粤北丹霞盆地长坝组与丹霞组岩性差异及其地貌响应OA

The Changba Formation and the Danxia Formation in the Danxia Basin of northern Guangdong are both Cretaceous continental red beds and are important stratigraphic units that constitute the characteristic of Danxia landscape,yet they exhibit significant differences in their field geomorphology.Through field surveys,rock mechanics testing,and quantitative landform analysis,this study systematically compared the lithological characteristics of the two formations and revealed their lithology-landform coupling mechanism.The results show that the Changba Formation is dominated by interbedded sandstone and mudstone of fluvial-lacustrine facies,with high grain roundness,abundant clay matrix,and relatively high contents of feldspar and rock fragments.The aver-age contents of CaO and SiO2 are 5.53 wt%and 67.55 wt%,respectively,and the chemical index of alteration(CIA)is 59.19.In contrast,the Danxia Formation mainly consists of massive sandstone and conglomerate of allu-vial fan and eolian facies,with greater single-layer thickness,dense cementation,low Ca content(average CaO 5.32 wt%),and high Si content(average SiO2 75.77 wt%),with a CIA of 58.71,relatively lower than that of the Changba Formation,indicating stronger resistance to erosion.Notably,Schmidt hammer tests show an average re-bound of 35.93 for the Danxia Formation and 24.59 for the Changba Formation,indicating that the overall rock hardness of the Danxia Formation is higher.Field observations show that the Changba Formation generally devel-ops gentle slopes and hills,whereas the Danxia Formation forms typical Danxia landscape such as steep cliffs,peak clusters,and stone pillars,indicating that lithology is the main factor leading to differential weathering.This study provides new evidence for the lithology-landform synergy in red-bed basins and offers a scientific basis for the protection and tourism development of Danxia landscape.