The Early Pleistocene environmental change in the northwestern Osaka sedimentary basin, southwestern Japan

2019 Humans and Nature  
Diatom assemblages in the sediments from two outcrops (Sites A and B) in the Nigawa green tract of land, Nishinomiya, were analyzed to clarify changes in sedimentary environments. These sites (120-130 m a.s.l.) exposing the clay/silt beds are situated below the nearby outcrop (149-153 m a.s.l.) with the sediments identified as the marine clay layer Ma1 of the Osaka Group, indicating the beds possibly correlative to any one of three marine clay layers (Ma-1, Ma0 or Ma0.5). We also performed the
more » ... iatom analyses of the samples from these marine clay layers of the GS-K3 core at Higashinada, Kobe. Stratigraphic comparison between the two outcrops and three layers based on their species composition suggested that the sediments at Sites A and B can be correlated with the Ma-1 and Ma0, respectively. Thus, we derived the late Early Pleistocene environmental change in the northwestern area of the Osaka sedimentary basin. During the Ma-1 deposition at 1.24 Ma corresponding to Marine Isotope Stage (MIS) 37, this area was lacustrine environments. During the Ma0 deposition (MIS 35, 1.17 Ma), the environment was inner bay conditions, although the marine influence was weaker than the Ma1 deposition (MIS 31, 1.07 Ma).
doi:10.24713/hitotoshizen.30.0_1 fatcat:ht2kosnfqnhn5lsjgbhbau2fym