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Book Chapter

High resolution sequence stratigraphy and depositional model

Published:
January 01, 2004

Abstract

High-frequency cycles (genetic units or parasequences), with a mean duration of 20000 years, have been identified in the Grè d'Annot turbidite system of the southern Alpine foreland basin (Late Eocene/Early Oligocene). They filled a narrow (2–8 km wide) synsedimentary syncline that formed a confined basin fed upward by a fan-delta located on a narrow shelf. These cycles are 10m thick, and each consists of a basal heterolithic component and an upper sandy homolithic unit, traceable over at least 10 km. They result from the superposition of (1) a progradational phase with an accretionary system (low-angle accretionary bedsets) and a feeder system (by-pass to high preservation oblique laminasets) and (2) an aggradational phase with a ‘spread’ system overlain by a condensed interval. The progradational phase shows very low-angle clinoforms (low-angle accretionary sets, 1–2 m high, a few tens to a few hundreds of metres long) fed by erosional structures (channels or large scours, 0.2–2 m deep, a few metres to a few tens of metres wide). The aggradational phase (subplanar laminasets, ‘scour and fill’ structures) forms a ramp, and drapes the underlying sediments. These progradational geometries may be explained by the narrow sub-basin morphology and by the transition from channelled flow (updip narrow part) to unconfined flow (downdip wider part). These genetic units directly record the variations in sedimentation rate of the feeding fan-delta on the shelf, which are controlled by the 20 000 year cycles of sea-level change.

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Geological Society, London, Special Publications

Deep-Water Sedimentation in the Alpine Basin of SE France: New perspectives on the Grès d'Annot and related systems

P. Joseph
P. Joseph
Institut Français du Pétrole, France
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S. A. Lomas
S. A. Lomas
Baker Atlas Geoscience, UK
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Geological Society of London
Volume
221
ISBN electronic:
9781862394698
Publication date:
January 01, 2004

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