Evolution of from Allochthonous Salt System, Southern Mars-Ursa Basin, Northern Gulf of Mexico

Angela Pell and Jeffrey A. Nunn
Geology and Geophysics, Louisiana State University, Baton Rouge, LA

This study examines the evolution of an allochthonous salt system in the southern Mars-Ursa basin. A seismic stratigraphic framework and biostratigraphic markers provided constraints on basin development and sediment accumulation from late Miocene to middle Pliocene time. External geometries for tectonostratigraphic packages are identified and are combined with analyses of brittle deformation to track salt evacuation in the study area. External geometries identified in the study include: wedge, layer and trough. Fifty-nine faults were mapped in basin and suprasalt strata and five phases of brittle deformation were identified. Eight evolutionary stages were identified for the time range of the study. The minibasin has previously been classified as part of a counterregional salt system. This study indicates that the minibasin has experienced phases of stepped counterregional development, quiescence and a phase of roho-style development. Thus, end-member salt system models do not accurately account for all phases of salt evacuation around the minibasin. Results indicate that salt has evacuated in multiple directions through time with a dominate phase of westward-directed salt evacuation. The salt system around the Mars-Ursa basin should be modeled in three dimensions. The basin is currently undergoing tectonic activity as the Champlain Salt undergoes reactive diapirism.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas