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doi:10.2204/iodp.sp.340.2011 IntroductionThe Lesser Antilles volcanic arc constitutes a unique setting where volcanic activity since the mid-Oligocene has resulted in construction of numerous volcanic edifices (Fig. F1). More than 12 of these edifices have been active in the last 10,000 y. Generally, volcanism along-strike the arc is characterized by an exceptional diversity of magma composition, production rate, and eruptive style, as well as of the frequency and style of flank collapses. These north–south variations are not fully understood but are probably related to the morphology and structure of the arc (Boudon et al., 2007). Furthermore, recent studies have shown that at least 52 flank-collapse events have occurred on volcanoes of the Lesser Antilles, 15 of which occurred within the last 12,000 y (Boudon et al., 2007; Lebas et al., 2011). Thus, the frequency of flank collapses in this area is at least an order of magnitude larger than at other regions (e.g., Hawaii: 1/350 k.y.; Moore et al., 1989). Two-dimensional seismic surveys around the Lesser Antilles have provided excellent images (Figs. AF01–AF18) of the debris avalanche deposits, including their basal surfaces (e.g., Deplus et al., 2001; Le Friant et al., 2003a), contrary to seismic lines in other geodynamic contexts. For the Lesser Antilles, Le Friant et al. (2009, 2010) have shown that as much as 70 vol% of the erupted products along the arc are finally deposited in the surrounding marine environment, emphasizing the need for submarine studies in this tectonic environment to retrieve a complete picture of the constructive and destructive processes associated with arc volcanism. Furthermore, the constructive as well as the destructive processes along island arcs are often associated with large geohazards. For example, (1) arc volcanoes could erupt explosively, producing large eruption clouds, and (2) flank collapses in these areas can be accompanied by large tsunamis. Nonetheless, the majority of marine volcanic studies targeting volcaniclastic sediments and/or debris avalanche deposits (1) were not associated with entire volcanic island arcs but with oceanic intraplate volcanism (Ocean Drilling Program [ODP] Leg 136: e.g., Garcia, 1993; Garcia and Meyerhoff Hull, 1994; ODP Leg 200: e.g., Garcia et al., 2006; ODP Leg 157: e.g., Schneider et al., 1997; Goldstrand, 1998; Schmincke and Sumita, 1998), (2) were drilled into distal turbidites away from the proximal parts of the debris avalanche deposits, or (3) used sampling techniques with only shallow ground penetration, thus retrieving only relatively recent samples. For instance, tephrochronological studies on several volcanoes of the Lesser Antilles arc using piston cores (length = ~7 m) have extended our knowledge about the eruptive history in this area to only the last 250,000 y (Duchoiselle, 2003; Vennat, 2004; Le Friant et al., 2008; fig. 5 in Machault, 2008). Therefore, this project will not only provide the first cores penetrating through volcanic debris avalanche deposits (DADs) but also cores covering more than the last 1 m.y. of magmatic activity along the Lesser Antilles arc. This expedition will focus on constraining the processes responsible for the diversity of magmatism and eruptive activity in space and time and their environmental effects by documenting the evolution of three volcanic centers of the Lesser Antilles arc, representing the full range of observed magmatism and eruptive styles (Fig. F1):
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