Shelf to Basin Evolution of Small Sandy Turbidite Systems Deposited off East Corsica Margin (Western Mediterranean)
Bruno Savoye1, Mark E. Deptuck2, Caroline Labaune1, David J. Piper3, and Anne Gervais4
1Marine Geosciences, Ifremer, Plouzané, France
2Dalhousie University, Halifax, NS, Canada
3Geological Survey of Canada Atlantic, Dartmouth, NS, Canada
4EPOC, Bordeaux 1 University, Bordeaux, France
Although, some fossil small turbidite systems have a great economic potential as oil and gas reservoirs, analog modern systems have received relatively little attention, compared to large muddy deep-sea fans (Mississippi, Congo, Amazon).
HR bathymetric mapping combined with 3.5 kHz echosounding and seismic profiles analysis allowed to precisely outline, along the East Corsican margin, a series of modern small fans of varying sizes (5 km to 30 km in length and width), some of them coalescing.
The island of Corsica is rugged and mountainous with a maximum height of 2700 m. Several small, high-gradient rivers transport coarse sand to fine silt and clay on the eastern side of Corsica. They feed a 5 to 25 km wide continental shelf (Stanley et al., 1980; Gervais, 2002). East of the shelf-break (at 110 m water depth), a narrow slope with an average gradient of 2-3° defines the western margin of a relatively shallow (<900 m), elongate (up to 150 km) and narrow (<50 km) fault-bounded depression. This slope is incised by several slightly sinuous canyons, that root on the shelf edge. Named the Corsican Trough, the basin is deepening and widening to the south. The eastern side of the trough is steep (3.5 to 7.5°), but the lack of canyons suggests that most of the recent sediment was derived from Corsica.
A close-spaced grid of high resolution and very high resolution seismic lines were acquired on the area in 1997, 1998 and 2001, using a 10 c.i. air-gun, a sparker and a boomer. They show a succession of “suprafan” like bodies that prograde into the basin. Thanks to the close-spaced grid of seismic lines and to cores, we are able to map in three-dimensions the different sedimentary bodies and to describe progradation and retrogradation cycles linked to relative sea-level variations and lowstand delta bodies growth.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas