Axial incision: The key to understand submarine canyon evolution (in the western Gulf of Lion)

Type Article
Date 2005-06
Language English
Author(s) Baztan Juan1, 2, Berne Serge2, Olivet Jean-Louis2, Rabineau MarinaORCID2, 5, Aslanian DanielORCID2, Gaudin Mathieu2, 3, Rehault Jean Pierre1, 2, Canals M4
Affiliation(s) 1 : Univ Bretagne Occidentale, UMR 6538, IUEM Domaines Ocean, F-29280 Plouzane, France.
2 : IFREMER, DRO GM, F-29280 Plouzane, France.
3 : Univ Bordeaux 1, Dept Geol & Oceanog, UMR 5805, F-33405 Talence, France.
4 : Univ Barcelona, GRC Geosci Marines, Barcelona S-08028, France.
Source Marine And Petroleum Geology (0264-8172) (Elsevier Sci Ltd), 2005-06 , Vol. 22 , N. 6-7 , P. 805-826
DOI 10.1016/j.marpetgeo.2005.03.011
WOS© Times Cited 84
Keyword(s) submarine canyon, axial incision, Gulf of Lion
Abstract A detailed morphological analysis of the outer shelf and continental slope of the Western Gulf of Lion is presented, based on swath bathymetry data together with sub-bottom profiles and high resolution seismic reflection profiles. These data reveal two main erosive features, of very different dimensions: the axial incision and the canyon's major valley. The height of axial incisions' flanks with respect to the canyon deepest point (the thalweg) ranges from 40 to 150 m. It creates a small axial erosive path within the canyon's major valley, which is typically bounded by flanks of more than 700 m in height. We interpret the axial incision observed in the sea floor as the imprint of turbidity currents that eroded the floor of canyons during phases of connection to rivers (hyperpycnal turbidity current). Such currents are most likely to have formed during the Last Glacial Maximum (LGM) as both proximity of the shoreline (due to the lowstand of sea level) and high detrital sediment supply (due to glacial abrasion upstream) increased the flow of sediments delivered to the canyon heads. Fossil axial incisions, observed in seismic lines, are related to equivalent conditions. The axial incision, however, has a key influence on canyon evolution as it triggers mass wasting of different sizes that affect the canyon's major valley (head and flanks). We interpret the geometry of the canyon's major valley as the result of recurrent activity of axial incisions. These periods of activity occurred during low sea levels at glacial maxima and show a cyclicity of 100,000 years for the last 400,000 years.
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