Paleo-environments of Late Pliocene to Early Pleistocene Foreland-Basin Deposits in the Western Foothills of South-Central Taiwan

NASA Astrophysics Data System (ADS)

Chiu, Tzu-Hsuan; Tien-Shun Lin, Andrew; Chi, Wen-Rong; Wang, Shih-Wei

2017-04-01

Lithofacies and paleo-environmental analyses of the Pliocene-Pleistocene deposits of Taiwan provide a framework to understand the stratigraphic development of foreland basin to the west of the orogenic belt. In this study, we performed lithofacies analyses and biostratigraphic studies on calcareous nannofossils in two areas in south-central Taiwan, the Jhuoshuei River, and the Hushan Reservoir, respectively. The studied lithostratigraphic units are the Chinshui Shale, the Cholan Formation, and the Toukoshan Formation, in an ascending order, with a total stratigraphic thickness more than 3500 m in central Taiwan. Sixteen lithofacies and four lithofacies associations are identified, pertaining to tide-dominated deltaic systems bordering a shallow marine setting in the foreland basin. A few wide-spread layers of thickly-bedded sandstones featuring ball-and-pillow structures are interpreted as resulting from earthquake shaking (i.e., seismites). In addition, the vertical facies change shows a coarsening and shallowing-upward succession, indicating the gradually filling up of the foreland basin by sediment progradation. The progradation is interpreted to result from westward migrating orogenic belt and an increase in sediment supply. The top 2000-m thick foreland succession (i.e., the uppermost part of the Cholan Formation, and the Toukoshan Formation) is dominantly fluvial deposits with occasional intercalations of shoreface sediments, indicating an extremely rapid and balanced rate of basin subsidence and sediment supply for the past 1.5 Ma. Vertebrate fossils of deer and elephants are identified in the upper Cholan Formation deposited in coastal to fluvial settings. Keywords: Pliocene-Pleistocene Epoch, lithofacies, foreland basin, Taiwan

Structural Features of the Western Taiwan Foreland Basin in the Eastern Taiwan Strait since Late Miocene

NASA Astrophysics Data System (ADS)

WANG, J. H.; Liu, C. S.; Chang, J. H.; Yang, E. Y.

2017-12-01

The western Taiwan Foreland Basin lies on the eastern part of Taiwan Strait. The structures in this region are dominated by crustal stretch and a series of flexural normal faults have been developed since Late Miocene owing to the flexural of Eurasia Plate. Through deciphering multi-channel seismic data and drilling data, these flexural features are observed in the offshore Changhua coastal area. The flexure normal faults are important features to realize structural activity in the western Taiwan Foreland Basin. Yang et al. (2016) mention that the reactivated normal faults are found north of the Zhushuixi estuary. It should be a significant issue to decipher whether these faults are still active. In this study, we have analyzed all the available seismic reflections profiles in the central part of the Taiwan Strait, and have observed many pre-Pliocene normal faults that are mainly distributed in the middle of the Taiwan Strait to Changyun Rise, and we tentatively suggest that the formation of these faults may be associated with the formation of the foreland basal unconformity. Furthermore, we will map the distribution of these normal faults and examine whether the reactivated normal faults have extended to south of the Zhushuixi estuary. Finally, we discuss the relation between the reactivated normal faults in the Taiwan Strait and those faults onshore. Key words: Multichannel seismic reflection profile, Taiwan Strait, Foreland basin, normal fault.

Quantifying the role of mantle forcing, crustal shortening and exogenic forcing on exhumation of the North Alpine Foreland Basin

NASA Astrophysics Data System (ADS)

von Hagke, C.; Luijendijk, E.; Hindle, D.

2017-12-01

In contrast to the internal zones of orogens, where the stacking of thrust sheets can overwhelm more subtle signals, foreland basins can record long-wavelength subsidence or uplift signals caused by mantle processes. We use a new and extensive compilation of geological and thermochronology data from the North Alpine Foreland Basin to understand the dynamics of foreland basins and their interaction with surface and geodynamic processes. We quantify cooling and exhumation rates in the basin by combining published and new vitrinite reflectance, apatite fission track and U-Th/He data with a new inverse burial and thermal history model, pybasin. No correlation is obvious between inferred cooling and exhumation rates and elevation, relief or tectonics. Uncertainty analysis shows that thermochronometers can be explained by cooling starting as early as the Miocene or as late as the Pleistocene. We compare derived temperature histories to exhumation estimates based on the retro-deformation of Molasse basin and the Jura mountains, and to exhumation caused by drainage reorganization and incision. Drainage reorganization can explain at most 25% of the observed cooling rates in the basin. Tectonic transport of the basin's sediments over the inclined basement of the alpine foreland as the Jura mountains shortened can explain part of the cooling signal in the western part of the basin. However, overall a substantial amount of cooling and exhumation remains unexplained by known tectonic and surface processes. Our results document basin wide exhumation that may be related to slab roll-back or other lithospheric processes. We suggest that new (U-Th)/He data from key areas close to the Alpine front may provide better constraints on the timing of exhumation.

Sedimentary Evolution of Marginal Ganga Foreland Basin during the Late Pleistocene

NASA Astrophysics Data System (ADS)

Ghosh, R.; Srivastava, P.; Shukla, U. K.

2017-12-01

Ganga foreland basin, an asymmetrical basin, was formed as result of plate-plate collision during middle Miocene. A major thrust event occurred during 500 ka when upper Siwalik sediments were uplifted and the modern Ganga foreland basin shifted towards craton, making a more wide and deep basin. The more distal part of this basin, south of axial river Yamuna, records fluvial sedimentary packages that helps to understand dynamics of peripheral bulge during the late Quaternary. Sedimentary architecture in conjunction with chemical index of alteration (CIA), paleocurrent direction and optically stimulated dating (OSL) from 19 stratigraphic sections helped reconstructing the variations in depositional environments vis-à-vis climate change and peripheral bulge tectonics. Three major units (i) paleosol; (ii) cratonic gravel; (iii) interfluve succession were identified. The lower unit-I showing CIA values close to 70-80 and micro-morphological features of moderately well-developed pedogenic unit that shows development of calcrete, rhizoliths, and mineralized organic matter in abundance. This is a regional paleosols unit and OSL age bracketed 200 ka. This is unconformably overlain by unit-II, a channelized gravel composed of sub-angular to sub-rounded clasts of granite, quartz, quartzite, limestone and calcrete. The gravel have low CIA value up to 55, rich in vertebrate fossil assemblages and mean paleocurrent vector direction is NE, which suggesting deposition by a fan of a river draining craton into foreland. This unit is dated between 100 ka and 54 ka. The top unit-III, interfluve succession of 10-15 m thick is composed of dark and light bands of sheet like deposit of silty clay to clayey silt comprises sand lenses of red to grey color and displaying top most OSL age is 12 ka. The basal mature paleosol signifies a humid climate developed under low subsidence rate at >100 ka. After a hiatus represented by pedogenic surface deposition of unit-II (gravel) suggests uplift

Influence of attenuated lithosphere and sediment loading on flexure of the deep-water Magallanes retroarc foreland basin, Southern Andes

NASA Astrophysics Data System (ADS)

Fosdick, Julie C.; Graham, Stephan A.; Hilley, George E.

2014-12-01

Flexural subsidence in foreland basins is controlled by applied loads—such as topography, water/sediment, and subcrustal forces—and the mechanical properties of the lithosphere. We investigate the controls on subsidence observed within the Upper Cretaceous Magallanes retroarc foreland basin of southern South America to evaluate the impact of lateral variations in flexural rigidity due to Late Jurassic extension. Conventional elastic models cannot explain the observed basin deflection and thick accumulation of deep-water Cenomanian-Turonian basin strata. However, models in which the lithosphere has been previously thinned and deflects under topographic and sedimentary loads successfully reproduce regional subsidence patterns. Results satisfy paleobathymetric observations in the Magallanes Basin and suggest that lithospheric thinning is necessary to produce both long-wavelength and deep subsidence during Late Cretaceous basin evolution. Results indicate that elastic thickness decreases westward from 45-25 km in the distal foreland to 37-15 km beneath the foredeep. These findings are consistent with a westward reduction in crustal thickness associated with the Jurassic extensional history of the Patagonian lithosphere. Our results also show that sediment loading exerts an important control on regional deflection patterns and promotes a wider region of subsidence and reduced forebulge uplift. We propose that lateral variations in mechanical properties and large sediment loads restrict depocenter migration and may cause the foredeep to remain fixed for prolonged periods of time. These findings confirm that loading of thinned lithosphere imposes different mechanical controls on the flexural profile and have potential implications for other retroarc foreland basins characterized by earlier extensional histories.

Erosion and deposition mode in a developing foreland basin: Temporal and spatial distribution of provenance in southwestern Taiwan

NASA Astrophysics Data System (ADS)

Yang, K. M.; Kun-an, H.; Chien, C. W.; Leh-chyun, W.; Chi-Cheng, Y.

2017-12-01

The foreland basin in southwestern Taiwan offers an idealistic example for the study of tectonostratigraphy in basin development. The subsidence analysis indicates that the recent basin development went through at least two rapid subsidence events, along with back-and-forth migration of the forebulge. This study aims to explore the interaction between the uplifting forebulge and coevally subsiding foredeep primarily based on petrofacies analysis, the results of which were then interpreted with the well-established tectonostratigraphic and biostratigraphic frameworks to infer the erosion and deposition mode during the basin development. The craton had been the sediment source to the west of the study area in the pre-orogenic period. In the initial stage of foreland basin development, the forebulge slowly elevated and started to obstruct sediment supplies from the craton. Before the period of NN19, the forebulge not only became the barrier of the most cratonic sediment supplies but also shed a major amount of detritus into the adjacent area. In addition, regional topographic relief, which was formed by syn-orogenic normal faulting during the NN11-15, locally changed the composition and transportation modes of the sediments; the exposed basement of the footwall also became the source of the sediments shed into the adjacent depo-centers. After the NN19, whole area was influenced predominantly by the orogenic belt from the east. Large amounts of slate fragments began to appear in the middle NN19 and relative percentage of the metamorphic lithics was increased upward and northward. As the orogen moved westward along with the foreland basin development, the studied area changed from the distal to proximal parts of the foredeep and sediment sources were controlled mainly by river systems derived from the orogen. The metamorphic lithics decreased southward and concentrated in the central part of the study area, suggesting that the slate fragments which were transported

Increasing influence of exotic terranes as sources of shales from the Sevier and Taconic Foreland basins : Evidence from Nd isotopes

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

Samson, S.D.; Andersen, C.B.

1994-03-01

The influence of outboard tectonostratigraphic terranes as a source of sediment to Ordovician foreland basins is unknown. To determine if there were changes in provenance, or changes in the importance of a given source region, the authors have analyzed shales from two foreland basins, the Tactonic Foreland basin of central New York and the Sevier Foreland basin of Tennessee, for their Nd isotopic compositions. Shales from the Taconic basin include those from the lower portion of Utica shale, Corynoides americanus graptolite Zone, and the uppermost portion of the Utica shale, including the Geniculograptus pygmaeus graptolite Zone. Initial [epsilon][sub Nd] valuesmore » for the oldest Taconic basin shales are [minus]12. Initial [epsilon][sub Nd] values for the younger Taconic basin shales range from [minus]9.7 to [minus]8.4. This increase in [epsilon][sub Nd] may reflect an increased influence of terranes outboard of the Laurentian margin. Samples from the Sevier basin include those from the Blockhouse and Tellico Formations. A sample of the lower Blockhouse Fm. has an initial [epsilon][sub Nd] of [minus]9.4, while mid-formation levels have [epsilon][sub Nd] = [minus]8.8. Initial [epsilon][sub Nd] ranges from [minus]8.0 to [minus]7.2 from Tellico Formation shales. Thus a trend towards increasing [epsilon][sub Nd] with decreasing age is also seen in the Sevier basin. This again suggests the possibility of an increasing influence from nearby terranes. The fact that the [epsilon][sub Nd] values are higher in the Sevier basin than in the Taconic basin indicates that the Sevier shales received detritus with a less evolved isotopic composition. This may reflect fundamentally different sources, such as a more juvenile terrane as an important source of Sevier basin shales.« less

Archean foreland basin tectonics in the Witwatersrand, South Africa

NASA Technical Reports Server (NTRS)

Burke, K.; Kidd, W. S. F.; Kusky, T. M.

1986-01-01

The Witwatersrand Basin of South Africa is the best-known of Archean sedimentary basins and contains some of the largest gold reserves in the world. Sediments in the basin include a lower flysch-type sequence and an upper molassic facies, both of which contain abundant silicic volcanic detritus. The strata are thicker and more proximal on the northwestern side of the basin which is, at least locally, bound by thrust faults. These features indicate that the Witwatersrand strata may have been deposited in a foreland basin and a regional geologic synthesis suggests that this basin developed initially on the cratonward side of an Andean-type arc. Remarkably similar Phanerozoic basins may be found in the southern Andes above zones of shallow subduction. It is suggested that the continental collision between the Kaapvaal and Zimbabwe Cratons at about 2.7 Ga caused further subsidence and deposition in the Witwatersrand Basin. Regional uplift during this later phase of development placed the basin on the cratonward edge of a collision-related plateau, now represented by the Limpopo Province. Similarities are seen between this phase of Witwatersrand Basin evolution and that of active basins north of the Tibetan Plateau. The geologic evidence does not agree with earlier suggestions that the Witwatersrand strata were deposited in a rift or half-graben.

Latest Cretaceous-Paleogene basin development and resultant sedimentation patterns in the thrust belt and broken foreland of central Utah

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

Lawton, T.F.; Franczyk, K.J.; Pitman, J.K.

1990-05-01

Latest Cretaceous tectonism in central and east-central Utah formed several intermontane basins both atop thrust sheets and between the thrust front and basement-involved uplifts in the former foreland basin. The upper Campanian Castlegate Sandstone and its inferred western equivalents were the last strata deposited prior to segmentation of the foreland basin. Thereafter, eastward transport of the thrust allochthon uplifted the most proximal part of the Castlegate depositional wedge. West of the thrust front, small intermontane basins formed on the allochthon. Sediment was transported into these basins from both eastern and western sources. In each basin, facies grade from basin-margin conglomeraticmore » alluvial fan deposits to basin-interior flood-plain and lacustrine deposits within a few kilometers. These intermontane basins existed from latest Campanian through the late Paleocene, and may have been transported a short distance eastward as they formed. East of the thrust front in the latest Campanian and contemporaneous with basin formation on the allochthon, a northward-northeastward-flowing big river system transported sediment into the foreland basin from feldspar-rich source areas southwest of the study area. Subsequently, major movement of the San Rafael uplift in the very late Campanian or early Maastrichtian gave rise to an intermontane basin between the thrust front and the San Rafael uplift. Northwestward-flowing, pebble-bearing braided rivers deposited the oldest sediments in this basin prior to an influx from the south and southwest of sediment that formed a thick Maastrichtian clastic sequence. In contrast to deposition in basins on the allochthon, deposition east of the thrust front in the Paleocene was intermittent and restricted to rapidly shifting centers of basin subsidence.« less

Influence of inherited structures on the growth of basement-cored ranges, basin inversion and foreland basin development in the Central Andes, from apatite fission-track and apatite Helium thermochronology.

NASA Astrophysics Data System (ADS)

Zapata, S.; Sobel, E. R.; Del Papa, C.; Jelinek, A. R.; Muruaga, C.

2017-12-01

The Central Andes in NW of Argentina is part of a long-lived subduction zone, active since the Paleozoic. This region experienced several tectonic cycles; each of which created an unique set of structures and may have reactivated preexisting structures. These inherited structures may exert a first-order control over the different foreland deformational styles observed along the strike in the Central Andes. Our study area is located between 26°S and 28°S on the transition between the broken foreland (Santa Barbara system), which expresses a combination of thin-skin and thick-skin styles, and the Sierras Pampeanas, which is deform in a thick-skin style. The Cumbres Calchaquies range and the associated Choromoro Basin are located in the northern part of the study area, and are the southern expression of the Santa Barbara system. Published thermochronology data suggest that the rocks from the basement experienced Late Cretaceous and Late Miocene exhumation; the associated sedimentary rocks within the Choromoro basin experienced Paleogene and Late Miocene deformational phases. In contrast, the Sierra Aconquija range, located immediately south on the transition to the Sierras Pampeanas (thick skin) foreland basin, exhibit larger amounts of Miocene exhumation and lack of Cretaceous exhumation; the associated sedimentary rocks from the Tucuman basin have not been deformed since the Cretaceous. Our goal is to understand the evolution of the structural blocks and the structures responsible for the along strike changes in foreland basin deformational styles and their relation with inherited structures from previous tectonic cycles. We are obtaining new apatite U-Th/He and fission track data to reconstruct the thermal history of the basement, accompanied by U-Pb geochronology and stratigraphy to constrain the evolution of the associated sedimentary basins. Preliminary results combined with published data suggest that inherited structures within the study area have evolved

Sediment provenance in contractional orogens: The detrital zircon record from modern rivers in the Andean fold-thrust belt and foreland basin of western Argentina

NASA Astrophysics Data System (ADS)

Capaldi, Tomas N.; Horton, Brian K.; McKenzie, N. Ryan; Stockli, Daniel F.; Odlum, Margaret L.

2017-12-01

This study analyzes detrital zircon U-Pb age populations from Andean rivers to assess whether active synorogenic sedimentation accurately records proportional contributions from varied bedrock source units across different drainage areas. Samples of modern river sand were collected from west-central Argentina (28-33°S), where the Andes are characterized by active uplift and deposition in diverse contractional provinces, including (1) hinterland, (2) wedge-top, (3) proximal foreland, and (4) distal broken foreland basin settings. Potential controls on sediment provenance were evaluated by comparing river U-Pb age distributions with predicted age spectra generated by a sediment mixing model weighted by relative catchment exposure (outcrop) areas for different source units. Several statistical measures (similarity, likeness, and cross-correlation) are employed to compare how well the area-weighted model predicts modern river age populations. (1) Hinterland basin provenance is influenced by local relief generated along thrust-bounded ranges and high zircon fertility of exposed crystalline basement. (2) Wedge-top (piggyback) basin provenance is controlled by variable lithologic durability among thrust-belt bedrock sources and recycled basin sediments. (3) Proximal foreland (foredeep) basin provenance of rivers and fluvial megafans accurately reflect regional bedrock distributions, with limited effects of zircon fertility and lithologic durability in large (>20,000 km2) second-order drainage systems. (4) In distal broken segments of the foreland basin, regional provenance signatures from thrust-belt and hinterland areas are diluted by local contributions from foreland basement-cored uplifts.

Stratigraphic Framework and Depositional Sequences in the Lower Silurian Regional Oil and Gas Accumulation, Appalachian Basin: From Licking County, Ohio, to Fayette County, West Virginia

USGS Publications Warehouse

Ryder, Robert T.

2006-01-01

The Lower Silurian regional oil and gas accumulation was named by Ryder and Zagorski (2003) for a 400-mile (mi)-long by 200-mi-wide hydrocarbon accumulation in the central Appalachian basin of the Eastern United States and Ontario, Canada. From the early 1880s to 2000, approximately 300 to 400 million barrels of oil and eight to nine trillion cubic feet of gas have been produced from the Lower Silurian regional oil and gas accumulation (Miller, 1975; McCormac and others, 1996; Harper and others, 1999). Dominant reservoirs in the regional accumulation are the Lower Silurian 'Clinton' and Medina sandstones in Ohio and westernmost West Virginia and coeval rocks in the Lower Silurian Medina Group (Grimsby Sandstone (Formation) and Whirlpool Sandstone) in northwestern Pennsylvania and western New York. A secondary reservoir is the Upper Ordovician(?) and Lower Silurian Tuscarora Sandstone in central Pennsylvania and central West Virginia, a more proximal eastern facies of the 'Clinton' sandstone and Medina Group (Yeakel, 1962; Cotter, 1982, 1983; Castle, 1998). The Lower Silurian regional oil and gas accumulation is subdivided by Ryder and Zagorski (2003) into the following three parts: (1) an easternmost part consisting of local gas-bearing sandstone units in the Tuscarora Sandstone that is included with the basin-center accumulation; (2) an eastern part consisting predominantly of gas-bearing 'Clinton' sandstone-Medina Group sandstones that have many characteristics of a basin-center accumulation (Davis, 1984; Zagorski, 1988, 1991; Law and Spencer, 1993); and (3) a western part consisting of oil- and gas-bearing 'Clinton' sandstone-Medina Group sandstones that is a conventional accumulation with hybrid features of a basin-center accumulation (Zagorski, 1999). With the notable exception of the offshore part of Lake Erie (de Witt, 1993), the supply of oil and (or) gas in the hybrid-conventional part of the regional accumulation continues to decline because of the many

Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin

USGS Publications Warehouse

Groshong, R.H.; Pashin, J.C.; McIntyre, M.R.

2009-01-01

Coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures. Basin-wide controls on the fractured coal reservoirs of the Black Warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells. Reservoir behavior depends on distance from the thrust front. Far from the thrust front, normal faults are barriers to fluid migration and compartmentalize the reservoirs. Close to the thrust front, rates are enhanced along some normal faults, and a new trend is developed. The two trends have the geometry of conjugate strike-slip faults with the same ??1 direction as the Appalachian fold-thrust belt and are inferred to be the result of late pure-shear deformation of the foreland. Face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map-scale production trend. ?? 2008 Elsevier Ltd. All rights reserved.

Evaporitic sedimentation in the Southeastern Anatolian Foreland Basin: New insights on the Neotethys closure

NASA Astrophysics Data System (ADS)

Yeşilova, Çetin; Helvacı, Cahit; Carrillo, Emilio

2018-07-01

We integrate stratigraphic, petrographic and geochemical analysis of subsurface data (wells) together with field surveys to study the sedimentation of a marginal Miocene sub-basin of the Southeastern Anatolian Foreland Basin (SEAFB; SE Turkey). This sub-basin, located in the Batman-Siirt region, is characterized by the existence of evaporites (carbonates, sulphates and chlorides) and alluvial detritus which were divided in the following five lithostratigraphic members, from older to younger: Lower and Upper Yapılar; and Lower, Middle and Upper Sulha. These members deposited in an epicontinental mudflat during the Early Miocene. Both the bromine content and the sulphur and oxygen isotope composition (δ34SV-CDT and δ18OV-SMOW) of halite and sulphates samples, respectively, also suggest a marine origin of the precipitation brines. However, influence of geothermal fluids and dissolution-and-re-precipitation of evaporites from uplifted areas in these brines, such as the Early Miocene members and/or Triassic units, is interpreted. Comparing and integrating our results with data documented in previous works, it is here recognized that the depositional model of the studied sub-basin differs from that which explain the coeval sedimentation of units situated in the western part of the SEAFB. Moreover, our model shows some depositional and paleoenvironmental similarities with Miocene evaporites located in the Mesopotamian Foreland Basin. This work provides valuable insights on the Middle Miocene Salinity Crisis which is related to the evolution of the Neotethys closure.

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

NASA Astrophysics Data System (ADS)

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

2009-04-01

The Pyrenees results from the collision between Spain and Europe and developed between the upper Cretaceous (Santonian) and the Miocene. Its foreland basins are characterised by a thick fill of detrital and carbonate sediments. The diversity of Eocene deposits in the southern Pyrenean foreland basin is of particular use in facies sedimentology due to their exceptional outcropping quality and well established stratigraphic framework and has been taken as type examples of many different sedimentary environments. Most studies have concerned facies sedimentology of detrital series in turbiditic environments, meandering and braided rivers, alluvial fans, and deltas. In contrast, the Eocene carbonate series have attracted less attention. The marine Guara limestones are a formation of lower to middle Eocene age deposited on the southern border of the western Pyrenean foreland basin (Jaca basin). They were deposited as a retrogradational carbonate platform dominated by large benthic foraminifers near or at the flexural forebulge of the foreland basin as the Pyrenean orogen developed. This formation represents the last episode of carbonate platform in the Pyrenees and remains poorly studied. In the present work our aim is to provide a detailed facies analysis and physiographic reconstructions of the Guara carbonate platform. This is crucial to unravel the respective influences of tectonics, climate and rheology of the lithosphere on the foreland basin tectonic and stratigraphic development, and it brings new constraints on the paleoenvironments and paleogeography during the Lutetian, i.e. at the beginning of the major phase of activity of the Pyrenean orogenesis. Two outcrops were studied in the Sierras Marginales at the localities of Arguis and Lusera. The Lusera section once restored in its initial position is located to the North of the Arguis section in a basinward direction such that comparing time-equivalent facies between these two sections helps us reconstructing

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

NASA Astrophysics Data System (ADS)

Painter, Clayton S.

Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_U-Pb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf). Appendix A is a combination of detailed isopach maps of the Upper Cretaceous Western Interior, flexural modeling and a comparison to dynamic subsidence models as applied to the region. Using these new isopach maps and modeling, I place the previously recognized but poorly constrained shift from flexural to non-flexural subsidence at 81 Ma. Appendix B is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation. Appendix C is a geo-thermochronologic study to measure the lag time of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. The maximum depositional ages using DZ U-Pb match existing biostratigraphic age controls. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4--5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed

Provenance and detrital zircon geochronologic evolution of lower Brookian foreland basin deposits of the western Brooks Range, Alaska, and implications for early Brookian tectonism

USGS Publications Warehouse

Moore, Thomas; O'Sullivan, Paul B.; Potter, Christopher J.; Donelick, Raymond A.

2015-01-01

The Upper Jurassic and Lower Cretaceous part of the Brookian sequence of northern Alaska consists of syntectonic deposits shed from the north-directed, early Brookian orogenic belt. We employ sandstone petrography, detrital zircon U-Pb age analysis, and zircon fission-track double-dating methods to investigate these deposits in a succession of thin regional thrust sheets in the western Brooks Range and in the adjacent Colville foreland basin to determine sediment provenance, sedimentary dispersal patterns, and to reconstruct the evolution of the Brookian orogen. The oldest and structurally highest deposits are allochthonous Upper Jurassic volcanic arc–derived sandstones that rest on accreted ophiolitic and/or subduction assemblage mafic igneous rocks. These strata contain a nearly unimodal Late Jurassic zircon population and are interpreted to be a fragment of a forearc basin that was emplaced onto the Brooks Range during arc-continent collision. Synorogenic deposits found at structurally lower levels contain decreasing amounts of ophiolite and arc debris, Jurassic zircons, and increasing amounts of continentally derived sedimentary detritus accompanied by broadly distributed late Paleozoic and Triassic (359–200 Ma), early Paleozoic (542–359 Ma), and Paleoproterozoic (2000–1750 Ma) zircon populations. The zircon populations display fission-track evidence of cooling during the Brookian event and evidence of an earlier episode of cooling in the late Paleozoic and Triassic. Surprisingly, there is little evidence for erosion of the continental basement of Arctic Alaska, its Paleozoic sedimentary cover, or its hinterland metamorphic rocks in early foreland basin strata at any structural and/or stratigraphic level in the western Brooks Range. Detritus from exhumation of these sources did not arrive in the foreland basin until the middle or late Albian in the central part of the Colville Basin.These observations indicate that two primary provenance areas provided

Neogene shortening and exhumation of the Zagros fold-thrust belt and foreland basin in the Kurdistan region of northern Iraq

NASA Astrophysics Data System (ADS)

Koshnaw, Renas I.; Horton, Brian K.; Stockli, Daniel F.; Barber, Douglas E.; Tamar-Agha, Mazin Y.; Kendall, Jerome J.

2017-01-01

The Zagros fold-thrust belt in the Kurdistan region of Iraq encroached southward toward a rapidly subsiding Neogene foreland basin and was later partitioned by out-of-sequence shortening focused along the Mountain Front Flexure (MFF), as defined by new low-temperature thermochronologic, stratigraphic, and provenance results. Apatite (U-Th)/He ages document rapid deformation advance from the Main Zagros Fault to southern frontal structures (Kirkuk, Shakal, and Qamar thrusts) at 10-8 Ma, followed by potential basement-involved out-of-sequence development of the MFF (Qaradagh anticline) by 5 Ma. Distinct shifts in detrital zircon U-Pb provenance signatures for Neogene foreland basin fill provide evidence for drainage reorganization during fold-thrust belt advance. U-Pb age spectra and petrologic data from the Injana (Upper Fars) Formation indicate derivation from a variety of Eurasian, Pan-African, ophiolitic and Mesozoic-Cenozoic volcanic terranes, whereas the Mukdadiya (Lower Bakhtiari) and Bai-Hasan (Upper Bakhtiari) Formations show nearly exclusive derivation from the Paleogene Walash-Naopurdan volcanic complex near the Iraq-Iran border. Such a sharp cutoff in Eurasian, Pan-African, and ophiolitic sources is likely associated with drainage reorganization and tectonic development of the geomorphic barrier formed by the MFF. As a result of Zagros crustal shortening, thickening and loading, the Neogene foreland basin developed and accommodated an abrupt influx of fluvial clastic sediment that contains growth stratal evidence of synkinematic accumulation. The apparent out-of-sequence pattern of upper crustal shortening in the hinterland to foreland zone of Iraqi Kurdistan suggests that structural inheritance and the effects of synorogenic erosion and accumulation are important factors influencing the irregular and episodic nature of orogenic growth in the Zagros.

Timing of the Blount and Martinsburg foreland basin development during the Taconic Orogeny based on the Deicke and Millbrig K-bentonite marker horizons

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

McVey, D.E.; Huff, W.D.

1993-03-01

During the Taconic Orogeny (Middle and Late Ordovician), the eastern continental margin of North America developed several foreland basins as a result of the collision of one or more island arc/microplate complexes. These collisions occurred along a subduction zone characterized by a string of explosively eruptive volcanoes which produced widespread K-bentonite beds. Volcanism coincided with the filling of thick accumulations of sediment in two of the basins: the Blount (southern Appalachians) and the Martinsburg (central Appalachians). Two prominent K-bentonites, the Deicke and Millbrig, have been correlated across the two basins in this study. These two K-bentonites are stratigraphically significant becausemore » they are excellent time lines since they represent short-term events in geologic history. The foreland basins developed by the Taconic Orogeny become successively younger to the north due to a shift in the focus of collision (Read, 1980). The Blount basin was nearly filled with sediment by the time the Martinsburg basin began to form. This coincides with previous suggestions that the Taconic Orogeny was not one climactic event but a series of events where the collisions migrated northward like the closing of a zipper. The Deicke and Millbrig K-bentonites occur within the platform carbonates of the Eggleston and Liberty Hall formations and the red bed clastic facies of the Bays formation in the Blount basin, and they occur within the slope carbonates of the New Enterprise Member of the Salona formation and the black shale and turbidite facies of the Martinsburg formation in the Martinsburg basin. This correlation establishes a more precise time framework for the formation of the two foreland basins.« less

Geochemical characteristics and reservoir continuity of Silurian Acacus in Ghadames Basin, Southern Tunisia

NASA Astrophysics Data System (ADS)

Mahmoudi, S.; Mohamed, A. Belhaj; Saidi, M.; Rezgui, F.

2017-11-01

The present work is dealing with the study of lateral and vertical continuity of the multi-layers Acacus reservoir (Ghadames Basin-Southern Tunisia) using the distribution of hydrocarbon fraction. For this purpose, oil-oil and source rock-oil correlations as well as the composition of the light fractions and a number of saturate and aromatic biomarkers parameters, including C35/C34 hopanes and DBT/P, have been investigated. Based on the ratios of light fraction and their fingerprints, the Acacus reservoir from Well1 and Well2 have found to be laterally non-connected although the hydrocarbons they contain have the same source rock. Moreover, the two oil samples from two different Acacus reservoir layers crossed by Well3-A3 and A9, display a similar hydrocarbons distribution, suggesting vertical reservoir continuity. On the other hand, the biomarker distributions of the oils samples and source rocks assess a Silurian ;Hot shale; that is the source rock feeding the Acacus reservoir. The biomarker distribution is characterized by high tricyclic terpanes contents compared to hopanes for the Silurian source rock and the two crude oils. This result is also confirmed by the dendrogram that precludes the Devonian source rocks as a source rock in the study area.

Quantifying retro-foreland evolution in the Eastern Pyrenees.

NASA Astrophysics Data System (ADS)

Grool, Arjan R.; Ford, Mary; Huismans, Ritske S.

2015-04-01

The northern Pyrenees form the retro-foreland of the Pyrenean orogen. Modelling studies show that retro-forelands have several contrasting characteristics compared to pro-forelands: They tend to show a constant tectonic subsidence during the growth phase of an orogen, and no tectonic subsidence during the steady-state phase. Retro-forelands are also not displaced into the core of the orogen once the steady state phase is achieved. This means they tend to preserve the subsidence history from the growth phase of the orogen, but little or no history from the steady state phase. The northeastern Pyrenees (Carcassonne high) are a good location to test these characteristics against real-world data, because syn-orogenic sediments are preserved and the lack of postrift thermal subsidence and Triassic salt reduce complicating factors. In order to test the model, quantification of the following parameters is needed: Timing, amount and distribution of deformation, subsidence and sedimentation. We use subsurface, field, map and literature data to construct 2 balanced and restored cross sections through the eastern north Pyrenean foreland, stretching from the Montagne Noire in the north, to the Axial Zone in the south. We will link this to published thermochronology data to further constrain the evolution of the retro-foreland and investigate the link with the Axial Zone towards the south. We will quantify subsidence, deformation and sedimentation and link them to exhumation phases in the North Pyrenean Zone (NPZ) and the Axial Zone. The north Pyrenean retro-foreland is divided into two parts: the external foreland basin (Aquitaine basin) to the north and the North Pyrenean Zone to the south, separated by the North Pyrenean Frontal Thrust (NPFT). South of the NPZ lies the Axial Zone, separated from the retro-foreland by the North Pyrenean Fault which is believed to be the suture between Iberia and Europe. The NPFT was the breakaway fault on the European continent during the

Properties of Silurian shales from the Barrandian Basin, Czech Republic

NASA Astrophysics Data System (ADS)

Weishauptová, Zuzana; Přibyl, Oldřich; Sýkorová, Ivana

2017-04-01

Although shale gas-bearing deposits have a markedly lower gas content than coal deposits, great attention has recently been paid to shale gas as a new potential source of fossil energy. Shale gas extraction is considered to be quite economical, despite the lower sorption capacity of shales, which is only about 10% of coal sorption capacities The selection of a suitable locality for extracting shale gas requires the sorption capacity of the shale to be determined. The sorption capacity is determined in the laboratory by measuring the amount of methane absorbed in a shale specimen at a pressure and a temperature corresponding to in situ conditions, using high pressure sorption. According to the principles of reversibility of adsorption/desorption, this amount should be roughly related to the amount of gas released by forced degassing. High pressure methane sorption isotherms were measured on seven representative samples of Silurian shales from the Barrandian Basin, Czech Republic. Excess sorption measurements were performed at a temperature of 45oC and at pressures up to 15 MPa on dry samples, using a manometric method. Experimental methane high-pressure isotherms were fitted to a modified Langmuir equation. The maximum measured excess sorption parameter and the Langmuir sorption capacity parameter were used to study the effect of TOC content, organic maturity, inorganic components and porosity on the methane sorption capacity. The studied shale samples with random reflectance of graptolite 0.56 to 1.76% had a very low TOC content and dominant mineral fractions. Illite was the prevailing clay mineral. The sample porosity ranged from 4.6 to 18.8%. In most samples, the micropore volumes were markedly lower than the meso- and macropore volumes. In the Silurian black shales, the occurrence of fractures parallel with the original sedimentary bending was highly significant. A greater proportion of fragments of carbonaceous particles of graptolites and bitumens in the

Link between Neogene and modern sedimentary environments in the Zagros foreland basin

NASA Astrophysics Data System (ADS)

Pirouz, Mortaza; Simpson, Guy; Bahroudi, Abbas

2010-05-01

The Zagros mountain belt, with a length of 1800 km, is located in the south of Iran and was produced by collision between the Arabian plate and the Iran micro plate some time in the early Tertiary. After collision, the Zagros carbonate-dominated sedimentary basin has been replaced by a largely clastic system. The Neogene Zagros foreland basin comprises four main depositional environments which reflect the progressive southward migration of the deformation front with time. The oldest unit - the Gachsaran formation - is clastic in the northern part of the basin, but is dominated by evaporates in southern part, being deposited in a supratidal Sabkha-type environment. Overlying the Gachsaran is the Mishan formation, which is characterized by the Guri limestone member at the base, overlain by marine green marls. The thickness of the Guri member increases dramatically towards the southeast. The next youngest unit is the Aghajari Formation which consists of well sorted lenticular sandstone bodies in a red silty-mudstone. This formation is interpreted as representing the floodplain of dominantly meandering rivers. Finally, the Bakhtiari formation consists of mainly coarse-grained gravel sheets which are interpreted to represent braided river deposits. Each of these Neogene depositional environments has a modern day equivalent. For example, the braided rivers presently active in the Zagros mountains are modern analogues of the Bakhtiari. In the downstream direction, these braided rivers become meandering systems, which are equivalents of the Aghajari. Eventually, the meandering rivers meet the Persian gulf which is the site of the ‘modern day' Mishan shallow marine marls. Finally, the modern carbonate system on the southern margin of Persian Gulf represents the Guri member paleo-environment, behind which Sabkha-type deposits similar to the Gachsaran are presently being deposited. One important implication of this link between the Neogene foreland basin deposits and the

Depositional and provenance record of the Paleogene transition from foreland to hinterland basin evolution during Andean orogenesis, northern Middle Magdalena Valley Basin, Colombia

NASA Astrophysics Data System (ADS)

Moreno, Christopher J.; Horton, Brian K.; Caballero, Victor; Mora, Andrés; Parra, Mauricio; Sierra, Jair

2011-10-01

The Central Cordillera and Eastern Cordillera of the northern Andes form the topographic flanks of the north-trending Magdalena Valley Basin. Constraining the growth of these ranges and intervening basin has implications for Andean shortening and the transformation from a foreland to hinterland basin configuration. We present sedimentological, paleocurrent, and sandstone petrographic results from Cenozoic type localities to provide insights into the tectonic history of the northern Middle Magdalena Valley Basin of Colombia. In the Nuevo Mundo Syncline, the mid-Paleocene transition from marine to nonmarine deposystems of the Lisama Formation corresponds with a paleocurrent shift from northward to eastward transport. These changes match detrital geochronological evidence for a contemporaneous shift from cratonic (Amazonian) to orogenic (Andean) provenance, suggesting initial shortening-related uplift of the Central Cordillera and foreland basin generation in the Magdalena Valley by mid-Paleocene time. Subsequent establishment of a meandering fluvial system is recorded in lower-middle Eocene strata of the lower La Paz Formation. Eastward paleocurrents in mid-Paleocene through uppermost Eocene fluvial deposits indicate a continuous influence of western sediment source areas. However, at the upper middle Eocene (˜40 Ma) boundary between the lower and upper La Paz Formation, sandstone compositions show a drastic decrease in lithic content, particularly lithic volcanic fragments. This change is accompanied by a facies shift from mixed channel and overbank facies to thick, amalgamated braided fluvial deposits of possible fluvial megafans, reflecting changes in both the composition and proximity of western sediment sources. We attribute these modifications to the growing influence of exhumed La Cira-Infantas paleohighs in the axial Magdalena Valley, features presently buried beneath upper Eocene-Quaternary basin fill along the western flank of the Nuevo Mundo Syncline. In

Early Paleozoic paleogeography of the northern Gondwana margin: new evidence for Ordovician-Silurian glaciation

NASA Astrophysics Data System (ADS)

Semtner, A.-K.; Klitzsch, E.

1994-12-01

During the Early Paleozoic, transgressions and the distribution of sedimentary facies on the northern Gondwana margin were controlled by a regional NNW-SSE to almost north-south striking structural relief. In Early Silurian times, a eustatic highstand enabled the sea to reach its maximum southward extent. The counterclockwise rotation of Gondwana during the Cambrian and Early Ordovician caused the northern Gondwana margin to shift from intertropical to southern polar latitudes in Ordovician times. Glacial and periglacial deposits are reported from many localities in Morocco, Algeria, Niger, Libya, Chad, Sudan, Jordan and Saudi Arabia. The Late Ordovician glaciation phase was followed by a period of a major glacioeustatic sea-level rise in the Early Silurian due to the retreat of the ice-cap. As a consequence of the decreasing water circulation in the basin centers (Central Arabia, Murzuk- and Ghadames basins), highly bituminous euxinic shales were deposited. These shales are considered to be the main source rock of Paleozoic oil and gas deposits in parts of Saudi Arabia, Libya and Algeria. The following regression in the southern parts of the Early Silurian sea was probably caused by a second glacial advance, which was mainly restricted to areas in Chad, Sudan and Niger. Evidence for glacial activity and fluvioglacial sedimentation is available from rocks overlying the basal Silurian shale in north-east Chad and north-west Sudan. The Early Silurian ice advance is considered to be responsible for the termination of euxinic shale deposition in the basin centers.

Evolution of the Neogene Andean foreland basins of the Southern Pampas and Northern Patagonia (34°-41°S), Argentina

NASA Astrophysics Data System (ADS)

Folguera, Alicia; Zárate, Marcelo; Tedesco, Ana; Dávila, Federico; Ramos, Victor A.

2015-12-01

The Pampas plain (30°-41°S) has historically been considered as a sector that evolved independently from the adjacent Andean ranges. Nevertheless, the study of the Pampas showed that it is reasonable to expect an important influence from the Andes into the extraandean area. The Pampas plain can be divided into two sectors: the northern portion, adjacent to the Pampean Ranges, has been studied by Davila (2005, 2007, 2010). The southern sector (34°-41°S) is the objective of the present work. The study of this area allowed to characterize two separate foreland basins: the Southern Pampa basin and the Northern Patagonian basin. The infill is composed of Late Miocene and Pliocene units, interpreted as distal synorogenic sequences associated with the late Cenozoic Andean uplift at this latitudinal range. These foreland basins have been defined based on facies changes, distinct depositional styles, along with the analysis of sedimentary and isopach maps. The basins geometries are proposed following De Celles and Gilles (1996) taking into account the infill geometry, distribution and grain size. In both cases, these depocenters are located remarkably far away from the Andean tectonics loads. Therefore they cannot be explained with short-wave subsidence patterns. Elastic models explain the tectonic subsidence in the proximal depocenters but fail to replicate the complete distal basins. These characteristics show that dynamic subsidence is controlling the subsidence in the Southern Pampas and Northern Patagonian basins.

Implications of Western-sourced Paleogene Flexural Foreland Basin Development in the Peruvian Altiplano on Andean Geodynamics

NASA Astrophysics Data System (ADS)

Sundell, K. E.; Saylor, J.; Lapen, T. J.; Styron, R. H.; Villarreal, D. P.; Usnayo Perales, W. P.; Cárdenas, J.

2017-12-01

Stratigraphy of the Peruvian Altiplano contains valuable information salient to debated geodynamic processes active during the Cenozoic construction of the Andean Plateau. Central to this discussion is the relative timing, location, and magnitude of basin subsidence and surface uplift; however, records of these processes are limited in the Andean Plateau of southern Peru. We measured 6200 m of non-marine clastic stratigraphy in the northernmost Altiplano, characterized through lithofacies and paleocurrent analysis, conglomerate clast counts, sandstone petrography, and detrital zircon U-Pb geochronology. We employ a host of new quantitative detrital zircon techniques including multidimensional scaling, mixture modeling, and quantification of zircon roundness. Results consistently show sediment sourcing from the Western Cordillera and/or western Altiplano, despite close proximity to the modern Eastern Cordillera. Sediment accumulation rates based on new detrital zircon U-Pb maximum depositional ages define an upward-convex, Paleogene subsidence profile with rates increasing from 36 m/Myr to >150 m/Myr. These rates are consistent with deposition and northeastward migration of a Paleogene flexural foreland basin system, which requires coeval lithospheric loading in the Western Cordillera and/or western Altiplano and relative subsidence in the location of the modern Eastern Cordillera. Transition to hinterland basin deposition is marked by a latest Oligocene to middle Miocene angular unconformity. Following this transition, sediment accumulation rates increase to >800 m/Myr during the late Miocene, consistent with strike-slip-induced subsidence, likely under Airy isostatic support. Results in the context of the greater Andean Plateau highlight along-strike variability in rates and timing of deposition in a regionally-contiguous foreland basin system extending from southern Peru to northwest Argentina, and support models of cyclical orogenic processes.

Silurian extension in the Upper Connecticut Valley, United States and the origin of middle Paleozoic basins in the Québec embayment

USGS Publications Warehouse

Rankin, D.W.; Coish, R.A.; Tucker, R.D.; Peng, Z.X.; Wilson, S.A.; Rouff, A.A.

2007-01-01

Pre-Silurian strata of the Bronson Hill arch (BHA) in the Upper Connecticut Valley, NH-VT are host to the latest Ludlow Comerford Intrusive Suite consisting, east to west, of a mafic dike swarm with sheeted dikes, and an intrusive complex. The rocks are mostly mafic but with compositions ranging from gabbro to leucocratic tonalite. The suite is truncated on the west by the Monroe fault, a late Acadian thrust that carries rocks of the BHA westward over Silurian-Devonian strata of the Connecticut Valley-Gaspe?? trough (CVGT). Dikes intrude folded strata with a pre-intrusion metamorphic fabric (Taconian?) but they experienced Acadian deformation. Twenty fractions of zircon and baddeleyite from three sample sites of gabbrodiorite spanning nearly 40 km yield a weighted 207Pb/206Pb age of 419 ?? 1 Ma. Greenschist-facies dikes, sampled over a strike distance of 35 km, were tholeiitic basalts formed by partial melting of asthenospheric mantle, with little or no influence from mantle or crustal lithosphere. The dike chemistry is similar to mid-ocean ridge, within-plate, and back-arc basin basalts. Parent magmas originated in the asthenosphere and were erupted through severely thinned lithosphere adjacent to the CVGT. Extensive middle Paleozoic basins in the internides of the Appalachian orogen are restricted to the Que??bec embayment of the Laurentian rifted margin, and include the CVGT and the Central Maine trough (CMT), separated from the BHA by a Silurian tectonic hinge. The NE-trending Comerford intrusions parallel the CVGT, CMT, and the tectonic hinge, and indicate NW-SE extension. During post-Taconian convergence, the irregular margins of composite Laurentia and Avalon permitted continued collision in Newfoundland (St. Lawrence promontory) and coeval extension in the Que??bec embayment. Extension may be related to hinge retreat of the northwest directed Brunswick subduction complex and rise of the asthenosphere following slab break-off. An alternative hypothesis is

Hinterland tectonics and drainage evolution recorded by foreland basin archives: the Neogene Siwaliks of the Himalaya

NASA Astrophysics Data System (ADS)

Huyghe, Pascale; van der Beek, Peter; Matthias, Bernet; Catherine, Chauvel; Jean-Louis, Mugnier; Laurent, Husson; François, Chirouze

2014-05-01

Provenance analysis and detrital thermochronology of detrital synorogenic sediments, derived from erosion of mountain belts and deposited in surrounding sedimentary basins, are well-established methods to examine the exhumation history of convergent zones, tectonic activity and the associated evolution of the drainage network. We have conducted multidisciplinary studies on magnetostratigraphically dated sections throughout the Neogene Siwalik foreland basin of the Himalayan belt since more than 10 years. Sr, Nd and Hf isotopes are used as provenance indicators, providing information on the nature and size of catchment basins and their evolution through time in response to tectonics. Detrital zircon and apatite thermochronology provides constraints on exhumation rates in the hinterland of the Himalaya and the deformation of the Sub-Himalayan foreland basin. Throughout the Himalaya, detrital zircons from the Siwaliks generally show three age peaks: two static peaks (i.e., displaying constant peak ages through time), and a moving peak. The latter shows a constant lag time of ~4 m.y. corresponding to source-area exhumation rates on the order of 1.8 km/my, while the two static peaks respectively reveal a major 15-20 Ma exhumation event in the belt, the significance of which is still debated, and inheritance of pre-Himalayan ages that indicate recycling of Tethyan sediments. Therefore, our ZFT results suggest that the exhumation dynamics are broadly similar throughout the Himalaya since at least 13 m.y, as also shown by the Bengal Fan detrital sediment record. We relate this switch in tectonic regime to the destabilization of the Himalayan wedge that is rendered overcritical as a response to the transience of dynamic topography caused by the deforming underlying Indian slab. Nonetheless, in detail, the timing of thrusting in the Siwalik domain is delayed by about 1 my eastward as demonstrated by both structural and apatite fission-track data, suggesting overall eastward

Nature, origin, and production characteristics of the Lower Silurian regional oil and gas accumulation, central Appalachian basin, United States

USGS Publications Warehouse

Ryder, R.; Zagorski, W.A.

2003-01-01

Low-permeability sandstones of the Lower Silurian regional oil and gas accumulation cover about 45,000 mi2 (117,000 km2) of the Appalachian basin and may contain as much as 30 tcf of recoverable gas resources. Major reservoirs consist of the "Clinton" sandstone and Medina Group sandstones. The stratigraphically equivalent Tuscarora Sandstone increases the area of the Lower Silurian regional accumulation (LSRA) by another 30,000 mi2 (78,000 km2). Approximately 8.7 tcf of gas and 400 million bbl of oil have been produced from the Clinton/Medina reservoirs since 1880. The eastern predominantly gas-bearing part of the LSRA is a basin-center gas accumulation, whereas the western part is a conventional oil and gas accumulation with hybrid features of a basin-center accumulation. The basin-center accumulations have pervasive gas saturation, water near irreducible saturation, and generally low fluid pressures. In contrast, the hybrid-conventional accumulations have less-pervasive oil and gas saturation, higher mobile-water saturation, and both normal and abnormally low fluid pressures. High mobile-water saturation in the hybrid-conventional reservoirs form the updip trap for the basin-center gas creating a broad transition zone, tens of miles wide, that has characteristics of both end-member accumulation types. Although the Tuscarora Sandstone part of the basin-center gas accumulation is pervasively saturated with gas, most of its constituent sandstone beds have low porosity and permeability. Commercial gas fields in the Tuscarora Sandstone are trapped in naturally fractured, faulted anticlines. The origin of the LSRA includes (1) generation of oil and gas from Ordovician black shales, (2) vertical migration through an overlying 1000-ft (305-m)-thick Ordovician shale; (3) abnormally high fluid pressure created by oil-to-gas transformation; (4) updip displacement of mobile pore water by overpressured gas; (5) entrapment of pervasive gas in the basin center; (6) postorogenic

Beginning of foreland subsidence in the Columbian-Sevier belts, southern Canada and northwest Montana

NASA Astrophysics Data System (ADS)

Gillespie, Janice M.; Heller, Paul L.

1995-08-01

Subsidence analysis and geometry of Jurassic-Cretaceous foreland strata in northwestern Montana and southern Alberta and British Columbia suggest that loading by the fold-thrust belt in Canada began as much as 40 m.y. earlier than in Montana. In Canada, early foreland basin deposits are Late Jurassic age, thicken rapidly westward, and are restricted to a narrow belt within 30 km of the thrust belt. In western Montana, contemporaneous deposits are widespread and do not increase markedly in thickness toward the thrust belt. The unconformity overlying these deposits also changes from Canada, where it is angular, to a disconformity in western Montana near Great Falls. Between these two areas, foreland geometry is transitional over a distance of <250 km. Beyond the transition zone, early foreland basin geometries are broadly consistent, showing Late Jurassic foreland subsidence in southern Canada and Early Cretaceous initial subsidence in the United States.

The radioisotopically constrained Viséan onset of turbidites in the Moravian-Silesian part of the Rhenohercynian foreland basin (Central European Variscides)

NASA Astrophysics Data System (ADS)

Jirásek, Jakub; Otava, Jiří; Matýsek, Dalibor; Sivek, Martin; Schmitz, Mark D.

2018-03-01

The Březina Formation represents the initiation of siliciclastic flysch turbidite sedimentation at the eastern margin of Bohemian Massif or within the Rhenohercynian foreland basin. Its deposition started after drowning of the Devonian carbonate platform during Viséan (Mississippian) times, resulting in a significant interval of black siliceous shale and variegated fossiliferous shale deposition in a starved basin. Near the top of the Březina Formation an acidic volcanoclastic layer (tuff) of rhyolitic composition has been dated with high precision U-Pb zircon chemical abrasion isotope dilution method at 337.73 ± 0.16 Ma. This new radiometric age correlates with the previously inferred stratigraphic age of the locality and the current calibration of the Early Carboniferous geologic time scale. Shales of the Březina Formation pass gradually upwards into the siliciclastics of the Rozstání Formation of the Drahany culm facies. Thus our new age offers one of the few available radioisotopic constraints on the time of onset of siliciclastic flysch turbidites in the Rhenohercynian foreland basin of the European Variscides.

Structuring and evolution of Neogene transcurrent basins in the Tellian foreland domain, north-eastern Tunisia

NASA Astrophysics Data System (ADS)

Melki, Fetheddine; Zouaghi, Taher; Harrab, Salah; Sainz, Antonio Casas; Bédir, Mourad; Zargouni, Fouad

2011-07-01

The Neogene sedimentary basins (Serravallian to Quaternary) of the Tellian tectonic foreland in north-eastern Tunisia formed within the overall NE-SW sinistral strike-slip tectonic framework of the Ras El Korane-Thibar and El Alia-Teboursouk fault systems. From stratigraphic logs, structural cross sections and interpretation of 2D seismic lines and boreholes, the pre-Neogene basement can be interpreted to be structured according to Eocene (NW-SE) compressional and Oligocene extensional phases. This basement comprises structural highs (anticlines and horsts) and subsiding areas (synclines, half-grabens and grabens) formed during the Neogene. The subsiding areas are delineated by faults striking N030E, N-S and N140E, defining (i) narrow, strongly subsiding synclines, (ii) lozenge-shaped basins and (iii) trapezoidal basins. The architecture of their fill results from the sedimentary balance between tectonics and eustatism. Halokinesis and clay diapirism (driven by Triassic and Neogene evaporites and clays) also played an important role in basin evolution, contributing to the formation of domes and diapirs along active faults.

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.

The role of Mesozoic sedimentary basin tapers on the formation of Cenozoic crustal shortening structures and foredeep in the western Sichuan Basin, China

NASA Astrophysics Data System (ADS)

Wang, M.

2017-12-01

The foreland basin records important clues of tectonic and sedimentary process of mountain-building, thus to explore its dynamic mechanism on the formation is an important issue of the mountain-basin interaction. The Longmen Shan fold-and-thrust belt and its adjacent Sichuan basin located in the eastern margin of Tibetan Plateau, are one of the most-concerned regions of studying modern mountain-building and seismic process, and are also a natural laboratory of studying the dynamics of the formation and development of foreland basin. However, it still need further explore on the mechanics of the development of the Cenozoic foreland basin and thrust-belts in the western Sichuan Basin. The Longmen Shan thrust belt has experienced multi-stages of tectonics evolution, foreland basin formation and topography growth since Late Triassic, and whether the early formed basin architecture and large Mesozoic sedimentary basin taper can influence the formation and development of the Cenozoic foreland basin and thrust belts? To solve these issues, this project aim to focus on the Cenozoic foreland basin and internal crustal shortening structures in the western Sichuan basin, on the basis of growth critical wedge taper theory. We will reconstruct the shape of multi-phases of sedimentary basin tapers, the temporal-spatial distribution of crustal shortening and thrusting sequences, and analyze the control mechanism of Mesozoic sedimentary basin taper on the formation of Cenozoic foreland basins, and final explore the interaction between the tectonics geomorphology, stress field and dynamic propagation of foreland basin.

Recycling an uplifted early foreland basin fill: An example from the Jaca basin (Southern Pyrenees, Spain)

NASA Astrophysics Data System (ADS)

Roigé, M.; Gómez-Gras, D.; Remacha, E.; Boya, S.; Viaplana-Muzas, M.; Teixell, A.

2017-10-01

In the northern Jaca basin (Southern Pyrenees), the replacement of deep-marine by terrestrial environments during the Eocene records a main drainage reorganization in the active Pyrenean pro-wedge, which leads to recycling of earlier foreland basin sediments. The onset of late Eocene-Oligocene terrestrial sedimentation is represented by four main alluvial fans: Santa Orosia, Canciás, Peña Oroel and San Juan de la Peña, which appear diachronously from east to west. These alluvial fans are the youngest preserved sediments deposited in the basin. We provide new data on sediment composition and sources for the late Eocene-Oligocene alluvial fans and precursor deltas of the Jaca basin. Sandstone petrography allows identification of the interplay of axially-fed sediments from the east with transversely-fed sediments from the north. Compositional data for the alluvial fans reflects a dominating proportion of recycled rock fragments derived from the erosion of a lower to middle Eocene flysch depocentre (the Hecho Group), located immediately to the north. In addition, pebble composition allows identification of a source in the North Pyrenean Zone that provided lithologies from the Cretaceous carbonate flysch, Jurassic dolostones and Triassic dolerites. Thus we infer this zone as part of the source area, located in the headwaters, which would have been unroofed from turbidite deposits during the late Eocene-Oligocene. These conclusions provide new insights on the response of drainage networks to uplift and topographic growth of the Pyrenees, where the water divide migrated southwards to its present day location.

Failed Silurian continental rifting at the NW margin of Gondwana: evidence from basaltic volcanism of the Prague Basin (Teplá-Barrandian Unit, Bohemian Massif)

NASA Astrophysics Data System (ADS)

Tasáryová, Zuzana; Janoušek, Vojtěch; Frýda, Jiří

2018-06-01

The Silurian volcanic rocks of the Prague Basin represent within-plate, transitional alkali to tholeiitic basalts, which erupted in a continental rift setting through the thick Cadomian crust of the Teplá-Barrandian Unit (Bohemian Massif). Despite the variable, often intense alteration resulting in post-magmatic replacement of the basalt mass due to carbonatization, the geochemical signatures of Silurian basalts are still sufficiently preserved to constrain primary magmatic processes and geotectonic setting. The studied interval of Silurian volcanic activity ranges from Wenlock (Homerian, 431 Ma) to late Ludlow (Gorstian, 425 Ma) with a distinct peak at the Wenlock/Ludlow boundary ( 428 Ma). Trace-element characteristics unambiguously indicate partial melting of a garnet peridotite mantle source. Wenlock basalts are similar to alkaline OIB with depleted radiogenic Nd signature compared to Ludlow basalts, which are rather tholeiitic, EMORB-like with enriched radiogenic Nd signature. The correlation of petrogenetically significant trace-element ratios with Nd isotopic compositions points to a mixing of partial melts of an isotopically heterogeneous, possibly two-component mantle source during the Wenlock-Ludlow melting. Lava eruptions were accompanied by intrusions of doleritic basalt and meimechite sills. The latter represent olivine-rich cumulates of basaltic magmas of probably predominantly Ludlow age. Meimechites with dolerites and, to a lesser extent, some lavas were subject to alteration due to wall-rock-fluid interaction. The trigger for the Wenlock-to-Ludlow (431-425 Ma) extension and related volcanism in the Prague Basin is related to far-field forces, namely slab-pull regime due to progressive closure of the Iapetus Ocean. The main stage of the Baltica-Laurentia collision then caused the Prague Basin rift failure at ca. 425 Ma that has never reached an oceanic stage.

The Tunas Formation (Permian) in the Sierras Australes foldbelt, east central Argentina: evidence for syntectonic sedimentation in a foreland basin

NASA Astrophysics Data System (ADS)

Lopez-Gamundi, O. R.; Conaghan, P. J.; Rossello, E. A.; Cobbold, P. R.

1995-04-01

The Tunas Formation, extensively exposed in the Sierras Australes foldbelt of eastern central Argentina, completes the sedimentation of the Gondwanan (Late Carboniferous-Permian) sequence, locally known as the Pillahuincó Group. The underlying units of the Group show an integrated depositional history which can be explained in terms of glaciomarine sedimentation (Sauce Grande Formation) and postglacial transgression (Piedra Azul and Bonete Formations). This succession also has a rather uniform quartz-rich, sand-sized composition indicative of a cratonic provenance from the Tandilia Massif to the northeast. Early to Late Permian deformation folded and thrusted the southwestern basin margin (Sierras Australes) and triggered the deposition of a 1,500 m — thick, synorogenic prograding wedge, the Tunas Formation, in the adjacent foreland basin (Sauce Grande or Claromecó Basin). Sandstone detrital modes for the Tunas deposits show moderate to low contents of quartz and abundant lithics, mostly of volcanic and metasedimentary origin. Paleocurrents are consistently from the SW. Tuffs interbedded with sandstones in the upper half of Tunas Formation (Early — early Late? Permian) are interpreted as being derived from volcanic glass-rich tuffs settled in a body of water. Extensive rhyolitic ignimbrites and consanguineous airborne tuffaceous material erupted in the northern Patagonian region during that period. The age constraints and similarities in composition between these volcanics and the tuffaceous horizons present in the Sauce Grande, Parana and Karoo Basins suggest a genetic linkage between these two episodes. The intimate relationship between volcanic activity inboard of the paleo-Pacific margin, deformation in the adjacent orogenic belt and subsidence and sedimentation in the contiguous foreland basin constitutes a common motif in the Sauce Grande and Karoo Basins of southwestern Gondwana.

The age of the Keystone thrust: laser-fusion 40Ar/39Ar dating of foreland basin deposits, southern Spring Mountains, Nevada

USGS Publications Warehouse

Fleck, R.J.; Carr, M.D.

1990-01-01

Nonmarine sedimentary and volcaniclastic foreland-basin deposits in the Spring Mountains are cut by the Contact and Keystone thrusts. These synorogenic deposits, informally designated the Lavinia Wash sequence by Carr (1980), previously were assigned a Late Jurassic to Early Cretaceous(?) age. New 40Ar.39Ar laser-fusion and incremental-heating studies of a tuff bed in the Lavinia Wash sequence support a best estimate age of 99.0 ?? 0.4 Ma, indicating that the Lavinia Wash sequence is actually late Early Cretaceous in age and establishing a maximum age for final emplacement of the Contact and Keystone thrust plates consistent with the remainder of the Mesozoic foreland thrust belt. -from Authors

Detrital zircon U-Pb and (U-Th)/He double-dating of Upper Cretaceous-Cenozoic Zagros foreland basin strata in the Kurdistan Region of northern Iraq

NASA Astrophysics Data System (ADS)

Barber, D. E.; Stockli, D. F.; Koshnaw, R. I.; Horton, B. K.; Tamar-Agha, M. Y.; Kendall, J. J.

2014-12-01

The NW Zagros orogen is the result of the multistage collisional history associated with Late Cretaceous-Cenozoic convergence of the Arabian and Eurasian continents and final closure of Neotethys. Siliciclastic strata preserved within a ~400 km segment of the NW Zagros fold-thrust belt and foreland basin in the Iraqi Kurdistan Region (IKR) provide a widespread record of exhumation and sedimentation. As a means of assessing NW Zagros foreland basin evolution and chronostratigraphy, we present coupled detrital zircon (DZ) U-Pb and (U-Th)/He geo-thermochronometric data of Upper Cretaceous to Pliocene siliciclastic strata from the Duhok, Erbil, and Suleimaniyah provinces of IKR. LA-ICP-MS U-Pb age analyses reveal that the foreland basin fill in IKR in general was dominantly derived from Pan-African/Arabian-Nubian, Peri-Gondwandan, Eurasian, and Cretaceous volcanic arc terrenes. However, the provenance of these strata varies systematically along strike and through time, with an overall increase in complexity upsection. DZ age distribution of Paleocene-Eocene strata is dominated by a ~95 Ma grain age population, likely sourced from the Late Cretaceous Hassanbag-Bitlis volcanic arc complex along the northern margin of Arabia. In contrast, DZ U-Pb age distributions of Neogene strata show a major contribution derived from various Eurasian (e.g., Iranian, Tauride, Pontide; ~45, 150, 300 Ma) and Pan-African (~550, 950 Ma) sources. The introduction of Eurasian DZ ages at the Paleogene-Neogene transition likely records the onset of Arabian-Eurasian collision. Along strike to the southeast, the DZ U-Pb spectra of Neogene strata show a decreased percentage of Pan-African, Peri-Gondwandan, Tauride, and Ordovician ages, coupled with a dramatic increase in 40-50 Ma DZ ages that correspond to Urumieh-Dokhtar magmatic rocks in Iran. Combined with paleocurrent data, this suggests that Neogene sediments were transported longitudinally southeastward through an unbroken foreland basin

Crustal investigations of the earthquake-prone Vrancea region in Romania - Part 2: Novel deep seismic reflection experiment in the southeastern Carpathian belt and its foreland basin - survey target, design, and first results

NASA Astrophysics Data System (ADS)

Mocanu, V. I.; Stephenson, R. A.; Diaconescu, C. C.; Knapp, J. H.; Matenco, L.; Dinu, C.; Harder, S.; Prodehl, C.; Hauser, F.; Raileanu, V.; Cloetingh, S. A.; Leever, K.

2001-12-01

Seismic studies of the outer Carpathian Orogen and its foreland (Focsani Basin) in the vicinity of the Vrancea Zone and Danube Delta (Romania) forms one component of a new multidisciplinary initiative of ISES (Netherlands Centre for Integrated Solid Earth Sciences) called DACIA PLAN ("Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics"). The study area, at the margin of the European craton, constitutes one of the most active seismic zones in Europe, yet has remained a geological and geodynamic enigma within the Alpine-Himalayan orogenic system. Intermediate depth (50-220 km) mantle earthquakes of significant magnitude occur in a geographically restricted area in the south-east Carpathians bend. The adjacent, foreland Focsani Basin appears to exhibit recent extensional deformation in what is otherwise understood to be a zone of convergence. The deep seismic reflection component of DACIA PLAN comprises a ~140-km near-vertical profile across the Vrancea Zone and Focsani Basin. Data acquisition took place in August-September 2001, as part of the integrated refraction/reflection seismic field programme "Vrancea-2001" co-ordinated at Karlsruhe University (cf. Abstract, Part 1), utilising 640 independently deployed recorders provided by UTEP and IRIS/PASSCAL ("Texans"). Station spacing was every 100-m with shots every 1-km. These data are to be integrated with industry seismic as well as planned new medium-high resolution seismic reflection profiling across key neotectonically active structures in the Focsani Basin. Particular goals of DACIA PLAN include: (1) the architecture of the Tertiary/Quaternary basins developed within and adjacent to this zone, including the foreland Focsani Basin; (2) the presence and geometry of structural detachment(s) in relation with foreland basin development, including constraints for balanced cross-sections and geodynamic modelling of basin origin and evolution; (3) the relationship between crustal

Evolution of Continental Environments and Chemical Weathering in the Western Himalayan Foreland Basin since 11 Ma

NASA Astrophysics Data System (ADS)

Zhou, P.; Clift, P. D.; Murray, R. W.; Blusztajn, J.; Ireland, T. J.; Feakins, S. J.; Liddy, H.

2017-12-01

The Asian monsoon is the dominant climatic phenomena in Southwest Asia and as the primary source of moisture is one of the major controls over the processes of chemical weathering, especially in the Himalayan foreland basin. The sedimentary records of the eastern Arabian Sea mostly reflect the evolving erosion and chemical weathering processes in the source mountains and foreland basin, with limited input from peninsular India. Analysis of the geochemistry of sediments from International Ocean Discovery Program (IODP) Sites U1456 and U1457 allow us to investigate how chemical weathering may relate to evolving environments and the intensity of the precipitation in the Indus catchment since 11 Ma. We employed X-ray diffraction methods to quantify clay mineral assemblages from the core samples of these two sites. kaolinite/(chlorite+illite) and illite crystallinity show a general long-term trend towards less chemical weathering from 10 Ma to 5 Ma. Meanwhile, the high-resolution hematite/goethite records were acquired from visible diffuse reflectance spectrophotometry from both Sites U1457 and U1456 show a general increase in hematite/goethite, This may represent a long-term drying of the climate and/or an increase in seasonality since 10 Ma, consistent with the long-term trend in carbon isotope values known from the Siwalik Group of the Himalayan foreland. In particular, there is an increase in the relative portion of hematite starting at 8.2 Ma with a subsequent decrease at 6.7 Ma, and a further notable increase after 5.7 Ma. Bulk sediment geochemistry allows us to calculate the Chemical Index of Alteration (CIA) as well other geochemical indices such as K/Al. Both these proxies indicate a strong decrease in chemical weathering intensity at 8.2 Ma, followed by a rapid increase in the degree of alteration after 7.8 Ma followed by a gradual decrease until 6.6 Ma. In general, drier/more seasonal conditions are associated with less chemical weathering over this critical

Characteristics of discrete and basin-centered parts of the Lower Silurian regional oil and gas accumulation, Appalachian basin; preliminary results from a data set of 25 oil and gas fields

USGS Publications Warehouse

Ryder, Robert T.

1998-01-01

Oil and gas trapped in Lower Silurian 'Clinton' sands and Medina Group sandstone constitute a regional hydrocarbon accumulation that extends 425 mi in length from Ontario, Canada to northeastern Kentucky. The 125-mi width of the accumulation extends from central Ohio eastward to western Pennsylvania and west-central New York. Lenticular and intertonguing reservoirs, a gradual eastward decrease in reservoir porosity and permeability, and poorly segregated gas, oil, and water in the reservoirs make it very difficult to recognize clear-cut geologic- and production-based subdivisions in the accumulation that are relevant to resource assessment. However, subtle variations are recognizable that permit the regional accumulation to be subdivided into three tentative parts: a western gas-bearing part having more or less discrete fields; an eastern gas-bearing part having many characteristics of a basin-centered accumulation; and a central oil- and gas-bearing part with 'hybrid' fields that share characteristics of both discrete and basin-centered accumulation. A data set of 25 oil and gas fields is used in the report to compare selected attributes of the three parts of the regional accumulation. A fourth part of the regional accumulation, not discussed here, is an eastern extension of basin-centered accumulation having local commercial gas in the Tuscarora Sandstone, a proximal facies of the Lower Silurian depositional system. A basin-centered gas accumulation is a regionally extensive and commonly very thick zone of gas saturation that occurs in low-permeability rocks in the central, deeper part of a sedimentary basin. Another commonly used term for this type of accumulation is deep-basin gas accumulation. Basin-centered accumulation is a variety of continuous-type accumulation. The 'Clinton' sands and Medina Group sandstone part of the basin-centered gas accumulation is characterized by: a) reservoir porosity ranging from about 5 to 10 percent; b) reservoir permeability

Detrital zircon microtextures and U-PB geochronology of Upper Jurassic to Paleocene strata in the distal North American Cordillera foreland basin

NASA Astrophysics Data System (ADS)

Finzel, E. S.

2017-07-01

Detrital zircon surface microtextures, geochronologic U-Pb data, and tectonic subsidence analysis from Upper Jurassic to Paleocene strata in the Black Hills of South Dakota reveal provenance variations in the distal portion of the Cordillera foreland basin in response to tectonic events along the outboard margin of western North America. During Late Jurassic to Early Cretaceous time, nonmarine strata record initially low rates of tectonic subsidence that facilitated widespread recycling of older foreland basin strata in eolian and fluvial systems that dispersed sediment to the northeast, with minimal sediment derived from the thrust belt. By middle Cretaceous time, marine inundation reflects increased subsidence rates coincident with a change to eastern sediment sources. Lowstand Albian fluvial systems in the Black Hills may have been linked to fluvial systems upstream in the midcontinent and downstream in the Bighorn Basin in Wyoming. During latest Cretaceous time, tectonic uplift in the study area reflects dynamic processes related to Laramide low-angle subduction that, relative to other basins to the west, was more influential due to the greater distance from the thrust load. Provenance data from Maastrichtian and lower Paleocene strata indicate a change back to western sources that included the Idaho-Montana batholith and exhumed Belt Supergroup. This study provides a significant contribution to the growing database that is refining the tectonics and continental-scale sediment dispersal patterns in North America during Late Jurassic-early Paleocene time. In addition, it demonstrates the merit of using detrital zircon grain shape and surface microtextures to aid in provenance interpretations.

Cenozoic foreland basin evolution during Andean shortening in the Malargüe region of western Argentina (35°S)

NASA Astrophysics Data System (ADS)

Ramirez, S. G.; Horton, B. K.; Fuentes, F.

2015-12-01

Cenozoic clastic deposits in western Argentina provide key opportunities to evaluate the timing and duration of Andean deformation and uplift. We studied the Malargüe segment of the Andean foreland basin at 35°S to better understand latest Cretaceous to Pliocene deformation and eastward propagation of Andean retroarc shortening. Our multi-technique approach included logging of a well-exposed ~1500m Paleocene-Miocene stratigraphic succession, paleocurrent measurements, conglomerate clast counts, and detrital zircon U-Pb geochronological analyses of basin fill exposed in the Sosneado region along the Rio Atuel. The Pircala and Coihueco Formations define the lowermost ~180 m of the section and are represented by fine to medium sandstones, siltstones, claystones and marls interpreted as distal fluvial floodplain and localized lacustrine deposits. Pircala paleocurrents show a major reversal from west- to east-directed flow. These finer deposits of the lower succession are separated from the overlying coarser-grained ~800 m thick Agua de la Piedra Formation by a conspicuous unconformity that spans up to roughly 20 Myr. The Agua de la Piedra Formation is composed of upward-coarsening amalgamated beds of massive medium to coarse sandstones and lenticular conglomerates interpreted as a prograding proximal fluvial to alluvial fan system. Conglomerate clast counts show initial dominance by Mesozoic detritus from the pre-Andean Neuquen basin system, with a progressive upsection increase in Cenozoic volcanic detritus from the Andean magmatic arc. Collectively, the paleocurrents, clast compositions, sedimentary facies associations, and emerging U-Pb results suggest a long-term shift, commencing in the Paleocene, from eastern cratonic sources to magmatic-arc and thrust-belt sources during a systematic eastward propagation of deformation, with a pronounced phase of Miocene magmatism and shortening that incorporated the proximal foreland basin into the advancing thrust belt.

The Itajaí foreland basin: a tectono-sedimentary record of the Ediacaran period, Southern Brazil

NASA Astrophysics Data System (ADS)

Basei, M. A. S.; Drukas, C. O.; Nutman, A. P.; Wemmer, K.; Dunyi, L.; Santos, P. R.; Passarelli, C. R.; Campos Neto, M. C.; Siga, O.; Osako, L.

2011-04-01

The Itajaí Basin located in the southern border of the Luís Alves Microplate is considered as a peripheral foreland basin related to the Dom Feliciano Belt. It presents an excellent record of the Ediacaran period, and its upper parts display the best Brazilian example of Precambrian turbiditic deposits. The basal succession of Itajaí Group is represented by sandstones and conglomerates (Baú Formation) deposited in alluvial and deltaic-fan systems. The marine upper sequences correspond to the Ribeirão Carvalho (channelized and non-channelized proximal silty-argillaceous rhythmic turbidites), Ribeirão Neisse (arkosic sandstones and siltites), and Ribeirão do Bode (distal silty turbidites) formations. The Apiúna Formation felsic volcanic rocks crosscut the sedimentary succession. The Cambrian Subida leucosyenogranite represents the last felsic magmatic activity to affect the Itajaí Basin. The Brusque Group and the Florianópolis Batholith are proposed as source areas for the sediments of the upper sequence. For the lower continental units the source areas are the Santa Catarina, São Miguel and Camboriú complexes. The lack of any oceanic crust in the Itajaí Basin suggests that the marine units were deposited in a restricted, internal sea. The sedimentation started around 600 Ma and ended before 560 Ma as indicated by the emplacement of rhyolitic domes. The Itajaí Basin is temporally and tectonically correlated with the Camaquã Basin in Rio Grande do Sul and the Arroyo del Soldado/Piriápolis Basin in Uruguay. It also has several tectono-sedimentary characteristics in common with the African-equivalent Nama Basin.

A new age model for the early-middle Miocene in the North Alpine Foreland Basin

NASA Astrophysics Data System (ADS)

Reichenbacher, Bettina; Krijgsman, Wout; Pippèrr, Martina; Sant, Karin; Kirscher, Uwe

2016-04-01

The establishment of high-resolution age models for sedimentary successions is crucial for numerous research questions in the geosciences and related disciplines. Such models provide an absolute chronology that permits precise dating of depositional episodes and related processes such as mountain uplift or climate change. Recently, our work in the Miocene sediments of the North Alpine Foreland Basin (NAFB) has revealed a significantly younger age (16.6 Myr) for sediments that were thought to have been deposited 18 Myr ago. This implies that a fundamentally revised new age model is needed for the entire suite of lower-middle Miocene sedimentary rocks in the NAFB (20 to 15-Myr). Our new data also indicate that previously published reconstructions of early-middle Miocene palaeogeography, sedimentation dynamics, mountain uplift and climate change in the NAFB all require a critical review and revision. Further, the time-span addressed is of special interest, since it encompasses the onset of a global warming phase. However, it appears that a fundamentally revised new age model for the entire suite of lower-middle Miocene sedimentary rocks in the NAFB can only be achieved based on a 500 m deep drilling in the NAFB for which we currently seek collaboration partners to develop a grant application to the International Continental Deep Drilling Program (ICDP). Reference: Reichenbacher, B., W. Krijgsman, Y. Lataster, M. Pippèrr, C. G. C. Van Baak, L. Chang, D. Kälin, J. Jost, G. Doppler, D. Jung, J. Prieto, H. Abdul Aziz, M. Böhme, J. Garnish, U. Kirscher, and V. Bachtadse. 2013. A new magnetostratigraphic framework for the Lower Miocene (Burdigalian/Ottnangian, Karpatian) in the North Alpine Foreland Basin. Swiss Journal of Geosciences 106:309-334.

Stratigraphy and structure of the Sevier thrust belt and proximal foreland-basin system in central Utah: A transect from the Sevier Desert to the Wasatch Plateau

USGS Publications Warehouse

Lawton, T.F.; Sprinkel, D.A.; Decelles, P.G.; Mitra, G.; Sussman, A.J.; Weiss, M.P.

1997-01-01

The Sevier orogenic belt in central Utah comprises four north-northwest trending thrust plates and two structural culminations that record crustal shortening and uplift in late Mesozoic and early Tertiary time. Synorogenic clastic rocks, mostly conglomerate and sandstone, exposed within the thrust belt were deposited in wedge-top and foredeep depozones within the proximal part of the foreland-basin system. The geologic relations preserved between thrust structures and synorogenic deposits demonstrate a foreland-breaking sequence of thrust deformation that was modified by minor out-of-sequence thrust displacement. Structural culminations in the interior part of the thrust belt deformed and uplifted some of the thrust sheets following their emplacement. Strata in the foreland basin indicate that the thrust sheets of central Utah were emplaced between latest Jurassic and Eocene time. The oldest strata of the foredeep depozone (Cedar Mountain Formation) are Neocomian and were derived from the hanging wall of the Canyon Range thrust. The foredeep depozone subsided most rapidly during Albian through Santonian or early Campanian time and accumulated about 2.5 km of conglomeratic strata (Indianola Group). The overlying North Horn Formation accumulated in a wedge-top basin from the Campanian to the Eocene and records propagation of the Gunnison thrust beneath the former foredeep. The Canyon Range Conglomerate of the Canyon Mountains, equivalent to the Indianola Group and the North Horn Formation, was deposited exclusively in a wedge-top setting on the Canyon Range and Pavant thrust sheets. This field trip, a three day, west-to-east traverse of the Sevier orogenic belt in central Utah, visits localities where timing of thrust structures is demonstrated by geometry of cross-cutting relations, growth strata associated with faults and folds, or deformation of foredeep deposits. Stops in the Canyon Mountains emphasize geometry of late structural culminations and relationships of

A revised 87Sr/86Sr curve for the Silurian: Implications for global ocean chemistry and the Silurian timescale

USGS Publications Warehouse

Cramer, Bradley D.; Munnecke, Axel; Schofield, D.I.; Haase, K.M.; Haase-Schramm, A.

2011-01-01

Recent recalibration of the Silurian timescale and improved global chronostratigraphic correlation of Silurian strata significantly altered the Silurian 87Sr/86Sr curve and the temporal extent of available data. Whereas previous Silurian 87Sr/86Sr composites showed a generally monotonic increase throughout the Silurian, revisions to the Silurian timescale now require a major increase in the rate of change in 87Sr/86Sr at or near the onset of the Gorstian Age of the Ludlow Epoch. Similarly, improved chronostratigraphic correlations between Silurian outcrops on Anticosti Island, Canada, and Gotland, Sweden, indicate that the middle part of the Telychian Age, which is roughly 10%-15% of the total duration of the Silurian period, is undersampled and underrepresented in Silurian 87Sr/86Sr composites. A revised Silurian 87Sr/86Sr curve based on 241 new and published analyses confirms the significant increase in the rate of change of 87Sr/86Sr toward more radiogenic values near the base of the Ludlow Series. On the basis of these data, we propose that the rapid trend toward more radiogenic 87Sr/86Sr values is indicative of increased weathering of old sialic crust exposed during the Silurian uplift of portions of Baltica, Laurentia, and Avalonia. Importantly, however, the actual rate of change of 87Sr/86Sr will remain equivocal until the durations of Silurian epochs and ages are better constrained. ?? 2011 by The University of Chicago. All rights reserved.

Using apatite fission track thermochronology to document the deformation sequence in an exhumed foreland basin: an example from the southern Pyrenees.

NASA Astrophysics Data System (ADS)

Meresse, F.; Labaume, P.; Jolivet, M.; Teixell, A.

2009-04-01

Université Montpellier 2, INSU-CNRS, Laboratoire Géosciences Montpellier, cc060, 34095 Montpellier Cedex 5, France florian.meresse@gm.univ-montp2.fr The study of foreland basins provides important constraints on the evolution of orogenic wedges. In particular, the study of tectonics-sedimentation relationships is essential to date the tectonic activity. However, processes linked to wedge growth are not always completely recorded by the tecto-sedimentary markers, and thermochronological study of the basin-fill can provide further insights. In this work, we have combined apatite fission track analysis (apatite FTA) with structural analysis to precise the timing of the deformation sequence and to characterise the coupling between thrust activity, burial and denudation in the south-Pyrenean foreland basin, a proximal foredeep of the Pyrenees that has been incorporated in the Pyrenean thrust wedge. We have focused the study on a NNE-SSW cross-section of the south-vergent thrust system from the southern flank of the Axial Zone to the South-Pyrenean Frontal Thrust (SPFT), in the west-central part of the belt. This section provides a complete transverse of the South-Pyrenean Zone, here corresponding to the Ainsa and Jaca basins. Apatite FTA provides important new constraints on the south-Pyrenean foreland basin evolution: (i) Data show the southward decrease of the fission track reset level, from a total reset (indicating heating at Tmax>110°C) in the Paleozoic of the Axial Zone, to a partial reset (110°C>Tmax>60°C) in the lower-middle Eocene Hecho Group turbidites in the northern part of the Jaca basin, and to the absence of reset (Tmax<60°C) in the middle Eocene-Oligocene continental sediments of the southern part of the Jaca basin. This indicates a decreasing amount of denudation going southwards, from more than 4.5 km in the north to less than 2.5 km in the south if we assume an average geothermal gradient around 25°/km. The structural setting of the Jaca basin

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

NASA Astrophysics Data System (ADS)

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

2013-09-01

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

Regional deformation of late Quaternary fluvial sediments in the Apennines foreland basin (Emilia, Italy)

NASA Astrophysics Data System (ADS)

Stefani, Marco; Minarelli, Luca; Fontana, Alessandro; Hajdas, Irka

2018-04-01

Our research is aimed at estimating the vertical deformation affecting late Quaternary units accumulated into the foreland basin of the Northern Apennines chain. Beneath the study alluvial plain, compressive fault-fold structures are seismically active. We reconstructed the stratigraphic architecture and the depositional evolution of the alluvial deposits, which accumulated in the first 40 m of subsurface, through the last 45,000 years, from before the Last Glacial Maximum to the present. A 58 km-long stratigraphic profile was correlated from the foothill belt near Bologna to the vicinity of the Po River. The analysis of the profile documents subsidence movements through the last 12,000 years, exceeding - 18 m in syncline areas, with subsidence rates of at least 1.5 m/ka. Anticlines areas experienced a much lower subsidence than the syncline ones.

