Upper Pennsylvanian and Lower Permian rocks of the eastern shelf in north-central Texas are composed of 10-15 repetitive sequences including open shelf, deltaic, fluvial, and interdeltaic depositional systems. Sediments derived from the Ouachita Mountains and associated piedmont were transported westward across a narrow coastal plain. Fluvial and deltaic sandstone facies define a southwest paleoslope of about 5 mi. Sandstones are delta-front, distributary-mouth-bar, distributary- and fluvial-channel, and destructional-bar facies.

Distributary patterns represent distal deposition in the upslope area. Belt sandstones, typified by unusually thick fluvial channels, prograded far downslope. Composite patterns include distributary and belt sandstones representing complex progradational history. Rocks display ½° northwest regional dip; negative structure residuals outline a broad area within which 70% of the deltaic facies were deposited.

Elongate sandstones generally are arranged parallel with paleoslope in vertically offset patterns controlled by differential compaction of fluvial and deltaic sands and interdistributary muds. Multistory sandstone bodies were deposited along narrow, structurally unstable belts which were periodically overloaded and later reoccupied by prograding deltas. Initial Cisco deltas followed a paleosurface grain controlled by underlying bank limestones; this paleoslope orientation was maintained during deposition of 1,200 ft of Cisco strata. Each fluvial-deltaic system inherited its geometry from previous systems and, in turn, provided control for the next deltaic episode. Stratigraphic and structural mapping utilizing mud decompaction techniques confirm the roles played by compaction and stru ture in controlling the geometry of sandstone bodies.

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