Formation of Scenery of Yuntaishan World Geopark in Jiaozuo City, Henan Province, China

摘要

Yuntaishan (Mt. Yuntai) National Geopark of Xiuwu County, Jiaozuo City, Henan Province, China, i.e. Mt. Yuntai scenic spot, one of five scenic spots in the Mt. Yuntai World Geopark, is located at the south part of Mts. Taihang. It is on the boundary of the second geomorphological step of China, the Huangtu (Loess) Plateau and the third geomorphological step, the North China Plain. The wonderful scenery of this geopark is formed by two extensive stream downcuttings after two planations. Most mounts and ranges in the park and in the adjacent southern Mts. Taihang with nearly the same elevations (from 1,100m to 1,300m a. a. 1.) or slightly tend to the east and the south directions are remnants of planation surface of Taihang Age formed in the late Palaeogene Period. After the Taihang Age, Zifang River and its tributaries cut down to about one thousand meters in the lower Palaeozoic Erathem with nearly horizontal occurrence which composed mainly of thick and hard resistant layers of limestone with some soft, easily eroded interbeded layers, such as shales, dolostones etc., forming a great canyon composed of big overhanging cliffs and small gentle slopes. But on the breaks of stream bed, a lot of waterfalls and cascades are formed, such as the "Great Yuntai Waterfall" with height of 314m. In this paper, this downcutting stage of the streams is named "Yuntai Age". In the middle part of the geopark, the valley of Zifang River has a wider and gentle bottom of valley formed in the late Neogene Period, the planation surface of the " Tangxian Age" which always consisted of gravels of 10 - 20m thick and partly cemented, the Tangxian Gravels, most of which have moderate roundness. After the Tangxian Age, mainly in the Quaternary Period, and in the middle part of the geopark , i.e. Hongshi (red stone) Valley where Zifang River cut down in the purplish red quartzitic sandstones or quartzarenites of Yunmengshan Group of the New Proterozoic Erathem over one hundred meters thick, forming a narrow gorge with dark red hanging cliffs, a series of waterfalls and cascades and gorge with very steep valley - side walls. In the frontier and periphery of the geopark, Zifang River is wider, where five stream terraces with heights of3-5m, 12-15m, 25 - 35 m. 35 -45m and 55 - 70m were formed since the Middle Pleistocene.