Shallow structure, stratigraphy, and carbonate sedimentary processes of West Florida upper continental slope

Journal Article · Mon Jul 01 04:00:00 EDT 1985 · AAPG Bull. (See CODEN: AAPGB); (United States)

OSTI ID:6406572

Doyle, L J; Holmes, C W

An extensive minisparker, 3.5-kHz, piston-coring survey of the continental slope above the West Florida Escarpment has revealed a Pleistocene sequence of up to 160-msec twoway traveltime, overlying a second, probably Miocene, strong reflector. South of 2720'N the contact between the two is clearly an erosional unconformity and includes a band of karstlike features. The Pleistocene drape thins to a minimum, locally even exposing the second layer, at about 500 m (1,650 ft) water depth and thickens dramatically downslope. We attribute this thinning to the north-south flowing Loop current blocking deposition and scouring the bottom. The ancestral Loop may have been responsible for an erosional unconformity, or it could have been due to subaerial erosion. If the latter is the case, present depth of the erosional surface suggests as much as 400 m (1,320 ft) of subsidence after its formation. From its southern limit to 2640'N, two parallel reefs mark the upper slope. Sediments on the upper slope are a foraminifera-coccolith ooze, the compositional equivalent of a chalk deposit. Radiocarbon dating shows ooze below the erosional minimum accumulating at over 30 cm/1,000 years (11.8 in./1,000 years) for at least 25,000 years--a surprisingly high rate--over an order of magnitude greater than that for a compositionally equivalent deep-sea ooze. High sedimentation rates are also reflected in a variety of mass wasting features from creep to massive slides to gravity-induced folds tens of kilometers long. The upper west Florida slope is only a temporary resting place for sediments that are moved downslope by mass wasting processes to the West Florida Escarpment.

• Research Organization: University of South Florida, Department of Marine Science, St. Petersburg, FL
• OSTI ID: 6406572
• Journal Information: AAPG Bull. (See CODEN: AAPGB); (United States), Journal Name: AAPG Bull. (See CODEN: AAPGB); (United States) Vol. 69:7; ISSN AABUD
• Country of Publication: United States
• Language: English

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