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Sample records for formation borbon basin

  1. Formation of lunar basin rings

    USGS Publications Warehouse

    Hodges, C.A.; Wilhelms, D.E.

    1978-01-01

    The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying

  2. Marcelina formation study - Maracaibo basin

    SciTech Connect

    D`Arlach, C.; Peralta, J.; Murillo, R.

    1996-08-01

    Recent development activity onshore, west of the Maracaibo Lake, has led to a better understanding of the Paleocene Marcelina formation in the basin. The Marcelina formation is divided into two sections, an upper coal dominated interval and a lower sand/claystone interval. The sandstone reservoir section consists of a number of fining upward sequences deposited in a fluvial environment. Laterally the section evolves to a shallow marine shaly and carbonatic section, or is truncated by a regional unconformity, being missing over much of the Lake area. The Marcelina sands are only commercially productive in the Alturitas Field, where oil is found in a combined stratigraphic/structural trap. This paper focuses on two aspects of the Marcelina. First, the study incorporates the field data into a regional framework to investigate the possibility of similar plays in the studied area. Second, the study integrates geology and engineering data to examine the Marcelina as a reservoir unit to optimize field development and increase the oil recovery efficiency. Information from seismic, logs, cores, reservoir pressures, and fluids is used to understand the depositional model and the field complexity. The study provides a model, supported by extensive data, which may help to develop other potential discoveries in the west coast area.

  3. Lunar basin formation and highland stratigraphy

    NASA Technical Reports Server (NTRS)

    Howard, K. A.; Wilhelms, D. E.; Scott, D. H.

    1974-01-01

    Multiring impact basins, formed after solidification of the lunar crust, account for most or all premare regional deposits and structures expressed in the lunar landscape and for major topographic and gravity variations. A fresh basin has two or more concentric mountain rings, a lineated ejecta blanket, and secondary impact craters. Crackled material on the floor may be impact melt. The ejecta blanket was emplaced at least partly as a ground-hugging flow and was probably hot. A suggested model of basin formation is that the center lifts up and the rings form by inward collapse during evisceration. The resulting basin is shallow and has a central uplift of the mantle. This results in a central gravity high and a ring low. Later flooding by mare basalt has since modified most near side basins. Highland deposits of plains, furrowed and pitted terrain, and various hills, domes, and craters that were interpreted before the Apollo missions as being volcanic can now be interpreted as being basin related.

  4. Formation of the Orientale lunar multiring basin

    NASA Astrophysics Data System (ADS)

    Johnson, Brandon C.; Blair, David M.; Collins, Gareth S.; Melosh, H. Jay; Freed, Andrew M.; Taylor, G. Jeffrey; Head, James W.; Wieczorek, Mark A.; Andrews-Hanna, Jeffrey C.; Nimmo, Francis; Keane, James T.; Miljković, Katarina; Soderblom, Jason M.; Zuber, Maria T.

    2016-10-01

    Multiring basins, large impact craters characterized by multiple concentric topographic rings, dominate the stratigraphy, tectonics, and crustal structure of the Moon. Using a hydrocode, we simulated the formation of the Orientale multiring basin, producing a subsurface structure consistent with high-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft. The simulated impact produced a transient crater, ~390 kilometers in diameter, that was not maintained because of subsequent gravitational collapse. Our simulations indicate that the flow of warm weak material at depth was crucial to the formation of the basin’s outer rings, which are large normal faults that formed at different times during the collapse stage. The key parameters controlling ring location and spacing are impactor diameter and lunar thermal gradients.

  5. Martian Sedimentary Basins and Central Mound Formation

    NASA Astrophysics Data System (ADS)

    Bennett, K. A.; Bell, J. F., III

    2014-12-01

    Central mounds on Mars are observed as sedimentary deposits within crater interiors, but the specific processes responsible for their formation and subsequent modification are still debated. The deposits are hypothesized to have been created by either subaerial or subaqueous processes through one of two general formation mechanisms. The prevailing hypothesis suggests that after their craters were formed, sediment filled the entire crater and was later eroded into the morphologies we observe today. Alternatively, the sediment could have been deposited as the features we observe today without any significant erosion contributing to their mound shape. We conducted a survey of central mounds that occur within craters larger than 25 km in diameter located between ± 60° latitude on Mars. We use mound locations, mound offsets within their host craters, and mound heights to address various mound formation hypotheses. The results of this survey support the hypothesis that mound sediment once filled the entire host crater and was later eroded into the features we observe today. We propose that large Martian impact craters act as simplistic sedimentary basins. These basins "catch" any sediment that is being transported through the region. Any geologic process that involves transport of material (airfall dust, explosive volcanism, impact ejecta, etc.) could have contributed to the growth of this sediment fill, although the dominant process could vary based on location. During this depositional phase, several processes (ice/frost, water, etc.) could have cemented the material; then, at some point, the environment changed from depositional to erosional, leading to the formation of isolated mounds of sediment within these craters. Our study reveals that most mounds are offset from the center of their host crater in the same direction as the regional winds. For example, the mounds in Arabia Terra are offset towards the western portion of their craters. This observation is

  6. Magmatism in rifting and basin formation

    NASA Astrophysics Data System (ADS)

    Thybo, H.

    2008-12-01

    Whether heating and magmatism cause rifting or rifting processes cause magmatic activity is highly debated. The stretching factor in rift zones can be estimated as the relation between the initial and the final crustal thickness provided that the magmatic addition to the crust is insignificant. Recent research demonstrates substantial magmatic intrusion into the crust in the form of sill like structures in the lowest crust in the presently active Kenya and Baikal rift zones and the DonBas palaeo-rift zone in Ukraine. This result may be surprising as the Kenya Rift is associated with large amounts of volcanic products, whereas the Baikal Rift shows very little volcanism. Identification of large amounts of magmatic intrusion into the crust has strong implications for estimation of stretching factor, which in the case of Baikal Rift Zone is around 1.7 but direct estimation gives a value of 1.3-1.4 if the magmatic addition is not taken into account. This may indicate that much more stretching has taken place on rift systems than hitherto believed. Wide sedimentary basins may form around aborted rifts due to loading of the lithosphere by sedimentary and volcanic in-fill of the rift. This type of subsidence will create wide basins without faulting. The Norwegian- Danish basin in the North Sea area also has subsided gradually during the Triassic without faulting, but only few rift structures have been identified below the Triassic sequences. We have identified several mafic intrusions in the form of large batholiths, typically more than 100 km long, 20-40 km wide and 20 km thick. The associated heating would have lifted the surface by about 2 km, which may have been eroded before cooling. The subsequent contraction due to solidification and cooling would create subsidence in a geometry similar to basins that developed by loading. These new aspects of magmatism will be discussed with regard to rifting and basin formation.

  7. Stratigraphy and lithofacies of Foster formation in Michigan basin

    SciTech Connect

    Luneau, B.A.; Longman, M.W.; Horne, J.C. )

    1989-08-01

    The Lower Ordovician Foster formation lies in apparent conformity on the Umlor formation and is both conformably and unconformably overlain by the St. Peter Sandstone (Bruggers Formation), the primary target of the Michigan basin deep gas play. The Foster is stratigraphically equivalent to the Shakopee Dolomite and New Richmond Sandstone of the Illinois basin. The Foster formation is composed of up to 500 m of shallow marine and peritidal deposits divisible into three intervals. The basal interval is relatively uniform in thickness throughout the basin and is recognized by its interbedded lithologies above the relatively massive Unlor formation. The basal interval is primarily dolomite and sandstone with minor anhydrite. The middle interval is thickest in the basin center and progressively onlaps the basin margins. This interval is primarily dolomite and anhydrite. The upper unit extends throughout the basin but is thinner and truncated from above along the basin margins. Shaly dolomite and sandstone are the major lithologies.

  8. K-Basin gel formation studies

    SciTech Connect

    Beck, M.A.

    1998-07-23

    A key part of the proposed waste treatment for K Basin sludge is the elimination of reactive uranium metal by dissolution in nitric acid (Fkirnent, 1998). It has been found (Delegard, 1998a) that upon nitric acid dissolution of the sludge, a gel sometimes forms. Gels are known to sometimes impair solid/liquid separation and/or material transfer. The purpose of the work reported here is to determine the cause(s) of the gel formation and to determine operating parameters for the sludge dissolution that avoid formation of gel. This work and related work were planned in (Fkunent, 1998), (Jewett, 1998) and (Beck, 1998a). This report describes the results of the tests in (Beck, 1998a) with non-radioactive surrogates.

  9. Investigating the onset of multi-ring impact basin formation

    NASA Astrophysics Data System (ADS)

    Potter, Ross W. K.

    2015-11-01

    Multi-ring basins represent some of the largest, oldest, rarest and, therefore, least understood impact crater structures. Various theories have been put forward to explain their formation; there is currently, however, no consensus. Here, numerical modeling is used to investigate the onset of multi-ring basin formation on the Moon using two thermal profiles suitable for the lunar basin-forming epoch. Various multi-ring basin formation hypotheses are discussed, compared, and evaluated against target deformation and strain distribution in the models, as well as geological and geophysical observations. The mechanism that most closely resembles the numerical models in terms of basin formation and structure, as well as observations, appears to be the ring tectonic theory, whereby ring formation is dependent on transient cavities penetrating entirely through the Moon's lithosphere into the asthenosphere below. The numerical models suggest that all lunar basins larger than Schrödinger (320 km diameter) should be capable of forming multiple rings, as their transient cavities penetrate into the asthenosphere for both thermal profiles. Additionally, the models demonstrate that the target's thermal profile starts to influence basin formation and structure when impact energy exceeds that of the Schrödinger event.

  10. Timing of Cenozoic Basin Formation in Northern Sundaland, Southeast Asia

    SciTech Connect

    Liew, K.K. )

    1994-07-01

    The present shorelines of northern Sundaland show preferential northwest-southeast elongation. This trend is parallel for subparallel to major faults and suture in this region. Continental wrench/shear basins developed on the western portion of this region and back-arc basins developed on the western portion of this region and back-arc basins in the rest of the region are also aligned to this trend. Different basin geometries and structural patterns among Cenozoic basins in northern Sundaland indicate different origins and/or timing of basin formation. Wrench faulting has played a significant role in the formation of these Cenozoic basins. The continued collision of the Indian subplate with the Eurasian plate during early Cenozoic has caused a redistribution of stress within this region. Zones of weakness have been reactivated or created with large lateral displacements by these changes, thus initiating the subsidence of these basins. The episodic initiation of Cenozoic basins may have begun as early as Jurassic and continued till Oligocene.

  11. The Deep Structure of Lunar Basins: Clues to the Understanding of Basin Formation and Modification

    NASA Technical Reports Server (NTRS)

    Bratt, S. R.; Solomon, S. C.; Head, J. W.; Thurber, C. H.

    1985-01-01

    Basin excavation has played a major role in shaping the surface and subsurface of the Moon. Though photogeologic observations provide estimates for the present volumes of lunar impact basins and their ejecta deposits, there is not sufficient information to describe completely either the geometry of the basins at the time of impact or their modification with time. Determination of the structure of the crust and upper mantle beneath large basins can provide important insight into the thermal and mechanical processes associated with basin formation and modification as well as the differences in these processes as functions of basin age and size. Using observed gravity and topography together with the seismically determined crustal thickness of the central nearside, a model for the structure of the crust and upper mantle of the nearside of the Moon is presented. With this model the deep structure of the largest lunar basins are compared. The implications for the processes of basin formation and modification at different stages in lunar history are explored.

  12. Linking lithosphere deformation and sedimentary basin formation over multiple scales

    NASA Astrophysics Data System (ADS)

    Huismans, Ritske S.

    2016-04-01

    Here we focus on the relationships between tectonic deformation and sedimentary basin formation. Resolving the interaction and feedback between tectonic crust-lithosphere scale deformation and surface processes through erosion of elevated areas and formation of sedimentary basins over multiple scales has been a long-standing challenge. While forward process based models have been successful at showing that a feedback is expected between tectonic deformation and redistribution of mass at the earth's surface by erosion, transport, and deposition, demonstrating this coupling for natural systems has been an even greater challenge and is strongly debated. Observational constraints on crust-lithosphere deformation and surface processes are typically collected at highly varying spatial and temporal scales, while forward process based models are typically run at either very large lithosphere-mantle scale, or at the scale of the sedimentary basin making it difficult to investigate and explore the detailed interaction and feedback between these systems. Here I will report on recent advances in forward modelling linking crust-lithosphere deformation with surface processes over a large range of scales resolving tectonic plate scale deformation and sedimentary basin formation at stratigraphic scales. The forward numerical models indicate a linkage and interaction between the structural style of thick-skinned large-scale mountain belt and rift-passive margin formation, erosion-transport-deposition processes operating at the surface, and the thin-skinned deformation occurring in the associated sedimentary basins.

  13. Linking lithosphere deformation and sedimentary basin formation over multiple scales

    NASA Astrophysics Data System (ADS)

    Huismans, Ritske S.

    2014-05-01

    In the spirit of Peter Ziegler we are interested in and explore the relationships between tectonic deformation and sedimentary basin formation. Resolving the interaction and feedback between tectonic crust-lithosphere scale deformation and surface processes through erosion of elevated areas and formation of sedimentary basins over multiple scales has been a long-standing challenge. While forward process based models have been successful at showing that a feedback is expected between tectonic deformation and redistribution of mass at the earth's surface by erosion, transport, and deposition, demonstrating this coupling for natural systems has been an even greater challenge and is strongly debated. Observational constraints on crust-lithosphere deformation and surface processes are typically collected at highly varying spatial and temporal scales, while forward process based models are typically run at either very large lithosphere-mantle scale, or at the scale of the sedimentary basin making it difficult to investigate and explore the detailed interaction and feedback between these systems. Here I will report on recent advances in forward modelling linking crust-lithosphere deformation with surface processes over a large range of scales resolving tectonic plate scale deformation and sedimentary basin formation at stratigraphic scales. The forward numerical models indicate a linkage and interaction between the structural style of thick-skinned large-scale mountain belt and rift-passive margin formation, erosion-transport-deposition processes operating at the surface, and the thin-skinned deformation occurring in the associated sedimentary basins.

  14. Oil migration examples in Irati Formation, Parana basin, Brazil

    SciTech Connect

    Espitalie, J.; Mizuta, K.; Carvalho, T.E.M.; Triguis, J.A.

    1983-03-01

    The Irati Formation (Late Permian), in the Parana basin, is a source rock with high oil generating potential. The TOC contents range from 0.5 to 13% according to the quality of the organic matter. Pyrolysis analysis indicates that the area where the Irati has the highest oil-generating source rock is in the north and south of the Parana basin. In these areas petroleum potential can reach 90 kg HC/t of rock. In the central part of the basin the Irati Formation might reach a depth of about 3200 m (10,498 ft). In many wells diabase intrusions have more or less completely cooked this formation, thus generating oil or gas, and leaving residual organic matter. The phenomenon of migration into the Irati Formation has been observed in many wells. In certain places, oil is accumulated in shales embedded between intrusion levels; in other places oil is accumulated into limestone beds, intercalated in the Irati Formation. It seems safe to assume that the oil accumulated in the deeper beds resulted from the effect of thermal intrusions and also from the effects of normal burial. Oil migration occurred after diabase intrusions (Late Cretaceous) during the increasing subsidence of the basin. In the Parana basin, the Irati Formation may be compared to a drain with a lateral oil migration. Vertical migration was hindered by the lack of enough porosity and permeability in the shales above the Irati source rock. Consequently, migration and accumulation of oil above and below the formation might have resulted from changes in facies of the Irati itself, by faulting, or by fractures due to diabase intrusions.

  15. Miocene temblor formation and related basin evolution, southwestern San Joaquin Basin, California

    SciTech Connect

    Gillespie, B.W.

    1988-01-01

    The southwestern San Joaquin basin is an area of great importance for the energy industry and academic basin analysts. Understanding basin evolution is a key concern for explorationists in this essentially pristine province. Temblor Formatio is exposed in an east-west-trending belt that comprises the north flank of the San Emigdio Mountains. Field and subsurface evidence were used to elucidate the geology, depositional environments, and age of the Temblor Formation. The formation represents sand-rich borderland sedimentation in a predominantly deep-marine setting. Deposition of Temblor clastics reflects deformation due to the impingement of the Farallon Pacific ridge with the California-North American plate margin during the middle Oliocene. As a result, severe uplift along the margins of the southern San Joaquin basin, reinforced by a lowstand of global seal level, caused large volumes of coarse, immature clastics to be shed into the rapidly subsiding deep-marine depocenter. Deposition of the Temblor was thus concurrent with the transformation from a convergent margin tectonic regime to one of dextral strike-slip. This transformation was marked by an episode of transform-extension indicated by volcanism, rapid subsidence, and marine transgression during the early Miocene. The Maricopa trough or oceanic connection from the San Joaquin basin to the Pacific Ocean is inferred to have existed between Recruit Pass and Maricopa. The age of the Temblor Formation is late Oligocene to early Miocene. Petroleum production is limited to the upper member in small oil fields flanking the northern Sam Emigdio Mountains.

  16. Formation of the Moon's Orientale multi-ring basin

    NASA Astrophysics Data System (ADS)

    Johnson, B. C.; Andrews-Hanna, J. C.; Zuber, M. T.; Melosh, J., IV; Blair, D. M.; Freed, A. M.; Collins, G. S.; Elbeshausen, D.

    2014-12-01

    We model the formation of the Moon's Orientale basin from impact to crater collapse using the iSALE hydrocode. Although we use GRAIL and LOLA data to constrain our models, we show that the modeled basin structure reveals more detail than inverse models can predict. Orientale exhibits three concentric topographic rings; the Outer Rook (R=330 km) and Cordillera (R=430 km), which are morphologically consistent with normal fault scarps; and the Inner Rook Ring (R=230 km), which is not. Our numerical models allow us to see, for the first time, how these ring structures form in real time. Shortly after ejecta emplacement, as the transient crater collapses, the Outer Rook fault forms followed by the Cordillera fault, with both faults cutting all the way through the crust. Subsequently, the topographic expression of the Inner Rook Ring is produced in part by the collapse of a central uplift, consistent with previous interpretation that the formation of Inner Rook Ring is analogous to the formation of peak-rings seen in smaller basins. The Inner Rook Ring is then modified by a secondary phase of inward collapse. The resultant basin structure is generally in good agreement with GRAIL derived crustal thickness models. Our modeling reveals that that two inflection points in the GRAIL derived crustal thickness are associated with Moho offsets of a few kilometers, which are the result of slip along the Cordillera and Inner Rook faults. In the future this association may be used to determine where faults are located in older mare filled basins. Our models also show that dilatant bulking is enhanced near the faults. Despite GRAIL's incredible sensitivity and resolution, localized Moho offsets and density changes associated with faults cannot be resolved by inverse modeling. A direct comparison of the gravity anomalies produced by these localized density features and present-day gravity could constrain the geometry of proposed ring dikes in the Orientale basin.

  17. Bouse Formation in the Bristol basin near Amboy, California, USA

    USGS Publications Warehouse

    Miller, David M.; Reynolds, Robert E.; Bright, Jordan E.; Starratt, Scott W.

    2014-01-01

    Limestone beds underlain and overlain by alluvial fan conglomerate near Amboy, California, are very similar in many respects to parts of the Bouse Formation, suggesting that an arm of the Pliocene Bouse water body extended across a wide part of the southern Mojave Desert. The deposits are north of the town of Amboy at and below an elevation of 290 m, along the northern piedmont of the Bristol “dry” Lake basin. The Amboy outcrops contain the Lawlor Tuff (4.83 Ma), which is also found in an outcrop of the Bouse Formation in the Blythe basin near Buzzards Peak in the Chocolate Mountains, 180 km southeast of Amboy. Bouse exposures near Amboy are ∼3.4 m thick, white, distinctly bedded, with limestone and calcareous sandstone as well as stromatolite mounds; we interpret these as nearshore deposits. The Bouse at Amboy contains ostracodes, diatoms, and mollusks that indicate saline lake or estuarine environments with an admixture of fresh-water forms. Along with wading bird tracks and a spine from a marine fish, these fossils suggest that the deposits formed in saline waters near a fresh-water source such as a perennial stream. Beds of the outcrop dip southward and are 113 m above the surface of Bristol Playa, where similar age sediments are buried 270+ m deep, indicating significant faulting and vertical tectonics in this part of the Eastern California Shear Zone during the past 5 m.y. Confirmation of the Bouse Formation at Amboy strengthens previous assignments to the Bouse Formation for mudstones in driller logs at Danby “dry” Lake, California, and suggests that areally extensive arms of the Bouse water body were west of the Blythe basin. The Bristol basin arm of the lower Bouse basin probably was restricted from the main water body by narrow passages, but Bouse sediment there is similar to that in the Blythe basin, suggesting generally similar water chemistry and environmental conditions. Examining the degree to which Bouse deposits in the western arms

  18. GRAIL Gravity Observations of Peak-Ring Basins on the Moon: Implications for Basin Formation

    NASA Astrophysics Data System (ADS)

    Baker, D. M.; Head, J. W.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2012-12-01

    Reassessment of the formation of peak-ring basins on the Moon using image and altimetry data from the Lunar Reconnaissance Orbiter has yielded a number of morphometric properties of these basin types that are helping to constrain the processes leading to their formation and the formation of larger multi-ring basins [1,2]. These analyses demonstrate the importance of the volume and depth of impact melting in modifying the interior morphology of large impact craters. At the onset diameter of peak-ring basins, the depth of the basin's melted zone approaches the depth of the transient crater, creating a strengthless interior melt cavity that facilitates gravitational collapse of the transient crater. The melt cavity suppresses central peak formation, and peak rings are formed outward from the melt zone boundary by the interaction of deep-seated rotational faults in the collapsing wall of the transient crater and huge vertical uplifts in the central portions of the basin. The final configuration of the peak-ring basin has a kilometers-thick slab of cooled residual impact melt resting on an uplifted mantle plug with little or no unmelted crustal material. Highly faulted and fractured, dilatant and possibly thickened crust should occur below and outward from the peak ring due to inward and upward translation of collapsed transient crater rim material. As a result of this configuration, the gravity structure should reflect an anomalously high density, uplifted impact melt plus mantle zone spatially confined to within the peak ring. Surrounding this should be a highly fractured, low density zone of possibly thickened crust. Bouguer gravity anomalies derived from Gravity Recovery and Interior Laboratoy (GRAIL) gravity data and Lunar Orbiter Laser Altimeter (LOLA) altimetry data show spatial patterns that are consistent with those predicted by the formation model briefly outlined above. Nearly all 17 peak-ring basins that have been cataloged on the Moon show positive Bouguer

  19. Sedimentation of shelf sandstones in Queen Formation, McFarland and Means fields, central basin platform of Permian basin

    SciTech Connect

    Malicse, A.; Mazzullo, J.; Holley, C.; Mazzullo, S.J.

    1988-01-01

    The Queen Formation is a sequence of carbonates, evaporites, and sandstones of Permian (Guadalupian) age that is found across the subsurface of the Central Basin platform of the Permian basin. The formation is a major hydrocarbon reservoir in this region, and its primary reservoir facies are porous shelf sandstones and dolomites. Cores and well logs from McFarland and Means fields (on the northwest margin of the Central Basin platform) were examined to determine the sedimentary history of the shelf sandstones.

  20. The deep structure of lunar basins - Implications for basin formation and modification

    NASA Technical Reports Server (NTRS)

    Bratt, S. R.; Solomon, S. C.; Head, J. W.; Thurber, C. H.

    1985-01-01

    Models for the crustal structure in the vicinity of nine impact basins, from an inversion of gravity and topographic data from the lunar nearside are presented. The models display a low-density nonmare crustal layer and a mare basalt layer, both of variable thicknesses. Assuming that topography in mare areas is isostatically compensated before the emplacement of mare basalts and that compensation of mare basalt units may be neglected, a decomposition of the gravity anomaly into contributions from Moho relief and mare fill is permitted. Minimum values for mare basalt thicknesses are obtained but because mare basalts and mantle material are similar in density, the thicknesses of the nonmare crust are estimated. An important constraint is the crustal thickness inferred from the Apollo 12 and 14 landing sites from seismic observations. The crustal thickness model indicates that the crust is thinner beneath each of the major nearside basins than in surrounding areas. New bounds on the volume of material ejected from each basin are derived. The geological implications of structural differences among basins for the processes of basin formation and modification are evaluated as functions of time on the moon.

  1. Basin-wide architecture of sandstone reservoirs in the Fort Union Formation, Wind River basin, Wyoming

    SciTech Connect

    Flores, R.M.; Keighin, C.W.; Keefer, W.R. )

    1991-06-01

    Architecture of hydrocarbon-bearing sandstone reservoirs of the Paleocene Fort Union Formation in the Wind River basin, Wyoming, was studied using lithofacies, grain size, bounding surfaces, sedimentary structures, internal organization, and geometry. Two principal groups of reservoirs, both erosionally based and fining upward, consist of either conglomeratic sandstone or sandstone lithofacies. Two types of architecture were recognized in conglomeratic sandstone reservoirs: (1) heterogeneous, multistacked, lenticular and (2) homogeneous, multiscoured, wedge-sheet bodies. Three types of architecture were recognized in sandstone reservoirs: (3) heterogeneous, multistacked, elongate; (4) homogeneous, multilateral, lenticular; and (5) homogeneous, ribbon-lensoid bodies. Conglomeratic sandstone reservoirs in the southern and southwestern parts of the basin suggest deposition in gravel-bedload fluvial systems influenced by provenance uplift of the Granite and southern Wind River mountains. Type 2 reservoirs represent deposits of eastward-flowing braided streams aggrading an alluvial valley in response to base level rise. Thus, to determine basin-wide architecture of reservoirs requires understanding the interplay between base level conditions, basin subsidence, and provenance uplift. These interrelated factors, in turn, control differences in hierarchies of fluvial systems throughout the basin.

  2. Basin Formation and Cratering on Mercury Revealed by MESSENGER

    NASA Astrophysics Data System (ADS)

    Chapman, C. R.; Fassett, C.; Marchi, S.; Merline, W. J.; Ostrach, L. R.; Prockter, L. M.

    2015-12-01

    Mercury has been bombarded by asteroids and comets throughout its history. The resulting craters and basins are the dominant topographic features on the planet. Although visible basins contain some of the most interesting tectonic features, plains, and evidence of vertical stratigraphy, they fall far short of saturating the surface. Nevertheless, Mercury has a greater spatial density of peak-ring basins and protobasins than any other Solar System body, partly because these morphologies begin at smaller sizes than on most bodies. Cratering at approximately three times the cratering rate on the Moon, combined with likely plains-forming volcanism, prevents recognition of surface features older than 4.0 to 4.1 Ga. Severe losses of craters <50 km in diameter (<20 km in some places) are ascribed to extensive formation of intercrater plains. Estimates of the cratering chronology of Mercury suggest that most plains formation ended about 3.6 to 3.7 Ga, though activity has continued in a few small regions until much more recently (e.g., inside the Rachmaninoff basin). Mercury, compared with other terrestrial bodies, is struck by projectiles impacting at much higher velocities, which is probably responsible for the formation of abundant secondary craters that dominate the numbers of craters <10 km diameter on older plains surfaces. The history of high-velocity bombardment has resulted in the production of abundant impact melts and has churned and processed the regolith, and eroded older topography, more thoroughly than on other Solar System bodies. Although the possible role of Mercury-specific impactors ("vulcanoids") cannot be excluded, imaging searches by MESSENGER have revealed no remaining vulcanoids and no other evidence suggests that Mercury has been bombarded by anything other than the same populations of asteroids and comets that have impacted the Moon and other terrestrial planets from the end of the period of heavy bombardment 3.8 to 3.9 Ga to the present.

  3. Formation and Evolution of the Junggar basin basement

    NASA Astrophysics Data System (ADS)

    He, D.

    2015-12-01

    Junggar Basin is located in the central part of the Central Asian Orogenic Belt (CAOB). Its basement nature is a highly controversial scientific topic, involving the basic style and processes of crustal growth.Based on the borehole data from over 300 wells drilled into the Carboniferous System, together with the high-resolution gravity and magnetic data (in a 1:50,000 scale), we made a detailed analysis of the basement structure, formation timing and process and later evolution on basis of core geochemical and isotopic analysis. Firstly, we defined the Mahu Precambrian micro-continental block in the juvenile crust of Junggar Basin according to the Hf isotopic analysis of the Carboniferous volcanic rocks. Secondly, the results of the tectonic setting and basin analysis suggest that the Junggar area incorporates three approximately E-W trending island arc belts (from north to south: Yemaquan-Wulungu-Chingiz, Jiangjunmiao-Luliang-Darbut and Zhongguai-Mosuowan-Baijiahai-Qitai respectively) and intervened three approximately E-W trending retro-arc or inter-arc basin belts from north to south, such as Santanghu-Suosuoquan-Emin, Wucaiwan-Dongdaohaizi-Mahu (Mahu block sunk as a bathyal basin during this phase) and Fukang-western well Pen1 accordingly. Thirdly, the closure of these retro-arc or inter-arc basins gradually toward the south led to the occurrence of collision and amalgamation of the above-mentioned island arcs during the Carboniferous, constituting the basic framework of the Junggar "block". Fourthly, the emplacement of large-scale mantle-derived magmas occurred in the latest Carboniferous or Early Permian. For instance, the well Mahu 5 penetrate the latest Carboniferous basalts with a thickness of over 20m, and these mantle-derived magmas concreted the above-mentioned island arc-collaged body. Therefore, the Junggar basin basement mainly comprises pre-Carboniferous collaged basement, and its formation is characterized by two-stage growth model, involving the

  4. Basin analysis and petroleum potential of Michigan Basin: deposition and subsidence history from Middle Ordovician (Trenton Formation) to Early Devonian

    SciTech Connect

    Nurmi, R.D.

    1984-12-01

    The history of the Michigan basin (Early Ordovician to Early Devonian) is that of a nonuniformly subsiding basin, with the Michigan basin, at times, nearly disappearing as either a topographic feature or a depositional center. This history is interpreted from the analysis of lithostratigraphic units, time stratigraphic features, and log formats (term by J. Forgotson). These units are defined for wells throughout the Michigan basin, and they extended eastward into the Appalachian basin. The definition and thickness mapping of these lithostratigraphic units and formats are accomplished using well cuttings, cores, and wire-line geophysical well logs. From these data, it is possible to interpret the major aspects of both the subsidence and depositional history of the basin. During deposition of both the Trenton limestones and Early Silurian carbonates and shales, the Michigan basin behaved as if it were part of the greater Appalachian basin, whereas prior to the deposition of the Trenton (Middle Ordovician) and during Middle and Late Silurian, the Michigan basin was an entity separate from, and with an apparent structural independence of, the greater Appalachian basin. The structural and topography of the Trenton prior to the deposition of the Utica Shale was mapped throughout Michigan to provide insight into the nature of petroleum entrapment in the Trenton formation. The structural entrapment of petroleum in southeast Michigan contrasts with the combination diagenetic to structural Albio-Scipio trend of south-central Michigan. Evidence is available that more of these two types of traps occur in unproducing areas of the Michigan basin.

  5. Potential for deep basin-centered gas accumulation in Travis Peak (Hosston) Formation, Gulf Coastal Basin

    USGS Publications Warehouse

    Bartberger, Charles E.; Dyman, Thaddeus S.; Condon, Steven M.

    2003-01-01

    The potential of Lower Cretaceous sandstones of the Travis Peak Formation in the northern Gulf Coast Basin to harbor a basin-centered gas accumulation was evaluated by examining (1) the depositional and diagenetic history and reservoir properties of Travis Peak sandstones, (2) the presence and quality of source rocks for generating gas, (3) the burial and thermal history of source rocks and time of gas generation and migration relative to tectonic development of Travis Peak traps, (4) gas and water recoveries from drill-stem and formation tests, (5) the distribution of abnormal pressures based on shut-in-pressure data, and (6) the presence or absence of gas-water contacts associated with gas accumulations in Travis Peak sandstones. The Travis Peak Formation (and correlative Hosston Formation) is a basinward-thickening wedge of terrigenous clastic sedimentary rocks that underlies the northern Gulf Coast Basin from eastern Texas across northern Louisiana to southern Mississippi. Clastic infl ux was focused in two main fl uvial-deltaic depocenters?one located in northeastern Texas and the other in southeastern Mississippi and northeastern Louisiana. Across the main hydrocarbon-productive trend in eastern Texas and northern Louisiana, the Travis Peak Formation is about 2,000 ft thick. Most Travis Peak hydrocarbon production in eastern Texas comes from drilling depths between 6,000 and 10,000 ft. Signifi cant decrease in porosity and permeability occurs through that depth interval. Above 8,000-ft drilling depth in eastern Texas, Travis Peak sandstone matrix permeabilities often are signifi cantly higher than the 0.1-millidarcy (mD) cutoff that characterizes tight-gas reservoirs. Below 8,000 ft, matrix permeability of Travis Peak sandstones is low because of pervasive quartz cementation, but abundant natural fractures impart signifi cant fracture permeability. Although pressure data within the middle and lower Travis Peak Formation are limited in eastern Texas

  6. Formation of the Gulf of Mexico Salt Basin

    NASA Astrophysics Data System (ADS)

    Norton, I. O.; Van Avendonk, H. J.; Christeson, G. L.; Eddy, D. R.

    2014-12-01

    component is a prerequisite for formation of marginal salt basins like the GOM, Aptian South Atlantic and present-day Red Sea.

  7. The role of rheology in extensional basin formation modelling

    NASA Astrophysics Data System (ADS)

    Fernàndez, M.; Ranalli, G.

    1997-12-01

    The rheology of the lithosphere determines its deformation under given initial and boundary conditions. This paper presents a critical discussion on how rheological properties are taken into account in extensional basin modelling. Since strength envelopes are often used in models, we review the uncertainties (in temperature and rheological parameters) and assumptions (in type of rheology and mode of deformation) involved in their construction. Models of extensional basins are classified into three groups: kinematic, kinematic with rheological constraints, and dynamic. Rheology enters kinematic models only implicitly, in the assumption of an isostatic compensation mechanism. We show that there is a critical level of necking that reconciles local isostasy with the finite strength of the lithosphere, which requires a flexural response. Kinematic models with rheological constraints make use of strength envelopes to assess the initial lateral variations of lithospheric strength and its evolution with time at the site of extension. Dynamic models are the only ones to explicitly introduce rheological constitutive equations (usually in plane strain or plane stress). They usually, however, require the presence of an initial perturbation (thickness variations, pre-existing faults, thermal inhomogeneities, rheological inhomogeneities). The mechanical boundary conditions (kinematic and dynamic) and the thermal boundary conditions (constant temperature or constant heat flux at the lower boundary of the lithosphere) may result in negative/positive feedbacks leading to cessation/acceleration of extension. We conclude that, while kinematic models (with rheological constraints if possible) are very successful in accounting for the observed characteristics of sedimentary basins, dynamic models are necessary to gain insight into the physical processes underlying basin formation and evolution.

  8. Depositional environments of Fort Union Formation, Bison Basin, Wyoming

    SciTech Connect

    Southwell, E.H.; Steidtmann, J.R.; Middleton, L.

    1983-08-01

    The Paleocene Fort Union Formation crops out in the vicinity of the Bison basin, approximately equidistant from the southeast terminus of the Wind River Range and the southwestern edge of the Granite Mountains uplift in central Wyoming. Early Laramide tectonic activity produced a series of uplifts north of the area forming a platform separating the Wind River and Great Divide basins. During middle to late Paleocene, aggrading fluvial systems flowing southward, rapidly deposited a sequence of thin, lenticular conglomerates and medium to coarse-grained planar-bedded sandstones in braided and anastomosing stream channels and carbonaceous overbank silt and claystones. Subaerially exposed interchannel areas developed cyclic pedogenic horizons. Early diagenetic cementation preserved tubular burrows and rhizoliths as well as impressions of fruits, nuts, leaves, and wood. Anomalous silicic cementation of mudstone, sandstone, and conglomerates probably are silcrete soil horizons developed in a warm temperature to subtropical humid climate. The sandstones are multicyclic containing fragments of preexisting siliceous sedimentary rocks (e.g., Tensleep Sandstone, Mowry Shale, and cherts from the Madison, Morrison, and Phosphoria Formations). Reworked glauconite is locally abundant in some Fort Union sandstones, reflecting the proximity of Paleozoic sources. Altered and embayed feldspars are present in trace amounts throughout most of the section, but significant accumulations of fresh feldspar are present near the top, indicating unroofing of Precambrian source before the Eocene.

  9. The formation of peak-ring basins: Working hypotheses and path forward in using observations to constrain models of impact-basin formation

    NASA Astrophysics Data System (ADS)

    Baker, David M. H.; Head, James W.; Collins, Gareth S.; Potter, Ross W. K.

    2016-07-01

    Impact basins provide windows into the crustal structure and stratigraphy of planetary bodies; however, interpreting the stratigraphic origin of basin materials requires an understanding of the processes controlling basin formation and morphology. Peak-ring basins (exhibiting a rim crest and single interior ring of peaks) provide important insight into the basin-formation process, as they are transitional between complex craters with central peaks and larger multi-ring basins. New image and altimetry data from the Lunar Reconnaissance Orbiter as well as a suite of remote sensing datasets have permitted a reassessment of the origin of lunar peak-ring basins. We synthesize morphometric, spectroscopic, and gravity observations of lunar peak-ring basins and describe two working hypotheses for the formation of peak rings that involve interactions between inward collapsing walls of the transient cavity and large central uplifts of the crust and mantle. Major facets of our observations are then compared and discussed in the context of numerical simulations of peak-ring basin formation in order to plot a course for future model refinement and development.

  10. Mass-movement deposits in the lacustrine Eocene Green River Formation, Piceance Basin, western Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Birdwell, Justin E.; Brownfield, Michael E.; Mercier, Tracey J.

    2015-01-01

    The Eocene Green River Formation was deposited in two large Eocene saline lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. Here we will discuss mass-movement deposits in just the Piceance Basin part of Lake Uinta.

  11. Geomechanics and elastic anisotropy of the Bakken Formation, Williston Basin

    NASA Astrophysics Data System (ADS)

    Ostadhassan, Mehdi

    Many of the earth's rocks exhibit anisotropic characteristics. Anisotropy is particularly common in many sedimentary rocks, such as shales. Anisotropy is defined as the spatial alignment of mineral grains, layers, fractures and stresses which causes elastic wave velocity and other elastic properties to vary with direction. There are two types of anisotropy: intrinsic and stress-induced. Intrinsic anisotropy is caused by beddings, microstructures or aligned fractures formed during deposition. Stress-induced anisotropy is caused by strain associated with external stresses. Intrinsic anisotropy originates in the absence of external stresses, while stress-induced anisotropy results from tectonic and overburden stresses. The style of earth material alignment causes two simplified, but convenient models of anisotropy: vertically transverse isotropy (VTI), like shale, and horizontally transverse isotropy (HTI), like vertically fractured medium. These models have been used to describe how physical properties of rock vary in a medium. Identifying the anisotropy in a formation is important in reservoir characterization seismic data processing and oil-field development. Deep shales are the most abundant yet least characterized sedimentary rocks in the Williston Basin of North Dakota. They are significant sources of hydrocarbon unconventional resources in this basin. This dissertation aims to fulfill an investigation of anisotropy in this rock type in several different facets through exploiting of field data. I seek to generate key information for better interplay of field in-situ stress and the existing natural fracture systems for the purpose of drilling, well completion, perforating, hydraulic fracturing and defining reservoir properties. In this study advanced sonic logging data has been processed and interpreted to calculate three independent shear moduli. These parameters then will be used to estimate Thomsen (1986) anisotropy parameters, elastic stiffness coefficients

  12. The mechanics of ringed basin formation. [lunar impact craters

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.; Mckinnon, W. B.

    1978-01-01

    The study investigates the mechanics of ring formation in lunar basins by collapse or slumping. Two classes of models are presented in order to broaden the range of plausible mechanisms involved. Extrusion flow models which assume a weak layer underlying a strong layer as well as plastic flow models which assume a continuous decrease of cohesion strength with depth are considered. In both classes, strength or resistance to deformation decreases with depth. If this decrease is rapid enough, in either set of models, at least one concentric fault scarp forms. The ratio between the scarp radius and the crater radius varies between 1.2 and about 2.7 depending on the model, and is thus in the range of observed radius ratios.

  13. Geologic Observations and Numerical Modeling: A Combined Approach to Understanding Crater and Basin Formation and Structure

    NASA Astrophysics Data System (ADS)

    Potter, R. W. K.; Head, J. W., III

    2014-12-01

    Impact cratering is a fundamental geological process throughout the Solar System. The Moon is an ideal location to document the impact cratering process due to the number and excellent state of preservation of large craters and basins, and the wide range of geological, geophysical, topographic, mineralogic, remote sensing and returned sample data. Despite the number and excellent preservation state of many large complex craters and basins, their formation and the origin of their structural features and the stages in their evolution remain contentious. To more comprehensively document the final stage of lunar impact basin formation, we have compiled detailed topographic, geological and mineralogic maps of several type examples of peak-ring and multi-ring basins, including the Orientale basin. These data include the mineralogic characteristics of basin ring structures and assist in the interpretation of the target stratigraphy, and the depth of origin of basin rings. Data for the current structure of basins is compared to numerical model outputs of basin-forming impacts, which track formation to the conclusion of dynamic processes (2 to 3 hours after impact). We use the Orientale basin as an example and provide combined correlations and interpretations that assign rings to various stages in the numerical models, and compare these candidates to crustal stratigraphy, with the ultimate aim of producing a consistent model for large crater/basin formation. The shock physics code iSALE is used to numerically model the basin-scale impacts. Constitutive equations and equations of state for materials analogous to the lunar crust (gabbroic anorthosite) and mantle (dunite) are used. Aspects of the numerically-produced lunar basins (e.g., material distribution and accumulated stress) are compared and contrasted to remote observations and geological maps of the Orientale rings and geological units, including ejecta and impact melt deposits.

  14. Laramide basin subsidence and fluvial architecture of the Fort Union and Wasatch Formations in the southern greater Green River basin

    SciTech Connect

    Johnson, P.L. )

    1990-05-01

    The late Paleocene Fort Union Formation and early Eocene Wasatch Formation exposed around the Rock Springs uplift demonstrate subsidence variations in the southern greater Green River basin. Total unit thickness and distribution of channel sandstones within overbank deposits record differences in subsidence rate across the basin. On the west flank of the Rock springs uplift, west of the bounding fault, channels have close spacing and thickness is low. On the south flank within the uplift, the thickness values are intermediary but channels are very closely spaced. Away from the uplift on the southeast flank, the thickness is greatest and channels are very widely spaced. Paleocurrents indicate that rivers flowed southward across the central basin to an eastward-flowing axis trunk river at the southern end of the basin. Both the south and southeast flank area were within the basin axis, but the west flank areas was within the central basin. Thickness trends represent subsidence variations across the basin. Subsidence was slowest at the west flank area. On the south flank, subsidence was greater, and the highest subsidence rate was on the southeast flank. Generally, thickness indicates increasing subsidence toward the Uinta uplift, but the south flank area is an exception. Basin subsidence occurred by flexure of the lithosphere under a tectonic load from the Uinta uplift to the south. Thickened lithosphere at the Rock springs uplift bounding fault was resistant to flexure. Thus, on the south flank near the fault, subsidence was slower than on the southeast flank where the lithosphere was not thickened. The closely spaced fluvial architecture on the south flank resulted from a narrow basin axis flood plain. A narrow flood plain possibly resulted from the subsidence resistance of thickened lithosphere at the Rock Springs uplift bounding fault or from topographic expression of the uplift itself.

  15. Horizontal drilling the Bakken Formation, Williston basin: A new approach

    SciTech Connect

    Lefever, J.A. )

    1990-05-01

    Horizontal drilling is an attractive new approach to exploration and development of the Mississippian/Devonian Bakken Formation in the southwestern part of North Dakota. This drilling technique increases the probability of success, the profit potential, the effective drainage area maximizing recoverable reserves, and the productivity by encountering more natural occurring fractures. The target formation, the Mississippian/Devonian Bakken, consists of three members in an overlapping relationship, a lower organic-rich black shale, a middle siltstone/limestone, and an upper organic-rich black shale. It attains a maximum thickness of 145 ft and thins to a feather edge along its depositional limit. Considered to be a major source rock for the Williston basin, the Bakken is usually overpressured where productive. Overpressuring is attributed to intense hydrocarbon generation. Reservoir properties are poor with core fluid porosities being generally 5% or less and permeabilities ranging from 0.1 to 0.2 md. The presence of natural fractures in the shale are necessary for production. Two types of fractures are associated with Bakken reservoirs: large vertical fractures (of tectonic origin) and microfractures (probably related to hydrocarbon generation). An economic comparison between horizontal and vertical wells show that well completion costs are approximately two times higher (average costs; $1,500,000 for a horizontal to $850,000 for a vertical) with average payout for horizontal wells projected to occur in half the time (1.5 yr instead of 3.4 yr). Projected production and reserves are considered to be 2 to 4 times greater from a horizontal well.

  16. Provenance and sediment dispersal of the Triassic Yanchang Formation, southwest Ordos Basin, China, and its implications

    NASA Astrophysics Data System (ADS)

    Xie, Xiangyang

    2016-04-01

    The Ordos Basin in north central China records a transition from marine to non-marine deposition during the late Paleozoic to early Mesozoic. As a result, the northern and southern regions of the Ordos Basin show different tectonic histories and very distinctive sedimentation styles. Two deformation belts, the Qinling orogenic belt to the south and the Liupanshan thrust and fold belt to the west, controlled the structural evolution of the southern Ordos Basin during the early Mesozoic. Paleocurrent analysis, net-sand ratio maps, sandstone modal analysis, and U-Pb detrital zircon geochronology were used to document sediment sources and dispersal patterns of the Triassic Yanchang Formation in the southwest Ordos Basin. Paleocurrent measurements suggest that the sediments were mainly derived from the Liupanshan and the Qinling orogenic belts. Net-sand ratio maps show that several fan delta systems controlled sediment delivery in the south Ordos Basin. Both sandstone modal analysis and U-Pb detrital zircon geochronology suggest that the Yanchang Formation is locally sourced from both of the basin marginal deformation belts; the lower and middle sections are recycled Paleozoic sedimentary rocks mainly derived from the north Qinling orogenic belt, whereas for the upper section, the Qilian-Qaidam terranes and possibly the west Qinling orogenic belt began to shed sediments into the southwest Ordos Basin. Results have important implications for basin marginal tectonics and its controls on sedimentation of intracratonic basins in China and similar settings.

  17. Depositional systems of Fountain formation and its basinal equivalents, northwestern Denver Basin, Colorado

    SciTech Connect

    Napp, K.F.; Ethridge, F.G.

    1985-05-01

    The objective of this study is to provide a better understanding of the depositional systems of the Pennsylvanian Fountain Formation in north-central Colorado. The study area is bounded by T4N, T11N, R66W, and R70W, encompassing portions of the foothills outcrop belt and the Denver basin. The sedimentary sequence observed in surface exposures displays little vertical variation. It is composed of vertically stacked, fining-upward, gravel to siltstone and mudstone cycles containing trough and planar cross-beds, horizontal beds, root structures, and nodular limestone. This succession represents deposition in Donjek-type braided streams and abandoned channel-fill sequences, and the development of soil horizons on a subaerial alluvial fan or alluvial plain. In the subsurface, the vertical succession begins with a basal course-grained 140-ft (43-m) thick interval that is identical on the rocks found in surface outcrops to the west. This interval is overlain be 410 ft (125 m) of red shale, siltstone, sandstone, and fossilferous limestone that grades eastward into black organic shale and limestone. Capping the sequence is a 500-ft (152 m) interval of red shale, siltstone, sandstone, gypsum- and anhydrite-bearing dolomites and fossiliferous limestones that interfinger with typical Fountain coarse-grained terrigenous clastics. This vertical succession of Fountain rocks in the subsurface suggests the following sequence of depositional systems from base to top: alluvial fan and braided alluvial plain, fan deltas, and small interfan embayments that grade eastward into a normal-salinity marine shoreface and an offshore hypersaline carbonate shelf. Normal salinity marine conditions were probably maintained in the parallic zone by the influx of ancestral Front Range runoff.

  18. Basin Analysis of the Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain

    SciTech Connect

    Mancini, Ernest A.

    2003-02-06

    The project objectives are improving access to information for the Mississippi Interior Salt Basin by inventorying data files and records of the major information repositories in the region, making these inventories easily accessible in electronic format, increasing the amount of information available on domestic sedimentary basins through a comprehensive analysis of the Mississippi Interior Salt Basin, and enhancing the understanding of the petroleum systems operating in the Mississippi Interior Salt Basin.

  19. Flow of formation waters in the cretaceous-miocene succession of the Llanos basin, Colombia

    SciTech Connect

    Villegas, M.E.; Ramon, J.C.; Bachu, S.; Underschultz, J.R.

    1994-12-01

    This study presents the hydrogeological characteristics and flow of formation waters in the post-Paleozoic succession of the Llanos basin, a mainly siliciclastic foreland sub-Andean sedimentary basin located in Columbia between the Cordillera Oriental and the Guyanan Precambrian shield. The porosity of the sandy formations is generally high, in the range of 16-20% on average, with a trend of decreasing values with depth. Permeabilities are also relatively high, in the 10{sup 2} and 10{sup 3} md range. THe salinity (total dissolved solids) of formation waters is generally low, in the 10,000-20,000 mg/L range, suggesting that at least some strata in the basin have been flushed by metoeoric water. The shaly units in the sedimentary succession are weak aquitards in the eastern and southern parts of the basin, but are strong in the central-western part. The pressure in the basin is close to or slightly subdepth, particularly in the central-western area. The flow of formation waters in the upper units is driven mainly by topography from highs in the southwest to lows in the northeast. Local systems from the foothills and from local topographic highs in the east feed into this flow system. The flow of formation waters in the lower units is driven by topography only in the southern, eastern, and northern parts of the basin. In the central-western part, the flow is downdip toward the thrust-fold belt, driven probably by pore-space rebound induced by erosional unloading, which also is the cause of underpressuring. Hydrocarbons generated in the Cretaceous organic-rich, shaly Gacheta Formation probably have migrated updip and to the north-northeast, driven by buoyancy and entrained by the topography-driven flow of formation waters in Cretaceous-Oligocene strata in the central-western part of the basin could have created conditions for hydrodynamic entrapment of hydrocarbons.

  20. Deep Water Compositions From the Los Angeles Basin and the Origin of Formation Water Salinity

    NASA Astrophysics Data System (ADS)

    Boles, J.; Giles, G.; Lockman, D.

    2005-12-01

    Deep basin formation waters represent original depositional waters that have been modified by diagenetic processes at elevated temperatures and pressures. In addition, they may be diluted by meteoric incursion from elevated structural blocks along basin flanks. It has long been thought that deep basin formation waters have salinities greater than sea water due to various processes like clay membrane filtration or other types of water-rock interaction. However, our work and similar studies in the San Joaquin basin show that formation waters in deep basins are more likely to become diluted rather than concentrated in the absence of soluble evaporite deposits that might underlie the basin. The idea of increased salinity with depth arose from studies in which the underpinning of the basin consisted of soluble evaporate deposits such as the Texas Gulf Coast, Illinois, Michigan, and some North Sea areas. There are very few deep formation water analyses from the Los Angeles Basin. Furthermore, very few of the current produced waters from any depth can be considered pristine because of the widespread formation water injection programs and commingling of fluids from different levels. Here, we describe the first analyses from a deep, previously untouched part of the basin that is currently being developed in the Inglewood Oil Field. We have analyzed a suite of formation waters from the mid-Miocene marine Sentous sandstone from sub-sea level depths of 2250 m to 2625 m at temperatures of about 110 to 126°C and pressures of about 27 MPa. The original depositional waters in the Sentous Formation were sea water whereas the sampled waters are diluted by about 20% from sea water and some show as much as 50% dilution. Based on comparison of oxygen and deuterium isotopes between the meteoric water trend and these waters, we conclude that the smectite to illite dehydration reaction is the major cause of dilution to the original formation water. Other notable differences include

  1. Effects of basin bottom slope on jet hydrodynamics and river mouth bar formation

    NASA Astrophysics Data System (ADS)

    Jiménez-Robles, A. M.; Ortega-Sánchez, M.; Losada, M. A.

    2016-06-01

    River mouth bars are strategic morphological units primarily responsible for the development of entire deltaic systems. This paper addresses the role of receiving basin slope in the hydrodynamics of an exiting sediment-laden turbulent jet and in resulting mouth bar morphodynamics. We use Delft3D, a coupled hydrodynamic and morphodynamic numerical model, along with a theoretical formulation to reproduce the physics of the problem, characterized by a fluvially dominated inlet free of waves and tides. We propose an updated theoretical model with a slope-dependent entrainment coefficient, showing that the rate at which ambient fluid is incorporated into a jet increases with higher basin slopes. Transient results reveal that the magnitude of a basin slope can alter the stability of a jet, favoring the formation of an unstable meandering jet. While a stable jet gives rise to "middle-ground" bars accompanied by diverging channels, a "lunate" mouth bar results from unstable jets. Additional morphodynamic simulations demonstrate that the time required for mouth bar stagnation in its final position increases linearly with the basin slope. In contrast, the distance at which the mouth bar eventually forms decreases until reaching an asymptotic value for slopes higher than 2%. Moreover, the basin slope highly influences sedimentary processes responsible for bar formation: for milder slopes, progradation processes prevail, while in steeper basins aggradation is more relevant. Finally, the minimum relative water depth over a bar crest that forces the flow to bifurcate around a fully developed bar decreases with the basin slope.

  2. Modes of sedimentary basin formation in the north-eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Stephenson, Randell; Starostenko, Vitaly; Sydorenko, Grygoriy; Yegorova, Tamara

    2016-04-01

    The Greater Caucasus and Black Sea sedimentary basins developed in a Mesozoic back-arc setting, the former older than the latter (Jurassic v. Cretaceous). Compressional shortening of the former and accompanying ongoing development of marginal basin depocentres in the north-eastern Black Sea - which is closely tied to the formation of the Crimea-Greater Caucasus orogen - is a Cenozoic phenomenon, starting in the Eocene and proceeding until the present day. Recently, the sedimentary basin/crust/lithosphere geometry of the study area has been characterised across a range of scales using regional seismic reflection profiling, long-offset refraction/wide-angle reflection profiling and local earthquake tomography. These provide a new integrated image of the present-day crustal structure and sedimentary basin architecture of the northern margin of the eastern Black Sea, north across the Azov Sea and provide evidence of the deeper expression of sedimentary basins and the processes controlling the geometry of their inversion during the Cenozoic. It is inferred that the Greater Caucasus paleo-Basin, lying stratigraphically below the Black Sea and younger sedimentary successions, extends further to the west than previously known. This basin has significant thickness in the area between the Azov and Black seas and probably forms the deeper core of the Crimea-Caucasus inversion zone. The Crimea-Greater Caucasus orogenic belt is the expression of "basin inversion" of the Jurassic Greater Caucasus paleo-Basin, the degree of inversion of which varies along strike. The Greater Caucasus foredeep basins - Indolo-Kuban and Sorokin-Tuapse troughs -represent syn-inversional marginal troughs to the main inversion zone. The Shatsky Ridge - the northern flank of the main East Black Sea Basin - may also be mainly a syn-inversional structure, underlain by a blind thrust zone expressed as a northward dipping zone of seismicity on the northern margin of the eastern Black Sea.

  3. Geologic and hydrologic controls on coalbed methane producibility, Williams Fork Formation, Piceance Basin, Colorado

    SciTech Connect

    Tyler, R.; Scott, A.R.; Kaiser, W.R.; Nance, H.S.; McMurry, R.G. )

    1996-01-01

    Structural and depositional setting, coal rank, gas content, permeability, hydrodynamics, and reservoir heterogeneity control the producibility of coalbed methane in the Piceance Basin. The coal-rich Upper Cretaceous, Williams Fork Formation is genetically defined and regionally correlated to the genetic sequences in the Sand Wash Basin, to the north. Net coal is thickest in north-south oriented belts which accumulated on a coastal plain, behind west-east prograding shoreline sequences. Face cleats of Late Cretaceous age strike E-NE and W-NW in the southern and northern parts of the basin, respectively, normal to the Grand Hogback thrust front. Parallelism between face-cleat strike and present-day maximum horizontal stresses may enhance or inhibit coal permeability in the north and south, respectively. Geopressure and hydropressure are both present in the basin with regional hydrocarbon overpressure dominant in the central part of the basin and hydropressure limited to the basin margins. The most productive gas wells in the basin are associated with structural terraces, anticlines, and/or correspond to Cameo-Wheeler-Fairfield coal-sandstone development, reflecting basement detached thrust-faulting, fracture-enhanced permeability, and reservoir heterogeneity. Depositional heterogeneties and thrusts faults isolate coal reservoirs along the Grand Hogback from the subsurface by restricting meteoric recharge and basinward flow of ground water. An evolving coalbed methane producibility model predicts that in the Piceance Basin extraordinary coalbed methane production is precluded by low permeability and by the absence of dynamic ground-water flow.

  4. Geologic and hydrologic controls on coalbed methane producibility, Williams Fork Formation, Piceance Basin, Colorado

    SciTech Connect

    Tyler, R.; Scott, A.R.; Kaiser, W.R.; Nance, H.S.; McMurry, R.G.

    1996-12-31

    Structural and depositional setting, coal rank, gas content, permeability, hydrodynamics, and reservoir heterogeneity control the producibility of coalbed methane in the Piceance Basin. The coal-rich Upper Cretaceous, Williams Fork Formation is genetically defined and regionally correlated to the genetic sequences in the Sand Wash Basin, to the north. Net coal is thickest in north-south oriented belts which accumulated on a coastal plain, behind west-east prograding shoreline sequences. Face cleats of Late Cretaceous age strike E-NE and W-NW in the southern and northern parts of the basin, respectively, normal to the Grand Hogback thrust front. Parallelism between face-cleat strike and present-day maximum horizontal stresses may enhance or inhibit coal permeability in the north and south, respectively. Geopressure and hydropressure are both present in the basin with regional hydrocarbon overpressure dominant in the central part of the basin and hydropressure limited to the basin margins. The most productive gas wells in the basin are associated with structural terraces, anticlines, and/or correspond to Cameo-Wheeler-Fairfield coal-sandstone development, reflecting basement detached thrust-faulting, fracture-enhanced permeability, and reservoir heterogeneity. Depositional heterogeneties and thrusts faults isolate coal reservoirs along the Grand Hogback from the subsurface by restricting meteoric recharge and basinward flow of ground water. An evolving coalbed methane producibility model predicts that in the Piceance Basin extraordinary coalbed methane production is precluded by low permeability and by the absence of dynamic ground-water flow.

  5. Orientale Impact Basin: Topographic Characterization from Lunar Orbiter Laser Altimeter (LOLA) Data and Implications for Models of Basin Formation and Filling

    NASA Astrophysics Data System (ADS)

    Head, James; Smith, David; Zuber, Maria; Neumann, Gregory; Fassett, Caleb; Whitten, Jennifer; Garrick-Bethell, Ian

    2010-05-01

    The 920 km diameter Orientale basin is the youngest and most well-preserved large multi-ringed impact basin on the Moon; it has not been significantly filled with mare basalts, as have other lunar impact basins, and thus the basin interior deposits and ring structures are very well-exposed and provide major insight into the formation and evolution of planetary multi-ringed impact basins. We report here on the acquisition of new altimetry data for the Orientale basin from the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter. Pre-basin structure had a major effect on the formation of Orientale; we have mapped dozens of impact craters underlying both the Orientale ejecta (Hevelius Formation-HF) and the unit between the basin rim (Cordillera ring-CR) and the Outer Rook ring (OR) (known as the Montes Rook Formation-MRF), ranging up in size to the 630 km diameter Mendel-Rydberg basin just to the south of Orientale; this crater-basin topography has influenced the topographic development of the basin rim (CR), sometimes causing the basin rim to lie at a topographically lower level than the inner basin rings (OR and Inner Rook-IR). In contrast to some previous interpretations, the distribution of these features supports the interpretation that the OR ring is the closest approximation to the basin excavation cavity. The total basin interior topography is highly variable and typically ranges ~6-7 km below the surrounding pre-basin surface, with significant variations in different quadrants. The inner basin depression is about 2-4 km deep below the IR plateau. These data aid in the understanding of the transition from peak-ring to multi-ringed basins and permit the quantitative assessment of post-basin-formation thermal response to impact energy input and uplifted isotherms. The Maunder Formation (MF) consists of smooth plains (on the inner basin depression walls and floor) and corrugated deposits (on the IR plateau); also observed are depressions

  6. The formation of deep basins in High Arctic from metamorphism in continental crust

    NASA Astrophysics Data System (ADS)

    Artyushkov, Eugene; Belyaev, Igor; Chekhovich, Peter; Petrov, Eugene; Poselov, Viktor

    2014-05-01

    In the East Barents and North Chukchi basins, 16-20 km deep, the crystalline crust is attenuated to 12-18 km (reference profiles 2-AR, 4-AR and 5-AR). P-wave velocities and densities in this layer are characteristic of the oceanic crust. However, the subsidence history in the basins is quite different from that typical of the oceanic crust. In both basins the subsidence continued for several hundred million years and one half of the deposits or more was formed long after the start of the subsidence when cooling of the oceanic plate would be already over. Moreover, the basins are 4-5 km deeper than it could be expected according to the thickness of the crystalline crust above the Moho boundary. In the absence of large free-air gravity anomalies, joint analysis of the gravity and seismic data indicates the existence under the Moho of thick layers of high-density and high-velocity eclogites. As can be seen in high resolution seismic profiles, the intensity of crustal stretching did not exceed 10% in the basins, and their formation can be predominantly attributed to a high-grade metamorphism in the mafic lower part of continental crust. At some episodes, strong increase in the rate of subsidence occurred in the basins. This indicates acceleration of metamorphism catalyzed by infiltration of mantle fluids. A set of the above features, abnormally large depth, long subsidence history with its acceleration at the late stages, and episodes of pronounced acceleration of the subsidence represent characteristic features of some other large hydrocarbon basins, e.g., of the North and South Caspian basins. These features can be used for prospecting new prolific provinces on the Arctic shelf. The Lomonosov ridge, Mendeleev high and the Makarov basin pertain to the same structural type. In the Oligocene they underwent erosion near to sea level with the formation of pronounced unconformity. Then at the end of Oligocene deep-water basins were formed in these regions. Rapid crustal

  7. Basin Analysis of Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain

    SciTech Connect

    Ernest Mancini

    2001-03-01

    Part 3 (Petroleum System Modeling of the Jurassic Smackover Formation) objectives are to provide an analysis of the Smackover petroleum system in Years 4 and 5 of the project and to transfer effectively the research results to producers through workshops and topical reports. Work Accomplished (Year 5): Task 1 - Basin Flow - Basin flow modeling has been completed and the topical report has been submitted to the U.S. DOE for review. Task 2 - Petroleum Source Rocks - Work on the characterization of Smackover petroleum source rocks has been integrated into the basin flow model. The information on the source rocks is being prepared for inclusion in the final report. Task 3 - Petroleum Reservoirs - Work on the characterization of Smackover petroleum reservoirs continues. The cores to be described have been identified and many of the cores for the eastern and western parts of the basin have been described. Task 4 - Reservoir Diagenesis - Work on reservoir diagenesis continues. Samples from the cores selected for the reservoir characterization are being used for this task. Task 5 - Underdeveloped Reservoirs - Two underdeveloped Smackover reservoirs have been identified. They are the microbial reef and shoal reservoirs. Work Planned (Year 5): Task 1 - Basin Flow - This task has been completed and the topical report has been submitted to the U.S. DOE. Task 2 - Petroleum Source Rocks - Petroleum source rock information will continue to be prepared for the final report. Task 3 - Petroleum Reservoirs - Characterization of petroleum reservoirs will continue through core studies. Task 4 - Reservoir Diagenesis - Characterization of reservoir diagenesis will continue through petrographic analysis. Task 5 - Underdeveloped Reservoirs - Study of Smackover underdeveloped reservoirs will continue with focus on the microbial reef and shoal reservoirs.

  8. The Lunar-wide Effects of the Formation of Basins on the Megaregolith

    NASA Technical Reports Server (NTRS)

    Petro, . E.; Pieters, C. M.

    2005-01-01

    The surface of the Moon underwent an intense bombardment during the first approx.700 my of it s history (e.g. [1]). During this time at least 43 basins [1,2] and countless smaller craters were formed across the entire surface [1,3]. A quantitative assessment of the regolith as formed and modified by basins is discussed here. The formation of the basins (craters >300km in diameter) caused a significant amount of material to be excavated and redistributed across the surface of the Moon [4,5,6,7]. The material excavated by each individual basin was deposited and laterally mixed with the surrounding surface. This resulted in the development of a lunar-wide mixed zone of fragmented material, several kilometers thick [5,8,9]. This mixed zone was developed further by subsequent impacts resulting in a fragmental zone 1-2km thick called the megaregolith [10]. The initial zone of mixed material formed by the basins is not expected to be uniform across the surface of the Moon because of the varied size and random distribution of the basins. The main topographic ring of the 43 basins discussed by Wilhelms and Spudis [1,2] are illustrated in Figure 1.

  9. Preliminary Stratigraphic Cross Sections of Oil Shale in the Eocene Green River Formation, Uinta Basin, Utah

    USGS Publications Warehouse

    Dyni, John R.

    2008-01-01

    Oil shale units in the Eocene Green River Formation are shown on two east-west stratigraphic sections across the Uinta Basin in northeastern Utah. Several units have potential value for recovery of shale oil, especially the Mahogany oil shale zone, which is a high grade oil shale that can be traced across most of the Uinta Basin and into the Piceance Basin in northwestern Colorado. Many thin medium to high grade oil shale beds above the Mahogany zone can also be traced for many miles across the basin. Several units below the Mahogany that have slow velocities on sonic logs may be low grade oil shale. These may have value as a source for shale gas.

  10. Neogene history of the Carapita Formation, Eastern Venezuela basin

    NASA Astrophysics Data System (ADS)

    Sanchez Zambrano, Dennis Alberto

    The planktonic and benthic foraminifera from the lower to middle Miocene shales of the Carapita Formation of Eastern Venezuela in three exploration wells and one outcrop section are analyzed with the objectives of establishing a precise biostratigraphy of the formation and its bathymetric history. Comparison with the well-preserved microfaunas of the correlative Cipero Formation of Trinidad made possible the achievement of these objectives. The formation, up to 4500 to 6000 m thick in outcrops, extends from northeastern Anzoategui and North of Monagas States to the Gulf of Paria and is both an important oil reservoir towards the east and the main seal rock for the Oligocene reservoir in the north of Monagas State. In the area studied the Carapita Formation spans lower to lower middle Miocene Zones N6/M3 to N9/M6; its upper part is unconstrained as only rare long ranging early Miocene to early Pliocene planktonic foraminifera occur above the Orbulina datum. Unexpectedly, we found that the four lower to middle Miocene sections are highly discontinuous, with hiastuses as long as 4 Myr. Based on the abundance patterns of sixty-nine species of benthic foraminifera and analysis of morphotype abundance following the methodology of Corliss and Chen (1988) and Corliss and Fois (1993), we show that the Carapita Formation was deposited at outer neritic to middle bathyal depths (≥200--1000 m), whereas the Cipero Formation was deposited at middle to lower bathyal depths (≥600--2000 m). Importantly, the bathymetric changes are associated with unconformities in all sections, strongly suggesting that both (shallowing and associated unconformities) were tectonically induced.

  11. Late Cretaceous biostratigraphy of the La Luna Formation, Maracaibo basin

    SciTech Connect

    Truskowski, I.; Galeaalvarez, F.; Sliter, W.V.

    1996-08-01

    Micropaleontological analysis, sedimentological studies, and geochemical data are presented for the Upper Cretaceous {open_quote}black shales{close_quote} of the La Luna Formation of Western Venezuela. The detailed planktonic foraminiferal studies allowed the establishment of the first biozonation, determination of sedimentation rates, and documentation of occurrences of benthic foraminifers for these unusually thick black shales that extend stratigraphically nearly 100 m. Hedbergellids, whiteinellids and Heterohelix characterize the lower part of the La Luna Formation, dated from the late Cenomanian Rotalipora cushmani Zone to middle Turonian Helvetoglobotruncana belvetica Zone. The high productivity of these groups associated with phosphatized fish remains suggest upwelling and a poorly stratified water column. The presence of buliminids and Favreina sp. at some levels, imply disoxic conditions in this anoxic interval. Planktonic foraminifers in the middle and upper parts of the formation range in age from the late Turonian Marginotruncana sigali- Dicarinella primitiva Zone to the early Campanian Globotruncanita elevata Zone. The increase in keeled planktonic foraminifers toward the top of the formation suggest more stratified, oligotrophic surface waters. Benthic foraminifers found at the top are indicative of dysaerobic conditions. This study provides new opportunities for utilizing the petroleum system in the La Luna Formation, arguably the most prolific source rock in northern South America.

  12. Formation of dome and basin structures: Results from scaled experiments using non-linear rock analogues

    NASA Astrophysics Data System (ADS)

    Zulauf, J.; Zulauf, G.; Zanella, F.

    2016-09-01

    Dome and basin folds are structures with circular or slightly elongate outcrop patterns, which can form during single- and polyphase deformation in various tectonic settings. We used power-law viscous rock analogues to simulate single-phase dome-and-basin folding of rocks undergoing dislocation creep. The viscosity ratio between a single competent layer and incompetent matrix was 5, and the stress exponent of both materials was 7. The samples underwent layer-parallel shortening under bulk pure constriction. Increasing initial layer thickness resulted in a decrease in the number of domes and basins and an increase in amplitude, A, arc-length, L, wavelength, λ, and layer thickness, Hf. Samples deformed incrementally show progressive development of domes and basins until a strain of eY=Z = -30% is attained. During the dome-and-basin formation the layer thickened permanently, while A, L, and λ increased. A dominant wavelength was not attained. The normalized amplitude (A/λ) increased almost linearly reaching a maximum of 0.12 at eY=Z = -30%. During the last increment of shortening (eY=Z = -30 to -40%) the domes and basins did not further grow, but were overprinted by a second generation of non-cylindrical folds. Most of the geometrical parameters of the previously formed domes and basins behaved stable or decreased during this phase. The normalized arc-length (L/Hf) of domes and basins is significantly higher than that of 2D cylindrical folds. For this reason, the normalized arc length can probably be used to identify domes and basins in the field, even if these structures are not fully exposed in 3D.

  13. Variations in vitrinite reflectance values for the Upper Cretaceous Mesaverde Formation, southeastern Piceance basin, northwestern Colorado

    SciTech Connect

    Nuccio, V.F.; Johnson, R.C.; Johnson, S.Y.

    1989-01-01

    The authors discuss how most of the Upper Cretaceous Mesaverde Formation in the southeastern Piceance basin is thermally mature enough to have produced hydrocarbons by thermal generation, but only part of the Mesaverde is thermally mature enough to have expelled significant amounts of natural gas. The Early Permian( ) Fryingpan Member of the Maroon Formation consists of quartz-rich, very fine to fine-grained sandstone deposited in eolian dune and interdune environments. The Fryingpan Member (formerly called the sandstone of the Fryingpan River) is removed from the State Bridge Formation and assigned to the Maroon Formation.

  14. Depositional patterns and diagenetic history of Trenton-Black River formations in Michigan basin

    SciTech Connect

    Budai, J.M.; Wilson, J.L.

    1986-08-01

    The Trenton-Black River formations (Middle Ordovician) exhibit depositional facies and regional thickness variations indicative of normal marine, carbonate platform accumulation adjacent to a deeper water, basinal environment. Thickening of both formations occurs in the southeast part of the Michigan basin, possibly in response to basement movement accompanied by a shift in the basin depocenter. Early mixed-water diagenesis introduced the first generation of replacive dolomite, which varied in minor element composition and abundance depending on proximity to structural highlands southwest and southeast of the Michigan basin. A ferroan cap dolomite is interpreted to be partly representative of this early dolomite stage. Later stage replacive dolomite and dolomite cements are commonly associated with large fracture systems active during the Paleozoic. Although ferroan dolomitization is common throughout the Trenton and Black River formations, it is most extensive within these fracture zones, which also host significant oil and gas deposits in several locations. In addition, several accessory minerals are associated with late-stage dolomite cements, including pyrite, calcite, anhydrite, barite, celestite, sphalerite, and fluorite. The trade occurrence of these minerals in association with late-stage ferroan dolomite cements indicates that the Trenton-Black River formations in southern Michigan have undergone hydrothermal alteration analogous to a typical Mississippian Valley-type deposit. Evidence based on the stratigraphic distribution of this mineralization indicates that the lower Paleozoic and Precambrian basement rocks were important sources for iron, sulfur, and other trace metals deposited in the Trenton-Black River during the late Paleozoic.

  15. Stresses and fractures in the Frontier Formation, Green River Basin, predicted from basin-margin tectonic element interactions

    SciTech Connect

    Lorenz, J.C.

    1996-01-01

    Natural fractures and in situ stresses commonly dictate subsurface reservoir permeability and permeability anisotropy, as well as the effectiveness of stimulation techniques in low-permeability, natural gas reservoirs. This paper offers an initial prediction for the orientations of the fracture and stress systems in the tight gas reservoirs of the Frontier Formation, in the Green River basin of southwestern Wyoming. It builds on a previous report that addressed fractures and stresses in the western part of the basin and on ideas developed for the rest of the basin, using the principle that thrust faults are capable of affecting the stress magnitudes and orientations in little-deformed strata several hundreds of kilometers in front of a thrust. The prediction of subsurface stresses and natural fracture orientations is an undertaking that requires the willingness to revise models as definitive data are acquired during drilling. The predictions made in this paper are offered with the caveat that geology in the subsurface is always full of surprises.

  16. Petrochemical constraints on lateral transport during lunar basin formation

    NASA Technical Reports Server (NTRS)

    Warren, P. H.; Taylor, G. J.

    1981-01-01

    Lunar ANT petrochemistry correlates with longitude, allowing the sampled region of the moon to be divided into three geochemical provinces: western (Apollo 12 and 14), near-eastern (Apollo 11, 15, 16 and 17) and far-eastern (Luna 16, 20 and 24). A western ANT rock has a far greater Eu anomaly for a given Sm content than does a near-eastern ANT rock, which is in turn has a somewhat greater Eu anomaly than does a far-eastern ANT rock. Distinct differences are also observed in Sc/Sm and Ti/Sm ratios (western ANT rocks have lower ratios) and in the abundances of alkali-rich anorthosites (five of the six known anorthosites from the west are approximately four times richer in Na and K than are ferroan anorthosites, whereas none of the 40 known anorthosites from the near east is alkali-rich). The existence of this distinct correlation of ANT geochemical properties with longitude implies that even during the first few hundred m.y. of lunar history basin-forming impacts were not capable of efficiently redistributing material laterally across the lunar surface.

  17. Organic petrology and geochemistry of mudrocks from the lacustrine Lucaogou Formation, Santanghu Basin, northwest China: Application to lake basin evolution

    USGS Publications Warehouse

    Hackley, Paul C.; Fishman, Neil; Wu, Tao; Baugher, Gregory

    2016-01-01

    Exploration for tight oil in the frontier Santanghu Basin of northwest China has resulted in recent commercial discoveries sourced from the lacustrine Upper Permian Lucaogou Formation, already considered a “world class source rock” in the Junggar Basin to the west. Here we apply an integrated analytical program to carbonate-dominated mudrocks from the Lucaogou Formation in Santanghu Basin to document the nature of organic matter (OM) in the context of an evolving lake system. The organic-rich samples (TOC 2.8–11.4 wt%; n = 10) were widely spaced from an ~ 200 m cored section, interpreted from textural and mineralogical evidence to document transition from a lower under-filled to an overlying balanced-filled lake. Organic matter is dominated by moderate to strongly fluorescent amorphous material with Type I geochemical signature (HI values 510–755; n = 10) occurring in a continuum from lamellar stringers, 10–20 μm thick, some ≥ 1 mm in length (possible microbial mat; preserved only in lower under-filled section) to finely-disseminated amorphous groundmass intimately intermixed with mineral matrix. Biomarkers for methanotrophs and photosynthetic cyanobacteria indicate a complex microbial consortium. A unicellular prasinophyte green alga(?), similar to Tasmanites in marine rocks, is present as discrete flattened discs 50–100 μm in diameter. Type III OM including vitrinite (some fluorescent) and inertinite also is abundant. Solid bitumen, indicating local kerogen conversion, fills voids and occurs throughout the cored section. Vitrinite reflectance values are 0.47–0.58%, consistent with strong OM fluorescence but may be “suppressed”. Other proxies, e.g., biomarker parameters, indicate the Lucaogou Formation is in the early oil window at this location. On average, slightly more amorphous OM and telalginite are present in the lower section, consistent with a shallow, stratified, saline environment with low sediment dilution. More

  18. Refined stratigraphy of the Middle Permian Abrahamskraal Formation (Beaufort Group) in the southern Karoo Basin

    NASA Astrophysics Data System (ADS)

    Jirah, Sifelani; Rubidge, Bruce S.

    2014-12-01

    Fluvially deposited rocks of the Abrahamskraal Formation of the lower Beaufort Group in the South African Karoo record sediment deposition during the Middle Permian, the earliest terrestrial environment of Gondwana. A rich diversity of fossil tetrapods from this Formation provides a unique opportunity for understanding Middle Permian biodiversity changes in Gondwanan terrestrial ecosystems, but this is dependent on the existence of a robust stratigraphic framework that has been hampered by lack of lateral continuity of lithological markers combined with structural complexities relating to formation of the Cape Fold Belt. Because the Abrahamskraal Formation covers a large geographic area of the main Karoo Basin previous stratigraphic studies have been undertaken over large areas. This study combines geology and palaeontology to refine the stratigraphy of the Abrahamskraal Formation in a part of the southwestern Karoo Basin and revealed mappable lithological units with lateral continuity throughout the study area. The measured stratigraphic section manifests a total thickness of 2565 m for the Formation (the thickest occurrence of the Abrahamskraal Formation in the Beaufort Group). For the first time stratigraphic ranges of biostratigraphically important Middle Permian index taxa which have restricted stratigraphic ranges have been determined and, apart from dicynodonts, include the parareptile Eunotosaurus and the biarmosuchid therapsid Hipposaurus. The Abrahamskraal Formation comprises a 1104 m thick basal Eodicynodon Assemblage Zone, overlain by a 1441 m thick Tapinocephalus Assemblage Zone whose upper limit is 20 m below the Poortjie Member of the Teekloof Formation.

