Izu-Bonin Arc tephrostratigraphy- evolution, provenance, cyclicities (IODP Exp. 350&352)

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The Izu-Bonin-Mariana (IBM) Arc is an ideal place to address arc-specific scientific questions as the process of (1) arc initiation, (2) origin of ophiolites and continental crust, and (3) the evolution of multiple arc and backarc phases. Tephra layers in the associated marine sediment record provide the opportunity to decode these mysteries. Our project will focus on tephra layers sampled during Expeditions 350 and 352 and we will closely collaborate with other shipboard scientists. It is our particular aim to establish a most complete arc-wide tephrostratigraphy that better classifies the origin, style and frequency of larger explosive eruptions from the Izu-Bonin arc. In detail, the ~600 Quaternary to Pliocene tephra layers sampled during Expedition 350, and ~150 Quaternary to Oligocene tephra layers recovered during Expedition 352 will enable us to achieve the following scientific objectives. We want to extend the former, locally restricted, investigations of Izu-Bonin´s geochemical and volcanological evolution based on tephra layers to a widespread temporal and spatial provenance study of the explosive volcanism in that entire region by using also correlations between tephra layers from older DSDP/ODP and our recent IODP sites. Provenance analyses will identify tephra source regions at the arc, thus facilitating to constrain temporal variations in the tephra productivity along the arc. Finally, concerning also the major cruise objectives, this will contribute to improve the knowledge of Izu-Bonin arc evolution.These objectives are complemented by studying the emplacement and origin of marine tephra layers that are deposited from flow rather than fall processes. Finally, we want to study cyclicities that have been observed in marine ash records on a range of time scales, especially at the ring of fire. Preliminary results from Expedition 350 and also 352 are promising and indicate probably periodicities in the IBM arc activity. The comparison to other long tephra time series (e.g., Central American Volcanic Arc) will additionally give us the possibility to consider global implications.