m diameter occur. Whereas these features are almost absent in the inner fjord, they are relatively abundant close to the fjord mouth. This may reflect localised fluid flow along tectonic lineaments as observed in other Spitsbergen fjords.

Forwick, Matthias; Sverre Laberg, Jan; Husum, Katrine

2014-05-01

296

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

297

Seismic stratigraphy and the Upper Minnelusa - a case study and related problems  

SciTech Connect

The Permian Upper Minnelusa member is a prolific oil producer in the northeastern Powder River basin, Wyoming. Most of the fields involve (1) unconformity traps, where porous sandstones are truncated updip by a shale-filled valley, and (2) facies traps, where porous sandstones grade updip into nonporous dolomites. Due to the acoustic properties of the sandstone, dolomite, and shale, seismic stratigraphy can be successfully used in exploring for buried topography and facies traps. Using case studies illustrates the interplay between changing geology and the limitations of seismic stratigraphy as an exploration tool. In particular, case studies can demonstrate (1) the error in confusing a tool's response with the geologic interpretation of the tool's response; (2) how completely the geologic parameters must be defined; and (3) the close union required between geologist and geophysicist to use seismic stratigraphy successfully.

Walker, V.A.; Gabay, S.H.

1986-08-01

298

Late Quaternary stratigraphy of the eastern Gulf of Maine  

SciTech Connect

Five distinct seismic facies describe the glacial, glacial-marine and postglacial sediments in the eastern Gulf of Maine. Regional cross-sections clearly document differences in the glacial-marine and postglacial stratigraphy between basins south of Truxton Swell, and Jordan basin to its north. Till occurs throughout the region as a thin veneer within basins, but thickens significantly over the ridges and swells separating basins. The ubiquitous presence of till suggests grounded ice occupied this area some time in the recent past. Ice-proximal glacial-marine (PGM) facies sediments of varying thickness mantle the entire area, occurring as a draped unit over pre-existing topography. Transitional glacial-marine (TGM) facies also occur as a draped unit, but they show onlap onto basin margins. Sediments of the TGM facies are restricted to areas south of Truxton Swell. Ice-distal glacial-marine (DGM) facies sediments also mantle the entire area, but they occur primarily as a ponded, infilling unit. The nature and distribution of these glacial-marine facies within the eastern Gulf of Maine documents changes in the environment of deposition during deglaciation. In the authors model PGM facies sediments are considered to represent settling through the water column of coarse material from the base of an ice shelf. TGM facies sediments indicate retreat of this ice margin coupled with calving of large icebergs with significant amounts of coarse debris, DGM facies sediments indicate further retreat of the ice margin and a lessening of the influence of icebergs. Stepwise ice-margin retreat from south to north through a series of grounding lines and associated pinning points is evident by these time transgressive sedimentary facies that can be correlated across the region.

Bacchus, T.S. (Univ. of Maine, Orono, ME (United States). Oceanography Dept.); Belknap, D.F. (Univ. of Maine, Orono, ME (United States). Geology Dept.)

1993-03-01

299

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

300

Bacterial community structure in aquifers corresponds to stratigraphy  

NASA Astrophysics Data System (ADS)

So far, groundwater microbiology with respect to different host rocks has not been well described in the literature. However, factors influencing the communities would be of interest to provide a tool for mapping groundwater paths. The Thuringian Basin (Germany) studied here, contains formations of the Permian (Zechstein) and also Triassic period of Buntsandstein, Muschelkalk and Keuper, all of which can be found to crop out at the surface in different regions. We analyzed the bacterial community of nine natural springs and sixteen groundwater wells of the respective rock formations as well as core material from the Zechstein salts. For that we sampled in a mine 3 differnet salt rock samples (carnallitite, halite and sylvinitite). To validate the different approaches, similar rock formations were compared and a consistent microbial community for Buntsandstein could be verified. Similary, for Zechstein, the presence of halophiles was seen with cultivation, isolation directly from the rock material and also in groundwater with DNA-dependent approaches. A higher overlap between sandstone- and limestone-derived communities was visible as if compared to the salt formations. Principal component analysis confirmed formation specific patterns for Muschelkalk, Buntsandstein and Zechstein for the bacterial taxa present, with some overlaps. Bacilli and Gammaproteobacteria were the major groups, with the genera Pseudomonas, Marinomonas, Bacillus, Marinobacter and Pseudoalteromonas representing the communities. The bacteria are well adapted to their respective environment with survival strategies including a wide range of salinity which makes them suitable as tracers for fluid movement below the ground. The results indicate the usefulness and robustness of the approach taken here to investigate aquifer community structures in dependence of the stratigraphy of the groundwater reservoir.

Beyer, Andrea; Möller, Silke; Neumann, Stefan; Burow, Katja; Gutmann, Falko; Lindner, Julia; Müsse, Steffen; Kothe, Erika; Büchel, Georg

2014-05-01

301

Stratigraphy and Facies of Cretaceous Schrader Bluff and Prince Creek Formations in Colville River Bluffs, North Slope, Alaska.  

National Technical Information Service (NTIS)

Stratigraphic and sedimentologic studies of facies of the Upper Cretaceous rocks along the Colville River Bluffs in the west-central North Slope of Alaska identified barrier shoreface deposits consisting of vertically stacked, coarsening-upward parasequen...

2007-01-01

302

Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean  

USGS Publications Warehouse

Sediment cores from the western Arctic Ocean obtained on the 2005 HOTRAX and some earlier expeditions have been analyzed to develop a stratigraphic correlation from the Alaskan Chukchi margin to the Northwind and Mendeleev-Alpha ridges. The correlation was primarily based on terrigenous sediment composition that is not affected by diagenetic processes as strongly as the biogenic component, and paleomagnetic inclination records. Chronostratigraphic control was provided by 14C dating and amino-acid racemization ages, as well as correlation to earlier established Arctic Ocean stratigraphies. Distribution of sedimentary units across the western Arctic indicates that sedimentation rates decrease from tens of centimeters per kyr on the Alaskan margin to a few centimeters on the southern ends of Northwind and Mendeleev ridges and just a few millimeters on the ridges in the interior of the Amerasia basin. This sedimentation pattern suggests that Late Quaternary sediment transport and deposition, except for turbidites at the basin bottom, were generally controlled by ice concentration (and thus melt-out rate) and transportation distance from sources, with local variances related to subsurface currents. In the long term, most sediment was probably delivered to the core sites by icebergs during glacial periods, with a significant contribution from sea ice. During glacial maxima very fine-grained sediment was deposited with sedimentation rates greatly reduced away from the margins to a hiatus of several kyr duration as shown for the Last Glacial Maximum. This sedimentary environment was possibly related to a very solid ice cover and reduced melt-out over a large part of the western Arctic Ocean.

Polyak, L.; Bischof, J.; Ortiz, J. D.; Darby, D. A.; Channell, J. E. T.; Xuan, C.; Kaufman, D. S.; Lovlie, R.; Schneider, D. A.; Eberl, D. D.; Adler, R. E.; Council, E. A.

2009-01-01

303

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

304

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

305

Stratigraphy and age of the Daohugou Bed in Ningcheng, Inner Mongolia  

Microsoft Academic Search

Recent fieldwork has extended the distribution of the Daohugou Bed deposits from the Daohugou Village to its several neighboring\\u000a areas. The fossil-bearing Daohugou deposits uncomformably overlie complex bedrocks, and comprise three major parts. The red\\u000a shales in the lower part were misidentified as belonging to the Tuchengzi Formation. Field excavation has indicated that the\\u000a shales of upper part of the

Xiaolin Wang; Zhonghe Zhou; Huaiyu He; Fan Jin; Yuanqing Wang; Jiangyong Zhang; Yuan Wang; Xing Xu; Fucheng Zhang

2005-01-01

306

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.

