Browsing by Subject "Depositional environment"
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Item Depositional environment and taphonomy of some fossil vertebrate occurrences in Lower Permian redbeds in Archer County, Texas(1984-12) Sander, Paul Martin; Langston, Wann, 1921-The Lower Permian Admiral Formation redbeds in north-central Texas are famous for their well-studied vertebrate fauna. Taphonomical and paleoecological aspects, however, are inadequately understood. The prerequisite for taphonomical interpretations is an analysis of the depositional environments. Low relief and low regional dip expose extensive paleoslopes in western Archer County. Three major depositional systems may be recognized: a fine-grained meanderbelt, a low sinuosity fine-grained fluvial system, and a tidal flat. The small scale of the sedimentation (average sandstone thickness 1. 5 m) is remarkable. Four types of vertebrate occurrences can be distinguished: Type 1: Mass death bonebeds are situated in a floodbasin facies comprised of gray and red mudstones with abundant Psaronius roots (a swamp-dwelling tree fern) which is associated with the fluvial systems. Such basins were covered by a dense swamp forest with a high diversity of vertebrates. This type is exemplified by the Geraldine Bonebed, which has yielded at least 45 partly articulated skeletons representing 4 genera of tetrapods, and remains of another 8 vertebrate taxa. The bones were found on a layer of fern, seed fern, and conifer foliage and wood. This occurrence was formed by a single catastrophic event, possibly a forest fire, which drove the animals of the swamp forest into a pond, where they died of suffocation and were concentrated into a bonebed by physical processes (wind). Type 2: Lag bonebeds, situated on the landward margin of tidal flat environments, are represented by the Rattlesnake Canyon Bonebed which consists mainly of a calcareous concretion conglomerate, which contains fragmentary bone, serpulid worm colonies (brackish water!), and calamitelean wood. The diversity of forms represented by articulated material is low. The ubiquitous predator Dimetrodon and an amphibian, Trimerorachis, which tolerates brackish water, are common. This type was deposited as lag in a storm washover deposit. Type 3: Ponds (abandoned channels, etc.) which contained a fauna dominated by aquatic forms (the fishes Xenacanthus and Ectosteorachis, and the amphibian Archeria) were gradually filled by fine-grained sediment and organic debris (vertebrates, plants). These oxbow lakes were probably rimmed by stands of Calamites. Four examples are described. Type 4: Single, complete skeletons examplified here by Diadectes are occasionally found in red floodplain mudstones.Item Depositional environment, sequence stratigraphy, and reservoir quality of the Tonkawa Sandstone in the western Anadarko Basin, Hemphill, Lipscomb and Roberts Counties, Texas(2015-05) Tussey, Logan Brien; Fisher, W. L. (William Lawrence), 1932-; Ambrose, William A.; Cutright, Bruce LThe Anadarko Basin contains some of the most prolific hydrocarbon reserves in all of North America. A recent USGS publication estimated undiscovered resources across the basin to be 495 million barrels of oil (MMBO), 27 trillion cubic feet of natural gas (TCFG), and 410 million barrels of natural gas liquids (MMBNGL). Pennsylvanian age sandstones contribute substantially to total estimated reserves within the basin. The focus of this study is the late Pennsylvanian Tonkawa Sandstone, the lowermost unit of the Douglas Group, Virgilian Series. Through the integration of core analysis, subsurface mapping, petrographic analysis, and porosity and permeability data, this study presents a detailed analysis of the Tonkawa Sandstone across approximately 1,400 mi² (3,630 km²) in the western Anadarko Basin. The Tonkawa Sandstone is comprised of three high-order transgressive-regressive sequences within one larger, lower-order sequence. Sandstone-body distribution varies greatly, depending upon depositional environments and their associated facies. The Tonkawa Sandstone was deposited in deltaic and estuarine environments with a source area to the northeast. The HST-2 interval, the oldest sandstone-rich sequence in the Tonkawa Sandstone, was deposited in a deltaic environment with a mixed wave and tide-dominated energy regime. The younger HST-3 interval was deposited in a tide-dominated deltaic environment. The youngest interval, TST-3, was deposited in a mixed wave and tide-dominated transgressive estuarine environment. The Tonkawa Sandstone is a sublitharenite to litharenite. Widespread quartz overgrowths minimize variation in reservoir quality