CONFIRMING QUATERNARY DISPLACEMENT RATES ON THE MEEMAN-SHELBY FAULT AND JOINER RIDGE HORST, EASTERN ARKANSAS

Detailed Quaternary fault slip rates do not exist for many faults within and near the New Madrid seismic zone. The Meeman-Shelby fault (~8 km from Memphis) and the Joiner ridge horst (~54 km from Memphis) are two blind structures in northeastern Arkansas that have no modern seismicity but do have reported Quaternary displacements and are the focus of this research. Previous studies suggest 28 m (~2 mm/yr) of vertical Quaternary displacement on the Meeman-Shelby fault and 20 m (~1 mm/yr) on the Joiner ridge horst. Cores from previous studies, drilled on the up-thrown side of the Meeman-Shelby and Joiner Ridge structures, have Quaternary alluvium (<20 ka) thicknesses of ~41 m and ~36 m, respectively. For this study, cores were collected from the down-thrown sides of both the Meeman-Shelby fault and east-bounding fault of Joiner Ridge, where the Quaternary-Eocene contact was at depths of ~55 m (?) and ~36 m, respectively. Sediments from multiple horizons in both cores were sampled for OSL, 14C, and pollen analyses. OSL dates will provide more detailed information regarding the age of the basal alluvium. Better constrained slip rates will be calculated by determining the age of the basal alluvium and the amount of displacement associated with these two faults.