Rapid oil developments in west Texas make necessary an interdistrict correlation for the petroleum geologist.

Geologically, west Texas is a structural geosyncline, and during Permian times it was a basin of deposition.

The Permian sea invaded from the southwest. Clastic sediments were derived from ancient Llanoria, from the Wichita Mountains, the igneous ridges of the Panhandle, and from the Ancestral Mountains of New Mexico. This material formed a border of red clastic sediments around the landward portion of the Permian sea, which, traced seaward in directions normal to the strand lines, grades into marine sediments, chiefly dolomitic limestones.

The latter constitute what is called the "Big Lime" series. The top of the Big Lime is the key bed used in subsurface work in west Texas. The upper part of the Big Lime is found to be of Double Mountain age, and may correlate with the Word formation of the Glass Mountain area and the Delaware formation of the Trans-Pecos area. It is considerably higher stratigraphically than the Big Lime of the Panhandle district.

Following the deposition of the Big Lime, a closed or restricted basin developed, the result being that the upper Permian measures are composed chiefly of anhydrite and salt, deposited from super-saline water.