among facies. However, more proximal facies display better reservoir quality. Detailed characterization of Pennsylvanian formations such as the Tonkawa Sandstone contributes greatly to the understanding of similar formations within the Anadarko Basin, and other foreland and cratonic basins worldwide.Item Geochemistry and high-resolution chemostratigraphy of the Haynesville Formation, East Texas(2015-05) Bitar Nehme, Rita Abdo; Rowe, Harry; Fisher, W. L. (William Lawrence), 1932-; Kerans, CharlesThe Upper Jurassic Haynesville Formation of East Texas and Louisiana is an organic-rich calcareous mudrock that is Kimmeridgian in age. It underlies the less calcareous Bossier Shale, and it overlies the Smackover Formation limestone. The Haynesville has low permeability, but a relative high porosity, compared to other mudrock formations. Mudrocks are the most common sedimentary rock and some of the most challenging to study, analyze and understand. Despite having a homogeneous appearance on a macroscopic scale, mudrocks often have high variability in facies and composition on the microscopic scale and elemental level. Many studies and methods have been developed to identify facies and stratigraphic variations in mudrocks. A complete understanding of these variations is valuable to comprehend paleoenvironments, paleoclimate and paleoceanographic conditions. Mudrocks studies are also beneficial to shale exploration because these formations, which have a high hydrocarbon content, can be targeted by oil and gas companies for exploration and production. Geochemical methods, chemostratigraphy in particular, will be used in this thesis to complement core description, petrophysical studies and sedimentological studies. This thesis focuses on acquiring chemostratigraphic data from X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) measurements to identify elemental and mineralogical variations in the T. W. George core, from the Haynesville Formation in Harrison County, Texas. The data are linked to core description and are analyzed using Hierarchical Cluster Analysis (HCA) to acquire a better understanding of the paleoceanographic conditions and depositional environments that controlled the sediment deposition of the Haynesville Formation. The Haynesville Formation comprises a Ca-rich lower Haynesville, a more Ca-rich upper Haynesville, and underlies the Si-rich and Ca-poor Bossier. The dominant condition during deposition is anoxic/euxinic in the lower Haynesville becoming dysoxic in the upper Haynesville and more oxygenated in the Bossier Formation. The greenhouse climate of the Late Jurassic led to the deposition of strata yielding petroleum source rocks such as the Haynesville Formation that today have great economic value. Thus, studying the Haynesville has both academic and economic importance.Item Geologically-based permeability anisotropy estimates for tidally-influenced reservoir analogs using lidar-derived, quantitative shale character data(2011-05) Burton, Darrin; Wood, Lesli J.; Steel, Ronald; Mohrig, David; Kim, Wonsuck; Hesse, Marc; Janson, XavierThe principle source of heterogeneity affecting flow behavior in conventional clastic reservoirs is discontinuous, low-permeability mudstone beds and laminae (shales). Simple ‘streamline’ models have been developed which relate permeability anisotropy (kv/kh ) at the reservoir scale to shale geometry, fraction, and vertical frequency. A limitation of these models, especially for tidally-influenced reservoirs, is the lack of quantitative geologic inputs. While qualitative models exist that predict shale character in tidally-influenced environments (with the largest shales being deposited near the turbidity maximum in estuaries, and in the prodelta-delta front), little quantitative shale character data is available. The purpose of this dissertation is to collect quantitative data to test hypothetical relationships between depositional environment and shale character and to use this data to make geologically-based estimates of for different reservoir elements. For this study, high-resolution, lidar point-clouds were used to measure shale length, thickness, and frequency. This dissertation reports a novel method for using distance-corrected lidar intensity returns to distinguish sandstone and mudstone lithology. Lidar spectral and spatial data, photo panels, and outcrop measurements were used to map and quantify shale character. Detailed shale characteristics were measured from four different tidally-influenced reservoir analogs: estuarine point bar (McMurray Formation, Alberta, Canada), tidal sand ridge (Tocito Sandstone, New Mexico), and unconfined and confined tidal bars (Sego Sandstone, Utah). Estuarine point bars have long (l=67.8 m) shales that are thick and frequent relative to the other units. Tidal sand ridges have short (l=8.6 m dip orientation) shales that are thin and frequent. Confined tidal bars contain shales that are thin, infrequent, and anisotropic, averaging 16.3 m in length (dip orientation). Unconfined tidal bars contain nearly equidimensional (l=18.6 m dip orientation) shales with moderate thicknesses and vertical frequency. The observed shale geometries agree well with conceptual models for tidal environments. The unique shale character of each unit results in a different distribution of estimated . The average estimated kv/kh values for each reservoir element are: 8.2*10^4 for estuarine point bars, 0.038 for confined tidal bars, 0.004 for unconfined tidal bars, and 0.011 for tidal sand ridges.Item Lithofacies, depositional environments, and sequence stratigraphy of the Pennsylvanian (Morrowan-Atokan) Marble Falls Formation, Central Texas(2013-08) Wood, Stephanie Grace; Ruppel, Stephen C.; Loucks, R. G.The Pennsylvanian Marble Falls Formation in the Llano Uplift region of the southern Fort Worth Basin (Central Texas) is a Morrowan-Atokan mixed carbonate-siliciclastic unit whose deposition was influenced by icehouse glacioeustatic sea-level fluctuations and foreland basin tectonics. Previous interpretations of the Marble Falls Formation focused on outcrop data at the fringes of the Llano Uplift. This study uses a series of 21 cores to create a facies architectural model, depositional environmental interpretation, and regional sequence stratigraphic framework. On the basis of core data, the study area is interpreted to have been deposited in a ramp setting with a shallower water upper ramp area to the south and a deeper water basin setting to the north. Analysis of cores and thin sections identified 14 inner ramp to basin facies. Dominant facies are: (1) burrowed sponge spicule packstone, (2) algal grain-dominated packstone to grainstone, (3) skeletal foraminiferal wackestone, and (4) argillaceous mudstone to clay shale. Facies stacking patterns were correlated and combined with chemostratigraphic data to improve interpretations of the unit’s depositional history and form an integrated regional model. The Marble Falls section was deposited during Pennsylvanian icehouse times in a part of the Fort Worth Basin with active horst and graben structures developing in response to the Ouachita Orogeny. The resulting depositional cycles reflect high-frequency sea-level fluctuations and are divided into 3 sequences. Sequence 1 represents aggradational ramp deposition truncated by a major glacioeustatic sea-level fall near the Morrowan-Atokan boundary (SB1). This fall shifted accommodation basinward and previously distal areas were sites of carbonate HST in Sequence 2 deposition following a short TST phase. Sequence 3 represents the final phase of carbonate accumulation that was diachronously drowned by Smithwick siliciclastics enhanced by horst and graben faulting. These findings contribute to our understanding of the depositional response to glacioeustatic sea-level changes during the Pennsylvanian and can also form the basis for constructing a sedimentological and facies analog for Morrowan to Atokan shallow- to deepwater carbonates in the Permian Basin and the northern Fort Worth Basin.Item Sedimentology and reservoir characterization of the Upper Pennsylvanian Cline Shale, Midland Basin, Texas(2016-08) Zheng, Hanyue; Fisher, W. L. (William Lawrence), 1932-; Fu, Qilong; Kerans, Charles; Hamlin, H. ScottThe Cline Shale, an organic rich mudrock comprising the Canyon and Cisco Groups in the Midland Basin, has recently become an exploration target and production interval. The Cline is a basin-restricted facies specific to the Midland Basin, and is interpreted to have been deposited in a deep water environment by hemipelagic suspension and mass transport debris flow and turbidity flow. Based on core description, thin section observation, and bulk compositional XRD data carried out on seven cores, seven lithofacies have been identified including various types of clay-rich mudstone, carbonate and sandstone. Regional stratigraphic sections show that the Cline structurally dips towards the Central Basin Platform and ranges from 117 ft to 530 ft in thickness. Gamma-ray log patterns can indicate vertical changes in lithology by responding to clay content and organic matter. Two types of cycles in the Midland Basin are identified by upward-increasing and upward-decreasing gamma ray patterns. Cycles in the Midland Basin are correlated to those on the shelf, and are interpreted to