1363 / 2019-08-09 18:41:08

High resolution OSL dating of aeolian activity at Qinghai Lake, Northeast Tibetan Plateau

1、第四纪地质与全球变化 > 专题6：第四纪年代学进展及应用

Qinghai Lake is the largest lake on the Tibetan Plateau (TP), located between the extremely arid Qaidam Basin to the west and the severely desertified Gonghe Basin to the south. Extensive aeolian sediment at Qinghai Lake is ideal material to reconstruct regional aeolian activity, and to better understand the relationship between desertification and climatic change in the lake basin. Aeolian sand accumulation is usually accompanied by erosion, hence, depositional hiatuses and disconformities must be identified for reliable reconstruction of regional aeolian activity. To date, the low density of age sampling around Qinghai Lake has hindered identification of hiatuses. In this study we report the first high density OSL dating; 41 OSL ages were obtained from two aeolian sand sections, Dongwei (DW) and Niaodao (ND). Sand accumulation trends recorded in the high-density OSL sampling sections were consistent with previously published probability density function (PDF) ages for the northeast TP. The middle Holocene (~7 to ~4 ka) was characterized by very low accumulation rates, with rapid sedimentation in the Late Glacial to Early Holocene (~14 to ~7 ka) and the Late Holocene (after ~4 ka). A ~3 ka hiatus in accumulation during ~7－4 ka was identified in the DW section, but the ND section showed successive accumulation since the Late Glacial (~14 ka), on sub-orbital and millennial scales. Our environmental reconstructions are consistent with previously published aeolian data and paleoshorelines records. The combined evidence shows: strong aeolian activity since ~14 to ~9 ka; initiation of pedogenesis at ~9 to 7 ka; intensified soil development between ~7 ka and ~4 ka (with the most intense pedogenesis and least aeolian activity from ~6 to ~4 ka); relatively weak paleosol formation from ~4 to ~2 ka; and renewed aeolian activity after ~2 ka.