307

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

308

Sedimentology, Petrography and Microfacies of the Paleogene Carbonate Sequence - Yaxcopoil-1 Borehole (Chicxulub, Yucatan)  

NASA Astrophysics Data System (ADS)

Chicxulub crater is one the three largest known impact craters on Earth, formed 66 Ma-old, with multi-ring basin morphology. Crater is located in northwestern Yucatan, southern Gulf of Mexico, with rim diameter of 200 km and crater center at Chicxulub Perto in the coastline. It is buried beneath the carbonate and evaporitic Cenozoic sequence. Study of the structure requires geophysics and drilling, with several boreholes drilled in the peninsula. The Yaxcopoil-1 borehole was drilled south of Merida, about 62 km from center, as part of the Chicxulub Scientific Drilling Program. One of the main objectives was to determine the role of the Chicxulub impact event in the K/Pg mass extinction and boundary events. We present a sedimentological and petrological study of the carbonate sequence in the interval from 404 m to 792 m overlying the K/Pg boundary. The well reached a depth of 1510.6 m. In this interval, we identified twelve units marked by different lithological and sedimentological changes, and supplemented by thin section analysis. Facies are composed mainly of marls, argillaceous, limestones, dolomitized limestones, calcareous breccias and calcarenites with shales thin beds. From the microfacies study we observed several major changes in the microfacies. From bottom of the sequence several textural changes cyclic from mudstone to bioclastic planktic foraminiferal wackestone, bioclastic packstone and some bioclastic grainstone. Two textures dominated in the calcareous sequence: bioclastic wackestone and packstone microfacies. From the microfacies study, we derived inferences on stable environmental conditions. We observed benthic and planktic foraminiferal layers. The benthic foraminifera strongly depend on environmental parameters, such as nutrient supply or oxygenation of the sea bottom water in the Paleocene and Eocene. Changes suggest occurrence of a progradational event, with a relative increase in sea level very slowly, with the sediment enough to overcome the elevation. In the last meters of Unit 2 (778-772 m), a series of thin layers of marl and calcareous shale interbedded with wackestone are interpreted as a transgressive event. In the first few meters of Unit 3 provides greater energy currents causing variations in the grain size. Petrographic observations show that planktonic and benthic facies are arranged as intermittent flows in parts of the unit, which points to flow currents. Predominance of coarse-grained facies rich in carbonates possibly indicates a prograding event into deep areas. In the sequence several possible changes in sea level are recorded, especially from Unit 5 to 8 Unit, where a possible limit between the Paleocene and Eocene is located between Unit 6 and Unit 7, at about 660 m. Biostratigraphy was obtained by zones corresponding to P4 and P5. In Unit 8 contains the first record of turbidite or storm deposits outer shelf environments that could be related to platform progradation. The Paleocene-Eocene thermal maximum represents a period of global warming and sea level rise. The sedimentological and micropaleontological changes may be correlated with the faunal turnover in the Gulf of Mexico, providing a complementary tool for biostratigraphic inferences.

Escobar-Sanchez, E.; Fucugauchi, J. U.

2013-05-01

309

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

Microsoft Academic Search

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

J. D. Humphrey; T. N. Kimbell

1989-01-01

310

Petrology, diagnosis, and sedimentology of oil reservoirs in Upper Cretaceous Shannon Sandstone Beds, Powder River basin, Wyoming  

SciTech Connect

This paper reports on a study of the petrology of the Shannon Sandstone Member that indicates diagenetic alterations of outcrop and near-surface sandstones cannot be used to predict the diagenesis of deeply buried sandstones. Textural relations show that oil migrated to reservoirs late in the postdepositional history of the Shannon. Petrologic and sedimentologic data suggest that an alternative depositional model (for example, a nearshore rather than mid-shelf setting) should be considered for the Shannon.

Hansley, P.L.; Whitney, C.G.

1990-01-01

311

The neogene stratigraphy of the Central Florida Panhandle  

NASA Astrophysics Data System (ADS)

Two groups, 10 formations, and one member are recognized and described from the Neogene strata of the central Florida panhandle. The Alum Bluff Group is redefined on the basis of lithology. Portions of three structural features are present in the central Florida panhandle. At least seven periods of deposition and at least seven periods of nondeposition are recognized. The periods of deposition include the following biostratigraphically equivalent formations: (1) undifferentiated Chickaswahayan deposits - Suwannee limestone of late Oligoene, Chattian age; (2) Chipola Formation - equivalent limestone of early Miocene, Burdigalian age; (3) Bruce Creek Limestone - Langhian age; (4) Whites Creek Member - late Langhian and early Serravallian age; (5) middle and upper Shoal River Formation - Serravallian age; (6) Choctawhatchee Formation of late Miocene, Tortonian age; and (7) Intracoastal Limestone - phosphoritic sand unit of Pliocene, late Zanclian to Piacenzian age. There is evidence that an eighth, late Pleistocene period of deposition is present.

Huddlestun, P. F.

1984-06-01

312

A laminated carbonate record of mid-continental climate during the late Glacial and Holocene from Martin Lake, northeastern Indiana: Initial sedimentological and chronological results  

NASA Astrophysics Data System (ADS)

Paleoclimate records from the mid-continental United States that span the late Glacial and Holocene with sub-decadal resolution are rare. This is especially true for geochemical records that capture the isotopic composition of precipitation or local precipitation/evaporation balances. As a result, many questions remain about the hydrologic expression of abrupt climate events in this region that today is one of the largest agricultural centers in the world. Here, we present preliminary limnological, sedimentological and chronologic data from a set of new sediment cores from Martin Lake in northeastern Indiana. Today, this kettle lake is hydrologically open with persistent water column stratification and bottom water anoxia. Imaging of the ~8 m composite sediment archive shows that mm-scale couplets composed of alternating layers of organic matter and carbonate minerals are present throughout the core. Ongoing radiometric dating of the cores will be used to determine the depositional significance of the couplets and their potential for additional chronologic constraint. Initial basal age estimates, however, suggest that the composite record may extend back as far as 19,000 cal yr B.P. The Martin Lake record therefore holds great potential for providing a carbonate d18O record of late Glacial and Holocene climate events at sub-decadal resolution.

Stamps, L. G.; Bird, B. W.; Gilhooly, W.

2013-12-01

313

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

314

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

315

Sedimentological characteristics of the surficial deposits of the Jal Az-Zor area, Kuwait  

NASA Astrophysics Data System (ADS)

The purpose of this article is to discuss the nature and characteristics of the surface geology of the Jal Az-Zor escarpment and the adjacent area, to better understand the sedimentology of desert landforms, and the main factors controlling depositional and diagenetic processes active in this environment. The oldest outcrops along the face of the escarpment are the sand and sandstone sequences of the Mutla and Jal Az-Zor Formations of the Kuwait Group (Neogene). Gravelly deposits of the upper member of the Kuwait Group, Dibdibba Formation (Pleistocene) are restricted to a few hillocks and ridges in the summit area of the escarpment. The Neogene deposits in most of the study area are overlain by a veneer of unconsolidated Holocene sediments. These were classified, according to their morphological setting and field occurrence, into: coastal deposits (intertidal mud, sabkha deposits, and sand dunes) and inland deposits (sand drifts, slope deposits, wadi fills, residual deposits and playa deposits). Wind-born quartzitic sand is the most common Holocene sediment in the study area indicating the dominance of the aeolian processes. Gypsum and carbonate present as cementing materials or in the form of gypcrete and calcrete, respectively, are characteristic sedimentological features of the pre-Holocene deposits. Gypcrete and gypsum cement are abundant in the upper section of the escarpment and decreases downward, whereas the carbonate (calcrete) shows a reverse pattern, i.e., it becomes more dominant in the lower section of the escarpment. The source of sulphate ions in the groundwater that is responsible for the development of gypcrete is believed to be the evaporites in the lower section of the Neogene sequence. The source of ions for the formation of calcrete and calcite cement is less understood due to the lack of significant primary carbonates in the near-surface deposits. It is believed that the nature and distribution of the chemically precipitated material (gypsum and carbonates) are controlled by the chemistry and hydrodynamics of the groundwater which in turn are controlled mostly by the climatic conditions, during their development, and the lithology of the host sediments. Arid and semi-arid climatic and paleoclimatic conditions are considered the most critical factors affecting the depositional and diagenetic processes impacting surficial deposits of the Jal Az-Zor area.

