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

增生棱镜是会聚板块造山带的主要组成部分之一，形成了上覆地壳板块的柔韧前缘。日本西南部的岛曼托增生杂岩最近得到了研究，因为部分地区暴露良好，可以研究详细的构造和地层关系。该研究的结果表明，这个吸积棱镜的部分是典型的在会聚板块边缘的简单吸积。构造异常包括始新世和中新世之间180°的构造极性反转和晚期的造山斜挠曲。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，验证这些异常可归因于中新世伸展脊俯冲的假设。研究结果有望阐明石曼托形变资料的意义，并探讨活跃伸展脊的俯冲作用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.