T. Mulder á O. Weber á P. Anschutz á F.J. Jorissen J.-M. Jouanneau A few months-old storm-generated turbidite deposited in the Capbreton Canyon Bay of Biscay, SW France) Received: 22 January 2001 / Revision accepted: 20 July 2001 / Published online: 11 October 2001 Ó Springer-Verlag 2001 Abstract A gravity core taken in the canyon of Capbreton shows a succession of sedimentary facies which can be interpreted as three superimposed Bouma sequences. The turbiditic sequences are covered by an oxidised layer which contains live benthic foraminiferal faunas indicating a reprisal of hemipelagic deposition. Activities of 234 Th and 210 Pb suggest that the most re- cent turbidite was deposited between early December 1999 and mid-January 2000. During this period, the most probable natural event able to trigger a turbidity current was the violent storm which aected the French Atlantic coast on 27 December 1999. The turbidity current could have been caused by a sediment failure due to an excess in pore pressure generated by the storm waves, an increase of the littoral drift, or the dissipation of the along-coast water bulge through the canyon. This sub-recent turbidite shows that the canyon experiences modern gravity processes, despite the lack of a direct connection with a major sediment source. Introduction Although turbidity currents and turbidites have been known for half a century Kuenen 1951, 1952a, 1952b, 1953, 1959; Bouma 1962), much controversy still exists concerning the processes of deposition Kneller and Branney 1995; Shanmugam 1997, 2000; Mulder and Alexander 2001), their origin Mulder and Cochonat 1996) and their recognition. Except for deposits related to processes in which the main particle-support mecha- nism is not turbulence, and which should not be termed ``turbidites'' Middleton and Hampton 1973; Mulder and Alexander 2001), it is now clear that, even for real turbidites i.e. sequences deposited by a turbulent ¯ow; Shanmugam 2000), the Bouma sequence is not an ubiq- uitous model. Several exceptions of the classical model exist, such as the Lowe sequence Lowe 1982) for coarse- grained turbidites, and the sequence de®ned for ®ne- grained turbidites Stow and Shanmugam 1980; Piper and Stow 1991; Piper and Deptuck 1997). However, the conceptual model of Bouma 1962) remains valid for turbulent ¯ows generated from sediment failure. Turbidity currents are recognised as a major particle transport process in marine environments. They are at the origin of deep-sea turbiditic systems such as ramps fed by multiple sources, and deep-sea fans in which sediment is supplied by a linear source Reading and Richards 1994). In both kinds of system, particles are transported through a canyon. A submarine canyon is de®ned as a sea valley with a V-shaped pro®le, high steep walls with rock outcrops, a winding course and numerous tributaries entering from both sides Shepard and Dill 1966). Canyons are dominated by erosional processes. Their formation includes retrogressive failures and erosion by particle-laden gravity currents Shepard 1981; Pratson et al. 1994). Turbidity currents have been indirectly observed in canyons on seismic pro®les Hay 1987; Viana et al. in press). Turbidity current activity is also indirectly indicated by cable failures on the Algerian slope Heezen and Ewing 1955), in the Gulf of Corinth Heezen and Hollister 1971), in the New Britain Trench Krause et al. 1970), in the Var Gennesseaux et al. 1980), o the Grand Banks and Laurentian channel Heezen and Ewing 1952; Hughes Clarke et al. 1990, 1992), and in the Zaire canyon e.g. Shepard and Dill 1966; Droz et al. 1996). Measurements of an along- bottom turbid ¯ow associated with velocities ranging from a few decimetres to a few metres per second are reported by Inman 1970), and Shepard et al. 1977, 1979) in La Jolla Canyon, by Gennesseaux et al. 1971) in the Var canyon, and by Wright et al. 1986) in the Huanghe delta China). Various processes can initiate Geo-Marine Letters 2001) 21: 149±156 DOI 10.1007/s003670100077 T. Mulder &) á O. Weber á P. Anschutz á F.J. Jorissen J.-M. Jouanneau DeÂpartement de GeÂologie et OceÂanographie, UMR 5805 EPOC, Universite Bordeaux I, Avenue des FaculteÂs, 33405 Talence cedex, France E-mail: t.mulder@geocean.u-bordeaux.fr