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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

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

4

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

5

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

6

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

7

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

8

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

9

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

10

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

11

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

Microsoft Academic Search

The geology of southern coastal Tanzania has remained poorly understood since the first comments on its stratigraphy were made over 100years ago. However, new field surveys combined with shallow drilling along the coast between Kilwa and Lindi are beginning to resolve the depositional history and structural evolution of this region over the past 85Ma. Here we present the first attempt

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

2006-01-01

12

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

Microsoft Academic Search

The geology of southern coastal Tanzania has remained poorly understood since the first comments on its stratigraphy were made over 100 years ago. However, new field surveys combined with shallow drilling along the coast between Kilwa and Lindi are beginning to resolve the depositional history and structural evolution of this region over the past 85 Ma. Here we present the

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

2006-01-01

13

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

14

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

15

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

16

Stratigraphy, sedimentology and tectonic significance of the Upper Cretaceous Virginian Ridge formation, Method Basin, Washington: Implications for tectonic history of the North Cascades  

NASA Astrophysics Data System (ADS)

Sediments in the basin beyond the delta platform comprise sandy and conglomeratic turbidities and submarine debris flow deposits. Calculations based on characteristics of these debris flows give a basin paleoslope estimate of less than two degrees. Internal stratigraphy of the Virginian Ridge Formation demonstrates a progression upward and westward from a quite, marine facies through delta platform and inner-delta facies to subaerial fluvial and alluvial fan facies. The later Cretaceous Methow Basin is interpreted as a wrench fault basin generated in response to transpressive dextral offset and uplift of a highland to the west. Stratigraphy and sedimentology of the Albian-campanian Methow sequence indicates that: (1) the basin was asymmetric normal to its axis; (2) the basin was asymmetric along its axis; (3) the relatively short and steep fan delta system deposited along the western margin was laterally amalgamated and possibly time-transgressive to the north.

Trexler, J. H., Jr.

1984-12-01

17

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

18

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

NASA Astrophysics Data System (ADS)

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

Sanabria, Diego Ignacio

2001-07-01

19

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

20

Stratigraphy, Sedimentology, and Depositional History At Southern Hydrate Ridge, Cascadia Margin, Interpreted from ODP Leg 204 Drill Sites and 3-D Seismic Data  

NASA Astrophysics Data System (ADS)

Hydrate Ridge, a gas hydrate-bearing thrust anticline located on the lower slope of the Cascadia accretionary wedge, was the site of Ocean Drilling Program (ODP) Leg 204 drilling in 2002. Drill sites were focused along transects over the southern summit of the ridge and into the adjoining eastern slope basin. 3-D seismic data, obtained in 2000, provide the high-resolution structural and stratigraphic context for each of the drill sites and detailed lithologic description, multi-sensor track (MST) logging, and logging while drilling (LWD) data characterize the sedimentology of the recovered cores and of the in situ stratigraphy. Sedimentological description and interpretation of the cores reveals a history of sedimentation dominated by turbidites and occasional debris flows, as well as intermittent volcanic glass emplacement, either as air fall ash or detrital glass in turbidites. Downhole variability in the micropaleontology data and abrupt changes in stratal geometry in the 3-D seismic data also suggest a history punctuated by both depositional hiatuses and erosion. Post-depositional compaction, biologic activity, deformation, dewatering, and diagenesis have overprinted the stratigraphy with bioturbation, iron-sulfide and authigenic carbonate precipitation, glauconite occurrences, and gas hydrate. Turbidite sands and silts and zones with concentrated volcanic glass shards provide the greatest porosity in the section and commonly contain overpressured gas and gas hydrate. Gas hydrate was also observed in the microfractures of some clay-rich sediments as well. Initial stratigraphic correlation across sites is encouraging, however, further integration of the lithologic, MST, LWD, and 3-D seismic data across the region will be presented and help to better decipher the geologic history of this region and to quantify the stratigraphic, structural, and sedimentological framework within which the gas hydrate system on Hydrate Ridge exists.

Johnson, J. E.; Chevalier, J.; Trehu, A. M.; Gracia, E.; Su, X.; Teichert, B. M. A.; Weinberger, J. L.; Shipboard Scientific Party Odp Leg, 204

2003-04-01

21

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

22

Stratigraphy and Surface Ages on Iapetus  

NASA Astrophysics Data System (ADS)

The examination of the geologic history of Iapetus is a major goal of the Cassini imaging experiment (ISS). Crater counting for the determination of model ages is a powerful tool to understand stratigraphic relationships between different terrain units. The shapes of the measured crater-size frequency distributions follow very closely the distribution of Earth's moon (after correction for the different impact conditions; Neukum et al. 2006), justifying its usage here for model age determinations. Following the models of Castillo-Rogez et al. (2007) and Neukum et al. (2006), an age of 4.4 Gyr is expected for the oldest parts of Iapetus’ surface. Based on these models, we measured different ages at neighboring morphologic units. A small part of the ridge near 96°W longitude and an "average" dark terrain sample north of the ridge shows dense cratering, indicating the most ancient surface ( 4.4 Gyr). The surroundings of the "landslide" crater (diameter 120 km; 6°N/36°W) in the south western part of a huge basin and a large, 420 km diameter basin on the leading side of Iapetus (34°N, 80°W) appear slightly younger ( 4.3 Gyr). The "landslide" crater and the landslide itself are sparsely cratered with a model age of 4.1 Gyr. These might be among the youngest areas on Iapetus. New high-resolution imagery data from the targeted flyby are expected for mid-September (see abstract by Denk et al., this meeting), with spatial resolutions down to 10 m/pxl. We expect to present first results at the meeting. References: Castillo-Rogez J.C., et al. (2007), Icarus, doi:10.1016/j.icarus.2007.02.018. Denk, T., et al. (2007), DPS, this conference. Neukum, G., et al. (2006), 1st EPSC, Berlin, p.610.

Schmedemann, Nico; Denk, T.; Wagner, R.; Neukum, G.

2007-10-01

23

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.

24

Sequence stratigraphy and sedimentology of a shelf-margin lowstand wedge in the deep Wilcox flexture trend of south Texas  

SciTech Connect

An integrated sedimentologic and biostratigraphic study of 15 wells and over 1400 ft (430 m) of core facilitated establishment of a sequence stratigraphic framework for the deep Wilcox Group of south Texas. This analysis also revealed the presence of a dip-restricted, sand-prone sediment wedge that produces hydrocarbons in growth-fault structures. A sequence stratigraphic framework for the Wilcox was constructed via the use of faunal-increase markers, thin intervals present in well cuttings characterized by rises in the relative abundance of planktonic foraminifera. These marine flooding horizons can be utilized to subdivide the Wilcox Group into four depositional sequences termed P(aleogene)-8, P-7, P-4, and P-3, in descending order. Identification of standard sequence-bounding unconformities is hampered by the poor seismic expression of the Wilcox and the structural complexity of the area.

Snedden, J.W. (Mobil Exploration Norway, Inc., Stavanger (Norway)); Cooke, J.C. (Mobil Exploration and Producing Services, Inc., Dallas, TX (United States)); Johnson, R.K.; Conrad, K.T. (Mobil Exploration and Producing, US, Houston, TX (United States))

1991-03-01

25

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

26

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

27

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

28

Mars North Polar Deposits: Stratigraphy, Age, and Geodynamical Response  

Microsoft Academic Search

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

Roger J. Phillips; Maria T. Zuber; Suzanne E. Smrekar; Michael T. Mellon; James W. Head; Kenneth L. Tanaka; Nathaniel E. Putzig; Sarah M. Milkovich; Bruce A. Campbell; Jeffrey J. Plaut; Ali Safaeinili; Roberto Seu; Daniela Biccari; Lynn M. Carter; Giovanni Picardi; Roberto Orosei; P. Surdas Mohit; Essam Heggy; Richard W. Zurek; Anthony F. Egan; Emanuele Giacomoni; Federica Russo; Marco Cutigni; Elena Pettinelli; John W. Holt; Carl J. Leuschen; Lucia Marinangeli

2008-01-01

29

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

30

Local and regional tectonic control on sedimentology and stratigraphy in a strike-slip basin: Miocene Temblor Formation of the Coalinga area, California, USA  

Microsoft Academic Search

Sedimentological study of the Lower to Middle Miocene Temblor Formation in the Coalinga area of the San Joaquin basin (California, USA) provides new results applicable to understanding patterns of sedimentation and stratigraphic architecture in strike-slip basins along tectonically active margins. Detailed investigation of surface outcrops on the Coalinga anticline is integrated with description of cores from an adjacent oil field.

Robert A Bridges; James W Castle

2003-01-01

31

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

PubMed

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 approximately 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. PMID:18483402

Phillips, Roger J; Zuber, Maria T; Smrekar, Suzanne E; Mellon, Michael T; Head, James W; Tanaka, Kenneth L; Putzig, Nathaniel E; Milkovich, Sarah M; Campbell, Bruce A; Plaut, Jeffrey J; Safaeinili, Ali; Seu, Roberto; Biccari, Daniela; Carter, Lynn M; Picardi, Giovanni; Orosei, Roberto; Mohit, P Surdas; Heggy, Essam; Zurek, Richard W; Egan, Anthony F; Giacomoni, Emanuele; Russo, Federica; Cutigni, Marco; Pettinelli, Elena; Holt, John W; Leuschen, Carl J; Marinangeli, Lucia

2008-05-15

32

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

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

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

35

Identifying Fracture Types and Relative Ages Using Fluid Inclusion Stratigraphy  

SciTech Connect

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

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

2008-06-30

36

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

37

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

38

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

39

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

40

Stratigraphy and isotopic age of the Lopian complex in the Lekhta structure of northern Karelia  

NASA Astrophysics Data System (ADS)

New data on the stratigraphy and isotopic age of supracrustal rocks from the lower part of the section constituting the northeastern limb of the Lekhta structure (northern Karelia) and their relationships with the basement are considered. Geological-petrographic, lithological-geochemical, and isotopic data are used to define three formations united into the Okhta Group. Immediate relationships between volcanics of the greenstone belt and granitoids of the basement represented by the oldest (for the Baltic Shield: 2.8 Ga) continental weathering crust after granites, are discussed. Isotopic age of volcanics and granite gneisses of the basement indicates that the Lopian supracrustal complex of the Lekhta structure was deposited in a period lasting 16 myr with duration of periods corresponding to formation of the Okhta and Pebozero groups being as long as 8 and 11 myr, respectively. In the regional stratigraphic scale, the entire Archean part of the supracrustal section in the Lekhta structure should be attributed to the Middle Lopian.

Matrenichev, V. A.; Alfimova, N. A.; Levchenkov, O. A.; Savatenkov, V. M.; Belyatskii, B. V.; Astaf'eva, M. M.; Makeev, A. F.; Yakovleva, S. Z.

2011-12-01

41

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

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

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

45

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

46

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

47

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

49

Ages and stratigraphy of mare basalts in Oceanus Procellarum, Mare Nubium, Mare Cognitum, and Mare Insularum  

NASA Astrophysics Data System (ADS)

Accurate estimates of mare basalt ages are necessary to place constraints on the duration and the flux of lunar volcanism as well as on the petrogenesis of lunar mare basalts and their relationship to the thermal evolution of the Moon. We performed new crater size-frequency distribution measurements in order to investigate the stratigraphy of mare basalts in Oceanus Procellarum and related regions such as Mare Nubium, Mare Cognitum, and Mare Insularum. We used high-resolution Clementine color data to define 86 spectrally homogeneous units within these basins, which were then dated with crater counts on Lunar Orbiter IV images. Our crater size-frequency distribution measurements define mineralogical and spectral surface units and offer significant improvements in accuracy over previous analyses. Our data show that volcanism in the investigated region was active over a long period of time from ~3.93 to 1.2 b.y., a total of ~2.7 b.y. Volumetrically, most of the basalts erupted in the Late Imbrian Period between ~3.3 and 3.7 b.y., and we see evidence that numerous units have been resurfaced. During the Eratosthenian Period, significantly less basalt was erupted. Depending on the absolute model ages that one can assign to the lunar chronostratigraphic systems, five units might be of Copernican age. Younger basalts are generally exposed in the center of the investigated area, that is, closer to the volcanic centers of the Aristarchus Plateau and Marius Hills. Older basalts occur preferentially along the northwestern margin of Oceanus Procellarum and in the southeastern regions of the studied area, i.e., in Mare Cognitum and Mare Nubium. Combining the new data with our previously measured ages for basalts in Mare Imbrium, Serenitatis, Tranquillitatis, Humorum, Australe, and Humboldtianum, we find that the period of active volcanism on the Moon lasted ~2.8 b.y., from ~4 b.y. to ~1.2 b.y. On the basis of the basalts dated so far, which do not yet include the potentially young basalts of Mare Smythii [e.g., Schultz and Spudis, 1983], we conclude that Oceanus Procellarum not only exhibits the widest range of ages of all investigated basins but probably also is the location of some of the youngest basalts on the lunar surface.

Hiesinger, H.; Head, J. W.; Wolf, U.; Jaumann, R.; Neukum, G.

2003-07-01

50

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

51

Implications for the early shield-stage evolution of Tenerife from K/Ar ages and magnetic stratigraphy  

NASA Astrophysics Data System (ADS)

The combined use of field geology, radioisotopic dating and magnetic stratigraphy applied to the old shield volcanoes of Tenerife provides a reliable time framework for the early, shield-stage evolution of the island. The greater part of this new set of ages, obtained from sequences of lava flows is in agreement with the astronomical polarity time scale. This approach illustrates that previous K-Ar data collected without a comprehensive stratigraphy should be viewed with caution, and in some cases discarded altogether. The shield volcanoes of Tenerife encompass a relatively small number of magnetozones, an observation consistent with the relatively short periods of growth shown by the new ages (1-2 my). The island was constructed by the aggregation of three successive shields: the Roque del Conde (Central shield), between about 11.9 and 8.9 Ma, and the Teno (6.2-5.6 Ma) and Anaga (4.9-3.9 Ma) volcanoes. This new oldest subaerial age of Tenerife fits with the others obtained in the Canaries in a clear west to east monotonous age progression, one of the main restrictions for hotspot-related island chains.

Guillou, Hervé; Carracedo, Juan Carlos; Paris, Raphael; Pérèz Torrado, Francisco José

2004-05-01

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

New U Pb age and geochemical constraints on the stratigraphy and distribution of the Lantau Volcanic Group, Hong Kong  

NASA Astrophysics Data System (ADS)

Seven new high precision U Pb single crystal zircon ages are reported from Jurassic and early Cretaceous volcanic rocks in the Hong Kong Special Administrative Region (SAR). These ages are used in combination with Zr vs. TiO2 ratios to refine the stratigraphy of the Lantau Volcanic Group on Lantau Island and in adjoining districts in Hong Kong. As a result, three major unconformities are proposed and the rift-controlled paleogeography of the region, which influenced the development of the Lantau Caldera and lacustrine basins during the latest Jurassic to earliest Cretaceous, is clarified. The data also suggest the possibility that the base of the Cretaceous System may be preserved within the sequence.

Campbell, S. D. G.; Sewell, R. J.; Davis, D. W.; So, A. C. T.

2007-10-01

54

KAr ages and magnetic stratigraphy of a hotspot-induced, fast grown oceanic island: El Hierro, Canary Islands  

Microsoft Academic Search

The combined use of accurate radiometric dating and magnetic stratigraphy can be applied to define the main stages of the building of oceanic volcanic islands. This method has been successfully applied on the island of El Hierro, the westernmost island of the Canaries Archipelago. For the emerged part of this island, built in the last 1.2 Ma, magnetic stratigraphy and

H. Guillou; J. C. Carracedo; F. Pérez Torrado; E. Rodriguez Badiola

1996-01-01

55

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

56

sup 40 Ar/ sup 39 Ar age calibration of the litho- and paleomagnetic stratigraphies of the Ngorora Formation, Kenya  

SciTech Connect

Precise eruptive ages have been determined by the laser-fusion, single-crystal {sup 40}Ar/{sup 39}Ar method for juvenile volcanic feldspars from reworked and contaminated volcaniclastic rocks of the middle Miocene Ngorora Formation, Kenya Rift Valley. These ages range from 13.06 Ma at the base to 10.51 Ma toward the top of the type section near Kabarsero. Correlation of the local paleomagnetic stratigraphies with the geomagnetic reversal time scale yields magnetochronologic age estimates that are younger than the isotopic ages by an average of 0.18 Ma. Much of the discrepancy can be eliminated if an inferred change in sea-floor spreading rate occurred at 13 Ma or earlier, rather than at 10.42 Ma as previously suggested. Sedimentation rates at Kabarsero calculated from the {sup 40}Ar/{sup 39}Ar results decrease from initial values of {approximately}25 cm/1,000 yr to {approximately}5 cm/1,000 yr toward the top of the section. The initial rapid sedimentation rates characterize the first 0.1 to 0.3 m.y. following emplacement of the underlying, voluminous, basin-filling Tiim Phonolites, indicating that the Baringo Basin at this time may not have existed as a rift valley created by extensional tectonics, but instead may have been a subsidence feature formed in response to removal of large volumes of magma from the lithosphere. A premolar tentatively identified as Proconsul sp. indet. found in the Ngorora Formation near the village of Bartabwa has been dated at {approximately}12.42 Ma, representing perhaps the last known occurrence of this genus in the fossil record.

Deino, A.; Drake, R. (Institute of Human Origins, Berkeley, CA (USA)); Tauxe, L. (Scripps Institute of Oceanography, La Jolla, CA (USA)); Monaghan, M. (Univ. of Chicago, IL (USA))

1990-07-01

57

Stratigraphic and sedimentological evidence for late Wisconsinan sub-glacial outburst floods to Laurentian Fan  

Microsoft Academic Search

Sub-glacial meltwater produces a distinctive stratigraphic and sedimentological response on the continental margin. Seismo-stratigraphy of Laurentian Channel reveals thick till deposits at its seaward end that pass laterally into stratified sediment in deeper basins, that may record periods of water build up beneath the ice. Two scales of meltwater discharge are recognised: large scale that caused catastrophic erosion and transported

David J. W. Piper; John Shaw; Kenneth I. Skene

2007-01-01

58

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

59

Spectral stratigraphy  

Microsoft Academic Search

Stratigraphic and structural studies of the Wind River and Bighorn basins, Wyoming, and the Guerrero-Morelos basin, Mexico, have resulted in development of 'spectral stratigraphy.' This approach to stratigraphic analysis uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. This paper reviews selected

Harold R. Lang

1991-01-01

60

C and O isotope stratigraphy in shallow-marine carbonate: a tool for sequence stratigraphy (example from the Lodève region, peritethian domain)  

Microsoft Academic Search

.  Carbon and Oxygen isotope profiles from a well-dated carbonate section spanning the Sinemurian time on the Caussenard High\\u000a (southeast France) are compared to sedimentological data and the results from sequence stratigraphy analysis, in order to\\u000a discuss the origin of isotopic variations in a shallow-marine carbonate succession. The sedimentological study has enabled\\u000a the identification of four types of depositional environments (peritidal,

Youri Hamon; Gilles Merzeraud

2007-01-01

61

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

62

Nonmarine stratigraphy of latest Cretaceous and early Tertiary age, southwestern New Mexico  

SciTech Connect

Recent fossil collections from nonmarine strata at localities in southwestern New Mexico indicate that the Ringbone formation, as originally defined, comprises units separated by a major hiatus that is represented in the field by an angular unconformity. The lower unit has yielded (NMMNH locality 298) two anterior caudal vertebral centra, morphologically and metrically indistinguishable from those of the Late Cretaceous tyrannosaurids Albertosaurus and Daspletosaurus. These dinosaur fossils establish a late Campanian or Maastrichtian age for the unit, indicating its equivalence with the McRae Formation of south-central New Mexico and the Fort Crittenden Formation of southeastern Arizona. The unit is composed of approximately 1,000 m of sedimentary-clast conglomerate, arkose, volcanic litharenite, and gray shale; it thus appears to contain detritus from several different source areas. The younger unit has yielded a low-diversity ostracod fauna of Paleocene to early Eocene age. Diagnostic taxa from the assemblage include Pseudoeocypris pagei and Cypridea arvadensis. The age of this fauna suggests equivalence with the Love Ranch and Lobo Formations of southern New Mexico. The unit consists of approximately 350 m of interbedded red siltstone and boulder conglomerate derived from Lower Cretaceous strata overlain by a sequence of laminated shale and subordinate sandstone with a preserved thickness of 150 m.

Lawton, T.F.; Mack, G.H.; Lucas, S.G.; Kietzke, K.K. (New Mexico State Univ., Las Cruces (USA))

1989-09-01

63

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

SciTech Connect

The analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent. Annual variations in visible dust layers, oxygen isotopes, microparticle concentrations, conductivity, and identification of the historical (A.D. 1600) Huaynaputina ash permit accurate dating and time-scale verification. The fact that the Little Ice Age (about A.D. 1500 to 1900) stands out as a significant climatic event in the oxygen isotope and electrical condutivity records confirms the worldwide character of this event.

Thompson, L.G.; Mosley-Thompson, E.; Dansgaard, W.; Grootes, P.M.

1986-10-17

64

Age, Stratigraphy, and Correlations of the Late Neogene Purisima Formation, Central California Coast Ranges  

USGS Publications Warehouse

The Purisima Formation is an important upper Miocene and Pliocene stratigraphic unit in central California, cropping out from the coast at Point Reyes north of San Francisco to more extensive exposures in the Santa Cruz Mountains to the south. The fine-grained rocks in the lower parts of the Purisima Formation record a latest Miocene transgressive event, whereas the middle and upper parts of the formation consist of increasingly clastic-rich siltstones and sandstones resulting from uplift of adjacent coastal regions and the Sierra Nevada during Pliocene transgressive and regressive sea-level events. Exposures of the Purisima occur in three different, fault-bounded, structural blocks - the Santa Cruz, Pigeon Point, and Point Reyes tectonic blocks - that complicate correlations and regional age assignments. We summarize and compare published and new biostratigraphic and geochronologic data for various exposures of the Purisima Formation on the basis of mollusks, diatoms, radiometric dating, magnetostratigraphy, tephrochronology, and strontium isotope dating. On the basis of these data, we conclude that the Purisima Formation ranges in age from the latest Miocene (about 7 Ma) to the late Pliocene (about 2.6 Ma). The Purisima Formation of Santa Cruz County, exposed in the sea cliffs from Santa Cruz to Rio del Mar, is here designated a supplementary reference section because it is the most complete and well studied Purisima section in central California.

Powell, Charles L., II; Barron, John A.; Sarna-Wojcicki, Andrei M.; Clark, Joseph C.; Perry, Frank A.; Brabb, Earl E.; Fleck, Robert J.

2007-01-01

65

Spectral stratigraphy  

NASA Astrophysics Data System (ADS)

Stratigraphic and structural studies of the Wind River and Bighorn basins, Wyoming, and the Guerrero-Morelos basin, Mexico, have resulted in development of 'spectral stratigraphy.' This approach to stratigraphic analysis uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. This paper reviews selected published examples that illustrate this new stratigraphic procedure. Visible to thermal infrared laboratory, spectral measurements of sedimentary rocks are the physical basis for spectral stratigraphy. Results show that laboratory, field, and remote spectroscopy can augment conventional laboratory and field methods for petrologic analysis, stratigraphic correlation, interpretation of depositional environments, and construction of facies models. Landsat thematic mapper data are used to map strata and construct stratigraphic columns and structural cross sections at 1:24,000 scale or less. Experimental multispectral thermal infrared aircraft data facilitate lithofacies/biofacies analyses. Visible short-wavelength infrared imaging spectrometer data allow remote determination of the stratigraphic distribution of iron oxides, quartz, calcite, dolomite, gypsum, specific clay species, and other minerals diagnostic of environments of deposition. Development of a desk-top, computer-based, geologic analysis system that provides for automated application of these approaches to coregistered digital image and topographic data portends major expansion in the use of spectral stratigraphy for purely scientific (lithospheric research) or practical (resource exploration) objectives.

Lang, Harold R.

1991-09-01

66

Carboniferous age for the East Greenland “Devonian” basin: Paleomagnetic and isotopic constraints on age, stratigraphy, and plate reconstructions  

NASA Astrophysics Data System (ADS)

New paleomagnetic and isotopic data from East Greenland indicate that this classical “Devonian” basin was partly formed in Carboniferous. The basin preserves a stratigraphically linked magnetic reversal pattern of primary character. Paleomagnetic data indicate that the two stratigraphically lowermost intrabasinal angular unconformities, identified on each side of the basin, in fact correlate as one unconformity. This implies a 2 km reduction of the estimated basin thickness, and thus that the unconformity represents a major depositional hiatus. Successions below the unconformity are taken to be Devonian (Givetian) in age, on the basis of correlation with paleomagnetic reference poles. However, we argue that the overlying strata are Carboniferous, rather than Devonian, in age, on the basis of a ca. 336 Ma 40Ar/39Ar extrusive age for a basalt flow and paleomagnetic data. A Carboniferous age for the strata has significant implications for vertebrate evolution; fossils of a terrestial tetrapod, Ichthyostega, are found above the unconformity. Ichthyostega is regarded as the earliest fossil of an animal known to walk on land; however, our data suggest that these dry footsteps are much younger than previously believed. Our results are also significant for plate reconstructions. Paleomagnetic data indicate that the lower part of the basin was deposited at low southerly latitudes. Sediments above our Early Carboniferous unconformity were deposited approximately at lat 4°N, indicating that the continent had drifted northward. A minor pole-longitude misfit between Devonian and Carboniferous poles from East Greenland and North America implies (1) a closer pre Labrador Sea Greenland North America fit; (2) counterclockwise block rotations (10° 15°) of the study area; or (3) a combination of both. The East Greenland “Devonian” basin formed along the Caledonian spine of Euramerica, and counterclockwise block rotation may have occurred between sinistral faults resulting from continued relative movement between Baltica and Laurentia during Devonian and Carboniferous time.

Hartz, E. H.; Torsvik, T. H.; Andresen, A.

1997-08-01

67

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

68

Sedimentology, clay mineralogy and grain-size as indicators of 65 ka of climate change from El’gygytgyn Crater Lake, Northeastern Siberia  

Microsoft Academic Search

El’gygytgyn Crater Lake, NE Siberia was investigated for sedimentological proxies for regional climate change with a focus\\u000a on the past 65 ka. Sedimentological parameters assessed relative to magnetic susceptibility include stratigraphy, grain size,\\u000a clay mineralogy and crystallinity. Earlier work suggests that intervals of high susceptibility in these sediments are coincident\\u000a with warmer (interglacial-like) conditions and well-mixed oxygenated bottom waters. In contrast,

Celeste A. Asikainen; Pierre Francus; Julie Brigham-Grette

2007-01-01

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

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

71

Stratigraphy, palynology, and conchostracans of a Lower Cretaceous sequence at the Cañadón Calcáreo locality, Extra-Andean central Patagonia: age and palaeoenvironmental significance  

Microsoft Academic Search

The first palynologic record in a Lower Cretaceous sequence at the Cañadón Calcáreo locality of Extra-Andean central Patagonia is presented. It contributes a more precise chronology and palaeoenvironmental characterization of the sequence. The conchostracan faunal records support the palynologic results. Sedimentary environments are studied in relation to a tectogenetic development model. Detailed measurement of stratigraphic\\/sedimentologic sections in the field was

Wolfgang Volkheimer; Oscar F. Gallego; Nora G. Cabaleri; Claudia Armella; Paula L. Narváez; Diego G. Silva Nieto; Manuel A. Páez

2009-01-01

72

Revised stratigraphy of the Blanchetown Clay, Murray Basin: age constraints on the evolution of paleo Lake Bungunnia  

Microsoft Academic Search

Paleo Lake Bungunnia covered more than 40 000 km of southern Australia during the Plio-Pleistocene, although the age and origin of the lake remain controversial. The Blanchetown Clay is the main depositional unit and outcrop at Nampoo Station in far-western New South Wales provides the most continuous lacustrine section preserved in the basin. Here the Blanchetown Clay represents the maximum lake

S. McLaren; M. W. Wallace; B. J. Pillans; S. J. Gallagher; J. A. Miranda; M. T. Warne

2009-01-01

73

Stratigraphy, age and petrography of the Beni Issef successions (External Rif; Morocco): Insights for the evolution of the Maghrebian Chain  

NASA Astrophysics Data System (ADS)

In the Beni Issef Massif, nearly 30 km west of Chefchaouen (Morocco), the thickest post-nappe succession within the Rifian sector of the Maghrebian Chain seals the tectonic contact between the Intrarifian External Tanger and Loukkos Units, related to the Rifian External Domain. This succession is very important for the reconstruction of the deformation timing of the Rifian Maghrebids. The age of its base, in fact, is an important constraint for defining an upper boundary to the stacking of both the Intrarifian and Maghrebian Flysch Basin Units, because clasts fed by the Melloussa and Numidian Flysch Nappes are abundant in the conglomerate layers. Field and biostratigraphic analyses pointed out the presence of a Lower Beni Issef Fm, unconformable on the Intrarifian External Tanger and Loukkos Units, and an Upper Beni Issef Fm, unconformable on both the Intrarifian Units and the Lower Beni Issef Fm. The Lower Beni Issef Fm, 150 m thick, consists of lenticular conglomerates with huge blocks in a marly-clayey matrix, followed by marls and minor sandstones. It deposited in a siliciclastic platform, shows a fining upward trend and is affected by metre- to hectometre-sized, locally reversed, folds. Samples collected 45-50 m above the base of the formation resulted not older than Late Tortonian in age, but an older age for the base of the formation cannot be excluded. The Upper Beni Issef Fm, up to 550 m thick, starts with coarse conglomerates followed by medium- to coarse-grained well-bedded sandstones and by grey-blue marls and mudrocks. It indicates deposition in a channelized marine delta, with evolution towards pro-delta pelites, and shows sub-horizontal or gently dipping beds towards the east. Biostratigraphic data indicate a probable Messinian age for this formation. The composition of the arenites of both Lower Beni Issef and Upper Beni Issef Fms is quartzolithic and all samples show a notable content of monocrystalline well-rounded quartz and sedimentary lithic fragments. Detrital modes, all falling in the Quartzose Recycled and Transitional Recycled fields, suggest a provenance from recycling of sedimentary successions, easily recognizable in the Flysch Basin and External Units, mainly the Numidian Nappe sandstones. A Tortonian age of the Lower Beni Issef Fm would agree with the Late Serravallian age of the uppermost beds of the External Tanger Unit and indicate that the most probable age for the stacking of the Intrarifian Units falls in the Late Serravallian-Middle Tortonian time span. The Lower Beni Issef Fm was involved in a compressive tectonic phase testified by north-south striking folds. Later, probably during Messinian, the Upper Beni Issef Fm deposited in a younger intramontane basin, resting on both the Intrarifian Units and the Lower Beni Issef Fm. Successively, the Upper Beni Issef Fm was passively transported piggyback on top of the fold and thrust belt during later tectonic evolution of the Rifian Maghrebids. This tectonic evolution results quite similar to that recognized in the Tellian and Sicilian Maghrebids and also in the southern Apennines.

Di Staso, Angelida; Perrone, Vincenzo; Perrotta, Sonia; Zaghloul, Mohamed Najib; Durand-Delga, Michel

2010-09-01

74

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

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

Sequence stratigraphy evolution since 1970  

Microsoft Academic Search

This paper will address mainly industrial aspects of sequence stratigraphy since the seventies: new advances in seismic marine acquisition and large efforts for margins exploration, provided continuous 2D set of data, from platform environment to deep marine basins, revealing the importance of non-deposition periods. The seismic stratigraphy then allowed the development of the sequence stratigraphy at the end of the

Christian Ravenne

2002-01-01

77

International Commission on Stratigraphy  

NSDL National Science Digital Library

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

Stratigraphy, International C.

78

Sedimentology and paleoenvironment from the Maar Lac du Bouchet for the last climatic cycle, 0-120,000 years (Massif Central, France)  

Microsoft Academic Search

This paper summarizes sedimentological and geochemical studies from seven cores taken from the Bouchet crater lake, France.\\u000a It includes studies of water and soils from the drainage basin. The sedimentary record is subdivided into 14 distinct sedimentary\\u000a units, which comprise different combinations of 8 recurring lithofacies. The lithostratigraphic results are correlated with\\u000a prior information from magnetic-, pollen-, diatom-, and chrono-stratigraphy

Elisabeth Truze; Kerry Kelts

1993-01-01

79

Stratigraphy of the Martian northern plains  

NASA Astrophysics Data System (ADS)

The northern plains of Mars are roughly defined as the large continuous region of lowlands that lies below Martian datum, plus higher areas within the region that were built up by volcanism, sedimentation, tectonism, and impacts. These northern lowlands span about 50 x 106 km2 or 35 percent of the planet's surface. The age and origin of the lowlands continue to be debated by proponents of impact and tectonic explanations. Geologic mapping and topical studies indicate that volcanic, fluvial, and eolian deposition have played major roles in the infilling of this vast depression. Periglacial, glacial, fluvial, eolian, tectonic, and impact processes have locally modified the surface. Because of the northern plains' complex history of sedimentation and modification, much of their stratigraphy was obscured. Thus the stratigraphy developed is necessarily vague and provisional: it is based on various clues from within the lowlands as well as from highland areas within and bordering the plains. The results are summarized.

Tanaka, K. L.

80

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 A.

81

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

82

High resolution sequence stratigraphy of Scythian-early Anisian continental deposits of east of Paris basin: Applications to gas storage  

SciTech Connect

Continental facies of Scythian-early Anisian age (Buntsandstein) of East of the Paris Basin form the underground gas storage reservoir exploited by Gaz de France in the area of Nancy (east of France). An accurate sedimentological study and the application of Genetic Stratigraphy principles lead to the understanding of the deposition of fluvial, which form the reservoirs, and to the reconstruction of their geometries. The subsurface data are calibrated on outcrops. Three types of fluvial systems (braided, sinuous to straight and anastomosed) are defined. A special focus on anastomosed channels permits to differentiate a proximal and a distal facies. Study of laterally continuous outcrops induces recurrent cycles of thickness, velocity and time variations (few tens to hundred ka). These correspond to the highest frequence stratigraphic units, i.e. parasequences or genetic units. Maximum of channel and levee presentation occurs during base-level rise: base-level fall is characterised by amalgamation of sets, by-pass and erosion. This method is applied to subsurface data by an accurate calibration of well logs on cores. Thus the electric expression of genetic units corresponding to different environments is determined as well as the expression of base-level variations. The correlation of these units using stacking pattern method leads to a very fine subdivision of reservoir between timelines. Different orders of depositional sequences are pointed out, resulting in reservoir geometry characterization and permeability barrier distribution.

Roselyne, F.; Guillocheau, F. [Geosciences Rennes (France); Wicquart, E. [Gaz de France, Wilson (France)] [and others

1995-08-01

83

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

84

Use of Radioactive Tracers in Dynamic Sedimentology.  

National Technical Information Service (NTIS)

In the first part, developments in the use of radioactive tracers in sedimentology are recalled together with the corresponding fields of application and the identities of the main users. The state-of-the-art in France is also discussed; The main characte...

F. Tola

1982-01-01

85

Maastrichtian to Paleocene depositional environment of the Dakhla Formation, Western Desert, Egypt: sedimentology, mineralogy, and integrated micro- and macrofossil biostratigraphies  

Microsoft Academic Search

Integrated sedimentology, mineralogy, geochemistry, and microfossil and macrofossil biostratigraphies of the Maastrichtian–early Paleocene Dakhla Formation of the Western Desert, Egypt, provide improved age resolution, information on the cyclic nature of sediment deposition, and the reconstruction of depositional environments. Age control based on integrated biostratigraphies of planktic foraminifera, calcareous nannofossils and macrofossils yields the following ages for stratigraphic and lithologic sequences.

A. A. Tantawy; G. Keller; T. Adatte; W. Stinnesbeck; A. Kassab; P. Schulte

2001-01-01

86

Sequence stratigraphy interpretation of the central shelf area, offshore Louisiana  

Microsoft Academic Search

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

B. Radovich; T. Powell; M. Lovell; R. Jr. Mitchum

1990-01-01

87

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

88

Stratigraphy and sedimentology of the Upper Devonian Aztec Siltstone, southern Victoria Land, Antarctica  

Microsoft Academic Search

The Aztec Siltstone is a redbed sequence deposited on a broad, low-lying alluvial plain during Late Devonian times in southern Victoria Land, Antarctica. It outcrops between the Mawson and Mulock Glaciers and is the uppermost formation of the Taylor Group, the lower of the two Beacon Supergroup subdivisions in southern Victoria Land. The formation consists largely of fine- to medium-grained,

John G. Mcpherson

1978-01-01

89

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

SciTech Connect

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

Cloft, H.S.

1983-03-01

90

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

Microsoft Academic Search

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

Harriet S. Cloft

1983-01-01

91

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

Microsoft Academic Search

World-class hydrocarbon accumulations occur in many ancient evaporite-related basins. Seals and traps of such accumulations are, in many cases, controlled by the stratigraphic distribution of carbonate–evaporite facies transitions. Evaporites may occur in each of the systems tracts within depositional sequences. Thick evaporite successions are best developed during sea level lowstands due to evaporative drawdown. Type 1 lowstand evaporite systems are

J. F Sarg

2001-01-01

92

STRATIGRAPHY AND SEDIMENTOLOGY OF THE UPPER JURASSIC MORRISON FORMATION, DILLON, MONTANA  

Microsoft Academic Search

Abstract—Red, purple and gray-green mudrocks near Dillon, Montana, have been mapped traditionally as the Up- per Jurassic Morrison Formation. There are very few studies of the Mesozoic strata in this area and questions exist as to whether this unit actually is the Morrison Formation, or whether it is similarly variegated mudrocks of other formations at nearly the same stratigraphic interval.

JON J. SMITH; STEPHEN T. HASIOTIS; WILLIAM J. FRITZ

2006-01-01

93

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

94

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

Microsoft Academic Search

Within the context of the Heidelberg Basin Drilling Project (Gabriel et al. 2008), a detailed sediment succession is presented here based upon deep drillings taken at Heidelberg UniNord and Mannheim Käfertal. Sediment structures, and micromorphological and pollen analyses were conducted and used to reconsider some of the climate transitions within the lower Pleistocene. A new and novel scenario is postulated

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

2010-01-01

95

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

96

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

97

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

98

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

99

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

100

SEDIMENTOLOGY AND STRATIGRAPHY OF THE UPPER MIOCENE EL BOLEO FORMATION, SANTA ROSALÍA, BAJA CALIFORNIA, MEXICO  

Microsoft Academic Search

The transtensional Upper Miocene Santa Rosalía basin, located in the east-central part of the Baja California Peninsula, consists of almost 500 m of non-marine to marine sedimentary deposits, and interbedded tuffaceous beds. The Santa Rosalía basin is a NW-SE elongated fault-bounded depocenter that records the sedimentation from Upper Miocene to Pleistocene time. The sequence is divided in El Boleo, La

Lucas Ochoa-Landín; Joaquín Ruiz; Thierry Calmus; Efrén Pérez-Segura; Francisco Escandón

101

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

Microsoft Academic Search

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

Philip Rae Teal

1979-01-01

102

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

NASA Astrophysics Data System (ADS)

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 least 7 m thick and define a “wetting-upward” succession which records a progressive increase in the influence of groundwater and, ultimately, surface water in controlling primary depositional processes. The Burns lower unit is interpreted as a dry dune field (though grain composition indicates an evaporitic source), whose preserved record of large-scale cross-bedded sandstones indicates either superimposed bedforms of variable size or reactivation of lee-side slip faces by episodic (possibly seasonal) changes in wind direction. The boundary between the lower and middle units is a significant eolian deflation surface. This surface is interpreted to record eolian erosion down to the capillary fringe of the water table, where increased resistance to wind-induced erosion was promoted by increased sediment cohesiveness in the capillary fringe. The overlying Burns middle unit is characterized by fine-scale planar-laminated to low-angle-stratified sandstones. These sandstones accumulated during lateral migration of eolian impact ripples over the flat to gently undulating sand sheet surface. In terrestrial settings, sand sheets may form an intermediate environment between dune fields and interdune or playa surfaces. The contact between the middle and upper units of the Burns formation is interpreted as a diagenetic front, where recrystallization in the phreatic or capillary zones may have occurred. The upper unit of the Burns formation contains a mixture of sand sheet facies and interdune facies. Interdune facies include wavy bedding, irregular lamination with convolute bedding and possible small tepee or salt-ridge structures, and cm-scale festoon cross-lamination indicative of shallow subaqueous flows marked by current velocities of a few tens of cm/s. Most likely, these currents were gravity-driven, possibly unchannelized flows resulting from the flooding of interdune/playa surfaces. However, evidence for lacustrine sedimentation, including mudstones or in situ bottom-growth evaporites, has not been observed so far at Eagle and Endurance craters. Mineralogical and elemental data indicate that the eolian sandstones of the lower and middle units, as well as the subaqueous and eolian deposits of the Burns upper unit, were derived from an evaporitic source. This indirectly points to a temporally equivalent playa where lacustrine evaporites or ground-water-generated efflorescent crusts were deflated to provide a source of sand-sized particles that were entrained to form eolian dunes and sand sheets. This process is responsible for the development of sulfate eolianites at White Sands, New Mexico, and could have provided a prolific flux of sulfate sediment at Meridiani. Though evidence for surface water in the Burns formation is mostly limited to the upper unit, the associated sulfate eolianites provide strong evidence for the critical role of groundwater in controlling sediment production and stratigraphic architecture throughout the formation.

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

2005-11-01

103

Sedimentology and stratigraphy of Prospect Formation, Te Anau Basin, western Southland, New Zealand  

Microsoft Academic Search

The syntectonic late Miocene—Pliocene Prospect Formation, comprising over 3000 m of gravels and sands, forms the uppermost preglacial unit in the central Te Anau Basin, western Southland, New Zealand. Its inferred distal correlatives, the marine Rowallan Sandstone and Te Waewae Formation, lie to the south in the Waiau Basin. These two units are removed from the Waiau Group and, together

V. Manville

1996-01-01

104

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

105

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

106

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

107

Stratigraphy, sedimentology, and structural geology of gypsum caves in east central New Mexico  

Microsoft Academic Search

Hundreds of solution caves have developed in evaporites and carbonates of the Permian San Andres Formation where it crops\\u000a out between Vaughn and Roswell, New Mexico, USA. Several of the caves are over 3.2 km (2 miles) in length, and the deepest\\u000a has a vertical extent of over 120 m (400 feet). These gypsum caves afford an extraordinary opportunity to

Jeffrey Forbes; Ray Nances

1997-01-01

108

Age of Zhoukoudian Homo erectus determined with (26)Al/(10)Be burial dating.  

PubMed

The age of Zhoukoudian Homo erectus, commonly known as 'Peking Man', has long been pursued, but has remained problematic owing to the lack of suitable dating methods. Here we report cosmogenic (26)Al/(10)Be burial dating of quartz sediments and artefacts from the lower strata of Locality 1 in the southwestern suburb of Beijing, China, where early representatives of Zhoukoudian Homo erectus were discovered. This study marks the first radioisotopic dating of any early hominin site in China beyond the range of mass spectrometric U-series dating. The weighted mean of six meaningful age measurements, 0.77 +/- 0.08 million years (Myr, mean +/- s.e.m.), provides the best age estimate for lower cultural layers 7-10. Together with previously reported U-series dating of speleothem calcite and palaeomagnetic stratigraphy, as well as sedimentological considerations, these layers may be further correlated to S6-S7 in Chinese loess stratigraphy or marine isotope stages (MIS) 17-19, in the range of approximately 0.68 to 0.78 Myr ago. These ages are substantially older than previously supposed and may imply early hominin's presence at the site in northern China through a relatively mild glacial period corresponding to MIS 18. PMID:19279636

Shen, Guanjun; Gao, Xing; Gao, Bin; Granger, Darryl E

2009-03-12

109

Ages and stratigraphy of lunar mare basalts in Mare Frigoris and other nearside maria based on crater size-frequency distribution measurements  

Microsoft Academic Search

We report on ages derived from impact crater counts for exposed mare basalt units in the northern part of the lunar nearside hemisphere (Mare Frigoris), the eastern and northeastern part of the nearside hemisphere (Lacus Temporis, Joliot, Hubble, Goddard, Mare Marginis, and Mare Smythii), the central part of the nearside hemisphere (Palus Putredinis, Mare Vaporum, and Sinus Medii), and the

H. Hiesinger; J. W. Head III; U. Wolf; R. Jaumann; G. Neukum

2010-01-01

110

Workshop on quantitative dynamic stratigraphy  

SciTech Connect

This document discusses the development of quantitative simulation models for the investigation of geologic systems. The selection of variables, model verification, evaluation, and future directions in quantitative dynamic stratigraphy (QDS) models are detailed. Interdisciplinary applications, integration, implementation, and transfer of QDS are also discussed. (FI)

Cross, T.A.

1988-04-01

111

Stratigraphy of the crater Copernicus  

NASA Astrophysics Data System (ADS)

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

Paquette, R.

1984-05-01

112

Sedimentological techniques applied to the hydrology of the Atlantic coastal plain in South Carolina and Georgia near the Savannah River Site  

SciTech Connect

Potential for migration of contaminants in ground water under the Savannah River from South Carolina into Georgia near the US Department of Energy (DOE) Savannah River Site (SRS). The SRS is located in the inner Atlantic Coastal Plain of South Carolina and is underlain by 200 to more than 300 meters of permeable, unconsolidated to poorly consolidated sediments of Cretaceous and Tertiary age. The US Geological Survey, in cooperation with the US Department of Energy and the Georgia Department of Natural Resources, is evaluating ground-water flow through the Coastal Plain sediments in the area. Preliminary hydrologic studies conducted to provide the data needed for digital modeling of the ground-water flow system identified the need for more extensive investigation into the influence of the geologic complexities on that flow system. The Coastal Plain physiographic province in South Carolina and Georgia is comprised of a complex wedge of fluvial, deltaic, and marine sedimentary deposits locally modified by faulting. Several techniques commonly used in petroleum basin analysis (sequence stratigraphy, biostratigraphy, detailed core description, and geophysical well log analysis), were used together with water-level measurements, aquifer-test data, and geochemical data to identify six regional aquifers. Hydraulic conductivity distribution maps within each of these aquifers were constructed using textural analysis of core materials, aquifer test data, and depositional system reconstruction. Sedimentological techniques were used to improve understanding of the depositional system and the ground-water flow system dynamics, and to help focus research in areas where additional hydrologic, geologic, and aquifer-test data are needed.

Falls, F.W. (Geological Survey, Columbia, SC (United States)); Baum, J.S. (Geological Survey, Atlanta, GA (United States)); Edwards, L.E. (Geological Survey, Reston, VA (United States))

1994-03-01

113

Integrating sequence stratigraphy and rock-physics to interpret seismic amplitudes and predict reservoir quality  

NASA Astrophysics Data System (ADS)

This dissertation focuses on the link between seismic amplitudes and reservoir properties. Prediction of reservoir properties, such as sorting, sand/shale ratio, and cement-volume from seismic amplitudes improves by integrating knowledge from multiple disciplines. The key contribution of this dissertation is to improve the prediction of reservoir properties by integrating sequence stratigraphy and rock physics. Sequence stratigraphy has been successfully used for qualitative interpretation of seismic amplitudes to predict reservoir properties. Rock physics modeling allows quantitative interpretation of seismic amplitudes. However, often there is uncertainty about selecting geologically appropriate rock physics model and its input parameters, away from the wells. In the present dissertation, we exploit the predictive power of sequence stratigraphy to extract the spatial trends of sedimentological parameters that control seismic amplitudes. These spatial trends of sedimentological parameters can serve as valuable constraints in rock physics modeling, especially away from the wells. Consequently, rock physics modeling, integrated with the trends from sequence stratigraphy, become useful for interpreting observed seismic amplitudes away from the wells in terms of underlying sedimentological parameters. We illustrate this methodology using a comprehensive dataset from channelized turbidite systems, deposited in minibasin settings in the offshore Equatorial Guinea, West Africa. First, we present a practical recipe for using closed-form expressions of effective medium models to predict seismic velocities in unconsolidated sandstones. We use an effective medium model that combines perfectly rough and smooth grains (the extended Walton model), and use that model to derive coordination number, porosity, and pressure relations for P and S wave velocities from experimental data. Our recipe provides reasonable fits to other experimental and borehole data, and specifically improves the predictions of shear wave velocities. In addition, we provide empirical relations on normal compaction depth trends of porosity, velocities, and VP/VS ratio for shale and clean sands in shallow, supra-salt sediments in the Gulf of Mexico. Next, we identify probable spatial trends of sand/shale ratio and sorting as predicted by the conventional sequence stratigraphic model in minibasin settings (spill-and-fill model). These spatial trends are evaluated using well data from offshore West Africa, and the same well data are used to calibrate rock physics models (modified soft-sand model) that provide links between P-impedance and quartz/clay ratio, and sorting. The spatial increase in sand/shale ratio and sorting corresponds to an overall increase in P-impedance, and AVO intercept and gradient. The results are used as a guide to interpret sedimentological parameters from seismic attributes, away from the well locations. We present a quantitative link between carbonate cement and seismic attributes by combining stratigraphie cycles and the rock physics model (modified differential effective medium model). The variation in carbonate cement volume in West Africa can be linked with two distinct stratigraphic cycles: the coarsening-upward cycles and the fining-upward cycles. Cemented sandstones associated with these cycles exhibit distinct signatures on P-impedance vs. porosity and AVO intercept vs. gradient crossplots. These observations are important for assessing reservoir properties in the West Africa as well as in other analogous depositional environments. Finally, we investigate the relationship between seismic velocities and time temperature index (TTI) using basin and petroleum system modeling at Rio Muni basin, West Africa. We find that both VP and VS increase exponentially with TTI. The results can be applied to predict TTI, and thereby thermal maturity, from observed velocities.

Dutta, Tanima

114

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

115

Sedimentological analysis using geophysical well logs  

SciTech Connect

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

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

1993-09-01

116

Lower Cretaceous nannofossil stratigraphy of the Great Valley sequence  

SciTech Connect

The calcareous nannofossil stratigraphy of four sections in the Great Valley Sequence of the Sacramento Valley, California, has been investigated in detail. These sections include Grindstone and Stony Creeks (Glenn County) and McCarty Creek and the Vestal Road segment of Dry Creek (both in Tehama County). The ages of the sections investigated, which have independently been studied by ammonite, pelecypod, and radiolaria biostratigraphers, range from Berriasian to Albian. Nannofossils occur rarely in these sediments and are restricted largely to mudstone deposited in the most distal portions of turbiditic sequences. Approximately 5% of the samples collected are nannofossiliferous. Assemblages contain some elements of Boreal floras but are dominated by Tethyan taxa. These assemblages are more directly comparable to those of stratotype sequences in Europe than are the other fossil groups, but the ages given are generally similar. However, two major discrepancies do exist. The results of this study indicate that the pelecypod, Buchia aff. B. okensis zone is Berriasian in age, not Tithonian as previously believed and the B. pacifica zone is not entirely Valanginian but partly Berriasian. Nannofossil data provide useful age calibrations for ammonite stratigraphy. The stratigraphy obtained supports structural interpretations based upon Buchia, in particular that the Paskenta fault zone remained active throughout the Early Cretaceous. The study illustrates that nannofossil biostratigraphy can be effectively used to date sediments deposited in convergent margin settings.

Bralower, T.J. (Florida International Univ., Miami, FL (USA))

1990-05-01

117

Simplifying the stratigraphy of time  

Microsoft Academic Search

We propose ending the distinction between the dual stratigraphic terminology of time-rock units (of chronostratigraphy) and geologic time units (of geochronology). The long-held, but widely misunderstood, distinction between these two essentially parallel time scales in stratigraphy has been rendered unnecessary by the widespread adoption of the global stratotype sections and points (GSSP---golden spike) principle in defining intervals of geologic time

Jan Zalasiewicz; Alan Smith; Patrick Brenchley; Jane Evans; Robert Knox; Nicholas Riley; Andrew Gale; F. John Gregory; Adrian Rushton; Philip Gibbard; Stephen Hesselbo; John Marshall; Michael Oates; Peter Rawson; Nigel Trewin

2004-01-01

118

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

119

Cycles and events in stratigraphy  

SciTech Connect

This book reviews and discusses the most up-to-date knowledge in the fields of cyclostratigraphy and event stratigraphy. The book contains 48 papers contributed by the most knowledgeable geologists and paleontologists in the fields of cycle and event stratigraphy. It is divided into two parts. Part one is concerned with the structure of individual beds and larger cycles and sequences and discusses; rhythmic stratification, event stratification, diagenetic overprint, cherts and phosphorites, and preservation and biologic destruction of laminated sediments. Part two, on larger cycles and sequences, looks at sequences, hierarchies, causes and environmental expression, and timing and correlation, i.e. the cycles of frequencies from millions of years to thousands of years (Milankovich band). Summaries on spectral analysis are also presented. There are 80 pages of references and a comprehensive index. It is extensively illustrated with line drawings and graphs. Practicing sedimentary geologists without access to a good library or find it hard to keep up with the plethora of journal articles and want a refresher in this area of stratigraphy will find the book particularly useful.

Einsele, G.; Ricken, W.; Seilacher, A. (eds.)

1991-01-01

120

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

121

Application of Fluorescent-and Radioactive Tracers in Sedimentology.  

National Technical Information Service (NTIS)

The development of techniques of sediment labelling, creating the possibility of using fluorescent and radioactive tracers not yet applied in Brazil, in the area of sedimentology, is studied. (Atomindex citation 14:771486)

L. M. L. de Alencar

1981-01-01

122

An Online Guide to Sequence Stratigraphy  

NSDL National Science Digital Library

This online guide focuses primarily on the application of sequence stratigraphy to outcrops. Topics covered include sediment accumulation and the accommodation space equation, parasequences, stacking patterns, depositional sequences, surfaces, type I and type II sequences, application of this information to outcrops, chronostratigraphic applications and carbonate sequence stratigraphy. There are references for this material and a glossary of terms to use with this guide.

Holland, Steven

123

Seismic stratigraphy moves towards interactive analysis  

SciTech Connect

Seismic stratigraphy aids interpretation of complex geology, particularly by helping effectively identify the right geologic environment for potential hydrocarbon traps. This, the third article in a series, reviews advanced geophysical techniques, including direct hydrocarbon indicators, shear waves and seismic modeling (the fourth key seismic stratigraphy approach).

Simson, S.F.; Nelson, M.R.

1985-04-01

124

Seismic stratigraphy moves towards interactive analysis  

SciTech Connect

Seismic stratigraphy aids interpretation of complex geology, particularly by helping effectively identify the right geologic environment for potential hydrocarbon traps. This article, the second in a series of three, reviews three of the four key approaches to interpreting stratigraphy from seismic, namely, seismic sequence analysis, seismic facies analysis and reflection character analysis.

Simson, S.F.; Nelson, H.R.

1985-03-01

125

Structure and stratigraphy of Home Plate from the Spirit Mars Exploration Rover  

NASA Astrophysics Data System (ADS)

Home Plate is a layered plateau observed by the Mars Exploration Rover Spirit in the Columbia Hills of Gusev Crater. The structure is roughly 80 m in diameter, and the raised margin exposes a stratigraphic section roughly 1.5 m in thickness. Previous work has proposed a pyroclastic surge, possibly followed by aeolian reworking of the ash, for the depositional origin for these beds. We have performed a quantitative analysis of the structure, stratigraphy, and sedimentology at this location. Our results are consistent with an explosive volcaniclastic origin for the layered sediments. Analysis of bedding orientations over half of the circumference of Home Plate reveals a radially inward dipping structure, consistent with deposition in the volcanic vent, or topographic draping of a preexisting depression. Detailed observations of the sedimentology show that grain sorting varies significantly between outcrops on the east and west sides. Observations on the western side show a well-sorted population of sand sized grains which comprise the bedrock, while the eastern margin shows a wider range of grain sizes, including some coarse granules. These observations are consistent with primary deposition by a pyroclastic surge. However, aeolian reworking of the upper stratigraphic unit is not ruled out. Identification of explosive volcanic products on Mars may implicate magma interaction with subsurface hydrologic reservoirs in the past.

Lewis, Kevin W.; Aharonson, Oded; Grotzinger, John P.; Squyres, Steven W.; Bell, James F.; Crumpler, Larry S.; Schmidt, Mariek E.

2008-11-01

126

Callovian-Volgian dinocyst stratigraphy of the Central Trough in the Danish North Sea Area  

Microsoft Academic Search

The Danish North Sea wells U-1 and E-1 have been dated on the basis of dinocysts and correlated with the established ammonite stratigraphy of Western Europe. The palynostratigraphy of the U-1 well shows that the age of the Jurassic lithostratigraphic units is of Callovian to Kimmeridgian age. In the E-1 well, only the upper part of the Farsund Formation (of

NIELS E. POULSEN

127

Organic micropollutants in lakes: A sedimentological approach  

SciTech Connect

Many very persistent and lipophilic compounds, considered to be of concern for chronic toxicity and bioaccumulation, are generally present in surface waters at very low and variable concentrations. Sediments represent a concentrated pool for these compounds and consequently they are often analyzed instead of water. Some theoretical models have been proposed recently in order to estimate the concentration of these pollutants in water and their potential risk for aquatic biota and human health. In this work sediments from three subalpine lakes located in Northern Italy, very close to each other but with different anthropogenic loads, were collected at several stations for determination of the classes of organic micropollutants of urban, industrial, and agricultural origin. Results show that urban and industrial pollution are predominant in this area. Two classes of micropollutants seem to be most related to anthropogenic activities: PAH and trichloroalkylphosphates. The first reaches lake sediments through atmospheric deposition and point sources; the second, present only in two lakes, is more likely to be due to industrial effluents. The advantages and limitations of the sedimentological approach for risk assessment in the aquatic environment are discussed.

Galassi, S.; Provini, A.; De Paolis, A. (Water Research Institute, Brugherio (Italy))

1990-04-01

128

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

129

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

130

A medial to distal volcaniclastic record of an andesite stratovolcano: detailed stratigraphy of the ring-plain succession of south-west Taranaki, New Zealand  

NASA Astrophysics Data System (ADS)

The >25 ka volcaniclastic ring-plain succession in south-west Taranaki has been remapped to establish a much more detailed understanding of the older stratigraphic record of Mt. Taranaki. Coastal cliff exposures show a range of volcaniclastic lithofacies, including debris-avalanche and lahar deposits, and allow a detailed chronological reconstruction of past volcanic and sedimentary events. Five new debris-avalanche deposits were identified, and their distribution in coastal cross-sections mapped. In addition, four previously described units were renamed and their stratigraphic position and lateral extent redefined. Chronostratigraphic control of the younger (<50 ka) sequence was obtained by radiocarbon dating of wood found within, or peat interbedded with, the deposits. Emplacement ages of the older units were estimated from their stratigraphic position and underlying marine wave-cut surfaces. Overall, at least 14 widespread debris-avalanche deposits occur within the <200 ka ring-plain record of Mt. Taranaki, suggesting one major edifice failure on average every 14,000 years, with an increase in frequency since 40 ka. The stratigraphic reconstruction of the ring-plain succession showed that the same pattern of deposition was repeatedly produced throughout the existence of Mt. Taranaki. Depending on their sedimentological characteristics, the different volcanic and sedimentary lithofacies can be related to phases of edifice-construction or collapse events. Based on the identified cyclic sedimentation pattern, we present a new episodic stratigraphy that integrates existing and new lithostratigraphic units into a coherent chronostratigraphic framework that can be applied to the entire volcanic and volcaniclastic succession at Mt. Taranaki. This model takes into account the complex geological processes that have taken place on the volcano and provides a more uniform stratigraphic terminology that could be applied to repeatedly collapsing stratovolcanoes elsewhere.

Zernack, A. V.; Cronin, S. J.; Neall, V. E.; Procter, J. N.

2011-11-01

131

Upper Neogene stratigraphy and tectonics of Death Valley — a review  

NASA Astrophysics Data System (ADS)

New tephrochronologic, soil-stratigraphic and radiometric-dating studies over the last 10 years have generated a robust numerical stratigraphy for Upper Neogene sedimentary deposits throughout Death Valley. Critical to this improved stratigraphy are correlated or radiometrically-dated tephra beds and tuffs that range in age from > 3.58 Ma to < 1.1 ka. These tephra beds and tuffs establish relations among the Upper Pliocene to Middle Pleistocene sedimentary deposits at Furnace Creek basin, Nova basin, Ubehebe-Lake Rogers basin, Copper Canyon, Artists Drive, Kit Fox Hills, and Confidence Hills. New geologic formations have been described in the Confidence Hills and at Mormon Point. This new geochronology also establishes maximum and minimum ages for Quaternary alluvial fans and Lake Manly deposits. Facies associated with the tephra beds show that ˜3.3 Ma the Furnace Creek basin was a northwest-southeast-trending lake flanked by alluvial fans. This paleolake extended from the Furnace Creek to Ubehebe. Based on the new stratigraphy, the Death Valley fault system can be divided into four main fault zones: the dextral, Quaternary-age Northern Death Valley fault zone; the dextral, pre-Quaternary Furnace Creek fault zone; the oblique-normal Black Mountains fault zone; and the dextral Southern Death Valley fault zone. Post - 3.3 Ma geometric, structural, and kinematic changes in the Black Mountains and Towne Pass fault zones led to the break up of Furnace Creek basin and uplift of the Copper Canyon and Nova basins. Internal kinematics of northern Death Valley are interpreted as either rotation of blocks or normal slip along the northeast-southwest-trending Towne Pass and Tin Mountain fault zones within the Eastern California shear zone.

Knott, J. R.; Sarna-Wojcicki, A. M.; Machette, M. N.; Klinger, R. E.

2005-12-01

132

Coastal chevron deposits - sedimentology, methods and aeolian versus tsunamigenic origin  

NASA Astrophysics Data System (ADS)

The origin of v-shaped sediment bodies, so-called "chevrons", is currently controversially discussed. The term "chevron" is presently only defined in terms of the morphology of the sediment body, but not in terms of its genesis. Both an aeolian and an impact-tsunami origin are discussed. In this study, the sedimentology and origin of chevrons is investigated, examining deposits from the US west coast and the coast of Western Australia. We use internal structures obtained in trenches or by ground penetrating radar surveys, trenches, ages gained by radiocarbon and optically stimulated luminescence dating, grain size analysis and the general sediment composition. If the chevrons were deposited by a tsunami, all chevrons along one coastline should possess the same depositional ages, the grain-size distribution should be polymodal indicating various sediment sources and internal structures should be restricted mainly to normal grading. In case of an aeolian origin, the ages of the individual chevrons may vary and internal ages will reflect the migration of the sediment body. Furthermore, cross bedding should be present throughout the sediment body and soil horizons may represent inactive phases. Preliminary results indicate the presence of internal cross bedding and an unimodal grain-size distribution of the surveyed chevrons. Ages decrease in landward transport direction and to the top within vertical successions. At some locations soil layers intercalate between well sorted sands. The mean grain size of the chevron sands is 0.11-0.25 mm. A comparison of the chevron components with the mineral content of possible sediment sources (e.g., rivers, beaches, cliffs) shows that the chevrons are composed of the fine grain size fraction of the respective sources. Sediments of this grain size can easily be transported by aeolian forces under the local prevailing wind conditions. Terrestrial gastropods found within the chevrons give evidence of a long term development of these sediment bodies. Therefore, results of this study point rather to an aeolian than a tsunamigenic origin of the surveyed chevrons.

