doi:10.2204/iodp.proc.340.106.2013
Site U13961
Expedition 340 Scientists2
Background and objectives
Integrated Ocean Drilling Program (IODP) Site U1396 (proposed Site CARI-01C; 16°30.49′N, 62°27.10′W; 801 meters below sea level [mbsl]) is the most western site drilled during Expedition 340 (Fig. F1).
The bathymetric survey for Site U1396 revealed a region bounded by a topographic high to the north and by two large canyons to the south. Site survey data indicated that this site could penetrate regular (unperturbed) seismic reflectors. The drill site is located on the topographic high to minimize any perturbations (e.g., related to turbidites). Site U1396 is located in the same area as the 5.75 m long CAR-MON 2 core taken during the Caraval cruise in 2002. Sediment recovered in the CAR-MON 2 core provides a stratigraphic record extending back ~250 k.y., as shown by δ18O chronostratigraphy. The calculated sedimentation rate (including tephra) is ~2.3 cm/k.y. (Le Friant et al., 2008). The recovered core also contained material from several explosive Plinian eruptions, which had not previously been identified on land (Le Friant et al., 2008).
The objective for Site U1396 was to characterize the eruptive history of Montserrat. Volcanism started on Montserrat at ~2.6 Ma at Silver Hills and moved to Centre Hills between 0.5 and 1.0 Ma, with the youngest volcanism being centered on the Soufrière Hills–South Soufrière Hills complex (~170 ka to present) (Harford et al., 2002). With conventional coring it is only possible to retrieve samples of recent volcanic activity. Drilling to a target depth of 132 meters below seafloor (mbsf) at Site U1396 was intended to extend our knowledge of the volcanic history of Montserrat to the birth of the island at at least ~2.5 Ma. Petrologic, lithologic, sedimentologic, and geochronologic analyses of volcanic rocks and volcaniclastic material from this site are expected to date as far back as 4 Ma (assuming a sedimentation rate of 2.3 cm/k.y. from the CAR-MON 2 study) and will provide significant new constraints on the early development of volcanism on Montserrat and on the spatial and temporal distribution of volcanic activity.