Sediment Distribution and Architecture Around from Intra-Basinal Structure - From Example from the Eastern Champsaur Basin, Annot Turbidite System, SE France

Jamie Vinnels, Bill McCaffrey, and Rob Butler
School of Earth and Environment, University of Leeds, Leeds, United Kingdom

Tectonically segmented turbidite basins can deflect or confine flows and pond sediment, controlling turbidite deposition and/or remobilisation. This has implications for the architecture of the basin fill, and may also influence sediment supply to downstream turbidite basins. Presented here is an outcrop case study from the Eastern Champsaur Basin which describes how intra-basinal bathymetry within a turbidite sub-basin controlled spatial and temporal flow behaviors, which have in turn driven quantifiable variations in sediment distribution patterns.

Within the Eastern Champsaur Basin is a well exposed onlap surface onto which a series of sheet-sandstone bodies were emplaced. These sandbodies are internally complex and are characterised by through-going turbidity current events, those that are most likely contained within the basin, and those that interact and entrain material from bounding slopes. Presented is a reconstruction of the bathymetric template of the Eastern Champsaur Basin prior to turbidite deposition, and the extent to which successive onlapping turbidity currents were controlled by this bathymetry, and what, if any, subsequent remobilisation the resulting deposits underwent, i.e. slumping or entrainment into later flows. Both facies and hence net to gross variations are observed in association with an intra-basinal high, which is thought to have contained flows upstream (SE), allowing a relatively finer fraction of the flow to be striped downstream (NW).

This study has application in aiding the understanding of sand emplacement processes at the fringes of turbidite basins, in particular in defining the genesis of stratigraphic trap architectures.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas