江西鹰潭月湖岩大型石拱地质特征及成因分析  

Geological characteristics and genesis of the large rock arch at Yuehuyan in Yingtan City of Jiangxi Province

作　　者：邓宗裕 陈留勤[1] 杨柳 刘鑫 DENG Zongyu;CHEN Liuqin;YANG Liu;LIU Xin(School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China)

机构地区：[1]东华理工大学地球科学学院,江西南昌330013

出　　处：《华东地质》2024年第4期478-487,共10页East China Geology

基　　金：国家自然科学基金“中国东南和西北地区丹霞地貌陡坡上洞穴成因对比研究(编号:42361002)”项目资助。

摘　　要：石拱是丹霞地貌区重要的景观要素之一,大者又被称为天生桥,具有重要的地貌学研究意义和旅游开发价值。月湖岩大型石拱位于江西信江盆地西部,是我国湿润区石拱的典型代表,目前对其成因鲜有报道。文章通过野外地质调查、水分测试及室内样品薄片显微观察和盐化学实验,研究月湖岩大型石拱的地质特征并探讨其成因。结果表明:研究区NNE向和近EW向断裂控制了石拱的空间产状;石拱由晚白垩世塘边组风成砂岩组成,地层产状平缓,发育大型交错层理,结构成熟度高,渗透性较好,但成分成熟度低,富含化学稳定性较弱的长石、岩屑及钙质胶结物,有利于发生溶蚀风化;断裂和层理交汇处的岩石较破碎,在河流侵蚀作用下易发生溶蚀,风化物质随流水从山体底部流出,随着溶蚀和崩塌的持续发生,研究区山体南、北两侧被侵蚀穿透,最终形成石拱。文章为理解丹霞地貌区石拱的成因机制提供了实际材料,同时对石拱保护和旅游开发具有参考价值。Rock arch is a type of remarkable landform in the danxia landscape area,and the large arch is usually named as natural bridge,which has important geomorphological meaning and tourism development value.The Yuehuyan arch is located in the western Xinjiang Basin of Jiangxi Province,which is a representative rock arch in the humid climate area of China.However,there were few reports on its formation process.The research in this paper conducted field survey,moisture test,observation under a polarizing microscope and salt chemistry experiment to study the characteristics and genesis of the Yuehuyan arch.The results show that both the NNE-trending and near EW-trending fractures controlled the spatial occurrence of the rock arch in the study area.The bedrock is composed of Upper Cretaceous aeolian sandstones of the Tangbian Formation,characterized by large-scale cross-beddings,high textural maturity and good permeability.They are conducive to dissolution weathering owing to low compositional maturity and abundant feldspar,lithic fragments and calcite cements.The sandstones at the intersection of fractures and bedding surfaces are prone to be broken,which is easily dissolvable under the action of river erosion,and the weathered materials were removed from the bottom of the rock mass.With the continuous dissolution weathering and collapse,the north and south flanks of the rock mass were eroded and pen-etrated into the arch eventually.This study provides solid materials for understanding the formation processes of arches in humid danxia landscape areas,which is significant for the protection and tourism development of arches.

关 键 词：石拱 丹霞地貌 溶蚀风化 湿润气候 风成砂岩 江西鹰潭 

分 类 号：P931[天文地球—自然地理学]