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doi:10.2204/iodp.proc.340.107.2013 Site U13971Expedition 340 Scientists2Background and objectivesIntegrated Ocean Drilling Program (IODP) Site U1397 (proposed Site CARI-10B; 14°54.41′N, 61°25.35′W; 2482 meters below sea level [mbsl]) is located west of Martinique (Fig. F1). The bathymetric survey for Site U1397 revealed a region with a topographic high bound by large canyons. Site survey seismic data indicated that this site could, in the upper part, penetrate regular (unperturbed) sedimentary reflectors, whereas in the lower part some chaotic reflectors are visible. The drill site is located on the topographic high to try to avoid perturbations. Site U1397 is located very close to Core CAR-MAR 4 (7 m long) taken during the Caraval cruise in 2002. The CAR-MAR 4 core provides a sedimentary record that extends to ~32 ka, as determined by δ18O chronostratigraphy. The sedimentation rate (including tephra) is ~20 cm/k.y. (Boudon et al., submitted). Correlating the tephra sampled in the core to onshore deposits of the Montagne Pelée Volcano shows that a significantly greater number of tephra layers are deposited in the marine environment than have been identified during onshore studies (e.g., 25 tephra layers were identified in the core between 5 and 15 ka, whereas only 10 magmatic events were previously recognized in onshore studies). The objective for Site U1397 was to characterize the eruptive history of Martinique and the chaotic units appearing in the seismic profiles of this site. The cores retrieved will significantly improve our understanding of the eruptive history of Martinique in space and time, as we plan to sample material reaching back >1 m.y. (assuming a sedimentation rate of 20 cm/k.y. and a total target depth of 314 meters below seafloor [mbsf]). We expect to identify and date layers related to the Montagne Pelée and Pitons du Carbet Volcanoes and to sample the region related to the transition of volcanism from the Pitons du Carbet and Mont Conil Volcanoes to the Montagne Pelée Volcano. The end of volcanic activity at the Pitons du Carbet and Mont Conil Volcanoes (~0.3–0.5 Ma) precedes the beginning of the Montagne Pelée activity. We want to test the hypothesis that more mafic and denser magma was erupted for a period of several thousand years following edifice collapse until a new lava cone reached sufficient volume to erupt more evolved lavas (Pinel and Jaupart, 2000; Boudon et al., 2007). This site could also contain tephra from Dominica volcanoes, which will be distinguished on the basis of geochemistry and microtextural characteristics (Machault, 2008). Volcanism on Dominica has been dominated by andesitic to dacitic eruption products since the Pleistocene (Lindsay et al., 2005). |
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