Growth of the Zagros Fold-Thrust Belt and Foreland Basin, Northern Iraq, Kurdistan

NASA Astrophysics Data System (ADS)

Koshnaw, Renas; Horton, Brian; Stockli, Daniel; Barber, Douglas; Ghalib, Hafidh; Dara, Rebwar

2016-04-01

The Zagros orogenic belt in the Middle Eastern segment of the Alpine-Himalayan system is among the youngest seismically active continental collision zones on Earth. However, due to diachronous and incremental collision, the precise ages and kinematics of shortening and deposition remain poorly understood. The Kurdistan region of the Zagros fold-thrust belt and foreland basin contains well-preserved Neogene wedge-top and foredeep deposits that include clastic nonmarine fill of the Upper Fars, Lower Bakhtiari, and Upper Bakhtiari Formations. These deposits record significant information about orogenic growth, fold-thrust dynamics, and advance of the deformation front. Thermochronologic and geochronologic data from thrust sheets and stratigraphic archives combined with local earthquake data provide a unique opportunity to address the linkages between surface and subsurface geologic relationships. This research seeks to constrain the timing and geometry of exhumation and deformation by addressing two key questions: (1) Did the northwestern Zagros fold-thrust belt evolve from initial thin-skinned shortening to later thick-skinned deformation or vice-versa? (2) Did the fold-thrust belt advance steadily under critical/supercritical wedge conditions involving in-sequence thrusting or propagate intermittently under subcritical conditions with out-of-sequence deformation? From north to south, apatite (U-Th)/He ages from the Main Zagros Thrust, the Mountain Front Flexure (MFF), and additional frontal thrusts suggest rapid exhumation by ~10 Ma, ~5 Ma, and ~8 Ma respectively. Field observations and seismic sections indicate progressive tilting and development of growth strata within the Lower Bakhtiari Formation adjacent to the frontal thrusts and within the Upper Bakhtiari Formation near the MFF. In the Kurdistan region of Iraq, a regional balanced cross section constrained by new thermochronometric results, proprietary seismic reflection profiles, and earthquake hypocenters

Lower Silurian `hot shales' in North Africa and Arabia: regional distribution and depositional model

NASA Astrophysics Data System (ADS)

Lüning, S.; Craig, J.; Loydell, D. K.; Štorch, P.; Fitches, B.

2000-03-01

large palaeohigh at that time. The depositional model presented may help in better understanding the source potential of the basal Silurian shales in less-explored regions of North Africa and Arabia including Morocco, northern Niger and the Kufra Basin in southeast Libya.

Discriminating Sediment Supply versus Accommodation Controls on Late Cretaceous Foreland Basin Stratigraphic Architecture in the Book Cliffs, Utah using Detrital Zircon Double Dating

NASA Astrophysics Data System (ADS)

Bartschi, N.; Saylor, J. E.

2016-12-01

Middle to late Campanian strata of the Book Cliffs, Utah record the Late Cretaceous deposition of three clastic wedges in the North American Cordilleran foreland basin east of the Sevier thrust-belt. Variations in wedge geometries provide an opportunity to evaluate the effects of sediment supply versus accommodation on foreland basin stratal architecture. There is a significant increase in eastward progradation rate from the Lower to the Upper Castlegate Sandstone. However, the progradation rate decreases in the overlying Bluecastle and Price River formations, as well as the laterally equivalent Farrer and Tuscher formations. Rapid progradation during Upper Castlegate deposition may be caused by increased sediment supply from either rapid exhumation of the Sevier thrust-belt or introduction of a new sediment source. Alternatively, reduced accommodation within the proximal foreland basin from uplifts associated with Laramide deformation, or a transition from flexural to dynamic subsidence, could produce the observed rapid wedge progradation. Changes in sediment provenance and source-area exhumation rate can be identified using a combination of detrital zircon U-Pb geochronology and (U-Th)/He thermochronology. Quantitative comparisons between collected samples and published provenance data indicates an upsection increase in a new sediment source, revealing a significant overall shift in provenance between wedge boundaries. This change in provenance is coupled by an upsection decrease in lag time between the Lower and Upper Castlegate, consistent with an increase in exhumation rate. Conversely, there is no change in lag time between the Upper Castlegate and overlying Price River Formation, suggesting a relatively constant exhumation rate. Near-zero lag times during the Upper Castlegate is consistent with rapid exhumation associated with increased thrusting of the Sevier thrust-belt. Therefore, progradation of the Upper Castlegate can be attributed to an increase in

Early Triassic development of a foreland basin in the Canadian high Arctic: Implications for a Pangean Rim of Fire

NASA Astrophysics Data System (ADS)

Hadlari, Thomas; Dewing, Keith; Matthews, William A.; Alonso-Torres, Daniel; Midwinter, Derrick

2018-06-01

Following the amalgamation of Laurasia and Gondwana to form Pangea, some Triassic tectonic models show an encircling arc system called the "Pangean Rim of Fire". Here we show that the stratigraphy and Early Triassic detrital zircon provenance of the Sverdrup Basin in the Canadian Arctic is most consistent with deposition in a retro-arc foreland basin. Late Permian and Early Triassic volcanism was accompanied by relatively high rates of subsidence leading to a starved basin with volcanic input from a magmatic arc to the northwest. The mostly starved basin persisted through the Middle and Late Triassic with nearly continuous input of volcanic ash recorded as bentonites on the northwestern edge of the basin. In the latest Triassic it is interpreted that decreasing subsidence and a significant influx of sand-grade sediment when the arc was exhumed led to filling of the basin at the end of an orogenic cycle. Combined with other hints of Early Triassic arc activity along the western margin of Laurentia we propose that the Pangean Rim of Fire configuration spanned the entire Triassic. This proposed configuration represents the ring of external subduction zones that some models suggest are necessary for the breakup of supercontinents such as Pangea.

The Silurian Hoedongri Formation in the Taebaeksan Basin of Korea Revisited: its Significance in the Tectonic Reconstruction of East Asia

NASA Astrophysics Data System (ADS)

Chae, S.; Hong, J.; Jung, S.; Ree, J.

2011-12-01

The Silurian Hoedongri Formation of the Taebaeksan Basin of South Korea has been used as a key unit to the correlation of tectonic provinces of East Asia since the South China craton (or Yangtz block) contains Silurian-Devonian sequences as well as Cambrian-Ordovician ones in the Paleozoic basins while the North China craton (or Sino-Korea block) is devoid of Silurian-Devonian sequences. In the Biryongdong area near the type locality of the Hoedongri Formation, it has been reported that the gray limestone of the Hoedongri Formation unconformably overlies brownish gray limestone of the Ordovician Haengmae Formation. However, our detailed examination on the Biryongdong section reveals that both of the brownish gray and gray limestones are mylonitic marbles with the boundary between the two units being a healed fault breccia zone (~ 12 m thick). The main difference of the two units is that repeated cycles of plastic deformation and fracturing occurred in the underlying brownish gray marble ('Haengmae') while the gray marble ('Hoedongri') deformed mainly by intracrystalline plasticity. The mylonitic foliation strikes NW with a low to moderate dip angle (20-60°) to NE. The ridge-in-groove type lineation on foliation surface trends NNW. The shape-preferred foliation of elongated calcite grains are oblique to the mylonitic foliation defined by layers with a grain-size variation, indicating a top-to-the-SSE shear sense. The mylonitic marble consists of elongated remnant grains (80-120 μm) with deformation twins and dynamically recrystallized matrix grains (10-40 μm). Grain boundaries and twin boundaries are lobate or wavy, indicating dynamic boundary migration. Some layers of the gray mylonitic marble are composed entirely of larger (80-120 μm) elongated calcite grains. In the brownish gray mylonitic marble unit, layers of brittle fracturing overprinting mylonitic foliation occur. In some of these layers, fragments (several cm - tens of cm) of the mylonitic marble are

Chronology and tectonic controls of late tertiary deposition in the southwestern Tian Shan foreland, NW China

USGS Publications Warehouse

Heermance, R.V.; Chen, J.; Burbank, D.W.; Wang, C.

2007-01-01

Magnetostratigraphy from the Kashi foreland basin along the southern margin of the Tian Shan in Western China defines the chronology of both sedimentation and the structural evolution of this collisional mountain belt. Eleven magnetostratigraphic sections representing ???13 km of basin strata provide a two- and three-dimensional record of continuous deposition since ???18 Ma. The distinctive Xiyu conglomerate makes up the uppermost strata in eight of 11 magnetostratigraphic sections within the foreland and forms a wedge that thins southward. The basal age of the conglomerate varies from 15.5??0.5 Ma at the northernmost part of the foreland, to 8.6??0.1 Ma in the central (medial) part of the foreland and to 1.9??0.2, ???1.04 and 0.7??0.1 Ma along the southern deformation front of the foreland basin. These data indicate the Xiyu conglomerate is highly time-transgressive and has prograded south since just after the initial uplift of the Kashi Basin Thrust (KBT) at 18.9??3.3 Ma. Southward progradation occurred at an average rate of ???3 mm year -1 between 15.5 and 2 Ma, before accelerating to ???10 mm year-1. Abrupt changes in sediment-accumulation rates are observed at 16.3 and 13.5 Ma in the northern part of the foreland and are interpreted to correspond to southward stepping deformation. A subtle decrease in the sedimentation rate above the Keketamu anticline is determined at ???4.0 Ma and was synchronous with an increase in sedimentation rate further south above the Atushi Anticline. Magnetostratigraphy also dates growth strata at <4.0, 1.4??0.1 and 1.4??0.2 Ma on the southern flanks the Keketamu, Atushi and Kashi anticlines, respectively. Together, sedimentation rate changes and growth strata indicate stepped migration of deformation into the Kashi foreland at least at 16.3, 13.5, 4.0 and 1.4 Ma. Progressive reconstruction of a seismically controlled cross-section through the foreland produces total shortening of 13-21 km and migration of the deformation front at

Late Mesozoic and Cenozoic thermotectonic evolution of the central Brooks Range and adjacent North Slope foreland basin, Alaska: Including fission track results from the Trans-Alaska Crustal Transect (TACT)

USGS Publications Warehouse

O'Sullivan, P. B.; Murphy, J.M.; Blythe, A.E.

1997-01-01

Apatite fission track data are used to evaluate the thermal and tectonic history of the central Brooks Range and the North Slope foreland basin in northern Alaska along the northern leg of the Trans-Alaska Crustal Transect (TACT). Fission track analyses of the detrital apatite grains in most sedimentary units resolve the timing of structures and denudation within the Brooks Range, ranging in scale from the entire mountain range to relatively small-scale folds and faults. Interpretation of the results indicates that rocks exposed within the central Brooks Range cooled rapidly from paleotemperatures 110?? to 50??C during discrete episodes at ???100??5 Ma, ???60??4 Ma, and ???24??3 Ma, probably in response to kilometer-scale denudation. North of the mountain front, rocks in the southern half of the foreland basin were exposed to maximum paleotemperatures 110??C in the Late Cretaceous to early Paleocene as a result of burial by Upper Jurassic and Cretaceous sedimentary rocks. Rapid cooling from these elevated paleotemperatures also occurred due to distinct episodes of kilometer-scale denudation at ???60??4 Ma, 46??3 Ma, 35??2 Ma, and ???24??3 Ma. Combined, the apatite analyses indicate that rocks exposed along the TACT line through the central Brooks Range and foreland basin experienced episodic rapid cooling throughout the Late Cretaceous and Cenozoic in response to at least three distinct kilometer-scale denudation events. Future models explaining orogenic events in northern Alaska must consider these new constraints from fission track thermochronology. Copyright 1997 by the American Geophysical Union.

Tectonic controls on deposition of Middle Jurassic strata in a retroarc foreland basin, Utah-Idaho trough, western interior, United States

NASA Astrophysics Data System (ADS)

Bjerrum, Christian J.; Dorsey, Rebecca J.

1995-08-01

An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 95TC01448, Tectonic controls on deposition of Middle Jurassic strata in a retroarc foreland basin, Utah-Idaho trough, western interior, United States, Christian J. Bjerrum and Rebecca J. Dorsey). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N. W., Washington, DC 20009; $15.00. Payment must accompany order. A thick succession of Jurassic nonmarine and marine sedimentary rocks is exposed in a large area from northern Arizona to eastern Idaho and western Wyoming. These sediments accumulated in the Utah-Idaho trough, a deep elongate cratonal basin whose origin has recently been debated. Detailed stratigraphic analysis, subsidence analysis, and first-order flexural modeling of these deposits (this study) provide new insights into the timing and mechanisms of subsidence in the Utah-Idaho trough. Lower and Middle Jurassic strata are divided into six unconformity-bounded sequences. In contrast to the overall uniform thickness of Lower Jurassic sequences (1 and 2), Middle Jurassic strata (sequences 3 through 6) consist of distinctly westward thickening sedimentary packages in which basal shallow marine deposits onlap eastward onto bounding unconformities. Basal strata of sequences 3 through 6 pass upward into widespread progradational continental deposits that are truncated progressively toward the east (cratonward) by the next unconformity. Decompacted total subsidence curves show that the rate of subsidence in most sections increased sharply at the end of sequence 2 time (J-2 unconformity; ˜170 Ma). This is interpreted to record the onset of Middle Jurassic deposition

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

Petrophysics of Lower Silurian sandstones and integration with the tectonic-stratigraphic framework, Appalachian basin, United States

USGS Publications Warehouse

Castle, J.W.; Byrnes, A.P.

2005-01-01

Petrophysical properties were determined for six facies in Lower Silurian sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2-18%) and permeability (0.002-450 md). With a transition-zone thickness of only 1-6 m (3-20 ft), fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%, typical of many gas reservoirs. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10-21%), high permeability (3-250 md), and low S iw (<20%). Lower shoreface sandstones, which are finer grained, have lower porosity (4-12%), lower permeability (0.0007-4 md), thicker transition zones (6-180 m [20-600 ft]), and higher S iw. In the tidal-channel, tidal-flat, and estuarine facies, low porosity (average < 6%), low permeability (average < 0.02 md), and small pore throats result in large transition zones (30-200 m; 100-650 ft) and high water saturations. The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along a collisional margin during the Taconic orogeny. Although the total thickness of the sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

Tectonics vs. Climate efficiency in triggering detrital input in sedimentary basins: the Po Plain-Venetian-Adriatic Foreland Basin (Northern Italy)

NASA Astrophysics Data System (ADS)

Amadori, Chiara; Di Giulio, Andrea; Toscani, Giovanni; Lombardi, Stefano; Milanesi, Riccardo; Panara, Yuri; Fantoni, Roberto

2017-04-01

The relative efficiency of tectonics respect to climate in triggering erosion of mountain belts is a classical but still open debate in geosciences. The fact that data both from tectonically active and inactive mountain regions in different latitudes, record a worldwide increase of sediment input to sedimentary basins during the last million years concomitantly with the cooling of global climate and its evolution toward the modern high amplitude oscillating conditions pushed some authors to conclude that Pliocene-Pleistocene climate has been more efficient than tectonics in triggering mountain erosion. Po Plain-Venetian-Adriatic Foreland System, made by the relatively independent Po Plain-Northern Adriatic Basin and Venetian-Friulian Basin, provides an ideal case of study to test this hypothesis and possibly quantify the difference between the efficiency of the two. In fact it is a relatively closed basin (i.e. without significant sediment escape) with a fairly continuous sedimentation (i.e. with a quite continuous sedimentary record) completely surrounded by collisional belts (Alps, Northern Apennines and Dinarides) that experienced only very weak tectonic activity since Calabrian time, i.e. when climate cooling and cyclicity increased the most. We present a quantitative reconstruction of the sediment flow delivered from the surrounding mountain belts to the different part of the basin during Pliocene-Pleistocene time. This flow was obtained through the 3D reconstruction of the Venetian-Friulian and Po Plain Northern Adriatic Basins architecture, performed by means of the seismic-based interpretation and time-to-depth conversion of six chronologically constrained surfaces (seismic and well log data from courtesy of ENI); moreover, a 3D decompaction of the sediment volume bounded by each couple of surfaces has been included in the workflow, in order to avoid compaction-related bias. The obtained results show in both Basins a rapid four-folds increase of the

Transition from marine deep slope deposits to evaporitic facies of an isolated foreland basin: case study of the Sivas Basin (Turkey)

NASA Astrophysics Data System (ADS)

Pichat, Alexandre; Hoareau, Guilhem; Legeay, Etienne; Lopez, Michel; Bonnel, Cédric; Callot, Jean-Paul; Ringenbach, Jean-Claude

2017-04-01

The Sivas Basin, located in the central part of the Anatolian Plateau in Turkey, formed after the closure of the northern Neotethys from Paleocene to Pliocene times. It developed over an ophiolitic basement obducted from the north during the Late Cretaceous. During Paleocene to Eocene times, the onset of the Tauride compression led to the development of a foreland basin affected by north-directed thrusts. The associate general deepening of the basin favored the accumulation of a thick marine turbiditic succession in the foredeep area, followed by a fast shallowing of the basin and thick evaporitic sequence deposition during the late Eocene. We present here the detailed sedimentological architecture of this flysch to evaporite transition. In the northern part of the basin, volcanoclastic turbidites gradually evolved into basinal to prodelta deposits regularly fed by siliciclastic material during flood events. Locally (to the NE), thick-channelized sandstones are attributed to the progradation of delta front distributary channels. The basin became increasingly sediment-starved and evolved toward azoic carbonates and shaly facies, interlayered with organic-rich shales before the first evaporitic deposits. In the southern part of the basin, in the central foredeep, the basinal turbidites become increasingly gypsum-rich and record a massive mega-slump enclosing olistoliths of gypsum and of ophiolitic rocks. Such reworked evaporites were fed by the gravitational collapsing of shallow water evaporites that had previously precipitated in silled piggy-back basins along the southern fold-and-thrust-belt of the Sivas Basin. Tectonic activity that led to the dismantlement of such evaporites probably also contributed to the closure of the basin from the marine domain. From the north to the south, subsequent deposits consist in about 70 meters of secondary massive to fine-grained gypsiferous beds interpreted as recording high to low density gypsum turbidites. Such facies were

Syn- and post-sedimentary controls on clay mineral assemblages in a tectonically active basin, Andean Argentinean foreland

NASA Astrophysics Data System (ADS)

Do Campo, Margarita; Nieto, Fernando; del Papa, Cecilia; Hongn, Fernando

2014-07-01

In the northern part of the Calchaquí Valley (NW Argentina), Palaeogene Andean foreland sediments are represented by a 1400-metre-thick continental succession (QLC: Quebrada de Los Colorados Formation) consisting of claystones, siltstones, sandstones, and conglomerates representing sedimentation in fluvial-alluvial plains and alluvial fan settings. To understand the main syn- and postsedimentary variables controlling the clay mineral assemblages of this succession, we have studied the fine-grained clastic sediments by X-ray diffraction and electron microscopy, along with a detailed sedimentary facies analysis, for two representative sections. In the northern section, the whole succession was sampled and analysed by XRD, whereas in the second section, a control point 15 km to the south, only the basal levels were analysed. The XRD study revealed a strong contrast in clay mineral assemblages between these two sections as well as with sections in the central Calchaquí Valley studied previously. In the northernmost part of the study area, a complete evolution from smectite at the top to R3 illite/smectite mixed-layers plus authigenic kaolinite at the bottom, through R1-type mixed-layers in between, has been recognized, indicating the attainment of late diagenesis. In contrast, the clay mineral assemblages of equivalent foreland sediments cropping out only 15 km to the south contain abundant smectite and micas, subordinate kaolinite and chlorite, and no I/S mixed-layers to the bottom of the sequence. Early diagenetic conditions were also inferred in a previous study for equivalent sediments of the QLC Formation cropping out to the south, in the central Calchaquí Valley, as smectite occurs in basal strata. Burial depths of approximately 3000 m were estimated for the QLC Formation in the central and northern Calchaquí Valley; in addition, an intermediate to slightly low geothermal gradient can be considered likely for both areas as foreland basins are regarded as

Foreland sedimentary record of Andean mountain building during advancing and retreating subduction

NASA Astrophysics Data System (ADS)

Horton, Brian K.

2016-04-01

As in many ocean-continent (Andean-type) convergent margins, the South American foreland has long-lived (>50-100 Myr) sedimentary records spanning not only protracted crustal shortening, but also periods of neutral to extensional stress conditions. A regional synthesis of Andean basin histories is complemented by new results from the Mesozoic Neuquén basin system and succeeding Cenozoic foreland system of west-central Argentina (34-36°S) showing (1) a Late Cretaceous shift from backarc extension to retroarc contraction and (2) an anomalous mid-Cenozoic (~40-20 Ma) phase of sustained nondeposition. New detrital zircon U-Pb geochronological results from Jurassic through Neogene clastic deposits constrain exhumation of the evolving Andean magmatic arc, retroarc thrust belt, foreland basement uplifts, and distal eastern craton. Abrupt changes in sediment provenance and distal-to-proximal depositional conditions can be reconciled with a complex Mesozoic-Cenozoic history of extension, post-extensional thermal subsidence, punctuated tectonic inversion involving thick- and thin-skinned shortening, alternating phases of erosion and rapid accumulation, and overlapping igneous activity. U-Pb age distributions define the depositional ages of several Cenozoic stratigraphic units and reveal a major late middle Eocene-earliest Miocene (~40-20 Ma) hiatus in the Malargüe foreland basin. This boundary marks an abrupt shift in depositional conditions and sediment sources, from Paleocene-middle Eocene distal fluviolacustrine deposition of sediments from far western volcanic sources (Andean magmatic arc) and subordinate eastern cratonic basement (Permian-Triassic Choiyoi igneous complex) to Miocene-Quaternary proximal fluvial and alluvial-fan deposition of sediments recycled from emerging western sources (Malargüe fold-thrust belt) of Mesozoic basin fill originally derived from basement and magmatic arc sources. Neogene eastward advance of the fold-thrust belt involved thick

2D Seismic Velocity Modelling in the Southeastern Romanian Carpathians and its Foreland (Vrancea Zone and Focsani Basin)

NASA Astrophysics Data System (ADS)

Stephenson, R.; Bocin, A.; Tryggvason, A.

2003-12-01

The DACIA-PLAN (Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics) deep seismic reflection survey was performed in August-September 2001, with the objective of obtaining of new information on the deep structure of the external Carpathians nappes and the architecture of Tertiary/Quaternary basins developed within and adjacent to the seismically-active Vrancea Zone, including the rapidly subsiding Focsani Basin. The DACIA-PLAN profile is about 140 km long, having a roughly NW-SE direction, from near the southeast Transylvanian Basin, across the mountainous southeastern Carpathians and their foreland to near the Danube Dalta. A high resolution 2D velocity model of the upper crust along the seismic profile has been determined from a first-arrival tomographic inversion of the DACIA-PLAN data. The shallowing of Palaeozoic-Mesozoic basement, and related structural heterogeneity within it, beneath the eastern flank of the Focsani Basin is clearly seen. Velocity heterogeneity within the Carpathian nappe belt is also evident and is indicative of internal structural complexity, including the presence of salt bodies and basement involvement in thrusting, thus favouring some current geological models over others. The presence of basement involvement implies the compressional reactivation of pre-existing basement normal faults. Members of the DACIA-PLAN/TomoSeis Working Group (see poster) should be considered as co-authors of this presentation.

The effect of drainage reorganization on paleoaltimetry studies: An example from the Paleogene Laramide foreland

NASA Astrophysics Data System (ADS)

Davis, Steven J.; Wiegand, Bettina A.; Carroll, Alan R.; Chamberlain, C. Page

2008-11-01

Using multiple isotope systems, we examine the complex effects of drainage reorganization in the Laramide Foreland in the context of stable isotope paleoaltimetry. Strontium, oxygen and carbon isotopic data from lacustrine carbonates formed in the southwestern Uinta Basin, Utah between the Late Cretaceous and late Middle Eocene reveal a two stage expansion in the drainage basin of Lake Uinta beginning at ~ 53 Ma culminating in the Mahogany highstand at 48.6 Ma. A marked increase in 87Sr/ 86Sr ratios of samples from the Main Body of the Green River Formation is interpreted as the result of water overflowing the Greater Green River Basin in Wyoming and entering Lake Uinta from the east via the Piceance Creek Basin of northwestern Colorado. This large new source of water caused a rapid expansion of Lake Uinta and was accompanied by a significant and rapid increase in the O isotope record of carbonate samples by ~ 6‰. The periodic overspilling of Lake Gosiute probably became continuous at ~ 49 Ma, when the lake captured low- δ18O water from the Challis and Absaroka Volcanic Fields to the north. However, evaporation in the Greater Green River and Piceance Creek Basins meant that the waters entering Lake Uinta were still enriched in 18O. By ~ 46 Ma, inflows from the Greater Green River Basin ceased, resulting in a lowstand of Lake Uinta and the deposition of bedded evaporites in the Saline Facies of the Green River Formation. We thus show that basin development and lake hydrology in the Laramide foreland were characterized by large-scale changes in Cordilleran drainage patterns, capable of confounding paleoaltimetry studies premised on too few isotopic systems, samples or localities. In the case of the North American Cordillera of the Paleogene, we further demonstrate the likelihood that (1) topographic evolution of distal source areas strongly influenced the isotopic records of intraforeland basins and (2) a pattern of drainage integration between the hinterland and

Main consistent patterns of Stromatoporoid Development in the Late Ordovician and Silurian in the North Urals Palaeobasin

NASA Astrophysics Data System (ADS)

Antropova, E.

2009-04-01

In the history of the Earth there have been no basins with similar characteristics. The North Urals palaeobasin had its own unique features. The dominant benthic organisms of basin ecosystem during the Ordovician and Silurian were stromatoporoids, corals, and brachiopods. This fauna is vitally important for the aims of stratigraphy so long as conodonts are extremely rare in sections of the Northern Urals area. The most complete ordering of stromatoporoid complexes has been established and made it possible to estimate rates and measures of extinction at a level of the province. It was also found out that stromatoporoids were organisms responsive to subtle changes of environment and that they accommodated differently to those changing conditions. The evolution of stromatoporoids was accompanied by phylogenetic reorganization and formation of endemic communities in the Late Ordovician and Early Silurian. In the Late Silurian taxonomical diversity of stromatoporoids was mainly controlled by migration processes and cosmopolites with wide palaeogeographic links prevailed in the palaeobasin. Therefore palaeobasin at that time was open to stromatoporoid fauna migration which is confirmed by the occurrence of genera and species that disperse in coeval deposits of many areas, for example, Baltic States, Sweden, Ukraine (Podolia), Western Siberia, Arctic islands of Russia, Mongolia, Canada (islands). The evolution of stromatoporoid communities in the Ordovician-Silurian was intermitted by biotic crises. The analysis of stromatoporoid development helps to define crucial points of ecosystem's reorganizations coinciding with critical geological and biotic events in the history of the North Urals palaeobasin existence, as well as global events during the Ordovician and Silurian (Hirnantian Event, Ireviken Event, Lau Event). The analysis of crises indicates local dependence of stromatoporoid biodiversity on depositional environments. Large local biocenos reorganizations and biotic

Climatic cycles recorded in the Middle Eocene hemipelagites from a Dinaric foreland basin of Istria (Croatia)

NASA Astrophysics Data System (ADS)

Lužar-Oberiter, Borna; Hochuli, Peter A.; Babić, Ljubomir; Glumac, Bosiljka; Tibljaš, Darko

2010-06-01

Middle Eocene hemipelagic marls from the Pazin-Trieste Basin, a foreland basin of the Croatian Dinarides, display repetitive alternations of two types of marls with different resistance to weathering. This study focuses on the chemical composition, stable isotopes, and palynomorph content of these marls in order to better understand the nature of their cyclic deposition and to identify possible paleoenvironmental drivers responsible for their formation. The less resistant marls (LRM) have consistently lower carbonate content, lower δ18O and δ13C values, and more abundant dinoflagellate cysts than the more resistant marls (MRM). We interpret these differences between the two marl types to be a result of climatic variations, likely related to Milankovitch oscillations. Periods with wetter climate, associated with increased continental runoff, detrital and nutrient influx produced the LRM. Higher nutrient supply sparked higher dinoflagellate productivity during these times, while reduced salinity and stratification of the water column may have hampered the productivity of calcareous nannoplankton and/or planktonic foraminifera. In contrast, the MRM formed during dryer periods which favoured higher carbonate accumulation rates. This study provides new information about the sedimentary record of short-scale climate variations reflected in wet-dry cycles during an overall warm, greenhouse Earth.

Foreland structure - Beartooth Mountains, Montana and Wyoming

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

Clark, D.M.

1996-06-01

Analysis of public drilling records from the AMOCO Beartooth Number 1 and 1 A sidetrack boreholes (SW1/4, SE1/4, Section 19, T.8 S., R.20 E., Carbon County, Montana) continues. Several additional inferences are made about this large foreland structure, and subsequent interpretation of the structural model of the northeast corner of the Beartooth Mountain Block and structural relationship with the Big Horn Basin. The structure is described as a large recumbent to sub-horizontal, synclinal fold with the overturned upper limb out diagonally by the Beartooth Thrust or Thrust Zone and a complex thrust fault zone below the Beartooth Thrust. The singlemore » recorded dip angle and direction of the Beartooth Thrust at depth was 19 degrees to the northwest(?). The dipmeter dip angle on the Beartooth Thrust, 19 degrees, validates foreland structural theory of decreasing dip angles at a vertical depth of 8,232 feet (2,509 m), in the Precambrian crystalline basement. The northwest dip direction may be attributable to secondary structural folding. The record of northwest, southeast, and southwest dip of bedding surfaces and faults in sections of the overturned upper limb, in both boreholes, suggests possible, less intense secondary folding, after thrust fault deformation. Given the overall geometry of this large foreland structure, there is little doubt that the average direction of maximum principal stress (sigma 1) was oriented in a northeast - southwest direction.« less

Absolute age constraints on rapid, axial progradation of a high-relief clinoform depositional system in the Colville foreland basin, Arctic Alaska

NASA Astrophysics Data System (ADS)

Lease, R. O.; Houseknecht, D. W.; Kylander-Clark, A. R.

2014-12-01

Lower Cretaceous strata of the Alaska North Slope contain the world's most voluminous (1.2 million km3), highest relief (>1 km thick), and longest (600 km west-east) foreland clinoform depositional sequence. Although the regional stratigraphic framework of the Torok-Nanushuk clinoform sequence is well known, absolute age constraints are lacking. Existing, relatively imprecise "Aptian-Albian" biostratigraphy has hindered a quantitative understanding of clinoform depositional processes. We establish chronostratigraphy for the Torok-Nanushuk clinoform sequence with detrital zircon U/Pb geochronology from 9 localities from exploration well cores and outcrop samples (n=1666 grains). Maximum depositional ages defined by young detrital zircon U/Pb age populations, likely derived from coeval volcanism in Russian Chukotka, become progressively younger in the direction of eastward progradation. These data reveal a major progradational surge between 116 and 104 Ma when the shelf margin prograded more than 525 km. The rapid progradation (~45 km/m.y.) and sediment flux (~100,000 km3/m.y.) of this high-relief clinoform deposystem was sustained for 12 m.y. and suggests a supply-dominated system. This deposystem filled relict Colville basin accommodation that had developed as a flexural response to earlier Brooks Range tectonic loading. Clinoform dip directions and detrital zircon provenance indicate that the sediment was derived primarily from Russian Chukotka during longitudinal, eastward sediment dispersal. Progradation slowed after 104 Ma when seismic stratigraphy shows a shift from progradational to aggradational shelf-margin trajectories. The shelf margin prograded only another 60 km eastward before a sequence-bounding retrogradation occurred at 96 Ma. Our chronostratigraphy quantifies that rates of progradation and sediment flux were three times greater than previously believed during the major phase of basin filling. These rates are among the highest in the world for a

3D crustal structure of the Alpine belt and foreland basins as imaged by ambient-noise surface wave

NASA Astrophysics Data System (ADS)

Molinari, Irene; Morelli, Andrea; Cardi, Riccardo; Boschi, Lapo; Poli, Piero; Kissling, Edi

2016-04-01

We derive a 3-D crustal structure (S wave velocity) underneath northern Italy and the wider Alpine region, from an extensive data set of measurements of Rayleigh-wave phase- and group-velocities from ambient noise correlation among all seismographic stations available to date in the region, via a constrained tomographic inversion made to honor detailed active source reflection/refraction profiles and other geological information. We first derive a regional-scale surface wave tomography from ambient-noise-based phase- and group- surface wave velocity observations (Verbeke et al., 2012). Our regional 3D model (Molinari et al., 2015) shows the low velocity area beneath the Po Plain and the Molasse basin; the contrast between the low-velocity crust of the Adriatic domain and the high-velocity crust of the Tyrrhenian domain is clearly seen, as well as an almost uniform crystalline crust beneath the Alpine belt. However, higher frequency data can be exploited to achieve higher resolution images of the Po Plain and Alpine foreland 3D crustal structure. We collected and analyze one year of noise records (2011) of ~100 North Italy seismic broadband stations, we derive the Green functions between each couple of stations and we measure the phase- and group-Rayleigh wave velocity. We conduct a suite of linear least squares inversion of both phase- and group-velocity data, resulting in 2-D maps of Rayleigh-wave phase and group velocity at periods between 3 and 40s with a resolution of 0.1x0.1 degrees. The maps are then inverted to get the 3D structure with unprecedented details. We present here our results, we compare them with other studies, and we discuss geological/geodynamical implications. We believe that such a model stands for the most up-to-date seismological information on the crustal structure of the Alpine belt and foreland basins, and it can represent a reliable reference for further, more detailed, studies to come, based on the high seismograph station density

In search of a Silurian total petroleum system in the Appalachian basin of New York, Ohio, Pennsylvania, and West Virginia: Chapter G.11 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Ryder, Robert T.; Swezey, Christopher S.; Trippi, Michael H.; Lentz, Erika E.; Avary, K. Lee; Harper, John A.; Kappel, William M.; Rea, Ronald G.; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

Although the TOC analyses in this study indicate that good to very good source rocks are present in the Salina Group and Wills Creek Formation of southwestern Pennsylvania and northern West Virginia, data are insufficient to propose a new Silurian total petroleum system in the Appalachian basin. However, the analytical results of this investigation are encouraging enough to undertake more systematic studies of the source rock potential of the Salina Group, Wills Creek Formation, and perhaps the Tonoloway Formation (Limestone) and McKenzie Limestone (or Member).

When did the Penglai orogeny begin on Taiwan?: Geochronological and petrographic constraints on the exhumed mountain belts and foreland-basin sequences

NASA Astrophysics Data System (ADS)

Chen, W. S.; Syu, S. J.; Yeh, J. J.

2017-12-01

Foreland basin receives large amounts of synorogenic infill that is eroded from the adjacent exhumed mountain belt, and therefore provides the important information on exhumation evolution. Furthermore, a complete stratigraphic sequence of Taiwan mountain belt consists of five units of Miocene sedimentary rocks (the Western Foothills and the uppermost sequence on the proto-Taiwan mountain belt), Oligocene argillite (the Hsuehshan Range), Eocene quartzite (the Hsuehshan Range), Eocene-Miocene slate and schist (Backbone Range), and Cretaceous schist (Backbone Range) from top to bottom. Based on the progressive unroofing history, the initiation of foreland basin received sedimentary lithic sediments from the uppermost sequence of proto-Taiwan mountain belt, afterwards, and receiving low- to medium-grade metamorphic lithic sediments in ascending order of argillite, quartzite, slate, and schist clasts. Therefore, the sedimentary lithics from mountain belt were deposited which represents the onset of the mountain uplift. In this study, the first appearance of sedimentary lithic sediments occurs in the Hengchun Peninsula at the middle Miocene (ca. 12-10 Ma). Thus, sandstone petrography of the late Miocene formation (10-5.3 Ma) shows a predominantly recycled sedimentary and low-grade metamorphic sources, including sandstone, argillite and quartzite lithic sediments of 10-25% which records erosion to slightly deeper metamorphic terrane on the mountain belt. Based on the results of previous thermogeochronological studies of the Yuli belt, it suggests that the middle Miocene occurred mountain uplift. The occurrence of low-grade metamorphic lithic sediments in the Hengchun Peninsula during late Miocene is coincident with the cooling ages of uplift and denuded Yuli schist belt at the eastern limb of Backbone Range.

Rock Magnetic Investigation of Soils and Sediments Overlying the Hydrocarbon-Bearing Silurian Pinnacle Reefs in the Michigan Basin

NASA Astrophysics Data System (ADS)

Smirnov, A. V.; Tresnak, J. P.; Anderson, K. L.

2017-12-01

Hydrocarbon reservoirs may be associated with significant magnetic anomalies arguably caused by diagenetic alteration of iron-bearing minerals in hydrocarbon seepage environments. However, complete understanding of the physical mechanisms and pathways of hydrocarbon-induced magnetic alteration requires a robust and representative observational database. In order to facilitate the fundamental understanding of the magnetic signature of hydrocarbons, we conducted an investigation of the relationship between the hydrocarbon migration and magnetic properties of sediments overlaying the oil-bearing formations of the Silurian northern pinnacle reef belt of the Michigan Basin. Several hundreds of near-surface soil and sediment samples were collected across several long transects across the trend of the Niagaran Reef System and represented areas both over and away from known hydrocarbon sources. The samples were investigated by a variety of microscopy and rock magnetic methods. Our data indicate that the relationship between the hydrocarbon reservoirs and low-field magnetic susceptibility over the Niagaran pinnacle reef belt in the Michigan Basin is not straightforward. Both very high and very low susceptibility values have been observed within the extent of the reef belt in the studied area. The observed magnetic susceptibility anomalies may reflect the hydrological gradients in the uppermost glaciofluvial aquifer. However, a good correlation with the Devonian hydrocarbon reservoirs outside of the reef belt indicates a potential of the surface magnetic susceptibility method for hydrocarbon detection at a smaller scale.

Geology and hydrocarbon potential of the Hamada and Murzuq basins in western Libya

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

Kirmani, K.U.; Elhaj, F.

1988-08-01

The Hamada and Murzuq intracratonic basins of western Libya form a continuation of the Saharan basin which stretches from Algeria eastward into Tunisia and Libya. The tectonics and sedimentology of this region have been greatly influenced by the Caledonian and Hercynian orogenies. Northwest- and northeast-trending faults are characteristic of the broad, shallow basins. The Cambrian-Ordovician sediments are fluvial to shallow marine. The Silurian constitutes a complete sedimentary cycle, ranging from deep marine shales to shallow marine and deltaic sediments. The Devonian occupies a unique position between two major orogenies. The Mesozoic strata are relatively thin. The Triassic consists of well-developedmore » continental sands, whereas the Jurassic and Cretaceous sediments are mainly lagoonal dolomites, evaporites, and shales. Silurian shales are the primary source rock in the area. The quality of the source rock appears to be better in the deeper part of the basin than on its periphery. The Paleozoic has the best hydrocarbon potential. Hydrocarbons have also been encountered in the Triassic and Carboniferous. In the Hamada basin, the best-known field is the El Hamra, with reserves estimated at 155 million bbl from the Devonian. Significant accumulations of oil have been found in the Silurian. Tlacsin and Tigi are two fields with Silurian production. In the Murzuq basin the Cambrian-Ordovician has the best production capability. However, substantial reserves need to be established before developing any field in this basin. Large areas still remain unexplored in western Libya.« less

3D Architecture and evolution of the Po Plain-Northern Adriatic Foreland basin during Plio-Pleistocene time

NASA Astrophysics Data System (ADS)

Amadori, Chiara; Toscani, Giovanni; Ghielmi, Manlio; Maesano, Francesco Emanuele; D'Ambrogi, Chiara; Lombardi, Stefano; Milanesi, Riccardo; Panara, Yuri; Di Giulio, Andrea

2017-04-01

The Pliocene-Pleistocene tectonic and sedimentary evolution of the eastern Po Plain and northern Adriatic Foreland Basin (PPAF) (extended ca. 35,000 km2) was the consequence of severe Northern Apennine compressional activity and climate-driven eustatic changes. According with the 2D seismic interpretation, facies analysis and sequence stratigraphy approach by Ghielmi et al. (2013 and references therein), these tectono-eustatic phases generated six basin-scale unconformities referred as Base Pliocene (PL1), Intra-Zanclean (PL2), Intra-Piacenzian (PL3), Gelasian (PL4), Base Calabrian (PS1) and Late Calabrian (PS2). We present a basin-wide detailed 3D model of the PPAF region, derived from the interpretation of these unconformities in a dense network of seismic lines (ca. 6,000 km) correlated with more than 200 well stratigraphies (courtesy of ENI E&P). The initial 3D time-model has been time-to-depth converted using the 3D velocity model created with Vel-IO 3D, a tool for 3D depth conversions and then validated and integrated with depth domain dataset from bibliography and well log. Resultant isobath and isopach maps are produced to inspect step-by-step the basin paleogeographic evolution; it occurred through alternating stages of simple and fragmented foredeeps. Changes in the basin geometry through time, from the inner sector located in the Emilia-Romagna Apennines to the outermost region (Veneto and northern Adriatic Sea), were marked by repeated phases of outward migration of two large deep depocenters located in front of Emilia arcs on the west, and in front of Ferrara-Romagna thrusts on the east. During late Pliocene-early Pleistocene, the inner side of the Emilia-Romagna arcs evolved into an elongated deep thrust-top basin due to a strong foredeep fragmentation then, an overall tectono-stratigraphic analysis shows also a decreasing trend of tectonic intensity of the Northern Apennine since Pleistocene until present.

Flexural bending of southern Tibet in a retro foreland setting

PubMed Central

Wang, Erchie; Kamp, Peter J. J.; Xu, Ganqing; Hodges, Kip V.; Meng, Kai; Chen, Lin; Wang, Gang; Luo, Hui

2015-01-01

The highest elevation of the Tibetan Plateau, lying 5,700 m above sea level, occurs within the part of the Lhasa block immediately north of the India-Tibet suture zone (Yarlung Zangbo suture zone, YZSZ), being 700 m higher than the maximum elevation of more northern parts of the plateau. Various mechanisms have been proposed to explain this differentially higher topography and the rock uplift that led to it, invoking crustal compression or extension. Here we present the results of structural investigations along the length of the high elevation belt and suture zone, which rather indicate flexural bending of the southern margin of the Lhasa block (Gangdese magmatic belt) and occurrence of an adjacent foreland basin (Kailas Basin), both elements resulting from supra-crustal loading of the Lhasa block by the Zangbo Complex (Indian plate rocks) via the Great Counter Thrust. Hence we interpret the differential elevation of the southern margin of the plateau as due originally to uplift of a forebulge in a retro foreland setting modified by subsequent processes. Identification of this flexural deformation has implications for early evolution of the India-Tibet continental collision zone, implying an initial (Late Oligocene) symmetrical architecture that subsequently transitioned into the present asymmetrical wedge architecture. PMID:26174578

Reinterpretation of Halokinetic Features in the Ancestral Rocky Mountains Paradox Salt Basin, Utah and Colorado

NASA Astrophysics Data System (ADS)

Thompson, J. A.; Giles, K. A.; Rowan, M. G.; Hearon, T. E., IV

2016-12-01

The Paradox Basin in southeastern Utah and southwestern Colorado is a foreland basin formed in response to flexural loading by the Pennsylvanian-aged Uncompaghre uplift during the Ancestral Rocky Mountain orogen. Thick sequences of evaporites (Paradox Formation) were deposited within the foreland basin, which interfinger with clastic sediments in the foredeep and carbonates around the basin margin. Differential loading of the Pennsylvanian-Jurassic sediments onto the evaporites drove synsedimentary halokinesis, creating a series of salt walls and adjacent minibasins within the larger foreland basin. The growing salt walls within the basin influenced patterns of sediment deposition from the Pennsylvanian through the Cretaceous. By integrating previously published mapping with recent field observations, mapping, and subsurface interpretations of well logs and 2D seismic lines, we present interpretations of the timing, geometry, and nature of halokinesis within the Paradox Basin, which record the complex salt tectonic history in the basin. Furthermore, we present recent work on the relationships between the local passive salt history and the formation of syndepositional counter-regional extensional fault systems within the foreland. These results will be integrated into a new regional salt-tectonic and stratigraphic framework of the Paradox Basin, and have broader implications for interpreting sedimentary records in other basins with a mobile substrate.

Cenozoic sedimentary dynamics of the Ouarzazate foreland basin (Central High Atlas Mountains, Morocco)

NASA Astrophysics Data System (ADS)

El Harfi, A.; Lang, J.; Salomon, J.; Chellai, E. H.

2001-06-01

Cenozoic continental sedimentary deposits of the Southern Atlas named "Imerhane Group" crop out (a) in the Ouarzazate foreland basin between the Precambrian basement of the Anti Atlas and the uplifted limestone dominated High Atlas, and (b) in the Aït Kandoula and Aït Seddrat nappes where Jurassic strata detached from the basement have been thrust southwards over the Ouarzazate Basin. New biostratigraphic and geochronological data constraining the final Eocene marine regression, the characterization of the new "Aït Ouglif Detrital Formation" presumed to be of Oligocene age, and the new stratigraphic division proposed for the Continental Imerhane Group clarify the major tectonogenetic alpidic movements of the Central High Atlas Range. Four continental formations are identified at regional scale. Their emplacement was governed principally by tectonic but also by eustatic controls. The Hadida and Aït Arbi formations (Upper Eocene) record the major Paleogene regression. They are composed of margino-littoral facies (coastal sabkhas and fluviatile systems) and reflect incipient erosion of the underlying strata and renewed fluvial drainage. The Aït Ouglif Formation (presumed Oligocene) had not been characterized before. It frequently overlies all earlier formations with an angular unconformity. It includes siliciclastic alluvial deposits and is composed predominantly of numerous thin fining-upward cycles. The Aït Kandoula Formation (Miocene-Pliocene) is discordant, extensive, and represents a thick coarsening-upward megasequence. It is composed of palustro-lacustrine deposits in a context of alluvial plain with localized sabkhas, giving way to alluvial fans and fluviatile environments. The Upper Conglomeratic Formation (Quaternary) is the trace of a vast conglomeratic pediment, forming an alluvial plain and terraces. The second and third formations correspond to two megasequences engendered by the uplift of the Central High Atlas in two major compressive phases

Provenance and geochronological insights into Late Cretaceous-Paleogene foreland basin development in the Subandean Zone and Oriente Basin of Ecuador

NASA Astrophysics Data System (ADS)

Gutierrez, E. G.; Horton, B. K.; Vallejo, C.

2017-12-01

The tectonic history of the Oriente foreland basin and adjacent Subandean Zone of Ecuador during contractional mountain building in the northern Andes can be revealed through integrated stratigraphic, geochronological, structural, and provenance analyses of clastic sediments deposited during orogenesis. We present new maximum depositional ages and a comprehensive provenance analysis for key stratigraphic units deposited in the western (proximal) Oriente Basin. Detrital zircon U-Pb ages were obtained from Upper Cretaceous and Cenozoic clastic formations from exposures in the Subandean Zone. The sampled stratigraphic intervals span critical timeframes during orogenesis in the Ecuadorian Andes. Cenozoic formations have poorly defined chronostratigraphic relationships and are therefore a primary target of this study. In addition, the newly acquired U-Pb age spectra allow clear identification of the various sediment source regions that fed the system during distinct depositional phases. Maximum depositional ages (MDA) were obtained for five samples from three formations: the Tena (MDA=69.6 Ma), Chalcana (MDA=29.3 Ma), and Arajuno (MDA= 17.1, 14.2, 12.8 Ma) Formations, placing them in the Maastrichtian, early Oligocene, and early-middle Miocene, respectively. Detrital zircon U-Pb ages identify clear signatures of at least four different sources: craton (1600-1300 Ma, 1250-900 Ma), Eastern Cordillera fold-thrust belt (600-450 Ma, 250-145 Ma), Western Cordillera magmatic arc (<88 Ma), and recycling of cratonic material from the Eastern Cordillera. The U-Pb age spectra of the Upper Cretaceous-Paleogene type sections allow us to recognize variations in the contribution of each recognized source over time. We identify recycled material with two dominant peak ages (1250-900 Ma and 600-450 Ma), material derived from the adjacent uplifted orogen or recycled from foredeep sediments incorporated into the deforming wedge. Finally, an apparent unroofing event is inferred from a 250

The Santa Cruz - Tarija Province of Central South America: Los Monos - Machareti(!) Petroleum System

USGS Publications Warehouse

Lindquist, Sandra J.

1999-01-01

The Los Monos - Machareti(!) total petroleum system is in the Santa Cruz - Tarija Province of Bolivia, Argentina and Paraguay. Province history is that of a Paleozoic, intracratonic, siliciclastic rift basin that evolved into a Miocene (Andean) foreland fold and thrust belt. Existing fields are typified by alternating reservoir and seal rocks in post-Ordovician sandstones and shales on anticlines. Thick Devonian and Silurian shale source rocks, depositionally and erosionally confined to this province, at a minimum have generated 4.1 BBOE known ultimate recoverable reserves (as of 1995, 77% gas, 15% condensate, 8% oil) into dominantly Carboniferous reservoirs with average 20% porosity and 156 md permeability. Major detachment surfaces within the source rocks contributed to the thin-skinned and laterally continuous nature of the deformation. Tertiary foreland burial adequate for significant source maturation coincided with the formation of compressional traps. Further hydrocarbon discovery in the fold and thrust belt is expected. In the foreland basin, higher thermal gradients and variable burial history - combined with the presence of unconformity and onlap wedges - create potential there for stratigraphic traps and pre-Andean, block-fault and forced-fold traps.

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

NASA Astrophysics Data System (ADS)

Jarochowska, Emilia; Munnecke, Axel

2016-04-01

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

The lithospheric-scale 3D structural configuration of the North Alpine Foreland Basin constrained by gravity modelling and the calculation of the 3D load distribution

NASA Astrophysics Data System (ADS)

Przybycin, Anna M.; Scheck-Wenderoth, Magdalena; Schneider, Michael

2014-05-01

The North Alpine Foreland Basin is situated in the northern front of the European Alps and extends over parts of France, Switzerland, Germany and Austria. It formed as a wedge shaped depression since the Tertiary in consequence of the Euro - Adriatic continental collision and the Alpine orogeny. The basin is filled with clastic sediments, the Molasse, originating from erosional processes of the Alps and underlain by Mesozoic sedimentary successions and a Paleozoic crystalline crust. For our study we have focused on the German part of the basin. To investigate the deep structure, the isostatic state and the load distribution of this region we have constructed a 3D structural model of the basin and the Alpine area using available depth and thickness maps, regional scale 3D structural models as well as seismic and well data for the sedimentary part. The crust (from the top Paleozoic down to the Moho (Grad et al. 2008)) has been considered as two-parted with a lighter upper crust and a denser lower crust; the partition has been calculated following the approach of isostatic equilibrium of Pratt (1855). By implementing a seismic Lithosphere-Asthenosphere-Boundary (LAB) (Tesauro 2009) the crustal scale model has been extended to the lithospheric-scale. The layer geometry and the assigned bulk densities of this starting model have been constrained by means of 3D gravity modelling (BGI, 2012). Afterwards the 3D load distribution has been calculated using a 3D finite element method. Our results show that the North Alpine Foreland Basin is not isostatically balanced and that the configuration of the crystalline crust strongly controls the gravity field in this area. Furthermore, our results show that the basin area is influenced by varying lateral load differences down to a depth of more than 150 km what allows a first order statement of the required compensating horizontal stress needed to prevent gravitational collapse of the system. BGI (2012). The International

Glacier meltwater flow paths and storage in a geomorphologically complex glacial foreland: The case of the Tapado glacier, dry Andes of Chile (30°S)

NASA Astrophysics Data System (ADS)

Pourrier, J.; Jourde, H.; Kinnard, C.; Gascoin, S.; Monnier, S.

2014-11-01

The Tapado catchment is located in the upper Elqui river basin (4000-5550 m) in northern Chile. It comprises the Tapado glacial complex, which is an assemblage of the Tapado glacier and the glacial foreland (debris-covered glacier, rock glacier, and moraines). Although the hydrological functioning of this catchment is poorly known, it is assumed to actively supply water to the lower semi-arid areas of the Elqui river basin. To improve our knowledge of the interactions and water transfers between the cryospheric compartment (glacier, debris-covered glacier, and rock glacier) and the hydrological compartment (aquifers, streams), the results of monitoring of meteorological conditions, as well as discharge, conductivity and temperature of streams and springs located in the Tapado catchment were analyzed. The hydrological results are compared to results inferred from a ground penetrating radar (GPR) survey of the underground structure of the glacial foreland. Water production from the Tapado glacier was shown to be highly correlated with daily and monthly weather conditions, particularly solar radiation and temperature. The resulting daily and monthly streamflow cycles were buffered by the glacial foreland, where underground transfers took place through complex flow paths. However, the development of a thermokarst drainage network in a portion of the glacial foreland enabled rapid concentrated water transfers that reduced the buffer effect. The glacial foreland was shown to act as a reservoir, storing water during high melt periods and supplying water to downstream compartments during low melt periods. GPR observations revealed the heterogeneity of the internal structure of the glacial foreland, which is composed of a mixture of ice and rock debris mixture, with variable spatial ice content, including massive ice lenses. This heterogeneity may explain the abovementioned hydrological behaviors. Finally, calculation of a partial hydrological budget confirmed the

Late Burdigalian sea retreat from the North Alpine Foreland Basin: new magnetostratigraphic age constraints

NASA Astrophysics Data System (ADS)

Sant, K.; Kirscher, U.; Reichenbacher, B.; Pippèrr, M.; Jung, D.; Doppler, G.; Krijgsman, W.

2017-05-01

Accurate reconstruction of the final sea retreat from the North Alpine Foreland Basin (NAFB) during the Burdigalian (Early Miocene) is hampered by a lack of reliable age constraints. In this high resolution magnetostratigraphic study we try to solve a significant age bias for the onset of the Upper Freshwater Molasse (OSM) deposition in the neighboring S-German and Swiss Molasse Basins. We measured > 550 samples from eleven drill cores covering the transition from marine to brackish to freshwater environments in the S-German Molasse Basin. Based on combined bio-, litho- and magnetostratigraphic constraints, the composite magnetostratigraphic pattern of these cores provides two reasonable age correlation options (model 1 and 2). In model 1, the base of the brackish succession lies within Chron C5Cr ( 16.7-17.2 Ma), and the onset of OSM deposition has an age of 16.5 Ma. Correlation model 2 suggests the transition to brackish conditions to be within C5Dr.1r ( 17.7-17.5 Ma), and yields an age around 16.7 Ma for the shift to the OSM. Most importantly, both models confirm a much younger age for the OSM base in the study area than previously suggested. Our results demonstrate a possible coincidence of the last transgressive phase (Kirchberg Fm) with the Miocene Climatic Optimum (model 1), or with the onset of this global warming event (model 2). In contrast, the final retreat of the sea from the study area is apparently not controlled by climate change. Supplementary material B. Profiles of the eleven studied drill cores including lithologies, all magnetostratigraphic data (inclinations), interpreted polarity pattern (this study and Reichenbacher et al., 2013) and magnetic susceptibility (this study). Legend for graphs on page 1. Samples without a stable direction above 200 °C or 20 mT are depicted as +-signs and plotted at 0° inclination. The interpreted normal (black), reversed (white) and uncertain (grey) polarity zones in the polarity columns are based on at least

Possible continuous-type (unconventional) gas accumulation in the Lower Silurian "Clinton" sands, Medina Group and Tuscarora Sandstone in the Appalachian Basin; a progress report of the 1995 project activities

USGS Publications Warehouse

Ryder, Robert T.; Aggen, Kerry L.; Hettinger, Robert D.; Law, Ben E.; Miller, John J.; Nuccio, Vito F.; Perry, William J.; Prensky, Stephen E.; Filipo, John J.; Wandrey, Craig J.

1996-01-01

INTRODUCTION: In the U.S. Geological Survey's (USGS) 1995 National Assessment of United States oil and gas resources (Gautier and others, 1995), the Appalachian basin was estimated to have, at a mean value, about 61 trillion cubic feet (TCF) of recoverable gas in sandstone and shale reservoirs of Paleozoic age. Approximately one-half of this gas resource is estimated to reside in a regionally extensive, continuous-type gas accumulation whose reservoirs consist of low-permeability sandstone of the Lower Silurian 'Clinton' sands and Medina Group (Gautier and others, 1995; Ryder, 1995). Recognizing the importance of this large regional gas accumulation for future energy considerations, the USGS initiated in January 1995 a multi-year study to evaluate the nature, distribution, and origin of natural gas in the 'Clinton' sands, Medina Group sandstones, and equivalent Tuscarora Sandstone. The project is part of a larger natural gas project, Continuous Gas Accumulations in Sandstones and Carbonates, coordinated in FY1995 by Ben E. Law and Jennie L. Ridgley, USGS, Denver. Approximately 2.6 man years were devoted to the Clinton/Medina project in FY1995. A continuous-type gas accumulation, referred to in the project, is a new term introduced by Schmoker (1995a) to identify those natural gas accumulations whose reservoirs are charged throughout with gas over a large area and whose entrapment does not involve a downdip gas-water contact. Gas in these accumulations is located downdip of the water column and, thus, is the reverse of conventional-type hydrocarbon accumulations. Commonly used industry terms that are more or less synonymous with continuous-type gas accumulations include basin- centered gas accumulation (Rose and others, 1984; Law and Spencer, 1993), tight (low-permeability) gas reservoir (Spencer, 1989; Law and others, 1989; Perry, 1994), and deep basin gas (Masters, 1979, 1984). The realization that undiscovered gas in Lower Silurian sandstone reservoirs of the

Linkages Between Cretaceous Forearc and Retroarc Basin Development in Southern Tibet

NASA Astrophysics Data System (ADS)

Orme, D. A.; Laskowski, A. K.

2015-12-01

Integrated provenance and subsidence analysis of forearc and retroarc foreland basin strata were used to reconstruct the evolution of the southern margin of Eurasia during the Early to Late Cretaceous. The Cretaceous-Eocene Xigaze forearc basin, preserved along ~600 km of the southern Lhasa terrane, formed between the Gangdese magmatic arc and accretionary complex as subduction of Neo-Tethyan oceanic lithosphere accommodated the northward motion and subsequent collision of the Indian plate. Petrographic similarities between Xigaze forearc basin strata and Cretaceous-Eocene sedimentary rocks of the northern Lhasa terrane, interpreted as a retroarc foreland basin, were previously interpreted to record N-S trending river systems connecting the retro- and forearc regions during Cretaceous time. New sandstone petrographic and U-Pb detrital zircon provenance analysis of Xigaze forearc basin strata support this hypothesis. Qualitative and statistical provenance analysis using cumulative distribution functions and Kolmogorov-Smirnov (K-S) tests show that the forearc basin was derived from either the same source region as or recycled from the foreland basin. Quartz-rich sandstones with abundant carbonate sedimentary lithic grains and rounded, cobble limestone clasts suggests a more distal source than the proximal Gangdese arc. Therefore, we interpret that the northern Lhasa terrane was a significant source of Xigaze forearc detritus and track spatial and temporal variability in the connection between the retro- and forearc basin systems during the Late Cretaceous. A tectonic subsidence curve for the Xigaze forearc basin shows a steep and "kinked" shape similar to other ancient and active forearc basins. Initial subsidence was likely driven by thermal relaxation of the forearc ophiolite after emplacement while additional periods of rapid subsidence likely result from periods of high flux magmatism in the Gangdese arc and changes in plate convergence rate. Comparison of the

Basins in ARC-continental collisions

USGS Publications Warehouse

Draut, Amy E.; Clift, Peter D.; Busby, Cathy; Azor, Antonio

2012-01-01

collisional orogenesis ends up in the foreland basin that forms as a result of collision, and may be preserved largely undeformed. Compared to continent-continent collisional foreland basins, arc-continent collisional foreland basins are short-lived and may undergo partial inversion after collision as a new, active continental margin forms outboard of the collision zone and the orogen whose load forms the basin collapses in extension.

Slab rollback orogeny in the Alps and evolution of the Swiss Molasse basin

PubMed Central

Schlunegger, Fritz; Kissling, Edi

2015-01-01

The stratigraphies of foreland basins have been related to orogeny, where continent–continent collision causes the construction of topography and the downwarping of the foreland plate. These mechanisms have been inferred for the Molasse basin, stretching along the northern margin of the European Alps. Continuous flexural bending of the subducting European lithosphere as a consequence of topographic loads alone would imply that the Alpine topography would have increased at least between 30 Ma and ca. 5–10 Ma when the basin accumulated the erosional detritus. This, however, is neither consistent with observations nor with isostatic mass balancing models because paleoaltimetry estimates suggest that the topography has not increased since 20 Ma. Here we show that a rollback mechanism for the European plate is capable of explaining the construction of thick sedimentary successions in the Molasse foreland basin where the extra slab load has maintained the Alpine surface at low, but constant, elevations. PMID:26472498

Foreland crustal structure of the New York recess, northeastern United States

USGS Publications Warehouse

Herman, G.C.; Monteverde, D.H.; Schlische, R.W.; Pitcher, D.M.

1997-01-01

A new structural model for the northeast part of the Central Appalachian foreland and fold-and-thrust belt is based on detailed field mapping, geophysical data, and balanced cross-section analysis. The model demonstrates that the region contains a multiply deformed, parautochthonous fold-and-thrust system of Paleozoic age. Our interpretations differ from previous ones in which the entire region north of the Newark basin was considered to be allochthonous. The new interpretation requires a substantial decrease in Paleozoic tectonic shortening northeastward from adjacent parts of the Central Appalachian foreland and illustrates the common occurrence of back-thrusting within the region. During early Paleozoic time northern New Jersey consisted of a Taconic orogenic foreland in which cover folds (F1) involved lower Paleozoic carbonate and flysch overlying Middle Proterozoic basement. F1 folds are open and upright in the foreland and more gently inclined to recumbent southeastward toward the trace of the Taconic allochthons. F1 structures were cut and transported by a fold-and-thrust system of the Allegheny orogeny. This thrust system mostly involves synthetic faults originating from a master decollement rooted in Proterozoic basement. Antithetic faults locally modify early synthetic overthrusts and S1 cleavage in lower Paleozoic cover and show out-of-sequence structural development. The synthetic parts of the regional thrust system are bounded in the northwestern foreland by blind antithetic faults interpreted from seismic-reflection data. This antithetic faulting probably represents Paleozoic reactivation of Late Proterozoic basement faults. Tectonic contraction in overlying cover occurred by wedge faulting where synthetic and antithetic components of the foreland fault system overlap. S2 cleavage in the Paleozoic cover stems from Alleghanian shortening and flattening and commonly occurs in the footwall of large overthrust sheets. Paleozoic structures in Proterozoic

Tectono-sedimentary evolution of the Neuquén basin (Argentina) between 39°S and 41°S during the Neogene

NASA Astrophysics Data System (ADS)

Huyghe, D.; Bonnel, C.; Nivière, B.; Messager, G.; Dhont, D.; Fasentieux, B.; Hervouët, Y.; Xavier, J.-P.

2012-04-01

Sedimentary rocks deposited in foreland basins are of primary interest, because they record the interactions between the growth of the orogenic wedge, the isostatic readjustment of the lithosphere, the variations of base-level and earth surface process. The Neuquén basin (32°S - 41°S) is a triangular shape foreland basin located on the eastern flank of the Andes. Its filling began during the late Triassic, first as back arc basin context and as compressive foreland basin since the upper Cretaceous. The structural inheritance is thus important and old basement structures, like the Huincul Ridge, generate significant variations of both deformation and shortening. Its Mesozoic history is well constrained due to its hydrocarbon potential. In comparison, its Cenozoic history remains poorly documented. The modern configuration of this basin results from several successive compressive tectonic phases. The last one is dated from the Miocene (Quechua phase) and has conditioned the segmentation of the foreland basin in several intra-mountainous sub-basins, whose sedimentary filling could reach several hundred meters. In this work, we document the relative chronology of the geological events and the sedimentary processes that have governed the Cenozoic history of the southern part of the Neuquen basin, to discriminate the relative rules of climatic and structural controlling factors on the evolution of the depocentres. Several NNW-SSE oriented intra-mountainous basins exist in this part of the Andes (Collon Cura basin and Catan Lil basin). On the contrary the associated foreland basin (Picun Leufu basin) is relatively underformed and is bounded to the North by the Huincul ridge and the North Patagonian massif to the South. Fifteen sedimentary sections have been studied along the Rio Limay River in the southern border of the basin, from the range to the external part of the foreland. The sedimentation is discontinuous in time and important retrogradations of the depocentres

Silurian shale origin for light oil, condensate, and gas in Algeria and the Middle East

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

Zumberge, J.E.; Macko, S.

1996-01-01

Two of the largest gas fields in the world, Hasi R'Mel, Algeria and North Dome, Qatar, also contain substantial condensate and light oil reserves. Gas to source rock geochemical correlation is difficult due to the paucity of molecular parameters in the former although stable isotope composition is invaluable. However, by correlating source rocks with light oils and condensates associated with gas production using traditional geochemical parameters such as biomarkers and isotopes, a better understanding of the origin of the gas is achieved. Much of the crude oil in the Ghadames/Illizi Basins of Algeria has long been thought to have beenmore » generated from Silurian shales. New light oil discoveries in Saudi Arabia have also been shown to originate in basal euxinic Silurian shales. Key sterane and terpane biomarkers as well as the stable carbon isotopic compositions of the C15+ saturate and aromatic hydrocarbon fractions allow for the typing of Silurian-sourced, thermally mature light oils in Algeria and the Middle East. Even though biomarkers are often absent due to advanced thermal maturity, condensates can be correlated to the light oils using (1) carbon isotopes of the residual heavy hydrocarbon fractions, (2) light hydrocarbon distributions (e.g., C7 composition), and (3) compound specific carbon isotopic composition of the light hydrocarbons. The carbon isotopes of the C2-C4 gas components ran then be compared to the associated condensate and light oil isotopic composition.« less

Silurian shale origin for light oil, condensate, and gas in Algeria and the Middle East

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

Zumberge, J.E.; Macko, S.

Two of the largest gas fields in the world, Hasi R`Mel, Algeria and North Dome, Qatar, also contain substantial condensate and light oil reserves. Gas to source rock geochemical correlation is difficult due to the paucity of molecular parameters in the former although stable isotope composition is invaluable. However, by correlating source rocks with light oils and condensates associated with gas production using traditional geochemical parameters such as biomarkers and isotopes, a better understanding of the origin of the gas is achieved. Much of the crude oil in the Ghadames/Illizi Basins of Algeria has long been thought to have beenmore » generated from Silurian shales. New light oil discoveries in Saudi Arabia have also been shown to originate in basal euxinic Silurian shales. Key sterane and terpane biomarkers as well as the stable carbon isotopic compositions of the C15+ saturate and aromatic hydrocarbon fractions allow for the typing of Silurian-sourced, thermally mature light oils in Algeria and the Middle East. Even though biomarkers are often absent due to advanced thermal maturity, condensates can be correlated to the light oils using (1) carbon isotopes of the residual heavy hydrocarbon fractions, (2) light hydrocarbon distributions (e.g., C7 composition), and (3) compound specific carbon isotopic composition of the light hydrocarbons. The carbon isotopes of the C2-C4 gas components ran then be compared to the associated condensate and light oil isotopic composition.« less

Investigating Environmental Tectonics in Northern Alpine Foreland of Europe

NASA Astrophysics Data System (ADS)

Cloetingh, Sierd; Ziegler, Peter; Cornu, Tristan; Ustaszewski, K.; Schmid, S.; Dezes, P.; Hinsch, R.; Decker, K.; Lopes Cardozo, G.; Granet, M.; Bertrand, G.; Behrmann, J.; Michon, L.; Pagnier, H.; van Wees, J. D.; Rozsa, S.; Heck, B.; Verdun, J.; Kahle, H. G.; Fracassi, U.; Winter, T.; Burov, E.

Until now, research on neotectonics and related seismicity has mostly focused on active plate boundaries characterized by a generally high level of earthquake activity. Current seismic hazard estimates for intraplate areas are commonly based on probabilistic analyses of historical and instrumental earthquake data. The accuracy of these hazard estimates is limited by the nature of the data (e.g., ambiguous historical sources), and by the restriction of available earthquake catalogues to time scales of only few hundred years. Both of these are geologically insignificant and unsuitable for describing tectonic processes causing earthquakes. This is especially relevant to intraplate regions, where faults show low slip rates resulting in long average recurrence times for large earthquakes (103 to 106 yrs), such as the devastating Basel earthquake of 1356, with an estimated magnitude of 6.5. The Alpine orogen and the intraplate sedimentary basins and rifts of its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed. Seismicity and stress indicator data, combined with geodetic and geomorphologic observations, demonstrate that the Northern Alpine foreland is being actively deformed [Cloetingh, 2000; Ziegler et al., 2002; Behrmann et al., 2003]. This has major implications for the assessment of their natural hazards and environmental degradation. The northwest European lithosphere has undergone a polyphase evolution, in which the interplay between upper mantle thermal perturbations [Goes et al., 2000; Ritter et al., 2001] and stress-induced intraplate deformation [Muller et al., 1992; Ziegler et al., 2002] played an important role. A number of recent findings point to an important role of lithospheric folding in thermally weakened lithosphere of the northwestern European foreland [Cloetingh et al., 1999].

Modeling and Inversion of three-dimensional crustal structures beneath the Pyrenees and their foreland basins based upon geological, gravimetric and seismological data

NASA Astrophysics Data System (ADS)

Spangenberg, Hannah; Chevrot, Sébastien; Courrioux, Gabriel; Guillen, Antonio

2017-04-01

Our goal is to obtain a three-dimensional (3D) model of mass density and seismic velocities beneath the Pyrenees and their foreland basins (Aquitaine and Ebro basins), which accounts for all the geological and geophysical information available for that region. This model covers the whole mountain range going from the Atlantic Ocean to the Mediterranean Sea, and from the Iberian range to the Massif Central. The model is described by different units: the lower, middle, and upper crusts, the accretionary prism, and the consolidated and unconsolidated sediment layers. Furthermore, a sub-continental, serpentinized European mantle is introduced to describe the exhumed mantle bodies which are responsible for the positive Bouguer gravity anomalies in the western Pyrenees. We build a first 3D model using all the geological information: drill-hole surveys, seismic sections, and the geological map. We use the potential field method implemented in Geomodeler to interpolate these geological data. However, these data are too sparse to build a model that explains seismic travel times or gravimetric data, especially the Labourd and the St. Gaudens Bouguer gravity anomalies. In addition, inconsistencies between the different data sets exist. We thus add by trial and error additional data points, comparing modeled and observed Bouguer gravimetric anomalies. The result of this procedure is a 3D geological model that respects the geological data and explains the measured Bouguer gravimetric anomalies. In a second step, we use this model to determine the average density and seismic velocities inside each geological unit assuming uniform layers. To constrain the seismic velocities we use travel time picks extracted from the bulletin of the Pyrenean seismicity released by the Observatoire Midi Pyrenées. In a third step, we use this 3D a priori model in a Monte Carlo inversion to invert jointly gravimetric data and seismic travel times from the bulletin. This probabilistic approach

Early Neogene foreland of the Zagros, implications for the initial closure of the Neo-Tethys and kinematics of crustal shortening

NASA Astrophysics Data System (ADS)

Pirouz, Mortaza; Avouac, Jean-Philippe; Hassanzadeh, Jamshid; Kirschvink, Joseph L.; Bahroudi, Abbas

2017-11-01

We study the transition from passive margin to foreland basin sedimentation now exposed in the High Zagros belt to provide chronological constraints on the initial stage of Arabia-Eurasia collision and closure of the Neo-Tethys. We performed magnetostratigraphy and strontium isotope stratigraphy along two sections near the Zagros suture which expose the oldest preserved foreland deposits: the Shalamzar section in the west and the Dehmoord section in the east. The top of the passive margin Asmari formation has an age of 28-29 Ma in the High Zagros and is overlain by foreland deposits with a major basal unconformity representing 7 Myr of hiatus. The base of the foreland deposits has an age of 21.5 Ma at Dehmoord and ca. 26 Ma at Shalamzar. The sedimentation rate increased from 30 m/Myr in the passive margin to 247 m/Myr in the foreland. Combined with available age constraints across the Zagros, our results show that the unconformity is diachronous and records the southwestward migration of the flexural bulge within the Arabian plate at an average rate of 24 ± 2 mm/yr over the last 27 Ma. The time evolution of sediment accumulation in the Zagros foreland follows the prediction from a flexural model, as the foreland is thrust beneath the orogenic wedge and loaded by the wedge and basin fill. We detect the onset of forebulge formation within the Asmari Formation around 25 Ma. We conclude that closure of the Neo-Tethys formed the Zagros collisional wedge at 27 ± 2 Ma. Hence, the Arabia-Eurasia collision was probably not the main driver of global cooling which started near the Eocene-Oligocene boundary (ca. 33.7 Ma). We estimate 650 km of forebulge migration since the onset of the collision which consists of 350 km of shortening across the orogen, and 300 km of widening of the wedge and increasing flexural rigidity of Arabia. We conclude the average rate of shortening across the Zagros to be ca. 13 mm/yr over the last 27 Myr; a value comparable to the modern rate

Chemostratigraphic and U-Pb geochronologic constraints on carbon cycling across the Silurian-Devonian boundary

NASA Astrophysics Data System (ADS)

Husson, Jon M.; Schoene, Blair; Bluher, Sarah; Maloof, Adam C.

2016-02-01

The Devonian Period hosts extraordinary changes to Earth's biosphere. Land plants began their rise to prominence, with early vascular vegetation beginning its colonization of near-shore environments in the latest Silurian. Across the Silurian-Devonian (Pridoli-Lochkovian) transition, carbon isotope analyses of bulk marine carbonates (δC13carb) from Laurentian and Baltic successions reveal a positive δC13carb shift. Known as the Klonk Event, values reach + 5.8 ‰, making it one of the largest carbon isotope excursions in the Phanerozoic. Assigning rates and durations to these significant events requires a robust, precise Devonian time scale. Here we present 675 micritic matrix and 357 fossil-specific δC13carb analyses from the lower Devonian Helderberg Group of New York and West Virginia that exhibit the very positive δC13carb values observed in other Silurian-Devonian basins. This chemostratigraphic dataset is coupled with 66 ID-TIMS U-Pb dates on single zircons from six ash falls intercalated within Helderberg sediments, including dates on the stratigraphically lowest Devonian ashes yet developed. In this work, we (a) demonstrate that matrix and fossil-specific δC13carb values track one another closely in the Helderberg Group, (b) estimate the Silurian-Devonian boundary age in New York to be 421.3 ± 1.2 Ma (2σ; including decay constant uncertainties), and (c) calculate the time required to evolve from baseline to peak δC13carb values at the onset of the Klonk event to be 1.00 ± 0.25 Myr. Under these constraints, a steady-state perturbation to the global carbon cycle can explain the observed excursion with modern fluxes, as long as DIC concentration in the Devonian ocean remained below ∼2× the modern value. Therefore, potential drivers, such as enhanced burial of organic carbon, need not rely on anomalously high total fluxes of carbon to explain the Klonk Event.

The largest Silurian vertebrate and its palaeoecological implications

PubMed Central

Choo, Brian; Zhu, Min; Zhao, Wenjin; Jia, Liaotao; Zhu, You'an

2014-01-01

An apparent absence of Silurian fishes more than half-a-metre in length has been viewed as evidence that gnathostomes were restricted in size and diversity prior to the Devonian. Here we describe the largest pre-Devonian vertebrate (Megamastax amblyodus gen. et sp. nov.), a predatory marine osteichthyan from the Silurian Kuanti Formation (late Ludlow, ~423 million years ago) of Yunnan, China, with an estimated length of about 1 meter. The unusual dentition of the new form suggests a durophagous diet which, combined with its large size, indicates a considerable degree of trophic specialisation among early osteichthyans. The lack of large Silurian vertebrates has recently been used as constraint in palaeoatmospheric modelling, with purported lower oxygen levels imposing a physiological size limit. Regardless of the exact causal relationship between oxygen availability and evolutionary success, this finding refutes the assumption that pre-Emsian vertebrates were restricted to small body sizes. PMID:24921626

Silurian to Early Carboniferous plate tectonic model of Central Europe

NASA Astrophysics Data System (ADS)

Golonka, Jan; Barmuta, Jan; Barmuta, Maria

2014-05-01

The presented plate tectonic model focuses on Silurian to Early Carboniferous evolution of Central Europe with special attention given to the Sudetes region (north and north-east part of the Bohemian Massif). During our studies, we tested alternative models focused on the position of the Armorican terranes, known as the Armorican Terrane Assembly (ATA) (e.g.: Matte, 2001) and tried to refine the existing reconstructions, which describe Armorica as an individual continent during the Late Silurian and Devonian (e.g. Lewandowski, 2003, Winchester, 2002). Our plate tectonic model depict that these small blocks were scattered along the northern margin of Gondwana, where they formed the "Armorican Spour" as suggested by Kroner and Romer (2013). The seaways were present between blocks. Because of the north dipping subduction zone along the southern margin of the Laurussia continent the back-arc basin and island arc were formed. The narrowing of the Rheic ocean led to the complicated collision of Gondwana and Laurussia. Three main stages of this event can be distinguished: (1) collision of the Armorican Spour with the Laurussian island arc, (2) back-arc basin closure, (3) final Gondwana and Laurussian collision. Those stages correlate well with Variscan Subduction Zone System proposed by Kroner and Romer (2013). Interactive modeling performed in GPlates, shows that the presented model is valid from kinematic and geometrical point of view. Kroner U., Romer R., L., 2013, Two plates - many subduction zones: the Variscan orogeny reconsidered. Gondwana Research, 24: 298-329. Lewandowski M., 2003, Assembly of Pangea: Combined paleomagnetic and paleoclimatic approach, Advances in Geophysics, 46: 199-236 Matte P., 2001, The Variscan collage and orogeny (480 290 Ma) and the tectonic definition of the Armorica microplate: a review. Terra Nova, 13: 122¨C128. Winchester J., A., The Pace TMR Network Team, 2002, Palaeozoic amalgamation of Central Europe: new results from recent

The Bolivian source rocks: Sub Andean Zone-Madre de Dios-Chaco

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

Moretti, I.; Montemurro, G.; Aguilera, E.

A complete study of source rocks has been carried out in the Bolivian foothills and foreland (Sub Andean Zone, Chaco and Madre de Dios) in order to quantify the petroleum potential of the area. Besides the classical mid-Devonian source rocks (Tequeje Formation in the north, Limoncito Formation in the center and Los Monos Formation in the south), others are important: the Tomachi Formation (late Devonian) in the north and the Copacabana Formation (Upper Carboniferous-lower Permian) in the northern Sub Andean Zone. Both show an excellent potential with S{sub 2} over 50 mg HC/g and average values higher than 10 mgmore » HC/g over few hundred meters. The Latest Cretaceous Flora Formation present locally a high potential but is very thin. Almost all the source rocks matured during the Neogene due to the subsidence in the Andean foreland and in the piggyback basins, and are thus involved on the current petroleum system. Silurian and Lower Paleozoic units also contain thick shale beds, but these source rocks were mature before the Jurassic in the south of the country. In the center, the Silurian is not nowadays overmature and may play an important role. The different zones are compared based on their Source Potential Index which indicates that the richest areas are the northern Sub Andean Zone and the Madre de Dios basin with SPI greater than 10 t/m{sup 2}. Since these two areas remain almost unexplored, these results allow us to be optimistic about the possibilities for future exploration.« less

Silurian Gastropoda from the Alexander terrane, southeast Alaska

USGS Publications Warehouse

Rohr, D.M.; Blodgett, R.B.

2008-01-01

Gastropods are described from Ludlow-age strata of the Heceta Limestone on Prince of Wales Island, southeast Alaska. They are part of a diverse megabenthic fauna of the Alexander terrane, an accreted terrane of Siberian or Uralian affinities. Heceta Limestone gastropods with Uralian affinities include Kirkospira glacialis, which closely resembles "Pleurotomaria" lindstromi Oehlert of Chernyshev, 1893, Retispira cf. R. volgulica (Chernyshev, 1893), and Medfracaulus turriformis (Chernyshev, 1893). Medfracaulus and similar morphotypes such as Coelocaulus karlae are unknown from rocks that are unquestionably part of the North American continent (Laurentia) during Late Silurian time. Beraunia is previously known only from the Silurian of Bohemia. Pachystrophia has previously been reported only from western North American terranes (Eastern Klamath, York, and Farewell terranes) and Europe. Bathmopterus Kirk, 1928, is resurrected and is only known from the Silurian of southeast Alaska. Newly described taxa include Hecetastoma gehrelsi n. gen. and n. sp. and Baichtalia tongassensis n. gen. and n. sp. ??2008 The Geological Society of America.

A three-dimensional model of the Pyrenees and their foreland basins from geological and gravimetric data

NASA Astrophysics Data System (ADS)

Wehr, H.; Chevrot, S.; Courrioux, G.; Guillen, A.

2018-06-01

We construct a three-dimensional geological model of the Pyrenees and their foreland basins with the Geomodeller. This model, which accounts for different sources of geological and geophysical informations, covers the whole Pyrenees, from the Atlantic Ocean to the Mediterranean Sea, and from the Iberian range to the Massif Central, down to 70 km depth. We model the geological structure with a stratigraphic column composed of a superposition of layers representing the mantle, lower, middle, and upper crusts. The sedimentary basins are described by two layers which allow us to make the distinction between Mesozoic and Cenozoic sediments, which are characterized by markedly different densities and seismic velocities. Since the Pyrenees result from the convergence between the Iberian and European plates, we ascribe to each plate its own stratigraphic column in order to be able to model the imbrication of Iberian and European crusts along this fossile plate boundary. We also introduce two additional units which describe the orogenic prism and the water column in the Bay of Biscay and in the Mediterranean Sea. The last ingredient is a unit that represents bodies of shallow exhumed and partly serpentinized lithospheric mantle, which are assumed to produce the positive Bouguer gravity anomalies in the North Pyrenean Zone. A first 3D model is built using only the geological information coming from geological maps, drill-holes, and seismic sections. We use the potential field method implemented in Geomodeller to interpolate these geological data. This model is then refined in order to better explain the observed Bouguer anomalies by adding new constraints on the main crustal interfaces. The final model explains the observed Bouguer anomalies with a standard deviation less than 3.4 mGal, and reveals anomalous deep structures beneath the eastern Pyrenees.

Controls of structural inheritance on orogenic curvature and foreland basin sedimentation: Insights from the Przemyśl area, Western Carpathians

NASA Astrophysics Data System (ADS)

Szaniawski, Rafał; Mazzoli, Stefano; Jankowski, Leszek

2017-10-01

Orogenic curvatures can have various origins and are widely debated worldwide. In the Poland-Ukraine border area, the Outer Western Carpathians are characterized by a marked curvature. The origin of this curvature was analysed by integrating stratigraphic information with structural constraints and anisotropy of the magnetic susceptibility (AMS) data. Hangingwall frontal ramp domains are characterized by a relatively simple deformation dominated by layer-parallel shortening and folding around a regional NW-SE trending axis, recorded by an AMS lineation with a similar trend. On the other hand, the N-S trending hangingwall oblique ramp domain is characterized by maximum AMS axes recording transpressional strain either dominated by simple shear (sub-horizontal AMS lineation) or pure shear (steeply plunging AMS lineation) components. Early Miocene basin inversion with two distinct depocentres created a number of different detachment surfaces and thickness variations for the sedimentary successions involved in thrusting. The main depocentre of the Lower-Middle Miocene foredeep was originally located in the recess area of the curved Carpathian front. On the other hand, the occurrence of a salient to the west resulted in the axial zone of the foreland flexure being filled with allochthonous units, thereby dramatically reducing the accommodation space for foredeep sediments in this area. Our results suggest that thrust-belt geometry was controlled by the inherited Mesozoic extensional basin architecture.

Geology and hydrocarbon potential of the Oued Mya Basin, Algeria

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

Benamrane, O.; Messaoudi, M.; Messelles, H.

1992-01-01

The hydrocarbon System Ourd Mya is located in the Sahara Basin. It is one of the producing basin in Algeria. The stratigraphic section consists of Paleozoic and Mesosoic, it is about 5000m thick. In the eastern part, the basin is limited by the Hassi-Messaoud high zone which is a giant oil field producing from the Cambrian sands. The western part is limited by Hassi R'mel which is one of the biggest gas field in the world, it is producing from the triassic sands. The Mesozoic section is laying on the lower Devonian and in the eastern part, on the Cambrian.more » The main source rock is the Silurian shale with an average thickness of 50m and a total organic matter of 6% (14% in some cases). Results of maturation modeling indicate that the lower Silurian source is in the oil window. The Ordovician shales are also a source rock, but in a second order. Clastic reservoirs are in the Triassic sequence which is mainly fluvial deposits with complex alluvial channels, it is the main target in the basin. Clastic reservoirs within the lower Devonian section have a good hydrocarbon potential in the east of the basin through a southwest-northeast orientation. The late Triassic-Early Jurassic evaporites overlie the Triassic clastic interval and extend over the entire Oued Mya Basin. This is considered as a super-seal evaporate package, which consists predominantly of anhydrite and halite. For Paleozoic targets, a large number of potential seals exist within the stratigraphic column. The authors infer that a large amount of the oil volume generated by the Silurian source rock from the beginning of Cretaceous until now, still not discovered could be trapped within structure closures and mixed or stratigraphic traps related to the fluvial Triassic sandstones, marine Devonian sands and Cambro-Ordovician reservoirs.« less

The preliminary data on the Aeronian (Silurian) machaerids from Lithuania (Baltic Basin)

NASA Astrophysics Data System (ADS)

Radzevičius, S.; Ekleris, A.

