基于成因-环境原则和多指标综合原则,依据昆仑山垭口地区的冰川地貌特征、冰碛物特征和孢粉信息,重建了该地区古环境演化历史。其中,冰碛物中的石英砂扫描电镜结果揭示了冰川、流水、风等地质营力对冰碛物的影响,孢粉分析结果在一定程...基于成因-环境原则和多指标综合原则,依据昆仑山垭口地区的冰川地貌特征、冰碛物特征和孢粉信息,重建了该地区古环境演化历史。其中,冰碛物中的石英砂扫描电镜结果揭示了冰川、流水、风等地质营力对冰碛物的影响,孢粉分析结果在一定程度上可以恢复当时的植被类型。根据垭口冰碛ESR年龄280 ka B.P.和冰碛剖面特征,将其时代暂定为300～260 ka B.P.;根据纳赤台地区的冰川地貌和沉积物特征,确定纳赤台后沟沉积为冰水扇沉积,纳赤台冰期为600～400 ka B.P.;根据玉虚峰U形谷两道侧碛垄的ESR和OSL年龄将其时代暂定为末次冰期早-中期。结合前人的研究成果,将昆仑山垭口地区的冰期序列厘定为望昆冰期(700～500 ka B.P.)、纳赤台冰期(600～400 ka B.P.)、垭口冰期(300～260 ka B.P.)、玉虚峰冰期(115～44 ka B.P.)、本头山冰期(20～13 ka B.P.)。展开更多
Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, f...Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ^(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ^(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ^(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.展开更多
云南点苍山是大理冰期的命名地,通过文献查询明确了大理冰期这一概念提出的过程.基于多次的实地考察,对云南点苍山冰川地貌进行了系统研究,建立了该地区第四纪以来冰川活动可靠的年代序列,明确了冰川发育的规模.研究结果表明,点苍山最...云南点苍山是大理冰期的命名地,通过文献查询明确了大理冰期这一概念提出的过程.基于多次的实地考察,对云南点苍山冰川地貌进行了系统研究,建立了该地区第四纪以来冰川活动可靠的年代序列,明确了冰川发育的规模.研究结果表明,点苍山最早的冰川活动发生于30～40 ka BP,之后经历了末次冰期晚阶段、晚冰期、新冰期等各次冰川前进,直至1.2～1.5 cal ka BP前后冰川最后消失.空间上,该地区的冰川活动仅局限于海拔3600m以上的主体部分,低海拔及其周边山体上没有冰川发育.展开更多
文摘基于成因-环境原则和多指标综合原则,依据昆仑山垭口地区的冰川地貌特征、冰碛物特征和孢粉信息,重建了该地区古环境演化历史。其中,冰碛物中的石英砂扫描电镜结果揭示了冰川、流水、风等地质营力对冰碛物的影响,孢粉分析结果在一定程度上可以恢复当时的植被类型。根据垭口冰碛ESR年龄280 ka B.P.和冰碛剖面特征,将其时代暂定为300～260 ka B.P.;根据纳赤台地区的冰川地貌和沉积物特征,确定纳赤台后沟沉积为冰水扇沉积,纳赤台冰期为600～400 ka B.P.;根据玉虚峰U形谷两道侧碛垄的ESR和OSL年龄将其时代暂定为末次冰期早-中期。结合前人的研究成果,将昆仑山垭口地区的冰期序列厘定为望昆冰期(700～500 ka B.P.)、纳赤台冰期(600～400 ka B.P.)、垭口冰期(300～260 ka B.P.)、玉虚峰冰期(115～44 ka B.P.)、本头山冰期(20～13 ka B.P.)。
基金financially supported by the National Science Foundation of China(41173031,41325011 and 41503001)the Fundamental Research Funds for the Central Universities(WK3410000004)
文摘Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ^(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ^(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ^(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ^(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.
文摘云南点苍山是大理冰期的命名地,通过文献查询明确了大理冰期这一概念提出的过程.基于多次的实地考察,对云南点苍山冰川地貌进行了系统研究,建立了该地区第四纪以来冰川活动可靠的年代序列,明确了冰川发育的规模.研究结果表明,点苍山最早的冰川活动发生于30～40 ka BP,之后经历了末次冰期晚阶段、晚冰期、新冰期等各次冰川前进,直至1.2～1.5 cal ka BP前后冰川最后消失.空间上,该地区的冰川活动仅局限于海拔3600m以上的主体部分,低海拔及其周边山体上没有冰川发育.
