Seismic Investigation of Surface Deformation Associated with the Kilmichael Dome, Montgomery County, Mississippi

S. D. Sloan and J. B. Harris
Millsaps College, Jackson, Missisippi

The Kilmichael Dome, first identified 70 years ago, is a circular feature exposed in unconsolidated Paleocene and Eocene sediments of north central Mississippi. The structural complexity of the area, including zones of intense faulting and uplifted strata, has led to several suggested origins for the Dome, including meteorite impact and regional tectonics. A shallow shear-wave, seismic reflection profile was collected over a complex zone of surface faults, the Salem Church Fault Zone, on the northern flank of the Kilmichael Dome. The goal was to image the subsurface expression of deformation associated with the fault zone. Acquisition of downhole seismic velocity data from the fault zone has enabled us to analyze the shear wave velocity structure of the shallow sediments and to identify possible shear-wave anisotropy.

Recent field studies have provided evidence of surface deformation in the area of the Dome. It suggests the presence of high fluid pressures and sediment flow. Initial interpretation is for a correlation between the alignment of these structures and the directions of polarization provided by the shear-wave data. In addition to increased seismic resolution gained by using shear waves in unconsolidated, water-saturated sediments, measurement of near-surface, shear-wave anisotropy may provide valuable information for identifying neotectonic deformation, evaluating associated earthquake hazards, and guiding future paleoseismologic investigations in the Kilmichael Dome area.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004