Mississippian system of Andrews and Gaines Counties, Texas

The Mississippian system confined to the subsurface between depths of 7,100 and 12,650 feet is composed of two formations. The lower is miscalled "the Mississippian limestone" in accordance with local usage; the upper, the shale-limestone formation. Data from electric and radioactive logs provide the means for subdividing the formations into members. The geographic distribution, thickness and composition of these are shown by means of a structure map, two isochore maps, and four cross sections. Fossils were not available to correlate the subsurface sections with the outcrop areas of central Texas, south-central New Mexico and Oklahoma. Grain size and lithologic composition suggest that the limestone of both formations was deposited near-shore and that the shale facies of the upper formation was deposited in a deeper basin.