浙江缙云县大洋山石鼓尖花岗岩坑穴成因  

On Genesis of the Granite Pits on Top of the Dayangshan Mountain of Jinyun County,Zhejiang Province

作　　者：朱诚[1] 崔之久[2] 李中轩[1] 高洁[1] 王立新[1] 邬祥林 郑朝贵[4] 沈庆凡 郑献章 

机构地区：[1]南京大学地理与海洋科学学院,南京210093 [2]北京大学城市与环境学院,北京100871 [3]浙江省地质调查院,萧山311203 [4]安徽滁州学院地理系,滁州239012 [5]浙江省缙云县人民政府,缙云321400 [6]浙江省缙云县气象局,缙云321400

出　　处：《地理学报》2008年第7期735-743,共9页Acta Geographica Sinica

基　　金：浙江省地质调查院“浙江缙云县区域地貌与景观地貌调查研究”项目资助~~

摘　　要：浙江缙云县大洋山石鼓尖海拔1477m,在其山顶花岗岩表面发现大量直径几十厘米至1m左右、深度10cm至45cm的坑穴。经对60处坑穴的形态量测发现,坑穴主要发育在山坡的NE和SE一侧;坑穴积水后出水口流向亦主要朝向NE和SE。对岩石标本的偏光显微镜和X荧光光谱鉴定分析发现,该处基岩为易风化、泥化明显的中细粒钾长花岗岩。该处年平均气温9.2oC,年降水量在1700mm以上,每年12月至翌年3月会经历4个月日气温在0oC上下波动的冰缘作用期,雨雪水冻融交替对基岩的崩解作用明显。该处位于夏季台风雨迎风坡(NE和SE坡)一侧,暴雨常伴随有10级以上大风。现场常可见风力吹蚀带动坑穴中细岩屑对坑穴内壁产生加速旋转磨蚀作用。上述研究表明,该处花岗岩坑穴形成的主要动力成因首先是冰缘寒冻风化作用,暴雨和山顶大风的风力吹蚀加速了坑穴的形成。观察表明,此种作用目前仍在进行之中,风向的转变是造成坑穴出现多种形态的主要原因。由于此处海拔距雪线尚有1500m高差,即使在第四纪盛冰期也仅是接近雪线高度,且因山顶无积雪屯冰的低洼地形,因此,第四纪"冰臼"成因说难以成立。On top of the Shigujian Peak （1477 m asl） of the Dayangshan Mountain in Jinyun County, Zhejiang Province, large amounts of granite pits with diameters ranging from several dozens of centimeters to one meter, and depth from 10 cm to 45 cm are found on the rock surface. These pits mainly appear on the NE and SE sides, and their discharge outlets are in the same direction. The identification results through micropolariscope and X-ray fluroscence spectrometer reveals that the bedrock of pits is from middle to fine-grained moyite being apt to be weathered and mudified. In Dayangshan region the annual mean temperature is 9.2 ℃ and the annual precipitation at over 1700 mm. On the one hand, there always experiences a period of periglaciation with temperature oscilating near 0 ℃ for 4 months from December to next March as a consequence, the freezing-thawing cycles may be remarkable to disintegrate the bedrock. On the other hand, the windward slope of Shigujian Peak meets typhoon of over force 10 on the Beaufort Scale in summer, therefore, the blowing makes suspending sands or pebbles grind in swirling form. Based on field investigation and periglaciological geomorphogy, the pits on top of the Shigujian Peak is attributed to frost weathering of periglaciation. Meanwhile, storm and strong wind accelerate the process. Observation shows that both the actions are still undergoing and variant directions of wind aree the main cause for making different shapes of the pits. Because the top of the Shigujian is 1500 m lower than the present snow line, some scholars consider that ＂glacial pothole＂ formed in the Quaternary is untenable, even though in the Quaternary Glacial Maximum.

关 键 词：浙江缙云大洋山石鼓尖 花岗岩坑穴 冰缘作用 风蚀作用 水蚀作用 寒冻风化 

分 类 号：P931.5[天文地球—自然地理学]