Sedimentary and stratigraphic evidence indicates that most Virgil and Wolfcamp elongate sandstones on the Eastern shelf of north-central Texas are segments of dip-fed fluvial and deltaic depositional systems. These sandstone bodies are composed of superposed delta front, channel-mouth bars, and distributary channels, on top of which are superimposed fluvial and peripheral sheet and small barlike bodies.

Fluvial facies consist of channel-fill sandstones and conglomerates, and overbank mudstones and siltstones; levee deposits are difficult to recognize. Elongate sandstones enclosed in overbank mudstone become finer upward, and characterize fine-grained meander-belt deposits; braided and coarse-grained meander-belt sandstones are extensive tabular to highly belted bodies with little mudstone.

Constructional deltaic sandstones become coarser upward. Delta-front facies display parallel and ripple bedforms, and commonly show distorted basal bedding resulting from subsidence into prodeltaic muds. Channel-mouth bars are normally distorted sandstones with trough crossbedding and small scour channels. Symmetrically filled distributary channels are shallow and up to 50 yd wide. Delta-front sandstones grade laterally into thin, destructive sheet sandstones and strandplain facies within adjacent interdeltaic areas.

Delta progradation, fluvial aggradation, compaction, avulsion, destruction, and marine transgression, followed by later reoccupation of deltaic and fluvial sites, result in distinctive lateral and vertical facies relations.

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