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Geomorphology and Controls on Carbonate Slope Sedimentation Along the Florida Escarpment


Megabreccia development within the Hernando dataset represents a world-class example of a carbonate slope system. This study documents an integrated structural and sedimentological interpretationof megabreccia heterogeneity on the West Florida shelf margin and associated slope relationship to internal carbonate platform evolution and structural heterogeneity. The high-quality 2010 Hernando 3D seismic volume was used to study the Cretaceous to Recent platform to basin evolution. Stratigraphic surfaces and faults were systematically mapped through the shelf margin portion of the seismic volume. This presentation will highlight the structural features, sedimentological deformation, and slope sedimentation formed in association with the gravitational collapse of the margin. Breccia geometry varies across the margin with examined controls being style of faulting (e.g. involvement of basement faults or not), present day slope angle, and predicted lithology. Three type areas were selected to test these controls on slope sedimentation. In addition, grain-rich versus mud-rich proportions are difficult to determine, but amplitude reflection suggests large blocks of carbonate breccia encased by mud-rich sediment. Timing of the collapse and associated debris appears to be post Mid-Cenomanian and pre-Miocene possibly associated with the Mid-Cenomanian unconformity. Characterization of the debris breccia and fault style has been defined in three areas: Area 1 is located near DeSoto Canyon where significant clastic sedimentation is present at the base of the slope;Area 2 is near the central part of survey where basement offset is higher and slope escarpment angle is steep; and Area 3 located on the eastern edge of survey where the escarpment angle is low and basement offset is diminished. Key observations from Area 1include the slope sediments are cut by incised valleys, the margin is supported by sediment onlap and the canyons cutting the slope are regularily spaced, likely controlled by the high frequency of shelf –margin faults. Key observations from Area 2 include the steep escarpment angle, presence ofunderlying basement faulting and the development of large (up to sq km in size) fault blocks shedding down the escarpment. Key observations in Area 3 are the sediments are dominated by large slumps of varying lithology, breccia bodies, and smaller blocks. The escarpment angle is lower than Area 2 and the rugosity is reduced.