Description: Site U1456 (location: 16°37.28′N, 68°50.33′E; length: 1109.4 m) was drilled at a water depth of 3640 m within the Laxmi Basin in the eastern Arabian Sea duirng International Ocean Discovery Program (IODP) Expedition 355. We here focus on the upper 82.02 m core composite depth below seafloor (CCSF) at Site U1456, deposited since ~700 ka. Sr-Nd isotopic compositions of the clay-sized detrital sediment fractions (12 samples) and concentrations of the total organic carbon (TOC, 101 samples), total nitrogen (TN, 101 samples), and biogenic silica (BSi, 101 samples) were analyzed using a thermal ionization mass spectrometer (Phoenix), a Carlo Erba Elemental Analyzer (1108), a CO2 Coulometer (CM5014), and a wet alkaline extraction method.

Description: The radiogenic strontium (Sr) and neodymium (Nd) isotope compositions of the detrital fraction of surface and subsurface sediments have been determined to trace sediment provenance and contributions from Asian dust off the east coast of Luzon Islands in the western Philippine Sea. The Sr and Nd isotope compositions have been very homogenous near the east coast of the Luzon Islands during the latest Quaternary yielding relatively least radiogenic Sr (87Sr/86Sr = 0.70453 to 0.70491) and more radiogenic Nd isotope compositions (εNd(0) = +5.3 to +5.5). These isotope compositions are similar to Luzon rocks and show that these sediments were mainly derived from the Luzon Islands. In contrast, the Sr and Nd isotope compositions of sediments on the Benham Rise and in the Philippine Basin are markedly different in that they are characterized by overall more variable and more radiogenic Sr isotope compositions (87Sr/86Sr = 0.70452 to 0.70723) and less radiogenic Nd isotope compositions (εNd(0) = −5.3 to +2.4). The Sr isotope composition in the Huatung Basin is intermediate between those of the east coast of Luzon and Benham Rise, but shows the least radiogenic Nd isotope compositions. The data are consistent with a two end-member mixing relationship between Luzon volcanic rocks and eolian dust from the Asian continent, which is characterized by highly radiogenic Sr and unradiogenic Nd isotope compositions. The results show that Asian continental dust contributes about 10–50% of the detrital fraction of the sediments on Benham Rise in the western Philippine Sea, which offers the potentials to reconstruct the climatic evolution of eastern Asia from these sediments and compare this information to the records from the central and northern Pacific.

Description: Sedimentary evidence for enhanced volcanic eruption during the glacial/interglacial transition in the volcanically active mid-ocean ridges is still lacking. Here, we present the sedimentary records of enhanced deglacial volcanic activity in a well-dated sediment core from the middle part of Central Indian Ridge (CIR), which can provide clue for comprehensively understanding of the temporal relation of increase in submarine volcanism relative to glacial/interglacial transition. Notably, the 35-kyr sediment core used in this study contains continuous, discernible pyroclastic deposit layers (0.5–5 cm thick), which are composed mainly of angular and curved fluidal shards with vesicles, possibly suggesting volatile-rich ridge eruptions. High-resolution elemental profiles of the core provide definite records of at least 17 volcanic eruptions during the past 35 kyr. Interestingly, volcanism was sparse during the Last Glacial Maximum (LGM), but increased significantly during the last deglaciation after ~18 kyr BP. The last deglaciation-associated volcanic eruptions in the CIR may be linked to decompression melting during the LGM sea-level lowstand, reaffirming an influence of sea level variability on global ocean ridge magmatism. Combining the previous results, furthermore, simultaneous strengthening of submarine and subaerial volcanic eruptions during the last deglaciation could have accelerated the rise of atmospheric CO2, with the ensuing warming constituting positive feedback upon deglaciation. Highlights • A succession of pyroclastic records in a well-dated sediment core from the CIR was identified. • The morphologies of the pyroclasts are consistent with volatile-rich submarine eruption. • Deglaciation-associated enhanced volcanism seems robust in the mid-ocean ridges. • Tentative support for a link between ridge volcanism and climate change is provided.