Classification and Stratigraphic Succession of Seismic Facies in Intraslope Basins, Deep Water Gulf of Mexico, USA

Bradford E. Prather, James R. Booth, Gary S. Steffens, Peter A. Craig

Seismic facies analysis is the primary tool for understanding the stratigraphic evolution of salt-floored intraslope basins in the deep-water Gulf of Mexico (GOM). Seismic parameters used in this scheme to classify seismic facies include, (1) bounding surface type, (2) external geometry of surface-bounded seismic facies, (3) event geometry internal to bounding surfaces, (4) seismic reflectivity and (5) event continuity.

Seismic facies analysis shows that most of the intraslope basins have undergone a transition from an early laterally confined (ponded) basin-fill to a later less laterally confined (bypass) fill. The assemblage of seismic facies that characterizes the ponded fill consists of repetitive successions of complete to top-absent convergent-baselapping facies overlain by localized chaotic facies and draping facies. The assemblage of seismic facies that characterizes the bypass fill consists of repetitive successions of complete to base-absent convergent-baselapping facies overlain by convergent-thinning facies and draping facies with widespread chaotic facies. The transition from "ponded" to "bypass" facies assemblages can be sharp or gradational over hundreds of meters. The majority of tran itions occurred in the Late Pliocene between 2.0 and 1.8 Ma, and in the early Pleistocene between 1.2 and 1.0 Ma.

Upward transition from ponded facies assemblages to bypass facies assemblages suggests that the early ponded basins aggrade to a profile of equilibrium. Nearly synchronous periods of transition throughout GOM upper-slope basins suggest that sediment supply resulting from a low-order sea level fall and onset of North American glaciation is the primary control on development of this large-scale stratigraphic architecture.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995