Lawrence A. Amy¹, William D. McCaffrey², Ben Kneller³

(1) University of Leeds, Leeds, United Kingdom
(2) Leeds University, Leeds, United Kingdom
(3) University of California, Santa Barbara, CA

ABSTRACT: Changes in architectural style as a confined turbidite system aggrades: the Peïra Cava system, south-east France

Confined turbidite systems are an important component of many deep-water hydrocarbon provinces. Seismic studies have identified that the large-scale architecture may change as these systems aggrade. However, there are few documented field examples of such architectural development - particularly in systems with good 3D control.

The Eocene/Oligocene Grès d'Annot Formation comprises deep marine clastic sediments deposited within the Tertiary foreland basin of SE France. Deposition initially occurred in a series of linked, topographically-confined sub-basins. This study is focused upon one such sub-basin, and in particular on the architectural changes within one well correlated 700 m stratigraphic interval over a down-stream length of 10 km that preserves back/lateral slope, base-of-slope and basinal settings.

Moving up section in certain parts of the basin, three distinct architectural styles are observed: Type 1, a high net-to-gross proximal slope-related facies dominated by complex amalgamated beds and sand filled mega-scours, interpreted as the result of sedimentation close to the break-of-slope; Type 2, a low net-to-gross basinal facies composed of sand-mud couplets with few thick sand beds or thick-bedded packages, interpreted as reflecting deposition in a basinal setting away from the break-of-slope; Type 3, a moderate net-to-gross basinal facies consisting of repeated thick-bedded sand packets separated by thinner-bedded packets, interpreted as indicating either the up-stream growth of a submarine fan or the initiation of spill-over into a downstream sub-basin. This sequence may represent a general basin-filling pattern common to confined turbidite systems and identifiable at a seismic-scale.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado