Sedimentological and Stratigraphic Associations of Earlandia Foraminifera; in the Early Triassic Succession of Khuff Carbonates; Central Saudi Arabia

NASA Astrophysics Data System (ADS)

Adam, Ammar; Kaminski, Michael; Abdullatif, Osman

2017-04-01

This work reports the first discovery Earlandia foraminifera in the Triassic succession of the Middle East, within the Upper Khartam Member of the Khuff Formation. The study area is located in central Saudi Arabia where four outcrop localities were logged in detail for sedimentology and micropaleontology. More than 300 samples were collected for detailed sedimentological and micropaleontological analysis. Of these, only six samples recovered fossil Earlandia; these are dominantly observed in the interlaminated quartz-bearing recrystallized limestone lithofacies type. The Earlandia occur in associations with quartz grains, peloids, ooids, ostracods, bivalves, bryozoans, cephalopods, and stromatolites. The defined fossils of Earlandia are restricted to the lower fourth-order sequence of the Upper Khartam member; where non-skeletal grains (mostly oolitic grainstones) prevail. The skeletal grains along with the Earlandia occur as a thin (20 cm) transgressive lag. Furthermore, the regional occurrences of the Earlandia are consistent with the previously established high-frequency sequence stratigraphic scheme, therefore, the Earlandia could be used as a biomarker for regional biostratigraphic correlation and enhance the high-resolution sequence stratigraphic correlations of the Upper Khartam Member. Essentially, the detailed sedimentological and micropaleontological analysis (Earlandia foraminifera) indicates a plate-wide extensive shallow epeiric sea. The latter is gently dipping and sporadically connected to the open marine system.

Upper Albian to Lower Turonian deposits and associated breccias along the Dahar cuestas (southeastern Tunisia): Origin and depositional environments

NASA Astrophysics Data System (ADS)

Krimi, Mabrouk; Ouaja, Mohamed; Zargouni, Fouad

2017-11-01

The carbonate Zebbag Formation of Upper Albian to Lower Turonian age which outcrops along the Dahar cuestas (south eastern Tunisia) includes several breccia intervals. The stratigraphic hierarchy of these breccia levels led to achieving a detailed sequential analysis within a spectrum of depositional environments extending from subtidal to inner to middle ramp settings. Six major transgressive/regressive sequences make up the stacking of the elementary sequences beginning with transgressive and/or storm wave breccias capped by desiccation and/or collapse breccias. The stratigraphic evolutionary history of the breccia facies are interpreted as the result of the interplay between eustatic and tectonic factors. This model is in accord with the tectonic activities common during Upper Albian-Lower Turonian responsible for the sequences onlapping.

Bed II Sequence Stratigraphic context of EF-HR and HWK EE archaeological sites, and the Oldowan/Acheulean succession at Olduvai Gorge, Tanzania.

PubMed

Stanistreet, Ian G; McHenry, Lindsay J; Stollhofen, Harald; de la Torre, Ignacio

2018-04-20

Archaeological excavations at EF-HR and HWK EE allow reassessment of Bed II stratigraphy within the Junction Area and eastern Olduvai Gorge. Application of Sequence Stratigraphic methods provides a time-stratigraphic framework enabling correlation of sedimentary units across facies boundaries, applicable even in those areas where conventional timelines, such as tephrostratigraphic markers, are absent, eroded, or reworked. Sequence Stratigraphically, Bed II subdivides into five major Sequences 1 to 5, all floored by major disconformities that incise deeply into the underlying succession, proving that simple "layer cake" stratigraphy is inappropriate. Previous establishment of the Lemuta Member has invalidated the use of Tuff IIA as the boundary between Lower and Middle Bed II, now redefined at the disconformity between Sequences 2 and 3, a lithostratigraphic contact underlying the succession containing the Lower, Middle, and Upper Augitic Sandstones. HWK EE site records Oldowan technology in the Lower Augitic Sandstone at the base of Sequence 3, within Middle Bed II. We suggest placement of recently reported Acheulean levels at FLK W within the Middle Augitic Sandstone, thus emphasizing that handaxes are yet to be found in earlier stratigraphic units of the Olduvai sequence. This would place a boundary between the Oldowan and Acheulean technologies at Olduvai in the Tuff IIB zone or earliest Middle Augitic Sandstone. A major disconformity between Sequences 3 and 4 at and near EF-HR cuts through the level of Tuff IIC, placing the main Acheulean EF-HR assemblage at the base of Sequence 4, within Upper rather than Middle Bed II. Sequence stratigraphic methods also yield a more highly resolved Bed II stratigraphic framework. Backwall and sidewall surveying of archaeological trenches at EF-HR and HWK EE permits definition of "Lake-parasequences" nested within the major Sequences that record downcutting of disconformities associated with lake regression, then sedimentation associated with lake transgression, capped finally by another erosional disconformity or hiatal paraconformity caused by the next lake withdrawal. On a relative time-scale rather than a vertical metre scale, the resulting Wheeler diagram framework provides a basis for recognizing time-equivalent depositional episodes and the position of time gaps at various scales. Relative timing of archaeological assemblage levels can then be differentiated at a millennial scale within this framework. Copyright © 2018 Elsevier Ltd. All rights reserved.

Correlation between high resolution sequence stratigraphy and mechanical stratigraphy for enhanced fracture characteristic prediction

NASA Astrophysics Data System (ADS)

Al Kharusi, Laiyyan M.

Sequence stratigraphy relates changes in vertical and lateral facies distribution to relative changes in sea level. These relative changes in carbonates effect early diagenesis, types of pores, cementation and dissolution patterns. As a result, in carbonates, relative changes in sea level significantly impact the lithology, porosity, diagenesis, bed and bounding surfaces which are all factors that control fracture patterns. This study explores these relationships by integrating stratigraphy with fracture analysis and petrophysical properties. A special focus is given to the relationship between mechanical boundaries and sequence stratigraphic boundaries in three different settings: (1) Mississippian strata in Sheep Mountain Anticline, Wyoming, (2) Mississippian limestones in St. Louis, Missouri, and (3) Pennsylvanian limestones intermixed with elastics in the Paradox Basin, Utah. The analysis of these sections demonstrate that a fracture hierarchy exists in relation to the sequence stratigraphic hierarchy. The majority of fractures (80%) terminate at genetic unit boundaries or the internal flooding surface that separates the transgressive from regressive hemicycle. Fractures (20%) that do not terminate at genetic unit boundaries or their internal flooding surface terminate at lower order sequence stratigraphic boundaries or their internal flooding surfaces. Secondly, the fracture spacing relates well to bed thickness in mechanical units no greater than 0.5m in thickness but with increasing bed thickness a scatter from the linear trend is observed. In the Paradox Basin the influence of strain on fracture density is illustrated by two sections measured in different strain regimes. The folded strata at Raplee Anticline has higher fracture densities than the flat-lying beds at the Honaker Trail. Cemented low porosity rocks in the Paradox Basin do not show a correlation between fracture pattern and porosity. However velocity and rock stiffness moduli's display a slight correlation to fracture spacing. Furthermore, bed thickness is found to be only one factor in determining fracture density but with increasing strain, internal bedforms and rock petrophysical heterogeneities influence fracture density patterns. This study illustrates how integrating sedimentologic and sequence stratigraphic interpretations with data on structural kinematics can lead to refined predictive understanding of fracture attributes.

Harmonic Analysis of Sedimentary Cyclic Sequences in Kansas, Midcontinent, USA

USGS Publications Warehouse

Merriam, D.F.; Robinson, J.E.

1997-01-01

Several stratigraphic sequences in the Upper Carboniferous (Pennsylvanian) in Kansas (Midcontinent, USA) were analyzed quantitatively for periodic repetitions. The sequences were coded by lithologic type into strings of datasets. The strings then were analyzed by an adaptation of a one-dimensional Fourier transform analysis and examined for evidence of periodicity. The method was tested using different states in coding to determine the robustness of the method and data. The most persistent response is in multiples of 8-10 ft (2.5-3.0 m) and probably is dependent on the depositional thickness of the original lithologic units. Other cyclicities occurred in multiples of the basic frequency of 8-10 with persistent ones at 22 and 30 feet (6.5-9.0 m) and large ones at 80 and 160 feet (25-50 m). These levels of thickness relate well to the basic cyclothem and megacyclothem as measured on outcrop. We propose that this approach is a suitable one for analyzing cyclic events in the stratigraphic record.

Petroleum system elements within the Late Cretaceous and Early Paleogene sediments of Nigeria's inland basins: An integrated sequence stratigraphic approach

NASA Astrophysics Data System (ADS)

Dim, Chidozie Izuchukwu Princeton; Onuoha, K. Mosto; Okeugo, Chukwudike Gabriel; Ozumba, Bertram Maduka

2017-06-01

Sequence stratigraphic studies have been carried out using subsurface well and 2D seismic data in the Late Cretaceous and Early Paleogene sediments of Anambra and proximal onshore section of Niger Delta Basin in the Southeastern Nigeria. The aim was to establish the stratigraphic framework for better understanding of the reservoir, source and seal rock presence and distribution in the basin. Thirteen stratigraphic bounding surfaces (consisting of six maximum flooding surfaces - MFSs and seven sequence boundaries - SBs) were recognized and calibrated using a newly modified chronostratigraphic chart. Stratigraphic surfaces were matched with corresponding foraminiferal and palynological biozones, aiding correlation across wells in this study. Well log sequence stratigraphic correlation reveals that stratal packages within the basin are segmented into six depositional sequences occurring from Late Cretaceous to Early Paleogene age. Generated gross depositional environment maps at various MFSs show that sediment packages deposited within shelfal to deep marine settings, reflect continuous rise and fall of sea levels within a regressive cycle. Each of these sequences consist of three system tracts (lowstand system tract - LST, transgressive system tract - TST and highstand system tract - HST) that are associated with mainly progradational and retrogradational sediment stacking patterns. Well correlation reveals that the sand and shale units of the LSTs, HSTs and TSTs, that constitute the reservoir and source/seal packages respectively are laterally continuous and thicken basinwards, due to structural influences. Result from interpretation of seismic section reveals the presence of hanging wall, footwall, horst block and collapsed crest structures. These structural features generally aid migration and offer entrapment mechanism for hydrocarbon accumulation. The combination of these reservoirs, sources, seals and trap elements form a good petroleum system that is viable for hydrocarbon exploration and development.

cyclostratigraphy, sequence stratigraphy and organic matter accumulation mechanism

NASA Astrophysics Data System (ADS)

Cong, F.; Li, J.

2016-12-01

The first member of Maokou Formation of Sichuan basin is composed of well preserved carbonate ramp couplets of limestone and marlstone/shale. It acts as one of the potential shale gas source rock, and is suitable for time-series analysis. We conducted time-series analysis to identify high-frequency sequences, reconstruct high-resolution sedimentation rate, estimate detailed primary productivity for the first time in the study intervals and discuss organic matter accumulation mechanism of source rock under sequence stratigraphic framework.Using the theory of cyclostratigraphy and sequence stratigraphy, the high-frequency sequences of one outcrop profile and one drilling well are identified. Two third-order sequences and eight fourth-order sequences are distinguished on outcrop profile based on the cycle stacking patterns. For drilling well, sequence boundary and four system tracts is distinguished by "integrated prediction error filter analysis" (INPEFA) of Gamma-ray logging data, and eight fourth-order sequences is identified by 405ka long eccentricity curve in depth domain which is quantified and filtered by integrated analysis of MTM spectral analysis, evolutive harmonic analysis (EHA), evolutive average spectral misfit (eASM) and band-pass filtering. It suggests that high-frequency sequences correlate well with Milankovitch orbital signals recorded in sediments, and it is applicable to use cyclostratigraphy theory in dividing high-frequency(4-6 orders) sequence stratigraphy.High-resolution sedimentation rate is reconstructed through the study interval by tracking the highly statistically significant short eccentricity component (123ka) revealed by EHA. Based on sedimentation rate, measured TOC and density data, the burial flux, delivery flux and primary productivity of organic carbon was estimated. By integrating redox proxies, we can discuss the controls on organic matter accumulation by primary production and preservation under the high-resolution sequence stratigraphic framework. Results show that high average organic carbon contents in the study interval are mainly attributed to high primary production. The results also show a good correlation between high organic carbon accumulation and intervals of transgression.

Sequence Stratigraphic Analysis and Facies Architecture of the Cretaceous Mancos Shale on and Near the Jicarilla Apache Indian Reservation, New Mexico-their relation to Sites of Oil Accumulation

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

Ridgley, Jennie

2001-08-21

The purpose of phase 1 and phase 2 of the Department of Energy funded project Analysis of oil- bearing Cretaceous Sandstone Hydrocarbon Reservoirs, exclusive of the Dakota Sandstone, on the Jicarilla Apache Indian Reservation, New Mexico was to define the facies of the oil producing units within the Mancos Shale and interpret the depositional environments of these facies within a sequence stratigraphic context. The focus of this report will center on (1) redefinition of the area and vertical extent of the ''Gallup sandstone'' or El Vado Sandstone Member of the Mancos Shale, (2) determination of the facies distribution within themore » ''Gallup sandstone'' and other oil-producing sandstones within the lower Mancos, placing these facies within the overall depositional history of the San Juan Basin, (3) application of the principals of sequence stratigraphy to the depositional units that comprise the Mancos Shale, and (4) evaluation of the structural features on the Reservation as they may control sites of oil accumulation.« less

Sedimentology and High Resolution Sequence Stratigraphy of the Middle Jurassic Dhruma Formation Carbonates Outcrops in the Central Saudi Arabia

NASA Astrophysics Data System (ADS)

Yousif, Ibrahim; Abdullatif, Osman; Makkawi, Mohammed; Abdulghani, Waleed

2017-04-01

This study investigates the microfacies and sequence stratigraphic frame work of the Middle Jurassic Dhruma Formation in outcrops in central Saudi Arabia. The study contributes to the efforts to understand and enhance local and regional stratigraphic relationship and correlation of the Jurassic carbonate sequences and their significance to reservoir description and prediction in the subsurcae. The study describes and characterizes the sedimentology, microfacies and the stratigraphy of Dhruma Formation from outcrop sections having a total thickness of 70 m. Detailed microfacies and high-resolution stratigraphical analysis were carried out to determine microfacies, cyclicity, sequences and staking pattern. The study revealed ten lithofacies namely: oolitic grainstone,bioclastic oolitic grainstone, oolitic grapestone, bioclastic grainstone,foraminiferal packstone, echinoderm packstone, peloidal packstone to grainstone,skeletal wackestone to packstone, mudstone, and marlstone.These lithofacies were grouped into five lithofacies associations that deposited on a carbonate ramp setting. The depositional environment ranging from low energy lagoonal setting to high-energy shoals and banks to low energy outer ramp setting. Five high-resolution composite sequences have been defined and each sequence is composed at the bottom of intercalated mudstone/wackestone that passing up into grainstone lithofacies.The composite sequences range in thickness from 7 to 15 m, while the parasequences range from 0.5 to 1.5 m. The composite sequences extend laterally for a distance of more than 350 m. The overall composite section shows a shallowing upward succession of the 4th to the 5th order high-resolution sequences.The dominant lithofacies are the grainy ones, which constitute 30%, 50% and 80% of the studied sections. Furthermore, the parasequences thickness and their bio-components are increasing towards the top. The muddy lithofacies intensively affected the vertical continuity of the lower reservoir interval compared to the upper interval. Detailed examination of thin-sections reflects a clear and well-developed reservoir interval in the uppermost part of the section, which is dominated by peloidal packstone and grainstone.The findings of this high-resolution outcrop analog might help to understand and predict lithofacies, stratigraphic heirachies and correlations of Dhruma Formation within the interwell spacing. Moreover, this study might also contribute to better reservoir description and assessment of its quality and architecture in subsurface equivalent reservoirs.

Lithofacies, paleoenvironment and high-resolution stratigraphy of the D5 and D6 members of the Middle Jurassic carbonates Dhruma Formation, outcrop analog, central Saudi Arabia

NASA Astrophysics Data System (ADS)

Yousif, Ibrahim M.; Abdullatif, Osman M.; Makkawi, Mohammad H.; Bashri, Mazin A.; Abdulghani, Waleed M.

2018-03-01

This study characterizes the lithofacies, paleoenvironment and stratigraphic architecture of the D5 and D6 members of carbonates Dhruma Formation outcrops in central Saudi Arabia. The study integrates detailed lithofacies analysis based on vertical and lateral profiles, in addition to thin-sections petrography to reveal the high-resolution architecture framework. Nine lithofacies types (LFTs) were defined namely: (1) skeletal peletal spiculitic wackestone (15%), (2) peloidal echinoderm packstone (19%), (3) fissile shale (36%), (4) peloidal spiculitic echinoderm pack-grainstone (5%), (5) cross-bedded peloidal skeletal oolitic grainstone (7%), (6) oolitic grainstone (2%), (7) intraformational rudstone (<1%), (8) skeletal peloidal foraminiferal packstone (12%) and (9) skeletal foraminiferal wackestone (4%). These lithofacies types were grouped into five major carbonate paleoenvironments that range from distal-to-proximal carbonate ramp setting. The detailed stratigraphic analysis revealed around 53 cycles and cycle sets with 5th to 6th orders magnitude, and thickness ranges from a few centimeters up to 6 m with an average of 1.5 m. Those are stacked to form four high-frequency sequences with thickness range from 1 m up to 14 m. The latter were grouped into a single depositional sequence of 3rd order magnitude. The architectural analysis also shows that the potential reservoir units were intensively affected by muddy-textured rocks which act as reservoir seals. These variations in the stratigraphic sequences in Middle Jurassic Dhruma Formation and its equivalents could be attributed to the eustatic sea-level changes, climate, tectonics, and local paleoenvironments. This study attempts to provide detailed insight into reservoir heterogeneity and architecture. The analog may help to understand and predict lithofacies heterogeneity, architecture, and quality in the subsurface equivalent reservoirs.

Lithofacies and sequence stratigraphic description of the upper part of the Avon Park Formation and the Arcadia Formation in U.S. Geological Survey G–2984 test corehole, Broward County, Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Robinson, Edward

2017-07-18

Rock core and sediment from U.S. Geological Survey test corehole G–2984 completed in 2011 in Broward County, Florida, provide an opportunity to improve the understanding of the lithostratigraphic, sequence stratigraphic, and hydrogeologic framework of the intermediate confining unit and Floridan aquifer system in southeastern Florida. A multidisciplinary approach including characterization of sequence stratigraphy, lithofacies, ichnology, foraminiferal paleontology, depositional environments, porosity, and permeability was used to describe the geologic samples from this test corehole. This information has produced a detailed characterization of the lithofacies and sequence stratigraphy of the upper part of the middle Eocene Avon Park Formation and Oligocene to middle Miocene Arcadia Formation. This enhancement of the knowledge of the sequence stratigraphic framework is especially important, because subaerial karst unconformities at the upper boundary of depositional cycles at various hierarchical scales are commonly associated with secondary porosity and enhanced permeability in the Floridan aquifer system.

A new third-order sequence stratigraphic framework applied to the Triassic of the Paraná Basin, Rio Grande do Sul, Brazil, based on structural, stratigraphic and paleontological data

NASA Astrophysics Data System (ADS)

Horn, B. L. D.; Melo, T. M.; Schultz, C. L.; Philipp, R. P.; Kloss, H. P.; Goldberg, K.

2014-11-01

The Santacruzodon assemblage zone was originally defined as a vertebrate fossil assemblage composed basically of non-mammalian cynodonts found in Santa Cruz do Sul and Venâncio Aires municipalities in Southern Brazil. This assemblage zone was positioned at the top of the Sequence I, in the Triassic Santa Maria Supersequence, Paraná Basin. However, the Santacruzodon assemblage zone does not occur across the entire area of the Santa Maria Supersequence. Based on new paleontological, structural and sedimentological data, we propose the existence of a new third-order sequence (Santa Cruz Sequence) between Sequences I and II in the Santa Maria Supersequence. Satellite image analysis was used to identify regional, NW- and NE-oriented lineaments that limit the occurrence zone. Outcrop data allowed the identification of a regional, angular unconformity that bounds the new sequence. The faunal content allowed the correlation of the new Santa Cruz Sequence with Madagascar's Isalo II fauna, corresponding to the Ladinian (Middle Triassic). New names were suggested for the sequences in the Santa Maria Supersequence, since the Santa Cruz Sequence was deposited between the former Sequences I and II. This unit was deposited or preserved exclusively on the hanging wall of normal faults, being absent from the adjacent structural blocks.

Use of Landsat Thematic Mapper images in regional correlation of syntectonic strata, Colorado river extensional corridor, California and Arizona

NASA Technical Reports Server (NTRS)

Beratan, K. K.; Blom, R. G.; Crippen, R. E.; Nielson, J. E.

1990-01-01

Enhanced Landsat TM images were used in conjunction with field work to investigate the regional correlation of Miocene rocks in the Colorado River extensional corridor of California and Arizona. Based on field investigations, four sequences of sedimentary and volcanic strata could be recognized in the Mohave Mountains (Arizona) and the eastern Whipple Mountains (California), which display significantly different relative volumes and organization of lithologies. The four sequences were also found to have distinctive appearances on the TM image. The recognition criteria derived from field mapping and image interpretation in the Mohave Mountains and Whipple Mountains were applied to an adjacent area in which stratigraphic affinities were less well known. The results of subsequent field work confirmed the stratigraphic and structural relations suggested by the Tm image analysis.

Stratigraphic palaeobiology around the Pliocene-Pleistocene boundary at Altavilla Milicia (Sicily, Italy)

NASA Astrophysics Data System (ADS)

Dominici, Stefano; Benvenuti, Marco; Garilli, Vittorio; Uchman, Alfred; Pollina, Francesco

2017-04-01

The Pliocene-Pleistocene around Altavilla Milicia, near Palermo (Sicily), includes a thick siliciclastic succession rich with shell beds, dominated by molluscs, brachiopods and annelids in fine-grained, totally bioturbated sandstones. Taphonomy of fossil assemblages indicates the importance of taphonomic feedback and within-habitat time-averaging in proximity of maximum flooding intervals. The trace fossil suite is characterized by the abundance of Thalassinoides paradoxicus boxworks and by local occurence of Scalichnus, Piscichnus, ?Scolicia, ?Bichordites, Ophiomorpha, ?Gyrolithes, Palaeophycus, Diopatrichnus and ?Taenidium. These trace fossils are typical of the archetypal Cruziana ichnofacies, with local elements of the proximal Cruziana ichnofacies, which point to deposition mainly below the fairweather wave base. Three depositional sequences, characterized by geometries driven by the interplay of eustatism and regional tectonics, were recognized through sedimentary facies analysis. Biostratigraphic data frame the oldest sequence in the upper Pliocene, whereas the thickest part of the succession, occupied by the second sedimentary sequence, includes biozone NN16b/17 of calcareous nannoplankton stratigraphy, thereby comprising the base of the Pleistocene. Transgressive deposits of the third and uppermost sequence are marked by encrusted and bioeroded pebbles with sparse oyster shells. The whole time interval is characterized by glacio-eustatic fluctuations in the 50-100 m range and with 100 ky-periodicity. We performed a multivariate analysis of 22 samples yielding 92 species of mollusks collected in the first and second sequences. Clustering and ordination analysis allowed to recognize a gradient controlled by depth-related environmental variables. At one end of the continuum we have a very-shallow water assemblage dominated by the bivalve Loripes orbiculatus, indicating an organic-rich seagrass bottom. Opposite in the continuum is an offshore assemblage dominated by Corbula gibba and the extinct gastropod Petaloconchus intortus. Both the shallowest and the deepest assemblages are from the first (Piacenzian) sequence. The gradient at intermediate depths is better characterized by restricting the analysis to 17 collections from the second sequence (Piacenzian-Gelasian). The shallowest assemblage is here dominated by upper shoreface species, such as Tellina spp. and Spisula subtruncata, and the deepest by muddy bottom, offshore transition species, such as Venus nux, the extinct gastropod Nassarius semistriatus and deposit-feeding nuculanoid bivalves. Plotting samples along the composite section allows to recognize two deepening-upward trends and two intervals of maximum flooding, in accordance with the sequence-stratigraphic interpretation. Stratigraphic palaeobiology proves to be a powerful tool to understand factors that control the geologic record during an interval of intense climate change.

The transitional depositional environment and sequence stratigraphy of Chasma Boreale

NASA Astrophysics Data System (ADS)

Brothers, S. C.; Kocurek, G.

2018-07-01

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

Presentations - Herriott, T.M. and others, 2015 | Alaska Division of

Science.gov Websites

Details Title: Sequence stratigraphic framework of the Upper Jurassic Naknek Formation, Cook Inlet forearc Resident Business in Alaska Visiting Alaska State Employees DGGS State of Alaska search Alaska Division of ., Wartes, M.A., and Decker, P.L., 2015, Sequence stratigraphic framework of the Upper Jurassic Naknek

Integrated Sedimentological Approach to Assess Reservoir Quality and Architecture of Khuff Carbonates: Outcrop Analog, Central Saudi Arabia

NASA Astrophysics Data System (ADS)

Osman, Mutsim; Abdullatif, Osman

2017-04-01

The Permian to Triassic Khuff carbonate reservoirs (and equivalents) in the Middle East are estimated to contain about 38.4% of the world's natural gas reserves. Excellent exposed outcrops in central Saudi Arabia provide good outcrop equivalents to subsurface Khuff reservoirs. This study conduct high resolution outcrop scale investigations on an analog reservoir for upper Khartam of Khuff Formation. The main objective is to reconstruct litho- and chemo- stratigraphic outcrop analog model that may serve to characterize reservoir high resolution (interwell) heterogeneity, continuity and architecture. Given the fact of the limitation of subsurface data and toolsin capturing interwell reservoir heterogeneity, which in turn increases the value of this study.The methods applied integrate sedimentological, stratigraphic petrographic, petrophysical data and chemical analyses for major, trace and rare earth elements. In addition, laser scanning survey (LIDAR) was also utilized in this study. The results of the stratigraphic investigations revealed that the lithofacies range from mudstone, wackestone, packestone and grainstone. These lithofacies represent environments ranging from supratidal, intertidal, subtidal and shoal complex. Several meter-scale and less high resolution sequences and composite sequences within 4th and 5th order cycles were also recognized in the outcrop analog. The lithofacies and architectural analysis revealed several vertically and laterally stacked sequences at the outcrop as revealed from the stratigraphic sections and the lidar scan. Chemostratigraphy is effective in identifying lithofacies and sequences within the outcrop analog. Moreover, different chemical signatures were also recognized and allowed establishing and correlating high resolution lithofacies, reservoir zones, layers and surfaces bounding reservoirs and non-reservoir zones at scale of meters or less. The results of this high resolution outcrop analog study might help to understand and evaluate Khuff reservoir heterogeneity, quality and architecture. It might also help to fill the gap in knowledge in reservoir characterization models based on low resolution subsurface data alone.

Regional stratigraphy of the south polar layered deposits (Promethei Lingula, Mars): "Discontinuity-bounded" units in images and radargrams

NASA Astrophysics Data System (ADS)

Guallini, Luca; Rossi, Angelo Pio; Forget, François; Marinangeli, Lucia; Lauro, Sebastian Emanuel; Pettinelli, Elena; Seu, Roberto; Thomas, Nicolas

2018-07-01

The Mars South Polar Layered Deposits (SPLD) are the result of depositional and erosional events, which are marked by different stratigraphic sequences and erosional surfaces. To unambiguously define the stratigraphic units at regional scale, we mapped the SPLD on the basis of observed discontinuities (i.e., unconformities, correlative discontinuities and conformities), as commonly done in terrestrial modern stratigraphy. This methodology is defined as "Discontinuity-Bounded Units" or allostratigraphy, and is complemented by geomorphological mapping. Our study focuses on Promethei Lingula (PL) and uses both high-resolution images (CTX, HiRISE) and radargrams (SHARAD) to combine surface and sub-surface observations and obtain a 3D geological reconstruction of the SPLD. One regional discontinuity (named AUR1) was defined within the studied stratigraphic succession and is exposed in several non-contiguous outcrops around PL as well as observed at depth within the ice sheet. This is the primary contact between two major depositional sequences, showing a different texture at CTX resolution. The lower sequence is characterized mainly by a "ridge and trough" morphology (Ridge and Trough Sequence; RTS) and the upper sequence shows mainly by a "stair-stepped" morphology (Stair-Stepped Sequence; SSS). On the basis of the observations, we defined two regional "discontinuity-bounded" units in PL, respectively coinciding with RTS and SSS sequences. Our stratigraphic reconstruction provides new hints on the major scale events that shaped this region. Oscillations in Martian axial obliquity could have controlled local climate conditions in the past, affecting the PL geological record.

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

NASA Astrophysics Data System (ADS)

Sitaula, R. P.; Aschoff, J.

2013-12-01

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

Stratigraphic evolution of the Late Jurassic Hanifa Formation along the Tuwaiq Escarpment, Saudi Arabia: Evidence for a carbonate ramp system

NASA Astrophysics Data System (ADS)

Fallatah, Mohammed I.; Kerans, Charles

2018-01-01

A sequence stratigraphic framework of the Late Jurassic (Oxfordian) Hanifa Formation at its exposure in Central Arabia is presented for the first time. This study offers the first high-resolution stratigraphic framework of the Hanifa along the Tuwaiq Escarpment by measuring 15 sections ( 770 m total thickness) over an oblique-to-dip distance of 260 km and collecting 295 samples for petrographic analysis. On the basis of these data, the Hanifa Formation can be subdivided into eight facies; 1) tabular cross-bedded quartz-peloidal-skeletal grainstone, 2) cross-bedded skeletal-peloidal grainstone, 3) bioturbated foraminiferal wackestone/mud-dominated packstone, 4) oncolitic rudstone, 5) stromatoporoid-coral biostrome/bioherm, 6) peloidal/composite-grain grain-dominated packstone/grainstone, 7) bioturbated spiculitic wackestone/mud-dominated packstone, and 8) thinly-bedded argillaceous mudstone/wackestone. The vertical and lateral distributions of these facies along the exposure define their sequence setting using the principals of sequence stratigraphy. By recognizing erosional surfaces, facies offset, and changes in facies proportions, five third-order sequences, with an average duration of 1.1 Myr, are interpreted for the Hanifa Formation. The correlation of the sequences across the study area shows that only four sequences are preserved in the north where shallow-water deposits are well-developed. Facies trends within these sequences are further illustrated in depositional models representing the highstand systems tracts (HST) and the transgressive systems tracts (TST) of the Hanifa Formation. These proposed models represent depositional settings of a carbonate ramp with normal open-marine conditions. The HST depositional model is characterized by a high-energy shoreline and depicts the presence of an offshore, structurally controlled skeletal-peloidal shoal body described here for the first time at the Hanifa exposure in the Hozwa area. This work provides a predictive framework and outcrop analog for applications in hydrocarbon exploration and development. Furthermore, a basinal setting predicted to the south of the study area is a potential site for unconventional plays.

Time Not Our Time: Physical Controls on the Preservation and Measurement of Geologic Time

NASA Astrophysics Data System (ADS)

Paola, Chris; Ganti, Vamsi; Mohrig, David; Runkel, Anthony C.; Straub, Kyle M.

2018-05-01

Sadler's (1981) analysis of how measured sedimentation rate decreases with timescale of measurement quantified the vanishingly small fractional time preservation—completeness—of the stratigraphic record. Generalized numerical models have shown that the Sadler effect can be recovered, through the action of erosional clipping and time removal (the “stratigraphic filter”), from even fairly simple topographic sequences. However, several lines of evidence suggest that most of the missing time has not been eroded out but rather represents periods of inactivity or stasis. Low temporal completeness could also imply that the stratigraphic record is dominated by rare, extreme events, but paleotransport estimates suggest that this is not generally the case: The stratigraphic record is strangely ordinary. It appears that the organization of the topography into a hierarchy of forms also organizes the deposition into concentrated events that tend to preserve relatively ordinary conditions, albeit for very short intervals. Our understanding of time preservation would benefit from insight about how inactivity is recorded in strata; better ways to constrain localized, short-term rates of deposition; and a new focus on integrated time–space dynamics of deposition and preservation.

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

USGS Publications Warehouse

Hallberg, G.R.

1986-01-01

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.

Facies analysis and sequence stratigraphic framework of upper Campanian strata (Neslen and Mount Garfield formations, Bluecastle Tongue of the Castlegate sandstone, and Mancos shale), Eastern Book cliffs, Colorado and Utah

USGS Publications Warehouse

Kirschbaum, Mark A.; Hettinger, Robert D.

2004-01-01

Facies and sequence-stratigraphic analysis identifies six high-resolution sequences within upper Campanian strata across about 120 miles of the Book Cliffs in western Colorado and eastern Utah. The six sequences are named after prominent sandstone units and include, in ascending order, upper Sego sequence, Neslen sequence, Corcoran sequence, Buck Canyon/lower Cozzette sequence, upper Cozzette sequence, and Cozzette/Rollins sequence. A seventh sequence, the Bluecastle sequence, is present in the extreme western part of the study area. Facies analysis documents deepening- and shallowing- upward successions, parasequence stacking patterns, downlap in subsurface cross sections, facies dislocations, basinward shifts in facies, and truncation of strata.All six sequences display major incision into shoreface deposits of the Sego Sandstone and sandstones of the Corcoran and Cozzette Members of the Mount Garfield Formation. The incised surfaces represent sequence-boundary unconformities that allowed bypass of sediment to lowstand shorelines that are either attached to the older highstand shorelines or are detached from the older highstand shorelines and located southeast of the main study area. The sequence boundary unconformities represent valley incisions that were cut during successive lowstands of relative sea level. The overlying valley-fill deposits generally consist of tidally influenced strata deposited during an overall base level rise. Transgressive surfaces can be traced or projected over, or locally into, estuarine deposits above and landward of their associated shoreface deposits. Maximum flooding surfaces can be traced or projected landward from offshore strata into, or above, coastal-plain deposits. With the exception of the Cozzette/Rollins sequence, the majority of coal-bearing coastal-plain strata was deposited before maximum flooding and is therefore within the transgressive systems tracts. Maximum flooding was followed by strong progradation of parasequences and low preservation potential of coastal-plain strata within the highstand systems tract. The large incised valleys, lack of transgressive retrogradational parasequences, strong progradational nature of highstand parasequences, and low preservation of coastal-plain strata in the highstand systems tracts argue for relatively low accommodation space during deposition of the Sego, Corcoran, and Cozzette sequences. The Buck Canyon/Cozzette and Cozzette/Rollins sequences contrast with other sequences in that the preservation of retrogradational parasequences and the development of large estuaries coincident with maximum flooding indicate a relative increase in accommodation space during deposition of these strata. Following maximum flooding, the Buck Canyon/Cozzette sequence follows the pattern of the other sequences, but the Cozzette/Rollins sequence exhibits a contrasting offlapping pattern with development of offshore clinoforms that downlap and eventually parallel its maximum flooding surface. This highstand systems tract preserves a thick coal-bearing section where the Rollins Sandstone Member of the Mount Garfield Formation parasequences prograde out of the study area, stepping up as much as 800 ft stratigraphically over a distance of about 90 miles. This progradational stacking pattern indicates a higher accommodation space and increased sedimentation rate compared to the previous sequences.

Sequence stratigraphy of the Raha Formation, Bakr Oil Field, Gulf of Suez, Egypt: Insights from electrical well log and palynological data

NASA Astrophysics Data System (ADS)

Mansour, Ahmed; Mohamed, Omar; Tahoun, Sameh S.; Elewa, Ashraf M. T.

2018-03-01

The current paper provides a high resolution sequence stratigraphic study of the Raha Formation from the productive Bakr Oil Field, central Gulf of Suez, Egypt. Sixty cutting rock samples spanning the Cenomanian from three wells (Bakr-114, B-115 and B-109) in the Bakr Basin, were palynologically investigated. The documented palynomorphs assemblage of either terrestrially-derived sporomorphs or marine inhabited dinocysts, allowed two palynological zones as well as their encompassing depositional palaeoenvironment to be recognized. These zones are Afropollis jardinus-Crybelosporites pannuceus Assemblage Zone (early-middle Cenomanian) and Classopollis brasiliensis-Tricolpites sagax Assemblage Zone (late Cenomanian). Detailed analysis of the particulate organic matter compositions suggested that the depositional palaeoenvironment of the Raha Formation was fluctuating between supratidal and distal-inner neritic conditions, due to successive oscillations of the Neo-Tethyan Ocean during the Cenomanian. The pronounced peaks of particulate organic matter versus gamma ray are markedly used in delineating the depositional sequences of the Raha Formation and their bounding surfaces. The Raha Formation probably corresponds to a second-order depositional sequence, which can be further subdivided into eight third-order depositional sequences, of which six are complete and two are incomplete ones. These depositional sequences are significantly synchronized based on a simple 2-D correlation model between the three wells. According to the hierarchical duration system, the Cenomanian herein was approximately attributed to 6 Myr, each of which has lower order depositional sequences that took approximately 0.9 Myr. Based on the sequence stratigraphic approach together with palynofacies analysis and gamma ray data, a condensed section was defined in the B-115.

Geoscience technology application to optimize field development, Seligi Field, Malay Basin

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

Ahmed, M.S.; Wiggins, B.D.

1994-07-01

Integration of well log, core, 3-D seismic, and engineering data within a sequence stratigraphic framework, has enabled prediction of reservoir distribution and optimum development of Seligi field. Seligi is the largest field in the Malay Basin, with half of the reserves within lower Miocene Group J reservoirs. These reservoirs consist of shallow marine sandstones and estuarine sandstones predominantly within an incised valley. Variation in reservoir quality has been a major challenge in developing Seligi. Recognizing and mapping four sequences within the Group J incised valley fill has resulted in a geologic model for predicting the distribution of good quality estuarinemore » reservoir units and intercalated low-permeability sand/shale units deposited during marine transgressions. These low-permeability units segregate the reservoir fluids, causing differential contact movement in response to production thus impacting completion strategy and well placement. Seismic calibration shows that a large impedance contrast exists between the low-permeability rock and adjacent good quality oil sand. Application of sequence stratigraphic/facies analysis coupled with the ability to identify the low-permeability units seismically is enabling optimum development of each of the four sequences at Seligi.« less

Geodynamic Evolution of Northeastern Tunisia During the Maastrichtian-Paleocene Time: Insights from Integrated Seismic Stratigraphic Analysis

NASA Astrophysics Data System (ADS)

Abidi, Oussama; Inoubli, Mohamed Hédi; Sebei, Kawthar; Amiri, Adnen; Boussiga, Haifa; Nasr, Imen Hamdi; Salem, Abdelhamid Ben; Elabed, Mahmoud

2017-05-01

The Maastrichtian-Paleocene El Haria formation was studied and defined in Tunisia on the basis of outcrops and borehole data; few studies were interested in its three-dimensional extent. In this paper, the El Haria formation is reviewed in the context of a tectono-stratigraphic interval using an integrated seismic stratigraphic analysis based on borehole lithology logs, electrical well logging, well shots, vertical seismic profiles and post-stack surface data. Seismic analysis benefits from appropriate calibration with borehole data, conventional interpretation, velocity mapping, seismic attributes and post-stack model-based inversion. The applied methodology proved to be powerful for charactering the marly Maastrichtian-Paleocene interval of the El Haria formation. Migrated seismic sections together with borehole measurements are used to detail the three-dimensional changes in thickness, facies and depositional environment in the Cap Bon and Gulf of Hammamet regions during the Maastrichtian-Paleocene time. Furthermore, dating based on their microfossil content divulges local and multiple internal hiatuses within the El Haria formation which are related to the geodynamic evolution of the depositional floor since the Campanian stage. Interpreted seismic sections display concordance, unconformities, pinchouts, sedimentary gaps, incised valleys and syn-sedimentary normal faulting. Based on the seismic reflection geometry and terminations, seven sequences are delineated. These sequences are related to base-level changes as the combination of depositional floor paleo-topography, tectonic forces, subsidence and the developed accommodation space. These factors controlled the occurrence of the various parts of the Maastrichtian-Paleocene interval. Detailed examinations of these deposits together with the analysis of the structural deformation at different time periods allowed us to obtain a better understanding of the sediment architecture in depth and the delineation of the geodynamic evolution of the region.

Diversity and distribution of archaea community along a stratigraphic permafrost profile from Qinghai-Tibetan Plateau, China.

PubMed

Wei, Shiping; Cui, Hongpeng; He, Hao; Hu, Fei; Su, Xin; Zhu, Youhai

2014-01-01

Accompanying the thawing permafrost expected to result from the climate change, microbial decomposition of the massive amounts of frozen organic carbon stored in permafrost is a potential emission source of greenhouse gases, possibly leading to positive feedbacks to the greenhouse effect. In this study, the community composition of archaea in stratigraphic soils from an alpine permafrost of Qinghai-Tibetan Plateau was investigated. Phylogenic analysis of 16S rRNA sequences revealed that the community was predominantly constituted by Crenarchaeota and Euryarchaeota. The active layer contained a proportion of Crenarchaeota at 51.2%, with the proportion of Euryarchaeota at 48.8%, whereas the permafrost contained 41.2% Crenarchaeota and 58.8% Euryarchaeota, based on 16S rRNA gene sequence analysis. OTU1 and OTU11, affiliated to Group 1.3b/MCG-A within Crenarchaeota and the unclassified group within Euryarchaeota, respectively, were widely distributed in all sediment layers. However, OTU5 affiliated to Group 1.3b/MCG-A was primarily distributed in the active layers. Sequence analysis of the DGGE bands from the 16S rRNAs of methanogenic archaea showed that the majority of methanogens belonged to Methanosarcinales and Methanomicrobiales affiliated to Euryarchaeota and the uncultured ZC-I cluster affiliated to Methanosarcinales distributed in all the depths along the permafrost profile, which indicated a dominant group of methanogens occurring in the cold ecosystems.

Diversity and Distribution of Archaea Community along a Stratigraphic Permafrost Profile from Qinghai-Tibetan Plateau, China

PubMed Central

Cui, Hongpeng; He, Hao; Hu, Fei; Su, Xin; Zhu, Youhai

2014-01-01

Accompanying the thawing permafrost expected to result from the climate change, microbial decomposition of the massive amounts of frozen organic carbon stored in permafrost is a potential emission source of greenhouse gases, possibly leading to positive feedbacks to the greenhouse effect. In this study, the community composition of archaea in stratigraphic soils from an alpine permafrost of Qinghai-Tibetan Plateau was investigated. Phylogenic analysis of 16S rRNA sequences revealed that the community was predominantly constituted by Crenarchaeota and Euryarchaeota. The active layer contained a proportion of Crenarchaeota at 51.2%, with the proportion of Euryarchaeota at 48.8%, whereas the permafrost contained 41.2% Crenarchaeota and 58.8% Euryarchaeota, based on 16S rRNA gene sequence analysis. OTU1 and OTU11, affiliated to Group 1.3b/MCG-A within Crenarchaeota and the unclassified group within Euryarchaeota, respectively, were widely distributed in all sediment layers. However, OTU5 affiliated to Group 1.3b/MCG-A was primarily distributed in the active layers. Sequence analysis of the DGGE bands from the 16S rRNAs of methanogenic archaea showed that the majority of methanogens belonged to Methanosarcinales and Methanomicrobiales affiliated to Euryarchaeota and the uncultured ZC-I cluster affiliated to Methanosarcinales distributed in all the depths along the permafrost profile, which indicated a dominant group of methanogens occurring in the cold ecosystems. PMID:25525409

Astronomical forcing of a Middle Permian chert sequence in Chaohu, South China

NASA Astrophysics Data System (ADS)

Yao, Xu; Zhou, Yaoqi; Hinnov, Linda A.

2015-07-01

Astronomical forcing has been shown to be a fundamental driver of climate change through geological time. Pelagic, bedded cherts deposited in Mesozoic ocean basins with chert-mudstone cycles have been shown to contain the imprint of Milankovitch astronomical climate forcing. In the Chaohu region, South China, we studied a Middle Permian radiolarian chert sequence (Gufeng Formation) with chert-mudstone couplets reminiscent of the Mesozoic cherts, but deposited on a continental shelf. Spectral analysis of lithologic bed thickness data from two sections of this chert sequence reveals that 13 cm to 20 cm chert-mudstone cycles in the stratigraphic domain match theoretical 32-kyr Middle Permian obliquity cycling, together with a hierarchy of other cycles with 12 cm, 9 cm, 7 cm, 6.6 cm and 5.4 cm wavelengths. Tuning the 13 cm to 20 cm stratigraphic cycles to Earth's obliquity cycle periodicity indicates that the cm-scale cycles are precession-scale variations with a strong ∼400 kyr amplitude modulation. Tuning to theoretical precession terms provides further support for the astronomical forcing of the chert sequence. We propose that monsoon-controlled upwelling contributed to the development of the chert-mudstone cycles. A seasonal monsoon controlled by astronomical forcing (i.e., insolation) influenced the intensity of upwelling. Stronger upwelling increased radiolarian productivity in the surface ocean, increasing silica deposition. Glacio-eustatic oscillations from ice sheet dynamics in southern Gondwana modulated terrigenous mud flux to the basin. The two processes jointly contributed to the astronomical rhythms of these tropical chert-mudstone sequences, which are characterized by comparably strong obliquity and precession responses. Subsequent diagenesis distorted the chert and mudstone layering, but not enough to destroy the original stratigraphic patterns. The resulting astronomical time scale (ATS) assumes a Roadian/Wordian boundary age of 268.8 Ma for the onset of the first chert layer at the base of the sequence and ends at 264.1 Ma, for a total duration of 4.7 myr.

Global stratigraphy of Venus: Analysis of a random sample of thirty-six test areas

NASA Technical Reports Server (NTRS)

Basilevsky, Alexander T.; Head, James W., III

1995-01-01

The age relations between 36 impact craters with dark paraboloids and other geologic units and structures at these localities have been studied through photogeologic analysis of Magellan SAR images of the surface of Venus. Geologic settings in all 36 sites, about 1000 x 1000 km each, could be characterized using only 10 different terrain units and six types of structures. Mapping of such units and structures in 36 randomly distributed large regions shows evidence for a distinctive regional and global stratigraphic and geologic sequence. On the basis of this sequence we have developed a model that illustrates several major themes in the history of Venus. Most of the history of Venus (that of its first 80% or so) is not preserved in the surface geomorphological record. The major deformation associated with tessera formation in the period sometime between 0.5-1.0 b.y. ago (Ivanov and Basilevsky, 1993) is the earliest event detected. Our stratigraphic analyses suggest that following tessera formation, extensive volcanic flooding resurfaced at least 85% of the planet in the form of the presently-ridged and fractured plains. Several lines of evidence favor a high flux in the post-tessera period but we have no independent evidence for the absolute duration of ridged plains emplacement. During this time, the net state of stress in the lithosphere apparently changed from extensional to compressional, first in the form of extensive ridge belt development, followed by the formation of extensive wrinkle ridges on the flow units. Subsequently, there occurred local emplacement of smooth and lobate plains units which are presently essentially undeformed. The major events in the latest 10% of the presently preserved history of Venus are continued rifting and some associated volcanism, and the redistribution of eolian material largely derived from impact crater deposits. Detailed geologic mapping and stratigraphic synthesis are necessary to test this sequence and to address many of the outstanding problems raised by this analysis.

Sequence stratigraphy of the Lower Cenomanian Bahariya Formation, Bahariya Oasis, Western Desert, Egypt

NASA Astrophysics Data System (ADS)

Catuneanu, O.; Khalifa, M. A.; Wanas, H. A.

2006-08-01

The Lower Cenomanian Bahariya Formation corresponds to a second-order depositional sequence that formed within a continental shelf setting under relatively low-rate conditions of positive accommodation (< 200 m during 3-6 My). This overall trend of base-level rise was interrupted by three episodes of base-level fall that resulted in the formation of third-order sequence boundaries. These boundaries are represented by subaerial unconformities (replaced or not by younger transgressive wave ravinement surfaces), and subdivide the Bahariya Formation into four third-order depositional sequences. The construction of the sequence stratigraphic framework of the Bahariya Formation is based on the lateral and vertical changes between shelf, subtidal, coastal and fluvial facies, as well as on the nature of contacts that separate them. The internal (third-order) sequence boundaries are associated with incised valleys, which explain (1) significant lateral changes in the thickness of incised valley fill deposits, (2) the absence of third-order highstand and even transgressive systems tracts in particular areas, and (3) the abrupt facies shifts that may occur laterally over relatively short distances. Within each sequence, the concepts of lowstand, transgressive and highstand systems tracts are used to explain the observed lateral and vertical facies variability. This case study demonstrates the usefulness of sequence stratigraphic analysis in understanding the architecture and stacking patterns of the preserved rock record, and helps to identify 13 stages in the history of base-level changes that marked the evolution of the Bahariya Oasis region during the Early Cenomanian.

Preliminary Stratigraphic Basis for Geologic Mapping of Venus

NASA Technical Reports Server (NTRS)

Basilevsky, A. T.; Head, J. W.

1993-01-01

The age relations between geologic formations have been studied at 36 1000x1000 km areas centered at the dark paraboloid craters. The geologic setting in all these sites could be characterized using only 16 types of features and terrains (units). These units form a basic stratigraphic sequence (from older to younger: (1) Tessera (Tt); (2-3) Densely fractured terrains associated with coronae (COdf) and in the form of remnants among plains (Pdf); (4) Fractured and ridged plains (Pfr); (5) Plains with wrinkle ridges (Pwr); (6-7) Smooth and lobate plains (Ps/Pl); and (8) Rift-associated fractures (Fra). The stratigraphic position of the other units is determined by their relation with the units of the basic sequence: (9) Ridge bells (RB), contemporary with Pfr; (10-11) Ridges of coronae and arachnoids annuli (COar/Aar), contemporary with wrinkle ridges of Pwr; (12) Fractures of coronae annuli (COaf) disrupt Pwr and Ps/Pl; (13) Fractures (F) disrupt Pwr or younger units; (14) Craters with associated dark paraboloids (Cdp), which are on top of all volcanic and tectonic units except the youngest episodes of rift-associated fracturing and volcanism; (15-16) Surficial streaks (Ss) and surficial patches (Sp) are approximately contemporary with Cdp. These units may be used as a tentative basis for the geologic mapping of Venus including VMAP. This mapping should test the stratigraphy and answer the question of whether this stratigraphic sequence corresponds to geologic events which were generally synchronous all around the planet or whether the sequence is simply a typical sequence of events which occurred in different places at diffferent times.

Biostratigraphy of Cretaceous-Paleogene marine succession, foraminiferal changes across the K/T boundary, sequence stratigraphy and response to sedimentary cyclicity in the Haymana Basin (Central Anatolia, Turkey)

NASA Astrophysics Data System (ADS)

Amirov, Elnur

2016-04-01

The aim of this study is to establish the planktonic foraminiferal biozonation, to construct the sequence stratigraphical framework and to determine the foraminiferal response to sedimentary cyclicity in the sedimentary sequence spanning Upper Cretaceous-Paleocene in the Haymana basin (Central Anatolia, Turkey). In order to achieve this study, the stratigraphic section was measured from sedimentary sequence of the Haymana, Beyobası and Yeşilyurt formations. The sedimentary sequence is mainly characterized by flyschoidal sequence that is composed of alternating of siliciclastic and carbonate units. On the account of the detailed taxonomic study of planktonic foraminifers, the biostratigraphic framework was established for the Maastrichtian-Paleocene interval. The biozonation includes 7 zones; Pseudoguembelina hariaensis, Pα, P1, P2, P3, P4 and P5 zones. The Cretaceous-Paleogene (K/P) boundary was delineated between the samples HEA-105 and 106. In order to construct the sequence-stratigraphical framework, the A, B, C and D-type meter-scale cycles were identified. Based on the stacking patterns of them, six depositional sequences, six third and two second order cycles were determined. Third order cycles coincide with the Global Sea Level Change Curve. On the account of the conducted petrographic analysis sandstone, mudstone, marl, limestone and muddy-limestone lithofacies were recorded in the studied samples. In order to demonstrate the response of foraminifers to cyclicity, quantitative analysis has been carried out by counting the individuals of planktonic, benthonic foraminifers and ostracods. The best response to sedimentary cyclicity was revealed from planktonic foraminifers. The average abundance of planktonic foraminifers increases in the transgressive systems tract and decreases in the highstand systems tract. Foraminifera are the most abundant marine protozoa in the benthic, epipelagic and pelagic realm. Because of the complexity and diversity of habitats, especially in the pelagic realm, planktonic foraminifera show high biodiversity and abundance as an effect of their different ecological requirements. Microfaunal analysis displays significant presence of foraminifers and an insignificant presence of ostracoda shells which represented by genera Leptocythere, Caspiella, Xestoleberis and etc. The foraminiferal assemblages of this sequence were determined in detail and quantitative analysis of them was carried out. By detail investigation of microfauna and determination of foraminifer species under the microscope, it was possible to pinpoint the C/P boundary in the studied section, which is indicating the mass extinctions of Cretaceous foraminifers represented by genera Archaeoglobigerina, Contusotruncana, Gansserina, Globigerinelloides, Globotruncana, Globorotalia, Hedbergella, Heterohelix, Planoglobulina and appearance of new small and non-keeled Danian species, represented by genera such as Chiloguembelina, Eoglobigerina, Globoconusa, Globanomalina, Igorina, Parvularugoglobigerina, Parasubbotina, Subbotina, Woodringina and etc. As a result of precise conducted research the significant bioevent has been revealed, namely that Hedbergella holmdelensis became extinct in Pα Zone.

The stratigraphic sequence of Scafati (Italy) - An archive of 10,000 years of volcanism, soil formation and land use in the shade of Mount Vesuvius

NASA Astrophysics Data System (ADS)

Maerker, Michael; Vogel, Sebastian; Hoelzmann, Phillip; Rellini, Ivano

2014-05-01

In this study we carried out a detailed lithostratigraphic, pedological and micromorphological analysis at a stratigraphic sequence close to Scafati, about 3 km east of ancient Pompeii. It consists of a multilayered succession of repeated volcanic deposition and pedogenesis caused by several phases of volcanic activity of Somma-Vesuvius and volcanic quiescence. This comprises, at least, the last 10,000 years of sedimentation history, on one hand, reflecting the entire spectrum of eruption types of Somma-Vesuvius from Plinian, sub-Plinian, rather small eruptions to effusive volcanic events and, on the other hand, soil formations of different durations, intensities and soil-forming environments. Furthermore, the paleosols repeatedly reveal clear evidence of anthropogenic activity by means of agriculture. Hence, a landscape evolution model was developed trying to reconstruct the last 10,000 years of volcanic activity, soil formation and land use in the hinterland of Pompeii.

Spectral and stratigraphic mapping of hydrated minerals associated with interior layered deposits near the southern wall of Melas Chasma, Mars

NASA Astrophysics Data System (ADS)

Liu, Yang; Goudge, Timothy A.; Catalano, Jeffrey G.; Wang, Alian

2018-03-01

Orbital remote sensing data acquired from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter (MRO), in conjunction with other datasets, are used to perform detailed spectral and stratigraphic analyses over a portion of south Melas Chasma, Mars. The Discrete Ordinate Radiative Transfer (DISORT) model is used to retrieve atmospherically corrected single scattering albedos from CRISM I/F data for mineral identification. A sequence of interbedded poly- and monohydrated sulfates associated with interior layered deposits (ILDs) is identified and mapped. Analyses from laboratory experiments and spectral unmixing of CRISM hyperspectral data support the hypothesis of precipitation and dehydration of multiple inputs of complex Mg-Ca-Fe-SO4-Cl brines. In this scenario, the early precipitated Mg sulfates could dehydrate into monohydrated sulfate due to catalytic effects, and the later-precipitated Mg sulfates from the late-stage "clean" brine could terminate their dehydration at mid-degree of hydration to form a polyhydrated sulfate layer due to depletion of the catalytic species (e.g., Ca, Fe, and Cl). Distinct jarosite-bearing units are identified stratigraphically above the hydrated sulfate deposits. These are hypothesized to have formed either by oxidation of a fluid containing Fe(II) and SO4, or by leaching of soluble phases from precursor intermixed jarosite-Mg sulfate units that may have formed during the later stages of deposition of the hydrated sulfate sequence. Results from stratigraphic analysis of the ILDs show that the layers have a consistent northward dip towards the interior of the Melas Chasma basin, a mean dip angle of ∼6°, and neighboring strata that are approximately parallel. These strata are interpreted as initially sub-horizontal layers of a subaqueous, sedimentary evaporite deposits that underwent post-depositional tilting from slumping into the Melas Chasma basin. The interbedded hydrated sulfate units and jarosite-bearing units, which have distinct stratigraphic relationships, are indicative of a complex sedimentary and aqueous history in south Melas Chasma.

Lower Badenian coarse-grained Gilbert deltas in the southern margin of the Western Carpathian Foredeep basin

NASA Astrophysics Data System (ADS)

Nehyba, Slavomír

2018-02-01

Two coarse-grained Gilbert-type deltas in the Lower Badenian deposits along the southern margin of the Western Carpathian Foredeep (peripheral foreland basin) were newly interpreted. Facies characterizing a range of depositional processes are assigned to four facies associations — topset, foreset, bottomset and offshore marine pelagic deposits. The evidence of Gilbert deltas within open marine deposits reflects the formation of a basin with relatively steep margins connected with a relative sea level fall, erosion and incision. Formation, progradation and aggradation of the thick coarse-grained Gilbert delta piles generally indicate a dramatic increase of sediment supply from the hinterland, followed by both relatively continuous sediment delivery and an increase in accommodation space. Deltaic deposition is terminated by relatively rapid and extended drowning and is explained as a transgressive event. The lower Gilbert delta was significantly larger, more areally extended and reveals a more complicated stratigraphic architecture than the upper one. Its basal surface represents a sequence boundary and occurs around the Karpatian/Badenian stratigraphic limit. Two coeval deltaic branches were recognized in the lower delta with partly different stratigraphic arrangements. This different stratigraphic architecture is mostly explained by variations in the sediment delivery and /or predisposed paleotopography and paleobathymetry of the basin floor. The upper delta was recognized only in a restricted area. Its basal surface represents a sequence boundary probably reflecting a higher order cycle of a relative sea level rise and fall within the Lower Badenian. Evidence of two laterally and stratigraphically separated coarse-grained Gilbert deltas indicates two regional/basin wide transgressive/regressive cycles, but not necessarily of the same order. Provenance analysis reveals similar sources of both deltas. Several partial source areas were identified (Mesozoic carbonates of the Northern Calcareous Alps and the Western Carpathians, crystalline rocks of the eastern margin of the Bohemian Massif, older sedimentary infill of the Carpathian Foredeep and/or the North Alpine Foreland Basin, sedimentary rocks of the Western Carpathian/Alpine Flysch Zone).

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

USGS Publications Warehouse

Kingsbury Stewart, Esther; Mauk, Jeffrey L.

2017-01-01

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

Earliest accumulation history of the north polar layered deposits, Mars from SHARAD

NASA Astrophysics Data System (ADS)

Nerozzi, Stefano; Holt, John W.

2018-07-01

The approximately 2 km thick north polar layered deposits (NPLD) are often considered to contain the most complete and detailed stratigraphic records of recent climate of Mars. Exposures of the dense layering within troughs and scarps allowed detailed reconstructions of the latest accumulation history of these water ice deposits, but we lack knowledge of their initial emplacement. The Shallow Radar (SHARAD) onboard Mars Reconnaissance Orbiter (MRO) penetrates the NPLD to their base and detects their internal layering, overcoming the limitation of scarce and scattered visible outcrops of the lowermost sequences. In this study, we map reflectors in SHARAD data that result from discrete stratigraphic horizons in order to delineate the three-dimensional stratigraphy of the lowermost ∼500 m NPLD sequence and reconstruct their accumulation history. We confirm the large-scale lateral continuity and thickness uniformity of the deposits previously detected within the lowermost NPLD. However, stratigraphic complexity-in the form of pinch-outs and significant thickness variations-arises when we examine single radar units. We find evidence of an initially limited geographic stability of water ice within two deposits that are centered at the North Pole and present-day Gemina Lingula. A period of lateral ice sheet growth followed, interrupted only once by a retreat episode. Lower net accumulation is observed on pre-existing slopes, suggesting a reduction of water ice stability due to increased solar radiation incidence and/or transport by katabatic winds. Lateral transport of water ice by wind is also suggested by thickness undulations toward the top of the sequence, resembling cyclic steps. Water ice accumulation models based on orbital forcing predict a sequence of deposition and retreat events that is generally compatible with our reconstructed accumulation history. Therefore, we interpret the stratigraphic complexity that we observe as regional and, possibly global, climate change induced by orbital forcing. We also find that at least two units are completely buried within the NPLD and do not outcrop, and that NPLD deposition in some places was contemporaneous with deposition of the stratigraphically underlying cavi unit in other places. Both of these findings show that radar reflector mapping is a necessary complement to any stratigraphic reconstruction based on visible exposures.

Sequence stratigraphic principles applied to the Miocene Hawthorn Group, west-central Florida

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

Norton, V.L.; Randazzo, A.F.

1993-03-01

Sequence boundaries for the Miocene Hawthorn Group in the ROMP 20 drill core from Osprey, Sarasota County, FL were generally delineated by lithologic variations recognized from core slabs, thin section analysis, and geophysical logs. At least six depositional sequences representing third order sea level fluctuations were identified. Depositional environments were determined on the basis of the characteristic lithologic constituents including rip-up clasts, pellets, fossils, laminations, burrow, degree of induration, and grain sorting. The sequence boundaries appear to have formed when the rate of the eustatic fall exceeded basin subsidence rates producing a relative sea level fall at a depositional shorelinemore » break. As a result of the basinward facies shift associated with this sequence type, peritidal facies may directly overlie deeper water facies. Subaerial exposure and erosion can be expected. The sequence of facies representing progressively deeper water depositional environments, followed by a progressive shallowing, were present between bounding surfaces. Among the six sequences recognized, four were clearly delineated as representative of regression, subaerial exposure, and subsequent transgression. Two sequences were less clearly defined and probably represent transitional facies which had exposure surfaces developed. Comparison of the petrologically established sequence stratigraphy with published sea level curves resulted in a strong correlation between the number of sequences recognized and the number of coastal on-lap/off-lap cycles depicted for the early to middle Miocene. This correlation suggests that petrologic examination of core slabs, with supplemental thin section data, can provide useful information regarding the recognition of stratigraphic sequences and relative sea level fluctuations, particularly, in situations where seismic data may not be available.« less

Sequence stratigraphy of the Maastrichtian-Paleocene succession at the Dakhla Oasis, Western Desert, Egypt

NASA Astrophysics Data System (ADS)

Hewaidy, Abdel Galil A.; Farouk, Sherif; Bazeen, Youssef S.

2017-12-01

The Maastrichtian-Paleocene succession at the Dakhla Oasis is marked by the presence of a typical Nile Valley Facies represented by the Dakhla and Tarawan formations in Edmonstone and Qur El Malik sections in the central and western parts of the oasis, while a mixed Nile Valley and Garra Al-Arbain facies represented by Dakhla, Kurkur and Tarawan formations in Teneida section in the eastern part of the oasis adjacent to the Abu Tartur Plateau. These sections were examined for their foraminiferal contents, lithologic characters and stratigraphic boundaries. The distribution of foraminifera in the studied sections is variable and inconstant, as the planktonics are concentrated only at certain levels, which may be considered as a time intervals of transgression and maximum flooding surfaces. Eight planktonic biozones are distinguished in this work; of theses two are of Maastrichtain age and six are of Paleocene age. Eight 3rd order depositional sequences are recognized in the studied Maastrichtian-Paleocene succession based on the time stratigraphic boundaries released from the planktonic foraminifera and sea level changes which are released from the paleoecologic interpretations. The distinguished sequences are subdivided into their systems tracts based on the paleobathymetric interpretations of P/B% and benthic biofacies analysis. These sequences are bounded by eight sequence boundaries (SB A - SB H) represented by unconformity surfaces and depositional hiatuses. The correlation of the sequence boundaries of the established depositional sequences with the eustatic sea level curve, suggesting that these depositional sequences were resulted from the interplay of eustatic sea-level changes and local tectonic activities.

Stratigraphic framework and evolution of the Cretaceous continental sequences of the Bauru, Sanfranciscana, and Parecis basins, Brazil

NASA Astrophysics Data System (ADS)

Batezelli, Alessandro; Ladeira, Francisco Sergio Bernardes

2016-01-01

With the breakup of the supercontinent Gondwana, the South American Plate has undergone an intense process of tectonic restructuring that led to the genesis of the interior basins that encompassed continental sedimentary sequences. The Brazilian Bauru, Sanfranciscana and Parecis basins during Late Cretaceous have had their evolution linked to this process of structuring and therefore have very similar sedimentary characteristics. The purpose of this study is to establish a detailed understanding of alluvial sedimentary processes and architecture within a stratigraphic sequence framework using the concept of the stratigraphic base level or the ratio between the accommodation space and sediment supply. The integration of the stratigraphic and facies data contributed to defining the stratigraphic architecture of the Bauru, Sanfranciscana and Parecis Basins, supporting a model for continental sequences that depicts qualitative changes in the sedimentation rate (S) and accommodation space (A) that occurred during the Cretaceous. This study discusses the origin of the unconformity surfaces (K-0, K-1 and K-1A) that separate Sequences 1, 2A and 2B and the sedimentary characteristics of the Bauru, Sanfranciscana and Parecis Basins from the Aptian to the Maastrichtian, comparing the results with other Cretaceous Brazilian basins. The lower Cretaceous Sequence 1 (Caiuá and Areado groups) is interpreted as a low-accommodation systems tract compound by fluvial and aeolian systems. The upper Cretaceous lacustrine, braided river-dominated alluvial fan and aeolian systems display characteristics of the evolution from high-to low-accommodation systems tracts (Sequences 2A and 2B). Unconformity K-0 is related to the origin of the Bauru Basin itself in the Early Cretaceous. In Sanfranciscana and Parecis basins, the unconformity K-0 marks the contact between aeolian deposits from Lower Cretaceous and Upper Cretaceous alluvial systems (Sequences 1 and 2). Unconformity K-1, which was generated in the Late Cretaceous, is related to an increase of the A/S ratio, whereas Unconformity K-1A is the result of the decrease in the A/S ratio. Unconformity K-1A bound Sequence 2A (lacustrine and fluvial systems) and Sequence 2B (alluvial deposits) in Bauru Basin whereas in the Sanfranciscana and Parecis basins this unconformity marks the transition from alluvial system to aeolian system (Sequences 2A and 2B). Changes in depositional style in both basins correspond to two distinct tectonic moments occurring within the South American plate. The first associated with post-volcanic thermal subsidence of the Early Cretaceous (Serra Geral and Tapirapuã volcanismos), and the second moment associated with the uplift occurred in the Late Cretaceous (Alto Paranaíba, Vilhena and Serra Formosa Arcs).

Refined δ13C trend of the Dal'nyaya Taiga series of the Ura uplift (Vendian, southern part of Middle Siberia)

NASA Astrophysics Data System (ADS)

Rud'ko, S. V.; Petrov, P. Yu.; Kuznetsov, A. B.; Shatsillo, A. V.; Petrov, O. L.

2017-12-01

New data were obtained on δ13Ccarb and δ18O variations in the sequence of deposits of the Dal'nyaya Taiga series at the western and eastern flanks of the Ura anticline. The summary δ13C curve was plotted in view of the correlation of sequence-stratigraphic data of the basin analysis. A series of positive anomalies was found within the succession. Alternatives for global chemostratigraphic correlation of the Dal'nyaya Taiga series of the Ura uplift were considered.

Facies and log signatures of sequence boundaries in Sembakung area, Tarakan Basin, East Kalimantan, Indonesia

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

Bambang, P.; Hardjono, M.; Silalahi, L.

1996-08-01

Tarakan basin is one of the basins in East Kalimantan having a complicated geological condition. Tectonic repetition developed in this area constructed various stratigraphic traps. Sedimentary development in log data shows continuous regression in Meliat and Tabul Formations (Middle Meocene), Santul Formation (Late Miocene), Tarakan Formation (Pliocene) and Bunyu Formation (Pleistocene), Supported by seismic data, stratigraphic sequence in the basin is obvious, especially in Sembakung-Bangkudulis area. The sequence boundaries, mainly {open_quotes}lowstand{close_quotes} distribution as good prospective trap, can be mapped by applying tract systems and studying wavelet extract as seismic expression character of a reservoir. Subtle changes in pattern of stratigraphicmore » sequences can become a hint of sedimentary environment and its lithology content, supporting both exploration and exploitation planning.« less

Characteristics, stratigraphic architecture, and time framework of multi-order mixed siliciclastic and carbonate depositional sequences, outcropping Cisco Group (Late Pennsylvanian and Early Permian), Eastern Shelf, north-central Texas, USA

NASA Astrophysics Data System (ADS)

Yang, Wan; Kominz, Michelle A.

2003-01-01

The Cisco Group on the Eastern Shelf of the Midland Basin is composed of fluvial, deltaic, shelf, shelf-margin, and slope-to-basin carbonate and siliciclastic rocks. Sedimentologic and stratigraphic analyses of 181 meter-to-decimeter-scale depositional sequences exposed in the up-dip shelf indicated that the siliciclastic and carbonate parasequences in the transgressive systems tracts (TST) are thin and upward deepening, whereas those in highstand systems tracts (HST) are thick and upward shallowing. The sequences can be subdivided into five types on the basis of principal lithofacies, and exhibit variable magnitude of facies shift corresponding to variable extents of marine transgression and regression on the shelf. The sequence stacking patterns and their regional persistence suggest a three-level sequence hierarchy controlled by eustasy, whereas local and regional changes in lithology, thickness, and sequence type, magnitude, and absence were controlled by interplay of eustasy, differential shelf subsidence, depositional topography, and pattern of siliciclastic supply. The outcropping Cisco Group is highly incomplete with an estimated 6-11% stratigraphic completeness. The average duration of deposition of the major (third-order) sequences is estimated as 67-102 ka on the up-dip shelf and increases down dip, while the average duration of the major sequence boundaries (SB) is estimated as 831-1066 ka and decreases down dip. The nondepositional and erosional hiatus on the up-dip shelf was represented by lowstand deltaic systems in the basin and slope.

Integration Of Digital Methodologies (Field, Processing, and Presentation) In A Combined Sedimentology/Stratigraphy and Structure Course

NASA Astrophysics Data System (ADS)

Malinconico, L. L., Jr.; Sunderlin, D.; Liew, C. W.

2015-12-01

Over the course of the last three years we have designed, developed and refined two Apps for the iPad. GeoFieldBook and StratLogger allow for the real-time display of spatial (structural) and temporal (stratigraphic) field data as well as very easy in-field navigation. Field techniques and methods for data acquisition and mapping in the field have dramatically advanced and simplified how we collect and analyze data while in the field. The Apps are not geologic mapping programs, but rather a way of bypassing the analog field book step to acquire digital data directly that can then be used in various analysis programs (GIS, Google Earth, Stereonet, spreadsheet and drawing programs). We now complete all of our fieldwork digitally. GeoFieldBook can be used to collect structural and other field observations. Each record includes location/date/time information, orientation measurements, formation names, text observations and photos taken with the tablet camera. Records are customizable, so users can add fields of their own choosing. Data are displayed on an image base in real time with oriented structural symbols. The image base is also used for in-field navigation. In StratLogger, the user records bed thickness, lithofacies, biofacies, and contact data in preset and modifiable fields. Each bed/unit record may also be photographed and geo-referenced. As each record is collected, a column diagram of the stratigraphic sequence is built in real time, complete with lithology color, lithology texture, and fossil symbols. The recorded data from any measured stratigraphic sequence can be exported as both the live-drawn column image and as a .csv formatted file for use in spreadsheet or other applications. Common to both Apps is the ability to export the data (via .csv files), photographs and maps or stratigraphic columns (images). Since the data are digital they are easily imported into various processing programs (for example for stereoplot analysis). Requiring that all maps, stratigraphic columns and cross-sections be produced digitally continues our integration on the use of digital technologies throughout the curriculum. Initial evaluation suggests that students using the Apps more quickly progress towards synthesis and interpretation of the data as well as a deeper understanding of complex 4D field relationships.

Sequence stratigraphic applications to deep-water exploration in the Makassar Strait, offshore East Kalimantan, Indonesia

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

Malacek, S.J.; Reaves, C.M.; Atmadja, W.S.

1994-07-01

A sequence stratigraphic study was conducted to help evaluate the exploration potential of the Makassar PSC, offshore East Kalimantan, Indonesia. The PSC is on the present-day slope in water depths of 500-3000 ft and borders the large oil and gas fields of the Mahakam delta. The study provided important insights on reservoir distribution, trapping style, and seismic hydrocarbon indicators. Lowstand deposition on a slope modified by growth faulting and shale diapirism controlled reservoir distribution within the prospective late Miocene section. Three major lowstand intervals can be seismically defined and tied to deep-water sands in nearby wells where log character andmore » biostratigraphic data support the seismic system tract interpretation. The three intervals appear to correlate with third-order global lowstand events and are consistent with existing sequence stratigraphic schemes for the shelf and upper slope in the Makassar area. Seismic mapping delineated lowstand features, including incised valleys and intraslope to basin-floor thicks. Regional information on positions of middle-late Miocene delta lobes and shelf edges, helped complete the picture for sand sources, transport routes, and depocenters.« less

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

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

Philip, J.M.; Borgomano, J.R.; Al Maskiry, S.

1993-09-01

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 conceptualmore » 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.« less

Stratigraphic framework for Pliocene paleoclimate reconstruction: The correlation conundrum

USGS Publications Warehouse

Dowsett, H.J.; Robinson, M.M.

2006-01-01

Pre-Holocene paleoclimate reconstructions face a correlation conundrum because complications inherent in the stratigraphic record impede the development of synchronous reconstruction. The Pliocene Research, Interpretation and Synoptic Mapping (PRISM) paleoenvironmental reconstructions have carefully balanced temporal resolution and paleoclimate proxy data to achieve a useful and reliable product and are the most comprehensive pre-Pleistocene data sets available for analysis of warmer-than-present climate and for climate modeling experiments. This paper documents the stratigraphic framework for the mid-Pliocene sea surface temperature (SST) reconstruction of the North Atlantic and explores the relationship between stratigraphic/temporal resolution and various paleoceanographic estimates of SST. The magnetobiostratigraphic framework for the PRISM North Atlantic region is constructed from planktic foraminifer, calcareous nannofossil and paleomagnetic reversal events recorded in deep-sea cores and calibrated to age. Planktic foraminifer census data from multiple samples within the mid-Pliocene yield multiple SST estimates for each site. Extracting a single SST value at each site from multiple estimates, given the limitations of the material and stratigraphic resolution, is problematic but necessary for climate model experiments. The PRISM reconstruction, unprecedented in its integration of many different types of data at a focused stratigraphic interval, utilizes a time slab approach and is based on warm peak average temperatures. A greater understanding of the dynamics of the climate system and significant advances in models now mandate more precise, globally distributed yet temporally synchronous SST estimates than are available through averaging techniques. Regardless of the precision used to correlate between sequences within the midd-Pliocene, a truly synoptic reconstruction in the temporal sense is unlikely. SST estimates from multiple proxies promise to further refine paleoclimate reconstructions but must consider the complications associated with each method, what each proxy actually records, and how these different proxies compare in time-averaged samples.

The terminal Permian in European Russia: Vyaznikovian Horizon, Nedubrovo Member, and Permian-Triassic boundary

NASA Astrophysics Data System (ADS)

Lozovsky, V. R.; Balabanov, Yu. P.; Karasev, E. V.; Novikov, I. V.; Ponomarenko, A. G.; Yaroshenko, O. P.

2016-07-01

The comprehensive analysis of the data obtained on terrestrial vertebrata, ostracods, entomologic fauna, megaflora, and microflora in deposits of the Vyaznikovian Horizon and Nedubrovo Member, as well as the paleomagnetic data measured in enclosing rocks, confirms heterogeneity of these deposits. Accordingly, it is necessary to distinguish these two stratons in the terminal Permian of the East European Platform. The combined sequence of Triassic-Permian boundary deposits in the Moscow Syneclise, which is considered to be the most complete sequence in the East European Platform, is as follows (from bottom upward): Vyatkian deposits; Vyaznikovian Horizon, including Sokovka and Zhukovo members; Nedubrovo Member (Upper Permian); Astashikha and Ryabi members of the Vokhmian Horizon (Lower Triassic). None of the sequences of Permian-Triassic boundary deposits known in the area of study characterizes this sequence in full volume. In the north, the Triassic deposits are underlain by the Nedubrovo Member; in the south (the Klyazma River basin), the sections are underlain by the Vyaznikovian Horizon. The Permian-Triassic boundary adopted in the General Stratigraphic Scale of Russia for continental deposits of the East European platform (the lower boundary of the Astashikha Member) is more ancient than the one adopted in the International Stratigraphic Chart. The same geological situation is observed in the German Basin and other localities where Triassic continental deposits are developed. The ways of solving this problem are discussed in this article.

Facies analysis and sequence stratigraphy of neoproterozoic Platform deposits in Adrar of Mauritania, Taoudeni basin, West Africa

NASA Astrophysics Data System (ADS)

Benan, C. A. A.; Deynoux, M.

The Neoproterozoic and Palaeozoic Taoudeni basin forms the flat-lying and unmetamorphosed sedimentary cover of the West African Craton. In the western part of this basin, the Char Group and the lower part of the Atar Group make up a 400-m-thick Neoproterozoic siliciclastic succession which rests on the Palaeoproterozoic metamorphic and granitic basement. Five erosional bounding surfaces of regional extent have been identified in this succession. These surfaces separate five stratigraphic units with lithofacies associations ranging from fluvial to coastal and fluvial-, tide-, or wave-dominated shallow marine deposits. Owing to their regional extent and their position within the succession, the erosive bounding surfaces correspond to relative sea-level falls, and accordingly the five stratigraphic units they bound represent allocyclic transgressive-regressive depositional sequences (S1-S5). Changes in the nature of the deposits forming the transgressive-regressive cycles reflect landward or seaward shifts of the stacked sequences. These successive relative sea-level changes are related to the reactivation of basement faults and tilting during rifting of the Pan-Afro-Brasiliano supercontinent 1000 m.y. ago. The stromatolite bearing carbonate-shale sequences which form the rest of the Atar Group mark the onset of a quiet period of homogeneous subsidence contemporaneous with the Pan-African I oceanization 800-700 m.y. ago.

Sequence stratigraphy of the ANDRILL Southern McMurdo Sound (SMS) project drillcore, Antarctica: an expanded, near-field record of Antarctic Early to Middle Miocene climate and relative sea-level change

NASA Astrophysics Data System (ADS)

Fielding, C. R.; Browne, G. H.; Field, B.; Florindo, F.; Harwood, D. M.; Krissek, L. A.; Levy, R. H.; Panter, K.; Passchier, S.; Pekar, S. F.; SMS Science Team

2008-12-01

Present understanding of Antarctic climate change during the Early to Middle Miocene, including definition of major cycles of glacial expansion and contraction, relies in large part on stable isotope proxy records from Ocean Drilling Program cores. Here, we present a sequence stratigraphic analysis of the Southern McMurdo Sound drillcore (AND-2A), which was acquired during the Austral Spring of 2007. This core offers a hitherto unavailable ice-proximal stratigraphic archive of the Early to Middle Miocene from a high-accommodation Antarctic continental margin setting, and provides clear evidence of repeated fluctuations in climate, ice expansion/contraction and attendant sea-level change over the period 20-14 Ma, with a more fragmentary record of the post-14 Ma period. A succession of seventy sequences is recognized, each bounded by a significant facies dislocation (sequence boundary), composed internally of deposits of glacimarine to open shallow marine environments, and each typically dominated by the transgressive systems tract. From changes in facies abundances and sequence character, a series of long-term (m.y.) changes in climate and relative sea-level is identified. The lithostratigraphy can be correlated confidently to glacial events Mi1b and Mi2, to the Miocene Climatic Optimum, and to the global eustatic sea-level curve. SMS provides a detailed, direct, ice-proximal reference point from which to evaluate stable isotope proxy records for Neogene Antarctic paleoclimate.

Stratigraphic and structural evolution of the Selenga Delta Accommodation Zone, Lake Baikal Rift, Siberia

NASA Astrophysics Data System (ADS)

Scholz, C. A.; Hutchinson, D. R.

Seismic reflection profiles from the Lake Baikal Rift reveal extensive details about the sediment thickness, structural geometry and history of extensional deformation and syn-rift sedimentation in this classic continental rift. The Selenga River is the largest single source of terrigenous input into Lake Baikal, and its large delta sits astride the major accommodation zone between the Central and South basins of the lake. Incorporating one of the world's largest lacustrine deltas, this depositional system is a classic example of the influence of rift basin structural segmentation on a major continental drainage. More than 3700km of deep basin-scale multi-channel seismic reflection (MCS) data were acquired during the 1989 Russian and the 1992 Russian-American field programs. The seismic data image most of the sedimentary section, including pre-rift basement in several localities. The MCS data reveal that the broad bathymetric saddle between these two major half-graben basins is underlain by a complex of severely deformed basement blocks, and is not simply a consequence of long-term deltaic deposition. Maximum sediment thickness is estimated to be more than 9km in some areas around the Selenga Delta. Detailed stratigraphic analyses of the Selenga area MCS data suggest that modes of deposition have shifted markedly during the history of the delta. The present mode of gravity- and mass-flow sedimentation that dominates the northern and southern parts of the modern delta, as well as the pronounced bathymetric relief in the area, are relatively recent developments in the history of the Lake Baikal Rift. Several episodes of major delta progradation, each extending far across the modern rift, can be documented in the MCS data. The stratigraphic framework defined by these prograding deltaic sequences can be used to constrain the structural as well as depositional evolution of this part of the Baikal Rift. An age model has been established for this stratigraphy, by tying the delta sequences to the site of the Baikal Drilling Project 1993 Drill Hole. Although the drill hole is only 100m deep, and the base of the cores is only 670ka in age, ages were extrapolated to deeper stratigraphic intervals using the Reflection-Seismic-Radiocarbon method of Cohen et al. (1993). The deep prograding delta sequences now observed in the MCS data probably formed in response to major fluctuations in sediment supply, rather than in response to shifts in lake level. This stratigraphic framework and age model suggest that the deep delta packages developed at intervals of approximately 400ka and may have formed as a consequence of climate changes affiliated with the northern hemisphere glaciations. The stratigraphic analysis also suggests that the Selenga Basin and Syncline developed as a distinct depocentre only during the past 2-3Ma.

Social and environmental impact of volcaniclastic flows related to 472 AD eruption at Vesuvius from stratigraphic and geoarcheological data

NASA Astrophysics Data System (ADS)

Di Vito, Mauro A.; de Vita, Sandro; Rucco, Ilaria; Bini, Monica; Zanchetta, Giovanni; Aurino, Paola; Cesarano, Mario; Ebanista, Carlo; Rosi, Mauro; Ricciardi, Giovanni

2017-04-01

There is a growing number of evidences in the surrounding plain of Somma-Vesuvius volcano which indicate that along with primary volcanic processes (i.e. fallout, pyroclastic density currents) the syn-eruptive and post-eruptive volcaniclastic remobilization has severely impacted the ancient civilizations, which flourished in the area. This represents an important starting point for understanding the future hazard related to a potential (and not remote) renewal of volcanic activity of the Campaniana volcanoes. We present geoarcheological and stratigraphic data obtained from the analysis of more than 160 sections in the Campanian plain showing the widespread impact of volcaniclastic debris flows and floods originated from the rapid remobilization of the products of the AD 472 eruption of Somma-Vesuvius, both on the environment and on the human landscape. This eruption was one of the two sub-Plinian historical events of Somma Vesuvius. This event largely impacted the northern and eastern territory surrounding the volcano with deposition of a complex sequence of pyroclastic-fallout and -current deposits. These sequences were variably affected by syn- and post-eruptive mobilization both along the Somma-Vesuvius slopes and the Apennine valleys with the emplacement of thick mud- and debris-flows which strongly modified the preexisting paleogeography of the Plain with irretrievable damages to the agricultural and urban landscape. The multidisciplinary approach to the study of the sequences permitted to reconstruct the palaeoenvironment before the eruption and the timing of the emplacement of both pyroclastic and volcanoclastic deposits. The preexisting landscape was characterized by intense human occupation, although showing strong evidences of degradation and abandonment due to the progressive decline of the Roman Empire. The impact of volcaniclastic flows continued for decades after the eruption as highlighted in the studied sequences by stratigraphic and archaeologic data. In fact the volcanoclastic flows emplacement continued at least until the following AD 512 eruption of Somma-Vesuvius, and likely contributed to the final decline of the Roman civilization in the area.

Sea-level changes vs. organic productivity as controls on Early and Middle Devonian bioevents: Facies- and gamma-ray based sequence-stratigraphic correlation of the Prague Basin, Czech Republic

NASA Astrophysics Data System (ADS)

Bábek, Ondřej; Faměra, Martin; Šimíček, Daniel; Weinerová, Hedvika; Hladil, Jindřich; Kalvoda, Jiří

2018-01-01

The Devonian marine stratigraphic record is characterized by a number of bioevents - overturns in pelagic and benthic faunal assemblages, which are associated with distinct changes in lithology. The coincidence of lithologic and biotic changes can be explained by the causal link between biotic evolution, carbonate production and relative sea-level changes. To gain insight into the sea-level history of Early and Middle Devonian bioevents (the Lochkovian/Pragian Event, Basal Zlíchovian E., Daleje E., and Choteč E.) we carried out a sequence-stratigraphic analysis of carbonate-dominated successions in the Prague Basin (peri-Gondwana), a classic area of Devonian bioevents. The study is based on a basin-wide correlation of facies and field gamma-ray spectrometry (GRS) logs from 18 sections (Lochkovian to Eifelian), supported by element geochemistry and published biostratigraphic and carbon isotope data. Devonian carbonate deposition in the Prague Basin alternated between two end-member modes: an oligotrophic, homoclinal ramp (Praha and Daleje-Třebotov Formations) and a mesotrophic, distally steepened ramp (Lochkov, Zlíchov, and Choteč Formations). They show contrasting facies, particularly the absence/presence of gravity-flow deposits, allochem composition, U/Th ratios, and geochemical composition (productivity proxies such as P/Al, Si/Al, Zn/Al, TOC and stable carbon isotopes). The mesotrophic systems reflect an increased availability of nutrients on the shelf during the late Lochkovian, early Emsian (Zlíchovian), and Eifelian periods when sea surface temperature, pCO2, and silicate weathering rates were higher. The oligotrophic systems deposited during the Pragian-to-earliest Emsian and late Emsian (Dalejan) periods reflect reversed palaeoclimatic trends. We identified three depositional sequences (DS), DS1 (base of Pragian to early Emsian); DS2 (early Emsian to mid Emsian); and DS3 (mid Emsian to mid Eifelian). These sequences were integrated into a peri-Gondwana relative sea-level curve, which was then compared with the Euramerican sea-level curve of Johnson et al. (1985). The bioevents coincided with several sequence stratigraphic surfaces, representing variable limbs of the relative sea-level curve. On the other hand, their conspicuous coincidence with the switching intervals between the colder oligotrophic and warmer mesotrophic modes suggests that organic production linked to global climate was the primary control on biotic overturns, while sea-level fluctuations may have only amplified its effects.

Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change

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

Thompson, P.R.; Baum, G.R.

1991-03-01

Early Eocene to late Oligocene marine sedimentary units in southwestern Alabama were sampled at closely spaced intervals to derive a precise time-stratigraphic framework and to determine the paleoecological and mineralogical responses to fluctuations in sea level. Paleontologic control consisted of planktonic, smaller and larger benthonic foraminifera, calcareous nannofossils, dinoflagellates, and megafossils. Paleomagnetic reversals were delineated in two boreholes which, when supplemented by strontium isotope dates and the biostratigraphic control, provided a robust in situ chronostratigraphy for the Gulf Coast lower Tertiary. Paleoecologic trends in regression and transgression can be clearly correlated across major regional facies changes. Using the chronostratigraphy developedmore » here, the second-, third-, and fourth-orders of Vail's global sea-level cycles can be recognized and demonstrate the influence of sea-level change on sedimentation. Stratigraphic systems tracts (SSTs) and bounding surfaces in outcrop were determined by lithologic variations and paleoecologic trends, and additionally by gamma logs in the cores. The lower sequence boundary occurs at a contact where an older, relatively fine-grained, deep-water, fossiliferous unit was abruptly succeeded by a coarse-grained, shallow-water, poorly fossiliferous unit. The transgressive surface occurs at the base of a fining- and deepening-upwards unit that was commonly glauconitic and very fossiliferous. Transgression culminated with a pulse of planktonic microfossils in a bed having reduced clastic sedimentation; on the log the surface of maximum starvation was marked by a gamma spike.« less

Early evolution of the southern margin of the Neuquén Basin, Argentina: Tectono-stratigraphic implications for rift evolution and exploration of hydrocarbon plays

NASA Astrophysics Data System (ADS)

D'Elia, Leandro; Bilmes, Andrés; Franzese, Juan R.; Veiga, Gonzalo D.; Hernández, Mariano; Muravchik, Martín

2015-12-01

Long-lived rift basins are characterized by a complex structural and tectonic evolution. They present significant lateral and vertical stratigraphic variations that determine diverse basin-patterns at different timing, scale and location. These issues cause difficulties to establish facies models, correlations and stratal stacking patterns of the fault-related stratigraphy, specially when exploration of hydrocarbon plays proceeds on the subsurface of a basin. The present case study corresponds to the rift-successions of the Neuquén Basin. This basin formed in response to continental extension that took place at the western margin of Gondwana during the Late Triassic-Early Jurassic. A tectono-stratigraphic analysis of the initial successions of the southern part of the Neuquén Basin was carried out. Three syn-rift sequences were determined. These syn-rift sequences were located in different extensional depocentres during the rifting phases. The specific periods of rifting show distinctly different structural and stratigraphic styles: from non-volcanic to volcanic successions and/or from continental to marine sedimentation. The results were compared with surface and subsurface interpretations performed for other depocentres of the basin, devising an integrated rifting scheme for the whole basin. The more accepted tectono-stratigraphic scheme that assumes the deposits of the first marine transgression (Cuyo Cycle) as indicative of the onset of a post-rift phase is reconsidered. In the southern part of the basin, the marine deposits (lower Cuyo Cycle) were integrated into the syn-rift phase, implying the existence of different tectonic signatures for Cuyo Cycle along the basin. The rift climax becomes younger from north to south along the basin. The post-rift initiation followed the diachronic ending of the main syn-rift phase throughout the Neuquén Basin. Thus, initiation of the post-rift stage started in the north and proceeded towards the south, constituting a diachronous post-rift event. This arrangement implies that the lower part of Cuyo Cycle, traditionally related to regional thermal subsidence, may be deposited during either mechanical subsidence or thermal subsidence according to its position within the basin.

The 1997 core drilling through Ordovician and Silurian strata at Röstånga, S. Sweden: preliminary stratigraphic assessment and regional comparison

USGS Publications Warehouse

Bergstrom, Stig M.; Huff, W.D.; Koren', T.; Larsson, K.; Ahlberg, P.; Kolata, Dennis R.

1999-01-01

A core drilling at Ro??sta??nga, the first such drilling ever undertaken in this classical Lower Paleozoic outcrop area in W-central Scania, penetrated an approximately 96 m thick succession of Lower Silurian-upper Middle Ordovician marine rocks. The drilling was stopped at a depth of 132.59 m in an interval of crushed rocks, probably a prominent fault zone, that proved impossible to drill through. The core contains a stratigraphical sequence from the basal Upper Llandoverian (Telychian Stage) to the upper Middle Ordovician (Harjuan Stage). The following units are recognized in descending stratigraphic order (approximate thickness in parenthesis): Kallholn Formation (35 m), Lindega??rd Mudstone (27 m), Fja??cka Shale (13 m), Mossen Formation (0.75 m), Skagen Formation (2.5 m), and Sularp Shale (19 m+). Except for the Skagen Formation, the drilled sequence consists of shales and mudstones with occasional thin limestone interbeds and is similar to coeval successions elsewhere in Scania. There are 11 K-bentonite beds in the Kallholn Formation, 2(3?) in the Lindega??rd Mudstone, 1 in the Mossen Formation, 7 in the Skagen Formation, and 33 in the Sularp Shale. The core serves as an excellent Lower Silurian-upper Middle Ordovician reference standard not only for the Ro??sta??nga area but also for southernmost Sweden in general because the cored sequence is the stratigraphically most complete one known anywhere in this region.

Final Pleistocene and Holocene pollen stratigraphic sequence from the Cloquet River area, St. Louis Co. , NE Minnesota

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

Hill, C.L.; Rapp, G.R. Jr.; Huber, J.K.

A five-meter pollen sequence from a bog has been studied as part of a project concerned with the late-Quaternary paleoenvironmental setting and prehistory of northeastern Minnesota. The stratigraphic sequence is situated on an outwash plain derived from the Automba phase of glaciation (ca. 15,000 B.P.) and is located near a series of surface archaeological localities containing possible late Paleoindian lithic assemblages. Loss-on-ignition and particle size analyses reveal that the top section of the core, to a depth of about 350 cm, is composed predominantly of organics, the remaining 150 cm is dominated by mud. Radicarbon ages of 9270 +/- 190more » B.P. (UCR-1825) for the 350-355 cm interval, and 9420 +/- 180 (UCR-1826) for the 350-364 cm interval, were obtained. Data derived from pollen counts made at 20 cm intervals throughout the sequence indicate the core can be divided into several pollen-stratigraphic zones. The lowest zone, from the base of the core to about 440 cm, contains Cyperaceae (initially at about 60% total pollen) and is also characterized by Picea and Salix. (ca5%). Above this, there is a zone which ends at about 360 cm and contains a Betula peak (>65%). These two zones are considered to reflect the presence of tundra-like and dwarf-birch tundra vegetational regimes in the area during the late Pleistocene. Several pollen stratigraphic zones above 360 cm provide an indication of the Holocene vegetational setting, and show the increasing dominance of Pinus. The paleoenvironmental record obtained from this core, along with studies of the geologic setting, late Quaternary glacial sequence, and physiographic situation of archaeological localities, may help to elucidate the conditions prevalent during this time and provide a basis for a clearer understanding of the prehistoric ecology of northeastern Minnesota.« less

Sequence stratigraphy of upper Paleogene to Neogene carbonates exposed from Guánica bay to Guayanilla, Southern Puerto Rico.

NASA Astrophysics Data System (ADS)

Flores Hots, V. E.; Santos, H.

2016-12-01

Detailed stratigraphic columns were measured and microfacies analysis was performed in southwestern Puerto Rico to conduct a sequence stratigraphic analysis of Paleogene to Neogene strata. Two of the best exposed outcrops include the Guánica Bay and outcrops along Highway PR-132 in Guayanilla. Three depositional sequences, separated by two major sequence boundaries were found. The lower sequence occurs within the Juana Díaz Formation and is an open shelf to reef facies indicative of a Transgressive System Tract (TST), that is overlain by a High Stand System Tract (HST) marked by reef progradation. The HST in both Guánica Bay and Guayanilla is characterized by coral-rhodolith cyclicity however sections in Guánica Bay show pervasive recrystallization due to diagenetic alteration as a result of a long periods of exposure. This first sequence is Oligocene in age. The middle sequence, exposed at the eastern section of the Guánica Bay is also part of the Juana Díaz Formation and includes a turbiditic Lowstand System Tract (LST) of slope-like deposits flow, a TST constituted by coral rubble and skeletal grainstones belonging to a shallow island slope environment; and a HST that consists of an island slope chalk facies intercalated with turbidite grainstones derived storm events at the Guayanilla location. During the deposition of the middle sequence the Guánica Bay west section was topographically higher and exposed. The upper depositional sequence is Miocene in age and is composed of a TST with the transgression starting distally in the Guánica area and transgressing northward toward the Guayanilla area. These was correlated using high resolution 87Sr/86Sr isotope concentrations of shallow marine mollusks Kuphus incrassatus in the Ponce Formation at the Guánica Bay and Guayanilla locations. Facies patterns like the ones in the studied outcrops of southwestern Puerto Rico provide an exemplary environmental model of variability of paleodepositional relief, tectonic setting, variability in depositional setting of reef Sediment acumulations, the influence of storm events and variability in rock porosity by diagenetic processes yielding valuable models that may apply to potential Oligocene - Miocene hydrocarbon reservoirs.

