The Western Gulf Coastal Plain of the United States lies entirely in the State of Texas. Underlying it and under the portion of the continental shelf in front of it, Mesozoic and Cenozoic sediments dip generally toward the present Gulf of Mexico.
Considerable control from subsurface information to a depth of about 2 miles has been used to construct subsurface and isopachous maps both of formations which outcrop and of others of substantial thickness known in this area only from subsurface data. From these maps, the volume of sediments of different ages was calculated.
The calculated volumes are 453,000 cubic miles under the land area of 90,000 square miles and 271,000 cubic miles under the continental shelf area of 29,000 square miles. The total volume therefore of Mesozoic and Cenozoic sediments is 724,000 cubic miles, representing a mean thickness of about 6 miles.