Erosion of the Florida Escarpment: Eastern Gulf of Mexico

David Cushman Twichell, University of Rhode Island

Abstract

The Florida Escarpment is a steep carbonate cliff that separates the shallow Florida Platform carbonate province from the deep terrigenous abyssal plain of the Gulf of Mexico. This platform edge has undergone erosion since initial construction during the Mesozoic. Seabeam bathymetry and GLORIA sidescan sonar data are used to define the types of erosion that have shaped this escarpment.^ The escarpment's morphology reflects these different erosional styles. North of 27$\sp\circ$N, it is covered by Cenozoic sediments that are incised by shallow ravines. South of 27$\sp\circ$N, Mesozoic limestone is exposed and is deeply incised by large box canyons. These canyons occur off two basins that underly the western Florida Platform. Offshore of the intervening arches, the escarpment is sculpted by ravines or is terraced along its lower part.^ Deposits along the base of the escarpment show an interplay of terrigenous fan deposits and carbonate deposits. The Mississippi Fan sediments comprise large slides and smaller trubidites or debris flows that create a laterally discontinuous facies. Off the northern part of the escarpment, carbonate gravity flows originating from the ravines form a thin continuous sheet that interfingers with the fan deposits. Erosion of the escarpment is not continuous south of 27$\sp\circ$N, as talus deposits, consisting of Mesozoic limestone, are found only at the heads of the box canyons.^ The different erosional styles appear to be surficial expressions of differences in the geology and/or hydrology of the platform itself. Erosion of the northern part is by the external processes of mass wasting and is limited to the Cenozoic sediment cover. Along the southern part, ground water sapping may play an important roll in the erosion. Undercutting of the cliff by sapping allows exfoliation, rockfall processes, or grain by grain removal to occur. The steep cliffs at the heads of the box canyons are sites where ground water sapping and exfoliation are the dominant process, while the presence of terraces elsewhere along the escarpment suggests that differential weathering of rocks of different lithologies may be the dominant process. The varied erosional styles of this escarpment are best explained by differences in lithology and permeability of the rocks of the basins and arches underlying the platform. ^

Subject Area

Geology

Recommended Citation

David Cushman Twichell, "Erosion of the Florida Escarpment: Eastern Gulf of Mexico" (1988). Dissertations and Master's Theses (Campus Access). Paper AAI8903072.
http://digitalcommons.uri.edu/dissertations/AAI8903072

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