The stratigraphic distribution of large marine vertebrates and shell beds in the Pliocene of Tuscany

NASA Astrophysics Data System (ADS)

Dominici, Stefano; Benvenuti, Marco; Danise, Silvia

2015-04-01

The record of 337 shark fossils, 142 cetaceans and 10 sea cows from the Pliocene of Tuscany, mostly from historical museum collections, is revised. The majority of these fossils are concentrated at a few geographic sites from separated hinterland basins, on the South-Western side of the Northern Apennines. To better understand the meaning of these concentrations, the sequence stratigraphic distribution of more recent findings of large marine vertebrates is reconstructed against a high-resolution framework based on sedimentary facies analysis. These remains are usually covered by, or included in mudstones deposited far from the coast (N=12), skeletons being usually articulated, slightly displaced, and often bioeroded. A minor part of better preserved articulated skeletons is associated with sandstones from deltaic paleonenvironments (N=2). Marine mammal and shark remains may be associated with laterally-continuous shell accumulations, a type of concentration occurring at maximum flooding surfaces, separating relatively coarse-grained facies from open marine mudstones. Shell beds were bulk-sampled at 66 locations from six basins, covering a wide range of sedimentary facies, and spanning a chronologic interval of about 2.5 million years. A dataset of 62,655 mollusc specimens belonging to 496 species formed the basis of a statistical study to reconstruct the structure of the benthic communities, and to estimate paleodepths from intertidal to upper bathyal settings. Mollusc associations closely mirror the distribution of sedimentary facies, allowing for a fine tuning of the sequence stratigraphic architecture. Merging paleogeographic, stratigraphic and paleoecologic data, we conclude that the more abundant and diverse accumulations of large vertebrates took place in settings under the influence of coastal upwelling. A modern analogue occurs today in the Ligurian Sea, on the Tuscan offshore, where abundant nutrients carried by deep-marine currents of Western origin, within an otherwise oligotrophic Mediterranean Sea, sustain a rich and diverse cetacean and shark, epipelagic and mesopelagic community. The modern steep bathymetric gradient was displaced towards the East during the Pliocene, before the latest phases of uplift of the Northern Apennines. An open marine, nutrient-rich ecosystem influenced hinterland basins during major transgressive pulses, leading to a higher productivity and the formation of laterally-continuos accumulations of biogenic hard parts. A comparison with the few available studies on the sequence-stratigraphic distribution of large marine vertebrates and shell beds suggests that a model integrating high-productivity and sea level rise, favouring bone bed and shell bed formation, can be applied at other settings, and other geologic intervals.

The Mohawkian Chronostratigraphic Problem: building a reliable timescale by combining biostratigraphy, chemostratigraphy, and tephrochronology

NASA Astrophysics Data System (ADS)

Sell, B. K.; Sadler, P.; Leslie, S.; Mitchell, C.; Samson, S. D.

2011-12-01

The abundant exposures of Mohawkian (late Sandbian to early Katian) sedimentary rocks in eastern North America have been well-studied for insights into the Taconic orogeny and potential petroleum sources. Considerable information has been published toward establishing the sequence stratigraphic architecture, biozones for conodonts, graptolites and chitinozoans, chemostratigraphic correlations and a tephrochronologic framework. And yet, correlation remains difficult. Problems arise from complex sedimentary facies changes across the Laurentian margin and associated provincalism of the faunas. The difficulties are exacerbated by some imprecise usage of bentonite names, the short time spans of key stratigraphic sections, and a paucity of sections with muliple kinds of information. Also, linking so many taxon range end, ash-fall, and stable isotope excursion events into a coherent stratigraphic sequence is a daunting numerical problem. It falls into the notorious "NP-Complete" category because the number of possible solutions grows so fast as the number of events increases. "Simulated annealing" is one of the algorithms developed for such problems. We adopt it to solve the stratigraphic sequencing problem as a constrained optimization (CONOP). Nevertheless, to realize the full potential, more bentonite charactization and dating is needed in sections with detailed range charts for fossil species. CONOP works best with the individual taxon ranges, not the derived biozone boundaries. We examine the potential resolving power of CONOP in the context of a re-evaluation of bentonite correlations and newly acquired CA-TIMS U-Pb zircon dates from sections with rich biostratigraphic data. In particular we use 206Pb/238U zircon dates from two bentonites in the Womble Shale at the Katian Global Stratotype Section and Point (452.8 ± 0.2 and 453.5 ± 0.3 Ma, weighted mean with 2σ internal error) to compare various correlations with other dated bentonites in eastern North America. Preliminary dates for five long-range (>1000 km) bentonite correlations made on the basis of single-crystal apatite trace-element analyses (Mg, Cl, Mn, Fe, Ce, Y) help resolve previous conflicts among various biostratgraphic data, but raise new questions about the interpretation of stratigraphic sequences and chemostratigraphic data.

The contexts and early Acheulean archaeology of the EF-HR paleo-landscape (Olduvai Gorge, Tanzania).

PubMed

de la Torre, Ignacio; Albert, Rosa M; Macphail, Richard; McHenry, Lindsay J; Pante, Michael C; Rodríguez-Cintas, Ágata; Stanistreet, Ian G; Stollhofen, Harald

2017-08-03

Renewed fieldwork at the early Acheulean site of EF-HR (Olduvai Gorge, Tanzania) has included detailed stratigraphic studies of the sequence, extended excavations in the main site, and has placed eleven additional trenches within an area of nearly 1 km 2 , to sample the same stratigraphic interval as in the main trench across the broader paleo-landscape. Our new stratigraphic work suggests that EF-HR is positioned higher in the Bed II sequence than previously proposed, which has implications for the age of the site and its stratigraphic correlation to other Olduvai Middle Bed II sites. Geological research shows that the main EF-HR site was situated at the deepest part of an incised valley formed through river erosion. Archaeological excavations at the main site and nearby trenches have unearthed a large new assemblage, with more than 3000 fossils and artefacts, including a hundred handaxes in stratigraphic position. In addition, our test-trenching approach has detected conspicuous differences in the density of artefacts across the landscape, with a large cluster of archaeological material in and around the main trench, and less intense human activity at the same level in the more distant satellite trenches. All of these aspects are discussed in this paper in the light of site formation processes, behavioral contexts, and their implications for our understanding of the early Acheulean at Olduvai Gorge. Copyright © 2017 Elsevier Ltd. All rights reserved.

Stratigraphic controls on saltwater intrusion in the Dominguez Gap area of coastal Los Angeles

USGS Publications Warehouse

Edwards, Brian D.; Ehman, Kenneth D.; Ponti, Daniel J.; Reichard, Eric G.; Tinsley, John; Rosenbauer, Robert J.; Land, Michael T.

2009-01-01

The Los Angeles Basin is a densely populated coastal area that significantly depends on groundwater. A part of this groundwater supply is at risk from saltwater intrusion-the impetus for this study. High-resolution seismic-reflection data collected from the Los Angeles-Long Beach Harbor Complex have been combined with borehole geophysical and descriptive geological data from four nearby ??400-m-deep continuously cored wells and with borehole geophysical data from adjacent water and oil wells to characterize the Pliocene to Holocene stratigraphy of the Dominguez Gap coastal aquifer system. The new data are shown as a north-south, two- dimensional, sequence-stratigraphic model that is compared to existing lithostratigraphic models of the Los Angeles Basin in an attempt to better understand pathways of saltwater intrusion into coastal aquifers. Intrusion of saltwater into the coastal aquifer system generally is attributed to over-pumping that caused the hydraulic gradient to reverse during the mid-1920s. Local water managers have used the existing lithostratigraphic model to site closely spaced injection wells of freshwater (barrier projects) attempting to hydraulically control the saltwater intrusion. Improved understanding of the stratigraphic relationships can guide modifications to barrier design that will allow more efficient operation. Allostratigraphic nomenclature is used to define a new sequence-stratigraphic model for the area because the existing lithostratigraphic correlations that have been used to define aquifer systems are shown not to be time-correlative. The youngest sequence, the Holocene Dominguez sequence, contains the Gaspur aquifer at its base. The Gaspur aquifer is intruded with saltwater and consists of essentially flat-lying gravelly sands deposited by the ancestral Los Angeles River as broad channels that occupied a paleovalley incised into the coastal plain during the last glacio-eustatic highstand. The underlying sequences are deformed into a broad anticlinal fold that occurs parallel to, but ??2 km north of, the axis of the Pliocene Wilmington anticline. The Dominguez sequence breaches the crest of the young anticline, cuts through the upper Pleistocene Mesa and Pacific sequences, and into the middle Pleistocene Harbor sequence. Saltwater migrates along channels within the Dominguez sequence and into the underlying sequences (composed mostly of shallow marine and tidal sands, silts, and clays) that contain the classically defined Gage and Lynwood aquifers. The newly recognized Pacific Coast Highway fault cuts through the core of this young fold and is downthrown on the northern side, thereby creating accommodation space for a thick succession of middle Pleistocene sediments that constitute the Upper Wilmington sequence. North of the Pacific Coast Highway fault, the Upper Wilmington sequence contains the classic Silverado aquifer (composed of fluviodeltaic deposits); the Silverado is the primary freshwater aquifer for the West Coast and Central Los Angeles Groundwater Basins. Pore fluid and electric log analyses show the upper part of this aquifer to be saline-intruded near the crest of the young fold. This relationship implies that some saltwater is migrating into deeper aquifers from above, across the regional unconformity that marks the base of the Harbor sequence (ca. 240-270 ka). This sequence-stratigraphic model provides new insight into the potential flow paths for saltwater intrusion, and as such, should allow improved characterization of fluidflow that will aid in transport model studies and in managing groundwater resources. ?? 2009 Geological Society of America.

Palynostratigraphy of the Erkovtsy field of brown coal (the Zeya-Bureya sedimentary basin)

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

Kezina, T.V.; Litvinenko, N.D.

2007-08-15

The Erkovtsy brown coal field in the northwestern Zeya-Bureya sedimentary basin (129-130{sup o}E, 46-47{sup o}N) is structurally confined to southern flank of the Mesozoic-Cenozoic Belogor'e depression. The verified stratigraphic scheme of the coalfield sedimentary sequence is substantiated by palynological data on core samples from 18 boreholes sampled in the course of detailed prospecting and by paleobotanical analysis of sections in the Yuzhnyi sector of the coalfield (data of 1998 by M.A. Akhmetiev and S.P. Manchester). Sections of the Erkovtsy, Arkhara-Boguchan, and Raichikha brown-coal mines are correlated. Stratigraphic subdivisions distinguished in the studied sedimentary succession are the middle and upper Tsagayanmore » subformations (the latter incorporating the Kivda Beds), Raichikha, Mukhino, Buzuli, and Sazanka formations.« less

Spectral analysis of time series of categorical variables in earth sciences

NASA Astrophysics Data System (ADS)

Pardo-Igúzquiza, Eulogio; Rodríguez-Tovar, Francisco J.; Dorador, Javier

2016-10-01

Time series of categorical variables often appear in Earth Science disciplines and there is considerable interest in studying their cyclic behavior. This is true, for example, when the type of facies, petrofabric features, ichnofabrics, fossil assemblages or mineral compositions are measured continuously over a core or throughout a stratigraphic succession. Here we deal with the problem of applying spectral analysis to such sequences. A full indicator approach is proposed to complement the spectral envelope often used in other disciplines. Additionally, a stand-alone computer program is provided for calculating the spectral envelope, in this case implementing the permutation test to assess the statistical significance of the spectral peaks. We studied simulated sequences as well as real data in order to illustrate the methodology.

Tyler sandstones (Pennsylvanian), Dickinson area, North Dakota: a 24-million barrel soil-zone stratigraphic trap

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

Land, C.B.

Approximately 24 million bbl of recoverable oil has been found in stratigraphic traps in the lower Pennsylvanian Tyler formation at the Dickinson, South Heart, and E. Green River Fields, Stark County, North Dakota. Production is from a multiple sequence of quartzose sandstones 5 to 18 ft (1.5 to 5 m) thick deposited as barrier islands along regressive shorelines. A typical vertical sequence is given. Throughout much of the subject area, porosity and permeability in the sandstones have been greatly reduced or completely destroyed by development of caliche paleosols. In the western part, the caliche consists of gray to brown limestonemore » nodules or nodular layers of limestone in the sandstones and contains abundant pyrite. It is estimated that the caliche destroys as much as 50% of the potential reservoir rock in the area and is an essential factor in the stratigraphic entrapment of the petroleum accumulations by providing an eastern (updip) barrier to migration.« less

High-resolution sequence stratigraphy of lower Paleozoic sheet sandstones in central North America: The role of special conditions of cratonic interiors in development of stratal architecture

USGS Publications Warehouse

Runkel, Anthony C.; Miller, J.F.; McKay, R.M.; Palmer, A.R.; Taylor, John F.

2007-01-01

Well-known difficulties in applying sequence stratigraphic concepts to deposits that accumulated across slowly subsiding cratonic interior regions have limited our ability to interpret the history of continental-scale tectonism, oceanographic dynamics of epeiric seas, and eustasy. We used a multi-disciplinary approach to construct a high-resolution stratigraphic framework for lower Paleozoic strata in the cratonic interior of North America. Within this framework, these strata proved readily amenable to modern sequence stratigraphic techniques that were formulated based on successions along passive margins and in foreland basins, settings markedly different from the cratonic interior. Parasequences, parasequence stacking patterns, systems tracts, maximum flooding intervals, and sequence-bounding unconformities can be confidently recognized in the cratonic interior using mostly standard criteria for identification. The similarity of cratonic interior and foreland basin successions in size, geometry, constituent facies, and local stacking patterns of nearshore parasequences is especially striking. This similarity indicates that the fundamental processes that establish shoreface morphology and determine the stratal expression of retreat and progradation were likewise generally the same, despite marked differences in tectonism, physiography, and bathymetry between the two settings. Our results do not support the widespread perception that Paleozoic cratonic interior successions are so anomalous in stratal geometries, and constitute such a poor record of time, that they are poorly suited for modern sequence stratigraphic analyses. The particular arrangement of stratal elements in the cratonic interior succession we studied is no more anomalous or enigmatic than the variability in architecture that sets all sedimentary successions apart from one another. Thus, Paleozoic strata of the cratonic interior are most appropriately considered as a package that belongs in a continuum of variable stratigraphic packages reflecting variable controls such as subsidence and shelf physiography. Special conditions of exceptionally slow subsidence rate, shallow bathymetry, and nearly flat regional shelf gradient are manifest mostly by the presence of individual systems tracts of relatively long duration that extend for much greater distances across depositional strike than those that characterize successions deposited in more dynamic tectonic and physiographic settings. These results suggest that if other cratonic interior successions are as anomalous as reported, a low sediment supply may have played a primary role in development of their apparently condensed stratal architecture. The results also lead us to suggest that a nonvegetated lower Paleozoic landscape played a relatively insignificant role in the development of what are commonly perceived to be enigmatic stratigraphic features of sheet sandstones, particularly their widespread yet thin geometry, and a scarcity of shale and siltstone. ?? 2007 Geological Society of America.

Sequence stratigraphy and sedimentary study on Mishrif formation of Fauqi Oilfield of Missan in south east Iraq

NASA Astrophysics Data System (ADS)

Sang, Hua; Lin, Changsong; Jiang, Yiming

2017-05-01

The reservoir of Mishrif formation has a large scale distribution of marine facies carbonate sediments in great thickness in central and south east Iraq. Rudist reef and shoal facies limestones of the Mishrif Formation (Late Cenomanian - Middle Turonian) form a great potential reservoir rocks at oilfields and structures of Iraq. Facies modelling was applied to predict the relationship between facies distribution and reservoir characteristics to construct a predictive geologic model which will assist future exploration and development in south east Iraq. Microfacies analysis and electrofacies identification and correlations indicate that the limestone of the Mishrif Formation were mainly deposited in open platform setting. Sequence stratigraphic analyses of the Mishrif Formation indicate 3 third order depositional sequences.

Sequence stratigraphy in the middle Ordovician shale successions, mid-east Korea: Stratigraphic variations and preservation potential of organic matter within a sequence stratigraphic framework

NASA Astrophysics Data System (ADS)

Byun, Uk Hwan; Lee, Hyun Suk; Kwon, Yi Kyun

2018-02-01

The Jigunsan Formation is the middle Ordovician shale-dominated transgressive succession in the Taebaeksan Basin, located in the eastern margin of the North China platform. The total organic carbon (TOC) content and some geochemical properties of the succession exhibit a stratigraphically distinct distribution pattern. The pattern was closely associated with the redox conditions related to decomposition, bulk sedimentation rate (dilution), and productivity. To explain the distinct distribution pattern, this study attempted to construct a high-resolution sequence stratigraphic framework for the Jigunsan Formation. The shale-dominated Jigunsan Formation comprises a lower layer of dark gray shale, deposited during transgression, and an upper layer of greenish gray siltstone, deposited during highstand and falling stage systems tracts. The concept of a back-stepped carbonate platform is adopted to distinguish early and late transgressive systems tracts (early and late TST) in this study, whereas the highstand systems tracts and falling stage systems tracts can be divided by changes in stacking patterns from aggradation to progradation. The late TST would be initiated on a rapidly back-stepping surface of sediments and, just above the surface, exhibits a high peak in TOC content, followed by a gradually upward decrease. This trend of TOC distribution in the late TST continues to the maximum flooding surface (MFS). The perplexing TOC distribution pattern within the late TST most likely resulted from both a gradual reduction in productivity during the late TST and a gradual increase in dilution effect near the MFS interval. The reduced production of organic matter primarily incurred decreasing TOC content toward the MFS when the productivity was mainly governed by benthic biota because planktonic organisms were not widespread in the Ordovician. Results of this study will help improve the understanding of the source rock distribution in mixed carbonate-siliciclastic successions within a stratigraphic framework, particularly for unconventional shale reservoirs.

Stratigraphic and structural evolution of the Selenga Delta Accommodation Zone, Lake Baikal Rift, Siberia

USGS Publications Warehouse

Scholz, C.A.; Hutchinson, D.R.

2000-01-01

Seismic reflection profiles from the Lake Baikal Rift reveal extensive details about the sediment thickness, structural geometry and history of extensional deformation and syn-rift sedimentation in this classic continental rift. The Selenga River is the largest single source of terrigenous input into Lake Baikal, and its large delta sits astride the major accommodation zone between the Central and South basins of the lake. Incorporating one of the world's largest lacustrine deltas, this depositional system is a classic example of the influence of rift basin structural segmentation on a major continental drainage. More than 3700 km of deep basin-scale multi-channel seismic reflection (MCS) data were acquired during the 1989 Russian and the 1992 Russian–American field programs. The seismic data image most of the sedimentary section, including pre-rift basement in several localities. The MCS data reveal that the broad bathymetric saddle between these two major half-graben basins is underlain by a complex of severely deformed basement blocks, and is not simply a consequence of long-term deltaic deposition. Maximum sediment thickness is estimated to be more than 9 km in some areas around the Selenga Delta. Detailed stratigraphic analyses of the Selenga area MCS data suggest that modes of deposition have shifted markedly during the history of the delta. The present mode of gravity- and mass-flow sedimentation that dominates the northern and southern parts of the modern delta, as well as the pronounced bathymetric relief in the area, are relatively recent developments in the history of the Lake Baikal Rift. Several episodes of major delta progradation, each extending far across the modern rift, can be documented in the MCS data. The stratigraphic framework defined by these prograding deltaic sequences can be used to constrain the structural as well as depositional evolution of this part of the Baikal Rift. An age model has been established for this stratigraphy, by tying the delta sequences to the site of the Baikal Drilling Project 1993 Drill Hole. Although the drill hole is only 100 m deep, and the base of the cores is only ∼670 ka in age, ages were extrapolated to deeper stratigraphic intervals using the Reflection-Seismic-Radiocarbon method of Cohen et al. (1993). The deep prograding delta sequences now observed in the MCS data probably formed in response to major fluctuations in sediment supply, rather than in response to shifts in lake level. This stratigraphic framework and age model suggest that the deep delta packages developed at intervals of approximately 400 ka and may have formed as a consequence of climate changes affiliated with the northern hemisphere glaciations. The stratigraphic analysis also suggests that the Selenga Basin and Syncline developed as a distinct depocentre only during the past ∼2–3 Ma.

Upside-down sequence stratigraphy, sandy highstands, and muddy prograding complexes in the Surma Basin, Bangladesh

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

Radovich, B.J.; Hoffman, M.W.; Perlmutter, M.A.

1995-12-31

Several large, TCF-size gas fields have been discovered in the Surma Basin, Bangladesh. Detailed sequence stratigraphy was performed on log and seismic data to study these fields and future potential of the area. The prospective section is Upper Miocene sands caught up in a series of younger compressional fault-related folds caused by the Indian Plate colliding with S.E. Asia in the late Tertiary. World-class gas/water contacts are observed on the seismic data over the fields. Sequence stratigraphic techniques reveal an ordered, predictable stratigraphic architecture of sandy highstands and transgressions, and muddy aggraded prograding complexes with deep incisions at each sequencemore » boundary. This serves as a framework to understand the hydrocarbon accumulations in the area. Cyclostratigraphy is used to understand the unusual lithology distributions in the basin.« less

Sedimentary sequence evolution in a Foredeep basin: Eastern Venezuela

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

Bejarano, C.; Funes, D.; Sarzalho, S.

1996-08-01

Well log-seismic sequence stratigraphy analysis in the Eastern Venezuela Foreland Basin leads to study of the evolution of sedimentary sequences onto the Cretaceous-Paleocene passive margin. This basin comprises two different foredeep sub-basins: The Guarico subbasin to the west, older, and the Maturin sub-basin to the east, younger. A foredeep switching between these two sub-basins is observed at 12.5 m.y. Seismic interpretation and well log sections across the study area show sedimentary sequences with transgressive sands and coastal onlaps to the east-southeast for the Guarico sub-basin, as well as truncations below the switching sequence (12.5 m.y.), and the Maturin sub-basin showsmore » apparent coastal onlaps to the west-northwest, as well as a marine onlap (deeper water) in the west, where it starts to establish. Sequence stratigraphy analysis of these sequences with well logs allowed the study of the evolution of stratigraphic section from Paleocene to middle Miocene (68.0-12.0 m.y.). On the basis of well log patterns, the sequences were divided in regressive-transgressive-regressive sedimentary cycles caused by changes in relative sea level. Facies distributions were analyzed and the sequences were divided into simple sequences or sub- sequences of a greater frequencies than third order depositional sequences.« less

Sequence stratigraphy of the Triassic in the Barentsz Sea

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

Skjold, L.JU.; Van Veen, P.M.; Gjelberg, J.

1990-05-01

A regional study of the Triassic in the Barentsz Sea (20-32{degree}E, 71-74{degree}N) revealed sequences that correlate seismically for hundreds of kilometers. Recent offshore drilling results enabled them to establish a biostratigraphic time framework. Comparisons with information from onshore outcrops (such as the Svalbard Archipelago) aided the piecing together of these superregional sequences. Seismic character analysis identified three units with composite progradational patterns (Induan, Olenekian, and Anisian). Fluvial, deltaic, and marine deposits can be distinguished and located relative to the paleocoastlines. Corresponding downlap surfaces suggest the development of condensed intervals, predicted to consist of organic-rich source rocks, as was later confirmedmore » by drilling. Regional predictions based on this sequence-stratigraphic approach have proved valuable when correlating and evaluating well information. The sequences identified also help define third-order sea level curves for the area; these improve published curves thought to have global significance.« less

Field-scale forward modelling of a shallow marine carbonate ramp: the Upper Jurassic Arab Formation (onshore Abu Dhabi - UAE)

NASA Astrophysics Data System (ADS)

Marchionda, Elisabetta; Deschamps, Rémy; Nader, Fadi H.; Ceriani, Andrea; Di Giulio, Andrea; Lawrence, David; Morad, Daniel J.

2017-04-01

The stratigraphic record of a carbonate system is the result of the interplay of several local and global factors that control the physical and the biological responses within a basin. Conceptual models cannot be detailed enough to take into account all the processes that control the deposition of sediments. The evaluation of the key controlling parameters on the sedimentation can be investigated with the use of stratigraphic forward models, that permit dynamic and quantitative simulations of the sedimentary basin infill. This work focuses on an onshore Abu Dhabi field (UAE) and it aims to provide a complete picture of the stratigraphic evolution of Upper Jurassic Arab Formation (Fm.). In this study, we started with the definition of the field-scale conceptual depositional model of the Formation, resulting from facies and well log analysis based on five wells. The Arab Fm. could be defined as a shallow marine carbonate ramp, that ranges from outer ramp deposits to supratidal/evaporitic facies association (from bottom to top). With the reconstruction of the sequence stratigraphic pattern and several paleofacies maps, it was possible to suggest multiple directions of progradations at local scale. Then, a 3D forward modelling tool has been used to i) identify and quantify the controlling parameters on geometries and facies distribution of the Arab Fm.; ii) predict the stratigraphic architecture of the Arab Fm.; and iii) integrate and validate the conceptual model. Numerous constraints were set during the different simulations and sensitivity analyses were performed testing the carbonate production, eustatic oscillations and transport parameters. To verify the geological consistency the 3D forward modelling has been calibrated with the available control points (five wells) in terms of thickness and facies distribution.

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

NASA Astrophysics Data System (ADS)

Cawood, Adam J.; Bond, Clare E.

2018-01-01

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

Depositional environments, sequence stratigraphy, and trap configuration of lower Wolfcampian clastics along eastern edge of Midland basin, west Texas

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

Stewart, N.R.; Reuter, S.G.

1989-03-01

The Lower Permian (lower Wolfcampian) along the eastern edge of the Midland basin, west Texas, is characterized by ramp-type shelf margins. During eustatic lowstand, nearshore sedimentation shifted drastically to the west into a basinal setting below the Pennsylvanian (Canyon) shelf margin. Core descriptions demonstrate that lowstand systems tract (LST) and transgressive systems tract (TST) siliciclastics were deposited in deltaic and coastal-plain environments. Prodelta, delta-front, and stream-mouth bar facies are associated with the LST. Coastal-plain and distributary channels are preserved in the TST. The sequence stratigraphic framework indicates type 1 sequence boundaries at 287 Ma, 282 Ma, and 280 Ma inmore » the lower Wolfcampian clastics. This lower Wolfcampian package of sedimentary rocks overlies the Pennsylvanian and is capped by the 279-Ma middle Wolfcampian unconformity. All three sequence boundaries and associated systems tract deposits exhibit a prograding stacking pattern within the sequence stratigraphic framework. Basinally restricted prograding LST deltaic rocks are overlain by backstepping TST deltaics and highstand systems tract (HST) outer marine shales. Production in lower Wolfcampian clastic fields is associated with fine-grained quartzarenites up to 45 ft thick which were deposited in stream-mouth bars. Delta-front and prodelta low-permeability shales encase the reservoir facies, forming lateral permeability barriers. HST outer marine shales deposited over the stream-mouth-bar sandstones act as a top seal, creating a stratigraphic trap and providing source for the high-BTU gas and oil produced from these basinally restricted LST deltaics.« less

Integration of borehole and seismic data to unravel complex stratigraphy: Case studies from the Mannville Group, Western Canada

NASA Astrophysics Data System (ADS)

Sarzalejo Silva, Sabrina Ester

Understanding the stratigraphic architecture of geologically complex reservoirs, such as the heavy oil deposits of Western Canada, is essential to achieve an efficient hydrocarbon recovery. Borehole and 3-D seismic data were integrated to define the stratigraphic architecture and generate 3-dimensional geological models of the Mannville Group in Saskatchewan. The Mannville is a stratigraphically complex unit formed of fluvial to marine deposits. Two areas in west-central and southern Saskatchewan were examined in this study. In west-central Saskatchewan, the area corresponds to a stratigraphically controlled heavy oil reservoir with production from the undifferentiated Dina-Cummings Members of the Lower Cretaceous Mannville Group. The southern area, although non-prospective for hydrocarbons, shares many similarities with time-equivalent strata in areas of heavy oil production. Seismic sequence stratigraphic principles together with log signatures permitted the subdivision of the Mannville into different packages. An initial geological model was generated integrating seismic and well-log data Multiattribute analysis and neural networks were used to generate a pseudo-lithology or gamma-ray volume. The incorporation of borehole core data to the model and the subsequent integration with the lithological prediction were crucial to capture the distribution of reservoir and non-reservoir deposits in the study area. The ability to visualize the 3-D seismic data in a variety of ways, including arbitrary lines and stratal or horizon slicing techniques helped the definition of stratigraphic features such as channels and scroll bars that affect fluid flow in hydrocarbon producing areas. Small-scale heterogeneities in the reservoir were not resolved due to the resolution of the seismic data. Although not undertaken in this study, the resulting stratigraphic framework could be used to help construct a static reservoir model. Because of the small size of the 3-D seismic surveys, horizontal slices through the data volume generally imaged only small portions of the paleogeomorphologic features thought to be present in this area. As such, it was only through the integration of datasets that the geological models were established.

Sedimentary facies analysis of the Mesozoic clastic rocks in Southern Peru (Tacna, 18°S): Towards a paleoenvironmental Redefinition and stratigraphic Reorganization

NASA Astrophysics Data System (ADS)

Alván, Aldo; Jacay, Javier; Caracciolo, Luca; Sánchez, Elvis; Trinidad, Inés

2018-07-01

The Mesozoic rocks of southern Peru comprise a Middle Jurassic to Early Cretaceous sedimentary sequence deposited during a time interval of approximately 34 Myr. In Tacna, these rocks are detrital and constitute the Yura Group (Callovian to Tithonian) and the Hualhuani Formation (Berriasian). Basing on robust interpretation of facies and petrographic analysis, we reconstruct the depositional settings of such units and provide a refined stratigraphic framework. Accordingly, nine types of sedimentary facies and six architectural elements are defined. They preserve the record of a progradational fluvial system, in which two styless regulated the dispersion of sediments: (i) a high-to moderate-sinuosity meandering setting (Yura Group), and a later (ii) incipient braided setting (Hualhuani Formation). The Yura Group (Callovian-Tithonian) represents the onset of floodplain deposits and lateral accretion of point-bar deposits sited on a semi-flat topography. Nonetheless, the progradational sequence was affected by at least two rapid marine ingressions occurred during Middle Callovian and Tithonian times. Such marine ingressions reveal the proximity of a shallow marine setting and incipient carbonate deposition. In response to increase in topographic gradient, the Hualhuani Formation (Berriasian) deposited as extensive multistory sandy channels. The mineralogy of the Mesozoic sediments suggests sediment supplies and intense recycling from a craton interior (i.e. Amazon Craton and/or plutonic sources) located eastward of the study area.

Extended period of K/T boundary mass extinction in the marine realm

NASA Technical Reports Server (NTRS)

Keller, G.

1988-01-01

The Cretaceous/Tertiary (K/T) boundary mass extinction has been widely recognized as a nearly instantaneous catastrophy among marine plankton such as foraminifera. However, the suddenness of this extinction event may have been overemphasized because most pelagic K/T boundary sequences are stratigraphically incomplete and generally lack the earliest Tertiary (Zones P0 and P1a) either due to carbonate dissolution and/or non-deposition. Stratigraphically complete sections appear to be restricted to continental shelf regions with high sedimentation rates and deposition well above the CCD. Such sections have been recovered from El Kef, Tunisia (1) and Brazos River, Texas. Quantitative foraminiferal analysis of these sections indicate an extinction pattern beginning below the K/T boundary and ending above the boundary. These data imply that the mass extinction event was not geologically instantaneous, but occurred over an extended period of time. Evidence supporting this conclusion is discussed.

Historical palaeohydrology and landscape resilience of a Mediterranean rambla (Castellón, NE Spain): Floods and people

NASA Astrophysics Data System (ADS)

Machado, M. J.; Medialdea, A.; Calle, M.; Rico, M. T.; Sánchez-Moya, Y.; Sopeña, A.; Benito, G.

2017-09-01

This paper provides a new methodological approach to analyse secular patterns of flooding (magnitude and frequency) from sedimentary evidence (palaeofloods), taking into account changes in channel geometry, and their links to historical environmental changes and the inherent social and demographic evolution within the catchment. A case study analysis was focused in Rambla de la Viuda (drainage area of 1500 km2) whose stream flow is related to extreme rainfalls. A 500 years sedimentary archive was reconstructed from eight stratigraphic profiles comprising continuous sequences of slackwater flood deposits interbedded with episodic colluvial and edaphic horizons. Discharge estimates associated to sedimentary flood evidences were obtained from one-dimensional hydraulic modelling. The stratigraphic units were sampled to characterise their geochemical and paleobotanical (phytoliths) contents. Palaeoflood chronology was obtained from radiocarbon and luminescence (OSL) dating, supported by documentary data (written historical documents). A high frequency and high magnitude palaeoflood period took place during the 15th-middle 16th century, which seem to correlate in time with general wetter conditions. Three short-term environment stability conditions (land use and climatic) also made possible the development of three paleosols. The lowest flood magnitude and discharges in the sedimentary record was found between the mid-17th to mid-18th centuries, under prevailing drier environmental conditions. Episodic high magnitude flooding took place at late 18th century, correlating in time with palaeovegetation and geochemical evidences of important changes on land use (deforestation and grazing). Poorer developed soils were found at upper stratigraphic sequences (19th century) characterised by thick units of colluvium deposits, usually culminating sequences of short-lived continuous slackwater flood units. Despite of the potential human influence (land-use) on soil hydrology, the long-term behaviour of high magnitude floods (>1000 m3 s-1) has been stationary over the last 500 years.

Identifying coseismic subsidence in tidal-wetland stratigraphic sequences at the Cascadia subduction zone of western North America

USGS Publications Warehouse

Nelson, Alan R.; Shennan, Ian; Long, Antony J.

1996-01-01

Tidal-wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the Cascadia subduction zone. However, determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic, hydrographic, and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins. Tidal-wetland stratigraphy at many Cascadia estuaries differs little from that at similar sites on passive-margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes. Methods developed through study of similar stratigraphic sequences in Europe provide a framework for investigating the Cascadia estuarine record. Five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes: the suddenness and amount of submergence, the lateral extent of submerged tidal-wetland soils, the coincidence of submergence with tsunami deposits, and the degree of synchroneity of submergence events at widely spaced sites. Evaluation of such criteria at the Cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes. Evidence for a coseismic origin remains equivocal, however, for the many peat-mud contacts in Cascadia stratigraphic sequences that lack (1) contrasts in lithology or fossils indicative of more than half a meter of submergence, (2) well-studied tsunami deposits, or (3) precise ages needed for regional correlation. Paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat-mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts. Reconstruction of a history of great earthquakes for the Cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations.

Sequence stratigraphic interpretation of parts of Anambra Basin, Nigeria using geophysical well logs and biostratigraphic data

NASA Astrophysics Data System (ADS)

Anakwuba, E. K.; Ajaegwu, N. E.; Ejeke, C. F.; Onyekwelu, C. U.; Chinwuko, A. I.

2018-03-01

The Anambra basin constitutes the southeastern lower portion of the Benue Trough, which is a large structural depression that is divided into lower, middle and upper parts; and is one of the least studied inland sedimentary basins in Nigeria. Sequence stratigraphic interpretation had been carried out in parts of the Anambra Basin using data from three wells (Alo-1 Igbariam-1 and Ajire-1). Geophysical well logs and biostratigraphic data were integrated in order to identify key bounding surfaces, subdivide the sediment packages, correlate sand continuity and interpret the environment of deposition in the fields. Biostratigraphic interpretation, using foraminifera and plankton population and diversity, reveals five maximum flooding surfaces (MFS) in the fields. Five sequence boundaries (SB) were also identified using the well log analysis. Four 3rd order genetic sequences bounded by maximum flooding surfaces (MFS-1 to MFS-6) were identified in the areas; four complete sequences and one incomplete sequence were identified in both Alo-1 and Igbariam-1 wells while Ajire-1 has an no complete sequence. The identified system tracts delineated comprises Lowstand Systems Tracts (progradational to aggradational to retrogradational packages), Transgressive Systems Tracts (retrogradational packages) and Highstand Systems Tracts (aggradational to progradational packages) in each well. The sand continuity across the fields reveal sands S1 to S5 where S1 is present in Ajire-1 well and Igbariam-1 well but not in Alo-1 well. The sands S4 to S5 run across the three fields at different depths. The formations penetrated by the wells starting from the base are; Nkporo Formation (Campanian), Mamu Formation (Late Campanian to Early Maastrichtian), Ajali Sandstone (Maastrichtian), Nsukka Formation (Late Maastrichtian to Early Palaeocene), Imo Formation (Palaeocene) and Nanka Sand (Eocene). The environments of deposition revealed are from coastal to bathyal. The sands of lowstand system tract and highstand system tract found in Ajali, Nsukka, Nkporo and Imo (Ebenebe Sandstone) Formations show good continuity and as such good reservoir qualities while the shales of the transgressive system tracts which includes the Imo Formation, Mamu, and Nkporo Formations where most of the maximum flooding surfaces were delineated, can serve as seals to the numerous reservoir units. Combinations of the reservoir sands of the lowstand system tract and highstand system tract and the shale units of the transgressive system tract can form good stratigraphic traps for hydrocarbon and hence should be hydrocarbon exploration targets.

Assessing site formation and assemblage integrity through stone tool refitting at Gruta da Oliveira (Almonda karst system, Torres Novas, Portugal): A Middle Paleolithic case study

PubMed Central

Zilhão, João

2018-01-01

We use stone tool refitting to assess palimpsest formation and stratigraphic integrity in the basal units of the Gruta da Oliveira archeo-stratigraphic sequence, layers 15–27, which TL and U-series dating places in late Marine Isotope Stage (MIS) 5 or early MIS 4. As in most karst contexts, the formation of this succession involved multiple and complex phenomena, including subsidence, bioturbation, carnivore activity and runoff as agents of potential post-depositional disturbance. During phases of stabilization, such as represented by layers 15, 21 and 22, the excavated area was inhabited and refits corroborate that post-depositional displacement is negligible. Layers 23–25 and 16–19 correspond to subdivisions that slice thick geological units primarily formed of material derived from the cave’s entrance via slope dynamics. Refit links are consistent with rapid fill-up of the interstitial spaces found in the Karren-like bedrock (for layers 23–25), or left between large boulders after major roof-collapse events (for layers 16–19). Layers 26 (the “Mousterian Cone”) and 27 are a “bottom-of-hourglass” deposit underlying the main sedimentary body; the refits show that this deposit consists of material derived from layers 15–25 that gravitated through fissures open in the sedimentary column above. Layer 20, at the interface between two major stratigraphic ensembles, requires additional analysis. Throughout, we found significant vertical dispersion along the contact between sedimentary fill and cave wall. Given these findings, a preliminary analysis of technological change across the studied sequence organized the lithic assemblages into five ensembles: layer 15; layers 16–19; layer 20; layers 21–22; layers 23–25. The lower ensembles show higher percentages of flint and of the Levallois method. Uniquely at the site, the two upper ensembles feature bifaces and cleavers. PMID:29451892

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Spatial greenstone-gneiss relationships: Evidence from mafic-ultramafic xenolith distribution patterns

NASA Technical Reports Server (NTRS)

Glikson, A. Y.

1986-01-01

The distribution patterns of mafic-ultramafic xenoliths within Archaean orthogneiss terrain furnish an essential key for the elucidation of granite-greenstone relations. Most greenstone belts constitute mega-xenoliths rather than primary basin structures. Transition along strike and across strike between stratigraphically low greenstone sequences and xenolith chains demonstrate their contemporaneity. These terrains represent least deformed cratonic islands within an otherwise penetratively foliated deformed gneiss-greenstone crust. Whereas early greenstone sequences are invariably intruded by tonalitic/trondhjemitic/granodioritic gneisses, stratigraphically higher successions may locally overlap older gneiss terrains and their entrained xenoliths unconformably. The contiguity of xenolith patterns suggests their derivation as relics of regional mafic-ultramafic volcanic crustal units and places limits on horizontal movements between individual crustal blocks.

Implemented Lomb-Scargle periodogram: a valuable tool for improving cyclostratigraphic research on unevenly sampled deep-sea stratigraphic sequences

NASA Astrophysics Data System (ADS)

Pardo-Iguzquiza, Eulogio; Rodríguez-Tovar, Francisco J.

2011-12-01

One important handicap when working with stratigraphic sequences is the discontinuous character of the sedimentary record, especially relevant in cyclostratigraphic analysis. Uneven palaeoclimatic/palaeoceanographic time series are common, their cyclostratigraphic analysis being comparatively difficult because most spectral methodologies are appropriate only when working with even sampling. As a means to solve this problem, a program for calculating the smoothed Lomb-Scargle periodogram and cross-periodogram, which additionally evaluates the statistical confidence of the estimated power spectrum through a Monte Carlo procedure (the permutation test), has been developed. The spectral analysis of a short uneven time series calls for assessment of the statistical significance of the spectral peaks, since a periodogram can always be calculated but the main challenge resides in identifying true spectral features. To demonstrate the effectiveness of this program, two case studies are presented: the one deals with synthetic data and the other with paleoceanographic/palaeoclimatic proxies. On a simulated time series of 500 data, two uneven time series (with 100 and 25 data) were generated by selecting data at random. Comparative analysis between the power spectra from the simulated series and from the two uneven time series demonstrates the usefulness of the smoothed Lomb-Scargle periodogram for uneven sequences, making it possible to distinguish between statistically significant and spurious spectral peaks. Fragmentary time series of Cd/Ca ratios and δ18O from core AII107-131 of SPECMAP were analysed as a real case study. The efficiency of the direct and cross Lomb-Scargle periodogram in recognizing Milankovitch and sub-Milankovitch signals related to palaeoclimatic/palaeoceanographic changes is demonstrated. As implemented, the Lomb-Scargle periodogram may be applied to any palaeoclimatic/palaeoceanographic proxies, including those usually recovered from contourites, and it holds special interest in the context of centennial- to millennial-scale climatic changes affecting contouritic currents.

Best Practices for Environmental Site Management: A Practical Guide for Applying Environmental Sequence Stratigraphy to Improve Conceptual Site Models

EPA Science Inventory

Presented here is a practical guide on the application of the geologic principles of sequence stratigraphy and facies models to the characterization of stratigraphic heterogeneity at hazardous waste sites. This technology is applicable to sites underlain by clastic aquifers (int...

Stenian Estuarine System and Early Neoproterozoic Microbial Records of Capiru Formation, Southern Ribeira Belt.

NASA Astrophysics Data System (ADS)

Cury, L. F.; Santos, L. D. R.; Leandro, R.; Lange, L.; Bahniuk Rumbelsperger, A.

2017-12-01

The Capiru formation is a low-grade metasedimentary sequence composed by slates, rhythmic phyllites, quartzites and marbles, disposed and disrupted in tectonic blocks delimited by thrust and strike-slip faults related to oblique collisions in the southern Ribeira Belt, Curitiba terrane, southern Brazil. The rocks of the Capiru formation crops out as a thrust-folded belt, delimited on the north by the transcurrent faults of Lancinha Shear Zone (LSZ), and to the south by thrust faults with large isograde variation. Three lithological sequences are recognized mainly by their compositional and stratigraphic records, including a (i) ferruginous sequence with quartzites, metasandstones and metaconglomerates with goethite/hematite cements and phyllites with magnetite; ii) metadolomites with stromatolites, interbeded with pelitic layers and iii) a metapelitic sequence with metarhythmites and metasandstones with well preserved organic-rich material. The records of two tectonic-metamorphic events related to thrust and transpressive tectonics are heterogeneously developed in all sequences, still been recognized sections with the original stratigraphic succession. The stratigraphic record suggests an estuarine environment with rising sea level developing tidal flats and tidal channels. U-Pb detrital zircon analyses characterizes Rhyacian ages (between 2.2-2.1 Ga) as the main sources, and Stenian ages (between 1.08-1.20 Ga) as maximum age for sedimentation. The metapelites mineral assemblage is composed by quartz, muscovite, sericite, illite, kaolinite, sepiolite, magnetite, goethite, hematite and carbonaceous material with bulk organic carbon content (BOC) ranging from 0.09 to 1.21 (%), a precambrian microbial activity record. The metadolomites are characterized by the presence of stromatolites in different types and dimensions, with microbial activity records supported by SEM-EDS (up to 91% C), with EPS-like morphologies within microporosity, NaCl compounds and clay minerals, probably indicative of microorganism contribution during the deposition.

Sequence-Stratigraphic Analysis of the Regional Observation Monitoring Program (ROMP) 29A Test Corehole and Its Relation to Carbonate Porosity and Regional Transmissivity in the Floridan Aquifer System, Highlands County, Florida

USGS Publications Warehouse

Ward, W. C.; Cunningham, K.J.; Renken, R.A.; Wacker, M.A.; Carlson, J.I.

2003-01-01

An analysis was made to describe and interpret the lithology of a part of the Upper Floridan aquifer penetrated by the Regional Observation Monitoring Program (ROMP) 29A test corehole in Highlands County, Florida. This information was integrated into a one-dimensional hydrostratigraphic model that delineates candidate flow zones and confining units in the context of sequence stratigraphy. Results from this test corehole will serve as a starting point to build a robust three-dimensional sequence-stratigraphic framework of the Floridan aquifer system. The ROMP 29A test corehole penetrated the Avon Park Formation, Ocala Limestone, Suwannee Limestone, and Hawthorn Group of middle Eocene to Pliocene age. The part of the Avon Park Formation penetrated in the ROMP 29A test corehole contains two composite depositional sequences. A transgressive systems tract and a highstand systems tract were interpreted for the upper composite sequence; however, only a highstand systems tract was interpreted for the lower composite sequence of the deeper Avon Park stratigraphic section. The composite depositional sequences are composed of at least five high-frequency depositional sequences. These sequences contain high-frequency cycle sets that are an amalgamation of vertically stacked high-frequency cycles. Three types of high-frequency cycles have been identified in the Avon Park Formation: peritidal, shallow subtidal, and deeper subtidal high-frequency cycles. The vertical distribution of carbonate-rock diffuse flow zones within the Avon Park Formation is heterogeneous. Porous vuggy intervals are less than 10 feet, and most are much thinner. The volumetric arrangement of the diffuse flow zones shows that most occur in the highstand systems tract of the lower composite sequence of the Avon Park Formation as compared to the upper composite sequence, which contains both a backstepping transgressive systems tract and a prograding highstand systems tract. Although the porous and permeable layers are not thick, some intervals may exhibit lateral continuity because of their deposition on a broad low-relief ramp. A thick interval of thin vuggy zones and open faults forms thin conduit flow zones mixed with relatively thicker carbonate-rock diffuse flow zones between a depth of 1,070 and 1,244 feet below land surface (bottom of the test corehole). This interval is the most transmissive part of the Avon Park Formation penetrated in the ROMP 29A test corehole and is included in the highstand systems tract of the lower composite sequence. The Ocala Limestone is considered to be a semiconfining unit and contains three depositional sequences penetrated by the ROMP 29A test corehole. Deposited within deeper subtidal depositional cycles, no zones of enhanced porosity and permeability are expected in the Ocala Limestone. A thin erosional remnant of the shallow marine Suwannee Limestone overlies the Ocala Limestone, and permeability seems to be comparatively low because moldic porosity is poorly connected. Rocks that comprise the lower Hawthorn Group, Suwannee Limestone, and Ocala Limestone form a permeable upper zone of the Upper Floridan aquifer, and rocks of the lower Ocala Limestone and Avon Park Formation form a permeable lower zone of the Upper Floridan aquifer. On the basis of a preliminary analysis of transmissivity estimates for wells located north of Lake Okeechobee, spatial relations among groups of relatively high and low transmissivity values within the upper zone are evident. Upper zone transmissivity is generally less than 10,000 feet squared per day in areas located south of a line that extends through Charlotte, Sarasota, DeSoto, Highlands, Polk, Osceola, Okeechobee, and St. Lucie Counties. Transmissivity patterns within the lower zone of the Avon Park Formation cannot be regionally assessed because insufficient data over a wide areal extent have not been compiled.

A not-so-big crisis: re-reading Silurian conodont diversity in a sequence-stratigraphic framework

NASA Astrophysics Data System (ADS)

Jarochowska, Emilia; Munnecke, Axel

2016-04-01

Conodonts are extensively used in Ordovician through Triassic biostratigraphy and fossil-based geochemistry. However, their distribution in rock successions is commonly taken at face value, without taking into account their diverse and poorly understood ecology. Multielement taxonomy, ontogenetic and environmental variability, difficulties in extraction, and relative rarity all contribute to the general lack of quantitative studies on conodont stratigraphic distribution and temporal turnover. With respect to Silurian conodonts, the concept of recurrent conodont extinction events - the so called Ireviken, Mulde and Lau events - has become a standard in the stratigraphic literature. The concept has been proposed based on qualitative observations of local extirpations of open-marine pelagic or nekto-benthic taxa and temporary dominance of shallow-water species in the Silurian succession of the Swedish island of Gotland. These changes coincided with positive carbon isotope excursions, abrupt facies shifts, "blooms" of benthic fauna, and changes in reef communities, which have all been combined into a general view of Silurian bio-geochemical events. This view posits a deterministic, reproducible pattern in Silurian conodont diversity, attributed to recurrent ecological or geochemical conditions. The growing body of sequence-stratigraphic interpretations across these events in Gotland and other sections worldwide indicate that in all cases the Silurian "events" are associated with rapid global regressions. This suggests that faunal changes such as the dominance of shallow-water, low-diversity conodont fauna and the increase of benthic invertebrate diversity and abundance represent predictable consequences of the variation in the completeness of the rock record and preservation potential of different environments. Our studies in Poland and Ukraine indicate that the magnitude of change in the taxonomic composition of conodont assemblages across the middle Silurian global regression and the hypothesized Mulde Event is proportional to the associated facies shift. Quantitative data on facies distribution of individual conodont species combined with sequence stratigraphic architecture provides a testable model for the impact of sea-level changes on perceived conodont diversity in a section or basin. This approach highlights the need for quantitative data on conodont distribution in their environmental context, their integration into conodont-based stratigraphy and geochemistry, and for the regular use of Occam's razor to interpretations of paleobiodiversity.

40Ar/39Ar dating of a Langhian biotite-rich clay layer in the pelagic sequence of the Cònero Riviera, Ancona, Italy

NASA Astrophysics Data System (ADS)

Mader, Dieter; Montanari, Alessandro; Gattacceca, Jérôme; Koeberl, Christian; Handler, Robert; Coccioni, Rodolfo

2001-12-01

A nearly complete and undisturbed Miocene carbonate sequence is present in the easternmost part of the Umbria-Marche basin, Italy, which is ideal for detailed and integrated stratigraphic investigations of the Miocene Epoch. In this study, we were trying to obtain evidence for the presence or absence of distal ejecta from the 15 Ma Ries impact structure in southern Germany, located about 600 km to the north-northwest of the Umbria-Marche basin. The first step is to find coeval strata in the Umbria-Marche sequence. At the La Vedova section, Cònero Riviera, we dated a volcaniclastic biotite-rich clay layer, the Aldo Level, which is situated within planktonic foraminiferal Zone N8, at 14.9±0.2 Ma, using the 40Ar/39Ar method. Together with detailed geologic and stratigraphic information about the Aldo Level, the resulting age can be used confidentially to calibrate the Langhian stage. Besides providing new constraints on Miocene geochronology, this age can now be used for impact stratigraphic studies. To directly correlate the biotite ages of the La Vedova section with rocks from the Ries impact event, Ries impact glass was also analyzed and found to be coeval. Although unrelated to this impact event, the biotite-rich clay layer should help in the search for evidence of distal ejecta related to the Ries crater.

Geologic evolution and sequence stratigraphy of the offshore Pelotas Basin, southeast Brazil

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

Abreu, V.S.

1996-01-01

The Brazilian marginal basins have been studied since the beginning of the 70s. At least nine large basins are distributed along the entire Eastern continental margin. The sedimentary infill of these basins consists of lower Cretaceous (continental/lacustrine) rift section underlying marine upper Cretaceous (carbonate platforms) and marine upper Cretaceous/Tertiary sections, corresponding to the drift phase. The sedimentary deposits are a direct result of the Jurassic to lower Cretaceous break-up of the Pangea. This study will focus on the geologic evolution and sequence stratigraphic analysis of the Pelotas basin (offshore), located in the Southeast portion of the Brazilian continental margin betweenmore » 28[degrees] and 34[degrees] S, covering approximately 50,000 Km[sup 2]. During the early Cretaceous, when the break-up of the continent began in the south, thick basaltic layers were deposited in the Pelotas basin. These basalts form a thick and broad wedge of dipping seaward reflections interpreted as a transitional crust. During Albian to Turonian times, due to thermal subsidence, an extensive clastic/carbonate platform was developed, in an early drift stage. The sedimentation from the upper Cretaceous to Tertiary was characterized by a predominance of siliciclastics in the southeast margin, marking an accentuate deepening of the basin, showing several cycles related to eustatic fluctuations. Studies have addressed the problems of hydrocarbon exploration in deep water setting within a sequence stratigraphic framework. Thus Pelotas basin can provide a useful analogue for exploration efforts worldwide in offshore passive margins.« less

Geologic evolution and sequence stratigraphy of the offshore Pelotas Basin, southeast Brazil

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

Abreu, V.S.

1996-12-31

The Brazilian marginal basins have been studied since the beginning of the 70s. At least nine large basins are distributed along the entire Eastern continental margin. The sedimentary infill of these basins consists of lower Cretaceous (continental/lacustrine) rift section underlying marine upper Cretaceous (carbonate platforms) and marine upper Cretaceous/Tertiary sections, corresponding to the drift phase. The sedimentary deposits are a direct result of the Jurassic to lower Cretaceous break-up of the Pangea. This study will focus on the geologic evolution and sequence stratigraphic analysis of the Pelotas basin (offshore), located in the Southeast portion of the Brazilian continental margin betweenmore » 28{degrees} and 34{degrees} S, covering approximately 50,000 Km{sup 2}. During the early Cretaceous, when the break-up of the continent began in the south, thick basaltic layers were deposited in the Pelotas basin. These basalts form a thick and broad wedge of dipping seaward reflections interpreted as a transitional crust. During Albian to Turonian times, due to thermal subsidence, an extensive clastic/carbonate platform was developed, in an early drift stage. The sedimentation from the upper Cretaceous to Tertiary was characterized by a predominance of siliciclastics in the southeast margin, marking an accentuate deepening of the basin, showing several cycles related to eustatic fluctuations. Studies have addressed the problems of hydrocarbon exploration in deep water setting within a sequence stratigraphic framework. Thus Pelotas basin can provide a useful analogue for exploration efforts worldwide in offshore passive margins.« less

A coherent high-precision radiocarbon chronology for the Late-glacial sequence at Sluggan Bog, Co. Antrim, Northern Ireland

NASA Astrophysics Data System (ADS)

Lowe, J. J.; Walker, M. J. C.; Scott, E. M.; Harkness, D. D.; Bryant, C. L.; Davies, S. M.

2004-02-01

Seventy-five radiocarbon dates are presented from Sluggan Bog in Co. Antrim, Northern Ireland. The Holocene peats are underlain by Late-glacial sediments, which also appear to have accumulated largely in a mire environment. The radiocarbon dates, from the Late-glacial and early Holocene part of the profile, were obtained from the humic and humin fractions of the sedimentary matrix, and from plant macrofossils. The last-named were dated by AMS and the sediment samples by radiometric (beta counting) methods. Age-depth models for the three dating series show a very high level of agreement between the two fractions and the macrofossils. No statistically significant difference is found between the beta counting and AMS results. Three tephras were located in the profile, the uppermost of which is in a stratigraphical position suggestive of the Vedde Ash, but the geochemical and radiocarbon evidence do not support this interpretation. The lower ashes are in the correct stratigraphical position for the Laacher See and Borrobol tephras, attributions substantiated by the radiocarbon evidence, but not by the geochemical data. The Sluggan sequence has generated one of the most internally consistent radiocarbon chronologies for any Late-glacial site in the British Isles, and it is suggested that in future more effort should be devoted to the search for, and analysis of, Late-glacial mire sequences, rather than the limnic records that have formed the principal focus of Late-glacial investigations hitherto. Copyright

Criteria for the recognition and correlation of sandstone units in the Precambrian and Paleozoic-Mesozoic clastic sequence in the near east

NASA Astrophysics Data System (ADS)

Weissbrod, T.; Perath, I.

A systematic study of the Precambrian and Paleozoic-Mesozoic clastic sequences (Nubian Sandstone) in Israel and Sinai, and a comparative analysis of its stratigraphy in neighbouring countries, has shown that besides the conventional criteria of subdivision (lithology, field appearance, photogeological features, fossil content), additional criteria can be applied, which singly or in mutual conjuction enable the recognition of widespread units and boundaries. These criteria show lateral constancy, and recurrence of a similar vertical sequence over great distances, and are therefore acceptable for the identification of synchronous, region-wide sedimentary units (and consequently, major unconformities). They also enable, once the units are established, to identify detached (not in situ) samples, samples from isolated or discontinous outcrops, borehole material or archive material. The following rock properties were tested and found to be usefuls in stratigraphic interpretation, throughout large distribution areas of the clastic sequence: Landscape, which is basically the response of a particular textural-chemic al aggregate to atmospheric weathering. Characteristic outcrop feature — styles of roundness or massivity, fissuring or fliatin, slope profile, bedding — express a basic uniformity of these platform-type clastics. Colors are often stratigraphically constant over hundreds of kilometers, through various climates and topographies, and express some intrinsic unity of the rock bodies. Grain size and sorting, when cross-plotted, enable to differentiate existing unit. The method requires the analysis of representative numbers of samples. Vertical trends of median grain size and sorting show reversals, typically across unconformities. Feldstar content diminishes from 15-50% in Precambrian-Paleozoic rocks to a mere 5% or less in Mesozoic sandstones — a distinctive regionwide time trend. Dominance of certain feldstar types characterizes Precambrian and Paleozoic units. Clay minerals, though subordinate, characterize certain units. Illite is usually the dominant clay mineral in the Precambrain-Paleozoic sediments, showing different degress of crystallization in different units. Kaolinite is the main, often the only clay mineral in Mesozoic units. Heavy minerals, whose species spectra reflect on parent rock and provenance terrain and whose differential response to degradation points to the sedimentary history of the deposit, show certain vertical regularities, such as the abrupt disappearance of species or whole assemblages at certain levels, indicating unconformities. Trace metals, which in places reach ore concentrations (e.g. copper), are often extensive, though of well-defined vertical distribution. They express adsorptive capacity of specific widespread lithologies, enabling the discrimination of units. Even though each of these criteria is not always by itself diagnostic, they may in conjuction with one or more other criteria amount to a petrographic fingerprint that enables fairly accurate identification of the age interval of the unit, and its relation both to the regional and the local stratigraphic sequence.

Palaeoredox conditions and sequence stratigraphy of the Cretaceous storm-dominated, mixed siliciclastic-carbonate ramp in the Eastern Cordillera Basin (Colombia): Evidence from sedimentary geochemical proxies and facies analysis

NASA Astrophysics Data System (ADS)

Rivera, Huber A.; Le Roux, Jacobus P.; Sánchez, L. Katherine; Mariño-Martínez, Jorge E.; Salazar, Christian; Barragán, J. Carolina

2018-10-01

The Cretaceous black shales of Colombia are among the most important successions in the north of South America and have attracted the attention of many geoscientists and exploration companies over the last few decades, because of their high hydrocarbon potential and the presence of emerald deposits. However, many uncertainties still remain with regard to their tectonic setting, sequence stratigraphy, depositional environments, palaeoxygenation conditions, and organic matter preservation. In order to develop a more integrated picture of these different processes and conditions, we conducted a detailed sedimentological, inorganic geochemical (U, V, Ni, Zn, Mn, Fe, Ti, Mo, Cu, Cr, Cd, Ba) and sequence stratigraphic analysis of the Cretaceous black shales in the Magdalena-Tablazo Sub-Basin (Eastern Cordillera Basin) of Colombia. Eleven lithofacies and five lithofacies associations of a storm-dominated, siliciclastic-carbonate ramp were identified, which range from basin to shallow inner ramp environments. These facies were grouped into six third-order stratigraphic sequences showing high-order cycles of marine transgression with constrained regressive pulses during the late Valanginian to early Coniacian. The black shales succession represents deposition under anoxic bottom water with some intervals representing dysoxic-suboxic conditions. The evolution of the sedimentary environments and their palaeoxygenation history reflect tectonic and eustatic sea-level controls that 1) produced a variable orientation and position of the coastline throughout the Cretaceous; 2) conditioned the low-gradient ramp geometry (<0.3°) and 3) modified the oxygenation conditions in the Magdalena-Tablazo Sub-Basin. An improved understanding of the sedimentary setting during deposition of the Cretaceous black shales in the Magdalena-Tablazo Sub-Basin assists in highlighting the interplay between the mechanism of sedimentation and continuum anoxic conditions prevailing in a basin, as well the important role of nutrient input from continental runoff as a trigger of high productivity and extended anoxia conditions.

Stratigraphic and technological evidence from the Middle Palaeolithic-Châtelperronian-Aurignacian record at the Bordes-Fitte rockshelter (Roches d'Abilly site, Central France).

PubMed

Aubry, Thierry; Dimuccio, Luca Antonio; Almeida, Miguel; Buylaert, Jan-Pieter; Fontana, Laure; Higham, Thomas; Liard, Morgane; Murray, Andrew S; Neves, Maria João; Peyrouse, Jean-Baptiste; Walter, Bertrand

2012-01-01

This paper presents a geoarchaeological study of Middle and Upper Palaeolithic (Châtelperronian, Aurignacian and Solutrean) occupations preserved at the Bordes-Fitte rockshelter in Central France. The lithostratigraphic sequence is composed of near-surface sedimentary facies with vertical and lateral variations, in a context dominated by run-off and gravitational sedimentary processes. Field description and micromorphological analysis permit us to reconstruct several episodes of sediment slope-wash and endokarst dynamics, with hiatuses and erosional phases. The archaeostratigraphic succession includes Châtelperronian artefacts, inter-stratified between Middle Palaeolithic and Aurignacian occupations. Systematic refitting and spatial analysis reveal that the Châtelperronian point production and flake blanks retouched into denticulates, all recovered in the same stratigraphic unit, result from distinct and successive occupations and are not a 'transitional' Middle to Upper Palaeolithic assemblage. The ages obtained by (14)C place the Châtelperronian occupation in the 41-48 ka cal BP (calibrated thousands of years before present) interval and are consistent with the quartz optically stimulated luminescence age of 39 ± 2 ka and feldspar infra-red stimulated luminescence age of 45 ± 2 ka of the sediments. The Bordes-Fitte rockshelter sequence represents an important contribution to the debate about the characterization and timing of the Châtelperronian, as well as its affinities to earlier and later industries. Copyright © 2011 Elsevier Ltd. All rights reserved.

Integrating bio-, chemo- and sequence stratigraphy of the Late Ordovician, Early Katian: A connection between onshore and offshore facies using carbon isotope analysis: Kentucky, Ohio, USA

NASA Astrophysics Data System (ADS)

Young, Allison; Brett, Carlton; McLaughlin, Patrick

2017-04-01

A common problem in stratigraphic correlation is the difficulty of bridging shallow water shelf carbonates and down ramp shale-rich facies. This issue is well exemplified by the Upper Ordovician (lower Katian) Lexington Limestone of Kentucky, USA and adjacent dark shale facies in the deeper water Sebree Trough, an elongate, narrow bathymetric low abruptly north of the outcrop belt in the Ohio subsurface. Chronostratigraphic schemes for this interval have been proposed on the basis of conodont and graptolite biostratigraphy, mapping of event beds, and sequence stratigraphy through facies analysis. The relation of the siliciclastic rich offshore records of the "Point Pleasant-Utica" interval, well known to drillers because of its oil and gas potential, with the up-ramp shallow water carbonate dominated equivalents of the Lexington Formation is complicated by convoluted nomenclature, a major, abrupt change in facies, and disparity in the availability and completeness of records. Current genetic models of organic rich shale intervals, such as the Point Pleasant-Utica interval, are still lacking in detail, and will greatly benefit from detailed correlation with shallow water settings where more is understood about paleoclimatic conditions. In order to understand the development and evolution of this Late Ordovician Laurentian basin, it is important to understand the age relationships of depositional processes occurring at a range of depths, particularly in the less well studied epeiric sea setting of the "Point Pleasant-Utica" interval of Ohio and partial lateral equivalent, Lexington Formation of central Kentucky. The outcrop area of central Kentucky, exposed by the later uplift of the Cincinnati Arch, hosts numerous world-class exposures of the Lexington Formation, nearly all of which are representative of the highly fossiliferous, shallow-water marine platform carbonates. These successions display well differentiated depositional sequences, with sharp facies offsets, and mineralized surfaces. They also contain well studied fossil assemblages and event beds, which at the scale of an outcrop, allow for detailed paleoenvironmental interpretation. The offshore record of this interval, known almost exclusively from a few drill cores, displays an abrupt transition to distal, siliciclastic dominated facies, recording a more dysoxic and organic rich interval. Internal correlation of these shales has relied mostly on limited graptolite biostratigraphic and geochemical analysis. Here we seek to establish age relationships across a major facies transition between these two interrelated paleoenvironmental settings using high resolution whole rock carbon isotope analysis to integrate new and previous work on lithostratigraphy, biostratigraphy, and sequence stratigraphy of a series of cores and outcrops. Results to date demonstrate the persistence of carbon isotopic patterns (including the globally recognized GICE positive carbon isotopic excursion) permitting extension of correlation into basinal facies where tracking of stratigraphic sequences becomes difficult. A complicated relationship across the region is emerging involving both rapid facies transitions and submarine erosional cutout of units toward the center of the Sebree Trough. This study demonstrates the utility of an integrated stratigraphic approach for establishing high resolution regional correlations allowing for interpretations across a major facies transitions.

3D seismic attribute expressions of deep offshore Niger Delta

NASA Astrophysics Data System (ADS)

Anyiam, Uzonna Okenna

Structural and stratigraphic interpretation of 3D seismic data for reservoir characterization in an area affected by dense faulting, such as the Niger Delta, is typically difficult and strongly model driven because of problems with imaging. In the Freeman field, located about 120km offshore southwestern Niger Delta at about 1300m water depth, 3D seismic attribute-based analogs, and structural and stratigraphic based geometric models are combined to help enhance and constrain the interpretation. The objectives being to show how 3D seismic attribute analysis enhances seismic interpretation, develop structural style and stratigraphic architecture models and identify trap mechanisms in the study area; with the main purpose of producing structural and stratigraphic framework analogs to aid exploration and production companies, as well as researchers in better understanding the structural style, stratigraphic framework and trap mechanism of the Miocene to Pliocene Agbada Formation reservoirs in the deep Offshore Niger Delta Basin. A multidisciplinary approach which involved analyses of calculated variance-based coherence cube, spectral decomposition box probe and root-mean-square amplitude attributes, sequence stratigraphy based well correlation, and structural modeling; were undertaken to achieve these objectives. Studies reveal a massive northwest-southeast trending shale cored detachment fold anticline, with associated normal faults; interpreted to have been folded and faulted by localized compression resulting from a combination of differential loading on the deep-seated overpressured-ductile-undercompacted-marine Akata shale, and gravitational collapse of the Niger delta continental slope due to influx of sediments. Crestal extension resulting from this localized compression, is believed to have given rise to the synthetic, antithetic and newly observed crossing conjugate normal faults in the study area. This structure is unique to the existing types of principal oil field structures in the Niger Delta. Stratigraphic results show that the Mid-Miocene to Pliocene Agbada Formation reservoirs of the Freeman field occur as part of a channelized fan system; mostly deposited as turbidites in an unconfined distributary environment; except one that occurs as channel sand within a submarine canyon that came across and eroded previously deposited distributary fan complex, at the time. Hence, prospective area for hydrocarbon exploration is suggested southwest of the Freeman field.

Stratigraphic Framework of Cambrian and Ordovician Rocks in the Appalachian Basin from Sequatchie County, Tennessee, through Eastern Kentucky, to Mingo County, West Virginia

USGS Publications Warehouse

Ryder, Robert T.; Crangle, Robert D.; Repetski, John E.; Harris, Anita G.

2008-01-01

Cross section H-H' is the seventh in a series of restored cross sections constructed by the lead author to show the stratigraphic framework of Cambrian and Ordovician rocks in the Appalachian basin from Pennsylvania to Tennessee. The sections show complexly intertongued carbonate and siliciclastic lithofacies, marked thickness variations, key marker horizons, unconformities, stratigraphic nomenclature of the Cambrian and Ordovician sequence, and major faults that offset Proterozoic basement and overlying lower Paleozoic rocks. Several of the drill holes along the cross section have yielded a variety of whole and (or) fragmented conodont elements. The identifiable conodonts are used to differentiate strata of Late Cambrian, Early Ordovician, and Middle Ordovician age, and their conodont color alteration index (CAI) values are used to establish the thermal maturity of the sequence. Previous cross sections in this series are G-G', F-F', E-E', D-D', C-C', and B-B'. Many of these cross sections (B-B', C-C', D-D', and G-G') have been improved with the addition of gamma-ray log traces, converted to digital images, and made accessible on the Web.

Global geological map of Venus

NASA Astrophysics Data System (ADS)

Ivanov, Mikhail A.; Head, James W.

2011-10-01

The surface area of Venus (∼460×106 km2) is ∼90% of that of the Earth. Using Magellan radar image and altimetry data, supplemented by Venera-15/16 radar images, we compiled a global geologic map of Venus at a scale of 1:10 M. We outline the history of geological mapping of the Earth and planets to illustrate the importance of utilizing the dual stratigraphic classification approach to geological mapping. Using this established approach, we identify 13 distinctive units on the surface of Venus and a series of structures and related features. We present the history and evolution of the definition and characterization of these units, explore and assess alternate methods and approaches that have been suggested, and trace the sequence of mapping from small areas to regional and global scales. We outline the specific defining nature and characteristics of these units, map their distribution, and assess their stratigraphic relationships. On the basis of these data, we then compare local and regional stratigraphic columns and compile a global stratigraphic column, defining rock-stratigraphic units, time-stratigraphic units, and geological time units. We use superposed craters, stratigraphic relationships and impact crater parabola degradation to assess the geologic time represented by the global stratigraphic column. Using the characteristics of these units, we interpret the geological processes that were responsible for their formation. On the basis of unit superposition and stratigraphic relationships, we interpret the sequence of events and processes recorded in the global stratigraphic column. The earliest part of the history of Venus (Pre-Fortunian) predates the observed surface geological features and units, although remnants may exist in the form of deformed rocks and minerals. We find that the observable geological history of Venus can be subdivided into three distinctive phases. The earlier phase (Fortunian Period, its lower stratigraphic boundary cannot be determined with the available data sets) involved intense deformation and building of regions of thicker crust (tessera). This was followed by the Guineverian Period. Distributed deformed plains, mountain belts, and regional interconnected groove belts characterize the first part and the vast majority of coronae began to form during this time. The second part of the Guineverian Period involved global emplacement of vast and mildly deformed plains of volcanic origin. A period of global wrinkle ridge formation largely followed the emplacement of these plains. The third phase (Atlian Period) involved the formation of prominent rift zones and fields of lava flows unmodified by wrinkle ridges that are often associated with large shield volcanoes and, in places, with earlier-formed coronae. Atlian volcanism may continue to the present. About 70% of the exposed surface of Venus was resurfaced during the Guineverian Period and only about 16% during the Atlian Period. Estimates of model absolute ages suggest that the Atlian Period was about twice as long as the Guineverian and, thus, characterized by significantly reduced rates of volcanism and tectonism. The three major phases of activity documented in the global stratigraphy and geological map, and their interpreted temporal relations, provide a basis for assessing the geodynamical processes operating earlier in Venus history that led to the preserved record.

Sequence and facies architecture of the upper Blackhawk Formation and the Lower Castlegate Sandstone (Upper Cretaceous), Book Cliffs, Utah, USA

NASA Astrophysics Data System (ADS)

Yoshida, S.

2000-11-01

High-frequency stratigraphic sequences that comprise the Desert Member of the Blackhawk Formation, the Lower Castlegate Sandstone, and the Buck Tongue in the Green River area of Utah display changes in sequence architecture from marine deposits to marginal marine deposits to an entirely nonmarine section. Facies and sequence architecture differ above and below the regionally extensive Castlegate sequence boundary, which separates two low-frequency (106-year cyclicity) sequences. Below this surface, high-frequency sequences are identified and interpreted as comprising the highstand systems tract of the low-frequency Blackhawk sequence. Each high-frequency sequence has a local incised valley system on top of the wave-dominated delta, and coastal plain to shallow marine deposits are preserved. Above the Castlegate sequence boundary, in contrast, a regionally extensive sheet sandstone of fluvial to estuarine origin with laterally continuous internal erosional surfaces occurs. These deposits above the Castlegate sequence boundary are interpreted as the late lowstand to early transgressive systems tracts of the low-frequency Castlegate sequence. The base-level changes that generated both the low- and high-frequency sequences are attributed to crustal response to fluctuations in compressive intraplate stress on two different time scales. The low-frequency stratigraphic sequences are attributed to changes in the long-term regional subsidence rate and regional tilting of foreland basin fill. High-frequency sequences probably reflect the response of anisotropic basement to tectonism. Sequence architecture changes rapidly across the faulted margin of the underlying Paleozoic Paradox Basin. The high-frequency sequences are deeply eroded and stack above the Paradox Basin, but display less relief and become conformable updip. These features indicate that the area above the Paradox Basin was more prone to vertical structural movements during formation of the Blackhawk-Lower Castlegate succession.

Facies analysis, diagenesis and sequence stratigraphy of the carbonate-evaporite succession of the Upper Jurassic Surmeh Formation: Impacts on reservoir quality (Salman Oil Field, Persian Gulf, Iran)

NASA Astrophysics Data System (ADS)

Beigi, Maryam; Jafarian, Arman; Javanbakht, Mohammad; Wanas, H. A.; Mattern, Frank; Tabatabaei, Amin

2017-05-01

This study aims to determine the depositional facies, diagenetic processes and sequence stratigraphic elements of the subsurface carbonate-evaporite succession of the Upper Jurassic (Kimmeridgian-Tithonian) Surmeh Formation of the Salman Oil Field (the Persian Gulf, Iran), in an attempt to explore their impacts on reservoir quality. The Surmeh Formation consists mainly of carbonate rocks, intercalated with evaporite layers. Petrographically, the Surmeh Formation consists of nine microfacies (MF1-MF9). These microfacies are grouped into three facies associations related to three depositional environments (peritidal flat, lagoon and high-energy shoal) sited on the inner part of a homoclinal carbonate ramp. The recorded diagenetic processes include dolomitization, anhydritization, compaction, micritization, neomorphism, dissolution and cementation. Vertical stacking patterns of the studied facies reveal the presence of three third-order depositional sequences, each of which consists of transgressive systems tract (TST) and highstand systems tract (HST). The TSTs comprise intertidal and lagoon facies whereas the HSTs include supratidal and shoal facies. In terms of their impacts on reservoir quality, the shoal facies represent the best reservoir quality, whereas the peritidal and lagoonal facies exhibit moderate to lowest reservoir quality. Also, poikilotopic anhydrite cement played the most significant role in declining the reservoir quality, whereas the widespread dissolution of labile grains and formation of moldic and vuggy pores contributed in enhancing the reservoir quality. In addition, the HSTs have a better reservoir quality than the TSTs. This study represents an approach to use the depositional facies, diagenetic alterations and sequence stratigraphic framework of carbonate -evaporite succession for a more successful reservoir characterization.

Pre-drill predictions versus post-drill results: use of sequence stratigraphic methods in reduction of exploration risk, Sarawak Deep-water Blocks, Malaysia

NASA Astrophysics Data System (ADS)

Mansor, Md Yazid; Snedden, J. W.; Sarg, J. F.; Smith, B. S.; Kolich, T.; Carter, M.

1999-04-01

Limited well control, great distances from age-equivalent producing fields, and a largely unknown stratigraphy necessitated use of sequence stratigraphic methods to assess exploration risk associated with reservoir, source and seal distribution in the Mobil-operated Deep-water Blocks of Sarawak, Malaysia. These methods allowed predictions to be made and reservoir risks to be halved in each of the locations drilled in 1995. Predictions regarding reservoir and stratigraphy proved correct, as the Mulu-1 and Bako-1 wells penetrated numerous high-quality, thick sandstone reservoirs in the Middle to Lower Miocene section. Shallow marine sandstones dominate the vertical succession in both wells, with characteristic aggradational, upward-coarsening log motifs. Cores display classic wave-generated stratification and hummocky cross-bedding. Evidence, such as marginal-marine to neritic microfauna in cuttings of both wells, supports these interpretations. Lack of hydrocarbon charge in the two wells may be due to their position relative to coaly hydrocarbon source beds. These prospects have high trap and seal integrity, being well defined on seismics as high relief horst blocks covered by a very thick shale-prone section. The Mulu-1 well, for example, is located at least 20-30 km down stratigraphic dip from mapped coeval lower coastal-plain deposits. Amplitude anomalies on the flank of the Mulu horst are probably derived from transported organics buried in deep Plio-Pleistocene kitchens in the northwest portion of the Mobil blocks. Remaining potential of mapped prospects is high and efforts continue at characterizing the petroleum system of the Deep-water Blocks. Seismic attribute and interval velocity analyses provide new clues to the location of probable coaly source rocks, especially when viewed in their regional and sequence stratigraphic context. Future work is planned and will serve to reduce risk to acceptable levels and support further drilling in this prospective hydrocarbon province.

Biothems: Sequence stratigraphic units and their implications for regional tectono-stratigraphic interpretations

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

Lane, H.R.; Frye, M.W.; Couples, G.D.

1992-01-01

Biothems are regional wedge- or lens-shaped bodies of strata that are bounded shelfward or cratonward by paleontologically recognizable unconformities; generally thicken on marine shelves, where they are typically conformable with underlying and overlying biothems; are commonly thinner or represent starved sequences further basinward; and in their most basinward extent, are either bounded by biostratigraphically recognizable unconformities or are conformable with underlying and overlying biothems. As recognized to date, biothems have a logical distribution of faunal and floral components, as well as facies groupings that represent internally consistent and logical sequences of depositional environments. A west-to-east transect within the North Americanmore » Mississippian System which extends from the Basin and Range Province, across the Transcontinental Arch (TA), into the Anadarko Basin, was constructed to demonstrate the regional distribution and tectono-stratigraphic significance of biothems relative to the axis of the TA. The relationships portrayed on the transect, tied to an understanding of North American Mississippian paleogeography, imply that biothems deposited during relative highstand events on one flank of the TA are time-equivalent to biothems deposited during relative lowstand events on the opposite flank of the TA. This distribution is interpreted to have been controlled by intraplate tectonic events that formed piano key basins along the flanks of the TA. The spatial patterns of these basins are not consistent with published models of basin evolution. A further conclusion is that the lack of coincident, transgressive or regressive Mississippian biothems on either flank of the TA suggests that it is inadvisable to impose the Mississippi Valley-derived eustasy curve on western flank depositional sequences.« less

Depositional sequence analysis and sedimentologic modeling for improved prediction of Pennsylvanian reservoirs (Annex 1). Annual report, February 1, 1991--January 31, 1992

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

Watney, W.L.

1992-08-01

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 linkmore » 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.« less

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

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

Watney, W.L.

1992-01-01

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 linkmore » 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.« less

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

USGS Publications Warehouse

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

2003-01-01

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

The massive dolomitization of platformal and basinal sequences: proposed models from the Paleocene, Northeast Sirte Basin, Libya

NASA Astrophysics Data System (ADS)

Mresah, Mohamed H.

1998-03-01

The Paleocene carbonate succession in the Northeast Sirte Basin is composed of two shallowing-upward ramp cycles, where each cycle is under- and overlain by deeper-water, pelagic facies. A significant proportion of each of these two cycles is dolomitized. Petrographic study, supported by geochemical data (stoichiometry, stable isotopes, trace elements, and fluid inclusions), and integrated with broader tectono-sedimentary information, has provided the basis for interpreting these Paleocene dolomites. The use of this integrated approach in the study of dolomites suggests that, despite the much publicized uncertainties in interpreting geochemical analyses of ancient dolomites, the results of the Paleocene dolomites show that the geochemical characteristics are generally consistent with regional stratigraphic distribution and petrographic observations. Four distinct types of dolomite have been recognized in this part of the Sirte Basin. Based on the stratigraphic position and petrographic criteria, two of these types have a platformal setting and the other two are basinal. The platform varieties consist of dolomicrites and pervasive stratal dolomites. The dolomicrites, interpreted to be of syn-sedimentary origin, were probably a product of reflux of seawater, with elevated salinity, as suggested by palaeoenvironmental analysis and supported by geochemical evidence (the average S'80 value is -0.1‰ PDB; the average Sr content is 639 ppm). The pervasive dolomites were formed during the progradation of the platform sequences, and probably stabilized and augmented during shallow burial. A meteoric-marine mixing-zone is thought to have been the most likely process for the formation of these dolomites. This interpretation is supported by geochemical evidence (the average δ18O is -2.4‰ PDB; the average Sr content is 72 ppm) combined with a favourable stratigraphic position. The most characteristic feature related to both mixing-zone and reflux dolomitization is the basinward movement of the dolomitizing fluids, which suggests that the formation of these platform dolomites was related to a lowstand system tract. The two basinal varieties comprise thick (over 300 m) basinal dolomudstones and fracture-filling, sparry dolomites. The stratigraphic position of the finely crystalline basinal dolomudstones, within very thick shale successions (as a result of being very close to the depocentre of the Sirte Basin) combined with geochemical evidence (the average δ18O is -6.4‰ PDB), suggest that the dolomitizing fluids were basin-derived, with Mg 2+ released from dewatering through compaction of basinal shales. The occurrence of this type of dolomite provides one of the rare examples of large-scale dolomitization of thick, basinal sequences. Late diagenetic fracture-filling dolomites exhibit a structural control on their distribution. Geochemical evidence (including fluid inclusion analysis and the lightest oxygen isotopic signature of -7.3‰ PDB) suggests that highly saline formation brines were the solutions responsible for their formation.

Sequence stratigraphic re-interpretation of [open quotes]stray[close quotes] sandstones in the Cretaceous Mancos Shale, Book Cliffs, Utah: Implications for exploration models

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

Hampson, G.J.; Howell, J.A.; Flint, S.S.

1996-01-01

The Mancos Shale, Book Cliffs, eastern Utah, represents the open marine mudstones of the Cretaceous Western Interior Seaway and contains a number of detached sandstone bodies ([open quotes]Mancos B[close quotes]) which are located 30-150 km down depositional dip from contemporaneous highstand shoreline deposits in the Blackhawk Formation. Examination of these [open quotes]stray[close quotes] sandstones reveals that they do not represent deep water deposition, as previously supposed, but instead comprise three shallow marine facies associations; (1) tidally-influenced fluvial channel fills, (2) fluvially-dominated delta front successions and (3) low-energy shorelines. Tidally-influenced fluvial channel fills are commonly stacked into multistorey bodies at discretemore » stratigraphic levels, thereby defining incised valley fill (IVF) networks. Fluvially-dominated deltas are eroded into by, and lie at the down-dip terminations of, IVFs and are therefore interpreted as falling stage and lowstand shorelines. Low-energy shorelines are inferred to lie along strike from these deltas. The above shallow marine deposits have been mapped at five discrete stratigraphic horizons, which can be either traced or projected up-dip to previously-documented IVFs in the Blackhawk Formation. Their paleocurrents imply that falling stage and lowstand shoreline trends were sub-parallel to mapped highstand shorelines, although there is evidence for a perpendicular lowstand shoreline trend in the east of the study area. This facies and sequence stratigraphic re-interpretation enables predictive exploration modelling of subsurface [open quotes]Mancos B[close quotes] gas reservoir sandstones.« less

Sequence stratigraphic re-interpretation of {open_quotes}stray{close_quotes} sandstones in the Cretaceous Mancos Shale, Book Cliffs, Utah: Implications for exploration models

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

Hampson, G.J.; Howell, J.A.; Flint, S.S.

1996-12-31

The Mancos Shale, Book Cliffs, eastern Utah, represents the open marine mudstones of the Cretaceous Western Interior Seaway and contains a number of detached sandstone bodies ({open_quotes}Mancos B{close_quotes}) which are located 30-150 km down depositional dip from contemporaneous highstand shoreline deposits in the Blackhawk Formation. Examination of these {open_quotes}stray{close_quotes} sandstones reveals that they do not represent deep water deposition, as previously supposed, but instead comprise three shallow marine facies associations; (1) tidally-influenced fluvial channel fills, (2) fluvially-dominated delta front successions and (3) low-energy shorelines. Tidally-influenced fluvial channel fills are commonly stacked into multistorey bodies at discrete stratigraphic levels, thereby definingmore » incised valley fill (IVF) networks. Fluvially-dominated deltas are eroded into by, and lie at the down-dip terminations of, IVFs and are therefore interpreted as falling stage and lowstand shorelines. Low-energy shorelines are inferred to lie along strike from these deltas. The above shallow marine deposits have been mapped at five discrete stratigraphic horizons, which can be either traced or projected up-dip to previously-documented IVFs in the Blackhawk Formation. Their paleocurrents imply that falling stage and lowstand shoreline trends were sub-parallel to mapped highstand shorelines, although there is evidence for a perpendicular lowstand shoreline trend in the east of the study area. This facies and sequence stratigraphic re-interpretation enables predictive exploration modelling of subsurface {open_quotes}Mancos B{close_quotes} gas reservoir sandstones.« less

Identifying Preserved Storm Events on Beaches from Trenches and Cores

NASA Astrophysics Data System (ADS)

Wadman, H. M.; Gallagher, E. L.; McNinch, J.; Reniers, A.; Koktas, M.

2014-12-01

Recent research suggests that even small scale variations in grain size in the shallow stratigraphy of sandy beaches can significantly influence large-scale morphology change. However, few quantitative studies of variations in shallow stratigraphic layers, as differentiated by variations in mean grain size, have been conducted, in no small part due to the difficulty of collecting undisturbed sediment cores in the energetic lower beach and swash zone. Due to this lack of quantitative stratigraphic grain size data, most coastal morphology models assume that uniform grain sizes dominate sandy beaches, allowing for little to no temporal or spatial variations in grain size heterogeneity. In a first-order attempt to quantify small-scale, temporal and spatial variations in beach stratigraphy, thirty-five vibracores were collected at the USACE Field Research Facility (FRF), Duck, NC, in March-April of 2014 using the FRF's Coastal Research and Amphibious Buggy (CRAB). Vibracores were collected at set locations along a cross-shore profile from the toe of the dune to a water depth of ~1m in the surf zone. Vibracores were repeatedly collected from the same locations throughout a tidal cycle, as well as pre- and post a nor'easter event. In addition, two ~1.5m deep trenches were dug in the cross-shore and along-shore directions (each ~14m in length) after coring was completed to allow better interpretation of the stratigraphic sequences observed in the vibracores. The elevations of coherent stratigraphic layers, as revealed in vibracore-based fence diagrams and trench data, are used to relate specific observed stratigraphic sequences to individual storm events observed at the FRF. These data provide a first-order, quantitative examination of the small-scale temporal and spatial variability of shallow grain size along an open, sandy coastline. The data will be used to refine morphological model predictions to include variations in grain size and associated shallow stratigraphy.

Friis Hills Drilling Project - Coring an Early to mid-Miocene terrestrial sequence in the Transantarctic Mountains to examine climate gradients and ice sheet variability along an inland-to-offshore transect

NASA Astrophysics Data System (ADS)

Lewis, A. R.; Levy, R. H.; Naish, T.; Gorman, A. R.; Golledge, N.; Dickinson, W. W.; Kraus, C.; Florindo, F.; Ashworth, A. C.; Pyne, A.; Kingan, T.

2015-12-01

The Early to mid-Miocene is a compelling interval to study Antarctic ice sheet (AIS) sensitivity. Circulation patterns in the southern hemisphere were broadly similar to present and reconstructed atmospheric CO2 concentrations were analogous to those projected for the next several decades. Geologic records from locations proximal to the AIS are required to examine ice sheet response to climate variability during this time. Coastal and offshore drill core records recovered by ANDRILL and IODP provide information regarding ice sheet variability along and beyond the coastal margin but they cannot constrain the extent of inland retreat. Additional environmental data from the continental interior is required to constrain the magnitude of ice sheet variability and inform numerical ice sheet models. The only well-dated terrestrial deposits that register early to mid-Miocene interior ice extent and climate are in the Friis Hills, 80 km inland. The deposits record multiple glacial-interglacial cycles and fossiliferous non-glacial beds show that interglacial climate was warm enough for a diverse biota. Drifts are preserved in a shallow valley with the oldest beds exposed along the edges where they terminate at sharp erosional margins. These margins reveal drifts in short stratigraphic sections but none is more than 13 m thick. A 34 m-thick composite stratigraphic sequence has been produced from exposed drift sequences but correlating beds in scattered exposures is problematic. Moreover, much of the sequence is buried and inaccessible in the basin center. New seismic data collected during 2014 reveal a sequence of sediments at least 50 m thick. This stratigraphic package likely preserves a detailed and more complete sedimentary sequence for the Friis Hills that can be used to refine and augment the outcrop-based composite stratigraphy. We aim to drill through this sequence using a helicopter-transportable diamond coring system. These new cores will allow us to obtain continuous measurements on unweathered material through the terrestrial sequence. Beds of tephra are exposed in outcrop and we expect to encounter these key age markers in the cored sequence. These new high quality, well-dated terrestrial data will be directly compared to marine cores to provide environmental data across a broad onshore-offshore transect.

The Midway sequence: A Timiskaming-type, pull-apart basin deposit in the western Wawa subprovince, Minnesota

USGS Publications Warehouse

Jirsa, M.A.

2000-01-01

The Midway sequence is an assemblage of subaerially deposited clastic and volcanic rocks that forms a narrow wedge within Neoarchean greenstone of the western Wawa subprovince of the Superior Province. Volcanic conglomerate in the Midway sequence contains clasts of stratigraphically older greenstone, together with clasts of a distinctive hornblende-phyric trachyandesite that is not represented among the older greenstone flows. The trachyandesite forms flows and pyroclastic units that are interbedded with lenticular deposits of volcanic conglomerate in a manner interpreted to indicate approximately coeval volcanism and alluvial fan - Fluvial sedimentation within a linear, restricted, and tectonically active depocentre. The Midway sequence unconformably overlies greenstone on one side and is bounded by a regional-scale, strike-slip fault on the other. Structural analyses show that the Midway sequence was deposited after an early, precleavage folding event (D1) in greenstone, but before the regional metamorphic cleavage-forming D2 deformation. Lithologic and structural attributes are consistent with deposition in a strike-slip "pull-apart" basin. The stratigraphic and structural characteristics of the Midway sequence are generally similar to those of the Timiskaming Group and Timiskaming-type rocks in Canada, and more specifically to those of the Shebandowan Group in the Thunder Bay district. This similarity implies that the latest Archean tectonic and magmatic history of the western Wawa subprovince may have been nearly synchronous over great distances.

ANALYSIS OF OIL-BEARING CRETACEOUS SANDSTONE HYDROCARBON RESERVOIRS, EXCLUSIVE OF THE DAKOTA SANDSTONE, ON THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO

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

Jennie Ridgley

2000-01-21

An additional 450 wells were added to the structural database; there are now 2550 wells in the database with corrected tops on the Juana Lopez, base of the Bridge Creek Limestone, and datum. This completes the structural data base compilation. Fifteen oil and five gas fields from the Mancos-ElVado interval were evaluated with respect to the newly defined sequence stratigraphic model for this interval. The five gas fields are located away from the structural margins of the deep part of the San Juan Basin. All the fields have characteristics of basin-centered gas and can be considered as continuous gas accumulationsmore » as recently defined by the U.S. Geological Survey. Oil production occurs in thinly interbedded sandstone and shale or in discrete sandstone bodies. Production is both from transgressive and regressive strata as redefined in this study. Oil production is both stratigraphically and structurally controlled with production occurring along the Chaco slope or in steeply west-dipping rocks along the east margin of the basin. The ElVado Sandstone of subsurface usage is redefined to encompass a narrower interval; it appears to be more time correlative with the Dalton Sandstone. Thus, it was deposited as part of a regressive sequence, in contrast to the underlying rock units which were deposited during transgression.« less

Stratigraphic controls on seawater intrusion and implications for groundwater management, Dominguez Gap area of Los Angeles, California, USA

USGS Publications Warehouse

Nishikawa, T.; Siade, A.J.; Reichard, E.G.; Ponti, D.J.; Canales, A.G.; Johnson, T.A.

2009-01-01

Groundwater pumping has led to extensive water-level declines and seawater intrusion in coastal Los Angeles, California (USA). A SUTRA-based solute-transport model was developed to test the hydraulic implications of a sequence-stratigraphic model of the Dominguez Gap area and to assess the effects of water-management scenarios. The model is two-dimensional, vertical and follows an approximate flow line extending from the Pacific Ocean through the Dominguez Gap area. Results indicate that a newly identified fault system can provide a pathway for transport of seawater and that a stratigraphic boundary located between the Bent Spring and Upper Wilmington sequences may control the vertical movement of seawater. Three 50-year water-management scenarios were considered: (1) no change in water-management practices; (2) installation of a slurry wall; and (3) raising inland water levels to 7.6 m above sea level. Scenario 3 was the most effective by reversing seawater intrusion. The effects of an instantaneous 1-m sea-level rise were also tested using water-management scenarios 1 and 3. Results from two 100-year simulations indicate that a 1-m sea-level rise may accelerate seawater intrusion for scenario 1; however, scenario 3 remains effective for controlling seawater intrusion. ?? Springer-Verlag 2009.

Analyse sismo-stratigraphique du bassin d'Abda (Maroc occidental), exemple de structures inverses pendant le rifting atlantiqueSeismo-stratigraphic analysis of the Abda Basin (West Morocco): a case of reverse structures during the Atlantic rifting

NASA Astrophysics Data System (ADS)

Echarfaoui, Hassan; Hafid, Mohamed; Salem, Abdallah Aı̈t; Abderrahmane, Aı̈t Fora

The review of the seismic reflection and well data from the coastal Abda Basin (western Morocco) shows that its Triassic and Jurassic sequences were deposited in a submeridean sag basin, whose eastern margin is characterised by progressive truncations and pinching out of these sequences against a prominent Palaeozoic high. The uplift of this latter is interpreted as a response to an Upper Triassic-Middle Jurassic local compressional event that controlled Triassic-Jurassic sedimentation within the Abda Basin. The present day 'West Meseta Flexure' is a surface expression of this uplift. To cite this article: H. Echarfaoui et al., C. R. Geoscience 334 (2002) 371-377.

3D stratigraphic forward modelling of Shu'aiba Platform stratigraphy in the Bu Hasa Field, Abu Dhabi, United Arab Emirates.

NASA Astrophysics Data System (ADS)

Hu, J.; Lokier, S. W.

2012-04-01

This paper presents the results of three dimensional sequence stratigraphic forward modelling of the Aptian age Shu'aiba Formation from Abu Dhabi, United Arab Emirates (UAE). The Shu'aiba Formation lies within the uppermost part of the Lower Cretaceous Thamama Group and forms one of the most prolific hydrocarbon reservoir intervals of the Middle East with production dating back to the 1960's. The Shu'aiba Formation developed as a series of laterally-extensive shallow-water carbonate platforms in an epeiric sea that extended over the northern margin of the African-Arabian Plate. This shallow sea was bounded by the Arabian Shield to the west and the passive margin with the Neo-Tethys Ocean towards the north and east (Droste, 2010). The exposed Arabian Shield acted as a source of siliciclastic sediments to westernmost regions, however, more offshore areas were dominated by shallow-water carbonate deposition. Carbonate production was variously dominated by Lithocodium-Baccinella, orbitolinid foraminifera and rudist bivalves depending on local conditions. While there have been numerous studies of this important stratigraphic interval (for examples see van Buchem et al., 2010), there has been little attempt to simulate the sequence stratigraphic development of the formation. During the present study modelling was undertaken utilising the CARBONATE-3D stratigraphic forward modelling software (Warrlich et al., 2008; Warrlich et al., 2002)) thus allowing for the control of a diverse range of internal and external parameters on carbonate sequence development. This study focuses on platform development in the onshore Bu Hasa Field - the first giant oilfield to produce from the Shu'aiba Formation in Abu Dhabi. The carbonates of the Bu Hasa field were deposited on the southwest slope of the intra-shelf Bab Basin, siliciclastic content is minor. Initially these carbonates were algal dominated with rudist mounds becoming increasingly important over time (Alsharhan, 1987). Numerous simulations were undertaken, employing different sea level curves, platform geometries, etc. in order to accurately constrain and compare simulated facies geometries with those hypothesised from subsurface correlations. An initial low-angle ramp geometry was later overprinted by the development of localised relief through faulting and salt diapirism. Areas of bathymetric relief became sites of enhanced carbonate development with over-production resulting in aggradational geometries rapidly evolving to progradational systems. Several different regional, global and composite relative sea level curves were employed in the simulations in order to produce stratigraphic geometries comparable to those reported from previous studies. We conclude that none of the published sea level curves produce facies geometries directly analogous to those hypothesised from the sub-surface. We infer that this disparity primarily results from previous models lacking sufficient accommodation space and employing unrealistic carbonate production rates.

Sequence stratigraphy and high-frequency cycles: New aspects for a quantitative evaluation of the Gulf of Suez basin, Egypt

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

Nio, S.D.; Yang, C.S.; Tewfik, N.

