张家口坝缘一带晚更新世冰川遗迹与深部地质作用的关系及其古气候意义

Relationship between Late Pleistocene Glacial Remnants and Deep Geological Processes in Bayuan Area, Zhangjiakou and Its Paleoclimatic Significance

深大断裂的强烈活动为火山喷发提供了重要的岩浆通道,火山喷发后形成的火山口、高出夷平面300~450m,最大厚度可达500m的火山熔岩垂向堆积,加上深部地质作用导致的地壳抬升,为冰川形成-滑动提供了有利的地形条件和气候条件。张家口西北坝缘一带首次发现的冰川遗迹主要有冰碛物、冰水沉积物及冰川地貌。电镜扫描石英砂粒表面可见冰川成因的冰蚀擦痕和碾磨压坑,孢粉显示为干燥寒冷的气候环境。获得了(121.22±6.54)ka和(81.13±4.48)ka的光释光年龄,与河北省第四纪第五冰期和第六冰期相对应,与平原区的黄骅海退和大城海退时间相吻合,显示张家口坝缘一带在晚更新世早中期经历了两期冰川作用。这一发现填补了研究区冰川遗迹研究的空白,为我国东部中低山区第四纪冰川的存在提供了有力的证据,丰富了我国东部中低山区第四纪冰川研究的年代学数据,对认识本区及我国东部大陆气候特征和第四纪环境变化具有重要意义。

The strong activities of the deep faults provide the important magma channel for volcanic eruption.The volcanic crater formed after volcanic eruption, the vertical accumulation of volcanic lava 300~450 m above planation surface, and the maximum thickness of volcanic lava up to 500 m, plus the uplift of the crust caused by deep geological processes, provide favorable topographic and climatic conditions for glacier formation and slipping. The glacial remnants first discovered in the northwest of Zhangjiakou mainly, consist of glacial moraines, glacial sediments and glacial landforms. The surface of the quartz sand grains by scanning of electron microscope shows glacial erosion scratches and grinding pits;and the pollens show a dry and cold climate environment. The OSL ages of(121.22±6.54) ka and(81.13±4.48) ka which correspond to the fifth and sixth glaciations in Hebei Province, and coincide with the Huanghua and Dacheng regressions in the plain area,indicating that Bayuan area, Zhangjiakou experienced two periods of glaciation in the early and middle of Late Pleistocene. This discovery fills the blank in the research of glacial remnants in the study area, and supply evidence for the existence of the quaternary glacier at the middle-low mountains in the eastern China, has enrich the quaternary glacial chronology data. It is of great significances for understanding characteristics of continental climate and the quaternary environmental changes in the study region and eastern China.