Al-Bakri, D.; Kittaneh, W.; Shublaq, W.

1988-10-01

316

Sedimentology and Rock Magnetism of Bailey River Peat Cores, Sudbury Area: Preliminary Results  

NASA Astrophysics Data System (ADS)

Magnetic measurements on peat can reveal atmospheric anthropogenic contamination. Two cores were collected from a marsh surrounding the Bailey River, 10 km north of Sudbury, Ontario, using a Russian peat borer. The BR1 core (1.4 m) was collected right at the river's edge, whereas the BR2 core (2.5 m) was collected about 50 m away from the river's edge, close to the edge of the marsh and near the forest. Significant sedimentological variation between the two cores was observed: core BR1 had several centimeter to decimeter scale fine to coarse grey sand layers at 0.14 m, 0.46 m and 0.87 m between thicker organic-rich (peat) zones, whereas core BR2 had only one 5 cm sand-rich layer at 0.94 m within the organic-rich material. The cores were subsampled at 2.5 cm intervals for laboratory magnetic analysis. Volume susceptibility was measured using a Bartington MS2B meter, and mass-specific susceptibility was then calculated. In core BR1, the sand layers had relatively higher susceptibility (13 x 10-8 m3/kg) , while the organic rich layers had very low susceptibility (0 - 2 x 10-8 m3/kg). In core BR2, which had little sand, the susceptibility variation was dominated by higher values near-surface (10 x 10-8 m3/kg), and very low susceptibility (0.3 x 10-8 m3/kg) below 0.3 m depth. Since the lithology in this core did not vary substantially, susceptibility variations may be controlled by anthropogenic deposition in the near-surface during the peak mining and smelting decades. These preliminary results suggest that any anthropogenic signal in core BR1 appears to be masked by the sedimentological variation. On pilot results from eight samples in core BR1, saturation isothermal remanence acquisition showed 95% saturation by 200 mT, and the S-ratios (0.3T/0.9T) were above 0.93, suggesting that magnetite is the major magnetization carrier. In core BR2, six out of eight samples showed similar results; however, two samples had slightly more higher coercivity minerals (90% saturation by 200 mT, and S-ratios between 0.9 and 0.93). More detailed rock magnetic property measurements could reveal variations grain size and magnetic mineralogy that could reflect climatic or watershed changes.

Yurtseven, A.; Cioppa, M. T.; Dean, K.

2009-05-01

317

Stratigraphic/sedimentological analysis of a Lower Cretaceous carbonate succession in the Actopan Platform, Hidalgo State, Mexico: documentation on an Early Albian deepening event  

NASA Astrophysics Data System (ADS)

The Actopan Platform, exposed near the town of Actopan, in the State of Hidalgo, is part of the system of carbonate platforms developed extensively in Mexico during the Early Cretaceous. However, despite the excellent outcrops and easy access this platform is still poorly studied. A sedimentologic and biostratigraphic analyisis of a 345 m-thick stratigraphic section located in the southwestern region of this platform was conducted. The collected information allowed, for the first time, to document the presence of deep-water calcareous facies of Lower Albian age. The results of the analysis of depositional textures, sedimentary structures, fossil content, and diagenetic attributes were used to identify facies and their depositional environments, and to define facies associations. The lower part of the section consists of the following facies: skeletal-peloidal mudstone/wackestone, peloidal-skeletal packstone/grainstone, oncoid packstone, boundstone of Chondrodonta sp. and requinids, and cryptalgal laminites. The depositional environments of the facies vary from shallow subtidal (lagoonal) to supratidal. These facies stack forming subtidal and peritidal cycles. The Choffatella decipiens benthic foraminifer is common in this facies and indicates an Aptian age. This shallow-water sedimentary package is normally overlain by a succession of pelagic facies with intercalations of gravity-induced, coarse-grained carbonate deposits including turbidites and debris flows. Colomiella recta, Favusella sp. and Microcalamoides diversus are typical planktic microfossils in this calcareous unit indicating a Lower Albian age. The large-scale trend of this Lower Cretaceous facies succession allowed documenting a deepening event that took place in the Early Albian and that had not been previously reported in this platform.

León-Francisco, J. M.; Murillo-Muñeton, G.; Franco-Navarrete, S. P.

2013-05-01

318

Well-log seismic sequence stratigraphy of Aruba and its application to the hydrocarbon exploration in the Caribbean Area  

SciTech Connect

Several wells have recently been drilled in offshore Aruba approximately 12 degrees NOrth Latitude and 70 degrees West Longitude, just north of the Westernpart of Venezuela, South Central Caribbean. One of the wells, the Oxy Chuchubi No. 1 well penetrated a largely carbonate section that ranged in age from early Pliocene to early Oligocene to late Eocene at its total depth of 9,210 feet. High resolution biostratigraphy of benthic and planktonic foraminifers and calcareous nannofossils provided the abundance and diversity histograms necessary to recognized a series of maximum flooding surface condensed sections (MSF). Fourteen maximum flooding surfaces within the MFS condensed sections were identified on the well log and dated using the planktonic foraminifers and calcareous nannofossils. These maximum flooding surfaces range in age from 4.0 Ma or possibly 36.5 Ma. The paleobathymetry varies from middle to outer neritic in the upper portion of the well to lower bathyal to abyssal in the lower portion of the well. Fourteen third order sequences and their systems tracts were identified and annotated on a well log. These sequences were correlated with the Global Cycle Chart of Hag, 1987. The sequence stratigraphy provides a means of chronostratigraphic correlation to Venezuela and provides a direct tie to the geological history and hydrocarbon potential of the area.

Wornardt, W.W. (Micro-Strat Inc., Houston, TX (United States)); Vail, P.R. (Rice Univ., Houston, TX (United States))

1993-02-01

319

The Cretaceous Paleogene (K P) boundary at Brazos, Texas: Sequence stratigraphy, depositional events and the Chicxulub impact  

NASA Astrophysics Data System (ADS)

Two cores from Brazos, Texas, spanning the Cretaceous-Paleogene (K-P) boundary, are investigated by a multidisciplinary approach aiming at unraveling environmental changes and sequence stratigraphic setting. In addition, the sedimentology of the K-P event deposit and its correlation with the K-P boundary is studied. Foraminifera and nannofossil stratigraphy indicates that both cores include a latest Maastrichtian (Zone CF1-CF2) and earliest Danian (P0, P? and P1a) shale sequence with a sandy and Chicxulub ejecta-bearing event deposit at the K-P boundary; a hiatus of unknown duration may be present by the unconformable base of the event deposit. Planktic foraminifera as well as calcareous nannofossil abundance and diversity both decline abruptly above the event deposit (K-P mass extinction), whereas benthic foraminifera show a pronounced faunal change but no mass extinction. Mineralogical and geochemical proxies suggest that-except for the sandwiched K-P event deposit-no facies change took place across the K-P boundary and no evidence for adverse an- or dysoxic sedimentary conditions following the Chicxulub impact was observed. Therefore, the interval bracketing the K-P event deposit is considered as highstand systems tract. Increased coarse detritus input and low planktic/benthic (P/B) foraminifera ratios during the earliest Paleocene (P0 and P?) both suggest an increased coastal proximity or relative sea-level lowering, although the K-P mass extinction of planktic foraminifera might have influenced the P/B ratios as well. Consequently, the sandy shales of the early Paleocene are considered as late regressive highstand or as lowstand deposit. During P1a, shales assigned as transgressive systems tract overlie a pyrite- and glauconite-rich bioturbated transgressive surface or type-2-sequence boundary. The smectite-dominated clay assemblage, with minor illite, kaolinite and chlorite indicates semiarid-humid climates with no obvious shifts across the K-P boundary. The magnetic susceptibility signature during the Maastrichtian reveals a subtle cyclic (or rhythmic) pattern, whereas a high-amplitude cyclic pattern is present during the early Danian. The K-P event deposit shows a succession of high-energetic debris flows and turbidites derived from multiple source areas, followed by a period of decreasing current energy. Deposition was likely triggered by multiple tsunami or tempestites followed by a prolonged period of reworking and settling. The Chicxulub ejecta at the base of the K-P event deposit consists of Mg-rich smectite-as well as Fe-Mg-rich chlorite-spherules. Their mineralogical composition points to target rocks of mafic to intermediate composition, presumably situated in the northwestern sector of the Chicxulub impact structure. Besides these silicic phases, the most prominent ejecta components are limestone clasts, accretionary carbonate clasts, and microspar, suggesting that the Texas area received ejecta also from shallow, carbonate-rich lithologies at the impact site on the Yucatán carbonate platform. The excellent correlation of Chicxulub ejecta at Brazos with ejecta found in the K-P boundary layer worldwide - along with the associated mass extinction - provides no evidence that Chicxulub predated the K-P boundary and allows for unequivocal positioning of the K-P boundary at the event deposit.

