Geological Circulars

Permanent URI for this collectionhttps://hdl.handle.net/2152/121888

Peer-reviewed geoscience research summaries, targeted on Bureau project areas in Texas and other locations, 1965–2003.

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Browsing Geological Circulars by Author "Basciano, Joyce M."

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    Geology and geohydrology of the East Texas basin: a report on the progress of nuclear waste isolation feasibility studies (1979)
    (University of Texas at Austin. Bureau of Economic Geology, 1980) Kreitler, Charles W.; Agagu, Olusegun Kokumo, 1948-; Basciano, Joyce M.; Collins, Edward W.
    Analysis during the second year was highlighted by a historical characterization of East Texas Basin infilling, the development of a model to explain the growth history of the domes, the continued studies of the Quaternary in East Texas, and a better understanding of the near-dome and regional hydrology of the basin. Each advancement represents a part of the larger integrated program addressing the critical problems of geologic and hydrologic stabilities of salt domes in the East Texas Basin. During the second year of the East Texas salt dome studies, significant advances in understanding the hydrologic and geologic stabilities of salt domes were based on the acquisition of much new data. Among these new sources of data are (1) 400 km (250 mi) of seismic reflection data that are both regional and site specific, (2) gravity data for the East Texas Basin, (3) 20 shallow boreholes over Oakwood Dome, (4) 1 hydrologic test hole downdip from Oakwood Dome, and (5) a complete core of the anhydrite-gypsum cap rock over Gyp Hill Dome in South Texas. The acquisition of seismic, gravity, and electric log data provided new understanding of the sedimentary infilling of the East Texas Basin and how it caused salt migration and dome growth. Deposition of the Travis Peak-Schuler sediments caused the first differential loading of the underlying Louann Salt and the migration of the salt into anticlinal ridges. Subsequent clastic depocenters occurred laterally to Travis Peak depocenters and caused further migration of the salt into diapirs. The greater the sediment loading, the further the salt anticline advanced through Trusheim's (1960) growth sequence: pillow structure to immature diapir and finally to a mature diapir. Most domes in the basin can be placed within this dome growth sequence. Analysis of the Gyp Hill cap rock showed that the cap rock was the result of salt dome dissolution and the accumulation of the insoluble residuum, anhydrite. Work completed on the Carrizo-Wilcox aquifer, the major fresh-water aquifer in the basin, shows that this aquifer has the greatest potential for causing dome dissolution leading to radionuclide transport. Ground-water circulation is controlled primarily by topography and structure. Fluid movement is generally downward because of the structural dip and leakage from overlying units. Chemical composition of the water evolves from a low-pH, oxidizing, calcium bicarbonate water in the outcrop to a high-pH, reducing, sodium bicarbonate water deeper in the aquifer. This chemical change has important implications for radionuclide transport.
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    Hydrology and water quality of the Eocene Wilcox group: significance for lignite development in east Texas
    (University of Texas at Austin. Bureau of Economic Geology, 1980) Henry, Christopher D.; Basciano, Joyce M.; Duex, Timothy W.
    Lignite development will place major demands on ground-water supplies. The Simsboro Formation and the Calvert Bluff Formation (a major lignite-bearing unit) of the Wilcox Group between the Colorado and Trinity Rivers constituted a test case to evaluate the availability and quality of ground water. Aquifer geometry (sand) was determined by comparing environmental geologic maps with subsurface sand-percent and net-sand maps constructed from electric logs (Kaiser, 1978). The combined maps correlate well and show that the Calvert Bluff Formation consists of a complex interfingering of coarse channel sands and fine interchannel muds. Sand outcrop areas occupying approximately 10 square miles separate much larger interchannel areas with few and minor sands. The Simsboro Formation consists of two parts - a thick multilateral sand (300 to 700 ft) in most of the southern outcrop belt and a series of channel sands (100 to 200 ft) interspersed with muds in the northern belt. Sands of the northern Simsboro belt are more like the Calvert Bluff channel sands than like the thick Simsboro sands. Available hydrologic data suggest that Simsboro and Calven Bluff sands have high hydraulic conductivity (6 to 20 mlday); interchannel muds have low hydraulic conductivity (1 to 2 m/day). Water compositions in the Simsboro and Calvert Bluff sands are similar and evolve similarly. Shallow ground water has a Ca-Mg-Cl-HC03 composition low in total dissolved solids (less than 500 mg/l). The water evolves over a depth range from 300 to 1,200 R to become a Na-HC03 water. Change in composition probably results from ion exchange with clays (caff for 2Na+) and solution of calcite (which contributes more Ca -- for exchange and increases HC03- concentration). Poor quality water is largely restricted to shallow wells (less than 100 ft) in muddy parts of the Calvert Bluff Formation.