PALEOCHANNEL PIERCING-POINT ANALYSIS OF THE MISSOURI BOOTHEEL LINEAMENT, NEW MADRID SEISMIC ZONE

Earthquakes in the New Madrid seismic zone are associated with subsurface faulting along two northeast-trending right-lateral strike-slip zones connected by a left-stepping compressive step-over, but surface ruptures of these faults are difficult to identify. Seismic and geomorphic studies suggest that the Bootheel lineament may be a surface rupture of a fault that bypasses the central step-over in the seismic zone. However, there is no subsurface sedimentological verification of tectonic movement along the lineament. A piercing-point analysis of a paleochannel truncated by the Bootheel lineament near Hayti, Missouri, was used to test this hypothesis. The paleochannel cuts into late Pleistocene braid-stream sand and is a west-flowing distributary channel originating from an abandoned meander bend of the Mississippi River. On aerial photography, the paleochannel is visible east of the lineament but not clearly visible to the west. Core transects across the visible channel, the lineament, and the buried channel expose two channel-fill units. Distribution of the upper channel fill delineates offset paleochannel cut-bank margins both east and west of the Bootheel lineament. The lower channel fill is restricted to the west side of the lineament terminating at the Bootheel lineament and at the channel cut-bank. The paleochannel cut-bank margin is bisected at the point of intersection with the lineament, and relative locations of the paleochannel east and west of the lineament show the Bootheel lineament to be a right-lateral strike-slip fault with horizontal and vertical offset.