Van den Berg, Aaron¹, Todd Lapinski¹, Renaud Bouroullec¹, Paul Weimer¹, Veit Matt¹, John Roesink¹ 
(1) University of Colorado, Boulder, CO

ABSTRACT: Structural and Stratigraphic Evolution of Mensa/Thunder Horse Areas, Mississippi Canyon, Northeastern Deep Gulf of Mexico

A detailed analysis of the Mensa/Thunder Horse minibasins was done using 378 square miles 3-D seismic data, 9 exploration wells and biostratigraphic data. The evolution of these two minibasins, were controlled by complex salt tectonics. The geometry of the basement structures, allochthonous salt bodies and welds, major and minor faults, as well as the anticlines, have been characterized in 3D and analyzed using a tectono-stratigraphic approach. 
Three allochthonous salt systems, emplaced at the top Albian surface, Top Cretaceous surface and within the Neogene strata, are recognized and show various configurations from remnant salt pillows, horizontal salt weld and salt stock/sheet, respectively. A growth fault striking NE/SW is located northeast of the Thunder Horse field. A large NNW/SSE trending strike-slip zone is identified west of the Mensa field. 
Both turtle structures associated with the fields formed on the Top Cretaceous allochthonous salt level and inverted around 14 Ma. However, isopach maps indicate each turtle had a distinct salt withdrawal history. Mensa turtle comprises a deep bowl-shape depo-thick (24-14 Ma) overlain by a series of southward migrating depo-thicks (15.3-9 Ma), creating its asymmetric geometry. Thunder Horse turtle began as a NNW/SSE trending trough (66-14 Ma) followed by symmetric growth wedging (14-9 Ma). The growth fault located northeast of the Thunder Horse field was active between 11.4 and 9 Ma and is associated with a raft (66-20.6 Ma strata) gliding 6 miles toward the southwest. This growth fault/raft structure is used as a salt withdrawal pathway for the Neogene Thunder Horse salt sheet.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.