张掖丹霞暨彩色丘陵地质成因分析

利用实际调查测试资料和已有研究成果,在简述丹霞暨彩色丘陵区自然地理条件、地层构造及分布特征的基础上,全面阐述了祁连造山带前古生代、古生代—中生代地质构造发展变化过程。认为丹霞暨彩色丘陵成景地层大约形成于中生代末期100～140Ma BP前后的早白垩纪,沉积环境为河流—湖泊相红色及杂色层状碎屑岩沉积,总厚度大于5 000m。以青藏高原隆升为契机,宏观分析了新生代以来喜马拉雅、青藏、昆(仑山)黄(河)、共和4大构造运动及其由此引起的外动力条件的变化对丹霞暨彩色丘陵地貌各个阶段的演化并最终成型的影响和控制。认为喜马拉雅构造运动末期8Ma BP前后,隆升效应波及到祁连山区,成景地层受到挤压抬升和变形缩短,进而发生轻微褶曲并被长期风蚀、水侵及夷平;6～7Ma BP上新世,丹霞暨彩色丘陵地貌的雏形基本形成;昆(仑山)黄(河)运动结束后,大约0.2～0.4Ma BP中更新世,张掖丹霞暨彩色丘陵地貌已完全形成;共和运动期间丹霞暨彩色丘陵地貌区祁连山平均上升幅度为1.32～2.34mm/a。微观分析了幼年期、中年期、老年期及消亡期丹霞地貌的形成机理和外观特征;从沉积物Fe3+/Fe2+含量及当时环境下的氧化—还原程度诠释了彩色地层的形成原因。

The Geologic Origins of Danxia and Colorful Hills Landform of Zhangye in China

This article introduces the development of Qilian Mountain orogenic belt in the geologic structure,which from the Prepaleozoic era to the Paleozoic, finally to the Mesozoic, using the practical research results and the achievements, which based on analyzing the physical geographic condition of Danxia and colorful hills,geologic structure and distribution characteristics. From the analyzing the depositional environment stratum,lithologic character, regional structure pattern and forming time, it is believed that the stratum was formed about100～140Ma BP, which is during the early cretaceous period. The stratum, total 5 000m in thickness, was belong to rivers-lakes red color and colorful lamellar clastic rocks deposition. It is clearly claimed that with the uplift of Tibetan Plateau, rudiment of Danxia and colorful hills were nearly formed during 6 ～7Ma BP of Pliocene,completely formed during 0.2～0.4Ma BP of middle Pleistocene since the four great tectonic movements, which are Himalaya（45～8Ma BP）, Qinghai-Tibet（3.6～1.5Ma BP）, Kunlun Mountain-Yellow River（1.2～0.5Ma BP） and Republic（0.15-0.01Ma BP）, and the influences, which were the changes of Danxia that under the external force from the four great tectonic movements. Besides, according to the internal and external forces of forming the Danxia and colorful hills, the article discusses infancy, middle age, old age and died out in micro level of formation mechanism and appearance features of Danxia geomorphology. What＇s more, the article explains the reasons to the forming of colorful stratum in terms of the percentage of sediments, which pointed out as Fe3＋/ Fe2＋,and the degree of redox reaction at that time. It is thought that the main color of the stratum was purplish red or brick-red if the percentage of Fe3＋in the stratum, that is to say, value of Fe3＋/ Fe2＋in a reduction environment were large. Otherwise, the main color of stratum is white or black. Zhanye Danxia has strong typicality, aesthetic value, scientific investiga