Spiske, Michaela; Garcia Garcia, Anna-Marietta; Tsukamoto, Sumiko; Schmidt, Volkmar

2013-04-01

133

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

134

Event Stratigraphy across the Cretaceous-Tertiary Boundary  

NASA Astrophysics Data System (ADS)

The Cretaceous-Tertiary (K-T) transition, that spans paleomagnetic Chron 29R, is one of the most widely studied intervals in Earth history. This interval spans a number of globally correlatable events, such as geochemical anomalies (iridium, PGE's), stable isotopes (carbon 13 shift, climate change), lithological changes (red and black clay layers), and biotic events (species evolution and extinction, the mass extinction of tropical and subtropical planktic foraminifera and calcareous nannoplankton). In addition, there are important, though regionally restricted correlatable events in Central America and the Caribbean that include multiple spherule-rich layers in the latest Maastrichtian and in the early Danian, and early Danian Ir and PGE anomalies. Integration of these diverse correlatable events provides high-resolution and globally reliable event stratigraphy for the K-T transition. Event stratigraphy reveals the relative ordering of a sequence of events through time, the higher the number of correlatable events in a stratigraphic sequence, the better the age resolution is. Events may be missing due to erosion or a hiatus, insufficient sample resolution, or tectonic disturbance, though the relative ordering of the remaining events remains the same. Chronostratigraphic ages for the various events can be derived based on paleomagnetic and radiometric dating, and extrapolation based on the assumption of constant sediment accumulation rates. Although uncertainties associated with each of the derived ages for the correlatable events provides significant error margins, the overall sequence of closely spaced events across the K-T transition provides high resolution time control.

Keller, G.

2001-05-01

135

Sedimentology of Arctic Fiords Experiment (SAFE): Project Introduction  

Microsoft Academic Search

The Geological Survey of Canada's project SAFE (Sedimentology of Arctic Fiords Experiment) was initiated in 1981 and is being car- ried out in a series of fiords situated along the east coast of Baffin Island. SAFE emphasizes the study of the Quaternary history and modern processes of arctic fiord environments. Project participants are interested in evaluating the significance of the

J. P. M. SYVITSKP; C. T. SCHAFER

136

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

137

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

138

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

139

Seismic stratigraphy of the Bahamas  

SciTech Connect

Seismic reflection profiles from the Straits of Florida, Northwest Providence Channel, Tongue of the Ocean, and Exuma Sound reveal a seismic stratigraphy characterized by a series of prograding Upper Cretaceous and Tertiary seismic sequences with seismic velocities generally less than 4 km/sec overlying a Lower Cretaceous section of low-amplitude reflections which are more nearly horizontal than the overlying prograding clinoforms and have seismic velocities greater than 5 km/sec. The prograding units are detrital shallow-water carbonates shed from nearby carbonate banks into deep intrabank basins that were established in the Late Cretaceous. The Lower Cretaceous units are probably shallow-water carbonate banks that were drowned in the middle Cretaceous but which, during the Early Cretaceous, extended from Florida throughout the Bahamas region. The seismic reflection profiles reveal a sharp angular unconformity at 5-sec two-way traveltime in northwest Tongue of the Ocean, suggesting a rift-drift unconformity and deposition on thinned continental crust. No such unconformity is seen in central and southeast Tongue of the Ocean or in Exuma Sound, suggesting that these areas are built on oceanic crust.

Ladd, J.W.; Sheridan, R.E.

1987-06-01

140

Paleozoic cratonal/miogeoclinal stratigraphy in the western Mojave Desert  

SciTech Connect

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

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

1991-02-01

141

Sedimentology of the Early Jurassic terrestrial Steierdorf Formation in Anina, Colonia Ceh? Quarry, South Carpathians, Romania  

NASA Astrophysics Data System (ADS)

K?dzior, A. and Popa, E.M. 2013. Sedimentology of the Early Jurassic terrestrial Steierdorf Formation in Anina, Colonia Ceh? Quarry, South Carpathians, Romania. Acta Geologica Polonica, 63 (2), 175-199. Warszawa. The continental, coal bearing Steierdorf Formation, Hettangian - Sinemurian in age, is included in the Mesozoic cover of the Re?i?a Basin, Getic Nappe, South Carpathians, Romania. The Steierdorf Formation can be studied in Anina, a coal mining center and an exceptional locality for Early Jurassic flora and fauna, occurring in the middle of the Re?i?a Basin. This paper presents the results of sedimentological, stratigraphical and paleobotanical researches undertaken in Colonia Ceh? open cast mine in Anina, where the Steierdorf Formation outcrops widely. Several sedimentary facies associations have been described, these associations permitting the reconstruction of various depositional systems such as alluvial fans, braided and meandering river systems, as well as lacustrine and coal generating marsh systems of the Steierdorf Formation. The sedimentary associations recorded within the Steierdorf Formation show a gradual fining upward trend, pointing to a rising marine water table and a decreasing relief within the source area.

K?dzior, Artur; Popa, Mihai E.

2013-06-01

142

Sedimentology and stratigraphy of the Palisades, Lower Comanche, and Arroyo Grande areas of the Colorado River Corridor, Grand Canyon, Arizona  

USGS Publications Warehouse

This report analyzes various depositional environments in three archaeologically significant areas of the Colorado River corridor in Grand Canyon. Archaeological features are built on and buried by fluvial, aeolian, and locally derived sediment, representing a complex interaction between geologic and cultural history. These analyses provide a basis for determining the potential influence of Glen Canyon Dam operations on selected archaeological sites and thus for guiding dam operations in order to facilitate preservation of cultural resources. This report presents initial results of a joint effort between geologists and archaeologists to evaluate the significance of various depositional processes and environments in the prehistoric formation and modern preservation of archaeological sites along the Colorado River corridor in Grand Canyon National Park. Stratigraphic investigations of the Palisades, Lower Comanche, and Arroyo Grande areas of Grand Canyon yield detailed information regarding the sedimentary history at these locations. Reconstruction of past depositional settings is critical to a thorough understanding of the geomorphic and stratigraphic evolution of these three archaeologically significant areas. This examination of past sedimentary environments allows the relative significance of fluvial, aeolian, debris-fan, and slope-wash sedimentary deposits to be identified at each site. In general the proportion of fluvial sediment (number and thickness of flood deposits) is shown to decrease away from the river, and locally derived sediment becomes more significant. Flood sequences often occur as 'couplets' that contain a fluvial deposit overlain by an interflood unit that reflects reworking of fluvial sediment at the land surface by wind and local runoff. Archaeological features are built on and buried by sediment of various depositional environments, implying a complex interaction between geologic and cultural history. Such field analysis, which combines geological and archaeological information and techniques, can provide a basis for future determination of the effects of Glen Canyon Dam operations on selected areas of the river corridor. This knowledge is essential to the development of preservation strategies for cultural resources in Grand Canyon.

Draut, Amy E.; Rubin, David M.; Dierker, Jennifer L.; Fairley, Helen C.; Griffiths, Ronald E.; Hazel, Joseph E., Jr.; Hunter, Ralph E.; Kohl, Keith; Leap, Lisa M.; Nials, Fred L.; Topping, David J.; Yeatts, Michael

2005-01-01

143

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

144

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

145

Sedimentology and Stratigraphy of the Palisades, Lower Comanche, and Arroyo Grande Areas of the Colorado River Corridor, Grand Canyon, Arizona.  

National Technical Information Service (NTIS)

This report presents initial results of a joint effort between geologists and archaeologists to evaluate the significance of various depositional processes and environments in the prehistoric formation and modern preservation of archaeological sites along...

A. E. Draut D. M. Rubin J. L. Dierker H. C. Fairley R. E. Griffiths

2005-01-01

146

Stratigraphy of nutrients and metals in sediment profiles of two dimictic lakes in North-Eastern Germany  

NASA Astrophysics Data System (ADS)

A sedimentological study of two dimitic lakes in North-Eastern Germany provided a record of anthropogenic impacts and historical changes of water quality. The upper 50 cm sediment profiles were compared for major nutrients and selected major trace elements. The sediments were dated by 210Pb and 137Cs measurement. The upper 50 cm sediment profiles represent approximately the last 100 years of history in both lakes. Element analyses show different characteristic stratigraphic patterns in both lakes. Based on the nutrient and metal stratification, three characteristic time periods can be documented for both lakes. In addition to agricultural use of the catchment area, atmospheric pollution greatly influenced the metal concentration in the sediment layers. Variation in the external loading and redox conditions in the hypolimnion explain the variation in the composition and accumulation of metals in the sediment stratigraphy. No increases or changes in the trophic level of either lake could be documented based on the accumulation of the nutrients C, N and P. The ratio of Fe/Mn and Fe/Ca characterized the changing redox conditions. The stratigraphy of Pb and Zn agrees with the historical variation in atmospheric pollution and confirms literature values for Central and North Europe. The drop in Pb and Zn over the last 10-15 years is a regional effect in North-Eastern Germany.

Selig, Uwe; Leipe, Thomas

2008-09-01

147

Seismic stratigraphy moves towards interactive analysis  

SciTech Connect

Seismic stratigraphy aids interpretation of complex geology, particularly by helping effectively identify the right geologic environment for potential hydrocarbon traps. This introductory article, the first in a three-part series, discusses some of the factors affecting interactive seismic stratigraphic interpretation, including phase effects, resolution and color softcopy.

Simson, S.F.; Nelson, H.R.

1984-12-01

148

Foraminiferal stratigraphy of Ranikot (Paleocene) of Pakistan  

Microsoft Academic Search

The sedimentary deposits of Pakistan are divided into three distinct basins: the Lower Indus basin, the Upper Indus basin, and the Baluchistan basin. The Lower Indus basin is further divided into two parts; the northern part is the Sulaiman Province, and the southern part is known as Kirthar Province. The tertiary stratigraphy of Kirthar Province is conspicuous for its characteristic

Kureshy

1983-01-01

149

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

150

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

151

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

152

Quaternary stratigraphy, geochronology and carbon isotope geology of alluvial deposits in the Texas panhandle  

NASA Astrophysics Data System (ADS)

Sedimentology, stratigraphy, and stable carbon isotopy were used to reconstruct geologic and climatic events on the Texas southern High Plains from ca. 13,000 yr B.P. to the present. The alluvial sediments in Yellowhouse and Blackwater Draws were used to construct the geologic history. The oldest valley alluvium comprises more than 13,000 yr B.P. fluvial sediments that were incised and buried by fluvial and lacustrine mediments dating ca. 13,000 to 4900 yr B.P. Lucustrine waters changed from ologotrophic to eutrophic and finally calcalitrophic. Regional valley erosion at 4900 yr. B.P. developed a widespread disconformity within the Yellowhouse Draw formation, which separates lower fluvial and lacustrine sediments (ca. 13,000 to 4900 yr B.P.) from the overlying sediments dating 4900 yr B.P. to present. After 4900 yr B.P., intermittent streams and eolian processes deposited several meters of sand the length of each valley. Clenegas returned to downstream reaches of both draws after 1500 to 2000 yr B.P.

Stafford, T. W., Jr.

1984-06-01

153

Loess stratigraphy of the Lower Mississippi Valley  

USGS Publications Warehouse

Loesses of the Lower Mississippi Valley (LMV) are world-famous. Sir Charles Lyell (1847), Hilgard (1860), Stafford (1869), Call (1891) and Mabry (1898), thought the LMV loess was a single water deposit although "double submergence" was noted by Call (1891) and Salisbury (1891). Shimek (1902) and Emerson (1918) recognized LMV loess as a wind deposit which came from the valley. Although wind-deposited loess gained wide acceptance, Russell (1944a) published his controversial theory of "loessification" which entailed weathering of backswamp deposits, downslope movement and recharge by carbonates to form loess. Wascher et al. (1947) identified three LMV loesses, mapped distributions and strongly supported eolian deposition. Leighton and Willman (1950), identified four loesses and supported eolian deposition as did Krinitzsky and Turnbull (1967) and Snowden and Priddy (1968), but Krinitzsky and Turnbull questioned the deepest loess. Daniels and Young (1968) and Touchet and Daniels (1970) studied the distribution of loesses in south-central Louisiana. West et al. (1980) and Rutledge et al. (1985) studied the source areas and wind directions which deposited the loesses on and adjoining Crowley's Ridge. B.J. Miller and co-workers (Miller et al., 1985, 1986, Miller and Alford, 1985) proposed that the Loveland Silt was Early Wisconsin rather than Illinoian age and advanced the name Sicily Island loess. They proposed the underlying loess was Illinoian and advanced the name Crowley's Ridge. We termed the loesses, from the surface downward, Peoria Loess, Roxana Silt, Loveland/Sicily Island loess, Crowley's Ridge Loess and Marianna loess. Researchers agree that the surfical Peoria Loess is Late Wisconsin and the Roxana Silt is Late to Middle Wisconsin, but little agreement exists on the age of the older loesses. Pye and Johnson (1988) proposed Early Wisconsin for the Loveland/Sicily Island. McKay and Follmer (1985) suggested this loess correlated with a loess under Illinoian till. Clark et al. (1989) agreed on Crowley's Ridge, but suggested the Loveland/Sicily Island loess on Sicily Island was older. Mirecki and Miller (1994) and Millard and Maat (1994) suggested an Illinoian age for the Loveland/Sicily Island loess. Miller and co-workers suggested, as did Pye and Johnson (1988), an Illinoian age for the Crowley's Ridge loess. McKay and Follmer (1985) suggested it correlated with a loess under "Kansan" till. Stratigraphy indicates the Marianna is the older of the five loesses. Researchers identified loess on both the east and west side of the LMV as well as on higher terraces within the valley. Many researchers assumed unaltered loesses were commonly yellowish brown, and silts or silt loams (West et al., 1980; Miller et al., 1986). The nonclay fraction of unweathered LMV loesses was dominated by quartz followed by carbonates, mainly dolomites, followed by feldspars, and micas. Clays were dominated by montmorillonite followed by micaceous minerals, kaolinite and vermiculite (Miller et al., 1986). Soils in the Crowley's Ridge loess are most developed, followed by the soils in the Loveland/Sicily Island which are more developed than the modern soils in the Peoria Loess. Soils in the Roxana and Marianna loesses are least developed and the Farmdale Soil of the Roxana is the weaker of the two (Miller et al., 1986). There is certainly overlapping range in the degree of soil development in the various loesses.

Rutledge, E. M.; Guccione, M. J.; Markewich, H. W.; Wysocki, D. A.; Ward, L. B.

1996-01-01

154

Magnetic stratigraphy of Peralkaline Volcanism in Sierra Libre, Sonora, Mexico  

NASA Astrophysics Data System (ADS)

Middle Miocene (~12 Ma) magmatism in NW Mexico was dominated by the appearance of anorogenic liquids associated with the Proto-Gulf of California. These correspond to a few occurrences of mafic volcanic rocks with transitional signatures (geochemically) and to a larger silicic volcanic event of peralkaline affinity. The silicic event is primarily composed of a large ignimbritic deposit widely recognized in Baja California as the Tuff of San Felipe (TSF), and in Sonora as the Hermosillo Ignimbrite. These are correlated by a number of characteristics including a unique low-inclination, reversed magnetization, probably associated with a field transition or a geomagnetic excursion within a reversed polarity subchron at 11.531-11.935 Ma (base of C5r.3r; Cande and Kent, 1995). Thick sections of deposits of this peralkaline volcanism crop out at Sierra Libre, geographically located ~45 km south of Hermosillo, Sonora. In this locality, a ~180m thick stack of middle Miocene volcanic units (both pyroclastic and lavas) were sampled for paleomagnetic studies focusing on the magnetic stratigraphy of a set of 9 units (7 to 12 cores per unit) from El Galindro Canyon, which represents the thickest volcanic pile genetically related to Tuff of San Felipe and Hermosillo ignimbrite. Previous studies indicated that the anomalous magnetization from TSF could be either an excursion or a reversal transition - its age is unconstrained except by direct radiological isotopes and relative stratigraphy. But most excursions recorded in high-deposition rate lakebeds, and less often in volcanic piles, trace simple "there-and-back" paths away from and returning to the ordinary geomagnetic secular variation locus for an age. By contrast, the Sierra Libre magnetizations wander erratically in declination and inclination, without following a simple sequential ''Path''. Polarity reversal transitions recorded in high-deposition rate lakebeds do behave that way. We therefore interpret TSF (and remarkably, most or all of the Sierra Libre peralkaline pile) as recording a reversal transition rather than an excursion.

Olguin-Villa, A. E.; Stock, J. M.; Vidal-Solano, J. R.

2011-12-01

155

Mapping Stratigraphy and Anomalies in Iron-Rich Volcanoclastics Using Ground-Penetrating Radar: Potential for Subsurface Exploration on Mars  

Microsoft Academic Search

Ground-penetrating radar (GPR) studies conducted in iron-rich volcanoclastics can yield valuable information for interpreting the subsurface stratigraphy resulting from lava flows and intervening unconsolidated volcanic and sedimentary deposits with different compositions and ages. GPR is also valuable for mapping subsurface anomalies and structures, such as rifts and lava tubes. We performed a geophysical field survey in Craters of the Moon

E. Heggy; S. Clifford; S. Khan; J. Fernandez; E. Wiggs; S. L. Gonzalez; D. Wyrick; R. Grimm; C. Dinwiddie; A. Pommerol

2004-01-01

156

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

Microsoft Academic Search

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

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

2007-01-01

157

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

158

Sedimentologic and geomorphologic tsunami imprints worldwide—a review  

NASA Astrophysics Data System (ADS)

Tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history, but considering geological timescales they occur frequently. At least 100 megatsunami in different parts of the world have been recorded in the past 2000 years—but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records. Therefore, the topic of paleotsunami requires inevitable sedimentological and geomorphological research. However, field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5% of the existing tsunami literature is related to this subject. Future efforts in paleotsunami research should focus on the geological evidence of these mega-events to clarify their contribution to coastal forming processes. This paper reviews the state-of-the-art knowledge of sedimentologic and geomorphic imprints of tsunami along the world's coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces.

Scheffers, A.; Kelletat, D.

2003-10-01

159

Age and Elevations of High-Level OIS2 Pluvial Lake Manly Shorelines, Northern and Central Death Valley: Implications for Lacustrine Sequence Stratigraphy in Southern Death Valley and the OIS6 Pluvial Lake Level  

NASA Astrophysics Data System (ADS)

New 14C ages of algal tufa from high-level Lake Manly shorelines at the Beatty Bar Complex (BBC) in Northern Death Valley (NDV) and on the west flank of the Black Mountains in Central Death Valley (CDV) indicate that shoreline features at elevations of up to 46 m and 61 m, respectively, formed during the latest- Pleistocene, OIS2 pluvial-lake cycle rather than the earlier OIS6 lake cycle as commonly interpreted. In-situ algal tufa clast coatings in the highest shoreline gravel bar at the BBC yielded an age of 26.97±0.62 14C kyrs B.P. The prominent horizon of tufa coatings lies ~1.5 m below the bar crest (46 m) and is interpreted to mark the static elevation of the OIS2 Lake Manly highstand. The tufa age is consistent with the gravel bar's youthful geomorphic expression and generally weak soil development, a previously reported TL age of 24.0±2.5 ka from fine-grained lagoonal(?) deposits behind this same gravel bar (45 m), a thinolitc-tufa age of 16.40-15.75 cal yrs B.P. from Mesquite Flat (37 m), and U-series ages (9.6±3.3 and 30.1±3.3 ka) and associated deep-lake ostracodes from core in CDV. In CDV, 2.5 km north of Badwater, prominent shoreline beach rock and algal tufa lie in deposition against the steep footwall escarpment of Black Mountains fault zone (BMFZ) to an elevation of ~61 m. Algal tufa collected at ~55 m yielded an age of 24.55±0.33 14C kyrs B.P. indicating that OIS2 Lake Manly highstand shorelines in CDV now lie at least 15 m higher than in NDV. The lack of major vertical-slip-rate faults in NDV suggests absolute footwall uplift adjacent to the prominent BMFZ (ala Borah Peak) may account for the difference. In Southern Death Valley (SDV), new mapping and tephra ages have defined a series of 3 lacustrine sequences well exposed along eastern traces of the Southern Death Valley fault zone (SDVFZ): 1) a lower sequence of highly-folded, late-Pliocene strata containing ~3.4 Ma Mesquite Springs tephra (correlative to strata in the eastern Noble Hills); 2) a gently- folded middle sequence of early-to-middle-Pleistocene strata containing Glass Mountain (1.2-0.9 Ma) and Lava Creek (0.64 Ma) tephra (age-correlative to strata in the Confidence Hills); and 3) a non-folded upper sequence, which is not dated, but clearly unconformably overlies the folded middle sequence. The upper sequence also shows only minor displacement along the SDVFZ. The upper sequence lies at a maximum elevation of ~45 m, the same as the BBC highstand gravel bar 100 km to the north. Hence, we correlate the undeformed upper lacustrine sequence in SDV to the OIS2 phase of Lake Manly. Although previously dated OIS6 shorelines (120-186 ka) along the Black Mountains escarpment lie at an elevation of ~90 m, we have yet to identify an OIS6 sequence of lacustrine deposits in SDV. Again, following the concept of absolute footwall uplift along the BMFZ, it is possible that the OIS6 Lake Manly highstand was considerably lower than 90 m and didn't spill into SDV. A relatively lower OIS6 lake level (<46 m OIS2) is consistent with our current understanding of the regional paleohydrology. During the OIS6 lake phase, the Amargosa River terminated in Lake Tecopa, and major flow into Death Valley was perhaps limited to spillover from the Owens-Searles- Panamint lake chain. During the OIS2 lake phase, both the Amargosa and Mojave rivers flowed into Death Valley.

Caskey, S.; Lackey, H. G.; Klinger, R. E.; Wan, E.; Sarna-Wojcicki, A.

2006-12-01

160

The utilization of sequence stratigraphy in reservoir geology  

Microsoft Academic Search

Initial applications of sequence stratigraphy focused on basin analysis and exploration problems. As finer scale studies were conducted using well logs and outcrops, it has become possible to apply the concepts to improving reservoir performance. Investigations of the fine scale sequence stratigraphy of carbonates has led to its application to enhance production in the complex Paleozoic carbonate reservoirs of the

J. R. Macurda; D. Bradford

1996-01-01

161

Risk reduction or why stratigraphy. [The use of stratigraphy to determine oil and gas exploration risks  

SciTech Connect

Risks and uncertainties are involved in the exploration for resources. This paper identifies these risks in terms of oil and gas exploration and how an interdisciplinary stratigraphic approach to exploration can reduce these risks. Risk factors involved in the search for oil and gas include four geologic factors: structure, reservoir, trapping conditions, and hydrocarbon charge. Exploration decisions involve the consideration of these risks and uncertainties when determining budgets, geotechnical predictions and serial exploration. To find oil and gas, three geologic factors must be determined - the source rock, the reservoir, and the trapping mechanism. The geologic branch known as stratigraphy is best equipped to deal with these unknowns. Using lithostratigraphy, biostratigraphy, and seismic stratigraphy, geologists can determine the nature and type of stratigraphic traps, as well as the risk factors involved with each. Once these factors are identified, ways to reduce them can be determined for development areas. Traps are identified using various tools. Drilling logs, fossil distribution charts, clastic analysis, and carbonate analysis, stratigraphic summaries and columns can be used for individual well sections. Area stratigraphy uses stratigraphic columns, strand line sequences, lithostratigraphic units and facies, previously known oil occurrences, cross sections, and stratigraphic sections. Seismic stratigraphy yields important information about the paleoenvironment and subsurface structures. With all the information collected, stratigraphers can apply Walther's law of facies succession to reduce risks in development areas.

Marks, E. (Marks and Associates, Whittier, CA (United States))

1991-02-01

162

Geomorphological and sedimentological characteristics of cyclone-generated landforms and washover deposits along the coasts of NW Australia  

NASA Astrophysics Data System (ADS)

Palaeotempestology, the study of prehistoric storms, uses sedimentary evidence to enlarge the temporal frame of storm occurrence patterns given by historical records. Different sedimentary archives storing traces of tropical cyclone impact (washover fans and sediments, beach ridge systems) were investigated along the coasts of the Exmouth Gulf and the NW Cape(W Australia) in order to evaluate their use for palaeotempestological research. (1) Along the W coast of the Exmouth Gulf, distinct lobate washover fans exhibit washover terraces, channel systems and delta-type sedimentation patterns. Their stratigraphy consists of shell debris layers, sand, coarse coral fragments and entire shells. Multiple reactivation of the washover fans is inferred from their complex pattern of accumulation and incision and a minimum of three palaeosols, each of them indicating one depositional event and a subsequent period of geomorphologic stability. (2) In Giralia Bay, S Exmouth Gulf, sandy chenier-like beach ridges characterize the landward boundary of extensive mud flats. Their geomorphology and stratigraphical architecture reflect the influence of intermittent phases of morphodynamic activity due to littoral-type processes and are assumed to record recurring cyclone impact. (3) Along the W coast of the NW Cape, subrecent tsunami sediments detected in back-barrier archives contain reworked foraminifers from the shelf and the littoral zone and are most likely related to the 1994 Java Tsunami. Below, several thin clastic sand layers intercalate carbonate mud sediments. In contrast to the mud units, most of the sandy layers are reflected by increased mean grain size and contain reworked foraminifers from the shelf and littoral zone. Underlying mud sediments and mangrove remains reflect coastal and palaeoenvironmental changes on Holocene time scales. Our preliminary findings suggest that the investigated sedimentary archives have a high potential for improving extreme wave histories (tsunamis, cyclone landfalls) of W Australia. Main challenges include dating (14C, OSL) and distinguishing between event and non-event processes, and between event types, based on sedimentology, microfauna, and shell taphonomy.

May, Simon Matthias; Engel, Max; Brückner, Helmut; Pint, Anna; Kelletat, Dieter; Scheffers, Anja; Squire, Peter

2013-04-01

163

Oxygen Isotopic Stratigraphy and Geomagnetic Field Intensity  

NASA Astrophysics Data System (ADS)

Nick Shackleton intellectual leadership in isotope stratigraphy had profound implications for paleoclimatology and paleoceanography. What is not so well enough known is that Nick contributed also to significant advances in studies of variations of the Earth's magnetic field. The first link between the two disciplines was certainly the paper that he produced with Neil Opdyke in 1973. About twenty years later Nick Shackleton obtained a very detailed isotope stratigraphy after analyzing the oxygen isotopes of bulk sediment of two cores from the Somali basin characterized by high resolution records of relative paleointensity for the past 140 kyr. This stratigraphy allowed us to correlate these two records with other independent data from the Mediterranean sea and to propose that the signal which was recorded at the two locations was global and thus of geomagnetic origin. The fast growing database made possible a stacking of the results for the past 200 ka and then for the past 800 kyr. The resulting curve was constructed from 33 paleointensity records and Shackleton's isotopic records were essential in many cases. Indeed without high resolution stratigraphy much information could not be retrieved due to uncertainties in correlating different records. The results revealed the very variable character of the field with large 20 to 60 kyr oscillations and changes in amplitude that can exceed a factor of five, but no apparent periodicity. Short periods of very low intensity occur at more or less regular intervals (roughly every 100 kyr) and correspond with geomagnetic excursions. The next step was to obtain a much longer record that would document the field changes across reversals and during entire polarity intervals. The opportunity was met during ODP Leg 138 with the recovery of beautifully magnetized sequences that covered at least 4 Myr of geomagnetic history. Nick was responsible for correlating sedimentary columns taken at each site. He performed a tremendeous task by orbitally tuning the density variations for thousands of meters of sediment. This allowed us to correlate the paleointensity signals from several holes and to produce the first long dataset with a very accurate time-depth control. Very recently the accumulation of data made it possible to stack records from different oceans for the past 2 Myr and to extract features of field intensity which add significant constraints to the modelling of the geodynamo. Alternatively this curve can be used as a stratigraphic reference, similarly to isotopes records.

Meynadier, L.; Valet, J.

2004-12-01

164

Sedimentology of Home Plate at Gusev Crater, Mars  

NASA Astrophysics Data System (ADS)

The analysis of the ~2 m vertical exposure of the rim of Home Plate allows a preliminary assessment of its sedimentologic characteristics. Pancam and MI images of the Barnhill and Rogan outcrops and that of several floats suggest that Home Plate could be divided intoat least two main units. Differences in morphology and sedimentology are noticeable at Pancam resolution. When scrutinized at MI resolution, the various facies are complex, with transitions from one unit to the next. Barnhill is made of ash-size material and granules (possibly lapillis). The morphology of the ash-like deposit bears a striking morphological resemblance with Pot- of-Gold documented in West Spur (sol 156 and 180). The Rogan unit consists mostly of granular, layered, rocks (medium sandstone-size material) with common cross-beds. While layered and granular rocks are numerous at Home Plate, they present differences suggesting variations in local conditions and/or processes. For instance, the rock Posey (a float) documented at the foot of Home Plate shows layers and crossbeds. However, its sedimentologic characteristics are distinct compared to that of the average Rogan outcrop. The matrix of the rock itself is clearly below MI resolution, which reminds of the Barnhill outcrop material but conversely to Barnhill, there are no lapilli-size grains embedded in Posey. Many 300-500 ?m average size rounded grains are observed in the rock instead, 900 ?m for the largest visible. Posey layers are made of sand- size material and the structure of the rock suggests sequencing in the layering with thick (700-900 ?m) and thin layers (130-300 ?m). The difference in size of the layering is accompanied by a difference in tone. Thicker layers have been exposed by erosion (protruding) and are subdivided. In summary, the diversity of materials exposed in Home Plate and their structure suggest a diversity of processes that could have been acting locally or regionally repeatedly during the early history of Gusev, or could reflect different phases of a single event (e.g., volcanic, impact, ).

Cabrol, N. A.

2006-12-01

165

Event Stratigraphy and Paleoceanography in the Fortuna Basin (Southeast Spain): A Scenario for the Messinian Salinity Crisis  

NASA Astrophysics Data System (ADS)

The timing and duration of evaporitic deposition during the Messinian in the Mediterranean is poorly known. To assist with this problem, we have correlated sedimentological events at widely separated locations in the Mediterranean and dated paleoceanographic events in the world ocean (event stratigraphy). Our working hypothesis is as follows: The Messinian Salinity Crisis caused the formation of evaporites in a deep desiccated basin which implies that (1) the evaporites were deposited during a steady marine influx, (2) multiple intervals of isolation led to drastic changes in the sediments and in the fauna of the Mediterranean, (3) the sea level of the Mediterranean Sea was mostly several hundreds of meters below that of the Atlantic Ocean, and (4) the seaways (Betic and Rif Strait) connecting the Mediterranean with the Atlantic during the late Miocene were affected by eustatic sea level changes caused by Antarctic glaciation. We found supporting evidence in the sedimentological and paleoceanographic records in the Betic Strait (Fortuna and Sorbas basins) which was one of the sites of major inflow into the late Miocene Mediterranean Sea. Drastic sea level changes and fluctuations during the late Tortonian and Messinian caused chronologically: (1) the deposition of brackish sediments overlying marine deposits, (2) the progradation of deltas, (3) reef growth at lower levels and their destruction by erosion and coverage by conglomerates, (4) evaporite deposition alternating with marine marls containing Atlantic diatom assemblages, and (5) five marine/terrestrial cycles associated with coral reefs. Based on event stratigraphy the following scenario for the Messinian "Salinity Crisis" is proposed: The Tripoli Formation (Chron 6R1/5N2: 5.93-5.7 Ma), the Lower Evaporites (Chron 5N2, 5R: 5.7-5.5 Ma), and the Upper Evaporites (lowermost Gilbert c: 5.25-5.15 Ma) were deposited during influx of Atlantic water into the Mediterranean. During this time, a unidirectional circulation dominated from the Atlantic through the Betic Strait. Only during the intra-Messinian inundation (Chron 5N1 into lowermost Gilbert c: 5.4-5.25 Ma) that occurred after a short intra-Messinian erosional event (Chron 5N1: 5.5-5.4 Ma) was a normal bidirectional circulation pattern established. This is reflected in the diatomites of the Chicamo Formation and the Mediterranean (site 124) as well as most likely in a reef on Cyprus. The marine record of the Pliocene filling of the Mediterranean is missing in these basins. Overall, marine water inflow into the Mediterranean through the Betic Strait dominated during the Messinian. The threefold marine/terrestrial cyclicity with severe paleoceanographic changes in the Fortuna and Sorbas basins favor the "deep, desiccated basin" model.

Müller, Daniel W.; Hsü, Kenneth J.

1987-12-01

166

Upper Jurassic of east Texas, a stratigraphic sedimentologic reevaluation  

SciTech Connect

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

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

1985-02-01

167

Predicting stratigraphy by evaluating depositional response to climate change and basin evolution  

SciTech Connect

Continental and marine stratigraphy can be predicted by integrating sediment flux as a function of the climatic succession, caused by orbital (Milankovitch) oscillations, with the long-term evolution of accommodation space. Total sediment volume of an interval can be calculated from seismic data. Variation in sediment flux is then estimated by evaluating climatic succession in concert with drainage area and elevation. Flux from drainage areas can vary by up to seventy times during an orbital cycle, depending on the succession and topography, creating a sediment supply cycle. Overall, highest yields occur during shifts from arid to subhumid climates. Climatic succession and, therefore, the phase relationships of lake level and sediment supply cycles to orbital cycles are functions of geographic position, with maximum yield and lake level occurring at any phase of an orbital cycle depending on succession. Maximum yield and lake level may or may not occur synchronously in any single climate belt. In addition, because sea level tends to be in phase with orbital cycles while sediment supply may not be, the phase relationship between sediment and sea level cycles also varied with basin location. After these relationships are determined, clastic and carbonate stratigraphy can be reliably forecast by integrating sediment flux with long-term, tectonically controlled evolution of accommodation space. This technique, called global cyclostratigraphy, has been used to predict the generalized stratigraphy of basins ranging in age from the Devonian to the Pleistocene.

Perlmutter, M.A.; Matthews, M.D. (Texaco EPTD, Houston, TX (United States))

1992-01-01

168

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

169

New sedimentological, bio-, and magnetostratigraphic data on the Jurassic-Cretaceous boundary interval of Eastern Crimea (Feodosiya)  

NASA Astrophysics Data System (ADS)

The first compiled composite section comprises continuous succession of upper Tithonian-lower Berriasian strata (Jacobi Zone) from different isolated outcrops of the Feodosiya area. Based on new magnetostratigraphic and sedimentological data, the paleomagnetic section is correlated with succession of M20r, M19n, M19r, M18b chrons and M18n.1r Subchron ("Brodno"). The thorough complex bio- and magnetostratigraphic correlation of the upper Tithonian-lower Berriasian interval (Jacobi Zone) carried out through the Western Tethys and Eastern Paratethys provided grounds for first defining age analogs of the Durangites Zone in the Crimean Mountains and specifying location of the boundary between the Jurassic and Cretaceous systems, as well as for determining late Tithonian age of strata in the Dvuyakornaya Bay section barren of fossils.

Guzhikov, A. Yu.; Arkad'ev, V. V.; Baraboshkin, E. Yu.; Bagaeva, M. I.; Piskunov, V. K.; Rud'ko, S. V.; Perminov, V. A.; Manikin, A. G.

2012-05-01

170

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

171

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

172

STRATIGRAPHY OF GLACIAL LAKE OJIBWAY AND IMPLICATIONS FOR THE 8200 YR EVENT  

NASA Astrophysics Data System (ADS)

Determining the timing and routing of meltwater discharges from relic ice sheets into the oceans remains problematic. One example is the suggested Holocene drainage of Lake Ojibway that covered portions Ontario and Quebec. Radiocarbon ages on marine shells overlying proglacial lake sediments south of Hudson’s Bay provide minimum ages about 8200 cal yr BP leading Barber et al. (1999) to suggest drainage of this lake was a trigger for the so-called 8200 yr cold event. Anteves (1925) reported multiple varve sections that he suggested represented some 1800 years covering the evolution of Lake Ojibway and its precursor. Thus placing the varve stratigraphy into an absolute time framework could confirm the Barber hypothesis. Alternatively, if the lake drained before the 8200 yr event or drained multiple times, it would imply a more complex relationship between meltwater discharge and climate change. One complication is that evidence for a reactivation of the Laurentide Ice Sheet, locally called the Cochrane Readvance, exists in the basin. Subottom profiling of some 30 lakes reveals that in areas outside the Cochrane limit, bedrock basins contain thick (up to 30 m) glaciaolacustrine sequences. These are generally conformable sequences draping over the bedrock. In limited cases slight unconformities lie below the most recent erosion (at local wave base) and organic lacustrine sediments. Areas covered by the Cochrane advance display a thin stratigraphy; notably lacking are glaciolacustrine sequences. The stratigraphy recovered in core sequences (N=16) show a similar pattern: thin with very limited varves over the Cochrane and thicker sequences in the larger basins. However examination of sediments show that the stratigraphy is predominately glacier proximal sediment (not distal varves) with local unconformities and evidence of slumping. This implies localized sedimentation sources. Of these only two are classic varves which allow potential correlation with the sequence established by Anteves (1925). This localized complexity has thus far prevents any regional events from being identified. Given the regional sediment patterns and detailed stratigraphy we suggest the possibility that Lake Ojibway sequence is largely a local one and that the drainage history is not a simple one. Further evidence to date is unclear rather the Cochrane advance occured before or after the 8200 yr cold event.

Lowell, T.; Stroup, J. S.; Breckenridge, A. J.; Smith, C. A.; Moser, J. V.; Sagredo, E.

2009-12-01

173

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

174

Extensional tectonics and stratigraphy of the North Atlantic margins  

SciTech Connect

The tectonics and stratigraphy or the north Atlantic continental margins are discussed. Forty articles are included in the book. Each of these items have been abstracted and indexed for the U.S. Department of Energy Energy Data Base.

Tankard, A.J.; Balkwill, H.R. (eds.)

1989-01-01

175

Quaternary Stratigraphy and Depositional Environments, Santa Monica Bay, Southern California.  

National Technical Information Service (NTIS)

High-resolution seismic-reflection profiles were used in conjunction with 51 vibracores to examine the Quaternary stratigraphy of the Santa Monica Shelf, southern California. Upper Pleistocene strata are confined to the central part of the shelf between t...

R. H. Osborne R. C. Scheidemann T. R. Nardin A. S. Harper

1980-01-01

176

Computer sedimentary simulation models sequence stratigraphy  

SciTech Connect

Sedpak is a collection of integrated computer programs written in the C programming language, under the MIT X Window System and Motif, for a UNIX workstation environment. It is a graphical simulation program designed to aid in the analysis and classification of stratigraphic sequences derived from seismic and well data. It permits the extrapolation of facies and structure away from control, embodying the concepts and processes of sequence stratigraphy, for a wide variety of basins. Sedpak has been used for a variety of different depositional settings. This article describes the findings for the following: the Cretaceous/Tertiary of the South Carolina Coastal Plain, the Plio-Pleistocene of the Gulf of Mexico, the Neogene of the Canterbury basin of New Zealand, the Cretaceous of the Baltimore Canyon, and the Triassic Dolomite Alps of northern Italy.

Kendall, C.G.S.C.; Whittle, G.L.; Ehrlich, R.; Moore, P.D.; Cannon, R.L.; Hellmann, D.R. (Univ. of South Carolina, Columbia (United States))

1993-04-26

177

Sequence stratigraphy buoys W. Indonesia basins  

SciTech Connect

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

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

1996-05-20

178

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

179

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

180

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

181

CRISM Analyses of Noachian Stratigraphy in Argyre Basin  

NASA Astrophysics Data System (ADS)

The Argyre basin is a >1500 km, well preserved impact basin in the southern highlands of Mars and the geologic units associated with the basin are mostly Noachian in age (Scott and Tanaka, 1986). Thus, Argyre is an ideal location to characterize the stratigraphy of ancient highland rocks. We analyzed 72-channel CRISM multispectral data that had been map projected to 256 ppd into 40 5-degree map tiles. The data were corrected for illumination by dividing by the cosine of the solar incidence angle. A multiplicative correction for atmospheric gas absorption was applied (Bibring et al., 2005). Spectrally distinct regions were identified by calculating summary parameters (Pelkey et al., 2007); spectra of key areas were examined in detail. A scarp is roughly associated with a contact between the Hpl3 and Npld units in NW Argyre. At the top of the scarp (unit Hpl3) CRISM has detected an olivine signature associated with a depression. Phyllosilicates have been identified extending laterally along the scarp, related to unit Npld (dissected impact breccias). Below the phyllosilicates are found deposits of high-Ca pyroxene hugging scarps in unit Npld. High-Ca pyroxene is also identified in unit Npl1 (undissected impact breccias), at the same stratigraphic level of the Npld pyroxenes. A high-standing knob in Npl1 has a phyllosilicate signature. CRISM investigations also support previous studies by OMEGA, which identified olivine and pyroxene in north Argyre (Gondet et al., 2007). A correlation appears between the low-Ca pyroxene/olivine exposures and the hills of unit Nplh, the oldest geologic unit in Argyre interpreted as uplifted by tectonism during the formation of the impact basin (Scott and Tanaka, 1986). We suggest that as a group these deposits reveal the stratigraphy of the Noachian crust in this region. At the bottom of the stratigraphic column are olivine and low-Ca pyroxene associated with uplifted ancient rocks (unit Nplh). Above these deposits are high-Ca pyroxenes associated with lavas and impact breccia (unit Npl1 and Npld). Within these same units but stratigraphically above the pyroxene are phyllosilicates, preserved in freestanding knobs and along scarp walls. At the top of the stratigraphic column in NW Argyre is olivine associated with the early Hesperian Hpl3 unit.

Buczkowski, D.; Murchie, S.; Seelos, F.; Malaret, E.; Hash, C.; CRISM Team

2007-12-01

182

Sequence stratigraphy of late Mesozoic rocks of the Colorado plateau  

SciTech Connect

The Zuni sequence, as defined by Sloss, encompasses rocks ranging in age from the latest Early Jurassic to about the Cretaceous-Tertiary boundary. In current Exxon sequence stratigraphic charts this Sloss sequence is divided into three global supersequence sets, all of which can be readily recognized in the rocks of the Colorado Plateau: (1) the lower Zuni A (global) corresponds to the San Rafael Group, (2) the lower Zuni B is represented by the Morrison Formation, and (3) the upper Zuni is the Late Cretaceous deltaic and marine package (Mancos Shale and equivalents). The global Zuni sequence is divisible into twelve supersequences, the boundaries of which generally correspond to major regional unconformities in the Rocky Mountains. Not all unconformities correspond to Exxon's global sequence boundaries, however, because processes such as regional marine transgression (base Curtis SS; J3 unconformity), foredeep rebound (intraformational unconformity in the Sanpete Formation) and forebulge migration (Dakota SS truncation) produce local unconformities totally independent of regional sea-level change. The stratigraphy of the Zuni sequence of the Colorado Plateau clearly supports the concept that global sea-level change is the principal determinant of large-scale lithofacies architecture, including those of mostly nonmarine origin. At the scale of the supersequences (10 m.y.), the globally recognized episodes of sea-level fall have all produced major unconformities within Zuni rocks of the Colorado Plateau. This suggests that the large-scale packaging of rocks in the Phanerozoic reflects eustatic cycles, not tectonic ones as maintained by Sloss.

Nummedal, D. (Louisiana State Univ., Baton Rouge (United States))

1991-03-01

183

Late tertiary structure and stratigraphy of north Sinai continental margin  

SciTech Connect

New seismic data provide information on the structural development and late Tertiary stratigraphy of the continental slope and rise off northern Sinai. The upper continental slope is characterized by a marginal plateau composed of a series of platforms or steps. The lower continental slope is smooth, except for a low ridge paralleling the western part. Numerous diapiric structures along the continental margin north of the Sinai Peninsula emerge from an evaporitic layer of late Tertiary age. The diapirs usually are aligned along west-northwest-trending faults. A salt ridge 90 km long produces a submarine ridge in the lower continental rise. Two main fault trends have been mapped. In the western part of the continental margin they trend west-northwest and, in the eastern part, northeast. These trends parallel the continental slopes of northern Sinai and southern Israel, respectively. The structural grain of the Sinai margin appears to be controlled by two main tectonic elements: (1) rejuvenated basement faults of the continent-ocean transition zone; and (2) salt diapirism due to loading of Messinian evaporites with Nile-derived upper Tertiary clastics.

Ben-Avraham, Z. (Oceanographic Inst., Haifa, Israel); Mart, Y.

1981-06-01

184

Eocene-Pliocene time scale and stratigraphy of the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB)  

NASA Astrophysics Data System (ADS)

We present a general stratigraphic synthesis for the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB) from Eocene to Pliocene times. The stratigraphic data were compiled both from literature and from research carried out by the authors during the past 6 years ; an index of the stratigraphically most important localitites is provided. We distinguish 14 geographical areas from the Helvetic domain in the South to the Hanau Basin in the North. For each geographical area, we give a synthesis of the biostratigraphy, lithofacies, and chronostratigraphic ranges. The relationships between this stratigraphic record and the global sea-level changes are generally disturbed by the geodynamic (e.g., subsidence) evolution of the basins. However, global sea-level changes probably affected the dynamic of transgression regression in the URG (e.g., Middle Pechelbronn Beds and Serie Grise corresponding with sea-level rise between Ru1/Ru2 and Ru2/Ru3 sequences, respectively) as well as in the Molasse basin (regression of the UMM corresponding with the sea-level drop at the Ch1 sequence). The URGENT-project (Upper Rhine Graben evolution and neotectonics) provided an unique opportunity to carry out and present this synthesis. Discussions with scientists addressing sedimentology, tectonics, geophysics and geochemistry permitted the comparison of the sedimentary history and stratigraphy of the basin with processes controlling its geodynamic evolution. Data presented here back up the palaeogeographic reconstructions presented in a companion paper by the same authors (see Berger et al. in Int J Earth Sci 2005).

Berger, Jean-Pierre; Reichenbacher, Bettina; Becker, Damien; Grimm, Matthias; Grimm, Kirsten; Picot, Laurent; Storni, Andrea; Pirkenseer, Claudius; Schaefer, Andreas

2005-09-01

185

Review and Comparison of Belly River Group and Edmonton Group Stratigraphy and Stratigraphic Architecture in the Southern Alberta Plains  

Microsoft Academic Search

The region of southern Alberta south of T35 and east of W5 contains laterally extensive-to-patchy exposures and subsurface strata of the Campanian- Maastrichtian age Belly River and Edmonton Groups. During the past 10 years the stratigraphy of the Belly River Group in this region has been re-interpreted and redefined using a sequence and event stratigraphic approach. More recently, portions of

David A. Eberth

186

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

SciTech Connect

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

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

1991-08-01

187

50 years of snow stratigraphy observations  

NASA Astrophysics Data System (ADS)

With start in autumn 1961 the Abisko Scientific Research Station (ASRS) located in the Swedish sub Arctic has performed snow stratigraphy observations, resulting in a unique 50 year long time series of data. The data set contains grain size, snow layer hardness, grain compactness and snow layer dryness, observed every second week during the winter season. In general snow and snow cover are important factors for the global radiation budget, and the earth's climate. On a more local scale the layered snowpack creates a relatively mild microclimate for Arctic plants and animals, and it also determines the water content of the snowpack (snow water equivalent) important for e.g. hydrological applications. Analysis of the snow stratigraphy data, divided into three consecutive time periods, show that there has been a change in the last time period. The variable most affected is the snow layer hardness, which shows an increase in hardness of the snowpack. The number of observations with a very hard snow layer/ice at ground level increased three-fold between the first two time periods and the last time period. The thickness of the bottom layer in the snowpack is also highly affected. There has been a 60% increase in layers thinner than 10 cm in the last time period, resulting in a mean reduction in the thickness of the bottom layer from 14 cm to 11 cm. Hence the living conditions for plants and animals at the ground surface have been highly changed. The changes in the snowpack are correlated to an increased mean winter air temperature. Thus, continued increasing, or temperatures within the same ranges as in the last time period, is likely to create harder snow condition in the future. These changes are likely to affect animals that live under the snow such as lemmings and voles or animals that graze sub-Arctic vegetation in winter (e.g. reindeer that would potentially require increased supplementary feeding that incurs financial costs to Sami reindeer herders). Any decrease in lemmings and vole populations is likely to have cascading effects on biodiversity, particularly predators such as arctic foxes and snowy owls.

Johansson, C.; Pohjola, V.; Jonasson, C.; Challagan, T. V.

2012-04-01

188

Sedimentological processes in lahars: Insights from optically stimulated luminescence analysis  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

189

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

190

Foraminiferal stratigraphy of Ranikot (Paleocene) of Pakistan  

SciTech Connect

The sedimentary deposits of Pakistan are divided into three distinct basins: the Lower Indus basin, the Upper Indus basin, and the Baluchistan basin. The Lower Indus basin is further divided into two parts; the northern part is the Sulaiman Province, and the southern part is known as Kirthar Province. The tertiary stratigraphy of Kirthar Province is conspicuous for its characteristic lithostratigraphic units. The Paleocene deposits of Kirthar Province are designated as Ranikot Group. The Ranikot Group was divided by Cheema et al in 1977 into three distinct lithostratigraphic units: the Khadro formation (Cardita beaumonti beds), Bara formation (Lower Ranikot), and Lakhra formation (Upper Ranikot). The Khadro and Lakhra formations are marine, characterized by foraminiferal assemblages. The characteristic planktonic forms are: Globigerina triloculinoides Plummer, Globorotalia pseudobulloids (Plummer), G. compressa (Plummer), G. valascoensis (Cushman), and G. pseudomenardii Bolli. The diagnostic forms of larger foraminifera are: Nummulites nuttalli Davies, Miscellanea (d'Archiac and Haime), Kathina major Smout, and Lockartia conditii (Nuttall). The planktonic foraminifera were assigned to Globorotali trinidadensis, G. pseudomenardii, and G. velasoensis zones of Kureshy in 1977, and larger foraminifera were assigned to Nummulities nuttalli zones of Kureshy in 1978.

Kureshy, A.A.

1983-03-01

191

Sedimentology-based reconstructions of paleoclimate changes in the Central Andes in response to the uplift of the Andes, Arica region between 19 and 21°S latitude, northern Chile  

Microsoft Academic Search

We focus on the sedimentological record of the Middle Miocene to modern deposits in the Andes of northern Chile between 19\\u000a and 21°S. These sediments, deposited at the Western Escarpment of the Central Depression, indicate successively more moisture\\u000a on the western margin of the Altiplano and the Western Cordillera where the sources are. At the Pacific Coast, 20-Ma-old exposure\\u000a ages

Fritz Schlunegger; Florian Kober; Gerold Zeilinger; Ruedi von Rotz

2010-01-01

192

ELASTIC-WAVEFIELD SEISMIC STRATIGRAPHY: A NEW SEISMIC IMAGING TECHNOLOGY  

SciTech Connect

The focus of elastic-wavefield seismic stratigraphy research shifted from onshore prospects to marine environments during this report period. Four-component ocean-bottom-cable (4-C OBC) seismic data acquired in water depths of 2400 to 2500 feet across Green Canyon Block 237 in the Gulf of Mexico were processed and analyzed. The P-P and P-SV images of strata immediately below the seafloor exhibit amazing differences in P-P and P-SV seismic facies. These data may be one of the classic examples of the basic concepts of elastic-wavefield seismic stratigraphy.

Bob A. Hardage

2004-05-06

193

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

194

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

195

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

SciTech Connect

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

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

1993-04-01

196

Sedimentological, Magnetic and Geochemical Proxies for Holocene Climate Change and Paleoseismology from Marine Anoxic Inlet Sediments  

NASA Astrophysics Data System (ADS)

Sediments deposited in anoxic basins are not bioturbated and thus hold high temporal resolution proxy recordings of climate and other physical controls. This paper focuses on the inner basin of Effingham Inlet on the west coast of Vancouver Island, Canada, a 120m deep fiord basin restricted from the open ocean by a 46m deep sill. Fifteen years of oceanographic monitoring have helped establish the physical and sedimentary processes at play. Freeze cores, piston cores, and especially the 40 m long MD02-2494 core hold a15 ka record of Late Pleistocene deglaciation, relative sea level change, Holocene climate and paleoseismology, revealed by sedimentological, magnetic and geochemical analysis. The age model is established using terrestrial 14C dates complemented by varve counting and paleomagnetic secular variation correlations. Annual laminations are formed of spring/summer diatom deposits following algal blooms and dominantly- winter deposits of clastics. These sediments provide proxies of Holocene weather with annual resolution. There are several episodes of rapid regime change from high seasonality warm climate to low seasonality wet-cold climate. Interspersed with the the annual laminations, there are two types of massive deposits: "homogenites" formed by remixing of suspended sediments by bottom-hugging currents, and "seismites" formed by mass wasting events associated with ground shaking. Magnetically, both the laminations and homogenites feature similar single-domain magnetic grains, while the seismites feature larger magnetic grains with multi-domain signatures, thus providing a simple tool for distinguishing the two visually similar deposit types. Homogenites, which result from La Nina-like oceanic conditions, first appear in core MD02- 2494 approximately 8 ka and have been increasing in frequency ever since.

Enkin, R. J.; Dallimore, A.; Baker, J.; Ivanochko, T.; Chang, A. S.

2009-05-01

197

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

SciTech Connect

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

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

1996-01-01

198

Mineralogical, geochemical, and sedimentological characteristics of clay deposits from central Uganda and their applications  

Microsoft Academic Search

In Uganda, Precambrian rocks have undergone extensive weathering and erosion, and are locally altered to form considerable clay deposits. We have studied the geochemical, mineralogical, and sedimentological characteristics of clay deposits from central Uganda to determine their composition, source rocks, deposition, and possible use in local industry. Samples were collected from the Kajjansi, Kitiko, Masooli, and Ntawo deposits (near Kampala),

George W. A Nyakairu; Hans Kurzweil; Christian Koeberl

2002-01-01

199

Chapter 11 The role of fuzzy logic in sedimentology and stratigraphic models  

Microsoft Academic Search

There has been a recent explosive growth in the theory and application of fuzzy logic and other related 'soft' computing techniques, opening new ways of modeling based on knowledge expressed in natural language. Fuzzy logic systems (based on fuzzy set theory), produce realistic sedimentation dispersal patterns in sedimentologic simulations in general and stratigraphic models in particular. The purposes of this

Robert V. Demicco; George J. Klir; Radim Belohlavek

2003-01-01

200

Paleohydrology of Andean saline lakes from sedimentological and isotopic records, Northwestern Argentina  

Microsoft Academic Search

The paleohydrological evolution of several high altitude, saline lakes located in the southernmost Altiplano (El Peinado and San Francisco basins, Catamarca province, NW Argentina) was reconstructed applying sedimentological, geochemical and isotopic techniques. Several playa lakes from the San Francisco basin (26 ° 56¢ S; 68 ° 08¢ W, 3800-3900 m a.s.l.) show evidence of a recent raise in the watertable

Blas L. Valero-Garcés; Antonio Delgado-Huertas; Norma Ratto; Ana Navas; Larry Edwards

2000-01-01

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

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

Microsoft Academic Search

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

Jeffrey S. Kargel; Jeffrey Moore; Timothy Parker

1993-01-01

203

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

204

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

205

Relation of sequence stratigraphy to modern sedimentary environments  

Microsoft Academic Search

One method of testing the concept of sequence stratigraphy is to compare it to Quaternary sediments in which chronology, stratigraphic relations, and facies geometry are more clearly understood than in older rocks. Rapid deposition rates during Quaternary glacial-eustatic cycles in large deltaic depocenters generate sequences comparable to those in the ancient stratigraphic record. In the northern Gulf of Mexico, the

Ron Boyd; John Suter; Shea Penland

1989-01-01

206

Near coast sedimentary stratigraphy as a proxy for climatic instability  

Microsoft Academic Search

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

J. McLivenny

2009-01-01

207

Perspective on the sequence stratigraphy of continental strata  

Microsoft Academic Search

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

K. W. Shanley; P. J. McCabe

1994-01-01

208

Cement stratigraphy of the Lisburne Group, northeastern Brooks Range, Alaska  

Microsoft Academic Search

Cement stratigraphy serves as a descriptive framework for the interpretation of the diagenetic history of the Carboniferous Lisburne Group, northeastern Brooks Range, Alaska. The Lisburne is a sequence of shallow-water, marine carbonate rocks that have experienced a wide spectrum of diagenetic events: early marine diagenesis, early subaerial exposure, significant erosion and karstification following final Lisburne deposition, deep burial of at

R. C. Carlson; R. H. Goldstein

1992-01-01

209

Clastic sedimentology and detrital geochronology: deciphering the growing phase of the Variscan belt.  

NASA Astrophysics Data System (ADS)

The late Palaeozoic Variscan Orogeny results from the convergence between two major plates: Laurussia and Gondwana. The relief created during the Variscan Orogeny has now been completely eroded away. However, the Devonian and Carboniferous sediments potentially record the birth of the relief and the exhumation of rocks during the early stages of this orogenesis. A multidisciplinary approach (structural, sedimentology and geochronology) is used in order to constrain the palaeogeography and the nature of the material being eroded during the growth of the Variscan belt. More specifically, two detrital dating methods, U/Pb on zircon and 39Ar-40Ar on white mica, are used as complementary tools in order to decipher the age of the detrital material sources. The weakly deformed Ordovician to Carboniferous sediments of the Mauges Unit (South-Armorican Domain, France) are located in the internal zones of the Variscan belt. Two Formations, respectively the Sainte-Anne Fm of Emsian (late Lower Devonian) age and the Ancenis Fm of Visean (Lower Carboniferous) age, are made up of gravity flow deposits that record the creation of a nearby relief. The pre-orogenic Sainte-Anne Fm consists of immature sandstones with a large amount of lithic fragments of mainly sedimentary and volcanic origin. Among the detrital zircons analyzed, a population dated at ca. 400 Ma is therefore contemporaneous to the sedimentation and is interpreted as volcanic in origin. Considering the tectonic setting proposed for the area, these detrital zircons could record the creation of a magmatic arc. The late-orogenic Ancenis Fm was deposited after the crustal stacking that occurred close to the Devonian/Carboniferous boundary (Champtoceaux Complex, Bosse et al., 2000; Pitra et al., 2009). Carboniferous sedimentation took place in a basin preserved due to a reactivation of the suture zone. The Ancenis Fm is a lacustrine to continental deposit, 3- to 6 km thick, and displays a coarsening-upwards mega-sequence; this implies that relief and subsequently the material removed were increasingly closer to the sedimentation area. This trend is associated with surface uplift and the progressive exhumation of Variscan magmatic and metamorphic rocks, as shown by the progressive appearance of younger zircons and/or white micas in the detrital record. In this study, the detrital record within the basin will be compared to the evolution of metamorphic and magmatic rocks in underlying units.

Ducassou, Céline; Ballèvre, Michel; Poujol, Marc; Ruffet, Gilles; Gallagher, Kerry

2010-05-01

210

Lower Palaeozoic stratigraphy of the East Greenland Caledonides  

Microsoft Academic Search

The Lower Palaeozoic stratigraphy of the East Greenland Caledonides, from the fjord region of North-East Greenland northwards to Kronprins Christian Land, is reviewed and a number of new lithostratigraphical units are proposed. The Slottet Formation (new) is a Lower Cambrian quartzite unit, containing Skolithos burrows, that is present in the Målebjerg and Eleonore Sø tectonic windows, in the nunatak region

M. Paul Smith; Jan Audun Rasmussen; Steve Robertson; A. K. Higgins; A. Graham Leslie

2005-01-01

211

Workshop on quantitative dynamic stratigraphy. Final conference report  

SciTech Connect

This document discusses the development of quantitative simulation models for the investigation of geologic systems. The selection of variables, model verification, evaluation, and future directions in quantitative dynamic stratigraphy (QDS) models are detailed. Interdisciplinary applications, integration, implementation, and transfer of QDS are also discussed. (FI)

Cross, T.A.

1988-04-01

212

Formal Quaternary stratigraphy—What do we expect and need?  

Microsoft Academic Search

At the start of my INQUA career a reasonable target for the long-term development of Quaternary stratigraphy was the construction of a table that listed a number (perhaps fewer than a dozen, perhaps more) of “stages” for each of the chief regions of the Earth, and which reliably indicated how these stages should be correlated from region to region. A

N. J. Shackleton

2006-01-01

213

Formal Quaternary stratigraphy---What do we expect and need?  

Microsoft Academic Search

At the start of my INQUA career a reasonable target for the long-term development of Quaternary stratigraphy was the construction of a table that listed a number (perhaps fewer than a dozen, perhaps more) of ``stages'' for each of the chief regions of the Earth, and which reliably indicated how these stages should be correlated from region to region. A

N. J. Shackleton

2006-01-01

214

New insight into the sedimentology and stratigraphy of the Dur At Talah tidal-fluvial transition sequence (Eocene-Oligocene, Sirt Basin, Libya)  

NASA Astrophysics Data System (ADS)

The Dur At Talah escarpment is exposed in the Abu Tumayam Trough at the southern part of the Sirt Basin, central Libya. The cliff (˜145 m high and ˜150 km long) is oriented along an E-W axis and faces southward. Only a few field studies have been previously carried out in this area, and these were mainly focused on the succession's famous vertebrate fossil-content. The reconstruction of the depositional environments, which is the purpose of this paper, remained poorly documented. In this study, the uppermost Eocene rock succession composing the Dur At Talah escarpment is divided into two stratigraphic units: the New Idam Unit at the base composed of highly bioturbated fine sand/claystone alternations, and the Sarir Unit at the top dominated by medium to very coarse grading sometimes to microconglomeratic sandstones. This complete succession is built up of shallow marine (New Idam Unit) to fluvial (upper part of Sarir Unit) deposits passing through a "marine/fluvial" transition zone (lower Sarir Unit). The stratigraphic succession suggests a global regressive trend. The marine part of the New Idam Unit is dominated by deposits attributed to tidal depositional environments including tidal flat, tidal channel and tidal bars as well as biostroms of oyster shells at the base of the unit. The lower part of the Sarir Unit appears to be deposited in a fluvial influenced, tide-dominated environment. The upper part of the Sarir Unit, made of coarse-grained to microconglomeratic sandstones interbedded with paleosoil horizons, is interpreted as being fluvial.

