The Quaternary strata on the Qinghai-Tibet Plateau contain rich information about the paleoclimate and environmental evolution,record the evolution process of the Quaternary regional tectonics,paleogeography,and geomo...The Quaternary strata on the Qinghai-Tibet Plateau contain rich information about the paleoclimate and environmental evolution,record the evolution process of the Quaternary regional tectonics,paleogeography,and geomorphology of the plateau,and are extremely important areas for studying the Quaternary geological events and regional environmental evolution.According to a comprehensive analysis of the regional stratigraphic data and the development and evolution characteristics of the biota,based on the differences in the lithostratigraphic units,sedimentary characteristics,landforms,and drainage systems,the Quaternary strata on the Qinghai-Tibet Plateau and its surrounding areas are divided into five stratigraphic regions:the Tarim region,Loess Plateau region,Qinghai-Tibet Plateau region,Yunnan-Guizhou Plateau region,and India-Ganges region.The Qinghai-Tibet Plateau stratigraphic region is divided into seven stratigraphic sub-regions:the West Kunlun-Karakorum,AltunQilian Mountains,Qaidam-Hehuang,East Kunlun-Bayan Har,Qiangtang,East Xizang-West Yunnan-West Sichuan,and Gangdise-Himalayan sub-regions.This paper briefly describes the lithostratigraphic units of the seven stratigraphic sub-regions of the Qinghai-Tibet Plateau.According to the lithostratigraphic sequence and its sedimentary characteristics,stratigraphic contact relationship,formation age,and evolution of the biota in each stratigraphic sub-region,the Quaternary tectonic paleogeographic evolution of the Qinghai-Tibet Plateau is divided into four stages.(1)The inherited differential uplift stage since the Pliocene(2.6-1.8/1.5 Ma):the regional sedimentary differences were significant,and the stratigraphic distribution was limited,the alluvial-proluvial sandy conglomerate was widely developed along the piedmont,and fluvial and lacustrine deposits were developed in the low-lying areas between the mountains.(2)The mountain range flattening stage(1.8/1.5-1.2/0.8 Ma):the erosion unconformity surfaces around the plateau were widely distributed,large rivers were 展开更多
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
Micrometric-thin cells(MCs)with alkali vapor atoms have been valuable for research and applications of hyperfine Zeeman splitting and atomic magnetometers under strong magnetic fields.We theoretically and experimental...Micrometric-thin cells(MCs)with alkali vapor atoms have been valuable for research and applications of hyperfine Zeeman splitting and atomic magnetometers under strong magnetic fields.We theoretically and experimentally study the saturated absorption spectra using a 100-μm cesium MC,where the pump and probe beams are linearly polarized with mutually perpendicular polarizations,and the magnetic field is along the pump beam.Because of the distinctive thin chamber of the MC,crossover spectral lines in saturated absorption spectra are largely suppressed leading to clear splittings of hyperfine Zeeman transitions in experiments,and the effect of spatial magnetic field gradient is expected to be reduced.A calculation method is proposed to achieve good agreements between theoretical calculations and experimental results.This method successfully explains the suppression of crossover lines in MCs,as well as the effects of magnetic field direction,propagation and polarization directions of the pump/probe beam on saturated absorption spectrum.The saturated absorption spectrum with suppressed crossover lines is used for laser frequency stabilization,which may provide the potential value of MCs for high spatial resolution strong-field magnetometry with high sensitivity.展开更多
基金supported by the China Geological Survey(Grant Nos.DD20221645,DD20221648,DD20190370)the National Natural Science Foundation of China(Grant No.91962219)。
文摘The Quaternary strata on the Qinghai-Tibet Plateau contain rich information about the paleoclimate and environmental evolution,record the evolution process of the Quaternary regional tectonics,paleogeography,and geomorphology of the plateau,and are extremely important areas for studying the Quaternary geological events and regional environmental evolution.According to a comprehensive analysis of the regional stratigraphic data and the development and evolution characteristics of the biota,based on the differences in the lithostratigraphic units,sedimentary characteristics,landforms,and drainage systems,the Quaternary strata on the Qinghai-Tibet Plateau and its surrounding areas are divided into five stratigraphic regions:the Tarim region,Loess Plateau region,Qinghai-Tibet Plateau region,Yunnan-Guizhou Plateau region,and India-Ganges region.The Qinghai-Tibet Plateau stratigraphic region is divided into seven stratigraphic sub-regions:the West Kunlun-Karakorum,AltunQilian Mountains,Qaidam-Hehuang,East Kunlun-Bayan Har,Qiangtang,East Xizang-West Yunnan-West Sichuan,and Gangdise-Himalayan sub-regions.This paper briefly describes the lithostratigraphic units of the seven stratigraphic sub-regions of the Qinghai-Tibet Plateau.According to the lithostratigraphic sequence and its sedimentary characteristics,stratigraphic contact relationship,formation age,and evolution of the biota in each stratigraphic sub-region,the Quaternary tectonic paleogeographic evolution of the Qinghai-Tibet Plateau is divided into four stages.(1)The inherited differential uplift stage since the Pliocene(2.6-1.8/1.5 Ma):the regional sedimentary differences were significant,and the stratigraphic distribution was limited,the alluvial-proluvial sandy conglomerate was widely developed along the piedmont,and fluvial and lacustrine deposits were developed in the low-lying areas between the mountains.(2)The mountain range flattening stage(1.8/1.5-1.2/0.8 Ma):the erosion unconformity surfaces around the plateau were widely distributed,large rivers were
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Project supported by the National Natural Science Foundation of China(Grant Nos.61571018 and 61531003).
文摘Micrometric-thin cells(MCs)with alkali vapor atoms have been valuable for research and applications of hyperfine Zeeman splitting and atomic magnetometers under strong magnetic fields.We theoretically and experimentally study the saturated absorption spectra using a 100-μm cesium MC,where the pump and probe beams are linearly polarized with mutually perpendicular polarizations,and the magnetic field is along the pump beam.Because of the distinctive thin chamber of the MC,crossover spectral lines in saturated absorption spectra are largely suppressed leading to clear splittings of hyperfine Zeeman transitions in experiments,and the effect of spatial magnetic field gradient is expected to be reduced.A calculation method is proposed to achieve good agreements between theoretical calculations and experimental results.This method successfully explains the suppression of crossover lines in MCs,as well as the effects of magnetic field direction,propagation and polarization directions of the pump/probe beam on saturated absorption spectrum.The saturated absorption spectrum with suppressed crossover lines is used for laser frequency stabilization,which may provide the potential value of MCs for high spatial resolution strong-field magnetometry with high sensitivity.
