Sedimentology and carbon-isotope stratigraphy of the Late Cretaceous Chalk Group in the Höllviken-1 core (SW Sweden)

NASA Astrophysics Data System (ADS)

Bøttger, Dorthe; Thibault, Nicolas; Anderskouv, Kresten

2016-04-01

The Höllviken-1 borehole is situated on the Skåne peninsula (SW Sweden) which was part of the Danish Basin in the Late Cretaceous. 1415 meters have been cored among which ca. 1100 meters cover the complete Upper Cretaceous to lower Danian Chalk Group. Besides the publication of a synthetic log and detailed foraminifer biozonation, supplemented by a number of rare macrofossil findings and description of a number of foraminifer holotypes (Brötzen, 1944), very few studies of the core have actually been performed, since the mid 1940s. A new project has thus been undertaken aiming at improving the stratigraphy of the Chalk Group in the Höllviken-1 core. The data presented here comprise the description of the interval 837-489 m covering a large part of the Campanian and the lower Maastrichtian. Two intervals with the presence of sand are noted in the Campanian and two intervals showing possibly progradational sequences of arenaceous marls to sand are present in the Maastrichtian. The purpose of this new study is to revise the foraminifer biostratigraphy of Brötzen and complement it with high-resolution carbon-isotope stratigraphy in order to establish a new age-model for the core and better constrain the timing of siliciclastic input into the Danish Basin. In addition, high-resolution sedimentological data will be used as a preliminary test for cyclostratigraphy of the chalk-marl intervals.

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.

Middle Eocene, older sequences in rifts key to potential in western Indonesia

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

Courteney, S.

1996-05-27

In Part 1 of this article three areas, the Tiga Puluh arch (Sumatra), the Tanjung Raya area (Kalimantan), and the East Java basin in western Indonesia were discussed in terms of sequence stratigraphy. Such data have been interpreted for each basin in western Indonesia and two example correlations are discussed. A correlation chart of the major basins of Western Indonesia is shown in this paper. This chart was prepared on the basis of the regional correlations using sequence stratigraphy discussed.

Sequence stratigraphy: A personal history of lows and highs

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

Sangree, J.B.; Mitchum, R.M. III

1995-12-31

We have been privileged to observe and to participate in the development of sequence stratigraphy over the last forty years. We have been mainly laborers in the vineyard, rather than vintners, but in a way this is our own story. We can only present it as a personal view of the history of the subject. Sequence stratigraphy has several roots and each has its own history. Sequence stratigraphy is an attempt to find practical physical applications for the ideas of chronostratigraphy, ideas that stretch back at least into the early nineteen hundreds. Another basic root is the concept of cyclicmore » patterns of onlap of coastal facies sediments onto the continents. This abstraction includes the idea that many of these longer term cycles may be synchronous on an intercontinental basis, at least within the limitations of current biostratigraphic age dates. A third root lies unexpectedly in the parallelism of seismic reflections an chronostratigraphic surfaces. Initially this notion meet with resistance and skepticism, but it has proved a sturdy tool in the development of our understanding of regional time-stratigraphy. Finally, and most controversially, is the notion that many cycles of continental onlap owe their origin to rise and fall of worldwide sea level. The nature and causes of eustasy look as though they will be debated into the next millennium, but the physical evidence for cyclic changes in sea level relative to the continent is now well fixed.« less

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.

A transgressive Santonian-Campanian boundary sequence revisited - High resolution planktonic and benthic foraminifera stratigraphy of the Schattau section, Northern Calcareous Alps.

NASA Astrophysics Data System (ADS)

Wolfgring, Erik; Wagreich, Michael; Summesberger, Herbert; Kroh, Andreas

2016-04-01

The Schattau section is part of the Austrian Gosau Group, Northern Calcareous Alps. We record a Santonian to early Campanian transgressive sequence. Previous investigations already provide a biostratigraphic framework; a multidisciplinary study to reveal the local stratigraphy and palaeoenvironmental properties: Planktonic foraminifera, calcareous nannoplankton, ammonite, echinoid and crinoid biostratigraphy data suggest a Santonian to earliest Campanian age for this section (see Wagreich et al., 2009). This work aims at a high resolution assessment of foraminiferal assemblages recorded from a time interval that has undergone significant palaeoenvironmental changes. The Santonian Hochmoos Formation, with the Sandkalkbank Member representing it's topmost subunit, is overlain by the Santonian to Campanian Bibereck Formation. While The Hochmoos Formation records a shallowing succession that finds the Sandkalkbank Member (representing very shallow conditions, sometimes sub aerial exposure) at its top. The overlying Bibereck Formation records a distinct deepening trend displaying increasingly marine, neritic to outer neritic conditions. The stratigraphically older subunits of the Schattau sections are characterised by abundant larger benthic foraminifera (Nummofallotia cretacea), miliolid foraminifera (Quinqueloculina spp, Spiroloculina fassistomata) as well as rotaliid foraminifera (Hoeglundia spp., Gavellina spp.). The Sandkalkbank member marks the end of the shallow water sequence recorded from foraminifera assemblages at the Schattau section. Up section communities are characterised by increasing share of planktonic foraminifera. Biostratigraphic marker fossils like Dicarinella asymetrica and Sigalia sp. (decoratissima?) were identified and indicate a Santonian age for the Bibereck Formation. The appearance of Globotruncanita elevata and disappearance of D. asymetrica and Sigalia sp. Suggests an early Campanian age for the topmost part of the Schattau section. Tubular and bi- and triserial agglutinated foraminifera (e.g. Ammobaculites spp., Dorothia spp., Gaudryina spp., Tritaxia spp.) as well as spiral calcareous benthic foraminifera (Gavellinella spp., Lenticulina spp.) are recorded in the younger deposits at the Schattau section (in the Bibereck Formation). Developments in benthic foraminiferal taxa do not only seem to provide valuable information on palaeoenvironmental properties. The succession of certain benthic taxa (e.g.. Gavellinella spp.) provides valuable data on local benthic foraminiferal biostratigraphy which is particularly valuable if environmental factors inhibit the occurrence of planktonic foraminiferal markers. References: Wagreich, M., Summesberger, H., Kroh, A., 2010. Late Santonian bioevents in the Schattau section, Gosau Group of Austria - implications for the Santonian - Campanian boundary stratigraphy. Cretaceous Research, 31, 2, 181-191

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.

Aqueous mineralogy and stratigraphy at and around the proposed Mawrth Vallis MSL Landing Site: New insights into the aqueous history of the region

USGS Publications Warehouse

Dobrea, Eldar Z. Noe; Michalski, Joseph; Swayze, Gregg

2011-01-01

In this work, we have confirmed the mineralogical stratigraphy previously inferred by other authors, but also demonstrate the presence of additional minerals, including a possible acid-leaching product near the top of the sequence, an Mh-OH bearing phyllosilicate at the to of the sequence, and potentially a Ca-sulfate at the bottom of the phyllosilicate sequence. The latter has important implications regarding the relative timing of sulfate vs clay formation on Mars.

High-resolution multi-channel seismic images of the Queen Charlotte Fault system offshore southeastern Alaska

NASA Astrophysics Data System (ADS)

Miller, N. C.; Brothers, D. S.; Kluesner, J.; Balster-Gee, A.; Ten Brink, U. S.; Andrews, B. D.; Haeussler, P. J.; Watt, J. T.; Dartnell, P.; East, A. E.

2016-12-01

We present high-resolution multi-channel seismic (MCS) images of fault structure and sedimentary stratigraphy along the southeastern Alaska margin, where the northern Queen Charlotte Fault (QCF) cuts the shelf-edge and slope. The QCF is a dominantly strike slip system that forms the boundary between the Pacific (PA) and North American (NA) plates offshore western Canada and southeastern Alaska. The data were collected using a 64 channel, 200 m digital streamer and a 0.75-3 kJ sparker source aboard the R/V Norseman in August 2016. The survey was designed to cross a seafloor fault trace recently imaged by multibeam sonar (see adjacent poster by Brothers et al.) and to extend the subsurface information landward and seaward from the fault. Analysis of these MCS and multibeam data focus on addressing key questions that have significant implications for the kinematic and geodynamic history of the fault, including: Is the imaged surface fault in multibeam sonar the only recently-active fault trace? What is the shallow fault zone width and structure, is the internal structure of the recently-discovered pull-apart basin a dynamically developing structure? How does sediment thickness vary along the margin and how does this variation affect the fault expression? Can previous glacial sequences be identified in the stratigraphy?

Bio-, Magneto- and event-stratigraphy across the K-T boundary

NASA Technical Reports Server (NTRS)

Preisinger, A.; Stradner, H.; Mauritsch, H. J.

1988-01-01

Determining the time and the time structure of rare events in geology can be accomplished by applying three different and independent stratigraphic methods: Biostratigraphy, magneto-stratigraphy and event-stratigraphy. The optimal time resolution of the two former methods is about 1000 years, while by means of event-stratigraphy a resolution of approximately one year can be achieved. For biostratigraphy across the Cretaceous-Tertiary (K-T) boundary micro- and nannofossils have been found best suited. The qualitative and quantitative analyses of minerals and trace elements across the K-T boundary show anomalies on a millimeter scale and permit conclusions regarding the time structure of the K-T event itself. The results of the analyses find a most consistent explanation by the assumption of an extraterrestrial impact. The main portion of the material rain from the atmosphere evidently was deposited within a short time. The long-time components consist of the finest portion of the material rain from the atmosphere and the transported and redeposited fall-out.

High-resolution record of the environmental response to climatic variations during the Last Interglacial-Glacial cycle in Central Europe: the loess-palaeosol sequence of Dolní Věstonice (Czech Republic)

NASA Astrophysics Data System (ADS)

Antoine, Pierre; Rousseau, Denis-Didier; Degeai, Jean-Philippe; Moine, Olivier; Lagroix, France; kreutzer, Sebastian; Fuchs, Markus; Hatté, Christine; Gauthier, Caroline; Svoboda, Jiri; Lisá, Lenka

2013-05-01

High-resolution multidisciplinary investigation of key European loess-palaeosols profiles have demonstrated that loess sequences result from rapid and cyclic aeolian sedimentation which is reflected in variations of loess grain size indexes and correlated with Greenland ice-core dust records. This correlation suggests a global connection between North Atlantic and west-European air masses. Herein, we present a revised stratigraphy and a continuous high-resolution record of grain-size, magnetic susceptibility and organic carbon δ13C of the famous of Dolní Vestonice (DV) loess sequence in the Moravian region of the Czech Republic. A new set of quartz OSL ages provides a reliable and accurate chronology of the sequence's main pedosedimentary events. The grain size record shows strongly contrasting variations with numerous abrupt coarse-grained events, especially in the upper part of the sequence between ca 20-30 ka. This time period is also characterised by a progressive coarsening of the loess deposits as already observed in other western European sequences. The base of the DV sequence exhibits an exceptionally well-preserved soil complex composed of three chernozem soil horizons and 5 aeolian silt layers (marker silts). This complex is, at present, the most complete record of environmental variations and dust deposition in the European loess belt for the Weichselian Early-glacial period spanning about 110 to 70 ka, allowing correlations with various global palaeoclimatic records. OSL ages combined with sedimentological and palaeopedological observations lead to the conclusion that this soil complex recorded all of the main climatic events expressed in the North GRIP record from Greenland Interstadials (GIS) 25 to 19.

Earth History databases and visualization - the TimeScale Creator system

NASA Astrophysics Data System (ADS)

Ogg, James; Lugowski, Adam; Gradstein, Felix

2010-05-01

The "TimeScale Creator" team (www.tscreator.org) and the Subcommission on Stratigraphic Information (stratigraphy.science.purdue.edu) of the International Commission on Stratigraphy (www.stratigraphy.org) has worked with numerous geoscientists and geological surveys to prepare reference datasets for global and regional stratigraphy. All events are currently calibrated to Geologic Time Scale 2004 (Gradstein et al., 2004, Cambridge Univ. Press) and Concise Geologic Time Scale (Ogg et al., 2008, Cambridge Univ. Press); but the array of intercalibrations enable dynamic adjustment to future numerical age scales and interpolation methods. The main "global" database contains over 25,000 events/zones from paleontology, geomagnetics, sea-level and sequence stratigraphy, igneous provinces, bolide impacts, plus several stable isotope curves and image sets. Several regional datasets are provided in conjunction with geological surveys, with numerical ages interpolated using a similar flexible inter-calibration procedure. For example, a joint program with Geoscience Australia has compiled an extensive Australian regional biostratigraphy and a full array of basin lithologic columns with each formation linked to public lexicons of all Proterozoic through Phanerozoic basins - nearly 500 columns of over 9,000 data lines plus hot-curser links to oil-gas reference wells. Other datapacks include New Zealand biostratigraphy and basin transects (ca. 200 columns), Russian biostratigraphy, British Isles regional stratigraphy, Gulf of Mexico biostratigraphy and lithostratigraphy, high-resolution Neogene stable isotope curves and ice-core data, human cultural episodes, and Circum-Arctic stratigraphy sets. The growing library of datasets is designed for viewing and chart-making in the free "TimeScale Creator" JAVA package. This visualization system produces a screen display of the user-selected time-span and the selected columns of geologic time scale information. The user can change the vertical-scale, column widths, fonts, colors, titles, ordering, range chart options and many other features. Mouse-activated pop-ups provide additional information on columns and events; including links to external Internet sites. The graphics can be saved as SVG (scalable vector graphics) or PDF files for direct import into Adobe Illustrator or other common drafting software. Users can load additional regional datapacks, and create and upload their own datasets. The "Pro" version has additional dataset-creation tools, output options and the ability to edit and re-save merged datasets. The databases and visualization package are envisioned as a convenient reference tool, chart-production assistant, and a window into the geologic history of our planet.

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

Characterization of stratigraphic sequences (T-R cycles or sequences) included outcrop studies, well log analysis and seismic reflection interpretation. These studies were performed by researchers at the University of Alabama, Wichita State University and McGill University. The outcrop, well log and seismic characterization studies were used to develop a depositional sequence model, a T-R cycle (sequence) model, and a sequence stratigraphy predictive model. The sequence stratigraphy predictive model developed in this study is based primarily on the modified T-R cycle (sequence) model. The T-R cycle (sequence) model using transgressive and regressive systems tracts and aggrading, backstepping, and infilling intervals or sectionsmore » was found to be the most appropriate sequence stratigraphy model for the strata in the onshore interior salt basins of the Gulf of Mexico to improve petroleum stratigraphic trap and specific reservoir facies imaging, detection and delineation. The known petroleum reservoirs of the Mississippi Interior and North Louisiana Salt Basins were classified using T-R cycle (sequence) terminology. The transgressive backstepping reservoirs have been the most productive of oil, and the transgressive backstepping and regressive infilling reservoirs have been the most productive of gas. Exploration strategies were formulated using the sequence stratigraphy predictive model and the classification of the known petroleum reservoirs utilizing T-R cycle (sequence) terminology. The well log signatures and seismic reflector patterns were determined to be distinctive for the aggrading, backstepping and infilling sections of the T-R cycle (sequence) and as such, well log and seismic data are useful for recognizing and defining potential reservoir facies. The use of the sequence stratigraphy predictive model, in combination with the knowledge of how the distinctive characteristics of the T-R system tracts and their subdivisions are expressed in well log patterns and seismic reflection configurations and terminations, improves the ability to identify and define the limits of potential stratigraphic traps and the stratigraphic component of combination stratigraphic and structural traps and the associated continental, coastal plain and marine potential reservoir facies. The assessment of the underdeveloped and undiscovered reservoirs and resources in the Mississippi Interior and North Louisiana Salt Basins resulted in the confirmation of the Monroe Uplift as a feature characterized by a major regional unconformity, which serves as a combination stratigraphic and structural trap with a significant stratigraphic component, and the characterization of a developing play in southwest Alabama, which involves a stratigraphic trap, located updip near the pinchout of the potential reservoir facies. Potential undiscovered and underdeveloped reservoirs in the onshore interior salt basins are identified as Jurassic and Cretaceous aggrading continental and coastal, backstepping nearshore marine and marine shelf, and infilling fluvial, deltaic, coastal plain and marine shelf.« less

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.

Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982

NASA Astrophysics Data System (ADS)

Drury, Anna Joy; Westerhold, Thomas; Hodell, David; Röhl, Ursula

2018-03-01

Ocean Drilling Program (ODP) Site 982 represents a key location for understanding the evolution of climate in the North Atlantic over the past 12 Ma. However, concerns exist about the validity and robustness of the underlying stratigraphy and astrochronology, which currently limits the adequacy of this site for high-resolution climate studies. To resolve this uncertainty, we verify and extend the early Pliocene to late Miocene shipboard composite splice at Site 982 using high-resolution XRF core scanning data and establish a robust high-resolution benthic foraminiferal stable isotope stratigraphy and astrochronology between 8.0 and 4.5 Ma. Splice revisions and verifications resulted in ˜ 11 m of gaps in the original Site 982 isotope stratigraphy, which were filled with 263 new isotope analyses. This new stratigraphy reveals previously unseen benthic δ18O excursions, particularly prior to 6.65 Ma. The benthic δ18O record displays distinct, asymmetric cycles between 7.7 and 6.65 Ma, confirming that high-latitude climate is a prevalent forcing during this interval. An intensification of the 41 kyr beat in both the benthic δ13C and δ18O is also observed ˜ 6.4 Ma, marking a strengthening in the cryosphere-carbon cycle coupling. A large ˜ 0.7 ‰ double excursion is revealed ˜ 6.4-6.3 Ma, which also marks the onset of an interval of average higher δ18O and large precession and obliquity-dominated δ18O excursions between 6.4 and 5.4 Ma, coincident with the culmination of the late Miocene cooling. The two largest benthic δ18O excursions ˜ 6.4-6.3 Ma and TG20/22 coincide with the coolest alkenone-derived sea surface temperature (SST) estimates from Site 982, suggesting a strong connection between the late Miocene global cooling, and deep-sea cooling and dynamic ice sheet expansion. The splice revisions and revised astrochronology resolve key stratigraphic issues that have hampered correlation between Site 982, the equatorial Atlantic and the Mediterranean. Comparisons of the revised Site 982 stratigraphy to high-resolution astronomically tuned benthic δ18O stratigraphies from ODP Site 926 (equatorial Atlantic) and Ain el Beida (north-western Morocco) show that prior inconsistencies in short-term excursions are now resolved. The identification of key new cycles at Site 982 further highlights the requirement for the current scheme for late Miocene marine isotope stages to be redefined. Our new integrated deep-sea benthic stable isotope stratigraphy and astrochronology from Site 982 will facilitate future high-resolution late Miocene to early Pliocene climate research.

Continuity of Permian Mengkareng formation through GPR interpretation in Merangin Geopark

NASA Astrophysics Data System (ADS)

Hanif, F.; Syahputra, R.; Kristyanto, T. H. W.; Tempessy, A. S.; Rokhmatuloh

2017-07-01

The Permian Mengkarang Formation was a part of the continental margin (Gondwana Land) which separated in the Devon Period. In this period, Gondwana Land experienced glaciation at the Paleo South Pole. However, the fossils found in Mengkarang Formation were tropical flora, had made the Merangin to be certified as one of the national geoparks. It also shows that the geological process (stratigraphy and tectonic) in the Merangin has occurred before the Indonesian archipelago was formed: namely the Permian to Triassic period. Ground Penetrating Radar (GPR) was chosen as an effective geophysical method to study shallow subsurface geology. GPR and seismic reflection method have the same common principle to identify the facies and sub-sequence stratigraphy but they are different in implementation. Therefore, this study aims to deliver the vertical continuity of the Permian Mengkarang Formation in high resolution unit. The GPR result showing the subsurface image is based on dielectric of the rock layers. The GPR sections show the absence of the unconformity delivered in the intercalation between mudstone, sandstone, and tuff. Thus, it can be concluded that the Permian Mengkareng Formation continues up to 20 m depth.

High Resolution Near Surface 3D Seismic Experiments: A Carbonate Platform vs. a Siliciclastic Sequence

NASA Astrophysics Data System (ADS)

Filippidou, N.; Drijkoningen, G.; Braaksma, H.; Verwer, K.; Kenter, J.

2005-05-01

Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over the past years. Many case studies presented, show that producing clear seismic images with this non-evasive method, is still a challenge. We use two test-sites where nearby outcrops are present so that an accurate geological model can be built and the seismic result validated. The first so-called natural field laboratory is located in Boulonnais (N. France). It is an upper Jurassic siliciclastic sequence; age equivalent of the source rock of N. Sea. The second one is located in Cap Blanc,to the southwest of the Mallorca island(Spain); depicting an excellent example of Miocene prograding reef platform (Llucmajor Platform); it is a textbook analog for carbonate reservoirs. In both cases, the multidisciplinary experiment included the use of multicomponent and quasi- or 3D seismic recordings. The target depth does not exceed 120m. Vertical and shear portable vibrators were used as source. In the center of the setups, boreholes were drilled and Vertical Seismic Profiles were shot, along with core and borehole measurements both in situ and in the laboratory. These two geologically different sites, with different seismic stratigraphy have provided us with exceptionally high resolution seismic images. In general seismic data was processed more or less following standard procedures, a few innovative techniques on the Mallorca data, as rotation of horizontal components, 3D F-K filter and addition of parallel profiles, have improved the seismic image. In this paper we discuss the basic differences as seen on the seismic sections. The Boulonnais data present highly continuous reflection patterns of extremenly high resolution. This facilitated a high resolution stratigraphic description. Results from the VSP showed substantial wave energy attenuation. However, the high-fold (330 traces ) Mallorca seismic experiment returned a rather discontinuous pattern of possible reflectors, opposing to the predicted seismic stratigraphy/geology of the area. The Llumajor Platform has been buried only a few meters at most, therefore primary and secondary porocity remains intact, creating a fractal like environment of scatterers and diffractors. We have interpreted two possible reflections, the top of the reef and the water table; the former is nicely coupled with the VSP. The seismic wave attenuation observed is believed to be predominantly due to the scattering effects.

High resolution seismic stratigraphy of Tampa Bay, Florida

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

Tihansky, A.B.; Hine, A.C.; Locker, S.D.

1993-03-01

Tampa Bay is one of two large embayments that interrupt the broad, regional nature of the carbonate ramp of the west coast of the Florida carbonate platform. It is believed to have formed as a result of preferential dissolution of the Cenozoic limestones beneath it. Highly reactive freshwater systems became hydrologically focused in the bay region as the surface and groundwater systems established themselves during sea-level lowstands. This weakening of the underlying limestone resulted in extensive karstification, including warping, subsidence, sinkhole and spring formation. Over 120 miles of high resolution seismic reflection data were collected within Tampa Bay. This recordmore » has been tied into 170 core borings taken from within the bay. This investigation has found three major seismic stratigraphic sequences beneath the bay. The lowermost sequence is probably of Miocene age. Its surface is highly irregular due to erosion and dissolution and exhibits a great deal of vertical relief as well as gentler undulations or warping. Much of the middle sequence consists of low angle clinoforms that gently downlap and fill in the underlying karst features. The uppermost sequence is a discontinuous unit comprised of horizontal to low angle clinoforms that are local in their extent. The recent drainage and sedimentation patterns within the bay area are related to the underlying structure controlled by the Miocene karst activity.« less

Cone penetration test for facies study: a review

NASA Astrophysics Data System (ADS)

Satriyo, N. A.; Soebowo, E.

2018-02-01

Engineering geology investigation through Cone Penetration Test (with pore-pressure measurements) approach is one of the most effective methods to find out sub surface layer. This method is generally used in Late Quaternary and typical deposit and can also be used for sedimentological purposes. CPTu and drilling core for high-resolution stratigraphy sub surface have been done in many research. These combined data can also be used to detail correlations of sub surface stratigraphy, to identify facies change and to determine the interpretation of sequence stratigraphy. The determination facies distribution research based on CPTu profile, which was included in quantitative data, is rarely done especially in Indonesia which has a different climate. Whereas drilling core description using grain size analysis will provide information on validation about physical lithology characteristics which are developed in research area. The interpretation is given using CPTu curve pattern and cone resistance parameter of CPTu’s data correlated with physical characteristics of drilling core. The cone resistance will provide the strength of the sediment layer which also gives the range of data between clay and sand. Finally, the review will show that each of developing facies characteristic provides a specific curve pattern and every sediment deposit facies can be determined by the transformation of CPTu curve profile. Despite the fact that the research using those methods are quite comprehensive, a review is presented on each of these methods related with the chronologic factor seen by the geological time and different characteristics sediment of different location.

A 3-Dimensional Model of Water-Bearing Sequences in the Dominguez Gap Region, Long Beach, California

USGS Publications Warehouse

Ponti, Daniel J.; Ehman, Kenneth D.; Edwards, Brian D.; Tinsley, John C.; Hildenbrand, Thomas; Hillhouse, John W.; Hanson, Randall T.; McDougall, Kristen; Powell, Charles L.; Wan, Elmira; Land, Michael; Mahan, Shannon; Sarna-Wojcicki, Andrei M.

2007-01-01

A 3-dimensional computer model of the Quaternary sequence stratigraphy in the Dominguez gap region of Long Beach, California has been developed to provide a robust chronostratigraphic framework for hydrologic and tectonic studies. The model consists of 13 layers within a 16.5 by 16.1 km (10.25 by 10 mile) square area and extends downward to an altitude of -900 meters (-2952.76 feet). Ten sequences of late Pliocene to Holocene age are identified and correlated within the model. Primary data to build the model comes from five reference core holes, extensive high-resolution seismic data obtained in San Pedro Bay, and logs from several hundred water and oil wells drilled in the region. The model is best constrained in the vicinity of the Dominguez gap seawater intrusion barrier where a dense network of subsurface data exist. The resultant stratigraphic framework and geologic structure differs significantly from what has been proposed in earlier studies. An important new discovery from this approach is the recognition of ongoing tectonic deformation throughout nearly all of Quaternary time that has impacted the geometry and character of the sequences. Anticlinal folding along a NW-SE trend, probably associated with Quaternary reactivation of the Wilmington anticline, has uplifted and thinned deposits along the fold crest, which intersects the Dominguez gap seawater barrier near Pacific Coast Highway. A W-NW trending fault system that approximately parallels the fold crest has also been identified. This fault progressively displaces all but the youngest sequences down to the north and serves as the southern termination of the classic Silverado aquifer. Uplift and erosion of fining-upward paralic sequences along the crest of the young fold has removed or thinned many of the fine-grained beds that serve to protect the underlying Silverado aquifer from seawater contaminated shallow groundwater. As a result of this process, the potential exists for vertical migration of seawater into the producing aquifers and subsequent landward migration of intruded waters beneath the existing Dominguez barrier. Incipient invasion of the Silverado aquifer by chloride-enriched waters is observed in a recently drilled well located along the crest of the fold seaward of the barrier and at a depth of 440 feet (134 meters). These new observations and interpretations indicate that the new sequence-based approach to defining the stratigraphy of the Dominguez Gap area may have important implications for seawater intrusion management. To test this, it will be useful to overlay existing water-quality and water level data onto the framework model and to incorporate the new stratigraphy into a transport model.

Development of levees on deep-sea channels: Insights from high-resolution AUV exploration of the Lucia Chica system, offshore central California

NASA Astrophysics Data System (ADS)

Maier, K. L.; Fildani, A.; Romans, B.; Paull, C. K.; McHargue, T.; Graham, S. A.; Caress, D. W.

2010-12-01

The Lucia Chica, a tributary channel system of the Lucia Canyon, offshore central California, was imaged using the Monterey Bay Aquarium Research Institute’s (MBARI) Autonomous Underwater Vehicle (AUV) in order to investigate seafloor and subsurface morphologies associated with low-relief submarine channels. In larger, previously investigated seafloor channel-levee systems, initial deposits are either eroded, compacted, or below the resolution of available imaging. In this dataset from the Lucia Chica, the unprecedented high-resolution multibeam bathymetry (1 m lateral resolution) and chirp sub-bottom profiles (11 cm vertical resolution) reveal a highly irregular seafloor with scours, depressions, and discontinuous low-relief conduits over an area of ~70 km2. Sediment packages associated with channels, levees, and deposits related to less confined flows are correlated between chirp profiles and with the multibeam bathymetric image to determine the stratigraphic evolution of the Lucia Chica and the sequence of channel-levee development. In the Lucia Chica, channels appear to have initiated as trains of scours that eventually coalesced into continuous channel thalwegs carved by erosional turbidity currents. Channel incision and stepped lateral migration led to the development of terraces, complex levee stratigraphy, and distinct morphologies associated with inner and outer bends of sinuous channels. The inner bend levee stratigraphy indicates that the channel position migrated in discrete shifts, as opposed to continuous channel migration associated with lateral accretion. Discrete levee packages, formed from flow-stripped turbidity currents, later infilled abandoned portions of the channel and overbank areas. While processes of initial channel and levee development are well established in fluvial settings, detailed examples are lacking for deep-sea systems. These results highlight the differences in initiation between submarine channel systems, their fluvial counterparts, and larger submarine channel-levee systems imaged only with lower-resolution technologies. High-resolution imaging and detailed mapping made possible by cutting-edge oceanographic technology provide an unprecedented examination of deep-water channel-levee morphology and improve understanding of deep-water channel migration and levee development.

Characterizing 2-D snow stratigraphy in forests based on high-resolution snow penetrometry

NASA Astrophysics Data System (ADS)

Teich, M.; Loewe, H.; Jenkins, M. J.; Schneebeli, M.

2016-12-01

Snow stratigraphy, the characteristic layering within a seasonal snowpack, has important implications for snow remote sensing, hydrology and avalanches. Forests modify snowpack properties through interception of falling snow by tree crowns, the reduction of near-surface wind speeds, and changes to the energy balance beneath and around trees leading to a highly variable stratigraphy in space and time. The lack of snowpack observations in forests limits our ability to understand the spatio-temporal evolution of snow stratigraphy as a function of forest structure and to observe snowpack response to changes in forest cover. We examined the snowpack in field campaigns using the SnowMicroPen (SMP) under tree canopies in an Engelmann spruce forest in the central Rocky Mountains in Utah, USA. Data were collected in plots beneath canopies of undisturbed, bark beetle-disturbed and salvage logged forest stands, and a non-forested meadow. In 2015 weekly-repeated SMP penetration measurements were taken along 10 m transects at 0.3 m intervals. In the winter of 2016 bi-weekly measurements were collected along 20 m transects every 0.5 m. Using a statistical model, we derived 2-D snow density profiles as a measure of stratigraphy. The small-scale patterns in snow density revealed a more heterogeneous stratigraphy in undisturbed dense stands and also beneath bark beetle-disturbed forest. In contrast, snow stratigraphy was more homogeneous in the harvested plot despite standing small diameter trees and woody debris with effective heights up to 95 cm. As expected, snow depth and layering in non-forested plots varied only slightly over the small spatial extent sampled. Observed patterns changed throughout the snow season dependent upon snow and meteorological conditions. The results contribute to the general understanding of forest-snowpack interactions at high spatial resolution, and can be used to validate snowpack and microwave models for avalanche formation processes and SWE retrieval in forests.

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.

New Sedimentary Records from Contourite Drifts on the West Antarctic Continental Margin: Reconstruction of Palaeoenvironmental Changes during the Late Quaternary by Combining an Integrated Chronostratigraphic Approach with Multi-Proxy Investigations

NASA Astrophysics Data System (ADS)

Hillenbrand, C. D.; Crowhurst, S.; Channell, J. E. T.; Williams, M.; Hodell, D. A.; Xuan, C.; Allen, C. S.; Ehrmann, W. U.; Graham, A. G. C.; Larter, R. D.

2016-12-01

Giant sediment drifts located on the continental rise west of the Antarctic Peninsula and in the Bellingshausen Sea contain a high-resolution archive of ice sheet history in West Antarctica and of palaeoceanographic changes in the Southern Ocean. However, previous studies on sediment cores recovered from these contourite drifts, including Ocean Drilling Program (ODP) Leg 178, were compromised by lack of reliable high-resolution chronological control. This shortcoming is mainly caused by the very low abundance of calcareous microfossils in the sediments that are required for applying radiocarbon dating and stable oxygen isotope (δ18O) stratigraphy. Moreover, sediments assumed to have been deposited during glacial periods consist almost entirely of terrigenous detritus, i.e. they lack even siliceous microfossils that could be utilised for biostratigraphic purposes. International Ocean Discovery Program (IODP) proposal 732-Full2 aims to obtain continuous, high-resolution records from sites on the West Antarctic sediment drifts and to develop reliable age models for them. The strategy for achieving the second objective is to use a range of chronostratigraphic techniques, including relative geomagnetic palaeointensity (RPI) and δ18O stratigraphy, on sedimentary sequences recovered from the shallowest parts of the drift crests, where the preservation of calcareous microfossils is expected be higher than in deeper water. Here we present preliminary results of multi-proxy investigations on new piston and box cores recovered from the proposed drill sites during site survey investigation cruise JR298 of the RRS James Clark Ross in 2015. Apart from the integrated chronological approach, the new cores augment previous assessments of palaeoenvironmental change on the West Antarctic continental margin during glacial-interglacial cycles of the Late Quaternary.

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction

PubMed Central

Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A.; Leorri, Eduardo

2016-01-01

The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches. PMID:27929122

Coastal barrier stratigraphy for Holocene high-resolution sea-level reconstruction.

PubMed

Costas, Susana; Ferreira, Óscar; Plomaritis, Theocharis A; Leorri, Eduardo

2016-12-08

The uncertainties surrounding present and future sea-level rise have revived the debate around sea-level changes through the deglaciation and mid- to late Holocene, from which arises a need for high-quality reconstructions of regional sea level. Here, we explore the stratigraphy of a sandy barrier to identify the best sea-level indicators and provide a new sea-level reconstruction for the central Portuguese coast over the past 6.5 ka. The selected indicators represent morphological features extracted from coastal barrier stratigraphy, beach berm and dune-beach contact. These features were mapped from high-resolution ground penetrating radar images of the subsurface and transformed into sea-level indicators through comparison with modern analogs and a chronology based on optically stimulated luminescence ages. Our reconstructions document a continuous but slow sea-level rise after 6.5 ka with an accumulated change in elevation of about 2 m. In the context of SW Europe, our results show good agreement with previous studies, including the Tagus isostatic model, with minor discrepancies that demand further improvement of regional models. This work reinforces the potential of barrier indicators to accurately reconstruct high-resolution mid- to late Holocene sea-level changes through simple approaches.

Modeling high resolution stratigraphy in the Cusiana Field, Eastern Colombia; static builds to dynamic simulation

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

Pulham, A.; MacDonald, D.; Colin, D.

1996-12-31

The Cusiana Field (BP, Ecopetrol, Total and Triton) is located in the Llanos Foothills of Eastern Colombia. The Cusiana reservoirs range from late Cretaceous, passive margin deltaic to early Tertiary, early foreland basin estuarine-fluvial. The key reservoir is the late Eocene Mirador Formation which comprises over 50% of reserves. Currently the Mirador reservoir is providing nearly all of the 180,00 bopd of production from the Cusiana Field. The Mirador reservoir comprises a stack of incised valley deposits. The fills of the valleys are sandstone-dominated and comprise the majority of the reservoir quality in the reservoir. Critical to an effective understandingmore » of reservoir behavior has been a detailed reservoir description and reservoir modeling of the incised valley stratigraphy in the Mirador. Models have been constructed using the deterministic information provided by extensive core (3000 feet) coupled with stochastic tools and techniques. Dynamic data, provided by extensive acquisition of production logs during early development drilling, have been integrated within the static-descriptions. Important reservoir characteristics such as degree of valley connectivity, intra-valley heterogeneities and textural controls on permeability have been captured in the modeling process. Upscaling of the high resolution static model has preserved the key sequence stratigraphic facets of the reservoir and also incorporated textural controls on relative permeability. Prediction of pressure transient behavior and fluid movement is working well in the full field simulator, VIP.« less

Mesoarchean Banded Iron Formation sequences in Dixon Island-Cleaverville Formation, Pilbara Australia: Oxygenic signal from DXCL project

NASA Astrophysics Data System (ADS)

Kiyokawa, S.; Ito, T.; Ikehara, M.; Yamaguchi, K. E.; Naraoka, H.; Onoue, T.; Horie, K.; Sakamoto, R.; Aihara, Y.; Miki, T.

2013-12-01

The 3.2-3.1 Ga Dixon island-Cleaverville formations are well-preserved Banded Iron Formation (BIF) within hydrothermal oceanic sequence at oceanic island arc setting (Kiyokawa et al., 2002, 2006, 2012). The stratigraphy of the Dixon Island (3195+15Ma) -Cleaverville (3108+13Ma) formations shows the well preserved environmental condition at the Mesoarchean ocean floor. The stratigraphy of these formations are formed about volcano-sedimentary sequences with hydrothermal chert, black shale and banded iron formation to the top. Based on the scientific drilling of DXCL project at 2007 and 2011, detail lithology between BIF sequence was clearly understood. Four drilling holes had been done at coastal sites; the Dixon Island Formation is DX site (100m) and the Cleaverville Formation is CL2 (40m), CL1 (60m) and CL3 (200m) sites and from stratigraphic bottom to top. Coarsening and thickening upward black shale-BIF sequences are well preserved of the stratigraphy form the core samples. The Dixon Island Formation consists komatiite-rhyolite sequences with many hydrothermal veins and very fine laminated cherty rocks above them. The Cleaverville Formation contains black shale, fragments-bearing pyroclastic beds, white chert, greenish shale and BIF. The CL3 core, which drilled through BIF, shows siderite-chert beds above black shale identified before magnetite lamination bed. U-Pb SHRIMP data of the tuff in lower Dixon Island Formation is 3195+15 Ma and the pyroclastic sequence below the Cleaverville BIF is 3108+13 Ma. Sedimentation rate of these sequence is 2-8 cm/ 1000year. The hole section of the organic carbon rich black shales below BIF are similar amount of organic content and 13C isotope (around -30per mill). There are very weak sulfur MIF signal (less 0.2%) in these black shale sequence. Our result show that thick organic rich sediments may be triggered to form iron rich siderite and magnetite iron beds. The stratigraphy in this sequence quite resemble to other Iron formation (eg. Hamersley BIF). So we investigate that the Cleaverville iron formation, which is one of the best well known Mesoarchean iron formation, was already started cyanobacteria oxygen production system to used pre-syn iron sedimentation at anoxic oceanic condition.

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.

Annual layers revealed by GPR in the subsurface of a prograding coastal barrier, southwest Washington, U.S.A

USGS Publications Warehouse

Moore, L.J.; Jol, H.M.; Kruse, S.; Vanderburgh, S.; Kaminsky, G.M.

2004-01-01

The southwest Washington coastline has experienced extremely high rates of progradation during the late Holocene. Subsurface stratigraphy, preserved because of progradation and interpreted using ground-penetrating radar (GPR), has previously been used successfully to document coastal response to prehistoric storm and earthquake events. New GPR data collected at Ocean Shores, Washington, suggest that the historic stratigraphy of the coastal barrier in this area represents a higher resolution record of coastal behavior than previously thought. GPR records for this location at 200 MHz reveal a series of gently sloping, seaward-dipping reflections with slopes similar to the modern beach and spacings on the order of 20-45 cm. Field evidence and model results suggest that thin (1-10 cm), possibly magnetite-rich, heavy-mineral lags or low-porosity layers left by winter storms and separated by thick (20-40 cm) summer progradational sequences are responsible for generating the GPR reflections. These results indicate that a record of annual progradation is preserved in the subsurface of the prograding barrier and can be quantified using GPR. Such records of annual coastal behavior, where available, will be invaluable in understanding past coastal response to climatic and tectonic forcing. ?? 2004.

Improving the Hydro-stratigraphic Model of the Oxnard Forebay, Ventura County, California, using Transient Electromagnetic Surveying

NASA Astrophysics Data System (ADS)

Quady, Maura Colleen

2013-01-01

To characterize the hydro-stratigraphy of an area, drilling and well logs provide high resolution electrical resistivity data, albeit for limited areas (points). The expense of drilling indirectly leads to sparse data and it is necessary to assume lateral homogeneity between wells when creating stratigraphic maps. Unfortunately, this assumption may not apply to areas in complex depositional and tectonically active settings. The goal of this study is to fill in data gaps between wells in a groundwater basin in order to better characterize the hydro-stratigraphy under existing and potential sites for managed aquifer recharge. Basins in the southern California study area have been used for decades to recharge surface water to an upper aquifer system; this work also addresses whether the local hydro-stratigraphy favors surface infiltration as a means to recharge water to the lower aquifer system. Here, soundings of transient electromagnetism (TEM), a surface geophysical method, are correlated with nearby down-hole resistivity and lithology well logs for grain size interpretations of the subsurface in unsaturated conditions. Grain size is used as a proxy for permeability (hydraulic conductivity), with resistivity contrasts highlighting variations in the media, which would affect groundwater flow in both vertical and horizontal directions. Results suggest a nearly horizontal, extensive, low permeability layer exists in the area and only a few noted locations are favorable for surface -to-lower aquifer system recharge. Furthermore, zones of higher permeability deeper than the upper aquifer system are discontinuous and isolated among lower permeability zones. However, the TEM profiles show areas where lower permeability zones are thin, and where alternatives to surface percolation methods could be explored. In addition, the survey adds information about the transition between the upper and lower aquifer systems, and adds detail to the topography of the base of freshwater. Finally, this work effectively decreases the interpolation distance between data points of wellbores, and when viewed in sequence the TEM profiles present a 3D depiction of basin hydro-stratigraphy.

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.

Complex carbonate and clastic stratigraphy of the inner shelf off west-central Florida

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

Locker, S.D.; Doyle, L.J.; Hine, A.C.

1990-05-01

The near surface stratigraphy (< 30 m) of the inner shelf off the west coast of Florida was investigated using high-resolution seismic, side-scan sonar, and continuous underwater video camera coverage. The simultaneous operation of all three systems provided a unique opportunity to calibrate acoustic data with actual video images of the sea floor in a geologically complex area characterized by limestone dissolution structures, hard-bottom exposures, and overlain by a limited supply of terrigenous clastics. Three principle bottom types, grass, sand, and hard-bottom mapped using video and side-scan sonographs, show a correlation with two subsurface stratigraphic zones. The nearshore subsurface zonemore » extending to 6-7 m water depth is characterized by flat or rolling strata and sinkholes that increase in size (200-1,200 m in diameter) and become more numerous further offshore. This zone is truncated by a major erosional unconformity overlain by a thin (<3 m) sequence of Holocene sediment, which together form a terrace upon which the Anclote Key barrier island formed. The offshore subsurface zone (7-11 m water depth) exhibits irregular and discontinuous high-amplitude flat or inclined reflections and few sinkholes. Offshore, extensive hard-bottom exposures are common with discontinuous sediment that occur as lenses or sand waves. The complex stratigraphy of the west Florida shelf includes outcropping Neogene limestones that have undergone dissolution during sea level lowstands. Carbonates and clastics dispersed during multiple sea level changes overlie the Neogene limestones. Dissolution styles and erosional unconformities produced bedrock topography and now control modern geological and biological processes.« less

Reconnaissance Marine Geophysical Survey for the Shallow Water Acoustics Program

DTIC Science & Technology

2013-09-30

Swift, D.J.P. (Ed.), Shelf Sand and Sandstone Bodies: Geometry, Facies and Sequence Stratigraphy, Wiley, Hoboken, New Jersey, Spec. Publs. Int. Ass...sequences, their component system tra cts, and bounding surfaces. In Swift, D.J.P. (Ed.), Shelf Sand and Sandstone Bodies: Geometry, Facies and Sequence

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

NASA Astrophysics Data System (ADS)

Barakat, Moataz; Dominik, Wilhelm

2010-05-01

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

Spectral stratigraphy

NASA Technical Reports Server (NTRS)

Lang, Harold R.

1991-01-01

A new approach to stratigraphic analysis is described which uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. The new stratigraphic procedure is illustrated by examples in the literature. The published results demonstrate the potential of spectral stratigraphy for mapping strata, determining dip and strike, measuring and correlating stratigraphic sequences, defining lithofacies, mapping biofacies, and interpreting geological structures.

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.

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.

Sequential filling of a late paleozoic foreland basin

USGS Publications Warehouse

Mars', J. C.; Thomas, W.A.

1999-01-01

Through the use of an extensive data base of geophysical well logs, parasequence-scale subdivisions within a late Paleozoic synorogenic clastic wedge resolve cycles of sequential subsidence of a foreland basin, sediment progradation, subsidence of a carbonate shelf edge, diachronously subsiding discrete depositional centers, and basinwide transgression. Although temporal resolution of biostratigraphic markers is less precise in Paleozoic successions than in younger basins, parasequence-scale subdivisions provide more detailed resolution within marker-defined units in Paleozoic strata. As an example, the late Paleozoic Black Warrior basin in the foreland of the Ouachita thrust belt is filled with a synorogenic clastic wedge, the lower part of which intertongues with the fringe of a cratonic carbonate facie??s in the distal part of the basin. The stratal geometry of one tongue of the carbonate facie??s (lower tongue of Bangor Limestone) defines a ramp that grades basinward into a thin black shale. An overlying tongue of the synorogenic clastic wedge (lower tongue of Parkwood Formation) consists of cyclic delta and delta-front deposits, in which parasequences are defined by marine-flooding surfaces above coarsening- and shallow ing-upward successions of mudstone and sandstone. Within the lower Parkwood tongue, two genetic stratigraphie sequences (A and B) are defined by parasequence offlap and downlap patterns and are bounded at the tops by basinwide maximum-flooding surfaces. The distribution of parasequences within sequences A and B indicates two cycles of sequential subsidence (deepening) and progradation, suggesting subsidence during thrust advance and progradation during thrust quiescence. Parasequence stacking in sequences A and B also indicates diachronous differential tectonic subsidence of two discrete depositional centers within the basin. The uppermost sequence (C) includes reworked sandstones and an overlying shallow-marine limestone, a vertical succession that reflects no tectonic subsidence, a very minor or null sediment supply, and basinwide transgression. The temporal resolution at parasequence scale significantly improves the resolution of the tectonic history of the thrust belt-foreland basin system. Copyright ?? 1999, SEPM (Society for Sedimentary Geology).

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

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.

Depositional architecture and sequence stratigraphy of the Upper Jurassic Hanifa Formation, central Saudi Arabia

NASA Astrophysics Data System (ADS)

El-Sorogy, Abdelbaset; Al-Kahtany, Khaled; Almadani, Sattam; Tawfik, Mohamed

2018-03-01

To document the depositional architecture and sequence stratigraphy of the Upper Jurassic Hanifa Formation in central Saudi Arabia, three composite sections were examined, measured and thin section analysed at Al-Abakkayn, Sadous and Maashabah mountains. Fourteen microfacies types were identified, from wackestones to boundstones and which permits the recognition of five lithofacies associations in a carbonate platform. Lithofacies associations range from low energy, sponges, foraminifers and bioclastic burrowed offshoal deposits to moderate lithoclstic, peloidal and bioclastic foreshoal deposits in the lower part of the Hanifa while the upper part is dominated by corals, ooidal and peloidal high energy shoal deposits to moderate to low energy peloidal, stromatoporoids and other bioclastics back shoal deposits. The studied Hanifa Formation exhibits an obvious cyclicity, distinguishing from vertical variations in lithofacies types. These microfacies types are arranged in two third order sequences, the first sequence is equivalent to the lower part of the Hanifa Formation (Hawtah member) while the second one is equivalent to the upper part (Ulayyah member). Within these two sequences, there are three to six fourth-order high frequency sequences respectively in the studied sections.

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

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

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

Jack C. Pashin; Robert A. Gastaldo

2004-07-15

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

Core segment 15008 - Regolith stratigraphy at Apennine Front Station 2 using multispectral imaging

NASA Technical Reports Server (NTRS)

Pieters, C. M.; Meloy, A.; Hawke, B. R.; Nagle, J. S.

1982-01-01

High precision multispectral images for Apennine Front core segment 15008 are presented. These data have a spatial resolution less than approximately 0.5 mm and are analyzed for their compositional information using image analysis techniques. The stratigraphy of the regolith sampled by 15008 is documented here as three distinct zones, the most prominent of which is a feldspathic fragment-rich zone with a chaotic fabric that occurs between 10 and 18 cm depth. It is suggested that this material is the primary rim crest deposit of the local 10 m crater. Above this zone the stratigraphy is more horizontal in nature. Below this zone the soil is observed to be relatively homogeneous with no distinctive structure to 23 cm depth.

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.

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.

Continental margin sedimentation: From sediment transport to sequence stratigraphy

USGS Publications Warehouse

Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P. M.; Wiberg, Patricia L.

2007-01-01

This volume on continental margin sedimentation brings together an expert editorial and contributor team to create a state-of-the-art resource. Taking a global perspective, the book spans a range of timescales and content, ranging from how oceans transport particles, to how thick rock sequences are formed on continental margins.- Summarizes and integrates our understanding of sedimentary processes and strata associated with fluvial dispersal systems on continental shelves and slopes- Explores timescales ranging from particle transport at one extreme, to deep burial at the other- Insights are presented for margins in general, and with focus on a tectonically active margin (northern California) and a passive margin (New Jersey), enabling detailed examination of the intricate relationships between a wide suite of sedimentary processes and their preserved stratigraphy- Includes observational studies which document the processes and strata found on particular margins, in addition to numerical models and laboratory experimentation, which provide a quantitative basis for extrapolation in time and space of insights about continental-margin sedimentation- Provides a research resource for scientists studying modern and ancient margins, and an educational text for advanced students in sedimentology and stratigraphy

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.

Importance of geologic characterization of potential low-level radioactive waste disposal sites

USGS Publications Warehouse

Weibel, C.P.; Berg, R.C.

1991-01-01

Using the example of the Geff Alternative Site in Wayne County, Illinois, for the disposal of low-level radioactive waste, this paper demonstrates, from a policy and public opinion perspective, the importance of accurately determining site stratigraphy. Complete and accurate characterization of geologic materials and determination of site stratigraphy at potential low-level waste disposal sites provides the frame-work for subsequent hydrologic and geochemical investigations. Proper geologic characterization is critical to determine the long-term site stability and the extent of interactions of groundwater between the site and its surroundings. Failure to adequately characterize site stratigraphy can lead to the incorrect evaluation of the geology of a site, which in turn may result in a lack of public confidence. A potential problem of lack of public confidence was alleviated as a result of the resolution and proper definition of the Geff Alternative Site stratigraphy. The integrity of the investigation was not questioned and public perception was not compromised. ?? 1991 Springer-Verlag New York Inc.

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.

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.

High-resolution seismic sequence stratigraphy and history of relative sea level changes since the Late Miocene, northern continental margin, South China Sea

NASA Astrophysics Data System (ADS)

Zhong, G.; Wang, L.

2013-12-01

The northern South China Sea (SCS) margin is suggested as one of the ideal sites for documenting the late Cenozoic sea level changes for its characteristics of rapid sedimentation and relatively stable structural subsidence since the Late Miocene. In this study, high-resolution seismic profiles acquired by the Guangzhou Marine Geological Survey, calibrated by well control from the ODP sites 1146 and 1148, were utilized to construct a time-significant sequence stratigraphic framework, from which the history of relative sea level changes since the Late Miocene on the northern SCS margin was derived. Our study area is situated in the middle segment of the margin, between the Hainan Island to the west and the Dongsha Islands to the east. This region is to a certain degree far away from the active structural zones and is suggested as the most stable region in the margin. Totally 4000 km seismic profiles were used, which controls an area of about 6×104 km2. The seismic data have a vertical resolution of 5 to 15 m for the Upper Miocene to Quaternary interval. Three regional seismic sequence boundaries were identified. They subdivide the Late Miocene to Quaternary into three mega-sequences, which correspond to the Quaternary, Pliocene and Late Miocene, respectively by tying to well control. The Late Miocene mega-sequence, including 13 component sequences, is characterized with a basal incised canyon-developed interval overlain by three sets of progradational sequences formed in deep-water slope environments. The Pliocene mega-sequence consists of four sets of progradational sequences. Each sequence set contains one to three component sequences. At least 7 component sequences can be identified. The Quaternary mega-sequence consists of five sets of progradational sequences, in which the lower two constitute a retrogressive sequence set and the upper three a progradational sequence set. At least 9 component sequences can be recognized. Most of the component sequences within the Pliocene and Quaternary mega-sequences occur adjacent to modern shelf margin, and therefore were interpreted as shelf-marginal progradational deltaic sequences. A relative sea level curve since the Late Miocene was compiled by integrating the shift trajectory of onlap points, the stacking pattern of component sequences, and the chronostratigraphic diagrams. The curve contains about 29 cycles of relative sea level changes, showing a much higher resolution than the previous results in the region. These cycles constitute three large relative sea level rise and fall cycles. General trend of sea level variations is rising since the Late Miocene, which is opposite to the global sea level changes and is in accordance with the previous regional researches. This deviation is ascribed to the combined effects of very rapid regional subsidence and relative deficiency of sediment supply. This research was funded by the National Natural Science Foundation of China (Grant Nos. 91028003 and 41076020).

Early Miocene sequence development across the New Jersey margin

USGS Publications Warehouse

Monteverde, D.H.; Mountain, Gregory S.; Miller, K.G.

2008-01-01

Sequence stratigraphy provides an understanding of the interplay between eustasy, sediment supply and accommodation in the sedimentary construction of passive margins. We used this approach to follow the early to middle Miocene growth of the New Jersey margin and analyse the connection between relative changes of sea level and variable sediment supply. Eleven candidate sequence boundaries were traced in high-resolution multi-channel seismic profiles across the inner margin and matched to geophysical log signatures and lithologic changes in ODP Leg 150X onshore coreholes. Chronologies at these drill sites were then used to assign ages to the intervening seismic sequences. We conclude that the regional and global correlation of early Miocene sequences suggests a dominant role of global sea-level change but margin progradation was controlled by localized sediment contribution and that local conditions played a large role in sequence formation and preservation. Lowstand deposits were regionally restricted and their locations point to both single and multiple sediment sources. The distribution of highstand deposits, by contrast, documents redistribution by along shelf currents. We find no evidence that sea level fell below the elevation of the clinoform rollover, and the existence of extensive lowstand deposits seaward of this inflection point indicates efficient cross-shelf sediment transport mechanisms despite the apparent lack of well-developed fluvial drainage. ?? 2008 The Authors. Journal compilation ?? 2008 Blackwell Publishing.

Allogenic controls on the fluvial architecture and fossil preservation of the Upper Triassic Ischigualasto Formation, NW Argentina

NASA Astrophysics Data System (ADS)

Colombi, Carina E.; Limarino, Carlos O.; Alcober, Oscar A.

2017-12-01

The Upper Triassic Ischigualasto Formation in NW Argentina was deposited in a fluvial system during the synrift filling of the extensional Ischigualasto-Villa Unión Basin. The expansive exposures of the fluvial architecture and paleosols provide a framework to reconstruct the paleoenvironmental evolution of this basin during the Upper Triassic using continental sequence stratigraphy. The Ischigualasto Formation deposition can be divided into seven sequential sedimentary stages: the 1) Bypass stage; 2) Confined low-accommodation stage; 3) Confined high accommodation stage; 4) Unstable-accommodation stage; 5) Unconfined high-accommodation stage; 6) Unconfined low-accommodation stage; and finally, 7) Unconfined high-accommodation stage. The sedimentary evolution of the Ischigualasto Formation was driven by different allogenic controls such as rises and falls in lake levels, local tectonism, subsidence, volcanism, and climate, which also produced modifications of the equilibrium profile of the fluvial systems. All of these factors result in different accommodations in central and flank areas of the basin, which led to different architectural configurations of channels and floodplains. Allogenic processes affected not only the sequence stratigraphy of the basin but also the vertebrate and plant taphocenosis. Therefore, the sequence stratigraphy can be used not only as a predictive tool related to fossil occurrence but also to understand the taphonomic history of the basin at each temporal interval.

Quantifying small-scale spatio-temporal variability of snow stratigraphy in forests based on high-resolution snow penetrometry

NASA Astrophysics Data System (ADS)

Teich, M.; Hagenmuller, P.; Bebi, P.; Jenkins, M. J.; Giunta, A. D.; Schneebeli, M.

2017-12-01

Snow stratigraphy, the characteristic layering within a seasonal snowpack, has important implications for snow remote sensing, hydrology and avalanches. Forests modify snowpack properties through interception, wind speed reduction, and changes to the energy balance. The lack of snowpack observations in forests limits our ability to understand the evolution of snow stratigraphy and its spatio-temporal variability as a function of forest structure and to observe snowpack response to changes in forest cover. We examined the snowpack under canopies of a spruce forest in the central Rocky Mountains, USA, using the SnowMicroPen (SMP), a high resolution digital penetrometer. Weekly-repeated penetration force measurements were recorded along 10 m transects every 0.3 m in winter 2015 and bi-weekly along 20 m transects every 0.5 m in 2016 in three study plots beneath canopies of undisturbed, bark beetle-disturbed and harvested forest stands, and an open meadow. To disentangle information about layer hardness and depth variabilities, and to quantitatively compare the different SMP profiles, we applied a matching algorithm to our dataset, which combines several profiles by automatically adjusting their layer thicknesses. We linked spatial and temporal variabilities of penetration force and depth, and thus snow stratigraphy to forest and meteorological conditions. Throughout the season, snow stratigraphy was more heterogeneous in undisturbed but also beneath bark beetle-disturbed forests. In contrast, and despite remaining small diameter trees and woody debris, snow stratigraphy was rather homogenous at the harvested plot. As expected, layering at the non-forested plot varied only slightly over the small spatial extent sampled. At the open and harvested plots, persistent crusts and ice lenses were clearly present in the snowpack, while such hard layers barely occurred beneath undisturbed and disturbed canopies. Due to settling, hardness significantly increased with depth at open and harvested plots, which was less distinctive at the other two plots. Our results contribute to the general understanding of forest-snowpack interactions and, if combined with density and specific surface area estimates, can be used to validate snowpack and microwave models for avalanche formation and SWE retrieval in forests.

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

NASA Astrophysics Data System (ADS)

Tillmann, Tanja; Ziehe, Daniel

2014-05-01

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

Influence of pre-existing basement faults on the structural evolution of the Zagros Simply Folded belt: 3D numerical modelling

NASA Astrophysics Data System (ADS)

Ruh, Jonas B.; Gerya, Taras

2015-04-01

The Simply Folded Belt of the Zagros orogen is characterized by elongated fold trains symptomatically defining the geomorphology along this mountain range. The Zagros orogen results from the collision of the Arabian and the Eurasian plates. The Simply Folded Belt is located southwest of the Zagros suture zone. An up to 2 km thick salt horizon below the sedimentary sequence enables mechanical and structural detachment from the underlying Arabian basement. Nevertheless, deformation within the basement influences the structural evolution of the Simply Folded Belt. It has been shown that thrusts in form of reactivated normal faults can trigger out-of-sequence deformation within the sedimentary stratigraphy. Furthermore, deeply rooted strike-slip faults, such as the Kazerun faults between the Fars zone in the southeast and the Dezful embayment and the Izeh zone, are largely dispersing into the overlying stratigraphy, strongly influencing the tectonic evolution and mechanical behaviour. The aim of this study is to reveal the influence of basement thrusts and strike-slip faults on the structural evolution of the Simply Folded Belt depending on the occurrence of intercrustal weak horizons (Hormuz salt) and the rheology and thermal structure of the basement. Therefore, we present high-resolution 3D thermo-mechnical models with pre-existing, inversively reactivated normal faults or strike-slip faults within the basement. Numerical models are based on finite difference, marker-in-cell technique with (power-law) visco-plastic rheology accounting for brittle deformation. Preliminary results show that deep tectonic structures present in the basement may have crucial effects on the morphology and evolution of a fold-and-thrust belt above a major detachment horizon.

Quaternary seismic stratigraphy and paleoenvironments on the continental shelf of the East China Sea

NASA Astrophysics Data System (ADS)

Liu, Zhen-Xia; Berne, Serge; Saito, Yoshiki; Lericolais, G.; Marsset, T.

2000-08-01

Paleoenvironments and stratigraphy have been interpreted from 4380 km of seismic profiling collected during a geological and geophysical cruise on the continental shelf of the East China Sea (ECS) undertaken in 1996. The geophysical data are correlated with a borehole situated on the outer shelf obtained by Shanghai Marine Geology Bureau, indicating that six seismic units have been preserved since oxygen-isotope stage 6, including four regressive-transgressive cycles. Seismic units U2, U3+U4+U5, U6, and U7 are interpreted to correspond respectively to oxygen-isotope stages 1, 3, 5, and 6, implying that sediment partitioning and sequence architecture in the ECS have been controlled by glacio-eustasy and global climate changes. Alternating continental and marine strata corresponding to glaciation and interglaciation are well preserved on the outer shelf of the ECS. Most of the cold environment strata, which formed on the outer shelf during oxygen-isotope stages 2 and 4, are too thin to be recognized on SIG 600J because of resolution, but corresponding erosion surfaces exist. Seismic unit U7 is widespread over the shelf, extending to the continental edge and showing little variation in thickness, as the regression was pronounced and lasted a long time. Thus, U7 can be used as a marker layer for correlation of Quaternary strata on the shelf of the ECS. Post-glacial transgression is obvious in the ECS. Marine strata with varied thickness were developed in the shallow sea of the inner shelf, thinning toward the outer shelf. The continental shelf of the ECS has been influenced by Pacific tide-wave systems for a long time, forming tidal sand-ridge sequences, developed during transgressions, corresponding to oxygen-isotope stages 7 (or 9), 5, 3 and 1.

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

NASA Astrophysics Data System (ADS)

Dutta, Tanima

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

Artificial delta growth

NASA Astrophysics Data System (ADS)

Mikeš, Daniel

2010-05-01

A deltaic sedimentary system has a point source; sediment is carried over the delta plain by distributary channels away from the point source and deposited at the delta front by distributary mouth bars. The established methods to describe such a sedimentary system are "bedding analysis", "facies analysis", and "basin analysis". We shall call the ambient conditions "input" and the rock record "output". There exist a number of methods to deduce input from output, e.g. "Sequence stratigraphy" (a.o. Vail et al. 1977, Catuneanu et al. 2009), "Shoreline trajectory" (a.o. Helland-Hansen & Martinsen 1996, Helland-Hansen & Hampson 2009) on the one hand and the complex use of established techniques on the other (a.o. Miall & Miall 2001, Miall & Miall 2002). None of these deductive methods seems to be sufficient. I claim that the common errors in all these attempts are the following: (1) a sedimentary system is four-dimensional (3+1) and a lesser dimensional analysis is insufficient; (2) a sedimentary system is complex and any empirical/deductive analysis is non-unique. The proper approach to the problem is therefore the theoretical/inductive analysis. To that end we performed six scenarios of a scaled version of a passive margin delta in a flume tank. The scenarios have identical stepwise tectonic subsidence and semi-cyclic sealevel, but different supply curves, i.e. supply is: constant, highly-frequent, proportional to sealevel, inversely proportional to sealevel, lagging to sealevel, ahead of sealevel. The preliminary results are indicative. Lobe-switching occurs frequently and hence locally sedimentation occurs shortly and hiatuses are substantial; therefore events in 2D (+1) cross-sections don't correlate temporally. The number of sedimentary cycles disequals the number of sealevel cycles. Lobe-switching and stepwise tectonic subsidence cause onlap/transgression. Erosional unconformities are local diachronous events, whereas maximum flooding surfaces are regional synchronous events. The evolution of the different scenarios is significantly different. These results demonstrate that the complexity of the deltaic system merits the inductive approach. References: Catuneanu, O. et al., 2009. Towards the standardization of sequence stratigraphy. Earth-Science Reviews, v. 92, p. 1-33. Helland-Hansen, W., and Martinsen, O.J., 1996, Shoreline trajectories and sequences: description of variable depositional dip scenarios: Journal of Sedimentary Research, v. 66, p. 670-688. Helland-Hansen, W. and Hampson, G.J., 2009, Trajectory analysis: concepts and applications. In: Basin Research Special Publication 21, p. 454-483. Miall, A.D., Miall, C.E., 2001, Sequence stratigraphy as a scientific enterprise: the evolution and persistence of conflicting paradigms, Earth Science Reviews, v. 54, p. 321-348. Miall, C.E., Miall, A.D., 2002, The Exxon Factor: the roles of corporate and academic science in the emergence and success of a new global model of sequence stratigraphy, Sociological Quarterly, v. 43-3, p. 307-334. Vail, P.R., Mitchum Jr., R.M., Todd, R.G., Widmier, J.M., Thompson III, S., 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. American Association of Petroleum Geologists Memoir, v. 26, p. 49-212.

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.

Sequence stratigraphy of the subaqueous Changjiang (Yangtze River) delta since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Xu, Taoyu; Wang, Guoqing; Shi, Xuefa; Wang, Xin; Yao, Zhengquan; Yang, Gang; Fang, Xisheng; Qiao, Shuqing; Liu, Shengfa; Wang, Xuchen; Zhao, Quanhong

2016-01-01

This study focuses on sedimentary research at the subaqueous Changjiang (Yangtze River) delta, based on five high-resolution seismic profiles and seven borehole cores with accurate AMS 14C datings. Three distinct seismic units were identified from the seismic profiles according to seismic reflection characteristics, and five sedimentary facies were recognized from borehole cores. These facies constituted a fining upward sedimentary sequence in relation to postglacial sea-level transgression. Three sequence surfaces (sequence boundary (SB), transgressive surface (TS), and maximum flooding surface (MFS)) demarcate the boundaries between early transgressive system tract (E-TST), late transgressive system tract (L-TST), early highstand system tract (E-HST) and late highstand system tract (L-HST), which constitute the sixth order sequence. These system tracts were developed coevally with postglacial sea-level rise. E-TST (~ 19-12 ka BP) corresponds to an incised-valley infilling in the early stages of postglacial transgression whereas L-TST (~ 12-7.5 ka BP) was formed during the last stage of postglacial transgression. The progradational structure of L-TST reflected in seismic profiles is possibly related to the intensification of the East Asian summer monsoon. E-HST (~ 7.5-2 ka BP) was deposited in response to the highstand after maximum postglacial transgression was reached, while L-HST (~ 2 ka BP-present) was initiated by accelerated progradation of the Changjiang delta.

Improved Quaternary North Atlantic stratigraphy using relative paleointensity (RPI), oxygen isotopes, and magnetic excursions (Invited)

NASA Astrophysics Data System (ADS)

Channell, J. E.

2013-12-01

Improving the resolution of Quaternary marine stratigraphy is one of the major challenges in paleoceanography. IODP Expedition 303/306, and ODP Legs 162 and 172, have yielded multiple high-resolution records (mean sedimentation rates in the 7-20 cm/kyr range) of relative paleointensity (RPI) that are accompanied by oxygen isotope data and extend through much of the Quaternary. Tandem fit of RPI and oxygen isotope data to calibrated templates (LR04 and PISO), using the Match protocol, yields largely consistent stratigraphies, implying that both RPI and oxygen isotope data are dominated by regional/global signals. Based on the recent geomagnetic field, RPI can be expected to be a global signal (i.e. dominated by the axial dipole field) when recorded at sedimentation rates less than several decimeters/kyr. Magnetic susceptibility, on the other hand, is a local/regional lithologic signal, and therefore less useful for long-distance correlation. Magnetic excursions are directional phenomena and, when adequately recorded, are manifest as paired reversals in which the virtual geomagnetic poles (VGPs) reach high latitudes in the opposite hemisphere, and they occupy minima in RPI records. Reversed VGPs imply that excursions are attributable to the main axial dipole, and therefore provide global stratigraphy. The so-called Iceland Basin excursion is recorded at many IODP/ODP sites and lies at the MIS 6/7 boundary at ~188 ka, with a duration of 2-3 kyr. Other excursions in the Brunhes chron are less commonly recorded because their duration (perhaps <~1 kyr) requires sedimentation rates >20 cm/kyr to be adequately recorded. On the other hand, several excursions within the Matuyama Chron are more commonly recorded in North Atlantic drift sediments due to relatively elevated durations. With some notable exceptions (e.g. Iberian Margin), high quality RPI records from North Atlantic sediments, together with magnetic excursions, can be used in tandem with oxygen isotope data to strengthen Quaternary (North Atlantic) stratigraphy.

Glacigenic landforms and sediments of the Western Irish Shelf

NASA Astrophysics Data System (ADS)

McCarron, Stephen; Monteys, Xavier; Toms, Lee

2013-04-01

Vibrocoring of possible glacigenic landforms identified from high resolution bathymetric coverage of the Irish Shelf by the Irish National Seabed Survey (INSS) has provided several clusters of short (<3m) cores that, due to a regional post-glacial erosional event, comprise last glacial age stratigraphies. In addition, new shallow seismic data and sedimentological information from across the Western Irish Shelf provide new insights into aspects of the nature, timing and pattern of shelf occupation by grounded lobate extensions of the last Irish Ice Sheet. Restricted chronological control of deglacial sequences in several cores indicates that northern parts of the western mid-shelf (south of a prominent outer Donegal Bay ridge) were ice free by ~24 ka B.P., and that ice had also probably retreated from outer shelf positions (as far west as the Porcupine Bank) at or before this time.

Paleontology and geochronology of the Long Beach core sites and monitoring wells, Long Beach, California

USGS Publications Warehouse

McDougall, Kristin; Hillhouse, John; Powell, Charles; Mahan, Shannon; Wan, Elmira; Sarna-Wojcicki, Andrei M.

2012-01-01

The U.S. Geological Survey's Focus on Quaternary Stratigraphy in Los Angeles (FOQUS-LA) project was a cooperative coring program between Federal, State, and local agencies. It was designed to provide a better understanding of earthquake potentials and to develop a stratigraphic model of the western Los Angeles Basin in California. The biostratigraphic, geochronologic, and paleoecologic analyses of eight wells drilled during the FOQUS-LA project are presented. These analyses are based on microfossils (benthic and planktic foraminifers), macrofossils, paleomagnetic stratigraphy, optically stimulated luminescence, thermoluminescence, radiocarbon dating, and tephrochronology. A geochronologic framework (incorporating paleomagnetism, luminescence, and tephrochronology) was used to calibrate the sequence stratigraphic units in the FOQUS-LA wells and also was used to calibrate the ages of the microfossil stage and zonal boundaries. The results of this study show that (1) the offshore California margin zones can be used in a nearshore setting, and (2) the California margin zonal scheme refines the chronostratigraphic resolution of the benthic foraminiferal biostratigraphic framework for the Pacific Coast. Benthic foraminiferal stages are modified by the recognition of an early Hallian substage, which is a faunal change recognized throughout the Los Angeles Basin. Although no detailed macrofossil zonations exist for the Quaternary of southern California, several species, whose distribution is regulated by the climatic conditions, are useful as secondary marker species in the shallower water deposits of the Los Angeles Basin.

Global Sea-level Changes Revealed in the Sediments of the Canterbury Basin, New Zealand: IODP Expedition 317

NASA Astrophysics Data System (ADS)

McHugh, C. M.; Fulthorpe, C.; Blum, P.; Rios, J.; Chow, Y.; Mishkin, K.

2012-12-01

Continental margins are composed of thick sedimentary sections that preserve the record of local processes modulated by global sea-level (eustatic) changes and climate. Understanding this regional variability permits us to extract the eustatic record. Integrated Ocean Drilling Program Expedition 317 drilled four sites in the offshore Canterbury Basin, eastern South Island of New Zealand, in water depths of 85 m to 320 m. One of the objectives of the expedition was to understand the influence of eustasy on continental margins sedimentation and to test the concepts of sequence stratigraphy. A high-resolution multiproxy approach that involves geochemical elemental analyses, lithostratigraphy and biostratigraphy is applied to understand the margin's sedimentation for the past ~5 million years. Multichannel seismic data (EW00-01 survey) provide a seismic sequence stratigraphic framework against which to interpret the multiproxy data. The mid- to late Pleistocene sedimentation is characterized by variable lithologies and changing facies. However, elemental compositions and facies follow predictable patterns within seismic sequences. Oxygen isotope measurements for the latest Pleistocene indicate that 100 ky Milankovich astronomical forcing controlled this variability. In contrast, Pliocene and early Pleistocene sediments are composed of repetitive siliciclastic and carbonate mud lithologies with less facies variability. Results of our analyses suggest that repetitive alternations of green and gray mud were deposited during warmer and cooler periods, respectively. Oxygen isotopes suggest that this cyclicity may reflect 40 ky Milankovich forcing. Ocean Drilling Program Legs 150 and 174A drilled on the New Jersey continental margin with similar objectives to those of Expedition 317. Results from this northern and southern hemisphere drilling reveal that eustasy, controlled by Milankovich forcing, strongly influences margin sedimentation and the formation of basin-wide unconformities. However, the correlation between eustasy and seismic sequence formation is not always one to one. High sedimentation rates in the Pleistocene offshore Canterbury Basin record a one- to-one correlation between glacioeustasy and seismic sequences, and in some sequences possibly a higher order frequency. But this is not the case for offshore New Jersey, where accumulation rates were lower and only the uppermost seismic sequences represent 100 ky cycles. Furthermore, Pliocene sedimentation in the Canterbury Basin was also controlled by eustasy, but does not show a one-to-one correlation between Milankovich cycles and seismic stratigraphy. Northern and southern hemisphere comparisons provide a powerful tool to better understand controls on regional sedimentation and extract a global signal.

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.

Phylogenetic stratigraphy in the Guerrero Negro hypersaline microbial mat.

PubMed

Harris, J Kirk; Caporaso, J Gregory; Walker, Jeffrey J; Spear, John R; Gold, Nicholas J; Robertson, Charles E; Hugenholtz, Philip; Goodrich, Julia; McDonald, Daniel; Knights, Dan; Marshall, Paul; Tufo, Henry; Knight, Rob; Pace, Norman R

2013-01-01

The microbial mats of Guerrero Negro (GN), Baja California Sur, Mexico historically were considered a simple environment, dominated by cyanobacteria and sulfate-reducing bacteria. Culture-independent rRNA community profiling instead revealed these microbial mats as among the most phylogenetically diverse environments known. A preliminary molecular survey of the GN mat based on only ∼1500 small subunit rRNA gene sequences discovered several new phylum-level groups in the bacterial phylogenetic domain and many previously undetected lower-level taxa. We determined an additional ∼119,000 nearly full-length sequences and 28,000 >200 nucleotide 454 reads from a 10-layer depth profile of the GN mat. With this unprecedented coverage of long sequences from one environment, we confirm the mat is phylogenetically stratified, presumably corresponding to light and geochemical gradients throughout the depth of the mat. Previous shotgun metagenomic data from the same depth profile show the same stratified pattern and suggest that metagenome properties may be predictable from rRNA gene sequences. We verify previously identified novel lineages and identify new phylogenetic diversity at lower taxonomic levels, for example, thousands of operational taxonomic units at the family-genus levels differ considerably from known sequences. The new sequences populate parts of the bacterial phylogenetic tree that previously were poorly described, but indicate that any comprehensive survey of GN diversity has only begun. Finally, we show that taxonomic conclusions are generally congruent between Sanger and 454 sequencing technologies, with the taxonomic resolution achieved dependent on the abundance of reference sequences in the relevant region of the rRNA tree of life.

Preliminary results of high resolution magneto-biostratigraphy of continental sequences in Chapala Basin, Southwestern Mexico

NASA Astrophysics Data System (ADS)

Mendez Cardenas, D. L.; Benammi, M.

2007-05-01

Chapala Lake is south from Guadalajara, Jalisco State (Southwestern Mexico). Belongs to a series of Pliocenic lakes along the Mexican Volcanic Belt. It is localized in the Chapala rift, and the entire area is controlled by the tectonic setting of the Colima, Tepic and Chapala rifts, constituting the triple junction rift-rift-rift. The deposits studied belong to volcanosedimentary sequences, composed by lacustrine and fluvial associations alternated with units of ash and pumice. The faunistic component reported consists at least of 27 mammals species, and the sediments were there're in have to work with special attention for seek rodents by handpicking. Probably these rodents will be the clue to determine the deposits correlation. Core demagnetization shows that they are low-coercivity magnetic minerals like magnetite or Ti-magnetite. It was verified that the characteristic magnetization corresponds to MNRp and the inversion test resulted good. Rodents are represented by Geomynae, Sigmondontinae and Sciurinae. The Geomynae family is the most common, and the faunistic association indicates Blancan age. This also allows a correlation with the polarity pattern in the GSS between 3,6 and 2,6 Ma. Actually, is known that this kind of studies in continental sequences supported with paleontological record of vertebrates could give us a more precised calibration of the age of such deposits. Allowing better understanding of the evolution of these mammals and their path trough geological record. This work shows the preliminary results of rodents palaeontology and high resolution magneto-stratigraphy in the units from to Chapala Basin.

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

USGS Publications Warehouse

Colman, Steven M.

2006-01-01

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

Seismic sequence stratigraphy of Miocene deposits related to eustatic, tectonic and climatic events, Cap Bon Peninsula, northeastern Tunisia

NASA Astrophysics Data System (ADS)

Gharsalli, Ramzi; Zouaghi, Taher; Soussi, Mohamed; Chebbi, Riadh; Khomsi, Sami; Bédir, Mourad

2013-09-01

The Cap Bon Peninsula, belonging to northeastern Tunisia, is located in the Maghrebian Alpine foreland and in the North of the Pelagian block. By its paleoposition, during the Cenozoic, in the edge of the southern Tethyan margin, this peninsula constitutes a geological entity that fossilized the eustatic, tectonic and climatic interactions. Surface and subsurface study carried out in the Cap Bon onshore area and surrounding offshore of Hammamet interests the Miocene deposits from the Langhian-to-Messinian interval time. Related to the basin and the platform positions, sequence and seismic stratigraphy studies have been conducted to identify seven third-order seismic sequences in subsurface (SM1-SM7), six depositional sequences on the Zinnia-1 petroleum well (SDM1-SDM6), and five depositional sequences on the El Oudiane section of the Jebel Abderrahmane (SDM1-SDM5). Each sequence shows a succession of high-frequency systems tract and parasequences. These sequences are separated by remarkable sequence boundaries and maximum flooding surfaces (SB and MFS) that have been correlated to the eustatic cycles and supercycles of the Global Sea Level Chart of Haq et al. (1987). The sequences have been also correlated with Sequence Chronostratigraphic Chart of Hardenbol et al. (1998), related to European basins, allows us to arise some major differences in number and in size. The major discontinuities, which limit the sequences resulted from the interplay between tectonic and climatic phenomena. It thus appears very judicious to bring back these chronological surfaces to eustatic and/or local tectonic activity and global eustatic and climatic controls.

Seismic stratigraphy and deformational styles of the offshore Cyrenaica (Libya) and bordering Mediterranean Ridge

NASA Astrophysics Data System (ADS)

Yem, Lionel Mbida; Camera, Laurent; Mascle, Jean; Ribodetti, Alessandra

2011-04-01

Off northwest Libya the Cyrenaica foreland basin domain and its Pan-African continental crust, which constitute the African promontory, are overthrusted by the Mediterranean Ridge Complex. The thrust belt contact and its seismic stratigraphy have been analysed using pre-stack depth-migrated multichannel seismic (MCS) lines recorded during the MEDISIS survey (2002). The geometry and sedimentary distribution analysis through the wedge-top depocentres allow reconstruction of schematic cross-sections of the tectono-sedimentary wedge that includes two major thrust sequences separated by an apparently poorly deformed transition zone. Based on time-space variation of several piggyback basins, we propose that these thrust sequences relate to distinct phases of shortening. (1) A first event, which probably occurred just prior to the Messinian crisis in latest Miocene (Tortonian times?) and (2) A second event, that has finally led to the present-day overthrusting of the Mediterranean Ridge over the Libyan continental slope.

Sequence stratigraphy buoys W. Indonesia basins

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

Courteney, S.

1996-05-20

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

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.

Snowpack modeling in the context of radiance assimilation for snow water equivalent mapping

NASA Astrophysics Data System (ADS)

Durand, M. T.; Kim, R. S.; Li, D.; Dumont, M.; Margulis, S. A.

2017-12-01

Data assimilation is often touted as a means of overcoming deficiences in both snowpack modeling and snowpack remote sensing. Direct assimilation of microwave radiances, rather than assimilating microwave retrievals, has shown promise, in this context. This is especially the case for deep mountain snow, which is often assumed to be infeasible to measure with microwave measurements, due to saturation issues. We first demonstrate that the typical way of understanding saturation has often been misunderstood. We show that deep snow leads to a complex microwave signature, but not to saturation per se, because of snowpack stratigraphy. This explains why radiance assimilation requires detailed snowpack models that adequatley stratgigraphy to function accurately. We examine this with two case studies. First, we show how the CROCUS predictions of snowpack stratigraphy allows for assimilation of airborne passive microwave measurements over three 1km2 CLPX Intensive Study Areas. Snowpack modeling and particle filter analysis is performed at 120 m spatial resolution. When run without the benefit of radiance assimilation, CROCUS does not fully capture spatial patterns in the data (R2=0.44; RMSE=26 cm). Assimlilation of microwave radiances for a single flight recovers the spatial pattern of snow depth (R2=0.85; RMSE = 13 cm). This is despite the presence of deep snow; measured depths range from 150 to 325 cm. Adequate results are obtained even for partial forest cover, and bias in precipitation forcing. The results are severely degraded if a three-layer snow model is used, however. The importance of modeling snowpack stratigraphy is highlighted. Second, we compare this study to a recent analysis assimilating spaceborne radiances for a 511 km2 sub-watershed of the Kern River, in the Sierra Nevada. Here, the daily Level 2A AMSR-E footprints (88 km2) are assimilated into a model running at 90 m spatial resolution. The three-layer model is specially adapted to predict "effective" stratigraphy. We compare and contrast these approaches to modeling snowpack stratigraphy, and highlight the critical role of models in radiance assimilation schemes.

A technique for extracting Radiolaria from radiolarian cherts.

NASA Technical Reports Server (NTRS)

Pessagno, E. A., Jr.; Newport, R. L.

1972-01-01

Differential solution of Mesozoic radiolarian cherts with hydrofluoric acid has yielded well-preserved, matrix-free Radiolaria. This technique allows the full utilization of Radiolaria in interpreting the stratigraphy of ophiolite sequences and of other successions where cherts are prevalent.

Stratigraphy of the north polar layered deposits of Mars from high-resolution topography

USGS Publications Warehouse

Becerra, Patricio; Byrne, Shane; Sori, Michael M.; Sutton, Sarah; Herkenhoff, Kenneth E.

2016-01-01

The stratigraphy of the layered deposits of the polar regions of Mars is theorized to contain a record of recent climate change linked to insolation changes driven by variations in the planet's orbital and rotational parameters. In order to confidently link stratigraphic signals to insolation periodicities, a description of the stratigraphy is required based on quantities that directly relate to intrinsic properties of the layers. We use stereo Digital Terrain Models (DTMs) from the High Resolution Imaging Science Experiment (HiRISE) to derive a characteristic of North Polar Layered Deposits (NPLD) strata that can be correlated over large distances: the topographic protrusion of layers exposed in troughs, which is a proxy for the layers’ resistance to erosion. Using a combination of image analysis and a signal-matching algorithm to correlate continuous depth-protrusion signals taken from DTMs at different locations, we construct a stratigraphic column that describes the upper ~500 m of at least 7% of the area of the NPLD, and find accumulation rates that vary by factors of up to two. We find that, when coupled with observations of exposed layers in orbital images, the topographic expression of the strata is consistently continuous through large distances in the top 300 – 500 m of the NPLD, suggesting it is better related to intrinsic layer properties than brightness alone.

Chronology of Eocene-Miocene sequences on the New Jersey shallow shelf: implications for regional, interregional, and global correlations

USGS Publications Warehouse

Browning, James V.; Miller, Kenneth G.; Sugarman, Peter J.; Barron, John; McCarthy, Francine M.G.; Kulhanek, Denise K.; Katz, Miriam E.; Feigenson, Mark D.

2013-01-01

Integrated Ocean Drilling Program Expedition 313 continuously cored and logged latest Eocene to early-middle Miocene sequences at three sites (M27, M28, and M29) on the inner-middle continental shelf offshore New Jersey, providing an opportunity to evaluate the ages, global correlations, and significance of sequence boundaries. We provide a chronology for these sequences using integrated strontium isotopic stratigraphy and biostratigraphy (primarily calcareous nannoplankton, diatoms, and dinocysts [dinoflagellate cysts]). Despite challenges posed by shallow-water sediments, age resolution is typically ±0.5 m.y. and in many sequences is as good as ±0.25 m.y. Three Oligocene sequences were sampled at Site M27 on sequence bottomsets. Fifteen early to early-middle Miocene sequences were dated at Sites M27, M28, and M29 across clinothems in topsets, foresets (where the sequences are thickest), and bottomsets. A few sequences have coarse (∼1 m.y.) or little age constraint due to barren zones; we constrain the age estimates of these less well dated sequences by applying the principle of superposition, i.e., sediments above sequence boundaries in any site are younger than the sediments below the sequence boundaries at other sites. Our age control provides constraints on the timing of deposition in the clinothem; sequences on the topsets are generally the youngest in the clinothem, whereas the bottomsets generally are the oldest. The greatest amount of time is represented on foresets, although we have no evidence for a correlative conformity. Our chronology provides a baseline for regional and interregional correlations and sea-level reconstructions: (1) we correlate a major increase in sedimentation rate precisely with the timing of the middle Miocene climate changes associated with the development of a permanent East Antarctic Ice Sheet; and (2) the timing of sequence boundaries matches the deep-sea oxygen isotopic record, implicating glacioeustasy as a major driver for forming sequence boundaries.

Using Seismic Reflection Analysis of Lacustrine Sediment Stratigraphy to Reconstruct 40,000 Years of Northern Hemisphere Andean Hydroclimate

NASA Astrophysics Data System (ADS)

Gibson, D. K.; Bird, B. W.; Wattrus, N. J.; Escobar, J.; Fonseca, H.; Velasco, F.; Polissar, P. J.

2017-12-01

Geophysical analysis of lacustrine seismic stratigraphy at Laguna de Tota (hereafter "Tota"), Boyaca, Colombia, provides a record of lake level fluctuations that ranges from the Late Quaternary to the present. Changes in Tota's volume indicated by off-lap and on-lap sequences show that regional hydroclimate varied considerably during at least the last 40 Ka. Modern lake level variability at Tota has been directly linked to the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), suggesting that past lake level changes identified in CHIRP seismic data may provide insight into past Pacific atmosphere-ocean dynamics. Here, we use high-resolution CHIRP data spanning the top 15 meters of sediment column and a preliminary age model based on Holocene sedimentation rates to investigate lake level variability over the past 40 Ka. Our data demonstrates that lake levels at Tota were generally lower between 40 and 30 Ka, experienced rapid and extreme fluctuations between 30 and 20 Ka (including the lowest recorded lake level at Tota during the LGM at 22 Ka), and gradually rose to the present day high stand between 20 and 0 Ka. Although the CHIRP data indicate significant late Quaternary lake level fluctuations, the timing and duration of these events needs to be more firmly constrained with additional investigations combining sediment core collection and analysis, geochronology, and other lake level proxies. Future work combining these methods holds tremendous potential in terms of reconstructing Late Quaternary atmosphere-ocean cycles.

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.

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.

Holocene alluvium around Lefkosia (Nicosia), Cyprus: An archive of land-use, tectonic processes, and climate change

USGS Publications Warehouse

Newell, Wayne L.; Stone, B.; Harrison, R.; ,

2004-01-01

Holocene alluvium of the Pedhicos River around Lefkosia (Nicosia), Cyprus, was studied. Alluvial stratigraphy was found to present serial flood deposits underlying river terraces and an extensive alluvial fan. It was found that the stratigraphy and geomorphology of the alluvium can be interpreted to distinguish not only the effects of climate change, but also land-use change, and the impact of particular engineering works. It was suggested that details of the physical properties of the flood deposit sequences and paleosols can contribute to modeling various geophysical and engineering properties and in predicting response to vertical acceleration during earthquakes.

Turbidite megabeds in an Oceanic Rift Valley recording jokulhlaups of late Pleistocene glacial lakes of the western United States

USGS Publications Warehouse

Zuffa, G.G.; Normark, W.R.; Serra, F.; Brunner, C.A.

2000-01-01

Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one ~60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.

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.

High resolution seismic stratigraphy and sedimentological signature of the Late Quaternary deposits in the northern Western Basin (Ross Sea, Antarctica)

NASA Astrophysics Data System (ADS)

Corradi, N.; Finocchiaro, F.; Ivaldi, R.; Melis, R.; Pittà, A.

2003-04-01

The northern Western Basin is a sector of the continental shelf of the Western Ross Sea that is considered to be the natural northward extension of the Drygalski Basin by many authors. The literature provides a general model of the evolution of the basin and the recent papers propose a seismic stratigraphy for the post-Miocene sedimentation. However, the sedimentary processes during the Late Quaternary and, in particular, the Last Glacial Maximum (LGM) are still little understood (Brambati et al., 2001). In this paper we present the preliminary results of the very high-resolution seismic surveys (Sub Bottom Profiler, Huntec Deep Tow Boomer and Sparker) and their calibration with the sediment samples collected during the three Marine Geology Campaigns of the PNRA (XIII, XIV and XVII), with the scientific objective of the research to investigate the role of the East Antarctic Ice Sheet (EAIS) in the morphogenesis and deposition of the Late Quaternary sedimentary series.

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

USGS Publications Warehouse

Pashin, J.C.

1998-01-01

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

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.

20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.

USGS Publications Warehouse

Molnia, B.F.; Post, A.; Carlson, P.R.

1996-01-01

Vitus Lake, the ice-marginal basin at the southeastern edge of Bering Glacier, Alaska, U.S.A., is a site of modern, rapid, glacial-marine sedimentation. Rather than being a fresh-water lake, Vitus Lake is a tidally influenced, marine to brackish embayment connected to the Pacific Ocean by an inlet, the Seal River. Vitus Lake consists of five deep bedrock basins, separated by interbasinal highs. Glacial erosion has cut these basins as much as 250 m below sea level. High-resolution seismic reflection surveys conducted in 1991 and 1993 of four of Vitus Lake's basins reveal a complex, variable three-component acoustic stratigraphy. Although not fully sampled, the stratigraphy is inferred to be primarily glacial-marine units of (1) basal contorted and deformed glacial-marine and glacial sediments deposited by basal ice-contact processes and submarine mass-wasting; (2) acoustically well-stratified glacial-marine sediment, which unconformably overlies the basal unit and which grades upward into (3) acoustically transparent or nearly transparent glacial-marine sediment. Maximum thicknesses of conformable glacial-marine sediment exceed 100 m. All of the acoustically transparent and stratified deposits in Vitus Lake are modern in age, having accumulated between 1967 and 1993. The basins where these three-part sequences of "present-day" glacial-marine sediment are accumulating are themselves cut into older sequences of stratified glacial and glacial-marine deposits. These older units outcrop on the islands in Vitus Lake. In 1967, as the result of a major surge, glacier ice completely filled all five basins. Subsequent terminus retreat, which continued through August 1993, exposed these basins, providing new locations for glacial-marine sediment accumulation. A correlation of sediment thicknesses measured from seismic profiles at specific locations within the basins, with the year that each location became ice-free, shows that the sediment accumulation at some locations exceeds 10 m year-1.

ICDP project DeepCHALLA: reconstructing East African climate change and environmental history over the past 250,000 years

NASA Astrophysics Data System (ADS)

Verschuren, Dirk; Van Daele, Maarten; Wolff, Christian; Waldmann, Nicolas; Meyer, Inka; Ombori, Titus; Peterse, Francien; O'Grady, Ryan; Schnurrenberger, Doug; Olago, Daniel

2017-04-01

Sediments on the bottom of Lake Challa, a 92-meter deep crater lake on the border of Kenya and Tanzania near Mt. Kilimanjaro, contain a uniquely long and continuous record of past climate and environmental change. The near-equatorial location and exceptional quality of this natural archive provide great opportunities to study tropical climate variability at both short (inter-annual to decadal) and long (glacial-interglacial) time scales; and the influence of this climate variability on the region's freshwater resources, the functioning of terrestrial ecosystems, and the history of the East African landscape in which modern humans (our species, Homo sapiens) evolved and have lived ever since. Supported in part by the International Continental Scientific Drilling Programme (ICDP), the DeepCHALLA project has now recovered the sediment record of Lake Challa down to 214.8 meter below the lake floor, with almost certain 100% cover of the uppermost 121.3 meter (ca.150,000 year BP to present) and estimated 85% cover over the lower part of the sequence, down to the lowermost distinct reflector in the available seismic stratigraphy. This reflector represents a 2 meter thick layer of volcanic sand and silt deposited ca.250,000 years ago, and overlies still older silty lacustrine clays deposited during early lake development. Down-hole logging produced continuous profiles of in-situ sediment composition that confer an absolute depth scale to both the recovered cores and their three-dimensional representation in seismic stratigraphy. As readily observed through the transparent core liners, Lake Challa sediments are finely laminated throughout most of the recovered sequence. Combined with the great time span, the exquisite temporal resolution of these sediments promises to greatly increase our understanding of tropical climate and ecosystem dynamics, and create a long-awaited equatorial counterpart to the high-latitude climate records extracted from the ice sheets of Greenland and Antarctica.

Application of carbon isotope stratigraphy to late miocene shallow marine sediments, new zealand.

PubMed

Loutit, T S; Kennett, J P

1979-06-15

A distinct (0.5 per mil) carbon-13/carbon-12 isotopic shift in the light direction has been identified in a shallow marine sedimentary sequence of Late Miocene age at Blind River, New Zealand, and correlated with a similar shift in Late Miocene Deep Sea Drilling Project sequences throughout the Indo-Pacific. A dated piston core provides an age for the shift of 6.2 +/- 0.1 million years. Correlations based on the carbon isotopic change require a revision of the previously established magnetostratigraphy at Blind River. The carbon shift at Blind River occurs between 6.2 and 6.3 +/- 0.1 million years before present. A new chronology provides an age for the evolutionary first appearance datum of Globorotalia conomiozea at 6.1 +/- 0.1 million years, the beginning of a distinct latest Miocene cooling event associated with the Kapitean stage at 6.2 +/- 0.1 million years, and the beginning of a distinct shallowing of water depths at 6.1 +/- 0.1 million years. The Miocene-Pliocene boundary as recognized in New Zealand is now dated at 5.3 +/- 0.1 million years. Extension of carbon isotope stratigraphy to other shallow Late Miocene sequences should provide an important datum for international correlation of Late Miocene shallow and deep marine sequences.

Stratigraphy of Pyroclastic Deposits of EL Aguajito Caldera, Baja California Sur, MÉXICO

NASA Astrophysics Data System (ADS)

Osorio Ocampo, L. S.; Macias, J. L.; García Sánchez, L.; Pola, A.; Saucedo, R.; Sánchez, J. M.; Avellán, D. R.; Cardona, S.; Reyes-Agustín, G.; Arce, J. L.

2015-12-01

El Aguajito caldera is located in the State of Baja California Sur, it comprises an area of 450 km2 and sits within the Santa Rosalía Basin which is controlled by NE-SW extensional structures and the NW-SE Cimarron Fault that transects the caldera structure. The oldest rocks are ~90 Ma granodiorites covered by an Oligocene-Miocene volcano-sedimentary sequence, the Miocene Santa Lucia Formation and La Esperanza basalt. Pliocene volcanism is represented by La Reforma caldera, El Aguajito caldera, and the Tres Vírgenes Volcanic complex. This study focuses on the cartography and stratigraphy of area in order to understand the evolution of the volcanic system. The stratigraphy from base to top consists of a series of shallow marine sediments (fossiliferous sandstones) covered by a thick sequence of ignimbrites and pyroclastic flows interbedded with volcaniclastic deposits (Gloria and El Infierno Formations). On top of these deposits is El Aguajito caldera, it consists of a 2 m thick pumice fallout followed by an ignimbrite with three transitional lithofacies: a ≤30-m thick light-pink pyroclastic flow enriched in pumice at the base that gradually becomes enrich in lithics towards the top with the occurrence of degasing pipes. On top rests a 15 m-thick light-purple ignimbrite slightly welded with fiammes and a sequence of pumiceous pyroclastic flows and fallouts. These deposits have been associate to the caldera formation with a collapse diameter of ~8 km marked by rhyolitic domes exposed along a ring collapse crowned the sequence as well as NW-SE aligned rhyolitic domes parallel to the seashore. This cartography allowed to present a preliminary new geological map with four stratigraphic units recognized so far, that were emplaced under subaerial conditions beginning with a Plinian column followed by the emplacement of El Aguajito ignimbrite with its subsequent caldera collapse and finally the extrusion of resurgent domes.

Global Geologic Map of Europa

NASA Technical Reports Server (NTRS)

Doggett, T.; Figueredo, P.; Greeley, R.; Hare, T.; Kolb, E.; Mullins, K.; Senske, D.; Tanaka, K.; Weiser, S.

2008-01-01

Europa, with its indications of a sub-ice ocean, is of keen interest to astrobiology and planetary geology. Knowledge of the global distribution and timing of Europan geologic units is a key step for the synthesis of data from the Galileo mission, and for the planning of future missions to the satellite. The first geologic map of Europa was produced at a hemisphere scale with low resolution Voyager data. Following the acquisition of higher resolution data by the Galileo mission, researchers have identified surface units and determined sequences of events in relatively small areas of Europa through geologic mapping using images at various resolutions acquired by Galileo's Solid State Imaging camera. These works provided a local to subregional perspective and employed different criteria for the determination and naming of units. Unified guidelines for the identification, mapping and naming of Europan geologic units were put forth by and employed in regional-to-hemispheric scale mapping which is now being expanded into a global geologic map. A global photomosaic of Galileo and Voyager data was used as a basemap for mapping in ArcGIS, following suggested methodology of all-stratigraphy for planetary mapping. The following units have been defined in global mapping and are listed in stratigraphic order from oldest to youngest: ridged plains material, Argadnel Regio unit, dark plains material, lineaments, disrupted plains material, lenticulated plains material and Chaos material.

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

NASA Astrophysics Data System (ADS)

Ekman, Sten R.

1998-09-01

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

Sequence stratigraphy on an early wet Mars

NASA Astrophysics Data System (ADS)

Barker, Donald C.; Bhattacharya, Janok P.

2018-02-01

The evolution of Mars as a water-bearing body is of considerable interest for the understanding of its early history and evolution. The principles of terrestrial sequence stratigraphy provide a useful conceptual framework to hypothesize about the stratigraphic history of the planets northern plains. We present a model based on the hypothesized presence of an early ocean and the accumulation of lowland sediments eroded from highland terrain during the time of the valley networks and later outflow channels. Ancient, global environmental changes, induced by a progressively cooling climate would have led to a protracted loss of surface and near surface water from low-latitudes and eventual cold-trapping at higher latitudes - resulting in a unique and prolonged, perpetual forced regression within basins and lowland depositional environments. The Messinian Salinity Crisis (MSC) serves as a potential terrestrial analogue of the depositional and environmental consequences relating to the progressive removal of large standing bodies of water. We suggest that the evolution of similar conditions on Mars would have led to the emplacement of diagnostic sequences of deposits and regional scale unconformities, consistent with intermittent resurfacing of the northern plains and the progressive loss of an early ocean by the end of the Hesperian era.

Refinement of late-Early and Middle Miocene diatom biostratigraphy for the east coast of the United States

USGS Publications Warehouse

Barron, John A.; Browning, James; Sugarman, Peter; Miller, Kenneth G.

2013-01-01

Integrated Ocean Drilling Program (IODP) Expedition 313 continuously cored Lower to Middle Miocene sequences at three continental shelf sites off New Jersey, USA. The most seaward of these, Site M29, contains a well-preserved Early and Middle Miocene succession of planktonic diatoms that have been independently correlated with the geomagnetic polarity time scale derived in studies from the equatorial and North Pacific. Shallow water diatoms (species of Delphineis, Rhaphoneis, and Sceptroneis) dominate in onshore sequences in Maryland and Virginia, forming the basis for the East Coast Diatom Zones (ECDZ). Integrated study of both planktonic and shallow water diatoms in Hole M29A as well as in onshore sequences in Maryland (the Baltimore Gas and Electric Company well) and Delaware (the Ocean Drilling Program Bethany Beach corehole) allows the refinement of ECDZ zones into a high-resolution biochronology that can be successfully applied in both onshore and offshore regions of the East Coast of the United States. Strontium isotope stratigraphy supports the diatom biochronology, although for much of the Middle Miocene it suggests ages that are on average 0.4 m.y. older. The ECDZ zonal definitions are updated to include evolutionary events of Delphineis species, and regional occurrences of important planktonic diatom marker taxa are included. Updated taxonomy, reference to published figures, and photographic images are provided that will aid in the application of this diatom biostratigraphy.

Carbon-isotope stratigraphy of the Lower Ordovician succession in Northeast Greenland: Implications for correlations with St. George Group in western Newfoundland (Canada) and beyond

NASA Astrophysics Data System (ADS)

Azmy, Karem; Stouge, Svend; Christiansen, Jørgen L.; Harper, Dave A. T.; Knight, Ian; Boyce, Douglas

2010-03-01

The Lower Ordovician sequence on the Ella Ø Island in Northeast (N-E) Greenland is a thick shallow marine platform carbonate sequence (˜ 1415 m thick) and constitutes the major part of the Kong Oscar Fjord Group. It consists, from bottom to top, of the Antiklinalbugt, Septembersø, and Cape Weber formations, which are believed to be respectively coeval with the Watts Bight, Boat Harbour, and Catoche formations of the St. George Group in western Newfoundland, Canada. Samples were collected from outcrops at high-resolution intervals and micritic materials were extracted by microdrilling after screening their petrographic and geochemical criteria to evaluate the degree of preservation. The δ13C and δ18O values of well preserved micrite microsamples range from -5.2‰ to 0.5‰ (VPDB) and from -10.3‰ to-6.5‰ (VPDB), respectively. The δ13C carb profile of the sequence reveals few negative shifts, which vary between ˜ 2 and 4.7‰ and are associated with unconformities/disconformities, thus reflecting the effect of significant sea-level changes. The δ13C shifts can be correlated with counterparts on the St. George Group and also on the global Lower Ordovician δ13C profiles around the early Tremadoc (˜ 2.3‰) and late Tremadoc-early Arenig (˜ 4.7‰).

Episodes of fluvial and volcanic activity in Mangala Valles, Mars.

PubMed

Keske, Amber L; Hamilton, Christopher W; McEwen, Alfred S; Daubar, Ingrid J

2015-01-01

A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700-800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400-500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300-350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars.

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.

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.

Expert systems for automated correlation and interpretation of wireline logs

USGS Publications Warehouse

Olea, R.A.

1994-01-01

CORRELATOR is an interactive computer program for lithostratigraphic correlation of wireline logs able to store correlations in a data base with a consistency, accuracy, speed, and resolution that are difficult to obtain manually. The automatic determination of correlations is based on the maximization of a weighted correlation coefficient using two wireline logs per well. CORRELATOR has an expert system to scan and flag incongruous correlations in the data base. The user has the option to accept or disregard the advice offered by the system. The expert system represents knowledge through production rules. The inference system is goal-driven and uses backward chaining to scan through the rules. Work in progress is used to illustrate the potential that a second expert system with a similar architecture for interpreting dip diagrams could have to identify episodes-as those of interest in sequence stratigraphy and fault detection- and annotate them in the stratigraphic column. Several examples illustrate the presentation. ?? 1994 International Association for Mathematical Geology.

Geologic map and map database of parts of Marin, San Francisco, Alameda, Contra Costa, and Sonoma counties, California

USGS Publications Warehouse

Blake, M.C.; Jones, D.L.; Graymer, R.W.; digital database by Soule, Adam

2000-01-01

This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (mageo.txt, mageo.pdf, or mageo.ps), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (mageo.txt, mageo.pdf, or mageo.ps), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller.

Material Units, Structures/Landforms, and Stratigraphy for the Global Geologic Map of Ganymede (1:15M)

NASA Technical Reports Server (NTRS)

Patterson, G. Wesley; Head, James W.; Collins, Geoffrey C.; Pappalardo, Robert T.; Prockter, Louis M.; Lucchitta, Baerbel K.

2008-01-01

In the coming year a global geological map of Ganymede will be completed that represents the most recent understanding of the satellite on the basis of Galileo mission results. This contribution builds on important previous accomplishments in the study of Ganymede utilizing Voyager data and incorporates the many new discoveries that were brought about by examination of Galileo data. Material units have been defined, structural landforms have been identified, and an approximate stratigraphy has been determined utilizing a global mosaic of the surface with a nominal resolution of 1 km/pixel assembled by the USGS. This mosaic incorporates the best available Voyager and Galileo regional coverage and high resolution imagery (100-200 m/pixel) of characteristic features and terrain types obtained by the Galileo spacecraft. This map has given us a more complete understanding of: 1) the major geological processes operating on Ganymede, 2) the characteristics of the geological units making up its surface, 3) the stratigraphic relationships of geological units and structures, and 4) the geological history inferred from these relationships. A summary of these efforts is provided here.

Stratigraphy and paleohydrology of delta channel deposits, Jezero crater, Mars

NASA Astrophysics Data System (ADS)

Goudge, Timothy A.; Mohrig, David; Cardenas, Benjamin T.; Hughes, Cory M.; Fassett, Caleb I.

2018-02-01

The Jezero crater open-basin lake contains two well-exposed fluvial sedimentary deposits formed early in martian history. Here, we examine the geometry and architecture of the Jezero western delta fluvial stratigraphy using high-resolution orbital images and digital elevation models (DEMs). The goal of this analysis is to reconstruct the evolution of the delta and associated shoreline position. The delta outcrop contains three distinct classes of fluvial stratigraphy that we interpret, from oldest to youngest, as: (1) point bar strata deposited by repeated flood events in meandering channels; (2) inverted channel-filling deposits formed by avulsive distributary channels; and (3) a valley that incises the deposit. We use DEMs to quantify the geometry of the channel deposits and estimate flow depths of ∼7 m for the meandering channels and ∼2 m for the avulsive distributary channels. Using these estimates, we employ a novel approach for assessing paleohydrology of the formative channels in relative terms. This analysis indicates that the shift from meandering to avulsive distributary channels was associated with an approximately four-fold decrease in the water to sediment discharge ratio. We use observations of the fluvial stratigraphy and channel paleohydrology to propose a model for the evolution of the Jezero western delta. The delta stratigraphy records lake level rise and shoreline transgression associated with approximately continuous filling of the basin, followed by outlet breaching, and eventual erosion of the delta. Our results imply a martian surface environment during the period of delta formation that supplied sufficient surface runoff to fill the Jezero basin without major drops in lake level, but also with discrete flooding events at non-orbital (e.g., annual to decadal) timescales.

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.

An integrated bio-chemostratigraphic framework for Lower Cretaceous (Barremian-Cenomanian) shallow-water carbonates of the Central Apennines (Italy)

NASA Astrophysics Data System (ADS)

Schmitt, Katharina; Heimhofer, Ulrich; Frijia, Gianluca; Huck, Stefan

2017-04-01

Shallow-water carbonate platform sections are valuable archives for the reconstruction of deep-time environmental and climatic conditions, but the biostratigraphic resolution is often rather low. Moreover, chemostratigraphic correlation with well-dated pelagic sections by means of bulk carbonate carbon-isotope stratigraphy is notoriously difficult and afflicted with large uncertainties, as shallow-water sections are particularly prone to the impact of diagenesis. In the current study, an integrated biostratigraphic-chemostratigraphic approach is applied to southern Tethyan Lower Cretaceous carbonate platform deposits (Santa Lucia, Monte La Costa sections) situated in the Central Apennines in Italy. The 500 m thick Santa Lucia section, representing an open lagoonal inner carbonate platform setting, provides a characteristic carbon- and oxygen-isotope pattern that allows for correlation with pelagic composite reference curves (Vocontian and Umbria Marche basins). Calibrated by means of foraminiferal biostratigraphy and rudist bivalve strontium-isotope stratigraphy, the section serves as local chemostratigraphic shallow-water reference for the Barremian to Cenomanian. The 250 m thick Monte La Costa section comprises predominantly coarse grained (biostromal) and often strongly cemented shelf margin deposits. Although benthic foraminifera are scarce and the carbonates evidently suffered strong diagenetic alteration, high-resolution (rudist shell) strontium-isotope stratigraphy in combination with superimposed carbon-isotope trends and biological-lithological changes (e.g., mass occurrences of Bacinella irregularis s.l) enables correlation with the Early Albian to Cenomanian portion of the Santa Lucia reference section. At both localities, chemostratigraphy indicates a major gap covering large parts of the Lower and middle Cenomanian. After having considerably improved the stratigraphic resolution of the studied sections, selected best-preserved rudist shells are going to be used for sclerochronological investigations. This will allow reconstructing the impact of long-term (Myr) and short-term (seasonal) paleoclimatic and paleoenvironmental changes on Cretaceous shallow seas.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, David S.; Catchings, Rufus D.; Goldman, Mark R.; Gohn, Gregory S.; Horton, J. Wright; Edwards, Lucy E.; Rymer, Michael J.; Gandhok, Gini

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (~5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientific Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderate-amplitude, discontinuous, dipping reflections below ~527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ~527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fill sediments and postimpact Eocene to Pleistocene sediments. Reflections with ~20-30 m of relief in the uppermost part of the crater-fill and lowermost part of the postimpact section suggest differential compaction of the crater-fill materials during early postimpact time. The top of the crater-fill section also shows ~20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostrati-graphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the first possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postim-pact section unrelated to structures in the crater fill indicates postimpact sediment compaction.

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.

ICDP Project DeepCHALLA: Reconstructing 250,000 Years of Climate Change and Environmental History on the East African Equator

NASA Astrophysics Data System (ADS)

Wolff, C.; Verschuren, D.; Van Daele, M. E.; Waldmann, N.; Meyer, I.; Lane, C. S.; Van der Meeren, T.; Ombori, T.; Kasanzu, C.; Olago, D.

2017-12-01

Sediments on the bottom of Lake Challa, a 92-m deep crater lake on the border of Kenya and Tanzania near Mt. Kilimanjaro, contain a uniquely long and continuous record of past climate and environmental change in easternmost equatorial Africa. Supported in part by the International Continental Scientific Drilling Programme (ICDP), the DeepCHALLA project has now recovered this sediment record down to 214.8 m below the lake floor, with 100% recovery of the uppermost 121.3 m (the last 160 kyr BP) and ca.85% recovery of the older part of the sequence, down to the lowermost distinct reflector identified in seismic stratigraphy. This acoustic basement represents a ca.2-m thick layer of coarsely laminated, diatom-rich organic mud mixed with volcanic sand and silt deposited 250 kyr ago, overlying an estimated 20-30 m of unsampled lacustrine deposits representing the earliest phase of lake development. Down-hole logging produced profiles of in-situ sediment composition that confer an absolute depth- scale to both the recovered cores and the seismic stratigraphy. An estimated 74% of the recovered sequence is finely laminated (varved), and continuously so over the upper 72.3 m (the last 90 kyr). All other sections display at least cm-scale lamination, demonstrating persistence of a tranquil, profundal depositional environment throughout lake history. The sequence is interrupted only by 32 visible tephra layers 2 to 9 mm thick; and by several dozen fine-grained turbidites up to 108 cm thick, most of which are clearly bracketed between a non-erosive base and a diatom-laden cap. Tie points between sediment markers and the corresponding seismic reflectors support a preliminary age model inferring a near-constant rate of sediment accumulation over at least the last glacial cycle (140 kyr BP to present). This great time span combined with the exquisite temporal resolution of the Lake Challa sediments provides great opportunities to study past tropical climate dynamics at both short (inter-annual to decadal) and long (glacial-interglacial) time scales; and to assess the multi-faceted impact of this climate change on the region's freshwater resources, the functioning of terrestrial ecosystems, and the history of the African landscape in which modern humans (our species, Homo sapiens) originally evolved and have lived ever since.

Late Holocene Regression of the Northern Peruvian Coast Near Rio Chicama

NASA Astrophysics Data System (ADS)

Ramirez, M. T.; Goodbred, S. L.; Dillehay, T. D.; Quivira, M. P.

2008-12-01

Many Peruvian archaeological sites lie at the interface between an arid coastal desert, a rich marine ecosystem, and some of the tallest mountains in the Western Hemisphere, providing several unique environments within a small geographic area. While the region has supported civilizations since at least 6000BP, it has also been subject to a complex history of environmental impacts evident in the stratigraphy of the surrounding coastal environment. Most notable in the stratigraphy are El Nino flood events, providing the majority of sediment input to the coast, and tsunami events that are occasionally marked in the stratigraphic record. Such evidence for a paleotsunami appears to exist within a sequence of regressive Holocene shoreline deposits. This possible event is characterized by a planar erosional surface, dipping shallowly seaward, truncating the entire sequence of Holocene shorelines. The surface also consists of a lag of gravel that has been subsequently weathered by subaerial exposure to salt and sun. In addition there appears to be residual evidence of a similar, earlier event, most of which has been eroded from the record by the younger event. This entire sequence of shoreface deposits is situated approximately 2m above present mean sea level, and is suspected to be younger than 3000 years (pending radiocarbon dates), suggesting a rapid, recent Holocene regression in this region.

Vegetation history and palaeoclimate of the last glacial period at Lago Grande di Monticchio, Southern Italy

NASA Astrophysics Data System (ADS)

Watts, W. A.; Allen, J. R. M.; Huntley, B.

A high-resolution palynological study of a 51 m core from Lago Grande di Monticchio, southern Italy, has provided a palaeonvironmental record for the last glacill. A annual lamination based chronology, supported by radiometric and tephrochronological dates, provides an absolute timescale for this record that spans 76,300 years. Correlations are established between the pollen stratigraphy, the GRIP ice core δ18O record and foraminiferal assemblages from Atlantic core V23-81. Both Dansgaard-Oeschger and Heinrich events are reflected by changes in the pollen stratigraphy. Revised dates are estimated for Heinrich events H1-H6. A quantitative palaeoclimate reconstruction based upon the pollen data provides evidence of the climate changes in southern Italy associated with these and other fluctuations during the last glacial.

Compositional stratigraphy of crustal material from near-infrared spectra

NASA Technical Reports Server (NTRS)

Pieters, Carle M.

1987-01-01

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

Implications for crustal accretion at fast spreading ridges from observations in Jurassic oceanic crust in the western Pacific

NASA Astrophysics Data System (ADS)

Pockalny, Robert A.; Larson, Roger L.

2003-01-01

Downhole logging data and basement stratigraphy interpretations are used to determine the spreading environment and crustal accretion history of the ocean basement cored at ODP Hole 801C located in the Jurassic Magnetic Quiet Zone of the western Pacific. High-resolution microresistivity data obtained with the Formation MicroScanner are used to measure the dip of the extrusive layers and indicate a 10°-30° increase in dip down the drill hole with lava flow contacts dipping back toward the original ridge axis. This structural pattern and the high proportion of massive flows relative to pillow units are consistent with prevailing crustal accretion models proposed for faster spreading ridges (e.g., >60 km/m.y., full-rate). A detailed analysis of the age data, basement lithology, related geochemistry, and structural attitudes suggest the shallowest 100 m of the drilled section (e.g., Sequences I-III) were emplaced just off the ridge (Sequence III) or significantly farther off-axis up to 5-15 m.y. later (Sequences I and II). The remainder of the drilled section (e.g., Sequences IV-VIII) has geochemical, lithological and physical trends that are assumed to be representative of crust created at faster spreading ridges. The pattern of dipping lava flow contacts from this deeper section of the drill hole suggests lava flows emanating from the ridge axis are limited to 1-2 km off-axis. Our results suggest ocean crust drilled at Hole 801C was created at faster spreading rates; however, caution should be used when incorporating Sequences I-III into geochemical reference sections for faster spreading ridges.

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

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Sections Geologic Communications Alaska Geologic Data Index (AGDI) Volcanology Alaska Volcano Observatory and Location Policy and Facilities Staff Seismic and Well Data Data Reports Contact Us Frequently Formation, Alaska - New insights into the sequence stratigraphy of the Late Jurassic Cook Inlet forearc

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.

Stratigraphy, climate and downhole logging data - an example from the ICDP Dead Sea deep drilling project

NASA Astrophysics Data System (ADS)

Coianiz, Lisa; Ben-Avraham, Zvi; Lazar, Michael

2017-04-01

During the late Quaternary a series of lakes occupied the Dead Sea tectonic basin. The sediments that accumulated within these lakes preserved the environmental history (tectonic and climatic) of the basin and its vicinity. Most of the information on these lakes was deduced from exposures along the marginal terraces of the modern Dead Sea, e.g. the exposures of the last glacial Lake Lisan and Holocene Dead Sea. The International Continental Drilling Program (ICDP) project conducted in the Dead Sea during 2010-2011 recovered several cores that were drilled in the deep depocenter of the lake (water depth of 300 m) and at the margin (depth of 3 m offshore Ein Gedi spa). New high resolution logging data combined with a detailed lithological description and published age models for the deep 5017-1-A borehole were used to establish a sequence stratigraphic framework for the Lakes Amora, Samra, Lisan and Zeelim strata. This study presents a stratigraphic timescale for reconstructing the last ca 225 ka. It provides a context within which the timing of key sequence surfaces identified in the distal part of the basin can be mapped on a regional and stratigraphic time frame. In addition, it permitted the examination of depositional system tracts and related driving mechanisms controlling their formation. The sequence stratigraphic model developed for the Northern Dead Sea Basin is based on the identification of sequence bounding surfaces including: sequence boundary (SB), transgressive surface (TS) and maximum flooding surface (MFS). They enabled the division of depositional sequences into a Lowstand systems tracts (LST), Transgressive systems tracts (TST) and Highstand systems tracts (HST), which can be interpreted in terms of relative lake level changes. The analysis presented here show that system tract stacking patterns defined for the distal 5017-1-A borehole can be correlated to the proximal part of the basin, and widely support the claim that changes in relative lake levels were synchronous across the northern Dead Sea, although differences do exist. These discrepancies can possibly be explained in part by the tectonic nature of the basin. Within the 5017-1-A section, the interpreted changes in depositional environments derived primarily from the gamma ray log patterns show a good correlation in time with sequence-chronostratigraphic framework, extracted lake level curves and paleohydrological records of other areas worldwide. Sequence stratigraphic analysis presented here allows for a detailed, high resolution examination of the sedimentary sequences in the Northern Dead Sea Basin together with an independent proxy that is an indirect indicator of changes in relative lake level.

Systematic vertical and lateral changes in quality and time resolution of the macrofossil record: insights from Holocene transgressive deposits, Po coastal plain, Italy

NASA Astrophysics Data System (ADS)

Azzarone, Michele; Scarponi, Daniele; Kusnerik, Kristopher; Amorosi, Alessandro; Bohacs, Kevin M.; Drexler, Tina M.; Kowalewski, Michał

2017-04-01

In siliciclastic marine settings, skeletal concentrations are a characteristic feature of transgressive intervals that provide insights into paleobiology and sequence stratigraphy. To investigate taphonomic signatures of transgressive intervals, we analyzed three cores from a Holocene depositional profile of the Po coastal plain, in northern Italy. Coupled multivariate taphonomic and bathymetric trends delineate spatial and temporal gradients in sediment starvation/bypassing, suggesting that quality and resolution of the fossil record vary predictably along the studied depositional profile. Moreover, joint consideration of taphonomic, bathymetric, and fossil density trends across the study area reveals distinctive signatures that are useful in characterizing facies associations and recognizing surfaces and intervals of sequence stratigraphic significance. Within the southern Po plain succession, taphonomic degradation of macroskeletal remains increases from proximal—nearshore to distal—offshore locations. This trend is discernible for both biologically-driven (bioerosion) and chemically/physically-driven (e.g., dissolution, abrasion) shell alterations. Compared to the up-dip (most proximal) core, the down-dip core is distinguished by shell-rich lithosomes affected by ecological condensation (co-occurrence of environmentally non-overlapping taxa) and by higher taphonomic alteration. The onshore-offshore taphonomic trend likely reflects variation in sediment-supply along the depositional profile of the Holocene Northern Adriatic shelf, with surface/near-surface residence-time of macroskeletal remains increasing down dip due to lower accumulation rates. These results indicate that, during transgressive phases, changes in sea-level (base level) are likely to produce down-dip taphonomic gradients across shelves, where the quality and resolution of the fossil record both deteriorate distally. The amino acid radiometrically calibrated dates on bivalves and the chronostratigraphic framework for this profile suggest that the high levels of taphonomic degradation observed distally developed over millennial time scales ( 8ky). The patterns documented here may be characteristic of siliciclastic-dominated depositional systems that experience high-frequency, base-level fluctuations.

Insights into the development of drumlin formation using ground-penetrating radar

NASA Astrophysics Data System (ADS)

Woodard, J.; Zoet, L.; Iverson, N. R.; Benediktsson, Í. Ö.; Schomacker, A.; Finlayson, A.

2016-12-01

Drumlins form as the result of subglacial slip, but the exact mechanisms responsible for their formation remain enigmatic. Resolution of drumlin internal stratigraphy provides a means for constraining the formation processes of drumlins, and thus the basal mechanics that result in their formation. Traditional litho-stratigraphic techniques have provided great insight into the internal stratigraphy of drumlins but are inherently limited to areas of natural exposure. We report on the application of geophysical methods used to image the internal stratigraphy of drumlins over a much larger area than is possible through litho-stratigraphic logging. Using ground penetrating radar we investigated the internal stratigraphy of seven drumlins from a recently exposed active drumlin field in the forefield of Múlajökull, Iceland. Data were collected using 100 and 200 MHz antennas that had maximum penetration depths of 15 m and 7 m with 0.4 m and 0.2 m resolution, respectively. Echograms demonstrated distinct layering of the diamictites. From the surface to ca. 2 m depth, till layers generally conformed to the longitudinal surface topography of the drumlins. Upper till layers exhibit unconformities on the flanks of the drumlins, except on their distal lee sides where layers were conformable. Till layers at approximately 2 m depth paralleled the drumlin surface and truncated lower layers. Below ca. 2 m depth distinct till layers dipped obliquely to the surface in the down-ice direction. These stratigraphic patterns were apparent in all drumlins measured at Múlajökull. The stratigraphic pattern observed in the drumlins of the Múlajökull forefield indicate a combination of deposition and erosion. Deposition occurred predominantly on the lee side and near the central axis of the drumlin, whereas erosion occurred along the flanks and stoss side. These observations support results from traditional litho-stratigraphic logs recorded on the same drumlins. Our observations suggest that drumlins migrated down ice and were initiated by a heterogeneous relief pattern in the drumlin forefield prior to the initial ice advance. This conceptual model supports observations that drumlins gained relief and became more elongated with time under the ice.

Interlobate esker architecture and related hydrogeological features derived from a combination of high-resolution reflection seismics and refraction tomography, Virttaankangas, southwest Finland

NASA Astrophysics Data System (ADS)

Maries, Georgiana; Ahokangas, Elina; Mäkinen, Joni; Pasanen, Antti; Malehmir, Alireza

2017-05-01

A novel high-resolution (2-4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70-100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick.

Advances through collaboration: sharing seismic reflection data via the Antarctic Seismic Data Library System for Cooperative Research (SDLS)

USGS Publications Warehouse

Wardell, N.; Childs, J. R.; Cooper, A. K.

2007-01-01

The Antarctic Seismic Data Library System for Cooperative Research (SDLS) has served for the past 16 years under the auspices of the Antarctic Treaty (ATCM Recommendation XVI-12) as a role model for collaboration and equitable sharing of Antarctic multichannel seismic reflection (MCS) data for geoscience studies. During this period, collaboration in MCS studies has advanced deciphering the seismic stratigraphy and structure of Antarctica’s continental margin more rapidly than previously. MCS data compilations provided the geologic framework for scientific drilling at several Antarctic locations and for high-resolution seismic and sampling studies to decipher Cenozoic depositional paleoenvironments. The SDLS successes come from cooperation of National Antarctic Programs and individual investigators in “on-time” submissions of their MCS data. Most do, but some do not. The SDLS community has an International Polar Year (IPY) goal of all overdue MCS data being sent to the SDLS by end of IPY. The community science objective is to compile all Antarctic MCS data to derive a unified seismic stratigraphy for the continental margin – a stratigraphy to be used with drilling data to derive Cenozoic circum-Antarctic paleobathymetry maps and local-to-regional scale paleoenvironmental histories.

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

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

Li, L.; Tull, J.F.

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

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

USGS Publications Warehouse

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

1975-01-01

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

Episodes of fluvial and volcanic activity in Mangala Valles, Mars

PubMed Central

Keske, Amber L.; Hamilton, Christopher W.; McEwen, Alfred S.; Daubar, Ingrid J.

2017-01-01

A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700–800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400–500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300–350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars. PMID:29176911

Influence of near-surface stratigraphy on coastal landslides at Sleeping Bear Dunes National Lakeshore, Lake Michigan, USA

USGS Publications Warehouse

Barnhardt, W.A.; Jaffe, B.E.; Kayen, R.E.; Cochrane, G.R.

2004-01-01

Lake-level change and landslides are primary controls on the development of coastal environments along the coast of northeastern Lake Michigan. The late Quaternary geology of Sleeping Bear Dunes National Lakeshore was examined with high-resolution seismic reflection profiles, ground-penetrating radar (GPR), and boreholes. Based on sequence-stratigraphic principles, this study recognizes ten stratigraphic units and three major unconformities that were formed by late Pleistocene glaciation and postglacial lake-level changes. Locally high sediment supply, and reworking by two regressions and a transgression have produced a complex stratigraphy that is prone to episodic failure. In 1995, a large landslide deposited approximately 1 million m3 of sediment on the lake floor. The highly deformed landslide deposits, up to 18 m thick, extend 3-4 km offshore and unconformably overlie well-stratified glacial and lacustrine sediment. The landslide-prone bluff is underlain by channel-fill deposits that are oriented nearly perpendicular to the shoreline. The paleochannels are at least 10 m deep and 400 m wide and probably represent stream incision during a lake-level lowstand about 10.3 ka B.P. The channels filled with sediment during the subsequent transgression and lake-level highstand, which climaxed about 4.5 ka B.P. As lake level fell from the highstand, the formation of beach ridges and sand dunes sealed off the channel and isolated a small inland lake (Glen Lake), which lies 5 m above the level of Lake Michigan and may be a source of piped groundwater. Our hypothesis is that the paleochannels act as conduits for pore water flow, and thereby locally reduce soil strength and promote slope failure.

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.

Stratigraphic Signatures of Forearc Basin Formation Mechanisms

NASA Astrophysics Data System (ADS)

Mannu, U.; Ueda, K.; Gerya, T.; Willett, S.; Strasser, M.

2014-12-01

Forearc basins are loci of active sedimentation above the landward portion of accretionary prisms. Although these basins typically remain separated from the frontal prism by a forearc high, their evolution has a significant impact on the structure and deformation of the entire wedge. Formation of forearc basins has been proposed as a consequence of changes in wedge stability due to an increase of slab dip in subduction zones. Another hypothesis attributes this to higher hinterland sedimentation, which causes the rear of the wedge to stabilize and eventually develop a forearc basin. Basin stratigraphic architecture, revealed by high-resolution reflection seismic data and borehole data allows interpretation of structural development of the accretionary prism and associated basins with the goal of determining the underlying driving mechanism(s) of basin formation. In this study we supplement data interpretation with thermo-mechanical numerical models including high-resolution isochronal surface tracking to visualize the developing stratigraphy of basins that develop in subduction zone and wedge dynamic models. We use a dynamic 2D thermo mechanical model incorporating surface processes, strain weakening and sediment subduction. The model is a modification of I2VIS model, which is based on conservative, fully staggered finite differences and a non-diffusive marker- in-cell technique capable of modelling mantle convection. In the model different driving mechanisms for basin formation can be explored. Stratigraphic simulations obtained by isochronal surface tracking are compared to reflection pattern and stratigraphy of seismic and borehole data, respectively. Initial results from a model roughly representing the Nankai Trough Subduction Zone offshore Japan are compared to available seismic and Integrated Ocean Drilling (IODP) data. A calibrated model predicting forearc basin stratigraphy will be used to discern the underlying process of basins formation and wedge dynamics.

Stratigraphy of the south polar region of Ganymede

NASA Technical Reports Server (NTRS)

Dehon, R. A.

1987-01-01

A preliminary assessment is made of the stratigraphy and geology in the south polar region of the Jovian satellite, Ganymede. Geologic mapping is based on inspection of Voyager images and compilation on an airbrush base map at a scale of 1:5M. Illumination and resolution vary greatly in the region. Approximately half of the quadripole is beyond the terminator. Low angle illumination over a large part of the area precludes distinction of some units by albedo characteristics. Several types of grooved terrain and groove related terrain occur in the southern polar region. Grooves typically occur in straight to curvilinear sets or lanes. Bright lanes and grooved lanes intersect at high angles outlining polygons of dark cratered terrain. Groove sets exhibit a range of ages as shown by superposition or truncation and by crater superposition ages.

Crustal heterogeneity of the moon viewed from the Galileo SSI camera: Lunar sample calibrations and compositional implications

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Belton, M.; Becker, T.; Carr, M. H.; Chapmann, C.; Fanale, F. P.; Fischer, Erich M.; Gaddis, L.; Greeley, Ronald; Greenberg, R.

1991-01-01

Summaries are given of the spectral calibration, compositional parameters, nearside color, and limb and farside color of the Moon. The farside of the Moon, a large area of lunar crust, is dominated by heavily cratered terrain and basin deposits that represent the products of the first half billion years of crustal evolution. Continuing analysis of the returned lunar samples suggest a magma ocean and/or serial magmatism model for evolution of the primordial lunar crust. However, testing either hypothesis requires compositional information about the crustal stratigraphy and lateral heterogeneity. Resolution of this important planetary science issue is dependent on additional data. New Galileo multispectral images indicate previously unknown local and regional compositional diversity of the farside crust. Future analysis will focus on individual features and a more detailed assessment of crustal stratigraphy and heterogeneity.

Geomorphic and sedimentary responses of the Bull Creek Valley (Southern High Plains, USA) to Pleistocene and Holocene environmental change

NASA Astrophysics Data System (ADS)

Arauza, Hanna M.; Simms, Alexander R.; Bement, Leland C.; Carter, Brian J.; Conley, Travis; Woldergauy, Ammanuel; Johnson, William C.; Jaiswal, Priyank

2016-01-01

Fluvial geomorphology and stratigraphy often reflect past environmental and climate conditions. This study examines the response of Bull Creek, a small ephemeral creek in the Oklahoma panhandle, to environmental conditions through the late Pleistocene and Holocene. Fluvial terraces were mapped and their stratigraphy and sedimentology documented throughout the course of the main valley. Based on their elevations, terraces were broadly grouped into a late-Pleistocene fill terrace (T3) and two Holocene fill-cut terrace sets (T2 and T1). Terrace systems are marked by similar stratigraphies recording the general environmental conditions of the time. Sedimentary sequences preserved in terrace fills record the transition from a perennial fluvial system during the late glacial period and the Younger Dryas to a semiarid environment dominated by loess accumulation and punctuated by flood events during the middle to late Holocene. The highest rates of aeolian accumulation within the valley occurred during the early to middle Holocene. Our data provide significant new information regarding the late-Pleistocene and Holocene environmental history for this region, located between the well-studied Southern and Central High Plains of North America.

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.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, D.S.; Catchings, R.D.; Goldman, M.R.; Gohn, G.S.; Horton, J. Wright; Edwards, L.E.; Rymer, M.J.; Gandhok, G.

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (??5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientifi c Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderateamplitude, discontinuous, dipping reflections below ??527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ??527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fi ll sediments and postimpact Eocene to Pleistocene sediments. Refl ections with ??20-30 m of relief in the uppermost part of the crater-fi ll and lowermost part of the postimpact section suggest differential compaction of the crater-fi ll materials during early postimpact time. The top of the crater-fi ll section also shows ??20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostratigraphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the fi rst possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postimpact section unrelated to structures in the crater fi ll indicates postimpact sediment compaction. ?? 2009 The Geological Society of America.

Calibration of a conodont apatite-based Ordovician 87Sr/86Sr curve to biostratigraphy and geochronology: Implications for stratigraphic resolution

USGS Publications Warehouse

Saltzman, M. R.; Edwards, C. T.; Leslie, S. A.; Dwyer, Gary S.; Bauer, J. A.; Repetski, John E.; Harris, A. G.; Bergstrom, S. M.

2014-01-01

The Ordovician 87Sr/86Sr isotope seawater curve is well established and shows a decreasing trend until the mid-Katian. However, uncertainties in calibration of this curve to biostratigraphy and geochronology have made it difficult to determine how the rates of 87Sr/86Sr decrease may have varied, which has implications for both the stratigraphic resolution possible using Sr isotope stratigraphy and efforts to model the effects of Ordovician geologic events. We measured 87Sr/86Sr in conodont apatite in North American Ordovician sections that are well studied for conodont biostratigraphy, primarily in Nevada, Oklahoma, the Appalachian region, and Ohio Valley. Our results indicate that conodont apatite may provide an accurate medium for Sr isotope stratigraphy and strengthen previous reports that point toward a significant increase in the rate of fall in seawater 87Sr/86Sr during the Middle Ordovician Darriwilian Stage. Our 87Sr/86Sr results suggest that Sr isotope stratigraphy will be most useful as a high-resolution tool for global correlation in the mid-Darriwilian to mid-Sandbian, when the maximum rate of fall in 87Sr/86Sr is estimated at ∼5.0–10.0 × 10–5 per m.y. Variable preservation of conodont elements limits the precision for individual stratigraphic horizons. Replicate conodont analyses from the same sample differ by an average of ∼4.0 × 10–5 (the 2σ standard deviation is 6.2 × 10–5), which in the best case scenario allows for subdivision of Ordovician time intervals characterized by the highest rates of fall in 87Sr/86Sr at a maximum resolution of ∼0.5–1.0 m.y. Links between the increased rate of fall in 87Sr/86Sr beginning in the mid-late Darriwilian (Phragmodus polonicus to Pygodus serra conodont zones) and geologic events continue to be investigated, but the coincidence with a long-term rise in sea level (Sauk-Tippecanoe megasequence boundary) and tectonic events (Taconic orogeny) in North America provides a plausible explanation for the changing magnitude and87Sr/86Sr of the riverine Sr flux to the oceans.

Stratigraphy and paleogeographic significance of a Late Pennsylvanian to Early Permian channeled slope sequence in the Darwin Basin, southern Darwin Hills, east-central California

USGS Publications Warehouse

Stevens, Calvin H.; Stone, Paul; Magginetti, Robert T.; Ritter, Scott M.

2015-01-01

The complex stratigraphy of late Paleozoic rocks in the southern Darwin Hills consists of regionally extensive Mississippian and Early to Middle Pennsylvanian rocks overlain by latest Pennsylvanian to Early Permian rocks, herein called the Darwin Hills sequence. Deposition of this latter sequence marked the beginning of the Darwin Basin. In Mississippian time, a carbonate platform prograded westward over slightly older slope deposits. In the Late Mississippian this platform was exposed to erosion and siliciclastic sediments were deposited. In Early to Middle Pennsylvanian time the area subsided, forming a west-facing ramp that was subjected to deformation and erosion in Middle or early Late Pennsylvanian time. Later this area was tilted westward and deep-water sediments were deposited on this slope. In latest Pennsylvanian to earliest Permian time, a major channel was cut through the older Pennsylvanian rocks and into the Upper Mississippian strata. This channel was gradually filled with increasingly finer grained, deep-water sediment as the area evolved into a basin floor by Early Permian (Sakmarian) time. Expansion of the Darwin Basin in Artinskian time led to a second phase of deposition represented by strata of the regionally extensive Darwin Canyon Formation. The geology in this small area thus documents tectonic events occurring during the early development of the Darwin Basin.

Persistence of exponential bed thickness distributions in the stratigraphic record: Experiments and theory

NASA Astrophysics Data System (ADS)

Straub, K. M.; Ganti, V. K.; Paola, C.; Foufoula-Georgiou, E.

2010-12-01

Stratigraphy preserved in alluvial basins houses the most complete record of information necessary to reconstruct past environmental conditions. Indeed, the character of the sedimentary record is inextricably related to the surface processes that formed it. In this presentation we explore how the signals of surface processes are recorded in stratigraphy through the use of physical and numerical experiments. We focus on linking surface processes to stratigraphy in 1D by quantifying the probability distributions of processes that govern the evolution of depositional systems to the probability distribution of preserved bed thicknesses. In this study we define a bed as a package of sediment bounded above and below by erosional surfaces. In a companion presentation we document heavy-tailed statistics of erosion and deposition from high-resolution temporal elevation data recorded during a controlled physical experiment. However, the heavy tails in the magnitudes of erosional and depositional events are not preserved in the experimental stratigraphy. Similar to many bed thickness distributions reported in field studies we find that an exponential distribution adequately describes the thicknesses of beds preserved in our experiment. We explore the generation of exponential bed thickness distributions from heavy-tailed surface statistics using 1D numerical models. These models indicate that when the full distribution of elevation fluctuations (both erosional and depositional events) is symmetrical, the resulting distribution of bed thicknesses is exponential in form. Finally, we illustrate that a predictable relationship exists between the coefficient of variation of surface elevation fluctuations and the scale-parameter of the resulting exponential distribution of bed thicknesses.

Identification of third-order (approx. 10{sup 6} yrs) and fourth-order (approx. 10{sup 5}/10{sup 4} yrs) stratigraphic cycles in the South Addition, West Cameron Lease Area, Louisiana offshore

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

Lowrie, A.; Meeks, P.; Hoffman, K.

In the highly explored South Addition of the West Cameron Lease Area, Louisiana offshore, interpretation of a six-mile ({approx}10 km) seismic section across a single intraslope basin yielded 20 sediment packages. Several interpretive tools were necessary. Seismic stratigraphy indicated that the shallower zone was an outer shelf marked by 8 major sea level oscillations. In the portion between 1 and 3 seconds, seismic stratigraphy and paleontology led to the interpretation of depositional environments such as upper slope, and paleobathymetrically deeper intervals with descent through the section. The intraslope basin, while small, may be viewed as a micro-continental margin. Each seamore » level oscillation cycle apparently made a distinct progradational unit, decipherable in the seismic data. Fourth order cycles have been provisionally interpreted, throughout most of the entire 3.7 second section. Such precision is possible only in explored basins with excellent seismic data. The sequence thickness showed a seven-fold variability, from 0.08 to 0.58 seconds. The shallower section, deposited along an outer shelf, has an average individual sequence thickness of 0.13 seconds. Individual seismic sequences in the deeper section, interpreted to have been deposited on an upper slope, have average thicknesses of 0.25 seconds. The thinner sequences of the shallower section are compatible with the notion that the outer shelf was a bypass zone during a glacial epoch. The thicker sequences of the deeper section are the result of deposition onto an aggrading upper slope within an intraslope basin during a highstand.« less

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.

A method for the division of the conglomerate depositional cycle under Milankovitch cycles

NASA Astrophysics Data System (ADS)

Chen, Panpan; Fang, Nianqiao; Li, Cunlei; Liu, Jianmei

2017-06-01

The conglomerate layer at the upper section of the 4th member of the Shahejie formation ({{{{S}}}4}{{u}}) of the Yongan district at the Donying depression is a well-developed sedimentation of several periods. It lacks stable muddy layers and sophisticated classification of the sedimentation periods and the proportion of sedimentary layering in each period has long been a difficult task for geologists. In addressing this problem, this paper attempts to introduce the theory of climatic cycles driven by astronomical periods from astronomical stratigraphy on the basis of the characteristics of the sedimentation under the turbidity current in the region of study. Through studying the conditions for the formation of the conglomerate layer and the factors of control, we pinpoint the formation of the layer in chronology and differentiate the cycle interface and correlation in the same formation period. Milankovitch analysis is conducted on the sedimentation of the conglomerate layer in the region of study to determine if the stratigraphy cycle of the region is primarily controlled by the eccentricity cycle and calculate MSC1 and MSC2 thicknesses of 189.3 m and 78.05 m, respectively. Milankovitch theory is the primary tool used in the analysis, in conjunction with petrographic analysis. The stratum at the {{{{S}}}4}{{u}} is classified into four IV-grade sequences and 11 V-grade sequences. The information on the dominant cycle frequency is used for wave filtering of the well logs and to determine the significant Milankovitch wave log. With the data from this curve, we may compare the stratigraphy cycle with the characteristics of the standard cycle and classify and compare the sedimentation periods of the conglomerate layers in further detail.

Community Sediment Transport Modeling, National Ocean Partnership Program

DTIC Science & Technology

2009-12-01

delta . A high-resolution, one-dimensional model that resolves the phase of the forcing gravity waves is being used to test the hypothesized mechanisms...dimensional process models to operational elements in the CSTMS framework. Sherwood and Ferre modified the existing algorithms for tracking stratigraphy ...Verdes shelf, California. Continental Shelf Research ( revised manuscript submitted), [refereed] Frank, D. P., D. L. Foster, and C. R. Sherwood

Austrian phase on the northern African margin inferred from sequence stratigraphy and sedimentary records in southern Tunisia (Chotts and Djeffara areas)

NASA Astrophysics Data System (ADS)

Lazzez, Marzouk; Zouaghi, Taher; Ben Youssef, Mohamed

2008-08-01

A multidisciplinary study concerning Aptian and Albian deposits is reported from petroleum wells and the exposed section. The biostratigraphic and sedimentological analysis defined four sedimentary units. Well-logging signals' analysis allows us to refine the record resolution on Aptian series and reveals, in the Djeffara field, a transgressive system tract (TST) and a highstand system tract (HST). Exceptionally, the first sequence (S1) in the Mareth 1 well and the fifth sequence in the two wells Mareth 1 and Gourine 1 reveal the lower-stand system tract (LST). The unconformities characterized by the absence of Upper Aptian (Clansayesian) and Lower to Middle Albian deposits signed by a significant gamma-ray reduction. The Middle and Upper Albian is represented by only one deposit sequence (S6) in Mareth 1. Towards the south, in the Gourine well, two deposit sequences were identified (S6 and S7); to specify the Aptian and Albian evolution of the deposit sequences, a tentative correlation has been established between the Chotts and Djeffara areas. This correlation allows us to characterize the sedimentary unconformities related to the tectonics and eustatic events. The Chotts and the Djeffara deposition areas were developed, characterized by an irregular subsidence and separated by the Tebaga Medenine high area. The Aptian-Albian subsidence platform of southern Tunisia may be considered as a block diagram of environmental deposit with regressive and transgressive trends, showing the impact of tectonic deformations on the palaeogeographic evolution of southeastern Tunisia during the Austrian phase. This study also must be replaced within regional structural patterns that may explain both the sequential and sedimentological evolution of the area. Deformations regionally identified are integrated in the more general context of both Tethyan and Atlantic areas related to the drift of the African platform.

Paleocene to Middle Miocene planktic foraminifera of the southwestern Salisbury Embayment, Virginia and Maryland: biostratigraphy, allostratigraphy, and sequence stratigraphy

USGS Publications Warehouse

Poag, C.W.; Commeau, J.A.

1995-01-01

The Paleocene to Middle Miocene sedimentary fill of the southwestern Salisbury Embayment contains a fragmental depositional record, interrupted by numerous local diastems and regional unconformities. Using planktic foraminiferal biostratigraphy, 15 unconformity-bounded depositional units have been identified, assigned to six formations and seven alloformations previously recognized in the embayment. The units correlate with second- and third-order sequences of the Exxon sequence stratigraphy model, and include transgressive and highstand systems tracts. Alloformation, formation, and sequence boundaries are marked by abrupt, scoured, burrowed, erosional surfaces, which display lag deposits, biostratigraphic gaps, and intense reworking of microfossils above and below the boundaries.Paleocene deposits represent the upper parts of upper Pleocene Biochronozones P4 and P5, and rest uncomformably  on Cretaceous sedimentary beds of various ages (Maastrichtian to Albian). Lower Eocene deposits represent parts of Biochronozones P6 and P9. Middle Eocene strata represent mainly parts of Biochronozones P11, P12, and P14. Upper Eocene sediments include parts of Biochronozones P15, P16, and P17. Oligocene deposits encompass parts of Biochronozones. N4b to N7 undifferentiated, P21a, and, perhaps, N4a. Lower Miocene deposits encompass parts of Biochronozones N4b to N7 undifferentiated. Middle Miocene strata represent mainly parts of Biochronorones N8, N9, and N10.Nine plates of scanning electron micrographs illustrate the principal planktic foraminifera used to establish the biostratigraphic framework. Two new informal formine of Praeterenuitella praegemma Li, 1987, are introduced.

Climate Proxy Signals in the Plio-Pleistocene Chemeron and Miocene Lukeino Formations, Baringo Basin, Kenya

NASA Astrophysics Data System (ADS)

Deino, A. L.; Kingston, J.; Hill, A.; Wilson, K. E.; Edgar, R.; Goble, E.

2009-12-01

The Chemeron Formation is a hominin-bearing, highly fossiliferous sequence of dominantly alluvial fan and fluvial sedimentary rocks, with climatically significant lacustrine intercalations, exposed within the Tugen Hills of the central Kenya Rift. As we have previously documented (Deino et al., 2006; Kingston et al., 2007), the formation contains a sequence of five 3-7 m thick diatomites in the interval 2.7-2.5 Ma that record, at precessional intervals, the repeated occurrence of deep-lake conditions in the Baringo Basin. These lakes appear abruptly, persist for only about 8,000 years of the ~23,000 year precessional cycle, and recede quickly. The oscillations have been tied to marine core and Mediterranean sapropel sections based on high-precision 40Ar/39Ar dating of K-feldspar in tuffs interspersed through the sequence, and paleomagnetic reversal stratigraphy. Ongoing paleontological investigations in the Tugen Hills are addressing the dynamics of high-resolution faunal and ecological change directly related to the fluctuating climatic background, including its effect on hominin evolution. This specific interval in the Baringo Basin/Tugen Hills has been identified by the Hominid Sites and Paleolakes Drilling Project Steering Committee as one of five target areas in East Africa for high-resolution coring studies. The drilling project is currently moving forward to the funding agency proposal development phase. Further exploration in the Tugen Hills has revealed a similar, older sequence of rhythmic alternating diatomites and non-lacustrine sediments in nearby drainages. These beds may represent a precessionally driven climate response possibly associated with the next older orbital eccentricity maximum from ~3.2-2.9 Ma. Characterization of the lithostratigraphy of this area is in progress, and samples of intercalated tuff beds suitable for high-precision single-crystal 40Ar/39Ar dating have been acquired. We have also extended our search for climate proxy records in the Tugen Hills to diatomaceous sequences between ~8-6 Ma that would specifically implicate precessional control as a pervasive factor in the formation of rift lake systems and by inference climate. Reconnaissance in summer ’09 of these older strata have revealed extensive lacustrine deposits indicating that this portion of the rift was inundated by major lake systems during the upper Miocene.

The Chicxulub Multiring Impact Crater and the Cretaceous/Paleogene Boundary: Results From Geophysical Surveys and Drilling

NASA Astrophysics Data System (ADS)

Urrutia-Fucugauchi, J.; Perez-Cruz, Ligia

2010-03-01

The Chicxulub crater has attracted considerable attention as one of the three largest terrestrial impact structures and its association with the Cretaceous/Paleogene boundary (K/Pg). Chicxulub is a 200 km-diameter multi-ring structure formed 65.5 Ma ago in the Yucatan carbonate platform in the southern Gulf of Mexico and which has since been buried by Paleogene and Neogene carbonates. Chicxulub is one of few large craters with preserved ejecta deposits, which include the world-wide K/Pg boundary clay layer. The impact has been related to the global major environmental and climatic effects and the organism mass extinction that mark the K/Pg boundary, which affected more than 70 % of organisms, including the dinosaurs, marine and flying reptiles, ammonites and a large part of the marine microorganisms. The impact and crater formation occur instantaneously, with excavation of the crust down to 25 km depths in fractions of second and lower crust uplift and crater formation in a few hundreds of seconds. Energy released by impact and crustal deformation generates seismic waves traveling the whole Earth, and resulting in intense fracturing and deformation at the target site. Understanding of the physics of impacts on planetary surfaces and modeling of processes of crustal deformation, rheological behavior of materials at high temperatures and pressures remain a major challenge in geosciences. Study of the Chicxulub crater and the global effects and mass extinction requires inter- and multidisciplinary approaches, with researchers from many diverse fields beyond the geosciences. With no surface exposures, geophysical surveys and drilling are required to study the crater. Differential compaction between the impact breccias and the surrounding carbonate rocks has produced a ring-fracture structure that at the surface reflects in a small topographic depression and the karstic cenote ring. The crater structure, located half offshore and half on-land, has been imaged by different geophysical aerial, land and marine methods including gravity, magnetics, electromagnetics and seismic refraction and reflection. The impact lithologies and carbonate sequence have been cored as part of several drilling projects. Here we analyze the stratigraphy of Chicxulub from borehole logging data and core analyses, with particular reference to studies on CSDP Yaxcopoil-1 and UNAM Santa Elena boreholes. Analyses of core samples have examined the stratigraphy of the cover carbonate sequence, impact breccia contact and implications for impact age, K/Pg global correlations and paleoenvironmental conditions following impact. The K/Pg age for Chicxulub has been supported from different studies, including Ar/Ar dating, magnetic polarity stratigraphy, geochemistry and biostratigraphy. A Late Maastrichtian age has also been proposed for Chicxulub from studies in Yaxcopoil-1 basal Paleocene carbonates, with impact occurring 300 ka earlier predating the K/Pg boundary. This proposal calls attention to the temporal resolution of stratigraphic and chronological methods, and the need for further detailed analyses of the basal carbonate sections in existing boreholes and new drilling/coring projects. Stratigraphy of impact ejecta and basal sediments in Yaxcopoil-1 and UNAM boreholes indicates a hiatus in the basal sequence. Modeling of post- impact processes suggest erosion effects due to seawater back surge, block slumping and partial rim collapse of post-impact crater modification. Analyses of stable isotopes and magnetostratigraphic data for the Paleocene carbonate sequences in Yaxcopoil-1 and Santa Elena boreholes permit to investigate the post- impact processes, depositional conditions and age of basal sediments. Correlation of stable isotopes with the global pattern for marine carbonate sediments provides a stratigraphic framework for the basal Paleocene carbonates. The analyses confirm a K/Pg boundary age for the Chicxulub impact. References: Collins et al, 2008. Earth Planetary Science Letters 270, 221-230; Gulick et al, 2008. Nature Geoscience 1, 131-135; Hildebrand et al, 1991. Geology 19: 867-871; Hildebrand, A.R. et al, 1998. Geological Society Sp. Publ 140, 153-173; Kring et al., 2004. Meteoritics Planetary Science 39, 879-897; Sharpton et al, 1992. Nature 359: 819-821; Urrutia Fucugauchi et al, 2004. Meteoritics Planetary Science 39: 787-790; Urrutia Fucugauchi et al, 2008. Comptes Rendus Geosciences 341, 801-810; Urrutia Fucugauchi & Perez Cruz, 2009. International Geology Review 51, doi: 10.1080/00206810902867161.

A field study of the confluence between Negro and Solimões Rivers. Part 2: Bed morphology and stratigraphy

NASA Astrophysics Data System (ADS)

Ianniruberto, Marco; Trevethan, Mark; Pinheiro, Arthur; Andrade, Joao Fernando; Dantas, Elton; Filizola, Naziano; Santos, André; Gualtieri, Carlo

2018-01-01

The confluence of the Negro and Solimões Rivers is an interesting study area under several points of view: it represents the second largest river confluence of the Amazon Basin; the rivers are characterized by very distinct hydrologic behaviour; and it is situated in a peculiar tectonic setting. A field investigation was undertaken to study the characteristics of this confluence, aiming to better understand the bed morphology and stratigraphy resulting from the complex interaction of geological setting, hydrodynamics, and sediment load. Two field campaigns were carried out, during low- and high-flow conditions, using high-resolution seismic, echosounding, and acoustic Doppler current profiling. A third campaign was carried out just in a limited area of the confluence, with a multi-beam echosounder. The results of these surveys provided a more detailed view of the geology, morphology and sediment distribution about the confluence.

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.

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.

High-resolution C and O stable isotope geochemistry of the early Aptian OAE1a at Cau (Prebetic Zone, Spain): Preliminary results from sediment core.

NASA Astrophysics Data System (ADS)

Alejandro Ruiz-Ortiz, Pedro; Aguado, Roque; Castro, José Manuel; Gallego, David; de Gea, Ginés Alfonso; Jarvis, Ian; Molina, José Miguel; Nieto, Luis Miguel; Pancost, Richard; Quijano, María Luisa; Reolid, Matías; Rodriguez, Rafael; Skelton, Peter; Weisser, Helmut

2017-04-01

The occurrence of time intervals of enhanced deposition of organic matter (OM) during the Cretaceous, defined as Oceanic Anoxic Events (OAE), reflect abrupt changes in global carbon cycling. The Aptian OAE1a (120 Ma), represents an excellent example, recorded in all the main ocean basins, associated to massive burial of organic matter in marine sediments [1]. Much research has been done on the OAE1a from different sections in the world over the last decades, including the definition of the C-isotope stratigraphy of the event [2]. Notwithstanding, higher-resolution studies across the entire event will be crucial to shed light into the precise timing and rates of the different environmental and biotic changes that occurred. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents the platform deposits of the Southern Iberian palaeomargin. The Lower Aptian of the Cau section is represented by a hemipelagic unit (Almadich Formation, ca. 200 m thick), deposited in a highly subsiding sector of a tilted block, located in the distal parts of the Prebetic Platform. Previous studies of the Lower Aptian of the Cau section have focused on the stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry [3], [4], and in the reconstruction of pCO2 from organic geochemistry proxies [5]. All these studies reveal that the Cau section represents an excellent site to investigate the OAE 1a, based on its unusual high thickness and stratigraphic continuity, the quality and preservation of fossils and the geochemical signatures. Here we present the first results of a high-resolution carbonate C-isotope study based on the the analysis of three new research cores drilled at Cau in autumn 2015 [6]. These new data represent an important advance in the knowledge of the C-isotope record of the OAE 1a, presenting a more continuous record at a higher resolution than previous studies. This leads to the refining of the correlation with previously defined and worldwide recognized C-isotope segments of Menegatti et al. [2]. Along with the C-isotope stratigraphy, correlated with previous biostratigraphic and geochemical data from outcrop studies, profiles of magnetic susceptibility data (measured from the core in the laboratory) and geophysical log profiles measured down-hole, are presented. Preliminary sedimentological analyses of the core have been completed, with a focus on lithology and sedimentary structures, including ichnofacies of bioturbated levels. The facies association is dominated by dark marlstones, displaying a cyclic vertical organization. These results confirm and refine previous data, and will be the base for ongoing analytical studies at a high-resolution scale, covering geochemical, biostratigraphic, sedimentological, ichnological and cyclostratigraphic analyses of the core. Acknowledgements: This work is a contribution of the research project CGL2014-55274-P (Gov. of Spain) and Research Group RNM-200 (PAIDI-JA). [1] Robinson et al. (2017). Sedimentology, 64, 1-15 [2] Menegatti et al. (1998). Paleoceanography 13, 530-545. [3] Gea et al. (2003) Palaeo3. 200, 207-219. [4] Quijano et al. (2012). Palaeo3. 365-366, 276-293. [5] Naafs et al. (2016). Nat. Geosc. 9 (2), 135-139. [6] Ruiz-Ortiz et al. (2016). Sci. Dril. 21, 41-46.

Remote Stratigraphic Analysis: Combined TM and AIS Results in the Wind River/bighorn Basin Area, Wyoming

NASA Technical Reports Server (NTRS)

Lang, H. R.; Paylor, E. D.; Adams, S.

1985-01-01

An in-progress study demonstrates the utility of airborne imaging spectrometer (AIS) data for unraveling the stratigraphic evolution of a North American, western interior foreland basin. AIS data are used to determine the stratigraphic distribution of mineralogical facies that are diagnostic of specific depositional environments. After wavelength and amplitude calibration using natural ground targets with known spectral characteristics, AIS data identify calcite, dolomite, gypsum and montmorillonite-bearing strata in the Permian-Cretaceous sequence. Combined AIS and TM results illustrate the feasibility of spectral stratigraphy, remote analysis of stratigraphic sequences.

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

NASA Astrophysics Data System (ADS)

Hayakawa, Tatsuya; Hirano, Hiromichi

2013-06-01

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

The Geology of Mars as Seen by MRO's HiRISE

NASA Astrophysics Data System (ADS)

McEwen, A. S.

2007-12-01

By September 2007 the High Resolution Imaging Science Experiment (HiRISE) had acquired more than 3,000 images of Mars at resolutions as high as 25 cm/pixel in the 3 PM mapping orbit of Mars Reconnaissance Orbiter, covering about 0.2 percent of the surface. These images are helping to address a broad range of science issues, as presented in dozens of abstracts to this conference. In this talk I will focus on several topics. (1) The color data is proving quite valuable to reduce the ambiguities of B&W images; to correlate deposits and better define the stratigraphy; and to extend mineral identifications to the scale of outcrops. (2) The nature of the Martian highlands is being revealed, with the identification of megabreccia, hydrous minerals (by OMEGA and CRISM spectrometers), and the detailed nature of the layered or massive stratigraphy where exposed in cross- section. (3) There is new evidence for the roles of water in the most recent large (at least 1 km diameter) impact craters, which may have implications for the altered mineralogy of the ancient crust. (4) New observations and measurements are leading to improved understanding of slope processes such as gullies, creep, and mass wasting. We are producing meter-scale digital elevation models to test high-priority science questions.

Seismic stratigraphy and tomography in the outer shelf and slope of the Central Basin, Ross Sea, Antarctica

NASA Astrophysics Data System (ADS)

Kim, Sookwan; De Santis, Laura; Böhm, Gualtiero; Kuk Hong, Jong; Jin, Young Keun; Geletti, Riccardo; Wardell, Nigel; Petronio, Lorenzo; Colizza, Ester

2014-05-01

The Ross Sea, located between Victoria Land and Marie Byrd Land in Antarctica, is one of the main drainage of the Antarctic Ice Sheet (AIS). Reflection seismic data acquired by many countries during several decades have provided insights into the history of the Ross Sea and the AIS evolution. However the majority of the existing seismic data are concentrated in the shelf area, where hiatus formed by grounding ice sheet erosion multiple events prevent to reconstruct the entire sedimentary sequences depositional evolution. On the outer shelf and upper slope, the sedimentary sequences are relatively well preserved. The main purpose of this study is the investigation of the Cenozoic Antarctic Ice Sheet evolution through the seismic sequence analysis of the outer shelf and slope of the Central Basin, in the Ross Sea. The data used are the new multi-channel seismic data, KSL12, were acquired on the outer shelf and upper slope of the Central Bain in February 2013 by Korea Polar Research Institute. The reflection seismic data, previously collected by the Italian Antarctic Program (PNRA) and other data available from the Seismic Data Library System (SDLS) are also used for velocity tomography and seismic sequence mapping. The seismic data were processed by a conventional processing flow to produce the seismic profiles. Preliminary results show well-developed prograding wedges at the mouth of glacial troughs, eroded by a major glacial unconformity, the Ross Sea Unconformity 4 (RSU-4), correlated to a main event between early- and mid-Miocene. The velocity anomalies shown along KSL12-1 can be interpreted as showing the occurrence of gas and fluids, diagenetic horizons and sediment compactions. The isopach maps of each sequence show the variation of thickness of the sediments depocenter shift. The seismic sequence stratigraphy and acoustic facies analysis provide information about different phases of ice sheet's advance and retreat related to the AIS Cenozoic dynamics.

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

Russell, J.S.

Several factors in the development of the East Wilmington oil field by THUMS Long Beach Co. are described. These include: critical path scheduling, complex stratigraphy, reservoir engineering, drilling program, production methods, pressure maintenance, crude oil processing, automation, transportation facilities, service lines, and electrical facilities. The complexity and closely scheduled operational events interwoven in the THUMS project demands a method for the carefully planned sequence of jobs to be done, beginning with island construction up through routine production and to the LACT system. These demanding requirements necessitated the use of a critical path scheduling program. It was decided to use themore » program evaluation technique. This technique is used to assign responsibilities for individual assignments to time assignments, and to keep the overall program on schedule. The stratigraphy of East Wilmington complicates all engineering functions associated with recovery methods and reservoir evaluation. At least 5 major faults are anticipated.« less

Upper crustal mechanical stratigraphy and the evolution of thrust wedges: insights from sandbox analogue experiments

NASA Astrophysics Data System (ADS)

Milazzo, Flavio; Storti, Fabrizio; Nestola, Yago; Cavozzi, Cristian; Magistroni, Corrado; Meda, Marco; Salvi, Francesca

2016-04-01

Crustal mechanical stratigraphy i.e. alternating mechanically weaker and stronger layers within the crust, plays a key role in determining how contractional deformations are accommodated at convergent plate boundaries. In the upper crust, evaporites typically provide preferential décollement layers for fault localization and foreland ward propagation, thus significantly influencing evolution of thrust-fold belts in terms of mechanical balance, geometries, and chronological sequences of faulting. Evaporites occur at the base of many passive margin successions that underwent positive inversion within orogenic systems. They typically produce salient geometries in deformation fronts, as in the Jura in the Northern Alps, the Salakh Arch in the Oman Mountains, or the Ainsa oblique thrust-fold belt in the Spanish Pyrenees. Evaporites frequently occur also in foredeep deposits, as in the Apennines, the Pyrenees, the Zagros etc. causing development of additional structural complexity. Low-friction décollement layers also occur within sedimentary successions involved in thrust-fold belts and they contribute to the development of staircase fault trajectories. The role of décollement layers in thrust wedge evolution has been investigated in many experimental works, particularly by sandbox analogue experiments that have demonstrated the impact of basal weak layers on many first order features of thrust wedges, including the dominant fold vergence, the timing of fault activity, and the critical taper. Some experiments also investigated on the effects of weak layers within accreting sedimentary successions, showing how this triggers kinematic decoupling of the stratigraphy above and below the décollements, thus enhancing disharmonic deformation. However, at present a systematic experimental study of the deformation modes of an upper crustal mechanical stratigraphy consisting of both low-friction and viscous décollement layers is still missing in the specific literature. In this contribution we present the results of such a study, where a three-décollement mechanical stratigraphy has been deformed in the sandbox at the same boundary conditions. Different rheological properties were assigned to the three décollements in different experiments, up to testing all possible mechanical stratigraphies. Implications on thrust propagation and slip rate history and cross-sectional thrust wedge architecture are discussed and compared with natural cases.

High-resolution stratigraphy with strontium isotopes.

PubMed

Depaolo, D J; Ingram, B L

1985-02-22

The isotopic ratio of strontium-87 to strontium-86 shows no detectable variation in present-day ocean water but changes slowly over millions of years. The strontium contained in carbonate shells of marine organisms records the ratio of strontium-87 to strontium-86 of the oceans at the time that the shells form. Sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium-87 to strontium-86 with a resolution that is similar to that of other techniques used in age correlation. This method may prove valuable for many geological, paleontological, paleooceanographic, and geochemical problems.

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.

Depositional systems and stratigraphy of Paleozoic and Lower Mesozoic rocks in outcrop, Tassili region, southwest Algeria

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

Hertig, S.P.; Tye, R.S.; Coffield, D.Q.

1991-08-01

Paleozoic to Lower Mesozoic strata of the southeastern Algerian Tassili are traditionally subdivided by regionally extensive unconformities such as the Pan African, Taconic, Caledonian, and Hercynian. Using outcrop data from southeastern Algeria, this classic approach is modified by reinterpreting the genesis of these unconformities and rock sequences. Five prominent sequences, defined within the Paleozoic and lower Mesozoic section, usually consist of a succession of lowstand, transgressive, and highstand system tracts separated by sequence boundaries or transgressive surfaces. The Pan-African, Taconic, Caledonian, and Hercynian unconformities are sequence boundaries. Important sequence boundaries also occur within the Ordovician and Silurian sections. These sequencesmore » correlate with subsurface data in the Illizi basin and provide a framework for renewed exploration in the subsurface of the Algerian Sahara, where more than 30 billion bbl of recoverable oil and oil equivalent have been generated and trapped.« 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

High Resolution Multichannel Imaging of Basin Growth Along a Continental Transform: The Marmara Sea Along the North Anatolian Fault in NW Turkey

NASA Astrophysics Data System (ADS)

Steckler, M. S.; Çifçi, G.; Demirbağ, E.; Akhun, S. D.; Büyükaşik, E.; Cevatoglu, M.; Coşkun, S.; Diebold, J.; Dondurur, D.; Gürçay, S.; Imren, C.; Kücük, H. M.; Kurt, H.; Özer, P. G.; Perinçek, E.; Seeber, L.; Shillington, D.; Sorlien, C.; Timur, D.

2008-12-01

The 1500-km-long North Anatolian continental transform (NAF) accommodates the westward motion of the Anatolian platelet relative to Asia. The Marmara Trough in western Turkey is a large composite Quaternary structure that includes three main extensional basins with water depths reaching ~1200m separated by shallower ridges. Syntectonic sedimentation in the basins with highly variable sea-level-related changes in accumulation rates provide valuable time-space markers for reconstructing structural growth and basin development in the Marmara Sea. The TAMAM (Turkish-American MArmara Multichannel) Project is a collaboration between several US and Turkish research institutes. During July 2008, TAMAM collected ~2700 km of multichannel profiles in the Marmara Sea using the R/V K. Piri Reis. MCS data were sampled with a 1-ms interval on the first 72 channels with 6.25m group spacing in a 600m streamer. The source was a 45/45 cu. in. GI air gun, which was fired every 12.5 or18.75m. The gun-streamer offset was 40 or 100 m depending on water depth. Both the gun and streamer were towed at a depth of 3 or 4m. This configuration yielded high-resolution images of the stratigraphy in the Marmara Sea. TAMAM follows a recent series of impressive seismotectonic studies of the NAF in the Marmara Sea area. Previous seismic cruises focused on deep penetration MCS imaging of the overall basin structure and faulting or very high-resolution imaging of the near-surface faulting. TAMAM fills a gap in resolution imaging the stratigraphy that records the history of deformation in the basins and linkages between faults. We will present preliminary high-resolution images of the stratigraphy and tectonics beneath the Marmara Sea highlighting the following exciting observations and initial results from this experiment: 1) Improved stratigraphic correlations between the major basins, a primary goal of the experiment; 2) Clearer imaging of active faults, including the NAF, the less studied southern branch of the NAF, the Imrali fault, and numerous smaller active faults; 3) Imaging of thrusts and thrust-related folds in parts of the basin; 4) Better constraints on variations in the dip and sense of motion (transpression vs. transtension) on the upper 1-2 km of the NAF; 5) Stratigraphic boundaries in the turbiditic sections in the deep basins that may be related to interactions between tectonics and changes in sedimentation rate driven by variations in sealevel and paleoclimate; 5) Extent of gravity slides at the edges of most of the subbasins; and 6) Imaging of a stack of lowstand deltas with a relatively even vertical spacing suggesting deposition tracking the ~100 ka late Quaternary glacial cycles.

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.

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).

Diatom and silicoflagellate biostratigraphy for the late Eocene: ODP 1090 (sub-Antarctic Atlantic)

USGS Publications Warehouse

Barron, John A.; Bukry, David B.; Gersonde, Rainer

2014-01-01

Abundant and well-preserved diatoms and silicofl agellate assemblages are documented through a complete late Eocene sequence, ODP Hole 1090B, recovered from the southern Agulhas Ridge in the sub-Antarctic South Atlantic. A sequence of Cestodiscus (diatom) species occurrence events involving C. pulchellus var. novazealandica, C. fennerae, C. antarcticus, C. convexus, C. trochus, and C. robustus is tied with paleomagnetic stratigraphy and provides the basis of proposing a new diatom zonation for the latest middle Eocene to early Oligocene (~37.6–33.4 Ma) of the sub-Antarctic South Atlantic. Comparison with previously published diatom occurrence charts suggested this zonation should be applicable throughout the low latitude regions of the world’s oceans. Silicofl agellates belong to the Dictyocha hexacantha and the overlying Corbisema apiculata Zones. The late Eocene succession of silicofl agellate species is dominated by Naviculopsis (20–60%). Naviculopsis constricta and N. foliacea dominate the D. hexacantha Zone, followed by the N. constricta, then N. biapiculata in the C. apiculata Zone. Cold-water Distephanus is most abundant in the latest Eocene along with N. biapiculata. The tops of zonal guide fossils Dictyocha hexacantha and Hannaites quadria (both 36.6 Ma) and Dictyocha spinosa (37.1 Ma) are tied with paleomagnetic stratigraphy.

High-resolution stratigraphy and multiple luminescence dating techniques to reveal the paleoseismic history of the central Dead Sea fault (Yammouneh fault, Lebanon)

NASA Astrophysics Data System (ADS)

Le Béon, Maryline; Tseng, Ya-Chu; Klinger, Yann; Elias, Ata; Kunz, Alexander; Sursock, Alexandre; Daëron, Mathieu; Tapponnier, Paul; Jomaa, Rachid

2018-07-01

Continuous sedimentation and detailed stratigraphy are key parameters for a complete paleo-earthquake record. Here, we present a new paleoseismological study across the main strike-slip fault branch of the Dead Sea fault in Lebanon. We aim to expand the current knowledge on local paleoseismicity and seismic behavior of strike-slip plate boundary faults and to explore the limitations of paleoseismology and dating methods. The trench, dug in the Jbab el-Homr basin, reveals a succession of remarkable, very thin (0.1 to 5 cm) palustrine and lacustrine layers, ruptured by at least 17 earthquakes. Absolute ages of 4 samples are obtained from three luminescence-dating techniques targeting fine-grain minerals. Blue-green stimulated luminescence (BGSL) on quartz and post-infrared infrared-stimulated luminescence at 225 °C on polymineral aliquots led to consistent ages, while ages from infrared-stimulated luminescence at 50 °C on polymineral aliquots appeared underestimated. The quartz BGSL ages are 26.9 ± 2.3 ka at 0.50 m depth and 30.8 ± 2.9 ka at 3.65 m depth. During this time period of 3.9 ka ([0; 9.1 ka]), 14 surface-rupturing events occurred with a mean return time of 280 years ([0; 650 years]) and probable clustering. This return time is much shorter than the 1127 ± 135 years return time previously determined at the Yammouneh site, located 30 km south. Although fault segmentation and temporal variations in the earthquake cycle remain possible causes for such different records, we argue that the high-resolution stratigraphy in Jbab is the main factor, enabling us to record small deformations related to smaller-magnitude events that may have been missed in the rougher strata of Yammouneh. Indeed, focusing only on larger events of Jbab, we obtain a mean return time of 720 years ([0; 1670 years]) that is compatible with the Yammouneh record.

Structural development of the Dieppe-Hampshire Basin (Eastern English Channel): Contribution of new seismic data

NASA Astrophysics Data System (ADS)

Jollivet-Castelot, Martin; Gaullier, Virginie; Paquet, Fabien; Chanier, Frank; Thinon, Isabelle; Lasseur, Eric; Averbuch, Olivier

2017-04-01

The Dieppe-Hampshire Basin is a Cenozoic basin crossing the eastern English Channel, between SE of England and the French coast. This basin and its borders developed during the Cenozoic, a period of overall tectonic inversion, in response to the opening of the North Atlantic Ocean and Pyrenean-alpine deformation episodes. Both extensional and subsequent compressional deformations within this area involve the reactivation of older major regional structures, inherited from the Variscan Orogeny. However, the detailed structural development of the Dieppe-Hampshire Basin still remains poorly constrained, as well as the detailed stratigraphic framework of Cenozoic series, notably in terms of seismic stratigraphy and sequence stratigraphy. New very high resolution seismic data, acquired during the oceanographic cruise "TREMOR" (R/V "Côtes de la Manche", 2014, 1800 kilometers of Sparker profiles), and bathymetric data from SHOM and UKHO, have allowed to image the sedimentary filling and tectonic structures of the Dieppe-Hampshire Basin and adjacent areas. The interpretation was first focused on a seismic facies analysis that led to evidence numerous unconformities and seismic units ranging from the Upper Cretaceous to the Bartonian (Late Eocene). The interpretation of the seismic profiles also allowed to map precisely many tectonic features, as faults, folds and monoclinal flexures. Thanks to the new data, we especially imaged the complexity of the deformation within the highest tectonized zones of the region, along the Nord-Baie de Seine Basin and offshore the Boulonnais coast with an unprecedented resolution. The expression of the deformation appears to be very different between the Mesozoic and the Cenozoic series, with prevailing folding affecting the Cenozoic strata whereas the Mesozoic series are predominantly faulted. This deformation pattern illustrates two major structural trends, respectively E-W and NW-SE directed, both syn- to post-Bartonian in age. The first one is consistent in age and orientation with a late Pyrenean or early Alpine deformation phase, while the second one appears to have a different origin, in regards to the overall geodynamic framework. We suggest that the major heterogeneities of crustal blocks underlying the basin played an important role on the development and orientations of these deformations. These preliminary results will be improved soon thanks to a new cruise, "TREMOR 2" (2017), which will be focused on the acquisition of new VHR seismic lines, bathymetric data and coring.

High-resolution chirp seismic reflection data acquired from the Cap de Creus shelf and canyon area, Gulf of Lions, Spain in 2004

USGS Publications Warehouse

Grossman, Eric E.; Hart, Patrick E.; Field, Michael E.; Triezenberg, Peter

2006-01-01

Seismic reflection data were collected from the Cap de Creus shelf and canyon in the southwest portion of the Gulf of Lions in October 2004. The data were acquired using the U.S. Geological Survey`s (USGS) high-resolution Edgetech CHIRP 512i seismic reflection system aboard the R/V Oceanus. Data from the shipboard 3.5 kHz echosounder were also collected but are not presented here. The seismic reflection data were collected as part of EuroSTRATAFORM funded by the Office of Naval Research. In October 2004, more than 200 km of high resolution seismic reflection data were collected in water depths ranging 30 m - 600 m. All data were recorded with a Delph Seismic PC-based digital recording system and processed with Delph Seismic software. Processed sections were georeferenced into tiff images for digital archive, processing and display. Penetration ranged 20-80 m. The data feature high quality vertical cross-section imagery of numerous sequences of Quaternary seismic stratigraphy. The report includes trackline maps showing the location of the data, as well as both digital data files (SEG-Y) and images of all of the profiles. The data are of high quality and provide new information on the location and thickness of sediment deposits overlying a major erosion surface on the Cap de Creus shelf; they also provide new insight into sediment processes on the walls and in the channel of Cap de Creus Canyon. These data are under study by researchers at the US Geological Survey, the University of Barcelona, and Texas A and M University. Copies of the data are available to all researchers.

High resolution seismic stratigraphy and Mass Transport Deposits of the proximal continental margin, offshore Quarteira, South Portugal: Preliminary Results.

NASA Astrophysics Data System (ADS)

Duarte, Débora; Santos, Joana; Terrinha, Pedro; Brito, Pedro; Noiva, João; Ribeiro, Carlos; Roque, Cristina

2017-04-01

More than 300 nautical miles of multichannel seismic reflection data were acquired in the scope of the ASTARTE project (Assessment Strategy and Risk Reduction for Tsunamis in Europe), off Quarteira, Algarve, South Portugal. The main goal of this very high resolution multichannel seismic survey was to obtain high-resolution images of the sedimentary record to try to discern the existence of high energy events, possibly tsunami backwash deposits associated with large magnitude earthquakes generated at the Africa-Eurasia plate boundary This seismic dataset was processed at the Instituto Português do Mar e da Atmosfera (IPMA), with the SeisSpace PROMAX Seismic Processing software. A tailor-made processing flow was applied, focusing in the removal of the seafloor multiple and in the enhancement of the superficial layers. A sparker source, using with 300 J of energy and a fire rate of 0,5 s was used onboard Xunauta, an 18 m long vessel. The preliminary seismostratigraphic interpretation of the Algarve ASTARTE seismic dataset allowed the identification of a complex sequence seismic units of progradational and agradational bodies as well as Mass Transported Deposits (MTD). The MTD package of sediments has a very complex internal structure, 20m of thickness, is apparently spatially controlled by an escarpment probably associated to past sea level low stands. The MTD covers across an area, approximately parallel to an ancient coastline, with >30 km (length) x 5 km (across). Acknowledgements: This work was developed as part of the project ASTARTE (603839 FP7) supported by the grant agreement No 603839 of the European Union's Seventh. The Instituto Portugues do Mar e da Atmosfera acknowledges support by Landmark Graphics (SeisWorks) via the Landmark University Grant Program.

Environmental and ice volume changes based on seismic stratigraphy in Sabrina Coast, East Antarctica: Preliminary results from NBP1402

NASA Astrophysics Data System (ADS)

Gulick, S. P. S.; Fernandez-Vasquez, R. A.; Frederick, B.; Saustrup, S., Sr.; Domack, E. W.; Lavoie, C.; Shevenell, A.; Blankenship, D. D.; Leventer, A.

2014-12-01

In 2014, the R/V Nathaniel B. Palmer (NBP1402) sailed to a virtually unexplored continental shelf along the Sabrina Coast, East Antarctica. The shelf contains the sedimentary record of environmental and ice volume changes within the Aurora Subglacial Basin (ASB), which is presently occupied by ~7 m sea level-rise equivalent of ice. We acquired 750 km of high-resolution seismic data proximal to the Reynolds Trough and Moscow University Ice Shelf glacial systems west of the Dalton Ice Tongue using dual 45/45 cu. in. G.I. guns and a 24 ch. streamer with 3.125 m groups providing a vertical resolution of ~3 m simultaneously with CHIRP data. These are the first images of this margin acquired and show a remarkable set of sequence stratigraphic transitions. Crystalline basement is at the seafloor landward and buried seaward with a transition to smoother reflection interface. Reflective sedimentary strata overlie the basement, dip seaward, and are capped by a landward-dipping regional angular unconformity. Above this are a series of transparent seismic facies that, along with the middle to outer shelf seafloor, dip landward towards a shelf-oblique glacial trough. The older, seaward-dipping strata include a deeper series of units that display at least three stratal architectures interpreted to be shelf deltas implying a pre-glacial, fluvial environment within the drainage basin. Above these sequences, the seismic facies transition to surfaces exhibiting significant erosion, small u-shaped valleys, and channel fill sequences, all of which are reminiscent of temperate glacial features. We interpret these sequences as including sub-ice tunnel valleys and grounding zone wedges with interspersed non-glacial to pro-glacial deposits. Increasing glaciogenic facies upsection suggests a gradual fluvial to glacial transition and increasing glacial extent with time. The subsequent transition to ice sheets is marked by erosion to basement landward and the angular unconformity seaward. The unconformity is overlain by glacial diamict, representing an incomplete record of cold-based glaciations after the ASB became ice-filled. Correlations with cores collected above and below the unconformity and deltaic unit should allow us to determine the ages of these transitions from fluvial to polythermal to ice sheets in East Antarctica.

Depositional history and neotectonics in Great Salt Lake, Utah, from high-resolution seismic stratigraphy

USGS Publications Warehouse

Colman, Steven M.; Kelts, K.R.; Dinter, D.A.

2002-01-01

High-resolution seismic-reflection data from Great Salt Lake show that the basinal sediment sequence is cut by numerous faults with N-S and NE-SW orientations. This faulting shows evidence of varied timing and relative offsets, but includes at least three events totaling about 12 m following the Bonneville phase of the lake (since about 13.5 ka). Several faults displace the uppermost sediments and the lake floor. Bioherm structures are present above some faults, which suggests that the faults served as conduits for sublacustrine discharge of fresh water. A shallow, fault-controlled ridge between Carrington Island and Promontory Point, underlain by a well-cemented pavement, separates the main lake into two basins. The pavement appears to be early Holocene in age and younger sediments lap onto it. Onlap-offlap relationships, reflection truncations, and morphology of the lake floor indicate a low lake, well below the present level, during the early Holocene, during which most of the basin was probably a playa. This low stand is represented by irregular reflections in seismic profiles from the deepest part of the basin. Other prominent reflectors in the profiles are correlated with lithologic changes in sediment cores related to the end of the Bonneville stage of the lake, a thick mirabilite layer in the northern basin, and the Mazama tephra. Reflections below those penetrated by sediment cores document earlier lacustrine cycles. ?? 2002 Elsevier Science B.V. All rights reserved.

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

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.

Using sequence stratigraphic approaches in a highly tectonic area: Case study - Nubia (A) sandstone in southwestern Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

Attia, Ibrahem; Helal, Iman; El Dakhakhny, Alaa; Aly, Said A.

2017-12-01

West Esh El Mallaha area is located west of the Hurghada shoreline. It pertains to the southwestern province of the Gulf of Suez. Nubia (A) sandstone is one of the prolific reservoirs in the western side along the Gulf of Suez area. To enhance further oil production and to develop this reservoir, it is important to gain a clear understanding of the reservoir in terms of its depositional origin. In west Esh El Mallaha area, the understanding of the depositional setting of Nubia (A) is relatively hard due to the limited number of cores. A comprehensive workflow which integrates all geological datasets (electrical logs pattern, the high resolution biostratigraphic analysis, and previous studies) which has been performed for the Nubia (A), enables to recognize different patterns of electrical logs, which are used to define the sequence stratigraphy and systems tracts for Nubia (A). The Lower Nubia (A) is characterized by fining-upward profile and well-developed coarsening-straight profile interpreted as a braided - fluvial facies (lowstand system tract). On the other hand, the upper Nubia (A) is characterized by fining-upward, coarsening-upward, and bell profile interpreted as meandering fluvial to fluvio-dominated delta (transgressive system tract). This study is an approach to build a reliable geological model, and give wide view to evaluate and develop the reservoir in the drilled areas and predict sand distribution in the undrilled areas despite the limited number of cores.

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.

Seismic stratigraphy and depositional history of late Quaternary deposits at the eastern Yellow Sea shelf

NASA Astrophysics Data System (ADS)

Yoo, Dong-Geun; Lee, Gwang-Soo; Kim, Gil-Young; Chang, Se-Won; Kim, Kyoung-Jin

2017-04-01

The late Quaternary stratigraphy and sedimentation at the eastern Yellow Sea shelf was studied using a dense network of high-resolution, single-channel seismic reflection profiles and sediment data. The shelf sequence in this area consists of six seismic units formed since the LGM. During the LGM, the study area was completely exposed, resulting in subaerial erosion associated with paleo-channel incision by the Huanghe and Korean Rivers. As the shelf was flooded, the incised channels were backfilled fluvial or coastal sediments, forming incised channel-fill deposits (SU1). The paleo-river may have supplied abundant terrigenous sediments to the study area around the paleo-river mouth and adjacent area. These sediments were trapped within the paleo-estuary and formed SU2, regarded as an estuarine deposit. Two types of serial sand ridges (SU3 and SU5) which correspond to transgressive deposits developed. SU3 on the southern part, west of Jeju Island (80 110 m deep) is regarded as a moribund-type mainly formed during the early to middle stage of transgression. These are thought to have ceased growing and remobilizing. In contrast, SU5 (occurring 30 50 m deep off the Korean Peninsula) is generally regarded as active sand ridges deposited during the late stage of transgression and is partly modified by modern tidal currents. As the transgression continued, the near-surface sediments were reworked and redistributed by shelf erosion, resulting in a thin veneer of transgressive sands (SU4). The uppermost unit (SU6) formed the Heuksan Mud Belt (HMB), which is one of the most prominent mud deposits in the Yellow Sea. The lower part of the HMD corresponds to shelf-mud deposited during the late stage of transgression, whereas the upper part consists of a recent shelf-delta developed after the highstand sea level at about 7 ka BP.

The snake geothermal drilling project. Innovative approaches to geothermal exploration

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

Shervais, John W.; Evans, James P.; Liberty, Lee M.

2014-02-21

The goal of our project was to test innovative technologies using existing and new data, and to ground-truth these technologies using slim-hole core technology. The slim-hole core allowed us to understand subsurface stratigraphy and alteration in detail, and to correlate lithologies observed in core with surface based geophysical studies. Compiled data included geologic maps, volcanic vent distribution, structural maps, existing well logs and temperature gradient logs, groundwater temperatures, and geophysical surveys (resistivity, magnetics, gravity). New data included high-resolution gravity and magnetic surveys, high-resolution seismic surveys, three slimhole test wells, borehole wireline logs, lithology logs, water chemistry, alteration mineralogy, fracture distribution,more » and new thermal gradient measurements.« less

Magnetic resonance imaging analyses of varved marine sedimentary records of the Gulf of California

NASA Astrophysics Data System (ADS)

Briskin, Madeleine; Robins, Jon; Riedel, William R.; Booker, Ron

1986-08-01

Nuclear Magnetic Resonance Imaging used for the first time to analyze marine sedimentary records of the Gulf of California is a remarkable improvement over the more conventional X-ray technique in the identification of organic rich layers. Analytical results indicate that NMRI differentiates clearly between organic rich (light) and organic poor (dark) deposits. It also provides a fine resolution of sedimentary structures, laminae and stratigraphic subtleties. It may be made to yield a three-dimensional stratigraphy; the procedure is nondestructive. The organic vs. inorganic resolution provided by NMRI technology complemented by X-ray when needed should facilitate future studies of paleoceanographic, paleoclimatic and biogeochemical cycles recorded in the vast deposits of marine clays.

Glaciotectonic deformation and reinterpretation of the Worth Point stratigraphic sequence: Banks Island, NT, Canada

NASA Astrophysics Data System (ADS)

Vaughan, Jessica M.; England, John H.; Evans, David J. A.

2014-05-01

Hill-hole pairs, comprising an ice-pushed hill and associated source depression, cluster in a belt along the west coast of Banks Island, NT. Ongoing coastal erosion at Worth Point, southwest Banks Island, has exposed a section (6 km long and ˜30 m high) through an ice-pushed hill that was transported ˜ 2 km from a corresponding source depression to the southeast. The exposed stratigraphic sequence is polydeformed and comprises folded and faulted rafts of Early Cretaceous and Late Tertiary bedrock, a prominent organic raft, Quaternary glacial sediments, and buried glacial ice. Three distinct structural domains can be identified within the stratigraphic sequence that represent proximal to distal deformation in an ice-marginal setting. Complex thrust sequences, interfering fold-sets, brecciated bedrock and widespread shear structures superimposed on this ice-marginally deformed sequence record subsequent deformation in a subglacial shear zone. Analysis of cross-cutting relationships within the stratigraphic sequence combined with OSL dating indicate that the Worth Point hill-hole pair was deformed during two separate glaciotectonic events. Firstly, ice sheet advance constructed the hill-hole pair and glaciotectonized the strata ice-marginally, producing a proximal to distal deformation sequence. A glacioisostatically forced marine transgression resulted in extensive reworking of the strata and the deposition of a glaciomarine diamict. A readvance during this initial stage redeformed the strata in a subglacial shear zone, overprinting complex deformation structures and depositing a glaciotectonite ˜20 m thick. Outwash channels that incise the subglacially deformed strata record a deglacial marine regression, whereas aggradation of glaciofluvial sand and gravel infilling the channels record a subsequent marine transgression. Secondly, a later, largely non-erosive ice margin overrode Worth Point, deforming only the most surficial units in the section and depositing a capping till. The investigation of the Worth Point stratigraphic sequence provides the first detailed description of the internal architecture of a polydeformed hill-hole pair, and as such provides an insight into the formation and evolution of an enigmatic landform. Notably, the stratigraphic sequence documents ice-marginal and subglacial glaciotectonics in permafrost terrain, as well as regional glacial and relative sea level histories. The reinterpreted stratigraphy fundamentally rejects the long-established paleoenvironmental history of Worth Point that assumed a simple ‘layer-cake’ stratigraphy including the type-site for an organically rich, preglacial interval (Worth Point Fm).

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.

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

USGS Publications Warehouse

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

2008-01-01

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

Investigation of sea-level changes and shelf break prograding sequences during the Late Quaternary offshore of Kusadasi (West Anatolia) and surroundings by high resolution seismic methods

NASA Astrophysics Data System (ADS)

Gurcay, Savas; Cifci, Gunay; Dondurur, Derman; Okay, Seda; Atgin, Orhan; Ozel, Ozkan; Mert Kucuk, Hilmi

2016-04-01

High Resolution multi-channel seismic reflection and Chirp data were collected by K. Piri Reis, research vessel of Dokuz Eylül University, in the central Aegean coast of the West Anatolia by research cruises carried out in 2005 and 2008, respectively. Submarine stratigraphic and structural features of Sıǧacık Gulf, Kuşadası Gulf and surroundings were investigated under this survey. The data were processed and interpreted in SeisLab, D.E.U. Marine Sciences and Technology seismic laboratory. Thirteen distinct unconformities can be traced below the study area that separate thirteen progradational stacked paleo-delta sequences (Lob1-Lob13) on seismic profiles following and cutting each other. As a result of comparison with the oxygen isotopic stages (δ18), these deltas (Lob1-L13) were interpreted that they have been deposited during the sea-level lowstands within Pleistocene glacial stages. In the study area the basement surface which observed as the lowest unconformity surface of the seismic sections was called 'Acoustic Basement'. This basement which traced approximately all of the seismic sections has generally quite wavy surface and underlain the upper seismic units. It was observed that these seismic units which terminated their formation in Pleistocene (Lob1-Lob13) and Holocene period were cut and uplifted by acoustic basement, like an intrusion. These type deformations were interpreted as a result of magmatic intrusion into these upper seismic units occurred in Late Pleistocene and Holocene period. Tectonic and structural interpretation was carried out to constitute the submarine active tectonic map of the study area by correlated active faults identified on seismic sections. Submarine active tectonic map and, basement topography and sediment thickness map were correlated together to present the relationship between tectonic deformation and stratigraphy.

Response of Late Cretaceous migrating deltaic facies systems to sea level, tectonics, and sediment supply changes, New Jersey Coastal Plain, U.S.A.

USGS Publications Warehouse

Kulpecz, A.A.; Miller, K.G.; Sugarman, P.J.; Browning, J.V.

2008-01-01

Paleogeographic, isopach, and deltaic lithofacies mapping of thirteen depositional sequences establish a 35 myr high resolution (> 1 Myr) record of Late Cretaceous wave- and tide-influenced deltaic sedimentation. We integrate sequences defined on the basis of lithologic, biostratigraphic, and Sr-isotope stratigraphy from cores with geophysical log data from 28 wells to further develop and extend methods and calibrations of well-log recognition of sequences and facies variations. This study reveals the northeastward migration of depocenters from the Cenomanian (ca. 98 Ma) through the earliest Danian (ca. 64 Ma) and documents five primary phases of paleodeltaic evolution in response to long-term eustatic changes, variations in sediment supply, the location of two long-lived fluvial axes, and thermoflexural basement subsidence: (1) Cenomanian-early Turonian deltaic facies exhibit marine and nonmarine facies and are concentrated in the central coastal plain; (2) high sediment rates, low sea level, and high accommodation rates in the northern coastal plain resulted in thick, marginal to nonmarine mixed-influenced deltaic facies during the Turonign-Coniacian; (3) comparatively low sediment rates and high long-term sea level in the Santonian resulted in a sediment-starved margin with low deltaic influence; (4) well-developed Campanian deltaic sequences expand to the north and exhibit wave reworking and longshore transport of sands, and (5) low sedimentation rates and high long-term sea level during the Maastrichtian resulted in the deposition of a sediment-starved glauconitic shelf. Our study illustrates the widely known variability of mixed-influence deltaic systems, but also documents the relative stability of deltaic facies systems on the 106-107 yr scale, with long periods of cyclically repeating systems tracts controlled by eustasy. Results from the Late Cretaceous further show that although eustasy provides the template for sequences globally, regional tectonics (rates of subsidence and accommodation), changes in sediment supply, proximity to sediment input, and flexural subsidence from depocenter loading determines the regional to local preservation and facies expression of sequences. Copyright ?? 2008, SEPM (Society for Sedimentary Geology).

Partitioning the Quaternary

NASA Astrophysics Data System (ADS)

Gibbard, Philip L.; Lewin, John

2016-11-01

We review the historical purposes and procedures for stratigraphical division and naming within the Quaternary, and summarize the current requirements for formal partitioning through the International Commission on Stratigraphy (ICS). A raft of new data and evidence has impacted traditional approaches: quasi-continuous records from ocean sediments and ice cores, new numerical dating techniques, and alternative macro-models, such as those provided through Sequence Stratigraphy and Earth-System Science. The practical usefulness of division remains, but there is now greater appreciation of complex Quaternary detail and the modelling of time continua, the latter also extending into the future. There are problems both of commission (what is done, but could be done better) and of omission (what gets left out) in partitioning the Quaternary. These include the challenge set by the use of unconformities as stage boundaries, how to deal with multiphase records in ocean and terrestrial sediments, what happened at the 'Early-Mid- (Middle) Pleistocene Transition', dealing with trends that cross phase boundaries, and the current controversial focus on how to subdivide the Holocene and formally define an 'Anthropocene'.

Permafrost as palaeo-environmental archive - potentials and limitations

NASA Astrophysics Data System (ADS)

Schirrmeister, L.; Wetterich, S.; Meyer, H.; Grosse, G.; Schwamborn, G.; Siegert, C.

2009-04-01

Since 1994, the Periglacial Research Group of the Alfred Wegener Institute is studying permafrost sequences of the Beringian landmass. The study sites in Siberia cover lake banks on Taymyr Peninsula, coastal sites at the Laptev and the East Siberian Seas, locations in the Lena Delta, at the lower Kolyma river, the middle Lena and the lower Aldan rivers, and the catchment area of the El'gygytgyn crater lake in Chukotka. In Alaska, permafrost tunnels near Fairbanks and Barrow, and coastal sites on the Seward Peninsula coast were studied. In addition, Canadian sites on Herschel Island in the Beaufort Sea and at the adjacent coast of the Yukon plain were studied. Subsurface exposures like tunnels and cellars provided the opportunity for three-dimensional studies of sedimentary and ground ice features, relatively ‘clean' field conditions for in-situ experiments, monitoring procedures, and detailed and repeatable sampling. Permafrost cores were drilled in order to study inaccessible sequences below the terrain surface and shelf sea floor. Cores were transported and stored frozen for further high-resolution analysis. Reference core sections were preserved for subsequent later studies. Terrestrial sediment cores are highly localized records, sometimes problematic in extrapolating horizons in inhomogeneous sediments like ground ice-deformed permafrost deposits, and drill campaigns are usually cost intensive and logistical challenging. Coastal permafrost cliffs often naturally expose large cross sections trough modern and ancient landscapes. Contrary to cores, they provide an opportunity to study the wider context of depositional environments and ground ice features. Due to the relative easy access to coasts and the recurring natural exposure of cliffs by thermo-abrasive wave action they are very convenient study objects for regional comparisons and correlation of past environmental conditions. Finally, palaeogeographical reconstructions are also guided by remote sensing-based analyses of geomorphological surface patterns, like Yedoma hills, thermokarst depressions, pingos or thermoerosional valleys. We generally relied on a multidisciplinary approach to study permafrost sequences in order to use the rich palaeo-environmental information stored in these frozen records. Cryofacies analysis describes both sediment and ice structures that allow interpretation of freezing conditions, thaw events, temperature regimes, and the local accumulation conditions. Ground ice bodies were sampled by ice screw and chain saw for analysis of hydrochemical and stable isotope composition. Several ground ice types were classified. The interaction between ice, sediment, and cryosoil were determined. The isotope signatures of sub-vertically layered ice wedges contain information about temperature variations, evaporation conditions and precipitation sources during different periods of ice wedge formation. The stratigraphy of the permafrost sequences was determined by lithostratigraphical classifications and geochronological results. Numerous sediment parameters were measured for differentiation between horizons in individual exposures, for local and regional stratigraphic correlation of permafrost sequences as well as for reconstruction of accumulation and transport conditions. Age determinations were carried out by radiocarbon analyses on organic remains, isochron uranium-thorium disequilibria technique on peats, optical stimulated luminescence on clastic sediments, and 36Cl/Cl stable isotope ratios measurements in ground ice. For palaeo-ecological reconstructions various fossil bioindicators were studied including pollen, plant macro-remains, insects, ostracods, testate amoebae, diatoms, chironomids, and mammal bones of the so-called mammoth fauna. By combining these data sets, we assembled a complex picture of the climate, landscape and vegetation dynamics of the studied regions during the Quaternary past. Derived palaeo-information includes mean annual air temperatures, mean winter temperatures, mean Juli temperatures, precipitation, humidity, soil climate and chemistry, hydrology and hydrochemistry of waters). The general potential of permafrost archives includes spatial (circumarctic, high arctic to boreal zones) and temporal (Mid Pleistocene to modern) environmental gradients. Lateral cross sections contain information about permafrost degradation during interglacial periods, the aggradation of ice-rich sequences during stadial and interstadial periods, and extreme changes in periglacial hydrology during the late Quaternary. The spatial reconstruction of ancient landscapes is possible by detailed study of kilometer-long coastal exposures. Temporally relative high resolution (about 50 years) isotope data from ice wedges reflect the Late Pleistocene to Holocene climate transition. Using transfer functions for pollen, plant macro remains or chironomids, the numerical estimation of palaeo-climate data (temperature and precipitation) is possible. The limitations of permafrost archives are the frequent lack of continuous sequences due to thermokarst or thermo-erosion events. Local stratigraphies are sometimes difficult to correlate on a regional scale because of permafrost degradation and neotectonic influence on the accumulative/erosive environment in some regions. Until now there are still uncertainties for comparing different geochronological methods, some of them related to unknown influences of permafrost processes on chemical and physical parameters important to the age determination technique. Due to strong cryoturbation patterns and sometimes challenging sampling situations on near-vertical frozen exposures the geochronological resolution in permafrost sequences is usually lower than in lacustrine sequences or glacial ice cores. Eventually, as for any other archive, we need to consider the effect of local versus regional signals derived from the palaeo-ecological interpretation of fossil records.

Stratigraphy and age estimate of Neogene shallow marine fossiliferous deposits in Brunei Darussalam (Ambug Hill, Tutong district)

NASA Astrophysics Data System (ADS)

Kocsis, László; Briguglio, Antonino; Roslim, Amajida; Razak, Hazirah; Ćorić, Stjepan; Frijia, Gianluca

2018-06-01

The Ambug Hill in Brunei is an exceptional geological site where a series of siliciclastic rocks crops out with some layers extremely rich in marine fossils. Such fossiliferous outcrops are extremely rare in the northern part of Borneo and their description is of primary importance as their fossil content can be used to correlate the regional depositional sequences with global biostratigraphic zonations. In this work we present for the first time a detailed sedimentary profile completed with Sr-isotopes and biostratigraphic dating. The succession is divided into four sedimentary units. The first unit comprises bioturbated sandstone followed by a second unit of clay-silt rich levels whose first 9.5 m contain rich marine fossil assemblages. Calcareous nannoplankton data indicate a Late Tortonian - Early Messinian (NN11) age, which is confirmed by Sr-isotope dating derived from bivalves giving a numerical age range from 8.3 to 6.2 My. After a major emersion surface, the third sedimentary unit of sand- and siltstone lacks suitable fossils for bio- and isotope stratigraphy. The age of emersion and the related sedimentary gap can be either correlated with the Me1 (7.25 My) or the Me2 (5.73 My) sequence boundary. A fourth, thin sedimentary unit is recognized on the top of the profile with silt- and claystone beds without age diagnostic remains and calcareous fossils.

Comparative sequence stratigraphy of low-latitude versus high-latitude lacustrine rift basins: Seismic data examples from the East African and Baikal rifts

USGS Publications Warehouse

Scholz, C.A.; Moore, T.C.; Hutchinson, D.R.; Golmshtok, A. Ja; Klitgord, Kim D.; Kurotchkin, A.G.

1998-01-01

Lakes Baikal, Malawi and Tanganyika are the world's three largest rift valley lakes and are the classic modem examples of lacustrine rift basins. All the rift lakes are segmented into half-graben basins, and seismic reflection datasets reveal how this segmentation controls the filling of the rift basins through time. In the early stages of rifting, basins are fed primarily by flexural margin and axial margin drainage systems. At the climax of syn-rift sedimentation, however, when the basins are deeply subsided, almost all the margins are walled off by rift shoulder uplifts, and sediment flux into the basins is concentrated at accommodation zone and axial margin river deltas. Flexural margin unconformities are commonplace in the tropical lakes but less so in high-latitude Lake Baikal. Lake levels are extremely dynamic in the tropical lakes and in low-latitude systems in general because of the predominance of evaporation in the hydrologic cycle in those systems. Evaporation is minimized in relation to inflow in the high-latitude Lake Baikal and in most high-latitude systems, and consequently, major sequence boundaries tend to be tectonically controlled in that type of system. The acoustic stratigraphies of the tropical lakes are dominated by high-frequency and high-amplitude lake level shifts, whereas in high-latitude Lake Baikal, stratigraphic cycles are dominated by tectonism and sediment-supply variations.

New Insights Into Valley Formation and Preservation: Geophysical Imaging of the Offshore Trinity River Paleovalley

NASA Astrophysics Data System (ADS)

Speed, C. M.; Swartz, J. M.; Gulick, S. P. S.; Goff, J.

2017-12-01

The Trinity River paleovalley is an offshore stratigraphic structure located on the inner continental shelf of the Gulf of Mexico offshore Galveston, Texas. Its formation is linked to the paleo-Trinity system as it existed across the continental shelf during the last glacial period. Newly acquired high-resolution geophysical data have imaged more complexity to the valley morphology and shelf stratigraphy than was previously captured. Significantly, the paleo-Trinity River valley appears to change in the degree of confinement and relief relative to the surrounding strata. Proximal to the modern shoreline, the interpreted time-transgressive erosive surface formed by the paleo-river system is broad and rugose with no single valley, but just 5 km farther offshore the system appears to become confined to a 10 km wide valley structure before again becoming unconfined once again 30 km offshore. Fluvial stratigraphy in this region has a similar degree of complexity in morphology and preservation. A dense geophysical survey of several hundred km is planned for Fall 2017, which will provide unprecedented imaging of the paleovalley morphology and associated stratigraphy. Our analysis leverages robust chirp processing techniques that allow for imaging of strata on the decimeter scale. We will integrate our geophysical results with a wide array of both newly collected and previously published sediment cores. This approach will allow us to address several key questions regarding incised valley formation and preservation on glacial-interglacial timescales including: to what extent do paleo-rivers remain confined within a single broad valley structure, what is the fluvial systems response to transgression, and what stratigraphy is created and preserved at the transition from fluvial to estuarine environments? Our work illustrates that traditional models of incised valley formation and subsequent infilling potentially fail to capture the full breadth of dynamics of past river systems.

Foraminiferal and seismic stratigraphy, paleoenvironments and depositional cycles in the Georges Bank Basin

NASA Astrophysics Data System (ADS)

Poag, C. W.

Biostratigraphic analyses of foraminiferal assemblages sampled from rotary cuttings taken at 10 ft to 90 ft intervals were used with interpretation of seismic sequences to determine the presence of nonconformities and to establish a chronostratigraphic framework for COST G-1 and G-2 wells. The chronostratigraphic sequences were then used to calculate sediment accumulation rates. Lithostratigraphic and chronostratigraphic units were compared with those of the Scotian Basin of Canada, and correlations were established between the COST G-2 and the Shell Mohican L-100 wells. Paleoenvironmental analysis was based on the microfossil record of the G-1 and G-2 wells and on interpretation of seismic facies along USGS multichannel line 19.

Accumulation and erosion of Mars' south polar layered deposits.

PubMed

Seu, Roberto; Phillips, Roger J; Alberti, Giovanni; Biccari, Daniela; Bonaventura, Francesco; Bortone, Marco; Calabrese, Diego; Campbell, Bruce A; Cartacci, Marco; Carter, Lynn M; Catallo, Claudio; Croce, Anna; Croci, Renato; Cutigni, Marco; Di Placido, Antonio; Dinardo, Salvatore; Federico, Costanzo; Flamini, Enrico; Fois, Franco; Frigeri, Alessandro; Fuga, Oreste; Giacomoni, Emanuele; Gim, Yonggyu; Guelfi, Mauro; Holt, John W; Kofman, Wlodek; Leuschen, Carlton J; Marinangeli, Lucia; Marras, Paolo; Masdea, Arturo; Mattei, Stefania; Mecozzi, Riccardo; Milkovich, Sarah M; Morlupi, Antonio; Mouginot, Jérémie; Orosei, Roberto; Papa, Claudio; Paternò, Tobia; Persi del Marmo, Paolo; Pettinelli, Elena; Pica, Giulia; Picardi, Giovanni; Plaut, Jeffrey J; Provenziani, Marco; Putzig, Nathaniel E; Russo, Federica; Safaeinili, Ali; Salzillo, Giuseppe; Santovito, Maria Rosaria; Smrekar, Suzanne E; Tattarletti, Barbara; Vicari, Danilo

2007-09-21

Mars' polar regions are covered with ice-rich layered deposits that potentially contain a record of climate variations. The sounding radar SHARAD on the Mars Reconnaissance Orbiter mapped detailed subsurface stratigraphy in the Promethei Lingula region of the south polar plateau, Planum Australe. Radar reflections interpreted as layers are correlated across adjacent orbits and are continuous for up to 150 kilometers along spacecraft orbital tracks. The reflectors are often separated into discrete reflector sequences, and strong echoes are seen as deep as 1 kilometer. In some cases, the sequences are dipping with respect to each other, suggesting an interdepositional period of erosion. In Australe Sulci, layers are exhumed, indicating recent erosion.

Application of high-resolution subsurface imaging techniques to water resource investigations. Final report

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

Sternberg, B.K.; Thomas, S.J.

1992-12-01

The overall objective of the project was to apply a new high-resolution imaging system to water resource investigations. This imaging system measures the ellipticity of received magnetic-field components. The source of the magnetic field is a long-line transmitter emitting frequencies from 30 Hz to 30 kHz. A new high-accuracy calibration method was used to enhance the resolution of the measurements. The specific objectives included: (1) refine the system hardware and software based on these investigations, (2) learn the limitations of this technology in practical water resource investigations, and (3) improve interpretation techniques to extract the highest possible resolution. Successful fieldmore » surveys were run at: (1) San Xavier Mine, Arizona - flow of injected fluid was monitored with the system. (2) Avra Valley, Arizona - subsurface stratigraphy was imaged. A survey at a third site was less successful; interpreted resistivity section does not agree with nearby well logs. Surveys are continuing at this site.« less

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.

Sea level changes in Sharm Abhur Red Sea Coast of Saudi Arabia, as Revealed from Seismic Stratigraphy

NASA Astrophysics Data System (ADS)

El-Abd, Yakout; Awad, Morad

High resolution seismic profiling has been carried out along Sharm Abhur (a tidal creek), north of Jeddah, Saudi Arabia, using a high resolution seismic refraction profiling system. A chronogram illustrating corresponding Holocene relative sea level changes was constructed. Since 16,750 yr. B.P. Sharm Abhur had been subjected to four stages of relative transgressions. The first one started at about 92.5 m below present sea level. A relative stillstand occurred between 12,500-11,000 yr. B.P. about 50 m below present sea level. An anomalous body is observed near the mouth of the Sharm which is believed to be uplifted between 13,250 and 12,500 yr. B.P.

Filling of a Salt-withdrawal Minibasin on the Continental Slope by Turbidity Currents: Futher Research and Results

NASA Astrophysics Data System (ADS)

Violet, J. A.; Sheets, B. A.; Paola, C.; Pratson, L. F.; Parker, G.

2002-12-01

We illustrate further research results on the transport and deposition of sediment by turbidity currents in an experimental basin, designed to model salt-withdrawal minibasins found along the northern continental slope of the Gulf of Mexico. The experiment was performed in 2001 in the subsiding EXperimental EarthScape facility (XES) at St. Anthony Falls Laboratory, University of Minnesota. The run consisted of two stages that each contained the same sequence of events, which were of three different variations (1.85-minute pulses of 1.5 liters/s discharges, 3.8-minute pulses of 4.5 liters/s discharges, or 36 minute events of 1.5 liters/s discharges). The sediment comprised three grades of silica with nominal diameters of 20 microns (45%), 45 microns (40%) and 110 microns (15%) and all flows had a volume concentration of sediment of 5%. The only difference between stage I and II was that no subsidence occurred during stage II, and that the 110 micron sand was removed from the flows late in stage II to study the effects of a smaller mean flow-grainsize. Research since the run has focused on the correction of high-frequency sonar data taken during the run, digital photography taken of dried deposit stratigraphy and grainsize data also taken at various locations in the dried deposit. The sonar data is utilized in the creation of post-event topographies and isopach maps to illustrate what the controls on erosion, deposition, flow path, deposit thickness and even the channelization of early flow events are. Comparisons of the stratigraphy and the grainsize data with the conclusions from the sonar data are made, as sonar is also constructed in a manner that exhibits synthetic or predicted stratigraphy (before compaction). Finally the stratigraphy is structurally described in the proximal, medial, and distal segments of the deposit and comparisons to the field are made.

The INTIMATE event stratigraphy of the last glacial period

NASA Astrophysics Data System (ADS)

Olander Rasmussen, Sune; Svensson, Anders

2015-04-01

The North Atlantic INTIMATE (INtegration of Ice-core, MArine and TErrestrial records) group has previously recommended an Event Stratigraphy approach for the synchronisation of records of the Last Termination using the Greenland ice core records as the regional stratotypes. A key element of these protocols has been the formal definition of numbered Greenland Stadials (GS) and Greenland Interstadials (GI) within the past glacial period as the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. Using a recent synchronization of the NGRIP, GRIP, and GISP2 ice cores that allows the parallel analysis of all three records on a common time scale, we here present an extension of the GS/GI stratigraphic template to the entire glacial period. In addition to the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice core records more than two decades ago, a number of short-lived climatic oscillations have been identified in the three synchronized records. Some of these events have been observed in other studies, but we here propose a consistent scheme for discriminating and naming all the significant climatic events of the last glacial period that are represented in the Greenland ice cores. In addition to presenting the updated event stratigraphy, we make a series of recommendations on how to refer to these periods in a way that promotes unambiguous comparison and correlation between different proxy records, providing a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations. The work presented is a part of a newly published paper in an INTIMATE special issue of Quaternary Science Reviews: Rasmussen et al., 'A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy', Quaternary Science Reviews, vol. 106, p. 14-24, 2014.

