ABSTRACT: Upper Plio-Pleistocene Salt Tectonics, Seismic Stratigraphy, and Seismic Facies on the Continental Slope in the Mississippi Canyon Area, Gulf of Mexico

LIU, JIA-YUH, Texas A&M University, College Station, TX

Exploration for hydrocarbons has been moving to deeper waters, although the understanding of sediment distribution and characteristics in these areas is limited. We have undertaken the study of the upper Plio-Pleistocene in the Mississippi Canyon area to help clarify our understanding of these phenomena. Our study is based on 1400 line miles of 32-fold migrated data provided by CGG at water depths ranging from 450 m (NW) to 2000 m (SE). The study area covers Shell's Mars prospect (M.C. Block 763) and Conoco's discovery (M.C. Block 243). Paleontologic data from nine wells are also incorporated in the study. Preliminary results are as follows.

From Lenticulina 1 to the present, eight seismic sequences have been identified. Three sequence bases correspond to benthic foraminifera (Lenticulina 1, Angulogerina B, and Trimosina A), and one corresponds to the Y-8 ash layer (late Wisconsin). Salt generally occurs as allochthonous tongue/sheet features and occupies approximately 40% of the area at two seconds of two-way travel time below the seafloor. The areas without salt are near the "spur" and in the canyon axis, except for one diapiric structure in the canyon axis.

Time-structure maps show that salt activity lasted at least until Angulogerina B, except for one salt diapir in the canyon, which pierced late Wisconsin sediments. Isochron maps indicate that the canyon served as a major sediment conduit since Lenticulina 1. A sediment source to the northeast was also prominent during the Lenticulina 1 to Trimosina A interval.

Seismic facies mapping shows mass transport deposits, channel-levee systems, turbidity current deposits, and pelagic and hemipelagic deposits. These seismic facies are composite features that resulted from sea level changes, shifts and rates of sediment input, and salt movement.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)