New Radiocarbon Ages from Unconsolidated Deposits in the Kitamatairi River Basin, the Eastern Mount Shirouma-dake, Central Japan

Abstract

 The Kitamatairi River basin has been considered to be a type-location of Pleistocene multiple glaciations of the northern Hida Mountains, central Japan. However, recent geomorphological studies performed in the adjacent area have clarified that the landforms and unconsolidated deposits both of which have been believed to be of glacial origin (i.e., moraines and tills) were deformed or actually formed by landslides. This suggests that both morphogenetic and chronologic reappraisals of landforms and deposits are also necessary in the Kitamatairi River basin. Hence, we measured new radiocarbon ages of unconsolidated deposits in the Kitamatairi River basin (replications for 7 samples from 2 sites and new measurements for 9 samples from 7 sites). All replications showed significant older ages (>20 ky) than previously reported ages. New ages range from late Holocene to late Pleistocene, or before. The chronological concept for landform development in the Kitamatairi River basin should be revised.