Abouessa, Ashour; Pelletier, Jonathan; Duringer, Philippe; Schuster, Mathieu; Schaeffer, Philippe; Métais, Eddy; Benammi, Mouloud; Salem, Mustafa; Hlal, Osama; Brunet, Michel; Jaeger, Jean-Jacques; Rubino, Jean-Loup

2012-04-01

215

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

216

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

217

Sedimentology and high-frequency sequence stratigraphy of a forearc extensional basin: The Miocene Caleta Herradura Formation, Mejillones Peninsula, northern Chile  

Microsoft Academic Search

Facies and sequence stratigraphic interpretation for the 380-m-thick Caleta Herradura Formation (Miocene) are presented, based on detailed and comprehensive outcrop data from the Caleta Herradura half-graben, Mejillones Peninsula, northern Chile. The Caleta Herradura Formation contains an array of lithofacies comprising sandstones, sandy mudstones, diatomites and breccio-conglomerates that are interpreted as the products of inner-shelf to non-marine depositional settings. Complete exposure

Claudio Di Celma; Gino Cantalamessa

2007-01-01

218

Project EARTH09-SPH3: Integrated Carbon-isotope stratigraphy and sedimentology of continental Early Jurassic deposits from Xinjiang, NW China  

Microsoft Academic Search

Major environmental changes took place during the Early Jurassic, particularly at the time of the Toarcian Oceanic Anoxic Event. The nature of the environmental change at this time is well known from the marine sedimentary record, but is much less well understood from continental deposits. The Early Jurassic sediments in Xinjiang province, NW China, were laid down in lacustrine and

Stephen Hesselbo; Shenghui Deng

219

Mapping the Stratigraphy of Booming Sand Dunes  

NASA Astrophysics Data System (ADS)

Booming dunes emit a loud rumbling sound after a man-made or natural sand avalanche is generated on the slip face of a large desert dune. The sound consist of one dominant frequency (70 - 105 Hz) with several higher harmonics. A recent publication (Vriend et al., 2007) presented a model of an internal, natural waveguide that propagates the booming emission, amplifies the sound, and sets the booming frequency. The mapping of the subsurface layering, which is necessary for the existence of a waveguide, prompted additional work on the dune structure and stratigraphy. The current work highlights geophysical measurements at Eureka Dunes in Death Valley National Park, CA and Dumont Dunes in the Mojave Desert, CA. Seismic refraction studies indicate strong layering with large velocity jumps across the interfaces. Ground Penetrating Radar (GPR) profiles, at frequencies of 100 MHz and 200 MHz, map out the stratigraphic structure of the dunes. Variations in the near surface layering are able to predict the seasonal variability in booming frequency both quantitatively and qualitatively. The Kirchhoff migrated GPR profiles are superimposed on the local topography obtained with a laser rangefinder. The complex dune structure is resolved to a depth of over 30 meters for the 100 MHz antenna. The GPR profiles of the longitudinal Eureka dune display complex internal structures from old dune crests. Both slopes have slip faces at 30 degrees with parallel layering (< 2m) at the near surface. At the transverse Dumont dune the GPR profile exhibits strong parallel layering on the booming leeward slipface only. The shallower windward face features a remarkable tilted repetitive layering that cuts through the surface. At Dumont Dunes the layering on the leeward face explains the change in booming frequency between 70 - 95 Hertz in the period 2005 - 2008. The tilted layering structure of the shallow windward face prevents the formation of a waveguide and is never able to sustain the booming sound. The Dumont dune progresses slowly, estimated at ~ 1 m/year from correlating satellite images, by forming new slip faces on the leeward face over time. Large precipitation events may cause a new layer to form. Sand sampling provides a quantitative measure on the chemical composition and water content of the layering.

Vriend, N. M.; Hunt, M. L.; Clayton, R. W.

2008-12-01

220

Cone-penetrometer exploration of Sinkholes: Stratigraphy and soil properties  

NASA Astrophysics Data System (ADS)

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. I and II represent Plio-Pleistocene marine sediments with Unit II being the zone of soil clay accumulation. III and IV are horizons residual from Miocene strata and indicate an episode of karstification prior to deposition of Units I and II. Conduit fill is a mixture of materials with low cohesion. The fill materials indicate centripetal and downward movement of insoluble sediments derived from the surrounding strata. Loss of cohesion results in near-zero friction ratios. Very low friction ratios, coupled with materials with little cohesion, indicate potentially-liquefiable soils in the immediate vicinity of zones where piping failure may be imminent. SPT does not provide sufficient data to predict these zones of potential, failure. 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 data fail to produce consistent indicators of sinkhole stratigraphy or properties. With laboratory soil data, SPT indicates general, inconclusive trends.

Bloomberg, D.; Upchurch, S. B.; Hayden, M. L.; Williams, R. C.

1988-10-01

221

Influence of barrier island stratigraphy and bathymetry on shoreline change  

SciTech Connect

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

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

1993-03-01

222

Great earthquakes along the Western United States continental margin: implications for hazards, stratigraphy and turbidite lithology  

NASA Astrophysics Data System (ADS)

We summarize the importance of great earthquakes (Mw ? 8) for hazards, stratigraphy of basin floors, and turbidite lithology along the active tectonic continental margins of the Cascadia subduction zone and the northern San Andreas Transform Fault by utilizing studies of swath bathymetry visual core descriptions, grain size analysis, X-ray radiographs and physical properties. Recurrence times of Holocene turbidites as proxies for earthquakes on the Cascadia and northern California margins are analyzed using two methods: (1) radiometric dating (14C method), and (2) relative dating, using hemipelagic sediment thickness and sedimentation rates (H method). The H method provides (1) the best estimate of minimum recurrence times, which are the most important for seismic hazards risk analysis, and (2) the most complete dataset of recurrence times, which shows a normal distribution pattern for paleoseismic turbidite frequencies. We observe that, on these tectonically active continental margins, during the sea-level highstand of Holocene time, triggering of turbidity currents is controlled dominantly by earthquakes, and paleoseismic turbidites have an average recurrence time of ~550 yr in northern Cascadia Basin and ~200 yr along northern California margin. The minimum recurrence times for great earthquakes are approximately 300 yr for the Cascadia subduction zone and 130 yr for the northern San Andreas Fault, which indicates both fault systems are in (Cascadia) or very close (San Andreas) to the early window for another great earthquake. On active tectonic margins with great earthquakes, the volumes of mass transport deposits (MTDs) are limited on basin floors along the margins. The maximum run-out distances of MTD sheets across abyssal-basin floors along active margins are an order of magnitude less (~100 km) than on passive margins (~1000 km). The great earthquakes along the Cascadia and northern California margins cause seismic strengthening of the sediment, which results in a margin stratigraphy of minor MTDs compared to the turbidite-system deposits. In contrast, the MTDs and turbidites are equally intermixed on basin floors along passive margins with a mud-rich continental slope, such as the northern Gulf of Mexico. Great earthquakes also result in characteristic seismo-turbidite lithology. Along the Cascadia margin, the number and character of multiple coarse pulses for correlative individual turbidites generally remain constant both upstream and downstream in different channel systems for 600 km along the margin. This suggests that the earthquake shaking or aftershock signature is normally preserved, for the stronger (Mw ? 9) Cascadia earthquakes. In contrast, the generally weaker (Mw = or <8) California earthquakes result in upstream simple fining-up turbidites in single tributary canyons and channels; however, downstream mainly stacked turbidites result from synchronously triggered multiple turbidity currents that deposit in channels below confluences of the tributaries. Consequently, both downstream channel confluences and the strongest (Mw ? 9) great earthquakes contribute to multi-pulsed and stacked turbidites that are typical for seismo-turbidites generated by a single great earthquake. Earthquake triggering and multi-pulsed or stacked turbidites also become an alternative explanation for amalgamated turbidite beds in active tectonic margins, in addition to other classic explanations. The sedimentologic characteristics of turbidites triggered by great earthquakes along the Cascadia and northern California margins provide criteria to help distinguish seismo-turbidites in other active tectonic margins.

Nelson, C. H.; Gutiérrez Pastor, J.; Goldfinger, C.; Escutia, C.

2012-11-01

223

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

224

Archaeological sedimentology of overbank silt deposits on the floodplain of the Ohio river near Louisville, Kentucky  

USGS Publications Warehouse

The surface of the floodplain of the Ohio River about 20km southwest of Louisville, Kentucky, is a series of linear ridges and swales that are subparallel to the channel of the river, which here is relatively straight and flows southward. Numerous prehistoric occupational sites are located on these ridges. The sediments that underlie the ridges, which were examined in four archaeological excavations as deep as 8 m, are predominantly sandy silt and silty fine to very fine sand and appear to be mainly the product of overbank deposition from suspended load. Abundant cultural material and occupational sites dating as early as 10,000 years BP are found in the sediments at depths as great as 6??5 m. The fine sediments of the floodplain are underlain by sand and gravel. The context of the cultural materials and the stratigraphy and morphology of the deposits indicate that the ridged deposits began as linear riverside sand and gravel bars. These were succeeded upward by fine-grained overbank deposits in which the ridged morphology was maintained because the overbank silt and fine sand were deposited as prograding elongate bars at high water. As the floodplain ridge built upward, the sedimentation rate decreased and the sand content of the sediments diminished, and as the river channel occasionally shifted, the ridged deposits were built in successive subparallel sequences. Two archaeological consequences are implicit in this depositional model of orderly growth of the floodplain. First, available archaeological data from floodplain segments along other parts of the river should confirm the model; and second, the model should make it possible to search the floodplains of the Ohio River for stratified sites of any desired age. ?? 1984.

Gray, H. H.

1984-01-01

225

Tethyan-to-boreal correlation in the Kimmeridgian using high-resolution sequence stratigraphy (Vocontian Basin, Swiss Jura, Boulonnais, Dorset)  

NASA Astrophysics Data System (ADS)

Ammonite biostratigraphy plays a central role in the definition of Jurassic stratigraphy. Nevertheless, the strong provincialism of European ammonite species during the Kimmeridgian is a long-standing problem in correlation attempts between the boreal and Tethyan faunal realms. Moreover, the sequence-stratigraphic interpretations for northern and southern Europe given in the Jurassic chronostratigraphic chart of Hardenbol et al. in SEPM Publ. 60 (chart) (1998) are different. The present study aims to resolve this correlation problem in order to better understand the connections between the boreal and the Tethyan realms during the Kimmeridgian. A sedimentological and high-resolution sequence-stratigraphic interpretation is presented for two unpublished sections (Cras d’Hermont and Roche de Mars) in the northern Swiss Jura, where recently discovered ammonites display both boreal and Tethyan influences. Then, these sections are correlated with the same time interval in the central Swiss Jura and Vocontian Basin, which belong to the Tethyan realm. Lastly, a long-distance transect is constructed between the Vocontian Basin, Swiss Jura, northern France, and southern England, the last two areas being part of the sub-boreal realm. The main results of this work are that: (1) third-order depositional sequences, and also higher-frequency sequences, can be correlated from the Tethyan to the boreal realm; (2) the sequence-stratigraphic interpretation given by Hardenbol et al. in SEPM Publ 60 (chart) (1998) for northern Europe seems to be accurate and agrees with the sequence-stratigraphic framework established in the Swiss Jura; (3) the Late Kimmeridgian of the Swiss Jura displays boreal influences; (4) integrated high-resolution sequence-stratigraphic and cyclostratigraphic studies are a valuable approach for bridging the correlation gap between northern and southern Europe.

Colombié, C.; Rameil, N.

2007-06-01

226

Geomorphic and Sedimentologic Characteristics of Alluvial Reaches in the Black Canyon of the Gunnison National Monument, Colorado.  

National Technical Information Service (NTIS)

This report summarizes geomorphic, hydraulic, and sedimentologic data collected in two alluvial reaches of Black Canyon (BLCA) in 1990, 1994, and 1995 and hydrologic data recorded since the early 20th century. The objective of this study was to determine ...

J. G. Elliott L. A. Hammack

1999-01-01

227

Stratigraphy and structure of the western Kentucky fluorspar district  

USGS Publications Warehouse

The western Kentucky fluorspar district is part of the larger Illinois-Kentucky fluorspar district, the largest producer of fluorspar in the United States. This report is based largely on data gathered from 1960 to 1974 during the U.S. Geological Survey-Kentucky Geological Survey cooperative geologic mapping program of Kentucky. It deals chiefly with the stratigraphy and structure of the district and, to a lesser extent, with the fluorspar-zinc-lead-barite deposits. Sedimentary rocks exposed in the district range in age from Early Mississippian (Osagean) to Quaternary. Most rocks exposed at the surface are Mississippian in age; two-thirds are marine fossiliferous limestones, and the remainder are shales, siltstones, and sandstones. Osagean deep-water marine silty limestone and chert are present at the surface in the southwestern corner of the district. Meramecian marine limestone is exposed at the surface in about half the area. Chesterian marine and fluvial to fluviodeltaic clastic sedimentary rocks and marine limestone underlie about one-third of the area. The total sequence of Mississippian rocks is about 3,000 ft thick. Pennsylvanian rocks are dominantly fluvial clastic sedimentary rocks that change upward into younger fluviodeltaic strata. Pennsylvanian strata of Morrowan and Atokan age are locally thicker than 600 ft along the eastern and southeastern margin and in the major grabens of the district where they have been preserved from erosion. Cretaceous and Tertiary sediments of the Mississippi embayment truncate Paleozoic formations in and near the southwestern corner of the district and are preserved mostly as erosional outliers. The deposits are Gulfian nonmarine gravels, sands, and clays as much as 170 ft thick and upper Pliocene fluvial continental deposits as thick as 45 ft. Pleistocene loess deposits mantle the upland surface of the district, and Quaternary fluvial and fluviolacustrine deposits are common and widespread along the Ohio and Cumberland Rivers and their major tributaries. Many mafic dikes and a few mafic sills are present. The mafic rocks are mostly altered mica peridotites or lamprophyres that are composed of carbonate minerals, serpentine, chlorite, and biotite and contain some hornblende, pyroxene, and olivine. Most of the dikes are in a north-north west-trending belt 6 to 8 mi wide and strike N. 20 0 -30 0 W. The dikes dip from 80 0 to 90 0 and are commonly 5 to 10 ft wide. Radioisotopic study indicates that the dikes are Early Permian in age. The district is just southeast of the intersection of the east-trending Rough Creek-Shawneetown and northeast-trending New Madrid fault systems. The district's principal structural features are a northwest-trending domal anticline, the Tolu Arch, and a series of steeply dipping to nearly vertical normal faults and fault zones that trend dominantly northeastward and divide the area into elongated northeast-trending grabens and horsts. Formation of these grabens and horsts was one of the major tectonic events in the district. Vertical displacement may be as much as 3,000 ft but commonly ranges from a few feet to a few hundred feet; no substantial horizontal movement is believed to have taken place. Many cross faults having only a few feet of displacement trend northwestward and are occupied at places by mafic dikes. Faulting was mostly post-Early Permian to pre-middle Cretaceous in age. Many theories have been advanced to explain the structural history of the district. A generally acceptable overall hypothesis that would account for all the structural complexities, however, is still lacking. Useful structural data, such as the structural differences between the grabens and the horsts, have been obtained, however, from the recently completed geologic mapping. Mapping also has more clearly shown the alinement of the Tolu Arch, the belt of dikes, and an unusually deep graben (the Griffith Bluff graben); this alinement suggests that possibl

Trace, R. D.; Amos, D. H.

1984-01-01

228

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

USGS Publications Warehouse

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

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

2008-01-01

229

High-resolution strontium isotope stratigraphy and biostratigraphy of the Miocene Monterey Formation, central California  

SciTech Connect

Detailed biostratigraphic and Sr isotope studies on two outcrop sections of the Miocene Monterey Formations of California demonstrate the applicability of the Sr isotope method for detailed biostratigraphic ages. These ages generally agree with Sr-isotope ages determined by correlating {sup 87}Sr/{sup 86}Sr ratios with a standard {sup 87}Sr/{sup 86}Sr vs. age curve constructed of data from Deep Sea Drilling Project (DSDP) Sites 575 and 590. Diagenetic modification of Sr-isotope ratios of the Monterey Formation was negligible. In the lower Miocene, strontium isotopes provide age resolutions of 0.1 to 0.2 Ma and reversals within a general trend of increasing {sup 87}Sr/{sup 86}Sr coincide with minor faults and slump structures. Biostratigraphy yields the more definitive age assignments in the younger siliceous rocks where diatoms in particular have more utility than the corresponding flat and polytonic portion of the isotopic curve. Strontium isotope correlation of the basal Monterey Formation with DSDP Site 575 indicates that Monterey deposition commenced 17.85 {plus minus} 0.10 Ma (within planktic foraminiferal zone N6 and calcareous nannofossil zone CN2). This event dates 0.35 {plus minus} 0.10 Ma before the beginning of the pronounced shift of {delta}{sup 13}C observed at Site 575, which argues against a causal link between the two. It is evident that Sr-isotope stratigraphy is a valuable supplement to biostratigraphy; the techniques are complementary in refining chronostratigraphic interpretations.

Finger, K.L. (Chevron Oil Field Research Co., La Habra, CA (USA)); DePaolo, D.J. (Univ. of California, Berkeley (USA))

1990-05-01

230

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

231

Chemo and litho-stratigraphy of the Neoproterozoic Katakturuk Dolomite, northeastern Brooks Range, Alaska, and implications for the origin of the Arctic Alaska-Chukotka Plate  

Microsoft Academic Search

The Katakturk Dolomite is a 2.2 km thick Neoproterozoic carbonate succession exposed in the northeastern Brooks Range of Alaska. A diamictite at the base of the Katakturuk is capped by a black limestone with peculiar roll-up structures. Carbon-isotope chemo-stratigraphy suggests this is a Sturtian-age glacial deposit. Approximately 500 meters above the diamictite, textures characteristic of a basal Ediacaran cap carbonate,

F. A. MacDonald; D. P. Schrag

2007-01-01

232

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

Microsoft Academic Search

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

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

2005-01-01

233

QUATERNARY STRATIGRAPHY OF RICHFIELD TOWNSHIP, SUMMIT COUNTY, OHIO1  

Microsoft Academic Search

Borings and measured sections were used to trace 3 Wisconsinan tills in Richfield Township of Summit County in northeastern Ohio. Various fluvial and glacio- fluvial deposits were found underlying, overlying, and between the tills. The tills were differentiated upon the basis of stratigraphy, texture, and mineralogy. Generally, the tills grade from coarse-grained with high quartz\\/feldspar and alkali feldspar\\/plagioclase values as

JOHN P. SZABO; MICHAEL P. ANGLE

1983-01-01

234

Stratigraphy and chronology of the Galeras volcanic complex, Colombia  

Microsoft Academic Search

An understanding of the evolution of the Galeras volcanic complex (GVC) is critical for assessing and refining hazards and eruption forecasting for the current reactivation of Galeras volcano. Detailed field geology and dating by14C and40Ar-39Ar methods help establish a comprehensive stratigraphie framework, defining six different stages in the evolution of the Galeras volcanic complex. The two oldest stages, Cariaco and

Marta Lucia Calvache v; Gloria Patricia Cortés J; Stanley N. Williams

1997-01-01

235

Alaskan Peninsula Cenozoic stratigraphy: stratigraphic sequences and current research  

Microsoft Academic Search

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

J. M. Armentrout

1985-01-01

236

Sedimentology of high-stage flood deposits of the Tagus River, Central Spain  

Microsoft Academic Search

This paper details the sedimentology of high-stage flood deposits, with the definition of sedimentary environments and their characteristic sequences, along two bedrock reaches of the Tagus River (Central Spain). High-stage flood deposits accumulated in bedrock canyons include slackwater flood deposits (SWD) and other types of deposits located at flow separation zones and associated with slow-moving flow (<1 m s?1). These

Gerardo Benito; Yolanda Sánchez-Moya; Alfonso Sopeña

2003-01-01

237

Geomorphic and sedimentologic evidence for the separation of Lake Superior from Lake Michigan and Huron  

Microsoft Academic Search

A common break was recognized in four Lake Superior strandplain sequences using geomorphic and sedimentologic characteristics.\\u000a Strandplains were divided into lakeward and landward sets of beach ridges using aerial photographs and topographic surveys\\u000a to identify similar surficial features and core data to identify similar subsurface features. Cross-strandplain, elevation-trend\\u000a changes from a lowering towards the lake in the landward set of

John W. Johnston; Todd A. Thompson; Douglas A. Wilcox; Steve J. Baedke

2007-01-01

238

Paleohydrology of Andean saline lakes from sedimentological and isotopic records, Northwestern Argentina  

Microsoft Academic Search

The paleohydrological evolution of several high altitude, saline lakes located in the southernmost Altiplano (El Peinado and San Francisco basins, Catamarca province, NW Argentina) was reconstructed applying sedimentological, geochemical and isotopic techniques. Several playa lakes from the San Francisco basin (26° 56' S; 68° 08' W, 3800-3900 m a.s.l.) show evidence of a recent raise in the watertable that led

Blas L. Valero-Garcés; Antonio Delgado-Huertas; Norma Ratto; Ana Navas; Larry Edwards

2000-01-01

239

Water chemistry and sedimentological observations in littlefield lake, michigan: Implications for lacustrine marl deposition  

Microsoft Academic Search

A combination of both water chemistry and sedimentological information was used to investigate the carbonate-producing mechanism\\u000a in Littlefield Lake, a small lake located in Isabella County, central Michigan. Data on temperature, dissolved oxygen, pH,\\u000a calcium carbonate (CaCO3) saturation, alkalinity, calcium, and magnesium were obtained on a monthly basis over a 13-month period, with each parameter\\u000a determined at 1m intervals over

Nina M. Duston; Robert M. Owen; Bruce H. Wilkinson

1986-01-01

240

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

241

Application of Sedimentologic-Geophysical Analysis for Coastal Zone Management in Albania.  

NASA Astrophysics Data System (ADS)

The areas under investigation encompassing a large expense of land of south- western part of Albanian coast zone. The paper examines the Quaternary history of dual (sedimentologic models and the evaluation impact of the geological environment in expansion of ancient civilization in this region). The work presented here is result of continued study about four last years and goes on in our days. The neotectonic structure of Butrint region is consisted off horst- graben structure, E-W trending. The Quaternary formations fill the lowest part of the region and have different origins and consisted of alluvial and lagoon deposits, about 80-m thickness. The lagoonal deposits are common around Butrint lake wile ancient town (Hellenistic- Roman- Byzantine) was extended mainly on the soft Holocene sediments. The soundings data, particularly resistivity variation are the base of sedimentologic and lithological studies due to the lack of boreholes. Two cycles of sedimentation can be observed within the thickness of 40- 50m: the first, gravel and sands and second mainly of clays in upper part of the cross section. In addition to, V.E.S. data and resistivity maps point out the features of sedimentologic environment distinguishing Pleistocene and Holocene deposits, delineated of water-bearing coarse-grained sands and gravels and land-sea interaction separating salty waters areas. Based on the sedimentologic and structural factors studied and geophysical maps and cross-sections, plenty of geomorphic problems are obvious now. This studies show the evidence to the advancement of the coastline is still occurring and the shoreline is still on the move.

Kavaja, V. S.; Durmishi, C.; Alikaj, P.; Jata, I.

2004-12-01

242

Archaeological recording and chemical stratigraphy applied to contaminated land studies.  

PubMed

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

Photos-Jones, Effie; Hall, Allan J

2011-10-02

243

The utilization of sequence stratigraphy in reservoir geology  

SciTech Connect

Initial applications of sequence stratigraphy focused on basin analysis and exploration problems. As finer scale studies were conducted using well logs and outcrops, it has become possible to apply the concepts to improving reservoir performance. Investigations of the fine scale sequence stratigraphy of carbonates has led to its application to enhance production in the complex Paleozoic carbonate reservoirs of the Permian and Paradox Basins. Studies of coastal plain and shallow marine sediments in the Colorado Plateau and Alberta Basin has led to effective utilization in Alberta Basin reservoirs. Outcrop of and subsurface investigations of fluvial and deltaic sediments in the North Sea has improved performance of Jurassic reservoirs in the North Sea. Geophysicists are refining statistical and numerical techniques for defining the seismic facies within reservoirs in Indonesia, Africa, and the Gulf of Mexico. Several sequence stratigraphic concepts are available for application (e.g. genetic sequences, T-R sequences, forced regressions, etc.). Allowing the data to speak for itself rather than slavish adherence to only one theory has greatly improved the utilization of sequence stratigraphy at the reservoir level.

Macurda, J.R.; Bradford, D. (The Energists, Houston, TX (United States))

1996-01-01

244

Stratigraphy and geochemistry of an early Aptian carbonate platform: interactions between relative sea level and environmental changes (Prebetic Zone, Spain)  

NASA Astrophysics Data System (ADS)

The Early Aptian was a time of development of large shallow carbonate platforms, punctuated with phases of growth crises and platform demise. Much research has been done over the past few years, focussed on characterizing the stratigraphic architecture of carbonate platforms and elucidating the possible link between platform demise and oceanic anoxic events. To explore this, we are investigating the Mariola stratigraphic section (Prebetic Zone, Betic Cordillera), deposited in the Southern Iberian Palaeomargin during the Mesozoic. The Lower Aptian of this section records the installation, development and demise of a carbonate platform, and the subsequent imprint of the OAE 1a. An integrated approach including sedimentology, biostratigraphy, and sequence stratigraphy, along with isotope stratigraphy, biomarker analysis and elemental geochemistry has been carried out. The studied section is located in the Sierra de Mariola, where the early Aptian succession is composed of three units: (1) The Llopis Fm., made of shallow platform carbonates with rudists, which is organized in a succession of shallowing-upwards parasequences defining a progradational-retrogradational cycle; (2) the Agres bed, formed by bioclastic calcarenites and marls, which represents a significant lithological and biotic change and is interpreted as deposited during a transgressive pulse coeval to a notable terrigenous input into the platform, and (3) the Almadich Fm., made of an alternation of marls and marlstones with planktonic foraminifers and ammonites, interpreted as the result of the drowning of the carbonate platform. The C-isotope curve shows a negative trend in the upper part of the Llopis Fm. with lowest values within the basal part of the Almadich Fm. This negative peak is followed by a positive shift, recorded within a level of organic-rich marls, considered to be the local record of the OAE1a. Finally, the values decrease through the upper part of the Almadich Fm. TOC values in the organic rich level vary between 0.2-0.6 wt.%. The biomarker characterization of the organic rich level has revealed that the organic matter is very immature and well preserved, and dominated by n-alkanes, with an important contribution of hopanes and minor amount of steranes. The analysis of the distribution of biomarkers suggests that the origin of the organic matter is dominated by terrestrial and marine plants, with a lower contribution of bacteria. The integration of stratigraphy and geochemistry suggests that the evolution of the early Aptian carbonate platform studied was the result of a combination of relative sea-level changes, leading to the initial progradational phase and the subsequent deposition of parasequences and, on the other hand, environmental changes reflected in the demise of the carbonate platform and the facies and faunal change recorded in the Agres bed. The OEA 1a took place after the drowning event, suggesting that the main environmental changes recorded in this section might be related to a combination of regional processes and the global changes predating and probably triggering the OAE1a. Acknowledgements: This work is a contribution of the research project CGL2009-10329.

Castro, J. M.; de Gea, G. A.; Ruiz-Ortiz, P. A.; Quijano, M. L.; Pancost, R. D.; Jimenez de Cisneros, C.; Caballero, E.

2012-04-01

245

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

246

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

247

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

248

Identifying climate change signals in the late Quaternary gravel-bed, braided river stratigraphy of the Canterbury Plains, New Zealand  

NASA Astrophysics Data System (ADS)

The gravel-bed, braided river stratigraphy of the Canterbury Plains, central South Island, New Zealand, was deposited over several Quaternary glacial-interglacial cycles and so potentially offers an important insight into fluvial responses to climate change. The uppermost 20 m of the section which is exposed along the east coast has yielded a radiocarbon age at the base of the coastal cliffs of ~33 ka cal BP and is capped by a Holocene loess sheet, implying that it includes New Zealand’s Last Glacial Maximum (22-18 ka). This part of the section contains several laterally-continuous surfaces representing periods of low aggradation or non-deposition, and it is tempting to link these hiatuses to one or more periods of glacial advance, still-stand or retreat. However, this requires a reliable chronology with which to tie the stratigraphy to the excellent high-resolution climate history established for the region. Optically stimulated luminescence (OSL) dating of quartz grains from sand bodies within the gravel stratigraphy provides the potential to develop this chronology. However, there is a perception that quartz from this area is a difficult candidate for luminescence dating for reasons connected with the short sediment transport distances and limited number of erosion-transport cycles which together reduce opportunities for sensitization of the luminescence signal and give low signal intensities. Recent advances in OSL dating techniques provide the opportunity to revisit this issue. In this study, nine samples from the Canterbury coastal stratigraphy were dated using OSL. The samples were collected from large sand channel fills and bar margins, five of them in vertical succession at one locality. A Single Aliquot Regenerative (SAR) dose protocol was used to generate equivalent dose (De) values from coarse-grained quartz. Standard screening criteria were applied to the SAR data prior to statistical analysis of the De distributions. The relative intensity and behaviour of the fast and medium components in the OSL signal used for dating was evaluated using signal deconvolution. The ages generated are in chronostratigraphic order and have uncertainties of about 2-3 ka (12%). We will discuss the methods used to verify the robustness of these ages and their implications for the late Quaternary depositional history of the Canterbury Plains.

Jones, M. A.; Rowan, A. V.; Covey-Crump, S. J.; Brocklehurst, S. H.; Roberts, H. M.; Duller, G. A.

2010-12-01

249

Stratigraphy of the Martian northern plains  

Microsoft Academic Search

The northern plains of Mars are roughly defined as the large continuous region of lowlands that lies below Martian datum, plus higher areas within the region that were built up by volcanism, sedimentation, tectonism, and impacts. These northern lowlands span about 50 x 106 km2 or 35 percent of the planet's surface. The age and origin of the lowlands continue

K. L. Tanaka

1993-01-01

250

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

251

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

252

Integrating sequence stratigraphy and rock-physics to interpret seismic amplitudes and predict reservoir quality  

Microsoft Academic Search

This dissertation focuses on the link between seismic amplitudes and reservoir properties. Prediction of reservoir properties, such as sorting, sand\\/shale ratio, and cement-volume from seismic amplitudes improves by integrating knowledge from multiple disciplines. The key contribution of this dissertation is to improve the prediction of reservoir properties by integrating sequence stratigraphy and rock physics. Sequence stratigraphy has been successfully used

Tanima Dutta

2009-01-01

253

Sequence stratigraphy as key to evolution of hydrocarbon prospects: Examples from northern Gulf of Mexico  

Microsoft Academic Search

Sequence stratigraphy is the study of rock relationships within a chronostratigraphic framework. Sequence stratigraphy is a guide to hydrocarbon prospect description and prediction. An individual sequence is a conformable succession of related strata bounded by major unconformities and corresponds to a 3rd order cycle, generally with a periodicity of a million or so years. successions of Within a sequence are

N. H. Sullivan; A. Lowrie

1990-01-01

254

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

255

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

256

Eustatic curve for the middle Jurassic-Cretaceous based on Russian platform and Siberian stratigraphy: Zonal resolution  

SciTech Connect

We have used the stratigraphy of the central part of the Russian platform and surrounding regions to construct a calibrated eustatic curve for the Bajocian through the Santonian. The study area is centrally located in the large Eurasian continental craton, and was covered by shallow seas during much of the Jurassic and Cretaceous. The geographic setting was a very low-gradient ramp that was repeatedly flooded and exposed. Analysis of stratal geometry of the region suggests tectonic stability throughout most of Mesozoic marine deposition. The paleogeography of the region led to extremely low rates of sediment influx. As a result, accommodation potential was limited and is interpreted to have been determined primarily by eustatic variations. The central part of the Russian platform thus provides a useful frame of reference for the quantification of eustatic variations throughout the Jurassic and Cretaceous. The biostratigraphy of the Russian platform provides the basis for reliably determining age and eustatic events. The Mesozoic section of the central part of the Russian platform is characterized by numerous hiatuses. In this study, we filled the sediment gaps left by unconformities in the central part of the Russian platform with data from stratigraphic information from the more continuous stratigraphy of the neighboring subsiding regions, such as northern Siberia. Although these sections reflect subsidence, the time scale of variations in subsidence rate is probably long relative to the duration of the stratigraphic gaps to be filled, so the subsidence rate can be calculated and filtered from the stratigraphic data. We thus have compiled a more complete eustatic curve than would be possible on the basis of Russian platform stratigraphy alone.

