Post-30-M.y. Sequence Stratigraphy, Northeastern Gulf of Mexico
Leipin He1, Nancye Dawers1, and Chuck Stelting2
1 Tulane University, New Orleans, LA
2 Chevron, Houston, TX
A comprehensive grid of oil industry seismic data is being used to develop a sequence stratigraphic framework for the northeaster Gulf of Mexico. Twenty type-1 sequence boundaries were identified. All sequences consist of highstand and lowstand tracts. Lowstand can be subdivided into early lowstand and late lowstand in some sequences. Transgressive systems tracts are not resolved seismically. Isopach maps of sequences T to A reveal that sequences are not of uniform thickness in either dip or strike directions, and depocenters are not uniformly distributed, which indicates one of the major rivers (Mississippi and Mobile) supplied more sediment than the other in certain time periods.
A total of six depositional episodes have been documented after 30 m.y. in the study area. 1) From 30 to 25.5 m.y., sedimentation rate was low and deposition occurred landward of the lower Cretaceous shelf margin. 2) Sedimentation rate increased slightly from 25.5 to 15.5 m.y., and deposition occurred both landward and seaward of the lower Cretaceous shelf margin; depocenters moved southward. 3) From 15.5 to 10.5 m.y. more deposition filled the deeper part of the basin, seaward of the lower Cretaceous shelf margin. 4) Uniform southward progradation and migration of depocenters occurred between 10.5 and 5.5 m.y.. 5) After 5.5 m.y., depocenters migrated eastward and progradation increased in the east relative to that in the west. 6) Early lowstand deposits moved from a basinal to slope setting and sedimentation rate dramatically increased after 3.8 m.y.