Regional outcrop and subsurface investigation of the Jackson Group in Texas indicates development of 5 main depositional systems. Dominant element in the central and east Texas Gulf basin (bounded by Guadalupe River on the south and Neches River on the

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east) is the Fayette fluvial-delta system consisting of dip-oriented, lobate wedges of sand, mud, and lignite. The vertical sequence in updip subsurface and outcrop, with gradation upward from marine mud through several delta facies and into fluvial sand and mud, reflects net regression and progradation of the system. Southwestward, transport of sand and mud from the delta system, principally by longshore drift, resulted in the South Texas strandplain-barrier bar system, made up of strike-trending sand bodies interbedded with marine and lagoonal mud. Landward of the strandplain-barrier-bar system and extending into outcrop is a complementary lagoonal-coastal plain system consisting of mud and minor, dip-oriented sand units. Gulfward of the strike-trending strandplain system is the Sou h Texas shelf system, formed by marine mud derived largely from the delta system on the northeast. Beneath the South Texas strandplain-barrier bar and Fayette delta systems and extending eastward into Louisiana and Mississippi is the Caddell-Yazoo shelf system consisting of marine, fossiliferous mud and minor glauconitic marl. Delineation of depositional systems, and specifically component facies of the various systems, facilitates definition of significant mineral trends (oil, gas, lignite, and uranium) that show the relation between current and potential areas of production.

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