FENG, JIANHUA, and RICHARD T. BUFFLER, Geophysical Sciences, Inst. for Geophysics, Univ. of Texas at Austin, Austin, TX

ABSTRACT: Post Mid-Cretacious Stratigraphy and Sediment Infill History, Deep Gulf of Mexico Basin

Eighteen post mid-Cretaceous seismic sequences have been defined based mainly on a pronounced depositional cyclicity in the deep Gulf of Mexico basin. Each seismic sequence is characterized by a low amplitude, variable continuity seismic facies (rapid deposition, distal lowstand systems tract deposits) capped by a regionally extensive, continuous, high amplitude reflection (sediment starvation, a regional condensed section interpreted to be the basinal equivalent of transgressive and highstand systems tract deposits present on the adjacent shelf and slope). A preliminary chronostratigraphic framework and isochron maps for each sequence allow us to document in detail a post mid-Cretaceous depositional history of the deep basin.

A backstripping study reveals that Laramide orogenic fold-thrust activities along the western flank of the basin have reshaped the western deep Gulf basin into a large foreland basin and produced an immense surge of sediments into it during the Late Cretaceous-Middle Eocene time. Isochron maps showthe rate of sediment input progressively increases in

western deep basin from Late Cretaceous to late Paleocene and starts to decrease gradually during Eocene. Major depocenters started to shift eastward at the middle Oligocene time. Accompanying development of the Mississippi drainage system, deposition of the Late Miocene-Pleistocene Mississippi Fan in the eastern Gulf was accompanied by other fan systems to the west and southwest.

The isochron maps also show that the general spatial and temporal distribution of the northwestern and southwestern deep basin depocenters is comparable with that of the major Cenozoic deltaic and paleocanyon systems along the adjacent shelf margins. Point sources have been a major form of sediment infill into the deep basin. These observations indicate that important sediment fairways must exist traversing the continental slope.

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