Stratigraphy of the Sarkisla area, Sivas basin, eastern central Anatolia

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

Bilgic, T.; Sumengen, M.; Terlemez, I.

1988-08-01

The stratigraphy of the Sarkisla area, southeastern Central Anatolian Massif, is characterized by a succession of rock units ranging from late Paleocene to Pliocene in age. The Caldag group mostly consists of deep-water units and forms the base of the Tertiary rocks. However, its relation to the basement rocks is not observed in the area. This group is represented by late Paleocene-Lutetian-age turbiditic pyroclastics and limestones, andesitic lavas and pyroclastics topped with reefal limestones, and turbiditic limestones and pyroclastics alternating with limestone blocks. During Lutetian to early Priabonian time, shallow marine clastics were deposited along the southern margin of themore » basin, while continental clastics and platform limestones accumulated along the northern margin. Late Priabonian to early Oligocene time is represented by gypsiferous deposits followed by late Oligocene-age fluvial clastics. The gypsiferous deposits conformably overlie the shallow marine formations but rest on the Caldag group unconformably. During early to middle Miocene time, alternating lacustrine limestones, gypsum, and basalts formed on the fluvial clastics; to the north, basalts formed on the platform limestones. The uppermost sequence of the basin, composed of Tortonian-early Pliocene-age fluvial clastics, lacustrine limestones, and fan deposits, unconformably overlies the older formations. The stratigraphy of the study area is similar to the Ulukisla basin, southwestern Central Anatolian Massif. Therefore, this basin can be considered to be the prolongation of the Ulukisla basin offset by the Ecemis fault.« less

Acoustic Imaging of Snowpack Physical Properties

NASA Astrophysics Data System (ADS)

Kinar, N. J.; Pomeroy, J. W.

2011-12-01

Measurements of snowpack depth, density, structure and temperature have often been conducted by the use of snowpits and invasive measurement devices. Previous research has shown that acoustic waves passing through snow are capable of measuring these properties. An experimental observation device (SAS2, System for the Acoustic Sounding of Snow) was used to autonomously send audible sound waves into the top of the snowpack and to receive and process the waves reflected from the interior and bottom of the snowpack. A loudspeaker and microphone array separated by an offset distance was suspended in the air above the surface of the snowpack. Sound waves produced from a loudspeaker as frequency-swept sequences and maximum length sequences were used as source signals. Up to 24 microphones measured the audible signal from the snowpack. The signal-to-noise ratio was compared between sequences in the presence of environmental noise contributed by wind and reflections from vegetation. Beamforming algorithms were used to reject spurious reflections and to compensate for movement of the sensor assembly during the time of data collection. A custom-designed circuit with digital signal processing hardware implemented an inversion algorithm to relate the reflected sound wave data to snowpack physical properties and to create a two-dimensional image of snowpack stratigraphy. The low power consumption circuit was powered by batteries and through WiFi and Bluetooth interfaces enabled the display of processed data on a mobile device. Acoustic observations were logged to an SD card after each measurement. The SAS2 system was deployed at remote field locations in the Rocky Mountains of Alberta, Canada. Acoustic snow properties data was compared with data collected from gravimetric sampling, thermocouple arrays, radiometers and snowpit observations of density, stratigraphy and crystal structure. Aspects for further research and limitations of the acoustic sensing system are also discussed.

Berriasian (Early Cretaceous) radiometric ages from the Grindstone Creek Section, Sacramento Valley, California

USGS Publications Warehouse

Bralower, T.J.; Ludwig, K. R.; Obradovich, J.D.

1990-01-01

The Grindstone Creek Section, Glenn County, Northern California is a sequence of hemipelagic mudstone, siltstone and sandstone interbedded with concretionary limestone and a few thin tuffs and bentonites. Two tuffs have been collected from a narrow interval of this sequence and subjected to mineralogical and isotopic analyses. UPb isotopic analyses of zircon fractions from these volcanic horizons indicate an age of 137.1 + 1.6/-0.6 Ma. A detailed investigation has been conducted on the calcareous nannofossil stratigraphy of this section based on numerous samples with moderately preserved assemblages. The nannoflora is largely of Tethyan affinity, and allows direct correlation with the Berriasian stratotype section, with sections with published magnetostratigraphies and with a DSDP site drilled between known magnetic anomalies. The dated tuffs lie in the lower part of the upper Berriasian Cretarhabdus angustiforatus Zone (Assipetra infracretacea Subzone) and within the narrow range of Rhagodiscus nebulosus. At three different sections, this subzone can be correlated with M-sequence Polarity Zones M16 and M16n. An independent magnetostratigraphic correlation is provided at DSDP Site 387, drilled between anomalies M15 and M16, where basal sediments contain R. nebulosus. Buchia collected within a meter of the lower tuff lie within the B. uncitoides Zone which is Berriasian in age. The upper tuff level, which occurs 65 m above the lower tuff, is situated within the overlying B. pacifica Zone. This zone had previously been correlated with the early Valanginian, but is clearly also partly of Berriasian age based on nannofossil stratigraphy. Our results allow an estimate of the age of the Berriasian-Valanginian and Jurassic-Cretaceous boundaries of 135.1 Ma and 141.1 Ma, respectively, and these fall within the range of, but differ significantiy from, several published time-scales. ?? 1990.

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.

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.

The Delta Box: a Table-top Glimpse Into Sequence Stratigraphy

NASA Astrophysics Data System (ADS)

Campbell, K. M.; Hickson, T.; Martin, J.; Paola, C.

2006-12-01

Physical models offer an effective means of providing greater understanding of surface processes and depositional products. At the National Center for Earth-surface Dynamics' research facility, St. Anthony Falls Laboratory; we have seen that in addition to being critically important to the advancement of surface process research, experiments are extremely effective tools for engaging students, especially undergraduates, in understanding these linkages. However, many colleges and universities cannot afford the space or time to support large research or teaching flumes, so we have devised an inexpensive table-top tank that can be used in teaching deltaic depositional processes and concepts of sequence stratigraphy. Our "Delta Box" measures approximately 1.2 by 0.6 meters and is built primarily of parts available at local hardware stores or lumberyards. A simple pond pump drives a water recirculation system, while a constant head tank constructed from PVC pipe regulates the rate of water flow into the flume. A sand/coal sediment mix, fed by hand into the tank, provides a very clear visual distinction between coarse and fine particles on a continental shelf and slope constructed of foam insulation. We have tested the box with a group of undergraduate faculty from around the United States at an "On the Cutting Edge" workshop, at which we were able to consistently build many classic deltaic features, as well as show delta progradation, the effects of waves on sediment transport and deposition, and the formation of sequence boundaries and the entire suite of key sequence stratigraphic features. A manual for building the box, as well as a short movie clip of the workshop participants experimenting with it, is available at http://www.nced.edu/SERC.html. Several of the participants are currently building additional boxes; we plan to post improved instructions and example exercises on the National Center for Earth-surface Dynamics website.

High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims

NASA Astrophysics Data System (ADS)

Vazquez, Jorge A.; Lidzbarski, Marsha I.

2012-12-01

Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9 ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9 ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.

High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims

USGS Publications Warehouse

Vazquez, Jorge A.; Lidzbarski, Marsha I.

2012-01-01

Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9 ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9 ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.

Late Miocene climate and time scale reconciliation: Accurate orbital calibration from a deep-sea perspective

NASA Astrophysics Data System (ADS)

Drury, Anna Joy; Westerhold, Thomas; Frederichs, Thomas; Tian, Jun; Wilkens, Roy; Channell, James E. T.; Evans, Helen; John, Cédric M.; Lyle, Mitch; Röhl, Ursula

2017-10-01

Accurate age control of the late Tortonian to early Messinian (8.3-6.0 Ma) is essential to ascertain the origin of benthic foraminiferal δ18O trends and the late Miocene carbon isotope shift (LMCIS), and to examine temporal relationships between the deep-sea, terrasphere and cryosphere. The current Tortonian-Messinian Geological Time Scale (GTS2012) is based on astronomically calibrated Mediterranean sections; however, no comparable non-Mediterranean stratigraphies exist for 8-6 Ma suitable for testing the GTS2012. Here, we present the first high-resolution, astronomically tuned benthic stable isotope stratigraphy (1.5 kyr resolution) and magnetostratigraphy from a single deep-sea location (IODP Site U1337, equatorial Pacific Ocean), which provides unprecedented insight into climate evolution from 8.3-6.0 Ma. The astronomically calibrated magnetostratigraphy provides robust ages, which differ by 2-50 kyr relative to the GTS2012 for polarity Chrons C3An.1n to C4r.1r, and eliminates the exceptionally high South Atlantic spreading rates based on the GTS2012 during Chron C3Bn. We show that the LMCIS was globally synchronous within 2 kyr, and provide astronomically calibrated ages anchored to the GPTS for its onset (7.537 Ma; 50% from base Chron C4n.1n) and termination (6.727 Ma; 11% from base Chron C3An.2n), confirming that the terrestrial C3:C4 shift could not have driven the LMCIS. The benthic records show that the transition into the 41-kyr world, when obliquity strongly influenced climate variability, already occurred at 7.7 Ma and further strengthened at 6.4 Ma. Previously unseen, distinctive, asymmetric saw-tooth patterns in benthic δ18O imply that high-latitude forcing played an important role in late Miocene climate dynamics from 7.7-6.9 Ma. This new integrated deep-sea stratigraphy from Site U1337 can act as a new stable isotope and magnetic polarity reference section for the 8.3-6.0 Ma interval.

Correlating Mediterranean shallow water deposits with global Oligocene-Miocene stratigraphy and oceanic events.

PubMed

Reuter, Markus; Piller, Werner E; Brandano, Marco; Harzhauser, Mathias

2013-12-01

Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene-Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene-Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene-late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO 3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale.

Palynology of the Last Interglacial Complex at Lake Ohrid: palaeoenvironmental and palaeoclimatic inferences

NASA Astrophysics Data System (ADS)

Sinopoli, Gaia; Masi, Alessia; Regattieri, Eleonora; Wagner, Bernd; Francke, Alexander; Peyron, Odile; Sadori, Laura

2018-01-01

In this article, we present new, high-resolution, pollen results obtained from the DEEP site sequence recovered from Lake Ohrid (Albania/FYROM) for the Last Interglacial Complex (LIC), corresponding to Marine Isotope Stage 5 (MIS 5) of the marine isotope stratigraphy. LIC covers the period between 130 and 70 ka and includes the Eemian (Last Interglacial, LI) and the succession of stadial and interstadial phases of the Early Last Glacial. During the LIC, the pollen record shows an alternation of periods characterized by forest and open vegetation, clearly resembling the well-known vegetational succession of other European records. Our results reveal three key phases for the LI: a first period (128-125 ka) with a rapid increase in temperature and precipitation, a central phase (125-118.5 ka) characterized by a slight cooling, and a late phase (118.5-112 ka), with a decline both in temperatures and precipitation. Besides the LI, we identify four more forested periods dominated by mesophilous trees and intercalated by colder and drier steppe phases, during which, however, most arboreal taxa never disappear. During the Early Last Glacial we also identify several abrupt events that can be correlated to the succession of cold events recorded in the Greenland ice core records, associated to a weakening of the North Atlantic Meridional Overturning Circulation. The new high-resolution record indicates that Lake Ohrid is an important site to understand the response of vegetation to fluctuations in regional moisture availability and temperature changes, and thus provides new evidence for the connection between the Mediterranean Region and Northern Hemisphere climate oscillations.

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

NASA Astrophysics Data System (ADS)

Martínez-Carreño, N.; García-Gil, S.

2017-10-01

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

Silurian deltaic progradation, Tassili n'Ajjer plateau, south-eastern Algeria: Sedimentology, ichnology and sequence stratigraphy

NASA Astrophysics Data System (ADS)

Djouder, Hocine; Lüning, Sebastian; Da Silva, Anne-Christine; Abdallah, Hussein; Boulvain, Frédéric

2018-06-01

The economic potential for unconventional shale oil and gas production in the Silurian of the Berkine - Ghadames and Illizi basins (BGI) in south-eastern Algeria has been recently confirmed through exploration drilling. The aim of the present paper attempts a better understanding of the Intra-Tassilian depression within the entire Silurian of the Tassili n'Ajjer plateau. The continuous deposits of the Silurian are exposed at the southern margin of the prolific BGI basins, in the Tassili n'Ajjer plateau, offering the chance to understand the sedimentology, ichnology, and to present a detailed sequence stratigraphy framework for the region. The 410 m-thick clastic Silurian sedimentary strata are subdivided into three formations in the context of sequence stratigraphy, namely: (i) the Oued Imihrou Fm. (Llandoverian) overlain by (ii) the Atafaïtafa Fm. (late Llandoverian to Wenlockian), and (iii) the Oued Tifernine Fm. (late Wenlockian to Pridolian). These can be also distinguished across the entire investigated area and laterally traceable over kilometers. Clear cyclic stacking patterns are identified within the four studied sections showing progressively a general trend of thickening- and coarsening-upward, over a complete 2nd-order megasequence (SIL-1 MS). This transgressive-regressive succession suggests deltaic progradation, shallowing and basin infilling as evidenced by numerous diagnostic sedimentary features and trace fossils, largely from eastern-to western-Tassili plateau. Indeed, the wealth of outcrop data in the Silurian siliciclastic succession enables us to distinct thirteen facies (facies A-M), ranging from shallow-to marginal-marine facies, and in turn, grouped into six facies associations (FA1-FA6). The lowermost part of the succession, which is the most prolific sources of hydrocarbons in North Africa, consists of thick organic-rich graptolite-yielding black 'hot' shales and 'lean' shales with sparse bioturbation with small Thalassinoides belonging to the distal Cruziana ichnofacies. In contrast, the uppermost part of the Silurian deposits becomes progressively coarser and fluvial in response to the progradation of the North African Akakus deltaic system, during regional sea level fall and uplifting of the region. These progradational deposits exhibit well-preserved trace fossils with moderate to high degree of bioturbation, such as Skolithos or the so-called "Tigillites" pipe-rock, Cruziana isp., Rusophycus isp., Monocraterion isp., and Syringomorpha. The SIL-1 MS is bounded by a post-glacial latest Hirnantian unconformity on the basal (SB1), as confirmed by the moderately diverse early Silurian graptolite faunas, and by the Caledonian unconformity on the top (SB7). Each of the three formations of SIL-1 MS reveals two major 3rd-order progradational sequences, commonly delineated by discontinuity surfaces (in ascending order, SB1 to SB7), and in turn, these six sequences (i.e. Si-1 to Si-6) are subdivided into at least ten shorter-term cycles. The regional extent of each unconformity is directly linked to significant facies changes and to inflection points on the global sea level curve.

The Stratigraphy and Lithofacies of the Paleoproterozoic Volcaniclastic Sequences in the Cape Three Points Area- Akodda section of the Southern in Ashanti Belt in the Birimian of southwest Ghana

NASA Astrophysics Data System (ADS)

Yoshimaru, S.; Kiyokawa, S.; Ito, T.; Ikehara, M.; Nyame, F. K.; Tetteh, G. M.

2015-12-01

The Paleoproterozoic Era is thought to have experienced one of the most significant changes in earth's environment during earth history. Early continents started to diverge and collide accompanied by first major oxidation of the atmosphere-oceanic system known as the Great Oxidation Environment (GOE). Due to their well-preserved oceanic sedimentary sequences, Paleoproterozoic belts are usually good targets for studies on the history of earth's past environment. In addition, these belts provide great help to understand the nature of the Paleoproterozoic deeper oceanic environments. Birimian greenstone belt in southwestern Ghana is likely to have made up of subduction of oceanic basin to form a volcanic island arc. Birimian rocks are separated by nonconformity from the Tarkwaian Group which is a younger paleoplacer deposit (Perrouty et al., 2012). The Birimian is made up of island-arc volcanic rocks; foreland basin made up of shale, sandstone, quartzite and turbidities derived from 2.17 Ga granite intrusions during Birimian volcanism. In this study, we focused on the coastal area around Cape Three Points at the southernmost part of the Ashanti (Axim-Konongo) belt in Ghana. In the eastern part of the area, excellently preserved Paleoprotorozoic deeper oceanic sedimentary sequences extensively outcrop for over 4km stretch. This volcano-sedimentary sequence has been affected by greenschist facies metamorphism. Structurally, this region preserves S1 cleavage and asymmetrical synform with west vergence and S0 younging to the east. Provisional stratigraphy is very continuous up to more than 2000m thick and, in addition, suggests at least four different fining upward sequences in the area to the east and west of Atwepo, west of Kwetakora and Akodda. These sub-sequences are mainly composed of volcaniclasitc, sandstone, black shale and rare volcanics such as pillow basalt or massive volcanic lava. In other words, this continuous sequence suggests distal submarine volcaniclastic rocks in an oceanic island arc around the West African Craton. Preliminary δ13C analysis gave values of -23.7~ -36.5 ‰ for black shale occupying the middle to upper part of the whole section. The very light carbon isotope ratios suggest deposition of the black shale under highly euxinic conditions like today's Black sea.

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

Stratigraphy and Age of Paleoproterozoic Birimian Volcaniclastic Sequence in the Cape Three Points area, Axim-Konongo (Ashanti) Belt, Southwest Ghana

NASA Astrophysics Data System (ADS)

Yoshimaru, S.; Kiyokawa, S.; Ito, T.; Ikehara, M.; Horie, K.; Takehara, M.; Sano, T.; Nyame, F. K.; Tetteh, G. M.

2016-12-01

This study investigated the depositional environments and bioactivities of well preserved volcaniclastic sequences in the Cape Three Points area in the Paleoproterozoic Axim-Konongo (Ashanti) belt in the Birimian of Ghana. Our current research outlines the stratigraphy, structure, approximate age and depositional setting of the volcaniclastic sequence in the Cape Three Points area in Ghana, West Africa.Axim-Konongo (Ashanti) belt is composed of mainly andesitic basalts, volcaniclastic rocks and belt type granitoids, which are unconformably overlain by Tarkwaian conglomerates and metasedimentary rocks. The rocks show NE-SW strike with maximum depositional age of overlying metasedimentary rocks of 2154±2 Ma (U-Pb zircon; Oberthür et al., 1998). The oldest age of an intrusive into Birimian volcanic rock near Sekondi is 2174±2 Ma (U-Pb zircon; Oberthür et al., 1998). Thick volcaniclastic succession over 4000 m thickness was reconstructed for 1000 m thickness after detailed field investigations. The succession shows approximately N-S strike mainly 60-80° dip to the east and generally upward sequence. The rocks were affected by greenschist facies metamorphism. TiO2/Al2O3 ratios of chromites and whole- rock trace elements compositions with low Nb concentration and high LREE concentration support deposition on mid-deep sea floor in a volcanic arc. New age data were obtained from foliated porphyritic dyke which occurs in the Cape Three Points area. Zircon grains, measured by SHRIMP at National Institute of Polar Research (NIPR), yielded a weighted mean 204Pb-corrected 207Pb/206Pb age of 2265.6±4.6 Ma (95% confidence). Thus, the volcaniclastic sequence was deposited before 2265.6±4.6 Ma and was deformed after 2265 Ma. 2260 Ma is the oldest age at which early volcanic activity in the Birimian terrane occurred (Loh and Hirdes, 1999). References Oberthür T et al. (1998) Precambrian Research 89: 129-143 Loh G and Hirdes W (1999) Exlplanatory Notes for the Geological Map of southwest Ghana, 1:100000. Ghana Geological Survey Bulletin No, 49, 106-112

Volcanic stratigraphy: A review

NASA Astrophysics Data System (ADS)

Martí, Joan; Groppelli, Gianluca; Brum da Silveira, Antonio

2018-05-01

Volcanic stratigraphy is a fundamental component of geological mapping in volcanic areas as it yields the basic criteria and essential data for identifying the spatial and temporal relationships between volcanic products and intra/inter-eruptive processes (earth-surface, tectonic and climatic), which in turn provides greater understanding of the geological evolution of a region. Establishing precise stratigraphic relationships in volcanic successions is not only essential for understanding the past behaviour of volcanoes and for predicting how they might behave in the future, but is also critical for establishing guidelines for exploring economic and energy resources associated with volcanic systems or for reconstructing the evolution of sedimentary basins in which volcanism has played a significant role. Like classical stratigraphy, volcanic stratigraphy should also be defined using a systematic methodology that can provide an organised and comprehensive description of the temporal and spatial evolution of volcanic terrain. This review explores different methods employed in studies of volcanic stratigraphy, examines four case studies that use differing stratigraphic approaches, and recommends methods for using systematic volcanic stratigraphy based on the application of the concepts of traditional stratigraphy but adapted to the needs of volcanological environment.

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.

A review on the Holocene evolution of an inner-shelf mud deposit in the southeastern Yellow Sea: the Huksan Mud Belt

NASA Astrophysics Data System (ADS)

Lee, Hee Jun

2015-12-01

The Huksan Mud Belt (HMB) has been extensively investigated with respect to its source and evolution since the 1980s. Studies on sediment budget or accumulation rates suggested two different origins, Korean and combined Korean and Chinese. However, neither of the suggested origins appears reliable because they were based on insufficient or inaccurate datasets on the basic sedimentological characteristics of the HMB. Although a major mud transport was inferred to be closely associated with either the Korean Coastal Current or the Yellow Sea Warm Current, their physical characters during the Holocene transgression have been rarely hind-casted thus far. The majority of studies on high-resolution seismic stratigraphy along with core log have suggested that the HMB stratigraphy consists of two units divided by an erosional boundary. The lower unit is further divided into two subunits by a subtle discontinuity that is laterally correlated with the erosional boundary. In line with the stratigraphy, the studies theorized that the erosion of the HMB had produced a re-deposited distal lobe, the younger lower subunit. In addition, this lobe was inferred to have prograded rapidly during the relatively short period of 6,500-5,500 yr B.P. Although the time interval of the erosion coincides with the decelerating rise in sea level, the hydrodynamic cause and effect of the erosion remain inexplicable. Therefore, the source and evolution of the HMB continue to be controversial, due largely to poor understanding of the paleo-physical oceanography of the Yellow Sea during the Holocene.

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

Lower Miocene stratigraphy of the Gebel Shabrawet area, north Eastern desert Egypt

NASA Astrophysics Data System (ADS)

Abdelghany, Osman

2002-05-01

The Lower Miocene carbonate/siliciclastic sequence of the Shabrawet area, comprises a complex alternation of autochthonous and allogenic sediments. The sequence can be subdivided into two lithostratigraphic units. The lower unit (unit I) is equivalent to the Gharra Formation. It is mainly clastic and composed of sandstones, siltstones and shales with minor limestone intercalations. These sediments are rich in Clypeaster spp., Scutella spp., Miogypsina intermedia, Operculina complanata, and smaller foraminifera. The upper unit (unit II) was considered by previous workers as being equivalent to the Marmarica Formation. It consists mainly of non-clastic rocks, dominated by sandy and chalky limestones rich in larger foraminifera (miogypsinids and nummulitids). This unit is topped by a highly fossiliferous ( Heterostegina, Operculina and Planostegina) sandy limestone. The present study places both units in the Gharra Formation and reports for the first time M. intermedia from the Miocene sequence of the Shabrawet area.

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.

Terrace aggradation during the 1978 flood on Powder River, Montana, USA

USGS Publications Warehouse

Moody, J.A.; Meade, R.H.

2008-01-01

Flood processes no longer actively increase the planform area of terraces. Instead, lateral erosion decreases the area. However, infrequent extreme floods continue episodic aggradation of terraces surfaces. We quantify this type of evolution of terraces by an extreme flood in May 1978 on Powder River in southeastern Montana. Within an 89-km study reach of the river, we (1) determine a sediment budget for each geomorphic feature, (2) interpret the stratigraphy of the newly deposited sediment, and (3) discuss the essential role of vegetation in the depositional processes. Peak flood discharge was about 930??m3 s- 1, which lasted about eight??days. During this time, the flood transported 8.2??million tons of sediment into and 4.5??million tons out of the study reach. The masses of sediment transferred between features or eroded from one feature and redeposited on the same feature exceeded the mass transported out of the reach. The flood inundated the floodplain and some of the remnants of two terraces along the river. Lateral erosion decreased the planform area of the lower of the two terraces (~ 2.7??m above the riverbed) by 3.2% and that of the higher terrace (~ 3.5??m above the riverbed) by 4.1%. However, overbank aggradation, on average, raised the lower terrace by 0.16??m and the higher terrace by 0.063??m. Vegetation controlled the type, thickness, and stratigraphy of the aggradation on terrace surfaces. Two characteristic overbank deposits were common: coarsening-upward sequences and lee dunes. Grass caused the deposition of the coarsening-upward sequences, which had 0.02 to 0.07??m of mud at the base, and in some cases, the deposits coarsened upwards to coarse sand on the top. Lee dunes, composed of fine and very fine sand, were deposited in the wake zone downstream from the trees. The characteristic morphology of the dunes can be used to estimate some flood variables such as suspended-sediment particle size, minimum depth, and critical shear velocity. Information about depositional processes during extreme floods is rare, and therefore, the results from this study aid in interpreting the record of terrace stratigraphy along other rivers.

Comprehensive investigation of submarine slide zones and mass movements at the northern continental slope of South China Sea

NASA Astrophysics Data System (ADS)

Chen, Hongjun; Liang, Jin; Gong, Yuehua

2018-02-01

Multi-beam bathymetry and seismic sequence surveys in the northern slope of the South China Sea reveal detailed geomorphology and seismic stratigraphy characteristics of canyons, gullies, and mass movements. Modern canyons and gullies are roughly elongated NNW-SSW with U-shaped cross sections at water depths of 400-1000 m. Mass movements include slide complexes, slide scars, and debris/turbidity flows. Slide complexes and slide scars are oriented in the NE-SW direction and cover an area of about 1790 and 926 km2, respectively. The debris/turbidity flows developed along the lower slope. A detailed facies analysis suggests that four seismic facies exist, and the late Cenozoic stratigraphy above the acoustic basement can be roughly subdivided into three sequences separated by regional unconformities in the study area. The occurrence of gas hydrates is marked by seismic velocity anomalies, bottom-simulating reflectors, gas chimneys, and pockmarks in the study area. Seismic observations suggest that modern canyons and mass movements formed around the transition between the last glacial period and the current interglacial period. The possible existence and dissociation of gas hydrates and the regional tectonic setting may trigger instability and mass movements on the seafloor. Canyons may be the final result of gas hydrate dissociation. Our study aims to contribute new information that is applicable to engineering construction required for deep-water petroleum exploration and gas hydrate surveys along any marginal sea.

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.

Paleomagnetic and magnetostratigraphic investigations of the whitehorse group/quartermaster (Dewey Lake) formation (upper permian-lowermost triassic) in the Palo Duro basin, northwest Texas, USA

NASA Astrophysics Data System (ADS)

Collins, Dylan R.

In northwest Texas, upper Permian to lowermost Triassic hematite-cemented detrital sedimentary rocks, which include a small number of regionally extensive ash beds, were deposited during the time interval of the greatest mass extinction event sequences in Earth history. The magnetic polarity stratigraphy, as well as key rock magnetic properties, of the upper Whitehorse Group (WH) and Quartermaster formations (QM) at selected sections in the Palo Duro Basin, have been determined using thermal, and chemical demagnetization approaches and anisotropy of magnetic susceptibility, acquisition of isothermal remanent magnetization (IRM) and backfield demagnetization, and thermal demagnetization of three component IRM methods. Demagnetization results show that the WH/QM contains a primary/near-primary characteristic remanent magnetization at each level sampled and thus the magnetic polarity stratigraphy for each section can be compared with existing polarity time scales across the Permian-Triassic boundary. Estimated site mean directions yield a paleomagnetic pole for the latest Permian for North America of 57.8°N, 130.6°E from 38 sampled sites.

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

NASA Astrophysics Data System (ADS)

Sheldon, Dane P. H.

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

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.

Late Holocene stratigraphy of the Tetimpa archaeological sites, northeast flank of Popocatepetl volcano, central Mexico

USGS Publications Warehouse

Panfil, M.S.; Gardner, T.W.; Hirth, K.G.

1999-01-01

Late Holocene (240 km2 on the east side of the volcano with >25 cm of tephra. Lavas from eruptive sequence I dammed drainage in the lowland area near the town of San Nicolas and caused local upstream deposition of as much as 30 m of lacustrine silts, clays, and sands. These lacustrine deposits record an eruptive hiatus for the Tetimpa area of about 750 14C yr: between ca. 2100 and ca. 1350 yr B.P., no major tephras were deposited in the Tetimpa area. In upland areas, this time period is represented by an unconformity and by Entisols formed in the top of pumice deposits and lavas from eruptive sequence I. Artifacts, agricultural furrows, and dwellings record human reoccupation of this surface. At the end of this hiatus, several lahars were deposited above the lacustrine sequence and locally above the Entisol in upland positions adjacent to streams. Between ca. 1350 and ca. 1200 yr B.P., tephras from eruptive sequence II buried these paleosols, occupation sites, lacustrine sediments, and lahars. Andesitic (~62% SiO2) pumice lapilli deposits in the Tetimpa area record three pumice-fall eruptions directed northeast and east of the crater. The first and smallest of these (maximum Tetimpa area thickness = 12 cm; >52 km2 covered by >25 cm) took place at ca. 1350 yr B.P. and was accompanied by pyroclastic surge events preserved in the Tetimpa area by charcoal, sand waves, and cross-stratified sand-sized tephra. At ca. 1200 yr B.P., the products of two Plinian-style events and additional pyroclastic surges reached the Tetimpa area. The largest of these tephra-fall events covered the Tetimpa area with 0.5-1 m of tephra and blanketed an area of >230 km2 with a thickness of >25 cm. The Tetimpa record confirms two of the four periods of explosive volcanism recognized by studies conducted around Popocatepetl in the past 30 yr. Eruptive sequence I corresponds to the explosive period between 2100 and 2500 yr B.P., and eruptive sequence II corresponds to the period between 900 and 1400 yr B.P. The archaeology and lacustrine stratigraphy of the Tetimpa area help constrain the timing of the Plinian phase of eruptive sequence I to ca. 2100 yr B.P. and suggest that the pumice-fall eruptions of eruptive sequence II took place in at least two intervals between ca. 1350 and ca. 1200 yr B.P.

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.

Rootless tephra stratigraphy and emplacement processes

NASA Astrophysics Data System (ADS)

Hamilton, Christopher W.; Fitch, Erin P.; Fagents, Sarah A.; Thordarson, Thorvaldur

2017-01-01

Volcanic rootless cones are the products of thermohydraulic explosions involving rapid heat transfer from active lava (fuel) to external sources of water (coolant). Rootless eruptions are attributed to molten fuel-coolant interactions (MFCIs), but previous studies have not performed systematic investigations of rootless tephrostratigraphy and grain-size distributions to establish a baseline for evaluating relationships between environmental factors, MFCI efficiency, fragmentation, and patterns of tephra dispersal. This study examines a 13.55-m-thick vertical section through an archetypal rootless tephra sequence, which includes a rhythmic succession of 28 bed pairs. Each bed pair is interpreted to be the result of a discrete explosion cycle, with fine-grained basal material emplaced dominantly as tephra fall during an energetic opening phase, followed by the deposition of coarser-grained material mainly as ballistic ejecta during a weaker coda phase. Nine additional layers are interleaved throughout the stratigraphy and are interpreted to be dilute pyroclastic density current (PDC) deposits. Overall, the stratigraphy divides into four units: unit 1 contains the largest number of sediment-rich PDC deposits, units 2 and 3 are dominated by a rhythmic succession of bed pairs, and unit 4 includes welded layers. This pattern is consistent with a general decrease in MFCI efficiency due to the depletion of locally available coolant (i.e., groundwater or wet sediments). Changing conduit/vent geometries, mixing conditions, coolant and melt temperatures, and/or coolant impurities may also have affected MFCI efficiency, but the rhythmic nature of the bed pairs implies a periodic explosion process, which can be explained by temporary increases in the water-to-lava mass ratio during cycles of groundwater recharge.

Integrated Late Eocene-Oligocene Stratigraphy of the Alabama Coastal Plain: Correlation of Hiatuses and Stratal Surfaces to Glacioeustatic Lowerings

NASA Astrophysics Data System (ADS)

Miller, Kenneth G.; Thompson, Peter R.; Kent, Dennis V.

1993-04-01

We integrated strontium and oxygen isotopic, biostratigraphic, and magnetostratigraphic studies of two upper Eocene-Oligocene boreholes drilled near Bay Minette and St. Stephens Quarry (SSQ), Alabama. Continuous coring provided fresh, unweathered material for magnetostratigraphic studies, minimizing problems reported from nearby outcrops. Difficulties with each technique were encountered because of diagenesis, absence of marker fossils, and the presence of unconformities; however, by integrating results from isotopic stratigraphy, biostratigraphy, and magnetostratigraphy, we correlated these relatively shallow-water deposits to the geomagnetic polarity time scale (GPTS). At the SSQ borehole, the upper Eocene to lower Oligocene section is apparently complete within our stratigraphic resolution (0.2-0.5 m.y.), allowing us to estimate the ages of several stratal surfaces. Late Eocene Sr isotope age estimates are as expected at the SSQ borehole, but Oligocene ages are ˜1 m.y. older than expected due to diagenesis. At the Bay Minette borehole, a latest Eocene-earliest Oligocene and a late early Oligocene hiatus were detected. We correlate these two hiatuses and stratal surfaces at SSQ with global δ18O increases inferred to represent glacioeustatic lowerings and with evidence for hiatuses on other continental margins: (1) a distinct disconformity at the base of the Chickasawhay Limestone at both boreholes and a hiatus at Bay Minette correlates with a global δ18O increase; we revise the age of this surface (equivalent to the TB 1.1 sequence boundary) making it ˜2 m.y. older than previously reported; and (2) a surface at the top of the Shubuta Member (lowermost Oligocene) has been interpreted both as a condensed section and a disconformity; this surface at SSQ and a hiatus at Bay Minette correlate with a sharp global δ18O increase and with hiatuses on the New Jersey and Irish margins. The timing of the hiatuses and stratal surfaces correlates with the inflection of the δ18O increases and not with the maximum values, supporting models that indicate that unconformities form during the maximum rates of sea level fall.

The transtensional offshore portion of the northern San Andreas fault: Fault zone geometry, late Pleistocene to Holocene sediment deposition, shallow deformation patterns, and asymmetric basin growth

USGS Publications Warehouse

Beeson, Jeffrey W.; Johnson, Samuel Y.; Goldfinger, Chris

2017-01-01

We mapped an ~120 km offshore portion of the northern San Andreas fault (SAF) between Point Arena and Point Delgada using closely spaced seismic reflection profiles (1605 km), high-resolution multibeam bathymetry (~1600 km2), and marine magnetic data. This new data set documents SAF location and continuity, associated tectonic geomorphology, shallow stratigraphy, and deformation. Variable deformation patterns in the generally narrow (∼1 km wide) fault zone are largely associated with fault trend and with transtensional and transpressional fault bends.We divide this unique transtensional portion of the offshore SAF into six sections along and adjacent to the SAF based on fault trend, deformation styles, seismic stratigraphy, and seafloor bathymetry. In the southern region of the study area, the SAF includes a 10-km-long zone characterized by two active parallel fault strands. Slip transfer and long-term straightening of the fault trace in this zone are likely leading to transfer of a slice of the Pacific plate to the North American plate. The SAF in the northern region of the survey area passes through two sharp fault bends (∼9°, right stepping, and ∼8°, left stepping), resulting in both an asymmetric lazy Z–shape sedimentary basin (Noyo basin) and an uplifted rocky shoal (Tolo Bank). Seismic stratigraphic sequences and unconformities within the Noyo basin correlate with the previous 4 major Quaternary sea-level lowstands and record basin tilting of ∼0.6°/100 k.y. Migration of the basin depocenter indicates a lateral slip rate on the SAF of 10–19 mm/yr for the past 350 k.y.Data collected west of the SAF on the south flank of Cape Mendocino are inconsistent with the presence of an offshore fault strand that connects the SAF with the Mendocino Triple Junction. Instead, we suggest that the SAF previously mapped onshore at Point Delgada continues onshore northward and transitions to the King Range thrust.

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.

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.

Towards an Accurate Orbital Calibration of Late Miocene Climate Events: Insights From a High-Resolution Chemo- and Magnetostratigraphy (8-6 Ma) from Equatorial Pacific IODP Sites U1337 and U1338

NASA Astrophysics Data System (ADS)

Drury, A. J.; Westerhold, T.; Frederichs, T.; Wilkens, R.; Channell, J. E. T.; Evans, H. F.; Hodell, D. A.; John, C. M.; Lyle, M. W.; Roehl, U.; Tian, J.

2015-12-01

In the 8-6 Ma interval, the late Miocene is characterised by a long-term -0.3 ‰ reduction in benthic foraminiferal δ18O and distinctive short-term δ18O cycles, possibly related to dynamic Antarctic ice sheet variability. In addition, the late Miocene carbon isotope shift (LMCIS) marks a permanent long-term -1 ‰ shift in oceanic δ13CDIC, which is the largest, long-term perturbation in the global marine carbon cycle since the mid Miocene Monterey excursion. Accurate age control is crucial to investigate the origin of the δ18O cyclicity and determine the precise onset of the LMCIS. The current Geological Time Scale in the 8-6 Ma interval is constructed using astronomical tuning of sedimentary cycles in Mediterranean outcrops. However, outside of the Mediterranean, a comparable high-resolution chemo-, magneto-, and cyclostratigraphy at a single DSDP/ODP/IODP site does not exist. Generating an accurate astronomically-calibrated chemo- and magneto-stratigraphy in the 8-6 Ma interval became possible with retrieval of equatorial Pacific IODP Sites U1337 and U1338, as both sites have sedimentation rates ~2 cm/kyr, high biogenic carbonate content, and magnetic polarity stratigraphies. Here we present high-resolution correlation of Sites U1337 and U1338 using Milankovitch-related cycles in core images and X-ray fluorescence core scanning data. By combining inclination and declination data from ~400 new discrete samples with shipboard measurements, we are able to identify 14 polarity reversals at Site U1337 from the young end of Chron C3An.1n (~6.03 Ma) to the onset of Chron C4n.2n (~8.11 Ma). New high-resolution (<1.5 kyr) stable isotope records from Site U1337 correlate highly with Site U1338 records, enabling construction of a high-resolution stack. Initial orbital tuning of the U1337-U1338 records show that the δ18O cyclicity is obliquity driven, indicating high-latitude climate forcing. The LMCIS starts ~7.55 Ma and is anchored in Chron C4n.1n, which is comparable to the north and equatorial Atlantic.

77 FR 15395 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-Cooperative...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-15

... Production Act of 1993--Cooperative Research Group on Mechanical Stratigraphy and Natural Deformation in... Research Group on Mechanical Stratigraphy and Natural Deformation in Eagle Ford Formation and Equivalent... Eagle Ford's planned activity is to understand mechanical stratigraphy and natural deformation in Eagle...

Correlating Mediterranean shallow water deposits with global Oligocene–Miocene stratigraphy and oceanic events☆

PubMed Central

Reuter, Markus; Piller, Werner E.; Brandano, Marco; Harzhauser, Mathias

2013-01-01

Shallow-marine sediment records have the strong potential to display sensitive environmental changes in sedimentary geometries and skeletal content. However, the time resolution of most neritic carbonate records is not high enough to be compared with climatic events as recorded in the deep-sea sediment archives. In order to resolve the paleoceanographic and paleoclimatic changes during the Oligocene–Miocene transition in the Mediterranean shallow water carbonate systems with the best possible time resolution, we re-evaluated the Decontra section on the Maiella Platform (central Apennines, Italy), which acts as a reference for the correlation of Oligocene–Miocene shallow water deposits in the Mediterranean region. The 120-m-thick late Oligocene–late Miocene carbonate succession is composed of larger foraminiferal, bryozoan and corallinacean limestones interlayered with distinct planktonic foraminiferal carbonates representing a mostly outer neritic setting. Integrated multi-proxy and facies analyses indicate that CaCO3 and total organic carbon contents as well as gamma-ray display only local to regional processes on the carbonate platform and are not suited for stratigraphic correlation on a wider scale. In contrast, new biostratigraphic data correlate the Decontra stable carbon isotope record to the global deep-sea carbon isotope record. This links relative sea level fluctuations, which are reflected by facies and magnetic susceptibility changes, to third-order eustatic cycles. The new integrated bio-, chemo-, and sequence stratigraphic framework enables a more precise timing of environmental changes within the studied time interval and identifies Decontra as an important locality for correlating not only shallow and deep water sediments of the Mediterranean region but also on a global scale. PMID:25844021

Assessing the deep drilling potential of Lago de Tota, Colombia, with a seismic survey

NASA Astrophysics Data System (ADS)

Bird, B. W.; Wattrus, N. J.; Fonseca, H.; Velasco, F.; Escobar, J.

2015-12-01

Reconciling orbital-scale patterns of inter-hemispheric South American climate during the Quaternary requires continuous, high-resolution paleoclimate records that span multiple glacial cycles from both hemispheres. Southern Andean Quaternary climates are represented by multi-proxy results from Lake Titicaca (Peru-Bolivia) spanning the last 400 ka and by pending results from the Lago Junin Drilling Project (Peru). Although Northern Andean sediment records spanning the last few million years have been retrieved from the Bogota and Fúquene Basins in the Eastern Cordillera of the Colombian Andes, climatic reconstructions based on these cores have thus far been limited to pollen-based investigations. When viewed together with the Southern Hemisphere results, these records suggest an anti-phased hemispheric climatic response during glacial cycles. In order to better assess orbital-scale climate responses, however, independent temperature and hydroclimate proxies from the Northern Hemisphere are needed in addition to vegetation histories. As part of this objective, an effort is underway to develop a paleoclimate record from Lago de Tota (3030 m asl), the largest lake in Colombia and the third largest lake in the Andes. One of 17 highland tectonic basins in Eastern Cordillera, Lago de Tota formed during Tertiary uplift that deformed pre-foreland megasequences, synrift and back-arc megasequences. The precise age and thickness of sediments in the Lago de Tota basin has not previously been established. Here, we present results from a recent single-channel seismic reflection survey collected with a small (5 cubic inch) air gun and high-resolution CHIRP sub-bottom data. With these data, we examine the depositional history and sequence stratigraphy of Lago de Tota and assess its potential as a deep drilling target.

The Influence of Stratigraphic History on Landscape Evolution

NASA Astrophysics Data System (ADS)

Forte, A. M.; Yanites, B.; Whipple, K. X.

2016-12-01

Variation in rock erodibility can play a significant role in landscape evolution. Using a version of the CHILD landscape evolution model that allows for variations in rock erodibility, we found surprisingly complex landscape evolution in simulations with simple, two unit stratigraphies with contrasting erodibility. This work indicated that the stratigraphic order of units in terms of erodibility, the orientation of the contact with respect to the main drainage direction, and the contact dip angle all have pronounced effects on landscape evolution. Here we expand that work to explore the implications of more complicated stratigraphies on landscape evolution. Introducing multiple units adds additional controls on landscape evolution, namely the thicknesses and relative erodibility of rock layers. In models with a sequence of five alternating hard and soft units embedded within arbitrarily thick over- and underlying units, the number of individual layers that noticeably influence landscape morphology decreases as the thickness of individual layers reduces. Contacts with soft rocks over hard produce the most noticeable effect in model output such as erosion rate and channel steepness. For large contrasts in erodibility of 25 m thick layers, only one soft over hard contact is clearly manifest in the landscape. Between 50 and 75 m, two such contacts are manifest, and by 100 m thickness, all three of these contacts are manifest. However, for a given thickness of layers, more units are manifest in the landscape as the erodibility contrast between units decreases. This is true even though the magnitude of landscape effects away from steady-state erosion rates or channel steepness also decrease with decreasing erodibility contrast. Finally, we explore suites of models with alternating layers reflecting either `hardening-' or `softening-upwards' stratigraphies and find that the two scenarios result in decidedly different landscape forms. Hardening-upwards sections produce a gradational change where as individual layers have more influence in the landscape form in softening-upwards sections. Generally, our modeling highlights that past depositional history can exert a fundamental control on landscape evolution during later erosion through the resulting layered stratigraphy.

Stratigraphy and Folding in the Cenozoic Cover of a Fold-Thrust Belt in the Nallıhan Region (Ankara, Central Turkey)

NASA Astrophysics Data System (ADS)

Karaaǧaç, Serdal; Koral, Hayrettin

2017-04-01

This study investigates stratigraphy and structural features in the Cenozoic sedimentary sequence of the fold-thrust belt of the Nallıhan-Ankara region, located to the north of the İzmir-Ankara-Erzincan Suture Zone. Permian-Triassic age marble intercalated with schist-phyllites, the upper Jurassic-lower Cretaceous age limestone and the upper Cretaceous age sandstone-shale alternation compose the basement in the study area. These rocks are unconformably overlain by the Cenozoic age terrestrial sedimentary and volcanic units. The Cenozoic stratigraphy begins with the Paleocene-Eocene age coal-bearing, at times, volcanic intercalated conglomerate-sandstone-mudstone alternation of alluvial-fluvial origins (Aksaklar Formation) and the tuff intercalated with lacustrine limestone, bituminous limestone (Kabalar Formation). These units are conformably overlain by the Eocene age basalt-andesite and pyroclastic rocks (Meyildere volcanics). The Paleocene-Eocene aged units are unconformably overlain by the conglomerate-sandstone-mudstone-marl of a lower-middle Miocene lacustrine environment (Hançili Formation). The terrestrial conglomerate-sandstone alternation (Örencik Formation) is the youngest unit in the Cenozoic stratigraphy, and is assumed to be of Pliocene age based its stratigraphic position on older units. Field study shows existence of both folds and faults in the sedimentary cover. Stereographic projections of bedding measured in the field shows N25W/45NW and N60W/4SE-oriented fold axes in the Paleocene-Eocene age units. There are also N76W/12SE and N88E/8NE-oriented folds. The difference in fold-axis orientations suggests that some folds may have been rotated in blocks bound by faults during the post-Paleocene/Eocene period. Whereas, the lower-middle Miocene units manifest N88W/13SE-oriented fold axes. It is thus proposed that the observed difference in the azimuth of fold axes represent two different folding phases, one with NE-SW and the other with N-S directed axis of compression. Open folds with E-W orientation seem to be structural elements developed during the last phase of the deformation.

Revised stratigraphy and reinterpretation of the Miocene Pohang basinfill, SE Korea: sequence development in response to tectonism and eustasy in a back-arc basin margin

NASA Astrophysics Data System (ADS)

Sohn, Y. K.; Rhee, C. W.; Shon, H.

2001-09-01

The Miocene Pohang Basin is a pull-apart basin formed along the eastern continental margin of Korea (ECMK) during the back-arc opening of the East Sea (Sea of Japan). The basin is filled by more than 1 km thick, nonmarine to deep-marine strata. These strata show extreme vertical and lateral lithofacies changes and have caused decades-long controversies on their nature and stratigraphy. Previous sedimentological studies suggest that the basinfill was deposited by a series of contemporaneously developed depositional systems, including fan delta, prodelta, slope apron, and basin plain. Detailed mapping and magnetotelluric surveying show, however, that the basinfill is composed of several packages of strata (sequences) that are bounded by distinct and laterally persistent stratigraphic discontinuities (sequence boundaries). This suggests that the depositional systems in the Pohang Basin developed sequentially rather than contemporaneously. Six packages of strata are identified in the basin: a nonmarine to shallow marine (transgressive) sequence (Sequence 1), a Gilbert-type-delta conglomerate (Sequence 2), and alternations of submarine conglomerates and hemipelagic mudstones (Sequences 3-6). The conglomerates and hemipelagic mudstones of the latter four sequences are interpreted to represent lowstand depositional systems (slope apron, submarine fan, and high-gradient delta) and condensed intervals, respectively. Compilation of geochronologic, paleomagnetic, and biostratigraphic data suggests that Sequence 1 formed during the gradual subsidence of the ECMK prior to 17 Ma, whereas Sequence 2 formed in response to abrupt downfaulting of the Pohang Basin at about 17 Ma. Both sequences are interpreted to have developed in response to the early Miocene back-arc-opening tectonism of the East Sea. On the other hand, Sequences 3-6 formed between 17 and about 10.5 Ma. The Pohang Basin was subject to only minor tectonism during this period and could record global sea-level fluctuations. We suggest that the four alternations of conglomerates (lowstand systems) and hemipelagic mudstones (condensed intervals) resulted most probably from the 3rd-order glacioeustatic cycles during the middle Miocene. This finding implies that the signatures of global sea-level fluctuations can be deciphered from a tectonically active sedimentary basin if the timing of regional tectonic development is well constrained, and the global sea-level chart of Haq et al. ( Haq, B.W., Hardenbol, J., Vail, P.R., 1987, Chronology of fluctuating sea levels since the Triassic. Science 235, 1156-1167; Haq, B.U., Hardenbol, J., Vail, P.R., 1988. Mesozoic and Cenozoic chronostratigraphy and eustatic cycles. In: Wilgus, C.K., Hastings, B.S., Posamentier, H., Van Wagoner, J., Ross, C.A., Kendall, C.G.S.C. (Eds.), Sea-Level Changes: an Integrated Approach: Soc. Econ. Paleont. Mineral. Spec. Publ. 42, pp. 71-108) may serve as a guide to basinfill interpretation even in tectonically active sedimentary basins.

The seismic stratigraphy of Okanagan Lake, British Columbia; a record of rapid deglaciation in a deep 'fiord-lake' basin

NASA Astrophysics Data System (ADS)

Eyles, Nicholas; Mullins, Henry T.; Hine, Albert C.

1991-09-01

This paper presents the first detailed data regarding the newly discovered deep infill of Okanagan Lake. Okanagan Lake (50°00'N, 119°30'W) is 120 km long, ˜ 3-5 km wide and occupies a glacially overdeepened bedrock basin in the southern interior of British Columbia. This basin, and other elongate lakes of the region (e.g. Shuswap, Kootenay, Kalamalka, Canim and Mahood lakes), mark the site of westward flowing ice streams within successive Cordilleran ice sheets. An air gun seismic survey of Okanagan Lake shows that the bedrock floor is nearly 650 m below sea-level, more than 2000 m below the rim of the surrounding plateau. The maximum thickness of Pleistocene sediment in Okanagan Lake basin approaches 800 m. Forty-six seismic reflection traverses and an axial profile show a relatively simple stratigraphy composed of three seismic sequences argued to be no older than the last glacial cycle (< 30 ka). A discontinuous basal unit (sequence I) characterized by large-scale diffractions, and up to 460 m thick, infills the narrow, V-shaped bedrock floor of the basin and is interpreted as a boulder gravel deposited by subglacial meltwaters. Overlying seismic sequence II is composed of two sub-sequences. Sub-sequence IIa is a chaotic to massive facies up to 736 m thick. Lakeshore exposures close to where this unit reaches lake level show deformed and chaotically-bedded glaciolacustrine silts containing gravel lens and large ice-rafted boulders. The surface topography of this sub-sequence is irregular and in general mimics the form of the underlying bedrock as a result of compaction. This sequence passes laterally into stratified facies (sub-sequence IIb) at the northern end of the basin. Seismic sequence II appears to record rapid ice-proximal dumping of glaciolacustrine silt as the Okanagan glacier backwasted upvalley in a deep lake. A thin (60 m max.) laminated seismic sequence (III) drapes the hummocky surface of sequence II and represents postglacial sedimentation from fan-deltas. The extreme thickness of sequences I and II in Okanagan Lake reflects the focussing of large volumes of meltwater and sediment into the basin during deglaciation; pre-existing sediments that pre-date the last glacial cycle appear to have been completely eroded. Glaciological conditions during sedimentation may have been similar to marine-based outlet glaciers calving in deep water in fiord basins. In contrast to marine settings where ice bergs are free to disperse, large volumes of dead ice were trapped within the basin; structural evidence for sedimentation around dead ice blocks has been previously used to argue that the Cordilleran Ice Sheet downwasted in situ. We emphasize in contrast, the trapping of dead ice left behind by rapidly calving lake-based outlet glaciers.

A History of Repeated Failures: Stratigraphy of the Currituck and Cape Fear Slide Complexes on the Central U.S. Atlantic Margin

NASA Astrophysics Data System (ADS)

Hill, J. C.; Brothers, D. S.; Ten Brink, U. S.

2016-12-01

The Currituck and Cape Fear Slide complexes, offshore of North Carolina, are two of the largest (>150 km3) submarine slope failure provinces on the U.S. Atlantic margin. Detailed stratigraphy of these slides and the surrounding regions is derived from a combination of high-resolution sparker multichannel seismic (MCS) data collected by the USGS in 2012, airgun MCS collected as part of the NSF GeoPRISMs Community Seismic Experiment in 2014 & legacy industry airgun MCS data collected in 1970s and 80s. Both the Currituck and Cape Fear Slide complexes are located in regions with high sediment input that resulted in the development of a broad, low gradient (<6°) margin with thick slope sediment accumulation since at least the Miocene. Bedding parallel failure planes highlight the influence of subsurface stratigraphy here. Differential compaction across buried scarps and other erosional surfaces found in proximity to many of the headwalls may have contributed to excess pore pressure in these zones, setting the stage for repeated failures. Within the Currituck Slide complex, there appear to be several buried mass transport deposits (MTDs) within both the Quaternary and Pliocene sections that may be related to buried scarps found beneath both the upper and lower headwalls. At the Cape Fear Slide, the Quaternary section upslope of a large salt diapir displays evidence of possible downslope creep folding within strata that downlap onto a possible buried failure plane. While submarine slope failure along this portion of the margin has long been linked with hydrate dissociation and/or salt tectonics, features that are pervasive along the margin, our new stratigraphic analyses suggest that antecedent margin physiography and sediment loading may be critical factors in determining the locations of large-scale slope failures.

Mladotice Lake, Czechia: The unique genesis and evolution of the lake basin

NASA Astrophysics Data System (ADS)

Janský, Bohumír; Šobr, Miroslav; Kliment, Zdeněk; Chalupová, Dagmar

2016-04-01

The Mladotice Lake is a lake of unique genetic type in Czechia. In May 1872 a landslide as a result an extreme rainfall event occurred in western Czechia, blocking the Mladoticky stream valley and creating the Mladotice Lake. The 1952 and 1975 air images document that collective farming had a great impact on the lake basin evolution when balks and field terraces were removed and fields were made much larger. Because of this change in land use we expected higher soil erosion and a related increase in the sedimentation rate. First bathymetric measurements of the newly created lake were carried out in 1972 and were repeated in 1999, in 2003 and in 2014. Our analysis of the sedimentary record aims to identify the sediment stratigraphy, its basic physical and chemical properties, isotope content and thin sections yield a detailed temporal resolution of the sedimentation chronology. In some areas a sediment thickness of 4 m was detected. Hence, the average sedimentation rate is from 2.2 to 2.7 cm per year. KEY WORDS: Mladotice Lake - extreme rainfall event - landslide - land use changes - flood events - bathymetric measurements - sedimentation dynamics - stratigraphy and geochemistry of lake sediments - analyses of isotopes - sedimentation rates.

Applying foraminiferal stratigraphy as a biomarker for heavy metal contamination and mining impact in a fiord in West Greenland.

PubMed

Elberling, Bo; Knudsen, Karen Luise; Kristensen, Peter H; Asmund, Gert

2003-04-01

Sulphidic mine waste disposed in marine environments constitutes an environmental risk to aquatic life due to potential uptake and accumulation of heavy metals in biota. Fiord sediments near the former Black Angel Mine in West Greenland are contaminated by lead and zinc as a result of submarine tailings disposal in 1973-1990. In 1999 cores were taken up to 10 km away from the disposal area. Analyses include heavy metals, radiochemical dating (210Pb) and high-resolution foraminiferal stratigraphy. The mining operation resulted in significant changes in the assemblage composition. In addition, up to 20% of the Melonis barleeanus population found in sediment deposited during nearby tailings disposal was deformed compared to a natural background of less than 5%. Throughout cores representing the last 100 years of sedimentation, the total numbers and frequency of morphological abnormalities among M. barleeanus revealed some correlation with heavy metals concentrations (up to r2 = 79%). We conclude that abnormalities among foraminifera may represent a useful biomarker for evaluating trends in the biological impact resulting of submarine tailings disposal as well as long-term environmental impact and subsequent recovery.

Application of {sup 87}Sr/{sup 86}Sr, {delta}{sup 18}O and {delta}{sup 13}C Isotopes to diagenesis, correlation and connectivity of a fractured chalk reservoir, the Sidi El Kilani Field Tunisia

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

Mearns, E.W.; Mcbride, J.J.; Bramwell, M.

1995-08-01

Strontium Stratigraphy Analysis of the primary matrix chalk of the Abiod Formation reservoir in the Sidi El Kilani Field indicate a Campanian to Maastrichtian age (Upper Cretaceous). A resolution of {+-}1Ma has been achieved and results suggest that there are no major stratigraphic breaks in the studied sequences. Sr-O-C isotope data from early fracture-filling calcite cements suggest they may have formed by the redistribution of CaCO{sub 3} from underlying carbonate sequences and may have precipitated at temperatures in the region of 35-55{degrees}C. The {sup 87}Sr/{sup 86}Sr isotope ratios of formation waters determined by residual salt analysis (SrRSA) suggest that themore » chemical evolution of waters during reservoir filling was controlled by the influx of basinal waters as opposed to in situ water-rock interaction. Late, fracture-filling dolomite and barite cements have Sr-O-C isotope characteristics consistent with precipitation from these migrating basinal fluids at temperatures similar to current reservoir conditions (70-75{degrees}C). Sr RSA results suggest that the reservoir section in two of the wells may have been in direct lateral communication at the time of oil emplacement. These wells however are separated by a strike-slip fault. The SrRSA results therefore suggest that the fault is a partial barrier which has restricted pressure equilibration in the relatively short timescale of oil production, but which may have allowed homogenization of Sr isotope ratios in formation water.« less

Correlation between protein sequence similarity and x-ray diffraction quality in the protein data bank.

PubMed

Lu, Hui-Meng; Yin, Da-Chuan; Ye, Ya-Jing; Luo, Hui-Min; Geng, Li-Qiang; Li, Hai-Sheng; Guo, Wei-Hong; Shang, Peng

2009-01-01

As the most widely utilized technique to determine the 3-dimensional structure of protein molecules, X-ray crystallography can provide structure of the highest resolution among the developed techniques. The resolution obtained via X-ray crystallography is known to be influenced by many factors, such as the crystal quality, diffraction techniques, and X-ray sources, etc. In this paper, the authors found that the protein sequence could also be one of the factors. We extracted information of the resolution and the sequence of proteins from the Protein Data Bank (PDB), classified the proteins into different clusters according to the sequence similarity, and statistically analyzed the relationship between the sequence similarity and the best resolution obtained. The results showed that there was a pronounced correlation between the sequence similarity and the obtained resolution. These results indicate that protein structure itself is one variable that may affect resolution when X-ray crystallography is used.

Geologic map of the Grand Canyon 30' x 60' quadrangle, Coconino and Mohave Counties, northwestern Arizona

USGS Publications Warehouse

Billingsley, G.H.

2000-01-01

This digital map database, compiled from previously published and unpublished data as well as new mapping by the author, represents the general distribution of bedrock and surficial deposits in the map area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the Grand Canyon area. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:100,000 or smaller.

Shallow geology, sea-floor texture, and physiographic zones of Buzzards Bay, Massachusetts

USGS Publications Warehouse

Foster, David S.; Baldwin, Wayne E.; Barnhardt, Walter A.; Schwab, William C.; Ackerman, Seth D.; Andrews, Brian D.; Pendleton, Elizabeth A.

2015-01-07

Geologic, sediment texture, and physiographic zone maps characterize the sea floor of Buzzards Bay, Massachusetts. These maps were derived from interpretations of seismic-reflection profiles, high-resolution bathymetry, acoustic-backscatter intensity, bottom photographs, and surficial sediment samples. The interpretation of the seismic stratigraphy and mapping of glacial and Holocene marine units provided a foundation on which the surficial maps were created. This mapping is a result of a collaborative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to characterize the surface and subsurface geologic framework offshore of Massachusetts.

Bedrock geologic and structural map through the western Candor Colles region of Mars

USGS Publications Warehouse

Okubo, Chris H.

2014-01-01

The structure and geology of the layered deposits in the Candor Colles region corresponding to units Avfs, Avme, and Hvl of Witbeck and others (1991) are reevaluated in this 1:18,000-scale map. The objectives herein are to gather high-resolution structural measurements to (1) refine the previous unit boundaries in this area established by Witbeck and others (1991), (2) revise the local stratigraphy where necessary, (3) characterize bed forms to help constrain depositional processes, and (4) determine the styles and extent of deformation to better inform reconstructions of the local post-depositional geologic history.

Resolving the age of Wilson Creek Formation tephras and the Mono Lake excursion using high-resolution SIMS dating of allanite and zircon rims

NASA Astrophysics Data System (ADS)

Vazquez, J. A.; Lidzbarski, M. I.

2012-12-01

Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and interbedded rhyolitic tephras yield discordant 14C and 40Ar/39Ar results due to open-system effects, carbon reservoir uncertainties, as well as abundant xenocrysts entrained during eruption. Ion microprobe (SIMS) 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yields ages that effectively date eruption of key tephra beds and resolve age uncertainties about the Wilson Creek stratigraphy. To date the final several micrometers of crystal growth, individual allanite and zircon crystals were embedded in soft indium to allow sampling of unpolished rims. Isochron ages derived from rims on coexisting allanite and zircon (± glass) from hand-selected pumiceous pyroclasts delimit the timing of Wilson Creek sedimentation between Ashes 7 and 19 (numbering of Lajoie, 1968) to the interval between ca. 27 to ca. 62 ka. The interiors of individual allanite and zircon crystals sectioned in standard SIMS mounts yield model 238U-230Th ages that are mostly <10 k.y. older than their corresponding rim age, suggesting a relatively brief interval of allanite + zircon crystallization before eruption. A minority of allanite and zircon crystals yield rim and interior model ages of ca. 90-100 ka, and are likely to be antecrysts recycled from relatively early Mono Craters volcanism and/or intrusions. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields a rim isochron age of ca. 41 ka indicating that the recorded event is instead the Laschamp excursion. The results are consistent with a depositional chronology from correlation of relative paleointensity (Zimmerman et al., 2006) that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation. Moreover, the results demonstrate that high-spatial resolution SIMS dating of accessory mineral rims is an alternative and promising approach for resolving the depositional ages of silicic tephras containing minerals that crystallized over protracted intervals or that are plagued by incorporation of xenocrysts and/or antecrysts. References: Lajoie, K., 1968, PhD Dissertation, UC Berkeley; Zimmerman et al., 2006, EPSL 252: 94-106.

Sequence stratigraphy applied to the hydrocarbon productive basins of Western Indonesia

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

Courteney, S.

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

Climate oscillations reflected in the Arabian Sea subseafloor microbiome

NASA Astrophysics Data System (ADS)

Orsi, William; Coolen, Marco; He, Lijun; Wuchter, Cornelia; Irigoien, Xabier; Chust, Guillem; Johnson, Carl; Hemingway, Jordon; Lee, Mitchell; Galy, Valier; Giosan, Liviu

2016-04-01

Marine sediment contains a vast microbial biosphere that influences global biogeochemical cycles over geological timescales. However, the environmental factors controlling the stratigraphy of subseafloor microbial communities are poorly understood. We studied a sediment core directly underlying the Arabian Sea oxygen minimum zone (OMZ), which exhibits organic carbon rich sapropelic laminae deposited under low oxygen conditions. Consistent with several other cores from the same location, age dating revealed the sapropelic layers coincide with warm North Atlantic millennial-scale Dansgaard-Oeschger events, indicating a direct link between the strength of the OMZ and paleoclimate. A total of 214 samples spanning 13 m and 52 Kyr of deposition were selected for geochemical analyses and paleoclimate proxy measurements, as well as high-throughput metagenomic DNA sequencing of bacteria and archaea. A novel DNA extraction protocol was developed that allowed for direct (unamplified) metagenomic sequencing of DNA from each sample. This dataset represents the highest resolved sedimentary metagenomic sampling profile to date. Analysis of these data together with multiple paleoceanographic proxies show that millennial-scale paleoenvironmental conditions correlate with the metabolism and diversity of bacteria and archaea over the last glacial-interglacial cycle in the Arabian Sea. The metabolic potential for bacterial denitrification correlates with climate-driven OMZ strength and concomitant nitrogen stable isotope fractionation, whereas catabolic potential reflects changing marine organic matter sources across the Last Glacial Maximum. These results indicate that the subsisting microbial communities had been stratified to a large extent by paleoceanographic conditions at the time of deposition. Paleoenvironmental conditions should thus be considered as a mechanism that can help explain microbiome stratigraphy in marine sediment.

A tale of phenocrysts: trace element contents of boninites and forearc basalts from IODP Expedition 352

NASA Astrophysics Data System (ADS)

Chapman, T.; Clarke, G. L.; Reagan, M. K.; Sakuyama, T.; Godard, M.; Shervais, J. W.; Prytulak, J.; Shimizu, K.; Nelson, W. R.; Heaton, D. E.; Whattam, S. A.; Li, H.; Pearce, J. A.

2016-12-01

The Izu-Bonin Mariana (IBM) forearc represents an ideal location to study the dynamics of subduction initiation and to reveal the volcanic sequences appropriate to assess ophiolite origins. The volcanic stratigraphy recovered on Expedition 352 illustrates an abrupt shift from forearc basalt (FAB) to boninite magmatism, with limited transitional rock types, as observed from submersible and previous drill work in the Izu-Bonin and Mariana sections. The transition represents a change from decompression melting to fluxed melting of the mantle wedge. The volcanic stratigraphy has several distinct boninite chemical evolution trends (basaltic boninite, low- and high-silica boninite). Mineral assemblages and phenocryst trace element compositions vary throughout the volcanic sequence providing an opportunity to explore more completely boninite and FAB transitions and petrogenesis. FABs are characterised by early plagioclase crystallization and HREE enriched clinopyroxene with high Ti contents. Basaltic boninite and some low-silica boninite lavas have overlapping REE concentrations consistent with early plagioclase growth preceded by clinopyroxene. In contrast, textures and HREE depleted concentrations of clinopyroxene in high-silica boninite imply late plagioclase growth relative to olivine and orthopyroxene. Variations in mineral compositions and paragenesis in boninites reflect changes in magma compositions and a progressive depletion of mantle sources over time. This is illustrated via key incompatible and compatible trace element ratios and concentrations (e.g. Zr/Ti & V or Cr). The transition from FAB to low-Si boninite was subtle in terms of mineral modes, but was more evident in terms of the phase and lava compositions.

INTIMATE: Integration of Ice-core Marine and Terrestrial records

NASA Astrophysics Data System (ADS)

Turney, C. S. M.; Hoek, W. Z.; Intimate Group

2009-04-01

The principal aim of the INTIMATE Project is to synthesize high-resolution ice, terrestrial and marine records spanning the period 60,000 to 8000 years ago (henceforth given as 60-8 ka) to better understand the impact and mechanisms of rapid and extreme climate change, thereby reducing the uncertainty of future predictions. The specific objectives of the INTIMATE Project are to: • lead the development of highly-precise and accurate age-depth models in ice-core, marine, and terrestrial records (including identification and validation of time-stratigraphic marker horizons) over the period 60-8 ka; • promote the development of quantified climate reconstruction methods; • determine the timing, rates of change, spatial variability and climate gradients during key periods at the regional, hemispheric and global level (in collaboration with the INQUA-recognized Australasian INTIMATE Project and future regional INTIMATE projects); • determine the environmental impact of rapid and extreme climate changes in the North Atlantic region (focusing on megafauna and vegetation); and develop climate and environmental reconstructions of change that may be used in climate modeling to better determine the mechanisms of change and how signals are propagated globally. For correlation, precise dating of the records from the different realms is imperative. The development of an event-stratigraphy for the Last Glacial-Interglacial Transition (Björck et al., 1998) provided a template to compare other, independently dated, palaeoclimate records with the high-resolution Greenland oxygen isotope records. The event-stratigraphy has recently been refined and updated to the new NGRIP record using the GICC05 timescale (Lowe et al., 2008), which will be outlined in this paper. References: Björck, S., Walker, M.J.C., Cwynar, L.C., Johnsen, S., Knudsen, K.-L., Lowe, J.J., Wohlfarth, B. and INTIMATE members (1998) An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland ice-core record: a proposal by the INTIMATE group, Journal of Quaternary Science 13, 283-292. Lowe, J.J., Rasmussen, S.O., Björck, S., Hoek, W.Z., Steffensen, J.P., Walker, M.J.C., Yu, Z. and INTIMATE group (2008) Precise dating and correlation of events in the North Atlantic region during the Last Termination: a revised protocol recommended by the INTIMATE group. Quaternary Science Reviews, 27, 6-17.

