Paleogeographic reconstruction of accreted oceanic rocks, Akiyoshi, southwest Japan

The depositional setting of an accreted oceanic rock succession of limestone, chert, and greenstone is reconstructed by using the stratigraphy, age, and lithologic features in the Akiyoshi terrane, southwest Japan. Stratigraphic and radiolarian paleontological results identify four coeval oceanic rock units, ranging in age from late early Carboniferous to late middle Permian. Sediments on the top, the upper flank, the lower flank, and the foot of the seamount and on the surrounding ocean floor are represented by reef limestone, detrital limestone with spicular chert, spicular chert with displaced limestone, and radiolaria-bearing chert, respectively; all units rest on greenstone. Radiolaria-bearing chert is interpreted as a more distal facies than spicular chert. These rocks are interpreted as sediments deposited on and around a basaltic seamount formed in an open-ocean realm that had no input of terrigenous materials.