1993-09-01

A new development in the application of sequence stratigraphic concepts in marine as well as continental basins is the recognition of high-frequency cyclic patterns in rock successions in the subsurface. Studies of six wells from the northern, central, and southern parts of the Gulf of Suez show the presence of well-preserved, high-frequency cycles with periodicities similar to the orbitally forced Malankovitch parameters. Subsurface rock successions, third-order sequences, and high-frequency cycles were compared with outcrops. After establishing the biostratigraphic framework for the above-mentioned wells, a sequence analysis was performed. Sequence boundaries and maximum flooding positions in each well were calibrated withmore » the occurrences and evaluation of the high-frequency cycles. It became obvious that there is an intimate relationship between these high-frequency Milankovitch cycles and sequence organization. In addition, a close relationship can be observed in the subsurface as well as in outcrops between high-frequency climatic changes (connected to the Milankovitch cycles) and (litho)facies variability. Quantitative evaluations of each sequence and/or systems tract can be computed with the International Geoservices' cyclicity analysis tool (MILABAR). The results are summarized in a well composite chart, rate (NAR), and ratio of preserved time. In correlations between the wells, an accuracy of 500-100 Ka can be obtained. The quantitative evaluation of the sequence and high-frequency cycle analysis gave some new aspects concerning the (litho)facies and geodynamic development during the pre- as well as the synrift stages of the Gulf of Suez Basin.« less

Stratigraphy and sedimentation of Mississippian Ste. Genevieve-Cedar Bluff interval, Southwestern Indiana

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

Breedon, D.; Droste, J.B.; Murray, H.H.

1983-09-01

The Ste. Genevieve Limestone and Cedar Bluff Group of Mississippian age, both important sources of hydrocarbons in the Illinois basin, were traced from a subsurface stratigraphic section in White County, Illinois (described by Swan in 1963, across Gibson and Daviess Counties, Indiana, using electric logs and sample descriptions from 84 wells. The Ste. Genevieve Limestone is subdivided into four members and the Cedar Bluff Group into three formations. Six cross sections and nine isopach maps based on 300 wells show that these units comprise a succession of alternating fine- and coarse-grained carbonate rocks with only minor interruptions of sandstone andmore » shale. Two complete coarsening-upward cycles are apparent, and a third cycle is incomplete. Each cycle consists of a lower sequence of lime mudstones and wackestones, and an upper sequence of oolitic and skeletal grainstones. These cycles are the record of successive shoaling-upward cycles of sedimentation on a shallow marine platform. The lower mudstone-wackestone sequence represents deposition in a shallow subtidal environment, and the upper oolitic-skeletal grainstone unit represents development of oolite shoals and tidal channels in very shallow waters. Terrigenous clastic sediments brought into the basin by the Michigan river periodically encroached into the marine environment. Dolomitization of the fine-grained carbonate sediments is largely restricted to areas which are overlain by oolitic grainstones. In eastern Daviess County, indentification of the individual stratigraphic units in this interval is somewhat tenuous, but tracing the units from eastern Illinois into Indiana made correlation and identification of the individual stratigraphic units possible by using electric logs and sample descriptions.« less

The Cenozoic seawater 87Sr/86Sr curve: Data review and implications for correlation of marine strata

NASA Astrophysics Data System (ADS)

Koepnick, R. B.; Denison, R. E.; Dahl, D. A.

1988-12-01

The strontium isotopic ratio (87Sr/86Sr) in seawater changes slowly over geologic time. This variation is caused by changes in the relative contribution of Sr from various isotopically distinct sources within the crust. The most important of these are high-ratio sialic rocks from continents and low-ratio mafic volcanic and mafic intrusive rocks from continental margins and ocean basins. A plot of Sr isotope ratio versus age for Phanerozoic marine samples produces a curve exhibiting many episodes of increasing and decreasing values. This variation can be used as a basis for temporal correlation of marine carbonate, sulfate, and phosphate sediments. Temporal correlations can be made between high-latitude and low-latitude sequences, deepwater and shallow-water sequences, and normal-marine and restricted-marine (hypersaline/hyposaline) sequences. Satisfactory biostratigraphic correlations between such sequences are often hampered by either the absence of age-diagnostic fossils or by the provinciality of faunal and floral assemblages. Rapid change that took place in the 87Sr/86Sr of seawater during most of the Cenozoic makes this era particularly well suited for precise temporal correlation. The seawater curve for the Cenozoic is subdivided into three segments: Quaternary to mid-Miocene, mid-Miocene to late Eocene, and late Eocene to early Paleocene. The mid-Miocene to late Eocene curve segment exhibits a particularly steep slope, making this a promising interval for high-resolution stratigraphic correlation. Although current data generally support the present configuration of the seawater curve, some revision of the curve is probably required in the vicinity of the Oligocene-Eocene boundary. Establishment of the general configuration of the seawater curve for the Cenozoic has promoted efforts to refine the curve on the basis of construction of detailed Sr isotope profiles within individual stratigraphic sequences. A Sr isotope profile at Deep Sea Drilling Project (DSDP) site 590B suggests a complex Neogene seawater curve characterized by minor slope changes in the Pliocene and Miocene. These slope changes are not specifically identified in the seawater curve constructed from multilocation data. On the basis of this more complex curve, and in the absence of diagenetic complications, the ultimate Neogene stratigraphic resolution is estimated to range from 0.1 to 2 million years. Both the verification and the general stratigraphic applicability of this more complex Neogene curve are largely dependent on the degree of preservation of the original seawater ratio in marine samples.

Regional Stratigraphy and Petroleum Systems of the Illinois Basin, U.S.A.

USGS Publications Warehouse

Swezey, Christopher S.

2009-01-01

The publication combines data on Paleozoic and Mesozoic stratigraphy and petroleum geology of the Illinois basin, U.S.A., in order to facilitate visualizing the stratigraphy on a regional scale and visualizing stratigraphic relations within the basin. Data are presented in eight schematic chronostratigraphic sections arranged approximately from north to south, with time denoted in equal increments along the sections, in addition to the areal extent of this structural basin. The stratigraphic data are modified from Hass (1956), Conant and Swanson (1961), Wilman and others (1975), American Association of Petroleum Geologists (1984, 1986), Olive and McDowell (1986), Shaver and others (1986), Thompson (1986), Mancini and others (1996), and Harrison and Litwin (1997). The time scale is taken from Gradstein and others (2004). Additional stratigraphic nomenclature is from Harland and others (1990), Babcock and others (2007), and Bergstrom and others (2008). Stratigraphic sequences as defined by Sloss (1963, 1988) and Wheeler (1963) also are included, as well as the locations of major petroleum source rocks and major petroleum plays. The stratigraphic units shown are colored according to predominant lithology, in order to emphasize general lithologic patterns and to provide a broad overview of the Illinois basin. For the purpose of comparison, three columns on the right show schematic depictions of stratigraphy and interpreted events in the Illinois basin and in the adjacent Michigan and Appalachian basins.

Identifying and Characterizing Impact Melt Outcrops in the Nectaris Basin

NASA Technical Reports Server (NTRS)

Cohen, B. A.; Lawerence, S. J.; Petro, N. E.; Bart, G. D.; Clegg-Watkins, R. N.; Denevi, B. W.; Ghent, R. R.; Klima, R. L.; Morgan, G. A.; Spudis, P. D.;

[open quotes]Rejuvenation[close quotes] of a very mature productive area: Application of sequence stratigraphy, depositional facies and reservoir architectural studies in inactive old fields - Dorsal de Huincul - Neuquen Basin, Argentina

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

Kokogian, D.A.; Vasquez, J.R.

1996-01-01

The project objectives were to define the upside potential and identified drilling locations, both for exploratory and development wells, in Loma Negra-Nl-Huincul old fields, inactive due to pressure depletion Fields are located in Dorsal de Huincul area (Huincul Range) which is a highly complex structure associated with a major transtensive-transpressive wrench system. Several angular unconformities are very noticeable, having eroded hundreds of meters of the stratigraphic column. Study was focused on the fluvial-deltaic sediments of the Cuyo Group (Bajocian-Bathonian), the main productive levels in the area. An understanding of the stratigraphic units, visible at outcrop, seismic and well scales, providedmore » the appropriated framework for the analysis. Seismic facies, detailed log and core analysis allowed us to generate paleogeographic maps and predict the reservoir distribution into each individual stratigraphic unit, Fluvial channels, overbank, crevasses splay, mouth-bar, interdistributary and delta front facies were recognized. Finally, the integrated model was compared and adjusted with the outcrop data. As a result of this study, exploratory and development wells were proposed, being all of them productive either gas or oil. Several of the new drilled wells found new productive horizons with original reservoir pressure, proving the presence of different tanks predicted by the model. This fact encourages the evaluation of the whole adjacent areas. Summing up, this integrated approach using the best outputs of the geology and geophysics in subsurface as well as in surface has been proved as a powerful tool to explore and reactivate a very mature area.« less

{open_quotes}Rejuvenation{close_quotes} of a very mature productive area: Application of sequence stratigraphy, depositional facies and reservoir architectural studies in inactive old fields - Dorsal de Huincul - Neuquen Basin, Argentina

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

Kokogian, D.A.; Vasquez, J.R.

1996-12-31

The project objectives were to define the upside potential and identified drilling locations, both for exploratory and development wells, in Loma Negra-Nl-Huincul old fields, inactive due to pressure depletion Fields are located in Dorsal de Huincul area (Huincul Range) which is a highly complex structure associated with a major transtensive-transpressive wrench system. Several angular unconformities are very noticeable, having eroded hundreds of meters of the stratigraphic column. Study was focused on the fluvial-deltaic sediments of the Cuyo Group (Bajocian-Bathonian), the main productive levels in the area. An understanding of the stratigraphic units, visible at outcrop, seismic and well scales, providedmore » the appropriated framework for the analysis. Seismic facies, detailed log and core analysis allowed us to generate paleogeographic maps and predict the reservoir distribution into each individual stratigraphic unit, Fluvial channels, overbank, crevasses splay, mouth-bar, interdistributary and delta front facies were recognized. Finally, the integrated model was compared and adjusted with the outcrop data. As a result of this study, exploratory and development wells were proposed, being all of them productive either gas or oil. Several of the new drilled wells found new productive horizons with original reservoir pressure, proving the presence of different tanks predicted by the model. This fact encourages the evaluation of the whole adjacent areas. Summing up, this integrated approach using the best outputs of the geology and geophysics in subsurface as well as in surface has been proved as a powerful tool to explore and reactivate a very mature area.« less

Analysis of fractures from borehole televiewer logs in a 500m deep hole at Xiaguan, Yunnan province, Southwest China

USGS Publications Warehouse

Zhai, Qingshan; Springer, J.E.; Zoback, M.D.

1990-01-01

Fractures from a 500 m deep hole in the Red River fault zone were analyzed using an ultrasonic borehole televiewer. Four hundred and eighty individual fractures were identified between 19 m and 465 m depth. Fracture frequency had no apparent relation to the major stratigraphic units and did not change systematically with depth. Fracture orientation, however, did change with stratigraphic position. The borehole intersected 14 m of Cenozoic deposits, 363 m of lower Ordovician clastic sediments, and 106 m of older ultramafic intrusions. The clastic sequence was encountered again at a depth of 484 m, suggesting a large fault displacement. Fractures in the top 162 m of the sedimentary section appear randomly distributed. Below that depth, they are steeply dipping with northerly and north-westerly strikes, parallel to the major active faults in the region. Fractures in the ultramafic section strike roughly eastwest and are steeply dipping. These orientations are confined to the ultramafic section and are parallel to an older, inactive regional fault set. ?? 1990.

Triassic North American paleodrainage networks and sediment dispersal of the Chinle Formation: A quantitative approach utilizing detrital zircons

NASA Astrophysics Data System (ADS)

Blum, M. D.; Umbarger, K.

2017-12-01

The Triassic Chinle Formation is a fluvial succession deposited in a backarc setting across the present-day Colorado Plateau of the southwestern United States. Existing studies have proposed various mechanisms responsible for the unique stratigraphic architecture and depositional sequences of the Chinle. However, these studies lack necessary age control to correlate stratigraphic patterns with contemporaneous mechanisms. This study will collect new samples for detrital zircon analysis, as well as upgrade existing samples (to n=300) from Dickinson and Gehrels (2008), to improve the resolution of Triassic sediment provenance from source-to-sink. The improved dataset allows appraisal of the multiple provenance terranes that contributed to the Chinle depositional system to delineate and reconstruct paleodrainage patterns. The additional samples will be collected systematically from the base of the Chinle, and vertically throughout the section to capture a regional story of how the continental scale drainage reorganized through time. U-Pb ages of detrital zircons will be utilized to provide quantitative fingerprinting information to constrain interpretations for the origin and transport history of the Chinle fluvial succession in time and space.

A Group Simulation of the Development of the Geologic Time Scale.

ERIC Educational Resources Information Center

Bennington, J. Bret

2000-01-01

Explains how to demonstrate to students that the relative dating of rock layers is redundant. Uses two column diagrams to simulate stratigraphic sequences from two different geological time scales and asks students to complete the time scale. (YDS)

The Oligocene-Miocene stratigraphic evolution of the Majella carbonate platform (Central Apennines, Italy)

NASA Astrophysics Data System (ADS)

Brandano, Marco; Cornacchia, Irene; Raffi, Isabella; Tomassetti, Laura

2016-03-01

The stratigraphic architecture of the Bolognano Formation documents the evolution of the Majella carbonate platform in response to global and local changes that affected the Mediterranean area during the Oligocene-Miocene interval. The Bolognano Formation consists of a homoclinal ramp that developed in a warm, subtropical environment. Five different lithofacies associations have been identified: Lepidocyclina calcarenites, cherty marly limestones, bryozon calcarenites, hemipelagic marls and marly limestones, and Lithothamnion limestones. Each association corresponds to a single lithostratigraphic unit except for the Lepidocyclina calcarenites that form two distinct lithostratigraphic units (Lepidocyclina calcarenites 1 and 2). These six units reflect alternation of shallow-water carbonate production and drowning. Specifically, two of the three stages of shallow-water carbonate production regard the development of wide dune fields within the middle ramp, one stage dominated by red algae and a sea-grass carbonate factory, whereas the two drowning phases are represented by marly cherty limestones and calcareous marls. A new biostratigraphic framework for Bolognano Formation is presented, based on high-resolution analysis of calcareous nannofossil assemblages, which proved to be very useful for biostratigraphic constraints also in shallow-water settings. Using this approach, we have linked the first drowning phase, late Chattian-Aquitanian p.p. in age, to western Mediterranean volcanism and the Mi-1 event, and the second drowning phase, late Burdigalian-Serravallian in age, to the closure of the Indo-Pacific passage and the occurrence of the global Monterey event. These results permit a new deciphering, in terms of sequence stratigraphy, of the Bolognano Formation that is interpreted as a 2nd-order super-sequence that can be subdivided into 3 transgressive-regressive sequences.

Environmental and faunal change in the Jurassic Sundance Seaway, western United States: a stratigraphic palaeobiological approach

NASA Astrophysics Data System (ADS)

Danise, Silvia; Holland, Steven

2017-04-01

Understanding how regional ecosystems respond to sea level and environmental perturbations is a main challenge in palaeoecology. Here we use quantitative abundance estimates, integrated within a sequence stratigraphic and environmental framework, to reconstruct benthic community changes through the 13 myr history of the Jurassic Sundance Seaway in the western United States. Faunal censuses of macroinvertebrates were obtained from marine rocks of the Gypsum Spring, Sundance and Twin Creek formations at 44 localities in Wyoming, Montana and South Dakota. Fossils were identified to species wherever possible. Ordination of samples shows a main turnover event at the Middle-Upper Jurassic transition, which coincided with the shift from carbonate to siliciclastic depositional systems in the Seaway. This shift was probably initiated by the northward migration of the North American Plate, which moved the study area from subtropical latitudes, fostering an arid climate, into progressively more humid conditions, and possibly also by global cooling at this time. Turnover was not uniform across the onshore-offshore gradient, but was higher in offshore environments, in both carbonate and siliciclastic settings. Both the Jaccard and the Bray-Curtis similarity measures indicate that taxonomic similarity decreases from onshore to offshore in successive third-order depositional sequences, although similarity values are low for both onshore and offshore environments The higher resilience of onshore communities to third-order sea-level fluctuations and to the change from a carbonate to a siliciclastic system was driven by a few abundant eurytopic species that persisted from the opening to the closing of the Seaway and that were not restricted to single depositional environments or sequences. Lower stability in offshore facies was instead controlled by the presence of more volatile stenotopic species. Such increased onshore stability in community composition contrasts with the well-documented onshore increase in taxonomic turnover rates, and indicates the need for ecological studies to complement taxonomic studies of macroevolutionary events. This study also shows how a stratigraphic palaeobiological approach is essential for understanding the link between environmental and faunal gradients, and for understanding the long-term changes in these gradients over time that produce the local stratigraphical pattern of changes in community composition.

Geochemistry and stratigraphic correlation of basalt lavas beneath the Idaho Chemical Processing Plant, Idaho National Engineering Laboratory

USGS Publications Warehouse

Reed, M.F.; Bartholomay, R.C.; Hughes, S.S.

1997-01-01

Thirty-nine samples of basaltic core were collected from wells 121 and 123, located approximately 1.8 km apart north and south of the Idaho Chemical Processing Plant at the Idaho National Engineering Laboratory. Samples were collected from depths ranging from 15 to 221 m below land surface for the purpose of establishing stratigraphic correlations between these two wells. Elemental analyses indicate that the basalts consist of three principal chemical types. Two of these types are each represented by a single basalt flow in each well. The third chemical type is represented by many basalt flows and includes a broad range of chemical compositions that is distinguished from the other two types. Basalt flows within the third type were identified by hierarchical K-cluster analysis of 14 representative elements: Fe, Ca, K, Na, Sc, Co, La, Ce, Sm, Eu, Yb, Hf, Ta, and Th. Cluster analyses indicate correlations of basalt flows between wells 121 and 123 at depths of approximately 38-40 m, 125-128 m, 131-137 m, 149-158 m, and 183-198 m. Probable correlations also are indicated for at least seven other depth intervals. Basalt flows in several depth intervals do not correlate on the basis of chemical compositions, thus reflecting possible flow margins in the sequence between the wells. Multi-element chemical data provide a useful method for determining stratigraphic correlations of basalt in the upper 1-2 km of the eastern Snake River Plain.

Role of different types of solid models in hydrodynamic modeling and their effects on groundwater protection processes

NASA Astrophysics Data System (ADS)

Bódi, Erika; Buday, Tamás; McIntosh, Richard William

2013-04-01

Defining extraction-modified flow patterns with hydrodynamic models is a pivotal question in preserving groundwater resources regarding both quality and quantity. Modeling is the first step in groundwater protection the main result of which is the determination of the protective area depending on the amount of extracted water. Solid models have significant effects on hydrodynamic models as they are based on the solid models. Due to the legislative regulations, on protection areas certain restrictions must be applied which has firm consequences on economic activities. In Hungarian regulations there are no clear instructions for the establishment of either geological or hydrodynamic modeling, however, modeling itself is an obligation. Choosing the modeling method is a key consideration for further numerical calculations and it is decisive regarding the shape and size of the groundwater protection area. The geometry of hydrodynamic model layers is derived from the solid model. There are different geological approaches including lithological and sequence stratigraphic classifications furthermore in the case of regional models, formation-based hydrostratigraphic units are also applicable. Lithological classification is based on assigning and mapping of lithotypes. When the geometry (e.g. tectonic characteristics) of the research area is not known, horizontal bedding is assumed the probability of which can not be assessed based on only lithology. If the geological correlation is based on sequence stratigraphic studies, the cyclicity of sediment deposition is also considered. This method is more integrated thus numerous parameters (e.g. electrofacies) are taken into consideration studying the geological conditions ensuring more reliable modeling. Layers of sequence stratigraphic models can be either lithologically homogeneous or they may include greater cycles of sediments containing therefore several lithological units. The advantage of this is that the modeling can handle pinching out lithological units and lenticular bodies easier while most hydrodynamic softwares cannot handle flow units related to such model layers. Interpretation of tectonic disturbance is similar. In Hungary groundwater is extracted mainly from Pleistocene and Pannonian aquifers sediments of which were deposited in the ancient Pannonian Lake. When the basin lost its open-marine connection eustasy had no direct effects on facies changes therefore subsidence and sediment supply became the main factors. Various basin-filling related facies developed including alluvial plain facies, different delta facies types and pelitic deep-basin facies. Creating solid models based on sequence stratigraphic methods requires more raw data and also genetic approaches, in addition more working hours hence this method is seldom used in practice. Lithology-based models can be transformed into sequence stratigraphic models by extending the data base (e.g. detecting more survey data). In environments where the obtained models differ significantly notable changes can occur in the supply directions in addition the groundwater travel-time of the two models even on equal extraction terms. Our study aims to call attention to the consequences of using different solid models for typical depositional systems of the Great Hungarian Plain and to their effects on groundwater protection.

Regional High-Frequency Stratigraphic Cyclicity Analysis of the Upper Cretaceous Juana Lopez Member of the Mancos Shale, New Mexico

NASA Astrophysics Data System (ADS)

Wiercigroch, M.; Bhattacharya, J.

2017-12-01

The Earth is considered to have been in a "greenhouse state" during the Cretaceous Period. High-frequency sedimentary cycles are observed throughout the Cretaceous section of the Western Interior Seaway. Even though this warm Cretaceous climate suggests an ice-free planet Earth, there has been much debate as to whether the observed high-frequency sedimentary cycles are climate-driven Milankovitch-scale cycles that would suggest glaciers during the Cretaceous Period. This study tests the hypothesis of a glacio-eustatic origin of high-frequency cyclicity in the Turonian Juana Lopez Member of the Mancos Shale in the San Juan Basin, New Mexico. Data for this study was obtained from two stratigraphic measured sections which are 3.2 km apart, and located southwest of Shiprock. The two sections are found approximately 60 km away from the Turonian shoreline in an offshore marine environment. A high-resolution thin bed facies analysis on both sections reveals the Juana Lopez to be deposited in a fluvial-dominated, mixed wave- and fluvial-influenced environment. The Juana Lopez is shown to be an overall coarsening-upward sequence, displaying a shallowing regressive environment. Correlations between the two sections reveal 13 correlated parasequences identified through the violation of Walther's Law. An average cyclicity frequency of ca 90 kyr was determined for the sequences by bracketing the Inocermus dimidus and Scaphites whitfieldi biostratigraphic zones within the Juana Lopez sections. This cyclicity represents short eccentricity Milankovitch cycles. Many studies have confirmed that the observed Milankovitch-scaled cyclicity in the Cretaceous must be controlled by glacio-eustasy. With similar Milankovitch cyclicity found in the Juana Lopez, the short eccentricity Milankovitch cycles are interpreted as being glacio-eustatic in origin, which supports the presence of ice in the Cretaceous Period.

Micromorphological aspects of various human activities recorded in the Scafati pedocomplex (Napoli, Italy).

NASA Astrophysics Data System (ADS)

Rellini, Ivano; Vogel, Sebastian; Märker, Michael

2014-05-01

The stratigraphic sequence of Scafati, about 3 km east of ancient Pompeii, is presented consisting of a multilayered sequence of repeated volcanic deposition and pedogenesis that was caused by several phases of volcanic activity and volcanic quiescence of Somma-Vesuvius, at least, the last 20,000 years. Micromorphological analysis were carried out at the soil material and selected volcanic deposits to establish a chronological succession of different phases of volcanic deposition, pedogenetic transformation but also to highlight the anthropogenic influence. The micromorphological analysis testified furrow irrigation and soil cultivation in the medieval stratigraphy and allowed the identification of very significant antropogenic features in the Bronze Age/Iron Age paleosol, i.e. complex depositional crusts and dusty clay coatings and hypocoatings, which are often used as an indicator for tillage activity. In contrast to the clear macroscopic and chemical evidence of ancient soil cultivation, the Roman paleosol did not exhibit distinct micromorphological signs of soil cultivation.

The Summerville Formation: Evidence for a sub-horizontal stratigraphic sequence below the post-rift unconformity in the Middleton Place Summerville Seismic Zone

NASA Astrophysics Data System (ADS)

Getz, Joseph Edward

The Middleton Place Summerville Seismic Zone (MPSSZ) near Summerville, South Carolina was the site of renewed extensive investigation, beginning in the 1970's, for the source of the 1886 Charleston earthquake. Reactivation of faults associated with a putative fault-bounded Triassic rift basin through analysis of seismic reflection, seismic refraction, and well data has since become the favored interpretation for the source of MPSSZ seismicity. Critical to this interpretation is the association of continental redbed sedimentary rocks with Triassic basins identified throughout the North American Atlantic margin. Reanalysis of 18 seismic reflection profiles and 25 seismic refraction profiles within the MPSSZ suggests that the red beds found here are a thin, sub-horizontal, regionally extensive, generally unbroken subsurface stratigraphic sequence distinct from the sedimentary architecture observed in analog Triassic rift systems. In addition, this sequence appears to unconformably overly a structural depression (the Jedberg basin) previously interpreted as a Triassic rift basin in the vicinity of the MPSSZ. In addition to the geometries observed on seismic reflection profiles, seismic refraction velocities ranging from 4.2 to 6.1 km/s can be correlated with (1) Jurassic basalt flows, (2) the newly proposed Summerville Formation, and (3) the Basement (B) sequences respectively. The current study maps the Summerville red bed section and its bounding reflectors. In addition to mapping the regional extent of the newly proposed Summerville Formation, refraction velocities and changes in reflection character, the lateral extent of the basalt flows can be changed to a more localized flow rather than a regionally extensive flow of which was previously thought. Reanalysis of data in the MPSSZ suggests that the area may not be part of the Triassic South Georgia Rift system due to the sub-horizontal geometry of the red bed reflections, the apparent lack of faulting, and their regional extent.

Seismic stratigraphy of barrier-island arc retreat paths in Mississippi River delta

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

Penland, S.; Suter, J.R.

1983-09-01

The stratigraphic record preserved in the retreat path of Mississippi delta barrier-island arcs is controlled by erosional shoreface retreat processes, relative sea level rise, and sediment supply. More than 500 km (300 mi) of high resolution shallow seismic profiles correlated with vibracores from retreat paths fronting the Isles Dernieres and Chandeleur barrier-island arcs, show contrasting stratigraphic sequences preserved on the inner continental shelf (Mississippian delta). The Isles Dernieres barrier-island arc developed as a consequence of the Caillou Headland abandonment in the early Lafourche delta approximately 800 years B.P. On the lower shoreface, channels can be seen projecting seaward under themore » central part of the island arc; associated with it is a beach-ridge plain extending eastward. On the inner shelf, a sand sheet up to 60 cm (2 ft) thick marks the retreat path of the Isles Dernieres. The Chandeleur barrier-island arc was generated by abandonment of the St. Bernard delta complex 1,500 years ago. Scattered outcrops of shell reefs and lagoonal deposits occur on the lower shoreface. Beyond the shoreface, a 1 to 5 m (3 to 16 ft) thick sand sheet, caps tidal inlet scars up to 10 m (33 ft) thick, as well as the basal portions of migrating barrier-island sequences associated with earlier shoreline positions. Differences seen in the two stratigraphic sequences are a function of distributary size and depositional history of each barrier-island arc. The Isles Dernieres developed from a series of small sand-deficient distributaries in the Lafourche delta complex, whereas the Chandeleur Islands developed from large sand-rich distributaries of the St. Bernard delta complex.« less

Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives

NASA Astrophysics Data System (ADS)

Govin, A.; Capron, E.; Tzedakis, P. C.; Verheyden, S.; Ghaleb, B.; Hillaire-Marcel, C.; St-Onge, G.; Stoner, J. S.; Bassinot, F.; Bazin, L.; Blunier, T.; Combourieu-Nebout, N.; El Ouahabi, A.; Genty, D.; Gersonde, R.; Jimenez-Amat, P.; Landais, A.; Martrat, B.; Masson-Delmotte, V.; Parrenin, F.; Seidenkrantz, M.-S.; Veres, D.; Waelbroeck, C.; Zahn, R.

2015-12-01

The Last Interglacial (LIG) represents an invaluable case study to investigate the response of components of the Earth system to global warming. However, the scarcity of absolute age constraints in most archives leads to extensive use of various stratigraphic alignments to different reference chronologies. This feature sets limitations to the accuracy of the stratigraphic assignment of the climatic sequence of events across the globe during the LIG. Here, we review the strengths and limitations of the methods that are commonly used to date or develop chronologies in various climatic archives for the time span (∼140-100 ka) encompassing the penultimate deglaciation, the LIG and the glacial inception. Climatic hypotheses underlying record alignment strategies and the interpretation of tracers are explicitly described. Quantitative estimates of the associated absolute and relative age uncertainties are provided. Recommendations are subsequently formulated on how best to define absolute and relative chronologies. Future climato-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations. Finally, we provide a sequence of major climatic events with associated age uncertainties for the period 140-105 ka, which should serve as a new benchmark to disentangle mechanisms of the Earth system's response to orbital forcing and evaluate transient climate simulations.

Automated recognition of stratigraphic marker shales from geophysical logs in iron ore deposits

NASA Astrophysics Data System (ADS)

Silversides, Katherine; Melkumyan, Arman; Wyman, Derek; Hatherly, Peter

2015-04-01

The mining of stratiform ore deposits requires a means of determining the location of stratigraphic boundaries. A variety of geophysical logs may provide the required data but, in the case of banded iron formation hosted iron ore deposits in the Hamersley Ranges of Western Australia, only one geophysical log type (natural gamma) is collected for this purpose. The information from these logs is currently processed by slow manual interpretation. In this paper we present an alternative method of automatically identifying recurring stratigraphic markers in natural gamma logs from multiple drill holes. Our approach is demonstrated using natural gamma geophysical logs that contain features corresponding to the presence of stratigraphically important marker shales. The host stratigraphic sequence is highly consistent throughout the Hamersley and the marker shales can therefore be used to identify the stratigraphic location of the banded iron formation (BIF) or BIF hosted ore. The marker shales are identified using Gaussian Processes (GP) trained by either manual or active learning methods and the results are compared to the existing geological interpretation. The manual method involves the user selecting the signatures for improving the library, whereas the active learning method uses the measure of uncertainty provided by the GP to select specific examples for the user to consider for addition. The results demonstrate that both GP methods can identify a feature, but the active learning approach has several benefits over the manual method. These benefits include greater accuracy in the identified signatures, faster library building, and an objective approach for selecting signatures that includes the full range of signatures across a deposit in the library. When using the active learning method, it was found that the current manual interpretation could be replaced in 78.4% of the holes with an accuracy of 95.7%.

Stratigraphic and structural configuration of the Navajo (Jurassic) through Ouray (Mississippian-Devonian) formations in the vicinity of Davis and Lavender Canyons, southeastern Utah

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

McCleary, J.R.; Romie, J.E.

1986-04-01

This study developed a three-dimensional computer model of stratigraphic and structural relationships within a 3497-km/sup 2/ (1350-mi/sup 2/) study area centered on the proposed site for a high-level nuclear waste repository in southeastern Utah. The model consists of a sequence of internally reconciled isopach and structure contour maps horizontally registered and stored in stratigraphic order. This model can be used to display cross sections, perspective block diagrams, or fence diagrams at any orientation; estimate depth of formation contacts and thicknesses for any new stratigraphic or hydrologic boreholes; facilitate ground-water modeling studies; and evaluate the structural and stratigraphic evolution of themore » study area. This study also includes limited evaluations of aquifer continuity in the Elephant Canyon and Honaker Trail Formations, and of salt dissolution and flowage features as interpreted from geophysical logs. The study identified a long history of movement in the fault system in the north-central part of the study area and a major salt flowage feature in the northeastern part. It describes the Elephant Canyon Formation aquifer as laterally limited, the Honaker Trail Formation aquifer as fairly continuous over the area, and Beef Basin in the southern part of the area as a probable dissolution feature. It also concludes that the Shay-Bridger Jack-Salt Creek Graben system is apparently a vertically continuous feature between the basement and ground surface. No stratigraphic or structural discontinuities were detected in the vicinity of Davis Canyon that appear to be detrimental to the siting of a waste repository.« less

Stratigraphic Stacking of Deepmarine Channel Levee Turbidites: Scales of Cyclicity and their Origin. Examples from the Laingsburg Fm. (Karoo, South Africa) and the Rosario Fm. (Baja, Mexico)

NASA Astrophysics Data System (ADS)

Kane, I. A.; Hodgson, D.

2009-12-01

Thinning upwards of the turbidite beds that form deepmarine channel levees is a common motif reported from modern and recent levees on the seafloor, from subsurface examples, and from outcropping ancient examples. Because levees are thought to be built by deposition from turbidity currents superelevated over their channel form, the volume and style of overbank deposition are controlled primarily by the relationship between levee height (i.e., thalweg to crest) and flow thickness, determining the amount of overspill. Thus stratigraphic variability of turbidite thickness is explained by some change in either or both of those factors, which may arise autocyclicly or allocyclicly. Variation in the ratio of intra-channel and extra-channel deposition can be an autocyclic stratigraphic response, e.g., in bypass dominated systems, thalweg aggradation may be retarded with respect to levee aggradation, hence as levee relief increases, flows become more confined and, given a relatively narrow range of flow sizes, the volume of overbank flow and deposit thickness decrease with stratigraphic height. However, the same stratigraphic response of the levee may occur due to allocyclic flow magnitude variation, i.e., through decreasing flow magnitude. In both the autocyclic and allocyclic case the stratigraphic response of the levee may be one of thinning upwards, even if the overall system response may be one of progradation (autocyclic bypassing case) or retrogradation (allocyclic decreasing flow magnitude case), with entirely different connotations for sequence stratigraphic interpretation. Here we report examples of different scales of bed thickness cyclicity (both thickening and thinning upward cycles superimposed by smaller scale cycles) within levees of the Rosario Formation, Baja California, Mexico, and from the Laingsburg Formation, Karoo, South Africa, and, together with published examples, discuss criteria for the recognition, and drivers of, autocyclic and allocyclic bed thickness trends.

Completed Ensemble Empirical Mode Decomposition: a Robust Signal Processing Tool to Identify Sequence Strata

NASA Astrophysics Data System (ADS)

Purba, H.; Musu, J. T.; Diria, S. A.; Permono, W.; Sadjati, O.; Sopandi, I.; Ruzi, F.

2018-03-01

Well logging data provide many geological information and its trends resemble nonlinear or non-stationary signals. As long well log data recorded, there will be external factors can interfere or influence its signal resolution. A sensitive signal analysis is required to improve the accuracy of logging interpretation which it becomes an important thing to determine sequence stratigraphy. Complete Ensemble Empirical Mode Decomposition (CEEMD) is one of nonlinear and non-stationary signal analysis method which decomposes complex signal into a series of intrinsic mode function (IMF). Gamma Ray and Spontaneous Potential well log parameters decomposed into IMF-1 up to IMF-10 and each of its combination and correlation makes physical meaning identification. It identifies the stratigraphy and cycle sequence and provides an effective signal treatment method for sequence interface. This method was applied to BRK- 30 and BRK-13 well logging data. The result shows that the combination of IMF-5, IMF-6, and IMF-7 pattern represent short-term and middle-term while IMF-9 and IMF-10 represent the long-term sedimentation which describe distal front and delta front facies, and inter-distributary mouth bar facies, respectively. Thus, CEEMD clearly can determine the different sedimentary layer interface and better identification of the cycle of stratigraphic base level.

An application of sedimentation simulation in Tahe oilfield

NASA Astrophysics Data System (ADS)

Tingting, He; Lei, Zhao; Xin, Tan; Dongxu, He

2017-12-01

The braided river delta develops in Triassic low oil formation in the block 9 of Tahe oilfield, but its sedimentation evolution process is unclear. By using sedimentation simulation technology, sedimentation process and distribution of braided river delta are studied based on the geological parameters including sequence stratigraphic division, initial sedimentation environment, relative lake level change and accommodation change, source supply and sedimentary transport pattern. The simulation result shows that the error rate between strata thickness of simulation and actual strata thickness is small, and the single well analysis result of simulation is highly consistent with the actual analysis, which can prove that the model is reliable. The study area belongs to braided river delta retrogradation evolution process, which provides favorable basis for fine reservoir description and prediction.

Late Devonian shale deposition based on known and predicted occurrence of Foerstia in Michigan basin

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

Matthews, R.D.

The fossil Foerstia (Protosalvinia) marks a time zone within Late Devonian shale sequences in the eastern US. Its recent discovery in Michigan has led to more accurate correlations among the three large eastern basins. Subdivisions of the Devonian-Mississippi shale sequence in Michigan based on gamma-ray correlations reveal an idealized black shale geometry common to other eastern black shales, such as the Sunbury of Michigan and Ohio, the Clegg Creek of Indiana, the Dunkirk of Pennsylvania and New York, and the lower Huron of Ohio and West Virginia. In Michigan, Foerstia occurs at a stratigraphic position postulated to mark a majormore » change in depositional conditions and source areas. This position strengthens the physical and paleontologic evidence for a formal division of the Antrim. Isopach maps of the shale sequence above and below Foerstia show a relatively uniform and continuous black shale deposit (units 1A, 1B, and 1C) below Foerstia. This deposit is unlike the wedge of sediment found above Foerstia, which is composed of a western facies (Ellsworth) and an eastern facies (upper Antrim) that should be combined in a single stratigraphic unit conforming to Forgotson's concept of a format.« less

First high-resolution stratigraphic column of the Martian north polar layered deposits

USGS Publications Warehouse

Fishbaugh, K.E.; Hvidberg, C.S.; Byrne, S.; Russell, P.S.; Herkenhoff, K. E.; Winstrup, M.; Kirk, R.

2010-01-01

This study achieves the first high-spatial-resolution, layer-scale, measured stratigraphic column of the Martian north polar layered deposits using a 1m-posting DEM. The marker beds found throughout the upper North Polar Layered Deposits range in thickness from 1.6 m-16.0 m +/-1.4 m, and 6 of 13 marker beds are separated by ???25-35 m. Thin-layer sets have average layer separations of 1.6 m. These layer separations may account for the spectral-power-peaks found in previous brightness-profile analyses. Marker-bed layer thicknesses show a weak trend of decreasing thickness with depth that we interpret to potentially be the result of a decreased accumulation rate in the past, for those layers. However, the stratigraphic column reveals that a simple rhythmic or bundled layer sequence is not immediately apparent throughout the column, implying that the relationship between polar layer formation and cyclic climate forcing is quite complex. Copyright ?? 2010 by the American Geophysical Union.

First high-resolution stratigraphic column of the Martian north polar layered deposits

NASA Astrophysics Data System (ADS)

Fishbaugh, Kathryn E.; Hvidberg, Christine S.; Byrne, Shane; Russell, Patrick S.; Herkenhoff, Kenneth E.; Winstrup, Mai; Kirk, Randolph

2010-04-01

This study achieves the first high-spatial-resolution, layer-scale, measured stratigraphic column of the Martian north polar layered deposits using a 1m-posting DEM. The marker beds found throughout the upper North Polar Layered Deposits range in thickness from 1.6 m-16.0 m +/- 1.4 m, and 6 of 13 marker beds are separated by ˜25-35 m. Thin-layer sets have average layer separations of 1.6 m. These layer separations may account for the spectral-power-peaks found in previous brightness-profile analyses. Marker-bed layer thicknesses show a weak trend of decreasing thickness with depth that we interpret to potentially be the result of a decreased accumulation rate in the past, for those layers. However, the stratigraphic column reveals that a simple rhythmic or bundled layer sequence is not immediately apparent throughout the column, implying that the relationship between polar layer formation and cyclic climate forcing is quite complex.

Paleocene Wilcox cross-shelf channel-belt history and shelf-margin growth: Key to Gulf of Mexico sediment delivery

NASA Astrophysics Data System (ADS)

Zhang, Jinyu; Steel, Ronald; Ambrose, William

2017-12-01

Shelf margins prograde and aggrade by the incremental addition of deltaic sediments supplied from river channel belts and by stored shoreline sediment. This paper documents the shelf-edge trajectory and coeval channel belts for a segment of Paleocene Lower Wilcox Group in the northern Gulf of Mexico based on 400 wireline logs and 300 m of whole cores. By quantitatively analyzing these data and comparing them with global databases, we demonstrate how varying sediment supply impacted the Wilcox shelf-margin growth and deep-water sediment dispersal under greenhouse eustatic conditions. The coastal plain to marine topset and uppermost continental slope succession of the Lower Wilcox shelf-margin sediment prism is divided into eighteen high-frequency ( 300 ky duration) stratigraphic sequences, and further grouped into 5 sequence sets (labeled as A-E from bottom to top). Sequence Set A is dominantly muddy slope deposits. The shelf edge of Sequence Sets B and C prograded rapidly (> 10 km/Ma) and aggraded modestly (< 80 m/Ma). The coeval channel belts are relatively large (individually averaging 11-13 m thick) and amalgamated. The water discharge of Sequence Sets B and C rivers, estimated by channel-belt thickness, bedform type, and grain size, is 7000-29,000 m3/s, considered as large rivers when compared with modern river databases. In contrast, slow progradation (< 10 km/Ma) and rapid aggradation (> 80 m/Ma) characterizes Sequence Sets D and E, which is associated with smaller (9-10 m thick on average) and isolated channel belts. This stratigraphic trend is likely due to an upward decreasing sediment supply indicated by the shelf-edge progradation rate and channel size, as well as an upward increasing shelf accommodation indicated by the shelf-edge aggradation rate. The rapid shelf-edge progradation and large rivers in Sequence Sets B and C confirm earlier suggestions that it was the early phase of Lower Wilcox dispersal that brought the largest deep-water sediment volumes into the Gulf of Mexico. Key factors in this Lower Wilcox stratigraphic trend are likely to have been a very high initial sediment flux to the Gulf because of the high initial release of sediment from Laramide catchments to the north and northwest, possibly aided by modest eustatic sea-level fall on the Texas shelf, which is suggested by the early, flat shelf-edge trajectory, high amalgamation of channel belts, and the low overall aggradation rate of the Sequence Sets B and C.

Sea-level and environmental changes around the Devonian-Carboniferous boundary in the Namur-Dinant Basin (S Belgium, NE France): A multi-proxy stratigraphic analysis of carbonate ramp archives and its use in regional and interregional correlations

NASA Astrophysics Data System (ADS)

Kumpan, Tomáš; Bábek, Ondřej; Kalvoda, Jiří; Matys Grygar, Tomáš; Frýda, Jiří

2014-08-01

The paper focuses on high-resolution multidisciplinary research on three Devonian-Carboniferous boundary sections in shallow-water carbonate rocks in the Namur-Dinant Basin (Belgium, France). The aim of the study is to provide palaeo-environmental reconstructions and correlations supported by several independent quantitative proxies. We describe several correlative horizons and provide their sequence-stratigraphic interpretation based on facies analysis, spectral gamma-ray data, element concentrations (XRF) and δ13Ccarb, with foraminifer-biostratigraphy age control. The most prominent surface is a basal surface of forced regression, which is indicated by a sharp basinwards facies shift and a drop in clay-gamma-ray values and Al concentrations at the base of the Hastière and Avesnelles formations in more distal settings. In proximal settings, this surface merges with a hiatus at the Devonian-Carboniferous boundary inferred from foraminifer biostratigraphy. This hiatus can be correlated with the global Hangenberg sandstone event, which indicates a glacioeustatic sea-level fall. Increasing values of Zr/Al, K/Al, Sr/Al and Mn/Al coincide with the proximal facies of the falling stage system tract and lowstand system tract in the Hastière and Avesnelles formations as a consequence of the enhanced input of siliciclastics and nutrients during low sea levels. The top of the middle Hastière member is interpreted as the maximum regression surface, which is overlain by transgressive system tract of the upper Hastière member. The patterns of gamma-ray, δ13Ccarb, Th/K, Al and Zr/Al curves are well correlated between the studied sections. The δ13Ccarb excursions are correlated with the unnamed excursion in the Upper expansa conodont zone (Carnic Alps) and with the global Hangenberg event s.l. excursion in the kockeli conodont zone. This sequence-stratigraphic framework is used for correlations with deltaic successions from the Tafilalt Basin, Morocco. The basal surface of the forced regression equivalent to the Hangenberg sandstone event, which is typical for deeper-water settings, is easily recognisable and correlatable with gaps in more-shallow water settings. We suggest that it should be taken into account as a possible candidate for the “natural solution” of the Devonian-Carboniferous boundary in discussions concerning its redefinition.

Problems of geological and isotopic age of the Okhotsk-Chukotsk Volcanogenic Belt (OCVB)

NASA Astrophysics Data System (ADS)

Belyi, V. F.

2008-12-01

The working stratigraphic chart accepted for the Okhotsk-Chukotsk Volcanogenic Belt (OCVB) at the 3rd Interdepartmental Regional Stratigraphic Conference (IRSC) integrated data of the medium-scale geological survey, the established succession of endemic floras of the developing volcanic highland, and the results of palynological and magnetostratigraphic study ( Resolutions of the 3rd…, 2003). The OCVB was formed during the middle Albian-Santonian (and initial Campanian probably). Sequences of the belt are attributed to the Buor-Kemyus (early-middle Albian), Arman (late Albian), Amka (Cenomanian), and Arkagala (Turonian-Santonian) phytostratigraphic horizons. The lack of data on relations between the horizons and fauna-bearing marine deposits is a serious obstacle for correlation of regional subdivisions with the general stratigraphic scale. The problem can be solved using geological methods of palynological and tephrochronological research. Isotopic ages of the OCVB rocks were determined applying the K-Ar and Rb-Sr isotopic dating in the early period and the Ar-Ar and U-Pb (SHRIMP) methods in recent years. The subdivision scheme of the OCVB volcanics based on the K-Ar relict and Rb-Sr isochron dates, which is accepted as addendum to the working stratigraphic chart, confirms in general the geological inferences concerning the OCVB age. The Ar-Ar and U-Pb dates (less than 100 determinations in total) obtained for the Okhotsk, Central Chukotsk, and Anadyr sectors of the OCVB external zone provoked opinions that the belt age should be radically revised. Analysis of new isotopic dates showed that they contradict in variable extent to geological data on the Okhotsk and Central Chukotsk sectors, whereas there is no significant discordance between isotopic and geological data on the Anadyr sector. Consequently, it can be empirically concluded that geological factors influenced the isotopic systems (“clock”). There is also a considerable discordance between the Ar-Ar and U-Pb isotopic dates. These uncertainties of the isotopic dating imply prematurity of idea to revise age of the OCVB.

Sequence stratigraphy of the Aux Vases Sandstone: A major oil producer in the Illinois basin

USGS Publications Warehouse

Leetaru, H.E.

2000-01-01

The Aux Vases Sandstone (Mississippian) has contributed between 10 and 25% of all the oil produced in Illinois. The Aux Vases is not only an important oil reservoir but is also an important source of groundwater, quarrying stone, and fluorspar. Using sequence stratigraphy, a more accurate stratigraphic interpretation of this economically important formation can be discerned and thereby enable more effective exploration for the resources contained therein. Previous studies have assumed that the underlying Spar Mountain, Karnak, and Joppa formations interfingered with the Aux Vases, as did the overlying Renault Limestone. This study demonstrates that these formations instead are separated by sequence boundaries; therefore, they are not genetically related to each other. A result of this sequence stratigraphic approach is the identification of incised valleys, paleotopography, and potential new hydrocarbon reservoirs in the Spar Mountain and Aux Vases. In eastern Illinois, the Aux Vases is bounded by sequence boundaries with 20 ft (6 m) of relief. The Aux Vases oil reservoir facies was deposited as a tidally influenced siliciclastic wedge that prograded over underlying carbonate-rich sediments. The Aux Vases sedimentary succession consists of offshore sediment overlain by intertidal and supratidal sediments. Low-permeability shales and carbonates typically surround the Aux Vases reservoir sandstone and thereby form numerous bypassed compartments from which additional oil can be recovered. The potential for new significant oil fields within the Aux Vases is great, as is the potential for undrained reservoir compartments within existing Aux Vases fields.

Quantification of the effects of eustasy, subsidence, and sediment supply on Miocene sequences, mid-Atlantic margin of the United States

USGS Publications Warehouse

Browning, J.V.; Miller, K.G.; McLaughlin, P.P.; Kominz, M.A.; Sugarman, P.J.; Monteverde, D.; Feigenson, M.D.; Hernandez, J.C.

2006-01-01

We use backstripping to quantify the roles of variations in global sea level (eustasy), subsidence, and sediment supply on the development of the Miocene stratigraphic record of the mid-Atlantic continental margin of the United States (New Jersey, Delaware, and Maryland). Eustasy is a primary influence on sequence patterns, determining the global template of sequences (i.e., times when sequences can be preserved) and explaining similarities in Miocene sequence architecture on margins throughout the world. Sequences can be correlated throughout the mid-Atlantic region with Sr-isotopic chronology (??0.6 m.y. to ??1.2 m.y.). Eight Miocene sequences correlate regionally and can be correlated to global ??18O increases, indicating glacioeustatic control. This margin is dominated by passive subsidence with little evidence for active tectonic overprints, except possibly in Maryland during the early Miocene. However, early Miocene sequences in New Jersey and Delaware display a patchwork distribution that is attributable to minor (tens of meters) intervals of excess subsidence. Backstripping quantifies that excess subsidence began in Delaware at ca. 21 Ma and continued until 12 Ma, with maximum rates from ca. 21-16 Ma. We attribute this enhanced subsidence to local flexural response to the progradation of thick sequences offshore and adjacent to this area. Removing this excess subsidence in Delaware yields a record that is remarkably similar to New Jersey eustatic estimates. We conclude that sea-level rise and fall is a first-order control on accommodation providing similar timing on all margins to the sequence record. Tectonic changes due to movement of the crust can overprint the record, resulting in large gaps in the stratigraphic record. Smaller differences in sequences can be attributed to local flexural loading effects, particularly in regions experiencing large-scale progradation. ?? 2006 Geological Society of America.

Facies architecture and high resolution sequence stratigraphy of an aeolian, fluvial and shallow marine system in the Pennsylvanian Piauí Formation, Parnaíba Basin, Brazil

NASA Astrophysics Data System (ADS)

Vieira, Lucas Valadares; Scherer, Claiton Marlon dos Santos

2017-07-01

The Pennsylvanian Piauí Formation records the deposition of aeolian, fluvial and shallow marine systems accumulated in the cratonic sag Parnaíba basin. Characterization of the facies associations and sequence stratigraphic framework was done by detailed description and logging of outcrops. Six facies associations were recognized: aeolian dunes and interdunes, aeolian sandsheets, fluvial channels, tidally-influenced fluvial channels, shoreface and shoreface-shelf transition. Through correlation of stratigraphic surfaces, the facies associations were organized in system tracts, which formed eight high frequency depositional sequences, bounded by subaerial unconformities. These sequences are composed of a lowstand system tract (LST), that is aeolian-dominated or fluvial-dominated, a transgressive system tract (TST) that is formed by tidally-influenced fluvial channels and/or shoreface and shoreface-shelf transition deposits with retrogradational stacking, and a highstand system tract (HST), which is formed by shoreface-shelf transition and shoreface deposits with progradational stacking. Two low frequency cycles were determined by observing the stacking of the high frequency cycles. The Lower Sequence is characterized by aeolian deposits of the LST and an aggradational base followed by a progressive transgression, defining a general TST. The Upper Sequence is characterized by fluvial deposits and interfluve pedogenesis concurring with the aeolian deposits of the LST and records a subtle regression followed by transgression. The main control on sedimentation in the Piauí Formation was glacioeustasy, which was responsible for the changes in relative sea level. Even though, climate changes were associated with glacioeustatic phases and influenced the aeolian and fluvial deposition.

Changing Concepts of the Nature and Significance of Fossils.

ERIC Educational Resources Information Center

Gregory, Joseph T.

1984-01-01

Provides information on early written accounts of fossils and contrasts historical phases regarding their organic or inorganic origin. Topic areas discussed include the deluge as a stimulant to geological investigation, stratigraphic sequences and earth history, extinction, faunal succession and organic evolution, and fossil evidence of…

Revised Cretaceous and Tertiary stratigraphic nomenclature in the Colville Basin, Northern Alaska

USGS Publications Warehouse

Mull, Charles G.; Houseknecht, David W.; Bird, Kenneth J.

2003-01-01

A revised stratigraphic nomenclature is proposed for Cretaceous and Tertiary geologic units of the central and western North Slope of Alaska. This revised nomenclature is a simplified and broadly applicable scheme suitable for a suite of digital geologic quadrangle maps being prepared jointly by the U.S. Geological Survey and the Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys and Division of Oil and Gas. This revised nomenclature scheme is a simplification of a complex stratigraphic terminology that developed piecemeal during five decades of geologic investigations of the North Slope. It is based on helicopter-supported geologic field investigations incorporating information from high-resolution aerial photography, satellite imagery, paleontology, reflection seismic records, and sequence stratigraphic concepts. This revised nomenclature proposes the abandonment of the Colville Group; demotion of the Nanushuk Group to formation status; abandonment of six formations (Kukpowruk, Tuktu, Grandstand, Corwin, Chandler, and Ninuluk); revision of four formations (Sagavanirktok, Prince Creek, Schrader Bluff, and Seabee); elevation of the Tuluvak Tongue of the Prince Creek Formation to formation status; revision of two members (Franklin Bluffs Member and Sagwon Member of the Sagavanirktok Formation); abandonment of eight members or tongues (Kogosukruk, Rogers Creek, Barrow Trail, Sentinel Hill, Ayiyak, Shale Wall, Niakogon, and Killik); and definition of one new member (White Hills Member of the Sagavanirktok Formation).

Overview of Petroleum Settings in Deep Waters of the Brazilian South Atlantic Margin

NASA Astrophysics Data System (ADS)

Anjos, Sylvia; Penteado, Henrique; Oliveira, Carlos M. M.

2015-04-01

The objective of this work is to present an overall view of the tectonic and stratigraphic evolution of the western South Atlantic with focus on the Brazilian marginal basins. It includes the structural evolution, stratigraphic sequences, depositional environments and petroleum systems model along the Brazilian marginal basins. In addition, a description of the main petroleum provinces and selected plays including the pre-salt carbonates and post-salt turbidite reservoirs is presented. Source-rock ages and types, trap styles, main reservoir characteristics, petroleum compositions, and recent exploration results are discussed. Finally, an outlook and general assessment of the impact of the large pre-salt discoveries on the present-day and future production curves are given.

2D and 3D Modeling of the Stratigraphic Sequences at the Adriatic and Rhone Continental Margins

DTIC Science & Technology

2005-09-30

Grenerczy, D. Medak, S. Stein, and J. C. Weber (Eds.). The Adria Microplate : GPS Geodesy, Tectonics , and Hazards. Kluwer Academic Publisher, pp. 93-116... tectonics , and their influences on sequence architecture. John Swenson, with assistance from Chris Paola, Juan Fedele, myself and others have jointly...exploration of the margin’s response to variations in sea level, sediment supply, tectonic subsidence, and wave climate over longer timescales. I am

Intra-eruption changes in composition of some mafic to intermediate tephras in Central America

NASA Astrophysics Data System (ADS)

Carr, Michael J.; Walker, James A.

1987-08-01

Tephras provide stratigraphic control that allows documentation of changes in magma composition during eruptions. Stratigraphic sections of five recent mafic tephra deposits show a variety of different changes in composition, but three patterns stand out: elements abundant in plagioclase, Al, Sr and to a lesser extent Ca, are sometimes concentrated in the earliest eruptive products; elements common in ferromagnesian minerals, Mg, Fe, Cr and Ni, are usually concentrated in the latest eruptive products; the incompatible elements and Si are highest during the early phases of the eruption, although the very first erupted material will not have the highest incompatible element and Si contents if a high proportion of plagioclase crystals are present. The unusual pattern is the enrichment of Al, Sr and Ca in the earliest phases of eruptions. The two most mafic tephra sequences show the most enrichment, the intermediate tephras show slight enrichment and the most silicic sequence, which also had the longest repose interval, has an opposite pattern. Plagioclase phenocrysts are able to float in some mafic magmas, especially, when aided by the adherence of vesicles to their surfaces. Mafic magmas, especially water-rich ones, appear to have low enough viscosity to allow phenocryst sorting during the rise of magma to the surface. Random samples will not represent either the liquid component of the erupted magma or the parental magmatic liquid. Stratigraphic sampling of tephras produced by disruption of such magma is essential for deducing preeruptive conditions.

Controls on Middle Pennsylvanian peat-forming floras in the Eastern United States

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

Eble, C.F.

1992-01-01

Middle Pennsylvanian strata in the Central Appalachian Basin contain numerous coal beds that provide an opportunity to study changes in coal-spore floras on an intra- and inter-bed scale. Vertical spore abundance patterns within individual coal beds record the ecological dynamics, both biologic and edaphic, of peat-forming systems in this interval. Coal palynofloras of this interval show a stratigraphic change in composition. Early to Middle Pennsylvanian spore floras are largely dominated by Lycospora. Species of Densosporites, a small lycopsid genus, Granulatisporites, a fern/pteridosperm( )-allied genus, and Laevigatosporites, a calamite-related genus, commonly displace Lycospora vertically within these beds, reflecting patterns of ecologicalmore » succession. Spore floras from stratigraphically younger coal beds in this sequence exhibit similar intra-bed spore variation, but contain increased percentages of tree-fern spores, and tend to be more florally heterogeneous overall. Areas of clastic deposition within the swamps are also marked by changes in spore composition. These changes in coal palynology are paralleled by stratigraphic changes in coal appearance and associated strata composition. The proportion of dull'' coal lithotypes, frequency of clastic partings, and amount of coarse clastics in the enclosing strata all increase toward the top of this sequence. Climate may have been more important in determining the floral composition of Early through mid-Middle Pennsylvanian peat swamps, whereas climate, tectonics, and eustasy interacted to determine sediment volume and type in this interval.« less

A continuous Late Holocene paleosecular variation record from Carmen Lake (Tierra del Fuego, Argentina)

NASA Astrophysics Data System (ADS)

Gogorza, Claudia S. G.; Irurzun, María A.; Orgeira, María J.; Palermo, Pedro; Llera, María

2018-07-01

Paleomagnetic secular variations (PSV) give us information on the mechanisms of the geodynamo and can also be used for stratigraphic correlation on a regional scale. In this article we present a high-resolution paleomagnetic and rock magnetic study of two cores, LCTF1 and LCTF2, collected at Carmen Lake (Tierra del Fuego, Argentina). An analysis of rock magnetic data suggests that the remanence signal is carried by Titanomagnetite grains in stable pseudo single domain (PSD) state. Notwithstanding the special mechanism of sedimentary deposition, the sequence is characterised by good paleomagnetic properties and can be used to reconstruct a continuous stratigraphic record that provides high-resolution declination, inclination and relative paleointensity curves for the period 1000-4000 cal years BP. The constructed PSV curves are in very good agreement with the available records of Southern Argentina, implying very promising results in the construction of curve patterns for the region. A comparison of the records of southern Argentina with the most recent models available demonstrates that there is a noticeable lack of agreement, which is interpreted as the critical need to add more data from the southern hemisphere in the construction of the geomagnetic field models.

Regional seismic stratigraphy and controls on the Quaternary evolution of the Cape Hatteras region of the Atlantic passive margin, USA

USGS Publications Warehouse

Mallinson, D.J.; Culver, S.J.; Riggs, S.R.; Thieler, E.R.; Foster, D.; Wehmiller, J.; Farrell, K.M.; Pierson, J.

2010-01-01

Seismic and core data, combined with amino acid racemization and strontium-isotope age data, enable the definition of the Quaternary stratigraphic framework and recognition of geologic controls on the development of the modern coastal system of North Carolina, U.S.A. Seven regionally continuous high amplitude reflections are defined which bound six seismic stratigraphic units consisting of multiple regionally discontinuous depositional sequences and parasequence sets, and enable an understanding of the evolution of this margin. Data reveal the progressive eastward progradation and aggradation of the Quaternary shelf. The early Pleistocene inner shelf occurs at a depth of ca. 20-40 m beneath the western part of the modern estuarine system (Pamlico Sound). A mid- to outer shelf lowstand terrace (also early Pleistocene) with shelf sand ridge deposits comprising parasequence sets within a transgressive systems tract, occurs at a deeper level (ca. 45-70 m) beneath the modern barrier island system (the Outer Banks) and northern Pamlico Sound. Seismic and foraminiferal paleoenvironmental data from cores indicate the occurrence of lowstand strandplain shoreline deposits on the early to middle Pleistocene shelf. Middle to late Pleistocene deposits occur above a prominent unconformity and marine flooding surface that truncates underlying units, and contain numerous filled fluvial valleys that are incised into the early and middle Pleistocene deposits. The stratigraphic framework suggests margin progradation and aggradation modified by an increase in the magnitude of sea-level fluctuations during the middle to late Pleistocene, expressed as falling stage, lowstand, transgressive and highstand systems tracts. Thick stratigraphic sequences occur within the middle Pleistocene section, suggesting the occurrence of high capacity fluvial point sources debouching into the area from the west and north. Furthermore, the antecedent topography plays a significant role in the evolution of the geomorphology and stratigraphy of this marginal system. ?? 2009 Elsevier B.V.

Tectonic evolution of the Paranoá basin: New evidence from gravimetric and stratigraphic data

NASA Astrophysics Data System (ADS)

Martins-Ferreira, Marco Antonio Caçador; Campos, José Eloi Guimarães; Von Huelsen, Monica Giannoccaro

2018-06-01

Field gravimetric and stratigraphic surveys were conducted with the aim to constraint the mechanisms responsible for the initiation of the Stenian-Tonian Paranoá basin, central Brazil, a subject not yet studied in detail. The Paranoá Group crops out in the external zone of the Brasília Belt, a Neoproterozoic orogen in the western margin of the São Francisco Craton. Detailed geological mapping confirmed the existence of a regional scale fault that controlled sedimentation of the Paranoá Group during the deposition of its basal formations, revealing important details about basin initiation and early evolution. Gravimetric modeling indicates the existence of paleorift structures beneath the Paranoá sequence in the study area. Results from both stratigraphic and gravimetric surveys show strong evidence of mechanical subsidence by faulting during basin initiation. Unsorted, angular, clasts cut by quartz veins and brecciated boulders present in the basal conglomerate, support this hypothesis. Basin initiation faults coincide with deeper paleorift faults and are thus interpreted as reactivations of the older Statherian Araí Rift. The reactivations favored an initial regime of mechanical subsidence, dominated by the development of epirogenic arches subsiding at different rates. Apart from faulting activity, the post-basal sequence presents no evidence of rift environment in the strict sense. Besides, the great lateral continuity and relatively constant thickness of facies, indicate that an initial mechanic subsidence rapidly gave way to flexural subsidence during subsequent stages of basin evolution. The Paranoá Group do not present reliable characteristics that would allow its strict classification as a passive margin. Its main stratigraphic characteristics, tectonic location and basement architecture, indicate that the Paranoá Group was deposited in a cratonic margin basin, and may have been either connected to a passive margin basin at times of sea level rise, or evolved to a passive margin later in time.

Implications of new stratigraphic data on volcanic hazard assessment for Nisyros volcano, Greece

NASA Astrophysics Data System (ADS)

Volentik, A.; Vanderkluysen, L.; Principe, C.; Hernandez, J.; Hunziker, J. C.

2003-04-01

The active quaternary Nisyros volcano, at the eastern end of the Aegean volcanic arc, is composed of a succession of lava flows, tephra layers and interbedded epiclastic deposits. The volcano is topped by a recent caldera, on average 4 km in diameter and 200 m in depth. A detailed geological map including 35 stratigraphic units (lava flows, tephra layers and epiclastic deposits) has been recently completed at the 1:10'000 scale, based on new stratigraphical data. Based on the identification of new plinian sequences (Lakki and Melisseri pyroclastic series) in the lowermost section of the reconstructed stratigraphical succession, on the re-interpretation of previously described deposits and on the discovery of eruptive facies, we construct a set of hazard maps for volcanic events at Nisyros. Sequences of sub-marine lavas to subaerial epiclastites combined with the occurrence of a marine terrace deposit in the north-western sector of the island highlight the potential for rapid vertical movements, in particular in the area of Mandraki. A period of intense off-centred strombolian to phreatomagmatic activity occurred in quite recent times on Nisyros along the major tectonic trends (N^o030, No070, N^o120 and N^o340), building up several scoria cones and tuff cones all around the island. A number of these tectonic trends are still active, as demonstrated by faults cutting through recent deposits (including the youngest deposits of the hydrothermal eruptions, inside the present caldera of Nisyros). This implies that not only intra-caldera phreatic eruptions, but also potential magmatic eruption may occur along the island’s major zones of weakness, with increased hazards where magma/water interaction may take place. Finally a newly recognized debris avalanche deposit (the so-called Vunàri debris avalanche), affecting a wide sector in the northern part of the island, unveils a new type of volcanic hazard on Nisyros, related to flank collapse and destruction of the volcanic edifice.

Age and stratigraphic context of Pliopithecus and associated fauna from Miocene sedimentary strata at Damiao, Inner Mongolia, China

NASA Astrophysics Data System (ADS)

Kaakinen, Anu; Abdul Aziz, Hayfaa; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Salminen, Johanna; Wang, Lihua; Krijgsman, Wout; Fortelius, Mikael

2015-03-01

Since the discovery of mammalian fossils in Central Inner Mongolia in the beginning of the 20th century, this area has produced a rich and diverse record of Miocene faunas. Nevertheless, the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous vertical exposures. Consequently, most age estimates of these Miocene sites are based on paleontological evidence alone, with very few sites having been dated independently. Our field investigations in Damiao, in Siziwang Qi, Inner Mongolia have yielded more than 30 new fossiliferous localities from three horizons, including a pliopithecid fauna. This study presents the litho-, bio- and magnetostratigraphy of the Damiao area and provides age estimates for the three fossil-bearing horizons. The sedimentary sequence is interpreted as the remains of a fluvial system comprising channels, subaerially exposed floodplains and floodbasin environments. The two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with species-rich vertebrate fossil localities. The paleomagnetic results and faunal evidence suggest a correlation of lowermost fossil horizon (DM16) producing relatively rich small mammal assemblage to the early Miocene chron C6Ar or C6An.1r, roughly in 20-21 Ma age range. The pliopithecid locality level (DM01) represents latest middle Miocene and has an age estimate of about 12.1 Ma while the youngest localities (DM02) with cervoids and abundant and diverse small mammal fauna represents the earliest late Miocene with an age estimate of about 11.6 Ma. Our magnetostratigraphic results confirm that the Damiao strata constitute one of the best sequences in Inner Mongolia with early, middle and late Miocene mammalian faunas in stratigraphic superposition. The results also provide constraints on the paleoenvironmental evolution and bioevents of the area. The occurrence of pliopithecid primates in the middle Miocene of Inner Mongolia suggests humid habitats and challenges the scenarios suggesting arid and highly seasonal conditions for Central Asia since Early Miocene. The presence of pliopithecids may also bear witness to locally humid environments and greater habitat heterogeneity than previously known in central Inner Mongolia.

Reservoir sequence analysis: A new technology for the 90`s and its application to oil and gas fields

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

Wornardt, W.W.

1996-08-01

Reservoir Sequence Analysis when applied to existing fields can increase the production, life of the field and extend the field with a minimum of cost. In this technology we identify reservoir sands in a standard-of-reference well, to establish a seismic sequence stratigraphic well-tie for the entire field. Age date the Maximum Flooding Surfaces and Sequence Boundaries above and below reservoir sands on a well-log and seismic pro- file and/or workstation using High Resolution Biostratigraphic Analysis, species abundance and diversity histograms and their patterns, and paleoenvironmental paleobathymetric changes. Identify the systems tracts and their corresponding reservoir sands in between age datedmore » Maximum Flooding Surfaces. Interpret the reservoir sands as to type, i.e. IVF, point bar, coastal belt, forced regression, falling stage, bottom-set (shingled) turbidites, slope fan channel, channel overbank, and basin floor fans. Identify and correlate the same individual sands in different wells, and note new sands in a well and sands that shale-out in a well. Correlate the Maximum Flooding Surfaces above and below the reservoir section in additional wells to see which part of the reservoir section and sands have been penetrated. Identify systems tracts in additional wells and construct isopach, sand percent maps of individual systems tract interval in each well. Correlate sand packages, with a high degree of confidence, from upthrown to downthrown fault blocks, around salt domes, and updip with downdip.« less

Late Cenozoic sedimentation and volcanism during transtensional deformation in Wingate Wash and the Owlshead Mountains, Death Valley

USGS Publications Warehouse

Luckow, H.G.; Pavlis, T.L.; Serpa, L.F.; Guest, B.; Wagner, D.L.; Snee, L.; Hensley, T.M.; Korjenkov, A.

2005-01-01

New 1:24,000 scale mapping, geochemical analyses of volcanic rocks, and Ar/Ar and tephrochronology analyses of the Wingate Wash, northern Owlshead Mountain and Southern Panamint Mountain region document a complex structural history constrained by syntectonic volcanism and sedimentation. In this study, the region is divided into five structural domains with distinct, but related, histories: (1) The southern Panamint domain is a structurally intact, gently south-tilted block dominated by a middle Miocene volcanic center recognized as localized hypabyssal intrusives surrounded by proximal facies pyroclastic rocks. This Miocene volcanic sequence is an unusual alkaline volcanic assemblage ranging from trachybasalt to rhyolite, but dominated by trachyandesite. The volcanic rocks are overlain in the southwestern Panamint Mountains by a younger (Late Miocene?) fanglomerate sequence. (2) An upper Wingate Wash domain is characterized by large areas of Quaternary cover and complex overprinting of older structure by Quaternary deformation. Quaternary structures record ???N-S shortening concurrent with ???E-W extension accommodated by systems of strike-slip and thrust faults. (3) A central Wingate Wash domain contains a complex structural history that is closely tied to the stratigraphic evolution. In this domain, a middle Miocene volcanic package contains two distinct assemblages; a lower sequence dominated by alkaline pyroclastic rocks similar to the southern Panamint sequence and an upper basaltic sequence of alkaline basalt and basanites. This volcanic sequence is in turn overlain by a coarse clastic sedimentary sequence that records the unroofing of adjacent ranges and development of ???N-S trending, west-tilted fault blocks. We refer to this sedimentary sequence as the Lost Lake assemblage. (4) The lower Wingate Wash/northern Owlshead domain is characterized by a gently north-dipping stratigraphic sequence with an irregular unconformity at the base developed on granitic basement. The unconformity is locally overlain by channelized deposits of older Tertiary(?) red conglomerate, some of which predate the onset of extensive volcanism, but in most of the area is overlain by a moderately thick package of Middle Miocene trachybasalt, trachyandesitic, ash flows, lithic tuff, basaltic cinder, basanites, and dacitic pyroclastic, debris, and lahar flows with localized exposures of sedimentary rocks. The upper part of the Miocene stratigraphic sequence in this domain is comprised of coarse grained-clastic sediments that are apparently middle Miocene based on Ar/Ar dating of interbedded volcanic rocks. This sedimentary sequence, however, is lithologically indistinguishable from the structurally adjacent Late Miocene Lost Lake assemblage and a stratigraphically overlying Plio-Pleistocene alluvial fan; a relationship that handicaps tracing structures through this domain. This domain is also structurally complex and deformed by a series of northwest-southeast-striking, east-dipping, high-angle oblique, sinistral, normal faults that are cut by left-lateral strike-slip faults. The contact between the southern Panamint domain and the adjacent domains is a complex fault system that we interpret as a zone of Late Miocene distributed sinistral slip that is variably overprinted in different portions of the mapped area. The net sinistral slip across the Wingate Wash fault system is estimated at 7-9 km, based on offset of Proterozoic Crystal Springs Formation beneath the middle Miocene unconformity to as much as 15 km based on offset volcanic facies in Middle Miocene rocks. To the south of Wingate Wash, the northern Owlshead Mountains are also cut by a sinistral, northwest-dipping, oblique normal fault, (referred to as the Filtonny Fault) with significant slip that separates the Lower Wingate Wash and central Owlshead domains. The Filtonny Fault may represent a young conjugate fault to the dextral Southern Death Valley fault system and may be the northwest

Glacial morphology and depositional sequences of the Antarctic Continental Shelf

USGS Publications Warehouse

ten Brink, Uri S.; Schneider, Christopher

1995-01-01

Proposes a simple model for the unusual depositional sequences and morphology of the Antarctic continental shelf. It considers the regional stratal geometry and the reversed morphology to be principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the ice grounding line. The model offers several guidelines for stratigraphic interpretation of the Antarctic shelf and a Northern Hemisphere shelf, both of which were subject to many glacial advances and retreats. -Authors

Banded iron-formations of late Proterozoic age in the central eastern desert, Egypt: geology and tectonic setting.

USGS Publications Warehouse

Sims, P.K.; James, H.L.

1984-01-01

Iron-formation occurs as stratigraphic units within a layered andesite-basalt sequence. The sequence is metamorphosed to greenschist facies, intruded by syntectonic granodiorite and post-tectonic granite, and complexly deformed and grossly fragmented; the rocks are allochthonous along thrust faults. The iron deposits are chemical precipitates, accumulated during lulls in volcanism, apparently in an intraoceanic island-arc environment. The deposits are of the Algoma type of iron-formation.-G.J.N.

Sequence stratigraphy as a scientific enterprise: the evolution and persistence of conflicting paradigms

NASA Astrophysics Data System (ADS)

Miall, Andrew D.; Miall, Charlene E.

2001-08-01

In the 1970s, seismic stratigraphy represented a new paradigm in geological thought. The development of new techniques for analyzing seismic-reflection data constituted a "crisis," as conceptualized by T.S. Kuhn, and stimulated a revolution in stratigraphy. We analyze here a specific subset of the new ideas, that pertaining to the concept of global-eustasy and the global cycle chart published by Vail et al. [Vail, P.R., Mitchum, R.M., Jr., Todd, R.G., Widmier, J.M., Thompson, S., III, Sangree, J.B., Bubb, J.N., Hatlelid, W.G., 1977. Seismic stratigraphy and global changes of sea-level. In: Payton, C.E. (Ed.), Seismic Stratigraphy—Applications to Hydrocarbon Exploration, Am. Assoc. Pet. Geol. Mem. 26, pp. 49-212.] The global-eustasy model posed two challenges to the "normal science" of stratigraphy then underway: (1) that sequence stratigraphy, as exemplified by the global cycle chart, constitutes a superior standard of geologic time to that assembled from conventional chronostratigraphic evidence, and (2) that stratigraphic processes are dominated by the effects of eustasy, to the exclusion of other allogenic mechanisms, including tectonism. While many stratigraphers now doubt the universal validity of the model of global-eustasy, what we term the global-eustasy paradigm, a group of sequence researchers led by Vail still adheres to it, and the two conceptual approaches have evolved into two conflicting paradigms. Those who assert that there are multiple processes generating stratigraphic sequences (possibly including eustatic processes) are adherents of what we term the complexity paradigm. Followers of this paradigm argue that tests of the global cycle chart amount to little more than circular reasoning. A new body of work documenting the European sequence record was published in 1998 by de Graciansky et al. These workers largely follow the global-eustasy paradigm. Citation and textual analysis of this work indicates that they have not responded to any of the scientific problems identified by the opposing group. These researchers have developed their own descriptive and interpretive language that is largely self-referential. Through the use of philosophical and sociological assumptions about the nature of human activity, and in particular the work of Thomas Kuhn, we have attempted to illustrate (1) how the preconceptions of geologists shape their observations in nature; (2) how the working environment can contribute to the consensus that develops around a theoretical approach with a concomitant disregard for anomalous data that may arise; (3) how a theoretical argument can be accepted by the geological community in the absence of "proofs" such as documentation and primary data; (4) how the definition of a situation and the use or non-use of geological language "texts" can direct geological interpretive processes in one direction or another; and (5) how citation patterns and clusters of interrelated "invisible colleges" of geologists can extend or thwart the advancement of geological knowledge.

SAS program for quantitative stratigraphic correlation by principal components

USGS Publications Warehouse

Hohn, M.E.

1985-01-01

A SAS program is presented which constructs a composite section of stratigraphic events through principal components analysis. The variables in the analysis are stratigraphic sections and the observational units are range limits of taxa. The program standardizes data in each section, extracts eigenvectors, estimates missing range limits, and computes the composite section from scores of events on the first principal component. Provided is an option of several types of diagnostic plots; these help one to determine conservative range limits or unrealistic estimates of missing values. Inspection of the graphs and eigenvalues allow one to evaluate goodness of fit between the composite and measured data. The program is extended easily to the creation of a rank-order composite. ?? 1985.

Early Permian transgressive-regressive cycles: Sequence stratigraphic reappraisal of the coal-bearing Barakar Formation, Raniganj Basin, India

NASA Astrophysics Data System (ADS)

Bhattacharya, Biplab; Bhattacharjee, Joyeeta; Bandyopadhyay, Sandip; Banerjee, Sudipto; Adhikari, Kalyan

2018-03-01

The present research is an attempt to assess the Barakar Formation of the Raniganj Gondwana Basin, India, in the frame of fluvio-marine (estuarine) depositional systems using sequence stratigraphic elements. Analysis of predominant facies associations signify deposition in three sub-environments: (i) a river-dominated bay-head delta zone in the inner estuary, with transition from braided fluvial channels (FA-B1) to tide-affected meandering fluvial channels and flood plains (FA-B2) in the basal part of the succession; (ii) a mixed energy central basin zone, which consists of transitional fluvio-tidal channels (FA-B2), tidal flats, associated with tidal channels and bars (FA-B3) in the middle-upper part of the succession; and (iii) a wave-dominated outer estuary (coastal) zone (FA-B4 with FA-B3) in the upper part of the succession. Stacked progradational (P1, P2)-retrogradational (R1, R2) successions attest to one major base level fluctuation, leading to distinct transgressive-regressive (T-R) cycles with development of initial falling stage systems tract (FSST), followed by lowstand systems tract (LST) and successive transgressive systems tracts (TST-1 and TST-2). Shift in the depositional regime from regressive to transgressive estuarine system in the early Permian Barakar Formation is attributed to change in accommodation space caused by mutual interactions of (i) base level fluctuations in response to climatic amelioration and (ii) basinal tectonisms (exhumation/sagging) related to post-glacial isostatic adjustments in the riftogenic Gondwana basins.

A 56 million year rhythm in North American sedimentation during the Phanerozoic

NASA Astrophysics Data System (ADS)

Meyers, Stephen R.; Peters, Shanan E.

2011-03-01

Long-term (> 10 Myr) fluctuations in climate, sea-level and sedimentation have been documented in the stratigraphic record, but the lack of well-constrained data series has made it difficult to rigorously evaluate cyclic (periodic or quasi-periodic) changes at this scale. Here we utilize a new compilation of the coverage area of sedimentary rocks in North America to investigate the dominant modes (“orders”) of stratigraphic variability, and to evaluate potential long-period cyclic changes in sedimentation on the continent during the Phanerozoic. Our analysis resolves two principal temporal modes of variability: (1) a strongly sinusoidal mode with a periodicity of 56 Myr +/- 3 Myr, and (2) a longer-term Phanerozoic mode (the “M-curve”, linked to the Wilson cycle), which is indistinguishable from a stochastic autoregressive process. The newly identified 56 Myr cycle in sedimentation delineates most of the cratonic sequences that have previously been identified qualitatively in North America, but here we propose a quantitative redefinition that includes nine distinct units and two mega-sequences. The timing of the 56 Myr beat in sedimentation is consistent with an orogenic oscillator source or an oscillatory dynamic in mantle convection, and its tempo is statistically similar to a known rhythm in number of marine animal genera in the global fossil record. Thus, the identification of a significant periodic signal in the sedimentary record of North America provides new evidence for an important tectonic- and/or mantle-scale cyclic process that links both large-scale biological evolution and physical environmental change.

Stratal stacking patterns and tectono-sedimentary evolution of hyperextended magma-poor rifted margins

NASA Astrophysics Data System (ADS)

Ribes, C.; Gillard, M.; Epin, M. E.; Ghienne, J. F.; Manatschal, G.; Karner, G. D.; Johnson, C. A.

2016-12-01

Research on the formation and evolution of deep-water rifted margins has undergone a major paradigm shift in recent years. An increasing number of studies of present-day and fossil rifted margins allow us to identify and characterize the structural architecture of the most distal parts of rifted margins, the so-called hyperextended, magma-poor rifted margins. However, at present, little is known about the depositional environments, sedimentary facies, stacking patterns, subsidence and thermal history within these domains. In this context, characterizing the stratal stacking patterns and understanding their spatial and temporal evolution is a new challenge. The major difficulty comes from the fact that the observed stratigraphic geometries and facies relationships are a result of the complex interplay between sediment supply and available accommodation, which is controlled by not only the regional generation of accommodation, but also by local tectono-magmatic processes. These parameters are poorly constrained or even sufficiently known in these tectonic settings. Indeed, the complex structural evolution of hyperextended magma-poor rifted margins, including the development of poly-phase in-sequence and out of sequence extensional detachment faults and associated mantle exhumation and magmatic activity, can generate complex accommodation patterns over a highly structured top basement. The presentation summarizes early results concerning the controlling parameters on ultra-deep water stratigraphic stacking patterns and to provide a conceptual framework. This observation-driven approach combines fieldwork from fossil Alpine Tethys margins exposed in the Alps and the analysis of seismic reflection data from present-day deep water rifted margins such as the Australian-Antarctic, East India and Iberia-Newfoundland margins.

High-resolution sequence stratigraphy and continental environmental evolution: An example from east-central Argentina

NASA Astrophysics Data System (ADS)

Beilinson, Elisa; Veiga, Gonzalo D.; Spalletti, Luis A.

2013-10-01

The aims of this contribution is to establish a high-resolution sequence stratigraphic scheme for the continental deposits that constitute the Punta San Andrés Alloformation (Plio-Pleistocene) in east-central Argentina, to analyze the basin fill evolution and to identify and assess the role that extrinsic factors such as climate and sea-level oscillations played during evolution of the unit. For the high-resolution sequence stratigraphical study of the Punta San Andrés Alloformation, high- and low-accommodation system tracts were defined mainly on the basis of the architectural elements present in the succession, also taking into account the relative degree of channel and floodplain deposits. Discontinuities and the nature of depositional systems generated during variations in accommodation helped identify two fourth-order high-accommodation system tracts and two fourth-order low-accommodation system tracts. At a third-order scale, the Punta San Andrés Alloformation may be interpreted as the progradation of continental depositional systems, characterized by a braided system in the proximal areas, and a low-sinuosity, single-channel system in the distal areas, defined by a high rate of sediment supply and discharge peaks which periodically flooded the plains and generated high aggradation rates during the late Pliocene and lower Pleistocene.

Influence of fluvial processes on the quaternary geologic framework of the continental shelf, North Carolina, USA

USGS Publications Warehouse

Boss, S.K.; Hoffman, C.W.; Cooper, B.

2002-01-01

Digital, single-channel, high-resolution seismic reflection profiles were acquired from the insular continental shelf of North Carolina, USA along a data grid extending from Oregon Inlet northward 48 km to Duck, North Carolina and from the nearshore zone seaward approximately 28 km (total surveyed area= 1334 km2). These data were processed and interpreted to delineate principal reflecting horizons and develop a three-dimensional seismic stratigraphic framework for the continental shelf that was compared to stratigraphic data from the shoreward back-barrier (estuarine) and barrier island system. Six principal reflecting horizons (designated R0 through R5) were present within the upper 60 m of the shelf stratigraphic succession. Three-dimensional mapping of reflector R1 demonstrated its origin from fluvial incision of the continental shelf during an episode (or episodes) of lowered sea-level. Fluvial processes during development of reflector R1 were responsible for extensive reworking and re-deposition of sediment throughout most of the northern half of the study area. Five seismic stratigraphic units (designated S1 through S5) were tentatively correlated with depositional sequences previously identified from the North Carolina back-barrier (estuarine) and barrier island system. These five stratigraphic units span the Quaternary Period (S1 = early Holocene; S2 = 51-78 ka; S3 = 330-530 ka; S4 = 1.1-1.8 Ma; S5 = earliest Pleistocene). Unit S1 is composed of fine-grained fluvial/estuarine sediment that back-filled incised streams during early Holocene sea-level rise. The four other stratigraphic units (S2-S5) display tabular depositional geometries, low total relief, and thicken toward the east-southeast as their basal reflectors dip gently between 0.41 m km-1 (0.02??) and 0.54 m km-1 (0.03??). Knowledge of the three-dimensional subsurface stratigraphic architecture of the continental shelf enhances understanding of the development of shelf depositional successions and provides a framework for development of better Quaternary sea-level data, especially offshore North Carolina where such data are sparse. ?? 2002 Elsevier Science B.V. All rights reserved.

Divisions of Geologic Time - Major Chronostratigraphic and Geochronologic Units

USGS Publications Warehouse

,

2007-01-01

Introduction Effective communication in the geosciences requires consistent uses of stratigraphic nomenclature, especially divisions of geologic time. A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and calibrated in years (Harland and others, 1982). Over the years, the development of new dating methods and refinement of previous ones have stimulated revisions to geologic time scales. Since the mid-1990s, geologists from the U.S. Geological Survey (USGS), State geological surveys, academia, and other organizations have sought a consistent time scale to be used in communicating ages of geologic units in the United States. Many international debates have occurred over names and boundaries of units, and various time scales have been used by the geoscience community.

Stratigraphy and erosional landforms of layered deposits in Valles Marineris, Mars

NASA Technical Reports Server (NTRS)

Komatsu, G.; Geissler, P. E.; Strom, R. G.; Singer, R. B.

1993-01-01

Satellite imagery is used to identify stratigraphy and erosional landforms of 13 layered deposits in the Valles Marineris region of Mars (occurring, specifically, in Gangis, Juventae, Hebes, Ophir-Candor, Melas, and Capri-Eos Chasmata), based on albedo and erosional styles. Results of stratigraphic correlations show that the stratigraphy of layered deposits in the Hebes, Juventae, and Gangis Chasmata are not well correlated, indicating that at least these chasmata had isolated depositional environments resulting in different stratigraphic sequences. On the other hand, the layered deposits in Ophir-Candor and Melas Chasmata appear to have been connected in each chasma. Some of the layered deposits display complexities which indicate changes in space and time in the dominant source materials.

Sequence stratigraphic analysis of Cenomanian greenhouse palaeosols: A case study from southern Patagonia, Argentina

NASA Astrophysics Data System (ADS)

Varela, Augusto N.; Veiga, Gonzalo D.; Poiré, Daniel G.

2012-10-01

The aim of this contribution is to analyse extrinsic (i.e., tectonics, climate and eustasy) and intrinsic (i.e., palaeotopography, palaeodrainage and relative sedimentation rates) factors that controlled palaeosol development in the Cenomanian Mata Amarilla Formation (Austral foreland basin, southwestern Patagonia, Argentina). Detailed sedimentological logs, facies analysis, pedofeatures and palaeosol horizon identification led to the definition of six pedotypes, which represent Histosols, acid sulphate Histosols, Vertisols, hydromorphic Vertisols, Inceptisols and vertic Alfisols. Small- and large-scale changes in palaeosol development were recognised throughout the units. Small-scale or high-frequency variations, identified within the middle section are represented by the lateral and vertical superimposition of Inceptisols, Vertisols and hydromorphic Vertisols. Lateral changes are interpreted as the result of intrinsic factors to the depositional systems, such as the relative position within the floodplain and the distance from the main channels, that condition the nature of parent material, the sedimentation rate and eventually the palaeotopographic position. Vertical stacking of different soil types is linked to avulsion processes and the relatively abrupt change in the distance to main channels as the system aggraded. The large-scale or low-frequency vertical variations in palaeosol type occurring in the Mata Amarilla Formation are related to long-term changes in depositional environments. The lower and upper sections of the studied logs are characterised by Histosols and acid sulphate Histosols, and few hydromorphic Vertisols associated with low-gradient coastal environments (i.e., lagoons, estuaries and distal fluvial systems). At the lower boundary of the middle section, a thick palaeosol succession composed of vertic Alfisols occurs. The rest of the middle section is characterised by Vertisols, hydromorphic Vertisols and Inceptisols occurring on distal and proximal fluvial floodplains, respectively. The palaeosol succession for the Mata Amarilla Formation can be analysed within a sequence stratigraphic scheme considering changes in depositional environments in relation to accommodation/supply conditions. The results contrast with classical models, mainly in that the palaeosols of the Mata Amarilla Formation are relatively well-developed throughout the whole sequence, including transgressive periods of relatively high aggradation rate. Also, even when during regressive episodes, when a thick palaeosol succession that marks the sequence boundary is developed in the classical models, the lack of incised valleys in this succession led to the preservation of thick palaeosol successions during lowstand conditions. The vertical and lateral palaeosol distribution identified in the Mata Amarilla Formation could be eventually extrapolated to other sequences deposited during climate optimums.

BasinVis 1.0: A MATLAB®-based program for sedimentary basin subsidence analysis and visualization

NASA Astrophysics Data System (ADS)

Lee, Eun Young; Novotny, Johannes; Wagreich, Michael

2016-06-01

Stratigraphic and structural mapping is important to understand the internal structure of sedimentary basins. Subsidence analysis provides significant insights for basin evolution. We designed a new software package to process and visualize stratigraphic setting and subsidence evolution of sedimentary basins from well data. BasinVis 1.0 is implemented in MATLAB®, a multi-paradigm numerical computing environment, and employs two numerical methods: interpolation and subsidence analysis. Five different interpolation methods (linear, natural, cubic spline, Kriging, and thin-plate spline) are provided in this program for surface modeling. The subsidence analysis consists of decompaction and backstripping techniques. BasinVis 1.0 incorporates five main processing steps; (1) setup (study area and stratigraphic units), (2) loading well data, (3) stratigraphic setting visualization, (4) subsidence parameter input, and (5) subsidence analysis and visualization. For in-depth analysis, our software provides cross-section and dip-slip fault backstripping tools. The graphical user interface guides users through the workflow and provides tools to analyze and export the results. Interpolation and subsidence results are cached to minimize redundant computations and improve the interactivity of the program. All 2D and 3D visualizations are created by using MATLAB plotting functions, which enables users to fine-tune the results using the full range of available plot options in MATLAB. We demonstrate all functions in a case study of Miocene sediment in the central Vienna Basin.

Subsurface Analysis of the Mesaverde Group on and near the Jicarilla Apache Indian Reservation, New Mexico-its implication on Sites of Oil and Gas Accumulation

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

Ridgley, Jennie

2001-08-21

The purpose of the phase 2 Mesaverde study part of the Department of Energy funded project ''Analysis of oil-bearing Cretaceous Sandstone Hydrocarbon Reservoirs, exclusive of the Dakota Sandstone, on the Jicarilla Apache Indian Reservation, New Mexico'' was to define the facies of the oil-producing units within the subsurface units of the Mesaverde Group and integrate these results with outcrop studies that defined the depositional environments of these facies within a sequence stratigraphic context. The focus of this report will center on (1) integration of subsurface correlations with outcrop correlations of components of the Mesaverde, (2) application of the sequence stratigraphicmore » model determined in the phase one study to these correlations, (3) determination of the facies distribution of the Mesaverde Group and their relationship to sites of oil and gas accumulation, (4) evaluation of the thermal maturity and potential source rocks for oil and gas in the Mesaverde Group, and (5) evaluation of the structural features on the Reservation as they may control sites of oil accumulation.« less

Direct evidence of 1,900 years of indigenous silver production in the Lake Titicaca Basin of Southern Peru.

PubMed

Schultze, Carol A; Stanish, Charles; Scott, David A; Rehren, Thilo; Kuehner, Scott; Feathers, James K

2009-10-13

Archaeological excavations at a U-shaped pyramid in the northern Lake Titicaca Basin of Peru have documented a continuous 5-m-deep stratigraphic sequence of metalworking remains. The sequence begins in the first millennium AD and ends in the Spanish Colonial period ca. AD 1600. The earliest dates associated with silver production are 1960 + or - 40 BP (2-sigma cal. 40 BC to AD 120) and 1870 + or - 40 BP (2-sigma cal. AD 60 to 240) representing the oldest known silver smelting in South America. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis of production debris indicate a complex, multistage, high temperature technology for producing silver throughout the archaeological sequence. These data hold significant theoretical implications including the following: (i) silver production occurred before the development of the first southern Andean state of Tiwanaku, (ii) the location and process of silverworking remained consistent for 1,500 years even though political control of the area cycled between expansionist states and smaller chiefly polities, and (iii) that U-shaped structures were the location of ceremonial, residential, and industrial activities.

Study on the application of seismic sedimentology in a stratigraphic-lithologic reservoir in central Junggar Basin

NASA Astrophysics Data System (ADS)

Yu, Yixin; Xia, Zhongmou

2017-06-01

This paper discusses the research idea of description for stratigraphic-lithologic reservoir based on seismic sedimentology methods. The sandstone reservoir of Jurrassic XiShanyao Formation in Junggar Basin is studied according to the theory and approaches of seismic sedimentology. By making full use of borehole data, the technologies of layer correlation based on the stratigraphic sequence framework, the forward seismic modeling, the stratal slicing and lithologic inversion are applied. It describes the range of denudation line, the distribution characteristics of sedimentary facies of the strata, the vertical and horizontal distribution of sand bodies and the favourable oil-gas bearing prospective area. The results shows that study area are dominated braided delta deposition including underwater distributary channel and distributary bay microfacies, the nip-out lines of the formation are northeast to southwest from north to south, the second Middle Jurassic sand body is the most widely distributed one among three sand bodies, the prospective oil-gas bearing area located in the south part and around the YG2 well area. The study result is effective on the practice of exploration in study area.

Cambrian-Ordovician Knox production in Ohio: Three case studies of structural-stratigraphic traps

USGS Publications Warehouse

Riley, R.A.; Wicks, J.; Thomas, Joan

2002-01-01

The Knox Dolomite (Cambrian-Ordovician) in Ohio consists of a mixed carbonate-siliciclastic sequence deposited in a tidal-flat to shallow-marine environment along a broad continental shelf. Knox hydrocarbon production occurs in porous sandstone and dolomite reservoirs in the Copper Ridge dolomite, Rose Run sandstone, and Beekmantown dolomite. In Ohio, historical Knox exploration and development have been focused on paleogeomorphic traps within the prolific Morrow Consolidated field, and more recently, within and adjacent to the Rose Run subcrop. Although these paleogeomorphic traps have yielded significant Knox production, structural and stratigraphic traps are being largely ignored. Three Knox-producing pools demonstrate structural and stratigraphic traps: the Birmingham-Erie pool in southern Erie and southwestern Lorain counties, the South Canaan pool in northern Wayne County, and the East Randolph pool in south-central Portage County. Enhanced porosity and permeability from fractures, as evident in the East Randolph pool, are also an underexplored mechanism for Knox hydrocarbon accumulation. An estimated 800 bcf of gas from undiscovered Knox resources makes the Knox one of the most attractive plays in the Appalachian basin.

Specimen-level phylogenetics in paleontology using the Fossilized Birth-Death model with sampled ancestors.

PubMed

Cau, Andrea

2017-01-01

Bayesian phylogenetic methods integrating simultaneously morphological and stratigraphic information have been applied increasingly among paleontologists. Most of these studies have used Bayesian methods as an alternative to the widely-used parsimony analysis, to infer macroevolutionary patterns and relationships among species-level or higher taxa. Among recently introduced Bayesian methodologies, the Fossilized Birth-Death (FBD) model allows incorporation of hypotheses on ancestor-descendant relationships in phylogenetic analyses including fossil taxa. Here, the FBD model is used to infer the relationships among an ingroup formed exclusively by fossil individuals, i.e., dipnoan tooth plates from four localities in the Ain el Guettar Formation of Tunisia. Previous analyses of this sample compared the results of phylogenetic analysis using parsimony with stratigraphic methods, inferred a high diversity (five or more genera) in the Ain el Guettar Formation, and interpreted it as an artifact inflated by depositional factors. In the analysis performed here, the uncertainty on the chronostratigraphic relationships among the specimens was included among the prior settings. The results of the analysis confirm the referral of most of the specimens to the taxa Asiatoceratodus , Equinoxiodus, Lavocatodus and Neoceratodus , but reject those to Ceratodus and Ferganoceratodus . The resulting phylogeny constrained the evolution of the Tunisian sample exclusively in the Early Cretaceous, contrasting with the previous scenario inferred by the stratigraphically-calibrated topology resulting from parsimony analysis. The phylogenetic framework also suggests that (1) the sampled localities are laterally equivalent, (2) but three localities are restricted to the youngest part of the section; both results are in agreement with previous stratigraphic analyses of these localities. The FBD model of specimen-level units provides a novel tool for phylogenetic inference among fossils but also for independent tests of stratigraphic scenarios.

Recovering data from historical collections: stratigraphic and spatial reconstruction of the outstanding carnivoran record from the Late Pleistocene Equi cave (Apuane Alps, Italy)

NASA Astrophysics Data System (ADS)

Ghezzo, Elena; Palchetti, Alessandro; Rook, Lorenzo

2014-07-01

Equi Terme is a hamlet located in northern Tuscany, in Apuan Alps regional Park. An outstanding fossil vertebrate collection housed in Florence is the result of excavations in the Equi cave and shelter during the period 1911-1919. This faunal assemblage (associated with Mousterian artefacts) may be correlated with the middle of MIS 3. All of the specimens recovered at Equi early in the last century were collected with attention to their stratigraphical positions. Detailed field annotation for nearly every specimen allowed us to organize them and attempt a stratigraphical and spatial reconstruction of the fossiliferous deposits. We present the results of the study of the spatial and stratigraphic distribution of the carnivoran species in the Equi cave and shelter, and re-evaluate the taphonomic agents of accumulation and the fossil distribution within the stratigraphic record. In particular, we evaluated the distribution of Panthera pardus, which, unusually for Europe, is abundant in the Equi cave assemblage. This analysis highlights the importance of the re-evaluation of historical collections and allows for future comparisons with data from more recent excavations at the Equi site. The analysis also provides an account of the distribution of carnivorans throughout the stratigraphic record. The constant presence and the predominance of leopards and wolves over lions and smaller carnivorans, allow for evaluations of their ethology and may be related to a short period of sediment accumulation.

Convolute laminations — a theoretical analysis: example of a Pennsylvanian sandstone

NASA Astrophysics Data System (ADS)

Visher, Glenn S.; Cunningham, Russ D.

1981-03-01

Data from an outcropping laminated interval were collected and analyzed to test the applicability of a theoretical model describing instability of layered systems. Rayleigh—Taylor wave perturbations result at the interface between fluids of contrasting density, viscosity, and thickness. In the special case where reverse density and viscosity interlaminations are developed, the deformation response produces a single wave with predictable amplitudes, wavelengths, and amplification rates. Physical measurements from both the outcropping section and modern sediments suggest the usefulness of the model for the interpretation of convolute laminations. Internal characteristics of the stratigraphic interval, and the developmental sequence of convoluted beds, are used to document the developmental history of these structures.

Cretaceous Vertebrate Tracksites - Korean Cretaceous Dinosaur Coast World Heritage Nomination Site

NASA Astrophysics Data System (ADS)

Huh, M.; Woo, K. S.; Lim, J. D.; Paik, I. S.

2009-04-01

South Korea is one of the best known regions in the world for Cretaceous fossil footprints, which are also world-renowned. Korea has produced more scientifically named bird tracks (ichnotaxa) than any other region in the world. It has also produced the world's largest pterosaur tracks. Dinosaur tracksites also have the highest frequency of vertebrate track-bearing levels currently known in any stratigraphic sequence. Among the areas that have the best track records, and the greatest scientific significance with best documentation, Korea ranks very highly. Objective analysis of important individual tracksites and tracksite regions must be based on multiple criteria including: size of site, number of tracks, trackways and track bearing levels, number of valid named ichnotaxa including types, number of scientific publications, quality of preservation. The unique and distinctive dinosaur tracksites are known as one of the world's most important dinosaur track localities. In particular, the dinosaur track sites in southern coastal area of Korea are very unique. In the sites, we have excavated over 10,000 dinosaur tracks. The Hwasun sites show diverse gaits with unusual walking patterns and postures in some tracks. The pterosaur tracks are the most immense in the world. The longest pterosaur trackway yet known from any track sites suggests that pterosaurs were competent terrestrial locomotors. This ichnofauna contains the first pterosaur tracks reported from Asia. The Haenam Uhangri pterosaur assigns to a new genus Haenamichnus which accomodates the new ichnospecies, Haenamichnus uhangriensis. At least 12 track types have been reported from the Haman and Jindong Formations (probably late Lower Cretaceous). These include the types of bird tracks assigned to Koreanornis, Jindongornipes, Ignotornis and Goseongornipes. In addition the bird tracks Hwangsanipes, Uhangrichnus, the pterosaur track Haenamichnus and the dinosaur tracks, Brontopodus, Caririchnium, Minisauripus and at least three other unnamed morphotypes are known . A total of 52 clutches containing 390 dinosaur eggs occur in several stratigraphic formations including seven dinosaur egg localities. The other fossils including turtles, crocodiles, fishes, wood fossil, plants, trace fossils and microfossils have also been discovered. The occurrences of Korean dinosaurs in diverse stratigraphic formations and sedimentological setting and in diverse sizes and morphotypes provide an opportunity to study the palaeoecologic and palaeoenvironmental conditions of the sites of the Late Cretaceous dinosaurs. Korea could serve as a global vertebrate ichnological standard for Cretaceous terrestrial sequences, and allow correlation with Japanese marine sequences to the east and classic Chinese sites to the west. The region plays a pivotal role in helping us understand vertebrate evolution and paleoecology on the margins of the Asian continent during the Cretaceous.

Sequence stratigraphy of the Monterey Formation, Santa Barbara County: Integration of physical, chemical, and biofacies data from outcrop and subsurface

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

Bohacs, K.M.

1990-05-01

Deep basinal rocks of the Monterey Formation can be allocated to different depositional environments based on an integration of bedding, facies stacking patterns, lithology, biofacies, and inorganic and organic chemistry. These rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level change and basin evolution. Even deep-basinal environments are affected by changing sea level through changes in circulation patterns and intensities nutrient budgets and dispersal patterns, and location and intensity of the oceanic oxygen minimum. The sequence-stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed by typingmore » the outcrop sections to an integrated well-log/seismic grid through outcrop gamma-ray-spectral profiles. Interpretation of a sequence boundary was based on increased proportions of hemipelagic facies, evidence of increased bottom-energy levels above the boundary, and local erosion and relief on the surface. The proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary, Downlap surfaces exhibited increased proportions of pelagic facies around the surface, evidence of decreased bottom-energy levels and terrigenous sedimentation rates, and little or no significant erosion on the surface. The proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface; there was no evidence of reworked individuals. The detailed sequence-stratigraphic framework makes it possible to the rock properties to genetic processes for construction of predictive models.« less

Cultural conservatism and variability in the Acheulian sequence of Gesher Benot Ya'aqov.

PubMed

Sharon, Gonen; Alperson-Afil, Nira; Goren-Inbar, Naama

2011-04-01

The Acheulian Technocomplex exhibits two phenomena: variability and conservatism. Variability is expressed in the composition and frequencies of tool types, particularly in the varying frequencies of bifaces (handaxes and cleavers). Conservatism is expressed in the continuous presence of bifaces along an immense time trajectory. The site of Gesher Benot Ya'aqov (GBY) offers a unique opportunity to study aspects of variability and conservatism as a result of its long cultural-stratigraphic sequence containing superimposed lithic assemblages. This study explores aspects of variability and conservatism within the Acheulian lithic assemblages of GBY, with emphasis placed on the bifacial tools. While variability has been studied through a comparison of typological frequencies in a series of assemblages from the site, evidence for conservatism was examined in the production modes expressed by the reduction sequence of the bifaces. We demonstrate that while pronounced typological variability is observed among the GBY assemblages, they were all manufactured by the same technology. The technology, size, and morphology of the bifaces throughout the entire stratigraphic sequence of GBY reflect the strong conservatism of their makers. We conclude that the biface frequency cannot be considered as a chrono/cultural marker that might otherwise allow us to distinguish between different phases within the Acheulian. The variability observed within the assemblages is explained as a result of different activities, tasks, and functions, which were carried out at specific localities along the shores of the paleo-Hula Lake in the early Middle Pleistocene. Copyright © 2010 Elsevier Ltd. All rights reserved.

A new stratigraphic model for the deposition of the Dammam Formation

NASA Astrophysics Data System (ADS)

Lokier, Stephen; Fiorini, Flavia; Min, Jina

2017-04-01

In recent years, mixed siliciclastic-carbonate successions have increasingly become targets for hydrocarbon exploration and production activities. Despite the abundance of these successions throughout the Middle East, there have been very few attempts to employ quantitative techniques to interpret their depositional settings and to develop constrained sequence stratigraphic models for their deposition. This study focuses on the Eocene age Dammam Formation that crops out on the flanks of the Jebel Hafeet anticline south of Al Ain in the United Arab Emirates. The Dammam Formation comprises units alternating between poorly-lithified, easily-weathered, siliciclastic and marly horizons and well-lithified limestones. These units were deposited in a foreland basin that formed in association with the Late Cretaceous obduction of the Semail Ophiolite onto the northeastern margin of the Arabian Plate. The Paleogene infilling of this basin is recorded in the shallowing-upward sedimentary sequence of the lithologies of the Pabdeh Group. This succession records the transition from marine carbonate sedimentation, through increasingly evaporitic-dominated units during the late Eocene to early Miocene to a fluvial-alluvial system by mid to late Miocene times. The Dammam Formation was deposited in an open shallow-marine setting strongly influenced by the influx of siliciclastic material sourced from the close-by uplifted massif of the obducted ophiolite. The skeletal assemblage of the Dammam Formation is dominated by Nummulites and Assilina larger benthic foraminifera along with subordinate smaller foraminifera, echinoids, bivalves, corals, bryozoan, gastropods, echinoids and calcareous algae. Previous studies of the Dammam Formation have employed the biotic component in the reconstruction of water depth. However, these studies neglected to consider that turbidity, associated with the abundant siliciclastic component, resulted in a reduction in the depth of the euphotic zone and a consequent response of the benthic biota. We employ a range of quantitative analytical techniques in order to constrain the influence of the siliciclastic component on the lithofacies of the Dammam Formation and present a new sequence stratigraphic model for the deposition of the formation.

Seismic stratigraphy, tectonics and depositional history in the Halk el Menzel region, NE Tunisia

NASA Astrophysics Data System (ADS)

Sebei, Kawthar; Inoubli, Mohamed Hédi; Boussiga, Haïfa; Tlig, Said; Alouani, Rabah; Boujamaoui, Mustapha

2007-01-01

In the Halk el Menzel area, the proximal- to pelagic platform transition and related tectonic events during the Upper Cretaceous-Lower Miocene have not been taken into adequate consideration. The integrated interpretation of outcrop and subsurface data help define a seismic stratigraphic model and clarify the geodynamic evolution of the Halk el Menzel block. The sedimentary column comprises marls and limestones of the Campanian to Upper Eocene, overlain by Oligocene to Lower Miocene aged siliciclastics and carbonates. Well to well correlations show sedimentary sequences vary considerably in lithofacies and thicknesses over short distances with remarkable gaps. The comparison of sedimentary sequences cut by borehole and seismic stratigraphic modelling as well help define ten third order depositional sequences (S1-S10). Sequences S1 through S6 (Campanian-Paleocene) are mainly characterized by oblique to sigmoid configurations with prograding sedimentary structures, whereas, sequences S7-S10 (Ypresian to Middle Miocene) are organized in shallow water deposits with marked clinoform ramp geometry. Sedimentary discontinuities developed at sequence boundaries are thought to indicate widespread fall in relative sea level. Angular unconformities record a transpressive tectonic regime that operated from the Campanian to Upper Eocene. The geometry of sequences with reduced thicknesses, differential dipping of internal seismic reflections and associated normal faulting located westerly in the area, draw attention to a depositional sedimentary system developed on a gentle slope evolving from a tectonically driven steepening towards the Northwest. The seismic profiles help delimit normal faulting control environments of deposition. In contrast, reef build-ups in the Eastern parts occupy paleohighs NE-SW in strike with bordering Upper Maastrichtian-Ypresian seismic facies onlapping Upper Cretaceous counterparts. During the Middle-Upper Eocene, transpressive stress caused reactivation of faults from normal to reverse play. This has culminated in propagation folds located to the west; whereas, the eastern part of the block has suffered progressive subsidence. Transgressive carbonate depositional sequences have predominated during the Middle Miocene and have sealed pre-existing tectonic structures.

Study of the Paleogene carbonate sequence in Campeche and Yucatan, southern Mexico

NASA Astrophysics Data System (ADS)

García Avendaño, A.; Fucugauchi, J. U.

2013-05-01

The relief in the northeastern sector of Yucatan Peninsula is marked in several features, like the Campeche-Hecelchakan fault that indicates a scarp where the carbonate factory was produced from the different processes of eustatic variation throughout all extensions of the shelf. The Campeche scarp is one of the major structures of the peninsula. In this work we present preliminary results of the study on the Paleogene carbonate sequence (stratigraphic age derived from previous works) along a regional transect from the town of Champoton Campeche till Maxcanu town and into nearby Sierra of Ticul in Yucatan state, Mexico. Along this route we carried field work to measure geologic columns and sampled outcrops for petrographic analysis, selected based in litofacies settings in two units Champoton-Maxcanu (CH-CM) and Ticul Sierra (TS), CH-CM unit is formed by interbedded clay, shale, limestone and marl of different thickness, in addition to the content of various bioclasts. ST unit is comprised mostly of collapse breccias. This paper presents the microfacies analysis, directed to highlight changes in lithological horizons within the sequence. The study of carbonates in this study area contributes to the interpretation of the Yucatan geomorphology and development of the carbonate platform, for which the karst topography indicates a gradual subaerial exposure environment. .

Lithostratigraphy and volcanology of the Serra Geral Group, Paraná-Etendeka Igneous Province in Southern Brazil: Towards a formal stratigraphical framework

NASA Astrophysics Data System (ADS)

Rossetti, Lucas; Lima, Evandro F.; Waichel, Breno L.; Hole, Malcolm J.; Simões, Matheus S.; Scherer, Claiton M. S.

2018-04-01

The volcanic rocks of the Lower Cretaceous Paraná-Etendeka Igneous Province, in Brazil, are grouped in the Serra Geral Group. The province can be chemically divided into low-TiO2, and high-TiO2. In southern Brazil, the low-TiO2 lava pile reaches a thickness of 1 km and is formed of heterogeneous lava packages here divided into four lava formations. Torres Formation (TF) is characterized by chemically more primitive basaltic (> 5 wt% MgO) compound pahoehoe flow fields; these lavas stratigraphically overly aeolian sandstones of Botucatu Formation and represent the onset of the volcanic activity. Vale do Sol Formation (VSF) groups vertically stacked sheet-like rubbly pahoehoe basaltic andesites (SiO2 > 51 wt%; MgO < 5 wt%). These lavas covered the former basalts in the Torres Syncline axis and pinch out towards southwest and represent the most voluminous mafic lava flows. Dacites and rhyolites of Palmas Formation (PF) overlay VSF flows in the central and eastern outcrop area and rest directly upon TF lavas in the west. The acidic units were emplaced as lava domes and widespread tabular lava flows. Esmeralda Formation (EF) is the upper stratigraphic unit and it is formed by a basaltic pahoehoe flow field emplaced during the waning phase of volcanic activity of the low-TiO2 lava sequence. Sedimentary interbeds are preserved throughout the whole lava pile and were deposited during quiescence periods of volcanic activity, and represent important stratigraphic markers (e.g. TF-VSF contact). The newly proposed stratigraphy provides promptly recognized stratigraphic units in a regional framework of fundamental importance for future correlations and provide vital information in the understanding of how the Paraná-Etendeka Igneous Province evolved through time.

Significance of a near-source tephra-stratigraphic sequence to the eruptive history of Hayes Volcano, south-central Alaska

USGS Publications Warehouse

Wallace, Kristi; Coombs, Michelle L.; Hayden, Leslie A.; Waythomas, Christopher F.

2014-01-01

Bluffs along the Hayes River valley, 31 km northeast and 40 km downstream from Hayes Volcano, reveal volcanic deposits that shed new light on its eruptive history. Three thick (>10 cm) and five thin (<10 cm) tephra-fall deposits are dacitic in whole rock composition and contain high proportions of amphibole to pyroxene and minor biotite and broadly correlate to Hayes tephra set H defined by earlier investigators. Two basal ages for the tephra-fall sequence of 3,690±30 and 3,750±30 14C yr B.P. are also consistent with the Hayes tephra set H timeframe. Distinguishing among Hayes tephra set H units is critical because the set is an important time-stratigraphic marker in south-central Alaska and this section provides a new reference section for Hayes tephra set H. Analysis of Fe-Ti oxide grains in the tephras shows promise for identifying individual Hayes deposits. Beneath the dacitic tephra sequence lies an older, poorly sorted tephra (tephra A) that contains dacite and rhyolite lapilli and whose basal age is 4,450±30 14C yr B.P. Immediately below the tephra-fall sequence (Unit III) lies a series of mass-flow deposits that are rich in rhyodacitic clasts (Unit II). Below Unit II and possibly coeval with it, is a 20–30 m thick pumiceous pyroclastic-flow deposit (Unit I) that extends to the valley floor. Here informally named the Hayes River ignimbrite, this deposit contains pumice clasts of rhyolite with quartz, sanidine, plagioclase, and biotite phenocrysts, an assemblage that is unique among known Quaternary volcanic products of Hayes and other Alaskan volcanoes. Units I, II, and tephra A of Unit III represent at least two previously unrecognized eruptions of Hayes Volcano that occurred prior to ~3,700 yr B.P. No compositionally equivalent distal tephra deposits correlative with Hayes Volcano rhyodacites or rhyolites have yet been identified, perhaps indicating that some of these deposits are pre-Holocene, and were largely removed by glacial ice during the last ice age. More field and analytical work is needed to further refine the eruptive history of Hayes Volcano.

Some debatable problems of stratigraphic classification

NASA Astrophysics Data System (ADS)

Gladenkov, Yury

2014-05-01

Russian geologists perform large-scale geological mapping in Russia and abroad. Therefore we urge unification of legends of geological maps compiled in different countries. It seems important to continuously organize discussions on problems of stratigraphic classification. 1. The stratigraphic schools (conventionally called "European" and "American") define "stratigraphy" in different ways. The former prefers "single" stratigraphy that uses data proved by many methods. The latter divides stratigraphy into several independent stratigraphers (litho-, bio-, magneto- and others). Russian geologists classify stratigraphic units into general (chronostratigraphic) and special (in accordance with a method applied). 2. There exist different interpretations of chronostratigraphy. Some stratigraphers suppose that a chronostratigraphic unit corresponds to rock strata formed during a certain time interval (it is somewhat formalistic because a length of interval is frequently unspecified). Russian specialists emphasize the historical-geological background of chronostratigraphic units. Every stratigraphic unit (global and regional) reflects a stage of geological evolution of biosphere and stratisphere. 3. In the view of Russian stratigraphers, the main stratigraphic units may have different extent: a) global (stage), b) regional (regional stage,local zone), and c) local (suite). There is no such hierarchy in the ISG. 4. Russian specialists think that local "lithostratigraphic" units (formations) which may have diachronous boundaries are not chronostratigraphic ones in strict sense (actually they are lithological bodies). In this case "lithostratigraphy" can be considered as "prostratigraphy" and employed in initial studies of sequences. Therefore, a suite is a main local unit of the Russian Code and differs from a formation, although it is somewhat similar. It does not mean that lithostratigraphy is unnecessary. Usage of marker horizons, members and other bodies is of great help. Lithostratigraphy may be regarded as the start of geological mapping on scales of 1 : 10 000, 1 : 25 000 or 1 : 50 000, and lithostratigraphic subdivisions can be used as the mapping units because they practically have isochronic boundaries when we deal with geological mapping on these scales. 5. Russian geologists interpret a chronozone (defined with due account of the standard assemblage-zone) as a part of a stage. In opinion of other specialists, zones serve as correction markers. This gives rise to controversy where zonal scales are needed for the Phanerozoic or whether stage scales are sufficient. In the Russian Code a chronozone is referred to general stratigraphic units (less than a stage). 6. The popular GSSP "concept" may be is inadequate in the broad sense because stages remain "empty" and do not reflect geological events. The search of "golden spikes" can be useful as a part of comprehensive investigations of stratigraphic subdivisions. "Silver" and other type spike-markers can be used as well as recommended by event stratigraphy (Ager, 1973). 7. A new version of "International Stratigraphic Guide" should include not only recommendations but also alternative views. However the work must not be done in a hurry! In avoid bias representatives of interested countries should be involved. Finally, I would like to make two proposals. Proposal 1. A special symposium should be held during the second International Congress on Stratigraphy-2015 to review national stratigraphic codes (USA, Germany, Great Britain, China, Russia, Australia and other countries). This can provide better understanding of their similarities and dissimilarities and enable to realize how much they differ from each other. The review may show the present state of the stratigraphic classification and reveal both pressing and alleged problems of stratigraphy of the early XXI century. Proposal 2. It would be appropriate to prepare a special publication presenting briefly codes of different countries. Every national code is described on two pages: a tabled stratigraphic classification on one page and comments on another. Such publication would be most helpful.

Eo-Ulrichian to Neo-Ulrichian views: The renaissance of "layer-cake stratigraphy"

USGS Publications Warehouse

Brett, Carlton E.; McLaughlin, P.I.; Baird, G.C.

2007-01-01

Classical notions of "layer-cake stratigraphy" have been denigrated as representing an antiquated "Neptunian" view of the geologic record with the American paleontologist-stratigrapher E.O. Ulrich vilified as its quintessential advocate. Some of the extreme "layer-cake" interpretations of E.O. Ulrich are demonstrably incorrect, especially where applied in marginal marine and terrestrial settings. However, close scrutiny of Ulrich's work suggests that the bulk was correct and demonstrated considerable insight for the time. Subsequent development of facies concepts revolutionized geologists' view of time-space relationships in stratigraphy, but rather than focusing on facies patterns within the established stratigraphic (layer-cake) frameworks many geologists in North America came to view strata as parts of diachronous facies mosaics. Recent advances in the development of event and sequence stratigraphic paradigms are beginning to swing the pendulum back the other way. Possible causes of "layer-cake" patterns are numerous and varied, including: (1) parallelism of depositional strike and outcrop belts, especially in foreland basins, (2) very widespread environmental belts developed in low-relief cratonic areas, (3) time-averaging homogenizes facies to a limited extent, resulting in a very subtle signature of lateral change, (4) condensed beds (hardgrounds, bone beds, ironstones, etc.) often form in responses to extrabasinal forces, thus they cross-cut facies, and (5) large events (i.e. hurricanes, floods, tsunamis, eruptions, etc.) are "over represented" in the rock record. A revised ("Neo-Ulrichian") layer-cake paradigm carries many of the original correct empirical observations of pattern, noted by Ulrich, recast in terms of event and sequence stratigraphy.

Stratigraphy of the crater Copernicus

NASA Technical Reports Server (NTRS)

Paquette, R.

1984-01-01

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.

A MATLAB®-based program for 3D visualization of stratigraphic setting and subsidence evolution of sedimentary basins: example application to the Vienna Basin

NASA Astrophysics Data System (ADS)

Lee, Eun Young; Novotny, Johannes; Wagreich, Michael

2015-04-01

In recent years, 3D visualization of sedimentary basins has become increasingly popular. Stratigraphic and structural mapping is highly important to understand the internal setting of sedimentary basins. And subsequent subsidence analysis provides significant insights for basin evolution. This study focused on developing a simple and user-friendly program which allows geologists to analyze and model sedimentary basin data. The developed program is aimed at stratigraphic and subsidence modelling of sedimentary basins from wells or stratigraphic profile data. This program is mainly based on two numerical methods; surface interpolation and subsidence analysis. For surface visualization four different interpolation techniques (Linear, Natural, Cubic Spline, and Thin-Plate Spline) are provided in this program. The subsidence analysis consists of decompaction and backstripping techniques. The numerical methods are computed in MATLAB® which is a multi-paradigm numerical computing environment used extensively in academic, research, and industrial fields. This program consists of five main processing steps; 1) setup (study area and stratigraphic units), 2) loading of well data, 3) stratigraphic modelling (depth distribution and isopach plots), 4) subsidence parameter input, and 5) subsidence modelling (subsided depth and subsidence rate plots). The graphical user interface intuitively guides users through all process stages and provides tools to analyse and export the results. Interpolation and subsidence results are cached to minimize redundant computations and improve the interactivity of the program. All 2D and 3D visualizations are created by using MATLAB plotting functions, which enables users to fine-tune the visualization results using the full range of available plot options in MATLAB. All functions of this program are illustrated with a case study of Miocene sediments in the Vienna Basin. The basin is an ideal place to test this program, because sufficient data is available to analyse and model stratigraphic setting and subsidence evolution of the basin. The study area covers approximately 1200 km2 including 110 data points in the central part of the Vienna Basin.

Paleocurrent analysis of a deformed Devonian foreland basin in the northern Appalachians, Maine, USA

USGS Publications Warehouse

Bradley, D.C.; Hanson, L.S.

2002-01-01

New paleocurrent data indicate that the widespread Late Silurian and Devonian flysch and molasse succession in Maine was deposited in an ancestral, migrating foreland basin adjacent to an advancing Acadian orogenic belt. The foreland-basin sequence spread across a varied Silurian paleogeography of deep basins and small islands-the vestiges of an intraoceanic arc complex that not long before had collided with the Laurentian passive margin during the Ordovician Taconic Orogeny. We report paleocurrents from 43 sites representing 12 stratigraphic units, the most robust and consistent results coming from three units: Madrid Formation (southwesterly paleoflow), Carrabassett Formation (northerly paleoflow), and Seboomook Group (westerly paleoflow). Deformation and regional metamorphism are sufficiently intense to test the limits of paleocurrent analysis requiring particular care in retrodeformation. ?? 2002 Elsevier Science B.V. All rights reserved.

The rock components and structures of Archean greenstone belts: An overview

NASA Technical Reports Server (NTRS)

Lowe, D. R.; Byerly, G. R.

1986-01-01

Knowledge of the character and evolution of the Earth's early crust is derived from the studies of the rocks and structures in Archean greenstone belts. Ability to resolve the petrologic, sedimentological and structural histories of greenstone belts, however, hinges first on an ability to apply the concepts and procedures of classical stratigraphy. Unfortunately, early Precambrian greenstone terrains present particular problems to stratigraphic analysis. Many current controversies of greenstone belt petrogenesis, sedimentology, tectonics and evolution arise more from an inability to develop a clear stratigraphic picture of the belts than from ambiguities in interpretation. Four particular stratigraphic problems that afflict studies of Archean greenstone belts are considered: determination of facing directions, correlation of lithologic units, identification of primary lithologies and discrimination of stratigraphic versus structural contacts.

Major and trace element abundances in volcanic rocks of orogenic areas.

NASA Technical Reports Server (NTRS)

Jakes, P.; White, A. J. R.

1972-01-01

The composition of recent island-arc volcanic rocks in relation to their geographic and stratigraphic relations is discussed. The differences in composition between volcanic rocks and those in continental margins are pointed out. Trace elements and major elements are shown to suggest a continuous gradational sequence from tholeiites through calc-alkaline rocks to shoshonites.

Divisions of geologic time-major chronostratigraphic and geochronologic units

USGS Publications Warehouse

,

2010-01-01

Effective communication in the geosciences requires consistent uses of stratigraphic nomenclature, especially divisions of geologic time. A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and is calibrated in years. Over the years, the development of new dating methods and the refinement of previous methods have stimulated revisions to geologic time scales. Advances in stratigraphy and geochronology require that any time scale be periodically updated. Therefore, Divisions of Geologic Time, which shows the major chronostratigraphic (position) and geochronologic (time) units, is intended to be a dynamic resource that will be modified to include accepted changes of unit names and boundary age estimates. This fact sheet is a modification of USGS Fact Sheet 2007-3015 by the U.S. Geological Survey Geologic Names Committee.

Stratigraphic and structural controls on groundwater flow in an outcropping fossil fan delta: the case of Sant Llorenç del Munt range (NE Spain)

NASA Astrophysics Data System (ADS)

Anglés, Marc; Folch, Albert; Oms, Oriol; Maestro, Eudald; Mas-Pla, Josep

2017-12-01

Hydrogeological models of mountain regions present the opportunity to understand the role of geological factors on groundwater resources. The effects of sedimentary facies and fracture distribution on groundwater flow and resource exploitation are studied in the ancient fan delta of Sant Llorenç de Munt (central Catalonia, Spain) by integrating geological field observations (using sequence stratigraphy methods) and hydrogeological data (pumping tests, hydrochemistry and environmental isotopes). A comprehensive analysis of data portrays the massif as a single unit, constituted by different compartments determined by specific layers and sets of fractures. Two distinct flow systems—local and regional—are identified based on pumping test analysis as well as hydrochemical and isotopic data. Drawdown curves derived from pumping tests indicate that the behavior of the saturated layers, whose main porosity is given by the fracture network, corresponds to a confined aquifer. Pumping tests also reflect a double porosity within the system and the occurrence of impervious boundaries that support a compartmentalized model for the whole aquifer system. Hydrochemical data and associated spatial evolution show the result of water-rock interaction along the flow lines. Concentration of magnesium, derived from dolomite dissolution, is a tracer of the flow-path along distinct stratigraphic units. Water stable isotopes indicate that evaporation (near a 5% loss) occurs in a thick unsaturated zone within the massif before infiltration reaches the water table. The hydrogeological analysis of this outcropping system provides a methodology for the conceptualization of groundwater flow in similar buried systems where logging and hydrogeological information are scarce.

Evolution of a Miocene sag basin in the Alboran Sea

NASA Astrophysics Data System (ADS)

Do Couto, D.; Gorini, C.; Jolivet, L.; Letouzey, J.; Smit, J.; d'Acremont, E.; Auxietre, J. L.; Le Pourhiet, L.; Estrada, F.; Elabassi, M.; Ammar, A.; Jabour, H.; Vendeville, B.

2012-04-01

The Alboran domain represents the westernmost termination of the peri-Mediterranean Alpine orogen. Its arcuate shape, delimited to the North by the Betic range and to the South by the Rif range, is the result of subduction, collision and slab migration processes. During the Neogene, several sedimentary basins formed on the Betics metamorphic basement, mainly due to the extensional collapse of the previously thickened crust of the Betic-Rif belt. The major sedimentary depocentre, the Western Alboran Basin (WAB), is surrounded by the Gibraltar arc, the volcanic Djibouti mounts and the Alboran ridge, and is partly affected by shale tectonics and associated mud volcanism. High-quality 2-D seismic profiles acquired along the Moroccan margin during the last decade reveal a complete history of the basin. Our study deals with the analysis of seismic profiles oriented parallel and orthogonal to the Mediterranean Moroccan margin. The stratigraphy was calibrated using well data from offshore Spain and Morocco. Our study focuses particularly on the tectono-stratigraphic reconstruction of the basin. The formation of the WAB began in the Early Miocene (Aquitanian - Burdigalian). A massive unit of Early Miocene to Lower Langhian shales and olistostromes forms a thick mobile décollement layer that controls and accommodates deformation of the basin fill. From the Upper Langhian to the Upper Tortonian, the basin is filled by a thick sequence of siliciclastic deposits. Stratigraphic geometries identified on seismic data clearly indicate that deformation of the basin fill started during deposition of Upper Langhian to the Upper Tortonian clastics. Shale tectonic deformation was re-activated recently, during the Messinian desiccation of the Mediterranean Sea (and the following catastrophic Pliocene reflooding) or during the Quaternary contourite deposition The sedimentary layers gently dip towards the basin centre and "onlaps" onto the basin margin, especially onto the basement high that bounds the basin toward the East. The contacts observed between the sediment and the basement reflectors are purely stratigraphic. These observations confirm that the geometry is essentially that of a sag basin. We discuss all these stratigraphic observations in the scope of the geodynamic evolution of the eastern and western Alboran basin and the extension recorded onshore during the basin development time interval.

Prehistoric floods on the Tennessee River—Assessing the use of stratigraphic records of past floods for improved flood-frequency analysis

USGS Publications Warehouse

Harden, Tessa M.; O'Connor, Jim E.

2017-06-14

Stratigraphic analysis, coupled with geochronologic techniques, indicates that a rich history of large Tennessee River floods is preserved in the Tennessee River Gorge area. Deposits of flood sediment from the 1867 peak discharge of record (460,000 cubic feet per second at Chattanooga, Tennessee) are preserved at many locations throughout the study area at sites with flood-sediment accumulation. Small exposures at two boulder overhangs reveal evidence of three to four other floods similar in size, or larger, than the 1867 flood in the last 3,000 years—one possibly as much or more than 50 percent larger. Records of floods also are preserved in stratigraphic sections at the mouth of the gorge at Williams Island and near Eaves Ferry, about 70 river miles upstream of the gorge. These stratigraphic records may extend as far back as about 9,000 years ago, giving a long history of Tennessee River floods. Although more evidence is needed to confirm these findings, a more in-depth comprehensive paleoflood study is feasible for the Tennessee River.

Stratigraphy of the Grande Savane Ignimbrite Sequence, Dominica, Lesser Antilles

NASA Astrophysics Data System (ADS)

Schneider, S.; Smith, A. L.; Deuerling, K.; Killingsworth, N.; Daly, G.

2007-12-01

The island of Dominica, located in the central part of the Lesser Antilles island arc has eight potentially active volcanoes. One of these, Morne Diablotins, is a composite stratovolcano with several superimposed stratigraphic sequences ranging in age from Pliocene (4-2 Ma) to "Younger" Pleistocene (<1.8 Ma). The most recent major eruptive activity from this volcano was a series of Plinian eruptions that produced ignimbrites that gave dates of >22,000 and >40,000 years B.P. The ignimbrite sequences form four flow fans that reached both the east and west coasts of the island. One of these flow fans, the Grande Savane, on the west coast of the island, also extends off-shore for a distance of at least 14 km as a distinctive submarine fan. Stratigraphical studies of the on- shore deposits that make up this fan indicate an older sequence of block and ash flow deposits, within which occurs a distinctive vulcanian fall deposit. These are overlain, with no evidence of an intervening paleosol, by a sequence of ignimbrites containing welded horizons (ranging in thickness from around 4 m to 16m). The lack of fall deposits beneath the ignimbrites suggest they may have been formed by instantaneous continuous collapse of the eruption column. This whole succession is overlain by a series of planar and dune bedded pumiceous surge deposits with interbedded pumiceous lapilli fall and ash fall deposits, that extend laterally outside of the main area of ignimbrite deposition. Beds within this upper sequence often contain accretionary lapilli and gas cavities suggesting magma-water interaction. The youngest deposits from Morne Diablotins appear to be valley- fill deposits of both ignimbrite and block and ash flow. A comparison of the of the Grande Savane pyroclastic sequence with the Pointe Ronde (west coast) and Londonderry (east coast) pyroclastic flow fans will provide information on the eruptive history of this major Plinian episode.

Stratigraphy and depositional environments of Fox Hills Formation in Williston basin

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

Daly, D.J.

The Fox Hills Formation (Maestrichtian), representing part of a regressive wedge deposited during the withdrawal of the sea from the Western Interior at the close of the Cretaceous, consists of marginal marine strata transitional between the offshore deposits of the underlying Pierre Shale and the terrestrial deltaic and coastal deposits of the overlying Hell Creek Formation. An investigation of outcrops of the Fox Hills Formation along the western and southern flanks of the Williston basin and study of over 300 oil and gas well logs from the central part of the basin indicate that the formation can be divided bothmore » stratigraphically and areally. Stratigraphically, the Fox Hills can be divided into lower and upper sequences; the lower includes the Trail City and Timber Lake Members, and the upper sequence includes the Colgate Member in the west and the Iron Lightning and Linton Members in the east. Areally, the formation can be divided into a northeastern and western part, where the strata are 30-45 m thick and are dominated by the lower sequence, and into a southeastern area where both the lower and upper sequences are well developed in a section 80-130 m thick. Typically, the lower Fox Hills consists of upward-coarsening shoreface or delta-front sequences containing hummocky bedding and a limited suite of trace fossils, most notably Ophiomorpha. In the southeast, however, these strata are dominated by bar complexes, oriented northeast-southwest, composed of cross-bedded medium to very fine-grained sand with abundant trace and body fossils. The upper Fox Hills represents a variety of shoreface, deltaic, and channel environments. The strata of the Fox Hills Formation exhibit facies similar to those reported for Upper Cretaceous gas reservoirs in the northern Great Plains.« less

Geology of natural gas reservoir: Upper Travis Peak Formation, western flank of Sabine Uplift, east Texas

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

Fracasso, M.A.

The Travis Peak Formation (Lower Cretaceous) in the eastern East Texas basin represents a sand-rich, fluvial-deltaic depositional system. This lobate, high-constructive deltaic system prograded radially to the southeast from an Upshur County locus. Regional studies of the Travis Peak established a threefold internal stratigraphic framework: a middle sand-rich fluvial and delta-plain sequence is gradationally overlain and underlain by a marine-influenced delta-fringe zone with a higher mud content. The entire Travis Peak succession thins over the Bethany dome on the western flank of the Sabine uplift. However, the delta-fringe sequences are relatively thicker over the structure because of a disproportionately greatermore » thinning of the middle sandy fluvial-deltaic sequence. Lesser sand deposition over the Bethany dome reflects an active structural control over facies distribution. Gas production in the Bethany field and surrounding area is concentrated in thin zones (5-15 ft) of the upper delta-fringe sequence. This distribution probably reflects the increased abundance of mudstone beds in the upper delta-fringe interval, which may have served as source rocks or barriers to upward gas migration, or as both. The predominant trapping mechanism in this region is stratigraphic sand pinch-out in a structurally updip direction on the flanks of major structures. Studies of core and closely spaced electric logs west of the Bethany dome help define the depositional systems in the upper delta-fringe producing interval. This sequence comprises a complex mosaic of continental and marine facies, and exhibits an overall upward trend of increasing marine influence that spans a gradual transition into transgressive carbonates of the Sligo Formation.« less

Stratigraphic implications of trace element and strontium-isotope analyses of Kimmeridgian shell calcite from the Lower Saxony Basin, Germany

NASA Astrophysics Data System (ADS)

Zuo, Fanfan; Heimhofer, Ulrich; Huck, Stefan; Erbacher, Jochen; Bodin, Stephane

2017-04-01

Stratigraphic uncertainties due to the lack of open marine marker fossils (e.g. ammonites) hamper the precise age assignment and stratigraphic correlation of Kimmeridgian strata found in the Lower Saxony Basin of Northern Germany. Correlation of these deposits with the Jurassic standard ammonite zonation is still difficult, since the existing ostracod biostratigraphy is facies-controlled and of only limited stratigraphic precision. In this study, a chemostratigraphic approach has been chosen and biogenic shell material produced by brachiopods, oysters and lithiotids is evaluated for its reliability to act as proxy of the original Jurassic seawater strontium isotope composition. Low-Mg calcite shells have been collected from three stratigraphic sections accessible in open-cast quarries located in the Lower Saxony Basin of Northern Germany. In order to identify diagenetically altered shell calcite, trace element and stable isotope analysis of 227 calcite samples (oysters=101; brachiopods=60; Trichites=52) has been carried out. The geochemical results reveal that (1) concentration of different trace elements varies between the different groups of shell-forming organisms, which may be related to vital effects and (2) high strontium contents, low Mn and Fe contents and the lack of correlation between these elements indicate near-pristine calcite shells, and therefore shells are supposed to record the ambient sea water composition during the Late Jurassic. Strontium-isotope (87Sr/86Sr) analysis of diagenetically screened samples indicates an Early Kimmeridgian age of the studied deposits, which is in accordance with ostracod biostratigraphic data. An increasing trend in 87Sr/86Sr with stratigraphic height fits well with the global strontium-isotope curve. Besides, similar 87Sr/86Sr ratios derived from different organisms from a single stratigraphic level highlight the suitability of the shells for strontium-isotope stratigraphy. Despite the shallow-marine character of the studied deposits, no evidence for significant riverine influence on the strontium-isotope signature is observed. The new chemostratigraphic data will provide a more precise age assignment for Kimmeridgian strata in the Lower Saxony Basin and thus enable the establishment of a solid integrated stratigraphic scheme that can be used for correlation on both regional and global scale.

A composite foraminiferal biostratigraphic sequence for the Lower Miocene deposits in the type area of the Qom Formation, central Iran, developed by constrained optimization (CONOP)

NASA Astrophysics Data System (ADS)

Daneshian, Jahanbakhsh; Ramezani Dana, Leila; Sadler, Peter

2017-01-01

Benthic foraminifera species commonly outnumber planktic species in the type area of the Lower Miocene Qom Formation, in north central Iran, where it records the Tethyan link between the eastern Mediterranean and Indo- Pacific provinces. Because measured sections preserve very different sequences of first and last occurrences of these species, no single section provides a completely suitable baseline for correlation. To resolve this problem, we combined bioevents from three stratigraphic sections into a single composite sequence by constrained optimization (CONOP). The composite section arranges the first and last appearance events (FAD and LAD) of 242 foraminifera in an optimal order that minimizes the implied diachronism between sections. The composite stratigraphic ranges of the planktic foraminifera support a practical biozonation which reveals substantial local changes of accumulation rate during Aquitanian to Burdigalian times. Traditional biozone boundaries emerge little changed but an order of magnitude more correlations can be interpolated. The top of the section at Dobaradar is younger than previously thought and younger than sections at Dochah and Tigheh Reza-Abad. The latter two sections probably extend older into the Aquitanian than the Dobaradar section, but likely include a hiatus near the base of the Burdigalian. The bounding contacts with the Upper Red and Lower Red Formations are shown to be diachronous.

Preliminary report on the geology and geophysics of drill hole UE25a-1, Yucca Mountain, Nevada Test Site

USGS Publications Warehouse

Spengler, Richard W.; Muller, D.C.; Livermore, R.B.

1979-01-01

A subsurface geologic study in connection with the Nevada Nuclear Waste Storage Investigations has furnished detailed stratigraphic and structural information about tuffs underlying northeastern Yucca Mountain on the Nevada Test Site. Drill hole UE25a-1 penetrated thick sequences of nonwelded to densely welded ash-flow and bedded tuffs of Tertiary age. Stratigraphic units that were identified from the drill-hole data include the Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff, tuffaceous beds of Calico Hills, and the Prow Pass and Bullfrog Members of the Crater Flat Tuff. Structural analysis of the core indicated densely welded zones to be highly fractured. Many fractures show near-vertical inclinations and are commonly coated with secondary silica, manganese and iron oxides, and calcite. Five fault zones were recognized, most of which occurred in the Topopah Spring Member. Shear fractures commonly show oblique-slip movement and some suggest a sizable component of lateral compression. Graphic logs are included that show the correlation of lithology, structural properties, and geophysical logs. Many rock units have characteristic log responses but highly fractured zones, occurring principally in the Tiva Canyon and Topopah Spring Members, restricted log coverage to the lower half of the drill hole.

New interpretation of the Gran Dolina-TD6 bearing Homo antecessor deposits through sedimentological analysis

PubMed Central

Campaña, I.; Pérez-González, A.; Benito-Calvo, A.; Rosell, J.; Blasco, R.; de Castro, J. M. Bermúdez; Carbonell, E.; Arsuaga, J. L.

2016-01-01

Gran Dolina is a cavity infilled by at least 25 m of Pleistocene sediments. This sequence contains the TD6 stratigraphic unit, whose records include around 170 hominin bones that have allowed the definition of a new species, Homo antecessor. This fossil accumulation was studied as a single assemblage and interpreted as a succession of several human home bases. We propose a complete stratigraphic context and sedimentological interpretation for TD6, analyzing the relationships between the sedimentary facies, the clasts and archaeo-palaeontological remains. The TD6 unit has been divided into three sub-units and 13 layers. Nine sedimentary facies have been defined. Hominin remains appear related to three different sedimentary facies: debris flow facies, channel facies and floodplain facies. They show three kinds of distribution: first a group of scattered fossils, then a group with layers of fossils in fluvial facies, and third a group with a layer of fossils in mixed fluvial and gravity flow facies. The results of this work suggest that some of these hominin remains accumulated in the cave by geological processes, coming from the adjacent slope above the cave or the cave entry, as the palaeogeography and sedimentary characteristics of these allochthonous facies suggest. PMID:27713562

Identifying and Interpreting Stratification in Sedimentary Rocks on Mars: Insight from Rover and Orbital Observations and Terrestrial Field Analogs

NASA Astrophysics Data System (ADS)

Edgar, Lauren A.

Sedimentary rocks on Mars provide insight into past aqueous and atmospheric processes, climate regimes, and potential habitability. The stratigraphic architecture of sedimentary rocks on Mars is similar to that of Earth, indicating that the processes that govern deposition and erosion on Mars can be reasonably inferred through reference to analogous terrestrial systems. This dissertation aims to understand Martian surface processes through the use of (1) ground-based observations from the Mars Exploration Rovers, (2) orbital data from the High Resolution Imaging Science Experiment onboard the Mars Reconnaissance Orbiter, and (3) the use of terrestrial field analogs to understand bedforms and sediment transport on Mars. Chapters 1 and 2 trace the history of aqueous activity at Meridiani Planum, through the reconstruction of eolian bedforms at Victoria crater, and the identification of a potential mudstone facies at Santa Maria crater. Chapter 3 uses Terrestrial Laser Scanning to study cross-bedding in pyroclastic surge deposits on Earth in order to understand sediment transport in these events and to establish criteria for their identification on Mars. The final chapter analyzes stratal geometries in the Martian North Polar Layered Deposits using tools for sequence stratigraphic analysis, to better constrain past surface processes and past climate conditions on Mars.

Zonal subdivision of marine sequences: achievements and discrepancies

NASA Astrophysics Data System (ADS)

Gladenkov, Yuri

2010-05-01

It was 150 years ago when a notion of zone was introduced into stratigraphy. By the present time zonal units with a duration of 0.3-3.0 M.y. in average have been established virtually for all systems and stages of the Phanerozoic. Their quantity reached 300. It is not a chance that zonal stratigraphy is considered to be one of the most significant achievement of the modern geology. There are different interpretations of essence and goals of zonal stratigraphy, techniques of separation of zones, and evaluation of zones as stratigraphic units. Particularly it is reflected in International Stratigraphic Guide (Murphy, Salvador, 1999), Russian Stratigraphic Code (Zhamoida, 2006), and a number of stratigraphic reports of the last years. It concerns different approaches to: (a) establishment of different types of zones (biostratigraphic zones and chronozones, oppel-zones and biohorizons, etc.); (b) assessment of spatial distribution of zones (global or provincial) and a role of sedimentological factor; (c) definition of zones as stratigraphic units (relationships with geostratigraphic units of the standard and regional scales). The latest publications show that because of the different interpretations of zones, authors should explain usage of certain type of zone (for example, when they use the terms "interval-zone" or "assemblage-zone", what limitations stem from application of datum-levels, and others). It is common opinion, that biostratigraphic zones used widely by paleontologists and stratigraphers cannot be a final goal of stratigraphy although they provide a base for solution of many important problems (definition of certain stratigraphic levels, correlation of different biofacies, and others). At the same time, the most important stratigraphic units are chronozones, which correspond to stages or phases of geological evolutio of basins and are marked by distinct fossil assemblages and other properties (magnetic and other characteristics) in the type sections. Therefore, in Russian Stratigraphic Code biostratigraphic zones are regarded as special units and chronozones as general units of integrated substantiation. Now it becomes clear that unlike chronozones, biostratigraphic zones often have diachronous boundaries and provincial but not global distribution. This is not frequently taken into account at practical correlations. A special attention should be paid to a scale of these occurrences when refining stratigraphic scales. It should not be forgotten that magneto-, litho-, and cyclostratigraphic markers should be used to assess isochronism of zonal boundaries. Many zonal reconstructions do not look faultless without such a control. If we consider zonal stratigraphy not only in applied aspect but in a wide scientific one, it fits in with the geohistorical concept of stratigraphy, which is now reflected in "dynamic", or "ecosystem", or biosphere stratigraphy (Gladenkov, 2004). Establishment of stages of geological development of the Earth and its separate parts, reconstructions of changes in the organic world at the biogeocoenotic and biospheric levels, complex study of paleobiotic assemblages are thought to be one of principal lines of stratigraphic investigations. At present discussions are being organized and experience of zonal stratigraphy is being summarized in Russia. In particular, a large book titled "Biozonal stratigraphy of the Phanerozoic in Russia" and devoted to this problem has been published recently (Koren, 2006). References 1. Gladenkov, Yu.B., 2004. Biosphere Stratigraphy (Stratigraphic Problems in the Early XXI Century). Moscow: GEOS, 120 pp. (in Russian). 2. Koren, T.N., ed., 2006. Biozonal stratigraphy of the Phanerozoic in Russia. Saint-Petersburg: VSEGEI Press, 256 рp. (in Russian). 3. Murphy, M.A., and Salvador, A., eds., 1999. International Stratigraphic Guide: An abridged version. Episodes, 22 (4): 255-271. 4. Zhamoida. A.I., ed., 2006. Russian Stratigraphic Guide (3rd Edition). Saint-Petersburg: VSEGEI Press, 95 pp. (in Russian).

Unearthing The Eruptive Personality Of El Salvador's Santa Ana (Ilamatepec) Volcano Though In-depth Stratigraphic Analysis Of Pre-1904 Deposits

NASA Astrophysics Data System (ADS)

Gallant, E.; Martinez-Hackert, B.

2011-12-01

The Santa Ana (Ilamatepec) volcano (2384 m) in densely populated El Salvador Central America presents serious volcanic hazard potential. The volcano is a prevalent part of every day life in El Salvador; the sugarcane and coffee belt of the country are to its Southern and Western flanks, recreational areas lies to its East, and second and third largest cities of El Salvador exist within its 25 km radius. Understanding the eruptive characteristics and history is imperative due to the volcano's relative size (the highest in the country) and it's explosive, composite nature. Historical records indicate at least 9 potential VEI 3 eruptions since 1521 AD. The volcano's relative inaccessibility and potential hazards do not promote a vast reservoir of research activity, as can be seen in the scarcity of published papers on topics prior to the 1904 eruption. This research represents the first steps towards creating a comprehensive stratigraphic record of the crater and characterizing its eruptive history, with an eventual goal of recreating the volcanic structure prior to its collapse. Samples of pre-1904 eruptive material were taken from the southern wall of an E-W oriented fluvial gully located within the SSW of the tertiary crater. These were analyzed using thin sections and optical microscopy, grain size distribution techniques, and scanning electron microscopy. The 15-layer sequence indicates an explosive history characterized by intense phreatomagmatic phases, plinian, sub-plinian and basaltic/andesitic composition strombolian activity. Another poster within the session will discuss an older sequence within the walls of the secondary crater. Further detailed studies will be required to gain a better understanding of the characteristics of Santa Ana Volcano.

Biostratigraphic sequence analysis of two Lower Miocene to Pliocene sections, Eastern Falcon, Northwestern Venezuela

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

Diaz De Gamero, M.L.; Giffuni, G.; Castro Mora, M.

1993-02-01

The eastern region of the Falcon Basin in northwestern Venezuela comprises a thick sedimentary sequence deposited from a deep marine bathyal to neritic environment, ranging in age from the Middle Eocene to the Pliocene. A detailed biostratigraphic study (foraminifera and calcareous nannoplankton) was carried out in two sedimentary sequences outcropping in Cumarebo and Piritu, adjacent areas of eastern Falcon, representing: platform, slope and basinal settings. The Cumarebo section is continuous in the studied interval, from the Middle Miocene to the Pliocene. The Piritu section is continuous from the Lower to the lower Upper Miocene, terminating unconformably beneath a thin intervalmore » of middle Pliocene platform sediments, indicating tectonism during the latest Miocene. The sequence stratigraphical interpretation was based on the biostratigraphic analysis of the benthic and planktonic fossils, facies distribution and sedimentological data. Systems tracts, sequence boundaries and maximum flooding surfaces from cycles TB2.4 to TB3.5 of the cycle chart were identified. In the Cumarebo section, the upper Middle and Upper Miocene is mostly composed of shales, with some turbiditic sands belonging to a LSW system tract. The upper most Miocene contains a thick carbonate buildup (HST), and it is overlain by a Pliocene section that shallows upward from upper slope to outer shelf depositional environments. In the basinal (Piritu) section, most of the sediments are deep-water shales belonging to a LSW system tract, with some turbiditic sands in the upper Lower Miocene. TST and HST sediments, with scattered carbonate buildups in the upper Middle Miocene were also identified.« less

Regional Stratigraphy and Petroleum Systems of the Michigan Basin, North America

USGS Publications Warehouse

Swezey, Christopher S.

2008-01-01

Although more than 100 years of research have gone into deciphering the stratigraphy of the Michigan basin of North America, it remains a challenge to visualize the basin stratigraphy on a regional scale and to describe stratigraphic relations within the basin. Similar difficulties exist for visualizing and describing the regional distribution of petroleum source rocks and reservoir rocks. This publication addresses these difficulties by combining data on Paleozoic and Mesozoic stratigraphy and petroleum geology of the Michigan basin. The areal extent of this structural basin is presented along with data in eight schematic chronostratigraphic sections arranged from north to south, with time denoted in equal increments along the sections. The stratigraphic data are modified from American Association of Petroleum Geologists (AAPG) (1984), Johnson and others (1992), Sanford (1993), and Cross (1998), and the time scale is taken from Harland and others (1990). Informal North American chronostratigraphic terms from AAPG (1984) are shown in parentheses. Stratigraphic sequences as defined by Sloss (1963, 1988) and Wheeler (1963) also are included, as well as the locations of major petroleum source rocks and major petroleum plays. The stratigraphic units are colored according to predominant lithology, in order to emphasize general lithologic patterns and to provide a broad overview of the Michigan basin. For purposes of comparison, schematic depictions of stratigraphy and interpreted events in the Michigan basin and adjacent Appalachian basin are shown. The paper version of this map is available for purchase from the USGS Store.

Trait-based diversification shifts reflect differential extinction among fossil taxa.

PubMed

Wagner, Peter J; Estabrook, George F

2014-11-18

Evolution provides many cases of apparent shifts in diversification associated with particular anatomical traits. Three general models connect these patterns to anatomical evolution: (i) elevated net extinction of taxa bearing particular traits, (ii) elevated net speciation of taxa bearing particular traits, and (iii) elevated evolvability expanding the range of anatomies available to some species. Trait-based diversification shifts predict elevated hierarchical stratigraphic compatibility (i.e., primitive→derived→highly derived sequences) among pairs of anatomical characters. The three specific models further predict (i) early loss of diversity for taxa retaining primitive conditions (elevated net extinction), (ii) increased diversification among later members of a clade (elevated net speciation), and (iii) increased disparity among later members in a clade (elevated evolvability). Analyses of 319 anatomical and stratigraphic datasets for fossil species and genera show that hierarchical stratigraphic compatibility exceeds the expectations of trait-independent diversification in the vast majority of cases, which was expected if trait-dependent diversification shifts are common. Excess hierarchical stratigraphic compatibility correlates with early loss of diversity for groups retaining primitive conditions rather than delayed bursts of diversity or disparity across entire clades. Cambrian clades (predominantly trilobites) alone fit null expectations well. However, it is not clear whether evolution was unusual among Cambrian taxa or only early trilobites. At least among post-Cambrian taxa, these results implicate models, such as competition and extinction selectivity/resistance, as major drivers of trait-based diversification shifts at the species and genus levels while contradicting the predictions of elevated net speciation and elevated evolvability models.

Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska

USGS Publications Warehouse

Waythomas, C.F.

1999-01-01

Akutan Volcano is one of the most active volcanoes in the Aleutian arc, but until recently little was known about its history and eruptive character. Following a brief but sustained period of intense seismic activity in March 1996, the Alaska Volcano Observatory began investigating the geology of the volcano and evaluating potential volcanic hazards that could affect residents of Akutan Island. During these studies new information was obtained about the Holocene eruptive history of the volcano on the basis of stratigraphic studies of volcaniclastic deposits and radiocarbon dating of associated buried soils and peat. A black, scoria-bearing, lapilli tephra, informally named the 'Akutan tephra,' is up to 2 m thick and is found over most of the island, primarily east of the volcano summit. Six radiocarbon ages on the humic fraction of soil A-horizons beneath the tephra indicate that the Akutan tephra was erupted approximately 1611 years B.P. At several locations the Akutan tephra is within a conformable stratigraphic sequence of pyroclastic-flow and lahar deposits that are all part of the same eruptive sequence. The thickness, widespread distribution, and conformable stratigraphic association with overlying pyroclastic-flow and lahar deposits indicate that the Akutan tephra likely records a major eruption of Akutan Volcano that may have formed the present summit caldera. Noncohesive lahar and pyroclastic-flow deposits that predate the Akutan tephra occur in the major valleys that head on the volcano and are evidence for six to eight earlier Holocene eruptions. These eruptions were strombolian to subplinian events that generated limited amounts of tephra and small pyroclastic flows that extended only a few kilometers from the vent. The pyroclastic flows melted snow and ice on the volcano flanks and formed lahars that traveled several kilometers down broad, formerly glaciated valleys, reaching the coast as thin, watery, hyperconcentrated flows or water floods. Slightly cohesive lahars in Hot Springs valley and Long valley could have formed from minor flank collapses of hydrothermally altered volcanic bedrock. These lahars may be unrelated to eruptive activity.

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

NASA Astrophysics Data System (ADS)

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

2011-04-01

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

Sediment facies of Enewetak Atoll lagoon. Geologic and geophysical investigations of Enewetak Atoll, Republic of the Marshall Islands. Professional paper

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

Wardlaw, B.R.; Henry, T.W.; Martin, W.E.

1991-01-01

Two sets of benthic (bottom-surface) samples were taken from the lagoon on Enewetak Atoll, Republic of the Marshall Islands, during the PEACE Program (1984-1985). These samples were collected to (1) familiarize project geologists with the distribution of sediment types and facies within Enewetak lagoon, (2) increase understanding of the distribution of modern microfaunas in the lagoon, and (3) supplement studies of the sea-floor features both within and near OAK and KOA craters. The benthic sample studies aided both evaluation of the stratigraphic sequence penetrated during the Drilling Phase and interpretation of the litho- and biostratigraphic framework used in analysis ofmore » OAK and KOA.« less

Integrated biostratigraphic and sequence stratigraphic framework for Upper Cretaceous strata of the eastern Gulf Coastal Plain, USA

USGS Publications Warehouse

Mancini, E.A.; Puckett, T.M.; Tew, B.H.

1996-01-01

Upper Cretaceous (Santonian-Maastrichtian stages) strata of the eastern US Gulf Coastal Plain represent a relatively complete section of marine to nonmarine mixed siliciclastic and carbonate sediments. This section includes three depositional sequences which display characteristic systems tracts and distinct physical defining surfaces. The marine lithofacies are rich in calcareous nannoplankton and planktonic foraminifera which can be used for biostratigraphic zonation. Integration of this zonation with the lithostratigraphy and sequence stratigraphy of these strata results in a framework that can be used for local and regional intrabasin correlation and potentially for global interbasin correlation. Only the synchronous maximum flooding surfaces of these depositional sequences, however, have chronostratigraphic significance. The sequence boundaries and initial flooding surfaces are diachronous, and their use for correlation can produce conflicting results. The availability of high resolution biostratigraphy is critical for global correlation of depositional sequences. ?? 1996 Academic Press Limited.

Sequence stratigraphy of the Monterey Formation, Santa Barbara County: Integration of physical, chemical, and biofacies data from outcrop and subsurface

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

Bohacs, K.M.

1991-02-01

Deep basinal rocks of the Monterey Formation can be allocated to different depositional environments based on an integration of bedding, stacking patterns of facies, lithology, biofacies, and inorganic and organic chemistry. These rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level changes and basin evolution. Even deep-basinal environments are affected by changing sea level through changes in circulation patterns and intensities, nutrient budgets and dispersal patterns, and location and intensity of the oceanic oxygen minimum. The sequence-stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed bymore » typing the outcrop sections to an integrated will-log/seismic grid through outcrop gamma-ray spectral profiles. Interpretation of a sequence boundary was based on increased proportions of hemipelagic facies and evidence of increased bottom-energy levels above the boundary, and local erosion and relief on the surface. The proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary. Downlap surfaces exhibited increased proportions of pelagic facies around the surface, a secular change in the dominant lithology across the surface, evidence of decreased bottom-energy levels and terrigenous sedimentation rates, and little or not significant erosion on the surface. The proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface; there was no evidence of reworked individuals. The detailed sequence-stratigraphic framework makes it possible to tie rock properties to genetic processes for construction of predictive models.« less

New U-series dates at the Caune de l'Arago, France

USGS Publications Warehouse

Falgueres, Christophe; Yokoyama, Y.; Shen, G.; Bischoff, J.L.; Ku, T.-L.; de Lumley, Henry

2004-01-01

In the beginning of the 1980s, the Caune de l'Arago was the focus of an interdisciplinary effort to establish the chronology of the Homo heidelbergensis (Preneandertals) fossils using a variety of techniques on bones and on speleothems. The result was a very large spread of dates particularly on bone samples. Amid the large spread of results, some radiometric data on speleothems showed a convergence in agreement with inferences from faunal studies. We present new U-series results on the stalagmitic formation located at the bottom of Unit IV (at the base of the Upper Stratigraphic Complex). Samples and splits were collaboratively analyzed in the four different laboratories with excellent interlaboratory agreement. Results show the complex sequence of this stalagmitic formation. The most ancient part is systematically at internal isotopic equilibrium (>350 ka) suggesting growth during or before isotopic stage 9, representing a minimum age for the human remains found in Unit III of the Middle Stratigraphical Complex which is stratigraphically under the basis of the studied stalagmitic formation. Overlaying parts of the speleothem date to the beginning of marine isotope stages 7 and 5. ?? 2003 Elsevier Science Ltd. All rights reserved.

Radiolarian biostratigraphic data from the Casiguran Ophiolite, Northern Sierra Madre, Luzon, Philippines: Stratigraphic and tectonic implications

NASA Astrophysics Data System (ADS)

Queano, Karlo L.; Marquez, Edanjarlo J.; Aitchison, Jonathan C.; Ali, Jason R.

2013-03-01

Results from the first detailed radiolarian biostratigraphic study conducted in Luzon are reported. The data were obtained from cherts associated with the Casiguran Ophiolite, a dismembered ophiolite mass consisting of serpentinized peridotites, gabbros, dolerite dikes and pillow basalts exposed along the eastern coast of the Northern Sierra Madre, Luzon, Philippines. Cherts and limestone interbeds conformably overlie the ophiolite. The radiolarian assemblages from the cherts constrain the stratigraphic range of the cherts to the Lower Cretaceous (upper Barremian-lower Aptian to Albian). This new biostratigraphic result is in contrast with the Upper Cretaceous stratigraphic range previously reported in the region. Radiolarian biostratigraphic results from the Casiguran Ophiolite provide additional evidence for the existence of Mesozoic oceanic substratum upon which Luzon and neighboring regions within the Philippine archipelago were likely built. Interestingly, the result closely resembles those reported for the ophiolite in southeastern Luzon as well as the oceanic crust of the Huatung Basin situated east of Taiwan and the ophiolites in eastern Indonesia. In light of this, along with previously gathered geochemical data from the ophiolites, a common provenance is being looked into for these crust-upper mantle sequences in the western Pacific region.

Global geologic mapping of Mars: The western equatorial region

USGS Publications Warehouse

Scott, D.H.

1985-01-01

Global geologic mapping of Mars was originally accomplished following acquisition of orbital spacecraft images from the Mariner 9 mission. The mapping program represented a joint enterprise by the U.S. Geological Survey and other planetary scientists from universities in the United States and Europe. Many of the Mariner photographs had low resolution or poor albedo contrast caused by atmospheric haze and high-sun angles. Some of the early geologic maps reflect these deficiencies in their poor discrimination and subdivision of rock units. New geologic maps made from higher resolution and better quality Viking images also represent a cooperative effort, by geologists from the U.S. Geological Survey, Arizona State University, and the University of London. This second series of global maps consists of three parts: 1) western equatorial region, 2) eastern equatorial region, and 3) north and south polar regions. These maps, at 1:15 million scale, show more than 60 individual rock-stratigraphic units assigned to three Martian time-stratigraphic systems. The first completed map of the series covers the western equatorial region of Mars. Accompanying the map is a description of the sequence and distribution of major tectonic, volcanic, and fluvial episodes as recorded in the stratigraphic record. ?? 1985.

New U-series dates at the Caune de l'Arago, France

USGS Publications Warehouse

Falgueres, Christophe; Yokoyama, Y.; Shen, G.; Bischoff, J.L.; Ku, T.-L.; de Lumley, Henry

2004-01-01

In the beginning of the 1980s, the Caune de l'Arago was the focus of an interdisciplinary effort to establish the chronology of the Homo heidelbergensis (Preneandertals) fossils using a variety of techniques on bones and on speleothems. The result was a very large spread of dates particularly on bone samples. Amid the large spread of results, some radiometric data on speleothems showed a convergence in agreement with inferences from faunal studies. We present new U-series results on the stalagmitic formation located at the bottom of Unit IV (at the base of the Upper Stratigraphic Complex). Samples and splits were collaboratively analyzed in the four different laboratories with excellent interlaboratory agreement. Results show the complex sequence of this stalagmitic formation. The most ancient part is systematically at internal isotopic equilibrium (>350 ka) suggesting growth during or before isotopic stage 9, representing a minimum age for the human remains found in Unit III of the Middle Stratigraphical Complex which is stratigraphically under the basis of the studied stalagmitic formation. Overlaying parts of the speleothem date to the beginning of marine isotope stages 7 and 5. ?? 2003 Elsevier Ltd. All rights reserved.

The source of anomalous radioactivity in the springs bordering the Sea of Galilee, Israel.

PubMed

Ilani, S; Minster, T; Kronfeld, J; Even, O

2006-01-01

Situated within the Jordan Rift Valley, along the shores of Lake Kinneret (Sea of Galilee) which serves as the national water reservoir of Israel, are saline hot springs that are notable for their enrichment in radon and radium. Though the anomalous radioactivity has been known for almost half a century, the source of the radioactive anomalies has been a subject of conjecture. Radiometric analysis of a rock core drilled through Mt. Arbel, situated to the west of the lake, reveals that the oil shale sequence of the Senonian En Zetim and Ghareb formations is strikingly deficient in radium. Mt. Arbel has been cut by Rift Valley related faults that serve as conduits for ascending brines. The organic matter enriched sequence is encountered in the subsurface at elevations lower than the water level of the nearby radioactive enriched hot springs. It is thus concluded that hot ascending brines underlying the lake flush through the organic matter enriched sequence and remove a substantial percentage of 226Ra from the uranium enriched organic material, before draining to the outlets of the springs. Saline springs that are in contact with organic matter enriched sequence show excess of radium and radon, while fresh water springs in the same stratigraphic position show only excess of radon.

The relationship between shellbed type and sequence architecture: examples from Japan and New Zealand

NASA Astrophysics Data System (ADS)

Kondo, Yasuo; Abbott, Stephen T.; Kitamura, Akihisa; Kamp, Peter J. J.; Naish, Tim R.; Kamataki, Takanobu; Saul, Gordon S.

1998-12-01

Examples of lithology, fossil content and taphonomic features of shellbeds and intervening less fossiliferous intervals are presented from four Plio-Pleistocene successions (Shimosa Group, Boso Peninsula, Omma Formation, Hokuriku area, Japan, and Okehu, Kai-iwi, and Shakespeare groups in Wanganui, and the Rangitikei Group along the Rangitikei River in New Zealand). As for pre-Pliocene 3rd- and 4th-order depositional sequences, Plio-Pleistocene 5th- to 7th-order depositional sequences contain a variety of shellbeds which are often associated with surfaces or intervals that are characterized by sedimentary condensation, omission or erosion (e.g. sequence boundaries, ravinement surfaces, downlap surfaces and condensed sections). Stratigraphic patterns of shellbed type tend to be similar and repetitive within a basin and a locality. This demonstrates that a specific palaeogeography played an important role in determining the nature of shellbeds. For example, shellbeds formed in the context of toplap are common only in the Shimosa Group, which was deposited in a moderately sheltered sea, the palaeo-Tokyo Bay. Toplap shellbeds are rare in other sequences formed in more open conditions. Despite the variability resulting from such basin characteristics, common styles of shellbeds can be recognized that formed under conditions of marine onlap, backlap, downlap and toplap. Each type of shellbed has a characteristic fossil composition and taphonomy. Onlap and toplap shellbeds contain low-diversity macrobenthic associations including Glycymeris, Mercenaria, Paphies or other bivalves having robust shells, which are often abraded or fragmented. Backlap shellbeds, which are equivalent to the condensed section formed at the maximum transgression, are characterized by dominance of epifaunal macrobenthos such as bryozoa, brachiopoda, pectinid and ostreid bivalves, preserved in a slightly cemented, glauconitic muddy matrix. In contrast to fossils in such condensed sections, the shell density and species diversity of downlap shellbed associations are rather low, and in a few examples the macrobenthic association was buried rapidly in a lower unit of the highstand systems tract (HST) stratigraphically located above the condensed sections. Variations in the stratigraphic distribution of shellbed types are reflected in symmetrical and asymmetrical sequence architectures. Symmetrical sequences have roughly the same thickness of transgressive systems tracts (TST) and highstand systems tracts (HST), and have well segregated shellbeds that were formed during marine onlap and backlap. Asymmetrical cycles have very thin TSTs and much thicker HSTs, and are characterized by the amalgamation of condensed onlap and backlap shellbeds. Such contrasting cycle architectures are interpreted to reflect inner (symmetrical) and outer (asymmetrical) shelf palaeodepositional settings. The amalgamated onlap/backlap shellbeds appear to be common in Plio-Pleistocene sequences. Owing to the short duration of glacio-eustatic sea-level changes with dominant frequencies of 20,000, 40,000 or 100,000 years, shellbeds in the Plio-Pleistocene are relatively simple and thin compared to those formed in ordinary third-order depositional sequences. Infauna-dominated benthic associations are generally more common than in third-order cycles, and epifaunal associations facilitated by taphonomic feedback on sediment-starved shell-gravel substrates occur only in the condensed section corresponding to maximum transgression in most Plio-Pleistocene sequences.

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

NASA Astrophysics Data System (ADS)

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

2008-12-01

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

Exploring the Middle Pleistocene Lake Suguta Sr-isotope Stratigraphic record

NASA Astrophysics Data System (ADS)

Vonhof, Hubert; Junginger, Annett; Agmon, Nadav; Trauth, Martin

2017-04-01

Several studies into the Quaternary stratigraphic record of the Sr-isotope composition of paleolake Turkana in the East African Rift System (EARS) show how variation of climate left a signal of changing lacustrine Sr isotope values. This Sr isotope signal was captured in the lacustrine fossil record of the Turkana Basin, and can be a useful chemostratigraphic tool (e.g. Joordens et al., 2011; van der Lubbe et al., submitted). Such lacustrine Sr-isotope changes are believed to be paced by orbital-forced insolation cyclicity, and interpreted to be the result of changing contribution of run-off from different sub-catchments of lake Turkana, as climate change shifted regional rainfall patterns. Here, we present a first set of data from a middle Pleistocene stratigraphical sequence in the Suguta Valley, South of the Turkana Basin in the EARS. This sequence spans a couple of sedimentological cycles that potentially represent precession-forced lake level variation. In this setting, the Sr-isotope data do not vary in phase with these sedimentological cycles, but demonstrate a long trend of Sr isotope change. This may suggest that the catchment configuration of the Suguta Valley in the Mid Pleistocene was less suitable to record precession-forced hydroclimate change in Lacustrine Sr isotope ratios. This may have implications for the Turkana Basin Sr isotope record as well, because the two basins are believed to have been hydrologically connected in the Middle Pleistocene. references: 1)Joordens, J.C.A. et al., 2011. An astronomically-tuned climate framework for hominins in the Turkana Basin. Earth and Planetary Science Letters 307, 1-8. 2)van der Lubbe et al., submitted. Gradual or abrupt? Changes in water source of Lake Turkana (Kenya) during the African Humid Period inferred from Sr isotope ratios

New chronology of the best developed loess/paleosol sequence of Hungary capturing the past 1.1 ma: Implications for correlation and proposed pan-Eurasian stratigraphic schemes

NASA Astrophysics Data System (ADS)

Sümegi, P.; Gulyás, S.; Molnár, D.; Sümegi, B. P.; Almond, P. C.; Vandenberghe, J.; Zhou, L.; Pál-Molnár, E.; Törőcsik, T.; Hao, Q.; Smalley, I.; Molnár, M.; Marsi, I.

2018-07-01

In this paper, we are presenting a revised chronology of the best developed, longest (100 m) LPS in Hungary dating back 1.1 Ma: borehole Udvari-2A. It is based on a non-tuned age-depth model, built on the position of the Matuyama-Brunhes Boundary, Jaramillo and Olduvai Subchrons. Furthermore, on the assignment of formerly recorded uninterpreted geomagnetic reversals in both chrons. Other chronometric tools (AMS 14C dating, biostratigraphy, tephrostratigraphy) yielding absolute ages and/or ensuring validation of these were also used. Records of a Middle Pleistocene gastropod index fossil Neostyriaca corynodes (400 -140 ka) facilitated verification of ages between MIS 10 and MIS 6. Multiple age control points at 15, 25, 27, 45, 120, 191, 362, 430, 670, 780, 900, 990, 1070 ka were established for the last ca. 1.1 Ma. The resulting chronology is the best resolved independent one so far among Danubian Basin LPSs. In light of our data, the S3-S4 units were fused as S3 in all Serbian, and some Romanian sites and re-correlated with MIS 9. The results also point to a misassignment of the S5 units at these sites to MIS 13-15 leading to erroneous conclusions regarding paleoclimatic conditions and cyclicity. In our new stratigraphic scheme, these S5 paleosols were taken to represent the S4 paleosol and recorrelated with MIS 11. Finally, an ideal stratigraphic column dating back 1.1 Ma for SW Hungary was constructed and correlated with the Chinese loess/paleosol sequence of Xifeng and the benthic oxygen isotope record down to MIS 31.

The Relationship between Litho-Sequential Stratigraphy, Chemostratigraphy of Khuff Carbonates: Implication for Facies and Paleoenvironmental Recognition and Correlation, Central Saudi Arabia

NASA Astrophysics Data System (ADS)

Abdullatif, Osman; Abdlmutalib, Ammar; Ahmed, Jarrah; Abdelgadir, Mohamed; Adam, Ammar

2017-04-01

The Permian-Triassic Khuff Formation carbonate reservoirs (and equivalents) in the Middle East are estimated to contain about 15-20 % of the world's gas reserves. Excellently exposed outcropping Khuff strata in central Saudi Arabia provide good outcrop equivalents to the Khuff Formation in the subsurface. The Khuff Formation is composed of five members and from bottom to top are Ash Shiqqah, Huqayl, Duhaysan, Midnab and Khartam members. The Carbonates lithofacies dominate with minor terrestrial clastics, and the paleoenvironments vary from terrestrial, sabkha, tidal-intertidal and open marine environments. This study investigates the relationship between lithostratigraphy, sequence stratigraphy and chemostratigraphy by integration of both field and laboratory sedimentological and chemical elements data. The vertical chemical elements profiles along the Khuff members show variations in their chemical elements content with the variation in lithofacies types, staking pattern, depositional and stratigraphic pattern. The chemostratigraphic distribution of the chemical elements also showed variation within and between the Khuff members. There is a general agreement between chemostratigraphic analyses based on vertical profiles and binary cross plots. The Khuff members and their stratigraphic boundaries can be differentiated based on their chemostratigraphic signatures. Moreover, the lithofacies and depositional paleoenvironmental of different Khuff members can be identified based on their chemical element contents. Chemostratigraphic zones or clusters are markedly established indicating different lithofacies and depositional paleoenvironments. Terrestrial, channel, lacustrine, shoreline to open marine carbonate lithofacies, as building blocks of sequence stratigraphy, all may be distinguished based on their chemical signatures. These outcrop analog results might be of significance to lithofacies, paleoenvironmental, stratigraphic identification, classification and correlation of Khuff Formation in the subsurface. The results might also provide guides and application to reservoir Khuff Formation identification, layering and zonation in the subsurface.

Evidence for synchronous thin-skinned and basement deformation in the Cordilleran fold-thrust belt: the Tendoy Mountains, southwestern Montana

NASA Astrophysics Data System (ADS)

McDowell, Robin John

1997-01-01

The Tendoy Mountains contain the easternmost thin-skinned thrust sheets in the Cordilleran fold-thrust belt of southwestern Montana, and are in the zone of tectonic overlap between the Rocky Mountain foreland and the Cordilleran fold-thrust belt. The three frontal thrust sheets of the Tendoy Mountains are from north to south, the Armstead, McKenzie, and Tendoy sheets. Near the southeastern terminus of the Tendoy thrust sheet is a lateral ramp in which the Tendoy thrust climbs along strike from the Upper Mississippian Lombard Limestone to lower Cretaceous rocks. This ramp coincides with the southeastern side of the Paleozoic Snowcrest trough and projection of the range-flanking basement thrust of the Blacktail-Snowcrest uplift, suggesting either basement or stratigraphic control on location of the lateral ramp. Axes of major folds on the southern part of the Tendoy thrust sheet are parallel to the direction of thrust transport and to the trend of the Snowcrest Range. They are a result of: (1) Pre-thrust folding above basement faults; (2) Passive transportation of the folds from a down-plunge position; (3) Minor reactivation of basement faults; and (4) Emplacement of blind, sub-Tendoy, thin-skinned thrust faults. The Tendoy sheet also contains a major out-of-sequence thrust fault that formed in thick Upper Mississippian shales and created large, overturned, foreland-verging folds in Upper Mississippian to Triassic rocks. The out-of-sequence fault can be identified where stratigraphic section is omitted, and by a stratigraphic separation diagram that shows it cutting down section in the direction of transport. The prominent lateral ramp at the southern terminus of the Tendoy thrust sheet is a result of fault propagation through strata folded over the edge of the Blacktail-Snowcrest uplift.

The STRATAFORM Project: U.S. Geological Survey geotechnical studies

USGS Publications Warehouse

Minasian, Diane L.; Lee, Homa J.; Locat, Jaques; Orzech, Kevin M.; Martz, Gregory R.; Israel, Kenneth

2001-01-01

This report presents physical property logs of core samples from an offshore area near Eureka, CA. The cores were obtained as part of the STRATAFORM Program (Nittrouer and Kravitz, 1995, 1996), a study investigating how present sedimentation and sediment transport processes influence long-term stratigraphic sequences preserved in the geologic record. The core samples were collected during four separate research cruises to the northern California study area, and data shown in the logs of the cores were collected using a multi-sensor whole core logger. The physical properties collected are useful in identifying stratigraphic units, ground-truthing acoustic imagery and sub-bottom profiles, and in understanding mass movement processes. STRATA FORmation on Margins was initiated in 1994 by the Office of Naval Research, Marine Geology and Geophysics Department as a coordinated multi-investigator study of continental-margin sediment transport processes and stratigraphy (Nittrouer and Kravitz, 1996). The program is investigating the stratigraphic signature of the shelf and slope parts of the continental margins, and is designed to provide a better understanding of the sedimentary record and a better prediction of strata. Specifically, the goals of the STRATAFORM Program are to (Nittrouer and Kravitz, 1995): - determine the geological relevance of short-term physical processes that erode, transport, and deposit particles and those processes that subsequently rework the seabed over time scales - improve capabilities for identifying the processes that form the strata observed within the upper ~100 m of the seabed commonly representing 104-106 years of sedimentation. - synthesize this knowledge and bridge the gap between time scales of sedimentary processes and those of sequence stratigraphy. The STRATAFORM Program is divided into studies of the continental shelf and the continental slope; the geotechnical group within the U.S. Geological Survey provides support to both parts of the project.

Climate change versus land management in the Po Plain (Northern Italy) during the Bronze Age: New insights from the VP/VG sequence of the Terramara Santa Rosa di Poviglio

NASA Astrophysics Data System (ADS)

Cremaschi, Mauro; Mercuri, Anna Maria; Torri, Paola; Florenzano, Assunta; Pizzi, Chiara; Marchesini, Marco; Zerboni, Andrea

2016-03-01

The sedimentary infilling of the moat surrounding the Villaggio Piccolo of the Terramara Santa Rosa di Poviglio was analysed in order to obtain palaeoenvironmental inferences from sediments and pollen assemblage. The high-resolution stratigraphic sequence preserves evidence of the environmental changes that occurred in the Po Plain, in Northern Italy, during the Late Holocene. Our interdisciplinary approach permitted to study climatic and anthropic contributions to the environmental changes in this region. The relationships between these changes and land-use changes were investigated focussing on adaptive strategies of the Terramare people during the Middle and Recent Bronze ages (1550-1170 yr BC). The Terramare are archaeological remains of banked and moated villages, located in the central alluvial plain of the Po river. The Terramara of Santa Rosa consists of two adjoining settlements (Villaggio Grande and Villaggio Piccolo); the moat that separates the two parts of the site is c. 23 m large and reaches a maximum depth of 4 m from the extant ground level. The stratigraphic sequence VP/VG exposed by archaeological excavation inside the moat was sampled for pedosedimentary, thin section, and pollen analyses. Chronology is based on archaeological evidence, stratigraphic correlations and radiocarbon dating. Pedosedimentary features and biological records (pollen of aquatics and algal remains) demonstrate that shallow water, probably subjected to seasonal water-level oscillations, has always been present in the moat. In the lower units of the sequence, the laminations indicate standing water, while occurrence of reworked pollen testified the supply of sediments to the plain from catchment zones located in the Apennine. Open vegetation was widespread; economy was based on wood management, fruit collection on the wild or from cultivated woody plants, crop fields with a fairly diversified set of cereals especially increasing in variety during dryness or phases of water crisis. Probably, grapevines were cultivated near the moat, where the wet habitat was favourable to the growing of wild plants. The extraordinary high-resolution of this sequence makes visible the management of woods (including coppicing) at the Middle Bronze and early Recent Bronze ages. The economy of Santa Rosa di Poviglio should have been probably less based on animal breeding than it was in the other Terramare villages already studied for pollen. This research also confirms the chronological correspondence between an environment stressed by dry conditions and the collapse of the Terramare civilization.

Sedimentological and stratigraphic evolution of the southern part of the Barberton greenstone belt: A case of changing provenance and stability

NASA Technical Reports Server (NTRS)

Lowe, D. R.; Byerly, G. R.

1986-01-01

The sedimentological and stratigraphic evolution of the 3.5 to 3.3 Ga Barberton Greenstone Belt can be divided into three principal stages: (1) the volcanic platform stage during which at least 8 km of mafic and ultramafic volcanic rocks, minor felsic volcanic units, and thin sedimentary layers (Onverwacht Group) accumulated under generally anorogenic conditions; (2) a transitional stage of developing instability during which widespread dacitic volcanism and associated pyroclastic and volcaniclastic sedimentation was punctuated by the deposition of terrigenous debris derived by uplift and shallow erosion of the belt itself (Fig Tree Group); (3) an orogenic stage involving cessation of active volcanism, extensive thrust faulting, and widespread deposition of clastic sediments representing deep erosion of the greenstone belt sequence as well as sources outside of the belt (Moodies Group).

Direct evidence of 1,900 years of indigenous silver production in the Lake Titicaca Basin of Southern Peru

PubMed Central

Schultze, Carol A.; Stanish, Charles; Scott, David A.; Rehren, Thilo; Kuehner, Scott; Feathers, James K.

2009-01-01

Archaeological excavations at a U-shaped pyramid in the northern Lake Titicaca Basin of Peru have documented a continuous 5-m-deep stratigraphic sequence of metalworking remains. The sequence begins in the first millennium AD and ends in the Spanish Colonial period ca. AD 1600. The earliest dates associated with silver production are 1960 ± 40 BP (2-sigma cal. 40 BC to AD 120) and 1870 ± 40 BP (2-sigma cal. AD 60 to 240) representing the oldest known silver smelting in South America. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis of production debris indicate a complex, multistage, high temperature technology for producing silver throughout the archaeological sequence. These data hold significant theoretical implications including the following: (i) silver production occurred before the development of the first southern Andean state of Tiwanaku, (ii) the location and process of silverworking remained consistent for 1,500 years even though political control of the area cycled between expansionist states and smaller chiefly polities, and (iii) that U-shaped structures were the location of ceremonial, residential, and industrial activities. PMID:19805127

Recognition, correlation, and hierarchical stacking patterns of cycles in the Ferry Lake - Uppe Glen Rose, East Texas Basin: Implications for grainstone reservoir distribution

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

Fitchen, W.M.; Bebout, D.G.; Hoffman, C.L.

1994-12-31

Core descriptions and regional log correlation/interpretation of Ferry Lake-Upper Glen Rose strata in the East Texas Basin exhibit the uniformity of cyclicity in these shelf units. The cyclicity is defined by an upward decrease in shale content within each cycle accompanied by an upward increase in anhydrite (Ferry Lake) or carbonate (Upper Glen Rose). Core-to-log calibration of facies indicates that formation resistivity is inversely proportional to shale content and thus is a potential proxy for facies identification beyond core control. Cycles (delineated by resistivity log patterns) were correlated for 90 mi across the shelf; they show little change in logmore » signature despite significant updip thinning due to the regional subsidence gradient. The Ferry-Lake-Upper Glen Rose intervals is interpreted as a composite sequence composed of 13 high-frequency sequences (4 in the Ferry Lake and 9 in the Upper Glen Rose). High-frequency sequences contain approximately 20 ({+-}5) cycles; in the Upper Glen Rose, successive cycles exhibit decreasing proportions of shale and increasing proportions of grain-rich carbonate. High-frequency sequences were terminated by terrigenous inundation, possibly preceded by subaerial exposure. Cycle and high-frequency sequence composition is interpreted to reflect composite, periodic(?) fluctuations is terrigeneous dilution from nearby source areas. Grainstones typically occur (stratigraphically) within the upper cycles of high-frequency sequences, where terrigeneous dilution and turbidity were least and potential for carbonate production and shoaling was greatest. Published mid-Cretaceous geographic reconstructions and climate models suggest that precipitation and runoff in the area were controlled by the seasonal amplitude in solar insolation. In this model, orbital variations, combined with subsidence, hydrography, and bathymetry, were in primary controls on Ferry Lake-Upper Glen Rose facies architecture and stratigraphic development.« less

T-R Cycle Characterization and Imaging: Advanced Diagnostic Methodology for Petroleum Reservoir and Trap Detection and Delineation

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

Ernest A. Mancini; William C. Parcell; Bruce S. Hart

The principal research effort for Year 2 of the project is on stratigraphic model assessment and development. The research focus for the first six (6) months of Year 2 is on T-R cycle model development. The emphasis for the remainder of the year is on assessing the depositional model and developing and testing a sequence stratigraphy model. The development and testing of the sequence stratigraphy model has been accomplished through integrated outcrop, well log and seismic studies of Mesozoic strata in the Gulf of Mexico, North Atlantic and Rocky Mountain areas.

Tectonostratigraphy and depositional history of the Neoproterozoic volcano-sedimentary sequences in Kid area, southeastern Sinai, Egypt: Implications for intra-arc to foreland basin in the northern Arabian-Nubian Shield

NASA Astrophysics Data System (ADS)

Khalaf, E. A.; Obeid, M. A.

2013-09-01

This paper presents a stratigraphic and sedimentary study of Neoproterozoic successions of the South Sinai, at the northernmost segment of the Arabian-Nubian Shield (ANS), including the Kid complex. This complex is composed predominantly of thick volcano-sedimentary successions representing different depositional and tectonic environments, followed by four deformational phases including folding and brittle faults (D1-D4). The whole Kid area is divisible from north to south into the lower, middle, and upper rock sequences. The higher metamorphic grade and extensive deformational styles of the lower sequence distinguishes them from the middle and upper sequences. Principal lithofacies in the lower sequence include thrust-imbricated tectonic slice of metasediments and metavolcanics, whereas the middle and upper sequences are made up of clastic sediments, intermediate-felsic lavas, volcaniclastics, and dike swarms. Two distinct Paleo- depositional environments are observed: deep-marine and alluvial fan regime. The former occurred mainly during the lower sequence, whereas the latter developed during the other two sequences. These alternations of depositional conditions in the volcano-sedimentary deposits suggest that the Kid area may have formed under a transitional climate regime fluctuating gradually from warm and dry to warm and humid conditions. Geochemical and petrographical data, in conjunction with field relationships, suggest that the investigated volcano-sedimentary rocks were built from detritus derived from a wide range of sources, ranging from Paleoproterozoic to Neoproterozoic continental crust. Deposition within the ancient Kid basin reflects a complete basin cycle from rifting and passive margin development, to intra-arc and foreland basin development and, finally, basin closure. The early phase of basin evolution is similar to various basins in the Taupo volcanics, whereas the later phases are similar to the Cordilleran-type foreland basin. The progressive change in lithofacies from marine intra-arc basin to continental molasses foreland basin and from compression to extension setting respectively, imply that the source area became peneplained, where the Kid basin became stabilized as sedimentation progressed following uplift. The scenario proposed of the study area supports the role of volcanic and tectonic events in architecting the facies and stratigraphic development.

Geoacoustic Models of the Hudson Canyon Area

DTIC Science & Technology

1987-01-01

structural basin , play a strong historical role In shaping the sediment distribution and topography in this region. Several prominent horizons, A", A...Ridge, a lower Cretaceous carbonate reef, and a deep structural basin , play a strong historical role in shaping the sediment distribution and...TERRIGENOUS DEPOSIT j I SHALE \\^^% DOLOMITIC MARL I:/ j ARGi ^ACEOUS LIMESTOUE \\^ BASALT I sm.LO:. ,’,;-ER ;;■;=_ Figure 3. Stratigraphic sequence

Astronomical Pacing of Relative Sea Level through OAE2 from the Expanded SH#1 Core, Southern Utah

NASA Astrophysics Data System (ADS)

Jones, M. M.; Sageman, B. B.; Oakes, R. L.; Bralower, T. J.; Parker, A. L.; Leckie, R. M.

2017-12-01

Proximal marine strata of the North American Western Interior Basin (WIB) preserve a rich record of faunal turnover linked to Oceanic Anoxic Event 2 (OAE2 - 94 Ma), a pronounced Late Cretaceous carbon cycle perturbation interpreted to reflect global warming and possible ocean acidification. To develop a more robust synthesis of paleobiologic and geochemical datasets spanning this major Earth-life transition, we drilled a 131-meter core (SH#1) on the Kaiparowits Plateau of southern Utah, recovering the Cenomanian-Turonian Boundary (CTB) interval of the Tropic Shale. A 17.5-meter positive excursion in high-resolution bulk carbon isotope chemostratigraphy (δ13Corg) of SH#1 characterizes the most expanded and detailed record of OAE2 recovered from the WIB. Additionally, we detect statistically significant evidence for astronomical cycles in a companion δ13Ccarb dataset, using advanced spectral techniques (evolutive average spectral misfit). Bandpass filtering and tracing of the short eccentricity cycle (97 ka) permit development of a floating astronomical time scale (ATS) for the CTB interval. The presence of radioisotopic dates within the time series provides an independent check on astrochronologic interpretations. We attribute some depleted δ13Ccarb values in SH#1, which cyclically punctuate the OAE2 excursion, to preferential carbonate diagenesis driven by periodic sea level oscillations. Accordingly, major flooding surfaces in SH#1 correlate well to an existing sequence stratigraphic framework from shoreface facies of the Markagunt Plateau ( 100 km west). Comparing the ATS and sequence stratigraphic surfaces in SH#1, we observe that stable eccentricity cycles (405 ka) pace stratigraphic sequences and associated saw-toothed trends in sedimentation rate estimates through OAE2. Furthermore, short eccentricity cycles pace nested parasequences. These results confirm astronomical and, therefore, climatic pacing of relative sea level trends during OAE2 in the WIB. The ATS, δ13C chemostratigraphy, and basin-wide correlation of the CTB interval provide an expanded, temporally-resolved record of OAE2 within the chronostratigraphic framework of the WIB, and help to resolve rates of paleobiologic and paleoenvironmental change in the context of oscillating relative sea levels.

Trait-based diversification shifts reflect differential extinction among fossil taxa

PubMed Central

Wagner, Peter J.; Estabrook, George F.

2014-01-01

Evolution provides many cases of apparent shifts in diversification associated with particular anatomical traits. Three general models connect these patterns to anatomical evolution: (i) elevated net extinction of taxa bearing particular traits, (ii) elevated net speciation of taxa bearing particular traits, and (iii) elevated evolvability expanding the range of anatomies available to some species. Trait-based diversification shifts predict elevated hierarchical stratigraphic compatibility (i.e., primitive→derived→highly derived sequences) among pairs of anatomical characters. The three specific models further predict (i) early loss of diversity for taxa retaining primitive conditions (elevated net extinction), (ii) increased diversification among later members of a clade (elevated net speciation), and (iii) increased disparity among later members in a clade (elevated evolvability). Analyses of 319 anatomical and stratigraphic datasets for fossil species and genera show that hierarchical stratigraphic compatibility exceeds the expectations of trait-independent diversification in the vast majority of cases, which was expected if trait-dependent diversification shifts are common. Excess hierarchical stratigraphic compatibility correlates with early loss of diversity for groups retaining primitive conditions rather than delayed bursts of diversity or disparity across entire clades. Cambrian clades (predominantly trilobites) alone fit null expectations well. However, it is not clear whether evolution was unusual among Cambrian taxa or only early trilobites. At least among post-Cambrian taxa, these results implicate models, such as competition and extinction selectivity/resistance, as major drivers of trait-based diversification shifts at the species and genus levels while contradicting the predictions of elevated net speciation and elevated evolvability models. PMID:25331898

Landscape maturity, fold growth sequence and structural style in the Kirkuk Embayment of the Zagros, northern Iraq

NASA Astrophysics Data System (ADS)

Obaid, Ahmed K.; Allen, Mark B.

2017-10-01

The Kirkuk Embayment is located in the southwest of the Zagros fold-and-thrust belt of Iraq. Like fold-and-thrust belts worldwide, the Zagros is conventionally understood to have grown sequentially towards the foreland. Here we use landscape maturity analysis to understand anticline growth in the embayment. Digital Elevation Model (DEM)-based geomorphic indices Hypsometric Integral (HI), Surface Roughness (SR) and their combination Surface Index (SI) have been applied to quantify landscape maturity. The results inform new ideas for the sequence of anticline growth. Maturity indices are highest for the QaraChauq Anticline in the center of the Embayment, then Makhool/Himreen to the south and lastly, the Kirkuk Anticline to the north. The pattern suggests the growth sequence is not classical 'piggy back' thrusting. This result fits the exhumation record, which is loosely constrained by the stratigraphic exposure level. Favored hypotheses for fold growth order are either i) the folds have grown at different times and out of sequence (QaraChauq first, then Makhool/Himreen, and Kirkuk last), or, ii) the growth occurred with different rates of exhumation but at broadly the same time. There are few constraints from available data on syn-tectonic sedimentation patterns. Fold growth across much of the Embayment might have begun within a limited timeframe in the late Miocene-Pliocene, during the deposition of the Mukdadiyah Formation. Another hypothesis is that folds grew in sequence towards the foreland with different rates of exhumation, but we consider this less likely. We also construct a new cross-section for the Embayment, which indicates limited Cenozoic strain: 5% shortening. Analysis of topography and drainage patterns shows two previously-undescribed anticlines with hydrocarbon trap potential, between the Makhool and QaraChauq anticlines.

Geology of the Devonian black shales of the Appalachian basin

USGS Publications Warehouse

Roen, J.B.

1983-01-01

Black shales of Devonian age in the Appalachian basin are a unique rock sequence. The high content of organic matter, which imparts the characteristic lithology, has for years attracted considerable interest in the shales as a possible source of energy. Concurrent with periodic and varied economic exploitations of the black shales are geologic studies. The recent energy shortage prompted the U.S. Department of Energy through the Eastern Gas Shales Project of the Morgantown Energy Technology Center to underwrite a research program to determine the geologic, geochemical, and structural characteristics of the Devonian black shales in order to enhance the recovery of gas from the shales. Geologic studies produced a regional stratigraphic network that correlates the 15-foot sequence in Tennessee with 3,000 feet of interbedded black and gray shales in central New York. The classic Devonian black-shale sequence in New York has been correlated with the Ohio Shale of Ohio and Kentucky and the Chattanooga Shale of Tennessee and southwestern Virginia. Biostratigraphic and lithostratigraphic markers in conjunction with gamma-ray logs facilitated long range correlations within the Appalachian basin and provided a basis for correlations with the black shales of the Illinois and Michigan basins. Areal distribution of selected shale units along with paleocurrent studies, clay mineralogy, and geochemistry suggests variations in the sediment source and transport directions. Current structures, faunal evidence, lithologic variations, and geochemical studies provide evidence to support interpretation of depositional environments. In addition, organic geochemical data combined with stratigraphic and structural characteristics of the shale within the basin allow an evaluation of the resource potential of natural gas in the Devonian shale sequence.

Formation and tectonic evolution of the Pattani Basin, Gulf of Thailand

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

Bustin, R.M.; Chonchawalit, A.

