Cosmogenic nuclide exposure dating is one of the most intensively applied dating methods with which to study glacial geomorphology.Glacial erratics have been the major dating objective in many studies.Some research ha...Cosmogenic nuclide exposure dating is one of the most intensively applied dating methods with which to study glacial geomorphology.Glacial erratics have been the major dating objective in many studies.Some research has proposed that glacial erratics may undergo rollover and re-transportation during the late exposure stage,which can affect the dating results.However,there is no direct evidence to confirm this possibility.In this study,we collected seven samples from a vertical section inside a glacial erratic in the paleo-Daocheng ice cap in the southeastern Tibetan Plateau,measuring their contents of the cosmogenic nuclides ^(10)Be and ^(26)Al.The results show that from the top to the bottom,the concentrations of 10Be were(1.21±0.05)×10^(6),(1.00±0.02)×10^(6),(0.88±0.03)×10^(6),(0.77±0.02)×10^(6),(0.75±0.03)×10^(6),(0.95±0.03)×10^(6) and(1.46±0.04)×10^(6) atoms/g.The ^(10)Be concentrations decreased from(1.21±0.05)×10^(6) atoms/g to(0.75±0.03)×10^(6) atoms/g and then increased to(1.46±0.04)×10^(6) atoms/g,which is not consistent with the theoretical prediction of a gradual decrease.This phenomenon indicates that the glacial erratic may have rolled over at least once.The lower surface of the erratic could have been on top at some time in the past.Therefore,its exposure age was greater than the exposure age that was expected,based on its current orientation.This study provides numerical evidence for an erratic rollover event.展开更多
Investigating topographic and climatic controls on erosion at variable spatial and temporal scales is essential to our understanding of the topographic evolution of the orogen.In this work,we quantified millennial-sca...Investigating topographic and climatic controls on erosion at variable spatial and temporal scales is essential to our understanding of the topographic evolution of the orogen.In this work,we quantified millennial-scale erosion rates deduced from cosmogenic^(10)Be and^(26)Al concentrations in 15 fluvial sediments from the mainstream and major tributaries of the Yarlung Zangbo River draining the southern Tibetan Plateau(TP).The measured ratios of^(26)Al/^(10)Be range from 6.33±0.29 to 8.96±0.37,suggesting steady-state erosion processes.The resulted erosion rates vary from 20.60±1.79 to 154.00±13.60 m Myr-1,being spatially low in the upstream areas of the Gyaca knickpoint and high in the downstream areas.By examining the relationships between the erosion rate and topographic or climatic indices,we found that both topography and climate play significant roles in the erosion process for basins in the upstream areas of the Gyaca knickpoint.However,topography dominantly controls the erosion processes in the downstream areas of the Gyaca knickpoint,whereas variations in precipitation have only a second-order control.The marginal Himalayas and the Yarlung Zangbo River Basin(YZRB)yielded significantly higher erosion rates than the central plateau,which indicated that the landscape of the central plateau surface is remarkably stable and is being intensively consumed at its boundaries through river headward erosion.In addition,our^(10)Be erosion rates are comparable to present-day hydrologic erosion rates in most cases,suggesting either weak human activities or long-term steady-state erosion in this area.展开更多
Background The deep-sea ferromanganese crust(DSFC)is a natural archive for recording the history of the Earth’s evolution,as one of the most common authigenic assemblages in marine sediments.Although the depositional...Background The deep-sea ferromanganese crust(DSFC)is a natural archive for recording the history of the Earth’s evolution,as one of the most common authigenic assemblages in marine sediments.Although the depositional age dating using meteoric ^(10)Be has been successfully used in the study on the chronology of DSFC,the research on ^(26)Al has not seen relevant reports in this aspect due to the influence of factors such as measurement sensitivity and ^(26)Al in situ production.Method The first exploration for ^(26)Al chronology in DSFC was carried out by using accelerator mass spectrometry(AMS)measurements of ^(10)Be and ^(26)Al,and the comparison of relationship between isotopic ratios and concentrations of Al and Be.Results The growth rates of G.R=(1.44±0.09)mm/Ma,(3.58±0.29)mm/Ma,(1.52±0.10)mm/Ma and(2.93±0.14)mm/Ma are derived using ^(10)Be/^(9)Be,^(26)Al/^(27)Al ratios,^(10)Be and ^(26)Al concentrations,respectively.Conclusion The ^(26)Al chronological methods have been explored based on a DSFC sample and encouraging results were obtained.The results are preliminary and insufficient;some information is still needed to explain the difference between ^(26)Al and ^(10)Be chronology.展开更多
