The expansion of inland Asia deserts has considerably influenced the environmental, social and economic activities in Asia. Aridification of inland Asia, especially timing of the initiation of Asian desertification, i...The expansion of inland Asia deserts has considerably influenced the environmental, social and economic activities in Asia. Aridification of inland Asia, especially timing of the initiation of Asian desertification, is a contentious topic in paleoclimatology. Late Cenozoic eolian loess-red clay sequences on the Chinese Loess Plateau, which possess abundant paleoclimatic and paleo-environmental information, can be regarded as an indicator of inland Asia desertification. Here we present a detailed magnetostratigraphic investigation of a new red clay sequence about 654 m in Zhuanglang located at the western Chinese Loess Plateau. Sedimentological, geochemical, mineralogical, and quartz morphological lines of evidence show that the red clay is of eolian origin. Magnetostratigraphic correlations indicate that this core sequence spans from 25.6 to 4.8 Ma, and typical eolian red clay appears as early as 25 Ma. This extends the lower limit of the red clay on the Chinese Loess Plateau from the previously thought early Miocene back into the late Oligocene. This new red clay record further implies that the inland Asia desertification was initiated at least by the late Oligocene. This sequence provides a unique high-resolution geological record for understanding the inland Asia desertification process since the late Oligocene.展开更多
We investigated the spatiotemporal distribution of1 37Cs radioactivity in surface sediment of Qinghai Lake,and developed the spatial pattern of sedimentation rate.The1 37Cs inventory is higher near the estuary/bank ar...We investigated the spatiotemporal distribution of1 37Cs radioactivity in surface sediment of Qinghai Lake,and developed the spatial pattern of sedimentation rate.The1 37Cs inventory is higher near the estuary/bank area,but lower at the central lake.On the other hand,the average1 37Cs activity is lower near the estuary/bank area,but higher at the central lake.The mass accumulation rate(MAR) and the fluxes and contents of the terrestrial detritus(e.g.SiO2,Fe2O3,and Ti) are higher near the estuary/bank area,but lower at the central lake.The chemical/biogenic deposits(e.g.the autogenic carbonates) take up higher fractions at the central lake.These suggest that the spatial pattern of recent sedimentation rate is dominated by the deposition of terrestrial detritus.The average MAR(0.0337 g cm-2a-1) was estimated based on those of different cores of Qinghai Lake and was verified by a Ca mass-balance method.The fluxes of total lake sediments,terrestrial detritus,and direct atmospheric deposits were also estimated.展开更多
基金supported by National Basic Research Program of China (Grants Nos. 2010CB833400, 2004CB720200)Innovation Program of Chinese Academy of Sciences (Grant No. KZCX2-YW-Q09-04)+1 种基金National Natural Science Foundation of China (Grants Nos. 41072142, 40921120406 and 40772116)State Key Laboratory of Loess and Quaternary Geology (SKLLQG)
文摘The expansion of inland Asia deserts has considerably influenced the environmental, social and economic activities in Asia. Aridification of inland Asia, especially timing of the initiation of Asian desertification, is a contentious topic in paleoclimatology. Late Cenozoic eolian loess-red clay sequences on the Chinese Loess Plateau, which possess abundant paleoclimatic and paleo-environmental information, can be regarded as an indicator of inland Asia desertification. Here we present a detailed magnetostratigraphic investigation of a new red clay sequence about 654 m in Zhuanglang located at the western Chinese Loess Plateau. Sedimentological, geochemical, mineralogical, and quartz morphological lines of evidence show that the red clay is of eolian origin. Magnetostratigraphic correlations indicate that this core sequence spans from 25.6 to 4.8 Ma, and typical eolian red clay appears as early as 25 Ma. This extends the lower limit of the red clay on the Chinese Loess Plateau from the previously thought early Miocene back into the late Oligocene. This new red clay record further implies that the inland Asia desertification was initiated at least by the late Oligocene. This sequence provides a unique high-resolution geological record for understanding the inland Asia desertification process since the late Oligocene.
基金supported by the National Key Technology R&D Program (Grant No.2007 BAC30B01)West Light Foundation of the Chinese Academy of Sciences(Grant No.2007ZD01)
文摘We investigated the spatiotemporal distribution of1 37Cs radioactivity in surface sediment of Qinghai Lake,and developed the spatial pattern of sedimentation rate.The1 37Cs inventory is higher near the estuary/bank area,but lower at the central lake.On the other hand,the average1 37Cs activity is lower near the estuary/bank area,but higher at the central lake.The mass accumulation rate(MAR) and the fluxes and contents of the terrestrial detritus(e.g.SiO2,Fe2O3,and Ti) are higher near the estuary/bank area,but lower at the central lake.The chemical/biogenic deposits(e.g.the autogenic carbonates) take up higher fractions at the central lake.These suggest that the spatial pattern of recent sedimentation rate is dominated by the deposition of terrestrial detritus.The average MAR(0.0337 g cm-2a-1) was estimated based on those of different cores of Qinghai Lake and was verified by a Ca mass-balance method.The fluxes of total lake sediments,terrestrial detritus,and direct atmospheric deposits were also estimated.
