--> ABSTRACT: Clastic Facies and Diagenesis, Lewis-Evans Interval in Black Warrior Basin, by Arthur W. Cleaves and David Bat; #91030 (2010)

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Clastic Facies and Diagenesis, Lewis-Evans Interval in Black Warrior Basin

Arthur W. Cleaves, David Bat

Subsurface maps of the Lewis and Evans sandstone-facies tracts (Chester Group) on the northern shelf of the Black Warrior basin document two distinct deltaic depositional systems, each having a source area from the Mid-Continent interior. Within the Lewis genetic interval, six dip-elongate, river-dominated, cratonic delta lobes comprise the principal coarse-grained clastic units. However, in the higher Evans interval, five strike-elongate (cuspate) wave-dominated lobes are present on the northwestern rim of the basin.

Petrographic evidence from four Mississippi cores associated with delta-plain and delta-front facies in the two sandstone units indicates a dominance of monocrystalline quartz and chert rock fragments and a relative absence of orogenic indicators such as polycrystalline quartz, muscovite, and metamorphic rock fragments. Porosity development results largely from the formation of moldic secondary porosity and enlarged intergranular porosity. Primary porosity is occluded by the precipitation of quartz overgrowths and early calcite cement. Secondary moldic porosity was generated through the dissolution of feldspars and shale fragments. Enlarged intergranular porosity resulted from the dissolution of detrital illite matrix. Secondary porosity itself is partially occluded by authigenic kaol nite and illite, as well as by late-stage pyrite and dolomite.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.