CENOZOIC STRATIGRAPHY AND STRUCTURE OF MISSISSIPPI EMBAYMENT SEDIMENTS OF SOUTHEASTERN MISSOURI

The New Madrid seismic zone is responsible for the three large earthquakes during the winter of 1811-1812 that occurred within the northern Mississippi Embayment. Mapping of coincident deformation in both the surface and subsurface has provided insight into Cenozoic fault activity and faulting mechanics. This project interprets four hundred thirty three, 300-foot-deep, lignite exploration electric and lithology logs to create structure-contour and facies maps to identify deformation as well as Eocene, Pleistocene, and Holocene depositional geometries in southeastern Missouri. The Eocene (Cockfield Formation?) is a predominantly clay unit with shoestring sands typical of meandering fluvial environments. A thick clay unit, probably representing an overbank floodplain environment, changes from a linear to arcuate body up section. This change in apparent river characteristics may be the result of syndepositional tectonic subsidence. The Quaternary alluvial section consists of braided Pleistocene ancestral Ohio River and meandering Holocene Mississippi River systems. The Holocene Mississippi floodplain location appears to be influenced by the 10,900 year old Charleston Fan and a possible northeast-trending structural high that is coincident with the northeastern extension of the New Madrid seismic zone.