The stratigraphic and structural evolution of the Pattani Basin, the most prolific petroleum basin in Thailand, reflects the extensional tectonic regime of continental Southeast Asia. E-W extension resulting from the northward collision of India with Eurasia since the Early Tertiary resulted in the formation of a series of N-S-trending sedimentary basins, which include the Pattani Basin. The sedimentary succession in the Pattani Basin is divisible into synrift and postrift sequences. Deposition of the synrift sequence accompanied rifting and extension, with episodic block faulting and rapid subsidence. The synrift sequence comprises three stratigraphic units: (1) Upper Eocene to Lower Olikgocene alluvial-fan,more » braided-river, and floodplain deposits; (2) Upper oligocene to Lowe Miocene floodplain and channel deposits; and (3) a Lower Miocene regressive package consisting of marine to nonmarine sediments. Post-rift succession comprises: (1) a Lower to Middle Miocene regressive package of shallow marine sediments through floodplain and channel deposits; (2) an upper Lower Miocene transgressive sequence; and (3) and Upper Miocene to Pleistocene transgressive succession. The post-rift phase is characterized by slower subsidence and decreased sediment influx. The present-day shallow-marine condition in the Gulf of Thailand is the continuation of this latest transgressive phase. The subsidence and thermal history of the Pattani Basin is consistent with a nonuniform lithospheric-stretching model. The amount of extension as well as surface heat flow generally increases from the margin to the basin center. The crustal stretching factor ({beta}) varies form 1.3 at the basin margin to 2.8 in the center. The subcrustal stretching factor ({delta}) ranges from 1.3 at the basin margin to more than 3.0 in the basin center. 31 refs., 13 figs., 4 tabs.« less

The Tule Springs local fauna: Rancholabrean vertebrates from the Las Vegas Formation, Nevada

USGS Publications Warehouse

Scott, Eric; Springer, Kathleen; Sagebiel, James C.

2017-01-01

A middle to late Pleistocene sedimentary sequence in the upper Las Vegas Wash, north of Las Vegas, Nevada, has yielded the largest open-site Rancholabrean vertebrate fossil assemblage in the southern Great Basin and Mojave Deserts. Recent paleontologic field studies have led to the discovery of hundreds of fossil localities and specimens, greatly extending the geographic and temporal footprint of original investigations in the early 1960s. The significance of the deposits and their entombed fossils led to the preservation of 22,650 acres of the upper Las Vegas Wash as Tule Springs Fossil Beds National Monument. These discoveries also warrant designation of the assemblage as a local fauna, named for the site of the original paleontologic studies at Tule Springs.The large mammal component of the Tule Springs local fauna is dominated by remains of Mammuthus columbi as well as Camelops hesternus, along with less common remains of Equus (including E. scotti) and Bison. Large carnivorans including Canis dirus, Smilodon fatalis, and Panthera atrox are also recorded. Micromammals, amphibians, lizards, snakes, birds, invertebrates, plant macrofossils, and pollen also occur in the deposits and provide important and complementary paleoenvironmental information. The fauna occurs within the Las Vegas Formation, an extensive and stratigraphically complex sequence of groundwater discharge deposits that represent a mosaic of desert wetland environments. Radiometric and luminescence dating indicates the sequence spans the last ∼570 ka, and records hydrologic changes in a dynamic and temporally congruent response to northern hemispheric abrupt climatic oscillations. The vertebrate fauna occurs in multiple stratigraphic horizons in this sequence, with ages of the fossils spanning from ∼100 to ∼12.5 ka.

Tectonic controls on rift basin morphology: Evolution of the northern Malawi (Nyasa) rift

NASA Technical Reports Server (NTRS)

Ebinger, C. J.; Deino, A. L.; Tesha, A. L.; Becker, T.; Ring, U.

1993-01-01

Radiometric (K-Ar and Ar-40/Ar-39) age determinations of volcanic and volcaniclastic rocks, combined with structural, gravity, and seismic reflection data, are used to constrain the age of sedimentary strata contained within the seismically and volcanically active northern Malawi (Nyasa) rift and to characterize changes in basin and flank morphologies with time. Faulting and volcanism within the Tukuyu-Karonga basin began at approximately 8.6 Ma, when sediments were deposited in abroad, initially asymmetric lake basin bounded on its northeastern side by a border fault system with minor topographic relief. Extensions, primarily by a slip along the border fault, and subsequent regional isostatic compensation led to the development of a 5-km-deep basin bounded by broad uplifted flanks. Along the low-relief basin margin opposite border fault, younger stratigraphic sequences commonly onlap older wedge-shaped sequences, although their internal geometry is often progradational. Intrabasinal faulting, flankuplift, and basaltic and felsic volcanism from centers at the northern end of the basin became more important at about 2.5 Ma when cross-rift transfer faults developed to link the Tukuyu-Karonga basin to the Rukwa basin. Local uplift and volcanic construction at the northern end of the basin led to a southeastward shift in the basin's depocenter. Sequence boundaries are commonly erosional along this low-relief (hanging wall) margin and conformable in the deep lake basin. The geometry of stratigraphic sequences and the distribution of the erosion indicate that horizontal and vertical crustal movements both across and along the length of the rift basin led to changes in levels of the lake, irrespective of paleoclimatic fluctuations.

Stratigraphic variations in the biomarker distribution of the Moreno Formation: Their correlation with San Joaquin basin oils

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

Bac, M.G.; Schulein, B.J.

1990-05-01

Variability in the biomarker compositions of petroleums is typically employed in the recognition and distinction of contributions from different source rocks. We demonstrate that the fluctuations in the biomarker distributions of different intervals within a single source rock sequence appear to account for specific compositional differences in a suite of oils from the San Joaquin basin California. Rock-Eval pyrolysis studies of a 100-m-thick immature, laminated, marine shale sequence within the Upper Cretaceous lo lower Paleocene portion of the Moreno Formation reveals TOC (total organic carbon) contents consistently around 2% and moderate hydrogen indices (i.e., 175-300 mg HC/g org. C) characteristicsmore » suggestive of a uniform depositional sequence with source rock potential. Analyses of the extractable aliphatic hydrocarbons of cored samples taken at approximately 10-m intervals from the sequence reveal significant variability in biomarker distributions. Such differences are exemplified by the triterpenoids (as seen in m/z 191 chromatograms from GC-MS and GC-MS/MS analyses) where the dominant component fluctuates from a 17{alpha}(h),21{beta}(H)-30-norhopane to 28,30-l8{alpha}(H)-bisnorhopane to 20S and 20R danunar-13(17)-enes. Some components are dominant in one interval, but are not detected in others, suggesting discrete stratigraphic variations in the biomarker characteristics of the Moreno. Similar discrepancies in biomarker distributions are evident in the aliphatic hydrocarbons of the suite of oils. The three petroleums reservoired in the San Carlos sandstone member of the Lodo Formation which directly overlies the Moreno, reflect biomarker contributions from a Moreno source, including compound distributions, and the occurrence of both alkanes (e.g., 28.30-bisnorhopane) and alkenes (e.g.. danunarenes and diasterenes).« less

Sequence stratigraphy, geodynamics, and detrital geothermochronology of Cretaceous foreland basin deposits, western interior U.S.A

NASA Astrophysics Data System (ADS)

Painter, Clayton S.

Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_U-Pb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf). Appendix A is a combination of detailed isopach maps of the Upper Cretaceous Western Interior, flexural modeling and a comparison to dynamic subsidence models as applied to the region. Using these new isopach maps and modeling, I place the previously recognized but poorly constrained shift from flexural to non-flexural subsidence at 81 Ma. Appendix B is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation. Appendix C is a geo-thermochronologic study to measure the lag time of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. The maximum depositional ages using DZ U-Pb match existing biostratigraphic age controls. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4--5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed from <8--9 km depth. Apatite U-Pb analyses indicate that volcanic contamination is a significant issue, without which, one cannot exclude the possibility that the youngest detrital AFT population is contaminated with significant amounts of volcanogenic apatite and does not represent source exhumation. AFT lag times are <5 Myr with relatively steady-state to slightly increasing exhumation rates. Lag time measurements indicate exhumation rates of ~0.9->>1 km/Myr.

Rhyolitic components of the Michipicoten greenstone belt, Ontario: Evidence for late Archaen intracontinental rifts or convergent plate margins in the Canadian Shield?

NASA Technical Reports Server (NTRS)

Sylvester, P. J.; Attoh, K.; Schulz, K. J.

1986-01-01

Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that characterize many late Archean greenstone belts of the Canadian Shield. The rhyolites primarily are pyroclastic flows (ash flow tuffs) emplaced following plinian eruptions, although deposits formed by laval flows and phreatomagmatic eruptions also are presented. Based both on measured tectono-stratigraphic sections and provenance studies of greenstone belt sedimentary sequences, the rhyolites are believed to have been equal in abundance to associated basaltic rocks. In many recent discussions of the tectonic setting of late Archean Canadian greenstone belts, rhyolites have been interpreted as products of intracontinental rifting . A study of the tectono-stratigraphic relationships, rock associations and chemical characteristics of the particularly ell-exposed late Archean rhyolites of the Michipicoten greenstone belt, suggests that convergent plate margin models are more appropriate.

Stratigraphy of the Anthropocene.

PubMed

Zalasiewicz, Jan; Williams, Mark; Fortey, Richard; Smith, Alan; Barry, Tiffany L; Coe, Angela L; Bown, Paul R; Rawson, Peter F; Gale, Andrew; Gibbard, Philip; Gregory, F John; Hounslow, Mark W; Kerr, Andrew C; Pearson, Paul; Knox, Robert; Powell, John; Waters, Colin; Marshall, John; Oates, Michael; Stone, Philip

2011-03-13

The Anthropocene, an informal term used to signal the impact of collective human activity on biological, physical and chemical processes on the Earth system, is assessed using stratigraphic criteria. It is complex in time, space and process, and may be considered in terms of the scale, relative timing, duration and novelty of its various phenomena. The lithostratigraphic signal includes both direct components, such as urban constructions and man-made deposits, and indirect ones, such as sediment flux changes. Already widespread, these are producing a significant 'event layer', locally with considerable long-term preservation potential. Chemostratigraphic signals include new organic compounds, but are likely to be dominated by the effects of CO(2) release, particularly via acidification in the marine realm, and man-made radionuclides. The sequence stratigraphic signal is negligible to date, but may become geologically significant over centennial/millennial time scales. The rapidly growing biostratigraphic signal includes geologically novel aspects (the scale of globally transferred species) and geologically will have permanent effects.

Characterizing avulsion stratigraphy in ancient alluvial deposits

NASA Astrophysics Data System (ADS)

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

2007-11-01

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

Comparison of transgressive and regressive clastic reservoirs, late Albian Viking Formation, Alberta basin

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

Reinson, G.E.

1996-06-01

Detailed stratigraphic analysis of hydrocarbon reservoirs from the Basal Colorado upwards through the Viking/Bow Island and Cardium formations indicates that the distributional trends, overall size and geometry, internal heterogeneity, and hydrocarbon productivity of the sand bodies are related directly to a transgressive-regressive (T-R) sequence stratigraphic model. The Viking Formation (equivalent to the Muddy Sandstone of Wyoming) contains examples of both transgressive and regressive reservoirs. Viking reservoirs can be divided into progradational shoreface bars associated with the regressive systems tract, and bar/sheet sands and estuary/channel deposits associated with the transgressive systems tract. Shoreface bars, usually consisting of fine- to medium-grained sandstones,more » are tens of kilometers long, kilometers in width, and in the order of five to ten meters thick. Transgressive bar and sheet sandstones range from coarse-grained to conglomeratic, and occur in deposits that are tens of kilometers long, several kilometers wide, and from less than one to four meters in thickness. Estuary and valley-fill reservoir sandstones vary from fine-grained to conglomeratic, occur as isolated bodies that have channel-like geometries, and are usually greater than 10 meters thick. From an exploration viewpoint the most prospective reservoir trends in the Viking Formation are those associated with transgressive systems tracts. In particular, bounding discontinuities between T-R systems tracts are the principal sites of the most productive hydrocarbon-bearing sandstones.« less

Global Stratigraphy of Venus: Analysis of a Random Sample of Thirty-Six Test Areas

NASA Technical Reports Server (NTRS)

Basilevsky, Alexander T.; Head, James W., III

1995-01-01

The age relations between 36 impact craters with dark paraboloids and other geologic units and structures at these localities have been studied through photogeologic analysis of Magellan SAR images of the surface of Venus. Geologic settings in all 36 sites, about 1000 x 1000 km each, could be characterized using only 10 different terrain units and six types of structures. These units and structures form a major stratigraphic and geologic sequence (from oldest to youngest): (1) tessera terrain; (2) densely fractured terrains associated with coronae and in the form of remnants among plains; (3) fractured and ridged plains and ridge belts; (4) plains with wrinkle ridges; (5) ridges associated with coronae annulae and ridges of arachnoid annulae which are contemporary with wrinkle ridges of the ridged plains; (6) smooth and lobate plains; (7) fractures of coronae annulae, and fractures not related to coronae annulae, which disrupt ridged and smooth plains; (8) rift-associated fractures; and (9) craters with associated dark paraboloids, which represent the youngest 1O% of the Venus impact crater population (Campbell et al.), and are on top of all volcanic and tectonic units except the youngest episodes of rift-associated fracturing and volcanism; surficial streaks and patches are approximately contemporary with dark-paraboloid craters. Mapping of such units and structures in 36 randomly distributed large regions (each approximately 10(exp 6) sq km) shows evidence for a distinctive regional and global stratigraphic and geologic sequence. On the basis of this sequence we have developed a model that illustrates several major themes in the history of Venus. Most of the history of Venus (that of its first 80% or so) is not preserved in the surface geomorphological record. The major deformation associated with tessera formation in the period sometime between 0.5-1.0 b.y. ago (Ivanov and Basilevsky) is the earliest event detected. In the terminal stages of tessera fon-nation, extensive parallel linear graben swarms representing a change in the style of deformation from shortening to extension were formed on the tessera and on some volcanic plains that were emplaced just after, and perhaps also during the latter stages of the major compressional phase of tessera emplacement. Our stratigraphic analyses suggest that following tessera formation, extensive volcanic flooding resurfaced at least 85% of the planet in the form of the presently-ridged and fractured plains. Several lines of evidence favor a high flux in the post-tessera period but we have no independent evidence for the absolute duration of ridged plains emplacement. During this time, the net state of stress in the lithosphere apparently changed from extensional to compressional, first in the form of extensive ridge belt development, followed by the formation of extensive wrinkle ridges on the flow units. Subsequently, there occurred local emplacement of smooth and lobate plains units which are presently essentially undefortned. The major events in the latest 10% of the presently preserved history of Venus (less than 50 m.y. ago) are continued rifting and some associated volcanism, and the redistribution of eolian material largely derived from impact crater deposits.

Late Albian dinosaur tracks from the cratonic (eastern) margin of the Western Interior Seaway, Nebraska, USA

USGS Publications Warehouse

Joeckel, R.M.; Cunningham, J.M.; Corner, R.G.; Brown, G.W.; Phillips, P.L.; Ludvigson, Greg A.

2004-01-01

At least 22 tridactyl dinosaur tracks, poorly preserved in various degrees of expression, have recently been found at an exposure in the Dakota Formation (Lower Cretaceous, Albian) in Jefferson County, Nebraska. These tracks generally have broad, blunt digits and a broad posterior margin. The largest of the tracks measures 57 cm in length and 58 cm in width. All of the tracks lie within a stratigraphic horizon of 40 cm or less, but they do not form a single trackway. We interpret the trackmakers to have been ornithopods.The Jefferson County tracks are in a well-cemented sandstone with oscillation ripples, at a stratigraphic level between two well-established sequence boundaries. Channel forms and lateral accretion units are common in the stratigraphic interval enclosing the tracks, and the site is interpreted as a bar or sand flat in a tidally influenced river.The Jefferson County tracks are only the second known occurrence of large Mesozoic tetrapod tracks east of the Rocky Mountain Front-High Plains Margin, including the Black Hills of South Dakota, west of the Atlantic Coastal Plain, and north of the Gulf Coastal Plain. Further, this paper is the first documentation of in situdinosaur fossils from the Nebraska-Iowa area.

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

NASA Astrophysics Data System (ADS)

Ielpi, Alessandro

2012-07-01

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

Tectono-stratigraphic evolution of the Comondú Group from Bahía de La Paz to Loreto, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Drake, William R.; Umhoefer, Paul J.; Griffiths, Alexis; Vlad, Ann; Peters, Lisa; McIntosh, William

2017-11-01

The late Oligocene to mid-Miocene volcanic and volcaniclastic rocks of the Comondú Group are well exposed along the Main Rift Escarpment of Baja California Sur from the Bahía de La Paz region to Bahía Concepción. New mapping and stratigraphic analysis of the Comondú Group from Bahía de La Paz to Loreto reveal facies trends and correlations that form the foundation for a continuous stratigraphic framework for the Comondú Group along a 300 km-long transect on the eastern coast of the Baja California peninsula. Broad but distinct lithostratigraphic trends, alluvial fan facies, and volcanic and volcaniclastic facies record an overall coarsening-upwards package that includes ignimbrite deposits within increasingly proximal alluvial fan deposits, both derived from the east. Geochronology of the unit, including 32 isotope ages and 12 previously unpublished 40Ar/39Ar ages, provide the timing of four main increasingly proximal depositional events. Non-marine sandstone, defining the base of the Comondú Group, was first deposited between 26 Ma and 24 Ma. Emplacement of rhyolitic ignimbrites initiated between 24 Ma and 23 Ma and marked a westward expansion of volcanic activity affiliated with the Sierra Madre Occidental ignimbrite sequences in southern Sinaloa, western Durango, and northern Nayarit. A change in volcanism occurred at 19 Ma to 18 Ma with more ignimbrites, increased intermediate compositions, and the appearance of local vents and proximal volcanic facies. A final localized change of volcanism occurred from 14 to 12 Ma in the Loreto area with an increase of proximal alluvial fan deposits and local volcanoes in the Upper Comondú Group. The bulk of the Upper Comondú Group is absent south of the Loreto area and has either been removed by erosion as a source for the Magdalena Fan in the Pacific Ocean, or was focused primarily in the Loreto area and northward. We use a pre-rift tectonic reconstruction of the Gulf of California to align broad stratigraphic trends along the peninsula, the Gulf conjugate margins, and within the Gulf. The Cascadia arc of Oregon and northern California may be a modern analog for the Comondú Group with a linear volcanic arc formed above shrinking subducting microplates, and a broad backarc region of moderate extension and scattered volcanism.

Technical Report for Proposed Ordnance Clearance at Fort George G. Meade

DTIC Science & Technology

1991-03-01

Potomac Group (including the Patapsco, Arundel Clay, and Patuxent Formations), the Magothy Formation and the Patuxent River terraces and associated...alluvium. The youngest geologic unit in theI stratigraphic sequence underlying Fort Meade is the Magothy Formation of Late Cretaceous age. This formation...Department of the Army, 1981). The Magothy Formation unconformably overlies the sediments of the Lower Cretaceous Potomac Group. i The formations of the

Statistical analysis of archeomagnetic samples of Teotihuacan, Mexico

NASA Astrophysics Data System (ADS)

Soler-Arechalde, A. M.

2012-12-01

Teotihuacan was the one of the most important metropolis of Mesoamerica during the Classic Period (1 to 600 AC). The city had a continuous growth in different stages that usually concluded with a ritual. Fire was an important element natives would burn entire structures. An example of this is the Quetzalcoatl pyramid in La Ciudadela (350 AC), it was burned and a new structure was built over it, also the Big Fire at 570 AC, that marks its end. These events are suitable to archaeomagnetic dating. The inclusion of ash in the stucco enhances the magnetic signal of detrital type that also allows us to make dating. This increases the number of samples to be processed as well as the number of dates. The samples have been analyzed according to their type: floor, wall, talud and painting and whether or not exposed to fire. Sequences of directions obtained in excavations in strict stratigraphic control will be shown. A sequence of images was used to analyze the improving of Teotihuacan secular variation curve through more than a decade of continuous work at the area.

Site formation processes at Pinnacle Point Cave 13B (Mossel Bay, Western Cape Province, South Africa): resolving stratigraphic and depositional complexities with micromorphology.

PubMed

Karkanas, Panagiotis; Goldberg, Paul

2010-01-01

Site PP13B is a cave located on the steep cliffs of Pinnacle Point near Mossel Bay in Western Cape Province, South Africa. The depositional sequence of the cave, predating Marine Isotopic Stage 11 (MIS 11) and continuing to present, is in the form of isolated sediment exposures with different depositional facies and vertical and lateral variations. Micromorphological analysis demonstrated that a suite of natural sedimentation processes operated during the development of the sequence ranging from water action to aeolian activity, and from speleothem formations to plant colonization and root encrustation. At the same time, anthropogenic sediments that are mainly in the form of burnt remains from combustion features (e.g., wood ash, charcoal, and burnt bone) were accumulating. Several erosional episodes have resulted in a complicated stratigraphy, as discerned from different depositional and post-depositional features. The cave is associated with a fluctuating coastal environment, frequent changes in sea level and climate controlled patterns of sedimentation, and the presence or absence of humans. Copyright © 2010 Elsevier Ltd. All rights reserved.

The orbital record in stratigraphy

NASA Technical Reports Server (NTRS)

Fischer, Alfred G.

1992-01-01

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

Silurian sequence stratigraphy in the North American craton, Great Lakes area

USGS Publications Warehouse

Shaver, R.H.; ,

1996-01-01

A notable circumstance of late Early through Late Silurian sedimentation on the Great Lakes area craton is that at least two and possibly three cycles of third-order duration (if eustatically considered) are recognized in basin and shallow-platform settings alike. Both virtually pure and siliciclastic-rich carbonate rocks exist in parts of platform-situated sections in contrast to siliciclastic-rich to evaporite-dominated basin sections. Knowledge of the reef history, together with evidence of incidental periodic incursions of siliciclastic sediments, permitted understanding of a regional event or sequence stratigraphy more than 15 years ago before conventional biostratigraphic and physical stratigraphic evidence became adequate to corroborate. This midwestern US and Ontario Silurian record has become strategic for testing different schools of thought that champion either tectonism or eustasy to explain cyclical sequences.

Tectonic control on coarse-grained foreland-basin sequences: An example from the Cordilleran foreland basin, Utah

NASA Astrophysics Data System (ADS)

Horton, Brian K.; Constenius, Kurt N.; Decelles, Peter G.

2004-07-01

Newly released reflection seismic and borehole data, combined with sedimentological, provenance, and biostratigraphic data from Upper Cretaceous Paleocene strata in the proximal part of the Cordilleran foreland-basin system in Utah, establish the nature of tectonic controls on stratigraphic sequences in the proximal to distal foreland basin. During Campanian time, coarse-grained sand and gravel were derived from the internally shortening Charleston-Nebo salient of the Sevier thrust belt. A rapid, regional Campanian progradational event in the distal foreland basin (>200 km from the thrust belt in <8 m.y.) can be tied directly to active thrust-generated growth structures and an influx of quartzose detritus derived from the Charleston-Nebo salient. Eustatic sea-level variation exerted a minimal role in sequence progradation.

Stratigraphic and palaeoenvironmental summary of the south-east Georgia embayment: a correlation of exploratory wells

USGS Publications Warehouse

Poppe, Lawrence J.; Popenoe, Peter; Poag, C. Wylie; Swift, B. Ann

1995-01-01

A Continental Offshore Stratigraphic Test (COST) well and six exploratory wells have been drilled in the south-east Georgia embayment. The oldest rocks penetrated are weakly metamorphosed Lower Ordovician quartz arenites and Silurian shales and argillites in the Transco 1005-1 well and Upper Devonian argillites in the COST GE-1 well. These marine strata, which are equivalent to the Tippecanoe sequence in Florida, underlie the post-rift unconformity and represent part of a disjunct fragment of Gondwana that was sutured to the North American craton during the late Palaeozoic Alleghanian orogeny. The Palaeozoic strata are unconformably overlain by interbedded non-marine Jurassic (Bajocian and younger) sandstones and shales and marginal marine Lower Cretaceous sandstones, calcareous shales and carbonates, which contain scattered beds of coal and evaporite. Together, these rocks are stratigraphically equivalent to the onshore Fort Pierce and Cotton Valley(?) Formations and rocks of the Lower Cretaceous Comanchean Provincial Series. The abundance of carbonates and evaporites in this interval, which reflects marine influences within the embayment, increases upwards, eastwards and southwards. The Upper Cretaceous part of the section is composed mainly of neritic calcareous shales and shaley limestones stratigraphically equivalent to the primarily marginal marine facies of the onshore Atkinson, Cape Fear and Middendorf Formations and Black Creek Group, and to limestones and shales of the Lawson Limestone and Peedee Formations. Cenozoic strata are primarily semiconsolidated marine carbonates. Palaeocene to middle Eocene strata are commonly cherty; middle Miocene to Pliocene strata are massive and locally phosphatic and glauconitic; Quaternary sediments are dominated by unconsolidated carbonate sands. The effects of eustatic changes and shifts in the palaeocirculation are recorded in the Upper Cretaceous and Tertiary strata.

On the Application of an Enthalpy Method to the Evolution of Fluvial Deltas Under Sea-Level Changes

NASA Astrophysics Data System (ADS)

Anderson, W.; Lorenzo-Trueba, J.; Voller, V. R.

2017-12-01

Fluvial deltas are composites of two primary sedimentary environments: a depositional fluvial region and an offshore region. The fluvial region is defined by two geomorphic moving boundaries: an alluvial-bedrock transition (ABT), which separates the sediment prism from the non-erodible bedrock basement, and the shoreline (SH), where the delta meets the ocean. The trajectories of these boundaries in time and space define the evolution of the shape of the sedimentary prism, and are often used as stratigraphic indicators, particularly in seismic studies, of changes in relative sea level and the identification of stratigraphic sequences. In order to better understand the relative role of sea-level variations, tectonics, and sediment supply on the evolution of these boundaries, we develop a forward stratigraphic model that captures the dynamic behavior of the fluvial surface and treats the SH and ABT as moving boundaries (i.e., internal boundaries whose location must be determined as part of the solution to the overall morphological evolution problem). This forward model extends a numerical technique from heat transfer (i.e., enthalpy method), previously applied to the evolution of sedimentary basins, to account for sea-level changes. The mathematics of the approach are verified by comparing predictions from the numerical model with both existing and newly developed closed form analytical solutions. Model results support previous work, which suggests that the migration of the ABT can respond very differently to the sea-level signal. This response depends on factors such as sediment supply and delta length, which can vary greatly between basins. These results can have important implications for the reconstruction of past sea-level changes from the stratigraphic record of sedimentary basins.

Facies Modeling of of Dam and Hofuf Formations: Outcrop Analog of Mixed Carbonate and Siliciclastic (Miocene-Pliocene) Succession, Eastern Saudi Arabia

NASA Astrophysics Data System (ADS)

Abdullatif, O.; Yassin, M.

2012-04-01

1KFUPM This study investigates the lithofacies types distribution of the carbonate and siliciclastic rocks of Dam and Hofuf Formations in eastern Saudi Arabia. The shallow burial of these formations and limited post depositional changes allowed significant preservation of porosity at outcrop scale. The mixed carbonate-siliciclastic succession represents important reservoirs in the Mesozoic and Tertiary stratigraphic succession in the Arabian Plate.This study integrates field work sedimentological and stratigraphical and lithofacies data to model the spatial distribution of facies of this shallow marine and fluvial depositional setting. The Dam Formation is characterized by very high percentage of grain- dominated textures representing high to low energy intertidal deposits a mixed of carbonate and siliciclastic succession. The middle Miocene Dam section is dominated by intra-clasts, ooids and peloids grainstones. The Hofuf Formation represents fluvial channel and overank facies which is characterized by mudclast abd gravel-rich erosive bases overlain by pebbly conglomerates which passes upward into medium to very coarse grained massive, horizontally stratified and trough cross-stratifed sandstone facies. Lithological stratigraphic sections data distributed over the Al-lidam escarpment were correlated on the basis of facies types and sequences. This allow mapping and building a framework for modeling the spatial distribution of the carbonate and siliciclastic facies in the area. The geological model shows variations in the facies distribution patterns which mainly reflect both dynamic and static depositional controls on facies types distribution. The geological model may act as a guide for facies types distribution, and provide better understanding and prediction of reservoir quality and architecture of stratigraphically equivalent carbonate-siliciclastic successions in the subsurface.

Stratigraphic Paleobiology of the Taranto Area

NASA Astrophysics Data System (ADS)

Scarponi, Daniele; Angeletti, Lorenzo; Taviani, Marco; Huntley, John Warren; Amorosi, Alessandro; Negri, Alessandra; Battista Vai, Gian

2015-04-01

The area surrounding Taranto, Italy is chronostratigraphically very important, as it is one of the few areas in the world where Upper Pleistocene marine successions are well exposed, easily accessible, and relatively thick. Several outcrops in this area were investigated as suitable marine sections for defining the Late Pleistocene GSSP. At these locations, the late Pleistocene bathymetric history of the Taranto area was depicted using macrobenthic assemblages from a network of outcrops and cores. Outcrops at Pontile, Fronte, and Garitta, along with two cores drilled at Cimino and Cantoro were densely sampled to conduct quantitatively-derived paleobathymetric reconstructions. These deposits yielded relatively diverse mollusk associations (> 250 species and > 9.000 specimens distributed among 55 samples), dominated by extant mollusk species of known bathymetric distribution. Multiple analytical approaches were applied to the macrobenthic dataset in a comparative fashion: (i) direct calibration by weighted averaging of taxa with known preferred depth recovered in a sample, (ii) posteriori-calibrated ordination (DCA) using bathymetric data of key extant taxa. These analyses were conducted at both species and genus level. Regardless of the choice of the analytical method, mollusk assemblages yielded bathymetric trends congruent with previous qualitative and semi-quantitative paleoecological and stratigraphic analyses: the bathymetric range of sampled deposits is bracketed between 140 and 0 meters. Secondly, macrobenthos-derived proxies provided an improved characterization of the marine deposits in terms of sample bathymetry and by discriminating shallowing-upward (regressive) trends from deepening-upward (transgressive) tendencies. Thirdly, mollusk-derived bathymetric inferences suggest spatial bathymetric gradients that are coherent with the morphology of the study area. In conclusion, the results provided an improved characterization of coastal depositional facies in a sequence stratigraphic perspective, which is one of the primary research goals of Stratigraphic Paleobiology.

Recognizing the Albian-Cenomanian (OAE1d) sequence boundary using plant carbon isotopes: Dakota Formation, Western Interior Basin, USA

USGS Publications Warehouse

Grocke, D.R.; Ludvigson, Greg A.; Witzke, B.L.; Robinson, S.A.; Joeckel, R.M.; Ufnar, David F.; Ravn, R.L.

2006-01-01

Analysis of bulk sedimentary organic matter and charcoal from an Albian-Cenomanian fluvial-estuarine succession (Dakota Formation) at Rose Creek Pit (RCP), Nebraska, reveals a negative excursion of ???3???, in late Albian strata. Overlying Cenomanian strata have ??13C values of -24???, to -23???, that are similar to pre-excursion values. The absence of an intervening positive excursion (as exists in marine records of the Albian-Cenomanian boundary) likely results from a depositional hiatus. The corresponding positive ??13C event and proposed depositional hiatus are concordant with a regionally identified sequence boundary in the Dakota Formation (D2), as well as a major regressive phase throughout the globe at the Albian-Cenomanian boundary. Data from RCP confirm suggestions that some positive carbon-isotope excursions in the geologic record are coincident with regressive sea-level phases. We estimate using isotopic correlation that the D2 sequence boundary at RCP was on the order of 0.5 m.y. in duration. Therefore, interpretations of isotopic events and associated environmental phenomena, such as oceanic anoxic events, in the shallow-marine and terrestrial record may be influenced by stratigraphic incompleteness. Further investigation of terrestrial ??13C records may be useful in recognizing and constraining sea-level changes in the geologic record. ?? 2006 Geological Society of America.

Sequence stratigraphy of the Upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: Transgressing assumptions of cratonic flooding

USGS Publications Warehouse

Eoff, Jennifer D.

2014-01-01

New data from detailed measured sections permit comprehensive analysis of the sequence framework of the Furongian (Upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. The sequence-stratigraphic architecture of the lower part of the Sunwaptan Stage at the base of the Tunnel City Group, at the contact between the Wonewoc Formation and Lone Rock Formation, records the first part of complex polyphase flooding (Sauk III) of the Laurentian craton, at a scale smaller than most events recorded by global sea-level curves. Flat-pebble conglomerate and glauconite document transgressive ravinement and development of a condensed section when creation of accommodation exceeded its consumption by sedimentation. Thinly-bedded, fossiliferous sandstone represents the most distal setting during earliest highstand. Subsequent deposition of sandstone characterized by hummocky or trough cross-stratification records progradational pulses of shallower, storm- and wave-dominated environments across the craton before final flooding of Sauk III commenced with carbonate deposition during the middle part of the Sunwaptan Stage. Comparison of early Sunwaptan flooding of the inner Laurentian craton to published interpretations from other parts of North America suggests that Sauk III was not a single, long-term accommodation event as previously proposed.

Sequence stratigraphy and hydrocarbon potential of the Phu Khanh Basin offshore central Vietnam, South China Sea

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

Lee, G.H.; Watkins, J.S.

1996-12-31

The Phu Khanh Basin offshore central Vietnam is one of the few untested basins on the Vietnam margin of the South China Sea. Analysis of over 1,600 km of multi-channel seismic reflection data indicates that the Phu Khanh Basin follows a typical rift-margin order: faulted basement, synrift sedimentation, a breakup unconformity, and postrift sedimentation. Postrift sedimentation consists of a transgressive phase characterized by ramp-like depositional geometries followed by a regressive phase characterized by prograding sequences. An early middle Miocene unconformity separates these two phases. During the transgressive phase rising sea level provided favorable conditions for carbonate buildup development. The regressivemore » interval contains a number of third-order depositional sequences composed of seismically resolvable lowstand, highstand, and rarely, transgressive systems tracts. Lacustrine sediments deposited in graben and half-graben lakes during the rifting stage are probably the principal source rocks. Fractured and/or weathered basement, carbonate complexes, basinfloor fans, and shallows water sands may have good reservoir quality. Potential traps include basement hills, carbonate complexes, fault taps, and stratigraphic traps within lowstand systems tracts. Hydrocarbon indicators such as flat spots, bright spots, gas chimneys with gas mounds on the seafloor occur at a number of locations.« less

Sequence stratigraphy and hydrocarbon potential of the Phu Khanh Basin offshore central Vietnam, South China Sea

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

Lee, G.H.; Watkins, J.S.

1996-01-01

The Phu Khanh Basin offshore central Vietnam is one of the few untested basins on the Vietnam margin of the South China Sea. Analysis of over 1,600 km of multi-channel seismic reflection data indicates that the Phu Khanh Basin follows a typical rift-margin order: faulted basement, synrift sedimentation, a breakup unconformity, and postrift sedimentation. Postrift sedimentation consists of a transgressive phase characterized by ramp-like depositional geometries followed by a regressive phase characterized by prograding sequences. An early middle Miocene unconformity separates these two phases. During the transgressive phase rising sea level provided favorable conditions for carbonate buildup development. The regressivemore » interval contains a number of third-order depositional sequences composed of seismically resolvable lowstand, highstand, and rarely, transgressive systems tracts. Lacustrine sediments deposited in graben and half-graben lakes during the rifting stage are probably the principal source rocks. Fractured and/or weathered basement, carbonate complexes, basinfloor fans, and shallows water sands may have good reservoir quality. Potential traps include basement hills, carbonate complexes, fault taps, and stratigraphic traps within lowstand systems tracts. Hydrocarbon indicators such as flat spots, bright spots, gas chimneys with gas mounds on the seafloor occur at a number of locations.« less

Basin analysis in the Southern Tethyan margin: Facies sequences, stratal pattern and subsidence history highlight extension-to-inversion processes in the Cretaceous Panormide carbonate platform (NW Sicily)

NASA Astrophysics Data System (ADS)

Basilone, Luca; Sulli, Attilio

2018-01-01

In the Mediterranean, the South-Tethys paleomargin experienced polyphased tectonic episodes and paleoenvironmental perturbations during Mesozoic time. The Cretaceous shallow-water carbonate successions of the Panormide platform, outcropping in the northern edge of the Palermo Mountains (NW Sicily), were studied by integrating facies and stratal pattern with backstripping analysis to recognize the tectonics vs. carbonate sedimentation interaction. The features of the Requienid limestone, including geometric configuration, facies sequence, lithological changes and significance of the top-unconformity, highlight that at the end of the Lower Cretaceous the carbonate platform was tectonically dismembered in various rotating fault-blocks. The variable trends of the subsidence curves testify to different responses, both uplift and downthrow, of various platform-blocks impacted by extensional tectonics. Physical stratigraphic and facies analysis of the Rudistid limestone highlight that during the Upper Cretaceous the previously carbonate platform faulted-blocks were subjected to vertical movements in the direction opposite to the displacement produced by the extensional tectonics, indicating a positive tectonic inversion. Comparisons with other sectors of the Southern Tethyan and Adria paleomargins indicate that during the Cretaceous these areas underwent the same extensional and compressional stages occurring in the Panormide carbonate platform, suggesting a regional scale significance, in time and kinematics, for these tectonic events.

Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

USGS Publications Warehouse

Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

2017-12-08

Deep well injection and disposal of treated wastewater into the highly transmissive saline Boulder Zone in the lower part of the Floridan aquifer system began in 1971. The zone of injection is a highly transmissive hydrogeologic unit, the Boulder Zone, in the lower part of the Floridan aquifer system. Since the 1990s, however, treated wastewater injection into the Boulder Zone in southeastern Florida has been detected at three treated wastewater injection utilities in the brackish upper part of the Floridan aquifer system designated for potential use as drinking water. At a time when usage of the Boulder Zone for treated wastewater disposal is increasing and the utilization of the upper part of the Floridan aquifer system for drinking water is intensifying, there is an urgency to understand the nature of cross-formational fluid flow and identify possible fluid pathways from the lower to upper zones of the Floridan aquifer system. To better understand the hydrogeologic controls on groundwater movement through the Floridan aquifer system in southeastern Florida, the U.S. Geological Survey and the Broward County Environmental Planning and Community Resilience Division conducted a 3.5-year cooperative study from July 2012 to December 2015. The study characterizes the sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower part of the intermediate confining unit aquifer and most of the Floridan aquifer system.Data obtained to meet the study objective include 80 miles of high-resolution, two-dimensional (2D), seismic-reflection profiles acquired from canals in eastern Broward County. These profiles have been used to characterize the sequence stratigraphy, seismic stratigraphy, and seismic structures in a 425-square-mile study area. Horizon mapping of the seismic-reflection profiles and additional data collection from well logs and cores or cuttings from 44 wells were focused on construction of three-dimensional (3D) visualizations of eight sequence stratigraphic cycles that compose the Eocene to Miocene Oldsmar, Avon Park, and Arcadia Formations. The mapping of these seismic-reflection and well data has produced a refined Cenozoic sequence stratigraphic, seismic stratigraphic, and hydrogeologic framework of southeastern Florida. The upward transition from the Oldsmar Formation to the Avon Park Formation and the Arcadia Formation embodies the evolution from (1) a tropical to subtropical, shallow-marine, carbonate platform, represented by the Oldsmar and Avon Park Formations, to (2) a broad, temperate, mixed carbonate-siliciclastic shallow marine shelf, represented by the lower part of the Arcadia Formation, and to (3) a temperate, distally steepened carbonate ramp represented by the upper part of the Arcadia Formation.In the study area, the depositional sequences and seismic sequences have a direct correlation with hydrogeologic units. The approximate upper boundary of four principal permeable units of the Floridan aquifer system (Upper Floridan aquifer, Avon Park permeable zone, uppermost major permeable zone of the Lower Floridan aquifer, and Boulder Zone) have sequence stratigraphic and seismic-reflection signatures that were identified on cross sections, mapped, or both, and therefore the sequence stratigraphy and seismic stratigraphy were used to guide the development of a refined spatial representation of these hydrogeologic units. In all cases, the permeability of the four permeable units is related to stratiform megaporosity generated by ancient dissolution of carbonate rock associated with subaerial exposure and unconformities at the upper surfaces of carbonate depositional cycles of several hierarchical scales ranging from high-frequency cycles to depositional sequences. Additionally, interparticle porosity also contributes substantially to the stratiform permeability in much of the Upper Floridan aquifer. Information from seismic stratigraphy allowed 3D geomodeling of hydrogeologic units—an approach never before applied to this area. Notably, the 3D geomodeling provided 3D visualizations and geocellular models of the depositional sequences, hydrostratigraphy, and structural features. The geocellular data could be used to update the hydrogeologic structure inherent to groundwater flow simulations that are designed to address the sustainability of the water resources of the Floridan aquifer system.Two kinds of pathways that could enable upward cross-formational flow of injected treated wastewater from the Boulder Zone have been identified in the 80 miles of high-resolution seismic data collected for this study: a near-vertical reverse fault and karst collapse structures. The single reverse fault, inferred to be of tectonic origin, is in extreme northeastern Broward County and has an offset of about 19 feet at the level of the Arcadia Formation. Most of the 17 karst collapse structures identified manifest as columniform, vertically stacked sagging seismic reflections that span early Eocene to Miocene age rocks equivalent to much of the Floridan aquifer system and the lower part of the overlying intermediate confining unit. In some cases, the seismic-sag structures extend upward into strata of Pliocene age. The seismic-sag structures are interpreted to have a semicircular shape in plan view on the basis of comparison to (1) other seismic-sag structures in southeastern Florida mapped with two 2D seismic cross lines or 3D data, (2) comparison to these structures located in other carbonate provinces, and (3) plausible extensional ring faults detected with multi-attribute analysis. The seismic-sag structures in the study area have heights as great as 2,500 vertical feet, though importantly, one spans about 7,800 feet. Both multi-attribute analysis and visual detection of offset of seismic reflections within the seismic-sag structures indicate faults and fractures are associated with many of the structures. Multi-attribute analysis highlighting chimney fluid pathways also indicates that the seismic-sag structures have a high probability for potential vertical cross-formational fluid flow along the faulted and fractured structures. A collapse of the seismic-sag structures within a deep burial setting evokes an origin related to hypogenic karst processes by ascending flow of subsurface fluids. In addition, paleo-epigenic karst related to major regional subaerial unconformities within the Florida Platform generated collapse structures (paleo-sinkholes) that are much smaller in scale than the cross-formational seismic-sag structures.

Depositional sequence stratigraphy and architecture of the cretaceous ferron sandstone: Implications for coal and coalbed methane resources - A field excursion

USGS Publications Warehouse

Garrison, J.R.; Van Den, Bergh; Barker, C.E.; Tabet, D.E.

1997-01-01

This Field Excursion will visit outcrops of the fluvial-deltaic Upper Cretaceous (Turonian) Ferron Sandstone Member of the Mancos Shale, known as the Last Chance delta or Upper Ferron Sandstone. This field guide and the field stops will outline the architecture and depositional sequence stratigraphy of the Upper Ferron Sandstone clastic wedge and explore the stratigraphic positions and compositions of major coal zones. The implications of the architecture and stratigraphy of the Ferron fluvial-deltaic complex for coal and coalbed methane resources will be discussed. Early works suggested that the southwesterly derived deltaic deposits of the the upper Ferron Sandstone clastic wedge were a Type-2 third-order depositional sequence, informally called the Ferron Sequence. These works suggested that the Ferron Sequence is separated by a type-2 sequence boundary from the underlying 3rd-order Hyatti Sequence, which has its sediment source from the northwest. Within the 3rd-order depositional sequence, the deltaic events of the Ferron clastic wedge, recognized as parasequence sets, appear to be stacked into progradational, aggradational, and retrogradational patterns reflecting a generally decreasing sediment supply during an overall slow sea-level rise. The architecture of both near-marine facies and non-marine fluvial facies exhibit well defined trends in response to this decrease in available sediment. Recent studies have concluded that, unless coincident with a depositional sequence boundary, regionally extensive coal zones occur at the tops of the parasequence sets within the Ferron clastic wedge. These coal zones consist of coal seams and their laterally equivalent fissile carbonaceous shales, mudstones, and siltstones, paleosols, and flood plain mudstones. Although the compositions of coal zones vary along depositional dip, the presence of these laterally extensive stratigraphic horizons, above parasequence sets, provides a means of correlating and defining the tops of depositional parasequence sets in both near-marine and non-marine parts of fluvial-deltaic depositional sequences. Ongoing field studies, based on this concept of coal zone stratigraphy, and detailed stratigraphic mapping, have documented the existence of at least 12 parasequence sets within the Last Chance delta clastic wedge. These parasequence sets appear to form four high frequency, 4th-order depositional sequences. The dramatic erosional unconformities, associated with these 4th-order sequence boundaries, indicate that there was up to 20-30 m of erosion, signifying locally substantial base-level drops. These base-level drops were accompanied by a basin ward shift in paleo-shorelines by as much as 5-7 km. These 4th-order Upper Ferron Sequences are superimposed on the 3rd-order sea-level rise event and the 3rd-order, sediment supply/accommodation space driven, stratigraphie architecture of the Upper Ferron Sandstone. The fluvial deltaic architecture shows little response to these 4th-order sea-level events. Coal zones generally thicken landward relative to the mean position of the landward pinch-out of the underlying parasequence set, but after some distance landward, they decrease in thickness. Coal zones also generally thin seaward relative to the mean position of the landward pinch-out of the underlying parasequence set. The coal is thickest in the region between this landward pinch-out and the position of maximum zone thickness. Data indicate that the proportion of coal in the coal zone decreases progressively landward from the landward pinch-out. The effects of differential compaction and differences in original pre-peat swamp topography have the effect of adding perturbations to the general trends. These coal zone systematics have major impact on approaches to exploration and production, and the resource accessment of both coal and coalbed methane.

Storage Thresholds for Relative Sea Level Signals in the Stratigraphic Record

NASA Astrophysics Data System (ADS)

Li, Q.; Yu, L.; Straub, K. M.

2015-12-01

Many argue that the tug of Relative Sea Level (RSL) change represents the most important allogenic forcing affecting deltas and is the primary control on stratigraphic architecture of deltas. However, the range of amplitudes and periodicities of RSL cycles stored in stratigraphy remains unknown. Here we use a suite of physical experiments to show that RSL cycles with magnitudes and periodicities less than the spatial and temporal scales of deltaic internal (autogenic) dynamics cannot confidently be extracted from the physical stratigraphic record. Additional analysis of deltaic morphodynamics also suggest no significant differences between an experiment with constant boundary conditions (control experiment) and an experiment with small magnitude and short periodicity RSL cycles, relative to the autogenic dynamics. Significant differences in the aspect ratio of channel bodies and deposit sand fractions do exists between our control experiment and those experiments with either large magnitudes or long periodicities RSL cycles. Using a compilation of data from major river delta systems, we show that our predicted thresholds for RSL signal storage often overlap with the magnitudes and periodicities of commonly discussed drivers of global sea level. This theory defines quantitative limits on the range of paleo-RSL information that can be extracted from the stratigraphic record, which could aid stratigraphic prediction and the inversion of stratigraphy for paleo- deltaic response to climate change.

Lateral fluid flow in a compacting sand-shale sequence: South Caspian basin.

USGS Publications Warehouse

Bredehoeft, J.D.; Djevanshir, R.D.; Belitz, K.R.

1988-01-01

The South Caspian basin contains both sands and shales that have pore-fluid pressures substantially in excess of hydrostatic fluid pressure. Pore-pressure data from the South Caspian basin demonstrate that large differences in excess hydraulic head exist between sand and shale. The data indicate that sands are acting as drains for overlying and underlying compacting shales and that fluid flows laterally through the sand on a regional scale from the basin interior northward to points of discharge. The major driving force for the fluid movement is shale compaction. We present a first- order mathematical analysis in an effort to test if the permeability of the sands required to support a regional flow system is reasonable. The results of the analysis suggest regional sand permeabilities ranging from 1 to 30 md; a range that seems reasonable. This result supports the thesis that lateral fluid flow is occurring on a regional scale within the South Caspian basin. If vertical conduits for flow exist within the basin, they are sufficiently impermeable and do not provide a major outlet for the regional flow system. The lateral fluid flow within the sands implies that the stratigraphic sequence is divided into horizontal units that are hydraulically isolated from one another, a conclusion that has important implications for oil and gas migration.-Authors

Early Pleistocene 40Ar/39Ar ages for Bapang Formation hominins, Central Jawa, Indonesia

PubMed Central

Larick, Roy; Ciochon, Russell L.; Zaim, Yahdi; Sudijono; Suminto; Rizal, Yan; Aziz, Fachroel; Reagan, Mark; Heizler, Matthew

2001-01-01

The Sangiran dome is the primary stratigraphic window for the Plio-Pleistocene deposits of the Solo basin of Central Jawa. The dome has yielded nearly 80 Homo erectus fossils, around 50 of which have known findspots. With a hornblende 40Ar/39Ar plateau age of 1.66 ± 0.04 mega-annum (Ma) reportedly associated with two fossils [Swisher, C.C., III, Curtis, G. H., Jacob, T., Getty, A. G., Suprijo, A. & Widiasmoro (1994) Science 263, 1118–1121), the dome offers evidence that early Homo dispersed to East Asia during the earliest Pleistocene. Unfortunately, the hornblende pumice was sampled at Jokotingkir Hill, a central locality with complex lithostratigraphic deformation and dubious specimen provenance. To address the antiquity of Sangiran H. erectus more systematically, we investigate the sedimentary framework and hornblende 40Ar/39Ar age for volcanic deposits in the southeast quadrant of the dome. In this sector, Bapang (Kabuh) sediments have their largest exposure, least deformation, and most complete tephrostratigraphy. At five locations, we identify a sequence of sedimentary cycles in which H. erectus fossils are associated with epiclastic pumice. From sampled pumice, eight hornblende separates produced 40Ar/39Ar plateau ages ranging from 1.51 ± 0.08 Ma at the Bapang/Sangiran Formation contact, to 1.02 ± 0.06 Ma, at a point above the hominin-bearing sequence. The chronological sequence of 40Ar/39Ar ages follows stratigraphic order across the southeast quadrant. An intermediate level yielding four nearly complete crania has an age of about 1.25 Ma. PMID:11309488

Early Pleistocene 40Ar/39Ar ages for Bapang Formation hominins, Central Jawa, Indonesia.

PubMed

Larick, R; Ciochon, R L; Zaim, Y; Sudijono; Suminto; Rizal, Y; Aziz, F; Reagan, M; Heizler, M

2001-04-24

The Sangiran dome is the primary stratigraphic window for the Plio-Pleistocene deposits of the Solo basin of Central Jawa. The dome has yielded nearly 80 Homo erectus fossils, around 50 of which have known findspots. With a hornblende (40)Ar/(39)Ar plateau age of 1.66 +/- 0.04 mega-annum (Ma) reportedly associated with two fossils [Swisher, C.C., III, Curtis, G. H., Jacob, T., Getty, A. G., Suprijo, A. & Widiasmoro (1994) Science 263, 1118-1121), the dome offers evidence that early Homo dispersed to East Asia during the earliest Pleistocene. Unfortunately, the hornblende pumice was sampled at Jokotingkir Hill, a central locality with complex lithostratigraphic deformation and dubious specimen provenance. To address the antiquity of Sangiran H. erectus more systematically, we investigate the sedimentary framework and hornblende (40)Ar/(39)Ar age for volcanic deposits in the southeast quadrant of the dome. In this sector, Bapang (Kabuh) sediments have their largest exposure, least deformation, and most complete tephrostratigraphy. At five locations, we identify a sequence of sedimentary cycles in which H. erectus fossils are associated with epiclastic pumice. From sampled pumice, eight hornblende separates produced (40)Ar/(39)Ar plateau ages ranging from 1.51 +/- 0.08 Ma at the Bapang/Sangiran Formation contact, to 1.02 +/- 0.06 Ma, at a point above the hominin-bearing sequence. The chronological sequence of (40)Ar/(39)Ar ages follows stratigraphic order across the southeast quadrant. An intermediate level yielding four nearly complete crania has an age of about 1.25 Ma.

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

NASA Astrophysics Data System (ADS)

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

2012-02-01

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

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

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

Crystallization and Melt Removal at Arenal Volcano, Polytopic Vector Analysis

NASA Astrophysics Data System (ADS)

Hidalgo, P. J.; Vogel, T. A.; Bolge, L. L.; Ehrlich, R.; Alvarado, G. E.

2007-12-01

Tephra sequences ET3 and ET4 from Arenal volcano in Costa Rica have recently been interpreted to be a product of crystal fractionation by Bolge and coworkers in a series of papers (2004, 2006). The two tephra units are part of a sequence of 22 tephra units that represent a 7000 year span of the Arenal volcano activity. The tephro- stratigraphy has been described extensively by Melson (1982; 1994). The ET3 and ET4 tephras were interpreted (based on major- and trace-element, isotopic analyses of whole rocks and microchemical analyses of individual phases) as clear evidence of crystal separation by gravity settling (Bolge et al., 2004, 2006). The lower ET4 tephra sequence (andesitic and crystal poor) and the upper ET3 tephra (basaltic and crystal rich) represent an inverted snapshot of the magma chamber with contrasting geochemical properties. The ET3 sequence (deeper part of the magma chamber) has nearly constant composition with only a few elements varying stratigraphically (best represented by CaO). This is consistent with gradually decreasing amounts of melt in the upper part of ET3. The lower ET4 tephra (upper part of the magma chamber) contains large chemical gradients in both incompatible and compatible elements. In the present study we use whole-rock geochemical data from the recent tephra sequences ET3 and ET4 as inputs to Polytopic Vector Analysis (PVA) (for a review of this method see Vogel and coworkers, in press). With this method we produce a three end member solution that is consistent with crystallization of Olivine, plagioclase and pyroxene from the most mafic end member (EM1) resulting in a crystal rich mush zone. As crystallization progresses the compositions of the liquids are driven towards an intermediate end member (EM3), which has an intermediate composition liquid. At EM3 composition, rapid depletion of FeO, MgO and TiO2 by crystallization of Fe-Ti oxides, rapidly drives the liquid composition towards the silicic EM1 (incompatible element enriched end member). Using PVA we refine the interpretations of Bolge and coworkers and show that melt from the crystalline rich ET3 tephra was removed and ponded in the magma chamber above the crystalline mush (top part of ET4 unit). Thus when the eruption occurred the most evolved tephra (ET4) were deposited first followed by the least evolved tephra (ET3), which resulted in sampling of a chemically zoned magma chamber. Using PVA on stratigraphically controlled whole-rock analyses of tephra samples, we can unambiguously identify processes and end members that are involved in crystal accumulation and liquid separation processes. Thus PVA is a rigorous analytical tool that uses only whole-rock chemical data to produce robust results that can be used with other analytical techniques to test petrological models.

An evaluation of Mesodon and other larger terrestrial gastropod shells for dating late Holocene and historic alluvium in the Midwestern USA

USGS Publications Warehouse

Rakovan, Monica T.; Rech, Jason A.; Pigati, Jeffery S.; Nekola, Jeffery C.; Wiles, Gregory C.

2013-01-01

Understanding the history of stream erosion and changes in channel morphology is important for managing and restoring unstable streams. One of the significant challenges in this type of research is establishing accurate dating of late Holocene and historic alluvium. Here we evaluate the potential of using 14C dating and amino acid racemization (AAR) to date large terrestrial gastropod shells that are often preserved within alluvial sediments. Many terrestrial gastropods incorporate old carbon from limestone or other carbonate rocks into their shells and therefore are unsuitable for radiocarbon dating. Recent studies, however, have shown that some taxa avoid this ‘limestone problem’ and can yield reliable 14C ages. In this study, we measured the 14C activity of specimens for the genera Mesodon, Ventridens, and Allogona collected live and from alluvial sequences dated independently by dendrochronology, 14C dating of wood, and/or 137Cs analyses. Mesodon zaletus contained old carbon in similar concentrations (up to ~ 30%) found in previous studies of other large taxa and should be avoided for 14C dating when possible. In contrast, shells of Ventridens ligera and Allogona profunda showed minimal limestone effects and therefore may be suitable for dating late Holocene alluvium. These results highlight the importance of taxonomic identification of gastropod taxa prior to their use for 14C dating and demonstrate that shell fragments that are not identifiable should be avoided. We also measured d/l ratios (n = 17) of aspartic and glutamic acid from eight different taxa of terrestrial gastropods recovered from four late Holocene and historic stratigraphic sequences. Average d/l ratios of aspartic and glutamic acid from historic sediments < 300 years old are lower in shells from younger stratigraphic units, indicating that AAR can be used to differentiate between multiple historic stratigraphic units.

Hierarchal Genetic Stratigraphy: A Framework for Paleoceanography

NASA Astrophysics Data System (ADS)

Busch, R. M.; West, R. R.

1987-04-01

A detailed, genetic stratigraphic framework for paleoceanographic studies can be derived by describing, correlating, interpreting, and predicting stratigraphic sequences relative to a hierarchy of their constituent time-stratigraphic transgressive-regressive units ("T-R units"). T-R unit hierarchies are defined and correlated using lithostratigraphic and paleoecologic data, but correlations can be enhanced or "checked" (tested to confirm or deny) with objective biostratigraphic, magnetostratigraphic, or chemostratigraphic data. Such chronostratigraphies can then be bracketed by radiometric ages, so that average periodicities for T-R units can be calculated and a hierarchal geochronology derived. T-R units are inferred to be the net depositional result of eustatic cycles of sea level change and can be differentiated from autocyclic deepening-shallowing units because the latter are noncorrelative intrabasinally. Boundaries between T-R units are conformable or unconformable "genetic surfaces" of two types: transgressive surfaces and "climate change surfaces". The latter are useful for correlating minor transgressive phases through nonmarine intervals, thereby deriving information linking paleoclimatic and paleoceanographic processes. Permo-Carboniferous sequences can be analyzed relative to a hierarchy of six scales of genetic T-R units having periodicities of 225-300 m.y. (first order), 20-90 m.y. (second order), 7-13 m.y. (third-order), 0.6-3.6 m.y. (fourth order), 300-500 × 10³ years (fifth order), and 50-130 × 10³ years or less (sixth-order). Paleogeographic maps for the time of maximum transgression ("transgressive apex") of successive fifth-order T-R units (5-25 m thick) in the Glenshaw Formation (Upper Pennsylvanian, Northern Appalachian Basin) delineate delta lobes, embayments, islands, and linear seaways. Relative extent of marine inundation on the fifth-order maps was used to delineate fourth-order T-R units, and the fourth-order T-R units constitute the transgressive half of a third-order T-R unit. This third-, fourth-, and fifth-order hierarchy is correlated more than 1200 km (750 miles) to the Western Interior "Basin," and is confirmed with limited objective biostratigraphy.

Digital database of microfossil localities in Alameda and Contra Costa Counties, California

USGS Publications Warehouse

McDougall, Kristin; Block, Debra L.

2014-01-01

The eastern San Francisco Bay region (Contra Costa and Alameda Counties, California) is a geologically complex area divided by faults into a suite of tectonic blocks. Each block contains a unique stratigraphic sequence of Tertiary sediments that in most blocks unconformably overlie Mesozoic sediments. Age and environmental interpretations based on analysis of microfossil assemblages are key factors in interpreting geologic history, structure, and correlation of each block. Much of this data, however, is distributed in unpublished internal reports and memos, and is generally unavailable to the geologic community. In this report the U.S. Geological Survey microfossil data from the Tertiary sediments of Alameda and Contra Costa counties are analyzed and presented in a digital database, which provides a user-friendly summary of the micropaleontologic data, locality information, and biostratigraphic and ecologic interpretations.

Sequence stratigraphic control on prolific HC reservoir development, Southwest Iran

USGS Publications Warehouse

Lasemi, Y.; Kondroud, K.N.

2008-01-01

An important carbonate formation in the Persian Gulf and the onshore oil fields of Southwest Iran is the Lowermost Cretaceous Fahliyan formation. The formation in Darkhowain field consists of unconformity-bounded depositional sequences containing prolific hydrocarbon reservoirs of contrasting origin. Located in the high stand systems tract (HST) of the lower sequence encompassing over 200m of oil column are the most prolific reservoir. Another reservoir is over 80m thick consisting of shallowing-upward cycles that are best developed within the transgressive systems tract of the upper sequence. Vertical facies distribution and their paleobathymetry and geophysical log signatures of the Fahliyan formation in the Darkhowain platform reveal the presence of two unconformity-bounded depositional sequences in Vail et al., Van Wagoner et al., and Sarg. The Fahliyan formation mainly consists of platform carbonates composed of restricted bioclastic lime mudstone to packstone of the platform interior, Lithocodium boundstone or ooid-intraclast-bioclast grainstone of the high energy platform margin and the bioclast packstone to lime mudstone related to the off-platform setting.

Combined ESR/U-series chronology of Acheulian hominid-bearing layers at Trinchera Galería site, Atapuerca, Spain.

PubMed

Falguères, Christophe; Bahain, Jean-Jacques; Bischoff, James L; Pérez-González, Alfredo; Ortega, Ana Isabel; Ollé, Andreu; Quiles, Anita; Ghaleb, Bassam; Moreno, Davinia; Dolo, Jean-Michel; Shao, Qingfeng; Vallverdú, Josep; Carbonell, Eudald; Bermúdez de Castro, Jose María; Arsuaga, Juan Luis

2013-08-01

The Sierra de Atapuerca, northern Spain, is known from many prehistoric and palaeontological sites documenting human prehistory in Europe. Three major sites, Gran Dolina, Galería and Sima del Elefante, range in age from the oldest hominin of Western Europe dated to 1.1 to 1.3 Ma (millions of years ago) at Sima del Elefante to c.a. 0.2 Ma on the top of the Galería archaeological sequence. Recently, a chronology based on luminescence methods (Thermoluminescence [TL] and Infrared Stimulated Luminescence [IRSL]) applied to cave sediments was published for the Gran Dolina and Galería sites. The authors proposed for Galería an age of 450 ka (thousands of years ago) for the units lower GIII and GII, suggesting that the human occupation there is younger than the hominid remains of Sima de los Huesos (>530 ka) around 1 km away. In this paper, we present new results obtained by combined Electron Spin Resonance/Uranium-series (ESR/U-series) dating on 20 herbivorous teeth from different levels at the Galería site. They are in agreement with the TL results for the upper part of the stratigraphic sequence (GIV and GIIIb), in the range of between 200 and 250 ka. But for the GIIIa to GIIb levels, the TL ages become abruptly older by 200 ka while ESR ages remain relatively constant. Finally, the TL and ESR data agree in the lowest part of the section (GIIa); both fall in the range of around 350-450 ka. Our results suggest a different interpretation for the GII, GIII and GIV units of Galería and the upper part of Gran Dolina (TD10 and TD11) than obtained by TL. The ESR/U-series results are supported by a Bayesian analysis, which allows a better integration between stratigraphic information and radiometric data. Copyright © 2013 Elsevier Ltd. All rights reserved.

Megascours: the morphodynamics of large river confluences

NASA Astrophysics Data System (ADS)

Dixon, Simon; Sambrook Smith, Greg; Nicholas, Andrew; Best, Jim; Bull, Jon; Vardy, Mark; Goodbred, Steve; Haque Sarker, Maminul

2015-04-01

River confluences are wildly acknowledged as crucial controlling influences upon upstream and downstream morphology and thus landscape evolution. Despite their importance very little is known about their evolution and morphodynamics, and there is a consensus in the literature that confluences represent fixed, nodal points in the fluvial network. Confluences have been shown to generate substantial bed scours around five times greater than mean depth. Previous research on the Ganges-Jamuna junction has shown large river confluences can be highly mobile, potentially 'combing' bed scours across a large area, although the extent to which this is representative of large confluences in general is unknown. Understanding the migration of confluences and associated scours is important for multiple applications including: designing civil engineering infrastructure (e.g. bridges, laying cable, pipelines, etc.), sequence stratigraphic interpretation for reconstruction of past environmental and sea level change, and in the hydrocarbon industry where it is crucial to discriminate autocyclic confluence scours from widespread allocyclic surfaces. Here we present a wide-ranging global review of large river confluence planforms based on analysis of Landsat imagery from 1972 through to 2014. This demonstrates there is an array of confluence morphodynamic types: from freely migrating confluences such as the Ganges-Jamuna, through confluences migrating on decadal timescales and fixed confluences. Along with data from recent geophysical field studies in the Ganges-Brahmaputra-Meghna basin we propose a conceptual model of large river confluence types and hypothesise how these influence morphodynamics and preservation of 'megascours' in the rock record. This conceptual model has implications for sequence stratigraphic models and the correct identification of surfaces related to past sea level change. We quantify the abundance of mobile confluence types by classifying all large confluences in the Amazon and Ganges-Brahmaputra-Meghna basins, showing these two basins have contrasting confluence morphodynamics. For the first time we show large river confluences have multiple scales of planform adjustment with important implications for infrastructure and interpretation of the rock record.

Combined ESR/U-series chronology of Acheulian hominid-bearing layers at Trinchera Galería site, Atapuerca, Spain

USGS Publications Warehouse

Falguères, Christophe; Bahain, Jean-Jacques; Bischoff, James L.; Pérez-González, Alfredo; Ortega, Ana Isabel; Ollé, Andreu; Quilles, Anita; Ghaleb, Bassam; Moreno, Davinia; Dolo, Jean-Michel; Shao, Qingfeng; Vallverdú, Josep; Carbonell, Eudald; María Bermúdez de Castro, Jose; Arsuaga, Juan Luis

2013-01-01

The Sierra de Atapuerca, northern Spain, is known from many prehistoric and palaeontological sites documenting human prehistory in Europe. Three major sites, Gran Dolina, Galería and Sima del Elefante, range in age from the oldest hominin of Western Europe dated to 1.1 to 1.3 Ma (millions of years ago) at Sima del Elefante to c.a. 0.2 Ma on the top of the Galería archaeological sequence. Recently, a chronology based on luminescence methods (Thermoluminescence [TL] and Infrared Stimulated Luminescence [IRSL]) applied to cave sediments was published for the Gran Dolina and Galería sites. The authors proposed for Galería an age of 450 ka (thousands of years ago) for the units lower GIII and GII, suggesting that the human occupation there is younger than the hominid remains of Sima de los Huesos (>530 ka) around 1 km away. In this paper, we present new results obtained by combined Electron Spin Resonance/Uranium-series (ESR/U-series) dating on 20 herbivorous teeth from different levels at the Galería site. They are in agreement with the TL results for the upper part of the stratigraphic sequence (GIV and GIIIb), in the range of between 200 and 250 ka. But for the GIIIa to GIIb levels, the TL ages become abruptly older by 200 ka while ESR ages remain relatively constant. Finally, the TL and ESR data agree in the lowest part of the section (GIIa); both fall in the range of around 350–450 ka. Our results suggest a different interpretation for the GII, GIII and GIV units of Galería and the upper part of Gran Dolina (TD10 and TD11) than obtained by TL. The ESR/U-series results are supported by a Bayesian analysis, which allows a better integration between stratigraphic information and radiometric data.

Seismic stratigraphy and structure of the Chukchi Borderland: implications for the opening of the Canada Basin

NASA Astrophysics Data System (ADS)

Ilhan, I.; Coakley, B.

2015-12-01

Interpretation of seismic reflection data from the western Chukchi Borderland has illuminated the structure and stratigraphy of the area. Basement rotated fault blocks are offset by two border fault systems (BFS1 and BFS2) and by secondary faults, striking curvilinear in the NW-SE direction, dipping to the NE. The BFS1 dissects the Chukchi Plateau into two first-order rotated blocks bounding two major sedimentary depocentres, the North Chukchi Basin and the Chukchi Plateau Central Basin. The BFS2, which has a larger offset than BFS1, forms the western boundary of the Northwind Basin. Much of the stratigraphy is controlled by sediment supply. The basins were starved early in their history, resulting in a limited syn-rift section. Substantial sediment accumulation in the Borderland appears to post-date large scale progradation of the depostional shelf edge across the Chukchi Shelf. Basin infill stratigraphies are subdivided into pre-rift, syn-rift, early-, middle-, late post-rift, and glacio-marine sequences (SB1-SB5). SB1 shows truncation of the remnants of the pre-rift strata below and onlap of the syn-rift sequence(s) above; the SB2 marks the termination of the rifting stage and is bounded by bi-directional onlap surface of the early post-rift strata above; the base of SB3 is an onlap surface marks the arrival of the prograding shelf margin sequence(s); the SB4 shows evidence of erosion at the base of the prograding late post-rift sequence(s); and the SB5 is an downloap surface marking the first arrival of the glacio-marine sediments eroded from the Chukchi Shelf. Two ages of the major sequence boundaries, the SB3 and SB4, can be directly tied to Popcorn and Crackerjack Chukchi Shelf well data, and the older ones, the end of rifting and the top of the pre-rift, are inferred based on stratigraphic observations. The stratigraphic relationship suggests that the Chukchi Borderland stratigraphy can be correlated in part to the Chukchi Shelf stratigraphy. The first and second-order rotated fault blocks and depositional history suggest that the Chukchi Borderland has been coupled to the Chukchi Shelf at least since the extension of the Borderland. Therefore we infer only small horizontal offsets between the Chukchi Borderland and the Chukchi Shelf, which have largely a shared geologic history.

Petrographic, mineralogical, and chemical characterization of certain Alaskan coals and washability products. Final report, July 11, 1978-October 11, 1980

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

Rao, P.D.; Wolff, E.N.

1981-05-01

Petrological, mineralogical and chemical characterization provides basic information needed for proper utilization of coals. Since many of these coals are likely to be beneficiated to reduce ash, the influence of coal washing on the characteristics of the washed product is important. Twenty samples of Alaskan coal seams were used for this study. The coals studied ranged in rank from lignite to high volatile A bituminous with vitrinite/ulminite reflectance ranging from 0.25 to 1.04. Fifteen raw coals were characterized for proximate and ultimate analysis reflectance rank, petrology, composition of mineral matter, major oxides and trace elements in coal ash. Washability productsmore » of three coals from Nenana, Beluga and Matanuska coal fields were used for characterization of petrology, mineral matter and ash composition. Petrological analysis of raw coals and float-sink products showed that humodetrinite was highest in top seam in a stratigraphic sequence« less

An integrated workflow to assess the remaining potential of mature hydrocarbon basins: a case study from Northwest Germany (Upper Jurassic/Lower Cretaceous, Lower Saxony Basin)

NASA Astrophysics Data System (ADS)

Seyfang, Björn; Aigner, Thomas; Munsterman, Dirk K.; Irmen, Anton

2017-04-01

Mature hydrocarbon provinces require a high level of geological understanding in order to extend the lives of producing fields, to replace reserves through smaller targets and to reduce the risks of exploring for more and more subtle hydrocarbon traps. Despite a large number of existing wells in the area studied in this paper, the depositional environments and the stratigraphic architecture were still poorly known. In order to improve the geological understanding, we propose a workflow to assess the remaining reservoir potential of mature hydrocarbon areas, integrating cores, cuttings, well-logs, biostratigraphy and seismic data. This workflow was developed for and is exemplified with the northwest of the Lower Saxony Basin (LSB), a mature hydrocarbon province in northwest Germany, but can be applied in a similar fashion to other areas. Systematic integration of lithofacies analysis, chrono- and sequence stratigraphy, combined with electrofacies analysis and modern digital methods like neural network-based lithology determination and 3D facies modelling provides a high-resolution understanding of the spatial facies and reservoir architecture in the study area. Despite widely correlatable litho-units in the Upper Jurassic and Lower Cretaceous in the LSB, complex heterogeneous sedimentary systems can be found in the basin's marginal parts. Two new play types were determined in the study area, showing a remaining potential for stratigraphic hydrocarbon traps. The results of this exploration scale study also provide the basis for re-evaluations on a field development scale. On a basin scale, this study may encourage further data acquisition and re-evaluations to discover previously unknown reservoirs.

Basin-floor Lake Bonneville stratigraphic section as revealed in paleoseismic trenches at the Baileys Lake site, West Valley fault zone, Utah

USGS Publications Warehouse

Hylland, Michael D.; DuRoss, Christopher B.; McDonald, Greg N.; Olig, Susan S.; Oviatt, Charles G.; Mahan, Shannon; Crone, Anthony J.; Personius, Stephen

2012-01-01

 Recent paleoseismic trenching on the Granger fault of the West Valley fault zone in Salt Lake County, Utah, exposed a nearly complete section of late Pleistocene Lake Bonneville deposits, and highlights challenges related to accurate interpretation of basin-floor stratigraphy in the absence of numerical age constraints. We used radiocarbon and luminescence dating as well as ostracode biostratigraphy to provide chronostratigraphic control on the Lake Bonneville section exposed at the Baileys Lake trench site. The fault trenches exposed folded and faulted pre- to post- Bonneville sediments, including about 0.7 m of pre-Bonneville wetland/fluvial-marsh deposits, a nearly complete Bonneville section 2.5–4.0 m thick, and 0.4–1.0 m of post-Bonneville deposits consisting primarily of loess with minor scarp-derived colluvium. The relatively thin Bonneville section compares favorably with basin-floor Bonneville sections documented in boreholes and seismic reflection profiles beneath Great Salt Lake. Distinctive features of the Bonneville section at the Baileys Lake site include a sequence of turbidites in the upper part of the Bonneville transgressive deposits, evidence for an earthquake during Provo-shoreline time that disturbed lake-bottom sediments and destroyed any stratigraphic signature of the Bonneville Flood, tufa deposition associated with Gilbert-phase shoreline transgression, and stratigraphic evidence for two Gilbert transgressions across the site.

Multiproxy Late Quaternary stratigraphy of the Nile deep-sea turbidite system — Towards a chronology of deep-sea terrigeneous systems

NASA Astrophysics Data System (ADS)

Ducassou, E.; Capotondi, L.; Murat, A.; Bernasconi, S. M.; Mulder, T.; Gonthier, E.; Migeon, S.; Duprat, J.; Giraudeau, J.; Mascle, J.

2007-08-01

Understanding the recent formation of a sedimentary system such as a deep-sea turbidite system (DSTS) requires an accurate stratigraphic control on deposits. Due to the important terrigeneous input which disrupts the sedimentary record, DSTS is an environment where stratigraphic control is difficult to assess. Most of the time, traditional stratigraphic tools are not accurate enough. This has led to a rather limited number of studies concerning stratigraphy in DSTS. In this study, we examine several hemipelagic long piston cores collected from the Nile DSTS (eastern Mediterranean), in order to understand the recent evolution of the complex sedimentary system in this area. The first aim of this study is to show how to obtain a reliable timeframe in DSTS. Indeed, we provided a detailed ecostratigraphical scheme based on planktonic foraminiferal distribution, oxygen isotope records and lithostratigraphy (sapropels and tephra) of three cores where the sedimentation is least disturbed. We have identified 29 foraminiferal ecozones during the last 250,000 years BP, with an approximately 2000-year time resolution. The time span of each ecozone was constrained by the oxygen isotope record, 14C AMS radiometric data, tephrochronology and the sapropel chronology. These high-resolution ecostratigraphical time subdivisions have been applied in discontinuous mixed hemipelagic/turbiditic sequences of a levee record. This example shows how to date gravity events, formation and time periods of sedimentary accumulations.

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

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

Constraints on the depositional age and tectonometamorphic evolution of marbles from the Biharia Nappe System (Apuseni Mountains, Romania)

NASA Astrophysics Data System (ADS)

Reiser, Martin Kaspar; Schuster, Ralf; Tropper, Peter; Fügenschuh, Bernhard

2017-04-01

Basement rocks from the Biharia Nappe System in the Apuseni Mountains comprise several dolomite and calcite marble sequences or lenses which experienced deformation and metamorphic overprint during the Alpine orogeny. New Sr, O and C-isotope data in combination with considerations from the lithological sequences indicate Middle to Late Triassic deposition of calcite marbles from the Vulturese-Belioara Series (Biharia Nappe s.str.). Ductile deformation and large-scale folding of the siliciclastic and carbonatic lithologies is attributed to NW-directed nappe stacking during late Early Cretaceous times (D2). The studied marble sequences experienced a metamorphic overprint under lower greenschist- facies conditions (316-370 °C based on calcite - dolomite geothermometry) during this tectonic event. Other marble sequences from the Biharia Nappe System (i.e. Vidolm and Baia de Arieș nappes) show similarities in the stratigraphic sequence and their isotope signature, together with a comparable structural position close to nappe contact. However, the dataset is not concise enough to allow for a definitive attribution of a Mesozoic origin to other marble sequences than the Vulturese-Belioara Series.

Hydrogeology of the Southeastern Coastal Plain aquifer system in Mississippi, Alabama, Georgia, and South Carolina

USGS Publications Warehouse

Renken, Robert A.

1996-01-01

The Southeastern Coastal Plain aquifer system consists of a thick sequence of unconsolidated to poorly consolidated Cretaceous and Tertiary rocks that extend from Mississippi to South Carolina. Four regional sand and gravel aquifers are separated by three regional confining units of clay, shale, and chalk that do not conform everywhere to stratigraphic boundaries. The change in geologic facies is the most important factor controlling the distribution of transmissivity within the aquifer system.

Integrated approaches to terminal Proterozoic stratigraphy: an example from the Olenek Uplift, northeastern Siberia

NASA Technical Reports Server (NTRS)

Knoll, A. H.; Grotzinger, J. P.; Kaufman, A. J.; Kolosov, P.

1995-01-01

In the Olenek Uplift of northeastern Siberia, the Khorbusuonka Group and overlying Kessyusa and Erkeket formations preserve a significant record of terminal Proterozoic and basal Cambrian Earth history. A composite section more than 350 m thick is reconstructed from numerous exposures along the Khorbusuonka River. The Khorbusuonka Group comprises three principal sedimentary sequences: peritidal dolomites of the Mastakh Formation, which are bounded above and below by red beds; the Khatyspyt and most of the overlying Turkut formations, which shallow upward from relatively deep-water carbonaceous micrites to cross-bedded dolomitic grainstones and stromatolites; and a thin upper Turkut sequence bounded by karst surfaces. The overlying Kessyusa Formation is bounded above and below by erosional surfaces and contains additional parasequence boundaries internally. Ediacaran metazoans, simple trace fossils, and vendotaenids occur in the Khatyspyt Formation; small shelly fossils, more complex trace fossils, and acritarchs all appear near the base of the Kessyusa Formation and diversify upward. The carbon-isotopic composition of carbonates varies stratigraphically in a pattern comparable to that determined for other terminal Proterozoic and basal Cambrian successions. In concert, litho-, bio-, and chemostratigraphic data indicate the importance of the Khorbusuonka Group in the global correlation of terminal Proterozoic sedimentary rocks. Stratigraphic data and a recently determined radiometric date on basal Kessyusa volcanic breccias further underscore the significance of the Olenek region in investigations of the Proterozoic-cambrian boundary.

Integrated approaches to terminal Proterozoic stratigraphy: an example from the Olenek Uplift, northeastern Siberia.

PubMed

Knoll, A H; Grotzinger, J P; Kaufman, A J; Kolosov, P

1995-01-01

In the Olenek Uplift of northeastern Siberia, the Khorbusuonka Group and overlying Kessyusa and Erkeket formations preserve a significant record of terminal Proterozoic and basal Cambrian Earth history. A composite section more than 350 m thick is reconstructed from numerous exposures along the Khorbusuonka River. The Khorbusuonka Group comprises three principal sedimentary sequences: peritidal dolomites of the Mastakh Formation, which are bounded above and below by red beds; the Khatyspyt and most of the overlying Turkut formations, which shallow upward from relatively deep-water carbonaceous micrites to cross-bedded dolomitic grainstones and stromatolites; and a thin upper Turkut sequence bounded by karst surfaces. The overlying Kessyusa Formation is bounded above and below by erosional surfaces and contains additional parasequence boundaries internally. Ediacaran metazoans, simple trace fossils, and vendotaenids occur in the Khatyspyt Formation; small shelly fossils, more complex trace fossils, and acritarchs all appear near the base of the Kessyusa Formation and diversify upward. The carbon-isotopic composition of carbonates varies stratigraphically in a pattern comparable to that determined for other terminal Proterozoic and basal Cambrian successions. In concert, litho-, bio-, and chemostratigraphic data indicate the importance of the Khorbusuonka Group in the global correlation of terminal Proterozoic sedimentary rocks. Stratigraphic data and a recently determined radiometric date on basal Kessyusa volcanic breccias further underscore the significance of the Olenek region in investigations of the Proterozoic-cambrian boundary.

Presence of stratigraphic traps in the back arc basins of the southern shelf of Cuba

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

Rodriguez, R.; Dominguez, R.; Touset, S.

For the last ten years the southern shelf of Cuba has been the object of seismic investigations, mainly in the Ana Maria and Guacanayabo areas. More than 4000 km of seismic lines with 3000 % had been shot. These seismic surveys had confirmed the following geological events: (1) Presence of back arc extensional basins as a result of the ocean-ocean subduction. These basins started to form since Middle Cretaceous; (2) Presence of sedimentary sequences which change in thickness between 3.0-7.0 km; (3) Predominance of the extensional regime since Middle Cretaceous with subsidence, accommodation and extending of the sediments; (4) Developmentmore » of stratigraphic traps, mainly associated with reef facies and slope fans of Late Cretaceous-Early Tertiary. These traps can reach some hundred square kilometers. They have very clear dynamic expression in the seismic section and usually form anomaly zones. Over these seismic anomalies some reverberation can be observed which could be related to hydrocarbon flows. The depth of the traps changes between 1.5-3.5 km. More than thirty of them have been localized; (5) Probably a wrench tectonic interested these basins since Middle Eocene; (6) in some wells has been found oil and gas seeps as well as seal sequences; (7) According to their origin and evolution they can be similar to the great oil basins of the Venezuela and Colombia.« less

Evidence for structural stacking and repetition in the greenstones of the Kalgoorlie district, western Australia

NASA Technical Reports Server (NTRS)

Martyn, J. E.

1986-01-01

Most previous stratigraphic interpretations of the southern part of the Norseman-Wiluna Greenstone Belt have proposed polycyclic sequences. These invoked two and sometimes three successive suites of mafic and/or ultimafic volcanics and intrusives separated by felsic volcanics and immature clastic sediments, however no distinctive lithological differences were reported between successive mafic-ultramaic sequences. When interpretations of the area further to the north are integrated, a total of four separate major mafic-ultramafic uites emerges for a large part of the Norseman-Wiluna Belt. Although the author does not intent to imply that all polycyclic stratigraphies are wrong in principle such a situation seems suspiciously over-complex and stimulates the need to look critically at the individual areas where the stratigraphies have seen erected. For the Kalgoorlie area in the south, some of the schemes have already provoked scepticism and a simpler model consisting of one cycle subject to structural repetition has been evolved by workers in the Geological Survey of Western Australia for part of this area. The latter drew attention to the carbon copy similarity between the elements of some polycyclic stratigraphies. Much more regionally extensive integrated structural and stratigraphic data is still required to evaluate the relationship between structure and stratigraphy more fully, an objective substantially limited by poor outcrop and deep weathering, but with due effort, far from unattainable.

Integrated study of high resolution geophysical and geological information of Osaka Bay, Southwest Japan

NASA Astrophysics Data System (ADS)

Inoue, Naoto; Kitada, Naoko; Itoh, Yasuto; Takemura, Keiji; Nakagawa, Koichi

The stratigraphic framework of Quaternary sediments in the Osaka Basin, Southwest Japan was revealed by high resolution geophysical and geological surveys acquired after the 1995 Kobe Earthquake. Osaka Bay is located in the central part of the Osaka Basin and is underlaid with Pre-Neogene basement rocks covered by an unconsolidated sequence of Plio-Pleistocene marine, fluvial and lacustrine sediments. Fifteen laterally continuous marine clays (from Ma-1 to Ma13, in ascending order) have been identified throughout the Osaka Basin that have been correlated with the marine eustatic record. Deep borehole and high resolution seismic data were acquired in Kobe (northern part of the basin) and Kansai International Airport (southern part of the basin). Sequence stratigraphy defined by seismic reflectors was used to reveal the stratigraphic differences between the two areas. By identifying reflectors as marine clay layers throughout the basin, we were able to divide the study area into three parts (northern, middle and southern parts) and to estimate the sedimentation rate in each location. The sedimentation rate increases from the northern and southern margins of the basin towards central Osaka Bay in the middle of the basin. In the southern parts, the sharp decline of sedimentation rate between Ma2 and Ma4 and thinning or complete lack of the reflectors corresponding to Ma5 and Ma6 layers result from tilting in this region.

Aquifer Vulnerability Assessment Based on Sequence Stratigraphic and ³⁹Ar Transport Modeling.

PubMed

Sonnenborg, Torben O; Scharling, Peter B; Hinsby, Klaus; Rasmussen, Erik S; Engesgaard, Peter

2016-03-01

A large-scale groundwater flow and transport model is developed for a deep-seated (100 to 300 m below ground surface) sedimentary aquifer system. The model is based on a three-dimensional (3D) hydrostratigraphic model, building on a sequence stratigraphic approach. The flow model is calibrated against observations of hydraulic head and stream discharge while the credibility of the transport model is evaluated against measurements of (39)Ar from deep wells using alternative parameterizations of dispersivity and effective porosity. The directly simulated 3D mean age distributions and vertical fluxes are used to visualize the two-dimensional (2D)/3D age and flux distribution along transects and at the top plane of individual aquifers. The simulation results are used to assess the vulnerability of the aquifer system that generally has been assumed to be protected by thick overlaying clayey units and therefore proposed as future reservoirs for drinking water supply. The results indicate that on a regional scale these deep-seated aquifers are not as protected from modern surface water contamination as expected because significant leakage to the deeper aquifers occurs. The complex distribution of local and intermediate groundwater flow systems controlled by the distribution of the river network as well as the topographical variation (Tóth 1963) provides the possibility for modern water to be found in even the deepest aquifers. © 2015, National Ground Water Association.

Monogenetic origin of Ubehebe Crater maar volcano, Death Valley, California: Paleomagnetic and stratigraphic evidence

NASA Astrophysics Data System (ADS)

Champion, Duane E.; Cyr, Andy; Fierstein, Judy; Hildreth, Wes

2018-04-01

Paleomagnetic data for samples collected from outcrops of basaltic spatter at the Ubehebe Crater cluster, Death Valley National Park, California, record a single direction of remanent magnetization indicating that these materials were emplaced during a short duration, monogenetic eruption sequence 2100 years ago. This conclusion is supported by geochemical data encompassing a narrow range of oxide variation, by detailed stratigraphic studies of conformable phreatomagmatic tephra deposits showing no evidence of erosion between layers, by draping of sharp rimmed craters by later tephra falls, and by oxidation of later tephra layers by the remaining heat of earlier spatter. This model is also supported through a reinterpretation and recalculation of the published 10Be age results (Sasnett et al., 2012) from an innovative and bold exposure-age study on very young materials. Their conclusion of multiple and protracted eruptions at Ubehebe Crater cluster is here modified through the understanding that some of their quartz-bearing clasts inherited 10Be from previous exposure on the fan surface (too old), and that other clasts were only exposed at the surface by wind and/or water erosion centuries after their eruption (too young). Ubehebe Crater cluster is a well preserved example of young monogenetic maar type volcanism protected within a National Park, and it represents neither a protracted eruption sequence as previously thought, nor a continuing volcanic hazard near its location.

Evidence for structural stacking and repetition in the greenstones of the Kalgoorlie district, western Australia

NASA Astrophysics Data System (ADS)

Martyn, J. E.

Most previous stratigraphic interpretations of the southern part of the Norseman-Wiluna Greenstone Belt have proposed polycyclic sequences. These invoked two and sometimes three successive suites of mafic and/or ultimafic volcanics and intrusives separated by felsic volcanics and immature clastic sediments, however no distinctive lithological differences were reported between successive mafic-ultramaic sequences. When interpretations of the area further to the north are integrated, a total of four separate major mafic-ultramafic uites emerges for a large part of the Norseman-Wiluna Belt. Although the author does not intent to imply that all polycyclic stratigraphies are wrong in principle such a situation seems suspiciously over-complex and stimulates the need to look critically at the individual areas where the stratigraphies have seen erected. For the Kalgoorlie area in the south, some of the schemes have already provoked scepticism and a simpler model consisting of one cycle subject to structural repetition has been evolved by workers in the Geological Survey of Western Australia for part of this area. The latter drew attention to the carbon copy similarity between the elements of some polycyclic stratigraphies. Much more regionally extensive integrated structural and stratigraphic data is still required to evaluate the relationship between structure and stratigraphy more fully, an objective substantially limited by poor outcrop and deep weathering, but with due effort, far from unattainable.

Microbial mat records in siliciclastic rocks: Examples from Four Indian Proterozoic basins and their modern equivalents in Gulf of Cambay

NASA Astrophysics Data System (ADS)

Sarkar, Subir; Banerjee, Santanu; Samanta, Pradip; Chakraborty, Nivedita; Chakraborty, Partha Pratim; Mukhopadhyay, Soumik; Singh, Arvind K.

2014-09-01

Microbial mat-related structures (MRS) in siliciclastics have been investigated from four Proterozic formations in India, namely the Marwar Supergroup, the Vindhyan Supergroup, the Chhatisgarh Supergroup and the Khariar Group for their spectral variations, genetic aspects, palaeo-environmental significance and influence on sequence stratigraphic architecture. The maximum diversification of MRS has been experienced in shallow marine coastal Precambrian successions. Observations made from modern environment as well as Precambrian rock records clearly indicates that the features like petee ridges, sand-cracks, gas domes, multi-directed ripples, reticulate surfaces, sieve-like surfaces and setulf are most likely to form in the shallowest part of the marine basins, in upper intertidal to supratidal conditions while wrinkle structures, roll-up structures and patchy ripples had a broader range of palaeogeographic settings from the supratidal to subtidal conditions. Discoidal microbial colony (DMC) represents a special variety of the mat-layer feature in modern environment that may have diverse internal architecture, sometimes falsely resembles Ediacaran medusoids. The uniqueness in sequence stratigraphic architecture of the microbial mat-covered sediment is reflected by the presence of more amalgamated HSTs compare to that of TSTs. The preservation of forced and normal regressive deposits on low-gradient epeiric shelf under low continental freeboard indicates microbial mat-infested sea-floor impedes erosion and concomitant sediment supply may facilitate formation and preservation of regressive packages.

Stratigraphic and structural characterization of the OU-1 area at the former George Air Force Base, Adelanto, Southern California

USGS Publications Warehouse

Catchings, R.D.; Gandhok, G.; Goldman, M.R.

2001-01-01

The former George Air Force Base (GAFB), now known as the Southern California Logistics Airport (SCLA), is located in the town of Adelanto, approximately 100 km northeast of Los Angeles, California (Fig. 1). In this report, we present acquisition parameters, data, and interpretations of seismic images that were acquired in the OU-1 area of GAFB during July 1999 (Fig. 2). GAFB is scheduled for conversion to civilian use, however, during its years as an Air Force base, trichlorethylene (TCE) was apparently introduced into the subsurface as a result of spills during normal aircraft maintenance operations. To comply with congressional directives, TCE contaminant removal has been ongoing since the early-tomid 1990s. However, only a small percentage of the TCE believed to have been introduced into the subsurface has been recovered, due largely to difficulty in locating the TCE within the subsurface. Because TCE migrates within the subsurface by ground water movement, attempts to locate the TCE contaminants in the subsurface have employed an array of ground-water monitoring and extraction wells. These wells primarily sample within a shallow-depth (~40 m) aquifer system. Cores obtained from the monitoring and extraction wells indicate that the aquifer, which is composed of sand and gravel channels, is bounded by aquitards composed largely of clay and other fine-grained sediments. Based on well logs, the aquifer is about 3 to 5 m thick along the seismic profiles. A more thorough understanding of the lateral variations in the depth and thickness of the aquifer system may be a key to finding and removing the remaining TCE. However, due to its complex depositional and tectonic history, the structural and stratigraphic sequences are not easily characterized. An indication of the complex nature of the structure and stratigraphy is the appreciable variation in stratigraphic sequences observed in some monitoring wells that are only a few tens of meters apart. To better characterize the shallow (upper 100 m) stratigraphy beneath GAFB, the US Environmental Protection Agency (USEPA) contracted the US Geological Survey (USGS) to acquire three seismic reflection/refraction profiles within an area known as Operational Unit #1 (OU-1). The principal objective of the seismic survey was to laterally characterize the subsurface with respect to structure and stratigraphy. In particular, we desired to (1) laterally “map” stratigraphic units (particularly aquifer layers) that were previously identified in monitoring wells within the OU-1 area and (2) identify structures, such as faults and folds, that affect the movement of ground water. Knowledge of lateral variations in stratigraphic units and structures that may affect those units is useful in constructing ground-water flow models, which aid in identifying possible TCE migration paths within the subsurface. Stratigraphic and structural characterization may also be useful in identifying surface locations and target depths for future wells (Catchings et al., 1996). Proper siting of wells is important because a welldefined aquifer is apparently not present in all locations at GAFB, as indicated by lithologic logs from existing wells (Montgomery Watson, 1995). Proper depth placement of monitoring and extraction wells is important because wells that are too shallow will not sample within the aquifer, and wells that are too deep risk puncturing the aquitard and allowing contaminants to flow to deeper levels.

Lavas and Sills in the Ferrar Large Igneous Province: Field and Geochemical Evidence for the Order of Emplacement.

NASA Astrophysics Data System (ADS)

Elliot, D. H.; Fleming, T. H.

2005-12-01

Many large igneous provinces, particularly those associated with Gondwana break-up, include major sill complexes as well as flood basalt fields. In the Ferrar province, radiometric dates of lavas and sills are indistinguishable. Nevertheless, in north Victoria Land (NVL) field evidence suggests the lavas had to have been erupted first in order to create the overburden needed for emplacement at shallow depths of thick sills, lacking vesicles, in a thin (100 m) Upper Triassic sedimentary sequence overlying basement. Elsewhere in the Transantarctic Mountains sills occur almost exclusively in a thick (2-2.5 km) Devonian-Triassic sedimentary sequence (Beacon Supergroup) that was possibly capped by 500+m of lavas before sill emplacement. For south Victoria Land (SVL), Marsh (2004) proposed that the most evolved rocks were erupted first as lavas, and sills were emplaced at progressively greater depth as increasingly more magnesian magmas and crystal mushes were injected into supracrustal and finally basement rocks. In NVL most lavas have MgO between 6-8% with a few as low as 4.5% MgO, whereas analyzed chilled margins of sills range from 3.7-5.6% MgO. In the Prince Albert Mountains (PAM), SVL, lava and sill compositions overlap (3.9-7.3% MgO). In the greater Dry Valleys region (SVL) lavas at Carapace Nunatak range from 3.6-6.7% MgO; chilled margins of Dry Valleys sills range from about 4.2 to 7.2% MgO. In the Queen Alexandra Range, central Transantarctic Mountains (CTM), lavas are predominantly 2.6-5.7% MgO; sills in the region range from 4.5% to 10.7% MgO. In the Otway Massif region (head of the Shackleton Glacier, CTM) most lavas are strongly evolved (2.7-3.4% MgO); sills in the Shackleton Glacier region range from 4.3-7.3% MgO. Nowhere do lavas show unequivocal systematic temporal change in MgO, and notably in CTM the initial flows are the most mafic (7.5-8.0% MgO). Olivine dolerite sills (chilled margins: -9% MgO) tend to occur low in the stratigraphic section. Except for NVL where Beacon strata exposures are limited, sills are thicker (100-200 m) and more regular in lower stratigraphic levels. Sills with orthopyroxene crystal-mush tongues are not known outside the Dry Valleys except perhaps the Warren Range (SVL). No province-wide systematic relationship is apparent between compositions of lavas and sill chilled margins. Nevertheless, in CTM most lavas are significantly more evolved than the sills; within the sills there is no clear relationship between MgO and stratigraphy, and some less evolved compositions occur at relatively high stratigraphic levels. In SVL compositional overlap is almost complete; locally, cross-cutting relations show more mafic sills and sheets cutting less mafic compositions. In NVL the chemical relations between lavas and sills are opposite from those that have been advocated for SVL. Interpretation is compounded by sills that exchange stratigraphic position or climb stratigraphically. Factors affecting magma emplacement include magma density, lithostatic pressure, overpressures required for lateral emplacement, and rock physical properties; when and where the evolving source was tapped may play an equal role in the emplacement order. Further, detailed work on the sills will show whether crystallization might have yielded lower density residual liquids that could have migrated and formed distal fingers of sills or migrated to higher stratigraphic levels.

Seismic stratigraphic architecture of the Disko Bay trough-mouth fan system, West Greenland

NASA Astrophysics Data System (ADS)

Hofmann, Julia C.; Knutz, Paul C.