2012-04-01

Machaerids are stem-Lophotrochozoans, closely related to the Annelids, and known from the Early Ordovician to Middle Permian. Machaerids is a group of worm-like benthic marine, bilaterally symmetrical, armoured invertebrate. Their body is covered by an external scleritome. The scleritome is imbricated of longitudinally arranged series of plates or sclerites. Completely articulated specimens of machaeridians are very rare, yet the systematic position of machaerids is controversial. Machaeridians had been assigned to different groups, such as barnacles, mollusks, echinoderms and annelids. The latter is prevailing, however their exact place within the annelids still remains unresolved. New findings of disarticulated Silurian machaerids have been recorded in western Lithuania, Geniai-1 core. This well has been drilled with exploration purposes regarding the Cambrian oil reservoir; therefore the biggest part of the Silurian core has not been collected. The exceptions are some parts of the Llandovery and Ludlow, which have partially recovered well core, but the identification of the precise stratigraphical position is complicated. Disarticulated sclerites of machaeridians have been found at the 1756.4 m depth, in the argillite, together with some graptolites and brachiopods. Several rhabdosome fragments of Normalograptus scalaris (Hisinger) were found together with the machaenid sclerites as well. N. scalaris has wide biostratigraphical distribution from the Rhudanian to the lower part of Telychian, which comprises the convolutus - triangulates graptolite biozones, corresponding to the 1756.8 - 1756 m depth. Convolutus - triangulates biozones represent Aeronian, and the machaeridian sclerites come from this interval, together with the Jonsea grayi (Davidson) brachiopod shells, which are very common and correspond to the BA 5-6 benthic assemblage, as well as do the graptolites found together. In previous studies, two orders of machaerids have been recognized: the

Neuquén Group (Upper Cretaceous): A case of underfilled-overfilled cycles in an Andean foreland basin, Neuquén basin, Argentina

NASA Astrophysics Data System (ADS)

Asurmendi, Estefanía; Sánchez, María Lidia; Fennell, Lucas

2017-12-01

The Nenquén Group was deposited during a period dominated by the Cretaceous Greenhouse and can be divided in three cycles correlated with large-scale changes in the evolution of the Andean foreland basin. The filling of the Neuquén Group is constituted by a complete cycle and two incomplete cycles of underfilled-overfilled, separated by first-order discontinuities assigned to the uplift of the Agrio fold-and-thrust belt during the Chasca/Catequil, Mid Ocean Ridge (CCMOR) collision, coinciding with first-order climatic changes within the Cretaceous greenhouse cycle. The Candeleros Formation in the base of this group was deposited in late underfilled conditions, showing prominent forebulge zones. It is demonstrated that during the Albian, with the cratonward migration of the uplifting forebulge zones, the axis of backbulge zones also migrated cratonwards and a wide uplifted forebulge zone was formed. On top, the Huincul Formation was deposited in an overfilled period without orogenic load, while the Cerro Lisandro Formation was deposited in early underfilled conditions with orogenic load. The Río Neuquén Subgroup started with a late underfilled period (Portezuelo Formation -second-order discontinuity), and after wards the Plottier Formation was deposited in an overfilled period without orogenic load. Finally, the Río Colorado Subgroup was deposited under late and early underfilled conditions (Bajo de la Carpa and Anacleto Formations respectively).

Geology and hydrocarbon potential of the Oued Mya basin, Algeria

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

Benamrane, O.; Messaoudi, M.; Messelles, H.

1993-09-01

The Oued Mya hydrocarbon system is located in the Sahara basin. It is one of the best producing basins in Algeria, along with the Ghadames and Illizi basins. The stratigraphic section consists of Paleozoic and Mesozoic, and is about 5000 m thick. This intracratonic basin is limited to the north by the Toughourt saddle, and to the west and east it is flanked by regional arches, Allal-Tilghemt and Amguid-Hassi Messaoud, which culminate in the super giant Hassi Messaoud and Hassi R'mel hydrocarbon accumulations, respectively, producing oil from the Cambrian sands and gas from the Trissic sands. The primary source rockmore » in this basin is lower Silurian shale, with an average thickness of 50 m and a total organic carbon of 6% (14% in some cases). Results of maturation modeling indicate that the lower Silurian source is in the oil window. The Ordovician shales are also source rocks, but in a second order. Clastic reservoirs are in the Trissic sequence, which is mainly fluvial deposits with complex alluvial channels, and the main target in the basin. Clastic reservoirs in the lower Devonian section have a good hydrocarbon potential east of the basin through a southwest-northwest orientation. The Late Trissic-Early Jurassic evaporites that overlie the Triassic clastic interval and extend over the entire Oued Mya basin, are considered to be a super-seal evaporite package, which consists predominantly of anhydrite and halite. For paleozoic targets, a large number of potential seals exist within the stratigraphic column. This super seal does not present oil dismigration possibilities. We can infer that a large amount of the oil generated by the Silurian source rock from the beginning of Cretaceous until now still is not discovered and significantly greater volumes could be trapped within structure closures and mixed or stratigraphic traps related to the fluvial Triassic sandstones, marine Devonian sands, and Cambrian-Ordovician reservoirs.« less

Agglutinated foraminifera from the Ludlow (Silurian) of Ireland

NASA Astrophysics Data System (ADS)

Kaminski, Michael; Ferretti, Annalisa; Messori, Fabio; Papazzoni, Cesare Andrea; Sevastopulo, George

2017-04-01

Agglutinated foraminifera are one of the most primitive groups of foraminifera, possibly already appearing in the Cryogenian but usually rare in lower Paleozoic rocks. Their mean standing diversity slowly increased during Cambrian and Ordovician times, reaching a stable value of about 50 genera in the mid-Silurian which remained fairly constant up to the Triassic. An assemblage of agglutinated foraminifera was unexpectedly found in conodont residue from material collected in the Dingle Peninsula, County Kerry, southwestern Ireland. This material comes from rare calcareous occurrences in volcanoclastics previously known for their rich trilobite and conodont assemblages. The limestones are trilobite-crinoidal silty wackestone to packstone, with local brachiopod concentrations, documenting brachiopod-trilobite-crinoidal dominated communities of shallow and well-ventilated water that might have periodically colonized the bottom intercalating with volcanic events and then successively redeposited in deeper waters. The conodont fauna indicates an early Ludlow (Gorstian-earliest Ludfordian) age (Kaminski et al., 2016). The foraminiferal assemblage has limited potential for stratigraphical correlation as long-range taxa are present, but it represents the first record from the Silurian of Ireland. The assemblage is dominated by tubothalamids (Rectoammodiscus and rare Sansabaina), with less abundant monothalamids (Psammosiphonella and Psammosphaera). The assemblage displays low diversity compared with other assemblages described from the British Isles (Kircher & Brasier, 1989). At the species level, this assemblage is identical to those described previously from the Silurian of North America but with lower diversity. Only Rectoammodiscus diai had apparently a wider geographic distribution, including not only the central USA (Oklahoma and Kansas) but also the Welsh Borderlands and Senegal. The affinities with the assemblages reported at several localities in the central

Long-lived Control of Sierras Pampeanas Ranges on Andean Foreland Basin Evolution Revealed by Coupled Low-temperature Thermochronology and Sedimentology

NASA Astrophysics Data System (ADS)

Stevens Goddard, A.; Carrapa, B.; Larrovere, M.; Aciar, R. H.

2017-12-01

The Sierras Pampeanas ranges of west-central Argentina (28º- 31ºS) are a classic example of thick-skinned style basement block uplifts. The style and timing of uplift in these mountain ranges has widely been attributed to the onset of flat-slab subduction in the middle to late Miocene. However, the majority of low-temperature thermochronometers in the Sierras Pampeanas have much older cooling dates. Thermal modeling derived from new low-temperature thermochronometers in Sierra de Velasco, one of the highest relief (> 4 km) mountains in the Sierras Pampeanas, suggest that the rocks in these ranges have been at near-surface temperatures (< 50ºC) since the Paleozoic. Reheating to temperatures between 80ºC and 100ºC occurred during late Cretaceous rifting and may be partially attributed to a temporary elevation of the regional geothermal gradient. Cooling attributed to late Miocene exhumation, and coincident with estimates of the onset of flat-slab subduction, contributed to modern relief, but cannot explain all of the modern topography. We compare the results from low-temperature thermochronology with the regional sedimentary basin record to confirm that paleorelief plausibly controlled sedimentation patterns throughout the development of the Cenozoic Andean foreland basin at these latitudes. We propose that the history of long-lived topography illustrated in Sierra de Velasco can be expanded to other ranges in the Sierras Pampeanas by integrating multiple data sets.

Geomorphology and dynamics of a traveling cuspate foreland, Authie estuary, France

NASA Astrophysics Data System (ADS)

Hesp, Patrick A.; Ruz, Marie-Hélène; Hequette, Arnaud; Marin, Denis; Miot da Silva, Graziela

2016-02-01

Cuspate forelands or salients occur all over the world in lakes, estuaries and on ocean shores, yet there have been few studies conducted on traveling cuspate forelands (or salients), that is, forelands that migrate or travel alongshore. This paper presents a study of a traveling foreland in the Authie estuary, France, termed the Bec du Perroquet. Historical shoreline changes may be traced from the 1200's AD and the region has experienced both marked intertidal-subtidal accretion extending from the south, and massive erosion in the north since this period. An analysis of aerial photographs from 1947 until the present shows that the original Bec foreland was established at the mouth of the Authie estuary, but gradually disappeared by the 1960's and a new foreland developed in the middle of the northern-central portion of the bay. This foreland was composed of a suite of foredune ridges which have been successively eroded on the northern margin and initiated on the southern margin as the foreland traveled or migrated southwards. As the foreland traveled south, from 1947 to 2009 the northern part of the bay retreated more than 350 m, while mid-bay, the coastline retreated ~ 215 m. As the foreland evolves and migrates, incipient foredunes can develop rapidly (e.g. 18 ridges formed in an 11 week period), while at other times the ridges form slowly and may be eroded and disappear. Two or more foredune ridges may blend into a single ridge over time depending on the initial degree of vegetation cover on the ridge and swale set. Aeolian processes in dune swales are much more important in this system than in typical prograding foredune plain systems due to the sometimes marked lack of vegetation colonization in the swales following foredune ridge development, and aeolian deflation of the swales (along with blowout development) is important particularly when they become open conduits to the beach as erosion of the NW foreland proceeds. The ages of each of the surviving ridges

Seismotectonics of Bhutan: Evidence for segmentation of the Eastern Himalayas and link to foreland deformation

NASA Astrophysics Data System (ADS)

Diehl, Tobias; Singer, Julia; Hetényi, György; Grujic, Djordje; Clinton, John; Giardini, Domenico; Kissling, Edi

2017-04-01

The instrumental seismicity of Bhutan is characterized by a lower activity compared to most other parts of the Himalayan arc. To understand this low activity and its impact on the seismic hazard, a seismic network was installed in Bhutan for 22 months between 2013 and 2014. From the recorded seismicity, earthquake moment tensors, and local earthquake tomography, we reveal along-strike variations in structure and crustal deformation regime. Imaged structural variations, primarily a thickened crust in western Bhutan, suggest lateral differences in stresses on the Main Himalayan Thrust (MHT), potentially affecting interseismic coupling and style of deformation. Sikkim, western Bhutan, and its foreland are characterized by strike-slip faulting in the Indian basement. Strain is particularly localized along a NW-SE striking dextral fault zone reaching from Chungthang in northeast Sikkim to Dhubri at the northwestern edge of the Shillong Plateau in the foreland. The dextral Dhubri-Chungthang fault zone (DCF) might segment the MHT between eastern Nepal and western Bhutan and connect the deformation front of the Himalaya with the Shillong Plateau in the foreland by forming the western boundary of a West-Assam block. In contrast, the eastern boundary of this block, hitherto associated with the Kopili foreland fault, appears to be diffuse. In eastern Bhutan, we image a seismogenic, flat portion of the MHT, which might be related to a partially creeping fault segment or increased background seismicity originating from the 2009 MW6.1 earthquake. In western-central Bhutan, clusters of micro-earthquakes at the front of the High-Himalayas indicate the presence of a mid-crustal ramp and stress buildup on a fully coupled MHT. The area bounded by the DCF in the west and the seismogenic MHT in the east has the potential for M7-8 earthquakes in Bhutan. Similarly, the DCF has the potential to host M7 earthquakes beneath the densely populated foreland basin as documented by the Dhubri

A New Noncalcified Dasycladalean Alga from the Silurian of Wisconsin

USGS Publications Warehouse

LoDuca, S.T.; Kluessendorf, Joanne; Mikulic, Donald G.

2003-01-01

Noncalcified thalli, consisting of a narrow main axis with numerous branched hairlike laterals in whorls and a subapical array of undivided clavate laterals, from the Silurian (Llandovery) Brandon Bridge Formation of southeastern Wisconsin, constitute the basis for a new genus and species of dasycladalean alga, Heterocladus waukeshaensis. A relationship within the family Triploporellaceae is indicated by the whorled arrangement of the laterals and the absence of gametophores on mature specimens. A compilation of occurrence data suggests that noncalcified dasyclads, as a whole, were more abundant and diverse during the Ordovician and Silurian than at any other time in their history. The heterocladous thallus architecture of this alga adds to a wide range of morphological variation documented among Ordovician and Silurian dasyclads, the sum of which indicates that Dasycladales underwent a significant evolutionary radiation during the early Paleozoic.

The paradox of vertical σ2 in foreland fold and thrust belts

NASA Astrophysics Data System (ADS)

Tavani, Stefano

2014-05-01

Occurrence of aesthetically appealing thrust systems and associated large scale anticlines, in both active and fossil foreland fold and thrust belts, is commonly interpreted as an evidence for Andersonian compressional framework. Indeed, these structures would testify for a roughly vertical σ3. Such a correlation between thrusts occurrence and stress field orientation, however, frequently fails to explain denser observations at a smaller scale. The syn-orogenic deformation meso-structures hosted in exposed km-scale thrust-related folds, in fact, frequently and paradoxically witness for a syn-thrusting strike-slip stress configuration, with a near-vertical σ2 and a sub-horizontal σ3. This apparent widespread inconsistency between syn-orogenic meso-structures and stress field orientation is here named "the σ2 paradox". A possible explanation for such a paradox is provided by inherited extensional deformation structures commonly developed prior to thrusting, in the flexural foreland basins located ahead of fold and thrust belts. Thrust nucleation and propagation is facilitated and driven by the positive inversion of the extensional inheritances, and their subsequent linkage. This process eventually leads to the development of large reverse fault zones and can occur both in compressive and strike-slip stress configurations.

Off-platform Silurian sequences in the Ambler River quadrangle: A section in Geologic studies in Alaska by the U.S. Geological Survey during 1987

USGS Publications Warehouse

Dumoulin, Julie A.; Harris, Anita G.

1988-01-01

Lithofacies changes in coeval upper Paleozoic rocks have been used to unravel the tectonic history of northern Alaska (for example, Mayfield and others, 1983). Conodont biostratigraphy and detailed petrologic studies are now revealing facies differences in lower Paleozoic rocks that can also be used to constrain their tectono-sedimentary framework (Dumoulin and Harris, 1987). A basic element of basin analysis is the discrimination of shallow-water shelf and platform sequences from deeper water slope and basinal deposits. This report documents several new localities of deeper water, off-platform Silurian deposits in the Ambler River quadrangle and briefly outlines some of their paleogeographic implications.

The influence of pre-existing basement structures on salt tectonics in the Upper Silurian Salina Group, Appalachian Basin, NE Pennsylvania: results from 3D seismic analysis and analogue modelling

NASA Astrophysics Data System (ADS)

Harding, M. R.; Rowan, C. J.

2013-12-01

The Upper Silurian Salina Group in Pennsylvania's Appalachian basin consists of several hundred feet of highly deformable and mobile salt that was a significant influence on the tectonic and structural development of the Appalachian Mountains during the late Paleozoic. Understanding how halokinesis and décollement thrusting of the Salina Group has contributed to the present-day structure of the Appalachian Basin is of intense current interest due to the energy resource potential of the overlying Marcellus Shale and underlying Utica Shale. Seismic data suggest that halokinesis of the Salina Group in the Appalachian Basin might be strongly influenced by the presence of preexisting faults in the underlying Neoproterozoic basement, which suggests that these structures may have interacted with the Salina Group or its interior during deformation. We examine these apparent interactions in more detail using high-resolution 3D seismic data from the Appalachian Basin of NE Pennsylvania to identify and characterize salt tectonic-related structures developed above and within the Salina Group during orogenesis, verify their geographic association with major basement faults, and document how reactivation of these preexisting faults might have influenced later deformation within and above the salt units. We also present the results of sandbox modelling of thin-skinned thrusting in a salt-analogue décollement. Multiple runs in the presence and absence of preexisting basement structures provide insight into how the modern structures observed in the seismic data initiated and evolved during progressively more intense orogenesis, and better constrain the physical processes that control the structural linkage through the Salina décollement.

Feast to famine: Sediment supply control on Laramide basin fill

NASA Astrophysics Data System (ADS)

Carroll, Alan R.; Chetel, Lauren M.; Elliot Smith, M.

2006-03-01

Erosion of Laramide-style uplifts in the western United States exerted an important first-order influence on Paleogene sedimentation by controlling sediment supply rates to adjacent closed basins. During the latest Cretaceous through Paleocene, these uplifts exposed thick intervals of mud-rich Upper Cretaceous foreland basin fill, which was quickly eroded and redeposited. Cretaceous sedimentary lithologies dominate Paleocene conglomerate clast compositions, and the volume of eroded foreland basin strata is approximately twice the volume of preserved Paleocene basin fill. As a result of this sediment oversupply, clastic alluvial and paludal facies dominate Paleocene strata, and are associated with relatively shallow and ephemeral freshwater lake facies. In contrast, large, long-lived, carbonate-producing lakes occupied several of the basins during the Eocene. Basement-derived clasts (granite, quartzite, and other metamorphic rocks) simultaneously became abundant in lower Eocene conglomerate. We propose that Eocene lakes developed primarily due to exposure of erosion-resistant lithologies within cores of Laramide uplifts. The resultant decrease in erosion rate starved adjacent basins of sediment, allowing the widespread and prolonged deposition of organic-rich lacustrine mudstone. These observations suggest that geomorphic evolution of the surrounding landscape should be considered as a potentially important influence on sedimentation in many other interior basins, in addition to more conventionally interpreted tectonic and climatic controls.

Silurian Micrometeorite Flux: The Demise of the Mid-Ordovician L-Chondrite Reign.

NASA Astrophysics Data System (ADS)

Martin, E.; Schmitz, B.

2017-12-01

Earth's sedimentary record holds information about the micrometeorite flux through time, reflecting the collisional evolution of the asteroid belt. Around 466 Ma ago in the mid-Ordovician period the L-chondrite parent body breakup (LCPB) took place in the main asteroid belt causing a massive increase, up to two orders of magnitude, in the flux of meteorites to Earth (Schmitz, 2013). What did the meteorite flux look like after the breakup event? And when in time can we see a decrease in the fraction of L-chondritic micrometeorites? We dissolved in acids condensed, marine limestone representing the mid-Ordovician and the late Silurian about 0.5 and 40 Ma, respectively after the LCPB, and searched the residues for spinel grains from equilibrated ordinary chondrites (EC). We used 102 kg from the mid-Ordovician Komstad Limestone Formation, Killeröd quarry in Sweden, and 321 kg from the Silurian Kok Formation, Cellon section in Austria. Elemental analyses of the spinel grains were used to link the grains to different types of meteorites. In the large grain size fraction (63-355 µm) there are 4.5 EC grains/kg of rock in the mid-Ordovician sample and only 0.03 EC grains/kg in the Silurian sample. Because the two formations formed at about the same rate (a few mm per kyr) the results represent strong evidence for a major tailing off in the L-chondritic meteorite contribution by the late Silurian. The EC grains have been divided into the H, L, and LL groups based on the TiO2 content. The results show that the fraction of L chondrites compared to H and LL chondrites had declined significantly by the late Silurian. In the study of Heck et al. (2016) it was shown that ≥99% of the ordinary chondritic micrometeorites were L chondrites right after the LCPB. Our data indicate that the L-chondrite fraction had decreased to 60% by the Silurian, with the H and LL chondrites making up 30% and 10% respectively of the flux.

Stratigraphy of the Silurian outcrop belt on the east side of the Cincinnati Arch in Kentucky, with revisions in the nomenclature

USGS Publications Warehouse

McDowell, Robert C.

1983-01-01

, is predominantly grayish-green clay shale with a thin (0.5-3 ft) dolomite member (the Waco, or its northern equivalent, the Dayton Dolomite Member, reduced in rank from Dayton Limestone) near the base. North of Bath County, the Lulbegrud Shale and Dayton Dolomite Members are reassigned to the underlying Drowning Creek Formation, the Estill Shale Member is elevated to formational status, and the Alger is dropped. The Bisher Dolomite, which overlies the Estill Shale in the northernmost part of the Silurian belt, ranges from 0 to 300 ft in thickness and is composed of medium-to coarse-grained, gray, fossiliferous dolomite. The Silurian section overlies Upper Ordovician rocks in apparent conformity, although faunal studies suggest a minor hiatus, and is overlain by Middle to Upper Devonian rocks in a regional angular unconformity that truncates the entire Silurian section at the southwest end of the outcrop belt, where it is nearest the axis of the Cincinnati Arch. All of the units recognized in the Silurian appear to thicken eastward, away from the axis of the arch and towards the Appalachian basin. This, with the presence of isolated remnants of the Brassfield near the axis, suggest that formation of the arch was initiated in Early Silurian time by subsidence of its eastern flank.

Geomorphology and Tectonics at the Intersection of Silurian and Death Valleys, Southern California - 2005 Guidebook Pacific Cell Friends of the Pleistocene

USGS Publications Warehouse

Miller, David M.; Valin, Zenon C.

2007-01-01

This publication describes results from new regional and detailed surficial geologic mapping, combined with geomorphologic, geochronologic, and tectonic studies, in Silurian Valley and Death Valley, California. The studies address a long-standing problem, the tectonic and geomorphic evolution of the intersection between three regional tectonic provinces: the eastern California shear zone, the Basin and Range region of southern Nevada and adjacent California, and the eastern Mojave Desert region. The chapters represent work presented on the 2005 Friends of the Pleistocene field trip and meeting as well as the field trip road log.

Using enteric pathogens to assess sources of fecal contamination in the Silurian Dolomite Aquifer: Preliminary results

USGS Publications Warehouse

Muldoon, Maureen A; Borchardt, Mark A.; Spencer, Susan K.; Hunt, Randall J.; Owens, David

2018-01-01

The fractured Silurian dolomite aquifer is an important, but vulnerable, source of drinking water in northeast Wisconsin (Sherrill in Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian dolomite, 1978; Bradbury and Muldoon in Hydrogeology and groundwater monitoring of fractured dolomite in the Upper Door Priority Watershed, Door County, Wisconsin, 1992; Muldoon and Bradbury in Assessing seasonal variations in recharge and water quality in the Silurian aquifer in areas with thicker soil cover. p 45, 2010). Areas underlain by the Silurian dolomite aquifer are extremely vulnerable to groundwater contamination from various land-use activities, especially the disposal of human wastewater and dairy manure. Currently there is no consensus as to which source of wastewater generates the greater impact to the aquifer.

Tectonic controls of Mississippi Valley-type lead-zinc mineralization in orogenic forelands

USGS Publications Warehouse

Bradley, D.C.; Leach, D.L.

2003-01-01

Most of the world's Mississippi Valley-type (MVT) zinc-lead deposits occur in orogenic forelands. We examine tectonic aspects of foreland evolution as part of a broader study of why some forelands are rich in MVT deposits, whereas others are barren. The type of orogenic foreland (collisional versus Andean-type versus inversion-type) is not a first-order control, because each has MVT deposits (e.g., Northern Arkansas, Pine Point, and Cevennes, respectively). In some MVT districts (e.g., Tri-State and Central Tennessee), mineralization took place atop an orogenic forebulge, a low-amplitude (a few hundred meters), long-wavelength (100-200 km) swell formed by vertical loading of the foreland plate. In the foreland of the active Banda Arc collision zone, a discontinuous forebulge reveals some of the physiographic and geologic complexities of the forebulge environment, and the importance of sea level in determining whether or not a forebulge will emerge and thus be subject to erosion. In addition to those on extant forebulges, some MVT deposits occur immediately below unconformities that originated at a forebulge, only to be subsequently carried toward the orogen by the plate-tectonic conveyor (e.g., Daniel's Harbour and East Tennessee). Likewise, some deposits are located along syn-collisional, flexure-induced normal and strike-slip faults in collisional forelands (e.g., Northern Arkansas, Daniel's Harbour, and Tri-State districts). These findings reveal the importance of lithospheric flexure, and suggest a conceptual tectonic model that accounts for an important subset of MVT deposits-those in the forelands of collisional orogens. The MVT deposits occur both in flat-lying and in thrust-faulted strata; in the latter group, mineralization postdated thrusting in some instances (e.g., Picos de Europa) but may have predated thrusting in other cases (e.g., East Tennessee).

Basin evolution during Cretaceous-Oligocene changes in sediment routing in the Eastern Precordillera, Argentina

NASA Astrophysics Data System (ADS)

Reat, Ellen J.; Fosdick, Julie C.

2018-07-01

The response of sedimentary basins to earliest onset of Andean contraction and lithospheric flexure in the southern Central Andes is debated and not well-resolved. The Upper Cretaceous to Oligocene strata of the Cuesta de Huaco anticline in the Argentine Precordillera record sedimentation, regional deformation, and climate patterns prior to the highly studied Oligocene-Miocene foreland basin phase. These deposits have recently been recognized as Cretaceous and Paleogene in age, prompting a re-evaluation of this depocenter as part of the early Andean system, prior to deposition of the aeolian foredeep sediments of the Oligocene Vallecito Formation. This work presents new data from the Argentine Precordillera fold-and-thrust belt at 30°S that sheds light on new reinterpretations of the timing of sedimentation for an important interval in Andean retroarc foreland basin history. We report the first Paleocene detrital radiometric ages from the Cuesta de Huaco 'red strata' of the pre-Oligocene Bermejo Basin. Detailed sedimentology and provenance data from the Cenomanian-Turonian Ciénaga del Río Huaco and Danian-Priabonian Puesto La Flecha formations reveal a Cenomanian-Turonian braided stream system that transitioned into a shallow freshwater lacustrine depocenter in Paleocene-Eocene time. During Late Cretaceous time, sediment in the braided river system was derived primarily from northeastern cratonic sources; during the Paleocene-Eocene, uplift and unroofing of the Andean arc and Frontal Cordillera resulted in an influx of western-derived sediment. We therefore suggest a revised timing of sedimentation for the transition to Andean retroarc foreland basin deposition.

The Eocene-Oligocene transition in the North Alpine Foreland Basin and subsequent closure of a Paratethys gateway

NASA Astrophysics Data System (ADS)

van der Boon, A.; Beniest, A.; Ciurej, A.; Gaździcka, E.; Grothe, A.; Sachsenhofer, R. F.; Langereis, C. G.; Krijgsman, W.

2018-03-01

During the Eocene-Oligocene transition (EOT), a major palaeoenvironmental change took place in the Paratethys Sea of central Eurasia. Restricted connectivity and increased stratification resulted in wide-spread deposition of organic-rich sediments which nowadays make up important hydrocarbon source rocks. The North Alpine Foreland Basin (NAFB) was a major gateway of the Paratethys Sea to the open ocean during the Eocene, but the age of closure of this gateway is still uncertain. The Ammer section in southern Germany documents the shallowing of this connection and subsequent disappearance of marine environments in the NAFB, as reflected in its sedimentary succession of turbidites to marls (Deutenhausen to Tonmergel beds), via coastal sediments (Baustein beds) to continental conglomerates (Weißach beds). Here, we apply organic geochemistry and date the lithological transitions in the Ammer section using integrated stratigraphy, including magnetostratigraphy and biostratigraphy. Nannoplankton and dinocyst results can be reconciled when dinoflagellate species Wetzeliella symmetrica is of late Eocene age. Our magnetostratigraphy then records C13r-C13n-C12r and allows calculation of sediment accumulation rates and estimation of ages of lithological transitions. We show that the shallowing from turbiditic slope deposits (Deutenhausen beds) to shelf sediments (Tonmergel beds) coincides with the Eocene-Oligocene boundary at 33.9 Ma. The transition to continental sediments is dated at ca. 33.15 Ma, significantly older than suggested by previous studies. We conclude that the transition from marine to continental sediments drastically reduced the marine connection through the western part of the NAFB and influenced the oxygen conditions of the Paratethys Sea.

A Systems Approach to Identifying Exploration and Development Opportunities in the Illinois Basin: Digital Portifolio of Plays in Underexplored Lower Paleozoic Rocks [Part 1 of 2

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

Seyler, Beverly; Harris, David; Keith, Brian

2008-06-30

This study examined petroleum occurrence in Ordovician, Silurian and Devonian reservoirs in the Illinois Basin. Results from this project show that there is excellent potential for additional discovery of petroleum reservoirs in these formations. Numerous exploration targets and exploration strategies were identified that can be used to increase production from these underexplored strata. Some of the challenges to exploration of deeper strata include the lack of subsurface data, lack of understanding of regional facies changes, lack of understanding the role of diagenetic alteration in developing reservoir porosity and permeability, the shifting of structural closures with depth, overlooking potential producing horizons,more » and under utilization of 3D seismic techniques. This study has shown many areas are prospective for additional discoveries in lower Paleozoic strata in the Illinois Basin. This project implemented a systematic basin analysis approach that is expected to encourage exploration for petroleum in lower Paleozoic rocks of the Illinois Basin. The study has compiled and presented a broad base of information and knowledge needed by independent oil companies to pursue the development of exploration prospects in overlooked, deeper play horizons in the Illinois Basin. Available geologic data relevant for the exploration and development of petroleum reservoirs in the Illinois Basin was analyzed and assimilated into a coherent, easily accessible digital play portfolio. The primary focus of this project was on case studies of existing reservoirs in Devonian, Silurian, and Ordovician strata and the application of knowledge gained to future exploration and development in these underexplored strata of the Illinois Basin. In addition, a review of published reports and exploration in the New Albany Shale Group, a Devonian black shale source rock, in Illinois was completed due to the recent increased interest in Devonian black shales across the United States

Glacier meltwater flow paths and storage in a geomorphologically complex glacial foreland: the case of the Tapado glacier, dry Andes of Chile (30°S)

NASA Astrophysics Data System (ADS)

Pourrier, J.; Jourde, H.; Kinnard, C.; Gascoin, S.; Monnier, S.

2013-12-01

In the Dry Andes, high altitude glacierized catchments are important contributor to streamflow and aquifer recharge. In this study we focused on the Tapado catchment, (30°S, 9 km2, elevation range: 4000m - 5550m) located in the upper Elqui river basin in northern Chile. This catchment encompasses the Tapado glacial complex, composed of an assemblage of the Tapado glacier and the glacial foreland (debris-covered glacier, rock glacier and moraines). Here we present the results of intensive hydrometeorological observations conducted over the 2011 glacier melt season (February to April). Weather, discharge and water electrical conductivity were monitored near the glacier snout and at the outlet of the glacial foreland. GPR observations realized on the glacial foreland are used to verify or complete interpretations of underground transfer modalities. The results show that the water production from the Tapado glacier is highly correlated with weather conditions, in particular incoming shortwave radiation and air temperature. Resulting daily and seasonal streamflow variability is buffered by the glacial foreland, where underground transfers occur through complex flow paths. However, the development of a thermokarst drainage network in a part of the glacial foreland, allows fast and concentrated water transfers, which reduces this buffering effect. The glacial foreland is shown to act as a reservoir, storing water during period of strong ice melt and providing water to downstream areas during periods of low melt. The internal structure of the glacial foreland revealed by GPR observations corroborates these analyses. The south-western part is composed by massive ice, covered by rock debris. The north-eastern part is composed by mixed ice and rock debris, presenting spatially variable ice content. Finally, the computation of the catchment water balance shows that the Tapado catchment presents a particularly high specific discharge in summer under a dry hydro

Gravity sliding in basinal setting, a surficial record of tectonic and geodynamic evolution; examples from the southern W. Alps and their foreland

NASA Astrophysics Data System (ADS)

Dumont, T.; Franzi, V.; Matthews, S. J.

2012-04-01

The occurrence of large-scale submarine landslides, although commonly observed in the present basins, is only exceptionally mentioned in the Alpine orogen and foreland. The southern part of the Western Alpine arc and the SE basin of France provide examples of such features which could be related with particular geodynamic events, in relation with the motion of the Iberian and Adriatic microplates : - A >50km2 slump scar formed in Aptian times at the northwestern edge of the SE France (so-called Vocontian) basin, giving a low-angle detachment surface which was onlapped by Albian hemipelagic marls (Ferry & Flandrin, 1979). The latter mark the maximum deepening stage of the basin, and the head of the scar is located over a deep-seated fault bounding the platform, which strongly suggest that sliding was caused by differential subsidence due to Middle Cretaceous extension, as a consequence of Iberia-Europe divergence. - Later on, a deep-marine erosion surface developed further down the basin over a >100km2 area (Dévoluy massif; Michard et al., 2010), which had been previously affected by Mid-Cretaceous extension. Typical inversion structures are found beneath the surface, which indicate that NS shortening overprinted the extensional pattern. The removal of up to 400m of Mesozoic sediments was controlled by gravity processes, probably triggered by the deformation of the basin floor following tectonic inversion. The overlying pelagic carbonates indicate that shortening occurred before the Campanian, which is closely comparable with the earliest stages of tectonic inversion in the Pyrenees. - The transition slope between the Paleogene Alpine flexural basin and the NW-ward propagating accretionary prism provides examples of basin floor degradation and of gravity-driven emplacement of large-scale blocks, generally regarded as thrust-sheets in the Alps. These features allow to reconstruct the early stages of the Adria-Europe collision, which strongly differ from the Oligo

Using enteric pathogens to assess sources of fecal contamination in the silurian dolomite aquifer: preliminary results

USDA-ARS?s Scientific Manuscript database

The fractured Silurian dolomite aquifer is an important, but vulnerable, source of drinking water in northeast Wisconsin. Areas underlain by the Silurian dolomite aquifer are extremely vulnerable to groundwater contamination from various land-use activities, especially the disposal of human wastewat...

Source versus depositional controls on sandstone composition in a foreland basin: The El Imperial Formation (Mid Carboniferous-Lower Permian), San Rafael basin, western Argentina

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

Espejo, E.S.; Lopez-Gamundi, O.R.

1994-01-01

The El Imperial Formation (mid-Carboniferous-Lower Permian) constitutes a progradational sandstone-rich succession deposited in the San Rafael foreland basin of western Argentina. Four facies associations have been identified: a basal glacial marine association, a shallow marine association, a deltaic association, and an uppermost fluvial association. Sand-prone deposits in the deltaic association, a shallow marine association, a deltaic association, and an uppermost fluvial association. Sand-prone deposits in the deltaic association are represented by prodelta and delta-front shales and subordinate fine sandstones (Facies A), deltaic platform, wave-reworked channel mouth-bar sandstones (Facies B), and fluvial-dominated distributary channel sandstones (Facies C). Analysis of framework grainsmore » of sandstone samples from Facies B and C shows two distinct mineral assemblages or petrofacies. The quartzose petrofacies is characterized by high contents of quartz and low percentages of feldspar and lithic grains. The quartzolithic petrofacies shows an increase in labile components, in particular lithic fragments, and a concomitant decrease in quartz. The quartzolithic petrofacies shows a source signature. Average detrital modes of sandstones from this petrofacies are similar to those from overlying fluvial sandstones. All wave-reworked, channel mouth-bar sandstones (Facies B) correspond compositionally to the quartzose petrofacies, whereas detrital modes from the distributary-channel sandstones (Facies C) fall into the quartzolithic petrofacies. This correspondence between depositional environment and petrofacies suggests a strong depositional influence on composition (depositional signature). Abrasion (mechanical breakdown) by wave action in shallow marine environments accounts for the quartz-rich nature and paucity of labile grains in the quartzose petrofacies.« less

Sperm carriers in Silurian sea scorpions

NASA Astrophysics Data System (ADS)

Kamenz, Carsten; Staude, Andreas; Dunlop, Jason A.

2011-10-01

Invasion of the land by arachnids required adaptations of numerous organs, such as gills evolving into lungs, as well as mechanisms facilitating sperm transfer in a terrestrial environment. Many modern arachnids use spermatophores for this purpose, i.e. sperm transmitters detached from the body. Exceptionally preserved Silurian (423 Ma) fossils of Eurypterus tetragonophthalmus Fischer, 1839 (Chelicerata: Eurypterida) preserve so-called `horn organs' which we here demonstrate as being equivalent to the spermatophore-producing parts of the genital tract in certain modern arachnids. This clarifies a long-running debate about sexing eurypterids based on the shape of the median abdominal (or genital) appendage. To our knowledge this is also the oldest direct evidence for spermatophore-mediated sperm transfer in the fossil record and suggests that eurypterids had evolved mating techniques using spermatophores as early as the Silurian, a valuable prerequisite for life on land. Spermatophores are absent in sea spiders (Pycnogonida) and horseshoe crabs (Xiphosura); thus the shared presence of sclerotized sperm-transfer devices in eurypterids and arachnids is a novel character, newly elucidated here, which offers explicit support for (Eurypterida + Arachnida). For this clade the name Sclerophorata n. nov. is proposed. Arachnida can be further defined by fusion of the originally paired genital opening.

Basin evolution and structural reconstruction of northeastern Morocco and northwestern Algeria

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

Scott, S.

1995-08-01

The high plateau region of Morocco and northwestern Algeria contains a Permo-Triassic rift basin with over 8,000 meters of Paleozoic, Mesozoic and Tertiary sediments. The area exhibits many similarities to the prolific Triassic basins of neighboring Algeria. Previous impediments to exploration in the high plateau area focused on the inability to seismically image sub-salt, pre-Jurassic block faulted structures and the perceived lack of adequate source rocks. This study combined seismic and basin modelling techniques to decipher the pre-salt structures, interpret basin evolution, and access source rock potential. Large structural and stratigraphic features can now be discerned where Permo-Triassic block faultedmore » structures are overlain by thick Triassic-Jurassic mobile evaporate seals and sourced by underlying Paleozoic shales. Contrary to the last published reports, over 20 years ago, oil and gas generation appears to have been continuous in the Carboniferous since 350 ma. Migration directly from the Carboniferous shales to Triassic conglomerates is envisaged with adequate seals provided by the overlying Triassic-Jurassic evaporate sequence. An earlier rapid pulse of oil and gas generation between 300-340 ma from the Silurian source rocks was probably too early to have resulted in hydrocarbon accumulation in the primary Triassic targets but if reservoir is present in the Carboniferous section, then those strata may have been sourced by the Silurian shales.« less

Silurian gastropoda from southeastern and west-central Alaska

USGS Publications Warehouse

Rohr, D.M.; Blodgett, R.B.; Fryda, J.

2008-01-01

Additional Silurian (Ludlovian) gastropods are described from the Heceta Formation in the Alexander terrane on Prince of Wales Island, southeastern Alaska. Species include Spinicharybdis krizi n. sp., Spinicharybdis boucoti n. sp., Morania wagneri n. sp., Haplospira craigi n. sp., Australonema sp., Pachystrophia cf. gotlandica (Lindstro??m, 1884), and Medfrazyga gilmulli n. sp. An additional new Silurian species, Morania nixonforkensis n. sp., is described from the Nixon Fork subterrane of the Farewell terrane of west-central Alaska. The spine-bearing Spinicharybdis is placed into a new subfamily Spinicharybdiinae together with Hystricoceras Jahn, 1894. Joint occurrences of genera Beraunia, Coelocaulus, and Morania, as well as members of subfamily Spinicharybdiinae in the gastropod fauna from the Heceta Formation, support its close relationship with gastropod fauna of Bohemia. Additionally, the occurrence of the genus Medfrazyga suggests a faunal link between the Alexander and Farewell terranes of Alaska. Medfrazyga gilmulli n. sp. is the oldest known and the only early Paleozoic member of the family Palaeozygopleuridae. Copyright ?? 2008, The Paleontological Society.

Geologic Assessment of Undiscovered Oil and Gas Resources of the North Cuba Basin, Cuba

USGS Publications Warehouse

Schenk, Christopher J.

2010-01-01

Petroleum generation in the North Cuba Basin is primarily the result of thrust loading of Jurassic and Cretaceous source rocks during formation of the North Cuba fold and thrust belt in the Late Cretaceous to Paleogene. The fold and thrust belt formed as Cuban arc-forearc rocks along the leading edge of the Caribbean plate translated northward during the opening of the Yucatan Basin and collided with the passive margin of southern North America in the Paleogene. Petroleum fluids generated during thrust loading migrated vertically into complex structures in the fold and thrust belt, into structures in the foreland basin, and possibly into carbonate reservoirs along the margins of the Yucatan and Bahama carbonate platforms. The U.S. Geological Survey (USGS) defined a Jurassic-Cretaceous Composite Total Petroleum System (TPS) and three assessment units (AU)-North Cuba Fold and Thrust Belt AU, North Cuba Foreland Basin AU, and the North Cuba Platform Margin Carbonate AU-within this TPS based mainly on structure and reservoir type (fig. 1). There is considerable geologic uncertainty as to the extent of petroleum migration that might have occurred within this TPS to form potential petroleum accumulations. Taking this geologic uncertainty into account, especially in the offshore area, the mean volumes of undiscovered resources in the composite TPS of the North Cuba Basin are estimated at (1) 4.6 billion barrels of oil (BBO), with means ranging from an F95 probability of 1 BBO to an F5 probability of 9 BBO; and (2) 8.6 trillion cubic feet of of gas (TCFG), of which 8.6 TCFG is associated with oil fields, and about 1.2 TCFG is in nonassociated gas fields in the North Cuba Foreland Basin AU.

Sichuan Basin and beyond: Eastward foreland growth of the Tibetan Plateau from an integration of Late Cretaceous-Cenozoic fission track and (U-Th)/He ages of the eastern Tibetan Plateau, Qinling, and Daba Shan

NASA Astrophysics Data System (ADS)

Yang, Zhao; Shen, Chuanbo; Ratschbacher, Lothar; Enkelmann, Eva; Jonckheere, Raymond; Wauschkuhn, Bastian; Dong, Yunpeng

2017-06-01

Combining 121 new fission track and (U-Th)/He ages with published thermochronologic data, we investigate the Late Cretaceous-Cenozoic exhumation/cooling history of the eastern Tibetan Plateau, Qinling, Daba Shan, and Sichuan Basin of east central China. The Qinling orogen shows terminal southwestward foreland growth in the northern Daba Shan thrust belt at 100-90 Ma and in the southern Daba Shan fold belt at 85-70 Ma. The eastern margin of Tibetan Plateau experienced major exhumation phases at 70-40 Ma (exhumation rate 0.05-0.08 mm/yr), 25-15 Ma (≤1 mm/yr in the Pengguan Massif; 0.2 mm/yr in the imbricated western Sichuan Basin), and since 11-10 Ma along the Longmen Shan ( 0.80 mm/yr) and the interior of the eastern Tibetan Plateau (Dadu River gorge, Min Shan; 0.50 mm/yr). The Sichuan Basin records two basin-wide denudation phases, likely a result of the reorganization of the upper Yangtze River drainage system. The first phase commenced at 45 Ma and probably ended before the Miocene; >1 km of rocks were eroded from the central and eastern Sichuan Basin. The second phase commenced at 12 Ma and denudated the central Sichuan Basin, Longmen Shan, and southern Daba Shan; more than 2 km of rocks were eroded after the lower Yangtze River had cut through the Three Gorges and captured the Sichuan Basin drainage. In contrast to the East Qinling, which was weakly effected by late Cenozoic exhumation, the West Qinling and Daba Shan have experienced rapid exhumation/cooling since 15-13 Ma, a result of growth of the Tibetan Plateau beyond the Sichuan Basin.

Silurian and Devonian in Vietnam—Stratigraphy and facies

NASA Astrophysics Data System (ADS)

Thanh, Tống Duy; Phương, Tạ Hoàng; Janvier, Philippe; Hùng, Nguyễn Hữu; Cúc, Nguyễn Thị Thu; Dương, Nguyễn Thùy

2013-09-01

Silurian and Devonian deposits in Viet Nam are present in several zones and regions, including Quang Ninh, East Bac Bo, and West Bac Bo Zones of the Bac Bo Region, the Dien Bien-Nghe An and Binh Tri Thien Zones of the Viet-Lao Region, and the South Trung Bo, and Western Nam Bo Zones of the South Viet Nam Region (Fig. 1). The main lithological features and faunal composition of the Silurian and Devonian Units in all these zones are briefly described. The Silurian consists of deep-water deposits of the upper parts of the Co To and Tan Mai Formations in the Quang Ninh Zone, the upper parts of the Phu Ngu Formation in the East Bac Bo Zone and the upper parts of the Long Dai and Song Ca Formations in the Viet-Lao Region. Shallow water facies Silurian units containing benthic faunas are more widely distributed, including the upper part of the Sinh Vinh and Bo Hieng Formations in the West Bac Bo Zone, the Kien An Formation in the Quang Ninh Zone, and, in the Viet-Lao Region, the Dai Giang Formation and the upper part of the Tay Trang Formation. No Lower and Middle Devonian deposits indicate deep water facies, but they are characterized by different shallow water facies. Continental to near shore, deltaic facies characterize the Lower Devonian Song Cau Group in the East Bac Bo Zone, the Van Canh Formation in the Quang Ninh Zone, and the A Choc Formation in the Binh Tri Thien Zone. Similar facies also occur in the Givetian Do Son Formation of the Quang Ninh Zone, and the Tan Lap Formation in the East Bac Bo Zone, and consist of coarse terrigenous deposits—cross-bedded conglomerates, sandstone, etc. Most Devonian units are characterized by shallow marine shelf facies. Carbonate and terrigenous-carbonate facies dominate, and terrigenous facies occur in the Lower and Middle Devonian sections in some areas only. The deep-water-like facies is characteriztic for some Upper Devonian formations in the Bac Bo (Bang Ca and Toc Tat Formations) and Viet-Lao Regions (Thien Nhan and

An Andean-type retro-arc foreland system beneath northwest South China revealed by SINOPROBE profiling

NASA Astrophysics Data System (ADS)

Li, Jianhua; Dong, Shuwen; Cawood, Peter A.; Zhao, Guochun; Johnston, Stephen T.; Zhang, Yueqiao; Xin, Yujia

2018-05-01

In the Mesozoic, South China was situated along the convergent margin between the Asian and Pacific plates, providing an excellent laboratory to understand the interactions between deformation, sedimentation and magmatism in a retroarc environment. The crustal architecture of northwest South China is displayed along the ∼600-km-long SINOPROBE deep seismic reflection profiles and reveals from east to west: (1) highly folded and truncated reflectors in the upper crust of the Yangtze Fold Zone, which correspond to thin- and thick-skinned thrust systems, and document large-scale intraplate structural imbrication and shortening; (2) a crustal-scale flat-ramp-flat structure, termed the Main Yangtze decollement, which forms a weak, viscous layer to accommodate strain decoupling and material transport in the thin- and thick-skinned systems; and (3) nearly flat-lying reflectors in the Sichuan Basin, which support interpretation of the basin as a weakly deformed depocentre. The Yangtze Fold Zone and the Sichuan Basin represent a retro-arc foreland basin system that is >800 km away from the continental-margin magmatic arc. We suggest that tectonic processes across the arc and retro-arc systems, including arc magma flare-up, basin sedimentation, retroarc thrust propagation, lithosphere underthrusting, root foundering, and extension-related magmatism were interrelated and governed mass transfer. Age data and geological relations link the tectonic processes to evolving geodynamics of the subducting Paleo-Pacific plate.

Detrital zircon geochronology of pre- and syncollisional strata, Acadian orogen, Maine Appalachians

USGS Publications Warehouse

Bradley, Dwight C.; O'Sullivan, Paul B.

2017-01-01

The Central Maine Basin is the largest expanse of deep-marine, Upper Ordovician to Devonian metasedimentary rocks in the New England Appalachians, and is a key to the tectonics of the Acadian Orogeny. Detrital zircon ages are reported from two groups of strata: (1) the Quimby, Rangeley, Perry Mountain and Smalls Falls Formations, which were derived from inboard, northwesterly sources and are supposedly older; and (2) the Madrid, Carrabassett and Littleton Formations, which were derived from outboard, easterly sources and are supposedly younger. Deep-water deposition prevailed throughout, with the provenance shift inferred to mark the onset of foredeep deposition and orogeny. The detrital zircon age distribution of a composite of the inboard-derived units shows maxima at 988 and 429 Ma; a composite from the outboard-derived units shows maxima at 1324, 1141, 957, 628, and 437 Ma. The inboard-derived units have a greater proportion of zircons between 450 and 400 Ma. Three samples from the inboard-derived group have youngest age maxima that are significantly younger than the nominal depositional ages. The outboard-derived group does not share this problem. These results are consistent with the hypothesised provenance shift, but they signal potential problems with the established stratigraphy, structure, and (or) regional mapping. Shallow-marine deposits of the Silurian to Devonian Ripogenus Formation, from northwest of the Central Maine Basin, yielded detrital zircons featuring a single age maximum at 441 Ma. These zircons were likely derived from a nearby magmatic arc now concealed by younger strata. Detrital zircons from the Tarratine Formation, part of the Acadian foreland-basin succession in this strike belt, shows age maxima at 1615, 980 and 429 Ma. These results are consistent with three episodes of zircon recycling beginning with the deposition of inboard-derived strata of the Central Maine Basin, which were shed from post-Taconic highlands located to the

Silurian pinnacle reefs of the Canadian Arctic

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

De Freitas, T.A.; Dixon, O.A.; Mayr, U.

1993-04-01

Pinnacle reefs are commonly an attractive target for oil exploration because they are usually porous carbonate bodies entombed in impervious, deep-water shales that provide both the source and the seal for hydrocarbons. Silurian pinnacle reefs, the first described in the Canadian Arctic Archipelago, are exposed on Ellesmere and Devon Islands. Two main reef trends occur, one of early middle Llandovery to middle Ludlow age and a second of middle Ludlow to Late Silurian or Early Devonian age. Reefs of both phases contain lime mudstone cores: some are stromatactoid-rich and others consist predominantly of microbialite-rich lime mudstone or microbial boundstone. Faciesmore » sequences of both reef phases show evidence of upward-shallowing overall, but, in the older reefs, isochronous capping facies are dominated either by coral-mirian or by stromatoporoid boundstone and floatstone. This difference perhaps reflects variation in wave stress and apparent ability of a few corals,thickly encrusted by or associated with microbial boundstone and skeletal algae, to withstand greater wave energy than a stromatoporoid-coral-rich reef community. These reefs constitute one of the bright prospects of hydrocarbon exploration in rocks of the Franklinian succession. 43 refs., 9 figs.« less

Geomorphic characterization of hilly relief in the north alpine foreland basin: The Hausruck- and Kobernaußerwald region

NASA Astrophysics Data System (ADS)

Baumann, Sebastian; Robl, Jörg; Keil, Melanie; Salcher, Bernhard

2014-05-01

The area of the Hausruck and Kobernaußerwald represents the highest relief of the Molasse Basin in Upper Austria. The region is characterized by a dissected landscape with elevation differences of 400 m and peaks reaching up to 800 m. The latest marine influence of this realm is dated to 11 Ma before present and constrains the onset of the inversion of the peripheral alpine foreland basin. Since that time the relief evolution is controlled by surface uplift and fluvial erosion. The Hausruck-Kobernaußerwald region forms a local watershed and is drained by three drainage systems that are tributaries of the Inn River, the Traun River and the Trattnach River. The Danube River represents the base level for all these streams. In contrary to the nearby Eastern Alps the study area shows no evidence for local deformation or glacial overprint. Therefore, the Hausruck- Kobernaußerwald region represents a perfect testing ground to explore the evolution of relief in a setting of regional uplift and relative base level lowering. This is done by characterizing the fluvial and hillslope system and exploring the effect of contrasting lithology and different base levels. We further give constraints on the geomorphological state of equilibrium and provide a discussion about the spatial position of the highest relief within the Molasse Basin in Upper Austria. Therefore, we have performed a series of morphometric analyses on a high resolution LiDAR digital elevation model. This includes longitudinal channel profiles, the best fit concavity index, the steepness and the normalized steepness index, the slope-area relationship, the slope elevation distribution and hypsometric curves of all individual catchments. All longitudinal channel profiles are graded and show a concave form without any natural knickpoints with best fit concavity indices in the range of 0.35 and 0.55. All observed knick points in the channel profiles could be traced back to an anthropogenic impact like bridges or

Basin fill evolution and paleotectonic patterns along the Samfrau geosyncline: the Sauce Grande basin-Ventana foldbelt (Argentina) and Karoo basin-Cape foldbelt (South Africa) revisited

NASA Astrophysics Data System (ADS)

López-Gamundí, O. R.; Rossello, E. A.

As integral parts of du Toit's (1927) ``Samfrau Geosyncline'', the Sauce Grande basin-Ventana foldbelt (Argentina) and Karoo basin-Cape foldbelt (South Africa) share similar paleoclimatic, paleogeographic, and paleotectonic aspects related to the Late Paleozoic tectono-magmatic activity along the Panthalassan continental margin of Gondwanaland. Late Carboniferou-earliest Permian glacial deposits were deposited in the Sauce Grande (Sauce Grande Formation) and Karoo (Dwyka Formation) basins and Falkland-Malvinas Islands (Lafonia Formation) during an initial (sag) phase of extension. The pre-breakup position of the Falkland (Malvinas) Islands on the easternmost part of the Karoo basin (immediately east of the coast of South Africa) is supported by recent paleomagnetic data, lithofacies associations, paleoice flow directions and age similarities between the Dwyka and the Lafonia glacial sequences. The desintegration of the Gondwanan Ice Sheet (GIS) triggered widespread transgressions, reflected in the stratigraphic record by the presence of inter-basinally correlatable, open marine, fine-grained deposits (Piedra Azul Formation in the Sauce Grande basin, Prince Albert Formation in the Karoo basin and Port Sussex Formation in the Falkland Islands) capping glacial marine sediments. These early postglacial transgressive deposits, characterised by fossils of the Eurydesma fauna and Glossopteris flora, represent the maximum flooding of the basins. Cratonward foreland subsidence was triggered by the San Rafael orogeny (ca. 270 Ma) in Argentina and propogated along the Gondwanan margin. This subsidence phase generated sufficient space to accommodate thick synorogenic sequences derived from the orogenic flanks of the Sauce Grande and Karoo basins. Compositionally, the initial extensional phase of these basins was characterized by quartz-rich, craton-derived detritus and was followed by a compressional (foreland) phase characterized by a paleocurrent reversal and dominance of

Vitrinite equivalent reflectance of Silurian black shales from the Holy Cross Mountains, Poland

NASA Astrophysics Data System (ADS)

Smolarek, Justyna; Marynowski, Leszek; Spunda, Karol; Trela, Wiesław

2014-12-01

A number of independent methods have been used to measure the thermal maturity of Silurian rocks from the Holy Cross Mountains in Poland. Black shales are characterized by diverse TOC values varying from 0.24-7.85%. Having calculated vitrinite equivalent reflectance using three different formulas, we propose that the most applicable values for the Silurian rocks are those based on Schmidt et al. (2015) equation. Based on this formula, the values range from % 0.71 VReqvVLR (the vitrinite equivalent reflectance of the vitrinite-like macerals) to % 1.96 VReqvVLR. Alternative, complementary methods including Rock Eval pyrolysis and parameters based on organic compounds (CPI, Pr/n-C17, Ph/n-C18, MPI1, and MDR) from extracts did not prove adequate as universal thermal maturity indicators. We have confirmed previous suggestions that Llandovery shales are the most likely Silurian source rocks for the generation of hydrocarbons in the HCM.

New Insights into Arctic Tectonics: Uranium-Lead, (Uranium-Thorium)/Helium, and Hafnium Isotopic Data from the Franklinian Basin, Canadian Arctic Islands

NASA Astrophysics Data System (ADS)

Anfinson, Owen Anthony

More than 2300 detrital zircon uranium-lead (U-Pb) ages, 32 176Hf/177Hf (eHf) isotopic values, 37 apatite helium (AHe) ages, and 72 zircon helium (ZHe) ages represent the first in-depth geochronologic and thermochronologic study of Franklinian Basin strata in the Canadian Arctic and provide new insight on >500 M.y. of geologic history along the northern Laurentian margin (modern orientation). Detrital zircon U-Pb age data demonstrate that the Franklinian Basin succession is composed of strata with three distinctly different provenance signatures. Neoproterozoic and Lower Cambrian formations contain detrital zircon populations consistent with derivation from Archean to Paleoproterozoic gneisses and granites of the west Greenland--northeast Canadian Shield. Lower Silurian to Middle Devonian strata are primarily derived from foreland basin strata of the East Greenland Caledonides (Caledonian orogen). Middle Devonian to Upper Devonian strata also contain detrital zircon populations interpreted as being primarily northerly derived from the continental landmass responsible for the Ellesmerian Orogen (often referred to as Crockerland). U-Pb age data from basal turbidites of the Middle to Upper Devonian clastic succession suggest Crockerland contributed sediment to the northern Laurentian margin by early-Middle Devonian time and that prior to the Ellesmerian Orogeny Crockerland had a comparable geologic history to the northern Baltica Craton. Detrital zircon U-Pb ages in Upper Devonian strata suggest Crockerland became the dominant source by the end of Franklinian Basin sedimentation. Mean eHf values from Paleozoic detrital zircon derived from Crockerland suggest the zircons were primarily formed in either an island arc or continental arc built on accreted oceanic crust setting. ZHe cooling ages from Middle and Upper Devonian strata were not buried deeper than 7 km since deposition and suggest Crockerland was partially exhumed during the Caledonian Orogen. AHe cooling ages

Composition of natural gas and crude oil produced from 10 wells in the Lower Silurian "Clinton" Sandstone, Trumbull County, Ohio: Chapter G.7 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Burruss, Robert A.; Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

Natural gases and associated crude oils in the “Clinton” sandstone, Medina Group sandstones, and equivalent Tuscarora Sandstone in the northern Appalachian basin are part of a regional, continuous-type or basin-centered accumulation. The origin of the hydrocarbon charge to regional continuoustype accumulations is poorly understood. We have analyzed the molecular and stable isotopic composition of gases and oils produced from 10 wells in the “Clinton” sandstone in Trumbull County, Ohio, in an initial attempt to identify the characteristics of the accumulated fluids. The analyses show that the fluids have remarkably uniform compositions that are similar to previously published analyses of oils (Cole and others, 1987) and gases (Laughrey and Baldasarre, 1998) in Early Silurian reservoirs elsewhere in Ohio; however, geochemical parameters in the oils and gases suggest that the fluids have experienced higher levels of thermal stress than the present-day burial conditions of the reservoir rocks. The crude oils have an unusual geochemical characteristic: they do not contain detectable levels of sterane and triterpane biomarkers. The origin of these absences is unknown.

Petroleum potential of the Reggane Basin, Algeria

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

Boudjema, A.; Hamel, M.; Mohamedi, A.

1990-05-01

The intracratonic Reggane basin is located on the Saharan platform, southwest of Algeria. The basin covers an area of approximately 140,000 km{sup 2}, extending between the Eglab shield in the south and the Ougarta ranges in the north. Although exploration started in the early 1950s, only a few wells were drilled in this basin. Gas was discovered with a number of oil shows. The sedimentary fill, mainly Paleozoic shales and sandstones, has a thickness exceeding 5,000 m in the central part of the basin. The reservoirs are Cambrian-Ordovician, Siegenian, Emsian, Tournaisian, and Visean sandstones with prospective petrophysical characteristics. Silurian Uppermore » Devonian and, to a lesser extent Carboniferous shales are the main source rocks. An integrated study was done to assess the hydrocarbon potential of this basin. Tectonic evolution source rocks and reservoirs distribution maturation analyses followed by kinetic modeling, and hydrogeological conditions were studied. Results indicate that gas accumulations could be expected in the central and deeper part of the basin, and oil reservoirs could be discovered on the basin edge.« less

Climate warming could increase recruitment success in glacier foreland plants.

PubMed

Mondoni, Andrea; Pedrini, Simone; Bernareggi, Giulietta; Rossi, Graziano; Abeli, Thomas; Probert, Robin J; Ghitti, Michele; Bonomi, Costantino; Orsenigo, Simone

2015-11-01

Glacier foreland plants are highly threatened by global warming. Regeneration from seeds on deglaciated terrain will be crucial for successful migration and survival of these species, and hence a better understanding of the impacts of climate change on seedling recruitment is urgently needed to predict future plant persistence in these environments. This study presents the first field evidence of the impact of climate change on recruitment success of glacier foreland plants. Seeds of eight foreland species were sown on a foreland site at 2500 m a.s.l., and at a site 400 m lower in altitude to simulate a 2·7 °C increase in mean annual temperature. Soil from the site of origin was used to reproduce the natural germination substrate. Recruitment success, temperature and water potential were monitored for 2 years. The response of seed germination to warming was further investigated in the laboratory. At the glacier foreland site, seedling emergence was low (0 to approx. 40 %) and occurred in summer in all species after seeds had experienced autumn and winter seasons. However, at the warmer site there was a shift from summer to autumn emergence in two species and a significant increase of summer emergence (13-35 % higher) in all species except two. Survival and establishment was possible for 60-75 % of autumn-emerged seedlings and was generally greater under warmer conditions. Early snowmelt in spring caused the main ecological factors enhancing the recruitment success. The results suggest that warming will influence the recruitment of glacier foreland species primarily via the extension of the snow-free period in spring, which increases seedling establishment and results in a greater resistance to summer drought and winter extremes. The changes in recruitment success observed here imply that range shifts or changes in abundance are possible in a future warmer climate, but overall success may be dependent on interactions with shifts in other components of the

Strontium isotopic evidence of shifting inflows to Eocene Lake Uinta in the Laramide foreland of Utah

NASA Astrophysics Data System (ADS)

Davis, S. J.; Wiegand, B. A.; Chamberlain, C. P.

2007-12-01

Isotopic records from the Uinta basin in Utah are evidence of an evolving landscape during the early Cenozoic. Combined with studies of provenance and paleoflow, oxygen and carbon isotopic results have recently been interpreted to reflect changes in hydrology and catchment hypsometry as the basin responded to developing relief in the foreland. We now present strontium isotope data from lacustrine limestones indicating significant and rapid (< 1 my) shifts in the source of inflowing surface waters. Provenance of Eocene sediments has been used to argue that water spilling south from an overfilled Lake Gosiute in the Greater Green River basin caused a highstand of the lake in the Piceance Creek basin, which in turn overtopped the Douglas Creek Arch and connected with Lake Uinta in the Uinta basin. The lake highstand was extremely productive, and resulted in the deposition of the rich "Mahogany zone" oil shales. New data shows that the 87Sr/86Sr ratio of lacustrine limestones collected in the Uinta basin is generally low (< 0.7105) for most of the Eocene, but spikes higher (to 0.7122) in samples of the Main Body of the Green River Formation near and within the Mahogany zone. We interpret this data to reflect a period of input of water from Lake Gosiute, where that lake's catchments included exposed basement that was much more radiogenic. The strontium data further supports the interpretation that intraforeland basin development in the central North American Cordillera was largely controlled by shifting drainage patterns as the landscape responded to ongoing Laramide tectonism.

Provenance Analysis of Upper Cretaceous - Paleogene Sandstones in the Foreland Basin System of the Tansen Unit, Central Nepal

NASA Astrophysics Data System (ADS)

Neupane, B.; Ju, Y.; Allen, C.

2016-12-01

The continental deposits foreland basin of Central Nepal, Amile Formation, Bhainskati Formation and Dumri Formation (Tansen unit) are the key region for provenance analysis, preserved almost complete sedimentation history of tectonic collision of Indian and Asian plates. Samples from two field traverses are examined petrographically and through zircon U-Pb dating, one traverse through the Tansen Group, and another through its potential source rocks, the Higher and Tethys Himalaya. The Tansen Group ages are well known through fossil assemblages. We examine sandstone-bearing units of the Tansen Group, the upper 3 of 5 Formations. The optical petrography data and resulting classify Tansen sediments as "recycled orogenic" and "Quartzose recycled", indicating that Indian cratonal sediments as the likely source of sediments for the Amile Formations, and the Tethyan Himalaya as the source for the Bhainskati Formation, and both the Tethys and Higher Himalaya as the major sources for the Dumri Formation. The Cretaceous to Paleocene pre-collisional Amile Formation is dominated by a broad 1830 Ma age peak with neither Paleozoic nor Neoproterozic zircons, but hosts a significant proportion (23%) of syndepositional Cretaceous zircons (121 to 105 Ma) indicative of nearby Cretaceous volcanism at that time. Therefore, the rare volcanic fragments in detritus of Amile Formation were derived from the Rajmahal Volcanic Province defining the middle to late Cretaceous depositional age. The other Formations of the Tansen Group are more similar to Tethys units than to Higher Himalaya. Further, the 23+/-1 Ma zircons in two of the crystalline Higher Himalaya units suggest that they could not have been exposed until at or after this time.

Structural Framework and Architecture of the Paleoproterozoic Bryah and Padbury Basins from Integrated Potential Field and Geological Datasets: Towards an Understanding of the Basin Evolution

NASA Astrophysics Data System (ADS)

Nigro R A Ramos, L.; Aitken, A.; Occhipinti, S.; Lindsay, M.

2017-12-01

The Bryah and Padbury Basins were developed along the northern margin of the Yilgarn Craton, in the southern portion of the Capricorn Orogen, which represents a Proterozoic tectonic zone that bounds the Yilgarn and Pilbara Cratons in Western Australia. These basins have been previously interpreted as developing in a rift, back-arc, and retro-arc foreland basins. Recent studies suggest that the Bryah Basin was deposited in a rift setting, while the overlying Padbury Basin evolved in a pro-foreland basin during the collision of the Yilgarn Craton and the Pilboyne block (formed by the Pilbara Craton and the Glenburgh Terrane), occurring in the Glenburgh Orogeny (2005-1960 Ma). This study focuses on characterizing the architecture and structural framework of the Bryah and Padbury Basins through analysis of geophysical and geological datasets, in order to better understand the different stages of the basins evolution. Gravity and magnetic data were used to define the main tectonic units and lithological boundaries, and to delineate major discontinuities in the upper and lower crust, as well as anomalies through a combination of map view interpretation and forward modelling. Geological mapping and drill core observations were linked with the geophysical interpretations. Fourteen magnetic domains are distinguished within the basins, while four main domains based on the Bouguer Anomaly are recognized. The highest gravity amplitude is related with an anomaly trending EW/NE-SW, which is coincident with the voluminous mafic rocks of the Bryah Basin, and may indicate the presence of an approximately 5km thick package of higher density mafic rocks. Magnetic depth estimations also indicate deep magnetic sources up to approximately 4,45km. These results can help to elucidate processes that occurred during the precursor rift of the early stages of the Bryah Basin, add information in relation to the basement control on sedimentation, allow the characterization of the varying

Evolving lithospheric flexure and paleotopography of the Pyrenean Orogen from 3D flexural modeling and basin analysis

NASA Astrophysics Data System (ADS)

Curry, M. E.; van der Beek, P.; Huismans, R. S.; Muñoz, J. A.

2017-12-01

The Pyrenees are an asymmetric, doubly-vergent orogen with retro- and pro- foreland basins that preserve a record of deformation since the Mesozoic. The extensive research and exploration efforts on the mountain belt and flanking foreland basins provide an exceptional dataset for investigating geodynamics and surface processes over large spatial and temporal scales in western Europe. We present the results of a numerical modeling study investigating the spatio-temporal variation in lithospheric flexure in response to the developing orogen. We employ a finite element method to model the 3D flexural deformation of the lithosphere beneath the Pyrenean orogen since the onset of convergence in the late Cretaceous. Using subsurface, geophysical, and structural data, we describe the evolving geometry of both the French Aquitaine and Spanish Ebro foreland basins at the present (post-orogenic), the mid-Eocene (peak orogenic), the Paleocene (early orogenic), and the end of the Cretaceous (pre- to early orogenic). The flexural modeling provides insight into how both the rigidity of the lithosphere and the paleotopographic load have varied over the course of orogenesis to shape the basin geometry. We find that the overriding European plate has higher rigidity than the subducting Iberian plate, with modern Effective Elastic Thickness (EET) values of 20 ± 2 and 12 ± 2 km, respectively. Modeling indicates that the modern rigidity of both plates decreases westward towards the Bay of Biscay. The lithospheric rigidity has increased by 50% since the Mesozoic with early Cenozoic EET values of 13 ± 2 and 8 ± 1 km for the European and Iberian plates, respectively. The topographic load began increasing with convergence in the late Cretaceous, reaching modern levels in the central and eastern Pyrenees by the Eocene. In contrast, the topographic load in the western Pyrenees was 70% of the modern value in the Eocene, and experienced topographic growth through the Oligo-Miocene. The

Successive reactivation of older structures under variable heat flow conditions evidenced by K-Ar fault gouge dating in Sierra de Ambato, northern Argentine broken foreland

NASA Astrophysics Data System (ADS)

Nóbile, Julieta C.; Collo, Gilda; Dávila, Federico M.; Martina, Federico; Wemmer, Klaus

2015-12-01

The Argentine broken foreland has been the subject of continuous research to determine the uplift and exhumation history of the region. High-elevation mountains are the result of N-S reverse faults that disrupted a W-E Miocene Andean foreland basin. In the Sierra de Ambato (northern Argentine broken foreland) the reverse faults offset Neogene sedimentary rocks (Aconquija Fm., ˜9 Ma) and affect the basement comprising Paleozoic metamorphic rocks that have been dated at ˜477-470 Ma. In order to establish a chronology of these faults affecting the previous continuous basin we date the formation age of clay minerals associated with fault gouge using the K-Ar dating technique. Clay mineral formation is a fundamental process in the evolution of faults under the brittle regime (<<300 °C). K-Ar ages (9 fractions from 3 samples collected along a transect in the Sierra de Ambato) vary from Late Devonian to Late Triassic (˜360-220 Ma). This age distribution can be explained by a long lasting brittle deformation history with a minimum age of ˜360 Ma and a last clay minerals forming event at ˜220 Ma. Moreover, given the progression of apparent ages decreasing from coarse to fine size fractions (˜360-311 Ma for 2-1 μm grain size fraction, ˜326-286 Ma for 1-0.2 μm and ˜291-219 Ma of <0.2 μm), we modeled discrete deformation events at ˜417 Ma (ending of the Famatinian cycle), ˜317-326 Ma (end of Gondwanic orogeny), and ˜194-279 Ma (Early Permian - Jurassic deformation). According to our data, the Neogene reactivation would not have affected the K-Ar system neither generated a significant clay minerals crystallization in the fault gouge, although an exhumation of more than 2 Km is recorded in this period from stratigraphic data.

Revised crustal architecture of the southeastern Carpathian foreland from active and passive seismic data

NASA Astrophysics Data System (ADS)

Enciu, Dana M.; Knapp, Camelia C.; Knapp, James H.

2009-08-01

Integration of active and passive source seismic data is employed in order to study the nature of the relationships between crustal seismicity and geologic structures in the southeastern (SE) Carpathian foreland of Romania and the possible connection with the Vrancea Seismogenic Zone (VSZ) of intermediate-depth seismicity, one of the most active earthquake-prone areas in Europe. Crustal epicenters and focal mechanisms are correlated with four deep industry seismic profiles, the reprocessed Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics (DACIA PLAN) profile and the Deep Reflection Acquisition Constraining Unusual Lithospheric Activity II and III (DRACULA) profiles in order to understand the link between neotectonic foreland deformation and Vrancea mantle seismicity. Projection of crustal foreland hypocenters onto deep seismic profiles identifies several active crustal faults in the SE Carpathian foreland and suggests a mechanical coupling between the mantle located VSZ and the overlying foreland crust. The coupled associated deformation appears to take place on the Trotus Fault, the Sinaia Fault, and the newly detected Ialomita Fault. Seismic reflection imaging reveals the absence of west dipping reflectors in the crystalline crust and a slightly east dipping to horizontal Moho in the proximity of the Vrancea area. These findings argue against previously purported mechanisms to generate mantle seismicity in the VSZ including oceanic lithosphere subduction in place and oceanic slab break off, furthermore suggesting that the Vrancea seismogenic body is undetached from the overlying crust in the foreland.

Integrated stratigraphy of the Ammer section, Northern Alpine Foreland Basin, Germany: examining the age and origin of the earliest deposits in the Paratethys

NASA Astrophysics Data System (ADS)

van der boon, Annique; Beniest, Anouk; Ciurej, Agnieszka; Gaździcka, Elzbieta; Grothe, Arjen; Sachsenhofer, Reinhard; Langereis, Cor; Krijgsman, Wout

2017-04-01

The Northern Alpine Foreland Basin (NAFB) was an arm of the epicontinental Paratethys Sea during the Oligocene. The Oligocene and Miocene deposits in the Paratethys are linked to a long-term phase of episodically oxygen-poor conditions. This led to the deposition of organic-rich shales over millions of years, which nowadays make up the most important part of the source rocks of the Paratethys. At the Eocene-Oligocene transition (EOT), global sea-level dropped by an estimated 70 meters. Both this eustatic sea-level drop and large scale tectonic movements are inferred as mechanisms for restriction of connections to the global ocean and consecutive basin isolation in the Paratethys. Discriminating sea-level effects from tectonic processes requires accurate dating of Oligocene deposits. Here, we use an integrated stratigraphic approach, combining different biostratigraphic techniques with magnetostratigraphy and organic geochemistry, to determine the age of the Tonmergel formation along the Ammer River in southern Germany. The Tonmergel formation is usually interpreted as the equivalent of the Paratethys Lower Oligocene organic-rich shales. The age of deposits (typically mapped as Oligocene) in this region is currently under debate, as some studies suggest they might be late Eocene in age. The absence of marker species for biostratigraphic zones, the scarcity of ash layers and the lack of formally defined boundaries of nannoplankton zones around the Eocene-Oligocene interval (e.g. the NP19-20/NP21 boundary) further obstruct accurate dating. Here we present the results of our magnetostratigraphy, biostratigraphy and organic geochemistry and interpret whether any lithological changes can be linked to climate forcing or tectonic processes. Based on the combined results of our study we provide several options for the age of these earliest Paratethys deposits, and discuss our preferred option.

Overdeeping and stratigraphy of a typical Alpine foreland glacier

NASA Astrophysics Data System (ADS)

Salcher, Bernhard; Reinhard, Starnberger; Götz, Joachim

2015-04-01

The Northern Alpine Foreland was repeatedly covered by massive piedmont glaciers during Quaternary peak glacial periods. Remnants of the Salzach foreland glacier (Austria/Germany) represent the easternmost of a series of piedmont glaciers entering the Foreland by major Alpine valleys reaching far into the Alpine Molasse. The area of the former Salzach foreland glacier (SFG) marks a unique place as remnants of at least 4 glacial maxima meet an abundant geodatabase including information on the digital topography and the internal built up of glacial deposits derived from outcrops and several hundreds of drillings. During the LGM, it covered an area of more than 1000 km² and was even more extensive during older peak glacial periods. The lack of absolute ages as well as systemic investigation of the internal built up did so far impede the reconstruction on its dynamics. Here we aim to bring more light into the erosional and depositional history of a typical north Alpine piedmont glacier, the SFG, by analyzing drill log data, field outcrops, topography and the depositional ages of sediments. We focus on the proximal (axial) and distal parts of the SFG lobe. Some of the major unresolved questions regarding the Quaternary evolution of the major Alpine foreland glaciers are: Is the glacial erosion of Miocene bedrock the consequence of one glacial cycle or does it rather reflect successive erosional events during each glacial period? What is the spatial variability and potential depth of erosion? What is the structure and internal built up these deposits? The intent of this study is not to answer these questions in detail but to deliver important constraints: Our results indicate that more than 300- 400 m of bedrock were eroded during an early peak glacial period (such as antepenultimate glacial period or even earlier). Erosion was rather uniform across the lobe with larger values only occurring in the center (axis) of the glacier. Accumulation of more than 100 m of

New insight on petroleum system modeling of Ghadames basin, Libya

NASA Astrophysics Data System (ADS)

Bora, Deepender; Dubey, Siddharth

2015-12-01

Underdown and Redfern (2008) performed a detailed petroleum system modeling of the Ghadames basin along an E-W section. However, hydrocarbon generation, migration and accumulation changes significantly across the basin due to complex geological history. Therefore, a single section can't be considered representative for the whole basin. This study aims at bridging this gap by performing petroleum system modeling along a N-S section and provides new insights on source rock maturation, generation and migration of the hydrocarbons using 2D basin modeling. This study in conjunction with earlier work provides a 3D context of petroleum system modeling in the Ghadames basin. Hydrocarbon generation from the lower Silurian Tanezzuft formation and the Upper Devonian Aouinet Ouenine started during the late Carboniferous. However, high subsidence rate during middle to late Cretaceous and elevated heat flow in Cenozoic had maximum impact on source rock transformation and hydrocarbon generation whereas large-scale uplift and erosion during Alpine orogeny has significant impact on migration and accumulation. Visible migration observed along faults, which reactivated during Austrian unconformity. Peak hydrocarbon expulsion reached during Oligocene for both the Tanezzuft and the Aouinet Ouenine source rocks. Based on modeling results, capillary entry pressure driven downward expulsion of hydrocarbons from the lower Silurian Tanezzuft formation to the underlying Bir Tlacsin formation observed during middle Cretaceous. Kinetic modeling has helped to model hydrocarbon composition and distribution of generated hydrocarbons from both the source rocks. Application of source to reservoir tracking technology suggest some accumulations at shallow stratigraphic level has received hydrocarbons from both the Tanezzuft and Aouinet Ouenine source rocks, implying charge mixing. Five petroleum systems identified based on source to reservoir correlation technology in Petromod*. This Study builds

A possible explanation for foreland thrust propagation

NASA Astrophysics Data System (ADS)

Panian, John; Pilant, Walter

1990-06-01

A common feature of thin-skinned fold and thrust belts is the sequential nature of foreland directed thrust systems. As a rule, younger thrusts develop in the footwalls of older thrusts, the whole sequence propagating towards the foreland in the transport direction. As each new younger thrust develops, the entire sequence is thickened; particularly in the frontal region. The compressive toe region can be likened to an advancing wave; as the mountainous thrust belt advanced the down-surface slope stresses drive thrusts ahead of it much like a surfboard rider. In an attempt to investigate the stresses in the frontal regions of thrustsheets, a numerical method has been devised from the algorithm given by McTigue and Mei [1981]. The algorithm yields a quickly computed approximate solution of the gravity- and tectonic-induced stresses of a two-dimensional homogeneous elastic half-space with an arbitrarily shaped free surface of small slope. A comparison of the numerical method with analytical examples shows excellent agreement. The numerical method was devised because it greatly facilitates the stress calculations and frees one from using the restrictive, simple topographic profiles necessary to obtain an analytical solution. The numerical version of the McTigue and Mei algorithm shows that there is a region of increased maximum resolved shear stress, τ, directly beneath the toe of the overthrust sheet. Utilizing the Mohr-Coulomb failure criterion, predicted fault lines are computed. It is shown that they flatten and become horizontal in some portions of this zone of increased τ. Thrust sheets are known to advance upon weak decollement zones. If there is a coincidence of increased τ, a weak rock layer, and a potential fault line parallel to this weak layer, we have in place all the elements necessary to initiate a new thrusting event. That is, this combination acts as a nucleating center to initiate a new thrusting event. Therefore, thrusts develop in sequence

Tectonic context of the penetrative fracture system origin in the Early Paleozoic shale complex (Baltic Basin, Poland/Sweden).

NASA Astrophysics Data System (ADS)

Jarosiński, Marek; Gluszynski, Andrzej; Bobek, Kinga; Dyrka, Ireneusz

2017-04-01

Characterization of natural fracture and fault pattern play significant role for reservoir stimulation design and evaluation of its results. Having structural observations limited to immediate borehole surrounding it is a common need to build up a fracture model of reservoir in a range of stimulation reservoir volume or even beyond. To do this we need both a 3D seismic model and a consistent concept of the regional tectonic evolution. We present the result of integrated tectonic study in several deep boreholes target the Lower Paleozoic shale complex of Baltic Basin (BB), combined with analysis of 3D seismic survey and outcrop screening in Scania (Swedish part of the BB). During deposition of shale complex in the Ordovician and Silurian the research area was located 200-300 km away from the continental margin of Baltica involved in the Caledonian collision with the Eastern Avalonia. This distance allowed the shale complex to avoid significant tectonic deformation. Regional seismic cross section reveals the general pattern of the BB infill characteristic for the foreland basin underwent post-collisional isostatic rebound. Due to stress changes in collisional context the shale complex was cross-cut by steep, mostly inverse faults trending NW-SE and NE-SW. The fault zones oriented NW-SE are associated with an array of en echelon faults characteristic for strike-slip displacement. In our interpretation, these faults of Silurian (Wenlock) age create pattern of the regional pop-up structure, which is simultaneously involved in the plate flexure extension. Seismic attributes (e.g. curvature or ant tracking) highlight lineaments which mostly mimic the faults orientation. However, attributes show also some artefacts that come from regular array of seismic sources and receivers, which mimic the orthogonal joint system. Structural observations on borehole core lead us to conclusion that regular, orthogonal fracture system developed after maximum burial of the complex

Pliocene Deep Water Channel System of Celebes Molasse as New Exploration Play In Banggai Sula Foreland Basin, Eastern Sulawesi-Indonesia

NASA Astrophysics Data System (ADS)

Prima Kurniawan, Anggoro; Purnomo Adi, Galang; Sundari, Wahyuni Tri; Arifin, Maikel; Jaya Panguriseng, Muharram; Hartanto, Sri; Herawati, Neni

2018-03-01

Banggai-Sula foreland basin in Matindok block is the product of Late Miocene to Early Pliocene collision between Banggai-Sula microcontinent and East Sulawesi Ophiolite (ESO)-magmatic arc of Sundaland. Proven petroleum system plays for Donggi, Senoro, and Matindok gas fields are Miocene build-up carbonate and platform carbonates related to wrench structures, sealed by Plio-Pleistocene Celebes Molasse consists of conglomerate, conglomeratic sandstone, shale and charged during early Pliocene related to collisional tectonic from Miocene marine clastic source rocks. Latest interpretation of 3D & 2D seismic datasets on onshore area of Matindok block shown that there is possibility of NE to SW trending channel systems existed in Plio-Pleistocene Celebes Molasse as post collision sediments. Based on biostratigraphy interpretation, Celebes Molasse interval was deposited in marine environment, generally outer sublittoral to upper bathyal. Channel filled pattern on seismic data expression shown onlap, divergent and mounded-onlap fills on 6 (six) interpreted channel bodies. Fining upward sequences is well recognized based on gamma ray log from several wells that penetrated those interpreted channel. The thicknesses of channel bodies vary from 50 m to 150 m with sand to shale ratio up to 40 % and gas composition reading from C1 to C3. Despite of there is no well testing data on these channels interval; we believed that this Pliocene deep water channel can become the new exploration play although several studies about seal effectiveness of channel bodies as stratigraphic traps, lateral and vertical migration pathways need to be carried out.

Linking time-Temperature history of the Aquitaine basin with post-orogenic evolution of the Pyrenees : new insights from borehole thermochronology

NASA Astrophysics Data System (ADS)

Fillon, Charlotte; Calassou, Sylvain; Mouthereau, Frédéric; Pik, Raphaël; Bellahsen, Nicolas; Gautheron, Cécile

2017-04-01

Within their sedimentary record, foreland basins document vertical movements of the lithosphere, climatic changes, paleogeograhic evolution but also history of exhumation of the adjacent mountain belt. Comparing vertical movements in a range and in its foreland is key to identify processes involved in growth and destruction of mountain belts. The Aquitaine basin, geomorphologically stable since the early Pyrenean orogenesis has the potential to help understanding the driving mechanisms during the late to post-orogenic phases, but the lack of outcrops makes the studies particularly difficult to achieve. To bring a new point of vue on the processes involved in the Cenozoic exhumation of this range, we present new low-Temperature thermochronology data from boreholes of the Aquitaine basin. With the objectives to study rift-related to post-orogenic processes, numerous low-T thermochronological ages ( 300 across the range) have been published, documenting pre-, syn- , and post-orogenic exhumation in the Pyrenees. Using thermal modeling of a new low-T database in the western Axial Zone, we show that a late Miocene (around 10 Ma) uplift occured in the western Pyrenees, which generalizes the post-orogenic signal already detected in the south central Pyrenees. In previous studies, we linked the post-orogenic exhumation in the Southern Pyrenees to the excavation of the foreland valleys caused by the opening of the endorheic Ebro basin towards the Mediterranean Sea. To the West, the tectonic out-of sequence reactivation of the Gavarnie thrust has been invoked to explain the late Miocene AHe ages in the Bielsa massif. These new data might lead us to re-think the causes for such an exhumation signal during "post-orogenic" times. We thus summarize all evidences for the post-orogenic phase and attempt to provide explanation for it: is exhumation driven by Aquitaine foreland basin evolution? Does it reflect a tectonic reactivation of the Pyrenees? or is the signature of a regional

Eocene Unification of Peruvian and Bolivian Altiplano Basin Depocenters

NASA Astrophysics Data System (ADS)

Saylor, J.; Sundell, K. E.; Perez, N.; Karsky, N.; Lapen, T. J.; Cárdenas, J.

