Surface faults of the south Louisiana growth-fault province

Abstract

Prior to the early 1990s, nearly all surface faults recognized in south Louisiana were faults of the Baton Rouge system. Since then, the number of surface fault traces interpreted in the region has increased dramatically, owing to a combination of (1) application of traditional analysis of cues on topographic maps and aerial- photographic imagery over increasingly large areas, particularly in southwest Louisiana, (2) the employment of geophysical surveying techniques in the Holocene delta plain where surface scarp relief is negligible, and (3) the advent of light detection and ranging (LiDAR) digital elevation models (DEMs). Like faults of the Baton Rouge system, newly recognized surface faults of the Tepetate system show distinctive depth-displacement relations in Quaternary and pre-Quaternary strata indicating that they are active and are the surface expressions of deep-subsurface older Cenozoic growth faults that have been reactivated following extended periods of quiescence. The differential displacement of older relative to younger Pleistocene terrace surfaces characteristic of individual Tepetate–Baton Rouge system faults also characterizes surface faults of the other systems, suggesting they may share similar movement histories. Commonplace recognition of active surface faults throughout south Louisiana now suggests that many of the known deep-subsurface growth-fault systems have surface expression reflecting their reactivation in the late Cenozoic. The recently amplified picture of surface faulting in this region highlights an important aspect of coastal tectonics in the northern Gulf of Mexico setting, and can provide useful constraints for modeling tectonics in this and other coastal settings characterized by reactivation of growth faults following lengthy intervals of quiescence.