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The sedimentary evolution of the Forth Worth basin may be explained by tectonic movement within the basin and bounding features. This tectonic activity was the primary constraint on the depositional environments and distribution of the clastic sediments from the basin's margins.
Previously, the lower Atoka Big Saline (Bend) conglomerates of the Fort Worth basin have been interpreted as a part of the larger Atokan clastic sequence derived from the Ouachita orogene. However, the distribution, progradation of depositional environments, and reservoir qualities of these sediments suggests an alternative interpretation. The Big Saline (Bend) conglomerates appear to be derived from the Muenster-Red River arch complex to the north and transported into the basin through a series of prograding, high-constructive deltas.
Seven primary deltaic facies are recognized for the Big Saline (Bend) sediments. The facies include (1) point bar; (2) distributary-mouth bar and bar finger; (3) distributary-channel fill; (4) meander-channel fill; (5) crevasse splay; (6) backswamp marsh; and (7) undifferentiated delta front and prodelta deposits.
Contemporaneous with Big Saline (Bend) deposition, clastics derived from the Ouachita orogene were deposited in the deeper, eastern part of the basin. Deposition occurred primarily in fan-delta complexes; however, deep-water sedimentation in the form of submarine-fan deposits is also recognized. This eastern influx of sediments continued after the cessation of Big Saline (Bend) deposition.
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