Understanding how the fill of bathymetrically complex turbitlite basins evolves, particularly g'auging the extent to which different length scales of bathymetric control are expressed within turbidite basin fills, is a key challenge. The interaction of turbidite systems with their substrate is examined using two complementary datasets; one from outcrops of the Tertiary Annot and Champsaur Turbidite Systems, and one from the modem turbidite systems of the SimI Accretionary Prism, with a view to understanding the extent to which the architectural expression ofthe basin fill represents the composite influence oflocal- and regional-scale slope interactions. Within the Eocene to Oligocene deposits of the Alpine Foreland Basin are a series of turbidite basins, whose development were influenced by early uplift of the Alpine foreland, and which contain spatially complex turbidite basin fills. Presented here is an outcrop case study from the Eastern and Western Champsaur Basins, found today in the Ecrins region of SE France, and separated by the Selle Fault Zone. These basins record the deposition ofdeep-water sediments onto the fringes of the ancestral Pelvoux Massif, itself deformed by local early Alpine-related fold and thrust structures. Within the Eastern Champsaur Basin, sediment facies and architecture are observed to vary systematically around an intra-basinal high, (the bathymetric expression of an early Alpine structure), which is interpreted to have partially contained the turbidity currents, allowing a relatively finer fraction of the flow to be stripped downstream, to the NW. Although the distal preserved remnants of the Eastern Champsaur Basin are truncated by the Selle Fault Zone, the sedimentology of the truncated basin fill suggests that turbidity currents were flowing over and beyond this structure. Within the easternmost part of the Western Champsaur Basin is a NE-feeding submarine channel, structurally truncated in its distal-most preserved section by the Selle Fault. Its form and internal architecture suggest it probably connected to deeper bathymetric levels towards the NE when active, and was therefore likely to have been of greater axial extent than its preserved dimensions. The Selle Fault is interpreted to have separated the volcaniclastic Western Champsaur Basin and the siliciclastic Eastern Champsaur Basin. Thus both the Western and Eastern Champsaur Basins are inferred to have originally been connected to deeper bathymetric levels towards the N or NW, suggesting that the ancestral Pelvoux Massif did not form a significant bathymetric barrier. The SimI Accretionary Prism and adjacent areas are fed by rivers that drain from volcanic Andean terranes which source large volumes of sediment to the Colombian Shelf into the Colombian Basin. Several basin filling styles are recognised, with ~avity current-dominated basins characterised by channel- and sheet-form architecture and hemipelagic dominated fills. Mass wasting-dominated basin fills show evidence both of localised fold-induced degradation, and also are affected by more regional-scale shelf collapse. This collapse is also responsible for the creation of local depocentres into which sediment subsequently accumulates. Both local and regional length scales of bathymetric control are evident within the intraslope basins of the SimI Accretionary Prism, which suggest that both local- and regional scale influences can occur in isolation, or co-exist, within a single part ofa submarine slope system. This study has direct application in aiding the understanding of sand emplacement processes at the fringes of turbidite basins, in particular in defining the genesis of stratigraphic trap geometries, and understanding the length scales of bathymetric control on the composite architecture ofturbidite system basin fills.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:490848 |
| Date | January 2008 |
| Creators | Vinnels, Jamie Simon |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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