石狩湾大陸棚から採取した泥炭層について

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One dredged peat and two core samples, ca. 240 cm in length, have been collected from the continental shelf of the Isikari Bay, Western Hokkaido, Japan. From the pedological observation of samples and from the topographical consideration of the continental shelf of the Isikari Bay, it seems hardly possible that the peats have deposited secondarily or by slumping, but have accumulated in situ. Radiocarbon date of one core collected from -84 m, which is composed of a sequence of peat bed, shows >40,000 y.B.P.. Pollen and spore assemblages are almost the same throughout the sequence and it contains Picea > Abies as a larger part and broad-leaved trees Betula, Corylus and Quercus as a minor part. This pollen assemblage resembles for the most part to that of the deposits in the early stage of the Last Ice Age in Hokkaido. Combined with the radiocarbon date, it is suggestsed that this peat was accumulated in this stage. In another core collected from -83 m pollen and spore are contained in the lower and upper peaty horizons but not contained in the middle tuffaceous sandy horizon, which bears some sandpipes. According to radiocarbon date of ca. 23,000 y.B.P., it is inferred that this peat had accumulated in the maximum stage of the Last Ice Age. In the pollen assemblage of the lower and upper horizons Picea > Larix are predominant with subordinate amounts of Abies, Pinus and Betula, and this assemblage resembles very much to that of the maximum stage of the Last Ice Age deposits of Hokkaido. But through further examination in detail, in the lower and upper transitional horizons to middle tuffaceous sandy part, both Picea and Tsuga are dominant and Larix decreases, which fact indicates the temperature condition changed from cold to less cold and then went cold again. This change of climate corresponds to the change of lithofacies of this core sample caused by the fluctuation of the sea level. Dredged peat sample from -85 m contains the pollen and fossil woods of Larix. As Larix occurred from about 40,000 y.B.P. to early stage of Holocene in Hokkaido, dreged sample may be assigned to this interval.
地学団体研究会の論文
1981-09-25

石狩湾大陸棚から採取した泥炭層について

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