Basinal mudrocks and associated facies assigned to the Wolfcamp and lower Leonard lithostratigraphic units in the Midland Basin are prolific producers of oil and gas. Four facies are recognized in core on the basis of macroscopic examination, XRD analysis, and ED-XRF elemental chemistry: (1) siliceous mudrock, (2) calcareous mudrock, (3) muddy bioclast–lithoclast floatstone, and (4) skeletal wackestone/packstone. Mudrocks are largely hemipelagic deposits of fine-grained sediment delivered by suspension settling.

This colorful geologic map published by AAPG—developed with assistance from the Bureau of Economic Geology—highlights state and regional surface rock outcrops, detailing their age, depositional environments, rock types, and formation names. The map is printed on a single sheet and folded to glove compartment size. It also features major highways, towns, landmarks, a stratigraphic column by state, mileage charts, and other interesting information about Texas geology.