Similarities and Differences in Salt Tectonics Between the Precaspian Basin, Russia and Northern Gulf of Mexico, USA
A. Lowrie1 and E. Kozlov2
1 Consultant, Picayune, Mississippi
2 Paradigm Geophysical Co., Moscow, Russia
Petroleum exploration has proceeded sufficiently deeply into the subsurface of salt-containing basins that detailed comparative analyses can be conducted. Some underlying rules of salt interactions appear applicable to all tectonics. Basement faults, underlying the salt, may provide elevated platforms and/or greater geothermal releases from which salt can begin its buoyant ascent. Local rising geothermal and geo-chemical anomalies may also inhibit salt occurrence above the active basement fault. Thus, basement faults may enhance or hamper salt emplacement. The overall basin configuration, whether open or closed, appears to control resulting salt migration, lateral and/or vertical. Also, the ability of salt to conduct heat impacts those areas of thermal maturation and those to be by-passed.
The Precaspian Basin, north of the Caspian Sea, is at present confined. Salt tectonics is generally vertical with numerous salt wings/overhangs. Regional gravity patterns may be interpreted as an intersecting set of linear anomalies trending NW-SE and NNE-SSW. Given basin rifting along a crudely E-W swath as an originating mechanism, the NNE-SSW trend could result from transform faults perpendicular to the extrusion. The two intersecting anomaly trends could have originated from basinal compression.
The northern Gulf of Mexico, incorporating offshore Texas and Louisiana, borders an ocean basin. Salt, compressed by encroaching terrigenous sediments along the basin's margins, can "escape" laterally basinward. The extensive lateral migrations produce a complex tapestry of maturation zones.
AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004