| 基于10Be暴露年代的北美洲晚第四纪冰川演化序列研究 |
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| 引用本文： | 刘亮,翟羿杰,张威,初智豪.基于10Be暴露年代的北美洲晚第四纪冰川演化序列研究[J].冰川冻土,2022,44(4):1283-1297. |
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| 作者姓名： | 刘亮 翟羿杰 张威 初智豪 |
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| 作者单位： | 辽宁师范大学 地理科学学院，辽宁 大连 116029 |
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| 基金项目： | 国家自然科学基金项目(41501068) |
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| 摘 要： | 对北美洲晚第四纪冰川10Be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（B?lling-Aller?d，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10Be暴露年代同样具有很好的对应关系。
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| 关 键 词： | 10Be暴露年代 冰川演化序列 气候事件 北美洲 |
| 收稿时间： | 2022-05-30 |
| 修稿时间： | 2022-08-07 |
Late Quaternary glaciations in North America based on 10Be exposure ages |
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| Liang LIU,Yijie ZHAI,Wei ZHANG,Zhihao CHU.Late Quaternary glaciations in North America based on 10Be exposure ages[J].Journal of Glaciology and Geocryology,2022,44(4):1283-1297. |
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| Authors: | Liang LIU Yijie ZHAI Wei ZHANG Zhihao CHU |
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| Institution: | School of Geography，Liaoning Normal University，Dalian 116029，Liaoning，China |
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| Abstract: | 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 10Be exposure ages of 4 357 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 1 956 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 United States， with peak ages of 138.7 ka and 118.7 ka， corresponding to the late MIS 6 and early MIS 5. Traces of a MIS 4/3 glaciation are only preserved in Alaska， possibly related to the atmospheric effect of the Laurentian Ice Sheet. The times when the LGM reached its maximum range may not be regionally synchronous. In addition to the principal mechanisms driven by the global climate change， changes in regional climates， the internal dynamics of different glaciers， and atmospheric effects brought about by the Laurentian Ice Sheet may also have been secondary factors. The responses of glaciers to the high-resolution climatic events known as the Heinrich Stadial 1 （HS-1）， the B?lling-Aller?d （B-A） interstadial and the Younger Dryas （YD） event， during the last period of deglaciation， appear to be synchronous， possibly affected by a significant change in the Atlantic meridional overturning circulation （AMOC）. The 10Be exposure ages of North American glaciers also correlate well with the high-resolution ‘Bond’ events that have occurred during the Holocene. In the future， more 10Be exposure age data and climate data are needed to enrich the study of the evolutionary glaciation sequence in North America during the late Quaternary. |
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| Keywords: | 10Be exposure ages evolutionary glaciation sequence climatic events North America |
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