  19. Numerical modeling of the formation and structure of the Orientale impact basin

    NASA Astrophysics Data System (ADS)

    Potter, Ross W. K.; Kring, David A.; Collins, Gareth S.; Kiefer, Walter S.; McGovern, Patrick J.

    2013-05-01

    The Orientale impact basin is the youngest and best-preserved lunar multi-ring basin and has, thus, been the focus of studies investigating basin-forming processes and final structures. A consensus about how multi-ring basins form, however, remains elusive. Here we numerically model the Orientale basin-forming impact with the aim of resolving some of the uncertainties associated with this basin. By using two thermal profiles estimating lunar conditions at the time of Orientale's formation and constraining the numerical models with crustal structures inferred from gravity data, we provide estimates for Orientale's impact energy (2-9 × 1025 J), impactor size (50-80 km diameter), transient crater size (˜320-480 km), excavation depth (40-55 km), and impact melt volume (˜106 km3). We also analyze the distribution and deformation of target material and compare our model results and Orientale observations with the Chicxulub crater to investigate similarities between these two impact structures.

  20. Distribution and formation conditions of noble metal mineralization in coal-bearing basins

    NASA Astrophysics Data System (ADS)

    Seredin, V. V.

    2007-02-01

    Original data and a survey of the literature indicate that Au and Au-PGE mineralization are abundant in coal measures. Anomalous contents of noble metals have been established in basins with various types of basement, composed of granite, volcanic rocks, schist, and limestone. These basins are located in Au-and PGE-bearing ore districts, as well as at a considerable distance from known ore deposits and occurrences. Ore formation in coal-bearing basins may occur during sedimentation, peat accumulation, and diagenesis of organic matter or may be epigenetic. Noble metals are supplied to sedimentary basins as minerals that are transported by water and air and as ion species migrating along with surface and subsurface in-and exfiltration solutions of various chemical and genetic types. Ore mineralization concentrates in coal seams and host sedimentary beds of various grain size, including conglomerate, sand, and clay, as well as in zones of hydrothermal alteration superimposed on basement rocks and the sedimentary cover. The mode of occurrence of noble metals in coal basins is diverse as well (noble metal minerals, isomorphic admixtures in sulfides, and organic compounds). The data presented allow coal-bearing basins to be regarded as promising for economic noble metal mineralization fit for recovery as by-products in the course of coal mining.

  1. Giant polygons and circular graben in western Utopia basin, Mars: Exploring possible formation mechanisms

    NASA Astrophysics Data System (ADS)

    Buczkowski, Debra L.; Seelos, Kim D.; Cooke, Michele L.

    2012-08-01

    Large-scale fracture systems surrounding the Utopia basin include giant polygons and circular graben. Data covering the northern Utopia basin now allow high-resolution mapping of these features in all regions of the basin. Giant polygons to the north and south of the basin are different in both size and morphology, leading to the polygon classifications (1) S-style, (2) subdued S-style, (3) northern S-style and (4) N-style. Also, ten circular graben have been identified to the north of the Utopia basin. These have generally larger diameters than southern circular graben, and their fracture morphology is similar to N-style giant polygons. As with southern circular graben, the surface relief of the depression inside the northern circular graben scales directly with diameter. However, northern circular graben have less steep trend slopes, larger average diameters and greater ring spacing compared to southern circular graben of the same diameter and similar distance to the center of the Utopia basin. Both the giant polygons and circular graben of Utopia Planitia are consistent with formation by volumetric compaction of a fine-grained sedimentary material covering an uneven buried surface. Giant polygon size variations can be explained by the material being wet to the south but frozen or partially frozen to the north, while differences between northern and southern circular graben may be attributed to changes in cover thickness. Differences in fracture morphology can be explained by subsequent alteration of the northern troughs due to polar processes.

  2. Dynamics mechanism on fault basin formation in the Lower Yangtze region

    NASA Astrophysics Data System (ADS)

    Xu, X.; Wang, W.; Xu, C.

    2013-12-01

    It is one of the critical issues of the rift basin to study the specific dynamical mechanism of the basin formulation in the Lower Yangtze Region. There still exist controversies on the genetical mechanism, although some previous studies have revealed various formulation models, such as rift basin model related to the Pacific subduction, continental rift basin model, transtensional basin model related to the dextral slip of TanLu fault, simple shear inherited thin skin basin model, basin mode related to extension and detachment of basement, pull-apart basin model related to Mekenzie(1978) pure shear. Among these various tectonic models, the dynamics of formation of fault basin in the Lower Yangtze block is not yet fully understood. Our purpose is to explain comprehensively the formation of the fault basin by an integrated approach, drawing conclusions from our geological field investigation, seismic interpretation and literatures and using the numerical modeling. By contributing a two-dimensional finite element model of the Lower Yangtze block and its environs in the Paleogene, we are able to estimate the surface velocity, stress field and strain rate field of model. The results reveal that there is the nearly southwestward movement of the northeast part of block in an equilibrium of the nearly NEE-SWW trending displacement field with the reference velocity of 100 mm/a, and crustal plastic flow from north to south in internal model, dragging the upper crust to produce nearly N-S striking tension. Displacement and deformation, associated with current seismologic correlation analysis, can be extended to the depth of at least 30KM. Consequently, The deformation of the Lower Yangtze block and its environs is not influenced by the dextral movement of Tan-Lu fault, but the regional extension and strain in the Subei-Southern South Yellow Sea area which has the extensional stress filed in the upper crust. The observations of modeling and evidence from our data and the

  3. The Pristane Formation Index, a molecular maturity parameter. Confirmation in samples from the Paris Basin

    SciTech Connect

    Goossens, H.; De Lange, F.; De Leeuw, J.W.; Schenck, P.A. )

    1988-10-01

    The value of the recently proposed molecular maturity parameter PFI (Pristane Formation Index) is evaluated by analysis of a suite of samples from the Paris Basin with known values of the molecular maturity parameters based on the sterane and hopane isomerization (SI and HI) and sterane aromatization (SA) reactions. The values of the pseudo-kinetic parameters E and A of the Arrhenius equation k = A exp({minus}E/RT), calculated for pristane formation in the Mahakam Delta, were used to compare the observed PFI values with calculated ones. The results indicate that the samples from the eastern part of the Paris Basin, which are at the surface at present, have been at higher temperatures for about 10-30 Ma, whereas the deeper samples, located around the center of the Basin, have not undergone considerable temperature changes in the past. These results are in agreement with the conclusions based on SI, SA and HI alone. Thus, the values of the pseudo-kinetic parameters E (59 kJ mol{sup minus 1}) and A (2.2*10{sup minus 7} s{sup minus 1}) for the pristane formation reaction can be applied in a different basin with a different type of kerogen. This confirms the value of PFI as a molecular maturity parameter.

  4. Formation pressure data file - Palo Duro Basin, Texas and New Mexico: unanalyzed data

    SciTech Connect

    Not Available

    1984-05-01

    This is an unanalyzed computer listing of drill stem test data being reviewed by Stone and Webster Engineering Corporation (SWEC). This file contains well data from counties in and immediately surrounding the Palo Duro Basin of West Texas. These data files, compiled from Petroleum Information Services (PI) prior to October 1983, are one part of an extensive program to define the geology and geohydrology of the Palo Duro Basin. The computer listing supplies geologic, hydrologic, and formation pressure data obtained from the drill-stem tests. These data are preliminary. They have been neither analyzed nor evaluated.

  5. New Magnetic Anomaly Compilation Illuminates the Formation of the Aleutian Basin

    NASA Astrophysics Data System (ADS)

    Scheirer, D. S.; Barth, G. A.; Scholl, D. W.; Stern, R. J.

    2013-12-01

    Aleutian Basin crust is deeply buried beneath 2 to 5 km of sediment, so magnetic data provide valuable insights into its structure and origin. A new compilation of marine magnetic anomalies, derived from one recent cruise (2011) and re-analysis of dozens of legacy cruises (primarily 1970's to 1980's), provides both a refined view of the magnetic field in the Bering Sea area and insights into the formation of the deep-water Aleutian and Bowers Basins. In the Aleutian Basin, the magnetic fabric can be divided into two similar-sized areas of distinct types. Type 1 magnetic fabric is characterized by north-south-oriented lineations in the southern Aleutian Basin. The lineations have irregular spacing, reminiscent of seafloor spreading stripes, and the amplitudes of the anomalies are also consistent with a magnetic source formed at spreading centers. Seismic reflection data show that the strongest magnetic lineations in the Type 1 area are not associated with basement relief, supporting an origin from remanent magnetization variations and consistent with their formation by seafloor spreading. This interpretation is consistent with OBS refraction results indicating that this is mafic crust ~8 km thick. The pattern of anomalies does not show an obvious symmetry about a possible fossil spreading axis, and attempts to assign the sequence of lineaments to the geomagnetic polarity timescale are not definitive. Thus, we cannot rule out either of the two hypotheses for the formation of the Aleutian Basin, as a Paleogene back-arc basin or as captured (old) plate trapped by formation of the Aleutian subduction zone at ~50 Ma. Type 2 magnetic fabric is characterized by higher-amplitude and more heterogeneous magnetic anomalies than Type 1 fabric, and it is located around the margins of the Aleutian Basin, to the north and west of the lineated fabric. Some features of the basement (e.g. Sounder Ridge) have corresponding magnetic anomalies in Type 2 areas, but other anomalies with

  6. Paleogeothermal gradients and timing of oil generation in the Belden Formation, Eagle Basin, northwestern Colorado

    USGS Publications Warehouse

    Nuccio, V.F.; Johnson, S.Y.; Schenk, C.J.

    1989-01-01

    Paleogeothermal gradients and timing of oil generation for the Lower and Middle Pennsylvanian Belden Formation have been estimated for four locations in the Eagle Basin of northwestern Colorado, by comparing measured vitrinite reflectance with maturity modeling. Two thermal models were made for each location: one assumes a constant paleogeothermal gradient through time while the other is a two-stage model with changing paleogeothermal gradients. The two-stage paleogeothermal gradient scenario is considered more geologically realistic and is used to estimate the timing of oil generation throughout the Eagle basin. From the data and interpretations, one would expect Belden oil to be found in either upper Paleozoic or Mesozoic reservoir rocks. -Authors

  7. Heat flow, deep formation temperature and thermal structure of the Tarim Basin, northwest China

    NASA Astrophysics Data System (ADS)

    Liu, Shaowen; Lei, Xiao; Feng, Changge; Li, Xianglan

    2016-04-01

    Geothermal regime of a sedimentary basin not only provides constraint on understanding the basin formation and evolution, but also offers fundamental parameters for hydrocarbon resources assessment. As one of three Precambrian blocks in China, the Tarim craton is also a current hydrocarbon exploration target where the largest sedimentary basin (Tarim Basin) develops with great potential. Although considerable advancement of geothermal regime of this basin has been made during the past decades, nearly all the temperature data in previous studies are from the exploration borehole formation testing temperatures. Recently, we have conducted the steady-state temperature logging in the Tarim basin, and measured abundant rock thermal properties, enabling us to re-visit the thermal regime of this area with more confidence. Our results show that the present-day geothermal gradients for the Tarim Basin vary from 23 K/km to 27 K/km, with a mean of 22 K/km; the values of heat flow range from 40 mW/m2 to 49 mW/m2, with a mean of 43 mW/m2. These new data confirmed that the Tarim Basin has relatively low heat flow and shares similar geothermal regime with other Precambrian cratons in the world. In addition, the new temperatures from the steady-state logs are larger than the bottom hole temperatures (BHT) as 22 degree Celsius, indicating the thermal non-equilibrium for the BHTs used in previous studies. Spatial distribution of the estimated formation temperatures-at-depth of 1~5km within the basin is similar and mainly controlled by crystalline basement pattern. Generally, the temperatures at the depth of 1km range from 29 to 41 degree Celsius, with a mean of 35 degree Celsius; while the temperatures at 3km vary from 63 to 100 degree Celsius, and the mean is 82 degree Celsius; at 5km below the surface, the temperatures fall into a range between 90 and 160 degree Celsius, with a mean of 129 degree Celsius. We further proposed the long-term low geothermal background and large burial

  8. New fossil record of a Jurassic pterosaur from Neuquen Basin, Vaca Muerta Formation, Argentina

    NASA Astrophysics Data System (ADS)

    Codorniú, Laura; Garrido, Alberto

    2013-12-01

    Discoveries of Jurassic pterosaurs in the Southern Hemisphere are extremely unusual. In Argentina, pterosaurs from the Upper Jurassic (Tithonian) have only been found in the Northwest of Patagonia (Neuquén Basin). These come from marine deposits and three specimens have been discovered up to the present. In this paper, we report a new finding from the Neuquén Basin. This material is identified as a tibiotarsus, which probably belonged to an osteologically adult individual and represents a new species of a pterodactyloid pterosaur of medium size. This discovery provides new evidence that at least two different species of pterodactyloid pterosaurs may have coexisted in Los Catutos Member, Vaca Muerta Formation, from the shallow marine deposits of the Neuquén Basin.

  9. Primary oil-shale resources of the Green River Formation in the eastern Uinta Basin, Utah

    SciTech Connect

    Trudell, L.G.; Smith, J.W.; Beard, T.N.; Mason, G.M.

    1983-04-01

    Resources of potential oil in place in the Green River Formation are measured and estimated for the primary oil-shale resource area east of the Green River in Utah's Uinta Basin. The area evaluated (Ts 7-14 S, Rs 19-25 E) includes most of, and certainly the best of Utah's oil-shale resource. For resource evaluation the principal oil-shale section is divided into ten stratigraphic units which are equivalent to units previously evaluated in the Piceance Creek Basin of Colorado. Detailed evaluation of individual oil-shale units sampled by cores, plus estimates by extrapolation into uncored areas indicate a total resource of 214 billion barrels of shale oil in place in the eastern Uinta Basin.

  10. Role of extensional tectonics in the formation of Talladega belt--Blue Ridge successor basins

    SciTech Connect

    Tull, J.F. . Dept. of Geology)

    1993-03-01

    Polydeformed and metamorphosed sequences occurring unconformably above the Cambrian-Ordovician (C-O) miogeoclinal sequence are nested within the Talladega belt (Talladega Group-TG) and Blue Ridge (Mineral Bluff Group-MBG). These successor basin sequences are 2.5--3 km thick and have a possible age range from Ordovician to Devonian, representing the youngest stratigraphic units east of the foreland. They are dominated by turbiditic metaclastic rocks derived from erosion of Grenville basement and its overlying cover of clastic and carbonate rock. Bimodal volcanic rocks occur in the TG, and within-plate mafic extrusive rocks are found in the MBG. The TG consists of a coarsening, thickening, and shallowing upward sequence with a submarine fan-like unit (Lay Dam Formation-LDF) at the base. The LDF contains a thick proximal boulder-bearing olistostromal facies with debris fan lobes stacked vertically and shed from a proximal fault scarp to the SE or S. The vertical stacking of olistostromal deposits, absence of crystalline-cored thrust sheets of this age at the structural top of the basin, and other relationships indicate that the basin did not result from detached deformation to the SE or transcurrent faulting, but rather from extensional faulting. Relationships within the C-O carbonate sequence (Sylacauga Marble Group) unconformably below the TG indicate that the TG basin developed above shallow shelf miogeoclinal rocks inboard of the continental margin hinge line, and thus indicate that Silurian-Devonian extensional structures affected relatively thick Laurentian crust. Similarities in lithofacies and stratigraphic sequence between the TG and MBG indicate that the settling of the MBG may have also been within an extensional basin but basin boundary faults have not yet been identified within the structural block below the pre-MBG unconformity. This basin developed above Laurentian crust previously thinned during late Protozoic rifting.

  11. Volume of Impact Melt Generated by the Formation of the South Pole-Aitken Basin

    NASA Technical Reports Server (NTRS)

    Petro, Noah E.

    2011-01-01

    The South Pole-Aitken Basin (SPA) is the largest, deepest, and oldest identified basin on the Moon and as such contains surfaces that are unique due to their age, composition, and depth of origin in the lunar crust [1-5] (Figure 1). SPA has been a target of intense interest as an area for robotic sample return in order to determine the age of the basin and the composition and origin of its interior [6-8]. In response to this interest there have been several efforts to estimate the likely provenance of regolith material within central SPA [9-12]. These model estimates suggest that, despite the formation of basins and craters following SPA, the regolith within SPA is dominated by locally derived material. An assumption of these models has been that the locally derived material is primarily SPA impact-melt as opposed to local basement material (e.g. unmelted lower crust). However, the definitive identification of SPA derived impact melt on the basin floor, either by remote sensing [5, 13] or via photogeology [2, 14] is extremely difficult due to the number of subsequent impacts and volcanic activity [4].

  12. Stratigraphic correlations of the Vaca Muerta formation in the southern Neuquén basin, Argentina

    NASA Astrophysics Data System (ADS)

    Nesma, Krim; Patrice, Imbert; Cedric, Bonnel; Charles, Aubourg

    2013-04-01

    The petroleum Neuquén basin, south west Argentina, contains a continuous late Triassic to Cenozoic succession including continental and marine sediments, deposited under a variety of tectonic regimes. The Vaca Muerta formation is one of the major source rocks of the Neuquén basin and was deposited during the Andic cycle. This formation consists of organic-rich dark brown to black shales and mudstones deposited during a major transgression, in euxinic conditions on a shelf and slope during the Tithonian. Over most of the basin, the Vaca Muerta formation overlies the continental deposits of the Tordillo formation. The contact between the two formations is isochronous throughout the basin and marks the Tithonian transgression (Leanza, 1981). After this transgression, prograding bodies were deposited and the Vaca Muerta corresponds to the distal part of this latest. It includes stages from Middle Tithonian in the south to Valanginian in the north (Leanza & Hugo, 1977). The Vaca Muerta formation is well exposed in the southern part of the Neuquén basin, from the Picun Leufu Anticline to the north of the town of Las Lajas. It corresponds in these two areas to a succession of dark to brown shales and carbonate beds. In details, we can divide it into two parts: the Lower Vaca Muerta and the Upper Vaca Muerta. Above, the Picun Leufu formation overlies the Vaca Muerta formation and consists of carbonaceous and siliciclastics prograditional bodies. This unit is absent in the "North Zapala Zone" and its lateral equivalent is less carbonaceous. In this poster; we propose eight detailed sedimentological logs, which are correlated along 120 km north-south trend (from the Picun Leufu Anticline to the south west to the Agrio thrust Belt (ATB) to the north). This correlation will be used to assess the vertical and lateral variability of the Vaca Muerta deposits and to define the palaeogeographic evolution of that region. This allowed us to identify two major prograding sequences

  13. Depositional systems of a synorogenic continental deposit. The upper paleocene and lower Eocene Wasatch formation in the Powder River basin, northeast Wyoming (chapter H). Evolution of sedimentary basins, Powder River Basin. Bulletin

    SciTech Connect

    Seeland, D.

    1992-01-01

    The synorogenic fluvial and paludal rocks of the upper Paleocene and lower Eocene Wasatch Formation in the Powder River Basin contain large deposits of coal and uranium. These rocks also record the culmination of Laramide tectonic events marked by subsidence in the basin and uplift of the bounding structures. The study establishes the early Eocene plaeogeography of the basin using a two-part approach consisting of (1) sedimentary particle-shape and -size analysis, and (2) paleocurrent studies.

  14. Cassiopidae gastropods, influence of Tethys Sea of the Romualdo Formation (Aptian-Albian), Araripe Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Pereira, Priscilla Albuquerque; Cassab, Rita de Cassia Tardin; Barreto, Alcina Magnólia Franca

    2016-10-01

    The Cassiopidae family belongs to a group of gastropods of the Tethyan Realm, whose origin and dispersion are related a transgression of the Tethys Sea during the Early Cretaceous. The Romualdo Formation in the Araripe Basin, located in Northeast Brazil, presents fossil assemblages with echinoids, bivalves and cassiopid gastropods, indicating a marine sedimentation at the top of the formation. This research reveals three new species of this fauna: Gymnentome (Craginia) beurleni sp. nov., 'Pseudomesalia' ('Pseudomesalia') mennessieri sp. nov and 'Pseudomesalia' ('Pseudomesalia') santanensis sp. nov. We also review two other species: Craginia araripensisBeurlen, 1964 and Gymnentome romualdoiBeurlen, 1964, which we reclassify taxonomically as Paraglauconia (Diglauconia) araripensis and Gymnentome (Gymnentome) romualdoi, respectively; Paraglauconia (Diglauconia) lyrica Maury, 1936 and Gymnentome (Gymnentome) carregozica Maury, 1936 were the first recorded species in the Araripe Basin. The occurrence of these cassiopid gastropod fauna in other basins, such as Sergipe, Potiguar and Parnaíba, indicate the influence of waters coming from the north through the Tethys Sea in the Aptian-Albian and in the marginal continental basins of the Brazilian Northeast.

  15. Numerical modeling of the ejecta distribution and formation of the Orientale basin on the Moon

    NASA Astrophysics Data System (ADS)

    Zhu, Meng-Hua; Wünnemann, Kai; Potter, Ross W. K.

    2015-12-01

    The formation and structure of the Orientale basin on the Moon has been extensively studied in the past; however, estimates of its transient crater size, excavated volume and depth, and ejecta distribution remain uncertain. Here we present a new numerical model to reinvestigate the formation and structure of Orientale basin and better constrain impact parameters such as impactor size and velocity. Unlike previous models, the observed ejecta distribution and ejecta thickness were used as the primary constraints to estimate transient crater size—the best measure of impact energy. Models were also compared to basin morphology and morphometry, and subsurface structures derived from high-resolution remote sensing observations and gravity data, respectively. The best fit model suggests a 100 km diameter impactor with a velocity of ~12 km s-1 formed the Orientale basin on a relatively "cold" Moon. In this impact scenario the transient crater diameter is ~400 km or 460 km depending on whether the crater is defined using the diameter of the excavation zone or the diameter of the growing cavity at the time of maximum crater volume, respectively. The volume of ejecta material is ~4.70 × 106 km3, in agreement with recent estimates of the Orientale ejecta blanket thickness from remote sensing studies. The model also confirms the remote sensing spectroscopic observations that no mantle material was excavated and deposited at Orientale's rim.

  16. Evidence for deep-water evaporite deposition in the Miocene Kareem Formation, Gemsa basin, eastern Egypt

    SciTech Connect

    May, J.A.; Stonecipher, S.A.; Steinmetz, J.C. ); Dyess, J.N. )

    1991-03-01

    The correct interpretation of intercalated Miocene siliciclastics and evaporites of Gemsa basin is crucial for understanding early rift tectonics of the Gulf of Suez, pinpointing the timing of isolation of the Gulf from the Mediterranean, and developing exploration plays. Evaporites of the Kareem Formation comprise celestites and massive, 'chicken-wire,' and laminated anhydrites. Although previously interpreted as sabkha deposits; sedimentologic, petrographic, and paleontologic analyses indicate these evaporites more likely formed in a submarine setting. Marls that encase the evaporites contain a diverse and abundant assemblage of nannoplankton, planktonic foraminifera, diatoms, pteropods, and fish scales indicative of basinal deposition. Associated turbidites also denote deep-water sedimentation. The paucity of benthic diatoms and foraminifera, plus the presence of unburrowed shales, phosphate nodules, early ferroan carbonate cements, and authigenic pyrite, suggest periodic anoxic, or at least disaerobic, bottom waters. These sequences probably represent partial isolation of the Gulf of Suez by middle Miocene, producing periodic basin restriction and evaporative drawdown. Episodes of increasing salinity likely caused the progressive decreases in foram abundance and diversity in marls beneath the anhydrites, culminating in subaqueous evaporite formation. Diverse, indigenous nannoplankton assemblages from shale seams within the anhydrites suggest Gemsa basin was stratified; shallow open-marine conditions coexisted with anhydrite crystallization from deeper hypersaline waters.

  17. An assessment on CO2 geosequestration in deep saline formations in the Taihsi Basin, central Taiwan

    NASA Astrophysics Data System (ADS)

    Cai, Mo-Si; Lin, Andrew T.; Fan, Jhen-Huei

    2015-04-01

    Geological storage of carbon dioxide (CO2) is to inject and store a large amount of anthropogenic CO2 in deep and sealed porous rocks in order to mitigate the aggravated threat of global climate changes. Borehole and reflection seismic data are used to understand the spatial distribution of suitable CO2 reservoirs and cap rocks in the Taihsi Basin, central Taiwan, where the level of seismicity is low. The Taihsi Basin was a rift basin during the Paleocene to Eocene, followed by a phase of post-rift subsidence during late Oligocene to late Miocene. The loading of the Taiwan mountain belt since late Miocene has turned the Taihsi Basin into a peripheral foreland basin, with strata gently dipping toward the mountain belts in the east. The coastal plain in central Taiwan (Changhua and Yunlin Counties) and its adjacent offshore areas are close to major CO2 emission sources and no active geological structures are found in these areas, making the study area a favorable CO2 storage site. Spatial distribution of formation thickness and depth for CO2 reservoirs and cap rocks indicates three CO2 storage systems existed in the study area. They are: (1) late Miocene to Pliocene Nanchuang Formation and Kueichulin Formation (reservoirs)-Chinshui Shale (seals) system (hereafter abbreviated as NK-C system), (2) early to middle Miocene Shihti Formation and Peiliao Formation (reservoirs)-Talu Shale (seals) system (SP-T system), (3) early Miocene Mushan Formation (reservoirs)-Piling Shale (seals) system (M-P system). The NK-C system contains multiple layers of porous sandstones from Nanchuang and Kueichulin formations, with total thickness around 210-280 m. In the vicinity of the northern bank of the Jhuoshuei River, reservoir top reaches a depth around 1850 m, with 60 m thick seal formation, the Chinshui Shale. However, the Chinshui Shale becomes sand-prone in the Changhua coastal and nearshore areas due to facies changes. The SP-T system consists of two porous sandstone layers from

  18. The Mechanics of Impact Basin Formation: Comparisons between Modeling and Geophysical Observations

    NASA Astrophysics Data System (ADS)

    Stewart, S. T.

    2010-12-01

    Impact basins are the largest geologic structures on planetary surfaces. Single or multiple ring-shaped scarps or arcuate chains of massifs typically surround basin-sized craters (e.g., larger than about 300 km diameter on the moon [1]). Impact basins also possess central mass anomalies related to ejection of a portion of the crust (and mantle) and uplift of the mantle. I will discuss insights into the mechanics of impact basin formation derived from numerical simulations and focus on features that may be compared with gravity and topography data. The simulations of basin formation use the method of [2] with an improved rheological model that includes dynamic weakening of faults and more accurate treatment of the mantle solidus. Two-dimensional simulations of vertical impacts onto spherical planets utilize a central gravity field, and three-dimensional simulations of oblique impacts include a self-gravity calculation. During the opening and collapse of the transient crater, localization of strain leads to deformation features that are interpreted as deep faults through the lithosphere. Based on simulations of mantle-excavating impacts onto the moon and Mars with thermal gradients that intersect the solidus in the asthenosphere, the final impact structure has three major features: (i) an inner basin filled with melt and bounded by the folded lithosphere, (ii) a broad shallow terrace of faulted and translated lithosphere with an ejecta deposit, and (iii) the surrounding autochthonous lithosphere with radially thinning ejecta. The folded lithosphere is a complex structure that experiences translation inward and then outward again during collapse of the transient cavity. The uplifted mantle within this structure is overlain by a thin layer of hot crustal material. In addition to asymmetry in the excavated material, 45-degree impact events produce an asymmetric terrace feature. The principal observations for comparison to the calculations are the inferred locations of

  19. Altered tuffaceous rocks of the Green River Formation in the Piceance Creek Basin, Colorado

    USGS Publications Warehouse

    Griggs, Roy Lee

    1968-01-01

    More than 50 ash-fall tuff beds which have altered to analcitized or feldspathized rocks have been found in the upper 500-600 feet of the Parachute Creek Member of the Green River Formation in the Piceance Creek Basin of northwestern Colorado. Similarly altered water-washed tuff occurs as tongues in the uppermost part of this member, and forms most of the lower 400-600 feet of the overlying Evacuation Creek Member of the Green River Formation. 'The altered ash-fall beds of the Parachute Creek Member are all thin and show a characteristic pattern of alteration. Most beds range in thickness from a fraction of an inch to a few inches. One bed reaches a maximum thickness of 5 feet, and, unlike the other beds, is composed of several successive ash falls. The pattern of alteration changes from the outer part to the center of the basin. Most beds in the outer part of the basin contain about 50 to 65 percent analcite,with the interstices between the crystals filled mainly by microlites of feldspar, opal, and quartz, and small amounts of carbonate. At the center of the basin .essentially all the beds -are composed of microlites of feldspar, opal, and quartz, and small amounts of carbonate. The tongues of water-washed tuff in the uppermost part of the Parachute Creek Member and the similar rocks composing the lower 400-600 feet of the Evacuation Creek Mewber are feldspathized rocks composed mainly of microlites of feldspar, opal, and quartz, varying amounts of carbonate, and in some specimens tiny subrounded crystals of analcite. The general trend in alteration of the tuffaceous rocks from analcitization near the margin to feidspathization near the center of the Piceance Creek Basin is believed to have taken place at shallow depth during diagenesis , as indicated by field observations and laboratory work. It is believed that during sedimentation and diagenesis the waters of the central part of the basin were more alkaline and following the breakdown of the original

  20. Depositional history of Lower Triassic Dinwoody Formation, Bighorn basin, Wyoming and Montana

    SciTech Connect

    Paull, R.A.; Paull, R.K.

    1986-08-01

    The Lower Triassic Dinwoody Formation in the Bighorn basin of Wyoming and Montana records the northeasternmost extent of the widespread and rapid Griesbachian transgression onto the Wyoming shelf. Depositional patterns document a progressive change from sparsely fossiliferous, inner-shelf marine conditions in the southwest and west to restricted, marginal-marine environments to the north and east. Characteristic lithologies include greenish-gray calcareous or dolomitic mudstone and siltstone, very thin to thick beds of gypsum, and thin-bedded, commonly laminated dolomite. A formation thickness of approximately 20 m persists throughout most of the basin but diminishes abruptly near the northern and eastern limits of deposition. The Dinwoody is disconformable on the Ervay Member of the Permian Park City Formation except in the northeasternmost part of the basin, where it locally overlies the Pennsylvanian Tensleep Sandstone. Considering the significant time interval involved, physical evidence at the Permian-Triassic boundary is generally limited to an abrupt lithologic change from light-colored shallow marine or intertidal Permian dolomite to greenish-gray Dinwoody siltstone. The Dinwoody grades vertically as well as laterally to the east and north into red beds of the Lower Triassic Red Peak Formation of the Chugwater Group. The Early Triassic depositional environment in the present-day Bighorn basin was hostile. A sparse molluscan fauna was observed at only one of the 20 sections studied, and no conodonts were recovered from Dinwoody carbonates. Significant amounts of gypsum within the Dinwoody suggest periodic high evaporation from hypersaline waters on a low-energy shallow shelf during intervals of reduced terrigenous sediment supply from the north and east. However, sufficient organic material was present to create reducing conditions, as evidenced by greenish rock color and abundant pyrite.

  1. Formation of phreatomagmatic pipes in the Tunguska Basin (Siberia, Russia) during the end-Permian

    NASA Astrophysics Data System (ADS)

    Polozov, Alexander; Svensen, Henrik; Planke, Sverre

    2010-05-01

    We recently proposed that numerous pipes piercing sedimentary rocks of Tunguska Basin triggered the Permian-Triassic mass extinction (Svensen et al., 2009). Large amounts of greenhouse and poisonous gases were released through the pipes and into P-Tr atmosphere, partly formed by heating of petroleum-bearing evaporites. The sub-volcanic part of the Siberian Traps was emplaced in the Tunguska Basin sedimentary sequences, which includes Pre-Cambrian source rocks, Early Cambrian evaporites, and Paleozoic terrigenous and coal-bearing rocks. Spectacular breccia pipes are numerous in the evaporate-parts of the basin, and are filled with volcaniclastic rocks and commercial magnetite mineralization. Although these pipes have been intensively studied in order to understand the iron ore formation, the origin and formation of the pipes is poorly understood. Many researchers emphasize that magma-sediments interaction as a key reason of pipe formation, whereas phreatomagmatic hypothesis are also proposed. In order to improve the understanding of pipe formation and ore-deposition, we have studied a basalt-rich breccia pipe piercing Cambrian evaporates at the Nepa locality in East Siberia. Textural features of the volcanic fragments in the breccias include lapilli, Pele's hear, glassy basalt and dolerite clasts, blocks of tuffs in addition to sedimentary rocks. Calcite and halite are the most common types of cement. We have studied minerals from the breccia cement and from reaction rims around clasts in order to understand the hydrothermal system that developed after the pipe formed. Calcite and dolomite are the dominating carbonates, and two types of anhydrite is present. Biotite, Cl-Fe-bearing amphibole (hastingsite), and Cl-F-apatite are amongst early hydrothermal minerals covering magmatic clast and lapillies. Our new data confirm (i) the phreatomagmatic nature of breccia filling in the Tunguska Basin pipes and (ii) the key role of sedimentary brine and petroleum involved in

  2. Soft-sediment deformation structures interpreted as seismites in the Kolankaya Formation, Denizli Basin (SW Turkey).

    PubMed

    Topal, Savaş; Özkul, Mehmet

    2014-01-01

    The NW-trending Denizli basin of the SW Turkey is one of the neotectonic grabens in the Aegean extensional province. It is bounded by normal faults on both southern and northern margins. The basin is filled by Neogene and Quaternary terrestrial deposits. Late Miocene- Late Pliocene aged Kolankaya formation crops out along the NW trending Karakova uplift in the Denizli basin. It is a typical fluviolacustrine succession that thickens and coarsens upward, comprising poorly consolidated sand, gravelly sand, siltstone and marl. Various soft-sediment deformation structures occur in the formation, especially in fine- to medium grained sands, silts and marls: load structures, flame structures, clastic dikes (sand and gravely-sand dike), disturbed layers, laminated convolute beds, slumps and synsedimentary faulting. The deformation mechanism and driving force for the soft-sediment deformation are related essentially to gravitational instability, dewatering, liquefaction-liquidization, and brittle deformation. Field data and the wide lateral extent of the structures as well as regional geological data show that most of the deformation is related to seismicity and the structures are interpreted as seismites. The existence of seismites in the Kolankaya Formation is evidence for continuing tectonic activity in the study area during the Neogene and is consistent with the occurrence of the paleoearthquakes of magnitude >5.

  3. Evaluation of gas bearing formations in the Greater Green river basin for horizontal well applications

    SciTech Connect

    Mroz, T.H.; Lopez, R.J.

    1992-05-01

    The present study involves locating a potential horizontal well test by evaluating the low permeability reservoirs of the Greater Green River Basin. A study of all formations to a depth of 12,000 feet is in progress to determine the feasibility of air drilling a horizontal well to improve production in the water sensitive low permeability gas sand formations. This is an expanded effort form an earlier study in the eastern part of the basin. The results of the earlier study are used as examples of the methodology applied to evaluate these resources and to establish areas amenable to air horizontal drilling technology. The areal distribution of the work now in progress is included to show the extent of the potential reservoir. Formations of interest in the Mesaverde Group include: Lewis Shale, Almond, Ericson, Blair, and Frontier. The main product of this effort will be a rationale to select horizontal well sites in the Greater Green River Basin, and may have potential use in other low permeability sand reservoirs.

  4. Formation of the enigmatic Matoush uranium deposit in the Paleoprotozoic Otish Basin, Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Alexandre, Paul; Kyser, Kurt; Layton-Matthews, Daniel; Beyer, Steve R.; Hiatt, Eric E.; Lafontaine, Jonathan

    2015-10-01

    The Matoush uranium deposit is situated in the Paleoproterozoic Otish Basin, northern Quebec, Canada, and is hosted by the Indicator Formation sandstones. Its sheet-like ore bodies are closely associated with the steeply dipping Matoush Fracture, which hosts mafic dykes and minor quartz-feldspar-tourmaline pegmatites. Regional diagenesis, involving oxidizing basinal fluids (δ2H ˜-15‰, δ18O ˜8‰), produced mostly illite and possibly leached U from accessory phases in the Indicator Formation sandstones. The bimodal Matoush dyke intruded the Indicator Formation along the Matoush Fracture, and the related metasomatism produced Cr-rich dravite and muscovite in both the dyke and the proximal sandstones. Uraninite formed when U6+ in the basinal brine was reduced to U4+ in contact with the mafic dyke and by Fe2+ in Cr-dravite and Cr-muscovite, and precipitated together with eskolaite and hematite. Because of its unique characteristics, the Matoush deposit cannot be easily classified within the generally accepted classification of uranium deposits. Two of its main characteristics (unusual reduction mechanism, structural control) do not correspond to the sandstone-hosted group of deposits (unconformity type, tabular, roll front), in spite of uranium being derived from the Otish Group sandstones.

  5. Soft-Sediment Deformation Structures Interpreted as Seismites in the Kolankaya Formation, Denizli Basin (SW Turkey)

    PubMed Central

    Topal, Savaş; Özkul, Mehmet

    2014-01-01

    The NW-trending Denizli basin of the SW Turkey is one of the neotectonic grabens in the Aegean extensional province. It is bounded by normal faults on both southern and northern margins. The basin is filled by Neogene and Quaternary terrestrial deposits. Late Miocene- Late Pliocene aged Kolankaya formation crops out along the NW trending Karakova uplift in the Denizli basin. It is a typical fluviolacustrine succession that thickens and coarsens upward, comprising poorly consolidated sand, gravelly sand, siltstone and marl. Various soft-sediment deformation structures occur in the formation, especially in fine- to medium grained sands, silts and marls: load structures, flame structures, clastic dikes (sand and gravely-sand dike), disturbed layers, laminated convolute beds, slumps and synsedimentary faulting. The deformation mechanism and driving force for the soft-sediment deformation are related essentially to gravitational instability, dewatering, liquefaction-liquidization, and brittle deformation. Field data and the wide lateral extent of the structures as well as regional geological data show that most of the deformation is related to seismicity and the structures are interpreted as seismites. The existence of seismites in the Kolankaya Formation is evidence for continuing tectonic activity in the study area during the Neogene and is consistent with the occurrence of the paleoearthquakes of magnitude >5. PMID:25152909

  6. The Role of Groundwater Flow and Faulting on Hydrothermal Ore Formation in Sedimentary Basins

    NASA Astrophysics Data System (ADS)

    Garven, G.

    2006-05-01

    Sediment-hosted ore formation is thought to occur as a normal outcome of basin evolution, due to deep groundwater flow, heat transport, and reactive mass transport ---all of which are intimately coupled. This paper reviews recent attempts to understand the hydrologic and geochemical processes forming some of the world's largest sediment-hosted ores. Several questions still dominate the literature (driving forces for flows, source and controls on metal acquisition, concentrations of ore-forming components, timing and duration, role of faults, effects of transient flows). This paper touches upon all of these questions. Coupled reactive transport models have been applied for understanding the genesis of sandstone-hosted uranium ores of North America and Australia, red-bed copper ores of North America and northern Europe, carbonate-hosted MVT lead-zinc ores of the U.S. Midcontinent and northwestern Canada, and the carbonate- hosted lead-zinc ores of Ireland and southeast France. Good progress has been made in using these computational methods for comparing and contrasting both carbonate hosted (MVT and Irish types) and shale- hosted (SEDEX type) Pb-Zn deposits. The former are mostly associated with undeformed carbonate platforms associated with distal orogenic belts and the later are mostly associated with extensional basins and failed rifts that are heavily faulted. Two giant ore provinces in extensional basins provide good examples of structural control on reactive mass transport: shale-hosted Pb-Zn ores of the Proterozoic McArthur basin, Australia, and shale-hosted Pb-Zn-Ba ores of the Paleozoic Kuna basin, Alaska. For the McArthur basin, hydrogeologic simulations of thermally-driven free convection suggest a strong structural control on fluid flow created by the north-trending fault systems that dominate this Proterozoic extensional basin. Brines appear to have descended to depths of a few kilometers along the western side of the basin, migrated laterally to the

  7. Stratigraphic framework of the upper Fort Union Formation, TA Hills, Western Powder River basin, Wyoming

    USGS Publications Warehouse

    Weaver, Jean N.; Flores, Romeo M.

    1985-01-01

    The purpose of this study is to interpret a relationship between the stratigraphy and the environment of deposition of the upper part of the Fort Union Formation in the TA Hills in the western part of the Powder River Basin, Johnson County, Wyoming.  This framework was used to map and correlate coal beds with those mapped by Hose (1955) and Mapel (1959) in the southern and northern parts of the study area, respectively.  More specifically, the established stratigraphic and environmental relationships of the coal beds and associated rocks contribute to a depositional model for the upper part of the Fort Union Formation in the TA Hills.

  8. Significance of loessite in the Maroon Formation (Middle Pennsylvanian to Lower Permian), Eagle Basin, northwest Colorado

    USGS Publications Warehouse

    Johnson, S.Y.

    1989-01-01

    The Maroon Formation includes a siltstone-dominated facies interpreted as loessite (lithified loess) along its downwind basin margin. The section of inferred loessite is locally at least 490 m thick and consists in large part of structureless and nearly structureless beds of homogeneous sandy siltstone. Bed contacts are generally planar to undulatory and are either horizontal or are characterized by gentle relief. Deposition of the Maroon Formation was probably strongly affected by cyclic climatic changes synchronous with fluctuations in late Paleozoic continental ice sheets. -from Author

  9. Laramide tectonic evolution of San Juan sag, Colorado: Implications of Animas and Blanco basin formations

    SciTech Connect

    Brister, B.S. )

    1989-09-01

    The lower member of the Animas Formation (McDermott Member) is a volcaniclastic sequence derived from a north-northwest source (San Juan-La Plata area). It consists of purple andesitic debris flows, green fan-delta sandstones and mud rocks, and dark gray conglomerates with clast compositions indicating that the Precambrian core of the source uplift was exposed. The upper member is a sand-dominated alluvial plain sequence deposited by southwest-flowing braided streams. It includes green-gray-brown carbonaceous mudstones and pebbly sandstones containing clasts of mudstone, andesite, and detritus from Precambrian and Mesozoic sources in the Brazos-San Luis uplift to the east and northeast. by the end of Animas deposition, the San Juan sag (then a northeastern extension of the San Juan basin) was a broad, southwest-plunging synclinal downwarp bounded by hogback monoclines to the north and east. An erosional period followed Animas deposition; the greatest thickness of Animas was preserved along the axis of this synclinal feature. Bright-red sandy mudstones and yellow-gray pebbly sandstones and cobble conglomerates comprise the proximal alluvial-fan deposits of the Blanco Basin Formation. They unconformably overlie Precambrian through Paleocene rocks and clast compositions reflect these sources. Renewed uplift and segmentation of the Brazos-San Luis uplift resulted in the shedding of detritus southwestward into the San Juan sag and eastward into a narrow, asymmetrical, north-trending wrench basin within the uplift. Following Blanco Basin deposition, the last Laramide event is represented by the separation of the San Juan sag from the San Juan basin by uplift of the Archuleta anticlinorium.

  10. Regional-scale flow of formation waters in the Williston basin

    SciTech Connect

    Bachu, S.; Hitchon, B.

    1996-02-01

    The Williston basin is a structurally simple intracratonic sedimentary basin that straddles the United States-Canada border east of the Rocky Mountains and that contains an almost continuous stratigraphic record since the Middle Cambrian. Based on the wealth of data generated by the oil industry, the regional-scale characteristics of the flow of formation waters were analyzed for the Canadian side of the basin, and integrated with previous studies performed on the American side. Several aquifers and aquifer systems identified in the basin were separated by intervening aquitards and aquicludes. The Basal, Devonian, and Mannville (Dakota) aquifers are open systems, being exposed at the land surface in both recharge and discharge areas. Recharge takes place in the west-southwest at relatively high altitude in the Bighorn and Big Snowy mountains and at the Black Hills and Central Montana uplifts, whereas discharge takes place in the east and northeast at outcrop along the Canadian Precambrian shield in Manitoba and the Dakotas. The Mississippian and Pennsylvanian aquifer systems are semi-open, cropping out only in the west-southwest where they recharge, but discharging in the northeast into adjacent aquifers through confining aquitards. On regional and geological scales, the entire system seems to be at steady-state, although locally transient flow is present in places due to water use and hydrocarbon exploitation, and to some erosional rebound in the uppermost confining shales. On the western flank of the basin, the interplay between the northeastward structural downdip direction and the northeastward flow of formation waters creates conditions favorable for hydrodynamic oil entrapment.

  11. Acritarchs from Ponta Grossa Formation and their stratigraphic significance: Devonian of Parana basin

    SciTech Connect

    Dino, R.

    1983-03-01

    The Devonian fossil record in the Parana basin of Brazil is restricted to the Ponta Grossa Formation, a potential source rock unit. Paleontological studies of the macrofauna from this formation indicated an Early Devonian age. For this paper a wide range of surface samples and core samples from eight wells drilled by Pauliperto (a CESP-IPT joint venture) have been studied. Microplankton from the Devonian of the Parana basin never before described are presented here, together with their biostratigraphical and paleoecological implications. Intrabasinal and interbasinal correlations are also made. From a total of 60 species identified until now, twenty forms having well-defined stratigraphic ranges and broad (intercontinental) geographic representation are described herein. This assemblage is marked by the presence and diversity of the Subgroups Polygonomorphitae and Pteromorphitae. The Subgroup Acanthomorphitae is also well represented. The Emsian-Frasnian age previously established for the Ponta Grossa Formation through other palynological studies is further confirmed by the paleomicroplankton evidence. Moreover, the chronostratigraphic limits of these sediments may now be refined even further. Thus, depsite the presence of long-ranging forms, other species, such as Triangulina alargada, which is restricted to the Emsian in the La Vid Formation in northern Spain, allow a better chronostratigraphic subdivision of the Ponta Grossa Formation. The abundance of forms of Tasmanites together with a large quantity and diversity of microplankton provides the basis for the paleoecologic interpretations.

  12. Geology of the Molina Member of the Wasatch Formation, Piceance Basin, Colorado

    SciTech Connect

    Lorenz, J.; Nadon, G.; LaFreniere, L.

    1996-06-01

    The Molina Member of the Wasatch Formation has been cored in order to assess the presence/absence and character of microbial communities in the deep subsurface. Geological study of the Molina Member was undertaken in support of the microbiological tasks of this project, for the purposes of characterizing the host strata and of assessing the potential for post-depositional introduction of microbes into the strata. The Molina Member comprises a sandy fluvial unit within a formation dominated by mudstones. Sandy to conglomeratic deposits of braided and meandering fluvial systems are present on the western and eastern margins of the basin respectively, although the physical and temporal equivalence of these systems cannot be proven. Distal braided facies of planar-horizontal bedded sandstones are recognized on the western margin of the basin. Natural fractures are present in all Molina sandstones, commonly as apparent shear pairs. Core from the 1-M-18 well contains natural fractures similar to those found in outcrops, and has sedimentological affinities to the meandering systems of the eastern margin of the basin. The hydrologic framework of the Molina, and thus any potential post-depositional introduction of microbes into the formation, should have been controlled by approximately east-west flow through the natural fracture system, the geometries and extent of the sandstones in which the fractures occur, and hydraulic gradient. Migration to the well site, from outcropping recharge areas at the edge of the basin, could have started as early as 40 million years ago if the cored strata are connected to the eastern sedimentary system.

  13. Age and depositional setting of the type Lospe Formation (Lower Miocene), Santa Maria basin, central California

    SciTech Connect

    Stanley, R.G. ); Johnson, S.Y.; Obradovich, J.D.; Tuttle, M.L. ); Thornton, M.L.C.; Vork, D.R.; Filewicz, M.V. ); Mason, M.A. ); Swisher, C.C. III )

    1990-05-01

    The Lospe Formation is an 800-m-thick sequence of sedimentary and minor volcanic rocks at the base of the petroliferous Neogene Santa Maria basin of central California. In its type area in the Casmalia Hills, the Lospe rests unconformably on Jurassic ophiolite, is conformably overlain by the lower Miocene (Sauceian and Relizian) Point Sal Formation, and is of earliest Miocene (Saucesian) age on the basis of palynomorphs, benthic foraminifers, and radiometric dating of tuffs. Alluvial fan and fan-delta facies at the base of the Lospe are as much as 200 m thick and consist mainly of conglomerate and sandstone derived from nearby fault-bounded uplifts of Mesozoic rocks. These coarse sediments grade upward into a sequence of interbedded turbidite sandstone and mudstone that accumulated in a lake or restricted coastal embayment. Lenses of tuff as much as 20 m thick occur sporadically throughout this sequence and contain blocks of Jurassic ophiolite up to 50 m long and 20 m across. The uppermost 30 m of the Lospe consist of storm-deposited sandstone and mudstone containing shallow marine microfossils. That these shelf deposits are abruptly overlain by black shale of the Point Sal Formation indicates rapid deepening to oxygen-poor bathyal environments. Overall, the Lospe Formation is a fining-upward sequence that records active faulting, volcanism, and a change from nonmarine to marine depositional environments during the initial formation of the Neogene Santa Maria basin. This history is consistent with several competing tectonic models that variously explain the origin of the basin as the result of regional rifting or local rotation of small crustal blocks.

  14. Geologic constraints on kinematic models and age of formation of the Amerasia Basin of the Arctic

    NASA Astrophysics Data System (ADS)

    Miller, E. L.

    2015-12-01

    A wealth of new geologic and geophysical data now exist for the Amerasia Basin, but the details of its age and the nature/kinematics of events that resulted in its formation remain elusive. Basement rock ages, detrital zircon signatures of sedimentary rocks, and sediment dispersal systems have been used to show how parts of the southern margin(s) of the Amerasia Basin (Arctic Alaska-Chukotka, AAC) match their rifted margin counterparts on the Eurasia and Canada side of the Amerasia Basin. Thus we know the approximate finite translations needed to restore the paleogeography of the Arctic, but not the kinematics involved. Important features of the Amerasia Basin that need to be explained in a model for its opening are the age and extent of the high Arctic LIP, the linearity of the strip of continental crust represented by the Lomonosov Ridge, its right angle intersection with the Canadian Arctic margin, and the directional fault patterns mapped bathymetrically and seismically across the Alpha-Lomonosov Ridge and surrounding seafloor. Across AAC, post-Early Cretaceous oroclinal bends provide insight into strike-slip components of deformation involved in opening of the Amerasia Basin: The Chukchi syntax offsets the Brooks Range in a right-lateral sense from Wrangel Island along the Herald Arch; right-lateral motion of Arctic Alaska with respect to the Chukchi Borderland during opening of the Canada Basin; right-lateral shear in Chukotka during 100 Ma magmatism; the tight bend in the northern Verkhoyansk, result of Cretaceous right-lateral shear. The land-based relationships imply a post-Early Cretaceous, younger than Barremian (~130 Ma) age for onset of magmatism and extension related to rifting and formation of the Amerasia Basin. At least two stages of extension are documented, with older E-W extension characterizing the longitude of the New Siberian Islands to Pevek, Russian Arctic, (ca.125 Ma to 100 Ma), with younger N-S extension superimposed on this system (ca

  15. The formation of the Tyrrhenian Basin by 3-D interaction among faulting and magmatism

    NASA Astrophysics Data System (ADS)

    Ranero, C. R.; Sallares, V.; Grevemeyer, I.; Zitellini, N.; Vendrell, M. G.; Prada, M.; Moeller, S.; de Franco, R.

    2012-12-01

    The Tyrrhenian basin has been formed by extension of overriding continental lithosphere driven by roll back of the Ionian slab across the mantle. The basin is not actively extending but the tectonic structure provides information of the processes that controlled rifting and formation of conjugate margins. The basin opened from west to east, with rifting stopping after progressively larger stretching factors from north to south. The northern region stopped opening at extension factors about 1.8. Towards the south extension continued until full crustal separation that produced first intense magmatism that subsequently was followed by mantle exhumation. The final structure displays two conjugate margins with structures that evolved from symmetric to asymmetric as extension rates increase and a complex tectonic structure in between. The basin provides a natural laboratory to investigate a full rift system with variable amounts of extension. We present observations from a two-ship wide-angle (WAS) and multichannel reflection seismic (MCS) experiment that took place in spring 2010. The experiment took place on two legs: The first leg with Spanish R/V Sarmiento de Gamboa and Italian R/V Urania collected five WAS profiles striking E-W across the entire basin recorded on ocean bottom seismic stations and land stations with a 4800 c.i. G-II gun array as source. The second leg with R/V Sarmiento de Gamboa collected 16 MCS profiles (about 1500 km) using a 3.75 km-long streamer and a 3100 c.i. G-II gun array as source. MCS profiles were shot coincident with WAS profiles. WAS - MCS transects were located in regions with different amount of extension the study the full structure including the two conjugate margins. Additional MCS lines were shot concentrated in the region where mantle exhumation has taken place. The seismic information is placed in a 3D context with the integration of the multibeam bathymetry that covers the entire basin. We present the interpretation of the

  16. Variations in the degree of crustal extension during formation of a back-arc basin

    NASA Astrophysics Data System (ADS)

    de Wit, Maarten J.; Stern, Charles R.

    1981-02-01

    Ophiolite complexes in southern Chile represent the remnants of the mafic portion of the floor of a Cretaceous back-arc basin which widened markedly from north to south over a length of 600 km. Detailed field and geochemical studies of ophiolites in the northern (Sarmiento complex) and southern (Tortuga complex) extremities of the originally wedge-shaped back-arc basin floor, indicate significant north—south differences in the mode of emplacement of basaltic magmas into the pre-existing continental crust, during the formation of the basin. In the northern narrow extremity of the original basin, mafic melts intruded into the continental crust over a diffuse zone causing extensive remobilization and reconstitution of the sialic continental crust. In the southern wider part of the original basin, mafic magmas appear to have been emplaced at a localized oceanic-type spreading centre. The observed north—south variations resulted in formation of back-arc floor with crustal characteristics ranging from intermediate between continental and oceanic to typically oceanic. These variations are interpreted as representing different stages of evolution of a back-arc basin which formed due to a subtle interplay between subduction induced back-arc mantle convection and the release of stress across the convergent plate boundary, possibly related to ridge subduction. Prior to the release of stress, heat transferred from mantle diapirs to the base of crust caused widespread silicic volcanism in South America. With the release of stress, mantle derived melts erupted to the surface along structural pathways resulting in extensive basaltic volcanism in a linear belt behind the island arc and the cessation of silicic volcanism. Initially, basaltic magmas intruded the continental crust over a diffuse region causing reconstitution of sialic crustal rocks. Progressive localization of the zone of intrusion of mafic magmas from the mantle eventually resulted in the development of an

  17. Coupling and Formation Mechanism of Continental Intraplate Basin and Orogen—Examples from the Qinghai-Tibet Plateau and Adjacent Basins

    NASA Astrophysics Data System (ADS)

    LI, Dewei; XIA, Yiping; XU, Ligui

    There are very close relationships between orogenic belts and their peripheral sedimentary basins: they are spatially interdependent in structure, mutually compensatory in material, interactive in tectonics, simultaneous in tectonic evolution. The relationships indicate a unified formation mechanism for the continental orogenic belts and the sedimentary basins, which can be presented as follows: lower crustal ductile lateral flow from the basin to the orogen, driven by thermal energy related to upwelling mantle plume in the intracontinental crust and by vertical diaper movement of dehydration and magma of the subduction plate on the active continental margin, results in the circulative movement of crust materials between basins and orogens. The coupling between the Qinghai-Tibet Plateau and its peripheral basins is a typical basin-orogen coupling occurring in the intraplate tectonic setting. The formation of the Qinghai-Tibet Plateau is not a result of collision between the India plate and the Eurasia plate, but rather the result of intraplate basin-orogen formation process driven by lower crustal flow. The tectonic evolution of intraplate basin-orogen system in the Qinghai-Tibet Plateau can be divided into two stages: (1) intraplate orogen-basin formation stage. During this stage, the spatial and temporal evolution of the intraplate orogens and basins in the Qinghai-Tibet Plateau is indicated by the successive geographic movement of the locations of the new basin-orogen systems from the northern and eastern, to the central, and finally to the southern Qinghai-Tibet Plateau, corresponding geochronologically to periods from 180-120 Ma, to 65-30 Ma, and finally to 23-7 Ma. This stage was manifested by extensive intraplate faulting, folding, block movement, magmatism and metallogeny. (2) isostatic mountain building and basin margin subsidence stage. In this stage, there were rapid uplift and strong erosion of the entire Qinghai-Tibet Plateau and rapid subsidence and

  18. Lithofacies and cyclicity of the Yates Formation, Permian basin: Implications for reservoir heterogeneity

    SciTech Connect

    Borer, J.M.; Harris, P.M. )

    1991-04-01

    Siliciclastics of the Yates Formation (Permian, upper Guadalupian) are significant hydrocarbon reservoirs in the US Permian basin. Subsurface and outcrop data show that the most porous lithofacies occur in a clastic-dominated middle shelf and that evaporitic inner shelf and carbonate outer shelf equivalents are mostly nonporous. Lithofacies relations and much of the heterogeneity in Yates reservoirs are related to the stacking of depositional sequences (i.e., siliciclastic-carbonate alternations and sandstone-argillaceous siltstone alternations) in response to three orders of orbitally forced, low-amplitude, eustatic variation. In general, siliciclastics dominated the Yates shelf during lowstand parts of asymmetric, 400-k.y. sea level fluctuations, whereas carbonates were deposited during sea level highstands. The character and position of sand depocenters on the Yates shelf during these lowstands were controlled by a longer duration third-order sea level variation. Shorter duration cycles controlled the heterogeneity within the 400-k.y. depositional sequences. The variation in cycle packaging, lithology, and reservoir quality between the Central Basin platform and Northwest shelf may be a response of eustatic variation on parts of the shelf with different slopes or subsidence profiles. The lithofacies described from the Yates Formation and the deposition model proposed to explain the stratigraphy may be valuable as analogs in other basins containing mixed siliciclastic-carbonate settings.

  19. Stratigraphy, sedimentology and paleontology of lower Eocene San Jose formation, central San Juan basin, New Mexico

    SciTech Connect

    Lucas, S.G.; Smith, L.N. )

    1989-09-01

    The lower Eocene San Jose Formation in the central portion of the San Juan basin (Gobernador-Vigas Canyon area) consists of the Cuba Mesa, Regina, Llaves, and Tapicitos Members. Well log data indicate that, from its 100-m thickness, the Cuba Mesa Member thins toward the basin center and pinches out to the northeast by lat. 36{degree}40'N, long. 107{degree}19'W. The Regina Member has the most extensive outcrops in the central basin, and it decreases in sandstone/mud rock ratio to the north. The Llaves and Tapicitos Members occur only at the highest elevations, are thin due to erosion, and are not mappable as separate units. Well log data and 1,275 m of measured stratigraphic section in the Regina, Llaves, and Tapicitos Members indicate these strata are composed of approximately 35% medium to coarse-grained sandstone and 65% fine-grained sandstone and mud rock. Sedimentology and sediment-dispersal patterns indicate deposition by generally south-flowing streams that had sources to the northwest, northeast, and east. Low-sinuosity, sand-bedded, braided( ) streams shifted laterally across about 1 km-wide channel belts to produce sheet sandstones that are prominent throughout the San Jose Formation. Subtle levees separated channel environments from floodplain and local lacustrine areas. Avulsion relocated channels periodically to areas on the floodplain, resulting in the typically disconnected sheet sandstones within muddy overbank deposits of the Regina Member.

  20. Soft sediment deformation structures in the Maastrichtian Ajali Formation Western Flank of Anambra Basin, Southern Nigeria

    NASA Astrophysics Data System (ADS)

    Olabode, Solomon Ojo

    2014-01-01

    Soft sediment deformation structures were recognized in the Maastrichtian shallow marine wave to tide influenced regressive sediments of Ajali Formation in the western flank of Anambra basin, southern Nigerian. The soft sediment deformation structures were in association with cross bedded sands, clay and silt and show different morphological types. Two main types recognised are plastic deformations represented by different types of recumbent folds and injection structure represented by clastic dykes. Other structures in association with the plastic deformation structures include distorted convolute lamination, subsidence lobes, pillars, cusps and sand balls. These structures are interpreted to have been formed by liquefaction and fluidization mechanisms. The driving forces inferred include gravitational instabilities and hydraulic processes. Facies analysis, detailed morphologic study of the soft sediment deformation structures and previous tectonic history of the basin indicate that the main trigger agent for deformation is earthquake shock. The soft sediment deformation structures recognised in the western part of Anambra basin provide a continuous record of the tectonic processes that acted on the regressive Ajali Formation during the Maastrichtian.

  1. Depositional history of the Lower Triassic Dinwoody Formation in the Wind River basin area, Wyoming

    SciTech Connect

    Paul, R.K.; Paull, R.A. )

    1993-04-01

    Thirty-three measured sections of the Dinwoody Formation, including five from the literature, provide information on thickness, lithology, paleontology, and stratigraphic relations within the Wind River basin and immediately adjacent areas of Wyoming. Most of these sections are in Fremont County, and some lie within the Wind River Indian Reservation. The Dinwoody becomes progressively thinner eastward, from a maximum thickness of 54.6 m in the northwestern Wind River Mountains to zero near the Natrona County line. The formation is characterized by yellowish-weathering, gray siltstone and silty shale. Variable amounts of limestone, sandstone, gypsum, and claystone are also present. Marine bivalves, gastropods, brachiopods (Lingula), and conodonts are common in the western part of the study area, but are absent to the northeast in gypsiferous strata, and near the eastern limit of Dinwoody deposition. The Dinwoody in the Wind River Basin area was deposited unconformably on the Upper Permian Ervary Member of the Park City Formation during the initial Mesozoic flood onto the Wyoming shelf during the Griesbachian, and represents the first of three Lower Triassic transgressive sequences in the western miogeocline. Conodonts of the Isarcica Chronozone document the rapid nature of this eastward transgression. The Permian surface underlying the Dinwoody rarely shows evidence of the long hiatus separating rocks of this age and earliest Triassic deposits. The Dinwoody transgression was followed by westward progradation of the Red Peak Formation of the Chugwater Group across the study area.

  2. Abo Formation alluvial facies and Associated Basin Fill, Sacramento Mountains, New Mexico

    SciTech Connect

    Speer, S.W.

    1986-03-01

    Outcrops of the Abo Formation (Wolfcampian to early Leonardian age) in the Sacramento Mountains of south-central New Mexico record the evolution of a dry alluvial fan system as it was deposited off the pedernal uplift into the Orogrande basin. The location and orientation of present-day outcrops allow us to observe an inferred east-to-west transverse facies tract consisting of: (1) proximal alluvial fans (lower Abo), which are contiguous in places with underlying Laborcita Formation fan-deltaic sediments; (2) medial anastomosed streams (middle Abo); and (3) distal low-gradient mud-dominated flood basins characterized by either distributary streams (upper Abo) or clastic tidal flats (Lee Ranch Tongue of the Abo) with associated marine carbonates (Pendejo Tongue of the Hueco Formation). Tectonism in the Pedernal highlands, which climaxed during the Late Pennsylvanian, apparently continued well into the Wolfcampian in this region, as evidenced by a major basal Abo unconformity and distinct stacked megasequences of lower Abo alluvial fan lithofacies. However, by the middle Abo, tectonic activity had quiesced and the uplift began eroding and retreating to the north and east. By the late Abo, a pediment surface had formed that was subsequently onlapped by upper Abo and eventually Yeso Formation sediments.

  3. Morphology of large impact craters and basins on Venus: Implications for ring formation

    NASA Astrophysics Data System (ADS)

    Alexopoulos, Jim S.; McKinnon, William B.

    1993-03-01

    A nearly complete examination of the Magellan radar data for the Venusian surface reveals 72 unequivocal peak-ring craters and 4 larger structures that we interpret to be multiringed. This report updates our earlier studies and that of the Magellan team. The general morphology of peak-ring craters, decreasing ring diameter ratio trends with increasing crater diameter, and the general size-morphology progression from complex central-peak crater to peak-ring crater on Venus and the terrestrial planets suggest similar processes of peak-ring formation. Observations are consistent with a model of dynamic collapse, downward and outward, of an unstable central peak to form a ring. We interpret the four larger ringed structures (Klenova, Lise Meitner, Mead, and Isabella) to be morphologically similar to the Orientale Basin on the Moon, and thus, true multiringed basins.

  4. Permian Bone Spring formation: Sandstone play in the Delaware basin. Part I - slope

    SciTech Connect

    Montgomery, S.L.

    1997-08-01

    New exploration in the Permian (Leonardian) Bone Spring formation has indicated regional potential in several sandstone sections across portions of the northern Delaware basin. Significant production has been established in the first, second, and third Bone Spring sandstones, as well as in a new reservoir interval, the Avalon sandstone, above the first Bone Spring sandstone. These sandstones were deposited as submarine-fan systems within the northern Delaware basin during periods of lowered sea level. The Bone Spring as a whole consists of alternating carbonate and siliciclastic intervals representing the downdip equivalents to thick Abo-Yeso/Wichita-Clear Fork carbonate buildups along the Leonardian shelf margin. Hydrocarbon exploration in the Bone Spring has traditionally focused on debris-flow carbonate deposits restricted to the paleoslope. Submarine-fan systems, in contrast, extend a considerable distance basinward of these deposits and have been recently proven productive as much as 40-48 km south of the carbonate trend.

  5. Morphology of large impact craters and basins on Venus: Implications for ring formation

    NASA Technical Reports Server (NTRS)

    Alexopoulos, Jim S.; Mckinnon, William B.

    1993-01-01

    A nearly complete examination of the Magellan radar data for the Venusian surface reveals 72 unequivocal peak-ring craters and 4 larger structures that we interpret to be multiringed. This report updates our earlier studies and that of the Magellan team. The general morphology of peak-ring craters, decreasing ring diameter ratio trends with increasing crater diameter, and the general size-morphology progression from complex central-peak crater to peak-ring crater on Venus and the terrestrial planets suggest similar processes of peak-ring formation. Observations are consistent with a model of dynamic collapse, downward and outward, of an unstable central peak to form a ring. We interpret the four larger ringed structures (Klenova, Lise Meitner, Mead, and Isabella) to be morphologically similar to the Orientale Basin on the Moon, and thus, true multiringed basins.

  6. Fluvial sedimentology of a Mesozoic petrified forest assemblage, Shishu Formation, Junggar foreland basin, Xinjiang, China

    SciTech Connect

    McKnight, C.L.; Gan, O.; Carroll, A.R.; Dilcher, D.; Zhao, M.; Liang, Y.H.; Graham, S.A.

    1988-02-01

    The Upper Jurassic(.) Shishu Formation of the eastern Junggar basin, Xinjiang, northwest China, is a fluvial sand unit containing an important assemblage of well-preserved, silicified tree trunks and rooted stumps. Numerous logs, up to 83 ft (25.5 m) long, occur at several levels within a 33.6-ft (10.3 m) stratigraphic section of fluvial sand, gravel, and mud and several paleosol horizons. The uppermost logbearing layer includes a number of rooted tree stumps in growth position, with diameters of up to 8 ft (2.5 m). The maximum root length observed is 40 ft (12.3 m). The trees have been identified by Chinese paleontologists as Cupressinoxylon. The petrified forest assemblage is preserved on the northeast margin of the Mesozoic Junggar foreland basin, a large continental basin subsiding under thrust loading from the south. Logs found within channel gravel units are oriented with their log axes parallel to the channel axis. Sedimentary structures, including epsilon and trough cross-stratification and imbricated channel gravels, indicate paleocurrent flow generally to the south, toward the basin center. The size of the logs suggests the presence of a major fluvial system. The epsilon cross-sets suggest a channel depth of 26 ft (8 m). The oriented silicified logs and their enclosing clastic sediments provide important information on the depositional systems active on the northeastern margin of the Junggar basin in the Late Jurassic(.) time. Hopefully, further detailed study of the fossil trees, including the spacing of the rooted stumps, will provide new information on the paleoecology of Mesozoic forests and the climatic conditions prevailing in the region at the time of deposition.

  7. Basin formation and Neogene sedimentation in a backarc setting, Halmahera, eastern Indonesia

    SciTech Connect

    Hall, R. ); Nichols, G.J. )

    1991-03-01

    It has been proposed that basins in backarc setting form in association with subduction by thinning of continental crust, backarc spreading in oceanic crust, compression, or trapping of pieces of oceanic plate behind an arc. The Halmahera basin in eastern Indonesia developed in a backarc setting but does not fall into these categories; it formed by subsidence of thickened crust made up of imbricated Mesozoic-Paleogene arc and ophiolite rocks. Halmahera lies at the western edge of the Philippine Sea Plate in a complex zone of convergence between the Eurasian margin, the oceanic plates of the West Pacific, and the Australian/Indian Plate to the south. The basement is an imbricated complex of Mesozoic to Paleogene ophiolite, arc, and arc-related rocks. During the Miocene this basement complex formed an area of thickened crust upon which carbonate reef and reef-associated sediments were deposited. The authors interpret this shallow marine region to be similar to many of the oceanic plateaus and ridges found within the Philippine Sea Plate today. In the Late Miocene, convergence between the Philippine Sea Plate and the Eurasian margin resulted in the formation of the Halmahera Trench to the west of this region of thickened crust. Subduction of the Molucca Sea Plate caused the development of a volcanic island arc. Subsidence in the backarc area produced a broad sedimentary basin filled by clastics eroded from the arc and from uplifted basement and cover rocks. The basin was asymmetric with the thickest sedimentary fill on the western side, against the volcanic arc. The Halmahera basin was modified in the Plio-Pleistocene by east-west compression as the Molucca Sea Plate was eliminated by subduction.

  8. Application of Landsat imagery to hydrocarbon exploration in Niobrara Formation, Denver basin

    SciTech Connect

    Merin, I.S.; Moore, W.R.

    1985-02-01

    The Niobrara Formation produces commercial quantities of oil from fractures in several places in the Denver basin. The Niobrara in this basin is an oil-prone, mature source rock having as much as 3.4% TOC, and has been in the generating window since early Eocene. This implies that hydrocarbon generation from the Niobrara is partly contemporaneous with the Laramide orogeny. The Laramide was a multiple-phase orogenic event that began with compression directed to the east-northeast during the Late Cretaceous to Paleocene and ended with compression directed to the northeast during the Eocene. The authors believe the Eocene phase activated northeast-trending extension fractures that may have acted as loci for storage and migration of hydrocarbons, locally generated in the Niobrara. The auto-fracing pressures related to hydrocarbon generation in the Niobrara theoretically would preferentially open and fill this northeast-trending fracture system. Examination of Landsat imagery shows that zones of northeast-trending lineaments are present throughout the basin. Numerous northeast-trending faults are present in the basin, and many overlie older zones that were reactivated during the Laramide. This suggests that these lineaments are previously unrecognized fracture zones. The authors have defined an exploration fairway within the basin based on subsurface isopach and resistivity mapping. The authors believe that mapping of northeast-trending fractures can help identify leads (within this fairway) prospective for Niobrara production. Support of this concept is the location of several apparently productive Niobrara wells along a zone of northeast-trending lineaments.

  9. Basin Analysis of the Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain

    SciTech Connect

    Ernest Mancini

    2000-12-31

    Part 3 (Petroleum System Modeling of the Jurassic Smackover Formation) objectives are to provide an analysis of the Smackover petroleum system in Years 4 and 5 of the project and to transfer effectively the research results to producers through workshops and topical reports. Work Accomplished (Year 5): Task 1 - Basin Flow - Basin flow modeling has been completed and the modeling results are being interpreted for report writing (Table 1). Task 2 - Petroleum Source Rocks - Work on the characterization of Smackover petroleum source rocks has been integrated into the basin flow model. Task 3 - Petroleum Reservoirs - Work on the characterization of Smackover petroleum reservoirs continues. The cores to be described have been identified and many of the cores for the eastern part of the basin have been described. Task 4 - Reservoir Diagenesis - Work on reservoir diagenesis has been initiated. Samples from the cores selected for the reservoir characterization are being used for this task. Work Planned (Year 5): Task 1 - Basin Flow - The report on basin flow will be completed. Task 2 - Petroleum Source Rocks - Petroleum source rock data will be reviewed in light of the basin flow model results. Task 3 - Petroleum Reservoirs - Characterization of petroleum reservoirs will continue through core studies. Task 4 - Reservoir Diagenesis - Characterization of reservoir diagenesis will continue through petrographic analysis.

  10. Thickness of Proximal Ejecta from the Orientale Basin from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for Multi-Ring Basin Formation

    NASA Technical Reports Server (NTRS)

    Fassett, Caleb I.a; Head, James W.; Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.

    2011-01-01

    Quantifying the ejecta distribution around large lunar basins is important to understanding the origin of basin rings, the volume of the transient cavity, the depth of sampling, and the nature of the basin formation processes. We have used newly obtained altimetry data of the Moon from the Lunar Orbiter Laser Altimeter (LOLA) instrument to estimate the thickness of ejecta in the region surrounding the Orientale impact basin, the youngest and best preserved large basin on the Moon. Our measurements yield ejecta thicknesses of approx.2900 m near the Cordillera Mountains, the topographic rim of Orientale, decaying to approx.1 km in thickness at a range of 215 km. These measurements imply a volume of ejecta in the region from the Cordillera ring to a radial range of one basin diameter of approx.2.9 x 10(exp 6)cu km and permit the derivation of an ejecta-thickness decay model, which can be compared with estimates for the volume of excavation and the size of the transient cavity. These data are consistent with the Outer Rook Mountains as the approximate location of the transient cavity s rim crest and suggest a volume of approx.4.8 x 10(exp 6)cu km for the total amount of basin ejecta exterior to this location.

  11. A statistical approach to understanding and predicting tropical storm formation in the east Pacific basin

    NASA Astrophysics Data System (ADS)

    Nelson, Dianna N.

    Despite its spatial confines, the east Pacific basin is one of the most active basins in the world for tropical cyclone (TC) genesis. While the TCs that form in the basin have important implications for Central America and the southwestern U.S., relatively little research (compared to other tropical basins) has been done on eastern Pacific tropical cyclogenesis. The present study uses two statistical techniques---linear discriminant analysis (LDA) and a Bayesian probabilistic model to identify those variables that are associated with the development of nascent vortices in the east Pacific and uses them to predict tropical storm formation for lead times out to 48 hours. All nascent vortices that last for a minimum of 48 hours and form during the 2001--2009 "peak" hurricane seasons (July-September) are considered in the study. An initial set of 27 spatially averaged variables is considered as potential predictors for the statistical models. Results from both the LDA algorithm and Bayes probabilistic model show that a number of predictors improve the forecast skill of both models. These predictors include the 900hPa relative vorticity, latitude of the vortex, 900hPa deformation fields, 900hPa-500hPa relative humidity, 900hPa zonal wind, and the 900hPa-200hPa equatorward vertical shear of the meridional wind. Using the aforementioned predictors as a basis, a composite-based conceptual model for environmental elements that favor tropical storm formation is constructed to explain the physical mechanisms of the process. In conjunction with the statistical and composite-based models, Tropical Storm Gil (a 2007 storm that is accurately forecast by the statistical models) and Tropical Storm Enrique (a 2009 case that is poorly forecast) are used to highlight the strengths and weaknesses of each model.

  12. Genetic stratigraphy of the Williams Fork Formation, Sand Wash Basin, Colorado and Wyoming

    SciTech Connect

    Hamilton, D.S. )

    1993-08-01

    The Williams Fork Formation forms the upper part of the Upper Cretaceous Mesaverde Group, Sand Wash basin. The formation can be divided into four genetic depositional sequences each bounded by regionally extensive, low-resistivity shale markers. The markers are continuous across the basin, extending from the southeastern margin to the southern Flank of the Rock Springs uplift. Recognizing these bounding surfaces was relatively straightforward in the eastern half of the basin, where they are interpreted to be maximum marine-flooding surfaces. Recognizing them in the continental facies to the northwest, however, was more difficult, but still achievable with detailed well-log correlation. Presence of the markers to the northwest indicates that either the marine flooding extended farther west than is generally recognized, or that the controls on the flooding (such as shutting off sediment supply) leave a record in the non-marine environment as surfaces of sediment starvation or non-deposition. The four genetic depositional sequences represent progradational clastic wedges of variable areal extend that were deposited during discrete episodes of basin filling. Geometry of the framework sandstones and log-facies character of each of the genetic units indicate a similar depositional style for genetic units 1-3. These units are characterized by upward-coarsening, sandstone-rich linear shoreline systems in the southeast that are bounded updip by aggradational coals and interbedded mudrocks of the coastal plain that, in turn, pass landward into aggradational log motifs of thick, stacked sandstone units and interbedded mudstones on the alluvial plain. Unit 4 is characterized throughout by mudstone-rich coal-bearing facies interpreted as alluvial-plain deposits with lacustrine influence.

  13. The Guasare Formation (Paleocene), Maracaibo Basin: A carbonate or a terrigeneous play?

    SciTech Connect

    Hernandez, E.; Oldershaw, A.; Krause, F.

    1996-08-01

    The Guasare Formation located in the Lama Field, Maracaibo Basin, represents a mixed carbonate-terrigenous clastic succession. We have identified 10 lithofacies in this succession: pelecypod floatstones-rudstones; black mudstones; grey siltstones; medium grained sandstones; laminated fine grained sandstones; rippled fine grained sandstones; bioturbated fine grained sandstones; calcareous massive sandstones; interbedded mudstones and sandstones; and mudstone clast conglomerates. These lithofacies represent coastal plain, nearshore, tide and storm influenced conditions during sedimentation, which resulted in a close temporal and spatial association of distinct carbonate and siliciclastic facies. Environmental reconstruction indicates that accumulation took place in a dynamic delta setting where delta lobe progradation, abandonment, transgression and renewed progradation were the dominant controlling factors on sedimentation. The formation typically has been visualized as a carbonate platform deposit. Our work instead illustrates that in the Lama Field this formation is a mixed carbonate-terrigenous succession dominated by brackish water to marine depositional systems.

  14. Hydrogeologic investigations of the Miocene Nogales Formation in the Nogales Area, Upper Santa Cruz Basin, Arizona

    USGS Publications Warehouse

    Page, William R.; Gray, Floyd; Bultman, Mark W.; Menges, Christopher M.