Sahagian, D.; Pinous, O. [Univ. of New Hampshire, Durham, NH (United States); Olferiev, A. [Centrgeologia, Moscow (Russian Federation); Zakharov, V. [Russian Academy of Sciences, Novosibirsk (Russian Federation)

1996-09-01

257

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

258

A Sedimentological Study of Modern and Ancient Lacustrine Environments at Michael Bay, Lake Huron  

Microsoft Academic Search

Modern and ancient environments associated with Lakes Algoma and Huron were studied according to attributes of stratigraphy, sediment texture, parameters, sediment size distribution, bedforms, and primary sedimentary structures. Results from a computation of wave refraction diagrams and from an examination of the wave climate characteristics indicate that the modern embayment is low energy.\\u000aA sediment texture comparison between modern and

Lindsay D. Nakashima

1977-01-01

259

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

260

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

261

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

262

Sequence stratigraphy applied to the hydrocarbon productive basins of Western Indonesia  

SciTech Connect

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

Courteney, S.

1994-07-01

263

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

264

Mineralogy and petrology aspects of Mesaverde Formation at Rifle Gap, Colorado, specific to the sedimentology and gas-bearing intervals in the subsurface  

Microsoft Academic Search

Rifle Gap, situated on the eastern edge of the Piceance Creek Basin, northwestern Colorado, has been the focus of sedimentological studies in an effort to understand the tight, gas-bearing intervals of the inner-basin subsurface. These Mesaverde Formation sandstone exposures were sampled and anlayzed for mineral content and grain morphology. Varying detrital mineralogy supports a sedimentological model for the area which

Heinze

1983-01-01

265

Geomorphological and sedimentological record of accelerated deglaciation of small mountain glacier, Ragnarbreen, Svalbard  

NASA Astrophysics Data System (ADS)

Most of the Svalbrad glaciers have been in retreat since the end of the Little Ice Age (LIA). Hence, they give a good opportunity to study the geomorphological and sedimentological record of deglaciation. The aim of the study is to describe main landsystem elements of Ragnar glacier and relate them to different stages of the glacier recession. The Ragnar glacier is located in the Svalbard archipelago, in the central part of the West Spitsbergen Isle, in the north branch of Billefjorden. Ragnar is a small (~ 6 km2), outlet glacier, which current clean ice edge has retreated ca. 1500 m from the position related to the maximum LIA extent. Fieldworks of the study comprised detailed geomorphological mapping and sedimentary works. Four main elements of the landsystem of the Ragnar glacier can be distinguished: 1) Clean glacier surface. Currently, the ice surface of Ragnar glacier is almost completely debris-free and with only several supraglacial streams. 2) Ice-marginal lake. The lake started to form after 1980 year. Since that time, its length has reached 1000 m. Distant (from the ice-edge) part of the lake is shallow (< 2 m) with several small islands. Part proximal to the current ice edge is deeper (up to 16 m) and devoid of islands. At the bottom of the lake some ice (probable of glacier origin) was detected. 3) Lateral moraines - were developed along the both valley sides, from frontal moraine complex - to ca. 2 km upward the glacier valley. 4) Frontal moraine complex. This complex comprises of several chains of ridges and depressions and is relatively distinct - elevated about 35 m above the valley bottom. The elements of the landsystem of the Ragnar glacier have undergone several transformations since the LIA maximum: 1) Formation of the frontal moraine complex can be related to the state of dynamic equilibrium of the glacier during the LIA maximum. During formation of the complex and shortly after it the main depositional agents were intense debris flows, which are recorded by thick covers of the old debris flow deposits. Nowadays, despite of ice-cores, frontal moraine complex is much more stable than the lateral moraines or ice-marginal lake. 2) As a consequence of lowering of the clean glacier surface and formation of the distinct lateral moraines, the debris delivering from the valley sides is limited only to very narrow zone of the glacier (i.e. only to the lateral moraine). 3) Accelerated recession of the ice mouth and limitation in delivery of debris from sides of the valley caused that amount of deposits released in the ice front is small. 4) Increasing amount of water flowing from the glacier was blocked by frontal moraine complex and the ice marginal lake was created. 5) The debris cover on the lateral moraines is relatively thin. In addition, as a consequence of the clean ice surface lowering, slopes of the lateral moraines are very steep. It causes that mass movement processes (especially debris flows) are ubiquitous. Contemporary, lateral moraines are the elements undergoing the most intense transformations. Observations made in the Ragnar marginal zone revealed spatial-temporal changes in distribution of the sediments and landforms. They also add some premises that in the first stage of deglaciation debris flow and other mass wasting processes are most common. In the later phase glaciolacustrine and glaciofluvial deposition also plays important role in transformation of landforms and sediments.

Ewertowski, Marek

2010-05-01

266

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

USGS Publications Warehouse

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 (Abrt), 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, Abbc) along with deposition of evenly-bedded light-toned ice- and moderate-toned dust-rich layers (Planum Boreum 1 unit, Abb1). 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 (Abbc). 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. ?? 2008 Elsevier Inc. All rights reserved.

Tanaka, K. L.; Rodriguez, J. A. P.; Skinner, Jr. , J. A.; Bourke, M. C.; Fortezzo, C. M.; Herkenhoff, K. E.; Kolb, E. J.; Okubo, C. H.

2008-01-01

267

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

268

Analysis of the Geoelectrical Stratigraphy of a Controlled LNAPL Release  

NASA Astrophysics Data System (ADS)

Various electrical and electromagnetic techniques are being used to geophysically characterize LNAPL impacted sites. This characterization is dependent on our understanding of the relationship between the geoelectrical stratigraphy and spatial distribution of pore fluids. A numerical model for the geoelectrical stratigraphy of an LNAPL impacted site was constructed using a modified version of the Lenhard and Parker method to predict vertical fluid distributions; Archie's Law and Topp's Equation were used to generate the corresponding electrical conductivity and dielectric permittivity profiles. Both the van Genuchten and Brooks-Corey equations for the fluid content-hydraulic head relationship were considered in the modeling. The modeling results were compared with geoelectrical data collected during a controlled LNAPL release in a large test cell (3 meter diameter, 1.7 meters depth) containing repacked Borden sand. There are significant differences between the predicted and actual electrical conductivity profiles for both the clean and contaminated cases. The commonly assumed value of 2 for the Archie saturation exponent is too high; a value of 1.6 is more appropriate for matching the low- and high-saturation resistivity data. Furthermore, the Archie saturation exponent varies in a systematic manner over the intermediate saturations for this data set. The predicted and actual dielectric permittivity profiles show some differences for the clean case; however, better agreement is obtained for the contaminated case.

Mickle, R. J.; Endres, A. L.

2004-05-01

269

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

270

Sequence stratigraphy on an early Cretaceous passive margin, Exmouth Plateau  

SciTech Connect

Permian-Jurassic rifting of northwestern Australia resulted in the development of a passive continental margin flanking the northeastern Indian Ocean. On this margin the relatively thin synrift to postrift sedimentary sequence of southern Exmouth Plateau was drilled during ODP Leg 122. A sequence-stratigraphy analysis of the complete Mesozoic-Cenozoic sedimentary succession at Sites 762 and 763 was derived from a synthesis of seismic stratigraphy, wireline logs, lithostratigraphy, biostratigraphy, and magnetostratigraphy. Results indicate that during breakup, the southern Exmouth Plateau was a transform margin with an extensional component. Between the Tithonian and Valanginian, a thick clastic wedge prograded from the transform margin south of Site 763 northwestward toward Site 762 and onto subsiding continental crust. Southern clastic supply decreased into the Aptian-Cenomanian, and cyclic deposition of deep-water mudstones continued during subsidence of the earlier shelf margin wedge. Between the Albian and Cenomanian, deposition gradually became dominated by pelagic carbonates. Two regional unconformities mark the Cenomanian/Turonian and Cretaceous/Tertiary boundaries. Each was an erosional event, succeeded by renewed pelagic carbonate deposition that began in the distal northern basin and onlapped progressively toward the topographic high, which persisted into the Tertiary along the southern margin. The entire Jurassic to Holocene record at the southern Exmouth Plateau ODP sites is less than 1500 m thick and represents a classic rift to mature ocean passive-margin succession.

Boyd, R.; Gorur, N.; Ito, M.; O'Brien, D.; Wilkens, R.; Tang, C.

1989-03-01

271

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

272

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

273

Geoarchaeology of Ancient Karnak's harbour (Upper Egypt) : preliminary results derived from sedimentological analyses  

NASA Astrophysics Data System (ADS)

This paper aims to detail the first results of a geomorphological study, led in the western part of the Karnak Temple, Upper Egypt. The geoarchaeological approach privileged here helps to better understand the Nile River dynamics in the neighbourhood of the ancient harbour and of the jetty identified by archaeologists. Based on the study of six stratigraphical profiles, realized by the Egyptian Supreme Council of Antiquities and sixteen manual auger boreholes (up to a maximum depth of 3.50m) drilled in November 2008, the results clearly indicate the continuous presence of Nile River westward of the first Pylon. The boreholes were drilled westward and eastward of the ancient fluvial harbour. Fluvial dynamics characterized by flood events, sandy accretions and large Nile silts depositions are presented and discussed here for later palaeoenvironmental reconstruction. The accurate levelling of the different profiles and boreholes, with the help a topographic survey, allow us to get long sedimentological sequences and to correlate the different sedimentary units. Perspectives of research are introduced with the possibility to realize sedimentological analyses which include the grain-size distribution (sieving method employed) and a magnetic susceptibility study of the different sediments described. Finally, in order to obtain chronostratigraphic sequences, it is also proposed to perform radiocarbon dating on charcoal samples.

Ghilardi, M.

2009-04-01

274

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

SciTech Connect

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

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

1993-02-01

275

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

276

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

SciTech Connect

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

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

1994-03-01

277

Determination of the historical variation of the trophic state in lakes using sediment stratigraphies  

NASA Astrophysics Data System (ADS)

Biogenic silica (BSi) and phosphorous (P) accumulation were investigated in sediment cores from Karlskärsviken, a bay of Lake Mälaren. The aim was to make use of BSi and P relations in sediment stratigraphies in order to investigate the historical nutrient trophy in a near shore lake environment since the Middle Ages, with focus on industrial times, and to evaluate anthropogenic influences on the bay's trophic state. The BSi accumulation in the sediments is a better indicator of former nutrient pelagic trophy than P accumulation in sediments and for this reason a BSi inferred P (BSi-P) water concentration is calculated. This method enables the determination of the background total phosphorous (TP) concentration (which is related to the reference conditions) in the investigated bay; this background TP is determined equal to 0.020-0.022 mg L-1. There is an increasing trend of BSi-P concentration in the bay since the Middle Ages to the present, about 0.025 mg L-1, with a small decrease in the inner bay section during the last decades. The P accumulation rate is not found to have changed since the 1960s and 1970s, which indicates that the P loading to Karlskärsviken has not decreased. In Karlskärsviken, the shallow inner section of the bay, where the water quality is dominated by loading from the bay catchment area, is less nutritious than the water in the outer section, which is influenced by the main streams from the western part of Lake Mälaren.

Olli, G.

2007-11-01

278

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

279

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

Microsoft Academic Search

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.

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

1999-01-01

280

Multidisciplinary studies at Cerro Tapera Vázquez site, Pre-Delta National Park, Argentina: The archaeological, sedimentological and paleobotanical evidence  

Microsoft Academic Search

The initial results of archaeological, sedimentological and paleoethnobotanical studies of Cerro Tapera Vázquez (CTV) archaeological site were analyzed. This research aims to characterize the ceramic, lithic and bone materials recorded at CTV, to establish the chronology of the site and to define the paleoenvironmental context during human occupation of the site. The site is located on the wide alluvial floodplain

Mariano Bonomo; María de los Milagros Colobig; Esteban Passeggi; Alejandro Fabián Zucol; Mariana Brea

2011-01-01

281

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

Microsoft Academic Search

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

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

2000-01-01

282

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

283

Sedimentology of the Moosebar Tongue and Bounding Strata, Lower Cretaceous Blairmore Group, South-Central Foothills, Alberta  

Microsoft Academic Search

This thesis provides detailed sedimentological descriptions and generalized interpretations of depositional environments within the Lower Cretaceous Blairmore Group of Alberta. In earliest Blairmore time (Hauterivian - Barremian ?), uplift to the west resulted in a period of extensive pedimentation and deposition of coarse clastics of the Cadomin Formation. Paleogeographic reconstructions indicate that a series of humid-climate alluvial fans to the

David R. Taylor

1981-01-01

284

DEPTH GRADIENT PROXIES: PALAEOECOLOGY VERSUS SEDIMENTOLOGY. CASE STUDY FROM THE TUREA GROUP DEPOSITS OF THE PALEOGENE TRANSYLVANIAN BASIN  

Microsoft Academic Search

We approached problems of paleobathymetry from two different, but interconnected directions: from a paleoecological point of view and from a sedimentological one. To approximate from paleoecology, in our preliminary study (Kovács and Arnaud-Vanneau, 2004), we defined 6 paleoecological assemblages focusing solely on the Ple?ca Valley 2 outcrop. After analyzing correlative sections, as we had actually forecast, it raised the demand

J. Szilamér KOVÁCS

285

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

286

Wind-Eroded Stratigraphy on the Floor of a Noachian Impact Crater, Noachis Terra, Mars  

NASA Astrophysics Data System (ADS)

Many Noachian flat-floored craters have wind-eroded stratigraphy on their floors. An unnamed crater in Noachis Terra contains three units and many branching sinuous ridges. Mineral detections include feldspars, pyroxene, and weathering products.

Irwin, R. P.; Wray, J. J.; Maxwell, T. A.; Mest, S. C.; Hansen, S. T.

2012-05-01

287

Sediments of the Lomonosov Ridge and Makarov Basin: A Pleistocene Stratigraphy for the North Pole.  

National Technical Information Service (NTIS)

Cores from the Canadian LOREX (Lomonosov Ridge Experiment) project provide a Pleistocene stratigraphy for the North Pole. Twelve sedimentary units distinguish the past 500,000 years of the Lomonosov Ridge and Makarov Basin. A new formation, the Makarov Ba...

T. H. Morris D. L. Clark S. M. Blasco

1985-01-01

288

The Artesian System in Georgia. Stratigraphy and Hydrology of the Ocala.  

National Technical Information Service (NTIS)

The report summarizes studies of rocks belonging to the Jackson Group in Southwestern Georgia (the Ocala Limestone). The stratigraphy of the Ocala is outlined. Field and laboratory work is documented including petrographic and stratigraphic analysis. Pale...

M. Rich E. A. Stanley

1969-01-01

289

The Aristarchus Plateau on the Moon: Nature and Stratigraphy of the Substratum  

NASA Astrophysics Data System (ADS)

From Clementine UVVIS and NIR spectral data, a statistical analysis and a mixture modeling, we present the mineralogy and the stratigraphy of the materials forming the substratum and volcanic deposits of the Aristarchus Plateau on the Moon.

Chevrel, S. D.; Pinet, P. C.; Daydou, Y.; Le Mouélic, S.; Langevin, Y.; Costard, F.; Erard, S.

2009-03-01

290

The Aristarchus Plateau on the Moon: Nature and Stratigraphy of the Substratum  

Microsoft Academic Search

From Clementine UVVIS and NIR spectral data, a statistical analysis and a mixture modeling, we present the mineralogy and the stratigraphy of the materials forming the substratum and volcanic deposits of the Aristarchus Plateau on the Moon.

S. D. Chevrel; P. C. Pinet; Y. Daydou; S. Le Mouélic; Y. Langevin; F. Costard; S. Erard

2009-01-01

291

Taphonomic sequences—A new tool for sequence stratigraphy  

NASA Astrophysics Data System (ADS)

The Middle-Upper Jurassic boundary in western Europe is characterized by extensive condensed sections containing authigenic minerals together with abundant and varied fossils, both reworked and not reworked. We have analyzed ammonite shells and chronologically ordered taphonomic events in a taphonomic sequence extending from the time the dead organism settled on the seafloor to the time it became permanently incorporated in the sediment. Three types of taphonomic sequence are recognized; they are characteristic of (1) sedimentation in depositional environments having little and only occasional hydrodynamic activity (coinciding with periods of increasing accommodation), (2) sedimentation during maximum regional reductions in accommodation corresponding to third-order sequence boundaries at the scale of western Europe, or (3) sedimentation involving a sudden lithological change and an onset of a large-scale transgressive trend. In condensed sections, where little sediment is preserved, applying this classification is a useful new tool for sequence stratigraphy.

Courville, P.; Collin, P. Y.

2002-06-01

292

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

293

Relation of sequence stratigraphy to modern sedimentary environments  

SciTech Connect

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

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

1989-10-01

294

Effects of sequence stratigraphy on distribution of Cambro-Ordovician siliciclastic hydrocarbon reservoirs in Michigan basin  

Microsoft Academic Search

The lateral and vertical distribution of Cambrian-Ordovician siliciclastic reservoir-potential rock types in the Michigan basin is governed by the sequence stratigraphy. The sequence stratigraphy is controlled primarily by the interaction of four variables: subsidence, eustasy, volume of sediments, and climate. Seven sequential stratigraphic intervals can be defined in the pre-Utica, Cambrian-Ordovician deposits of the Michigan basin. Each of these unconformity-bounded

J. C. Horne; C. L. Reel; G. D. Cummins

1989-01-01

295

Application of portable X-ray fluorescence analyses to metabasalt stratigraphy, Plutonic Gold Mine, Western Australia  

Microsoft Academic Search

Stratigraphy, structure and host-rock chemistry are dominant controls on the location of Au in Archaean greenstone-hosted Au deposits, but the stratigraphy in such deposits is seldom obvious due to the monotonous nature of the host rocks or pervasive alteration associated with Au mineralisation. Portable, hand-held, X-ray fluorescence (pXRF) spectrometry provides a method to rapidly collect large amounts of whole-rock geochemical

Michael F. Gazley; Julie K. Vry; Ettienne du Plessis; Monica R. Handler

2011-01-01

296

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

297

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

298

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

299

Pre-Wisconsin glacial stratigraphy of the central plains region in Iowa, Nebraska, Kansas, and Missouri  

USGS Publications Warehouse

Recent investigations have documented the presence of several tills and interglacial paleosols that were not recognized in the simple Kansan-Aftonian-Nebraskan stratigraphic sequence. Also, the single 'Pearlette ash' recognized by early workers now is known to be three different Pearlette family ash beds of greatly contrasting ages. The complexity of the stratigraphy, as it is currently understood, and the miscorrelations of early work necessitate abandonment of the archaic terms Kansan, Aftonian, and Nebraskan in stratigraphic terminology. Continued use of those terms will only promote confusion of stratigraphic nomenclature and erroneous correlations of stratigraphic units. The limited chronometric control available within the early and middle Pleistocene stratigraphic sequence is provided directly by dating or by correlation of buried soils and volcanic ash beds and it is provided inferentially by interpretation of magnetic polarity data. These controls provide, at best, a general time framework to begin a new synthesis of the Quaternary history of the region. New methods of dating are needed to facilitate long-distance correlation of early and middle Pleistocene deposits. ?? 1986.

Hallberg, G. R.

1986-01-01

300

A review of magnetic stratigraphy investigations in Cretaceous pelagic carbonate rocks  

NASA Astrophysics Data System (ADS)

Pelagic carbonate rocks possess many suitable characteristics for paleomagnetic and magnetostratigraphic studies. Paleomagnetic results are summarized for seven lengthy sections of pelagic limestones and marls from Umbria and the southern Alps in Italy. Differences in apparent polar wander paths from these two regions are interpreted in terms of tectonic rotation of allochthonous Umbria. The magnetic stratigraphies of the paleontologically dated sections are independent of their tectonic differences and are combined to form a continuous record of geomagnetic polarity for the Barremian through Maastrichtian stages of the Cretaceous. All but one of the reversals in these sections are confirmed by duplication in at least one other section. Additional Cretaceous reversals have been reported in other land sections and in DSDP (Deep Sea Drilling Project) and IPOD (International Program of Ocean Drilling) cores. Some of these reversals are not defined well magnetically, and confirmation of others is clouded by imprecise paleontological dates. If real, they are probably of short duration. The confirmed reversal sequence correlates well with the Cretaceous oceanic magnetic anomaly sequence. The ages of certain key anomalies are altered: Late Cretaceous anomalies 29-34 are younger, and Early Cretaceous anomalies M0 and M1 are older than previously thought. The longer duration of the Cretaceous magnetic quiet interval of normal polarity results in a reduction of corresponding sea floor spreading rates to about 70% of earlier values, but they are still appreciably higher than during formation of the preceding M sequence anomalies.

Lowrie, W.; Channell, J. E. T.; Alvarez, W.

1980-07-01

301

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

302

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

2009-01-10

303

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

304

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

305

Sedimentological, Geochemical and Magnetic Properties of Colima Beach Sands, Mexico - Influence of Climate and Coastal Processes  

NASA Astrophysics Data System (ADS)

Studies of sediments on beaches contribute to understanding of sedimentological processes and source, transport and dynamics of sandy coastlines. Results of a geological and geophysical study of sandy beaches on the coast of Colima, Mexico employing sedimentological, geochemical and magnetic methods are presented and used to investigate on climate and coastal processes. Colima is part of the active subduction margin in southern Mexico. We studied thirteen different beaches distributed along the coast. The coastal transect investigated crosses three river drainage basins of the Cihuatlan, Armeria and Coahuayana rivers. Along the coastline there are abundant medium to fine sands moderately sorted to well-sorted. Towards the southeast, sediments are fine-grained, darker colors and better classified compared with sediments at the northwest sector. Towards the southeast there is greater abundance of heavy minerals of volcanic origin with high-rank, higher values of natural remnant magnetization and high magnetic susceptibilities associated with the abundance of iron and titanium oxides. The magnetic hysteresis loops are characterized by saturation in low fields, suggesting titanomagnetites and magnetite as major minerals. In the plot of hysteresis ratio parameters, samples plot in the pseudo-single domain field, suggesting mixtures of single and multiple domain states. Silica is the main constituent and shows a trend to decrease towards the southeast. Results show that sediments are primarly derived from the volcanic and plutonic rocks in the margin. There is an attenuation of one order of magnitude in magnetic susceptibility in magnetic concentrates. It is inferred that there is more wave action on sands of beaches at the southeastern sector generated primarily by waves, wind and tides in volcanic rocks that outcrop in the region. Backshore area in Santiago Bay is identified as an area of protected beach off the coast where the processes of weathering of the sands seem to be limited by this natural barrier. Effects along the Pacific Ocean coast of ENSO events and ITCZ migration on precipitation and erosion are discussed.

Sanchez-Guillen, L.; Carranza-Edwards, A.; Perez-Cruz, L. L.; Fucugauchi, J. U.

2011-12-01

306

Initial India-Asia Collision: Sedimentologic, Paleomagnetic and Paleontologic Evidence From the Ghazij Formation, Balochistan, Pakistan  

NASA Astrophysics Data System (ADS)

Initial continental collision between India and Asia is thought to have caused significant changes to global climate and biota, yet its timing and biogeographic consequences are uncertain. Structural and geophysical evidence indicates initial collision during the early Paleogene, but sedimentary evidence of this has been controversial owing to the intense deformation and metamorphism along the suture zone. Modern orders of mammals that appeared abruptly on northern continents coincident with the global warming event marking the Paleocene-Eocene boundary are hypothesized to have originated on the Indian subcontinent, but no relevant paleontologic information has been available to test this idea. Here we present sedimentologic, paleomagnetic, and paleontologic results that show the lower Eocene Ghazij Formation of western Pakistan records continental sedimentation and mammalian dispersal associated with initial India-Asia collision. Sedimentologically, the Ghazij exhibits a clear transition from shallow-marine facies in the lower part, to paralic deltaic facies in the middle part, and continental fluvial facies in the upper part. Paleomagnetic data indicate that Ghazij deposition occurred just before a pronounced decrease in the sea-floor spreading rate of the Indian Ocean. Large fossil mammal assemblages show strong endemism in the middle part of the formation but increasing cosmopolitanism and affiliation with northern continents higher in the formation. Our results support the hypothesis that initial continent-continent contact occurred near the Paleocene-Eocene boundary along the northwest edge of the Indo-Pakistan plate and that subsequent closure occurred diachronously along the rest of the suture. However, it appears that during initial collision, modern orders of mammals dispersed into India rather than out of it.

Clyde, W. C.; Khan, I. H.; Gingerich, P. D.

2003-12-01

307

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

USGS Publications Warehouse

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

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

2009-01-01

308

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

309

The role of stratotypes in stratigraphy. Part 1. Stratotype functions  

NASA Astrophysics Data System (ADS)

Because our concepts of various "natural" geological events and entities are always subject to modification with new data, we must provide a principled answer to the question: "How much can the scope of a stratigraphic or temporal unit change and yet still be called by the same name?" This issue is clarified by noting that stratotypes have three distinct functions in stratigraphy—the boundary-defining, example-providing, and name-bearing functions. Suggested names to denote these functions are "boundary-defining stratotype" (including unit- and boundary stratotypes), "exemplary stratotype," and "nominal stratotype." The analogy between type specimens in biology and type sections in stratigraphy is valid for nominal and exemplary stratotypes, but invalid for boundary-defining stratotypes. The terms boundary-defining, exemplary, and nominal refer to the functions performed by a given stratotype, whereas the terms holo-, para-, lecto-, neo-, and hypostratotype refer mainly to the historical circumstances under which a given stratotype is designated. Unit- and boundary stratotypes delimit an author's concept of the boundaries of a given stratigraphic entity in a particular section at a given time, but generally cannot be expected to permanently fix those boundaries. Important exceptions are the strict boundary stratotypes known as Global Stratotype Sections and Points (GSSPs). Exemplary stratotypes serve as examples of an author's concept of a given stratigraphic entity, but neither define nor constrain the boundaries of that entity. Nominal stratotypes constrain, but do not define the boundaries of a stratigraphic entity. They are divided into "loose" and "strict" subcategories, the former being appropriate for lithostratigraphic units, the latter for biochronologic units with geographic names. Both kinds of nominal stratotypes are also relevant to standard global chronostratigraphy. The designation of boundary-defining stratotypes for biostratigraphic units with binomial names is possible but essentially pointless, and such units are better characterized by exemplary stratotypes. For several reasons, however, biostratigraphic units with binomial names cannot have nominal stratotypes. An alternative method of attaching a name to a span of time involves what are here called nominal points, which are best used for the nominal definition of provincial biochronologic units with geographic names. While permitting much instability in our concept of a given biochron, the nominal point method does not suffer from the problem of potential temporal overlap inherent in the strict nominal stratotype approach. These distinctions should be made in future revisions of stratigraphic codes and guides.

Walsh, Stephen L.

310

Correlation of Lithology to Sequence Stratigraphy: Canterbury Basin, New Zealand  

NASA Astrophysics Data System (ADS)

A major objective of IODP Expedition 317 to the Canterbury Basin, New Zealand was to date and sample clinoformal seismic sequences, sequence boundaries, and their associated facies to understand the role of eustasy in shaping sedimentation on this continental margin. Canterbury Basin stratigraphy has also been influenced by tectonics and along strike currents that must also be taken into consideration when evaluating the evolution of the margin. Sesimic stratigraphic analysis provided the large-scale framework for understanding margin architecture and for drilling Sites U1351 through U1354 across the shelf and upper slope. Nineteen regional seismic sequence bounding surfaces (U1-U19) were identified from the middle Miocene to Holocene in the sediments offshore of Canterbury Basin, New Zealand. Correlation of the lithology to seismic stratigraphy permits the identification of sedimentary packages with boundaries near the predicted depths of sequence boundaries U1-U19. These sedimentary packages have sharp basal contacts that separate coarse-grained sediment above from fine grained beneath. The coarse-grained sediment above the contacts is composed of greenish gray, fine to medium muddy sand or sandy mud containing abundant shells. Each sedimentary package can be as thick as 6 m. In contrast, the sediment beneath is composed of fine-grained mud that is heavily bioturbated. Remarkable correlation was found between the depths at which some basal contacts occur and the depths predicted for sequence boundaries U11-U19 (early Pliocene to Holocene) across the shelf and upper slope. Heterolithic lithologies characterize the depositional environments within mid- and late Pleistocene seismic sequences. In contrast, alternations of gray and green mud are common in the early Pleistocene and Pliocene. Marlstones with wavy laminations, ripples and sand lenses suggestive of current activity are typical of Miocene lithologies beneath the slope while chalks and limestones dominate the Oligocene sequences. These lithologic changes are also manifested in the architecture of the margin that evolved from a ramp morphology to a progradational margin with steeper slopes and abrupt shelf breaks. Further studies of the facies within depositional sequences and the associated sedimentary packages will permit improved correlation between lithology and seismics and a better understanding of the relative contributions of eustasy, along-strike currents and tectonics to sedimentation. Sesimic stratigraphic analysis will also permit comparison with other margins where similar sea level studies are underway, such as New Jersey.

Ryan-Mishkin, K.; McHugh, C. M.; Fulthorpe, C.; Morgan, D.; Shipboard Scientific Party, E.

2010-12-01

311

Stratigraphy of Phyllosilicates and Sulfates in Northern Meridiani Planum, Mars  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

312

Proto-orogeny: stratigraphy, tectonics and neotectonics at the northern Australia collisional margin  

NASA Astrophysics Data System (ADS)

The ongoing arc-continent collision at the northern Australian margin causes a variety of crustal responses, both at the collisional front and in the hinterland. From fieldwork in East Timor (collisional front) and extensive seismic structural interpretation across the North West Shelf (hinterland) we propose that continental collision initiated with the arrival of an offshore plateau of the Australian margin at the subduction zone at 10.8 Ma, and that remnants of this collided plateau occur throughout Timor. Detailed stratigraphic analyses and biostratigraphic age determinations have been crucial to re-evaluating the stratigraphy of East Timor, and thus re-defining kinematic and geodynamic models for deformation in this very young orogenic belt. Using these tools in addition to structural mapping and geochemical analyses, we have significantly altered age determinations and tectono-stratigraphic affinities for key units (e,g the type section of the Miocene is a thrust stack of Triassic-Cretaceous material), recognised new stratigraphic associations (e.g. thick Australian-derived pelagites in association with thrust slices of exotic material), identified a previously unrecognised slices of ocean floor material, and documented new structural relationships between Australian and exotic units (shear zones, identification of a crush breccia terrane boundary along late, high-angle faults). In addition we have recognised various basaltic compositions indicating both mid-ocean ridge and ocean-island basalts within thrust sequences, at unique structural levels, and proposed new, well-constrained models, for tectonic events. Significant shortening at the collisional front protected much of the hinterland from collisional strain, to the extent that shortening behind the collision is limited to approximately 1per cent. We attribute hinterland deformation to elastic flexure and structural re-amplification of pre-existing topography. Further west, the collisional segment of the margin transitions into a passive margin, where deformation is dominated by far-field stresses generated elsewhere along the Australian plate margin, generating anomalous intraplate seismicity.

Keep, M.; Haig, D. W.

