TOMASSO, MARK, School of Earth Sciences, University of Birmingham, Edgbaston, Birmingham, UK

ABSTRACT: Base-of-Slope Facies Below Perched Slope Basins: Documentation from Outcrop

The fill-and-spill development of perched slope mini-basins in the Gulf of Mexico represent a first-order control on stratigraphic architecture. Current understanding of these processes is derived from sub-surface information. The first outcrop documentation of these processes has been determined using field studies from the Lower Oligocene Annot Sandstones of SE France, where turbidite sandstones onlap onto several confining topographic slopes.

Palaeogeographic reconstructions for the western outcrops of the Annot Sandstones, using onlap geometries and restoration of structural dips, indicate a northern and a southern sub-basin, separated by an incised topographic high. From this, we can see that each sub-basin is directly analogous in both size and shape to those mini-basins on the Gulf of Mexico continental slope.

Analysis of basin fill and palaeocurrent data has allowed the relative timing of basinal filling to be determined, with the southern sub-basin filling prior to the one to the north, bypassing sediment northward. Documentation of base-of-slope facies styles in the northern sub-basin forms the next step in the progression of understanding of the fill-and-spill process.

Other authors' work on the base of continental slopes has identified the presence of 'plunge pools' where change in slope leads to a hydrodynamic jump causing erosional scouring. The aim is to identify and document this change in slope and the, different sedimentary and erosional styles associated with this. This will be coupled with analysis of classical palaeoflow data from the sandstones to examine how flow changes with movement from a restricted trough into an unrestricted basin.

This abstract is on pages 1874-1875.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid