南岭最高夷平面上发育了深厚的红色风化壳,研究这些风化壳对于认识夷平面具有重要意义.以粤北大布镇夷平面上的风化壳为例,通过化学成分的研究,认为大布镇的风化壳厚度为60 ～70 m,风化壳顶层的母岩当量厚度可达到24m/m.据此,恢复得到已风化母岩(奥陶系砂岩)厚度达790 m,其中的淋失量为724 m,再根据珠江流域50 a平均溶蚀速率估算,该风化壳的年龄约为19.6 Ma,即中新世早期,大致可认为是南岭夷平面发育终结和新一轮地貌循环——“南岭运动”开始的时间.%Thick weathering crusts are developing on the planation surfaces of the Nanling summits.Studying these weathering crusts is very significant for us to understand the planation surfaces.The authors take the weathering crust profile on Dabuzhen,north Guangdong of China as an example,studied its chemical components and characters,and reconstructed the thickness of the weathering crust,its equivalent bedrock thickness and timing using a new method.The results show that the weathering crust on Dabuzhen probably approach 70 m thick.The bedrock equivalent thickness for weathering crust of 1 m reaches 24 m.Based analysis of the weathered degree of the profile,we reconstructed a thickness of 790 m weathered bedrock,of which 724 m has been dissolved and flow out with ground water.According to the dissolution rate of past 50 years in the Pearl River,the age of the Dabuzhen weathering crust is estimated about 19.6 Ma BP,namely early Miocene when the development of the Nanling Planation surface ended and a new geomorphologic cycle,the Nanling Movement began.
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