Mars Stratigraphy Mission

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

From the valley floor to the peaks: Stratigraphy and landscape evolution of the Alpine Lateglacial in the Kitzbühel Alps (Tyrol, Austria)

NASA Astrophysics Data System (ADS)

Dippenaar, Elijah; Reitner, Jürgen

2017-04-01

Our understanding of Alpine landscape evolution and more specifically, chronology of glacier activity during the Alpine Lateglacial (ALG; c. 19 - 11.7 ka) i.e. the timespan between the Würmian Pleniglacial (= Alpine Last Glacial Maximum; AlpLGM) and the beginning of the Holocene, is based on the evidence of only few areas in the Alps. In order to get a better understanding of glaciation and palaeoclimate during this phase, N-S and E-W transects are needed. The Kitzbühel Alps, which are currently not glaciated, span an area of 1700km2 and have peaks that reach c. 2400m a.s.l. They lie at the center of the Eastern Alps on the northern rim, which is more humid than the relatively dry central parts. A modern geological investigation of the ALG record is missing in the Kitzbühel Alps. In order to overcome this gap of knowledge and to gain a more complete understanding of the ALG landscape development, a pioneering study has been performed in the area of Langer Grund Valley, a tributary valley of the Kelchsau Valley. This was done through detailed field mapping, thereby describing the shape and sediment composition of Quaternary morphological features, such as moraines, landslides and rock glacier deposits. Sedimentary evidence of one short glacial advance and two glacial stadials were identified. In chronological order they were named the: Frommbach advance, the Arnbach (glacier) halt and the Küharn halt. Where possible, palaeoglaciers were constructed using ArcGIS. With the palaeoglaciers, equlibrium line altitudes (ELA) were calculated and compared to ELA values of known glacial stadials in an attempt to correlate the relative local stratigraphy to the Lateglacial stratigraphy. Four methods to calculate ELAs were used; Maximum Elevation of Lateral Moraines (MELM), Toe to Headwall Altitude Ratio (THAR), Area x Altitude (AA) and Accumulation Area Ratio (AAR). Furthermore, the glacial sedimentary sequence of the study area was compared to that of the Gschnitz Valley (following the approach of Reitner et al. 2016). The result of which was that the glacial sedimentary sequences were very similar. Through the comparison of ELAs and sedimentary sequences, the Frommbach advance is correlated to the Phase of Ice-decay. Compared to the data of Reitner (2007) the Frommbach advance represents a second glacier advance in the Kelchsau Valley within this short-lasting phase around 19 ka. The Arnbach halt represents most likely the Gschnitz stadial (16-17 ka). The Küharn halt is correlated to the Younger Dryas-aged Egesen stadial (Younger Dryas; 12.8-11.7 ka). In addition, the relative timing of the activity of (nowadays relict) rock glaciers and of the onset of deep-seated gravitational slope deformations (DSGSDs) could be constrained based on the overlap of those features with the reconstructed glacial record. References: Reitner J.M., 2007: Glacial dynamics at the beginning of Termination I in the Eastern Alps and their stratigraphic implications. Quaternary International 164-165: 64-84. Reitner, J.M., Ivy-Ochs, S., Drescher-Schneider, R., Hajdas, I., Linner, M., 2016: Reconsidering the current stratigraphy of the Alpine Lateglacial: Implications of the sedimentary and morphological record of the Lienz area (Tyrol/Austria). E&G Quaternary Science Journal 65: 113-144.

Trace element and Sm Nd systematics of volcanic and intrusive rocks from the 3 Ga Lumby Lake Greenstone belt, Superior Province: evidence for Archean plume arc interaction

NASA Astrophysics Data System (ADS)

Hollings, Pete; Wyman, Derek

1999-02-01

The metavolcanic Lumby Lake belt comprises mafic tholeiites intercalated with thin felsic pyroclastic units. Al-undepleted komatiites are present towards the top of the stratigraphy. Identification of Al-depleted pyroclastic komatiites associated with chemical and siliciclastic sedimentary rocks indicates the upper portion of the 3 Ga Lumby Lake stratigraphy is directly comparable to a stratigraphic sequence developed on a paleoregolith in the nearby Steep Rock greenstone belt. The lower portion of the Lumby Lake sequence therefore represents a rarely preserved association of komatiite-tholeiite and calc alkaline volcanism developed prior to rifting episodes identified in ˜3 Ga terranes of the northern Superior Province. Al-undepleted komatiites are characterised by elevated MgO (18-24 wt.%) and Ni (600-1500 ppm) contents, in conjunction with variable LREE depletion (La/Sm n=0.5-0.8). Intercalated spinifex textured komatiitic basalts possess lower MgO (10-11 wt.%) and Ni (150-180 ppm) and flat to weakly enriched LREE (La/Sm n=0.9-1.1). Pyroclastic Al-depleted komatiites (Al 2O 3/TiO 2=4-5) are strongly LREE enriched (La/Yb n=6.7-10.5) with variable HFSE anomalies. Compositionally uniform tholeiites with variably depleted to enriched LREE (La/Sm n=0.8-1.2) and minor HFSE anomalies dominate the stratigraphy of the belt. A distinct subset of tholeiites, occurring towards the centre of the belt, is characterised by low Al 2O 3/TiO 2 ratios, LREE enrichment and the absence of HFSE anomalies. Minor intermediate (SiO 2=53-64 wt.%) volcanic rocks with pronounced REE fractionation (La/Yb n=0.8-1.1), high Al 2O 3/TiO 2 and Zr/Y ratios also occur throughout the belt. Two distinct subtypes of felsic pyroclastic rocks are recognised intercalated sporadically throughout the stratigraphy. Both types display pronounced LREE enrichment (La/Sm n=3.9-6.1) but Type 1 has strongly fractionated HREE patterns (Gd/Yb n=1.5-4.6) whereas, Type 2 HREE patterns are generally flat (Gd/Yb n=1.7-1.9). Intrusive counterparts to both subtypes have been identified within the Marmion Lake batholith to the south of the greenstone belt. The felsic subtypes may be derived from similar parental magmas by variable degrees of hornblende involvement during fractionation processes. Sm/Nd isotope systematics from a range of rock compositions have yielded ɛNd values of +2 to +5, typical of the range for Archean volcanic and intrusive rocks. Komatiite-tholeiite associations within Archean terranes are interpreted as the result of plume related magmatism likely in a geodynamic setting comparable to Phanerozoic oceanic plateaux. In contrast intermediate and felsic rocks are typical of calc alkaline suites generally attributed to Archean subduction related environments. The coeval eruption of the two magma suites in the Lumby Lake belt is best interpreted as the result of the sporadic subduction of plume-modified oceanic spreading centres over 10s of m.y. and the eventual impingement of a mantle plume upon an active subduction zone. This process can also account for the young age of basement material relative to overlying rift sequences in 3 Ga terranes of the Superior Province.

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.

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.

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.

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.

Preliminary stratigraphy and facies analysis of the Upper Cretaceous Kaguyak Formation, including a brief summary of newly discovered oil stain, upper Alaska Peninsula

USGS Publications Warehouse

Wartes, Marwan A.; Decker, Paul L.; Stanley, Richard G.; Herriott, Trystan M.; Helmold, Kenneth P.; Gillis, Robert J.

2013-01-01

The Alaska Division of Geological and Geophysical Surveys has an ongoing program aimed at evaluating the Mesozoic forearc stratigraphy, structure, and petroleum systems of lower Cook Inlet. Most of our field studies have focused on the Jurassic component of the petroleum system (this report). However, in late July and early August of 2012, we initiated a study of the stratigraphy and reservoir potential of the Upper Cretaceous Kaguyak Formation. The Kaguyak Formation is locally well exposed on the upper Alaska Peninsula (fig. 25) and was named by Keller and Reiser (1959) for a sequence of interbedded siltstone and sandstone of upper Campanian to Maastrichtian age that they estimated to be 1,450 m thick.Subsequent work by Detterman and Miller (1985) examined 900 m of section and interpreted the unit as the record of a prograding submarine fan.This interpretation of deep-water deposition contrasts with other Upper Cretaceous rocks exposed along the Alaska Peninsula and lower Cook Inlet that are generally described as nonmarine to shallow marine (Detterman and others, 1996; LePain and others, 2012).Based on foraminifera and palynomorphs from the COST No. 1 well, Magoon (1986) concluded that the Upper Cretaceous rocks were deposited in a variety of water depths and environments ranging from upper bathyal to nonmarine. During our recent fieldwork west and south of Fourpeaked Mountain, we similarly encountered markedly varying lithofacies in the Kaguyak Formation (fig. 25), and we also found oil-stained rocks that are consistent with the existence of an active petroleum system in Upper Cretaceous rocks on the upper Alaska Peninsula and in lower Cook Inlet. These field observations are summarized below.

Reconstructing the geomorphic history of Liang Bua, Flores, Indonesia: a stratigraphic interpretation of the occupational environment.

PubMed

Westaway, K E; Sutikna, T; Saptomo, W E; Jatmiko; Morwood, M J; Roberts, R G; Hobbs, D R

2009-11-01

Liang Bua, in Flores, Indonesia, was formed as a subterranean chamber over 600ka. From this time to the present, a series of geomorphic events influenced the structure of the cave and cave deposits, creating a complex stratigraphy. Within these deposits, nine main sedimentary units have been identified. The stratigraphic relationships between these units provide the evidence needed to reconstruct the geomorphic history of the cave. This history was dominated by water action, including slope wash processes, channel formation, pooling of water, and flowstone precipitation, which created waterfalls, cut-and-fill stratigraphy, large pools of water, and extensive flowstone cappings. The reconstructed sequence of events over the last 190k.yr. has been summarized by a series of time slices that demonstrate the nature of the occupational environment in Liang Bua. The earliest artifacts at the site, dated to approximately 190ka, testify to hominin presence in the area, but the reconstructions suggest that occupation of the cave itself may not have been possible until after approximately 100ka. At approximately 95ka, channel erosion of a basal unit, which displays evidence of deposition in a pond environment, created a greater relief on the cave floor, and formed remanent areas of higher ground that later became a focus for hominin occupation from 74-61ka by the west wall and in the center of the cave, and from approximately 18-17ka by the east wall. These zones have been identified according to the sloping nature of the stratigraphy and the distribution of artifacts, and their locations have implications for the archaeological interpretation of the site.

Stratigraphy of the Descartes region /Apollo 16/ - Implications for the origin of samples

NASA Technical Reports Server (NTRS)

Head, J. W.

1974-01-01

Analysis of terrain in the Apollo 16 Descartes landing region shows a series of features that form a stratigraphic sequence which dominates the history and petrogenesis at the site. An ancient 150-km diam crater centered on the Apollo 16 site is one of the earliest recognizable major structures. Nectaris ejecta was concentrated in a regional low at the base of the back slope of the Nectaris basin to form the Descartes Mountains. Subsequently, a 60-km diam crater formed in the Descartes Mountains centered about 25 km to the west of the site. This crater dominates the geology and petrogenetic history of the site. Stone and Smoky Mountains represent the degraded terraced crater walls, and the dark matrix breccias and metaclastic rocks derived from North and South Ray craters represent floor fallback breccias from this cratering event. The interpretation is developed that the stratigraphy of the Cayley and Descartes, and thus the historical record of the Apollo 16 region, documents the complex interaction of deposits and morphology of local and regional impact cratering events. Large local 60- to 150-km diam craters have had a dramatic and previously unrecognized effect on the history and petrology of the Apollo 16 site.

Morphology, stratigraphy, and surface roughness properties of Venusian lava flow fields

NASA Astrophysics Data System (ADS)

Byrnes, Jeffrey M.; Crown, David A.

2002-10-01

Morphologic characteristics, flow stratigraphy, and radar backscatter properties of five lava flow fields on Venus (Turgmam Fluctus, Zipaltonal Fluctus, Tuli Mons/Uilata Fluctus, Var Mons, and Mylitta Fluctus) were examined to understand flow field emplacement mechanisms and relationships to other surface processes. These analyses indicate that the flow fields studied developed through emplacement of numerous, thin flow units, presumably over extended periods of time. Although the Venusian fields display flow morphologies similar to those observed within terrestrial flow fields, the Venusian flow units are significantly larger and have a larger range of radar backscatter coefficients. Both simple and compound flow emplacement appear to have occurred within the flow fields. A potential correlation between flow rheology and radar brightness is suggested by differences in planform morphology, apparent flow thickness, and apparent sensitivity to topography between bright and dark flows. Distributary flow morphologies may result from tube-fed flows, and postemplacement modification by processes such as flow inflation and crustal foundering is consistent with discrete zones of increased radar brightness within individual flow lobes. Mapping of these flow fields does not indicate any simple evolutionary trend in eruptive/resurfacing style within the flow fields, or any consistent temporal sequence relative to other tectonic and volcanic features.

In vitro resolution of the dimer bridge of the minute virus of mice (MVM) genome supports the modified rolling hairpin model for MVM replication.

PubMed

Liu, Q; Yong, C B; Astell, C R

1994-06-01

Previous characterization of the terminal sequences of the minute virus of mice (MVM) genome demonstrated that the right hand palindrome contains two sequences, each the inverted complement of the other. However, the left hand palindrome was shown to exist as a unique sequence [Astell et al., J. Virol. 54: 179-185 (1985)]. The modified rolling hairpin (MRH) model for MVM replication provided an explanation of how the right hand palindrome could undergo hairpin transfer to generate two sequences, while the left end palindrome within the dimer bridge could undergo asymmetric resolution and retain the unique left end sequence. This report describes in vitro resolution of the wild-type dimer bridge sequence of MVM using recombinant (baculovirus) expressed NS-1 and a replication extract from LA9 cells. The resolution products are consistent with those predicted by the MRH model, providing support for this replication mechanism. In addition, mutant dimer bridge clones were constructed and used in the resolution assay. The mutant structures included removal of the asymmetry in the hairpin stem, inversion of the sequence at the initiating nick site, and a 2-bp deletion within one stem of the dimer bridge. In all cases, the mutant dimer bridge structures are resolved; however, the resolution pattern observed with the mutant dimer bridge compared with the wild-type dimer bridge is shifted toward symmetrical resolution. These results suggest that sequences within the left hand hairpin (and hence dimer bridge sequence) are responsible for asymmetric resolution and conservation of the unique sequence within the left hand palindrome of the MVM genome.

Curiosity's Mars Hand Lens Imager (MAHLI) Investigation

USGS Publications Warehouse

Edgett, Kenneth S.; Yingst, R. Aileen; Ravine, Michael A.; Caplinger, Michael A.; Maki, Justin N.; Ghaemi, F. Tony; Schaffner, Jacob A.; Bell, James F.; Edwards, Laurence J.; Herkenhoff, Kenneth E.; Heydari, Ezat; Kah, Linda C.; Lemmon, Mark T.; Minitti, Michelle E.; Olson, Timothy S.; Parker, Timothy J.; Rowland, Scott K.; Schieber, Juergen; Sullivan, Robert J.; Sumner, Dawn Y.; Thomas, Peter C.; Jensen, Elsa H.; Simmonds, John J.; Sengstacken, Aaron J.; Wilson, Reg G.; Goetz, Walter

2012-01-01

The Mars Science Laboratory (MSL) Mars Hand Lens Imager (MAHLI) investigation will use a 2-megapixel color camera with a focusable macro lens aboard the rover, Curiosity, to investigate the stratigraphy and grain-scale texture, structure, mineralogy, and morphology of geologic materials in northwestern Gale crater. Of particular interest is the stratigraphic record of a ?5 km thick layered rock sequence exposed on the slopes of Aeolis Mons (also known as Mount Sharp). The instrument consists of three parts, a camera head mounted on the turret at the end of a robotic arm, an electronics and data storage assembly located inside the rover body, and a calibration target mounted on the robotic arm shoulder azimuth actuator housing. MAHLI can acquire in-focus images at working distances from ?2.1 cm to infinity. At the minimum working distance, image pixel scale is ?14 μm per pixel and very coarse silt grains can be resolved. At the working distance of the Mars Exploration Rover Microscopic Imager cameras aboard Spirit and Opportunity, MAHLI?s resolution is comparable at ?30 μm per pixel. Onboard capabilities include autofocus, auto-exposure, sub-framing, video imaging, Bayer pattern color interpolation, lossy and lossless compression, focus merging of up to 8 focus stack images, white light and longwave ultraviolet (365 nm) illumination of nearby subjects, and 8 gigabytes of non-volatile memory data storage.

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.

Geologic map and map database of the Palo Alto 30' x 60' quadrangle, California

USGS Publications Warehouse

Brabb, E.E.; Jones, D.L.; Graymer, R.W.

2000-01-01

This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (pamf.ps, pamf.pdf, pamf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller.

Geologic map and map database of western Sonoma, northernmost Marin, and southernmost Mendocino counties, California

USGS Publications Warehouse

Blake, M.C.; Graymer, R.W.; Stamski, R.E.

2002-01-01

This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (wsomf.ps, wsomf.pdf, wsomf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller.

Strategic Analysis for the MER Cape Verde Approach

NASA Technical Reports Server (NTRS)

Gaines, Daniel; Belluta, Paolo; Herman, Jennifer; Hwang, Pauline; Mukai, Ryan; Porter, Dan; Jones, Byron; Wood, Eric; Grotzinger, John; Edgar, Lauren;

New insights into Holocene eruption episodes from proximal deposit sequences at Mt. Taranaki (Egmont), New Zealand

NASA Astrophysics Data System (ADS)

Torres-Orozco, Rafael; Cronin, Shane J.; Pardo, Natalia; Palmer, Alan S.

2017-01-01

Upper stratovolcano flanks contain the most nuanced depositional record of long eruption episodes, but steep, irregular terrain makes these sequences difficult to correlate and interpret. This necessitates development of a detailed and systematic approach to describing localized depositional facies and relating these to eruptive processes. In this work, the late-Holocene eruption history of Mt. Taranaki/Egmont, New Zealand, was re-assessed based on a study of proximal deposits spanning the 14C-dated age range of 5.0-0.3 cal ka B.P. Mt. Taranaki is a textbook-example stratovolcano, with geological evidence pointing to sudden switches in scale, type and frequency of eruptions over its 130 ka history. The proximal stratigraphy presented here almost doubles the number of eruptions recognized from previous soil-stratigraphy studies. A total of 53 lithostratigraphic bed-sets record eruptions of the summit crater and parasitic vents like Fanthams Peak (the latter between 3.0 and 1.5 cal ka B.P.). At least 12 of the eruptions represented by these bed-sets comprise deposits comparable with or thicker than those of the latest sub-Plinian eruption of AD 1655. The largest eruption episode represented is the 4.6-4.7-cal ka B.P. Kokowai. Contrasting eruption styles were identified, from stable basaltic-andesite eruption columns at Fanthams Peak, to andesitic lava-dome extrusion, blasts and partial collapse of unstable eruption columns at Mt. Taranaki's summit. The centemetre-scale proximal deposit descriptions were used to identify several previously unknown, smaller eruption events. These details are indispensable for building a comprehensive probabilistic event record and in the development of realistic eruptive scenarios for complex eruption episodes prior to re-awakening of a volcano.

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.

Subsurface control on seafloor erosional processes offshore of the Chandeleur Islands, Louisiana

NASA Astrophysics Data System (ADS)

Twichell, David; Pendleton, Elizabeth; Baldwin, Wayne; Flocks, James

2009-12-01

The Chandeleur Islands lie on the eastern side of the modern Mississippi River delta plain, near the edge of the St. Bernard Delta complex. Since abandonment approximately 2,000 years b.p., this delta complex has undergone subsidence and ravinement as the shoreline has transgressed across it. High-resolution seismic-reflection, sidescan-sonar, and bathymetry data show that seafloor erosion is influenced by locally variable shallow stratigraphy. The data reveal two general populations of shallow erosional depressions, either linear or subcircular in shape. Linear depressions occur primarily where sandy distributary-channel deposits are exposed on the seafloor. The subcircular pits are concentrated in areas where delta-front deposits crop out, and occasional seismic blanking indicates that gas is present. The difference in erosional patterns suggests that delta-front and distributary-channel deposits respond uniquely to wave and current energy expended on the inner shelf, particularly during stormy periods. Linear depressions may be the result of the sandy distributary-channel deposits eroding more readily by waves and coastal currents than the surrounding delta-front deposits. Pits may develop as gas discharge or liquefaction occurs within fine-grained delta-front deposits, causing seafloor collapse. These detailed observations suggest that ravinement of this inner shelf surface may be ongoing, is controlled by the underlying stratigraphy, and has varied morphologic expression.

Subsurface control on seafloor erosional processes offshore of the Chandeleur Islands, Louisiana

USGS Publications Warehouse

Twichell, David; Pendleton, Elizabeth A.; Baldwin, Wayne E.; Flocks, James G.

2009-01-01

The Chandeleur Islands lie on the eastern side of the modern Mississippi River delta plain, near the edge of the St. Bernard Delta complex. Since abandonment approximately 2,000 years b.p., this delta complex has undergone subsidence and ravinement as the shoreline has transgressed across it. High-resolution seismic-reflection, sidescan-sonar, and bathymetry data show that seafloor erosion is influenced by locally variable shallow stratigraphy. The data reveal two general populations of shallow erosional depressions, either linear or subcircular in shape. Linear depressions occur primarily where sandy distributary-channel deposits are exposed on the seafloor. The subcircular pits are concentrated in areas where delta-front deposits crop out, and occasional seismic blanking indicates that gas is present. The difference in erosional patterns suggests that delta-front and distributary-channel deposits respond uniquely to wave and current energy expended on the inner shelf, particularly during stormy periods. Linear depressions may be the result of the sandy distributary-channel deposits eroding more readily by waves and coastal currents than the surrounding delta-front deposits. Pits may develop as gas discharge or liquefaction occurs within fine-grained delta-front deposits, causing seafloor collapse. These detailed observations suggest that ravinement of this inner shelf surface may be ongoing, is controlled by the underlying stratigraphy, and has varied morphologic expression.

A 20,000-year record of environmental change from Laguna Kollpa Kkota, Bolivia

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

Seltzer, G.O.; Abbott, M.B.

Most records of paleoclimate in the Bolivian Andes date from the last glacial-to-interglacial transition. However, Laguna Kollpa Kkota and other lakes like it, formed more than 20,000 yr BP when glaciers retreated and moraines dammed the drainage of the valleys they are located in. These lakes were protected from subsequent periods of glaciation because the headwalls of these valleys are below the level of the late-Pleistocene glacial equilibrium-line altitude. The chemical, mineral, and microfossil stratigraphies of these glacial lakes provide continuous records of environmental change for the last 20,000 years that can be used to address several problems in paleoclimatemore » specific to tropical-subtropical latitudes. Preliminary results from Laguna Kollpa Kkota indicate that glacial equilibrium-line altitudes were never depressed more than 600 m during the last 20,000 years, suggesting that temperatures were reduced only a few-degrees celsius over this time period. Sedimentation rates and the organic carbon stratigraphy of cores reflect an increase in moisture in the late Pleistocene just prior to the transition to a warmer and drier Holocene. The pollen and diatom concentrations in the sediments are sufficient to permit the high resolution analyses needed to address whether or not there were climatic reversals during the glacial-to-interglacial transition.« less

High-resolution sub-bottom seismic and sediment core records from the Chukchi Abyssal Plain reveal Quaternary glaciation impacts on the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Joe, Y. J.; Seokhoon, Y.; Nam, S. I.; Polyak, L.; Niessen, F.

2017-12-01

For regional context of the Quaternary history of Arctic marine glaciations, such as glacial events in northern North America and on the Siberian and Chukchi margins, we used CHIRP sub-bottom profiles (SBP) along with sediment cores, including a 14-m long piston core ARA06-04JPC taken from the Chukchi abyssal plain during the RV Araon expedition in 2015. Based on core correlation with earlier developed Arctic Ocean stratigraphies using distribution of various sedimentary proxies, core 04JPC is estimated to extend to at least Marine Isotope Stage 13 (>0.5 Ma). The stratigraphy developed for SBP lines from the Chukchi abyssal plain to surrounding slopes can be divided into four major seismostratigraphic units (SSU 1-4). SBP records from the abyssal plain show well preserved stratification, whereas on the surrounding slopes this pattern is disrupted by lens-shaped, acoustically transparent sedimentary bodies interpreted as glaciogenic debris flow deposits. Based on the integration of sediment physical property and SBP data, we conclude that these debris flows were generated during several ice-sheet grounding events on the Chukchi and East Siberian margins, including adjacent ridges and plateaus, during the middle to late Quaternary.

Rover mounted ground penetrating radar as a tool for investigating the near-surface of Mars and beyong

NASA Technical Reports Server (NTRS)

Grant, J. A.; Schultz, P. H.

1993-01-01

In spite of the highly successful nature of recent planetary missions to the terrestrial planets and outer satellites a number of questions concerning the evolution of their surfaces remain unresolved. For example, knowledge of many characteristics of the stratigraphy and soils comprising the near-surface on Mars remains largely unknown, but is crucial in order to accurately define the history of surface processes and near-surface sedimentary record. Similar statements can be made regarding our understanding of near-surface stratigraphy and processes on other extraterrestrial planetary bodies. Ground penetrating radar (GPR) is a proven and standard instrument capable of imaging the subsurface at high resolution to 10's of meters depth in a variety of terrestrial environments. Moreover, GPR is portable and easily modified for rover deployment. Data collected with a rover mounted GPR could resolve a number of issues related to planetary surface evolution by defining shallow stratigraphic records and would provide context for interpreting results of other surface analyses (e.g. elemental or mineralogical). A discussion of existing GPR capabilities is followed first by examples of how GPR might be used to better define surface evolution on Mars and then by a brief description of possible GPR applications to the Moon and other planetary surfaces.

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

NASA Astrophysics Data System (ADS)

Stephens, Mark

1994-05-01

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

An 84-kyr paleomagnetic record from the sediments of Lake Baikal, Siberia

USGS Publications Warehouse

Peck, J.A.; King, J.W.; Colman, Steven M.; Kravchinsky, V.A.

1996-01-01

We have conducted a paleomagnetic study of sediment cores obtained from the Selenga prodelta region of Lake Baikal, Russia. This record, which spans approximately the last 84 kyr, contributes to a better understanding of the nature of geomagnetic field behavior in Siberia and is a useful correlation and dating tool. We demonstrate that the Lake Baikal sediments are recording variations in the geomagnetic field. The directional record displays secular variation behavior with a geomagnetic excursion at 20 ka and additional excursions appearing as large-amplitude secular variation at 41, 61, and 67 ka. Smoothing of the geomagnetic excursion behavior occurs in Lake Baikal sediments owing to the intermediate sedimentation rate (13 cm kyr-1). The Lake Baikal relative paleointensity record correlates to absolute paleointensity data for the last 10 kyr and to relative paleointensity records from the Mediterranean Sea and Indian Ocean for the last 84 kyr. This correlation suggests a strong global (i.e., dipole) component to these records and further supports the reliability of sediments as recorders of relative geomagnetic paleointensity. We show that a relative geomagnetic intensity stratigraphy has a potential resolution of 7 kyr by correlating continental and marine records. The geomagnetic intensity stratigraphy helps constrain the age of the difficult to date Lake Baikal sediments.

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).

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.

The stratigraphy of the southern Pab Range, Pakistan

NASA Astrophysics Data System (ADS)

White, H. J.

The Cretaceous strata exposed in the southern Pab Range, southeast Baluchistan, Pakistan is investigated. It records the precollision deposition history of the Indo-Pakistani continental shelf. The strata comprise two depositional successions, namely, The Early to Late Cretaceous Sembar-Goru-Parh sequence and the Maestrichtian Mughal Kot-Pab sequence. The former began with deposition of black shales on the continental slope (Sembar Formation), succeeded by calcareous shale, marl and micstone of outer shelf origin (Goru Formation), and ended with inner shelf platform carbonates (Parh Limestone). These deep to shallow water lithofacies prograted westward over the continental shelf of the north-advancing Subcontinent. The Mughal Kot-Pab propagation contains the first significant influx of terrigenous sand reaching the western portion of the continental shelf. Deposition environments in the Mughal Kot Formation include inner shelf, prodelta, delta front and distributary channel. A thick succession of shoreface cycles comprises the Pab sandstone.

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

Episodic Sediment Failure in Northern Flemish Pass, Eastern Canadian Margin: Interplay of Seismicity, Contour Current Winnowing, and Excess Pore Pressures

NASA Astrophysics Data System (ADS)

Piper, D.

2015-12-01

Episodic sediment failures are recognised on continental slopes around Flemish Pass and Orphan Basin from multibeam bathymetry, seismic reflection profiles and piston cores. Seismic stratigraphy is tied to published long cores with O-isotope data back to before MIS 6 and carbonate rich Heinrich layers in places produce marker reflections in high-resolution sparker profiles. Heinrich layers, radiocarbon dates and peaks in diatom abundance provide core chronology. Slope sedimentation was strongly influenced by the Labrador Current and the silty muds show architecture characteristic of contourites. Variation in Labrador Current strength is known from the sortable silt proxy over the past 125 ka. Large slope failures were mapped from seismic reflection profiles and their age estimated from seismic stratigraphy (3-5 ka resolution) and in some cases refined from cores (1-3 ka resolution). Large slope failures occurred apparently synchronously over margin lengths of 50-350 km. Such failures were earthquake triggered: other mechanisms for producing laterally extensive synchronous failure do not apply. Triaxial shear measurements show a Su/σ' ratio of typical slope sediment of 0.48, implying considerable stability. However, some silty muds have Atterberg limits that suggest susceptibility to liquefaction under cyclic loading, particularly in Holocene deposits and by analogy those of past full interglacials. Basal failure planes of some large failures correspond with either the last interglacial or the MIS 6 glacial maximum. Comparison with seismological models suggests that the observed slope failures represent earthquakes ranging from Mw ~5.6 to ~7.6. Mean recurrence interval of M = 7 earthquakes at any point on the margin is estimated at 30 ka from seismological models and 40 ka from the sediment failure record. In northern Flemish Pass, a spatial cluster of several failures over 30 ka preceded by a long interval with no failures suggests that some other mechanism has preconditioned the slope for earthquake triggering. There is circumstantial evidence that such preconditioning is related to excess pore pressures, released by fluid drainage at head scarps.

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.

Comparison of Dixon Sequences for Estimation of Percent Breast Fibroglandular Tissue

PubMed Central

Ledger, Araminta E. W.; Scurr, Erica D.; Hughes, Julie; Macdonald, Alison; Wallace, Toni; Thomas, Karen; Wilson, Robin; Leach, Martin O.; Schmidt, Maria A.

2016-01-01

Objectives To evaluate sources of error in the Magnetic Resonance Imaging (MRI) measurement of percent fibroglandular tissue (%FGT) using two-point Dixon sequences for fat-water separation. Methods Ten female volunteers (median age: 31 yrs, range: 23–50 yrs) gave informed consent following Research Ethics Committee approval. Each volunteer was scanned twice following repositioning to enable an estimation of measurement repeatability from high-resolution gradient-echo (GRE) proton-density (PD)-weighted Dixon sequences. Differences in measures of %FGT attributable to resolution, T1 weighting and sequence type were assessed by comparison of this Dixon sequence with low-resolution GRE PD-weighted Dixon data, and against gradient-echo (GRE) or spin-echo (SE) based T1-weighted Dixon datasets, respectively. Results %FGT measurement from high-resolution PD-weighted Dixon sequences had a coefficient of repeatability of ±4.3%. There was no significant difference in %FGT between high-resolution and low-resolution PD-weighted data. Values of %FGT from GRE and SE T1-weighted data were strongly correlated with that derived from PD-weighted data (r = 0.995 and 0.96, respectively). However, both sequences exhibited higher mean %FGT by 2.9% (p < 0.0001) and 12.6% (p < 0.0001), respectively, in comparison with PD-weighted data; the increase in %FGT from the SE T1-weighted sequence was significantly larger at lower breast densities. Conclusion Although measurement of %FGT at low resolution is feasible, T1 weighting and sequence type impact on the accuracy of Dixon-based %FGT measurements; Dixon MRI protocols for %FGT measurement should be carefully considered, particularly for longitudinal or multi-centre studies. PMID:27011312

Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

NASA Technical Reports Server (NTRS)

Goudge, T. A.; Mohrig, D.; Cardenas, B. T.; Hughes, C. M.; Fassett, C. I.

2017-01-01

The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

NASA Astrophysics Data System (ADS)

Gouramanis, Chris; Switzer, Adam D.; Jankaew, Kruawun; Bristow, Charles S.; Pham, Dat T.; Ildefonso, Sorvigenaleon R.

2017-03-01

The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.

High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand

PubMed Central

Gouramanis, Chris; Switzer, Adam D.; Jankaew, Kruawun; Bristow, Charles S.; Pham, Dat T.; Ildefonso, Sorvigenaleon R.

2017-01-01

The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past. PMID:28276445

Volcanic Chemostratigraphy on the Outcrop Using Field-Portable X-Ray Fluorescence: An Example from the Basaltic Flows of Hewitt's Cove, MA.

NASA Astrophysics Data System (ADS)

Wall, A. M.; Brabander, D. J.

2005-05-01

The area of Hewitt's Cove, Hingham, Massachusetts structurally represents the southern extent of the Boston Basin, and as such, provides the opportunity to identify and recognize basin-wide events. While the stratigraphy of the Boston Basin has been developed since the advent of U-Pb geochronology and formal stratigraphic facies descriptions (Socci and Smith, 2001), the stratigraphy of the Hewitt's Cove area has not been thoroughly addressed since the work of William O. Crosby in 1894 (Billings, 1976, Bailey and Bland, 2001). Hewitt's Cove consists of an andesitic basaltic flow, approximately 150 m thick, overlain by siltstone and conglomeratic sequences. Field-Portable X-Ray Fluorescence (FP-XRF) was used on fresh and weathered surfaces on the outcrop and in hand samples, and these analyses were compared with conventional laboratory XRF analyses. The in situ field-based analyses produced a reproducible chemostratigraphy that is consistent with subsequent laboratory-based analyses. These data suggest that the series of andesitic basalt flows at Hewitt's Cove are the result of compositionally different magmatic pulses. Additional analyses must be completed to determine the extent of these pulses and the extent of variation in this area before further conclusions can be made. This study particularly demonstrates the utility of using FP-XRF in igneous geologic applications.

High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand.

PubMed

Gouramanis, Chris; Switzer, Adam D; Jankaew, Kruawun; Bristow, Charles S; Pham, Dat T; Ildefonso, Sorvigenaleon R

2017-03-09

The 26 th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.

Integrating palaeoenvironmental and climate cyclicities - Optimizing the stratigraphic framework in the non-marine Lower Cretaceous

NASA Astrophysics Data System (ADS)

Sames, Benjamin

2015-04-01

Studies on changing paleoenvironments and climate cycles in non-marine archives of the Cretaceous greenhouse earth are hitherto rare, primarily a result of the lack of high-resolution stratigraphy and correlations to the marine record. On the other hand, recent refinements of the geological time scale have made major advances for the Cretaceous to yield a resolution comparable to that of younger Earth history. In the Cretaceous marine record is now possible to correlate and date short-term sea-level records and their possible relation to climate and/or tectonic events with appropriate resolution. Correlation in the non-marine realm ('continental' aquatic) has long been fraught with considerable problems and limitations, especially on supraregional (i.e., inter-basinal) to global scales, thus often hampering serious attempts at dating and chronological linking of events documented by the respective deposits - let alone appropriate correlation to marine successions. A new interdisciplinary project and multi-proxy study funded by the Austrian Science Fund (FWF) uses the Lower Cretaceous European record (English Wealden) as a test site for the integration of ostracod biostratigraphy and assemblage changes, and cyclostratigraphy (orbitally/climate driven cycles). Ostracods (microcrustaceans with a calcified shell) are the most useful biostratigraphical and palaeoenvironmental tool in Lower Cretaceous non-marine sequences. During the past two decades, research progress in late Mesozoic non-marine ostracods led to their extended applicability, whereas their wide dispersal ability has become a key conside-ration in their supraregional (inter-basinal to global) biostratigraphical utility. The integrative methodology applied in this project, targets the correlation of the ostracod faunal composition change with the variation of geochemical and sedimentological parameters through time and inferences on controlling (palaeoenvironmental) factors and their regulating mechanisms ('climate changes', orbital cycles?). The approach is multiple: 1) Biostratigraphy in the supraregional to global context, 2) cyclostratigraphy using ostracods, lithologic parameters and sediment geochemistry, 3) stable isotope geochemistry, and 4) magnetostratigraphy for chronological control. The methods used, evaluated and optimized within the scope of this project can then be efficiently applied on larger scopes and to larger datasets towards a better linking of marine and non-marine Cretaceous successions, enhancement of resolution in the considerable (particularly Lower) Cretaceous non-marine record, and integration of these data into the Cretaceous timescale.

3D Model of the San Emidio Geothermal Area

DOE Data Explorer

James E. Faulds

2013-12-31

The San Emidio geothermal system is characterized by a left-step in a west-dipping normal fault system that bounds the western side of the Lake Range. The 3D geologic model consists of 5 geologic units and 55 faults. Overlying Jurrassic-Triassic metasedimentary basement is a ~500 m-1000 m thick section of the Miocene lower Pyramid sequence, pre- syn-extensional Quaternary sedimentary rocks and post-extensional Quaternary rocks. 15-30º eastward dip of the stratigraphy is controlled by the predominant west-dipping fault set. Both geothermal production and injection are concentrated north of the step over in an area of closely spaced west dipping normal faults.

High resolution carbon isotope stratigraphy and glendonite occurrences of the Christopher Formation, Sverdrup Basin (Axel Heiberg Island, Canada): implications for mid Cretaceous high latitude climate change

NASA Astrophysics Data System (ADS)

Herrle, Jens O.; Schröder-Adams, Claudia J.; Galloway, Jennifer M.; Pugh, Adam T.

2013-04-01

Understanding the evolution of Canada's Arctic region, as a crucial component of Earth's climate system, is fundamental to assess short and long-term climate, environmental, and paleogeographic change. However, the stratigraphy and paleoenvironmental evolution of the Cretaceous Arctic is poorly constrained and a detailed bio- and chemostratigraphic correlation of major mid-Cretaceous paleoceanographic turning points such as Oceanic Anoxic Events, cold snaps, and biotic turnovers with key locations of the high- and low latitudes is missing. Here we present for the first time a high resolution bio- and carbon isotope stratigraphy of the Arctic Albian Christopher Formation of the Sverdrup Basin at Glacier Fiord in the southern part of Axel Heiberg Island, Canadian High Arctic. By using these techniques we developed a high temporal framework to record major environmental changes as it is indicated by the occurrence of glendonites and sandstone intervals of our studied Albian succession. The Albian Christopher Formation is a shale dominated marine unit with a thickness of approximately 1200 m. Several transgressive/ regressive cycles can be recognized by prograding shoreface units that break up mudrock deposition. In addition, glendonites are mainly found in the lower part of the Christopher Formation. Glendonites are pseudomorphs of calcite, after the metastable mineral ikaite, and have been often described from high latitude Permian, Jurassic and Cretaceous marine environments from the Canadian Arctic, Spitsbergen and Australia. The formation of glendonites takes place in the uppermost layer of the sediment and requires near-freezing temperatures, high salinity, and orthophosphate-rich bottom water. Although the presence of glendonites implies a range of paleoenvironmental conditions there is a consensus in the scientific literature that they reflect cooler paleoenvironmental conditions. Preliminary bio- and carbon isotope stratigraphic results suggest that the glendonites are concentrated in regular beds during the late Aptian to early Albian of the Christopher Formation supporting the idea of a cold snap (Kemper, 1987; Herrle & Mutterlose 2003; Mutterlose et al. 2009) within the mid-Cretaceous greenhouse period. References Herrle, J.O., Mutterlose, J., 2003. Calcareous nannofossils from the Aptian - early Albian of SE France: Paleoecological and biostratigraphic implications. Cretaceous Research 24, 1-22. Kemper, E., 1987. Das Klima der Kreide-Zeit. Geologisches Jahrbuch 96, 185 pp. Mutterlose, J., Bornemann, A., Herrle, J.O., 2009. The Aptian - Albian cold snap: Evidence for "mid" Cretaceous icehouse interludes. Neues Jahrbuch für Geologie und Palaeontologie, Abhandlungen 252, 217-225.

[Usefulness of stratigraphy and computerized tomography in the initial staging of osteosarcoma of the extremities. Retrospective study of 217 cases].

PubMed

Pelotti, P; Ciminari, R; Bacci, G; Avella, M; Briccoli, A

1988-01-01

The value of stratigraphy and pulmonary CT in the initial work-up of osteosarcoma of the extremities is assessed with reference to 217 patients encountered in the Bone Tumour Centre of Rizzoli Orthopaedic Institute in May 1983-May 1986. Stratigraphy revealed lung metastases not identified by standard radiography in 4 patients (1.8%), while CT revealed metastases not identified by either standard X-rays or stratigraphy in a further 6 cases (2.7%). It is concluded that the increase in the percentage of cures (about 30%) reported in the last 10 years in osteosarcoma cases given adjuvant chemotherapy cannot be explained by any difference in initial selection due to the use of these techniques that were not adopted in the historical series.

Lower shoreface seismic stratigraphy and morphology off Fire Island, New York: Evidence for lobate progradation and linear erosion

NASA Astrophysics Data System (ADS)

Liu, Shihao; Goff, John A.

2018-07-01

Under rising sea level conditions, barrier islands are largely ephemeral features, eroded on the seaward side by the transgressing shoreline and reformed by overwash to a more landward position. Locally, however, and over shorter time scales, shorelines can either advance or retreat, even in an overall transgressive environment, and the stratigraphy and morphology of the shoreface can be significantly impacted by the evolution of shoreface-attached bedforms. Fire Island, New York, is a well-studied example of such variability, with a stable-to-accreting shoreline at the western end and a retreating shoreline on the eastern end. In this study, we seek to better understand these differences by investigating the lower-shoreface stratigraphy at both stable/accreting (Fire Island West, or FIW) and retreating (Fire Island East, or FIE) shorefaces, using ultra-high resolution chirp seismic reflection data. Within the barrier/marine sands (the seismic unit between seafloor and shoreface ravinement), we identify six seismic units (WSUs 1-6 from bottom to top) in the FIW survey and two units (ESU1 and ESU2 from bottom to top) in the FIE survey; these units constitute the modern lower shoreface wedge. The barrier shoreface in the FIW survey is dominated by discrete and spatially-confined lobes. Isopach maps indicate that the lobe shifting was an episodic process with westward-migrating depocenters. The prograding shoreface was constructed by this lobate deposition; we speculate that these are related to ebb deposition from ephemeral barrier breaches/inlets. In the FIE survey, ESU2 accounts for the majority accumulation of the barrier shoreface and it is more linear than the lobate structure observed within the FIW survey, possibly derived from eroded shoreface sediments. Portions of this unit are absent however, exposing lower Pleistocene units to the erosive forces.

SAR Tomography for Terrestrial Snow Stratigraphy

NASA Astrophysics Data System (ADS)

Lei, Y.; Xu, X.; Baldi, C.; Bleser, J. W. D.; Yueh, S. H.; Elder, K.

2017-12-01

Traditional microwave observation of snowpack includes brightness temperature and backscatter. The single baseline configuration and loss of phase information hinders the retrieval of snow stratigraphy information from microwave observations. In this paper, we are investigating the tomography of polarimetric SAR to measure snow stratigraphy. In the past two years, we have developed a homodyne frequency modulated continuous wave radar (FMCW), operation at three earth exploration satellite bands within the X-band and Ku-band spectrums (centered at 9.6 GHz, 13.5 GHz, and 17.2 GHz) at Jet Propulsion Laboratory. The transceiver is mounted to a dual-axis planar scanner (60cm in each direction), which translates the antenna beams across the target area creating a tomographic baseline in two directions. Dual-antenna architecture was implemented to improve the isolation between the transmitter and receiver. This technique offers a 50 dB improvement in signal-to-noise ratio versus conventional single-antenna FMCW radar systems. With current setting, we could have around 30cm vertical resolution. The system was deployed on a ground based tower at the Fraser Experimental Forest (FEF) Headquarters, near Fraser, CO, USA (39.847°N, 105.912°W) from February 1 to April 30, 2017 and run continuously with some gaps for required optional supports. FEF is a 93-km2 research watershed in the heart of the central Rocky Mountains approximately 80-km West of Denver. During the campaign, in situ measurements of snow depth and other snowpack properties were performed every week for comparison with the remotely sensed data. A network of soil moisture sensors, time-lapse cameras, acoustic depth sensors, laser depth sensor and meteorological instruments was installed next to the site to collect in situ measurements of snow, weather, and soil conditions. Preliminary tomographic processing of ground based SAR data of snowpack at X- and Ku- band has revealed the presence of multiple layers within the snowpack and clear melting/refrozen cycle, which is consistant with the in-situ measurement.

Coastal Geomorphology, Growth Patterns and Stratigraphy of Uplifted Coral-Reef Terraces of Sumba Island, Indonesia: Towards a Re-Evaluation of Quaternary Sea-Level Highstands

NASA Astrophysics Data System (ADS)

Rigaud, S.; Leclerc, F.; Abidin, H. Z.; Bijaksana, S.; Chiang, H. W.; Ginting Munthe, F. A.; Liu, X.; Meilano, I.; Pradipta, G. C.; Ramdhani, B. D.; Tapponnier, P.; Wang, X.

2016-12-01

The island of Sumba (Indonesia) is uniquely located within the Sunda-Banda forearc, at the transition between oceanic subduction and arc-continent collision, and has experienced vertical movements for the last 7 Myrs (Fortuin et al., 1997). The spectacular flights of coral-reef terraces exposed on the northern coast have served as benchmarks to reconstruct Quaternary sea-level highstands (stages 5 to 23). Sea-level paleo-elevations were established using reef crests and marine notches as geomorphological markers, assuming a constant uplift rate of 0.49 mm/yr and neglecting erosion and weathering processes (Pirazzoli et al., 1991, 1993). Recent and fossil coral reefs of the northern coast of Sumba Island are fringing, leeward reefs. A new examination of the morphology and stratigraphy of fossil terraces shows that they are primarily built by prograding complexes formed during forced regressions. The current geomorphological expression of reef crests, therefore, does not correspond to the highest position of past sea-levels. The same is true for marine notches, which may only indicate intermediary still-stand phases and are barely distinguishable from weathering surfaces in terraces older than stages 5-7. In our study, we use the elevation of the inner edges of coral terraces as indicators of the highest position of the sea-level during Quaternary highstands. At the island scale, our geomorphological investigations, U/Th dating and high-resolution correlations point to high discrepancies in the deformation patterns, especially at Cape Laundi where the position of past sea-level highstands was established. Through a multi-disciplinary study involving geomorphology, stratigraphy, tectonic, sedimentology, paleontology and geochronology, we offer new estimates for uplift rates at the island scale and re-evaluate the elevation of past sea-level highstands. References : Fortuin et al. 1997. Journal of Asian Earth Sciences 15, p. 61-88. Pirazzoli et al. 1991. Science 252, p. 1834-1836. Pirazzoli et al. 1993. Marine Geology 109, p. 221-236.

Holocene sedimentation and coastal wetlands response to rising sea level at the Aucilla river mouth, a low energy coast in the Big Bend area of Florida

USGS Publications Warehouse

Garrett, Connie; Hertler, Heidi; Hoenstine, Ronald; Highley, Brad

1993-01-01

The shallow dip of the Florida carbonate platform results in low wave energy on Florida ???Big Bend??? coasts. Therefore sedimentation is dominated by river-and tidal-hydrodynamics near the Aucilla River mouth. Where present, Holocene sediments are thin and unconformably overlie Oligocene-aged Suwannee Limestone. The oldest unlithified sediments include reworked carbonate rubble with clay and wood fragments (seven thousand years old or less, based on wood radio-carbon dating). Although this basal sequence is observed in most areas, the sediments that overlie it vary. Sediment sequences from the outer littoral to submarine environments include organic-rich sands, oyster biotherm remains, and cleaner sands with organic-filled burrows. Inner littoral (salt-marsh) sequences generally consist of sandy, fining-upwards sequences in which dry weights of fine-grained clastics and organic components increase up-sequence at similar rates. Offshore sediments preserve greatly attenuated fluvial and salt-marsh facies, if these facies are preserved at all. With sea-level rise, erosion can result from insufficient sediment supply and down-cutting by tidal currents (Dolotov, 1992; and Dalrymple et al., 1992). Dolotov (1992) attributes displacement of original coastal stratigraphy to insufficient sediments for beach profile maintenance, while Dalrymple et al. (1992) attribute erosional truncation (ravinement) or complete removal of portions of typical estuarine sequences to headward migration of tidal channels.

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

The Oligo-Miocene of Eil (NE Somalia): a prograding coral- Lepidocyclina system

NASA Astrophysics Data System (ADS)

Bosellini, A.; Russo, A.; Arush, M. A.; Cabdulqadir, M. M.

The Oligo-Miocene succession of Eil is the product of a depositional regression and constitutes a 120-150 m thick depositional sequence that prograded seaward for at least 20-25 km. Its time-transgressive stratigraphy is documented physically by well exposed tangential clinoforms (previously considered as evidence of a tectonic coastal flexure) and biostratigraphically by the occurrence of calcareous nannoplankton, planktonic and benthonic foraminifera, and a rich coral fauna. The upper boundary of the sequence is indicated by a reefal toplap, which constitutes the flat surface of the Nogal Plateau. Age (Chattian to Burdigalian) and toplap relationships of the sequence indicate clearly that progradation took place after the Late Oligocene flooding which followed the strong fall of sea-level during the Chattian. Because of the horizontal geometry of the entire sedimentary system, it has been possible to make a clear environmental reconstruction and a facies model with original water depths. A worldwide Tertiary facies—the Lepidocyclina beds— was confined to the front of the reef, at depths ranging from 35-40 to 120-130 m.

The stratigraphy of Mars

NASA Technical Reports Server (NTRS)

Tanaka, Kenneth L.

1986-01-01

A global stratigraphy of Mars was developed from a global geologic map series derived from Viking images; the stratigraphy is composed of three maps. A new chronostratigraphic classification system which consists of lower, middle, and upper Noachian, Hesperian, and Amazonian systems is described. The crater-density boundaries of the chronostratigraphic units and the absolute ages of the Martian epochs aer estimated. The relative ages of major geologic units and featues are calculated and analyzed. The geologic history of Mars is summarized on the maps in terms of epochs.

Two distinct origins for Archean greenstone belts

NASA Astrophysics Data System (ADS)

Smithies, R. Hugh; Ivanic, Tim J.; Lowrey, Jack R.; Morris, Paul A.; Barnes, Stephen J.; Wyche, Stephen; Lu, Yong-Jun

2018-04-01

Applying the Th/Yb-Nb/Yb plot of Pearce (2008) to the well-studied Archean greenstone sequences of Western Australia shows that individual volcanic sequences evolved through one of two distinct processes reflecting different modes of crust-mantle interaction. In the Yilgarn Craton, the volcanic stratigraphy of the 2.99-2.71 Ga Youanmi Terrane mainly evolved through processes leading to Th/Yb-Nb/Yb trends with a narrow range of Th/Nb ('constant-Th/Nb' greenstones). In contrast, the 2.71-2.66 Ga volcanic stratigraphy of the Eastern Goldfields Superterrane evolved through processes leading to Th/Yb-Nb/Yb trends showing a continuous range in Th/Nb ('variable-Th/Nb' greenstones). Greenstone sequences of the Pilbara Craton show a similar evolution, with constant-Th/Nb greenstone evolution between 3.13 and 2.95 Ga and variable-Th/Nb greenstone evolution between 3.49 and 3.23 Ga and between 2.77 and 2.68 Ga. The variable-Th/Nb trends dominate greenstone sequences in Australia and worldwide, and are temporally associated with peaks in granite magmatism, which promoted crustal preservation. The increasing Th/Nb in basalts correlates with decreasing εNd, reflecting variable amounts of crustal assimilation during emplacement of mantle-derived magmas. These greenstones are typically accompanied in the early stages by komatiite, and can probably be linked to mantle plume activity. Thus, regions such as the Eastern Goldfields Superterrane simply developed as plume-related rifts over existing granite-greenstone crust - in this case the Youanmi Terrane. Their Th/Nb trends are difficult to reconcile with modern-style subduction processes. The constant-Th/Nb trends may reflect derivation from a mantle source already with a high and constant Th/Nb ratio. This, and a lithological association including boninite-like lavas, basalts, and calc-alkaline andesites, all within a narrow Th/Nb range, resembles compositions typical of modern-style subduction settings. These greenstones are very rare, and were probably only preserved when fortuitously stabilised by granitic magmatism related to the evolution of later variable-Th/Nb greenstones. The rarity of constant-Th/Nb trends suggests that either processes forming them never dominated Archean greenstone evolution, or that such greenstones simply were rarely preserved. Metamorphic mobility of Th renders the Th/Yb-Nb/Yb plot inappropriate for interpreting Eoarchean greenstone units worldwide. Nevertheless, such sequences appear dominated by volcanic rocks that, in modern settings, reflect only the embryonic or initiation stages of subduction. They probably record subduction failure rather than anything resembling modern-style subduction.

A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy

NASA Astrophysics Data System (ADS)

Rasmussen, Sune O.; Bigler, Matthias; Blockley, Simon P.; Blunier, Thomas; Buchardt, Susanne L.; Clausen, Henrik B.; Cvijanovic, Ivana; Dahl-Jensen, Dorthe; Johnsen, Sigfus J.; Fischer, Hubertus; Gkinis, Vasileios; Guillevic, Myriam; Hoek, Wim Z.; Lowe, J. John; Pedro, Joel B.; Popp, Trevor; Seierstad, Inger K.; Steffensen, Jørgen Peder; Svensson, Anders M.; Vallelonga, Paul; Vinther, Bo M.; Walker, Mike J. C.; Wheatley, Joe J.; Winstrup, Mai

2014-12-01

Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial-Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard-Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard-Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations.

Stratigraphy -- The Fall of Continuity.

ERIC Educational Resources Information Center

Byers, Charles W.

1982-01-01

Reviews advances in stratigraphy as illustrated in the current geological literature, discussing discontinuity and how the recognition of discontinuity in the stratigraphic record is changing views of Superposition and Original Lateral Continuity. (Author/JN)

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

Eridania Basin: An ancient paleolake floor as the next landing site for the Mars 2020 rover

NASA Astrophysics Data System (ADS)

Pajola, Maurizio; Rossato, Sandro; Carter, John; Baratti, Emanuele; Pozzobon, Riccardo; Erculiani, Marco Sergio; Coradini, Marcello; McBride, Karen

2016-09-01

The search for traces of past Martian life is directly connected to ancient paleolakes, where ponding water or low-energy water fluxes were present for long time intervals. The Eridania paleolakes system, located along the 180° meridian, is one of the largest lacustrine environments that were once present on Mars. Morphological features suggest that it was constituted by connected depressions filled by water to maximum depths of ∼2400 m and a volume of at least 562,000 km3. We focused our attention on the northern side of the Eridania Basin, where high-albedo, uneven patches of material characterized by the absence of dust are present. Based on OMEGA and CRISM orbital imaging spectroscopy data, a large clay-bearing unit has been identified there. In particular, a set of aqueous minerals in present in the stratigraphy, being visible through erosional windows in the first several tens of meters of the sedimentary sequence. Below this capping unit, a thin Al-rich clay stratum attributable to Al-smectite and/or kaolins is present. This overlies a Fe-rich clay stratum, attributable to the nontronite smectite. At the base of the mineralogic sequence a stratum that could be either a zeolite or more likely a hydrated sulfate is present. In addition, small deposits of alunite (a rare phase on Mars), and jarosite are here found at several locations. Such stratigraphy is interpreted as originating from a surface weathering process similar to terrestrial abiotic pedogenesis; nonetheless, possible exobiologic processes can be also invoked to explain it. NASA's Spirit rover landed on Gusev crater in 2004, near the mouth of the Ma'adim Vallis, which connects this crater with the considered paleolakes system. The Eridania site provides the unique opportunity to complete the measurements obtained in Gusev crater, while investigating the exposed mineralogical sequence in its depositionary setting. In addition, the extremely favorable landing parameters, such as elevation, slope, roughness, rock distribution, thermal inertia and dust coverage, support this location as a possible landing site for the NASA Mars 2020 rover.

The Cretaceous-Tertiary boundary interval in Badlands National Park, South Dakota

USGS Publications Warehouse

Stoffer, Philip W.; Messina, Paula; Chamberlain, John A.; Terry, Dennis O.

2001-01-01

A marine K-T boundary interval has been identified throughout the Badlands National Park region of South Dakota. Data from marine sediments suggest that deposits from two asteroid impacts (one close, one far away) may be preserved in the Badlands. These impact-generated deposits may represent late Maestrichtian events or possibly the terminal K-T event. Interpretation is supported by paleontological correlation, sequence stratigraphy, magnetostratigraphy, and strontium isotope geochronology. This research is founded on nearly a decade of NPS approved field work in Badlands National Park and a foundation of previously published data and interpretations. The K-T boundary occurs within or near the base of a stratigraphic interval referred to as the "Interior Zone." We interpret the stratigraphy of the Interior Zone as a series of distinct, recognizable lithologic members and units from oldest to youngest, an upper weathered interval of the Elk Butte Member of the Pierre Shale (early late Maestrichtian), a complete (albeit condensed) interval of Fox Hill Formation, a pedogenically altered K-T Boundary "Disturbed Zone," and a generally unresolved sequence of marine to marginal marine units ranging in age from possibly latest Maestrichtian to late Paleocene (the "Yellow Mounds"), that underlie a basal red clay unit (the late Eocene overbank channel facies of the Chamberlain Pass Formation at the base of the White River Group). Within this sequence is a series of unconformities that all display some degree of subaerial weathering and erosion. The dating of marine fossils above and below these unconformities are in line with generally accepted global sea-level changes recognized for the late Campanian through early Eocene. Within the greater framework of regional geology, these findings support that the Western Interior Seaway and subsequent Cannonball Seaway were dependently linked to the changing base-level controlled by sea-level of the global ocean through the Gulf of Mexico and possibly the Arctic Ocean. The variation of facies preserved in Late Cretaceous strata in the Badlands National Park area were in part controlled by local or regional tectonic blocks that were either rising or sinking contemporaneous with deposition.

Publications - GMC 305 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 305 Publication Details Title: Fluid inclusion stratigraphy (FIS) data for the following Reference Middleton, 2002, Fluid inclusion stratigraphy (FIS) data for the following exploratory oil/gas

Yucatan Subsurface Stratigraphy from Geophysical Data, Well Logs and Core Analyses in the Chicxulub Impact Crater and Implications for Target Heterogeneities

NASA Astrophysics Data System (ADS)

Canales, I.; Fucugauchi, J. U.; Perez-Cruz, L. L.; Camargo, A. Z.; Perez-Cruz, G.

2011-12-01

Asymmetries in the geophysical signature of Chicxulub crater are being evaluated to investigate on effects of impact angle and trajectory and pre-existing target structural controls for final crater form. Early studies interpreted asymmetries in the gravity anomaly in the offshore sector to propose oblique either northwest- and northeast-directed trajectories. An oblique impact was correlated to the global ejecta distribution and enhanced environmental disturbance. In contrast, recent studies using marine seismic data and computer modeling have shown that crater asymmetries correlate with pre-existing undulations of the Cretaceous continental shelf, suggesting a structural control of target heterogeneities. Documentation of Yucatan subsurface stratigraphy has been limited by lack of outcrops of pre-Paleogene rocks. The extensive cover of platform carbonate rocks has not been affected by faulting or deformation and with no rivers cutting the carbonates, information comes mainly from the drilling programs and geophysical surveys. Here we revisit the subsurface stratigraphy in the crater area from the well log data and cores retrieved in the drilling projects and marine seismic reflection profiles. Other source of information being exploited comes from the impact breccias, which contain a sampling of disrupted target sequences, including crystalline basement and Mesozoic sediments. We analyze gravity and seismic data from the various exploration surveys, including multiple Pemex profiles in the platform and the Chicxulub experiments. Analyses of well log data and seismic profiles identify contacts for Lower Cretaceous, Cretaceous/Jurassic and K/Pg boundaries. Results show that the Cretaceous continental shelf was shallower on the south and southwest than on the east, with emerged areas in Quintana Roo and Belize. Mesozoic and upper Paleozoic sediments show variable thickness, possibly reflecting the crystalline basement regional structure. Paleozoic and Precambrian basement outcrops are located farther to the southeast in Belize and northern Guatemala. Inferred shelf paleo-bathymetry supports existence of a sedimentary basin extending to the northeast, where crater rim and terrace zones are subdued in the seismic images.

A Subsurface Soil Composition and Physical Properties Experiment to Address Mars Regolith Stratigraphy

NASA Technical Reports Server (NTRS)

Richter, L.; Sims, M.; Economou, T.; Stoker, C.; Wright, I.; Tokano, T.

2004-01-01

Previous in-situ measurements of soil-like materials on the surface of Mars, in particular during the on-going Mars Exploration Rover missions, have shown complex relationships between composition, exposure to the surface environment, texture, and local rocks. In particular, a diversity in both compositional and physical properties could be established that is interpreted to be diagnostic of the complex geologic history of the martian surface layer. Physical and chemical properties vary laterally and vertically, providing insight into the composition of rocks from which soils derive, and environmental conditions that led to soil formation. They are central to understanding whether habitable environments existed on Mars in the distant past. An instrument the Mole for Soil Compositional Studies and Sampling (MOCSS) - is proposed to allow repeated access to subsurface regolith on Mars to depths of up to 1.5 meters for in-situ measurements of elemental composition and of physical and thermophysical properties, as well as for subsurface sample acquisition. MOCSS is based on the compact PLUTO (PLanetary Underground TOol) Mole system developed for the Beagle 2 lander and incorporates a small X-ray fluorescence spectrometer within the Mole which is a new development. Overall MOCSS mass is approximately 1.4 kilograms. Taken together, the MOCSS science data support to decipher the geologic history at the landing site as compositional and textural stratigraphy if they exist - can be detected at a number of places if the MOCSS were accommodated on a rover such as MSL. Based on uncovered stratigraphy, the regional sequence of depositional and erosional styles can be constrained which has an impact on understanding the ancient history of the Martian near-surface layer, considering estimates of Mars soil production rates of 0.5... 1.0 meters per billion years on the one hand and Mole subsurface access capability of approximately 1.5 meters. An overview of the MOCSS, XRS instrument accomodation and the impact that these instruments have on Mars science is discussed.

Strategic analysis for the MER Cape Verde approach

USGS Publications Warehouse

Gaines, D.; Belluta, P.; Herman, J.; Hwang, P.; Mukai, R.; Porter, D.; Jones, B.; Wood, E.; Grotzinger, J.; Edgar, L.; Hayes, A.; Hare, T.; Squyres, S.

2009-01-01

The Mars Exploration Rover Opportunity has recently completed a two year campaign studying Victoria Crater. The campaign culminated in a close approach of Cape Verde in order to acquire high resolution imagery of the exposed stratigraphy in the cliff face. The close approach to Cape Verde provided significant challenges for every subsystem of the rover as the rover needed to traverse difficult, uncharacterised terrain and approach a cliff face with the potential of blocking out solar energy and communications with Earth. In this paper we describe the strategic analyses performed by the science and engineering teams so that we could successfully achieve the science objectives while keeping the rover safe. ??2009 IEEE.

Shallow geology, sea-floor texture, and physiographic zones of Vineyard and western Nantucket Sounds, Massachusetts

USGS Publications Warehouse

Baldwin, Wayne E.; Foster, David S.; Pendleton, Elizabeth A.; Barnhardt, Walter A.; Schwab, William C.; Andrews, Brian D.; Ackerman, Seth D.

2016-09-02

Geologic, sediment texture, and physiographic zone maps characterize the sea floor of Vineyard and western Nantucket Sounds, Massachusetts. These maps were derived from interpretations of seismic-reflection profiles, high-resolution bathymetry, acoustic-backscatter intensity, bottom photographs/video, and surficial sediment samples collected within the 494-square-kilometer study area. Interpretations of seismic stratigraphy and mapping of glacial and Holocene marine units provided a foundation on which the surficial maps were created. This mapping is a result of a collaborative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to characterize the surface and subsurface geologic framework offshore of Massachusetts.

Evidence for an unorthodox firing sequence employed by the Berlin Painter. Deciphering ancient ceramic firing conditions through high-resolution material characterization and replication

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

Cianchetta, I.; Trentelman, K.; Maish, J.

XANES spectroscopy was used to complement the results previously obtained with Raman spectroscopy by the same group to determine the firing conditions used in the production of a single vessel painted by the Berlin Painter in the 5th century B.C. The vessel, part of the collection of the J. Paul Getty Museum, presents a complicated layered architecture of black and red gloss, with different stratigraphies present on the interior and exterior surfaces. The study of two samples, one each from the interior and exterior surface of the vessel, was performed with the complementary analytical techniques of X-ray nano- and micro-spectroscopymore » (X-ray fluorescence spectroscopy (XRF) and full-field transmission X-ray micro-spectroscopy (FF-XANES) across the Fe K edge), and supported by a replication study. The replicates, made in a laboratory furnace providing complete control over the firing temperature and oxygen partial pressure, provided a paradigm for the comparison of the mineralogical phases observed in the ancient samples, which led to a deeper understanding of the firing conditions necessary for the production of the Berlin Painter's vessel. Our results confirm the necessity of multiple firings and painting applications to obtain the Berlin Painter's architecture and provide a further example of the multiplicity of techniques and practices employed by the potters of the Kerameikos in ancient Athens.« less

Evidence for an unorthodox firing sequence employed by the Berlin Painter. Deciphering ancient ceramic firing conditions through high-resolution material characterization and replication

DOE PAGES

Cianchetta, I.; Trentelman, K.; Maish, J.; ...

2014-12-10

XANES spectroscopy was used to complement the results previously obtained with Raman spectroscopy by the same group to determine the firing conditions used in the production of a single vessel painted by the Berlin Painter in the 5th century B.C. The vessel, part of the collection of the J. Paul Getty Museum, presents a complicated layered architecture of black and red gloss, with different stratigraphies present on the interior and exterior surfaces. The study of two samples, one each from the interior and exterior surface of the vessel, was performed with the complementary analytical techniques of X-ray nano- and micro-spectroscopymore » (X-ray fluorescence spectroscopy (XRF) and full-field transmission X-ray micro-spectroscopy (FF-XANES) across the Fe K edge), and supported by a replication study. The replicates, made in a laboratory furnace providing complete control over the firing temperature and oxygen partial pressure, provided a paradigm for the comparison of the mineralogical phases observed in the ancient samples, which led to a deeper understanding of the firing conditions necessary for the production of the Berlin Painter's vessel. Our results confirm the necessity of multiple firings and painting applications to obtain the Berlin Painter's architecture and provide a further example of the multiplicity of techniques and practices employed by the potters of the Kerameikos in ancient Athens.« less

Characterization and depositional and evolutionary history of the Apollo 17 deep drill core

NASA Technical Reports Server (NTRS)

Morris, R. V.; Lauer, H. V., Jr.; Gose, W. A.

1979-01-01

With a depth resolution of about 0.5 cm, the stratigraphy of the approximately 3 m Apollo 17 deep drill core by measurement of the total FeO concentration is characterized along with the FMR surface exposure (maturity) index Is/FeO, the metallic iron concentration Fe-vsm, and the FMR linewidth delta-H. For stratigraphic characterization, the first two parameters are the most important. Most of the core is characterized by a FeO concentration of approximately 15.5 wt. %; there is a more mafic zone in the upper approximately 75 cm where the maximum FeO concentration is approximately 18.5 wt. %, and a more felsic zone between approximately 225 and 260 cm where the minimum FeO concentration is approximately 14.0%. As indicated by Is/FeO, most of the soil in the core is submature to mature; the only immature zone is located between approximately 20 and 60 cm and is one of the most distinctive features in the core. A two stage model for the depositional and evolutionary history of the Apollo 17 deep drill core is proposed: (1) deposition by one event approximately 110 m.y. ago or deposition by a sequence of closely spaced events initating a maximum of approximately 200 m.y. ago and terminating approximately 110 m.y. ago, (2) in situ reworking (gardening) to a depth of approximately 26 cm in the period between approximately 110 m.y. ago and the present day.

Trench logs, terrestrial lidar system imagery, and radiocarbon data from the kilometer-62 site on the Greenville Fault, southeastern Alameda County, California, 2014

USGS Publications Warehouse

Lienkaemper, James J.; DeLong, Stephen B.; Avdievitch, Nikita N.; Pickering, Alexandra J; Guilderson, Thomas P.

2015-01-01

In 2014, we investigated an abrupt 8.5-meter (m), right-laterally deflected stream channel located near the Greenville Fault in southeastern Alameda County, California (-121.56224° E, 37.53430° N) that we discovered using 0.5-m resolution, 2011 aerial lidar imagery flown along the active fault trace. Prior to trenching we surveyed the site using a terrestrial lidar system (TLS) to document the exact geomorphic expression of this deflected stream channel before excavating a trench adjacent to it. We trenched perpendicular to the fault hoping to document the prehistoric history of earthquake ruptures along the fault. However, the alluvial stratigraphy that we document in these trench logs shows conclusively that this trench did not expose any active fault trace. Using other local geomorphic evidence for the fault location, a straight fault scarp immediately north of this stream projects slightly upslope of the west end of our trench and may be the actual location of the active fault trace. Five radiocarbon samples establish age control for the alluvial sequence documented in the trench, which may in the future be useful in constraining the long-term slip rate of the Greenville Fault. The deflection had been caused by an abrupt nontectonic termination of unit u30, a relatively thick (0.15–0.35 m) silt that is more erosion resistant than the adjacent cohesionless sand and gravel. 

3D-Reconstruction of recent volcanic activity from ROV-video, Charles Darwin Seamounts, Cape Verdes

NASA Astrophysics Data System (ADS)

Kwasnitschka, T.; Hansteen, T. H.; Kutterolf, S.; Freundt, A.; Devey, C. W.

2011-12-01

As well as providing well-localized samples, Remotely Operated Vehicles (ROVs) produce huge quantities of visual data whose potential for geological data mining has seldom if ever been fully realized. We present a new workflow to derive essential results of field geology such as quantitative stratigraphy and tectonic surveying from ROV-based photo and video material. We demonstrate the procedure on the Charles Darwin Seamounts, a field of small hot spot volcanoes recently identified at a depth of ca. 3500m southwest of the island of Santo Antao in the Cape Verdes. The Charles Darwin Seamounts feature a wide spectrum of volcanic edifices with forms suggestive of scoria cones, lava domes, tuff rings and maar-type depressions, all of comparable dimensions. These forms, coupled with the highly fragmented volcaniclastic samples recovered by dredging, motivated surveying parts of some edifices down to centimeter scale. ROV-based surveys yielded volcaniclastic samples of key structures linked by extensive coverage of stereoscopic photographs and high-resolution video. Based upon the latter, we present our workflow to derive three-dimensional models of outcrops from a single-camera video sequence, allowing quantitative measurements of fault orientation, bedding structure, grain size distribution and photo mosaicking within a geo-referenced framework. With this information we can identify episodes of repetitive eruptive activity at individual volcanic centers and see changes in eruptive style over time, which, despite their proximity to each other, is highly variable.

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

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

NASA Astrophysics Data System (ADS)

Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

2014-05-01

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

Astrobiology Exploration Strategies for the Mars Polar Regions Using Balloon Platforms

NASA Technical Reports Server (NTRS)

Mahaffy, P. R.; Atreya, S. A.; Fairbrother, D. A.; Farrell, W. M.; Gorevan, S.; Jones, J.; Mitrofanov, I.; Scott, J.

2003-01-01

Montgolfiere balloons can provide a unique near-surface platform for an extended traverse over the polar regions of Mars. During the polar summer, such solar powered balloons would remain in the constant sun of the polar summer and could remain airborne for many weeks or even months as the atmospheric circulation would drive the balloons around the polar region many times before the balloon would cross the terminator. Such a platform for scientific measurements could provide in situ sampling of the atmosphere for trace disequilibrium species that might be indicators of present geological or biological activity in this region. It could furthermore provide high resolution imaging, deep electromagnetic (EM) sounding for subsurface stratigraphy and liquid water, and high spatial resolution neutron measurements of subsurface ice. Technologies for robust balloon deployment on entry and controlled encounters with the surface and near subsurface for sample acquisition in otherwise inaccessible regions are presently being studied and developed with support from NASA.

Astrobiology Exploration Strategies for the Mars Polar Regions Using Balloon Platforms

NASA Technical Reports Server (NTRS)

Mahaffy, P. R.; Atreya, S. A.; Fairbrother, D. A.; Farrell, W. M.; Gorevan, S.; Jones, J.; Mitrofanov, I.; Scott, J.

2003-01-01

Montgolfiere balloons can provide a unique near-surface platform for an extended traverse over the polar regions of Mars. During the polar summer, such solar powered balloons would remain in the constant sun of the polar summer and could remain airborne for many weeks or even months as the atmospheric circulation would drive the balloons around the polar region many times before the balloon would cross the terminator. Such a platform for scientific measurements could provide in situ sampling of the atmosphere for trace disequilibrium species that might be indicators of present geological or biological activity in this regon. It could furthermore provide high resolution imaging, deep electromagnetic (EM) sounding for subsurface stratigraphy and liquid water, and high spatial resolution neutron measurements of subsurface ice. Technologies for robust balloon deployment on entry and controlled encounters with the surface and near subsurface for sample acquisition in otherwise inaccessible regions are presently being studied and developed with support from NASA.

High-resolution seismic stratigraphy of an Holocene lacustrine delta in western Lake Geneva (Switzerland)

USGS Publications Warehouse

Baster, I.; Girardclos, S.; Pugin, A.; Wildi, W.

2003-01-01

A high-resolution seismic survey was conducted in western Lake Geneva on a small delta formed by the Promenthouse, the Asse and the Boiron rivers. This dataset provides information on changes in the geometry and sedimentation patterns of this delta from Late-glacial to Present. The geometry of the deposits of the lacustrine delta has been mapped using 300-m spaced grid lines acquired with a 12 kHz Echosounder subbottom profiler. A complete three dimensional image of the sediment architecture was reconstructed through seismic stratigraphic analysis. Six different delta lobes have been recognized in the prodelta area. Depositional centers and lateral extension of the delta have changed through time, indicating migration and fluctuation of river input as well as changes in lake currents and wind regime from the time of glacier retreat to the Present. The delta slope is characterized by a high instability causing stumps developing and by the accumulation of biogenic gas that prevents seismic penetration.

Revised Late Oligocene to Early Miocene magnetic stratigraphy recorded by drift sediments at Sites U1405 and U1406, IODP Expedition 342 (Newfoundland, NW Atlantic)

NASA Astrophysics Data System (ADS)

van Peer, Tim; Xuan, Chuang; Wilson, Paul; Liebrand, Diederik; Lippert, Peter

2015-04-01

The nannofossil oozes drilled at IODP Expedition 342 (Paleogene Newfoundland Sediment Drifts) Sites U1405 and U1406 provide an exceptional sedimentary archive of the Late Oligocene to Early Miocene due to high sedimentation rates (2-6 cm/kyr at U1406 and up to 20 cm/kyr at U1405) and their ideal location below the Deep Western Boundary Current. These drift sediment sequences provide a unique opportunity to study the Oligocene-Miocene Transition (OMT) and Mi1-event (a transient 1‰ positive oxygen isotope excursion) at an unprecedented resolution from a Northern Hemisphere perspective. The exact timing of the OMT and its rate of change require a reliable and high-resolution magnetic stratigraphic age control, as Chron C6Cn with its three subchrons roughly spans the Mi1 event and the reversal C6Cn.2n/C6Cn.2r defines the Oligocene-Miocene boundary. Natural Remanent Magnetisation (NRM) was measured on 140 m of u-channel samples at U1405 and 190 m at U1406. The u-channel sample based magnetostratigraphy is in good agreement with that based on the shipboard data and reveal distinctive well-defined patterns of normal and reversed polarities, which can be correlated to the Geomagnetic Polarity Time Scale between C6Bn.2n and C9n (ca. 22.2 to 27 Ma) at U1406 and between C6Bn.2n and C6Cr (ca. 22.2 to 23.5 Ma) at U1405. Furthermore, putative cryptochrons in Chron C6Br and C7Ar, previously reported at Site U1334 (IODP Expedition 320), are observed in the u-channel magnetic stratigraphy for Sites U1405 and U1406. Anhysteretic Remanent Magnetisation (ARM) intensity variations are combined with X-Ray Fluorescence (XRF) generated elemental measurements to refine the shipboard splice of both U1405 and U1406. Latest Oligocene to earliest Miocene splice refinements are complicated by the presence of large-scale stratigraphic gaps (up to 25 m at U1405) unrelated to drilling disturbances. The depth and estimated age of these stratigraphic gaps vary from hole to hole, and do not appear to impact the completeness of the spliced magnetostratigraphic record. Rock and mineral magnetic studies of selected samples are currently ongoing to characterise the magnetic mineralogy of the sediments and how it changes across the stratigraphic gaps and intervals with contrasting lithological and/or palaeomagnetic properties. These data will help us understand the origin of the palaeomagnetic signal and test its reliability, while providing insights on the nature of the observed stratigraphic gaps and how they relate to global climate dynamics of the OMT and the Deep Western Boundary Current.

Dating young tephras - a distal solution to proximal controversy

NASA Astrophysics Data System (ADS)

Chen, Xuanyu; Blockley, Simon; Xu, Yigang; Menzies, Martin

2017-04-01

In-situ dating of young volcanic rocks (<50ka) is fraught with difficulties, a classic example being Changbaishan Volcano NE China. During the caldera-forming 'Millennium' eruption (ca. 940-950 CE) tephra was deposited around the world and as primary fall deposits on the caldera rims. The proximal deposits have been studied using multiple dating methods (e.g. 14C, 40Ar/39Ar, U-series and TL) but controversy and contradiction surrounds the age of these tephra deposits and, as a consequence, the proximal stratigraphy of the 'Millennium' eruption. Accurate characterization of the 'Millennium' tephra is vital if the tephras are to be used to reliably link disparate palaeoclimate archives on a hemispheric-wide scale. Our approach has been to use glass geochemistry to correlate the proximal units with a distal lake sequence from Lake Kushu Japan ca. 1100 km from Changbaishan. Investigation of a 19 m lake core revealed a crypto-tephra deposit with an approximate 'Millennium' age (i.e., 913-1395 cal. CE, 95.4% confidence), confirmed by the 14C-based Bayesian age model of the sedimentary record. Geochemical analysis of tephra shards for both proximal and distal deposits, confirmed identical major, minor and trace element chemistry. This allowed us to correlate the distal crypto-tephra with proximal pyroclastic fall units and to revise the 'Millennium' stratigraphy. Contrary to published data we propose that the 'Millennium' eruption is evident as a composite proximal sequence and that there is no evidence of any post-caldera deposits at the investigated profile (Chen et al., 2016). This is a significant step in our understanding of the nature and timing of Changbaishan eruptions and allows us to resolve an uncertain stratigraphy and eruption history. The correlation of the Lake Kushu crypto-tephra deposit to the distal Millennium (i.e., B-Tm) tephra reported from the Greenland ice-core (Sun et al., 2014) allows the use of high resolution ice-core tephra ages to validate and improve the radiocarbon-based Bayesian age model of the lacustrine sedimentary record. Modelling reveals that the import of ice-core ages (e.g. GICC05 timescale) has placed significant constraints on our correlative tephra, narrowing down the resultant age to 933-949 cal. CE (95.4% confidence). This improves the chronological control on forthcoming proxy data and subsequent tephra layers identified in the lake core within the same timeframe. The 'Millennium' tephra (i.e., B-Tm) is a hemispheric-wide chronological maker that is closely associated in time with the Medieval Climate Anomaly (ca. 900-1300 CE). Interestingly the timing, amplitude and duration of this Holocene anomaly may vary (Broecker, 2001; Ge and Wu, 2011) and could be evaluated by integration of chronological and environmental data. Assessment of the temporal and spatial variations of such climatic events will help us better understand the dynamics of these rapid and short-lived climatic episodes. References: Broecker, W.S., 2001. Was the Medieval Warm Period Global? Science, 291(5508): 1497-1499. Chen, X.-Y., Blockley, S.P.E., Tarasov, P.E., Xu, Y.-G., McLean, D., Tomlinson, E.L., Albert, P.G., Liu, J.-Q., Müller, S., Wagner, M. and Menzies, M.A., 2016. Clarifying the distal to proximal tephrochronology of the Millennium (B-Tm) eruption, Changbaishan Volcano, northeast China. Quat. Geochronol., 33: 61-75. Ge, Q. and Wu, W., 2011. Climate during the Medieval Climate Anomaly in China. PAGES news, 19: 24-26. Sun, C., Plunkett, G., Liu, J., Zhao, H., Sigl, M., McConnell, J.R., Pilcher, J.R., Vinther, B., Steffensen, J.P. and Hall, V., 2014. Ash from Changbaishan Millennium eruption recorded in Greenland ice: Implications for determining the eruption's timing and impact. Geophys. Res. Lett., 2013GL058642.

Wave equation datuming applied to S-wave reflection seismic data

NASA Astrophysics Data System (ADS)

Tinivella, U.; Giustiniani, M.; Nicolich, R.

2018-05-01

S-wave high-resolution reflection seismic data was processed using Wave Equation Datuming technique in order to improve signal/noise ratio, attenuating coherent noise, and seismic resolution and to solve static corrections problems. The application of this algorithm allowed obtaining a good image of the shallow subsurface geological features. Wave Equation Datuming moves shots and receivers from a surface to another datum (the datum plane), removing time shifts originated by elevation variation and/or velocity changes in the shallow subsoil. This algorithm has been developed and currently applied to P wave, but it reveals the capacity to highlight S-waves images when used to resolve thin layers in high-resolution prospecting. A good S-wave image facilitates correlation with well stratigraphies, optimizing cost/benefit ratio of any drilling. The application of Wave Equation Datuming requires a reliable velocity field, so refraction tomography was adopted. The new seismic image highlights the details of the subsoil reflectors and allows an easier integration with borehole information and geological surveys than the seismic section obtained by conventional CMP reflection processing. In conclusion, the analysis of S-wave let to characterize the shallow subsurface recognizing levels with limited thickness once we have clearly attenuated ground roll, wind and environmental noise.

A Geostatistical Toolset for Reconstructing Louisiana's Coastal Stratigraphy using Subsurface Boring and Cone Penetrometer Test Data

NASA Astrophysics Data System (ADS)

Li, A.; Tsai, F. T. C.; Jafari, N.; Chen, Q. J.; Bentley, S. J.

2017-12-01

A vast area of river deltaic wetlands stretches across southern Louisiana coast. The wetlands are suffering from a high rate of land loss, which increasingly threats coastal community and energy infrastructure. A regional stratigraphic framework of the delta plain is now imperative to answer scientific questions (such as how the delta plain grows and decays?) and to provide information to coastal protection and restoration projects (such as marsh creation and construction of levees and floodwalls). Through years, subsurface investigations in Louisiana have been conducted by state and federal agencies (Louisiana Department of Natural Resources, United States Geological Survey, United States Army Corps of Engineers, etc.), research institutes (Louisiana Geological Survey, LSU Coastal Studies Institute, etc.), engineering firms, and oil-gas companies. This has resulted in the availability of various types of data, including geological, geotechnical, and geophysical data. However, it is challenging to integrate different types of data and construct three-dimensional stratigraphy models in regional scale. In this study, a set of geostatistical methods were used to tackle this problem. An ordinary kriging method was used to regionalize continuous data, such as grain size, water content, liquid limit, plasticity index, and cone penetrometer tests (CPTs). Indicator kriging and multiple indicator kriging methods were used to regionalize categorized data, such as soil classification. A compositional kriging method was used to regionalize compositional data, such as soil composition (fractions of sand, silt and clay). Stratigraphy models were constructed for three cases in the coastal zone: (1) Inner Harbor Navigation Canal (IHNC) area: soil classification and soil behavior type (SBT) stratigraphies were constructed using ordinary kriging; (2) Middle Barataria Bay area: a soil classification stratigraphy was constructed using multiple indicator kriging; (3) Lower Barataria Bay and Lower Breton Sound areas: a soil texture stratigraphy was constructed using soil compositional data and compositional kriging. Cross sections were extracted from the three-dimensional stratigraphy models to reveal spatial distributions of different stratigraphic features.

Effectiveness of Hydraulic Parameterization Strategies for Simulating Moisture Dynamics in a Deep Semi-Arid Vadose Zone

NASA Astrophysics Data System (ADS)

Zhang, Y.; Schaap, M. G.

2012-12-01

Over the past fifteen years, the University of Arizona has carried out four controlled infiltration experiments in a 3600 m2, 15 meter deep vadose zone (Maricopa, Arizona) in which the evolution of moisture content (9 wells, 25 cm resolution), and matric potential (27 locations) was monitored and the subsurface stratigraphy, texture (1042 samples), and bulk density (251 samples) was characterized. In order to simulate the subsurface moisture dynamics it is necessary to define the 3D structure of the subsurface hydraulic characteristics (i.e. moisture retention and hydraulic functions). Several simple to complex strategies are possible ranging from stratigraphy based layering using hydraulic parameters derived from core samples to sophisticated numerical inversions based on 3D geostatistics and site-specific pedotransfer functions. A range of approaches will be evaluated on objective metrics that quantify how well the observed moisture dynamics are matched by simulations. We will evaluate the worth of auxiliary data such as observed matric potentials and quantity the number of texture samples needed to arrive at effective descriptions of subsurface structure. In addition, we will discuss more subjective metrics that evaluate the relative effort involved and estimate monetary cost of each method. While some of the results will only be valid for the studied site, some general conclusions will be possible about the effectiveness of particular methods for other semi-arid sites.

Using Kettle Lake Records to Date and Interpret Holocene Ash Deposition in Upper Cook Inlet, Anchorage, AK

NASA Astrophysics Data System (ADS)

Werner, A.; Kathan, K. M.; Kaufman, D. S.; Hancock, J. R.; Waythomas, C. F.; Wallace, K. L.

2004-12-01

Fourteen sediment cores recovered from three kettle lakes (Goose, Little Campbell and Lorraine) near Anchorage, AK were used to document and date Holocene volcanic ash deposition in the upper Cook Inlet area. Small lakes (<0.5 km2) with small (<1.5 km2), low relief (<50 m), and well-vegetated drainage areas were selected in order to minimize ash remobilization by mass wasting and fluvial processes. The resulting stratigraphic records are interpreted as primary terpha-fall stratigraphies. Relative to the surrounding lacustrine sediments, the ash layers exhibit low organic-matter content (as determined by loss-on-ignition, LOI), high magnetic susceptibility (MS), increased density (X-radiographs), and bubble-wall glass shards. Some ash layers are up to 1 cm thick (macrotephra) consisting of pure glass, some occur as light bands, while others (microtephra) can only be located using non-visual techniques (MS, LOI and X-radiography). The thinnest microtephras observed occur either as discrete (1 mm) layers or diffuse laminations composed of tephra mixed with ambient lake sediment. Forty-five AMS C-14 dates on terrestrial macro fossils were used to constrain sedimentation-rate models for the cores, and to assign absolute ages to ash units. Comparison of inferred tephra ages corroborates our intra and inter basin stratigraphic correlations (+/- 200 yrs) based on physical and MS stratigraphy. Ten out of 12 macrotephras can be confidently correlated among all three lakes, whereas, two of the prominent tephras occur in one basin but not in the others. This suggests subtle differences in ash plume extents or differences in tephra preservation between lakes. A total of 24 Holocene ash units (12 macro and 12 micro) have been recognized and dated in the Anchorage area, suggesting an ash-fall frequency of about 2.4/1000 yrs. By comparison, historical records suggest more frequent ash-fall events (120/1000 yrs). Our data indicate that, either the ash layers are not consistently preserved in the kettle basins, or more likely, these records lack the resolution to differentiate closely spaced ash-fall events. Core top stratigraphies support the latter interpretation: The 10-12 historically observed ash-fall events are represented by two diffuse zones in the upper 15 cm of the cores. As such, ash records from small kettle lakes should be regarded as conservative statements of ash deposition. Further, ash plumes can have narrow geographic distributions and ash-fall thicknesses can change markedly over short distances. Therefore distal ash-fall stratigraphies underestimate eruption frequencies.

Remanent magnetization stratigraphy of lunar cores

NASA Technical Reports Server (NTRS)

Banerjee, S. K.; Gingrich, D.; Marvin, J. A.

1977-01-01

Depth dependent fluctuations have been observed in the natural remanent magnetizations (NRM) of drive cores and drill strings from Apollo 16 and 17 missions. Partial demagnetization of unstable secondary magnetizations and identification of characteristic error signals from a core which is known to have been recently disturbed allow us to identify and isolate the stable NRM stratigraphy in double drive core 60010/60009 and drill strings 60002-60004. The observed magnetization fluctuations persist after normalization to take into account depth dependent variations in the carriers of stable NRM. We tentatively ascribe the stable NRM stratigraphy to instantaneous records of past magnetic fields at the lunar surface and suggest that the stable NRM stratigraphy technique could develop as a new relative time-stratigraphic tool, to be used with other physical measurements such as relative intensity of ferromagnetic resonance and charged particle track density to study the evolution of the lunar regolith.

Reconstruction of Sea/Lake-Level Changes in an Active Strike-Slip Basin (Gulf of Cariaco, NE Venezuela)

NASA Astrophysics Data System (ADS)

van Daele, M.; Audemard, F.; Beck, C.; de Batist, M.; van Welden, A.; Moernaut, J.; 2006 Shipboard Party, G.

2008-05-01

In January 2006, 76 high-resolution reflection seismic profiles were acquired in the Gulf of Cariaco, Northeast Venezuela. In the upper 100 m of sedimentary infill, 17 unconformity-bounded sequences were identified and mapped throughout the basin. Up to now, no core or borehole information is available to provide age constraints on these units. The sedimentary infill is cut by several faults, Riedel faults in the central part and the El Pilar fault (one of the main faults of the South American-Caribbean plate boundary) in the southern part of the gulf. The connection of the Gulf of Cariaco with the adjacent Cariaco Basin occurs at a present-day water depth of ~ 55 m. This implies that the gulf was disconnected from the world ocean and functioned as a lake during a large part of the last glacial. The main rivers entering the gulf drain the coastal mountain ranges and tend to form pronounced deltas at their inlet. During times when the gulf was a lake, periods with a dry climate resulted in dramatic lake-level lowstands and even complete desiccation/evaporation. The present-day depths of delta offlap breaks and the presence of lowstand/evaporite deposits can thus be used to estimate sea/lake level at the time of their formation. Detailed analysis of these stratigraphic sea/lake-level indicators allowed reconstructing the sea/lake-level history for the period encompassed by the 17 identified sequences. This sea/lake-level reconstruction also needed to be corrected for tectonic subsidence, affecting different parts of the gulf with different intensity. The reconstructed sea/lake-level curve of the Gulf of Cariaco was compared with the eustatic sea-level curve and with results of previous paleoclimate studies in Venezuela. The striking coherence between the eustatic curve and the amplitudes and absolute heights of successive reconstructed lowstands and highstands compelled us to tune our record to the eustatic curve in order to achieve a rough age estimate for our units. According to this age model, our seismic stratigraphy reaches back to MIS6, and the average sedimentation rate in the central parts of the gulf since MIS5e is 0.92 mm/y. Our data show that reconstructed lake levels in the Gulf of Cariaco, which represent a proxy for climate in NE- Venezuela, are very strongly coupled to the global stadials and interstadials of the last glacial period. Also the Younger Dryas is recognised in the sedimentary record of the Gulf of Cariaco as lowstand deposit resulting from an (almost) complete desiccation. Our data reveal that the stratigraphy of the Gulf of Cariaco holds a very accurate, complete and promising record of eustasy and climate change, at least since the penultimate glacial maximum. The quality of this record and the vicinity to the iconic Cariaco Basin make the Gulf of Cariaco an ideal target for future ocean drilling (or long coring).

Plio-Pleistocene magnetostratigraphy of the Turkana basin, Kenya

NASA Astrophysics Data System (ADS)

Lepre, C. J.; Quinn, R.; Feibel, C. S.; Brown, F. H.; Kent, D. V.

2012-12-01

Archaeological and fossil sites from the Turkana basin provide a unique record of important human evolutionary junctures, which have been linked to terrestrial environmental change as a consequence of late Cenozoic climate phenomenon. However, because of low geochronological resolution, spatial discontinuities, and the episodic nature of sedimentation in the half-graben basins of the East African Rift System, it has been difficult to directly connect the terrestrial sites with marine archives of Pliocene and Pleistocene climate. For the purpose of addressing these issues, a magnetic polarity stratigraphy and a corresponding geochronology are presented for 12 sampling sites spanning about 400 m of continental sediments that crop out in eastern (Areas 118 and 130 of the Karari ridge, Areas 102 and 104 of the Koobi Fora ridge, Areas 107 and 123 of Bara Hasuma) and western (Kokiselei, Naiyena Engol, Kalochoro, Lomekwi, South Turkwel, and Kanapoi) parts of the Turkana basin. Characteristic magnetizations isolated through thermal demagnetization experiments on mudstone specimens pass reversal tests and are indistinguishable in mean direction regardless if samples were collected from ancient fluvial floodplain or lacustrine strata of correlative stratigraphic intervals. The sequence of the composite paleomagnetic reversal stratigraphy consists of 15 magnetozones that vary from less than a meter to tens of meters thick and can be unambiguously correlated within limits of the previously established tephrochronology to the Gilbert through Matuyama portion of the Geomagnetic Polarity Time Scale dated to about 4.0-1.5 Ma. Sedimentation rates through lacustrine intervals (e.g., 22-29 cm/kyr) are comparable with high-fidelity marine cores. This factor coupled with copious amounts of magnetic mineral detritus from basin-bounding rift volcanics probably contributes to a high natural remanent magnetization of the sediments and the recording of temporally brief magnetozones (e.g., Vrica Subchron, upper and lower Reunion Subchrons, Kaena and Mammoth Subchrons) typically often not observed in continental records. Across-basin (50-100 km) comparisons of the stratigraphic positions for the same reversal boundaries demonstrate not only heterogeneity in paleoenvironmental records based on the stable-isotopic composition of paleosol carbonates and sedimentary facies, but also diachroneity for the onset of lacustrine systems that mark transitions from fluvial-dominated intervals of the basin's history. Although some lake-level oscillations might be linked with global climate changes operating at timescales on the order of 20-40 thousand years, differences between the nature and timing of the spatially disparate paleoenvironmental records are interpreted to reflect a strong influence on sedimentary patterns by local reorganizations of basin-boundary faults, underlying half-graben structure, and volcano-tectonic events. Conflicting aridity and humidity hypotheses of human evolution for the period of 3.5-1.5 Ma are compared using the newly constructed magnetostratigraphy to directly integrate the basin's paleoenvironmental and evolutionary records with dust-flux chronologies, Mediterranean sapropel sequences, and oxygen isotope proxies of global ice volume.

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

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.

Paleomagnetic and rock magnetic results from Koko Seamount (ODP Leg 197, Site 1206): Implications for hotspot motion

NASA Astrophysics Data System (ADS)

Olton, G.; Cottrell, R. D.; Tarduno, J. A.; Carvallo, C.; Torii, M.; Doubrovine, P. V.

2002-12-01

ODP Leg 197 sought to test whether the Hawaiian hotspot was fixed in the mantle during Late Cretaceous to Early Tertiary times. The principal goal was the recovery of basalt sequences from several of the Emperor seamounts and the main tool to be applied was paleomagnetism. Koko Seamount, near the bend in the Hawaiian-Emperor Seamounts, was the southernmost site drilled during Leg 197. Fifteen basalt units separated by thick volcaniclastic units were recovered in 278 m of penetration. Based on nannofossil stratigraphy of the sediments above basalt, the top of the volcanic section is 43.5-49.7 m.y.-old. Shipboard geochemical analyses (Initial Reports, Leg 197) indicate the lavas include tholeiites, suggesting that the age of the sequence recovered is similar to that of the major phase of shield building. Detailed, stepwise alternating field demagnetization experiments, and subsequent principal component analysis (all conducted aboard the JOIDES Resolution) yielded 14 inclination groups suggesting a mean paleolatitude of 21.7o N, slightly steeper than that the present-day latitude of Hawaii. Shore-based hysteresis measurements of basalt samples indicate single to pseudo-single domain behavior (mean Hc = 170 Oe, Hcr = 309 Oe, Mr/Ms = 0.274), whereas unblocking temperatures range from 200-300 oC and 550-600 oC. These data suggest the presence of high titanium titanomagnetite and magnetite. Shore-based thermal demagnetization inclinations are similar to the shipboard alternating field demagnetization data. The paleomagnetic data from Koko Seamount, together with results from Detroit, Suiko and Nintoku Seamounts form a southward decreasing series of paleolatitudes that appear to track motion of the Hawaiian ``hotspot" in the mantle. Rates of motion based on paleolatitudes of the Emperor Seamounts range from 30-50 mm/yr, similar to that observed for some continental plates.

Influence of Molecular Resolution on Sequence-Based Discovery of Ecological Diversity among Synechococcus Populations in an Alkaline Siliceous Hot Spring Microbial Mat ▿ †

PubMed Central

Melendrez, Melanie C.; Lange, Rachel K.; Cohan, Frederick M.; Ward, David M.

2011-01-01

Previous research has shown that sequences of 16S rRNA genes and 16S-23S rRNA internal transcribed spacer regions may not have enough genetic resolution to define all ecologically distinct Synechococcus populations (ecotypes) inhabiting alkaline, siliceous hot spring microbial mats. To achieve higher molecular resolution, we studied sequence variation in three protein-encoding loci sampled by PCR from 60°C and 65°C sites in the Mushroom Spring mat (Yellowstone National Park, WY). Sequences were analyzed using the ecotype simulation (ES) and AdaptML algorithms to identify putative ecotypes. Between 4 and 14 times more putative ecotypes were predicted from variation in protein-encoding locus sequences than from variation in 16S rRNA and 16S-23S rRNA internal transcribed spacer sequences. The number of putative ecotypes predicted depended on the number of sequences sampled and the molecular resolution of the locus. Chao estimates of diversity indicated that few rare ecotypes were missed. Many ecotypes hypothesized by sequence analyses were different in their habitat specificities, suggesting different adaptations to temperature or other parameters that vary along the flow channel. PMID:21169433

HetMappsS: Heterozygous mapping strategy for high resolution Genotyping-by-Sequencing Markers

USDA-ARS?s Scientific Manuscript database

Reduced representation genotyping approaches, such as genotyping-by-sequencing (GBS), provide opportunities to generate high-resolution genetic maps at a low per-sample cost. However, missing data and non-uniform sequence coverage can complicate map creation in highly heterozygous species. To facili...

Ground penetrating radar imaging of cap rock, caliche and carbonate strata

USGS Publications Warehouse

Kruse, S.E.; Schneider, J.C.; Campagna, D.J.; Inman, J.A.; Hickey, T.D.

2000-01-01

Field experiments show ground penetrating radar (GPR) can be used to image shallow carbonate stratigraphy effectively in a variety of settings. In south Florida, the position and structure of cap rock cover on limestone can be an important control on surface water flow and vegetation, but larger scale outcrops (tens of meters) of cap rock are sparse. GPR mapping through south Florida prairie, cypress swamp and hardwood hammock resolves variations in thickness and structure of cap rock to ~3 m and holds the potential to test theories for cap rock-vegetation relationships. In other settings, carbonate strata are mapped to test models for the formation of local structural anomalies. A test of GPR imaging capabilities on an arid caliche (calcrete) horizon in southeastern Nevada shows depth penetration to ~2 m with resolution of the base of caliche. GPR profiling also succeeds in resolving more deeply buried (~5 m) limestone discontinuity surfaces that record subaerial exposure in south Florida. (C) 2000 Elsevier Science B.V. All rights reserved.Field experiments show ground penetrating radar (GPR) can be used to image shallow carbonate stratigraphy effectively in a variety of settings. In south Florida, the position and structure of cap rock cover on limestone can be an important control on surface water flow and vegetation, but larger scale outcrops (tens of meters) of cap rock are sparse. GPR mapping through south Florida prairie, cypress swamp and hardwood hammock resolves variations in thickness and structure of cap rock to approx. 3 m and holds the potential to test theories for cap rock-vegetation relationships. In other settings, carbonate strata are mapped to test models for the formation of local structural anomalies. A test of GPR imaging capabilities on an arid caliche (calcrete) horizon in southeastern Nevada shows depth penetration to approx. 2 m with resolution of the base of caliche. GPR profiling also succeeds in resolving more deeply buried (approx. 5 m) limestone discontinuity surfaces that record subaerial exposure in south Florida.

High-resolution seismic-reflection profiles collected aboard R/V James M. Gilliss Cruise GS-7903-3, over the Atlantic Continental Slope and Rise off New England

USGS Publications Warehouse

Bailey, Norman G.; Aaron, John M.

1982-01-01

During June 1979, the U.S. Geological Survey (USGS) collected 4,032 km of single-channel seismic-reflection data from the Atlantic Continental Slope and Rise off New England. The work was conducted aboard R/V JAMES M. GILLISS (cruise GS-7903-3). The purpose of the cruise was to determine the characteristics of mass sediment movement on the Continental Slope, and to study and correlate the stratigraphy of the Jurassic and Cretaceous strata lying north and south of the New England seamount chain.Seismic instrumentation included 40-in3, 160-in3, and 500-in3 airguns; a Teledyne 800-joule minisparker system; a 3-5-kHz to 7-kHz, hull-mounted tunable transducer; and a 7-channel analog tape recorder.Navigation control during the cruise was provided by a Western Integrated Navigation System capable of integrating satellite, rho-rho Loran-C, hyperbolic Loran-C, gyro compass, and doppler speed-log position data. The prime navigation sensor was the rho-rho Loran-C automatically recorded at 20-second intervals and manually plotted every 15 minutes, backed up by hyperbolic Loran-C fixes automatically recorded every 5 minutes.Of the 4,032 km of data collected, 3,257 km of 3-5-kHz, minisparker and 40-in3 airgun were for the sediment-slump studand the other 775 km of 3-5-kHz, minis parker, 160-in3 air gun and 500-in3 airgun were for the deep stratigraphy study. Overall, the quality of the data is excellent with good resolution and penetration.The original data may be examined at the U.S. Geological Survey, Woods Hole, MA 02543. Copies of the data can be purchased only from the National Geophysical and Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder, CO 80303 (303-497-6338).

Major controls on architecture, sequence stratigraphy and paleosols of middle Pleistocene continental sediments ("Qc Unit"), eastern central Italy

NASA Astrophysics Data System (ADS)

Di Celma, Claudio; Pieruccini, Pierluigi; Farabollini, Piero

2015-05-01

Middle Pleistocene continental sediments in central Italy ("Qc Unit") record the oldest fluvial accumulation along the uplifting margin of the Peri-Adriatic basin. The architecture of the sediment body can be divided into two unconformity-bounded, fining-upward cycles interpreted as genetically related depositional sequences. These sequences highlight the systematic adjustment of the fluvial system to changes in the ratio between accommodation space and sediment supply (A/S ratio) and, from base to top, comprise the following surfaces and stratal components: (i) a regionally correlative sequence boundary resulting from an A/S ratio ≤ 0; (ii) a low-accommodation systems tract characterized by conglomerate-rich, amalgamated channel fills and recording an A/S ratio < 1; (iii) an expansion surface marking the turnaround point from low-accommodation systems tract to high-accommodation systems tract deposits; (iv) a high-accommodation systems tract dominated by floodplain fines encasing lens-like, fluvial channel deposits and denoting an A/S ratio > 1; and (v) a mature red argillic paleosol. To constrain the climatic signal for paleosols formation, the two sequence-capping mature paleosols have been investigated. The results of these studies suggest that they were developed under humid and warm climatic conditions associated with interglacial phases, which have been correlatively attributed to Marine Oxygen Isotope Stages 11 and 9.

Biostratigraphy of a Middle Miocene-Pliocene sequence from Cumarebo area, Falcon State, northwestern Venezuela

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

Giffuni, G.

1991-03-01

The southern Caribbean region offers little in the way of continuous sequences for the late Neogene. An upward facies shallowing trend unfavorable for planktonic foraminifers and erosional truncation seems to be almost a rule for such sediments. A fairly complete sedimentary sequence mainly represented by clays, silts, and carbonate rocks from the Cumarebo region, Falcon State, northwestern Venezuela, was chosen to study the biostratigraphy of the late Neogene using foraminifers. More than one hundred surface samples were analyzed throughout. The study of foraminiferal fossil assemblages and other microfossils was also used to define paleoenvironments of deposition. Four formations are involvedmore » in this work. From base to top they are the Socorro, Caujarao, El Veral, and Tucupido. From the study of planktonic foraminifers, six biostratigraphic zones were recognized: Globorotalia mayeri Zone, Globorotalia menardii Zone, Globorotalia acostaensis Zone, Globorotalia humerosa Zone, Globorotalia margaritae Zone, and Globorotalia miocenica Zone. These zones indicate that the age of the sequence ranks from late middle Miocene to middle Pliocene. Generally speaking, with some variations, the paleoenvironments of the sequence show a shallowing trend from marine upper-middle bathyal to middle neritic. These results make an important contribution to the stratigraphy and geologic history of the Cumarebo area, which is related to the Agua Salada basin, and may help clarify the paleogeography and paleotectonic evolution of this region for petroleum exploration.« less

Morphology and stratigraphy of small barrier-lagoon systems in Maine

USGS Publications Warehouse

Duffy, W.; Belknap, D.F.; Kelley, J.T.

1989-01-01

The coast of Maine contains over 200 individual barrier-lagoon systems, most quite small, with an aggregate length of nearly 100 km. Although they represent less than 5% of the tidally influenced coastline of Maine, they are widely distributed and occur in a variety of dynamic regimes and physiographic regions. Their morphology and backbarrier stratigraphy are different from better studied coastal plain systems, and provide important clues to the Holocene evolution of the Maine coast. In a study of geomorphic form and backbarrier stratigraphy, inlet processes and Holocene sea-level rise have been identified as the principal controls on coarse-grained barrier stratigraphy. Barriers in Maine are found in five distinct geomorphic forms, identified herein as: barrier spits, pocket barriers, double tombolos, cuspate barriers and looped barriers. The few long sandy beaches in southwestern Maine are mostly barrier spits. The remainder of the barrier types is composed primarily of gravel or mixed sand and gravel. The barriers protect a variety of backbarrier environments: fresh and brackish ponds, lagoons and fresh- and saltwater marshes. The barriers may or may not have inlets. Normal wave action, coarse-grain size and a deeply embayed coast result in barriers with steep, reflective profiles several meters above MHW. Occasional storm events completely wash over the barriers, building steep, lobate gravel fans along their landward margin. Few, if any, extensive storm layers are recognized as extending into the distal backbarrier environments, however. During sea-level rise and landward barrier retreat, this abrupt, storm-generated transition zone inters the backbarrier sediments. Statistical comparisons of barrier morphology, location and backbarrier environment type with backbarrier stratigraphy show that Holocene backbarrier stratigraphy is best predicted by the modern backbarrier environment type. This, in turn, is influenced most by the absence or presence, and long-term stability or instability of a tidal inlet. Geomorphic barrier form and location in coastal geomorphic compartments show little or no correlation with backbarrier stratigraphy. In contrast to previous classifications of barrier-lagoon systems based primarily on sandy, coastal plain examples, in Maine the shape or origin of the backbarrier system is relatively unimportant. The presence or absence of a tidal inlet is of paramount importance in shaping the Holocene stratigraphy of the backbarrier region. ?? 1989.

A high-resolution cattle CNV map by population-scale genome sequencing

USDA-ARS?s Scientific Manuscript database

Copy Number Variations (CNVs) are common genomic structural variations that have been linked to human diseases and phenotypic traits. Prior studies in cattle have produced low-resolution CNV maps. We constructed a draft, high-resolution map of cattle CNVs based on whole genome sequencing data from 7...

Sequence stratigraphy and a revised sea-level curve for the Middle Devonian of eastern North America

USGS Publications Warehouse

Brett, Carlton E.; Baird, G.C.; Bartholomew, A.J.; DeSantis, M.K.; Ver Straeten, C.A.

2011-01-01

The well-exposed Middle Devonian rocks of the Appalachian foreland basin (Onondaga Formation; Hamilton Group, Tully Formation, and the Genesee Group of New York State) preserve one of the most detailed records of high-order sea-level oscillation cycles for this time period in the world. Detailed examination of coeval units in distal areas of the Appalachian Basin, as well as portions of the Michigan and Illinois basins, has revealed that the pattern of high-order sea-level oscillations documented in the New York-Pennsylvania section can be positively identified in all areas of eastern North America where coeval units are preserved. The persistence of the pattern of high-order sea-level cycles across such a wide geographic area suggests that these cycles are allocyclic in nature with primary control on deposition being eustatic sea-level oscillation, as opposed to autocylic controls, such as sediment supply, which would be more local in their manifestation. There is strong evidence from studies of cyclicity and spectral analysis that these cycles are also related to Milankovitch orbital variations, with the short and long-term eccentricity cycles (100. kyr and 405. kyr) being the dominant oscillations in many settings. Relative sea-level oscillations of tens of meters are likely and raise considerable issues about the driving mechanism, given that the Middle Devonian appears to record a greenhouse phase of Phanerozoic history. These new correlations lend strong support to a revised high-resolution sea-level oscillation curve for the Middle Devonian for the eastern portion of North America. Recognized third-order sequences are: Eif-1 lower Onondaga Formation, Eif-2: upper Onondaga and Union Springs formations; Eif-Giv: Oatka Creek Formation; Giv-1: Skaneateles, Giv-2: Ludlowville, Giv-3: lower Moscow, Giv-4: upper Moscow-lower Tully, and Giv-5: middle Tully-Geneseo formations. Thus, in contrast with the widely cited eustatic curve of Johnson et al. (1985), which recognizes just one major transgressive-regressive (T-R) cycle in the early-mid Givetian (If) prior to the major late Givetian Taghanic unconformity (IIa, upper Tully-Geneseo Shale), we recognize four T-R cycles: If (restricted), Ig, Ih, and Ii. We surmise that third-order sequences record eustatic sea-level fluctuations of tens of meters with periodicities of 0.8-2. myr, while their medial-scale (fourth-order) subdivisions record lesser variations primarily of 405. kyr duration (long-term eccentricity). This high-resolution record of sea-level change provides strong evidence for high-order eustatic cycles with probable Milankovitch periodicities, despite the fact that no direct evidence for Middle Devonian glacial sediments has been found to date. ?? 2010.

Reading the climate record of the martian polar layered deposits

USGS Publications Warehouse

Hvidberg, C.S.; Fishbaugh, K.E.; Winstrup, M.; Svensson, A.; Byrne, S.; Herkenhoff, K. E.

2012-01-01

The martian polar regions have layered deposits of ice and dust. The stratigraphy of these deposits is exposed within scarps and trough walls and is thought to have formed due to climate variations in the past. Insolation has varied significantly over time and caused dramatic changes in climate, but it has remained unclear whether insolation variations could be linked to the stratigraphic record. We present a model of layer formation based on physical processes that expresses polar deposition rates of ice and dust in terms of insolation. In this model, layer formation is controlled by the insolation record, and dust-rich layers form by two mechanisms: (1) increased summer sublimation during high obliquity, and (2) variations in the polar deposition of dust modulated by obliquity variations. The model is simple, yet physically plausible, and allows for investigations of the climate control of the polar layered deposits (PLD). We compare the model to a stratigraphic column obtained from the north polar layered deposits (NPLD) (Fishbaugh, K.E., Hvidberg, C.S., Byrne, S., Russel, P.S., Herkenhoff, K.E., Winstrup, M., Kirk, R. [2010a]. Geophys. Res. Lett., 37, L07201) and show that the model can be tuned to reproduce complex layer sequences. The comparison with observations cannot uniquely constrain the PLD chronology, and it is limited by our interpretation of the observed stratigraphic column as a proxy for NPLD composition. We identified, however, a set of parameters that provides a chronology of the NPLD tied to the insolation record and consistently explains layer formation in accordance with observations of NPLD stratigraphy. This model dates the top 500 m of the NPLD back to ∼1 million years with an average net deposition rate of ice and dust of 0.55 mm a−1. The model stratigraphy contains a quasi-periodic ∼30 m cycle, similar to a previously suggested cycle in brightness profiles from the NPLD (Laskar, J., Levrard, B., Mustard, F. [2002]. Nature, 419, 375–377; Milkovich, S., Head, J.W. [2005]. J. Geophys. Res. 110), but here related to half of the obliquity cycles of 120 and 99 kyr and resulting from a combination of the two layer formation mechanisms. Further investigations of the non-linear insolation control of PLD formation should consider data from other geographical locations and include radar data and other stratigraphic datasets that can constrain the composition and stratigraphy of the NPLD layers.

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.

How to Make Eccentricity Cycles in Stratigraphy: the Role of Compaction

NASA Astrophysics Data System (ADS)

Liu, W.; Hinnov, L.; Wu, H.; Pas, D.

2017-12-01

Milankovitch cycles from astronomically driven climate variations have been demonstrated as preserved in cyclostratigraphy throughout geologic time. These stratigraphic cycles have been identified in many types of proxies, e.g., gamma ray, magnetic susceptibility, oxygen isotopes, carbonate content, grayscale, etc. However, the commonly prominent spectral power of orbital eccentricity cycles in stratigraphy is paradoxical to insolation, which is dominated by precession index power. How is the spectral power transferred from precession to eccentricity in stratigraphy? Nonlinear sedimentation and bioturbation have long been identified as players in this transference. Here, we propose that in the absence of bioturbation differential compaction can generate the transference. Using insolation time series, we trace the steps by which insolation is transformed into stratigraphy, and how differential compaction of lithology acts to transfer spectral power from precession to eccentricity. Differential compaction is applied to unique values of insolation, which is assumed to control the type of deposited sediment. High compaction is applied to muds, and progressively lower compaction is applied to silts and sands, or carbonate. Linear differential compaction promotes eccentricity spectral power, but nonlinear differential compaction elevates eccentricity spectral power to dominance and precession spectral power to near collapse as is often observed in real stratigraphy. Keywords: differential compaction, cyclostratigraphy, insolation, eccentricity

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

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

Late Holocene Lake Level Fluctuations at Laguna Arapa, Peru and Connections to Human Demography

NASA Astrophysics Data System (ADS)

Hillman, A. L.; Abbott, M. B.; Werne, J. P.; Arkush, E.; Thompson, L. G.; Ferland, T.; Holmes, E.; Puhnaty, C.; Woods, A.

2016-12-01

The relationship between variations in hydroclimate and human demography on the Peruvian Altiplano has significant implications for understanding how people in the past have adapted to changes in freshwater resources. To investigate these human-environmental interactions, this project presents a 2,000 year sediment record from Laguna Arapa, a large lake that is <20 km NW of Lake Titicaca. Using sedimentology and stratigraphy as well as a suite of organic geochemical proxies including fecal 5β-stanols and leaf waxes (long chain n-alkanoic acids), we aim to tie together proxies of human population with indicators of regional hydroclimate. Preliminary results of sedimentology and stratigraphy show notable transitions from sand to silt to clay, suggesting rising lake level sequences at 500 and 700 AD. The last 1,300 years of sediment are characterized by alternating layers of organic rich material with abundant charcoal and black inorganic clay, suggesting intermittent periods of aridity and/or anthropogenic fire-setting. These layers are particularly frequent during the Medieval Climate Anomaly, which was characterized by dry and warm conditions. These results agree well with other records of hydroclimate from regional lakes as well as accumulation rate and temperature from the Quelccaya ice cap. Organic geochemical work is currently in progress and shows promise for linking together proxies of human demography with hydroclimate to understand the relationship between human settlement and climate change.

Improved imaging of cochlear nerve hypoplasia using a 3-Tesla variable flip-angle turbo spin-echo sequence and a 7-cm surface coil.

PubMed

Giesemann, Anja M; Raab, Peter; Lyutenski, Stefan; Dettmer, Sabine; Bültmann, Eva; Frömke, Cornelia; Lenarz, Thomas; Lanfermann, Heinrich; Goetz, Friedrich

2014-03-01

Magnetic resonance imaging of the temporal bone has an important role in decision making with regard to cochlea implantation, especially in children with cochlear nerve deficiency. The purpose of this study was to evaluate the usefulness of the combination of an advanced high-resolution T2-weighted sequence with a surface coil in a 3-Tesla magnetic resonance imaging scanner in cases of suspected cochlear nerve aplasia. Prospective study. Seven patients with cochlear nerve hypoplasia or aplasia were prospectively examined using a high-resolution three-dimensional variable flip-angle turbo spin-echo sequence using a surface coil, and the images were compared with the same sequence in standard resolution using a standard head coil. Three neuroradiologists evaluated the magnetic resonance images independently, rating the visibility of the nerves in diagnosing hypoplasia or aplasia. Eight ears in seven patients with hypoplasia or aplasia of the cochlear nerve were examined. The average age was 2.7 years (range, 9 months-5 years). Seven ears had accompanying malformations. The inter-rater reliability in diagnosing hypoplasia or aplasia was greater using the high-resolution three-dimensional variable flip-angle turbo spin-echo sequence (fixed-marginal kappa: 0.64) than with the same sequence in lower resolution (fixed-marginal kappa: 0.06). Examining cases of suspected cochlear nerve aplasia using the high-resolution three-dimensional variable flip-angle turbo spin-echo sequence in combination with a surface coil shows significant improvement over standard methods. © 2013 The American Laryngological, Rhinological and Otological Society, Inc.

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.

Terrain types and local-scale stratigraphy of grooved terrain on ganymede

NASA Technical Reports Server (NTRS)

Murchie, Scott L.; Head, James W.; Helfenstein, Paul; Plescia, Jeffrey B.

1986-01-01

Grooved terrain is subdivided on the basis of pervasive morphology into: (1) groove lanes - elongate parallel groove bands, (2) grooved polygons - polygonal domains of parallel grooves, (3) reticulate terrain - polygonal domains of orthogonal grooves, and (4) complex grooved terrain - polygons with several complexly cross-cutting groove sets. Detailed geologic mapping of select areas, employing previously established conventions for determining relative age relations, reveals a general three-stage sequence of grooved terrain emplacement: first, dissection of the lithosphere by throughgoing grooves, and pervasive deformation of intervening blocks; second, extensive flooding and continued deformation of the intervening blocks; third, repeated superposition of groove lanes concentrated at sites of initial throughgoing grooves. This sequence is corroborated by crater-density measurements. Dominant orientations of groove sets are parallel to relict zones of weakness that probably were reactivated during grooved terrain formation. Groove lane morphology and development consistent with that predicted for passive rifts suggests a major role of global expansion in grooved terrain formation.

Obtaining a more resolute teleost growth hormone phylogeny by the introduction of gaps in sequence alignment.

PubMed

Rubin, D A; Dores, R M

1995-06-01

In order to obtain a more resolute phylogeny of teleosts based on growth hormone (GH) sequences, phylogenetic analyses were performed in which deletions (gaps), which appear to be order specific, were upheld to maintain GH's structural information. Sequences were analyzed at 194 amino acid positions. In addition, the two closest genealogically related groups to the teleosts, Amia calva and Acipenser guldenstadti, were used as outgroups. Modified sequence alignments were also analyzed to determine clade stability. Analyses indicated, in the most parsimonious cladogram, that molecular and morphological relationships for the orders of fishes are congruent. With GH molecular sequence data it was possible to resolve all clades at the familial level. Analyses of the primary sequence data indicate that: (a) the halecomorphean and chondrostean GH sequences are the appropriate outgroups for generating the most parsimonious cladogram for teleosts; (b) proper alignment of teleost GH sequence by the inclusion of gaps is necessary for resolution of the Percomorpha; and (c) removal of sequence information by deleting improperly aligned sequence decreases the phylogenetic signal obtained.

High-resolution ultrashort echo time (UTE) imaging on human knee with AWSOS sequence at 3.0 T.

PubMed

Qian, Yongxian; Williams, Ashley A; Chu, Constance R; Boada, Fernando E

2012-01-01

To demonstrate the technical feasibility of high-resolution (0.28-0.14 mm) ultrashort echo time (UTE) imaging on human knee at 3T with the acquisition-weighted stack of spirals (AWSOS) sequence. Nine human subjects were scanned on a 3T MRI scanner with an 8-channel knee coil using the AWSOS sequence and isocenter positioning plus manual shimming. High-resolution UTE images were obtained on the subject knees at TE = 0.6 msec with total acquisition time of 5.12 minutes for 60 slices at an in-plane resolution of 0.28 mm and 10.24 minutes for 40 slices at an in-plane resolution of 0.14 mm. Isocenter positioning, manual shimming, and the 8-channel array coil helped minimize image distortion and achieve high signal-to-noise ratio (SNR). It is technically feasible on a clinical 3T MRI scanner to perform UTE imaging on human knee at very high spatial resolutions (0.28-0.14 mm) within reasonable scan time (5-10 min) using the AWSOS sequence. Copyright © 2011 Wiley Periodicals, Inc.

Reading and Abstracting Journal Articles in Sedimentology and Stratigraphy.

ERIC Educational Resources Information Center

Conrad, Susan Howes

1991-01-01

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

Advances in DNA sequencing technologies for high resolution HLA typing.

PubMed

Cereb, Nezih; Kim, Hwa Ran; Ryu, Jaejun; Yang, Soo Young

2015-12-01

This communication describes our experience in large-scale G group-level high resolution HLA typing using three different DNA sequencing platforms - ABI 3730 xl, Illumina MiSeq and PacBio RS II. Recent advances in DNA sequencing technologies, so-called next generation sequencing (NGS), have brought breakthroughs in deciphering the genetic information in all living species at a large scale and at an affordable level. The NGS DNA indexing system allows sequencing multiple genes for large number of individuals in a single run. Our laboratory has adopted and used these technologies for HLA molecular testing services. We found that each sequencing technology has its own strengths and weaknesses, and their sequencing performances complement each other. HLA genes are highly complex and genotyping them is quite challenging. Using these three sequencing platforms, we were able to meet all requirements for G group-level high resolution and high volume HLA typing. Copyright © 2015 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

A Holocene temperature reconstruction from northern New Zealand: a test of North Atlantic Holocene climate patterns as a global template

NASA Astrophysics Data System (ADS)

van den Bos, Valerie; Rees, Andrew; Newnham, Rewi; Augustinus, Paul

2017-04-01

Holocene climate variability has been well defined in the North Atlantic (Walker et al., 2012), but the global extent of this climate change stratigraphy is debatable. If the North Atlantic serves as a global template for Holocene climate, then New Zealand (NZ) is ideally positioned to test this assertion, as it is distal from the northern drivers. Additionally, it is one of the few landmasses in the Southern Hemisphere that is influenced by both sub-tropical and extra-tropical climatic regimes, which may be more important controls in the southern mid-latitudes. Although much work has been done to characterise the Holocene in NZ using pollen, most of these records lack the resolution or sensitivity to determine whether abrupt or short-lived events occurred. The NZ-INTIMATE climate event stratigraphy lacks a type section for the Holocene (Alloway et al., 2007). Records from northern NZ typically show little change, other than a possible early Holocene warming. Here, we present a combined pollen and chironomid temperature reconstruction from Lake Pupuke (northern NZ), the first of its kind in NZ that covers the entire Holocene. By comparing mean annual temperatures reconstructed from fossil pollen and mean summer temperatures inferred from chironomid remains, we can assess changes in seasonality. Mean summer temperature was reconstructed from the chironomid record using a weighted averaging partial least squares (WA-PLS) model (n comp = 2, r2booth = 0.77, RMSEP = 1.4°C) developed from an expanded version of Dieffenbacher-Krall et al. (2007)'s chironomid training set. Preliminary results show evidence for cool summers during the early Holocene as well as around the period of the Little Ice Age as defined in the North Atlantic region. These and other climate patterns determined from the Pupuke chironomid and pollen records will be compared with other evidence from northern New Zealand and with the North Atlantic record of Holocene climate variability. References: Alloway, B.V., Lowe, D.J., Barrell, D.J.A., Newnham, R.M., Almond, P.C., Augustinus, P.C., Bertler, N.A.N., Carter, L., Litchfield, N.J., McGlone, M.S., Shulmeister, J., Vandergoes, M.J., Williams, P.W., and NZ-INTIMATE members. 2007. Towards a climate event stratigraphy for New Zealand over the past 30 000 years (NZ-INTIMATE project). Journal of Quaternary Science, 22, 9-35. Dieffenbacher-Krall, A.C., Vandergoes, M.J., Denton, G.H. 2007. An inference model for mean summer air temperatures in the Southern Alps, New Zealand, using subfossil chironomids. Quaternary Science Reviews, 26, 2587-2504. Walker, M.J.C., Berkelhammer, M., Björck, S., Cwynar, L.C., Fisher, D.A., Long, A.J., Lowe, D.J., Newnham, R.M., Rasmussen, S.O., Weiss, H. 2012. Formal subdivision of the Holocene Series/Epoch: a discussion paper by a working group of INTIMATE (Integration of ice-core, marine and terrestrial records) and the Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy). Journal of Quaternary Science, 27, 649-659.

Geologic map and map database of northeastern San Francisco Bay region, California, [including] most of Solano County and parts of Napa, Marin, Contra Costa, San Joaquin, Sacramento, Yolo, and Sonoma Counties

USGS Publications Warehouse

Graymer, Russell Walter; Jones, David Lawrence; Brabb, Earl E.

2002-01-01

This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (nesfmf.ps, nesfmf.pdf, nesfmf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller.

BOREHOLE NEUTRON ACTIVATION: THE RARE EARTHS.

USGS Publications Warehouse

Mikesell, J.L.; Senftle, F.E.

1987-01-01

Neutron-induced borehole gamma-ray spectroscopy has been widely used as a geophysical exploration technique by the petroleum industry, but its use for mineral exploration is not as common. Nuclear methods can be applied to mineral exploration, for determining stratigraphy and bed correlations, for mapping ore deposits, and for studying mineral concentration gradients. High-resolution detectors are essential for mineral exploration, and by using them an analysis of the major element concentrations in a borehole can usually be made. A number of economically important elements can be detected at typical ore-grade concentrations using this method. Because of the application of the rare-earth elements to high-temperature superconductors, these elements are examined in detail as an example of how nuclear techniques can be applied to mineral exploration.

Distribution and geologic history of materials excavated by the lunar crater Bullialdus

NASA Technical Reports Server (NTRS)

Tompkins, Stefanie; Pieters, Carle M.; Mustard, John F.

1993-01-01

The crater Bullialdus is a 61 km, Eratosthenian-age impact crater located on the western edge of Mare Nubium. Previous analysis of the spatial distribution of materials in the area using nine telescopic near-infrared spectra suggested a possible three-layer structure prior to the impact event: two shallow gabbroic layers and one deeper noritic layer (from a potential depth of 5.5 km). The initial interpretation of this stratigraphy was that Bullialdus may have tapped a layered mafic pluton, such as have been invoked to explain the existence of Mg-suite rocks. High-spatial resolution CCD images of Bullialdus were analyzed to better map the spatial distribution of the observed lithologies, and to assess the plausibility of the pluton interpretation.

Chirp seismic-reflection data from the Baltimore, Washington, and Norfolk Canyons, U.S. mid-Atlantic margin

USGS Publications Warehouse

Obelcz, Jeffrey B.; Brothers, Daniel S.; ten Brink, Uri S.; Chaytor, Jason D.; Worley, Charles R.; Moore, Eric M.

2014-01-01

A large number of high-resolution geophysical surveys between Cape Hatteras and Georges Bank have been conducted by federal, state, and academic institutions since the turn of the century. A major goal of these surveys is providing a continuous view of bathymetry and shallow stratigraphy at the shelf edge in order to assess levels of geological activity during the current sea level highstand. In 2012, chirp seismic-reflection data was collected by the U.S. Geologial Survey aboard the motor vessel Tiki XIV near three United States mid-Atlantic margin submarine canyons. These data can be used to further our understanding of passive continental margin processes during the Holocene, as well as providing valuable information regarding potential submarine geohazards.

Geology and biostratigraphy of the Potomac River cliffs at Stratford Hall, Westmoreland County, Virginia

USGS Publications Warehouse

Weems, Robert E.; Edwards, Lucy E.; Landacre, Bryan D.

2017-01-01

The cliffs along the Potomac River at Stratford Hall display extensive exposures of Miocene marine strata that belong successively to the Calvert, Choptank, St. Marys, and Eastover Formations. Within the lower part of this sequence, in the Calvert and Choptank Formations, there is well-developed cyclic stratigraphy. Above the Miocene units lies the marginal marine to deltaic Pleistocene Bacons Castle Formation, which is the highest and youngest formation exposed in the cliffs. The goals of this field trip guide are to (1) show the Miocene formations exposed in the cliffs and discuss the paleoenvironments within which they formed, (2) demonstrate the cyclicity in the Miocene marine formations and discuss its origin, (3) compare and contrast the section exposed at the Stratford and Nomini Cliffs with the classic Miocene Calvert Cliffs sequence exposed to the northeast in Calvert County, Maryland, and the Miocene sequence recovered in the Haynesville cores to the southeast in Richmond County, Virginia, (4) discuss and explain why a detailed correlation among these three places has been so difficult to attain, and (5) show typical lithologies of the Bacons Castle Formation and discuss the paleoenvironments in which they formed.

Paleosoils in the loess deposits of eastern Uzbekistan

NASA Astrophysics Data System (ADS)

Abdunazarov, U. K.; Stelmakh, A. G.

2010-12-01

Loess deposits of the eastern Uzbekistan are difficult to study the stratigraphy of the object. Clarification of the relationship of age and genetic features of the considered entities by traditional methods is difficult due to scarcity of remnants of the fauna and flora, the active Quaternary tectonics, the homogeneity of the rocks, especially the formation of loess sequences, specific conditions of geological and tectonic development, etc. In this regard, particularly relevant is the study of loess deposits by paleosoils subdivision and correlation. Paleosoils, which are present in the sections of loess sequences, distinct from loess-like loams, dividing them among themselves. Color these paleosoils noticeable brownish or brown, while the loess is a powdery mildew gray rock. Typically, the general scheme of occurrence of loess cover is linked with levels of relief mountainous areas. Recent studies show that the loess in the piedmont plains overlie a complex manner and include uneven paleosoils. Therefore, loess sequences of different geomorphological levels from the lower parts of slopes to the watershed have been studied in research paleosoils. The scheme was drawn up as a result of the studies. This scheme shows the main horizons paleosoils in loess deposits. Even-aged paleosoils and share their loess were identified in this scheme.

Comment on "The May 20 (MW 6.1) and 29 (MW 6.0), 2012, Emilia (Po Plain, Northern Italy) earthquakes: New seismotectonic implications from subsurface geology and high-quality hypocenter location" by Carannante et al., 2015

NASA Astrophysics Data System (ADS)

Bonini, Lorenzo; Toscani, Giovanni; Seno, Silvio

2016-10-01

Carannante et al. (2015) proposed an original seismotectonic interpretation of the Ferrara arc in the Po Plain (Italy) based on an accurate hypocenter relocation of the 2012 Emilia earthquake sequence and on structural analyses of sub-surface data. They contend that the causative faults of the 2012 sequence do not belong to the fold-and-thrusts system comprising the Ferrara Arc but in fact are located in the underlying basement. In our view this interpretation does not agree with observations, including: 1) the structural interpretation of the seismic reflection lines, that contrasts with some of the available data, e.g. the stratigraphy inferred from deep wells; 2) the seismotectonic setting, that is based exclusively on the correlation between inferred structural features and the location of late aftershocks; and 3) the inconsistency of the proposed seismogenic sources with the elevation changes caused by the sequence. All these points compromise the Carannante et al.'s interpretation and, as a consequence, previously proposed seismotectonic models are still valid.

A new sediment core from the early Aptian OAE1a: the Cau section (Prebetic Zone, Spain)

NASA Astrophysics Data System (ADS)

Alejandro Ruiz-Ortiz, Pedro; Castro, José Manuel; de Gea, Ginés A.; Jarvis, Ian; Loeser, Hannes; Molina, José Miguel; Nieto, Luis Miguel; Pancost, Richard; Quijano, María Luisa; Reolid, Matías; Skelton, Peter; Weissert, Helmut

2016-04-01

The occurrence of time intervals of enhanced deposition of organic matter (OM) during the Cretaceous, defined as Oceanic Anoxic Events (OAE), reflect abrupt changes in global carbon cycling. The exemplary Aptian OAE1a (120 Ma), is recorded in all the main ocean basins and associated with massive burial of OM in marine sediments [1]. OAE1a is concomitant with the 'nannoconid crisis', which represents a major biotic turnover [2], and also with widespread demise of carbonate platforms [1]. Much research has been done on the OAE1a from different sections in the world over the last decades, since the definition of the C-isotope stratigraphy of the event [3]. Notwithstanding, high-resolution studies across the entire event will be crucial to elucidate the precise timing and rates of the different environmental and biotic changes involved. In order to perform high-resolution studies, drill-cores can represent the best option. Previous cores with successful scientific results has been performed in two reference sections, the Cismon Apti-core [4], and more recently in La Bédoule [5]. Here we present a new drill-core from southern Spain, the Cau section core, drilled in the last quarter of 2015. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents the platform deposits of the Southern Iberian Palaeomargin. The lower Aptian of the Cau section is represented by an hemipelagic unit (Almadich Formation, ca. 200 m thick), deposited in a highly subsiding sector of a tilted block, located in the distal parts of the Prebetic Platform. Previous studies of the early Aptian of the Cau section have focused on the stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry [6], [7], among others. A recent study on the Cau section based on biomarkers has presented a detailed record of the PCO2, [8]. All these studies reveal that the Cau section represents an excellent site to investigate the OAE1a, based on its exceptional thickness and stratigraphic continuity, the quality and preservation of fossils and the geochemical signatures. Acknowledgements: This work is a contribution of the research project CGL2014-55274-P (Gov. of Spain). [1] Föllmi (2012). Cret. Res. 35, 230-257. [2] Erba et al. (2010). Science. 329, 428-432. [3] Menegatti et al. (1998). Paleoceanography 13, 530-545. [4] Erba et al. (1999). Jour. For. Res. 29, 371-391. [5] Lorenzen et al. (2013). Cret. Res. 39, 6-16. [6] Gea et al. (2003) Palaeo3. 200, 207-219. [7] Quijano et al. (2012). Palaeo3. 365-366, 276-293. [8] Naafs et al. (2016). Nat. Geosc. DOI: 10.1038/NGEO2627.

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.

Magnetic stratigraphy of the Danube loess: A composite Titel-Stari Slankamen loess section over the last one million years in Vojvodina, Serbia

NASA Astrophysics Data System (ADS)

Song, Yang; Guo, Zhengtang; Marković, Slobodan; Hambach, Ulrich; Deng, Chenglong; Chang, Lin; Wu, Jianyu; Hao, Qingzhen

2018-04-01

In Europe, the most complete loess-paleosol sequences over the past million years are preserved in the Serbian part of the Danube River drainage basin. The similarity in stratigraphy and climatic cycles between the Serbian and the Chinese loess sequences suggests that the loess deposits in these two regions could play an important role in the study of intercontinental climatic correlations and linkage. However, previous magnetostratigraphic studies of the Serbian loess, mainly conducted using the alternating field (AF) demagnetization approach, show significant differences with the Chinese loess, especially the stratigraphic positioning of the Matuyama-Brunhes boundary (MBB). Here, we conduct a detailed magnetostratigraphic investigation of a composite Titel-Stari Slankamen loess section in the Vojvodina (northern Serbia), using thermal and hybrid demagnetization methods, aiming to establish new chronological constraints for the Danube Basin loess. Based on the analyses of the mineral magnetic properties, anisotropy of magnetic susceptibility, progressive thermal and hybrid demagnetization, the MBB was determined within S8, broadly consistent with the MBB position seen in the Chinese loess. Present evidence supports the hypothesis that the overall normal polarity in the upper part of L9, with a thickness of 2.1 m, was possibly caused by a combination of the remagnetization of remanence-carrying coarse-grained magnetite during the Brunhes normal chron and bioturbation during the forming of the overlying paleosol S8. Thus, our magnetostratigraphic results provide solid chronological evidence for the coherence of pedostratigraphy and climatostratigraphy for the loess deposits in the Danube Basin and China. The synchronous occurrence of the strongest developed paleosol S5 (corresponding to MISs 15-13) and the least weathered thick loess unit L9 (corresponding to MISs 24-22) in the two regions confirms that extreme climatic events during these two intervals are possibly common features of the climate in the Northern Hemisphere at those times.

The Depositional and Erosional History of Northwestern Aeolis Mons, Gale Crater, Mars: Insights from Detailed 1:2K Geologic Mapping

NASA Astrophysics Data System (ADS)

Edgar, L. A.; Calef, F. J., III; Thomson, B. J.

2017-12-01

The Mars Science Laboratory (MSL) Curiosity rover is currently exploring the stratigraphy exposed in Aeolis Mons, the central mound of Gale crater. Gale crater has been the target of numerous remote sensing studies, aimed at understanding the origin and evolution of the mound, informally known as Mt. Sharp. A number of efforts have produced geologic maps of the mound and the MSL traverse path, in order to investigate the stratigraphic relationships between different sedimentary units. However, a scale gap exists between local mapping and stratigraphic analyses of the area explored by Curiosity and regional mapping of Aeolis Mons. As Curiosity explores the northwest flank of Aeolis Mons, there is a critical need for investigations to bridge this gap to enable rover-scale observations to be tied to orbital interpretations. This study is focused on detailed geologic mapping and stratigraphic correlations for the northwest flank of Aeolis Mons, including an area that the Curiosity rover will likely explore. The study region covers a 5.8 x 10 km area from approximately 137.27 to 137.44 °E and -4.70 to -4.82 °N. A 25 cm/pixel mosaic produced from images acquired by the High Resolution Imaging Science Experiment (HiRISE) camera provides a basemap for all mapping, and topographic information is provided by a HiRISE 1 m Digital Terrain Model. Preliminary digital geologic mapping was carried out at a scale of 1:10,000 to provide a framework for detailed geologic mapping efforts. Higher-resolution geologic mapping was then conducted at a scale of 1:2,000, and type localities were identified. As a result of newer, higher-resolution datasets that are now available and more narrowly focused mapping, we identify a number of new geologic units. Erosional remnants of some units point to a substantial erosional history. Collectively, the stratigraphy records diverse sedimentary environments and more variability in the depositional and erosional histories than previously identified. This study helps bridge the gap between previous mapping efforts and detailed rover-scale mapping, and will enable rover observations to be more closely tied to orbital interpretations across the northwest flank of Aeolis Mons.

Towards the Redefinition of the Global Stratigraphy of Mercury: The Case of Intermediate Plains

NASA Astrophysics Data System (ADS)

Galluzzi, V.; Rothery, D. A.; Massironi, M.; Ferranti, L.; Mercury Mapping Team

2018-05-01

Observations based on an average mapping scale of 1:400k provide context for the redefinition of the global stratigraphy of Mercury. Results show that the Intermediate Plains unit should be re-introduced as an official mappable terrain.

Digital Stratigraphy: Contextual Analysis of File System Traces in Forensic Science.

PubMed

Casey, Eoghan

2017-12-28

This work introduces novel methods for conducting forensic analysis of file allocation traces, collectively called digital stratigraphy. These in-depth forensic analysis methods can provide insight into the origin, composition, distribution, and time frame of strata within storage media. Using case examples and empirical studies, this paper illuminates the successes, challenges, and limitations of digital stratigraphy. This study also shows how understanding file allocation methods can provide insight into concealment activities and how real-world computer usage can complicate digital stratigraphy. Furthermore, this work explains how forensic analysts have misinterpreted traces of normal file system behavior as indications of concealment activities. This work raises awareness of the value of taking the overall context into account when analyzing file system traces. This work calls for further research in this area and for forensic tools to provide necessary information for such contextual analysis, such as highlighting mass deletion, mass copying, and potential backdating. © 2017 American Academy of Forensic Sciences.

Studying and Dating Indian Ocean Tsunamis by Using Benthic Foraminifera in the Sediment Stratigraphy of South Andaman Islands, India

NASA Astrophysics Data System (ADS)

Johnson, F. C.

2015-12-01

We analyzed the foraminifera and dated them to identify the sea level fluctuations in the coastal sediment stratigraphy of Andaman Islands. Our recent paleotsunami investigations are specially focused on unusual large magnitude earthquake and tsunamis in the south coast of Andaman. Our detailed study on the foraminifers preserved in the near sub surface stratigraphy and AMS ages show a strong signature of the tsunami event very much similar to the modern tsunami of December 2004. We found that foraminifer is an ideal geological key to bracket paleotsunami events. The AMS ages of these foraminifers supports the ages given by corals of Sumatra with a small error bar. The recent research approach to identify the ruptures and tsunami based on the corals of south Sumatra suggests a large time span of 1000 years for such mega events. Our foraminiferal archives obtained from 10g soil samples from the 2.5m deep Holocene stratigraphy suggests four seismic predecessors similar to the 2004 event with ~Mw9 with huge rupture. Huge foraminiferal population in the sedimentary stratigraphy is an indicative of sea level changes and the signatures of abrasion in the foraminifer's test (180µm) indicate strong wave surges and bead load transport during tsunami events. Spontaneous death of organisms due to tsunami waves gives an exact time frame with a narrow age limit than the charcoal. Sediment stratigraphy of south Andaman had such changes in each millennium. Sediment stratigraphy sections shows the huge population and assemblages and the AMS dates of this foraminifera in south Andaman shows four mega events. This kind of fossil assemblages are commonly associated with the sea regression and transgressions in the geological time scale. Tamil 'Sangam literatures' one of the oldest literature available in Indian main land and the corals ages from Sumatra are also emphasizes the predecessors of such unusual large magnitude earthquakes and tsunamis in the Indian Ocean. All these signatures are indicators of sea level fluctuations associated with tsunamis due to large magnitude Earthquakes (~Mw9).

Build-and-fill sequences: How subtle paleotopography affects 3-D heterogeneity of potential reservoir facies

USGS Publications Warehouse

McKirahan, J.R.; Goldstein, R.H.; Franseen, E.K.

2005-01-01

This study analyzes the three-dimensional variability of a 20-meter-thick section of Pennsylvanian (Missourian) strata over a 600 km2 area of northeastern Kansas, USA. It hypothesizes that sea-level changes interact with subtle variations in paleotopography to influence the heterogeneity of potential reservoir systems in mixed carbonate-silidclastic systems, commonly produdng build-and-fill sequences. For this analysis, ten lithofacies were identified: (1) phylloid algal boundstone-packstone, (2) skeletal wackestone-packstone, (3) peloidal, skeletal packstone, (4) sandy, skeletal grainstone-packstone, (5) oolite grainstone-packstone, (6) Osagia-brachiopod packstone, (7) fossiliferous siltstone, (8) lenticular bedded-laminated siltstone and fine sandstone, (9) organic-rich mudstone and coal, and (10) massive mudstone. Each facies can be related to depositional environment and base-level changes to develop a sequence stratigraphy consisting of three sequence boundaries and two flooding surfaces. Within this framework, eighteen localities are used to develop a threedimensional framework of the stratigraphy and paleotopography. The studied strata illustrate the model of "build-and-fill". In this example, phylloid algal mounds produce initial relief, and many of the later carbonate and silidclastic deposits are focused into subtle paleotopographic lows, responding to factors related to energy, source, and accommodation, eventually filling the paleotopography. After initial buildup of the phylloid algal mounds, marine and nonmarine siliciclastics, with characteristics of both deltaic lobes and valley fills, were focused into low areas between mounds. After a sea-level rise, oolitic carbonates formed on highs and phylloid algal facies accumulated in lows. A shift in the source direction of siliciclastics resulted from flooding or filling of preexisting paleotopographic lows. Fine-grained silidclastics were concentrated in paleotopographic low areas and resulted in clay-rich phylloid algal carbonates that would have made poor reservoirs. In areas more distant from silidclastic influx, phylloid algal facies with better reservoir potential formed in topographic lows. After another relative fall in sea level, marine carbonates and silidclastics were concentrated in paleotopographic low areas. After the next relative rise in sea level, there is little thickness or fades variation in phylloid algal limestone throughout the study area because: (1) substrate paleotopography had been subdued by filling, and (2) no silidclastics were deposited in the area. Widespread subaerial exposure and erosion during a final relative fall in sea level resulted in redevelopment of variable paleotopography. Build-and-fill sequences, such as these, are well known in other surface and subsurface examples. Initial relief is built by folding or faulting, differential compaction, erosion, or deposition of relief-building facies, such as phylloid algal and carbonate grainstone reservoir fades, or silidclastic wedges. Relief is filled through deposition of reservoir-fades siliciclastics, phylloid algal fades, and grainy carbonates, as well as nonreservoir facies, resulting in complex heterogeneity.

Eruptive stratigraphy of the Tatara-San Pedro complex, 36°S, sourthern volcanic zone, Chilean Andes: reconstruction method and implications for magma evolution at long-lived arc volcanic centers

USGS Publications Warehouse

Dungan, M.A.; Wulff, A.; Thompson, R.

2001-01-01

The Quaternary Tatara-San Pedro volcanic complex (36°S, Chilean Andes) comprises eight or more unconformity-bound volcanic sequences, representing variably preserved erosional remnants of volcanic centers generated during 930 ky of activity. The internal eruptive histories of several dominantly mafic to intermediate sequences have been reconstructed, on the basis of correlations of whole-rock major and trace element chemistry of flows between multiple sampled sections, but with critical contributions from photogrammetric, geochronologic, and paleomagnetic data. Many groups of flows representing discrete eruptive events define internal variation trends that reflect extrusion of heterogeneous or rapidly evolving magna batches from conduit-reservoir systems in which open-system processes typically played a large role. Long-term progressive evolution trends are extremely rare and the magma compositions of successive eruptive events rarely lie on precisely the same differentiation trend, even where they have evolved from similar parent magmas by similar processes. These observations are not consistent with magma differentiation in large long-lived reservoirs, but they may be accommodated by diverse interactions between newly arrived magma inputs and multiple resident pockets of evolved magma and / or crystal mush residing in conduit-dominated subvolcanic reservoirs. Without constraints provided by the reconstructed stratigraphic relations, the framework for petrologic modeling would be far different. A well-established eruptive stratigraphy may provide independent constraints on the petrologic processes involved in magma evolution-simply on the basis of the specific order in which diverse, broadly cogenetic magmas have been erupted. The Tatara-San Pedro complex includes lavas ranging from primitive basalt to high-SiO2 rhyolite, and although the dominant erupted magma type was basaltic andesite ( 52-55 wt % SiO2) each sequence is characterized by unique proportions of mafic, intermediate, and silicic eruptive products. Intermediate lava compositions also record different evolution paths, both within and between sequences. No systematic long-term pattern is evident from comparisons at the level of sequences. The considerable diversity of mafic and evolved magmas of the Tatara-San Pedro complex bears on interpretations of regional geochemical trends. The variable role of open-system processes in shaping the compositions of evolved Tatara-San Pedro complex magmas, and even some basaltic magmas, leads to the conclusion that addressing problems such as are magma genesis and elemental fluxes through subduction zones on the basis of averaged or regressed reconnaissance geochemical datasets is a tenuous exercise. Such compositional indices are highly instructive for identifying broad regional trends and first-order problems, but they should be used with extreme caution in attempts to quantify processes and magma sources, including crustal components, implicated in these trends.

Sequence stratigraphy, sedimentary systems and petroleum plays in a low-accommodation basin: Middle to upper members of the Lower Jurassic Sangonghe Formation, Central Junggar Basin, Northwestern China

NASA Astrophysics Data System (ADS)

Feng, Youliang; Jiang, Shu; Wang, Chunfang

2015-06-01

The Lower Jurassic Junggar Basin is a low-accommodation basin in northwestern China. Because of low subsidence rates and a warm, wet climate, deposits of the Central subbasin of the Junggar Basin formed from fluvial, deltaic, shallow lake facies. Sequence stratigraphy and sedimentary systems of the Lower Jurassic members of the Sangonghe Formation (J1s) were evaluated by observing cores, interpreting wireline logs and examining seismic profiles. Two third-order sequences were recognized in the strata. The distribution of the sedimentary systems in the systems tracts shows that tectonic movement, paleorelief, paleoclimate and changes in lake level controlled the architecture of individual sequences. During the development of the lowstand systems tract (LST), the intense structural movement of the basin resulted in a significant fall in the water level in the lake, accompanied by rapid accommodation decrease. Braided rivers and their deltaic systems were also developed in the Central Junggar Basin. Sediments carried by braided rivers were deposited on upward slopes of the paleorelief, and braid-delta fronts were deposited on downward slopes. During the transgressive systems tract (TST), the tectonic movement of the basin was quiescent and the climate was warm and humid. Lake levels rose and accommodation increased quickly, shoal lines moved landward, and shore- to shallow-lake deposits, sublacustrine fans and deep-lake facies were deposited in shallow- to deep-lake environments. During the highstand systems tract (HST), the accommodation no longer increased but sediment supply continued, far exceeding accommodation. HST deposits slowly formed in shallow-lake to meandering river delta-front environments. Relatively low rates of structural subsidence and low accommodation resulted in coarse-grained successions that were fining upward. Deposits were controlled by structural movement and paleorelief within the LST to TST deposits in the Central subbasin. Fine- to medium-grained coarsening-upward successions developed during the HST. The sand bodies of braid-delta fronts on the downward slopes of the paleorelief in the LST and the sublacustrine fans in the TST became reservoirs for hydrocarbon accumulation. Petroleum plays have only been found in the Sangonghe Formation (J1s) located on structural ridges that consist of sand bodies comprising these sequences. Favorable conditions for petroleum plays in HST1-LST2 occur where the sand bodies have been fractured by faults and sealed by denudation and pinch-out lines, then overlain by deep lake mudstone in TST2. The favorable condition of the sand bodies within TST2 occurs where isolated sand bodies have been fractured by faults.

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

NASA Astrophysics Data System (ADS)

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

2004-10-01

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

Miocene depositional history, sequences and chronostratigraphy of the ANDRILL AND-2A drillcore, Victoria Land Basin, Antarctica

NASA Astrophysics Data System (ADS)

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

2009-12-01

ANDRILL’s Southern McMurdo Sound Project (SMS) completed the AND-2A drillhole (77°45.488 S; 165°16.613 E) from a floating sea-ice platform (~8.5 meters thick), over ~380 meters of water, reaching a total depth of 1138.54 mbsf, and obtaining an excellent quality core with 98% recovery through the cored interval. This sedimentary archive comprises an expanded early and middle Miocene section deposited in a high-accommodation continental margin location, proximal to glacial ice influence from the West Antarctic Ice Sheet, East Antarctic Ice Sheet, and local ice in the Transantarctic Mountains. Stratigraphic sequences and facies interpretations reveal a cyclical history of environmental variation influenced by climate, glacial advance/retreat cycles, and water depth variation. A well-developed chronostratigraphic framework developed through integrated diatom biostratigraphy, magneto-stratigraphy, Sr isotope geochemistry, and radiometric dating of volcanic materials, allows for the comparison of events recognized in this drillcore with events identified in distal proxy records from deep-sea stable isotope studies, and in sea-level reconstructions based on continental shelf sequence stratigraphy. The AND-2A drillcore recovered a 600 m-thick stratigraphic interval documenting the Antarctic coastal environment during the warm middle Miocene climatic optimum (17.5 to 14.5 Ma). A disconformity separating the middle and upper Miocene intervals in the AND-2A drillcore represents a substantial climate step into cold, glacial conditions of the late Miocene. Lower and middle Miocene shallow marine sediments were deposited in the subsiding Victoria Land Basin, during a period of relatively steady thermal subsidence, on the coastal plain and continental shelf seaward of the rising Transantarctic Mountains. More than 60 sequences recognized in the AND-2A drillcore represent repeating lithological changes in glacimarine, terrigenous, volcanic and biogenic sediments, deposited during a dynamic climate regime, and likely reflecting Milankovitch forcing. Fossils preserved in these strata suggest non-polar climate conditions similar to southern Patagonia and southwestern New Zealand today, influenced by high sediment discharge from river run-off, and high coastal turbidity. The AND-2A drillcore represents the third high-quality drillcore in Southern Victoria Land to record early Miocene paleoenvironmental changes (the other two records are preserved in the CRP-1 and CRP-2 drillcores), so that the timing and magnitude of glacial and eustatic variations can be examined at several sites along the Southern Victoria Land margin.

Cone-penetrometer exploration of sinkholes: Stratigraphy and soil properties

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

Bloomberg, D.; Upchurch, S.B.; Hayden, M.L.

1988-10-01

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

Stable isotope analysis of Dacryoconarid carbonate microfossils: a new tool for Devonian oxygen and carbon isotope stratigraphy.

PubMed

Frappier, Amy Benoit; Lindemann, Richard H; Frappier, Brian R

2015-04-30

Dacryoconarids are extinct marine zooplankton known from abundant, globally distributed calcite microfossils in the Devonian, but their shell stable isotope composition has not been previously explored. Devonian stable isotope stratigraphy is currently limited to less common invertebrates or bulk rock analyses of uncertain provenance. As with Cenozoic planktonic foraminifera, isotopic analysis of dacryoconarid shells could facilitate higher-resolution, geographically widespread stable isotope records of paleoenvironmental change, including marine hypoxia events, climate changes, and biocrises. We explored the use of Dacryoconarid isotope stratigraphy as a viable method in interpreting paleoenvironments. We applied an established method for determining stable isotope ratios (δ(13) C, δ(18) O values) of small carbonate microfossils to very well-preserved dacryoconarid shells. We analyzed individual calcite shells representing five common genera using a Kiel carbonate device coupled to a MAT 253 isotope ratio mass spectrometer. Calcite shell δ(13) C and δ(18) O values were compared by taxonomic group, rock unit, and locality. Single dacryoconarid calcite shells are suitable for stable isotope analysis using a Kiel-IRMS setup. The dacryoconarid shell δ(13) C values (-4.7 to 2.3‰) and δ(18) O values (-10.3 to -4.8‰) were consistent across taxa, independent of shell size or part, but varied systematically through time. Lower fossil δ(18) O values were associated with warmer water temperature and more variable δ(13) C values were associated with major bioevents. Dacryoconarid δ(13) C and δ(18) O values differed from bulk rock carbonate values. Dacryoconarid individual microfossil δ(13) C and δ(18) O values are highly sensitive to paleoenvironmental changes, thus providing a promising avenue for stable isotope chemostratigraphy to better resolve regional to global paleoceanographic changes throughout the upper Silurian to the upper Devonian. Our results warrant further exploration of dacryoconarid stable isotope proxy sensitivity, the isotopic contrast among dacryoconarids, other taxa, and bulk rock, as well as other potential dacryoconarid proxies (Mg/Ca, Sr/Ca, (87) Sr/(86) Sr, microlaser and ion microprobe isotope techniques, and clumped isotopes) for stratigraphic research. Copyright © 2015 John Wiley & Sons, Ltd.

78 FR 42977 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-Cooperative...

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Federal Register 2010, 2011, 2012, 2013, 2014

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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.

Stratigraphy, structure and regional correlation of eastern Blue Ridge sequences in southern Virginia and northwestern North Carolina: an interim report from new USGS mapping

USGS Publications Warehouse

Carter, Mark W.; Merschat, Arthur J.

2014-01-01

The contact between eastern Blue Ridge stratified rocks above Mesoproterozoic basement rocks is mostly faulted (Gossan Lead and Red Valley). The Callaway fault juxtaposes Ashe and Lynchburg rocks above Wills Ridge Formation. Alligator Back Formation rocks overlie Ashe and Lynchburg rocks along the Rock Castle Creek fault, which juxtaposes rocks of different metamorphism. The fault separates major structural domains: rocks with one penetrative foliation in the footwall, and pin-striped recrystallized compositional layering, superposed penetrative foliations, and cleavage characterize the hanging wall. These relationships are ambiguous along strike to the southwest, where the Ashe and Alligator Back formations are recrystallized at higher metamorphic grades.

Assessment of Undiscovered Oil and Gas Resources of the Uinta-Piceance Province of Colorado and Utah, 2002

USGS Publications Warehouse

,

2002-01-01

The U.S. Geological Survey (USGS) recently completed an assessment of the undiscovered oil and gas potential of the UintaPiceance Province of northwestern Colorado and northeastern Utah (fig. 1). The assessment of the Uinta-Piceance Province is geology based and uses the Total Petroleum System concept. The geologic elements of Total Petroleum Systems include hydrocarbon source rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy, petrophysical properties), and hydrocarbon traps (trap formation and timing). Using this geologic framework, the USGS defined five Total Petroleum Systems and 20 Assessment Units within these Total Petroleum Systems, and quantitatively estimated the undiscovered oil and gas resources within each Assessment Unit (table 1).

Modeling the stratigraphy and preservation potential of meandering stream deposits

NASA Astrophysics Data System (ADS)

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

2003-12-01

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

Paroxysmal dome explosion during the Merapi 2010 eruption: Processes and facies relationships of associated high-energy pyroclastic density currents

NASA Astrophysics Data System (ADS)

Komorowski, Jean-Christophe; Jenkins, Susanna; Baxter, Peter J.; Picquout, Adrien; Lavigne, Franck; Charbonnier, Sylvain; Gertisser, Ralf; Preece, Katie; Cholik, Noer; Budi-Santoso, Agus; Surono

2013-07-01

An 11-minute sequence of laterally-directed explosions and retrogressive collapses on 5 November 2010 at Merapi (Indonesia) destroyed a rapidly-growing dome and generated high-energy pyroclastic density currents (PDCs) spreading over 22 km2 with a runout of 8.4 km while contemporaneous co-genetic valley-confined PDCs reached 15.5 km. This event formed Stage 4 of the multi-stage 2010 eruption, the most intense eruptive episode at Merapi since 1872. The deposits and the widespread devastating impact of associated high-energy PDCs on trees and buildings show striking similarities with those from historical volcanic blasts (Montagne Pelée, Martinique, Bezymianny, Russia, Mount St. Helens, USA, Soufrière Hills, Montserrat). We provide data from stratigraphic and sedimentologic analyses of 62 sections of the first unequivocal blast-like deposits in Merapi's recent history. We used high resolution satellite imagery to map eruptive units and flow direction from the pattern of extensive tree blowdown. The stratigraphy of Stage 4 consists of three depositional units (U0, U1, U2) that we correlate to the second, third and fourth explosions of the seismic record. Both U1 and U2 show a bi-partite layer stratigraphy consisting each of a lower L1 layer and an upper L2 layer. The lower L1 layer is typically very coarse-grained, fines-poor, poorly-sorted and massive, and was deposited by the erosive waxing flow head. The overlying L2 layer is much finer grained, fines-rich, moderately to well-sorted, with laminar to wavy stratification. L2 was deposited from the waning upper part and wake of the PDC. Field observations indicate that PDC height reached ~ 330 m with an internal velocity of ~ 100 m s- 1 within 3 km from the source. The summit's geometry and the terrain morphology formed by a major transversal ridge and a funneling deep canyon strongly focused PDC mass towards a major constriction, thereby limiting the loss of kinetic energy. This favored elevated PDC velocities and high particle concentration, promoted overspilling of PDCs across high ridges into other river valleys, and generated significant dynamic pressures to distances of 6 km that caused total destruction of buildings and the forest. The Merapi 2010 eruption highlights that explosive and gravitational disintegration of a rapidly growing dome can generate devastating high-energy, high-velocity PDCs. This constitutes a credible high impact scenario for future multi-stage eruptions at Merapi and at other volcanoes that pose particular monitoring, crisis response, and risk reduction challenges.

Clustering and Hazard Estimation in the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Cronin, S. J.; Bebbington, M. S.

2009-12-01

The Auckland Volcanic Field (AVF) with its 49 eruptive centres formed over the last c. 250 ka presents several unique challenges to our understanding of distributed volcanic field construction and evolution. Due to the youth of the field, high-resolution stratigraphy of eruption centres and ash-fall sequences is possible, allowing time-breaks, soil and peat formation between eruption units to be identified. Radiocarbon dating of sediments between volcanic deposits shows that at least five of the centres have erupted on more than one occasion, with time breaks of 50-100 years between episodes. In addition, paleomagnetic and ash fall evidence implies that there has been strong clustering of eruption events over time, with a specific “flare-up” event involving over possibly up to 19 eruptions occurring between 35-25 ka, in spatially disparate locations. An additional complicating factor is that the only centre that shows any major evidence for evolution out of standard alkali basaltic compositions is also the youngest and largest in volume by several orders of magnitude. All of these features of the AVF, along with relatively poor age-control for many of the vents make spatio-temporal hazard forecasting for the field based on assumptions of past behaviour extremely difficult. Any relationships that take volumetric considerations into account are particularly difficult, since any trend analysis produces unreasonably large future eruptions. The most reasonable model is spatial, via eruption location. We have re-examined the age progression of eruptive events in the AVF, incorporating the most reliable sources of age and stratigraphic data, including developing new correlations between ashfall records in cores and likely vent locations via a probabilistic model of tephra dispersal. A Monte Carlo procedure using the age-progression, stratigraphy and dating constraints can then randomly reproduce likely orderings of events in the field. These were fitted by a clustering-based model of vent locations as originally applied by Magill et al (2005: Mathematical Geol. 37: 227-242) to the Allen and Smith (1994; Geosci. Report Shizuoka Univ 20: 5-14) age ordering of volcanism at AVF. Applying this model, modified by allowing continuation of activity at or around the youngest event, to sampled age orderings from the Monte Carlo procedure shows a very different spatial forecast to the earlier analysis. It is also different to the distribution from randomly ordered events, implying there is at least some clustering control on the location of eruptions in the field. Further iterations of this modelling approach will be tested in relation to eruptive volume and applied to other comparative volcanic fields.

High-resolution heavily T2-weighted magnetic resonance imaging for evaluation of the pituitary stalk in children with ectopic neurohypophysis.

PubMed

El Sanharawi, Imane; Tzarouchi, Loukia; Cardoen, Liesbeth; Martinerie, Laetitia; Leger, Juliane; Carel, Jean-Claude; Elmaleh-Berges, Monique; Alison, Marianne

2017-05-01

In anterior pituitary deficiency, patients with non visible pituitary stalk have more often multiple deficiencies and persistent deficiency than patients with visible pituitary stalk. To compare the diagnostic value of a high-resolution heavily T2-weighted sequence to 1.5-mm-thick unenhanced and contrast-enhanced sagittal T1-weighted sequences to assess the presence of the pituitary stalk in children with ectopic posterior pituitary gland. We retrospectively evaluated the MRI data of 14 children diagnosed with ectopic posterior pituitary gland between 2010 and 2014. We evaluated the presence of a pituitary stalk using a sagittal high-resolution heavily T2-weighted sequence and a 1.5-mm sagittal T1-weighted turbo spin-echo sequence before and after contrast medium administration. A pituitary stalk was present on at least one of the sequences in 10 of the 14 children (71%). T2-weighted sequence depicted the pituitary stalk in all 10 children, whereas the 1.5-mm-thick T1-weighted sequence depicted 2/10 (20%) before contrast injection and 8/10 (80%) after contrast injection (P=0.007). Compared with 1.5-mm-thick contrast-enhanced T1-weighted sequences, high-resolution heavily T2-weighted sequence demonstrates better sensitivity in detecting the pituitary stalk in children with ectopic posterior pituitary gland, suggesting that contrast injection is unnecessary to assess the presence of a pituitary stalk in this setting.

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.

Controls on facies and sequence stratigraphy of an upper Miocene carbonate ramp and platform, Melilla basin, NE Morocco

USGS Publications Warehouse

Cunningham, K.J.; Collins, Luke S.

2002-01-01

Upwelling of cool seawater, paleoceanographic circulation, paleoclimate, local tectonics and relative sea-level change controlled the lithofacies and sequence stratigraphy of a carbonate ramp and overlying platform that are part of a temporally well constrained carbonate complex in the Melilla basin, northeastern Morocco. At Melilla, from oldest to youngest, a third-order depositional sequence within the carbonate complex contains (1) a retrogradational, transgressive, warm temperate-type rhodalgal ramp; (2) an early highstand, progradational, bioclastic platform composed mainly of a temperate-type, bivalve-rich molechfor facies; and (3) late highstand, progradational to downstepping, subtropical/tropical-type chlorozoan fringing Porites reefs. The change from rhodalgal ramp to molechfor platform occurred at 7.0??0.14 Ma near the Tortonian/Messinian boundary. During a late stage in the development of the bioclastic platform a transition from temperate-type molechfor facies to subtropical/tropical-type chlorozoan facies occurred and is bracketed by chron 3An.2n (??? 6.3-6.6 Ma). Comparison to a well-dated carbonate complex in southeastern Spain at Cabo de Gata suggests that upwelling of cool seawater influenced production of temperate-type limestone within the ramp and platform at Melilla during postulated late Tortonian-early Messinian subtropical/tropical paleoclimatic conditions in the western Paleo-Mediterranean region. The upwelling of cool seawater across the bioclastic platform at Melilla could be related to the beginning of 'siphoning' of deep, cold Atlantic waters into the Paleo-Mediterranean Sea at 7.17 Ma. The facies change within the bioclastic platform from molechfor to chlorozoan facies may be coincident with a reduction of the siphoning of Atlantic waters and the end of upwelling at Melilla during chron 3An.2n. The ramp contains one retrogradational parasequence and the bioclastic platform three progradational parasequences. Minor erosional surfaces that bound the upper surface of the ramp and upper surface of the oldest platform parasequence are related to relative falls in sea level induced by local volcanism and associated tectonic uplift. These local relative falls had little influence on a broader-scale rise to stillstand in relative sea level that controlled development of the transgressive and early highstand systems tracts represented in the ramp and platform, respectively. ?? 2002 Elsevier Science B.V. All rights reserved.

Non-zero Δ33S preserved in rocks from the Basal Ultramafic Sequence indicate crustal contamination in the most primitive magma of the Rustenburg Layered Suite (Bushveld Complex, South Africa)

NASA Astrophysics Data System (ADS)

Magalhaes, N.; Wilson, A.; Penniston-Dorland, S.; Farquhar, J.

2017-12-01

The sulfur isotope composition of the Rustenburg Layered Suite (RLS) of the Bushveld Complex is different than expected from a magma sourced from the mantle (Δ33S=0), as measurements indicate the presence of an Archean surface-derived sulfur component. The Basal Ultramafic Sequence (BUS) is thought to be the most primitive magma of the RLS, as it is the lowest in the stratigraphy, has the highest Mg# (>0.92) for primary phases (olivine and orthopyroxene), and is in direct contact with the Magaliesberg quartzite of the Pretoria Group.We have measured the composition of sulfides in rocks from the Lower Zone, Marginal Zone, and the BUS, which were sampled in a 2300m drill core from the Clapham area, in the eastern Bushveld Complex. While the rocks of the Lower Zone have a relatively homogeneous non-zero Δ33S of 0.065‰, comparable to previous findings, there is an abrupt increase in the value of Δ33S (up to +0.301‰) in the Marginal Zone, which may be consistent with the observation in hand sample of assimilation of country rocks. The BUS also shows a surface-derived signal (average of 0.040‰), which is the lowest measured for any zone of the RLS.The non-zero Δ33S found in the Basal Ultramafic Sequence is evidence of the contamination of the magma with surface-derived material. In the upper parts of the intrusion, the Δ33S signature relates to whole-rock Sr and Nd isotopes, and their relationship suggests multiple sources of contamination. However, the relationship between sulfur and in-situ strontium isotope compositions (plagioclase) in this section of the RLS is not as clear as it is further up in the stratigraphy. This might reflect small-scale processes during the magmatic chamber stage, different compositions of local wall rock compared to deeper contaminants, or the presence of decoupled behavior between the isotope systems.These differences in the sulfur isotope composition between the different stratigraphic layers have been preserved regardless of any late magmatic processes that may have occurred, which further supports that the sulfur isotope composition of the RLS was not fully homogenized at a later stage by fluid migration.

Neogene sequence stratigraphy, Nam Con Son Basin, offshore Vietnam

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

McMillen, K.J.; Do Van Luu; Lee, E.K.

1996-12-31

An integrated well log, biostratigraphic, and seismic stratigraphic study of Miocene to Recent deltaic sediments deposited in the Nam Con Son Basin offshore from southern Vietnam shows the influence of eustacy and tectonics on sequence development. Sediments consist of Oligocene non-marine rift-basin fill (Cau Formation), early to middle Miocene tide-dominated delta plain to delta front sediments (TB 1.5 to TB 2.5, Due and Thong Formations), and late Miocene to Recent marine shelf sediments (TB. 2.6 to TB 3.1 0, Mang Cau, Nam Con Son, and Bien Dong Formations). Eustacy controlled the timing of key surfaces and sand distribution in themore » tectonically-quiet early Miocene. Tectonic effects on middle to late Miocene sequence development consist of thick transgressive systems tracts due to basin-wide subsidence and transgression, sand distribution in the basin center, and carbonate sedimentation on isolated fault blocks within the basin. Third-order sequence boundaries (SB) are identified by spore peaks, sand stacking patterns, and channel incision. In the basin center, widespread shale beds with coal occur above sequence boundaries followed by transgressive sandstone units. These TST sandstones merge toward the basin margin where they lie on older HST sandstones. Maximum flooding surfaces (MFS) have abundant marine microfossils and mangrove pollen, a change in sand stacking pattern, and often a strong seismic reflection with downlap. Fourth-order genetic-type sequences are also interpreted. The MFS is the easiest marker to identify and correlate on well logs. Fourth-order SB occur within these genetic units but are harder to identify and correlate.« less

Neogene sequence stratigraphy, Nam Con Son Basin, offshore Vietnam

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

McMillen, K.J.; Do Van Luu; Lee, E.K.

1996-01-01

An integrated well log, biostratigraphic, and seismic stratigraphic study of Miocene to Recent deltaic sediments deposited in the Nam Con Son Basin offshore from southern Vietnam shows the influence of eustacy and tectonics on sequence development. Sediments consist of Oligocene non-marine rift-basin fill (Cau Formation), early to middle Miocene tide-dominated delta plain to delta front sediments (TB 1.5 to TB 2.5, Due and Thong Formations), and late Miocene to Recent marine shelf sediments (TB. 2.6 to TB 3.1 0, Mang Cau, Nam Con Son, and Bien Dong Formations). Eustacy controlled the timing of key surfaces and sand distribution in themore » tectonically-quiet early Miocene. Tectonic effects on middle to late Miocene sequence development consist of thick transgressive systems tracts due to basin-wide subsidence and transgression, sand distribution in the basin center, and carbonate sedimentation on isolated fault blocks within the basin. Third-order sequence boundaries (SB) are identified by spore peaks, sand stacking patterns, and channel incision. In the basin center, widespread shale beds with coal occur above sequence boundaries followed by transgressive sandstone units. These TST sandstones merge toward the basin margin where they lie on older HST sandstones. Maximum flooding surfaces (MFS) have abundant marine microfossils and mangrove pollen, a change in sand stacking pattern, and often a strong seismic reflection with downlap. Fourth-order genetic-type sequences are also interpreted. The MFS is the easiest marker to identify and correlate on well logs. Fourth-order SB occur within these genetic units but are harder to identify and correlate.« less

Sequence stratigraphy of an Oligocene carbonate shelf, Central Kalimantan, Indonesia

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

Saller, A.; Armin, R.; Ichram, L.O.

1991-03-01

Interpretations of Oligocene shelfal limestones from Central Kalimantan, Indonesia, suggest caution in predicting sea-level lowstands from seismic reflector patterns or published sea-level curves. Three major depositional sequences, each 200-400 m thick, were delineated in outcrops and seismic lines: late Eocene to early Oligocene (34-38 Ma), middle Oligocene (29.7-32 Ma), and early late Oligocene (28-29.7 Ma). The lowest sequence is mainly shale with tin sandstones and limestones (large-foram wackestone). The middle and upper sequences are carbonate with transgressive systems tracts (TSTs) overlain by highstand systems tracts (HSTs). TSTs contain large-foram wackestone-packstones and coral wackestone-packstones. HSTs are characterized by (1) shale andmore » carbonate debris flows deposited on the lower slope, (2) argillaceous large-foram wackestones on the upper slope, (3) discontinuous coral wackestones and boundstones on the shelf margin, (4) bioclastic packstones and grainstones on backreef flats and shelf-margin shoals, and (5) branching-coral and foraminiferal wackestones in the lagoon. Bases of sequences are characterized by transgression and onlap. Deepending and/or drowning of the carbonate shelf occurred at the top of the middle and upper sequences. Basinal strata that apparently onlap the middle and upper carbonate shelf margins might be misinterpreted as lowstand deposits, although regional studies indicate they are prodelta sediments baselapping against the shelf. Shallowing the subaerial exposure of the carbonates might be expected during the large mid-Oligocene (29.5-30 Ma) sea-level drop of Haq et al. (1987), instead of the observed deepening and local drowning.« less

Stratigraphic correlations in mid- to late-Proterozoic carbonates of the Democratic Republic of Congo using magnetic susceptibility

NASA Astrophysics Data System (ADS)

Delpomdor, Franck R. A.; Devleeschouwer, Xavier; Spassov, Simo; Préat, Alain R.

2017-04-01

In this paper, we have tested the application of magnetic susceptibility measurements in Cu-Ag-Zn-Pb-(Fe)-mineralized carbonates of the BIe subgroup (Democratic Republic of Congo) as an efficient tool for regional and global high-resolution stratigraphic correlations in the Neoproterozoic marine carbonates. To achieve this goal, we integrate the low-field magnetic susceptibility (XLF) data with facies analyses, geochemistry and isotope stratigraphy. The microfacies analyses of two cores, Tshinyama#S70 and Kafuku#15, drilled in the early Neoproterozoic carbonates of the Mbuji-Mayi Supergroup reveal a deep carbonate ramp setting associated with a microbial/stromatolitic mid-ramp environment. High-resolution stratigraphic correlations using magnetic susceptibility and C-isotope curves established for both cores, 190 km apart, suggest a sedimentary hiatus at the base of the Tshinyama#S70 succession. C-O and Sr isotopes and Sr/Ca and Fe abundances show that a diagenetic meteoric overprint affected the series of the Tshinyama#S70 core and a thermal effect related to mineralizing fluids affected the Kafuku#15 core carbonates.

High-resolution stratigraphy of a Mississippi subdelta-lobe progradation in the Barataria Bight, north-central Gulf of Mexico

USGS Publications Warehouse

Flocks, J.G.; Ferina, N.F.; Dreher, C.; Kindinger, J.L.; FitzGerald, D.M.; Kulp, M.A.

2006-01-01

The coastal zone of southeastern Louisiana is the product of numerous cycles of progradation, abandonment, and marine transgression of the Mississippi River delta. Currently, the shoreline in the Barataria Bight is undergoing significant erosion and retreat, and understanding its evolution is crucial in stabilization efforts. This study uses an extensive collection of geophysical and sediment core data from Barataria Bay and offshore to develop a geologic model of the shallow (< 10 m) subsurface. The purpose of the model is twofold: (1) establish the stratigraphic architecture of a subdelta lobe of the Bayou des Families delta, deposited by the Mississippi River approximately 4000 years before present; and (2) provide a high-resolution description of the geologic framework in a context that can be applied to coastal management issues in similar fluvially dominated coastal environments worldwide. The results of the study demonstrate how high-quality geologic data from the coastal environment can be used not only to further our understanding of shoreline evolution but also to provide pertinent information for coastal management needs.

Learning to tell Neoproterozoic time

NASA Technical Reports Server (NTRS)

Knoll, A. H.

2000-01-01

In 1989, the International Commission on Stratigraphy established a Working Group on the Terminal Proterozoic Period. Nine years of intensive, multidisciplinary research by scientists from some two dozen countries have markedly improved the framework for the correlation and calibration of latest Proterozoic events. Three principal phenomena--the Marinoan ice age, Ediacaran animal diversification, and the beginning of the Cambrian Period--specify the limits and character of this interval, but chemostratigraphy and biostratigraphy based on single-celled microfossils (acritarchs), integrated with high-resolution radiometric dates, provide the temporal framework necessary to order and evaluate terminal Proterozoic tectonic, biogeochemical, climatic, and biological events. These data also provide a rational basis for choosing the Global Stratotype Section and Point (GSSP) that will define the beginning of this period. A comparable level of stratigraphic resolution may be achievable for the preceding Cryogenian Period, providing an opportunity to define this interval, as well, in chronostratigraphic terms--perhaps bounded at beginning and end by the onset of Sturtian glaciation and the decay of Marinoan ice sheets, respectively. Limited paleontological, isotopic, and radiometric data additionally suggest a real but more distant prospect of lower Neoproterozoic correlation and stratigraphic subdivision.

Geomorphic Transport Laws and the Statistics of Topography and Stratigraphy

NASA Astrophysics Data System (ADS)

Schumer, R.; Taloni, A.; Furbish, D. J.

2016-12-01

Geomorphic transport laws take the form of partial differential equations in which sediment motion is a deterministic function of slope. The addition of a noise term, representing unmeasurable, or subgrid scale autogenic forcing, reproduces scaling properties similar to those observed in topography, landforms, and stratigraphy. Here we describe a transport law that generalizes previous equations by permitting transport that is local or non-local in addition to different types of noise. More importantly, we use this transport law to link the character of sediment transport to the statistics of topography and stratigraphy. In particular, we link the origin of the Sadler effect to the evolution of the earth surface via a transport law.

Non-invasive NMR stratigraphy of a multi-layered artefact: an ancient detached mural painting.

PubMed

Di Tullio, Valeria; Capitani, Donatella; Presciutti, Federica; Gentile, Gennaro; Brunetti, Brunetto Giovanni; Proietti, Noemi

2013-10-01

NMR stratigraphy was used to investigate in situ, non-destructively and non-invasively, the stratigraphy of hydrogen-rich layers of an ancient Nubian detached mural painting. Because of the detachment procedure, a complex multi-layered artefact was obtained, where, besides layers of the original mural painting, also the materials used during the procedure all became constitutive parts of the artefact. NMR measurements in situ enabled monitoring of the state of conservation of the artefact and planning of minimum representative sampling to validate results obtained in situ by solid-state NMR analysis of the samples. This analysis enabled chemical characterization of all organic materials. Use of reference compounds and prepared specimens assisted data interpretation.

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.

'Combined reflectance stratigraphy' - subdivision of loess successions by diffuse reflectance spectrometry (DRS)

NASA Astrophysics Data System (ADS)

Szeberényi, Jozsef; Bradak-Hayashi, Balázs; Kiss, Klaudia; Kovács, József; Varga, György; Balázs, Réka; Szalai, Zoltán; Viczián, István

2016-04-01

The different varieties of loess (and intercalated paleosol layers) together constitute one of the most widespread terrestrial sediments, which was deposited, altered, and redeposited in the course of the changing climatic conditions of the Pleistocene. To reveal more information about Pleistocene climate cycles and/or environments the detailed lithostratigraphical subdivision and classification of the loess variations and paleosols are necessary. Beside the numerous method such as various field measurements, semi-quantitative tests and laboratory investigations, diffuse reflectance spectroscopy (DRS) is one of the well applied method on loess/paleosol sequences. Generally, DRS has been used to separate the detrital and pedogenic mineral component of the loess sections by the hematite/goethite ratio. DRS also has been applied as a joint method of various environmental magnetic investigations such as magnetic susceptibility- and isothermal remanent magnetization measurements. In our study the so-called "combined reflectance stratigraphy method" were developed. At First, complex mathematical method was applied to compare the results of the spectral reflectance measurements. One of the most preferred multivariate methods is cluster analysis. Its scope is to group and compare the loess variations and paleosol based on the similarity and common properties of their reflectance curves. In the Second, beside the basic subdivision of the profiles by the different reflectance curves of the layers, the most characteristic wavelength section of the reflectance curve was determined. This sections played the most important role during the classification of the different materials of the section. The reflectance value of individual samples, belonged to the characteristic wavelength were depicted in the function of depth and well correlated with other proxies like grain size distribution and magnetic susceptibility data. The results of the correlation showed the significance of the "combined reflectance stratigraphy" as a stratigraphical method and as an environmental proxy also. Acknowledgment Bradák-Hayashi, B.'s fellowship at Department of Planetology (Kobe University, Japan) was supported by the Japan Society for the Promotion of Science (JSPS). The investigation was supported by International Visegrad Fund. Project No: 11410020.

Avulsion Clusters in Alluvial Systems: An Example of Large-Scale Self-Organization in Ancient and Experimental Basins

NASA Astrophysics Data System (ADS)

Hajek, E.; Heller, P.; Huzurbazar, S.; Sheets, B.; Paola, C.

2006-12-01

The stratigraphic record of at least some alluvial basins exhibits a spatial structure that may reflect long time- scale (103-105 yr in natural basins) autogenic organization of river avulsions. Current models of avulsion-dominated alluvial sequences emphasize the spatial and temporal distribution of coarse-grained channel-belt deposits amid fine-grained floodplain materials. These models typically assume that individual avulsions move, either randomly or deterministically, to low spots distributed throughout the model space. However, our observations of ancient deposits and experimental stratigraphy indicate a previously unrecognized pattern of channel-belt organization, where clusters of closely-spaced channel-belt deposits are separated from each other by extensive intervals of overbank deposits. We explore potential causes of and controls on avulsion clustering with outcrop and subsurface data from Late Cretaceous/Early Paleogene fluvial deposits in the Rocky Mountains (including the Ferris, Lance, and Fort Union formations of Wyoming) and results of physical stratigraphy experiments from the St. Anthony Falls Lab, University of Minnesota. We use Ripley's K-function to determine the degree and scales of clustering in these basins with results that show moderate statistical clustering in experimental deposits and strong clustering in the Ferris Formation (Hanna Basin, Wyoming). External controls (base level, subsidence rate, and sediment/water supplies) were not varied during the experiment, and therefore not factors in cluster formation. Likewise, the stratigraphic context of the ancient system (including the absence of incised valleys and lack of faulting) suggests that obvious extrinsic controls, such as base level change and local tectonics, were not major influences on the development of clusters. We propose that avulsion clusters, as seen in this study, reflect a scale of self-organization in alluvial basins that is not usually recognized in stratigraphy. However cursory examination of other ancient systems suggests that such structure may be common in the rock record. Understanding mechanisms driving avulsion clustering will shed light on the dominant processes in alluvial basins over long time scales. Furthermore, characterizing autogenic avulsion clusters will be an important factor to consider when interpreting allogenic signals in ancient basin fills.

Deterministic chaos in a model of a simple delta network

NASA Astrophysics Data System (ADS)

Salter, G.; Voller, V. R.; Paola, C.

2017-12-01

An important aspect of delta dynamics is how sediment flux is partitioned to different parts of the delta through time, affecting patterns of land-building/loss, and the formation of stratigraphy. Here, we present results from a model of a simple distributary network consisting of two orders of bifurcations: an upstream channel splits into two branches, each of which splits into two additional branches. The 1D bed elevation profiles of each branch are modeled through time, and a nodal condition accounting for a transverse bed slope just upstream of the bifurcation is used to partition the flow at bifurcations. The model generates surprisingly complex dynamics despite its simplicity. Constrained by the need to distribute sediment evenly between branches in the long-run, the system undergoes repeated full and partial avulsions. We find that the solution to the system is aperiodic, but bounded. We also observe a sensitive dependence on the initial conditions: simulations started with slightly different initial conditions diverge exponentially. These observations are the hallmark of chaos, summarized by Edward Lorenz as "where the present determines the future, but the approximate present does not approximately determine the future." In our model, chaos results from the two-way coupling between upstream and downstream bifurcations. We find that a single bifurcation may be periodic, but it is never chaotic. However, when coupled, avulsions in the upstream channel change the upstream boundary conditions for the downstream bifurcations, and conversely, avulsions in the downstream bifurcations affect the slope of their feeder channel, propagating upstream to the first bifurcation. We explore how the system generates stratigraphy, using the Shields stress at the time of deposition as a proxy. We compare the stratigraphy to the single bifurcation case, which is periodic rather than chaotic. We also examine stratigraphic completeness, and find that hiatuses in the upstream portion of the domain tend to be erosional, whereas hiatuses further downstream tend to represent pauses. Our work suggests that deltas have a limited window of predictability, and indicates that chaotic and cyclic avulsion sequences should be distinguishable in the stratigraphic record.

The INTIMATE event stratigraphy and recommendations for its use

NASA Astrophysics Data System (ADS)

Rasmussen, Sune O.

2014-05-01

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

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.

High-resolution phylogenetic microbial community profiling

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

Singer, Esther; Coleman-Derr, Devin; Bowman, Brett

2014-03-17

The representation of bacterial and archaeal genome sequences is strongly biased towards cultivated organisms, which belong to merely four phylogenetic groups. Functional information and inter-phylum level relationships are still largely underexplored for candidate phyla, which are often referred to as microbial dark matter. Furthermore, a large portion of the 16S rRNA gene records in the GenBank database are labeled as environmental samples and unclassified, which is in part due to low read accuracy, potential chimeric sequences produced during PCR amplifications and the low resolution of short amplicons. In order to improve the phylogenetic classification of novel species and advance ourmore » knowledge of the ecosystem function of uncultivated microorganisms, high-throughput full length 16S rRNA gene sequencing methodologies with reduced biases are needed. We evaluated the performance of PacBio single-molecule real-time (SMRT) sequencing in high-resolution phylogenetic microbial community profiling. For this purpose, we compared PacBio and Illumina metagenomic shotgun and 16S rRNA gene sequencing of a mock community as well as of an environmental sample from Sakinaw Lake, British Columbia. Sakinaw Lake is known to contain a large age of microbial species from candidate phyla. Sequencing results show that community structure based on PacBio shotgun and 16S rRNA gene sequences is highly similar in both the mock and the environmental communities. Resolution power and community representation accuracy from SMRT sequencing data appeared to be independent of GC content of microbial genomes and was higher when compared to Illumina-based metagenome shotgun and 16S rRNA gene (iTag) sequences, e.g. full-length sequencing resolved all 23 OTUs in the mock community, while iTags did not resolve closely related species. SMRT sequencing hence offers various potential benefits when characterizing uncharted microbial communities.« less

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.

Sequence stratigraphy, tectonics and hydrocarbon trap geometries of Middle Tertiary strata in the southern San Joaquin Basin, California

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

Phillips, S.; Hewlett, J.S.; Bazeley, W.J.M.

1996-01-01

Tectonic evolution of the southern San Joaquin basin exerted a fundamental control on Cenozoic sequence boundary development, reservoir, source and seal facies distribution, and hydrocarbon trap development. Spatial and temporal variations in Tertiary sequence architecture across the basin reflect differences in eastside versus westside basin-margin geometries and deformation histories. Deposition of Tertiary sequences initiated in a forearc basin setting, bounded on the east by a ramp-margin adjacent to the eroded Sierran arc complex and on the west by the imbricated accretionary wedge of the Coast Ranges thrust. The major stages of Cenozoic basin evolution are: (1) Episodic compressional folding andmore » thrusting associated with oblique convergence of the Farallon and North American plates (Late Cretaceous to Oligocene), (2) localized folding and onset of basin subsidence related to Pacific Plate reorganization, microplate formation and rotation (Oligocene to Early Miocene), (3) transtensional faulting, folding basin subsidence associated with initiation of the San Andreas transform and continued microplate rotation (Micocene to Pliocene), and (4) compressional folding, extensional and strike- slip faulting related to evolution of the Pacific-North American transform boundary (Plio- Pleistocene). Complex stratigraphic relationships within Eocene to Middle Miocene rocks provide examples of tectonic influences on sequence architecture. These include development of: (1) Tectonically enhanced sequence boundaries (Early Eocene base Domengine unconformity) and local mid-sequence angular unconformities, (2) westside-derived syntectonic [open quotes]lowstand[close quotes] systems (Yokut/Turitella Silt wedge and Leda Sand/Cymric/Salt Creek wedge), (3) regional seals associated with subsidence-related transgressions (Round Mountain Silt), and (4) combination traps formed by structural inversion of distal lowstand delta reservoirs (e.g. Coalinga East Extension field).« less

Sequence stratigraphy, tectonics and hydrocarbon trap geometries of Middle Tertiary strata in the southern San Joaquin Basin, California

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

Phillips, S.; Hewlett, J.S.; Bazeley, W.J.M.

1996-12-31

Tectonic evolution of the southern San Joaquin basin exerted a fundamental control on Cenozoic sequence boundary development, reservoir, source and seal facies distribution, and hydrocarbon trap development. Spatial and temporal variations in Tertiary sequence architecture across the basin reflect differences in eastside versus westside basin-margin geometries and deformation histories. Deposition of Tertiary sequences initiated in a forearc basin setting, bounded on the east by a ramp-margin adjacent to the eroded Sierran arc complex and on the west by the imbricated accretionary wedge of the Coast Ranges thrust. The major stages of Cenozoic basin evolution are: (1) Episodic compressional folding andmore » thrusting associated with oblique convergence of the Farallon and North American plates (Late Cretaceous to Oligocene), (2) localized folding and onset of basin subsidence related to Pacific Plate reorganization, microplate formation and rotation (Oligocene to Early Miocene), (3) transtensional faulting, folding basin subsidence associated with initiation of the San Andreas transform and continued microplate rotation (Micocene to Pliocene), and (4) compressional folding, extensional and strike- slip faulting related to evolution of the Pacific-North American transform boundary (Plio- Pleistocene). Complex stratigraphic relationships within Eocene to Middle Miocene rocks provide examples of tectonic influences on sequence architecture. These include development of: (1) Tectonically enhanced sequence boundaries (Early Eocene base Domengine unconformity) and local mid-sequence angular unconformities, (2) westside-derived syntectonic {open_quotes}lowstand{close_quotes} systems (Yokut/Turitella Silt wedge and Leda Sand/Cymric/Salt Creek wedge), (3) regional seals associated with subsidence-related transgressions (Round Mountain Silt), and (4) combination traps formed by structural inversion of distal lowstand delta reservoirs (e.g. Coalinga East Extension field).« less

The Last Interglacial-Glacial cycle (MIS 5-2) re-examined based on long proxy records from central and northern Europe

NASA Astrophysics Data System (ADS)

Helmens, Karin F.

2014-02-01

Current multi-proxy studies on a long sediment sequence preserved at Sokli (N Finland), i.e. in the central area of Fennoscandian glaciations, are drastically changing classic ideas of glaciations, vegetation and climate in northern Europe during the Late Pleistocene. The sediments in the Sokli basin have escaped major glacial erosion due to non-typical bedrock conditions. In this review, the Sokli record is compared in great detail with other long proxy records from central, temperate and northern, boreal Europe. These comprise the classic records of La Grande Pile (E France) and Oerel (N Germany) and more recently obtained records from Horoszki Duże (E Poland) and Lake Yamozero (NW Russia). The focus of the review is on pollen, lithology and macrofossil- and insect-based temperature inferences. The long records are further compared with recent proxy data from nearby terrestrial sites as well as with the rapidly accumulating high-resolution proxy data from the ocean realm. The comparison allows a re-examination of the environmental history and climate evolution of the Last Interglacial-Glacial (LI-G) cycle (MIS 5-2). It shows that environmental and climate conditions during MIS 5 (ca 130-70 ka BP) were distinctly different from those during MIS 4-2 (ca 70-15 ka BP). MIS 5 is characterized by three long forested intervals (broadly corresponding to MIS 5e, 5c, 5a), both in temperate and northern boreal Europe. These mild periods were interrupted by two short, relatively cold and dry intervals (MIS 5d and 5b) with mountain-centered glaciation in Fennoscandia. Millennial scale climate events were superimposed upon these longer lasting climate fluctuations. The time interval encompassing MIS 4-2 shows open vegetation. It is characterized by two glacial maxima (MIS 4 and 2) with sub-continental scale glaciation over northern Europe and dry conditions in strongly continental eastern European settings. High amplitude climate oscillations of millennial duration characterized the climate variability of MIS 3. Mild climate conditions in early MIS 3 caused large-scale deglaciation of the Fennoscandian Ice Sheet, and ice-free conditions with Betula-dominated vegetation (including tree birch) persisted over large parts of Fennoscandia, possibly interrupted by glaciation, during major part of MIS 3 till ca 35 ka BP. Overall, MIS 5 was mostly mild with warmest or peak interglacial conditions at the very start during MIS 5e. MIS 4-2 was mostly cold with most extreme or peak glacial conditions in the closing phase during MIS 2. This points to a subdivision of the last climate cycle into an early, overall mild interglacial half and a late, overall cold glacial half, each with duration of ca 50 ka. This review also shows that the climate variability in central and northern Europe during the LI-G cycle was mostly in degrees of continentality with major shifts in winter temperature and precipitation values; summer temperatures, on the other hand, remained largely unchanged. It points to the waxing and waning of sea-ice over the North Atlantic Ocean as a possible characteristic feature of the Late Pleistocene. The present compilation, based on long terrestrial sequences, high-resolution multi-proxy data from the oceans, and quantified paleo-climate data, strongly favors a definition of entire Marine Oxygen Isotope Stage 5 as the Last Interglacial similar as in the original marine stratigraphy and the stratigraphy at La Grande Pile in France. The proxy-based climate data places the start of the Last Glacial at the base of MIS 4 and the northwest European Pleniglacial. It shows that the division between the Eemian (MIS 5e) and the Early Weichselian (MIS 5d-a) is not useful, as not relevant from a climate point of view.

Magnetic polarity stratigraphy of the middle Pleistocene (Ensenadan) Tarija Formation of southern Bolivia

NASA Astrophysics Data System (ADS)

MacFadden, Bruce J.; Siles, Oscar; Zeitler, Peter; Johnson, Noye M.; Campbell, Kenneth E.

1983-03-01

The Tarija Formation of southern Bolivia, which is well known for its classic vertebrate faunas, is of prime importance in understanding of the chronology of the Ensenadan Land Mammal Age. This formation consists of well-exposed and relatively fossiliferous sections of clays, clayey silts, sands, gravels, and tuffs which were deposited in a predominately fluviatile regime in a Pleistocene structural basin. Four stratigraphic sections, each measuring 110 m or less, were studied to establish a magnetic polarity stratigraphy. Paleomagnetic samples were collected from the finer-grained sediments at 100 sites spaced at stratigraphic intervals of 5 m or less. All paleomagnetic specimens were demagnetized in alternating fields of least 250 oersteds (oe). Some specimens were also thermally demagnetized at 200°C or more. Of the 100 sites, 77 were ultimately used to determine the magnetic polarity zonation. Based on the four sections sampled, the Tarija Formation spans a time interval from about 1 my to about 0.7 my B.P. or perhaps younger. The lower half of the composite section is of reversed polarity punctuated by a short normal event. This sequence probably represents the late Matuyama chron with the Jaramillo subchron. The upper part of the section is of normal polarity and represents early Brunhes time. A tuffaceous unit 43 m above the Brunhes-Matuyama boundary yielded a fission track (zircon) age of 0.7 ± 0.2 by B.P. These data indicate that the classic Tarija fauna is middle Pleistocene Ensendan in age.

Evolution of fault zones in carbonates with mechanical stratigraphy - Insights from scale models using layered cohesive powder

NASA Astrophysics Data System (ADS)

van Gent, Heijn W.; Holland, Marc; Urai, Janos L.; Loosveld, Ramon

2010-09-01

We present analogue models of the formation of dilatant normal faults and fractures in carbonate fault zones, using cohesive hemihydrate powder (CaSO 4·½H 2O). The evolution of these dilatant fault zones involves a range of processes such as fragmentation, gravity-driven breccia transport and the formation of dilatant jogs. To allow scaling to natural prototypes, extensive material characterisation was done. This showed that tensile strength and cohesion depend on the state of compaction, whereas the friction angle remains approximately constant. In our models, tensile strength of the hemihydrate increases with depth from 9 to 50 Pa, while cohesion increases from 40 to 250 Pa. We studied homogeneous and layered material sequences, using sand as a relatively weak layer and hemihydrate/graphite mixtures as a slightly stronger layer. Deformation was analyzed by time-lapse photography and Particle Image Velocimetry (PIV) to calculate the evolution of the displacement field. With PIV the initial, predominantly elastic deformation and progressive localization of deformation are observed in detail. We observed near-vertical opening-mode fractures near the surface. With increasing depth, dilational shear faults were dominant, with releasing jogs forming at fault-dip variations. A transition to non-dilatant shear faults was observed near the bottom of the model. In models with mechanical stratigraphy, fault zones are more complex. The inferred stress states and strengths in different parts of the model agree with the observed transitions in the mode of deformation.

40Ar/(39)Ar geochronology and paleomagnetic stratigraphy of the Lukeino and lower Chemeron Formations at Tabarin and Kapcheberek, Tugen Hills, Kenya.

PubMed

Deino, Alan L; Tauxe, Lisa; Monaghan, Marc; Hill, Andrew

2002-01-01

(40)Ar/(39)Ar single-crystal laser-fusion dating, K-Ar dating, and paleomagnetic reversal stratigraphy have been used to determine the chronostratigraphy of the Kabarnet Trachyte, Lukeino Formation, Kaparaina Basalt Formation, and Chemeron Formation at the sites of Kapcheberek (BPRP#77) and Tabarin (BPRP#77) in the Tugen Hills, Kenya. The succession ranges in age from 6.56-3.8 Ma. The upper Lukeino Formation at Kapcherberek, including the fauna from the site BPRP#76, was deposited during chron C3r and can be constrained to the interval 5.88-5.72 Ma. The Chemeron Formation at Tabarin includes at the base an ignimbrite and associated basal air-fall tuff with a combined age of 5.31+/-0.03 Ma. Sedimentary and volcaniclastic rocks of the Chemeron Formation which unconformably overlie the ignimbrite record chrons C3n.2n through C2Ar. The combined(40)Ar/(39)Ar and paleomagnetic data constrain the age of this sequence to 4.63-3.837 Ma. The age of the Tabarin mandible fragment (KNM-TH 13150) and associated fauna at site BPRP#77 in the Chemeron Formation is 4.48-4.41 Ma, marginally older than similar early hominids from Aramis, Ethiopia. Basin subsidence appears to be defining an overall accumulation rate of about 17 cm/ka over the 2.7 Ma represented at Tabarin and Kapcheberek, despite episodes of rapid accumulation and hiatuses. Copyright 2002 Academic Press.

Utility of aeromagnetic studies for mapping of potentially active faults in two forearc basins: Puget Sound, Washington, and Cook Inlet, Alaska

USGS Publications Warehouse

Saltus, R.W.; Blakely, R.J.; Haeussler, Peter J.; Wells, R.E.

2005-01-01

High-resolution aeromagnetic surveys over forearc basins can detect faults and folds in weakly magnetized sediments, thus providing geologic constraints on tectonic evolution and improved understanding of seismic hazards in convergent-margin settings. Puget Sound, Washington, and Cook Inlet, Alaska, provide two case histories. In each lowland region, shallow-source magnetic anomalies are related to active folds and/or faults. Mapping these structures is critical for understanding seismic hazards that face the urban regions of Seattle, Washington, and Anchorage, Alaska. Similarities in aeromagnetic anomaly patterns and magnetic stratigraphy between the two regions suggest that we can expect the aeromagnetic method to yield useful structural information that may contribute to earth-hazard and energy resource investigations in other forearc basins.

Formation of the Orientale lunar multiring basin.

PubMed

Johnson, Brandon C; Blair, David M; Collins, Gareth S; Melosh, H Jay; Freed, Andrew M; Taylor, G Jeffrey; Head, James W; Wieczorek, Mark A; Andrews-Hanna, Jeffrey C; Nimmo, Francis; Keane, James T; Miljković, Katarina; Soderblom, Jason M; Zuber, Maria T

2016-10-28

Multiring basins, large impact craters characterized by multiple concentric topographic rings, dominate the stratigraphy, tectonics, and crustal structure of the Moon. Using a hydrocode, we simulated the formation of the Orientale multiring basin, producing a subsurface structure consistent with high-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft. The simulated impact produced a transient crater, ~390 kilometers in diameter, that was not maintained because of subsequent gravitational collapse. Our simulations indicate that the flow of warm weak material at depth was crucial to the formation of the basin's outer rings, which are large normal faults that formed at different times during the collapse stage. The key parameters controlling ring location and spacing are impactor diameter and lunar thermal gradients. Copyright © 2016, American Association for the Advancement of Science.

High-Resolution Functional Mapping of the Venezuelan Equine Encephalitis Virus Genome by Insertional Mutagenesis and Massively Parallel Sequencing

DTIC Science & Technology

2010-10-14

High-Resolution Functional Mapping of the Venezuelan Equine Encephalitis Virus Genome by Insertional Mutagenesis and Massively Parallel Sequencing...Venezuelan equine encephalitis virus (VEEV) genome. We initially used a capillary electrophoresis method to gain insight into the role of the VEEV...Smith JM, Schmaljohn CS (2010) High-Resolution Functional Mapping of the Venezuelan Equine Encephalitis Virus Genome by Insertional Mutagenesis and

Geologic field-trip guide to the Lassen segment of the Cascades Arc, northern California

USGS Publications Warehouse

Clynne, Michael A.; Muffler, L. J. Patrick

2017-08-17

This field-trip guide provides an overview of Quaternary volcanism in and around Lassen Volcanic National Park, California, emphasizing the stratigraphy of the Lassen Volcanic Center. The guide is designed to be self-guided and to focus on geologic features and stratigraphy that can be seen easily from the road network.

Geotechnical soil characterization of intact Quaternary deposits forming the March 22, 2014 SR-530 (Oso) landslide, Snohomish County, Washington

USGS Publications Warehouse

Riemer, Michael F.; Collins, Brian D.; Badger, Thomas C.; Toth, Csilla; Yu, Yat Chun

2015-01-01

This report provides a description of the methods used to obtain and test the intact soil stratigraphy behind the headscarp of the March 22 landslide. Detailed geotechnical index testing results are presented for 24 soil samples representing the stratigraphy at 19 different depths along a 650 ft (198 m) soil profile. The results include (1) the soil's in situ water content and unit weight (where applicable); (2) specific gravity of soil solids; and (3) each sample's grain-size distribution, critical limits for fine-grain water content states (that is, the Atterberg limits), and official Unified Soil Classification System (USCS) designation. In addition, preliminary stratigraphy and geotechnical relations within and between soil units are presented.

Global stratigraphy. [of planet Mars

NASA Technical Reports Server (NTRS)

Tanaka, Kenneth L.; Scott, David H.; Greeley, Ronald

1992-01-01

Attention is given to recent major advances in the definition and documentation of Martian stratigraphy and geology. Mariner 9 provided the images for the first global geologic mapping program, resulting in the recognition of the major geologic processes that have operated on the planet, and in the definition of the three major chronostratigraphic divisions: the Noachian, Hesperian, and Amazonian Systems. Viking Orbiter images permitted the recognition of additional geologic units and the formal naming of many formations. Epochs are assigned absolute ages based on the densities of superposed craters and crater-flux models. Recommendations are made with regard to future areas of study, namely, crustal stratigraphy and structure, the highland-lowland boundary, the Tharsis Rise, Valles Marineris, channels and valley networks, and possible Martian oceans, lakes, and ponds.

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.

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

Martian soil stratigraphy and rock coatings observed in color-enhanced Viking Lander images

NASA Technical Reports Server (NTRS)

Strickland, E. L., III

1979-01-01

Subtle color variations of martian surface materials were enhanced in eight Viking Lander (VL) color images. Well-defined soil units recognized at each site (six at VL-1 and four at VL-2), are identified on the basis of color, texture, morphology, and contact relations. The soil units at the Viking 2 site form a well-defined stratigraphic sequence, whereas the sequence at the Viking 1 site is only partially defined. The same relative soil colors occur at the two sites, suggesting that similar soil units are widespread on Mars. Several types of rock surface materials can be recognized at the two sites; dark, relatively 'blue' rock surfaces are probably minimally weathered igneous rock, whereas bright rock surfaces, with a green/(blue + red) ratio higher than that of any other surface material, are interpreted as a weathering product formed in situ on the rock. These rock surface types are common at both sites. Soil adhering to rocks is common at VL-2, but rare at VL-1. The mechanism that produces the weathering coating on rocks probably operates planet-wide.

Eocene to Miocene Out-of-Sequence Deformation in the Eastern Tibetan Plateau: Insights From Shortening Structures in the Sichuan Basin

NASA Astrophysics Data System (ADS)

Tian, Yuntao; Kohn, Barry P.; Qiu, Nansheng; Yuan, Yusong; Hu, Shengbiao; Gleadow, Andrew J. W.; Zhang, Peizhen

2018-02-01

A distinctive NNE trending belt of shortening structures dominates the topography and deformation of the eastern Sichuan Basin, 300 km east of the Tibetan Plateau. Debate continues as to whether the structures resulted from Cenozoic eastward growth of the Tibetan Plateau. A low-temperature thermochronology (AFT and AHe) data set from four deep boreholes and adjacent outcrops intersecting a branch of the shortening structures indicates distinctive differential cooling at 35-28 Ma across the structure, where stratigraphy has been offset vertically by 0.8-1.3 km. This result forms the first quantitative evidence for the existence of a late Eocene-Oligocene phase of shortening in the eastern Sichuan Basin, synchronous with the early phase of eastward growth and extrusion of the Tibetan Plateau. Further, a compilation of regional Cenozoic structures reveals a Miocene retreat of deformation from the foreland basin to the hinterland areas. Such a tectonic reorganization indicates that Eocene to Miocene deformation in the eastern Tibetan Plateau is out-of-sequence and was probably triggered by enhanced erosion in the eastern Tibetan Plateau.

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.

Automated brain tumor segmentation using spatial accuracy-weighted hidden Markov Random Field.

PubMed

Nie, Jingxin; Xue, Zhong; Liu, Tianming; Young, Geoffrey S; Setayesh, Kian; Guo, Lei; Wong, Stephen T C

2009-09-01

A variety of algorithms have been proposed for brain tumor segmentation from multi-channel sequences, however, most of them require isotropic or pseudo-isotropic resolution of the MR images. Although co-registration and interpolation of low-resolution sequences, such as T2-weighted images, onto the space of the high-resolution image, such as T1-weighted image, can be performed prior to the segmentation, the results are usually limited by partial volume effects due to interpolation of low-resolution images. To improve the quality of tumor segmentation in clinical applications where low-resolution sequences are commonly used together with high-resolution images, we propose the algorithm based on Spatial accuracy-weighted Hidden Markov random field and Expectation maximization (SHE) approach for both automated tumor and enhanced-tumor segmentation. SHE incorporates the spatial interpolation accuracy of low-resolution images into the optimization procedure of the Hidden Markov Random Field (HMRF) to segment tumor using multi-channel MR images with different resolutions, e.g., high-resolution T1-weighted and low-resolution T2-weighted images. In experiments, we evaluated this algorithm using a set of simulated multi-channel brain MR images with known ground-truth tissue segmentation and also applied it to a dataset of MR images obtained during clinical trials of brain tumor chemotherapy. The results show that more accurate tumor segmentation results can be obtained by comparing with conventional multi-channel segmentation algorithms.

Gigapixel imaging as a resource for geoscience teaching, research, and outreach

NASA Astrophysics Data System (ADS)

Bentley, C.; Pitts, A.; Rohrback, R. C.; Dudek, M.

2015-12-01

The Mid-Atlantic Geo-Image Collection is a repository of gigapixel-resolution geologic imagery intended as a tool for geoscience professionals, educators, students, & researchers (http://gigapan.com/groups/100/galleries). GigaPan provides a unique combination of context & detail, with images that maintain a high level of resolution through every level of magnification. Using geological GigaPans, physically disabled students can participate in virtual field trips, instructors can bring inaccessible outcrops into the classroom, & students can zoom in on hand samples without expensive microscopes. Because GigaPan images permit detailed visual examination of geologic, MAGIC is particularly suitable for use in online geology courses. The images are free to use and tag. Our 10 contributors (3 faculty, 2 graduate students, & 6 undergraduates) use 4 models of mobile robot cameras (outcrop/landscape), 2 laboratory-based GIGAmacro imaging systems (hand samples) & 2 experimental units: 1 for thin sections, 1 for GigaPans of scanning electron microscopy. Each of these has strengths & weaknesses. MAGIC has suites of images of Appalachian structure & stratigraphy, Rocky Mountains, Snowball Earth hypothesis, & doomed outcrops of Miocene strata on Chesapeake Bay. Virtual field trips with our imagery have been developed for: Billy Goat Trail, MD; Helen Lake, AB; Wind River Canyon, WY; the Canadian Rockies; El Paso, TX; glaciation around the world; and Corridor H, WV (a GSA field trip in Nov. 2015). Virtual sample sets have been developed for introductory minerals, igneous, sedimentary, & metamorphic rocks, the stratigraphy of VA's physiographic provinces, & the Snowball Earth hypothesis. The virtual field trips have been tested in both online & onsite courses. There are close to a thousand images in the collection, each averaging about 0.9 gigapixels in size, with close to 900,000 views total. A new viewer for GigaPans was released this year by GIGAmacro. This new viewer allows measurement and calibration, automatically resizing scale bars, side-by-side comparisons between 2 images, overlapping presentation of 2 images, & annotation by users. Comparative viewers are particularly useful for the presentation of before/after imagery; raw vs. annotated imagery, & polarized views of thin sections.

Snowpack spatial variability: Towards understanding its effect on remote sensing measurements and snow slope stability

NASA Astrophysics Data System (ADS)

Marshall, Hans-Peter

The distribution of water in the snow-covered areas of the world is an important climate change indicator, and it is a vital component of the water cycle. At local and regional scales, the snow water equivalent (SWE), the amount of liquid water a given area of the snowpack represents, is very important for water resource management, flood forecasting, and prediction of available hydropower energy. Measurements from only a few automatic weather stations, such as the SNOTEL network, or sparse manual snowpack measurements are typically extrapolated for estimating SWE over an entire basin. Widespread spatial variability in the distribution of SWE and snowpack stratigraphy at local scales causes large errors in these basin estimates. Remote sensing measurements offer a promising alternative, due to their large spatial coverage and high temporal resolution. Although snow cover extent can currently be estimated from remote sensing data, accurately quantifying SWE from remote sensing measurements has remained difficult, due to a high sensitivity to variations in grain size and stratigraphy. In alpine snowpacks, the large degree of spatial variability of snowpack properties and geometry, caused by topographic, vegetative, and microclimatic effects, also makes prediction of snow avalanches very difficult. Ground-based radar and penetrometer measurements can quickly and accurately characterize snowpack properties and SWE in the field. A portable lightweight radar was developed, and allows a real-time estimate of SWE to within 10%, as well as measurements of depths of all major density transitions within the snowpack. New analysis techniques developed in this thesis allow accurate estimates of mechanical properties and an index of grain size to be retrieved from the SnowMicroPenetrometer. These two tools together allow rapid characterization of the snowpack's geometry, mechanical properties, and SWE, and are used to guide a finite element model to study the stress distribution on a slope. The ability to accurately characterize snowpack properties at much higher resolutions and spatial extent than previously possible will hopefully help lead to a more complete understanding of spatial variability, its effect on remote sensing measurements and snow slope stability, and result in improvements in avalanche prediction and accuracy of SWE estimates from space.

