贺兰山西侧紫泥湖地区晚更新世以来冰缘地貌过程与环境变化

PERIGLACIAL LANDFORM PROCESS AND ITS ENVIRONMENTAL CHANGES IN THE ZINIHU REGION AT THE WESTERN SIDE OF THE HELAN MOUNTAINS SINCE THE LATE PLEISTOCENE

紫泥湖地区座落在贺兰山西边45km处,海拔高度约1200m,区域地形呈现向北“V”字形开口的箕状洼地,其上生长旱生植被群落,沿自南而北流的沟谷阶地上发育了冻融褶皱、冰楔和砂楔等冰缘地貌类型和过程,研究结果表明区域年平均气温末次冰期早期(55—35ka B P)较今低10.5-12.5℃,末次冰期盛期(20—15ka B P)较今低12.5-13.7℃,早全新世(9.5—8.0kaB P)较今低9.5—10.5℃;降雨状况逐渐向更干燥变化。

The Zinihu region, with an altitude of about 1200 m above sea level, is situated 45 km west of the foot of the Helan Mountains (which is an important geographical boundary for separating the monsoon climates from non-monsoon climates in China). Topographically the region is a listric depression in the shape of 'V' opening to the north. On the surface there occur semifixed dunes and fixed sandy land and grow xerophilous plant communities. In the late Pleistocene to early Holocene, a lot of periglacial landforms, such as freeze-thaw folds, ice wedges and sand wedges, developed on the terraces of intermittent gullies flowing from south to north. Study indicates that the mean annual temperature was 10. 5 - 12. 5℃ lower in the early part of the Last Ice Age (55 - 35 Ka B. P. ) ,12. 5 - 13. 7℃ lower in the acme of the Last Ice Age (20-15 Ka B. P. ) and 9. 5 - 10. 5℃ lower in the early Holocene (9. 5 - 8. 0 Ka B. P. ) than that at the present and that the region became gradually arid during this period with diminishing precipitation.