Recognition of the Marine Oxygen Isotope Stage 6 Fluvial Terrace in Kawasaki Basin, Miyagi Prefecture, and Its Significance

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Accumulating data on the stratigraphy of fluvial terraces is very important for estimating uplift during late Quaternary. For this purpose, we reconsidered terrace stratigraphy in Kawasaki basin, Miyagi prefecture, by airphoto interpretation, field survey, and tephra chronology. The Kawauchi terrace, which was correlated to stage 3 in previous research, is a fill-top terrace, and we obtained Aso-4 tephra in the deposit overlying this terrace. We concluded that this terrace surface was probably formed in stage 6 on the basis of these data and of topographic features obtained by the airphoto interpretation. We suggest the following: (1) the Adachi-Medeshima Pumice (Ac-Md) was deposited earlier than in stage 6, because the Kawauchi terrace is not covered by Ac-Md. It has been estimated to have been deposited 90-100ka. (2) The formation ages of terraces that are covered by the Adachi-Medeshima Pumice are older than the previous estimation. (3) The uplift in/around the survey area during the last 100, 000 years, which was estimated by fluvial terrace stratigraphy in previous reports, is overestimated.