陕西汉中小南海天坑群形成时代的多维度年代学约束OACHSSCD

The Xiaonanhai Tiankeng Group in Hanzhong,located in the Daya Taiguan area of Xiaonanhai Town,Nanzheng District,Hanzhong City,Shaanxi Province,is the karst system developed at the northernmost boundary of China's humid tropical-subtropical karst landform region at 32°N latitude.It has been discovered to contain 20 tiankengs,over 90 caves,and more than 20 geological relics such as shafts,cliffs,canyons,peak clusters,and depressions.Its development and distribution are strictly controlled by geological structures,with the intermittent uplift and tectonic denudation of the neotectonic movement significantly affecting the vertical evolution of karst landscapes.Based on a systematic review of the geological background and tectonic evolution history of the region,combined with previous multi-dimensional data analysis on apatite and zircon fission tracks,dissolution rates,burial ages of cave quartz cosmogenic nuclides 26Al/10Be,terrace chronology,and valley incision rates,this study clarifies that the upper limit of the formation age of the Xiaonanhai Tiankeng Group is 0.68 Ma,with the main development period concentrated between 0.189 and 0.126 Ma,belonging to the late Middle Pleistocene to early Late Pleistocene.The study also finds that there is no direct causal relationship between the size of tiankengs and their formation age,their development is more dependent on geological structures,stratigraphic lithology,hydrodynamic conditions,and the intensity and rhythm of neotectonic movement.This study not only provides key empirical evidence for the study of the formation age of karst landforms in humid regions at mid-to-high latitudes but also offers important clues for understanding the changes in regional paleogeographic environments.