IODP Expedition 340: Lesser Antilles Volcanism and Landslides Site U1400 Summary

Integrated Ocean Drilling Program Site U1400 (CARI-07C, 14°32.58’N, 61°27.55’W, 2745 m below seafloor) is located west of Martinique. Site U1400 was dedicated to the study of debris avalanche emplacement and associated erosional processes. The evolution of the active Montagne Pelée volcano on Martinique is characterized by three major flank collapse events (~0.1 Ma, ~25 ka, and ~9,000 years ago), which systematically destroyed the western flank of the volcano (Le Friant et al., 2003; Boudon et al., 2005, 2007). The volume of material displaced by these collapses varies from 2 to 25 km. The debris avalanches caused by these events were transported into the Grenada Basin. The Pitons du Carbet Volcano also experienced a sector-collapse at 0.3 Ma (Boudon et al., 1992; 2007; Samper et al., 2007). The bathymetric and seismic data obtained during several pre-site surveys, we expected coring to 510 mbsf would penetrate through volcanic and biogenic sediments with intercalated large chaotic debris avalanche deposits (deposit 1 and 2). A special focus of this site is to study the contacts between the different avalanche units not only to distinguish between the different deposits but also to better understand avalanche transport dynamics, especially in the basal part of the avalanche. This will provide fundamental constraints on friction parameters needed for realistic avalanche propagation models. The sediments above the avalanche deposit will be dated using O chronostratigraphy to better constrain the age of this event. The seismic profiles show that a ~70-m-thick well-bedded sedimentary layer overlies deposit 2 and that it increases in thickness towards the NE. We will test the hypothesis that, following a flank collapse, the on land drainage system was drastically modified resulting in increasing erosion and thus sedimentation rates in the Grenada Basin.