紀伊半島室生山地の完新統の花粉分析

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At the eastern foothill of Kuroso-san situated at the prefectural boundary of Nara and Mie, some marshes were scattered in the topographic depression of geologic basement, Muro Welded Tuff Member, but nowadays many of them were cultivated and/or afforested. At one of them, Ike-no-hira which is now in low-moor condition, we obtained a short geologically and paleontologically interesting columnar sample with a hand auger technique. The present sample offers us indispensable Holocene geological and vegetational informations in the Muro mountain. We attempted stratigraphical, chronological and palynological investigation on 78-6 Core and discussed mainly on the Holocene vegetational change in this district.78-6 Core consists of peat, peaty sand and mud, and intercalate two volcanic ash layers. Inferred from a historical document, Kofukuji-Nendaiki, the upper thin ash layer is supposed that it fell in ca. 1, 000y. B.P., and the lower thick layer is correlated with the Akahoya Tuff based on its glass feature and heavy mineral composition. 14C dates processed with peaty sediment were given 5, 630±70y. B.P. for the overlying peat of the Akahoya Tuff, 6, 680±85y. B.P. for the underlying peat of the same tuff, and 11, 000±120y. B.P. at the lowest part of the sequence. The present core, therefore, covers the entire Holocene.Concerning to biostratigraphy we distinguished six pollen assemblage zones. Moreover, based on its sedimentation ratio geologic ages of their boundary were calculated. The present fossil evidences tell us that the cool temperate deciduous forest flourished during the latest Pleistocene to early Holocene time (ca. 12, 000-8, 400y. B.P.). The warm temperate ecotone forest was developed during early to middle Holocene (ca. 8, 400-6, 300y. B.P.). The climax condition of the laurel forest in this area was 1, 500-2, 000y, later than that of the environs of Osaka Bay and was in ca. 4, 300y. B.P. The laurel forest which appeared in ca. 900y. B.P. was characterized by coexistence of Pinus, Cryptomeria and Quercus. This may indicate artificial effects against the natural forest. The appearance of this forest was ca. 1, 000y. later than those of the Nara and Tawara Basins.

紀伊半島室生山地の完新統の花粉分析

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