Affordable Access

Detailed stratigraphy of the GS-K2 and GS-K3 drilling cores mainly based on the correlation of volcanic ashes in the northwestern part of the Osaka sedimentary basinSouthwestern Japan

Authors
Publication Date
Disciplines
  • Archaeology
  • Earth Science

Abstract

Journal of Geosciences, Osaka City University Vol. 45, Art. 8, p. 101-123, March, 2002 Detailed stratigraphy of the GS-K2 and GS-K3 drilling cores mainly based on the correlation of volcanic ashes in the northwestern part of the Osaka sedimentary basin, Southwestern Japan KOBAY ASHI Gaku *, MITAMURA Muneki *, YOSHIKAWA Shusaku *, KATOH Shigehiro** and HYODO Masayuki *** *Department of Geosciences, Faculty of Science, Osaka City University, Osaka 558-8585, Japan * * Museum of Nature and Human Activities, Hyogo, Sanda 669-1546, Japan *** Research Center for Inland Seas, Kobe University, Kobe 657-8501, Japan Abstract The Osaka sedimentary basin is a Cenozoic tectonic subsidence basin including Osaka Bay and the Osaka Plain, and is filled with thick deposits: the Pliocene to Pleistocene Osaka Group, middle to upper Pleistocene terrace deposits and upper Pleistocene to Holocene alluvial deposits. After the 1995 Hyogoken - Nanbu Earthquake, many organizations surveyed the su bsurface geology and underground structure in the Kobe area. The GS - K2 and GS - K3 cores were dri lied at the southern foot of the Rokko Mountains, at Ishiyagawa, Nada - ku, Kobe City. But, because these cores consist of thick gravel beds on the upper parts, many stratigraphic problems have been unsolved. The purpose of this paper is to provide a better stratigraphy of these cores, especially of the upper parts, by means of magnetostratig- raphy and correlation of the volcanic ashes with the known marker tephra layers in the Osaka sedi- mentary basin. In the GS - K2 core, 2 volcanic ash horizons were identified at depths of 349 m and II 01, as well as a volcanic ash layer at depth of 181 m. The K2 - 349 volcanic ash horizon is correlated with Sayama volcanic ash layer for the similarities of shapes of glass shards and its refractive index. As a result of this correlation, the marine sand bed, at depth from 330.0 to 323.2 m is correspondent to the Ma 4 bed. The measurement of the paleomagnetism of the GS - K2 core

There are no comments yet on this publication. Be the first to share your thoughts.