Reconstruction of the lost Triassic stratigraphy of shallow marine formations in the Mino terrane : Link between deep and shallow marine formations in accretionary complex

虽然二叠纪至早侏罗世的远洋深海放射虫硅质岩和二叠纪的远洋浅海石灰岩作为增生的大洋岩石出现在米诺湾，但没有三叠纪至侏罗纪的浅海石灰岩已知出现在米诺湾。这可能是二叠纪浅海沉积物堆积的洋岛和洋台沉降的结果。另一方面，九条八幡和赤坂地区的二叠纪石灰岩有洞穴沉积物和三叠纪混合牙形石动物群，深海硅质岩含有来自较浅地区的碎屑颗粒。这些岩石表明三叠纪浅海灰岩的存在。我们在高山、九条八幡、上阿索、三山、新和伊吹地区检查了与燧石互层的石灰岩。它们是（1）碎屑灰岩与二叠纪硅质岩互层，（2）碎屑灰岩与时代未知的硅质岩互层，（3）远洋深海灰岩与三叠系硅质岩互层，未发现碎屑灰岩与三叠系硅质岩互层，表明三叠系浅海灰岩的存在。白色硅质岩与三叠系硅质岩互层，可能是碎屑灰岩，但显微镜观察和年龄测定均未提供证据。我们在俄罗斯远东的萨马尔卡河（Samarka）也做了类似的初步研究，萨马尔卡河是米诺河的北方延伸。秩父河的大丰和Kamura的三叠纪石灰岩具有指示间断和化学溶解的层位;美浓河的石灰岩中可能发生类似的现象。

Although pelagic deep-sea radiolarian chert of Permian to Early Jurassic age and pelagic shallow-marine limestone of Permian age occur as accreted oceanic rocks in the Mino terrane, no shallow-marine limestone of Triassic to Jurassic age are known to occur in the terrane. This might be resulted from the subsidence of the oceanic islands and plateaus on which the Permian shallow-marine sediments were accumulated. On the other hand, Permian limestones in the Gujo-hachiman and Akasaka areas have cave deposits with mixed-Triassic conodont fauna, and deep-sea cherts contain clastic grains derived from shallower areas. These rocks indicate existence of the Triassic shallow-marine limestone. We examined limestone interbedded with chert in the Takayama, Gujo-hachiman, Kamiaso, Miyama, Neo and Ibuki areas. They are (1)clastic limestone interbedded with Permian chert, (2)clastic limestone interbedded with chert of unknown age, and (3)pelagic deep-sea limestone interbedded with Triassic chert; we could not find clastic limestone interbedded with Triassic chert, which indicate the existence of Triassic shallow-marine limestone. White chert interbedded with Triassic chert might have been originally clastic limestone, but our microscope observation and age determination provide no evidence. We made similar preliminary examinations in the Samarka terrane, Fareast Russia, which is the northern ]extension of the Mino terrane. Triassic limestone at Taho and Kamura in the Chichibu terrane have horizons indicating hiatus and chemical disolution ; similar fenomena might occur in limestone of the Mino terrane.