KOLLA, V., Elf Aquitaine Petroleum, Pau, France; and M. A. PERLMUTTER, Texaco EPTD, Houston, TX

ABSTRACT: Late Continuation of Turbidite Sedimentation to the Mississippi Fan: A Need for Revision of Sequence Stratigraphic Models

Sandy turbidite sedimentation on the Mississippi Fan during the last glacio-eustatic cycle, initiated during falling and maximum relative lowstand stages of sea level, continued to be significant well into mid to late sea-level rise, until at least the Holocene, 12,000-11,000 yrs. B.P. Late continuation of sandy turbidite sedimentation is suggested by several factors: (1) landward extension of the Mississippi Canyon into mid-shelfal depths as sea level rose, (2) a major increase in glacial melt-water discharge and sediment loads (pebble to clay sizes) delivered directly to the head of the canyon by the Mississippi River during rising sea level, (3) interception of longshore drift by the canyon as it eroded landward, (4) steep gradients at the head of the canyon, favoring slumping of d pocenters and formation of turbidity currents, and (5) absence of expected coarse-grained lithologies and deltaic stratal patterns within the canyon, indicating sediment bypass into deep water. Late sand-prone turbidite sedimentation inferred for the Mississippi Fan is compatible with the occurrence of sandy turbidites in the middle Amazon Fan subsequent to 13,285 +/- 650 yrs. B.P. and significant deposition of turbidites until the Holocene elsewhere in the deep ocean. Sandy turbidite sedimentation into the mid/late rise of sea level is in contrast to idealized sequence-stratigraphic models which indicate turbidite/fan sedimentation occurs mainly during falling, maximum lowstand and early rise of sea level. Late sandy turbidite deposition will impact subsurface stratigraphic calibrations and inferences of depositional

systems and reservoir predictions. We therefore suggest existing sequence-stratigraphic models be revised to include such occurrences.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.