A walk down the Cap de Creus canyon, Northwestern Mediterranean Sea: Recent processes inferred from morphology and sediment bedforms
|Author(s)||Lastras G1, 2, Canals M1, Urgeles R1, Amblas D1, Ivanov M3, Droz Laurence4, Dennielou Bernard5, Fabres J1, Schoolmeester T1, Akhmetzhanov A2, Orange D6, 7, Garcia Garcia A6, 7|
|Affiliation(s)||1 : Univ Barcelona, Fac Geol, GRC Geociencies Marines, E-08028 Barcelona, Spain.
2 : Natl Oceanog Ctr, Southampton SO14 3ZH, Hants, England.
3 : Moscow MV Lomonosov State Univ, UNESCO, Ctr Marine Geol & Geophys, Moscow, Russia.
4 : Univ Bretagne Occidentale, CNRS, F-29280 Plouzane, France.
5 : IFREMER, Dept Geosci Marines, F-29280 Plouzane, France.
6 : Univ Calif Santa Cruz, Dept Earth Sci, Santa Cruz, CA 95064 USA.
7 : AOA Geophys Inc, Moss Landing, CA 94039 USA.
|Source||Marine Geology (0025-3227) (Elsevier), 2007-12 , Vol. 246 , N. 2-4 , P. 176-192|
|WOS© Times Cited||67|
|Keyword(s)||Gulf of Lion, Bedform, Swath bathymetry, Side scan sonar, Submarine canyon|
|Abstract||The Cap de Creus canyon, northwestern Mediterranean Sea, belongs to a complex network of submarine canyons cutting the western Gulf of Lion continental shelf and opening into the larger Sete canyon. Swath bathymetry data, MAKAM deep-towed side-scan sonar imagery and 5 kHz high resolution seismic reflection profiles show striking morphologies in the Cap de Creus canyon floor and walls. As a consequence of the canyon head and the upper reach severe incision, the continental shelf dramatically narrows in front of the Creus Cape promontory. The upper canyon has a flat-bottomed thalweg incised in a megascale sediment furrow field displaying hyperbolic seismic facies. The tens of kilometres long linear furrows extend also over the middle canyon down to 1400 in of water depth. The furrows on either side of the canyon are not parallel but oblique and display varying degrees of excavation. Mid-channel sediment bars are locally present in the thalweg, which is made of sandy lag deposits, as revealed by its acoustic response and verified by sediment samples. The middle canyon is linear and steep, with an up to 700 in high southern wall, contrasting with the sinuous, smooth lower canyon, which is controlled by flowage of the underlying Messinian evaporites. Large sections of the canyon are affected by sediment instability processes. The lower Cap de Creus canyon hangs up to 260 in over its distalmost reach and the Sete canyon through a narrow, less than 1 km wide, gorge. Numerous scours up to 10 in deep suggesting bed load transport occupy the lower Sete canyon immediately downstream of the Cap de Creus canyon mouth. The data set provides the first complete very-high resolution imaging of a submarine canyon from its upper part down to its distalmost reach. The observations evidence a wide set of erosion, transport and deposition processes along the Cap de Creus canyon, including sediment entrapment at the canyon head, furrow-generating dense water cascading through the southern wall, along-channel currents strong enough to excavate specific sections of the channel floor and bed load sediment transport as demonstrated by the presence of mega-ripples, crescent scours and grooves in the lower canyon. (c) 2007 Elsevier B.V. All rights reserved.|