内蒙古大青山水磨沟发现末次冰期冰川堆积物  

Discovery of glacial deposits in last glaciation of the Shuimogou area, Daqing Shan Mountain, Inner Mongolia

作　　者：胡健民[1] 公王斌[2] 杨勇[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]国土资源部古地磁与古构造重点实验室,北京100081

出　　处：《科学通报》2016年第9期915-918,共4页Chinese Science Bulletin

基　　金：国家自然科学基金(41472211;41502199);中国地质调查局项目(1212011120099;12120114042101)资助

摘　　要：内蒙古大青山水磨沟发现晚第四纪冰川堆积物.冰碛物主要为红褐色泥砾混杂堆积,不发育层理,杂基支撑,泥砂质成分约占60%,砾石占40%.砾石磨圆好,表面发育铁质膜及不同方向擦痕.大于50%的砾石发生了蠕动剪切变形,形成各种张扭剪切破裂.分析认为,松散堆积物中大量砾石具有这种变形破裂,很可能是冰川蠕动变形的结果.上覆沉积物的^(14)C测年结果限定这套冰碛物形成于1.3万年之前.因此,这应该是华北北部41°N附近的中低山区发现的可靠的末次冰期冰川遗迹.The current Quaternary glaciers in China only distribute on the high mountains surrounding the Tibetan Plateau in the west of 105°E. In the east of 105°E, glaciers only exist in Taibai Mountain, Changbai Mountain, and Snow Mountain and Yushan Mountain in Taiwan. Whether the Quaternary glaciation reached the lower elevation foothills and uplands in the east of 105°E is usually causing intense disputations among the researchers. This discovery of the glacier deposits in the Shuimogou areas of the Daqing Shan Mountain has provided confident evidence that the glaciers did cover the lower elevation hill ranges during the late Quaternary glaciation. Daqing Shan Mountain is located in the middle part of the Yinshan Mountain, Inner Mongolia. The highest peak is 2200 m above see-level. Remote sensing images indicate that there are two glacier eroded depressions within the Shuimogou valley. In the northern depression, the glacier deposits distribute around 500 m in NS direction and 400 m in EW direction and overlap the Proterozoic marble. The glacial deposits are mainly brownish red tillites composed with 60% sandy mud and 40% pebbles. There is no clear bedding within these morainic sediments. Pebbles have poor sorting, well rounding, and are cemented by mud and muddy sand. The major components of the pebbles are granite, gneiss, diabase, plagio-amphibolite. No underlying Proterozoic marble pebble has been found in the tillites, so the tillite components should experience long-distance transportation from their source regions. The pebbles have following characters：（1） the smooth pebble surface is coated with brownish red iron jacket;（2） the glacial striae on the pebble surface show random directions;（3） on all of outcrops, almost all pebbles with the size larger than 10 cm show the fractures of the strong extensional twisted shear deformation. The presence of intensive twisted pebbles distributing in the loose sediments indicates that the pebbles must be deformed during their transportation—glacier movem

关 键 词：第四纪 冰碛物 末次冰期 大青山 水磨沟 内蒙古 

分 类 号：P343.6[天文地球—水文科学] P534.63[天文地球—地球物理学]