SEDIMENT ACCUMULATION AND PALEOCEANOGRAPHY OF THE NORTHEASTERN CARIBBEAN: IODP SITE U1396 OFF MONTSERRAT, LESSER ANTILLES

Site U1396 was drilled as a part of Integrated Ocean Drilling Project Expedition 340 to establish a longer record of Lesser Antilles volcanism than previously known. To that end, a ~150 m sediment succession was recovered from three holes cored on a bathymetric high ~33 km southwest of Montserrat. A series of shipboard and newly generated chronostratigraphic tools (biostratigraphy, magnetostratigraphy, astrochronology, and stable isotope chemostratigraphy) were employed to generate an integrated age model. Two possible chronostratigraphic interpretations for the Brunhes chron are presented, with hypotheses to explain the discrepancies seen between this study and Wall-Palmer et al. (2014). The recent Wade et al. (2011) planktic foraminiferal biostratigraphic calibration is tested, with significant mismatches between calibrated ages of secondary datums, while primary datums are observed largely as expected. Lastly, sedimentation rates are calculated, both including and excluding the contribution of discrete volcanic sediment layers in the succession. Rates are found to be ‘pulsed’ or highly variable within the Pliocene interval, declining through the 1.5-2.4 Ma interval, and then lower through the Pleistocene. Possible explanations for the observed trends in the sedimentation rates include orbitally-forced biogenic production spikes, elevated contributions of cryptotephra (dispersed ash), and changes in bottom waters and flow rates with increased winnowing in the area of Site U1396 into the Pleistocene.