Alternative radiocarbon age-depth model from Lake Baikal sediment; Implication for past hydrological changes for last glacial to the Holocene

バイカル湖堆積物の放射炭素年代モデル; 最終氷期以後の水文学的変化への考察

奈良 郁子*   ; 渡邊 隆広   ; Lougheed, B.*; Obrochta, S.*

Nara, Fumiko*; Watanabe, Takahiro; Lougheed, B.*; Obrochta, S.*

南シベリアのバイカル湖堆積物の放射性炭素年代測定結果を新たに取得しコア試料の年代軸を再構築した。コア試料の年代値と堆積深度の不確実性を考慮するために、本研究では新しい年代-深度モデル(age-depth modeling routine, undatable)を使用した。その結果、19cal kaBPと14cal kaBPのメルトウォーターパルス時期、及び21-20cal kaBPの最終氷期最盛期において堆積速度の著しい変動が認められた。

We present an updated radiocarbon age model using IntCal20 to calibrated new AMS data applied to a Lake Baikal sediment core in south Siberia. Radiocarbon measurements showed that the core extends to 32 cal kaBP. To take into account uncertainties in radiocarbon age and sedimentation depth in the core, a new age-depth modeling routine, undatable, was used in this study. Undatable revealed that the significant changes in the sedimentation rate correspond to global climate events, either warm or cold, which are the Meltwater pulses (MWP) at 19 and 14 cal kaBP and the Last glacial maximum (LGM) at 21-20 cal kaBP. Since the Selenga River accounts for 50 % of the total river inflow to Lake Baikal, we interpret that these changes in sedimentation rate could be signals of significant increase in Selenga River discharge to the lake, which is expected to be affected by global climate change.