• 责任者：Wang Wei (Geography School ; South China Normal University ; Guangzhou 510631 ; China) ; Xu Liubin
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(5)
• 关键词：风化作用 ; weathering ; 海岸地形 ; coastal features ; 广东 ; Guangdong
• 页码：p.1016-1033
• 图表：14 illus., 7 tables, 44 refs.
• 分类号：0200
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

     Weathering pits and marine potholes are depressions on exposed rock surfaces with different morphological features due to completely different origins and formation processes.However,they are often confused with each other and considered to be the same thing formed by glaciations in China.In recent years,we have investigated two places with different geographic environments,one of which is Shapa Town in west Guangdong on the coast of South China,and the other is Miaowan Island off Pearl River Estuary. Weathering pits and marine potholes are found in these two places,even though the coast of Shapa Town is composed of granodiorite and granite gneiss while that of Miaowan island is of biotite granite.This paper presents a detailed comparison between the weathering pits and the marine potholes developed on the coasts of Shapa and Miaowan to explain the differences in their origins and formation processes.The studies in respects of geomorphology,sedimentology,petrochemistry and mineralogy show that the formation of the weathering pits results from localized weathering induced by the stagnant water in rock surface depressions,while the marine potholes are produced by mechanical erosion of sea waves,although both are capable of being formed in the same rock.The evidences to set them clearly apart include the following：1）the weathering pits in these two places are formed at various heights above mean high tide level,but only on the flat rock surfaces facing upwards.There is no weathering pit that can be formed under the mean high tide level in these two places,while the positions of the marine potholes can extend to levels lower than the high tide level,but not more than 3m above the level; 2）the marine potholes are morphologically distinct from the weathering pits in their side walls,rims,bottoms,breadth-to-depth ratio,etc.because of their different formation processes; 3）roundnesses and sorting degrees of the clastic particles in the marine potholes are better than those in the weathering pits because the pothole grains are abraded by wave actions,while the fragments in the weathering pits are broken down by the weathering undergoing in stagnant water; 4）the particles in the weathering pits have higher values of chemical index of alteration（CIA）and a higher quartz-to-feldspar ratio than the rock on which the pits were formed because the weathering process within the pits is stronger than that of the rock.However,the CIA value as well as the quartz-to-feldspar ratio cannot be used to distinguish clastic particles in the pothole from those in the weathering pits; 5）clay minerals in the weathering pits are mainly illite since the pits are formed close to the sea that creates an alkaline environment for the weathering process in which kaolinite cannot be formed,and no clay minerals are found in the potholes due to a weak weathering process and a strong wave action; 6）the two types of the particles have quite different chemical element migration characteristics also because of their different origins and formation processes.