Abstract

In central and eastern Alabama there are 13 Upper Cretaceous (late Santonian to latest Maastrichtian; 85 to 67 Ma) depositional sequences in the outcrop and shallow-subsurface stratigraphic section. Each depositional sequence is composed of paralic and shelfal facies associations within their transgressive and highstand systems tracts. Within each depositional sequence the gross depositional-strike mode and specific position of shoreline trend are both directly related, to second- and third-order changes of sea level, respectively. Depositional-sequence paleogeography and the sedimentary facies relations within depositional sequences, and their constituent systems tracts (both transgressive and highstand), dictate the distribution of coarse-clastic paralic (aquifer) facies that have significant primary permeabilities. The coarse-clastic facies, specifically barrier island and lower-shoreface facies, are significant local confined clastic aquifers that, taken together, constitute significant regional aquifer systems. All depositional sequences and the facies tracts within them have locally and regionally correlative bounding surfaces of hydrogeologic significance.

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