The glacial landforms of the Qinghai-Tibetan Plateau （QTP） provide a unique opportunity to research hemispheric and global environmental changes. In this study, we focus on the glacial history of the palaeo-Daocheng...The glacial landforms of the Qinghai-Tibetan Plateau （QTP） provide a unique opportunity to research hemispheric and global environmental changes. In this study, we focus on the glacial history of the palaeo-Daocheng Ice Cap （p-DIC） in the southeastern QTP during the last glacial cycle. Based on field investigations, morphostratigraphy, and surface exposure dating of roche moutonnée, polished surface and moraine debris through the terrestrial cosmogenic nuclides （TCN） ^10Be and ^26Al. We identify glacial deposits of the last deglaciation, with minimum ages of 14.9±1.3-18.7±1.7 ka, the Last Glacial Maximum （LGM） of 24.7±2.2 ka, and the early part of the last glacial period （marine oxygen isotope stage （MIS） 3） of 37.1±3.4-45.2±3.9 ka. Our results show that in this region, the extent of the glacial advance during MIS 3 was larger than that during the traditional LGM （MIS 2）. These ages are consistent with prior chronologies, and the ^10Be age is consistent with the ^26Al age for the same sample. Thus, these data provide reliable constraints on climate change in the QTP, during the last glaciation.展开更多
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
基金supported by the National Natural Science Foundation of China (Grant No.40572097)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) (Grant No.164320H116)by the Yulong Mountain tourism development and management committee special project
文摘The glacial landforms of the Qinghai-Tibetan Plateau （QTP） provide a unique opportunity to research hemispheric and global environmental changes. In this study, we focus on the glacial history of the palaeo-Daocheng Ice Cap （p-DIC） in the southeastern QTP during the last glacial cycle. Based on field investigations, morphostratigraphy, and surface exposure dating of roche moutonnée, polished surface and moraine debris through the terrestrial cosmogenic nuclides （TCN） ^10Be and ^26Al. We identify glacial deposits of the last deglaciation, with minimum ages of 14.9±1.3-18.7±1.7 ka, the Last Glacial Maximum （LGM） of 24.7±2.2 ka, and the early part of the last glacial period （marine oxygen isotope stage （MIS） 3） of 37.1±3.4-45.2±3.9 ka. Our results show that in this region, the extent of the glacial advance during MIS 3 was larger than that during the traditional LGM （MIS 2）. These ages are consistent with prior chronologies, and the ^10Be age is consistent with the ^26Al age for the same sample. Thus, these data provide reliable constraints on climate change in the QTP, during the last glaciation.
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.
