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

重建米诺地体中丢失的三叠纪浅海地层地层：增生杂岩中深海地层和浅海地层之间的联系

基本信息

批准号：
13640457
负责人：
KOJIMA Satoru
金额：
$ 1.79万
依托单位：
Gifu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640457/
关键词：
Mino terrane Triassic chert limestone radiolarians accretionary complex

项目摘要

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.

虽然在米诺地体中存在二叠纪至早侏罗世的远洋放射虫岩和二叠纪时代的远洋浅海灰岩，但在米诺地体中未发现三叠纪至侏罗世的浅海灰岩。这可能是由于二叠纪浅海沉积聚集的海洋岛屿和高原的沉降所致。古州-八幡和赤坂地区二叠系灰岩中有溶洞沉积，具有三叠系牙形石混合动物群，深海燧石中含有浅层碎屑颗粒。这些岩石表明存在三叠纪浅海相灰岩。我们在高山、古州八幡、神宫、宫山、Neo和Ibuki地区考察了与燧石互层的石灰岩。(1)碎屑灰岩与二叠系燧石互层；(2)碎屑灰岩与年龄不详的燧石互层；(3)远洋深海灰岩与三叠系燧石互层；未发现碎屑灰岩与三叠系燧石互层，表明三叠系浅海相灰岩的存在。与三叠纪燧石互层的白燧石最初可能是碎屑灰岩，但我们的显微镜观察和年龄测定没有提供证据。我们在俄罗斯远东的Samarka地块（米诺地块的北部延伸）进行了类似的初步检查。秩父地体的Taho和Kamura的三叠纪灰岩具有表明断裂和化学溶蚀的层位；类似的现象也可能发生在米诺地层的石灰岩中。