HOLOCENE TEPHRA OF KUNASHIR I. (KURIL ISLANDS)

Abstract

Based on the study of the mineralogy, chemistry, and particle size of late Pleistocene tephra from the marine and alluvial terraces of southern and central Kunashir I., five tephra groups were identified: four of these were traced to different phases of Golovnin eruptive activity during the late Pleistocene (43-30 thousand years ago) and one to the caldera-forming eruption of Mendeleev Volcano. A number of large paleoeruptions were dated on the basis of a biostratigraphic study of the tephra-enclosing rocks and radiocarbon dating. It was found that the chemical composiiton of tephra had changed from that of dacite to basaltic andesite during the caldera-forming eruption. Pyroclastics dispersal sectors were mapped on the basis of ash thickness variations.