内蒙古赤峰召庙花岗岩表面的冰川壶穴、泄水槽、盐风化穴和剥离面理  

Glacial potholes,meltwater channels,salt weathering tafoni and exfoliation on the granite surface in Zhaomiao,Chifeng,Inner Mongolia

作　　者：吕洪波[1] 浦津 高于 LYU Hongbo;PU Jin;GAO Yu(School of Geosciences,China University of Petroleum,Qingdao 266580,Shandong,China;International Department(IB Program)of Nanjing Foreign Language School,Nanjing 210008,Jiangsu,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛226580 [2]南京外国语学校国际部IB课程班,江苏南京210008

出　　处：《地质通报》2022年第4期517-532,共16页Geological Bulletin of China

摘　　要：在内蒙古赤峰市巴林左旗林东镇以南约20 km的召庙,出露一片面积约20 km^(2)的花岗岩,称为召庙花岗岩体。该岩体被至少2组垂直节理及与地面起伏一致的剥离面理切割成大小不等的弧形岩块,构成高于周围地表300~400 m的花岗岩山区。在多条花岗岩山脊上保存有大小不等的壶穴,山脊两侧则发育从上到下紧密排列的泄水槽,而泄水槽则被剥离面理横向切割,沿剥离面理的露头线发育大小不等的风化穴。通过详细的野外调查,认为花岗岩山脊上的壶穴不是风蚀和风化所致,而是晚更新世冰盖上的冰川融水下泄冲刷形成的;山脊两侧的泄水槽也是冰川融水下泄冲刷的结果;剥离面理是第四纪冰川发育导致地表之下岩石温度变化的热变应力所致,可用于恢复第四纪冰川作用时期的基岩古地貌;盐风化穴是第四纪冰川退缩后本区重要的物理风化类型,优先沿着剥离面理发育。本区3种微型地貌景观和大型的剥离面理共生组合记录了更新世以来召庙花岗岩山区的地貌演化史。A granite hill,about 20 km^(2) in area,is situated 20 km to the south of Lindong Town in the Bairin Left Banner,Chifeng,Inner Mongolia,China.The Yanshannian coarse granite is mainly composed of K-feldspar and quartz.The granite intrusive body has been cut by two sets of vertical joints and a set of exfoliation joints that undulate with topographic relief.The granite hill is about 300~400 m higher than the surrounding area.We investigated the following three mini-landforms,potholes,meltwater channels and salt weathering tafoni and analyzed their formation mechanisms.We also examined the exfoliation and its origin.Potholes on the granite ridge in this area had been reported as wind-erosion evidence by some researchers 20 years ago,or interpreted as a result of chemical weathering lately.However,they were not formed by wind or weathering,but by the fast erosion of melt water from the surface of ice sheet above.According to our explanation,there was a vast icesheet over the Greater Khingan Mountains and the vicinity area in the northeast of Asia in the Late Pleistocene.The thick icesheet tended to create fractures over the granite ridges because of its gravity and drained the melt water through these fractures and thus eroded the bedrock to form potholes on the ridges.Apart from forming potholes on the granite ridges,melt water mainly formed meltwater channels on the surface of the hillside.Meltwater channels are rows of closely spaced erosional notches or grooves on the hillside surface,extending from hilltop to the piedmont,scoured by high-pressure melt water between granite surface and the overlying icesheet.There are abundant tafoni,large and small,along the gently undulating exfoliation joints in this area.These tafoni had been treated as a result of wind erosion and called“wind-eroded habitacles”in the past decades.However,these concave structures are not wind-erosion landforms but typical salt weathering tafoni.Salt weathering is the granular fragmentation of rocks affected by the salt crystallization near

关 键 词：花岗岩体 壶穴 泄水槽 盐风化 风化穴 剥离面理 更新世冰盖 内蒙古 

分 类 号：P534.63[天文地球—第四纪地质学] P588.12[天文地球—古生物学与地层学]