    2016-01-01

    Hydrogeologic investigations were conducted to evaluate the groundwater resource potential for the Miocene Nogales Formation in the Nogales area, southern Arizona. Results indicate that parts of the formation may provide new, deeper sources of groundwater for the area. Geologic mapping determined the hydrogeologic framework of the formation by defining lithologic, mineralogic, and stratigraphic characteristics; identifying potential aquifers and confining units; and mapping faults and fractures which likely influence groundwater flow. Geophysical modeling was used to determine the basin geometry and thickness of the Nogales Formation and younger alluvial aquifers and to identify target areas (deep subbasins) which may prove to be productive aquifers.Volcaniclastic sandstone samples from the formation were analyzed for porosity, bulk density, saturated hydraulic conductivity, and fabric. Effective porosity ranges from 16 to 42 percent, bulk density from 1.6 to 2.47 grams per cubic centimeter, and saturated hydraulic conductivity (SHC) from 4 to 57 centimeters per day (4.9×10-5 to 6.7×10-4 centimeters per second). Thin sections show that sandstone framework grains consist of quartz, feldspar, biotite, hornblende, pumice, volcanic glass, and opaque minerals. The matrix in most samples consists of pumice fragments, and some contain predominantly silt and clay. Samples with a mostly silt and clay matrix have lower porosity and SHC compared to samples with mostly pumice, which have higher and wider ranges of porosity and SHC. Pore space in the Nogales Formation sediments includes moldic, intercrystalline, and fracture porosity. Some intercrystalline pore space is partially filled with calcite cement. About one third of the samples contain fractures, which correspond to fractures noted in outcrops in all members of the formation.Scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses indicate that most of the samples contained the zeolite clinoptilolite

  15. Hydrogeologic investigations of the Miocene Nogales Formation in the Nogales Area, Upper Santa Cruz Basin, Arizona

    USGS Publications Warehouse

    Page, William R.; Gray, Floyd; Bultman, Mark W.; Menges, Christopher M.

    2016-07-28

    Hydrogeologic investigations were conducted to evaluate the groundwater resource potential for the Miocene Nogales Formation in the Nogales area, southern Arizona. Results indicate that parts of the formation may provide new, deeper sources of groundwater for the area. Geologic mapping determined the hydrogeologic framework of the formation by defining lithologic, mineralogic, and stratigraphic characteristics; identifying potential aquifers and confining units; and mapping faults and fractures which likely influence groundwater flow. Geophysical modeling was used to determine the basin geometry and thickness of the Nogales Formation and younger alluvial aquifers and to identify target areas (deep subbasins) which may prove to be productive aquifers.Volcaniclastic sandstone samples from the formation were analyzed for porosity, bulk density, saturated hydraulic conductivity, and fabric. Effective porosity ranges from 16 to 42 percent, bulk density from 1.6 to 2.47 grams per cubic centimeter, and saturated hydraulic conductivity (SHC) from 4 to 57 centimeters per day (4.9×10-5 to 6.7×10-4 centimeters per second). Thin sections show that sandstone framework grains consist of quartz, feldspar, biotite, hornblende, pumice, volcanic glass, and opaque minerals. The matrix in most samples consists of pumice fragments, and some contain predominantly silt and clay. Samples with a mostly silt and clay matrix have lower porosity and SHC compared to samples with mostly pumice, which have higher and wider ranges of porosity and SHC. Pore space in the Nogales Formation sediments includes moldic, intercrystalline, and fracture porosity. Some intercrystalline pore space is partially filled with calcite cement. About one third of the samples contain fractures, which correspond to fractures noted in outcrops in all members of the formation.Scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses indicate that most of the samples contained the zeolite clinoptilolite

  16. Stratigraphy and depositional environments of Fox Hills Formation in Williston basin

    SciTech Connect

    Daly, D.J.

    1988-07-01

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

  17. Stratigraphy and depositional environments of Fox Hills Formation (Late Cretaceous), Williston basin

    SciTech Connect

    Daly, D.J.

    1986-08-01

    The Fox Hills Formation (Late Cretaceous, Maestrichtian) was investigated where it crops out along the southern flank of the Williston basin and in the subsurface over the central portion of the basin, using 300 well logs. The formation is conformable and gradational with the underlying Pierre formation and can be either conformable or unconformable with the overlying Hell Creek Formation. The Fox Hills Formation is younger, thicker, and stratigraphically more complex to the east and is comprised of marginal marine sediments deposited during the final Cretaceous regression. To the west, the Fox Hills Formation is an upward-coarsening unit generally 30 to 45 m thick and usually contains three members: from the base, Trail City, Timber Lake, and Colgate. The lower Fox Hills (Trail City, Timber Lake) is generally dominated by hummocky bedding and contains a variety of trace fossils, most notably Ophiomorpha. The upper Fox Hills (Colgate), where present, is characterized by cross-bedding. To the east, including the type area, the section is generally 80 to 100 m thick and contains four members: from the base, Trail City, Timber Lake, Iron Lightning (Colgate and Bullhead lithofacies), and Linton. In contrast to the section in the west, this section is as much as three times thicker, contains abundant body fossils, generally lacks hummocky bedding, and contains the Bullhead and Linton strata. In the west, the strata represent lower shoreface deposits, predominantly of storm origin (lower Fox Hills), overlain by upper shoreface and fluvial deposits (upper Fox Hills). In the east, the lower Fox Hills contains deposits of the lower shoreface (Trail City) and a barrier bar complex (Timber Lake), overlain by the deltaic deposits of the upper Fox Hills (Iron Lightning, Linton).

  18. Paleoenvironmental reconstruction of the Early Eocene Wind River Formation in the Wind River Basin, Wyoming

    NASA Astrophysics Data System (ADS)

    Hyland, E.; Fan, M.; Sheldon, N. D.

    2011-12-01

    Terrestrial basin systems provide important information on paleoclimatic, paleoecological, and paleoenvironmental factors and how they control and respond to global changes and spatio-temporal heterogeneity. Examining these dynamics is crucial for times of major global change like the broad-scale climatic trends (warm/wet/high-CO2 conditions) of the Early Eocene Climatic Optimum (EECO). As most climatic records of such events are derived from global marine datasets, regional terrestrial studies such as these provide a better model for understanding ecological responses and the localized effects of events like the EECO. The formation of the Wind River Basin (northwestern Wyoming) has been studied for decades, but its regional climatic, environmental, and ecological dynamics have been largely overlooked. Recent work in other contemporaneous sites in the Green River Basin has suggested that the dynamics and rapidity of climate change in terrestrial interiors during the EECO may have been significantly different than what is indicated by the marine record, so to address these issues on a more regional scale we examined paleosols preserved in the fluvial, basin-margin Wind River Formation preserved near Dubois, Wyoming. Field identification of the paleosols indicated a suite that includes primarily Inceptisols and Alfisols; most exhibited significant redoximorphic features and Bg horizons that indicate a ponded floodplain paleoenvironment, while others contained deep Bk horizons (>100 cm) consistent with more well-drained, but still sub-humid to humid conditions. Based on the identification of these well-developed soil features, along with distinct horizonation and root development, paleosols were robustly correlated and sampled throughout the Formation, and environmental descriptors were assigned. To further examine the question of regional terrestrial climate/environmental change, whole rock geochemistry (XRF) samples from paleosol depth profiles were analyzed for use

  19. Paleomagnetic and magnetostructural study of the Gara Djebilet Jurassic magmatic formations (Tindouf Basin, Southwest Algeria)

    NASA Astrophysics Data System (ADS)

    Amira Boussada, Mejda; Merabet, Nacer-eddine; Mahdjoub, Yamina; Maouche, Said; Charaf Chabou, Moulay; Aifa, Tahar; Ayache, Mohamed

    2015-04-01

    Recent geochemical analyses and 40Ar/39Ar dating of dolerite sills and dykes and basalt lava flows in southwestern Algeria (Tindouf, Reggane, Bechar area and Hank basins) showed that these rocks are linked to the Central Atlantic Magmatic Province (CAMP). The later is one of the largest identified Mesozoic basalt provinces formed approximately 200 Ma ago as a preamble to the Pangea dismemberment. These data were strong arguments to undertake geological field observations and a sampling for paleomagnetic and magnetic fabric study in CAMP province formations. Three long doleritic dykes (198.9 ± 1.8 Ma) in the Tindouf basin were targeted in order to point out the structural context of their emplacement (magnetic fabric) and to determine a new reliable Mesozoic pole. The magnetic fabric, in almost the whole sampled sections, is defined mainly by clustering of k1 and k2 axes on the dyke plane whereas the k3 axis is nearly perpendicular to it. This fabric is therefore interpreted as due to magma flow. The new Jurassic paleomagnetic pole, of excellent quality, is very close to those obtained from coeval detrital Algerian Saharan formations and also close to those recently determined from coeval Morrocan igneous formations. It is very close to the 200 Ma mean NW African pole too. These results represent a considerable contribution of to a better knowledge of the geodynamical context during this period.

  20. Eustatic control on epicontinental basins: The example of the Stuttgart Formation in the Central European Basin (Middle Keuper, Late Triassic)

    NASA Astrophysics Data System (ADS)

    Franz, M.; Nowak, K.; Berner, U.; Heunisch, C.; Bandel, K.; Röhling, H.-G.; Wolfgramm, M.

    2014-11-01

    The deposition of the Stuttgart Formation ('Schilfsandstein'), commonly considered as a type-example of the Carnian Pluvial Event, was controlled by high frequent 4th order sequences that resulted in pre-, intra- and post-Schilfsandstein transgressions from Tethyan waters into the epicontinental Central European Basin (CEB). The pre-Schilfsandstein transgression flooded the CEB trough gates to the Southeast and resulted in a wide-spread inland sea that was characterised by increased biological productivity, predominantly oxic conditions and enabled the immigration of euryhaline marine fauna with plankton, ostracodes, fishes, bivalves and the gastropods Omphaloptychia suebica n. sp. and Settsassia stuttgartica n. sp. The rather short-term intra- and post-Schilfsandstein transgressions flooded the CEB from the Southwest and Southeast and established a shallow brackish inland sea that stretched up to North Germany. Both, the 4th and 3rd order sequences derived from the succession in the CEB correlate well with those derived from successions of Tethyan shelfs. Therefore pronounced circum-Tethyan eustatic cycles are evidenced and may have had considerable impact on prominent middle Carnian events: Reingraben turnover, Carnian Pluvial Event, Carnian Crisis and Mid Carnian Wet Intermezzo. The broad circum-Tethyan evidence of 106-year scale cycles suggests glacioeustatic sea-level changes even in the Triassic Greenhouse period.

  1. 3D structure and formation of hydrothermal vent complexes in the Møre Basin

    NASA Astrophysics Data System (ADS)

    Kjoberg, Sigurd; Schmiedel, Tobias; Planke, Sverre; Svensen, Henrik H.; Galland, Oliver; Jerram, Dougal A.

    2016-04-01

    The mid-Norwegian Møre margin is regarded as a type example of a volcanic rifted margin, with its formation usually related to the influence of the Icelandic plume activity. The area is characterized by the presence of voluminous basaltic complexes such as extrusive lava sequences, intrusive sills and dikes, and hydrothermal vent complexes within the Møre Basin. Emplacement of hydrothermal vent complexes is accommodated by deformation of the host rock. The edges of igneous intrusions mobilize fluids by heat transfer into the sedimentary host rock (aureoles). Fluid expansion may lead to formation of piercing structures due to upward fluid migration. Hydrothermal vent complexes induce bending of overlying strata, leading to the formation of dome structures at the paleo-surface. These dome structures are important as they indicate the accommodation created for the intrusions by deformation of the upper layers of the stratigraphy, and may form important structures in many volcanic margins. Both the morphological characteristics of the upper part and the underlying feeder-structure (conduit-zone) can be imaged and studied on 3D seismic data. Seismic data from the Tulipan prospect located in the western part of the Møre Basin have been used in this study. The investigation focusses on (1) the vent complex geometries, (2) the induced surface deformation patterns, (3) the relation to the intrusions (heat source), as well as (4) the emplacement depth of the hydrothermal vent complexes. We approach this by doing a detailed 3D seismic interpretation of the Tulipan seismic data cube. The complexes formed during the initial Eocene, and are believed to be a key factor behind the rapid warming event called the Paleocene-Eocene thermal maximum (PETM). The newly derived understanding of age, eruptive deposits, and formation of hydrothermal vent complexes in the Møre Basin enables us to contribute to the general understanding of the igneous plumbing system in volcanic basins and

  2. Simplified stratigraphic cross sections of the Eocene Green River Formation in the Piceance Basin, northwestern Colorado

    USGS Publications Warehouse

    Dietrich, John D.; Johnson, Ronald C.

    2013-01-01

    Thirteen stratigraphic cross sections of the Eocene Green River Formation in the Piceance Basin of northwestern Colorado are presented in this report. Originally published in a much larger and more detailed form by Self and others (2010), they are shown here in simplified, page-size versions that are easily accessed and used for presentation purposes. Modifications to the original versions include the elimination of the detailed lithologic columns and oil-yield histograms from Fischer assay data and the addition of ground-surface lines to give the depth of the various oil shale units shown on the cross section.

  3. Diagenesis and porosity evolution of tight sand reservoirs in Carboniferous Benxi Formation, Southeast Ordos Basin

    NASA Astrophysics Data System (ADS)

    Hu, Peng; Yu, Xinghe; Shan, Xin; Su, Dongxu; Wang, Jiao; Li, Yalong; Shi, Xin; Xu, Liqiang

    2016-04-01

    The Ordos Basin, situated in west-central China, is one of the oldest and most important fossil-fuel energy base, which contains large reserves of coal, oil and natural gas. The Upper Palaeozoic strata are widely distributed with rich gas-bearing and large natural gas resources, whose potential is tremendous. Recent years have witnessed a great tight gas exploration improvement of the Upper Paleozoic in Southeastern Ordos basin. The Carboniferous Benxi Formation, mainly buried more than 2,500m, is the key target strata for hydrocarbon exploration, which was deposited in a barrier island and tidal flat environment. The sandy bars and flats are the favorable sedimentary microfacies. With an integrated approach of thin-section petrophysics, constant velocity mercury injection test, scanning electron microscopy and X-ray diffractometry, diagenesis and porosity evolution of tight sand reservoirs of Benxi Formation were analyzed in detail. The result shows that the main lithology of sandstone in this area is dominated by moderately to well sorted quartz sandstone. The average porosity and permeability is 4.72% and 1.22mD. The reservoirs of Benxi Formation holds a variety of pore types and the pore throats, with obvious heterogeneity and poor connection. Based on the capillary pressure curve morphological characteristics and parameters, combined with thin section and phycical property data, the reservoir pore structure of Benxi Formation can be divided into 4 types, including mid pore mid throat type(I), mid pore fine throat type(II), small pore fine throat type(III) and micro pro micro throat type(Ⅳ). The reservoirs primarily fall in B-subsate of middle diagenesis and late diagenesis, which mainly undergo compaction, cmentation, dissolution and fracturing process. Employing the empirical formula of different sorting for unconsolideated sandstone porosity, the initial sandstone porosity is 38.32% on average. Quantitative evaluation of the increase and decrease of

  4. Basin and range-age reactivation of the ancestral Rocky Mountains in Texas Panhandle: evidence from Ogallala Formation

    SciTech Connect

    Budnik, R.T.

    1984-04-01

    The Ogallala Formation (Neogene) is a widespread syntectonic alluvial apron that was shed eastward from the Rio Grande rift and related uplifts in Colorado and New Mexico during Basin and Range extension. In the Texas Panhandle, the Ogallala completely buried Ancestral Rocky Mountain (Pennsylvanian) structures. Renewed movement on these older structures during the Neogene influenced the thickness and facies distribution of the Ogallala. The Ogallala thickens into the Palo Duro, Dalhart, and Anadarko basins. Major distributary channels on Ogallala alluvial fans coincide with the axes of these basins, whereas major interchannel areas overlie intervening uplifts. Second-order structures subtly influenced the unit as well. For example, the Carson basin, a Pennsylvanian rhomb graben along the Amarillo uplift, the Ogallala is over 250 m (820 ft) thick compared with 90 m (275 ft) in adjacent areas. Within the Palo Duro basin, local highs controlled the distribution of thin, interchannel flood-basin and lacustrine deposits. Thicker, braided-stream channel deposits follow local lows. Later movement on the Amarillo uplift broadly folded the Ogallala. The southern high plains surface subtly reflects basement structure, with topographic highs overlying basement highs, suggesting post-Ogallala deformation within the Palo Duro basin. The Amarillo uplift is approximately perpendicular to the Rio Grande rift and parallel to the direction of Basin and Range extension. Thus, the stress field that produced the rift may have caused strike-slip movement and reactivation of the Carson basin along the Amarillo uplift.

  5. Generation and expulsion of petroleum and gas from Almond Formation Coal, Greater Green River Basin, Wyoming

    SciTech Connect

    Garcia-Gonzalez, M.; Surdam, R.C.; Lee, M.L.

    1997-01-01

    Petrographic and geochemical studies of coal from the Almond Formation in the Greater Green River basin demonstrate that the coal contains important volumes of stored liquid petroleum, as well as methane. Modeling indicates that at the basin center, most of the oil generated in the coal has been thermally cracked to gas, whereas at the basin flank the oil-to-gas reaction has barely proceeded. Several new concepts are presented about the mechanism of petroleum generation in coal based on (1) natural maturation trends gleaned form examination of Almond coal samples from different burial depths and (2) similar maturation trends observed in hydrous pyrolysis experiments using immature Almond coal samples. These new concepts show that the oil in the coal was generated during the alteration of desmocollinite and liptinite macerals to exsudatinite (waxy oil) and inertinite solid residue; that the waxy oil was initially stored in porous structures and subsequently in vesicles as the coal matured under increasing temperature; that primary migration of the oil occurred as the generation of a sufficient volume of exsudatinite microfractured the vitrinite-semifusinite vesicles, interconnecting vesicles and pores; and that the thermal cracking of exsudatinite generated a sufficient volume of gas to fracture the vesiculated coal as pore pressure increased and allowed migration of hydrocarbons out of the coal.

  6. Synextensional basin evolution, lower Miocene Clews Formation, central Mojave Desert, California

    SciTech Connect

    Fillmore, R.P.; Walker, J.D. )

    1991-02-01

    The lower Miocene Clews Formation at Alvord Mountain, Mojave Desert, California, consists of up to 400 m of coarsening-upward continental deposits. During the initial stage of basin development, the depocenter was delineated by a lacustrine system that was bound to the west by alluvial fans and graded northward into a south-flowing fluvial braidplain. Lacustrine strata, composed of claystone, siltstone and carbonate, suggest an initially closed basin. Conglomerate and sandstone to the west represent small, sheetflood-dominated fans and contain igneous clasts and southeasterly paleoflow indicative of a proximal, relatively low relief source in the western Alvord Mountains. The second stage of deposition was dominated by coarse conglomerate and megabreccia with west-southwesterly paleotransport indicators and a distinctive metaigneous petrofacies that indicate a provenance in the Cronese Hills, 8 km to the east. These strata reflect rapid westward progradation of debris flow-dominated alluvial fans that advanced across the facia braidplain, eventually onlapping the smaller Alvord Mountain sourced fans across the basin. Influx of sediment from the paradise Range ceased. Based development resulted from regional northeast-southwest extensional deformation. The Alvord Mountain-Cronese Hills region was transported northeast as a single block on an east-dipping, low-angle normal fault associated with the Waterman Hills core complex 30 km to the west. Development of westward prograding fans is believed to record subsequence propagation of a northwest-trending, west-dipping normal fault associated with, but antithetic to the low-angle master fault.

  7. Chemical composition and geologic history of saline waters in Aux Vases and Cypress Formations, Illinois Basin

    USGS Publications Warehouse

    Demir, I.; Seyler, B.

    1999-01-01

    Seventy-six samples of formation waters were collected from oil wells producing from the Aux Vases or Cypress Formations in the Illinois Basin. Forty core samples of the reservoir rocks were also collected from the two formations. Analyses of the samples indicated that the total dissolved solids content (TDS) of the waters ranged from 43,300 to 151,400 mg/L, far exceeding the 35,400 mg/mL of TDS found in typical seawater. Cl-Br relations suggested that high salinities in the Aux Vases and Cypress formation waters resulted from the evaporation of original seawater and subsequent mixing of the evaporated seawater with concentrated halite solutions. Mixing with the halite solutions increased Na and Cl concentrations and diluted the concentration of other ions in the formation waters. The elemental concentrations were influenced further by diagenetic reactions with silicate and carbonate minerals. Diagenetic signatures revealed by fluid chemistry and rock mineralogy delineated the water-rock interactions that took place in the Aux Vases and Cypress sandstones. Dissolution of K-feldspar released K into the solution, leading to the formation of authigenic illite and mixed-layered illite/smectite. Some Mg was removed from the solution by the formation of authigenic chlorite and dolomite. Dolomitization, calcite recrystallization, and contribution from clay minerals raised Sr levels significantly in the formation waters. The trend of increasing TDS of the saline formation waters with depth can be explained with density stratification. But, it is difficult to explain the combination of the increasing TDS and increasing Ca/Na ratio with depth without invoking the controversial 'ion filtration' mechanism.

  8. The Stratigraphy of the Aquitanian-Burdigalian Asmari Formation of Lorestan Sub-Basin, Iran: an Inclusive Study

    NASA Astrophysics Data System (ADS)

    Lankarani, M.; Amini, A.; Swennen, R.

    2012-04-01

    The Asmari Formation is the most important hydrocarbon reservoir in the oilfields of the Zagros pro-foreland basin. The shallow carbonates of this formation have been producing oil for nearly one century. However, detailed stratigraphic aspects of this significant rock unit in some parts of the basin, especially Lorestan sub-basin, are poorly studied. So, because of the necessity, several outcrops of the Asmari Formation in this region were inclusively studied in the framework of this project. The Lorestan sub-basin is a narrow, northwest-southeast trending intrashelf depression in the Zagros basin which is created during the Mesozoic. By the end of Mesozoic, continental collision between Iran and Arabian plates resulted in the formation of the Zagros fold-thrust belt and its associated pro-foreland basin, in which the Asmari Formation was deposited. Detailed paleontological investigations done by this study (based on the distribution of the index fossils) showed that age range of the Asmari Formation in this region is Aquitanian-Burdigalian. The main grain associations forming the facies of the formation were found rhodoliths, large benthic foraminifera (rotaliids), green algae, bivalves (mostly oysters), bryozoans, and echinoderms. The biotic associations suggest that carbonate sedimentation took place in tropical waters under oligotrophic conditions. This Aquitanian-Burdigalian carbonate deposits, which were deposited on an oligotrophic tropical carbonate ramp developed in a foredeep tectonic setting, have unconformable boundaries with the overlying and underlying formations. Comprehensive sequence stratigraphic investigations proved that deposition of the Asmari Formation in the studied region has been generally coincident with a transgressive event during the time of global second order sea-level highstand. So, the whole Asmari rock unit in the Lorestan sub-basin comprises a supersequence formed as a result of the second-order eustatic sea-level changes

  9. Map showing structure contours on the top of the upper Jurassic Morrison Formation, Powder River basin, Wyoming and Montana

    USGS Publications Warehouse

    Crysdale, B.L.

    1991-01-01

    This map is one in a series of U.S. Geological Survey Miscellaneous Field Studies (MF) maps showing computer-generated structure contours, isopachs, and cross sections of selected formations in the Powder River basin, Wyoming and Montana. The map and cross sections were constructed from information stored in a U.S. Geological Survey Evolution of Sedimentary Basins data base. This data base contains picks of geologic formation and (or) unit tops and bases determined from electric resistivity and gamma-ray logs of 8,592 wells penetrating Tertiary and older rocks in the Powder River basin. Well completion cards (scout tickets) were reviewed and compared with copies of all logs, and formation or unit contacts determined by N. M. Denson, D.L. Macke, R. R. Schumann and others. This isopach map is based on information from 2,429 of these wells that penetrate the Minnelusa Formation and equivalents.

  10. Tectonics and sedimentation of Oligo-Miocene Vasquez Formation, Soledad basin, southern California

    SciTech Connect

    Hendrix, E.D.

    1987-05-01

    The nonmarine Oligo-Miocene Vasquez Formation represents the earliest sedimentation within the Soledad basin. Basin analysis of this unit provides important clues to the tectonic regimen during the convergent/transform-margin transition in southern California during the mid-Tertiary. The Vasquez crops out in three separate subbasins or depocenters; from south to north, these are the Vasquez Rocks, Texas Canyon, and Charlie Canyon subbasins. Basaltic-andesitic volcanism and rapid subsidence punctuated the initial rifting event which generated the Vasquez Rocks half-graben and Texas Canyon graben. Small, thick alluvial fans were shed into these two subbasins, with sediment derived via erosion of local plutonic, metamorphic, and volcanic source terranes. A minimum of four discrete uplift events generated development of 250 to 600-m thick, upward-fining alluvial megacycles in both the Vasquez Rocks and Texas Canyon depocenters. In the absence of biostratigraphic control, these allocyclic megasequences provide a tangible means of lithostratigraphic correlation between these separate subbasins. A major uplift and drainage basin reorganization event subsequently modified the Vasquez depositional system, facilitating physical interconnection of the two southern subbasins. The northernmost subbasin, Charlie Canyon, is characterized by a single, thick, upward-coarsening alluvial fan sequence. There are no megacycles or clast suites to suggest interconnection with or evolutionary similarities to the other two depocenters. This sedimentologic uniqueness may support a mid-Tertiary palinspastic reconstruction which places the Charlie Canyon region 80-100 km northwest of its current location. Soledad basin rifting and Vasquez sedimentation are consistent with a tectonic model involving lithospheric extension north of the unstable Mendocino triple junction.

  11. Nahcolite Resources in the Green River Formation, Piceance Basin, Northwestern Colorado

    USGS Publications Warehouse

    Brownfield, Michael E.; Johnson, Ronald C.; Self, Jesse G.; Mercier, Tracey J.

    2009-01-01

    The U.S. Geological Survey (USGS) recently completed an assessment of in-place nahcolite (NaHCO3) resources in the Piceance Basin, northwestern Colorado. Nahcolite is present in the oil shale deposits of the Parachute Creek Member of the Eocene Green River Formation. It occurs as disseminated aggregates, nodules, bedded units of disseminated brown crystals, and white crystalline beds associated with dawsonite (NaAl(OH)2CO3) and halite (NaCl). The nahcolite-bearing facies are divided into an unleached part containing the nahcolite and halite, which is estimated to be as much as 1,130 ft thick, and an upper leached part several hundred feet thick containing minor nahcolite aggregates and nodules. Locally, thick beds of halite and brown fine-grained nahcolite lie in the depocenter of the basin, but thin laterally away from the basin center and grade into beds of white, coarse-grained nahcolite. In the central part of the study area, the top of the nahcolite-bearing rocks range in depth from about 1,300 to 2,000 ft. Dissolution of water-soluble minerals, mostly nahcolite and halite, in the upper part of the nahcolite-bearing facies has created a collapsed leached zone as much as 580 ft thick that consists of laterally continuous units of solution breccia and fractured oil shale containing solution cavities. The top of the leached zone is not yet defined in the basin, but it probably extends into the A groove in the upper part of the Parachute Creek Member.

  12. Sedimentary facies and sequence stratigraphy of the Asmari Formation at Chaman-Bolbol, Zagros Basin, Iran

    NASA Astrophysics Data System (ADS)

    Amirshahkarami, Mahnaz; Vaziri-Moghaddam, Hossein; Taheri, Azizolah

    2007-03-01

    The Oligocene-Miocene Asmari Formation of the Zagros Basin is a thick sequence of shallow water carbonate. In the study area, it is subdivided into 14 microfacies that are distinguished on the basis of their depositional textures, petrographic analysis and fauna. Based on the paleoecology and lithology, four distinct depositional settings can be recognized: tidal flat, lagoon, barrier, and open marine. The Asmari Formation represents sedimentation on a carbonate ramp. In the inner ramp, the most abundant lithofacies are medium grained wackestone-packstone with imperforated foraminifera. The middle ramp is represented by packstone-grainstone to floatstone with a diverse assemblage of larger foraminifera with perforate wall, red algae, bryozoa, and echinoids. The outer ramp is dominated by argillaceous wackestone characterized by planktonic foraminifera and large and flat nummulitidae and lepidocyclinidae. Three third-order depositional sequences are recognized from deepening and shallowing trends in the depositional facies, changes in cycle stacking patterns, and sequence boundary features.

  13. Studies of the Permian Phosphoria Formation and related rocks, Great Basin-Rocky Mountain region

    USGS Publications Warehouse

    Wardlaw, Bruce R.

    1979-01-01

    PART A: The transgression of the Permian Retort Phosphatic Shale Member of the Phosphoria Formation is dated by the occurrence of diagnostic brachiopods. The complex pattern of this transgression reflects the paleogeography and indicates two initial basins of deposition: one in southwestern Montana and one in southeastern Idaho. PART B: A new formation is proposed for middle Permian rocks of a transitional facies positioned laterally between the Rex Chert Member of the Phosphoria Formation in northeastern Utah and southeastern Idaho and the Plympton Formation in northeastern Nevada and northwestern Utah. PART C: The relationships of the Permian Park City Group to the Phosphoria and Park City Formations are clarified by the stratigraphy of four sections in northwestern Utah, northeastern Nevada, and southern Idaho. PART D: Five biostratigraphic zones based on the distribution of brachiopods and conodonts are proposed for the Park City Group. They are: the Peniculauris ivesi-Neostreptognathodus prayi Zone, the Peniculauris bassi-Neostreptognathodus sulcoplicatus Zone, the Peniculauris bassi-Neostreptognathodus sp. C Zone, the Thamnosia depressa Zone, and the Yakovlevia. multistriata-Neogondolella bitteri Zone. They range in age from Leonardian to Wordian.

  14. Geology and geochemistry of the La Luna Formation type sections in the Maracaibo basin, Venezuela

    SciTech Connect

    Baptista, N.; Scherer, W.

    1996-08-01

    The Upper Cretaceous La Luna Formation is the most important source rock of hydrocarbons in Western Venezuela. Curiously enough it has two type sections, the formation was first defined in 1926 in Perija on the western flank of the Maracaibo basin; 30 years later the La Aguada, Chejende and Timbetes members were defined 260 km toward the east, on the shelf of the basin. The purpose of this study is to compare these sections and to define the vertical and horizontal variability of geological and geochemical characteristics that might have influenced the generation of hydrocarbons. The study consisted of detailed, bed level sampling, macroscopic sedimentary descriptions, petrography of 168 thin sections with 40 variables recorded in a statistical data matrix for determination of lithomicrofacies, as well as geochemical analysis of total organic carbon (TOC), visual kerogen, Rock-Eval pyrolysis and gas chromatography. The western type section is characterized by alternating thinly laminated and massive bedded limestones. Thermally immature, amorphous organic matter of marine origin is abundant in this section; TOC values range from 0.23% to 8.56%, generally increasing toward the top. Hydrogen index values range from 327 to 1078, indicating good to excellent oil generating potential. The eastern type sections have a higher level of thermal maturity; they show increasing amounts of clastic material, less authigenic minerals and abundant Favreina sp crab fecal pellets. The mainly terrestrially derived organic matter concentrations are considerably less, ranging from 0.07 to 3.39, again increasing toward the top of the section.

  15. Gold-bearing reefs of the Witwatersrand Basin: A model of synsedimentation hydrothermal formation

    NASA Astrophysics Data System (ADS)

    Safonov, Yu. G.; Prokof'ev, V. Yu.

    2006-12-01

    The current concepts concerning the genesis of the unique ore-bearing reefs of the Witwatersrand Basin and its gold resource potential are considered. The results of microscopic examination of ore from the Black, Ventersdorp Contact, Carbon Leader, and Vaal reefs, as well as of thermobarometric study of quartz, are presented. A model of synsedimentation hydrothermal origin of the reefs in the process of evolution of primary colloidal-disperse systems is substantiated on the basis of these results and the data published by other authors. The formation of these systems is related to the periodic gain of deep ore-bearing gas-saturated fluids. The gold mineralization was formed under conditions of partially closed systems, where various mineral-forming processes developed (metasomatism, crystallization of true solutions and gels, gel metasomatism, dispersion of crystalline phases, segregation of mineral particles, formation of early minerals, etc.). New data on REE specialization of ore-bearing fluids are discussed. The specific features of the gold, carbonic, and uranium mineralization of the intracratonic basin are emphasized.

  16. Frontier formation stratigraphy on the Moxa Arch, Green River Basin, Wyoming

    SciTech Connect

    Hamlin, H.S.

    1996-04-01

    Frontier Formation terrigenous clastics record early Late Cretaceous shoreline progradation and cyclic marine and nonmarine sedimentation in a foreland basin. In this study well-log correlations and studies of core were used to establish the stratigraphic framework of the Frontier along the Moxa Arch, a north-trending intrabasin structure in the western Green River Basin. Regional marine flooding surfaces and surfaces of erosion were traced along the Moxa Arch, which is subparallel to Frontier depositional strike, and from the north end of the Moxa Arch eastward to the Rock Springs Uplift. Nonmarine facies composed of fluvial channel-fill sandstone and interchannel mudstone form lowstand depositional systems tracts overlying subaerial erosion surfaces, whereas marine shoreface sandstones in progradational parasequence sets form highstand depositional systems tracts. Lowstand system tracts are separated from overlying highstand systems tracts by maximum flooding surfaces. Transgressive systems tracts composted of retrogradational parasequence sets are generally thin or missing. By tracing systems tracts from the Moxa Arch westward to outcrops in the Thrust Belt, correlations were made between subsurface and outcrop members of the Frontier Formation. Outcrop chronostratigraphy was then used to compare local sequence development to a global sea-level record. On the Moxa Arch, variations in both depositional thickness and erosional truncation along strike indicate that tectonically controlled subsidence and sediment input were important controls on sequence development and masked the influence of most reported third-order eustatic sea-level fluctuations. More accurate reservoir characterization and attribute prediction are possible within this stratigraphic framework.

  17. Sedimentology and genetic stratigraphy of Dean and Spraberry Formations (Permian), Midland basin, Texas

    SciTech Connect

    Handford, C.R.

    1981-09-01

    The Spraberry trend of west Texas, once known as the world's largest uneconomic oil field, will undoubtedly become an increasingly important objective for the development of enhanced oil recovery techniques in fine-grained, low-permeability, low-pressure reservoirs. As the trend expands, facies and stratigraphic data should be integrated into exploration strategies. The Spraberry and Dean Formations may be divided into three genetic sequences, each consisting of several hundred feet of interbedded shale and carbonate overlain by a roughly equal amount of sandstone and siltstone. These sequences record episodes of shelf-margin progradation, deep-water resedimentation of shelf-derived carbonate debris, followed by influxes of terrigenous clastics into the basin by way of feeder channels or submarine canyons, and suspension settling of fine-grained sediment from the water column. Four lithofacies comprise the terrigenous clastics of the Spraberry and Dean Fomations: (1) cross-laminated, massive, and parallel-laminated sandstone, (2) laminated siltstone, (3) bioturbated siltstone, and (4) black, organic-rich shale. Carbonate lithofacies occur mostly in the form of thin-bedded turbidites, slump, and debris-flow deposits. Terrigenous clastic rocks display facies sequences, isopach patterns, and sedimentary structures suggestive of deposition from turbidity currents, and long-lived saline density underflow and interflow currents. Clastic isopach patterns reflect an overall southward thinning of clastics in the Midland basin. Channelized flow and suspension settling were responsible for the formation of elongate fan-shaped accumulations of clastic sediments.

  18. Concentration and mineralogical residence of elements in rich oil shales of the Green River Formation, Piceance Creek basin, Colorado, and the Uinta Basin, Utah - A preliminary report

    USGS Publications Warehouse

    Desborough, G.A.; Pitman, J.K.; Huffman, C.

    1976-01-01

    Ten samples from drillcore of two rich oil-shale beds from the Parachute Creek Member of the Eocene Green River Formation, Piceance Creek basin, Colorado, and Uinta Basin, Utah, were analyzed for 37 major, minor, and trace elements. For 23 of these elements, principal mineralogical residence is established or suggested and such studies may provide data which are useful for predicting the kinds and amounts of elements and compounds that might be released into the environment by oil-shale mining operations. ?? 1976.

  19. Asynchronous timing of extension and basin formation in the South Rhodope core complex, SW Bulgaria, and northern Greece

    NASA Astrophysics Data System (ADS)

    Stübner, Konstanze; Drost, Kerstin; Schoenberg, Ronny; Böhme, Madelaine; Starke, Jessica; Ehlers, Todd A.

    2016-01-01

    Upper crustal extensional structures range from steep normal faults to shallow-dipping detachments. The relationship between extension and formation of synkinematic hanging wall basins including their relative timing is not well understood. The South Rhodope core complex, Southern Balkans, has experienced extension for >40 Ma leading to a number of extensional structures and Cenozoic sedimentary basins. We present new bedrock and basin detrital zircon and apatite (U-Th-Sm)/He ages from the Pirin and Rila Mountains and the Sandanski basin. Results identify three episodes of Cenozoic extension in SW Bulgaria accommodated by (1) the Eocene/Oligocene Mesta detachment; (2) the early to middle Miocene Gorno Spanchevo fault (circa 18-15 Ma), which is the northern prolongation of the Strymon low-angle detachment; and (3) the late Miocene West Pirin fault (≤10 Ma). Detachment faulting on the Strymon fault accommodated tens of kilometers of ENE-WSW extension and created ~1500 m topographic relief, but because the resulting hillslopes were gentle (≤10°), extension did not lead to enhanced footwall erosion or formation of a hanging wall basin. In contrast, the West Pirin normal fault resulted in mostly vertical motion of its footwall causing steep topography, rapid erosion, and formation of the synrift Sandanski basin. Digital topographic analysis of river channel profiles identifies the latest episodes of deformation including westward tilting of the Sandanski and Strymon basins and Quaternary N-S extension. This study demonstrates that basin formation in the South Rhodope core complex is related to normal faulting postdating the main episode of crustal stretching by detachment faulting.

  20. Fluvial sedimentology and basin analyses of the Permian Fairchild and Buckley formations, Beardmore Glacier region, and the Weller Coal Measures, southern Victoria Land, Antarctica

    SciTech Connect

    Isbell, J.L.

    1990-01-01

    The Beardmore Glacier region contains a 1-km-thick Permian fluvial sequence that was deposited in an elongate basin along the margin of the East Antarctica craton. Fluvial architecture, sandstone composition and paleocurrents within the basin record a change from an early Permian cratonic to a late Permian foreland basin. The Lower Permian Fairchild Formation consists entirely of overlapping channel-form sandstone bodies deposited by braided streams. Arkosic sandstone was deposited by SE flowing streams. Fairchild strata record slow subsidence within a broad cratonic basin. The Lower to Upper Permian Buckley Formation consists of an arkosic lower member and a volcaniclastic upper member. Paleocurrents which consist of transverse and longitudinal paleocurrents, suggest a cratonward migration of the basin axis through time. The Buckley Formation was deposited within a braided stream setting and is an important unit because it contains interstratified channel-sandstone sheets, shale and coal, along with evidence of channel-belt avulsions. Sandstone sheets predominate at the base of the formation, while flood-plain deposits thicken and increase in abundance upward. The interaction between fluvial processes and subsidence rates produced this alluvial stratigraphy. The Lower Permian Weller Coal Measures in southern Victoria Land were deposited within a narrow basin located cratonward of the foreland basin. Basin geometry and depositional patterns are similar to those of fault-bounded basins. Although basin formation is not constrained, deposition of the Weller was contemporaneous with the development of the foreland basin. This suggests a relationship between subsidence within the two basins.

  1. Sedimentology, petrography and diagenesis of Eocene Oligocene evaporites: the Tuzhisar Formation, SW Sivas Basin, Turkey

    NASA Astrophysics Data System (ADS)

    Gündogan, Ibrahim; Önal, Mehmet; Depçi, Tolga

    2005-08-01

    The study area is situated in the southwestern part of the Sivas Basin. Sediments of the Ortaköy Formation (Middle-Upper Eocene) of flysch facies were deposited in a shallow marine environment and consist of interstratified sandstone, shale and calcareous mudstone. The Karaziyaret basaltic dikes cut the Ortaköy Formation. The Ortaköy Formation is comformably overlain by the evaporite-dominated Tuzhisar Formation. Gradual transitions between these two stratigraphic units crop out between Yeniköy and Yenituzhisar villages. The Tuzhisar Formation is composed mainly of secondary gypsum, which originated from the hydration of precursor anhydrite rock. The formation has been subdivided into three members: Yeniköy, Küllü and Selimiye members. Yeniköy (lower evaporite unit) and Küllü (upper evaporite unit) members contain gypsum sequences up to 70 m thick. The Selimiye member (Lower-Middle Oligocene), which consists mainly of red clastic units interrupt and gradationally overlies (laterally and vertically) these two members. In the gypsum of the Yeniköy Member nodular, nodular-banded, laminated-banded lithofacies with enterolithic and chicken-wire structures are distinguished. These associations indicate a sabkha or shallow-water setting of deposition such as a lagoon. Secondary gypsum in the Tuzhisar Formation generally displays alabastrine and porphyroblastic textures with corroded anhydrite relics. Associated minerals are dolomite, calcite, celestite, and lutecite. The Küllü Member is composed of irregular thick-bedded, massive, locally brecciated secondary gypsum, probably formed by multiple synsedimentary collapse after the dissolution of pre-existing soluble minerals and/or by paleoslumping related to synsedimentary tectonism. However, most of the evidence for the origin of the breccia has been destroyed by intense karstification.

  2. Lacustrine and fluvial-deltaic depositional systems, Fort Union Formation (Paleocene), Powder River basin, Wyoming and Montana

    SciTech Connect

    Ayers, W.B. Jr.

    1986-11-01

    The Powder River basin is a Laramide foreland basin that was filled by a combination of fluvial, deltaic, paludal, and lacustrine sediments. The depositional history of the Fort Union Formation was unraveled in a regional subsurface study using data from approximately 1400 geophysical well logs. The depositional model developed from the subsurface study was tested by selective fieldwork. The Powder River basin originated as a structural and depositional basin in earliest middle Paleocene. As a result of rapid subsidence, a lake (Lake Lebo) formed along the basin axis. Lake Lebo, documented in the mudstone of the Lebo Shale Member, spread rapidly to cover an area greater than 10,000 mi/sup 2/ (25,900 km/sup 2/). During the middle through late Paleocene, Lake Lebo was filled peripherally by fluvial-deltaic systems that are recorded in the coarser clastics of the Tongue River Member. Primary basin fill was from: (1) the eastern margin by elongate deltas fed by suspended to mixed-load fluvial systems issuing from the ancestral Black Hills, and (2) the southwestern margin by mixed to bed-load streams emanating from the Wind River basin. Secondary fill was from the northwest by an elongate delta system fed by a suspended to mixed-load fluvial system flowing from the Bull Mountain basin. 17 figures.

  3. Implications for the formation of the Hollywood Basin from gravity interpretations of the northern Los Angeles Basin, California

    USGS Publications Warehouse

    Hildenbrand, Thomas G.; Davidson, Jeffrey G.; Ponti, Daniel J.; Langenheim, V.E.

    2001-01-01

    Gravity data provide insights on the complex tectonic history and structural development of the northern Los Angeles Basin region. The Hollywood basin appears to be a long (> 12 km), narrow (up to 2 km wide) trough lying between the Santa Monica Mountains and the Wilshire arch. In the deepest parts of the Hollywood basin, the modeled average thickness ranges from roughly 250 m if filled with only Quaternary sediments to approximately 600 m if Pliocene sediments are also present. Interpretations of conflicting drill hole data force us to consider both these scenarios. Because of the marked density contrast between the dense Santa Monica Mountains and the low-density sediments in the Los Angeles Basin, the gravity method is particularly useful in mapping the maximum displacement along the Santa Monica-Hollywood-Raymond fault zone. The gravity-defined Santa Monica–Hollywood fault zone deviates, in places, from the mapped active fault and fold scarps located with boreholes and trenching and by geomorphological mapping by Dolan and others (1997). Our models suggest that the Santa Monica–Hollywood fault zone dips northward approximately 63°. Three structural models are considered for the origin of the Hollywood basin: pull-apart basin, flexural basin, and a basin related to a back limb of a major fold. Although our preferred structural model involves flexure, the available geologic and geophysical data do not preclude contributions to the deepening of the basin from one or both of the other two models. Of particular interest is that the distribution of red-tagged buildings and structures damaged by the Northridge earthquake has a strong spatial correlation with the axis of the Hollywood basin defined by the gravity data. Several explanations for this correlation are explored, but two preferred geologic factors for the amplification of ground motion besides local site effects are (1) focussing of energy by a fault along the axis of the Hollywood basin and (2

  4. Paleomagnetic Results From Triassic Rock Formations of Junggar Basin, NW China

    NASA Astrophysics Data System (ADS)

    Zhao, X.; Li, J.; Guo, R.; Zhang, W.; Yuan, W.

    2015-12-01

    Our knowledge of the kinematics and duration of collisional events between the Chinese blocks and Siberia is still inadequate. Likewise, the accretionary history of the Central Asian fold belt itself is contentious. The primary goal for this study was to address key questions about the geographic positions of the Junggar Basin in Paleozoic and Mesozoic times and its tectonic relationship with other major Asian blocks by generating high-quality paleomagnetically inferred paleolatitudes and basin histories. Another objective is to see what it can tell us about intraplate motions within central Asia and to recognize vertical-axis tectonic rotations in the region. We collected 348 samples from 42 sites in Paleozoic and Mesozoic stratigraphic sections of east Junggar Basin. Useful results were obtained by progressive demagnetization for sandstone samples of Xiaoquan Formation dated paleontologically as mid to late Triassic. The ChRM direction for the Xiaoquan Formation is directed easterly with intermediate to steep downward inclination in geographic coordinates. After tectonic correction, the mean direction of the ChRM becomes northeasterly with intermediate to shallow inclination, which corresponds to a mean paleolatitude of 20.7° within a 95% confidence band of ± 12 degrees. It is obvious from the data that Junggar and other major parts of eastern Asia did not occupy the same relative positions in terms of paleolatitudes in Late Triassic. Paleomagnetic declinations indicate clockwise vertical-axis rotations of R = 98.3° +/- 16° for the Late Triassic rock unit relative to North China Block (NCB), and 12.4° +/- 16.2° relative to South China Block (SCB). The paleomagnetically inferred latitudinal displacements between Junggar and SCB are general statistically insignificant, as well as the rotational data. These data suggest that Junggar Basin may have been very close to SCB during the Triassic time. A plausible cause of the rotation is the westward rotational

  5. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.

    PubMed

    Liu, Ziliang; Shen, Fang; Zhu, Xiaomin; Li, Fengjie; Tan, Mengqi

    2015-01-01

    A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km). The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front" character. PMID

  6. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China

    PubMed Central

    Liu, Ziliang; Shen, Fang; Zhu, Xiaomin; Li, Fengjie; Tan, Mengqi

    2015-01-01

    A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km). The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a “small plain, big front” character. PMID

  7. Formation Conditions and Sedimentary Characteristics of a Triassic Shallow Water Braided Delta in the Yanchang Formation, Southwest Ordos Basin, China.

    PubMed

    Liu, Ziliang; Shen, Fang; Zhu, Xiaomin; Li, Fengjie; Tan, Mengqi

    2015-01-01

    A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km). The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front" character.

  8. Interfacial film formation: influence on oil spreading rates in lab basin tests and dispersant effectiveness testing in a wave tank.

    PubMed

    King, Thomas L; Clyburne, Jason A C; Lee, Kenneth; Robinson, Brian J

    2013-06-15

    Test facilities such as lab basins and wave tanks are essential when evaluating the use of chemical dispersants to treat oil spills at sea. However, these test facilities have boundaries (walls) that provide an ideal environment for surface (interfacial) film formation on seawater. Surface films may form from surfactants naturally present in crude oil as well as dispersant drift/overspray when applied to an oil spill. The objective of this study was to examine the impact of surface film formation on oil spreading rates in a small scale lab basin and on dispersant effectiveness conducted in a large scale wave tank. The process of crude oil spreading on the surface of the basin seawater was influenced in the presence of a surface film as shown using a 1st order kinetic model. In addition, interfacial film formation can greatly influence chemically dispersed crude oil in a large scale dynamic wave tank. PMID:23623652

  9. Catagenesis of organic matter of oil source rocks in Upper Paleozoic coal formation of the Bohai Gulf basin (eastern China)

    SciTech Connect

    Li, R.X.; Li, Y.Z.; Gao, Y.W.

    2007-05-15

    The Bohai Gulf basin is the largest petroliferous basin in China. Its Carboniferous-Permian deposits are thick (on the average, ca. 600 m) and occur as deeply as 5000 m. Coal and carbonaceous shale of the Carboniferous Taiyuan Formation formed in inshore plain swamps. Their main hydrocarbon-generating macerals are fluorescent vitrinite, exinite, alginite, etc. Coal and carbonaceous shale of the Permian Shanxi Formation were deposited in delta-alluvial plain. Their main hydrocarbon-generating macerals are vitrinite, exinite, etc. The carbonaceous rocks of these formations are characterized by a high thermal maturity, with the vitrinite reflectance R{sub 0} > 2.0%. The Bohai Gulf basin has been poorly explored so far, but it is highly promising for natural gas.

  10. Improved recovery using horizontal drilling in the Dundee Formation Michigan Basin

    SciTech Connect

    Harrison, W.B. III; Wood, J.R.; Huntoon, J.E.; Pennington, W.; Tester, C.; Taylor, E.

    1996-12-31

    The goal of this project is to demonstrate that oil production from selected fields in the Dundee Formation (Dev.) of Michigan can be substantially increased, perhaps restored to near--original production levels in some fields in Michigan, by utilizing horizontal drain wells. Devonian rocks have been the most prolific hydrocarbon producers of any system in the Michigan Basin. The Traverse, Dundee, and Lucas Formations have produced nearly all of the 525 Mbbls of oil and 150 Bcf of gas since the late 1920`s, 50% of the state`s oil and 7% of the state`s natural gas production. The Dundee Formation is Michigan`s all-time leader with 352 million barrels of oil and 42 billion cubic feet of gas. Crystal Field in Montcalm County, MI, selected as a field trial for this project is such a field. Analysis of production data for Crystal Field suggests that an additional 200,000 bbls of oil can be produced using 1 strategically located horizontal well. Total addition production from the Crystal Field could be as much as 6-8 Mbbls. Spin-offs from the technology developed in this project to other fields has the potential to increase Dundee production in Michigan by 35%, adding 80-100 Mbbls to the cumulative production. The approach combines proven, cost-effective horizontal drilling technology with modern reservoir characterization and management. A total of 30 Dundee fields will be characterized including the Crystal Field. Well logs, other well data, drilling, and production data and rock samples from the Dundee Fm. will be obtained, assembled, and input into digital databases designed for this project. Computer models describing the diagenetic, stratigraphic and thermal evolution of the Michigan Basin will be developed and applied to the Crystal Field reservoir. A post-mortem study is scheduled to monitor the effect of the horizontal well on Crystal Field production.

  11. Shelf-to-basin iron shuttling enhances vivianite formation in deep Baltic Sea sediments

    NASA Astrophysics Data System (ADS)

    Reed, Daniel C.; Gustafsson, Bo G.; Slomp, Caroline P.

    2016-01-01

    Coastal hypoxia is a growing and persistent problem largely attributable to enhanced terrestrial nutrient (i.e., nitrogen and phosphorus) loading. Recent studies suggest phosphorus removal through burial of iron (II) phosphates, putatively vivianite, plays an important role in nutrient cycling in the Baltic Sea - the world's largest anthropogenic dead zone - yet the dynamics of iron (II) phosphate formation are poorly constrained. To address this, a reactive-transport model was used to reconstruct the diagenetic and depositional history of sediments in the Fårö basin, a deep anoxic and sulphidic region of the Baltic Sea where iron (II) phosphates have been observed. Simulations demonstrate that transport of iron from shelf sediments to deep basins enhances vivianite formation while sulphide concentrations are low, but that pyrite forms preferentially over vivianite when sulphate reduction intensifies due to elevated organic loading. Episodic reoxygenation events, associated with major inflows of oxic waters, encourage the retention of iron oxyhydroxides and iron-bound phosphorus in sediments, increasing vivianite precipitation as a result. Results suggest that artificial reoxygenation of the Baltic Sea bottom waters could sequester up to 3% of the annual external phosphorus loads as iron (II) phosphates, but this is negligible when compared to potential internal phosphorus loads due to dissolution of iron oxyhydroxides when low oxygen conditions prevail. Thus, enhancing vivianite formation through artificial reoxygenation of deep waters is not a viable engineering solution to eutrophication in the Baltic Sea. Finally, simulations suggest that regions with limited sulphate reduction and hypoxic intervals, such as eutrophic estuaries, could act as important phosphorus sinks by sequestering vivianite. This could potentially alleviate eutrophication in shelf and slope environments.

  12. Ordovician carbonate formation waters in the Illinois Basin: Chemical and isotopic evolution beneath a regional aquitard

    SciTech Connect

    Stueber, A.M. ); Walter, L.M. . Dept. of Geological Sciences)

    1992-01-01

    Formation waters from carbonate reservoirs in the upper Ordovician Galena Group of the Illinois Basin have been analyzed geochemically to study origin of salinity, chemical and isotopic evolution, and relation to paleohydrologic flow systems. These carbonate reservoirs underlie the Maquoketa Shale Group of Cincinnatian age, which forms a regional aquitard. Cl-Br relations and Na/Br-Cl/Br systematics indicate that initial brine salinity resulted from subaerial evaporation of seawater to a point not significantly beyond halite saturation. Subsequent dilution in the subsurface by meteoric waters is supported by delta D-delta O-18 covariance. Systematic relations between Sr-87/Sr-86 and 1/Sr suggest two distinct mixing events: introduction of a Sr-87 enriched fluid from a siliciclastic source, and a later event which only affected reservoir waters from the western shelf of the basin. The second mixing event is supported by covariance between Sr-87/Sr-86 and concentrations of cations and anions; covariance between Sr and O-D isotopes suggests that the event is related to meteoric water influx. Systematic geochemical relations in ordovician Galena Group formation waters have been preserved by the overlying Maquoketa shale aquitard. Comparison with results from previous studies indicates that waters from Silurian-Devonian carbonate strata evolved in a manner similar to yet distinct from that of the Ordovician carbonate waters, whereas waters from Mississippian-Pennsylvanian strata that overlie the New Albany Shale Group regional aquitard are marked by fundamentally different Cl-Br-Na and Sr isotope systematics. Evolution of these geochemical formation-water regimes apparently has been influenced significantly by paleohydrologic flow systems.

  13. Fluvioglacial Formation Scenario for Valleys and Ridges at the Deuteronilus Contact of the Isidis Basin, Mars

    NASA Astrophysics Data System (ADS)

    Erkeling, G.; Reiss, D.; Hiesinger, H.; Ivanov, M. A.; Bernhardt, H.

    2012-09-01

    Numerous small valleys are incised into the plains of the southern Isidis basin rim between 82˚/90˚E and 3˚/6˚N and trend tens of kilometers to the north following the topographic gradient toward the center of the basin. The valleys originate exclusively north of the mountainous terrain of the Libya Montes (Fig. 1A, red unit) [e.g.,1-4] and are indicative of Late Hesperian fluvial activity [1,4,6], which was spatially and temporarily distinct from intense and repeated Noachian fluvial activity in the Libya Montes [1-4,6]. Most of the valleys terminate on the smooth Isidis exterior plains (hereafter IEP; Fig. 1A, green unit). A few of them continue across the boundary between the IEP and the knobby Isidis interior plains (hereafter IIP; Fig. 1A, blue unit) and occur then as sinuous ridges in the IIP. This boundary has been discussed as a part of the Deuteronilus contact [e.g.,7,8] and is characterised by an onlap of the IIP onto the IEP, i.e., the IIP are superposed on the IEP. Therefore, the ridges occur stratigraphically higher than the valleys. Because the valleys transition to ridges into less-eroded terrain, their formation is difficult to explain by relief inversion scenarios proposed for sinuous ridges common on Mars [e.g.,9-11] and Earth [e.g.,12,13]. Based on our investigations we propose an alternative fluvioglacial formation scenario for the morphologic-geologic setting at the Deuteronilus contact. We suggest that the ridges could be glacial meltwater or subglacial streams (eskers) similar to possible eskers identified elsewhere on Mars and Earth [e.g.,14-17] and that their formation is associated with a stationary ice sheet of a proposed Late Hesperian Isidis sea that readily froze and sublimed and resulted in the formation of the IIP [4,6]. The proposed formation scenario has also implications for the formation of the Isidis thumbprint terrain (hereafter TPT) [e.g.,5,6] that is located in the IIP.

  14. High resolution sequence stratigraphic analysis of the Late Miocene Abu Madi Formation, Northern Nile Delta Basin

    NASA Astrophysics Data System (ADS)

    Sarhan, Mohammad Abdelfattah

    2015-12-01

    Abu Madi Formation represents the Upper Miocene Messinian age in the Nile Delta basin. It consists mainly of sandstones and shale intercalations and because of its richness in hydrocarbon, it has been subdivided by the petroleum companies into Level-I, Level-II and Level-III, respectively according to the increase in the sandstone to the shale ratio. The Miocene cycle in the northern subsurface section of the Nile Delta encompasses three main formations namely from the base; Sidi Salim formation, Qawasim Formation and Abu Madi Formation at the top. The high resolution sequence stratigraphic analysis, using gamma ray responses, has been done for the Late Miocene formation in the northern part of the Nile delta subsurface section. For this purpose, the gamma-ray logs of ten deep wells, arranged in four cross-sections trending in almost north-south direction throughout the northern region of the Nile Delta, were analyzed. The analysis has revealed that the interpreted 4th order depositional cycles within Abu Madi Formation display great variations in both number and gamma ray responses in each investigated well, and cannot be traced laterally, even in the nearest well. These variations in the interpreted 4th order depositional sequences could be attributed to the presence of normal faults buried in the inter-area laying between the investigated wells. This finding matches with the conclusion of that Abu Madi Formation represents a part of the Upper Miocene Nile Delta syn-rift megasequence, developed during the Upper Miocene rift phase of the Red Sea - Gulf of Suez province in Egypt. Accordingly, in the sequence stratigraphic approach, the depositional history of Abu Madi Formation was strongly overprinted by the tectonic controls rather than the relative sea-level changes which are assumed to be of a secondary influence. Regarding the hydrocarbon aspects of the Abu Madi Formation, the present work recommends to direct the drilling efforts into the stratigraphic traps

  15. Reconstruction of groundwater formation in the Baltic Artesian basin through water stable isotopes

    NASA Astrophysics Data System (ADS)

    Babre, A.; Delina, A.; Retike, I.

    2012-04-01

    Subsurface hydrology of the Baltic Artesian basin has changed rapidly during the Quaternary period. Glacial and several interglacial phases as well as the change in the sea level led to complicated subsurface hydrology and a large difference in groundwater chemical as much as isotopic content. Baltic artesian basin fully covers territory of Latvia, Lithuania and Estonia; also parts of Poland, Russia, and Belarus are included. This work aims to give better overview of the complexity of the groundwater recharge and discharge dynamics beyond country borders, taking into account only shared geological framework, common climate conditions and development during the Quaternary period. To maintain better understanding of the processes that took part in the formation of groundwater that can be observed nowadays several methods were applied placing major emphasis on the new oxygen and hydrogen stable isotope ratio results. Additionally large scale modeling as well as hydrochemistry and trace element concentrations was used. Paleowaters usually are isotopically lighter, that facilitate to detect their presence. Earlier investigations in the northern part of the basin indicated glacial melt water intrusion in the Cambrian-Vendian aquifer corrected radiocarbon age suggests that this meltwater intrusion took place during the late Weichelian. Several radiocarbon and stable isotope studies in groundwater have been done at the southern part of the basin as well reporting extensive groundwater recharge during the Late Pleistocene in the Devonian aquifers; authors suggest that recharge took place under different recharge mechanisms compared with the northern part. So far no similar studies were accomplished in the central part of the basin, thus to make clearer picture and possibility to find the mixing line between groundwater bodies of different origin, the new groundwater samples were collected from more than 200 wells mainly in the territory of Latvia. New stable isotope samples

  16. In-place oil shale resources of the Mahogany zone sorted by grade, overburden thickness and stripping ratio, Green River Formation, Piceance Basin, Colorado and Uinta Basin, Utah

    USGS Publications Warehouse

    Birdwell, Justin E.; Mercier, Tracey J.; Johnson, Ronald C.; Brownfield, Michael E.

    2015-01-01

    A range of geological parameters relevant to mining oil shale have been examined for the Mahogany zone of the Green River Formation in the Piceance Basin, Colorado, and Uinta Basin, Utah, using information available in the U.S. Geological Survey Oil Shale Assessment database. Basinwide discrete and cumulative distributions of resource in-place as a function of (1) oil shale grade, (2) Mahogany zone thickness, (3) overburden thickness, and (4) stripping ratio (overburden divided by zone thickness) were determined for both basins on a per-acre basis, and a resource map showing the areal distribution of these properties was generated. Estimates of how much of the Mahogany zone resource meets various combinations of these parameters were also determined. Of the 191.7 billion barrels of Mahogany zone oil in-place in the Piceance Basin, 32.3 percent (61.8 billion barrels) is associated with oil shale yielding at least 25 gallons of oil per ton (GPT) of rock processed, is covered by overburden 1,000 feet thick or less, and has a stripping ratio of less than 10. In the Uinta Basin, 14.0 percent (29.9 billion barrels) of the 214.5 billion barrels of Mahogany zone oil in-place meets the same overburden and stripping ratio criteria but only for the lower grade cutoff of 15 GPT.

  17. Finding the Plateau: Paleogene Topography and Basin Formation in the Cordilleran Hinterland

    NASA Astrophysics Data System (ADS)

    Cassel, E. J.; Smith, M. E.; Canada, A.; Henry, C.; Breecker, D.

    2014-12-01

    /or broad dynamic and thermal uplift associated with Farallon slab rollback likely drove basin formation. Late Oligocene δD values from fluvially interbedded tephras suggest < 500-900 m of uplift following rollback, while stratigraphy indicates a coincident westward shift in the locus of deposition.

  18. Depositional systems and oil reservoirs in Spraberry Formation (Permian), Midland Basin, Texas

    SciTech Connect

    Tyler, N.; Guevara, E.H.; Gholston, J.C.

    1988-01-01

    Terrigenous clastic submarine-fan facies comprise the upper and lower parts of the Spraberry Formation (Permian, Leonardian) of west Texas. The Jo Mill submarine-fan system makes up the lower Spraberry. The upper Spraberry comprises the Driver and the overlying Floyd submarine-fan systems. The Midland basin plain system, composed mainly of shales and carbonates with thinner, interbedded sandstones, makes up the middle Spraberry and vertically separates the Jo Mill and Driver fans. Sand-rich inner fan facies of all three fan systems extend 50 mi into the Midland basin from the northern shelf edge. The abrupt transition from inner to midfan facies coincides with the underlying Horseshoe atoll, suggesting this bathymetrically positive feature influenced sedimentation patterns in younger sediments. Midfan to outer fan facies extend downdip from the subjacent atoll 100 mi farther into the basin. Sand contents decrease and interbedded mudstones thicken basinward. Recovery efficiencies are strongly related to submarine-fan facies. Recoveries in inner fan, incised-channel reservoirs (24% in Jo Mill field) are higher than in midfan and outer fan reservoirs (5% in the Spraberry trend to 15% in Benedum field). These more distal reservoirs consist of anastomosing to meandering channel-fill and interchannel facies associations. Stacking of channels through time resulted in dipelongate depositional axes in which wells have produced from two to as much as six times more oil than wells tapping interaxial areas. Pronounced stratigraphic heterogeneity and current well completion practices result in partly drained reservoir compartments, providing abundant opportunities for additional oil recovery.

  19. REGIONAL PARADOX FORMATION STRUCTURE AND ISOCHORE MAPS, BLANDING SUB-BASIN, UTAH

    SciTech Connect

    Kevin McClure; Craig D. Morgan; Thomas C. Chidsey Jr.; David E. Eby

    2003-12-01

    Over 400 million barrels (64 million m{sup 3}) of oil have been produced from the shallow-shelf carbonate reservoirs in the Pennsylvanian (Desmoinesian) Paradox Formation in the Paradox Basin, Utah and Colorado. With the exception of the giant Greater Aneth field, the other 100 plus oil fields in the basin typically contain 2 to 10 million barrels (0.3-1.6 million m{sup 3}) of original oil in place. Most of these fields are characterized by high initial production rates followed by a very short productive life (primary), and hence premature abandonment. Only 15 to 25 percent of the original oil in place is recoverable during primary production from conventional vertical wells. An extensive and successful horizontal drilling program has been conducted in the giant Greater Aneth field (figure 1). However, to date, only two horizontal wells have been drilled in small Ismay and Desert Creek fields. The results from these wells were disappointing due to poor understanding of the carbonate facies and diagenetic fabrics that create reservoir heterogeneity. These small fields, and similar fields in the basin, are at high risk of premature abandonment. At least 200 million barrels (31.8 million m{sup 3}) of oil will be left behind in these small fields because current development practices leave compartments of the heterogeneous reservoirs undrained. Through proper geological evaluation of the reservoirs, production may be increased by 20 to 50 percent through the drilling of low-cost single or multilateral horizontal legs from existing vertical development wells. In addition, horizontal drilling from existing wells minimizes surface disturbances and costs for field development, particularly in the environmentally sensitive areas of southeastern Utah and southwestern Colorado.

  20. Sequence stratigraphy of the Pennsylvanian Morrow Formation, northern Delaware basin, New Mexico

    SciTech Connect

    Bay, A.R.; Baltensperger, P.A. )

    1990-05-01

    Stratigraphic sequence analysis of the Pennsylvanian Morrow Formation is a new technique useful in predicting and understanding shifts in sand trends that can help locate Morrow gas reservoirs in the mature northern Delaware basin. Morrow sandstone reservoirs are fluvial deltaic channel fill and transgressive beach deposits that typically are 10-30 ft thick and consistently less than 1 mi wide. Detailed mapping and correlation within the systems tracts of each sequence can high-grade specific areas in the basin for exploration. Based on subsurface log correlations, the Morrow clastics and Atoka carbonates in the northern Delaware basin are interpreted as three stratigraphic sequences bounded by subregional type I unconformities. The post-Mississippian unconformity represents the oldest sequence boundary in the Morrow-to-Atoka succession and formed as the base level dropped and the shoreline shifted at least 50 mi basinward. The uplifted Pedernal Highlands supplied sediment to dip-trending lower Morrow channels that downcut into the exposed Mississippian carbonate ramp surface. The transgressive systems tract in this sequence consists of landward-stepping, wave-dominated deltaic deposit. The Morrow shale, a regionally correlatable organic-rich shale that separates the lower Morrow from the middle Morrow, represents the highstand deposits as base level that rose to a maximum. Another base level drop occurred at the end of Morrow shale deposition and resulted in dip-trending channel-fill sandstones and, stacked landward stepping transgressive beach and offshore ridge deposits oriented parallel to strike. The highstand progradational deposits of this sequence formed a terrace that supplied a shelf margin system of deltaic and slope-apron sediments during the succeeding third sequence. The shelf margin deposits are capped by highstand shelf carbonates of the upper Morrow and lower Atoka.

  1. Preliminary Simulations of CO2 Transport in the Dolostone Formations in the Ordos Basin, China

    SciTech Connect

    Hao, Y; Wolery, T; Carroll, S

    2009-04-30

    This report summarizes preliminary 2-D reactive-transport simulations on the injection, storage and transport of supercritical CO{sub 2} in dolostone formations in the Ordos Basin in China. The purpose of the simulations was to evaluate the role that basin heterogeneity, permeability, CO{sub 2} flux, and geochemical reactions between the carbonate geology and the CO{sub 2} equilibrated brines have on the evolution of porosity and permeability in the storage reservoir. The 2-D simulation of CO{sub 2} injection at 10{sup 3} ton/year corresponds to CO{sub 2} injection at a rate of 3 x 10{sup 5} ton/year in a 3-D, low permeable rock. An average permeability of 10 md was used in the simulation and reflects the upper range of permeability reported for the Ordos Basin Majiagou Group. Transport and distribution of CO{sub 2} between in the gas, aqueous, and solid phases were followed during a 10-year injection phase and a 10-year post injection phase. Our results show that CO{sub 2} flux and the spatial distribution of reservoir permeability will dictate the transport of CO{sub 2} in the injection and post injection phases. The injection rate of supercritical CO{sub 2} into low permeable reservoirs may need to be adjusted to avoid over pressure and mechanical damage to the reservoir. Although it should be noted that 3-D simulations are needed to more accurately model pressure build-up in the injection phase. There is negligible change in porosity and permeability due to carbonate mineral dissolution or anhydrite precipitation because a very small amount of carbonate dissolution is required to reach equilibrium with respect these phases. Injected CO{sub 2} is stored largely in supercritical and dissolved phases. During the injection phase, CO{sub 2} is transport driven by pressure build up and CO{sub 2} buoyancy.

  2. Using a novel Mg isotope tracer to investigate the dolomitization of the Red River Formation in the Williston Basin

    NASA Astrophysics Data System (ADS)

    Kimmig, S. R.; Holmden, C. E.; Qing, H.

    2015-12-01

    The Williston Basin is a sub-circular intracratonic basin spanning central North America with its center in NW North Dakota. The Late Ordovician Red River Formation is an economically viable unit in the Williston Basin containing large hydrocarbon reserves in Saskatchewan, North Dakota, Manitoba, and Montana. Red River dolomitization contributed to the reservoir-quality porosity and permeability observed today with three types of dolomite (burrow, matrix, and saddle) possibly representing three events. Dolomitization is widely believed to have resulted from downward percolating brines, due to the stratigraphically close association between dolomite deposits and overlying basin-scale evaporites. However, in contrast, Sr isotope evidence suggests an upward fluid migration in the basin. Spatial variation of Mg isotopes (δ26Mg) may serve as a direct tracer of dolomitizing fluid flow. Dolomite sequesters light isotopes of Mg from dolomitizing fluids, therefore, the fluid will evolve with time and distance to heavier δ26Mg values. Accordingly, the δ26Mg values of the Red River dolomite should increase in the direction of fluid flow. We test this hypothesis on Red River burrow dolomite from the Williston Basin; the first event most often attributed to downward infiltration of brines. Burrow δ26Mg values range between -1.89‰ and -1.31‰. Using contouring software, the data are shown to form a pattern of increasing δ26Mg values out from the center of the Williston Basin, indicating an up-dip migration of dolomitizing fluids through the burrow network, rather than down-dip as suggested by the brine reflux model. We conclude that dolomitization of the Red River carbonate is not tied to the spatial and temporal history of evaporite deposition in the Williston Basin, but rather to the thermal history of the basin, suggesting dolomitization likely occurred during a late Paleozoic heating event that drove Mg-rich connate waters ponded in the center of the basin upwards

  3. The Lower Cretaceous Chinkeh Formation: A frontier-type play in the Liard basin of western Canada

    SciTech Connect

    Leckie, D.A. ); Potocki, D.J. ); Visser, K. )

    1991-08-01

    The Lower Cretaceous Liard basin in western Canada covers an area of 9,500 km{sup 2} (3,668 mi{sup 2}) but is relatively unexplored despite its size. The present-day expression of the basin, which formed during the latest Cretaceous to early Tertiary, trends north-south and is delineated by the outcrop of the coarse-clastic Upper Cretaceous Dunvegan Formation. The lowermost Cretaceous unit, herein named the Chinkeh Formation, is up to 32 m (105 ft) thick and unconformably overlies older Paleozoic strata. The Chinkeh Formation contains four major lithotypes: (1) conglomeratic breccia interpreted as debris-flow or talus deposits, (2) interbedded coal, carbonaceous as nonmarine valley fill or channel deposits, (3) conglomeratic lag related to marine deposits, (3) conglomeratic lag related to marine transgression, and (4) upward-coarsening sandstone interpreted as abandoned shoreline deposits. Cretaceous strata in the Liard basin have gave petroleum source-rock and reservoir potential, and hydrocarbons may be present in sandstone of the Chinkeh Formation. Potential play types include stratigraphic traps formed by incised-valley deposits and shallow-marine sandstone pinching out laterally into marine shales of the Garbutt Formation. A potential structural play may occur along the Bovie fault zone where reservoirs may abut against a shale seal on the eastern side of the fault. Potential source rocks include the lowermost Garbutt Formation and underlying Triassic Toad Garbutt formations. The Chinkeh Formation sandstone has porosity values of 8-18%.

  4. Characterization of petroleum reservoirs in the Eocene Green River Formation, Central Uinta Basin, Utah

    USGS Publications Warehouse

    Morgan, C.D.; Bereskin, S.R.

    2003-01-01

    The oil-productive Eocene Green River Formation in the central Uinta Basin of northeastern Utah is divided into five distinct intervals. In stratigraphically ascending order these are: 1) Uteland Butte, 2) Castle Peak, 3) Travis, 4) Monument Butte, and 5) Beluga. The reservoir in the Uteland Butte interval is mainly lacustrine limestone with rare bar sandstone beds, whereas the reservoirs in the other four intervals are mainly channel and lacustrine sandstone beds. The changing depositional environments of Paleocene-Eocene Lake Uinta controlled the characteristics of each interval and the reservoir rock contained within. The Uteland Butte consists of carbonate and rare, thin, shallow-lacustrine sandstone bars deposited during the initial rise of the lake. The Castle Peak interval was deposited during a time of numerous and rapid lake-level fluctuations, which developed a simple drainage pattern across the exposed shallow and gentle shelf with each fall and rise cycle. The Travis interval records a time of active tectonism that created a steeper slope and a pronounced shelf break where thick cut-and-fill valleys developed during lake-level falls and rises. The Monument Butte interval represents a return to a gentle, shallow shelf where channel deposits are stacked in a lowstand delta plain and amalgamated into the most extensive reservoir in the central Uinta Basin. The Beluga interval represents a time of major lake expansion with fewer, less pronounced lake-level falls, resulting in isolated single-storied channel and shallow-bar sandstone deposits.

  5. Geochemical evaluation of upper cretaceous fruitland formation coals, San Juan Basin, New Mexico and Colorado

    USGS Publications Warehouse

    Michael, G.E.; Anders, D.E.; Law, B.E.

    1993-01-01

    Geochemical analyses of coal samples from the Upper Cretaceous Fruitland Formation in the San Juan Basin of New Mexico and Colorado were used to determine thermal maturity, type of kerogen, and hydrocarbon generation potential. Mean random vitrinite reflectance (%Rm) of the Fruitland coal ranges from 0.42 to 1.54%. Rock-Eval pyrolysis data and saturated to aromatic hydrocarbon ratio indicate that the onset of thermal hydrocarbon generation begins at about 0.60% Rm and peak generation occurs at about 0.85% Rm. Several samples have hydrogen index values between 200 and 400, indicating some potential for liquid hydrocarbon generation and a mixed Type III and II kerogen. Pentacyclic and tricyclic terpanes, steranes, aromatic steroids and methylphenanthrene maturity parameters were observed through the complete range of thermal maturity in the Fruitland coals. Aromatic pentacyclic terpanes, similar to those found in brown coals of Australia, were observed in low maturity samples, but not found above 0.80% Rm. N-alkane depleted coal samples, which occur at a thermal maturity of approx. 0.90% Rm, paralleling peak hydrocarbon generation, are fairly widespread throughout the basin. Depletion of n-alkanes in these samples may be due to gas solution stripping and migration fromthe coal seams coincident with the development of pressure induced fracturing due to hydrocarbon generation; however, biodegradation may also effect these samples. ?? 1993.

  6. Geochemical Characteristics and its Geological Significance of Oil Shale from the Youganwo Formation, Maoming Basin, China

    NASA Astrophysics Data System (ADS)

    Zhou, Yuanyuan; Qiu, Nansheng

    2016-04-01

    Geochemical elements of oil shale in the Maoming Basin were analyzed to discuss provenance attribute and depositional environment of the Youganwo formation. Experimental date of the major elements, trace elements and rare earth elements of 24 samples from the Maoye 1 well were examined.The analyzed oil shale samples were characterized by enrichment of Th, U, Pb and LREE, depleted of Zr, Cr and Hf,negative Eu and Ce anomalies, indicating that these samples were originated from continental crust. The chemical index of alteration (CIA) values and the Zr/Sc-Th/Sc diagrams indicate that source rocks had undergone intense chemical weathering and deposition recirculation. Based on the La/Th-Hf and La/Yb-∑REE diagrams and the negative anomaly of Eu element, the oil shale in the Maoming Basin has diverse sources, which mainly came from felsic source region of the upper crust or the mixture of felsic volcanic rocks, granite and sedimentary rocks. Ratios of the Sr/Cu, MgO/CaO suggest that oil shale was formed in fresh water under warm and humid climate, shallow water column became deeper during the middle and late sedimentary period. The depositional environment is interpreted to be limnetic with weak reduction at the early stage and gradually turned into semi-deep to deep lacustrine.

  7. Progradational sequences in lower Ordovician portion of Deadwood Formation, Williston basin

    SciTech Connect

    Anderson, D.

    1988-07-01

    In the Williston basin, the Cambrian and Ordovician Deadwood Formation can be divided into six informal members based on gamma-ray log characteristics. Members C through F are Early Ordovician (Tremadocian to Arenigian) and consist of three progradational sequences. In ascending order, the sequences consist of (1) a mixed sandstone-limestone lithotype, (2) limestone lithotypes ranging from mudstone to grainstone, (3) bioturbated, peloidal, calcareous, siliciclastic mudstone and siltstone, (4) bioturbated to planar-laminated, peloidal, calcareous siltstone and sandstone, (5) Skolithos-bored, cross-bedded to planar-laminated quartzarenite, (6) bioturbated dolomite and anhydrite-cemented fossiliferous quartz wacke, and (7) silty laminated dolomudstone. The asymmetrical sequences represent progradation of a siliciclastic shoreline, back-barrier lagoon, and intertidal algal flat over a siliciclastic shelf and a distal carbonate shoal. The present distribution of the sequences and individual lithotypes in the Williston basin is a function of the limited eastward advance of the carbonate shoal during transgression, the limited westward advance of the shoreline during progradation, deep shoreface erosion of the previous sequence during rapid transgression, and Middle Ordovician erosion.

  8. Ultimate recovery analysis by formation and play for deep Anadarko Basin and estimation of undiscovered gas potential

    SciTech Connect

    Hugman, R.H.

    1988-01-01

    Deep gas resources have assumed a growing role in the United States gas picture since the mid-1960s. The deep Anadarko basin has been one of the areas of heavy activity, and is thought to contain a significant portion of the remaining unproven deep gas resource in the lower-48 states. A detailed analysis of gas production and proven reserves in the deep basin has established the characteristics and historical importance of each of the major plays and productive formations. The analysis should prove to be a valuable tool in estimating the undiscovered gas potential of the deep basin. Through 1985, there were 908 completions in the deep Anadarko basin. These completions accounted for 6.10 tcf of proven ultimate recovery, an average of 6.72 bcf per completion. In general, there is one completion per well and one well per section. Thus, ultimate recovery per completion represents ultimate recovery per section. The Hunton Group has the highest mean ultimate recovery at 15.3 bcf, followed by the Arbuckle Group at 10.1 bcf. In an attempt to evaluate existing resource appraisals of the deep basin, the areal distribution of production by formation was determined for the mature, shallow part of the basin. Over 20,000 completions were included in this analysis, demonstrating a significant database application. By using this distribution as a guide, along with certain other constraints, a range of 15-47 tcf of undiscovered potential was estimated.

