[H-QR23_1PO1] Diachronic dynamics of human-environment interactions

[HQR23-P03] Paleoenvironments analysis for the past 50 ka based on TOC and TN of the sediment cores INW2012-1 and -2,Lake Inawashiro

*Kei WATANABE¹, Yoshitaka NAGAHASHI², Kotaro HIROSE³, Fujio KUMON⁴ (1.Graduate School of Science, Shinshu University, 2.Faculty of Symbiotic Systems Science, Fukushima University, 3.Graduate School of Systems and Technology, Fukushima University, 4.Department of Environmental Sciences, Faculty of Science, Shinshu University)

Keywords:Lake Inawashiro, TOC, TN, C/N, paleoenvironments, paleoclimate

The total organic carbon (TOC) and total nitrogen (TN) were measured at 2 cm interval for the long sediment cores (INW2012-1, INW2012-2) taken from a central site of 90 m depth in Lake Inawashiro in Fukushima Prefecture. Depth-age relationship has been established based on six 14C data, and the bottom of the drilled core, about 28 m, is estimated as old as 48 ka. Sampleinterval is 50 to100 years. The compilation of information on lithology, TOC and TN concentrations, C/N ratio and water contents of INW2012-1 and -2 enable us to reveal the paleoenvironments of Lake Inawashiro from the early stage to the present with high temporal resolution. Deep condition of Lake Inawashiro started 42,000 years ago and then the lake has been constantly deep until now.Temporal change of TOC concentration of Lake Inawashiro shows the quasi-periodical fluctuation similar to the marine isotope curve known as LR04, and corresponds well to that of TOC concentration of Lake Nojiri in Nagano Prefecture. Vegetation change revealed at theYanohara, moor in Fukushima Prefecture corresponds with the TOC fluctuation of TOC in the lake. Therefore, Temporal change of the TOC concentration in Lake Inawashiro seems to be controlled mainly by climate, probably temperature, and can be one of the useful paleoclimate records in the Tohoku region, Japan.