Cementation and Compaction in Tuscumbia Limestone (Mississippian) of Northern Alabama

D. Ramsey Fisher

The Tuscumbia Limestone (Meramecian) of northern Alabama consists predominantly of pelmatozoan/bryozoan grain-supported rocks, which were deposited on a shallow, wave-agitated shelf. Although the Tuscumbia has undergone a complex diagenetic history, the two major processes responsible for porosity reduction in Tuscumbia grain-supported units were the precipitation of meteoric-influenced cements (syntaxial overgrowth and drusy mosaic) and the grain-to-grain compaction of sediments. The precipitation of these meteoric-influenced cements accounted for approximately a 40% loss of porosity in grain-supported units. The strong substrate selectivity of these overgrowth and drusy mosaic cements for pelmatozoan and bryozoan grains, respectively, and the cements' coarse crystal siz indicate that meteoric-influenced waters were only mildly oversaturated with respect to calcite.

Compaction accounted for approximately a 50% loss of porosity in Tuscumbia grain-supported units. Petrographic evidence reveals that a relationship exists between grain microstructure and compactability. Petrographic study also revealed that a hierarchy of grain-type responses to physical/chemical compaction occurs and that degrees of compaction intensity are accompanied by predictable patterns of grain response.

AAPG Search and Discovery Article #91036©1988 GCAGS and SEPM Gulf Coast Section Meeting; New Orleans, Louisiana, 19-21 October 1988.