Stratigraphic distribution of Hemiptelea (Ulmaceae) pollen from Pleistocene sediments in the Osaka sedimentary basin, southwest Japan

Abstract

Pollen of Hemiptelea, now extinct in Japan, obtained from Pleistocene sediments from Kobe City, Kinki District, southwest Japan, provides key information on stratigraphic variations that correlate with seasonal variations in paleotemperature and paleoprecipitation.In the Osaka sedimentary basin, Hemiptelea pollen is distributed stratigraphically from the Ma 2 marine clay bed, which corresponds to the upper part of the Lower Pleistocene, to the Ma 12 marine clay bed, which corresponds to the lower part of the Upper Pleistocene sediments. Moreover, pollen of this genus occurs stably throughout marine clay beds Ma 3 to Ma 11, which correspond to the Middle Pleistocene. The climatic conditions where Hemiptelea davidii grows naturally at present, for example, in the central and northern parts of the Korean Peninsula and in continental China, together with the results of the present study imply that the Middle Pleistocene paleoclimate in Kinki District was cooler and drier than that of the Early Pleistocene, especially during the winter.