The Interaction Between Accommodation Space and Sediment Supply on Depositional Fill Patterns within the Greater Mars Basin, Deep Water Gulf of Mexico, USA

Michael J. Mahaffie, Robert S. Barnard, John W. Kendrick, Larry B. Franceware

The interaction between available accommodation space and sediment supply represent a leading factor controlling the deposition and preservation of turbidite systems within the salt mini-basin setting of the Gulf of Mexico. Stratigraphic studies within the Greater Mars Basin have led to the recognition of two stages of deposition, related to interaction between accommodation space and sediment supply, associated with salt and basin evolution: (1) an early ponded interval composed of vertically stacked, deep water fan complexes, and (2) a later bypass setting comprising a mixed-energy assemblage of overlapping and partially dissected fan systems and associated channels.

These early ponded sequences are characterized by sufficient accommodation space, owing in part to rapid subsidence as deep salt underlying the basin floor is evacuated due to the sediment load. As basin equilibrium is established with respect to the underlying mobile salt substrate, the rate of subsidence decreases resulting in a gradual filling of the basin bathymetry. The reduction in available accommodation space leads to a departure from the vertically stacked, laterally continuous turbidite fan deposition towards a compensational stacking pattern accompanied with fan dissection as local baselevel conditions are reached. This pattern of fill continues until all remaining space is eliminated. Once this occurs, either turbidite systems bypass the basin completely, or erosion in the form of discrete channels or large-scale channel valleys occurs. Later modifications in basin morphology due to salt remobilization and/or sediment compaction result in a repetitive cycle of abbreviated ponded to bypass conditions.

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