Schulte, Peter; Speijer, Robert; Mai, Hartmut; Kontny, Agnes

2006-02-01

320

Stratigraphy of a proposed wind farm site southeast of Block Island: Utilization of borehole samples, downhole logging, and seismic profiles  

NASA Astrophysics Data System (ADS)

Seismic stratigraphy, sedimentology, lithostratigraphy, downhole geophysical logging, mineralogy, and palynology were used to study and interpret the upper 70 meters of the inner continental shelf sediments within a proposed wind farm site located approximately two to three nautical miles to the southeast of Block Island, Rhode Island. Core samples and downhole logging collected from borings drilled for geotechnical purposes at proposed wind turbine sites along with seismic surveys in the surrounding area provide the data for this study. Cretaceous coastal plain sediments that consist of non-marine to marine sand, silt, and clay are found overlying bedrock at a contact depth beyond the sampling depth of this study. The upper Cretaceous sediments sampled in borings are correlated with the Magothy/Matawan formations described regionally from New Jersey to Nantucket. An unconformity formed through sub-aerial, fluvial, marine, and glacial erosion marks the upper strata of the Cretaceous sediments separating them from the overlying deposits. The majority of Quaternary deposits overlying the unconformity represent the advance, pulsing, and retreat of the Laurentide ice sheet that reached its southern terminus in the area of Block Island approximately 25,000 to 21,000 years before present. The sequence consists of a basal glacial till overlain by sediments deposited by meltwater environments ranging from deltaic to proglacial lakefloor. A late Pleistocene to early Holocene unconformity marks the top of the glacial sequence and was formed after glacial retreat through fluvial and subaerial erosion/deposition. Overlying the glacial sequence are sediments deposited during the late Pleistocene and Holocene consisting of interbedded gravel, sand, silt, and clay. Sampling of these sediments was limited and surficial reflectors in seismic profiles were masked due to a hard bottom return. However, two depositional periods are interpreted as representing fluvial and estuarine/marine environments respectively. One sample recovered at five meters contained shell fragments within a gray fine to coarse sand possibly representing a shallow estuarine to marine environment. A coarse near surface deposit described but not recovered in all borings may represent a transgressive unconformity and resulting lag deposit however due to lack of sampling and seismic resolution in the upper 5 meters, the nature of this deposit is merely speculation. In areas where depth to the glacial surface increased, sediments ranging from sand to fine-grained silt and clay were encountered in borings. In summary, the upper 70 meters of the inner continental shelf section within the study site consists of unconsolidated sediments spanning three major depositional periods. Sediments derived from glacial activity represent the bulk of samples collected. The glacial sequences represent various depositional environments, although most samples are interpreted to be the product of glacial meltwater deposition with distribution determined by source as well as highs and lows present in the antecedent topography. Finely laminated (varved) sediment to the south of Block Island indicates the presence of proglacial lakes in the area during the time of glacial retreat. Overlying sediments represent environments ranging from fluvial to marine.

Sheldon, Dane P. H.

321

After a century-Revised Paleogene coal stratigraphy, correlation, and deposition, Powder River Basin, Wyoming and Montana  

USGS Publications Warehouse

The stratigraphy, correlation, mapping, and depositional history of coal-bearing strata in the Paleogene Fort Union and Wasatch Formations in the Powder River Basin were mainly based on measurement and description of outcrops during the early 20th century. Subsequently, the quality and quantity of data improved with (1) exploration and development of oil, gas, and coal during the middle 20th century and (2) the onset of coalbed methane (CBM) development during the late 20th and early 21st centuries that resulted in the drilling of more than 26,000 closely spaced wells with accompanying geophysical logs. The closeness of the data control points, which average 0.5 mi (805 m) apart, made for better accuracy in the subsurface delineation and correlation of coal beds that greatly facilitated the construction of regional stratigraphic cross sections and the assessment of resources. The drillhole data show that coal beds previously mapped as merged coal zones, such as the Wyodak coal zone in the Wyoming part of the Powder River Basin, gradually thinned into several discontinuous beds and sequentially split into as many as 7 hierarchical orders westward and northward. The thinning and splitting of coal beds in these directions were accompanied by as much as a ten-fold increase in the thicknesses of sandstone-dominated intervals within the Wyodak coal zone. This probably resulted from thrust loading by the eastern front of the Bighorn uplift accompanied by vertical displacement along lineaments that caused subsidence of the western axial part of the Powder River Basin during Laramide deformation in Late Cretaceous and early Tertiary time. Accommodation space was thereby created for synsedimentary alluvial infilling that controlled thickening, thinning, splitting, pinching out, and areal distribution of coal beds. Equally important was differential subsidence between this main accommodation space and adjoining areas, which influenced the overlapping, for example, of the Dietz coal zone in Montana, over the Wyodak coal zone in Wyoming. Correlation in a circular track of the Wyodak coal zone in the southern part of the basin also demonstrates overlapping with lower coal zones. Recognition of this stratigraphic relationship has led to revision of the correlations and nomenclature of coal beds because of inconsistency within these zones as well as those below and above them, which have long been subjects of controversy. Also, it significantly changes the traditional coal bed-to-bed correlations, and estimates of coal and coalbed methane resources of these coal zones due to thinning and pinching out of beds. More notably, thickness isopach, orientation, and distribution of the merged Wyodak coal bodies in the south-southeast part of the basin suggest that differential movement of lineament zones active during the Cretaceous was not a major influence on coal accumulation during the Paleocene. Improved knowledge of alluvial depositional environments as influenced by external and internal paleotectonic conditions within the Powder River Basin permits more accurate correlation, mapping, and resource estimation of the Fort Union and Wasatch coal beds. The result is a better understanding of the sedimentology of the basin infill deposits in relation to peat bog accumulation.

Flores, Romeo M.; Spear, Brianne D.; Kinney, Scott A.; Purchase, Peter A.; Gallagher, Craig M.

2010-01-01

322

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

323

Upper Cenozoic stratigraphy and paleogeographic evolution of Myrtoon and adjacent basins, Aegean Sea, Greece  

Microsoft Academic Search

The southern Aegean Sea has undergone major subsidence as a result of back-arc extension during the Neogene. The details of this subsidence and the resulting sedimentation patterns have been examined in the Myrtoon basin and adjacent areas, including the south Evoikos, Saronikos and Argolikos gulfs, by comparing seismic stratigraphy and facies interpretation from multichannel seismic profiles with the stratigraphic and

George Anastasakis; David J. W. Piper; Michael D. Dermitzakis; Vassilios Karakitsios

2006-01-01

324

Seismic stratigraphy and the Upper Minnelusa - a case study and related problems  

Microsoft Academic Search

The Permian Upper Minnelusa member is a prolific oil producer in the northeastern Powder River basin, Wyoming. Most of the fields involve (1) unconformity traps, where porous sandstones are truncated updip by a shale-filled valley, and (2) facies traps, where porous sandstones grade updip into nonporous dolomites. Due to the acoustic properties of the sandstone, dolomite, and shale, seismic stratigraphy

V. A. Walker; S. H. Gabay

1986-01-01

325

Study of Dome C site (East Antartica) variability by comparing chemical stratigraphies  

Microsoft Academic Search

This paper compares chemical stratigraphies from snowpits collected at Dome C (East Antarctica) in order to assess site variability in terms of spatial distribution of chemical markers, annual accumulation rate and chemical species persistence in the snow layers. Since Dome C was chosen for deep drilling down to the bedrock in the framework of EPICA (European Project for Ice Coring

R. Traversi; S. Becagli; E. Castellano; O. Cerri; A. Morganti; M. Severi; R. Udisti

2009-01-01

326

Mixed carbonate–siliciclastic sequence stratigraphy of a Paleogene transition zone continental shelf, southeastern USA  

Microsoft Academic Search

The sequence stratigraphy and facies of the Paleogene in the subsurface of the Albemarle Basin, North Carolina was defined using 1600 thin sections of plastic impregnated well cuttings from 24 wells, wireline logs, biostratigraphic data, and seismic data. The facies formed in the transition zone between warm subtropical and temperate conditions on a swell-wave dominated, open shelf exposed to major

Brian P Coffey; J Fred Read

2004-01-01

327

Paleozoic stratigraphy of two areas in southwestern Indiana. [Pennsylvanian, Mississippian, Devonian, Silurian, and Ordovician  

Microsoft Academic Search

Two areas recommended for evaluation as solid waste disposal sites lie along the strike of Paleozoic rocks in southwestern Indiana. Thin Pennsylvanian rocks and rocks of the upper Mississippian are at the bedrock surface in maturely dissected uplands in both areas. The gross subsurface stratigraphy beneath both areas is the same, but facies and thickness variation in some of the

Droste

1976-01-01

328

Well log-seismic sequence and stratigraphy analysis: An integrated approach to exploration and development  

Microsoft Academic Search

Well log-seismic sequence stratigraphy analysis is a new technology that integrates high-resolution biostratigraphic and paleobathymetric data and the characteristics of the well log signatures with seismic reflection profiles. This methodology permits the biostratigrapher, geologist, and geophysicist to work together to subdivide a stratigraphic section into packages of sediments bounded by chronostratigraphically significant condensed sections and their associated maximum flooding surfaces

P. R. Vail; W. W. Jr. Wornardt

1991-01-01

329

Role of stratigraphy in governing pore water seepage from salt marsh sediments  

Microsoft Academic Search

Numerical modeling experiments have been used to study the effects of marsh stratigraphy on the seepage of pore water into tidal channels. If the mud-sand contact lies at the elevation of the channel bottom and the hydraulic conductivity of the basal sand is at least an order of magnitude greater than the overlying mud, the locus of maximum seepage shifts

Leonard Robert Gardner

2007-01-01

330

Stratigraphy of late-Holocene deposits of the ancient harbour of Marseilles, southern France  

Microsoft Academic Search

The late-Holocene stratigraphy of Marseilles harbour is presented together with archaeological evidence and radiocarbon data. An anthropogenic oyster midden, dated between c. 4260 and 3400 14C yr BP is followed by a period of siltation that ended the accretionary growth of an algal (marl) deposit. This event was caused by early human settlement. Subsequently the coastline was subject to progradation.

C. Morhange; F. Blanc; S. Schmitt-Mercury; M. Bourcier; P. Carbonel; C. Oberlin; A. Prone; D. Vivent; A. Hesnard

2003-01-01

331

Stratigraphy, geochemistry and mineralogy of Eocene rocks from the Toa Baja drillhole  

SciTech Connect

The stratigraphy of the Eocene rocks of the Toa Baja drillhole is dominated by volcaniclastic sediments which are interbedded with marly pelagic limestones, especially in the lower part of the hole, and lava flows. Petrological, geochemical and paleontological evidence suggest that the site of deposition was a deep marine basin and the source of the volcanics were subaerial or shallow submarine island arc volcanoes.

Smith, A.L.; Severin, K.; Larue, D.K. (Univ. of Puerto Rico, Mayaguez (Puerto Rico))

1991-03-01

332

STRATIGRAPHY AND URANIUM POTENTIAL OF THE BURRO CANYON FORMATION IN THE SOUTHERN CHAMA BASIN, NEW MEXICO  

Microsoft Academic Search

STRATIGRAPHY The geology of the Chama basin is fairly well known, mostly through publications of the New Mexico State Bureau of Mines and Mineral Resources, and from a number of Univer- sity of New Mexico Master's theses. In reviewing the earlier work one finds that the prospective unit has been placed in the Morrison Formation by some workers (Lookingbill, 1953;

A. E. SAUCIER

333

Late Neogene stratigraphy, biochronology, faunal diversity and environments of South-West Bulgaria (Struma River Valley)  

Microsoft Academic Search

Th e stratigraphy of the Neogene deposits along the Middle Struma River (SW Bulgaria) is revised. Five genetic lithocomplexes are recognized, replacing the numerous lithostratigraphic formations currently used. Th e basic concept is that the upper Miocene alluvial-proluvial deposits along the Middle Struma River Valley are a product of \\

Nikolaï SPASSOV; Tzanko TZANKOV; Denis GERAADS

2006-01-01

334

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

335

Seismic stratigraphy of the Upper Pliocene and Quaternary deposits in the South Caspian Basin  

Microsoft Academic Search

More than 10,000 km of seismic data were used for seismic stratigraphic analysis and differentiation of major depositional environments of Upper Pliocene and Quaternary strata in the central deepwater and eastern parts of the South Caspian Basin (SCB). The study shows that the conventional sequence stratigraphy concept works well in the South Caspian Basin. Clinoform complexes within Paleo-Amudarya shelf margin

N. R Abdullayev

2000-01-01

336

Stratigraphy and multi-phase tectonic history of the Chukchi Borderland from MCS data  

NASA Astrophysics Data System (ADS)

The Chukchi Edges project was designed to establish the relationship between the Chukchi Shelf and Borderland and indirectly test theories of opening for the Canada Basin. During this cruise, ~5300 km of 2D multi-channel seismic profiles and other geophysical measurements (swath bathymetry, gravity, magnetics, sonobuoy refraction seismic) were collected from the RV Marcus G. Langseth across the transition between the Chukchi Shelf and Chukchi Borderland. These profiles reveal extended basins separated by faulted high-standing blocks. Basin stratigraphy can be subdivided on the basis of gross stratal geometry, reflection terminations and inferred unconformities. The wedge-shaped synrift sequences terminate against the basement highs and/or major faults, burying the basement topography. The inferred postrift seismic units are more nearly tabular, but thicken locally due to compaction of underlying synrift sediments. Reflection character is dominated by alternating high and low amplitude continuous reflectors which may be consistent with pelagic or turbidite sediments. Chaotic units are also observed, which may indicate mass-flow deposits. The truncated sediments over the basement highs of the Chukchi Shelf, Chukchi Plateau and Northwind Ridge suggest major erosion due both to glacial planation and earlier erosional events perhaps associated with basement uplift prior to or during rifting and extension. It is believed that the bulk of the synrift sediments are Mesozoic in age. Certainly Cenozoic sediments are also preserved in these basins, but the position of the boundary is uncertain. Locally, continuous reflectors are observed underlying the rift basin fill. These older units, of very uncertain age, would, if sampled, provide constraint on the history and affinities of the Chukchi Borderland. In addition to the extensional basins, a number of small symmetric basins are observed on the flanks of the Chukchi Plateau. These basins may be transtensional and argue for a 2nd phase of tectonism, which overprinted the obvious extensional fabric of the Borderland. This is supported by the observation of uplifted postrift sediments on the flanks of some of the intermedial basement highs.

Ilhan, I.; Coakley, B.

