地理科学

地理科学 ›› 1983, Vol. 3 ›› Issue (4): 339-344.doi: 10.13249/j.cnki.sgs.1983.04.339

• 论文 • 上一篇    下一篇

大同盆地古冰楔(砂楔)和晚更新世自然环境

杨景春1, 孙建中2, 李树德1, 王一峋3   

  1. 1. 北京大学地理系;
    2. 国家地震局地质研究所;
    3. 北京师范学院地理系
  • 出版日期:1983-07-20 发布日期:1983-07-20

FOSSIL ICE WEDGES AND LATE PLEISTOCENE ENVIRONMENT IN DATONG BASIN,SHANXI PROVINCE

Yang Jingchun1, Sun Jianzhong2, Li Shude1, Wang Yixun3   

  1. 1. Department of Geography, Peking University;
    2. Institute of Geolegy, State Seismological Bureau;
    3. Department of Geography, Beijing Teachers College
  • Online:1983-07-20 Published:1983-07-20

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63

摘要： 山西省大同盆地是一个断陷山间盆地,盆地底部拔海约1000米,盆地南部山地最高峰拔海2600米左右。盆地底部出露大片中更新世到晚更新世的灰绿色和灰黄色湖相粘土以及晚更新世的黄土和砂。另外,盆地平原上还有20多座火山锥和微微起伏的玄武岩垄岗。盆地东部大同县许堡的东边,有一条小河从北往南流向西水地然后汇入桑干河。从许堡沿小河往南行约1公里,靠河流左岸的灰绿色湖相粘土层中,发育30多个古冰楔(砂楔)(图1,图版Ⅰ照片1)。

Abstract: In the east of Datong basin (about 1000m above sea level),we found some fossil ice wedges of late Pleistocene.The surface polygons were composed of ice wedges with meshes measured as large as 3m across.The ice wedges themselves were dominantly vertical and extend to a depth of 120 cm and widened to a width of 20～30cm.Upon the thawing of ice,the cavity of the ice wedge left was filled by fineroundish,eolian sand,forming a cast of sand wedge. Because of the lateral growth and squeeze of the wedge,adjacent lacustrine clay sediments usually developed an upward bend.This fossil ice wedge indicated a rather arid and windy periglacial environment with its mean annual temperatures estimated as some 11.5°to 16℃ colder than those of the present.About 26000 years ago,the southern boundary of late Pleistocene permafrost extended to the latitudes 40°N.