The Claiborne Group of East Texas
An ancestral coastal plain was the principal setting for the deposition of the Claiborne Group. Units within the Claiborne dip to the southeast at one to two degrees. Generally the Claiborne formations crop out in an arcuate pattern across the east Texas area, with the older formations cropping out farther to the north and west while the younger formations crop out nearer to the present coast.
The ancestral coastal plains area of Texas consists of several major structural features: Sabine Uplift in extreme East Texas, Tyler Basin in east Texas, San Marcos Arch in central Texas, and Rio Grande Embayment in southern Texas (Fig. 1). Formation of these structural features influenced the deposition of the Claiborne units. High areas, such as the Sabine Uplift and the San Marcos Arch, caused rivers to reroute and diverge their courses. This resulted in minimal amounts of material being deposited in those areas of uplift. Subsidence created the basinal features such as the Tyler Basin and Rio Grande Embayment, and great thicknesses of material were deposited in these susiding lows. Normal faulting has vertically displaced the Claiborne units throughout the area.
Claiborne exposures discussed here are located within approximately 6 mi (10 km) of Jacksonville, Texas, in Cherokee County (Fig. 2). Outcrops that primarily expose the Queen City and Weches formations are easily accessible along U.S. 69 north and south of Jacksonville and along U.S. 79 west of Jacksonville. In several localities, upper and lower contacts of the Queen City and Weches formations are visible. The formations are