2012-12-01

337

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

338

Sedimentology and sandstone diagenesis of Hibernia formation in Hibernia oil field, Grand Banks of Newfoundland  

SciTech Connect

The Hibernia oil field is the largest discovery off the east coast of North America. The most important reservoir unit in the field is the Upper Jurassic-Lower Cretaceous Hibernia formation, which averages 200 m in thickness and occurs at depths between 3475 and 4200 m. On the basis of sedimentological descriptions of cores and downhole log responses, five lithofacies have been defined, and the formation has been subdivided into two lithostratigraphic units. The Main Hibernia zone is dominated by thick medium to very coarse-grained quartzarenites, interpreted as distributary channel deposits of a deltaic plain environment. The Upper Hibernia zone consists of relatively thin very fine to medium-grained quartzarenites interbedded with mudstones and siltstones. This zone is interpreted as deposits of a shallow marine delta-front environment. Porosities observed in thin section and provided by core analysis in the Hibernia sandstones range from 1 to 22%. Many sandstones with high porosities show evidence of dissolution of carbonate cement and some framework grains. This late enhancement of porosity by decarbonatization preceded main hydrocarbon migration and is a major factor in both the accumulation of large reserves and the potential producibility of the field. Lower porosities are associated mainly with well-compacted sandstones or those retaining abundant unleached carbonate cements. Time-temperature index modeling constrains the interpreted time and depth of hydrocarbon generation and accumulation in the sandstone reservoirs. 17 figures, 2 tables.

Brown, D.M.; McAlpine, K.D.; Yole, R.W.

1989-05-01

339

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

340

Workshop on the Martian Northern Plains: Sedimentological, Periglacial, and Paleoclimatic Evolution, Part 2.  

NASA Astrophysics Data System (ADS)

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, Jeffrey S.; Moore, Jeffrey; Parker, Timothy

341

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

342

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

343

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

344

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

345

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

Microsoft Academic Search

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,

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

2010-01-01

346

The International Subcommission on Stratigraphic Classification of the International Commission on Stratigraphy: The Knowledge  

NASA Astrophysics Data System (ADS)

The International Subcommission on Stratigraphic Classification (ISSC) was born in 1955 as an effort to promote awareness of stratigraphic principles and encourage worldwide standardization of stratigraphic approaches and terminology. The first major achievement of ISSC was the 1976 publication of the International Stratigraphic Guide. It was revised in 1994, with an abridged version appearing in 1999. These documents achieved their goals magnificently: cited innumerable times and forming the core of many national stratigraphic codes. As the discipline has evolved, particularly from technological advances and ocean drilling, new tools and methodologies have been developed and these have led to ever finer resolution of geological time and ever more exact correlation of stratigraphic units and events, thereby enhancing the understanding of the genesis of the geological record. Under the leadership of M. B. Cita, ISSC embarked in 2002 on a renewed initiative to disseminate to the global geological community these newer developments, and ultimately incorporate them into a third edition of the Guide. To this aim, traditional and new branches of stratigraphy are being treated: chemostratigraphy, cyclostratigraphy, magnetostratigraphy, lithostratigraphy, sequence stratigraphy, biostratigraphy, and chronostratigraphy. An open-access review paper is dedicated to each and published in Newsletters on Stratigraphy. The next edition of the Guide will be inclusive of all branches of stratigraphy and also embrace igneous and metamorphic rocks. It is envisaged that a textbook on stratigraphy based on these papers and the revised Guide could prove a timely contribution, especially to younger generations of practitioners, and aid global communication and understanding of stratigraphic principles and methods.

Pratt, Brian

2014-05-01

347

Regional geology and stratigraphy of Saturn's icy moon Tethys  

NASA Astrophysics Data System (ADS)

Tethys, with a diameter of 1060 km one of the 6 mid-sized icy moons of Saturn, was imaged for the first time in the early 1980ies by the cameras aboard the two Voyager spacecraft at resolutions of 1 km/pxl and lower [1][2][3]. These images show that most of Tethys is densely cratered and displays two major landmarks: the ~ 400 km large impact structure Odysseus and the huge graben system of Ithaca Chasma [1][2]. Since July 2004, Cassini has been in orbit about Saturn and has made several close passes at Tethys, providing an almost complete global image coverage at regional scale (200 - 500 m/pxl). However, varying viewing geometries between images taken during different orbits still impede the identification and mapping of geologic units. In this work we present an update of Tethys' regional geology and stratigraphy, based on Cassini ISS images. Crater distribution measurements, by us and in comparison with measurements of other groups [4], are used to support stratigraphic findings. Most of Tethys' surface consists of a hilly, rugged, heavily cratered plains unit, as identified in Voyager images [1][2][3]. A smooth, less densely cratered plains unit in the trailing hemisphere was previously observed by [2] which is also identifiable in Cassini ISS, but its exact boundaries are difficult to map due to varying viewing geometries of ISS observations. Another sparsely cratered plains unit not seen in Voyager images can be located to the south of Odysseus. It features remnants of highly degraded large craters superimposed by younger fresher craters with a lower crater density compared to the heavily cratered plains. Its distinct linear northern contact with the heavily cratered plains suggests an origin related to tectonism. Again, varying viewing conditions hamper to map the exact boundaries of this unit. The prominent graben system of Ithaca Chasma represents fractured cratered plains. The high resolution of Cassini ISS images reveals that tectonism on Tethys is more widespread. Numerous fractures can be identified locally in the heavily cratered plains. Impact crater materials can be subdivided into three degradational classes. Oldest crater forms are heavily degraded impact structures, such as Telemus. Odysseus is a fresh to partly degraded large impact structure with a central peak complex, wall terraces, secondary crater chains, and slivers of smooth deposits within the heavily cratered plains, possibly impact ejecta. According to previous ISS-based crater measurements, Odysseus is younger than Ithaca Chasma and possibly did not cause the formation of this graben system [5]. The youngest and freshest craters are represented by Telemachus, characterized by a sharp crater rim, well-discernible ejecta blankets, and a low superimposed crater frequency. Locally, features of mass wasting, e.g. landslides, can be observed in craters. References: [1] Smith B. A. et al. (1981), Science 212, 163-191. [2] Smith B. A. et al. (1982), Science 215, 504-537. [3] Moore J. M. and Ahern J. L. (1983), JGR 88 (suppl.), A577-A584. [4] Kirchoff M. R. and Schenk P. M. (2010), Icarus 206, 485-497. [5] Giese B. et al. (2007), GRL 34, doi:10.1029/2007GL031467.

Wagner, Roland; Stephan, Katrin; Schmedemann, Nico; Roatsch, Thomas; Kersten, Elke; Neukum, Gerhard; Porco, Carolyn C.

2013-04-01

348

Bathymetry and seismic stratigraphy of East Greenland fjords and sounds  

NASA Astrophysics Data System (ADS)

Swath bathymetry and high-resolution penetration echo sounder (chirp) data from fjords and sounds between Kong Oscars Fjord (~72°30') and Bredefjord (~75°30'), East Greenland, reveal a variety of sedimentary processes related to glacial activity and mass wasting, as well as evidence of tectonic activity. The large-scale bathymetry of most fjords and sounds is characterized by sills that occasionally are shallower than 30 m, and basins reaching maximum water depths of more than 760 m. Multiple "steps", some more than 250 meters high and with gradients exceeding 60° (e.g. in Bredefjord) are most probably related to vertical movements along tectonic lineaments. The basin floors are typically smooth suggesting sedimentation predominantly from suspension settling. However, an approx. 100 m wide and 5 m deep channel in Kempefjord provides evidence of gravity-flow erosion sub-parallel to the fjord axis. Multiple sediment lobes along the fjord sides reflect repeated mass wasting. Relatively straight linear features oriented parallel to the fjord axes are interpreted to be glacial lineations that were formed beneath fast-flowing ice draining the Greenland Ice Sheet. They occur rarely on shallower plateaus and are often overlain by transverse ridges. In Youngsund, such ridges are typically 1-2 m high, 50 m wide and the distances between crests are most often approx. 100 m. The ridges are most probably 'retreat moraines' that were deposited during minor halts and/or re-advances during the last deglaciation. More curvilinear and randomly oriented furrows with raised rims are most probably iceberg ploughmarks that were formed from grounded icebergs calving off the Greenland Ice Sheet during the last deglaciation (e.g. in Rudis Bugt). Elongated to round, randomly distributed depressions of up to >10 m depth and >200 m width occur, e.g. in the inner parts of Tyrolerfjord. They are often filled with acoustically stratified sediments and we assume that they might have resulted from post-glacial tectonic activity. Up to 180 ms two-way travel time thick acoustically stratified sequences dominate the fjord-fill and sound-fill stratigraphies. These deposits are suggested to reflect repeatedly changing physical conditions in a glacimarine environment where deposition occurred from suspension fall-out, ice rafting from icebergs and sea ice, as well as smaller-scale mass wasting. An acoustically transparent drape overlies these deposits rarely (e.g. in Rudis Bugt). Multiple acoustically transparent bodies with irregular geometries intercalated within the stratified deposits are suggested to reflect repeated larger-scale mass wasting, either from slope failures along fjord sides or related to glacier advances (e.g. in Nordfjord). Occasional distortions and blanking of reflections (e.g. in Nordfjord and Kong Oscar Fjord) might be related to relatively recent tectonic activity and fluid flow/gas expansion.

