THE CHARLESTON UPLIFT OF SOUTHEASTERN MISSOURI

A N46°E trending subsurface structural high in Mississippi County of southeastern Missouri, herein called the Charleston uplift, is identified in structure contour and lithologic maps through the interpretation of 517 (91-m-deep) electric and geologic well logs. This 30 by 7.2 km structural high consists of Paleocene Flour Island Formation displaced vertically against the Eocene Claiborne Group. Structure contour mapping reveals a relief of 36 m on the base of the Quaternary Mississippi River alluvium while two seismic-reflection soundings, one within and the other north of the uplift, reveal the top of the Paleozoic displaced 60 meters and the top of the Cretaceous 47 meters. We interpret the Charleston Uplift to be an erosionally modified positive flower structure that is the northeastern extension of the New Madrid North fault, which overlies the western margin fault zone of the Reelfoot rift. Although the Charleston Uplift is relatively aseismic it appears to be responsible for the M 3.9 February 12, 2012 and probably the ~M 6.6 October 31, 1895 earthquakes. The apparent displacement of the base of the Quaternary and anomalous reaches of the Holocene Mississippi River leads us to propose that the Charleston uplift is an active linking fault between the New Madrid seismic zone and Quaternary faulting in southern Illinois and western Kentucky.