2017-12-01

Paleogene evolution of the Altiplano basin has been characterized as a flexural foreland basin which developed in response to magmatic and thrust loading along its western margin. Research focused in southern Peru and Bolivia points to broadly synchronous foredeep deposition in a basin assumed to be have been contiguous from at least 14°-23°S. We investigated Paleogene strata exposed on the southwestern margin of Lake Titicaca near the Peru/Bolivia border in order to establish sediment dispersal systems, sediment sources, and the chronology of deposition. A data set of >1,000 paleocurrent measurements throughout the section consistently indicates a western sediment source. The results of detrital zircon mixture modeling are consistent with derivation from Cretaceous volcanic sources, and Cretaceous and Ordovician sedimentary strata exposed in the Western Cordillera. These results confirm previous models in which sedimentary sources for the Altiplano basin are dominated by the Western Cordillera throughout the Paleogene. The detrital zircon signatures from strata in this stratigraphic section where paleocurrent orientation is well constrained provide a benchmark for future research seeking to determine sediment sources for the Altiplano basin. However, refined chronologies based on detrital zircon U-Pb maximum depositional ages (MDAs) point to development of at least two Paleocene depocenters in Peru and Bolivia separated by a zone of nondeposition or erosion in southern Peru. The basal Muñani Formation in southern Peru yields MDAs of 36.9-40.2 Ma, which requires revision of the previously determined middle Paleocene onset of deposition. The Muñani Formation overlies the Vilquechico Group which has been biostratigraphically determined to range from Campanian-Maastrichtian (or possibly Paleocene, 60 Ma). The revised chronology for the Muñani Formation requires a disconformity of at least 20 Myr during which deposition continued in both the Peruvian and Bolivian

Tectonic constraints on the development and individualization of the intermontane Ronda basin (external Betics, southern Spain): a structural and geomorphologic approach.

NASA Astrophysics Data System (ADS)

Jiménez-Bonilla, Alejandro; Balanyá, Juan Carlos; Expósito, Inmaculada; Díaz-Azpiroz, Manuel; Barcos, Leticia

2014-05-01

As a result of progressive shortening and orogenic wedge thickening, marine foreland basins tend to emerge and divide. We have analyzed possible recent tectonic activity within the late evolution stage of the Ronda basin, an intermontane basin located in the external wedge of the Gibraltar Arc, formerly connected with the Betic foreland basin and infilled by marine Upper-Miocene sediments. We analyze (1) the structures responsible for the basinward relief drop along the arc strike and the different topography of their boundaries; (2) qualitative and quantitative geomorphologic indices to asses which structures could present recent activity; and 3) the structures causing the division of the former Betic foreland basin and the isolation of the Ronda basin. Within the deformational history of the Ronda basin, late structures that control high topographic gradients and generate remarkable fault scarps group into three main types: (a) Extensional structures represented by NW-SE striking normal faults, clustered close to the current SW and NE boundaries of the basin. They usually dip towards the basin and their vertical displacement is maximum up to 1,5 km. These structures partially affect the basal unconformity of the Upper Miocene basin infill and are scarcely developed inside the basin infill. (b) Shortening structures developed both in the basin infill and in the outcropping basement near the Northeastern and Southwestern basin boundaries. They are represented by NE-SW directed plurikilometric box-folds and reverse faults, responsible for the alternation of sierras (altitudes 1000-1500 m) and valleys. (c) Strike-slip dominated structural associations where WSW-ENE lateral faults combined with folds and normal and reverse faults defined a NE-SW directed deformation band constituting the NW basin boundary. This band includes some sierras up to 1.100 m. Regarding the relief of the Ronda basin area, the abrupt slopes of the outcropping basement (heights between 500

Géodynamique et évolution thermique de la matière organique: exemple du bassin de Qasbat-Tadla, Maroc centralBasin geodynamics and thermal evolution of organic material: example from the Qasbat-Tadla Basin, central Morocco

NASA Astrophysics Data System (ADS)

Er-Raïoui, H.; Bouabdelli, M.; Bélayouni, H.; Chellai, H.

2001-05-01

Seismic data analysis of the Qasbat-Tadla Basin allows the deciphering of the main tectonic and sedimentary events that characterised the Hercynian orogen and its role in the basin's structural development. The global tectono-sedimentary framework involves structural evolution of an orogenic foreland basin and was the source of rising geotherms in an epizonal metamorphic environment. The complementary effects of these parameters has led to different source rock maturity levels, ranging from oil producing to graphite domains. Different maturity levels result from three distinct structural domains within the basin, each of which exhibit characteristic geodynamic features (tectonic contraints, rate of subsidence, etc.).

Structural setting of the Metán Basin (NW Argentina): new insights from 2D seismic profiles

NASA Astrophysics Data System (ADS)

Conti, Alessia; Maffucci, Roberta; Bigi, Sabina; Corrado, Sveva; Giordano, Guido; Viramonte, José G.

2017-04-01

The Metán Basin is located in the sub-Andean foreland, in the southernmost portion of the Santa Barbara system structural province (NW Argentina). The upper crust in this region shows a strong segmentation due to inherited stratigraphic and structural discontinuities, related to a Palaeozoic orogenic event and to a Cretaceous to Paleogene rifting event (Kley et al., 1999; Iaffa et al., 2011). This study seeks to unravel the deep structural setting of the basin, in order to better understand the tectonic evolution of the area. Different seismic sections are analysed, located in the Metán basin and acquired by YPF (Yacimientos Petrolíferos Fiscales, former national oil company of Argentina) in different surveys during the '70s - '80s. Stratigraphic control for the seismic interpretation is provided by petroleum exploratory wells drilled in the basin; they show a stratigraphic succession of syn-rift and post-rift deposits, mainly constituted by a continental succession of red beds, with minor limestone intercalations (Salta Group), overlain by a thick continental foreland basin succession (Orán Group) (Salfity et al., 1981). From a structural point of view, the Metán basin is characterized by a variety of structural trends, with thrust faults and related folds mainly trending N-S, NE-SW and NNE-SSW. Different mechanism can be responsible for the folding of the sedimentary cover; hangingwall anticlines are represented both by high angle thrust faults produced by inversion of Cretaceous extensional faults (Maffucci et al., 2015), and by fault propagation folds formed during the Andean shortening event. The study of the interaction between the older reactivated faults and the newly generated ones could provide new insights to unravel the complex structural setting of the area. References Iaffa D. N., Sàbat, F., Muñoz, J.A., Mon, R., Gutierrez, A.A., 2011. The role of inherited structures in a foreland basin evolution. The Metán Basin in NW Argentina. Journal of

Tectonic and thermal history of the western Serrania del Interior foreland fold and thrust belt and Guarico Basin, north central Venezuela: Implications of new apatite fission track analysis and seismic interpretation

NASA Astrophysics Data System (ADS)

Perez de Armas, Jaime Gonzalo

Structural analysis, interpretation of seismic reflection lines, and apatite fission-track analysis in the Western Serrania del Interior fold and thrust belt and in the Guarico basin of north-central Venezuela indicate that the area underwent Mesozoic and Tertiary-to-Recent deformation. Mesozoic deformation, related to the breakup of Pangea, resulted in the formation of the Espino graben in the southernmost portion of the Guarico basin and in the formation of the Proto-Caribbean lithosphere between the diverging North and South American plates. The northern margin of Venezuela became a northward facing passive margin. Minor normal faults formed in the Guarico basin. The most intense deformation took place in the Neogene when the Leeward Antilles volcanic island arc collided obliquely with South America. The inception of the basal foredeep unconformity in the Late Eocene-Early Oligocene marks the formation of a perisutural basin on top of a buried graben system. It is coeval with minor extension and possible reactivation of Cretaceous normal faults in the Guarico basin. It marks the deepening of the foredeep. Cooling ages derived from apatite fission-tracks suggest that the obduction of the fold and thrust belt in the study area occurred in the Late Oligocene through the Middle Miocene. Field data and seismic interpretations suggest also that contractional deformation began during the Neogene, and specifically during the Miocene. The most surprising results of the detrital apatite fission-track study are the ages acquired in the sedimentary rocks of the easternmost part of the study area in the foreland fold and thrust belt. They indicate an Eocene thermal event. This event may be related to the Eocene NW-SE convergence of the North and South American plates that must have caused the Proto-Caribbean lithosphere to be shortened. This event is not related to the collision of the arc with South America, as the arc was far to the west during the Eocene.

Paleozoic evolution of active margin basins in the southern Central Andes (northwestern Argentina and northern Chile)

NASA Astrophysics Data System (ADS)

Bahlburg, H.; Breitkreuz, C.

The geodynamic evolution of the Paleozoic continental margin of Gondwana in the region of the southern Central Andes is characterized by the westward progression of orogenic basin formation through time. The Ordovician basin in the northwest Argentinian Cordillera Oriental and Puna originated as an Early Ordovician back-arc basin. The contemporaneous magmatic arc of an east-dipping subduction zone was presumably located in northern Chile. In the back-arc basin, a ca. 3500 meter, fining-up volcaniclastic apron connected to the arc formed during the Arenigian. Increased subsidence in the late Arenigian allowed for the accomodation of large volumes of volcaniclastic turbidites during the Middle Ordovician. Subsidence and sedimentation were caused by the onset of collision between the para-autochthonous Arequipa Massif Terrane (AMT) and the South American margin at the Arenigian-Llanvirnian transition. This led to eastward thrusting of the arc complex over its back-arc basin and, consequently, to its transformation into a marine foreland basin. As a result of thrusting in the west, a flexural bulge formed in the east, leading to uplift and emergence of the Cordillera Oriental shelf during the Guandacol Event at the Arenigian-Llanvirnian transition. The basin fill was folded during the terminal collision of the AMT during the Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin

2.5D seismic velocity modelling in the south-eastern Romanian Carpathians Orogen and its foreland

NASA Astrophysics Data System (ADS)

Bocin, Andrei; Stephenson, Randell; Tryggvason, Ari; Panea, Ionelia; Mocanu, Victor; Hauser, Franz; Matenco, Liviu

2005-12-01

The DACIA-PLAN (Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics) deep seismic reflection survey was performed in August-September 2001, with the objective of obtaining new information on the deep structure of the external Carpathians nappe system and the architecture of the Tertiary/Quaternary basins developed within and adjacent to the Vrancea zone, including the rapidly subsiding Focsani Basin. The DACIA-PLAN profile is about 140 km long, having a roughly WNW-ESE direction, from near the southeast Transylvanian Basin, across the mountainous south-eastern Carpathians and their foreland to near the Danube River. A high resolution 2.5D velocity model of the upper crust along the seismic profile has been determined from a tomographic inversion of the DACIA-PLAN first arrival data. The results show that the data fairly accurately resolve the transition from sediment to crystalline basement beneath the Focsani Basin, where industry seismic data are available for correlation, at depths up to about 10 km. Beneath the external Carpathians nappes, apparent basement (material with velocities above 5.8 km/s) lies at depths as shallow as 3-4 km, which is less than previously surmised on the basis of geological observations. The first arrival travel-time data suggest that there is significant lateral structural heterogeneity on the apparent basement surface in this area, suggesting that the high velocity material may be involved in Carpathian thrusting.

Bimodal Silurian and Lower Devonian volcanic rock assemblages in the Machias-Eastport area, Maine

USGS Publications Warehouse

Gates, Olcott; Moench, R.H.

1981-01-01

Exposed in the Machias-Eastport area of southeastern Maine is the thickest (at least 8,000 m), best exposed, best dated, and most nearly complete succession of Silurian and Lower Devonian volcanic strata in the coastal volcanic belt, remnants of which crop out along the coasts of southern New Brunswick, Canada, and southeastern New England in the United States. The volcanics were erupted through the 600-700-million-year-old Avalonian sialic basement. To test the possibility that this volcanic belt was a magmatic arc above a subduction zone prior to presumed Acadian continental collision, samples representing the entire section in the Machias-Eastport area of Maine were chemically analyzed. Three strongly bimodal assemblages of volcanic rocks and associated intrusives are recognized, herein called the Silurian, older Devonian, and younger Devonian assemblages. The Silurian assemblage contains typically nonporphyritic high-alumina tholeiitic basalts, basaltic andesites, and diabase of continental characterand calc-alkalic rhyolites, silicic dacites, and one known dike of andesite. These rocks are associated with fossiliferous, predominantly marine strata of the Quoddy, Dennys, and Edmunds Formations, and the Leighton Formation of the Pembroke Group (the stratigraphic rank of both is revised herein for the Machias-Eastport area), all of Silurian age. The shallow marine Hersey Formation (stratigraphic rank also revised herein) of the Pembroke Group, of latest Silurian age (and possibly earliest Devonian, as suggested by an ostracode fauna), contains no known volcanics; and it evidently was deposited during a volcanic hiatus that immediately preceded emergence of the coastal volcanic belt and the eruption of the older Devonian assemblage. The older Devonian assemblage, in the lagoonal to subaerial Lower Devonian Eastport Formation, contains tholeiitic basalts and basaltic andesites, typically with abundant plagioclase phenocrysts and typically richer in iron and

Composition of natural gas and crude oil produced from 14 wells in the Lower Silurian "Clinton" Sandstone and Medina Group Sandstones, northeastern Ohio and northwestern Pennsylvania: Chapter G.6 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

USGS Publications Warehouse

Burruss, Robert A.; Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

2014-01-01

The geochemical processes that control the distribution of hydrocarbons in the regional accumulation of natural gas and crude oil in reservoirs of Early Silurian age in the central Appalachian basin are not well understood. Gas and oil samples from 14 wells along a down-dip transect through the accumulation in northeastern Ohio and northwestern Pennsylvania were analyzed for molecular and stable isotopic compositions to look for evidence of hydrocarbon source, thermal maturation, migration, and alteration parameters. The correlation of carbon and hydrogen stable isotopic composition of methane with thermal maturation indicates that the deepest gases are more thermally mature than independent estimates of thermal maturity of the reservoir horizon based on the conodont alteration index. This correlation indicates that the natural gas charge in the deepest parts of the regional accumulation sampled in this study originated in deeper parts of the Appalachian basin and migrated into place. Other processes, including mixing and late-stage alteration of hydrocarbons, may also impact the observed compositions of natural gases and crude oils.

Evidences of Silurian dextral transpression in the Scandinavian Caledonides

NASA Astrophysics Data System (ADS)

Torgersen, Espen; Viola, Giulio

2017-04-01

The Scandinavian Caledonides are classically interpreted as a fold and thrust belt resulting from the collision between Laurentia and Baltica during the Silurian, which involved the up-to-400 km ESE-wards translation of nappes onto the Baltoscandian platform. It has been suggested that the Caledonian fold and thrust belt formed through several distinct orogenic episodes, from early shortening in the Late Ordovician to orogenic collapse in the Devonian. The classic Caledonian, orogen-perpendicular ESE-ward nappe transport is constrained by abundant and consistently oriented stretching lineations across the entire orogen and unambiguous kinematic indicators. However, there is also a large number of NW-SE-trending and roughly orogen-parallel lineations, particularly in the upper ophiolite- and eclogite-bearing nappes, which are more challenging to interpret with the traditional orogeny evolution model. The analysis of the areal extent, spatial distribution and geometrical relationships of the Caledonian nappes in southern and central Norway, however, offers new insights and allows for new constraints on the bulk kinematic framework of the shortening history of the belt. Here we present new, first-order geological observations that demonstrate a two-fold compressional history and associated strain partitioning during Caledonian convergence. More specifically, we propose that Late Ordovician NNW-SSE shortening caused early compression, followed by WNW-ESE Early Silurian shortening, which resulted in strain partitioning along the planar fabrics and discontinuities from the earlier event. In detail, orogen-parallel dextral wrench tectonics caused significant lateral displacement along at least three, orogen-scale NE-SW striking corridors, wherein the nappes appear to be consistently displaced in a dextral fashion. We propose that the Møre-Trøndelag Fault Complex, which accommodated significant sinistral displacements during the later Devonian orogenic collapse

Thermally Altered Silurian Cyanobacterial Mats: A Key to Earth's Oldest Fossils

NASA Astrophysics Data System (ADS)

Kazmierczak, Józef; Kremer, Barbara

2009-10-01

Diagenetic changes in thermally altered cyanobacterial mats from early Silurian black radiolarian cherts of southwestern Poland (Bardzkie Montains, Sudetes) have been studied. These early diagenetically silicified mats are composed of variously degraded remains of benthic microbes that resemble some modern chroococcalean and pleurocapsalean cyanobacteria. Two modes of degradational processes have been recognized in the studied mats: (i) early postmortem biodegradation and (ii) late diagenetic thermal or thermobaric degradation. The latter led to partial transformation of the fossilized organic remnants of cyanobacterial sheaths and capsules, which resulted in the formation of objects morphologically distant from the original microbiota but preserved features that allow for their identification as bona fide biogenic structures. Some of these thermally generated Silurian fossils are highly similar to the controversial microfossil-like carbonaceous structures described from the Early Archean Apex Chert of Australia. This similarity opens a promising way for credible recognition of remnants of cyanobacteria and similar microbiota in other thermally metamorphosed Archean sedimentary rocks

Geologic summary of the Appalachian Basin, with reference to the subsurface disposal of radioactive waste solutions

USGS Publications Warehouse

Colton, G.W.

1962-01-01

the older sequence is absent, the Early Cambrian sequence rests on the basement complex. Interbedded fine- to coarse-grained noncarbonate detrital rocks comprise the bulk of the sequence, but some volcanic and carbonate rocks are included. Next above is the Cambrian-Ordovician carbonate sequence which consists largely of limestone and dolomite. Some quartzose sandstone is present in the lower part in the western half of the basin, and much shale is present in the upper part in the southeast part of the basin. The next higher sequence is the Late Ordovician clastic sequence, which consists largely of shale, siltstone, and sandstone. Coarse-grained light-gray to red rocks are common in the sequence along the eastern side of the basin, whereas fine-grained dark-gray to black calcareous rocks are common along the west side. The Late Ordovician clastic sequence is overlain--unconformably in many places--by the Early Silurian clastic sequence. The latter comprises a relatively thin wedge of coarse-grained clastic rocks. Some of the most prolific oil- and gas-producing sandstones in the Appalachian basin are included. Among these are the 'Clinton' sands of Ohio, the Medina Sandstones of New York and Pennsylvania, and the Keefer or 'Big Six' Sandstone of West Virginia and Kentucky. Conformably overlying the Early Silurian clastic sequence is the Silurian-Devonian carbonate sequence, which consists predominantly of limestone and dolomite. It also contains a salt-bearing unit in the north-central part of the basin and a thick wedge of coarse-grained red beds in the northeastern part. The sequence is absent in much of the southern part of the basin. Large volumes of gas and much oil are obtained from some of its rocks, especially from the Oriskany Sandstone and the Huntersville Chert. The Silurian-Devonian carbonate sequence is abruptly overlain by the Devonian clastic sequence--a thick succession of interbedded shale, mudrock, siltstone, and sandstone. Colors range f

Arthrophycus in the Silurian of Alabama (USA) and the problem of compound trace fossils

USGS Publications Warehouse

Rindsberg, Andrew K.; Martin, A.J.

2003-01-01

Arthrophycus brongniartii (Harlan, 1832) is common in marginal-marine deposits in the Silurian Red Mountain Formation of Alabama. The ichnospecies, the second to be named in North America, is revived and emended after long disuse. Transitional forms to Rusophycus isp. and other morphologic evidence indicate that the maker of Arthrophycus was an arthropod, perhaps a trinucleine (raphiophorid?) trilobite. Interconnection of Arthrophycus and Nereites biserialis, as well as intergradation of Arthrophycus with Cruziana aff. quadrata, Phycodes flabellum, and Asterosoma ludwigae, indicate that these Red Mountain trace fossils were made by the same species of arthropod. Possible relationships with Arthrophycus alleghaniensis (Harlan, 1831) in the Silurian belt from Ontario to Tennessee are also explored. Ichnofamily Arthrophycidae Schimper, 1879 is emended. The ichnofamily is interpreted as chiefly the work of arthropods. Arthrophycus and other trace fossils from the Silurian of Alabama constitute a test case to build criteria for recognizing the members of complexes of trace fossils. In general, criteria such as interconnection of different forms, intergradation among unconnected forms, similarity of size, similarity of morphologic elements, and co-occurrence should be examined in order to determine the biologic and ethologic interrelationships of trace fossils. ?? 2003 Elsevier Science B.V. All rights reserved.

Analogue modeling of 3-D structural segmentation in fold-and-thrust belts: interactions between frictional and viscous provinces in foreland basins

NASA Astrophysics Data System (ADS)

Borderie, Sandra; Graveleau, Fabien; Witt, César; Vendeville, Bruno C.

2016-04-01

Accretionary wedges are generally segmented both across and along strike because of diverse factors including tectonic and stratigraphic inheritance. In fold-and-thrust belts, along-strike stratigraphic changes in the foreland sequence are classically observed and cause a curvature of the deformation front. Although the parameters controlling this curvature are well documented, the structural interactions and mutual influences between adjacent provinces are much less analyzed. To investigate this question, we deformed analogue models in a compressional box equipped with digital cameras and a topographic measurement apparatus. Models where shortened above a basal frictional detachment (glass microbeads) and segmentation was tested by having a region in which we added an interbedded viscous level (silicone polymer) within the sedimentary cover (dry sand). By changing the number (2 or 3) and the relative width of the purely frictional and viscous provinces, our goal was to characterize geometrically and kinematically the interactions between the viscous and the purely frictional provinces. We used a commercial geomodeller to generate 3-D geometrical models. The results indicate that regardless of the relative width of the purely frictional vs. viscous provinces, the deformation style in the frictional province is not influenced by the presence of the adjacent viscous province. On the contrary, the structural style and the deformation kinematics in the viscous province is significantly impacted by the presence or absence of an adjacent purely frictional province. At first order, the deformation style in the viscous province depends on its width, and three structural styles can be defined along strike. Far from the frictional area, structures are primarily of salt-massif type, and they do not seem to be influenced by the frictional wedge province. Towards the frictional province, deformation changes gradually to a zone of purely forethrusts (foreland verging), and

Andean stratigraphic record of the transition from backarc extension to orogenic shortening: A case study from the northern Neuquén Basin, Argentina

NASA Astrophysics Data System (ADS)

Horton, Brian K.; Fuentes, Facundo; Boll, Andrés; Starck, Daniel; Ramirez, Sebastian G.; Stockli, Daniel F.

2016-11-01

The temporal transition from backarc extension to retroarc shortening is a fundamental process in the evolution of many Andean-type convergent margins. This switch in tectonic regime is preserved in the 5-7 km thick Mesozoic-Cenozoic stratigraphic record of west-central Argentina at 34-36°S, where the northern Neuquén Basin and succeeding Cenozoic foreland succession chronicle a long history of fluctuating depositional systems and diverse sediment source regions during Andean orogenesis. New findings from sediment provenance and facies analyses are integrated with detrital zircon U-Pb geochronological results from 16 samples of Jurassic through Miocene clastic deposits to delineate the progressive exhumation of the evolving Andean magmatic arc, retroarc fold-thrust belt, and foreland province. Abrupt changes in provenance and depositional conditions can be reconciled with a complex Mesozoic-Cenozoic history of extension, postextensional thermal subsidence, punctuated tectonic inversion, thick- and thin-skinned shortening, overlapping igneous activity, and alternating phases of basin accumulation, sediment bypass, and erosion. U-Pb age distributions constrain the depositional ages of Cenozoic units and reveal a prolonged late middle Eocene to earliest Miocene (roughly 40-20 Ma) hiatus in the retroarc foreland basin. This stratigraphic gap is expressed as a regional disconformity that marks a pronounced shift in depositional conditions and sediment sources, from (i) slow Paleocene-middle Eocene accumulation of distal fluviolacustrine sediments (Pircala and Coihueco Formations) contributed from far western magmatic arc sources (Cretaceous-Paleogene volcanic rocks) and subordinate eastern basement rocks (Permian-Triassic Choiyoi igneous complex) to (ii) rapid Miocene-Quaternary accumulation of proximal fluvial to megafan sediments (Agua de la Piedra, Loma Fiera, and Tristeza Formations) recycled from emerging western thrust-belt sources of Mesozoic basin fill

The age of volcanic tuffs from the Upper Freshwater Molasse (North Alpine Foreland Basin) and their possible use for tephrostratigraphic correlations across Europe for the Middle Miocene

NASA Astrophysics Data System (ADS)

Rocholl, Alexander; Schaltegger, Urs; Gilg, H. Albert; Wijbrans, Jan; Böhme, Madelaine

2018-03-01

The Middle Miocene Upper Freshwater Molasse sediments represent the last cycle of clastic sedimentation during the evolution of the North Alpine Foreland Basin. They are characterized by small-scale lateral and temporal facies changes that make intra-basin stratigraphic correlations at regional scale difficult. This study provides new U-Pb zircon ages as well as revised 40Ar/39Ar data of volcanic ash horizons in the Upper Freshwater Molasse sediments from southern Germany and Switzerland. In a first and preliminary attempt, we propose their possible correlation to other European tephra deposits. The U-Pb zircon data of one Swiss (Bischofszell) and seven southern German (Zahling, Hachelstuhl, Laimering, Unterneul, Krumbad, Ponholz) tuff horizons indicate eruption ages between roughly 13.0 and 15.5 Ma. The stratigraphic position of the Unterneul and Laimering tuffs, bracketing the ejecta of the Ries impact (Brockhorizon), suggests that the Ries impact occurred between 14.93 and 15.00 Ma, thus assigning the event to the reversed chron C5Bn1r (15.032-14.870 Ma) which is in accordance with paleomagnetic evidence. We combine our data with published ages of tuff horizons from Italy, Switzerland, Bavaria, Styria, Hungary, and Romania to derive a preliminary tephrochronological scheme for the Middle Miocene in Central Europe in the age window from 13.2 to 15.5 Ma. The scheme is based on the current state of knowledge that the Carpathian-Pannonian volcanic field was the only area in the region producing explosive calc-alkaline felsic volcanism. This preliminary scheme will require verification by more high-quality ages complemented by isotopic, geochemical and paleomagnetic data.

Late quaternary deltaic and carbonate sedimentation in the Gulf of Papua foreland basin: Response to sea-level change

USGS Publications Warehouse

Harris, P.T.; Pattiaratchi, C.B.; Keene, J.B.; Dalrymple, R.W.; Gardner, J.V.; Baker, E.K.; Cole, A.R.; Mitchell, D.; Gibbs, P.; Schroeder, W.W.

1996-01-01

The rivers that drain the wet, mountainous island of New-Guinea discharge about 1.5 billion tonnes/yr of sediments into the adjacent seas, including the foreland basin between New Guinea and Australia. Despite this huge sediment input, there appears to have been only limited deposition in the Gulf of Papua during the (Holocene) postglacial rise in sea level. Seismic and core data indicate that the transgressive systems tract in the Gulf of Papua is thin and patchy. It is confined to regions within and north of an incised, east-west-trending shelf-valley system. Of the possible explanations for the absence of a significant transgressive systems tract, inland storage and along- and off-shelf transport of the sediment are of greatest significance. Reef growth up to the latitude of the east-west-trending incised-valley system in the southern Gulf of Papua is considered to have been facilitated by a northward-flowing coastal boundary current, the Coral Sea Coastal Current. This current now sweeps turbid, brackish waters and terrigenous sediments discharged by the rivers northwards away from the reefs. An observed northward offset in transgressive sediments in relation to the axis of the shelf valleys suggests that such a northward-flowing shelf current operated during the late Pleistocene and early Holocene. The northern limit of the Great Barrier Reef could thus be controlled by the balance between fluvial sediment supply and northward advection of suspended sediment by the Coral Sea Coastal Current. This current may also be important in maintaining a supply of clear water to the eastern Gulf of Papua, thus enabling photosynthesis and the flourishing of calcareous-algae (Halimeda) bioherms or biostromes at depths of up to 100 m over much of the middle and outer shelf, directly offshore of the modern Fly Delta. These carbonate sediments represent the exposed maximum flooding surface and condensed section. Modern highstand delta deposits have begun to prograde over this

Rifting to India-Asia Reactivation: Multi-phase Structural Evolution of the Barmer Basin, Rajasthan, northwest India

NASA Astrophysics Data System (ADS)

Kelly, M. J.; Bladon, A.; Clarke, S.; Najman, Y.; Copley, A.; Kloppenburg, A.

2015-12-01

The Barmer Basin, situated within the West Indian Rift System, is an intra-cratonic rift basin produced during Gondwana break-up. Despite being a prominent oil and gas province, the structural evolution and context of the rift within northwest India remains poorly understood. Substantial subsurface datasets acquired during hydrocarbon exploration provide an unrivalled tool to investigate the tectonic evolution of the Barmer Basin rift and northwest India during India-Asia collision. Here we present a structural analysis using seismic datasets to investigate Barmer Basin evolution and place findings within the context of northwest India development. Present day rift structural architectures result from superposition of two non-coaxial extensional events; an early mid-Cretaceous rift-oblique event (NW-SE), followed by a main Paleocene rifting phase (NE-SW). Three phases of fault reactivation follow rifting: A transpressive, Late Paleocene inversion along localised E-W and NNE-SSW-trending faults; a widespread Late Paleocene-Early Eocene inversion and Late Miocene-Present Day transpressive strike-slip faulting along NW-SE-trending faults and isolated inversion structures. A major Late Eocene-Miocene unconformity in the basin is also identified, approximately coeval with those identified within the Himalayan foreland basin, suggesting a common cause related to India-Asia collision, and calling into question previous explanations that are not compatible with spatial extension of the unconformity beyond the foreland basin. Although, relatively poorly age constrained, extensional and compressional events within the Barmer Basin can be correlated with regional tectonic processes including the fragmentation of Gondwana, the rapid migration of the Greater Indian continent, to subsequent collision with Asia. New insights into the Barmer Basin development have important implications not only for ongoing hydrocarbon exploration but the temporal evolution of northwest India.

Tectono-stratigraphy of the Orhaniye Basin, Turkey: Implications for collision chronology and Paleogene biogeography of central Anatolia

NASA Astrophysics Data System (ADS)

Licht, A.; Coster, P.; Ocakoğlu, F.; Campbell, C.; Métais, G.; Mulch, A.; Taylor, M.; Kappelman, John; Beard, K. Christopher

2017-08-01

Located along the İzmir-Ankara-Erzincan Suture (IAES), the Maastrichtian - Paleogene Orhaniye Basin has yielded a highly enigmatic -yet poorly dated- Paleogene mammal fauna, the endemic character of which has suggested high faunal provincialism associated with paleogeographic isolation of the Anatolian landmass during the early Cenozoic. Despite its biogeographic significance, the tectono-stratigraphic history of the Orhaniye Basin has been poorly documented. Here, we combine sedimentary, magnetostratigraphic, and geochronological data to infer the chronology and depositional history of the Orhaniye Basin. We then assess how our new data and interpretations for the Orhaniye Basin impact (1) the timing and mechanisms of seaway closure along the IAES and (2) the biogeographic evolution of Anatolia. Our results show that the Orhaniye Basin initially developed as a forearc basin during the Maastrichtian, before shifting to a retroarc foreland basin setting sometime between the early Paleocene and 44 Ma. This chronology supports a two-step scenario for the assemblage of the central Anatolian landmass, with incipient collision during the Paleocene - Early Eocene and final seaway retreat along the IAES during the earliest Late Eocene after the last marine incursion into the foreland basin. Our dating for the Orhaniye mammal fauna (44-43 Ma) indicates the persistence of faunal endemism in northern Anatolia until at least the late Lutetian despite the advanced stage of IAES closure. The tectonic evolution of dispersal corridors linking northern Anatolia with adjacent parts of Eurasia was not directly associated with IAES closure and consecutive uplifts, but rather with the build-up of continental bridges on the margins of Anatolia, in the Alpine and Tibetan-Himalayan orogens.

The Comparison of Detrital Zircon Ages to Point Count Provenance Analysis for the Pottsville Sandstone in the Northern Appalachian Foreland Basin Venango County, Pennsylvania

NASA Astrophysics Data System (ADS)

Loveday, S.; Harris, D. B.; Schiappa, T.; Pecha, M.

2017-12-01

The specific sources of sediments deposited in the Appalachian basin prior to and immediately following the Alleghenian orogeny has long been a topic of debate. Recent advances in U-Pb dating of detrital zircons have greatly helped to determine some of the sources of these sediments. For this study, sandstone samples were collected from the Pottsville Formation in the northern Appalachian Foreland Basin, Venango County, Pennsylvania to provide supplementary data for previous work that sought to describe the provenance of the same sediments by point counts of thin sections of the same units. Results of this previous work established that the provenance for these units was transitional recycled orogenic, including multiple recycled sediments, and that a cratonic contribution was not able to be determined clearly. The previous results suggested that the paleoenvironment was a fluvial dominated delta prograding in the northern direction. However, no geochronologic data was found during this study to confirm this interpretation. We sought to verify these results by U-Pb analysis of detrital zircons. Samples were collected from the areas where the previous research took place. U-Pb ages were found from sample at the highest elevation and lowest elevation. In the first sample, sample 17SL01 (younger sample stratigraphically), the zircons yield U-Pb age range peaks at 442-468 ma and 1037-1081 ma. The probability density plot for this specific sample displays a complete age gap from 500 ma to 811 ma. In the second sample, sample 17SL03 (older rock stratigraphically), the zircons yield U-Pb ages range peaks of 424-616 ma and 975-1057 ma. This sample doesn't show any ages younger than 424 ma and it doesn't display the sample age gap as sample 17SL01 does. The ages of zircons are consistent with thin section point counting provenance results from previous research suggesting zircon transport from the northern direction.

Early Oligocene paleosols of the Dagshai Formation, India: A record of the oldest tropical weathering in the Himalayan foreland

NASA Astrophysics Data System (ADS)

Srivastava, Pankaj; Patel, Subhra; Singh, Nandita; Jamir, Toshienla; Kumar, Nandan; Aruche, Manini; Patel, Ramesh C.

2013-08-01

This study reports paleopedological features of the fossil soils that formed during the earliest phase of continental sedimentation in the Himalayan foreland. The fluvial sequence of the Dagshai Formation (31.6 ± 3.9 Ma to 30.3 ± 3.9 Ma) exposed along the Koshaliya River, NW Himalaya, contains four pedofacies (named Pedofacies A-D) of ferruginous paleosol sequences contained within overbank sediments. The Dagshai Formation unconformably overlies the marine Subathu Formation. Pedofacies A consists of 3-4 well-developed ferruginous paleosols overlain by gray sandstone beds. Pedofacies B-D are marked by a progressive decrease in pedogenesis. These paleosols occur as 0.5 m to 1.5 m thick Bw/Bt/Btk/Bk/Bss horizons that are marked by extensive development of rhizoliths, pedogenic carbonate, and iron-rich clay pedofeatures that correspond to modern Entisols, Inceptisols, Alfisols and Vertisols. Based on early Oligocene paleogeographic position of the northward-drifting Indian Plate, it is inferred that these paleosols were formed at ~ 18°N paleolatitude in the Dagshai sub-basin in the Himalayan foreland. Micromorphology, geochemical analyses, weathering indices, and stable isotope composition of paleosols indicate tropical climate (paleoprecipitation of 947-1256 mm and paleotemperature of ~ 25 °C) with an initial phase of monsoonal conditions during pedogenesis. These paleoclimatic conditions favored C3 paleovegetation immediately after the transition from greenhouse to icehouse conditions.

Bacterial community succession in a high-altitude subarctic glacier foreland is a three-stage process.

PubMed

Kazemi, Sina; Hatam, Ido; Lanoil, Brian

2016-11-01

Alpine glaciers are retreating rapidly, exposing foreland minerals, which develop into soils. Bacterial communities in glacier forelands exhibit high rates of turnover and undergo dramatic shifts in composition within the first 50 years after deglaciation, followed by relative stabilization and convergence. This period of microbial development occurs simultaneously with plant colonization in most systems; thus, it remains unclear whether the changes in the bacterial communities occur primarily as the result of edaphic, climatic or biotic factors. We examined bacterial community structure along two replicate chronosequences within the glacial foreland of Duke River Glacier, Yukon, Canada. This foreland is estimated to include >200 years of bare soils before an appreciable grassline, likely due to the high latitude and altitude of the glacier. This enabled us to examine bacterial community development prior to plant colonization over a longer period than previous studies. We observed three successional groups in the chronosequence: (i) an 'early' group in soils of less than approximately 50 years since deglaciation; (ii) an 'intermediate' group within bare soils, after the early period but before the grassline, containing communities with a relatively high degree of variability in composition; and (iii) a 'grassline' group in soils collected after plant colonization with higher diversity but lower age-group variability in community composition. These findings suggest rapid replacement and addition of species better adapted to glacier foreland conditions followed by slower community shifts over the next 150 years and, finally, indications of a possible response to plant colonization. © 2016 John Wiley & Sons Ltd.

Foreland uplift during flat subduction: Insights from the Peruvian Andes and Fitzcarrald Arch

NASA Astrophysics Data System (ADS)

Bishop, Brandon T.; Beck, Susan L.; Zandt, George; Wagner, Lara S.; Long, Maureen D.; Tavera, Hernando

2018-04-01

Foreland deformation has long been associated with flat-slab subduction, but the precise mechanism linking these two processes remains unclear. One example of foreland deformation corresponding in space and time to flat subduction is the Fitzcarrald Arch, a broad NE-SW trending topographically high feature covering an area of >4 × 105 km2 in the Peruvian Andean foreland. Recent imaging of the southern segment of Peruvian flat slab shows that the shallowest part of the slab, which corresponds to the subducted Nazca Ridge northeast of the present intersection of the ridge and the Peruvian trench, extends up to and partly under the southwestern edge of the arch. Here, we evaluate models for the formation of this foreland arch and find that a basal-shear model is most consistent with observations. We calculate that 5 km of lower crustal thickening would be sufficient to generate the arch's uplift since the late Miocene. This magnitude is consistent with prior observations of unusually thickened crust in the Andes immediately south of the subducted ridge that may also have been induced by flat subduction. This suggests that the Fitzcarrald Arch's formation by the Nazca Ridge may be one of the clearest examples of upper plate deformation induced through basal shear observed in a flat-slab subduction setting. We then explore the more general implications of our results for understanding deformation above flat slabs in the geologic past.

Plio-Pleistocene paleo-erosion rates as a recorder of orographic barrier uplift in the NW-Argentine Andes (Humahuaca Basin)

NASA Astrophysics Data System (ADS)

Pingel, Heiko; Schildgen, Taylor; Wittmann, Hella

2017-04-01

As an integral part of the Eastern Cordillera, the intermontane Humahuaca Basin in the NW Argentine Andes is located in transition between the arid and internally drained Puna Plateau to the west and the humid broken foreland to the east. In combination with moisture-bearing air masses sourced in the Atlantic Ocean and the Amazon Basin, the present-day topographic gradient of the eastern Andean margin comprises an efficient orographic barrier that results in a strong precipitation gradient, with rainfall of more than 2,000 mm/a along the eastern flanks and <200 mm/a on the plateau. Ultimately, variable moisture availability affects surface processes, such as fluvial erosion and transport of eroded material, with decreasing erosion rates towards the orogenic hinterland. Paleoenvironmental reconstructions of the Humahuaca Basin suggest that this region became disconnected from the foreland during the Mio-Pliocene by the growth of fault-bounded mountain ranges. This led to an increase in accommodation space and enabled the trapping of largely fluvial, late Miocene to Quaternary basin filling units. Subsequently, the basin was uplifted and internally deformed. Fossil records, sedimentologic evidence, and stable-isotopes (δD from volcanic glass) moreover imply that the re-routing of the fluvial network, an initial increase in precipitation, and, as the windward ranges attained threshold elevations to incoming moisture, reduced moisture availability by ca. 3 Ma, were all a consequence of the Mio-Pliocene uplift. In this study, we present first results of terrestrial cosmogenic nuclide-derived paleo-erosion rates from quartz-bearing fluvial sands and gravels of known stratigraphic age. In most cases, the age control is based on previously published U-Pb zircon data of intercalated volcanic ash deposits, but also utilizes new OSL and AMS14C ages. A reassessment of the sediment-accumulation history of the basin highlights important changes of the depositional system

A new osteichthyan from the late Silurian of Yunnan, China.

PubMed

Choo, Brian; Zhu, Min; Qu, Qingming; Yu, Xiaobo; Jia, Liantao; Zhao, Wenjin

2017-01-01

Our understanding of early gnathostome evolution has been hampered by a generally scant fossil record beyond the Devonian. Recent discoveries from the late Silurian Xiaoxiang Fauna of Yunnan, China, have yielded significant new information, including the earliest articulated osteichthyan fossils from the Ludlow-aged Kuanti Formation. Here we describe the partial postcranium of a new primitive bony fish from the Kuanti Formation that represents the second known taxon of pre-Devonian osteichthyan revealing articulated remains. The new form, Sparalepis tingi gen. et sp. nov., displays similarities with Guiyu and Psarolepis, including a spine-bearing pectoral girdle and a placoderm-like dermal pelvic girdle, a structure only recently identified in early osteichthyans. The squamation with particularly thick rhombic scales shares an overall morphological similarity to that of Psarolepis. However, the anterior flank scales of Sparalepis possess an unusual interlocking system of ventral bulges embraced by dorsal concavities on the outer surfaces. A phylogenetic analysis resolves Sparalepis within a previously recovered cluster of stem-sarcopterygians including Guiyu, Psarolepis and Achoania. The high diversity of osteichthyans from the Ludlow of Yunnan strongly contrasts with other Silurian vertebrate assemblages, suggesting that the South China block may have been an early center of diversification for early gnathostomes, well before the advent of the Devonian "Age of Fishes".

Insights upon upper crustal arhitecture of a subduction zone and its surroundings - Vrancea Zone and Focsani Basin - substantiated by geophysical studies

NASA Astrophysics Data System (ADS)

Bocin, A.; Stephenson, R.; Mocanu, V.

2007-12-01

The DACIA PLAN (Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics) deep seismic reflection survey was performed in August-September 2001, with the proposed objective of obtaining new information on the deep structure of the external Carpathians nappes and the architecture of Tertiary/Quaternary basin developed within and adjacent to the Vrancea zone, including the rapidly subsiding Focsani Basin. The DACIA-PLAN profile is about 140 km long, having a roughly NW-SE direction, from near the southeast Transylvanian Basin, across the mountainous southeastern Carpathians and their foreland to near the Danube River. A high resolution 2.5D velocity model of the upper crust along the seismic profile has been determined from a tomographic inversion and a 2D ray tracing forward modelling of the DACIA PLAN first arrival data. Peculiar shallow high velocities indicate that pre-Tertiary basement in the Vrancea Zone (characterised by velocities greater than 5.6 km/s) is involved in Carpathian thrusting while rapid alternance, vertically or horizontally, of velocity together with narrowingly contemporary crustal events suggests uplifting. Further to the east, at the foreland basin-thrust belt transition zone (well defined within velocity values), the velocity model suggests a nose of the Miocene Subcarpathians nappe being underlain by Focsani Basin units. A Miocene and younger Focsani Basin sedimentary succession of ~10 km thickness is ascertained by a gradual increase of velocities and strongly defined velocity boundaries.

Intraguild predation in pioneer predator communities of alpine glacier forelands

PubMed Central

Raso, Lorna; Sint, Daniela; Mayer, Rebecca; Plangg, Simon; Recheis, Thomas; Brunner, Silvia; Kaufmann, Rüdiger; Traugott, Michael

2014-01-01

Pioneer communities establishing themselves in the barren terrain in front of glacier forelands consist principally of predator species such as carabid beetles and lycosid spiders. The fact that so many different predators can co-inhabit an area with no apparent primary production was initially explained by allochthonous material deposited in these forelands. However, whether these populations can be sustained on allochthonous material alone is questionable and recent studies point towards this assumption to be flawed. Intraguild predation (IGP) might play an important role in these pioneer predator assemblages, especially in the very early successional stages where other prey is scarce. Here, we investigated IGP between the main predator species and their consumption of Collembola, an important autochthonous alternative prey, within a glacier foreland in the Ötztal (Austrian Alps). Multiplex PCR and stable isotope analysis were used to characterize the trophic niches in an early and late pioneer stage over 2 years. Results showed that intraguild prey was consumed by all invertebrate predators, particularly the larger carabid species. Contrary to our initial hypothesis, the DNA detection frequency of IGP prey was not significantly higher in early than in late pioneer stage, which was corroborated by the stable isotope analysis. Collembola were the most frequently detected prey in all of the predators, and the overall prey DNA detection patterns were consistent between years. Our findings show that IGP appears as a constant in these pioneer predator communities and that it remains unaffected by successional changes. PMID:24383765

Late Alpine to recent thick-skinned tectonics of the central Swiss Molasse Basin, Canton of Bern, Switzerland

NASA Astrophysics Data System (ADS)

Mock, Samuel; Allenbach, Robin; Wehrens, Philip; Reynolds, Lance; Kurmann-Matzenauer, Eva; Michael, Salomè; Herwegh, Marco

2017-04-01

The Swiss Molasse Basin (SMB) forms part of the North Alpine Foreland Basin. It is a typical peripheral foreland basin, which developed in Paleogene and Neogene times in response to flexural bending of the European lithosphere induced by the orogenic loading of the advancing Alpine thrust wedge. The tectonics of the SMB and the role of Paleozoic and Mesozoic structures are still poorly understood. It is widely accepted that during the main deformation phase of the Jura fold-and-thrust belt, the SMB was riding piggy-back above a major detachment horizon situated within Triassic evaporites. In recent years it has been observed that the Jura fold-and-thrust belt is today deforming in a thick-skinned tectonic style. As for the western and central SMB, most authors still argue in favor of a classical foreland type, thin-skinned style of deformation. Based on the geological 3D modeling of seismic interpretations, we present new insights into the structural configuration of the central SMB. Revised and new interpretations of 2D reflection seismic data from the 1960s to the 1980s reveal a major strike-slip fault zone affecting not only the Mesozoic and Cenozoic cover, but also the crystalline basement beneath. The fault zone reactivated late Paleozoic synsedimentary normal faults bounding a Permo-Carboniferous trough. Basement-involved thrusting observed in the southern part of the SMB seems to be controlled by the presence of slightly inverted Permo-Carboniferous troughs as well. These observations, combined with a compiled structural map and the distribution of recent earthquake hypocenters suggest a late stage, NNW-SSE directed, compressional thick-skinned and strike-slip dominated tectonic activity of the central SMB, post-dating the main deformation phase of the Jura fold-and-thrust belt. This still ongoing deformation might be related to the slab rollback of the European plate and the associated lower crustal delamination as recently suggested by Singer et al. (2014

Early Silurian Foraminifera from Gondwana - an early origin of the multichambered globothalamids?

NASA Astrophysics Data System (ADS)

Kaminski, Michael

2017-04-01

Early Silurian foraminifera until now have been regarded to consist of simple single-chambered monothalamids and two-chambered tubothalamids with an agglutinated wall. Although pseudo-multichambered agglutinated foraminifera first appeared in the mid-Ordovician (Kaminski et al. 2009), the origin of true multichambered forms was not believed to have taken place until the early or middle Devonian at the earliest (Holcová, 2002). New discoveries from the Lower Silurian Qusaiba Shale Member in Saudi Arabia point to an earlier origin of the multichambered globothalamid Foraminifera than the currently accepted estimate of 350 Ma (Pawlowski et al. 2003). The agglutinated foraminiferal genera Ammobaculites and Sculptobaculites have been recovered from dark graptolite-bearing claystones of Telychian age, from the transitional facies between the Qusaiba and Sharawa Members of the Qasim Formation at the type locality near Qusaiba town, Saudi Arabia. The multichambered lituolids occur as rare components in a foraminiferal assemblage consisting mostly of monothalamids. This new finding revises our understanding of the early evolution of the multichambered globothalamid foraminifera. The fossil record now shows that the globothalamids were already present in Gondwana by 435 m.y. Holcová, K. 2002. Silurian and Devonian foraminifers and other acid-resistant microfossils from the Barrandian area. Acta Musei Nationalis Pragae, Series B, Historia Naturalis, 58 (3-4), 83-140. Kaminski, M.A., Henderson, A.S., Cetean, C.G. & Waskowska-Oliwa, A. 2009. A new family of agglutinated foraminifera: the Ammolagenidae n.fam., and the evolution of multichambered tests. Micropaleontology, 55 (5), 487-494. Pawlowski, J., Holzmann, M., Berney, C., Fahrni, J.F., Gooday, Aj., Cedhagen, T., Habura, A., & Bowser, SS. 2003. The evolution of early Foraminifera. Proceedings of the National Academy of Sciences, 100 (20), 11494-11498

Cenozoic evolution of the Pamir plateau recorded in surrounding basins, implications on Asian climate and land-sea distribution

NASA Astrophysics Data System (ADS)

Dupont-Nivet, Guillaume; Yang, Wei; Blayney, Tamsin; Proust, Jean-Noel; Guo, Zhaojie; Grothe, Arjen; Mandic, Oleg; Fionori, Chiara; Bougeois, Laurie; Najman, Yanina

2015-04-01

The Cenozoic Pamir orogen formed in response to the India-Asia collision. Existing datasets shows that the range grew since ca. 25 Ma, however the early Cenozoic history remains particularly enigmatic. In that peculiar period, global climate changed from greenhouse to icehouse, the proto-Paratethys sea retreated out of Asia and continental aridification as well as monsoons established over Asia. These environmental changes are held responsible for major floral and faunal crises including the emergence of plant communities and the dispersion of key mammal groups from Asia onto other continents. However, the causal relationships between these events remains to be established because of the lack of accurate age constraints on their geological records. Here, we provide well-dated stratigraphic records using magneto- and bio-stratigraphy from the basins surrounding the Pamir. Southeast of the Pamir, along the Kunlun Shan into the southwestern Tarim Basin, Eocene marine deposits are continuously overlain by 41 to 15 Ma continental redbeds themselves overlain by conglomerates in a classic foreland sequence with upward increasing grain-size, accumulation rates and provenance proximity. However, North of the Pamir along the southwestern Tian Shan and West of the Pamir into the Afghan-Tadjik Basin, the entire Oligocene period appears to be missing from the record between the last marine and the first continental sediments dated to the Early Miocene. This supports a simple basin evolution model in response to initial Pamir indentation with Eocene foreland basin activation in the Southeast related to the Kunlun Shan northward thrusting, followed much later by early Miocene activation of the northern foreland basin related to the southwestern Tian Shan overthrusting. The coeval activation of a lithospheric right-lateral strike-slip system along the Pamir/Tarim boundary may have enabled to transfer deformation from the India-Asia collision zone to the Tian Shan and possibly the

Middle Pennsylvanian recurrent uplift of the Ouachita fold belt and basin subsidence in the Arkoma basin, Oklahoma

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

Elmore, R.D.; Sutherland, P.K.; White, P.B.

1990-09-01

Recurrent uplift of the Ouachita fold belt in Oklahoma coincided with the disruption of the Arkoma basin following the deposition of the Boggy Formation (early Desmoinesian time). The Boggy, composed of sandstone-shale sequences that record southerly progradation of coal-bearing, fluvially dominated deltaic complexes into the Arkoma basin, was folded at the time of uplift of the Ouachita fold belt. The uplift ended the progressive subsidence of the Arkoma basin and shifted the depocenter to the northwest. Subsequently, the Thurman Formation (middle Desmoinesian), which had a source in the southeast, was deposited in the smaller resurgent foreland basin over the foldedmore » and eroded surface of the Boggy. Chert-pebble conglomerates in the Thurman were derived from the erosion of newly elevated Ordovician and Devonian cherts in the core of the Ouachita foldbelt. Sandstone-shale packages are found in both formations. The origin of the coal-bearing cycles in the Boggy are enigmatic, but they probably were controlled by a combination of factors such as glacio-eustatic changes in sea level and delta-lobe abandonment. In contrast, cycles in the Thurman probably were strongly influenced by episodic thrust faulting and uplift in the Ouachitas.« less

Cenozoic evolution of the Pamir plateau recorded in surrounding basins, implications on Asian climate, land-sea distribution and biotic crises

NASA Astrophysics Data System (ADS)

Dupont Nivet, G.; Yang, W.; Blayney, T.; Bougeois, L.; Manceau, C.; Najman, Y.; Proust, J. N.; Guo, Z.; Grothe, A.; Mandic, O.; Fioroni, C.

2014-12-01

The Cenozoic Pamir orogen formed in response to the India-Asia collision. Existing datasets shows that the range grew since ca. 25 Ma, however the early Cenozoic history remains unconstrained. In that period, global climate changed from greenhouse to icehouse, the proto-Paratethys sea retreated out of Asia and continental aridification as well as monsoons established over Asia. These environmental changes are held responsible for major floral and faunal crises. However, the causal relationships between these events remains to be established because of the lack of accurate age constraints on their geological records. Here, we provide well-dated stratigraphic records using magneto- and bio-stratigraphy from the basins surrounding the Pamir. Southeast of the Pamir, along the Kunlun Shan into the southwestern Tarim Basin, Eocene marine deposits are continuously overlain by 41 to 15 Ma continental redbeds themselves overlain by conglomerates in a classic foreland sequence with upward increasing grain-size, accumulation rates and provenance proximity. However, North of the Pamir along the southwestern Tian Shan and West of the Pamir into the Afghan-Tadjik Basin, the entire Oligocene period appears to be missing from the record between the last marine and the first continental sediments dated to the Early Miocene. This supports a simple model in response to initial Eocene Pamir indentation with foreland basin activation in the Southeast related to the Kunlun Shan northward thrusting, followed much later by early Miocene activation of the northern foreland basin related to the southwestern Tian Shan overthrusting. The coeval activation of a lithospheric right-lateral strike-slip system along the Pamir/Tarim boundary may have enabled to transfer deformation from the India-Asia collision to the Tian Shan and possibly the Talas Fergana fault. This simple model suggests the following two-stage paleoenvironmental evolution: (1) Late Eocene sea retreat linked to the onset of

Assessment of potential shale-oil and shale-gas resources in Silurian shales of Jordan, 2014

USGS Publications Warehouse

Schenk, Christopher J.; Pitman, Janet K.; Charpentier, Ronald R.; Klett, Timothy R.; Tennyson, Marilyn E.; Mercier, Tracey J.; Nelson, Philip H.; Brownfield, Michael E.; Pawlewicz, Mark J.; Wandrey, Craig J.

2014-01-01

Using a geology-based assessment methodology, the U.S. Geological Survey estimated means of 11 million barrels of potential shale-oil and 320 billion cubic feet of shale-gas resources in Silurian shales of Jordan.

Mississippian Lodgepole Play, Williston Basin: A review

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

Montgomery, S.L.

1996-06-01

Waulsortian-type carbonate mud mounds in the lower Mississippian Lodgepole formation (Bottineau interval, Madison Group) comprise an important new oil play in the Williston basin with strong regional potential. The play is typified by wells capable of producing 1000-2500 bbl of oil per day and by reserves that have as much as 0.5-3.0 million bbl of oil per well. Currently centered in Stark County, North Dakota, along the southern flank of the basin, the play includes 38 wells, with 21 producers and 6 new fields. Initial discovery was made at a Silurian test in Dickinson field, traditionally productive from Pennsylvanian sands.more » The largest pool discovered to date is Eland field, which has 15 producers and estimated total reserves of 12-15 million bbl. This report summarizes geologic, well-log, seismic, and production data for this play, which promises to expand considerably in the years to come.« less

Mechanisms of intracratonic and rift basin formation: Insights from Canning Basin, northwest Australia

NASA Astrophysics Data System (ADS)

Bender, Andre Adriano

2000-10-01

The Canning basin was investigated in order to determine the mechanisms responsible for its initiation and development. The basement morphology, determined using magnetic and gravity inversion techniques, was used to map the distribution, amplitude and subsidence history of the basin. The sag development of the Canning basin is hypothesized to be a consequence of a major late Proterozoic thermal event that induced broad-scale uplift, extrusion of tholeiitic basalt, and substantial crustal erosion. The development of the Canning basin is consistent with removal of up to 11 km of crustal rocks, followed by isostatic re-adjustment during the cooling of the lithosphere. Earlier models that employed both lower crustal metamorphism and erosion are considered inappropriate mechanisms for intracratonic basin formation because this work has shown that their effects are mutually exclusive. The time scale for the metamorphic-related subsidence is typically short (<10 m.y.) and the maximum subsidence is small (<4 km) compared to the long subsidence (ca. 200 m.y.) and maximum depths (6--7 km) recorded in the Canning basin. Observed amplitudes and rates of basement subsidence are compatible with a thermal anomaly that began to dissipate in the early Cambrian and lasted until the Permian. Punctuating the long-lived intracratonic basin subsidence is a series of extensional pulses that in Silurian to Carboniferous/Permian time led to the development of several prominent normal faults in the northeastern portion of the Canning basin (Fitzroy graben). Stratigraphic and structural data and section-balancing techniques have helped to elucidate the geometry and evolution of the basin-bounding fault of the Fitzroy graben. The fault is listric, with a dip that decreases from approximately 50° at the surface to 20° at a depth of 20 km, and with an estimated horizontal offset of 32--41 km. The southern margin of the Fitzroy graben was tilted, truncated, and onlapped from the south

Correlation of aptian-albian carbon isotope excursions in continental strata of the cretaceous Foreland Basin, Eastern Utah, U.S.A.

USGS Publications Warehouse

Ludvigson, Greg A.; Joeckel, R.M.; Gonzalez, Luis A.; Gulbranson, E.L.; Rasbury, E.T.; Hunt, G.J.; Kirkland, J.I.; Madsen, S.

2010-01-01

Nodular carbonates ("calcretes") in continental foreland-basin strata of the Early Cretaceous Cedar Mountain Formation (CMF) in eastern Utah yield ??13C and ??O records of changes in the exogenic carbon cycle related to oceanic anoxic events (OAEs), and terrestrial paleoclimate. Chemostratigraphic profiles of both forebulge and foredeep sections show two prominent positive ??13C excursions, each with a peak value of -3% VPDB, and having background ??13C values of about -6% VPDB. These excursions correlate with the global early Aptian (Ap7) and late Aptian-early Albian (Apl2-All) carbon isotope excursions. Aptian-Albian positive ??13C excursions in the CMF also correspond to 3-4 per mil increases in carbonate ??18O. These phenomena record local aridification events. The chemostratigraphic profile on the thinner forebulge section of the CMF is calibrated, for the first time, by a radiogenic U-Pb date of 119.4 ?? 2.6 Ma on a carbonate bed, and by detrital zircon U-Pb dates on two bounding sandstone units (maximum depositional ages of 146 Ma and 112 Ma). P??trographie observations and diagenetic analyses of micritic to microsparitic carbonates from nodules indicate palustrine origins and demonstrate that they crystallized in shallow early meteoric phreatic environments. Meteoric calcite lines derived from CMF carbonates have ??18O values ranging between -8.1 to -7.5%o VPDB, supporting an estimate of zonal mean groundwater ??18O of -6% VSMOW for an Aptian-Albian paleolatitude of 34?? N. Furthermore, our two chemostratigraphic profiles exhibit a generally proportionate thinning of correlative strata from the foredeep on to the forebulge, suggesting that there were consistently lower rates of accumulation on the forebulge during the Aptian-Albian. Identification of the global Aptian-Albian ??13C excursions in purely continental strata, as demonstrated in this paper, opens a new avenue of research by identifying specific stratigraphie intervals that record the terrestrial

Cyclicity in Silurian island-arc carbonates, Alexander terrane, Alaska

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

Kittredge, L.E.; Soja, C.M.

1993-03-01

Silurian carbonates from Alaska (Alexander terrane) record the evolution of a submarine platform during waning volcanism in an island arc. A detailed stratigraphic analysis of a 47 meter-thick sequence revealed the existence of cyclically repeated limestones: coral-stromatoporoid wackestones alternate with oncoid packstones and bioturbated, silty lime mudstones. The coral-stromatoporoid deposits are characterized by a low-diversity assemblage of dendroid corals, massive stromatoporoids, Atrypoidea brachiopods, and rare occurrences of biostromes associated with Solenopora, high-spired gastropods, and crinoids. Oncoids typically are 2-6 mm in diameter and form massive, meter-thick units. Coated grains are symmetrically developed, have a shell or algal nucleus, and aremore » also a minor component of coral-stromatoporoid beds. These lithologic units form seven, shallowing-upwards cycles (parasequences) that range in thickness from 3-9 meters. Coral-stomatoporoid wackestones form the base of each cycle and grade upwards into oncoid packstones with silty, lime mudstones at the top. This succession of lithofacies within each cycle reflects an increase in energy levels from relatively deeper water environments to relatively shallower ones. The lack of abrasion in the corals and stromatoporoids suggests predominantly quiet-water conditions in shallow subtidal areas affected by periodic turbulence. Comparison with correlative sections in Alaska and lack of correspondence with global sea level curves suggest that the primary cause of cyclicity was tectonic perturbations with secondary eustatic effects. Cyclic deposition in peri/subtidal sites was terminated by rapid drowning of the carbonate platform during late Silurian orogenesis.« less

Diagenesis of Upper Carboniferous rocks in the Ouachita foreland shelf in mid-continent USA: an overview of widespread effects of a Variscan-equivalent orogeny

USGS Publications Warehouse

Walton, A.W.; Wojcik, K.M.; Goldstein, R.H.; Barker, C.E.

1995-01-01

Diagenesis of Upper Carboniferous foreland shelf rocks in southeastern Kansas took place at temperatures as high as 100-150?? C at a depth of less than 2 km. High temperatures are the result of the long distance (hundreds of kilometers) advection of groundwater related to collisional orogeny in the Ouachita tectonic belt to the south. Orogenic activity in the Ouachita area was broadly Late Carboniferous, equivalent to the Variscan activity of Europe. Mississippi Valley-type Pb-Zn deposits and oil and gas fields in the US midcontinent and elsewhere are commonly attributed to regional groundwater flow resulting from such collisional events. This paper describes the diagenesis and thermal effects in sandstone and limestone of Upper Carboniferous siliciclastic and limestone-shale cyclothems, the purported confining layer of a supposed regional aquifer. Diagenesis took place in early, intermediate, and late stages. Many intermediate and late stage events in the sandstones have equivalents in the limestones, suggesting that the causes were regional. The sandstone paragenesis includes siderite cement (early stage), quartz overgrowths (intermediate stage), dissolution of feldspar and carbonates, followed by minor Fe calcite, pore-filling kaolinite and sub-poikilotopic Ca ankerite (late stage). The limestone paragenesis includes calcite cement (early stage); megaquartz, chalcedony, and Fe calcite spar (intermediate stage); and dissolution, Ca-Fe dolomite and kaolinite (late stage). The Rm value of vitrinite shows a regional average of 0.6-0.7%; Rock-Eval TmaX suggests a comparable degree of organic maturity. The Th of aqueous fluid inclusions in late stage Ca-Fe-Mg carbonates ranges from 90 to 160?? and Tmice indicates very saline water (>200000 ppm NaCl equivalent); ??18O suggests that the water is of basinal origin. Local warm spots have higher Rm, Tmax, and Th. The results constrain numerical models of regional fluid migration, which is widely viewed as an artesian flow

Tectonic stages in Southern Greater Caucasus and Adjara Trialeti belt in Georgia: new results on timing and structures of inverted basins

NASA Astrophysics Data System (ADS)

Candaux, Zoé; Sosson, Marc; Adamia, Shota; Sadradze, Nino; Alania, Victor; Enukidze, Onise; Chabukiani, Alexandre

2017-04-01

The Greater Caucasus mountain belt is the result of a long live subduction process and collisions of continental microplates (e.g. Dercourt et al., 1986; Barrier and Vrielynck, 2008). The northward subduction of Tethys beneath Eurasian plate initiated a back-arc basin: the Greater Caucasus basin (e.g. Adamia et al., 1981; Zonenshain and Le Pichon, 1986; Roberston et al., 1996; Stephenson and Schellart, 2010 among others). It took place from Middle Jurassic to Late Cretaceous. First compression stage started at the end of Cretaceous in the Lesser Caucasus (e.g. Rolland et al., 2010; Sosson et al. 2010, 2016) and Palaeocene-early Eocene in Crimean Mountains (northwestern continuation of the Greater Caucasus) (Sheremet et al., 2016). In southern Greater Caucasus (Georgian area) the age of deformation during the beginning of the collision is still a subject of debate: Oligocene-Lower Miocene at the frontal part (e.g. Adamia et al. 2010) or Eocene (Mosar et al., 2010). The deformation continues at Miocene, Pliocene and actual time in Kura and Rioni foreland basins (Forte et al., 2010; 2013; Mosar et al., 2010). The different timing is interpreted to be the result of the Taurides-Anatolides-South Armenian microcontinent collision with Eurasia, followed by the collision with Arabia. During the first collision, during Paleocene-Eocene, the so-called Adjara-Trialeti basin opened north of the volcanic arc. One question is if this local extension affect the timing of compression observed in the Greater Caucasus or not. In Georgia, we investigated new structural analyses, and considered unconformities and growth strata at the frontal part of deformations in Kura and Rioni forelands basins (in front of the Greater Caucasus). Our results evidence different tectonic stages and their timing. In Adjara-Trialeti, Kura and south Rioni basins deformation starts at Middle-Late Miocene. In northern Rioni basin Upper Cretaceous-Lower Paleocene compression is evidenced. The structures

Report of the Workshop on Geologic Applications of Remote Sensing to the Study of Sedimentary Basins

NASA Technical Reports Server (NTRS)

Lang, H. R. (Editor)

1985-01-01

The Workshop on Geologic Applications of Remote Sensing to the Study of Sedimentary Basins, held January 10 to 11, 1985 in Lakewood, Colorado, involved 43 geologists from industry, government, and academia. Disciplines represented ranged from vertebrate paleontology to geophysical modeling of continents. Deliberations focused on geologic problems related to the formation, stratigraphy, structure, and evolution of foreland basins in general, and to the Wind River/Bighorn Basin area of Wyoming in particular. Geological problems in the Wind River/Bighorn basin area that should be studied using state-of-the-art remote sensing methods were identified. These include: (1) establishing the stratigraphic sequence and mapping, correlating, and analyzing lithofacies of basin-filling strata in order to refine the chronology of basin sedimentation, and (2) mapping volcanic units, fracture patterns in basement rocks, and Tertiary-Holocene landforms in searches for surface manifestations of concealed structures in order to refine models of basin tectonics. Conventional geologic, topographic, geophysical, and borehole data should be utilized in these studies. Remote sensing methods developed in the Wind River/Bighorn Basin area should be applied in other basins.

Regional stratigraphy and petroleum potential, Ghadames basin, Algeria

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

Emme, J.J.; Sunderland, B.L.

1991-03-01

The Ghadames basin in east-central Algeria extends over 65,000 km{sup 2} (25,000 mi{sup 2}), of which 90% is covered by dunes of the eastern Erg. This intracratonic basin consists of up to 6000 m (20,000 ft) of dominantly clastic Paleozoic through Mesozoic strata. The Ghadames basin is part of a larger, composite basin complex (Ilizzi-Ghadames-Triassic basins) where Paleozoic strata have been truncated during a Hercynian erosional event and subsequently overlain by a northward-thickening wedge of Mesozoic sediments. Major reservoir rocks include Triassic sandstones that produce oil, gas, and condensate in the western Ghadames basin, Siluro-Devonian sandstones that produce mostly oilmore » in the shallower Ilizzi basin to the south, and Cambro-Ordovician orthoquartzites that produce oil at Hassi Messaoud to the northwest. Organic shales of the Silurian and Middle-Upper Devonian are considered primary source rocks. Paleozoic shales and Triassic evaporite/red bed sequences act as seals for hydrocarbon accumulations. The central Ghadames basin is underexplored, with less than one wildcat well/1700 km{sup 2} (one well/420,000 ac). Recent Devonian and Triassic oil discoveries below 3500 m (11,500 ft) indicate that deep oil potential exists. Exploration to date has concentrated on structural traps. Subcrop and facies trends indicate that potential for giant stratigraphic or combination traps exists for both Siluro-Devonian and Triassic intervals. Modern seismic acquisition and processing techniques in high dune areas can be used to successfully identify critical unconformity-bound sequences with significant stratigraphic trap potential. Advances in seismic and drilling technology combined with creative exploration should result in major petroleum discoveries in the Ghadames basin.« less

Sediment supply as a driver of river evolution in the Amazon Basin

NASA Astrophysics Data System (ADS)

Ahmed, Joshua; Constantine, José Antonio; Dunne, Thomas; Legleiter, Carl; Lazarus, Eli D.

2015-04-01

The Amazon represents the only large river basin in the world where there is a sufficient range of sediment supplies and a lack of engineering controls to assess how sediment supply drives the evolution of meandering rivers. Despite recent analytical advances (Asahi et al., 2013; Pittaluga and Seminara, 2011), modern theory does not yet identify or explain the effects of externally imposed sediment supplies, a fundamental river characteristic, on meandering river evolution. These sediment supplies would be radically reduced by the construction of large dams proposed for the Amazon Basin (Finer and Jenkins, 2012). Here, we demonstrate that the sediment loads imposed by their respective drainage basins determine planform changes in lowland rivers across the Amazon. Our analysis, based on Landsat image sequences, indicates that rivers with high sediment loads draining the Andes and associated foreland basin experience annual migration rates that are on average four times faster than rivers with lower sediment loads draining the Central Amazon Trough and shields. Incidents of meander cutoff also occur more frequently along the rivers of the Andes and foreland basin, where the number of oxbows in the floodplains is more than twice that observed in the floodplains of the Central Amazon Trough and shields. Our results, which cannot be explained by differences in channel slope or hydrology, highlight the importance of sediment supply in modulating the ability of meandering alluvial rivers to reshape the floodplain environment through river migration. Asahi, K., Shimizu, Y., Nelson, J., Parker, G., 2013. Numerical simulation of river meandering with self-evolving banks. Journal of Geophysical Research: Earth Surface, 118(4), 2013JF002752. Finer, M., Jenkins, C.N., 2012. Proliferation of hydroelectric dams in the Andean Amazon and implications for Andes-Amazon connectivity. PLOS One, 7(4), e35126. Pittaluga, M.B., Seminara, G., 2011. Nonlinearity and unsteadiness in river

Depositional Record of the Bagua Basin, Northern Peru: Implications for Climate and Tectonic Evolution of Tropical South America

NASA Astrophysics Data System (ADS)

Moreno, F.; George, S. W. M.; Williams, L. A.; Horton, B. K.; Garzione, C. N.

2015-12-01

The Andes Mountains exert critical controls on the climate, hydrology, and biodiversity of South America. The Bagua Basin, a low elevation (400-600 m) intermontane basin in northern Peru, offers a unique opportunity to study the ecological, climatic, and structural evolution of the western topographic boundary of the Amazonian foreland. Situated between the Marañon fold-thrust belt of the Western Cordillera and basement block uplifts of the Eastern Cordillera, the Bagua region contains a protracted, semi-continuous record of Triassic through Pleistocene sedimentation. Whereas Triassic-Cretaceous marine deposits were potentially related to extension and regional thermal subsidence, a Paleocene-Eocene shift to shallow marine and fluvial systems marks the onset of foreland basin conditions. Oligocene-Miocene sedimentation corresponds to a braided-meandering fluvial system with exceptional development of paleosols. In this study, we use new detrital zircon U-Pb geochronologic and oxygen stable isotopic datasets to establish a chronology of pre-Andean and Andean processes within the Bagua Basin. Detrital zircon geochronology provides constraints on when the Western and Eastern cordilleras shed sediments into the basin. Syndepositional zircons within Eocene, Oligocene and Miocene strata provide key age control for a previously poorly constrained depositional chronology. Preliminary results suggest a dramatic provenance shift in which Paleocene deposits contain almost exclusively cratonic populations (500-1600 Ma) whereas Eocene deposits show a mix of syndepositional zircons from the magmatic arc, recycled Mesozoic zircons, and cratonic zircon populations. Oxygen stable isotopes (δ18O) of carbonate nodules from Neogene paleosols will help elucidate when the Eastern Cordillera became an orographic barrier intercepting moisture from the Amazon basin to the east. Together, these records will help uncover the history of tectonics and climate interaction in tropical South

Joint Interpretation of Magnetotelluric and Gravimetric Data from the South American Paraná Basin

NASA Astrophysics Data System (ADS)

Santos, E. B.; Santos, H. B.; Vitorello, I.; Pádua, M. B.

2013-05-01

The Paraná Basin is a large sedimentary basin in central-eastern South America that extends through Brazil, Paraguay, Uruguay and Argentina. Evolved completely over the South American continental crust, this Paleozoic basin is filled with sedimentary and volcanic rocks deposited from the Silurian to the Cretaceous, when a significant basaltic effusion covered almost the entire area of the basin. A series of superposed sedimentary and volcanic rock layers were laid down under the influence of different tectonic settings, probably originated from distant collisional dynamics of continental boards that led to the amalgamation of Gondwanaland. The current boundaries of the basin can be the result of issuing erosional or of tectonic origin, such as the building up of large arches and faults. To evaluate the deep structural architecture of the lithosphere under a sedimentary basin is a great challenge, requiring the integration of different geophysical and geological studies. In this paper, we present the resulting Paraná Basin lithospheric model, obtained from processing and inversion of broadband and long-period magnetotelluric soundings along an E-W profile across the central part of the basin, complemented by a qualitative joint interpretation of gravimetric data, in order to obtain a more precise geoelectric model of the deep structure of the region.

Rates and style of Cenozoic deformation around the Gonghe Basin, northeastern Tibetan Plateau

USGS Publications Warehouse

Craddock, William H.; Kirby, Eric; Zhang, Huiping; Clark, Marin K.; Champagnac, Jean-Daniel; Yuan, Daoyang

2014-01-01

The northeastern Tibetan Plateau constitutes a transitional region between the low-relief physiographic plateau to the south and the high-relief ranges of the Qilian Shan to the north. Cenozoic deformation across this margin of the plateau is associated with localized growth of fault-cored mountain ranges and associated basins. Herein, we combine detailed structural analysis of the geometry of range-bounding faults and deformation of foreland basin strata with geomorphic and exhumational records of erosion in hanging-wall ranges in order to investigate the magnitude, timing, and style of deformation along the two primary fault systems, the Qinghai Nan Shan and the Gonghe Nan Shan. Structural mapping shows that both ranges have developed above imbricate fans of listric thrust faults, which sole into décollements in the middle crust. Restoration of shortening along balanced cross sections suggests a minimum of 0.8–2.2 km and 5.1–6.9 km of shortening, respectively. Growth strata in the associated foreland basin record the onset of deformation on the two fault systems at ca. 6–10 Ma and ca. 7–10 Ma, respectively, and thus our analysis suggests late Cenozoic shortening rates of 0.2 +0.2/–0.1 km/m.y. and 0.7 +0.3/–0.2 km/m.y. along the north and south sides of Gonghe Basin. Along the Qinghai Nan Shan, these rates are similar to late Pleistocene slip rates of ∼0.10 ± 0.04 mm/yr, derived from restoration and dating of a deformed alluvial-fan surface. Collectively, our results imply that deformation along both flanks of the doubly vergent Qilian Shan–Nan Shan initiated by ca. 10 Ma and that subsequent shortening has been relatively steady since that time.

A Multi-Proxy Analysis of two Loess-Paleosol Sequences in the Northern Harz Foreland

NASA Astrophysics Data System (ADS)

Krauss, Lydia; Zens, Joerg; Zeeden, Christian; Schulte, Philipp; Eckmeier, Eileen; Lehmkuhl, Frank

2016-04-01

Within the second phase of the "Collaborative Research Centre 806 (CRC806) - Our Way to Europe - Culture-Environment Interaction and Human Mobility in the Late Quaternary" two loess-paleosol sections in the northern Harz foreland are being investigated. The region is part of the Northern European loess belt. The northern edge of the loess distribution is characterized by an interlocking of Weichselian silt and sand sized aeolian sediments. To the south the Northern European loess belt is limited by the central German uplands (Mittelgebirge). Here the continuous loess cover disperses into separated loess basins. In comparison to relatively long, continuous and intensively studied sections, e.g. along the Rhine river, investigations on loess-paleosol sequences in the northern Harz foreland have been sparse so far. In 2006 REINECKE created an overview of Pleistocene landscape developments by investigating terrace sequences and loess sections in this area. Due to improvements of research methods over the last ten years, the two loess-paleosol sequences Hecklingen and Zilly are being reinvestigated. Aiming towards a better understanding of the paleoenvironmental conditions during the Weichselian in an area close to the Scandinavian ice sheet, results from grain size, geochemical (XRF, CNS) and color measurements are combined. The results show an increased input of aeolian material during the last glacial maximum and the last cover loess period, supporting the theory of dryer and colder conditions during this time frame. Further, we can see a stronger short distant input within the recent soil and during the last glacial maximum in both profiles. In Hecklingen this is also observed within the MIS 3 soil material. Since soil material dating to the MIS 3 is present, we can assume that surface processes where less intrusive during the MIS 3 and 2 as in e.g. the Lower Rhine Embayment. REINECKE, V. (2006): Untersuchungen zur mittel- und jungpleistozänen Reliefentwicklung und

Ghaba salt basin province and Fahud salt basin province, Oman; geological overview and total petroleum systems

USGS Publications Warehouse

Pollastro, Richard M.

1999-01-01

Natih limestones account for most of the production in the Fahud Salt Basin with about 50 percent of the basin?s production from porous, fractured Shu?aiba limestones in Yibal field, thus the name North Oman Huqf? Shu?aiba(!) TPS. Deep gas is produced mainly from Middle Cambrian to Lower Ordovician clastic reservoirs of the Haima Supergroup. Traps in nearly all hydrocarbon accumulations of these petroleum systems are mainly structural and were formed by one or more 3 mechanisms. These trap-forming mechanisms were mainly periodic halokinesis of the thick Cambrian Ara Salt and consequent folding and faulting from basin loading, rifting, or other major tectonic events, particularly those events forming the Oman Mountains and associated foreland-basin system during the Late Cretaceous and late Tertiary. Many of the future new-field targets will likely be low-relief, subtle structures, as many of the large structures have been drilled. Oman?s recent interest and commitments to liquid natural gas export make deep gas a primary objective in the two North Oman Huqf petroleum systems. New-field exploration of deep gas and exploring deeper targets for gas in existing fields will likely identify a significant gas resource in the next 30 years. Moreover, salt-diapir flank traps in these two North Oman Huqf petroleum systems and salt basin provinces have gone essentially untested and will likely be targeted in the near future. The middle Cretaceous Natih(!) TPS is a small efficient system of the Fahud Salt Basin. Natih source rocks are only mature in the Late Cretaceous/Tertiary foredeep and production is primarily from Natih reservoirs; minor production from the Shu?aiba limestone is documented along fault-dip structures. Most traps are structural and are related to development of the foreland basin and formation of the Oman Mountains. Future targets of the Natih TPS will be less obvious

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

Temporal evolution of fault systems in the Upper Jurassic of the Central German Molasse Basin: case study Unterhaching

NASA Astrophysics Data System (ADS)

Budach, Ingmar; Moeck, Inga; Lüschen, Ewald; Wolfgramm, Markus

2018-03-01

The structural evolution of faults in foreland basins is linked to a complex basin history ranging from extension to contraction and inversion tectonics. Faults in the Upper Jurassic of the German Molasse Basin, a Cenozoic Alpine foreland basin, play a significant role for geothermal exploration and are therefore imaged, interpreted and studied by 3D seismic reflection data. Beyond this applied aspect, the analysis of these seismic data help to better understand the temporal evolution of faults and respective stress fields. In 2009, a 27 km2 3D seismic reflection survey was conducted around the Unterhaching Gt 2 well, south of Munich. The main focus of this study is an in-depth analysis of a prominent v-shaped fault block structure located at the center of the 3D seismic survey. Two methods were used to study the periodic fault activity and its relative age of the detected faults: (1) horizon flattening and (2) analysis of incremental fault throws. Slip and dilation tendency analyses were conducted afterwards to determine the stresses resolved on the faults in the current stress field. Two possible kinematic models explain the structural evolution: One model assumes a left-lateral strike slip fault in a transpressional regime resulting in a positive flower structure. The other model incorporates crossing conjugate normal faults within a transtensional regime. The interpreted successive fault formation prefers the latter model. The episodic fault activity may enhance fault zone permeability hence reservoir productivity implying that the analysis of periodically active faults represents an important part in successfully targeting geothermal wells.

Ghaba salt basin province and Fahud salt basin province, Oman; geological overview and total petroleum systems

USGS Publications Warehouse

Pollastro, R.M.

1999-01-01

Natih limestones account for most of the production in the Fahud Salt Basin with about 50 percent of the basin's production from porous, fractured Shu'aiba limestones in Yibal field, thus the name North Oman Huqf ? Shu'aiba(!) TPS. Deep gas is produced mainly from Middle Cambrian to Lower Ordovician clastic reservoirs of the Haima Supergroup. Traps in nearly all hydrocarbon accumulations of these petroleum systems are mainly structural and were formed by one or more mechanisms. These trap-forming mechanisms were mainly periodic halokinesis of the thick Cambrian Ara Salt and consequent folding and faulting from basin loading, rifting, or other major tectonic events, particularly those events forming the Oman Mountains and associated foreland-basin system during the Late Cretaceous and Late Tertiary. Many of the future new-field targets will likely be low-relief, subtle structures, as many of the large structures have been drilled. Oman's recent interest and commitments to liquid natural gas export make deep gas a primary objective in the two North Oman Huqf petroleum systems. New-field exploration of deep gas and exploring deeper targets for gas in existing fields will likely identify a significant gas resource in the next thirty years. Moreover, salt-diapir flank traps in these two North Oman Huqf petroleum systems and salt basin provinces have gone essentially untested and will likely be targeted in the near-future. The Middle Cretaceous Natih(!) TPS is a small efficient system of the Fahud Salt Basin. Natih source rocks are only mature in the Late Cretaceous/Tertiary foredeep and production is primarily from Natih reservoirs; minor production from the Shu'aiba limestone is documented along fault-dip structures. Most traps are structural and are related to development of the foreland basin and formation of the Oman Mountains. Future targets of the Natih TPS will be less obvious than those of Fahud and Natih fields and likely includ

Controls on the deposition and preservation of the Cretaceous Mowry Shale and Frontier Formation and equivalents, Rocky Mountain region, Colorado, Utah, and Wyoming

USGS Publications Warehouse

Kirschbaum, Mark A.; Mercier, Tracey J.

2013-01-01

Regional variations in thickness and facies of clastic sediments are controlled by geographic location within a foreland basin. Preservation of facies is dependent on the original accommodation space available during deposition and ultimately by tectonic modification of the foreland in its postthrusting stages. The preservation of facies within the foreland basin and during the modification stage affects the kinds of hydrocarbon reservoirs that are present. This is the case for the Cretaceous Mowry Shale and Frontier Formation and equivalent strata in the Rocky Mountain region of Colorado, Utah, and Wyoming. Biostratigraphically constrained isopach maps of three intervals within these formations provide a control on eustatic variations in sea level, which allow depositional patterns across dip and along strike to be interpreted in terms of relationship to thrust progression and depositional topography. The most highly subsiding parts of the Rocky Mountain foreland basin, near the fold and thrust belt to the west, typically contain a low number of coarse-grained sandstone channels but limited sandstone reservoirs. However, where subsidence is greater than sediment supply, the foredeep contains stacked deltaic sandstones, coal, and preserved transgressive marine shales in mainly conformable successions. The main exploration play in this area is currently coalbed gas, but the enhanced coal thickness combined with a Mowry marine shale source rock indicates that a low-permeability, basin-centered play may exist somewhere along strike in a deep part of the basin. In the slower subsiding parts of the foreland basin, marginal marine and fluvial sandstones are amalgamated and compartmentalized by unconformities, providing conditions for the development of stratigraphic and combination traps, especially in areas of repeated reactivation. Areas of medium accommodation in the most distal parts of the foreland contain isolated marginal marine shoreface and deltaic sandstones

Ordovician and Silurian Phi Kappa and Trail Creek formations, Pioneer Mountains, central Idaho; stratigraphic and structural revisions, and new data on graptolite faunas

USGS Publications Warehouse

Dover, James H.; Berry, William B.N.; Ross, Reuben James

1980-01-01

Recent geologic mapping in the northern Pioneer Mountains combined with the identification of graptolites from 116 new collections indicate that the Ordovician and Silurian Phi Kappa and Trail Creek Formations occur in a series of thrust-bounded slices within a broad zone of imbricate thrust faulting. Though confirming a deformational style first reported in a 1963 study by Michael Churkin, our data suggest that the complexity and regional extent of the thrust zone were not previously recognized. Most previously published sections of the Phi Kappa and Trail Creek Formations were measured across unrecognized thrust faults and therefore include not only structural repetitions of graptolitic Ordovician and Silurian rocks but also other tectonically juxtaposed lithostratigraphic units of diverse ages as well. Because of this discovery, the need to reconsider the stratigraphic validity of these formations and their lithology, nomenclature, structural distribution, facies relations, and graptolite faunas has arisen. The Phi Kappa Formation in most thrust slices has internal stratigraphic continuity despite the intensity of deformation to which it was subjected. As revised herein, the Phi Kappa Formation is restricted to a structurally repeated succession of predominantly black, carbonaceous, graptolitic argillite and shale. Some limy, light-gray-weathering shale occurs in the middle part of the section, and fine-grained locally pebbly quartzite is present at the base. The basal quartzite is here named the Basin Gulch Quartzite Member of the Phi Kappa. The Phi Kappa redefined on a lithologic basis represents the span of Ordovician time from W. B. N. Berry's graptolite zones 2-4 through 15 and also includes approximately 17 m of lithologically identical shale of Early and Middle Silurian age at the top. The lower contact of the formation as revised is tectonic. The Phi Kappa is gradationally overlain by the Trail Creek Formation as restricted herein. Most of the coarser

Dynamic coupling among channel flow, plateau growth, foreland shortening, and the formation of metamorphic core complexes: Application to the Tibetan plateau

NASA Astrophysics Data System (ADS)

Rey, P. F.; Teyssier, C.; Whitney, D. L.

