Abstract

The purpose of this study is to provide an inquiry into paleovegetation(paleoenvironment), eruption age and inferred emplacement temperature of pyroclastic deposit using charcoal occurred in the Quaternary Nari Caldera, Ulleung Island. In order to obtain the data, we carried out species identification, tree-ring analysis, and radiocarbon dating for the charcoal. This sample was collected from pumiceous deposit in lowermost member(Member N-5) of the Nari Tephra Formation, which corresponds to the wood branch that has well preserved the tree-ring structure. Speciation and outermost tree-ring of wood reveal Picea spp. and 263+α years. The calibrated ages from the center( pith) to the outermost tree-ring are 20,260±230, 19,995±245, and 19,975±265 cal BP, respectively, which are accordant with the tree-ring position. The youngest age, <19,710 cal BP would have implications for the eruptive age of Member N-5. Our results indicate that Picea spp. is the paleovegetation representing that Nari Caldera was under cold and wet climate conditions during the late Pleistocene. Based on the silky luster, brittleness, color, and streak of charcoal, etc., the lowest emplacement temperatures of pyroclastic flow are interpreted to have been at least as high as 350~500°C.

Keywords Ulleung Island, charcoal, wood species, tree-ring analysis, radiocarbon dating