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

伊豆-博宁-马里亚纳（IBM）弧是解决弧相关科学问题的理想场所，如：(1)弧的起始，(2)蛇绿岩和大陆地壳的起源，以及(3)多个弧和弧后阶段的演化过程。相关海洋沉积物记录中的Tephra层提供了解码这些谜团的机会。我们的项目将集中在350号和352号科考期间取样的羚羊层，我们将与船上的其他科学家密切合作。我们的特别目标是建立一个最完整的全弧温度地层学，以更好地分类伊豆-波宁弧大爆发的起源、风格和频率。350考察期间采集的~600个第四纪至上新世温层和352考察期间采集的~150个第四纪至渐新世温层将使我们能够实现以下科学目标。我们希望通过使用更老的DSDP/ODP和我们最近的IODP站点的tephra层之间的相关性，将以前基于局部限制的Izu-Bonin地球化学和火山学演化的调查扩展到整个地区爆发火山作用的广泛的时空来源研究。物源分析将确定弧上的麻黄源区域，从而有助于限制沿弧麻黄生产力的时间变化。最后，关于主要的巡航目标，这将有助于提高对伊豆-波宁弧演变的认识。这些目标的补充是研究由流动而不是下降过程沉积的海洋温层的就位和起源。最后，我们想研究在一定时间尺度上海洋火山灰记录中观察到的周期性，特别是在火环上。远征350和远征352的初步结果是有希望的，并表明IBM弧活动可能是周期性的。与其他长的火山时间序列（例如，中美洲火山弧）的比较将使我们有可能考虑全球影响。

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.