2009-04-01

Gravitational potential energy stored in an orogenic plateau can be sufficiently strong to deform the surrounding region (foreland), hence contributing to both plateau growth and collapse. Gravity-driven channel flow from the plateau lower crust into the foreland lower crust, or channel extrusion, has been proposed as a main contributor to the eastward growth of the Tibetan plateau, possibly driving the lower crust channel as far as 1000 km beneath the foreland (eg. Royden et al., 2008). On the basis of numerical modeling using temperature-dependent viscosities and densities, we show that four processes impose severe limitations to channel extrusion: (1) cooling of the extruded channel, (2) convective motion in the plateau channel, (3) surface extension of the plateau, and (4) erosion of the plateau edge. Model results show that peak velocities in the extrusion channel drop rapidly (in less than a few My) from ca. 5 cm/year to less than 1 cm/year, owing to the rapid cooling in the channel from 750-850°C to 650-550°C as it travels into the foreland region. Channel flow extrusion is further slowed when convective flow initiates in the plateau channel as a result of only a few percent drop in density. This convection inhibits laminar flow in the channel, reduces the peak horizontal velocity in the channel to a few mm, and even drives a counter flow at the base of the channel, preventing its propagation toward the foreland. If the foreland is actively pulled away from the plateau (extending boundaries), the plateau upper crust undergoes extension and the lower crust moves up efficiently into a metamorphic core complex, which inhibits flow of the channel away from the plateau and even generates a counter flow from the foreland to the metamorphic core complex. If the foreland is fixed, the same phenomenon occurs as long as the foreland upper crust undergoes shortening (likely weakened by high pore fluid pressure), which enhances extension of the plateau and upward flow

Hydraulic Testing of Silurian and Ordovician Strata at the Bruce Site

NASA Astrophysics Data System (ADS)

Beauheim, R. L.; Avis, J. D.; Chace, D. A.; Roberts, R. M.; Toll, N. J.

2009-05-01

Ontario Power Generation is proposing a Deep Geologic Repository (DGR) for the long-term management of its Low and Intermediate Level Radioactive Waste (L&ILW) within a Paleozoic-age sedimentary sequence beneath the Bruce Site near Tiverton, Ontario, Canada. The concept envisions that the DGR would be excavated at a depth of approximately 680 m within the Ordovician Cobourg Formation, a massive, dense, argillaceous limestone. A key attribute of the Bruce site is the extremely low permeabilities associated with the thick Ordovician carbonate and argillaceous bedrock formations that will host and enclose the DGR. Such rock mass permeabilities are thought sufficiently low to contribute toward or govern a diffusion-dominated transport regime. To support this concept, hydraulic testing was performed in 2008 and 2009 in two deep boreholes at the proposed repository site, DGR-3 and DGR-4. The hydraulic testing was performed using a straddle-packer tool with a 30.74-m test interval. Sequential tests were performed over the entire open lengths of the boreholes from the F Unit of the Silurian Salina Formation into the Ordovician Gull River Formation, a distance of approximately 635 m. The tests consisted primarily of pressure-pulse tests, with a few slug tests performed in several of the higher permeability Silurian units. The tests are analyzed using the nSIGHTS code, which allows the entire pressure history a test interval has experienced since it was penetrated by the drill bit to be included in the test simulation. nSIGHTS also allows the model fit to the test data to be optimized over an n-dimensional parameter space to ensure that the final solution represents a true global minimum rather than simply a local minimum. The test results show that the Ordovician-age strata above the Coboconk Formation (70+ m below the Cobourg) have average horizontal hydraulic conductivities of 1E-13 m/s or less. Coboconk and Gull River hydraulic conductivities are as high as 1E-11 m

Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian Dolomite

USGS Publications Warehouse

Sherrill, Marvin G.

1978-01-01

Door County is in northeastern Wisconsin and is an area of 491 square miles. The county forms the main body of the peninsula between Green Bay and Lake Michigan. The land surface is an upland ridge controlled by the underlying bedrock. The west edge of the ridge forms an escarpment facing Green Bay. Silurian dolomite is the upper bedrock unit throughout most of the county and is the most important aquifer. This bedrock is exposed in much of the county, particularly north of Sturgeon Bay; elsewhere, it is covered by a generally thin mantle of soil or drift. The bedrock units are divided into two major aquifer systems in Door County; the Silurian dolomite aquifer system and the sandstone aquifer system, consisting of Ordovician and Cambrian bedrock units. These two major systems are separated by the Maquoketa Shale of Ordovician age, a nearly impermeable, generally nonproductive unit. The Silurian dolomite aquifer system is itself divided into the Niagaran aquifer and the underlying Alexandrian aquifer. Water occurs in the Silurian dolomite aquifer system in two types of openings-nearly vertical joints (fractures) and horizontal to slightly dipping bedding-plane joints. Vertical joints are more common in the upper part of the Niagaran aquifer. These yield small amounts of water to wells. Bedding-plane joints transmit most of the water in the lower part of the Niagaran aquifer and in the Alexandrian aquifer. The bedding-plane joints, because they are poorly interconnected, act as semiartesian conduits separated by impermeable rock. Eight water-bearing zones in generally continuous bedding-plane joints have been mapped. The dolomite is recharged from direct precipitation and snowmelt. It discharges water to pumping wells and by natural springs discharge to Lake Michigan and Green Bay and to interior lakes and streams. Wells in the Silurian dolomite aquifer system have adequate yields to meet most needs, except in the southwest corner of the county, where the dolomite

Sedimentology of the Ripogenus Formation, Maine: A Silurian carbonate-siliciclastic depositional system

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

Comrie, T.A.; Caldwell, D.W.

The Ripogenus Formation of north-central Maine is shallow marine unit of probable Wenlockian age characterized by interbeds of sandstone and limestone less than 50 cm. in thickness and separated by sharp, often erosional, contacts. Reefal material with abundant stromatoporoids is exposed in the eastern part of the formation and is overlain locally by Silurian andesite and Siluro-Devonian redbeds. Sediment size and bed thickness decrease to the west, as does the relative amount of carbonate sediment. Common fossils also include stromatolites, brachiopods, gastropods, crinoids, and corals. Large fossils, notably the stromatoporoids and stromatolites, are often found in growth position, but smallermore » fossils are usually found to have been abraided and transported. The formation was deposited in an area shown by paleogeographic reconstructions to have been located just south of the equator (probably near one or more islands) in the lapetus Ocean prior to its closure. Although sedimentary structures are often not well preserved due to its closure. Although sedimentary structures are often not well preserved due to soft-sedimentary deformation and slight metamorphism, there is some evidence of storm-controlled deposition. Deposition of this unit and other Silurian carbonates found in Maine and the Maritime Provinces are unlike those found throughout N. America in that they are the product of localized deposition in an unstable tectonic environment.« less

The Areal Extent of Continuous Type Gas Accumulations in Lower Silurian Clinton Sands and Medina Group Sandstones of the Appalachian Basin and the Environments Affected by Their Development

USGS Publications Warehouse

Wandrey, C.J.; Ryder, Robert T.; Nuccio, Vito F.; Aggen, Kerry L.

1997-01-01

In order to best preserve and manage our energy and natural resources we must understand the relationships between these resources and the impacts of their development. To further this understanding the U.S. Geological Survey is studying unconventional continuous-type and, to a lesser extent, conventional oil and gas accumulations and the environmental impacts associated with their development. Continuous-type gas accumulations are generally characterized by low matrix permeabilities, large areal extents, and no distinct water contacts. This basin scale map shows the overall extent of these accumulations and the general land use types that may be impacted by their development. The Appalachian Basin has the longest history of oil and gas exploration and production in the United States. Since Drake's Titusville discovery well was drilled in 1859, oil and gas has been continuously produced in the basin. While there is still a great deal of oil and gas production, new field discoveries are rare and relatively small. For most of the second half of the 20th century the Appalachian basin has been considered a mature petroleum province because most of the large plays have already been discovered and developed. One exception to this trend is the Lower Silurian Clinton Sands and Medina Group Gas play which is being developed in New York, Pennsylvania, and Ohio. This continuous-type gas play has been expanding since the early 1970's (see inset maps). In the 1980's economic incentives such as large increases in wellhead prices further stimulated continuous-type gas resource development. Continuous-type gas plays can be large in areal extent and in thickness. 'Sweetspots' (areas of greater prodcution) are hard to predict and generally associated with better than average permeabilities, and enhanced by natural fracture systems. With an overall success rate often approaching 90%, drilling most of the play with closely spaced wells is often the best way to maximize gas recovery

Regional Landscape Response to Wedge-Top Basin Formation

NASA Astrophysics Data System (ADS)

Ruetenik, G.; Moucha, R.; Hoke, G. D.; Val, P.

2017-12-01

Wedge-top basins are the result of regionally variable uplift along thrust faults downstream of a mountain range and provide an ideal environment to study the regional stream and surface response to local variations in rock uplift. In this study, we simulate the formation and evolution of a wedge-top basin using a landscape evolution model. In line with a previous study, we find that during deformation in the fold-and-thrust belt adjacent to a wedge-top basin, both channel slope and erosion rates are reduced, and these changes propagate as a wave of low erosion into the uplands. For a uniform background uplift rate, this reduced rate of erosion results in a net surface uplift and a decreased slope within and upstream of the wedge-top basin. Following the eventual breach of the basin's bounding thrust belt, a wave of high erosion propagates through the basin and increases the channel slope. We expand upon previous studies by testing our model against a wide range of model parameters, although in general we find that the onset of increased erosion can be delayed by up to several million years. The amount of surface uplift is highly dependent on flexural isostasy and therefore it is heavily influenced by the elastic thickness and erodbility parameters. Observed paleoerosion rates in a paired wedge-top foreland sequence in the Argentine Precordillera reveal similar histories of paleo-erosion, and present day stream profiles show evidence that support model outcomes.

Algoma-, Superior-, and oolitic-type iron deposits of the Islamic Republic of Mauritania (phase V, deliverable 83): Chapter O in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

USGS Publications Warehouse

Taylor, Cliff D.; Finn, Carol A.; Anderson, Eric D.; Joud, M. Y.; Taleb, M. A.; Horton, John D.

2015-01-01

Phanerozoic oolitic ironstones are hosted in the upper Silurian and lower Devonian rocks of the Gara Bouya Ali Group and the Zemmour Group in the Tindouf Basin in northern Mauritania and in the end Ordovician Tichit Group, the Silurian Oued Chig Group, and the lower Devonian Tenemouj Group in the Taoudeni Basin near Tidjikja. These rock groups define 11 permissive tracts for Algoma-, Superior-, and oolitic-type iron deposits in Mauritania.

New observations of the early land plant Eocooksonia Doweld from the Pridoli (Upper Silurian) of Xinjiang, China

NASA Astrophysics Data System (ADS)

Xue, Jinzhuang; Wang, Qi; Wang, Deming; Wang, Yi; Hao, Shougang

2015-04-01

As an early land plant previously reported from the Upper Silurian (Pridoli) of Xinjiang, Northwest China and Central Kazakhstan, the circumscription of Eocooksonia sphaerica (Senkevitsch) Doweld remains ill-defined because of the paucity of specimens and poor preservation in marine deposits. New specimens of this plant are described from the Pridoli-aged Wutubulake Formation of the Junggar Basin, Xinjiang. New observations and comparisons with the type material from Kazakhstan confirm the pseudomonopodial branching pattern, which forms an apparent main axis with lateral dichotomously branching systems. Our specimens demonstrate that the terminal sporangia of Eocooksonia Doweld consist of a central body and a border with four to eight elongate-triangular emergences, a character shown in the published illustrations of the type material but not mentioned in the original diagnosis. Eocooksonia may be close to Cooksonia Lang and Pertonella Fanning, Edwards et Richardson in affinities, particularly to the latter that has terminal discoidal sporangia with spiny emergences. It is deduced that the sporangial central body of Eocooksonia contains sporogenous tissues, which are covered by a distal surface wall with radiated emergences. One sporangium specimen of an unnamed plant is also described from the Wutubulake Formation of Xinjiang; it shows a central body with a wide border lacking emergences, and represents a taxon superficially similar to Eocooksonia.

Paleozoic shale gas resources in the Sichuan Basin, China

USGS Publications Warehouse

Potter, Christopher J.

2018-01-01

The Sichuan Basin, China, is commonly considered to contain the world’s most abundant shale gas resources. Although its Paleozoic marine shales share many basic characteristics with successful United States gas shales, numerous geologic uncertainties exist, and Sichuan Basin shale gas production is nascent. Gas retention was likely compromised by the age of the shale reservoirs, multiple uplifts and orogenies, and migration pathways along unconformities. High thermal maturities raise questions about gas storage potential in lower Paleozoic shales. Given these uncertainties, a new look at Sichuan Basin shale gas resources is advantageous. As part of a systematic effort to quantitatively assess continuous oil and gas resources in priority basins worldwide, the US Geological Survey (USGS) completed an assessment of Paleozoic shale gas in the Sichuan Basin in 2015. Three organic-rich marine Paleozoic shale intervals meet the USGS geologic criteria for quantitative assessment of shale gas resources: the lower Cambrian Qiongzhusi Formation, the uppermost Ordovician Wufeng through lowermost Silurian Longmaxi Formations (currently producing shale gas), and the upper Permian Longtan and Dalong Formations. This study defined geologically based assessment units and calculated probabilistic distributions of technically recoverable shale gas resources using the USGS well productivity–based method. For six assessment units evaluated in 2015, the USGS estimated a mean value of 23.9 tcf (677 billion cubic meters) of undiscovered, technically recoverable shale gas. This result is considerably lower than volumes calculated in previous shale gas assessments of the Sichuan Basin, highlighting a need for caution in this geologically challenging setting.

Carboniferous Proto-type Basin Evolution of Junggar Basin in Northwest China: Implications for the Growth Models of Central Asia Orogenic Belt

NASA Astrophysics Data System (ADS)

He, D.

2016-12-01

The Junggar Basin locates in the central part of Paleo-Asian Ocean tectonic domain, and records the dynamic processes of the Central Asian Orogenic Belt from subduction-accretion-collision to later intracontinental deformations. Carboniferous is the key period from subduction to closure in the tectonic evolution of Paleo-Asian Ocean. Based on the borehole, outcrop, seismic and gravity and magnetic anomaly data, the paper made analysis of the Carboniferous basin evolution.Geo-chronological results for the borehole volcanic rocks suggest that the Junggar Basin and adjacent area had five periods of volcanic activities, including two periods in the Early Carboniferous (359-347Ma 347-331Ma and 331-324Ma) and three periods in the Late Carboniferous (323-307Ma and 307-300Ma). Regional unconformities divided the Carboniferous into two tectono-stratigraphic sequences: Lower Carboniferous and Upper Carboniferous. The former is characterized by compressional structures and involves massive calc-alkaline basalts, andesites, dacites and rhyolites, whereas the later is mainly controlled by extensional faults and dominated by intermediate-mafic volcanic rocks, with bimodal volcanic rocks in parts. The paper determined four Carboniferous arc-basin belts in the Junggar Basin and adjacent area from north to south: the Saur-Fuhai-Dulate, Heshituoluogai-Wulungu-Yemaquan, Darbut-Luliang-Karamaili, and Zhongguai-Mosuowan-Baijiahai-Qitai, and identified multi-type basins, such as fore-arc basin, retro-arc basin, intra-arc rift basin, foreland basin and passive continental margin basin,etc.. The Carboniferous proto-type basin evolution of the Junggar Basin can be divided into three phases such as, the early to middle Early Carboniferous subduction-related compressional phase, the late Early Carboniferous to middle Late Carboniferous subduction-related extensional phase and the late Late Carboniferous intra-continental fault-sag phase. The study discloses that the Junggar Basin is likely

Origin of Silurian reefs in the Alexander Terrane of southeastern Alaska

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

Soja, C.M.

1991-04-01

Lower to Upper Silurian (upper Llandovery-Ludlow) limestones belonging to the Heceta Formation record several episodes of reef growth in the Alexander terrane of southeastern Alaska. As the oldest carbonates of wide-spread distribution in the region, the Heceta limestones represent the earliest development of a shallow-marine platform within the Alexander arc and the oldest foundation for reef evolution. These deposits provide important insights into the dynamic processes, styles, and bathymetry associated with reef growth in tectonically active oceanic islands. Massive stromatoporoids, corals, and red algae are preserved in fragmental rudstones and represent a fringing reef that formed at the seaward edgemore » of the incipient marine shelf. Accessory constituents in this reef include crinoids and the cyanobacterium Girvanella. Small biostromes were constructed by ramose corals and stromatoporoids on oncolitic substrates in backreef or lagoonal environments. These buildups were associated with low-diversity assemblages of brachiopods and with gastropods, amphiporids, calcareous algae and cyanobacteria. Microbial boundstones reflect the widespread encrustation of cyanobacteria and calcified microproblematica on shelly debris as stromatolitic mats that resulted in the development of a stromatactoid-bearing mud mound and a barrier reef complex. Epiphytaceans, other microbes, and aphrosalpingid sponges were the primary frame-builders of the barrier reefs. These buildups attained significant relief at the shelf margin and shed detritus as slumped blocks and debris flows into deep-water sites along the slope. The similarity of these stromatolitic-aphrosalpingid reefs to those from Siluro-Devonian strata of autochthonous southwestern Alaska suggests paleobiogeographic ties of the Alexander terrane to cratonal North America during the Silurian.« less

Origin and Evolution of The Early- Silurian Land Vascular Plants: Evidence From Biomarkers

NASA Astrophysics Data System (ADS)

Jin, R.

2016-12-01

Origin and early evolution of land vascular plants, is one of the most intriguing hotspots in the life science research. During the 1970s and 1980s,Pinnatiramosus qianensis was found in early-Silurian strata in guizhou of south China.43 years have passed. But so far, the biological characteristics and belonging of the age of this unique plant have been debated again and again, up in the air.Biomarkers have a good stability in the process of organic evolution, no more or less changed, so they have a special `function of mark'. While biomarkers can provide information about organic matter of hydrocarbon source rock (the source), the period of deposition and burial (diagenesis) environmental conditions, and many other aspects of information.This paper obtained the sedimentary environment, source of organic matter input and other relevant information, through extracting and analyzing biomarkers of the 26 samples in the late Ordovician to early Silurian strata in NorthGuizhou areas. According to the results, Pr/Ph of late Ordovician Meitan Fm-early Silurian Hanjiadian Fm is high.It manifests more pristane, characterized by reductive environment. At the bottom of the Hanjiadian Fm, Pr/Ph has a volatility.Some huge environmental changes may have taken place in the corresponding period. N-alkanes do not have parity advantage or has even carbon advantage slightly.The peak carbon is mainly in low carbon number.(C21 + C22)/(C28 + C29) is high.Aquatic organisms is a major source of organic matter during this period,C21-/C22+ is low.This may be caused by the relatively serious loss of light hydrocarbon during the separation of components. In the Hanjiadian Fm,information of C29/C27 sterane ratios and oleanane index showed a trend of rising at the same time, indicating that during this period, there was a gradual increase input in the number of higher plants.The stable carbon isotope of saturated hydrocarbon and aromatic hydrocarbon in the Hanjiadian Fm also gradually become

Hydrologic environment of the Silurian salt deposits in parts of Michigan, Ohio, and New York

USGS Publications Warehouse

Norris, Stanley E.

1978-01-01

The aggregate thickness of evaporites (salt, gypsum, and anhydrite) in the Silurian Salina sequence in Michigan exceeds 1200 feet in areas near the periphery of the Michigan basin, where the salt beds are less than 3000 feet below land surface. In northeast Ohio the aggregate thickness of salt beds is as much as 200 feet in places, and in western New York it is more than 500 feet, where th beds are less than 3000 feet deep. The salt-bearing rocks dip regionally on the order of 50 feet per mile; those in Michigan dip toward the center of the Michigan basin, and those in Ohio and New York, in the Appalachian basin, dip generally southward. The rocks in both basins thicken downdip. Minor folds and faults occur in the salt-bearing rocks in all three states. Some of this defrmation has been attenuated or absorbed bo the salt beds. Occuring near the middle of thick sedimentary sequences, the salt beds are bounded aboe and below by beds containing water having dissolved-solids concentrations several times that seawter. The brines occur commonly in discrete zones of high permeability at specific places in the stratigraphic sequence. In northeast Ohio two prominent brine zones are recognized by the driller, the Devonian Oriskany Sandstone, or 'first water' zone, above the Salina Formation, and the Newburg or 'second water' zone below the Salina. In each aquifer there is a vertical component of hydraulic head, but little brine probably moves through the salt beds because their permeability is extremely low. Also, ther is little evidence of dissolution of the salt in areas distant from the outcrop, suggesting that if brine does move through the salt, movement is at a slow enough rate so that, in combination with the saturated or near-saturated condition of the water, it precludes significant dissolution. Principal brine movement is probably in the permeable zones in the direction of the hydraulic gradient. Two areas in Michigan and one area each in Ohio and New York appear

Timing of deformation and rapid subsidence in the northern Altiplano, Peru: Insights from detrital zircon geochronology of the Ayaviri hinterland basin

NASA Astrophysics Data System (ADS)

Horton, B. K.; Perez, N. D.; Saylor, J. E.

2011-12-01

Although age constraints on crustal deformation and sediment accumulation prove critical to testing hypotheses of orogenic plateau construction, a common lack of marine facies, volcanic tuffs, and suitable fossils hinders many attempts at chronological reconstructions. A series of elevated retroarc basins along the axis of the Andean orogenic belt provide opportunities to define the timing of deformation and transformation from foreland to hinterland basin configurations. In this study, we present new U-Pb ages of detrital zircons in the Ayaviri intermontane basin of southern Peru (~4 km elevation) in the northern part of the central Andean (Altiplano) plateau. Nearly all sandstone samples show strong unimodal U-Pb age peaks (generally defined by > 5-50 zircons), suggesting these age peaks represent syndepositional volcanism and can be regarded as accurate estimates of true depositional (stratigraphic) age. Integration of these ages with structural and stratigraphic relationships demonstrate the utility of zircon U-Pb geochronology in defining both (1) the timing of basin partitioning and (2) the pace of sediment accumulation. (1) U-Pb ages for several sandstone samples from growth-strata packages associated with two basin-bounding faults reveal structural partitioning of the Ayaviri basin from late Oligocene to Miocene time. In the north, displacement along the southwest-directed Ayaviri thrust fault commenced in late Oligocene time (~28-24 Ma), inducing initial structural partitioning of an upper Eocene-Oligocene, > 5 km thick succession potentially representing an early Andean retroarc foreland basin. In the south, the Ayaviri basin was further disrupted by initial displacement along the northeast-directed Pasani thrust fault in early to middle Miocene time (~18-15 Ma). (2) Additional U-Pb analyses from the Ayaviri basin fill help delimit the long-term rates of sedimentation, suggesting relatively short-lived (< 5 Myr) pulses of accelerated accumulation. Rapid

Tectonic evolution of the Arizaro basin of the Puna plateau, NW Argentina: Implications for plateau-scale processes

NASA Astrophysics Data System (ADS)

Boyd, John D.

Sedimentary basins of the Altiplano-Puna Plateau within the Andean Plateau in South America contain the record of retro-arc foreland basin evolution during the Cenozoic. The deformation of these basins is characterized by high angle reverse faults and thrusts deforming crystalline basement and sedimentary covers. The mechanism/s responsible for deformation within the region are not fully understood in detail. The relative abundance of intercalated tuffs within these basins and those within the bounding Eastern Cordillera enables the spatial-temporal pattern of deformation across the orogen to be constrained. This study uses the systematic combination of structural, geochronologic and sedimentalogical techniques applied to Cenozoic sedimentary rocks within the Arizaro Basin to investigate the timing of deformation across within the region in order to test two end member models for basin deformation in response to lithospheric processes. The first model attributes the deformation of the basins to internal deformation within an orogenic wedge as part of the taper building process required prior to propagation eastward towards the foreland basin system. The second model attributes basin deformation to isostatic adjustments resulting from small-scale lithospheric foundering. Detailed geologic mapping of the Arizaro Basin reveals a complex interplay of coeval thick-skinned and thin-skinned deformation, which deforms the thick Miocene succession of fluvial-lacustrine strata in both a brittle and ductile manner. Zircon U-Pb analyses of intercalated tuffs from the Vizcachera Formation reveal that approximately three km of the section was deposited between the Early Miocene (ca. 18.3) and the Middle Miocene (ca. 13.9). One tuff in the uppermost Vizcachera Formation constrains the lower limit of timing of deformation for the Arizaro Basin to be 13.9 +/- 0.7 Ma. When combined with published geochronological data across the Puna Plateau and Eastern Cordillera, the new data

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

NASA Astrophysics Data System (ADS)

Nehyba, Slavomír

2018-02-01

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

Tectonothermal modeling of hydrocarbon maturation, Central Maracaibo Basin, Venezuela

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

Manske, M.C.

1996-08-01

The petroliferous Maracaibo Basin of northwestern Venezuela and extreme eastern Colombia has evolved through a complex geologic history. Deciphering the tectonic and thermal evolution is essential in the prediction of hydrocarbon maturation (timing) within the basin. Individual wells in two areas of the central basin, Blocks III and V, have been modeled to predict timing of hydrocarbon generation within the source Upper Cretaceous La Luna Formation, as well as within interbedded shales of the Lower-Middle Eocene Misoa Formation reservoir sandstones. Tectonic evolution, including burial and uplift (erosional) history, has been constrained with available well data. The initial extensional thermal regimemore » of the basin has been approximated with a Mackenzie-type thermal model, and the following compressional stage of basin development by applying a foreland basin model. Corrected Bottom Hole Temperature (BHT) measurements; from wells in the central basin, along with thermal conductivity measurements of rock samples from the entire sedimentary sequence, resulted in the estimation of present day heat flow. An understanding of the basin`s heat flow, then, allowed extrapolation of geothermal gradients through time. The relation of geothermal gradients and overpressure within the Upper Cretaceous hydrocarbon-generating La Luna Formation and thick Colon Formation shales was also taken into account. Maturation modeling by both the conventional Time-Temperature Index (TTI) and kinetic Transformation Ratio (TR) methods predicts the timing of hydrocarbon maturation in the potential source units of these two wells. These modeling results are constrained by vitrinite reflectance and illite/smectite clay dehydration data, and show general agreement. These results also have importance regarding the timing of structural formation and hydrocarbon migration into Misoa reservoirs.« less

40Ar/39Ar Temporal Constraints on Eocene Uplift, Subsidence, and Paleohydrology in the Laramide Foreland, Western U. S.

NASA Astrophysics Data System (ADS)

Smith, M. E.; Carroll, A. R.; Singer, B. S.

2004-12-01

Due to their sensitivity to relatively subtle changes in regional drainage patterns, Eocene lake deposits of the Green River Formation offer a unique and richly detailed record of landscape modification caused by orogenic processes in the broken foreland of the western U. S. Recently obtained 40Ar/39Ar age determinations for 22 interbedded tephras provide excellent temporal resolution of this record, and enable inter-basin correlations at an unprecedented level of precision (approaching 2σ uncertainties of ± k.y.). Green River Formation strata span an interval of ~8 m.y., beginning and ending with freshwater fluvial-lacustrine deposits. Two episodes of regional basin closure and evaporite deposition, each lasting ˜1-2 m.y., coincide with evidence for active Laramide faulting at basin margins and increased rates of sediment accumulation. Evaporite deposition therefore appears to have been principally caused by enhanced uplift of basin sills rather than increased aridity. Regional stratigraphic relations, facies types, and 40Ar/39Ar geochronology permit deduction of the following paleodrainage history: 1) > ˜51.3 Ma: Fluvial-lacustrine deposition occurred in greater Green River, Piceance Creek and Uinta basins. The onset of lacustrine deposition is not well-dated due to a paucity of tephras. 2) ˜51.3-49.7 Ma: The greater Green River and Piceance Creek basins both became terminal sinks that received overflow from neighboring freshwater basins. Coarse clastic basin-marginal alluvial strata, cross-cutting fault relations, and pronounced differential subsidence in both basins indicate active uplift of the Uinta Mountains and surrounding ranges. 3) ˜49.7-49.1 Ma: Lake Gosiute expanded in extent, coincident with an influx of water and sediment derived from volcanic centers to the north. Episodic overflow over the eastern Uinta uplift flushed dissolved solutes southward, freshening Lake Gosiute while evaporite deposition continued in Lake Uinta. 4) ˜49.1-48.4 Ma

Formation waters from Mississippian-Pennsylvanian reservoirs, Illinois basin, USA: Chemical and isotopic constraints on evolution and migration

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

Stueber, A.M.; Walter, L.M.; Huston, T.J.

1993-02-01

We have analyzed a suite of seventy-four formation-water samples from Mississippian and Pennsylvanian carbonate and siliciclastic strata in the Illinois basin for major, minor, and trace element concentrations and for strontium isotopic composition. A subset of these samples was also analyzed for boron isotopic composition. Data are used to interpret origin of salinity and chemical and Sr isotopic evolution of the brines and in comparison with a similar data set from an earlier study of basin formation waters from Silurian-Devonian reservoirs. Systematics of Cl-Br-Na show that present Mississippian-Pennsylvanian brine salinity can be explained by a combination of subaerial seawater evaporationmore » short of halite saturation and subsurface dissolution of halite from an evaporite zone in the middle Mississippian St. Louis Limestone, along with extensive dilution by mixing with meteoric waters. Additional diagenetic modifications in the subsurface interpreted from cation/Br ratios include K depletion through interaction with clay minerals, Ca enrichment, and Mg depletion by dolomitization, and Sr enrichment through CaCO[sub 3] recrystallization and dolomitization. Ste. Genevieve Limestone (middle Mississippian) formation waters show [sup 87]Sr/[sup 86]Sr ratios in the range 0.70782-0.70900, whereas waters from the siliciclastic reservoirs are in the rante 0.70900-0.71052. Inverse correlations between [sup 87]Sr/[sup 86]Sr and B,Li, and Mg concentrations suggest that the brines acquired radiogenic [sup 87]Sr through interaction with siliciclastic minerals. Completely unsystematic relations between [sup 87]Fr/[sup 86]Sr and 1/Sr are observed; Sr concentrations in Ste. Genevieve and Aux Vases (middle Mississippian) waters appear to be buffered by equilibrium with respect to SrSo[sub 4]. These formation waters are distinguished from Silurian-Devonian brines in the basin by elevated Cl/Br and Na/Br ratios and by unsystematic Sr isotope relationships.« less

Strontium isotopic study of subsurface brines from Illinois basin

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

hetherington, E.A.; Stueber, A.M.; Pushkar, P.

1986-05-01

The abundance of the radiogenic isotope /sup 87/Sr in a subsurface brine can be used as a tracer of brine origin, evolution, and diagenetic effects. The authors have determined the /sup 87/Sr//sup 86/Sr ratios of over 60 oil-field waters from the Illinois basin, where brine origin is perplexing because of the absence of any significant evaporite strata. Initially, they analyzed brines from 15 petroleum-producing sandstone and carbonate units; waters from Ordovician, Silurian, Devonian, and Mississippian strata have /sup 87/Sr//sup 86/Sr ratios in the range 0.7079-0.7108. All but those from the Ste. Genevieve Limestone (middle Mississippian) are more radiogenic in /supmore » 87/Sr//sup 86/Sr than seawater values for this interval of geologic time. The detrital source of the more radiogenic /sup 87/Sr may be the New Albany Shale group, considered to be a major petroleum source rock in the basin. The /sup 87/Sr//sup 86/Sr ratios of Ste. Genevieve brines apparently evolved without a contribution from fluid-shale interaction.« less

Andean Basin Evolution Associated with Hybrid Thick- and Thin-Skinned Deformation in the Malargüe Fold-Thrust Belt, Western Argentina

NASA Astrophysics Data System (ADS)

Horton, B. K.; Fuentes, F.

2015-12-01

Andean deformation and basin evolution in the Malargüe fold-thrust belt of western Argentina (34-36°S) has been dominated by basement faults influenced by pre-existing Mesozoic rift structures of the hydrocarbon-rich Neuquen basin. However, the basement structures diverge from classic inversion structures, and the associated retroarc basin system shows a complex Mesozoic-Cenozoic history of mixed extension and contraction, along with an enigmatic early Cenozoic stratigraphic hiatus. New results from balanced structural cross sections (supported by industry seismic, well data, and surface maps), U-Pb geochronology, and foreland deposystem analyses provide improved resolution to examine the duration and kinematic evolution of Andean mixed-mode deformation. The basement structures form large anticlines with steep forelimbs and up to >5 km of structural relief. Once the propagating tips of the deeper basement faults reached cover strata, they fed slip to shallow thrust systems that were transported in piggyback fashion by newly formed basement structures, producing complex structural relationships. Detrital zircon U-Pb ages for the 5-7 km-thick basin fill succession reveal shifts in sedimentation pathways and accumulation rates consistent with (1) local basement sources during Early-Middle Jurassic back-arc extension, (2) variable cratonic and magmatic arc sources during Late Jurassic-Cretaceous postrift thermal subsidence, and (3) Andean arc and thrust-belt sources during irregular Late Cretaceous-Cenozoic shortening. Although pulses of flexural subsidence can be attributed to periods of fault reactivation (inversion) and geometrically linked thin-skinned thrusting, fully developed foreland basin conditions were only achieved in Late Cretaceous and Neogene time. Separating these two contractional episodes is an Eocene-lower Miocene (roughly 40-20 Ma) depositional hiatus within the Cenozoic succession, potentially signifying forebulge passage or neutral to

Origin of the Uinta recess, Sevier fold thrust belt, Utah: influence of basin architecture on fold thrust belt geometry

NASA Astrophysics Data System (ADS)

Paulsen, Timothy; Marshak, Stephen

1999-11-01

Structural trends in the Sevier fold-thrust belt define a pronounced concave-to-the-foreland map-view curve, the Uinta recess, in north-central Utah. This recess separates two convex-to-the-foreland curves, the Provo salient on the south and the Wyoming salient on the north. The two limbs of the recess comprise transverse zones (fault zones at a high-angle to the regional trend of the orogen) that border the flanks of the east-west-trending Uinta/Cottonwood arch. Our structural analysis indicates that the transverse zones formed during the Sevier orogeny, and that they differ markedly from each other in structural style. The Charleston transverse zone (CTZ), on the south side of the arch, initiated as a complex sinistral strike-slip fault system that defines the abrupt northern boundary of the Provo salient. The Mount Raymond transverse zone (MRTZ), on the north side of the arch, represents the region in which the southeast-verging southern limb of the gently curving Wyoming salient was tilted northwards during the Laramide phase of uplift of the Uinta/Cottonwood arch. In effect, the MRTZ represents an oblique cross section through a thrust belt. The contrasting architecture of these transverse zones demonstrates how pre-deformation basin geometry influences the geometry of a fold-thrust belt. Analysis of isopach maps indicates that, at the time the Sevier fold-thrust belt formed, the area just north of the present site of the Uinta/Cottonwood arch was a basement high, with a gently dipping north flank, and a steeply dipping south flank. Thus, predeformational sediment thickened abruptly to the south of the high and thickened gradually to the north of the high. As illustrated by sandbox models, the distance that a fold-thrust belt propagates into the foreland depends on the thickness of the sedimentary layer being deformed, so the shape of the salient mimics the longitudinal cross-sectional shape of the sedimentary basin. Where basins taper gradually along strike

Algeria: structural evolution and hydrocarbon potential of a complicated Tectonic province

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

Knudsen, H.W.

1985-02-01

During most of the pre-Carboniferous, Algeria was part of a stable foreland platform on which a thick clastic sequence was deposited. Caledonian tectonics were primarily epeirogenic, but they established structural alignments that were further reinforced by the much stronger movements of the Carboniferous Hercynian orogeny. In northern and eastern Algeria, a variable basal sandstone and a thick sequence of Triassic and Lower Jurassic evaporites were deposited over the eroded Hercynian surface. This provided a seal for subsequent hydrocarbon migration from the underlying Silurian and Devonian source rocks. Important epeirogenic events and tensional faulting occurred during the Jurassic and Cretaceous. Compressionalmore » forces in the tertiary culminated in the Alpine orogeny. A broad zone of uplift and southward-directed imbricate thrusting formed along the northern margins of Algeria obscuring much of the sub-Tertiary depositional and structural features. Hydrocarbon accumulation in Algeria has been predominantly controlled by the relationships among the Silurian-Devonian source rocks, the Hercynian unconformity, and the distribution of the overlying Triassic clastic and evaporite sequence. More than 65% of the recoverable oil reserves and 90% of the gas reserves are trapped immediately below or above the Hercynian unconformity, with the evaporites providing the seal. Heretofore, the complex geology of the Tertiary overthrust zone has been a deterrent to exploration in both the autochthonous Miocene basins and the sub-Tertiary sequence. However, improved seismic techniques and renewed interest in the potential of overthrust provinces point to increased activity in this area.« less

Tectonic history of the Illinois basin

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

Kolata, D.R.; Nelson, J.W.

1990-05-01

The Illinois basin began as a failed rift that developed during breakup of a supercontinent approximately 550 Ma. A rift basin in the southernmost part of the present Illinois basin subsided rapidly and filled with about 3,000 m of probable Early and Middle Cambrian sediments. By the Late Cambrian, the rift-bounding faults became inactive and a broad relatively slowly subsiding embayment, extending well beyond the rift and open to the Iapetus Ocean, persisted through most of the Paleozoic Era. Widespread deformation swept through the proto-Illinois basin beginning in the latest Mississippian, continuing to the end of the Paleozoic Era. Upliftmore » of basement fault blocks resulted in the formation of many major folds and faults. The timing of deformation and location of these structures in the forelands of the Ouachita and Alleghanian orogenic belts suggest that much of the deformation resulted from continental collision between North America and Gondwana. The associated compressional stress reactivated the ancient rift-bounding faults, upthrusting the northern edge of a crustal block approximately 1,000 m within the rift. Concurrently, dikes (radiometrically dated as Early Permian), sills, and explosion breccias formed in or adjacent to the reactivated rift. Subsequent extensional stress, probably associated with breakup of Pangea, caused the crustal block within the rift to sink back to near its original position. High-angle, northeast- to east-west-trending normal faults, with as much as 1,000 m of displacement, formed in the southern part of the basin. These faults displace some of the northwest trending Early Permian dikes. Structural closure of the southern end of the Illinois basin was caused by uplift of the Pascola arch sometime between the Late Pennsylvanian and Late Cretaceous.« less

Hydrocarbon potential of Central Monagas, Eastern Venezuela Basin, Venezuela

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

Barrios, F.; Daza, J.; Iusco, G.

1996-08-01

The Central Monagas area is part of the foreland sub-basin located on the southern flank of the Eastern Venezuela Basin. The sedimentary column of the Central Monagas is at least 7500 in thick and consists of Mesozoic (Cretaceous) and Cenozoic rocks. Interpretations of 60 regional seismic sections have been integrated with data from 12 existing wells, which cover an area of 1200 km{sup 2}. From these interpretations, basin-wide structure and interval isopach maps were constructed in order to aid the depiction of the basin architecture and tectonic history. The sub-basin developed on the southern flank of the Eastern Venezuela Basinmore » is tightly linked to its evolution from a Mesozoic extensional regime into a Cenozoic compressional and strike-slip stage. The basin formed in the Middle Mesozoic by crustal extension of a rifting process. Regional northward tilting of the slab continued during the Late Cretaceous. Finally, the transpression of the Caribbean Plate during the Oligocene-Neogene induced the overprint of compressional deformation associated with the deposition of a foredeep wedge. Geochemical source rock analysis gave an average of 1.2 TOC, and R{sub o} of 0.66 indicating a mature, marine source. The modeling of the hydrocarbon generative history of the basin indicates that the oil migration started in the Middle Miocene, after the trap was formed. Analysis and mapping of reservoir rocks and seal rocks defined the effective area limits of these critical factors. The main play in the area is the extension of the Lower Oficina Formation which is the proven petroleum target in the Eastern Venezuela Basin.« less

Late Eocene Inversion and Exhumation of the Sivas Basin (Central Anatolia) Based On Low-Temperature Thermochronometry: Implications for Diachronous Initiation of Arabia-Eurasia Collision

NASA Astrophysics Data System (ADS)

Darin, M. H.; Umhoefer, P. J.; Thomson, S. N.; Schleiffarth, W. K.

2017-12-01

The timing of initial Arabia-Eurasia collision along the Bitlis-Zagros suture is controversial, with widely varying estimates from middle Eocene to late Miocene ( 45-10 Ma). The Cenozoic Sivas Basin (central Anatolia) preserves a detailed record of the initial stages of Arabia collision directly north of the suture in the Eurasian foreland. New apatite fission track and (U-Th)/He thermochronology data from Late Cretaceous to Paleogene units indicate rapid basin inversion and initiation of the north-vergent Southern Sivas Fold and Thrust Belt (SSFTB) during the late Eocene to early Oligocene ( 40-30 Ma), consistent with the age of a basin-wide unconformity and switch from marine to nonmarine sedimentation. We interpret late Eocene exhumation and the predominantly north-vergent kinematics of the SSFTB to reflect northward propagation of contraction into the Sivas retro-foreland basin due to initial collision of the Arabian passive margin with the Anatolide-Tauride block along the southern Eurasian margin during the late middle Eocene. We test this hypothesis by comparing our new results with regional-scale compilations of both published thermochronology and geochronology data from the entire Arabia-Eurasia collision zone. Low-temperature thermochronology data from eastern Anatolia, the Caucasus, Zagros, and Alborz demonstrate that rapid cooling and intraplate deformation occurred across much of the Eurasian foreland during the middle Eocene to early Oligocene ( 45-30 Ma). Our regional compilation of published geochronology data from central and eastern Anatolia reveals a distinct magmatic lull during the latest Eocene, Oligocene, and earliest Miocene (ca. 38-20 Ma), slightly earlier than a diachronous magmatic lull initiating at 25-5 Ma from northwest to southeast in Iran (Chiu et al., 2013). These results support a tectonic model for diachronous collision in which initial collision of the Arabia promontory occurred in central-eastern Anatolia during the middle

The diversity and biogeography of the communities of Actinobacteria in the forelands of glaciers at a continental scale

NASA Astrophysics Data System (ADS)

Zhang, Binglin; Wu, Xiukun; Zhang, Gaosen; Li, Shuyan; Zhang, Wei; Chen, Ximing; Sun, Likun; Zhang, Baogui; Liu, Guangxiu; Chen, Tuo

2016-05-01

Glacier forelands, where the initially exposed area is unvegetated with minimal human influence, are an ideal place for research on the distributions and biogeography of microbial communities. Actinobacteria produce many bioactive substances and have important roles in soil development and biogeochemical cycling. However, little is known about the distribution and biogeography of Actinobacteria in glacier forelands. Therefore, we investigated the patterns of diversity and the biogeography of actinobacterial communities of the inhabited forefields of 5 glaciers in China. Of the bacteria, the mean relative abundance of Actinobacteria was 13.1%, and 6 classes were identified in the phylum Actinobacteria. The dominant class was Actinobacteria (57%), which was followed in abundance by Acidimicrobiia (19%) and Thermoleophilia (19%). When combined, the relative abundance of the other three classes, the MB-A2-108, Nitriliruptoria and Rubrobacteria, was only 2.4%. A biogeographic pattern in the forelands of the 5 glaciers in China was not detected for actinobacterial communities. Compared with 7 other actinobacterial communities found in the forelands of glaciers globally, those in the Southern Hemisphere were significantly different from those in the Northern Hemisphere. Moreover, the communities were significantly different on the separate continents of the Northern Hemisphere. The dissimilarity of the actinobacterial communities increased with geographic distance (r = 0.428, p = 0.0003). Because of environmental factors, the effect of geography was clear when the distance exceeded a certain continent-level threshold. With the analysis of indicator species, we found that each genus had a geographic characteristic, which could explain why the communities with greater diversity were more strongly affected by biogeography.

New Insights into the Provenance of the Southern Junggar Basin in the Jurassic from Heavy Mineral Analysis and Sedimentary Characteristics

NASA Astrophysics Data System (ADS)

Zhou, T. Q.; Wu, C.; Zhu, W.

2017-12-01

Being a vital component of foreland basin of Central-western China, Southern Junggar Basin has observed solid evidences of oil and gas in recent years without a considerable advancement. The key reason behind this is the lack of systematic study on sedimentary provenance analysis of the Southern Junggar basin. Three parts of the Southern Junggar basin, including the western segment (Sikeshu Sag), the central segment (Qigu Fault-Fold Belt) and the eastern segment (Fukang Fault Zone), possess varied provenance systems, giving rise to difficulties for oil-gas exploration. In this study, 3468 heavy minerals data as well as the sedimentary environment analysis of 10 profiles and 7 boreholes were used to investigate the provenances of the deposits in the southern Junggar basin . Based on this research, it reveals that: Sikeshu sag initially shaped the foreland basin prototype in the Triassic and its provenance area of the sediments from the Sikeshu sag has primarily been situated in zhongguai uplift-chepaizi uplift depositional systems located in the northwestern margin of the Junggar Basin. From the early Jurassic, the key sources were likely to be late Carboniferous to early Permain post-collisional volcanic rocks from the North Tian Shan block to Centrao Tian Shan. In the Xishanyao formation, Abundant lithic metamorphic, epidote and garnet that suggests the source rocks were possibly late Carboniferous subduction-related arc volcanic rocks of the Central Tian Shan. In the Toutunhe formation, Bogda Mountains began uplifting and gradually becoming the major provenance. Moreover, the sedimentary boundaries of Junggar basin have also shifted towards the North Tian Shan again. In the late Jurassic, the conglomerates of the Kalazha formation directly overlie the fine-grained red beds of Qigu formation, which throw light on the rapid tectonic uplift of the North Tian Shan. In the eastern segment, meandering river delta and shore-lacustrine environments were fully developed

Subsurface stratigraphic cross sections of cretaceous and lower tertiary rocks in the Wind River Basin, central Wyoming: Chapter 9 in Petroleum systems and geologic assessment of oil and gas resources in the Wind River Basin Province, Wyoming

USGS Publications Warehouse

Finn, Thomas M.

2007-01-01

The stratigraphic cross sections presented in this report were constructed as part of a project conducted by the U.S. Geological Survey to characterize and evaluate the undiscovered oil and gas resources of the Wind River Basin (WRB) in central Wyoming. The primary purpose of the cross sections is to show the stratigraphic framework and facies relations of Cretaceous and lower Tertiary rocks in this large, intermontane structural and sedimentary basin, which formed in the Rocky Mountain foreland during the Laramide orogeny (Late Cretaceous through early Eocene time). The WRB is nearly 200 miles (mi) long, 70 mi wide, and encompasses about 7,400 square miles (mi2) (fig. 1). The basin is structurally bounded by the Owl Creek and Bighorn Mountains on the north, the Casper arch on the east, the Granite Mountains on the south, and the Wind River Range on the west.

Phanerozoic stratigraphy of Northwind Ridge, magnetic anomalies in the Canada Basin, and the geometry and timing of rifting in the Amerasia Basin, Arctic Ocean

USGS Publications Warehouse

Grantz, A.; Clark, D.L.; Phillips, R.L.; Srivastava, S.P.; Blome, C.D.; Gray, L.-B.; Haga, H.; Mamet, B.L.; McIntyre, D.J.; McNeil, D.H.; Mickey, M.B.; Mullen, M.W.; Murchey, B.I.; Ross, C.A.; Stevens, C.H.; Silberling, Norman J.; Wall, J.H.; Willard, D.A.

1998-01-01

Cores from Northwind Ridge, a high-standing continental fragment in the Chukchi borderland of the oceanic Amerasia basin, Arctic Ocean, contain representatives of every Phanerozoic system except the Silurian and Devonian systems. Cambrian and Ordovician shallow-water marine carbonates in Northwind Ridge are similar to basement rocks beneath the Sverdrup basin of the Canadian Arctic Archipelago. Upper Mississippian(?) to Permian shelf carbonate and spicularite and Triassic turbidite and shelf lutite resemble coeval strata in the Sverdrup basin and the western Arctic Alaska basin (Hanna trough). These resemblances indicate that Triassic and older strata in southern Northwind Ridge were attached to both Arctic Canada and Arctic Alaska prior to the rifting that created the Amerasia basin. Late Jurassic marine lutite in Northwind Ridge was structurally isolated from coeval strata in the Sverdrup and Arctic Alaska basins by rift shoulder and grabens, and is interpreted to be a riftogenic deposit. This lutite may be the oldest deposit in the Canada basin. A cape of late Cenomanian or Turonian rhyodacite air-fall ash that lacks terrigenous material shows that Northwind Ridge was structurally isolated from the adjacent continental margins by earliest Late Cretaceous time. Closing Amerasia basin by conjoining seafloor magnetic anomalies beneath the Canada basin or by uniting the pre-Jurassic strata of Northwind Ridge with kindred sections in the Sverdrup basin and Hanna trough yield simular tectonic reconstructions. Together with the orientation and age of rift-marine structures, these data suggest that: 1) prior to opening of the Amerasia basin, both northern Alaska and continental ridges of the Chukchi borderland were part of North America, 2) the extension that created the Amerasia basin formed rift-margin graben beginning in Early Jurassic time and new oceanic crust probably beginning in Late Jurassic or early Neocomian time. Reconstruction of the Amerasia basin on the

[sup 40]Ar/[sup 39]Ar mineral ages from southwestern Penobscot Bay, Maine: Evidence for Silurian metamorphism

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

West, D.P. Jr.; Guidotti, C.V.; Lux, D.R.

1992-01-01

The nature and timing of metamorphic events in the Coastal Lithotectonic Block of Maine remain poorly understood. Immediately west and southwest of Penobscot Bay the rocks are polymetamorphic showing evidence for at least two episodes of amphibolite facies metamorphism and later, perhaps regionally extensive, retrograde events. Hornblende mineral separates from two amphibolites din the Port Clyde area have identical Ar-40/Ar-39 plateau ages of 414.0 [+-] 3.3 and 414.0 [+-] 3.9 Ma. These ages are interpreted to reflect the time of cooling following the last significant thermal event in this area. Biotite from an amphibolite in the Port Clyde area givesmore » a total gas age of 346.5 [+-] 3.2 Ma. Hornblende from an amphibolite 7 km to the west near Friendship gives a nearly concordant release spectrum with a plateau age of 369.0 [+-] 3.7 Ma. Coexisting biotite from this amphibolite gives a total gas age of 289.2 [+-] 2.7 Ma. Muscovite from the Waldoboro pluton has a nearly concordant release spectrum with a plateau age of 306.3 [+-] 2.2 Ma. Biotite from this sample gives a total gas age of 288.9 [+-] 2.2 Ma. The 414.0 Ma hornblende cooling ages from the Port Clyde area reflect cooling following a significant high grade Silurian thermal event. This Silurian metamorphism is the same age as tectonothermal events in the Nashoba Terrane in eastern Massachusetts, the Kingston Complex in southern New Brunswick, the Aspy Terrane in Cape Breton island, Nova Scotia, and the Hermitage Flexure in southern Newfoundland.d Thus a distinctive Silurian tectonothermal province located along the western edge of the Avalon Zone appears to extend discontinuously from Massachusetts to Newfoundland.« less

Denan Depression controlled by northeast-directed Olongbulak Thrust Zone in northeastern Qaidam basin: Implications for growth of northern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Yu, Xiangjiang; Guo, Zhaojie; Zhang, Qiquan; Cheng, Xiang; Du, Wei; Wang, Zhendong; Bian, Qing

2017-10-01

The Denan Depression is a unique depression in the northeastern Qaidam basin, with a maximum Cenozoic sedimentary thickness of 5 km. Detailed field work, interpretation of seismic profiles and analyzation of well data were conducted to define the Cenozoic tectonic evolution of the northeastern Qaidam basin. All geological evidences indicate that the Denan Depression is controlled by the northeast-directed Olongbulak Thrust at its southern boundary. The Denan Depression grew in concert with the development of the northeast-directed Olongbulak Thrust at least since it began to accept the Xiaganchaigou Formation, supporting the early Cenozoic growth of the northern Tibetan Plateau. Surface and subsurface data both point to enhanced tectonic activity since the Quaternary in the northeastern Qaidam basin, leading to a more individual Denan Depression relative to the main Qaidam basin. The northern boundary of the Denan Depression is a passive boundary, and no foreland developed at the northern slope of the Denan Depression.

Late Quaternary stratigraphy, sedimentology, and geochemistry of an underfilled lake basin in the Puna (north-west Argentina)

USGS Publications Warehouse

McGlue, Michael M.; Cohen, Andrew S.; Ellis, Geoffrey S.; Kowler, Andrew L.

2013-01-01

Depositional models of ancient lakes in thin-skinned retroarc foreland basins rarely benefit from appropriate Quaternary analogues. To address this, we present new stratigraphic, sedimentological and geochemical analyses of four radiocarbon-dated sediment cores from the Pozuelos Basin (PB; northwest Argentina) that capture the evolution of this low-accommodation Puna basin over the past ca. 43 cal kyr. Strata from the PB are interpreted as accumulations of a highly variable, underfilled lake system represented by lake-plain/littoral, profundal, palustrine, saline lake and playa facies associations. The vertical stacking of facies is asymmetric, with transgressive and thin organic-rich highstand deposits underlying thicker, organic-poor regressive deposits. The major controls on depositional architecture and basin palaeogeography are tectonics and climate. Accommodation space was derived from piggyback basin-forming flexural subsidence and Miocene-Quaternary normal faulting associated with incorporation of the basin into the Andean hinterland. Sediment and water supply was modulated by variability in the South American summer monsoon, and perennial lake deposits correlate in time with several well-known late Pleistocene wet periods on the Altiplano/Puna plateau. Our results shed new light on lake expansion–contraction dynamics in the PB in particular and provide a deeper understanding of Puna basin lakes in general.

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.

Active shortening, intermontane basin formation, and geomorphic evolution in an orogenic plateau: Central Puna Plateau, NW Argentina (24°37'S, 67°03'W)

NASA Astrophysics Data System (ADS)

Strecker, Manfred R.; Alonso, Ricardo N.; Bookhagen, Bodo; Freymark, Jessica; Pingel, Heiko

2017-04-01

The high-elevation Andean Plateau (Altiplano-Puna; 4km) is a first-order morphotectonic province of the Central Andes and constitutes the world's second largest orogenic plateau. While there are many unifying basin characteristics in this region, including internal drainage, semi-arid to arid climate and associated deposition of evaporites, there are notable differences between the northern and southern parts of the plateau. In contrast to the vast basins of the Altiplano (north) and incipient establishment of fluvial connectivity and sediment transport to the foreland, the Puna (south) comprises numerous smaller basins, bordered by reverse-fault bounded ranges up to 6 km high. The plateau is internally drained and fluvial connectivity with the foreland does not exist leading to thick sedimentary basin fills that comprise continental evaporites, volcanic and clastic deposits, typically between 3 and 5 km thick. However, repeated impacts of climate change and superposed tectonic activity in the southern plateau have resulted in further basin differentiation, abandonment or re-arrangement of fluvial networks and impacts on sediment transport. Here we report evidence for sustained contractional tectonic activity in the Pocitos Basin in the southern plateau. On the western margin of the basin fanning of dipping strata and regraded, steeply inclined gravel-covered pediment surfaces and wind gaps associated with gravel derived from distant sources in the west document late Tertiary to Pleistocene growth of an approximately N-S oriented and N plunging anticline. The growth of the eastern limb of this anticline has caused the isolation of a formerly more extensive basin. In addition, Late Pleistocene and Holocene lake shorelines and lacustrine deposits are tilted eastward along the same structure and InSAR measurements of deformed lake terraces document that the fold is growing. Despite widely reported extensional faulting in the southern Puna, we conclude (1) that the

Restoration and evolution of the intermontane Indus molasse basin, Ladakh Himalaya, India

NASA Astrophysics Data System (ADS)

Searle, M. P.; Pickering, K. T.; Cooper, D. J. W.

1990-03-01

Collision of the Indian Plate with the Karakorum Plate-Lhasa Block during the Eocene (ca. 55-50 Ma) created predominantly a S- or SW-verging thrust culmination across the Himalaya. During the late Tertiary, two molasse basins existed — the Siwalik Bain, formed in the late Miocene to Present on the Indian foreland south of the Himalaya, and the mid-Eocene to late Miocene Indus Basin along the Indus Suture Zone north of the High Himalaya. The Indus Basin is approximately 2000 km long, extending eastwards from Ladakh across South Tibet. A balanced cross-section along the Zanskar River shows a minimum 36 km shortening in the Eocene-?late Miocene molasse, and suggests that the minimum basin width was approximately 60 km in Ladakh. More than 2000 m of post-Eocene alluvial fan, fluvial and fluvio-lacustrine sediments accumulated in the Ladakh sector with petrographies suggesting derivation mainly from the deeply dissected and uplifted northern granodioritic Ladakh batholith (Aptian-Eocene), with only minor amounts of debris derived from the deformed southern Tethyan passive margin. Palaeocurrents show predominant E-W, axis-parallel, sediment transport, with subordinate lateral input paths being preserved. The Indus molasse basin is deformed by numerous, post-Eocene, N-directed backthrusts, many of which cut the entire stratigraphy and, therefore, were active at least into late Tertiary times.

Deciphering the mid-Carboniferous eustatic event in the central Appalachian foreland basin, southern West Virginia, USA

USGS Publications Warehouse

Blake, B.M.; Beuthin, J.D.

2008-01-01

A prominent unconformity, present across shallow shelf areas of the Euramerican paleoequatorial basins, is used to demark the boundary between the Mississippian and Pennsylvanian subsystems. This unconformity, the mid-Carboniferous eustatic event, is generally attributed to a major glacio-eustatic sea-level fall. Although a Mississippian-Pennsylvanian unconformity is recognized throughout most of the Appalachian region, the record of the mid-Carboniferous eustatic event in the structurally deepest part of the basin has been controversial. Based on early reports that suggested the most complete Pennsylvanian section was present in southern West Virginia, various conceptual depositional models postulated continuous sedimentation between the youngest Mississippian Bluestone Formation and the oldest Penn-sylvanian Pocahontas Formation. In contrast, tabular-erosion models envisioned axial drainage systems that evolved in response to changing basin dynamics. These models predicted a Mississippian-Pennsylvanian unconformity. All these models suffered from a lack of biostratigraphic control. The presence of a sub-Pocahontas paleovalley, herein named the Lashmeet paleovalley, has been confirmed in southern West Virginia. The Lashmeet paleovalley was incised over 35 m into Bluestone strata and filled by lithic sands derived from the Appalachian orogen to the northeast and east. The polygenetic Green Valley paleosol complex marks the Bluestone-Pocahontas contact on associated interfluves. Together, these features indicate a substantial period of subaerial exposure and argue strongly in favor of a Mississippian-Pennsylvanian unconformity. Paleontologic data from the Bluestone Formation, including marine invertebrates and conodonts from the marine Bramwell Member and paleofloral data, support a late, but not latest, Arnsbergian age assignment. Marine fossils are not known from the Pocahontas Formation, but macrofloral and palynomorph taxa support a Langsettian age for most of

Organoporosity Evaluation of Shale: A Case Study of the Lower Silurian Longmaxi Shale in Southeast Chongqing, China

PubMed Central

Chen, Fangwen; Lu, Shuangfang; Ding, Xue

2014-01-01

The organopores play an important role in determining total volume of hydrocarbons in shale gas reservoir. The Lower Silurian Longmaxi Shale in southeast Chongqing was selected as a case to confirm the contribution of organopores (microscale and nanoscale pores within organic matters in shale) formed by hydrocarbon generation to total volume of hydrocarbons in shale gas reservoir. Using the material balance principle combined with chemical kinetics methods, an evaluation model of organoporosity for shale gas reservoirs was established. The results indicate that there are four important model parameters to consider when evaluating organoporosity in shale: the original organic carbon (w(TOC0)), the original hydrogen index (I H0), the transformation ratio of generated hydrocarbon (F(R o)), and the organopore correction coefficient (C). The organoporosity of the Lower Silurian Longmaxi Shale in the Py1 well is from 0.20 to 2.76%, and the average value is 1.25%. The organoporosity variation trends and the residual organic carbon of Longmaxi Shale are consistent in section. The residual organic carbon is indicative of the relative levels of organoporosity, while the samples are in the same shale reservoirs with similar buried depths. PMID:25184155

Preliminary Results from Outcrop-Based Spectral Gamma-Ray Measurements on the Lower Silurian Longmaxi Shale, in Chongqing and Its Adjacent Areas

NASA Astrophysics Data System (ADS)

Zou, C.; Nie, X.; Qiao, L.; Pan, L.; Hou, S.

2013-12-01

The Longmaxi Shale in the Lower Silurian has been recognized as a favorable target of shale gas exploration in Sichuan basin, China. One important feature of shale gas reservoirs is of high total organic carbon (TOC). Many studies have shown that the spectral gamma-ray measurements are positively correlated to the TOC contents. In this study, the spectral gamma ray responses of five shale outcrop profiles are measured in Chongqing and its adjacent areas, Sichuan basin. Three of the five profiles are located in Qijiang, Qianjiang and Changning in Chongqing, and the other two are located in Qilong and Houtan in Guizhou. The main lithologies of the profiles include mainly black shale, gray shale and silty shale. The spectral gamma-ray measurements provide the contents of potassium (K), uranium (U), and thorium (Th). The result of the five profiles shows that the K and Th contents of gray shale are close to the ones of black shale, while the U contents in the black shale are significantly higher than that in the other rocks. The TOC contents are estimated by using the outcrop-based measurements with an empirical formula. The result shows that the TOC contents are the highest in black shale of Changning profile. It indicates that there is a most promising exploration potential for shale gas in this area. In the future, the outcrop data will be used to construct detailed lithofacies profiles and establish relationships between lithofacies both in outcrop and the subsurface gamma-ray logs. Acknowledgment: We acknowledge the financial support of the National Natural Science Foundation of China (41274185) and the Fundamental Research Funds for the Central Universities.

Stable isotopic perturbation at the Ordovician-Silurian transition in NE Poland

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

Hoffman, A.; Gruszczynski, M.; Malkowski, K.

1992-01-01

An interpretation of the time series of stable isotopic proportions of carbon, oxygen, and sulfur in rock samples from subsurface Ordovician-Silurian transition in north-eastern Poland demonstrates a clearcut perturbation that must imply some global scale controlling factors. This perturbation is particularly emphasized by its comparison to the sustained secular Paleozoic trend in isotopic characteristics of the oceanic system. On the other hand, this isotopic perturbation contrasts with unidirectional local changes in geochemical elemental proportions in the same rock samples. The perturbation is most parsimoniously explained as linked to the onset of a major glaciation. Its relationship to the second largestmore » mass extinction in the history of the biosphere still remains to be elucidated.« less

Seismo-stratigraphic evolution of the northern Austral Basin and its possible relation to the Andean tectonics, onshore Argentina.

NASA Astrophysics Data System (ADS)

Sachse, Victoria; Anka, Zahie; Pagan, Facundo; Kohler, Guillermina; Cagnolatti, Marcelo; di Primio, Rolando; Rodriguez, Jorge

2013-04-01

The Austral Basin is situated in a formerly and recently high active tectonic zone in southern Argentina. The opening of the South Atlantic to the east, the opening of the Drake Passage in the south, and the subduction related to the rise of the Andes to the west, had major influence on the study area. To identify the impact of the tectonic events on basin geometry, sediment thickness and depocenter migration through time, 2D seismic interpretation was performed for an area of approx. 180.000 km² covering the onshore northern Austral Basin. A total of 10 seismic horizons were mapped and tied to the stratigraphy from well reports, representing 9 syn- and post- rift sequences. The main units are: Basement (U1), Jurassic Tobifera Formation (U2), Early Cretaceous (U3), Late Cretaceous (U4), sub-unit Campanian (U4A), Paleocene (U5), Eocene (U6), Oligocene (U7), Miocene (U8), and Plio-Pleistocene (U9). Main tectonic events are identified representing the break-up phase forming graben systems and the evolution from the ancient backarc Rocas Verdes Basin to the foreland Austral Basin. Inversion and changes in the tectonic regime are concomitant with onlapping and thinning of the base of the Upper Cretaceous to Campanian sediments, while the Top of the Upper Cretaceous represents a Maastrichtian unconformity. Units depth maps show a triangular geometry since the Jurassic, tracing the north-eastern basement high and deepening to the south. Since the Campanian the former geometry of basin fill changed and deepening to the south stopped. Beginning of the foreland phase is assigned to this time as well as changes in the stress regime. Paleogene times are marked by a relatively high sedimentation rate coupled with enduring thermal subsidence, on-going rise of the Andes and changes in the convergence rates of the Nazca relative to the South American plate. Onset of sediment supply from the Andes (Incaic phase) resulted in enhanced sedimentation rates during the Paleocene

Crustal-scale geological and thermal models of the Beaufort-Mackenzie Basin, Arctic Canada

NASA Astrophysics Data System (ADS)

Sippel, Judith; Scheck-Wenderoth, Magdalena; Kröger, Karsten; Lewerenz, Björn

2010-05-01

The Beaufort-Mackenzie Basin is a petroliferous province in northwest Arctic Canada and one of the best-known segments of the Arctic Ocean margin due to decades of exploration. Our study is part of the programme MOM (Methane On the Move), which aims to quantify the methane contribution from natural petroleum systems to the atmosphere over geological times. Models reflecting the potential of a sedimentary basin to release methane require well-assessed boundary conditions such as the crustal structure and large-scale temperature variation. We focus on the crustal-scale thermal field of the Beaufort-Mackenzie Basin. This Basin has formed on a post-rift, continental margin which, during the Late Cretaceous and Tertiary, developed into the foreland of the North American Cordilleran foldbelt providing space for the accumulation of up to 16 km of foreland deposits. We present a 3D geological model which integrates the present topography, depth maps of Upper Cretaceous and Tertiary horizons (Kroeger et al., 2008, 2009), tops of formations derived from interpreted 2D reflection seismic lines and 284 boreholes (released by the National Energy Board of Canada), and the sequence stratigraphic framework established by previous studies (e.g. Dixon et al., 1996). To determine the position and geometry of the crust-mantle boundary, an isostatic calculation (Airýs model) is applied to the geological model. We present different crustal-scale models combining isostatic modelling, published deep reflection and refraction seismic lines (e.g. Stephenson et al., 1994; O'Leary et al., 1995), and calculations of the 3D conductive thermal field. References: Dixon, J., 1996. Geological Atlas of the Beaufort-Mackenzie Area, Geological Survey of Canada Miscellaneous Report, 59, Ottawa, 173 pp. Kroeger, K.F., Ondrak, R., di Primio, R. and Horsfield, B., 2008. A three-dimensional insight into the Mackenzie Basin (Canada): Implications for the thermal history and hydrocarbon generation potential

Polygenetic Karsted Hardground Omission Surfaces in Lower Silurian Neritic Limestones: a Signature of Early Paleozoic Calcite Seas

NASA Astrophysics Data System (ADS)

James, Noel P.; Desrochers, André; Kyser, Kurt T.

2015-04-01

Exquisitely preserved and well-exposed rocky paleoshoreline omission surfaces in Lower Silurian Chicotte Formation limestones on Anticosti Island, Quebec, are interpreted to be the product of combined marine and meteoric diagenesis. The different omission features include; 1) planar erosional bedding tops, 2) scalloped erosional surfaces, 3) knobs, ridges, and swales at bedding contacts, and 4) paleoscarps. An interpretation is proposed that relates specific omission surface styles to different diagenetic-depositional processes that took place in separate terrestrial-peritidal-shallow neritic zones. Such processes were linked to fluctuations in relative sea level with specific zones of diagenesis such as; 1) karst corrosion, 2) peritidal erosion, 3) subtidal seawater flushing and cementation, and 4) shallow subtidal deposition. Most surfaces are interpreted to have been the result of initial extensive shallow-water synsedimentary lithification that were, as sea level fell, altered by exposure and subaerial corrosion, only to be buried by sediments as sea level rose again. This succession was repeated several times resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. Synsedimentary cloudy marine cements are well preserved and are thus interpreted to have been calcitic originally. Aragonite components are rare and thought to have to have been dissolved just below the Silurian seafloor. Large molluscs that survived such seafloor removal were nonetheless leached and the resultant megamoulds were filled with synsedimentary calcite cement. These Silurian inner neritic-strandline omission surfaces are temporally unique. They are part of a suite of marine omission surfaces that are mostly found in early Paleozoic neritic carbonate sedimentary rocks. These karsted hardgrounds formed during a calcite-sea time of elevated marine carbonate saturation and extensive marine cement precipitation. The contemporaneous greenhouse

A comparative analysis of pre-Silurian crustal building blocks of the northern and the southern Appalachian orogen

USGS Publications Warehouse

Hibbard, J.P.; van Staal, C.R.; Rankin, D.W.

2007-01-01

The New York promontory serves as the divide between the northern and southern segments of the Appalachian orogen. Antiquated subdivisions, distinct for each segment, implied that they had lithotectonic histories that were independent of each other. Using new lithotectonic subdivisions we compare first order features of the pre-Silurian orogenic 'building blocks' in order to test the validity of the implication of independent lithotectonic histories for the two segments. Three lithotectonic divisions, termed here the Laurentian, Iapetan, and the peri-Gondwanan realms, characterize the entire orogen. The Laurentian realm, composed of native North American rocks, is remarkably uniform for the length of the orogen. It records the multistage Neoproterozoic-early Paleozoic rift-drift history of the Appalachian passive margin, formation of a Taconic Seaway, and the ultimate demise of both in the Middle Ordovician. The Iapetan realm encompasses mainly oceanic and magmatic arc tracts that once lay within the Iapetus Ocean, between Laurentia and Gondwana. In the northern segment, the realm is divisible on the basis of stratigraphy and faunal provinciality into peri-Laurentian and peri-Gondwanan tracts that were amalgamated in the Late Ordovician. South of New York, stratigraphic and faunal controls decrease markedly; rock associations are not inconsistent with those of the northern Appalachians, although second-order differences exist. Exposed exotic crustal blocks of the peri-Gondwanan realm include Ganderia, Avalonia, and Meguma in the north, and Carolinia in the south. Carolinia most closely resembles Ganderia, both in early evolution and Late Ordovician-Silurian docking to Laurentia. Our comparison indicates that, to a first order, the pre-Silurian Appalachian orogen developed uniformly, starting with complex rifting and a subsequent drift phase to form the Appalachian margin, followed by the consolidation of Iapetan components and ending with accretion of the peri

Structure and structural evolution of the Rechnitz window and adjacent units, Eastern Alps: changing Neogene extension directions due to motion around a foreland promontory

NASA Astrophysics Data System (ADS)

Neubauer, Franz; Cao, Shuyun

2013-04-01

The Rechnitz window is part of Penninic window group exposed along the South Burgenland basement high within the large Neogene Pannonian basin, which is formed by changing the extension directions during the motion of the Alcapa block around the Bohemian foreland promontory. Based on new data of the structural history of Penninic units, its burial and exhumation is proposed during eastward and northeastward motion around the Bohemian foreland promontory. Two tectonic units within the Rechnitz window are distinguished, the Schlaining unit with ophiolites, which show a Paleogene history of subduction (deformation stage D1), and the Köszeg unit with distal continental margin successions indicated by their richness of continent-derived clastic material. Previous fossil findings indicate a persistence of sedimentation until early Late Cretaceous. Both units were subducted during Paleogene and suffered blueschist metamorphism. The age of ophiolite obduction onto the Köszeg unit must be between latest Paleocene and earliest Miocene associated with peak temperature conditions (deformation stage D2, likely at 22 Ma). A new 40Ar/39Ar white mica age shows a plateau-type pattern at 22.3 ± 0.2 Ma and a subsequent thermal event of Ar loss at 19.2 ± 0.5 Ma. Exhumation and extension of buried Penninic rocks were facilitated by a sequence of normal faults and the change of the motion direction from northeastward to eastward motion (D3 and D4a). In present-day coordinates, the initial stage of faulting along a major ductile low-angle normal fault was directed northeastward at ca. 19 Ma. In the subsequent stage (Early Miocene), extension resulted in a ca. eastward prograding rolling hinge, which separates the Rechnitz window from Danube basin located in the east (D4a). Gently W-dipping thrust faults indicate ca. WSW-ENE shortening and also resulted in ca. N-S trending E-vergent folds occur in lower sectors of the Köszeg unit (deformation stage D4b). Finally, small Late Miocene

Neogene deformation of thrust-top Rzeszów Basin (Outer Carpathians, Poland)

NASA Astrophysics Data System (ADS)

Uroda, Joanna

2015-04-01

The Rzeszów Basin is a 220 km2 basin located in the frontal part of Polish Outer Carpathians fold-and-thrust belt. Its sedimentary succession consist of ca. 600 m- thick Miocene evaporates, litoral and marine sediments. This basin developed between Babica-Kąkolówka anticline and frontal thrust of Carpathian Orogen. Rzeszów thrust-top basin is a part of Carpathian foreland basin system- wedge-top depozone. The sediments of wedge -top depozone were syntectonic deformed, what is valuable tool to understand kinematic history of the orogen. Analysis of field and 3D seismic reflection data showed the internal structure of the basin. Seismic data reveal the presence of fault-bend-folds in the basement of Rzeszów basin. The architecture of the basin - the presence of fault-releated folds - suggest that the sediments were deformed in last compressing phase of Carpathian Orogen deformation. Evolution of Rzeszów Basin is compared with Bonini et.al. (1999) model of thrust-top basin whose development is controlled by the kinematics of two competing thrust anticlines. Analysis of seismic and well data in Rzeszów basin suggest that growth sediments are thicker in south part of the basin. During the thrusting the passive rotation of the internal thrust had taken place, what influence the basin fill architecture and depocentre migration opposite to thrust propagation. Acknowledgments This study was supported by grant No 2012/07/N/ST10/03221 of the Polish National Centre of Science "Tectonic activity of the Skole Nappe based on analysis of changes in the vertical profile and depocentre migration of Neogene sediments in Rzeszów-Strzyżów area (Outer Carpathians)". Seismic data by courtesy of the Polish Gas and Oil Company. References Bonini M., Moratti G., Sani F., 1999, Evolution and depocentre migration in thrust-top basins: inferences from the Messinian Velona Basin (Northern Apennines, Italy), Tectonophysics 304, 95-108.

Geochemical study of calcite veins in the Silurian and Devonian of the Barrandian Basin (Czech Republic): evidence for widespread post-Variscan fluid flow in the central part of the Bohemian Massif

NASA Astrophysics Data System (ADS)

Suchy, V.; Heijlen, W.; Sykorova, I.; Muchez, Ph; Dobes, P.; Hladikova, J.; Jackova, I.; Safanda, J.; Zeman, A.

2000-03-01

Carbonate fracture cements in limestones have been investigated by fluid inclusion and stable isotope analysis to provide insight into fluid evolution and deformation conditions of the Barrandian Basin (Silurian-Devonian) of the Czech Republic. The fractures strike generally north-south and appear to postdate major Variscan deformation. The most common fracture cement is calcite that is locally accompanied by quartz, natural bitumen, dolomite, Mn-oxides and fluorite. Three successive generations of fracture-filling calcite cements are distinguished based on their petrographical and geochemical characteristics. The oldest calcite cements (Stage 1) are moderate to dull brown cathodoluminescent, Fe-rich and exhibit intense cleavage, subgrain development and other features characteristic of tectonic deformation. Less tectonically deformed, variable luminescent Fe-poor calcite corresponds to a paragenetically younger Stage 2 cement. First melting temperatures, Te, of two-phase aqueous inclusions in Stages 1 and 2 calcites are often around -20°C, suggesting that precipitation of the cements occurred from H 2O-NaCl fluids. The melting temperature, Tm, has values between 0 and -5.8°C, corresponding to a low salinity between 0 and 8.9 eq. wt% NaCl. Homogenization temperatures, Th, from calcite cements are interpreted to indicate precipitation at about 70°C or less. No distinction could be made between the calcite of Stages 1 and 2 based on their fluid inclusion characteristics. In some Stage 2 cements, inclusions of highly saline (up to 23 eq. wt% NaCl) brines appear to coexist with low-salinity inclusions. The low salinity fluid possibly contains Na-, K-, Mg- and Ca-chlorides. The high salinity fluid has a H 2O-NaCl-CaCl 2 composition. Blue-to-yellow-green fluorescing hydrocarbon inclusions composed of medium to higher API gravity oils are also identified in some Stages 1 and 2 calcite cements. Stage 1 and 2 calcites have δ18O values between -13.2‰ and -7.2‰ PDB

Transgressive-regressive events and facies through the Upper Ordovician - Lower Silurian of Peary Land, North Greenland

NASA Astrophysics Data System (ADS)

Harper, D. A. T.; Rasmussen, C. M. Ø.; Munnecke, A.; Jin, J.; Stouge, S.; Rasmussen, J. A.

2012-04-01

Key sections through the Upper Ordovician (Katian-Hirnantian) and Lower Silurian (Rhuddanian) in Peary Land, North Greenland, demonstrate a succession of events related to the waxing and waning of contemporary glaciation on the far-off supercontinent of Gondwana. The Børglum River Formation was deposited in the palaeoequatorial marginal seas of Laurentia during the Katian. The upper Børglum River Formation contains a thick (130 m) unit of thick-bedded carbonate with pervasive Thalassinoides ichnofacies, which is also typical of the Selkirk Member (c. 40 m) of the Red River Formation in Canada and coeval rocks in Nevada. In addition to these ichnofossils, the shelly faunas are also similar, emphasized by the dominance of giant nautiloids, relatively abundant stromatoporoids and receptaculitids, and large gastropods. The Thalassinoides ichnofacies points to a remarkable palaeogeographic extension from an intracratonic basin to a pericratonic shelf over a distance of 11,000 km. This facies consistency implies a near homogeneous and stable depositional environment along the palaeoequator of Laurentia during the Late Ordovician. The succeeding Turesø Formation is more variable and less laterally extensive, characterized in its lower part by mud mounds, shelly coquinas and peritidal, cyclical deposits in a regressive sequence. These shallower-water facies are associated with a marked positive carbon isotope excursion that elsewhere is associated with the end Ordovician extinction. Following a probable hiatus, transgression is associated with the sequential development of Viridita and Virgiana dominated coquinas during the Rhudannian, taxa with widespread distributions across the rest of Laurentia and beyond.

Silurian trace fossils in carbonate turbidites from the Alexander Arc of southeastern Alaska

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

Soja, C.M.

Early to Late Silurian (Wenlock-Ludlow) body and trace fossils from the Heceta Formation are preserved in the oldest widespread carbonates in the Alexander terrane of southeastern Alaska. They represent the earliest shelly benthos to inhabit a diversity of marine environments and are important indicators of the early stages in benthic community development within this ancient island arc. The trace fossils are significant because they add to a small but growing body of knowledge about ichnofaunas in deep-water Paleozoic carbonates. Proximal to medial carbonate turbidites yield a low-diversity suite of trace fossils that comprises five distinct types of biogenic structures. Beddingmore » planes reveal simple epichnial burrows (Planolites), cross-cutting burrows (Fucusopsis), and tiny cylindrical burrows. These and other casts, including chondrites( )-like burrow clusters, represent the feeding activities (fodinichnia) of preturbidite animals. Hypichnial burrows and rare endichnial traces reflect the activities of postturbidite animals. Broken and offset traces indicate that infaunal biota commenced burrowing before slumping and subsequent soft-sediment deformation. The abundance and density of trace fossils increases offshore in the medial turbidites associated with a decrease in the size and amount of coarse particles and with an increase in mud and preserved organic material. Although diversity levels are similar in the proximal and medial turbidite facies, they are much lower than in Paleozoic siliciclastic turbidites. This may reflect unfavorable environmental conditions for infaunal biota or paleobiogeographic isolation of the Alexander terrane during the Silurian. A greater use of trace fossils in terrane analysis will help to resolve this issue and should provide new data for reconstructing the paleogeography of circum-Pacific terranes.« less

Mechanisms of crustal shortening in the foreland of the central Andes, Argentina: insights from data-driven three-dimensional gravity, thermal and rheological modelling

NASA Astrophysics Data System (ADS)

Meeßen, Christian; Scheck-Wenderoth, Magdalena; Sippel, Judith; Strecker, Manfred

2017-04-01

Thin- and thick-skinned deformation styles in the foreland of the central Andes are the result of ongoing crustal shortening since the early Neogene. The mechanisms proposed for these different styles range from variations in subduction angle of the Nazca plate, lithospheric thickening to variations in temperature and strength of the crystalline crust. The latter hypothesis states a cold and strong lithosphere in the foreland of the Altiplano Plateau, facilitating thin-skinned shortening. In contrast, the foreland of the Puna plateau is proposed to be characterized by a warm lithosphere and strong upper crust, resulting in thick-skinned deformation. Whilst this hypothesis has been confirmed in numerical thermomechanical experiments, there is no evidence for this mechanism from data integrative modelling. We test this hypothesis by means of three-dimensional data integrative gravity, thermal and rheological modelling. Therefore, we constructed a lithospheric-scale density model of the foreland of northern Argentina and southern Bolivia using gravity forward modelling and inversion techniques. Into this density model we implemented sediment isopachs, data from receiver functions and densities from shear-wave velocities of the upper mantle. The model was verified using the observed Bouguer gravity anomaly. By assigning thermal and rheological properties to the modelled units we are able to quantify the strength of the lithosphere and test the predictions by the thermomechanical models.

Late-Miocene thrust fault-related folding in the northern Tibetan Plateau: Insight from paleomagnetic and structural analyses of the Kumkol basin

NASA Astrophysics Data System (ADS)

Lu, Haijian; Fu, Bihong; Shi, Pilong; Xue, Guoliang; Li, Haibing

2018-05-01

Constraints on the timing and style of the Tibetan Plateau growth help spur new understanding of the tectonic evolution of the northern Tibetan Plateau and its relation to the India-Asia continental collision. In this regard, records of tectonic deformation with accurate ages are urgently needed, especially in regions without relevant studies. The Kumkol basin, located between two major intermontane basins (the Hoh Xil and Qaidam basins), may hold clues to how these major basins evolve during the Cenozoic. However, little has been known about the exact ages of the strata and tectonic deformation of the basin. Herein, detailed paleomagnetic and structural studies are conducted on the southern Baiquanhe section in the central Kumkol basin, northern Tibetan Plateau. The magnetostratigraphic study indicates that the southern Baiquanhe section spans a time interval of 8.2-4.2 Ma. Well-preserved growth strata date to 7.5 Ma, providing evidence for a significant thrust fault-related folding. This thrust-related folding has also been identified in the Tian Shan foreland and in the northern Tibetan Plateau, most likely implying a pulsed basinward deformation during the late Miocene.

