Abstract
The Margaritifera Laevis is known as long living freshwater bivalve and their aragonite shells could be useful and unique materials for reconstructing the past changes in river environments. Here we present the sclerochronological and geochemical results of Margaritifer shells collected in the Shiribetsu river, central part of Hokkaido, Japan. The combined approaches of SEM and optical microscopes observations and trace elemental analysis using LA-ICP-MS have been done for comparing with the in situ hourly environmental data of temperature, pH and dissolved oxygen and monthly meteorological records. The number of fine (daily) growth lines were corresponding with that of days when average daily temperature was higher than 10 °C degree and the daily growth width patterns were correlated with that of daily temperature changes. Annual extension rates have negative correlation to annual volume of water charges and the concentration of several trace elements were high in the shell part during Spring. These results indicate that the Margaritifera shells could be powerful tool for reconstructing the river environments and air conditions during winter around central Hokkaido. Our future works will apply this strategy to the modern long living and fossil shells which we have recently found in different river and midden archaeological sites.
