EOCENE FAULTING AND STRUCTURE, TIPTON COUNTY, TN, WITH IMPLICATIONS FOR CENOZOIC STRESS FIELD ROTATION

At the Mississippi River bluff line north of Memphis, TN, lies the complex intersection of the eastern Reelfoot Rift margin, the Meeman-Shelby Fault, and a newly identified thrust fault, the Sugar Creek fault. The Eastern Reelfoot Rift Margin is a seismogenic, reactivated Proterozoic/early Paleozoic normal fault zone which strikes approximately N45E and shows right-lateral focal-plane mechanism solutions and reverse displacement in the Cenozoic. Investigations in Shelby County have revealed evidence of Quaternary and Holocene fault offsets in the Meeman-Shelby fault zone, a pair of high-angle reverse faults striking N25E, with a possible right-lateral strike-slip component. Both the Reelfoot Rift margin and Meeman-Shelby Fault are consistent with the modern E-W horizontal compressive stress field. Twenty kilometers further northeast, mapping of Eocene and younger strata exposed in Tipton County has revealed an east-west striking thrust fault, the Sugar Creek fault, that is limited to Eocene strata. Mapping has also revealed an asymmetric, south verging, E-W striking anticline that shows evidence of Quaternary deformation. The strikes of both the Sugar Creek fault and the anticline are consistent with an anomalous Cenozoic N-S compressional stress. Fracture data suggest a NW-SE to N-S compressive stress. This would require a clockwise rotation of 45-90^o from either the modern stress field or the oft-invoked NE-SW Eocene stress field based on subsidence in the Mississippi Embayment.