The Delaware Mountain Group in the Delaware basin of West Texas and southeast New Mexico consists of a thick sequence of Upper Permian clastic rocks deposited in a deep-water, marine setting. The basinal facies and depositional environments of these sediments may be interpreted from the uppermost part of this sequence, and pre-Lamar Bell Canyon sandstones. Three basic lithofacies are present: lutite, laminite, and arenite. These are defined by texture and composition as well as by sedimentary structures.

The lutite lithofacies is a pelagic, organic, fissile shale. It is rich in finely divided organic matter, relatively clay poor, and contains varied amounts of silt and mica. Closely related to the lutite is the laminite lithofacies. It is a laminated, coarse-grained siltstone (mean size 0.05 mm) with alternate laminae having concentrations of organic material, suggesting deposition from suspension. Bedding is marked by Nereites-type trace fossils which indicate a bathyal environment. A finer organic-poor laminite also is present in limited amounts and is inferred to have been deposited from turbidity currents because of its turbidite features.

The arenite lithofacies is present in linear submarine-channel areas and is a feldspar-rich quartz sandstone with very fine texture (mean size of 0.065 to 0.95 mm) and low matrix content. Sedimentary structures within this unit indicate deposition from turbidity currents as well as from other fluid-density currents. The channel patterns suggest a major southwest depositional trend but no submarine canyons. Hydrocarbon traps have developed along the channels because of regional tilting eastward and an updip facies change from arenite to laminite and biolaminite lithofacies. The remaining nonchannel sediments are interchannel deposits and wedged lobate deposits along marginal areas, especially in the northern half of the basin.