Facies analysis of the Balta Formation: Evidence for a large late Miocene fluvio-deltaic system in the East Carpathian Foreland

NASA Astrophysics Data System (ADS)

Matoshko, Anton; Matoshko, Andrei; de Leeuw, Arjan; Stoica, Marius

2016-08-01

Deposits of the Balta Fm are preserved in a large arcuate sediment body that covers about 60,000 km2 and is up to 350 m thick. The Balta Fm spans ca. 5 Ma as constrained by underlying Tortonian (Bessarabian) and overlying Messinian (early Pontian) Paratethys strata. It contains frequent terrestrial mammal fossils and fresh- as well as brackish-water (Paratethys) molluscs and ostracods. Over the past 140 years our understanding of the sedimentary architecture of the formation and its origins has remained in its infancy, which has limited insight into the evolution of the East Carpathian Foreland. Here, we provide the first modern sedimentary facies analysis of the Balta Fm, which is integrated with an extensive review of previously published local literature. It is supported with micropalaeontological results and a wealth of historical borehole information. We show that the Balta Fm has a tripartite vertical division. Its lowermost part is clay dominated and consists of subordinate delta front sand bodies interspersed between muds. The middle unit contains separate delta plain channels or channel belts encased in thick muds. These are overlain by a unit with amalgamated delta plain channel deposits with only minor amounts of associated mud. The abundance of upper flow regime sedimentary structures in channel sands, the absence of peats (or coals) and the presence of calcareous nodules suggest a strongly seasonal and relatively dry climate with a flashy discharge regime. Deposition of the Balta Fm in an area previously characterized by distal shelf and prodelta environments indicates large-scale progradation triggered by high sediment volume from the uplifting Carpathian Orogen and enhanced by a general lowering of Paratethys sea-level. The tripartite internal architecture of the Balta Fm indicates that progradation continued during deposition. Its wedge-shaped geometry suggests that tectonic activity in the Carpathians generated a 300 km wide foreland basin that

A Bohemian-type Silurian (Wenlockian) pelecypod faunule from Arctic Canada.

USGS Publications Warehouse

Pojeta, J.; Norford, B.S.

1987-01-01

The pelecypod genera Slava and Rhombopteria are reported for the first time from Canada, where they occur in a limestone concretion within the Cape Phillips Formation, Cornwallis Island, Arctic Archipelago. These genera are characteristic of Silurian rocks in Bohemia, Czechoslovakia. Graptolites from the same concretion indicate the Monograptus ludensis Zone (uppermost Wenlockian); this age is substantiated by associated conodonts, trilobites, vertebrates, and pelecypods but with less precision. It is difficult to explain the occurrence of Slava and Rhombopteria in the middle of Laurentia on the basis of some map reconstructions of the Wenlockian world. The Canadian material of Slava novaterra n. sp. and Rhombopteria cf. R. mira (Barrande) is described. Leptodesma (Leptodesma) sp. A and an indeterminate grammysiid pelecypod from the same concretion are illustrated. Information is provided to show that Newsomella Foerste, from Wenlockian-Ludlovian rocks of Illinois, Wisconsin, and Tennessee, is not a subgenus of Rhombopteria Jackson. -Authors

Role of Neogene Exhumation and Sedimentation on Critical-Wedge Kinematics in the Zagros Orogenic Belt, Northeastern Iraq, Kurdistan

NASA Astrophysics Data System (ADS)

Koshnaw, R. I.; Horton, B. K.; Stockli, D. F.; Barber, D. E.; Tamar-Agha, M. Y.; Kendall, J. J.

2014-12-01

The Zagros orogenic belt and foreland basin formed during the Cenozoic Arabia-Eurasia collision, but the precise histories of shortening and sediment accumulation remain ambiguous, especially at the NW extent of the fold-thrust belt in Iraqi Kurdistan. This region is characterized by well-preserved successions of Cenozoic clastic foreland-basin fill and deformed Paleozoic-Mesozoic hinterland bedrock. The study area provides an excellent opportunity to investigate the linkage between orogenic wedge behavior and surface processes of erosion and deposition. The aim of this research is to test whether the Zagros orogenic wedge advanced steadily under critical to supercritical wedge conditions involving in-sequence thrusting with minimal erosion or propagated intermittently under subcritical condition involving out-of-sequence deformation with intense erosion. These endmember modes of mountain building can be assessed by integrating geo/thermochronologic and basin analyses techniques, including apatite (U-Th)/He thermochronology, detrital zircon U-Pb geochronology, stratigraphic synthesis, and seismic interpretations. Preliminary apatite (U-Th)/He data indicate activation of the Main Zagros Fault (MZF) at ~10 Ma with frontal thrusts initiating at ~8 Ma. However, thermochronometric results from the intervening Mountain Front Flexure (MFF), located between the MZF and the frontal thrusts, suggest rapid exhumation at ~6 Ma. These results suggest that the MFF, represented by the thrust-cored Qaradagh anticline, represents a major episode of out-of-sequence deformation. Detrital zircon U-Pb analyses from the Neogene foreland-basin deposits show continuous sediment derivation from sources to the NNE in Iraq and western Iran, suggesting that out-of-sequence thrusting did not significantly alter sedimentary provenance. Rather, intense hinterland erosion and recycling of older foreland-basin fill dominated sediment delivery to the basin. The irregular distribution of

The structure and stratigraphy of deepwater Sarawak, Malaysia: Implications for tectonic evolution

NASA Astrophysics Data System (ADS)

Madon, Mazlan; Kim, Cheng Ly; Wong, Robert

2013-10-01

The structural-stratigraphic history of the North Luconia Province, Sarawak deepwater area, is related to the tectonic history of the South China Sea. The Sarawak Basin initiated as a foreland basin as a result of the collision of the Luconia continental block with Sarawak (Sarawak Orogeny). The foreland basin was later overridden by and buried under the prograding Oligocene-Recent shelf-slope system. The basin had evolved through a deep foreland basin ('flysch') phase during late Eocene-Oligocene times, followed by post-Oligocene ('molasse') phase of shallow marine shelf progradation to present day. Seismic interpretation reveals a regional Early Miocene Unconformity (EMU) separating pre-Oligocene to Miocene rifted basement from overlying undeformed Upper Miocene-Pliocene bathyal sediments. Seismic, well data and subsidence analysis indicate that the EMU was caused by relative uplift and predominantly submarine erosion between ˜19 and 17 Ma ago. The subsidence history suggests a rift-like subsidence pattern, probably with a foreland basin overprint during the last 10 Ma. Modelling results indicate that the EMU represents a major hiatus in the sedimentation history, with an estimated 500-2600 m of missing section, equivalent to a time gap of 8-10 Ma. The EMU is known to extend over the entire NW Borneo margin and is probably related to the Sabah Orogeny which marks the cessation of sea-floor spreading in the South China Sea and collision of Dangerous Grounds block with Sabah. Gravity modelling indicates a thinned continental crust underneath the Sarawak shelf and slope and supports the seismic and well data interpretation. There is a probable presence of an overthrust wedge beneath the Sarawak shelf, which could be interpreted as a sliver of the Rajang Group accretionary prism. Alternatively, magmatic underplating beneath the Sarawak shelf could equally explain the free-air gravity anomaly. The Sarawak basin was part of a remnant ocean basin that was closed by

Structural features of northern Tarim basin: Implications for regional tectonics and petroleum traps

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

Dong Jia; Juafu Lu; Dongsheng Cai

1998-01-01

The rhombus-shaped Tarim basin in northwestern China is controlled mainly by two left-lateral strike-slip systems: the northeast-trending Altun fault zone along its southeastern side and the northeast-trending Aheqi fault zone along its northwestern side. In this paper, we discuss the northern Tarim basin`s structural features, which include three main tectonic units: the Kalpin uplift, the Kuqa depression, and the North Tarim uplift along the northern margin of the Tarim basin. Structural mapping in the Kalpin uplift shows that a series of imbricated thrust sheets have been overprinted by strike-slip faulting. The amount of strike-slip displacement is estimated to be 148more » km by restoration of strike-slip structures in the uplift. The Kuqa depression is a Mesozoic-Cenozoic foredeep depression with well-developed flat-ramp structures and fault-related folds. The Baicheng basin, a Quaternary pull-apart basin, developed at the center of the Kuqa depression. Subsurface structures in the North Tarim uplift can be divided into the Mesozoic-Cenozoic and the Paleozoic lithotectonic sequences in seismic profiles. The Paleozoic litho-tectonic sequence exhibits the interference of earlier left-lateral and later right-lateral strike-slip structures. Many normal faults in the Mesozoic-Cenozoic litho-tectonic sequence form the negative flower structures in the North Tarim uplift; these structures commonly directly overlie the positive flower structures in the Paleozoic litho-tectonic sequence. The interference regions of the northwest-trending and northeast-trending folds in the Paleozoic tectonic sequence have been identified to have the best trap structures. Our structural analysis indicates that the Tarim basin is a transpressional foreland basin rejuvenated during the Cenozoic.« less

Formation and inversion of transtensional basins in the western part of the Lachlan Fold Belt, Australia, with emphasis on the Cobar Basin

NASA Astrophysics Data System (ADS)

Glen, R. A.

The Palaeozoic history of the western part of the Lachlan Fold Belt in New South Wales was dominated by strike-slip tectonics. In the latest Silurian to late Early Devonian, an area of crust >25,000 km 2 lying west of the Gilmore Suture underwent regional sinistral transtension, leading to the development of intracratonic successor basins, troughs and flanking shelves. The volcaniclastic deep-water Mount Hope Trough and Rast Trough, the siliciclastic Cobar Basin and the volcanic-rich Canbelego-Mineral Hill Belt of the Kopyje Shelf all were initiated around the Siluro-Devonian boundary. They all show clear evidence of having evolved by both active syn-rift processes and passive later post-rift (sag-phase) processes. Active syn-rift faulting is best documented for the Cobar Basin and Mount Hope Trough. In the former case, the synchronous activity on several fault sets suggests that the basin formed by sinistral transtension in response to a direction of maximum extension oriented NE-SW. Structures formed during inversion of the Cobar Basin and Canbelego-Mineral Hill Belt indicate closure under a dextral transpressive strain regime, with a far-field direction of maximum shortening oriented NE-SW. In the Cobar Basin, shortening was partitioned into two structural zones. A high-strain zone in the east was developed into a positive half-flower structure by re-activation of early faults and by formation of short-cut thrusts, some with strike-slip movement, above an inferred steep strike-slip fault. Intense subvertical cleavage, a steep extension lineation and variably plunging folds are also present. A lower-strain zone to the west developed by syn-depositional faults being activated as thrusts soling into a gently dipping detachment. A subvertical cleavage and steep extension lineation are locally present, and variably plunging folds are common. Whereas Siluro-Devonian basin-opening appeared to be synchronous in the western part of the fold belt, the different period of

The Sredne-Amursky basin: A migrating cretaceous depocenter for the Amur river, eastern Siberia

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

Light, M.; Maslanyj, M.; Davidson, K.

1993-09-01

Recently acquired seismic, well, and regional geological data imply favorable conditions for the accumulation of oil and gas in the 20,000 km[sup 2] Sredne-Amursky basin. Major graben and northeast-trending sinistral wrench-fault systems are recognized in the basin. Lower and Upper Cretaceous sediments are up to 9000 and 3000 m thick, respectively. Paleogeographic reconstructions imply that during the Late Triassic-Early Cretaceous the Sredne-Amursky basin was part of a narrow marine embayment (back-arc basin), which was open to the north. During the Cretaceous, the region was part of a foreland basin complicated by strike-slip, which produced subsidence related to transtension during obliquemore » collision of the Sikhote-Alin arc with Eurasian margin. Contemporaneous uplift also related to this collision migrated from south to north and may have sourced northward-directed deltas and alluvial fans, which fed northward into the closing back-arc basin between 130 and 85 Ma. The progradational clastic succession of the Berriasian-Albian and the Late Cretaceous fluvial, brackish water and paralic sediments within the basin may be analogous to the highly productive late Tertiary clastics of the Amur River delta in the northeast Sakhalin basin. Cretaceous-Tertiary lacustrine-deltaic sapropelic shales provide significant source and seal potential and potential reservoirs occur in the Cretaceous and Tertiary. Structural plays were developed during Cretaceous rifting and subsequent strike-slip deformation. If the full hydrocarbon potential of the Sredne-Amursky basin is to be realized, the regional appraisal suggests that exploration should be focused toward the identification of plays related to prograding Cretaceous deltaic depositional systems.« less

The age of the Tunas formation in the Sauce Grande basin-Ventana foldbelt (Argentina): Implications for the Permian evolution of the southwestern margin of Gondwana

NASA Astrophysics Data System (ADS)

López-Gamundí, Oscar; Fildani, Andrea; Weislogel, Amy; Rossello, Eduardo

2013-08-01

New SHRIMP radiogenic isotope dating on zircons in tuffs (280.8 ± 1.9 Ma) confirms the Early Permian (Artinskian) age of the uppermost section of the Tunas Formation. Tuff-rich levels in the Tunas Formation are exposed in the Ventana foldbelt of central Argentina; they are part of a deltaic to fluvial section corresponding to the late overfilled stage of the Late Paleozoic Sauce Grande foreland basin. Recent SHRIMP dating of zircons from the basal Choiyoi volcanics exposed in western Argentina yielded an age of 281.4 ± 2.5 Ma (Rocha-Campos et al., 2011). The new data for the Tunas tuffs suggest that the volcanism present in the Sauce Grande basin can be considered as the distal equivalent of the earliest episodes of the Choiyoi volcanism of western Argentina. From the palaeoclimatic viewpoint the new Tunas SHRIMP age confirms that by early Artinskian glacial conditions ceased in the Sauce Grande basin and, probably, in adajacent basins in western Gondwana.

Palaeoclimate records 60-8 ka in the Austrian and Swiss Alps and their forelands

NASA Astrophysics Data System (ADS)

Heiri, Oliver; Koinig, Karin A.; Spötl, Christoph; Barrett, Sam; Brauer, Achim; Drescher-Schneider, Ruth; Gaar, Dorian; Ivy-Ochs, Susan; Kerschner, Hanns; Luetscher, Marc; Moran, Andrew; Nicolussi, Kurt; Preusser, Frank; Schmidt, Roland; Schoeneich, Philippe; Schwörer, Christoph; Sprafke, Tobias; Terhorst, Birgit; Tinner, Willy

2014-12-01

The European Alps and their forelands provide a range of different archives and climate proxies for developing climate records in the time interval 60-8 thousand years (ka) ago. We review quantitative and semi-quantitative approaches for reconstructing climatic variables in the Austrian and Swiss sector of the Alpine region within this time interval. Available quantitative to semi-quantitative climate records in this region are mainly based on fossil assemblages of biota such as chironomids, cladocerans, coleopterans, diatoms and pollen preserved in lake sediments and peat, the analysis of oxygen isotopes in speleothems and lake sediment records, the reconstruction of past variations in treeline altitude, the reconstruction of past equilibrium line altitude and extent of glaciers based on geomorphological evidence, and the interpretation of past soil formation processes, dust deposition and permafrost as apparent in loess-palaeosol sequences. Palaeoclimate reconstructions in the Alpine region are affected by dating uncertainties increasing with age, the fragmentary nature of most of the available records, which typically only incorporate a fraction of the time interval of interest, and the limited replication of records within and between regions. Furthermore, there have been few attempts to cross-validate different approaches across this time interval to confirm reconstructed patterns of climatic change by several independent lines of evidence. Based on our review we identify a number of developments that would provide major advances for palaeoclimate reconstruction for the period 60-8 ka in the Alps and their forelands. These include (1) the compilation of individual, fragmentary records to longer and continuous reconstructions, (2) replication of climate records and the development of regional reconstructions for different parts of the Alps, (3) the cross-validation of different proxy-types and approaches, and (4) the reconstruction of past variations in climate

Hydrogeology and simulation of ground-water flow in the Silurian-Devonian aquifer system, Johnson County, Iowa

USGS Publications Warehouse

Tucci, Patrick; McKay, Robert M.

2006-01-01

The greatest limitation to the model is the lack of measured or estimated water-budget components for comparison to simulated water-budget components. Because the model is only calibrated to measured water levels, and not to water-budget components, the model results are nonunique. Other model limitations include the relatively coarse grid scale, lack of detailed information on pumpage from the quarry and from private developments and domestic wells, and the lack of separate water-level data for the Silurian- and Devonian-age rocks.

The structural evolution of the Ghadames and Illizi basins during the Paleozoic, Mesozoic and Cenozoic: Petroleum implications

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

Gauthier, F.J.; Boudjema, A.; Lounis, R.

1995-08-01

The Ghadames and Illizi basins cover the majority of the eastern Sahara of Algeria. Geologicaly, this part of the Central Saharan platform has been influenced by a series of structural arches and {open_quotes}moles{close_quotes} (continental highs) which controlled sedimentation and structure through geologic time. These features, resulting from and having been affected by nine major tectonic phases ranging from pre-Cambrian to Tertiary, completely bound the Ghadames and Illizi Basins. During the Paleozoic both basins formed one continuous depositional entity with the Ghadames basin being the distal portion of the continental sag basin where facies and thickness variations are observed over largemore » distances. It is during the Mesozoic-Cenozoic that the Ghadames basin starts to evolve differently from the Illizi Basin. Eustatic low-stand periods resulted in continental deposition yielding the major petroleum-bearing reservoir horizons (Cambrian, Ordovician, Siluro-Devonian and Carboniferous). High-stand periods corresponds to the major marine transgressions covering the majority of the Saharan platform. These transgressions deposited the principal source rock intervals of the Silurian and Middle to Upper Devonian. The main reservoirs of the Mesozoic and Cenozoic are Triassic sandstone sequences which are covered by a thick evaporite succession forming a super-seal. Structurally, the principal phases affecting this sequence are the extensional events related to the breakup of Pangea and the Alpine compressional events. The Ghadames and Illizi basins, therefore, have been controlled by a polphase tectonic history influenced by Pan African brittle basement fracturing which resulted in complex structures localized along the major basin bounding trends as well as several subsidiary trends within the basin. These trends, as demonstrated with key seismic data, have been found to contain the majority of hydrocarbons trapped.« less

Stress field variations in the Swiss Alps and the northern Alpine foreland derived from inversion of fault plane solutions

USGS Publications Warehouse

Kastrup, U.; Zoback, M.L.; Deichmann, N.; Evans, Kenneth F.; Giardini, D.; Michael, A.J.

2004-01-01

This study is devoted to a systematic analysis of the state of stress of the central European Alps and northern Alpine foreland in Switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5. The most robust feature of the results is that the azimuth of the minimum compressive stress, S3, is generally well constrained for all data subsets and always lies in the NE quadrant. However, within this quadrant, the orientation of S3 changes systematically both along the structural strike of the Alpine chain and across it. The variation in stress along the mountain belt from NE to SW involves a progressive, counterclockwise rotation of S3 and is most clear in the foreland, where it amounts to 45??-50??. This pattern of rotation is compatible with the disturbance to the stress field expected from the indentation of the Adriatic Block into the central European Plate, possibly together with buoyancy forces arising from the strongly arcuate structure of the Moho to the immediate west of our study area. Across the Alps, the variation in azimuth of S3 is defined by a progressive, counterclockwise rotation of about 45?? from the foreland in the north across the Helvetic domain to the Penninic nappes in the south and is accompanied by a change from a slight predominance of strike-slip mechanisms in the foreland to a strong predominance of normal faulting in the high parts of the Alps. The observed rotation can be explained by the perturbation of the large-scale regional stress by a local uniaxial deviatoric tension with a magnitude similar to that of the regional differential stress and with an orientation perpendicular to the strike of the Alpine belt. The tensile nature and orientation of this stress is consistent with the "spreading" stress expected from lateral density changes due to a crustal root beneath the Alps. Copyright 2004 by the American Geophysical Union.

Walled Sedimentary Basins of China: Perpetrators or Victims of Plateau Growth?

NASA Astrophysics Data System (ADS)

Carroll, A. R.; Graham, S. A.; Smith, M. E.

2004-12-01

Western China and adjacent areas of central Asia are characterized by low relief, internally drained sedimentary basins that are divided by actively uplifting mountain ranges. The margins of these basins often show evidence for extensive contractional deformation, yet their interiors are surprisingly stable. Basins such as the Tarim and Junggar also exhibit long and apparently continuous histories of closed drainage in the same approximate location (over 250 my in the case of Junggar). In contrast to traditional foreland basins, these basins are not uniquely associated with a specific thrust belt, nor do they show evidence for underlying decollements. We therefore propose the new term "walled basin", in recognition of the essential role of peripheral orogenic walls in creating and maintaining closed drainage and impounding sediments. Walled basins in Asia currently are restricted to areas that receive less than 40 cm/yr precipitation, suggesting that aridity plays a role in preventing fluvial breach of the basin walls (cf., Sobel et al., 2003). Entrapment of sediment within the closed Qaidam basin in the northeast Tibetan plateau has been implicated as a potential mechanism of plateau growth, based on the observations that the basin retains mass within the orogen and creates level topography. However, we propose that the Qaidam instead represents a walled basin that has been elevated due to underplating of the plateau, and is fated to eventual destruction as deformation continues. Several lines of reasoning support this conclusion. First, DEM analysis shows that modern drainage divides for the Qaidam and other walled basins never rise more than 1-2 km above the basin floors, limiting the amount of possible topgraphic infill. Second, the Tarim and Junggar basins presently remain well below 2000 m and probably have never been higher, despite receiving large influxes of detritus from adjacent ranges. Third, the Qaidam basin, like the Tarim and Junggar basins, has an

Eocene lake basins in Wyoming and Nevada record rollback of the Farallon flat-slab beneath western North America

NASA Astrophysics Data System (ADS)

Smith, M. E.; Cassel, E. J.; Jicha, B. R.; Singer, B. S.; Carroll, A.

2014-12-01

Numerical and conceptual models of flat-slab rollback predict broad initial dynamic subsidence above the slab hinge then uplift and volcanism triggered by the advection of asthenosphere beneath the overriding plate. These predicted surface effects provide a viable but largely untested explanation for lake basin formation in Cordilleran-type orogenies. We argue that the hydrologic closure of both the foreland (early Eocene) and hinterland (late Eocene) of the North American Cordillera were caused by a trenchward-migrating wave of dynamic and thermal topography resulting from progressive removal of the Farallon flat-slab. Two major episodes of hydrologic drainage closure are recorded by Eocene terrestrial strata in the western United States. The first occurred in the retroarc foreland during the early Eocene, and resulted in the deposition of the Green River Fm. The second occurred in the hinterland during the late Eocene and resulted in accumulation of the Elko Fm. In both regions, lake strata overlie fluvial strata and become progressively more evaporative up-section, and are overlain by volcaniclastic strata. Both successions were then truncated by regional unconformities that extend until the Oligocene. We interpret these stratigraphic successions to record trenchward propagation of a regional topographic wave, caused by slab rollback. Migration of the slab-hinge initially caused dynamic subsidence and initiation of lacustrine deposition. Regional surface uplift followed, and was associated with scattered volcanism. Uplift promoted formation of endorheic basins and ultimately the development of regional unconformities. The height of the uplift can be roughly approximated by the preserved thickness of lacustrine and other nonmarine deposits at both locations (0.2-1.0 km). The 40Ar/39Ar and U-Pb geochronology of Green River Fm ash beds indicate that this surface topographic wave migrated trenchward (SW) across the foreland from 53 to 47 Ma at a velocity of ~6 cm

Deformation History of the Haymana Basin: Structural Records of Closure-Collision and Subsequent Convergence (Indentation) Events at the North-Central Neotethys (Central Anatolia, Turkey)

NASA Astrophysics Data System (ADS)

Gülyüz, Erhan; Özkaptan, Murat; Kaymakcı, Nuretdin

2016-04-01

Gondwana- (Tauride Platfrom and Kırşehir Block) and Eurasia (Pontides) - derived continental blocks bound the Haymana basin, in the south and north, respectively. Boundaries between these blocks are signed by İzmir-Ankara-Erzincan and debatable Intra-Tauride Suture zones which are straddled by the Haymana Basin in the region. In this regard, deformation recorded in the upper Cretaceous to middle Eocene deposits of the basin is mainly controlled by the relative movements of these blocks. Therefore, understanding the structural evolution of the Haymana Basin in a spatio-temporal concept is crucial to shed some light on some debatable issues such as ; (1) timing of late stage subduction histories of various branches of Neotethys and subsequent collision events, (2) effects of post-collisional tectonic activity in the Haymana region. Fault kinematic analyses (based on 623 fault-slip data from 73 stations) indicate that the basin was subjected to initially N-S to NNE-SSW extension until middle Paleocene and then N-S- to NNE-SSW- directed continuous compression and coeval E-W to ESE-WNW extension up to middle Miocene. These different deformation phases correspond to the fore-arc (closure) and foreland (collision and further convergence) stages of the basin. Additionally, fold analyses (based on 1017 bedding attitudes) and structural mapping studies show that development of folds and major faults are coeval and they can be explained by principle stress orientations of the second deformation phase. The Haymana basin is, based on the trends of E-W- and WNW-ESE- directed structures at the south-eastern and the north-western parts of the basin, respectively, divided into two structural segments. The balanced cross-sections also indicate ~4% and ~25% shortening at the north-western and south-eastern segments, respectively. The differences in amounts of shortenings are explained by reduce in effectiveness zone of basin-bounding thrust faults towards west. On the other hand

Phase I (Year 1) Summary of Research--Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

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

G. Michael Grammer

2005-11-09

This topical report covers the first 12 months of the subject 3-year grant, evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). Phase I tasks, including Developing a Reservoir Catalog for selected dolomite reservoirs in the Michigan Basin, Characterization of Dolomite Reservoirs in Representative Fields and Technology Transfer have all been initiated and progress is consistent with our original scheduling. The development of a reservoir catalog for the 3 subject formations in themore » Michigan Basin has been a primary focus of our efforts during Phase I. As part of this effort, we currently have scanned some 13,000 wireline logs, and compiled in excess of 940 key references and 275 reprints that cover reservoir aspects of the 3 intervals in the Michigan Basin. A summary evaluation of the data in these publications is currently ongoing, with the Silurian Niagara Group being handled as a first priority. In addition, full production and reservoir parameter data bases obtained from available data sources have been developed for the 3 intervals in Excel and Microsoft Access data bases. We currently have an excess of 25 million cells of data for wells in the Basin. All Task 2 objectives are on time and on target for Phase I per our original proposal. Our mapping efforts to date, which have focused in large part on the Devonian Dundee Formation, have important implications for both new exploration plays and improved enhanced recovery methods in the Dundee ''play'' in Michigan--i.e. the interpreted fracture-related dolomitization control on the distribution of hydrocarbon reservoirs. In an exploration context, high-resolution structure mapping using quality-controlled well data should provide leads to convergence zones of fault/fracture trends

Near-vertical seismic reflection image using a novel acquisition technique across the Vrancea Zone and Foscani Basin, south-eastern Carpathians (Romania)

NASA Astrophysics Data System (ADS)

Panea, I.; Stephenson, R.; Knapp, C.; Mocanu, V.; Drijkoningen, G.; Matenco, L.; Knapp, J.; Prodehl, K.

2005-12-01

The DACIA PLAN (Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics) deep seismic sounding survey was performed in August-September 2001 in south-eastern Romania, at the same time as the regional deep refraction seismic survey VRANCEA 2001. The main goal of the experiment was to obtain new information on the deep structure of the external Carpathians nappes and the architecture of Tertiary/Quaternary basins developed within and adjacent to the seismically-active Vrancea zone, including the Focsani Basin. The seismic reflection line had a WNW-ESE orientation, running from internal East Carpathians units, across the mountainous south-eastern Carpathians, and the foreland Focsani Basin towards the Danube Delta. There were 131 shot points along the profile, with about 1 km spacing, and data were recorded with stand-alone RefTek-125s (also known as "Texans"), supplied by the University Texas at El Paso and the PASSCAL Institute. The entire line was recorded in three deployments, using about 340 receivers in the first deployment and 640 receivers in each of the other two deployments. The resulting deep seismic reflection stacks, processed to 20 s along the entire profile and to 10 s in the eastern Focsani Basin, are presented here. The regional architecture of the latter, interpreted in the context of abundant independent constraint from exploration seismic and subsurface data, is well imaged. Image quality within and beneath the thrust belt is of much poorer quality. Nevertheless, there is good evidence to suggest that a thick (˜10 km) sedimentary basin having the structure of a graben and of indeterminate age underlies the westernmost part of the Focsani Basin, in the depth range 10-25 km. Most of the crustal depth seismicity observed in the Vrancea zone (as opposed to the more intense upper mantle seismicity) appears to be associated with this sedimentary basin. The sedimentary successions within this basin and other horizons

An exceptionally preserved myodocopid ostracod from the Silurian of Herefordshire, UK

PubMed Central

Siveter, David J.; Briggs, Derek E. G.; Siveter, Derek J.; Sutton, Mark D.

2010-01-01

An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, UK, represents only the third fully documented Palaeozoic ostracod with soft-part preservation. Appendages, gills, gut system, lateral compound eyes and even a medial eye with a Bellonci organ are preserved, allowing assignment of the fossil to a new genus and species of cylindroleberidid myodocope (Myodocopida, Cylindroleberididae). The Bellonci organ is recorded for the first time in fossil ostracods. The find also represents a rare occurrence of gills in fossil ostracods and confirms the earliest direct evidence of a respiratory-cum-circulatory system in the group. The species demonstrates remarkably conserved morphology within myodocopes over a period of 425 Myr. Its shell morphology more closely resembles several families of myodocopes other than the Cylindroleberididae, especially the Cypridinidae and Sarsiellidae, thus questioning the utility of the carapace alone in establishing the affinity of fossil ostracods. PMID:20106847

Detrital zircon U-Pb geochronology and whole-rock Nd-isotope constraints on sediment provenance in the Neoproterozoic Sergipano orogen, Brazil: From early passive margins to late foreland basins

NASA Astrophysics Data System (ADS)

Oliveira, E. P.; McNaughton, N. J.; Windley, B. F.; Carvalho, M. J.; Nascimento, R. S.

2015-11-01

SHRIMP U-Pb detrital zircon geochronology and depleted-mantle Nd-model ages of clastic rocks were combined to understand the sediment provenance in the Neoproterozoic Sergipano Belt. The Sergipano is the main orogenic belt between the Borborema province and the São Francisco Craton, eastern South America; it is divisible into several lithostratigraphic domains from North to South: Canindé, Poço Redondo-Marancó, Macururé, Vaza Barris, and Estância. Nd model ages (TDM) and detrital zircon U-Pb SHRIMP geochronology indicate that the protoliths of clastic metasedimentary rocks from the Marancó and Macururé domains were mostly derived from eroded late Mesoproterozoic to early Neoproterozoic rocks (1000-900 Ma), whereas detritus of similar rocks from the Canindé domain came from a younger source (ca. 700 Ma and 1000 Ma). Samples from the Vaza Barris domain show the greatest scatter of both TDM and zircon ages amongst all domains, but with important contributions from Proterozoic sources (690-1050 Ma and ca. 2100 Ma) and less from Archaean sources. The Estância domain samples have zircon population peaks at 570 Ma, 600 Ma, and 920-980 Ma, with a few older grains; one diamictite contains only ca. 2150 Ma zircon grains. Our preliminary results support a model in which sediments of the Marancó and Macururé domains were deposited on a continental margin of the ancient Borborema plate before its collision with the São Francisco Craton; the Canindé domain is likely to be an aborted Neoproterozoic rift assemblage within the southern part of the Borborema plate (Pernambuco-Alagoas massif). The basal units of the Vaza Barris and Estância domains have clast sources from the São Francisco Craton and are best interpreted as passive margin sediments. However, the uppermost units of the Estância and Vaza Barris domains come from foreland basins formed during collision of Borborema plate with the São Francisco Craton.

Sediment aggradation and erosional dynamics of intermontane basins in NW Argentina

NASA Astrophysics Data System (ADS)

Bookhagen, Bodo; Castino, Fabiana; Purinton, Ben; Strecker, Manfred

2017-04-01

The NW Argentine Andes constitute the Andean Plateau (Altiplano-Puna), the second-largest orogenic plateau on Earth, an internally drained highland with a mean elevation of 4.0 ± 0.5 km (±2 sigma). The Puna is flanked by the externally drained Eastern Cordillera thrust belt and the adjacent broken foreland that are connected to the Atlantic Ocean. These mountain ranges lie in the south-central Andes and are characterized by steep topographic and climatic gradients: The first windward topographic rise east of the Puna forms a significant orographic barrier resulting in high orographic rainfall causing some of the wettest places on Earth. In contrast, the higher-elevation areas of the windward flanks become progressively drier westward, until arid conditions are attained in the central Puna. During the Quaternary the south-central Andes have repeatedly experienced significant paleoclimatic changes associated with deeper penetration of moisture into the orogen, and thus an orogenward shift of the climate gradient. This mechanism has resulted in large variations in erosion dynamics and sediment transfer toward the foreland, resulting in thick valley fills and multiple terrace levels. At much shorter timescales, climate variability during the Holocene has caused similar, yet less pronounced hydrologic trends and associated sedimentation- and erosion processes. Here, we use a time series of Digital Elevation Models (DEMs) to reconstruct land-level changes in the intramontane basins in NW Argentina. We generated the DEMs and height measurements based on stereo airphotos from the 1980s, ASTER satellite imagery, ICESat and dGPS measurements during the past decade, and several TerraSAR-X and TanDEM-X CoSSC pairs starting in 2013. Our data show a strong signal of fluvial sediment aggradation during the past 30 years, in places up to 0.5m per decade, which explains the regionally observed, modern sediment accumulation in basins that has caused major infrastructural problems

Molecular Identification of Adult and Juvenile Linyphiid and Theridiid Spiders in Alpine Glacier Foreland Communities

PubMed Central

Raso, Lorna; Sint, Daniela; Rief, Alexander; Kaufmann, Rüdiger; Traugott, Michael

2014-01-01

In glacier forelands spiders constitute a large proportion of the invertebrate community. Therefore, it is important to be able to determine the species that can be found in these areas. Linyphiid and theridiid spider identification is currently not possible in juvenile specimens using traditional morphological based methods, however, a large proportion of the population in these areas are usually juveniles. Molecular methods permit identification of species at different life stages, making juvenile identification possible. In this study we tested a molecular tool to identify the 10 most common species of Linyphiidae and Theridiidae found in three glacier foreland communities of the Austrian Alps. Two multiplex PCR systems were developed and over 90% of the 753 field-collected spiders were identified successfully. The species targeted were found to be common in all three valleys during the summer of 2010. A comparison between the molecular and morphological data showed that although there was a slight difference in the results, the overall outcome was the same independently of the identification method used. We believe the quick and reliable identification of the spiders via the multiplex PCR assays developed here will aid the study of these families in Alpine habitats. PMID:25050841

Uncoupled vs. coupled thrust belt-foreland deformation: a model for northern Patagonia inferred from U-Th/He and apatite fission track dating

NASA Astrophysics Data System (ADS)

Savignano, Elisa; Mazzoli, Stefano; Zattin, Massimiliano; Gautheron, Cécile; Franchini, Marta

2017-04-01

The study of the Cretaceous - Cenozoic evolution of the Patagonian Andes represents a great opportunity to investigate the effects of coupling between deep lithospheric processes and near-surface deformation. Low-temperature thermochronological systems are ideally suited for detecting events involving rocks in the uppermost part of the crust because they record time and rates of cooling related to exhumation of the top few kilometers of the crust. The Patagonia region, although characterized by a general continuity of the Andean orogen along its strike, shows an appreciable internal tectonic segmentation (marked by a variable position of the magmatic arc and of the deformation front in the retroarc area) at various latitudes. This complex structural architecture has been interpreted as the result of different processes acting since the Late Cretaceous. The present-day configuration of the southern Andes is interpreted to have been controlled by alternating stages of flat- and steep-slab subduction, which produced shortening and upper plate extension episodes,, respectively. Furthermore, the deformation in this whole retroarc sector varied not only in time (i.e. with major 'cycles' of mountain building and orogenic collapse), but also in space, due to the variable transmission of horizontal compressive stress away from the orogen, that produced an irregular unroofing pattern. In this study, we have integrated field structural observations with new apatite (U-Th)/He data (AHe) and apatite fission-track (AFT) ages in the north Patagonia region (at latitudes between 40° and 44°S) in order to analyse and compare the exhumation patterns from the frontal part of the orogen and from the adjacent foreland sector, as well as to gain new insights into the timing and modes of coupling vs. uncoupling of the deformation between the northern Patagonian fold and thrust belt and its foreland. The obtained data indicate a markedly different unroofing pattern between the 'broken

Palaeozoic gas charging in the Ahnet-Timimoun basin, Algeria

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

Cawley, S.J.; Wilson, N.P.; Primmer, T.

1995-08-01

The Ahnet-Timimoun Basin, Southern Algeria, contains significant gas reserves expelled from originally oil prone Silurian and Frasnian shales. The gas is reservoired in Devonian and Carboniferous clastics in inversion anticlines formed, primarily, during the Hercynian orogeny. Integration of organic and inorganic geochemical techniques, such as AFTA, ZFTA, fluid inclusion analysis, vitrinite and chitinizoan reflectance, is entirely consistent with gas generation 300 +/- 30MY, immediately prior to or synchronous with the Hercynian orogeny. Data from gas fields has shown the remobilisation of gas during post Hercynian tectonics. A {open_quotes}two-event{close_quotes} heating/cooling history is proposed: (1) Maximum burial and palaeotemperature at ca. 300more » +/- 30MY prior to or synchronous with Hercynian uplift and cooling. (2) Cooling from a secondary peak (lower than maximum) palaeotemperature at ca. 30-60My following Creataceous burial. Calibrated thermal modelling indicates that Palaeozoic source rocks were heated above 200{degrees}C in the Late Carboniferous. Such high temperatures are consistent with the widespread occurrence of pyrophyllite in Silurian shales. Two end-member thermal models can account for the observed maturities. The first is a constant high Pre-Hercynian heat flow which rapidly decreases during Hercynian uplift to remain at Present day values of 50-75mW/m{sup 2}. Gas expulsion in this case commences much earlier than trap formation. The second is {open_quotes}normal{close_quotes} heat flow of ca. 50mW/m{sup 2} until ca. 310My with a rapid increase at ca. 290My followed by an equally rapid drop to constant present day values - in this model, petroleum generation and expulsion is late in relation to structuring.« less

Seismotectonics of Bhutan: Evidence for segmentation of the Eastern Himalayas and link to foreland deformation

NASA Astrophysics Data System (ADS)

Diehl, Tobias; Singer, Julia; Hetényi, György; Grujic, Djordje; Clinton, John; Giardini, Domenico; Kissling, Edi; Gansser Working Group

2017-08-01

The instrumental record of Bhutan is characterized by a lower seismicity compared to other parts of the Himalayan arc. To understand this low activity and its impact on the seismic hazard, a seismic network was installed in Bhutan for 22 months between 2013 and 2014. Recorded seismicity, earthquake moment tensors and local earthquake tomography reveal along-strike variations in structure and crustal deformation regime. A thickened crust imaged in western Bhutan suggests lateral differences in stresses on the Main Himalayan Thrust (MHT), potentially affecting the interseismic coupling and deformation regime. Sikkim, western Bhutan and its foreland are characterized by strike-slip faulting in the Indian basement. Strain is particularly localized along a NW-SE striking mid-crustal fault zone reaching from Chungthang in northeast Sikkim to Dhubri at the northwestern edge of the Shillong Plateau in the foreland. The dextral Dhubri-Chungthang fault zone (DCF) causes segmentation of the Indian basement and the MHT between eastern Nepal and western Bhutan and connects the deformation front of the Himalaya with the Shillong Plateau by forming the western boundary of the Shillong block. The Kopili fault, the proposed eastern boundary of this block, appears to be a diffuse zone of mid-crustal seismicity in the foreland. In eastern Bhutan we image a seismogenic, flat portion of the MHT, which might be either related to a partially creeping segment or to increased background seismicity originating from the 2009 MW 6.1 earthquake. In western-central Bhutan clusters of micro-earthquakes at the front of the High-Himalayas indicate the presence of a mid-crustal ramp and stress buildup on a fully coupled MHT. The area bounded by the DCF in the west and the seismogenic MHT in the east has the potential for M7-8 earthquakes in Bhutan. Similarly, the DCF has the potential to host M7 earthquakes as documented by the 2011 Sikkim and the 1930 Dhubri earthquakes, which were potentially

Geodynamics and synchronous filling of rift-type basin evolved through compression tectonics

NASA Astrophysics Data System (ADS)

Papdimitriou, Nikolas; Nader, Fadi; Gorini, Christian; Deschamps, Remy

2016-04-01

The Levant Basin falls in the category of frontier basins, and is bounded by the Eratosthenes seamount to the West, the Nile cone delta to the south, Cyprus to the north and Lebanon to the east. The Levant Basin was initially a rift type basin, which is located at a major plate boundary since the Late Triassic. It evolved later on through compression tectonics. The post-rift phase prevailed since the Late Jurassic and is expressed by the gradual initiation of a passive margin. A thick infill, mostly of deep water sediments (about 12 km thick) is accounted for the Levant Basin. The post-rift sediments are pinching-out along the slope of the well preserved (and imaged) eastern margin of the Eratosthenes seamount, which is essentially made up of Mesozoic platform carbonates (about 5 km). Thus, the Eratosthenes carbonate platform was adjacent to the deep marine facies of the Levant Basin until the late Cretaceous/Cenozoic. At that time, both the Eratosthenes seamount and the Levant Basin became part of a foreland basin along the Cyprus Arc zone as a result of the collision of the African and Eurasian plates. The objective of this contribution is to investigate the timing and the mechanisms of flexural subsidence as well as the sedimentary filling of Levant Basin (through a source-to-sink approach) in a well-deformed tectonic region. The interpretation of twenty-four 2D seismic profiles coupled with the available ODP wells, offshore Cyprus, aims to define the primary reflectors and seismic packages. Then, concepts of seismic stratigraphy and sequence stratigraphy are applied to achieve a better understanding of the tectonostratigraphy and sedimentary architecture of the Eratosthenes seamount (as an isolated carbonate platform) and its surroundings. Recent offshore discoveries south of the Eratosthenes seamount (e.g., Zhor) have confirmed the presence of gas accumulations exceeding 30Tcf in subsalt Lower Miocene carbonate buildups, making out the understanding of the

Depositional environment and organic matter accumulation of Upper Ordovician–Lower Silurian marine shale in the Upper Yangtze Platform, South China

USGS Publications Warehouse

Li, Yangfang; Zhang, Tongwei; Ellis, Geoffrey S.; Shao, Deyong

2017-01-01

The main controlling factors of organic matter accumulation in the Upper Ordovician Wufeng–Lower Silurian Longmaxi Formations are complex and remain highly controversial. This study investigates the vertical variation of total organic carbon (TOC) content as well as major and trace element concentrations of four Ordovician–Silurian transition sections from the Upper Yangtze Platform of South China to reconstruct the paleoenvironment of these deposits and to improve our understanding of those factors that have influenced organic matter accumulation in these deposits.The residual TOC content of the Wufeng Formation averages 3.2% and ranges from 0.12 to 6.0%. The overlying lower Longmaxi Formation displays higher TOC content (avg. 4.4%), followed upsection by consistent and lower values that average 1.6% in the upper Longmaxi Formation. The concentration and covariation of redox-sensitive trace elements (Mo, U and V) suggest that organic-rich intervals of the Wufeng Formation accumulated under predominantly anoxic conditions. Organic-rich horizons of the lower Longmaxi Formation were deposited under strongly anoxic to euxinic conditions, whereas organic-poor intervals of the upper Longmaxi Formation accumulated under suboxic conditions. Positive correlations between redox proxies and TOC contents suggest that organic matter accumulation was predominantly controlled by preservation. Barium excess (Baxs) values indicate high paleoproductivity throughout the entire depositional sequence, with an increase in the lower Longmaxi Formation. Increased productivity may have been induced by enhanced P recycling, as evidenced by elevated Corg/Ptot ratios. Mo–U covariation and Mo/TOC values reveal that the Wufeng Formation was deposited under extremely restricted conditions, whereas the Longmaxi Formation accumulated under moderately restricted conditions. During the Late Ordovician, the extremely restricted nature of ocean circulation on the Upper Yangtze Platform in

Petroleum geology and resources of the middle Caspian Basin, Former Soviet Union

USGS Publications Warehouse

Ulmishek, Gregory F.

2001-01-01

The Middle Caspian basin occupies a large area between the Great Caucasus foldbelt and the southern edge of the Precambrian Russian craton. The basin also includes the central part of the Caspian Sea and the South Mangyshlak subbasin east of the sea. The basin was formed on the Hercynian accreted terrane during Late Permian?Triassic through Quaternary time. Structurally, the basin consists of the fold-and-thrust zone of the northern Caucasus foothills, the foredeep and foreland slope, the Stavropol-Prikumsk uplift and East Manych trough to the north of the slope, and the South Mangyshlak subbasin and slope of the Karabogaz arch east of the Caspian Sea. All these major structures extend offshore. Four total petroleum systems (TPS) have been identified in the basin. The South Mangyshlak TPS contains more than 40 discovered fields. The principal reserves are in Lower?Middle Jurassic sandstone reservoirs in structural traps. Source rocks are poorly known, but geologic data indicate that they are in the Triassic taphrogenic sequence. Migration of oil and gas significantly postdated maturation of source rocks and was related to faulting and fracturing during middle Miocene to present time. A single assessment unit covers the entire TPS. Largest undiscovered resources of this assessment unit are expected in the largely undrilled offshore portion of the TPS, especially on the western plunge of the Mangyshlak meganticline. The Terek-Caspian TPS occupies the fold-and-thrust belt, foredeep, and adjoining foreland slope. About 50 hydrocarbon fields, primarily oil, have been discovered in the TPS. Almost all hydrocarbon reserves are in faulted structural traps related to thrusting of the foldbelt, and most traps are in frontal edges of the thrust sheets. The traps are further complicated by plastic deformation of Upper Jurassic salt and Maykop series (Oligocene? lower Miocene) shale. Principal reservoirs are fractured Upper Cretaceous carbonates and middle Miocene sandstones

Drainage reorganization and divide migration induced by the excavation of the Ebro basin (NE Spain)

NASA Astrophysics Data System (ADS)

Vacherat, Arnaud; Bonnet, Stéphane; Mouthereau, Frédéric

2018-05-01

Intracontinental endorheic basins are key elements of source-to-sink systems as they preserve sediments eroded from the surrounding catchments. Drainage reorganization in such a basin in response to changing boundary conditions has strong implications on the sediment routing system and on landscape evolution. The Ebro and Duero basins represent two foreland basins, which developed in response to the growth of surrounding compressional orogens, the Pyrenees and the Cantabrian mountains to the north, the Iberian Ranges to the south, and the Catalan Coastal Range to the east. They were once connected as endorheic basins in the early Oligocene. By the end of the Miocene, new post-orogenic conditions led to the current setting in which the Ebro and Duero basins are flowing in opposite directions, towards the Mediterranean Sea and the Atlantic Ocean. Although these two hydrographic basins recorded a similar history, they are characterized by very different morphologic features. The Ebro basin is highly excavated, whereas relicts of the endorheic stage are very well preserved in the Duero basin. The contrasting morphological preservation of the endorheic stage represents an ideal natural laboratory to study the drivers (internal and/or external) of post-orogenic drainage divide mobility, drainage network, and landscape evolution. To that aim, we use field and map observations and we apply the χ analysis of river profiles along the divide between the Ebro and Duero drainage basins. We show here that the contrasting excavation of the Ebro and Duero basins drives a reorganization of their drainage network through a series of captures, which resulted in the southwestward migration of their main drainage divide. Fluvial captures have a strong impact on drainage areas, fluxes, and their respective incision capacity. We conclude that drainage reorganization driven by the capture of the Duero basin rivers by the Ebro drainage system explains the first-order preservation of

Geochronology, stratigraphy and geochemistry of Cambro-Ordovician, Silurian and Devonian volcanic rocks of the Saxothuringian Zone in NE Bavaria (Germany)—new constraints for Gondwana break up and ocean-island magmatism

NASA Astrophysics Data System (ADS)

Höhn, Stefan; Koglin, Nikola; Klopf, Lisa; Schüssler, Ulrich; Tragelehn, Harald; Frimmel, Hartwig E.; Zeh, Armin; Brätz, Helene

2018-01-01

Stratigraphically well-defined volcanic rocks in Palaeozoic volcano-sedimentary units of the Frankenwald area (Saxothuringian Zone, Variscan Orogen) were sampled for geochemical characterisation and U-Pb zircon dating. The oldest rock suite comprises quartz keratophyre, brecciated keratophyre, quartz keratophyre tuff and basalt, formed in Upper Cambrian to Tremadocian time (c. 497-478 Ma). Basaltic volcanism continued until the Silurian. Quartz keratophyre shows post-collisional calc-alkaline signature, the Ordovician-Silurian basalt has alkaline signature typical of continental rift environments. The combined datasets provide evidence of Cambro-Ordovician bimodal volcanism and successive rifting until the Silurian. This evolution very likely resulted from break-up of the northern Gondwana margin, as recorded in many terranes throughout Europe. The position at the northern Gondwana margin is supported by detrital zircon grains in some tuffs, with typical Gondwana-derived age spectra mostly recording ages of 550-750 Ma and minor age populations of 950-1100 and 1700-2700 Ma. The absence of N-MORB basalt in the Frankenwald area points to a retarded break-off of the Saxothuringian terrane along a continental rift system from Uppermost Cambrian to Middle Silurian time. Geochemical data for a second suite of Upper Devonian basalt provide evidence of emplacement in a hot spot-related ocean-island setting south of the Rheic Ocean. Our results also require partial revision of the lithostratigraphy of the Frankenwald area. The basal volcanic unit of the Randschiefer Formation yielded a Tremadocian age and, therefore, should be attributed to the Vogtendorf Formation. Keratophyre of the Vogtendorf Formation, previously assigned to the Tremadoc, is most likely of Upper Devonian age.

Comparison of the petroleum systems of East Venezuela in their tectonostratigraphic context

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

Stronach, N.J.; Kerr, H.M.; Scotchmer, J.

1996-08-01

The Maturin and Guarico subbasins of East Venezuela record the transition from Cretaceous passive margin to Tertiary foreland basin with local post-orogenic transtensional basins. Petroleum is reservoired in several units ranging from Albian (El Cantil Formation) to Pliocene (Las Piedras Formation) age. Source rocks are principally in the Upper Cretaceous (Querecual Formation), and Miocene (Carapita Formation) in the Maturin subbasin and in the Upper Cretaceous (Tigre Formation) and Oligocene (Roblecito and La Pascua Formations) in the Guarico subbasin. An extensive well database has been used to address the distribution and provenance of hydrocarbons in the context of a tectonostratigraphic modelmore » for the evolution of the East Venezuela basin. Nine major plays have been described, comprising thirteen petroleum systems. The principal factors influencing the components of individual petroleum systems are as follows: (1) structural controls on Upper Cretaceous source rock distribution, relating to block faulting on the proto-Caribbean passive margin; (2) paleoenvironmental controls on source rock development within the Oligocene-Miocene foreland basin; and (3) timing of subsidence and maturation within the Oligocene-Upper Miocene foreland basin and the configuration of the associated fold and thrust belt, influencing long range and local migration routes (4) local development of Pliocene post-orogenic transtensional basins, influencing hydrocarbon generation, migration and remigration north of the Pirital High.« less

National water-quality assessment of the Lake Erie-Lake St. Clair Basin, Michigan, Indiana, Ohio, Pennsylvania, and New York; environmental and hydrologic setting

USGS Publications Warehouse

Casey, G.D.; Myers, Donna N.; Finnegan, D.P.; ,

1998-01-01

The Lake Erie-Lake St. Clair Basin covers approximately 22,300 mi ?(square miles) in parts of Indiana, Michigan, Ohio, Pennsylvania, and New York. Situated in two major physiographic provinces, the Appalachian Plateaus and the Central Lowland, the basin includes varied topographic and geomorphic features that affect the hydrology. As of 1990, the basin was inhabited by approximately 10.4 million people. Lake effect has a large influence on the temperature and precipitation of the basin, especially along the leeward southeast shore of Lake Erie. Mean annual precipitation generally increases from west to east, ranging from 31.8 inches at Detroit, Mich., to 43.8 inches at Erie, Pa. The rocks that underlie the Lake Erie-Lake St. Clair Basin range in age from Cambrian through Pennsylvanian, but only Silurian through Pennsylvanian rocks are part of the shallow ground-water flow system. The position of the basin on the edge of the Michigan and Appalachian Basins is responsible for the large range in geologic time of the exposed rocks. Rock types range from shales, siltstones, and mudstones to coarse-grained sandstones and conglomerates. Carbonate rocks consisting of limestones, dolomites, and calcareous shales also underlie the basin. All the basin is overlain by Pleistocene deposits- till, fine-grained stratified sediments, and coarse-grained stratified sediments-most of Wisconsinan age. A system of buried river valleys filled with various lacustrine, alluvial, and coarse glacial deposits is present in the basin. The soils of the Lake Erie-Lake St. Clair Basin consist of two dominant soil orders: Alfisols and Inceptisols. Four other soil orders in the basin (Mollisols, Histisols, Entisols, and Spodosols) are of minor significance, making up less than 8 percent of the total area. The estimated water use for the Lake Erie-Lake St. Clair Basin for 1990 was 10,649 Mgal/d (million gallons per day). Power generation accounted for about 77 percent of total water withdrawals for

Mesozoic evolution of the Amu Darya basin

NASA Astrophysics Data System (ADS)

Brunet, Marie-Françoise; Ershov, Andrey; Korotaev, Maxim; Mordvintsev, Dmitriy; Barrier, Eric; Sidorova, Irina

2014-05-01

of the basin is occupied by the Pre-Kopet Dagh Cenozoic foreland basin NW oriented, possibly underlain by an earlier extensional trough. The main elements of the sedimentary pile, which can be partly observed in the South-Western Gissar are: Lower to Middle Jurassic continental to paralic clastic rocks; upper Middle to Upper Jurassic marine carbonate then thick Tithonian evaporite rocks, sealing the reservoirs in the Jurassic carbonates; continental Neocomian clastic rocks and red beds, Aptian to Paleogene marine carbonate and clastic rocks. To reconstruct the geodynamic evolution of the Amu Darya Basin, we analysed the subsidence by backstripping of some wells/pseudo-wells and of three cross-sections with some examples of thermal modelling on the periods of maturation of the potential source rocks. The crustal thinning events take place in the Permo-Triassic? (depending on the age of the rifts underlying the basin), in Early-Middle Jurassic and during the Early Cretaceous, resulting in increases of the tectonic subsidence rates.

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.

Observations of paraglacial processes on glacier forelands in Aoraki/Mount Cook National Park, Southern Alps, New Zealand

NASA Astrophysics Data System (ADS)

Winkler, Stefan

2015-04-01

The large and extensively debris-covered valley glaciers in Aoraki/Mount Cook National Park immediate east of the Main Divide in the Southern Alps of New Zealand experienced a substantial frontal retreat and vertical downwasting during the past few decades, often connected with the development of a proglacial lake and retreat by calving. Their Holocene glacier forelands are characterised by huge lateral moraines and multi-ridged lateral moraine systems alongside smaller terminal moraines and frontal outwash heads. Placed within a very dynamic general geomorphological regime of various efficient process-systems, these Holocene glacier forelands are currently affected by substantial paraglacial modification. These paraglacial processes have already caused some consequences for the touristic infrastructure in the area and are likely to cause further problems for the accessibility of established tramping routes, tourist huts, and lookouts in the near and medium future. One of the first steps in a project under development presented here is a detailed visual comparison of changes documented during the past 15 Years on the glacier forelands of Hooker, Mueller and Tasman Glaciers in Aoraki/Mount Cook National Park. It reveals considerable erosion especially on the proximal slopes of the lateral moraines by gully development and retreat of erosion scars at their crest in order of several metres in just a few years. Different processes contribute to high erosion rates, among others rill erosion connected to mid-slope springs that only are temporarily active following substantial rainfall events, efficient gully incision, and slumping. Although any quantification of the actual erosion rates is just preliminary and further studies are necessary in order to make reliable predictions for future development, the amount of paraglacial erosion in this environment is very high compared to other regions and highlights the current importance of the paraglacial process-system in the

Mongolian Oil Shale, hosted in Mesozoic Sedimentary Basins

NASA Astrophysics Data System (ADS)

Bat-Orshikh, E.; Lee, I.; Norov, B.; Batsaikhan, M.

2016-12-01

Mongolia contains several Mesozoic sedimentary basins, which filled >2000 m thick non-marine successions. Late Triassic-Middle Jurassic foreland basins were formed under compression tectonic conditions, whereas Late Jurassic-Early Cretaceous rift valleys were formed through extension tectonics. Also, large areas of China were affected by these tectonic events. The sedimentary basins in China host prolific petroleum and oil shale resources. Similarly, Mongolian basins contain hundreds meter thick oil shale as well as oil fields. However, petroleum system and oil shale geology of Mongolia remain not well known due to lack of survey. Mongolian oil shale deposits and occurrences, hosted in Middle Jurassic and Lower Cretaceous units, are classified into thirteen oil shale-bearing basins, of which oil shale resources were estimated to be 787 Bt. Jurassic oil shale has been identified in central Mongolia, while Lower Cretaceous oil shale is distributed in eastern Mongolia. Lithologically, Jurassic and Cretaceous oil shale-bearing units (up to 700 m thick) are similar, composed mainly of alternating beds of oil shale, dolomotic marl, siltstone and sandstone, representing lacustrine facies. Both Jurassic and Cretaceous oil shales are characterized by Type I kerogen with high TOC contents, up to 35.6% and low sulfur contents ranging from 0.1% to 1.5%. Moreover, S2 values of oil shales are up to 146 kg/t. The numbers indicate that the oil shales are high quality, oil prone source rocks. The Tmax values of samples range from 410 to 447, suggesting immature to early oil window maturity levels. PI values are consistent with this interpretation, ranging from 0.01 to 0.03. According to bulk geochemistry data, Jurassic and Cretaceous oil shales are identical, high quality petroleum source rocks. However, previous studies indicate that known oil fields in Eastern Mongolia were originated from Lower Cretaceous oil shales. Thus, further detailed studies on Jurassic oil shale and its

Tectono-climatic implications of Eocene Paratethys regression in the Tajik basin of central Asia

NASA Astrophysics Data System (ADS)

Carrapa, Barbara; DeCelles, Peter G.; Wang, Xin; Clementz, Mark T.; Mancin, Nicoletta; Stoica, Marius; Kraatz, Brian; Meng, Jin; Abdulov, Sherzod; Chen, Fahu

2015-08-01

Plate tectonics and eustatic sea-level changes have fundamental effects on paleoenvironmental conditions and bio-ecological changes. The Paratethys Sea was a large marine seaway that connected the Mediterranean Neotethys Ocean with Central Asia during early Cenozoic time. Withdrawal of the Paratethys from central Asia impacted the distribution and composition of terrestrial faunas in the region and has been largely associated with changes in global sea level and climate such as cooling associated with the Eocene/Oligocene transition (EOT). Whereas the regression has been dated in the Tarim basin (China), the pattern and timing of regression in the Tajik basin, 400 km to the west, remain unresolved, precluding a test of current paleogeographic models. Here we date the Paratethys regression in Tajikistan at ca. 39 million years ago (Ma), which is several million years older than the EOT (at ca. 34 Ma) marking the greenhouse to icehouse climate transition of the Cenozoic. Our data also show a restricted, evaporitic marine environment since the middle-late Eocene and establishment of desert like environments after ca. 39 Ma. The overall stratigraphic record from the Tajik basin and southern Tien Shan points to deposition in a foreland basin setting by ca. 40 Ma in response to active tectonic growth of the Pamir-Tibet Mountains at the same time. Combined with the northwestward younging trend of the regression in the region, the Tajik basin record is consistent with northward growth of the Pamir and suggests significant tectonic control on Paratethys regression and paleoenvironmental changes in Central Asia.

Black shale source rocks and oil generation in the Cambrian and Ordovician of the central Appalachian Basin, USA

USGS Publications Warehouse

Ryder, R.T.; Burruss, R.C.; Hatch, J.R.

1998-01-01

Nearly 600 million bbl of oil (MMBO) and 1 to 1.5 trillion ft3 (tcf) of gas have been produced from Cambrian and Ordovician reservoirs (carbonate and sandstone) in the Ohio part of the Appalachian basin and on adjoining arches in Ohio, Indiana, and Ontario, Canada. Most of the oil and gas is concentrated in the giant Lima-Indiana field on the Findlay and Kankakee arches and in small fields distributed along the Knox unconformity. Based on new geochemical analyses of oils, potential source rocks, bitumen extracts, and previously published geochemical data, we conclude that the oils in both groups of fields originated from Middle and Upper Ordovician blcak shale (Utica and Antes shales) in the Appalachian basin. Moroever, we suggest that approximately 300 MMBO and many trillions of cubic feet of gas in the Lower Silurian Clinton sands of eastern Ohio originated in the same source rocks. Oils from the Cambrian and Ordovician reservoirs have similar saturated hydrocarbon compositions, biomarker distributions, and carbon isotope signatures. Regional variations in the oils are attributed to differences in thermal maturation rather than to differences in source. Total organic carbon content, genetic potential, regional extent, and bitument extract geochemistry identify the balck shale of the Utica and Antes shales as the most plausible source of the oils. Other Cambrian and Ordovician shale and carbonate units, such as the Wells Creek formation, which rests on the Knox unconformity, and the Rome Formation and Conasauga Group in the Rome trough, are considered to be only local petroleum sources. Tmax, CAI, and pyrolysis yields from drill-hole cuttings and core indicate that the Utica Shale in eastern and central Ohio is mature with respect to oil generation. Burial, thermal, and hydrocarbon-generation history models suggest that much of the oil was generated from the Utica-Antes source in the late Paleozoic during the Alleghanian orogeny. A pervasive fracture network

Hydrocarbon source potential of the Tanezzuft Formation, Murzuq Basin, south-west Libya: An organic geochemical approach

NASA Astrophysics Data System (ADS)

El Diasty, W. Sh.; El Beialy, S. Y.; Anwari, T. A.; Batten, D. J.

2017-06-01

A detailed organic geochemical study of 20 core and cuttings samples collected from the Silurian Tanezzuft Formation, Murzuq Basin, in the south-western part of Libya has demonstrated the advantages of pyrolysis geochemical methods for evaluating the source-rock potential of this geological unit. Rock-Eval pyrolysis results indicate a wide variation in source richness and quality. The basal Hot Shale samples proved to contain abundant immature to early mature kerogen type II/III (oil-gas prone) that had been deposited in a marine environment under terrigenous influence, implying good to excellent source rocks. Strata above the Hot Shale yielded a mixture of terrigenous and marine type III/II kerogen (gas-oil prone) at the same maturity level as the Hot Shale, indicating the presence of only poor to fair source rocks.

Geochemistry and field geology of shoshonitic magmas in the Late Cretaceous foreland fold and thrust belt of southwestern Montana: Results from the North Doherty Mountain Intrusive Complex

NASA Astrophysics Data System (ADS)

Beranek, L. P.; Burton, B. R.; Ihinger, P. D.

2002-12-01

The North Doherty Mountain Intrusive Complex (NDMIC) is one of several satellite plutons related to the areally extensive Boulder batholith of southwestern Montana. The Boulder batholith comprises multiple plutons and intrusive phases, and the magmatism has long been thought to be the result of subduction due to its calc-alkaline granodioritic composition. The batholith is situated in the Helena salient, which differs from other parts of the North American Cordilleran foreland because there, magmatism spatially and temporally overlaps with deformation in the foreland fold and thrust belt. The North Doherty Mountain Intrusive Complex (NDMIC) is one of several satellite plutons related to the Boulder batholith and represents an ideal microcosm of the batholith for petrogenetic and structural studies because it exposes both mafic and felsic units and was emplaced in the limb of a major thrust related fold. We present new geologic mapping and detailed trace element geochemical analyses to show that the entire mafic-to-felsic suite of rocks in the NDMIC are cogenetic and shoshonitic in character. Shoshonites are unusual magmas that are distinguished by their high concentrations of K, Rb, Sr, Ba, Zr, and Th contents, and are thought to represent partial melting at great depths within the mantle wedge above a subducting slab. The presence of shoshonitic magma in the Cordilleran foreland fold and thrust belt provides important clues into the nature of the formation of this unusual magma type and can provide insights into our understanding of magmatism in foreland structural settings.

Active shortening and intermontane basin formation in the central Puna Plateau: Salar de Pocitos, NW Argentina (24° 37S, 67° 03W)

NASA Astrophysics Data System (ADS)

Strecker, M. R.; Bookhagen, B.; Alonso, R.

2012-12-01

With average elevations of about 3.7 km, the semi-arid to arid Puna Plateau is a first-order morphotectonic province of the southern central Andes and is an integral part of the world's second largest orogenic plateau. With few exceptions, this region consists of internally drained, partly coalesced sedimentary basins that are mainly bordered by 5- to 6-km high reverse-fault bounded basement ranges or volcanic edifices. The basins contain continental evaporites, volcanic and clastic deposits, typically between 3 and 5 km thick, and record protracted sedimentation since the Eo-Oligocene. While these basins and ranges are related to contraction, extensional tectonics associated with mafic volcanism characterizes the eastern and southern sectors of the Puna Plateau, while the eastern flanks of the plateau and the adjacent foreland are subjected to shortening. The changeover from contraction to extension in the Puna appears to have been diachronous. Along the SE plateau margin the changeover based on previously published age dating took place between 7 and 5 Ma, while areas in the central and northern Puna document shortening until 6 and 9 Ma, respectively. In the latter two areas, however, evidence for extension comparable to the eastern and southeastern plateau is scarce. This is compatible with our new observations from the Salar de Pocitos area in the western interior of the plateau, which has been characterized by protracted shortening from the Tertiary to the present-day. The N-S oriented Salar de Pocitos basin (435 km2) is the vestige of a formerly contiguous sedimentary basin that extended to the Salar de Arizaro in the west. Unlike many other basins in this region, the Pocitos basin is bordered by the limb of an anticline developed in Tertiary sedimentary rocks on the west, while the east side comprises the reverse-faulted range front of Sierra Qda. Honda. To the north the basin is closed by transverse-oriented late Miocene volcanic edifices, and to the south

The South China - Indochina collision: a perspective from sedimentary basins analysis

NASA Astrophysics Data System (ADS)

Rossignol, Camille; Bourquin, Sylvie; Hallot, Erwan; Poujol, Marc; Roger, Françoise; Dabard, Marie-Pierre; Martini, Rossana; Villeneuve, Michel; Cornée, Jean-Jacques; Peyrotty, Giovan

2017-04-01

material, emplaced under continental setting and representing the product of the erosion of the Indosinian mountain belt. To the North, the Song Da Basin is characterized by strongly diachronous deposits over a basal unconformity developed at the expense of volcanic and volcaniclastic deposits related to the Emeishan Large Igneous Province. The sedimentary succession indicates a foreland setting during the Early to the Middle Triassic, which contrasts with the commonly assumed rift setting for these sediments. Thus, the Song Da Basin documents the formation of the Indosinian thrust belt, located immediately to the South of the basin.

SHRIMP U-Pb evidence for a Late Silurian age of metasedimentary rocks in the Merrimack and Putnam-Nashoba terranes, eastern New England

USGS Publications Warehouse

Wintsch, R.P.; Aleinikoff, J.N.; Walsh, G.J.; Bothner, Wallace A.; Hussey, A.M.; Fanning, C.M.

2007-01-01

U-Pb ages of detrital, metamorphic, and magmatic zircon and metamorphic monazite and titanite provide evidence for the ages of deposition and metamorphism of metasedimentary rocks from the Merrimack and Putnam-Nashoba terranes of eastern New England. Rocks from these terranes are interpreted here as having been deposited in the middle Paleozoic above Neoproterozoic basement of the Gander terrane and juxtaposed by Late Paleozoic thrusting in thin, fault-bounded slices. The correlative Hebron and Berwick formations (Merrimack terrane) and Tatnic Hill Formation (Putnam-Nashoba terrane), contain detrital zircons with Mesoproterozoic, Ordovician, and Silurian age populations. On the basis of the age of the youngest detrital zircon population (???425 Ma), the Hebron, Berwick and Tatnic Hill formations are no older than Late Silurian (Wenlockian). The minimum deposition ages of the Hebron and Berwick are constrained by ages of cross-cutting plutons (414 ?? 3 and 418 ?? 2 Ma, respectively). The Tatnic Hill Formation must be older than the oldest metamorphic monazite and zircon (???407 Ma). Thus, all three of these units were deposited between ???425 and 418 Ma, probably in the Ludlovian. Age populations of detrital zircons suggest Laurentian and Ordovician arc provenance to the west. High grade metamorphism of the Tatnic Hill Formation soon after deposition probably requires that sedimentation and burial occurred in a fore-arc environment, whereas time-equivalent calcareous sediments of the Hebron and Berwick formations probably originated in a back-arc setting. In contrast to age data from the Berwick Formation, the Kittery Formation contains primarily Mesoproterozoic detrital zircons; only 2 younger grains were identified. The absence of a significant Ordovician population, in addition to paleocurrent directions from the east and structural data indicating thrusting, suggest that the Kittery was derived from peri-Gondwanan sources and deposited in the Fredericton Sea

Shifts in bacterial community structure during succession in a glacier foreland of the High Arctic.

PubMed

Kim, Mincheol; Jung, Ji Young; Laffly, Dominique; Kwon, Hye Young; Lee, Yoo Kyung

2017-01-01

Primary succession after glacier retreat has been widely studied in plant communities, but bacterial succession is still poorly understood. In particular, few studies of microbial succession have been performed in the Arctic. We investigated the shifts in bacterial community structure and soil physicochemical properties along a successional gradient in a 100-year glacier foreland of the High Arctic. Multivariate analyses revealed that time after glacier retreat played a key role in associated bacterial community structure during succession. However, environmental filtering (i.e. pH and soil temperature) also accounted for a different, but substantial, proportion of the bacterial community structure. Using the functional trait-based approach, we found that average rRNA operon (rrn) copy number of bacterial communities is high in earlier successional stages and decreased over time. This suggests that soil bacterial taxa with higher rrn copy number have a selective advantage in early successional stages due to their ability of rapidly responding to nutrient inputs in newly exposed soils after glacier retreat. Taken together, our results demonstrate that both deglaciation time and environmental filters play key roles in structuring bacterial communities and soil bacterial groups with different ecological strategies occur in different stages of succession in this glacier foreland. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Tectono-stratigraphic evolution of salt-controlled minibasins in a fold and thrust belt, the Oligo-Miocene central Sivas Basin

NASA Astrophysics Data System (ADS)

Kergaravat, Charlie; Ribes, Charlotte; Callot, Jean-Paul; Ringenbach, Jean-Claude

2017-09-01

The Central Sivas Basin (Turkey) provides an outcrop example of a minibasin province developed above a salt canopy within a foreland-fold and thrust belt. Several minibasins are examined to assess the influence of regional Oligo-Miocene shortening during the development of a minibasin province. The results are based on extensive field work, including regional and detailed outcrop mapping of at least 15 minibasin margins and analysis of the structural elements at all scales. This reveals a progressive increase in shortening and a decrease in salt tectonics during evolution of the province. The initiation of minibasins is driven mostly by the salt-induced accommodation forming a polygonal network of salt structures with mainly local halokinetic sequences (i.e. hooks and wedges). The initiation of shortening is marked by an abrupt increase in sedimentation rate within the flexural foreland basin causing burial of the preexisting salt structures. Subsequently, orogenic compression encourages the rejuvenation of linear salt structures oriented at right angle to the regional shortening direction. The influence of orogenic shortening during the last steps of the minibasin province evolution is clearly shown by: (i) the squeezing of salt structures to form welds which are developed both at right angle and oblique to the regional shortening direction, (ii) the emergence of thrust faults, (iii) the tilting and rotation of minibasins about vertical axis associated with the formation of strike-slip fault zones, and (iv) the extrusion of salt sheets. The pre-shortening geometry of the salt structures pattern, polygonal network of walls and diapirs versus linear and sub-parallel walls, influence the resultant structural style of the minibasin province subjected to shortening. Preexisting linear depocenter limited by sub-parallel walls accommodate preferentially the shortening compare to the preexisting sub-circular depocenter limited by polygonal network of salt walls and

External controls on formation and preservation of fluvial terrace staircases in the Southern Pyrenees foreland

NASA Astrophysics Data System (ADS)

Stange, K. M.; van Balen, R. T.; Carcaillet, J.

2012-04-01

abandonment (incision) and interglacial periods, and point to a terrace formation (aggradation) related to glacial periods in the Pyrenean headwaters. Sedimentological outcrop observations corroborate a cold-climate based genesis of the terraces and present numerous braided channels, ice rafted boulders and frozen sand clasts. Morphologically, the extensive terraces surfaces point to a more than 4km wide presumably braided river system during formation of TQ1 and TQ2. The longitudinal terraces correlation reveals a downstream diverging trend along the lower reaches (foreland stretch) which is most likely base-level controlled. We link the divergence of the Segre terraces to the downcutting history of the Catalan Coastal Range that borders the Ebro foreland basin to the Mediterranean Sea. The stepped morphology with several topographic levels at the breach record the downcutting history of the Catalan Coastal Range. Our longitudinal Segre terrace profiles point to a base-level of about 200m a.s.l. at the begin of terrace formation at the Segre and indicate gradual incision since at least the Middle Pleistocene. We argue, that the Catalan Coastal Range functioned as a local base-level upstream the sea outlet presumably until the Late Pleistocene. Hence, the preservation of terrace staircases at the Southern Central Pyrenees does not require tectonic uplift (although it can not be excluded) and can be explained by base-level mechanisms, while the terrace formation is climate triggered and the result of glacial-interglacial-cycles in the Pyrenees.

Late Permian rivers draining the uplifted Cape Fold Belt: magnetostratigraphy and detrital thermochronology of Karoo Basin sediments

NASA Astrophysics Data System (ADS)

Tohver, E.; Schmieder, M.; Arosio, R.; Lanci, L.; Jourdan, F.; Wilson, A.; Ratcliffe, K.; Payenberg, T.; Flint, S.

2017-12-01

The Cape Fold Belt and Karoo Basin of southern Africa formed during the Permian orogeny that affected the 13,000 km southern margin of the Gondwanan continent. In this report, we synthesize new and recent magnetostratigraphic and geochronologic data to establish a chronostratigraphic framework for Karoo Basin sedimentation for comparison with the thermal/exhumation history of the Cape Fold Belt. The source-sink model is evaluated using new data from detrital muscovite and zircon from 2 km composite section of fluvial sandstone and mudstones deposited at ca.275 - 260 Ma. Coherent age populations of detrital zircon grains indicate rapid incorporation of contemporary volcanic ashbeds into the sedimentary record. In contrast, cooling age distributions of detrital muscovite are typically ca. 5 - 10 Ma older than the age of deposition; similar lag times are observed from modern sediments in active mountain belts. Trace element geochemical signatures demonstrate a clear shift towards crustal recycling via headland erosion in the Beaufort Group relative to the underlying Ecca Group. These observations pinpoint the age of uplift for the Cape Fold Belt, which began to function as the major sediment source for the foreland Karoo Basin with the deposition of the uppermost Ecca Group and basal Beaufort Group.

Miocene unconformities in the Central Apennines: geodynamic significance and sedimentary basin evolution

NASA Astrophysics Data System (ADS)

Cipollari, Paola; Cosentino, Domenico

1995-12-01

This paper shows the results obtained from an integrated study (geology, biostratigraphy and geochemistry) carried out on the Miocene edimentary deposits in Central Italy in order to define the timing of the sedimentary basin evolution. This paper deals also with the causes of the unconformities recorded in these basins. In the Miocene deposits of the Latina Valley and the Ernici-Simbruini Mts. several unconformities which distinguish different stratigraphic sequences have been recognized (D 0, D 1, D 2 D 3 and D 4). For each unconformity a general description together with a geodynamical significance is provided. In particular, D 0 unconformity appears to be related to a regional tectonic event (Adria-Europe collision). As a consequence, the Adria lithosphere folded and the area underwent a regional erosive event. D 1, D 2 and D 3 unconformities have had a more local tectonic control since they represent the stratigraphic record of the migration of the Apennines thrust belt/foredeep system. D 1 and D 2 unconformities are related to the late Tortonian foredeep stage, whereas D 3 is linked to the early Messinian piggy-back stage. Moreover, the D 4 unconformity, which took place during the Messinian piggy-back stage, is strictly linked to the sea-level drop of the Messinian salinity crisis. In this paper the genesis and evolution of a late Tortonian foreland basin is also stressed (Latina Valley foredeep basin). Finally, taking into account sequence boundaries, nannofossil biostratigraphy and geochemistry isotopic data, a comparison with the curve of the 3rd order of the relative coastal onlap (Haq et al., 1988) has been attempted in order to distinguish the unconformities controlled either by tectonic or eustatic processes.

Crustal structure and evolution of the NW Zagros Mountains (Iran): Insights from numerical modeling of the interplay between surface and tectonic processes

NASA Astrophysics Data System (ADS)

Saura, Eduard; Garcia-Castellanos, Daniel; Casciello, Emilio; Vergés, Jaume

2014-05-01

Protracted Arabia-Eurasia convergence resulted in the closure of the >2000 km wide Neo-Tethys Ocean from early Late Cretaceous to Recent. This process was controlled by the structure of the NE margin of the Arabian plate, the NE-dipping oceanic subduction beneath Eurasia, the obduction of oceanic lithosphere and the collision of small continental and volcanic arc domains of the SW margin of Eurasia. The evolution of the Zagros Amiran and Mesopotamian foreland basins is studied in this work along a ~700 km long transect in NW Zagros constrained by field, seismic and published data. We use the well-defined geometries and ages of the Amiran and Mesopotamian foreland basins to estimate the elastic thickness of the lithosphere and model the evolution of the deformation to quantitatively link the topographic, tectonic and sedimentary evolution of the system. Modelling results show two major stages of emplacement. The obduction (pre-collision) stage involves the thin thrust sheets of the Kermanshah complex together with the Bisotun basement. The collision stage corresponds to the emplacement of the basement duplex and associated crustal thickening, coeval to the out of sequence emplacement of Gaveh Rud and Imbricated Zone in the hinterland. The geodynamic model is consistent with the history of the foreland basins, with the regional isostasy model, and with a simple scenario for the surface process efficiency. The emplacement of Bisotun basement during obduction tectonically loaded and flexed the Arabian plate triggering deposition in the Amiran foreland basin. The basement units emplaced during the last 10 My, flexed the Arabian plate below the Mesopotamian basin. During this stage, material eroded from the Simply Folded belt and the Imbricated zone was not enough to fill the Mesopotamian basin, which, according to our numerical model results, required a maximum additional sediment supply of 80 m/Myr. This additional supply had to be provided by an axial drainage system

Orbital forcing in the early Miocene alluvial sediments of the western Ebro Basin, Northeast Spain

NASA Astrophysics Data System (ADS)

Garces, M.; Larrasoaña, J. C.; Muñoz, A.; Margalef, O.; Murelaga, X.

2009-04-01

Paleoclimatic reconstructions from terrestrial records are crucial to assess the regional variability of past climates. Despite the apparent direct connection between continental sedimentary environments and climate, interpreting the climatic signature in ancient non-marine sedimentary sequences is often overprinted by source-area related signals. In this regard, foreland basins appear as non-ideal targets as tectonically-driven subsidence and uplift play a major control on the distribution and evolution of sedimentary environments and facies. Foreland basins, however, often yield among the thickest and most continuous stratigraphic records available on continents. The Ebro Basin (north-eastern Spain) is of particular interest among the circum-mediterranean alpine foreland basins because it evolved into a land-locked closed basin since the late Eocene, leading to the accumulation of an exceptionally thick (>5500 m) and continuous sequence of alluvial-lacustrine sediments over a period of about 25 Myr. In this paper we present a detailed cyclostratigraphic study of a 115 m thick section in the Bardenas Reales de Navarra region (western Ebro Basin) in order to test orbital forcing in the Milankovitch frequency band. The study section corresponds to the distal alluvial-playa mud flats which developed in the central sector of the western Ebro Basin, with sediments sourced from both the Pyrenean and Iberian Ranges. Sediments consist of brown-red alluvial clay packages containing minor fine-grained laminated sandstones sheet-beds and channels, grey marls and thin bedded lacustrine limestones arranged in 10 to 20 m thick fining-upwards sequences. Red clayed intervals contain abundant nodular gypsum interpreted as representing a phase of arid and low lake level conditions, while grey marls and limestones indicate wetter intervals recording the expansion of the inner shallow lakes. A magnetostratigraphy-based chronology indicates that the Peñarroya section represents a

Iberian-Europe convergence: evolution of the Cretaceous and Eocene basins in Pyrenees and Provence

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

Muller, J.; Ducassel, L.; Guieu, G.

1988-08-01

During Cretaceous time the geodynamic evolution of Northern and Western Pyrenean basins was related to scissors-shaped rifting which evolved as a passive margin filled by thick flysch deposits. In Provence, the carbonate platform was marked since the late Albian by the arrival of significant detrital flows originated from an uplifted Paleozoic block situated in the Gulf of Lion. In Provence the northward migration of the basin from Cenomanian to Eocene and Oligocene indicates the growing of the Gulf of Lion-South Provence crustal uplift and its northward displacement. The Cretaceous opening of the western Pyrenean, Parentis, and Bay of Biscay basinsmore » is synchronous with the first stages of compression in the Gulf of Lion. These features are induced by the rotation of Iberia. During the Eocene the compression, resulting from the Iberian-Europe convergence, affected nearly the whole Pyrenean-Provencal area. In the southern part of the Pyrenees east of the Pamplona fault, the successive dislocations of carbonate platforms, migration of reefs, and filling of foreland basins became the signature of the intracontinental subduction of Iberia. The transform fault pattern, still well preserved in spite of the Eocene compression, prevents any important strike-slip movement between Europe and Iberia, especially along the so-called North Pyrenean fault zone, which shows several discontinuities in the western part of Pyrenees. The final evolution of Gulf of Lion crustal uplift generated a gliding of its cover (Provence overthrusts) and, during Oligocene, the opening of the Ligurian-Provencal basin by a propagating rift process.« less

Geophysical evidence of pre-sag rifting and post-rifting fault reactivation in the Parnaíba basin, Brazil

NASA Astrophysics Data System (ADS)

Lopes de Castro, David; Hilário Bezerra, Francisco; Adolfo Fuck, Reinhardt; Vidotti, Roberta Mary

2016-04-01

This study investigated the rifting mechanism that preceded the prolonged subsidence of the Paleozoic Parnaíba basin in Brazil and shed light on the tectonic evolution of this large cratonic basin in the South American platform. From the analysis of aeromagnetic, aerogravity, seismic reflection and borehole data, we concluded the following: (1) large pseudo-gravity and gravity lows mimic graben structures but are associated with linear supracrustal strips in the basement. (2) Seismic data indicate that 120-200 km wide and up to 300 km long rift zones occur in other parts of the basins. These rift zones mark the early stage of the 3.5 km thick sag basin. (3) The rifting phase occurred in the early Paleozoic and had a subsidence rate of 47 m Myr-1. (4) This rifting phase was followed by a long period of sag basin subsidence at a rate of 9.5 m Myr-1 between the Silurian and the late Cretaceous, during which rift faults propagated and influenced deposition. These data interpretations support the following succession of events: (1) after the Brasiliano orogeny (740-580 Ma), brittle reactivation of ductile basement shear zones led to normal and dextral oblique-slip faulting concentrated along the Transbrasiliano Lineament, a continental-scale shear zone that marks the boundary between basement crustal blocks. (2) The post-orogenic tectonic brittle reactivation of the ductile basement shear zones led to normal faulting associated with dextral oblique-slip crustal extension. In the west, pure-shear extension induced the formation of rift zones that crosscut metamorphic foliations and shear zones within the Parnaíba block. (3) The rift faults experienced multiple reactivation phases. (4) Similar processes may have occurred in coeval basins in the Laurentia and Central African blocks of Gondwana.

Hydrocarbon potential of Morocco

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

Achnin, H.; Nairn, A.E.M.

1988-08-01

Morocco lies at the junction of the African and Eurasian plates and carries a record of their movements since the end of the Precambrian. Four structural regions with basins and troughs can be identified: Saharan (Tarfaya-Ayoun and Tindouf basins); Anti-Atlas (Souss and Ouarzazate troughs and Boudnib basin); the Essaouria, Doukkala, Tadla, Missour, High Plateau, and Guercif basins; and Meseta and Rif (Rharb and Pre-Rif basins). The targets in the Tindouf basin are Paleozoic, Cambrian, Ordovician (clastics), Devonian (limestones), and Carboniferous reservoirs sourced primarily by Silurian shales. In the remaining basins, excluding the Rharb, the reservoirs are Triassic detritals, limestones atmore » the base of the Lias and Dogger, Malm detritals, and sandy horizons in the Cretaceous. In addition to the Silurian, potential source rocks include the Carboniferous and Permo-Carboniferous shales and clays; Jurassic shales, marls, and carbonates; and Cretaceous clays. In the Rharb basin, the objectives are sand lenses within the Miocene marls. The maturation level of the organic matter generally corresponds to oil and gas. The traps are stratigraphic (lenses and reefs) and structural (horsts and folds). The seals in the pre-Jurassic rocks are shales and evaporites; in the younger rocks, shales and marl. Hydrocarbon accumulations have been found in Paleozoic, Triassic, Liassic, Malm, and Miocene rocks.« less

Precise U/Pb zircons dates of bentonites in Upper Ordovician and Lower Silurian reference sections in North America and Britain.

