HANNAN, ANDREW E., NORMAN E. BILES, and GEORGE A. JAMIESON, Schlumberger Geco-Prakla, Houston, TX

Abstract: Late Miocene Mississippi Fan Fold Belt Effect on Deepwater Deposition in the Atwater Valley Area

The Mississippi Fan Fold Belt is located in abyssal water depth offshore Louisiana in front of the Sigsbee Escarpment. The northeast trending Fold Belt is characterized by steeply dipping asymmetrical, basinward, thrusting anticlines and associated overthrust faults from the northwest. Isopach map of regional seismic data indicates Late Miocene thinning over the Fold Belt.

Deepwater slope fan sediments were deposited just to the north of the Mississippi Fan Fold Belt in a salt withdrawal basin that contains the Late Miocene to Pliocene Mars and Ursa Fields in the Mississippi Canyon Area. Late Miocene and Pliocene sands are not present in the Atwater Valley Block 471 Shell #1 well on the crest of one of the Fold Belt structures. Seismic data tied to regional well control indicates possibly sand rich Late Miocene and Pliocene section onlaps the north flank of the Fold Belt. Thick wedges of Late Miocene to Pliocene section with possible hydrocarbon indicators occur on the north flank of the Fold Belt. The section is thin on the crest of the Fold Belt. There may have been some topographic relief on the Fold Belt during Late Miocene and Pliocene that was a barrier to deposition for sediments coming down the Louisiana slope from the north. There is an isopach thin to the south of the Fold Belt that would have been in the shadow of the topographic high. 

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana