Gerald J. Kuecher¹, Harry H. Roberts²
(1) Baker Atlas Geoscience, Spring, TX
(2) Coastal Studies Institute, Louisiana State University, Baton Rouge, LA

Abstract: Seismic, electromagnetic, subsidence, and biozonation evidence for active growth faults in South Louisiana

This study examines strong evidence for active growth faults in south Louisiana and the implications of these findings for vertical fluid flow and compartmentalization models in similar terranes.

Two sub-parallel growth fault systems, namely the Golden Meadow and the Lake Hatch Fault, were seismically mapped in Terrbonne Parish, Louisiana. These fault systems commonly produce turbid lakes or swamps on the fault’s downthrown block and radiocarbon-determined rates of subsidence grater on the downthrown rather than the corresponding upthrown block. In addition, vegetation biozones typical for saline, intermediate, and freshwater marsh were found to be limited by the location of these subcropping faults.

These faults were surveyed by electromagnetics in order to obtain conductivity profiles in numerous locations along each fault. Positive, spatially restricted conductivity spikes were encountered in several traverses, indicating currently active regions of these faults while traverses across these faults marked by no such conductivity spike were considered presently inactive.

These findings indicate active growth faults actively vent subsurface (in this case, saline) fluids, thus providing accommodation space for continued downward movement. Conversely, areas along growth faults not considered to be active do not vent fluids. In this way, downthrown blocks consist of subsiding terranes that alternate between active and inactive status.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana