A S-N Paleogene Progradational Stratigraphic Wedge, Walker Ridge, and Its Implication in Depositional History of Deepwater GOM

A south-north progradational stratigraphic geometry is identified on a pre-stack depth migration seismic survey in the Walker Ridge area (around Block 842). The well defined, northernly prograding package is bounded above by Upper Oligocene and below by Upper Paleocene, and has a thickness of >7,000 feet and duration of ~30.0 m.y. (second order depositional cycle). Both boundaries display clinoform geometries and erosional characteristics. The Upper Paleocene boundary illustrates onlap and downlap of overlying strata. Offlap of underlying strata below Upper Oligocene boundary is also recognized. Although some authors revealed a northern thinning Lower Tertiary wedge existing in the adjacent Lund area, they were unable to address the stratigraphic stacking patterns within the wedge. The northward prograding clinoforms suggest that the sediment in this area was transported from the Yucatan platform in the south during the Lower Tertiary time. Previous authors have indicated that sediments were derived from the Laramide uplands located in the north, northwest, and west of Gulf of Mexico. Some areas, like Walker Ridge and Keathley Canyon, in the deep water Gulf of Mexico were designated by previous authors as sediment starved or non-deposition during the Paleogene time. However, this study indicates that the sedimentation rate (without decompaction) from Eocene to Oligocene in the Walker Ridge area can reach as high as 230 feet per m.y..