Abstract

Compilation of fault-line scarps and traces from existing geologic mapping and revision of the resulting compilation using remote sensing data and various aerial images revealed a complex pattern of Quaternary fault-line scarps within southwest Louisiana. Numerous, generally east-west trending, fault-line scarps form a 24 km wide east-west trending belt lying south of a line between Ville Platte, Louisiana and Kirbyville, Texas. The southern edge of it is marked by a relatively continuous set of fault-line scarps associated with the Tepetate fault zone. Numerous fault-line scarps occur between the Tepetate fault zone and the shoreline of the Gulf of Mexico. However, these fault-line scarps lack any regional pattern, and many are associated with local salt domes and growth faults. The northernmost fault-line scarps found within southwest Louisiana consist of a narrow belt of prominent east-west trending scarps within southern Rapides Parish.

Many of these Quaternary fault-line scarps are the surface expressions of known Tertiary growth faults, a number of which are associated with roll-over structures containing oil and gas fields. Such oil and gas fields were formed as the result of reactivation of the faults during the Pleistocene. The reactivation of these faults and the associated formation of these scarps represent the results of the loading of the Gulf of Mexico margin starting in Late Pliocene time. This loading has had the effect of reactivating regional fault trends such as the Tepetate fault zone and causing the renewed flowage of deep-seated salt.