Stratigraphic study on the bedded manganese deposits distributed in the northern area of the Otaniyama mine, southeastern part of the Northern Kitakami Mountains, Northeast Japan

Abstract

In the northern Kitakami Mountains, bedded manganese deposits were formed which were closely related to the formation of chert beds of the Pre-Miyakoan sedimentary rocks. The geological age and setting of bedded manganese deposits of the Toyomane, Kogawa and Minamikawame mine areas, located in the southeastern part of the Kuzumaki-Kamaishi Belt, are micropaleontologically studied.
The Pre-Miyakoan sequences distributed in the three mine areas are divided into four units, namely UNIT I, II, III and S. Their geological age and lithofacies areas follows; UNIT I: Lower Permian limestone, UNIT II : Lower Permian to Lower Triasssic chert, UNIT III: Lower to Upper Triassic chert, UNIT S: Jurassic to Lower Cretaceous elastic sediments. The UNIT I, II and III are included as the exotic sheets or blocks in the UNIT S.
The bedded manganese ore bodies are included in the UNIT III and are deposited successively on the chert beds of Neogondolella polygnathiformis zone (Camian). The geological age of the bedded manganese ores coincides with the age of the Otaniyama mine. This clearly indicates the bedded manganese deposits are strata-bound type.