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Studies of Japanese Triassic foraminifers

日本三叠纪有孔虫的研究

基本信息

批准号：
10640453
负责人：
KOBAYASHI Fumio
金额：
$ 1.22万
依托单位：
Inst. Nat. Envir. Sci., Himeji Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640453/
关键词：
Foraminiferal fossils Triassic Late Permian Limestone faces Paleobiogeography Faunal analysis

项目摘要

The present study has first clarified the general aspect of the Japanese Triassic foraminifers, in relation to limestone faces deeply concerned with the Japanese pre-Cretaceous tectonics. Their results are important as the basic data and available for the discussion on the Triassic foraminiferal faunal comparison, paleo-biogeography, and tectonic development of Tethyan and Circum-Pacific regions.Triassic limestones in the Kurosegawa and Maizuru Belts are lenticularly intercalated within clastic racks having many Triassic neritic faunas. The Kurosegawa Smithian limestone, gradually changing into the surrounding black mudstone, is packed densely with small thin-shelled bivalves (onquina limestone) containing rare foraminifers. Most of the Kurosegawa foraminiferal faunas are found in ooid grainstone and bioclastic grainstone containing large amount of detrital quartz grains and rock fragments. They consists of Glomospira densa, Meandrospira dinarica, Arenovidalina amylovoluta, and many others, index species of the European Anisian. Similar faunas to those of the Kurosegawa are also obtained from the Maizuru.Triassic limestones are most widely distributed in the South Chichibu Belt. In its southern part (Sambosan Belt), numerous huge Triassic limestone blocks are prevailing in association with exotic blocks of basaltic rocks and chert. Pelagic limestone of the Sambosan Belt yields many late Triassic foraminifers assignable to Angulodiscus and other involutinids, and megalodontid bivalves typical to the Upper Triassic Tethyan Realm.In the northern part of the South Chichibu Belt, Lower (Smithian and Spathian), Middle (Anisian), and Upper Triassic (Norian) limestones are unconformable in each other. The coquina limestone is throughout and radiolarian limestone is dominant in their upper part. Foraminiferal faunas seem to be rather dissimilar to other Japanese contemporaneous ones with respect to subordinate involutinids.

本研究首次阐明了与日本前白垩纪构造密切相关的灰岩面有关的日本三叠纪有孔虫的总体方面。这些结果对特提斯和环太平洋地区三叠纪有孔虫区系比较、古生物地理学和构造发育等研究具有重要的基础资料和参考价值。黑川带和舞鹤带的三叠纪灰岩呈透镜状嵌套在碎屑岩架中，碎屑岩架中有许多三叠纪浅海动物。黑川史密斯石灰岩，逐渐转变为周围的黑色泥岩，密集地包裹着含有稀有有孔虫的小薄壳双壳类（onquina石灰岩）。黑家川有孔虫动物群主要分布在含大量碎屑石英颗粒和岩屑的卵状颗粒岩和生物碎屑颗粒岩中。它们包括密集球囊螺旋体（Glomospira denarica）、Meandrospira dinarica、Arenovidalina amylovoluta和许多其他的欧洲亚种的指数种。与黑川相似的动物群也从舞鹤中获得。三叠纪灰岩在南秩父带分布最为广泛。在它的南部（三宝山带），大量巨大的三叠纪石灰岩块体与外来的玄武岩块体和燧石块体一起盛行。三波山带的远洋灰岩中发现了许多晚三叠世的有孔虫，可归为Angulodiscus和其他involutinids类，以及上三叠世特提斯领域典型的巨齿类双壳类。在南秩父带北部，下三叠统（史密斯统和斯帕塔统）、中三叠统（阿尼西统）和上三叠统（诺里统）灰岩相互不整合。其上部以放射虫灰岩为主。有孔虫动物群似乎与日本同时代的其他有孔虫动物群在从属的渐开线纲方面相当不同。