correspond to sea level changes on the shelf. Fifteen stratigraphic cycles have been distinguished from a typical basin center core, where eight are in the Lower Cline and seven are in the Upper Cline. These cycles are laterally continuous across the Midland Basin. More stratigraphic cycles can be recognized near the toe of slope, because not all the depositions occurred within a cycle extend across the basin floor. It is inferred from correlation of gamma ray patterns that high-frequency sea-level fluctuation affected depositional processes on the platform and controlled sediment deposition in the basin. Wireline logs are a crucial tool for providing a quantitative evaluation of reservoir quality. The Cline pay zone is defined based on (1) Gamma ray>110 API, (2) Density porosity (DPHI)>3.4%, (3) TOC>2.0 wt.%. The possible exploration target is located in northern Glasscock, western Howard and southern Martin counties. The pay zone thickness varies from 50 ft to 100 ft. The average TOC of pay zones is greater than 2.5 wt.% and the average dry helium porosity is greater than 5.0%.Item Sequence stratigraphy, depositional environment and reservoir geology of wave-influence deltaic systems in the lower and middle Frio Formation, Redfish Bay, Corpus Christi, Texas(2013-05) Zhang, Jinyu, active 2013; Fisher, W. L. (William Lawrence), 1932-; Ambrose, William A.The sequence stratigraphy, depositional systems and reservoir geology of the lower and middle Oligocene Frio Formation in the Red Fish Bay field, Nueces County, Texas, are examined based on 1,800 feet (548.6 m) of core, 28 wireline-logs and 30 mi2 of 3-D seismic data. The study interval is composed of an incomplete 3rd-order stratigraphic sequence with an incomplete lowstand systems tract (LST), a complete transgressive systems tract (TST) and an incomplete highstand system tract (HST). This 3rd-order succession is divided into 12 4th-order sequences with average thickness of 150 feet (45.7 m). The lowstand system tract (LST) from 4th-order sequence 1 to 4th-order sequence 7 displays an aggradational stacking pattern in cross-sections. The regressive part of each 4th-order sequence has an upward-coarsening trend that reflects a transition of depositional environments from offshore to lower, middle and upper shoreface. The transgressive part of each 4th-order sequence exhibits an upward-fining trend, commonly associated with backstepping cycles composed of shoreface, washover-fan, and back-barrier lagoonal deposits. Sandstone maps of 4th-order sequence and stratal-slice maps from 3-D seismic data within 3rd-order lowstand system tracts display a strike-elongate geometry, indicating wave-dominated depositional systems. The 3rd-order transgressive system tract (TST) displays a retrogradational stacking pattern in cross-sections. The overall upward-fining trend records water deepening during transgression, interpreted as a transition from lower-shoreface to shelf environments. The 3rd-order highstand system tract (HST) from 4th-order sequence 8 to 4th-order sequence 12 displays a progradational stacking pattern in cross-sections. It is upward-coarsening and upward-thickening, indicating a transition from to distal- to proximal-shoreline setting. The geometry of framework sandstone bodies, inferred from gross-sandstone and stratal-slice maps is relatively lobate, suggesting a wave-modified deltaic system. The sandstone body continuity is very good and heterogeneity is very low within shoreface or wave-dominated deltaic systems in LST and HST sequences in Redfish Bay. Sandstone thickness expands towards the growth fault, owing to structurally controlled accommodation, but is thicker in the southwest part of study area, where it is controlled by paleogeomorphology, related to the presence of a deltaic depocenter. The sandstone body thickness of each 4th-order sequence is as much as 240 ft (73.2 m) and commonly ~100 ft (30.5 m) in average. Sandstone development in the study succession is controlled by the sequence stratigraphic context, and modification by depositional processes. The average porosity and permeability of study interval are 19.4% and 33.6 md respectively. Lithology is the main control on porosity and permeability. Sedimentary and biogenic structures also modify grain-size sorting, indirectly affecting porosity and permeability. Reservoir quality in LST is higher than that in the HST, as the depositional environment in LST is within proximal-delta-front facies, whereas in the HST is within distal-delta-front facies. Reservoir quality varies greatly within each 4th-order sequence, owing to different levels of intensity in bioturbation per each sandstone bed.