2007-12-01

313

Molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction  

NASA Astrophysics Data System (ADS)

A 40 cm deep Sphagnum-dominated peat monolith from Bolton Fell Moss in Northern England was systematically investigated by lipid molecular stratigraphy and compound-specific ? 13C and ?D analysis using gas chromatography (GC), GC-mass spectrometry (GC-MS), GC-combustion-isotope ratio-MS (GC-C-IRMS) and GC-thermal conversion-IRMS (GC-TC-IRMS) techniques. 210Pb dating showed the monolith accumulated during the last ca. 220 yr, a period encompassing the second part of Little Ice Age. While the distributions of lipids, including n-alkan-1-ols, n-alkan-2-ones, wax esters, sterols, n-alkanoic acids, ?,?-alkandioic acids and ?-hydroxy acids, display relatively minor changes with depth, the cooler climate event was recorded in the concentrations of n-alkanes and organic carbon, CPI values of n-alkanes and n-alkanoic acids, and the ratio of 5- n-alkylresorcinols/sterols. Superimposed on the fossil fuel effect, the relatively cooler climate event was also recorded by ? 13C values of individual hydrocarbons, especially the C 23n-alkane, a major compound in certain Sphagnum spp. The ?D values of the C 29 and C 33n-alkanes correlated mainly with plant composition and were relatively insensitive to climatic change. In contrast the C 23n-alkane displayed variation that correlated strongly with recorded temperature for the period represented by the monolith, agreeing with previously reported deuterium records in tree ring cellulose spanning the same period in Scotland, Germany and the USA, with more negative values occurring during the second part of Little Ice Age. These biomarker characteristics, including the compound-specific ? 13C and ?D records, provide a new set of proxies of climatic change, potentially independent of preserved macrofossils which will be of value in deeper sections of the bog where the documentary records of climate are unavailable and humification is well advanced.

Xie, Shucheng; Nott, Chris J.; Avsejs, Luke A.; Maddy, Darrel; Chambers, Frank M.; Evershed, Richard P.

2004-07-01

314

The Late Holocene Stratigraphy of an Inlet-Dominated Barrier Island, Pea Island, North Carolina  

Microsoft Academic Search

Sedimentological, foraminiferal, geochemical, and geophysical data sets as well as aerial photographs have been used to investigate the natural processes (inlet dynamics, ocean\\/estuarine washover, and sea-level change) responsible for the late Holocene units preserved in the barrier island subsurface at Pea Island National Wildlife Refuge. Historic nautical charts indicate that three inlets characterized Pea Island between early European exploration (1590)

C. G. Smith; D. Ames; D. R. Corbett; S. Culver; D. Mallinson; S. R. Riggs; D. Vance

2002-01-01

315

Depositional sequence analysis and sedimentologic modeling for improved prediction of Pennsylvanian reservoirs (Annex 1)  

SciTech Connect

Interdisciplinary studies of the Upper Pennsylvanian Lansing and Kansas City groups have been undertaken in order to improve the geologic characterization of petroleum reservoirs and to develop a quantitative understanding of the processes responsible for formation of associated depositional sequences. To this end, concepts and methods of sequence stratigraphy are being used to define and interpret the three-dimensional depositional framework of the Kansas City Group. The investigation includes characterization of reservoir rocks in oil fields in western Kansas, description of analog equivalents in near-surface and surface sites in southeastern Kansas, and construction of regional structural and stratigraphic framework to link the site specific studies. Geologic inverse and simulation models are being developed to integrate quantitative estimates of controls on sedimentation to produce reconstructions of reservoir-bearing strata in an attempt to enhance our ability to predict reservoir characteristics.

Watney, W.L.

1992-01-01

316

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

317

Stratigraphy of snow profiles using near-infrared photography  

NASA Astrophysics Data System (ADS)

The detailed representation of the layers in snow profiles is extremly time consuming. Translucent profiles are used to reveal layer boundaries, however no method is known to relate the transmitted light intensity to morphologic parameters. We use digital near-infrared photography (NIP), centered at a wavelength of 890 nm, to determine optical grainsize on snow profiles. The reflectivity was calibrated with snow samples of different grain size and shape. The digital image of a snow profile is optically and geometrically corrected and the intensities are then converted to optical grainsize. The measured snow profiles on different slopes are compared to planar sections and classical snow profiles. In several cases the NIP image revealed thin layers, layer transitions and disturbances which are also visible in the planar section, but were not recorded in the snow profile. NIP profiles could be as large as 1 m high and 3 m long at very high spatial resolution by assembling several images. NIP of snow profiles is well suited to document and analyse snow stratigraphy and to determine optical diameter .

Matzl, M.; Schneebeli, M.

2002-12-01

318

Yucatán subsurface stratigraphy: Implications and constraints for the Chicxulub impact  

NASA Astrophysics Data System (ADS)

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 to Maastrichtian section across the northern Yucatán peninsula. These data suggest that major disturbance of strata by an impact would have been confined to within about 100 km of the proposed impact center near Chicxulub. The only unusual lithologic unit is polymict breccia, which apparently was penetrated at or near the top of the Cretaceous section in all the deep wells of northern Yucatán. This breccia in Pemex wells Yucatán 1, 2, 4, 5A, and 6 is composed predominantly of detrital dolomite, limestone, and anhydrite clasts set in dolomitized carbonate mud matrix, which contains upper Maastrichtian foraminifers. These constituents, mixed with fragments of altered glass or melt rock, shocked quartz and feldspar, and basement rock, suggest an impact as the most likely origin for the breccia. The timing of brecciation is poorly constrained by biostratigraphic data. There is some evidence, however, that the breccia unit is overlain by about 18 m of uppermost Maastrichtian marls, suggesting an impact before the Cretaceous-Tertiary boundary. In addition, there may have been more than one episode of breccia deposition.

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

1995-10-01

319

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

320

Seismic stratigraphy a solution to deepwater drilling problems  

SciTech Connect

Serious drilling problems have been encountered by a number of deepwater operators in the Gulf of Mexico. The problem stems from the presence of geologically young unconsolidated sands that provide an excellent conduit for high-pressured interstitial fluids when pierced by the drillbit. Furthermore, the shallow nature of these formations is problematic in that casing is not always installed when the sands are perforated, and mud weights necessary to overcome formation pressures cannot be used as these may in turn fracture the sands and cause a rapid loss in circulation. A partial solution to the problem may be obtained by mapping the shallow seismic sequence stratigraphy, with emphasis on the depth, thickness, and types of sand-bearing facies or systems tracts, according to the model of Vail et al. This article reviews the application of the seismic stratigraphic concept as a basis for the interpretation of Pleistocene sedimentary sequences to depths of 3,000 ft on the continental slope, northern Gulf of Mexico.

Trabant, P.K.

1993-09-27

321

Sequence stratigraphy in Neogene expanded sections, Gulf of Mexico  

SciTech Connect

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 in an interpreted eustatic cycle and has recognizable signatures in well logs and seismic data. The high-frequency eustatic cyclicity is superimposed on the equally important tectonic and sediment-supply controls of a given basin. The depositional model for the Gulf of Mexico is in a typical diapir-controlled subbasin with a large contemporaneous expansion fault. A high depositional rate controlled by high-frequency glacio-eustatic oscillations coupled with rapid subsidence produces a very thick, complex sediment column whose environment of deposition is closely related to the history of fault development. The approach is based upon the integration of four basic data sets, each of which is independently reached but incomplete within itself. These include (1) core-calibrated well-log responses of deposits in each systems tract, (2) seismic facies of each systems tract (reflection termination and configuration patterns), (3) biostratigraphic and paleoecologic zonation of wells penetrating the section, and (4) eustatic cycle charts with correlation of local biostratigraphy for dating physically recognized sequence boundaries. Reservoir sand distribution is characteristic and predictable for each systems tract. Carefully planned evaluation and completion techniques are based on these characteristics.

Mitchum, R.M.; Sangree, J.B. (Sangree, Sneider and Mitchum, Houston, TX (USA)); Vail, P.R. (Rice Univ., Houston, TX (USA))

1990-05-01

322

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

323

Ferron sandstone - stratigraphy and reservoir analogs, East-Central Utah  

SciTech Connect

The Ferron Sandstone (Upper Cretaceous) crops out along the west flank of the San Rafael Swell of east-central Utah. Exposures were described on photomosaics to better define the stratigraphy, to enhance facies prediction, and establish rules for reservoir modeling within fluvial-deltaic rocks. Major regressive cycles are recognized as parasequence sets composed of several to many parasequences. Each of the seaward-stepping parasequence sets recognized in the Ferron begins with a rapidly thickening and stratigraphically climbing, wave-modified shoreface. In later stages of progradation, deposition is dominated by river influences. Continued regression of the seaway is recorded in outcrop and shows a complex history of delta lobe progradation, switching, and abandonment. Onlapping and stacking of parasequences creates a collage of potential reservoir sweet spots, baffles, and barriers within a parasequence set. Shoreface and delta-front deposits of the older parasequences are commonly eroded by younger distributary and meanderbelt systems that fed younger parasequences of the parasequence sets. The result is numerous and locally thick channel sandstone bodies incised into shoreface and delta-front deposits. Published studies and recently completed work show that upper shoreface, stream mouth-bar, and channel sandstones constitute the best potential reservoir rocks within the Ferron Sandstone.

Anderson, P.B. [Consulting Geologist, Salt Lake City, UT (United States); Ryer, T.A. [ARIES Group, Inc., Louisville, CO (United States); Chidsey, T.C. Jr. [Utah Geological Survey, Salt Lake City, UT (United States)

1996-06-01

324

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

325

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

326

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

327

Depositional environments and regional sedimentological control of Caseyville Formation, southern Illinois basin  

SciTech Connect

During the Morrowan Epoch (earliest Pennsylvanian), the Eastern Interior basins of the US were characterized by a fluviatile system draining generally southwestward from central Pennsylvanian to the Arkoma basin of northern Arkansas. In the southern Illinois basin, the system deposited the Casevylle Formation, consisting of two prominent cliff-forming quartzose sandstones with common quartz gravel, separated and succeeded by finer-grained, clastic intervals. Outcrop mapping in southernmost Illinois indicates that these cliff formers, the Battery Rock and Pounds Sandstone members, are laterally widespread and generally continuous, but variable in thickness. The underlying Wayside Sandstone Member, the intervening Drury Shale Member, and strata immediately succeeding the Caseyville consist of variable sequences of shales, siltstones, thin-bedded sandstones, and local ledge-forming sandstones. Rare lenticular coals are scattered through the Caseyville. The authors interpret the sandstone members to be dominantly of fluviatile-deltaic origin and the intervening, finger-grained intervals to be of deltaic and, at least in part, marginal-marine origin. Marine strata within the Drury Shale Member and the strata immediately overlying the Caseyville Formation contain scattered body fossils and trace fossils suggesting marine deposition. The Wayside/Battery Rock and Drury/Pounds cycles are tentatively correlated with similar cycles in the Appalachian and Arkoma basins. This correlation suggests regional sedimentological control.

Nelson, W.J.; Pius Weibel, C. (Illinois State Geological Survey, Champaign (USA))

1989-08-01

328

Quantifying Barrier Island Overwash Through Sedimentological, Geophysical, and Geospatial Analyses: Onslow Beach, NC  

NASA Astrophysics Data System (ADS)

A combination of sedimentological, geophysical, and geospatial datasets were utilized to quantify the amount of barrier island sediment that can be attributed to overwash events. A variety of processes including inlet dynamics, longshore and aeolian transport, and oceanic overwash are capable of driving barrier island migration. As sea level continues to rise and concerns of potential increased storm activities are peaked, it is important that we parameterize these primary mechanisms of sediment exchange and work towards physics- based models of barrier island migration. High-resolution chirp sub-bottom profiles were collected in Onslow Bay (depths <10 m) and along the back side of the island in the Atlantic Intracoastal Waterway. These data were subsequently coupled with ground- penetrating radar (GPR) collected over the top of the barrier island and used to estimate the depth of the shallowest cohesive substrate. The distance between this cohesive substrate and topographic elevations of the island (determined from lidar) enable an estimate of the total volume of sediment on Onslow Beach. Information from the GPR, in combination with numerous sediment vibracores, provide an estimate of what percentage of the active sand prism was deposited in overwash events. A time series of aerial photographs and satellite imagery reveals how the surficial expression of overwash fans has changed in both area and distribution since the 1950s and is interpreted in the context of published historical shoreline erosion rates for the region.

Foxgrover, A. C.; McNinch, J. E.; Wadman, H. M.; Rodriguez, A. B.

2008-12-01

329

Sedimentological model for lacustrine shoreline deposition, Lower Green River formation (Eocene), Northeastern Uinta Basin, Utah  

SciTech Connect

Sedimentological analysis and subsurface paleoenvironmental mapping in a 250-mi/sup 2/ area of the northeastern Uinta basin indicate that laterally continuous sandstone bodies represent depostion in lacustrine barrier-beach complexes. A lacustrine shoreline depositional model was developed using interpretations from approximately 1,500 ft of continuous core from 24 wells in the general area of Wonsits Valley and Red Wash oil fields. The model can be applied to interpreting depositional environments of ancient lacustrine deposits and to predicting subsurface distributioon of lacustrine shoreline sandstones. Coarsening-upward sequences observed in cores represent deposition in high-energy, wave-dominated shoreline systems that prograded into low-energy, open lacustrine environments. The vertical sequence consists of: lacustrine shale overlaid by transitional siltstone and silty sandstone beds; lower shoreface very fine-grained sandstone; upper shoreface fine-grained sandstone; swash-backwash fine to medium-grained sandstone; and backshore fine to medium-grained sandstone and interbedded algal-laminated shale. Paleoenvironmental mapping using interpretations from cores and well logs indicates that maximum dimensions of the barrier-beach complexes studies are approximately 10 mi long and 3 mi wide. Thickness ranges from approximately 10 to 35 ft. Mapping shows that barrier complexes were separated from onshore fluvial systems by a mudflatlagoon depositional environment. The barrier-beach deposits in the lower Green River Formation are similar to some modern and ancient, marine, siliciclastic shoreline deposits formed along microtidal coasts.

Castle, J.W.

1988-01-01

330

Sedimentology and geochemistry of thermokarst ponds in discontinuous permafrost, subarctic Quebec, Canada  

NASA Astrophysics Data System (ADS)

Thermokarst (thaw) ponds and lakes are distributed throughout arctic and subarctic regions; however their natural variability and temporal evolution recorded in the bottom sediments are poorly understood. This paper presents a multiproxy study conducted in a subarctic site with many thermokarst ponds near Kuujjuarapik-Whapmagoostui, on the eastern shore of Hudson Bay. Sedimentological, geochemical and chronological analyses have been performed on short sediment cores (10-20 cm) retrieved from limnologically contrasted ponds. Analyses revealed two distinct sedimentary facies, from bottom to top: 1) massive marine silts and clays deposited during postglacial Tyrrell Sea transgression (ca. 8000 to 6000 cal yr BP), subsequently emerged by glacio-isostatic rebound and more recently (ca. 1500 to 400 cal yr BP) affected by permafrost inception and growth; 2) laminated organic-rich lacustrine muds deposited since permafrost thawing and subsidence, i.e., since thermokarst pond inception (the last centuries). Despite displaying strikingly different water colors, the study ponds showed similar long-term developmental patterns regarding their physico-chemical properties (as recorded in the sediments), such as decreasing mineral grain size (from silts to clays), decreasing major chemical element concentrations, increasing organic matter content, and decreasing bottom water oxygen concentrations (from well-oxygenated to anoxic/hypoxic conditions).

Bouchard, FréDéRic; Francus, Pierre; Pienitz, Reinhard; Laurion, Isabelle

2011-06-01

331

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

332

Water chemistry and sedimentological observations in littlefield lake, michigan: Implications for lacustrine marl deposition  

NASA Astrophysics Data System (ADS)

A combination of both water chemistry and sedimentological information was used to investigate the carbonate-producing mechanism in Littlefield Lake, a small lake located in Isabella County, central Michigan. Data on temperature, dissolved oxygen, pH, calcium carbonate (CaCO3) saturation, alkalinity, calcium, and magnesium were obtained on a monthly basis over a 13-month period, with each parameter determined at 1m intervals over a depth range of 20m. The loss of dissolved carbon dioxide (CO2) from warm surface waters during direct degassing, and to a lesser extent during photosynthetic uptake by lacustrine macrophytes and phytoplankton during the summer, results in massive precipitation of the low-magnesium calcite which predominates in all Littlefield Lake sedimentary facies However, despite the fact that carbonate precipitation in this rather typical temperate-region marl lake is directly related to, and may be driven by, seasonal variation in these physiochemical parameters, most calcite forms as encrustations around cyanophytic and chlorophytic macrophytes. Such relationships demonstrate that carbonate precipitation in marl lakes may result from complex interactions between both biochemical and physiochemical processes. As such, marl formation in this, and probably many other calcareous lake systems, can not be simply ascribed to one or the other of these two general mechanisms.

Duston, Nina M.; Owen, Robert M.; Wilkinson, Bruce H.

1986-12-01

333

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

334

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

335

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

336

Sedimentology and reservoir characteristics of tight gas sandstones, Frontier formation, southwestern Wyoming  

SciTech Connect

The lower Frontier Formation, Moxa arch area, southwestern Wyoming, is one of the most prolific gas-producing formations in the Rocky Mountain region. Lowr Frontier sediments were deposited as strandplains and coalescing wave-dominated deltas that prograding into the western margin of the Cretaceous interior seaway during the Cenomanian. In this study, sedimentologic, petrologic, and stratigraphic analyses were conducted on cores and logs of Frontier wells from the Whiskey Buttes and Moxa fields. Twelve sedimentary facies have been identified. The most common sequence consists of burrowed to cross-bedded near shore marine (delta-front and inner-shelf) sandstones disconformably overlain by crossbedded (active) to deformed (abandoned) distributary-channel sandstones and conglomerates. The sequence is capped by delta-plain mudstones and silty sandstones. Tight-gas sandstone reservoir facies are nonhomogenous and include crevasse splay, abandoned and active distributary channel, shoreface, foreshore, and inner shelf sandstones. Distributary-channel facies represent 80% of perforated intervals in wells in the southern part of the Moxa area, but only 50% to the north. Channel sandstone bodies are occasionally stacked, occur on the same stratigraphic horizon, and are laterally discontinuous with numerous permeability barriers. Percentage of perforated intervals in upper shoreface and foreshore facies increases from 20% in the south to 50% in the north.

Moslow, T.F.; Tillman, R.W.

1984-04-01

337

Sedimentology and reservoir characteristics of tight gas sandstones, Frontier formation, southwestern Wyoming  

SciTech Connect

The lower Frontier Formation, Moxa arch area, southwestern Wyoming, is one of the most prolific gas-producing formations in the Rocky Mountain region. Lower Frontier sediments were deposited as strandplains and coalescing wave-dominated deltas that prograding into the western margin of the Cretaceous interior seaway during the Cenomanian. In this study, sedimentologic, petrologic, and stratigraphic analyses were conducted on cores and logs of Frontier wells from the Whiskey Buttes and Moxa fields. Twelve sedimentary facies have been identified. The most common sequence consists of burrowed to cross-bedded near shore marine (delta-front and inner-shelf) sandstones disconformably overlain by cross-bedded (active) to deformed (abandoned) distributary-channel sandstones and conglomerates. The sequence is capped by delta-plain mudstones and silty sandstones. Tight-gas sandstone reservoir facies are non-homogenous and include crevasse splay, abandoned and active distributary channel, shoreface, foreshore, and inner shelf sandstones. Distributary-channel facies represent 80% of perforated intervals in wells in the southern part of the Moxa area, but only 50% to the north. Channel sandstone bodies are occasionally stacked, occur on the same stratigraphic horizon, and are laterally discontinuous with numerous permeability barriers. Percentage of perforated intervals in upper shoreface and foreshore facies increases from 20% in the south to 50% in the north.

Moslow, T.F.; Tillman, R.W.

1984-04-01

338

A sedimentological and mineralogical study of the Koogah Formation, New South Wales  

NASA Astrophysics Data System (ADS)

A detailed sedimentological and mineralogical study was undertaken in the Early Permian Koogah Formation which is located a little to the northeast of Wingen in the Hunter Valley, NSW, with the principal objective being a better understanding of the conditions responsible for the development of this unusual sedimentary unit. From the outset it was realized that the formation comprises two distinctive and to some extent contrasting facies: that forming the lower part, consisting essentially of kaolinite clayrocks or flint clays up to 75 meters thick; and that constituting the upper section almost entirely of quartz-lithic sandstones and conglomerates. Nevertheless coal seams are generally lenticular and non-commercial are common to both facies. The Lower Koogah Formation is underlain by the Werrie Basalts, a two kilometer thick lava pile composed of fractionated alkaline basalt flows. The topmost flows are altered due to chemical weathering and several alteration profiles exist. Analysis of vertical sequences within the Lower Koogah Formation enabled four lithofacies to be identified. The Upper Koogah Formation consists of conglomerates, sandstones, siltstones, shales, and coals with minor interbeds of kaolinite clayrocks and are typical coal measures deposited in a floodplain setting. The body of evidence favors an allochthonous origin for the bulk of the kaolinite clayrocks.

Nichol, Douglas

1986-06-01

339

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

340

Tectonic features on Saturns satellites Dione and Rhea: Morphology and stratigraphy derived from Cassini ISS images  

NASA Astrophysics Data System (ADS)

Introduction: The second- and fourth-largest satellites of Saturn, Rhea (1528 km in diameter) and Dione (1124 km), harbor old, densely cratered surfaces but also show evidence of resurfacing through tectonism in the images taken by the two ISS cameras aboard the Cassini spacecraft since July 2004. On Dione, tectonic features are more widespread than on Rhea implying that geologic activity has been going on for a longer time, whereas on Rhea tectonic activity may have ceased early in its history. The tectonic inventory of both satellites incorporates (a) troughs (graben), (b) scarps, (c) ridges, (d) lineaments, and (e) plateaus on Dione. Procedure: In this paper we focus on the stratigraphic sequence of events which created these tectonic landforms, independent of specific stress origins which are the topic of further work. Our investigation is based on the global ISS image coverage at regional (150 - 500 m/pxl), and, for selected target areas, at high-resolution scale (< 50 m/pxl). Relative ages of tectonic landforms are constrained by (1) cross-cutting relationships, (2) by their degree of degradation, (3) and by their superimposed crater frequency. On Dione, the image resolutions are sufficient to examine stratigraphic relationships between tectonic features while on Rhea the areas affected by tectonism could not yet be observed so far at regional or high resolution. Stratigraphy: On both satellites, densely cratered plains are the dominant geologic units with inferred high ages of ~ 3 - 4.2 Gyr from cratering chronology models. Degraded, densely cratered graben in the high northern and southern latitudes on Dione were formed early in its history. On Rhea, ridges seen in stereo data also appear to be rather old features. Troughs and graben on Rhea's trailing hemisphere could be old, but further regional- and high-resolution imaging is needed for detailed investigations. On Dione's trailing hemisphere, a stratigraphic sequence of horsts, graben and scarps has been derived by mutual crosscutting and truncation. Three age groups can be observed: (1) Clusium and Carthage Fossae are the oldest, truncated by (2) Eurotas and Palatine Chasmata which in turn were truncated by (3) Padua Chasmata representing the youngest set of troughs. Time and duration of tectonic activity on the two satellites is difficult to determine because of uncertainties in cratering chronology models. In the Eurotas Chasmata region, for example, cratering models suggest either older tectonism of about ~ 3 Gyr, or even younger events of about ~ 1 Gyr. No age determinations of tectonic events on Rhea have been made so far due to lack of sufficient image coverage.

Wagner, R. J.; Neukum, G.; Stephan, K.; Giese, B.; Roatsch, T.; Wolf, U.; Porco, C. C.

2009-04-01

341

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.

342

Seismic Stratigraphy of the Mariana Forearc Sedimentary Basin  

NASA Astrophysics Data System (ADS)

A grid of seismic reflection profiles across the Mariana forearc between 14N-18N reveals a sedimentary basin between the Oligocene-Miocene frontal arc and the Eocene outer forearc highs. We identify and correlate several seismic stratigraphic units and use them to constrain the local and regional tectonics, which vary significantly from north to south. Four major sediment packages are distinguished in the southern forearc basin. The oldest unit, U-4, is conformable to arcward-tilted, rotated fault blocks formed during early extension, possibly associated with early Oligocene rifting prior to Parece Vela Basin spreading. Onlap relationships between the oldest sedimentary units indicate that deposition occurred before, during and after block rotation. On one profile, the U-4 sequence is deformed above a blind thrust fault in an otherwise extensional environment. Sediments that comprise the third unit, U-3, thin trenchward and onlap onto U-4. U-2 sediments onlap both sides of the basin and are characterized by nearly uniform thicknesses across the southern section. They currently dip trenchward, but are bypassed and onlapped arcward by thin recent deposits, U-1, on the three southern lines, suggesting recent relative subsidence of the outer forearc. The onset of this subsidence (during deposition of the upper strata of U-2) may have generated slope instability that triggered a large submarine slump off the frontal arc high into the forearc basin ENE of Saipan. The seismic stratigraphic units reveal both pre- and post-slump depositional boundaries including a possible post-slump debris apron around the perimeter of the toe thrust. The central region (near 16N), absent of the large rotated basement fault blocks found in the south, is characterized by high-angle normal faults that offset the seafloor by as much as 200 m. The upper section of U-4 is visible in isolated sections, but the coherency of the oldest layers is lost. Because a clear basement reflection is not resolved in this area, it is uncertain whether the absence of the oldest sediment reflections represents a lack of deposition or the limits of our imaging capabilities. The basin stratigraphy reveals a northward thickening of U-2 and U-3, indicating greater extension and increased sediment supply in the central region during deposition. U-1 is absent suggesting that the large relative subsidence of the outer forearc is restricted to the southern region. The stratigraphy of the northern forearc basin (near 18N) is interrupted by several local basement highs. U-4 and the lower sediments of U-3 are not imaged in this area. The upper strata of U-3 are resolvable in small basins formed between local highs. Above this, U-2 comprises most of the coherent basin fill. Ongoing work seeks to correlate these sequences with dated cores drilled in the area at ODP Leg 60 Sites 458 and 459.

Chapp, E.; Taylor, B.; Oakley, A.; Moore, G.

2005-12-01

343

Sequence stratigraphy of a Mesozoic carbonate platform-to-basin system in western Sicily  

NASA Astrophysics Data System (ADS)

Sequence stratigraphic studies of the Triassic through Paleogene carbonate successions of platform, slope and basin in western Sicily (Palermo and Termini Imerese Mountains) have identified a sedimentary cyclicity mostly caused by relative oscillations of sea level. The stratigraphic successions of the Imerese and Panormide palaeogeographic domains of the southern Tethyan continental margin were studied with physical-stratigraphy and facies analysis to reconstruct the sedimentary evolution of this platform-to-basin system. The Imerese Basin is characterized by a carbonate and siliceous-calcareous succession, 1200-1400m thick, Late Triassic to Eocene in age. The strata display a typical example of a carbonate platform margin, characterized by resedimented facies with progradational stacking patterns. The Panormide Carbonate Platform is characterized by a carbonate succession, 1000-1200 m thick, Late Triassic to Late Eocene, mostly consisting of shallow-water facies with periodic subaerial exposure. The cyclic arrangement has been obtained by the study of the stratigraphic signatures (unconformities, facies sequences, erosional surfaces and stratal geometries) found in the slope successions. The recognized pattern has been compared with coeval facies of the shelf. This correlation provided evidence of sedimentary evolution, influenced by progradation and backstepping of the shelf deposits. The stratigraphic architecture of the platform-to-basin system is characterized by four major transgressive/regressive cycles during the late Triassic to late Eocene. These cycles, framed in a chronostratigraphic chart, allows the correlation of the investigated shelf-to-basin system with the geological evolution of the African continental margin during the Mesozoic, showing tectono-eustatic cycles. The first cycle, encompassing the late Triassic to early Jurassic, appears to be related to the late syn-rift stage of the continental margin evolution. The following three cycles, spanning from the Jurassic to Eocene, can be related to the post-rift evolution and to thermal subsidence changes.

Basilone, Luca

2009-09-01

344

Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean  

NASA Astrophysics Data System (ADS)

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, Leonid; Bischof, Jens; Ortiz, Joseph D.; Darby, Dennis A.; Channell, James E. T.; Xuan, Chuang; Kaufman, Darrell S.; Løvlie, Reidar; Schneider, David A.; Eberl, Dennis D.; Adler, Ruth E.; Council, Edward A.

2009-07-01

345

Paleosols and carbonate sequence stratigraphy, Carboniferous, S. Kazakstan  

SciTech Connect

Carbonate platform facies in the Karatau Mountains of S. Kazakhstan are analogs for coeval oil and gas fields in the N. Caspian Basin, W. Kazakhstan. Understanding the sequence stratigraphy of these analogs is enhanced by the recognition and interpretation of paleosols. Thirty four paleosols subdivide 620 in of Visean-Bashkirian carbonates that span [approx] 30 my. M. and U. Visean strata consists of slope apron to platform margin skeletal/oolitic grainstone subdivided by 15 paleosols, that stack into 5 upward-thinning sequence sets. The U. Visean marks a significant increase in accommodation where shelf lagoon burrowed, skeletal wackestone/packstone shoal upward into skeletal/oncolitic grainstonelpackstone. Here depositional units thicken and are capped by thin peritidal laminates, not paleosols. The Serpukovian has 13 paleosols developed in biostromal open shelf grainstone/packstone and skeletal/oolitic grain shoal complexes. The L. Bashkirian records a major flooding event where lower slope laminates lie only 7 m above three stacked, deeply-rooted paleosols. This section shoals upward into upper slope acid-rich turbidites. Sequence boundaries are marked by 4 burrowed firmgrounds in the lower slope facies and by paleosols in the upper slope facies. Paleosols are characterized by the following: (1) laminated micrite crusts (i.e. Multer crusts), (2) rhizoliths, (3) alveolar texture, (4) brown isopachous and pendant spar, (5) desiccation cracks, (6) glaebules, (7) micritized grains, and (8) tangential needle fibers of calcite. Most rhizoliths and micrite crusts penetrate less than 1 m of strata. The shallow penetration, dark color of the michte crusts and rhizoliths, and common isopachous cements may indicate significant paleosol formation in a humid climate. The repeated occurrence of paleosols on subtidal upper slope, platform margin and platform interior facies strongly suggests a eustatic or glacio-eustatic origin.

Lehmann, P.J. (Exxon Ventures (CIS), Houston, TX (United States)); Cook, H.E. (USGS, Menlo Park, CA (United States)); Zempolich, W.G. (Mobil Oil, Dallas, TX (United States)) (and others)

1996-01-01

346

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.

