Abstract
Ten levels of erosional terraces straddle the main stream of the upper reaches of the Naka River, in western Tokushima Prefecture, southwest Japan, and in addition there are five and two levels along the tributary Kaikawadani and Minami Rivers. The 26-29-ka Aira-Tn (AT) and 7.3-ka Kikai-Akahoya (K-Ah) tephra, and degree of weathering involved in the terrace chronology that most terraces were formed in the Oxygen Marine Isotope Stage (MIS) 4-2, or otherwise in MIS 6. No valley filling would have occurred during such a glacial period. The late Quaternary uplift rate of the east Shikoku Range exceeded 0.45mm/year and reached 0.9-1.0mm/year at the maximum.
