SWLGS Luncheon Topics
Updated Nov. 4, 2008
Nov 11, 2008
Evolution of an Allochthonous Salt System, Southern MArs-URSA Basin, Northern Gulf of Mexico
By Angela Pell and Jeffrey A. Nunn, Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA
Seismic data from TGS and well data and biostratigraphic markers from Shell provide constraints on basin development and sediment accumulation in the southern Mars-Ursa basin, Northern Gulf of Mexico, from late Miocene to middle Pliocene time. External geometries of tectonostratigraphic packages are identified and combined with analyses of brittle deformation to track salt evacuation in the study area. External geometries identified in the study area 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 from late Miocene to middle Pliocene time. 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, a single end-member salt system model does 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 unde rgoes reactive diapirism.
Jeffrey Nunn is currently the Ernest and Alice Neal Professor of Geology and Geology and Geophysics Department Chair at Lousiana State University, Baton Rouge. He has taught at LSU since 1981. His interests range from heat flow, subsurface fluid flow associated with faults to near surface imaging of the subsurface. Education includes a BS Amherst College and MS, PhD from Northwestern University, Chicago, IL.