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作 者:刘亮[1] 翟羿杰 张威[1] 初智豪 LIU Liang;ZHAI Yijie;ZHANG Wei;CHU Zhihao(School of Geography,Liaoning Normal University,Dalian 116029,Liaoning,China)
机构地区:[1]辽宁师范大学地理科学学院,辽宁大连116029
出 处:《冰川冻土》2022年第4期1283-1297,共15页Journal of Glaciology and Geocryology
基 金:国家自然科学基金项目(41501068,42071013)资助。
摘 要:对北美洲晚第四纪冰川^(10)Be暴露年代进行汇编与聚集程度置信等级划分,构建了北美洲各区域的冰川演化序列,并进一步对比和分析了冰川演化序列对高分辨率气候事件的响应情况,使用较好和中等聚集程度的暴露年代漂砾组对北美洲各区域进行冰期划分。结果表明:北美洲冰川序列横跨6个深海氧同位素阶段(marine isotope stage,MIS),保守估计至少在MIS 6/5、MIS 4/3、MIS 2时期出现了规模性冰进,其记录可信区间为约150 ka至今。末次冰盛期(Last Glacial Maximum,LGM)之前的冰川演化存在区域性,这可能与劳伦泰德冰盖的大气效应存在一定的相关性。LGM的冰川达到最大范围的时间不同步,揭示了不同地区冰川演化的影响因素不尽相同。LGM以来的冰川作用对于高分辨率气候事件,如海因里希事件1(Heinrich Stadial 1,HS1)、B-A事件(Bølling-Allerød,B-A)、新仙女木事件(Younger Dryas,YD)的响应存在同步性。对于全新世更高分辨率的邦德事件(Bond),北美洲的冰川^(10)Be暴露年代同样具有很好的对应关系。North America is rich in late Quaternary glaciation remnants.Over recent years,a large number of exposed ages of glacial boulders or bedrock have been obtained using cosmogenic radionuclide(CRN)dating,allowing a potential reconstruction of the North America’s late Quaternary evolutionary glaciation sequence.In this paper,the ^(10)Be exposure ages of 4357 independent samples from North America were compiled and classified according to confidence classes(A-C).All exposure ages were grouped according to the original literature and recalculated using the latest version of the exposure age calculator.Since the erosion rate of each study area could not be determined,the calculation of exposure ages in this study was based on a zero erosion assumption.We considered the ages we adopted to be minimum exposure ages.After division into confidence classes,424 groups of 1956 exposure ages with well-clustered and moderately-clustered classes were obtained.Due to considerable overlap of data,the overall range in glaciation in North America appeared too wide.We therefore constructed an evolutionary glaciation sequence and determined the peak age of the probability density curve for four large regions and 15 subregions in North America.The subdivision of regions at all levels was based on glacier shape,scale and topographic conditions.Combining these results with paleoclimate data,we compared and analyzed the response of the resulting evolutionary glaciation sequence to high-resolution climatic events,thereby summarizing the characteristics of each stage of the North American evolutionary glaciation sequence.The results showed that North America has experienced many glaciations in the past 150 ka.It is conservatively estimated that the glaciers in North America have experienced large-scale glaciations during at least marine isotope stage(MIS)6/5,MIS 4/3 and MIS 2.The evolution of glaciers before the Last Glacial Maximum(LGM)was regional.Of these glaciations,the MIS 6/5 glaciation was concentrated in the western part of the Unit
关 键 词:^(10)Be暴露年代 冰川演化序列 气候事件 北美洲
分 类 号:P534.63[天文地球—第四纪地质学] P931.4[天文地球—古生物学与地层学]
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