[M-IS18] Drilling Earth Science

[MIS18-P07] Geochemistry of the Youngest Toba Tuff in deep-sea sediments of the western margin of the Bay of Bengal

*Junichiro Kuroda¹, Yuki Ota², Jun-Ichi Kimura³, Qing Chang³, Shigeyuki Wakaki⁴, Kazuya Nagaishi⁵, Tatsuya Kawai⁵, Hodaka Kawahata¹ (1.Atmosphere and Ocean Research Institute, the University of Tokyo, 2.National Institute of Advanced Industrial Science and Technology, 3.Japan Agency for Marine-Earth Science and Technology, 4.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology , 5.Marine Works Japan Ltd.)

Keywords:Youngest Toba Tuff, The Bay of Bengal, LA-ICP-MS, radiogenic isotopes (Sr, Nd and Pb)

During the Indian National Gas Hydrate Program (NGHP) Expedition 02, D/V Chikyu drilled subseafloor sediments at several sites in the Krishna-Godavari Basin in the western margin of the Bay of Bengal, and recovered hemipelagic muddy sediments. A ~6 cm-thick volcanic ash layer was identified in the late Pleistocene interval at two sites (NGHP-02-19 and NGHP-02-22), where continuous hemipelagic sediments were recovered without slumping or slope failure. Here we present a geochemical dataset of the volcanic ash layer, that includes major and trace element concentrations of glass shards, trace element concentrations and radiogenic isotopic compositions of strontium (⁸⁷Sr/⁸⁶Sr), neodymium (¹⁴³Nd/¹⁴⁴Nd) and lead (²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb) of bulk samples. The geochemical data of the glass shards and bulk samples are all identical to the previously reported values of the Youngest Toba Tuff (YTT), which was supplied by an eruption of the Toba Caldera in Sumatra at ~74 ka. We also examined the age of YTT based on the oxygen isotopic ratios of foraminifera separated from the hemipelagic mud. Our findings further constrain the age and distribution of YTT in the Indian Ocean.