Generation principle of ancient karst in marine carbonate rock hiatus, west of Xuefeng Mountain

During the Caledonian Movement,the Cambrian Niutitang-Sinian Dengying and Upper Cambrian-Ordovician parallel unconformities were found in the west of Xuefeng Mountain.Due to multi-stages of tectonic movements,several regional unconformities were formed in the study area.During different stages,the duration of sedimentary hiatus controlled the generation of carbonate rock karst,and further controlled connectivity.The unconformities seldom outcropped in the study area.Two typical outcrops from field works were studied and the controls of Niutitang-Dengying and Upper Cambrian-Lower Ordovician unconformities on ancient karst were analyzed.