Background A compact ^(14)C AMS system extended for ^(10)Be and ^(26)Al(XCAMS)was installed at Tianjin University in Octo-ber 2017.As an initial testing result,a detection limit of 4.4×10^(−16) for ^(14)C/^(12)C,...Background A compact ^(14)C AMS system extended for ^(10)Be and ^(26)Al(XCAMS)was installed at Tianjin University in Octo-ber 2017.As an initial testing result,a detection limit of 4.4×10^(−16) for ^(14)C/^(12)C,3.8×10^(−15) for ^(10)Be/^(9)Be and 6.9×10^(−15) for ^(26)Al/^(27)Al was achieved,respectively.Method The system was gradually smoothed and optimized based on a series of standard,blank and real samples measurement.Results The detection limit was down to 4.0×10^(−16) for ^(14)C/^(12)C,2.2×10^(−15) for ^(10)Be/^(9)Be and 5.6×10^(−15) for ^(26)Al/^(27)Al,respectively.More than one thousand samples of ^(14)C,^(10)Be and ^(26)Al have been successfully measured and analyzed.Conclusion The cosmogenic multi-nuclide of ^(14)C,^(10)Be and ^(26)Al AMS has been available for studies in archaeology,Earth science and environmental science,and some significant jobs still need to be carried out in the near future.展开更多
Introduction Accelerator mass spectrometry(AMS)has been used for the analysis of a lot nuclides in many scientific fields and is one of the most optimal methods to determine very low concentrations of long-lived nucli...Introduction Accelerator mass spectrometry(AMS)has been used for the analysis of a lot nuclides in many scientific fields and is one of the most optimal methods to determine very low concentrations of long-lived nuclides.The XCAMS system is an extension of the Compact ^(14)C Accelerator Mass Spectrometer for ^(10)Be and ^(26)Al.A description of the first Chinese XCAMS system and initial performance of three nuclides of ^(14)C,^(10)Be,and ^(26)Al,respectively,will be reported.Experimental procedures Solid sample material(graphite,Al_(2)O_(3),and BeO)is loaded into cathode holders for AMS analysis.The negatively charged ions(C−,Al−,and BeO−)are extracted and accelerated to the terminal,broken-up,and some orbital electrons stripped off to form positively charged atomic ions,and accelerated further.In the post-acceleration region,the magnetic and electrostatic devices act on momentum and energy analysis,respectively.A multi-anode detector is used for the identification and detection of relevant isotopes and isobars.System performance The test criteria of three rare isotopes each were set for beam current intensity,measurement precision,and machine background.The corresponding material and cathode holder were,respectively,used for ^(14)C,^(10)Be,and ^(26)Al test.Several batches of real sample have already been analyzed by the new AMS system based on the acceptance test results.In addition,several secondary standards were measured to check the stability of the system.Conclusion The new XCAMS facility has been installed successfully,and the latest performance also showed that the machine is reliable enough,in general.Both the hardware components and software system were in good condition for accurate and precise data analysis in the near future.展开更多
基金supported by the National Natural Science Foundation of China(Grant nos.41971009 and 41503054)the CASKJZD-EW-G03-04 project(Grant No.Y4422101001)+1 种基金the General Financial Grant of the China Postdoctoral Science Foundation(Grant No.2015M582728)the Priority AcademicProgram Development of Jiangsu Higher EducationInstitutions(Grant No.164320H116)。
文摘Cosmogenic nuclide exposure dating is one of the most intensively applied dating methods with which to study glacial geomorphology.Glacial erratics have been the major dating objective in many studies.Some research has proposed that glacial erratics may undergo rollover and re-transportation during the late exposure stage,which can affect the dating results.However,there is no direct evidence to confirm this possibility.In this study,we collected seven samples from a vertical section inside a glacial erratic in the paleo-Daocheng ice cap in the southeastern Tibetan Plateau,measuring their contents of the cosmogenic nuclides ^(10)Be and ^(26)Al.The results show that from the top to the bottom,the concentrations of 10Be were(1.21±0.05)×10^(6),(1.00±0.02)×10^(6),(0.88±0.03)×10^(6),(0.77±0.02)×10^(6),(0.75±0.03)×10^(6),(0.95±0.03)×10^(6) and(1.46±0.04)×10^(6) atoms/g.The ^(10)Be concentrations decreased from(1.21±0.05)×10^(6) atoms/g to(0.75±0.03)×10^(6) atoms/g and then increased to(1.46±0.04)×10^(6) atoms/g,which is not consistent with the theoretical prediction of a gradual decrease.This phenomenon indicates that the glacial erratic may have rolled over at least once.The lower surface of the erratic could have been on top at some time in the past.Therefore,its exposure age was greater than the exposure age that was expected,based on its current orientation.This study provides numerical evidence for an erratic rollover event.
