We made multi-proxy analysis of 14C, grain size, microfossils, plant seeds, and geochemical elements on samples from a profile in the central West Lake of Lop Nur. The grain size suggests relatively stable sedimentary...We made multi-proxy analysis of 14C, grain size, microfossils, plant seeds, and geochemical elements on samples from a profile in the central West Lake of Lop Nur. The grain size suggests relatively stable sedimentary environment around the Medieval Warm Period (MWP) with weak storm effect, which is followed by frequent strong storm events. Abundant microfossils and plant seeds in this stage indicate a warm and humid fresh to brackish lake environment. C, N, and stable elements are high in content in the sediments while Rb/Sr, Ba/Sr, and Ti/Sr are in a steady low level. In addition, plenty of red willows lived here prior to about 700 a B.P., indicating a favorable environmental condition. The results indicate that the environment in Lop Nur and its west bank turned to be favorable at about 2200 a B.P., where the Loulan Culture began to thrive. Then the climate and environment came to be in the good condition in the Tang and Song Dynasties, when the storm effect became weaker, rainfall increased and the salty lake water turned to be brackish to fresh lake water. Hence, limnic biomass increased with higher species diversity.展开更多
Carbon isotope of loess through S0 to S 11 at luochuan section in Shaanxi Province were experimented.The curve of δ 13C compares well to the oxygen isotope curves of deep sea sediments from DSDP607 drill.There is obv...Carbon isotope of loess through S0 to S 11 at luochuan section in Shaanxi Province were experimented.The curve of δ 13C compares well to the oxygen isotope curves of deep sea sediments from DSDP607 drill.There is obviously negative peak of δ 13C within S5 paleosol where the content of δ 13C is-16.615‰,that shows the climatic optimum,and the vegetation during the period is likely forest.Comparing with the pollen analysis,the vegetation type of paleosol S0,S1,S4,S8,S9 which δ 13C content is-5.85‰～-10.00‰,is forest-grass.δ 13C content of paleosol S2、S3、S6、S7 is-8.72‰～-6.95‰,their vegetation is grass.The loess layer L1、L2、L5、L6、L8、L9 represent the severe cold-dry glacial period with δ 13C content of-3.7‰～-2.27‰,their vegetation belonging to steppe-desert.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 40701190)the University Doctoral Foundation (Grant No. 20070284067)the Opening Test Foundation of Institute of Earth Environment, CAS and the Test Foun-dation of Modern Analyses Center of Nanjing University
文摘We made multi-proxy analysis of 14C, grain size, microfossils, plant seeds, and geochemical elements on samples from a profile in the central West Lake of Lop Nur. The grain size suggests relatively stable sedimentary environment around the Medieval Warm Period (MWP) with weak storm effect, which is followed by frequent strong storm events. Abundant microfossils and plant seeds in this stage indicate a warm and humid fresh to brackish lake environment. C, N, and stable elements are high in content in the sediments while Rb/Sr, Ba/Sr, and Ti/Sr are in a steady low level. In addition, plenty of red willows lived here prior to about 700 a B.P., indicating a favorable environmental condition. The results indicate that the environment in Lop Nur and its west bank turned to be favorable at about 2200 a B.P., where the Loulan Culture began to thrive. Then the climate and environment came to be in the good condition in the Tang and Song Dynasties, when the storm effect became weaker, rainfall increased and the salty lake water turned to be brackish to fresh lake water. Hence, limnic biomass increased with higher species diversity.
文摘Carbon isotope of loess through S0 to S 11 at luochuan section in Shaanxi Province were experimented.The curve of δ 13C compares well to the oxygen isotope curves of deep sea sediments from DSDP607 drill.There is obviously negative peak of δ 13C within S5 paleosol where the content of δ 13C is-16.615‰,that shows the climatic optimum,and the vegetation during the period is likely forest.Comparing with the pollen analysis,the vegetation type of paleosol S0,S1,S4,S8,S9 which δ 13C content is-5.85‰～-10.00‰,is forest-grass.δ 13C content of paleosol S2、S3、S6、S7 is-8.72‰～-6.95‰,their vegetation is grass.The loess layer L1、L2、L5、L6、L8、L9 represent the severe cold-dry glacial period with δ 13C content of-3.7‰～-2.27‰,their vegetation belonging to steppe-desert.
