The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in thi...The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.展开更多
Cretaceous climate was warmer than today.The Songliao Basin contains one of the most important Late Cretaceous non-marine deposits in China for the research of the paleoenvironment and paleoclimate.This research is ba...Cretaceous climate was warmer than today.The Songliao Basin contains one of the most important Late Cretaceous non-marine deposits in China for the research of the paleoenvironment and paleoclimate.This research is based on core samples from the SK1(S)borehole.The strata sampled are the upper part of the Quantou Formation to member 2 of the Nenjiang Formation,where spores,pollen,dinoflagellates,and other microfossils are abundantly preserved.Based on analysis of the spores and pollen fossils from the core samples,the following six fossil assemblage zones have been recognized in ascending order:The Cicatricosisporites-Cyathidites-Pinuspollenites,Schizaeoisporites-Cyathidites-Classopollis,Cyathidites-Schizaeoisporites,Schizaeoisporites-Cyathidites-Proteacidites,Proteacidites-Cyathidites-Dictyotriletes,and the Lythraites-Callistipollenites-Schizaeoisporites zones.The six fossil zones range from the late Cenomanian to early Campanian.The Late Cretaceous dinoflagellate cysts in the Songliao Basin are of high abundance and low diversity.Specific phytoplankton types reflect salinity changes of the Songliao Lake.Paleoecology of the dinoflagellates suggests that sediments of members 2 and 3 of the Yaojia Formation(K2y2+3)were deposited in a freshwater environment,whereas members 2 and 3 of the Qingshankou Formation(K2q2+3)and members 1 and 2 of the Nenjiang Formation(K2n1+2)were deposited in freshwater to brackish water environments.Combined with the paleoecology of dinoflagellates and the palynomorph biozones,valuable information of the paleoclimate was provided.The quantitative analyses of spores and pollen fossils,such as vegetation type,climate type,and humidity type,diversity and dominance,indicate a relatively sub-humid,mid-subtropical paleoclimate,with slight climatic fluctuation and/or temporal change.展开更多
The Liuqu Conglomerates consist of a suit of terrestrial molasse deposits formed in a foreland basin of the Himalaya-Tibet orogenic belt before the collision of India and Eurasia.These deposits record considerable geo...The Liuqu Conglomerates consist of a suit of terrestrial molasse deposits formed in a foreland basin of the Himalaya-Tibet orogenic belt before the collision of India and Eurasia.These deposits record considerable geological information regarding the late tectonic evolution of the Neotethyan ocean.The palynological study of interlayers of mudstone and mud-sandstones indicates an Oligocene age.The palynological assemblage consists mainly of deciduous broad-leaved angiosperms,with some coniferous gymnosperms and evergreen broad-leaved angiosperms.The deposits reflect a broad-leaved deciduous forest or mixed with conifer-broad-leaved forest ecotypes,showing a warm-temperate or temperate zone climatic environment.This work provides significant new information about the tectonic evolution,paleogeography,and paleoenvironment of southern Tibet during the Cenozoic.展开更多
文摘The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.
基金supported by National Basic Research Program of China(Grant No.2012CB822002)National Natural Science Foundation of China(Grant No.41172037),China Geological Survey(Grant No.1212011120145)+1 种基金State Key Laboratory of Palaeobiology and Stratigraphy(Nanjing Institute of Geology and Palaeontology,CAS)(Grant No.123111)Fundamental Research Funds for the Central Universities(Grant No.2012011)
文摘Cretaceous climate was warmer than today.The Songliao Basin contains one of the most important Late Cretaceous non-marine deposits in China for the research of the paleoenvironment and paleoclimate.This research is based on core samples from the SK1(S)borehole.The strata sampled are the upper part of the Quantou Formation to member 2 of the Nenjiang Formation,where spores,pollen,dinoflagellates,and other microfossils are abundantly preserved.Based on analysis of the spores and pollen fossils from the core samples,the following six fossil assemblage zones have been recognized in ascending order:The Cicatricosisporites-Cyathidites-Pinuspollenites,Schizaeoisporites-Cyathidites-Classopollis,Cyathidites-Schizaeoisporites,Schizaeoisporites-Cyathidites-Proteacidites,Proteacidites-Cyathidites-Dictyotriletes,and the Lythraites-Callistipollenites-Schizaeoisporites zones.The six fossil zones range from the late Cenomanian to early Campanian.The Late Cretaceous dinoflagellate cysts in the Songliao Basin are of high abundance and low diversity.Specific phytoplankton types reflect salinity changes of the Songliao Lake.Paleoecology of the dinoflagellates suggests that sediments of members 2 and 3 of the Yaojia Formation(K2y2+3)were deposited in a freshwater environment,whereas members 2 and 3 of the Qingshankou Formation(K2q2+3)and members 1 and 2 of the Nenjiang Formation(K2n1+2)were deposited in freshwater to brackish water environments.Combined with the paleoecology of dinoflagellates and the palynomorph biozones,valuable information of the paleoclimate was provided.The quantitative analyses of spores and pollen fossils,such as vegetation type,climate type,and humidity type,diversity and dominance,indicate a relatively sub-humid,mid-subtropical paleoclimate,with slight climatic fluctuation and/or temporal change.
基金supported by National Natural Science Foundation of China (Grant No. 40631004)
文摘The Liuqu Conglomerates consist of a suit of terrestrial molasse deposits formed in a foreland basin of the Himalaya-Tibet orogenic belt before the collision of India and Eurasia.These deposits record considerable geological information regarding the late tectonic evolution of the Neotethyan ocean.The palynological study of interlayers of mudstone and mud-sandstones indicates an Oligocene age.The palynological assemblage consists mainly of deciduous broad-leaved angiosperms,with some coniferous gymnosperms and evergreen broad-leaved angiosperms.The deposits reflect a broad-leaved deciduous forest or mixed with conifer-broad-leaved forest ecotypes,showing a warm-temperate or temperate zone climatic environment.This work provides significant new information about the tectonic evolution,paleogeography,and paleoenvironment of southern Tibet during the Cenozoic.
