MORE FIELD DATA FROM THE KILMICHAEL STRUCTURE, MONTGOMERY COUNTY, MISSISSIPPI

The Kilmichael Structure is a circular feature of unknown origin located in Paleocene and Eocene sediments of north central Mississippi. The structure, first identified around 1930, has been of interest to structural geologists, geophysicists and residents of the area. Mechanisms of surface deformation are of some debate, and possibilities include meteor impact, pluton or diapir emplacement, and restraining or releasing bend uplift on a strike-slip system.

We measured attitudes of mesoscale deformation at outcrops along a southwest-northeast traverse of the Kilmichael Structure. Field observations include folds, small domes (less than five meter diameter), and faults (normal, reverse and strike-slip). These small scale domes, along with sand dikes, ptygmatic folds, and matrix supported breccias, suggest high fluid pressures and sediment flow. Within the breccias there are large clasts (greater than a meter in diameter) of underlying stratigraphic units, suggesting significant vertical transport in a fluid matrix.

The data we collected to date do not conclusively rule out any of the proposed mechanisms of deformation. However, there is a potential for active tectonism in this region (for example, the New Madrid fault system), and to better understand the regional tectonic setting we plan to collect additional field data to more quantitatively characterize the Kilmichael Structure.