武陵源峰林地貌形成的大地构造条件

武陵源峰林是一种新被认识的峰林地貌类型。出于它是以千姿百态、形神兼备的石峰石柱密集,幽峡深壑纵横交错,并衬托以密茂的植被和碧清的溪湖之胜驰名于世,经联合国教科文组织批准列入世界自然遗产名录,成为世界级的重点保护地区。因其所构成的岩石、成因和产生的大地构造历史背景和发育环境具有自己的特色,遂在地貎学上饶有研究价值。在亚洲大地构造图中,武陵源位于东亚壳体南段,云贵地洼区的湘西黔东地穹列的东北端。构成上述峰林的岩石为时代属于晚泥盆世的地台构造层的石英砂岩。这种砂岩为本区地台阶段和缓期的产物,由于它所具有的稳定区型沉积建造特征所决定,其物质组份单纯,粒度和园度也分选性好,质地致密坚硬;同时又因其所在的部位受中生代地洼阶段造山运动的褶皱作用影响较弱,且他于一个宽展型向斜层轴部的末端,岩层产状尚保持平缓,而垂直节理及断层却十分发育,遂于第四纪新构造运动期内上升过程中,在风化、水蚀及重力的综合作用配合下,形成了这样奇丽的峰林景色。

GEOTECTONIC CONDITIONS OF FORMATION OF THE WULINGYUAN PEAK- FOREST LANDFORM, CHINA

The Wulingyuan peak-forest is a newly recognized type of peak-forest landform . It is world—famous for its dense and fantastic rock peaks and pillars with various shapes and criss cross secluded val leys and deep gullys, with thick vegetation and limpid lakes. It has been listed by the UNESCO as a world natural heritage and became a world-level region for priority protection. Because it has its own charactcrisitic feturos m the rock making up it, in genesis, in geotectonic-historical stting of occurrenec and in environment of development, it is of consideradle value in geomorphology. In the Tectonic Map of Asia Wulinsynan is situated in the southern segment of the East Asia crustobody, at the northeastern end of the West Hunan—East Guizhou geodome series of thc Yunnan—Guizhou diwa region. The rock making up the above—mentioned peak—forest is quartzose sandstone of the Late Devonian platform struetural layer. This sandstone is the product of the maximum—stability period of the platform stage. Determined by its characteristics of a stable—region—type sedimentary formation, it is simple in material composition, well—sorted in grain size and roundness and compact end hard. Moreover,it is affected by folding weakly during the Mesozoic diwa orogeny and located at the termination of the axis of a broad syncline. Therefore, the hed keeps a gentle attitude, but vertical joints and faults are well—developed. As a consequence, such a spectacular peak—forest scenc is formed by the combined action of weathering, erosion and gravity in the process of uplift at the Quaternary neotectonic stage.