渥美層群中下部から産出する植物遺体
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概要
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In the Atsumi Peninsula, Pleistocene deposits called Atsumi group are extensively distributed, and consist of Futagawa, Tahara and Toyohashi formations in ascending order.The lower or the Futagawa formation composed mainly of silt and sand is overlain by the Tahara formation with disconformity, and the latter underlies the Toyohashi formation with local disconformity. Many fossil plant remains have been obtained from various horizons of the group.In this paper the writer reports on the floras of the Futagawa and the Tahara formations.The lower part of the Futagawa formation includes some broad-leaved evergreen trees, which are found generally in the present flora of this peninsula and its vicinity. The climate at that time, therefore, may have been as today. The climate in the age of the upper part of the formation seems, however, to have become cooler, judging from the predominance of the temperate elements.The Tahara formation is divided into three members implying a submergence, the upper two of which are concerned here. The plant remain assemblage of the middle member is composed of broad-leaved deciduous and evergreen trees identical or closely related to the species now living in Central Japan. However, that of the upper lacks in deciduous trees suggesting temperate climate. Consequently, it is assumed that the former represents a little cooler condition than that of the present, whereas the latter as warm as today.It is noticed that Fagus aff. Hayatae, Abies firma and Cyclobalanopsis occur in abundance in the remains of the Tahara formation, compared with those of the Futagawa formation.On the geologic ages of these formations, the writer believes that they are assigned to the early and the middle Pleistocene respectively, judging from no characteristic elements of the Pliocene and also of the late Pleistocene in the floras.
- 日本第四紀学会の論文