NASA Astrophysics Data System (ADS)

Suarez, S. E.; Brookfield, M. E.; Catlos, E. J.; Stockli, D. F.; Batchelor, R. A.

2016-12-01

The end of the Ordovician marks one of the greatest of the Earth's mass extinctions. One hypothesis explains this mass extinction as the result of a short-lived, major glaciation preceded by episodes of increased volcanism brought on by the Taconic orogeny. K-bentonites, weathered volcanic ash, provide evidence for increased volcanism. However, there is a lack of modern precise U-Pb dating of these ashes and some confusion in the biostratigraphy. The aim of this study is to obtain more precise U-Pb zircon ages from biostratigraphically constrained bentonites which will lead to better correlation of the Upper Ordovician and Lower Silurian relative time scales, as well as time the pulses of eruption. Zircon grains were extracted from the samples by heavy mineral separation and U-Pb dated using the Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer at the University of Texas-Austin. We report here 3 precise U-Pb zircon ages from the Trenton Group, Ontario, Canada, and Dob's Linn, Scotland. The youngest age from the top of the Kirkfield Formation in Ontario is 448.0 +/- 18 Ma, which fits with existing late Ordovician stratigraphic ages. At Dob's Linn, Scotland, the site of the Ordovician/Silurian Global Boundary Stratigraphic Section and Point (GSSP), the youngest age for DL7, a bentonite 5 meters below the GSSP is 402.0 +/- 12.0 Ma, and for DL24L, a bentonite 8 meters above the GSSP is 358.2 +/- 7.9 Ma. These are Devonian ages in current timescales - the current age for the GSSP is 443.8 +/- 1.8 Ma, based on an U/Pb dates from a bentonite 1.6 meters above the GSSP at Dob's Linn. We are confident that our techniques rule out contamination and the most likely explanation is that the small zircons we analyzed either suffered Pb loss, or grew overgrowths during low grade hydrothermal metamorphism of the sediments during the intrusion of the Southern Upland Devonian granites during the Caledonian orogeny. These Devonian ages suggest that the 443.8 +/- 1.8 Ma age

Early to Middle Ordovician back-arc basin in the southern Appalachian Blue Ridge: characteristics, extent, and tectonic significance

USGS Publications Warehouse

Tull, James; Holm-Denoma, Christopher S.; Barineau, Clinton I.

2014-01-01

Fault-dismembered segments of a distinctive, extensive, highly allochthonous, and tectonically significant Ordovician (ca. 480–460 Ma) basin, which contains suites of bimodal metavolcanic rocks, associated base metal deposits, and thick immature deep-water (turbiditic) metasediments, occur in parts of the southern Appalachian Talladega belt, eastern Blue Ridge, and Inner Piedmont of Alabama, Georgia, and North and South Carolina. The basin's predominantly metasedimentary strata display geochemical and isotopic evidence of a mixed provenance, including an adjacent active volcanic arc and a provenance of mica (clay)-rich sedimentary and felsic plutonic rocks consistent with Laurentian (Grenvillian) upper-crustal continental rocks and their passive-margin cover sequences. Geochemical characteristics of the subordinate intercalated bimodal metavolcanic rocks indicate formation in a suprasubduction environment, most likely a back-arc basin, whereas characteristics of metasedimentary units suggest deposition above Neoproterozoic rift and outer-margin lower Paleozoic slope and rise sediments within a marginal basin along Ordovician Laurentia's Iapetus margin. This tectonic setting indicates that southernmost Appalachian Ordovician orogenesis (Taconic orogeny) began as an extensional accretionary orogen along the outer margin of Laurentia, rather than in an exotic (non-Laurentian) arc collisional setting. B-type subduction polarity requires that the associated arc-trench system formed southeast of the palinspastic position of the back-arc basin. This scenario can explain several unique features of the southern Appalachian Taconic orogen, including: the palinspastic geographic ordering of key tectonic elements (i.e., back-arc, arc, etc.), and a lack of (1) an obducted arc sensu stricto on the Laurentian margin, (2) widespread Ordovician regional metamorphism, and (3) Taconic klippen to supply detritus to the Taconic foreland basin.

Abrupt global-ocean anoxia during the Late Ordovician-early Silurian detected using uranium isotopes of marine carbonates.

PubMed

Bartlett, Rick; Elrick, Maya; Wheeley, James R; Polyak, Victor; Desrochers, André; Asmerom, Yemane

2018-05-21

Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ 238 U values of marine limestones as a global seawater redox proxy. The δ 238 U trends at Anticosti Island, Canada, document an abrupt late Hirnantian ∼0.3‰ negative shift continuing through the early Silurian indicating more reducing seawater conditions. The lack of observed anoxic facies and no covariance among δ 238 U values and other local redox proxies suggests that the δ 238 U trends represent a global-ocean redox record. The Hirnantian ocean anoxic event (HOAE) onset is coincident with the extinction pulse indicating its importance in triggering it. Anoxia initiated during high sea levels before peak Hirnantian glaciation, and continued into the subsequent lowstand and early Silurian deglacial eustatic rise, implying that major climatic and eustatic changes had little effect on global-ocean redox conditions. The HOAE occurred during a global δ 13 C positive excursion, but lasted longer indicating that controls on the C budget were partially decoupled from global-ocean redox trends. U cycle modeling suggests that there was a ∼15% increase in anoxic seafloor area and ∼80% of seawater U was sequestered into anoxic sediments during the HOAE. Unlike other ocean anoxic events (OAE), the HOAE occurred during peak and waning icehouse conditions rather than during greenhouse climates. We interpret that anoxia was driven by global cooling, which reorganized thermohaline circulation, decreased deep-ocean ventilation, enhanced nutrient fluxes, stimulated productivity, which lead to expanded oxygen minimum zones. Copyright © 2018 the Author(s). Published by PNAS.

Rock magnetism and magnetic fabric of the Triassic rocks from the West Spitsbergen Fold-and-Thrust Belt and its foreland

NASA Astrophysics Data System (ADS)

Dudzisz, Katarzyna; Szaniawski, Rafał; Michalski, Krzysztof; Chadima, Martin

2018-03-01

Magnetic fabric and magnetomineralogy of the Early Triassic sedimentary rocks, collected along the length of the West Spitsbergen Fold-and-Thrust Belt (WSFTB) and from subhorizontal beds on its foreland, is presented with the aim to compare magnetic mineralogy of these areas, determine the carriers of magnetic fabric and identify tectonic deformation reflected in the magnetic fabric. Magnetic mineralogy varies and only in part depends on the lithology. The magnetic fabric at all sampling sites is controlled by paramagnetic minerals (phyllosilicates and Fe-carbonates). In the fold belt, it reflects the low degree of deformation in a compressional setting with magnetic lineation parallel to fold axis (NW-SE). This is consistent with pure orthogonal compression model of the WSFTB formation, but it also agrees with decoupling model. Inverse fabric, observed in few sites, is carried by Fe-rich carbonates. In the WSFTB foreland, magnetic lineation reflects the Triassic paleocurrent direction (NE-SW). The alternation between normal and inverse magnetic fabric within the stratigraphic profile could be related to sedimentary cycles.

Tectonic Evolution of the Izmir Ankara Suture Zone in Northwest Turkey Using Zircon U-Pb Geochronology and Zircon Lu-Hf Isotopic Tracers

NASA Astrophysics Data System (ADS)

Campbell, C.; Taylor, M. H.; Licht, A.; Mueller, M.; Ocakglu, F.; Moeller, A.; Metais, G.; Beard, K. C.

2017-12-01

Detrital zircons from a Cretaceous forearc basin and Tertiary foreland basin located along the Sakarya Zone of the Western Pontides were analyzed to better understand the closure history of the Tethyan oceans. The Variscan Orogeny is characterized by abundant 350-300 Ma U-Pb ages and vertical ɛHf arrays, consistent with a mature magmatic arc that emplaced plutons through a southward growing accretionary margin. An ɛHf pull-up is observed from 300-250 Ma interpreted as rifting of the Intra-Pontide Ocean. The Cimmerian Orogeny is characterized by a 250-230 Ma ɛHf pull-down, followed by a 230-200 Ma magmatic gap consistent with underthrusting of the Karakaya Complex. From 200-120 Ma another magmatic lull is observed. The Alpine Orogeny is characterized by an ɛHf pull-down from 120-85 Ma within Cretaceous forearc sediments and a 100 Ma deviant ɛHf vertical array within Tertiary foreland basin sediments. Minor zircon U-Pb age peaks and contrasting inter-basinal ɛHf evolution are interpreted to represent onset of Andean-style subduction along the southern margin of the Sakarya Zone at 120 Ma followed by crustal thickening until 85 Ma. The deviant 100 Ma ɛHf vertical array within foreland basin detritus is interpreted as initiation of intra-oceanic subduction within the Izmir-Ankara Ocean. An 85-75 Ma ɛHf pull-up from forearc basin sediments is interpreted as slab roll-back along the southern margin of the Sakarya Zone, responsible for final rifting of the Western Black Sea. At 80 Ma, a vertical ɛHf array from Tertiary foreland basin deposits is interpreted to represent synchronous melting of the Tavsanli Zone and intra-oceanic slab break-off. A single 66 Myr pre-collisional grain defines a sharp ɛHf pull-down immediately prior to total arc shut-off, interpreted to represent incipient collision between the Sakarya and Tavsanli zones. A 52 Ma syn-collisional tuff yields minimally intermediate ɛHf values followed by a slight 48 Ma ɛHf pull-down, interpreted as a

Maps showing thermal maturity of Upper Cretaceous marine shales in the Bighorn Basin, Wyoming and Montana

USGS Publications Warehouse

Finn, Thomas M.; Pawlewicz, Mark J.

2014-01-01

The Bighorn Basin is one of many structural and sedimentary basins that formed in the Rocky Mountain foreland during the Laramide orogeny, a period of crustal instability and compressional tectonics that began in latest Cretaceous time and ended in the Eocene. The basin is nearly 180 mi long, 100 mi wide, and encompasses about 10,400 mi2 in north-central Wyoming and south-central Montana. The basin is bounded on the northeast by the Pryor Mountains, on the east by the Bighorn Mountains, and on the south by the Owl Creek Mountains). The north boundary includes a zone of faulting and folding referred to as the Nye-Bowler lineament. The northwest and west margins are formed by the Beartooth Mountains and Absaroka Range, respectively. Important conventional oil and gas resources have been discovered and produced from reservoirs ranging in age from Cambrian through Tertiary. In addition, a potential unconventional basin-centered gas accumulation may be present in Cretaceous reservoirs in the deeper parts of the basin. It has been suggested by numerous authors that various Cretaceous marine shales are the principal source rock for these accumulations. Numerous studies of various Upper Cretaceous marine shales in the Rocky Mountain region have led to the general conclusion that these rocks have generated or are capable of generating oil and (or) gas. In recent years, advances in horizontal drilling and multistage fracture stimulation have resulted in increased exploration and completion of wells in Cretaceous marine shales in other Rocky Mountain Laramide basins that were previously thought of only as hydrocarbon source rocks. Important parameters controlling hydrocarbon production from these shale reservoirs include: reservoir thickness, amount and type of organic matter, and thermal maturity. The purpose of this report is to present maps and a cross section showing levels of thermal maturity, based on vitrinite reflectance (Ro), for selected Upper Cretaceous marine

Geology and depositional environments of the Guadalupian rocks of the northern Del Norte Mountains, West Texas

USGS Publications Warehouse

Rudine, S.F.; Wardlaw, B.R.; Rohr, D.M.; Grant, R.E.

2000-01-01

The Guadalupian rocks of the northern Del Norte Mountains were deposited in a foreland basin between land of the Marathon orogen and a carbonate shoal established on the geanticline separating the foreland basin from the Delaware basin. Deposition was alternately influenced by coarse clastic input from the orogen and carbonate shoal, which interrupted shallow basinal siltstone depletion. Relatively deeper-water deposition is characterized by carbonate input from the shoal, and relatively shallow-water deposition is characterized by sandstone input from the orogen. Deposition was in five general transgressive-regressive packages that include (1) the Road Canyon Formation and the first siltstone member and first sandstone member of the Word Formation, (2) the second siltstone member, Appel Ranch Member, and limy sandy siltstone member of the Word Formation, (3) the Vidrio Formation, (4) the lower and part of the middle members of the Altuda Formation, and (5) part of the middle and upper members of the Altuda Formation.

Flexural subsidence and basement tectonics of the Cretaceous Western Interior basin, United States

NASA Astrophysics Data System (ADS)

Pang, Ming; Nummedal, Dag

1995-02-01

The flexural subsidence history recorded in Cenomanian to early Campanian (97 to 80 Ma) strata in the Cretaceous U.S. Western Interior basin was studied with two-dimensional flexural backstripping techniques. Results indicate that the flexural subsidence resulting from thrust loading was superimposed on epeirogenic subsidence in the foreland basin. The flexural component exhibits significant spatial and temporal variations along both the strike and dip relative to the Sevier thrust belt. The greatest cumulative subsidence occurred in southwestern Wyoming and northern Utah. Concurrent subsidence in northwestern Montana and southern Utah was insignificant. Temporal trends in subsidence also show a distinct regional pattern. From the Cenomanian to late Turonian (97 to 90 Ma), subsidence rates were high in Utah and much lower in Wyoming and Montana. In contrast, during the Coniacian and Santonian (90 to 85 Ma) subsidence accelerated rapidly in Wyoming, increased slightly in Montana, and decreased in Utah. We suggest that these spatially and temporally varying subsidence patterns reflect the interplay of several geodynamic factors, including: (1) temporal and spatial variation in emplacement of the thrust loads, (2) segmentation of the basement into adjacent blocks with different rheological properties, (3) reactivation of basement fault trends, and (4) regional dynamic topographic effects.

Lithospheric buckling and far-foreland deformation during the Laramide and Appalachian orogenies

NASA Astrophysics Data System (ADS)

Tikoff, B.; Siddoway, C. S.

2017-12-01

Major intraplate tectonics within North America (Laurentia) occurs during times of major orogenesis along the plate margins. During mountain building, typical structures of the hinterland are an orogenic plateau and fold-and-thrust belts, while in the far foreland (intraplate) areas long-wavelength ( 200 km or longer) folds and fault-reactivation features form. Long-wavelength folds are evident in both the Appalachian and Laramide orogenic forelands, with the stratigraphy recording the timing of the uplift. This contribution examines the model of lithospheric buckling - periodic folding associated with a horizontal endload on the edge of the plate - based on scaled, physical experiments and corroborated by numerical models. The Laramide (75-55 Ma) intraplate orogen in the classical location in Wyoming contains basement-cored arches spaced 200 km apart, for which the mechanism of uplift is questioned. Seismic evidence obtained for the Bighorn uplift, Wyoming, obtained by the EarthScope Bighorn project, shows an upwarp of the Moho beneath, but oblique to the trend of the surface exposure of the basement arch. Both the surface and Moho exhibit approximately the same structural relief. The seismic data exhibit no evidence for a regionally continuous decollement, nor is there evidence of rotation of structural markers within these features, of the type that is observed in the detached fold-and-thrust belt. The intraplate region affected by long-wavelength folding includes western Wyoming, with continuation of some features across the E-W-oriented Cheyenne belt (e.g., Rock Springs-Douglas Creek arch), Colorado Plateau, and High Plains east of the Rocky Mountains, where surface and subsurface structures display a series of anticlinal arches ("plains-type" folds). Appalachian mountain building also caused long-wavelength folding, with a spacing consistent with lithospheric buckling, mostly associated with the Devonian Acadian orogeny. The Laramide arches in the High Plains

Along-strike variations of structural styles in the imbricated Molasse of Salzburg and Upper Austria: a 3-D seismic perspective

NASA Astrophysics Data System (ADS)

Hinsch, Ralph; Linzer, Hans-Gert

2010-05-01

At the southern border of the Northern Alpine Foreland Basin syntectonic deposits (Molasse Sediments) are partly incorporated into Alpine contractional deformation. Along the alpine chain style and timing of this deformation varies significantly. In this study we use one of the largest European on-shore 3-D seismic datasets, spanning the Molasse basin of Upper Austria and Salzburg states, to investigate the along-strike structural architecture of the alpine deformation front. In the Austrian Part of the Molasse basin, foredeep sedimentation started in Upper-Eocene times (Wagner, 1996). The sediments cover the European margin, consisting of a crystalline basement covered by variously thick Mesozoic sediments (Nachtmann und Wagner, 1987). In Oligocene to Lower Miocene times, syntectonic foredeep sedimentation took place in a deep marine environment, comprising an axial channel system (Linzer 2001, DeRuig and Hubbard, 2006). Parts of these syntectonic sediments are subsequently affected by the advancing thrust wedge. Within the study area, three distinct fold-and-thrust belt segments of different structural architecture can be defined. 1) The Perwang Imbricates are a promontory mostly situated in Salzburg at the border to Germany. Complexly deformed small thrust sheets evolve above a detachment horizon situated in Late Cretaceous shaly marls in Oligocene times. Syntectonic piggy-back and thrust top basins evolve (Covault et al. 2008), which are partly affected by subsequent Miocene overthrusting. 2) The Regau Segment is the area west of the Perwang lobe. It is dominated by few number of thrust sheets in the Molasse sediments. Instead, over-thrusting by the alpine wedge (pre-deformed Flysch and Helvetic thrust sheets) dominates. 3) The Sierning Imbricates segment is located further to the east, at the border of Upper Austria to Lower Austria. The structural inventory of this thrust belt is comprises varying numbers of thrust sheets along strike (1-5), ramp

Cenozoic basin thermal history reconstruction and petroleum systems in the eastern Colombian Andes

NASA Astrophysics Data System (ADS)

Parra, Mauricio; Mora, Andres; Ketcham, Richard A.; Stockli, Daniel F.; Almendral, Ariel

2017-04-01

Late Mesozoic-Cenozoic retro-arc foreland basins along the eastern margin of the Andes in South America host the world's best detrital record for the study of subduction orogenesis. There, the world's most prolific petroleum system occur in the northernmost of these foreland basin systems, in Ecuador, Colombia and Venezuela, yet over 90% of the discovered hydrocarbons there occur in one single province in norteastern Venezuela. A successful industry-academy collaboration applied a multidisciplinary approach to the study of the north Andes with the aim of investigating both, the driving mechanisms of orogenesis, and its impact on hydrocarbon accumulation in eastern Colombia. The Eastern Cordillera is an inversion orogen located at the leading edge of the northern Andes. Syn-rift subsidence favored the accumulation of km-thick organic matter rich shales in a back-arc basin in the early Cretaceous. Subsequent late Cretaceous thermal subsidence prompted the accumulation of shallow marine sandstones and shales, the latter including the Turonian-Cenomanian main hydrocarbon source-rock. Early Andean uplift since the Paleocene led to development of a flexural basin, filled with mainly non-marine strata. We have studied the Meso-Cenozoic thermal evolution of these basins through modeling of a large thermochronometric database including hundreds of apatite and zircon fission-track and (U-Th)/He data, as well as paleothermometric information based on vitrinite reflectance and present-day temperatures measured in boreholes. The detrital record of Andean construction was also investigated through detrital zircon U-Pb geochronometry in outcrop and borehole samples. A comprehensive burial/exhumation history has been accomplished through three main modeling strategies. First, one-dimensional subsidence was used to invert the pre-extensional lithospheric thicknesses, the magnitude of stretching, and the resulting heat flow associated to extension. The amount of eroded section and

Tectonic Evolution of the Central Andes during Mesozoic-Cenozoic times: Insights from the Salar de Atacama Basin

NASA Astrophysics Data System (ADS)

Peña Gomez, M. A.; Bascunan, S. A.; Becerra, J.; Rubilar, J. F.; Gómez, I.; Narea, K.; Martínez, F.; Arriagada, C.; Le Roux, J.; Deckart, K.

2015-12-01

The classic Salar de Atacama Basin, located in the Central Andes of northern Chile, holds a remarkable yet not fully understood record of tectonic events since mid-Cretaceous times. Based on the growing amount of data collected over the last years, such as high-detail maps and U-Pb geochronology, we present an updated model for the development of this area after the Triassic. A major compressional event is recorded around the mid-Late Cretaceous (ca. 107 Ma) with the deposition of synorogenic continental successions reflecting the uplift of the Coastal Cordillera area farther to the west, and effectively initiating the foreland basin. The deformation front migrated eastwards during the Late Campanian (ca. 79 Ma), where it exhumed and deformed the Late Cretaceous magmatic arc and the crystalline basement of Cordillera de Domeyko. The K-T Event (ca. 65 Ma), recently identified in the basin, involved the same source areas, though the facies indicate a closer proximity to the source. The compressional record of the basin is continued by the Eocene Incaic Event (ca. 45 Ma), with deep exhumation of the Cordillera de Domeyko and the cannibalization of previous deposits. A change to an extensional regime during the Oligocene (ca. 28 Ma) is shown by the deposition of more than 4 km of evaporitic and clastic successions. A partial inversion of the basin occurred during the Miocene (ca.10 Ma-present), as shown by the deformation seen in the Cordillera de la Sal. As such, the basin shows that the uplift of the Cordillera de Domeyko was not one isolated episode, but a prolonged and complex event, punctuated by episodes of major deformation. It also highlights the need to take into account the Mesozoic-Cenozoic deformation events for any model trying to explain the building of the modern-day Andes.

The combined effects of eustasy, tectonism, and clastic influx on the development of Pennsylvanian cyclic carbonates, southern Sangre de Cristo Mountains, New Mexico

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

Gong Shouyeh; Humphrey, J.D.

1991-03-01

Pennsylvania cyclothems are well documented on stable continental shelves and the cyclicity has generally been attributed to glacio-eustasy. As a contrast, Atokan-Desmoinesian cyclic carbonates of the southern Sangre de Cristo Mountains developed in a tectonically active foreland basin, formed by thrusting along the Picuris-Pecos fault during early Pennsylvanian time. Strata exposed in two sections (Dalton Bluff, 260 m; Johnson Mesa, 340 m) are characterized by (1) shallowing-upward cycles, (2) cycles of variable thickness (5-20 m), (3) incomplete cycles, (4) cycles interrupted by terrigenous clastic input, and (5) noncyclic intervals. Allocyclic mechanisms alone cannot fully explain these observations; the authors hereinmore » propose that a complex interplay among eustasy, tectonism, and clastic sediment supply were responsible for the observed cycles. Lithofacies analysis indicates that location within the foreland basin played a significant role in cycle attributes. In the deeper portions of the basin (e.g., Dalton Bluff), an idealized cycle, from base to top consists of (1) shale/marl facies, (2) brachiopod wackestone facies, (3) phylloid algal facies, and (4) marine clastic facies. No evidence for subaerial exposure of cycle caps is noted. In contrast, in shallow portions of the basin near the forebulge (e.g., Johnson Mesa) the marine clastic facies is substituted by crinoidal grainstone/packstone facies that is capped by subaerial exposure surface. Each of the two cycles displays an overall grand (lower order) shallowing-upward cycle. This grand cycle developed as sediments infilled the initially starved foreland basin.« less

Detrital-zircon fission-track geochronology of the Lower Cenozoic sediments, NW Himalayan foreland basin: Clues for exhumation and denudation of the Himalaya during the India-Asia collision

NASA Astrophysics Data System (ADS)

Jain, A.; Lal, N.; Suelmani, B.; Awasthi, A. K.; Singh, S.; Kumar, R.

2007-12-01

Detrital-zircon fission-track geochronology of the synorogenically-deposited Subathu-Dagshai-Kasauli-Lower Siwalik Formations of the Sub-Himalayan Lower Cenozoic foreland basin reflects progressive effects of the Himalayan tectonometamorphic events on the Proterozoic-Paleozoic source rock as a consequence of the India-Asia collision. The oldest transgressive marine Subathu Formation (57.0-41.5 Ma) contains a very dominant 302.4 ± 21.9 Ma old detrital zircon FT suite with a few determinable 520.0 Ma grains. This old suite was derived by mild erosion of the Zircon Partially Annealed Zone (ZPAZ) of 240-180 oC, which affected the Himalayan Proterozoic basement and its Tethyan sedimentary cover as a consequence of first imprint of the collision. In addition, 50.0 Ma old detrital zircons in this formation were derived possibly from the Indus Tsangpo Suture Zone and the Trans-Himalayan Ladakh Batholith. Sudden source rock changes and unroofing are manifested in the overlying fluvial Dagshai (~30-20 Ma) and Kasauli (20-13 Ma) molassic sediments, which are characterised by dominant 30.0 and 25.0 Ma old youngest zircon FT peaks, respectively. A distinct unconformity spanning for about 10 Myr gets established between the Subathu-Dagshai formations on the basis of detrital- zircon FT ages. Molassic sedimentation since ~30 Ma coincides with the depletion of detritus from the suture zone, and the bulk derivation from the main Higher Himalayan source rock, which has undergone sequentially the UHP-HP-amphibolite facies metamorphism (53-40 Ma) in the extreme north and widespread Eo- and Neo-Himalayan tectonothermal events in the middle. Strength of the Pre-Himalayan Peaks (PHP) >50 Ma in these younger sediments gradually decreases with the intensification of the Himalayan thermal events till the end of the Kasauli sedimentation. Widespread Eo- and Neo-Himalayan metamorphic events (40.0-30.0 and 25.0-15.0 Ma) have almost remobilised the provenance and obliterated most of the

Biogeography of late Silurian and devonian rugose corals

USGS Publications Warehouse

Oliver, W.A.

1977-01-01

Three marine benthic faunal realms can be recognized in the Early and Middle Devonian. The Eastern Americas Realm consisted of most of the eastern half of North America and South America north of the Amazon. This realm extended in a southwest direction from the Devonian equator to approximately 35??S and was an isolated epicontinental sea during much of its history. The Eastern Americas Realm was bounded on the west by the Transcontinental Arch, on the north by the Canadian Shield and on the east and southeast by a peninsular extension of the Old Red Continent. These barriers were emergent during much, but not all, of Devonian time. Seaways beyond these barriers belonged to the Old World Realm. The Malvinokaffric Realm that was farther south was apparently temperate to arctic in climate and latitudinal position and contained few corals. Rugose corals in the Eastern Americas Realm show increasing generic-level endemism from the Late Silurian through the Early Devonian; during the late Early Devonian, 92% of the rugosan genera are not known anywhere else in the world. Endemism decreased through the Middle Devonian to zero in the early Late Devonian. The Early Devonian increase in endemism paralleled, and was probably related to, the development of the Old Red Continent as a barrier between America and Africa-Europe. The waning of endemism in the Middle Devonian reflects the breaching of the land barriers. This permitted some migration in and out of the realm in early Middle Devonian time but greatest movements were in late Middle Devonian time. Principal migration directions were from western or Arctic North America into the Michigan-Hudson Bay area and from the southern Appalachian area into Africa. ?? 1977.

Plateau growth around the Changma Basin in NE Tibet

NASA Astrophysics Data System (ADS)

Vernon, Rowan; Cunningham, Dickson; Zhang, Jin; England, Richard

2014-05-01

displacement. Structural transects reveal a lack of intra-range reactivation of inherited structures or fabrics, concentrating uplift on the lithologically-controlled intra-range thrust faults and the major range-bounding thrust and oblique-slip faults. Northeast of the Changma Basin, in the Qilian Shan foreland, an east-trending belt of low folds and faulted ridges along the ATF marks the structural continuation of the Yumen Shan range. We find that uplift and growth of northeastern Tibet is complex with local variations in structural vergence, degree of strain partitioning, fault reactivation and basin inversion. This complexity reflects both the buttressing effect of the rigid Archaean basement directly to the north and the variation in the structural trends and lithologies of the Qilian basement, as well as the competition between uplift and erosion in the region.

The geology of a part of Acadia and the nature of the Acadian orogeny across Central and Eastern Maine

USGS Publications Warehouse

Tucker, R.D.; Osberg, P.H.; Berry, H.N.

2001-01-01

The zone of Acadian collision between the Medial New England and Composite Avalon terranes is well preserved in Maine. A transect from northwest (Rome) to southeast (Camden) crosses the eastern part of Medial New England comprising the Central Maine basin, Liberty-Orrington thrust sheet, and Fredericton trough, and the western part of Composite Avalon, including the Graham Lake, Clarry Hill, and Clam Cove thrust sheets. U-Pb geochronology of events before, during, and after the Acadian orogeny helps elucidate the nature and distribution of tectonostrati& graphic belts in this zone and the timing of some Acadian events in the Northern Appalachians. The Central Maine basin consists of sedimentary and volcanic rocks of Middle Ordovician (???470 to ???460 Ma) age overlain with probable conformity by latest Ordovician(?) through earliest Devonian marine rift and flysch sedimentary rocks; these are intruded by weakly to undeformed plutonic rocks of Early and Middle Devonian age (???399??378 Ma). The Fredericton trough consists of Early Silurian gray pelite and sandstone to earliest Late Silurian calcareous turbidite, deformed and variably metamorphosed prior to the emplacement of Late Silurian (???422 Ma) and Early to Late Devonian (???418 to ???368 Ma) plutons. The Liberty-Orrington thrust sheet consists of Cambrian(?)-Ordovician (>???474 to ???469 Ma and younger) clastic sedimentary and volcanic rocks intruded by highly deformed Late Silurian (???424 to ???422 Ma) and Devonian (???418 to ???389 Ma) plutons, possibly metamorphosed in Late Silurian time (prior to ???417 Ma), and metamorphosed to amphibolite facies in Early to Middle Devonian time (???400 to ???381 Ma). The Graham Lake thrust sheet contains possible Precambrian rocks, Cambrian sedimentary rocks with a volcanic unit dated at ???503 Ma, and Ordovician rocks with possible Caradocian Old World fossils, metamor& phosed and deformed in Silurian time and intruded by mildly to undeformed Late Silurian (???421 Ma

Age and position of the sedimentary basin of the Ocoee Supergroup western Blue Ridge tectonic province, southern Appalachians

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

Unrug, R.; Unrug, S.; Ausich, W.I.

The stratigraphic continuity of the Ocoee Supergroup established recently allows one to extrapolate the Paleozoic age of the Walden Creek Group determined on paleontological evidence to the entire Ocoee succession. The Walden Creek Group rocks contain a fossil assemblage of fenestrate bryozoan, algal, trilobite, ostracod, brachiopod and echinozoan fragments and agglutinated foraminifer tests that indicate Silurian or younger Paleozoic age. The fossils occur in carbonate clasts in polymict conglomerates, and debris-flow breccia beds, and in olistoliths of bedded carbonate and shale, and calcarenite turbidite beds. These carbonate lithologies form a minor, but characteristic constituent of the Walden Creek Group. Fossilmore » have been found also in shale and mudstone siliciclastic lithologies of the Walden Creek Group. The fossils are fragmented and poorly preserved because of several cycles of cementation and solution in the carbonate rocks and a pervasive cleavage in the fine-grained siliciclastic rocks. Recently reported Mississippian plant fossils from the Talladega belt indicate widespread occurrence of Middle Paleozoic basins in the Western Blue Ridge. These pull-apart basins formed in the stress field generated by northward movement of Laurentia past the western margin of Gondwana after the Taconian-Famatinian collision in the Ordovician.« less

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

USGS Publications Warehouse

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

1999-01-01

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

Chemostratigraphical Characterisation of the Lower Silurian Formigoso Formation: A Case Study from Aralla (Cantabrian Mountains, Province Leon, NW Spain)

NASA Astrophysics Data System (ADS)

Ferriday, T.; Montenari, M.

2012-04-01

The Silurian black shale deposits of the peri-Gondwanan region are one of the most important Palaeozoic source rocks for hydrocarbons world-wide. Despite intensive research, questions regarding the genesis and the palaeoenvironmental and palaeogeographic factors controlling the deposition of these shales are a matter of ongoing debate. The area investigated lies within the Cantabria-Asturias Arc of Northern Spain in the autonomous region of Castilla y León. The Cantabrian Arc formed as a result of the collision between Gondwana and Laurussia during the formation of the supercontinent Pangea and has been divided into five major tectonostratigraphic units. The 'Folds and Nappes' unit is of particular interest, especially the contained Somiedo-Corecillas thrust system, as here the best preserved Formigoso-sections and exposures can be found. This study focuses on the deposition of the L-Silurian black shales of the Formigoso Formation (Fm) within the Somiedo-Corecillas thrust system at Aralla, approximately 10km east-southeast of San Emiliano. A high resolution geochemical analysis of major and trace elements has been utilised on a 25cm scale throughout the section. A total of 241 samples were prepared and analysed using a NITON XL3t X-ray fluorescence instrument. The data obtained have provided new insights into the sedimentation patterns and the prevailing environmental conditions during deposition of the Formigoso Fm. Initial results show prominent regular cycles within the concentrations of red/ox-sensitive chemical elements, starting from the very onset of the anoxic black shales; these repetitions become less apparent towards to top of the formation. Eight cyclic pulses are clearly evident in the concentrations of the elements Uranium (U), Thorium (Th), Vanadium (V) and Chromium (Cr) and apparent in Rubidium (Rb), Zinc (Zn), Copper (Cu), Nickel (Ni), Titanium (Ti), Sulphur (S) and Barium (Ba). The cyclic behaviour of U4+ between 'Anoxia'-U enriched (18ppm)- and

Quaternary deformation in the central Neuquén basin (35°-37°S), Argentina: evidences for active strain partitioning.

NASA Astrophysics Data System (ADS)

Niviere, B.; Backé, G.

2006-12-01

The tectonic evolution of the Central Andes is a consequence of the relative convergence between the Nazca and the South American plates. The Neuquén basin is located in the southernmost part of the Central Andes, between latitudes 32°S and 40°S. The present day geometry of the basin has been inherited from different compressive pulses, separated by times of relative tectonic quiescence since the late Cretaceous. The complex tectonic evolution of the area has often been explained by changes in the geometry of the subducted plate. The last broad scale tectonic event in the Neuquén basin is the Miocene compressive stage referred to as the Quechua phase. The tectonic evolution of the outer part of the Neuquén Basin from the late Miocene onwards is still a matter of debate. For instance, strain partitioning has been described in the inner part of the basin, which corresponds to the modern arc area close to the Chile Argentina border. The strain regime in the foreland between 35°S and 37°S is more uncertain. Extensional tectonic features have been described in different areas of the basin, leading to the formulation of a possible orogenic collapse in response to the steepening of the oceanic slab that followed a late Miocene shallow subduction. This model accounts for the occurrence of large Pleistocene to Quaternary back-arc volcanism in the Neuquén basin. However, field structural data and borehole breakout analysis strongly support on-going compression in the basin. Our study is based on the morphostructural analysis of remote sensing data (satellite and digital elevation model images) complemented by field work. Here we show that strike-slip faulting and localized extension in the outer zone of the basin is coeval with active thrusting and folding. This can be explained by strain partitioning or segmentation processes due to the oblique convergence between the Nazca and the South American plates.

Sedimentology and Sedimentary Dynamics of the Desmoinesian Cherokee Group, Deep Anadarko Basin, Texas Panhandle

NASA Astrophysics Data System (ADS)

Hu, N.; Loucks, R.; Frebourg, G.

2015-12-01

Understanding the spatial variability of deep-water facies is critical to deep-water research because of its revealing information about the relationship between desity flow processes and their resultant sedimentary sequences. The Cherokee Group in the Anadarko Basin, northeastern Texas Panhandle, provides an opportunity to investigate an icehouse-greenhouse Pennsylvanian hybrid system that well demonstrates the intricacies of vertical and lateral facies relationships in an unconfined fan-delta fed deep-water slope to basinal setting. The stratigraphic section ranges in thickness from 150 to 460 m. The cyclic sedimentation and foreland basin tectonics resulted in a complex stratal architecture that was sourced by multiple areas of sediment input. This investigation consists of wireline-log and core data. Five-thousand wireline logs were correlated in an area of over 9500 sq km to map out six depositional sequences that are separated by major flooding events. These events are correlative over the whole area of study. Six cores, that sample nearly the complete section, were described for lithofacies. Lithofacies are recognized based on depositional features and mineralogy:(1) Subarkose, (2) Lithicarkoses, (3) Sandy siliciclastic conglomerate, (4) Muddy calcareous conglomerate, (5) Crinoidal packstone, (6) Oodic grainstone, (7)Pelodic grainstone, (8) Ripple laminated mudrock, (9) faint laminated mudrock. The integration of isopachs of depositional sequences with the lithofacies has allowed the delineation of the spatial and temporal evolution of the slope to basin-floor system. Thin-to-thick bedded turbidites, hyperconcentrated density flow deposits (slurry beds), and debris and mud flow deposits were observed and can be used to better predicte lithofacies distributions in areas that have less data control. These mixed siliciclastic and carbonate deposits can be carrier beds for the hydrocarbons generated from the enclosing organic-rich (TOC ranges from 0.55 to 6.77wt

A new crustacean from the Herefordshire (Silurian) Lagerstätte, UK, and its significance in malacostracan evolution

PubMed Central

Briggs, Derek E. G.; Siveter, Derek J.; Sutton, Mark D.; Legg, David

2017-01-01

Cascolus ravitis gen. et sp. nov. is a three-dimensionally preserved fossil crustacean with soft parts from the Herefordshire (Silurian) Lagerstätte, UK. It is characterized by a head with a head shield and five limb pairs, and a thorax (pereon) with nine appendage-bearing segments followed by an apodous abdomen (pleon). All the appendages except the first are biramous and have a gnathobase. The post-mandibular appendages are similar one to another, and bear petal-shaped epipods that probably functioned as a part of the respiratory–circulatory system. Cladistic analysis resolves the new taxon as a stem-group leptostracan (Malacostraca). This well-preserved arthropod provides novel insights into the evolution of appendage morphology, tagmosis and the possible respiratory–circulatory physiology of a basal malacostracan. PMID:28330926

Provenance and accommodation pathways of late Quaternary sediments in the deep-water northern Ionian Basin, southern Italy

NASA Astrophysics Data System (ADS)

Perri, Francesco; Critelli, Salvatore; Dominici, Rocco; Muto, Francesco; Tripodi, Vincenzo; Ceramicola, Silvia

2012-12-01

The northern Calabria along the southeastern coast of Italy provides a favorable setting in which to study complete transects from continental to deep-marine environments. The present northern Ionian Calabrian Basin is a wedge-top basin within the modern foreland-basin system of southern Italy. The Ionian margin of northern Calabria consists of a moderately developed fluvial systems, the Crati and Neto rivers, and diverse smaller coastal drainages draining both the Calabria continental block (i.e., Sila Massif) and the southern Apennines thrust belt (i.e., Pollino Massif). The main-channel sand of the Crati and Neto rivers is quartzofeldspathic with abundant metamorphic and plutonic lithic fragments (granodiorite, granite, gneiss, phyllite and sedimentary lithic fragments). Sedimentary lithic fragments were derived from Jurassic sedimentary successions of the Longobucco Group. The mud samples contain mostly phyllosilicates, quartz, calcite, feldspars and dolomite. Traces of gypsum are present in some samples. The I-S mixed layers, 10 Å-minerals (illite and micas), chlorite and kaolinite are the most abundant phyllosilicates, whereas smectite and chlorite/smectite mixed layers are in small amounts. The geochemical signatures of the muds reflect a provenance characterized by both felsic and mafic rocks with a significant input from carbonate rocks. Furthermore, the degree of source-area weathering was most probably of low intensity rather than moderately intense because CIA values for the studied mud samples are low. Extrapolation of the mean erosion budget from 1 to 25 Ma suggests that at least 5 to 8 km of crust have been removed from the Calabrian orogenic belt and deposited in the marine basins. The Calabrian microplate played an important role in the dynamic evolution of southern Italian fossil and modern basins, representing the key tectonic element of the entire orogenic belt.

The immature thrust belt of the northern front of the Tianshan

NASA Astrophysics Data System (ADS)

Chen, Ke; Gumiaux, Charles; Augier, Romain; Chen, Yan; Wang, Qingchen

2010-05-01

The modern Tianshan (central Asia), which extends east-west on about 2500 km long with an average of more than 2000 m in altitude, is considered as a direct consequence of the reactivation of a Paleozoic belt due to the India - Asia collision. At first order, the finite structure of this range obviously displays a significant uprising of Paleozoic "basement" rocks - as a crustal-scale ‘pop-up' - surrounded by two Cenozoic foreland basins. In order to characterize the coupling history of this Cenozoic orogeny with its northern foreland basin (Junggar basin), a detailed structural field work has been carried out on the northern piedmont of Tianshan. From Wusu to Urumqi, on about 250 km long, the thrusting of the Paleozoic basement on the Mesozoic or Cenozoic sedimentary series of the basin is remarkably exposed along several river valleys. In contrast, in other sections, the Triassic to Jurassic sedimentary series can be followed from the basin to the range where they unconformably overlie on the Carboniferous basement. These series are only gently folded along the "range front". These features imply that, at regional-scale, the Cenozoic reactivation of the Tianshan has not produced important deformation along its contact with the juxtaposed Junggar basin. The shortening ascribed to the Cenozoic intra-continental collision would either be localized in the range, mostly accommodated by reactivated Paleozoic structures or faults in the basement units, or in the distal parts of the Junggar basin, by folds and faults within the Cenozoic sedimentary series. Alternative hypothesis would be that the Tianshan uplift and the movements associated with along its northern front structures, which are traditionally assigned to its Cenozoic reactivation, might be reduced. Such characteristic significantly differs from other well-known orogenic ranges, such as the Canadian Rocky Mountains, the Appalachians, the Pyrenees which display highly folded foreland basins and thrust belts

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

Comparison of the Eastern and Western Kentucky coal fields (Pennsylvanian), USA-why are coal distribution patterns and sulfur contents so different in these coal fields?

USGS Publications Warehouse

Greb, S.F.; Eble, C.F.; Chesnut, D.R.

2002-01-01

More than 130 Mt of Pennsylvanian coal is produced annually from two coal fields in Kentucky. The Western Kentucky Coal Field occurs in part of the Illinois Basin, an intercratonic basin, and the Eastern Kentucky Coal Field occurs in the Central Appalachian Basin, a foreland basin. The basins are only separated by 140 km, but mined western Kentucky coal beds exhibit significantly higher sulfur values than eastern Kentucky coals. Higher-sulfur coal beds in western Kentucky have generally been inferred to be caused by more marine influences than for eastern Kentucky coals. Comparison of strata in the two coal fields shows that more strata and more coal beds accumulated in the Eastern than Western Kentucky Coal Field in the Early and Middle Pennsylvanian, inferred to represent greater generation of tectonic accommodation in the foreland basin. Eastern Kentucky coal beds exhibit a greater tendency toward splitting and occurring in zones than time-equivalent western Kentucky coal beds, which is also inferred to represent foreland accommodation influences, overprinted by autogenic sedimentation effects. Western Kentucky coal beds exhibit higher sulfur values than their eastern counterparts, but western Kentucky coals occurring in Langsettian through Bolsovian strata can be low in sulfur content. Eastern Kentucky coal beds may increase in sulfur content beneath marine zones, but generally are still lower in sulfur than mined Western Kentucky coal beds, indicating that controls other than purely marine influences must have influenced coal quality. The bulk of production in the Eastern Kentucky Coal Field is from Duckmantian and Bolsovian coal beds, whereas production in the Western Kentucky Coal Field is from Westphalian D coals. Langsettian through Bolsovian paleoclimates in eastern Kentucky were favorable for peat doming, so numerous low-sulfur coals accumulated. These coals tend to occur in zones and are prone to lateral splitting because of foreland tectonic and

Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina

NASA Astrophysics Data System (ADS)

Rossello, E. A.; Massabie, A. C.; López-Gamundí, O. R.; Cobbold, P. R.; Gapais, D.

1997-12-01

, immediately west of the Sierras Australes. In the Sierras Septentrionales of Buenos Aires, Precambrian through early Paleozoic deposits of La Tinta, Sierras Bayas, Las Aguilas and Balcarce Formations rest on Precambrian crystalline basement of the La Plata craton. These exposed rocks are affected by subordinate, right lateral wrench faulting; some thrusting indicates tectonic transport toward the NE. In northeast Patagonia (Sierra Grande region) synkinematic deformation of early Permian (261 ± 5 Ma, {Rb}/{Sr} whole rock) age has been identified in Silurian metasediments of the Sierra Grande Formation. Bands of deformation in Sierra Grande quartzites indicate right lateral wrenching in a N-S direction. Contraction in a NE-SW direction is evidenced by folding. Three stages of tectonic evolution can be discerned for the above regions: (1) Early Paleozoic platform sedimentation, punctuated by episodes of accelerated subsidence during the Silurian and early Devonian, as shown by transgressive episodes, (2) late Paleozoic sedimentation and deformation, and (3) Meso-Cenozoic extensional inversion due to the South Atlantic opening. The late Paleozoic sedimentation and deformation (stage 2) includes late Carboniferous-earliest Permian glacial deposits of the Sierras Australes and Colorado offshore basin, deposited during an initial phase of extension, and cratonward foreland subsidence triggered sedimentation of the synorogenic deposits of the Permian Tunas Formation. Tuffs are intercalated in the upper half of this unit. These tuffs are associated with the silicic volcanism along the Andes and Patagonia (Choiyoi magmatic province) that peaked between the late early Permian and late Permian. Likewise, the first widespread appearance of tuffs in the Karoo basin is in the Whitehill Formation, of late early Permian (260 Ma) age. The deformation described in this paper can be considered as part of a large scale intracontinental deformation in SW Gondwanaland inboard of an Andean

Estimate of ground water in storage in the Great Lakes basin, United States, 2006

USGS Publications Warehouse

Coon, William F.; Sheets, Rodney A.

2006-01-01

Hydrogeologic data from Regional Aquifer System Analyses (RASA) studies by the U.S. Geological Survey in the Great Lakes Basin, United States, during 1978-95, were compiled and used to estimate the total volume of water that is stored in the many aquifers of the basin. These studies focused on six regional aquifer systems: the Cambrian-Ordovician aquifer system in Wisconsin, Illinois, and Indiana; the Silurian- Devonian aquifers in Wisconsin, Michigan, Illinois, Indiana, and Ohio; the surficial aquifer system (aquifers of alluvial and glacial origin) found throughout the Great Lakes Basin; and the Pennsylvanian sandstone and carbonate-rock aquifers and the Mississippian sandstone aquifer in Michigan. Except for the surficial aquifers, all of these aquifer systems are capable of yielding substantial quantities of water and are not small aquifers with only local importance. Individual surficial aquifers, although small in comparison to the bedrock aquifers, collectively represent large potential sources of ground water and therefore have been treated as a regional system. Summation of ground-water volumes in the many regional aquifers of the basin indicates that about 1,340 cubic miles of water is in storage; of this, about 984 cubic miles is considered freshwater (that is, water with dissolved-solids concentration less than 1,000 mg/L). These volumes should not be interpreted as available in their entirety to meet water-supply needs; complete dewatering of any aquifer is environmentally undesirable. The amount of water that is considered available on the basis of water quality and environmental, economic, and legal constraints has not been determined. The effect of heavy pumping in the Chicago, Ill., and Milwaukee, Wis., areas, which has caused the regional ground-water divide in the Cambrian-Ordovician aquifer system to shift westward, has been included in the above estimates. This shift in the ground-water divide has increased the amount of water in storage in the

Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway.

PubMed

Kirkland, Christopher L; MacGabhann, Breandán A; Kirkland, Brian L; Daly, J Stephen

2016-01-01

The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later.

Undiscovered oil and gas resources of Lower Silurian Qusaiba-Paleozoic total petroleum systems, Arabian Peninsula

USGS Publications Warehouse

Ahlbrandt, T.S.; Pollastro, R.M.; Schenk, C.J.

2002-01-01

The U.S. Geological Survey (USGS) recently completed an assessment of the undiscovered conventional oil and gas potential of 128 of the world’s petroleum provinces (U.S. Geological Survey World Energy Assessment Team, 2000). In each province, the USGS defined Total Petroleum Systems, and Assessment Units in each Total Petroleum System, and then quantitatively estimated the undiscovered conventional oil and gas resources. Of the eight global regions studied by the USGS, the Arabian Peninsula portion of the Middle East region was estimated to contain the greatest volumes of undiscovered oil and gas. The Lower Silurian Qusaiba Member of the Qalibah Formation is the source rock for some of the most important Total Petroleum Systems of the Middle East region. For example, the sources of the gas in the supergiant North field of Qatar and Iran and recent giant light oil discoveries in central Saudi Arabia were largely organic-rich, Qusaiba marine mudstones.

Cryptic Disc Structures Resembling Ediacaran Discoidal Fossils from the Lower Silurian Hellefjord Schist, Arctic Norway

PubMed Central

MacGabhann, Breandán A.; Kirkland, Brian L.; Daly, J. Stephen

2016-01-01

The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred basal conglomerate to this formation must be part of an older stratigraphic element, as it is cross-cut by a 546 ± 4 Ma pegmatite. These results confirm that the Hellefjord Schist is separated from underlying older Proterozoic rocks by a thrust. It has previously been argued that the Cambrian Substrate Revolution destroyed the ecological niches that the Neoproterozoic frond-holdfasts organisms occupied. However, the discovery of these fossils in Silurian rocks demonstrates that the environment and substrate must have been similar enough to Neoproterozoic settings that frond-holdfast bodyplans were still ecologically viable some hundred million years later. PMID:27783643

Bagua Basin: an Archive of the Tectonic Evolution of the Northern Peruvian Andes.

NASA Astrophysics Data System (ADS)

Moreno, F.; Garzione, C. N.; George, S. W. M.; Williams, L. A.

2017-12-01

The Cenozoic sediments of the intermontane Bagua Basin contain the record of the orogenic history of the northern Peruvian Andes. This Andean segment is constituted by a relatively narrow and low elevation orogen compared to the Central Andean Plateau. Understanding the similarities and differences of the tectonic evolution between these two provinces provides insights into the processes that govern the evolution of fold-thrust belts and orogenic plateaus. We use stratigraphic and sedimentologic field observations, detrital zircons (DZ) provenance analysis and stable isotopes paleoenvironmental analysis to reconstruct the regional tectonic history. Our results reveal the evolution of Bagua Basin, as a foreland basin related to the Andean belt since late Cretaceous time. The late Cretaceous Fundo el Triunfo Fm. records shelf deposits in a backbulge setting associated with a distant orogenic load. The Early Cretaceous DZ signature contained in these deposits reveal the early exhumation of Mesozoic rocks in the forebulge. The Paleocene fluvial deposits of the Rentema Fm. and the estuarine deposits of the Eocene Series record the transition to a forebulge setting. The Jurassic and Triassic DZ signature contained in the Paleocene and Eocene deposits reveal the continued exhumation of Mesozoic rocks during forebulge migration. The fluvial-floodplain succession of the Sambimera Fm. overlays the Eocene Series, recording intermediate and proximal foredeep deposition. Sambimera deposits contains sin-depositional Cenozoic DZ populations that reveal strong magmatism in the west. Comparison of δ18O and δ13C values from Sambimera and Rentema pedogenic carbonate nodules (δ18O -9‰ vs. -5‰ and δ13C -12.5‰ vs. -10‰) suggests that the Sambimera fluvial-floodplain system was more distal from the shoreline, based on the relatively negative δ18O values, and deposited in a drier climate, based on the relatively positive δ13C values. A four million year unconformity

Ichnology applied to sequence stratigraphic analysis of Siluro-Devonian mud-dominated shelf deposits, Paraná Basin, Brazil

NASA Astrophysics Data System (ADS)

Sedorko, Daniel; Netto, Renata G.; Savrda, Charles E.

2018-04-01

Previous studies of the Paraná Supersequence (Furnas and Ponta Grossa formations) of the Paraná Basin in southern Brazil have yielded disparate sequence stratigraphic interpretations. An integrated sedimentological, paleontological, and ichnological model was created to establish a refined sequence stratigraphic framework for this succession, focusing on the Ponta Grossa Formation. Twenty-nine ichnotaxa are recognized in the Ponta Grossa Formation, recurring assemblages of which define five trace fossil suites that represent various expressions of the Skolithos, Glossifungites and Cruziana ichnofacies. Physical sedimentologic characteristics and associated softground ichnofacies provide the basis for recognizing seven facies that reflect a passive relationship to bathymetric gradients from shallow marine (shoreface) to offshore deposition. The vertical distribution of facies provides the basis for dividing the Ponta Grossa Formation into three major (3rd-order) depositional sequences- Siluro-Devonian and Devonian I and II-each containing a record of three to seven higher-order relative sea-level cycles. Major sequence boundaries, commonly coinciding with hiatuses recognized from previously published biostratigraphic data, are locally marked by firmground Glossifungites Ichnofacies associated with submarine erosion. Maximum transgressive horizons are prominently marked by unbioturbated or weakly bioturbated black shales. By integrating observations of the Ponta Grossa Formation with those recently made on the underlying marginal- to shallow-marine Furnas Formation, the entire Paraná Supersequence can be divided into four disconformity-bound sequences: a Lower Silurian (Llandovery-Wenlock) sequence, corresponding to lower and middle units of the Furnas; a Siluro-Devonian sequence (?Pridoli-Early Emsian), and Devonian sequences I (Late Emsian-Late Eifelian) and II (Late Eifelian-Early Givetian). Stratigraphic positions of sequence boundaries generally coincide with

Immediate and delayed signal of slab breakoff in Oligo/Miocene Molasse deposits from the European Alps

PubMed Central

Schlunegger, Fritz; Castelltort, Sébastien

2016-01-01

High-resolution 32–20 Ma-old stratigraphic records from the Molasse foreland basin situated north of the Alps, and Gonfolite Lombarda conglomerates deposited on the southern Alpine margin, document two consecutive sedimentary responses - an immediate and delayed response - to slab breakoff beneath the central Alps c. 32–30 Ma ago. The first signal, which occurred due to rebound and surface uplift in the Alps, was a regional and simultaneous switch from basin underfill to overfill at 30 Ma paired with shifts to coarse-grained depositional environments in the foreland basin. The second signal, however, arrived several million years after slab breakoff and was marked by larger contributions of crystalline clasts in the conglomerates, larger clast sizes, larger sediment fluxes and shifts to more proximal facies. We propose that this secondary pulse reflects a delayed whiplash-type erosional response to surface uplift, where erosion and sediment flux became amplified through positive feedbacks once larger erosional thresholds of crystalline bedrock were exceeded. PMID:27510939

Silurian sponges and some associated fossils from the Heceta Limestone, Prince of Wales Island, southeastern Alaska

USGS Publications Warehouse

Rigby, J.K.; Rohr, D.M.; Blodgett, R.B.; Britt, B.B.

2008-01-01

A small faunule of hypercalcified agelasiid demosponges has been recovered from outcrops of the Silurian Heceta Formation on Prince of Wales Island in southeastern Alaska. Included are abundant Girtyocoeliana epiporata (Rigby and Potter, 1986), of the Girtyocoeliidae Finks and Rigby, 2004; fragments of Alaskaspongiella laminosa n. gen. and sp., Polyplacospongia nodosa n. gen. and sp., and Monolaminospongia gigantia n. gen. and sp., of the Auriculospongiidae Termier and Termier, 1977, and Cladospongia alaskensis n. gen. and sp., Virgulaspongia uniforma n. gen. and sp., and Stipespongia laminata n. gen. and sp. of the Preperonidellidae Finks and Rigby, 2004. Also included are a few fossils of uncertain taxonomic placement, including Turbospongia biperforata n. gen. and sp., along with a small, chambered, tubular fragment and several porous tubular stems that may be additional poriferans. Some isolated octactine-based heteractinid spicules were also recovered from the etched residues. Copyright ?? 2008, The Paleontological Society.

Detrital zircon U-Pb geochronology and stratigraphy of the Cretaceous Sanjiang Basin in NE China: Provenance record of an abrupt tectonic switch in the mode and nature of the NE Asian continental margin evolution

NASA Astrophysics Data System (ADS)

Zhang, Feng-Qi; Chen, Han-Lin; Batt, Geoffrey E.; Dilek, Yildirim; A, Min-Na; Sun, Ming-Dao; Yang, Shu-Feng; Meng, Qi-An; Zhao, Xue-Qin

2015-12-01

The age spectra obtained from 505 spots of detrital zircon U-Pb ages of five representative sandstone samples from the Sanjiang Basin in NE China point to a significant change in its provenance during the Coniacian-Santonian. The predominant detrital source for the Sanjiang Basin during the early Cretaceous was the Zhangguangcai Range magmatic belt and Jiamusi Block along its western and southern periphery, whereas it changed in the late Cretaceous to its eastern periphery. The timing of these inferred changes in the detrital source regions and drainage patterns nearly coincide with the age of a regional unconformity in and across the basin. The time interval of non-deposition and unconformity development was coeval with a transitional period between an extensional tectonic regime in the early Cretaceous and a contractional deformation episode in the late Cretaceous. The Sanjiang Basin evolved during this time window from a backarc to a foreland basin. The migration of the coastal orogenic belt and the fold and thrust belt development farther inland during the late Cretaceous marked the onset of regional-scale shortening and surface uplift in the upper plate of a flat (or very shallow-dipping) subduction zone. The stratigraphic record, the detrital source and geochronology of the basinal strata, and the internal structure of the Sanjiang Basin present, therefore, an important record of a tectonic switch in the nature of continental margin evolution of Northeast Asia during the late Mesozoic.

Chapter 27: Geology and petroleum potential of the north and east margins of the Siberian Craton, north of the Arctic Circle

USGS Publications Warehouse

Klett, T.R.; Wandrey, C.J.; Pitman, Janet K.

2011-01-01

The Siberian Craton consists of crystalline rocks and superimposed Precambrian sedimentary rocks deposited in rift basins. Palaeozoic rocks, mainly carbonates, were deposited along the margins of the craton to form an outwardly younger concentric pattern that underlies an outward-thickening Mesozoic sedimentary section. The north and east margins of the Siberian Craton subsequently became foreland basins created by compressional deformation during collision with other tectonic plates. The Tunguska Basin developed as a Palaeozoic rift/sag basin over Proterozoic rifts. The geological provinces along the north and east margins of the Siberian Craton are immature with respect to exploration, so exploration-history analysis alone cannot be used for assessing undiscovered petroleum resources. Therefore, other areas from around the world having greater petroleum exploration maturity and similar geological characteristics, and which have been previously assessed, were used as analogues to aid in this assessment. The analogues included those of foreland basins and rift/sag basins that were later subjected to compression. The US Geological Survey estimated the mean undiscovered, technically recoverable conventional petroleum resources to be approximately 28 billion barrels of oil equivalent, including approximately 8 billion barrels of crude oil, 103 trillion cubic feet of natural gas and 3 billion barrels of natural gas liquids. ?? 2011 The Geological Society of London.

Paleozoic fluid history of the Michigan Basin: Evidence from dolomite geochemistry in the Middle Ordovician St. Peter Sandstone

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

Winter, B.L.; Johnson, C.M.; Simo, J.A.

1995-04-03

The isotope (Sr and O) and elemental (Mg, Ca, Mn, Fe, and Sr) compositions of the various dolomites in the Middle Ordovician St. Peter Sandstone in the Michigan Basin are determined and the variations are modeled in terms of fluid-rock interaction or as mixing relations. These geochemical models, combined with the paragenetic sequence of the dolomites and late anhydrite cement, suggest the existence of at least four distinct diagenetic fluids in the St. Peter Sandstone during the paleozoic. Fluid 1 has a composition consistent with a modified older (pre-Middle Ordovician) seawater origin, which indicates that the flow path for thismore » fluid had a major upward component. This fluid resulted in the first and volumetrically most important burial dolomitization event, producing dolomite in both carbonate and quartz sandstone lithofacies in the St. Peter Sandstone. Fluid 2 has a composition consistent with a modified Middle to early Late Ordovician seawater origin, suggesting a major downward component for fluid flow. Fluid 2 produced dolomite cement in the carbonate lithofacies that postdates Fluid 1 dolomite. The composition of Fluid 3 is best interpreted to reflect a heated, deep basinal brine that had previously interacted with the K-feldspar-rich rocks near the Cambrian-Precambrian unconformity in the Michigan Basin, indicating a major upward component for fluid flow. Fluid 3 produced dolomite cement in quartz sandstone lithofacies that postdates Fluid 1 dolomite. Fluid 4 resulted in precipitation of late anhydrite in fractures. The {sup 87}Sr/{sup 86}Sr ratio of the anhydrite is consistent with Fluid 4 originating as a dilute fluid that interacted extensively with Silurian gypsum in the Michigan Basin; this indicates that the flow path of Fluid 4 had a major downward component.« less

Crustal Structure of the Andean Foreland in Northern Argentina: Results From Data-Integrative Three-Dimensional Density Modeling

NASA Astrophysics Data System (ADS)

Meeßen, C.; Sippel, J.; Scheck-Wenderoth, M.; Heine, C.; Strecker, M. R.

2018-02-01

Previous thermomechanical modeling studies indicated that variations in the temperature and strength of the crystalline crust might be responsible for the juxtaposition of domains with thin-skinned and thick-skinned crustal deformation along strike the foreland of the central Andes. However, there is no evidence supporting this hypothesis from data-integrative models. We aim to derive the density structure of the lithosphere by means of integrated 3-D density modeling, in order to provide a new basis for discussions of compositional variations within the crust and for future thermal and rheological modeling studies. Therefore, we utilize available geological and geophysical data to obtain a structural and density model of the uppermost 200 km of the Earth. The derived model is consistent with the observed Bouguer gravity field. Our results indicate that the crystalline crust in northern Argentina can be represented by a lighter upper crust (2,800 kg/m3) and a denser lower crust (3,100 kg/m3). We find new evidence for high bulk crustal densities >3,000 kg/m3 in the northern Pampia terrane. These could originate from subducted Puncoviscana wackes or pelites that ponded to the base of the crystalline crust in the late Proterozoic or indicate increasing bulk content of mafic material. The precise composition of the northern foreland crust, whether mafic or felsic, has significant implications for further thermomechanical models and the rheological behavior of the lithosphere. A detailed sensitivity analysis of the input parameters indicates that the model results are robust with respect to the given uncertainties of the input data.

Structure, paleogeographic inheritance, and deformation history of the southern Atlas foreland fold and thrust belt of Tunisia

NASA Astrophysics Data System (ADS)

SaïD, Aymen; Baby, Patrice; Chardon, Dominique; Ouali, Jamel

2011-12-01

Structural analysis of the southern Tunisian Atlas was carried out using field observation, seismic interpretation, and cross section balancing. It shows a mix of thick-skinned and thin-skinned tectonics with lateral variations in regional structural geometry and amounts of shortening controlled by NW-SE oblique ramps and tear faults. It confirms the role of the Late Triassic-Early Jurassic rifting inheritance in the structuring of the active foreland fold and thrust belt of the southern Tunisian Atlas, in particular in the development of NW-SE oblique structures such as the Gafsa fault. The Late Triassic-Early Jurassic structural pattern is characterized by a family of first-order NW-SE trending normal faults dipping to the east and by second-order E-W trending normal faults limiting a complex system of grabens and horsts. These faults have been inverted during two contractional tectonic events. The first event occurred between the middle Turonian and the late Maastrichtian and can be correlated with the onset of the convergence between Africa and Eurasia. The second event corresponding to the principal shortening tectonic event in the southern Atlas started in the Serravalian-Tortonian and is still active. During the Neogene, the southern Atlas foreland fold and thrust belt propagated on the evaporitic décollement level infilling the Late Triassic-Early Jurassic rift. The major Eocene "Atlas event," described in hinterland domains and in eastern Tunisia, did not deform significantly the southern Tunisian Atlas, which corresponded in this period to a backbulge broad depozone.

Orogenic front propagation in the basement involved Malargüe fold and thrust belt, Neuquén Basin, (Argentina)

NASA Astrophysics Data System (ADS)

Branellec, Matthieu; Nivière, Bertrand; Callot, Jean-Paul; Ringenbach, Jean-Claude

2015-04-01

The Malargüe fold and thrust belt (MFTB) and the San Rafael Block (SRB) are located in the northern termination of the Neuquén basin in Argentina. This basin is a wide inverted intracratonic sag basin with polyphased evolution controlled at large scale by the dynamic of the Pacific subduction. By late Triassic times, narrow rift basins developed and evolved toward a sag basin from middle Jurassic to late Cretaceous. From that time on, compression at the trench resulted in various shortening pulses in the back-arc area. Here we aim to analyze the Andean system at 35°S by comparing the Miocene structuration in the MFTB and the current deformation along the oriental border or the San Rafael Block. The main structuration stage in the MFTB occurred by Miocene times (15 to 10 Ma) producing the principal uplift of the Andean Cordillera. As shown by new structural cross sections, Triassic-early Jurassic rift border faults localized the Miocene compressive tectonics. Deformation is compartmentalized and does not exhibit a classical propagation of homogeneous deformation sequence expected from the critical taper theory. Several intramontane basins in the hangingwall of the main thrusts progressively disconnected from the foreland. In addition, active tectonics has been described in the front of the MFTB attesting for the on-going compression in this area. 100 km farther to the east, The San Rafael Block, is separated from the MFTB by the Rio Grande basin. The SRB is mostly composed of Paleozoic terranes and Triassic rift-related rocks, overlain by late Miocene synorogenic deposits. The SRB is currently uplifted along its oriental border along several active faults. These faults have clear morphologic signatures in Quaternary alluvial terraces and folded Pleistocene lavas. As in the MFTB, the active deformation localization remains localized by structural inheritance. The Andean system is thus evolving as an atypical orogenic wedge partly by frontal accretion at the front

Paleozoic oil/gas shale reservoirs in southern Tunisia: An overview

NASA Astrophysics Data System (ADS)

Soua, Mohamed

2014-12-01

During these last years, considerable attention has been given to unconventional oil and gas shale in northern Africa where the most productive Paleozoic basins are located (e.g. Berkine, Illizi, Kufra, Murzuk, Tindouf, Ahnet, Oued Mya, Mouydir, etc.). In most petroleum systems, which characterize these basins, the Silurian played the main role in hydrocarbon generation with two main 'hot' shale levels distributed in different locations (basins) and their deposition was restricted to the Rhuddanian (Lllandovery: early Silurian) and the Ludlow-Pridoli (late Silurian). A third major hot shale level had been identified in the Frasnian (Upper Devonian). Southern Tunisia is characterized by three main Paleozoic sedimentary basins, which are from North to South, the southern Chotts, Jeffara and Berkine Basin. They are separated by a major roughly E-W trending lower Paleozoic structural high, which encompass the Mehrez-Oued Hamous uplift to the West (Algeria) and the Nefusa uplift to the East (Libya), passing by the Touggourt-Talemzane-PGA-Bou Namcha (TTPB) structure close to southern Tunisia. The forementioned major source rocks in southern Tunisia are defined by hot shales with elevated Gamma ray values often exceeding 1400 API (in Hayatt-1 well), deposited in deep water environments during short lived (c. 2 Ma) periods of anoxia. In the course of this review, thickness, distribution and maturity maps have been established for each hot shale level using data for more than 70 wells located in both Tunisia and Algeria. Mineralogical modeling was achieved using Spectral Gamma Ray data (U, Th, K), SopectroLith logs (to acquire data for Fe, Si and Ti) and Elemental Capture Spectroscopy (ECS). The latter technique provided data for quartz, pyrite, carbonate, clay and Sulfur. In addition to this, the Gamma Ray (GR), Neutron Porosity (ΦN), deep Resistivity (Rt) and Bulk Density (ρb) logs were used to model bulk mineralogy and lithology. Biostratigraphic and complete

Late Cenozoic Deformation in the Western Tarim Basin, NW China

NASA Astrophysics Data System (ADS)

Thompson, J. A.; Burbank, D. W.; Chen, J.; Li, T.

2009-12-01

The Tian Shan in NW China is one of the most active regions of intracontinental deformation in the world, accommodating a large fraction (~40%) of the shortening from the Indo-Eurasian collision. The western Tarim Basin, situated between the southern Tian Shan and Pamir Mountains, manifests this deformation through a series of east-west trending fault-related folds that have formed during the late Cenozoic. Previous studies in this region have focused on the kinematics, style, and timing of detachment folds related to folding within the foreland basin of the southern Tian Shan. In contrast, this study focuses on the deformation caused by fault-propagation folding resulting from the northward movement of the Pamir. The rates of deformation are calculated using a combination of optically stimulated luminescence (OSL) ages, structural mapping and differential GPS surveys of fault scarps and deformed terrace surfaces crossing active folds. OSL dating provides the time since the sediment was last exposed to daylight, i.e., time since burial. Consequently, OSL is useful for dating the abandonment of terrace surfaces due to tectonic (fold growth) or climatic events. OSL quartz samples were collected from silt lenses within gravel topping the terraces. Most of the quartz OSL signals are weak, thus several grain sizes (silt (4-11 µm, 8-15 µm) and sand (90-125 µm)) were analyzed and different integrations of the shine-down curves were explored to calculate equivalent doses. The implications for different equivalent doses and ages on the calculation of rates of deformation are also addressed.

Thick-skinned tectonics within the intracontinental easternmost Atlas foreland-and-thrust belt (Tunisia): Meso-Cenozoic kinematics and implications for regional geodynamics

NASA Astrophysics Data System (ADS)

Belkhiria, W.; Boussiga, H.; Inoubli, M. H.

2017-05-01

The transition zone between western and central Mediterranean domains presents a key area to investigate kinematic interactions within the adjacent orogen systems such as the easternmost Atlas foreland-and-thrust belt. Gravity and seismic data revealed a highly structured basement, characterizing a series of structural highs and lows delimited by high-angle N-S, E-W, and NW-SE extensional faults. This basement architecture is inherited from successive extensional events related to the openings of the Triassic-Early Cretaceous Tethys oceans (i.e., Alpine Tethys, Ligurian Tethys, and Mesogea). Throughout this period, this mosaic of continental blocks significantly controlled the thickness and facies distributions. Early stages of diapirism took place along these basement faults and allowed maximum subsidence in minibasins revealed by the development of growth strata. In response to the Late Cretaceous-Eocene shortenings, these extensional faults have been reactivated as trasnpressional shear zones, giving rise to narrow pop-up structures. In addition, gravity modeling indicates crustal thinning and deep-rooted faults affecting the crust south of the Zaghouan Thrust and along E-W transfer zones. From the late Miocene, a drastic change in the stress regime is attributed to the effect of the adjacent Sicily channel on the study area. This promotes crustal thinning, basin subsidence, and channeling up of mantle-derived helium along lithospheric-scale weak zones. Our results give rise to new insights into the reactivation of inherited weakness zones of southern Tethys margin in response to the complex interaction between African and Eurasian plates accommodated by subduction, rollback, collision, and slab segmentation.

Zircon (U-Th)/He evidence for pre-Eocene orogenic exhumation of eastern North Pyrenean massifs, France

NASA Astrophysics Data System (ADS)

Ternois, Sébastien; Vacherat, Arnaud; Pik, Raphaël; Ford, Mary; Tibari, Bouchaïb

2017-04-01

Orogens and their associated foreland basins are considered as part of a single dynamic system evolving from an early, non equilibrated, growth stage to a late, mature, steady-state stage. Most of our understanding in foreland basins, in particular early convergence-stage deposition, comes from the subducting plate, so that the classic paradigm for foreland basins is the pro-wedge. Models that clearly depict the relationship between erosion of the orogenic wedge and sedimentation into its associated foreland basin only focus on the late post-orogenic phase. Relatively little is known and understood about the very long phase of initiation of orogenesis. In the doubly wedged Pyrenean orogen, where we know and understand relatively little about how the early retro-wedge developed, the record of the onset of orogenic denudation from massifs is quite limited, not only in time but also in space. As part of the OROGEN project funded by TOTAL and the BRGM, this study presents first single-grain zircon (U-Th)/He data from two Palaeozoic massifs of the external Northern Pyrenean Zone, the Agly and Salvezines massifs. It aims at constraining the exhumation history of eastern Pyrenean massifs and understanding what is their significance for early orogenic wedge growth. The Pyrenean orogeny was generated from end Santonian (84 Ma) to Oligocene-Miocene due to convergence of the Iberian and European plates. Aquitaine foreland basin history (Ariège region) indicates that convergence took place in two phases, Campanian to Maastrichian and Eocene, separated by a quiet Paleocene phase. Yet, only Eocene cooling events are recorded by low-temperature thermochronometers in the central Pyrenean massifs (Arize and Trois-Seigneurs). Nine bedrock samples were collected along a WNW-ESE traverse (Salvezines and Saint-Arnac granites, Belesta-Caramany gneisses) and analysed for ZHe dating. Zircon (U-Th)/He data for the Agly and Salvezines massifs, together with forward modelling of data for

Association of orogenic activity with the Ordovician radiation of marine life

NASA Technical Reports Server (NTRS)

Miller, A. I.; Mao, S.

1995-01-01

The Ordovician radiation of marine life was among the most substantial pulses of diversification in Earth history and coincided in time with a major increase in the global level of orogenic activity. To investigate a possible causal link between these two patterns, the geographic distributions of 6576 individual appearances of Ordovician vician genera around the world were evaluated with respect to their proximity to probable centers of orogeny (foreland basins). Results indicate that these genera, which belonged to an array of higher taxa that diversified in the Middle and Late Ordovician (trilobites, brachiopods, bivalves, gastropods, monoplacophorans), were far more diverse in, and adjacent to, foreland basins than they were in areas farther removed from orogenic activity (carbonate platforms). This suggests an association of orogeny with diversification at that time.

Lower and lower Middle Pennsylvanian fluvial to estuarine deposition, central Appalachian basin: Effects of eustasy, tectonics, and climate

USGS Publications Warehouse

Greb, S.F.; Chesnut, D.R.

1996-01-01

Interpretations of Pennsylvanian sedimentation and peat accumulation commonly use examples from the Appalachian basin because of the excellent outcrops and large reserve of coal (>100 billion metric tons) in the region. Particularly controversial is the origin of Lower and lower Middle Pennsylvanian quartzose sandstones; beach-barrier, marine-bar, tidalstrait, and fluvial models all have been applied to a series of sand bodies along the western outcrop margin of the basin. Inter-pretations of these sandstones and their inferred lateral relationships are critical for understanding the relative degree of eustatic, tectonic, and climatic controls on Early Pennsylvanian sedimentation. Cross sections utilizing >1000 subsurface records and detailed sedimentological analysis of the Livingston Conglomerate, Rockcastle Sandstone, Corbin Sandstone, and Pine Creek sandstone (an informal member) of the Breathitt Group were used to show that each of the principal quartzose sandstones on the margin of the central Appalachian basin contains both fluvial and marginal marine facies. The four sandstones are fluvially dominated and are inferred to represent successive bed-load trunk systems of the Appalachian foreland. Base-level rise and an associated decrease in extra-basinal sediment at the end of each fluvial episode led to the development of local estuaries and marine reworking of the tops of the sand belts. Each of the sand belts is capped locally by a coal, regardless of whether the upper surfaces of the sand belts are of fluvial or estuarine origin, suggesting allocyclic controls on deposition. Peats were controlled by a tropical ever-wet climate, which also influenced sandstone composition through weathering of stored sands in slowly aggrading braidplains. Recurrent stacking of thick, coarse-grained, fluvial deposits with extra-basinal quartz pebbles; dominance of bed-load fluvial-lowstand deposits over mixed-load, estuarine-transgressive deposits; thinning of sand belts

Paleomagnetic constraints on the Cenozoic kinematic evolution of the Pamir plateau from the Western Kunlun Shan foreland

NASA Astrophysics Data System (ADS)

Li, Zhenyu; Ding, Lin; Lippert, Peter C.; Wei, Honghong

2013-09-01

Thick Cenozoic marine and terrestrial sediments are widely distributed along the perimeter of the Pamir plateau and provide valuable information on the kinematic evolution of the region. Here, we report new biostratigraphic and paleomagnetic results from the piedmont of the Western Kunlun Shan to constrain the magnitude and timing of vertical-axis rotations along the eastern margin of the Pamir. Sampling sites were selected by rock formations and ages, which are based on previous field mapping and on litholostratigraphic and biostratigraphic work presented here. Thermomagnetic analysis, step-wise thermal demagnetization behavior, and positive field tests all suggest that the characteristic remanent magnetization (ChRM) directions most probably have a primary detrital and chemical origin. Our results indicate variable, minor, but in some intervals significant vertical axis rotations with respect to a stable Asian reference frame. This pattern of rotations is similar to paleomagnetic data reported in previously published studies from the Eastern Pamir foreland. In contrast, published paleomagnetic data from the Western Pamir foreland consistently indicate significant CCW rotations within that region. Collectively, these results challenge simple oroclinal bending models for the origin of the Pamir salient, and instead are more consistent with an asymmetric "half-orocline" kinematic model in which the curvature of the Western Pamir is the product of a combination of lithospheric bending of an originally quasi-linear mountain belt and radial thrusting, and the subdued curvature of the eastern edge of the plateau is the result of lateral translation of the Pamir plateau northward past Tibet and Tarim along the Kashgar-Yecheng transfer system. Our results are consistent with activity on the Kashgar-Yecheng transfer system in the Early Miocene.

The Lower Silurian Osmundsberg K-bentonite. Part I: Stratigraphic position, distribution, and palaeogeographic significance

USGS Publications Warehouse

Bergstrom, Stig M.; Huff, W.D.; Kolata, Dennis R.

1998-01-01

A large number of Lower Silurian (Llandovery) K-bentonite beds have been recorded from northwestern Europe, particularly in Baltoscandia and the British Isles, but previous attempts to trace single beds regionally have yielded inconclusive results. The present study suggests that based on its unusual thickness, stratigraphic position and trace element geochemistry, one Telychian ash bed, the Osmundsberg K-bentonite, can be recognized at many localities in Estonia, Sweden and Norway and probably also in Scotland and Northern Ireland. This bed, which is up to 115 cm thick, is in the lower-middle turriculatus Zone. The stratigraphic position, thickness variation and geographic distribution of the Osmundsberg K-bentonite are illustrated by means of 12 selected Llandovery successions in Sweden, Estonia, Norway, Denmark, Scotland and Northern Ireland. In Baltoscandia, the Osmundsberg K-bentonite shows a trend of general thickness increase in a western direction suggesting that its source area was located in the northern Iapetus region between Baltica and Laurentia. Because large-magnitude ash falls like the one that produced the Osmundsberg K-bentonite last at most a few weeks, such an ash bed may be used as a unique time-plane for a variety of regional geological and palaeontological studies.

Tectono-sedimentary evolution of salt controlled minibasin in a fold-an-thrust belt setting Example from the Sivas Basin Turkey and physical model.

NASA Astrophysics Data System (ADS)

Kergaravat, Charlie; Ribes, Charlotte; Darnault, Romain; Callot, Jean-Paul; Ringenbach, Jean-Claude

2017-04-01

The aim of this study is to present the influence of regional shortening on the evolution of a minibasin province and the associated foldbelt geometry based on a natural example, the Sivas Basin, then compared to a physical experiment. The Sivas Basin in the Central Anatolian Plateau (Turkey) is a foreland fold-and-thrust belt, displaying in the central part a typical wall and basin province characterized by spectacularly exposed minibasins, separated by continuous steep-flanked walls and diapirs over a large area (45x25 km). The advance of the orogenic wedge is expressed within the second generation of minibasins by a shortening-induced squeezing of diapirs. Network of walls and diapirs evolve form polygonal to linear pattern probably induced by the squeezing of pre-existing evaporite walls and diapirs, separating linear primary minibasins. From base to top of secondary minibasins, halokinetic structures seem to evolve from small-scale objects along diapir flanks, showing hook and wedges halokinetic sequences, to large stratigraphic wedging, megaflap and salt sheets. Minibasins show progressively more linear shape at right angle to the regional shortening and present angular unconformities along salt structures related to the rejuvenation of pre-existing salt diapirs and walls probably encouraged by the shortening tectonic regime. The advance of the fold-and-thrust belts during the minibasins emplacement is mainly expressed during the late stage of minibasins development by a complex polygonal network of small- and intermediate-scale tectonic objects: (1) squeezed evaporite walls and diapirs, sometimes thrusted forming oblique or vertical welds, (2) allochthonous evaporite sheets, (3) thrusts and strike-slip faults recording translation and rotation of minibasins about vertical axis. Some minibasins are also tilted, with up to vertical position, associated with both the salt expulsion during minibasins sinking, recorded by large stratigraphic wedge, and the late

Determining the source and genetic fingerprint of natural gases using noble gas geochemistry: a northern Appalachian Basin case study

USGS Publications Warehouse

Hunt, Andrew G.; Darrah, Thomas H.; Poreda, Robert J.

2012-01-01

Silurian and Devonian natural gas reservoirs present within New York state represent an example of unconventional gas accumulations within the northern Appalachian Basin. These unconventional energy resources, previously thought to be noneconomically viable, have come into play following advances in drilling (i.e., horizontal drilling) and extraction (i.e., hydraulic fracturing) capabilities. Therefore, efforts to understand these and other domestic and global natural gas reserves have recently increased. The suspicion of fugitive mass migration issues within current Appalachian production fields has catalyzed the need to develop a greater understanding of the genetic grouping (source) and migrational history of natural gases in this area. We introduce new noble gas data in the context of published hydrocarbon carbon (C1,C2+) (13C) data to explore the genesis of thermogenic gases in the Appalachian Basin. This study includes natural gases from two distinct genetic groups: group 1, Upper Devonian (Marcellus shale and Canadaway Group) gases generated in situ, characterized by early mature (13C[C1  C2][13C113C2]: –9), isotopically light methane, with low (4He) (average, 1  103 cc/cc) elevated 4He/40Ar and 21Ne/40Ar (where the asterisk denotes excess radiogenic or nucleogenic production beyond the atmospheric ratio), and a variable, atmospherically (air-saturated–water) derived noble gas component; and group 2, a migratory natural gas that emanated from Lower Ordovician source rocks (i.e., most likely, Middle Ordovician Trenton or Black River group) that is currently hosted primarily in Lower Silurian sands (i.e., Medina or Clinton group) characterized by isotopically heavy, mature methane (13C[C1 – C2] [13C113C2]: 3), with high (4He) (average, 1.85  103 cc/cc) 4He/40Ar and 21Ne/40Ar near crustal production levels and elevated crustal noble gas content (enriched 4He,21Ne, 40Ar). Because the release of each crustal noble gas (i.e., He, Ne, Ar

Publications - GMC 398 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 398 Publication Details Title: Porosity and permeability, core sample photos from five Cook from five Cook Inlet basin wells: Deep Creek #1-RD, Foreland Channel State #1-A, Redoubt Unit #5A

Geologic controls on thermal maturity patterns in Pennsylvanian coal-bearing rocks in the Appalachian basin

USGS Publications Warehouse

Ruppert, L.F.; Hower, J.C.; Ryder, R.T.; Levine, J.R.; Trippi, M.H.; Grady, W.C.

2010-01-01

Thermal maturation patterns of Pennsylvanian strata in the Appalachian basin were determined by compiling and contouring published and unpublished vitrinite reflectance (VR) measurements. VR isograd values range from 0.6% in eastern Ohio and eastern Kentucky (western side of the East Kentucky coal field) to greater than 5.5% in eastern Pennsylvania (Southern Anthracite field, Schuylkill County), corresponding to ASTM coal rank classes of high volatile C bituminous to meta-anthracite. VR isograds show that thermal maturity of Pennsylvanian coals generally increases from west to east across the basin. The isograds patterns, which are indicative of maximum temperatures during burial, can be explained by variations in paleodepth of burial, paleogeothermal gradient, or a combination of both. However, there are at least four areas of unusually high-rank coal in the Appalachian basin that depart from the regional trends and are difficult to explain by depth of burial alone: 1) a west-northwestward salient centered in southwestern Pennsylvania; 2) an elliptically-shaped, northeast-trending area centered in southern West Virginia and western Virginia; 3) the eastern part of Black Warrior coal field, Alabama; and 4) the Pennsylvania Anthracite region, in eastern Pennsylvania. High-rank excursions in southwest Pennsylvania, the Black Warrior coal field, and the Pennsylvania Anthracite region are interpreted here to represent areas of higher paleo-heat flow related to syntectonic movement of hot fluids towards the foreland, associated with Alleghanian deformation. In addition to higher heat flow from fluids, the Pennsylvania Anthracite region also experienced greater depth of burial. The high-rank excursion in southwest Virginia was probably primarily controlled by overburden thickness, but may also have been influenced by higher geothermal gradients.

Using U-Pb Detrital Zircon to Identify Evolution of Sediment Drainage in the South Central Pyrenean Foreland Basin, Spain

NASA Astrophysics Data System (ADS)

Clark, J. D.; Stockli, D. F.; McKay, M. P.; Thomson, K.; Puigdefabregas, C.; Castelltort, S.; Dykstra, M.; Fildani, A.

