[S-GL42_29AM2] 地球年代学・同位体地球科学

[SGL42-P04_PG] 滋賀県余呉湖細粒堆積物のルミネッセンス年代測定と環境変動解析

ポスター講演3分口頭発表枠

*伊藤 一充¹ (1.産業技術総合研究所 地質調査総合センター)

キーワード：OSL年代測定, pIRIR年代測定, 湖沼堆積物

We applied optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), post-IR IRSL (pIRIR) and ¹⁴C dating to the sediment core YG11-3 (294cm) from Lake Yogo, Japan. The fine grained quartz and polymineral sample are used for equivalent dose (D_e) estimation. As a result of several basically test, the preheat temperature of 200 ^oC for 10 s and a cut heat of 160 ^oC were suitable to all OSL measurements. The accepted aliquots are about 90 % per measurement discs and the range of D_es are 0.3 ~ 3.5 (Gy). The bulk ¹⁴C ages are ca. 300 years older than these of plant residue. After subtracting this age difference from bulk ¹⁴C ages, the corrected ages agree with the OSL ages except the ages of sediments from some depths. Two excepted OSL ages are older than the corrected bulk ¹⁴C ages (YG11-3-245, YG11-3-343) and these layers include a lot of plant residue enough to analyze the plant residue ¹⁴C ages. It seems that these sediments from two layers have been transported quickly in muddy stream based on a temporary environmental event. Additionally, the result of the IRSL_50/225 and pIRIR₂₂₅ age confirms the existence of this temporary event. By comparing the OSL ages with ¹⁴C, IRSL and pIRIR ages, the quartz from the small catchment area can be applied to reconstruct the age model of sediment core in Japan.