Quartz sandstone peak forest landforms of Zhangjiajie Geopark, northwest Hunan Province, China: pattern, constraints and comparison
The Zhangjiajie Sandstone Peak Forest Geopark in northwest Hunan Province, China, is a comprehensive geopark containing many spectacular quartz sandstone landforms, limestone karst landscapes and various other important geoheritage resources. It is listed as a UNESCO World Geopark and is also part of the World Heritage Wulingyuan Scenic and Historic Interest Area for its important landscape features. Many of the sandstone landforms, particularly the vast number of thin pillars or spires, are very unusual and serve as the core landscapes of the geopark. But Zhangjiajie displays a diverse range of landform types, exhibiting spectacular patterns and regular distributions. In this paper, the geomorphic traits, distribution pattern and constraints of the sandstone landforms of the Zhangjiajie Geopark are examined. Our study indicates that in the outcropping areas, the sandstones display four distinctive levels from 300 to 1,000 m above sea level, and these extend clearly from the highest sandstone plateau platform to the center of the valleys. The high sandstone platforms developed close to a flat high-level erosional surface, and subsequent erosion into this plateau has resulted in successively lower levels of landforms that transition gradually from peak walls, peak clusters, peak forests and peak pillars to remnant peaks in the lower valley bottoms. The form and distribution of the Zhangjiajie sandstone landforms are primarily dominated by the geological setting, particularly the presence of brittle structures (fractures and joint sets) trending NNW, ENE and NE. Triggered by the episodic tectonic movements, major streams and escarpments frequently occur along these structural directions, while some of the peak walls, peak clusters and peak forests have their longer elongated axes corresponding to NE or NNW directions, with an increased density of peak forms at the intersection of these fractures and joints. The geometry of the diverse sandstone landforms is also influenced to a certain degree by the climatic, water system distribution, lithologic properties, biological process, meteorological features and denudation processes. The suite of quartz sandstone landforms in Zhangjiajie can be compared with other sandstone landscapes regionally, and our interpretation of the sandstone peak forest formation processes offers a significant contribution to the study of topographic features and the geomorphic evolution of sandstone landscapes.