Carboniferous ammonoids and corals from seamount limestone in an accretionary complex within the North Kitakami Belt, Northeast Japan

Abstract

Late Carboniferous (probably Moscovian) ammonoids and associated corals were recovered from limestone blocks in a Jurassic accretionary complex of the Kuzumaki-Kamaishi Sub-belt of the North Kitakami Belt, within the drainage basin of the Mabechigawa River, south of Ichinohe, Northern Kitakami Massif, Northeast Japan. The limestone blocks are associated with basalts of oceanic island origin; together, these rocks probably constitute a seamount-reef complex. The ammonoids, which are the first Paleozoic ammonoids and the first reliable Carboniferous fossils to be described from the North Kitakami Belt, indicate that the oceanic plate associated with formation of the accretionary complex in the Kuzumaki-Kamaishi Sub-belt had already formed by the Late Carboniferous.