Xitaijinair （XT） Salt Lake, located in the western Qaidam Basin, is significant for recon- structing the evolution of inland drying climate. However, the chronological and mineralogical records from this lake are ra...Xitaijinair （XT） Salt Lake, located in the western Qaidam Basin, is significant for recon- structing the evolution of inland drying climate. However, the chronological and mineralogical records from this lake are rare. This study investigated the chronology （accelerator mass spectrometry （AMS） 14C ages and optically stimulated luminescence （OSL） ages） and mineral compositions of sediment in the 240-cm-deep XT Section of the Xitaijinair Salt Lake region. The conclusions are drawn as follows： （1） Nine AMS 14C ages, ranging between 33 and 40 cal ka BP, are obviously younger than the two OSL ages （57.9 and 69.1 ka）. The 14C ages probably reflect contamination with modern carbon. （2） Both 14C and OSL ages indicate that the surface of Xitaijinair Salt Lake region has suffered erosion. （3） The se- diments of XT Section are composed of silicates （quartz, muscovite, clinochlore and albite）, carbonates （calcite, dolomite, and ankertie）, halite and gypsum.展开更多
The Neogene eolian deposits in the Xining Basin are valuable archive for studying the evolution of the Asian monsoon system and geomorphic processes of Northwest China. The Neogene eolian deposits that paleomagnetical...The Neogene eolian deposits in the Xining Basin are valuable archive for studying the evolution of the Asian monsoon system and geomorphic processes of Northwest China. The Neogene eolian deposits that paleomagnetically dated at about 14 Ma probably were sourced from the middle and west Qinghai-Tibetan Plateau（QTP） as indicated by elemental compositions and magnetic properties. This study provides the Sr-Nd-Pb isotopic ratios of different sediments（gravels from the river terraces, Neogene eolian deposits and Quaternary loess） in the Xining Basin. The results show that：（1） Sr-Nd isotopic compositions of terrace gravels are different from those of the Neogene and Quaternary eolian deposits, although the Nd isotope ratios of gravel on the 10 th terrace（T10） and eolian deposits are similar.（2） Pb isotopic compositions of river gravels are obviously different from the eolian deposits in the Xining Basin. However, Pb isotopic compositions of eolian deposits in the basin are similar to those of eolian deposits in the central Chinese Loess Plateau.（3） Sr-Nd-Pb isotope results indicate that the Neogene eolian deposits in the Xining Basin were probably sourced from remote areas outside of the basin by long-distance transportation. The Qaidam Basin is probably an important source area for the eolian deposits in the Xining Basin.展开更多
Total organic carbon（TOC） in lake sediments and its stable carbon isotope（δ（13）C（org）） are widely applied to investigate paleoenvironmental changes even though their implications are complicated and multi-exp...Total organic carbon（TOC） in lake sediments and its stable carbon isotope（δ（13）C（org）） are widely applied to investigate paleoenvironmental changes even though their implications are complicated and multi-explanatory. Organic geochemistry studies of lake sediments from Qinghai Lake have been investigated, but some interpretations are controversial. In this study, TOC of one Holocene eolian section and δ（13）C（org） of three eolian sections were studied around Qinghai Lake. Results indicate that the TOC content in eolian deposits was low during the Early Holocene, and gradually increased to high values during the Middle and Late Holocene. The variation in TOC content of eolian deposits is different from that in the lacustrine sequence from Qinghai Lake during the Holocene. The δ（13）C（org） values in the eolian sections were relatively stable, with oscillation amplitudes of 4‰（ranging from-25.8‰ to-22.1‰）, in contrast to 10‰ variation s in δ（13）C（org） values（varying from-30‰ to-20‰） in lacustrine sediments. Through comparison of TOC and δ（13）C（org） values between eolian deposits and lacustrine sediments, we can confirm indications that the organic matter in Qinghai Lake sediments during the Holocene was primarily a contribution of the aquatic species in the lake. This is significant for understanding the origin of organic matter in lake sediments on the northeastern Qinghai-Tibetan Plateau and for paleoenvironmental inferences using such proxies.展开更多
基金supported by the National Natural Science Foundation of China(No.41402314)the KLSLRC(No.KLSLRC-KF-13-DX-11)+1 种基金the Youth Guidance Foundation of ISL-CAS(No.Y460261051)the China Geological Survey(No.12120113033029)
文摘Xitaijinair （XT） Salt Lake, located in the western Qaidam Basin, is significant for recon- structing the evolution of inland drying climate. However, the chronological and mineralogical records from this lake are rare. This study investigated the chronology （accelerator mass spectrometry （AMS） 14C ages and optically stimulated luminescence （OSL） ages） and mineral compositions of sediment in the 240-cm-deep XT Section of the Xitaijinair Salt Lake region. The conclusions are drawn as follows： （1） Nine AMS 14C ages, ranging between 33 and 40 cal ka BP, are obviously younger than the two OSL ages （57.9 and 69.1 ka）. The 14C ages probably reflect contamination with modern carbon. （2） Both 14C and OSL ages indicate that the surface of Xitaijinair Salt Lake region has suffered erosion. （3） The se- diments of XT Section are composed of silicates （quartz, muscovite, clinochlore and albite）, carbonates （calcite, dolomite, and ankertie）, halite and gypsum.
