Estimation of accretionary complex growth by micropaleontological mapping

利用Matsuoka（1995）的侏罗纪-下白垩统放射虫分带框架及其数值年龄标定，对不同构造地层单位的大洋板块地层进行了3-5倍精度的对比。以岩相为主要依据，划分了秩父复式岩系的构造地层单位。位于北方秩父地体的上吉田单元和柏木单元的OPS分别类似于位于秩父地体南部的户野单元和三保山单元的OPS。文中还指出了上述两个构造岩相单元的OPS存在的一些重要差异。这表明北秩父和南秩父两个板块是由同一大洋板块沿沿着同一条俯冲带在横向上相距较远的地方俯冲而成的，它们在后来以走滑运动为特征的构造事件中并置。日本西南部侏罗纪增生杂岩的OPSs对比表明，主要的走滑错动发生在沿着黑濑川构造带，而不是沿构造中线。太平洋-日本放射虫分带方案也适用于藏南雅鲁藏布江缝合带、菲律宾北巴拉望地块和俄罗斯远东锡霍特阿林的增生杂岩。通过对西太平洋ODP 801站上侏罗统放射虫生物地层学的研究，发现太平洋-日本和北美两个独立提出的分带方案具有很好的对比性。

The oceanic plate stratigraphy (OPS) of different tectonostratigraphic units is compared with 3-5 times accuracy by using a framewok of Jurassic-Lower Cretaceous radiolarian zonation and its numerical age callibration of Matsuoka (1995). A tectonostratigraphic unit division for the Chichibu composite terrane is poroposed on the basis mainly of lithofacies. The OPSs of the Kamiyoshida Unit and Kashiwagi Unit in the Northern Chichibu terrane are similar to those of the Togano and Sambosan Unit in the Southern Chichibu Terrane, respectively. Some critical differences in OPS of the above-mentioned pair of the tectonositratigraphic units are also recognized. This indicates that the Nothern Chichibu and Southern Chichibu terranes were formed by the subduction of the same oceanic plate along a single subduction zone at laterally distant places and they were juxtaposed in later tectonic events characterized by strike-slip movements. Comparison of OPSs among Jurassic accretionary complexes in Southwest Japan suggests that the main strike-slip dislocation took place along the Kurosegawa Tectonic Zone rather than the Median Tectonic Line.The Pacific-Japan radiolarian zonal scheme is also applicable to accretionary complexes of the Yarlung Zangbo Suture Zone in southern Tibet, of the North Palawan Block in the Philippines, and of Sikhote Alin in Russian Far East. Detailed radiolarian biostratigraphic research on Upper Jurassic interval at ODP Site 801 in the western Pacific reveals that two zonal schemes proposed independently from Pacific-Japan and North America are well correlated with each other.