Genetic units/parasequences of the Annot turbidite system, SE France
Published:January 01, 2004
François Guillocheau, Jean-Marie Quéméner, Cécile Robin, Philippe Joseph, Olivier Broucke, 2004. "Genetic units/parasequences of the Annot turbidite system, SE France", Deep-Water Sedimentation in the Alpine Basin of SE France: New perspectives on the Grès d'Annot and related systems, P. Joseph, S. A. Lomas
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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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Deep-Water Sedimentation in the Alpine Basin of SE France: New perspectives on the Grès d'Annot and related systems
The Grès d′Annot Formation of SE France constitutes a classic and outstanding example of a sand-rich turbidite system controlled by synsedimentary tectonics, and has often been used as an outcrop analogue for deep-water hydrocarbon reservoirs. Over the last 10 years, research efforts by different academic and industrial teams have led to important reappraisals of prevailing ideas on the Gres d′Annot, particularly on the nature and controlling factors of the depositional processes, the small-scale architecture and sequence organization of the deposits, the tectonic regime of the basin and its impact on palaeogeography, and the interaction between sediment gravity flows and basin-floor topography.
This volume offers a multidisciplinary overview and draws up the ′state-of-the-art′ of scientific knowledge on this influential turbidite system. Complementary aspects are covered, from structural geology, sedimentology and sequence stratigraphy, to modelling of sedimentary processes and architectures, geochemistry, reservoir characterization, seismic modelling and uses as analogues for deep-marine hydrocarbon fields.
This book will be of use to both academic researchers (geologists and geophysicists) and industry professionals dealing with the characterization and modelling of deep-water sediments.