Late Miocene climate and orbital time scale reconciliation from a deep-sea perspective

NASA Astrophysics Data System (ADS)

Drury, Anna Joy; Westerhold, Thomas; Frederichs, Thomas; Tian, Jun; Wilkens, Roy; Channell, James E. T.; Evans, Helen; John, Cédric M.; Lyle, Mitch; Röhl, Ursula

2017-04-01

The late Tortonian to early Messinian (8-6 Ma) is characterised by a long-term reduction in benthic foraminiferal δ18O, with distinctive short-term δ18O cycles superimposed. Coevally, a permanent -1‰ change in oceanic δ13CDIC, the late Miocene carbon isotope shift (LMCIS), marks the last major permanent shift in the carbon cycle expressed in all oceanic basins, after which near-modern δ13C gradients are established around 6.7 Ma. Accurate age control is crucial to ascertain the origin of the δ18O cyclicity and the LMCIS, as constraining the precise timing of such events can allow temporal and causal relationships to be established between the deep-sea, terrestrial and cryosphere records. Here, we present the first independent high-resolution chemo-, magneto-, and cyclostratigraphy for the interval between 8.3-6.0 Ma from a single deep-sea site. Generated at equatorial Pacific Integrated Ocean Drilling Program (IODP) Site U1337, our integrated astronomically tuned benthic stable isotope stratigraphy (1.5 kyr resolution) and magnetostratigraphy is suitable to test the current Tortonian-Messinian Geological Time Scale (GTS2012), currently based on astronomically calibrated Mediterranean sections. Between 7.7-6.9 Ma, the new benthic δ18O and δ13C data from IODP U1337 show distinctive obliquity-driven saw-tooth patterns suggesting that high-latitude forcing dominated late Miocene climate dynamics. For the first time, the LMCIS is astronomically calibrated and anchored to the GPTS between Chrons C4n.1n and C3An.2n. Anchoring the LMCIS facilitates comparison with terrestrial records of the C3/C4 vegetation shift, which has been linked to the LMCIS. The astronomically calibrated Site U1337 magnetostratigraphy additionally provides robust ages for polarity Chrons C3An.1n to C4r.1r, with ages changing by 2-50 kyr relative to the GTS2012. The new integrated deep-sea stratigraphy from Site U1337 has potential as a new stable isotope and magnetic polarity reference section for the 8.3-6.0 Ma interval.

Forearc Basin Stratigraphy and Interactions With Accretionary Wedge Growth According to the Critical Taper Concept

NASA Astrophysics Data System (ADS)

Noda, Atsushi

2018-03-01

Forearc basins are important constituents of sediment traps along subduction zones; the basin stratigraphy records various events that the basin experienced. Although the linkage between basin formation and accretionary wedge growth suggests that mass balance exerts a key control on their evolution, the interaction processes between basin and basement remain poorly understood. This study performed 2-D numerical simulations in which basin stratigraphy was controlled by changes in sediment fluxes with accretionary wedge growth according to the critical taper concept. The resultant stratigraphy depended on the degree of filling (i.e., whether the basin was underfilled or overfilled) and the volume balance between the sediment flux supplied to the basin from the hinterland and the accommodation space in the basin. The trenchward progradation of deposition with onlapping contacts on the trenchside basin floor occurred during the underfilled phase, which formed a wedge-shaped sedimentary unit. In contrast, the landward migration of the depocenter, with the tilting of strata, was characteristic for the overfilled phase. Condensed sections marked stratigraphic boundaries, indicating when sediment supply or accommodation space was limited. The accommodation-limited intervals could have formed during the end of wedge uplift or when the taper angle decreased and possibly associated with the development of submarine canyons as conduits for bypassing sediments from the hinterland. Variations in sediment fluxes and their balance exerted a strong influence on the stratigraphic patterns in forearc basins. Assessing basin stratigraphy could be a key to evaluating how subduction zones evolve through their interactions with changing surface processes.

Characterising and modelling regolith stratigraphy using multiple geophysical techniques

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

Stratigraphy of the Perrine and Nun Sulci quadrangles (Jg-2 and Jg-5), Ganymede

NASA Technical Reports Server (NTRS)

Mcgill, George E.; Squyres, Steven W.

1991-01-01

Dark and light terrain materials in the Perrine and Nun Sulci quadrangles are divided into nine map units, four dark, and five light. These are placed in time-stratigraphic sequence primarily by means of embayment and cross-cutting relationships. Dark terrain is generally more heavily cratered and thus older that light terrain but, at least in these quadrangles, crater densities are not reliable indicators of relative ages among the four dark material units. The four mapped material units within dark terrain are: cratered dark materials (dc), grooved dark materials (dg), transitional dark materials (di), and dark materials, undivided (d). The five mapped units within light terrain are: intermediate light materials (li), grooved light materials (lg), irregularly grooved light materials (lgl), smooth light materials (ls), and light materials, undivided.

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.

Stratigraphy Exposed by an Impact Crater

NASA Image and Video Library

2017-05-10

Geologists love roadcuts because they reveal the bedrock stratigraphy (layering). Until we have highways on Mars, we can get the same information from fresh impact craters as shown in this image from NASA's Mars Reconnaissance Orbiter. This image reveals these layers filling a larger crater, perhaps a combination of lava, impact ejecta, and sediments. https://photojournal.jpl.nasa.gov/catalog/PIA21631

IMRT sequencing for a six-bank multi-leaf system.

PubMed

Topolnjak, R; van der Heide, U A; Lagendijk, J J W

2005-05-07

In this study, we present a sequencer for delivering step-and-shoot IMRT using a six-bank multi-leaf system. Such a system was proposed earlier and combines a high-resolution field-shaping ability with a large field size. It consists of three layers of two opposing leaf banks with 1 cm leaves. The layers are rotated relative to each other at 60 degrees . A low-resolution mode of sequencing is achieved by using one layer of leaves as primary MLC, while the other two are used to improve back-up collimation. For high-resolution sequencing, an algorithm is presented that creates segments shaped by all six banks. Compared to a hypothetical mini-MLC with 0.4 cm leaves, a similar performance can be achieved, but a trade-off has to be made between accuracy and the number of segments.

A Boreal high-resolution d13C-carb record of the Albian-Cenomanian transition from NW Germany

NASA Astrophysics Data System (ADS)

Bornemann, André; Erbacher, Jochen; Heldt, Matthias; Wilmsen, Markus; Lübke, Nathalie; Heimhofer, Ulrich

2015-04-01

The upper Albian of the central NW German Basin is represented by a monotonous (marly) claystone succession of several hundred meters thickness, which becomes siliceous in the topmost Albian (Flammenmergel facies) and shows a gradual increase in carbonate content during the early to middle Cenomanian. Here we present a new ~160-m-thick composite record spanning the uppermost Albian to middle Cenomanian based on two cored drill sites at Anderten, east of Hannover (Germany). We successfully correlated the long-term d13C record to other European reference sections in England (Speeton; Mitchell et al., 1996) and Italy (Contessa - Stoll and Schrag, 2000) as well as to records from the NW German Basin (Wunstorf - Mitchell et al., 1996; Konrad 101 - unpublished). Based on the observed pattern we are able to identify the d13C expression of (1) the Oceanic Anoxic Event 1d, (2) the Albian-Cenomanian boundary, (3) possibly the Lower Cenomanian Event(s) (LCE) and, finally, (4) the Mid-Cenomanian Event (MCE) I close to the top of the record. Chemostratigraphic age assignments are supported by biostratigraphic results. Calcareous nannofossils indicate an extended CC9 zone up to the lowermost CC10 (UC0-UC3 according to Burnett et al., 1998) as indicated by the FAD of Microrhabdulus decoratus at the top. Moreover, previously described influxes of Rotalipora aff. reicheli and the occurrence of the ostracod Neocythere steghausi support a mid-Cenomanian age for the upper part of the studied succession. Due to both moderately well preserved microfossils and high sedimentation rates the drilled succession can be considered as a potential reference for the Albian-Cenomanian transition in the Boreal realm. References: Burnett, J. (1998). Upper Cretaceous Calcareous Nannofossil Biostratigraphy, 132-199. - in: Bown, P. (Ed.) Calcareous Nannofossil Biostratigraphy (Kluwer Academic Publishers). Mitchell, S., Paul, C., Gale, A. (1996). Carbon isotopes and sequence stratigraphy. Geol. Soc. London Spec. Publ., 104, 11-24. Stoll, H.M., Schrag, D.P. (2000). High-resolution stable isotope records from the Upper Cretaceous rocks of Italy and Spain: Glacial episodes in a greenhouse planet? Geol. Soc. Am. Bull., 112, 308-319.

Tectonics and metallogenesis of Proterozoic rocks of the Reading Prong

USGS Publications Warehouse

Gundersen, L.C.S.

2004-01-01

Detailed geologic mapping, petrography, and major and trace-element analyses of Proterozoic rocks from the Greenwood Lake Quadrangle, New York are compared with chemical analyses and stratigraphic information compiled for the entire Reading Prong. A persistent regional stratigraphy is evident in the mapped area whose geochemistry indicates protoliths consistent with a back-arc marginal basin sequence. The proposed marginal basin may have been floored by an older sialic basement and overlain by a basin-fill sequence consisting of a basal tholeiitic basalt, basic to intermediate volcanic or volcaniclastic rocks and carbonate sediments, a bimodal calc-alkaline volcanic sequence, and finally volcaniclastic, marine, and continental sediments. The presence of high-chlorine biotite and scapolite may indicate circulation of brine fluids or the presence of evaporite layers in the sequence. Abundant, stratabound magnetite deposits with a geologic setting very unlike that of cratonic, Proterozoic banded-iron formations are found throughout the proposed basin sequence. Associated with many of the magnetite deposits is unusual uranium and rare-earth element mineralization. It is proposed here that these deposits formed in an exhalative, volcanogenic, depositional environment within an extensional back-arc marginal basin. Such a tectonic setting is consistent with interpretations of protoliths in other portions of the Reading Prong, the Central Metasedimentary Belt of the Canadian Grenville Province, and recent interpretation of the origin of the Franklin lead-zinc deposits, suggesting a more cohesive evolving arc/back-arc tectonic model for the entire Proterozoic margin of the north-eastern portion of the North American craton. Published by Elsevier Ltd.

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.

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

Sedimentary dynamics and high-frequency sequence stratigraphy of the southwestern slope of Great Bahama Bank

NASA Astrophysics Data System (ADS)

Wunsch, Marco; Betzler, Christian; Eberli, Gregor P.; Lindhorst, Sebastian; Lüdmann, Thomas; Reijmer, John J. G.

2018-01-01

New geophysical data from the leeward slope of Great Bahama Bank show how contour currents shape the slope and induce re-sedimentation processes. Along slope segments with high current control, drift migration and current winnowing at the toe of slope form a deep moat. Here, the slope progradation is inhibited by large channel incisions and the accumulation of large mass transport complexes, triggered by current winnowing. In areas where the slope is bathed by weaker currents, the accumulation of mass transport complexes and channel incision is rather controlled by the position of the sea level. Large slope failures were triggered during the Mid-Pleistocene transition and Mid-Brunhes event, both periods characterized by changes in the cyclicity or the amplitude of sea-level fluctuations. Within the seismic stratigraphic framework of third order sequences, four sequences of higher order were identified in the succession of the upper Pleistocene. These higher order sequences also show clear differences in function of the slope exposure to contour currents. Two stochastic models emphasize the role of the contour currents and slope morphology in the facies distribution in the upper Pleistocene sequences. In areas of high current influence the interplay of erosional and depositional processes form a complex facies pattern with downslope and along strike facies alterations. In zones with lower current influence, major facies alternations occur predominately in downslope direction, and a layer-cake pattern characterizes the along strike direction. Therefore, this study highlights that contour currents are an underestimated driver for the sediment distribution and architecture of carbonate slopes.

A buried marine depositional sequence (Presumpscot FM. ) N. of the marine limit, Waterboro, Maine

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

Morency, R.E.

Subsurface investigations conducted in Waterboro, ME (York Co.) in connection with studies of two hazardous waste sites and a municipal water supply exploration project, have demonstrated that a laterally extensive sequence of marine deposits underlies surficial sediments mapped as non-esker ice contact glacio-fluvial deposits. The marine deposits consist of a fining-downwards sequence of grey, micaceous sands (fine to medium, grading down to a silty-fine sand), which grade downward into a thick ([plus minus] 30 feet) grey silt/clay unit, which itself shows a fining-downward trend. The stratigraphy is likely correlative to the Presumpscot Formation, as described by Bloom (1963). The bottommore » of the regressive marine sequence is marked at several locations by a thin layer of sand-sized biotite mica. Lodgement till was encountered only at scattered localities (in boreholes) at each site. The bedrock surface is of considerable relief, with changes of 200--300 feet over short distances detected. The sequence appears to be the record of a rapidly transgressing sea which inundated a valley where outwash had been deposited by meltwater ahead of retreating ice. As the sea retreated, up to 70 feet of sediment was deposited in a continuous, coarsening-upwards sequence. Subsequent to the marine regression, the sediments were reworked in a subaerial (braided stream) environment. The Surficial Geologic Map of Maine shows that the inland limit of late-glacial marine submergence is located approximately 8 miles southwest of Waterboro, in Alfred, Maine. The marine limit in Alfred takes the form of a NNE trending, blunt-ended embayment. The results of this study suggest that the marine embayment once extended northward from Alfred, and is now a buried feature, possibly representing a preglacial valley, which hosted an estuary in late Wisconsonian time.« less

Geologic control on the evolution of the inner shelf morphology offshore of the Mississippi barrier islands, northern Gulf of Mexico, USA

USGS Publications Warehouse

Flocks, James G.; Kindinger, Jack G.; Kelso, Kyle W.

2015-01-01

Between 2008 and 2013, high-resolution geophysical surveys were conducted around the Mississippi barrier islands and offshore. The sonar surveys included swath and single-beam bathymetry, sidescan, and chirp subbottom data collection. The geophysical data were groundtruthed using vibracore sediment collection. The results provide insight into the evolution of the inner shelf and the relationship between the near surface geologic framework and the morphology of the coastal zone. This study focuses on the buried Pleistocene fluvial deposits and late Holocene shore-oblique sand ridges offshore of Petit Bois Island and Petit Bois Pass. Prior to this study, the physical characteristics, evolution, and interrelationship of the ridges between both the shelf geology and the adjacent barrier island platform had not been evaluated. Numerous studies elsewhere along the coastal margin attribute shoal origin and sand-ridge evolution to hydrodynamic processes in shallow water (<20 m). Here we characterize the correlation between the geologic framework and surface morphology and demonstrate that the underlying stratigraphy must also be considered when developing an evolutionary conceptual model. It is important to understand this near surface, nearshore dynamic in order to understand how the stratigraphy influences the long-term response of the coastal zone to sea-level rise. The study also contributes to a growing body of work characterizing shore-oblique sand ridges which, along with the related geology, are recognized as increasingly important components to a nearshore framework whose origins and evolution must be understood and inventoried to effectively manage the coastal zone.

Geologic control on the evolution of the inner shelf morphology offshore of the Mississippi barrier islands, northern Gulf of Mexico, USA

NASA Astrophysics Data System (ADS)

Flocks, James G.; Kindinger, Jack L.; Kelso, Kyle W.

2015-06-01

Between 2008 and 2013, high-resolution geophysical surveys were conducted around the Mississippi barrier islands and offshore. The sonar surveys included swath and single-beam bathymetry, sidescan, and chirp subbottom data collection. The geophysical data were groundtruthed using vibracore sediment collection. The results provide insight into the evolution of the inner shelf and the relationship between the near surface geologic framework and the morphology of the coastal zone. This study focuses on the buried Pleistocene fluvial deposits and late Holocene shore-oblique sand ridges offshore of Petit Bois Island and Petit Bois Pass. Prior to this study, the physical characteristics, evolution, and interrelationship of the ridges between both the shelf geology and the adjacent barrier island platform had not been evaluated. Numerous studies elsewhere along the coastal margin attribute shoal origin and sand-ridge evolution to hydrodynamic processes in shallow water (<20 m). Here we characterize the correlation between the geologic framework and surface morphology and demonstrate that the underlying stratigraphy must also be considered when developing an evolutionary conceptual model. It is important to understand this near surface, nearshore dynamic in order to understand how the stratigraphy influences the long-term response of the coastal zone to sea-level rise. The study also contributes to a growing body of work characterizing shore-oblique sand ridges which, along with the related geology, are recognized as increasingly important components to a nearshore framework whose origins and evolution must be understood and inventoried to effectively manage the coastal zone.

Detailed structure and tectonics of the Ninetyeast Ridge near Site ODP 758 (on new geophysical data from KNOX06RR cruise of R/V Roger Revelle)

NASA Astrophysics Data System (ADS)

Levchenko, O.; Eisin, A. E.; Ivanenko, A. N.; Marinova, J. G.; Paul, C. F.; Sborshchikov, I. M.; Sager, W. W.

2008-12-01

Detailed geophysical survey was carried out during the NSF-funded KNOX06RR cruise of R/V Roger Revelle in July 2007 over the ~70×70 km area near ODP Site 758, the northern Ninetyeast Ridge (NER). In addition to multibeam echo-sounder bathymetry, 3.5 kHz echo-sounder profiles, magnetic, and gravity data, high-resolution multichannel seismic reflection data were collected on eight orthogonal profiles of total length ~270 km. Large NE-trending depressions with complicated horst and graben morphology dominate the whole detailed survey area. The numerous basement faults extend upward into overlying sediments filling out these depressions. Thickness of the sedimentary fill is highly variable due to very rough basement topography, and is up to 800 m maximum. This fill is divided in two clear sedimentary layers: transparent pelagic sediments above and stratified shallow-water ones below. Two high ~400-450 m isometric seamounts extend from the surrounding NER seafloor. High-resolution seismic records show that these igneous basement highs are covered by thin transparent pelagic sediments which hamper the dredging of volcanic rocks. Seismic stratigraphy analyses for sedimentary cover over the seamounts buried slopes suggest that they seem to be recent volcanoes superimposed on the main NER edifice. Both volcanoes are clearly delineated in the constructed map of total anomaly magnetic field. Since water depths are ~2.5 km above these seamounts, the lower edge of the magnetic body in these volcanoes is situated deep at ~7 km under sea level. That appears to represent deep roots of the volcanoes. Preliminary magnetic modeling shows that they were generated during negative chron of the geomagnetic scale rather not long ago and not far from their present location, seeming to confirm the inference that these volcanoes are recent in origin. In general, one may assume a secondary phase of magmatic activity on the NER. It is important to reveal, any recent phase of tectonic and magnetic activity occurred over the northern NER during the same time of well-known intense intraplate deformation in the Central Indian Basin which was initiated ~8 Ma in response to growing regional compression due to continental collision Hindustan and Eurasia. It appears to be nonrandom that this NER segment is located in an anomalous zone of high oceanic intraplate seismicity. Seismic stratigraphy analyses of high-resolution seismic records over the fault features simultaneously with careful study of reflectors on the buried slopes of the recent volcanoes will allow us to examine this problem.

Evolution of the Sedimentary Basin Within the Eastern Eez Polygon at the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Valle, S.; Mortera-Gutierrez, C. A.; Bandy, W. L.; Escobar-Briones, E. G.; Perez, D. A.

2013-05-01

This study shows the seafloor structures and magnetic anomalies inside the eastern EEZ polygon at the Gulf of Mexico. The objective of this study is to examine the previous hypothesis of the Gulf of Mexico opening, based on the seafloor magnetic character. Researchers from the "Instituto de Ciencias del Mar y Limnología" at UNAM, collected , multibeam bathymetric data, high-resolution seismic reflection and magnetic profiles along 37 E-W transects during two campaigns on board the UNAM vessel, BO JUSTO SIERRA, SIGSBEE-11 in 2008 and SIGSBEE-13 in 2010. Results of the bathymetry data gathered with the EM300 multibeam echo sounder (Kongsberg) and processed with the software Caraibes from IFREMER has generated a bathymetry chart of seafloor at the Eastern Polygon, and a mosaic of back-scattering images. The high-resolution seismic profiles gathered with the subbottom profiler TOPAS PS-18 (Kongsberg) provide information on the stratigraphy sediment packages across this polygon and across the deep Mississippi Canyon. The magnetic anomalies are reduced from the data gathered with a proton-precession magnetometer, G877 (GEOMETRICS). The anomalies are modeled, based on a N_S rift at the Gulf central sector. The bathymetric chart and reflectivity mosaics of SIGSBEE-11 and SIGSBEE-13 documented the smooth relief of the seabed slope toward the Gulf central sector and abrupt morphological features associated to the meanders of the Mississippi Canyon that trend to the East. The multibeam bathymetry chart shows a relief depth that goes from 2,900 to 3,400 m from north to south. Meanders are observed in the seabed within the Eastern Polygon which is related to turbidity currents from the Mississippi River, and having a trend from west to east. The relief of the canyon shows channels with widths between 400 and 1800 m, and canyon depths up to 80 m. The high-resolution seismic sections, show well defined stratigraphy packages, where clear sediment strata are interrupted by transparent sediment stratification. Likewise these opaque sediment packages showing in the seismic sections are product of the enormous contribution of turbidite flowing from the Mississippi River, so the seabed stratification within the Eastern Polygon consists mostly of turbidite deposits. These channels or turbidite deposits have been moving continuously along its evolution, and these structures are areas of great interest, for exploration of hydrocarbon deposits. The magnetic data were obtained covering a small area of the Gulf of Mexico and are integrated to other magnetic data set to revise the Gulf of Mexico opening models.

Land subsidence and recovery in the Albuquerque Basin, New Mexico, 1993–2014

USGS Publications Warehouse

Driscoll, Jessica M.; Brandt, Justin T.

2017-08-14

The Albuquerque Bernalillo County Water Utility Authority (ABCWUA) drinking water supply was almost exclusively sourced from groundwater from within the Albuquerque Basin before 2008. In 2008, the San Juan-Chama Drinking Water Project (SJCDWP) provided surface-water resources to augment the groundwater supply, allowing for a reduction in groundwater pumping in the Albuquerque Basin. In 2013, the U.S. Geological Survey, in cooperation with the ABCWUA, began a study to measure and compare aquifer-system and land-surface elevation change before and after the SJCDWP in 2008. Three methods of data collection with different temporal and spatial resolutions were used for this study: (1) aquifer-system compaction data collected continuously at a single extensometer from 1994 to 2013; (2) land-surface elevation change from Global Positioning System (GPS) surveys of a network of monuments collected in 1994–95, 2005, and 2014; and (3) spatially distributed Interferometric Synthetic Aperture Radar (InSAR) satellite data from 1993 to 2010. Collection of extensometer data allows for direct and continuous measurement of aquifer-system compaction at the extensometer location. The GPS surveys of a network of monuments allow for periodic measurements of land-surface elevation change at monument locations. Interferograms are limited in time by lifespan of the satellite, orbital pattern, and data quality but allow for measurement of gridded land-surface elevation change over the study area. Each of these methods was employed to provide a better understanding of aquifer-system compaction and land-surface elevation change for the Albuquerque Basin.Results do not show large magnitudes of subsidence in the Albuquerque Basin. High temporal-resolution but low spatial-resolution data measurements of aquifer-system compaction at the Albuquerque extensometer show elastic aquifer-system response to recovering groundwater levels. Results from the GPS survey of the network of monuments show inconsistent land-surface elevation changes over the Albuquerque Basin, likely because of the lack of significant change and the complexity of subsurface stratigraphy in addition to the spatial and temporal heterogeneity of groundwater withdrawals over the study period. Results from the InSAR analysis show areas of land-surface elevation increase after 2008, which could be attributed to elastic recovery of the aquifer system. The spatial extent to which elastic recovery of the aquifer system has resulted in recovery of land-surface elevation is limited to the in-situ measurements at the extensometer. Examination of spatially distributed InSAR data relative to limited spatial extent of the complex heterogeneity subsurface stratigraphy may explain some of the heterogeneity of land-surface elevation changes over this study period.

High-resolution phylogenetic microbial community profiling

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

Singer, Esther; Bushnell, Brian; Coleman-Derr, Devin

Over the past decade, high-throughput short-read 16S rRNA gene amplicon sequencing has eclipsed clone-dependent long-read Sanger sequencing for microbial community profiling. The transition to new technologies has provided more quantitative information at the expense of taxonomic resolution with implications for inferring metabolic traits in various ecosystems. We applied single-molecule real-time sequencing for microbial community profiling, generating full-length 16S rRNA gene sequences at high throughput, which we propose to name PhyloTags. We benchmarked and validated this approach using a defined microbial community. When further applied to samples from the water column of meromictic Sakinaw Lake, we show that while community structuresmore » at the phylum level are comparable between PhyloTags and Illumina V4 16S rRNA gene sequences (iTags), variance increases with community complexity at greater water depths. PhyloTags moreover allowed less ambiguous classification. Last, a platform-independent comparison of PhyloTags and in silico generated partial 16S rRNA gene sequences demonstrated significant differences in community structure and phylogenetic resolution across multiple taxonomic levels, including a severe underestimation in the abundance of specific microbial genera involved in nitrogen and methane cycling across the Lake's water column. Thus, PhyloTags provide a reliable adjunct or alternative to cost-effective iTags, enabling more accurate phylogenetic resolution of microbial communities and predictions on their metabolic potential.« less

High-resolution phylogenetic microbial community profiling

DOE PAGES

Singer, Esther; Bushnell, Brian; Coleman-Derr, Devin; ...

2016-02-09

Over the past decade, high-throughput short-read 16S rRNA gene amplicon sequencing has eclipsed clone-dependent long-read Sanger sequencing for microbial community profiling. The transition to new technologies has provided more quantitative information at the expense of taxonomic resolution with implications for inferring metabolic traits in various ecosystems. We applied single-molecule real-time sequencing for microbial community profiling, generating full-length 16S rRNA gene sequences at high throughput, which we propose to name PhyloTags. We benchmarked and validated this approach using a defined microbial community. When further applied to samples from the water column of meromictic Sakinaw Lake, we show that while community structuresmore » at the phylum level are comparable between PhyloTags and Illumina V4 16S rRNA gene sequences (iTags), variance increases with community complexity at greater water depths. PhyloTags moreover allowed less ambiguous classification. Last, a platform-independent comparison of PhyloTags and in silico generated partial 16S rRNA gene sequences demonstrated significant differences in community structure and phylogenetic resolution across multiple taxonomic levels, including a severe underestimation in the abundance of specific microbial genera involved in nitrogen and methane cycling across the Lake's water column. Thus, PhyloTags provide a reliable adjunct or alternative to cost-effective iTags, enabling more accurate phylogenetic resolution of microbial communities and predictions on their metabolic potential.« less

A ~600 kyr duration Early Pleistocene record from the West Turkana (Kenya) HSPDP drill site: elemental XRF variability to reconstruct climate change in Turkana Boy's backyard

NASA Astrophysics Data System (ADS)

Stockhecke, M.; Beck, C. C.; Brown, E. T.; Cohen, A.; Deino, A. L.; Feibel, C. S.; Sier, M.

2015-12-01

Outcrops in the Kenyan and Ethiopian rift valleys document repeated occurrences of freshwater lakes and wooded landscapes over the past 4 million years at locations that are currently seasonally-dry savanna. Studies of the rich fossil records, in combination with outcropping lacustrine sequences, led to major breakthroughs in our knowledge of driving factors in human evolution. However, study of continuous drill core from ancient lake basins provides a basis for to unravel East African climate dynamics in an unseen fashion. The Hominin Sites and Paleolakes Drilling Project (HSPDP), and the related Olorgesailie Drilling Project, recovered ~2 km of drill core since 2012. A major project goal is characterization of East African paleoclimate in order to evaluate its impact on hominin evolution. XRF core scanning data provide a means of evaluating records of past environmental conditions continuously and at high resolution. However, the HSPDP records contain complex lithologies reflecting repeated episodes of inundation and desiccation of the lake basins. Nevertheless, careful data evaluation based on detailed lithostratigraphy, which includes smear-slide microscopic analyses and X-radiographic images, allows disentanglement of complex signals and robust identification of continuous sequences for any cyclostratigraphic and statistical analysis. At the HSPDP Turkana Basin site a 175.6 m-long core the covers the Early Pleistocene time window during which hominids first expanded out of Africa and marine records document reorganization of tropical climate and the development of the strong Walker circulation. This drill site carries particular interest as it is located in only 2.5 km from the location of one of the most complete hominin skeletons ever recovered (Turkana Boy). Here we present a methodological approach to address the highly variable lithostratigraphy of the East African records to establish comprehensive and environmentally meaningful paleoclimate timeseries. In addition, the XRF record of the changing hydroclimate of the West Turkana Basin from 1.3 to 1.9 kyrs will be explored in relation to regional reconstructions and marine stratigraphies.

A New Oceanic Anoxic Event 2 record from the Central North Atlantic at South East Newfoundland Ridge, IODP Expedition 342, Newfoundland Drifts

NASA Astrophysics Data System (ADS)

Junium, C. K.; Bornemann, A.; Bown, P. R.; Friedrich, O.; Moriya, K.; Kirtland Turner, S.; Whiteside, J. H.

2013-12-01

The recovery of Cretaceous, Cenomanian-Turonian black shales deposited during Oceanic Anoxic Event 2 (OAE 2) at Site U1407, South East Newfoundland Ridge (SENR), was an unexpected but fortuitous discovery that fills a gap in the pelagic Tethyan and North Atlantic geologic records. Drilling operations recovered the OAE sequence in all three holes drilled at Site U1407 defined initially on the basis of lithology and calcareous nannofossil biostratigraphy and confirmed by carbon isotope stratigraphy post-expedition. The SENR OAE 2 sequence is a classic chalk sequence punctuated by a prominent black band. Prior to OAE 2, greenish white pelagic carbonate is interrupted by thin, 2 to 5 cm thick organic-rich, gray calcareous clays. A sharp transition from greenish-white chalk to carbonate-poor sediments marks the occurrence of the organic carbon-rich black band. Within the black band are finely laminated to massive, pyritic black shales and laminated gray clays that are relatively organic carbon-lean, free of preserved benthic foraminifera and rich in radiolarians. Finely laminated greenish-gray marls overlay the black band and grade into approximately 1 meter of greenish white chalks with common 1cm chert layers and nodules. The remainder of the Turonian sequence is characterized by a notable transition to pink chalks. The thickness of the black band ranges from 15-40 cm between Holes A through C. The differences in the thickness of beds between Holes is due in part to drilling disturbances and mass wasting indicated by slump features in the overlying Turonian strata. Core scanning XRF and carbon isotopes can help resolve the nature of these differences and inform future sampling and study. Carbonate and organic carbon isotopes reveal that the δ13C excursion marking the initiation of OAE 2 is below the base of the black band. At U1407A the δ13C rise is immediately below (3 cm) the black shale, with δ13C maxima in the black band. At U1407C the initial δ13C rise is below the black shale by 60 cm, in the underlying chalk. The temporal transience of TOC-enrichment is typical of OAE 2 sequences, particularly in the Tethyan realm (Gubbio, Italy; Ferriby, UK; Tarfaya, Morocco; Wunsorf, Germany), but the mechanism is unknown. In many ways, Site U1407 bears the distinct characteristics of the Tethyan region. Prior to the OAE, there are several black and dark gray bands interbedded with carbonate-rich (>80 wt. %), greenish white chalks. The color progression of white to black to pink through the OAE at U1407 is similar to C-T boundary sequences from the Umbria-Marche basin of Italy. The greenish white to pink nannofossil chalks are reminiscent of the Scaglia Bianca/Rossa limestones that bound the Bonarelli horizon. Associated lithologies include the presence of radiolarian sands interbedded with the black shales and cherts. This stratigraphic progression is similar to the Italian sequences, but the δ13C stratigraphy indicates that the excursion leads black shale deposition and in this sense is more similar to shallow continental records from the UK, USA and mainland Europe. This new δ13C record can be used to correlate SENR with other OAE 2 sections, allowing us to better understand possible mechanisms for the temporal transience of the black shales and paleoceanographic change during OAE2.

Heterozygous mapping strategy (HetMapps)for high resolution genotyping-by-sequencing markers: a case study in grapevine

USDA-ARS?s Scientific Manuscript database

Genotyping by sequencing (GBS) provides opportunities to generate high-resolution genetic maps at a low per-sample genotyping cost, but missing data and under-calling of heterozygotes complicate the creation of GBS linkage maps for highly heterozygous species. To overcome these issues, we developed ...

Publications - GMC 395 | Alaska Division of Geological & Geophysical

Science.gov Websites

investigations of the diatom stratigraphy of Borehole TA8, Portage Alaska: Alaska Division of Geological & Visiting Alaska State Employees DGGS State of Alaska search Alaska Division of Geological & Geophysical DGGS GMC 395 Publication Details Title: Preliminary investigations of the diatom stratigraphy of

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

Treesearch

David S. Leigh; Paul A. Webb

2006-01-01

Holocene colluvial and alluvial stratigraphy and a radiocarbon chronology are presented for the valley of the lower three kilometers of Raven Fork, a mountain stream draining 194 km2 of high relief (1.3 km) terrain of the Southern Blue Ridge Mountains in western North Carolina, USA, which is in a region that lacks good chronological data. Lower hillslopes, alluvial/...

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

Using Airborne Radar Stratigraphy to Model Surface Accumulation Anomaly and Basal Control over Deformed Basal Ice in Greenland

NASA Astrophysics Data System (ADS)

Das, I.; Bell, R. E.; Creyts, T. T.; Wolovick, M.

2013-12-01

Large deformed ice structures have been imaged at the base of northern Greenland ice sheet by IceBridge airborne radar. Numerous deformed structures lie along the base of both Petermann Glacier and Northeast Ice stream catchments covering 10-13% of the catchment area. These structures may be combinations of basal freeze-on and folded ice that overturns and inverts stratigraphy. In the interior, where the ice velocity is low, the radar imaged height of the deformed structures are frequently a significant fraction of the ice thickness. They are related to basal freeze on and stick-slip at the base of the ice sheet and may be triggered by subglacial water, sediments or local geological conditions. The larger ones (at times up to 700 m thick and 140 km long) perturb the ice stratigraphy and create prominent undulations on the ice surface and modify the local surface mass balance. Here, we investigate the relationship between the deformed structures and surface processes using shallow and deep ice radar stratigraphy. The surface undulations caused by the deformed structures modulate the pattern of local surface snow accumulation. Using normalized differences of several near-surface stratigraphic layers, we have calculated the accumulation anomaly over these deformed structures. The accumulation anomalies can be as high as 20% of the local surface accumulation over some of the larger surface depressions caused by these deformed structures. We observe distinct differences in the phases of the near-surface internal layers on the Petermann and Northeast catchments. These differences indicate that the deformed bodies over Petermann are controlled by conditions at the bed different from the Northeast Ice stream. The distinctly different near-surface stratigraphy over the deformed structures in the Petermann and Northeast catchments have opened up a number of questions including their formation and how they influence the ice dynamics, ice stratigraphy and surface mass balance. In this study we will model the different physical conditions at the bed and ice rheology from their distinct signatures in the near-surface strata. The results will identify the distinct mechanisms that form these bodies and their control over the surface morphology and snow accumulation.

Studying the spatial organization of membrane proteins by means of tritium stratigraphy: bacteriorhodopsin in purple membrane.

PubMed

Shishkov, A V; Ksenofontov, A L; Bogacheva, E N; Kordyukova, L V; Badun, G A; Alekseevsky, A V; Tsetlin, V I; Baratova, L A

2002-05-15

The topography of bacteriorhodopsin (bR) in situ was earlier studied by using the tritium bombardment approach [Eur. J. Biochem. 178 (1988) 123]. Now, having the X-ray crystallography data of bR at atom resolution [Proc. Natl. Acad. Sci. 95 (1998) 11673], we estimated the influence of membrane environment (lipid and protein) on tritium incorporation into amino acid residues forming transmembrane helices. We have determined the tritium flux attenuation coefficients for residues 10-29 of helix A. They turned out to be low (0.04+/-0.02 A(-1)) for residues adjacent to the lipid matrix, and almost fourfold higher (0.15+/-0.05 A(-1)) for those oriented to the neighboring transmembrane helices. We believe that tritium incorporation data could help modeling transmembrane segment arrangement in the membrane.

Seismic Stratigraphy of the Mariana Forearc Sedimentary Basin

NASA Astrophysics Data System (ADS)

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

2005-12-01

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

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.

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.;

Application of [sup 87]Sr/[sup 86]Sr, [delta][sup 18]O and [delta][sup 13]C isotopes to diagenesis correlation and connectivity of a fractured chalk reservoir, the Sidi El Kilani field, Tunisia

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

Mearns, E.W.; McBride, J.J.; Bramwell, M.

1996-01-01

Oil is produced primarily from open fracture porosity in Upper Cretaceous chalk in the Sidi El Kilani oil field. Strontium Stratigraphy analyses of primary, unaltered matrix chalk has confirmed a Campanian to Maastrichtian age and has allowed dating of the reservoir with a resolution of [+-]1 Ma. This has facilitated reservoir correlation and has indicated where section is missing in certain wells due to faulting. [sup 87]Sr/[sup 86]Sr, [delta][sup 18]O and [delta][sup 13]C analyses suggest an early generation of fracture fill calcite cement may have formed by redistribution of CaCO[sub 3] from underlying carbonate sequences at temperatures in the regionmore » 35-55[degrees]C. Calcite cemented fractures tend to be healed and are not productive. Strontium Isotope Residual Salt Analyses (SrRSA) conducted on core, provide information on the formation water chemistry and reservoir connectivity at the time of oil filling. These data suggest that the NW-SE trending fault system that bisects the field is sealed across much of the fault plane. The main oil pool lies SW of the fault. A later generation of dolomite and barite cements, associated with productive open fractures, have Sr-O-C composition consistent with precipitation from fluids circulating at the time of hydrocarbon charge at temperatures close to current reservoir conditions of 70-75[degrees]C. Predicting the distribution of dolomite cemented open fractures has thus helped guide the development strategy of the field.« less

Application of {sup 87}Sr/{sup 86}Sr, {delta}{sup 18}O and {delta}{sup 13}C isotopes to diagenesis correlation and connectivity of a fractured chalk reservoir, the Sidi El Kilani field, Tunisia

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

Mearns, E.W.; McBride, J.J.; Bramwell, M.

1996-12-31

Oil is produced primarily from open fracture porosity in Upper Cretaceous chalk in the Sidi El Kilani oil field. Strontium Stratigraphy analyses of primary, unaltered matrix chalk has confirmed a Campanian to Maastrichtian age and has allowed dating of the reservoir with a resolution of {+-}1 Ma. This has facilitated reservoir correlation and has indicated where section is missing in certain wells due to faulting. {sup 87}Sr/{sup 86}Sr, {delta}{sup 18}O and {delta}{sup 13}C analyses suggest an early generation of fracture fill calcite cement may have formed by redistribution of CaCO{sub 3} from underlying carbonate sequences at temperatures in the regionmore » 35-55{degrees}C. Calcite cemented fractures tend to be healed and are not productive. Strontium Isotope Residual Salt Analyses (SrRSA) conducted on core, provide information on the formation water chemistry and reservoir connectivity at the time of oil filling. These data suggest that the NW-SE trending fault system that bisects the field is sealed across much of the fault plane. The main oil pool lies SW of the fault. A later generation of dolomite and barite cements, associated with productive open fractures, have Sr-O-C composition consistent with precipitation from fluids circulating at the time of hydrocarbon charge at temperatures close to current reservoir conditions of 70-75{degrees}C. Predicting the distribution of dolomite cemented open fractures has thus helped guide the development strategy of the field.« less

Oligo-Miocene foraminiferal record (Miogypsinidae, Lepidocyclinidae and Nummulitidae) from the Western Taurides (SW Turkey): Biometry and implications for the regional geology

NASA Astrophysics Data System (ADS)

Özcan, Ercan; Less, György; Báldi-Beke, Mária; Kollányi, Katalin; Acar, Ferhat

2009-05-01

The marine Oligo-Miocene units of western Taurides, deposited under different tectonic regimes (in Bey Dağları platform in foreland and coeval sequences in hinterland), were studied to establish a high-resolution biostratigraphic framework. Biometric study of the full spectrum of larger foraminifera in a regional scale allowed us correlating them with the shallow benthic zonation (SBZ) system introduced by [Cahuzac, B., Poignant, A., 1997. Essai de biozonation de l'Oligo-Miocène dans les bassins européens à l'aide des grands foraminifères néritiques. Bulletin de la Société géologique de France 168, 155-169], and to determine the ages of these sites on zonal precision for the first time. In correlating these assemblages to standard shallow benthic zones, planktonic data were also used whenever possible. Taxa, classified under the genera Nummulites, Miogypsina, Miolepidocyclina, Nephrolepidina, Eulepidina, Heterostegina, Operculina and Cycloclypeus (?) and their assemblages, closely resemble to the fauna described from European basins. These groups characterize the SBZ 22B to 25 zones referring to a time interval from early Chattian to Burdigalian. However, a main gap in late Chattian (SBZ 23) and in early part of the Aquitanian (SBZ 24) is also recorded in the platform succession. In the meantime, rare Eulepidina in the Burdigalian levels suggest a clear Indo-Pacific influence. Based on the discovery of early Chattian (SBZ 22B) deposits (previously mapped under Eocene/Miocene units), the Oligo-Miocene stratigraphy of the Bey Dağları platform is also revised. A more precise chronology for regional Miocene transgression is presented based on the miogypsinid evolutionary scale.

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?

Geology and sequence stratigraphy of undiscovered oil and gas resources in conventional and continuous petroleum systems in the Upper Cretaceous Eagle Ford Group and related strata, U.S. Gulf Coast Region

USGS Publications Warehouse

Dubiel, Russell F.; Pearson, Ofori N.; Pitman, Janet K.; Pearson, Krystal M.; Kinney, Scott A.

2012-01-01

The U.S. Geological Survey (USGS) recently assessed the technically recoverable undiscovered oil and gas onshore and in State waters of the Gulf Coast region of the United States. The USGS defined three assessment units (AUs) with potential undiscovered conventional and continuous oil and gas resources in Upper Cretaceous (Cenomanian to Turonian) strata of the Eagle Ford Group and correlative rocks. The assessment is based on geologic elements of a total petroleum system, including hydrocarbon source rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy and petrophysical properties), and traps (formation, timing, and seals). Conventional oil and gas undiscovered resources are in updip sandstone reservoirs in the Upper Cretaceous Tuscaloosa and Woodbine Formations (or Groups) in Louisiana and Texas, respectively, whereas continuous oil and continuous gas undiscovered resources reside in the middip and downdip Upper Cretaceous Eagle Ford Shale in Texas and the Tuscaloosa marine shale in Louisiana. Conventional resources in the Tuscaloosa and Woodbine are included in the Eagle Ford Updip Sandstone Oil and Gas AU, in an area where the Eagle Ford Shale and Tuscaloosa marine shale display vitrinite reflectance (Ro) values less than 0.6%. The continuous Eagle Ford Shale Oil AU lies generally south of the conventional AU, is primarily updip of the Lower Cretaceous shelf edge, and is defined by thermal maturity values within shales of the Eagle Ford and Tuscaloosa that range from 0.6 to 1.2% Ro. Similarly, the Eagle Ford Shale Gas AU is defined downdip of the shelf edge where source rocks have Ro values greater than 1.2%. For undiscovered oil and gas resources, the USGS assessed means of: 1) 141 million barrels of oil (MMBO), 502 billion cubic feet of natural gas (BCFG), and 4 million barrels of natural gas liquids (MMBNGL) in the Eagle Ford Updip Sandstone Oil and Gas AU; 2) 853 MMBO, 1707 BCFG, and 34 MMBNGL in the Eagle Ford Shale Oil AU; and 3) 50,219 BCFG and 2009 MMBNGL in the Eagle Ford Shale Gas AU.

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.

Sequence stratigraphic controls on reservoir characterization and architecture: case study of the Messinian Abu Madi incised-valley fill, Egypt

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Mohamed I.; Slatt, Roger M.

2013-12-01

Understanding sequence stratigraphy architecture in the incised-valley is a crucial step to understanding the effect of relative sea level changes on reservoir characterization and architecture. This paper presents a sequence stratigraphic framework of the incised-valley strata within the late Messinian Abu Madi Formation based on seismic and borehole data. Analysis of sand-body distribution reveals that fluvial channel sandstones in the Abu Madi Formation in the Baltim Fields, offshore Nile Delta, Egypt, are not randomly distributed but are predictable in their spatial and stratigraphic position. Elucidation of the distribution of sandstones in the Abu Madi incised-valley fill within a sequence stratigraphic framework allows a better understanding of their characterization and architecture during burial. Strata of the Abu Madi Formation are interpreted to comprise two sequences, which are the most complex stratigraphically; their deposits comprise a complex incised valley fill. The lower sequence (SQ1) consists of a thick incised valley-fill of a Lowstand Systems Tract (LST1)) overlain by a Transgressive Systems Tract (TST1) and Highstand Systems Tract (HST1). The upper sequence (SQ2) contains channel-fill and is interpreted as a LST2 which has a thin sandstone channel deposits. Above this, channel-fill sandstone and related strata with tidal influence delineates the base of TST2, which is overlain by a HST2. Gas reservoirs of the Abu Madi Formation (present-day depth ˜3552 m), the Baltim Fields, Egypt, consist of fluvial lowstand systems tract (LST) sandstones deposited in an incised valley. LST sandstones have a wide range of porosity (15 to 28%) and permeability (1 to 5080mD), which reflect both depositional facies and diagenetic controls. This work demonstrates the value of constraining and evaluating the impact of sequence stratigraphic distribution on reservoir characterization and architecture in incised-valley deposits, and thus has an important impact on reservoir quality evolution in hydrocarbon exploration in such settings.

Multishot versus Single-Shot Pulse Sequences in Very High Field fMRI: A Comparison Using Retinotopic Mapping

PubMed Central

Gatenby, J. Christopher; Gore, John C.; Tong, Frank

2012-01-01

High-resolution functional MRI is a leading application for very high field (7 Tesla) human MR imaging. Though higher field strengths promise improvements in signal-to-noise ratios (SNR) and BOLD contrast relative to fMRI at 3 Tesla, these benefits may be partially offset by accompanying increases in geometric distortion and other off-resonance effects. Such effects may be especially pronounced with the single-shot EPI pulse sequences typically used for fMRI at standard field strengths. As an alternative, one might consider multishot pulse sequences, which may lead to somewhat lower temporal SNR than standard EPI, but which are also often substantially less susceptible to off-resonance effects. Here we consider retinotopic mapping of human visual cortex as a practical test case by which to compare examples of these sequence types for high-resolution fMRI at 7 Tesla. We performed polar angle retinotopic mapping at each of 3 isotropic resolutions (2.0, 1.7, and 1.1 mm) using both accelerated single-shot 2D EPI and accelerated multishot 3D gradient-echo pulse sequences. We found that single-shot EPI indeed led to greater temporal SNR and contrast-to-noise ratios (CNR) than the multishot sequences. However, additional distortion correction in postprocessing was required in order to fully realize these advantages, particularly at higher resolutions. The retinotopic maps produced by both sequence types were qualitatively comparable, and showed equivalent test/retest reliability. Thus, when surface-based analyses are planned, or in other circumstances where geometric distortion is of particular concern, multishot pulse sequences could provide a viable alternative to single-shot EPI. PMID:22514646

Multishot versus single-shot pulse sequences in very high field fMRI: a comparison using retinotopic mapping.

PubMed

Swisher, Jascha D; Sexton, John A; Gatenby, J Christopher; Gore, John C; Tong, Frank

2012-01-01

High-resolution functional MRI is a leading application for very high field (7 Tesla) human MR imaging. Though higher field strengths promise improvements in signal-to-noise ratios (SNR) and BOLD contrast relative to fMRI at 3 Tesla, these benefits may be partially offset by accompanying increases in geometric distortion and other off-resonance effects. Such effects may be especially pronounced with the single-shot EPI pulse sequences typically used for fMRI at standard field strengths. As an alternative, one might consider multishot pulse sequences, which may lead to somewhat lower temporal SNR than standard EPI, but which are also often substantially less susceptible to off-resonance effects. Here we consider retinotopic mapping of human visual cortex as a practical test case by which to compare examples of these sequence types for high-resolution fMRI at 7 Tesla. We performed polar angle retinotopic mapping at each of 3 isotropic resolutions (2.0, 1.7, and 1.1 mm) using both accelerated single-shot 2D EPI and accelerated multishot 3D gradient-echo pulse sequences. We found that single-shot EPI indeed led to greater temporal SNR and contrast-to-noise ratios (CNR) than the multishot sequences. However, additional distortion correction in postprocessing was required in order to fully realize these advantages, particularly at higher resolutions. The retinotopic maps produced by both sequence types were qualitatively comparable, and showed equivalent test/retest reliability. Thus, when surface-based analyses are planned, or in other circumstances where geometric distortion is of particular concern, multishot pulse sequences could provide a viable alternative to single-shot EPI.

A Major Unconformity Between Permian and Triassic Strata at Cape Kekurnoi, Alaska Peninsula: Old and New Observations on Stratigraphy and Hydrocarbon Potential

USGS Publications Warehouse

Blodgett, Robert B.; Sralla, Bryan

2008-01-01

A major angular unconformity separates carbonates and shales of the Upper Triassic Kamishak Formation from an underlying unnamed sequence of Permian agglomerate, volcaniclastic rocks (sandstone), and limestone near Puale Bay on the Alaska Peninsula. For the first time, we photographically document the angular unconformity in outcrop, as clearly exposed in a seacliff ~1.3 mi (2.1 km) west of Cape Kekurnoi in the Karluk C?4 and C?5 1:63,360-scale quadrangles. This unconformity is also documented by examination of core chips, ditch cuttings, and (or) open-hole electrical logs in two deep oil-and-gas-exploration wells (Humble Oil & Refining Co.?s Bear Creek No. 1 and Standard Oil Co. of California?s Grammer No. 1) drilled along the Alaska Peninsula southwest of Puale Bay. A third well (Richfield Oil Corp.?s Wide Bay Unit No. 1), south of and structurally on trend with the other two wells, probed deeply into the Paleozoic basement, but Triassic strata are absent, owing to either a major unconformity or a large fault. Here we briefly review current and newly acquired data on Permian and Triassic rocks of the Puale Bay-Becharof Lake-Wide Bay area on the basis of an examination of surface and subsurface materials. The resulting reinterpretation of the Permian and Triassic stratigraphy has important economic ramifications for oil and gas exploration on the Alaska Peninsula and in the Cook Inlet basin. We also present a history of petroleum exploration targeting Upper Triassic reservoirs in the region.

Seismic stratigraphy of the Mississippi-Alabama shelf and upper continental slope

USGS Publications Warehouse

Kindinger, J.L.

1988-01-01

The Mississippi-Alabama shelf and upper continental slope contain relatively thin Upper Pleistocene and Holocene deposits. Five stages of shelf evolution can be identified from the early Wisconsinan to present. The stages were controlled by glacioeustatic or relative sea-level changes and are defined by the stratigraphic position of depositional and erosional episodes. The stratigraphy was identified on seismic profiles by means of geomorphic pattern, high-angle clinoform progradational deposits, buried stream entrenchments, planar conformities, and erosional unconformities. The oldest stage (stage 1) of evolution occurred during the early Wisconsinan lowstand; the subaerially exposed shelf was eroded to a smooth seaward-sloping surface. This paleosurface is overlain by a thin (< 10 m) drape of transgressive deposits (stage 2). Stage 3 occurred in three phases as the late Wisconsinan sea retreated: (1) fluvial channel systems eroded across the shelf, (2) deposited a thick (90 m) shelf-margin delta, and (3) contemporaneously deposited sediments on the upper slope. Stage 4 included the rapid Holocene sea-level rise that deposited a relatively thin transgressive facies over parts of the shelf. The last major depositional episode (stage 5) was the progradation of the St. Bernard delta over the northwestern and central parts of the area. A depositional hiatus has occurred since the St. Bernard progradation. These Upper Quaternary shelf and slope deposits provide models for analogous deposits in the geologic record. Primarily, they are examples of cyclic sedimentation caused by changes in sea level and may be useful in describing short-term, sandy depositional episodes in prograding shelf and slope sequences. ?? 1988.

Imaging Reservoir Siltation and Quaternary Stratigraphy Beneath the Mactaquac Headpond by Acoustic and Ground Penetrating Radar Sub-bottom Imaging

NASA Astrophysics Data System (ADS)

Grace, M.; Butler, K. E.; Peter, S.; Yamazaki, G.; Haralampides, K.

2016-12-01

The Mactaquac Hydroelectric Generating Station, located on the Saint John River in New Brunswick, Canada, is approaching the end of its life due to deterioration of the concrete structures. As part of an aquatic ecosystem study, designed to support a decision on the future of the dam, sediment in the headpond, extending 80 km upriver, is being examined. The focus of this sub-study lies in (i) mapping the thickness of sediments that have accumulated since inundation in 1968, and (ii) imaging the deeper glacial and post-glacial stratigraphy. Acoustic sub-bottom profiling surveys were completed during 2014 and 2015. An initial 3.5 kHz chirp sonar survey proved ineffective, lacking in both resolution and depth of the penetration. A follow-up survey employing a boomer-based "Seistec" sediment profiler provided better results, resolving sediment layers as thin as 12 cm, and yielding coherent reflections from the deeper Quaternary sediments. Post-inundation sediments in the lowermost 25 km of the headpond, between the dam and Bear Island, are interpreted to average 26 cm in thickness with the thickest deposits (up to 65 cm) in deep water areas overlying the pre-inundation riverbed west of Snowshoe Island, and south and east of Bear Island. A recent coring program confirmed the presence of silty sediment and showed good correlation with the Seistec thickness estimates. In the 15 km stretch upriver of Bear Island to Nackawic, the presence of gas in the uppermost sediments severely limits sub-bottom penetration and our ability to interpret sediment thicknesses. Profiles acquired in the uppermost 40 km reach of the headpond, extending to Woodstock, show a strong, positive water bottom reflection and little to no sub-bottom penetration, indicating the absence of soft post-inundation sediment. Deeper reflections observed within 5 km of the dam reveal a buried channel cut into glacial till, extending up to 20 m below the water bottom. Channel fill includes a finely laminated unit interpreted to be glaciolacustrine clay-silt and a possible esker - similar to stratigraphy found 20 - 30 km downriver at Fredericton. Future plans include a small scale survey in late summer, 2016 to evaluate the suitability of waterborne ground penetrating radar (GPR) profiling as an alternative to acoustic profiling in areas of gas-charged sediment.

High-resolution 40Ar 39Ar chronology of Oligocene volcanic rocks, San Juan Mountains, Colorado

USGS Publications Warehouse

Lanphere, M.A.

1988-01-01

The central San Juan caldera complex consists of seven calderas from which eight major ash-flow tuffs were erupted during a period of intense volcanic activity that lasted for approximately 2 m.y. about 26-28 Ma. The analytical precision of conventional K-Ar dating in this time interval is not sufficient to unambiguously resolve this complex history. However, 40Ar 39Ar incremental-heating experiments provide data for a high-resolution chronology that is consistent with stratigraphie relations. Weighted-mean age-spectrum plateau ages of biotite and sanidine are the most precise with standard deviations ranging from 0.08 to 0.21 m.y. The pooled estimate of standard deviation for the plateau ages of 12 minerals is about 0.5 percent or about 125,000 to 135,000 years. Age measurements on coexisting minerals from one tuff and on two samples of each of two other tuffs indicate that a precision in the age of a tuff of better than 100,000 years can be achieved at 27 Ma. New data indicate that the San Luis caldera is the youngest caldera in the central complex, not the Creede caldera as previously thought. ?? 1988.

A GLOBAL GEOLOGIC MAP OF GANYMEDE

NASA Astrophysics Data System (ADS)

Patterson, G.; Collins, G. C.; Head, J. W.; Pappalardo, R. T.; Prockter, L. M.; Lucchitta, B. K.

2009-12-01

Ganymede is a planet-sized world, the solar system’s largest satellite with a radius of 2631 km. Its physiography, geology, geophysics, surface composition, and evolution are correspondingly planet-like in intricacy. We have completed a global geological map of Ganymede that represents the most recent understanding of the satellite on the basis of Galileo mission results. This contribution builds on important previous accomplishments in the study of Ganymede utilizing Voyager data and incorporates the many new discoveries that were brought about by examination of Galileo data. Material units have been defined, structural landforms have been identified, and an approximate stratigraphy has been determined utilizing a global mosaic of the surface with a nominal resolution of 1 km/pixel assembled by the USGS. This mosaic incorporates the best available Voyager and Galileo regional coverage and high resolution imagery (100-200 m/pixel) of characteristic features and terrain types obtained by the Galileo spacecraft. This effort has provided a more complete understanding of: 1) the major geological processes operating on Ganymede, 2) the characteristics of the geological units making up its surface, 3) the stratigraphic relationships of geological units and structures, and 4) the geological history inferred from these relationships.

Grizzly Valley fault system, Sierra Valley, CA

USGS Publications Warehouse

Gold, Ryan; Stephenson, William; Odum, Jack; Briggs, Rich; Crone, Anthony; Angster, Steve

2012-01-01

The Grizzly Valley fault system (GVFS) strikes northwestward across Sierra Valley, California and is part of a network of active, dextral strike-slip faults in the northern Walker Lane (Figure 1). To investigate Quaternary motion across the GVFS, we analyzed high-resolution (0.25 m) airborne LiDAR data (Figure 2) in combination with six, high-resolution, P-wave, seismic-reflection profiles [Gold and others, 2012]. The 0.5- to 2.0-km-long seismic-reflection profiles were sited orthogonal to suspected tectonic lineaments identified from previous mapping and our analysis of airborne LiDAR data. To image the upper 400–700 m of subsurface stratigraphy of Sierra Valley (Figure 3), we used a 230-kg accelerated weight drop source. Geophone spacing ranged from 2 to 5 m and shots were co-located with the geophones. The profiles reveal a highly reflective, deformed basal marker that we interpret to be the top of Tertiary volcanic rocks, overlain by a 120- to 300-m-thick suite of subhorizontal reflectors we interpret as Plio-Pleistocene lacustrine deposits. Three profiles image the principle active trace of the GVFS, which is a steeply dipping fault zone that offsets the volcanic rocks and the basin fill (Figures 4 & 5).

Advances in planetary geology

NASA Technical Reports Server (NTRS)

1983-01-01

Topics discussed include: (1) Martian global tectonics; (2) the origin and evolution of a circular and an irregular lunar mare; (3) stratigraphy of Oceanus Procellarum basalts: sources and styles of emplacement; (4) the tectonic evolution of the Oceanus Procellarum Basin; (5) charting the Southern Seas: the evolution of the Lunar Mare Australe; (6) the stratigraphy of Mare Imbrium; and (7) Storms and rains: a comparison of the Lunar Mare Imbrium and Oceanus Procellarum.

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

NASA Technical Reports Server (NTRS)

Maxwell, T. A.

1976-01-01

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

Archaeological recording and chemical stratigraphy applied to contaminated land studies.

PubMed

Photos-Jones, Effie; Hall, Allan J

2011-11-15

The method used by archaeologists for excavation and recording of the stratigraphic evidence, within trenches with or without archaeological remains, can potentially be useful to contaminated land consultants (CLCs). The implementation of archaeological practice in contaminated land assessments (CLAs) is not meant to be an exercise in data overkill; neither should it increase costs. Rather, we suggest, that if the excavation and recording, by a trained archaeologist, of the stratigraphy is followed by in-situ chemical characterisation then it is possible that much uncertainty associated with current field sampling practices, may be removed. This is because built into the chemical stratigraphy is the temporal and spatial relationship between different parts of the site reflecting the logic behind the distribution of contamination. An archaeological recording with chemical stratigraphy approach to sampling may possibly provide 'one method fits all' for potentially contaminated land sites (CLSs), just as archaeological characterisation of the stratigraphic record provides 'one method fits all' for all archaeological sites irrespective of period (prehistoric to modern) or type (rural, urban or industrial). We also suggest that there may be practical and financial benefits to be gained by pulling together expertise and resources stemming from different disciplines, not simply at the assessment phase, but also subsequent phases, in contaminated land improvement. Copyright © 2011 Elsevier B.V. All rights reserved.

Geologic and Site Survey Setting for JIP Gulf of Mexico Gas Hydrate Drilling

NASA Astrophysics Data System (ADS)

Hutchinson, D. R.; Snyder, F.; Hart, P. E.; Ruppel, C. D.; Pohlman, J.; Wood, W. T.; Coffin, R. B.; Edwards, K. M.

2005-12-01

The JIP Gulf of Mexico drilling program targeted two contrasting geologic settings to understand natural gas hydrates: a salt-withdrawal minibasin and a mound/seep site, both at mid-slope water depths of about 1300 m. The minibasin site (lease block Keathley Canyon 151) contains a Bottom Simulating Reflection (BSR) that deepens from 260 m below the sea floor near the edge of the basin to 500 mbsf towards the center of the basin. Drilling was conducted at a site in which the BSR is about 415 mbsf. Seismic stratigraphy of the minibasin consists of continuous laminated sequences of variable thicknesses alternating with more massive units of discontinuous reflections. These sequences represent uniform hemipelagic deposition, which drapes the basin, and turbidite deposition, which pinches out along the basin edges. The BSR crosses several of these sequences. A map of amplitude values at the BSR shows a strong banding pattern indicative of the layering, with the highest amplitudes interpreted to be trapped gas in the coarser-grained units. Prior to drilling, piston-core data indicated extensive shallow mass wasting near the edges of the minibasin. Heat flow data indicated thermal gradients that in general predicted a BSR deeper than observed in the seismic data. Full-waveform inversion of 3D multichannel data indicated a probable thick zone of low-saturation hydrate immediately above the BSR. There is little coherent seismic stratigraphy at the mound/seep site in the Mississippi Canyon (lease blocks Atwater Valley 13/14), as the canyon fill is dominated by a complex mix of turbidite and mass-wasting deposits. Hints of a possible BSR that is warped upwards beneath the mound can be seen in both 3D and 2D multichannel seismic data, but it cannot be traced laterally away from the mound with any certainty. A seismic pull-down pseudo-structure beneath the mound suggests the presence of a free-gas low-velocity zone at shallow depths. Pore-water analyses from shallow piston cores and closely-spaced heat-flow data indicate the mound is a site of probable fluid venting. A transect of bottom photographs crosses a possible mud flow and numerous bacterial mats, consistent with features seen in fluid venting at other sites in the Gulf. Prestack inversion of the multichannel data did not predict significant gas hydrate at the site on the edge of the mound. However, at the control site off the mound, predictions were more favorable for low hydrate saturations in the deeper part of the drill hole.

High-resolution community profiling of arbuscular mycorrhizal fungi.

PubMed

Schlaeppi, Klaus; Bender, S Franz; Mascher, Fabio; Russo, Giancarlo; Patrignani, Andrea; Camenzind, Tessa; Hempel, Stefan; Rillig, Matthias C; van der Heijden, Marcel G A

2016-11-01

Community analyses of arbuscular mycorrhizal fungi (AMF) using ribosomal small subunit (SSU) or internal transcribed spacer (ITS) DNA sequences often suffer from low resolution or coverage. We developed a novel sequencing based approach for a highly resolving and specific profiling of AMF communities. We took advantage of previously established AMF-specific PCR primers that amplify a c. 1.5-kb long fragment covering parts of SSU, ITS and parts of the large ribosomal subunit (LSU), and we sequenced the resulting amplicons with single molecule real-time (SMRT) sequencing. The method was applicable to soil and root samples, detected all major AMF families and successfully discriminated closely related AMF species, which would not be discernible using SSU sequences. In inoculation tests we could trace the introduced AMF inoculum at the molecular level. One of the introduced strains almost replaced the local strain(s), revealing that AMF inoculation can have a profound impact on the native community. The methodology presented offers researchers a powerful new tool for AMF community analysis because it unifies improved specificity and enhanced resolution, whereas the drawback of medium sequencing throughput appears of lesser importance for low-diversity groups such as AMF. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Application of population sequencing (POPSEQ) for ordering and inputting genotyping-by-sequencing markers in hexaploid wheat

USDA-ARS?s Scientific Manuscript database

The advancement of next-generation sequencing technologies in conjunction with new bioinformatics tools enabled fine-tuning of sequence-based high resolution mapping strategies for complex genomes. Although genotyping-by-sequencing (GBS) provides a large number of markers, its application for assoc...

In vivo Proton Electron Double Resonance Imaging of Mice with Fast Spin Echo Pulse Sequence

PubMed Central

Sun, Ziqi; Li, Haihong; Petryakov, Sergey; Samouilov, Alex; Zweier, Jay L.

2011-01-01

Purpose To develop and evaluate a 2D fast spin echo (FSE) pulse sequence for enhancing temporal resolution and reducing tissue heating for in vivo proton electron double resonance imaging (PEDRI) of mice. Materials and Methods A four-compartment phantom containing 2 mM TEMPONE was imaged at 20.1 mT using 2D FSE-PEDRI and regular gradient echo (GRE)-PEDRI pulse sequences. Control mice were infused with TEMPONE over ∼1 min followed by time-course imaging using the 2D FSE-PEDRI sequence at intervals of 10 – 30 s between image acquisitions. The average signal intensity from the time-course images was analyzed using a first-order kinetics model. Results Phantom experiments demonstrated that EPR power deposition can be greatly reduced using the FSE-PEDRI pulse sequence compared to the conventional gradient echo pulse sequence. High temporal resolution was achieved at ∼4 s per image acquisition using the FSE-PEDRI sequence with a good image SNR in the range of 233-266 in the phantom study. The TEMPONE half-life measured in vivo was ∼72 s. Conclusion Thus, the FSE-PEDRI pulse sequence enables fast in vivo functional imaging of free radical probes in small animals greatly reducing EPR irradiation time with decreased power deposition and provides increased temporal resolution. PMID:22147559

Dating the upper Cenozoic sediments in Fisher Valley, southeastern Utah ( USA).

USGS Publications Warehouse

Colman, Steven M.; Choquette, Anne F.; Rosholt, J.M.; Miller, G.H.; Huntley, D.J.

1986-01-01

More than 140 m of upper Cenozoic basin-fill sediments were deposited and then deformed in Fisher Valley between about 2.5 and 0.25 m.y. ago, in response to uplift of the adjacent Onion Creek salt diapir. In addition to these basin-fill sediments, minor amounts of eolian and fluvial sand were depositd in Holocene time. The sediments, whose relative ages are known from the stratigraphy, are predominantly sandy, second-cycle red beds derived from nearby Mesozoic rocks; most were deposited in a vertical sequence, filling a sedimentary basin now exposed by fluvial dissection. We have applied a variety of established and experimental dating methods to the sediments in Fisher Valley to establish their age and to provide time control for the recent history of the Onion Creek salt diapir.-from Authors

Miocene-Oligocene sequence stratigraphy of the Malay Basin

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

Lovell, R.; Elias, M.R.; Hill, R.E.

1994-07-01

The Malay Basin has experienced extension of the Eocene ( ) through Oligocene, sag in the early Miocene, and compression in the middle Miocene through Pliocene-Pleistocene. The interaction of structurally induced and glacial-eustatic accommodation changes has resulted in complex, interrelated play elements, including multiple reservoirs, diverse nonmarine sources, discontinuous migration pathways, and thin seals. Extensional subbasins were filled with braided streams, associated coastal plain, lacustrine deltas, and thick lake shales (groups M-K). This initial rift fill comprises an overall second order progradational cycle punctuated by 3rd-order cycles. These 3rd-order cycles are capped by thick, source-rich, lacustrine shale packages. The lowermore » Miocene section (groups I and J) consists of progradational to aggradational fluvial to tidally-dominated estuarine sands. Hydrocarbons are generated from interbedded coals and other coal-related lithologies.« less

Preliminary Physical Stratigraphy and Geophysical Data From the USGS Dixon Core, Onslow County, North Carolina

USGS Publications Warehouse

Seefelt, Ellen L.; Gonzalez, Wilma Aleman B.; Self-Trail, Jean M.; Weems, Robert E.; Edwards, Lucy E.; Pierce, Herbert A.; Durand, Colleen T.

2009-01-01

In October through November 2006, scientists from the U. S. Geological Survey (USGS) Eastern Region Earth Surface Processes Team (EESPT) and the Raleigh (N.C.) Water Science Center (WSC), in cooperation with the North Carolina Geological Survey (NCGS) and the Onslow County Water and Sewer Authority (ONWASA), drilled a stratigraphic test hole and well in Onslow County, N.C. The Dixon corehole was cored on ONWASA water utility property north of the town of Dixon, N.C., in the Sneads Ferry 7.5-minute quadrangle at latitude 34deg33'35' N, longitude 77deg26'54' W (decimal degrees 34.559722 and -77.448333). The site elevation is 66.0 feet (ft) above mean sea level as determined using a Paulin precision altimeter. The corehole attained a total depth of 1,010 ft and was continuously cored by the USGS EESPT drilling crew. A groundwater monitoring well was installed in the screened interval between 234 and 254 ft below land surface. The section cored at this site includes Upper Cretaceous, Paleogene, and Neogene sediments. The Dixon core is stored at the NCGS Coastal Plain core storage facility in Raleigh. The Dixon corehole is the fourth and last in a series of planned North Carolina benchmark coreholes drilled by the USGS Coastal Carolina Project. These coreholes explore the physical stratigraphy, facies, and thickness of Cretaceous, Paleogene, and Neogene Coastal Plain sediments in North Carolina. Correlations of lithologies, facies, and sequence stratigraphy can be made with the Hope Plantation corehole, N.C., near Windsor in Bertie County (Weems and others, 2007); the Elizabethtown corehole, near Elizabethtown, N.C., in Bladen County (Self-Trail and others, 2004b); the Smith Elementary School corehole, near Cove City, N.C., in Craven County (Harris and Self-Trail, 2006; Crocetti, 2007); the Kure Beach corehole, near Wilmington, N.C., in New Hanover County (Self-Trail and others, 2004a); the Esso#1, Esso #2, Mobil #1, and Mobil #2 cores in Albermarle and Pamlico Sounds, N.C. (Zarra, 1989); and the Cape Fear River outcrops in Bladen County, N.C. (Farrell, 1998; Farrell and others, 2001). This report contains the lithostratigraphic summary recorded at the drill site, core photographs, geophysical data, and calcareous nannofossil biostratigraphic correlations.