Evolution of Late Cenozoic Minibasins and Growth Faulting, Green Canyon Area, Northwestern Gulf of Mexico
Akhun, Selin Deniz 1984-
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The northern margin of the Gulf of Mexico has a complex geologic history involving growth faulting, the emplacement of allochthonous salt bodies and the evolution of small-scale Neogene depocenters overlying the mobile salt bodies (called ‘minibasins’). My study area is located in the northwestern Gulf of Mexico and lies along the continental shelf edge. The presence of salt welds on many seismic profiles indicates that high rates of sedimentation during the Pliocene and Pleistocene likely caused mobilization and complete evacuation of an allochthonous Miocene salt sheet. This movement is interpreted to have caused the formation of minibasins overlying the salt and many basinward-dipping growth faults in the study area. I interpreted faults, salt structures and sedimentary rocks using high resolution seismic reflection data covering an area of 2,800 km2 in the northwestern Gulf of Mexico. Throw-depth plots are created to clarify the growth history of selected faults. Time-structure maps were generated to understand salt-sediment-fault kinematic interaction. Finally, isopach maps were generated to understand the effect of faulting and salt movement in sediment thickness. Three different fault families have been identified: (1) basinward-dipping growth faults family, (2) landward-dipping growth faults, and the (3) radial faults located within the sediments overlying rising salt diapirs. The observation that most of the faults sole into a salt structure implies that the kinematics of faulting and salt movement are linked. For basin-bounding faults, I suggest that these faults formed in response to the salt flowage away from the center of the minibasin and that this flowage has led to syn-depositional, minibasin subsidence. Time-structure maps indicate the presence of fault linkages and relay ramps along normal faults in the northern part of the study area which means that these faults are soft-linked and that they act as a system. Interpreted seismic sections and time-structure maps show that salt flows both laterally or downdip so does not exhibit a primary flow direction. I conclude that the gentle slope of the continental shelf slope initiated salt flowage but sedimentary loading keeps the fault system active and is also the primary cause controlling salt evacuation in the study area.