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Mark Tomasso1, Hugh D. Sinclair2
(1) The University of Birmingham, Birmingham, United Kingdom
(2) The University of Edinburgh, Edinburgh, United Kingdom

Abstract: Fill-and-spill development of perched slope basins: implications from outcrop for deep-water prospectivity

The fill-and-spill development of perched slope basins in the Gulf of Mexico represent a first-order control on stratigraphic architecture. Current understanding of these processes is derived from 3D seismic surveys. This study aims to provide the first outcrop documentation of fill-and-spill processes, and so provide information at the scale of reservoir heterogeneity and seal characteristics in these settings. The outcrops presented are from the Lower Oligocene Annot Sandstones of south-east France.

Palaeogeographic reconstructions for the western outcrops of the Annot Sandstones indicate a northern and a southern sub-basin separated by a topographic high. The southern sub-basin was progressively infilled by approximately 600m of tabular, amalgamated, coarse sandstone turbidites that record flow deflection, ponding and onlap. Above these facies is an abrupt transition into offset-stacked coarse channel systems which correlate northward with a channelised incision surface into the topographic high; this incision represents the spillpoint through to the northern sub-basin. At the base of slope in the northern sub-basin, approximately 200m below the spillpoint, onlapping coarse sandstones record scouring, amalgamation, dewatering and slumping. Approximately 300m downcurrent from these base of slope deposits, the succession is tabular bedded, with mud intervals separating beds. Hence, the base-of-slope sands provide a high degree of interconnectedness with good seal potential, but are broken up by shale partitions more basinward. Having filled the northern sub-basin, both basins are blanketed firstly by thick overbank fines, and then by a 200m thick channel/sheet complex.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana