STRATIGRAPHY, SEDIMENTOLOGY, AND LIQUEFACTION ALONG THE CENTRAL PORTION OF THE BOOTHEEL LINEAMENT, NEW MADRID SEISMIC ZONE, CENTRAL UNITED STATES

Surface evidence of fault movement in the New Madrid seismic zone has been difficult to document. One possible surface rupture is the Bootheel lineament, which extends 135 kilometers from Marked Tree, Arkansas, northeastward through the Missouri bootheel to New Madrid, Missouri. The lineament was originally described using aerial photography and satellite imagery and is composed of a series of shorter trends defined by relatively abrupt contrasts sand blow densities, shallow linear depressions, linear sand bodies, and the apparent truncation of some geomorphologic features. Although the orientation of the lineament does not correspond to mapped seismic trends in the region, its potentially seismic characteristics have led some researchers to suggest that it may be the surface expression of a fault. Initial investigations of the lineament using seismic reflection profiling, widely spaced shallow coring, and trenching techniques have produced ambiguous evidence of fault movement.

This study utilizes a dense network of sediment cores straddling a small section of the central portion of the lineament to investigate possible fault motion. Cored sediments were described in detail and used to establish stratigraphic relationships. Despite pervasive liquefaction, a distinct lateral change in subsurface deposits across the lineament is clearly expressed; however, the change cannot be conclusively attributed to offset produced by fault movement. In addition, stratigraphic relationships farther from the lineament cannot be sufficiently explained using a faulting scenario. Instead, the data more compellingly suggests that observed sedimentologic relationships, both adjacent to and away from the lineament, may be associated with fluvial processes and deposits known to occur in the region. Findings also indicate that distribution of the sand blows that define the position of the lineament in the study area may be controlled by a simple juxtaposition of sedimentologic units, rather than an intervening fault plane.