  9. Geochemistry and origin of formation waters in the western Canada sedimentary basin-I. Stable isotopes of hydrogen and oxygen

    USGS Publications Warehouse

    Hitchon, B.; Friedman, I.

    1969-01-01

    Stable isotopes of hydrogen and oxygen, together with chemical analyses, were determined for 20 surface waters, 8 shallow potable formation waters, and 79 formation waters from oil fields and gas fields. The observed isotope ratios can be explained by mixing of surface water and diagenetically modified sea water, accompanied by a process which enriches the heavy oxygen isotope. Mass balances for deuterium and total dissolved solids in the western Canada sedimentary basin demonstrate that the present distribution of deuterium in formation waters of the basin can be derived through mixing of the diagenetically modified sea water with not more than 2.9 times as much fresh water at the same latitude, and that the movement of fresh water through the basin has redistributed the dissolved solids of the modified sea water into the observed salinity variations. Statistical analysis of the isotope data indicates that although exchange of deuterium between water and hydrogen sulphide takes place within the basin, the effect is minimized because of an insignificant mass of hydrogen sulphide compared to the mass of formation water. Conversely, exchange of oxygen isotopes between water and carbonate minerals causes a major oxygen-18 enrichment of formation waters, depending on the relative masses of water and carbonate. Qualitative evidence confirms the isotopic fractionation of deuterium on passage of water through micropores in shales. ?? 1969.

  10. Diatoms in coal: Miocene Venado Formation, Limon Basin, Costa Rica, Central America

    SciTech Connect

    Sanchez, J.D.; Coates, D.A.; Bradbury, J.P.; Bohor, B.F.

    1985-01-01

    Diatoms occur in coal in the Venado Formation on the southwest flank of the Limon Basin in Provincia Alajuela, northern Costa Rica. The Venado Formation contains more than 300 m of mudstones, siltstones, sandstones, limestones, and coal beds that crop out on the northeast flank of the Cordillera de Tilaran. Coal beds of unknown extent and correlation occur mainly in the middle part of the formation. The coal deposit here named informally the Pataste coal bed. Coal samples were examined with a scanning electron microscope and an x-ray analyzer attachment. Part A contains abundant diatoms and macerated diatom material and rare spicules of freshwater sponges. Diatoms identified are Melosira ambigua, Pinularia, Eunotia spp. and Achnathes exigua. Parts B and C of the coal bed contain fewer diatom remains and more sponge spicules than part A. The common presence of Melosira ambigua in A implies the proximity of open-water lacustrine environments. The other diatom species are benthic or bottom-dwelling forms that lived in slightly acidic, humic-rich paludal environments. Presumably, the swamp in which the coal was formed was most extensive during the deposition of A, and became progressively restricted thereafter. The increase of sponge spicules relative to diatoms in B and C suggests progressively, shallower lacustrine or restricted swamp conditions. The comparatively great abundance of biogenic opaline material in the coal is due to the influx of silica form a volcanic source represented by the tonstein layers.

  11. Macrofossils of Bakken Formation (Devonian and Mississippian), Williston Basin, North Dakota

    SciTech Connect

    Thrasher, L.; Holland, F.D. Jr.

    1983-08-01

    Results of this study of the macrofossils of the Bakken Formation in North Dakota have reinforced the suggestion, based on previous paleontological work in Saskatchewan, that the Bakken is of both Devonian and Mississippian age, rather than being entirely of Lower Mississippian age as originally considered. Increased drilling and coring activity in the North Dakota part of the Williston Basin has provided the opportunity for acquiring a larger fauna that was previously available. Based on lithologic character, the Bakken has been divided into three informal members. These consist of a calcareous siltstone unit between two lithologically similar units of carbonaceous shale. These black shales contain similar faunas distinct from that of the middle member. The black shales contain inarticulate brachiopods, conchostracans, and rare cephalopods and fish remains as well as more abundant conodonts, ostracods, and palynomorphs. The middle siltstone unit contains a more abundant and diverse fauna consisting of inarticulate and articulate brachiopods together with corals, gastropods, cephalopods, ostracods, echinoderm remains, and trace fossils. This is the first report of cephalopods, conchostracans, ostracods, corals, trace fossils, and some of the brachiopods in the Bakken, although all, except the gastropods, have been reported from stratigraphic equivalents (Exshaw Formation of south-central Montana, the Leatham Formation of northeastern Utah, and the middle member of the Pilot Shale in western Utah and eastern Nevada).

  12. 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.

  13. Effect of Smoke on Cloud Formation during the Biomass Burning Season over the Amazon Basin

    NASA Technical Reports Server (NTRS)

    Koren, I.; Kaufman, Y. J.; Remer, L. A.

    2003-01-01

    Aerosol absorption of sunlight reduces surface irradiation and heats the aerosol layer. The consequent changes in the temperature and humidity profiles can affect cloud formation extent and life time, which is called the semi-direct effect. We evaluate this aerosol semi-direct effect using data collected during the 2002 biomass burning season over the Amazon basin from the MODIS instrument on the Aqua satellite. MODIS measures the cloud coverage and the aerosol optical thickness among the clouds. We found that the radiative heating of the atmosphere and cooling of the surface due to the presence of the smoke decreases the cloud coverage. A very clear negative correlation emerges between the cloud fraction and the smoke optical depth. The results are compared to calculations using 1-D radiation model (M.D. Chou), and used to calculate this regional semi direct effect on climate forcing.

  14. The origin and formation model of Permian dolostones on the northwestern margin of Junggar Basin, China

    NASA Astrophysics Data System (ADS)

    Lu, Xinchuan; Shi, Ji'an; Zhang, Shuncun; Zou, Niuniu; Sun, Guoqiang; Zhang, Shengyin

    2015-06-01

    This study investigates the mechanism of dolostone formation and establishes a dolomitization model in the Permian strata on the northwestern margin of Junggar Basin, China. Dolomitic rock samples are collected from the Permian Fengcheng Formation in Urho area and then characterized by petrological, mineralogical, carbon and oxygen isotope, and trace element geochemical analyses. Results show that the major types of dolomitic rocks include dolomitic mudstone, dolomitic siltstone, dolomitized tuffaceous siltstone, and dolomitized tuffaceous mudstone. The dolomitized rocks are dominated by euhedral or subhedral powder- and fine-crystal dolomites formed by replacement lacustrine argilla-calcareous and siliceous (tuffaceous) components and commonly filled with residual and late calcite cements. The parameters of dolomitic rocks show great variations, including the V/Ni ratio (1.02-4.88), Sr content (95.9-783.6 μg/g), Mg/Ca ratio (0.68-5.13), degree of ordering (0.39-1.00), δ18OPDB (-14.8‰ to 3.2‰), and δ13CPDB (-1‰ to 5.2‰). The dolomitic rocks have multi-stage origins and were formed in a semi-closed continental brackish-saltwater bay with weak hydrodynamic processes, deep water bodies, and relatively quiet conditions. In the Permian depositional stage, a combination of complex tectonic activities, fault development, hot subtropical climate, and frequent volcanic activities provided not only Mg2+ source for dolomitization but also channels for rapid flow and seepage of Mg-rich fluids. The origins of dolostones in the study area include penecontemporaneous dolomitization, burial dolomitization, and hydrothermal dolomitization. This study lays a foundation for further studies on dolomite formation and dolomite reservoir, and provides effective methods for researching complex dolostone (tuffaceous, shale and silty dolomite) formation.

  15. Assessment of Undiscovered Oil Resources in the Devonian-Mississippian Bakken Formation, Williston Basin Province, Montana and North Dakota, 2008

    USGS Publications Warehouse

    Pollastro, Richard M.; Cook, Troy A.; Roberts, Laura N.R.; Schenk, Christopher J.; Lewan, Michael D.; Anna, Lawrence O.; Gaswirth, Stephanie B.; Lillis, Paul G.; Klett, Timothy R.; Charpentier, Ronal R.

    2008-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered volumes of 3.65 billion barrels of oil, 1.85 trillion cubic feet of associated/dissolved natural gas, and 148 million barrels of natural gas liquids in the Bakken Formation of the Williston Basin Province, Montana and North Dakota.

  16. Assessment of In-Place Oil Shale Resources of the Green River Formation, Uinta Basin, Utah and Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Mercier, Tracey J.; Brownfield, Michael E.; Self, Jesse G.

    2010-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated a total of 1.32 trillion barrels of oil in place in 18 oil shale zones in the Eocene Green River Formation in the Uinta Basin, Utah and Colorado.

  17. Assessment of undiscovered continuous oil and gas resources in the Monterey Formation, Los Angeles Basin Province, California, 2015

    USGS Publications Warehouse

    Tennyson, Marilyn E.; Charpentier, Ronald R.; Klett, Timothy R.; Brownfield, Michael E.; Pitman, Janet K.; Gaswirth, Stephanie B.; Hawkins, Sarah J.; Le, Phuong A.; Lillis, Paul G.; Marra, Kristen R.; Mercier, Tracey J.; Leathers-Miller, Heidi M.; Schenk, Christopher J.

    2016-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey assessed technically recoverable mean resources of 13 million barrels of oil, 22 billion cubic feet of gas, and 1 million barrels of natural gas liquids in the Monterey Formation of the Los Angeles Basin Province, California.

  18. Assessment of undiscovered continuous oil and gas resources in the Monterey Formation, Los Angeles Basin Province, California, 2015

    USGS Publications Warehouse

    Tennyson, Marilyn E.; Charpentier, Ronald R.; Klett, Timothy R.; Brownfield, Michael E.; Pitman, Janet K.; Gaswirth, Stephanie B.; Hawkins, Sarah J.; Le, Phuong A.; Lillis, Paul G.; Marra, Kristen R.; Mercier, Tracey J.; Leathers-Miller, Heidi M.; Schenk, Christopher J.

    2016-07-08

    Using a geology-based assessment methodology, the U.S. Geological Survey assessed technically recoverable mean resources of 13 million barrels of oil, 22 billion cubic feet of gas, and 1 million barrels of natural gas liquids in the Monterey Formation of the Los Angeles Basin Province, California.

  19. Vegetation canopy cover effects on sediment erosion processes in the upper Colorado River Basin mancos shale formation, Price, Utah

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study provides new parameterizations for applying the Rangeland Hydrology and Erosion Model (RHEM) on the highly erosive, rangeland saline soils of the Mancos Shale formation in the Price-San Rafael River Basin in east central Utah. Calibrated hydrologic parameters (Kss and K') values are gener...

  20. 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

  1. Lithologic variations and diagenesis of Lower Cretaceous Muddy Formation in northern Powder River basin, Wyoming

    SciTech Connect

    Walker, A.L.; Patterson, P.E.

    1986-08-01

    Regional facies studies show that sandstones in the Muddy Formation, northern Powder River basin, were deposited in fluvial and nearshore marine paleoenvironments. Most sandstones of the fluvial facies contain only minor amounts of clay matrix and are classified as quartzarenite or sublitharenite, whereas those of the shoreface facies contain appreciable clay and are classified as litharenite or arkose. The arkoses are concentrated along a narrow belt that trends northeastward, parallel to the inferred paleoshoreline. Both the fluvial and shoreface sandstones have been variably affected by postdepositional alteration. During early stages of diagenesis, matrix clay was formed predominantly within the shoreface sandstones, owing mainly to alteration of volcanic material. Later, quartz overgrowths and calcite cement were precipitated within the remaining pore spaces in both fluvial and shoreface sandstones. Calcite also replaced detrital framework grains and some of the previously formed matrix clay. During intermediate diagenetic stages, detrital feldspar grains, particularly those in the arkosic shoreface sandstones, were replaced by albite, which characteristically lacks twinning or displays distinctive chessboard texture. Microprobe analyses indicate that both forms are essentially pure albite. During later stages of diagenesis, following maximum burial, much of the calcite was dissolved, producing secondary porosity. Inasmuch as the calcite was precipitated early, i.e., prior to significant compaction, and inasmuch as it replaced both framework grains and authigenic matrix clay, the secondary pores exhibit a relatively high level of interconnection. It is this secondary porosity that has contributed to the migration and storage of hydrocarbons in the Muddy Formation.

  2. Seismic facies analysis of lacustrine system: Paleocene upper Fort Union Formation, Wind River basin, Wyoming

    SciTech Connect

    Liro, L.M.; Pardus, Y.C.

    1989-03-01

    The authors interpreted seismic reflection data, supported by well control, to reconstruct the stratigraphic development of Paleocene Lake Waltman in the Wind River basin of Wyoming. After dividing the upper Fort Union into eight seismic sequences, the authors mapped seismic attributes (amplitude, continuity, and frequency) within each sequence. Interpretation of the variation in seismic attributes allowed them to detail delta development and encroachment into Lake Waltman during deposition of the upper Fort Union Formation. These deltas are interpreted as high-energy, well-differentiated lobate forms with distinct clinoform morphology on seismic data. Prograding delta-front facies are easily identified on seismic data as higher amplitude, continuous events within the clinoforms. Seismic data clearly demonstrate the time-Transgressive nature of this facies. Downdip of these clinoforms, homogeneous shales, as evidenced by low-amplitude, generally continuous seismic events, accumulated in an interpreted quiet, areally extensive lacustrine setting. Seismic definition of the lateral extent of this lacustrine facies is excellent, allowing them to effectively delineate changes in the lake morphology during deposition of the upper Fort Union Formation. Encasing the upper Fort Union lacustrine deposits are fluvial-alluvial deposits, interpreted from discontinuous, variable-amplitude seismic facies. The authors highlight the correlation of seismic facies data and interpretation to well log data in the Frenchie Draw field to emphasize the accuracy of depositional environment prediction from seismic data.

  3. Identifying and Remediating High Water Production Problems in Basin-Centered Formations

    SciTech Connect

    R.L. Billingsley

    2005-12-01

    Through geochemical analyses of produced waters, petrophysics, and reservoir simulation we developed concepts and approaches for mitigating unwanted water production in tight gas reservoirs and for increasing recovery of gas resources presently considered noncommercial. Only new completion research (outside the scope of this study) will validate our hypothesis. The first task was assembling and interpreting a robust regional database of historical produced-water analyses to address the production of excessive water in basin-centered tight gas fields in the Greater Green (GGRB ) and Wind River basins (WRB), Wyoming. The database is supplemented with a sampling program in currently active areas. Interpretation of the regional water chemistry data indicates most produced waters reflect their original depositional environments and helps identify local anomalies related to basement faulting. After the assembly and evaluation phases of this project, we generated a working model of tight formation reservoir development, based on the regional nature and occurrence of the formation waters. Through an integrative approach to numerous existing reservoir concepts, we synthesized a generalized development scheme organized around reservoir confining stress cycles. This single overarching scheme accommodates a spectrum of outcomes from the GGRB and Wind River basins. Burial and tectonic processes destroy much of the depositional intergranular fabric of the reservoir, generate gas, and create a rock volume marked by extremely low permeabilities to gas and fluids. Stress release associated with uplift regenerates reservoir permeability through the development of a penetrative grain bounding natural fracture fabric. Reservoir mineral composition, magnitude of the stress cycle and local tectonics govern the degree, scale and exact mechanism of permeability development. We applied the reservoir working model to an area of perceived anomalous water production. Detailed water analyses

  4. CONSOLIDATION OF K BASIN SLUDGE DATA AND EXPERIENCES ON AGGLOMERATE FORMATION

    SciTech Connect

    HILL SR

    2010-06-10

    The formation of high sludge strength agglomerates is a key concern to the Sludge Treatment Project (STP) to ensure the sludge can be retrieved after planned storage for up to 10 years in Sludge Transport and Storage Containers (STSC) at T Plant. This report addresses observations of agglomerate formation, conditions that the data shows lead to agglomeration, the frequency of agglomerate formation and postulated physiochemical mechanisms that may lead to agglomeration. Although the exact underlying chemistry of K Basin sludge agglomerate formation is not known, the factors that lead to agglomeration formation, based on observations, are as follows: (1) High Total Uranium Content (i.e., sample homogeneity and influence from other constituents); (2) Distribution of Uranium Phases (i.e., extent of conversion from uraninite to uranium oxide hydroxide compounds); (3) Sample Dry-out (loss of cover water); (4) Elevated temperature; (5) Solubility ofU(IV) phases vs. U(VI) phases; and (6) Long storage times. Agglomerated sludge has occurred infrequently and has only been observed in four laboratory samples, five samples subjected to hydrothermal testing (performed for 7 to 10 hours at {approx}185 C and 225 psig), and indirectly during six sampling events in the KE Basin. In the four laboratory samples where agglomerates were observed, the agglomerates exhibited high shear strength and the sample container typically had to be broken to remove the solids. The total uranium content (dry basis) for the four samples (KE Pit, KC-2/3 SS, KC-2/3 M250 and 96-13) were {approx}8 wt%, {approx}59.0 wt%, 68.3 wt% and 82 wt%. The agglomerates that were present during the six sampling events were undoubtedly disturbed and easily broken apart during sample collection, thus no agglomerates were observed in subsequent laboratory analyses. The highest shear strengths measured for K Basin sludge samples were obtained after hydrothermal treatment (7 to 10 hr at 185 C) of high-uranium-content KE

  5. Peleolakes and impact basins in southern Arabia Terra, including Meridiani Planum: Implications for the formation of hematite deposits on Mars

    USGS Publications Warehouse

    Newsom, Horton E.; Barber, C.A.; Hare, T.M.; Schelble, R.T.; Sutherland, V.A.; Feldman, W.C.

    2003-01-01

    The hematite deposit in Meridiani Planum was selected for a Mars Exploration Rover (MER) landing site because water could be involved in the formation of hematite, and water is a key ingredient in the search for life. Our discovery of a chain of paleolake basins and channels along the southern margin of the hematite deposits in Meridiani Planum with the presence of the strongest hematite signature adjacent to a paleolake basin, supports the possible role of water in the formation of the hematite and the deposition of other layered materials in the region. The hematite may have formed by direct precipitation from lake water, as coatings precipitated from groundwater, or by oxidation of preexisting iron oxide minerals. The paleolake basins were fed by an extensive channel system, originating from an area larger than Texas and located south of the Schiaparelli impact basin. On the basis of stratigraphic relationships, the formation of channels in the region occurred over much of Mars' history, from before the layered materials in Meridiani Planum were deposited until recently. The location of the paleolake basins and channels is connected with the impact cratering history of the region. The earliest structure identified in this study is an ancient circular multiringed basin (800-1600 km diameter) that underlies the entire Meridiani Planum region. The MER landing site is located on the buried northern rim of a later 150 km diameter crater. This crater is partially filled with layered deposits that contained a paleolake in its southern portion. Copyright 2003 by the American Geophysical Union.

  6. Characteristics of hydrothermal sedimentation process in the Yanchang Formation, south Ordos Basin, China: Evidence from element geochemistry

    NASA Astrophysics Data System (ADS)

    He, Cong; Ji, Liming; Wu, Yuandong; Su, Ao; Zhang, Mingzhen

    2016-11-01

    Hydrothermal sedimentation occurred in the Triassic Yanchang Formation, Ordos Basin, China. However, their macroscopic features at the scale of the stratum and hydrothermal sources still lack correlational research. This paper performed element geochemical study on a large number of core samples collected from the Yanchang Formation of a new drilling well located in the south Ordos Basin. The SiO2/(K2O + Na2O) vs. MnO/TiO2 crossplot and Fe vs. Mn vs. (Cu + Co + Ni) × 10 ternary diagram demonstrate that the Yanchang stratum in the study area has, in general, hydrothermal components. The Al/(Al + Fe + Mn) and (Fe + Mn)/Ti ratios of the core samples range from 0.34 to 0.84 and 4.81 to 50.54, averaging 0.66 and 10.67, respectively, indicating that the stratum is a set of atypical hydrothermal sedimentation with much terrigenous input. Data analysis shows that the hydrothermal source in the study area was from the deep North Qinling Orogen around the south margin of the basin, where some active tectonic and volcanic activities took place, rather than from the relatively stable internal basin. Early Indosinian movement and volcanic activities activated basement faults around the southern margin of the basin, providing vents for the deep hydrothermal fluid upwelling. The hydrothermal indicators suggest that the study area experienced 4 episodes of relatively stronger hydrothermal activity, namely during the Chang 10, Chang 9-1, Chang 7-3 and Chang 6-2 periods. We also propose a new hydrothermal sedimentation model of hydrothermal fluids overflowing from basin margin faults, for the Yanchang Formation, which is reported here for the first time.

  7. Formation of nanoporous pyrobitumen residues during maturation processes within the Barnett Shale (Fort Worth Basin)

    NASA Astrophysics Data System (ADS)

    Bernard, S.; Wirth, R.; Schreiber, A.; Schulz, H.-M.; Horsfield, B.

    2012-04-01

    Hydrocarbon generation processes occur within organic-rich shales as a response to increases in thermal maturation. Shale gas reservoir quality is thought to be largely dependent on the extent to which solid organic material has been converted to pore space during catagenesis. Although pores may drastically vary in variety and abundance within differing shales, the occurrence of nanopores within organic particles has recently been documented for an important number of gas shale systems (i.e., Barnett, Haynesville, Utica, Eagle Ford, Woodford, Horn River, Marcellus, Posidonia …). However, despite their ubiquitous nature, the formation and the geochemical nature of these nanoporous organic compounds remain unclear. Here, we present the characterization of samples from the organic-rich Mississippian Barnett shale gas system (Fort Worth Basin, Texas, USA) at varying stages of thermal maturation. Using a combination of compositional organic geochemistry and spectromicroscopy techniques, including synchrotron-based scanning transmission X-ray microscopy (STXM - data collected using the CLS 10ID-1 STXM beamline) and transmission electron microscopy (TEM), we document a net increase in sample geochemical heterogeneity with increasing maturity. In addition to the presence of bitumen in samples of oil window maturity, very likely genetically derived from thermally degraded kerogen, the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity, likely resulting from the formation of gaseous hydrocarbons by secondary cracking of bitumen compounds. By providing in-situ insights into the fate of bitumen and pyrobitumen as a response to the thermal evolution of the macromolecular structure of kerogen, the present contribution constitutes an important step towards better constraining hydrocarbon generation processes occurring within unconventional gas shale systems.

  8. Sedimentology and sequence stratigraphy of Lower Shihezi Formation in Shenguhao area, northern Ordos basin, China

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Lu, Yongchao; Lin, Zi

    2015-04-01

    The structural location of Shenguhao area locates at the transition zone of Yimeng uplift and Yishan slope of northern Ordos basin, China. The study area is in erosion condition until Late Carboniferous and has deposited Taiyuan Formation (C2t), Shanxi Formation (P1s), Lower Shihezi Formation (P1x), Upper Shihezi Formation (P2s) and Shiqianfeng Formation (P2sh) in succession during Late Paleozoic, which mainly develops transition facies and alluvial plain facies. The fluvial sandstone of Lower Shihezi Formation is the major target layer of gas exploration and development in this area. This study is based on the interpretation of 38 wells and 113 sesmic reflection profiles. Three significant lithofacies were identified with sedimentological analysis of cores from the Shenguhao area: fluvial conglomerates, fluvial sandstone and floodplain mudstone, which represent fluvial depositional environment. Based on sequence stratigraphy methodology, well log patterns and lithofacies analysis, Lower Shihezi Formation can be divided into four depositional sequence cycles (1-4) bounded by fluvial scouring erosional surfaces. Each sequence succession shows the trend of base level rising and overall performs fining-upward feature, which characterized by coarsening-upward lower to upper fluvial sandstone and floodplain mudstone. In ascending order, sequence 1 records the transition from the underlying braided river delta plain fine-grained sediments of Shanxi Formation into the overlying fluvial sandstone of Lower Shihezi Formation and develops scouring erosional unconformity at the base, representing a regression. Sequence 1 consists of a package of progradting thick layer of amalgamated fluvial sandstone at the lower part passing into aggrading thin layer of floodplain mudstone at the upper part, suggesting that accommodation growing rate is gradually greater than deposition supply rate under the background of base level gradual increase. Sequence 2 and 3 record similar

  9. Selected hydrologic and physical properties of Mesozoic formations in the Upper Colorado River Basin in Arizona, Colorado, Utah, and Wyoming; excluding the San Juan Basin

    USGS Publications Warehouse

    Weigel, J.F.

    1987-01-01

    Data for hydrologic and physical properties of Mesozoic formations in the Upper Colorado River Basin, excluding the San Juan Basin, have been collected by government agencies, private industry, property owners, and other sources. These data were compiled and analyzed so that they would be available for use by hydrologists, earth scientists, planners, and others. Five methods of data analysis are discussed. The results of these five methods are not directly comparable because of differences in the volume of an aquifer represented by each method. Aquifer tests represent the largest volume of an aquifer, specific capacity and drill-stem tests represent a smaller volume, slug-injection tests represent a still smaller volume, and laboratory tests represent the smallest volume. Because they represent large volumes of an aquifer, aquifer tests were considered to give the best estimates of hydrologic characteristics. Laboratory data for permeability to air and hydraulic conductivity were determined to be related by a simple power function. (Author 's abstract)

  10. Revised Subsurface Stratigraphic Framework of the Fort Union and Wasatch Formations, Powder River Basin, Wyoming and Montana

    USGS Publications Warehouse

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

    2010-01-01

    Described in this report is an updated subsurface stratigraphic framework of the Paleocene Fort Union Formation and Eocene Wasatch Formation in the Powder River Basin (PRB) in Wyoming and Montana. This framework is graphically presented in 17 intersecting west-east and north-south cross sections across the basin. Also included are: (1) the dataset and all associated digital files and (2) digital files for all figures and table 1 suitable for large-format printing. The purpose of this U.S. Geological Survey (USGS) Open-File Report is to provide rapid dissemination and accessibility of the stratigraphic cross sections and related digital data to USGS customers, especially the U.S. Bureau of Land Management (BLM), to facilitate their modeling of the hydrostratigraphy of the PRB. This report contains a brief summary of the coal-bed correlations and database, and is part of a larger ongoing study that will be available in the near future.

  11. Factors controlling Li concentration and isotopic composition in formation waters and host rocks of Marcellus Shale, Appalachian Basin

    USGS Publications Warehouse

    Phan, Thai T.; Capo, Rosemary C; Stewart, Brian W.; Macpherson, Gwen; Rowan, Elisabeth L.; Hammack, Richard W.

    2015-01-01

    In Greene Co., southwest Pennsylvania, the Upper Devonian sandstone formation waters have δ7Li values of + 14.6 ± 1.2 (2SD, n = 25), and are distinct from Marcellus Shale formation waters which have δ7Li of + 10.0 ± 0.8 (2SD, n = 12). These two formation waters also maintain distinctive 87Sr/86Sr ratios suggesting hydrologic separation between these units. Applying temperature-dependent illitilization model to Marcellus Shale, we found that Li concentration in clay minerals increased with Li concentration in pore fluid during diagenetic illite-smectite transition. Samples from north central PA show a much smaller range in both δ7Li and 87Sr/86Sr than in southwest Pennsylvania. Spatial variations in Li and δ7Li values show that Marcellus formation waters are not homogeneous across the Appalachian Basin. Marcellus formation waters in the northeastern Pennsylvania portion of the basin show a much smaller range in both δ7Li and 87Sr/86Sr, suggesting long term, cross-formational fluid migration in this region. Assessing the impact of potential mixing of fresh water with deep formation water requires establishment of a geochemical and isotopic baseline in the shallow, fresh water aquifers, and site specific characterization of formation water, followed by long-term monitoring, particularly in regions of future shale gas development.

  12. Oxfordian reef architecture of the La Manga Formation, Neuquén Basin, Mendoza Province, Argentina

    NASA Astrophysics Data System (ADS)

    Palma, Ricardo M.; Kietzmann, Diego A.; Adamonis, Susana; Gómez, José López

    2009-11-01

    The Neuquén back-arc basin is located on the west margin of the South American platform between latitudes 36° and 40° S. The basin is famous for its continuous sedimentary record from the Late Triassic to Cenozoic comprising continental and marine clastic, carbonate, and evaporitic deposits up to 2.600 m in thickness. The stratigraphical and paleontological studies of the outcrops of the La Manga Formation, Argentina, located near the Bardas Blancas region, Mendoza province (35° S and 69° O) allow the reconstruction of the sedimentary environments of an Oxfordian carbonate ramp, where outer ramp, middle ramp, inner ramp (oolitic shoal), inner ramp margin (patch reef) lagoon and paleokarst were differentiated. The reefs consist of back reef facies and insitu framework of coral boundstones that was formed at the top of shallowing-upward succession. Coral reefs were analyzed by defining coral colonies shapes, paleontological content, coral diversity and taphonomy studies. In some studied sections abundant fragments of gryphaeids, encrusting bryozoans, and isolated sponges provided a suitable substrate for coral colonization; however, other sections show an increase in the proportions of ooids, peloidal and coral intraclasts. The core reef facies is composed of white-grey unstratified and low diversity scleractinian coral limestone dominated by robust and thinly branching corals with cerioid-phocoid growths and massive coral colonies with meandroid-thamnasteroid growth forms. The assemblage is characterized by Actinastraea sp., Australoseris sp., Thamnasteria sp. and Garateastrea sp. Internal facies organization and different types of coral colonies allow to recognize the development of varying framework as well as intercolony areas. A superstratal growth fabric characterizes the coral assemblage. On the basis of coral growth fabric (branche and domal types), the reef of La Manga Formation is considered a typical mixstones. The intercolony areas consist of

  13. Two-stage formation model of the Junggar basin basement: Constraints to the growth style of Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    He, Dengfa

    2016-04-01

    Junggar Basin is located in the central part of the Central Asian Orogenic Belt (CAOB). Its basement nature is a highly controversial scientific topic, involving the basic style and processes of crustal growth. Some researchers considered the basement of the Junggar Basin as a Precambrian continental crust, which is not consistent with the petrological compositions of the adjacent orogenic belts and the crust isotopic compositions revealed by the volcanic rocks in the basin. Others, on the contrary, proposed an oceanic crust basement model that does not match with the crustal thickness and geophysical characteristics of the Junggar area. Additionally, there are several viewponits, such as the duplex basement with the underlying Precambrian crystalline rocks and the overlying pre-Carboniferous folded basement, and the collaged basement by the Precambrian micro-continent block in the central part and the Hercynian accretionary folded belts circling it. Anyway, it is necessary to explain the property of basement rock, its strong inhomogeneous compositions as well as the geophysical features. In this paper, based on the borehole data from more than 300 industry wells drilled into the Carboniferous System, together with the high-resolution gravity and magnetic data (in a scale of 1:50,000), we made a detailed analysis of the basement structure, formation timing and processes and its later evolution on a basis of core geochemical and isotopic analysis. Firstly, we defined the Mahu Pre-Cambrian micro-continental block in the juvenile crust of Junggar Basin according to the Hf isotopic analysis of the Carboniferous volcanic rocks. Secondly, the results of the tectonic setting and basin analysis suggest that the Junggar area incorporates three approximately E-W trending island arc belts (from north to south: Yemaquan- Wulungu-Chingiz, Jiangjunmiao-Luliang-Darbut and Zhongguai-Mosuowan- Baijiahai-Qitai island arcs respectively) and intervened three approximately E-W trending

  14. Dynamic processes in the lithosphere leading to extension, rifting and basin formation

    NASA Astrophysics Data System (ADS)

    Anderson, Thomas

    2014-05-01

    The similarity of ages of extensional core complexes, co-genetic basin formation, and kinematically compatible movements along large strike-slip faults in western North America to ages of comparable events within the Himalayas-Alps orogenic belt leads to the speculation that strain related to changes in Pacific (PAC)-North America(NA) plate motions may be recorded on a global scale affecting the coupled plates and extending eastward across Eurasia. The contemporaneous global deformation reflects abrupt changes in PAC-NA plate motions in response to coupling following convergence of buoyant oceanic lithosphere, commonly part of a spreading center, which impedes subduction and leads to collision followed by coupling when the buoyant lithosphere binds against the base of the overriding continental plate. Critical coupling of a sufficiently long ridge segment leads to "capture", after which the former movements of the newly coupled plates are integrated abruptly and changed from previous directions. In western North America, episodes of capture of the NA plate by the (PAC) plate are recorded by break-up unconformities (ca. 55, 35, and 17 Ma) and basins commonly within extensional domains distinguished by age and direction of tectonic transport (Eocene [~55-42 Ma], ca. 285o, Oligocene [~35-20 Ma], 240o, Miocene [17-0 Ma], ca. 280o). The transport directions record the integration of the southwesterly motion of NA , related to mantle convection, and the northwesterly motion of PAC, driven by slab pull. Following each coupling event, PAC moves westward dragging: 1) the formerly subducting Farallon slab, 2) the coupled, formerly overriding, NA plate, and 3) Eurasia (EA), with it. In response to the strong extension that is imposed upon rocks within domains encompassed by the PAC-NA coupled region, and along the southern margin of Eurasia, brittle deformation, accommodated by normal and strike-slip faults, and formation of contemporaneous basins, takes place. Core

  15. Paleobotany and palynology of the Bristol Hill Coal Member (Bond Formation) and Friendsville Coal Member (Mattoon Formation) of the Illinois Basin (Upper Pennsylvanian)

    USGS Publications Warehouse

    Willard, D.A.; Phillips, T.L.

    1993-01-01

    Late Pennsylvanian coal swamps of the Illinois Basin were dominated by Psarnius tree ferns with a spatially heterogeneous distribution of medullosan pteridosperms (subdominant), calamites, sigillarian lycopsids, and cordaites. Miospore and coal-ball plant assemblages from the Missourian-age Bristol Hill Coal Member (Mattoon Formation) of southeastern Illinois were quantified to analyze vegetational patterns in Late Pennsylvanian peat swamps and to compare vegetational composition of the coals. -from Authors

  16. Reservoir characteristics of Putnam zone (Silurian Interlake Formation) lithofacies, southwestern Williston basin

    SciTech Connect

    Inden, R. ); Oglesby, C. ); Byrnes, A. ); Cluff, B. )

    1991-06-01

    Reservoirs in the Putnam zone (lower Interlake Formation) in the southwestern part of the Williston basin include oolitic-pellet dolomite grainstone, fossil-pellet grainstone, and a wide spectrum of reef-related, fossil-corral dolomite packstones and coral-stromatoporoid rudstone/boundstones. Each of these potential reservoirs has a unique pore system and, thus a different set of petrophysical properties which define their reservoir characteristics. Oolitic grainstones have a homogeneous intercrystalline-micro-crystalline pore system, whereas the fossil-pellet dolomite grainstone facies consists of separate mesovugs dispersed in well-interconnected intercrystalline porosity. Capillary pressure curves indicate that pore-throat heterogeneity is greater, and entry pressures lower, for reefal lithofacies than for pelletal grainstones. These curves also demonstrate why many of the producing fields tend to have high water cuts. In many oolitic-pellet grainstone units, irreducible water saturations of 10% would not be reached until a hydrocarbon column of 700 ft was reached. High water production characteristics are therefore expected because Red River/Interlake structures attain only 50-100 ft of closure. This, however, does not mean that Putnam is not an economic zone, especially as a secondary objective. Wells in Putnam and Crane fields, for instance, have reserves in excess of 300,000 bbl of oil. The reservoirs here may be dominated by the reef-related facies, which have an extremely high relative permeability to oil.

  17. Depositional model, dolomitization, and porosity of Henryhouse Formation (Silurian), Anadarko basin, Oklahoma

    SciTech Connect

    Beardall, G.B.

    1987-08-01

    The Upper Silurian Henryhouse Formation, which is part of the Hunton Group, is a major hydrocarbon reservoir in the Anadarko basin. Three basic lithofacies are present in the Henryhouse, based on sedimentary structures, lithology, fossil content, and fabric relationships. These facies, represented in general by massive lime mudstone with diverse fauna, burrowed dolowackestone/packstone with mainly crinoids, and massive to laminated dolomudstone with fenestral fabrics and sparse fauna, are inferred to represent subtidal, intertidal, and supratidal environments, respectively. These facies comprise a vertical sequence that represents regressive deposition. The Henryhouse consists of several of these sequences. The Henryhouse commonly is partly or completely dolomitized in western Oklahoma. Three stages of dolomitization were documented: (1) penecontemporaneous hypersaline dolomite occurring as brownish, hypidiotopic rhombs concentrated in the supratidal and intertidal facies, (2) mixed marine and freshwater dolomite occurring as white rims around preexisting hypersaline dolomite, and as subhedral, white rhombs in vugs and molds, and (3) deep-burial vug, mold, and fracture-filling saddle dolomite. Production in the Henryhouse is generally from porous zones in dolomite. However, lithofacies reflecting depositional environments in which they were formed are equally important in porosity development.

  18. Formation and Identification of Unresolved Complex Mixtures in Lacustrine Biodegraded Oil from Nanxiang Basin, China

    PubMed Central

    Guo, Pengfei; He, Sheng; Zhu, Shukui; Chai, Derong; Yin, Shiyan; Dai, Wei; Zhang, Wanfeng

    2014-01-01

    A comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) method has been developed for the formation and identification of unresolved complex mixtures (UCMs) in lacustrine biodegraded oils that with the same source rock, similar maturity, and increasing degradation rank from Nanxiang Basin, China. Normal alkanes, light hydrocarbons, isoprenoids, steranes, and terpanes are degraded gradually from oil B330 to oil G574. The compounds in biodegraded oil (oil G574) have fewer types, the polarity difference of compounds in different types is minor, and the relative content of individual compounds is similar. All the features make the compounds in biodegraded oil coelute in GC analysis and form the raised “baseline hump” named UCMs. By injecting standard materials and analyzing mass spectrums of target compounds, it is shown that cyclic alkanes with one to five rings are the major components of UCMs. Furthermore, UCMs were divided into six classes. Classes I and II, composed of alkyl-cyclohexanes, alkyl-naphthanes, and their isomers, are originated from the enrichment of hydrocarbons resistant to degradation in normal oils. Classes III ~ VI, composed of sesquiterpenoids, tricyclic terpanes, low molecular steranes, diasteranes, norhopanes, and their isomers, are probably from some newly formed compounds during the microbial transformation of oil. PMID:25177711

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

    SciTech Connect

    Castle, J.W.

    1988-01-01

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

  20. Belly River Formation of western Alberta, Canada: anatomy of an emerging deep basin oil play

    SciTech Connect

    Putnam, P.E.

    1989-03-01

    The Campanian Belly River Formation of western Alberta appears to form a largely bypassed deep basin type of oil play. In this setting hydrocarbons are found in lenticular fluvial reservoirs located upon folds or intersected by northwest-striking thrust faults and northeast-striking fractures. In the western fold and thrust belt, primary porosity is preserved within relatively thick and widespread grain-supported conglomerates. To the east, secondary porosity predominates in sandy lithofacies, and the best developed porosity is found proximal to fractures which enhanced fluid migration and grain dissolution. To the west, the unit exhibits progressive underpressuring, which reflects postorogenic sediment stripping combined with westward ground-water flow. A manifestation of the hydrodynamic regime is that many wells appear to have damaged Belly River zones because historically most exploration has been focused on deeper targets which require heavier mud weights. This style of hydrocarbon accumulation in the Belly River zone appears to cover several thousand square kilometers. The prior emphasis on deeper targets has also inhibited seismic delineation of Belly River reservoirs. Seismic acquisition must be designed to account for the relatively shallow depth and complex geometry of potential targets. Shear wave data appear to be a promising source of information in locating the distribution of reservoirs relative to fractures. The structural, depositional, diagenetic, and hydrodynamic development of the Belly River in western Alberta is similar to other clastic wedges formed during Laramide orogenic events. Thus, hydrocarbon accumulations may be anticipated in these other areas as well.

  1. Formation and identification of unresolved complex mixtures in lacustrine biodegraded oil from Nanxiang Basin, China.

    PubMed

    Guo, Pengfei; He, Sheng; Zhu, Shukui; Chai, Derong; Yin, Shiyan; Dai, Wei; Zhang, Wanfeng

    2014-01-01

    A comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) method has been developed for the formation and identification of unresolved complex mixtures (UCMs) in lacustrine biodegraded oils that with the same source rock, similar maturity, and increasing degradation rank from Nanxiang Basin, China. Normal alkanes, light hydrocarbons, isoprenoids, steranes, and terpanes are degraded gradually from oil B330 to oil G574. The compounds in biodegraded oil (oil G574) have fewer types, the polarity difference of compounds in different types is minor, and the relative content of individual compounds is similar. All the features make the compounds in biodegraded oil coelute in GC analysis and form the raised "baseline hump" named UCMs. By injecting standard materials and analyzing mass spectrums of target compounds, it is shown that cyclic alkanes with one to five rings are the major components of UCMs. Furthermore, UCMs were divided into six classes. Classes I and II, composed of alkyl-cyclohexanes, alkyl-naphthanes, and their isomers, are originated from the enrichment of hydrocarbons resistant to degradation in normal oils. Classes III ~ VI, composed of sesquiterpenoids, tricyclic terpanes, low molecular steranes, diasteranes, norhopanes, and their isomers, are probably from some newly formed compounds during the microbial transformation of oil.

  2. Gas, Water, and Oil Production from the Wasatch Formation, Greater Natural Buttes Field, Uinta Basin, Utah

    USGS Publications Warehouse

    Nelson, Philip H.; Hoffman, Eric L.

    2009-01-01

    Gas, oil, and water production data were compiled from 38 wells with production commencing during the 1980s from the Wasatch Formation in the Greater Natural Buttes field, Uinta Basin, Utah. This study is one of a series of reports examining fluid production from tight gas reservoirs, which are characterized by low permeability, low porosity, and the presence of clay minerals in pore space. The general ranges of production rates after 2 years are 100-1,000 mscf/day for gas, 0.35-3.4 barrel per day for oil, and less than 1 barrel per day for water. The water:gas ratio ranges from 0.1 to10 barrel per million standard cubic feet, indicating that free water is produced along with water dissolved in gas in the reservoir. The oil:gas ratios are typical of a wet gas system. Neither gas nor water rates show dependence upon the number of perforations, although for low gas-flow rates there is some dependence upon the number of sandstone intervals that were perforated. Over a 5-year time span, gas and water may either increase or decrease in a given well, but the changes in production rate do not exhibit any dependence upon well proximity or well location.

  3. Peritidal cyclic sedimentation from La Manga Formation (Oxfordian), Neuquén Basin, Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Palma, Ricardo M.; Kietzmann, Diego A.; Bressan, Graciela S.; Martín-Chivelet, Javier; López-Gómez, José; Farias, María E.; Iglesias Llanos, María P.

    2013-11-01

    The La Manga Formation consists of marine carbonates and represents most of the sedimentary record of the Callovian-Oxfordian in the Neuquén Basin. Three localities in the southern Mendoza province were studied and their cyclicity was determined by means of facies analysis and their vertical arrangement. Facies of inner ramp, that were deposited in extremely shallow-water environments with intermittent subaerial exposures have been broken down into shallow subtidal, and intertidal-supratidal environments. Shallow subtidal facies are arranged into decimetre scale upward-shallowing cycles composed of marls, laminated or massive mudstones or bioclastic wackestones and intraclastic wackestone-packstones. Intertidal-supratidal centimetre-scale cycles consist of an upward-shallowing succession of restricted facies, overlaid by horizontal or crinkle microbial laminites, flat pebble conglomerates or breccias beds. The defined cycles show a shallowing upward trend in which the evidence of relative sea-level lowering is accepted. The interpretation of Fischer plots allowed the recognition of changes in accommodation space.

  4. Exploration for shallow, compaction-induced gas accumulations, Fort Union Formation, Powder River Basin, Wyoming

    SciTech Connect

    Oldham, D.W.

    1996-06-01

    Commercial quantities of gas have been produced from shallow sandstone reservoirs of the Fort Union Formation (Paleocene) in the Powder River Basin of Wyoming. The two largest accumulations discovered to date, Oedekoven and Chan pools, were drilled on prospects which invoked differential compaction as a mechanism for gas entrapment and prospect delineation. Gas is believed to have accumulated in localized structural highs early in the burial history of lenticular sands. Structural relief is due to the compaction contrast between sand and stratigraphically-equivalent fine-grained sediments. A shallow Fort Union gas play was based on reports of shallow gas shows, the occurrence of thick coals which could have served as sources for bacterial gas, and the presence of lenticular sandstones which may have promoted the development of compaction structures early in the burial process, to which bacterial gas migrated. Five geologic elements related to compactional trap development were used to rank prospects. Drilling of the Oedekoven prospect, which possessed all prospect elements, led to the discovery of the Oedekoven Fort Union gas pool at a depth of 340 ft (104 m). The uncemented, very fine grained, well-sorted {open_quotes}Canyon sand{close_quotes} pay has extremely high intergranular porosity. Low drilling and completion costs associated with shallow, high-permeability reservoirs, an abundance of subsurface control with which to delineate prospects, and existing gas-gathering systems make Fort Union sandstones attractive primary targets in shallow exploration efforts as well as secondary objectives in deeper drilling programs.

  5. The nonopaque, detrital heavy mineralogy of the Morrison Formation near Crownpoint, San Juan Basin, New Mexico

    USGS Publications Warehouse

    Hansley, Paula L.

    1983-01-01

    Description and quantification of the nonopaque, detrital heavy mineralogy of the Upper Jurassic Morrison Formation in the southwestern part of the San Juan Basin have helped to identify stratigraphic trends, source-area lithologies, and zones of post-depositional alteration possibly related to uranium mineralization. A synthesis of stratigraphic variations in mineral species and diversity in Morrison sandstones reveals an increasing upward igneous component, characterized by euhedral zircon and subhedral apatite. Complementing this trend, the predominantly well-rounded assemblage of the Recapture Member changes to a mixed assemblage of rounded and angular grains in the Westwater Canyon Member. Overall, the low diversity in mineral species indicates a sedimentary, low- to medium-grade-metamorphic, and acid igneous parentage for Morrison sediments; however, post-depositional processes have played a significant role in determining the present mineralogy. The roles that diagenesis and weathering have played in determining the present aspect of the assemblage, which is a mature garnet-zircon-apatite-tourmaline suite, cannot be overemphasized. For instance, the presence of authigenically etched to skeletal garnet and staurolite implies that entire grains have been destroyed. Comparison of cores with measured sections indicates that near-surface weathering has caused the destruction of some minerals, notably apatite, sensitive to acidic conditions. Therefore, in order to interpret the sedimentology, stratigraphic intervals in which post-depositional processes have affected the mineralogy were identified. These diagenetic zones may prove to be most useful in delineating the past movements and compositions of interstitial, possibly ore-forming, fluids.

  6. Sequence stratigraphy and stratigraphic trap potential of the Villeta Formation (Cretaceous), Putumayo Basin, Columbia

    SciTech Connect

    Robertson, H.C.; Cregg, A.; Cleveland, G.

    1996-12-31

    The Villeta Formation, which was deposited in -15 Ma (Cenomanian-Campanian), includes four 3rd-order sequences representing marine shelf, siliciclastic shoreface, and lower coastal-plain environments. Although these environments transgressed landward across the pre-Cretaceous basement during a 2nd-order base-level rise, several brief but important base-level falls and abrupt basinward and downward facies-shifts interrupted this trend. The 3rd-order base-level falls and subsequent transgressions led to the deposition of important hydrocarbon-bearing sandstones in the Villeta Formation. Sequence boundaries record abrupt downward facies shifts and separate black marine shales and deep-shelf limestones below from fluvial to tidally- and wave-influenced shoreface sandstones above. Each of these sands (Arenisca T, U inferior, U superior, and M2) laps out landward and passes upward into transgressive shales and thin highstand limestones. Base-level rise and retrogradation of the shoreline is indicated by upward thinning of transgressive sandstones and upward increase in marine shale. Sandstones thin or downlap basinward into shales. Transgressive deposits dominate the sequences. Highstand progradation of siliciclastic shorelines was minimal and limited by a relatively high accommodation/sediment-supply ratio. Base-level falls, however, allowed shorelines to advance basinward long distances. The stratigraphic geometries of the Villeta sandstones, as indicated by seismic data and well-log correlations, indicate that potentially large stratigraphic traps are present in the Putumayo Basin. Stratigraphic entrapment is indicated by landward onlap of the Villeta sandstones, the presence of shales and tight limestones overlying porous sandstones, and known hydrocarbon accumulations in the sandstones over structural highs.

  7. Sequence stratigraphy and stratigraphic trap potential of the Villeta Formation (Cretaceous), Putumayo Basin, Columbia

    SciTech Connect

    Robertson, H.C. ); Cregg, A.; Cleveland, G. )

    1996-01-01

    The Villeta Formation, which was deposited in -15 Ma (Cenomanian-Campanian), includes four 3rd-order sequences representing marine shelf, siliciclastic shoreface, and lower coastal-plain environments. Although these environments transgressed landward across the pre-Cretaceous basement during a 2nd-order base-level rise, several brief but important base-level falls and abrupt basinward and downward facies-shifts interrupted this trend. The 3rd-order base-level falls and subsequent transgressions led to the deposition of important hydrocarbon-bearing sandstones in the Villeta Formation. Sequence boundaries record abrupt downward facies shifts and separate black marine shales and deep-shelf limestones below from fluvial to tidally- and wave-influenced shoreface sandstones above. Each of these sands (Arenisca T, U inferior, U superior, and M2) laps out landward and passes upward into transgressive shales and thin highstand limestones. Base-level rise and retrogradation of the shoreline is indicated by upward thinning of transgressive sandstones and upward increase in marine shale. Sandstones thin or downlap basinward into shales. Transgressive deposits dominate the sequences. Highstand progradation of siliciclastic shorelines was minimal and limited by a relatively high accommodation/sediment-supply ratio. Base-level falls, however, allowed shorelines to advance basinward long distances. The stratigraphic geometries of the Villeta sandstones, as indicated by seismic data and well-log correlations, indicate that potentially large stratigraphic traps are present in the Putumayo Basin. Stratigraphic entrapment is indicated by landward onlap of the Villeta sandstones, the presence of shales and tight limestones overlying porous sandstones, and known hydrocarbon accumulations in the sandstones over structural highs.

  8. Origin of tuff deposits in the lower Miocene Lospe Formation, Santa Maria basin, California

    SciTech Connect

    Cole, R.B. ); Stanley, R.G. ); Johnson, S.Y. )

    1991-02-01

    The Lospe Formation contains at least five mappable tuff units (17-18 Ma) which were erupted during initial stages of Neogene Santa Maria basin subsidence. Individual tuff units are lenticular, as much as 15-20 m thick, and 1-3 km wide; they were deposited predominantly in a lacustrine setting. Subaqueous deposition is indicated by facies of the interbedded nonvolcanic Lospe Formation. The lowermost Lospe Tuff unit, however, which overlies Jurassic basement, is interpreted as a subaerial deposit. Each subaqueous tuff unit contains two or more eruption units. Each eruption unit consists of three zones which are, from base to top: (1) massive vitric tuff comprising about 50% of the eruption unit, (2) thin- to medium-bedded vitric tuff with pumice concentrations at the tops of beds and mud drapes between beds, and (3) a thin-bedded interval of massive to planar laminated tuffaceous siltstone-mudstone. The predominance of delicate cuspate vitric shards and pumice, and the near absence of nonvolcanic detritus indicates that little or no reworking of the ash occurred prior to deposition. The Lospe tuffs are predominantly distal pyroclastic flow (zones 1 and 2) and pyroclastic turbidite (zones 2 and 3) deposits, derived from subaerial magmatic eruptions. A possible source for the Lospe tuffs is located at Tranquillon Mountain, 30 km to the south in the westernmost Transverse Range, where 17-18 Ma proximal pyroclastic deposits of welded lithic tuff breccia and thick pumiceous fallout tuffs are present. The similar ages, stratigraphic positions, and petrology, as well as the lateral facies relations suggests a correlation between the Tranquillon volcanic center and the Lospe tuff units. The authors are currently testing this hypothesis on the basis of geochemical and isotopic analyses.

  9. New discoveries of early Paleocene (Torrejonian) primates from the Nacimiento Formation, San Juan Basin, New Mexico.

    PubMed

    Silcox, Mary T; Williamson, Thomas E

    2012-12-01

    Primates underwent a period of diversification following the extinction of non-avian dinosaurs. Although the Order first appeared near the Cretaceous-Paleogene boundary, it is not until the Torrejonian (the second North American Land Mammal Age of the Paleocene) that a diversity of families began to emerge. One of the lithological units critical to understanding this first primate adaptive radiation is the early Paleocene Nacimiento Formation of the San Juan Basin (SJB; New Mexico). Primates previously described from this formation comprise six species of palaechthonid and paromomyid plesiadapiforms, all known from very limited material. Collecting has increased the sample of primate specimens more than fivefold. Included in the new sample is the first specimen of a picrodontid plesiadapiform from the Torrejonian of the SJB, referable to Picrodus calgariensis, and the first paromomyid specimen complete enough to allow for a species level taxonomic assignment, representing a new species of Paromomys. With respect to the 'Palaechthonidae', the current report describes large collections of Torrejonia wilsoni and Palaechthon woodi, and the first new specimens attributed to Plesiolestes nacimienti and Anasazia williamsoni since 1972 and 1994, respectively. These collections demonstrate previously unknown morphological variants, including the presence of a metaconid on the p4 of some specimens of T. wilsoni, a discovery that supports previous inferences about a close relationship between Torrejonia and Plesiolestes problematicus. This new sample considerably improves our knowledge of the poorly understood 'Palaechthonidae', and about the biostratigraphy, biogeography, and early evolution of North American primates. In particular, the rarity of paromomyids, the continuing absence of plesiadapid and carpolestid plesiadapiforms, and the presence of a number of endemic palaechthonid species in the SJB contrast with plesiadapiform samples from contemporaneous deposits to the

  10. Estimation of subsurface formation temperature in the Tarim Basin, northwest China: implications for hydrocarbon generation and preservation

    NASA Astrophysics Data System (ADS)

    Liu, Shaowen; Lei, Xiao; Feng, Changge; Hao, Chunyan

    2016-07-01

    Subsurface formation temperature in the Tarim Basin, northwest China, is vital for assessment of hydrocarbon generation and preservation, and of geothermal energy potential. However, it has not previously been well understood, due to poor data coverage and a lack of highly accurate temperature data. Here, we combined recently acquired steady-state temperature logging data with drill stem test temperature data and measured rock thermal properties, to investigate the geothermal regime and estimate the subsurface formation temperature at depth in the range of 1000-5000 m, together with temperatures at the lower boundary of each of four major Lower Paleozoic marine source rocks buried in this basin. Results show that heat flow of the Tarim Basin ranges between 26.2 and 66.1 mW/m2, with a mean of 42.5 ± 7.6 mW/m2; the geothermal gradient at depth of 3000 m varies from 14.9 to 30.2 °C/km, with a mean of 20.7 ± 2.9 °C/km. Formation temperature estimated at the depth of 1000 m is between 29 and 41 °C, with a mean of 35 °C, while 63-100 °C is for the temperature at the depth of 3000 m with a mean of 82 °C. Temperature at 5000 m ranges from 97 to 160 °C, with a mean of 129 °C. Generally spatial patterns of the subsurface formation temperature at depth are basically similar, characterized by higher temperatures in the uplift areas and lower temperatures in the sags, which indicates the influence of basement structure and lateral variations in thermal properties on the geotemperature field. Using temperature to identify the oil window in the source rocks, most of the uplifted areas in the basin are under favorable condition for oil generation and/or preservation, whereas the sags with thick sediments are favorable for gas generation and/or preservation. We conclude that relatively low present-day geothermal regime and large burial depth of the source rocks in the Tarim Basin are favorable for hydrocarbon generation and preservation. In addition, it is found that the

  11. Palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin, northern South China Sea.

    PubMed

    Li, Wenhao; Zhang, Zhihuan; Wang, Weiming; Lu, Shuangfang; Li, Youchuan; Fu, Ning

    2014-01-01

    The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter.

  12. Palaeoenvironment and Its Control on the Formation of Miocene Marine Source Rocks in the Qiongdongnan Basin, Northern South China Sea

    PubMed Central

    Li, Wenhao; Zhang, Zhihuan; Wang, Weiming; Lu, Shuangfang; Li, Youchuan; Fu, Ning

    2014-01-01

    The main factors of the developmental environment of marine source rocks in continental margin basins have their specificality. This realization, in return, has led to the recognition that the developmental environment and pattern of marine source rocks, especially for the source rocks in continental margin basins, are still controversial or poorly understood. Through the analysis of the trace elements and maceral data, the developmental environment of Miocene marine source rocks in the Qiongdongnan Basin is reconstructed, and the developmental patterns of the Miocene marine source rocks are established. This paper attempts to reveal the hydrocarbon potential of the Miocene marine source rocks in different environment and speculate the quality of source rocks in bathyal region of the continental slope without exploratory well. Our results highlight the palaeoenvironment and its control on the formation of Miocene marine source rocks in the Qiongdongnan Basin of the northern South China Sea and speculate the hydrocarbon potential of the source rocks in the bathyal region. This study provides a window for better understanding the main factors influencing the marine source rocks in the continental margin basins, including productivity, preservation conditions, and the input of terrestrial organic matter. PMID:25401132

  13. Basin Analysis of the Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain, Final Report and Topical Reports 5-8 on Smackover Petroleum system and Underdevelopment Reservoirs

    SciTech Connect

    Mancini, Ernest A.; Puckett, T. Markham; Parcell, William C.; Llinas, Juan Carlos; Kopaska-Merkel, David C.; Townsend, Roger N.

    2002-03-05

    The Smackover Formation, a major hydrocarbon-producing horizon in the Mississippi Interior Salt Basin (MISB), conformably overlies the Norphlet Formation and is conformably overlain by the Buckner Anhydrite Member of the Haynesville Formation. The Norphlet-Smackover contact can be either gradational or abrupt. The thickness and lithofacies distribution of the Smackover Formation were controlled by the configuration of incipient paleotopography. The Smackover Formation has been subdivided into three informal members, referred to as the lower, middle and upper members.

  14. Iron and manganese shuttles control the formation of authigenic phosphorus minerals in the euxinic basins of the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Jilbert, Tom; Slomp, Caroline P.

    2013-04-01

    Microanalysis of epoxy resin-embedded sediments is used to demonstrate the presence of authigenic iron (Fe) (II) phosphates and manganese (Mn)-calcium (Ca)-carbonate-phosphates in the deep euxinic basins of the Baltic Sea. These minerals constitute major burial phases of phosphorus (P) in this area, elevating the total P burial rate above that expected for a euxinic depositional environment. Particle shuttles of Fe and Mn oxides into the deep euxinic basins act as drivers for P-bearing mineral authigenesis. While Fe(II) phosphates are formed continuously in the upper sediments following the sulfidization of Fe-oxyhydroxides and release of associated P, Mn-Ca-carbonate-phosphates are formed intermittently following inflow events of oxygenated North Sea water into the deep basins. The mechanism of Fe(II) phosphate formation differs from previously reported occurrences of vivianite formation in marine sediments, by occurring within, rather than below, the sulfate-methane transition zone. The spatial distribution of both authigenic phases in Baltic sediments varies in accordance with the periodic expansion of anoxia on centennial to millennial timescales. The results highlight the potential importance of authigenic P-bearing minerals other than carbonate fluorapatite for total P burial in euxinic basins.

  15. Detailed cross sections of the Eocene Green River Formation along the north and east margins of the Piceance Basin, western Colorado, using measured sections and drill hole information

    USGS Publications Warehouse

    Johnson, Ronald C.

    2014-01-01

    This report presents two detailed cross sections of the Eocene Green River Formation in the Piceance Basin, northwestern Colorado, constructed from eight detailed measured sections, fourteen core holes, and two rotary holes. The Eocene Green River Formation in the Piceance Basin contains the world’s largest known oil shale deposit with more than 1.5 billion barrels of oil in place. It was deposited in Lake Uinta, a long-lived saline lake that once covered much of the Piceance Basin and the Uinta Basin to the west. The cross sections extend across the northern and eastern margins of the Piceance Basin and are intended to aid in correlating between surface sections and the subsurface in the basin.

  16. Assessment of in-place oil shale resources of the Green River Formation, Greater Green River Basin in Wyoming, Colorado, and Utah

    USGS Publications Warehouse

    Johnson, R.C.; Mercier, T.J.; Brownfield, M.E.

    2011-01-01

    The U.S. Geological Survey (USGS) recently (2011) completed an assessment of in-place oil shale resources, regardless of grade, in the Eocene Green River Formation of the Greater Green River Basin in southwestern Wyoming, northwestern Colorado, and northeastern Utah. Green River Formation oil shale also is present in the Piceance Basin of western Colorado and in the Uinta Basin of eastern Utah and western Colorado, and the results of these assessments are published separately. No attempt was made to estimate the amount of oil that is economically recoverable because there has not yet been an economic method developed to recover the oil from Green River Formation oil shale.

  17. Paleontology and sedimentology of upper clastic member of Wanakah Formation, Chama basin, New Mexico: Lacustrine paleoenvironmental implications

    SciTech Connect

    Good, S.J.; Ridgley, J.L. )

    1989-09-01

    Lacustrine strata of the upper part of the Jurassic Wanakah Formation were restricted to the Chama basin of north-central New Mexico by mid-Jurassic tectonic activity in the Brazos and Nacimiento uplifts and along the Gallina-Archuleta anticlinorium. Lateral and vertical facies of the upper Wanakah exposed around the southern margin of the Chama basin indicate that the deeper part of the lake was north of the outcrop belt. The upper 3-5 m of the Wanakah consists of thin-bedded rippled sandstone, interbedded mudstone, and limestone containing trace fossils and freshwater mollusks characteristic of marginal lacustrine facies. Taphonomic studies of mollusks in the Wanakah Formation have been combined with application of ecophenotypic variation documented in extant unionid bivalves to produce paleoenvironmental interpretations of these lacustrine rocks.

  18. Sulphur isotope geochemistry of pyrite from the Upper Cretaceous Marshybank Formation, Western Interior Basin

    NASA Astrophysics Data System (ADS)

    McKay, J. L.; Longstaffe, F. J.

    2003-04-01

    Variations in the texture and sulphur isotopic composition of pyrite in the Upper Cretaceous Marshybank Formation are linked to depositional environment. Abundant, framboidal (and lesser euhedral) pyrite precipitated in offshore marine rocks. Moderate quantities of pyrite also crystallized in brackish, coastal plain rocks. However, in contrast to marine pyrite, coastal plain pyrite is dominantly euhedral in texture, reflecting direct precipitation from a porewater with a relatively low dissolved sulphide concentration. In the marine rocks, pyrite δ34S values range from -35.7‰ to +27.4‰ (avg. -4.8‰ Canyon Diablo Troilite, CDT). Pyrite within carbonate concretions hosted in these marine rocks has a similar isotopic composition (-49.8‰ to +10.6‰ CDT). However, isotopic values are often highly variable within individual concretions as a result of the heterogeneous nature of sulphate reduction and pyrite formation within marine sediments. Pyrite in coastal plain rocks is characterized by relatively high δ34S values (-4.2‰ to +35.5‰, avg. +13.2‰ CDT), while the overlying sideritized conglomerates have the lowest δ34S values reported for Cretaceous rocks from the Western Interior Basin of North America (-49.8‰ to -41.7‰ CDT). Very low δ34S values, which are only observed in the marine rocks, are indicative of microbial sulphate reduction and pyrite formation in a sulphate-replete (i.e., open) system. Higher δ34S values (up to +18‰), which were obtained for both the marine and coastal plain rocks, are indicative of progressive pyrite crystallization in a sulphate-limited (i.e., closed) system. Such conditions are expected in marine sediments as burial occurs, and in brackish (i.e., low sulphate) sediments. Pyrite with very high δ34S values (>+18‰) is common in the coastal plain rocks. These high values are the result of influx of 34S-enriched, residual sulphide derived from overlying marine units. A minor amount of 34S-enriched pyrite is also

  19. Constraining back-arc basin formation in the eastern Coral Sea: preliminary results from the ECOSAT voyage

    NASA Astrophysics Data System (ADS)

    Seton, M.; Williams, S.; Mortimer, N. N.; Meffre, S.; Moore, J.; Micklethwaite, S.; Zahirovic, S.

    2013-12-01

    The eastern Coral Sea region is an underexplored area at the northeastern corner of the Australian plate, where long-lived interaction between the Pacific and Australian plate boundaries has resulted in an intricate assemblage of deep oceanic basins and ridges, continental fragments and volcanic products. A paucity of marine geophysical and geological data from this complex region has resulted in the lack of a clear conceptual framework to describe its formation, ultimately affecting our understanding of the connection between the plate boundaries of the SW Pacific and SE Asia. In particular, the tectonic relationship between two back-arc basins, the Santa Cruz and d'Entrecasteaux Basins, and the South Rennell Trough, has yet to be resolved. In October-November, 2012, we collected 6,200 km of marine magnetic, 6,800 km of gravity and over 13,600 km2 of swath bathymetry data from the eastern Coral Sea onboard the RV Southern Surveyor. A complementary dredging program yielded useful samples from 14 seafloor sites. Our preliminary geochemical interpretation of the dredge samples obtained from the South Rennell Trough reveal volcanic rocks resembling MORB or BABB-type basalts, similar in composition to the recently re-analysed and dated ORSTOM dredges from the area that yielded ~28 Ma MORB-like basalts. Swath bathymetry profiles from the Santa Cruz Basin reveal that the South Rennell Trough extends into this basin, with seafloor spreading fabric being parallel to the trough. Preliminary analysis of the three full and four partial new magnetic anomaly profiles across the Santa Cruz Basin, coupled with limited existing profiles, reveals that the basin may have formed between Chrons 13-18 (~32-38 Ma), with an extinct spreading ridge along the inferred continuation of the South Rennell Trough, consistent with ORSTOM age dates. Our results suggest that the South Rennell Trough is an extinct southwestward propagating spreading ridge, which may have initiated along a pre

  20. New occurrences of fossilized feathers: systematics and taphonomy of the Santana Formation of the Araripe Basin (Cretaceous), NE, Brazil

    PubMed Central

    Anelli, Luiz Eduardo; Petri, Setembrino; Romero, Guilherme Raffaeli

    2016-01-01

    Here we describe three fossil feathers from the Early Cretaceous Santana Formation of the Araripe Basin, Brazil. Feathers are the most complex multiform vertebrate integuments; they perform different functions, occurring in both avian and non-avian dinosaurs. Despite their rarity, fossil feathers have been found across the world. Most of the Brazilian feather fossil record comes from the Santana Formation. This formation is composed of two members: Crato (lake) and Romualdo (lagoon); both of which are predominantly reduced deposits, precluding bottom dwelling organisms, resulting in exceptional preservation of the fossils. Despite arid and hot conditions during the Cretaceous, life teemed in the adjacency of this paleolake. Feathered non-avian dinosaurs have not yet been described from the Crato Member, even though there are suggestions of their presence in nearby basins. Our description of the three feathers from the Crato laminated limestone reveals that, despite the small sample size, they can be referred to coelurosaurian theropods. Moreover, based on comparisons with extant feather morphotypes they can be identified as one contour feather and two downy feathers. Despite their rareness and low taxonomic potential, fossilized feathers can offer insights about the paleobiology of its owners and the paleoecology of the Araripe Basin. PMID:27441102

  1. New occurrences of fossilized feathers: systematics and taphonomy of the Santana Formation of the Araripe Basin (Cretaceous), NE, Brazil.

    PubMed

    Prado, Gustavo M E M; Anelli, Luiz Eduardo; Petri, Setembrino; Romero, Guilherme Raffaeli

    2016-01-01

    Here we describe three fossil feathers from the Early Cretaceous Santana Formation of the Araripe Basin, Brazil. Feathers are the most complex multiform vertebrate integuments; they perform different functions, occurring in both avian and non-avian dinosaurs. Despite their rarity, fossil feathers have been found across the world. Most of the Brazilian feather fossil record comes from the Santana Formation. This formation is composed of two members: Crato (lake) and Romualdo (lagoon); both of which are predominantly reduced deposits, precluding bottom dwelling organisms, resulting in exceptional preservation of the fossils. Despite arid and hot conditions during the Cretaceous, life teemed in the adjacency of this paleolake. Feathered non-avian dinosaurs have not yet been described from the Crato Member, even though there are suggestions of their presence in nearby basins. Our description of the three feathers from the Crato laminated limestone reveals that, despite the small sample size, they can be referred to coelurosaurian theropods. Moreover, based on comparisons with extant feather morphotypes they can be identified as one contour feather and two downy feathers. Despite their rareness and low taxonomic potential, fossilized feathers can offer insights about the paleobiology of its owners and the paleoecology of the Araripe Basin.

  2. New occurrences of fossilized feathers: systematics and taphonomy of the Santana Formation of the Araripe Basin (Cretaceous), NE, Brazil.

    PubMed

    Prado, Gustavo M E M; Anelli, Luiz Eduardo; Petri, Setembrino; Romero, Guilherme Raffaeli

    2016-01-01

    Here we describe three fossil feathers from the Early Cretaceous Santana Formation of the Araripe Basin, Brazil. Feathers are the most complex multiform vertebrate integuments; they perform different functions, occurring in both avian and non-avian dinosaurs. Despite their rarity, fossil feathers have been found across the world. Most of the Brazilian feather fossil record comes from the Santana Formation. This formation is composed of two members: Crato (lake) and Romualdo (lagoon); both of which are predominantly reduced deposits, precluding bottom dwelling organisms, resulting in exceptional preservation of the fossils. Despite arid and hot conditions during the Cretaceous, life teemed in the adjacency of this paleolake. Feathered non-avian dinosaurs have not yet been described from the Crato Member, even though there are suggestions of their presence in nearby basins. Our description of the three feathers from the Crato laminated limestone reveals that, despite the small sample size, they can be referred to coelurosaurian theropods. Moreover, based on comparisons with extant feather morphotypes they can be identified as one contour feather and two downy feathers. Despite their rareness and low taxonomic potential, fossilized feathers can offer insights about the paleobiology of its owners and the paleoecology of the Araripe Basin. PMID:27441102

  3. Glacial recharge and paleohydrologic flow systems in the Illinois basin: Evidence from chemistry of Ordovician carbonate (Galena) formation waters

    SciTech Connect

    Stueber, A.M. ); Walter, L.M. )

    1994-11-01

    The Illinois basin provides an opportune setting for elucidating the roles of remnant evaporite brines and meteoric waters in the evolution of formation waters in an intracratonic sedimentary basin. Formation waters from carbonate reservoirs in the Upper Ordovician Galena Group have been analyzed geochemically to study the origin of their salinity, their chemical and isotopic evolution, and their relationship to paleohydrologic flow systems. Chloride/bromide ratios and Cl/Br-Na/Br relations indicate that initial brine salinity resulted from subaerial evaporation of seawater rather than from halite dissolution. Subsequent subsurface dilution of the brines by meteoric waters is disclosed by [delta]D-[delta][sup 18]O covariance; however, the remnant evaporite brine has not been completely expelled from these Ordovician strata. Galena formation waters have [sup 87]Sr/[sup 86]Sr ratios that range from 0.708 17 (a value nearly equal to that of coeval seawater) to 0.710 43. This is the greatest range of Sr isotopic ratios found in waters from any stratigraphic unit in the basin. Two fluid mixing events are revealed in plots of [sup 87]Sr/[sup 86]Sr vs. 1/Sr. 41 refs., 11 figs., 1 tab.

  4. Makah Formation; a deep-marginal-basin sequence of late Eocene and Oligocene age in the northwestern Olympic Peninsula, Washington

    USGS Publications Warehouse

    Snavely, P. D.; Niem, A.R.; MacLeod, N.S.; Pearl, J.E.; Rau, W.W.

    1980-01-01

    The Makah Formation of the Twin River Group crops out in a northwest-trending linear belt in the northwesternmost part of the Olympic Peninsula, Wash. This marine sequence consists of 2800 meters of predominantly thin-bedded siltstone and sandstone that encloses six distinctive newly named members--four thick-bedded amalgamated turbidite sandstone members, an olistostromal shallow-water marine sandstone and conglomerate member, and a thin-bedded water-laid tuff member. A local unconformity of submarine origin occurs within the lower part of the Makah Formation except in the central part of the study area, where it forms the contact between the older Hoko River Formation and the Makah. Foraminiferal faunas indicate that the Makah Formation ranges in age from late Eocene (late Narizian) to late Oligocene (Zemorrian) and was deposited in a predominantly lower to middle bathyal environment. The Makah Formation is part of a deep-marginalbasin facies that crops out in the western part of the Olympic Peninsula, in southwesternmost Washington and coastal embayments in northwestern Oregon, and along the central part of the coast of western Vancouver Island. On the basis of limited subsurface data from exploratory wells, correlative deep-marginal-basin deposits underlie the inner continental shelf of Oregon and the continental shelf (Tofino basin) along the southwestern side of Vancouver Island. Directional structures in the Makah Formation indicate that the predominantly lithic arkosic sandstone that forms the turbidite packets was derived from the northwest. A possible source of the clastic material is the dioritic, granitic, and volcanic terranes in the vicinity of the Hesquiat Peninsula and Barkley Sound on the west coast of Vancouver Island. Vertical and lateral variations of turbidite facies suggest that the four packets of sandstone were formed as depositional lobes on an outer submarine fan. The thin-bedded strata between the turbidite packets have characteristics of

  5. Dolomitized cells within chert of the Permian Assistência Formation, Paraná Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Calça, Cléber P.; Fairchild, Thomas R.; Cavalazzi, Barbara; Hachiro, Jorge; Petri, Setembrino; Huila, Manuel Fernando Gonzalez; Toma, Henrique E.; Araki, Koiti

    2016-04-01

    Dolomitic microscopic structures in the form of microspheres, "horseshoe- shaped" objects, and thin botryoidal crusts found within microfossiliferous chert within stromatolites of the Evaporite Bed (EB) of the Permian Assistência Formation, Irati Subgroup, Paraná Basin, Brazil, have been investigated by means of optical microscopy, X-ray fluorescence, scanning electron microscopy, Raman spectrometry and energy-dispersive X-ray spectrometry. The microspheres were identified as dolomitized coccoidal cyanobacteria based on similarity in size, spheroidal and paired hemispheroidal morphologies and colonial habit to co-occurring silicified organic-walled cyanobacteria embedded within the same microfabric and rock samples. The co-occurrence of dolomite, pyrite framboids, and abundant dispersed carbonaceous material and silicified cells is consistent with a hypersaline depositional environment with abundant cyanobacterial mats and elevated Mg2 +/Ca2 + ratios and reducing conditions with active anoxic microbial processes near the water-(bio)sediment interface. The abundance of extracellular polymeric substances facilitated anoxic microbial processes (sulfate reduction), providing essential conditions for possible primary microbially induced dolomitization. In most of the dolomitized cells dolomite occurs only as an external layer; in fully dolomitized cells magnesium is richest in the outermost layer. Presumably, the dolomitization process was favored by the presence of anoxic microbial degraders and negatively charged functional groups at the surface of the cyanobacterial cells. Botryoidal dolomite rims of silica-filled fenestrae formed by a similar process and inherited the botryoidal morphology of the cell as originally lining the fenestrae. Silicification interrupted the dolomitization of the largely organic biosediment, mostly by permineralization, but locally by substitution, thereby preserving not only dolomitic microspheres, but also huge numbers of structurally

  6. RESERVOIR CHARACTERIZATION OF THE LOWER GREEN RIVER FORMATION, SOUTHWEST UINTA BASIN, UTAH

    SciTech Connect

    S. Robert Bereskin

    2003-02-11

    Anastamosing, low gradient distributary channels produce {approx}30 gravity, paraffinic oils from the Middle Member of the lacustrine Eocene Green River Formation in the south-central portion of the Uinta Basin. This localized depocenter was situated along the fluctuating southern shoreline of Lake Uinta, where complex deposits of marginal-lacustrine to lower delta plain accumulations are especially characteristic. The Middle Member contains several fining-upward parasequences that can be recognized in outcrop, core, and downhole logs. Each parasequence is about 60 to 120 feet thick and consists of strata deposited during multiple lake level fluctuations that approach 30 to 35 feet in individual thickness. Such parasequences represent 300,000-year cycles based on limited absolute age dating. The subaerial to subaqueous channels commonly possess an erosional base and exhibit a fining upward character. Accordingly, bedding features commonly range from large-scale trough and planar cross bedding or lamination at the base, to a nonreservoir, climbing ripple assemblage near the uppermost reservoir boundary. The best reservoir quality occurs within the laminated to cross-stratified portions, and the climbing ripple phase usually possesses more deleterious micas and/or detrital clays. Diagenesis also exerts a major control on reservoir quality. Certain sandstones were cemented by an early, iron-poor calcite cement, which can be subsequently leached. Secondary intergranular porosity (up to 20%) is largely responsible for the 10 -100 millidarcy rock, which represents petrophysical objectives for both primary and secondary production. Otherwise, intense compaction, silicic and iron-rich carbonate cements, and authigenic clays serve to reduce reservoir quality to marginal economic levels.

  7. Petrology, geochemistry, and palynology of Joggins Formation (Westphalian A) coals, Cumberland basin, Nova Scotia

    SciTech Connect

    Hower, J.C.; Calder, J.H.; Cortland, F.E.

    1996-09-01

    Five Westphalian A coals were collected from the Joggins Formation section exposed along Chignecto Bay at Joggins, Nova Scotia. Several of the coal beds along the bay were mined beginning in the early 17th century. There has been little detailed investigation of the coal beds of this classic section. The lowermost coal, the Upper Coal 29 (Fundy), is a high-vitrinite coal with a spore assemblage dominated by arboreous lycopod spores with tree ferns subdominant. The upper portions of the coal bed have the highest ratio of well-preserved to poorly-preserved telinite of any of the coals investigated. Coal 19 (Forty Brine) has 88% total vitrinite but, unlike the Fundy coal bed, the telinite has a poor preservation ratio and half of the total vitrinite population comprises gelocollinite and vitrodetrinite. The latter coal bed is directly overlain by a basin-wide limestone bed. The Lower Kimberly (Coal 15) shows good preservation of vitrinite with relatively abundant telinite among the total vitrinite. The Upper Kimberly, which underlies the tetrapod-bearing lycopsid trees found by Lyell and Dawson in 1852, exhibits an upward decrease in arboreous lycopod spores and an increase in the tree fern spore Punctatisporites minutus. The megaspore record is similarly dominated by Lagenicularugosa paralycopodites and tree fern spores. Telinite preservation increases upwards in the Upper Kimberly but overall is well below the preservation ratio of the Fundy coal bed. The coals are all high sulfur, up to 13.7% total sulfur for the lower lithotype of the Fundy coal bed. The Kimberly coals are not only high in total and pyritic sulfur, but also have high concentrations of chalcophile elements.

