CHARACTERISTICS OF THE LATE QUATERNARY TEPHRA LAYERS IN THE EAST/JAPAN SEA AND THEIR NEW OCCURRENCES IN WESTERN ULLEUNG BASIN SEDIMENTS

Abstract

Lithologies and stratigraphic relationships of late Quaternary core sediments were examined in three piston cores, recovered from the western Ulleung Basin. The approximately 8-m long cores consist of muddy sediments that are interbedded with lapilli and ash layers. The morphological and major element compositional studies suggest that volcanic glass shards of the tephra layers are equivalent to those of fallout deposits of the Ulleung—Oki (ca. 9.3 ka), Aira—Tanzawa (ca. 22–24.3 ka), and Ulleung—Yamato (ca. 25–33 ka). The occurrence of the lapilli layers in the western Ulleung Basin implies that the known fallout distribution of pumicetype glass shards can be extended about 50 to 100 km to the west.