Research on the characteristics and value of geological relics in the Enshi Grand Canyon-Tenglongdong Cave Global Geopark

Enshi is situated in the northeastern extension of the Yunnan–Guizhou Plateau, at the juncture of the Daba Mountain and the Wuling Mountains. This area is characterized by extensive deposits of carbonate rocks, which have resulted in highly distinctive and rich karst geological relics. Nevertheless, due to its remote location and inconvenient transportation, there has been little scientific research on this region,as well as a lack of systematic and professional studies,This study aims at conducting a comprehensive assessment of the geological relics within the Enshi Grand Canyon-Tenglongdong Cave Global Geopark and determining its boundary scope. By analyzing the scientific, popular science, and tourism development values of the geological relics within the park, this study provides a scientific basis for the planning and management of the geological park. It also promotes the rational utilization and effective protection of these geological relics.

Based on the field surveys, this study systematically analyzed the types and development characteristics of the geological relics within the park. In accordance with "Investigation Specifications for Geological Relics" and "Technical Requirements and Work Guidelines for the Construction of National Geological Parks in China", and with reference to the existing research results on the evaluation of geological relics, an evaluation index system for the geological relics of the Enshi Grand Canyon-Tenglongdong Cave Global Geopark was constructed. A comprehensive evaluation was conducted on 77 geological relics within the park, combining both qualitative and quantitative assessments.

The study outcomes elucidate several key points,(1) The park is situated in the transitional slope area between the second and third steps of China’s giant geomorphological units, with a significant hydraulic gradient. The extensive carbonate rocks within the park have been subjected to the long-term and intense effects of surface water and groundwater, resulting in the unique karst landscape of the region. (2) Geological relics within the park can be categorized into three major classes, eight subclasses, and eleven minor classes based on their origins, conditions, and functional roles. The main types include karst landscapes such as peak clusters and depressions, peak forests, isolated peaks, gorges, stone pillar forests, stone buds, underground rivers, caves, and sinkholes, supplemented by water features, geological profiles, paleontological fossils, geological disasters, geological structures, etc. (3) The Tenglongdong Cave system in Lichuan and the stone pillar forest in Enshi are world-class geological formations that represent the most internationally significant geological relics within the park. They are characterized by their typicality, rarity, and scientific significance. The bio-reef limestone in Jiantianba in Lichuan, the Chaodongyan Gorge in Enshi, the karst cave system of the Banqiao Underground River, the fissure of the Yunlong River, and 14 other sites are national-level geological relics that possess exceptional scientific and aesthetic value, ranking among the best in China. Additionally, Daweng Sinkhole and Tuanbao Black Cave in Lichuan, Gaojiatang Cave in Enshi, the stone buds and solution doline groups in Shibanling, along with 59 other sites, are classified as provincial-level geological relics, which are important components of the park. (4) The synergistic evolution of the terrestrial Enshi Grand Canyon, the subterranean Tenglongdong Cave system, and the multi-layered karst landforms within the park represents one of the best and most complete regional responses to the intermittent crustal uplift movements resulting from the uplift of the Qinghai–Xizang Plateau in Central China. This phenomenon holds significant scientific value and international relevance for the study of the Qinghai–Xizang Plateau’s uplift and the geomorphological responses in Central China. The formation and evolution of the swallet stream in Qingjiang offer essential insights into the formation of the Three Gorges of the Yangtze River over the past million years. Additionally, they shed light on the geomorphology and the spatial distribution of surface water and groundwater in Central China, holding significant comparative value in the field of international geological sciences.

The park boasts a diverse array of geological relics and numerous distinctive characteristics. Prominent among these are the geological relics associated with carbonate rocks, including the swallet stream in Qingjiang, the system of Tenglongdong Cave, the Enshi Grand Canyon, and the stone pillar forest in Enshi. These geological relics not only exemplify significant scientific research value but also holds great potential for popularizing geological science and enhancing tourism development. In conclusion, the Enshi Grand Canyon-Tenglongdong Cave Geopark possesses the requisite resources to be designated as a Global Geopark and meets the standards and requirements established by UNESCO Global Geoparks.