Deep-Water Current Deposits in from Ocean Basin Setting: Lessons from the Miocene-Pliocene of the Straits of Florida
Kelly Bergman1 and Gregor Eberli2
1Energy Technology Company, Chevron Corporation, San Ramon, CA
2Division of Geology and Geophysics, University of Miami-RSMAS, Miami, FL
The interaction of ocean currents within the narrow seaway of the Straits of Florida (SoF) has resulted in a variety of discrete deep-water geomorphic current features that include current scour, erosive discontinuities and channels, sediment waves and sediment drift deposits. The most ubiquitous of these are large-scale drift deposits, Miocene to Pliocene in age, measuring over 24,000km2 in area and up to 1000m thick. The SoF is a constricted ocean gateway and offers an ideal setting to evaluate the influence of oceanographic processes on deep-water sedimentation. Seismic facies analysis was carried out on seismic data located in the SoF. Drift deposits exhibit typical features: internal discontinuities, reflection divergence, moat development and migration toward an axis of flow; but are unique in that they form beneath surface currents. They occur in three distinct bathymetric settings: shelfal slope, seaway and downcurrent of isolated platforms. External morphologies include detached, confined and separated mounds and internally contain single or multiple centers of deposition, clinoform geometries and discontinuities. Their accumulation corresponds to the initiation and intensification of the modern Loop Current/Gulf Stream system and can be placed within a larger context of the growth of deep-water drift deposits throughout the North Atlantic basin since the Oligocene corresponding to the establishment of the western boundary current circulation in the North Atlantic. As suggested by drifts in the SoF and North Atlantic, the distribution of drifts in large ocean basins are related to the current circulation pathway associated with major circulation gyres. Consequently, drift deposits may also be more common during periods in geologic time when continental distribution allowed for the establishment of major circulation gyres as in the Late Cenozoic.
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