Diatom analysis of the uppermost Pleistocene to Holocene drilled core at Sarufutsu, northern Hokkaido, Japan:

Investigation of salinity index and electrical conductivity

Abstract

In order to clarify sedimentary environment of the latest Pleistocene to Holocene sediments, Chuseki-so, geologic core of 33 m (HU-SRN-1) and 9 m core (AEM-1) in length were obtained at the Sarufutsu, northern Hokkaido. Radiocarbon dating, electrical conductivity measurement, diatom analysis and lithofacies division were carried out on the cores. Results of diatom analysis of the HU-SRN-1 core show the sedimentary environment changed fresh waters, brackish waters and fresh waters in ascending order, and seawater inundation during Holocene transgression occurred at 27 m in depth (15.2 m below sea level) at ca. 8,990 cal BP. Correlation coefficient in the HU-SRN-1, ca. 0.38, is computed by electrical conductivity and salinity index, determined from diatom assemblages. Distinctive features in curved lines of salinity index infer possibility of stratigraphic correlation of Chuseki-so in two different areas, Ishikari, central Hokkaido, and Sarufutsu.