Three closely spaced oblique-slip faults displace a Quaternary gravel and sand unit overlying Eocene Claiborne strata in the Trinity River Valley, Leon County. These steeply dipping faults strike east-northeast; two of them are downthrown toward the south, with a smaller, antithetic, central fault downthrown to the north. Maximum slip on individual faults is 118 cm (46.5 inches), decreasing to 66 cm (26 inches) where these faults displace the overlying Quaternary gravels. The location and trend of these faults are consistent with the configuration of the Mt.

Secondary leached porosity is common to dominant in near surface to deep subsurface lower Tertiary sandstone reservoirs along the Texas Gulf Coast. This secondary porosity is in the form of leached feldspar grains, volcanic rock fragments, carbonate cements, and carbonate-replaced grains. Leached porosity occurs in sandstones with compositions ranging from volcanic litharenite and lithic arkose to quartzose sublitharenite and quartzose subarkose.

Since early 1977, the Bureau of Economic Geology has been evaluating several salt-bearing basins within the State of Texas as part of the national nuclear repository program. The Bureau, a research unit of The University of Texas at Austin and the State of Texas, is carrying out a long-term program to gather and interpret all geologic and hydrologic information necessary for description, delineation, and evaluation of salt-bearing strata in the Palo Duro and Dalhart Basins of the Texas Panhandle.