The Loess Plateau-Northeastern Tibetan Plateau in China is famous for its deep andcontmuous distributed loess, in which soils (developed from loess) vary gradually with differentbiological climates changing from subhu...The Loess Plateau-Northeastern Tibetan Plateau in China is famous for its deep andcontmuous distributed loess, in which soils (developed from loess) vary gradually with differentbiological climates changing from subhumid to arid, which provide a natural proving ground forstUd}' the coupling of loess-paleosol and climatic changes quantitatively. Thirty-two sections weresampled (collected) for measuring chemical element contents, clay content (and other items) and 60sections were collected for carbonate analysis to establish transfer functions between pedogenesisand climate. Finally, we estimated the paleoclAnate (P/T) in the region with transfer functions,It isrevealed that the variation of paleocldriate reflected by transfer functions accorded closely with theclimatic pattern resulted from recent work. Specifically, it was about 140 ha BP that summermonsoon reached Lanzhou or further, paleosol S1 (equaling to MIS 5 in deep sea records) developedstrongly in a large scale, even touching upon northeanstern Tibetan Plateau. And, the estimated P/Tinformation also indicated the cold and humid period during 50-30 ka BP, mean annual Precipitationwas about 400-500 nun in Angutan recorded by mega-interstadial paleosol Sm.展开更多
This paper summarizes the work from the INQUA 1997 Project "Response of soilformation to short-warm-episodes of Asian summer monsoon" and its seeded related internationaland domestic grants. It reviews the e...This paper summarizes the work from the INQUA 1997 Project "Response of soilformation to short-warm-episodes of Asian summer monsoon" and its seeded related internationaland domestic grants. It reviews the effects of the millennial monsoonal changes on the loess-paleosols of the Chinese Loess and Tibetan Plateaus. High-resolution proxy records ofpedogenesis and monsoons demonstrate that both Asian winter and summer monsoons wereunstable and synchronously and inversely coupled during the last glaciation. During that timerapid episodic cycles of cold surges and warm enhancements spanned only ca. 1-2 ka in high-frequency domain. Sub-Milankovitch cycles (6-8 ka) of progressive cooling or weakening in low-frequency domain generally resembled the pattern of the North Atlantic climatic change. However,during the last interglacial, Asian winter and summer monsoons seemed to vary independently, theformer being stable and the later unstable. Soil formation seems to occur in surprisingly fastresponse to the summer monsoon warm enhancements, resulting in weakly or moderatelydeveloped paleosol sequences. North Atlantic and polar cold air surges though the westerlies andother paths, and the north-south swing of the westerlies beside the Tibetan Plateau, may be thealternative mechanisms for the rapid monsoonal changes during the last glacial. But in the lastinterglacial, the summer monsoons worked largely independently.展开更多
Grain size of eolian deposits from the Loess Plateau in China has been widely used to reconstruct the history of the East Asian winter monsoon. However, the grain size of bulk samples is only partially indicative to t...Grain size of eolian deposits from the Loess Plateau in China has been widely used to reconstruct the history of the East Asian winter monsoon. However, the grain size of bulk samples is only partially indicative to the strength of the winter monsoon because post-depositional weathering processes have significantly changed the grain size of original eolian particles. Here, non-weathered loess samples were separated into eight different particle fractions, and major chemical elements were determined in order to establish a geochemical indicator of original eolian grain size. The results show that SiO2and AI2O3contents and the SiO2/AI203 ratio in different fractions vary regularly with grain size, and that a good linear relation exists between the SiO2/AI2O3 ratio and grain size for the fractions【50μm. Because Al and Si are among the most stable elements and pedogenic processes in the Loess Plateau cannot affect the SiO2/AI2O3 ratio, this index can be used to reflect the grain size of original eolian展开更多
文摘The Loess Plateau-Northeastern Tibetan Plateau in China is famous for its deep andcontmuous distributed loess, in which soils (developed from loess) vary gradually with differentbiological climates changing from subhumid to arid, which provide a natural proving ground forstUd}' the coupling of loess-paleosol and climatic changes quantitatively. Thirty-two sections weresampled (collected) for measuring chemical element contents, clay content (and other items) and 60sections were collected for carbonate analysis to establish transfer functions between pedogenesisand climate. Finally, we estimated the paleoclAnate (P/T) in the region with transfer functions,It isrevealed that the variation of paleocldriate reflected by transfer functions accorded closely with theclimatic pattern resulted from recent work. Specifically, it was about 140 ha BP that summermonsoon reached Lanzhou or further, paleosol S1 (equaling to MIS 5 in deep sea records) developedstrongly in a large scale, even touching upon northeanstern Tibetan Plateau. And, the estimated P/Tinformation also indicated the cold and humid period during 50-30 ka BP, mean annual Precipitationwas about 400-500 nun in Angutan recorded by mega-interstadial paleosol Sm.
文摘This paper summarizes the work from the INQUA 1997 Project "Response of soilformation to short-warm-episodes of Asian summer monsoon" and its seeded related internationaland domestic grants. It reviews the effects of the millennial monsoonal changes on the loess-paleosols of the Chinese Loess and Tibetan Plateaus. High-resolution proxy records ofpedogenesis and monsoons demonstrate that both Asian winter and summer monsoons wereunstable and synchronously and inversely coupled during the last glaciation. During that timerapid episodic cycles of cold surges and warm enhancements spanned only ca. 1-2 ka in high-frequency domain. Sub-Milankovitch cycles (6-8 ka) of progressive cooling or weakening in low-frequency domain generally resembled the pattern of the North Atlantic climatic change. However,during the last interglacial, Asian winter and summer monsoons seemed to vary independently, theformer being stable and the later unstable. Soil formation seems to occur in surprisingly fastresponse to the summer monsoon warm enhancements, resulting in weakly or moderatelydeveloped paleosol sequences. North Atlantic and polar cold air surges though the westerlies andother paths, and the north-south swing of the westerlies beside the Tibetan Plateau, may be thealternative mechanisms for the rapid monsoonal changes during the last glacial. But in the lastinterglacial, the summer monsoons worked largely independently.
基金the National Basic Research Project (GrantNo. 1998040800), the National Natural Science Foundation of China (Grant Nos. 49725206, 49894170-06 and 40024202) and the Chinese Academy of Sciences (Grant No. KZCX2-108).
文摘Grain size of eolian deposits from the Loess Plateau in China has been widely used to reconstruct the history of the East Asian winter monsoon. However, the grain size of bulk samples is only partially indicative to the strength of the winter monsoon because post-depositional weathering processes have significantly changed the grain size of original eolian particles. Here, non-weathered loess samples were separated into eight different particle fractions, and major chemical elements were determined in order to establish a geochemical indicator of original eolian grain size. The results show that SiO2and AI2O3contents and the SiO2/AI203 ratio in different fractions vary regularly with grain size, and that a good linear relation exists between the SiO2/AI2O3 ratio and grain size for the fractions【50μm. Because Al and Si are among the most stable elements and pedogenic processes in the Loess Plateau cannot affect the SiO2/AI2O3 ratio, this index can be used to reflect the grain size of original eolian