Forwick, Matthias; Sverre Laberg, Jan; Husum, Katrine; Olsen, Ingrid L.

2014-05-01

349

Insights into the October-November 2010 Gunung Merapi eruption (Central Java, Indonesia) from the stratigraphy, volume and characteristics of its pyroclastic deposits  

NASA Astrophysics Data System (ADS)

The 2010 eruption of Merapi was the second most deadly in the historic record of this volcano, claiming over 380 lives. By relating the observations of this eruption with detailed examination of deposit distribution, stratigraphy and sedimentology, a reconstruction of the properties of the pyroclastic density currents (PDCs) is presented, including the valley controlled block-and-ash flows (BAFs) and widespread, energetic pyroclastic surges. The distribution, volume and mobility characteristics of all types of PDC during the eruption sequence show evidence for levels of intensity unseen since the large-scale 1872 and 1930 eruption phases, especially during the climactic events of October 26 and November 5. Many tephra falls interbedded with PDC units show that most dome-collapse events occurred along with and between explosive vulcanian eruptions. The 2010 eruption produced very long-runout BAFs, reaching 16.1 km in the Kali Gendol on November 5. This runout could be explained by its large-volume (20 million m3), around 10 times that of previous Merapi BAFs during the last 130 years. Major avulsion of these dense BAFs to form overbank deposits became more common through the eruptive sequence as the valley was progressively filled with successive PDC deposits. Spreading avulsed BAFs were a particular hazard downstream of ~ 10 km where the landscape is less dissected. Less clear, however, is why pyroclastic surges extended up to 10 km from the vent on November 5 and > 6.4 km on October 26. These expanded much farther from BAF margins (~ 2 km) than ever seen before at Merapi. In one location they were decoupled from valley-centered BAFs with high momentum, traveling initially laterally across steep valley systems, before draining downslope. At this site, on the western side of the upper Gendol at around 3 km from source, surge decoupling was apparently exacerbated by upstream collision and deflection of high-flux, hot and gas-rich BAFs against the cliffs of Gunung Kendil. The 1.4 km-long cliff face was impacted directly for the first time in 2010 events, and may have been responsible for the formation of larger than normal turbulent ash-rich clouds above BAFs. These results imply that future eruption events under the present summit and upper flow-path configuration are also highly likely to generate wide dispersal pyroclastic surges and extreme hazard, especially now that dense forest has been destroyed on the upper southern slopes of the volcano.

Cronin, Shane J.; Lube, Gert; Dayudi, Devi S.; Sumarti, Sri; Subrandiyo, S.; Surono

2013-07-01

350

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

351

Progress report on the stratigraphy of the Triassic and associated formations in part of the Colorado Plateau region  

USGS Publications Warehouse

Stratigraphic studies involving regional stratigraphy, sedimentary structures, pebbles, and sedimentary petrology are designed to furnish information regarding areal distribution, stratigraphic relationship, source areas, and depositional environment of the Triassic Shinarump conglomerate.

Williams, G.A.; Cadigan, R.A.; Albee, H.F.; Stewart, J.H.

1953-01-01

352

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

353

Stratigraphy and palaeodepositional environment of the Palaeoproterozoic volcano-sedimentary Konse Group in Tanzania  

NASA Astrophysics Data System (ADS)

The Konse Group is a volcano-sedimentary assemblage of Palaeoproterozoic age located in central Tanzania between the Tanzanian Archaean Craton (to the west) and the high-grade Palaeoproterozoic Isimani Suite (to the east). The Konse Group is unconformably deposited on the high-grade Isimani Suite and it is only mildly metamorphosed to greenschist facies. Although the Konse Group is quite old, its deformational pattern is not complex and the order of superposition of its constituant lithologies can be outlined. There are also abundant primary sedimentary and volcanic structures which are still preserved in it. The Konse Group is therefore one amongst the very few oldest (if not the oldest) sedimentary basins in eastern Africa with preserved stratigraphy and primary structures, hence the basin serves as an important site for palaeodepositional environment, palaeoclimatology, and palaeotectonic studies in Africa and Gondwanaland as a whole. The Konse Group is made up of six lithologically distinct, conformable units. Its basal unit is a well-sorted orthoquartzite (the Mkulula Formation), which is shallow sea or epicontinental sands deposited on the sea shore. The basal orthoquartzite is overlain by a matrix-supported polymictic conglomerate (the Ruaha River Formation), which is either a lag gravel, point bar or channel bar deposit. The conglomerate is, in turn, overlain by thinly laminated silts and muds (the Kilimbe Formation) representing off-shore or shelf zone (distal) facies. The Kilimbe Formation is overlain by the Kikuyu Formation, which is made up of subaqueous volcanics of basic pillow lavas and basic tuffs with lapilli pockets which show low angle, cross-stratification. The subaqueous volcanics are overlain by dolomitic marble (the Ihumbirisa Formation) of the shallow water carbonate shelves fades and they are in turn overlain by the Mhwana Formation, which constitute the top-most unit of the Konse Group. The Mhwana is dominated by fine arenites intercalated with a banded quartz-Fe formation and a Mn-rich quartz formation. The Konse basing is interpreted as a peripheral foreland basin formed at the margin of the Tanzanian Archaean Craton during the :main phase of the Usagaran deformation.

Mruma, A. H.

1995-08-01

354

Upper Devonian vertebrate taphonomy and sedimentology from the Klunas fossil site, Tervete Formation, Latvia  

NASA Astrophysics Data System (ADS)

