| 美国中西部第四纪冰川与黄土研究的进展和问题 |
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| 引用本文： | 冯兆东.美国中西部第四纪冰川与黄土研究的进展和问题[J].第四纪研究,1994,14(4):362-368. |
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| 作者姓名： | 冯兆东 |
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| 作者单位： | 美国犹他大学地质系 |
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| 摘 要： | 本文对美国中西部和中国黄土高原０．５Ｍａ以来的气候序列进行了对比。０．５—０．１ＭａＢ．Ｐ．，美国中西部间冰期以干暖为特征，１０００００—３５０００ａＢ．Ｐ．，气候从干暖向温湿转化。本次冰进阶段，冰盖达到最大后，风尘堆积占优势，气候湿凉为主。全新世先从温凉转为温湿，继而干暖，后又转向湿凉。总之，０．５Ｍａ以来除末次冰期外，美国中西部与中国黄土高原温度变化的总趋势是一致的，但两地的湿度变化是相反的。
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| 关 键 词： | 黄土 古土壤层 气候变化 盛冰期 全新世 |
PROGRESS AND PROBLEMS OF QUATERNARY GLACIATION AND LOESS STUDY IN THE MIDWESTERN UNITED STATES |
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| Institution: | Department of Ceography, University of Utah, USA |
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| Abstract: | Late Quaternary eolian deposits and buried soils in the central Great Plains are expected to reflect the fluctuation of climatic conditions under which they were formed.The Loveland Loess was deposited approximately between 0.5-0.1Ma B. P. Within the loess are four zones of pedogenic carbonate accumulation: after 0.416±0.035Ma B. P. before 0.26 ±0.025Ma B. P., around 0.193±0.022Ma B. P. and before 92 000± 7 000aB. P. The pedogenic carbonate zones were probably formed under warm and dry conditions. The moderately-weathered Barton sand at the Barton section and the equivalent Sandy Silt II at other sections, deposited between 92 000 ± 7000aB. P. and 69 000 ± 6 400a B. P., suggest windy, probably warm, and fluctuating moisture conditions. A reddish pedocomplex was formed from 70 000 to 35 000a B. P. under relatively warm and moist climatic conditions with a very low rate of loess deposition.Overlying the reddish pedocomplex is the Sandy Silt I, probably a stratigraphic equivalent to the Roxana Silt dated at 40 000-30 000a B. P. in the CentralLowlands.The Gilman Canyon Formation (35 000-20 000aB.P.), a thick .cumulic loessial and organic-matter-rich pedocomplex, was developed under; relatively moist and probably cool conditions. The Peoria Loess was deposited at a very rapid rate under dry and cold conditions. The Brady Soil (10 500-8 500aB.P.) was formed under relatively warm and moist conditions. Holocene soils developed in the eolian sequences of central Great Plains indicate that the eolian activity was much less miens during the major cool periods: around 9 000, 7 200 (fluvial soil), 5 500, 2 900, 1 600, 800 a B.P.,and probably 200a B. P. when the surface soil developed, with an exception of 1 200a B.P. soil developed in a warm period. This contrasts with the eolian activity in the Loess Plateau of China which was much more intensive during the major cool periods. |
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