Late Permian Early Triassic paleogeography of northern Japan: Did Pacific microplates accrete to Japan?

Extensive and detailed field studies were conducted in the Kitakami Mountains of northern Japan in order to sample Permian rocks and to make paleogeographic reconstructions for Permian time. These field studies demonstrate that large landmasses were present on both sides of the Honshu geosyncline during Permian time (i.e., on both the Pacific Ocean and the Sea of Japan sides). These landmasses appear, on the basis of sediment studies, to have been present during Permian, Mesozoic, and Paleogene time. The paleogeographic reconstructions presented here and papers by other authors show that neither the accretion of microplates from the Pacific nor major horizontal movements of the Japanese part of Tethys occurred in Mesozoic time. *Present address: 164-2 Fujima, Kawagoe City, Saitama Prefect 356, Japan