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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 4. (April)

First Page: 471

Last Page: 471

Title: Shallow Structure and Carbonate Sedimentation of West Florida Upper Continental Slope: ABSTRACT

Author(s): Larry J. Doyle, Charles W. Holmes


An extensive mini-sparker (3.5 kHz) and piston-coring survey of the continental slope above the West Florida Escarpment has revealed a Pleistocene sequence up to 160-msec (2-way travel time) thick overlying a second strong reflector of either Pliocene or Miocene age. South of 27°20^primeN, the contact between the two is clearly erosional and includes a band of karst features. The Pleistocene drape thins to a minimum, in some places exposing the second layer, at about 525 m (1,725 ft) water depth, and then thickens dramatically downslope. We attribute this thinning to the north-south-flowing Loop Current blocking deposition and scouring the bottom. Present depth of the erosional surface suggests as much as 400 m (1,300 ft) of subsidence after its formation.

Two parallel reefs mark the upper slope from its southern limit to 26°40^primeN. Sediments on the upper slope are a foraminifera-coccolith ooze, the compositional equivalent of a chalk deposit. Radiocarbon dating indicates that ooze below the erosional minimum accumulated at more than 60 cm/1,000 years (24 in./1,000 years) for at least the last 25,000 years, a surprisingly high rate. High sedimentation rates are also reflected in a wide variety of mass-wasting features from creep to massive slides to gravity-induced folds tens of kilometers long.

Fan deposits have formed at the foot of the continental slope off the southwestern corner of the west Florida margin. Orientation of sandwave fields on the outermost shelf suggests that offbank transport combined with high slope sedimentation rates and subsequent mass wasting have provided material for these deposits.

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