  8. Depositional environments of the Santa Margarita Formation in the Miocene Santa Maria basin, Huasna syncline

    SciTech Connect

    Phillips, R.L. )

    1991-02-01

    Preliminary investigation of the depositional environments of the middle sandstone member of the late middle Miocene Santa Margarita Formation in the Huasna syncline suggests a current-dominated shallow shelf environment. Progradation of coarse-grained clastic and bioclastic-rich sediment over siltstone documents the initial stage of deposition of this sand body. Overlying the basal intensely bioturbated bioclastic sediments are large-scale tabular cross-beds, up to 16 m thick, interbedded with tabular lag deposits of barnacles, oysters, and echinoids. The tabular fossil-rich beds, which form sequences up to 6 m thick between the large-scale cross-beds, represent either deposition of bottom set beds of the large-scale cross-beds or current swept lag deposits. Increasing energy conditions are recorded vertically by a decrease in the amount of bioturbation and by an increase in large-scale cross-bed sets and cosets. however, in the northern outcrop area subtidal channels are incised into the upper bioclastic sediments suggesting local shoaling conditions. Paleocurrent data record a unidirectional southwest-directed current trend normal to the basin axis and the East Huasna fault. The coarse clastic deposition terminates with deposition of siltstone as energy conditions decreased and water depth again increased. A current-swept shallow shelf containing extensive sandwaves comprises the major depositional environments. The paleocurrent data and large-scale cross-beds suggest that the shallow shelf extended to the east of the Huasna syncline and that the currents were most likely tidal in origin.

  9. Composition and provenance of the Puente Formation (Miocene), Los Angeles Basin

    SciTech Connect

    Critelli, S. ); Rumelhart, P.E.; Ingersoll, R.V. )

    1994-04-01

    The Puente Formation (PFm) is a middle to upper Miocene clastic unit lying unconformably on the middle to lower Miocene El Modeno Volcanics and Topanga Group, within the Los Angeles basin (LAB). The PFm, about 3900m thick, is composed of sandstone, conglomerate, and mudrock deposited on a submarine fan at bathyal depths. Several intrabasinal discordances suggest active tectonics during deposition. The succession consists of two main upward thickening and coarsening megacycles reflecting submarine fan progradation. The PFm is characterized up-section by: (1) thin-bedded fine sandstone and shale (La Vida M.) grading to thick-bedded coarse sandstone an conglomerate (soquel M.); (2) thin-bedded siltstone, mudrock and sandstone (Yorba M.) grading to thick- to very thick-bedded coarse-grained sandstone and conglomerate (Sycamore Canyon M.). Sandstones of the PFm are quartzofeldspathic and suggest a probable local provenance from the plutonic, volcanic, and metamorphic rocks of the San Gabriel Mountains. Petrological parameters, however, suggest variable contribution of these source rock units through time. Coarse-grained plutonic rock fragments are abundant for the entire succession and consist of plagioclase-rich plutonic rocks perhaps sourced from the Lowe granodiorite. Microlitic, lathwork to felsitic volcanic lithic grains are also present in the lower and middle part. In the Yorba M. there is a local increase of volcanic detritus (Lv/L - 0.80), represented by larger volcanic lithics and abundant volcaniclastic matrix. Metamorphic detritus is not very abundant; it is concentrated in the La Vida M. the PFm represents sedimentation during tectonically active time in the evolution of southern California.

  10. Diagenesis of the sandflat and mudflat facies of the upper Queen Formation, Midland basin, Texas

    SciTech Connect

    Mckone, C.J.; Malicse, A.; Mazzullo, J.M. )

    1991-03-01

    The upper Queen Formation (Permian, Guadalupian) of the Midland basin, Texas, consists of cyclically interbedded clastics and evaporites that were deposited in a fluvial-dominated continental sabkha environment. Fluvial sandflat deposits, consisting of thin units (0.2-5.0 m) of very fine grained arkosic sandstones constitute reservoir horizons, whereas 0.1-1.3 m thick units of coarse siltstones and evaporites of playa-mudflat deposits are nonproductive. This study addresses the diagenetic histories of the reservoir and nonreservoir clastics. The primary porosity of the clastics was first reduced by pore-filling hematitic smectite clay, anhydrite, and dolomite during an early diagenetic phase. Subsequent dissolution of the anhydrite and dolomite by acidic pore-waters created high porosities (mean = 15%) and permeabilities (mean = 70 md) in the sandflat deposits, porosities which were only slightly occluded by later dissolution and reprecipitation of grain-lining smectite. Pore-water movement and subsequent hydrocarbon migration were both controlled by the coarser grain size and lower clay-matrix and silt content of these sandflat deposits. In contrast, the finer grain size and higher clay-matrix and silt content prevented similar dissolution of cements within the mudflat facies, which have significantly lower porosities (mean{lt}10%) and permeabilities (mean{lt}0.1 md). Fluids and gases used in enhanced recovery techniques will follow pathways created by dissolution of anhydrite and dolomite cements within the sandflat facies. However, caution must be used with fluids that can cause swelling of the grain-lining smectite.

  11. Tectonic evolution of Gulf of Anadyr and formation of Anadyr and Navarin basins

    SciTech Connect

    Marlow, M.S.; Childs, J.R.; Cooper, A.K.

    1983-04-01

    The Gulf of Anadyr is underlain by two major sedimentary basins, Kresta basin and East Anadyr trough, that trend east to southeast and contain, in places, more than 9 km (29,500 ft) of fill. The basins are flanked on the east and north by the Okhotsk-Chukotsk volcanic belt, a broad bedrock high composed of plutonic and volcanic rocks that extends from eastern Siberia along the inner Bering Sea shelf at least to St. Matthew Island. The East Anadyr trough extends onshore and connects with the larger Anadyr basin, which underlies the lowlands between the Koryak Range and Okhotsk-Chukotsk volcanic belt of eastern Siberia. New seismic reflection and refraction data reveal that Anadyr basin is separated from Navarin basin by Anadyr ridge, a southeast-northwest-trending bedrock high that is characterized by high-amplitude, short-wavelength magnetic anomalies. Anadyr ridge may be an offshore extension of the melange belt underlying the Koryak Range Sonobuoy refraction data indicate that the velocity profile of strata in East Anadyr trough is similar to that in Navarin basin.

  12. Reconnaissance geochronology of tuffs in the Miocene Barstow Formation: implications for basin evolution and tectonics in the central Mojave Desert

    USGS Publications Warehouse

    Miller, D.M.; Leslie, S.R.; Hillhouse, J.W.; Wooden, J.L.; Vazquez, J.A.; Reynolds, R.E.

    2010-01-01

    Early to middle Miocene lacustrine strata of the Barstow Formation are well dated in just a few places, limiting our ability to infer basin evolution and regional tectonics. At the type section in the Mud Hills, previous studies have shown that the lacustrine interval of the Barstow Formation is between ~16.3 Ma and ~13.4 Ma. Elsewhere, lake beds of the Barstow Formation have yielded vertebrate fossils showing the Hemingfordian/Bartovian transition at ~16 Ma but are otherwise poorly dated. In an attempt to clarify the age and depositional environments of the lake deposits, we are mapping the Barstow Formation and dating zircons from interbedded tuffs, as well as testing ash-flow tuffs for the distinctive remanent magnetization direction of the widespread Peach Spring Tuff. Thus far, our new U-Pb zircon ages inficate that the Barstow lake beds contain tuff beds as old as 19.1 Ma and as young as 15.3 Ma. At Harvard Hill, Barstow lake beds contain a thick tuff dated at 18.7 Ma. On the basis of zircon ages, mineralogy, zircon chemistry, and paleomagnetic results, we consider the thick tuff to be a lacustrine facies of the Peach Spring Tuff. We have identified the Peach Spring Tuff by similar methods at eight localities over a broad area, providing a timeline for several fluvial and lacustrine sections. The new dates indicate that long-lived lacustrine systems originated before 19 Ma and persisted to at least 15 Ma. The onset of lacustrine conditions predates the Peach Spring Tuff in most Barstow Formation sections and may be older than 19.5 Ma in some places. The new data indicate that the central Mojave Desert contained narrow to broad lake basins during and after extension, and that Barstow lacustrine deposits did not exclusively postdate extensional tectonics. At present, it is unclear whether several separate, small lake basins coexisted during the early to middle Miocene, or if instead several small early Miocene basins gradually coalesced over about 6 millions

  13. Reconnaissance geochronology of tuffs in the Miocene Barstow Formation: implications for basin evolution and tectonics in the central Mojave Desert

    USGS Publications Warehouse

    Miller, David M.; Leslie, Shannon R.; Hillhouse, John W.; Wooden, Joseph L.; Vazquez, Jorge A.; Reynolds, R.E.

    2010-01-01

    Early to middle Miocene lacustrine strata of the Barstow Formation are well dated in just a few places, limiting our ability to infer basin evolution and regional tectonics. At the type section in the Mud Hills, previous studies have shown that the lacustrine interval of the Barstow Formation is between ~16.3 Ma and ~13.4 Ma. Elsewhere, lake beds of the Barstow Formation have yielded vertebrate fossils showing the Hemingfordian/Barstovian transition at ~16 Ma but are otherwise poorly dated. In an attempt to clarify the age and depositional environments of the lake deposits, we are mapping the Barstow Formation and dating zircons from interbedded tuffs, as well as testing ash-flow tuffs for the distinctive remanent magnetization direction of the widespread Peach Spring Tuff. Thus far, our new U-Pb zircon ages indicate that the Barstow lake beds contain tuff beds as old as 19.1 Ma and as young as 15.3 Ma. At Harvard Hill, Barstow lake beds contain a thick tuff dated at 18.7 Ma. On the basis of zircon ages, mineralogy, zircon chemistry, and paleomagnetic results, we consider the thick tuff to be a lacustrine facies of the Peach Spring Tuff. We have identified the Peach Spring Tuff by similar methods at eight localities over a broad area, providing a timeline for several fluvial and lacustrine sections. The new dates indicate that long-lived lacustrine systems originated before 19 Ma and persisted to at least 15 Ma. The onset of lacustrine conditions predates the Peach Spring Tuff in most Barstow Formation sections and may be older than 19.5 Ma in some places. The new data indicate that the central Mojave Desert contained narrow to broad lake basins during and after extension, and that Barstow lacustrine deposits did not exclusively postdate extensional tectonics. At present, it is unclear whether several separate, small lake basins coexisted during the early to middle Miocene, or if instead several small early Miocene basins gradually coalesced over about 6 million

  14. Rifting of the Tyrrhenian Basin: A Natural Laboratory to Study Extension of Continental Lithosphere and Conjugate Rifted Margin Formation

    NASA Astrophysics Data System (ADS)

    Ranero, C. R.; Sallares, V.; Grevemeyer, I.; Zitellini, N.; Vendrell, M. G.; Prada, M.; Moeller, S.; Party, M. C.; Medoc Cruise Party

    2011-12-01

    The Tyrrhenian basin has been created by extension of continental lithosphere above a retreating slab during the Neogene. The basin is not currently extending, but its structure preserves information of the time evolution of the rifting process. The basin opened from north to south with different amounts of extension. The northern region stopped opening after relatively low extension. The amount of extension increases southwards to a region where full crustal separation produced mantle exhumation. The final structure displays two conjugate margins with an asymmetric structure. We present results from a two-vessel seismic experiment that took place in spring 2010. The cruise was carried out with the Spanish R/V Sarmiento de Gamboa (SdG) and the Italian R/V Urania in a first leg. The ships collected 5 E-W trending wide-angle seismic (WAS) profiles across the entire basin using 17 Ocean Bottom Seismometers and 25 Ocean Bottom Hydrophones and a 4800 c.i. G-II gun array. During the second leg the R/V SdG collected 16 Multichannel Seismic Reflection (MCS) profiles using a 3.75 km-long streamer and a 3000 c.i. G-II gun array. MCS profiles were acquired coincident with the WAS profiles, and a number of additional lines concentrated in the central region of the basin where mantle exhumation took place. The seismic data covers the region of the basin that experienced different amount of extension from north to south. In this presentation we compare observations from different transects to study the evolution of the processes of continental margin formation by trading space (different areas with different extension factors) for time (evolution of extension). Each transect provides the tectonic structure, the geometry of sedimentary deposits, and seismic velocity distribution. This information allows to interpret the mechanisms of deformation and to study the symmetry-asymmetry structure of the conjugated margins, and thus of the processes involved in their formation. The

  15. Chapter 5. Assessment of undiscovered conventional oil and gas resources-Lower Cretaceous Travis Peak and Hosston formations, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

    USGS Publications Warehouse

    Dyman, T.S.; Condon, S.M.

    2006-01-01

    The petroleum assessment of the Travis Peak and Hosston Formations was conducted by using a total petroleum system model. A total petroleum system includes all of the important elements of a hydrocarbon fluid system needed to develop oil and gas accumulations, including source and reservoir rocks, hydrocarbon generation, migration, traps and seals, and undiscovered accumulations. A total petroleum system is mappable and may include one or more assessment units. For each assessment unit, reservoir rocks contain similar geology, exploration characteristics, and risk. The Jurassic Smackover Interior Salt Basins Total Petroleum System is defined for this assessment to include (1) Upper Jurassic Smackover carbonates and calcareous shales and organic-rich shales of the Upper Jurassic Bossier Shale of the Cotton Valley Group and (2) Lower Cretaceous Travis Peak and Hosston Formations. The Jurassic Smackover Interior Salt Basins Total Petroleum System includes three conventional Travis Peak-Hosston assessment units: Travis Peak-Hosston Gas and Oil (AU 50490205), Travis Peak-Hosston Updip Oil (AU 50490206), and Travis Peak-Hosston Hypothetical Updip Oil (AU 50490207). A fourth assessment unit, the Hosston Hypothetical Slope-Basin Gas Assessment Unit, was named and numbered (AU 50490208) but not geologically defined or quantitatively assessed owing to a lack of data. Together, assessment units 50490205 to 50490207 are estimated to contain a mean undiscovered conventional resource of 29 million barrels of oil, 1,136 billion cubic feet of gas, and 22 million barrels of natural gas liquids.

  16. Megabreccia deposits in an extensional basin: The Miocene-Pliocene Horse Camp Formation, east-central Nevada

    SciTech Connect

    Schmitt, J.G.; Brown, C.L. )

    1991-06-01

    Three varieties of megabreccia deposits are present in alluvial-lacustrine extensional basin fill of the Miocene-Pliocene Horse Camp Formation of east-central Nevada. Coherent debris sheets (150-300 m thick; up to 1,500 m long) consist of Oligocene-Miocene volcanic rock masses which are internally fractured yet retain their stratigraphic integrity. Fracture zones show variable amounts of displacement (up to 5 cm) and brecciation. These debris sheets overlie horizontally stratified sandstone and laminated claystone interpreted as playa deposits and are overlain by lithified grus. Emplacement of these coherent debris sheets was by landslide or block slide. Associated deposits of large boulders within playa facies suggest gliding of blocks broken from the edges of the landslides across wet playa surfaces. Large (1.6 - 2.4 km-long) allochthonous blocks consist of intact Paleozoic and Tertiary volcanic stratigraphic sequences which are brecciated and attenuated. Brecciation is accompanied in places by incorporation of muddy sand matrix. These blocks may be fragments of the upper plate of low-angle detachment faults which broke away as gravity-driven blocks from the nearby Horse Range and slid along the uplifted former detachment surface into the adjacent Horse Camp basin. Megabreccia deposits characterize Teritary extensional basins in western North America. Detailed analysis of their stratigraphic, sedimentologic, and structural relations can provide a better understanding of the complex tectonosedimentary history of these basins.

  17. Geothermal energy from the Main Karoo Basin (South Africa): An outcrop analogue study of Permian sandstone reservoir formations

    NASA Astrophysics Data System (ADS)

    Campbell, Stuart A.; Lenhardt, Nils; Dippenaar, Matthys A.; Götz, Annette E.

    2016-04-01

    The geothermal potential of the South African Main Karoo Basin has not been addressed in the past, although thick siliciclastic successions in geothermal prone depths are promising target reservoir formations. A first assessment of the geothermal potential of the Karoo Basin is based on petro- and thermophysical data gained from an outcrop analogue study of Permian sandstones in the Eastern Cape Province, and evaluation of groundwater temperature and heat flow values from literature. A volumetric approach of the sandstones' reservoir potential leads to a first estimation of 2240 TWh (8.0 EJ) of power generation within the central and southern part of the basin. Comparison with data from other sedimentary basins where deep geothermal reservoirs are identified shows the high potential of the Karoo for future geothermal resource exploration, development and production. The mainly low permeability lithotypes may be operated as stimulated systems, depending on the fracture porosity in the deeper subsurface. In some areas auto-convective thermal water circulation might be expected and direct heat use becomes reasonable. The data presented here serve to identify exploration areas and are valuable attributes for reservoir modeling, contributing to (1) a reliable reservoir prognosis, (2) the decision of potential reservoir stimulation, and (3) the planning of long-term efficient reservoir utilization.

  18. Depositional systems and coal occurrence in the Fort Union Formation (Paleocene), Powder River Basin, Wyoming and Montana

    SciTech Connect

    Ayers, W.B. Jr.

    1984-01-01

    The Powder River Basin is a Laramide foreland basin which was formed as a structural and depositional entity in the Paleocene and was filled by fluvial-deltaic, paludal, and lacustrine sediments of the Fort Union Formation. A regional subsurface study shows that, as a result of rapid subsidence in the middle paleocene, a lake (Lebo Shale Member) formed along the axis of the Powder River Basin and rapidly transgressed an area greater than 10,000 sq mi. (25,900 sq km). From middle through late Paleocene, Lake Lebo was filled peripherally by fluvially dominated deltas (Tongue River Member). Primary fill was from: (1) the east by elongate deltas fed by suspended-load fluvial systems issuing from the Black Hills and; (2) the southwest by lobate deltas fed by mixed-to-bed-load streams sourced to the west. Secondary fill was from the northwest by an elongate delta fed by a suspended-load fluvial system flowing through the Bull Mountain trough. A detailed study of Tongue River coal seams near the center of the basin shows that coal occurrence is facies controlled.

  19. Porosity and Permeability of Jurassic-Triassic Formations of the South Georgia Rift Basin: Potential Implications for CO2 Storage

    NASA Astrophysics Data System (ADS)

    Akintunde, O. M.; Knapp, C. C.; Knapp, J. H.; Prasad, M.; Olsen, P. E.

    2011-12-01

    Porosity and permeability are critical for evaluating reservoir injectivity and seal integrity for subsurface CO2 storage. Both properties are needed to determine the effective CO2 storage capacity. In addition, the ability to model and understand the physical interactions of the CO2 reservoir systems under in situ conditions is dependent on the reservoir porosity. We present results of rock physics evaluation of the porosity and permeability of the buried Jurassic-Triassic formations of the South Georgia Rift (SGR) basin using existing well and new experimental data. The SGR basin covers parts of South Carolina, Georgia, Alabama, and Florida and is buried beneath Cretaceous and younger Coastal Plain sediments. We focused our study on the South Carolina portion of the basin that has been identified in the Carbon Sequestration Atlas of United States and Canada as containing saline formations suitable for subsurface CO2 storage. Results of our rock physics analysis confirm the presence of porous reservoir units capped by low-porosity diabase sills. These potential reservoirs appear to have the capacity (pore volume and porosity) to store significant quantities of supercritical CO2. Our analysis further suggests that the SGR basin may contain distinct porosity-permeability regimes (geo-hydrologic systems) that are influenced by depositional environments. These regimes are: (1) high-porosity, low/medium permeability, as observed in the Norris Lightsey well with Triassic formation porosity of 20 - 32.5 percent and core-derived permeability of 1.5 - 8.9 mD, and (2) low-porosity, low-permeability, based on the average total porosity of 6.3 percent and permeability of 6.6 (E-5) - 1.6 (E-2) mD reported in the literature for the Dunbarton Triassic sediments. The Norris Lightsey sedimentary rocks are primarily lacustrine deposits and consist of fine-grained Triassic sandstone with interbedded layers of siltstone and mudstone, while the Dunbarton basin is dominated by fluvial

  20. Porous media of the Red River Formation, Williston Basin, North Dakota: a possible Sedimentary Enhanced Geothermal System

    NASA Astrophysics Data System (ADS)

    Hartig, Caitlin M.

    2016-09-01

    Fracture-stimulated enhanced geothermal systems (EGS) can be developed in both crystalline rocks and sedimentary basins. The Red River Formation (Ordovician) is a viable site for development of a sedimentary EGS (SEGS) because the formation temperatures exceed 140 °C and the permeability is 0.1-38 mD; fracture stimulation can be utilized to improve permeability. The spatial variations of the properties of the Red River Formation were analyzed across the study area in order to understand the distribution of subsurface formation temperatures. Maps of the properties of the Red River Formation-including depth to the top of the formation, depth to the bottom of the formation, porosity, geothermal gradient, heat flow, and temperature-were produced by the Kriging interpolation method in ArcGIS. In the future, these results may be utilized to create a reservoir simulation model of an SEGS in the Red River Formation; the purpose of this model would be to ascertain the thermal response of the reservoir to fracture stimulation.

  1. Paleoceanographic and paleoclimatic controls on ooid mineralogy of the Smackover Formation, Mississippi salt basin: Implications for Late Jurassic seawater composition

    SciTech Connect

    Heydari, E.; Moore, C.H. )

    1994-01-01

    The Late Jurassic Smackover Formation in the Mississippi salt basin consists of two 150 m thick shoaling-upward cycles, each capped by ooid grainstones. During deposition of the lower cycle, originally calcite ooids formed on the seaward side of the basin and former aragonite ooids were precipitated on the landward side. In the upper cycle, originally calcite ooids were precipitated on both the seaward and the landward sides of the basin. Because kinetic variables are incapable of totally preventing aragonite formation the authors suggest that Smackover calcite ooids were precipitated from seawater with low carbonate saturation state (possibly undersaturated relative to aragonite). The shift from seaward calcite to landward aragonite ooids in the lower cycle was controlled by a shoreward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in seawater salinity. The net effect of the salinity gradient was a landward increase in the carbonate saturation state in response to decreasing dissolved CO[sub 2] and increasing CO[sub 3][sup 2[minus

  2. Assessment of Undiscovered Technically Recoverable Oil and Gas Resources of the Bakken Formation, Williston Basin, Montana and North Dakota, 2008

    USGS Publications Warehouse

    Pollastro, R.M.; Roberts, L.N.R.; Cook, T.A.; Lewan, M.D.

    2008-01-01

    The U.S. Geological Survey (USGS) has completed an assessment of the undiscovered oil and associated gas resources of the Upper Devonian to Lower Mississippian Bakken Formation in the U.S. portion of the Williston Basin of Montana and North Dakota and within the Williston Basin Province. The assessment is based on geologic elements of a total petroleum system (TPS), which include (1) source-rock distribution, thickness, organic richness, maturation, petroleum generation, and migration; (2) reservoir-rock type (conventional or continuous), distribution, and quality; and (3) character of traps and time of formation with respect to petroleum generation and migration. Framework studies in stratigraphy and structural geology and modeling of petroleum geochemistry, combined with historical exploration and production analyses, were used to estimate the undiscovered, technically recoverable oil resource of the Bakken Formation. Using this framework, the USGS defined a Bakken-Lodgepole TPS and seven assessment units (AU) within the system. For the Bakken Formation, the undiscovered oil and associated gas resources were quantitatively estimated for six of these AUs.

  3. Organic facies characteristics of the Miocene Soma Formation (Lower Lignite Succession-KM2), Soma Coal Basin, western Turkey

    NASA Astrophysics Data System (ADS)

    Hokerek, Selin; Ozcelik, Orhan

    2015-04-01

    The Soma coal basin is one of the largest economic lignite-bearing alluvial basins of western Turkey. The Miocene succession (Soma Formation) of the coalfield contains two lignite seams successions; Lower Lignite, Middle Lignite .The Lower Lignite (KM2) is a seam 15 m thick and found in contact between siliciclastic and carbonate deposits (marlstones). Detailed data from thick Miocene sediments (Soma Formation) made it possible to construct an organic facies framework using different zonations. Organic matter is composed predominantly of woody material. Kerogen in the deposits is type III, as indicated by organic petrographic observations and Rock-Eval data. Total organic carbon (TOC) values are generally between 28.45 and 72.66 %, but reach 73.38 % in the formation. Tmax values vary between 403 and 429 °C, confirming maturation trends indicated by vitrinite reflectance data (between 0.35-0.48 Ro %). Organic facies type C and CD were identified in the investigated units. Organic facies C and CD are related to clayey coal and coal lithofacies. These facies are characterized by average values of HI around 126 mg HC/g TOC (equivalent to type III kerogen), TOC around 56.61 %, and an average of S2 of 72.4 mg HC/g of rock. The organic matter is partly oxidized/oxidized and reworked. Keywords: Western Turkey; Soma Formation; organic facies; organic geochemistry

  4. The formation of the intra-Carpathian basins as determined from subsidence data

    NASA Astrophysics Data System (ADS)

    Sclater, J. G.; Royden, L.; Horvath, F.; Burchfiel, B. C.; Semken, S.; Stegena, L.

    1980-11-01

    The Carpathian arc is the result of continental collision during subduction of the European plate beneath a Pannonian continental block. In the Early/Middle Miocene, during and after the last stages of thrusting in the Outer Carpathians, several "back-arc" basins started to form within the Carpathian loop. These basins are of two types: (1) those lying in the peripheral regions of the intra-Carpathian lowlands (Vienna, West Danube, Transcarpathian and Transylvanian), and (2) those lying in the central intra-Carpathian region (East Danube, Little Hungarian and Great Hungarian (Pannonian)). Though both groups of basins have thin crust, the subsidence history and the present heat flow are different. The peripheral basins exhibit a rapid initial subsidence followed by a much slower general increase in depth. Their heat flow is close to the average for continental areas. In contrast the central basins have no initial subsidence but do show a fast linear increase in depth which has continued until the present. The heat flow is nearly twice the average for continents. We believe that the basins are thermal in origin and are the direct result of the continental collision which formed the Carpathian arc. The peripheral basins appear to be the result of uniform stretching of the lithosphere by about a factor of two. The rapid initial subsidence is an immediate isostatic adjustment to the stretching, the slower linear subsidence is due to conductive cooling of the thinned lithosphere. In the central basins, uniform stretching by about a factor of 3 could explain the thermal subsidence and the high heat flow. Unfortunately such a simple explanation is not supported by either the geology or the absence of a clearly defined initial subsidence. Alternative explanation involve crustal stretching with additional subcrustal thinning or, alternatively, attenuation of the whole subcrustal lithosphere and part of the crust by melting and erosion. Both explanations create a very thin

  5. Isopach and structure contour maps of the Burro Canyon(?) Formation in the Chama-El Vado Area, Chama Basin, New Mexico

    USGS Publications Warehouse

    Ridgley, Jennie L.

    1983-01-01

    In the Chama Basin a wequence of conglomerate, sandstone, and red, gray-green, and pale-purple mudstone occurs stratigraphically between the Upper Jurassic Morrison Formation and Upper Cretaceous Dakota Sandstone. This stratigraphic interval has been called the Burro Canyon Formation by several workers (Craig and others, 1959; Smith and others, 1961; Saucier, 1974). Although similarities in lithology and stratigraphic position exist between this unit and the Burro Canyon Formation in Colorado, no direct correlation has been made between the two. For this reason the unit in the Chama Basin is called the Burro Canyon(?) Formation

  6. Isopach and structure contour maps of the Burro Canyon(?) Formation in the Mesa Golondrina and Mesa de los Viejos areas, Chama Basin, New Mexico

    USGS Publications Warehouse

    Ridgley, Jennie L.

    1983-01-01

    In the Chama Basin a wequence of conglomerate, sandstone, and red, gray-green, and pale-purple mudstone occurs stratigraphically between the Upper Jurassic Morrison Formation and Upper Cretaceous Dakota Sandstone. This stratigraphic interval has been called the Burro Canyon Formation by several workers (Craig and others, 1959; Smith and others, 1961; Saucier, 1974). Although similarities in lithology and stratigraphic position exist between this unit and the Burro Canyon Formation in Colorado, no direct correlation has been made between the two. For this reason the unit in the Chama Basin is called the Burro Canyon(?) Formation

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

    SciTech Connect

    Stueber, A.M. ); Walter, L.M.; Huston, T.J. ); Pushkar, P. )

    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 evaporation 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.

  8. Isopach and isoresource maps for oil shale deposits in the Eocene Green River Formation for the combined Uinta and Piceance Basins, Utah and Colorado

    USGS Publications Warehouse

    Mercier, Tracey J.; Johnson, Ronald C.

    2012-01-01

    The in-place oil shale resources in the Eocene Green River Formation of the Piceance Basin of western Colorado and the Uinta Basin of western Colorado and eastern Utah are estimated at 1.53 trillion barrels and 1.32 trillion barrels, respectively. The oil shale strata were deposited in a single large saline lake, Lake Uinta, that covered both basins and the intervening Douglas Creek arch, an area of comparatively low rates of subsidence throughout the history of Lake Uinta. Although the Green River Formation is largely eroded for about a 20-mile area along the crest of the arch, the oil shale interval is similar in both basins, and 17 out of 18 of the assessed oil shale zones are common to both basins. Assessment maps for these 17 zones are combined so that the overall distribution of oil shale over the entire extent of Lake Uinta can be studied. The combined maps show that throughout most of the history of Lake Uinta, the richest oil shale was deposited in the depocenter in the north-central part of the Piceance Basin and in the northeast corner of the Uinta Basin where it is closest to the Piceance Basin, which is the only area of the Uinta Basin where all of the rich and lean oil shale zones, originally defined in the Piceance Basin, can be identified. Both the oil shale and saline mineral depocenter in the Piceance Basin and the richest oil shale area in the Uinta Basin were in areas with comparatively low rates of subsidence during Lake Uinta time, but both areas had low rates of clastic influx. Limiting clastic influx rather than maximizing subsidence appears to have been the most important factor in producing rich oil shale.

  9. Biomarker variations in relation to paleogeography in the Saltos Shale member of the Monterey Formation, Cuyama basin, California

    SciTech Connect

    Lillis, P.G. )

    1990-05-01

    The Miocene stratigraphy of the Cuyama basin provides an excellent opportunity to correlate geology with molecular organic geochemistry (e.g., biomartker compounds) because the paleogeography and paleobathymetry of the basin are well constrained by surface and subsurface geologic mapping and detailed micropaleontology. The Monterey Formation is composed of biogenous and terrigenous sediments that accumulated in a deep marine borderland basin adjacent to a Miocene shoreline. the lower member, the Saltos Shale, is predominately terrigenous sediment interbedded with impure carbonates that consist of foraminifera and calcareous nannofossils. The upper member, the Whiterock Bluff Shale, is composed of highly biogenous (siliceous and carbonate) sediments. The biomarker composition of the Saltos Shale is dependent on the relative contributions of planktonic and benthonic organisms, bacteria, and terrigenous organic matter transported from the nearby landmass. A general trend in biomarker distribution is observed in relation to paleogeography (i.e. proximity to shoreline). Pristane/phytane ratios, hopane/sterane ratios, oleanane/hopane ratios, and diasterane/sterane ratios are higher near the shoreline (to the east) because of increased terrigenous input. The more distal western basin sediments contain biomarkers that were predominately derived from marine phytoplankton and bacteria. Submarine fan sediments in the Saltos Shale were deposited in the eastern basin east of the penecontemporaneous Cox fault. Ponding of terrigenous organic matter at the base of slope is reflected by high ratios of pristane/phytane (2.7), oleanane/hopane (0.79), C{sub 29}/C{sub 27} {alpha}{alpha}{alpha}2OR steranes (1.56), and relatively large amounts of waxy n-alkanes (C{sub 27}, C{sub 29}, C{sub 31}). In contrast, the prefan and postfan sediments contain lower concentrations of these terrigenous biomarkers.

  10. Interior layered deposits within a perched basin, southern Coprates Chasma, Mars: Evidence for their formation, alteration, and erosion

    NASA Astrophysics Data System (ADS)

    Fueten, F.; Flahaut, J.; Le Deit, L.; Stesky, R.; Hauber, E.; Gwinner, K.

    2011-02-01

    A basin-like area containing three interior layer deposits (ILDs) on the southern margin of Coprates Chasma was studied. We interpret the area as an ancestral basin and demonstrate that ILD deposition postdates the formation of the current wall rock slopes. The geometry of the ILD and the wall rock spurs form a catchment area between each ILD and the plateau to the south. Erosional remnants of extensive ash or dust layers deposited on the plateau south of Valles Marineris also crop out on the southern plateau of Coprates Chasma. A mass balance calculation suggests that the volume of each ILD is compatible with the volume of the ash or dust that would have been deposited within each catchment area. We propose that the ILDs likely formed by episodically washing such aerially deposited material down from chasma walls. Rifting of the Ius-Melas-Coprates graben opened the enclosed basin and removed any standing water. Faults within the ILDs are compatible with this chasm opening. Sulfates are associated with the ILDs and light-toned material on the basin floor. We suggest that they result from water alteration of preexisting deposits, though the timing of that alteration may predate or postdate the breaching of the basin. Scours within one ILD are similar to terrestrial glacial scours. During a period of high obliquity ice would accumulate in this region; hence we argue the scours are Martian glacial scours. A late deposited layer marks the end of the active local geological history between 100 My and 1 Gy.

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

    SciTech Connect

    Lauren P. Birgenheier; Michael D. Vanden Berg,

    2011-04-11

    An integrated detailed sedimentologic, stratigraphic, and geochemical study of Utah's Green River Formation has found that Lake Uinta evolved in three phases (1) a freshwater rising lake phase below the Mahogany zone, (2) an anoxic deep lake phase above the base of the Mahogany zone and (3) a hypersaline lake phase within the middle and upper R-8. This long term lake evolution was driven by tectonic basin development and the balance of sediment and water fill with the neighboring basins, as postulated by models developed from the Greater Green River Basin by Carroll and Bohacs (1999). Early Eocene abrupt global-warming events may have had significant control on deposition through the amount of sediment production and deposition rates, such that lean zones below the Mahogany zone record hyperthermal events and rich zones record periods between hyperthermals. This type of climatic control on short-term and long-term lake evolution and deposition has been previously overlooked. This geologic history contains key points relevant to oil shale development and engineering design including: (1) Stratigraphic changes in oil shale quality and composition are systematic and can be related to spatial and temporal changes in the depositional environment and basin dynamics. (2) The inorganic mineral matrix of oil shale units changes significantly from clay mineral/dolomite dominated to calcite above the base of the Mahogany zone. This variation may result in significant differences in pyrolysis products and geomechanical properties relevant to development and should be incorporated into engineering experiments. (3) This study includes a region in the Uinta Basin that would be highly prospective for application of in-situ production techniques. Stratigraphic targets for in-situ recovery techniques should extend above and below the Mahogany zone and include the upper R-6 and lower R-8.

  12. Continuously increasing δ98Mo values in Neoarchean black shales and iron formations from the Hamersley Basin

    NASA Astrophysics Data System (ADS)

    Kurzweil, Florian; Wille, Martin; Schoenberg, Ronny; Taubald, Heinrich; Van Kranendonk, Martin J.

    2015-09-01

    We present Mo-, C- and O-isotope data from black shales, carbonate- and oxide facies iron formations from the Hamersley Group, Western Australia, that range in age from 2.6 to 2.5 billion years. The data show a continuous increase from near crustal δ98Mo values of around 0.50‰ for the oldest Marra Mamba and Wittenoom formations towards higher values of up to 1.51‰ for the youngest sample of the Brockman Iron Formation. Thereby, the trend in increasing δ98Mo values is portrayed by both carbonate facies iron formations and black shales. Considering the positive correlation between Mo concentration and total organic carbon, we argue that this uniformity is best explained by molybdate adsorption onto organic matter in carbonate iron formations and scavenging of thiomolybdate onto sulfurized organic matter in black shales. A temporal increase in the seawater δ98Mo over the period 2.6-2.5 Ga is observed assuming an overall low Mo isotope fractionation during both Mo removal processes. Oxide facies iron formations show lowest Mo concentrations, lowest total organic carbon and slightly lower δ98Mo compared to nearly contemporaneous black shales. This may indicate that in iron formation settings with very low organic matter burial rates, the preferential adsorption of light Mo isotopes onto Fe-(oxyhydr)oxides becomes more relevant. A similar Mo-isotope pattern was previously found in contemporaneous black shales and carbonates of the Griqualand West Basin, South Africa. The consistent and concomitant increase in δ98Mo after 2.54 billion years ago suggests a more homogenous distribution of seawater molybdate with uniform isotopic composition in various depositional settings within the Hamersley Basin and the Griqualand West Basin. The modeling of the oceanic Mo inventory in relation to the Mo in- and outflux suggests that the long-term build-up of an isotopically heavy seawater Mo reservoir requires a sedimentary sink for isotopically light Mo. The search for this

  13. Petrophysical properties of carbonate rocks: example from the cretaceous Jandaira Formation, Potiguar basin - Brazil

    NASA Astrophysics Data System (ADS)

    Nogueira, Francisco; Soares, José; Bezerra, Francisco; Cavalcanti, Bruno; Cazarin, Caroline

    2015-04-01

    Carbonate sediments are prone to rapid and pervasive diagenetic alterations that change the mineralogy and pore structure within carbonate units. In particular, cementation and dissolution processes continuously modify the pore structure to create or destroy porosity. In extreme cases these modifications can completely change the mineralogy from calcite to dolomite, in the properties of rock for soil (Caliche), or reverse the pore distribution whereby original grains are dissolved to produce pores as the original pore space is filled with cement to form the rock. These processes are common in fractured carbonate units. All these modifications alter the elastic properties of the rock and, therefore, the sonic velocity. This study presents the result of relationship among diagenesis, porosity, grain density, and sonic velocity, in limestones, dolomites and caliche samples from the Jandaíra Formation, Potiguar basin, Brasil. This stratigraphic unit have been subjected to fracturing since the late Cretaceous. The rock and soil samples were collected in outcrops, prepared as plugs, and analyzed at ambient temperature. The porosity and grain density analysis were performed under ambient pressure, while elastic properties analyses were conducted with samples under confining pressure between 5 and 40 MPa. The result is a wide range of sonic velocity in carbonates, in which compressional-wave velocity (VP) ranges from 3507 to 6119 m/s and shear-wave velocity (VS) range from 2114 to 3451 m/s. The ratio VS1/VS2 indicate a level of anisotropy equal to 2%, without any clear relationship with porosity. The elastics properties are affected by rock alteration process or by modification of mineral composition, due to the presence of clay minerals and organic matter, The porosity and grain density values range from 3.2 to 21.5%, and 2.7 to 2.8 (g/cm3), respectively. The grain density analysis in the carbonate rocks indicate the existence of two groups: the first group of calcareous

  14. Origin of dolomites in the Lower Cambrian Xiaoerbulak Formation in the Tarim Basin, NW China: Implications for porosity development

    NASA Astrophysics Data System (ADS)

    Li, Qing; Jiang, Zaixing; Hu, Wenxuan; You, Xuelian; Hao, Guoli; Zhang, Juntao; Wang, Xiaolin

    2016-01-01

    Dolomites occur pervasively in the Cambrian strata in the Tarim Basin, NW China. Although the Cambrian strata have been deeply buried and affected by multiple phases of dolomitization, some intervals in the upper part of the Lower Cambrian Xiaoerbulak Formation developed high porosity. The goal of this study is to understand the origin of different types of dolomites and the formation mechanism of the porosity in the Xiaoerbulak Formation. The geochemistry of matrix dolomites suggests that they formed from middle rare earth element (MREE)-enriched anoxic pore fluids, close to or within the zone of iron reduction. The similar REE + Y patterns and overlapping δ13C values between pore-filling and matrix dolomites indicate that the fluids that were responsible for the precipitation of pore-filling dolomite apparently inherited the signatures of the formation waters that were stored in the host strata. Low δ18O values coupled with high Ba, Zn, and rare earth element (REE) content of pore-filling dolomites indicate that pore-filling dolomites were formed at elevated temperatures. The precipitation of authigenic quartz and saddle dolomites and high Mn content in pore-filling dolomites indicate that hydrothermal fluids that mostly originated from Cambrian basinal clastic units or basement rocks were involved. The mixture of formation water and external hydrothermal fluids is the most likely explanation for the formation of significant porosity and precipitation of pore-filling dolomites at depth. Breccia dolomite, zebra dolomite, and saddle dolomite occur mostly in areas that are close to faults, which suggests that hydrothermal fluids passed through strike-slip faults in this area when these faults were activated. The development of permeable layers in the upper part of the Xiaoerbulak Formation overlain by impermeable layers of the Wusongger Formation suggests a possible potential diagenetic trap. When the faults were activated, high-pressure and high

  15. U-Pb geochronology and geochemistry of the McCoy Mountains Formation, southeastern California: A Cretaceous retroarc foreland basin

    USGS Publications Warehouse

    Barth, A.P.; Wooden, J.L.; Jacobson, C.E.; Probst, K.

    2004-01-01

    The timing of deposition of fluvial sediments now forming the >7-km-thick McCoy Mountains Formation is one of the key uncertainties in reconstructing the Mesozoic poleogeography of southern California and western Arizona. Ion-microprobe U-Pb geochronologic data for individual zircons from nine sandstones from the McCoy Mountains type section and six associated igneous rocks provide significant new constraints on the tectonic setting and the timing of deposition within the northwest-trending McCoy basin. U-Pb zircon data from a metavolcanic rock of the underlying Dome Rock sequence in the Palen Mountains confirm that the McCoy Mountains Formation was deposited after regional Middle to Late Jurassic arc magmatism. U-Ph zircon data from a Late Cretaceous granodiorite intruding the formation in the Coxcomb Mountains confirm that the formation was deformed and metamorphosed prior to 73.5 ?? 1.3 Ma. Populations of detrital zircons vary systematically with both rock type and stratigraphic height; lithic arkoses predominantly derived from the west have consistently more abundant younger zircons than do litharenite sandstones predominantly derived from the north, and the youngest zircons yield maximum depositional ages that decrease from 116 Ma near the base to 84 Ma near the top of the section. The detrital-zircon data permit a Late Jurassic age for the basal, comparatively quartz-rich sandstone. However, the data further suggest that >90% of the formation was deposited between middle Early and middle Late Cretaceous time. These results are consistent with the hypothesis that most of the McCoy Mountains Formation represents a retroarc foreland basin, deposited behind the active, evolving Cretaceous Cordilleran continental-margin magmatic arc that lay to the west and in the foreland of the actively deforming Cretaceous Maria fold-and-thrust belt.

  16. Volumetric analysis of complex lunar craters - Implications for basin ring formation

    NASA Technical Reports Server (NTRS)

    Hale, W. S.; Grieve, R. A. F.

    1982-01-01

    The crater to basin transition in complex lunar craters is characterized by combining morphological and volumetric analyses of their central peaks with subsurface data from terrestrial complex impact structures which suggest that the amount of uplifted material, as judged from its depth of origin, continues to increase with increasing rim diameter. This latter phenomenon implies that a redistribution of uplifted material away from a centralized peak may occur in the larger craters. The morphological and volumetric changes described occur over a rim diameter range of 51-80 km, which is considerably lower than the previously proposed range for the crater to basin transition of 140-175 km. Evidence is given in support of a crater to basin transition which begins at 51-80 km, and is characterized by a relative reduction in central peak volume and a development of rings of floor roughening which may be precursors of peak ring development.

  17. Formation mechanism of a basin of attraction for passive dynamic walking induced by intrinsic hyperbolicity

    NASA Astrophysics Data System (ADS)

    Obayashi, Ippei; Aoi, Shinya; Tsuchiya, Kazuo; Kokubu, Hiroshi

    2016-06-01

    Passive dynamic walking is a useful model for investigating the mechanical functions of the body that produce energy-efficient walking. The basin of attraction is very small and thin, and it has a fractal-like shape; this explains the difficulty in producing stable passive dynamic walking. The underlying mechanism that produces these geometric characteristics was not known. In this paper, we consider this from the viewpoint of dynamical systems theory, and we use the simplest walking model to clarify the mechanism that forms the basin of attraction for passive dynamic walking. We show that the intrinsic saddle-type hyperbolicity of the upright equilibrium point in the governing dynamics plays an important role in the geometrical characteristics of the basin of attraction; this contributes to our understanding of the stability mechanism of bipedal walking.

  18. Seismic effects from major basin formation on the Moon and Mercury

    NASA Technical Reports Server (NTRS)

    Schultz, P. H.; Gault, D. E.

    1974-01-01

    Grooved and hilly terrains are reported which occur at the antipode of major basins on the Moon (Imbrium, Orientale) and Mercury (Caloris). Order-of-magnitude calculations, for an Imbrium-size impact on the Moon, indicate P-wave-induced surface displacements of 10 m at the basin antipode that would arrive prior to secondary ejecta. Comparable surface waves are reported which would arrive subsequent to secondary ejecta impacts and would increase in magnitude as they converge at the antipode. Other seismically induced surface features include: subdued, furrowed crater walls produced by landslides and concomitant secondary impacts; emplacement and leveling of light plains units owing to seismically induced "fluidization" of slide material; knobby, pitted terrain around old basins from enhancement of seismic waves in ancient ejecta blankets; and the production and enhancement of deep-seated fractures that led to the concentration of farside lunar maria in the Apollo-Ingenii region.

  19. A numerical study of strike-slip bend formation with application to the Salton Sea pull-apart basin

    NASA Astrophysics Data System (ADS)

    Ye, Jiyang; Liu, Mian; Wang, Hui

    2015-03-01

    How stepovers of strike-slip faults connect to form bends is a question important for understanding the formation of push-up ranges (restraining bends) and pull-apart basins (releasing bends). We investigated the basic mechanics of this process in a simple three-dimensional viscoelastoplastic finite element model. Our model predicts localized plastic strain within stepovers that may eventually lead to the formation of strike-slip bends. Major parameters controlling strain localization include the relative fault strength, geometry of the fault system, and the plasticity model assumed. Using the Drucker-Prager plasticity model, in which the plastic yield strength of the crust depends on both shear and normal stresses, our results show that a releasing bend is easier to develop than a restraining bend under similar conditions. These results may help explain the formation of the Salton Sea pull-apart basin in Southern California 0.5-0.1 Ma ago, when the stepover between the Imperial Fault and the San Andreas Fault was connected by the Brawley seismic zone.

  20. New constraints on the mechanism for the formation of the Pannonian basin

    NASA Astrophysics Data System (ADS)

    Horváth, Ferenc; Fodor, László; Balázs, Attila; Musitz, Balázs; Koroknai, Balázs

    2013-04-01

    The epoch making cooperation with the MIT group (especially Wiki Royden) in the 1980's on the Pannonian basin arrived at two main conclusions: i) modest to medium value of synrift crustal extension was accompanied by dramatic attenuation of the mantle lithosphere, and ii) subduction and rollback of the Alpine Tethys controlled the extrusion of Alcapa and Tisza-Dacia terranes into the Carpathian embayment. These early results already went beyond a thermomechanical model and suggested the importance of dynamic influences exerted by upper mantle flows. Recent results of SKS anisotropy determinations (Kovács et al. 2012) has been interpreted in terms of a west-east directed flow sub-parallel with the main strike of the Eastern Alps at the western and central part of the basin, and a toroidal flow around the subducted Carpathian slab more towards the east. Horváth and Faccenna (2011) have put forward the idea that inflow of upper mantle material into the Pannonian basin was derived from the sub-Adriatic lithosphere via the northern Dinaric slab window since the late Oligocene, when rollback of oceanic lithosphere commenced on the western and eastern side of Adria. The importance of Dinaric subduction in the evolution of the Pannonian basin has been spectacularly demonstrated recently by the recognition of a number of metamorphic core complexes in the Sava-zone, which were exhumed during the synrift phase of the Pannonian basin (e.g. Ustaszewski et al. 2010, Matenco et al. 2012). Inside the basin the Sava zone represents a complex transfer fault system between the Alcapa and Tisza-Dacia terranes. High quality seismic sections will be presented with new interpretation to show the complicated structural features and the massive volcanism interpreted in terms of leaky transforms. The seismic sections will also show new time constraint for the postrift fill of the basin, which shed new light on the dramatically anomalous subsidence and uplift pattern during the late

  1. Stratigraphy of Blair formation, an Upper Cretaceous slope and basin deposit, eastern flank of the Rock Springs Uplift, Wyoming

    SciTech Connect

    Shannon, L.T.

    1985-05-01

    The Blair Formation (Upper Cretaceous) is the lowermost unit of the Mesaverde Group in southwestern Wyoming. Outcrop study of the Blair exposures on the east flank of the Rock Springs uplift reveals 1,100 ft (330 m) of sandstone, siltstone, and shale. The formation has a sharp conformable to locally erosional basal contact and contains intraformational channeling, syndepositional slumping, and high-energy sedimentary structures. Facies relationships indicate the Blair represents a slope and basinal deposit laterally equivalent to the shelf and delta complex of the lower Rock Springs Formation to the north. Overall stratification types, textures, and southeast paleotransport directions recorded within the Blair, which are normal to the southwest-trending Rock Springs shoreline, support this interpretation. High sedimentation rates in excess of subsidence rates during the early Campanian, possibly related to early movement on the Absaroka thrust and a eustatic lowering of sea level approximately 81 Ma, caused rapid shoreline progradation and favored the development of a narrow shelf. These conditions enabled sand-sized material to bypass the shelf and be deposited in slope and basin environments. A present-day example of these relationships is the modern Mississippi delta located near the shelfslope break of the Gulf of Mexico. Recognition of a narrow shelf in southwestern Wyoming during the early Campanian requires a modification of Late Cretaceous paleogeography to incorporate the concept of depositional topography. The occurrence of slope and basin sandstones in the Blair suggests that new interpretations may be needed to explain sandstone distribution for other stratigraphic intervals within the Cretaceous of the Western Interior.

  2. Hydrocarbon migration and accumulation in the Upper Cretaceous Qingshankou Formation, Changling Sag, southern Songliao Basin: Insights from integrated analyses of fluid inclusion, oil source correlation and basin modelling

    NASA Astrophysics Data System (ADS)

    Dong, Tian; He, Sheng; Wang, Dexi; Hou, Yuguang

    2014-08-01

    The Upper Cretaceous Qingshankou Formation acts as both the source and reservoir sequence in the Changling Sag, situated in the southern end of the Songliao Basin, northeast China. An integrated approach involving determination of hydrocarbon charging history, oil source correlation and hydrocarbon generation dynamic modeling was used to investigate hydrocarbon migration processes and further predict the favorable targets of hydrocarbon accumulations in the Qingshankou Formation. The hydrocarbon generation and charge history was investigated using fluid inclusion analysis, in combination with stratigraphic burial and thermal modeling. The source rocks began to generate hydrocarbons at around 82 Ma and the hydrocarbon charge event occurred from approximately 78 Ma to the end of Cretaceous (65.5 Ma) when a large tectonic uplift took place. Correlation of stable carbon isotopes of oils and extracts of source rocks indicates that oil was generated mainly from the first member of Qingshankou Formation (K2qn1), suggesting that hydrocarbon may have migrated vertically. Three dimensional (3D) petroleum system modeling was used to evaluate the processes of secondary hydrocarbon migration in the Qingshankou Formation since the latest Cretaceous. During the Late Cretaceous, hydrocarbon, mainly originated from the Qianan depression, migrated laterally to adjacent structural highs. Subsequent tectonic inversion, defined as the late Yanshan Orogeny, significantly changed hydrocarbon migration patterns, probably causing redistribution of primary hydrocarbon reservoirs. In the Tertiary, the Heidimiao depression was buried much deeper than the Qianan depression and became the main source kitchen. Hydrocarbon migration was primarily controlled by fluid potential and generally migrated from relatively high potential areas to low potential areas. Structural highs and lithologic transitions are potential traps for current oil and gas exploration. Finally, several preferred hydrocarbon

  3. Salt-Formation by Progressive Evaporation of Brine Waters in the Endurance Crater Basin at Meridiani

    NASA Astrophysics Data System (ADS)

    Rao, M. N.; Nyquist, L. E.; Wentworth, S. J.; Garrison, D. H.; Herrin, J. S.

    2007-03-01

    The sulfate/chloride vs. Cl and chloride/bromide vs. Br relationships in the salt-assemblages on Meridiani (RAT) rock-rinds indicate that these salts likely formed by progressive evaporative concentration of brine waters filling the Endurance Crater basin

  4. Oil shale resources in the Eocene Green River Formation, Greater Green River Basin, Wyoming, Colorado, and Utah

    USGS Publications Warehouse

    ,

    2011-01-01

    The U.S. Geological Survey (USGS) recently completed a comprehensive assessment of in-place oil in oil shales in the Eocene Green River in the Greater Green River Basin, Wyoming, Colorado, and Utah. This CD-ROM includes reports, data, and an ArcGIS project describing the assessment. A database was compiled that includes about 47,000 Fischer assays from 186 core holes and 240 rotary drill holes. Most of the oil yield data were analyzed by the former U.S. Bureau of Mines oil shale laboratory in Laramie, Wyoming, and some analyses were made by private laboratories. Location data for 971 Wyoming oil-shale drill holes are listed in a spreadsheet and included in the CD-ROM. Total in-place resources for the three assessed units in the Green River Formation are: (1) Tipton Shale Member, 362,816 million barrels of oil (MMBO), (2) Wilkins Peak Member, 704,991 MMBO, and (3) LaClede Bed of the Laney Member, 377,184 MMBO, for a total of 1.44 trillion barrels of oil in place. This compares with estimated in-place resources for the Piceance Basin of Colorado of 1.53 trillion barrels and estimated in-place resources for the Uinta Basin of Utah and Colorado of 1.32 trillion barrels.

  5. Selected water-level data for Mesozoic formations in the upper Colorado River basin in Arizona, Colorado, Utah, and Wyoming; excluding the San Juan Basin

    USGS Publications Warehouse

    Weigel, J.F.

    1987-01-01

    The base of the moderately saline water (water that contains from 3,000 to 10,000 mg/L of dissolved solids) was mapped by using available water quality data and by determining formation-water resistivities from geophysical well logs based on the resistivity-porosity, spontaneous-potential, and resistivity-ratio methods. The contour map developed from these data showed a mound of very saline and briny water, mostly of sodium chloride and sodium bicarbonate type, in most of that part of the Uinta Basin that is underlain by either the Green River or Wasatch Formations. Along its northern edge, the mound rises steeply from below sea level to within 2,000 ft of the land surface and, locally, to land surface. Along its southern edge, the mound rises less steeply and is more complex in outline. This body of very saline to briny water may be a lens; many wells or test holes drilled within the area underlain by the mound re-entered fresh to moderately saline water at depths of 8,000 to 15,000 ft below land surface. (Author 's abstract)

  6. Map showing contours on the top of the Pennsylvanian and Permian Minnelusa Formation and equivalents, Powder River basin, Wyoming and Montana

    USGS Publications Warehouse

    Crysdale, B.L.

    1990-01-01

    This map is one in a series of U.S. Geological Survey Miscellaneous Field Studies (MF) maps showing computer-generated structure contours, isopachs, and cross sections of selected formations in the Powder River basin, Wyoming and Montana. The map and cross sections were constructed from information stored in a U.S. Geological Survey Evolution of Sedimentary Basins data base. This data base contains picks of geologic formation and (or) unit tops and bases determined from electric resistivity and gamma-ray logs of 8,592 wells penetrating Tertiary and older rocks in the Powder River basin. Well completion cards (scout tickets) were reviewed and compared with copies of all logs, and formation or unit contacts determined by N. M. Denson, D.L. Macke, R. R. Schumann and others. This isopach map is based on information from 1,480 of these wells that penetrate the Minnelusa Formation and equivalents.

  7. Isopach map of the interval from surface elevation to the top of the Pennsylvanian and Permian Minnelusa Formation and equivalents, Powder River basin, Wyoming and Montana

    USGS Publications Warehouse

    Crysdale, B.L.

    1990-01-01

    This map is one in a series of U.S. Geological Survey Miscellaneous Field Studies (MF) maps showing computer-generated structure contours, isopachs, and cross sections of selected formations in the Powder River basin, Wyoming and Montana. The map and cross sections were constructed from information stored in a U.S. Geological Survey Evolution of Sedimentary Basins data base. This data base contains picks of geologic formation and (or) unit tops and bases determined from electric resistivity and gamma-ray logs of 8,592 wells penetrating Tertiary and older rocks in the Powder River basin. Well completion cards (scout tickets) were reviewed and compared with copies of all logs, and formation or unit contacts determined by N. M. Denson, D.L. Macke, R. R. Schumann and others. This isopach map is based on information from 1,480 of these wells that penetrate the Minnelusa Formation and equivalents.

  8. Magnetostratigraphy of the Willwood Formation, Bighorn Basin, Wyoming: new constraints on the location of Paleocene/Eocene boundary

    USGS Publications Warehouse

    Tauxe, L.; Gee, J.; Gallet, Y.; Pick, T.; Bown, T.

    1994-01-01

    The lower Eocene Willwood Formation in the Bighorn Basin of Wyoming preserves a rich and diverse mammalian and floral record. The paleomagnetic behavior of the sequence of floodplain paleosols of varying degrees of maturation ranges from excellent to poor. We present a magnetostratigraphic section for a composite section near Worland, Wyoming, by using a set of strict criteria for interpreting the step-wise alternating field and thermal demagnetization data of 266 samples from 90 sites throughout the composite section. Correlation to the geomagnetic reversal time scale was achieved by combining magnetostratigraphic and biostratigraphic data from this section, from a section in the Clark's Fork Basin in northern Wyoming, and from DSDP Site 550, with the isotopic data determined on a tuff near the top of our section. Our correlation suggests that the Bighorn Basin composite section in the Worland area spans from within Chron C24r to near the top of Chron C24n, or from approximately 55 to 52 Ma. This correlation places the Paleocene/Eocene boundary within the vicinity of the base of the section. Cryptochron C24r.6 of Cande and Kent is tentatively identified some 100 m above the base of the section. The temporal framework provided here enables correlation of the mammalian biostratigraphy of the Bighorn Basin to other continental sequences as well as to marine records. It also provides independent chronological information for the calculation of sediment accumulation rates to constrain soil maturation rates. We exclude an age as young as 53 Ma for the Paleocene/Eocene boundary and support older ages, as recommended in recent time scales. The location of a tuff dated at 52.8 ?? 0.3 Ma at the older boundary C24n.1 is consistent with the age of 52.5 Ma estimated by Cande and Kent and inconsistent with that of 53.7 Ma, from Harland et al. ?? 1994.

  9. Uranium enrichment in lacustrine oil source rocks of the Chang 7 member of the Yanchang Formation, Erdos Basin, China

    NASA Astrophysics Data System (ADS)

    Yang, Hua; Zhang, Wenzheng; Wu, Kai; Li, Shanpeng; Peng, Ping'an; Qin, Yan

    2010-09-01

    The oil source rocks of the Chang 7 member of the Yanchang Formation in the Erdos Basin were deposited during maximum lake extension during the Late Triassic and show a remarkable positive uranium anomaly, with an average uranium content as high as 51.1 μg/g. Uranium is enriched together with organic matter and elements such as Fe, S, Cu, V and Mo in the rocks. The detailed biological markers determined in the Chang 7 member indicate that the lake water column was oxidizing during deposition of the Chang 7 member. However, redox indicators for sediments such as S 2- content, V/Sc and V/(V + Ni) ratios demonstrate that it was a typical anoxic diagenetic setting. The contrasted redox conditions between the water column and the sediment with a very high content of organic matter provided favorable physical and chemical conditions for syngenetic uranium enrichment in the oil source rocks of the Chang 7 member. Possible uranium sources may be the extensive U-rich volcanic ash that resulted from contemporaneous volcanic eruption and uranium material transported by hydrothermal conduits into the basin. The uranium from terrestrial clastics was unlike because uranium concentration was not higher in the margin area of basin where the terrestrial material input was high. As indicated by correlative analysis, the oil source rocks of the Chang 7 member show high gamma-ray values for radioactive well log data that reflect a positive uranium anomaly and are characterized by high resistance, low electric potential and low density. As a result, well log data can be used to identify positive uranium anomalies and spatial distribution of the oil source rocks in the Erdos Basin. The estimation of the total uranium reserves in the Chang 7 member attain 0.8 × 10 8 t.

  10. Geochemical characteristics of crude oil from a tight oil reservoir in the Lucaogou Formation, Jimusar Sag, Junggar Basin

    NASA Astrophysics Data System (ADS)

    Cao, Z.

    2015-12-01

    Jimusar Sag, which lies in the Junggar Basin,is one of the most typical tight oil study areas in China. However, the properties and origin of the crude oil and the geochemical characteristics of the tight oil from the Lucaogou Formation have not yet been studied. In the present study, 23 crude oilsfrom the Lucaogou Formation were collected for analysis, such as physical properties, bulk composition, saturated hydrocarbon gas chromatography-mass spectrometry (GC-MS), and the calculation of various biomarker parameters. In addition,source rock evaluation and porosity permeability analysis were applied to the mudstones and siltstones. Biomarkers of suitable source rocks (TOC>1, S1+S2>6mg/g, 0.7%basin modeling was performed. The oil-filling history was also defined by means of basin modeling and microthermometry. The results indicated the presence of low maturity to mature crude oils originating from the burial of terrigenous organic matter beneath a saline lake in the source rocks of mainly type II1kerogen. In addition, a higher proportion of bacteria and algae was shown to contribute to the formation of crude oil in the lower section when compared with the upper section of the Lucaogou Formation. Oil-source correlations demonstrated that not all mudstones within the Lucaogou Formation contributed to oil accumulation.Crude oil from the upper and lower sections originated from thin-bedded mudstones interbedded within sweet spot sand bodies. A good coincidence of filling history and hydrocarbon generation history indicated that the Lucaogou reservoir is a typical in situ reservoir. The mudstones over or beneath the sweet spot bodies consisted of natural caprocks and prevented the vertical movement of oil by capillary forces. Despite being thicker, the thick-bedded mudstone between the upper and lower sweet spots had no obvious contribution to

  11. The Permian Whitehill Formation (Karoo Basin, South Africa): deciphering the complexity and potential of an unconventional gas resource

    NASA Astrophysics Data System (ADS)

    Götz, Annette E.

    2014-05-01

    A key energy policy objective of the South African government is to diversify its energy mix from coal which constitutes 85% of the current mix. Gas will play a key role in the future South African economy with demand coming from electricity generation and gas-to-liquids projects. A study on world shale reserves conducted by the Energy Information Agency (EIA) in 2011 concluded that there could be as much as 485 Tcf recoverable reserves of shale gas in the South African Karoo Basin. However, the true extent and commercial viability is still unknown, due to the lack of exploration drilling and modern 3D seismic. The present study compiles existing data from literature review and new data from outcrop analogue studies on the Permian Whitehill Formation, the main target formation for future shale gas production, including thickness, depth, maturity, TOC, lithologies, sedimentary and organic facies, and dolerite occurrence to provide a first reference dataset for further investigations and resource estimates.

  12. Formation resistivity as an indicator of the onset of oil generation in the Woodford Shale, Anadarko Basin, Oklahoma

    USGS Publications Warehouse

    Schmoker, James W.; Hester, Timothy C.

    1989-01-01

    The Upper Devonian and Lower Mississippian Woodford Shale is a black, organic-rich shale that is a major hydrocarbon source rock in the Anadarko basin. With the onset of oil generation, nonconductive hydrocarbons begin to replace conductive pore water in the Woodford, and formation resistivity increases. Crossplots of formation resistivity versus either vitrinite reflectance (RO) or Lopatin's time-temperature index of thermal maturity (TTI) define two data populations that represent immature shales and shales that have generated oil. The midpoint of the resistivity zone marking the transition between immature and mature shales is -35 ohm-m. The onset of appreciable oil generation in the Woodford Shale of the study area occurs at maturity levels of RO near 0.57% and of TTI between 33 and 48.

  13. Formation and evolution of strike-slip faults, rifts, and basins during the India-Asia collision - An experimental approach

    NASA Astrophysics Data System (ADS)

    Peltzer, Gilles; Tapponnier, Paul

    1988-12-01

    The processes which have governed the formation and evolution of large tertiary strike-slip faults during the penetration of India into eastern Asia are investigated by plane strain indentation experiments on layered plasticine models. The results show the influence of boundary conditions as well as that of the internal structure of the plasticine model on the faulting sequence. The ubiquity of strain softening in experimental deformation of a variety of rocks, as well as the widespread occurrence of shear zones in nature, suggest that long-term deformation of the continental lithosphere may also be primarily influenced by the geometry of large faults which rapidly develop with increasing strain. The deformation and faulting sequence observed in the plasticine indentation experiments may thus be compared to collision-induced strike-slip faulting in Asia, particularly to total offsets and rates of movements on the faults. The experiments also illustrate mechanisms for the formation of extension basins near active continental margins.

  14. Shallow lacustrine system of the Permian Pedra de Fogo Formation, Western Gondwana, Parnaíba Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Araújo, Raphael Neto; Nogueira, Afonso César Rodrigues; Bandeira, José; Angélica, Rômulo Simões

    2016-04-01

    The Permian Period of the Parnaíba Basin, northern Brazil, represented here by deposits from the Pedra de Fogo Formation, records important events that occurred in Western Gondwana near its boundary with the Mesozoic Era. The analysis of outcrop based facies from the Permian Pedra de Fogo Formation, which is 100 m thick, carried out along the eastern and western borders of the Parnaiba Basin, allowed the identification of eleven sedimentary facies, which were grouped into three distinct facies associations (FA), representative of a shallow lacustrine system associated with mudflats and ephemeral rivers. Bioturbation, desiccation cracks, silcretes and various siliceous concretions characterize the Pedra de Fogo deposits. The FA1 mudflat deposits occur predominantly at the base of the Pedra de Fogo Formation and consist of laminated claystone/mudstone, mudcrack-bearing sandstones/mudstones and sandstones exhibiting cross-lamination, massive and megaripple bedding. Popcorn-like silicified nodules and casts indicate evaporite deposits. Other common features are silica concretions, silicified tepees and silcretes. FA2 represents nearshore deposits and consists of fine-grained sandstones with evenly parallel lamination, climbing ripple cross-lamination, massive and megaripple bedding and mudstone/siltstone showing evenly parallel lamination. FA3 refers to wadi/inundite deposits, generally organized as fining-upward cycles of metric size, composed of conglomerates and medium-grained pebbly sandstones showing massive bedding and cross-stratification, as well as claystone/siltstone showing evenly parallel to undulate lamination. Scour-and-fill features are isolated in predominantly tabular deposits composed of mudstones interbedded with fine to medium-grained sandstones showing planar to slightly undulate lamination. Silicified plant remains previously classified as belonging to the Psaronius genus found in the uppermost levels of the Pedra de Fogo Formation, near the

  15. Archosauriform remains from the Late Triassic of San Luis province, Argentina, Quebrada del Barro Formation, Marayes-El Carrizal Basin

    NASA Astrophysics Data System (ADS)

    Gianechini, Federico A.; Codorniú, Laura; Arcucci, Andrea B.; Castillo Elías, Gabriela; Rivarola, David

    2016-03-01

    Here we present archosauriform remains from 'Abra de los Colorados', a fossiliferous locality at Sierra de Guayaguas, NW San Luis Province. Two fossiliferous levels were identified in outcrops of the Quebrada del Barro Formation (Norian), which represent the southernmost outcrops of the Marayes-El Carrizal Basin. These levels are composed by massive muddy lithofacies, interpreted as floodplain deposits. The specimens consist of one incomplete maxilla (MIC-V718), one caudal vertebra (MIC-V719), one metatarsal (MIC-V720) and one indeterminate appendicular bone (MIC-V721). The materials can be assigned to Archosauriformes but the fragmentary nature and lack of unambiguous synapomorphies preclude a more precise taxomic assignment. The maxilla is remarkably large and robust and represents the posterior process. It preserved one partially erupted tooth with ziphodont morphology. This bone shows some anatomical traits and size match with 'rauisuchians' and theropods. MIC-V719 corresponds to a proximal caudal vertebra. It has a high centrum, a ventral longitudinal furrow, expanded articular processes for the chevrons, a posteriorly displaced diapophysis located below the level of the prezygapophyses, and short prezygapophyses. This vertebra would be from an indeterminate archosauriform. MIC-V720 presents a cylindrical diaphysis, with a well-developed distal trochlea, which present resemblances with metatarsals of theropods, pseudosuchians, and silesaurids, although the size matches better with theropods. MIC-V721 has a slender diaphysis and a convex triangular articular surface, and corresponds to an indeterminate archosauriform. Despite being fragmentary, these materials indicate the presence of a diverse archosauriforms association from Late Triassic beds of San Luis. Thus, they add to the faunal assemblage recently reported from this basin at San Juan Province, which is much rich and diverse than the coeval paleofauna well known from Los Colorados Formation in the

  16. Tectonic significance of porosity and permeability regimes in the red beds formations of the South Georgia Rift Basin

    NASA Astrophysics Data System (ADS)

    Akintunde, Olusoga M.; Knapp, Camelia C.; Knapp, James H.

    2014-09-01

    A simple, new porosity/permeability-depth profile was developed from available laboratory measurements on Triassic sedimentary red beds (sandstone) from parts of the South Georgia Rift (SGR) basin in order to investigate the feasibility for long-term CO2 storage. The study locations were: Sumter, Berkeley, Dunbarton, Clubhouse Crossroad-3 (CC-3) and Norris Lightsey wells. As expected, both porosity and permeability show changes with depth at the regional scale that was much greater than at local scale. The significant changes in porosity and permeability with depth suggest a highly compacted, deformed basin, and potentially, a history of uplift and erosion. The permeability is generally low both at shallow (less than 1826 ft/556.56 m) and deeper depths (greater than 1826 ft/556.56 m). Both porosity and permeability follow the normal trend, decreasing linearly with depth for most parts of the study locations with the exception of the Norris Lightsey well. A petrophysical study on a suite of well logs penetrating the Norris Lightsey red beds at depths sampled by the core-derived laboratory measurements shows an abnormal shift (by 50%) in the acoustic travel time and/or in the sonic-derived P-wave velocity that indicates possible faulting or fracturing at depth. The departure of the Norris Lightsey's porosities and permeabilities from the normal compaction trend may be a consequence of the existence of a fault/fracture controlled abnormal pressure condition at depth. The linear and non-linear behaviors of the porosity/permeability distribution throughout the basin imply the composition of the SGR red beds, and by extension analog/similar Triassic-Jurassic formations within the Eastern North American Margin have been altered by compaction, uplift, erosion and possible faulting that have shaped the evolution of these Triassic formations following the major phase of rifting.

  17. Diagenesis and fracture development in the Bakken Formation, Williston Basin; implications for reservoir quality in the middle member

    USGS Publications Warehouse

    Pitman, Janet K.; Price, Leigh C.; LeFever, Julie A.

    2001-01-01

    The middle member of the Bakken Formation is an attractive petroleum exploration target in the deeper part of the Williston Basin because it is favorably positioned with respect to source and seal units. Progressive rates of burial and minor uplift and erosion of this member led to a stable thermal regime and, consequently, minor variations in diagenesis across much of the basin. The simple diagenetic history recorded in sandstones and siltstones in the middle member can, in part, be attributed to the closed, low-permeability nature of the Bakken petroleum system during most of its burial history. Most diagenesis ceased in the middle member when oil entered the sandstones and siltstones in the Late Cretaceous. Most oil in the Bakken Formation resides in open, horizontal fractures in the middle member. Core analysis reveals that sandstones and siltstones associated with thick mature shales typically have a greater density of fractures than sandstones and siltstones associated with thin mature shales. Fractures were caused by superlithostatic pressures that formed in response to increased fluid volumes in the source rocks during hydrocarbon generation

  18. A new Xenacanthiformes shark (Chondrichthyes, Elasmobranchii) from the Late Paleozoic Rio do Rasto Formation (Paraná Basin), Southern Brazil.

    PubMed

    Pauliv, Victor E; Dias, Eliseu V; Sedor, Fernando A; Ribeiro, Ana Maria

    2014-03-01

    The Brazilian records on Xenacanthiformes include teeth and cephalic spines from the Parnaíba, Amazonas and Paraná basins. This work describes a new species of Xenacanthidae, collected in an outcrop of Serrinha Member of Rio do Rasto Formation (Wordian to Wuchiapingian), Paraná Basin, municipality of Jacarezinho, State of Paraná. The teeth of the new species are two or three-cuspidated and the aboral surface show a smooth concavity and one rounded basal tubercle. The coronal surface presents one semi-spherical and subcircular coronal button, and also two lateral main cusps and one central (when present) with less than one fifth of the size of the lateral cusps in the labial portion. The lateral cusps are asymmetric or symmetric, rounded in transversal section, lanceolate in longitudinal section, devoid of lateral carinae and lateral serrations, and with few smooth cristae of enameloid. In optical microscope the teeth show a trabecular dentine (osteodentine) base, while the cusps are composed by orthodentine, and the pulp cavities are non-obliterated by trabecular dentine. The fossil assemblage in the same stratigraphical level and in the whole Rio do Rasto Formation indicates another freshwater record for xenacanthid sharks.

  19. Sedimentary characteristics of carbonate intra-platform shoals and their formation in Ordovician Tarim Basin, West China

    NASA Astrophysics Data System (ADS)

    Meng, M.

    2015-12-01

    The widely distributed carbonate intra-platform shoals has become a new important exploration target within the Tarim Basin, where reservoirs of Yubei oil-field (discovered in 2011) and the Shunnan oil-field (discovered in 2013) occur. Better understanding of the sedimentary characteristics and formation of intra-platform shoals is significant for predicting the distribution of Ordovician shoal reservoirs. The sedimentary characteristics, distribution patterns and formation mechanisms of carbonate intra-platform shoals in Ordovician Tarim Basin were studied based on outcrop analogue, core data, thin section observation, seismic, and well log data. Those shoals include oolitic shoal, intraclast shoal and bioclastic shoal. The intra-platform shoal consists of three sedimentary units: shoal base, shoal core and shoal cover, which are adjacent to intershoal sea faces. Laterally, the intra-platform shoals occurred as a more continuous sheet-like body.The intra-platform shoals deposited mainly in the lowstand systems tract and late stage of highstand systems tract. Several factors were probably responsible for the occurrence of intra-platform shoals, including: (i) a relatively shallow-water condition with a strong hydrodynamic environment, (ii) high-frequency oscillations of the sea level, and (iii) Subtle paleo-highs and relatively weak structural activities, which are important for the spatial distribution of reservoir facies.

  20. On a moderately diverse continental ichnofauna from the Permian Ikakern Formation (Argana Basin, Western High Atlas, Morocco)

    NASA Astrophysics Data System (ADS)

    Hminna, Abdelkbir; Voigt, Sebastian; Saber, Hafid; Schneider, Jörg W.; Hmich, Driss

    2012-06-01

    The Permian Ikakern Formation of the Argana Basin yielded important tetrapod skeletal remains but is still poorly known for any other kind of fossils. Here we present a moderately diverse assemblage of invertebrate and vertebrate traces from red beds in the upper part of the formation (Tourbihine Member, T2) near Timezgadiouine. Recorded ichnotaxa include Spongeliomorpha carlsbergi (Bromley and Asgaard, 1979), Striatichnium natalisWalter, 1982, AmphisauropusHaubold, 1970, HyloidichnusGilmore, 1927, ErpetopusMoodie, 1929, and DromopusMarsh, 1894. The traces occur in laminated muddy siltstone and fine-grained sandstone that we interpret as slack-water deposits in an episodically high energy fluvial setting. Including arthropod burrows, arthropod grazing traces and tetrapod footprints, the ichnofossil assemblage corresponds to the Scoyenia ichnofacies. The described trace fossils provide evidence for various invertebrates and vertebrates hitherto unknown from the body fossil record of the study area. By extending the stratigraphic and geographic range of some of the recorded ichnotaxa, our finds strongly emphasise the importance of the Argana Basin for the reconstruction and understanding of Late Palaeozoic terrestrial ecosystems.

  1. Ichnological constraints on the depositional environment of the Sawahlunto Formation, Kandi, northwest Ombilin Basin, west Sumatra, Indonesia

    NASA Astrophysics Data System (ADS)

    Zonneveld, J.-P.; Zaim, Y.; Rizal, Y.; Ciochon, R. L.; Bettis, E. A.; Aswan; Gunnell, G. F.

    2012-02-01

    A low diversity trace fossil assemblage is described from the Oligocene Sawahlunto Formation near Kandi, in the northwestern part of the Ombilin Basin in western Sumatra, Indonesia. This trace fossil assemblage includes six ichnogenera attributed to invertebrate infaunal and epifaunal activities ( Arenicolites, Diplocraterion, Planolites, Monocraterion/ Skolithos and Coenobichnus) and two ichnotaxa attributed to vertebrate activity (avian footprints: two species of Aquatilavipes). Arenicolites, Diplocraterion and Monocraterion/ Skolithos record the suspension feeding activities of either arthropods (most likely amphipods) or vermiform organisms. Planolites reflects the presence of an infaunal deposit feeder. Coenobichnus records the walking activities of hermit crabs. Both the Coenobichnus and the avian footprints record the surficial detritus scavenging of epifaunal organisms within a subaerial setting. These traces occur within a fine-grained sandstone succession characterized by planar laminae and low-relief, asymmetrical, commonly mud-draped (locally bidirectional) ripples. The presence of traces attributable to suspension feeders implies deposition in a subaqueous setting. Their occurrence (particularly the presence of Arenicolites and Diplocraterion) in a sandstone bed characterized by mud-draped and bidirectional ripples implies emplacement in a tidally-influenced marine to marginal marine setting. Co-occurrence of these traces with well-preserved avian footprints ( Aquatilavipes) further implies periodic subaerial exposure. Thus, it is most likely that the Sawahlunto Formation near Kandi records deposition within an intertidal flat setting. Definitive evidence of marine influences in the Oligocene interval of the Ombilin Basin implies a more complex tectono-stratigraphic history than has previously been implied.

  2. A preliminary study of the calcite beef found in the Cretaceous Jinju Formation, Gyeongsang Basin, South Korea

    NASA Astrophysics Data System (ADS)

    Ha, S.; Chae, Y. U.; Son, M.; Jeong, G. Y.; Paik, I. S.; Lim, H. S.

