陕北丹霞地貌特征及国内外对比研究

通过野外考察,并结合地质资料和样品分析,对陕北丹霞地貌形成的地质构造背景、红层岩性、形态特征、演化过程等进行系统阐述,并与中国东南部湿润区及国外的典型丹霞地貌进行对比,总结其共性和差异.结果表明:陕北丹霞地貌形成的构造环境为大型内陆坳陷盆地——鄂尔多斯盆地,主要成景地层为洛河组紫红色中-细粒长石石英砂岩,形成于早白垩世...

Characteristics of Danxia Landform in the Northern Shaanxi and A Compar-ison with Other Danxia Areas in and Outside China

The northern Shaanxi is a key region for the distribution of red beds and Danxia landform in China, it has significant differences with Danxia landform in southeast China and abroad. However, few research was concerned with this issue. Based on field investigation and analysis of geologic literature and rock samples, this study focuses on the development of Danxia landform in the northern Shaanxi from the aspects of geologic background, lithologic characteristics, geomorphic features, and evolution process. Then, a comparison with Danxia landform in the humid southeast China and foreign countries was conducted to summarize their commonalities and differences. It reveals that Danxia landform in the northern Shaanxi is developed in a large inland depression basin, the Ordos Basin. The dominant red beds for the development of Danxia landform is Luohe Formation, which is mainly composed of medium to fine-grained sandstone and was deposited in an arid desert during Early Cretaceous, and featured by large cross-bedding. Experimental analysis shows that the Luohe sandstones are well-sorted and well-rounded but poorly cemented, typical features of aeolian sandstone such as disc-shaped impact craters are found on surfaces of quartz particles. The most remarkable geomorphic feature of Danxia landform in the northern Shaanxi is that there is a Quaternary loess cap on the top, forming a type of covered Danxia. In terms of landform evolution, Danxia landform in the northern Shaanxi is generally in young stage, featured by a combination of plateau and canyons, with closely spaced gullies and continuous Danxia cliffs developed, but there are few isolated individual landforms. The developmental process of Danxia landform in the northern Shaanxi could be divided into four stages: 1) Red beds deposition during Early Cretaceous; 2) Tectonic uplift and the development of paleo-Danxia landform during Late Cretaceous; 3) Intermittent uplift since Paleogene and covered by loess in Quaternary. As for comparison with Danxia landform in other regions at home and abroad, Danxia landform in the northern Shaanxi has many differences with those in the humid Southeast China, but it has more similarities with Danxia landform in the western United States. The current theories based on Danxia landform in the humid southeast China cannot well reflect these regional differences, more further comparative research on Danxia landform in and outside China should be conducted, so as to improve our understanding on Danxia landform.