Geology and Geohydrology of the East Texas Basin, A Report on the Progress of Nuclear Waste Isolation Feasibility Studies (1979

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.
Charles W. Kreitler
Olusegun K. Agagu
Joyce M. Basciano
Edward W. Collins
Owen R. Dix
Shirley P. Dutton
Graham E. Fogg
Alis B. Giles
Edgar H. Guevara
David W. Harris
David K. Hobday
Joseph H. McGowen
D. Pass
Debra H. Wood

Kreitler, C. W., Agagu, O. K., Basciano, J. M., Collins, E. W., and others, 1980, Geology and Geohydrology of the East Texas Basin A Report on the Progress of Nuclear Waste Isolation Feasibility Studies (1979): The University of Texas at Austin, Bureau of Economic Geology Geologic Circular 80-12, 112 p.

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The University of Texas at Austin, Bureau of Economic Geology
Geological Circular