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Deltaic and barrier-bar depositional systems from the Chester and Pottsville Groups of the Black Warrior basin produce natural gas and minor oil from 11 Mississippian sandstone reservoirs and four Pennsylvanian clastic units. Within the Chester, four major genetic sequences containing cratonic delta systems have been mapped. These include, in ascending stratigraphic position, the lobate, river-dominated Lewis system, the wave-dominated Evans and Hartselle systems, the river-dominated, elongate, and lobate deltas of the Muldon complex (Rea, Abernathy, Sanders, and Carter), and the hybrid Gilmer system.
Chester deltas prograded southeastward onto the stable northern shelf from a cratonic source area, most likely the Ozark uplift. Net sandstone isolith maps for discrete genetic units demonstrate a northwest-to-southeast
progradational trend and a tendency for the sub-Millerella units to thicken updip to the line of post-Carboniferous erosional truncation. An isopach map of the Tuscumbia-Millerella interval shows thickening toward the north, away from the Ouachita orogenic source area.
Limited petrographic evidence from Lewis and Carter sandstone bodies associated with the principal subsurface deltaic facies tract indicates a dominance of monocrystalline quartz and chert rock fragments, as well as an absence of lithologic indicators for an orogenic provenance. By way of contrast, outcrop studies of the Hartselle and Parkwood units in Alabama by W. A. Thomas et al describe an abundance of polycrystalline quartz in the Hartselle and both metamorphic quartz and phyllite rock fragments in the Parkwood. The Parkwood samples containing the orogenic indicators are restricted to the folded Appalachians.
The Pottsville Group can be broken down into a maximum of 10 regionally mappable subsurface intervals. Widespread delta destructional coal seams and marine reworked sandstone bodies serve as marker units. Pottsville gas production derives from barrier bar facies in the lowest two genetic intervals and from the mixed barrier-bar and deltaic sandstone units of interval 3 (Nason). This Lower Pennsylvanian clastic wedge has its predominant source area to the south in the Ouachita orogenic belt. An isopach map of the total Pottsville documents significant thickening to an excess of 10,000 ft (3,000 m) in central Mississippi. All of the previously mentioned orogenic indicators are noted in the outcropping deltaic Pottsville facies.
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