Variations in the styles of erosion along the Florida Escarpment, eastern Gulf of Mexico

GLORIA sidescan sonographs and Seabeam bathymetric data show morphological differences along the Florida Escarpment which reflect that different erosional styles have been active along different parts of this carbonate platform edge. The northern half of the escarpment is cut by numerous small ravines spaced 1-5 km apart. Its southern half is deeply incised by large box canyons that have flat floors and steep headwalls. The northern half of the escarpment is covered by Cenozoic-aged sediments, and erosion appears to be limited to this Cenozoic cover. An apron of this eroded material is accumulating along the base of this half of the escarpment, extending as much as 30 km from its base. South of 27??N, active erosion of older strata of the escarpment is shown by talus deposits of Lower Cretaceous limestone that occur at the heads of box canyons. The box canyons are not evenly distributed, but instead are most abundant where two basins that underlie the Florida Platform intersect the escarpment. Pleistocene-aged sediments eroded from the slope above the escarpment are funnelled through small valleys into the heads of the box canyons. The smooth headwalls of the box canyons suggest that downslope transport of the material from the slope above the escarpment does little to erode the escarpment. Instead, erosion triggered by dissolution of the carbonate rocks by acidic brines that seep out of the escarpment is the proposed mechanism of escarpment retreat. The concentration of the erosion at the heads of the box canyons may indicate sites where the platform rocks are more intensely fractured, thus enhancing permeability and flow of brines. The concentration of box canyons in the escarpment sections adjacent to sedimentary basins beneath the platform may reflect regional differences in the geology and hydrology of the platform. ?? 1990.