Gotlandian Stratigraphy of the Outer Zone of Southwest Japan

Abstract

Many localities of the Gotlandian rocks have been found in the Outer Zone of Southwest Japan since Kobayashi and Iwaya's discovery of Halysites-bearing limestone at Imose, Kochi Prefecture, Shikoku in 1940. However, little has been done in their stratigraphy and paleontology. Here, the writer describes a tentative division of the Gotlandian strata with reference to the Halysitidae. The bed G4, which is composed of thick acidic volcanic and clastic materials, is presumed to be the Gotlandio-Devonian passage bed, and is correlated to the Takainari, Ono and the, lower half of the Nakazato series in the Kitakami mountains, Northeast Honshu, because of the predominance of acidic rocks. The so-called Upper Gotlandian Fukuji formation in Gifu Prefecture, Hida plateau is also brought into comparison. The strong acidic volcanic activities in these Gotlandio-Devonian rocks suggest that the “Oboke sandstone schists” in the lower part of the so-called Sambagawa metamorphic complex of the Sakawa orogenic zone are the ...