347

Three-dimensional sedimentary architecture of Quaternary sand and gravel resources: a case study of economic sedimentology (SW Germany)  

Microsoft Academic Search

Quaternary sands and gravels form important, yet often highly heterogeneous economic deposits. Detailed 3-D analysis of the\\u000a sedimentary structure and stratigraphy of these deposits allows for an accurate estimation of exploitable material. This paper\\u000a presents a case study in SW Germany reconstructing the 3-D distribution of glacial sediments based on a high-resolution, process-orientated\\u000a sedimentary facies classification and lithostratigraphy integrated within

Boris Kostic; M. Peter Süss; Thomas Aigner

2007-01-01

348

A sedimentary facies model for glacial-age sediments in Baldwin Lake, Southern California  

Microsoft Academic Search

A combined sedimentological and high-resolution petrographic analysis was conducted on a glacial-age (20,000–65,000 cal yr BP) sediment core from Baldwin Lake, Southern California. The results of this research represent the most complete glacial-age, terrestrial climate record from Southern California to date. These results are used to characterize the different sediment types and to investigate the difference in depositional processes and environments

Michael A. Blazevic; Matthew E. Kirby; Adam D. Woods; Brandon L. Browne; David D. Bowman

2009-01-01

349

Barrier\\/lagoon and shoreface Holocene stratigraphy: Masonboro Island, N. C  

Microsoft Academic Search

Masonboro Island, located at the southwestern extremity of Onslow Bay, is a low relief 13 km long overwash dominated transgressive barrier. The stratigraphy and Holocene history of the barrier, estuary and shoreface was investigated utilizing 70 vibracores recovered from the estuary and the shoreface to water depths of 15 m. An additional 200 hand driven 3 m long cores were

W. J. Cleary; S. R. Riggs; E. R. Thieler

1993-01-01

350

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

351

Borehole geophysical techniques to define stratigraphy, alteration and aquifers in basalt  

Microsoft Academic Search

This paper concerns the interpretation of borehole geophysical data from basalt sequences, especially continental basalt sequences that host aquifers. Based on modifications of the rules used for interpreting borehole data from sedimentary rocks, new rules are proposed to identify the internal stratigraphy, aquifer boundaries, and alteration features in continental basalts.The value of several wireline tools is critiqued. Natural gamma logs

Catherine M Helm-Clark; David W Rodgers; Richard P Smith

2004-01-01

352

Stratigraphy, paleoceanography, and evolution of Cretaceous Pacific guyots; relics from a greenhouse Earth  

Microsoft Academic Search

Many guyots in the north Pacific are built of drowned Cretaceous shallow-water carbonates that rest on edifice basalt. Dating of these limestones, using strontium- and carbon-isotope stratigraphy, illustrates a number of events in the evolution of these carbonate platforms: local deposition of marine black shales during the early Aptian oceanic anoxic event; synchronous development of oolitic deposits during the Aptian;

HUGH C. JENKYNS; PAUL A. WILSON

1999-01-01

353

Tertiary Volcanic Stratigraphy and Structure of the Sonora Pass Region, Central Sierra Nevada, California  

Microsoft Academic Search

Mapping north and west of Sonora Pass provides information about the paleogeography and structure of the Sierra Nevada-Basin Range transition in Oligocene to Miocene time. The stratigraphy includes: (1) Late Oligocene-Early Miocene (?) Valley Springs Formation, composed of at least 5-6 petrographically distinctive silicic ignimbrites, overlain with erosional unconformity by (2) Early to Middle Miocene (?) \\

C. J. Busby; D. Rood; D. Wagner

2003-01-01

354

Comparative stratigraphy and subsidence history of Mesozoic rift basins of north Atlantic  

Microsoft Academic Search

The North Atlantic Mesozoic basins share many features because they had a common origin controlled by intracontinental rifting and subsequent separation of Europe and North America. Pulses of extension generally are reflected in the stratigraphy of all of the basins. Superimposed on this record are the effects of eustatic sea level variations. The main difference between the Canadian Jeanne d'Arc

R. N. Hiscott; R. C. L. Wilson; F. M. Gradstein; V. Pujalte; J. Garcia-Mondejar; R. R. Boudreau; H. A. Wishart

1990-01-01

355

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

Microsoft Academic Search

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

C. P. Swager

1997-01-01

356

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

357

Influence of mechanical stratigraphy and initial stress state on the formation of two fault propagation folds  

Microsoft Academic Search

Kinematic and mechanical modeling of the Rip Van Winkle (SE New York, USA) and La Zeta (SW Mendoza, Argentina) anticlines illustrate the influence of mechanical stratigraphy and initial stress state on the kinematics of fault propagation folding. In both anticlines, faults nucleating at distinct stratigraphic levels open upward into triangular zones of folding. Folding intensity and finite strain attenuates with

Néstor Cardozo; Richard W. Allmendinger; Julia K. Morgan

2005-01-01

358

Stratigraphy of the Lower and Middle Triassic Union Wash Formation, East-Central California.  

National Technical Information Service (NTIS)

In the report the authors describe the lithology, stratigraphy, and contact relations of the Union Wash Formation at its type locality and at two additional localities: (1) the Cerro Gordo area near the crest of the Inyo Mountains, 25 km southeast of Unio...

P. Stone C. H. Stevens M. J. Orchard

1991-01-01

359

Effects of global eustatic sea level variations and tectonism on stratigraphy of Iraq  

Microsoft Academic Search

The stratigraphy of Iraq is marked by complex vertical and lateral facies sequences controlled predominantly by two factors: (1) eustatic sea level variations, and (2) tectonic movements. Analysis of the sedimentary cycles provides a framework for evaluating the relative economic importance of transgressive versus regressive facies within the Iraq stratigraphic succession. Most reservoir rocks, principally reefal and neritic limestones and

S. L. Gawarecki; S. Schamel

1986-01-01

360

Sedimentologic succession of uplifted coral community, Urvina Bay, Isabela Island, Galapagos Archipelago, Ecuador  

SciTech Connect

In March 1954, along the west-central coast of Isabela Island, an upward movement of magma suddenly raised Urvina Bay over 6 m and exposed several square kilometers of carbonate deposits covering a young aa lava flow (around 1000 years old). Results from 6 transect lines across the uplift, 30 cores, and 10 trenches describe the sedimentologic and ecologic transition from barren basalt to diverse carbonate sediments with small coral reefs. Along horizontal transects spanning from 0 to 7 m paleowater depth, there is a seaward progression from beaches, mangroves, and basalt to thick deposits (> 1.6 m) of carbonate sands and small coral reefs. Variation in water depth, degree of wave exposure, and irregularity of the aa lava topography provided many microhabitats where coral, calcareous algae, and mollusks settled and grew. Eight hermatypic coral species are found throughout the shelf, and three species (i.e., Pavona clavus, Pocillopora damicornis, and Porites lobata) produced five small, isolated, monospecific, coral-reef frameworks. The vertical section seen in cores and trenches shows that calcium carbonate increased upward, whereas volcanic sediments decreased; however, episodic layers occur with high concentrations of basaltic sands. In vertical samples from the central portion of the shelf, the coral population changed from small, isolated colonies of Psammocora (Plesioseris) superficalis near the basalt basement to large reef-forming colonies of Pocillopora damicornis farther upsection. Reefs of the Galapagos Islands are small and less diverse than most Pacific reefs. Nonetheless, understanding their temporal successional development should throw light on the origin and history of larger oceanic reefs in the Pacific.

Colgan, M.W.; Hollander, D.

1987-05-01

361

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

362

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

2011-12-16

363

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

364

Sedimentologic and tectonic history of the Chilhowee group: Virginia, Tennessee, and North Carolina  

SciTech Connect

The Upper Proterozoic to Lower Cambrian Chilhowee Group records the critical transition from the final stages of rifting to the initial development of the Iapetan passive margin. Detailed process-sedimentological analysis of the Chilhowee Group have permitted identification of distal alluvial fan to outer-shelf depositional settings. Examination of geographic and vertical variation of these depositional environments in conjunction with differences in sandstone petrology permit comparison between the evolution of the Chilhowee Group in Virginia and Tennessee. Systematic changes in lithologic character, facies distribution, stratigraphic thickness, and occurrence of mafic rocks indicate a significant variation in the tectonic history of the Virginia Promontory and Tennessee Embayment. Major and minor trace-element composition of the Unicoi Formation basalts are similar to the Catoctin Formation basalts, suggesting possible stratigraphic equivalence as previously proposed. Above the braided-alluvial deposits of the Unicoi and Cochran Formations, marine depositional environments within the Iapetan passive margin are stacked into parasequences that compose a regionally correlative sequence that starts within the upper Unicoi and Weverton Formations and continues through the Hampton Formation into the upper part of the Erwin Formation. Within this sequence stratigraphic framework detailed intraformational correlation from northern Virginia to southern Tennessee can be made and subsidence histories can be compared across the incipient passive margin. Calculated subsidence values from equivalent Chilhowee marine sequences show higher rates in the Virginia Promontory ([approximately]8 cm/1,000 yrs) than in Tennessee Embayment ([approximately]3 cm/1,000 yrs.). This distribution of rates may indicate margin stabilization occurred earlier to the south, supporting a diachronous model for Iapetus basin opening.

Simpson, E.L. (Kutztown Univ., PA (United States). Dept. of Physical Sciences); Walker, D. (North Carolina Geological Survey, Raleigh, NC (United States))

1993-03-01

365

Sedimentological effects of tsunamis, with particular reference to impact-generated and volcanogenic waves  

NASA Astrophysics Data System (ADS)

Impulse-generated waves (tsunamis) may be produced, at varying scales and global recurrence intervals (RI), by several processes. Meteorite-water impacts will produce tsunamis, and asteroid-scale impacts with associated mega-tsunamis may occur. A bolide-water impact would undoubtedly produce a major tsunami, whose sedimentological effects should be recognizable. Even a bolide-land impact might trigger major submarine landslides and thus tsunamis. In all posulated scenarios for the K/T boundary event, then, tsunamis are expected, and where to look for them must be determined, and how to distinguish deposits from different tsunamis. Also, because tsunamis decrease in height as they move away from their source, the proximal effects will differ by perhaps orders of magnitude from distal effects. Data on the characteristics of tsunamis at their origin are scarce. Some observations exist for tsunamis generated by thermonuclear explosions and for seismogenic tsunamis, and experimental work was conducted on impact-generated tsunamis. All tsunamis of interest have wave-lengths of 0(100) km and thus behave as shallow-water waves in all ocean depths. Typical wave periods are 0(10 to 100) minutes. The effect of these tsunamis can be estimated in the marine and coastal realm by calculating boundary shear stresses (expressed as U*, the shear velocity). An event layer at the K/T boundary in Texas occurs in mid-shelf muds. Only a large, long-period wave with a wave height of 0(50) m, is deemed sufficient to have produced this layer. Such wave heights imply a nearby volcanic explosion on the scale of Krakatau or larger, or a nearby submarine landslide also of great size, or a bolide-water impact in the ocean.

Bourgeois, Joanne; Wiberg, Patricia L.

366

Sedimentology and petroleum occurrence, Schoolhouse Tongue of Weber Sandstone (lower Permian), Northwest Colorado  

SciTech Connect

The Schoolhouse Tongue of the Weber Sandstone, an extensive paleo-petroleum reservoir in northwest Colorado, consists mainly of bleached or oil-stained sandstone of inferred eolian sand-sheet origin. Low-angle to parallel-bedded, very fine to fine-grained sandstone is the dominant facies. Low-angle deflationary surfaces and deflation lags are common. Cross-bedded dune deposits are a less common sand-sheet facies. Interbedded fluvial deposits are present in most sections. The sand-sheet deposits of the Schoolhouse Tongue are sedimentologically similar to those in the gradationally underlying red beds of the Middle Pennsylvanian to Lower Permian Maroon Formation, and the Schoolhouse Tongue is best constructed as the uppermost sand sheet in the Maroon sequence. At Rifle Creek, the site of a late Paleozoic-early Mesozoic structural high, the Schoolhouse Tongue is 66 m thick and oil staining extends several hundred meters down into the underlying Maroon Formation. Away from Rifle Creek, the Schoolhouse Tongue thins to the north and pinches out to the southeast and east (within 40-65 km), and oil staining in the Maroon is minimal. The distribution of oil-stained rock suggests that hydrocarbons were introduced at a point source, possibly related to faults on the margins of the paleohigh. Oil in the Schoolhouse Tongue mainly occurs in secondary pore space resulting from the dissolution of carbonate cement by migrating organic acids. Oil was trapped below overlying red siltstones. Geochemical typing of the hydrocarbons is consistent with a late Paleozoic source rock.

Johnson, S.Y.; Schenk, C.J.; Anders, D.E.; Tuttle, M.L.

1988-01-01

367

Application of HRSC Data to North Polar Layered Deposit Stratigraphy  

NASA Astrophysics Data System (ADS)

HRSC imaging data from Mars Express provide coverage of the north polar cap at resolutions suitable for regional analysis of the polar layered deposits (PLD) and trough systems. In order to analyze the interior structure of the PLD and address the role of troughs in layer formation and evolution, the orientation of the layers in three dimensions was examined using HRSC polar images (50 m/pxl) co-registered with MOLA gridded topography data. The stereo data from the HRSC camera was unavailable at the time of this study. As the polar MOLA data set is of comparable resolution to the data set that will be derived from HRSC stereo images (114 m/pxl and 100 m/pxl, respectively), utilizing the MOLA data was considered to be an excellent first step in this type of analysis. Layers exposed in local topographic variations such as a hill or depression within a trough were selected for analysis. To measure the orientation of an individual layer, the position of the layer was identified by locating at least eight specific points along the layer. The spatial information for each point in three dimensions was then extracted from the spacecraft data. Next, a trend plane was fitted to the points using a least-squares fit. Finally, the slope and aspect of the trend plane was calculated, providing the dip and strike of the layer. Measurement of 38 layers located around the cap and at different depths in the PLD stratigraphy reveals several trends in layer orientation. A majority of layers have strikes trending parallel to the orientation of the trough in which they are exposed; rather than following a circular pattern as might be expected of layers in a simple dome they follow the spiraling pattern of the troughs. A slight majority (21 out of 38) of layers dip away from the pole. The remaining (17 out of 38) layers dip toward the pole. The magnitude of the dip of an individual layer does not tend to reflect the surface slope of the portion of the cap surface immediately surrounding the trough within which the layer is exposed. These observations of PLD strike and dip are consistent with both 1) models of layer behavior in the presence of polar ice flow and 2) models of static ice accumulation in the presence of preexisting troughs. Further assessments of the potential existence and magnitude of flow of ice and ice-dust mixtures in the polar cap are required before we can successfully distinguish between these two possibilities or propose new interpretations that might involve combinations of these processes.

Milkovich, S. M.

2005-12-01

368

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

369

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

370

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

Microsoft Academic Search

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

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

1986-01-01

371

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

372

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

373

A re-analysis of the Late Bronze Age eruption and tsunami of Santorini, Greece, and the implications for the volcano–tsunami hazard  

Microsoft Academic Search

The paroxysmal eruption of Santorini (ca. 3500 BP), referred to as the Late Bronze Age (LBA) eruption, probably generated multiple tsunami; their occurrence and impacts being cited frequently in scientific papers and articles. This paper examines what is known about any LBA tsunami, noting possible mechanisms of generation and identifying sedimentological traces. Firstly, the eruption sequence is outlined providing the

Dale Dominey-Howes

2004-01-01

374

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

375

Subtle traps prediction using sequence stratigraphy and 3D seismic technology: A case study from Qikou depression in Huanghua basin  

Microsoft Academic Search

Forecasting subtle traps by sequence stratigraphy and 3D seismic data is a sensitive topic in hydrocarbon exploration. Research\\u000a on subtle traps by geophysical data is the most popular and difficult. Based on the sufficiently drilling data, log data,\\u000a core data and 3D seismic data, sediment sequence of Qikou depression, Huanghua basin was partitioned by using sequence stratigraphy\\u000a theory. Each sediment

Ning-bo Mao; Ta-gen Dai; Sheng-lin Peng

2005-01-01

376

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

Microsoft Academic Search

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

K. M. Farrell

2001-01-01

377

Hydrocarbon potential, organic matter diagenesis, sedimentology, and paleoenvironment of upper Mesozoic dark shales, northern Himalayas and Argo abyssal plain  

SciTech Connect

The Late Jurassic was a time favorable for the deposition of black shale-type sediments in shallow environments as known from circum-North Atlantic basins, North Sea, and Himalayan Tethys regions. Locally these shales have excellent hydrocarbon source potential. The site of the Spiti shales in the Thakkola region of north-central Nepal provides the opportunity to study a long-term (Oxfordian-Tithonian) stable, shallow, and oxygen-depleted environment. Strata with calcareous benthic communities show that the environment was not anoxic. Organic geochemical and sedimentological analyses on the Spiti shales (Oxfordian-Valanginian) were done to understand the hydrocarbon potential, organic matter diagenesis, sedimentology, and paleoenvironment of this sequence. The depositional environment changed, driven by tectono-eustatic and climatic events, from an open shelf (approximately 250 m) with low amounts of detrital input and rich macrofossil communities to an extremely shallow, partly continental environment with intercalations of quartzose channel fill, silty shales, rare lumachelle layers, and coal seams. Paleocurrents suggest a north-facing continental margin bordering the Tethys Sea. The organic matter changed from marine (Jurassic) to terrestrial in the Cretaceous. Analysis of coeval strata, deposited in the deep-marine environment off the northern Indian shelf (contiguous with the present-day Argo abyssal plain), demonstrates the changing shallow to deep-water hydrocarbon potential. It reflects the more advanced organic matter maturation of the onshore material due to Himalayan tectonics and allows tracing the transport of the organic matter.

Thurow, J.; Gibling, M.

1989-03-01

378

Responses of the Okhotsk Sea environment and sedimentology to global climate changes at the orbital and millennial scale during the last 350 kyr  

NASA Astrophysics Data System (ADS)

We measured productivity proxies (chlorin, carbonate and organic carbon, opal, and biogenic Ba content) and lithophysical proxies (magnetic susceptibility, water content, density, and coarse sediment fraction) in sediment of central Okhotsk Sea core PC-7R. The age model covering the last 350 kyr of this core was constructed by correlating the dated series of relative paleointensity lows recognized in geomagnetic intensity records, marine isotope stage (MIS) boundaries determined in broad variations of the lithophysical and productivity proxies, and tephrochronology. The orbital changes of the lithophysical and productivity proxy stacks lag behind Northern Hemisphere summer radiation by approximately 6.3 and 5.9 kyr, respectively. This lag is consistent with a Milankovich model of climate control by solar radiation through the northern ice sheet volume and sea surface and surrounding land responses, which are fast compared with sedimentological evidence. Productivity proxies of the Okhotsk Sea also demonstrate 52 abrupt, pronounced productivity minima associated with regional climate coolings during the last 350 kyr, which present useful indicators of millennial-scale climate changes in this marginal sea. Based on the postulated synchronicity of Dansgaard-Oeschger cycles in the Northern Hemisphere and the established simultaneity of 11 Okhotsk Sea coolings in the last 77 kyr with abrupt severe cold events in the Greenland ice core and North Atlantic Heinrich events, all of these may be regarded as Heinrich-equivalent event anomalies. The Okhotsk Sea events have their counterparts in the records of North Atlantic sediments, the Greenland ice sheet, East Asia summer monsoon, and the Antarctic ice sheet. Probably the Arctic Oscillation was the main factor determining orbital and millennial climate oscillations in the high-latitude Northern Hemisphere, including the Okhotsk Sea region.

Gorbarenko, Sergey A.; Harada, Naomi; Malakhov, Mikhail I.; Velivetskaya, Tatyana A.; Vasilenko, Yuriy P.; Bosin, Aleksandr A.; Derkachev, Aleksandr N.; Goldberg, Evgenyi L.; Ignatiev, Aleksandr V.

2012-02-01

379

Sedimentology and stratigraphic development of the upper Nyalau Formation (Early Miocene), Sarawak, Malaysia: A mixed wave- and tide-influenced coastal system  

NASA Astrophysics Data System (ADS)

This work presents the first detailed facies analysis of the upper Nyalau Formation exposed around Bintulu, Sarawak, Malaysia. The Lower Miocene Nyalau Formation exposures in NW Sarawak represent one of the closest sedimentological outcrop analogues to the age equivalent, hydrocarbon-bearing, offshore deposits of the Balingian Province. Nine types of facies associations are recognised in the Nyalau Formation, which form elements of larger-scale facies successions. Wave-dominated shoreface facies successions display coarsening upward trends from Offshore, into Lower Shoreface and Upper Shoreface Facies Associations. Fluvio-tidal channel facies successions consist of multi-storey stacks of Fluvial-Dominated, Tide-Influenced and Tide-Dominated Channel Facies Associations interbedded with minor Bay and Mangrove Facies Associations. Estuarine bay facies successions are composed of Tidal Bar and Bay Facies Associations with minor Mangrove Facies Associations. Tide-dominated delta facies successions coarsen upward from an Offshore into the Tidal Bar Facies Association. The Nyalau Formation is interpreted as a mixed wave- and tide-influenced coastal depositional system, with an offshore wave-dominated barrier shoreface being incised by laterally migrating tidal channels and offshore migrating tidal bars. Stratigraphic successions in the Nyalau Formation form repetitive high frequency, regressive-transgressive cycles bounded by flooding surfaces, consisting of a basal coarsening upward, wave-dominated shoreface facies succession (representing a prograding barrier shoreface and/or beach-strandplain) which is sharply overlain by fluvio-tidal channel, estuarine bay or tide-dominated delta facies successions (representing more inshore, tide-influenced coastal depositional environments). An erosion surface separates the underlying wave-dominated facies succession from overlying tidal facies successions in each regressive-transgressive cycle. These erosion surfaces are interpreted as unconformities formed when base level fall resulted in deep incision of barrier shorefaces. Inshore, fluvio-tidal successions above the unconformity display upward increase in marine influence and are interpreted as transgressive incised valley fills.

Amir Hassan, Meor H.; Johnson, Howard D.; Allison, Peter A.; Abdullah, Wan Hasiah

2013-10-01

380

Biogeomorphological influence of slope processes and sedimentology on vascular talus vegetation in the southern Cascades, California  

NASA Astrophysics Data System (ADS)

The vascular vegetation of alpine talus slopes between 2035 and 3095 m altitude was studied at Lassen Volcanic National Park (California) in the Cascade Range. Taluses show a diverse flora, with 79 plant species; growth forms include coniferous trees, shrubs, suffrutices, herbs, graminoids, and ferns. Spatial patterns of plant distribution were studied along 40 point-intercept transects. Plant cover was low (0-32.7%) on all slopes, spatially variable, and showed no consistent trends. Sedimentological characteristics were determined by photosieving next to 1500 plants; this census indicated preferential plant growth on blocks and cobbles, with 43.2% and 23.3% of the plants growing on these stones, respectively; fewer specimens were rooted on pebbles (13%) or on stone-free gravel areas (20.5%). Growth forms displayed different substrate preferences: 92.5% of the shrubs and 83% of the suffrutices colonized blocks or cobbles, but only 57.2% of the herbs and 59.8% of the graminoids grew on large stones. Plants are associated with large clasts because (1) coarse talus is more stable than fine sediment areas, which are more frequently disturbed by various geomorphic processes, and (2) large stones help conserve substrate water beneath them while moisture quickly evaporates from fine debris. Root patterns were studied for 30 plant species; 10 specimens for each species were excavated and inspected, and several root growth ratios calculated. All species exhibited pronounced root asymmetry, as roots for most plants grew upslope from their shoot base. For 23 species, all specimens had 100% of their roots growing upslope; for the other 7 species, 92.2-99.3% of below-ground biomass extended uphill. This uneven root distribution is ascribed to continual substrate instability and resulting talus shift; as cascading debris progressively buries roots and stems, plants are gradually pushed and/or stretched downhill. Various disturbance events affect root development. Slope erosion following rubble removal often exposes plant roots. Debris deposition can completely bury plants; some may survive sedimentation, producing new shoots that grow through accumulated debris. Shrubs may propagate by layering, as adventitious roots develop along buried stems; or produce new clones along their roots. Slope processes may damage and transport plant pieces downhill; some species can sprout from severed, displaced root or stem fragments. Vegetation interacts with several geomorphic processes, including debris flows, grain flows, rockfall, snow avalanches, frost creep, and runoff. Larger plants may alter local patterns of debris movement and deposition, damming cascading debris on their upslope side and deflecting sediments laterally to plant margins, where they form narrow elongated stone stripes.

Pérez, Francisco L.

2012-02-01

381

Sedimentology of the December 26, 2004, Sumatra tsunami deposits in eastern India (Tamil Nadu) and Kenya  

NASA Astrophysics Data System (ADS)

The December 26, 2004 Sumatra tsunami caused severe damage at the coasts of the Indian ocean. We report results of a sedimentological study of tsunami run-up parameters and the sediments laid down by the tsunami at the coast of Tamil Nadu, India, and between Malindi and Lamu, Kenya. In India, evidence of three tsunami waves is preserved on the beaches in the form of characteristic debris accumulations. We measured the maximum run-up distance at 580 m and the maximum run-up height at 4.85 m. Flow depth over land was at least 3.5 m. The tsunami deposited an up to 30 cm thick blanket of moderately well to well-sorted coarse and medium sand that overlies older beach deposits or soil with an erosional unconformity. The sand sheet thins inland without a decrease of grain-size. The deposits consist frequently of three layers. The lower one may be cross-bedded with foresets dipping landward and indicating deposition during run-up. The overlying two sand layers are graded or parallel-laminated without indicators of current directions. Thus, it remains undecided whether they formed during run-up or return flow. Thin dark laminae rich in heavy minerals frequently mark the contacts between successive layers. Benthic foraminifera indicate an entrainment of sediment by the tsunami from water depths less than ca. 30 m water depth. On the Indian shelf these depths are present at distances of up to 5 km from the coast. In Kenya only one wave is recorded, which attained a run-up height of 3 m at a run-up distance of ca. 35 m from the tidal water line at the time of the tsunami impact. Only one layer of fine sand was deposited by the tsunami. It consists predominantly of heavy minerals supplied to the sea by a nearby river. The sand layer thins landward with a minor decrease in grain-size. Benthic foraminifera indicate an entrainment of sediment by the tsunami from water depths less than ca. 30 m water depth, reaching down potentially to ca. 80 m. The presence of only one tsunami-related sediment layer in Kenya, but three in India, reflects the impact of only one wave at the coast of Kenya, as opposed to several in India. Grain-size distributions in the Indian and Kenyan deposits are mostly normal to slightly positively skewed and indicate that the detritus was entrained by the tsunami from well sorted pre-tsunami deposits in nearshore, swash zone and beach environments.

Bahlburg, Heinrich; Weiss, Robert

2007-11-01

382

Sedimentology of box cores from the Cap-Ferret Canyon area (Bay of Biscay)  

NASA Astrophysics Data System (ADS)

Sedimentological and geochemical investigations of 45 box cores collected in various morphological settings of the Cap-Ferret Canyon (Bay of Biscay) are presented to document accurately present-day sedimentary processes on the eastern Atlantic continental slope. The magnitude and variations through time and space of the canyon's channelling or sinking effect on fine-grained particles behaviour in comparison with sediment flux across the continental margin was particularly considered and discussed: 1. All the parameters (grain-size, carbonate and water content, major and trace elements), measured both in surface sediment and downcore, demonstrate that the characteristics at the sediment interface vary with water depth and with the morphological setting. 2. Surface sediment is generally coarser-grained, more terrigenous and deposited at higher rate in the canyon than outside. The terrigenous particle supply must be preferentially directed and trapped within the canyon's depression due to present-day dynamic conditions. 3. The downcore gradients reflected in grain-size variations yield information on settling processes. The coarse-grained population has the characteristics of a winnowed sediment similar to those on the outer shelf, while the fine-grained population has grain-size spectra very similar to the present-day fine-grained suspensions. 4. The carbonate particles are partly derived from direct pelagic production (distinct grain-size distribution) and, like terrigenous grains, are partly reworked (similar downslope decrease in the coarse grained fraction). The relatively low CaCO 3 content observed in the canyon, and its downward increase up to values observed at shallower depths, may result from a channelling of terrigenous suspensions within the canyon. 5. At the present high sea-level stand, the canyon should become a trap for sediments without much gravity remobilisation, as indicated by a lack of sedimentary structures in box cores. However, a simple increase in sediment trapping can hardly account for the downcore gradients observed in the box cores. These trends, which are observed on other continental margins ( Monaco et al., 1993, Journées spécialisées de la Soc. Géol. France: Géosciences Marines, 16-17 December 1994, Abstract p. 83.), indicate a probable increase in terrigenous supplies and/or in settling energy.

Cremer, Michel; Weber, Olivier; Jouanneau, Jean-Marie

1999-10-01

383

Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants  

NASA Astrophysics Data System (ADS)

In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodibility, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, and may increase bank stability, infiltration into substrates, and bed roughness. Vegetation also promotes the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Early Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Early Palaeozoic alluvial successions laid down prior to and during the initial colonization of the Earth's surface by plants. A comprehensive review of 144 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 34 alluvial successions across Europe and North America. The study was designed to identify changes in alluvial style during the period that vegetation was evolving and first colonizing alluvial environments. An increase in mudrock proportion and sandstone maturity is apparent, along with a decrease in overall sand grain size through the Early Palaeozoic. These trends suggest that primitive vegetation cover promoted the production and preservation of muds from the mid Ordovician onwards and increased the residence time of sand-grade sediment in alluvial systems. The compilation also enables the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and related to the evolution of specific palaeobotanical adaptations. The first markedly heterolithic alluvial sequences appeared at about the same time as the most primitive terrestrial vegetation in the Ordovician, and prolific pedogenic calcite, charcoal and bioturbated floodplain fines first appeared in the rock record at about the same time as vascular-plant macrofossils became abundant in the late Silurian. Lateral accretion sets in channel deposits appeared near the Silurian-Devonian boundary, at or shortly before the appearance of underground rooting systems, and become progressively more abundant in the record during the Devonian, implying a major expansion of meandering rivers as rooted plants stabilized river banks. Coals become abundant after the development of plant arborescence. The analysis suggests that the evolution of embryophytes had a profound effect on fluvial processes and deposits, and this period of landscape evolution must be considered amongst the most significant environmental and geomorphological changes in Earth history, with profound consequences for all aspects of the Earth system.

Davies, Neil S.; Gibling, Martin R.

2010-02-01

384

Sedimentology and geomorphology of a relict lacustrine system in Tingri, Tibet, China  

NASA Astrophysics Data System (ADS)

A patchy sequence of near horizontal sedimentary deposits composed of consolidated carbonate-rich laminated gravelly sand and silt are exposed on the hill slopes near Tingri, Tibet, China. They are classified as mid- to late-Pleistocene and Holocene lacustrine deposits in Chinese geological maps, but the style and nature of lacustrine deposition and the facies associations in the sequence have never been reported. This study presents a number of sections in the locality showing the varied sedimentology of the deposits. The deposits are interpreted as relict sandy or gravelly dune ridges and plains, salt pans, prograded deltas, and lacustrine sediments. Interpretation was primarily based on a comparison with modern inland lakes in the Tibetan Plateau as analogues of processes in arid mountain lake systems. Relict dune ridges appear on the margins of many Tibetan inland lakes where the highly erosive regime allowed an abundant supply of gravels and sand to deposit along lake shorelines. The strong winds in Tibet have also allowed high to medium energy shoreline systems to develop in exposed areas. The high gravel and carbonate content in the gravelly ridges provided ample resistance to erosion and they often remain a topographically pronounced feature after lake drainage. Salt pans and gravelly or sandy ridge fields are also left after lake regression along with rare lacustrine deltas represented by the lakeward prograding beds. Laminated shelly sand or silt preserved in pockets near the valley floor characterise deposition at deeper lacustrine regimes. At Tingri the exposures of the palaeoshoreline deposits can reach 20 m in thickness and are identified at an elevation ranging from 4286 to 4404 masl. Although patchy in occurrence the sequence suggests a relatively long lived relict lake system. The timing of lake phases is poorly constrained by optically stimulated luminescence mid-to-late Pleistocene and Holocene. A number of incised channels are observed in various deposits in Tingri, indicating high energy drainage during lake regression. The final drainage history leading to the disappearance of this large compound lake system is uncertain, but this rapid, high volume drainage of lake water downstream may provide a partial explanation for the rapid incision of the Arun Gorge located at the southeastern boundary of the reconstructed lake of Tingri.

Chiu, H.; Switzer, A. D.; Aitchison, J.

2010-12-01

385

Effect of explicit representation of detailed stratigraphy on brine and gas flow at the Waste Isolation Pilot Plant  

SciTech Connect

Stratigraphic units of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) disposal room horizon includes various layers of halite, polyhalitic halite, argillaceous halite, clay, and anhydrite. Current models, including those used in the WIPP Performance Assessment calculations, employ a ``composite stratigraphy`` approach in modeling. This study was initiated to evaluate the impact that an explicit representation of detailed stratigraphy around the repository may have on fluid flow compared to the simplified ``composite stratigraphy`` models currently employed. Sensitivity of model results to intrinsic permeability anisotropy, interbed fracturing, two-phase characteristic curves, and gas-generation rates were studied. The results of this study indicate that explicit representation of the stratigraphy maintains higher pressures and does not allow as much fluid to leave the disposal room as compared to