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Submarine canyon and slope sedimentation ( Grès d'Annot) in the French Maritime Alps

Abstract : The Annot Sandstone Formation, a thick marine sequence of Uppermost Eocene te Lower Oligocene age in the Maritime Alps of France and Italy, presents remarkably well -exposed massive sandstone, pebbly sandstone and pebbly mudstone sequences associated with the more classic alternating sandstone turbidite-shale flysch facies associated with this formation. The purpose of this presentation is to review the salient characteristics of these coarse , shoe-string bodies interpreted as submarine valley deposits, and to examine details of channel (including submarine canyon) fill, submarine valley wall, intervalley slope and submarine fan lithofacies. The interrelation of these facies in space and time is observed , and an interpretation is made of the dominant processes responsible for the transport of sediment from basin margins ta deeper environments. A bathyal depth is indicated by ichnofossil assemblages and additional sedimentological evidence. Formulation of a submarine canyon sedimentation model, based in part on studies in modern canyons, is made using as example the channelized sandflow and related deposits at the Annot, Contes and Menton localities. In contrast, facies observed in the more distal localities to the north (Lac d 'Allos, Peïra-Cava and Sospel regions) display fewer and thinner massive units and a higher proportion of turbidites and shales; these sequences are interpreted in terrns of the now reasonably well-defined submarine fan sedimentation models. Exarnples of both inner and more distal outer fan facies are distinguished. Mapping of the canyon to fan transition provides greater precision to the Annot Basin paleogeographie interpretations. Furtherrnore, these channel deposits, unusual in the sense that *they-can be traced so clearly laterally along paleoslopes afford a rare opportunity te observe the downslope transforrnation of subaqueous flow mechanisms (i.e., slump, debris flow and diverse sand flow processes including grain/fluidized and turbidity currents). The massive sandstone units of Annot Sandstone examined here are designated as a type example of the submarine canyon-fan valley continuum.
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  • HAL Id : insu-00684561, version 1

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Daniel Jean Stanley. Submarine canyon and slope sedimentation ( Grès d'Annot) in the French Maritime Alps. 1975. ⟨insu-00684561⟩

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