Genetic stratigraphy of the Dockum Group (Triassic), Palo Duro Canyon, Panhandle, Texas

The Triassic Dockum Group is a complex assemblage of lacustrine, deltaic, and fluvial facies. Excellent exposures of these rocks were studied in and around Palo Duro State Park where the Prairie Dog Town Fork of the Red River and its tributaries have carved a network of steep-walled canyons. Three-dimensional exposures of the Dockum have permitted study of lateral as well as vertical facies relationships. Three progradational genetic sequences were delineated within the study area. A genetic sequence consists in ascending order of: lacustrine mudstone, deltaic siltstone-sandstone-conglomerate, and fluvial sandstone-conglomerate. The following three lines of evidence indicate that complex base-level changes, caused by fluctuations in lake area and depth, occurred during deposition of the Dockum Group. Within the first genetic sequence burrowed lacustrine mudstones are interbedded with caliche horizons. These caliche horizons contain discrete burrowed and pisolitic carbonate nodules that are composed of microspar calcite, sparry calcite, and minor dolomite. Silicified evaporite nodules occur at the base of this unit. The second genetic sequence comprises a progradational lacustrine delta system which was truncated by a valley-fill system which formed in response to diminished lake depth and area. The valley-fill system comprises a transgressive fluvial-deltaic-lacustrine sequence encased within an overall progradational sequence. The third genetic sequence is composed of classic "Gilbert-type" lacustrine deltas with prominent foreset beds indicating deposition in 8 to 15 m of water. Ephemeral lakes characterized the first and second progradational sequences. Lacustrine fan deltas formed in water 1 to 10 m deep. The third progradational sequence was deposited in more continuously deep-water (10-20 m) lakes. A vertical sequence through Dockum Group rocks reveals a change from alternating humid and arid conditions of the first and second progradational sequences toward continuously humid conditions which prevailed during deposition of the third progradational sequence.Geological Science

Report of Investigations No. 133 Three-Dimensional Ground-Water Modeling in Depositional Systems, Wilcox Group, Oakwood Salt Dome Area, East Texas

UT Librarie

Characterization of Mineral and Geothermal Resources in the Eagle Flat Region, West Texas

The location and distribution of mineral and geothermal resources of the Eagle Flat study area have been described as part of the geologic characterization of the proposed site for the Texas low-level radioactive waste repository. Mineral localities were evaluated within the 400 mi2 (1,024 km2) Eagle Flat study area (Allamoore, Grayton Lake, Devil Ridge, Sierra Blanca, Bean Hill, and Dome Peak 7.5-minute topographic quadrangles) surrounding the proposed site. In order to more fully evaluate the regional trends and mineralogic associations, mineral localities were also characterized within a larger 900 mi2 (2,304 km2) reconnaissance area that includes 16 additional 7.5-minute quadrangles immediately surrounding the study area. The distribution and character of known mineral resources are important to the evaluation of the potential for economic mineral deposits on the siting area of the Texas low-level radioactive waste repository on the north Paskin Ranch. Excluding sand and gravel, which are ubiquitous in the basin, talc and possibly beryllium are the only known economic mineral deposits in the area. At the proposed site, basin-fill sediments in excess of 150 ft (45 m) thick probably preclude open-pit mining of talc or beryllium, and no favorable host rocks for talc are known to be present beneath the site. Beryllium is also highly unlikely because there are no drilling or geophysical data that indicate the occurrence of igneous intrusions beneath the basin-fill sediments of north Paskin Ranch. In addition, the site is located in a basin, not a highland, as is typical of intrusion-associated, Tertiary hydrothermal systems that occur elsewhere in the region.Bureau of Economic Geolog

Wilcox Group Facies and Syndepositional Salt Dome Growth, southern East Texas Basin

Shallow salt diapirs in the East Texas sedimentary basin are currently being considered as repositories of high-level nuclear waste (Kreitler, 1980; Kreitler and others, 1980; Kreitler and others, 1981). A crucial aspect of such an assessment involves understanding how fresh meteoric groundwater may impact long-term dome stability through dissolution. In the East Texas Basin, the zone of fresh meteoric groundwater includes the Wilcox Group, which encases or surrounds the upper 100 to 500 m (330 to 1640 ft) of most shallow diapirs. The distribution of Wilcox depositional facies may strongly influence flow directions and velocities of groundwater around salt domes. The Wilcox Formation exhibits extreme heterogeneity due to lateral and vertical variations in the distribution of highly permeable sands and other sandstones, mudstones, and lignites with low permeabilities. Variables affecting aquifer characteristics include thickness and hydraulic conductivity, which vary partly as a function of depositional facies and sand-body geometry, including sand body thickness, permeability, and interconnectedness. This report provides the basic facies and sand body data for computer modeling of groundwater flow around Oakwood Dome (Fogg, 1980a). Two main problems are addressed in this study: (1) determining the facies distribution and sand-body geometry of sandstones with high hydraulic conductivities and the greatest potential for possible dome dissolution, and (2) understanding how facies distribution is affected by syndepositional dome growth.Bureau of Economic Geolog

Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas: Barrier-Bar Tidal-Channel Reservoir Facies Architecture, Jackson Group, Prado Field, South Texas

Sandstone reservoirs in the Jackson barrier/strandplain play are characterized by low recovery efficiencies and thus contain a large hydrocarbon resource target potentially amenable to advanced recovery techniques. Prado field, Jim Hogg County, South Texas, has produced over 23 million barrels of oil and over 32 million cubic feet of gas from combination structural-stratigraphic traps in the Eocene lower Jackson Group. Hydrocarbon entrapment at Prado field is a result of anticlinal nosing by differential compaction and updip pinch-out of barrier bar sandstone. Relative base-level lowering resulted in forced regression that established lower Jackson shoreline sandstones in a relatively distal location in central Jim Hogg County. Reservoir sand bodies at Prado field comprise complex assemblages of barrier-bar, tidal-inlet fill, back-barrier bar, and shoreface environments. Subsequent progradation built the barrier-bar system seaward 1 to 2 miles. Within the barrier-bar system, favorable targets for hydrocarbon reexploration are concentrated in tidal-inlet facies because they possess the greatest degree of depositional heterogeneity.Bureau of Economic Geolog

Oil and Gas Resource Atlas Series: OffShore Northern Gulf of Mexico

The goal of the Oil and Gas Resource Atlas Series: Offshore Northern Gulf of Mexico is to develop an atlas of hydrocarbon plays that integrates data for oil and gas reservoirs with large-scale patterns of basin fill and age. During the second year of the 4-year program, tasks centered on program management and analysis of reservoir data. Approximately 140 plays have been identified in the Federal OCS and Texas State waters. Plays in Texas State waters are gas-prone and structurally trapped in rollover anticlines. In the Federal OCS, highly productive structural styles include growth-faulted rollover anticlines and salt domes. Lower Miocene plays are characterized by progradational and submarine-fan reservoirs of Lenticulina and Siphonina davisi chrono zones. Middle Miocene plays are characterized by progradational and retrogradational depositional styles. Upper Miocene plays are dominated by progradational depositional style, and Plio-Pleistocene plays include abundant progradational and submarine-fan reservoirs.Bureau of Economic Geolog

Depositional Setting of the Triassic Dockum Group, Texas Panhandle Eastern New Mexico

The upper Triassic Dockum Group accumulated in relict Paleozoic basins defined in Texas by the Amarillo Uplift on the north and the Glass Mountains on the south. These basins were reactivated during the late Paleozoic or early Mesozoic by tectonic activity that was probably related to the opening of the Gulf of Mexico. As basins subsided and some relict positive elements were uplifted, sedimentation rates increased. More than 2,000 ft (610 m) of terrigenous elastics, derived chiefly from Paleozoic sedimentary rocks, accumulated within the basin. Source areas were in Texas, Oklahoma, and New Mexico; sediment transport was from the south, east, north, and west. The Dockum Group accumulated in a variety of depositional environments including: (1) braided and meandering streams; (2) alluvial fans and fan deltas; (3) distributary-type lacustrine deltas (high-constructive elongate deltas); (4) ephemeral and relatively long-lived lakes; and (5) mud flats. Alternation of wet and dry climate caused cyclic sedimentation in the Dockum. The main control on climate was most likely tectonism. During wet periods, lake level was relatively stable. Meandering streams supplied sediment to high-constructive elongate deltas in the central basin area of Texas and New Mexico, whereas braided streams and fan deltas were dominant depositional elements along southern and northern basin margins. Lake area and depth decreased when dry conditions prevailed. Under these conditions, base level was lowered, valleys were cut into older Dockum deposits, and small fan deltas were built into ephemeral lakes; evaporites, calcretes, silcretes, and soils developed upon emergent surfaces ranging from floors of ephemeral lakes to delta platforms.Bureau of Economic Geolog

Sedimentary Record of Cretaceous and Teritiary Salt Movement, East Texas Basin: Times, Rates and Volumes of Salt Flow Implications to Nuclear-Waste Isolation and Petroleum Exploration

