Expediting the Identification, Analysis, and Interpretation of Paleogene Volcaniclastic Facies at IODP Site U1438, Expedition 351

The University Corporation, Northridge, Northridge CA

Investigators

Abstract

The Izu-Bonin-Mariana (IBM) system was the focus of International Ocean Discovery Program (IODP) Expeditions 350, 351, and 352 in 2014. These expeditions were designed to answer questions about the fundamental plate-tectonic processes of convergent-margin initiation and crustal development in intra-oceanic settings. The proposed research addresses primary objectives for Expedition 351, specifically the history of magmatic arc initiation and evolution as recorded in the overlying stratigraphic section. During the expedition, a 1.6 km volcanic/sedimentary section was cored. This core records the Eocene to Oligocene stratigraphic record, including the inception of subduction, initiation of the magmatic arc, arc development, and arc decline ? when arc rifting led to seafloor spreading in the Shikoku Basin and eastward migration of the axis of arc magmatism to its present position south of Japan. A detailed analysis of the sedimentology and sedimentary petrology of the core will be performed. The analyses will provide insights into the nature, eruption mechanism, proximity, and magmatic evolution of the volcanic sources (s) for the sedimentary succession. The sedimentary facies analysis includes an assessment of the processes by which these sediments were produced and then transported to the basin, based on integration of shipboard core description and compositional and textural information from petrographic examination of discrete samples. Results are tabulated and summarized in detailed stratigraphic columns and facies motifs. Results will be integrated with other post-cruise studies of specific mineral and glass component geochemistry and isotopic analyses, pore water geochemistry, diagenetic studies, and logging data. The research directly addresses a topic featured in the IODP 2013-2023 Science Plan, but also the NSF GeoPRISMS Science Plan for the Subduction Cycles and Deformation initiative. Thus, results from this study are scientifically relevant to a broad global audience of geoscientists and are fundamental to the understanding of subduction initiation and magmatic arc development.