基金Second Tibetan Plateau Scientific Expedition and Research(STEP)Program,No.2019QZKK0707National Key Research and Development Program of China,No.2020YFA0607700+1 种基金National Natural Science Foundation of China,No.41930863China Seismic Experimental Site,No.2019CSES0104。
文摘Investigating topographic and climatic controls on erosion at variable spatial and temporal scales is essential to our understanding of the topographic evolution of the orogen.In this work,we quantified millennial-scale erosion rates deduced from cosmogenic^(10)Be and^(26)Al concentrations in 15 fluvial sediments from the mainstream and major tributaries of the Yarlung Zangbo River draining the southern Tibetan Plateau(TP).The measured ratios of^(26)Al/^(10)Be range from 6.33±0.29 to 8.96±0.37,suggesting steady-state erosion processes.The resulted erosion rates vary from 20.60±1.79 to 154.00±13.60 m Myr-1,being spatially low in the upstream areas of the Gyaca knickpoint and high in the downstream areas.By examining the relationships between the erosion rate and topographic or climatic indices,we found that both topography and climate play significant roles in the erosion process for basins in the upstream areas of the Gyaca knickpoint.However,topography dominantly controls the erosion processes in the downstream areas of the Gyaca knickpoint,whereas variations in precipitation have only a second-order control.The marginal Himalayas and the Yarlung Zangbo River Basin(YZRB)yielded significantly higher erosion rates than the central plateau,which indicated that the landscape of the central plateau surface is remarkably stable and is being intensively consumed at its boundaries through river headward erosion.In addition,our^(10)Be erosion rates are comparable to present-day hydrologic erosion rates in most cases,suggesting either weak human activities or long-term steady-state erosion in this area.
基金National Natural Science Foundation of China,11775157,Kejun Dong.
文摘Background The deep-sea ferromanganese crust(DSFC)is a natural archive for recording the history of the Earth’s evolution,as one of the most common authigenic assemblages in marine sediments.Although the depositional age dating using meteoric ^(10)Be has been successfully used in the study on the chronology of DSFC,the research on ^(26)Al has not seen relevant reports in this aspect due to the influence of factors such as measurement sensitivity and ^(26)Al in situ production.Method The first exploration for ^(26)Al chronology in DSFC was carried out by using accelerator mass spectrometry(AMS)measurements of ^(10)Be and ^(26)Al,and the comparison of relationship between isotopic ratios and concentrations of Al and Be.Results The growth rates of G.R=(1.44±0.09)mm/Ma,(3.58±0.29)mm/Ma,(1.52±0.10)mm/Ma and(2.93±0.14)mm/Ma are derived using ^(10)Be/^(9)Be,^(26)Al/^(27)Al ratios,^(10)Be and ^(26)Al concentrations,respectively.Conclusion The ^(26)Al chronological methods have been explored based on a DSFC sample and encouraging results were obtained.The results are preliminary and insufficient;some information is still needed to explain the difference between ^(26)Al and ^(10)Be chronology.
基金This work was partly supported by the National Natural Science Foundations of China(NSFC),under Grant Nos.11775157 and 11575296.
文摘Background A compact ^(14)C AMS system extended for ^(10)Be and ^(26)Al(XCAMS)was installed at Tianjin University in Octo-ber 2017.As an initial testing result,a detection limit of 4.4×10^(−16) for ^(14)C/^(12)C,3.8×10^(−15) for ^(10)Be/^(9)Be and 6.9×10^(−15) for ^(26)Al/^(27)Al was achieved,respectively.Method The system was gradually smoothed and optimized based on a series of standard,blank and real samples measurement.Results The detection limit was down to 4.0×10^(−16) for ^(14)C/^(12)C,2.2×10^(−15) for ^(10)Be/^(9)Be and 5.6×10^(−15) for ^(26)Al/^(27)Al,respectively.More than one thousand samples of ^(14)C,^(10)Be and ^(26)Al have been successfully measured and analyzed.Conclusion The cosmogenic multi-nuclide of ^(14)C,^(10)Be and ^(26)Al AMS has been available for studies in archaeology,Earth science and environmental science,and some significant jobs still need to be carried out in the near future.
基金This work was mainly supported by the National Natural Science Foundations of China(NSFC)under Grant Nos.11775157 and 11575296.
文摘Introduction Accelerator mass spectrometry(AMS)has been used for the analysis of a lot nuclides in many scientific fields and is one of the most optimal methods to determine very low concentrations of long-lived nuclides.The XCAMS system is an extension of the Compact ^(14)C Accelerator Mass Spectrometer for ^(10)Be and ^(26)Al.A description of the first Chinese XCAMS system and initial performance of three nuclides of ^(14)C,^(10)Be,and ^(26)Al,respectively,will be reported.Experimental procedures Solid sample material(graphite,Al_(2)O_(3),and BeO)is loaded into cathode holders for AMS analysis.The negatively charged ions(C−,Al−,and BeO−)are extracted and accelerated to the terminal,broken-up,and some orbital electrons stripped off to form positively charged atomic ions,and accelerated further.In the post-acceleration region,the magnetic and electrostatic devices act on momentum and energy analysis,respectively.A multi-anode detector is used for the identification and detection of relevant isotopes and isobars.System performance The test criteria of three rare isotopes each were set for beam current intensity,measurement precision,and machine background.The corresponding material and cathode holder were,respectively,used for ^(14)C,^(10)Be,and ^(26)Al test.Several batches of real sample have already been analyzed by the new AMS system based on the acceptance test results.In addition,several secondary standards were measured to check the stability of the system.Conclusion The new XCAMS facility has been installed successfully,and the latest performance also showed that the machine is reliable enough,in general.Both the hardware components and software system were in good condition for accurate and precise data analysis in the near future.
