Intimate Relationships: Growth Faulting and Diapirism in South Louisiana: ABSTRACT

Data published during the recent past have improved understanding of initiation of salt and shale diapirism and of growth faulting on the central Gulf continental slope. Growth faults appear on diapir flanks during initial development, as well as along upper-slope depocenter flanks and the continental shelf edge. Rapid deposition, differential loading and subsidence on the upper slope and outer shelf enhances segmentation of salt ridge or massifs into individual diapiric spines, causing additional diapir-related growth faulting. Most growth faults originating on the slope remain active and, projected upward 5,000-20,000 ft, provide the structural framework within which south Louisiana petroleum exploration takes place. Study of 31 piercement and 19 semipiercement salt domes plus 117 nonpiercement domes formed by salt and/or shale diapirs reveals important growth fault variations genetically related to diapiric structure type. Fault patterns associated with piercement and semipiercement salt domes are different and more complex than those on nonpiercement features. Counter-regional faults, commonly in compensating or crossing patterns, are far more common; fault splitting and crestal grabens are particularly common on semipiercement structures. Local growth faults related to differing flank subsidence rates around high-relief diapirs play a major role on these structures. In contrast, fault patterns are less complex on nonpiercement diapiric structures. Counter-regional faults, compensating and cross ng systems and splitting are less common; most major faults appear to be regional growth faults only indirectly related to diapir development. Implications for additional deep exploration diapiric structures exist. End_of_Article - Last_Page 254------------