Collaborative Research: Spreading Ridge-Trench Interaction Recorded in an Accretionary Prism: The Tertiary Shimanto Belt, Southern Japan

吸积棱柱是会聚板块造山带的主要组成部分，构成了上覆地壳板块的柔韧前缘。位于日本西南部的岛曼都增生杂岩最近得到了研究，因为部分区域暴露得很好，因此可以调查详细的构造和地层关系。这项研究的结果表明，这种吸积棱柱的部分是典型的会聚板块边缘的简单吸积。构造异常包括始新世与中新世之间构造极性的180°反转、吸积包和晚期造山斜挠曲。这次更新将通过计算机模拟程序和对现有数据的进一步分析来检验这些异常是由中新世扩张山脊俯冲事件造成的假设。这些结果有望阐明岛曼托变形数据的意义，并探索活跃扩张的海脊在增生杂岩中的作用。

Accretionary prisms are one of the major components of convergent plate orogens, forming the pliant leading edge of the overriding crustal plate. The Shimanto accretionary complex in southwest Japan has received recent study because portions are well-exposed so that detailed structural and stratigraphic relation-ships can be investigated. Results of that study have revealed t hat parts of this accretionary prism are a typical of simple accretion at convergent plate margins. The structural anomalies include a 180o reversal in structural polarity between Eocene and Miocene accreted packets and late stage oroclinal flexing. This renewal will test the hypothesis that these anomalies are attributable to a Miocene episode of spreading-ridge subduction, by a program of computer modeling and further analysis of existing data. Results are expected to clarify the significance of the Shimanto deformational data and explore the role of subduction of actively spreading ridges in accretionary complexes.