北日本の最終間氷期-氷期サイクルの古気候

抄録

There are few complete and high-resolution pollen records in the last interglacial-glacial cycle in Japan. We made clear in the recent paper (1990) that the paleoclimate from the Last Interglacial to the Lastglacial maximum in Hokkaido coincided closely with oxygen-isotope records from deep-sea cores by a pollen analytical study on the peat or peaty layers intercalated in the terrace deposits of the Hidaka district, southern Hokkaido, adding the terrestrial paleoclimatic evidence of paleo-glacial, paleo-periglacial, paleo-dunes, and so on.
The Hidaka district is one of the best successively developed areas of marine and fluvial terraces in Japan. We continued the survey in the same district and collected many samples for pollen analysis from the terrace deposits of different places and different ages. The stratigraphical sequence of the samples was mainly determined by the tephra layers which were inter-calated in the terrace deposits and were dated by various methods. The aim of this paper is to show the more detailed paleoclimatic features of the last interglacial-glacial cycle by syn-thesizing the former pollen records and newly obtained ones.
Five climatic types, glacial maximum (GM), glacial sub-maximum (GM′), glacial (G), lateglacial (LG), and postglacial (PG), were classified as a criterion for the zoning of pollen assemblages based on the pollen records of Kuromatsunai, southwestern Hokkaido and also Sakhalin which were obtained by the senior author. The synthesized results are shown in Fig. 8. The paleoclimatic diagram obtained is closely coincident with the normalized oxygen-isotope curve which is proposed by Martinson et at.(1987).
The pollen of Sciadopitys varticillata which is separately distributed in central and western Japan south of 37°C37'N and is not existent in Hokkaido (Fig. 6), is recognized around 140 ka BP, 90-100 ka BP, and 40-45 ka BP in the Hidaka district and is co-existent with boreal -type pollen. The occurrence of Sciadopitys pollen is also recognized in some locations in southern Hokkaido. The main occurrence periods of Sciadopitys pollen during the late Pleistocen e are well coincident through over Japan. These periods are considered to have been mo re humid.