2015-04-01

Spatial and temporal changes of the Greenland Ice Sheet on the continental shelf bordering Baffin Bay remain poorly constrained. Then as now, fast-flowing ice streams and outlet glaciers have played a key role for the mass balance and stability of polar ice sheets. Despite their significance for Greenland Ice Sheet dynamics and evolution, our understanding of their long-term behaviour is limited. The central West Greenland margin is characterized by a broad continental shelf where a series of troughs extend from fjords to the shelf margin, acting as focal points for trough-mouth fan (TMF) accummulations. The sea-ward bulging morphology and abrupt shelf-break of these major depositional systems is generated by prograding depocentres that formed during glacial maxima when ice streams reached the shelf edge, delivering large amounts of subglacial sediment onto the continental slope (Ó Cofaigh et al., 2013). The aim of this study is to unravel the seismic stratigraphic architecture and depositional processes of the Disko Bay TMF, aerially the largest single sedimentary system in West Greenland, using 2D and 3D seismic reflection data, seabed bathymetry and stratigraphic information from exploration well Hellefisk-1. The south-west Disko Bay is intersected by a deep, narrow trough, Egedesminde Dyb, which extends towards the southwest and links to the shallower and broader cross-shelf Disko Trough (maximum water depths of > 1000 m and a trough length of c. 370 km). Another trough-like depression (trough length of c. 120 km) in the northern part of the TMF, indicating a previous position of the ice stream, can be distinguished on the seabed topographic map and the seismic images. The Disko Bay TMF itself extends from the shelf edge down to the abyssal plain (abyssal floor depths of 2000 m) of the southern Baffin Bay. Based on seismic stratigraphic configurations relating to reflection terminations, erosive patterns and seismic facies (Mitchum et al., 1977), the TMF succession has been divided into five seismic units, each representing different stages in the progradational accumulation of the TMF system. This poster and ongoing study will discuss how the ice-stream flow switching is linked to changes in depocentres of sedimentary sequences and further investigate the major controls, e.g. ice-sheet dynamics, ocean-climate changes, tectonic forcing and subglacial geology, that determined the evolution of the Disko Bay TMF. Essencial bibliography Mitchum, R.M. Jr., Vail, P.R., Sangree, J.B., 1977. Seismic stratigraphy and global changes of sea level, Part 6: Stratigraphic interpretation of seismic reflection patterns in depositional sequences. AAPG Memoir 26, 117-133. Ó Cofaigh, C., Andrews, J.T., Jennings, A.E., Dowdeswell, J.A., Hogan, K.A., Kilfeather, A.A., Sheldon, C., 2013. Glacimarine lithofacies, provenance and depositional processes on a West Greenland trough-mouth fan. Journal of Quaternary Science, 28(1), 13-26.

Research of Houjiayao Unit in North China

NASA Astrophysics Data System (ADS)

Ji, Y.

2012-12-01

"Houjiayao Group" is the standard stratigraphic unit of late Pleistocene in northern China, which was created by Jia Lanpo and Wei Qi during their research on Houjiayao site. Based on the mammal, ancient human fossils and Paleolithic features, "Houjiayao Group" was thought as late Pleistocene sediments. "Houjiayao Group" was defined as late Pleistocene stratigraphic units. However, the problems of the age of "Houjiayao Group", stratigraphic division and other issues, have not yet been well resolved. These issues include: the differences of age-dating results, the unclear comparison between stratigraphic units and regional contrast, the uncertain relationship between "Houjiayao Group" and "Nihewan Layer ", and so on. Houjiayao site which located in the southeast of Houjiayao village in Dongjingji town Yangyuan County, Hebei province of China, is a very important paleolithic site. But some researches show that Houjiayao site is located at the 3th terrace of Liyigou valley and there are many opinions about the age of Houjiayao site, which varies from 20-500 thousand years. Combined with former research results and many research methods, our study was mainly focused on the key problems existing in the study of "Houjiayao Group". Through the use of sequence stratigraphy, chronostratigraphy, biostratigraphy and other theoretical methods, stratigraphic section was studied in the late Pleistocene stratigraphy and sedimentary environment. Through environmental indicators and the age-dating tests, the evolution of ancient geography and environment were identified elementarily. After analyzing informations of this area, geomorphologic investigation and stratum comparation in and around Houjiayao site were done. Houjiayao site is located on the west bank of Liyigou river, which has a tributary named Black Stone River. Two or three layers of volcanic materials were found in this area, those sediments are from a buried paleovolcano in upstream of Black Stone River. The volcanic material layers played an important role in the track of stratum, especially the lower strata. Heights of volcanic sediments become lower south of paleovolcano along the Liyigou River and Black Stone River. The stratum in Houjiayao site shows that the sand-clayey silt-silty clay sediments which are more than 6 meters thick have river sediments characters and they are covered on the culture layers. Culture layers were formed by river and lake. Among the cultural layers, there were two sub-clay layers weak pedogenesis. There is an unconformity sedimentary sequence between the culture layers and the underlying yellow-green lacustrine strata (Nihewan layer). Some volcanic sediments with the K-Ar ages between 0.4-0.5Ma were found in the gray-green Nihewan formation under the culture layers. In general, detailed stratum surveys of this area have not been done before, so this work provided the Lithostratigraphic information for the area research. And with this work, we get the conclusion that Houjiayao site is not located on the 3th terrace of Liyigou valley, and its sediment is one part of Nihewan layers with the age of late Pleistocene.

Lateral variations of carbonate platform facies and cycles: The Dachstein Limestone (Late Triassic, Northern Calcareous Alps, Austria)

NASA Astrophysics Data System (ADS)

Samankassou, Elias; Enos, Paul

2017-04-01

The driving mechanisms of cyclic patterns in shallow-water platform carbonates remain controversial. The focus of the present paper is to quantify lateral facies variations for a long stratigraphic record in an extensive, continuous, well-exposed cliff of the Dachstein platform that is composed, as many other Phanerozoic carbonate platforms, of peritidal deposits. We noted the lateral continuity of the beds to the degree permitted by the outcrop, generally a few tens or hundreds of meters; exceptionally up to 1.7 km. The study demonstrates the importance of quantification to evaluate origins of sedimentary cycles. The upper 885 m of the Triassic Dachstein platform limestone at Steinernes Meer, Saalfelden, Austria, includes 241 peritidal cycles overlain by 275 m of subtidal, non-cyclic and weakly cyclic limestone. Of 558 subtidal and intertidal beds measured, 121 (21.7%) disappear laterally. An additional 74 beds (13.3%) show significant (>10%) lateral variations in thickness. Mean thickness variation is 50%. Both lateral variations and discontinuities appear to lack a spatial vector. Disappearances toward the inferred platform interior (west), total 10.4% of the beds. East toward the inferred platform margin 11.3% of the beds disappear. Thickness changes occur in 6.6% of beds in each direction. The lack of lateral continuity of beds is consistent with a non-eustatic component to stratification. Erosion of intertidal intervals is the process that can be most readily documented. Erosion, transport, and non-uniform distribution of sediments, superposed on stratigraphic sequences driven by eustacy, are the likely processes which produced the complex, randomly recorded cycle patterns. Cycle duration may not be exclusively determined by Milankovitch processes, as suggested by the discrepancies in the cycle duration and interpretation among stratigraphers of the Dachstein, as well as other Phanerozoic carbonate platforms. Signals deduced from linearly measured sections likely represent composite inherent and extrabasinal factors; they should not be automatically interpreted as exclusive records of eustatic orbital forcing. Lateral discontinuities and thickness variations could also present problems in spectral analysis of thickness patterns, typically conducted in search of "Milankovich frequencies", as well as in construction of "Fischer plots," to analyze long-period oscillations in relative sea level. Any section subjected to cycle analysis should be examined for lateral changes, to the extent permitted by the exposures, in order to produce the most complete (composite) section possible.

North American Commission on Stratigraphic Nomenclature Note 66: records of Stratigraphic Commission, 2003-2013

USGS Publications Warehouse

Easton, Robert M.; Catuneanu, Octavian; Donovan, Art D.; Fluegeman, Richard H.; Hamblin, A.P.; Harper, Howard; Lasca, Norman P.; Morrow, Jared R.; Orndorff, Randall C.; Sadler, Peter; Scott, Robert W.; Tew, Berry H.

2014-01-01

Note 66 summarizes activities of the North American Commission on Stratigraphic Nomenclature (NACSN) from November 2003 to October 2013 and is condensed from the minutes of the NACSN’s 58th to 68th annual meetings1. The purposes of the Commission are to develop statements of stratigraphic principles,recommend procedures applicable to the classification and nomenclature of stratigraphic and related units, review problems in classifying and naming stratigraphic and related units, and formulate expressions of judgment on these matters.

Building a geological reference platform using sequence stratigraphy combined with geostatistical tools

NASA Astrophysics Data System (ADS)

Bourgine, Bernard; Lasseur, Éric; Leynet, Aurélien; Badinier, Guillaume; Ortega, Carole; Issautier, Benoit; Bouchet, Valentin

2015-04-01

In 2012 BRGM launched an extensive program to build the new French Geological Reference platform (RGF). Among the objectives of this program is to provide the public with validated, reliable and 3D-consistent geological data, with estimation of uncertainty. Approx. 100,000 boreholes over the whole French national territory provide a preliminary interpretation in terms of depths of main geological interfaces, but with an unchecked, unknown and often low reliability. The aim of this paper is to present the procedure that has been tested on two areas in France, in order to validate (or not) these boreholes, with the aim of being generalized as much as possible to the nearly 100,000 boreholes waiting for validation. The approach is based on the following steps, and includes the management of uncertainty at different steps: (a) Selection of a loose network of boreholes owning a logging or coring information enabling a reliable interpretation. This first interpretation is based on the correlation of well log data and allows defining 3D sequence stratigraphic framework identifying isochronous surfaces. A litho-stratigraphic interpretation is also performed. Be "A" the collection of all boreholes used for this step (typically 3 % of the total number of holes to be validated) and "B" the other boreholes to validate, (b) Geostatistical analysis of characteristic geological interfaces. The analysis is carried out firstly on the "A" type data (to validate the variogram model), then on the "B" type data and at last on "B" knowing "A". It is based on cross-validation tests and evaluation of the uncertainty associated to each geological interface. In this step, we take into account inequality constraints provided by boreholes that do not intersect all interfaces, as well as the "litho-stratigraphic pile" defining the formations and their relationships (depositing surfaces or erosion). The goal is to identify quickly and semi-automatically potential errors among the data, up to the geologist to check and correct the anomalies, (c) Consistency tests are also used to verify the appropriateness of interpretations towards other constraints (geological map, maximal formation extension limits, digital terrain model ...), (d) Construction of a 3D geological model from "A"+ "B" boreholes: continuous surfaces representation makes it possible to assess the overall consistency and to validate or invalidate interpretations. Standard-deviation maps allow visualizing areas where data from available but not yet validated boreholes could be added to reduce uncertainty. Maps of absolute or relative errors help to quantify and visualize model uncertainty. This procedure helps to quickly identify the main errors in the data. It guarantees rationalization, reproducibility and traceability of the various stages of validation. Automation aspect is obviously important when it comes to dealing with datasets that can contain tens of thousands of surveys. For this, specific tools have been developed by BRGM (GDM/ MultiLayer software, R scripts, GIS tools).

Oolitic sandbody depositional models and geometries, Mississippian of southwest Britain: implications for petroleum exploration in carbonate ramp settings

NASA Astrophysics Data System (ADS)

Burchette, Trevor P.; Paul Wright, V.; Faulkner, Tom J.

1990-07-01

A 1000 m thick early Mississippian carbonate supersequence, the "Carboniferous Limestone" of southwest Britain, consists of three third-order depositional sequences. These comprise parasequences in various configurations, and the whole forms a carbonate ramp stack. Within this framework five major oolitic carbonate sandbodies developed: (a) Castell Coch Limestone, (b) Stowe Oolite, (c) Brofiscin Oolite, (d) Gully Oolite, and (e) High Tor Limestone. The depositional regime was storm- and wave-dominated throughout and the major sandbodies represent a range of progradational carbonate beaches, barriers and detached subtidal shoals. Analysis of the three-dimensional shapes and distribution of these five examples shows that they evolved to produce three major carbonate sandbody geometries: (a) strings, (b) sheets, and (c) wedges. These geometries are characterised using the five field examples and offered as a template which may assist in the exploration and reservoir modelling of petroleum-rich high-energy ramp systems. Progradation, for up to 40 km, of barrier islands (Stowe Oolite) and beach-ridge plains (Gully Oolite Formation) generated strings, and "thick" sheets individually up to 10-20 m thick. "Thin" shoreface-retreat carbonate packstone/grainstone sheets up to 5 m thick (High Tor limestone) developed during transgressions as veneers across flooding surfaces. These are comparable with sheet sands developed in siliciclastic shelf depositional systems. Progradation, for up to 30 km, and vertical aggradation of shoreline-detached oolite shoals (Castell Coch limestone, Brofiscin Oolite), generated basinwards-expanding or thinning wedges up to 30 m thick. Tectonically controlled stacking of strandplain sheets produced a composite carbonate sandbody up to 80 m thick (Gully Oolite). The intrinsic (sedimentary) and extrinsic (eustacy, tectonism, climate) factors which controlled these sandbody geometries are addressed. Establishing the positions of the sandbodies accurately within depositional sequences allows them to be located within inferred seismic sequence geometries and provides one possible solution to the difficult problem of predicting carbonate facies distribution in subtle stratigraphic plays. In this ramp system, the most homogeneous sandbodies (up to 30 m grainstones), with greatest reservoir facies potential, are represented by shoal-belt wedges. Potential grainstone reservoir facies in the prograding shorelines are limited to the upper parts of individual shoreface sequences (max. 10 m grainstones). For shoreline carbonate sandbodies, the greatest reservoir and stratigraphic trapping potential exists in the earliest ramp parasequences where enveloping offshore sediments are siliciclastic mudstones. In later stages, potential seals are likely to be less reliable, low-porosity outer ramp carbonates.

Using 3D visualization and seismic attributes to improve structural and stratigraphic resolution of reservoirs

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

Kerr, J.; Jones, G.L.

1996-01-01

Recent advances in hardware and software have given the interpreter and engineer new ways to view 3D seismic data and well bore information. Recent papers have also highlighted the use of various statistics and seismic attributes. By combining new 3D rendering technologies with recent trends in seismic analysis, the interpreter can improve the structural and stratigraphic resolution of hydrocarbon reservoirs. This paper gives several examples using 3D visualization to better define both the structural and stratigraphic aspects of several different structural types from around the world. Statistics, 3D visualization techniques and rapid animation are used to show complex faulting andmore » detailed channel systems. These systems would be difficult to map using either 2D or 3D data with conventional interpretation techniques.« less

Using 3D visualization and seismic attributes to improve structural and stratigraphic resolution of reservoirs

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

Kerr, J.; Jones, G.L.

1996-12-31

Recent advances in hardware and software have given the interpreter and engineer new ways to view 3D seismic data and well bore information. Recent papers have also highlighted the use of various statistics and seismic attributes. By combining new 3D rendering technologies with recent trends in seismic analysis, the interpreter can improve the structural and stratigraphic resolution of hydrocarbon reservoirs. This paper gives several examples using 3D visualization to better define both the structural and stratigraphic aspects of several different structural types from around the world. Statistics, 3D visualization techniques and rapid animation are used to show complex faulting andmore » detailed channel systems. These systems would be difficult to map using either 2D or 3D data with conventional interpretation techniques.« less

Signatures of mountain building: Detrital zircon U/Pb ages from northeast Tibet

USGS Publications Warehouse

Lease, Richard O.; Burbank, Douglas W.; Gehrels, George E.; Wang, Zhicai; Yuan, Daoyang

2007-01-01

Although detrital zircon has proven to be a powerful tool for determining provenance, past work has focused primarily on delimiting regional source terranes. Here we explore the limits of spatial resolution and stratigraphic sensitivity of detrital zircon in ascertaining provenance, and we demonstrate its ability to detect source changes for terranes separated by only a few tens of kilometers. For such an analysis to succeed for a given mountain, discrete intrarange source terranes must have unique U/Pb zircon age signatures and sediments eroded from the range must have well-defined depositional ages. Here we use ∼1400 single-grain U/Pb zircon ages from northeastern Tibet to identify and analyze an area that satisfies these conditions. This analysis shows that the edges of intermontane basins are stratigraphically sensitive to discrete, punctuated changes in local source terranes. By tracking eroding rock units chronologically through the stratigraphic record, this sensitivity permits the detection of the differential rock uplift and progressive erosion that began ca. 8 Ma in the Laji Shan, a 10-25-km-wide range in northeastern Tibet with a unique U/Pb age signature.

Transitions in Lava Emplacement Recorded in the Deccan Traps Sequence (India)

NASA Astrophysics Data System (ADS)

Vanderkluysen, L.; Self, S.; Jay, A. E.; Sheth, H. C.; Clarke, A. B.

2015-12-01

Transitions in the style of lava flow emplacement are recognized in the stratigraphic sequence of several mafic large igneous provinces (LIPs), including the Etendeka (Namibia), the Faeroe Islands (North Atlantic LIP), the Ethiopian Traps, and the Deccan Traps (India). These transitions, from units dominated by meter-sized pāhoehoe toes and lobes to those dominated by inflated sheet lobes tens to hundreds of meters in width and meters to tens of meters in height, seems to be a fundamental feature of LIP emplacement. In the Deccan, this volcanological transition is thought to coincide with deeper changes to the volcano-magmatic system expressed, notably, in the trace element and isotopic signature of erupted flows. We investigated this transition in the Deccan Traps by logging eight sequences along the Western Ghats, an escarpment in western India where the Deccan province is thickest and best exposed. The Deccan province, which once covered ~1 million km2 of west-central India, is subdivided in eleven chemo-stratigraphic formations in the type sections of the Western Ghats. Where the lower Deccan formations are exposed, we found that as much as 65% of the exposed thickness (below the Khandala Formation) is made up of sheet lobes, from 40% in the Bhimashankar Formation to 75% in the Thakurvadi Formation. Near the bottom of the sequence, 25% of the Neral Formation is composed of sheet lobes ≥15 m in thickness. On this basis, the traditional view that inflated sheet lobes are an exclusive feature of the upper part of the stratigraphy must be challenged. Several mechanisms have been proposed to explain the development of compound flows and inflated sheet lobes, involving one or more of the following factors: underlying slope, varying effusion rate, and source geometry. Analogue experiments are currently under way to test the relative influence of each of these factors in the development of different lava flow morphologies in LIPs.

Sedimentation and basin-fill history of the Neogene clastic succession exposed in the southeastern fold belt of the Bengal Basin, Bangladesh: a high-resolution sequence stratigraphic approach

NASA Astrophysics Data System (ADS)

Royhan Gani, M.; Mustafa Alam, M.

2003-02-01

The Tertiary basin-fill history of the Bengal Basin suffers from oversimplification. The interpretation of the sedimentary history of the basin should be consistent with the evolution of its three geo-tectonic provinces, namely, western, northeastern and eastern. Each province has its own basin generation and sediment-fill history related mainly to the Indo-Burmese and subordinately to the Indo-Tibetan plate convergence. This paper is mainly concerned with facies and facies sequence analysis of the Neogene clastic succession within the subduction-related active margin setting (oblique convergence) in the southeastern fold belt of the Bengal Basin. Detailed fieldwork was carried out in the Sitapahar anticline of the Rangamati area and the Mirinja anticline of the Lama area. The study shows that the exposed Neogene succession represents an overall basinward progradation from deep marine through shallow marine to continental-fluvial environments. Based on regionally correlatable erosion surfaces the entire succession (3000+ m thick) has been grouped into three composite sequences C, B and A, from oldest to youngest. Composite sequence C begins with deep-water base-of-slope clastics overlain by thick slope mud that passes upward into shallow marine and nearshore clastics. Composite sequence B characteristically depicts tide-dominated open-marine to coastal depositional systems with evidence of cyclic marine regression and transgression. Repetitive occurrence of incised channel, tidal inlet, tidal ridge/shoal, tidal flat and other tidal deposits is separated by shelfal mudstone. Most of the sandbodies contain a full spectrum of tide-generated structures (e.g. herringbone cross-bedding, bundle structure, mud couplet, bipolar cross-lamination with reactivation surfaces, 'tidal' bedding). Storm activities appear to have played a subordinate role in the mid and inner shelf region. Rizocorallium, Rosselia, Planolites and Zoophycos are the dominant ichnofacies within the shelfal mudstone. This paralic sedimentation of Neogene succession in the study area can serve as a good point of reference for tide-dominated regressive shelf depositional systems. The top of the composite sequence B is marked by a pronounced erosion surface indicating the final phase of marine regression followed by the gradual establishment of continental-fluvial depositional systems represented by composite sequence A. In this composite sequence, stacked channel bars of low-sinuosity braided rivers gradually pass upsequence into high-sinuosity meandering river deposits. A sequence stratigraphic approach has been adopted to interpret the basin-fill history with respect to relative sea-level changes; and to subdivide the rock record into several sequences and units (systems tracts and parasequences) based on identified bounding discontinuities, such as transgressive erosion surface (TES), regressive erosion surface (RES), marine flooding surface (MFS), and incised valley floor (IVF). This approach provides new insight for both exploration and exploitation strategy for hydrocarbon plays that may prove vital to the oil companies engaged in exploration activities in the Bengal Basin. It is strongly recommended here that the traditional lithostratigraphic classification of this part of the basin, which is based on the Assam stratigraphy, be abandoned or at least revised. A tentative allostratigraphic scheme is presented, and it is suggested that to formalize the scheme further study, both surface and subsurface, is needed.

Barrier island arcs along abandoned Mississippi River deltas

USGS Publications Warehouse

Penland, S.; Suter, J.R.; Boyd, Ron

1985-01-01

Generation of transgressive barrier island arcs along the Mississippi River delta plain and preservation of barrier shoreline facies in their retreat paths on the inner shelf is controlled by: (1) shoreface translation; (2) age of the transgression; and (3) the thickness of the barrier island arc sediment package. Barrier island arcs experience an average relative sea level rise of 0.50-1.00 cm yr-1 and shoreface retreat rates range from 5-15 m yr-1. Young barrier island arc sediment packages (Isles Dernieres) are thin and have experienced limited landward retreat of the shoreface. Older barrier island arcs (Chandeleur Islands) are thicker and have experienced significant landward movement of the shoreface because of the greater time available for retreat. If the transgressed barrier shoreline sediment package lies above the advancing ravinement surface, the entire sequence is truncated. A thin reworked sand sheet marks the shoreface retreat path. The base of the transgressive sediment package can lie below the ravinement surface in older barrier shorelines. In this setting, the superstructure of the barrier shoreline is truncated, leaving the basal portion of the transgressive sequence preserved on the inner shelf. A variety of transgressive stratigraphic sequences from sand sheets to truncated barrier islands to sand-filled tidal inlet scars have been identified by high resolution seismic profiling across the shoreface retreat paths of Mississippi delta barrier island arcs. One of these examples, the Isles Dernieres, represents a recently detached barrier island arc in the early stages of transgression. An older example, the Chandeleur Islands, represents a barrier island arc experiencing long-term shoreface retreat. This paper describes the stratigraphic character and preserved transgressive facies for the Isles Dernieres and Chandeleur Islands. ?? 1985.

Morphometric analysis of Eocene nummulitids in Western and Central Cuba - inferences on taxonomy, biostratigaphy and evolutionary trends

NASA Astrophysics Data System (ADS)

Ives Torres-Silva, Ana; Eder, Wolfgang; Hohenegger, Johann; Briguglio, Antonino

2017-04-01

None other larger benthic foraminifera (LBF) group in the Caribbean realm has led to such diverse opinions and controversy about their classification than the nummulitids. Unlike the Tethys species, where delimitation and details of evolutionary changes within species are well known, intraspecific evolution in the Caribbean remains understudied and generic nomenclature has not reached consensus yet. Morphometric studies appear to be the most appropriate methods in solving this unsatisfactory taxonomical situation. For every proposed species, morphological variations correlating with paleoecological factors and precise stratigraphic occurrence and range has to be studied in detail. Thus, the morphology in equatorial sections of nummulitids without chamber partitions was quantified at seven localities from Western and Central Cuba and interpreted by eleven growth-independent and/or growth-invariant characters and attributes. 102 isolated megalospheric individuals originating from Cuban localities, spanning the time interval from lower Middle Eocene to lower Oligocene, were classified by nonmetric multidimensional scaling and cluster analysis. Thirteen Caribbean specimens, which are considered as type material, were included. Two clearly differentiated morphogroups could be differentiated according to cluster and ordination analysis into the genera Nummulites and Palaeonummulites. Main differences in morphological characters between the morphogroups were confirmed by discriminant analysis. Nummulites differs from Palaeonummulites in a weak increase of the marginal radius and weak backbend angles. All specimens of Nummulites s.stricto from different localities were regarded as Nummulites striatoreticulatus. Based on discriminant analysis, N. striatoreticulatus specimens with similar depositional environments, but of different stratigraphic occurrence, are strongly separated. The older forms have a smaller backbend angle, perimeter ratio and proloculus nominal diameter, thus documenting stratigraphic and evolutionary trends. The species Nummulites striatoreticulatus in the Cuban sections ranges from lower middle Eocene to lower Priabonian. Within the Palaeonummulites group, the exceptional range of morphological variation tends to obscure the fact that there are several well-defined morphological species. Based on discriminant analysis the species P. willcoxi, P. trinitatensis, P. floridensis, P. ocalanus and P. soldadensis were classified ranging from tightly coiled individuals that are very similar to Nummulites to loosely coiled moprhotypes. Major separators between the species are the marginal radius, proloculus nominal diameter, spiral chamber height increase and the length of the first chamber. Stratigraphic trends within species were not clearly detectable, but paleogeographic differences and the morphological overlap between morphogroups in certain species are obvious. Paleonummulites species have long stratigraphic ranges from late Middle Eocene to probably lower Oligocene.

Sudbury project (University of Muenster-Ontario Geological Survey): Petrology, chemistry, and origin of breccia formations

NASA Technical Reports Server (NTRS)

Stoeffler, D.; Deutsch, A.; Avermann, M.; Brockmeyer, P.; Lakomy, R.; Mueller-Mohr, V.

1992-01-01

Within the Sudbury Project of the University of Muenster and the Ontario Geological Survey special emphasis was put on the breccia formations exposed at the Sudbury structure (SS) because of their crucial role for the impact hypothesis. They were mapped and sampled in selected areas of the north, east, and south ranges of the SS. The relative stratigraphic positions of these units are summarized. Selected samples were analyzed by optical microscopy, SEM, microprobe, XRF and INAA, Rb-Sr and SM-Nd-isotope geochemistry, and carbon isotope analysis. The results of petrographic and chemical analysis for those stratigraphic units that were considered the main structural elements of a large impact basin are summarized.

Alkyl substituted cyclic ethers in 2,300 M yr old Transvaal algal stromatolite

NASA Technical Reports Server (NTRS)

Zumberge, J. E.; Nagy, B.

1975-01-01

Two cyclic ethers have been identified for the first time from insoluble polymer-like kerogen in a Precambrian rock by ozonolysis, gas chromatography, and mass spectrometry. The ethers are 2-n-propyl-3-methyltetrahydrofuran and 2-n-propyltetrahydropyran. These compounds could prove to be the oldest indigenous biochemical fossils. The sample was obtained 750 m stratigraphically above the base of the Transvaal Sequence from an outcrop approximately 315 km north-east of Johannesburg, South Africa.

Evolving Continents

NASA Astrophysics Data System (ADS)

Hamilton, Warren

Brian Windley succeeds very well indeed at the formidable task he sets for himself in this greatly revised second edition of a book that first appeared in 1977. He synthesizes primarily the tectonic and petrologic evolution of the continents and secondarily their economic geologic, stratigraphic, and biologic history. The book is organized in well-balanced time sequence and topical chapters, followed by a fine overview. The author describes examples, generalizes from them, and seeks understanding of variations with time and with depth of the process acting on continents within a plate tectonic framework.

Metre-scale cyclicity in Middle Eocene platform carbonates in northern Egypt: Implications for facies development and sequence stratigraphy

NASA Astrophysics Data System (ADS)

Tawfik, Mohamed; El-Sorogy, Abdelbaset; Moussa, Mahmoud

2016-07-01

The shallow-water carbonates of the Middle Eocene in northern Egypt represent a Tethyan reef-rimmed carbonate platform with bedded inner-platform facies. Based on extensive micro- and biofacies documentation, five lithofacies associations were defined and their respective depositional environments were interpreted. Investigated sections were subdivided into three third-order sequences, named S1, S2 and S3. Sequence S1 is interpreted to correspond to the Lutetian, S2 corresponds to the Late Lutetian and Early Bartonian, and S3 represents the Late Bartonian. Each of the three sequences was further subdivided into fourth-order cycle sets and fifth-order cycles. The complete hierarchy of cycles can be correlated along 190 km across the study area, and highlighting a general "layer-cake" stratigraphic architecture. The documentation of the studied outcrops may contribute to the better regional understanding of the Middle Eocene formations in northern Egypt and to Tethyan pericratonic carbonate models in general.

Tectonic controls on deposition of Middle Jurassic strata in a retroarc foreland basin, Utah-Idaho trough, western interior, United States

NASA Astrophysics Data System (ADS)

Bjerrum, Christian J.; Dorsey, Rebecca J.

1995-08-01

An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 95TC01448, Tectonic controls on deposition of Middle Jurassic strata in a retroarc foreland basin, Utah-Idaho trough, western interior, United States, Christian J. Bjerrum and Rebecca J. Dorsey). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N. W., Washington, DC 20009; $15.00. Payment must accompany order. A thick succession of Jurassic nonmarine and marine sedimentary rocks is exposed in a large area from northern Arizona to eastern Idaho and western Wyoming. These sediments accumulated in the Utah-Idaho trough, a deep elongate cratonal basin whose origin has recently been debated. Detailed stratigraphic analysis, subsidence analysis, and first-order flexural modeling of these deposits (this study) provide new insights into the timing and mechanisms of subsidence in the Utah-Idaho trough. Lower and Middle Jurassic strata are divided into six unconformity-bounded sequences. In contrast to the overall uniform thickness of Lower Jurassic sequences (1 and 2), Middle Jurassic strata (sequences 3 through 6) consist of distinctly westward thickening sedimentary packages in which basal shallow marine deposits onlap eastward onto bounding unconformities. Basal strata of sequences 3 through 6 pass upward into widespread progradational continental deposits that are truncated progressively toward the east (cratonward) by the next unconformity. Decompacted total subsidence curves show that the rate of subsidence in most sections increased sharply at the end of sequence 2 time (J-2 unconformity; ˜170 Ma). This is interpreted to record the onset of Middle Jurassic deposition in the distal part of a retroarc foreland basin. The unconformities and distinctive stratal geometries may have formed in response to forebulge migration caused by episodic thrusting in the Cordilleran orogen to the west. First-order flexural modeling was carried out to test the hypothesis of flexural subsidence in the Utah-Idaho trough. Trial-and-error comparisons produce a close match between decompacted stratigraphic profiles and model deflection profiles. The best fit is obtained using an infinite elastic plate (D = 1 × 1024 Nm), a moderate load topography, elevated base level, and an overfilled basin. Using recently published tectonic reconstructions for Nevada and Utah, we find close spatial agreement between a large Middle Jurassic fold-thrust belt and the supracrustal load inferred from model simulations. Our integrated basin analysis thus supports the interpretation of some previous studies that the Middle Jurassic Utah-Idaho trough was a retroarc foreland basin that formed east of a belt of regional contractile deformation and crustal thickening in western and central Nevada and southeastern California. Late Jurassic extension and normal faulting in northeastern Nevada may have been related to gravitational collapse of overthickened crust in the Cordilleran orogen. This coincides with a period of slowed subsidence in the Utah-Idaho trough that began at about 157 Ma.

Salt tectonics and sequence-stratigraphic history of minibasins near the Sigsbee Escarpment, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Montoya, Patricia

The focus of this research is to understand the stratigraphic and structural evolution of lower-slope minibasins in the Gulf of Mexico by examining the influence of salt tectonics on sediment transport systems and deep-water facies architecture. Results showed that gravitational subsidence and shortening can cause variations in the relief of salt massifs on opposing sides of a minibasin. These bathymetric variations, combined with changes in sedimentation rates through time, affected not only the distribution of deep-water facies inside the minibasins, but also influenced the evolution of sediment transport systems between minibasins. In order to understand the evolution of salt massifs, this dissertation presents a new approach to evaluate qualitatively the rate of relative massif uplift based on depoaxis shifts and channel geometries identified in minibasins surrounded by mobile salt. From these results it was established that compression was long-lived, and that extension only dominated during late intervals. Stratigraphic analyses showed that there is a strong cyclicity in deep-water facies stacking patterns within lower-slope minibasins, related primarily to cyclical changes in sedimentation rates. A typical sequence starts with a period of slow sedimentation associated with drape facies above each sequence boundary. Then, towards the middle and final stages of the sequence, sedimentation rates increase and turbidity flows fill the minibasin. Previous studies describe processes of fill-and-spill for two adjacent minibasins in the upper and middle slope. However, these models fail to adequately explain fill-and-spill processes in lower slope minibasins surrounded by mobile salt. In particular, they do not consider the effect of variations in bathymetric relief of the intervening massif, nor do they examine multidirectional connections between proximal and distal minibasins. A new dynamic-salt fill-and-spill model is proposed in this dissertation in order to understand the origin and distribution of sediment pathways and variations in connection styles. In this model, connection styles are controlled by changes in salt massifs relief and sedimentation rates through time. Four connection styles exist between minibasins: no connection, wide connection, narrow connection and bypass connection. Low sedimentation rates tend to shut down connection between minibasins, whereas high sedimentation rates favor development of pathways that connect minibasins. In summary, the most important contribution from this research is that variations in salt-massif relief, combined with changes in sedimentation rates through time, can yield different filling histories and connection styles for nearby minibasins. So by understanding the influence of these factors, the complicated task of identifying sediment pathways in salt-controlled environments can be attempted in a more effective way.

Recognition of maximum flooding events in mixed siliciclastic-carbonate systems: Key to global chronostratigraphic correlation

USGS Publications Warehouse

Mancini, E.A.; Tew, B.H.

1997-01-01

The maximum flooding event within a depositional sequence is an important datum for correlation because it represents a virtually synchronous horizon. This event is typically recognized by a distinctive physical surface and/or a significant change in microfossil assemblages (relative fossil abundance peaks) in siliciclastic deposits from shoreline to continental slope environments in a passive margin setting. Recognition of maximum flooding events in mixed siliciclastic-carbonate sediments is more complicated because the entire section usually represents deposition in continental shelf environments with varying rates of biologic and carbonate productivity versus siliciclastic influx. Hence, this event cannot be consistently identified simply by relative fossil abundance peaks. Factors such as siliciclastic input, carbonate productivity, sediment accumulation rates, and paleoenvironmental conditions dramatically affect the relative abundances of microfossils. Failure to recognize these complications can lead to a sequence stratigraphic interpretation that substantially overestimates the number of depositional sequences of 1 to 10 m.y. duration.

Porosity and grain size controls on compaction band formation in Jurassic Navajo Sandstone

USGS Publications Warehouse

Schultz, Richard A.; Okubo, Chris H.; Fossen, Haakon

2010-01-01

Determining the rock properties that permit or impede the growth of compaction bands in sedimentary sequences is a critical problem of importance to studies of strain localization and characterization of subsurface geologic reservoirs. We determine the porosity and average grain size of a sequence of stratigraphic layers of Navajo Sandstone that are then used in a critical state model to infer plastic yield envelopes for the layers. Pure compaction bands are formed in layers having the largest average grain sizes (0.42–0.45 mm) and porosities (28%), and correspondingly the smallest values of critical pressure (-22 MPa) in the sequence. The results suggest that compaction bands formed in these layers after burial to -1.5 km depth in association with thrust faulting beneath the nearby East Kaibab monocline, and that hardening of the yield caps accompanied compactional deformation of the layers.

Stratigraphy, Sequence, and Crater Populations of Lunar Impact Basins from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for the Late Heavy Bombardment

NASA Technical Reports Server (NTRS)

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

2012-01-01

New measurements of the topography of the Moon from the Lunar Orbiter Laser Altimeter (LOLA)[1] provide an excellent base-map for analyzing the large crater population (D.20 km)of the lunar surface [2, 3]. We have recently used this data to calculate crater size-frequency distributions (CSFD) for 30 lunar impact basins, which have implications for their stratigraphy and sequence. These data provide an avenue for assessing the timing of the transitions between distinct crater populations characteristic of ancient and young lunar terrains, which has been linked to the late heavy bombardment (LHB). We also use LOLA data to re-examine relative stratigraphic relationships between key lunar basins.

Geologic framework of oil and gas genesis in main sedimentary basins from Romania Oprea Dicea

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

Ionescu, N.; Morariu, C.D.

1991-03-01

Oil and gas fields located in Moldavic nappes are encompassed in Oligocene and lower Miocene formations, mostly in the marginal folds nappe, where Kliwa Sandstone sequences have high porosity, and in the Black Sea Plateau. The origin of the hydrocarbon accumulations from the Carpathian foredeep seems to be connected to the Oligocene-lower Miocene bituminous formations of the marginal folds and sub-Carpathian nappes. In the Gethic depression, the hydrocarbon accumulations originate in Oligocene and Miocene source rocks and host in structural, stratigraphical, and lithological traps. The accumulations connected with tectonic lines that outline the areal extension of the Oligocene, Miocene, andmore » Pliocene formations are in the underthrusted Moesian platform. The hydrocarbon accumulations related to the Carpathian foreland represent about 40% of all known accumulations in Romania. Most of them are located in the Moesian platform. In this unit, the oil and gas fields present a vertical distribution at different stratigraphic levels, from paleozoic to Neogene, and in all types of reservoirs, suggesting multicycles of oleogenesis, migration, accumulation, and sealing conditions. The hydrocarbon deposits known so far on the Black Sea continental plateau are confined in the Albian, Cenomanian, Turonian-Senonian, and Eocene formations. The traps are of complex type structural, lithologic, and stratigraphic. The reservoirs are sandstones, calcareous sandstones, limestones, and sands. The hydrocarbon source rocks are pelitic and siltic Oligocene formations. Other older source rocks are probably Cretaceous.« less

Comprehensive, quantitative micropaleontological analysis as a tool for paleoenvironmental interpretation and sequence stratigraphy, with an example from the Yegua Formation, southeast Texas

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

Lagoe, M.B.; Layman, T.B.

Traditional industrial approaches to biostratigraphy and paleoenvironmental analysis largely use only a small portion of the available microfossil assemblage, concentrating on various marker taxa({open_quotes}tops{close_quotes} of index fossils and paleoenvironmental guide fossils). Sequence-stratigraphic approaches may place more emphasis on the entire assemblage, but efficient analytical strategies still need to be developed to extract maximum information from micropaleontological data. Microfossil assemblages are produced by three types of processes: (1) in-situ accumulation of taxa living at the sample site; (2) postmortem transport of specimens into and out of the sample site ({open_quotes}down-slope transport{close_quotes}), and (3) taphonomic/diagenetic processes such as dissolution, which can altermore » taxon proportions. Recognizing and evaluating the effects of these processes on the microfossil assemblage can lead to a better geological interpretation. We propose an analytical strategy to address these issues, consisting of (1) bulk faunal descriptors (faunal abundance, preservation, diversity, planktic microfossil abundance) combined with lithologic information (e.g., abundance of glauconite) to identify broad paleoenvironmental patterns; (2) biofacies definition based on cluster analysis and factor analysis of the entire microfossil data set to refine these patterns; (3) interpretation and modeling of biofacies trends using detrended reciprocal averaging, and (4) analysis of faunal mixing patterns using polytopic vector analysis. We apply this analytical strategy to foraminiferal data from the middle Eocene Yegua Formation of southeast Texas. Seven biofacies are recognized along a short, three-well, dip transect, representing paleoenvironments ranging from marginal marine delta plain to outer neritic muddy shelf.« less

Evaluating order in vertical successions of deltaic Holocene sediments on the Ganges-Brahmaputra-Meghna delta

NASA Astrophysics Data System (ADS)

Sincavage, R.; Goodbred, S. L., Jr.

2017-12-01

Most stratigraphic models are predicated on the presence of cyclicity or some form of order in vertical successions of strata. In spite of this a priori assumption of ordered stratigraphy, rarely are statistical metrics employed to quantify cyclicity in sedimentary packages. The presence or absence of preserved order in vertical sedimentary successions has important implications for the nature of environmental signals that are transmitted into the rock record. We interrogate the Holocene sedimentary archive of the Ganges-Brahmaputra-Meghna delta (GBMD) in an effort to explore to what extent fluvio-deltaic deposits exhibit recognizable order. Specifically, we focus on grain size data to evaluate 1.) if stratigraphic order in vertical sedimentary successions can be identified and quantified, and 2.) if there are spatial patterns of stratigraphic order across the GBMD. A runs order metric r is used to identify sequences of coarsening and fining within an extensive borehole network. Observed grain size data are shuffled enough times to generate synthetic "random" stratigraphy, and a Monte Carlo simulation generates 5000 realizations. The distribution of r values from the Monte Carlo are compared to the r metric calculated from observed data to determine how likely the observed metric could be generated by chance. The spatial distribution of order metrics indicates a relationship between areas of enhanced mass extraction and preservation of fluvial successions that scale with modern bar deposits on the Jamuna River. Similarly, probability metrics indicate that vertical successions of grain size data unlikely to have been generated by chance are more likely to be found on distal areas of the delta where 60% of the input mass has been extracted. Combining a mass balance framework with simple statistical metrics has the potential of improving predictions of the stratigraphic architecture and the preservation of ordered vs. disordered signals in the sedimentary record.

Petroleum geology and resources of the Dnieper-Donets Basin, Ukraine and Russia

USGS Publications Warehouse

Ulmishek, Gregory F.

2001-01-01

The Dnieper-Donets basin is almost entirely in Ukraine, and it is the principal producer of hydrocarbons in that country. A small southeastern part of the basin is in Russia. The basin is bounded by the Voronezh high of the Russian craton to the northeast and by the Ukrainian shield to the southwest. The basin is principally a Late Devonian rift that is overlain by a Carboniferous to Early Permian postrift sag. The Devonian rift structure extends northwestward into the Pripyat basin of Belarus; the two basins are separated by the Bragin-Loev uplift, which is a Devonian volcanic center. Southeastward, the Dnieper-Donets basin has a gradational boundary with the Donbas foldbelt, which is a structurally inverted and deformed part of the basin. The sedimentary succession of the basin consists of four tectono-stratigraphic sequences. The prerift platform sequence includes Middle Devonian to lower Frasnian, mainly clastic, rocks that were deposited in an extensive intracratonic basin. 1 The Upper Devonian synrift sequence probably is as thick as 4?5 kilometers. It is composed of marine carbonate, clastic, and volcanic rocks and two salt formations, of Frasnian and Famennian age, that are deformed into salt domes and plugs. The postrift sag sequence consists of Carboniferous and Lower Permian clastic marine and alluvial deltaic rocks that are as thick as 11 kilometers in the southeastern part of the basin. The Lower Permian interval includes a salt formation that is an important regional seal for oil and gas fields. The basin was affected by strong compression in Artinskian (Early Permian) time, when southeastern basin areas were uplifted and deeply eroded and the Donbas foldbelt was formed. The postrift platform sequence includes Triassic through Tertiary rocks that were deposited in a shallow platform depression that extended far beyond the Dnieper-Donets basin boundaries. A single total petroleum system encompassing the entire sedimentary succession is identified in the Dnieper-Donets basin. Discovered reserves of the system are 1.6 billion barrels of oil and 59 trillion cubic feet of gas. More than one-half of the reserves are in Lower Permian rocks below the salt seal. Most of remaining reserves are in upper Visean-Serpukhovian (Lower Carboniferous) strata. The majority of discovered fields are in salt-cored anticlines or in drapes over Devonian horst blocks; little exploration has been conducted for stratigraphic traps. Synrift Upper Devonian carbonate reservoirs are almost unexplored. Two identified source-rock intervals are the black anoxic shales and carbonates in the lower Visean and Devonian sections. However, additional source rocks possibly are present in the deep central area of the basin. The role of Carboniferous coals as a source rock for gas is uncertain; no coal-related gas has been identified by the limited geochemical studies. The source rocks are in the gas-generation window over most of the basin area; consequently gas dominates over oil in the reserves. Three assessment units were identified in the Dnieper-Donets Paleozoic total petroleum system. The assessment unit that contains all discovered reserves embraces postrift Carboniferous and younger rocks. This unit also contains the largest portion of undiscovered resources, especially gas. Stratigraphic and combination structural and stratigraphic traps probably will be the prime targets for future exploration. The second assessment unit includes poorly known synrift Devonian rocks. Carbonate reef reservoirs along the basin margins probably will contain most of the undiscovered resources. The third assessment unit is an unconventional, continuous, basin-centered gas accumulation in Carboniferous low-permeability clastic rocks. The entire extent of this accumulation is unknown, but it occupies much of the basin area. Resources of this assessment unit were not estimated quantitatively.

Depositional History and Sequence Stratigraphy of the Middle Ordovician Yeongheung Formation (Yeongweol Group), Taebaeksan Basin, mid-east Korea

NASA Astrophysics Data System (ADS)

Kwon, Yoo Jin; Kwon, Yi Kyun

2017-04-01

The Middle Ordovician Yeongheung Formation consists of numerous meter-scale, shallowing-upward cycles which were deposited on a shallow-marine carbonate platform. Many diagnostic sedimentary textures and structures such as supratidal laminite, tepee structure, and solution-collapsed breccia are observed, which enable to infer the dry climate and high salinity conditions during deposition of the formation. In order to understand its depositional history, this study focuses on vertical and spatial stacking patterns of the second- to third-order sequences through the detailed outcrop description and geologic mapping. A total 19 lithofacies have been recognized, which can be grouped into 5 facies associations (FAs): FA1 (Supratidal flat), FA2 (Supratidal or dolomitization of peritidal facies), FA3 (Intertidal flat), FA4 (Shallow subtidal to peritidal platform), FA5 (Shallow subtidal shoal). Global mega-sequence boundary (Sauk-Tippecanoe) occurs in solution-collapsed breccia zone in the lower part of the formation. Correlation of the shallowing-upward cycle stacking pattern across the study area defines 6 transgressive-regressive depositional sequences. Each depositional sequences comprises a package of vertical and spatial staking of shallow subtidal cycles in the lower part and peritidal cycles in the upper part of the formation. According to sequence stratigraphic interpretation, the reconstructed relative sea-level curve of the Yeongweol platform is very similar to that of the Taebaek platform. Based on the absence of siliciclastic sequence such as the Jigunsan Formation and the lithologic & stratigraphic differences, however, the Yeongweol and Taebaek groups might not belong to a single depositional system within the North China platform. The Yeongweol Group can be divided by the four subunits into their unique lithologic successions and geographic distributions. The Eastern subunit of the Yeongweol Group is composed dominantly of carbonate rocks with a high composition ratio of siliciclastic materials dominated facies in the upper part of the Yeongheung Formation. The Middle1 subunit is pervasively recognized by subaerial exposures facies (carbonate breccia, paleosol), whereas the Middle2 subunit is similar to the Middle1 subunit except for the absence of subaerial exposure features. The Western subunit lost some of its primary sedimentary structure and texture in comparison to other subunits, because of the active recrystallization, metamorphism, structural deformation and carbonate diagenesis. This study reveals depositional history and refines sequence stratigraphy of the Yeongheung Formation, promoting understanding of the basin evolution of the Yeongweol Group.

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

NASA Astrophysics Data System (ADS)

Tanner, Lawrence H.; Lucas, Spencer G.

2010-01-01

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

The Statistical Signal of Morphological Process in Stratigraphy

NASA Astrophysics Data System (ADS)

Esposito, C. R.; Straub, K. M.

2013-12-01

The most widely used classification of river delta morphologies, Galloway's ternary diagram, holds that the surface characteristics of a delta, including the distribution of depositional environments, and shoreline shape, can be predicted by the relative strengths of the fluvial and marine processes that influence the delta. Though almost 40 years old, Galloway's diagram of wave, river, and tide dominated deltas is still widely referred to in textbooks and in literature as a way of describing the relationship between morphological processes and the distribution of depositional environments over a single delta 'event' such as the progradation of one delta lobe. However, there is no complimentary classification scheme that addresses the ways in which deltaic stratigraphy under varying forcing conditions is preserved over sequences of many such events. Such sequences operating over a range of time scales set the architecture of sedimentary basins, so a method of classifying the stratigraphic result is an important goal. In this study, we use Delft3D to examine the autogenic behavior of thick packages of simulated deltaic stratigraphy (>10 channel depths) under the influence of a range of wave, tide, and flood-dominated conditions, as well as a variety of sedimentary inputs. We quantify the strength and type of autogenic behavior by measuring stratigraphic completeness and compensation index. Both metrics have been observed to vary systematically in field scale systems, and in experimental deltas deposited under a range of river dominated conditions. This work will extend that range into deltas with significant wave, tide, and flood influence.

Hydrocarbon traps within a seismic sequence framework, Stevens turbidites, southern San Joaquin Valley, CA

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

Hewlett, J.S.; Jordan, D.W.; Crebs, T.J.

1991-02-01

Interpretation of the seismic sequence framework and log and lithologic character of upper Miocene Stevens turbidites on the Bakersfield arch has led to an improved understanding of the expression of stratigraphic trapping that should reduce exploration risk in the basin, and may aid exploration efforts in similar sand-rich systems globally. These deepwater sandstones are contained within three lowstand turbidite systems (LTS) that were deposited in a narrow deepwater basin adjacent to the ancestral Sierra Nevada. the oldest LTS, the Coulter, was transported through several submarine canyons incised into the Fruitvale Shale. In contrast, numerous smaller scale erosional features located onmore » the high-relief slopes of the highstand Santa Margarita deltas, fed the overlying Gosford and Bellevue LTS. The systems consist of sandy, high-density (primarily) and low-density turbidites that were deposited within channel-lobe complexes. On the arch, 472 MMBO and 1.3 tcf have been produced from four seismically detectable traps with strong stratigraphic components: (1) sandstone permeability changes within turbidite wedges that thin rapidly onto structure (2) confined (channelized) turbidites that lap out on a structure (e.g., F-1 sand, South Coles levee), (3) channelized turbidites that pinch out within slope gullies, and (4) depositional compaction anticlines occurring in conjunction with low-gradient regional structure. Condensed section sediments form regional and reservoir-scale seals. Rapid lateral facies changes and grain size variations provide additional seal facies.« less

Geology and hydrocarbon potential in the state of Qatar, Arabian Gulf

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

Alsharhan, A.S.; Nairn, A.E.M.

The state of Qatar is situated in the southern Arabian Gulf and covers an area of 12,000 km{sup 2}. It is formed by a large, broad anticline, which is part of the regional south-southwest-north-northeast-trending Qatar-South Fars arch. The arch separates the two Infracambrian salt basins. The Dukhan field was the first discovery, made in 1939, in the Upper Jurassic limestones. Since then, a series of discoveries have been made so that Qatar has become one of the leading OPEC oil states. Hydrocarbon accumulations are widely dispersed throughout the stratigraphic column from upper Paleozoic to Cretaceous producing strata. The most prolificmore » reservoirs are the Permian and Mesozoic shelf carbonate sequences. Minor clastic reservoirs occur in the Albian and Paleozoic sequences. Seals, mainly anhydrite and shale. occur both intraformationally and regionally. Several stratigraphic intervals contain source rocks or potential source rocks. The Silurian shales arc the most likely source of the hydrocarbon stored in the upper Paleozoic clastics and carbonates. The upper Oxfordian-middle Kimmeridgian rocks formed in the extensive starved basin during the Mesozoic period of sea level rise. Total organic carbon ranges between 1 and 6%, with the sulfur content approximately 9%. The source material consists of sapropelic liptodetrinite and algae. The geological background of the sedimentary facies through geologic time, stratigraphy, and structural evolution which control source, and the subsequent timing and migration of large-scale hydrocarbon generation are presented in detail.« less

A >400 kyrs archive of sedimentation in Scladina cave (Belgium)

NASA Astrophysics Data System (ADS)

Vonhof, Hubert; Bonjean, Dominique; Pirson, Stéphane; van der Lubbe, Jeroen; Hellstrom, John; Scholz, Denis; Verheyden, Sophie

2017-04-01

Scladina Cave, near the Meuse River in Belgium, is well-known for its well preserved Neanderthal fossils and stone tools. Cave research started in the 1970's, when archeological findings near the entrance of the cave initiated a long-running excavation programme in the -at that time- almost completely sediment-infilled cave. Over the past decades, a wealth of mammal fossils, stone tools, and a mandible of a Neanderthal child were found, and the complex sedimentary context of the cave strata was reconstructed in high detail. Crucial to understanding the cave stratigraphy is the construction of an absolutely dated age model. Until recently, this age model was based on a number of OSL ages, pollen stratigraphy and a few U-series ages on flowstone and stalagmite calcite. These U-series ages, however, had much lower precision than can be obtained by modern MC-ICP-MS techniques. In this study, we present new and more precise U-series ages for the major flow stone levels in Scladina Cave (upper stratigraphical sequence), and two flowstone levels from Sous-Saint-Paul Cave (lower stratigraphical sequence). The oldest flow stone layer dates back to > 400 ka, and the youngest represents the Holocene. The age model shows that flow stone formation typically occurred during warm climate conditions. These findings help to improve the existing age model for Scladina Cave significantly, and place better constraints on the age of individual fossils, and fossil assemblages in the cave.

Evolving Concepts and Teaching Approaches In Tectonics and Sedimentation.

ERIC Educational Resources Information Center

Graham, Stephan Alan

1983-01-01

Discusses five recent advances in sedimentary tectonics, noting how they are incorporated into college curricula. Advances discussed include basin type, tectonic setting, facies analysis (in conjunction with basin type/setting), stratigraphic analysis of reflection seismic data, and quantitative analysis of subsidence histories of sedimentary…

Petroleum prospects for offshore sedimentary basins in the eastern Papua New Guinea and Solomon Islands regions

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

Bruns, T.R.; Vedder, J.G.

Intra-arc basins in the Buka-Bougainville region of Papua New Guinea and in the Solomon Islands contain thick sedimentary sequences that may be prospective for petroleum. The Queen Emma basin, between Bougainville and New Ireland, contains as much as 8 km of deformed Oligocene and younger strata. The Central Solomons Trough, which underlies New Georgia Sound, is a composite intra-arc basin that contains late Oligocene and younger strata as much as 7 km thick. Farther east, beneath Indispensable Strait, the down-faulted Indispensable basin locally contains as much as 5.4 km of Miocene( ) and younger strata, and the offshore part ofmore » Mbokokimbo basin off eastern Guadalcanal includes 6 km or more of late Miocene and younger strata. All of these basins have some of the attributes necessary to generate and trap petroleum. Structural and stratigraphic traps are common, including faulted anticlines, sedimentary wedges, and carbonate reefs and reef-derived deposits on submarine ridges and along the basin margins. The thickness of the basin deposits ensures that some strata are buried deeply enough to be within the thermal regime required for hydrocarbon generation. However, little source or reservoir rock information is available because of the lack of detailed surface and subsurface stratigraphy. Moreover, much of the basin sediment is likely to consist of volcaniclastic material, derived from uplifted volcanogenic rocks surrounding the basins, and may be poor in source and reservoir rocks. Until additional stratigraphic information is available, analysis of the petroleum potential of these basins is a matter of conjecture.« less

Eolian paleotopographic highs as stratigraphic traps: origin and distinction

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

Eschner, T.B.; Kocurek, G.A.

1985-02-01

Significant hydrocarbon accumulations occur where eolian paleotopographic highs are preserved beneath transgressive marine deposits. Paleotopographic highs can represent erosional remnants of an unconformity, or partly preserved eolian dunes, or combinations of both. Paleotopography reflects the extent of modification undergone by eolian units prior to or during transgression. Modification varies between extremes of (1) destruction - where eolian deposits are deeply eroded and the former dunal profile is lost, and (2) preservation - where dunes and interdune areas are preserved nearly intact. The extent of modification that occurs during transgression is controlled primarily by (1) the energy of the transgressing sea,more » (2) the speed of transgression, and (3) the abundance of sand-stabilizing early cements or plants. High-energy seas destroy dunes through persistent erosion by tides and waves and by initiating dune collapse and mass flowage of dune sands. Preservation occurs where quiescent seas flood interdune areas and create shallow to periodically emergent marine environments, such as interdune sabkhas or tidal flats. Gradual filling of interdune areas with shallow marine sediments can fortify and preserve adjacent dunes. These varied processes that interact between marine and eolian environments to create different types of topography are exemplified in ancient eolian-marine sequences of the Western Interior of North America, and preserved Holocene dunes of coastal Australia. Different types of eolian highs can be recognized by analysis of bounding surfaces in outcrop or core. An understanding of eolian-marine processes and environments that create topography allows for prediction of areas of potential stratigraphic traps.« less

Salinity stratification of the Mediterranean Sea during the Messinian crisis: A first model analysis

NASA Astrophysics Data System (ADS)

Simon, Dirk; Meijer, Paul Th.

2017-12-01

In the late Miocene, a thick and complex sequence of evaporites was deposited in the Mediterranean Sea during an interruption of normal marine sedimentation known as the Messinian Salinity Crisis. Because the related deposits are mostly hidden from scrutiny in the deep basin, correlation between onshore and offshore sediments is difficult, hampering the development of a comprehensive stratigraphic model. Since the various facies correspond to different salinities of the basin waters, it would help to have physics-based understanding of the spatial distribution of salt concentration. Here, we focus on modelling salinity as a function of depth, i.e., on the stratification of the water column. A box model is set up that includes a simple representation of a haline overturning circulation and of mixing. It is forced by Atlantic exchange and evaporative loss and is used to systematically explore the degree of stratification that results under a wide range of combinations of parameter values. The model demonstrates counterintuitive behaviour close to the saturation of halite. For parameter values that may well be realistic for the Messinian, we show that a significantly stratified Mediterranean water column can be established. In this case, Atlantic connectivity is limited but may be closer to modern magnitudes than previously thought. In addition, a slowing of Mediterranean overturning and a larger deep-water formation region (both in comparison to the present day) are required. Under these conditions, we would expect a longer duration of halite deposition than currently considered in the MSC stratigraphic consensus model.

Late Holocene paleoseismicity, tsunamis and relative sea- level changes along the south-central Cascadia subduction zone, southern Oregon, United States of America

NASA Astrophysics Data System (ADS)

Witter, Robert Carleton

1999-10-01

This dissertation investigates stratigraphic evidence for great (M w >= 8) earthquakes, tsunamis and relative sea-level change at three coastal sites above the Cascadia subduction zone (CSZ). Accelerator mass spectrometry radiocarbon analyses, diatom analyses and vibracoring techniques were employed. Euchre Creek marsh stratigraphic sequences contain four sand beds deposited by extreme storm waves within the last 600 years and a tsunami ~300 years ago. A 150- year recurrence interval for sand deposition compared to an average recurrence interval of 500-540 years for great Cascadia, earthquakes precludes local tsunamis that accompany Cascadia earthquakes as the only candidate depositional mechanism for the sand beds. Alternatively, magnitude-frequency analyses of extreme ocean levels generated during El Niño years suggest that storm- wave runup is a more likely mechanism for sand deposition in washover settings than either locally or remotely generated tsunamis. Late Holocene stratigraphic sequences at the Coquille River estuary provide a ~6600-year record of twelve great Cascadia earthquakes and attendant tsunamis in southern Oregon. A relative sea-level history chronicles repeated sudden expansion followed by gradual emergence of the Coquille estuary in response to the earthquake cycle. The average earthquake-recurrence interval for the central CSZ (~570-590 yrs) overlaps similar estimates for northern Oregon estuaries. In contrast, more inferred earthquakes recorded at Willapa and Humboldt Bays in the last ~2000 years compared to the earthquake record at Coquille suggest that segmented rupture of the CSZ occurs. Late Holocene (since 6.3 ka) relative sea-level data generated within the Coquille estuary allow 20 m of vertical deformation across the Coquille anticline in the last 80 ky. Contrasting relative sea-level histories in southern Oregon provide evidence for late Holocene contraction on upper-plate anticlines. Two relative sea-level curves, 35 km apart, show 0.5-0.6 m/ka difference in uplift rate, although both sites demonstrate long-term tectonic uplift. Upper-plate structures above the central CSZ probably deform during megathrust events. The Cape Blanco and Coquille anticlines overlie a candidate segment boundary because they separate subduction zone segments with different earthquake histories. This dissertation includes co-authored material.

Geochemistry of glacial sediments in the area of the Bend massive sulfide deposit, north-central Wisconsin

USGS Publications Warehouse

Woodruff, L.G.; Attig, J.W.; Cannon, W.F.

2004-01-01

Geochemical exploration in northern Wisconsin has been problematic because of thick glacial overburden and complex stratigraphic record of glacial history. To assess till geochemical exploration in an area of thick glacial cover and complex stratigraphy samples of glacial materials were collected from cores from five rotasonic boreholes near a known massive sulfide deposit, the Bend deposit in north-central Wisconsin. Diamond drilling in the Bend area has defined a long, thin zone of mineralization at least partly intersected at the bedrock surface beneath 30-40 m of unconsolidated glacial sediments. The bedrock surface has remnant regolith and saprolite resulting from pre-Pleistocene weathering. Massive sulfide and mineralized rock collected from diamond drill core from the deposit contain high (10s to 10,000s ppm) concentrations of Ag, As, Au, Bi, Cu, Hg, Se, Te, and Tl. Geochemical properties of the glacial stratigraphic units helped clarify the sequence and source areas of several glacial ice advances preserved in the section. At least two till sheets are recognized. Over the zone of mineralization, saprolite and preglacial alluvial and lacustrine samples are preserved on the bedrock surface in a paleoriver valley. The overlying till sheet is a gray, silty carbonate till with a source hundreds of kilometers to the northwest of the study area. This gray till is overlain by red, sandy till with a source to the north in Proterozoic rocks of the Lake Superior area. The complex glacial stratigraphy confounds down-ice geochemical till exploration. The presence of remnant saprolite, preglacial sediment, and far-traveled carbonate till minimized glacial erosion of mineralized material. As a result, little evidence of down-ice glacial dispersion of lithologic or mineralogic indicators of Bend massive sulfide mineralization was found in the samples from the rotasonic cores. This study points out the importance of determining glacial stratigraphy and history, and identifying favorable lithologies required for geochemical exploration. Drift prospecting in Wisconsin and other areas near the outer limits of the Pleistocene ice sheets may not be unsuccessful, in part, because of complex stratigraphic sequences of multiple glaciations where deposition dominates over erosion. ?? 2004 Elsevier B.V. All rights reserved.

Structural and stratigraphic constraints on tsunamigenic rupture along the frontal Sunda megathrust from MegaTera bathymetric and seismic reflection data

NASA Astrophysics Data System (ADS)

Bradley, K. E.; Qin, Y.; Villanueva-Robles, F.; Hananto, N.; Leclerc, F.; Singh, S. C.; Tapponnier, P.; Sieh, K.; Wei, S.; Carton, H. D.; Permana, H.; Avianto, P.; Nugroho, A. B.

2017-12-01

The joint EOS/IPG/LIPI 2015 MegaTera expedition collected high-resolution seismic reflection profiles and bathymetric data across the Sunda trench, updip of the Mw7.7, 2010 Mentawai tsunami-earthquake rupture patch. These data reveal rapid lateral variations in both the stratigraphic level of the frontal Sunda megathrust and the vergence of frontal ramp faults. The stratigraphic depth of the megathrust at the deformation front correlates with ramp-thrust vergence and with changes in the basal friction angle inferred by critical-taper wedge theory. Where ramp thrusts verge uniformly seaward and have an average dip of 30°, the megathrust decollement resides atop a high-amplitude reflector that marks the inferred top of pelagic sediments. Where ramp thrusts are bi-vergent (similar throw on both landward- and seaward-vergent faults) and have an average dip of 42°, the decollement is higher, within the incoming clastic sequence, above a seismically transparent unit inferred to represent distal fan muds. Where ramp thrusts are uniformly landward vergent, the decollement sits directly on top of the oceanic crust that forms the bathymetrically prominent, subducting Investigator Ridge. The two, separate regions of large tsunamigenic ground-surface uplift during the 2010 tsunami earthquake that have been inferred from joint inversions of seismic, GPS, and tsunami data (e.g. Yue et al., 2014; Satake et al., 2013) correspond to the areas of frontal bi-vergence in the MegaTera data. We propose that enhanced surface uplift and tsunamigenesis during this event occurred when rupture propagated onto areas where the decollement sits directly above the basal muds of the incoming clastic sequence. Thus we hypothesize that frontal bi-vergence may mark areas of enhanced tsunami hazard posed by small magnitude, shallow megathrust ruptures that propagate to the trench. [Yue, H. et al., 2014, Rupture process of the…, JGR 119 doi:10.1002/2014JB011082; Satake, K. et al., 2013, Tsunami Source of the…, P&AG 170, 9-10

Tsunami Stratigraphy in a Coastal Salt Pond, St. Croix, US Virgin Islands

NASA Astrophysics Data System (ADS)

Russell, P.; Browning, T. N.; Brooks, G.; Larson, R. A.; Cook, A.; Sawyer, D. E.

2017-12-01

The Caribbean has significant exposure to tsunamis from multiple sources, such as earthquakes, volcanoes, and landslides. Due to the limited historical record in the region, paleotsunami deposits provide important information about the size, location, and sources of these events. In turn, these data inform the public and policymakers about the tsunamigenic threat to their communities. A key challenge is that tsunami deposits are often poorly preserved. However, a good candidate for high preservation potential are coastal salt ponds commonly found on the perimeter of tropical islands. The US Virgin Islands has both high susceptibility to tsunamis and large, low lying salt ponds. The most prominent historical example of a tsunami in the US Virgin Islands is the 1867 event which caused widespread devastation throughout the region, including Puerto Rico. One of the hardest hit locations was Frederiksted, on the western end of St. Croix, US Virgin Islands with 7m runups that beached the USS Monongahela. Frederiksted is also in close proximity to a large coastal salt pond. We targeted this, and older, events by collecting a series of sediment cores at four sites in the salt pond during a summer 2017 field campaign. At each location we acquired a 3" aluminum core and a 4" acrylic companion core to core refusal, which most often occurred at a impenetrable horizon. Maximum core recovery was .79m and the average was .54m. Each 4" core was extruded in 1cm intervals and used to determine grain size, total carbon content, and age dating via radioisotope dating. The 3" core was scanned in a X-Ray CT Lab, split, described, and samples from key layers were targeted for detailed sedimentological analyses. The defining stratigraphic sequence is fine-grained muds interspersed with coarse-grained units that exhibit a fining-upwards trend and contained a variety of marine debris, which we infer to represent tsunami or tropical storm event deposits. However, each core did not exhibit the same stratigraphic sequence, suggesting that core location is highly important to accurately establishing the tsunami record. Further analyses will constrain age and stratigraphic control.

Structural plays in Ellesmerian sequence and correlative strata of the National Petroleum Reserve, Alaska

USGS Publications Warehouse

Moore, Thomas E.; Potter, Christopher J.

2003-01-01

Reservoirs in deformed rocks of the Ellesmerian sequence in southern NPRA are assigned to two hydrocarbon plays, the Thrust-Belt play and the Ellesmerian Structural play. The two plays differ in that the Thrust-Belt play consists of reservoirs located in allochthonous strata in the frontal part of the Brooks Range fold-and-thrust belt, whereas those of the Ellesmerian Structural play are located in autochthonous or parautochthonous strata at deeper structural levels north of the Thrust-Belt play. Together, these structural plays are expected to contain about 3.5 TCF of gas but less than 6 million barrels of oil. These two plays are analyzed using a two-stage deformational model. The first stage of deformation occurred during the Neocomian, when distal strata of the Ellesmerian sequence were imbricated and assembled into deformational wedges emplaced northward onto regionally south-dipping authochon at 140-120 Ma. In the mid-Cretaceous following cessation of the deformation, the Colville basin, the foreland basin to the orogen, was filled with a thick clastic succession. During the second stage of deformation at about 60 Ma (early Tertiary), the combined older orogenic belt-foreland basin system was involved in another episode of north-vergent contractional deformation that deformed pre-existing stratigraphic and structurally trapped reservoir units, formed new structural traps, and caused significant amounts of uplift, although the amount of shortening was relatively small in comparison to the first episode of deformation. Hydrocarbon generation from source strata (Shublik Formation, Kingak Shale, and Otuk Formation) and migration into stratigraphic traps occurred primarily by sedimentary burial principally between 100-90 Ma, between the times of the two episodes of deformation. Subsequent burial caused deep stratigraphic traps to become overmature, cracking oil to gas, and some new generation to begin progressively higher in the section. Structural disruption of the traps in the Early Tertiary is hypothesized to have released sequestered hydrocarbons and caused remigration into newly formed structural traps formed at higher structural levels. Because of the generally high maturation of the Colville basin at the time of the deformation and remigration, most of the hydrocarbons available to fill traps were gas. In the the Thrust-Belt play, the primary reservoir lithology is expected to be dolomitic carbonate rocks of the Lisburne Group, which contain up to 15% porosity. Antiformal stacks of imbricated Lisburne Group strata form the primary trapping configuration, with chert and shale of the overlying Etivluk Group forming seals on closures. Traps are expected to have been charged primarily with remigrated gas, but oil generated from local sources in the Otuk Formation may have filled some traps at high structural levels. The timing for migration of gas into traps is excellent, but only moderate for oil because peak oil generation for the play as a whole occurred 30 to 40 m.y. before trap formation. Reservoir and seal quality in the play are questionable, reducing the likelyhood of hydrocarbon accumulations being present in the play. Our analysis suggests that the play will hold 5.7 million barrels of technically recoverable oil and 1.5 TCF gas (mean values). In the Ellesmerian Stuctural play, the primary reservoir lithologies will be dolomitic carbonate rocks of the Lisburne Group and, less likely, clastic units in the Ellesmerian sequence. Traps in the play are anticlinal closures caused by small amounts of strain in the footwall below the basal detachment for most early Tertiary thrusting. Because these traps lie beneath the main source rock units (Shublik, Kingak, lower Brookian sequence), reservoirs that are juxtaposed by faulting against source-rock units are expected to have the most favorable migration pathways. The charge will be primarily remigrated gas; no oil is expected because of the great depths (15,000 to 26,000 ft) and consequent high thermal maturity of this play. Although the the probability of charge and timeliness of trap formation and gas remigration are excellent, seal and reservoir qualities are anticipated to be poor. Our analysis suggests that about 2.0 TCF of techncially recoverable gas can be expected in the play.

Analysis of some seismic expressions of Big Injun sandstone and its adjacent interval

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

Xiangdong, Zou; Wilson, T.A.; Donaldson, A.C.

1991-08-01

The Big Injun sandstone is an important oil and gas reservoir in western West Virginia. The pre-Greenbrier unconformity has complicated correlations, and hydrocarbon explorationists commonly have misidentified the Big Injun in the absence of a regional stratigraphic study. Paleogeologic maps on this unconformity show the West Virginia dome, with the Price/Pocono units truncated resulting in pinch-outs of different sandstones against the overlying Big Lime (Greenbrier Limestone). Drillers have named the first sandstone below the Big Lime as Big Injun, and miscorrelated the real Big Injun with Squaw, upper Weir, and even the Berea sandstone. In this report, an 8-mi (13-km)more » seismic section extending from Kanawha to Clay counties was interpreted. The study area is near the pinch-out of the Big Injun sandstone. A stratigraphic cross section was constructed from gamma-ray logs for comparison with the seismic interpretation. The modeling and interpretation of the seismic section recognized the relief on the unconformity and the ability to determine facies changes, too. Both geophysical wireline and seismic data can be used for detailed stratigraphic analysis within the Granny Creek oil field of Clay and Roane countries.« less

Geologic map and database of the Roseburg 30' x 60' quadrangle, Douglas and Coos counties, Oregon

USGS Publications Warehouse

Wells, Ray E.; Jayko, A.S.; Niem, A.R.; Black, G.; Wiley, T.; Baldwin, E.; Molenaar, K.M.; Wheeler, K.L.; DuRoss, C.B.; Givler, R.W.

2001-01-01

The Roseburg 30' x 60' Quadrangle covers the southeastern margin of the Oregon Coast Range and its tectonic boundary with Mesozoic terranes of the Klamath Mountains (see figures 1 and 2 in pamphlet, also shown on map sheet). The geologic framework of the Roseburg area was established by the pioneering work of Diller (1898), Wells and Peck, (1961) and Ewart Baldwin (1974) and his students (see figure 3 in pamphlet, also shown on map sheet). Baldwin and his students focussed on the history of the Eocene Tyee basin, where the sediments lap across the tectonic boundary with the Mesozoic terranes and record the accretion of the Coast Range basement to the continent. Others have examined the sedimentary fill of the Tyee basin in detail, recognizing the deep marine turbidite facies of the Tyee Formation (Snavely and others, 1964) and proposing several models for the Eocene evolution of the forearc basin (Heller and Ryberg, 1983; Chan and Dott, 1983; Heller and Dickinson, 1985; Molenaar, 1985; see Ryu and others, 1992 for a comprehensive summary). Along the eastern margin of the quadrangle, both the Tyee basin and the Klamath terranes are overlain by Eocene volcanic rocks of the Western Cascade arc (Walker and MacLeod, 1991). The thick Eocene sedimentary sequence of the Tyee basin has significant oil and gas potential (Armentrout and Suek, 1985; Gautier and others, 1993; Ryu and others, 1996). Although 13 deep test wells have been drilled in the Roseburg quadrangle (see figure 2 and table 1 in pamphlet, also shown on map sheet), exploration to date has been hampered by an incomplete understanding of the basin�s tectonic setting and evolution. In response, the Oregon Department of Geology and Mineral Industries (DOGAMI) initiated a five year assessment of the oil and gas potential of the Tyee basin. This map is a product of a cooperative effort by the U. S. Geological Survey, Oregon State University, and DOGAMI to systematically map the sedimentary facies and structure of the Tyee basin. New geologic mapping of twenty-eight 7.5' quadrangles is summarized on the map (see figure 3, also shown on map sheet), and the digital database contains geologic information suitable for both 1:100K and 1:24K scale analysis. DOGAMI has published a compilation and synthesis of previous mapping (Niem and Niem, 1990), a basin-wide sequence stratigraphic model and correlations (Ryu and others, 1992), and a report on the oil and gas potential (Ryu and others, 1996). Readers interested in the oil and gas potential of the Roseburg quadrangle should use the map in combination with Ryu and others (1996) to address specific stratigraphic units and structural plays. Stratigraphic terminology for the Tyee basin adopts the type sections, formation names, and framework of Ryu and others (1992, 1996), which were developed concurrently with the mapping and are recognized throughout the basin. For detailed discussion of nomenclature, type sections, lithology, thickness and distribution, age, contact relationships, and depositional environment of stratigraphic units, the reader is referred to Ryu and others (1992). In this report we focus on the spatial, temporal, and structural relationships between units revealed by geologic mapping. Map unit ages (see figure 4 in pamphlet, also shown on map sheeet) are adjusted slightly from Ryu and others (1992, 1996) to fit new coccolith age determinations (D. Bukry, cited in pamphlet), paleomagnetic polarity data (Simpson, 1977 and new data cited in pamphlet), and the time scale of Berggren and others (1995).

Ages of subsurface stratigraphic intervals in the Quaternary of Enewetak Atoll, Marshall Islands

USGS Publications Warehouse

Szabo, B. J.; Tracey, J.I.; Goter, E.R.

1985-01-01

Drill cores of Enewetak Atoll, Marshall Islands, reveal six stratigraphic intervals, numbered in downward sequence, which represent vertical coral growth during Quaternary interglaciations. Radiocarbon dates indicate that the Holocene sea transgressed the emergent reef platform by about 8000 yr B.P. The reef grew rapidly upward (about 5 to 10 mm/yr) until about 6500 yr B.P. Afterward vertical growth slowed to about 0.5 mm/yr, then lateral development became dominant during the last several thousand years. The second interval is dated at 131,000 ?? 3000 yr B.P. by uranium series. This unit correlates with oxygen-isotope substage 5e and with terrace VIIa of Huon Peninsula, New Guinea, and of Main Reef-2 terrace at Atauro Island. The third interval is not dated because corals were recrystallized and it is tentatively correlated with either oxygen-isotope stages 7 or 9. The age of the fourth interval is estimated at 454,000 ?? 100,000 yr B.P. from measured 234U 238U activity ratios. This unit is correlated with either oxygen-isotope stage 9, 11, or 13. ?? 1985.

Stratigraphic and Paleomagnetic Comparisons of Mesoproterozoic Strata and Sills from the Belt Basin, NW Montana, USA, and NW Anabar Shield, Russia: Testing a Precambrian Plate Reconstruction

NASA Astrophysics Data System (ADS)

Sears, J. W.; Pavlov, V.; Veselovskiy, R.; Khudoley, A.

2008-12-01

Mesoproterozoic sedimentary strata and mafic sills overlie Archean and Paleoproterozoic basement rocks with profound unconformity in NW Montana and along the NW margin of the Anabar Shield in northern Siberia. The two localities plot adjacent to one another on a Precambrian plate reconstruction proposed by Sears and Price (2003) that places the NE margin of the Siberian craton against the SW margin of the North American craton. The plate reconstruction predicts that these strata occupied contiguous parts of an intracratonic basin prior to late Neoproterozoic breakup of Rodinia. Here we show that the Mesoproterozoic stratigraphic sequences, sedimentary structures, and lithologies of the NW Anabar margin closely match the Neihart, Chamberlain, and Newland formations of the Little Belt Mountains of Montana. They may predate opening of the Belt Supergroup rift basin at ca. 1500 Ma, when a major mafic magmatic episode occurred in both regions. Preliminary paleomagnetic data from the Siberian section will be compared with the Laurentian APWP to evaluate the reconstruction.

Tephra layers of blind Spring Valley and related upper pliocene and pleistocene tephra layers, California, Nevada, and Utah: isotopic ages, correlation, and magnetostratigraphy

USGS Publications Warehouse

Sarna-Wojcicki, Andrei M.; Reheis, Marith C.; Pringle, Malcolm S.; Fleck, Robert J.; Burbank, Doug; Meyer, Charles E.; Slate, Janet L.; Wan, Elmira; Budahn, James R.; Troxel, Bennie; Walker, James P.

2005-01-01

Numerical ages have been determined for a stratigraphic sequence of silicic tephra layers exposed at the Cowan Pumice Mine in Blind Spring Valley, near Benton Hot Springs, east-central California, as well as at Chalk Cliffs, north of Bishop, Calif. The tephra layers at these sites were deposited after eruptions from nearby sources, most of them from near Glass Mountain, and some from unknown sources. The ages were determined primarily by the laser-fusion 40Ar/39Ar method, mostly on sanidine feldspar; two were determined by conventional K-Ar analysis on obsidian clasts. These tephra layers, all underlying the Bishop ash bed and listed in order of concordant age and stratigraphic position, are: Tephra Unit Method Material Age Bishop Tuff (air-fall pumice) Ar/Ar sanidine 0.759?0.002 Ma* Upper tuffs of Glass Mountain Ar/Ar sanidine 0.87?0.02 Ma Upper tuffs of Glass Mountain Ar/Ar sanidine 1.13?0.19 Ma Lower tuffs of Glass Mountain K-Ar obsidian 1.86?0.09 Ma (avg of 2 dates) Ar/Ar sanidine 1.92?0.02 Ma (avg of 2 dates) Tuffs of Blind Spring Valley Ar/Ar sanidine 2.135?0.02 to sanidine 2.219?0.006 Ma (10 dates) Tuffs of Benton Hot Springs Ar/Ar plagioclase 2.81?0.02 Ma *Date published previously The above tephra layers were also petrographically examined and the volcanic glass shards of the layers were chemically analyzed using the electron microprobe and, for some samples, instrumental neutron activation analysis and X-ray fluorescence. The same types of chemical and petrographic analyses were conducted on stratigraphic sequences of tephra layers of suspected upper Pliocene and Pleistocene age in several past and present depositional basins within the region outside of Blind Spring Valley. Chemical characterization, combined with additional dates and with magnetostratigraphy of thick sections at two of the distal sites, allow correlation of the tephra layers at the Cowan Pumice Mine with layers present at the distal sites and provide age constraints for other intercalated tephra layers and sediments for which age data were previously lacking. The identification at several sections of the widespread Huckleberry Ridge ash bed, derived from the Yellowstone eruptive source area in Wyoming, as well as a new 40Ar/39Ar age on this ash bed from a proximal locality, provide additional age constraints to several of the distal sections. The dated or temporally bracketed distal units, in order of concordant age and stratigraphic position, are: Tephra Unit Method Material Age Tephra layers of Glass Mountain (undiff.) P-mag.*; correlation N/A 1.78 , 1.96, 1.96, 2.22, 2.57, <2.89 Ma Tephra layers of Benton Hot Springs Ar/Ar; correlation plagioclase 2.89?0.03 Ma *Magnetostratigraphic polarity determination At the Cowan Pumice Mine, only a partial section of the eruptive record is preserved, but the best materials for laser-fusion 40Ar/39Ar and other isotopic dating methods were obtained. In the more distal Willow Wash and Confidence Hills sections, both persistent depositional basins for most of late Pliocene time, more complete sections of upper Pliocene tephra layers were preserved. In the region of Glass Mountain, the tephra layers that make up each of the mapped and dated pyroclastic units are multiple and complex, but a progressive simplification of the stratigraphy away from the source area was observed for more distal sites in southern and southwestern California and in Utah. This progressive

A Detailed Study of the Delacroix Island Major Fault and Its Role on Stratigraphic Horizons from the Middle Miocene to Present

NASA Astrophysics Data System (ADS)

Levesh, J. L.; McLindon, C.; Kulp, M. A.

2017-12-01

An in-depth field study of the Delacroix Island producing field illustrates the evolution of the main East-West trending Delacroix Island fault over the last thirteen million years. Well log correlation and 3-D seismic interpretation of eighteen bio-stratigraphic horizons across the fault reveal a range of stratigraphic thicknesses. A cross section, created with wells upthrown and downthrown to the fault, visually demonstrates varying degrees of thickening and displacement of the stratigraphic intervals across the fault. One upthrown and one downthrown well, with well log curve data up to 30 meters below the surface, were used to calculate interval thicknesses between the main tops as well as five more Pliocene/Pleistocene biostratigraphic markers. Isopach maps, created with these interval thicknesses, depict two styles of interval thickening both of which indicate differential subsidence across the fault. An interval thickness analysis was plotted in both depth and time as well as plots showing the rate of sediment accumulation and depth versus fault displacement. A lineation on the marsh surface consistent with a projection of the fault plane suggests that the fault movement has been episodically continuous to the present and that recent movement may have played a role in submerging the downthrown side of the surface fault trace.

New geochronologic and palaeomagnetic data for the hominid-bearing Hadar Formation of Ethiopia

USGS Publications Warehouse

Aronson, J.L.; Schmitt, T.J.; Walter, R.C.; Taieb, M.; Tiercelin, J.J.; Johanson, D.C.; Naeser, C.W.; Nairn, A.E.M.

1977-01-01

A 2.6 Myr K/Ar age has been derived for a primary unreworked tuff high in the hominid-bearing Hadar Formation (Kada Hadar Member), stratigraphically above all the important fossil finds. A 2.6 Myr fission track age has been derived on zircons from this tuff. New K/Ar results on the Kadada Moumou basalt (Sidi Hakoma Member) suggest a 3.0 Myr age. Preliminary interpretation of a detailed continuous palaeomagnetic section through the formation indicates the existence of persistent normal and reversed sequences. With the radiometric age control this magnetic sequence appears to correlate with the Gauss Epoch. These initial results imply the fossil-rich Hadar Formation spans from somewhat older than 3.1 Myr to somewhat younger than 2.6 Myr. ?? 1977 Nature Publishing Group.

Acid processing of pre-Tertiary radiolarian cherts and its impact on faunal content and biozonal correlation

USGS Publications Warehouse

Blome, C.D.; Reed, K.M.

1993-01-01

Destruction of radiolarians during both diagenesis and HF processing severely reduces faunal abundance and diversity and affects the taxonomic and biostratigraphic utility of chert residues. The robust forms that survive the processing represent only a small fraction of the death assemblage, and delicate skeletal structures used for species differentiation, are either poorly preserved or dissolved in many coeval chert residues. First and last occurrences of taxa in chert sequences are likely to be coarse approximations of their true stratigraphic ranges. Precise correlation is difficult between biozonations based solely on index species from cherts and those constructed from limestone faunas. Careful selection of samples in sequence, use of weaker HF solutions, and study of both chert and limestone faunas should yield better biostratigraphic information. -from Authors

Depositional framework and sequence stratigraphic aspects of the Coniacian Santonian mixed siliciclastic/carbonate Matulla sediments in Nezzazat and Ekma blocks, Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

El-Azabi, M. H.; El-Araby, A.

2007-04-01

Superb outcrops of mixed siliciclastic/carbonate rocks mark the Coniacian-Santonian Matulla Formation exposed in Nezzazat and Ekma blocks, west central Sinai. They are built up of various lithofacies that reflect minor fluctuations in relative sea-level from lower intertidal to slightly deep subtidal settings. Relying on the facies characteristics and stratal geometries, the siliciclastic rocks are divided into seven depositional facies, including beach foreshore laminated sands, upper shoreface cross-bedded sandstone, lower shoreface massive bioturbated and wave-rippled sandstones, shallow subtidal siltstone and deep subtidal shale/claystone. The carbonate rocks comprise lower intertidal lime-mudstone, floatstone and dolostone, shallow subtidal skeletal shoal of oyster rudstone/bioclastic grainstone, and shoal margin packstone. Oolitic grain-ironstone and ferribands are partially intervened the facies types. Deposition has taken place under varied conditions of restricted, partly open marine circulation, low to high wave energy and normal to raised salinity during alternating periods of abundant and ceased clastic supply. The facies types are arranged into asymmetric upward-shallowing cycles that record multiple small-scale transgressive-regressive events. Lime-mudstone and sandstone normally terminate the regressive events. Four sequence boundaries marking regional relative sea-level falls divide the Matulla Formation into three stratigraphic units. These boundaries are Turonian/Coniacian, intra-Coniacian, Coniacian/Santonian and Santonian/Campanian. They do not fit with those sequence boundaries proposed in Haq et al.'s global eustatic curves (1988) except for the sea-level fall associated with the intra-Coniacian boundary. Other sequence boundaries have resulted from regional tectonic impact of the Syrian Arc Fold System that has been initiated in north Egypt during the Latest Turonian-Coniacian. These boundaries enclose three well-defined 3rd order depositional sequences; their enclosing shallowing-upward cycles (i.e. parasequences) record the 4th order relative sea-level fluctuations. 34 and 20 parasequence sets, in the order of a few meters to tens of meters thick, mark the Matulla sequences in Nezzazat and Ekma blocks respectively. Each sequence shows an initial phase of rapid sea-level rise with retrogradational sets, followed by lowering sea-level and progradation/aggradation of the parasequence sets. The transgressive deposits display predominance of deep subtidal lagoonal facies, while highstand deposits show an increase in siliciclastic and carbonate facies with the progressive decrease of lagoonal facies. The sedimentary patterns and environments suggest that the regional, partly eustatic sea-level (i.e. intra-Coniacian) changes controlled the overall architecture of the sequence distribution, whereas changes in the clastic input controlled the variations in facies associations within each depositional sequence.

Formation of the Martian Polar Layered Terrains: Quantifying Polar Water Ice and Dust Surface Deposition during Current and Past Orbital Epochs with the NASA Ames GCM

NASA Astrophysics Data System (ADS)

Emmett, Jeremy; Murphy, Jim

2016-10-01

Structural and compositional variability in the layering sequences comprising Mars' polar layered terrains (PLT's) is likely explained by orbital-forced climatic variations in the sedimentary cycles of water ice and dust from which they formed [1]. The PLT's therefore contain a direct, extensive record of the recent climate history of Mars encoded in their structure and stratigraphy, but deciphering this record requires understanding the depositional history of their dust and water ice constituents. 3D Mars atmosphere modeling enables direct simulation of atmospheric dynamics, aerosol transport and quantification of surface accumulation for a range of past and present orbital configurations. By quantifying the net yearly polar deposition rates of water ice and dust under Mars' current and past orbital configurations characteristic of the last several millions of years, and integrating these into the present with a time-stepping model, the formation history of the north and south PLT's will be investigated, further constraining their age and composition, and, if reproducible, revealing the processes responsible for prominent features and stratigraphy observed within the deposits. Simulating the formation of the deposits by quantifying net deposition rates during past orbital epochs and integrating these into the present, effectively 'rebuilding' the terrains, could aid in understanding deeper stratigraphic trends, correlating between geographically-separated deposits, explaining the presence and shapes of large-scale polar features, and correlating stratigraphy with geological time. Quantification of the magnitude and geographical distribution of surface aerosol accumulation will build on the work of previous GCM-based investigations [3]. Construction and analysis of hypothetical stratigraphic sequences in the PLT's will draw from previous climate-controlled stratigraphy methodologies [2,4], but will utilize GCM-derived net deposition rates to model orbital influences on sedimentation and erosion.[1] Milkovich S.M. and Head J. W. (2005) JGR, 110. [2] Laskar J.B. and Mustard J.F. (2002) Nature, 419, 375-377 [3] Newman C.E. et al. (2005) Icarus, 174, 135-160. [4] Hvidberg C.S. et al. (2012) Icarus, 221, 405-419.

Along-strike structural variation and thermokinematic development of the Cenozoic Bitlis-Zagros fold-thrust belt, Turkey and Iraqi Kurdistan

NASA Astrophysics Data System (ADS)

Barber, Douglas E.; Stockli, Daniel F.; Koshnaw, Renas I.; Tamar-Agha, Mazin Y.; Yilmaz, Ismail O.

2016-04-01

The Bitlis-Zagros orogen in northern Iraq is a principal element of the Arabia-Eurasia continent collision and is characterized by the lateral intersection of two structural domains: the NW-SE trending Zagros proper system of Iran and the E-W trending Bitlis fold-thrust belt of Turkey and Syria. While these components in northern Iraq share a similar stratigraphic framework, they exhibit along-strike variations in the width and style of tectonic zones, fold morphology and trends, and structural inheritance. However, the distinctions of the Bitlis and Zagros segments remains poorly understood in terms of timing and deformation kinematics as well as first-order controls on fold-thrust development. Structural and stratigraphic study and seismic data combined with low-T thermochronometry provide the basis for reconstructions of the Bitlis-Zagros fold-thrust belt in southeastern Turkey and northern Iraq to elucidate the kinematic and temporal relationship of these two systems. Balanced cross-sections were constructed and incrementally restored to quantify the deformational evolution and use as input for thermokinematic models (FETKIN) to generate thermochronometric ages along the topographic surface of each cross-section line. The forward modeled thermochronometric ages from were then compared to new and previously published apatite and zircon (U-Th)/He and fission-track ages from southeastern Turkey and northern Iraq to test the validity of the timing, rate, and fault-motion geometry associated with each reconstruction. The results of these balanced theromokinematic restorations integrated with constraints from syn-tectonic sedimentation suggest that the Zagros belt between Erbil and Suleimaniyah was affected by an initial phase of Late Cretaceous exhumation related to the Proto-Zagros collision. During the main Zagros phase, deformation advanced rapidly and in-sequence from the Main Zagros Fault to the thin-skinned frontal thrusts (Kirkuk, Shakal, Qamar) from middle to latest Miocene times, followed by out-of-sequence development of the Mountain Front Flexure (Qaradagh anticline) by ~5 Ma. In contrast, initial exhumation in the northern Bitlis belt occurred by mid-Eocene time, followed by collisional deformation that propagated southward into northern Iraqi Kurdistan during the middle to late Miocene. Plio-Pleistocene deformation was partitioned into out-of-sequence reactivation of the Ora thrust along the Iraq-Turkey border, concurrent with development of the Sinjar and Abdulaziz inversion structures at the edge of the Bitlis deformation front. Overall, these data suggest the Bitlis and Zagros trends evolved relatively independently during Cretaceous and early Cenozoic times, resulting in very different structural and stratigraphic inheritance, before being affected contemporaneously by major phase of in-sequence shortening during middle to latest Miocene and out-of-sequence deformation since the Pliocene. Limited seismic sections corroborate the notion that the structural style and trend of the Bitlis fold belt is dominated by inverted Mesozoic extensional faults, whereas the Zagros structures are interpreted mostly as fault-propagation folds above a Triassic décollement. These pre-existing heterogeneities in the Bitlis contributed to the lower shortening estimates, variable anticline orientation, and irregular fold spacing and the fundamentally different orientations of the Zagros-Bitlis belt in Iraqi Kurdistan and Turkey.

Holocene Geomorphic and Stratigraphic Framework of Archeological Sites Along the Missouri River, Central South Dakota

DTIC Science & Technology

1987-03-01

South Dakota 13 2 Description of the Lower Brule Section MT-i, now submerged by the waters of Lake Sharpe, Lyman County, South Dakota 15 3 Sequence...MT-i, now submerged by the waters of Lake Sharpe, Lyman County, South Dakota Unit # Description Thickness 1 Gray, thinbedded Cretaceous Pierre Shale...14,000 10000 C- 14 YBP WISCONSlNAN HOLOCENE AGE LATE EARLY MIDDLE LATE 10 M.I1. AGGIE BROWN PICK CITY OW MID.UPE MBR MEMBER M EMBER RIVERDALE MEMBER OAHE

Mediterranean Sea potential seen in area south of Malta

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

Bishop, W.F.; Debono, G.

Seismic data and stratigraphic projections indicate that an entirely different facies exists in Area 4 in the Mediterranean Sea south of Malta than the continuous carbonate sequence of the Malta platform. Japan National Oil Corp., in September 1989 under authority of the government of Malta, conducted a 3,615 line km geophysical survey (seismic, gravity, magnetics) in Area 4, which comprises about 13,000 sk km and is 40 km south of Malta. The paper describes the geology of Malta Area 4, its inferred stratigraphy, seismic results, and potential geologic traps.

Geology of the Sklodowska Region, Lunar Farside. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Kauffman, J. D.

1974-01-01

Investigation of an area on the lunar farside has resulted in a geologic map, development of a regional stratigraphic sequence, and interpretation of surface materials. Apollo 15 metric photographs were used in conjunction with photogrammetric techniques to produce a base map to which geologic units were later added. Geologic units were first delineated on the metric photographs and then transferred to the base map. Materials were defined and described from selected Lunar Orbiter and Apollo 15 metric, panoramic, and Hasselblad photographs on the basis of distinctive morphologic characteristics.

High-resolution stratigraphic analyses of Permian-Triassic core material recovered in central Spitsbergen

NASA Astrophysics Data System (ADS)

Sleveland, Arve; Planke, Sverre; Zuchuat, Valentin; Franeck, Franziska; Svensen, Henrik; Midtkandal, Ivar; Hammer, Øyvind; Twitchett, Richard; Deltadalen Study Group

2017-04-01

The Siberian Traps voluminous igneous activity is considered a likely trigger for the Permian-Triassic global extinction event. However, documented evidence of the Siberian Traps environmental effects decreases away from the centre of volcanic activity in north-central Russia. Previous research on the Permian-Triassic boundary (PTB) mostly relies on field observations, and resolution has thus depended on outcrop quality. This study reports on two 90 m cored sedimentary successions intersecting the PTB in Deltadalen, Svalbard, providing high-quality material to a comprehensive documentation of the stratigraphic interval. Sequence stratigraphic concepts are utilised to help constrain the Permian-Triassic basin development models in Svalbard and the high-Arctic region. The cored sections are calibrated with outcrop data from near the drill site. One core has been systematically described and scanned using 500-μm and 200-μm resolution XRF, hyperspectral imagery and microfocus CT (latter only on selected core sections). The base of both cores represents the upper 15 m of the Permian Kapp Starostin Formation, which is dominated by green glauconitic sandstones with spiculitic cherts, and exhibit various degrees of bioturbation. The Kapp Starostin Formation is in turn sharply overlain by 2 m of heavily reworked sand- and mudstones, extensively bioturbated, representing the base of the lower Triassic Vikinghøgda Formation. These bioturbated units are conformably overlain by 9 m of ash-bearing laminated black shale where signs of biological activity both on micro- and macro-scale are limited, and is thus interpreted to have recorded the Permian-Triassic extinction interval. Descriptive sedimentology and sequence stratigraphic concepts reveal the onset of relative sea level rise at the Vikinghøgda Formation base. The disappearance of bioturbation and extensive presence of pyrite in the overlying laminated black shale of the Vikinghøgda Formation suggest near anoxic conditions. The maximum flooding surface is recorded 6 m above the base of the Vikinghøgda Formation, in the middle of the laminated black shale and indicates that the lower ash-layers are tied to igneous activity at a time of relatively high sea level. The remaining succession above the laminated black shale is an overall aggradational interval of interbedded clay- and siltstones of the Vikinghøgda Formation, marking the return of biological activity at its base. The Vikinghøgda Formation includes 18 preserved zircon-bearing ash-layers, providing an opportunity for accurate U/Pb dating. Detailed cyclostratigraphic analyses of the laminated black shale suggest a sedimentation rate of approximately 0.5 cm/kyr, and provides thus, together with the U/Pb zircon ages, a great tool for high-resolution documentation of the PTB interval.