Post-Aptian strata (younger than 112 Ma) in the East Texas Basin were strongly influenced by halokinesis and record the evolution of associated salt structures. Comparisons with model diapirs and dome-induced changes in patterns of sandstone distribution, depositional facies, and reef growth indicate that thickness variations in strata surrounding domes were caused by syndepositional processes rather than by tectonic distortion. Salt domes in the East Texas Basin exhibit three stages of growth: pillow, diapir, and post-diapir. Each stage affected surrounding strata differently. Pillow growth caused broad uplifting of strata over the crest of the pillows. The resulting topographic swells influenced depositional trends and were susceptible to erosion. Fluvial-channel systems bypassed pillow crests and stacked vertically in primary peripheral sinks on the updip flanks of the pillows. Diapir growth was characterized by expanded sections of shelf and deltaic strata in secondary peripheral sinks around the diapirs. Lower Cretaceous (Aptian) reefs on topographic saddles between secondary peripheral sinks now host major oil production at Fairway Field. Post diapir crestal uplifting and peripheral subsidence affected smaller areas than did equivalent processes that occurred during pillow or diapir stages. Pre-Aptian domes grew in three areas around the margin of the diapir province, apparently in pre-Aptian depocenters. Maximum dome growth along the basin axis coincided with maximum regional sedimentation there during the mid-Cretaceous (Aptian, Albian, and Cenomanian stages). In the Late Cretaceous, the sites of maximum diapirism migrated to the margin of the diapir province. Diapirism began after pillows were erosionally breached, which led to salt extrusion and formation of peripheral sinks.Bureau of Economic Geolog

Koefisien Serap Bunyi Papan Partikel Dari Bahan Serbuk Kayu Kelapa

Telah dilakukan penelitian untuk mengetahui karakteristik koefisien serap bunyi papan partikel dari bahan dasar serbuk kayu kelapa. Papan partikel dibuat dengan mencampur serbuk kayu kelapa dengan tepung kanji, dicetak, dan dikeringkan. Sampel berbentuk silinder, dibuat sebanyak 4 buah dengan tebal : (1,15 cm), (1,95 cm), (2,95 cm) dan (4,05 cm). Nilai koefisien serap bunyi sampel diukur menggunakan alat ukur koefisien serap bunyi. Hasil penelitian menunjukkan, ketebalan sampel mempengaruhi nilai koefisien serap bunyi (α) yaitu pada frekuensi 600 Hz. Koefisien serap bunyi (α) semakin menurun dengan bertambahnya ketebalan papan partikel (sampel penyerap).The research had been doing to know characteristic sound absorption coefficient of particle board which made from base material coconut wood dust. The particle board made by mix of coconut wood dust with cornstarch then pressed and dried. The particle board as a sample is cylinder with diameter 8,5 cm. The thick of four samples are 1,15 cm, 1,95 cm, 2,95 cm, and 4,15 cm. The sound absorption coefficient have measured by sound absorption coefficient instruments. The result is sample thickness has influence to sound absorption coefficient values such as at 600 Hz frequencies. Sound absorption coefficients is decreasing to the increasing of the particle board thickness (absorber sample)

Suitability of Salt Domes in The East Texas Basin For Nuclear-Waste Isolation: Final Summary of Geologic and Hydrogeologic Research

This report summarizes results of the East Texas Waste Isolation program from January 1, 1978, to March 30, 1983. Using an extensive database, the study comprised 33 different lines of research by 67 scientists and research assistants. The program covered both basin-wide and site-specific (mainly around Oakwood Dome) studies using surface and subsurface data. A wide range of pertinent geologic and economic data for all 15 shallow salt domes is summarized in Appendix 2. Mesozoic opening of the Gulf of Mexico accompanied thermal processes that controlled sedimentation during filling of the East Texas Basin. The basin contains up to 7,000 meters of shallow-marine and continental sediments overlying the Louann Salt. Deformation in the basin resulted from subsidence of its floor and gravitational flow of salt. The East Texas Basin is divided into four provinces based on the shape of salt structures. Five forces drive salt flow; they operate from near surface to the deepest parts of the basin. Salt flow began in pre-Gilmer (Late Jurassic) time with the growth of salt pillows. Three groups of diapirs can be differentiated based on age and distribution. The growing salt structures affected topography, thereby influencing depositional facies. Low-permeability facies generally surround the salt stocks. Two types of structural inversion affected the structure of strata during diapirism. Geomorphic evidence does not preclude Quaternary uplift over Oakwood Dome, but its southern flank may have subsided. The rates of dome growth declined exponentially with time to rates less than 0.6 meters per 10^4 years. All regional fault systems in the basin appear to be related to slow gravitational creep of salt. Nevertheless, at least eight probable earthquakes were recorded near the southern margin of the basin in 1981 and 1982, and their probable focus - the Mount Enterprise fault - is poorly understood.Bureau of Economic Geolog