ABSTRACT

The Paleocene portion of the Paleocene-Eocene Wilcox Group in the subsurface of Sabine Parish, Louisiana, is a thick, deltaic sequence of siliciclastics with rare calcareous zones. Comparisons of microbiological content, electric-log deflections, and core lithologies between Holocene Mississippi River delta sediments and Sabine Parish Wilcox deposits reveal similar depositional environments and sequences. Four Wilcox paleoenvironments are recognized from foraminiferal assemblages: nearshore shelf, deltaic marine (delta front), hyposaline to normal-marine lagoon, and interdistributary bay/hyposaline lagoon. A fifth paleoenvironment, marsh, is recognized by occurrences of lignite beds.

Both transgressive and regressive deltaic deposits occur in the Wilcox Group. Transgressive deposits are characterized by lagoonal foraminiferal assemblages, calcareous zones, and fining-upward depositional sequences. Regressive deposits are identified by deltaic marine foraminiferal assemblages and coarsening-upward depositional sequences.

Evidence for a marine transgression of possible regional significance is observed in an interval which includes the Odontogryphaea thirsae bed (P4). The maximum foraminiferal diversity (17 benthic and 6 planktic species) encountered in the entire 658-m (2,158-ft) interval of cored Wilcox occurs in a thin sand located 0.3 m (1ft) above the O. thirsae bed. This sand is a nearshore shelf deposit and represents a condensed section.