The deposits of the Tervete Formation, Famennian Stage of Latvia, comprising weakly cemented sandstone and sand intercalated with dolomitic marls, siltstone and clay, have been traditionally interpreted as having formed in a shallow, rather restricted sea with lowered salinity. During seven field seasons the excavations took place in the south-western part of Latvia, at the Klunas site, and resulted in extensive palaeontological and sedimentological data. The taphonomical analysis has been performed, having evaluated the size, sorting, orientation of the fossils, articulation and skeletal preservation as well as the degree of fragmentation and abrasion. The sedimentological analysis involved interpretation of sedimentary structures, palaeocurrent direction reconstruction, grain-size analysis and approximate water depth calculations. The vertebrate assemblage of the Klunas site represents all known taxa of the Sparnene Regional Stage of the Baltic Devonian, comprising placoderms Bothriolepis ornata Eichwald, B. jani Lukševi?s, Phyllolepis tolli Vasiliauskas, Dunkleosteus sp. and Chelyophorus sp., sarcopterygians Holoptychius nobilissimus Agassiz, Platycephalichthys skuenicus Vorobyeva, Cryptolepis sp., Conchodus sp., Glyptopomus ? sp., "Strunius" ? sp., and Dipterus sp., as well as an undetermined actinopterygian. Placoderms Bothriolepis ornata and B. jani dominate the assemblage. The fossils are represented in the main by fully disarticulated placoderm plates and plate fragments, sarcopterygian scales and teeth, rarely bones of the head and shoulder girdle, and acanthodian spines and scales. The characteristic feature is the great amount of fragmentary remains several times exceeding the number of intact bones. The horizontal distribution of the bones over the studied area is not homogenous, distinct zones of increased or decreased density of fossils can be traced. Zones of the increased density usually contain many elements of various sizes, whereas zones of the decreased density might be subdivided into two types: 1, with limited number of large bones; 2, with scattered relatively small scales or fragments. The shape and size of zones of increased density of fossils slightly resemble that of subaqueous dunes. Within the Klunas fossil site three taphonomically distinct oryctocoenoses can be traced, differing in the compactness of accumulation, size, disarticulation and fragmentation of bones and showing various degree of mixing of repeatedly buried and very fresh, partially articulated material. Analysis of similarities and differences between these oryctocoenoses demonstrates that all are sedimentary concentrations and have to be assessed as allochtonous assemblages. However, despite these differences, the 1st and the 3rd oryctocoenoses, which have been formed as vertebrate bone accumulations on the bottom of an erosional channel, have much in common contrary to the 2nd oryctocoenosis, which exemplifies the lens of fossil bearing cross-stratified sandstone formed in subaqueous dunes. The concentrations of vertebrate remains have been formed under the influence of fluvial and tidal processes in the shallow water environment, most probably deltaic or estuarine settings. It has been found also that elongated placoderm and sarcopterygian bones might be better indicators of the palaeoflow direction in comparison with very elongated, but dense acanthodian spines or sarcopterygian teeth.

Vasiļkova, J.; Lukševi?s, E.; Stinkulis, Ä.¢.; Zupinš, I.

2012-04-01

355

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

356

Changing sedimentary environment during the Late Quaternary: Sedimentological and isotopic evidence from the distal Bengal Fan  

NASA Astrophysics Data System (ADS)

The sediments recovered from two gravity cores of the lower and distal Bengal Fan were investigated for sedimentological properties and Sr-Nd isotopes. Each core exhibits two distinct units, the lower unit 2 and upper unit 1 sediments. The unit 2 sediments are predominantly olive black/grey in colour with abundant finer silt-size fractions, low organic carbon and CaCO 3, quartz and mica in the coarse fraction, dominant illite and chlorite in the <2 ?m fraction and uniform rock-magnetic properties. Biogenic constituents are extremely rare or restricted to the lower part of unit 2. The unit 1 sediments, on the other hand, are moderate brown/yellowish brown in colour with intermittent thin dark-coloured sediment layers. Higher clay, organic carbon, CaCO 3, and biogenic constituents in the coarse fraction, and enriched smectite and kaolinite in the <2 ?m fraction are typical. Magnetic susceptibility values are higher and correlate well with acid-insoluble residue content. Higher Rb, Sr, Sm and Nd concentrations, 87Sr/ 86Sr ratios and more radiogenic ? values are characteristic for unit 2 sediments compared to unit 1 in both the cores. The unit 2 sediments represent Pleistocene hemiturbidites, older than 13 14C kyr BP with their source from the northern Bay of Bengal (NBOB), derived from the Himalayas and transported by the Ganges-Brahmaputra (G-B) River system. Unit 1 sediments are calcareous pelagic sediments, which started depositing ˜12 14C kyr BP, with its clastic sediments derived from the Himalayas and SE Indian/Sri Lankan margins. The change in lithofacies from unit 2 to unit 1 suggests that the sediment deposition by turbidity current activity ceased in the distal Bengal Fan at ˜12 14C kyr BP, perhaps because of the rapid rise in sea-level during the melt water pulse 1A and Holocene.

Kessarkar, Pratima M.; Rao, V. Purnachandra; Ahmad, S. M.; Patil, S. K.; Anil Kumar, A.; Anil Babu, G.; Chakraborty, Sukalyan; Soundar Rajan, R.

2005-09-01

357

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

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

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

360

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

361

Sedimentology of a Permian playa lake: the Boda Claystone Formation, Hungary  

NASA Astrophysics Data System (ADS)

The Upper Permian Boda Claystone Formation (BCF) in SW Hungary has been previously been identified as a saline lake deposit. A country-wide screening found this 800-1000 m thick succession the most suitable for the disposal of high-level radioactive waste in Hungary, and research into this formation has consequently been intensified since. The investigations included a detailed study of the sedimentological characteristics. Data obtained by mapping of the 25 km2 outcrop area of the formation and from more than 40 boreholes were processed. The sedimentary structures were investigated on outcrop to microscopic scales, and cycles in the succession were interpreted. The main lithofacies, sedimentary structures and ichnofossils are presented. They indicate that the major part of the succession was deposited in a playa mudflat and is not of lacustrine origin in a strict sense. The lake sediments are represented by laminated and ripple-marked/flaser-type cross-laminated claystones and siltstones and by massive dolomites; trace fossils include crawling traces and burrows. Partial or complete drying out of the lake commonly occurred after the formation of carbonate mud by evaporation. Periodic fluvial influx is recorded by cross-bedded sandstones and unsorted gravelly sandstones of up to pebble-sized angular grains. Fenestral and stromatolitic structures reflect the repeated appearance of playa mudflat conditions. The silty claystones, which compose the major part of the succession, lost their primary structures due to pedogenic processes and indicate prolonged subaerial intervals with soil formation and only ephemeral inundations. The presence of pedogenic carbonate concretions supports the interpretation of an arid climate and a relatively shallow groundwater table. Drying-out events shown by desiccation cracks and authigenic breccias can be traced all over the succession. The various facies form small-scale sedimentary cycles showing a shallowing-upward trend and the growing influence of aridity and subaerial exposure.

Konrád, Gyula; Sebe, Krisztina; Halász, Amadé; Babinszki, Edit

2010-04-01

362

Distribution and Stratigraphy of Basaltic Lavas in the Southwest Portion of the Quaternary Big Pine Volcanic Field, California  

NASA Astrophysics Data System (ADS)

The Pleistocene Big Pine Volcanic Field (BPVF), located in the Owens Valley of eastern California, is dominated by basaltic cinder cones and lavas, and poses a potential volcanic hazard to local infrastructure, in particular Highway 395 and the Los Angeles Aqueduct. However, despite numerous petrologic studies, the volcanic history and distribution of products from individual BPVF eruptions are poorly known. Using detailed field mapping and petrology, we have determined the distribution and stratigraphy of basaltic lavas in the southwest portion of the BPVF, which contains the largest number exposed vents and lava. In the Aberdeen area, individual cinder cones and fissure vents are aligned along N-S trending lineaments, with local clustering of vents and lavas. Approximately 19 cones, and at least 14 lava flows occur in the area. Two cinder cones located near the valley floor are partly buried by younger lavas and alluvium. In most cases, lavas are aa in character and traveled ca. 7 km down alluvial fans (8% gradient) towards the Owens River. On average, individual lavas cover ca. 10-12 km2, with average individual volumes of ca. 0.065 km3. Two general groups of basaltic lavas characterize the Aberdeen area: 1) xenocryst-rich and 2) xenolith-poor basalts. Xenolith-rich basalts contain variable amounts of ultramafic, mafic, granitic, and metamorphic lithologies, whereas xenolith-poor lavas are dominated by olivine phenocrysts. Overlapping flow margins define relative ages between adjacent basalts. In both north and south portions of the Aberdeen area, flows composing the base of the volcanic stratigraphy are the xenolith-rich variety, and are typically overlain by xenolith-poor flows. In general, these younger xenolith-poor lavas are approximately 25% larger in volume than the older xenolith-rich lavas. Several vents record changes in lava type during individual eruptions, suggesting transitions in magma discharge rate. At one vent cluster, pahoehoe is restricted to within ca. 1.5 km of its fissure vent and overlies more extensive aa from the same vent, suggesting a decrease in discharge rate of basalt over the course of the eruption. In contrast, lavas from a cinder cone on the eastern portion of BPVF comprise thin (<