Three closely spaced oblique-slip faults displace a Quaternary gravel and sand unit overlying Eocene Claiborne strata in the Trinity River Valley, Leon County.

For the past decade, geologists at the Bureau of Economic Geology, The University of Texas at Austin, have prepared various maps of the Texas Coastal Zone.

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.