Secondary Basins and Sediment Pathways in Green Canyon, Deepwater Gulf of Mexico

Moore, Vernon; Hinton, Doug

Regional WAZ RTM seismic calibrated to well data has been interpreted to investigate the distribution and depositional history of secondary basins across the Green Canyon protraction area, deepwater Gulf of Mexico. Where well control is limited, relative ages were interpreted based on proximity to seafloor, structural style, and relationships in the growth stratigraphy. A variety of structural styles are observed in the secondary basins: 1) basins welded on top of the primary basin section; 2) basins that have subsided into a salt feeder, some extending down to the autochthonous salt level (aka "bucket weld" basins); 3) basins encased in salt; 4) stacked basins separated by a weld or salt; 5) expulsion roll-over basins; and 6) basins with highly asymmetric growth stratigraphy. Top and base of salt, salt welds, and the top primary basin surface were utilized to generate accurate gross isochore maps in complex areas near salt feeders, significant salt overhangs, multiple salt welds, and stacked basins. Isochore maps indicate that secondary basin deposition began in the early Middle Miocene, forming a NE-SW trending arc across the Green Canyon protraction area. This trend was further in-filled with new basins during the Late Miocene. In general, Miocene basins are relatively symmetrical and were prone to becoming partially or fully encased by salt. During the Pliocene, the existing basins aggraded while new basins were deposited by in-filling both up-slope and down-slope of the earlier Miocene basin trend. In the Pleistocene, deposition of new basins occurred down-slope of the Plio-Miocene basins, resulting in the inflation of the salt canopy towards the southeast. It is common for the Plio-Pleistocene basins to be highly asymmetric, to prograde to form expulsion roll-overs, or form "bucket weld" basins over 25,000' thick. Sediment pathways evolve from broad corridors in the primary basins between salt feeders and walls during the Early Miocene to narrower pathways between both primary and secondary basins during the Miocene, and finally to secondary basin-to-secondary basin routes during the Plio-Pleistocene.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013