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Salt Cored Convergent Transfer Zone in a Listric Normal Fault System: From Example from South Timbalier Block 54, Gulf of Mexico

Bose, Shamik 1; Mitra, Shankar 1
1 ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, OK.

Passive margin settings such as the Gulf of Mexico are abundant in counter regional faults which form complex transfer zones with the regional fault systems, where the displacement from one fault is transferred to the other. South Timbalier Block 54 (ST 54) lies in the middle shelf region of the Northern Gulf of Mexico. 3D seismic data of four offshore blocks adjacent to ST 54 reveals a generally NW-SE trending convergent transfer zone between a pair of regional and counter-regional listric growth faults associated with an underlying allochthonous salt body. The master faults forming the transfer zone detach within Miocene sediments, and shallows up to the crest of the salt body within the transfer zone. The salt structure, believed to be a protruding tongue of an allochthonous salt sheet, rose to its present position by evacuation from the footwalls of the major faults into the transfer zone. The structural geometry varies as well from a symmetrical collapse crest structure at the transfer zone to an asymmetric half-graben structure away from it. The secondary synthetic and antithetic faults associated with the two master faults are principally responsible for the transfer of slip from one master fault to the other. Reconstruction of the kinematic evolution of the structure with the help of a series of cross sections across the transfer zone enables the establishment of the relationship between the growth of the faults, the salt evacuation process and the formation of the transfer zone itself, while also providing insights on the presence of a large number of counter regional faults in the Northern Gulf of Mexico.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009