<国立科博専報>赤石山地の水窪層・和田層に関する新事実

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The results of the radiolarian analytical investigations of the Cretaceous Misakubo and the Tertiary Wada Formations exposed in the southern part of the Akaishi Mountains (Fig. 1) are reported. A radiolarian assemblage of Calocycletta virgnis Zone including such species as Cyrtocapsella cornuta, C. tetrapera, C. japonica, Stichocorys wolffii, S. delmontensis, Lychnocanoma elongata, Carpocanistrum sp., Eucyrtidium sp., and Liriospyris spp., Early Miocene species, was recognized in a part of the shale formerly assigned to the Cretaceous Misakubo Formation in the Misakubo area. By radiolarian analysis a quite similar fossil assemblage of the Early Miocene species such as Cyrtocapsella cornuta, C. tetrapera, Calocycletta virginis, Eucyrtidium sp., Spongodiscus spp., Ommatodiscus sp., and Solenophaera sp., was also confirmed in the Tertiary shale of the type localities of Wada Formation. Therefore, it is clear that a part of the strata which were assigned to the Misakubo Formation should be reasonably regarded as the Wada Formation on the basis of the radiolarian fossil evidence. These Radiolaria are shown on Plate 8. Another interesting fact is that the newly discovered Early Miocene localities are distributed in a zone extending from north to south along the border of Akaishi tectonicline (Fig. 2), although partly interrupted by the Misakubo Formation. Thus, based on the radiolarian species, it is suggested that the Akaishi tectonic-line may have formed at least after the middle of Early Miocene. Newly revised geological map (Fig. 2) is presented. A few Cretaceous radiolarian fossils such as cryoptothoracic Nassellaria were discovered in the type locality of Misakubo Formation, which may be correlated with the Upper A1bian to Lower Cenomanian Middle Formation of Goshonoura Group in Kyushu, as suggested by MATSUMOTO (1954) and MATSUMOTO and TASHIRO (1975).
国立科学博物館の論文
1979-12-01

<国立科博専報>赤石山地の水窪層・和田層に関する新事実

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