关键词: 丹霞地貌, 景观类型, 红层岩性, 构造切割, 风化

Abstract:

Danxiashan UNESCO Global Geopark is characterized by well-developed Danxia landscape in humid climate of South China, where geomorphologic features and genetic analysis of individual landforms have received much attention in previous studies. However, the controlling factors of landscape development across the Danxia Basin remain poorly understood, and the relationship between fault systems and peaks is yet to be well recognized. In this study, methods such as field survey, rock hardness measurement, remote sensing interpretation of liner structures, and experimental analysis of rock samples were used to illustrate the roles of lithology, depositional facies, and tectonic uplift and dissection in shaping the landscape evolution and to propose a gene-tic and morphologic classification of Danxia landscape. The Upper Cretaceous continental red beds in the Danxia Basin consist of the Changba and Danxia formations. The Changba Formation has a larger outcrop area, forming gentle low hills, while the Danxia Formation is concentrated and characterized by well development of cliffs, representing the typical Danxia landscape. The Danxia Formation is composed of coarse clastic rocks of alluvial fans and eolian sandstones, and is featured by having great thickness, tight cementation, high density and hardness, and being resistant to weathering. In contrast, the Changba Formation consists dominantly of fine-grained muddy clastic rocks deposited in river and lake environments, which are less resistant to weathering and cannot support Danxia landscape with cliffs. The Himalayan tectonic movement likely caused the overall uplift of the Danxia Basin, which resulted in the formation of a series of NE-trending faults and NNE-, NW-, and nearly EW-trending joints. The fracture surfaces may have facilitated subsequent weathering and erosion, producing prominent cliffs, reticulated valleys, and peculiar peaks and rocks. The Danxiashan area is in a subtropical humid climate, where weathering, collapse, water erosion, and karst processes are the main landscape-shaping external forces. Accordingly, the genesis of Danxia landscape is classified into five categories, i.e., collapse-scour, collapse-accumulation, weathering-denudation, river erosion, and dissolution-sedimentation types. The cliff development is a key element of Danxia landscape, and the different combinations of cliff quantities and types formed hills and gorges. Based on these features, the morphological types of Danxia landscape in Danxia-shan are divided into six major categories and twenty-two specific types. This paper has theoretical significance and practical values because it provides a better understanding of the formation processes of Danxia landscape in humid climate, and foundational materials for construction of national park, scientific mountain, and geoscience study travel.

Key words: Danxia landscape, landscape type, red bed lithology, tectonic dissection, weathering