Correlation and taphonomy of late Cretaceous vertebrate localities in Fruitland and Kirtland formations, San Juan basin, New Mexico

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

Hunt, A.P.

Most fossil vertebrates in the Fruitland and Kirtland formations occur in two narrow stratigraphic intervals. The upper interval comprises the approximately 30 m-thick Naashoibito Member of the Kirtland formation. Fossiliferous localities within this interval are physically correlatable within the small and continuous outcrop belt of this unit. The lower fossiliferous interval comprises a 20 m-thick sequence between the stratigraphically highest, thick coal bed (1 m thick) in the Fruitland Formation and distinctive brown tabular sandstones in the lower Kirtland formation, which differ in color and geometry from adjacent sandstone bodies. Localities within this interval occur in physically discontinuous outcrops, principallymore » between Hunter Wash in the northwest and Coal Creek in the southeast. These localities can be correlated utilizing the upper Fruitland coal, the lower Kirtland sandstones, and a series of volcanic ashes. Measurement of 38 stratigraphic sections and examination of more than 100 subsurface geophysical logs has allowed detailed correlation between the principal areas of vertebrate-fossil occurrences in Hunter Wash and the Fossil Forest. The occurrence of fossils in the Naashoibito is related to energy of depositional environment. Farther north, coarser deposits of the McDermott Member of the Animas Formation, which represent proximal facies of the Naashoibito, lack abundant fossil vertebrates. The geographic extent of vertebrate fossils in the upper Fruitland and lower Kirtland coincides with the extent of the tabular brown sandstones in the lower Kirtland and is related to Laramide downwarping of the central San Juan basin.« less

Petroleum prospectivity of the Canada Basin, Arctic Ocean

USGS Publications Warehouse

Grantz, Arthur; Hart, Patrick E.

2012-01-01

Reconnaissance seismic reflection data indicate that Canada Basin is a >700,000 sq. km. remnant of the Amerasia Basin of the Arctic Ocean that lies south of the Alpha-Mendeleev Large Igneous Province, which was constructed across the northern part of the Amerasia Basin between about 127 and 89-83.5 Ma. Canada Basin was filled by Early Jurassic to Holocene detritus from the Beaufort-Mackenzie Deltaic System, which drains the northern third of interior North America, with sizable contributions from Alaska and Northwest Canada. The basin contains roughly 5 or 6 million cubic km of sediment. Three fourths or more of this volume generates low amplitude seismic reflections, interpreted to represent hemipelagic deposits, which contain lenses to extensive interbeds of moderate amplitude reflections interpreted to represent unconfined turbidite and amalgamated channel deposits.Extrapolation from Arctic Alaska and Northwest Canada suggests that three fourths of the section in Canada Basin is correlative with stratigraphic sequences in these areas that contain intervals of hydrocarbon source rocks. In addition, worldwide heat flow averages suggest that about two thirds of Canada Basin lies in the oil or gas windows. Structural, stratigraphic and combined structural and stratigraphic features of local to regional occurrence offer exploration targets in Canada Basin, and at least one of these contains bright spots. However, deep water (to almost 4000 m), remoteness from harbors and markets, and thick accumulations of seasonal to permanent sea ice (until its possible removal by global warming later this century) will require the discovery of very large deposits for commercial success in most parts of Canada Basin. ?? 2011 Elsevier Ltd.

Brookian sequence well log correlation sections and occurrence of gas hydrates, north-central North Slope, Alaska

USGS Publications Warehouse

Lewis, Kristen A.; Collett, Timothy S.

2013-01-01

Gas hydrates are naturally occurring crystalline, ice-like substances that consist of natural gas molecules trapped in a solid-water lattice. Because of the compact nature of their structure, hydrates can effectively store large volumes of gas and, consequently, have been identified as a potential unconventional energy source. First recognized to exist geologically in the 1960s, significant accumulations of gas hydrate have been found throughout the world. Gas hydrate occurrence is limited to environments such as permafrost regions and subsea sediments because of the pressure and temperature conditions required for their formation and stability. Permafrost-associated gas hydrate accumulations have been discovered in many regions of the Arctic, including Russia, Canada, and the North Slope of Alaska. Gas hydrate research has a long history in northern Alaska. This research includes the drilling, coring, and well log evaluation of two gas hydrate stratigraphic test wells and two resource assessments of gas hydrates on the Alaska North Slope. Building upon these previous investigations, this report provides a summary of the pertinent well log, gas hydrate, and stratigraphic data for key wells related to gas hydrate occurrence in the north-central North Slope. The data are presented in nine well log correlation sections with 122 selected wells to provide a regional context for gas hydrate accumulations and the relation of the accumulations to key stratigraphic horizons and to the base of the ice-bearing permafrost. Also included is a well log database that lists the location, available well logs, depths, and other pertinent information for each of the wells on the correlation section.

Mapping of magnetic chrons: paleomagnetic polarity map of East Iceland, 0-13 Myr

NASA Astrophysics Data System (ADS)

Helgason, Johann

2016-04-01

Through data on palaeomagnetism, stratigraphy and radiometric age dating an immense database on magnetic chrons has been established for the lava succession in Iceland (e.g. Kristjánsson, 2008). Correlation of magnetic chrons with the geomagnetic time scale provides a reasonable age estimate for vast stratigraphic sequences. The basalt lava succession in Iceland has a thickness of tens of kilometers. The magnetostratigraphic data offer, through the help of paleomagnetism and radiometric dating, a detailed timing of events in the evolution of the Iceland mantle plume region. Yet a magnetic polarity map for Iceland has been lacking but during the last 50 years, comprehensive stratigraphic mapping has paved the way for a magnetic polarity map in various parts of Iceland. Here, such a map is presented for a segment of East Iceland, i.e. for lavas ranging in age from 0 to 13 M yr. The map is a compilation based on various studies into the cliff section and stratigraphic work performed by numerous research initiatives, both in relation to hydroelectric research as well as academic projects. References: Kristjánsson, L., 2008. Paleomagnetic research on Icelandic lava flows. Jökull, 58, 101-116. Helgason, J., Duncan, R.A., Franzson, H., Guðmundsson, Á., and M. Riishuus., 2015. Magnetic polarity map of Akrafjall and Skarðsheiði and new 40Ar-39Ar age dating from West Iceland., Presentation at the spring conference of the Icelandic Geological Society, held on March 13th 2015 at the University of Iceland.

North American Commission on Stratigraphic Nomenclature Report 12 – Revision of article 37, lithodemic units, of the North American Stratigraphic Code

USGS Publications Warehouse

Easton, Robert M.; Edwards, Lucy E.; Orndorff, Randall C.; Duguet, Manuel; Ferrusquia-Villafranca, Ismael

2017-01-01

At the 71st Annual Meeting of the North American Commission on Stratigraphic Nomenclature, 26 September, 2016, in Denver, Colorado, the Commission voted unanimously to accept the revision of Article 37 of the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 2005), printed below. It replaces all older versions of this Article. An application for this revision (Easton et al. 2015) was published in Stratigraphy more than one year prior to the meeting; thus, the vote on this application for revision follows Article 21 of the Code.

Sawfishes and Other Elasmobranch Assemblages from the Mio-Pliocene of the South Caribbean (Urumaco Sequence, Northwestern Venezuela)

PubMed Central

2015-01-01

The Urumaco stratigraphic sequence, western Venezuela, preserves a variety of paleoenvironments that include terrestrial, riverine, lacustrine and marine facies. A wide range of fossil vertebrates associated with these facies supports the hypothesis of an estuary in that geographic area connected with a hydrographic system that flowed from western Amazonia up to the Proto-Caribbean Sea during the Miocene. Here the elasmobranch assemblages of the middle Miocene to middle Pliocene section of the Urumaco sequence (Socorro, Urumaco and Codore formations) are described. Based on new findings, we document at least 21 taxa of the Lamniformes, Carcharhiniformes, Myliobatiformes and Rajiformes, and describe a new carcharhiniform species (†Carcharhinus caquetius sp. nov.). Moreover, the Urumaco Formation has a high number of well-preserved fossil Pristis rostra, for which we provide a detailed taxonomic revision, and referral in the context of the global Miocene record of Pristis as well as extant species. Using the habitat preference of the living representatives, we hypothesize that the fossil chondrichthyan assemblages from the Urumaco sequence are evidence for marine shallow waters and estuarine habitats. PMID:26488163

The Early to Middle Triassic continental-marine transition of NW Bulgaria: sedimentology, palynology and sequence stratigraphy

NASA Astrophysics Data System (ADS)

Ajdanlijsky, George; Götz, Annette E.; Strasser, André

2018-04-01

Sedimentary facies and cycles of the Triassic continental-marine transition of NW Bulgaria are documented in detail from reference sections along the Iskar river gorge between the villages of Tserovo and Opletnya. The depositional environments evolved from anastomosing and meandering river systems in the Petrohan Terrigenous Group to mixed fluvial and tidal settings in the Svidol Formation, and to peritidal and shallow-marine conditions in the Opletnya Member of the Mogila Formation. For the first time, the palynostratigraphic data presented here allow for dating the transitional interval and for the precise identification of a major sequence boundary between the Petrohan Terrigenous Group and the Svidol Formation (Iskar Carbonate Group). This boundary most probably corresponds to the major sequence boundary Ol4 occurring in the upper Olenekian of the Tethyan realm and thus enables interregional correlation. The identification of regionally traceable sequence boundaries based on biostratigraphic age control is a first step towards a more accurate stratigraphic correlation and palaeogeographic interpretation of the Early to early Middle Triassic in NW Bulgaria.

Geochemistry of volcanic rocks from the Wawa greenstone belt

NASA Technical Reports Server (NTRS)

Schulz, K. J.; Sylvester, P. J.; Attoh, K.

1983-01-01

The Wawa greenstone belt is located in the District of Algoma and extends east-northeast from Lake Superior to the western part of the Sudbury District in Ontario, Canada. Recent mapping by Attoh has shown that an unconformity at the base of the Dore' Formation and equivalent sedimentary rocks marks a significant stratigraphic break which can be traced throughout the volcanic belt. This break has been used to subdivide the volcanic-sedimentary into pre- and post-Dore' sequences. The pre-Dore' sequence includes at least two cycles of mafic-to-felsic volcanism, each capped by an iron-formation unit. The post-Dore' sequence includes an older mafic-to-felsic unit, which directly overlies sedimentary rocks correlated with the Dore' Formation, and a younger felsic breccia unit interpreted to have formed as debris flows from a felsic volcanic center. In the present study, samples of both the pre-and post-Dore' volcanic sequences were analyzed for major and trace elements, incuding rare earths (REE). This preliminary study is part of an ongoing program to assess the petrogenesis of the volcanic rocks of the Wawa greenstone belt.

Seismic sequence stratigraphy and platform to basin reservoir structuring of Lower Cretaceous deposits in the Sidi Aïch-Majoura region (Central Tunisia)

NASA Astrophysics Data System (ADS)

Azaïez, Hajer; Bédir, Mourad; Tanfous, Dorra; Soussi, Mohamed

2007-05-01

In central Tunisia, Lower Cretaceous deposits represent carbonate and sandstone reservoir series that correspond to proven oil fields. The main problems for hydrocarbon exploration of these levels are their basin tectonic configuration and their sequence distribution in addition to the source rock availability. The Central Atlas of Tunisia is characterized by deep seated faults directed northeast-southwest, northwest-southeast and north-south. These faults limit inherited tectonic blocks and show intruded Triassic salt domes. Lower Cretaceous series outcropping in the region along the anticline flanks present platform deposits. The seismic interpretation has followed the Exxon methodologies in the 26th A.A.P.G. Memoir. The defined Lower Cretaceous seismic units were calibrated with petroleum well data and tied to stratigraphic sequences established by outcrop studies. This allows the subsurface identification of subsiding zones and thus sequence deposit distribution. Seismic mapping of these units boundary shows a structuring from a platform to basin blocks zones and helps to understand the hydrocarbon reservoir systems-tract and horizon distribution around these domains.

Evidence for thermal convection in the deep carbonate aquifer of the eastern sector of the Po Plain, Italy

NASA Astrophysics Data System (ADS)

Pasquale, V.; Chiozzi, P.; Verdoya, M.

2013-05-01

Temperatures recorded in wells as deep as 6 km drilled for hydrocarbon prospecting were used together with geological information to depict the thermal regime of the sedimentary sequence of the eastern sector of the Po Plain. After correction for drilling disturbance, temperature data were analyzed through an inversion technique based on a laterally constant thermal gradient model. The obtained thermal gradient is quite low within the deep carbonate unit (14 mK m- 1), while it is larger (53 mK m- 1) in the overlying impermeable formations. In the uppermost sedimentary layers, the thermal gradient is close to the regional average (21 mK m- 1). We argue that such a vertical change cannot be ascribed to thermal conductivity variation within the sedimentary sequence, but to deep groundwater flow. Since the hydrogeological characteristics (including litho-stratigraphic sequence and structural setting) hardly permit forced convection, we suggest that thermal convection might occur within the deep carbonate aquifer. The potential of this mechanism was evaluated by means of the Rayleigh number analysis. It turned out that permeability required for convection to occur must be larger than 3 10- 15 m2. The average over-heat ratio is 0.45. The lateral variation of hydrothermal regime was tested by using temperature data representing the aquifer thermal conditions. We found that thermal convection might be more developed and variable at the Ferrara High and its surroundings, where widespread fracturing may have increased permeability.

The stratigraphic record of Khawr Al Maqta, Abu Dhabi, United Arab Emirates

NASA Astrophysics Data System (ADS)

Lokier, S. W.; Herrmann, S.

2012-04-01

Well-constrained modern depositional analogues are vital to the development of accurate geological reservoir models. The development of realistic hydrocarbon reservoir models requires the application of high-precision, well-constrained outcrop and sub-surface data sets with accurately-documented facies geometries and depositional sequence architectures. The Abu Dhabi coastline provides the best modern analogue for the study of ramp-style carbonate depositional facies akin to those observed in the sub-surface reservoirs of the United Arab Emirates (UAE). However, all previous studies have relied on temporally limited surface datasets. This study employed thirty five shallow subsurface cores spanning the width of the Khawr Al Maqta - the narrow shallow tidal channel that separates Abu Dhabi Island from the mainland. The cores were taken over a transect measuring 1.2 km in length by 50 m wide thus providing a high-resolution record of sub-surface facies geometries in a stratigraphically complex setting. Geometries in these Pleistocene to Holocene facies are complex with interdigitating, laterally heterogeneous carbonate, siliciclastic and evaporite units represented throughout the area of the study. Carbonate facies range from molluscan rudstones to marls and are all indicative of deposition in a shallow, relatively low energy marine setting akin to that seen in the environs of Abu Dhabi Island today. Texturally mature quartz sands occur as thin lenses and as thin cross bedded or laminated horizons up to twenty five centimetres thick. Glauconitic mudstones are common and locally exhibit evidence of rootlets and desiccation cracks. Evaporites are present in the form of gypsum occurring as isolated crystals and nodules or as massive chicken-wire units in excess of three metres thick. All of these textures are consistent with evaporite development in the shallow subsurface. Early, shallow-burial diagenesis has been important. Bioclasts are pervasively leached throughout the stratigraphic sequence thereby resulting in a significant enhancement in porosity in the carbonate lithologies. This pervasive mouldic porosity is locally occluded by the precipitation of gypsum cements. The displacive precipitation of significant quantities of gypsum has resulted in the deformation of primary sedimentary structures. This complex sequence of mixed carbonate-siliciclastic-evaporite lithofacies is interpreted to record repeated episodes of flooding and sub-aerial exposure associated with the waxing and waning of the Pleistocene ice-sheets. During periods of relative sea-level fall carbonate sequences entered the meteoric realm with the consequent dissolution of unstable bioclasts. Transgression and reflooding once again isolated Abu Dhabi Island from the mainland, thus permitting the precipitation of shallow-water carbonate lithofacies. During sea-level highstands the north-westerly Shamal wind transported carbonate sediments into the lee-of the island resulting in the south-easterly shore-wards development of a tombolo. However, the strong tidal currents of the Khawr Al Maqta prevented final connection to the mainland, thus ensuring the isolation of Abu Dhabi until the subsequent regression.

Milankovitch Modulated Eocene Growth Strata From the Jaca Piggyback Basin, Spanish Pyrenees

NASA Astrophysics Data System (ADS)

Anastasio, D. J.; Hinnov, L. A.; Newton, M. L.; Kodama, K. P.

2005-12-01

New stratigraphic and rock magnetic data from the southern margin of the Jaca basin, Spanish Pyrenees, shows evidence of Eocene sedimentary cycles modulated by the climatic effects of Milankovitch orbital forcing. Tectonic processes simultaneously controlled larger-scale stratigraphic sequences and overall wedge-top basin development. Within the context of existing magnetostratigraphy, we described 1 km of marine basinal and prodeltaic rocks near Pico del Aguila, a large-scale synsedimentary fold, and collected samples every ~4krs for ~4myrs for lithologic and rock magnetic analysis. In magnetochrons C17r, C18n.1n, and C18n.1r (1.27myrs) anhysteretic remanent magnetization (ARM) variations occur with strong hierarchical bundling patterns suggestive of precession-scale cycles grouped into 100 kyr eccentricity cycles, and "super bundled" into 400 kyr eccentricity cycles. This pattern was exploited to construct an "eccentricity time scale" for the series producing a minimally tuned time series that is 1.3 myrs in duration; comparing well with the magnetochron calibration. Spectral analysis of this ARM time series shows that the 100-kyr tuning has aligned power into all of the principal orbital frequency bands: long eccentricity (1/(400 kyrs)), obliquity (1/(40.4 kyrs)), long precession (1/(24.4 kyrs)), and short precession (1/(20 kyrs)). Lithologic data, including bed thickness and grain size also shows high frequency periodicity we attribute to precessional forcing. ARM variations may result from climate modulated carbonate production or more likely, variable detrital inputs such as atmospheric dust (varying wind intensity or aridity) or watershed erosion (runoff variation) rather than diagenetic sources. The Milankovitch based chronology within the growth stratigraphy was then used to calculate deformation rates. Tilt rates of 9 degrees / myr for folding are comparable to other studies in which deformation was averaged over more time. We show that Milankovitch rhythms in growth strata can be used to develop novel high resolution, long-term deformation histories.

Metasomatic alteration of an early Archean komatiite sequence into chert: field and petrographic evidence

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

Duchac, K.C.; Hanor, J.S.

Stratiform units of pervasively silicified ultramafic rock occur near the top of the Onverwacht group, Barberton Mountian Land, South Africa. The origin of these units has been variously ascribed to early Archean subaerial weathering, submarine weathering, cataclastic metamorphism, and the alteration of silicic tuffs at the top of mafic to felsic volcanic sequences. The authors have studied a 40 m thick stratigraphic sequence that is exceptionally well-exposed for 1.5 km within the Skokohla River valley. Well-preserved ghosts of spinifex- and cumulate-olivines and pyroxenes establish the komatiitic ancestry of these rocks. The entire sequence has been pervasively altered, however, to chertsmore » dominated by quartz and Cr-rich muscovite and containing lesser and variable amounts of chlorite, dolomite, rutile, and chrome spinel. The present Skokohla rocks can be divided into five distinct correlatable facies of laterally variable thickness which probably represent different flow units. Alteration apparently occurred early, prior to any significant tectonic deformation. The observed pervasive sericitization is inconsistent with an origin by subaerial weathering. It is most likely that the sequence was altered by large volumes of ascending hydrothermal fluids.« less

Storm-related sedimentation influenced by coastal configuration in the stratigraphic record of a tectonically active shelf (Upper Pleistocene Le Castella terrace, Italy)

NASA Astrophysics Data System (ADS)

Nalin, Ronald; Massari, Francesco

2018-03-01

Analysis of patterns of coastal circulation and sediment dispersal is an essential step for the study of controlling factors influencing the long-term dynamics of coastal systems. Modern settings offer the possibility to monitor relevant parameters over relatively short time spans. However, geological examples complement this perspective by providing a time-averaged record where longer trends and stratigraphically significant processes can be evaluated. This study investigates the shallow marine deposits of Le Castella terrace (Upper Pleistocene, southern Italy) to document how patterns of circulation influenced by coastline configuration can affect the preserved millennial-scale depositional record of a progradational shoreline system. The regressive portion of the Le Castella terrace deposits, developed during a relative sea-level highstand and falling stage, consists of a progradational wedge mainly composed of redistributed skeletal particles of a coeval shallow water carbonate factory. Preservation of the morphology of the paleocoastline and abundant current-related sedimentary structures allow reconstruction of the predominant sediment dispersal dynamics responsible for the formation of this sedimentary wedge. Facies and paleocurrent analysis indicate offshore and alongshore sediment transport modes, consistent with coastal circulation driven by storms normally incident to the shoreline and a sharp change in coastline orientation. This coastal inflection influenced circulation patterns causing flow separation and eddy formation in the lee of the curved coastline. Syndepositional tectonic deformation also affected the architecture of the preserved deposits, controlling the nucleation and development of a clinostratified body and determining localized lateral stratigraphic variability. This study illustrates how transient but recurrent circulation patterns associated with changes in coastal orientation and related to high-energy storm events can leave a predominant signature in the stratigraphic record of microtidal shallow-marine successions.

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

NASA Astrophysics Data System (ADS)

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

2014-08-01

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

Age accuracy and resolution of Quaternary corals used as proxies for sea level

NASA Astrophysics Data System (ADS)

Edinger, E. N.; Burr, G. S.; Pandolfi, J. M.; Ortiz, J. C.

2007-01-01

The accuracy of global eustatic sea level curves measured from raised Quaternary reefs, using radiometric ages of corals at known heights, may be limited by time-averaging, which affects the variation in coral age at a given height. Time-averaging was assessed in uplifted Holocene reef sequences from the Huon Peninsula, Papua New Guinea, using radiocarbon dating of coral skeletons in both horizontal transects and vertical sequences. Calibrated 2σ age ranges varied from 800 to 1060 years along horizontal transects, but weighted mean ages calculated from 15-18 dates per horizon were accurate to a resolution within 154-214 yr. Approximately 40% of the variability in age estimate resulted from internal variability inherent to 14C estimates, and 60% was due to time-averaging. The accuracy of age estimates of sea level change in studies using single dated corals as proxies for sea level is probably within 1000 yr of actual age, but can be resolved to ≤ 250 yr if supported by dates from analysis of a statistical population of corals at each stratigraphic interval. The range of time-averaging among reef corals was much less than that for shelly benthos. Ecological time-averaging dominated over sedimentological time averaging for reef corals, opposite to patterns reported from shelly benthos in siliciclastic environments.

Pennsylvanian tropical rain forests responded to glacial-interglacial rhythms

NASA Astrophysics Data System (ADS)

Falcon-Lang, Howard J.

2004-08-01

Pennsylvanian tropical rain forests flourished during an icehouse climate mode. Although it is well established that Milankovitch-band glacial-interglacial rhythms caused marked synchronous changes in Pennsylvanian tropical climate and sea level, little is known of vegetation response to orbital forcing. This knowledge gap has now been addressed through sequence- stratigraphic analysis of megafloral and palynofloral assemblages within the Westphalian D Cantabrian Sydney Mines Formation of eastern Canada. This succession was deposited in a low- accommodation setting where sequences can be attributed confidently to glacio-eustasy. Results show that long-lived, low-diversity peat mires dominated by lycopsids were initiated during deglaciation events, but were mostly drowned by rising sea level at maximum interglacial conditions. Only upland coniferopsid forests survived flooding without significant disturbance. Mid- to late interglacial phases witnessed delta-plain progradation and establishment of high-diversity, mineral-substrate rain forests containing lycopsids, sphenopsids, pteridosperms, cordaites, and tree ferns. Renewed glaciation resulted in sea-level fall, paleovalley incision, and the onset of climatic aridity. Glacial vegetation was dominated by cordaites, pteridosperms, and tree ferns; hydrophilic lycopsids and sphenopsids survived in paleovalley refugia. Findings clearly demonstrate the dynamic nature of Pennsylvanian tropical ecosystems and are timely given current debates about the impact of Quaternary glacial-interglacial rhythms on the biogeography of tropical rain forest.

The linkage between fluvial meander-belt morphodynamics and the depositional record improves paleoenvironmental interpretations, Western Interior Basin, Alberta, Canada

NASA Astrophysics Data System (ADS)

Durkin, P.; Hubbard, S. M.

2016-12-01

Enhanced stratigraphic interpretations are possible when linkages between morphodynamic processes and the depositional record are resolved. Recent studies of modern and ancient meander-belt deposits have emphasized morphodynamic processes that are commonly understated in the analysis of stratigraphic products, such as intra-point bar erosion and rotation, counter-point-bar (concave bank-bench) development and meander-bend abandonment. On a larger scale, longitudinal changes in meander-belt morphology and processes such as changes in meander-bend migration rate, channel-belt width/depth ratio and sinuosity have been observed as rivers flow through the tidal backwater zone. However, few studies have attempted to recognize the impact of the backwater zone in the stratigraphic record. We consider ancient meander-belt deposits of the Cretaceous McMurray Formation and document linkages between morphodynamic processes and their stratigraphic product to resolve more detailed paleoenvironmental interpretations. The ancient meander belt was characterized by paleochannels that were 600 m wide and up to 50 m deep, resolved in a particularly high quality subsurface dataset consisting of 600 km2 of high-quality 3-D seismic data and over 1000 wellbores. A 3-D geocellular model and reconstructed paleochannel migration patterns reveal the evolutionary history of seventeen individual meander belt elements, including point bars, counter point bars and their associated abandoned channel fills. At the meander-bend scale, intra-point-bar erosion surfaces bound accretion packages characterized by unique accretion directions, internal stratigraphic architecture and lithologic properties. Erosion surfaces and punctuated bar rotation are linked to upstream changes in channel planform geometry (meander cut-offs). We provide evidence for downstream translation and development of counter-point bars that formed in response to valley-edge and intra-meander-belt confinement. At the meander-belt scale, analysis of changes in morphology over time reveal a decrease in channel-belt width/thickness ratio and sinuosity, which we attribute to the landward migration of the paleo-backwater limit due to the oncoming and overlying transgression of the Cretaceous Boreal Sea into the Western Interior Basin.

Reconstruction of the Paleoproterozoic deeper ocean environment: Preliminary Report of the Ghana Birimian Greenstone Belt Drilling Project (GHB)

NASA Astrophysics Data System (ADS)

Kiyokawa, S.; Yoshimaru, S.; Miki, T.; Sakai, S.; Ikehara, M.; Yamaguchi, K. E.; Ito, T.; Onoue, T.; Takehara, M.; Tetteh, G. M.; Nyame, F. K.

2016-12-01

The Paleoproterozoic Era are one of the most rapid environmental change when the earth surface environment was affected by formation of continents and increasing atmospheric oxygen levels. Major oxidation of Great Oxidation Event (GOE) are reported this ages (eg. Holland, 2006; Condie, 2001; Lyons et al., 2014). The nature of deep sea environments at this time have not been clearly identified and oceanic sediments are mostly involved in subduction. The Paleoproterozoic Birimian Greenstone Belt is an ophiolitic volcaniclastic sequence in Ghana, with depositional age of over 2.3-2.2 Ga (Petersson et al., 2016). Detail research was conducted of the Ashanti (Axim-Konongo) Belt of the Birimian Greenstone Belt along the coast near Cape Three Points area. Very thick volcaniclastic and organic-rich sedimentary rocks, which we now refer to as the Cape Three Points Group, crop out in the lower part of the Birimian Greenstone Belt. Stratigraphically, three unit identified; the lower portion contains thick vesicular volcaniclastic rocks, the middle portion is made up of laminated volcaniclastics and black shale, and the upper portion dominated by fine laminated volcaniclastics with more black shale sequence. Continuous core drilling from Dec 3-12th 2015 of the upper part of the sequence intersected saprolite to a depth of 30m and fresh, well preserved stratigraphy with graded bedding and lamination to a depth of 195m. Half cut cores show well laminated organic rich black shale and relative carbonate rich layers with very fine pyrite grains. SHRIMP age data from a porphyry intrusion into this sequence indicate an age of 2250 Ma. Carbon isotope analysis shows δ13C = -43 to -37‰ for black shale with the very light isotope values for cyanobacterial signature.The fining-upward sequences, well laminated bed and black shales and REE data suggest this sequence situated partly silent stagnant with volcanic activity ocean floor environment around an oceanic island arc condition.

The role of sediment supply in large-scale stratigraphic architecture of ancient Gilbert-type deltas (Pliocene Siena-Radicofani Basin, Italy)

NASA Astrophysics Data System (ADS)

Martini, Ivan; Ambrosetti, Elisa; Sandrelli, Fabio

2017-04-01

Aggradation, progradation and retrogradation are the main patterns that define the large-scale architecture of Gilbert-type deltas. These patterns are governed by the ratio between the variation in accommodation space and sediment supply experienced during delta growth. Sediment supply variations are difficult to estimate in ancient settings; hence, it is rarely possible to assess its significance in the large-scale stratigraphic architecture of Gilbert-type deltas. This paper presents a stratigraphic analysis of a Pliocene deltaic complex composed of two coeval and narrowly spaced deltaic branches. The two branches recorded the same tectonic- and climate-induced accommodation space variations. As a result, this deltaic complex represents a natural laboratory for testing the effects of sediment supply variations on the stratigraphic architecture of Gilbert-type deltas. The field data suggest that a sediment supply which is able to counteract the accommodation generated over time promotes the aggradational/progradational attitude of Gilbert-type deltas, as well as the development of thick foreset deposits. By contrast, if the sediment supply is not sufficient for counterbalancing the generated accommodation, an aggradational/retrogradational stratigraphic architecture is promoted. In this case, the deltaic system is forced to withdraw during the different phases of generation of accommodation, with the subsequent flooding of previously deposited sub-horizontal topset deposits (i.e., the delta plain). The subsequent deltaic progradation occurs above these deposits and, consequently, the available space for foresets growth is limited to the water depth between the base-level and the older delta plain. This leads to the vertical stacking of relatively thin deltaic deposits with an overall aggradatational/retrogradational attitude.

Ordovician volcanic and plutonic complexes of the Sakmara allochthon in the southern Urals

NASA Astrophysics Data System (ADS)

Ryazantsev, A. V.; Tolmacheva, T. Yu.

2016-11-01

The Ordovician terrigenous, volcanic-sedimentary and volcanic sequences that formed in rifts of the active continental margin and igneous complexes of intraoceanic suprasubduction settings structurally related to ophiolites are closely spaced in allochthons of the Sakmara Zone in the southern Urals. The stratigraphic relationships of the Ordovician sequences have been established. Their age and facies features have been specified on the basis of biostratigraphic and geochronological data. The gabbro-tonalite-trondhjemite complex and the basalt-andesite-rhyolite sequence with massive sulfide mineralization make up a volcanic-plutonic association. These rock complexes vary in age from Late Ordovician to Early Silurian in certain structural units of the Sakmara Allochthon and to the east in the southern Urals. The proposed geodynamic model for the Ordovician in Paleozoides of the southern Urals reconstructs the active continental margin, whose complexes formed under extension settings, and the intraoceanic suprasubduction structures. The intraoceanic complexes display the evolution of a volcanic arc, back-, or interarc trough.

Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

NASA Astrophysics Data System (ADS)

Wüthrich, Lorenz; Bliedtner, Marcel; Kathrin Schäfer, Imke; Zech, Jana; Shajari, Fatemeh; Gaar, Dorian; Preusser, Frank; Salazar, Gary; Szidat, Sönke; Zech, Roland

2017-12-01

We present the results of leaf wax analyses (long-chain n-alkanes) from the 6.8 m deep loess sequence of Möhlin, Switzerland, spanning the last ˜ 70 kyr. Leaf waxes are well preserved and occur in sufficient amounts only down to 0.4 m and below 1.8 m depth, so no paleoenvironmental reconstructions can be done for marine isotope stage (MIS) 2. Compound-specific δ2Hwax analyses yielded similar values for late MIS 3 compared to the uppermost samples, indicating that various effects (e.g., more negative values due to lower temperatures, more positive values due to an enriched moisture source) cancel each other out. A pronounced ˜ 30 ‰ shift towards more negative values probably reflects more humid conditions before ˜ 32 ka. Radiocarbon dating of the n-alkanes corroborates the stratigraphic integrity of leaf waxes and their potential for dating loess-paleosol sequences (LPS) back to ˜ 30 ka.

Palæomagnetism of Hawaiian lava flows

USGS Publications Warehouse

Doell, Richard R.; Cox, Allan

1961-01-01

PALÆOMAGNETIC investigations of volcanic rocks extruded in various parts of the world during the past several million years have generally revealed a younger sequence of lava flows magnetized nearly parallel to the field of a theoretical geocentric axial dipole, underlain by a sequence of older flows with exactly the opposite direction of remanent magnetization. A 180-degree reversal of the geomagnetic field, occurring near the middle of the Pleistocene epoch, has been inferred by many workers from such results1–3. This is a preliminary report of an investigation of 755 oriented samples collected from 152 lava flows on the island of Hawaii, selected to represent as many stratigraphic horizons as possible. (Sampling details are indicated in Table 1.) This work was undertaken because Hawaii's numerous thick sequences of lava flows, previously mapped as Pliocene to Historic by Stearns and Macdonald4, and afterwards assigned ages ranging from later Tertiary to Recent, by Macdonald and Davis5, appeared to offer an ideal opportunity to examine the most recent reversal of Earth's field.

Kinderhookian (Lower Mississippian) calcareous rocks of the Howard Pass quadrangle, western Brooks Range: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1995

USGS Publications Warehouse

Dumoulin, Julie A.; Harris, Anita G.

1997-01-01

Calcareous rocks of Kinderhookian (early Early Mississippian) age are widely distributed across the Howard Pass quadrangle in the western Brooks Range. Most occur in the lower part of the Lisburne Group (herein called the Rough Mountain Creek unit) and the upper part of the Endicott Group (Kayak Shale) in two sequences (Key Creek and Aniuk River) of the Endicott Mountains allochthon. Kinderhookian strata are also found in the Kelly River allochthon (Utukok Formation?) and in sections of uncertain stratigraphic affinity and structural level spatially associated with mafic volcanic rocks.Predominant Kinderhookian lithologies in the Lisburne Group are skeletal supportstone (rich in pelmatozoans, bryozoans, and brachiopods) and lesser spiculite; skeletal supportstone and calcarenite are the chief calcareous rock types in the Kayak Shale. Conodont and brachiopod faunas indicate that all of the Rough Mountain Creek unit and much of the Kayak Shale in the study area are of late Kinderhookian age. Lithologic and paleontologic data suggest that Kinderhookian strata in the Howard Pass quadrangle were deposited largely in inner- and middle-shelf settings with normal marine salinity and locally high energy. Overall, calcareous beds in the Rough Mountain Creek unit accumulated in a wider range of environments, less subject to siliciclastic input, than did calcareous beds in the Kayak, and Kinderhookian beds of both units in the Key Creek sequence formed in less diverse, somewhat shallower environments than correlative rocks in the Aniuk River sequence. Lithofacies patterns and contact relations imply that decreased siliciclastic influx, perhaps accompanied by relative sea-level rise, initiated deposition of the Rough Mountain Creek unit; relative sea-level rise and concurrent circulatory restriction most likely ended its deposition.Kinderhookian calcareous rocks in the Howard Pass quadrangle have several implications for middle Paleozoic paleogeography of the western Brooks Range. First, sequences of the Endicott Mountains allochthon that contain the Rough Mountain Creek unit contrast sharply with other sequences included in this allochthon that contain thicker and younger Carboniferous platform carbonate successions. These differences in stratigraphic succession suggest significant shortening within the Endicott Mountains allochthon. Second, Kinderhookian calcareous rocks in the Howard Pass quadrangle may have been a secondary source for carbonate turbidites of the Rim Butte unit (Ipnavik allochthon).

Mio-Pliocene to Pleistocene paleotopographic evolution of Brittany (France) from a sequence stratigraphic analysis: relative influence of tectonics and climate

NASA Astrophysics Data System (ADS)

Brault, N.; Bourquin, S.; Guillocheau, F.; Dabard, M.-P.; Bonnet, S.; Courville, P.; Estéoule-Choux, J.; Stepanoff, F.

2004-01-01

The Mio-Pliocene in Western Europe is a period of major climatic and tectonic change with important topographic consequences. The aim of this paper is to reconstruct these topographic changes (based on sedimentological analysis and sequence stratigraphy) for the Armorican Massif (western France) and to discuss their significance. The Mio-Pliocene sands of the Armorican Massif (Red Sands) are mainly preserved in paleovalleys and are characterized by extensive fluvial sheetflood deposits with low-preservation and by-pass facies. This sedimentological study shows that the Red Sands correspond to three main sedimentary environments: fluvial (alluvial fan, low-sinuosity rivers and braided rivers), estuarine and some rare open marine deposits (marine bioclastic sands: "faluns" of French authors). Two orders of sequences have been correlated across Brittany with one or two minor A/ S cycles comprised within the retrogradational trend of a major cycle. The unconformity at the base of the lower cycle is more marked than the unconformity observed at the top, which corresponds to a re-incision of the paleovalley network. A comparison of the results of the sequence stratigraphy analysis with eustatic variations and tectonic events during the Mio-Pliocene allows (1) to discuss their influence on the evolution of the Armorican Massif and (2) to compare the stratigraphic record with other west-European basins. The unconformity observed at the base of the first minor cycle may be attributed to Serravallian-Tortonian tectonic activity and/or eustatic fall, and the unconformity of the second minor cycle may be attributed to Late Tortonian-Early Messinian tectonic activity. The earlier unconformity is coeval with the development of a "smooth" paleovalley network compared to the jagged present-day relief. A single episode of Mio-Pliocene deformation recorded in Brittany may be dated as Zanclean, thus explaining the lack of the maximum flooding surface except in isolated areas. From this study, five paleogeographic maps were drawn up also indicating paleocurrent directions: three maps for the lower cycle (Tortonian retrogradational trend, Late Tortonian to Early Messinian maximum flooding surface and Messinian progradational trend) and two for the upper cycle (Pliocene retrogradational trend and Piacenzian maximum flooding surface). These maps show (1) the variations of paleocurrent directions during the Mio-Pliocene, (2) the extent of estuarine environments during the maximum flooding intervals and (3) a paleodrainage watershed oriented NNW-SSE following the regional Quessoy/Nort-sur-Erdre Fault during the retrogradational trend of the upper cycle and possibly during the progradational trend of the lower cycle. The present-day morphology of the Armorican Massif is characterized by (1) incised valleys and jagged topography, in contrast with the "smooth" morphology described for Mio-Pliocene times and (2) a main East-West drainage watershed, located to the north, separating rivers flowing towards the English Channel from rivers flowing towards the Atlantic Ocean. The Mio-Pliocene/Pleistocene paleotopographic changes seem to be controlled by climatic effects. These can be related to the change in runoff associated with warmer and wetter conditions during the Mio-Pliocene, which control the river discharge and lead to the development of extensive fluvial sheetflood deposits. Tectonic or eustatic factors exert a second-order control.

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

NASA Astrophysics Data System (ADS)

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

2015-08-01

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

Stratigraphic architecture and depositional history of lower Miocene, Planulina Zone, Southern Louisiana

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

Gates, B.C.; Galloway, W.E.

1988-01-01

The Planulina zone is a wedge of clastic sediment positioned between the Anahuac shale below and the Oakville sandstone interval above. Planulna sediments were deposited on an erosional surface, during a general rise in the sea level, and formed a retrogradational wedge. Within the study area, the Planulina zone consists of two large depositional complexes: the Mud Lake complex in west Cameron Parish, Louisiana, and the East Cameron complex in east Cameron Parish. The lowermost depositional sequence in the East Cameron complex is preserved in a network of submarine canyons that were eroded into the upper slope. Framework sands weremore » deposited in channel systems confined to the axis of the canyons, and the sands are encased in marine shale containing benthonic foraminifera indicative of an upper to middle slope paleoenvironment. Two younger depositional sequences overlie the submarine canyon facies and were deposited by deltaic systems that prograded basinward. A zone of expansion extends east to west through the Planulina interval and is named the ''Planulina flexure.'' The flexure is a large fault located at the relict shelf edge and soles out downdip inn the Anahuac shale. Several thousand feet of sediment downthrown on the flexure is equivalent to several hundred feet upthrown, and the flexure represented the boundary dividing updip deltaic processes from downdip slope processes during the beginning of Planulina deposition. The Planulina depositional history and stratigraphic architecture are directly related to the displacement along the flexure and the structural deformation of the underlying Anahuac shale.« less

Classical seismic sequence stratigraphic interpretation of intraslope basin fill: Deepwater Nigeria

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

Duncan, E.A.

Detailed interpretation of seismic facies patterns performed within the workstation environment provides an observation based methodology for constructing depositional models of turbidite and other reservoir bearing systems expected in deepwater Nigeria. The increased fidelity of the workstation allows greater detail and accuracy to be imposed onto depositional model construction by vastly improving the discrimination of depositional from structural seismic reflection geometries. In deepwater Nigeria interslope basins, depositional cyclicity is clearly indicated by vertical seismic facies successions in the same way as can be recognized in bed thickness trends from outcrop or well log data. The recognition of the seismic faciesmore » successions appears to break the stratigraphy into at least fourth and fifth order scale sequences. Highly {open_quotes}zoomed{close_quotes} instantaneous phase displays enhance the reflection character so that near outcrop scale (resolution less than 50 mters) interpretations of depositional facies can be made. Common seismic facies and geologic interpretation include: (1) low angle erosional surfaces as channel scour or mass wasting detachment; (2) low relief mounds, often in compensation cycle overlapping stacks reflecting compacted channelbelt fill; (3) unidirectional, low angle clinoform sets suggesting laterial accretion within a channel belt or possible contourite mounds; (4) abrupt, shingled blocks illustrating tilted fault blocks of small scale intraformation slumping; and (5) high reflection amplitude and continuous, parallel reflections of pelagic and hemipelagic condensed sections. There are other subtle seismic facies resolvable given the incraesed fidelity of the workstation interpretation. Mapping and translation of these geometries into more robust stratigraphic predictions should have positive impact on exploration and development success.« less

Unifying tephrostratigraphic approaches to redefine major Holocene marker tephras, Mt. Taranaki, New Zealand

NASA Astrophysics Data System (ADS)

Damaschke, M.; Cronin, S. J.; Torres-Orozco, R.; Wallace, R. C.

2017-05-01

In this study, geochemical fingerprinting of glass shards and titanomagnetite phenocrysts was used to match twenty complex pyroclastic deposits from the flanks of Mt. Taranaki to major tephra fall ;marker beds; in medial and distal deposition sites. These correlations hinged upon identifying time-bound compositional changes (a chemostratigraphy) in distal Taranaki tephra-fall sequences preserved in lake and peat sediment records around the volcano. The current work shows that previous soil-stratigraphy based studies led to miscorrelations, because they relied upon radiocarbon dates, a ;counting back; approach, and an underestimate of the number of eruptions that actually occurred in any time frame. The new tephrostratigraphy proposed at Mt. Taranaki resulted from stratigraphic rearranging of several earlier-defined units. Some tephra units are older than previously determined (e.g., Waipuku, Tariki, and Mangatoki; 6 to 9 cal ka BP), while one of the most prominent Taranaki marker tephra deposit, the Korito, is shown to lie stratigraphically above a widespread rhyolitic marker bed from Taupo volcano, the Stent Tephra (also known as unit Q; 4.3 cal ka BP). Pyroclastic tephra deposits previously dated between 6 to 4 cal ka BP at a key tephra section, c. 40 km NE of Mt. Taranaki's summit, were misidentified and are now shown to comprise new marker tephra deposits, including the Kokowai ( 4.7 cal ka BP), which is a prominent marker horizon on the eastern flanks of the volcano. A new local proximal stratigraphy for < 5 cal ka BP tephra units can be well correlated to tephra layers within distal lake and peat sequences, but the differences between the two records indicates an overall larger number of eruptions have occurred at this volcano than previously thought. This study additionally demonstrates the utility of titanomagnetite chemistry for discrimination and correlation of groups or sequences of tephra deposits - even if unique compositions cannot be identified.

Site Effects estimation in the Po Plain area (Northern Italy): correlation between passive geophysical surveys and stratigraphic evidence

NASA Astrophysics Data System (ADS)

Mascandola, Claudia; Massa, Marco; Barani, Simone; Argnani, Andrea; Poggi, Valerio; Martelli, Luca; Albarello, Dario; Pergalani, Floriana; Compagnoni, Massimo; Lovati, Sara

2017-04-01

The recent case of the 2012, Mw 6.1, Emilia seismic sequence (Northern Italy) highlighted the importance of the site effects estimation in the Po Plain, the larger and deeper Italian sedimentary basin. This study, applied on extensive collection of geophysical and geological data in the entire area, allows a macrozonation of the site effects estimation, useful for scientific and applied purpose. In particular, site-response analysis can be performed in defined macrozones, where the geological-geotecnical and geophysical characteristics are homogeneous at macroscale. The collection of the available stratigraphic discontinuities and passive geophysical surveys (single station and array measurements) allowed defining a general macrozonation in terms of amplified frequencies and shear waves velocity (Vs) gradients. The correlation between the obtained geophysical evidence and the known geological information can then be crucial in order to define the most important stratigraphic discontinuities responsible for the local seismic amplification. In particular, ambient vibration data, recorded by all permanent and temporary seismic stations installed in the target region, were collected and then analyzed with the Nakamura technique, to determine the H/V spectral ratio. Moreover, all the available ambient vibration arrays where collected and analyzes to assess the local Vs profile, considering the Rayleigh waves fundamental mode. The Po Plain stratigraphy is defined by regional unconformities (aquifer limits) that have been extensively mapped throughout the basin and by regional geological and structural maps. In general, the H/V results show two ranges of amplified frequencies, both lower than 1 Hz: the former at frequencies lower than about 0.25 Hz and the latter between 0.4 and 1 Hz. The higher frequency range moves from about 0.4 Hz, in the eastern-Adriatic part of the plain, to about 0.8-1.0 Hz in the central and western part. Based on the available seismic array results, this amplification peak seems related to a velocity discontinuity, located in general between 100 m and 300 m of depth, where the Vs exceed 800 m/s. This interface can be ascribed to the seismic bedrock according to the actual seismic code (NTC 2008, Vs> 800 m/s, class A) and may be related to different stratigraphic discontinuities moving from East to West. In order to verify the supposed correspondence between geophysical and geological data, also the H/V ratio where inverted, considering the Sanchez-Sesma method and the nearest array velocity profile as indicative for the target inversion. Finally, an empirical relation between amplified frequencies and depths was calculated, allowing to preliminary map, at regional scale, the most important geological discontinuities for the site effects evaluation. An example of site-specific hazard analysis was performed in correspondence of the INGV seismic station CTL8 in terms of displacement response spectra for periods up to 10 s. The results show that neglecting the effects of the deep discontinuities implies underestimation in hazard evaluation of up to about 49% for MRP of 475 years and about 57% for MRP of 2,475 years, with possible consequences on the design of very tall buildings and large bridges.

Investigating the Age of Mercury's Pyroclastic Deposits

NASA Astrophysics Data System (ADS)

Jozwiak, L. M.; Izenberg, N. R.; Olson, C. L.; Head, J. W.

2018-05-01

We use a combination of stratigraphic and comparative spectral analysis to investigate the ages of Mercury's pyroclastic deposits. We find that pyroclastic deposits have continued to form into Mercury's recent geologic history.

Tephrostratigraphy of the A.D. 79 pyroclastic deposits in perivolcanic areas of Mt. Vesuvio (Italy)

NASA Astrophysics Data System (ADS)

Lirer, Lucio; Munno, Rosalba; Petrosino, Paola; Vinci, Anna

1993-11-01

Correlations between pyroclastic deposits in perivolcanic areas are often complicated by lateral and vertical textural variations linked to very localized depositional effects. In this regard, a detailed sampling of A.D. 79 eruption products has been performed in the main archaeological sites of the perivolcanic area, with the aim of carrying out a grain-size, compositional and geochemical investigation so as to identify the marker layers from different stratigraphic successions and thus reconstruct the eruptive sequence. In order to process the large number of data available, a statistical approach was considered the most suitable. Statistical processing highlighted 14 marker layers among the fall, stratified surge and pyroclastic flow deposits. Furthermore statistical analysis made it possible to correlate pyroclastic flow and surge deposits interbedded with fall, interpreted as a lateral facies variation. Finally, the passage from magmatic to hydromagmatic activity is marked by the deposition of pyroclastic flow, surge and accretionary lapilli-bearing deposits. No transitional phase from magmatic to hydromagmatic activity has been recognized.

The systematic geologic mapping program and a quadrangle-by-quadrangle analysis of time-stratigraphic relations within oil shale-bearing rocks of the Piceance Basin, western Colorado

USGS Publications Warehouse

Johnson, Ronald C.

2012-01-01

During the 1960s, 1970s, and 1980s, the U.S. Geological Survey mapped the entire area underlain by oil shale of the Eocene Green River Formation in the Piceance Basin of western Colorado. The Piceance Basin contains the largest known oil shale deposit in the world, with an estimated 1.53 trillion barrels of oil in place and as much as 400,000 barrels of oil per acre. This report places the sixty-nine 7½-minute geologic quadrangle maps and one 15-minute quadrangle map published during this period into a comprehensive time-stratigraphic framework based on the alternating rich and lean oil shale zones. The quadrangles are placed in their respective regional positions on one large stratigraphic chart so that tracking the various stratigraphic unit names that have been applied can be followed between adjacent quadrangles. Members of the Green River Formation were defined prior to the detailed mapping, and many inconsistencies and correlation problems had to be addressed as mapping progressed. As a result, some of the geologic units that were defined prior to mapping were modified or discarded. The extensive body of geologic data provided by the detailed quadrangle maps contributes to a better understanding of the distribution and characteristics of the oil shale-bearing rocks across the Piceance Basin.

Cretaceous system stratigraphy and shallow gas resources on the Fort Peck reservation, northeastern Montana

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

Monson, L.M.; Lund, D.F.

1991-06-01

Five shallow gas-bearing Cretaceous intervals have been identified on the Fort Peck Reservation of northeastern Montana. They include the Lower Judith River Sandstone and shaly sandstone intervals in the Gammon, Niobrara, Greenhorn, and Mowry Formations, Stratigraphic correlations have been carried from southwestern Saskatchewan through the Bowdoin gas field to the reservation. Sparse yet widely distributed gas shows confirm this relatively untested resource. Each of these gas-bearing intervals belongs to a recognized stratigraphic cycle characterized by thick shales overlain by progradational shaly sandstones and siltstones. The bottom cycle (Skull Creek to Mowry) contains considerable nonmarine deposits, especially within the Muddy Sandstonemore » interval, which is thickly developed in the eastern part of the reservation as a large valley-fill network. Some individual sandstone units are not continuous across the reservation. These, and those that correlate, appear to be related to paleotectonic features defined by northwest-trending lineament zones, and by lineament zone intersections. Northeast-trending paleotectonic elements exert secondary influence on stratigraphic isopachs. Circular tectonic elements, which carry through to basement, also have anomalous stratigraphic expression. Conventional drilling has not been conducive to properly testing the Cretaceous gas potential on the reservation, but empirical well-log analysis suggests that gas can be identified by various crossover techniques. The Judith River Formation did produce gas for field use at East Poplar.« less

A multiproxy reconstruction of the palaeoenvironment and palaeoclimate of the Late Pleistocene in northeastern Iberia: Cova dels Xaragalls, Vimbodí-Poblet, Paratge Natural de Poblet, Catalonia

USGS Publications Warehouse

López-García, Juan Manuel; Blain, Hugues-Alexandre; Bennàsar, Maria; Euba, Itxaso; Bañuls, Sandra; Bischoff, James; López-Ortega, Esther; Saladié, Palmira; Uzquiano, Paloma; Vallverdú, Josep

2012-01-01

The Cova dels Xaragalls is a small open karst system, located in the municipality of Vimbodí-Poblet (Tarragona, Catalonia, NE Spain). It is an important Holocene archaeological site that was inspected in the 1970s but from which little has been published. New excavations starting in 2008 have exposed a deep Late Pleistocene stratigraphical sequence. In this paper, we present for the first time palaeoenvironmental and palaeoclimatic reconstructions of this Late Pleistocene succession on the basis of both the small-vertebrate assemblages and the charcoals. Results from the small-vertebrate associations along the sequence indicate that the landscape had open-woodland habitats in the vicinity of the Cova del Xaragalls, with wet points in the surrounding area. Woodland habitats were dominant throughout the sequence, as evidenced by the abundance of the species Apodemus sylvaticus, but were better developed during warm periods (layers C5 and C8), whereas during cold periods (layers C4 and C3) the environment was slightly more humid in response to higher mean annual precipitation and the opening of the landscape. The charcoal analysis indicates that the woodland surrounding the cave was composed mainly of Pinus (more than 90% was identified as Pinus), but that during the cold period (C3–C4) it incorporated some Quercus ilex/coccifera and Angiosperm indet., probably linked with greater precipitation. Comparisons are made with other long palaeoenvironmental sequences from the northeastern Iberian Peninsula and with global marine isotopic curves, providing a scenario for the palaeoclimatic and palaeoenvironmental changes that occurred during the Late Pleistocene in the woodland areas surrounding the Cova dels Xaragalls.

Lithological and Petrographic Analyses of Carbonates and Sandstones From the Southern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Garcia-Avendaño, A.; Urrutia-Fucugauchi, J.

2012-04-01

We present results of sedimentological and petrological studies of drill cores from the Bay of Campeche in the southern Gulf of Mexico. Based on reports on drill cores obtained from oil exploratory wells in the Cantarell Complex located 80 kilometres offshore in the Bay of Campeche and studies related to regional geology composite simplified stratigraphic columns for offshore Campeche region have been constructed up to depths of approximately 5000 m. The stratigraphic column is formed by a thick sediment sequence of Middle Jurassic age (evaporites, Callovian), Late Jurassic (terrigenous, calcareous clays and calcareous layers), Lower Cretaceous (carbonates), Upper Cretaceous-Paleogene (calcareous breccias), Paleogene-Neogene (terrigenous-carbonates intercalations) and Quaternary (terrigenous). The core samples studied come from wells in the Sihil and Akal fields in Cantarell. Analysis of reports on lithological descriptions indicates that these wells sample dolomitized sedimentary breccias from the Upper Cretaceous-Paleocene and fine-grained sandstones from the Late Jurassic Tithonian, respectively. Based on results of petrographic studies, the texture, cementing material and porosity of the units have been documented. The thin sections for carbonates were classified based on their texture according to Dunham (1962) for carbonate rocks, classified according to their components using the ternary diagrams of Folk (1974). Percentages refer to the data presented in tables, which were obtained by point-counting technique (with a total 250). Photomicrographs of scanning electron microscope (SEM) provide magnification for easy documentation of crystalline arrangements and description of micro-porous for different types of carbonates such as dolomite, in addition to the morphology of authigenic clays. Results of these studies and previous works in the area permit characterization of diagenetic processes of the carbonate sediments in the Campeche Bay, and provide information related to oil maturation, storage and potential flow in the Cantarell reservoirs.

3D architecture modeling of reservoir compartments in a Shingled Turbidite Reservoir using high-resolution seismic data and sparse well control, example from Mars {open_quotes}Pink{close_quotes} reservoir, Mississippi Canyon Area, Gulf of Mexico

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

Chapin, M.A.; Mahaffie, M.J.; Tiller, G.M.

1996-12-31

Economics of most deep-water development projects require large reservoir volumes to be drained with relatively few wells. The presence of reservoir compartments must therefore be detected and planned for in a pre-development stage. We have used 3-D seismic data to constrain large-scale, deterministic reservoir bodies in a 3-D architecture model of Pliocene-turbidite sands of the {open_quotes}E{close_quotes} or {open_quotes}Pink{close_quotes} reservoir, Prospect Mars, Mississippi Canyon Areas 763 and 807, Gulf of Mexico. Reservoir compartmentalization is influenced by stratigraphic shingling, which in turn is caused by low accommodation space predentin the upper portion of a ponded seismic sequence within a salt withdrawal mini-basin.more » The accumulation is limited by updip onlap onto a condensed section marl, and by lateral truncation by a large scale submarine erosion surface. Compartments were suggested by RFT pressure variations and by geochemical analysis of RFT fluid samples. A geological interpretation derived from high-resolution 3-D seismic and three wells was linked to 3-D architecture models through seismic inversion, resulting in a reservoir all available data. Distinguishing subtle stratigraphical shingles from faults was accomplished by detailed, loop-level mapping, and was important to characterize the different types of reservoir compartments. Seismic inversion was used to detune the seismic amplitude, adjust sandbody thickness, and update the rock properties. Recent development wells confirm the architectural style identified. This modeling project illustrates how high-quality seismic data and architecture models can be combined in a pre-development phase of a prospect, in order to optimize well placement.« less

3D architecture modeling of reservoir compartments in a Shingled Turbidite Reservoir using high-resolution seismic data and sparse well control, example from Mars [open quotes]Pink[close quotes] reservoir, Mississippi Canyon Area, Gulf of Mexico

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

Chapin, M.A.; Mahaffie, M.J.; Tiller, G.M.

1996-01-01

Economics of most deep-water development projects require large reservoir volumes to be drained with relatively few wells. The presence of reservoir compartments must therefore be detected and planned for in a pre-development stage. We have used 3-D seismic data to constrain large-scale, deterministic reservoir bodies in a 3-D architecture model of Pliocene-turbidite sands of the [open quotes]E[close quotes] or [open quotes]Pink[close quotes] reservoir, Prospect Mars, Mississippi Canyon Areas 763 and 807, Gulf of Mexico. Reservoir compartmentalization is influenced by stratigraphic shingling, which in turn is caused by low accommodation space predentin the upper portion of a ponded seismic sequence withinmore » a salt withdrawal mini-basin. The accumulation is limited by updip onlap onto a condensed section marl, and by lateral truncation by a large scale submarine erosion surface. Compartments were suggested by RFT pressure variations and by geochemical analysis of RFT fluid samples. A geological interpretation derived from high-resolution 3-D seismic and three wells was linked to 3-D architecture models through seismic inversion, resulting in a reservoir all available data. Distinguishing subtle stratigraphical shingles from faults was accomplished by detailed, loop-level mapping, and was important to characterize the different types of reservoir compartments. Seismic inversion was used to detune the seismic amplitude, adjust sandbody thickness, and update the rock properties. Recent development wells confirm the architectural style identified. This modeling project illustrates how high-quality seismic data and architecture models can be combined in a pre-development phase of a prospect, in order to optimize well placement.« less

Provenance implications of Th U Pb electron microprobe ages from detrital monazite in the Carboniferous Upper Silesia Coal Basin, Poland

NASA Astrophysics Data System (ADS)

Kusiak, Monika Agnieszka; Kędzior, Artur; Paszkowski, Mariusz; Suzuki, Kazuhiro; González-Álvarez, Ignacio; Wajsprych, Bolesław; Doktor, Marek

2006-05-01

This paper reports the results of CHIME (chemical Th-U-Pb isochron method) dating of detrital monazites from Carboniferous sandstones in the Upper Silesia Coal Basin (USCB). A total of 4739 spots on 863 monazite grains were analyzed from samples of sandstone derived from six stratigraphic units in the sedimentary sequence. Age distributions were identified in detrital monazites from the USCB sequence and correlated with specific dated domains in potential source areas. Most monazites in all samples yielded ca. 300-320 Ma (Variscan) ages; however, eo-Variscan, Caledonian and Cadomian ages were also obtained. The predominant ages are comparable to reported ages of certain tectonostratigraphic domains in the polyorogenic Bohemian Massif (BM), which suggests that various crystalline lithologies in the BM were the dominant sources of USCB sediments.

Modeling Stratigraphic Architecture of Deep-water Deposits Using a Small Unmanned Aircraft: Neogene Thin-bedded Turbidites, East Coast Basin, New Zealand

NASA Astrophysics Data System (ADS)

Nieminski, N.; Graham, S. A.

2014-12-01

One of the outstanding challenges of field geology is inaccessibility of exposure. The ability to view and characterize outcrops that are difficult to study from the ground is greatly improved by aerial investigation. Detailed stratigraphic architecture of such exposures is best addressed by using advances and availability of small unmanned aircraft systems (sUAS) that can safely navigate from high-altitude overviews of study areas to within a meter of the exposure of interest. High-resolution photographs acquired at various elevations and azimuths by sUAS are then used to convert field measurements to digital representations in three-dimensions at a fine scale. Photogrammetric software is used to capture complex, detailed topography by creating digital surface models with a range imaging technique that estimates three-dimensional structures from two-dimensional image sequences. The digital surface model is overlain by detailed, high-resolution photography. Pairing sUAS technology with readily available photogrammetry software that requires little processing time and resources offers a revolutionary and cost-effective methodology for geoscientists to investigate and quantify stratigraphic and structural complexity of field studies from the convenience of the office. These methods of imaging and modeling remote outcrops are demonstrated in the East Coast Basin, New Zealand, where wave-cut platform exposures of Miocene deep-water deposits offer a unique opportunity to investigate the flow processes and resulting characteristics of thin-bedded turbidite deposits. Stratigraphic architecture of wavecut platform and vertically-dipping exposures of these thin-bedded turbidites is investigated with sUAS coupled with Structure from Motion (SfM) photogrammetry software. This approach allows the geometric and spatial variation of deep-water architecture to be characterized continuously along 2,000 meters of lateral exposure, as well as to measure and quantify cyclic variations in thin-bedded turbidites at centimeter scale. Results yield a spatial and temporal understanding of a deep-water depositional system at a scale that was previously unattainable using conventional field geology techniques, and a virtual outcrop that can be used for classroom education.

Exploring coral reef responses to millennial-scale climatic forcings: insights from the 1-D numerical tool pyReef-Core v1.0

NASA Astrophysics Data System (ADS)

Salles, Tristan; Pall, Jodie; Webster, Jody M.; Dechnik, Belinda

2018-06-01

Assemblages of corals characterise specific reef biozones and the environmental conditions that change spatially across a reef and with depth. Drill cores through fossil reefs record the time and depth distribution of assemblages, which captures a partial history of the vertical growth response of reefs to changing palaeoenvironmental conditions. The effects of environmental factors on reef growth are well understood on ecological timescales but are poorly constrained at centennial to geological timescales. pyReef-Core is a stratigraphic forward model designed to solve the problem of unobservable environmental processes controlling vertical reef development by simulating the physical, biological and sedimentological processes that determine vertical assemblage changes in drill cores. It models the stratigraphic development of coral reefs at centennial to millennial timescales under environmental forcing conditions including accommodation (relative sea-level upward growth), oceanic variability (flow speed, nutrients, pH and temperature), sediment input and tectonics. It also simulates competitive coral assemblage interactions using the generalised Lotka-Volterra system of equations (GLVEs) and can be used to infer the influence of environmental conditions on the zonation and vertical accretion and stratigraphic succession of coral assemblages over decadal timescales and greater. The tool can quantitatively test carbonate platform development under the influence of ecological and environmental processes and efficiently interpret vertical growth and karstification patterns observed in drill cores. We provide two realistic case studies illustrating the basic capabilities of the model and use it to reconstruct (1) the Holocene history (from 8500 years to present) of coral community responses to environmental changes and (2) the evolution of an idealised coral reef core since the last interglacial (from 140 000 years to present) under the influence of sea-level change, subsidence and karstification. We find that the model reproduces the details of the formation of existing coral reef stratigraphic sequences both in terms of assemblages succession, accretion rates and depositional thicknesses. It can be applied to estimate the impact of changing environmental conditions on growth rates and patterns under many different settings and initial conditions.

Paleo-ocean environments before and after the Ordovician glaciation and the correlation with heterogeneous marine black shale: a stratigraphic case study of Wufeng-Longmaxi formation in Fuling, Sichuan basin, SW China

NASA Astrophysics Data System (ADS)

Lu, Yangbo; Hao, Fang; Lu, Yongchao

2017-04-01

The discovery of Fuling gas field in the Sichuan basin led China shale gas exploration to an unprecedented boom. The most important shale gas plays are the upper Ordovician Wufeng formation and Lower Silurian Longmaxi formation which demonstrate intriguing characteristics which are comprising of stable regional distribution, high abundance of organic matter, high thermal maturity and high brittle mineral content etc. As the Ordovician-Silurian transition was a critical interval in Earth's history marked by dramatic climatic, oceanic, and biological turnovers; these two advantageous organic rich shale deposited before and after Hirnantian glaciation are showing differences in many aspects. In this study, the stratigraphy and lithofacies within the stratigraphy framework of the upper Ordovician Wufeng formation and Lower Silurian Longmaxi formation in Fuling were quantitatively analyzed based on outcrops, cores, well logs data, and geochemical proxies. A total of three third-order sequences were divided based on the recognition of four third-order boundaries. The Wufeng Formation is equivalent to a third-order sequence and is subdivided into a transgressive system tract (TST) (black shale of lower Wufeng Formation) and a highstand system tract (HST) (Guanyinqiao Member of upper Wufeng Formation). Long-1 Member is equivalent to a third-order sequence and is subdivided into a TST, an early highstand system tract (EHST) and a late highstand system tract (LHST); Long-2 and Long-3 Member are combined to be one third-order sequence and is subdivided into a lowstand system tract (LST), a TST and a HST. Sequence development and sedimentary environment characteristics were analyzed within each system tract unit. TOC% was correlated to V/Cr and EF-Ni respectively within each system tract unit, suggesting paleoproductivity and water redox condition are the main controlling factors of organic enrichment and its preservation. The heterogeneity in shale lithofacies throughout the stratigraphic frame work reflects the vertical evolution of the paleo-climate and paleo-ocean environment across the Ordovician-Silurian transition. We suggest that the high primary productivity of Wufeng formation was due to the boom of diatom triggered by large scale coverage of volcanic ash before Hirnantian glaciation. Marine anoxia may have been a kill mechanism that cause the mass extinction of marine macro-organism during the glacial period. And the up sequence TOC deterioration of Longmaxi formation is likely subjected to influence of ocean bottom flow and slow recovery of marine organism after the glaciation.

Expanded U.S. mid-Atlantic Margin Deep-Water Allostratigraphy; Bottom-Current Controls on Margin Evolution

NASA Astrophysics Data System (ADS)

Gibson, J. C.; Miller, N. C.; Hutchinson, D. R.; Ten Brink, U. S.; Mountain, G. S.; Chaytor, J. D.; Shillington, D. J.

2017-12-01

There is a long history of seismic stratigraphic interpretation/analysis of the sedimentary sequence along the U.S. mid-Atlantic Margin (MAM). Here we expand the allostratigraphic (unconformity-bound) framework from the outer continental shelf to the Hatteras Abyssal Plain by correlating recently acquired 2D multi-channel seismic reflection data with existing drill sites and legacy 2D seismic data collected over the past 42 yrs. The new 2D post-stack Kirchhoff time migrated seismic data were acquired using R/V Marcus G. Langseth in 2014-2015 during USGS ECS surveys MGL1407 & MGL1506 and NSF-funded ENAM-CSE survey MGL1408. We map six seismic horizons along 1.5x104 km of 2D data and tie each to stratigraphic unconformities sampled at DSDP site 603 (lower rise). From shallow to deep they are: (1) M2, latest Miocene; (2) X, middle Miocene; (3) Au, late Oligocene; (4) A*, Late Cretaceous; (5) Km, early Late Cretaceous; and (6) Beta, middle Early Cretaceous. The horizons were converted to depth (mbsl) using high-resolution interval velocity models generated for each 2D survey line and isopachs were produced using the depth-converted stratigraphic framework for each allostratigraphic unit. The time-to-depth function was confirmed to be within 5% of drilling results at DSDP Sites 603 and nearby 105. Additionally, we tie horizon Au to upper-slope ODP Sites 902 & 1073, and trace it to the outer shelf. Interpretation of the framework and resulting isopachs show total sediment thickness uniformly decreasing seaward from the shelf edge, and overall thickening to the south. Regional depositional trends display a combination of both down slope and along slope processes (e.g. mass wasting, submarine fan formation, contourite and sediment drift deposits). The unit bound by horizons Au & Beta confirms pervasive excavation from the mid-slope to the continental rise and across the central and southern MAM (from New Jersey to North Carolina). How the excavated sediments were redistributed is unknown, but the magnitude and spatial extent of the bottom-current erosion are well constrained by our study. The southern MAM has experienced a number of significant mass wasting events spanning the Miocene-Pleistocene, suggesting that bottom-current erosion may have played a role in undercutting, and therefore over-steepening the slope.

Vombat: an open source proof-of-concept for the use of Digital outcrop models as reference frame for stratigraphic observations

NASA Astrophysics Data System (ADS)

Penasa, Luca; Franceschi, Marco; Preto, Nereo; Girardeau-Montaut, Daniel

2015-04-01

Three-dimensional Virtual Outcrop Models (VOMs), often produced using terrestrial laser scanning or photogrammetry, have become popular in the Geosciences. The main feature of a VOM is that it allows for a quantification of the 3D geometry and/or distribution of geologic features that range from rock properties to structural elements. This actually generated much of the interest in VOMs by the oil and gas industry. The potential importance of a VOM in stratigraphy, however, does not seems completely disclosed yet. Indeed outcrops are the primary sources of data for a number of stratigraphic studies (e.g. palaeontology, sedimentology, cyclostratigraphy, geochemistry...). All the observations are typically reported on stratigraphic logs which constitute an idealized representation of the stratigraphic series, drawn by the researcher on the basis of the features that has to be highlighted. The observations are localized by means of manual measurements and a certain amount of subjectivity in log drawing is involved. These facts can prevent the log from being properly pinned to the real outcrop. Moreover, the integration of stratigraphic logs made by different researchers studying the same outcrop may be difficult. The exposure conditions of outcrops can change through time, to the point that they can become unaccessible or even be destroyed. In such a case, linking the stratigraphic log to its physical counterpart becomes impossible. This can be particularly relevant when a classical outcrop or even a GSSP is considered. A VOM may prove useful to tackle these issues, by providing a more objective stratigraphic reference for measurements and by preserving an outcrop through time as a visual representation, thus permitting reference and accurate comparison between observations made through time. Finally, a VOM itself may contain relevant stratigraphic information (e.g. scalar fields associated with the point cloud as intensity, rgb data or hyperspectral information from passive remote sensing devices). This information requires to be merged with geological data collected in the field, in a consistent and reproducible way. We present Vombat, a proof-of-concept of open-source software to illustrate some of the possibilities in terms of information storage, visualization and exploitation of outcrop stratigraphic information. Our solution integrates with CloudCompare, a software that permits to visualize and edit point clouds. A dedicated algorithm estimates stratigraphic attitudes from point cloud data, without the need of exposed planar bedding surfaces. These attitudes can be used to define a virtual stratigraphic section. Composite sections can then be realized defining stratigraphic constraints between different reference frames. Any observation can be displayed in a stratigraphic framework that is directly generated from a VOM. The virtual outcrop, the samples and the stratigraphic reference frames can be saved into an XML file. In the future, the adoption of a standard format (e.g. GeoSciML) will permit easier exchange of stratigraphic data among researchers. The software constitutes a first step towards the full exploitation of VOMs in stratigraphy, is stored at http://github.com/luca-penasa/vombat‏ and is open source. Comments and suggestions are most welcome and will help focusing and refining the software and its tools.

Valles Marineris Basin Beds: a Complex Story

NASA Technical Reports Server (NTRS)

Lucchitta, B. K.

1985-01-01

High resolution stereoimages of the central Valles Marineris enabled detailed geologic mapping on Ophir and Candor Chasmata. Abundant light colored deposits, both layered and massive, fill the chasmata in this region. Units within these deposits were identified by their erosional characteristics and superposition and cross cutting relations. The Valles Marineris beds reflect a history of repeated faulting, volcanic eruptions, and deposition and erosion, resulting in stratigraphic sequences with several unconformities. Because of the preponderance of apparent volcanic deposits inside the troughs, the chasmata may not be simple grabens, but rather giant volcano tectonic depressions. Major events in chasmata development are examined.

Constraining controls on carbonate sequences with high-resolution chronostratigraphy: Upper Miocene, Cabo de Gata region, SE Spain

USGS Publications Warehouse

Montgomery, P.; Farr, M.R.; Franseen, E.K.; Goldstein, R.H.

2001-01-01

A high-resolution chronostratigraphy has been developed for Miocene shallow-water carbonate strata in the Cabo de Gata region of SE Spain for evaluation of local, regional and global factors that controlled platform architecture prior to and during the Messinian salinity crisis. Paleomagnetic data were collected from strata at three localities. Mean natural remanent magnetization (NRM) ranges between 1.53 ?? 10-8 and 5.2 ?? 10-3 Am2/kg. Incremental thermal and alternating field demagnetization isolated the characteristic remanent magnetization (ChRM). Rock magnetic studies show that the dominant magnetic mineral is magnetite, but mixtures of magnetite and hematite occur. A composite chronostratigraphy was derived from five stratigraphic sections. Regional stratigraphic data, biostratigraphic data, and an 40Ar/39Ar date of 8.5 ?? 0.1 Ma, for an interbedded volcanic flow, place the strata in geomagnetic polarity Chrons C4r to C3r. Sequence-stratigraphic and diagenetic evidence indicate a major unconformity at the base of depositional sequence (DS)3 that contains a prograding reef complex, suggesting that approximately 250 000 yr of record (Subchrons C3Br.2r to 3Br.1r) are missing near the Messinian-Tortonian boundary. Correlation to the GPTS shows that the studied strata represent five third- to fourth-order DSs. Basal units are temperate to subtropical ramps (DS1A, DS1B, DS2); these are overlain by subtropical to tropical reefal platforms (DS3), which are capped by subtropical to tropical cyclic carbonates (Terminal Carbonate Complex, TCC). Correlation of the Cabo de Gata record to the Melilla area of Morocco, and the Sorbas basin of Spain indicate that early - Late Tortonian ramp strata from these areas are partially time-equivalent. Similar strata are extensively developed in the Western Mediterranean and likely were influenced by a cool climate or influx of nutrients during an overall rise in global sea-level. After ramp deposition, a sequence boundary (SB3) in Cabo de Gata correlates with a sequence boundary in Morocco and a published third-order eustatic fall suggesting at least a partial eustatic control for the sequence boundary. Coral reefs began to develop earlier in Cabo de Gata than at Melilla or Sorbas, arguing for local factors affecting this major environmental transition. Later Messinian reefs (DS3) from all areas are time-equivalent, suggesting a regional or global control on their formation. Some Halimeda-rich horizons in the Western Mediterranean are not time-equivalent event strata as hypothesized by others. Correlation of the relative sea-level curve for the fringing reef complex (DS3) with a published eustatic curve suggests at least a partial third-order global eustatic control for the highstand part of the sequence. Downstepping DS3 reefs and initial subaerial exposure of earlier DS3 reef strata approximately correlate with initiation of a series of subaerial unconformities in the South Pacific. The longer-term relative fall in sea-level during DS3 downstepping reef progradation does not correlate with a published third-order eustatic fall. Eustatic sea-level fluctuations may have been associated with initiation of the Mediterranean Messinian salinity crisis, but the longer-term fall may have been linked to tectonic uplift in the Mediterranean region. Widespread distribution of 'TCC-style' cycles of approximately the same age suggests a regional (Western Mediterranean) or global control on sea-level change responsible for TCC cycles. In addition, four subaerial exposure-capped TCC cycles may correlate with similar subaerial unconformities in the South Pacific, suggesting at least a partial eustatic control on TCC cyclicity. The high rates of relative sea-level change needed to generate a minimum of 25-30 m sea-level changes associated with each cycle are consistent with glacio-eustacy along with rapid evaporitic drawdown in the Mediterranean. ?? 2001 Elsevier Science B.V. All rights reserved.

Quantifying assemblage turnover and species contributions at ecologic boundaries.

PubMed

Hayek, Lee-Ann C; Wilson, Brent

2013-01-01

Not all boundaries, whether stratigraphical or geographical, are marked by species-level changes in community composition. For example, paleodata for some sites do not show readily discernible glacial-interglacial contrasts. Rather, the proportional abundances of species can vary subtly between glacials and interglacials. This paper presents a simple quantitative measure of assemblage turnover (assemblage turnover index, ATI) that uses changes in species' proportional abundances to identify intervals of community change. A second, functionally-related index (conditioned-on-boundary index, CoBI) identifies species contributions to the total assemblage turnover. With these measures we examine benthonic foraminiferal assemblages to assess glacial/interglacial contrasts at abyssal depths. Our results indicate that these measures, ATI and CoBI, have potential as sequence stratigraphic tools in abyssal depth deposits. Many peaks in the set of values of ATI coincide with terminations at the end of glaciations and delineate peak-bounded ATI intervals (PATIs) separated by boundaries that approximate to glacial terminations and to transgressions at neritic depths. These measures, however, can be used to evaluate the assemblage turnover and composition at any defined ecological or paleoecological boundary. The section used is from Ocean Drilling Program (OPD) Hole 994C, drilled on the Blake Ridge, offshore SE USA.

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

NASA Astrophysics Data System (ADS)

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

2007-05-01

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

Potentiometric-surface map of the Wyodak-Anderson Coal Bed, Powder River Structural Basin, Wyoming, 1973-84

USGS Publications Warehouse

Daddow, Pamela B.

1986-01-01

Previous water level maps of shallow aquifers in the Powder River structural basin in Wyoming were based on water levels from wells completed in different stratigraphic intervals within thick sequences of sedimentary rocks. A potentiometric surface using water levels from a single aquifer had never been mapped throughout the basin. The sandstone aquifers in the Fort Union Formation of Paleocene age and the Wasatch Formation of Eocene age are discontinuous and lenticular, and do not extend even short distances. Coal aquifers are more continuous and the Wyodak-Anderson coal bed, in the Fort Union Formation, has been mapped in much of the Powder River structural basin in Wyoming. Water level altitudes in the Wyodak-Anderson coal bed and other stratigraphically equivalent coal beds were mapped to determine if they represent a continuous potentiometric surface in the Powder River structural basin. The potentiometric surface, except in the vicinity of the Wyodak mine east of Gillette, represents a premining condition as it was based on water level measurements made during 1973-84 that were not significantly affected by mining. The map was prepared in cooperation with the U.S. Bureau of Land Management. (Lantz-PTT)

Quantifying Assemblage Turnover and Species Contributions at Ecologic Boundaries

PubMed Central

Hayek, Lee-Ann C.; Wilson, Brent

2013-01-01

Not all boundaries, whether stratigraphical or geographical, are marked by species-level changes in community composition. For example, paleodata for some sites do not show readily discernible glacial-interglacial contrasts. Rather, the proportional abundances of species can vary subtly between glacials and interglacials. This paper presents a simple quantitative measure of assemblage turnover (assemblage turnover index, ATI) that uses changes in species' proportional abundances to identify intervals of community change. A second, functionally-related index (conditioned-on-boundary index, CoBI) identifies species contributions to the total assemblage turnover. With these measures we examine benthonic foraminiferal assemblages to assess glacial/interglacial contrasts at abyssal depths. Our results indicate that these measures, ATI and CoBI, have potential as sequence stratigraphic tools in abyssal depth deposits. Many peaks in the set of values of ATI coincide with terminations at the end of glaciations and delineate peak-bounded ATI intervals (PATIs) separated by boundaries that approximate to glacial terminations and to transgressions at neritic depths. These measures, however, can be used to evaluate the assemblage turnover and composition at any defined ecological or paleoecological boundary. The section used is from Ocean Drilling Program (OPD) Hole 994C, drilled on the Blake Ridge, offshore SE USA. PMID:24130679

Correlating carbon and oxygen isotope events in early to middle Miocene shallow marine carbonates in the Mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy

PubMed Central

Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias

2015-01-01

Abstract During the Miocene prominent oxygen isotope events (Mi‐events) reflect major changes in glaciation, while carbonate isotope maxima (CM‐events) reflect changes in organic carbon burial, particularly during the Monterey carbon isotope excursion. However, despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions. The Decontra section on the Maiella Platform (central Apennines, Italy), however, allows to resolve them for the first time in such a setting during the early to middle Miocene. The present study improves the stratigraphic resolution of parts of the Decontra section via orbital tuning of high‐resolution gamma ray (GR) and magnetic susceptibility data to the 405 kyr eccentricity metronome. The tuning allows, within the established biostratigraphic, sequence stratigraphic, and isotope stratigraphic frameworks, a precise correlation of the Decontra section with pelagic records of the Mediterranean region, as well as the global paleoclimatic record and the global sea level curve. Spectral series analyses of GR data further indicate that the 405 kyr orbital cycle is particularly well preserved during the Monterey Event. Since GR is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the Decontra section, it follows the same long‐term orbital pacing as observed in the carbon isotope records. The 405 kyr GR beat is thus correlated with the carbon isotope maxima observed during the Monterey Event. Finally, the Mi‐events can now be recognized in the δ18O record and coincide with plankton‐rich, siliceous, or phosphatic horizons in the lithology of the section. PMID:27546980

Correlating carbon and oxygen isotope events in early to middle Miocene shallow marine carbonates in the Mediterranean region using orbitally tuned chemostratigraphy and lithostratigraphy

NASA Astrophysics Data System (ADS)

Auer, Gerald; Piller, Werner E.; Reuter, Markus; Harzhauser, Mathias

2015-04-01

During the Miocene prominent oxygen isotope events (Mi-events) reflect major changes in glaciation, while carbonate isotope maxima (CM-events) reflect changes in organic carbon burial, particularly during the Monterey carbon isotope excursion. However, despite their importance to the global climate history they have never been recorded in shallow marine carbonate successions. The Decontra section on the Maiella Platform (central Apennines, Italy), however, allows to resolve them for the first time in such a setting during the early to middle Miocene. The present study improves the stratigraphic resolution of parts of the Decontra section via orbital tuning of high-resolution gamma ray (GR) and magnetic susceptibility data to the 405 kyr eccentricity metronome. The tuning allows, within the established biostratigraphic, sequence stratigraphic, and isotope stratigraphic frameworks, a precise correlation of the Decontra section with pelagic records of the Mediterranean region, as well as the global paleoclimatic record and the global sea level curve. Spectral series analyses of GR data further indicate that the 405 kyr orbital cycle is particularly well preserved during the Monterey Event. Since GR is a direct proxy for authigenic uranium precipitation during increased burial of organic carbon in the Decontra section, it follows the same long-term orbital pacing as observed in the carbon isotope records. The 405 kyr GR beat is thus correlated with the carbon isotope maxima observed during the Monterey Event. Finally, the Mi-events can now be recognized in the δ18O record and coincide with plankton-rich, siliceous, or phosphatic horizons in the lithology of the section.

The Miocene Topanga Group of Southern California - A 100-Year History of Changes in Stratigraphic Nomenclature

USGS Publications Warehouse

Campbell, Russell H.; McCulloh, Thane H.; Vedder, John G.

2007-01-01

A review of selected literature summarizes the origin and chronology of changes in usage of 'Topanga' in the Miocene stratigraphic nomenclature of the Los Angeles Basin and adjacent areas in southern California. The review was done to summarize and reconcile some differences in Miocene stratigraphic nomenclature as applied to geologic map compilations of the Santa Ana (Morton, 2004), San Bernardino (Morton and Miller, 2003), Long Beach (Saucedo and others, 2003) and Los Angeles (Yerkes and Campbell, 2005) 30' x 60' quadrangles, all of which are products of the cooperative (California Geological Survey-U.S. Geological Survey) Southern California Areal Mapping Project (SCAMP). The deposition of the Topanga Group spans about 6 my (from as old as about 18 ma to as young as about 12 ma), and the sequence of included strata records changes in provenance and depositional environments that are contemporaneous with part of a major Miocene tectonic episode in southern California -- the 'basin-inception phase' in the evolution of the Neogene Los Angeles basin (Yerkes and others, 1965). The area of Topanga deposition extends to the southern, eastern, northern, and northwestern sides of the Los Angeles basin, as well as the southern part of the eastern Ventura Basin. Topanga beds are inferred to underlie the thick upper Miocene and Pliocene deposits of the central Los Angeles Basin and the southern part of the eastern Ventura Basin; however, they have been reached by drilling only in marginal areas, where the overlying deposits are relatively thin. Post-Topanga strata were deposited in more-restricted areas of rapid subsidence. Selected papers are summarized as they relate to the Topanga nomenclature, and are presented in chronological order.

New seismo-stratigraphic and marine magnetic data of the Gulf of Pozzuoli (Naples Bay, Tyrrhenian Sea, Italy): inferences for the tectonic and magmatic events of the Phlegrean Fields volcanic complex (Campania)

NASA Astrophysics Data System (ADS)

Aiello, Gemma; Marsella, Ennio; Fiore, Vincenzo Di

2012-06-01

A detailed reconstruction of the stratigraphic and tectonic setting of the Gulf of Pozzuoli (Naples Bay) is provided on the basis of newly acquired single channel seismic profiles coupled with already recorded marine magnetics gathering the volcanic nature of some seismic units. Inferences for the tectonic and magmatic setting of the Phlegrean Fields volcanic complex, a volcanic district surrounding the western part of the Gulf of Naples, where volcanism has been active since at least 50 ka, are also discussed. The Gulf of Pozzuoli represents the submerged border of the Phlegrean caldera, resulting from the volcano-tectonic collapse induced from the pyroclastic flow deposits of the Campanian Ignimbrite (35 ka). Several morpho-depositional units have been identified, i.e., the inner continental shelf, the central basin, the submerged volcanic banks and the outer continental shelf. The stratigraphic relationships between the Quaternary volcanic units related to the offshore caldera border and the overlying deposits of the Late Quaternary depositional sequence in the Gulf of Pozzuoli have been highlighted. Fourteen main seismic units, both volcanic and sedimentary, tectonically controlled due to contemporaneous folding and normal faulting have been revealed by geological interpretation. Volcanic dykes, characterized by acoustically transparent sub-vertical bodies, locally bounded by normal faults, testify to the magma uprising in correspondence with extensional structures. A large field of tuff cones interlayered with marine deposits off the island of Nisida, on the western rim of the gulf, is related to the emplacement of the Neapolitan Yellow Tuff deposits. A thick volcanic unit, exposed over a large area off the Capo Miseno volcanic edifice is connected with the Bacoli-Isola Pennata-Capo Miseno yellow tuffs, cropping out in the northern Phlegrean Fields.

Application of ground penetrating radar for identification of washover deposits and other stratigraphic features: Assateague Island, MD

USGS Publications Warehouse

Zaremba, Nicholas; Smith, Christopher G.; Bernier, Julie C.; Forde, Arnell S.

2016-01-01

A combination of ground penetrating radar (GPR) data, core data, and aerial photographs were analyzed to better understand the evolution of two portions of Assateague Island, Maryland. The focus of the study was to investigate the applicability of using GPR data to image washover deposits in the stratigraphic record. High amplitude reflections observed in two shore-perpendicular GPR profiles were correlated to shallow (<1 m) lithologic contacts observed in sediment cores. At these contacts, deposits consisting primarily of quartz sand overlie sediments with organic matter that include degraded plant root or stem material. The underlying organic matter likely represents the vegetated portion of the barrier island that was buried by washover fans deposited during hurricanes Irene (2011) and Sandy (2012), as indicated in high-resolution aerial photographs. The GPR data were able to delineate the washover deposits from the underlying stratigraphic unit; however, the radar data did not resolve finer structures necessary to definitively differentiate washover facies from other sand-rich deposits (e.g., flood-tide deltas and dunes). Other GPR profiles contain reflections that likely correlate to geomorphic features like tidal channels and vegetated zones observed in historical aerial imagery. Burial of these features by overwash fluxes were observed in the aerial imagery and thus the resulting radar sequence is largely interpreted as washover deposits. Deeper, channel-like features that have been infilled were also observed in shore-parallel profiles and these features coincide with scour channels observed in the 1966 aerial photography. Additional sedimentological data are required to determine what role overwash played in the in-filling of these features.

Integrating remote sensing and subsurface geological data to characterize a tidally-influenced paleodrainage from the mid-late Holocene succession of the Po Delta Plain (Italy)

NASA Astrophysics Data System (ADS)

Giacomelli, Serena; Rossi, Veronica; Amorosi, Alessandro; Bruno, Luigi; Campo, Bruno; Ciampalini, Andrea; Civa, Andrea; de Souza Filho, Roberto Carlos; Sgavetti, Maria

2017-04-01

A tidally-influenced, mid-late Holocene paleodrainage system from the Po Delta Plain (N Adriatic Sea, Italy) is reconstructed coupling remote sensing (RS) and subsurface geological data. Optical satellite images, DTM LiDAR, soil reflectance spectral features and core stratigraphy were combined in a GIS environment following a fully integrated methodological approach. The stratigraphic significance of RS-derived data (traces) was defined in terms of both depositional facies and depth, furnishing new insights on the role of RS in reconstructing the recent evolution of paleodrainages in coastal-deltaic settings. Sixteen images from Landsat 7 ETM+ (Enhanced Thematic Mapper Plus), Landsat 8 OLI (Operational Land Imager), Sentinel-2 MSI (Multispectral Instruments), and Hyperion satellites were collected from the USGS and the Scientific Hub ESA-Copernicus on-line databases, and integrated with Google Earth imagery. The visual interpretation of the images, mostly based on the brightness contrast (high and low reflectance values) and aimed to the recognition of traces, has been facilitated by the RGB combinations of the spectral bands most sensitive to lithology and moisture content and supported by a semi-automatic processing, including unsupervised classification and the spectral bands Principal Component Analysis (PCA). Multitemporal analysis of satellite imagery have been also performed. Two main traces, interpreted as meanders, have been analyzed for their sedimentological and stratigraphic characteristics. Following a field survey aimed to describe the morphology, grain-size, colors, and accessory materials of surface deposits, 11 soil samples have been collected for the extraction of the reflectance spectral signature and coring along the traces and in adjacent areas (bright and dark portions). Cores have been sampled for benthic foraminifer/ostracod analysis (42 samples) and stratigraphic cross-sections were constructed transversal to the meandering traces. Nine radiocarbon ages allowed to set the depositional evolution of the two meanders into a definite chronological framework. The integrated, RS-stratigraphic methodological approach revealed a meandering paleodrainage system buried > 2 m below the ground level. Its surface visibility is guided by the spatial distribution of surface moisture, which mainly depends on subsurface stratigraphic architecture and, in particular, on the distribution of organic-rich deposits laterally to the migrating meanders. The formation and activity of the buried paleochannels dates back to the early Holocene highstand (6000-2500 cal yr BP), when a drainage system likely developed under tide-influenced conditions.

Petrological constraints on the high-Mg basalts from Capo Marargiu (Sardinia, Italy): Evidence of cryptic amphibole fractionation in polybaric environments

NASA Astrophysics Data System (ADS)

Tecchiato, Vanni; Gaeta, Mario; Mollo, Silvio; Scarlato, Piergiorgio; Bachmann, Olivier; Perinelli, Cristina

2018-01-01

This study deals with the textural and compositional characteristics of the calc-alkaline stratigraphic sequence from Capo Marargiu Volcanic District (CMVD; Sardinia island, Italy). The area is dominated by basaltic to intermediate hypabyssal (dikes and sills) and volcanic rocks (lava flows and pyroclastic deposits) emplaced during the Oligo-Miocene orogenic magmatism of Sardinia. Interestingly, a basaltic andesitic dome hosts dark-grey, crystal-rich enclaves containing up 50% of millimetre- to centimetre-sized clinopyroxene and amphibole crystals. This mineral assemblage is in equilibrium with a high-Mg basalt recognised as the parental magma of the entire stratigraphic succession at CMVD. Analogously, centimetre-sized clots of medium- and coarse-grained amphibole + plagioclase crystals are entrapped in andesitic dikes that ultimately intrude the stratigraphic sequence. Amphibole-plagioclase cosaturation occurs at equilibrium with a differentiated basaltic andesite. Major and trace element modelling indicates that the evolutionary path of magma is controlled by a two-step process driven by early olivine + clinopyroxene and late amphibole + plagioclase fractionation. In this context, enclaves represent parts of a cumulate horizon segregated at the early stage of differentiation of the precursory high-Mg basalt. This is denoted by i) resorption effects and sharp transitions between Mg-rich and Mg-poor clinopyroxenes, indicative of pervasive dissolution phenomena followed by crystal re-equilibration and overgrowth, and ii) reaction minerals found in amphibole coronas formed at the interface with more differentiated melts infiltrating within the cumulate horizon, and carrying the crystal-rich material with them upon eruption. Coherently, the mineral chemistry and phase relations of enclaves indicate crystallisation in a high-temperature, high-pressure environment under water-rich conditions. On the other hand, the upward migration and subsequent fractionation of the residual basaltic andesite in a shallower, colder, and hydrous region of the CMVD plumbing system lead to the formation of the amphibole-plagioclase crystal clots finally entrained by the andesitic dikes. Indeed, phenocrysts from these more evolved products record the final crystallisation path of magma during ascent towards the surface. Magma decompression and volatile loss cause the formation of amphibole reaction coronas and the crystallisation of a more sodic plagioclase in equilibrium with basaltic andesitic to andesitic melts. The bulk-rock geochemical signature of these products testifies to open-system, polybaric magma dynamics, accounting for variable degrees of crustal assimilation of the Hercynian basement of Sardinia.

Sequence-stratigraphic controls on sandstone diagenesis: An example from the Williams Fork formation, Piceance Basin, Colorado

NASA Astrophysics Data System (ADS)

Aboktef, Adel

This study documents the distribution of diagenetic alterations in Williams Fork fluvial sandstones, assess sequence stratigraphic controls on diagenetic features, and addresses diagenetic impacts on porosity. Petrographic point counts of 220 thin sections from six wells forms the database. The near absence of potassium feldspar and volcanic rock fragments in the lower Williams Fork interval and increasing plagioclase content upward represent changes in sediment provenance rather than stratigraphic variability in diagenesis. The lower Williams Fork sands are from sedimentary sources whereas middle and upper Williams Fork sands include input from magmatic arcs and basement uplifts. Compaction, early and late cementation, dissolution, and replacement by calcite or clay minerals combined to alter Williams Fork sandstones. Infiltration of clays occurred prior to any burial. Chlorite, quartz, non-ferroan calcite, compaction and dissolution features, and kaolinite formed during eo-diagenesis at <70°C. More quartz, compaction and dissolution features, plus albite, illite, mixed-layer illite/smectite, ferroan calcite, and dolomite formed in the meso-diagenetic realm (>70°C). Four of these features show spatial variability with respect to systems tracts. Infiltrated clays are concentrated in lowstand systems tracts (LST) and highstand systems tracts (HST) because accommodation space rose slow or fell during deposition of those sands, which led to prolonged sand body exposure on floodplain and ample opportunities for downward percolation of mud during flood events. Concentration of pseudomatrix (mud intraclasts) in HST and LST deposits resulted from floodplain erosion when base-level fell with decreasing accommodation space. Authigenic chlorite formed in the HST and transgressive systems tracts (TST) of the upper half of the Williams Fork Formation because volcanic clasts are abundant in that interval. Quartz overgrowths are more likely to exceed 7% in TST deposits for reasons that are unknown. High total clay content (infiltrated, grain coatings, pseudomatrix) does inhibit quartz overgrowths in all systems tracts. Williams Fork sandstones form low-permeability tight-gas reservoirs. Primary porosity was almost entirely destroyed by compaction and cementation. Reservoir rock resulted from one of two pathways. Eogenetic authigenic chlorite and/or calcite inhibited quartz cementation, minimized compaction and protected some primary porosity. Alternately, dissolution of framework grains or cements created secondary porosity. The later pathway tends to be the more dominant.

Evolution of the Puente Hills Thrust Fault

NASA Astrophysics Data System (ADS)

Bergen, K. J.; Shaw, J. H.; Dolan, J. F.

