Abstract
A study using diatom analysis combined with selective chemical extraction was conducted to interpret paleoenvironmental changes in the core sediment obtained near the Maruyama-gawa River in Toyooka Basin, Hyogo Prefecture.A sediment sample was leached subsequently with 1N HCl and 30% H2O2. The remaining silicate fraction was used for the diatom analysis. In the present study, pyrite-sulfur (FeS2-S) content determined in the 30% H2O2 soluble fraction was employed to distinguish marine from freshwater depositional condition and a new diatom-based index of paleosalinity (DIPs) was proposed for the estimation of salinity changes in sedimentary environments. Because of the complementarity between pyrite and diatom analysis in muddy sediments, this method provided continuous and detailed information on the paleoenvironmental changes.Based on the variation of the DIPs and pyrite content, six phases were distinguished in the present core sample, reflecting salinity changes in sedimentary environments probably caused by the marine transgressions and regressions. The phase variations were consistent with Holocene sea-level changes presumed by variations in δ13C values and the C/N ratios in the same core sample (NAKAI et al., 1989).
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Schedule a callMore From: Japanese Journal of Limnology (Rikusuigaku Zasshi)
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