Abstract
To begin the clarification of uplift/subsidence history along the southern Sanriku coast, a 40-m-long core sample (RT1 core) was extracted from the lower reaches of Rikuzentakata Plain, northeast Japan. On the basis of features of the core sediment, sedimentary facies was divided into braided river, tidal influenced environment, delta, and terrestrial marsh, in ascending order. Age-depth curve was described based on twenty-five 14C ages. For the estimation of Holocene vertical movement, observed relative sea-level (RSL) was compared with theoretical RSL. RSL at 9.5 to 8.6ka was estimated at −30 to −24m by using the altitude of depositional surface of tidal deposits shown by both age-depth curve and molluscan shells in intertidal zone. Estimated RSL is lower than theoretical RSL without tectonic effect. Probable cause of this discrepancy is Holocene tectonic subsidence of the studied area.