2013-12-01

This study aims to assess the evolution of the blind Puente Hills thrust fault system (PHT) by determining its age of initiation, lateral propagation history, and changes in slip rate over time. The PHT presents one of the largest seismic hazards in the United States, given its location beneath downtown Los Angeles. The PHT is comprised of three fault segments: the Los Angeles (LA), Santa Fe Springs (SFS), and Coyote Hills (CH). The LA and SFS segments are characterized by growth stratigraphy where folds formed by uplift on the fault segments have been continually buried by sediment from the Los Angeles and San Gabriel rivers. The CH segment has developed topography and is characterized by onlapping growth stratigraphy. This depositional setting gives us the unique opportunity to measure uplift on the LA and SFS fault segments, and minimum uplift on the CH fault segment, as the difference in sediment thicknesses across the buried folds. We utilize depth converted oil industry seismic reflection data to image the fold geometries. Identifying time-correlative stratigraphic markers for slip rate determination in the basin has been a problem for researchers in the past, however, as the faunal assemblages observed in wells are time-transgressive by nature. To overcome this, we utilize the sequence stratigraphic model and well picks of Ponti et al. (2007) as a basis for mapping time-correlative sequence boundaries throughout our industry seismic reflection data from the present to the Pleistocene. From the Pleistocene to Miocene we identify additional sequence boundaries in our seismic reflection data from imaged sequence geometries and by correlating industry well formation tops. The sequence and formation top picks are then used to build 3-dimensional surfaces in the modeling program Gocad. From these surfaces we measure the change in thicknesses across the folds to obtain uplift rates between each sequence boundary. Our results show three distinct phases of deformation on the LA and SFS segments: an early period characterized by fault-propagation or structural wedge kinematics that terminates in the early Pleistocene, followed by a period of quiescence. The faults were subsequently reactivated in the middle Pleistocene and propagated upward to detachments, with the deformation characterized by fold-bend folding kinematics. Slip on the LA segment decreases to the West, suggesting lateral growth in that direction. Our work highlights the need to assess along-strike variability in slip rate when assessing the seismic hazard of a compressional fault, as marginal sites may significantly underestimate fault activity. Ponti, D. J. et al. A 3-Dimensional Model of Water-Bearing Sequences in the Dominguez Gap Region, Long Beach, California. US Geological Survey Open-File Report 1013 (2007).

Aptian (lower Cretaceous) ammonite biostratigraphy of the Francisco Zarco Dam stratigraphic section (Durango State, northeast Mexico)

NASA Astrophysics Data System (ADS)

Moreno-Bedmar, Josep Anton; Barragán Manzo, Ricardo; Company Sempere, Miguel; Bulot, Luc Georges

2013-03-01

This work deals with the study of the ammonoid record of a classical stratigraphic section of Aptian age, the Francisco Zarco Dam (Durango State, northeast Mexico). A detailed biostratigraphical analysis considered 1281 specimens systematically sampled on a bed-by-bed basis. Taphonomy, taxonomic composition and paleocology of the studied assemblage, were also stressed. We formally propose an ammonite zonation for this section, which consists of two interval zones, Dufrenoyia justinae and Gargasiceras? adkinsi, one taxon range zone Caseyella aguilerae, and one biohorizon Huastecoceras trispinosoides. Among those biostratigraphic units, three are of new definition. Another topic discussed herein concerns to the problematic definition of the Lower-Upper Aptian boundary using the first stratigraphical appearance of the genus Epicheloniceras. From a paleoecological point of view, we recognized the ammonoid assemblage of the Francisco Zarco Dam section, to be representative of a distal platform environment. Finally, we compared the zonation built for this section with that considered the standard zonation for the Tethyan Domain, concluding that the differences are so substantial that an independent zonation for the Central Atlantic is necessary.

The geological history of Northeast Syrtis Major, Mars

NASA Astrophysics Data System (ADS)

Bramble, Michael S.; Mustard, John F.; Salvatore, Mark R.

2017-09-01

As inferred from orbital spectroscopic data, Northeast Syrtis Major bears considerable mineral diversity that spans the Noachian-Hesperian boundary despite its small geographic area. In this study we use observations from the High Resolution Imaging Science Experiment, supplemented with Context Camera imagery, to characterize and map the lateral extent of geomorphic units in Northeast Syrtis Major, and constrain the geomorphic context of the orbital-identified mineral signatures. Using recent observations, we confirm previous mineralogy identified with the Compact Reconnaissance Imaging Spectrometer for Mars, and greatly extend the lateral extent of visible to near-infrared investigation utilizing the greater coverage. Analysis of Thermal Emission Imaging System observations reveals further physical properties and distribution of the geomorphic units. The stratigraphy, which spans the Noachian-Hesperian boundary, displays significant morphological heterogeneity at the decameter scale, but it is unifiable under five distinct geomorphic units. Our paired morphological and mineralogical analysis allows us to construct a detailed geological history of Northeast Syrtis Major. Several geological events that occurred in Northeast Syrtis Major-including the formation of the post-Isidis crust, the emplacement of an olivine-rich unit, the formation of sulfate minerals, and the emplacement of the Syrtis Major Volcanics-can be related to regional and global processes constraining the local chronology. Other mineralogical indicators, particularly the formation of Al-phyllosilicates, are difficult to place in the temporal sequence. They are observed in isolated patches on the post-Isidis crust, not as a distinct stratigraphic unit as observed elsewhere in Nili Fossae, suggesting their formation via isolated leaching or through alteration of initial compositional heterogeneities within the crust. Exposures of an olivine-rich unit are intermittently observed to form quasi-circular landforms, suggestive of emplacement in circular depressions, which may indicate a period of cratering between the formation of the Isidis basin and the deposition of the olivine-rich unit. We identify and discuss intriguing large linear features of the olivine-rich unit, reminiscent of dyke-fed volcanism, that have raised bounding ridges suggestive of contact metamorphism with the crust. We compile, review, and discuss many of the outstanding questions and running hypotheses relevant to our mapping area. A synthesis of our geomorphic mapping with recent literature reveals a well-defined geological history with extensive aqueous activity at Northeast Syrtis Major that is amassed in a stratigraphic sequence spanning a time likely greater than 250 million years of geological history. Our geomorphic and spectral analyses confirm that Northeast Syrtis Major exhibits considerable geomorphic and mineralogic diversity within a relatively small geographic area that is representative of the geologic processes occurring throughout the broader Nili Fossae region during the Noachian and Hesperian. Northeast Syrtis Major adds to this sequence by exposing the diverse environmental history of this region as observed through the presence of alteration minerals not present in this fidelity or proximity elsewhere in Nili Fossae.

Sequence stratigraphy of the Kingak Shale (Jurassic-Lower Cretaceous), National Petroleum Reserve in Alaska

USGS Publications Warehouse

Houseknecht, D.W.; Bird, K.J.

2004-01-01

Beaufortian strata (Jurassic-Lower Cretaceous) in the National Petroleum Reserve in Alaska (NPRA) are a focus of exploration since the 1994 discovery of the nearby Alpine oil field (>400 MMBO). These strata include the Kingak Shale, a succession of depositional sequences influenced by rift opening of the Arctic Ocean Basin. Interpretation of sequence stratigraphy and depositional facies from a regional two-dimensional seismic grid and well data allows the definition of four sequence sets that each displays unique stratal geometries and thickness trends across NPRA. A Lower to Middle Jurassic sequence set includes numerous transgressive-regressive sequences that collectively built a clastic shelf in north-central NPRA. Along the south-facing, lobate shelf margin, condensed shales in transgressive systems tracts downlap and coalesce into a basinal condensed section that is likely an important hydrocarbon source rock. An Oxfordian-Kimmeridgian sequence set, deposited during pulses of uplift on the Barrow arch, includes multiple transgressive-regressive sequences that locally contain well-winnowed, shoreface sandstones at the base of transgressive systems tracts. These shoreface sandstones and overlying shales, deposited during maximum flooding, form stratigraphic traps that are the main objective of exploration in the Alpine play in NPRA. A Valanginian sequence set includes at least two transgressive-regressive sequences that display relatively distal characteristics, suggesting high relative sea level. An important exception is the presence of a basal transgressive systems tract that locally contains shoreface sandstones of reservoir quality. A Hauterivian sequence set includes two transgressive-regressive sequences that constitute a shelf-margin wedge developed as the result of tectonic uplift along the Barrow arch during rift opening of the Arctic Ocean Basin. This sequence set displays stratal geometries suggesting incision and synsedimentary collapse of the shelf margin. ?? 2004. The American Association of Petroleum Geologists. All rights reserved.

Tertiary and Quaternary Research with Remote Sensing Methods

NASA Technical Reports Server (NTRS)

Conel, J. E.

1985-01-01

Problems encountered in mapping the Quaternary section of the Wind River Region using remote sensing methods are discussed. Analysis of the stratigraphic section is a fundamental aspect of the geologic study of sedimentary basins. Stratigraphic analysis of post-Cretaceous rocks in the Wind River Basin encounters problems of a distinctly different character from those involved in studying the pre-Cretaceous section. The interior of the basin is predominantly covered by Tertiary and Quaternary sediments. These rocks, except on the basin margin to the north, are mostly flat lying or gently dipping. The Tertiary section consists of sandstones, siltstones, and tuffaceous sediments, some variegated, but in general poorly bedded and of great lithologic similarity. The Quaternary sediments consist of terrace, fan, and debris tongue deposits, unconsolidated alluvium occupying the bottoms of modern watercourses, deposits of eolian origin and tufa. Terrace and fan deposits are compositionally diverse and reflect the lithologic diversity of the source terranes.

A paleomagnetic record in loess-paleosol sequences since late Pleistocene in the arid Central Asia

NASA Astrophysics Data System (ADS)

Li, Guanhua; Xia, Dunsheng; Appel, Erwin; Wang, Youjun; Jia, Jia; Yang, Xiaoqiang

2018-03-01

Geomagnetic excursions during Brunhes epoch have been brought to the forefront topic in paleomagnetic study, as they provide key information about Earth's interior dynamics and could serve as another tool for stratigraphic correlation among different lithology. Loess-paleosol sequences provide good archives for decoding geomagnetic excursions. However, the detailed pattern of these excursions was not sufficiently clarified due to pedogenic influence. In this study, paleomagnetic analysis was performed in loess-paleosol sequences on the northern piedmont of the Tianshan Mountains (northwestern China). By radiocarbon and luminance dating, the loess section was chronologically constrained to mainly the last c.130 ka, a period when several distinct geomagnetic excursions were involved. The rock magnetic properties in this loess section are dominated by magnetite and maghemite in a pseudo-single-domain state. The rock magnetic properties and magnetic anisotropy indicate weakly pedogenic influence for magnetic record. The stable component of remanent magnetization derived from thermal demagnetization revealed the presence of two intervals of directional anomalies with corresponding intensity lows in the Brunhes epoch. The age control in the key layers indicates these anomalies are likely associated with the Laschamp and Blake excursions, respectively. In addition, relative paleointensity in the loess section is basically compatible with other regional and global relative paleointensity records and indicates two low-paleointensity zones, possibly corresponding to the Blake and Laschamp excursions, respectively. As a result, this study suggests that the loess section may have the potential to record short-lived excursions, which largely reflect the variation of dipole components in the global archives.

Upper Lower Cambrian depositional sequence in Avalonian New Brunswick

USGS Publications Warehouse

Landing, E.; Westrop, S.R.

1996-01-01

The Hanford Brook Formation (emended) is a thin (up to 42+ m), upper Lower Cambrian depositional sequence that is unconformably bounded by the lower Lower Cambrian (Random Formation) and the middle Middle Cambrian (Fossil Brook Member of the Chamberlain's Brook Formation). These stratigraphic relationships of the trilobite-bearing Hanford Brook Formation indicate deposition on the Avalonian marginal platform in the Saint John, New Brunswick, region and provide more evidence for a uniform, latest Precambrian-Cambrian epeirogenic history and cover sequence in Avalon. The Hanford Brook Formation is a deepening - shoaling sequence with (i) lower, transgressive sandstone deposited in episodically high-energy environments (St. Martins Member, new); (ii) highstand-regressive, dysaerobic mudstone - fine-grained sandstone with volcanic ashes (Somerset Street Member, new); and (iii) upper, regressive, planar and hummocky cross-stratified sandstone (Long Island Member, new). Trilobites are common in the distal Somerset Street Member, and ostracodes and brachiopods dominate the St. Martins and Long Island members. Condensation of the St. Martins Member and absence of the Long Island Member where the Random Formation and Fossil Brook Member are thinnest suggest onlap of the Hanford Brook and pronounced, sub-Middle Cambrian erosion across epeirogenically active blocks in southern New Brunswick.

The use of piezocone tests for high-resolution stratigraphy of Quaternary sediment sequences in the Brazilian coast.

PubMed

de Mio, Giuliano; Giacheti, Heraldo L

2007-03-01

Correlations between mapping units of costal sedimentary basin and interpretation of piezocone test results are presented and discussed based on examples from Caravelas strandplain, (State of Bahia), Paranaguá (State of Paraná) and Guarujá bays (State of São Paulo), Brazil. Recognizing that the sedimentary environment was mainly controlled by sea level fluctuations led to the interpretation of transgressive and regressive sedimentary sequences, which is in a good agreement with the sea level fluctuation curves currently accepted for these regions. The interpretation of piezocone test results shows that the sedimentary sequences of Caravelas and Guarujá sites are similar and they have a good correlation to the sea level fluctuation curve accepted for Salvador region, State of Bahia. On the other hand, the piezocone test results from Paranaguá site indicate a different sedimentary sequence from the previous ones, relating to the sea level fluctuation curve accepted for Paranaguá region. The results show the high applicability of piezocone testing for stratigraphical logging and suggest that it is possible to integrate it with other current techniques used for paleo-environmental studies in Brazil, in accordance with recent approaches used in international research on the subject.

Gas production from a cold, stratigraphically-bounded gas hydrate deposit at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Implications of uncertainties

USGS Publications Warehouse

Moridis, G.J.; Silpngarmlert, S.; Reagan, M.T.; Collett, T.; Zhang, K.

2011-01-01

As part of an effort to identify suitable targets for a planned long-term field test, we investigate by means of numerical simulation the gas production potential from unit D, a stratigraphically bounded (Class 3) permafrost-associated hydrate occurrence penetrated in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well on North Slope, Alaska. This shallow, low-pressure deposit has high porosities (?? = 0.4), high intrinsic permeabilities (k = 10-12 m2) and high hydrate saturations (SH = 0.65). It has a low temperature (T = 2.3-2.6 ??C) because of its proximity to the overlying permafrost. The simulation results indicate that vertical wells operating at a constant bottomhole pressure would produce at very low rates for a very long period. Horizontal wells increase gas production by almost two orders of magnitude, but production remains low. Sensitivity analysis indicates that the initial deposit temperature is by the far the most important factor determining production performance (and the most effective criterion for target selection) because it controls the sensible heat available to fuel dissociation. Thus, a 1 ??C increase in temperature is sufficient to increase the production rate by a factor of almost 8. Production also increases with a decreasing hydrate saturation (because of a larger effective permeability for a given k), and is favored (to a lesser extent) by anisotropy. ?? 2010.

Stratigraphic distribution, taphonomy and paleoenvironments of Spinicaudata in the Triassic and Jurassic of the Paraná Basin

NASA Astrophysics Data System (ADS)

Jenisch, Alan Gregory; Lehn, Ilana; Gallego, Oscar Florencio; Monferran, Mateo Daniel; Horodyski, Rodrigo Scalise; Faccini, Ubiratan Ferrucio

2017-12-01

Due to the chitino-phosphatic nature of Spinicaudata conchostracan exoskeletons, their carapaces exhibit a low preservational potential compared to other bivalve groups. However, the recent studies point towards the increased tolerance of the carapace against the physical processes. Due to this peculiar characteristic, conchostracan carapace have been utilized as precise temporal markers in estimating stratigraphic and taphonomic parameters. The same characteristic also makes the spinicaudatans useful in evaluating the depositional processes and environments. The present work aims at providing a paleoenvironmental and stratigraphic analysis of conchostracans (Spinicaudata) from the Triassic-Jurassic of the Paraná Basin (Santa Maria and Caturrita formations) in terms of the sedimentary facies analysis, depositional system characterization, and analysis of the taphonomic signatures of the fossiliferous horizons within these formations. The results from the taphonomic study delineates the presence of 4 distinct fossil assemblages based on the causative mechanism and fundamental characteristics of the fossil concentrations: two taphonomic assemblages in the laminated mudstone beds deposited from the decanting fine-grained sediments in floodplains; the sandstone beds with plane parallel laminations and dune- and ripple-cross-stratifications deposited from the flooding-related overflow in the floodplains; and the association of laminated mudstone and massive sandstone beds deposited as the river mouth bars. The results show that the taphonomic signatures, e.g., closed valves, may indicate the various patterns of autochthony and allochthony. In the fine-grained floodplain assemblages, the high degree of preservation can be attributed to autochthony in the conchostracans, whereas the preservational condition of floodplain sandstone sheet and mouth bar assemblages point toward parautochthony and even allochthony. Therefore, the preservational quality of conchostracan exoskeletons is likely a function of parameters, e.g., the transport duration, the distance from life position, and the magnitude of events causing their final burial. Within the observed species, the recognition of Eustheria minuta in the stratigraphic level of the Passo das Tropas creek corroborates an age for these deposits between the late Middle Triassic and early Upper Triassic. The presence of a new form, likely related to the family Fushunograptidae in sediments from the Caturrita Formation, suggests a Jurassic age for these deposits.

Chronology of Fluctuating Sea Levels since the Triassic

NASA Astrophysics Data System (ADS)

Haq, Bilal U.; Hardenbol, Jan; Vail, Peter R.

1987-03-01

Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic frame-work. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.

Kaletepe Deresi 3 (Turkey): archaeological evidence for early human settlement in Central Anatolia.

PubMed

Slimak, Ludovic; Kuhn, Steven L; Roche, Hélène; Mouralis, Damase; Buitenhuis, Hijlke; Balkan-Atli, Nur; Binder, Didier; Kuzucuoğlu, Catherine; Guillou, Hervé

2008-01-01

Located in the Central Anatolian Volcanic Province, Kaletepe Deresi 3 was discovered in the summer of 2000 and has been under investigation since that time. Volcanic activity in the region generated a number of obsidian intrusions that have attracted humans to the area throughout prehistory. The stratigraphic sequence at Kaletepe Deresi 3, more than 7 m in depth, presents a series of archaeological horizons representing the Lower and Middle Paleolithic. The site contains the longest open-air Paleolithic sequence excavated in Turkey, as well as the first in situ Acheulean industry documented in Anatolia. Tephras in the upper Middle Paleolithic horizons and the rhyolithic bedrock bracket the timespan represented at Kaletepe Deresi 3. The lithic industry at the site illustrates a wide range of technological behaviors and documents changes in raw-material exploitation and artifact manufacture through the Lower and Middle Paleolithic.

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

Haq, B.U.; Hardenbol, J.; Vail, P.R.

Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic andmore » accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.« less

Multidisciplinary studies on ancient sandstone quarries of Western Sardinia (Italy).

NASA Astrophysics Data System (ADS)

Grillo, Silvana Maria; Del Vais, Carla; Naitza, Stefano

2013-04-01

The ancient coastal quarries of Mediterranean are increasingly considered geosites of multidisciplinary relevance. They are sites of historical-archaeological interest that show ancient techniques of stone extraction; they are significant for cultural heritage conservation and restoration, as sources of the stones used in ancient buildings and monuments; they are sites of geological relevance, as often retain important stratigraphic sections; they are also useful markers of secular changes in the sea level. A multisciplinary study is in progress on the ancient quarries of the Sinis region (western Sardinia island), integrating archaeological, geological, minero-petrographical data. In Sardinia, coastal quarries have been established from Punic and Roman times. Many of them exploited Quaternary sediments along the southern and western coasts of the island. They consist of middle-late Pleistocene marine conglomerates and carbonate sandstones, and of coastal (aeolian) carbonate sandstones. Sandstone blocks of different sizes have been widely used in ancient cities for buildings, defensive works, harbours, etc. Three main areas of stone extraction (San Giovanni di Sinis, Punta Maimoni, Is Arutas) have been so far recognized in the Sinis. GIS-supported mapping and documentation of the sites includes their geology and stratigraphy, the extension and layout of the quarries, and an evaluation of volumes of extracted rocks. Documented archaeological evidences include ancient extraction fronts, spoil heaps, working areas, working traces in the old fronts, transport routes of blocks, and traces of loading facilities. The study is aimed at reconstructing the relationships of the quarries with the urban areas of Sinis, as the ancient Punic-Roman city of Tharros. Consequently, a minero-petrographical characterization (optical microscopy, XRD) is performed on sandstones sampled in each quarry, and in historical buildings in Tharros and other centres of the region (Cabras, Oristano, Santa Giusta). They are prevailing fine-medium grained carbonate sandstones, and subordinate coarse sandstones and micro-conglomerates, variably cemented. In the studied areas, stratigraphic sequences grade from coarser facies of marine environment to fine-grained aeolian deposits, marked by cross-stratification. The Quaternary sedimentary sequence rests on Miocene limestones and clays, and on Plio-Pleistocene basalts. On optical microscopy, sandstones show grain-supported texture, with abundant carbonate bioclasts, intraclasts and algal nodules, with quartz, feldspars and fragments of granitoids, quartzites, volcanics. Grainsize in sandstone sequences progressively decreases towards the top, corresponding to an increase of fine bioclastic components. Terrigenous components change from the northernmost outcrops (Is Arutas quarries), where clasts of granitoid origin are dominant, to the southern outcrops (San Giovanni di Sinis quarries), which show a more marked compositional heterogeneity, with frequent volcanic feldspars and lithoclasts. The calcitic cement also shows distinct variations, both along the stratigraphic sequence and at areal scale, between the sparitic type and the micro/cryptocrystalline type. First evidences on samples from Tharros city walls indicate that sandstone blocks may come, almost in part, from the quarries of San Giovanni di Sinis that, consequently, could have started to work during the Punic age. Other evidences in the area, however, indicate that quarrying activities in Sinis continued well over the Ancient times, presumably including all the Middle Ages.

Tracing marine cryptotephras in the North Atlantic during the last glacial period: Improving the North Atlantic marine tephrostratigraphic framework

NASA Astrophysics Data System (ADS)

Abbott, Peter M.; Griggs, Adam J.; Bourne, Anna J.; Chapman, Mark R.; Davies, Siwan M.

2018-06-01

Tephrochronology is increasingly being recognised as a key tool for the correlation of disparate palaeoclimatic archives, underpinning chronological models and facilitating climatically independent comparisons of climate proxies. Tephra frameworks integrating both distal and proximal tephra occurrences are essential to these investigations providing key details on their spatial distributions, geochemical signatures, eruptive sources as well as any available chronological and/or stratigraphic information. Frameworks also help to avoid mis-correlation of horizons and provide important information on volcanic history. Here we present a comprehensive chronostratigraphic framework of 14 tephra horizons from North Atlantic marine sequences spanning 60-25 cal ka BP. Horizons previously discovered as visible or coarse-grained deposits have been combined with 11 newly recognised volcanic deposits, identified through the application of cryptotephra identification and characterisation methods to a wide network of marine sequences. Their isochronous integrity has been assessed using their physical characteristics. All horizons originated from Iceland with the vast majority having a basaltic composition sourced from the Grímsvötn, Kverkfjöll, Hekla/Vatnafjöll and Katla volcanic systems. New occurrences, improved stratigraphic placements and a refinement of the geochemical signature of the NAAZ II are reported and the range of the FMAZ IV has been extended. In addition, several significant geochemical populations that further investigations could show to be isochronous are reported. This tephra framework provides the foundation for the correlation and synchronisation of these marine records to the Greenland ice-cores and European terrestrial records to investigate the phasing, rate, timing and mechanisms controlling rapid climate changes that characterised the last glacial period.

Louisiana continental slope: geologic and seismic stratigraphic framework

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

Ray, P.K.; Cooke, D.W.

1987-05-01

The continental slope of Louisiana from Green Canyon to Mississippi Canyon was studied by interpreting seismic CDP data and wells in the area. The slope is characterized by blocked canyon intraslope basins of various dimensions with maximum thickness of sediments in excess of 21,000 ft, rotational slump blocks and large-scale submarine slides. In the subsurface, the outer shelf and upper slope show contrasting character with that of the lower slope, especially below the Sigsbee Scarp. The seismic stratigraphic units established for the deep sea area can be recognized in their entirety up to a water depth of 6000 to 5500more » ft. In shallower water salt tectonics obliterates the sequence. Fragmental records of the sequence, especially the top of Challenger boundary, have been recognized in as shallow as 2000 to 3000 ft of water. The Tertiary units often downlap and onlap directly on the Challenger unit, indicating the progradational nature of the clastic slope. The Sigsbee unit has been traced through the entire slope area and can be divided into five subunits of unique acoustical characteristics. The slope constantly regrades in response to Neogene sea level fluctuations. Loading of the shelf by deltaic deposition contributes to salt sill formation and flowage of salt over deep-water sediments on the slope during high sea level. Regressive sea is represented by slope failure, formation of large-scale submarine slides, filling of blocked canyon intraslope basins which show similar seismic facies to that of Orca and Pigmy basins as reported from DSDP studies, and sporadic uplifting of salt diapirs and massifs and the formation of linear transverse salt ridges.« less

Miocene unconformities in the Central Apennines: geodynamic significance and sedimentary basin evolution

NASA Astrophysics Data System (ADS)

Cipollari, Paola; Cosentino, Domenico

1995-12-01

This paper shows the results obtained from an integrated study (geology, biostratigraphy and geochemistry) carried out on the Miocene edimentary deposits in Central Italy in order to define the timing of the sedimentary basin evolution. This paper deals also with the causes of the unconformities recorded in these basins. In the Miocene deposits of the Latina Valley and the Ernici-Simbruini Mts. several unconformities which distinguish different stratigraphic sequences have been recognized (D 0, D 1, D 2 D 3 and D 4). For each unconformity a general description together with a geodynamical significance is provided. In particular, D 0 unconformity appears to be related to a regional tectonic event (Adria-Europe collision). As a consequence, the Adria lithosphere folded and the area underwent a regional erosive event. D 1, D 2 and D 3 unconformities have had a more local tectonic control since they represent the stratigraphic record of the migration of the Apennines thrust belt/foredeep system. D 1 and D 2 unconformities are related to the late Tortonian foredeep stage, whereas D 3 is linked to the early Messinian piggy-back stage. Moreover, the D 4 unconformity, which took place during the Messinian piggy-back stage, is strictly linked to the sea-level drop of the Messinian salinity crisis. In this paper the genesis and evolution of a late Tortonian foreland basin is also stressed (Latina Valley foredeep basin). Finally, taking into account sequence boundaries, nannofossil biostratigraphy and geochemistry isotopic data, a comparison with the curve of the 3rd order of the relative coastal onlap (Haq et al., 1988) has been attempted in order to distinguish the unconformities controlled either by tectonic or eustatic processes.

Regional stratigraphy and petroleum potential, Ghadames basin, Algeria

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

Emme, J.J.; Sunderland, B.L.

1991-03-01

The Ghadames basin in east-central Algeria extends over 65,000 km{sup 2} (25,000 mi{sup 2}), of which 90% is covered by dunes of the eastern Erg. This intracratonic basin consists of up to 6000 m (20,000 ft) of dominantly clastic Paleozoic through Mesozoic strata. The Ghadames basin is part of a larger, composite basin complex (Ilizzi-Ghadames-Triassic basins) where Paleozoic strata have been truncated during a Hercynian erosional event and subsequently overlain by a northward-thickening wedge of Mesozoic sediments. Major reservoir rocks include Triassic sandstones that produce oil, gas, and condensate in the western Ghadames basin, Siluro-Devonian sandstones that produce mostly oilmore » in the shallower Ilizzi basin to the south, and Cambro-Ordovician orthoquartzites that produce oil at Hassi Messaoud to the northwest. Organic shales of the Silurian and Middle-Upper Devonian are considered primary source rocks. Paleozoic shales and Triassic evaporite/red bed sequences act as seals for hydrocarbon accumulations. The central Ghadames basin is underexplored, with less than one wildcat well/1700 km{sup 2} (one well/420,000 ac). Recent Devonian and Triassic oil discoveries below 3500 m (11,500 ft) indicate that deep oil potential exists. Exploration to date has concentrated on structural traps. Subcrop and facies trends indicate that potential for giant stratigraphic or combination traps exists for both Siluro-Devonian and Triassic intervals. Modern seismic acquisition and processing techniques in high dune areas can be used to successfully identify critical unconformity-bound sequences with significant stratigraphic trap potential. Advances in seismic and drilling technology combined with creative exploration should result in major petroleum discoveries in the Ghadames basin.« less

The Carrancas Formation, Bambuí Group: A record of pre-Marinoan sedimentation on the southern São Francisco craton, Brazil

NASA Astrophysics Data System (ADS)

Uhlein, Gabriel J.; Uhlein, Alexandre; Halverson, Galen P.; Stevenson, Ross; Caxito, Fabrício A.; Cox, Grant M.; Carvalho, Jorge F. M. G.

2016-11-01

The Carrancas Formation outcrops in east-central Brazil on the southern margin of the São Francisco craton where it comprises the base of the late Neoproterozoic Bambuí Group. It is overlain by the basal Ediacaran cap carbonate Sete Lagoas Formation and was for a long time considered to be glacially influenced and correlative with the glaciogenic Jequitaí Formation. New stratigraphic, isotopic and geochronologic data imply that the Carrancas Formation was instead formed by the shedding of debris from basement highs uplifted during an episode of minor continental rifting. Reddish dolostones in the upper Carrancas Formation have δ13C values ranging from +7.1 to +9.6‰, which is a unique C isotopic composition for the lowermost Bambuí Group but similar to values found in the Tijucuçu sequence, a pre-glacial unit in the Araçuaí fold belt on the eastern margin of the São Francisco craton. The stratigraphic position below basal Ediacaran cap carbonates and the highly positive δ13C values together indicate a Cryogenian interglacial age for the Carrancas Formation, with the high δ13C values representing the so-called Keele peak, which precedes the pre-Marinoan Trezona negative δ13C excursion in other well characterized Cryogenian sequences. Hence, The Carrancas Formation pre-dates de Marinoan Jequitaí Formation and represents an interval of Cryogenian stratigraphy not previously known to occur on the southern margin of São Francicso craton. Documentation of Cryogenian interglacial strata on the São Francisco craton reinforces recent revisions to the age of Bambuí Group strata and has implications for the development of the Bambuí basin.

A three-dimensional stratigraphic model for aggrading submarine channels based on laboratory experiments, numerical modeling, and sediment cores

NASA Astrophysics Data System (ADS)

Limaye, A. B.; Komatsu, Y.; Suzuki, K.; Paola, C.

2017-12-01

Turbidity currents deliver clastic sediment from continental margins to the deep ocean, and are the main driver of landscape and stratigraphic evolution in many low-relief, submarine environments. The sedimentary architecture of turbidites—including the spatial organization of coarse and fine sediments—is closely related to the aggradation, scour, and lateral shifting of channels. Seismic stratigraphy indicates that submarine, meandering channels often aggrade rapidly relative to lateral shifting, and develop channel sand bodies with high vertical connectivity. In comparison, the stratigraphic architecture developed by submarine, braided is relatively uncertain. We present a new stratigraphic model for submarine braided channels that integrates predictions from laboratory experiments and flow modeling with constraints from sediment cores. In the laboratory experiments, a saline density current developed subaqueous channels in plastic sediment. The channels aggraded to form a deposit with a vertical scale of approximately five channel depths. We collected topography data during aggradation to (1) establish relative stratigraphic age, and (2) estimate the sorting patterns of a hypothetical grain size distribution. We applied a numerical flow model to each topographic surface and used modeled flow depth as a proxy for relative grain size. We then conditioned the resulting stratigraphic model to observed grain size distributions using sediment core data from the Nankai Trough, offshore Japan. Using this stratigraphic model, we establish new, quantitative predictions for the two- and three-dimensional connectivity of coarse sediment as a function of fine-sediment fraction. Using this case study as an example, we will highlight outstanding challenges in relating the evolution of low-relief landscapes to the stratigraphic record.

Provenance analysis and tectonic setting of the Neoproterozoic sediments within the Taoudeni Basin, Northern Mauritania

NASA Astrophysics Data System (ADS)

Nicoll, Graeme; Straathof, Gijs; Tait, Jenny; Lo, Khalidou; Ousmane, N'diaye; El Moctar Dahmada, Mohamed; Berndt, Jasper; Key, Roger

2010-05-01

We have dated over 800 detrital zircon grains from the Neoproterozoic sediments within the Taoudeni Basin of Mauritania on the West African craton. This sequence of sediments preserves a relatively condensed mixed continental and marine succession as well as Neoproterozoic glacial and glacially influenced deposits. The underlying Archaean and Birimian basement of the West African craton is exposed on the Reguibat shield in the north, and on the Leo shield in the south although smaller inliers occur scattered along the Bassaride and Mauritanide belts, as well as in the core of the Anti-Atlas belt. The large West African craton is totally surrounded by Pan-African fold belts. Sedimentation within the Taoudeni basin started around 1000Ma and lasted until the end of the Carboniferous. The basin is 1000-1500 km in diameter and the sedimentary pile is on average 3000 m thick. All dated zircons in the stratigraphically lowest Char and Atar Groups are older than ~1800Ma. These groups show a strong input of 2950 and 2075Ma ages, indicating sourcing from the local underlying granitic and gneissic basement. These basal sediments also include a large input from a rare 2475Ma source. Samples from the upper Assebet El Hassiane Group contain numerous zircons of 2000-900Ma. While the Neoproterozoic Marinoan glaciogenic "Triad" Jbeliat Group and stratigraphically above formations show a large range of 3200-595Ma ages. We have also undertaken a detailed Carbon isotope profile study through the carbonates which cap the Glacial Jbeliat Group. The upper part of the Jbeliat cap carbonate displays a distinct and pronounced rise from -4.3 to +3.8 13C, followed by the final demise of carbonate productivity. This positive trend is consistent with the upper part of the globally extensive Ghaub/Nantuo/Marinoan cap carbonate sequences. This world-wide sequence is characterized by composite negative-to-positive trends up section and so this isotope stratigraphy along with the zircon data helps to date this Mauritanian sequence more precisely. The eroded sediments of the upper sections of the Neoproterozoic Taoudeni basin reflect a fundamental change in provenance up section. The majority of which show previously unreported ages for the West African craton particularly a large amount of post Craton stabilisation ages <1700 Ma and "Grenvillian-type" ages. Most zircons of 2000-900Ma were probably derived from sources outside the West-African craton. This new data helps to further constrain the age of the Neoproterozoic sections of the Taoudeni basin and highlights changing source regions during successive stages of the Pan African orogenic cycle from initial rifting to final collisions. Sedimentary geochemistry combined with well established palaeocurrent directions and the detailed detrital zircon study give a strong indication of what areas surrounding the Taoudeni basin were being eroded during the Neoproterozoic to Early Cambrian and substantially aid palaeographic reconstructions for the historically data poor West African Craton.

The Quequén Salado river basin: Geology and biochronostratigraphy of the Mio-Pliocene boundary in the southern Pampean plain, Argentina

NASA Astrophysics Data System (ADS)

Beilinson, E.; Gasparini, G. M.; Tomassini, R. L.; Zárate, M. A.; Deschamps, C. M.; Barendregt, R. W.; Rabassa, J.

2017-07-01

The Quequén Salado river basin has been the focus of several contributions since the first decades of the XX century, namely dealing with the general geological features of the deposits and with the vertebrate remains. In this paper, the Neogene geological history documented by the Quequén Salado river exposures is reconstructed by means of stratigraphic, sedimentological and paleomagnetic studies along with the paleontological analysis of vertebrate remains. The study area is a crucial setting not only to better understand the evolution of the southern Pampas basin during the late Miocene-early Pliocene interval, but also to test the validity of the biochronologic and biostratigraphic schemes, especially the "Irenense". A geological model for the Quequén Salado river valley is proposed: a case of downcutting and headward erosion that contributes with a coherent interpretation to explain the spatial distribution of facies and fossil taxa: the younger in the distal sector of the Quequén Salado middle basin and the older in the lower basin. The sedimentary record is believed to represent the distal reaches of a distributary fluvial system that drained from the Ventania ranges. The stratigraphic section of Paso del Indio Rico results a key stratigraphic site to fully understand the stratigraphic nature of the boundary between the Miocene and the Pliocene (the Huayquerian and Montehermosan stages/ages). In this sense, two stratigraphically superposed range zones have been recognized in the area: Xenodontomys ellipticus Range Zone (latest Miocene-early Pliocene; late Huayquerian), and Eumysops laeviplicatus Range Zone (early Pliocene; Montehermosan). Taking into account the available geological and paleontological evidences, the "Irenense" would not represent a valid biostratigraphic unit, since, according to the geological model here proposed, it would be represented by elements of the Xenodontomys ellipticus Range Zone in the lower QS basin and by elements of the Eumysops laeviplicatus Range Zone in the middle QS basin.

The stratigraphic filter and bias in measurement of geologic rates

USGS Publications Warehouse

Schumer, Rina; Jerolmack, Douglas; McElroy, Brandon

2011-01-01

Erosion and deposition rates estimated from the stratigraphic record frequently exhibit a power-law dependence on measurement interval. This dependence can result from a power-law distribution of stratigraphic hiatuses. By representing the stratigraphic filter as a stochastic process called a reverse ascending ladder, we describe a likely origin of power-law hiatuses, and thus, rate scaling. While power-law hiatuses in certain environments can be a direct result of power-law periods of stasis (no deposition or erosion), they are more generally the result of randomness in surface fluctuations irrespective of mean subsidence or uplift. Autocorrelation in fluctuations can make hiatuses more or less heavy-tailed, but still exhibit power-law characteristics. In addition we show that by passing stratigraphic data backward through the filter, certain statistics of surface kinematics from their formative environments can be inferred.

Sequence stratigraphy and reservoir architecture of the J18/20 and J15 sequences in PM-9, Malay Basin

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

Rahman, R.A.; Said, Md.J.; Bedingfield, J.R.

1994-07-01

The group J stratigraphic interval is lower Miocene (18.5-21 Ma) in age and was deposited during the early sag phase of the Malay Basin structural development. Reduction in depositional relief and first evidence of widespread marine influence characterize the transition into this interval. Twelve group J sequences have been identified. Reservoirs consist of progradational to aggradational tidally-dominated paralic to shallow marine sands deposited in the lowstand systems tract. Transgressive and highstand deposits are dominantly offshore shales. In PM-9, the original lift-related depocenters, coupled with changes in relative sea level, have strongly influenced group J unit thickness and the distribution ofmore » reservoir and seal facies. Two important reservoir intervals in PM-9 are the J18/20 and J15 sands. The reservoirs in these intervals are contained within the lowstand systems tracts of fourth-order sequences. These fourth-order sequences stack to form sequence sets in response to a third-order change in relative sea level. The sequences of the J18/20 interval stack to form part of a lowstand sequence set, whereas the J15 interval forms part of the transgressive sequence set. Reservoir facies range from tidal bars and subtidal shoals in the J18/20 interval to lower shoreface sands in the J15. Reservoir quality and continuity in group J reservoirs are dependent on depositional facies. An understanding of the controls on the distribution of facies types is crucial to the success of the current phase of field development and exploration programs in PM-9.« less

Black shale deposition during Toarcian super-greenhouse driven by sea level

NASA Astrophysics Data System (ADS)

Hermoso, M.; Minoletti, F.; Pellenard, P.

2013-12-01

One of the most elusive aspects of the Toarcian oceanic anoxic event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the end of the overarching positive trend in the carbon isotopes that characterises the T-OAE. In the present study, we have attempted to establish a sequence stratigraphic framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a combination of mineralogical (quartz and clay relative abundance) and geochemical (Si, Zr, Ti and Al) measurements. Combined with the evolution in redox sensitive elements (Fe, V and Mo), the data suggest that expression of anoxia was hampered in European epicontinental seas during most of the T-OAE (defined by the positive carbon isotope trend) due to insufficient water depth that prevented stratification of the water column. Only the first stratigraphic occurrence of black shales in Europe corresponds to the "global" event. This interval is characterised by >10% Total Organic Carbon (TOC) content that contains relatively low concentration of molybdenum compared to subsequent black shale horizons. Additionally, this first black shale occurrence is coeval with the record of the major negative Carbon Isotope Excursion (CIE), likely corresponding to a period of transient greenhouse intensification likely due to massive injection of carbon into the atmosphere-ocean system. As a response to enhanced weathering and riverine run-off, increased fresh water supply to the basin may have promoted the development of full anoxic conditions through haline stratification of the water column. In contrast, post T-OAE black shales during the serpentinum and bifrons Zones were restricted to epicontinental seas (higher Mo to TOC ratios) during a period of relative high sea level, and carbon isotopes returning to pre-T-OAE values. Comparing palaeoredox proxies with the inferred sequence stratigraphy for Sancerre suggests that episodes of short-term organic carbon enrichment were primarily driven by third-order sea level changes. These black shales exhibit remarkably well-expressed higher-frequency cyclicities in the oxygen availability in the water column whose nature has still to be determined through cyclostratigraphic analysis.

Decoding depositional sequences in carbonate systems: Concepts vs experience

NASA Astrophysics Data System (ADS)

Pomar, Luis; Haq, Bilal U.

2016-11-01

Efficacy of sequence stratigraphic concepts in siliciclastic systems has been proven by successful applications in both academia and the industry over the past four decades. However, experience has demonstrated repeatedly that the relatively simple advective transportational approach of these models is less than successful when applied to the more complex carbonate systems and can lead to erroneous interpretations. Instead, an approach that includes the use of the changes in the biotic components of carbonate deposits to infer the sea-level trajectory and thereby placing it in the proper sequence framework is deemed to be more meaningful. This is exemplified with several well-studied examples that illustrate the variety of ways in which the biotic components can build carbonate platforms, and how these have changed through the ages prompted by biological evolution. This extended review discusses carbonate production, source to sink transportation influenced by sea-level changes, surface waves, as well as the less understood and under-appreciated internal waves, and the resulting variety of platforms that can be built by the interaction of these factors, as well as the changing patterns of biotic components with time. Their effect on the carbonate reservoir is considerable, understanding of which is the ultimate objective of carbonate research for applications in the industry. Key elements in the carbonate environments that differ from the siliciclastic systems are: 1) intrabasinal conditions (nutrients, salinity, temperature, water energy, transparency) are important controls on carbonate production and therefore also control in-situ accommodation and how it may be filled; 2) depositional accommodation can be both physical (controlled by hydrodynamics) and ecological (in the building-up above the base level mode); 3) because carbonates are products of biological activity, their production modes have been changing with time as their biotic components have evolved; 4) seafloor morphology determines the size and efficiency of the carbonate factory; 5) several carbonate factories may coexist or alternate, in-phase, out-of-phase with or independently of the sea level changes. The complexity and interplay of all of these governing factors contribute to very diverse carbonate production styles and edifices. Consequently, sequence-stratigraphic interpretations in carbonates are more meaningful when seen through the lens of process-product relationships, rather than simply through bedding patterns and bounding surfaces characterization.

Palaeoclimate characteristics in interior Siberia of MIS 6-2: first insights from the Batagay permafrost mega-thaw slump in the Yana Highlands

NASA Astrophysics Data System (ADS)

Ashastina, Kseniia; Schirrmeister, Lutz; Fuchs, Margret; Kienast, Frank

2017-07-01

Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level lowstands. Syngenetic deposition implies that all material, both mineral and organic, freezes parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of Late Pleistocene palaeoclimate. Most studied permafrost outcrops are situated in the coastal lowlands of northeastern Siberia; inland sections are, however, scarcely available. Here, we describe the stratigraphical, cryolithological, and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Sakha Republic (Yakutia), Russia, with focus on the Late Pleistocene Yedoma ice complex (YIC). The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a climate record close to Verkhoyansk, which has the most severe continental climate in the Northern Hemisphere. Geochronological dating (optically stimulated luminescence, OSL, and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition. The sequence of lithological units indicates a succession of several distinct climate phases: a Middle Pleistocene ice complex indicates cold stage climate. Then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise in temperature. Full interglacial climate conditions existed during accumulation of an organic-rich layer - plant macrofossils reflected open forest vegetation existing under dry conditions during Marine Isotope Stage (MIS) 5e. The Late Pleistocene YIC (MIS 4-MIS 2) suggests severe cold-stage climate conditions. No alas deposits, potentially indicating thermokarst processes, were detected at the site. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences, both coastal and inland, is made to highlight common features and differences in their formation processes and palaeoclimatic histories. Fluvial and lacustrine influence is temporarily common in the majority of permafrost exposures, but has to be excluded for the Batagay sequence. We interpret the characteristics of permafrost deposits at this location as a result of various climatically induced processes that are partly seasonally controlled. Nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season.

Stratigraphic, Granulometric and Geochemical Studies of a Major Plinian Eruption on Dominica, Lesser Antilles

NASA Astrophysics Data System (ADS)

Smith, A. L.; Daly, G.; Killingsworth, N.; Deuerling, K.; Schneider, S.; Fryxell, J. E.

2008-12-01

The island of Dominica, located in the center of the Lesser Antilles island arc has witnessed, probably within the last 100,000 years, three large volume Plinian eruptions. One of these, associated with the Morne Diablotins center, forms the Grande Savane pyroclastic flow fan, that extends off shore as a distinctive submarine feature for a distance of at least 14 km. Stratigraphical studies of road cuts and well-exposed sea cliffs indicate the fan is composed of an older unit composed of reworked deposits at the base followed by at least four sequences, based on the presence of paleosols, of block and ash flow deposits. The upper unit of block and ash flows is overlain, with no evidence of an intervening paleosol, by a sequence of ignimbrites and pumiceous surges (representing the Plinian eruption). There is no evidence of an initial Plinian fall deposit, so the lowest bed in the succession is an ignimbrite with a highly irregular base that cuts into the underlying block and ash flow deposits, the upper parts of which are colored red due to thermal effects. This lowest ignimbrite is welded (minimum porosity of 15%) throughout its thickness (maximum thickness of greater than 21 m), although a few outcrops near the margins show a thin (20-30 cm) non-welded but lithified zone beneath the welded zone. The remainder of the sequence is composed of lithified ignimbrite that can be subdivided into three units separated by pumiceous surge layers. The ignimbrite succession is overlain, with no obvious break, by a thin fall deposit containing accretionary lapilli and gas cavities, followed by three pumiceous surge deposits (lower and upper show planar stratification and the middle surge shows massive bedding); towards the north the upper two surge deposits are separated by thin pumiceous lapilli fall and ash fall deposits. This surge sequence extends laterally outside of the main area of ignimbrite deposition. The pumice clasts from the ignimbrites are andesitic in composition and show essentially no variation up stratigraphy. In contrast, the surges are more variable in composition, ranging from andesite to dacite. Modeling of these data will provide information on the dynamics of this major Plinian eruption including the effects of water/magma interaction.

30 CFR 280.71 - What is the timetable for release of data and information?

Code of Federal Regulations, 2010 CFR

2010-07-01

... related to the deep stratigraphic test at the earlier of the following times: (1) Twenty-five years after...) of this section. (a) If the data and information are not related to a deep stratigraphic test, we... party submit the information (4) Data and information related to a deep stratigraphic test 25 years...

A stratigraphic network across the Subtropical Front in the central South Atlantic: Multi-parameter correlation of magnetic susceptibility, density, X-ray fluorescence and @d^1^8O records [rapid communication

NASA Astrophysics Data System (ADS)

Hofmann, Daniela I.; Fabian, Karl; Schmieder, Frank; Donner, Barbara; Bleil, Ulrich

2005-12-01

Computer aided multi-parameter signal correlation is used to develop a common high-precision age model for eight gravity cores from the subtropical and subantarctic South Atlantic. Since correlations between all pairs of multi-parameter sequences are used, and correlation errors between core pairs ( A, B) and ( B, C) are controlled by comparison with ( A, C), the resulting age model is called a stratigraphic network. Precise inter-core correlation is achieved using high-resolution records of magnetic susceptibility κ, wet bulk density ρ and X-ray fluorescence scans of elemental composition. Additional δ18O records are available for two cores. The data indicate nearly undisturbed sediment series and the absence of significant hiatuses or turbidites. After establishing a high-precision common depth scale by synchronously correlating four densely measured parameters (Fe, Ca, κ, ρ), the final age model is obtained by simultaneously fitting the aligned δ18O and κ records of the stratigraphic network to orbitally tuned oxygen isotope [J. Imbrie, J. D. Hays, D. G. Martinson, A. McIntyre, A. C. Mix, J. J. Morley, N. G. Pisias, W. L. Prell, N. J. Shackleton, The orbital theory of Pleistocene climate: support from a revised chronology of the marine δ18O record, in: A. Berger, J. Imbrie, J. Hays, G. Kukla, B. Saltzman (Eds.), Milankovitch and Climate: Understanding the Response to Orbital Forcing, Reidel Publishing, Dordrecht, 1984, pp. 269-305; D. Martinson, N. Pisias, J. Hays, J. Imbrie, T. C. Moore Jr., N. Shackleton, Age dating and the orbital theory of the Ice Ages: development of a high-resolution 0 to 300.000-Year chronostratigraphy, Quat. Res. 27 (1987) 1-29.] or susceptibility stacks [T. von Dobeneck, F.Schmieder, Using rock magnetic proxy records for orbital tuning and extended time series analyses into the super-and sub-Milankovitch Bands, in: G. Fischer, G. Wefer (Eds.), Use of proxies in paleoceanography: Examples from the South Atlantic, Springer-Verlag, Berlin (1999), pp. 601-633.]. Besides the detection and elimination of errors in single records, the stratigraphic network approach allows to check the intrinsic consistency of the final result by comparing it to the outcome of more restricted alignment procedures. The final South Atlantic stratigraphic network covers the last 400 kyr south and the last 1200 kyr north of the Subtropical Front (STF) and provides a highly precise age model across the STF representing extremely different sedimentary regimes. This allows to detect temporal shifts of the STF by mapping δMn / Fe. It turns out that the apparent STF movements by about 200 km are not directly related to marine oxygen isotope stages.

Assessing Biological and Stratigraphic Determinants of Fossil Abundance: A Case Example from the Late Quaternary of Po Plain, Italy

NASA Astrophysics Data System (ADS)

Kowalewski, Michal; Azzarone, Michele; Kusnerik, Kristopher; Dexter, Troy; Wittmer, Jacalyn; Scarponi, Daniele

2017-04-01

Absolute fossil abundance [AFA] can be defined as a relative concentration of identifiable fossils per unit of sediment. AFA, or "sediment shelliness", is controlled by the interplay between the rate of input of skeletal remains (biological productivity), pace of shell destruction (taphonomy), rate of sedimentation, and sediment compaction. Understanding the relative importance of those drivers can augment both stratigraphic and biological interpretations of the fossil record. Using 336 samples from a network of late Quaternary cores drilled in Po Plain (Italy), we examined the importance of those factors in controlling the stratigraphic distribution of fossils. All samples were vertically and volumetrically equivalent, each representing a 10 cm long interval of a core with a diameter of 7 cm ( 0.375 dm3 sediment per sample). Sample-level estimates of AFA (1) varied over 4 orders of magnitudes (from <4 to 44200 specimens per dm3 of sediment); (2) appeared invariant to core depth (rho=-0.04, p=0.72); (3) were statistically indistinguishable (chi-square=1.53, p=0.46) across systems tracts; and (4) did not vary substantially across facies (chi-square=6.04, p=0.20) representing a wide range of depositional and taphonomic settings. These outcomes indicate that compaction (which should increase downcore), sedimentation rates (which vary predictably across systems tracts), and pace of shell destruction (expected to differ across depositional settings) are unlikely to have played important role in controlling fossils density in the sampled cores. In contrast, samples with very high shell density (AFA > 4000 specimens per dm3) were characterized by exceedingly low evenness reflecting dominance by one super-abundant species (Berger-Parker index > 0.8 in all cases). These super-abundant species were limited to small r-selective mollusks capable of an explosive population growth: the marine corbulid bivalve Lentidium mediterraneum and the brackish hyrdobiid gastropod Ecrobia ventrosa. Moreover, despite high mollusk diversity (534 species total), >80% of samples are dominated by one of the five mollusk species, which all represent small, r-selective, deposit and suspension feeders. Trends in absolute fossil abundance within late Quaternary deposits of the Po Plain appear to have been driven primarily by biological productivity of opportunistic shelly species from lowest trophic levels. In the studied system, biodiversity and shelliness of samples is unlikely to reflect stratigraphic or taphonomic overprints, but rather records the ecological importance of r-selective species that dominated the investigated area throughout the late Quaternary. The joint consideration of sequence stratigraphy, facies architecture, and paleontological data, can provide insights regarding both stratigraphic (the origin of sedimentary biofabrics) and biological (the drivers of bio-productivity and observed biodiversity) aspects of the fossil record.

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

NASA Astrophysics Data System (ADS)

Kluiving, Sjoerd; de Ridder, Tim; van Dasselaar, Marcel; Roozen, Stan; Prins, Maarten

2016-06-01

The medieval city of Vlaardingen (the Netherlands) was strategically located on the confluence of three rivers, the Maas, the Merwede, and the Vlaarding. A church of the early 8th century AD was already located here. In a short period of time, Vlaardingen developed in the 11th century AD into an international trading place and into one of the most important places in the former county of Holland. Starting from the 11th century AD, the river Maas repeatedly threatened to flood the settlement. The flood dynamics were registered in Fluvisol archives and were recognised in a multidisciplinary sedimentary analysis of these archives. To secure the future of these vulnerable soil archives an extensive interdisciplinary research effort (76 mechanical drill holes, grain size analysis (GSA), thermo-gravimetric analysis (TGA), archaeological remains, soil analysis, dating methods, micromorphology, and microfauna) started in 2011 to gain knowledge on the sedimentological and pedological subsurface of the settlement mound as well as on the well-preserved nature of the archaeological evidence. Pedogenic features are recorded with soil description, micromorphological, and geochemical (XRF - X-ray fluorescence) analysis. The soil sequence of 5 m thickness exhibits a complex mix of "natural" as well as "anthropogenic" layering and initial soil formation that enables us to make a distinction between relatively stable periods and periods with active sedimentation. In this paper the results of this interdisciplinary project are demonstrated in a number of cross-sections with interrelated geological, pedological, and archaeological stratification. A distinction between natural and anthropogenic layering is made on the basis of the occurrence of the chemical elements phosphor and potassium. A series of four stratigraphic and sedimentary units record the period before and after the flooding disaster. Given the many archaeological remnants and features present in the lower units, in geological terms it is assumed that the medieval landscape was submerged while it was inhabited in the 12th century AD. In reaction to a final submersion phase in the late 12th century AD, the inhabitants started to raise the surface of the settlement. Within archaeological terms the boundary between natural and anthropogenic layers is stratigraphically lower, so that in the interpretation of archaeologists, the living ground was dry during the 12th and the 13th centuries AD. In this discussion, the geological interpretation will be compared with alternative archaeological scenarios.

Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America

PubMed Central

Fowler, Denver Warwick

2017-01-01

Interbasinal stratigraphic correlation provides the foundation for all consequent continental-scale geological and paleontological analyses. Correlation requires synthesis of lithostratigraphic, biostratigraphic and geochronologic data, and must be periodically updated to accord with advances in dating techniques, changing standards for radiometric dates, new stratigraphic concepts, hypotheses, fossil specimens, and field data. Outdated or incorrect correlation exposes geological and paleontological analyses to potential error. The current work presents a high-resolution stratigraphic chart for terrestrial Late Cretaceous units of North America, combining published chronostratigraphic, lithostratigraphic, and biostratigraphic data. 40Ar / 39Ar radiometric dates are newly recalibrated to both current standard and decay constant pairings. Revisions to the stratigraphic placement of most units are slight, but important changes are made to the proposed correlations of the Aguja and Javelina formations, Texas, and recalibration corrections in particular affect the relative age positions of the Belly River Group, Alberta; Judith River Formation, Montana; Kaiparowits Formation, Utah; and Fruitland and Kirtland formations, New Mexico. The stratigraphic ranges of selected clades of dinosaur species are plotted on the chronostratigraphic framework, with some clades comprising short-duration species that do not overlap stratigraphically with preceding or succeeding forms. This is the expected pattern that is produced by an anagenetic mode of evolution, suggesting that true branching (speciation) events were rare and may have geographic significance. The recent hypothesis of intracontinental latitudinal provinciality of dinosaurs is shown to be affected by previous stratigraphic miscorrelation. Rapid stepwise acquisition of display characters in many dinosaur clades, in particular chasmosaurine ceratopsids, suggests that they may be useful for high resolution biostratigraphy. PMID:29166406

Revised geochronology, correlation, and dinosaur stratigraphic ranges of the Santonian-Maastrichtian (Late Cretaceous) formations of the Western Interior of North America.

PubMed

Fowler, Denver Warwick

2017-01-01

Interbasinal stratigraphic correlation provides the foundation for all consequent continental-scale geological and paleontological analyses. Correlation requires synthesis of lithostratigraphic, biostratigraphic and geochronologic data, and must be periodically updated to accord with advances in dating techniques, changing standards for radiometric dates, new stratigraphic concepts, hypotheses, fossil specimens, and field data. Outdated or incorrect correlation exposes geological and paleontological analyses to potential error. The current work presents a high-resolution stratigraphic chart for terrestrial Late Cretaceous units of North America, combining published chronostratigraphic, lithostratigraphic, and biostratigraphic data. 40Ar / 39Ar radiometric dates are newly recalibrated to both current standard and decay constant pairings. Revisions to the stratigraphic placement of most units are slight, but important changes are made to the proposed correlations of the Aguja and Javelina formations, Texas, and recalibration corrections in particular affect the relative age positions of the Belly River Group, Alberta; Judith River Formation, Montana; Kaiparowits Formation, Utah; and Fruitland and Kirtland formations, New Mexico. The stratigraphic ranges of selected clades of dinosaur species are plotted on the chronostratigraphic framework, with some clades comprising short-duration species that do not overlap stratigraphically with preceding or succeeding forms. This is the expected pattern that is produced by an anagenetic mode of evolution, suggesting that true branching (speciation) events were rare and may have geographic significance. The recent hypothesis of intracontinental latitudinal provinciality of dinosaurs is shown to be affected by previous stratigraphic miscorrelation. Rapid stepwise acquisition of display characters in many dinosaur clades, in particular chasmosaurine ceratopsids, suggests that they may be useful for high resolution biostratigraphy.

Aminostratigraphy of surface and subsurface Quaternary sediments, North Carolina coastal plain, USA

USGS Publications Warehouse

Wehmiller, John F.; Thieler, E. Robert; Miller, D.; Pellerito, V.; Bakeman, Keeney V.; Riggs, S.R.; Culver, S.; Mallinson, D.; Farrell, K.M.; York, L.L.; Pierson, J.; Parham, P.R.

2010-01-01

The Quaternary stratigraphy and geochronology of the Albemarle Embayment of the North Carolina (NC) Coastal Plain is examined using amino acid racemization (AAR) in marine mollusks, in combination with geophysical, lithologic, and biostratigraphic analysis of 28 rotasonic cores drilled between 2002 and 2006. The Albemarle Embayment is bounded by structural highs to the north and south, and Quaternary strata thin westward toward the Suffolk paleoshoreline, frequently referred to as the Suffolk Scarp. The Quaternary section is up to ∼90 m thick, consists of a variety of estuarine, shelf, back-barrier, and lagoonal deposits, and has been influenced by multiple sea-level cycles. The temporal resolution of the amino acid racemization method is tested statistically and with the stratigraphic control provided by this geologic framework, and it is then applied to the correlation and age estimation of subsurface units throughout the region. Over 500 specimens (primarily Mercenaria and Mulinia) from the subsurface section have been analyzed using either gas chromatographic (GC) or reverse-phase liquid chromatographic (RPLC) techniques. The subsurface stratigraphic data are compared with AAR results from numerous natural or excavated exposures from the surrounding region, as well as results from NC beach collections, to develop a comprehensive aminostratigraphic database for the entire Quaternary record within the NC coastal system. Age mixing, recognized in the beach collections, is also seen in subsurface sections, usually where major seismic reflections or core lithology indicate the presence of stratigraphic discontinuities. Kinetic models for racemization are tested within the regional stratigraphic framework, using either radiocarbon or U-series calibrations or comparison with regional biostratigraphy. Three major Pleistocene aminozones [AZ2, AZ3, and AZ4] are found throughout the region, all being found in superposition in several cores. Each can be subdivided, yielding a total of at least eight stratigraphically and statistically distinct aminozones. Kinetic modeling, supplemented with local calibration, indicates that these aminozones represent depositional events ranging from ∼80 ka to nearly 2 Ma. Three prominent seismic reflections are interpreted to represent the base of the early, middle, and late Pleistocene, respectively, roughly 2 Ma, 800 ka, and 130 ka. The large number of samples and the available stratigraphic control provide new insights into the capabilities and limitations of aminostratigraphic methods in assessing relative and numerical ages of Atlantic Coastal Plain Quaternary deposits.

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

Davis, R.J.; Johnson, C.A.; Gilreath, J.A.

Depositional systems in the Medina Group (Lower Silurian) of western New York have been studied using stratigraphic dipmeter data. Results of this study indicate a nearshore-deltaic-interdeltaic depositional environment. Only minor deltaic episodes are preserved in the study area. This fits the generally arid climate with seasonal wet periods suggested by C.D. Laughrey. Facies recognized include: longshore-current sand waves in a shoreface environment, distributary mouth bars, distributary channels, tidal inlets, flood deltas, beaches, sandy tidal flats on which beach ridges were formed, and possible upper delta-plain sediments. Once the depositional sequences are recognized, paleocurrents within key sand units can be interpretedmore » to determine favorable directions for successfully locating offset wells.« less

Sedimentary, tectonic, and sea-level controls on submarine fan and slope-apron turbidite systems

USGS Publications Warehouse

Stow, D.A.V.; Howell, D.G.; Nelson, C.H.

1984-01-01

To help understand factors that influence submarine fan deposition, we outline some of the principal sedimentary, tectonic, and sea-level controls involved in deep-water sedimentation, give some data on the rates at which they operate, and evaluate their probable effects. Three depositional end-member systems, two submarine fan types (elongate and radial), and a third nonfan, slope-apron system result primarily from variations in sediment type and supply. Tectonic setting and local and global sea-level changes further modify the nature of fan growth, the distribution of facies, and the resulting vertical stratigraphic sequences. ?? 1984 Springer-Verlag New York Inc.

Geochemistry and stratigraphic relations of middle Proterozoic rocks of the New Jersey Highlands

USGS Publications Warehouse

Volkert, Richard A.; Drake, Avery Ala

1999-01-01

Middle Proterozoic rocks of the New Jersey Highlands consist of a basement of dacitic, tonalitic, trondhjemitic, and charnockitic rocks that constitute the Losee metamorphic suite. These rocks are unconformably overlain by a layered supracrustal sequence of quartzo-feldspathic and calcareous rocks. Abundant sheets of hornblende- and biotite-bearing rocks of the Byram intrusive suite and clinopyroxene-bearing rocks of the Lake Hopatcong intrusive suite were synkinematically emplaced at about 1,090 Ma. These intrusive suites constitute the Vernon Supersuite. The postorogenic Mount Eve Granite has been dated at 1,020?4 Ma and is confined to the extreme northern Highlands.

Hawaii scientific drilling protect: Summary of preliminary results

USGS Publications Warehouse

DePaolo, D.; Stolper, E.; Thomas, D.; Albarede, F.; Chadwick, O.; Clague, D.; Feigenson, M.; Frey, F.; Garcia, M.; Hofmann, A.; Ingram, B.L.; Kennedy, B.M.; Kirschvink, J.; Kurz, M.; Laj, Carlo; Lockwood, J.; Ludwig, K.; McEvilly, T.; Moberly, R.; Moore, G.; Moore, J.; Morin, R.; Paillet, F.; Renne, P.; Rhodes, M.; Tatsumoto, M.; Taylor, H.; Walker, G.; Wilkins, R.

1996-01-01

Petrological, geochemical, geomagnetic, and volcanological characterization of the recovered core from a 1056-m-deep well into the flank of the Mauna Kea volcano in Hilo, Hawaii, and downhole logging and fluid sampling have provided a unique view of the evolution and internal structure of a major oceanic volcano unavailable from surface exposures. Core recovery was ~90%, yielding a time series of fresh, subaerial lavas extending back to ~400 ka. Results of this 1993 project provide a basis for a more ambitious project to core drill a well 4.5 km deep in a nearby location with the goal of recovering an extended, high-density stratigraphic sequence of lavas.

Origins and relationships of colonial Heliophyllum in the upper Middle Devonian (Givetian) of New York

USGS Publications Warehouse

Oliver, W.A.

1997-01-01

Heliophyllum halli Milne-Edwards and Haime is common to abundant in many Lower and Middle Devonian stratigraphic units in New York. Most Heliophyllum are solitary, but both branching and massive colonies are known. Four 'populations' of colonial Heliophyllum in the Givetian part of the sequence are distinct, as is a fifth form that occurs through the section. Each of the colonial forms is interpreted as an independent derivative of solitary forms of H. halli. The relationships appear to range from infrasubspecific to specific, and it is suggested that the complex should be recognized as the Heliophyllum halli species group.

The stratigraphic filter and bias in measurement of geologic rates

USGS Publications Warehouse

Schumer, R.; Jerolmack, D.; McElroy, B.

2011-01-01

Erosion and deposition rates estimated from the stratigraphic record frequently exhibit a power-law dependence on measurement interval. This dependence can result from a power-law distribution of stratigraphic hiatuses. By representing the stratigraphic filter as a stochastic process called a reverse ascending ladder, we describe a likely origin of power-law hiatuses, and thus, rate scaling. While power-law hiatuses in certain environments can be a direct result of power-law periods of stasis (no deposition or erosion), they are more generally the result of randomness in surface fluctuations irrespective of mean subsidence or uplift. Autocorrelation in fluctuations can make hiatuses more or less heavy-tailed, but still exhibit power-law characteristics. In addition we show that by passing stratigraphic data backward through the filter, certain statistics of surface kinematics from their formative environments can be inferred. Copyright ?? 2011 by the American Geophysical Union.

Evaluating controls on fluvial sand-body clustering in the Ferris Formation (Cretaceous/Paleogene, Wyoming, USA)

NASA Astrophysics Data System (ADS)

Hajek, E. A.; Heller, P.

2009-12-01

A primary goal of sedimentary geologists is to interpret past tectonic, climatic, and eustatic conditions from the stratigraphic record. Stratigraphic changes in alluvial-basin fills are routinely interpreted as the result of past tectonic movements or changes in climate or sea level. Recent physical and numerical models have shown that sedimentary systems can exhibit self-organization on basin-filling time scales, suggesting that structured stratigraphic patterns can form spontaneously rather than as the result of changing boundary conditions. The Ferris Formation (Upper Cretaceous/Paleogene, Hanna Basin, Wyoming) exhibits stratigraphic organization where clusters of closely-spaced channel deposits are separated from other clusters by intervals dominated by overbank material. In order to evaluate the role of basinal controls on deposition and ascertain the potential for self-organization in this ancient deposit, the spatial patterns of key channel properties (including sand-body dimensions, paleoflow depth, maximum clast size, paleocurrent direction, and sediment provenance) are analyzed. Overall the study area lacks strong trends sand-body properties through the stratigraphic succession and in cluster groups. Consequently there is no indication that the stratigraphic pattern observed in the Ferris Formation was driven by systematic changes in climate or tectonics.

Burrow-generated false facies and phantom sequences

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

Wanless, H.R.; Tagett, M.

Callianassa (=Ophiomorpha) and other burrowers deeply rework shallow marine sequences. Through in-situ reworking, they create false sedimentary facies and stratigraphic sequences. Callianassa's key to effectiveness is that it expels sand and mud from burrow excavations but concentrates coarse material at the base of the burrow complex. Coarse material can be derived by falling into the burrow entrance, by reworking the existing sediment sequence, or by a combination of both. Examples come from shallow marine carbonate environments of south Florida and the Turks and Caicos Islands, British West Indies. Many mudbanks in south Florida are formed as stacks of layered mudstonemore » units 20-100 cm thick. Between events, seagrasses may recolonize, and a burrowing benthic community may repopulate the substrate. The layered mudstone beneath older areas of mudbank flats can gradually be converted to a bioturbated skeletal wackestone by the deep burrowing community. Burrowing also causes mixing of faunal assemblages. On Caicos Bank, an extensive carbonate tidal flat (3-4 m thick) is slowly being transgressed. About 1 m of tidal-flat sequence is eroded at the shoreline. The remaining 2-3 m could be preserved as part of the transgressive sequence. Callianassa burrowing, however, quickly reworks the sequence, replacing tidal-flat sands and muds with marine peloidal and skeletal sediment. Within 100 m of the shoreline, the only evidence of the tidal-flat sequence is a concentration of high-spired gastropods in Calliannassa burrows at the base of the Holocene sequence and a few patches of tidal-flat sediment that burrowers missed. What looks like a basal transgressive lag is in fact a biogenic concentrate from in-situ reworking of a now phantom sequence.« less

Distribution of "Compound" and "Simple" Flows in the Deccan Traps (India)

NASA Astrophysics Data System (ADS)

Vanderkluysen, L.; Self, S.; Jay, A. E.; Sheth, H. C.; Clarke, A. B.

2014-12-01

The Deccan Traps are a dominantly mafic large igneous province (LIP) that, prior to erosion, covered ~1 million km2 of west-central India with lava flows. The type sections of the Western Ghats escarpment, where the Deccan lava pile reaches a maximum reconstructed stratigraphic thickness of ~3400 m, are subdivided into eleven formations defined on chemo-stratigraphic grounds. Earlier work recognized that emplacement of Deccan basalt flows primarily occurs following two main modes: as a stack of meter-sized pāhoehoe toes and lobes, termed "compound" flows; or as inflated sheet lobes tens to hundreds of meters in width and meters to tens of meters in height, previously termed "simple" flows. Initially, the distribution of small lobes and sheet lobes in the Deccan was thought to be controlled by distance from source, but later work suggested the distribution to be mainly controlled along stratigraphic, formational boundaries, with six of the lower formations being composed exclusively of compound flows, and the upper 4-5 formations being wholly built of sheet lobes. This simple stratigraphic subdivision of lava flow morphologies has also been documented in the volcanic architecture of other LIPs, e.g., the Etendeka, the Ethiopian Traps, and in the Faeroe Islands (North Atlantic LIP). Upon examination of eight sections carefully logged along the Western Ghats, this traditional view must be challenged. Where the lower Deccan formations crop out, we found that as much as 65% of the exposed thickness (below the Khandala Formation) is made up of sheet lobes, from 40% in the Bhimashankar Formation to 75% in the Thakurvadi Formation. Near the bottom of the sequence, 25% of the Neral Formation is composed of sheet lobes ≥15 m in thickness. This distribution in lava flow morphology does not seem to be noticeably affected by the inferred distance to the source (based on the location of similar-composition dikes for each formation). Several mechanisms have been proposed to explain the development of compound flows and inflated sheet lobes, involving one or more of the following factors: underlying slope, varying effusion rate, and source geometry. Analogue experiments are currently under way to test the relative influence of each of these factors in the development of different lava flow morphologies in LIPs.

Is cratonic sedimentation consistent with available models? An example from the Upper Proterozoic of the West African craton

NASA Astrophysics Data System (ADS)

Bertrand-Sarfati, Janine; Moussine-Pouchkine, Alexis

1988-08-01

The Atar Group, part of the Upper Proterozoic sequence covering the West African craton, stable since 2000 Ma, is characterized by an alternation of extensive carbonate beds and mixed siliciclastic and carbonate facies. The carbonate beds comprise essentially columnar stromatolite biostromes and bioherms which reflect sublittoral environments. The mixed facies contain a variety of laterally discontinuous facies which imply more variable environmental conditions. The settings of the mixed facies are not always clear but they do not contain thick sequences of high-energy facies. Few obvious facies sequences are discernable; those that are present are considered to be punctuated aggradational cycles (PACs) and they always start with biostromes of columnar stromatolites with very few sediments. Composite sequences are interpreted as due to shallowing upward or increasing energy environments that may be laterally contiguous, despite the fact that the contacts are not gradational. However, much of the stratigraphic sequence cannot be subdivided into cycles and seems to consist of unrelated individual facies, bound by sharp boundaries. The basin analysis reveals that biostromes of columnar stromatolites start after an instantaneous geological event corresponding to a sea-level rise. Consequently, their appearance can be considered as a time-line. We describe, in the Atar Group and its equivalents, three sedimentation trends, all of which are interpreted to be of shallowing upward character. The Atar Group appears to have been deposited in an epeiric sea (i.e. an extremely flat ramp). There are two contrasting styles of sedimentation: (1) after the submergence of the whole area, columnar stromatolites built extensive biostromes; (2) during the stable phase, sediments are deposited in a mosaic of laterally-discontinuous facies. Tidal influence cannot be recognized in the sequence, neither can a salinity increase toward the land; both common features in published epeiric sea models. A cratonic sedimentation area such as this is characterized by its size and flatness. Only during the stable phase of the cycle does small-scale topographic relief lead to deposition of a mosaic of facies. The sedimentation is storm- and wave-dominated.

High Resolution Stratigraphic Mapping in Complex Terrain: A Comparison of Traditional Remote Sensing Techniques with Unmanned Aerial Vehicle - Structure from Motion Photogrammetry

NASA Astrophysics Data System (ADS)

Nesbit, P. R.; Hugenholtz, C.; Durkin, P.; Hubbard, S. M.; Kucharczyk, M.; Barchyn, T.

2016-12-01

Remote sensing and digital mapping have started to revolutionize geologic mapping in recent years as a result of their realized potential to provide high resolution 3D models of outcrops to assist with interpretation, visualization, and obtaining accurate measurements of inaccessible areas. However, in stratigraphic mapping applications in complex terrain, it is difficult to acquire information with sufficient detail at a wide spatial coverage with conventional techniques. We demonstrate the potential of a UAV and Structure from Motion (SfM) photogrammetric approach for improving 3D stratigraphic mapping applications within a complex badland topography. Our case study is performed in Dinosaur Provincial Park (Alberta, Canada), mapping late Cretaceous fluvial meander belt deposits of the Dinosaur Park formation amidst a succession of steeply sloping hills and abundant drainages - creating a challenge for stratigraphic mapping. The UAV-SfM dataset (2 cm spatial resolution) is compared directly with a combined satellite and aerial LiDAR dataset (30 cm spatial resolution) to reveal advantages and limitations of each dataset before presenting a unique workflow that utilizes the dense point cloud from the UAV-SfM dataset for analysis. The UAV-SfM dense point cloud minimizes distortion, preserves 3D structure, and records an RGB attribute - adding potential value in future studies. The proposed UAV-SfM workflow allows for high spatial resolution remote sensing of stratigraphy in complex topographic environments. This extended capability can add value to field observations and has the potential to be integrated with subsurface petroleum models.

Stratal Control Volumes and Stratal Control Trajectories: A New Method to Constrain, Understand and Reconcile Results from Stratigraphic Outcrop Analysis, Subsurface Analysis and Analogue and Numerical Modelling

NASA Astrophysics Data System (ADS)

Burgess, P. M.; Steel, R. J.

2016-12-01

Decoding a history of Earth's surface dynamics from strata requires robust quantitative understanding of supply and accommodation controls. The concept of stratigraphic solution sets has proven useful in this decoding, but application and development of this approach has so far been surprisingly limited. Stratal control volumes, areas and trajectories are new approaches defined here, building on previous ideas about stratigraphic solution sets, to help analyse and understand the sedimentary record of Earth surface dynamics. They may have particular application reconciling results from outcrop and subsurface analysis with results from analogue and numerical experiments. Stratal control volumes are sets of points in a three-dimensional volume, with axes of subsidence, sediment supply and eustatic rates of change, populated with probabilities derived from analysis of subsidence, supply and eustasy timeseries (Figure 1). These empirical probabilities indicate the likelihood of occurrence of any particular combination of control rates defined by any point in the volume. The stratal control volume can then by analysed to determine which parts of the volume represent relative sea-level fall and rise, where in the volume particular stacking patterns will occur, and how probable those stacking patterns are. For outcrop and subsurface analysis, using a stratal control area with eustasy and subsidence combined on a relative sea-level axis allows similar analysis, and may be preferable. A stratal control trajectory is a history of supply and accommodation creation rates, interpreted from outcrop or subsurface data, or observed in analogue and numerical experiments, and plotted as a series of linked points forming a trajectory through the stratal control volume (Figure 1) or area. Three examples are presented, one from outcrop and two theoretical. Much work remains to be done to build a properly representative database of stratal controls, but careful comparison of stratal control volume and trajectories constructed from outcrop analysis, subsurface analysis and experimental models may help the convergence, reconciliation and future evolution of these different approaches.

Cyclostratigraphy across a Mississippian carbonate ramp in the Esfahan-Sirjan Basin, Iran: implications for the amplitudes and frequencies of sea-level fluctuations along the southern margin of the Paleotethys

NASA Astrophysics Data System (ADS)

Bayet-Goll, Aram; Esfahani, Fariba Shirezadeh; Daraei, Mehdi; Monaco, Paolo; Sharafi, Mahmoud; Mohammadi, Amir Akbari

2018-03-01

The Tournaisian-Visean carbonate successions of the Esfahan-Sirjan Basin (ESB) from Sanandaj-Sirjan Zone, Iran, have been used to generate a sequence stratigraphic model that enhances facies characterization and improves paleoenvironmental interpretation of shallow marine successions deposited along the southern margin of the Paleotethys. Detailed facies analysis allowed to differentiate seven facies, which, in order of decreasing abundance, are: (1) shaly and marly, F1; (2) peloidal mudstones/wackestones, F2; (3) peloidal/bioclastic packstones, F3; (4) intraclastic/bioclastic packstones/grainstones, F4; (5) oolitic/bioclastic packstone/grainstone, F5; (6) sandy intraclastic/bioclastic grainstones, F6; (7) sandy oolitic/bioclastic grainstones, F7. The different facies can be grouped into three facies associations that correspond to different environments of a carbonate platform with ramp geometry (homoclinal), from outer ramp (F1 and F2), mid-ramp (F3, F4 and F6) to inner ramp areas (F5 and F7). Meter-scale cycles are the basic building blocks of shallow marine carbonate successions of the Tournaisian-Viséan ramp of the ESB. Small-scale cycles are stacked into medium-scale cycles that in turn are building blocks of large-scale cycles. According to the recognized facies and the stacking pattern of high-frequency cycles across the ramp, five large-scale cycles in the southeastern outcrops (Tournaisian-Viséan) and three large-scale cycles in the northwest outcrops (Viséan) related to eustatic sea-level changes can be recognized. The overall retrogradational nature of the carbonate ramp, illustrated by both vertical facies relationships and the stacking patterns of high-frequency cycles within the third-order cycles, implies that the deposition of the Tournaisian-Viséan successions mainly took place under a long-term transgressive sea-level trend. The stratigraphic architectural style of the sequences, characterized by the lack of lowstand deposits and exposure surfaces, associated with the evidence of progressive increase in the proportion of backstepping of facies belts across bounding surfaces and predominant subtidal characteristics, is in accordance with the long-term transgressive sea-level trend and greenhouse conditions during the Tournaisian-Viséan. The continued transgression on this broad shelfal platform could lead to the shutdown of the shallow water carbonate factory, reduction in sediment supply or sediment transport towards the offshore setting and the development of give-up sequences. The association of transgressive events with the deposition of thick open-marine marls/shales is a common feature in Tournaisian to Viséan times of the southern margin of the Paleotethys.

Three-dimensional geologic mapping of the Cenozoic basin fill, Amargosa Desert basin, Nevada and California

USGS Publications Warehouse

Taylor, Emily M.; Sweetkind, Donald S.

2014-01-01

Understanding the subsurface geologic framework of the Cenozoic basin fill that underlies the Amargosa Desert in southern Nevada and southeastern California has been improved by using borehole data to construct three-dimensional lithologic and interpreted facies models. Lithologic data from 210 boreholes from a 20-kilometer (km) by 90-km area were reduced to a limited suite of descriptors based on geologic knowledge of the basin and distributed in three-dimensional space using interpolation methods. The resulting lithologic model of the Amargosa Desert basin portrays a complex system of interfingered coarse- to fine-grained alluvium, playa and palustrine deposits, eolian sands, and interbedded volcanic units. Lithologic units could not be represented in the model as a stacked stratigraphic sequence due to the complex interfingering of lithologic units and the absence of available time-stratigraphic markers. Instead, lithologic units were grouped into interpreted genetic classes, such as playa or alluvial fan, to create a three-dimensional model of the interpreted facies data. Three-dimensional facies models computed from these data portray the alluvial infilling of a tectonically formed basin with intermittent internal drainage and localized regional groundwater discharge. The lithologic and interpreted facies models compare favorably to resistivity, aeromagnetic, and geologic map data, lending confidence to the interpretation.

High-resolution hydro- and geo-stratigraphy at Atlantic Coastal Plain drillhole CR-622 (Strat 8)

USGS Publications Warehouse

Wrege, B.M.; Isely, J.J.

2009-01-01

We interpret borehole geophysical logs in conjunction with lithology developed from continuous core to produce high-resolution hydro- and geo-stratigraphic profiles for the drillhole CR-622 (Strat 8) in the Atlantic Coastal Plain of North Carolina. The resulting hydrologic and stratigraphic columns show a generalized relation between hydrologic and geologic units. Fresh-water aquifers encountered are the surficial, Yorktown, Pungo River and Castle Hayne. Geologic units present are of the middle and upper Tertiary and Quaternary periods, these are the Castle Hayne (Eocene), Pungo River (Miocene), Yorktown (Pliocene), James City and Flanner Beach (Pleistocene), and the topsoil (Holocene). The River Bend Formation (Oligocene) is missing as a distinct unit between the Pungo River Formation and the Castle Hayne Formation. The confining unit underlying the Yorktown Aquifer corresponds to the Yorktown Geologic Unit. The remaining hydrologic units and geologic units are hydrologically transitional and non-coincident. The lower Pungo River Formation serves as the confining unit for the Castle Hayne Aquifer, rather than the River Bend Aquifer, and separates the Pungo River Aquifer from the upper Castle Hayne Aquifer. All geologic formations were bound by unconformities. All aquifers were confined by the anticipated hydrologic units. We conclude that CR-622 (Strat 8) represents a normal sequence in the Atlantic Coastal Plain.

Geological structure, recharge processes and underground drainage of a glacierised karst aquifer system, Tsanfleuron-Sanetsch, Swiss Alps

NASA Astrophysics Data System (ADS)

Gremaud, Vivian; Goldscheider, Nico; Savoy, Ludovic; Favre, Gérald; Masson, Henri

2009-12-01

The relationships between stratigraphic and tectonic setting, recharge processes and underground drainage of the glacierised karst aquifer system ‘Tsanfleuron-Sanetsch’ in the Swiss Alps have been studied by means of various methods, particularly tracer tests (19 injections). The area belongs to the Helvetic nappes and consists of Jurassic to Palaeogene sedimentary rocks. Strata are folded and form a regional anticlinorium. Cretaceous Urgonian limestone constitutes the main karst aquifer, overlain by a retreating glacier in its upper part. Polished limestone surfaces are exposed between the glacier front and the end moraine of 1855/1860 (Little Ice Age); typical alpine karrenfields can be observed further below. Results show that (1) large parts of the area are drained by the Glarey spring, which is used as a drinking water source, while marginal parts belong to the catchments of other springs; (2) groundwater flow towards the Glarey spring occurs in the main aquifer, parallel to stratification, while flow towards another spring crosses the entire stratigraphic sequence, consisting of about 800 m of marl and limestone, along deep faults that were probably enlarged by mass movements; (3) the variability of glacial meltwater production influences the shape of the tracer breakthrough curves and, consequently, flow and transport in the aquifer.

An approach of understanding acid volcanics and tuffaceous volcaniclastics from field studies: A case from Tadpatri Formation, Proterozoic Cuddapah basin, Andhra Pradesh, India

NASA Astrophysics Data System (ADS)

Goswami, Sukanta; Upadhyay, P. K.; Bhagat, Sangeeta; Zakaulla, Syed; Bhatt, A. K.; Natarajan, V.; Dey, Sukanta

2018-03-01

The lower stratigraphic part of the Cuddapah basin is marked by mafic and felsic volcanism. Tadpatri Formation consists of a greater variety of rock types due to bimodal volcanism in the upper part. Presence of bimodal volcanism is an indication of continental rift setting. Various genetic processes involved in the formation of such volcanic sequence result in original textures which are classified into volcaniclastic and coherent categories. Detailed and systematic field works in Tadpatri-Tonduru transect of SW Cuddapah basin have provided information on the physical processes producing this diversity of rock types. Felsic volcanism is manifested here with features as finger print of past rhyolite-dacite eruptions. Acid volcanics, tuffs and associated shale of Tadpatri Formation are studied and mapped in the field. With supporting subordinate studies on geochemistry, mineralogy and petrogenesis of the volcanics to validate field features accurately, it is understood that volcanism was associated with rifting and shallow marine environmental condition. Four facies (i.e., surge, flow, fall and resedimented volcaniclastic) are demarcated to describe stratigraphic units and volcanic history of the mapped area. The present contribution focuses on the fundamental characterization and categorization of field-based features diagnostic of silica-rich volcanic activities in the Tadpatri Formation.

Glacially-derived overpressure in the northeastern Alaskan subduction zone: combined tomographic and morphometric analysis of shallow sediments on the Yakutat shelf and slope, Gulf of Alaska

NASA Astrophysics Data System (ADS)

Clary, W. A.; Worthington, L. L.; Scuderi, L. A.; Daigle, H.; Swartz, J. M.

2017-12-01

The Pamplona zone fold and thrust belt is the offshore expression of convergence and shallow subduction of the Yakutat microplate beneath North America in the northeastern Alaska subduction zone. The combination of convergent tectonics and glaciomarine sedimentary processes create patterns of deformation and deposition resulting in a shallow sedimentary sequence with varying compaction, fluid pressure, and fault activity. We propose that velocity variations observed in our tomographic analysis represent long-lived fluid overpressure due to loading by ice sheets and sediments. Regions with bathymetric and stratigraphic evidence of recent ice sheets and associated sedimentation should be collocated with evidence of overpressure (seismic low velocity zones) in the shallow sediments. Here, we compare a velocity model with shelf seismic stratigraphic facies and modern seafloor morphology. To document glacially derived morphology we use high resolution bathymetry to identify channel and gully networks on the western Yakutat shelf-slope then analyze cross-channel shape indices across the study area. We use channel shape index measurements as a proxy of recent ice-proximal sedimentation based on previously published results that proposed a close correlation. Profiles taken at many locations were fitted with a power function and assigned a shape - U-shape channels likely formed proximal to recent ice advances. Detailed velocity models were created by a combination of streamer tomography and pre-stack depth migration velocities with seismic data including: a 2008 R/V Langseth dataset from the St. Elias Erosion and Tectonics Project (STEEP); and a 2004 high-resolution R/V Ewing dataset. Velocity-porosity-permeability relationships developed using IODP Expedition 341 drilling data inform interpretation and physical properties analyses of the shallow sediments. Initial results from a 35 km profile extending SE seaward of the Bering glacier and subparallel to the Bering trough suggest a spatial relationship between the extent of U-shaped profiles and low-velocity shallow sediments. Towards the SE end of the model we observe a large overlap of U-shaped indices, and a shallow low-velocity zone in the mapped extent of the last glacial maximum suggestive of overpressure due to loading by ice sheet activity.

Palynological composition of a Lower Cretaceous South American tropical sequence: climatic implications and diversity comparisons with other latitudes.

PubMed

Mejia-Velasquez, Paula J; Dilcher, David L; Jaramillo, Carlos A; Fortini, Lucas B; Manchester, Steven R

2012-11-01

Reconstruction of floristic patterns during the early diversification of angiosperms is impeded by the scarce fossil record, especially in tropical latitudes. Here we collected quantitative palynological data from a stratigraphic sequence in tropical South America to provide floristic and climatic insights into such tropical environments during the Early Cretaceous. We reconstructed the floristic composition of an Aptian-Albian tropical sequence from central Colombia using quantitative palynology (rarefied species richness and abundance) and used it to infer its predominant climatic conditions. Additionally, we compared our results with available quantitative data from three other sequences encompassing 70 floristic assemblages to determine latitudinal diversity patterns. Abundance of humidity indicators was higher than that of aridity indicators (61% vs. 10%). Additionally, we found an angiosperm latitudinal diversity gradient (LDG) for the Aptian, but not for the Albian, and an inverted LDG of the overall diversity for the Albian. Angiosperm species turnover during the Albian, however, was higher in humid tropics. There were humid climates in northwestern South America during the Aptian-Albian interval contrary to the widespread aridity expected for the tropical belt. The Albian inverted overall LDG is produced by a faster increase in per-sample angiosperm and pteridophyte diversity in temperate latitudes. However, humid tropical sequences had higher rates of floristic turnover suggesting a higher degree of morphological variation than in temperate regions.

Palynological composition of a Lower Cretaceous South American tropical sequence: Climatic implications and diversity comparisons with other latitudes.

USGS Publications Warehouse

Mejia-Velasquez, Paula J.; Dilcher, David L.; Jaramillo, Carlos A.; Fortini, Lucas B.; Manchester, Steven R.

2012-01-01

Premise of the study: Reconstruction of floristic patterns during the early diversification of angiosperms is impeded by the scarce fossil record, especially in tropical latitudes. Here we collected quantitative palynological data from a stratigraphic sequence in tropical South America to provide floristic and climatic insights into such tropical environments during the Early Cretaceous. Methods: We reconstructed the floristic composition of an Aptian-Albian tropical sequence from central Colombia using quantitative palynology (rarefied species richness and abundance) and used it to infer its predominant climatic conditions. Additionally, we compared our results with available quantitative data from three other sequences encompassing 70 floristic assemblages to determine latitudinal diversity patterns. Key results: Abundance of humidity indicators was higher than that of aridity indicators (61% vs. 10%). Additionally, we found an angiosperm latitudinal diversity gradient (LDG) for the Aptian, but not for the Albian, and an inverted LDG of the overall diversity for the Albian. Angiosperm species turnover during the Albian, however, was higher in humid tropics. Conclusions: There were humid climates in northwestern South America during the Aptian-Albian interval contrary to the widespread aridity expected for the tropical belt. The Albian inverted overall LDG is produced by a faster increase in per-sample angiosperm and pteridophyte diversity in temperate latitudes. However, humid tropical sequences had higher rates of floristic turnover suggesting a higher degree of morphological variation than in temperate regions.

Quantitative allochem compositional analysis of Lochkovian-Pragian boundary sections in the Prague Basin (Czech Republic)

NASA Astrophysics Data System (ADS)

Weinerová, Hedvika; Hron, Karel; Bábek, Ondřej; Šimíček, Daniel; Hladil, Jindřich

2017-06-01

Quantitative allochem compositional trends across the Lochkovian-Pragian boundary Event were examined at three sections recording the proximal to more distal carbonate ramp environment of the Prague Basin. Multivariate statistical methods (principal component analysis, correspondence analysis, cluster analysis) of point-counted thin section data were used to reconstruct facies stacking patterns and sea-level history. Both the closed-nature allochem percentages and their centred log-ratio (clr) coordinates were used. Both these approaches allow for distinguishing of lowstand, transgressive and highstand system tracts within the Praha Formation, which show gradual transition from crinoid-dominated facies deposited above the storm wave base to dacryoconarid-dominated facies of deep-water environment below the storm wave base. Quantitative compositional data also indicate progradative-retrogradative trends in the macrolithologically monotonous shallow-water succession and enable its stratigraphic correlation with successions from deeper-water environments. Generally, the stratigraphic trends of the clr data are more sensitive to subtle changes in allochem composition in comparison to the results based on raw data. A heterozoan-dominated allochem association in shallow-water environments of the Praha Formation supports the carbonate ramp environment assumed by previous authors.

Late Paleozoic tectonics of the Solonker Zone in the Wuliji area, Inner Mongolia, China: Insights from stratigraphic sequence, chronology, and sandstone geochemistry

NASA Astrophysics Data System (ADS)

Shi, Guanzhong; Song, Guangzeng; Wang, Hua; Huang, Chuanyan; Zhang, Lidong; Tang, Jianrong

2016-09-01

The geology in the Wuliji area (including the Enger Us and Quagan Qulu areas) is important for understanding the Late Paleozoic tectonics of the Solonker Zone. Ultramafic/mafic rocks in the Enger Us area, previously interpreted as an ophiolitic suture, are actually lava flows and sills in a Permian turbiditic sequence and a small body of fault breccia containing serpentinite. Subduction zone features, such as accretionary complexes, magmatic arc volcanics or LP/HP metamorphism are absent. Early Permian N-MORB mafic rocks and Late Permian radiolarian cherts accompanied by turbidites and tuffeous rocks indicate a deep water setting. In the Quagan Qulu area, outcrops of the Late Carboniferous to Permian Amushan Formation are composed of volcano-sedimenary rocks and guyot-like reef limestone along with a Late Permian volcano-sedimentary unit. A dacite lava in the Late Permian volcano-sedimentary unit yields a zircon U-Pb age of 254 Ma. The gabbros in the Quagan Qulu area are intruded into the Amushan Formation and caused contact metamorphism of country rocks. Sandstones in the Upper Member of the Amushan Formation contain detrital clasts of volcanic fragments and mineral clasts of crystalline basement rocks (i.e. biotite, muscovite and garnet). Geochemical analysis of volcaniclastic sandstones shows a magmatic affinity to both continental island arc (CIA) and active continental margin (ACM) tectonic settings. A Late Permian incipient rift setting is suggested by analyzing the lithostratigraphic sequence and related magmatism in the Wuliji area. The volcano-sedimentary rocks in the Wuliji area experienced a nearly N-S shortening that was probably related to the Early Mesozoic nearly N-S compression well developed in other areas close to the Wuliji area.

Paleomagnetic directions and thermoluminescence dating from a bread oven-floor sequence in Lübeck (Germany): A record of 450 years of geomagnetic secular variation

NASA Astrophysics Data System (ADS)

Schnepp, Elisabeth; Pucher, Rudolf; Goedicke, Christian; Manzano, Ana; Müller, Uwe; Lanos, Philippe

2003-02-01

A record of about 450 years of geomagnetic secular variation is presented from a single archaeological site in Lübeck (Germany) where a sequence of 25 bread oven floors has been preserved in a bakery from medieval times until today. The age dating of the oven-floor sequence is based on historical documents, 14C-dating and thermoluminescence dating. It confines the time interval from about 1300 to 1800 A.D. Paleomagnetic directions have been determined from each oven floor by means of 198 oriented hand samples. After alternating field as well as thermal demagnetization experiments, the characteristic remanent magnetization direction was obtained using principal component analysis. The mean directions of 24 oven floors are characterized by high Fisherian precision parameters (>146) and small α95 confidence limits (1.2°-4.6°). For obtaining a smooth curve of geomagnetic secular variation for Lübeck, a spherical spline function was fitted to the data using a Bayesian approach, which considers not only the obtained ages, but also stratigraphic order. Correlation with historical magnetic records suggests that the age estimation for the upper 10 layers was too young and must date from the end of the sixteenth to the mid of the eighteenth century. For the lowermost 14 layers, dating is reliable and provides a secular variation curve for Germany. The inclination shows a minimum in the fourteenth century and then increases by more than 10°. Declination shows a local minimum around 1400 A.D. followed by a maximum in the seventeenth century. This is followed by the movement of declination about 30° to western directions.

Mesoscale barrier estuary behaviour in response to sea-level rise, storms and sediment supply.

NASA Astrophysics Data System (ADS)

Hamilton, Christine; Kirby, Jason; Plater, Andrew; Lane, Timothy

2017-04-01

Future vulnerability and resilience of coastal landscapes, and their associated communities, infrastructure and nature conservation interests, is of increasing concern due to the combined effects of climate change and sea-level rise. The Suffolk coast, UK, characterised by gravel barrier beaches and a spit feature of international geomorphological interest, has changed dramatically. However, existing Holocene research in this respect is limited. Sediments preserved within the enclosed valleys and back-barrier wetlands of Suffolk provide an opportunity to improve understanding of the complex mesoscale (years-decades-centuries) behaviour of coastlines and their geomorphological response to changes in natural forcing. This research aims to reconstruct Holocene changes in coastline behaviour to develop reconstructions of coastal evolution relating to changes in relative sea level, sediment supply and storm incidence. Litho- and bio-stratigraphic analysis (sedimentology, particle size, and diatom analysis) has been undertaken on three marsh and wetland sites in a 5 km section between Walberswick and Dunwich. Though intra-site sediment variability is high, a consistent pattern of interbedded intertidal and freshwater units separated by transitional marsh deposits is seen at all sites. Diatom analysis from two sites (Westwood Marsh and Oldtown Marsh) indicates increased marine and brackish conditions across the organic-minerogenic transitions. The diatom assemblage from Great Dingle Hill, a more seaward site, is dominated by brackish species, with an increase in marine conditions across the main organic-minerogenic stratigraphic transition. Freshwater and salt tolerant species are minimal in this assemblage, indicating a constant saltwater input. The onset of peat deposition has been dated to 6950-6790 cal. BP at the base of the Westwood Marsh sequence. These results contrast with existing research from the Blyth estuary (5 km north) where peat deposition was dated to 7714-7479 cal. BP. Submitted radiocarbon analysis will provide further chronological constraint for the timing of the major coastal behavioural changes identified from the analysis. Combined, these results indicate that this section of the Suffolk coast has been subject to periodic opening and closing during the Holocene. Though currently unresolved, longshore sediment supply, high magnitude-low frequency storm events, sea-level change, and the position of offshore banks are likely causal mechanisms for these changes. These results will improve understanding of the long term (Holocene) natural signal of coastal change and are significant given that the regional Shoreline Management Plan has recommended managed realignment for this section of the Suffolk coast.