SYMPOSIUM: RECENT PROGRESS IN TEPHROCHRONOLOGY OF JAPAN

This symposium was designed to review the present tephrochronological studies in Japan and to discuss the problems of future research. The papers presented by reporters and commentators are as follows. (1) Relationships between development of volcanoes and tephras, by Ichio MORIYA, (2) Tephrochronological study of Mt. Ontake volcano, by Takehiko KOBAYASHI, (3) Identification of tephra, by Fusao ARAI, (4) Tephrochronology of deep-sea sediments, by Toshio FURUTA and Kazuo KOBAYASHI, (5) Correlation and chronology of coastal terraces and associated sediments around Tokyo Bay in middle Pleistocene analyzed by marker-tephras, by Shigeo SUGIHARA, Fusao ARAI and Hiroshi MACHIDA, (6) The 1977 tephra of Mt. Usu volcano, by Yoshio KATSUI, (7) Some problems of tephras in Shikoku region, by Yoshio YASUDA and Hiromi MITSUSHIO, (8) Slope development with reference to tephrochronology, by Toshikazu TAMURA and Michio NOGAMI, (9) Some properties of soils of tephra origin, by Naganori YOSHINAGA, (10) Quaternary air circulation analyzed by distribution of tephra, by Masatoshi YOSHINO, (11) “Akahoya ash” in Southern Kyushu identified by determination of minor elements in ferromagnetite from tephra, by Yoshitaka NAGATOMO, (12) Forming processes of tephric soils with reference to tephrochronology, by Shigeo ASAMI. Discussions (1) Tephrochronology would be most useful for establishing eruptive history of a volcano. (2) Substantial descriptions based on petrographic and chemical determinations of most tephras in Japan are being carried out and could contribute to the finding of the wide-spread and the most important time-marker tephras. (3) Tephrochronology of deep-sea sediments will no doubt contribute to the developments of Quaternary studies on worldwide climatic history as well as on volcanism. (4) A detailed tephrochronology would provide a basis for revising and constructing geomorphological development and stratigraphy over extensive areas. (5) Drifted tephras by currents will be meaningful for correlating marine sediments and estimating palaeo oceanic currents. (6) Quaternary wind systems will be more precisely restored by distribution of tephra formations and/or groups over various ages. (7) Slope processes and its developments should be more fully analyzed by observations of tephra mantling. (8) Soil forming processes and the rates would be successfully clarified from the standpoint of tephrochronology.