基金supported by NSFC (Nos. 41402314, 41472313)Natural Science Foundation of Qinghai Province (No. 2012-Z-933Q)+2 种基金KLSLRC (No. KLSLRC-KF-13-DX-11)Youth Guidance Foundation of ISL-CAS (Nos. Y460261051, Y360441058)China Geological Survey (No. 12120113033029)
文摘The Neogene eolian deposits in the Xining Basin are valuable archive for studying the evolution of the Asian monsoon system and geomorphic processes of Northwest China. The Neogene eolian deposits that paleomagnetically dated at about 14 Ma probably were sourced from the middle and west Qinghai-Tibetan Plateau（QTP） as indicated by elemental compositions and magnetic properties. This study provides the Sr-Nd-Pb isotopic ratios of different sediments（gravels from the river terraces, Neogene eolian deposits and Quaternary loess） in the Xining Basin. The results show that：（1） Sr-Nd isotopic compositions of terrace gravels are different from those of the Neogene and Quaternary eolian deposits, although the Nd isotope ratios of gravel on the 10 th terrace（T10） and eolian deposits are similar.（2） Pb isotopic compositions of river gravels are obviously different from the eolian deposits in the Xining Basin. However, Pb isotopic compositions of eolian deposits in the basin are similar to those of eolian deposits in the central Chinese Loess Plateau.（3） Sr-Nd-Pb isotope results indicate that the Neogene eolian deposits in the Xining Basin were probably sourced from remote areas outside of the basin by long-distance transportation. The Qaidam Basin is probably an important source area for the eolian deposits in the Xining Basin.
基金funded by Chinese Post-doctoral Research Fund (No. 2014T70951)the National Natural Science Foundation of China (Nos. 41201014, 41371028, 41402314)
文摘Total organic carbon（TOC） in lake sediments and its stable carbon isotope（δ（13）C（org）） are widely applied to investigate paleoenvironmental changes even though their implications are complicated and multi-explanatory. Organic geochemistry studies of lake sediments from Qinghai Lake have been investigated, but some interpretations are controversial. In this study, TOC of one Holocene eolian section and δ（13）C（org） of three eolian sections were studied around Qinghai Lake. Results indicate that the TOC content in eolian deposits was low during the Early Holocene, and gradually increased to high values during the Middle and Late Holocene. The variation in TOC content of eolian deposits is different from that in the lacustrine sequence from Qinghai Lake during the Holocene. The δ（13）C（org） values in the eolian sections were relatively stable, with oscillation amplitudes of 4‰（ranging from-25.8‰ to-22.1‰）, in contrast to 10‰ variation s in δ（13）C（org） values（varying from-30‰ to-20‰） in lacustrine sediments. Through comparison of TOC and δ（13）C（org） values between eolian deposits and lacustrine sediments, we can confirm indications that the organic matter in Qinghai Lake sediments during the Holocene was primarily a contribution of the aquatic species in the lake. This is significant for understanding the origin of organic matter in lake sediments on the northeastern Qinghai-Tibetan Plateau and for paleoenvironmental inferences using such proxies.