2014-12-01

Until the 2011 Mw9.0 Tohoku earthquake, the role of earthquakes as agents of sediment dispersal and deposition at erosional trenches was largely under-appreciated. A series of cruises carried out after the 2011 event has revealed a variety of unsuspected sediment transport mechanisms, such as tsunami-triggered sheet turbidites, suggesting that great earthquakes may in fact be important agents for dispersing sediments across trench slopes. To complement these observational data, we have modeled the pathways of sediments across the trench slope based on bathymetric grids. Our approach assumes that transport direction is controlled by slope azimuth only, and ignores obstacles smaller than 0.6-1 km; these constraints are meant to approximate the behavior of turbidites. Results indicate that (1) most pathways issued from the upper slope terminate near the top of the small frontal wedge, and thus do not reach the trench axis; (2) in turn, sediments transported to the trench axis are likely derived from the small frontal wedge or from the subducting Pacific plate. These results are consistent with the stratigraphy imaged in seismic profiles, which reveals that the slope apron does not extend as far as the frontal wedge, and that the thickness of sediments at the trench axis is similar to that of the incoming Pacific plate. We further applied this modeling technique to the Cascadia, Nankai, Middle-America, and Sumatra trenches. Where well-defined canyons carve the trench slopes, sediments from the upper slope may routinely reach the trench axis (e.g., off Costa Rica and Cascadia). In turn, slope basins that are isolated from the canyons drainage systems must mainly accumulate locally-derived sediments. Therefore, their turbiditic infill may be diagnostic of seismic activity only - and not from storm or flood activity. If correct, this would make isolated slope basins ideal targets for paleoseismological investigation.

Assessment of Appalachian Basin Oil and Gas Resources: Utica-Lower Paleozoic Total Petroleum System

USGS Publications Warehouse

Ryder, Robert T.

2008-01-01

The Utica-Lower Paleozoic Total Petroleum System (TPS) is an important TPS identified in the 2002 U.S. Geological Survey (USGS) assessment of undiscovered, technically recoverable oil and gas resources in the Appalachian basin province (Milici and others, 2003). The TPS is named for the Upper Ordovician Utica Shale, which is the primary source rock, and for multiple lower Paleozoic sandstone and carbonate units that are the important reservoirs. Upper Cambrian through Upper Silurian petroleum-bearing strata that constitute the Utica-Lower Paleozoic TPS thicken eastward from about 2,700 ft at the western margin of the Appalachian basin to about 12,000 ft at the thrust-faulted eastern margin of the Appalachian basin. The Utica-Lower Paleozoic TPS covers approximately 170,000 mi2 of the Appalachian basin from northeastern Tennessee to southeastern New York and from central Ohio to eastern West Virginia. The boundary of the TPS is defined by the following geologic features: (1) the northern boundary (from central Ontario to northeastern New York) extends along the outcrop limit of the Utica Shale-Trenton Limestone; (2) the northeastern boundary (from southeastern New York, through southeastern Pennsylvania-western Maryland-easternmost West Virginia, to northern Virginia) extends along the eastern limit of the Utica Shale-Trenton Limestone in the thrust-faulted eastern margin of the Appalachian basin; (3) the southeastern boundary (from west-central and southwestern Virginia to eastern Tennessee) extends along the eastern limit of the Trenton Limestone in the thrust-faulted eastern margin of the Appalachian basin; (4) the southwestern boundary (from eastern Tennessee, through eastern Kentucky, to southwestern Ohio) extends along the approximate facies change from the Trenton Limestone with thin black shale interbeds (on the east) to the equivalent Lexington Limestone without black shale interbeds (on the west); (5) the northern part of the boundary in southwestern Ohio

Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

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

G. Michael Grammer

2006-09-30

This topical report covers the year 2 of the subject 3-year grant, evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). The characterization of select dolomite reservoirs has been the major focus of our efforts in Phase II/Year 2. Fields have been prioritized based upon the availability of rock data for interpretation of depositional environments, fracture density and distribution as well as thin section, geochemical, and petrophysical analyses. Structural mapping and log analysismore » in the Dundee (Devonian) and Trenton/Black River (Ordovician) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault related NW-SE and NE-SW structural trends. A high temperature origin for much of the dolomite in the 3 studied intervals (based upon initial fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. For the Niagaran (Silurian), a comprehensive high resolution sequence stratigraphic framework has been developed for a pinnacle reef in the northern reef trend where we had 100% core coverage throughout the reef section. Major findings to date are that facies types, when analyzed at a detailed level, have direct links to reservoir porosity and permeability in these dolomites. This pattern is consistent with our original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at

Potential for technically recoverable unconventional gas and oil resources in the Polish-Ukrainian Foredeep, Poland, 2012

USGS Publications Warehouse

Gautier, Donald L.; Pitman, Janet K.; Charpentier, Ronald R.; Cook, Troy; Klett, Timothy R.; Schenk, Christopher J.

2012-01-01

Using a performance-based geological assessment methodology, the U.S. Geological Survey estimated mean volumes of 1,345 billion cubic feet of potentially technically recoverable gas and 168 million barrels of technically recoverable oil and natural gas liquids in Ordovician and Silurian age shales in the Polish- Ukrainian Foredeep basin of Poland.

87Sr/ 86Sr Concentrations in the Appalachian Basin: A Review

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

Mordensky, Stanley P.; Lieuallen, A. Erin; Verba, Circe

This document reviews 87Sr/ 86Sr isotope data across the Appalachian Basin from existing literature to show spatial and temporal variation. Isotope geochemistry presents a means of understanding the geochemical effects hydraulic fracturing may have on shallow ground substrates. Isotope fractionation is a naturally occurring phenomenon brought about by physical, chemical, and biological processes that partition isotopes between substances; therefore, stable isotope geochemistry allows geoscientists to understand several processes that shape the natural world. Strontium isotopes can be used as a tool to answer an array of geological and environmental inquiries. In some cases, strontium isotopes are sensitive to the introductionmore » of a non-native fluid into a system. This ability allows strontium isotopes to serve as tracers in certain systems. Recently, it has been demonstrated that strontium isotopes can serve as a monitoring tool for groundwater and surface water systems that may be affected by hydraulic fracturing fluids (Chapman et al., 2013; Kolesar Kohl et al., 2014). These studies demonstrated that 87Sr/ 86Sr values have the potential to monitor subsurface fluid migration in regions where extraction of Marcellus Shale gas is occurring. This document reviews publicly available strontium isotope data from 39 sample locations in the Appalachian Basin (Hamel et al., 2010; Chapman et al., 2012; Osborn et al., 2012; Chapman et al., 2013; Capo et al., 2014; Kolesar Kohl et al., 2014). The data is divided into two sets: stratigraphic (Upper Devonian/Lower Mississippi, Middle Devonian, and Silurian) and groundwater. ArcMap™ (ESRI, Inc.) was used to complete inverse distance weighting (IDW) analyses for each dataset to create interpolated surfaces in an attempt to find regional trends or variations in strontium isotopic values across the Appalachian Basin. 87Sr/ 86Sr varies up to ~ 0.011 across the Appalachian Basin, but the current publicly available data is

Fault reactivation by stress pattern reorganization in the Hyblean foreland domain of SE Sicily (Italy) and seismotectonic implications

NASA Astrophysics Data System (ADS)

Cultrera, Fabrizio; Barreca, Giovanni; Scarfì, Luciano; Monaco, Carmelo

2015-10-01

Between the October 2011 and the July 2012, several seismic swarms occurred in the Hyblean foreland domain of SE Sicily (Italy) along the Cavagrande Canyon, one of the most impressive fluvial incisions of Sicily. Despite the low magnitude of the events (main shock with M ~ 3.7), they represent the biggest strain release of the Hyblean area over the last 10 years. A careful waveform analysis of the earthquakes revealed that most of them form a family of "multiplets". These findings allow us to reconstruct the attitude of the accountable fault plane by interpolating their high-precision 3D location parameters into a GIS platform. A detailed morpho-structural analysis, performed at the ideal updip projection of the modeled plane, showed that during the Middle-Late Pleistocene the epicentral area has been deformed by a belt of extensional faults, a segment of which matches well with the computer-generated surface. Despite the field evidence, computed focal solutions support contrasting strike-slip kinematics on the same fault plane, clearly indicating a dextral shearing on this pre-existing normal fault. The seismic swarms nucleated on a small rupture area along a ~ 10 km long, NW-SE trending fault segment, that could be able to generate M ~ 6 earthquakes. Following our analysis and looking at seismicity distribution in the SE portion of Hyblean area, we assess that a stress pattern reorganization occurred all over the Hyblean foreland between the Late Pleistocene and present-day. Change in the trajectory of the max stress axes (from vertical to horizontal) seems to have involved a pre-existing large-scale fault configuration with considerable seismotectonic implications.

Late Devonian glacigenic and associated facies from the central Appalachian Basin, eastern United States

USGS Publications Warehouse

Brezinski, D.K.; Cecil, C.B.; Skema, V.W.

2010-01-01

Late Devonian strata in the eastern United States are generally considered as having been deposited under warm tropical conditions. However, a stratigraphically restricted Late Devonian succession of diamictite- mudstonesandstone within the Spechty Kopf and Rockwell Formations that extends for more than 400 km along depositional strike within the central Appalachian Basin may indicate other wise. This lithologic association unconformably overlies the Catskill Formation, where a 3- to 5-m-thick interval of deformed strata occurs immediately below the diamictite strata. The diamictite facies consists of several subfacies that are interpreted to be subglacial, englacial, supraglacial meltout, and resedimented deposits. The mudstone facies that overlies the diamictite consists of subfacies of chaotically bedded, clast-poor mudstone, and laminated mudstone sub facies that represent subaqueous proximal debris flows and distal glaciolacustrine rhythmites or varvites, respectively. The pebbly sandstone facies is interpreted as proglacial braided outwash deposits that both preceded glacial advance and followed glacial retreat. Both the tectonic and depositional frameworks suggest that the facies were deposited in a terrestrial setting within the Appalachian foreland basin during a single glacial advance and retreat. Regionally, areas that were not covered by ice were subject to increased rainfall as indicated by wet-climate paleosols. River systems eroded deeper channels in response to sea-level drop during glacial advance. Marine facies to the west contain iceborne dropstone boulders preserved within contemporaneous units of the Cleveland Shale Member of the Ohio Shale.The stratigraphic interval correlative with sea-level drop, climate change, and glacigenic succession represents one of the Appalachian Basin's most prolific oil-and gas-producing intervals and is contemporaneous with a global episode of sea-level drop responsible for the deposition of the Hangenberg Shale

Cretaceous combined structure in eastern Sichuan Basin, China

NASA Astrophysics Data System (ADS)

Wang, P.; Liu, S.

2009-12-01

Eastern Sichuan Basin is confined by two thin-skinned fold-thrust belt, NW-trending Southern Daba Shan (Shan=Mountain) (SDB) in the northeast and NNE- or NE-trending Western XueFeng Shan (WXF) in the southeast, which constitute two convergent salients convex to the inner basin respectively. Although many factors can lead to the formation of fold-thrust belt salients, the eastern Sichuan salients would be attributed to the combined structure (firstly nominated by Chinese geologist, Li Siguang), which means the interaction of two structural belts in the same period. By field surveying and geological map interpreting, we found that WXF deformation began in Late Jurassic along the eastern side of structral belt, where the synclines cored by Upper-Middle Jurassic rock. The initial time of SDB deformation remains poorly determined, however our palaeocurrent data of Lower Cretaceous rock in adjecent foreland basin indicate the provenance from northeast or east. Hence we considered the two fold-thrust belt started interactive in Late Jurassic and mainly combined during Cretaceous. In Early Cretaceous, the front belt of WXF salient arrived near KaiXian where NEE-trending arc-shape folds converged with the NWW-trending arc-shape folds of SDB.The two salients shaped like an westward "open mouth", east of which EW-trending folds of two structural belts juxtaposed. Particularly in the middle belt of WXF (FengJie - WuFeng) the earlier NEE-trending folds were refolded by later NNE-trending folds. We interpret the NEE-trending folds as the front belt of earlier (maybe Late Jurassic) WXF salient. When the two combined fold belts propagated westward together, the original NNE-trending front belt of WXF constrained by the front belt of SDB and formed the curved fold trend lines convex to NNW. Then as WXF deformation continued but SDB gradually terminated, the consequent NNE-trending folds could not be curved and would superpose on the earlier NEE-trending folds.In Late Cretaceous

Contributions of gravity and field data on the structural scheme updating of the Tellian domain and its foreland (Nefza-Bizerte region, northern Tunisia)

NASA Astrophysics Data System (ADS)

Essid, El Mabrouk; Kadri, Ali; Balti, Hadhemi; Gasmi, Mohamed; Zargouni, Fouad

2018-03-01

The Nefza-Bizerte region, eastern part of the Tunisian Alpine chain, covers the thrust sheets domain called the Tell and its Atlassic foreland. The deep structures under the Tellian thrust sheets are not enough explored. The structural interpretation of magmatic rocks, Triassic outcrops and the depressions are still a subject of discussion. In this work, we intend to investigate deep faults and their eventual role in magmatism and Triassic salt setting up and to explain the depression genesis. Analysis of the Bouguer anomaly map and its derivatives reveals the main gravity lineaments, organized in major NE- and NW-trending systems. The NE-trending system, dipping towards the NW, is the main component of the structural scheme and has controlled the tectonic evolution of this area. After the immobilization of the Tellian thrust sheets during the uppermost Langhian, the Tell and its Atlassic foreland were affected by the Tortonian compressive event with a NW-trending maximum horizontal stress. The reverse kinematics of the NE-trending deep-seated faults created at their front continental environments filled later by post-nappes Neogene deposits. After the early Pleistocene, a NNW-directed compressional stress regime deformed the post-nappes Neogene series and generated NW-trending grabens. This coexistence of compression-extension continues until present day.

Detrital zircon ages in Korean mid-Paleozoic meta-sandstones (Imjingang Belt and Taean Formation): Constraints on tectonic and depositional setting, source regions and possible affinity with Chinese terranes

NASA Astrophysics Data System (ADS)

Han, Seokyoung; de Jong, Koen; Yi, Keewook

2017-08-01

(4) should be viewed as independent tectonic units that had sources not exposed in Korea. A thorough literature review reveals that the Yeoncheon Complex and the Taean Formation were potentially sourced from the Liuling, Nanwan and Foziling groups in the Qinling-Dabie Belt, which all show very similar detrital zircon age spectra. These immature middle-late Devonian sandstones were deposited in a pro-foreland basin formed as a result of the aborted subduction of the South Qinling Terrane below the North Qinling Terrane, which was uplifted and eroded during post-collision isostatic rebound. The submarine fans where the mature distal turbiditic Yeoncheon and Taean sandstones were deposited may have constituted the eastern terminal part of a routing system originating in the uplifted and eroded middle Paleozoic Qinling Belt and adjacent part of the foreland basin.

Rewriting the Landform History of One of Africa's Three Largest Basins

NASA Technical Reports Server (NTRS)

Wilkinson, Justin

2014-01-01

The Kalahari Basin in southern Africa - one of the largest basins in Africa, along with the Congo and Chad basins - has attracted attention since David Livingstone traveled through the area in the 1840s. It is a semiarid desert with a large freshwater swampland known as the Okavango Swamp (150 km radius). This prominent megafan (a fan with radii >100 km), with its fingers of dark green forests projecting into the dun colors of the dunes of the Kalahari semi-desert, has been well photographed by astronauts over the years. The study area in the northern Kalahari basin is centered on the Okavango megafan of northwest Botswana, whose swampland has become well known as an African wildlife preserve of importance to biology and tourism alike. The Okavango River is unusual because it has deposited not one but two megafans along its course: the Okavango megafan and the Cubango megafan. The Okavango megafan is one of only three well-known megafans in Africa. Megafans on Earth were once thought to be rare, but recent research has documented 68 in Africa alone. Eleven megafans, plus three more candidates, have been documented in the area immediately surrounding the Okavango feature. These 11 megafans occupy the flattest and smoothest terrains adjacent to the neighboring upland and stand out as the darkest areas in the roughness map of the area. Megafan terrains occupy at least 200,000 sq km of the study area. The roughness map shown is based on an algorithm used first on Mars to quantify topographic roughness. Research of Earth's flattest terrains is just beginning with the aid of such maps, and it appears that these terrains are analogous to the flattest regions of Mars. Implications: 1. The variability in depositional style in each subbasin may apply Africa-wide: rift megafan length is dominated by rift width, whereas Owambo subbasin megafans are probably controlled by upland basin size; Zambezi subbasin megafans appear more like foreland basin types, with the position of

Stable Isotopic Constraints on Abiogenic Hydrocarbon gas Contributions to Thermogenic Natural gas Resources in the Northern Appalachian Basin, USA

NASA Astrophysics Data System (ADS)

Burruss, R. C.; Laughrey, C. D.

2006-05-01

The generation of abiogenic methane by serpentinization or by graphite-water reactions in high-grade metamorphic rocks is well documented by isotopic, fluid inclusion, and petrographic studies. However, geochemical evidence is equivocal for abiogenic generation of higher hydrocarbon gases (ethane through pentane) in economic resources. Thermogenic hydrocarbon gases, generated by thermal cracking of sedimentary organic matter of biological origin, are progressively enriched in 13C as a function of increasing number of carbon atoms in the molecule. The isotopic composition is controlled by the kinetic isotope effect (KIE) during carbon-carbon bond breaking with the largest KIE for methane. Published work on gases in Precambrian rocks in Canada and South Africa suggest that some were generated by abiogenic Fischer-Tropsch type reactions that produced gases with carbon isotopic compositions that are reversed from the thermogenic trend. We have documented reversed isotopic compositions in natural gas accumulations in lower Paleozoic reservoirs of the Appalachian basin regionally from West Virginia and eastern Ohio through Pennsylvania to central New York. The regional accumulation in lower Silurian age strata shows progressive enhancement of the isotopic reversal with increasing depth in the basin. Multivariate analysis of the molecular and isotopic data define an end-member in the deep basin with an approximate composition of 98 mol % CH4, 1-2 mol % C2H6, << 1 mol % C3H8, and δ13C (CH4) = -27 ‰, δ13C (C2H6) = -40 ‰, δ13C (C3H8) = - 41‰. The nominal similarity of isotopic reversals in the gases from Precambrian rocks to those in the lower Paleozoic rocks of the Appalachian basin suggests that abiogenic F-T reactions may have generated some fraction of the gases in the deep basin. Comparison of molecular and hydrogen isotopic compositions show that the gases of putative abiogenic F-T origin are significantly different from Appalachian basin gases. All the

The Indosinian orogeny: A perspective from sedimentary archives of north Vietnam

NASA Astrophysics Data System (ADS)

Rossignol, Camille; Bourquin, Sylvie; Hallot, Erwan; Poujol, Marc; Dabard, Marie-Pierre; Martini, Rossana; Villeneuve, Michel; Cornée, Jean-Jacques; Brayard, Arnaud; Roger, Françoise

2018-06-01

The Triassic stratigraphic framework for the Song Da and the Sam Nua basins, north Vietnam, suffers important discrepancies regarding both the depositional environments and ages of the main formations they contain. Using sedimentological analyses and dating (foraminifer biostratigraphy and U-Pb dating on detrital zircon), we provide an improved stratigraphic framework for both basins. A striking feature in the Song Da Basin, located on the southern margin of the South China Block, is the diachronous deposition, over a basal unconformity, of terrestrial and marine deposits. The sedimentary succession of the Song Da Basin points to a foreland setting during the late Early to the Middle Triassic, which contrasts with the commonly interpreted rift setting. On the northern margin of the Indochina Block, the Sam Nua basin recorded the activity of a proximal magmatic arc during the late Permian up to the Anisian. This arc resulted from the subduction of a southward dipping oceanic slab that separated the South China block from the Indochina block. During the Middle to the Late Triassic, the Song Da and Sam Nua basins underwent erosion that led to the formation of a major unconformity, resulting from the erosion of the Middle Triassic Indosinian mountain belt, built after an ongoing continental collision between the South China and the Indochina blocks. Later, during the Late Triassic, as syn- to post-orogenic foreland basins in a terrestrial setting, the Song Da and Sam Nua basins experienced the deposition of very coarse detrital material representing products of the mountain belt erosion.

A methodology for studying tectonic subsidence variations: insights from the Fernie Formation of west-central Alberta

NASA Astrophysics Data System (ADS)

McCartney, Tannis Maureen

Tectonic subsidence curves for over 300 subsurface wells in west-central Alberta indicate that the Western Canada Foreland Basin was initiated at the same time the lower units of the Fernie Formation were being deposited. This evidence is further supported by sedimentological data and fits with the timing of the onset of deformation in the Cordillera and the initiation of the foreland basin in Montana. The volume of subsidence curves in this study required an innovative methodology. Subsidence calculations were performed using customized macros in a spreadsheet. The tectonic subsidence variations were displayed in a tectonic subsidence envelope, which showed the total variation in the subsidence curves, and three suites of maps: tectonic subsidence, tectonic subsidence residuals, and tectonic subsidence ratios. Collectively, the maps of the tectonic subsidence in the Fernie Formation show that there was a western influence on subsidence during deposition of the oldest members of the Fernie Formation.

Relation of the lower Pennsylvanian unconformity to a mid-carboniferous eustatic event in the eastern United States

USGS Publications Warehouse

Englund, K.J.; Thomas, R.E.

1997-01-01

Two contrasting concepts specifying the age and duration of the hiatus resulting from a mid-Carboniferous eustatic event in the eastern United States are based on different evidence. The original model indicated that the hiatus is at an unconformity in cratonic areas that was assumed to coincide with the Mississippian-Pennsylvanian boundary at the contact between the Mississippian Bluestone Formation and the Pennsylvanian Pocahontas Formation in the Appalachian foreland basin. This concept was adhered to exclusively until 1969 and continues to reappear in reports dealing with global correlations and division of the Carboniferous into the Mississippian and Pennsylvanian Systems. This division is at a major eustatic event that supposedly occurred at about 330 Ma in scattered parts of the world, including the Appalachian basin. An alternative concept, fully supported by geologic mapping and biostratigraphic studies, indicates that the unconformity and associated hiatus are much younger because they originate in the Appalachian foreland basin in the lower part (upper Namurian) of the Lower Pennsylvanian New River Formation, about 260 m above the Mississippian-Pennsylvanian boundary. The duration of this hiatus increases in a northwesterly direction onto the cratonic shelf because the unconformity progressively truncated the underlying Lower Pennsylvanian and Upper Mississippian successions. The westward onlap of Pennsylvanian strata onto the eroded surface resulted in a hiatus from the Early Mississippian (Tournaisian) to the Middle Pennsylvanian (Westphalian B). The systemic boundary, which is in a depositional continuous sequence of strata in the Appalachian foreland basin, was correlated biostratigraphically by Pfefferkorn and Gillespie in 1982 with Gothan's "Florensprung" (floral break) described in 1913 at the Namurian A-B boundary in the Upper Silesian basin. An intra-Namurian erosive event was noted also in the Upper Silesian basin by Havlena, who reported in

Trans-Amazon Drilling Project (TADP): origins and evolution of the forests, climate, and hydrology of the South American tropics

NASA Astrophysics Data System (ADS)

Baker, P. A.; Fritz, S. C.; Silva, C. G.; Rigsby, C. A.; Absy, M. L.; Almeida, R. P.; Caputo, M.; Chiessi, C. M.; Cruz, F. W.; Dick, C. W.; Feakins, S. J.; Figueiredo, J.; Freeman, K. H.; Hoorn, C.; Jaramillo, C.; Kern, A. K.; Latrubesse, E. M.; Ledru, M. P.; Marzoli, A.; Myrbo, A.; Noren, A.; Piller, W. E.; Ramos, M. I. F.; Ribas, C. C.; Trnadade, R.; West, A. J.; Wahnfried, I.; Willard, D. A.

2015-12-01

This article presents the scientific rationale for an ambitious ICDP drilling project to continuously sample Late Cretaceous to modern sediment in four different sedimentary basins that transect the equatorial Amazon of Brazil, from the Andean foreland to the Atlantic Ocean. The goals of this project are to document the evolution of plant biodiversity in the Amazon forests and to relate biotic diversification to changes in the physical environment, including climate, tectonism, and the surface landscape. These goals require long sedimentary records from each of the major sedimentary basins across the heart of the Brazilian Amazon, which can only be obtained by drilling because of the scarcity of Cenozoic outcrops. The proposed drilling will provide the first long, nearly continuous regional records of the Cenozoic history of the forests, their plant diversity, and the associated changes in climate and environment. It also will address fundamental questions about landscape evolution, including the history of Andean uplift and erosion as recorded in Andean foreland basins and the development of west-to-east hydrologic continuity between the Andes, the Amazon lowlands, and the equatorial Atlantic. Because many modern rivers of the Amazon basin flow along the major axes of the old sedimentary basins, we plan to locate drill sites on the margin of large rivers and to access the targeted drill sites by navigation along these rivers.

Trans-Amazon Drilling Project (TADP): origins and evolution of the forests, climate, and hydrology of the South American tropics

USGS Publications Warehouse

Baker, P.A.; Fritz, S.C.; Silva, C.G.; Rigsby, C.A.; Absy, M.L.; Almeida, R.P.; Caputo, Maria C.; Chiessi, C.M.; Cruz, F.W.; Dick, C.W.; Feakins, S.J.; Figueiredo, J.; Freeman, K.H.; Hoorn, C.; Jaramillo, C.A.; Kern, A.; Latrubesse, E.M.; Ledru, M.P.; Marzoli, A.; Myrbo, A.; Noren, A.; Piller, W.E.; Ramos, M.I.F.; Ribas, C.C.; Trinadade, R.; West, A.J.; Wahnfried, I.; Willard, Debra A.

2015-01-01

This article presents the scientific rationale for an ambitious ICDP drilling project to continuously sample Late Cretaceous to modern sediment in four different sedimentary basins that transect the equatorial Amazon of Brazil, from the Andean foreland to the Atlantic Ocean. The goals of this project are to document the evolution of plant biodiversity in the Amazon forests and to relate biotic diversification to changes in the physical environment, including climate, tectonism, and the surface landscape. These goals require long sedimentary records from each of the major sedimentary basins across the heart of the Brazilian Amazon, which can only be obtained by drilling because of the scarcity of Cenozoic outcrops. The proposed drilling will provide the first long, nearly continuous regional records of the Cenozoic history of the forests, their plant diversity, and the associated changes in climate and environment. It also will address fundamental questions about landscape evolution, including the history of Andean uplift and erosion as recorded in Andean foreland basins and the development of west-to-east hydrologic continuity between the Andes, the Amazon lowlands, and the equatorial Atlantic. Because many modern rivers of the Amazon basin flow along the major axes of the old sedimentary basins, we plan to locate drill sites on the margin of large rivers and to access the targeted drill sites by navigation along these rivers.

The New Albany Shale Petroleum System, Illinois Basin - Data and Map Image Archive from the Material-Balance Assessment

USGS Publications Warehouse

Higley, Debra K.; Henry, M.E.; Lewan, M.D.; Pitman, Janet K.

2003-01-01

The data files and explanations presented in this report were used to generate published material-balance approach estimates of amounts of petroleum 1) expelled from a source rock, and the sum of 2) petroleum discovered in-place plus that lost due to 3) secondary migration within, or leakage or erosion from a petroleum system. This study includes assessment of cumulative production, known petroleum volume, and original oil in place for hydrocarbons that were generated from the New Albany Shale source rocks.More than 4.00 billion barrels of oil (BBO) have been produced from Pennsylvanian-, Mississippian-, Devonian-, and Silurian-age reservoirs in the New Albany Shale petroleum system. Known petroleum volume is 4.16 BBO; the average recovery factor is 103.9% of the current cumulative production. Known petroleum volume of oil is 36.22% of the total original oil in place of 11.45 BBO. More than 140.4 BBO have been generated from the Upper Devonian and Lower Mississippian New Albany Shale in the Illinois Basin. Approximately 86.29 billion barrels of oil that was trapped south of the Cottage Grove fault system were lost by erosion of reservoir intervals. The remaining 54.15 BBO are 21% of the hydrocarbons that were generated in the basin and are accounted for using production data. Included in this publication are 2D maps that show the distribution of production for different formations versus the Rock-Eval pyrolysis hydrogen-indices (HI) contours, and 3D images that show the close association between burial depth and HI values.The primary vertical migration pathway of oil and gas was through faults and fractures into overlying reservoir strata. About 66% of the produced oil is located within the generative basin, which is outlined by an HI contour of 400. The remaining production is concentrated within 30 miles (50 km) outside the 400 HI contour. The generative basin is subdivided by contours of progressively lower hydrogen indices that represent increased levels of

Active fold-thrust belts in the foreland of eastern Tibet, the Longquan and Xiongpu anticlines in Sichuan, China

NASA Astrophysics Data System (ADS)

Lee, Jian-Cheng; Chan, Yu-Chang; Lu, Chia-Yu; Chen, Chih-Tung; Chu, Hao-Tsu; Liu, Yuiping; Li, Jianzhong

2016-04-01

The 2008 M7.9 Wenchuan earthquake ruptured from the Longmenshan fault system, which is the frontal thrust system in eastern Tibet. Further east toward the foreland area in the Sichuan basin, it sits two anticlinal structures, the Longquan and Xiongpu anticlines, which trends sub-parallel to the Longmenshan range with a distance of about 70-100 km to the mountain front. It is widely considered that these two anticlinal features are attributed to propagation of the eastward extrusion of the eastern Tibetan plateau, similar to the stress system the Wenchuan earthquake. In this study, we carried out field investigations on these two active anticlinal structures in order to characterize the bulk deformation of the anticlines. We also conducted fracture analysis and fault-slip data analysis, in an attempt to characterize the fracture developments of the rock and the paleostress states related to the faulting events associated growth of the anticlines. We thus constructed a series of geological cross sections along these two anticlines. Our results show that the Longquan anticline is characterized by pop up structure with a dominant west-vergent thrust (i.e., backthrust) on the western limb. On the other hand to the eastern limb, an east-vergent thrust only well developed in the middle part of the anticline and die out toward the north and the south. For the Xiongpu anticline, it is characterized by a pre-dominant west-vergent backthrust system without developing an east-vergent thrust. A strike-slip fault and a series of N-S-trending pop-up thrusts cut across the Xiongpu anticline indicate a rather complex stress system with two dominant compression directions, NW-SE and E-W, subsequently or alternatively affected the area. Finally, the fracture analysis revealed that 2-3 pre-dominant bedding-perpendicular fracture sets are commonly developed in the massive sandstone layers. Most of them seemingly are of the characteristics of the mode I open joint, without clear

Miocene to present-day shortening and intermontane basin formation in the Andean Puna Plateau, NW Argentina (24°30'S)

NASA Astrophysics Data System (ADS)

Strecker, M. R.; Bookhagen, B.; Alonso, R. N.; Pingel, H.; Freymark, J.

2015-12-01

With average elevations of about 3.7 km the Altiplano-Puna Plateau of the southern central Andes constitutes the world's second largest orogenic plateau. The plateau generally consists of internally drained, partly coalesced sedimentary basins bordered by reverse-fault bounded ranges, >5 km high. In the Puna, the Argentine sector of the plateau, active tectonism has been interpreted to be characterized by a low level of strike-slip and normal faulting associated with mafic volcanism. In contrast, the eastern plateau margins and the adjacent foreland record a higher level of seismicity and ongoing contraction. Despite ubiquitous Plio-Pleistocene normal faulting along the eastern plateau margins, our new observations record contraction in the plateau interior. Fanning of E-dipping Miocene sedimentary strata involved in the formation of an anticline in the Pocitos Basin of the central Puna interior indicates growth, which must have begun after 7 Ma; 1.5-m.y.-old lacustrine strata as well as tilted Pleistocene lacustrine shorelines associated with this structure indicate sustained uplift into the Quaternary. Corresponding observations along the eastern border of the Pocitos Basin show that <3.5-m.y.-old strata are involved in contractile deformation and basin compartmentalization. Shortening in the central Puna is compatible with Plio-Pleistocene shortening in the low-elevation Salar de Atacama farther west, and may indicate that low-elevation sectors of the plateau have not yet reached a critical elevation that is conducive to normal faulting as observed elsewhere. The onset of extensional deformation in the Puna is thus highly disparate in space and time. Coeval regional thrusting, strike-slip, and normal faulting do not support a structural and topographic setting that promotes wholesale extension and orogenic collapse of the plateau realm.

Continental Delamination of the Romanian Eastern Carpathians: A Lower Crustal Origin of the Vrancea Seismogenic Zone?

NASA Astrophysics Data System (ADS)

Fillerup, M. A.; Knapp, J. H.; Knapp, C. C.

2006-12-01

Two lithosphere-scale, explosive-source seismic reflection profiles (DRACULA I and DACIA PLAN), inclusive of the hinterland and foreland of the Romanian Eastern Carpathians, provide new evidence for the geodynamic origin of the Vrancea Seismogenic Zone (VSZ) of Romania. These data, collected to evaluate existing subduction-related and delamination geodynamic models proposed to explain the intermediate depth seismicity associated with the Vrancea zone, show evidence of continental crust extending continuously above the VSZ from the Carpathian foreland well into the Transylvanian hinterland. Crustal thicknesses inferred from these data based on reflectivity show a 40-45 km crust below the Transylvanian basin abruptly shallowing to 32 km for ~120 km beneath the fold and thrust belt of the main Carpathian orogen and thickening again to 38-42 km crust in the foreland. This thinned crust outlines an apparent lower crustal sub-orogenic cavity that is overlain by a relatively subhorizontal reflective fabric absent of dipping reflectivity. The northwest dipping Vrancea seismogenic body, a 30x70x200 km volume of intermediate depth earthquakes, is located on the eastern flank of the apparently thin crust beneath the Carpathian orogen. Amplitude decay curves show penetration of seismic energy to a depth of ~60 km in the vicinity of the sub-orogenic cavity, implying this non- reflective zone is a geologic signature. Rotation of the VSZ about a hinge beneath the foreland basin at a depth of ~50 km restores to fill the lower-crustal cavity under the orogen, suggesting the VSZ represents a portion of brittle lower crust delaminated during continental lithospheric delamination which may have caused regional uplift of the Transylvanian basin. The lack of through-going, dipping crustal-scale boundaries along this composite lithospheric transect would appear to preclude subduction as an explanation for seismicity in the VSZ, consistent with abundant surface geologic data. These

Preliminary Depositional and Provenance Records of Mesozoic Basin Evolution and Cenozoic Shortening in the High Andes, La Ramada Fold-Thrust Belt, Southern-Central Andes (32-33°S)

NASA Astrophysics Data System (ADS)

Mackaman-Lofland, C.; Horton, B. K.; Fuentes, F.; Constenius, K. N.; McKenzie, R.; Alvarado, P. M.

2015-12-01

The Argentinian Andes define key examples of retroarc shortening and basin evolution above a zone of active subduction. The La Ramada fold-thrust belt (RFTB) in the High Andes provides insights into the relative influence and temporal records of diverse convergent margin processes (e.g. flat-slab subduction, convergent wedge dynamics, structural inversion). The RFTB contains Mesozoic extensional basin strata deformed by later Andean shortening. New detrital zircon U-Pb analyses of Mesozoic rift sediments reveal: (1) a dominant Permo-Triassic age signature (220-280 Ma) associated with proximal sources of effective basement (Choiyoi Group) during Triassic synrift deposition; (2) upsection younging of maximum depositional ages from Late Triassic through Early Cretaceous (230 to 100 Ma) with the increasing influence of western Andean arc sources; and (3) a significant Late Cretaceous influx of Paleozoic (~350-550 Ma) and Proterozoic (~650-1300 Ma) populations during the earliest shift from back-arc post-extensional subsidence to upper-plate shortening. The Cenozoic detrital record of the Manantiales foreland basin (between the Frontal Cordillera and Precordillera) records RFTB deformation prior to flat-slab subduction. A Permo-Triassic Choiyoi age signature dominates the Miocene succession, consistent with sources in the proximal Espinacito range. Subordinate Mesozoic (~80-250 Ma) to Proterozoic (~850-1800 Ma) U-Pb populations record exhumation of the Andean magmatic arc and recycling of different structural levels in the RFTB during thrusting/inversion of Mesozoic rift basin strata and subjacent Paleozoic units. Whereas maximum depositional ages of sampled Manantiales units cluster at 18-20 Ma, the Estancia Uspallata basin (~50 km to the south) shows consistent upsection younging of Cenozoic populations attributed to proximal volcanic centers. Ongoing work will apply low-temperature thermochronology to pinpoint basin accumulation histories and thrust timing.

Analysis of reworked sediments as a basis of the Palaeogene-Neogene palaeogeography reinterpretation: Case study of the Roztocze region (SE Poland)

NASA Astrophysics Data System (ADS)

Margielewski, Włodzimierz; Jankowski, Leszek; Krąpiec, Marek; Garecka, Małgorzata; Hałas, Stanisław; Urban, Jan

2017-05-01

Radiometric K/Ar dating of glauconite and nanno- and micropaleontologic analyses of calcareous nannoplankton, foraminifers and dinoflagellates isolated from the Miocene rocks in the Polish part of the Roztocze region, a northeastern part of the fore-bulge of the Carpathian Foreland Basin System - CFBS), SE Poland, reveal that these strata contain numerous microfossils and glauconite grains of the Upper Eocene and Lower Oligocene age. Such occurrences clearly indicate that these materials were redeposited from the Upper Eocene and Lower Oligocene marine rocks that must have originally covered most of the Roztocze and the surrounding area. It is therefore proposed herein that the geographical extent of the boreal, epi-continental basin during the Eocene-Oligocene was much greater than previously considered. Moreover, it appears that this basin was connected with the back-bulge zone of the warm Carpathian Basin (originally a northern part of the Tethys Basin which since Eocene/Oligocene boundary remained isolated as the Paratethys Basin). Hence, it is unlikely that the Roztocze region was uplifted during the Palaeogene as part of the Meta-Carpathian Swell, as it was earlied hypothesized. Instead, the Roztocze Swell formed during the Sarmatian, in the last stage of the development of the fore-bulge structure in the foreland of the up-thrust Carpathian orogenic belt. Multiple redeposition of sediments is the reason that the absolute dating (K/Ar) of glauconite, as well as incomprehensive palaeontological analysis could result in erroneous stratigraphic and palaeogeographic interpretations.

Deep versus shallow controlling factors of the regional thermal field in the Beaufort-Mackenzie Basin (Arctic Canada)

NASA Astrophysics Data System (ADS)

Scheck-Wenderoth, M.; Sippel, J.; Lewerenz, B.

2011-12-01

The present-day temperature distribution of the Beaufort-Mackenzie Basin as observed in boreholes indicates large-scale thermal anomalies which have been related to specific tectonic domains and heat transported by convection along major discontinuities (Chen et al., 2008). We have integrated seismic and well data into a crust-scale 3D structural model of the basin, which we have additionally constrained by 3D gravity modelling. This structural model is composed of seven Mesozoic-Cenozoic tectonostratigraphic units which - as a result of a complex foreland depositional and erosional history - tend to be younger, less compacted, and thus less thermally conductive towards the north. The underlying continental crust comprises a low-density upper part (2720 kg/m3 ) and a moderately dense lower part (2850 kg/m3), and it thins considerably towards the north where it passes over to oceanic crust (2900 kg/m2 ). We use the structural model to calculate the 3D conductive thermal field of the basin based on a Finite-Element method, thereby taking one step further towards a quantification of heat transporting processes in this petroliferous region. For the validation of the modelling results, we make use of public domain temperature data from more than 230 wells reaching depths of up to 5000 m. Thermal conductivities are assigned to the different units according to available data sets including also the observed lithology-dependent relationship between conductivity and porosity in the region. The upper boundary condition for the thermal calculations is provided by the well-known depth distribution of the base of permafrost (0 °C isotherm). Assuming a constant heat flow of 30 mW/m2 at the Moho, we find that the modelled temperatures are widely consistent with the observed temperatures in most parts of the basin. Only where large tectonic discontinuities structure the margins of the basin, the misfits are considerable, thus indicating convective heat transport to be an

Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian dolomite

USGS Publications Warehouse

Sherrill, Marvin G.

1977-01-01

Door County, a recreational and fruit-growing area bordering Lake Michigan in northeastern Wisconsin, has had a long history of ground-water contamination from surface and near-surface sources. Contamination is most severe in late summer when fruit-canning operations and the influx of tourists create additional wastes. Silurian dolomite is the upper bedrock unit in the county and yields generally adequate supplies of very hard water with locally objectionable concentrations of iron and nitrate. Thin soil cover and well-fractured dolomitic bedrock give easy entry to ground-water contaminants throughout large parts of Door County. Many contaminants enter the dolomite by surface or near-surface seepage. There is little attenuation of contamination concentrations in the well-jointed dolomite, and contaminants may travel long distances underground in a relatively short time. The major source of ground-water contamination is bacteria, from individual waste-disposal systems, agricultural, industrial, and municipal wastes. Areas of the county underlain by contaminated zones include only a small percentage of the total ground-water system and are separated by large volumes of ground water free of contamination. (Woodard-USGS)

Sr and Nd isotopes of suspended sediments from rivers of the Amazon basin

NASA Astrophysics Data System (ADS)

Hatting, Karina; Santos, Roberto V.; Sondag, Francis

2014-05-01

The Rb-Sr and Sm-Nd isotopic systems are important tools to constrain the provenance of sediment load in river systems. This study presents the isotopic composition of Sr and Nd isotopes and major and minor elements in suspended sediments from the Marañón-Solimões, Amazonas and Beni-Madeira rivers. The data were used to constrain the source region of the sediments and to better understand the main seasonal and spatial transport processes within the basin based on the variations of the chemical and isotopic signals. They also allow establishing a relationship between sediment concentrations and flow rate values. The study presents data collected during a hydrological year between 2009 and 2010. The Marañón-Solimões River presents low Sr isotopic values (0.7090-0.7186), broad EpslonNd(0) range (-15.17 to -8.09) and Nd model (TDM) ages varying from 0.99 to 1.81 Ga. Sources of sediments to the Marañón-Solimões River include recent volcanic rocks in northern Peru and Ecuador, as well as rocks with long crustal residence time and carbonates from the Marañón Basin, Peru. The Beni-Madeira River has more radiogenic Sr isotope values (0.7255-0.7403), more negative EpslonNd(0) values (-20.46 to -10.47), and older Nd isotope model ages (from 1.40 to 2.35 Ga) when compared to the Marañón-Solimões River. These isotope data were related to the erosion of Paleozoic and Cenozoic foreland basins that are filled with Precambrian sediments derived from the Amazonian Craton. These basins are located in Bolivian Subandina Zone. The Amazon River presents intermediate isotopic values when compared to those found in the Marañón-Solimões and Beni-Madeira rivers. Its Sr isotope ratios range between 0.7193 and 0.7290, and its EpslonNd(0) values varies between -11.09 and -9.51. The Nd isotope model ages of the suspended sediments vary between 1.28 and 1.77 Ga. Concentrations of soluble and insoluble elements indicate a more intense weathering activity in sediments of the Beni

Carbon and hydrogen isotopic reversals in deep basin gas: Evidence for limits to the stability of hydrocarbons

USGS Publications Warehouse

Burruss, R.C.; Laughrey, C.D.

2010-01-01

During studies of unconventional natural gas reservoirs of Silurian and Ordovician age in the northern Appalachian basin we observed complete reversal of the normal trend of carbon isotopic composition, such that ??13C methane (C1) >??13C ethane (C2) >??13C propane (C3). In addition, we have observed isotopic reversals in the ??2H in the deepest samples. Isotopic reversals cannot be explained by current models of hydrocarbon gas generation. Previous observations of partial isotopic reversals have been explained by mixing between gases from different sources and thermal maturities. We have constructed a model which, in addition to mixing, requires Rayleigh fractionation of C2 and C3 to cause enrichment in 13C and create reversals. In the deepest samples, the normal trend of increasing enrichment of 13C and 2H in methane with increasing depth reverses and 2H becomes depleted as 13C becomes enriched. We propose that the reactions that drive Rayleigh fractionation of C2 and C3 involve redox reactions with transition metals and water at late stages of catagenesis at temperatures on the order of 250-300??C. Published ab initio calculated fractionation factors for C-C bond breaking in ethane at these temperatures are consistent with our observations. The reversed trend in ??2H in methane appears to be caused by isotopic exchange with formation water at the same temperatures. Our interpretation that Rayleigh fractionation during redox reactions is causing isotopic reversals has important implications for natural gas resources in deeply buried sedimentary basins. ?? 2010.

Oxygen isotopes of marine mollusc shells record Eocene elevation change in the Pyrenees

NASA Astrophysics Data System (ADS)

Huyghe, Damien; Mouthereau, Frédéric; Emmanuel, Laurent

2012-09-01

Constraining paleoaltimetry of collisional orogens is critical to understand the dynamics of topographic evolution and climate/tectonics retroactions. Here, we use oxygen stable-isotope record on oyster shells, preserved in marine foreland deposits, to examine the past elevation of the Pyrenees during the Eocene. Our approach is based on the comparison with the Paris basin, an intracratonic basin not influenced by orogenic growth. The finding of a shift of 1.5‰ between 49 and 41 Ma, indicating more negative δ18Oc in the south Pyrenean foreland, is interpreted to reflect the inflow of river water sourced from higher elevation in the Pyrenees. To test this and provide paleoelevation estimate, we adopt a morphologic-hydrological model accounting for the hypsometry of drainage basin. Our best fitting model shows that the Pyrenees rose up to 2000 m. This indicates that the Pyrenees reached high elevation in the Eocene, thus providing new critical constraints on their long-term orogenic development. δ18O of marine mollusc shells are proved potentially attractive for paleoelevation studies, especially for mountain belts where elevated continental surfaces have not been preserved.

Cretaceous sedimentation in the outer Eastern Carpathians: Implications for the facies model reconstruction of the Moldavide Basin

NASA Astrophysics Data System (ADS)

Roban, R. D.; Krézsek, C.; Melinte-Dobrinescu, M. C.

2017-06-01

The mid Cretaceous is characterized by high eustatic sea-levels with widespread oxic conditions that made possible the occurrence of globally correlated Oceanic Red Beds. However, very often, these eustatic signals have been overprinted by local tectonics, which in turn resulted in Lower Cretaceous closed and anoxic basins, as in the Eastern Carpathians. There, the black shale to red bed transition occurs in the latest Albian up to the early Cenomanian. Although earlier studies discussed the large-scale basin configuration, no detailed petrography and sedimentology study has been performed in the Eastern Carpathians. This paper describes the Hauterivian to Turonian lithofacies and interprets the depositional settings based on their sedimentological features. The studied sections crop out only in tectonic half windows of the Eastern Carpathians, part of the Vrancea Nappe. The lithofacies comprises black shales interbedded with siderites and sandstones, calcarenites, marls, radiolarites and red shales. The siliciclastic muddy lithofacies in general reflects accumulation by suspension settling of pelagites and hemipelagites in anoxic (black shale) to dysoxic (dark gray and gray to green shales) and oxic (red shales) conditions. The radiolarites alternate with siliceous shales and are considered as evidence of climate changes. The sandstones represent mostly low and high-density turbidite currents in deep-marine lobes, as well as channel/levee systems. The source area is an eastern one, e.g., the Eastern Carpathians Foreland, given the abundance of low grade metamorphic clasts. The Hauterivian - lower Albian sediments are interpreted as deep-marine, linear and multiple sourced mud dominated systems deposited in a mainly anoxic to dysoxic basin. The anoxic conditions existed in the early to late Albian, but sedimentation changed to a higher energy mud/sand-dominated submarine channels and levees. This coarsening upwards tendency is interpreted as the effect of the

The Sirte Basin province of Libya; Sirte-Zelten total petroleum system

USGS Publications Warehouse

Ahlbrandt, Thomas S.

2001-01-01

in the Early Cre-taceous and syn-rift sedimentary filling during Cretaceous through Eocene time, and post-rift deposition in the Oligocene and Miocene. Multiple reservoirs are charged largely by verti-cally migrating hydrocarbons along horst block faults from Upper Cretaceous source rocks that occupy structurally low posi-tions in the grabens. Evaporites in the middle Eocene, mostly post-rift, provide an excellent seal for the Sirte-Zelten hydrocarbon system. The offshore part of the Sirte Basin is complex, with subduction occurring to the northeast of the province boundary, which is drawn at the 2,000-meter isobath. Possible petroleum systems may be present in the deep offshore grabens on the Sirte Rise such as those involving Silurian and Eocene rocks; however, potential of these systems remains speculative and was not assessed.

Tectonics versus eustatic control on supersequences of the Zagros Mountains of Iran

NASA Astrophysics Data System (ADS)

Heydari, Ezat

2008-04-01

epeirogenic movements. Although tectonic events did not produce supersequences of the Zagros Mountains, they influenced regional lithofacies patterns through the formation of intrashelf depressions such as the Hormoz Salt Basin during the Precambrian and the Dezful Embayment and the Lorestan Basin during the Mesozoic. Tectonic events also affected sedimentation during the Tertiary collision of Arabia and the Central Iran microplate through uplift, erosion, and the formation of the Zagros Foreland Basin. The results of this investigation necessitate a re-evaluation of the role and the significance of pre-Tertiary tectonic events commonly used to interpret the geological evolution of the Zagros Mountains.

The North Patagonian orogenic front and related foreland evolution during the Miocene, analyzed from synorogenic sedimentation and U/Pb dating (˜42°S)

NASA Astrophysics Data System (ADS)

Ramos, Miguel E.; Tobal, Jonathan E.; Sagripanti, Lucía; Folguera, Andrés; Orts, Darío L.; Giménez, Mario; Ramos, Victor A.

2015-12-01

Miocene sedimentary successions of the Ñirihuau and Collón Cura formations east of the El Maitén Belt constitute a partial record of the Andean exhumation, defining a synorogenic infill of the Ñirihuau Basin in the foothills of the North Patagonian fold and thrust belt. Gravimetric and seismic data allow recognizing the internal arrangement and geometry of these depocenters that host both units, separating a synextensional section previous to the Andean development at these latitudes, from a series of syncontractional units above. A series of progressive unconformities in the upper terms shows the synorogenic character of these units corresponding to the different pulses of deformation that occurred during the middle Miocene. New U-Pb ages constrain these pulses to the ˜13.5-12.9 Ma interval and allow reconstructing the tectonic history of this region based on the detrital zircon source populations. The U-Pb maximum ages of sedimentation give to the Ñirihuau Formation in particular a younger age than previously assumed. Additionally, synsedimentary deformation in strata of the upper exposures of the Collón Cura Formation associated with contractional structures and U-Pb ages allow identifying a younger paleoseismogenic pulse in ˜11.3 Ma. Thus, based on these data and a compilation of previous datasets, a tectonic evolution is proposed characterized by a contractional episode that migrated eastwardly since ˜19 to 15 Ma producing the Gastre broken foreland and then retracted to the eastern North Patagonian Precordillera, where out-of-sequence thrusts cannibalized the wedge top zone in the El Maitén belt at ˜13.5-11.3 Ma.

Earthquakes, gravity, and the origin of the Bali Basin: An example of a Nascent Continental Fold-and-Thrust Belt

NASA Astrophysics Data System (ADS)

McCaffrey, Robert; Nabelek, John

1987-01-01

We infer from the bathymetry and gravity field and from the source mechanisms and depths of the eight largest earthquakes in the Bali region that the Bali Basin is a downwarp in the crust of the Sunda Shelf produced and maintained by thrusting along the Flores back arc thrust zone. Earthquake source mechanisms and focal depths are inferred from the inversion of long-period P and SH waves for all events and short-period P waves for two of the events. Centroidal depths that give the best fit to the seismograms range from 10 to 18 km, but uncertainties in depth allow a range from 7 to 24 km. The P wave nodal planes that dip south at 13° to 35° (±7°) strike roughly parallel to the volcanic arc and are consistent with thrusting of crust of the Bali Basin beneath it. The positions of the earthquakes with respect to crustal features inferred from seismic and gravity data suggest that the earthquakes occur in the basement along the western end of the Flores thrust zone. The slip direction for the back arc thrust zone inferred from the orientation of the earthquake slip vectors indicates that the thrusting in the Bali Basin is probably part of the overall plate convergence, as it roughly coincides with the convergence direction between the Sunda arc and the Indian Ocean plate. Summation of seismic moments of earthquakes between 1960 and 1985 suggests a minimum rate of convergence across the thrust zone of 4 ± 2 mm/a. The presence of back arc thrusting suggests that some coupling between the Indian Ocean plate and the Sunda arc occurs but mechanisms such as continental collision or a shallow subduction of the Indian Ocean plate probably can be ruled out. The present tectonic setting and structure of the Bali Basin is comparable to the early forelands of the Andes or western North America in that a fold-and-thrust belt is forming on the continental side of an arc-trench system at which oceanic lithosphere is being subducted. The Bali Basin is flanked by the Tertiary Java

Petrophysics of low-permeability medina sandstone, northwestern Pennsylvania, Appalachian Basin

USGS Publications Warehouse

Castle, J.W.; Byrnes, A.P.

1998-01-01

Petrophysical core testing combined with geophysical log analysis of low-permeability, Lower Silurian sandstones of the Appalachian basin provides guidelines and equations for predicting gas producibility. Permeability values are predictable from the borehole logs by applying empirically derived equations based on correlation between in-situ porosity and in-situ effective gas permeability. An Archie-form equation provides reasonable accuracy of log-derived water saturations because of saturated brine salinities and low clay content in the sands. Although measured porosity and permeability average less than 6% and 0.1 mD, infrequent values as high as 18% and 1,048 mD occur. Values of effective gas permeability at irreducible water saturation (Swi) range from 60% to 99% of routine values for the highest permeability rocks to several orders of magnitude less for the lowest permeability rocks. Sandstones having porosity greater than 6% and effective gas permeability greater than 0.01 mD exhibit Swi less than 20%. With decreasing porosity, Swi sharply increases to values near 40% at 3 porosity%. Analysis of cumulative storage and flow capacity indicates zones with porosity greater than 6% generally contain over 90% of flow capacity and hold a major portion of storage capacity. For rocks with Swi < 20%, gas relative permeabilities exceed 45%. Gas relative permeability and hydrocarbon volume decrease rapidly with increasing Swi as porosity drops below 6%. At Swi above 40%, gas relative permeabilities are less than approximately 10%.

Facies patterns and conodont biogeography in Arctic Alaska and the Canadian Arctic Islands: Evidence against juxtaposition of these areas during early Paleozoic time

USGS Publications Warehouse

Dumoulin, Julie A.; Harris, A.G.; Bradley, D.C.; De Freitas, T. A.

2000-01-01

Differences in lithofacies and biofacies suggest that lower Paleozoic rocks now exposed in Arctic Alaska and the Canadian Arctic Islands did not form as part of a single depositional system. Lithologic contrasts are noted in shallow- and deep-water strata and are especially marked in Ordovician and Silurian rocks. A widespread intraplatform basin of Early and Middle Ordovician age in northern Alaska has no counterpart in the Canadian Arctic, and the regional drowning and backstepping of the Silurian shelf margin in Canada has no known parallel in northern Alaska. Lower Paleozoic basinal facies in northern Alaska are chiefly siliciclastic, whereas resedimented carbonates are volumetrically important in Canada. Micro- and macrofossil assemblages from northern Alaska contain elements typical of both Siberian and Laurentian biotic provinces; coeval Canadian Arctic assemblages contain Laurentian forms but lack Siberian species. Siberian affinities in northern Alaskan biotas persist from at least Middle Cambrian through Mississippian time and appear to decrease in intensity from present-day west to east. Our lithologic and biogeographic data are most compatible with the hypothesis that northern Alaska-Chukotka formed a discrete tectonic block situated between Siberia and Laurentia in early Paleozoic time. If Arctic Alaska was juxtaposed with the Canadian Arctic prior to opening of the Canada basin, biotic constraints suggest that such juxtaposition took place no earlier than late Paleozoic time.

Structural, micro-structural and kinematic analyses of channel flow in the Karmostaj salt diapir in the Zagros foreland folded belt, Fars province, Iran

NASA Astrophysics Data System (ADS)

Sarkarinejad, Khalil; Sarshar, Maryam Asadi; Adineh, Sadegh

2018-02-01

One of the main characteristic of the Zagros foreland fold-and-thrust belt and the Zagros foreland folded belt are wide distributions of surface extrusion from the Hormuz salt diapirs. This study examines the structure and kinematic of channel flow in the Karmostaj salt diapir in the southwestern part of the Zagros foreland folded belt. This diapir has reached the surface as a result of the channel flow mechanism and has extruded in the southern limb of the Kuh-Gach anticline which is an asymmetric décollement fold with convergence to the south. Structural and microstructural studies and quantitative finite strain (Rs) and kinematic vorticity number (Wk) analyses were carried out within this salt diapir and its namakier. This was in order to investigate the structural evolution in the salt diapiric system, the characteristics and mechanism of the salt flow and the distribution of flow regimes within the salt diapir and interaction of regional tectonics and salt diaprism. The extruded salt has developed a flow foliation sub-parallel to the remnant bedding recorded by different colors, a variety of internal folds including symmetrical and asymmetrical folds and interference fold patterns, shear zones, and boudins. These structures were used to analyze mechanisms and history of diapiric flow and extrusion. The microstructures, reveal various deformation mechanisms in various parts of salt diapir. The measurements of finite strain show that Rs values in the margin of salt diapir are higher than within its namakier which is consistent with the results of structural studies. Mean kinematic vorticity number (Wm) measured in steady state deformation of diapir and namakier is Wm = 0.45-0.48 ± 0.13. The estimated mean finite deformation (Wm) values indicate that 67.8% pure shear and 32.2% simple shear deformation were involved; the implications of which are discussed. The vorticity of flow indicates that in the early stage of growth, Poiseuille flow was the dominate

Glacier foreland colonisation: distinguishing between short-term and long-term effects of climate change.

PubMed

Kaufmann, Rüdiger

2002-02-01

By comparing short-term (6 years) observations with long-term (>100 years) community changes reconstructed from the chronosequence along a glacier foreland, I show that the colonisation of recently deglaciated terrain by invertebrates may constitute a process reacting sensitively to temperature fluctuations. Early colonising stages (<30 years old) currently develop faster, and intermediate successional stages (30-50 years old) slower, than would be indicated by the long-term chronosequence pattern. These differences between the chronosequence approach and direct observation can be explained by a simple model relating the rate of community evolution to the temperature record. It would mean that an increase of 0.6°C in summer temperatures approximately doubled the speed of initial colonisation, whereas later successional stages were less sensitive to climate change. The present situation appears to result from unusually warm summers around 1950 and a warm period accelerating glacier retreat since 1980. In contrast to the long-term trend, all except the youngest communities have suffered a loss in diversity in recent years.

Tectonic control on sediment sources in the Jaca basin (Middle and Upper Eocene of the South-Central Pyrenees)

NASA Astrophysics Data System (ADS)

Roigé, Marta; Gómez-Gras, David; Remacha, Eduard; Daza, Raquel; Boya, Salvador

2016-03-01

The Eocene clastic systems of the Jaca foreland Basin (southern Pyrenees) allow us to identify changes in sediment composition through time. We provide new data on sediment composition and sources of the northern Jaca basin, whose stratigraphic evolution from Middle Lutetian deep-marine to Priabonian alluvial systems record a main reorganization in the active Pyrenean prowedge. Petrological analysis shows that the Banastón and the Lower Jaca turbidite systems (Middle-Upper Lutetian) were fed from an eastern source, which dominated during the sedimentation of the Hecho Group turbidites. In contrast, the upper part of the Jaca turbidite systems (Lutetian-Bartonian transition) records an increase in the number of subvolcanic rock and hybrid-sandstone fragments (intrabasinal and extrabasinal grains) being the first system clearly fed from the north. This change is interpreted as associated with an uplifting of the Eaux-Chaudes/Lakora thrust sheet in the northern Axial Zone. The Middle Bartonian Sabiñánigo sandstone derives from eastern and northeastern source areas. In contrast, the overlying Late Bartonian-Early Priabonian Atarés delta records sediment input from the east. The Santa Orosia alluvial system records a new distinct compositional change, with a very high content of hybrid-sandstone clasts from the Hecho Group, again from a northern provenance. Such cannibalized clasts were sourced from newly emerged areas of the hinterland, associated with the basement-involved Gavarnie thrust activity in the Axial Zone.

Initiation and evolution of the Arabia-Eurasia collision in the Caucasus region constrained by detrital zircon geochronology

NASA Astrophysics Data System (ADS)

Tye, A. R.; Niemi, N. A.

2016-12-01

The Greater Caucasus (GC) mountain range is composed of thrust sheets of Paleozoic (Pz) - Mesozoic (Mz) flysch. Crystalline basement is exposed in the western part of the range, but not in the eastern. Detrital zircon ages from Eocene - recent foreland strata to the south of the western GC in Georgia suggest sediment sourcing from GC basement or Pz strata since Eocene time, requiring significant exhumation prior to or coincident with the onset of Arabia-Eurasia collision 30 Ma. We sampled foreland basin sedimentary rocks and modern river sands whose catchment areas together span the potential source rocks exposed in the western Greater Caucasus (GC) in Georgia. We find that GC basement rocks and lower Pz strata contain a diagnostic 450 Ma zircon population that is absent from the upper Pz and Mz sedimentary strata that are exposed throughout most of the range. These 450 Ma zircons are from an unknown source with an age distinct from the Hercynian ( 300 Ma) and Pan-African ( 600 Ma) orogens. Despite their absence in late Pz and Mz strata, the 450 Ma zircons are prevalent in Eocene - recent foreland basin deposits, whose ages were determined biostratigraphically [1]. Paleocurrent directions also indicate a GC source for Eocene strata [2], necessitating early Cenozoic exposure of GC basement or Pz strata. Exposing GC basement or Pz strata during Eocene time requires erosional removal of >3500 m of Mesozoic and late Paleozoic strata [1]. The detrital zircon age observations suggest that erosional removal of these strata took place prior to the initiation of the Arabia-Eurasia collision at 30 Ma and well before the ongoing episode of rapid GC exhumation and erosion from 5 Ma - present. Foreland basin detrital zircon ages also reveal a lack of input from Late Cretaceous to Paleogene volcanism of the Adjara-Trialet zone. This finding is consistent with the existence of a Paleogene ocean basin between the Greater Caucasus and Lesser Caucasus wide enough to prevent

Tectono-thermal Evolution of the Lower Paleozoic Petroleum Source Rocks in the Southern Lublin Trough: Implications for Shale Gas Exploration from Maturity Modelling

NASA Astrophysics Data System (ADS)

Botor, Dariusz

2018-03-01

The Lower Paleozoic basins of eastern Poland have recently been the focus of intensive exploration for shale gas. In the Lublin Basin potential unconventional play is related to Lower Silurian source rocks. In order to assess petroleum charge history of these shale gas reservoirs, 1-D maturity modeling has been performed. In the Łopiennik IG-1 well, which is the only well that penetrated Lower Paleozoic strata in the study area, the uniform vitrinite reflectance values within the Paleozoic section are interpreted as being mainly the result of higher heat flow in the Late Carboniferous to Early Permian times and 3500 m thick overburden eroded due to the Variscan inversion. Moreover, our model has been supported by zircon helium and apatite fission track dating. The Lower Paleozoic strata in the study area reached maximum temperature in the Late Carboniferous time. Accomplished tectono-thermal model allowed establishing that petroleum generation in the Lower Silurian source rocks developed mainly in the Devonian - Carboniferous period. Whereas, during Mesozoic burial, hydrocarbon generation processes did not develop again. This has negative influence on potential durability of shale gas reservoirs.

Incorporation of New and Old Tectonics Concepts Into a Modern Course in Tectonics.

ERIC Educational Resources Information Center

Hatcher, Robert D., Jr.

1983-01-01

Describes a graduate-level tectonics course which includes the historical basis for modern tectonics concepts and an in-depth review of pros/cons of plate tectonics. Tectonic features discussed include: ocean basins; volcanic arcs; continental margins; continents; orogenic belts; foreland fold and thrust belts; volcanic/plutonic belts of orogens;…

Stratigraphic cross sections of the Niobrara interval of the Cody Shale and associated rocks in the Wind River Basin, central Wyoming

USGS Publications Warehouse

Finn, Thomas M.

2017-02-07

The Wind River Basin in Wyoming is one of many structural and sedimentary basins that formed in the Rocky Mountain foreland during the Laramide orogeny. The basin is nearly 200 miles long, 70 miles wide, and encompasses about 7,400 square miles in central Wyoming. The basin is bounded by the Washakie Range, Owl Creek uplift, and southern Bighorn Mountains on the north, the Casper arch on the east, the Granite Mountains on the south, and Wind River Range on the west.Many important conventional oil and gas fields producing from reservoirs ranging in age from Mississippian through Tertiary have been discovered in this basin. In addition, an extensive unconventional overpressured basin-centered gas accumulation has been identified in Cretaceous and Tertiary strata in the deeper parts of the basin. It has long been suggested that various Upper Cretaceous marine shales, including the Cody Shale, are the principal hydrocarbon source rocks for many of these accumulations. With recent advances and success in horizontal drilling and multistage fracture stimulation, there has been an increase in exploration and completion of wells in these marine shales in other Rocky Mountain Laramide basins that were traditionally thought of only as hydrocarbon source rocks.The two stratigraphic cross sections presented in this report were constructed as part of a project carried out by the U.S. Geological Survey to characterize and evaluate the undiscovered continuous (unconventional) oil and gas resources of the Niobrara interval of the Upper Cretaceous Cody Shale in the Wind River Basin in central Wyoming. The primary purpose of the cross sections is to show the stratigraphic relationship of the Niobrara equivalent strata and associated rocks in the lower part of the Cody Shale in the Wind River Basin. These two cross sections were constructed using borehole geophysical logs from 37 wells drilled for oil and gas exploration and production, and one surface section along East Sheep Creek

Bacterial diversity in a glacier foreland of the high Arctic.

PubMed

Schütte, Ursel M E; Abdo, Zaid; Foster, James; Ravel, Jacques; Bunge, John; Solheim, Bjørn; Forney, Larry J

2010-03-01

Over the past 100 years, Arctic temperatures have increased at almost twice the global average rate. One consequence is the acceleration of glacier retreat, exposing new habitats that are colonized by microorganisms whose diversity and function are unknown. Here, we characterized bacterial diversity along two approximately parallel chronosequences in an Arctic glacier forefield that span six time points following glacier retreat. We assessed changes in phylotype richness, evenness and turnover rate through the analysis of 16S rRNA gene sequences recovered from 52 samples taken from surface layers along the chronosequences. An average of 4500 sequences was obtained from each sample by 454 pyrosequencing. Using parametric methods, it was estimated that bacterial phylotype richness was high, and that it increased significantly from an average of 4000 (at a threshold of 97% sequence similarity) at locations exposed for 5 years to an average of 7050 phylotypes per 0.5 g of soil at sites that had been exposed for 150 years. Phylotype evenness also increased over time, with an evenness of 0.74 for 150 years since glacier retreat reflecting large proportions of rare phylotypes. The bacterial species turnover rate was especially high between sites exposed for 5 and 19 years. The level of bacterial diversity present in this High Arctic glacier foreland was comparable with that found in temperate and tropical soils, raising the question whether global patterns of bacterial species diversity parallel that of plants and animals, which have been found to form a latitudinal gradient and be lower in polar regions compared with the tropics.

Sedimentology of the lower Karoo Supergroup fluvial strata in the Tuli Basin, South Africa

NASA Astrophysics Data System (ADS)

Bordy, Emese M.; Catuneanu, Octavian

2002-11-01

The Karoo Supergroup in the Tuli Basin (South Africa) consists of a sedimentary sequence (˜450-500 m) composed of four stratigraphic units, namely the informal Basal, Middle and Upper Units, and the formal Clarens Formation. The units were deposited in continental settings from approximately Late Carboniferous to Middle Jurassic. This paper focuses on the ˜60-m-thick Basal Unit, which was examined in terms of sedimentary facies and palaeo-environments based on evidence provided by primary sedimentary structures, palaeo-flow measurements, palaeontological findings, borehole data (59 core descriptions) and stratigraphic relations. Three main facies associations have been identified: (i) gravelstone (breccias and conglomerate-breccias), (ii) sandstone and (iii) fine-grained sedimentary rocks. The coarser facies are interpreted as colluvial fan deposits, possibly associated with glaciogenic diamictites. The sandstone facies association is mainly attributed to channel fills of low sinuosity, braided fluvial systems. The coal-bearing finer-grained facies are interpreted as overbank and thaw-lake deposits, and represent the lower energy correlatives of the sandy channel fills. Sediment aggradation in this fluvio-lacustrine system took place under cold climatic conditions, with floating lake ice likely associated with lacustrine environments. Palaeo-current indicators suggest that the highly weathered, quartz-vein-rich metamorphic rock source of the Basal Unit was situated east-northeast of the study area. The accumulation of the Basal Unit took place within the back-bulge depozone of the Karoo foreland system. In addition to flexural subsidence, the amount of accommodation in this tectonic setting was also possibly modified by extensional tectonism in the later stages of the basin development. Based on sedimentological and biostratigraphic evidence, the coal-bearing fine-grained facies association displays strong similarities with the Vryheid Formation of the main Karoo

Diagenesis and late-stage porosity development in the pennsylvanian strawn formation, val verde basin, Texas, U.S.A

USGS Publications Warehouse

Newell, K. David; Goldstein, R.H.; Burdick, C.J.

2005-01-01

The Middle Pennsylvanian (Desmoinesian) Strawn Formation in the Trans-Pecos area of Texas was deposited during relative tectonic quiescence that prevailed before rapid infilling of the Val Verde Basin. It represents one of a series of backstepping carbonate ramps formed on the craton side of this foreland basin. Strawn Formation carbonate rocks in three cores - Conoco Anna McClung #3-1, Alex Mitchell S2-1R, and Creek Ranch #10-1 - show several shallowing-up ward sequences, each a few meters thick. The Creek Ranch core displays the deepest-water characteristics of the three cores; the lower part of this core is dominated by graded bedding. The Mitchell and McClung cores contain skeletal-rich carbonates. Both of these cores display characteristics of shallow-water bank or lagoonal environments. All three cores have approximately the same diagenetic history. Primary fluid inclusions indicate early porosity-occluding interparticle and mold-filling calcite precipitated from water with a narrow range of salinities. Modal salinities are that of seawater, but slightly lesser salinities (indicating mixing of seawater and meteoric water) and slightly greater salinities (indicating evaporative concentration of seawater) are also indicated. The influence of meteoric groundwater can be detected by stable-isotope analyses of the early cements at stratigraphic levels that correlate to the tops of the major shallowing-upward depositional sequences. However, subaerial exposure surfaces are not demonstrated in these cores but were likely to be present updip. Most porosity is cement-reduced vugs, dissolution-enlarged (and cement-reduced) molds (> 1/16 mm, < 4 mm), and fractures. Minor intraparticle, intercrystalline, and shelter porosity is also present. Reservoir porosity is caused by fracturing and a late-stage dissolution event. Dissolution in the Creek Ranch core is not as pronounced as in the other cores because of a dearth of skeletal material. Porous zones in the McClung and

Paleo-environment in the upper amazon basin during early to middle Miocene times

NASA Astrophysics Data System (ADS)

van Soelen, Els; Hoorn, Carina; Santos, Roberto V.; Dantas, Elton L.; Sinninghe Damsté, Jaap S.; Kim, Jung-Hyun

2014-05-01

The Amazon River has the largest catchment in the world and is responsible for the largest water discharge from land to the ocean. The river system that flows from the Andes to the Atlantic Equatorial Margin exists since the late Miocene, and results from Andean uplift which strongly affected erosion/deposition and major flow patterns in northern South-America. Two outcrop sites from the Solimões basin, Mariñame (17.7-16.1 Ma) and Los Chorros (14.2-12.7 Ma), may shed light on the inland paleo-environmental conditions during a period of active Andean uplift in the early to middle Miocene. Earlier works revealed the Mariñame outcrops to represent a river born in Amazonia. Instead the Los Chorros outcrops are relics of the Amazon River system, characterized by extensive wetlands consisting of swamps, shallow lakes, crevasse splays channels and crevasse-delta lakes (e.g. Hoorn et al., 2010). The freshwater ecosystems alternate with some intervals that are rich in marine palynomorphs (such as dinocysts), mangrove pollen, brackish tolerant molluscs and ostracods, which indicate brackish conditions and a marine influence. It is thought that these marine incursion are related to phases of global sea-level rise and rapid subsidence in the Andean foreland (Marshall & Lundberg, 1996). Still, much remains unknown about the Miocene river systems, like the extent and diversity of the wetland system and the nature of the marine incursions. To get a better understanding of the sources of the (in)organic material, geochemical methods were used. Strontium (Sr) and Neodymium (Nd) isotopes were analyzed on bulk sediments, and used for a paleo-provenance study. The Sr and Nd isotopic signature in the older section (Mariñame) is in general more radiogenic compared to the Los Chorros section. The most radiogenic values are comparable to those found nowadays in the the Precambrian Guyana shield. A Guyana sediment source would suggest a distinctly different flow direction of the major

Late Wenlock (middle Silurian) bio-events: Caused by volatile boloid impact/s

NASA Technical Reports Server (NTRS)

Berry, W. B. N.; Wilde, P.

1988-01-01

Late Wenlockian (late mid-Silurian) life is characterized by three significant changes or bioevents: sudden development of massive carbonate reefs after a long interval of limited reef growth; sudden mass mortality among colonial zooplankton, graptolites; and origination of land plants with vascular tissue (Cooksonia). Both marine bioevents are short in duration and occur essentially simultaneously at the end of the Wenlock without any recorded major climatic change from the general global warm climate. These three disparate biologic events may be linked to sudden environmental change that could have resulted from sudden infusion of a massive amount of ammonia into the tropical ocean. Impact of a boloid or swarm of extraterrestrial bodies containing substantial quantities of a volatile (ammonia) component could provide such an infusion. Major carbonate precipitation (formation), as seen in the reefs as well as, to a more limited extent, in certain brachiopods, would be favored by increased pH resulting from addition of a massive quantity of ammonia into the upper ocean. Because of the buffer capacity of the ocean and dilution effects, the pH would have returned soon to equilibrium. Major proliferation of massive reefs ceased at the same time. Addition of ammonia as fertilizer to terrestrial environments in the tropics would have created optimum environmental conditions for development of land plants with vascular, nutrient-conductive tissue. Fertilization of terrestrial environments thus seemingly preceded development of vascular tissue by a short time interval. Although no direct evidence of impact of a volatile boloid may be found, the bioevent evidence is suggestive that such an impact in the oceans could have taken place. Indeed, in the case of an ammonia boloid, evidence, such as that of the Late Wenlockian bioevents may be the only available data for impact of such a boloid.

The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system

NASA Astrophysics Data System (ADS)

Latrubesse, Edgardo M.; Cozzuol, Mario; da Silva-Caminha, Silane A. F.; Rigsby, Catherine A.; Absy, Maria Lucia; Jaramillo, Carlos

2010-05-01

On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimões Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian-Mesopotamian mammalian biozones, spanning 9-6.5 Ma. Additionally, we present results that demonstrate that deposits in Peruvian Amazonia attributed to Miocene tidal environments are actually fluvial sediments that have been misinterpreted (both environmentally and chronologically) by several authors. The entire Late Miocene sequence was deposited in a continental environment within a subsiding basin. The facies analysis, fossil fauna content, and palynological record indicate that the environment of deposition was dominated by avulsive rivers associated with megafan systems, and avulsive rivers in flood basins (swamps, lakes, internal deltas, and splays). Soils developed on the flatter, drier areas, which were dominated by grasslands and gallery forest in a tropical to subtropical climate. These Late Miocene sediments were deposited from westward of the Purus arch up to the border of Brazil with Peru (Divisor Ranges) and Bolivia (Pando block). Eastward of the Iquitos structural high, however, more detailed studies, including vertebrate paleontology, need to be performed to calibrate with more precision the ages of the uppermost levels of the Solimões Formation. The evolution of the basin during the late Miocene is mainly related to the tectonic behavior of the Central Andes (˜ 3°-15°S). At approximately 5 Ma, a segment of low angle of subduction was well developed in the Nazca Plate, and the deformation in the Subandean foreland produced the inland reactivation of the Divisor/Contamana Ranges and tectonic arrangements in the Eastern Andes. During the Pliocene southwestern Brazilian Amazonia ceased to be an effective sedimentary

Mesozoic to Recent, regional tectonic controls on subsidence patterns in the Gulf of Mexico basin

NASA Astrophysics Data System (ADS)

Almatrood, M.; Mann, P.; Bugti, M. N.

2016-12-01

We have produced subsidence plots for 26 deep wells into the deeper-water areas of the Gulf of Mexico (GOM) in order to identify regional tectonic controls and propose tectonic phases. Our results show three sub-regions of the GOM basin that have distinctive and correlative subsidence patterns: 1) Northern GOM from offshore Texas to central Florida (9 wells) - this area is characterized by a deeply buried, Triassic-early Jurassic rift event that is not represented by our wells that penetrate only the post-rift Cretaceous to recent passive margin phase. The sole complexity in the passive margin phase of this sub-region is the acceleration of prograding clastic margins including the Mississippi fan in Miocene time; 2) Southeastern GOM in the Straits of Florida and Cuba area (5 wells) - this area shows that the Cretaceous passive margin overlying the rift phase is abruptly drowned in late Cretaceous as this part of the passive margin of North America that is flexed and partially subducted beneath the Caribbean arc as it encroaches from the southwest to eventually collide with the North American passive margin in the Paleogene; 3) Western GOM along the length of the eastern continental margin of Mexico (12 wells) - this is the most complex of the three areas in that shares the Mesozic rifting and passive margin phase but is unique with a slightly younger collisional event and foreland basin phase associated with the Laramide orogeny in Mexico extending from the KT boundary to the Oligocene. Following this orogenic event there is a re-emergence of the passive margin phase during the Neogene along locally affected by extensional and convergent deformation associated with passive margin fold belts. In summary, the GOM basin exhibits evidence for widespread rifting and passive margin formation associated with the breakup of Pangea in Mesozoic times that was locally superimposed and deformed during the late Cretaceous-Paleogene period by: 1) Caribbean subduction and

The Lower Triassic Sorkh Shale Formation of the Tabas Block, east central Iran: Succesion of a failed-rift basin at the Paleotethys margin

USGS Publications Warehouse

Lasemi, Y.; Ghomashi, M.; Amin-Rasouli, H.; Kheradmand, A.

2008-01-01

The Lower Triassic Sorkh Shale Formation is a dominantly red colored marginal marine succession deposited in the north-south trending Tabas Basin of east central Iran. It is correlated with the unconformity-bounded lower limestone member of the Elika Formation of the Alborz Mountains of northern Iran. The Sorkh Shale is bounded by the pre-Triassic and post-Lower Triassic interregional unconformities and consists mainly of carbonates, sandstones, and evaporites with shale being a minor constituent. Detailed facies analysis of the Sorkh Shale Formation resulted in recognition of several genetically linked peritidal facies that are grouped into restricted subtidal, carbonate tidal flat, siliciclastic tidal flat, coastal plain and continental evaporite facies associations. These were deposited in a low energy, storm-dominated inner-ramp setting with a very gentle slope that fringed the Tabas Block of east central Iran and passed northward (present-day coordinates) into deeper water facies of the Paleotethys passive margin of northern Cimmerian Continent. Numerous carbonate storm beds containing well-rounded intraclasts, ooids and bioclasts of mixed fauna are present in the Sorkh Shale Formation of the northern Tabas Basin. The constituents of the storm beds are absent in the fair weather peritidal facies of the Sorkh Shale Formation, but are present throughout the lower limestone member of the Elika Formation. The Tabas Block, a part of the Cimmerian continent in east central Iran, is a rift basin that developed during Early Ordovician-Silurian Paleotethys rifting. Facies and sequence stratigraphic analyses of the Sorkh Shale Formation has revealed additional evidence supporting the Tabas Block as a failed rift basin related to the Paleotethys passive margin. Absence of constituents of the storm beds in the fair weather peritidal facies of the Sorkh Shale Formation, presence of the constituents of the storm beds in the fair weather facies of the Elika Formation (the

Provenance of Cretaceous-Pliocene Clastic Sediments in the Tachira Saddle, Western Venezuela, and Implications for Sediment Dispersal Patterns in the Northern Andes

NASA Astrophysics Data System (ADS)

Gomez, Ali Ricardo

Northwestern South America is highly deformed due to the transpressive plate boundary associated with complex interactions between the Caribbean plate, the South American plate, the Nazca plate and the Panama arc. Previous studies suggest that the Cenozoic uplift of the Merida Andes and Eastern Cordillera of Colombia affected sediment dispersal patterns in the region, shifting from a Paleocene foreland basin configuration to the modern isolated basins. Well-exposed Cretaceous to Pliocene strata in the Tachira Saddle provides a unique opportunity to test proposed sediment dispersal patterns in the region. U-Pb detrital zircon geochronology and supplementary XRD heavy mineral data are used together to document the provenance of the Tachira Saddle sediments and refine the sediment dispersal patterns in the region. Results from the U-Pb detrital zircon geochronology show that there are six age groups recorded in these samples. Two groups are related to the Precambrian Guyana shield terranes and Putumayo basement in the Eastern Cordillera, and four groups are related to different magmatic episodes occurring during the Andean orogenic process. The transition between the Cretaceous passive margin and the Paleocene foreland basin and the initial uplift of the Eastern Cordillera and the uplift of the Merida Andes by the Early Miocene were also recorded in the Tachira saddle detrital zircon signature.

Roseomonas arctica sp. nov., isolated from arctic glacial foreland soil.

PubMed

Qiu, Xia; Qu, Zhihao; Jiang, Fan; Lin, Yingjun; Zhang, Yumin; Chang, Xulu; Da, Xuyang; Deng, Sangsang; Kim, Myongchol; Fang, Chengxiang; Peng, Fang

2016-03-01

A novel psychrotolerant bacterium, designed strain M6-79 T , was isolated from an arctic glacial foreland soil sample collected from Ny-Ålesund in the Svalbard Archipelago, Norway. Cells of strain M6-79 T were Gram-stain-negative, rod-shaped and produced a red-pigment. Strain M6-79 T was strictly aerobic, non-motile, non-endospore-forming, oxidase-negative and catalase-positive. Based on 16S rRNA gene sequence analysis, strain M6-79 T was phylogenetically related to Roseomonas aquatica TR53 T (95.2 % 16S rRNA gene sequence similarity), Roseomonas lacus TH-G33 T (94.3 %), ' Roseomonas sediminicola' FW-3 (94.3 %), Roseomonas terrae DS-48 T (94.1 %) and Roseomonas soli 5N26 T (94.1 %). The unique isoprenoid quinone detected in strain M6-79 T was Q-9. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, one unknown aminolipid and one unknown lipid. Strain M6-79 T possessed C 18 : 1 ω7 c , C 16 : 0 and summed feature 3 (C 16 : 1 ω6 c and/or C 16 : 1 ω7 c ) as the predominant fatty acids, and the DNA G+C content was 71.2 mol%. Combined data from phylogenetic, phenotypic and chemotaxonomic studies revealed that strain M6-79 T represents a novel species of the genus Roseomonas , for which the name Roseomonas arctica sp. nov. is proposed. The type strain is strain M6-79 T ( = CCTCC AB 2013101 T  = LMG 28251 T ).

An improved evaluation method for measuring TOC of the Longmaxi Formation shale in the Sichuan Basin, south China

NASA Astrophysics Data System (ADS)

Zhang, Y.; Hu, C.; Wang, M.

2017-12-01

The evaluation of total organic carbon (TOC) in shale using logging data is one of the most crucial steps in shale gas exploration. However, it didn't achieve the ideal effect for the application of `ΔlogR' method in the Longmaxi Formation shale of Sichuan Basin.The reason may be the organic matter carbonization in Longmaxi Formation. An improved evaluation method, using the classification by lithology and sedimentary structure: 1) silty mudstone (wellsite logging data show silty); 2) calcareous mudstone (calcareous content > 25%); 3) laminated mudstone (laminations are recognized by core and imaging logging technology); 4) massive mudstone (massive textures are recognized by core and imaging logging technology, was proposed. This study compares two logging evaluation methods for measuring TOC in shale: the △logR method and the new proposed method. The results showed that the correlation coefficient between the calculated TOC and the tested TOC, based on the △logR method, was only 0.17. The correlation coefficient obtained according to the new method reached 0.80. The calculation results illustrated that, because of the good correlation between lithologies and sedimentary structure zones and TOC of different types of shale, the shale reservoirs could be graded according to four shale types. The new proposed method is more efficient, faster, and has higher vertical resolution than the △logR method. In addition, a new software had been completed. It was found to be especially effective under conditions of insufficient data during the early stages of shale gas exploration in the Silurian Longmaxi Formation, Muai Syncline Belt, south of the Sichuan Basin.

Emsian synorogenic paleogeography of the Maine Applachians