    2015-12-01

    The term "beef" refers to fibrous minerals in bedding-parallel veins, where the fibers are approximately perpendicular to the vein margins (Cobbold et al., 2013). It mostly appears within organic-rich black shale layers in sedimentary basin. Although the veins can consist of white gangue minerals, such as calcite, gypsum, or quartz, the commonest mineral in the fibers is calcite. According to the worldwide localities of calcite beef compiled by Cobbold et al (2012), they concentrated in some areas, especially around the Atlantic Ocean. However, they have been rarely reported in the western Pacific margin, except Australia and New Zealand. Recently, calcite beefs have been found in the Cretaceous Jinju Formation, Gyeongsang Basin, Korea. As far as we know, this is the first report of calcite beef in Korea. The lacustrine Jinju Formation is about 1,200 m thick, and made up mainly of lacustrine dark grey to black mudstones. In the study area, calcite beefs were commonly found in the organic-rich black shale layers. The vein thickness is anywhere between a few millimeters to maximum 3 centimeters, and their length ranges from a few centimeters to several tens of meters. The interval between successive veins is from a few centimeters to about 1 meter. Most of them occur parallel to the bedding planes, although some of them are developed along fault planes or within deformed layers. In case of relatively thick beefs, the center of veins often shows a dark grey to black central median line, defined by fine-grained calcite grains, fluid inclusion lines, or wall rock particles. Based on the orientation of fibrous calcite, they can be divided into two types: straight and sigmoidal types. The fibrous calcites are thought to have been symmetrically grown from the median lines to top and bottom of wall rock. The formation mechanism of horizontal fractures, and the formation temperature of beefs in the study area remain as a matter to be studied further.

  3. Marine redox conditions in the middle Proterozoic ocean and isotopic constraints on authigenic carbonate formation: Insights from the Chuanlinggou Formation, Yanshan Basin, North China

    NASA Astrophysics Data System (ADS)

    Li, Chao; Planavsky, Noah J.; Love, Gordon D.; Reinhard, Christopher T.; Hardisty, Dalton; Feng, Lianjun; Bates, Steven M.; Huang, Jing; Zhang, Qirui; Chu, Xuelei; Lyons, Timothy W.

    2015-02-01

    To improve our understanding of ocean chemistry and biogeochemical cycling following the termination of large-scale Paleoproterozoic iron formation (IF) deposition (∼1.85 billion years ago [Ga]), we conducted a Fe-S-C-Mo geochemical study of the ∼1.65 Ga Chuanlinggou Formation, Yanshan Basin, North China. Despite the cessation of IF deposition, our results suggest the presence of anoxic but non-euxinic (ferruginous) conditions persisted below the surface mixed layer for the deepest portion of the continental rifting basin and that this pattern is apparently independent of the local organic carbon content. However, our paired S-isotope data of carbonate-associated sulfate and pyrite suggest presence of sulfate in pore fluids, which is not consistent with insufficient sulfate for bacterial sulfate reduction in the water column. Despite evidence for deposition under anoxic conditions, sedimentary molybdenum (Mo) concentrations are mostly not enriched relative to average continental crust. This relationship is consistent with the notion that sulfide-dominated conditions in the water column and/or the sediments are required for Mo enrichment and validates past assertions that Mo enrichment patterns in ancient shales track both the local presence and global distribution of euxinia specifically. In addition, we identified extensive diagenetic carbonate precipitation in the upper Chuanlinggou Formation with only moderately negative δ13C values (-3.4 ± 1.4‰). We propose, with support from a numerical model, that these diagenetic carbon isotope values were most likely derived from precipitation of carbonates dominantly in the methanic zone within the sediments. Diagenetic carbonate precipitation in the methanic zone is likely to have been more extensive in the Proterozoic than the Phanerozoic due to porewater oxidant limitation.

  4. Conditions of formation of the gas deposits in the Dneprovsk-Donets basin

    SciTech Connect

    Solov'ev, B.A.

    1986-06-01

    The major part of the gas resources of the Dneprovsk-Donets basin, concentrated in the southeast of the region, is associated with a complex of Late Carboniferous-Early Permian age, predominantly redbeds and extraordinarily poor in organic matter. In the northwest, these sediments are associated with oil deposits and in the central part of the basin with oil and gas deposits. The hydrocarbons in this complex undoubtedly entered from underlying petroleum source beds. An analysis of the observed zonation of hydrocarbons in the Upper Carboniferous-Lower Permian sequence leads to the conclusion that it was controlled to a decisive degree by the kind of original organic matter in the underlying sequences. These deposits offer an interesting history of interacting tectonic and hydrodynamic processes. 9 references.

  5. Seismic effects from major basin formations on the moon and Mercury

    NASA Technical Reports Server (NTRS)

    Schultz, P. H.; Gault, D. E.

    1975-01-01

    Grooved and hilly terrains occur at the antipode of major basins on the moon (Imbrium, Orientale) and Mercury (Caloris). Such terrains may represent extensive landslides and surface disruption produced by impact-generated P-waves and antipodal convergence of surface waves. Order-of-magnitude calculations for an Imbrium-size impact on the moon indicate P-wave-induced surface displacements of 10 m at the basin antipode that would arrive prior to secondary ejecta. Comparable surface waves would arrive subsequent to secondary ejecta impacts beyond 1000 km and would increase in magnitude as they converge at the antipode. Other seismically induced surface features include: subdued, furrowed crater walls produced by landslides and concomitant secondary impacts; emplacement and leveling of light plains units owing to seismically induced 'fluidization' of slide material; and perhaps the production and enhancement of deep-seated fractures that led to the concentration of farside lunar maria in the Apollo-Ingenii region.

  6. Reservoir Characterization of the Lower Green River Formation, Southwest Uinta Basin, Utah

    SciTech Connect

    Morgan, Craig D.; Chidsey, Jr., Thomas C.; McClure, Kevin P.; Bereskin, S. Robert; Deo, Milind D.

    2002-12-02

    The objectives of the study were to increase both primary and secondary hydrocarbon recovery through improved characterization (at the regional, unit, interwell, well, and microscopic scale) of fluvial-deltaic lacustrine reservoirs, thereby preventing premature abandonment of producing wells. The study will encourage exploration and establishment of additional water-flood units throughout the southwest region of the Uinta Basin, and other areas with production from fluvial-deltaic reservoirs.

  7. Depositional history of the Mississippian Ullin and Fort Payne Formations in the Illinois Basin

    SciTech Connect

    Lasemi, Z.; Treworgy, J.D.; Norby, R.D. )

    1994-04-01

    Field and subsurface data suggest that the mid-Mississippian Ullin Limestone in the Illinois Basin is composed of coalesced Waulsortian-type mounds and porous bryozoan-dominated buildups. Waulsortian mounds in the basin contain a lime mudstone to wackestone core that is flanked and capped by in situ porous bryozoan bafflestone or transported crinoidal-bryozoan packstone and grainstone. The mound core facies appear to be most common in the lower part of the Ullin and is thicker in a deeper outer-ramp setting. Shoreward and up-section (upper part of the outer-ramp through mid-ramp setting), the core facies is generally thinner, while the flanking and capping facies are thicker. Isopachous maps of the Ullin and Fort Payne suggest the presence of several large areas of thick carbonate buildups (Ullin) surrounded by a deep-water, sub-oxic environment (Fort Payne) in the Illinois Basin. Progradation of these buildups and associated facies resulted in a shallower ramp setting during deposition of the upper Ullin. Storm-generated carbonate sandwaves became widespread on this ramp. Sandwaves were mobile and for the most part unfavorable sites for further development of thick mud mounds and/or in situ bryozoan buildups. However, isolated mounds and flanking buildups are present in the upper part of the Ullin, and, together with the sandwaves, formed an irregular topography that led to the development of oolitic grainstone shoals during deposition of the overlying Salem Limestone.

  8. Estimation of Geologic Storage Capacity of Carbon Dioxide in the Bukpyeong Basin, Korea Using Integrated Three-Dimensional Geologic Formation Modeling and Thermo-Hydrological Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Kim, J.; Kihm, J.; Park, S.; SNU CO2 GEO-SEQ TEAM

    2011-12-01

    A conventional method, which was suggested by NETL (2007), has been widely used for estimating the geologic storage capacity of carbon dioxide in sedimentary basins. Because of its simple procedure, it has been straightforwardly applied to even spatially very complicate sedimentary basins. Thus, the results from the conventional method are often not accurate and reliable because it can not consider spatial distributions of fluid conditions and carbon dioxide properties, which are not uniform but variable within sedimentary basins. To overcome this limit of the conventional method, a new method, which can consider such spatially variable distributions of fluid conditions and carbon dioxide properties within sedimentary basins, is suggested and applied in this study. In this new method, a three-dimensional geologic formation model of a target sedimentary basin is first established and discretized into volume elements. The fluid conditions (i.e., pressure, temperature, and salt concentration) within each element are then obtained by performing thermo-hydrological numerical modeling. The carbon dioxide properties (i.e., phase, density, dynamic viscosity, and solubility to groundwater) within each element are then calculated from thermodynamic database under corresponding fluid conditions. Finally, the geologic storage capacity of carbon dioxide with in each element is estimated using the corresponding carbon dioxide properties as well as porosity and element volume, and that within the whole sedimentary basin is determined by summation over all elements. This new method is applied to the Bukpyeong Basin, which is one of the prospective offshore sedimentary basins for geologic storage of carbon dioxide in Korea. A three-dimensional geologic formation model of the Bukpyeong Basin is first established considering the elevation data of the boundaries between the geologic formations obtained from seismic survey and geologic maps at the sea floor surface. This geologic

  9. 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

  10. Authigenic molybdenum formation in marine sediments: A link to pore water sulfide in the Santa Barbara Basin

    USGS Publications Warehouse

    Zheng, Yen; Anderson, Robert F.; VanGeen, A.; Kuwabara, J.

    2000-01-01

    Pore water and sediment Mo concentrations were measured in a suite of multicores collected at four sites along the northeastern flank of the Santa Barbara Basin to examine the connection between authigenic Mo formation and pore water sulfide concentration. Only at the deepest site (580 m), where pore water sulfide concentrations rise to >0.1 ??M right below the sediment water interface, was there active authigenic Mo formation. At shallower sites (550,430, and 340 m), where pore water sulfide concentrations were consistently <0.05 ??M, Mo precipitation was not occuring at the time of sampling. A sulfide concentration of ???0.1 ??M appears to be a threshold for the onset of Mo-Fe-S co-precipitation. A second threshold sulfide concentration of ???100 ??M is required for Mo precipitation without Fe, possibly as Mo-S or as particle-bound Mo. Mass budgets for Mo were constructed by combining pore water and sediment results for Mo with analyses of sediment trap material from Santa Barbara Basin as well as sediment accumulation rates derived from 210Pb. The calculations show that most of the authigenic Mo in the sediment at the deepest site is supplied by diffusion from overlying bottom waters. There is, however, a non-lithogenic particulate Mo associated with sinking particles that contributes ???15% to the total authigenic Mo accumulation. Analysis of sediment trap samples and supernant brine solutions indicates the presence of non-lithogenic particulate Mo, a large fraction of which is easily remobilized and, perhaps, associated with Mn-oxides. Our observations show that even with the very high flux of organic carbon reaching the sediment of Santa Barbara Basin, active formation of sedimentary authigenic Mo requires a bottom water oxygen concentration below 3 ??M. However, small but measurable rates of authigenic Mo accumulation were observed at sites where bottom water oxygen ranged between 5 and 23 ??M, indicating that the formation of authigenic Mo occured in the

  11. The stratotype and facies of the glacial Lower Vendian Nichatka Formation, Chara River basin, Central Siberia

    NASA Astrophysics Data System (ADS)

    Chumakov, N. M.; Kernitskii, V. V.

    2016-07-01

    Sediments of the Nichatka Formation are facially studied and thoroughly described, the sections are correlated, and the subformations are recognized. The formation represents a key stratigraphic unit to reveal the origin of the Central Siberian glacial horizon and to correlate it with glacial horizons in other regions of the world, namely, with the Laplandian Horizon of the Lower Vendian, Nantou and Marino tillites, etc. The Nichatka Formation is correlated with the glacial Bolshoi Patom (Dzhemkukan) Formation of the Vendian reference section at the Ura Uplift. Unlike the latter, it is mainly composed of continental glacial deposits and is marked by a complex facies composition. The glacial origin of the Nichatka Formation is reliably determined on the basis of a set of diagnostic characters. This permits a more complete reconstruction of the Early Vendian depositional environments. In addition to typical basal tillites and marginal moraine deposits, the formation includes glaciolacustrine and fluvioglacial sediments along with aquatillites, allotillites, and the glacial fan, including subaqueous, deposits.

  12. Applied velocity versus offset (VVO) to validated & characterized fracturing zone in intra Baturaja Formation, South Sumatera Basin

    NASA Astrophysics Data System (ADS)

    Mardiyan, Hilman; Rusli, Saifatur

    2016-01-01

    The velocity versus offset (VVO) as new geophysical method can be applied to detect some geological phenomenon, such as hydrocarbon trap, structural-fracture anomaly, facies changes, etc. The VVO method is data driven, based on the normal move out equation (NMO) and measuring the local event correlation between adjacent traces to get velocity gradient attributes which is derived from cross-plotting the velocity versus offset (VVO). This paper is describing applied VVO model that controlled by well data which indicated fracture from logs data, especially Resistivity Imager Logs or Formation Micro Imager (FMI). Images FMI logs data at Intra-Baturaja Carbonate Formation (BRF) in South Palembang Sub-basin (SPB), South Sumatera, shows vugs with fractures which orientation is roughly NNW-SSE. Meanwhile, the 2D NMO seismic gathers indicated those all as hockey stick at far offset. By applying VVO method, hockey stick can be identified and then used to validated, characterized and localized where the fracturing zone in intra-Baturaja Formation is. Laterally, VVO quantified as velocity gradient attribute which associated with geological model as the fracturing zone in study area. Characterization fracturing zone in Intra Baturaja Formation as geological lateral model by design is a challenging task for most exploration and production. In term of exploration where limited data is available, it can be used step ahead as carbonate fracture reservoir candidate in proven area and adjacent, especially in SPB South Sumatra.

  13. Geochemical Aspects of Formation of Large Oil Deposits in the Volga-Ural Sedimentary Basin

    NASA Astrophysics Data System (ADS)

    Plotnikova, I.; Nosova, F.; Pronin, N.; Nosova, J.; Budkevich, T.

    2012-04-01

    C35/hC34, GAM / HOP, S27/S28/S29 (steranes), DIA / REG, Ts / Tm, MOR / HOP, NOR / HOP, TET / TRI, C29SSR, C29BBAA, C31HSR, S30STER, TRI / PENT, TRI / HOP. Comparison in the rock-oil system was performed primarily according to the parameters indicating the depositional environment of the source rock that contains syngenetic DOM - according to the coefficients that determine lithological conditions for the formation of the supposed oil-source bed strata (DIA / REG, Ts / Tm, NOR / HOP, TRI / HOP and STER / PENT). Biomarker ratios indicate a different type of sedimentation basins. Sediments, which accumulated DOM from Semilukskiy horizon, can be characterized by low clay content, or its absence, that is consistent with the carbonate type of cut of the horizon. The bacterial material that was accumulated under reducing conditions of sedimentation appeared to be the source of syngenetic OM. Chemofossils found in oils from Pashiyskiy horizon are typical of sedimentary strata that contain clay - for clastic rocks, which in the study area are mainly represented by deposits and Eyfel Givetian layers of the Middle Devonian and lowfransk substage of the Upper Devonian. The study of correlations obtained for the different coefficients of OM and oils showed that only the relationships between Ts/Tm and DIA/REG and between NOR/HOP and TRI/HOP are characteristic of close, almost similar values of correlation both for the dispersed organic matter and for oil. In all other cases, the character of the correlation of OM is significantly different from that of oil. The differences in values and ranges of biomarker ratios as well as the character of their correlation indicates the absence of genetic connection between the oil from Pashiyskiy horizon for the dispersed organic matter from Semilukskiy horizon. This conclusion is based on the study of five biomarker parameters (DIA/REG, Ts/Tm, NOR/HOP, TRI/HOP and STER/PENT). The research results described in the article clearly indicate the

  14. Organic Aerosol Formation and Processing in the Los Angeles Basin: Role of Gasoline vs. Diesel Emissions

    NASA Astrophysics Data System (ADS)

    Bahreini, R.; Middlebrook, A. M.; De Gouw, J. A.; Warneke, C.; Trainer, M.; Brown, S. S.; Dube, B.; Holloway, J. S.; Perring, A. E.; Schwarz, J. P.; Spackman, J. R.; Stark, H.; Wagner, N.; Parrish, D. D.

    2011-12-01

    During the CalNex-2010 field project in May-June 2010, the NOAA WP-3D aircraft performed flights up- and down-wind of metropolitan, industrial, agricultural and animal feeding sites in central-southern California. Here airborne data on organic aerosol (OA) properties as measured by a compact time-of-flight aerosol mass spectrometer along with measurements of trace gases affecting secondary production of aerosols in the Los Angeles Basin are presented. The analysis presented indicates that the ratio of organic aerosol to carbon monoxide (OA/CO) is significantly higher than the previously observed ratios of primary OA/CO downwind of urban areas, indicating that even on short time scales of transport within the basin, there is significant production of secondary organic aerosol (SOA). The increase in the ratio of OA/CO is also accompanied by an increase in the fraction of oxygenated species of OA, providing evidence for production of more oxidized SOA as air masses are photochemically processed. Despite a smaller contribution from Diesel vehicles to traffic on weekends, analysis of the weekend vs. weekday data indicates that similar values of ΔOA/ΔCO are observed on the weekends compared to weekdays, for air masses with similar degrees of photochemical processing. This indicates that emissions of gas phase organic species from Diesel vehicles are not significant for OA production in the LA Basin. Our calculated steady-state concentrations of hydroxyl radical (OH) indicate that OH concentrations at mid-day are substantially higher on weekends compared to weekdays, indicating faster chemical processing of air masses during a fixed length of time on the weekends compared to weekdays.

  15. A brief lithostratigraphic review of the Abrahamskraal and Koonap formations of the Beaufort Group, South Africa: Towards a basin-wide stratigraphic scheme for the Middle Permian Karoo

    NASA Astrophysics Data System (ADS)

    Day, Michael Oliver; Rubidge, Bruce Sidney

    2014-12-01

    The basal strata of the Beaufort Group of the South African Karoo Basin, comprising the western Abrahamskraal and eastern Koonap formations, contain the most time extensive record of Middle Permian fossil tetrapods and hold the key to understanding Middle Permian biodiversity change in the continental realm. To determine faunal stratigraphic ranges a reliable lithostratigraphic framework for Middle Permian Beaufort deposits is essential. Until now this has proved difficult to achieve, largely due to the homogeneity of the fluvial succession coupled with structural complexity as a result of Cape Fold Belt orogenesis. Accordingly, the Abrahamskraal Formation has been only locally subdivided on the basis of sandstone packages but regional stratigraphic subdivision has not yet achieved satisfactorily. Collation of stratigraphic sections from around the Karoo Basin for this study demonstrates the presence of four sandstone packages are present within the Abrahamskraal Formation in the south-western corner of the basin. These sandstone packages are given member status, based upon the nomenclature of Le Roux (1985) with the addition of the newly recognised Grootfontein Member. The Combrinkskraal and Grootfontein Members occur in the lower half of the Abrahamskraal Formation and are laterally persistent along the southern margin of the basin. The Koornplaats Member is more restricted to the south west corner of the basin, where it quite thick, suggesting the narrowing of the highly channelized area. The overlying Moordenaars Member, more extensive towards the north than underlying packages, indicates subsequent northwesterly expansion of the locus of active channelization with time. Although thin sandstone packages in the more easterly positioned and stratigraphically equivalent Koonap Formation, this does not facilitate lithostratigraphic subdivision of this part of the stratigraphic succession and may indicate a different form of fluvial architecture. Our study provides

  16. Minerals and trace elements in silcretes of the Sado basin (Alentejo, southern Portugal) and implications for silcrete formation

    NASA Astrophysics Data System (ADS)

    Sauer, Daniela; Kullmann, Sarah; Zarei, Mehdi; Stahr, Karl

    2014-05-01

    Soils in the eastern part of the Sado basin (southern Portugal) are often characterized by massive cementations caused by silica. The thickness and massive character of these silcretes led to the hypothesis that accumulation of silica took place not only vertically within a soil profile, but also by enrichment through lateral water and element flow into the Sado basin. The aims of the study reported here were: 1) to characterize the cementing agent with regard to its mineralogy; 2) to test the hypothesis that silification was enhanced through lateral silica transport from the adjacent Alto Alentejo into the Sado basin. Aim 1) was achieved by scratching silica coatings from ped surfaces of the silicified soil horizons and cleaning them manually in the lab under a binocular microscope. After careful smashing with a mortar, density separation by sodium polytungstate solution was applied to remove any remaining mineral grains from the silica samples. The cleaned silica samples were then subjected to XRD and SEM in combination with EDS. Aim 2) was attained by using trace element contents of predominant rock types of the Alto Alentejo and of the silcretes in the Sado basin for identifying lateral pathways of water and silica in the landscape. Ten rock samples from the assumed source area of silica were combusted by fusion melt, and their contents of Ba, Co, Cs, Nb, Pb, Rb, Sr, Y and Zr were analyzed by ICP-MS. The same elements were analyzed in NaOH extracts of the cemented soil horizons in the Sado basin. The X-ray diagrams of the silica coatings show the expected broad hump of amorphous silica. In addition, quartz, kaolinite, and surprisingly high amounts of halloysite are identified, the latter reflecting conditions of intensive weathering and pedogenesis during the formation of the silica coatings. This intensive soil formation and hence silification most likely took place during Pliocene. Greater age is impossible, because the silification took place in Pliocene

  17. Provenance and paleogeography of the Late Cretaceous Mengyejing Formation, Simao Basin, southeastern Tibetan Plateau: Whole-rock geochemistry, U-Pb geochronology, and Hf isotopic constraints

    NASA Astrophysics Data System (ADS)

    Wang, Licheng; Liu, Chenglin; Gao, Xiang; Zhang, Hua

    2014-05-01

    The Late Cretaceous Mengyejing Formation, which contains the only pre-Quaternary potash salt deposit in the Simao Basin, southeastern Tibet, is thought to be genetically related to the Maha Sarakham Formation in the Khorat Basin. The provenance and paleogeography of these two basins have been under debate, although little diagnostic evidence has been previously published. A combined analysis of whole rock geochemistry, zircon U-Pb chronology, and Hf isotopic compositions was performed to characterize the provenance of the Mengyejing Formation. These formation's sandstones are characterized by moderate chemical index of alteration (CIA) values. These values, together with plots of the Th/U-Th ratios, suggest that certain samples have undergone moderate weathering and sedimentary recycling. The major and trace elements (La/Th-Hf, Th/Sc-Zr/Sc, Eu/Eu*-Th/Sc, TiO2-Fe2O3T + MgO, Al2O3/SiO2-Fe2O3T + MgO, K2O/Na2O-SiO2) indicate that the sedimentary sources were felsic rocks from an active continental margin or continental arc with a minor amount of recycled sediment from a passive continental margin. The Mengyejing Formation contains detrital zircons primarily with U-Pb ages of 2.45-2.57 Ga, 1.8-1.9 Ga, 740-880 Ma, 410-470 Ma, and 215-300 Ma. The results reveal that the pre-Devonian zircons are derived from the recycled sediments of the Yangtze block originating in the Qinling Orogenic Belt, and they share this provenance with the coeval sediments in the Khorat Basin. The magmatic rocks of the Ailaoshan and Lincang areas are responsible for supplying the Devonian to Triassic detrital zircons. These provenance data combined with published paleocurrent results suggest that the Simao Basin was situated on the western margin of the Khorat Basin during the Late Cretaceous. The basins were connected when marine incursion occurred. We propose that pre-Devonian materials from the southwestern Sichuan Basin first supplied detritus to the Simao Basin and subsequently to the Khorat

  18. Saharan dust deposition in the Carpathian Basin and its possible effects on interglacial soil formation

    NASA Astrophysics Data System (ADS)

    Varga, György; Cserháti, Csaba; Kovács, János; Szalai, Zoltán

    2016-09-01

    Several hundred tons of windblown dust material are lifted into the atmosphere and are transported every year from Saharan dust source areas towards Europe having an important climatic and other environmental effect also on distant areas. According to the systematic observations of modern Saharan dust events, it can be stated that dust deflated from North African source areas is a significant constituent of the atmosphere of the Carpathian Basin and Saharan dust deposition events are identifiable several times in a year. Dust episodes are connected to distinct meteorological situations, which are also the determining factors of the different kinds of depositional mechanisms. By using the adjusted values of dust deposition simulations of numerical models, the annual Saharan dust flux can be set into the range of 3.2-5.4 g/m2/y. Based on the results of past mass accumulation rates calculated from stratigraphic and sedimentary data of loess-paleosol sequences, the relative contribution of Saharan dust to interglacial paleosol material was quantified. According to these calculations, North African exotic dust material can represent 20-30% of clay and fine silt-sized soil components of interglacial paleosols in the Carpathian Basin. The syngenetic contribution of external aeolian dust material is capable to modify physicochemical properties of soils and hereby the paleoclimatic interpretation of these pedogene stratigraphic units.

  19. Formation of layered and schlieren migmatites by partial melting at Aspen Basin, New Mexico

    SciTech Connect

    Metcalf, R.V.

    1985-01-01

    Although several recent studies of layered migmatites have suggested that they originated by subsolidus differentiation, both layered and schlieren-type migmatites at Aspen Basin formed by partial melting. Proterozoic supracrustal rocks at Aspen Basin were intruded by a suite of calc-alkalic diorite, tonalite and granite, intensely deformed, then intruded by younger aplite and granite. The supra-crustal rocks consist of migmatitic, sillimanite-grade metagreywacke, felsic gneiss and amphibolite. Within the metagreywackes, concordant coarse-grained neosomes (leucosomes + melanosomes) are interlayered with fine-grained grey gneiss. These layered migmatites grade toward schlieren-type migamtites at deeper levels, where the proportions of leucocratic material and degree of discordance increase. Two pieces of evidence demonstrate that leucosomes crystallized from melts. Partial melting is favored over injection on the basis of major and trace element chemical analyses. None of the plutonic units have appropriate composition to serve as the migmatite source, and the chemical and mineralogical compositions of leucosomes and leucogranites correlate to their metamorphic host rock, implying local derivation. The transition from layered to schlieren migmatites is marked by an increase in Rb, Rb/Sr, and K/sub 2/O/Na/sub 2/O within the leucosomes and leucogranites, and apparently represents an increase in the degree of partial melting.

  20. Wetland river flow interaction in a sedimentary formation of the white Volta basin, Ghana

    NASA Astrophysics Data System (ADS)

    Nyarko, B. K.; Diekkruger, B.; Van De Giesen, N.; Barry, B.

    2011-12-01

    Groundwater resources in the floodplain wetlands of the White Volta River basin of Ghana is a major source of water for irrigation activities of communities living around and baseflow to sustain the flow of the river. Hydrology of the floodplain wetlands in the basin are complex, characterized by temporally variable storage volumes with erratic contribution to streamflow. For the continual usage of groundwater resources in the floodplains there is a need to study the form of interaction between the main river and floodplain wetlands. The study, adopted the PM-WIN (MODFLOW) model for simulating the interaction between the wetland and stream. Additionally, the lower boundary discharge output from the HYDRUS-1D model is the estimated recharge. This input quantifies the temporal and spatial variations in sub-surfaces discharges in the floodplain wetland. The simulation of the sub-surface hydraulic head of the wetland indicates a systematic variation relative to the White Volta River response to changes in the rainfall pattern. The interaction conditions vary from season to season with March, April, and May showing the least leakage (estimated values of 0.03mm/day, 0.06mm/day, and 0.15 mm/day, respectively) from the river into the floodplain wetland. Notably, the interaction between the wetland and the river as simulated is bidirectional. With most of the flow coming out from the river into the floodplain wetland, this condition persists in the months of August and September.

  1. Ground water budget analysis and cross-formational leakage in an arid basin.

    PubMed

    Hutchison, William R; Hibbs, Barry J

    2008-01-01

    Ground water budget analysis in arid basins is substantially aided by integrated use of numerical models and environmental isotopes. Spatial variability of recharge, storage of water of both modern and pluvial age, and complex three-dimensional flow processes in these basins provide challenges to the development of a good conceptual model. Ground water age dating and mixing analysis with isotopic tracers complement standard hydrogeologic data that are collected and processed as an initial step in the development and calibration of a numerical model. Environmental isotopes can confirm or refute a priori assumptions of ground water flow, such as the general assumption that natural recharge occurs primarily along mountains and mountain fronts. Isotopes also serve as powerful tools during postaudits of numerical models. Ground water models provide a means of developing ground water budgets for entire model domains or for smaller regions within the model domain. These ground water budgets can be used to evaluate the impacts of pumping and estimate the magnitude of capture in the form of induced recharge from streams, as well as quantify storage changes within the system. The coupled analyses of ground water budget analysis and isotope sampling and analysis provide a means to confirm, refute, or modify conceptual models of ground water flow.

  2. Sill intrusion driven fluid flow and vent formation in volcanic basins: Modeling rates of volatile release and paleoclimate effects

    NASA Astrophysics Data System (ADS)

    Iyer, Karthik; Schmid, Daniel

    2016-04-01

    Evidence of mass extinction events in conjunction with climate change occur throughout the geological record and may be accompanied by pronounced negative carbon isotope excursions. The processes that trigger such globally destructive changes are still under considerable debate. These include mechanisms such as poisoning from trace metals released during large volcanic eruptions (Vogt, 1972), CO2 released from lava degassing during the formation of Large Igneous Provinces (LIPs) (Courtillot and Renne, 2003) and CH4 release during the destabilization of sub-seafloor methane (Dickens et al., 1995), to name a few. Thermogenic methane derived from contact metamorphism associated with magma emplacement and cooling in sedimentary basins has been recently gaining considerable attention as a potential mechanism that may have triggered global climate events in the past (e.g. Svensen and Jamtveit, 2010). The discovery of hydrothermal vent complexes that are spatially associated with such basins also supports the discharge of greenhouse gases into the atmosphere (e.g. Jamtveit et al., 2004; Planke et al., 2005; Svensen et al., 2006). A previous study that investigated this process using a fluid flow model (Iyer et al., 2013) suggested that although hydrothermal plume formation resulting from sill emplacement may indeed release large quantities of methane at the surface, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales observed in the fossil record. Here, we reinvestigate the rates of gas release during sill emplacement in a case study from the Harstad Basin off-shore Norway with a special emphasis on vent formation. The presented study is based on a seismic line that crosses multiple sill structures emplaced around 55 Ma within the Lower Cretaceous sediments. A single well-defined vent complex is interpreted above the termination of the

  3. Hydrogeochemistry of the formation waters in the San Francisco field, UMV basin, Colombia - A multivariate statistical approach

    NASA Astrophysics Data System (ADS)

    Cortes, J. E.; Muñoz, L. F.; Gonzalez, C. A.; Niño, J. E.; Polo, A.; Suspes, A.; Siachoque, S. C.; Hernández, A.; Trujillo, H.

    2016-08-01

    A wide variety of hydrogeochemical data were obtained through the analysis of the formation water samples collected from 118 producing wells from the San Francisco Oilfield (SFO) in the Upper Magdalena Valley (UMV) basin, Huila, Colombia. The study area is composed of deposited sandstone in fluvial-lacustrine marine environment, which characterized the formation waters as chloride-sodium water type. The brackish-saline facies identified can be attributed to evaporation, halite and dolomite dissolution along with water recharge of meteoric waters somewhere in the basin, probably from Magdalena River, the contribution of the SFO injection water system and significantly by the rock-water interaction. Some ionic ratios were used to confirm clearly that water-rock interactions play a significant role in the evolution of the hydrogeochemistry process in the SFO. The charge balance error ranges between -5.88% and 2.62% indicating very well balanced and mature water for blocks 1, 2 and 3 (north part of the field), and partially equilibrated and immature waters for blocks 4, 5, 6, 7, and 8 as is confirmed by Piper, Giggenbach, and Schöeller diagrams. Calculated scale and stability indices (Langelier, Ryznar, and Puckorius), besides halite and dolomite indexes, indicate that these formation waters are slightly saturated with respect to the calcite and dolomite and have strong tendency to the scale formation as well. Concentration maps were used to identify the geological factors that could have influenced its chemical composition and the hydrogeochemical processes involved in the field, such as halite dissolution, calcite or dolomite precipitation and cationic exchange reactions. The mineralogical distribution leads to the conclusion that the halite dissolution is mostly distributed in the Northeastern area of the SFO between B1, B3, B4, B5, and B6 blocks, the dolomite and calcite have greater concentrations between B5 and B6 blocks. The dissolved minerals followed the

  4. Regional distribution and chronostratigraphy of the Qusaiba member of the Qalibah formation in the Nafud Basin, Northwestern Saudia Arabia

    SciTech Connect

    Aoudeh, S.M.; Al-Hajri, S.A.

    1995-08-01

    The Qusaiba Member of the Qalibah Formation (Silurian age) is a thick sequence consisting of massive dark gray shales. Only the very basal shales are black and highly organic rich. The basal {open_quote}Hot Shale{close_quote} unit is a prolific source correlated to all the Paleozoic discoveries in Central and Eastern Saudi Arabia. In the Nafud Basin, Northwest Saudi Arabia, this same sequence acts as both source and seal to the underlying Ordovician reservoir, making the understanding of this sequence essential to the current exploration program underway in the region. Acquiring high resolution blostratigraphy and detailed source rock analysis substantially contributed to the better understanding of the regional depositional setting of the seal, source, and the reservoirs in the area. Graptolites and chitinozoans zonation were utilized to fine-tune the chronostratigraphy and to further subdivide this huge basin into more manageable subbasins. Regional chronostratigraphic analysis has indicated that the early Qusaiba transgression took place swiftly and covered all of the Arabian plate during early Rhuddanian time. Only high areas not covered by the Rhuddanian transgression and areas that experienced later uplift and erosion lack the Rhuddanian deposits.

  5. The coal-forming plants of the upper part of the Lower Cretaceous Starosuchan Formation (Partizansk Basin, South Primorye region)

    NASA Astrophysics Data System (ADS)

    Bugdaeva, E. V.; Markevich, V. S.; Volynets, E. B.

    2014-05-01

    The plant remains and palynological assemblages are studied in detail in the section of the coal-bearing upper part of the Aptian Starosuchan Formation near the village of Molchanovka (Partizansk Basin, South Primorye region). On the basis of the light and electron microscopic study of the disperse cuticles, it was established that the coals are mostly composed of remains of taxodialean Elatides asiatica (Yok.) Krassil., subordinate Miroviaceae, rare ginkgoalean Pseudotorellia sp., and bennettite Nilssoniopteris rithidorachis (Krysht.) Krassil. The spores Gleicheniidites and pollen Taxodiaceaepollenites are dominant in the palynospectrum of the coal interlayer. It was found that dominant taxodialeans and gleicheniaceous ferns with less abundant Miroviaceae, ginkgoaleans, and rare bennettites occurred in the Aptian swamp communities of the Partizansk basin. Shoots and leaves of Elatides asiatica, fronds of Birisia onychioides (Vassil. et K.-M.) Samyl., are dominant in the burials of plants from the clastic rocks. The fragments of leaves of Nilssoniopteris, scale-leaved conifers, and Ginkgo ex gr. adiantoides are rare. The disperse cuticle of these layers mostly includes Pseudotorellia sp.; however, its remains in burials were not found. The spores Laevigatosporites are dominant in the palynospectra from the clastic interlayers. Ginkgocycadophytus and taxa close to Pinaceae are plentiful among the pollen of gymnosperms.

  6. Evolutionary relationships of a new genus and three new species of Omomyid primates (Willwood Formation, Lower Eocene, Bighorn Basin, Wyoming)

    USGS Publications Warehouse

    Bown, T.M.

    1991-01-01

    Studies of new finds of omomyid primates from the lower Eocene Willwood Formation of northwest Wyoming reveal the presence of a new genus and two new species of anaptomorphines and a new species of omomyine. All were apparently short-lived immigrants into the Bighorn Basin. The new genus and speciesTatmanius szalayi is typified by a diminutive single-rooted p3 and a bilobed-rooted p4 with a crown smaller than ml. These traits were probably derived fromPseudotetonius and parallel similar conditions inTrogolemur andNannopithex. The new speciesArapahovius advena is the first occurrence ofArapahovius outside the Washakie Basin, where it appears to have also been a vagrant species.Steinius annectens, sp. nov., is larger than the olderSteinius vespertinus and strengthens the alliance between this genus and BridgerianOraorays carteri, although which species ofSteinius is closer toOmomys is not yet clear. The available evidence suggests a derivation ofOmomys (Omomyini) fromSteinius and all Washakiini from the anaptomorphineTeilhardina, which would indicate that Omomyinae were at least diphyletic. Preliminary evidence suggests that the geographic distributions of at least some Willwood omomyids correlate with paleosol distributions.

  7. Basin formation and hydrocarbon potential: the role of shear heating, tectonic pressure, differential thinning and rate of rifting

    NASA Astrophysics Data System (ADS)

    Medvedev, Sergei; Hartz, Ebbe; Schmid, Dani

    2014-05-01

    Nature displays numerous examples of basin formation and inversion that cannot be explained by simple rift and post-rift subsidence models. One example is the super-regional Base Cretaceous Unconformity, mapped on-land East Greenland and most of the Norwegian continental shelf. This uplift and erosion unconformity matches a major phase of continental extension, a time for which standard models predict major subsidence. These models attribute surface displacement to tectonic events and thermal contraction. Here we present numerical simulations to quantify the influence of several mechanisms during lithospheric thinning. Mineral phase transitions within the lithosphere, differential thinning of the lithosphere, and rates of sedimentation may subdue syn-rift subsidence and increase post-rift subsidence. We demonstrate that shear heating and tectonic pressure may dramatically shift predictions of basin evolution and lead to syn-extensional uplift and more pronounced post-extensional subsidence. Evidently our understanding, and even apparent observation of structural events (e.g. rifting), and particularly their timing, is intimately linked to our concepts of the involved processes.

  8. Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin

    SciTech Connect

    Dubiel, R.F. )

    1989-09-01

    Sedimentologic study of the Upper Triassic Chinle Formation in the San Juan basin (SJB) indicates that Late Triassic paleoclimate and tectonic movements influenced the distribution of continental lithofacies. The Shinarump, Monitor Butte, and Petrified Forest Members in the lower part of the Chinle consist of complexly interfingered fluvial, floodplain, marsh, and lacustrine rocks; the Owl Rock and Rock Point Members in the upper part consists of lacustrine-basin and eolian sandsheet strata. Facies analysis, vertebrate and invertebrate paleontology, and paleoclimate models demonstrate that the Late Triassic was dominated by tropical monsoonal circulation, which provided abundant precipitation interspersed with seasonally dry periods. Owl Rock lacustrine strata comprise laminated limestones that reflect seasonal monsoonal precipitation and larger scale, interbedded carbonates and fine-grained clastics that represent longer term, alternating wet and dry climatic cycles. Overlying Rock Point eolian sand-sheet and dune deposits indicate persistent alternating but drier climatic cyclicity. Within the Chinle, upward succession of lacustrine, alternating lacustrine/eolian sand-sheet, and eolian sand-sheet/dune deposits reflects an overall decrease in precipitation due to the northward migration of Pangaea out of low latitudes dominated by monsoonal circulation.

  9. The formation of the South Tharsis Ridge Belt: Basin and Range-style extension on early Mars?

    NASA Astrophysics Data System (ADS)

    Karasözen, Ezgi; Andrews-Hanna, Jeffrey C.; Dohm, J. M.; Anderson, R. C.

    2016-06-01

    The South Tharsis Ridge Belt (STRB) is located along the northeastern edge of Terra Sirenum and partially surrounds the southwestern part of Tharsis in an arc. It consists of 29 large ridges separated by distances 130 to 260 km, with average relief of 1.5 km above the surrounding plains. Because the STRB is among the oldest tectonic features associated both spatially and developmentally with Tharsis, it may provide key information on the early evolution of Tharsis and possibly pre-Tharsis processes. Earlier studies concluded that the ridges formed through compressional tectonism. However, the shape, size, and separation of the ridges support the interpretation that the STRB resembles the extensional Basin and Range Province on Earth. Both regions are characterized by series of parallel mountain ranges separated by broad valleys. In this study, we evaluate both extensional and compressional hypotheses for the origin of the ridges using evidence from topography, deformed craters, crustal thickness models, and strain modeling. Though neither interpretation explains all aspects of the ridges, the topography of the ridges and crustal thinning associated with the western part of the ridge belt support an extensional origin. Strain models predict that Basin and Range-style wide rifting would be expected for early Martian conditions. This extension may have been initiated by plume-induced uplift in the early stages of Tharsis formation, but the large amount of extensional strain inferred in the western STRB must have been accommodated by compression elsewhere, possibly in the heavily deformed craters of western Terra Sirenum.

  10. Assessment of the Geologic Carbon Dioxide Storage Resources of the Clinton, Medina, and Tuscarora Formations in the Appalachian Basin

    NASA Astrophysics Data System (ADS)

    Doolan, C.

    2013-12-01

    The U.S. Geological Survey (USGS) has completed an assessment of the geologic carbon dioxide (CO2) storage potential within the Appalachian Basin. This assessment was performed as part of the USGS national assessment of geologic CO2 storage resources in which individual sedimentary basins are divided into storage assessment units (SAUs) based on geologic characteristics such as lithology, porosity, permeability, reservoir depth, formation water salinity, and the presence of a regional sealing formation. This study focuses on the assessment of the Clinton, Medina and Tuscarora Formations storage assessment unit (SAU) that covers an area of 48.9 million acres in eastern Kentucky and Ohio, West Virginia, northern and western Pennsylvania, and southwestern New York. The areal extent of the SAU is defined on the western boundary by the 100 foot isopach contour of the combined Rochester and Rose Hill Shales that acts as the regional sealing formation and is defined by the 3,000 foot depth to top contour of the Clinton and Tuscarora Formations elsewhere. Depth-to-top and isopach contours were derived from IHS Energy Group, 2011 data for over 25,000 unique boreholes located throughout the area of the SAU. The Clinton, Medina and Tuscarora Formations SAU is composed of the porous intervals of the Lower to Middle Silurian strata that is bounded by the underlying Ordovician age Queenston Shale, and the overlying Silurian age Rochester and Rose Hill Shales. Porous intervals were deposited in a variety of wave and tidal dominated environments as a result of a Lower Silurian shoreline that prograded southeast to northwest. Porous units in the Tuscarora Formation in southwestern and central Pennsylvania and West Virginia are predominantly fine to medium grained sands of alluvial plain facies and those of the Clinton and Medina Formations in southwestern New York, northeastern Pennsylvania, eastern Ohio and northeastern Kentucky are typically fine grained quartzarenites deposited

  11. Well-log signatures of alluvial-lacustrine reservoirs and source rocks, Lagoa-Feia Formations, Lower Cretaceous, Campos Basin, offshore Brazil

    SciTech Connect

    Abrahao, D.; Warme, J.E.

    1988-01-01

    The Campos basin is situated in offshore southeastern Brazil. The Lagoa Feia is the basal formation in the stratigraphic sequence of the basin, and was deposited during rifting in an evolving complex of lakes of different sizes and chemical characteristics, overlying and closely associated with rift volcanism. The stratigraphic sequence is dominated by lacustrine limestones and shales (some of them organic-rich), and volcaniclastic conglomerates deposited on alluvial fans. The sequence is capped by marine evaporites. In the Lagoa Feia Formation, complex lithologies make reservoirs and source rocks unsuitable for conventional well-log interpretation. To solve this problem, cores were studied and the observed characteristics related to log responses. The results have been extended through the entire basin for other wells where those facies were not cored. The reservoir facies in the Lagoa Feia Formation are restricted to levels of pure pelecypod shells (''coquinas''). Resistivity, sonic, neutron, density, and gamma-ray logs were used in this work to show how petrophysical properties are derived for the unconventional reservoirs existing in this formation. The same suite of logs was used to develop methods to define geochemical characteristics where source rock data are sparse in the organic-rich lacustrine shales of the Lagoa Feia Formation. These shales are the main source rocks for all the oil discovered to date in the Campos basin.

  12. Radiocarbon constraints on fossil thinolite tufa formation in the Mono Basin, CA, USA

    NASA Astrophysics Data System (ADS)

    Leroy, S. L.; Zimmerman, S. R.; Hemming, S. R.; Stine, S.; Guilderson, T. P.

    2009-12-01

    Mono Lake is a terminal lake located at the western edge of the Great Basin, and is famous for its tufa towers. Thinolite, which is thought to be a CaCO3 pseudomorph of ikaite, is found around the Mono Basin in many fossil tufa towers, particularly at elevations above 2000 meters. The subaqueous parent mineral ikaite forms at low temperatures (< 6 °C) (Bischoff et al., 1993) and requires specific water chemistry. Previous radiocarbon dating of fossil tufa towers around the Mono Basin has yielded a rather small range of ages for the highest elevation towers, between 11.8 and 14.1 14C kyr BP (no corrections for reservoir effects have been made). A thinolite fan collected from outcrops in Mill Creek, just north of the current Mono Lake yielded an age of 10,690 ± 45 14C yr BP (12,750 ± 80 cal yr BP), consistent with a ca. 1000 year reservoir age and coincidence with thinolite crystals found in a core from the northwestern embayment of Mono Lake (Davis, 1999, QR), and thus correlating with the Younger Dryas cooling event as exhibited in the GISP2 δ18O record. While most of the thinolite textures are found at high elevations, we sampled a mound at 1955 meters (near the current shoreline, north of the lake and just east of Black Point) that has many concentric layers, some containing thinolite textures. Although tufa mounds can form very rapidly, the location at low elevation and the presence of at least 19 distinct layers led us to consider that this mound might represent a long term record of Mono Lake’s chemistry. The new data confirm that the mound formed over a long period within the last glacial cycle, with ages ranging beyond the current limits of measurement (>34 kyr) to as young as 15.5 14C kyr BP. In general there is a consistent stratigraphic trend of ages within the mound, but the thinolite ages are anomalously young and one thinolite sample shows a large age reversal. The best estimate of the age of the precipitation of this tufa mound is given by the

  13. Stratigraphy and depositional systems of the lower cretaceous Travis Peak Formation, East Texas basin. Topical report, July 1987-October 1988

    SciTech Connect

    Tye, R.S.; Diggs, T.N.

    1989-02-01

    The Travis Peak Formation of the East Texas Basin was divided into five lithostratigraphic units. Formation of a fluvial-deltaic-paralic-shelf depositional systems tract was interpreted from analyses of stratigraphic and sedimentologic data that were acquired for each lithostratigraphic unit from well logs and cores. During early Travis Peak development, braided streams deposited channelbelt, floodplain, and overbank sediments in most of the study area. Downdip of the braided streams, deltas prograded to the south and southeast over a shallow, stable shelf. As braided streams migrated and enlarged, the site of deltaic deposition advanced southward and expanded to the northeast. Estuaries developed in relatively sediment-starved, embayed portions of the shoreline between centers of deltaic deposition. Seaward of the deltas, shelf sandstones accumulated through sediment-gravity processes triggered by high sediment loads and rapid deposition in the deltas. Channelbelts coursed across a coastal plain with expansive floodplains and lakes and fed a few small retrogradational deltas. Estuaries enlarged and became a dominant coastal feature as submergence of the coastal plain progressed. With continued transgression, marine limestone of the Sligo Formation onlapped the Travis Peak.

  14. Origin of dolomitic rocks in the lower Permian Fengcheng formation, Junggar Basin, China: evidence from petrology and geochemistry

    NASA Astrophysics Data System (ADS)

    Zhu, Shifa; Qin, Yi; Liu, Xin; Wei, Chengjie; Zhu, Xiaomin; Zhang, Wei

    2016-09-01

    Although dolomitization of calcite minerals and carbonatization of volcanic rocks have been studied widely, the extensive dolomitic rocks that originated from altered volcanic and volcaniclastic rocks have not been reported. The dolomitic rocks of the Fengcheng Formation in the Junggar Basin of China appear to be formed under unusual geologic conditions. The petrological and geochemical characteristics indicate that the dolomitizing host rock is devitrified volcanic tuff. After low-temperature alteration and calcitization, these tuffaceous rocks are replaced by Mg-rich brine to form massive dolomitic tuffs. We propose that the briny (with -2 ‰ ~ 6 ‰ of δ13CPDB and -5 ‰ ~ 4 ‰ of δ18OPDB) and Mg-rich marine formation water (with 0.7060 ~ 0.7087 of 87Sr/86Sr ratio), the thick and intermediate-mafic volcanic ashes, and the tectonically compressional movement may have favored the formation of the unusual dolomitic rocks. We conclude that the proposed origin of the dolomitic rocks can be extrapolated to other similar terranes with volcaniclastic rocks, seabed tuffaceous sediment, and fracture filling of sill.

  15. Paleoenvironmental reconstruction based on palynofacies analyses of the Cansona Formation (Late Cretaceous), Sinú-San Jacinto Basin, northwest Colombia

    NASA Astrophysics Data System (ADS)

    Juliao-Lemus, Tatiana; Carvalho, Marcelo de Araujo; Torres, Diego; Plata, Angelo; Parra, Carlos

    2016-08-01

    To reconstruct the paleoenvironments of the Cansona Formation, a Cretaceous succession in Colombia that has controversial paleoenvironmental interpretation, occasionally deep marine and occasionally shallow marine, palynofacies analyses were conducted on 93 samples from four sections of the Sinú San Jacinto Basin in the north, midwest, and southwest sectors. For the palynofacies analyses, the kerogen categories were counted and subjected to cluster analyses. Four palynofacies associations were revealed for the four sections: Palynofacies Association I (PA I), which consisted of microforaminiferal linings, scolecodonts, dinoflagellate cysts, pollen grains, and fungi hyphae; PA II, which consisted of phytoclast translucent non-biostructured and biostructured, opaque phytoclasts (equidimensional and lath shaped); PA III, which consisted of pseudoamorphous particles, cuticles, resin, and fungal spores; and PA IV, which consisted of fluorescent and non-fluorescent amorphous organic matter and the fresh-water algae Botryococcus. In contrast to early studies that suggested a generalization of the depositional environment for the Cansona Formation (deep or shallow conditions), this study suggests that the formation reflects conspicuous stratigraphic and lateral changes and hence different depositional environments. The Cerro Cansona (CC4 section) and Chalán (AP section) areas are a more marine proximal settings (Early Campanian-Maastrichtian), and there is an intermediate setting for the Lorica area (SC section) and deeper conditions for the Montería area (CP2 section).

  16. Mineralogy and geochemistry of the Green River Formation, Colorado Core Hole No. 1, Piceance Creek Basin, Colorado: Final report

    SciTech Connect

    Slaughter, M.; Mathews, A.

    1984-03-01

    Selected samples of the Green River Formation, Colorado Core Hole No. 1, were analyzed to aid characterization and understanding of the genesis of the oil shales of the Piceance Creek Basin, Colorado. About 120, 2-4 inch samples from the Parachute Creek and Garden Gulch Members were analyzed for 18 major and minor elements, 12 selected race elements and quantitative mineral content. About 70 samples were scanned, perpendicular to the bedding, by electron microprobe to determine semiquantitative elemental microstratigraphy of nine selected elements. This report describes the analytical procedures, presents the results, includes photos, and interprets the depositional geochemistry which produced the analyzed rocks. The seven appendices include; (1) descriptions and photographs of samples; (2) chemical and mineral analyses; (3) electron microprobe analyses; (4) down-section elemental distribution; (5) down-section mineral distribution; (6) down-section mineral content; and (7) organic content. 38 refs.

  17. Two-dimensional simulation of clastic and carbonate sedimentation, consolidation, subsidence, fluid flow, heat flow and solute transport during the formation of sedimentary basins

    NASA Astrophysics Data System (ADS)

    Bitzer, Klaus

    1999-05-01

    Geological processes that create sedimentary basins or act during their formation can be simulated using the public domain computer code `BASIN'. For a given set of geological initial and boundary conditions the sedimentary basin evolution is calculated in a forward modeling approach. The basin is represented in a two-dimensional vertical cross section with individual layers. The stratigraphic, tectonic, hydrodynamic and thermal evolution is calculated beginning at an initial state, and subsequent changes of basin geometry are calculated from sedimentation rates, compaction and pore fluid mobilization, isostatic compensation, fault movement and subsidence. The sedimentologic, hydraulic and thermal parameters are stored at discrete time steps allowing the temporal evolution of the basin to be analyzed. A maximum flexibility in terms of geological conditions is achieved by using individual program modules representing geological processes which can be switched on and off depending on the data available for a specific simulation experiment. The code incorporates a module for clastic and carbonate sedimentation, taking into account the impact of clastic sediment supply on carbonate production. A maximum of four different sediment types, which may be mixed during sedimentation, can be defined. Compaction and fluid flow are coupled through the consolidation equation and the nonlinear form of the equation of state for porosity, allowing nonequilibrium compaction and overpressuring to be calculated. Instead of empirical porosity-effective stress equations, a physically consistent consolidation model is applied which incorporates a porosity dependent sediment compressibility. Transient solute transport and heat flow are calculated as well, applying calculated fluid flow rates from the hydraulic model. As a measure for hydrocarbon generation, the Time-Temperature Index (TTI) is calculated. Three postprocessing programs are available to provide graphic output in Post

  18. Origin and chemical evolution of formation waters from Silurian-Devonian strata in the Illinois basin, USA

    SciTech Connect

    Stueber, A.M. ); Walter, L.M. )

    1991-01-01

    A suite of formation-water samples from Silurian-Devonian reservoirs in the Illinois basin has been analyzed for major, minor, and trace element concentrations and for H, O, and Sr isotopic compositions in order to interpret origin of salinity and geochemical evolution of brine compositions in this evaporite- and shale-poor cratonic basin. Although chloride concentrations range from 2,000 to 137,000 mg/L, Cl/Br ratios (291 {plus minus} 18) are consistent with those of seawater or seawater evaporated short of halite saturation (Cl/Br = 292). Thus, during Silurian-Devonian time, subaerially evaporated, penesaline brine entered the subsurface where it was chemically modified through brine-rock interactions. Cation/Br ratios and mineralogy of associated strata indicate that Na and K were depleted through interaction with clay minerals, Ca was enriched and Mg depleted by dolomitization, and Sr was enriched as a result of CaCO{sub 3} recrystallization and dolomitization. Brine {sup 87}Sr/{sup 86}Sr ratios range from 0.7092 to 0.7108; when these ratios are plotted versus 1/Sr, a two-component mixing trend is suggested, although Sr concentrations have experienced local diagenetic modification. A {sup 87}Sr-enriched fluid may have accompanied petroleum migration from New Albany shales into adjacent Silurian-Devonian carbonates where it mixed with remnant evaporated seawater. This event probably preceded the influx of meteoric water, as {delta}D and {delta}{sup 18}O are not correlated with Sr isotopic compositions of formation waters.

  19. Sedimentologic and stratigraphic framework of the upper part of the Fort Union Formation, western Powder River basin, Wyoming

    USGS Publications Warehouse

    Weaver, J.N.; Flores, R.M.

    1987-01-01

    The purpose of this study is to describe the stratigraphy and interpret the environments of deposition in the upper part of the Paleocene Fort Union Formation. Of all the lithofacies present within the study area, sandstone is the most dominant and makes up most of the upper part of the Fort Union Formation along the western edge of the Powder River basin, Wyoming. This sandstone lithofacies occurs in three forms: 1) pink conglomeratic sandstone, 2) coarse-grained sandstone, and 3) fine-grained sandstone. The pink conglomeratic sandstone lithofacies forms a series of Stacked channel bodies in which the clasts are as much as 1 3/4 in. in diameter. The coarse-grained sandstone lithofacies is laterally equivalent to the pink conglomeratic sandstone sequence, but contains smaller clasts; it is arranged en echelon (offset) to the north. The fine-grained sandstone lithofacies, limited to the northern part of the study area, is not as laterally continuous as the pink conglomeratic sandstone lithofacies to the south. Basal lag conglomerate underlies both the conglomeratic sandstone and coarse-grained sandstone lithofacies, but not the fine-grained sandstone. The presence of a fine-grained sandstone lithofacies lateral to the conglomeratic sandstone and coarse-grained sandstone lithofacies suggests the presence of a coarse-grained braided and meandering fluvial system coeval with a fine-grained meandering fluvial system.. The meandering fluvial systems drained the alluvial plain flanking the Bighorn Mountains on the west and the Casper arch on the southwest, and flowed north-northeastward within the Powder River basin.

  20. Organic geochemical characterisation of shallow marine Cretaceous formations from Yola Sub-basin, Northern Benue Trough, NE Nigeria

    NASA Astrophysics Data System (ADS)

    Sarki Yandoka, Babangida M.; Abdullah, Wan Hasiah; Abubakar, M. B.; Hakimi, Mohammed Hail; Jauro, Aliyu; Adegoke, Adebanji Kayode

    2016-05-01

    The shallow marine shales of the Cretaceous formations namely Yolde, Dukul, Jessu, Sekuliye and Numanha ranging in age from Cenomanian to Coniacian within the Yola Sub-basin in the Northern Benue Trough, northeastern Nigeria were analysed to provide an overview on their hydrocarbon generation potential. This study is based on pyrolysis analysis, total organic carbon content (TOC), extractable organic matter (EOM), biomarker distributions and measured vitrinite reflectance. The present-day TOC contents range between 0.24 and 0.71 wt. % and Hydrogen Index (HI) values between 8.7 and 113 mg HC/g TOC with Type III/IV kerogens. Based on the present-day kerogen typing, the shale sediments are expected to generate mainly gas. Biomarker compositions indicates deposition in a marine environment under suboxic conditions with prevalent contribution of aquatic organic matter and a significant amount of terrigenous organic matter input. Organic matter that is dominated by marine components contains kerogens of Type II and Type II-III. This study shows that the organic matter has been affected by volcanic intrusion and consequently, have reached post-mature stage of oil generation. These higher thermal maturities levels are consistent with the vitrinite reflectance ranging from 0.85 to 2.35 Ro % and high Tmax (440-508 °C) values as supported by biomarker maturity ratios. Based on this study, a high prospect for major gas and minor oil generation potential is anticipated from the shallow marine Cretaceous formations from Yola Sub-basin.

  1. Paleocene-Eocene palaeoenvironmental conditions of the main phosphorite deposits (Chouabine Formation) in the Gafsa Basin, Tunisia

    NASA Astrophysics Data System (ADS)

    Kocsis, László; Ounis, Anouar; Baumgartner, Claudia; Pirkenseer, Claudius; Harding, Ian C.; Adatte, Thierry; Chaabani, Fredj; Neili, Salah Mohamed

    2014-12-01

    A detailed sedimentary section of the marine Chouabine Formation in the palaeogeographic Gafsa Basin, south-western Tunisia, was investigated in order to characterize environmental and depositional conditions focusing on the interval that spans the Paleocene-Eocene transition. We did stable isotope analyses of bulk sediments. Both phosphorite and carbonate yielded relatively similar isotopic compositions; while marls show observable trends, with negative shifts in both δ13Cinorg and δ18O values at the Paleocene-Eocene transition. The diversity of the calcareous microfossils is low. The presence of few environmentally tolerant small benthic foraminifera and the absence of planktic forms indicate a restricted palaeoenvironment subject to variation in salinity and temperature. The ostracod fauna is more diverse and is rather comparable to Paleocene and PETM (Paleocene-Eocene thermal maximum) assemblages in northwest Tunisia. While all these microfossils demonstrate various diagenetic features (i.e., phosphatization, secondary mineral overgrowths and infills), the different groups retain distinct stable isotopic compositions, suggesting partial preservation of signatures derived from their respective ecological niches. Few organic-rich layers below the negative δ13C shift yielded dinoflagellate assemblages with the common forms of Adnatosphaeridium sp., Operculodinium sp., Spiniferites spp. and Thalassiphora sp. The rare presences of Apectodinium-complex agree with depositional age prior to the PETM. The combined data emphasize that most of the Chouabine Formation in the Gafsa Basin was deposited during the late Paleocene. The most negative isotopic values from marls are believed to represent the onset of PETM or pre-PETM record, and the related perturbation of the carbon cycle in shallow water deposits in Tunisia.

  2. Geological and geochemical characterization of the Lower Cretaceous Pearsall Formation, Maverick Basin, south Texas: A future shale gas resource?

    USGS Publications Warehouse

    Hackley, Paul C.

    2012-01-01

    As part of an assessment of undiscovered hydrocarbon resources in the northern Gulf of Mexico onshore Mesozoic section, the U.S. Geological Survey (USGS) evaluated the Lower Cretaceous Pearsall Formation of the Maverick Basin, south Texas, as a potential shale gas resource. Wireline logs were used to determine the stratigraphic distribution of the Pearsall Formation and to select available core and cuttings samples for analytical investigation. Samples used for this study spanned updip to downdip environments in the Maverick Basin, including several from the current shale gas-producing area of the Pearsall Formation.The term shale does not adequately describe any of the Pearsall samples evaluated for this study, which included argillaceous lime wackestones from more proximal marine depositional environments in Maverick County and argillaceous lime mudstones from the distal Lower Cretaceous shelf edge in western Bee County. Most facies in the Pearsall Formation were deposited in oxygenated environments as evidenced by the presence of biota preserved as shell fragments and the near absence of sediment laminae, which is probably caused by bioturbation. Organic material is poorly preserved and primarily consists of type III kerogen (terrestrial) and type IV kerogen (inert solid bitumen), with a minor contribution from type II kerogen (marine) based on petrographic analysis and pyrolysis. Carbonate dominates the mineralogy followed by clays and quartz. The low abundance and broad size distribution of pyrite are consistent with the presence of oxic conditions during sediment deposition. The Pearsall Formation is in the dry gas window of hydrocarbon generation (mean random vitrinite reflectance values, Ro = 1.2–2.2%) and contains moderate levels of total organic carbon (average 0.86 wt. %), which primarily resides in the inert solid bitumen. Solid bitumen is interpreted to result from in-situ thermal cracking of liquid hydrocarbon generated from original type II kerogen

  3. Geomorphology of crater and basin deposits - Emplacement of the Fra Mauro formation

    NASA Technical Reports Server (NTRS)

    Morrison, R. H.; Oberbeck, V. R.

    1975-01-01

    Characteristics of continuous deposits near lunar craters larger than about 1 km wide are considered, and it is concluded that (1) concentric dunes, radial ridges, and braided lineations result from deposition of the collision products of ejecta from adjacent pairs of similarly oriented secondary-crater chains and are, therefore, concentrations of secondary-crater ejecta; (2) intracrater ridges are produced within preexisting craters surrounding a fresh primary crater by ricocheting and focusing of secondary-crater ejecta from the preexisting craters' walls; and (3) secondary cratering has produced many of the structures of the continuous deposits of relatively small lunar craters and is the dominant process for emplacement of most of the radial facies of the continuous deposits of large lunar craters and basins. The percentages of Imbrium ejecta in deposits and the nature of Imbrium sculpturing are investigated.

  4. New insights into Gondwana paleography based on palinological data from Morro do Chaves Formation (Sergipe-Alagoas Basin, Brazil)

    NASA Astrophysics Data System (ADS)

    Gonçalves Garcia, Gustavo; Vasconcellos Garcia, Antônio Jorge; Henriques, Maria Helena

    2016-04-01

    The Sergipe-Alagoas basin (NE Brazil) has been widely studied in the frame of oil exploration, because it displays the most complete exposition of the stratigraphic sequences from the basins of the Brazilian continental margin. In this context, the aim of this workis to present the results of the bio-stratigraphic and paleo-environmental analysis of Morro do Chaves Formation (Lower Cretaceous), in Alagoas Sub-basin, part of the transitional section situated between the rift phase and restricted marine environment associated with the South Atlantic ocean opening. The material was analyzed from the palynological point of view and was collected in the InterCement quarry, located in São Miguel dos Campos, State of Alagoas. From 17 outcrop rock samples collected, nine had palynological content; among these only six were considered for biostratigraphic analysis purposes. In addition to outcrop samples, 28 samples were processed from four core drill. The paleoenvironmental analysis was based on the palynological content of the collected samples and on the paleontological and geological information available. The studied sedimentary package corresponds to carbonate and fine siliciclastic deposits, with approximately 70.0 m in thickness. The unit in question is formed by carbonatic "coquinóides" rocks interspersed with shale levels of dark green color. Palinofloristic assemblages were recuperated between 5.0 m and 70.0 m of the outcropping section. In the recovered material it was possible to identify 9 kinds of spores and 8 kinds of pollen grains, and two genera of fungi. Due to the degree of preservation of the material, age was established by the occurrence of Dicheiropollis etruscus specimens, which has enabled the recognition of the Dicheiropollis etruscus palinozone (upper Barremian). In microscopic observations under fluorescent light some algalic vesicles components were also recognized and classified as possible algae of the Prasinophyceae class, indicating

  5. The oleaginous Botryococcus from the Triassic Yanchang Formation in Ordos Basin, Northwestern China: Morphology and its paleoenvironmental significance

    NASA Astrophysics Data System (ADS)

    Ji, Li-ming; Yan, Kui; Meng, Fan-wei; Zhao, Min

    2010-05-01

    High abundance but rather low diversity algal fossils were found in the hydrocarbon source rocks of the Ch 7-2-Ch 7-3 section, Triassic Yanchang Formation in the Xifeng area of southwest Ordos Basin, which are mainly composed of prolific Leiosphaeridia and Botryococcus. Botryococcus colonies are of various forms; the majority is nubbly, with some of cluster and cotton shape. The nubbly colonies appear globular, cordiform, ternate petal, obtuse triangle, chrysanthemum shape and so on. Most Botryococcus are saffron or brown and are frequently covered with clay under transmission microscope, and shows strong yellow and light brown under fluorescence microscope. Botryococcus could live in freshwater and brackish water. The Botryococcus colonies that lived in fresh water are small with small single cells arranged radially, with undulant or indented edges. The Botryococcus colonies that lived in brackish water are bigger, with larger single cells arranged irregularly, with slippery contours. The most of Botryococcus are discovered from the organic-rich argillaceous sediment with abundant pyrites in the semi- and deep-lake facies, and shows they were preserved in low-energy reducing environments. Taphonomic characteristics of various microfossils and the present of Pediastrum in the phytoplankton flora indicate that they are in situ or near burial. The lake area of the Ordos Basin was gradually expanding and reaching its most extensive flood surface in the Ch 7 of Yanchang Formation interval during the Middle and Late Triassic, with warm climate, plentiful rainfall, and luxuriant vegetation, as determined by the environmental analysis with Botryococcus in Xifeng area. The presence of two ecological types of Botryococcus indicates that the salinity of lake water was fluctuating in the Ch 7 interval. The occurrence of symbiotic acritarchs and geochemical salinity indices show that the Ordos Lake was a typical fresh-water lake, which was gradually desalted, and its salinity

  6. Hydrology of the Upper Cretaceous Fruitland Formation and the producibility of coal-bed methane, San Juan basin, Colorado and New Mexico

    SciTech Connect

    Kaiser, W.R. ); Swartz, T.E. )

    1990-05-01

    Fruitland coal seams contain 49 tcf of methane, which is produced from abnormally pressured coals in a variety of hydrologic settings. In a study funded by the Gas Research Institute, the authors calculated bottom-hole pressures from wellhead shut-in pressures to map hydraulic head and pressure regime, and estimated vertical pressure gradients to evaluate Fruitland hydrology and its relation to methane producibility. They inferred relative permeability from hydraulic head, pressure regime, and hydrochemistry, and related these hydrologic elements to established production. In the Fruitland Formation, coal seams are the primary aquifers, receiving recharge mainly from the elevated, wet, north and northwest margins of the basin. Formation waters in the north-central part of the basin have low chlorinities and high alkalinities, whereas those in the southern part of the basin are saline Na-Cl type similar to seawater. Regional discharge is to the San Juan River valley in the western part of the basin. Overpressuring in the north-central part of the basin is explained hydrodynamically and is attributed to artesian conditions. They infer enhanced coal-bed permeability where the potentiometric surface is flat and reduced permeability where it is steep. Overpressuring indicates enhanced permeability because permeability in coal seams is stress dependent. In the overpressured region, groundwater is fresh, indicative of an active, dynamic flow system and of permeable pathways. In contrast, connate seawater in the underpressured southern part of the basin implies negligible permeability; strata are too tight to accept and transmit measurable recharge. The basin's most productive coal bed-methane wells are overpressured and occur at hydrologic transitions from a flat to a steep potentiometric surface, overpressuring to underpressuring, and low- to high-chloride formation waters.

  7. Formation of South Pole-Aitken Basin as the Result of an Oblique Impact: Implications for Melt Volume and Source of Exposed Materials

    NASA Technical Reports Server (NTRS)

    Petro, N. E.

    2012-01-01

    The South Pole-Aitken Basin (SPA) is the largest, deepest, and oldest identified basin on the Moon and contains surfaces that are unique due to their age, composition, and depth of origin in the lunar crust [1-3] (Figure 1). SPA has been a target of interest as an area for robotic sample return in order to determine the age of the basin and the composition and origin of its interior [3-6]. As part of the investigation into the origin of SPA materials there have been several efforts to estimate the likely provenance of regolith material in central SPA [5, 6]. These model estimates suggest that, despite the formation of basins and craters following SPA, the regolith within SPA is dominated by locally derived material. An assumption inherent in these models has been that the locally derived material is primarily SPA impact-melt as opposed to local basement material (e.g. unmelted lower crust). However, the definitive identification of SPA derived impact melt on the basin floor, either by remote sensing [2, 7] or via photogeology [8] is extremely difficult due to the number of subsequent impacts and volcanic activity [3, 4]. In order to identify where SPA produced impact melt may be located, it is important to constrain both how much melt would have been produced in a basin forming impact and the likely source of such melted material. Models of crater and basin formation [9, 10] present clear rationale for estimating the possible volumes and sources of impact melt produced during SPA formation. However, if SPA formed as the result of an oblique impact [11, 12], the volume and depth of origin of melted material could be distinct from similar material in a vertical impact [13].

  8. Sedimentology, rhythmicity and basin-fill architecture of a carbonate ramp depositional system with intermittent terrigenous influx: The Albian Kharfot Formation of the Jeza-Qamar Basin, Dhofar, Southern Oman

    NASA Astrophysics Data System (ADS)

    Salad Hersi, O.; Abbasi, I. A.; Al-Harthy, A.

    2016-01-01

    The Albian Kharfot Formation is preserved in the eastern margin of the Jeza-Qamar Basin which straddles across the Oman-Yemen border. This study addresses the sedimentological attributes of the formation and deduces its depositional setting, cyclicity and relative sea level changes in local (within the basin) and regional (Arabian) contexts. The interaction among siliciclastic influxes, in-situ carbonate production and tectono-climatic controls on the stacking nature of the various lithofacies that build-up the formation is discussed. In the study area, the formation lies unconformably over Barremian-Aptian Qishn Formation and conformably under late Albian-?Turonian Dhalqut Formation. The Kharfot Formation thickens from ~ 140 m in the eastern side of the study area to ~ 300 m at the Oman-Yemen border. It consists of eight lithofacies: Orbitolina-rich marls, peloidal bioclastic packstone, bioclastic mudstone to wackestone, argillaceous, bioclastic floatstone to rudstone, bioclastic rudstone, sandy, peloidal, bioclastic mudstone to packstone, peloidal, bioclastic grainstone and dolostone. The vertical arrangement of these lithofacies defines recurring meter- to decameter-scale, shallowing-upward units deposited on a westward-deepening inner- to outer-ramp setting. Tectonic rejuvenation of the siliciclastic source area was accompanied by warm, humid climatic conditions as suggested by high kaolinitic marls of the Kharfot Fm. and coeval quartz-rich sandstone units (Harshiyat Fm.). The shallowing-upward rhythmic sedimentation of the formation has close resemblance with cycles of the Nahr Umr Formation in northern Oman and partially comparable with the global sea level changes. The Kharfot basin was an intrashelf depression that was part of the much larger Arabian epeiric platform. The latter is defined by a rimmed margin in northern Oman where Al-Hassanat Formation represents platform margin deposits and Nahr Umr Formation representing back-rim intrashelf depression

  9. Seismic structural investigation and reservoir characterization of the Moki Formation in Maari Field, Taranaki Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Alotaibi, Mohammed Dhaifallah M.

    The Maari Field is a large oil field located in the southern part of the Taranaki Basin, New Zealand. The field is bounded by two major structures, the Eastern Mobile Belt and Western Stable Platform. The Maari Field produces 40,000 BOPD (Barrels of Oil per Day) from five wells from reservoirs in the Moki Formation. The Miocene Moki Formation was deposited as part of the Wai-iti Group and consists of sandstone interbedded with siltstone and claystone. The sandstone of the Moki Formation is characterized by a submarine fan. It is distributed along the southern and central Taranaki shelf. Three-dimensional seismic data and well logs were recorded by the Geco-Prakla Company. Time and depth structural maps on the top of the Moki Formation are subdivided into a main structure with high and low elevations of topography, which are separated by a major fault, the Kiwi Fault. The fault trends from the south toward the northeast. Seismic attributes, such as coherence and edge detection, were mapped to interpret the major and minor faults. In the Maari Field, there are more than seventeen faults. Seismic data and well log data were used to determine the petrophysical properties in the Moki reservoir. Using the well logs, the transition zone (oil-water contact) between the oil and water was found to be 1352 m. The Moki reservoir has good quality oil, with an average porosity at Maari-1, Maui-4, Kea-1, Moki, and Maari-2 ranging from 14 to 19 percent. Gamma ray, resistivity, and spontaneous potential logs were used to determine correlation between well and lithology of the Moki reservoir. The net thickness of the reservoir is 320 m to 360 m. The distribution of shale is less than 10 percent throughout the Moki reservoir.

  10. Assessment of undiscovered oil and gas resources in the Uteland Butte Member of the Eocene Green River Formation, Uinta Basin, Utah

    USGS Publications Warehouse

    Johnson, Ronald C.; Birdwell, Justin E.; Mercier, Tracey J.; Brownfield, Michael E.; Charpentier, Ronald R.; Klett, Timothy R.; Leathers, Heidi M.; Schenk, Christopher J.; Tennyson, Marilyn E.

    2015-09-03

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered resources of 214 million barrels of oil, 329 billion cubic feet of associated/dissolved natural gas, and 14 million barrels of natural gas liquids in the informal Uteland Butte member of the Green River Formation, Uinta Basin, Utah.

  11. Geology and hydrocarbon potential of Dawson Bay Formation carbonate unit (Middle Devonian), Williston basin, North Dakota

    SciTech Connect

    Pound, W.

    1988-07-01

    The Middle Devonian Dawson Bay Formation carbonate unit is present in the subsurface of North Dakota except where truncated by postdepositional erosion. The carbonate unit thickens from the erosional limit to a maximum thickness of 47.5 m (156 ft) in Renville County and reaches a maximum depth of 3798 m (12,460 ft) below the surface in McKenzie County. In North Dakota, a submarine hardground separates the carbonate unit from the underlying second red bed member of the Dawson Bay Formation. The upper contact with the Souris River Formation is conformable except in those areas where the Dawson Bay Formation was exposed to subaerial erosion prior to deposition of the Souris River sediments. The Dawson Bay carbonate unit is predominantly dolomitic and fossiliferous limestone or fossiliferous dolostone. The carbonate unit can be subdivided into five lithofacies on the basis of characteristic fossil fauna, flora, and other lithologic features. Lithofacies analysis of the Dawson Bay carbonates suggests a shallowing-upward succession of depositional environments and associated energy zones as follows: shallow epeiric sea (very low energy), stromatoporoid biostrome/bioherm (low energy), very shallow epeiric sea (very low energy), restricted shallow epeiric sea (extremely low energy), and shallow epeiric sea shoreline (variable energy). Eogenetic diagenesis includes color-mottling, dolomitization of micrite to microcrystalline dolomite with penecontemporaneous anhydrite replacement of cryptalgal mudstones and boundstones, cementation by sparry calcite, and vuggy porosity development. Mesogenetic diagenesis includes formation of mosaic dolomites, cementation by blocky equant calcite, neomorphism, pressure-solution, fracturing, halite cementation, and hydrocarbon emplacement.

  12. Microbial methane formation in deep aquifers of a coal-bearing sedimentary basin, Germany

    PubMed Central

    Gründger, Friederike; Jiménez, Núria; Thielemann, Thomas; Straaten, Nontje; Lüders, Tillmann; Richnow, Hans-Hermann; Krüger, Martin

    2015-01-01

    Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, and Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport. PMID:25852663

  13. Kinetic modeling of petroleum formation in the Maracaibo Basin: Final report, Annex 12

    SciTech Connect

    Burnham, A.K.; Braun, R.L.; Sweeney, J.J.; Reynolds, J.G.; Vallejos, C.; Talukdar, S.

    1992-07-01

    The purpose of this project is to develop and test improved kinetic models of petroleum generation and cracking, pore pressure buildup, and fluid expulsion. The work was performed jointly between Lawrence Livermore National Laboratory and Research Organization of the Venezuelan National Petroleum Company under Annex 12 of an agreement between DOE and the Venezuelan Ministry of Energy and Mines. Laboratory experiments were conducted at both LLNL and INTEVEP to obtain the reaction rate and product composition information needed to develop chemical kinetic models. Experiments at INTEVEP included hydrous pyrolysis and characterization of oils by gas and liquid chromatography. Experiments at LLNL included programmed pyrolysis in open and self-purging reactors, sometimes including on-line gas analysis by tandem mass spectrometry, and characterization of oils by gas chromatography and nuclear magnetic resonance. The PMOD code was used to develop a detailed pyrolysis mechanism from the extensive laboratory data. This mechanism is able to predict yield of bitumen, oil, and gas as a function of time and temperature for such diverse laboratory conditions as hydrous pyrolysis and rapid, programmed, open pyrolysis. PMOD calculations were compared to geologic observations for 22 wells in the Maracaibo basin. When permeability parameters are chosen to match calculated pore pressures with measured present day values, the PMOD calculations indicate that organic maturation reactions contribute a significant fraction of the overpressure during oil generation and early oil cracking. Calculations agreed with observed geochemical maturity parameters of the source rock. 37 refs., 64 figs., 20 tabs.

  14. Hydrocarbon potential evaluation of the source rocks from the Abu Gabra Formation in the Sufyan Sag, Muglad Basin, Sudan

    NASA Astrophysics Data System (ADS)

    Qiao, Jinqi; Liu, Luofu; An, Fuli; Xiao, Fei; Wang, Ying; Wu, Kangjun; Zhao, Yuanyuan

    2016-06-01

    The Sufyan Sag is one of the low-exploration areas in the Muglad Basin (Sudan), and hydrocarbon potential evaluation of source rocks is the basis for its further exploration. The Abu Gabra Formation consisting of three members (AG3, AG2 and AG1 from bottom to top) was thought to be the main source rock formation, but detailed studies on its petroleum geology and geochemical characteristics are still insufficient. Through systematic analysis on distribution, organic matter abundance, organic matter type, organic matter maturity and characteristics of hydrocarbon generation and expulsion of the source rocks from the Abu Gabra Formation, the main source rock members were determined and the petroleum resource extent was estimated in the study area. The results show that dark mudstones are the thickest in the AG2 member while the thinnest in the AG1 member, and the thickness of the AG3 dark mudstone is not small either. The AG3 member have developed good-excellent source rock mainly with Type I kerogen. In the Southern Sub-sag, the AG3 source rock began to generate hydrocarbons in the middle period of Bentiu. In the early period of Darfur, it reached the hydrocarbon generation and expulsion peak. It is in late mature stage currently. The AG2 member developed good-excellent source rock mainly with Types II1 and I kerogen, and has lower organic matter abundance than the AG3 member. In the Southern Sub-sag, the AG2 source rock began to generate hydrocarbons in the late period of Bentiu. In the late period of Darfur, it reached the peak of hydrocarbon generation and its expulsion. It is in middle mature stage currently. The AG1 member developed fair-good source rock mainly with Types II and III kerogen. Throughout the geological evolution history, the AG1 source rock has no effective hydrocarbon generation or expulsion processes. Combined with basin modeling results, we have concluded that the AG3 and AG2 members are the main source rock layers and the Southern Sub-sag is

  15. Early Callovian ingression in southwestern Gondwana. Palaeoenvironmental evolution of the carbonate ramp (Calabozo Formation) in southwestern Mendoza, Neuquen basin, Argentina

    NASA Astrophysics Data System (ADS)

    Armella, Claudia; Cabaleri, Nora G.; Cagnoni, Mariana C.; Panarello, Héctor O.

    2013-08-01

    The carbonatic sequence of the Calabozo Formation (Lower Callovian) developed in southwestern Gondwana, within the northern area of the Neuquén basin, and is widespread in thin isolated outcrops in southwestern Mendoza province, Argentina. This paper describes the facies, microfacies and geochemical-isotopic analysis carried out in five studied localities, which allowed to define the paleoenvironmental conditions of a homoclinal shallow ramp model, highly influenced by sea level fluctuations, where outer, mid and inner ramp subenvironments were identified. The outer ramp subenvironment was only recognized in the south of the depocenter and is characterized by proximal outer ramp facies with shale levels and interbedded mudstone and packstone layers. The mid ramp subenvironment is formed by low energy facies (wackestone) affected by storms (packstones, grainstones and floatstones). The inner ramp subenvironment is the most predominant and is characterized by tidal flat facies (wackestones, packstones and grainstones) over which a complex of shoals (grainstones and packstones) dissected by tidal channels (packstone, grainstones and floatstones) developed. In the north area, protected environment facies were recorded (bioturbated wackestones and packstones). The vertical distribution of facies indicates that the paleoenvironmental evolution of the Calabozo Formation results from a highstand stage in the depocenter, culminating in a supratidal environment, with stromatolitic levels interbedded with anhydrite originated under restricted water circulation conditions due to a progressive isolation of the basin. δ13C and δ18O values of the carbonates of the Calabozo Formation suggest an isotopic signature influenced by local palaeoenvironmental parameters and diagenetic overprints. The δ13C and δ18O oscillations between the carbonates of the different studied sections are related with lateral facies variations within the carbonate ramp accompanied with dissimilar

  16. Ichnofabrics of the Capdevila Formation (early Eocene) in the Los Palacios Basin (western Cuba): Paleoenvironmental and paleoecological implications

    NASA Astrophysics Data System (ADS)

    Villegas-Martín, Jorge; Netto, Renata Guimarães; Lavina, Ernesto Luis Correa; Rojas-Consuegra, Reinaldo

    2014-12-01

    The ichnofabrics present in the early Eocene siliciclastic deposits of the Capdevila Formation exposed in the Pinar del Rio area (Los Palacios Basin, western Cuba) are analyzed in this paper and their paleoecological and paleoenvironmental significance are discussed. Nine ichnofabrics were recognized in the dominantly sandy sedimentary succession: Ophiomorpha, Asterosoma, Thalassinoides, Palaeophycus, Scolicia, Bichordites-Thalassinoides, Rhizocorallium, Scolicia-Thalassinoides and rhizobioturbation. Diversity of ichnofauna is low and burrows made by detritus-feeding organisms in well oxygenated and stenohaline waters predominate. Suites of the Cruziana and Skolithos Ichnofacies lacking their archetypical characteristics were recognized, being impoverished in diversity and presenting dominance of echinoderm and decapods crustacean burrows as a response to the environmental stress caused by the high frequency of deposition. The ichnofabric distribution in the studied succession, its recurrence in the sandstone beds and the presence of a Glossifungites Ichnofacies suite with rhizobioturbation associated reflect a shoaling-upward event with subaerial exposure of the substrate. The integrated analysis of the ichnology and the sedimentary facies suggests deposition in a shallow slope frequently impacted by gravitational flows and high-energy events. The evidence of substrate exposure indicates the occurrence of a forced regression and suggests the existence of a sequence boundary at the top of the Capdevila Formation.

  17. Preliminary paleogeographic reconstruction of the Illinois basin during deposition of the Mississippian Aux Vases Formation: Implications for hydrocarbon recovery

    SciTech Connect

    Cole, R.D. )

    1991-03-01

    Extensive outcrop investigation and selective subsurface study allow definition of Illinois basin paleogeography during deposition of the Mississippian (Valmeyeran-Meramecian) Aux Vases Formation. The results incorporate an integrated approach utilizing field observations and petrographic analysis, wireline logs, subsurface maps, and cores. The Aux Vases Formation depositional system has been determined to be composed of subtidal to intertidal facies. Depositional facies in outcrop are based on rock body geometries, sedimentary structure assemblages, paleocurrent analysis, paleontology of body and trace fossils, facies relationships, and petrography. Depositional facies determined from subsurface data are based on correlation of lithologic interpretations from wireline logs, sand body geometries form isopach maps, and petrography. Specific depositional facies observed in outcrop and core and inferred from wireline logs and isopach maps are offshore bars and tidal channel complexes, extensive subtidal to lower intertidal, ripple-laminated, fine-grained quartzose sandstone. Carbonate facies occur as subtidal grainstones at or near the base of a sequence, or as high energy deposits which have been tidally reworked. This depositional system produces reservoir heterogeneities that complicate efficient hydrocarbon recovery. This diverse facies architecture is modified by tectonic and diagenetic overprinting, further segregating potential producing zones. To significantly improve recovery efficiency, predictions regarding compartmentalization can be used prior to designing a drilling program, an infill drilling program, or an application of enhanced recovery techniques.

  18. Assessment of In-Place Oil Shale Resources of the Green River Formation, Piceance Basin, Western Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Mercier, Tracey J.; Brownfield, Michael E.; Pantea, Michael P.; Self, Jesse G.

    2009-01-01

    The U.S. Geological Survey (USGS) recently completed a reassessment of in-place oil shale resources, regardless of richness, in the Eocene Green River Formation in the Piceance Basin, western Colorado. A considerable amount of oil-yield data has been collected after previous in-place assessments were published, and these data were incorporated into this new assessment. About twice as many oil-yield data points were used, and several additional oil shale intervals were included that were not assessed previously for lack of data. Oil yields are measured using the Fischer assay method. The Fischer assay method is a standardized laboratory test for determining the oil yield from oil shale that has been almost universally used to determine oil yields for Green River Formation oil shales. Fischer assay does not necessarily measure the maximum amount of oil that an oil shale can produce, and there are retorting methods that yield more than the Fischer assay yield. However, the oil yields achieved by other technologies are typically reported as a percentage of the Fischer assay oil yield, and thus Fischer assay is still considered the standard by which other methods are compared.

  19. Relationships between petrophysical, sedimentological and microstructural properties of the Oolithes Blanche formation, a saline aquifer in the Paris Basin.

    NASA Astrophysics Data System (ADS)

    Casteleyn, Lisa; Robion, Philippe; Collin, Pierry-Yves; Menéndez, Beatriz; David, Christian; Fernandes, Nathalie; Desaubliaux, Guy; Dreux, Rémi; Rigollet, Christophe; Badinier, Guillaume

    2010-05-01

    The Paris Basin appears to be appropriate in terms of CO2 capture and storage when considering both the amount of CO2 produced and the availability of depleted fields and deep saline aquifers. The purpose of this study is to investigate the petrophysical properties in relation with the sedimento-diagenetic environment of the "Oolithe Blanche" formation (Dogger), a deep saline aquifer considered as a potential candidate for CO2 storage. Regarding the scarcity of the core data in the Paris Basin, our investigation was firstly based on the study of field analogs in the south-east of the Paris Basin. The Oolithe Blanche Formation is composed of very shallow marine oolitic and bioclastic limestones, mainly grainstones. Three main sedimentological fabrics were defined: tide-dominated, wave-dominated (oolitic shoal) and prograding oolitic shoal fabrics. These three fabrics show subtle variations in composition (ooliths vs bioclasts) and in the distribution of the carbonate textures. The Oolithe Blanche Formation (Bathonian) is 70-80 meters thick and water salinity ranges from 1 to 4 g NaCl/l. 18 oriented blocks were collected on outcrops selected for the different sedimentological facies recognised in the formation: 9 blocks in the Bierry Lès Belles Fontaines quarry (Yonne), 5 blocks in the Ravières quarries (Côte d'Or) and 4 blocks in the Massangis quarry (Yonne). On each block, several petrophysical properties were measured on three perpendicular plugs: porosity, pore size distribution derived from mercury injection tests, permeability, capillary imbibition parameters, electrical conductivity and acoustic velocities. The sedimento-diagenetic fabric and microstructural analysis was defined by using optical microscope and scanning electron microscopy, coupled with image analysis on thin sections. The porosity measured using the water saturation triple weight method ranges from 6% to 34%. The permeability values are low, between 0.1 mD and 9 mD. The data from the

  20. Palynology of the Heath Formation (Miocene) from the Progreso Basin, Peru

    SciTech Connect

    Engelhardt, D.W. ); Wood, G.D. )

    1993-02-01

    A diverse and well preserved assemblage of pollen, spores, dinoflagellates, and acritarchs were recovered from outcrop samples of the Heath Formation, exposed along Bocapan Creek near Tumbes, Peru. The pollen and spores include representatives of Arecipites, Bombacacidites, Caryapollenites, Cicatricosisporites, Couperipollis, Cyathidites, Diporisporites, Distaverrusporites, Dyadosporites, Echiperiporites, Faramea, Foveodiporites, Foveotriletes, Fusiformisporites, Gothanipollis, Granitricolpites, Hymenophyllum, Hexpollenties, Involutisporites, Laevigatosporites, Lygodiumsporites, Magniperiporites, Malvacearumpollis, Monocolpopollenites, Perissyncolporites, Peritheciumites, Phragmothyrites, Polyadadporites, Polypodiaceisporites, Polypodiisporites, Retibrevitricolpites, Striadisporites, Tetracolporites, Tricolporopollenties, and Verrucosisporites. Plankton are assignable to Lejeunecysta, Operculodinium, Pterospermella, Selenopemphix, Spiniferites, Sumatradinium, Tythodiscus, and Tuberculodinium. The palynomorph assemblage can be placed in the Early Miocene based on the co-occurrence of Cicatricosisporites dorogensis, Couperipollis rarispinosus, Echiperiporites estelae, Magniperiporites echinatus, Perisyncolporites porkornii, Polypodiaceoisporites minor, P. potoniei, Reticolporites guianesnsis, R. irregularis, Scabriporites asymetricus, Selenopemphix nephroides and Tuberculodinium vancampoae. This is an agreement with foraminiferal evidence which positions the Heath Formation in the Early Miocene Catapsydrax dissimilis, Catapsydrax stainforthi and oldest portion of the Globigerinatella insueta zones.

  1. Radiometric age determinations on Pliocene/Pleistocene formations in the lower Omo basin, Ethiopia

    USGS Publications Warehouse

    Brown, F.H.; Lajoie, K.R.

    1971-01-01

    THE potassium-argon ages presented here were obtained during 1966 to 1969 in order to provide an absolute time scale for the stratigraphic work by the international Omo Research Expedition in the Pliocene/Pleistocene formations (unpublished work of F. H. B., J. de Heinzelin and F. C. Howell) in south-west Ethiopia. Although some of these dates are not new1-3, most of the analytical procedures and data have not been presented. We also present a list of fossil localities recorded by the University of Chicago contingent of the expedition within the Shungura Formation. Preliminary descriptions of the Hominidae have been published already3,4. ?? 1971 Nature Publishing Group.

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

    SciTech Connect

    Reinson, G.E.

    1996-06-01

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

  3. The significance of stylolitization and intergranular pressure solution in the formation of pressure compartment seals in the St. Peter Sandstone, Ordovician, Michigan basin

    SciTech Connect

    Drzewiecki, P.A.; Simo, T.; Moline, G.; Bahr, J.M.; Nadon, G.; Shepherd, L.; Vandrey, M.R. )

    1991-03-01

    The Middle to Late Ordovician St. Peter Sandstone of the Michigan basin is a fine- to medium-grained quartz sandstone. Extensive stylolitization and intergranular pressure solution have been major factors in reducing the porosity of certain horizons within the St. Peter, resulting in pressure compartmentation of the reservoir. Pressure versus depth data for various Michigan basin wells indicate that the basin contains compartments that are overpressured by as much as 500 psi. Horizons bounding these compartments are often affected by intense stylolitization (or intergranular pressure solution) and quartz cementation and have been correlated with zones of low porosity and permeability ({phi} = 0-3%, k = <50 {mu}d). These tight zones can be correlated within single gas fields, and some may extend across the Michigan basin. The St. Peter Sandstone has been buried to depths of about 3,500 m in the central part of the basin and 1,500 m at the margins. Intensely stylolitized zones are found at all depths throughout the basin and do not appear to change in abundance or style with depths. Factors that influence the formation, morphology, and abundance of stylolites in the St. Peter include (1) clay intraclasts, (2) intergranular clay, and (3) fine-grained, feldspar-rich sand. Stylolites also occur at contacts between quartz-cemented and carbonate-cemented zones and within well-cemented sands. Intergranular pressure solution and stylolites may be responsible for the formation of a compartment seal. Understanding their genesis can allow prediction of variations in porosity in Michigan basin well cores.

  4. Late Pleistocene to Holocene alluvial tableland formation in an intra-mountainous basin in a tectonically active mountain belt ― A case study in the Puli Basin, central Taiwan

    NASA Astrophysics Data System (ADS)

    Tseng, Chia-Han; Lüthgens, Christopher; Tsukamoto, Sumiko; Reimann, Tony; Frechen, Manfred; Böse, Margot

    2016-01-01

    The morphology in Taiwan is a product of high tectonic activity at the convergent margin and East Asian monsoon climate. Tablelands are prominent geomorphic features in the Puli Basin in central Taiwan. These tablelands provide an archive to understand links between past climatic evolution and tectonic events resulting in the formation of the present-day landforms. To establish a geochronological framework for the alluvium underlying the tablelands in the Puli Basin, optically stimulated luminescence dating was applied to obtain burial ages. The numerical data indicate an accumulation phase of alluvial fans in the Late Pleistocene to Early Holocene transition. The study area in the Taomi River catchment, an obvious longer precursor of the Taomi River, originating from west of the Yuchih Basin, transported the sediments forming the present-day southern tablelands. During the Pleistocene-Holocene transition, the climate changed to wetter and warmer conditions, so that slope processes might have changed and an increasing transport in the fluvial system was stimulated. Fluvial and fan terraces in other river catchments in Taiwan also indicate a period of increased fluvial transport and deposition. A geomorphic evolution model in the Puli Basin is reconstructed on the basis of the chronological framework and of sedimentological features. Fluvial processes controlled by climatic change and accompanied by tectonic activities have created the diverse topography in the Puli Basin.

  5. Sedimentologic evolution of a submarine canyon in a forearc basin, Upper Cretaceous Rosario Formation, San Carlos, Mexico

    SciTech Connect

    Morris, W.R.; Busby-Spera, C.J.

    1988-06-01

    The walls, floor, and fill of a submarine canyon are well-exposed near San Carlos, Mexico, in forecarc strata of the Upper Cretaceous Rosario Formation. The submarine canyon is about 7 km wide and at least 230 m deep and has eroded a minimum of 150 m into underlying fluvial red beds. It is unclear whether subaerial or submarine processes initiated the canyon cutting; however, marine processes, especially debris flows, modified the morphology of the submarine canyon. The submarine canyon fill and overlying slope deposits form two major fining-upward sequences. The first includes a 120 m thick lower conglomerate-sandstone unit (LCSU) at the base of the canyon fill overlain by a 50-110 m thick middle mudstone-sandstone unit (MMSU). The MMSU consists predominantly of mudstone and thin-bedded sandstone, but includes a channel filled with sandstone beds that form a fining- and thinning-upward sequence. This sequence is overlain by the second major sequence, a 0-60 m thick upper conglomerate-sandstone unit (UCSU), which is confined to three channels within the submarine canyon and passes gradationally upward into slope mudstone. Each of the two major fining-upward sequences records a gradual decrease in supply of coarse-grained sediment to the submarine canyon head. The first fining-upward sequence may correspond to a lowstand and subsequent rise in global sea level or, alternatively, may have resulted from local downdropping of the basin. The second fining-upward sequence does not correspond to global sea level fluctuations but is age-correlative with a drop then rise in relative sea level recognized by other workers 300-400 km to the north in the San Diego-Ensenada area. This sea level drop is inferred to have been a regional-scale tectonic event that affect the forearc basin along its length. 18 figures, 2 tables.

  6. Tectonic and climate control of oil shale deposition in the Upper Cretaceous Qingshankou Formation (Songliao Basin, NE China)

    NASA Astrophysics Data System (ADS)

    Jia, Jianliang; Liu, Zhaojun; Bechtel, Achim; Strobl, Susanne A. I.; Sun, Pingchang

    2013-09-01

    Oil shales were deposited in the Songliao Basin (NE China) during the Upper Cretaceous period, representing excellent hydrocarbon source rocks. High organic matter (OM) contents, a predominance of type-I kerogen, and a low maturity of OM in the oil shales are indicated by bulk geochemical parameters and biomarker data. A major contribution of aquatic organisms and minor inputs from terrigenous land plants to OM input are indicated by n-alkane distribution patterns, composition of steroids, and organic macerals. Strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane/phytane ratios, high C14-aryl-isoprenoid contents, homohopane distribution patterns, and high V/Ni ratios. Enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values, low MTTC ratios, high β-carotene contents, low TOC/S ratios, and high Sr/Ba ratios. The stratified water column with anoxic conditions in the bottom water enhanced preservation of OM. Moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations. In this study, environmental conditions in the paleo-lake leading to OM accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics. The first Member of the Qingshankou Formation (K2qn1) in the Songliao Basin, containing the oil shale sequence, encompasses a third-order sequence that can be divided into three system tracts (transgressive system tract—TST, highstand system tract—HST, and regressive system tract—RST). Enrichment of OM changed from low values during TST-I to high-moderate values during TST-II/III and HST-I/II. Low OM enrichment occurs during RST-I and RST-II. Therefore, the highest enrichment of OM in the sediments is related to stages of mid-late TST and early HST.

  7. Exploration for shallow compaction-induced gas accumulations in sandstones of the Fort Union Formation, Powder River Basin, Wyoming

    SciTech Connect

    Oldham, D.W.

    1997-01-01

    Commercial quantities of gas have been produced from shallow sandstone reservoirs of the Tongue River Member of the Fort Union Formation (Paleocene) in the Wyoming portion of the Powder River Basin. The two largest accumulations discovered to date, Oedekoven and Chan pools, were drilled on prospects which invoked differential compaction as a mechanism for gas entrapment and prospect delineation. Coal-sourced bacterial gas may have accumulated in localized structural highs early in the burial history of lenticular sand bodies and associated sediments. Structural relief is due to the compaction contrast between sand and stratigraphically equivalent fine-grained sediments. A shallow gas play targeting sandstones as potential reservoirs was initiated in the Recluse area in response as sources for bacterial gas, and the presence of lenticular sandstones that may have promoted the development of compaction structures early in the burial process, to which early-formed bacterial gas migrated. Prospects were ranked based on a number of geologic elements related to compaction-induced trap development. Drilling of the Oedekoven prospect, which possessed all prospect elements, led to the discovery and development of the Oedekoven Fort Union gas pool, which has produced nearly 2 BCF of gas from a depth of 340 ft. Production figures from the Oedekoven and Chan pools demonstrate the commercial gas potential of Fort Union sandstone reservoirs in the Powder River Basin. The shallow depths of the reservoirs, coupled with low drilling and completion costs, an abundance of subsurface control with which to delineate prospects, and an existing network of gas-gathering systems, make them attractive primary targets in shallow exploration efforts as well as secondary objectives in deeper drilling programs.

  8. Diagenesis and late-stage porosity development in the pennsylvanian strawn formation, val verde basin, Texas, U.S.A

    USGS Publications Warehouse

    David, Newell K.; 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

  9. Taphonomic and paleoenvironmental considerations for the concentrations of macroinvertibrate fossils in the Romualdo Member, Santana Formation, Late Aptian - Early Albian, Araripe Basin, Araripina, NE, Brazil

    NASA Astrophysics Data System (ADS)

    Prado, Ludmila Alves Cadeira Do; Pereira, Priscilla Albuquerque; Sales, Alexandre Magno Feitosa; Barreto, Alcina Magnólia Franca

    2015-10-01

    Benthic macroinvertebrate fossils can be seen towards to the top of the Romualdo Member of the Santana Formation, in the Araripe Basin, Northeast Brazil, and can provide paleoenvironmental and paleobiogeographical information regarding the Cretaceous marine transgression which reached the interior basins in Northeast Brazil. We analyse taphonomic characteristics of macroinvertebrate concentrations of two outcrops (Torrinha and Torre Grande) within the municipality Araripina, Pernambuco, in order to enhance our understanding of the Cretaceous paleoenvironment in the western portion of the Araripe Basin. At the outcrop Torrinha, proximal tempestitic taphofacies were identified. These predominantly consist of ceritid, cassiopid, and later, naticid gastropods as well as undetermined bivalves. Given this lack of variability it can be deduced that there were no significant paleoenvironmental changes during the successive stages tempestitic sedimentation. In the Torre Grande outcrop distal to proximal tempestitic taphofacies were identified from the base to the top respectively pointing to a decrease in paleodepth. Asides from the macroinvertebrates present in Torrinha, there are also echinoids - unequivocal evidence for marine conditions. These occurrences appear to be restricted to Romualdo Member outcrops in the Araripina municipality (the Southeast portion of the Araripe Basin) confirming a previously published hypothesis suggesting that the Cretaceous marine transgression originated from the neighbouring Parnaíba Basin to the west. This study identified marine molluscs of a similar age to those in the Romualdo Member's equivalent rock units in the Parnaíba and Sergipe-Alagoas (SE-AL) basins suggesting a marine connection between these basins and the Araripe Basin during the Early Cretaceous.

  10. Ozone formation potentials of organic compounds from different emission sources in the South Coast Air Basin of California

    NASA Astrophysics Data System (ADS)

    Chen, Jianjun; Luo, Dongmin

    2012-08-01

    Different organic compounds exhibit different propensities for ozone formation. Two approaches were used to study the ozone formation potentials or source reactivities of different anthropogenic organic compounds emission categories in California's South Coast Air Basin (SoCAB). The first approach was based on the combination of total organic gases (TOG) emission speciation profiles and the maximum incremental reactivity (MIR) scale of organic species. The second approach quantified ozone impacts from different emission sources by performing 3-dimensional air quality model sensitivity analysis involving increased TOG emissions from particular sources. The source reactivities derived from these two approaches agree reasonably well for 58 anthropogenic organic compounds emission categories in the SoCAB. Both approaches identify TOG emissions from mobile sources as having the highest reactivity. Source reactivities from both approaches were also combined with TOG emissions from each source category to produce a 2005 reactivity-based anthropogenic TOG emission inventory for the SoCAB. The top five reactivity-based anthropogenic TOG emission sources in the SoCAB during 2005 were: light-duty passenger cars, off-road equipment, consumer products, light-duty trucks category 2 (i.e., 3751-5750 lb), and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that livestock waste and composting emission categories were two of the five largest mass-based anthropogenic TOG emission sources. The reactivity-based TOG emission inventory is an important addition to the mass-based TOG emission inventory because it represents the ozone formation potentials from emission sources and can be used to assist in determining targeted sources for developing organic compounds reduction policies.

  11. Ozone Formation Potentials from Different Anthropogenic Emission Sources of Volatile Organic Compounds in California's South Coast Air Basin

    NASA Astrophysics Data System (ADS)

    Chen, J.; Luo, D.; Croes, B.

    2010-12-01

    Different volatile organic compounds (VOC) exhibit different propensities for ozone formation. Two approaches were used to study the relative ozone formation potentials (source reactivities) of different anthropogenic VOC emission source categories in California’s South Coast Air Basin (SoCAB). The first approach combined emission speciation profiles for total organic gases (TOG) with maximum incremental reactivity (MIR) scales for VOC species. The second approach quantified ozone impacts from different sources by performing 3-dimensional air quality model sensitivity analyses involving increased TOG emissions from particular sources. The source reactivities for 58 VOC emission categories in SoCAB derived from these two approaches agree reasonably well (R2 = ~0.9). Both approaches revealed the two emissions source types with the highest TOG reactivity were mobile sources and managed forest burning. Also, a reactivity-based TOG emission inventory for SoCAB in 2005 was produced by combining the source reactivities from both approaches with TOG emissions from anthropogenic source categories. The top five reactivity-based source categories are: light-duty passenger cars, off-road equipments, consumer products, light-duty trucks, and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that farming operations (mainly from animal waste) was one of the five largest mass-based anthropogenic TOG emission sources. Compared to the mass-based TOG emission inventory, the reactivity-based TOG emission inventory more appropriately represents the ozone formation potentials from emission sources, and highlights those sources that should be targeted for future regulations.

  12. Tight gas sand production from the Almond Formation, Washakie Basin, Wyoming

    SciTech Connect

    Iverson, W.P.; Surdam, R.C.

    1995-12-31

    Gas production from the Almond Formation in the Standard Draw trend can only be accounted for by draining numerous layers of tight gas sands via the permeable upper bar sand. Discovery of this field originally focused upon production from this bar sand. But continued development cannot be explained simply by considering depletion of a 30 foot sand. Gas volumetrics verify the need to include lower sands in reservoir analysis. Core obtained from the Almond bar sand confirm petrophysical constants used in the authors` models. Their results imply that economic levels of gas production should be possible wherever a similar horizontal conduit can be tied into gas saturated layers through massive hydraulic fracturing.

  13. Detachment vs. normal faulting: Diachronous Cenozoic extension and rift basin formation in the Southern Balkans (Pirin Mts. and Sandanski basin, SW Bulgaria)

    NASA Astrophysics Data System (ADS)

    Stübner, Konstanze; Böhme, Madelaine; Ehlers, Todd

    2016-04-01

    The Southern Balkans are a landscape of basins and ranges formed by more than 40 Ma of extension in thickened post-collisional crust and above the retreating Hellenic trench. One of the best-studied extensional systems in the Southern Balkans is the South Rhodope core complex in northern Greece and southern Bulgaria, which records multiple stages of detachment faulting, including the Miocene Strymon detachment. Paleogene, Neogene and Quaternary basins are associated with stages of extension. We present new (U-Th)/He thermochronology ages from bedrock samples of the Pirin mountains and detrital samples of the adjacent Sandanski basin, SW Bulgaria. In combination with sediment paleomagnetic ages, structural data, and geomorphic analyses, our results document two episodes of Eocene/Oligocene and early to middle Miocene detachment faulting that were probably not associated with significant relief or basin development. In contrast, the Sandanski basin formed in the late Miocene (10-6 Ma) above the West Pirin and Melnik normal faults. Late Miocene E-W extension resulted in uplift of the Pirin Mts. and the development of a mountain landscape similar to the modern topography. In the Quaternary, the stress field switched to N-S extension reflected in E-W trending faults and Quaternary basins and recorded by river profiles. Our results advance our understanding of extension processes in the Southern Balkans in general and yield first constraints on the Neogene evolution of topography in the Southern Balkans with important implications on the evolution of regional climate and on Neogene paleoecology. Our study also documents a dichotomy between low-relief detachment faulting and steeply dipping normal faulting associated with relief and basin development.

  14. Is there a remnant Variscan subducted slab in the mantle beneath the Paris basin? Implications for the late Variscan lithospheric delamination process and the Paris basin formation

    NASA Astrophysics Data System (ADS)

    Averbuch, O.; Piromallo, C.

    2012-08-01

    The Paris basin (northern France) is a Late Paleozoic-Mesozoic intracratonic basin that settled upon the collapsed Variscan collisional belt. The lithospheric roots of the Variscan orogenic system, below the Paris basin, have been investigated using a European-scale P-wave velocity tomographic model. Tomography points out the existence of a significant high velocity anomaly in the upper mantle below the western part of the basin. At ~ 150-200 km depth, the anomaly extends with a NW-SE trend along the buried Northern France trace of the Northern Variscan Suture Zone i.e. the Bray segment of the Upper Carboniferous Lizard-Rhenohercynian (LRH) suture. Moreover, the high-velocity anomaly is spatially correlated with the prominent Paris Basin Magnetic Anomaly. Its downdip extent reaches depths greater than 200 km below the southern margin of the Paris basin. As suggested in previous tomographic studies below ancient suture zones, these data argue for such anomaly being the remnant of a Variscan subducted slab that escaped the extensive late orogenic delamination process affecting the lithospheric roots by Late Carboniferous-Early Permian times and that was preserved stable over 300 Ma at the base of the lithosphere. On a general geodynamical perspective, these results provide a new insight into the long-term evolution of subducted lithosphere into the mantle. In the case of the Western European Variscan orogenic belt, they suggest that the subduction of the LRH slab below the previously thickened Variscan crust, and its final detachment from the orogenic root, have played an important role in the collapse of the belt, inducing thermal erosion and extension of the overriding lithosphere. The spatial evolution of late orogenic extension across the belt and of subsequent thermal subsidence in the Paris basin is suggested to result from the heterogeneous delamination of the lithospheric roots along strike and from the resultant pattern of asthenospheric rise.

  15. Ichnofossils of the alluvial Willwood Formation (lower Eocene), Bighorn Basin, northwest Wyoming, U.S.A

    USGS Publications Warehouse

    Bown, T.M.; Kraus, M.J.

    1983-01-01

    The ichnofossil assemblage of the lower Eocene Willwood Formation consists of at least nine distinct endichnia that are preserved in full relief. Four forms (three ichnogenera and four ichnospecies) are new and represent fodinichnia and domichnia of oligochaete worms, an insect or spider, an unknown vertebrate (probably a mammal), and domichnia of an unidentified organism. Other potential trace makers of the ichnofauna include insects, mollusks, and decapods. In contrast to an Egyptian Oligocene fluvial ichnofauna produced largely by animals that burrowed in stream channel deposits, the Willwood assemblage is principally of flood-plain origin. Though the ichnofauna occurs in a variety of paleosol types, most of the fossils are restricted in distribution to specific sediment and soil types and, within paleosols, to specific identifiable horizons. This attribute will make them valuable indiced of paleoenvironment once they are better known in other ancient alluvial sequences. The environment suggested by the Willwood trace fossils (damp, but not wet soils with fluctuating water tables) is consistent with the warm temperate to subtropical (possibly monsoonal) conditions that are interpreted for the Willwood Formation by independent evidence of body fossils and paleopedology. ?? 1983.

  16. Genetic and temporal relations between formation waters and biogenic methane: Upper Devonian Antrim Shale, Michigan Basin, USA

    NASA Astrophysics Data System (ADS)

    Martini, A. M.; Walter, L. M.; Budai, J. M.; Ku, T. C. W.; Kaiser, C. J.; Schoell, M.

    1998-05-01

    Controversy remains regarding how well geochemical criteria can distinguish microbial from thermogenic methane. Natural gas in most conventional deposits has migrated from a source rock to a reservoir, rarely remaining associated with the original or cogenetic formation waters. We investigated an unusual gas reservoir, the Late Devonian Antrim Shale, in which large volumes of variably saline water are coproduced with gas. The Antrim Shale is organic-rich, of relatively low thermal maturity, extensively fractured, and is both source and reservoir for methane that is generated dominantly by microbial activity. This hydrogeologic setting permits integration of chemical and isotopic compositions of coproduced water and gas, providing a unique opportunity to characterize methane generating mechanisms. The well-developed fracture network provides a conduit for gas and water mass transport within the Antrim Shale and allows invasion of meteoric water from overlying aquifers in the glacial drift. Steep regional concentration gradients in chemical and isotopic data are observed for formation waters and gases; dilute waters grade into dense brines (300,000 ppm) over lateral distances of less than 30 km. Radiogenic ( 14C and 3H) and stable isotope ( 18O and D) analyses of shallow Antrim Shale formation waters and glacial drift groundwaters indicate recharge times from modern to 20,000 yr BP. Carbon isotope compositions of methane from Antrim Shale wells are typical of the established range for thermogenic or mixed gas (δ 13C = -47 to -56‰). However, the unusually high δ 13C values of CO 2 coproduced with methane (˜+22‰) and dissolved inorganic carbon (DIC) in formation waters (˜+28‰) require bacterial mediation. The δD values of methane and coproduced formation water provide the strongest evidence of bacterial methanogenesis. Methane/[ethane + propane] ratios and δ 13C values for ethane indicate: (1) the presence of a thermogenic gas component that increases

  17. Palynostratigraphy of the Nayband Formation, Tabas, Central Iran Basin: Paleogeographical and paleoecological implications

    NASA Astrophysics Data System (ADS)

    Sajjadi, F.; Hashemi, H.; Borzuee, E.

    2015-11-01

    Reasonably diverse and moderately preserved palynofloras of exclusively terrestrial derivation occur in surface samples of the Nayband Formation, Kamar Macheh Kuh, southeastern Tabas, east-central Iran. No marine palynomorphs encountered in the samples examined. The palynofloras comprise 62 species including radially symmetrical and monolete spores (37 species allocated to 27 genera) and pollen (25 species designated to 19 genera). Of the latter, such bisaccate taxa as Ovalipollis ovalis, Alisporites spp., Falcisporites nuthallensis, the inaperturate Araucariacites australis, and the monosulcate Chasmatosporites major dominate the assemblages. Representatives of such trilete spores as Dictyophyllidites mortonii, Kyrtomisporis laevigatus, and Gleicheiniidites senonicus are essentially abundant in the palynofloras examined. Vertical distribution of miospores allows erection within the Nayband Formation of three informal distinctive stratigraphically successive interval biozones, viz., A. australis-Annulispora folliculosa biozone, Conbaculatisporites sp.-Ricciisporites tuberculatus biozone, and R. tuberculatus-Polypodiisporites polymicroforatus biozone based on the First Observed Occurrence (FOO) and Last Observed Occurrence (LOO) of selected taxa. These are compared with palynozones from ±coeval strata in Iran and elsewhere. Additionally, two non-palyniferous intervals, one at the base (188 m thick) and another (18 m in thickness) at uppermost part of the section studied are identified. Based on the association of such key misopore species as Lunatisporites rhaeticus, O. ovalis (alias pseudoalatus), A. folliculosa, Polycingulatisporites mooniensis, Limbosporites lundbladii, Quadraeculina anellaeformis, R. tuberculatus, Conbaculatisporites sp., P. polymicroforatus, and Striatisaccus novimundi within the Nayband palynofloras, the host strata are assigned to Late Triassic (Norian-Rhaetian). This dating while corroborating previous attempts made with reference to mostly

  18. Stratigraphic framework and estuarine depositional environments of the Miocene Bear Lake Formation, Bristol Bay Basin, Alaska: Onshore equivalents to potential reservoir strata in a frontier gas-rich basin

    USGS Publications Warehouse

    Finzel, E.S.; Ridgway, K.D.; Reifenstuhl, R.R.; Blodgett, R.B.; White, J.M.; Decker, P.L.

    2009-01-01

    The Miocene Bear Lake Formation is exposed along the coast and mountains of the central Alaska Peninsula and extends offshore as part of the Bristol Bay Basin. The Bear Lake Formation is up to 2360 m (7743 ft) thick in an offshore well and is considered to have the highest reservoir potential in this gasrich frontier basin. Our new macrofossil and palynological data, collected in the context of measured stratigraphic sections, allow us to construct the first chronostratigraphic framework for this formation. Biostratigraphic age assignments for the numerous, commonly isolated, onshore exposures of the Bear Lake Formation show that deposition initiated sometime before the middle Miocene (15 Ma) and extended to possibly the earliest Pliocene. The bulk of the Bear Lake Formation, however, was deposited during the middle and late Miocene based on our new findings. We interpret the Bear Lake Formation as the product of a regional transgressive estuarine depositional system based on lithofacies analysis. The lower part of the formation is characterized by trough cross-stratified sandstone interbedded with coal and pedogenic mudstone deposited in fluvial and swamp environments of the uppermost parts of the estuarine system. The lower-middle part of the formation is dominated by nonbioturbated, wavy- and flaser-bedded sandstone and siltstone that were deposited in supratidal flat environments. The uppermiddle part of the Bear Lake Formation is characterized by inclined heterolithic strata and coquinoid mussel beds that represent tidal channel environments in the middle and lower tracts of the estuarine system. The uppermost part of the formation consists of tabular, bioturbated sandstone with diverse marine invertebrate macrofossil faunas. We interpret this part of the section as representing the subtidal tract of the lower estuarine system and possibly the adjacent shallow inner shelf. A comparison of our depositional framework for the Bear Lake Formation with core and

  19. Geochemistry of water in the Fort Union formation of the northern Powder River basin, southeastern Montana

    USGS Publications Warehouse

    Lee, Roger W.

    1981-01-01

    Shallow water in the coal-bearing Paleocene Fort Union Formation of southeastern Montana was investigated to provide a better understanding of its geochemistry. Springs, wells less than 200 feet deep, and wells greater than 200 feet deep were observed to have different water qualities. Overall, the ground water exists as two systems: a mosaic of shallow, chemically dynamic, and localized recharge-discharge cells superimposed on a deeper, chemically static regional system. Water chemistry is highly variable in the shallow system; whereas, waters containing sodium and bicarbonate characterize the deeper system. Within the shallow system, springs and wells less than 200 feet deep show predominantly sodium and sulfate enrichment processes from recharge to discharge. These processes are consistent with the observed aquifer mineralogy and aqueous chemistry. However, intermittent mixing with downward moving recharge waters or upward moving deeper waters, and bacterially catalyzed sulfate reduction, may cause apparent reversals in these processes.

  20. Geochemistry of water in the Fort Union Formation of the northern Powder River basin, southeastern Montana

    USGS Publications Warehouse

    Lee, Roger W.

    1980-01-01

    Shallow water in the coal-bearing Fort Union Formation of southeastern Montana was investigated to provide a better understanding of the geochemistry. Springs, wells less than 200 feet deep, and wells greater then 200 feet deep were observed to have different water qualities. Overall, the ground water exists as two systems: a mosaic of shallow, chemically dynamic, and localized recharge-discharge cells superimposed on a deeper, chemically static regional system. Water chemistry is highly variable in the shallow system, whereas sodium and bicarbonate waters characterize the deeper system. Within the shallow system , springs, and wells less than 200 feet deep show predominantly sodium and sulfate enrichment processes from recharge to discharge. These processes are consistent with the observed aquifer mineralogy and aqueous chemistry. However, intermittent mixing with downward moving recharge waters or upward moving deeper waters, and bacterially catalyzed sulfate reduction, may cause apparent reversals in these processes. (USGS)

  1. Stability of rock exposures and formation conditions for cave-ins in the Krivoi Rog basin

    SciTech Connect

    Shadrin, A.G.; Sazonov, A.V.

    1985-07-01

    In the underground working of ore deposits at depth, cavities are formed which create the potential for sudden caving-in of the earth's surface and the danger of air impact in the mine. In a number of cases, these phenomena are accompanied by catastrophic consequences. In mines in the Krovoi Rod deposits, many uncollapsed cavities have been noted. In the most complicated situations, it is extremely important to evaluate the stability of the exposures and the time of possible cave-in, and considering this, to work out measures for the elimination of cavities and the safe performance of mining operations in this region. The authors present a method for evaluating the stability of exposures and formation conditions for cave-ins which is being applied in combined site development.

  2. Artificial maturation of oil shale: The Irati Formation from the Parana Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Gayer, James L.

    Oil shale samples from the Irati Formation in Brazil were evaluated from an outcrop block, denoted Block 003. The goals of this thesis include: 1) Characterizing the Irati Formation, 2) Comparing the effects of two different types of pyrolysis, anhydrous and hydrous, and 3) Utilizing a variety of geophysical experiments to determine the changes associated with each type of pyrolysis. Primary work included determining total organic carbon, source rock analysis, mineralogy, computer tomography x-ray scans, and scanning electron microscope images before and after pyrolysis, as well as acoustic properties of the samples during pyrolysis. Two types of pyrolysis (hydrous and anhydrous) were performed on samples cored at three different orientations (0°, 45°, and 90°) with respect to the axis of symmetry, requiring six total experiments. During pyrolysis, the overall effective pressure was maintained at 800 psi, and the holding temperature was 365°C. The changes and deformation in the hydrous pyrolysis samples were greater compared to the anhydrous pyrolysis. The velocities gave the best indication of changes occurring during pyrolysis, but it was difficult to maintain the same amplitude and quality of waveforms at higher temperatures. The velocity changes were due to a combination of factors, including thermal deformation of the samples, fracture porosity development, and the release of adsorbed water and bitumen from the sample. Anhydrous pyrolysis in this study did not reduce TOC, while TOC was reduced due to hydrous pyrolysis by 5%, and velocities in the hydrous pyrolysis decreased by up to 30% at 365°C compared to room temperature. Data from this study and future data that can be acquired with the improved high-temperature, high-pressure experiment will assist in future economic production from oil shale at lower temperatures under hydrous pyrolysis conditions.

  3. Past, present and future formation of groundwater resources in northern part of Baltic Artesian Basin

    NASA Astrophysics Data System (ADS)

    Marandi, A.; Vallner, L.; Vaikmae, R.; Raidla, V.

    2012-04-01

    Cambrian-Vendian Aquifer System (CVAS) is the deepest confined aquifer system used for water consumption in northern part of Baltic Artesian Basin (BAB). A regional groundwater flow and transport model (Visual Modflow) was used to investigate the paleohydrogeological scientific and contemporary management problems of CVAS. The model covers the territory of Estonia and its close surrounding, all together 88,000 km2 and includes all main aquifers and aquitards from ground surface to as low as the impermeable part of the crystalline basement. Three-dimensional distribution of groundwater heads, flow directions, velocities, and rates as well as transport and budget characteristics were simulated by the model. Water composition was changed significantly during the last glaciations.Strongly depleted O and H stable isotope composition, absence of 3H and low radiocarbon concentration are the main indicators of glacial origin of groundwater in the Cambrian-Vendian aquifer in northern Estonia. The noble gas analyses allowed concluding, that palaeorecharge took place at temperatures around the freezing point. While in North Estonia, most of water was changed by glacial melt water, high salinity water is till preserved in Southern part of Estonia.First results of modeling suggest that during the intrusion period lasting 7.3-9.3 ka the front of glacial thaw water movement had southeast direction and reachedto 180-220 kmfrom CVAS outcrop in Baltic Sea. Confining layer of CVAS is cut through by deep buried valleys in several places in North Estonia making possible for modern precipitation to infiltrate into aquifer system in present day. In case of natural conditions, the water pressure of CVAS is few meters above sea level and most of valleys act as discharge areas for aquifers system. Two regional depression ones have formed in North Estonia as a result of groundwater use from CVAS. Water consumption changes the natural groundwater gradient, flow direction and thereforerecharge

  4. Outcrops, Fossils, Geophysical Logs, and Tectonic Interpretations of the Upper Cretaceous Frontier Formation and Contiguous Strata in the Bighorn Basin, Wyoming and Montana

    USGS Publications Warehouse

    Merewether, E.A.; Cobban, W.A.; Tillman, R.W.

    2010-01-01

    In the Bighorn Basin of north-central Wyoming and south-central Montana, the Frontier Formation of early Late Cretaceous age consists of siliciclastic, bentonitic, and carbonaceous beds that were deposited in marine, brackish-water, and continental environments. Most lithologic units are laterally discontinuous. The Frontier Formation conformably overlies the Mowry Shale and is conformably overlain by the Cody Shale. Molluscan fossils collected from outcrops of these formations and listed in this report are mainly of marine origin and of Cenomanian, Turonian, and Coniacian ages. The lower and thicker part of the Frontier in the Bighorn Basin is of Cenomanian age and laterally equivalent to the Belle Fourche Member of the Frontier in central Wyoming. Near the west edge of the basin, these basal strata are disconformably overlain by middle Turonian beds that are the age equivalent of the Emigrant Gap Member of the Frontier in central Wyoming. The middle Turonian beds are disconformably overlain by lower Coniacian strata. Cenomanian strata along the south and east margins of the basin are disconformably overlain by upper Turonian beds in the upper part of the Frontier, as well as in the lower part of the Cody; these are, in turn, conformably overlain by lower Coniacian strata. Thicknesses and ages of Cenomanian strata in the Bighorn Basin and adjoining regions are evidence of regional differential erosion and the presence of an uplift during the early Turonian centered in northwestern Wyoming, west of the basin, probably associated with a eustatic event. The truncated Cenomanian strata were buried by lower middle Turonian beds during a marine transgression and possibly during regional subsidence and a eustatic rise. An uplift in the late middle Turonian, centered in north-central Wyoming and possibly associated with a eustatic fall, caused the erosion of lower middle Turonian beds in southern and eastern areas of the basin as well as in an adjoining region of north

  5. Late-glacial to Early Holocene lake basin and river valley formation within Pomeranian moraine belt near Dobbertin (Mecklenburg-Vorpommern, NE Germany)

    NASA Astrophysics Data System (ADS)

    Zawiska, Izabela; Lorenz, Sebastian; Börner, Andreas; Niessner, Dominique; Słowiński, Michał; Theuerkauf, Martin; Pieper, Hagen; Lampe, Reinhard

    2014-05-01

    In central Mecklenburg-Vorpommern vast areas between the terminal moraine belts of the Frankfurt (W1F) and Pomeranian Phase (W2) were covered by glaciolacustrine basins which were embedded in the outwash plains. With deglaciation of the Pomeranian Phase around 17-18 ka BP the basins north to the villages Dobbertin and Dobbin were part of a glaciofluvial river system in combination with ice-dammed lake basins. During the late-glacial after ~14 ka cal BP the melting of buried dead ice reshaped the lake basin morphology by new depressions, in- and outlets. We study late-glacial basin and landscape development using cores collected along a pipeline trench crossing the Dobbin-Dobbertin basin. Core analysis includes sedimentological (carbon content, grainsize distribution) and palaeoecological (pollen, plant macrofossils, Cladocera) proxies. Radiocarbon dates indicate that peat formation started soon after the start of the Weichselian late-glacial. High resolution analysis of a basal peat layer indicates that initial organic and lacustrine sedimentation started in shallow ponding mires, evolving from buried dead ice sinks in the glaciofluvial sequence, in which telmatic plants (Carex aquatilis, Schoenoplectus lacustris) dominated. Chydorus sphaericus, the only cladocera species recorded, is ubiquitous and can survive in almost all reservoir types in very harsh conditions. Findings of Characeae than point at the formation of shallow lakes. The expansion of rich fen communities, including Scorpidium scorpoides, and a decline in Cladocera diversity show that these lakes soon again terrestrialised with peat formation. The appearance of Alona costata points at a lowering of pH values in that process. A tree trunk of birch (14.2 ka cal. BP) shows that first trees established during this first telmatic period. At this position in the basin, the basal peat layer is covered by minerogenic sediments, which points at a period of higher water levels and fluvial dynamics, possibly

  6. Modeling of wind gap formation and development of sedimentary basins during fold growth: application to the Zagros Fold Belt, Iran.

    NASA Astrophysics Data System (ADS)

    Collignon, Marine; Yamato, Philippe; Castelltort, Sébastien; Kaus, Boris

    2016-04-01

    Mountain building and landscape evolution are controlled by the interactions between river dynamics and tectonic forces. Such interactions have been largely studied but a quantitative evaluation of tectonic/geomorphic feedbacks remains required for understanding sediments routing within orogens and fold-and-thrust belts. Here, we employ numerical simulations to assess the conditions of uplift and river incision necessary to deflect an antecedent drainage network during the growth of one or several folds. We propose that a partitioning of the river network into internal (endorheic) and longitudinal drainage arises as a result of lithological differences within the deforming crustal sedimentary cover. We show with examples from the Zagros Fold Belt (ZFB) that drainage patterns can be linked to the incision ratio R between successive lithological layers, corresponding to the ratio between their relative erodibilities or incision coefficients. Transverse drainage networks develop for uplift rates smaller than 0.8 mm.yr-1 and -10 < R < 10. Intermediate drainage network are obtained for uplift rates up to 2 mm.yr-1 and incision ratios of 20. Parallel drainage networks and formation of sedimentary basins occur for large values of incision ratio (R >20) and uplift rates between 1 and 2 mm.yr-1. These results have implications for predicting the distribution of sediment depocenters in fold-and-thrust belts, which can be of direct economic interest for hydrocarbon exploration.

  7. Integrated reservoir characterization to define a hydrodynamic model in the Misoa formation, Eocene, Center Lake Field, Maracaibo Basin, Venezuela

    SciTech Connect

    Azuaje, V.; Gil, J.

    1996-08-01

    The Center Lake Field is one of the most important light oil reservoirs in the Maracaibo Basin. Field production of {open_quotes}C{close_quotes} sandstones, Misoa formation, Eocene, started in 1968. Actual cumulative production is 630 MMBls, which represents 23% of the original oil in place. Flank water injection programs have been executed since 1976; however, reservoirs within this field still have shown pressure and production declination. A multidisciplinary study has been conducted to produce an updated hydrodynamic model which matches the static and dynamic behavior of the reservoirs. An integrated interpretation team has merged geological, geophysical and engineering data and criteria to generate an updated and consistent interpretation of today`s performance of reservoirs. The integration of a 3D seismic survey with a sequence- stratigraphy analysis, petrophysical and production data allowed us to determine a new structural and stratigraphic framework. The first important conclusion is that active aquifer is not located at the flanks of the structure, as traditionally worked out. Instead, a water-bottom drive system was interpreted and validated with production data so a different strategy for water injection was recommended. The latter interpretation restricted the injection to those areas where rock volume calculation, permeability, porosity and depositional environment make it suitable and profitable. A pattern injection program is going to be developed in C-4-X.46 reservoir and 21.6 MMBls additional recovery is expected in respect to the old production scheme.

  8. Reservoir heterogeneity and hydrocarbon production in mixed dolomitic-clastic sequence: Escandalosa Formation, Barinas-Apure basin, southwestern Venezuela

    SciTech Connect

    Escalona, N.; Abud, J.

    1989-03-01

    Widespread dedolomitization and differential leaching occur in the Turonian O Member of the Escandalosa Formation, Barinas-Apure basin. Within this dolostone-dominated succession, calcite was developed through a dedolomitization process occurring in deeply buried dolomitized lime sediments previously deposited on a carbonate platform as well as dedolomitization on the associated glauconitic-quartzose sandstones of small-scale channels that scoured the platform. The dolomitized intervals have a strata-bound nature, and their original fabric is totally obliterated. The dolomitization process generated a sucrose-textured mosaic of saddle dolomite. Initial dolomite was of the scattered type, but progressive replacement of the host produced a mosaic dolostone with both idiotopic and xenotopic textures. A general increase occurred in the iron and manganese content, and goethite was exsolved from the curved rhombs of saddle dolomite. Calcite usually postdates dolomitization, except in the highly fossiliferous packstones; calcite veins develop in both dolostones and limestones. Leaching is restricted essentially to glauconitic sandstones where calcite and some clay have been leached. This has produced very low intercrystalline porosity within the dolostones and partially dissolved, corroded and floating grains with oversized pores in the sandstones. These sandy intervals exhibit maximum potential for hydrocarbon storage, due to contrasting diagenetic influence associated with reservoir heterogeneity.

  9. Diagenesis and reservoir quality of the Lower Cretaceous Quantou Formation tight sandstones in the southern Songliao Basin, China

    NASA Astrophysics Data System (ADS)

    Xi, Kelai; Cao, Yingchang; Jahren, Jens; Zhu, Rukai; Bjørlykke, Knut; Haile, Beyene Girma; Zheng, Lijing; Hellevang, Helge

    2015-12-01

    The Lower Cretaceous Quantou Formation in the southern Songliao Basin is the typical tight oil sandstone in China. For effective exploration, appraisal and production from such a tight oil sandstone, the diagenesis and reservoir quality must be thoroughly studied first. The tight oil sandstone has been examined by a variety of methods, including core and thin section observation, XRD, SEM, CL, fluorescence, electron probing analysis, fluid inclusion and isotope testing and quantitative determination of reservoir properties. The sandstones are mostly lithic arkoses and feldspathic litharenites with fine to medium grain size and moderate to good sorting. The sandstones are dominated by feldspar, quartz, and volcanic rock fragments showing various stages of disintegration. The reservoir properties are quite poor, with low porosity (average 8.54%) and permeability (average 0.493 mD), small pore-throat radius (average 0.206 μm) and high displacement pressure (mostly higher than 1 MPa). The tight sandstone reservoirs have undergone significant diagenetic alterations such as compaction, feldspar dissolution, quartz cementation, carbonate cementation (mainly ferrocalcite and ankerite) and clay mineral alteration. As to the onset time, the oil emplacement was prior to the carbonate cementation but posterior to the quartz cementation and feldspar dissolution. The smectite to illite reaction and pressure solution at stylolites provide a most important silica sources for quartz cementation. Carbonate cements increase towards interbedded mudstones. Mechanical compaction has played a more important role than cementation in destroying the reservoir quality of the K1q4 sandstone reservoirs. Mixed-layer illite/smectite and illite reduced the porosity and permeability significantly, while chlorite preserved the porosity and permeability since it tends to be oil wet so that later carbonate cementation can be inhibited to some extent. It is likely that the oil emplacement occurred

  10. Formation of hydrothermal deposits at Kings Triple Junction, northern Lau back-arc basin, SW Pacific: The geochemical perspectives

    NASA Astrophysics Data System (ADS)

    Paropkari, Anil L.; Ray, Durbar; Balaram, V.; Surya Prakash, L.; Mirza, Imran H.; Satyanarayana, M.; Gnaneshwar Rao, T.; Kaisary, Sujata

    2010-04-01

    An inactive hydrothermal field was discovered near Kings Triple Junction (KTJ) in northern Lau back-arc basin during 19th cruise of R/V Akademik Mstislav Keldysh in 1990. The field consisted of a large elongated basal platform 'the pedestal' with several 'small' chimneys on its periphery and one 'main mound' superposed over it. The surrounding region is carpeted with lava pillows having ferromanganese 'precipitate' as infillings. The adjoining second field consisted of small chimney like growths termed as 'Christmas Tree' Field. The basal pedestal, the peripheral chimneys and small 'Christmas Tree' like growths (samples collected by MIR submersibles), though parts of the same hydrothermal field, differ significantly in their mineralogy and elemental composition indicating different history of formation. The pedestal slab consisting of chalcopyrite and pyrite as major minerals and rich in Cu is likely to have formed at higher temperatures than sphalerite dominated peripheral chimney. Extremely low concentration of high field strength elements (e.g. Zr, Hf, Nb and Ta) and enrichment of light REE in these sulfides indicate prominent influence of aqueous arc-magma, rich in subduction components. The oxide growths in the 'Christmas Tree' Field have two distinct layers, Fe rich orange-red basal part which seems to have formed at very low temperature as precipitates from diffused hydrothermal flows from the seafloor whereas Mn rich black surface coating is formed from hydrothermal fluids emanated from the seafloor during another episode of hydrothermal activity. Perhaps this is for the first time such unique hydrothermal oxide growths are being reported in association with hydrothermal system. Here, we discuss the possible processes responsible for the formation of these different hydrothermal deposits based on their mineralogy and geochemistry.

  11. A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina

    PubMed Central

    Apaldetti, Cecilia; Martinez, Ricardo N.; Alcober, Oscar A.; Pol, Diego

    2011-01-01

    Background Argentinean basal sauropodomorphs are known by several specimens from different basins; Ischigualasto, El Tranquilo, and Mogna. The Argentinean record is diverse and includes some of the most primitive known sauropodomorphs such as Panphagia and Chromogisaurus, as well as more derived forms, including several massospondylids. Until now, the Massospondylidae were the group of basal sauropodomorphs most widely spread around Pangea with a record in almost all continents, mostly from the southern hemisphere, including the only record from Antarctica. Methodology/Principal Finding We describe here a new basal sauropodomorph, Leyesaurus marayensis gen. et sp. nov., from the Quebrada del Barro Formation, an Upper Triassic-Lower Jurassic unit that crops out in northwestern Argentina. The new taxon is represented by a partial articulated skeleton that includes the skull, vertebral column, scapular and pelvic girdles, and hindlimb. Leyesaurus is diagnosed by a set of unique features, such as a sharply acute angle (50 degrees) formed by the ascending process of the maxilla and the alveolar margin, a straight ascending process of the maxilla with a longitudinal ridge on its lateral surface, noticeably bulging labial side of the maxillary teeth, greatly elongated cervical vertebrae, and proximal articular surface of metatarsal III that is shelf-like and medially deflected. Phylogenetic analysis recovers Leyesaurus as a basal sauropodomorph, sister taxon of Adeopapposaurus within the Massospondylidae. Moreover, the results suggest that massospondylids achieved a higher diversity than previously thought. Conclusions/Significance Our phylogenetic results differ with respect to previous analyses by rejecting the massospondylid affinities of some taxa from the northern hemisphere (e.g., Seitaad, Sarahsaurus). As a result, the new taxon Leyesaurus, coupled with other recent discoveries, suggests that the diversity of massospondylids in the southern hemisphere was higher

  12. Assessment of the Mowry Shale and Niobrara Formation as Continuous Hydrocarbon Systems, Powder River Basin, Montana and Wyoming

    USGS Publications Warehouse

    Anna, Lawrence O.; Cook, Troy A.

    2008-01-01

    A recent U.S. Geological Survey (USGS) oil and gas assessment of the Powder River Basin , Wyoming and Montana, identified the Upper Cretaceous Mowry Shale and Niobrara Formation as the primary hydrocarbon sources for Cretaceous conventional and unconventional reservoirs. Cumulative Mowry-sourced petroleum production is about 1.2 BBO (billion barrels of oil) and 2.2 TCFG (trillion cubic feet of gas) and cumulative Niobrara-sourced oil production is about 520 MMBO (million barrels of oil) and 0.95 TCFG. Burial history modeling indicated that hydrocarbon generation for both formations started at about 0.60 percent Ro at depths of about 8,000 ft. At maximum depths, Ro for the Mowry is about 1.2 to 1.3 percent and about 0.80 percent for the Niobrara. The Mowry and Niobrara continuous reservoirs were assessed using a cell-based methodology that utilized production data. The size of each cell was based on geologic controls and potential drainage areas in analog fields. Current and historical production data were used to determine the estimated ultimate recovery (EUR) distribution for untested cells. Only production data from unconventional fractured shale reservoirs with vertical wells were used. For the Mowry, the minimum, median, and maximum total recovery volumes per cell for untested cells are (1) 0.002, 0.25, and 0.35 MMBO, respectively; and for the Niobrara (2) 0.002, 0.028, and 0.5 MMBO. Sweet spots were identified by lineaments and faults, which are believed to be areas having the greatest petroleum potential; an upper limit of 8,000 ft depth was defined by overpressuring caused by hydrocarbon generation. Mean estimates of technically recoverable undiscovered continuous resource for the Mowry are 198 MMBO, 198 BCF (billion cubic feet of gas), and 11.9 MMBNGL (million barrels of natural gas liquid), and those for the Niobrara are 227 MMBO, 227 BCFG, and 13.6 MMBNGL.

  13. Geochemical fingerprinting of Wilson Creek formation tephra layers (Mono Basin, California) using titanomagnetite compositions

    USGS Publications Warehouse

    Marcaida, Mae; Mangan, Margaret T.; Vazquez, Jorge A.; Bursik, Marcus; Lidzbarski, Marsha I.

    2014-01-01

    Nineteen tephra layers within the Wilson Creek formation near Mono Lake provide a record of late Pleistocene to early Holocene volcanic activity from the nearby Mono Craters and are important chronostratigraphic markers for paleomagnetic, paleoclimatic, and paleoecologic studies. These stratigraphically important tephra deposits can be geochemically identified using compositions of their titanomagnetite phenocrysts. Titanomagnetite compositions display a broad range (XUsp 0.26–0.39), which allow the tephra layers to be distinguished despite the indistinguishable major-element glass compositions (76–77 wt% SiO2) of their hosts. The concentrations of Ti and Fe in titanomagnetite display geochemical and stratigraphic groupings that allow clear discrimination between older (> 57 ka) and younger (2O3 contents. In addition, a few tephra layers can be correlated to their source vents by their titanomagnetite compositions. The unique geochemical fingerprint of the Mono Craters-sourced titanomagnetites also allows the discrimination of two tephra layers apparently sourced from nearby Mammoth Mountain volcano in Long Valley.

  14. Lower Cisco Formation (Pennsylvanian-Virgilian) paleokarst, Wolf Flat field Palo Duro basin, Texas

    SciTech Connect

    Trentham, R.C. ); Lindsay, R.F. ); Pack, D.D. )

    1996-01-01

    Wolf Flat field produces from karstified Lower Cisco Formation at the rimmed northeast shelf margin. Mounds, peripheral skeletal debris, and oolitic facies form the vertical/lateral succession. Mounds are composed of crinoids, bryozoans, corals and algae. Skeletal packstone/grainstones surround mounds, With back-mound wackestone. Ooid grainstone formed in high-energy passages onto the shelf and cap shallowing-upward cycles. Karstification resulted from two 100+ ft. (30+ m) sea level drops, that dropped in a step-by-step manner to form [approximately]20 porous intervals that extend through all facies and lithologies in the field. Aragonitic mound and skeletal grainstone/wackestones experienced intense dissolution. Calcitic ooid grainstones dissolved less and form cave roofs and floors. Dissolution was in two phases: first, small vertically oriented pipes formed, resembling a [open quotes]swiss cheese[close quotes] texture; second, was intense lateral dissolution that created a [open quotes]sponge[close quotes] texture, with porosities up to 60-70%. Eventually, collapse breccias formed, with some clasts transported in the karst system. Porosity was reduced by vadose silt, breccia clasts, speleothem cements, transgressive shale infilling, and burial saddle dolomite. Portions of the field nearest the rimmed margin were dolomitized. [delta][sup 18]O is within the range of early meteoric diagenesis and [delta][sup 13]C is negative and becomes more negative toward the exposure surface.

  15. Mineralogy of the Mahogany marker tuff of the Green River Formation, Piceance Creek Basin, Colorado

    SciTech Connect

    Mason, G.M.

    1983-04-01

    The Mahogany marker tuff is a chronostratigraphic marker which was deposited in Eocene Lake Uinta approximately 45-46 million years ago when the lake was at its maximum size. The Mahogany marker lies 3 to 6 meters above the Mahogany oil shale bed in the upper part of the Parachute Creek Member of the Green River Formation. The mineralogy of the marker was studied in drill cores by X-ray diffraction and hand specimen examination. The Mahogany marker consists of authigenic sodium feldspar, analcime, quartz, ankerite, dolomite, potassium, feldspar, calcite with lesser amounts of siderite, hematite, pyrite, undifferentiated clays, pyrrhotite, biotite, marcasite, and locally dawsonite. Analcime is not present in all samples and in samples which are analcime-free, K-feldspar shows a greater abundance. Dawsonite is locally present only in analcime-free samples. The presence or absence of analcime and K-feldspar is attributed to the geochemical conditions that existed in the lake at the time of deposition of the Mahogany marker. The evidence supports a stratified lake model of oil shale deposition, with extremely alkaline pH values existing in deeper central portions of Lake Uinta.

  16. Chester (Mississippian) ostracodes from Bangor Formation of Black Warrior basin, northern Alabama

    SciTech Connect

    Devery, H.; Dewey, C.

    1986-05-01

    A previously unreported ostracode fauna is described from the Bangor Limestone in Franklin, Lawrence, and Colbert Counties, Alabama. The Bangor formation is a Chesterian (Mississippian) platformal carbonate sequence. The predominant carbonates are bioclastic and oolitic grainstones to wackestones with less abundant micritic claystones. Intercalated fine clastics are common in the upper and lower parts of the sequence. This study focuses on the bioclastic limestones with interbedded shales of the lower Bangor. The megafaunal associations include crinoid and blastoid pelmatozoans, orthotetid, and spiriferid brachiopids, and both fenestrate and nonfenestrate bryozoans. Solitary rugose corals and trilobites may be locally abundant. Gastropods and bivalves form a consistent but accessory part of the fauna, which indicates a shallow, nearshore shelf environment. A diverse ostracode fauna of variable abundance has been collected from the shaly units and friable limestones. The ostracode fauna indicates shallow, open-marine conditions and is dominated by bairdiaceans, including Bairdia spp. Rectobairdia and Bairdiacypris. Several species of Cavellina, healdia, and Seminolites are also abundant. Palaeocopids present include Coryellina, Kirkbya, and Polytylites. Kloedenellaceans include Beyrichiopsis, Glyptopleura, Glypotpleurina, and .Hypotetragona. Paraparchitaceans are notably more scarce, but specimens of Shishaella have been found. Some sample have a high valve to carapace ratio, suggesting postmortem transport. Although diversity is high, numerical abundances can be low. Initial studies suggest the ostracodes have a Mid-Continent affinity, which may indicate that the Appalachians were acting as a barrier to migration of European forms.

  17. Geochemical fingerprinting of Wilson Creek formation tephra layers (Mono Basin, California) using titanomagnetite compositions

    NASA Astrophysics Data System (ADS)

    Marcaida, Mae; Mangan, Margaret T.; Vazquez, Jorge A.; Bursik, Marcus; Lidzbarski, Marsha I.

    2014-03-01

    Nineteen tephra layers within the Wilson Creek formation near Mono Lake provide a record of late Pleistocene to early Holocene volcanic activity from the nearby Mono Craters and are important chronostratigraphic markers for paleomagnetic, paleoclimatic, and paleoecologic studies. These stratigraphically important tephra deposits can be geochemically identified using compositions of their titanomagnetite phenocrysts. Titanomagnetite compositions display a broad range (XUsp 0.26-0.39), which allow the tephra layers to be distinguished despite the indistinguishable major-element glass compositions (76-77 wt% SiO2) of their hosts. The concentrations of Ti and Fe in titanomagnetite display geochemical and stratigraphic groupings that allow clear discrimination between older (> 57 ka) and younger (< 41 ka) tephras. Some individual tephra layers can be uniquely identified on the basis of titanomagnetite MgO, MnO, and Al2O3 contents. In addition, a few tephra layers can be correlated to their source vents by their titanomagnetite compositions. The unique geochemical fingerprint of the Mono Craters-sourced titanomagnetites also allows the discrimination of two tephra layers apparently sourced from nearby Mammoth Mountain volcano in Long Valley.

  18. Lower Cisco Formation (Pennsylvanian-Virgilian) paleokarst, Wolf Flat field Palo Duro basin, Texas

    SciTech Connect

    Trentham, R.C.; Lindsay, R.F.; Pack, D.D.

    1996-12-31

    Wolf Flat field produces from karstified Lower Cisco Formation at the rimmed northeast shelf margin. Mounds, peripheral skeletal debris, and oolitic facies form the vertical/lateral succession. Mounds are composed of crinoids, bryozoans, corals and algae. Skeletal packstone/grainstones surround mounds, With back-mound wackestone. Ooid grainstone formed in high-energy passages onto the shelf and cap shallowing-upward cycles. Karstification resulted from two 100+ ft. (30+ m) sea level drops, that dropped in a step-by-step manner to form {approximately}20 porous intervals that extend through all facies and lithologies in the field. Aragonitic mound and skeletal grainstone/wackestones experienced intense dissolution. Calcitic ooid grainstones dissolved less and form cave roofs and floors. Dissolution was in two phases: first, small vertically oriented pipes formed, resembling a {open_quotes}swiss cheese{close_quotes} texture; second, was intense lateral dissolution that created a {open_quotes}sponge{close_quotes} texture, with porosities up to 60-70%. Eventually, collapse breccias formed, with some clasts transported in the karst system. Porosity was reduced by vadose silt, breccia clasts, speleothem cements, transgressive shale infilling, and burial saddle dolomite. Portions of the field nearest the rimmed margin were dolomitized. {delta}{sup 18}O is within the range of early meteoric diagenesis and {delta}{sup 13}C is negative and becomes more negative toward the exposure surface.

  19. RESERVOIR CHARACTERIZATION OF THE LOWER GREEN RIVER FORMATION, SOUTHWEST UINTA BASIN, UTAH

    SciTech Connect

    Milind D. Deo

    2003-02-11

    Reservoir simulations of different fields in the Green River Formation are reported. Most extensive simulations were performed on the Monument Butte Northeast unit. Log data were used to construct detailed geostatistical models, which were upscaled to obtain reasonable number of grid blocks for reservoir simulation. Porosities, permeabilities, and water saturations required for reservoir simulation were thus generated. Comparison of the production results with the field data revealed that there was a phenomenological deficiency in the model. This was addressed by incorporating hydraulic fractures into the models. With this change, much better agreement between simulation results and field data was obtained. Two other fields, Brundage Canyon and Uteland Butte, were simulated in primary production. Only preliminary simulations were undertaken since a number of critical data elements were missing and could not be obtained from the operators. These studies revealed that the production performance of the Brundage Canyon field is much better than what can be predicted from simulations of a typical non-fractured, undersaturated reservoir. Uteland Butte field performance was that of a typical undersaturated reservoir.

  20. Geologic map of the Peach Orchard Flat quadrangle, Carbon County, Wyoming, and descriptions of new stratigraphic units in the Upper Cretaceous Lance Formation and Paleocene Fort Union Formation, eastern Greater Green River Basin, Wyoming-Colorado

    USGS Publications Warehouse

    Honey, J.D.; Hettinger, R.D.

    2004-01-01

    This report provides a geologic map of the Peach Orchard Flat 7.5-minute quadrangle, located along the eastern flank of the Washakie Basin, Wyo. Geologic formations and individual coal beds were mapped at a scale of 1:24,000; surface stratigraphic sections were measured and described; and well logs were examined to determine coal correlations and thicknesses in the subsurface. In addition, four lithostratigraphic units were named: the Red Rim Member of the Upper Cretaceous Lance Formation, and the China Butte, Blue Gap, and Overland Members of the Paleocene Fort Union Formation.

  1. K/Ar chronologies of tephra units from the Middle Jurassic Sundance, and Late Early Cretaceous Mowry and Shell Creek Formations, Big Horn Basin, WY

    NASA Astrophysics Data System (ADS)

    Jiang, H.; Meyer, E. E.; Johnson, G. D.

    2013-12-01

    The Middle Jurassic Sundance and Late Early Cretaceous Shell Creek and Mowry Formations of the Big Horn Basin, Wyoming, contain an extensive record of altered tephra. These tephra are likely related to contemporary volcanic activity in the Sierra Nevada and various Coast Range terranes to the west and provide valuable chronometric control on the sedimentary record within a portion of the Sevier-aged and later Cordilleran foreland basin. In addition, several of these altered tephra (bentonites) provide a valuable economic resource. Despite the prominence of these strata across the basin, few isotopic ages have been reported to date. Here we present new K/Ar ages on biotite phenocrysts from those tephra occurrences as a chronometric check on samples that contained zircons with significant Pb loss, that preclude more precise U/Pb age determinations. A bulk biotite sample extracted from an altered tuff in the Lower Sundance Formation gives an age of 167.5 × 5 Ma. This tuff occurs just above a dinosaur track-bearing peritidal sequence. Bulk biotite ages from the lower Shell Creek Formation give an age of 100.3 × 3 Ma and are statistically indistinguishable from biotite grains dated at 103.1 × 3 Ma extracted from the economically important 'Clay Spur' bentonite found at the top of the Mowry Shale. This work provides important new chronometric constraints on a portion of the Medial Jurassic to Late Early Cretaceous stratigraphy of the Big Horn Basin, Wyoming, and may be useful in understanding the regional tectonics that helped shape the development of the Sevier foreland basin and Western Interior Seaway.

  2. Fluvial architecture variations linked to changes in accommodation space: Río Chico Formation (Late Paleocene), Golfo San Jorge basin, Argentina

    NASA Astrophysics Data System (ADS)

    Foix, Nicolás; Paredes, José M.; Giacosa, Raúl E.

    2013-08-01

    The Upper Paleocene Río Chico Formation is a 50-180 m thick fluvial succession developed in a passive-margin setting, Golfo San Jorge basin, Central Patagonia, Argentina. A detailed description and interpretation of outcrops was carried out, analyzing exposures from the northern basin margin to the most complete successions at the southern depocenter. The unit is characterized by a regional fluvial system that flowed to the south-east. Five main lithofacies associations were defined: (I) active fluvial channels, with three sub-types: braided, meandering and low-sinuosity, (II) sheet-flood deposits, (III) proximal floodplain (natural levee and crevasse-splay), (IV) distal floodplain, and (V) abandoned channels. Lateral/vertical changes in fluvial architecture of the Río Chico Formation were recognized by variations in preserved thickness, fluvial styles, geometry of fluvial channels, regional paleoflow directions, and channel/floodplain ratios. Close to the northern basin margin, the fluvial succession is 50-60 m thick, composed of braided channels, sheet-flow deposits, and high channel/floodplain ratio. In a basinward direction, the alluvial succession increases to 180 m in thickness, the dominant fluvial styles change to low-sinuosity and meandering channels and channel/floodplain ratio reduces. The fluvial architecture of the Río Chico Formation shows two main depositional trends that resulted from changes in accommodation space across the basin. The interpreted break-point coincides with the underlying Cretaceous basin-boundary, thus the synsedimentary extensional reactivation of the pre-existing tectonic lineament generated differential subsidence, delimiting two different accommodation settings.

  3. 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.

  4. Paleoclimate controls on late paleozoic sedimentation and peat formation in the central appalachian basin (U.S.A.)

    USGS Publications Warehouse

    Cecil, C.B.; Stanton, R.W.; Neuzil, S.G.; Dulong, F.T.; Ruppert, L.F.; Pierce, B.S.

    1985-01-01

    In the central Appalachian basin, at least two major climate changes affected sedimentation during the late Paleozoic. Stratigraphically, these two changes are indicated by the distribution of coal beds, the variation in coal quality, and the variation in rock lithologies. In latest Mississippian or earliest Pennsylvanian time, the climate changed from dry-seasonal tropical to ever-wet (equable) tropical. The equable climate prevailed into the Middle Pennsylvanian, influencing the morphology and geochemistry in peat-forming environments. Many of the peat deposits, which formed under the equable climate, were probably domed (raised bogs); low concentrations of dissolved solids in peat formation water resulted in low buffering capacity. Organic acids caused acidic (pH < 4), antiseptic conditions that resulted in intense leaching of mineral matter, minimal degradation of organic matter, and low-ash and low-sulfur peat deposits; the resulting coal beds are also low in ash and sulfur. Associated rocks are noncalcareous and consist of sequences of interbedded shale, siltstone, and sandstone including quartz arenite. Another climate change occurred in late Middle Pennsylvanian time when evapopation periodically exceeded rainfall resulting in an increase of both dissolved solids and pH (4 to ??? 7) in surface and near-surface water. Throughout the remainder of the Pennsylvanian, the surfaces of peat deposits were probably planar (not domed); water in peat-forming and other depositional environments became more nearly neutral. The coal beds derived from these peats are highly variable in both ash and sulfur contents. Drier or more seasonal climates are also indicated by sequences of (1) calcareous sandstone and shale, (2) nonmarine limestone that shows shallow-water and subaerial exposure features, and (3) calcareous paleosols that have caliche characteristics. Our data and observations indicate that physical depositional environment models for the origin of coal do not

  5. An in situ occurrence of coal balls in the Amburgy coal bed, Pikeville Formation (Duckmantian), central Appalachian Basin, USA

    USGS Publications Warehouse

    Greb, S.F.; Eble, C.F.; Chesnut, D.R.; Phillips, T.L.; Hower, J.C.

    1999-01-01

    Carbonate concretions containing permineralized peat, commonly called coal balls, were encountered in the Amburgy coal, a generally low-ash (9.4%), but commonly high-sulfur (3.6%), Middle Pennsylvanian coal of the Eastern Kentucky Coal Field. These are the first coal balls from the Amburgy coal, and one of only a few reported occurrences from the central Appalachian Basin. The coal balls occur in the upper part of the coal, between two paleochannel cut-outs at the top of the Pikeville Formation, and immediately beneath a scour with a marine fossil lag at the base of the Kendrick Shale Member, Hyden Formation. The coal is thickest (1.3 m) in a narrow (<300 m), elongate depression between the bounding paleochannels, and thins toward the occurrence of coal balls. Total biovolume as measured from acetate peels of coal balls indicates cordaites or lycopsid (36.1% each) dominance. Vertical sampling through one coal-ball aggregate shows zoning from a lower cordaites-dominant (88.7%) assemblage, to a middle, degraded, sphenopsid-rich assemblage, to an upper lycopsid-dominant (88.6%) assemblage. Beneath the coal balls, palynologic and petrographic analyses indicate the basal and middle portions of the bed are dominated by arborescent lycopsid spores and cordaites pollen, and by vitrinite macerals. The top part of the bed, above the coal balls, contains increased intertinite macerals, increased percentages of small fern spores, and variable ash yield (5-21%). Thickening of the Amburgy coal along a structural low, in combination with basal high-ash yields, vitrinite-dominance, and heterogenous palynoflora, indicate paleotopographic control on initial peat accumulation. Abundant lycopsid spores in the basal and middle part of the coal reflect rheotrophic conditions consistent with accumulation in a paleotopographic depression. Apparent zonation preserved in one of the coal-ball masses may document plant successions in response to flooding. Similar percentages of cordaites and

  6. Compositional variability of glauconites within the Upper Cretaceous Karai Shale Formation, Cauvery Basin, India: Implications for evaluation of stratigraphic condensation

    NASA Astrophysics Data System (ADS)

    Banerjee, Santanu; Bansal, Udita; Pande, Kanchan; Meena, S. S.

    2016-01-01

    A detailed mineral chemical investigation of glauconite within the condensed section deposits of the Cretaceous Karai Shale Formation, Cauvery Basin, India reflects a wide spectrum in chemical composition related to origin and evolution in different substrates, stratigraphic condensation, and post-depositional alteration. Fe- and Mg-rich glauconite, comprising up to 60% of the sedimentary rocks, occurs as replaced forms of fecal pellets, as infillings within pores and chambers of bioclasts including those of foraminifera, ostracoda, bryozoa, and algae, and as altered forms of mica exhibiting vermiforms. Authigenic precipitation of K- and Fe-poor glauconite, followed by addition of Fe and K into the lattice and concomitant release of Al and Si explains the origin of glauconite pellets and infillings; the origin of glauconite vermiforms in partly degraded mica involves only the second stage of Fe and K addition. Glauconite pellets and vermiforms exhibit sharply defined alteration zones along peripheries to form rims, and in proximity to cracks or cleavages with reduced K2O and Fe2O3 (total) and enhanced Al2O3 and SiO2, related to late-stage meteoric water actions. Cores of glauconite pellets and unaltered zones of vermiforms reflect 'evolved' characteristics with > 6% K2O, typical of a condensed section, while other glauconite varieties occurring at the same stratigraphic level exhibit 'slightly evolved' nature, not consonant with stratigraphic condensation. Increasing abundance of glauconite pellets from the bottom to the top of the transgressive systems tract, accompanied by slight increase in K2O within their cores, reflects the effect of stratigraphic condensation on the evolution of glauconite. High Fe2O3 (total) content of glauconite in the Karai Shale Formation may be related to upwelling, although the Fe may be contributed partly by the biotite substrate. Mössbauer spectroscopy of glauconites reveals significant total Fe substitution in both tetrahedral and

  7. Hydraulic, textural and geochemical characteristics of the Ajali Formation, Anambra Basin, Nigeria: implication for groundwater quality

    NASA Astrophysics Data System (ADS)

    Tijani, Moshood N.; Nton, Matthew E.

    2009-01-01

    This study highlights the distribution of hydraulic conductivity ( K) in the regional aquiferous Ajali Formation of SE-Nigeria on one hand and assesses the possible influences of textural and geochemical characteristics on the hydraulic conductivity on the other hand. The investigation approach involved field sampling and collection of 12 sandstone samples from different outcrop locations, followed by laboratory studies such as grain-size analysis (GSA), constant head permeameter test and geochemical analysis of major and trace elements using X-ray fluorescence method. GSA and textural studies show that the sandstones range from fine to medium sands, constituting about <75-99% sand fraction, with graphic mean grain size of 0.23-0.53 mm. Other parameters such as coefficient of uniformity ( C u) range from 1.58 to 5.25 (av. 2.75), while standard deviation (sorting) values of 0.56Ø-1.24Ø imply moderately well sorted materials. In addition, the order of the estimated K values is K permeameter > K Beyer > K Hazen > K Kozeny-Carmen > K Fair-Hatch with average values of 1.4 × 10-3, 4.4 × 10-4, 3.8 × 10-4, 2.2 × 10-4 and 8.1 × 10-5 m/s, respectively. These values fall within the range of 10-5 and 10-3 m/s for fine to medium sands. However, multivariate factor analysis of the data revealed significant positive dependence of the empirically determined K values on graphic mean grain size and percentage sand content and much less dependence on sorting and total porosity. Geochemical profiles of the fresh samples are dominated by quartz with corresponding SiO2 content of 76.1-98.2% (av. 89.7%) while other major oxides are generally below 1.0 wt.% in the fresh samples. However, the ferruginized samples exhibited elevated concentrations of Al2O3 (3.50-11.60 wt.%) and Fe2O3 (1.80-3.60 wt.%), which are clear indications of weathering/ferruginization processes with attendant trace metal release/enrichment (2.5 mg/l Cu, 7.5 mg/l Pb, 6.5 mg/l Zn, 3.9 mg/l Ni and 19.6 mg/l Cr

  8. Estimates of primary ejecta and local material for the Orientale basin: Implications for the formation and ballistic sedimentation of multi-ring basins

    NASA Astrophysics Data System (ADS)

    Xie, Minggang; Zhu, Meng-Hua

    2016-04-01

    A clear understanding of thickness distributions of primary ejecta and local material is critical to interpreting the process of ballistic sedimentation, provenances of lunar samples, the evolution of the lunar surface, and the origin of multi-ring basins. The youngest lunar multi-ring basin, Orientale, provides the best preserved structure for determining the thicknesses of primary ejecta and local material. In general, the primary ejecta thickness was often estimated using crater morphometry. However, previous methods ignored either crater erosion, the crater interior geometry, or both. In addition, ejecta deposits were taken as mostly primary ejecta. And, as far as we know, the local material thickness had not been determined for the Orientale. In this work, we proposed a model based on matching measurements of partially filled pre-Orientale craters (PFPOCs) with the simulations of crater erosion to determine their thicknesses. We provided estimates of primary ejecta thickness distribution with the thickness of 0.85 km at Cordillera ring and a decay power law exponent of b = 2.8, the transient crater radius of 200 km, excavation volume of 2.3 ×106 km3, primary ejecta volume of 2.8 ×106 km3. These results suggest that previous works (e.g., Fassett et al., 2011; Moore et al., 1974) might overestimate the primary ejecta thicknesses of Orientale, and the primary ejecta thickness model of Pike (1974a) for multi-ring basins may give better estimates than the widely cited model of McGetchin et al. (1973) and the scaling law for impacts into Ottawa Sand (Housen et al., 1983). Structural uplift decays slower than previously thought, and rim relief is mostly rim uplift for Orientale. The main reason for rim uplift may be the fracturing and squeezing upward of the surrounding rocks. The proportion of local material to ejecta deposits increases with increasing radial distance from basin center, and the thickness of local material is larger than that of primary ejecta at

  9. Long-term Variations of CO2 Trapped in Different Mechanisms in Deep Saline Formations: A Case Study of the Songliao Basin, China

    SciTech Connect

    Zhang, Wei; Li, Yilian; Xu, Tianfu; Cheng, Huilin; Zheng, Yan; Xiong, Peng

    2008-06-10

    The geological storage of CO{sub 2} in deep saline formations is increasing seen as a viable strategy to reduce the release of greenhouse gases to the atmosphere. There are numerous sedimentary basins in China, in which a number of suitable CO{sub 2} geologic reservoirs are potentially available. To identify the multi-phase processes, geochemical changes and mineral alteration, and CO{sub 2} trapping mechanisms after CO{sub 2} injection, reactive geochemical transport simulations using a simple 2D model were performed. Mineralogical composition and water chemistry from a deep saline formation of Songliao Basin were used. Results indicate that different storage forms of CO{sub 2} vary with time. In the CO{sub 2} injection period, a large amount of CO{sub 2} remains as a free supercritical phase (gas trapping), and the amount dissolved in the formation water (solubility trapping) gradually increases. Later, gas trapping decreases, solubility trapping increases significantly due to migration and diffusion of the CO{sub 2} plume, and the amount trapped by carbonate minerals increases gradually with time. The residual CO{sub 2} gas keeps dissolving into groundwater and precipitating carbonate minerals. For the Songliao Basin sandstone, variations in the reaction rate and abundance of chlorite, and plagioclase composition affect significantly the estimates of mineral alteration and CO{sub 2} storage in different trapping mechanisms. The effect of vertical permeability and residual gas saturation on the overall storage is smaller compared to the geochemical factors. However, they can affect the spatial distribution of the injected CO{sub 2} in the formations. The CO{sub 2} mineral trapping capacity could be in the order of ten kilogram per cubic meter medium for the Songliao Basin sandstone, and may be higher depending on the composition of primary aluminosilicate minerals especially the content of Ca, Mg, and Fe.

  10. Assessment of undiscovered oil resources in the Bakken and Three Forks Formations, Williston Basin Province, Montana, North Dakota, and South Dakota, 2013

    USGS Publications Warehouse

    Gaswirth, Stephanie B.; Marra, Kristen R.; Cook, Troy A.; Charpentier, Ronald R.; Gautier, Donald L.; Higley, Debra K.; Klett, Timothy R.; Lewan, Michael D.; Lillis, Paul G.; Schenk, Christopher J.; Tennyson, Marilyn E.; Whidden, Katherine J.

    2013-01-01

    Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered volumes of 7.4 billion barrels of oil, 6.7 trillion cubic feet of associated/dissolved natural gas, and 0.53 billion barrels of natural gas liquids in the Bakken and Three Forks Formations in the Williston Basin Province of Montana, North Dakota, and South Dakota.

  11. Sedimentology and sequence stratigraphy from outcrops of the Kribi-Campo sub-basin: Lower Mundeck Formation (Lower Cretaceous, southern Cameroon)

    NASA Astrophysics Data System (ADS)

    Ntamak-Nida, Marie Joseph; Bourquin, Sylvie; Makong, Jean-Claude; Baudin, François; Mpesse, Jean Engelbert; Ngouem, Christophe Itjoko; Komguem, Paul Bertrand; Abolo, Guy Martin

    2010-08-01

    The Kribi-Campo sub-basin is composed of an Early to Mid Cretaceous series from West Africa's Atlantic coast and is located in southern Cameroon in the Central African equatorial rain forest. It is the smallest coastal basin in Cameroon and forms the southern part of the Douala/Kribi-Campo basin known as Douala basin ( s.l.). Until now, no detailed sedimentological studies have been carried out on the outcrops of this basin located in the Campo area. The aim of this study was to characterise the depositional environments, vertical evolution and tectonic context of these Lower Cretaceous series in order to make a comparison with adjacent basins and replace them in the geodynamic context. Facies analysis of the Lower Mundeck Formation (Lower Cretaceous) indicates the presence of four major, interfigered facies associations, that are inferred to represent elements of an alluvial to lacustrine-fan delta system. The clast lithologies suggest proximity of relief supplying coarse-grained sediment during the deposition of the Lower Mundeck Formation at Campo. The general dip and direction of the bedding is approximately 10°-12°NW, which also corresponds to the orientation of the foliations in the underlying metamorphic basement. The main sedimentary succession is characterised by a major retrogradational/progradational cycle of Late Aptian age, evaluated at about 3 Ma, with a well-developed progradational trend characterised by fluctuations of the recognised depositional environments. Fluctuations in lake level and sediment supply were possibly controlled by active faults at the basin margin, although climatic changes may have also played a role. The consistently W-WNW palaeoflow of sediments suggests that the palaeorelief was located to the east and could be oriented in a NNE-SSW direction, downthrown to the west. Local outcrops dated as Albian, both north and south of the main outcrop, display some marine influence. These deposits are cut by 040-060 faults parallel to

  12. Paleogeographic and paleoecologic model as a predictive tool for Late Miocene accumulation of biosiliceous sediments in the Monterey Formation of the San Joaquin basin, California

    SciTech Connect

    Bulter, T.H. ); Dumont, M.P. )

    1991-03-01

    The marine ecology of diatoms in the Pacific Ocean can be invoked to explain late Miocene diatom population trends. The impact of seafloor physiography on diatom productivity in the modern ocean was compared with mappable biosiliceous trends in the Monterey Formation of the San Joaquin basin, California. A depositional model is proposed to explain the significance of paleogeography on variations in the biosiliceous content of the Monterey Formation. Diatoms thrive where nutrient-rich bottom waters flow upslope to replace the surface waters moved basinward by atmospherically induced circulation. Organic-rich siliceous material settles through the water column beneath the upwelling region. Oxidation of organic matter within the water column below the areas of intense upwelling creates an oxygen-depleted layer and limits bioturbation at the sediment-water interface. The resultant sedimentary rocks are laminated siliceous shales characteristic of the Monterey Formation. Forty-two Monterey well penetrations form a variety of locations in the San Joaquin basin were analyzed for biosiliceous content. Biosiliceous facies trends were established by relating the quantity of siliceous material to depositional environment and paleobathymetry. Lithofacies trends were then modeled using the paleogeography of the San Joaquin basin during the late Miocene. According to the model, the rocks with the highest content of biogenic silica are expected in a slope setting. This model also suggests that slop angle controls the intensity of upwelling and subsequent diatom productivity.

  13. Miocene fossil plants from Bukpyeong Formation of Bukpyeong Basin in Donghae City, Gangwon-do Province, Korea and their palaeoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Jeong, Eun Kyoung; Kim, Hyun Joo; Uemura, Kazuhiko; Kim, Kyungsik

    2016-04-01

    The Tertiary sedimentary basins are distributed along the eastern coast of Korean Peninsula. The northernmost Bukpyeong Basin is located in Donghae City, Gangwon-do Province, Korea. The Bukpyeong Basin consists of Bukpyeong Formation and Dogyeongri Conglomerate in ascending order. The geologic age of Bukpyeong Formation has been suggested as from Early Miocene to Pliocene, In particular, Lee & Jacobs (2010) suggested the age of the Bukpyeong Formation as late Early Miocene to early Middle Miocene based on the fossils of rodent teeth. Sedimentary environment has been thought as mainly fresh water lake and/or swamp partly influenced by marine water. Lately, new outcrops of Bukpyeong Formation were exposed during the road construction and abundant fossil plants were yielded from the newly exposed outcrops. As a result of palaeobotanical studies 47 genera of 23 families have been found. This fossil plant assemblage is composed of gymnosperms and dicotyledons. Gymnosperms were Pinaceae (e.g., Pinus, Tsuga), Sciadopityaceae (e.g., Sciadopitys) and Cupressaceae with well-preserved Metasequoia cones. Dicotyledons were deciduous trees such as Betulaceae (e.g., Alnus, Carpinus) and Sapindaceae (e.g., Acer, Aesculus, Sapindus), and evergreen trees such as evergreen Fagaceae (e.g., Castanopsis, Cyclobalanopsis, Pasania) and Lauraceae (e.g., Cinnamomum, Machilus). In addition, fresh water plants such as Hemitrapa (Lytraceae) and Ceratophyllum (Ceratophyllaceae) were also found. The fossil plant assemblage of the Bukpyeong Formation supported the freshwater environment implied by previous studies. It can be suggested that the palaeoflora of Bukpyeong Formation was oak-laurel forest with broad-leaved evergreen and deciduous trees accompanying commonly by conifers of Pinaceae and Cupressaceae under warm-temperate climate.

  14. Availability of free oxygen in deep bottom water of some Archean-Early Paleoproterozoic ocean basins as derived from iron formation facies analyses

    NASA Astrophysics Data System (ADS)

    Beukes, N. J.; Smith, A.

    2013-12-01

    Archean to Early Paleoproterozoic ocean basins are commonly, although not exclusively, depicted as rather static systems; either permanently stratified with shallow mixed oxygenated water overlying anoxic deep water or with a totally anoxic water column. The anoxic water columns are considered enriched in dissolved ferrous iron derived from hydrothermal plume activity. These sourced deposition of iron formations through precipitation of mainly ferrihydrite via reaction with free oxygen in the stratified model or anaerobic iron oxidizing photoautotrophs in the anoxic model. However, both these models face a simple basic problem if detailed facies reconstructions of deepwater microbanded iron formations (MIFs) are considered. In such MIFs it is common that the deepest water and most distal facies is hematite rich followed shoreward by magnetite, iron silicate and siderite facies iron formation. Examples of such facies relations are known from jaspilitic iron formation of the ~3,2 Ga Fig Tree Group (Barberton Mountainland), ~ 2,95 Ga iron formations of the Witwatersrand-Mozaan basin and the ~2,5 Ga Kuruman Iron Formation, Transvaal Supergroup, South Africa. Facies relations of these MIFs with associated siliciclastics or carbonates also indicate that the upper water columns of the basins, down to below wave base, were depleted in iron favoring anoxic-oxic stratification rather than total anoxia. In the MIFs it can be shown that hematite in the distal facies represents the earliest formed diagenetic mineral; most likely crystallized from primary ferrihydrite. The problem is one of how ferrihydrite could have been preserved on the ocean floor if it was in direct contact with reducing ferrous deep bottom water. Rather dissolved ferrous iron would have reacted with ferrihydrite to form diagenetic magnetite. This dilemma is resolved if in the area of deepwater hematite MIF deposition, the anoxic ferrous iron enriched plume was detached from the basin floor due to buoyancy

  15. Integrated biostratigraphy and stage boundaries of the Abderaz Formation, east of the Kopeh-Dagh sedimentary basin, NE Iran

    NASA Astrophysics Data System (ADS)

    Vahidinia, Mohammad; Youssef, Mohamed; Shafiee Ardestani, Meysam; Sadeghi, Abbas; Dochev, Docho

    2014-02-01

    The foraminiferal content of the well-known, foraminifera-rich Abderaz Formation of the Kopeh-Dagh basin in northeastern Iran was analyzed to determine biostratigraphy, age dating, chronostratigraphy and evolutionary trends. The Abderaz Formation was sampled at the following four sections: the Qarehso section, the Abderaz village section, the Muzduran section and the Shorab section. The Qarehso section is approximately 540 m thick and consists of 77 planktonic foraminifera species belonging to 18 genera in 5 biozones, 10 echinoid species belonging to 4 genera and 8 inoceramid species belonging to 5 genera. Based on this fossil content, the Qarehso section was dated to the lowermost Turonian to the upper Santonian. Based on the first occurrence datums of Cremnoceramus walterdorfensis walterdorfensis and Cremnoceramus deformis deformis and on the FODs of Micraster cortestudinarium and Dicarinella concavata, the Turonian-Conician boundary was detected in this section. In addition, based on the FODs of Echinocorys gr. scutata forma vulgaris, Echinocorys gr. scutata forma vulgaris-planodama and Di. Asymetrica, the base of the Santonian stage was also detected in the Qarehso section. The Abderaz village section is 556.5 m thick and contains 17 genera and 68 species of planktonic foraminifera that have been identified in 9 biozones and 7 genera and 15 species of invertebrates. The lowermost Turonian to the lowermost Campanian ages have been established in the Abderaz Formation. In the Abderaz village section, 3 boundaries were identified. Based on the FODs of Cremnoceramus walterdorfensis walterdorfensis, C. deformis deformis and C. crassus crassus and on the FODs of Contusotruncana fornicata and C. pateliformis, the base of the Coniacian stage was identified. Based on the FODs of Di. asymetrica and Macroglobigerinelloides alvarezi, the Coniacian-Santonian boundary was identified. Additionally, based on the extinction of the Marginotruncanid group and on the LOD of

  16. Stratigraphy, petrology, depositional and post-depositional histories and their effects upon reservoir properties of the Parkman Formation of the Mesa Verde group, Powder River Basin, Wyoming

    NASA Astrophysics Data System (ADS)

    Dogan, A. U.

    The depositional system within which deposition of the Upper Cretaceous Parkman Formation (= Parkman Sandstone Member of the Mesaverde Formation) in the Wyoming portion of the Powder River Basin took place, was delineated using a combination of data from outcrops, subsurface cores, and geophysical well logs. The post-depositional history of these rocks was determined, semi-quantitative compositional analyses of authigenic components were made, and paragenetic sequences were established with the aid of scanning electron microscope and transmission electron microscope both equipped with energy dispersive X-ray microanalyzer.

  17. Fault kinematics and depocenter evolution of oil-bearing, continental successions of the Mina del Carmen Formation (Albian) in the Golfo San Jorge basin, Argentina

    NASA Astrophysics Data System (ADS)

    Paredes, José Matildo; Plazibat, Silvana; Crovetto, Carolina; Stein, Julián; Cayo, Eric; Schiuma, Ariel

    2013-10-01

    Up to 10% of the liquid hydrocarbons of the Golfo San Jorge basin come from the Mina del Carmen Formation (Albian), an ash-dominated fluvial succession preserved in a variably integrated channel network that evolved coeval to an extensional tectonic event, poorly analyzed up to date. Fault orientation, throw distribution and kinematics of fault populations affecting the Mina del Carmen Formation were investigated using a 3D seismic dataset in the Cerro Dragón field (Eastern Sector of the Golfo San Jorge basin). Thickness maps of the seismic sub-units that integrate the Mina del Carmen Formation, named MEC-A-MEC-C in ascending order, and mapping of fluvial channels performed applying geophysical tools of visualization were integrated to the kinematical analysis of 20 main normal faults of the field. The study provides examples of changes in fault throw patterns with time, associated with faults of different orientations. The "main synrift phase" is characterized by NE-SW striking (mean Az = 49°), basement-involved normal faults that attains its maximum throw on top of the volcanic basement; this set of faults was active during deposition of the Las Heras Group and Pozo D-129 formation. A "second synrift phase" is recognized by E-W striking normal faults (mean Az = 91°) that nucleated and propagated from the Albian Mina del Carmen Formation. Fault activity was localized during deposition of the MEC-A sub-unit, but generalized during deposition of MEC-B sub-unit, producing centripetal and partially isolated depocenters. Upward decreasing in fault activity is inferred by more gradual thickness variation of MEC-C and the overlying Lower Member of Bajo Barreal Formation, evidencing passive infilling of relief associated to fault boundaries, and conformation of wider depocenters with well integrated networks of channels of larger dimensions but random orientation. Lately, the Mina del Carmen Formation was affected by the downward propagation of E-W to ESE-WNW striking

  18. Ar-40 to Ar-39 dating of pseudotachylites from the Witwatersrand basin, South Africa, with implications for the formation of the Vredefort Dome

    NASA Technical Reports Server (NTRS)

    Trieloff, M.; Kunz, J.; Jessberger, E. K.; Reimold, W. U.; Boer, R. H.; Jackson, M. C.

    1992-01-01

    The formation of the Vredefort Dome, a structure in excess of 100 km in diameter and located in the approximate center of the Witwatersrand basin, is still the subject of lively geological controversy. It is widely accepted that its formation seems to have taken place in a single sudden event, herein referred to as the Vredefort event, accompanied by the release of gigantic amounts of energy. It is debated, however, whether this central event was an internal one, i.e., a cryptoexplosion triggered by volcanic or tectonic processes, or the impact of an extraterrestrial body. The results of this debate are presented.

  19. Modeling reservoir heterogeneity within outer ramp carbonate facies using an outcrop analog, San Andres Formation of the Permian Basin

    SciTech Connect

    Eisenberg, R.A.; Harris, P.M.; Grant, C.W.

    1994-09-01

    Variably cyclic, fusulinid-rich, outer ramp facies of the Permian San Andres Formation are exposed along the Algerita escarpment, Guadalupe Mountains, New Mexico. We have used the outcrop exposures and cored wells drilled adjacent to the outcrop to assess reservoir- and interwell-scale variability of permeability as a potential analog for carbonate reservoirs in the Permian basin and elsewhere. Permeability distribution was evaluated using a field permeameter and conventional measurements on small core plugs taken along vertical and horizontal outcrop traverses and from the slim-hole cores. Geostatistical models of permeability variation, honoring the geologic and petrophysical data, were constructed and input into a waterflood simulator to understand the interactions between heterogeneity and flow. Different vertical variogram characteristics are displayed by cyclic and less distinctly cyclic parts of the San Andres. Variograms constructed for horizontal transect data from three distinct stratigraphic units have nearly identical properties. Overall, the ranges of correlation are short (3-3.5 in; 10-12 ft) when compared to typical interwell distances, supporting a nearly uncorrelated and highly variable permeability model. Using observed short ranges of vertical and horizontal correlation and honoring the vertical transect data, cross sectional, conditionally simulated permeability fields were generated and used in simulated waterfloods to investigate the sensitivities to an oil recovery model and overall fluid injection rate for this style of stratigraphy and cyclicity. Cyclic parts of the section are characterized by a potential for early water breakthrough and relatively high vertical sweep efficiencies. Within the less distinctly cyclic section, waterflood fronts have a fingerlike profile and vertical sweep efficiency is generally poorer.

  20. Facies-controlled reservoir properties in ramp-fan and slope-apron deposits, Miocene Puente Formation, Los Angeles basin

    SciTech Connect

    Lyons, K.T.; Geving, R.L.; Suchecki, R.K.

    1989-03-01

    The Miocene Puente Formation in outcrops of the eastern Los Angeles basin is interpreted as a succession of slope-apron and ramp-fan deposits that accumulated in a prism-rise wedge. The principal depositional components of this dominantly base-of-slope and ramp system are ramp-fan channels and lobes, and slope-channel and slope-apron channel/interchannel deposits. Facies-specific textural, compositional, and diagenetic attributes observed in thin section assist in the classification of depositional facies. Specifically, occurrence of carbonate cement, clay mineralogy, and abundance of organic material vary as a function of component facies architecture of the depositional system. Slope and ramp-fan channel-fill sandstones are characterized by pervasive carbonate cements, including poikilotopic and fine-grained calcite, fine-grained and baroque dolomite, and minor siderite. Diagenetic clays predate carbonate cements, and dolomite predates coarser, void-filling calcite. Ramp-fan lobe and interchannel deposits are carbonate free but are rich in detrital clay and organic matter. Diagenetic clays include mixed-layer illite/smectite and kaolinite. Sediments deposited in slope-apron channel fill are virtually cement free except for small amounts of authigenic illite/smectite. Slope-apron interchannel deposits are characterized by high content of organic matter and clay-rich matrix. Potential reservoir characteristics, such as grain size, sorting, and abundance of depositional clay matrix, are related to the primary sedimentary properties of depositional architectural components in the ramp-fan and slope-apron system. Additional diagenetic modifications, without consideration of compaction, were controlled by precipitation reactions associated with fluid flow along pathways related to the depositional architectural framework.

  1. Variations in fluvial style in the Westwater Canyon Member, Morrison formation (Jurassic), San Juan basin, Colorado plateau

    USGS Publications Warehouse

    Miall, A.D.; Turner-Peterson, C. E.

    1989-01-01

    Techniques of architectural element analysis and lateral profiling have been applied to the fluvial Westwater Canyon Member of the Morrison Formation (Jurassic) in southern San Juan Basin. On a large scale, the sandstone-body architecture consists mainly of a series of tabular sandstone sheets 5-15 m thick and hundreds of meters wide, separated by thin fine-grained units. Internally these sheets contain lateral accretion surfaces and are cut by channels 10-20 m deep and at least 250 m wide. On a more detailed scale, interpretations made from large-scale photomosaics show a complex of architectural elements and bounding surfaces. Typical indicators of moderate- to high-sinuosity channels (lateral accretion deposits) coexist in the same outcrop with downstream-accreted macroform deposits that are typical of sand flats of low-sinuosity, multiple-channel rivers. Broad, deep channels with gently to steeply dipping margins were mapped in several of the outcrops by carefully tracing major bounding surfaces. Locally thick accumulations of plane-laminated and low-angle cross-laminated sandstone lithofacies suggest rapid flow, probably transitional to upper flow regime conditions. Such a depositional style is most typical of ephemeral rivers or those periodically undergoing major seasonal (or more erratic) stage fluctuations, an interpretation consistent with independent mineralogical evidence of aridity. Fining-upward sequences are rare in the project area, contrary to the descriptions of Campbell (1976). The humid alluvial fan model of Galloway (1978) cannot be substantiated and, similarly, the architectural model of Campbell (1976) requires major revision. Comparisons with the depositional architecture of the large Indian rivers, such as the Ganges and Brahmaputra, still seem reasonable, as originally proposed by Campbell (1976), although there is now convincing evidence for aridity and for major stage fluctuations, which differs both from those modern rivers and Campbell

  2. Reservoir characterization of the Ordovician Red River Formation in southwest Williston Basin Bowman County, ND and Harding County, SD

    SciTech Connect

    Sippel, M.A.; Luff, K.D.; Hendricks, M.L.; Eby, D.E.

    1998-07-01

    This topical report is a compilation of characterizations by different disciplines of the Red River Formation in the southwest portion of the Williston Basin and the oil reservoirs which it contains in an area which straddles the state line between North Dakota and South Dakota. Goals of the report are to increase understanding of the reservoir rocks, oil-in-place, heterogeneity, and methods for improved recovery. The report is divided by discipline into five major sections: (1) geology, (2) petrography-petrophysical, (3) engineering, (4) case studies and (5) geophysical. Interwoven in these sections are results from demonstration wells which were drilled or selected for special testing to evaluate important concepts for field development and enhanced recovery. The Red River study area has been successfully explored with two-dimensional (2D) seismic. Improved reservoir characterization utilizing 3-dimensional (3D) and has been investigated for identification of structural and stratigraphic reservoir compartments. These seismic characterization tools are integrated with geological and engineering studies. Targeted drilling from predictions using 3D seismic for porosity development were successful in developing significant reserves at close distances to old wells. Short-lateral and horizontal drilling technologies were tested for improved completion efficiency. Lateral completions should improve economics for both primary and secondary recovery where low permeability is a problem and higher density drilling is limited by drilling cost. Low water injectivity and widely spaced wells have restricted the application of waterflooding in the past. Water injection tests were performed in both a vertical and a horizontal well. Data from these tests were used to predict long-term injection and oil recovery.

  3. Integration of sequence stratigraphy and process sedimentology: Miocene Rincon and Topanga Formations, Santa Barbara basin near Point Mugu, California

    SciTech Connect

    Jordan, D.W.; Marquard, R.S. )

    1990-05-01

    The Miocene Rincan and Topanga formations exposed at Point Mugu comprise over 1,200 ft of interbedded sandstones, siltstones, claystones, and clay shales that were deposited in a tectonically active marine basin adjacent to the present Santa Monica Mountains. Integration of sequence stratigraphic interpretation techniques and process sedimentology demonstrates that this section originated as shelfal deposits during sea level rise that were cut by a submarine canyon during subsequent sea level lowstand. The base of the sequence contains a bioturbated silty sandstone indicative of a transgressive deposit within the sequence stratigraphic framework. Upsection, dark clay shales of a condensed section contain fish fragments and sponge progradational highstand shelf sandstones. An erosional surface flooring a deep-water canyon cuts the highstand deposits and marks a sequence boundary. Within the submarine canyon fill, deep-water deposits represent at least two episodes of sediment gravity flows. A predominantly deformed lower section is cut by an erosional surface (another sequence boundary ) overlain by undeformed strata. The deformed section was caused by slumping of a canyon wall within a slope environment and deposition of high-density turbidites and debris flows. The undeformed section contains Bouma sequences, graded beds, dish structures, and biogenic structures. Interstratified bed-thinning and bed-thickening sequences suggest minor progradational events and small feeder channels within the undeformed section. These relationships demonstrate that not all sequences comprising deep-water deposits can be easily assigned to facies, such as channels and lobes, based on vertical and lateral profiles. This integration of sequence stratigraphy and sedimentology has assisted in understanding the vertical and lateral heterogeneities present within exploration and production areas in the adjacent Santa Barbara Channel.

  4. Reservoir characterization of the Upper Jurassic geothermal target formations (Molasse Basin, Germany): role of thermofacies as exploration tool

    NASA Astrophysics Data System (ADS)

    Homuth, S.; Götz, A. E.; Sass, I.

    2015-06-01

    The Upper Jurassic carbonates of the southern German Molasse Basin are the target of numerous geothermal combined heat and power production projects since the year 2000. A production-orientated reservoir characterization is therefore of high economic interest. Outcrop analogue studies enable reservoir property prediction by determination and correlation of lithofacies-related thermo- and petrophysical parameters. A thermofacies classification of the carbonate formations serves to identify heterogeneities and production zones. The hydraulic conductivity is mainly controlled by tectonic structures and karstification, whilst the type and grade of karstification is facies related. The rock permeability has only a minor effect on the reservoir's sustainability. Physical parameters determined on oven-dried samples have to be corrected, applying reservoir transfer models to water-saturated reservoir conditions. To validate these calculated parameters, a Thermo-Triaxial-Cell simulating the temperature and pressure conditions of the reservoir is used and calorimetric and thermal conductivity measurements under elevated temperature conditions are performed. Additionally, core and cutting material from a 1600 m deep research drilling and a 4850 m (total vertical depth, measured depth: 6020 m) deep well is used to validate the reservoir property predictions. Under reservoir conditions a decrease in permeability of 2-3 magnitudes is observed due to the thermal expansion of the rock matrix. For tight carbonates the matrix permeability is temperature-controlled; the thermophysical matrix parameters are density-controlled. Density increases typically with depth and especially with higher dolomite content. Therefore, thermal conductivity increases; however the dominant factor temperature also decreases the thermal conductivity. Specific heat capacity typically increases with increasing depth and temperature. The lithofacies-related characterization and prediction of reservoir

  5. Relationships among in-situ stress, fractures and faults, and fluid flow: Monterey formation, Santa Maria Basin, California

    USGS Publications Warehouse

    Finkbeiner, T.; Barton, C.A.; Zoback, M.D.

    1997-01-01

    We used borehole televiewer (BHTV) data from four wells within the onshore and offshore Santa Maria basin, California, to investigate the relationships among fracture distribution, orientation, and variation with depth and in-situ stress. Our analysis of stress-induced well-bore breakouts shows a uniform northeast maximum horizontal stress (SH max) orientation in each well. This direction is consistent with the SH max direction determined from well-bore breakouts in other wells in this region, the northwest trend of active fold axes, and kinematic inversion of nearby earthquake focal plane mechanisms. In contrast to the uniformity of the stress field, fracture orientation, dip, and frequency vary considerably from well to well and within each well. With depth, fractures can be divided into distinct subsets on the basis of fracture frequency and orientation, which correlate with changes of lithology and physical properties. Although factors such as tectonic history, diagenesis, and structural variations obviously have influenced fracture distribution, integration of the in-situ stress and fracture data sets indicates that many of the fractures, faults, and bedding planes are active, small-scale strike-slip and reverse faults in the current northeast-trending transpressive stress field. In fact, we observed local breakout rotations in the wells, providing kinematic evidence for recent shear motion along fracture and bedding-parallel planes. Only in the onshore well do steeply dipping fractures strike parallel to SHmax. Drill-stem tests from two of the offshore wells indicate that formation permeability is greatly enhanced in sections of the wells where fractures are favorably oriented for shear failure in the modern stress field. Thus, relatively small-scale active faults provide important conduits along which fluids migrate.

  6. Organofacies and kerogen tranformation kinetics: Implications for hydrocarbon generation in the Bucomazi Formation, lower Congo coastal basin

    SciTech Connect

    Burwood, R.; Fortems, G.; Mycke, B.; Paulet, J.; De Witte, S.M. )

    1993-09-01

    Deposited under lacustrine conditions during the rift-phase opening of the southern Atlantic, the lower Congo Bucomazi Formation is a highly productive source rock sequence. Reaching considerable thickness (1.8 km), a heterogeneous organofacies reflects both rapid accumulation and changing conditions during Early Cretaceous Barremian sedimentation. As a component of organofacies, low resolution studies showed kerogen kinetic parameters (Ea/A) varied widely according to the gross paleoenvironmental conditions prevailing during deposition. As a a general trend, refractory (type I, higher Ea) kerogens of the [open quotes]basin fill[close quotes] Organic Rich Zone (ORZ) give way to more labile (type II, lower Ea) assemblages in the up-section [open quotes]sheet drape[close quotes] sediments. At higher resolution, a considerable fine structure in Ea fluctuation, presumably reflecting micropaleoenvironment control, becomes evident. Using Ea values assembled for the Bucomazi type section, subsidence modeling for a Ponta Vermelha depocenter section showed a wide disparity in behavior. Being more representative of the sheet-drape episode, type II assemblages matured earlier, at lesser overburdens, and provided the initial hydrocarbon charge. For the ORZ assemblages, the dominant type I component was of retarded maturation, only becoming productive at commensurately greater overburdens. Cumulatively, these events merge to provide an extended period of hydrocarbon generation with implications for production of aggregate oils of varied emplacement histories. Significantly, the net effect of the observed Ea contrast results in the less prolific (but more labile) uppermost Bucomazi assuming a more important charging role than the ORZ of superior source richness. The latter can only realize its full potential under the greatest overburdens attainable in the most subsident depocenters.

  7. Review of consequences of uranium hydride formation in N-Reactor fuel elements stored in the K-Basins

    SciTech Connect

    Weber, J.W.

    1994-09-28

    The 105-K Basins on the Hanford site are used to store uranium fuel elements and assemblies irradiated in and discharged from N Reactor. The storage cylinders in KW Basin are known to have some broken N reactor fuel elements in which the exposed uranium is slowly reacting chemically with water in the cylinder. The products of these reactions are uranium oxide, hydrogen, and potentially some uranium hydride. The purpose of this report is to document the results f the latest review of potential, but highly unlikely accidents postulated to occur as closed cylinders containing N reactor fuel assemblies are opened under water in the KW basin and as a fuel assembly is raised from the basin in a shipping cask for transportation to the 327 Building for examination as part of the SNF Characterization Program. The postulated accidents reviews in this report are considered to bound all potential releases of radioactivity and hydrogen. These postulated accidents are: (1) opening and refill of a cylinder containing significant amounts of hydrogen and uranium hydride; and (2) draining of the single element can be used to keep the fuel element submerged in water after the cask containing the can and element is lifted from the KW Basin. Analysis shows the release of radioactivity to the site boundary is significantly less than that allowed by the K Basin Safety Evaluation. Analysis further shows there would be no damage to the K Basin structure nor would there be injury to personnel for credible events.

  8. Metalliferous coals of the Westphalian A Joggins Formation, Cumberland basin, Nova Scotia, Canada: Petrology, geochemistry, and palynology

    USGS Publications Warehouse

    Hower, J.C.; Calder, J.H.; Eble, C.F.; Scott, A.C.; Robertson, J.D.; Blanchard, L.J.

    2000-01-01

    Five coals of Westphalian A (early Middle Pennsylvanian) age were sampled from the Joggins Formation section exposed along Chignecto Bay at Joggins, Nova Scotia. Coal beds along the bay were mined beginning in the early 17th century, yet there have been few detailed published investigation of the coal beds of this classic section. The lowermost coal, the Upper Coal 28 (Upper Fundy), is a high-vitrinite coal with a spore assemblage dominated by arboreous lycopsid spores with tree ferns subdominant. The upper portions of the coal bed have the highest ratio of well-preserved to poorly-preserved telinite of any of the coals investigated. Coal 19 ('clam coal') has 88% total vitrinite but, unlike the Fundy coal bed, the telinite has a poor preservation ratio and half the total vitrinite population comprises gelocollinite and vitrodetrinite. The latter coal bed is directly overlain by a basin-wide limestone bed. The Lower Kimberly coal shows good preservation of vitrinite with relatively abundant telinite among the total vitrinite. The Middle Kimberly coal, which underlies the tetrapod-bearing lycopsid trees found by Lyell and Dawson in 1852, exhibits an upward decrease in arboreous lycopod spores and an upward increase in the tree fern spore Punctatisporites minutus. Telinite preservation increases upwards in the Middle Kimberly but overall is well below the preservation ratio of the Upper Fundy coal bed. The coals all have high sulfur contents, yielding up to 13.7% total sulfur for the lower lithotype of the Upper Fundy coal bed. The Kimberly coals are not only high in total and pyritic sulfur, but also have high concentrations of chalcophile elements. Zinc, ranging up to 15,000 ppm (ash basis), is present as sphalerite in fusain lumens. Arsenic and lead each exceed 6000 ppm (ash basis) in separate lithotypes of the Kimberly coals. Together these data are consistent with elevated pH in planar mires. The source of the elemental enrichment in this presumed continental

  9. Holocene ice dynamics and bottom-water formation associated with Cape Darnley polynya activity recorded in Burton Basin, East Antarctica

    NASA Astrophysics Data System (ADS)

    Borchers, Andreas; Dietze, Elisabeth; Kuhn, Gerhard; Esper, Oliver; Voigt, Ines; Hartmann, Kai; Diekmann, Bernhard

    2016-03-01

    A multi-proxy study including sedimentological, mineralogical, biogeochemical and micropaleontological methods was conducted on sediment core PS69/849-2 retrieved from Burton Basin, MacRobertson Shelf, East Antarctica. The goal of this study was to depict the deglacial and Holocene environmental history of the MacRobertson Land-Prydz Bay region. A special focus was put on the timing of ice-sheet retreat and the variability of bottom-water formation due to sea ice formation through the Holocene. Results from site PS69/849-2 provide the first paleo-environmental record of Holocene variations in bottom-water production probably associated to the Cape Darnley polynya, which is the second largest polynya in the Antarctic. Methods included end-member modeling of laser-derived high-resolution grain size data to reconstruct the depositional regimes and bottom-water activity. The provenance of current-derived and ice-transported material was reconstructed using clay-mineral and heavy-mineral analysis. Conclusions on biogenic production were drawn by determination of biogenic opal and total organic carbon. It was found that the ice shelf front started to retreat from the site around 12.8 ka BP. This coincides with results from other records in Prydz Bay and suggests warming during the early Holocene optimum next to global sea level rise as the main trigger. Ice-rafted debris was then supplied to the site until 5.5 cal. ka BP, when Holocene global sea level rise stabilized and glacial isostatic rebound on MacRobertson Land commenced. Throughout the Holocene, three episodes of enhanced bottom-water activity probably due to elevated brine rejection in Cape Darnley polynya occured between 11.5 and 9 cal. ka BP, 5.6 and 4.5 cal. ka BP and since 1.5 cal. ka BP. These periods are related to shifts from warmer to cooler conditions at the end of Holocene warm periods, in particular the early Holocene optimum, the mid-Holocene warm period and at the beginning of the neoglacial. In

  10. Petroleum systems and geologic assessment of undiscovered oil and gas, Cotton Valley group and Travis Peak-Hosston formations, East Texas basin and Louisiana-Mississippi salt basins provinces of the northern Gulf Coast region. Chapters 1-7.

    USGS Publications Warehouse

    ,

    2006-01-01

    The purpose of the U.S. Geological Survey's (USGS) National Oil and Gas Assessment is to develop geologically based hypotheses regarding the potential for additions to oil and gas reserves in priority areas of the United States. The USGS recently completed an assessment of undiscovered oil and gas potential of the Cotton Valley Group and Travis Peak and Hosston Formations in the East Texas Basin and Louisiana-Mississippi Salt Basins Provinces in the Gulf Coast Region (USGS Provinces 5048 and 5049). The Cotton Valley Group and Travis Peak and Hosston Formations are important because of their potential for natural gas resources. This assessment is based on geologic principles and uses the total petroleum system concept. The geologic elements of a total petroleum system include hydrocarbon source rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (sequence stratigraphy and petrophysical properties), and hydrocarbon traps (trap formation and timing). The USGS used this geologic framework to define one total petroleum system and eight assessment units. Seven assessment units were quantitatively assessed for undiscovered oil and gas resources.

  11. Evidence for formation of a flexural backarc basin by compression and crustal thickening in the central Alaska peninsula

    SciTech Connect

    Bond, G.C.; Lewis, S.D.; Taber, J.; Steckler, M.S.; Kominz, M.A. )

    1988-12-01

    The North Aleutian Basin is a large, Cenozoic sedimentary basin in the northern part of the central Alaska Peninsula and the southern Bering shelf. The gravity anomaly pattern, the geometry, and the structure of the basin suggest that if formed by downward flexure of the backarc lithosphere. Basin modeling suggests that the flexure was driven by the emplacement of surface and subsurface loads having densities comparable to those of oceanic crust and mantle rocks, at approximately the position of the present-day volcanic arc and forearc. The authors suggest that the inferred loads consist of tectonically thickened mafic crustal materials lying beneath the arc and forearc of the central Alaska Peninsula. The crustal thickening may have occurred within a dominantly transpressional regime resulting from oblique convergence between the North American and Pacific plates during the Cenozoic.

  12. Altered volcanic ash partings in Wasatch Formation coal beds of the northern Powder River basin: composition and geologic applications

    USGS Publications Warehouse

    Bohor, Bruce Forbes; Phillips, Richard E.; Pollastro, Richard M.

    1979-01-01

    In contrast to the coal-bearing rocks of the Appalachian and Eastern Interior Basins, those of the northern Powder River Basin exhibit more complex stratigraphic and facies relationships, and regional correlations of coal beds are, therefore, more difficult to establish. Recently, however, several coal beds in the Powder River Basin, as well as coal beds in several other coal basins of the Rocky Mountain region, have been found to contain thin but persist·ent layers. of altered volcanic ash described as kaolinitic bentonites (Bohor, 1976, 1977, 1978, Bohor and others, 1976, 1978, Bohor and Pillmore, 1976). These layers serve as isochronous marker horizons which aid in correlating coal beds over broad areas.

  13. Formation and Evolution of Scalloped Depressions on Malea Planum and the southern rim of the Hellas Basin, Mars

    NASA Astrophysics Data System (ADS)

    Zanetti, M.; Hiesinger, H.; Reiss, D.; Neukum, G.

    2008-09-01

    Introduction: Scalloped depressions are an erosional surface morphology characterized as a type of dissected mantle terrain by Milliken and Mustard [1]. They are identified by their asymmetrical north-south profile which shows a steep pole-facing scarp, a flat floor, and a gentle equator-facing slope which grades into the surrounding terrain [1]. They are found in latitudedependent, ice-rich surface mantles in both the northern and southern hemispheres [1]. The mantle material is presumably composed of atmospherically derived dust and water ice, and is thought to be related to obliquity-driven ice activity as recently as 2.1-0.4 Myr ago [3]. Previous researchers, [e.g. 1,2,4-7] have attributed the formation of scallops to the sublimation of interstitial ice. Morgenstern et al. [6] suggested that the asymmetric profile of scallops can be explained by enhanced solar insolation on the equator-facing slope which leads to enhanced sublimation of interstial ice and thereby increases the area of the depression. By this process they can also grow and coalesce to form large degraded areas [6]. Building on our previous work [7], we investigate this hypothesis using HiRISE and THEMIS-IR images. We also propose a hypothesis for the nucleation and evolution of scallops. Previous Work: Our previous work surveyed the southern hemisphere using HRSC images for the presence of scalloped terrain, and revealed that almost all scalloped terrains are in the Malea Planum region near the southern wall of the Hellas basin [7]. We mapped the distribution of scalloped terrain between 50° and 70° E and 50° and 70° S. The results of the map showed that the scalloped terrains contour the southern wall of the Hellas basin between the elevations of 1000 m and -2000 m, and that the icerich mantle is thickest in this region [7]. Data and Methods: High resolution HiRISE images of the scalloped terrain of Malea Planum were used to investigate small scale features. Daytime infrared images from

  14. Formation and Evolution of Scalloped Depressions on Malea Planum and the southern rim of the Hellas Basin, Mars

    NASA Astrophysics Data System (ADS)

    Zanetti, M.; Hiesinger, H.; Reiss, D.; Neukum, G.

    2008-09-01

    Introduction: Scalloped depressions are an erosional surface morphology characterized as a type of dissected mantle terrain by Milliken and Mustard [1]. They are identified by their asymmetrical north-south profile which shows a steep pole-facing scarp, a flat floor, and a gentle equator-facing slope which grades into the surrounding terrain [1]. They are found in latitudedependent, ice-rich surface mantles in both the northern and southern hemispheres [1]. The mantle material is presumably composed of atmospherically derived dust and water ice, and is thought to be related to obliquity-driven ice activity as recently as 2.1-0.4 Myr ago [3]. Previous researchers, [e.g. 1,2,4-7] have attributed the formation of scallops to the sublimation of interstitial ice. Morgenstern et al. [6] suggested that the asymmetric profile of scallops can be explained by enhanced solar insolation on the equator-facing slope which leads to enhanced sublimation of interstial ice and thereby increases the area of the depression. By this process they can also grow and coalesce to form large degraded areas [6]. Building on our previous work [7], we investigate this hypothesis using HiRISE and THEMIS-IR images. We also propose a hypothesis for the nucleation and evolution of scallops. Previous Work: Our previous work surveyed the southern hemisphere using HRSC images for the presence of scalloped terrain, and revealed that almost all scalloped terrains are in the Malea Planum region near the southern wall of the Hellas basin [7]. We mapped the distribution of scalloped terrain between 50° and 70° E and 50° and 70° S. The results of the map showed that the scalloped terrains contour the southern wall of the Hellas basin between the elevations of 1000 m and -2000 m, and that the icerich mantle is thickest in this region [7]. Data and Methods: High resolution HiRISE images of the scalloped terrain of Malea Planum were used to investigate small scale features. Daytime infrared images from

  15. Godiva Rim Member: A new stratigraphic unit of the Green River Formation in southwest Wyoming and northwest Colorado. Geology of the Eocene Wasatch, Green River, and Bridger (Washakie) Formations, Greater Green River Basin, Wyoming, Utah, and Colorado. Professional paper

    SciTech Connect

    Roehler, H.W.

    1991-01-01

    The report names and describes the Godiva Rim Member of the Green River Formation in the eastern part of the Washakie basin in southwest Wyoming and the central part of the Sand Wash basin in northwest Colorado. The Godiva Rim Member comprises lithofacies of mixed mudflat and lacustrine origin situated between the overlying lacustrine Laney Member of the Green River Formation and the underlying fluvial Cathedral Bluffs Tongue of the Wasatch Formation. The Godiva Rim Member is laterally equivalent to and grades westward into the LaClede Bed of the Laney Member. The Godiva Rim Member of the Green River Formation was deposited along the southeast margins of Lake Gosiute and is correlated to similar lithologic units that were deposited along the northeast margins of Lake Uinta in the Parachute Creek Member of the Green River Formation. The stratigraphic data presented provide significant evidence that the two lakes were periodically connected around the east end of the Uinta Mountains during the middle Eocene.

  16. Uplift, subsidence, and volcanism in the southern Neiva Basin, Colombia, Part 2: Influence on fluvial deposition in the Miocene Gigante Formation

    NASA Astrophysics Data System (ADS)

    van der Wiel, A. M.; van den Bergh, G. D.; Hebeda, E. H.

    1992-02-01

    The fluvial and volcaniclastic deposits of the Miocene Gigante Formation of the southern Neiva Basin record the transition from fluvial deposition to a type of sedimentation strongly influenced by volcanic activity of the Central Cordillera volcanic arc. The lower part of the formation, reflecting the influence of uplift of the Central Cordillera to the south and west of the basin, consists of mixed-load sediments deposited by a braided river system. In middle Miocene times, this braided, north-flowing paleo-Magdalena River was forced eastward by coalescing volcanic aprons that probably originated along the front of a reactivated thrust fault. Sedimentation processes on these aprons were dominated by debris flows and hyperconcentrated flows as well as by unconfined sheetfloods on the more proximal parts of the aprons and by unconfined and confined sheetfloods and overbank deposition on the dstal parts of the aprons grading into the alluvial plain. Average sedimentation rates on the volcanic aprons measured between 0.36 and 0.42 mm/year. When volcanism abated, the paleo-Magdalena River returned to its former course. During this period, fluvial deposition was influenced by renewed uplift of the Garzón Massif to the east of the basin.

  17. Calibrating Late Cretaceous Terrestrial Cyclostratigraphy with High-precision U-Pb Zircon Geochronology: Qingshankou Formation of the Songliao Basin, China

    NASA Astrophysics Data System (ADS)

    Wang, T.; Ramezani, J.; Wang, C.

    2015-12-01

    A continuous succession of Late Cretaceous lacustrine strata has been recovered from the SK-I south (SK-Is) and SKI north (SK-In) boreholes in the long-lived Cretaceous Songliao Basin in Northeast China. Establishing a high-resolution chronostratigraphic framework is a prerequisite for integrating the Songliao record with the global marine Cretaceous. We present high-precision U-Pb zircon geochronology by the chemical abrasion isotope dilution thermal-ionization mass spectrometry method from multiple bentonite core samples from the Late Cretaceous Qingshankou Formation in order to assess the astrochronological model for the Songliao Basin cyclostratigraphy. Our results from the SK-Is core present major improvements in precision and accuracy over the previously published geochronology and allow a cycle-level calibration of the cyclostratigraphy. The resulting choronostratigraphy suggest a good first-order agreement between the radioisotope geochronology and the established astrochronological time scale over the corresponding interval. The dated bentonite beds near the 1780 m depth straddle a prominent oil shale layer of the Qingshankou Formation, which records a basin-wide lake anoxic event (LAE1), providing a direct age constraint for the LAE1. The latter appears to coincide in time with the Late Cretaceous (Turonian) global sea level change event Tu4 presently constrained at 91.8 Ma.

  18. Propagation of a fold-and-thrust belt vs. timing of flexural basin formation: a case-study in the Betics (Gibraltar Arc System)

    NASA Astrophysics Data System (ADS)

    Jiménez-Bonilla, Alejandro; Torvela, Taija; Exposito, Inmaculada; Balanya, Juan Carlos; Diaz-Azpiroz, Manuel; Barcos, Leticia; Crespo-Blanc, Ana

    2015-04-01

    Tectonic load associated to the progressive fold-and-thrust belt (FTB) building in the external zones of orogens commonly leads to the lower plate lithosphere flexure, subsequent foreland basin formation, and syn-sedimentary deposits. In this contribution, we focus on a case-study situated in the northern branch of the Gibraltar Arc System. The interpretation of seismic sections together with updated structural data from the Subbetic FTB, formed by paleomargin deposits detached from the South Iberian basement, and the central to eastern Guadalquivir foreland basin, permit us to characterize the variations of deformational style across the Subbetic and the spatial and temporal relationships between the Subbetic and the foreland basin infill, in particular in terms of migration of the FTB deformation front. From the most internal FTB to foreland basin, various structural styles have been characterized: (1) The inner FTB is formed by buckle folds, WSW-ENE striking, kilometre-scale and non-cylindrical, controlled by a detachment within Triassic evaporites. (2) The central FTB is characterized by a thrust system, detached also in Triassic evaporites and whose direction varies from NE-SW to E-W towards a more external position. Ramp geometries and associated fault-bend folds show that this thrust system has N-ward vergence. Syn-compressional Serravallian to Langhian sediments deposited during the back and fore-thrusting permit to constrain the age of the deformation. (3) The frontal FTB is characterised by a tectonically complex area without dominant vergence. The Subbetic competent rocks are surrounded by a clayey matrix, attributed to Langhian-Serravallian age. Finally, seismic lines in the Guadalquivir foreland basin show that the Langhian-Serravallian units were thrust onto a younger Tortonian to Messinian, post-deformational sequence. Our data suggest that the compressional deformation observed in the inner and central FTB corresponds mostly with a Lower to Middle

  19. Synthesis of Late Cretaceous-Quaternary tectonic, sedimentary and magmatic processes and basin formation related to episodic subduction-collision in the easternmost Mediterranean region

    NASA Astrophysics Data System (ADS)

    Robertson, Alastair; Kinnaird, Timothy; McCay, Gillian; Palamakumbura, Romesh; Taslı, Kemal

    2015-04-01

    Mesozoic oceanic crust of the easternmost Mediterranean has experienced northwards subduction during Late Cretaceous-Cenozoic, either continuously or discontinuously based on kinematic evidence. Much of the existing information on sedimentation within the easternmost Mediterranean oceanic basin comes from the non-emplaced continental margins of the Levant and North Africa. In addition, sedimentary basins related to plate convergence are recorded along the northern margin of the Southern Neotethyan ocean, mainly in the Kyrenia Range of northern Cyprus and its extension into the Misis Mountains of southern Turkey, coupled with the adjacent submerged areas. In a setting of only incipient continental collision such as the easternmost Mediterranean the sedimentary basins would be expected to remain entirely submarine. In contrast, the Kyrenia Range has been strongly uplifted and subaerially exposed during Late Pliocene-Quaternary time. This allows the recognition of a number of discrete phases of sedimentary basin formation: 1. Late Cretaceous (Campanian-Maastrichtian): silicic volcanism to create a subaqueous volcaniclastic apron; 2. Maastrichtian-Paleocene: pelagic carbonate deposition interspersed with proximal gravity flows and within-plate type alkaline volcanics; 3. Early Eocene: large-scale sedimentary melange (olistostrome) emplacement; 4. Late Eocene-Late Miocene: terrigenous gravity-flow deposition in a deep-water fault dissected 'fore arc' setting. Initial, Late Eocene non-marine coarse clastic alluvial fan deposition was succeeded by Oligocene-Miocene deep-marine siliciclastic gravity flow deposits, fining and shallowing upwards during the Late Miocene; 5. Messinian: localised precipitation of evaporites in small fault-controlled basins; 6. Pliocene: shallow-marine siliciclastic-carbonate deposition in a shelf-depth, overall regressive setting; 7. Latest Pliocene to mid-Pleistocene: gravitational accumulation of coarse talus along a strongly uplifting

  20. Trilobites, scolecodonts and fish remains occurrence and the depositional paleoenvironment of the upper Monte Alegre and lower Itaituba formations, Lower – Middle Pennsylvanian of the Amazonas Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Moutinho, Luciane Profs; Nascimento, Sara; Scomazzon, Ana Karina; Lemos, Valesca Brasil

    2016-12-01

    This study aims to characterize the scolecodonts, trilobite pygidium fragments and fish remains of an outcropped region in the southern Amazonas Basin, comprising the uppermost section of the Monte Alegre Formation and the basal section of the Itaituba Formation. These, correspond to part of the marine portion of the Tapajós Group, related to an intracratonic carbonate platform. The Monte Alegre Formation includes a deposition of fluvial-deltaic and aeolian sandstones, siltstones and shales of interdunes and lakes, intercalated with transgressive carbonates of a shallow restrict nearshore marine environment. The Itaituba Formation comprises a thickest deposit of marine carbonates, representing the establishment of widespread marine conditions, and is the richest interval containing organisms of shallow marine environment in the Pennsylvanian of the Amazonas Basin. The associated fauna includes brachiopods, bivalves, gastropods, crinoids, echinoids, bryozoans, corals, foraminifers, sponges, ostracods, trilobites, scolecodonts, fish remains and conodonts, mainly in the packstones, and subordinately in the wackestones and mudstones. Conodonts Neognathodus atokaensis, Diplognathodus orphanus, Idiognathodus incurvus, and foraminifers Millerella extensa, Millerella pressa, Millerella marblensis, Eostaffella ampla, Eostaffella pinguis and Eostaffella advena characterizes a predominant Atokan age to the analyzed profile. The fossil association herein presented is taxonomically diversified and biologically interesting, comprising an important and well preserved, for the first time occurrence of two molds and two fragments of Proetida trilobites. Well preserved Eunicida and Phyllodocida scolecodonts and paleonisciform fish remains. These fossils help in the paleoenvironmental establishment of the studied interval in the Amazonas Basin and as a potential biostratigraphic and paleoecological tool to correlate regionally and globally the Pennsylvanian.

  1. Evaporite cycles and cycle boundaries in the upper part of the Paradox Member, Hermosa Formation of Pennsylvanian age in the Paradox basin, Utah and Colorado

    SciTech Connect

    Raup, O.B.; Hite, R.J. )

    1991-03-01

    The evaporites of the Paradox Member of the Hermosa Formation of Pennsylvanian age in southeastern Utah and southwestern Colorado are direct precipitates from marine brines and have been changed only slightly by subsequent events. Geophysical logs of deep wells indicate that the Paradox Member is composed of at least 30 evaporite cycles. Lithologies that make up the cycles, in order of increasing salinity, are organic carbon-rich carbonate shale (black shale), dolomite, anhydrite, and halite (with or without potash). Studies of core from two wells in the central part of the basin show that some of the cycles in the upper part of the Paradox Member are remarkably symmetrical, indicating regular changes in salinity. Detailed petrologic studies have revealed newly recognized lithologic textures and cycle boundaries in 11 evaporite cycles, indicating very regular cyclicity of subaqueous sedimentation in a basin in which salinity was probably controlled by Gondwana glaciation.

  2. Nonassociated gas resources in low-permeability sandstone reservoirs, lower tertiary Wasatch Formation, and upper Cretaceous Mesaverde Group, Uinta Basin, Utah

    SciTech Connect

    Fouch, T.D.; Schmoker, J.W.; Boone, L.E.; Wandrey, C.J.; Crovelli, R.A.; Butler, W.C.

    1994-08-01

    The US Geological Survey recognizes six major plays for nonassociated gas in Tertiary and Upper Cretaceous low-permeability strata of the Uinta Basin, Utah. For purposes of this study, plays without gas/water contacts are separated from those with such contacts. Continuous-saturation accumulations are essentially single fields, so large in areal extent and so heterogeneous that their development cannot be properly modeled as field growth. Fields developed in gas-saturated plays are not restricted to structural or stratigraphic traps and they are developed in any structural position where permeability conduits occur such as that provided by natural open fractures. Other fields in the basin have gas/water contacts and the rocks are water-bearing away from structural culmination`s. The plays can be assigned to two groups. Group 1 plays are those in which gas/water contacts are rare to absent and the strata are gas saturated. Group 2 plays contain reservoirs in which both gas-saturated strata and rocks with gas/water contacts seem to coexist. Most units in the basin that have received a Federal Energy Regulatory Commission (FERC) designation as tight are in the main producing areas and are within Group 1 plays. Some rocks in Group 2 plays may not meet FERC requirements as tight reservoirs. However, we suggest that in the Uinta Basin that the extent of low-permeability rocks, and therefore resources, extends well beyond the limits of current FERC designated boundaries for tight reservoirs. Potential additions to gas reserves from gas-saturated tight reservoirs in the Tertiary Wasatch Formation and Cretaceous Mesaverde Group in the Uinta Basin, Utah is 10 TCF. If the potential additions to reserves in strata in which both gas-saturated and free water-bearing rocks exist are added to those of Group 1 plays, the volume is 13 TCF.

  3. The floating astronomical time scale for the terrestrial Late Cretaceous Qingshankou Formation from the Songliao Basin of Northeast China and its stratigraphic and paleoclimate implications

    NASA Astrophysics Data System (ADS)

    Wu, Huaichun; Zhang, Shihong; Jiang, Ganqing; Huang, Qinghua

    2009-02-01

    The Upper Cretaceous Qingshankou Formation (K 2qn) in the Songliao Basin (SLB) of Northeast China consists of up to 550 m thick, lacustrine mudstone and shale that constitute one of the most important source rocks of the Daqing oil field. A high-resolution cyclostratigraphic analysis of the natural gamma-ray logging from 10 wells of the Qingshankou Formation (K 2qn) reveals orbital cycles of precession (20 ka), obliquity (40 ka) and eccentricity (100 ka and 405 ka), providing strong evidence for astronomically driven climate changes in the Late Cretaceous terrestrial environments. Floating astronomical time scales (ATS) are established for all sections, which demonstrate variable durations of K 2qn across the basin (1.09 Ma-5.20 Ma) and strong diachroneity of the lacustrine strata. Four periods of high depositional rates can be identified in the central parts of the basin, possibly recording deposition during times of sustained wet climate and high chemical weathering. An ATS established from well M206 in the central depression zone of the basin, where the most complete and stable Milankovitch cycles are present, suggests that the maximum duration of the K 2qn is 5.20 Ma (from 94.27 Ma to 89.07 Ma; Late Cenomanian to Early Coniacian). The lacustrine anoxic event 1 (LAE1) at the Cenomanian-Turonian boundary lasted ~ 210-310 ka, during which the most prolific petroleum source rocks in SLB were deposited. The onset (~ 94.21-94.18 Ma) and duration (~ 210-310 Ka) of LAE1 in SLB are comparable to those of the oceanic anoxic event 2 (OAE2; onset at 94.21 Ma and duration of ~ 320-900 ka), suggesting that the same trigger mechanism, such as increased atmospheric CO 2 from large-scale igneous activity, may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems.

  4. Sedimentary environments for the massive formation of the lacustrine organic rich petroleum source rocks of late Cretaceous from Songliao Basin, China

    NASA Astrophysics Data System (ADS)

    Zhiguang, S.

    2009-12-01

    Songliao Basin is the major oil-bearing and production basin in China and containing two major sets of excellent organic matter rich source rocks developed during the two related short periods of later Cretaceous time. For a long time, these source rocks were considered unquestionably being formed under fresh or brackish lacustrine environment. However, increasing evidence and studies suggest that this may be not the case anymore, as possible marine transgression and much high salinity lacustrine environment has been suggested or implied from a number of recent studies for Songliao Basin. Here, we show our recent extensive organic geochemical studies carried out on the core samples of Nenjiang formation from a newly drilled scientific exploration well of No. 1 in Songliao Basin. The overall evidence of organic matter and biomarkers suggest that: 1) the main source rocks were likely formed under a much saline(even mesosaline) lacustrine environment, as the existence of a number high saline related biomarkers and their ratios such Pr/Ph, MTTCI, α-MTTC/δ-MTTC, α-MTTC /γ-MTTC, Gammacerane/C30hop are in favor of a mesosaline to saline environments; 2) during the major source rocks formation periods, a photic zone oxygen depletion and stratified water column was suggested by the strong occurrence of a series of aryl isoprenoids and Isorenieratane; 3) a general mild to strong reduced sedimentary environments were concluded from the consistent of a number of index. Fig 1 Correlation between MTTCI vs Pr/Ph ratios with indication of salinity fields (after SCHWARK et al., 1998)

  5. Uplift, subsidence, and volcanism in the southern Neiva Basin, Colombia, Part 1: Influence on fluvial deposition in the Miocene Honda Formation

    NASA Astrophysics Data System (ADS)

    van der Wiel, A. M.; van den Bergh, G. D.

    1992-02-01

    In the southern Neiva Basin, four large-scale sedimentary sequences are recognized in the deposits of the Miocene Honda Formation on the basis of maximum clast diameter, fluvial channel/overbank deposit ratio, thickness of the overbank and channel sequences, and lithology of the sandstones. These sequences can be related to tectonic activity of the Central Cordillera and the Garzón Massif, to volcanism, and to the rate of basin subsidence. They may be interpreted in terms of different alluvial fan systems and volcanic aprons that prograded onto a broad plain during periods of active uplift or volcanism and braided and meandering river systems that developed during the intervening periods of greater volcanic and tectonic quiescence. The lower two sequences were deposited under relatively quiet tectonic conditions, following the major and final phase of thrust faulting of the Central Cordillera. During deposition of these sequences, sediment loading let to subsidence of the basin. The depositional processes of these sequences, furthermore, were influenced by activity of the Central Cordillera volcanic arc. Radiometric age determinations on two tuff beds located some 300 meters above the base of the formation in the lowermost sequence gave ages of 15.8 ± 0.6 and 14.3 ± 0.5 Ma, respectively. Conglomerates of the third sequence record pronounced uplift of the source area, i.e., the Central Cordillera. Deposition of this sequence very probably coincided with uplift of the Garzón Massif, the southermost extension of the Eastern Cordillera, which took place at about 12 Ma. Uplift of both cordilleras led to rapid subsidence of the basin. The upper sequence was deposited under conditions of waning tectonic activity.

  6. Spatial and stratigraphic distribution of water in oil shale of the Green River Formation using Fischer assay, Piceance Basin, northwestern Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Mercier, Tracey J.; Brownfield, Michael E.

    2014-01-01

    The spatial and stratigraphic distribution of water in oil shale of the Eocene Green River Formation in the Piceance Basin of northwestern Colorado was studied in detail using some 321,000 Fischer assay analyses in the U.S. Geological Survey oil-shale database. The oil-shale section was subdivided into 17 roughly time-stratigraphic intervals, and the distribution of water in each interval was assessed separately. This study was conducted in part to determine whether water produced during retorting of oil shale could provide a significant amount of the water needed for an oil-shale industry. Recent estimates of water requirements vary from 1 to 10 barrels of water per barrel of oil produced, depending on the type of retort process used. Sources of water in Green River oil shale include (1) free water within clay minerals; (2) water from the hydrated minerals nahcolite (NaHCO3), dawsonite (NaAl(OH)2CO3), and analcime (NaAlSi2O6.H20); and (3) minor water produced from the breakdown of organic matter in oil shale during retorting. The amounts represented by each of these sources vary both stratigraphically and areally within the basin. Clay is the most important source of water in the lower part of the oil-shale interval and in many basin-margin areas. Nahcolite and dawsonite are the dominant sources of water in the oil-shale and saline-mineral depocenter, and analcime is important in the upper part of the formation. Organic matter does not appear to be a major source of water. The ratio of water to oil generated with retorting is significantly less than 1:1 for most areas of the basin and for most stratigraphic intervals; thus water within oil shale can provide only a fraction of the water needed for an oil-shale industry.

  7. Spatial and stratigraphic distribution of water in oil shale of the Green River Formation using Fischer Assay, Piceance Basin, northwestern Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Mercier, Tracey J.; Brownfield, Michael E.

    2014-01-01

    The spatial and stratigraphic distribution of water in oil shale of the Eocene Green River Formation in the Piceance Basin of northwestern Colorado was studied in detail using some 321,000 Fischer assay analyses in the U.S. Geological Survey oil-shale database. The oil-shale section was subdivided into 17 roughly time-stratigraphic intervals, and the distribution of water in each interval was assessed separately. This study was conducted in part to determine whether water produced during retorting of oil shale could provide a significant amount of the water needed for an oil-shale industry. Recent estimates of water requirements vary from 1 to 10 barrels of water per barrel of oil produced, depending on the type of retort process used. Sources of water in Green River oil shale include (1) free water within clay minerals; (2) water from the hydrated minerals nahcolite (NaHCO3), dawsonite (NaAl(OH)2CO3), and analcime (NaAlSi2O6.H20); and (3) minor water produced from the breakdown of organic matter in oil shale during retorting. The amounts represented by each of these sources vary both stratigraphically and areally within the basin. Clay is the most important source of water in the lower part of the oil-shale interval and in many basin-margin areas. Nahcolite and dawsonite are the dominant sources of water in the oil-shale and saline-mineral depocenter, and analcime is important in the upper part of the formation. Organic matter does not appear to be a major source of water. The ratio of water to oil generated with retorting is significantly less than 1:1 for most areas of the basin and for most stratigraphic intervals; thus water within oil shale can provide only a fraction of the water needed for an oil-shale industry.

  8. Superficial and deep-seated gravity-driven deformation horizons within basinal succession: the case study of Maiolica Formation, Gargano Promontory, Southern Italy

    NASA Astrophysics Data System (ADS)

    Jablonská, Danica; Di Celma, Claudio; Tondi, Emanuele

    2016-04-01

    Gravitational phenomena on the paleoslope of continental margins play a significant role both in redistribution of sediment and formation of new structural features within sedimentary basins worldwide. Mass-transport deposits (MTDs) represent important heterogeneities within the succession and occur on various scales (tens of centimetres to hundreds of metres). Small- to medium-scale MTDs (up to tens of meters) act as layers of different petrophysical properties, whereas large-scale MTDs (tens to hundreds of meters) form both stratigraphic and structural discontinuities (faults, thrusts, erosional surfaces, dykes or injections) within the succession. The Maiolica Formation, Early Cretaceous deep basinal succession cropping out in Gargano Promontory of Southeast Italy is represented by undisturbed intervals of flat-lying thin-bedded, cherty micritic limestone interstratified with intervals of lithologically similar, but structurally distorted beds. For this reason, the studied outcrops provide a good opportunity to characterize the geometry and the internal deformation of small- and medium-scale carbonate MTDs. At the outcrop scale, small- to medium-sized MTDs can be simply identified as sheets of deformed strata alternated with packages of undeformed beds. However, several observed features such as folded stylolites with radially oriented peaks within some of these deformed packages and the presence of large vertical clastic-dyke-like bodies in the succession suggest that some of these deformed packages represent deep-seated basal gliding horizons of large-scale MTDs. In this study, we present MTDs on two different scales that have a crucial influence on the evolution of slope to basinal successions. Moreover, we define the features that distinguish superficial MTDs from the deep-seated gravity-driven deformation horizons within basinal carbonates.

  9. REDUCING RISK IN LOW-PERMEABILITY GAS FORMATIONS: UNDERSTANDING THE ROCK/FLUID CHARACTERISTICS OF ROCKY MOUNTAIN LARAMIDE BASINS

    SciTech Connect

    Ronald C. Surdam

    2003-12-29

    An anomalous velocity model was constructed for the Wind River Basin (WRB) based on {approx}2000 mi of 2-D seismic data and 175 sonic logs, for a total of 132,000 velocity/depth profiles. Ten cross sections were constructed through the model coincident with known gas fields. In each cross section, an intense, anomalously slow velocity domain coincided with the gas-productive rock/fluid interval. The anomalous velocity model: (1) Easily isolates gas-charged rock/fluid systems characterized by anomalously slow velocities and water-rich rock/fluid systems characterized by normal velocities; and (2) Delineates the regional velocity inversion surface, which is characterized by steepening of the Ro/depth gradient, a significant increase in capillary displacement pressure, a significant change in formation water composition, and acceleration of the reaction rate of smectite-to-illite diagenesis in mixed-layer clays. Gas chimneys are observed as topographic highs on the regional velocity inversion surface. Beneath the surface are significant fluid-flow compartments, which have a gas-charge in the fluid phase and are isolated from meteoric water recharge. Water-rich domains may occur within regional gas-charged compartments, but are not being recharged from the meteoric water system (i.e., trapped water). The WRB is divided into at least two regionally prominent fluid-flow compartments separated by the velocity inversion surface: a water-dominated upper compartment likely under strong meteoric water drive and a gas-charged, anomalously pressured lower compartment. Judging from cross sections, numerous gas-charged subcompartments occur within the regional compartment. Their geometries and boundaries are controlled by faults and low-permeability rocks. Commercial gas production results when a reservoir interval characterized by enhanced porosity/permeability intersects one of these gas-charged subcompartments. The rock/fluid characteristics of the Rocky Mountain Laramide

  10. A resource evaluation of the Bakken Formation (Upper Devonian and Lower Mississippian) continuous oil accumulation, Williston Basin, North Dakota and Montana

    USGS Publications Warehouse

    Schmoker, J.W.

    1996-01-01

    The Upper Devonian and Lower Mississippian Bakken Formation in the United States portion of the Williston Basin is both the source and the reservoir for a continuous oil accumulation - in effect a single very large field - underlying approximately 17,800 mi2 (46,100 km2) of North Dakota and Montana. Within this area, the Bakken Formation continuous oil accumulation is not significantly influenced by the water column and cannot be analyzed in terms of conventional, discrete fields. Rather, the continuous accumulation can be envisioned as a collection of oil-charged cells, virtually all of which are capable of producing some oil, but which vary significantly in their production characteristics. Better wellperformance statistics are linked regionally to higher levels of thermal maturity and to lower levels of reservoir heterogeneity. Although portions of the Bakken Formation continuous oil accumulation have reached a mature stage of development, the accumulation as a whole is far from depleted.

  11. Isotopic and geochemical characterization of fossil brines of the Cambrian Mt. Simon Sandstone and Ironton-Galesville Formation from the Illinois Basin, USA

    NASA Astrophysics Data System (ADS)

    Labotka, Dana M.; Panno, Samuel V.; Locke, Randall A.; Freiburg, Jared T.

    2015-09-01

    Geochemical and isotopic characteristics of deep-seated saline groundwater provide valuable insight into the origin and evolving composition, water-rock interaction, and mixing potential of fossil brines. Such information may yield insight into intra- and interbasinal brine movement and relationships between brine evolution and regional groundwater flow systems. This investigation reports on the δ18O and δD composition and activity values, 87Sr/86Sr ratios and Sr concentrations, and major ion concentrations of the Cambrian-hosted brines of the Mt. Simon Sandstone and Ironton-Galesville Formation and discusses the evolution of these brines as they relate to other intracontinental brines. Brines in the Illinois Basin are dominated by Na-Ca-Cl-type chemistry. The Mt. Simon and overlying Ironton-Galesville brines exhibit total dissolved solids concentrations of ∼195,000 mg/L and ∼66,270 mg/L, respectively. The δD of brine composition of the Mt. Simon ranges from -34‰ to -22‰ (V-SMOW), and the Ironton-Galesville is ∼-53.2‰ (V-SMOW). The δ18O composition of the Mt. Simon brine ranges from -5.0‰ to -2.8‰ (V-SMOW), and the Ironton-Galesville brine is ∼-6.9‰ (V-SMOW). The 87Sr/86Sr values in the Mt. Simon brine range from 0.7110 to 0.7116. The less radiogenic Ironton-Galesville brine has an average 87Sr/86Sr value of 0.7107. Evaluation of δ18O and δD composition and activities and 87Sr/86Sr ratios suggests that the Mt. Simon brine is likely connate seawater and recirculating deep-seated brines that have been diluted with meteoric water and influenced by the dissolution of evaporites with a minimal halite contribution based on Cl/Br ratios. The Ironton-Galesville brine is also likely originally connate seawater that mixed with other brines and meteoric waters, including possibly Pleistocene glacial recharge. The Ca-excess vs. Na-deficiency comparison with the Basinal Fluid Line suggests the Mt. Simon and Ironton-Galesville brines have been

  12. Petrology and diagenetic history of the upper shale member of the Late Devonian–Early Mississippian Bakken Formation, Williston Basin, North Dakota

    USGS Publications Warehouse

    Neil S. Fishman,; Sven O. Egenhoff,; Boehlke, Adam; Lowers, Heather

    2015-01-01

    The organic-rich upper shale member of the upper Devonian–lower Mississippian Bakken Formation (Williston Basin, North Dakota, USA) has undergone significant diagenetic alteration, irrespective of catagenesis related to hydrocarbon generation. Alteration includes precipitation of numerous cements, replacement of both detrital and authigenic minerals, multiple episodes of fracturing, and compaction. Quartz authigenesis occurred throughout much of the member, and is represented by multiple generations of microcrystalline quartz. Chalcedonic quartz fills radiolarian microfossils and is present in the matrix. Sulfide minerals include pyrite and sphalerite. Carbonate diagenesis is volumetrically minor and includes thin dolomite overgrowths and calcite cement. At least two generations of fractures are observed. Based on the authigenic minerals and their relative timing of formation, the evolution of pore waters can be postulated. Dolomite and calcite resulted from early postdepositional aerobic oxidation of some of the abundant organic material in the formation. Following aerobic oxidation, conditions became anoxic and sulfide minerals precipitated. Transformation of the originally opaline tests of radiolaria resulted in precipitation of quartz, and quartz authigenesis is most common in more distal parts of the depositional basin where radiolaria were abundant. Because quartz authigenesis is related to the distribution of radiolaria, there is a link between diagenesis and depositional environment. Furthermore, much of the diagenesis in the upper shale member preceded hydrocarbon generation, so early postdepositional processes were responsible for occlusion of significant original porosity in the member. Thus, diagenetic mineral precipitation was at least partly responsible for the limited ability of these mudstones to provide porosity for storage of hydrocarbons.

  13. New Sakmarian ages for the Rio Bonito formation (Paraná Basin, southern Brazil) based on LA-ICP-MS U-Pb radiometric dating of zircons crystals

    NASA Astrophysics Data System (ADS)

    Cagliari, Joice; La