Features and Geological Significance of Geological Relics of Yuntaishan Geopark
Total Page:16
File Type:pdf, Size:1020Kb
International Journal of Geoheritage. 2017, 5(2): 43-55 DOI: 10.17149/ijg.j.issn.2210.3382.2017.02.004 © 2017 Darswin Publishing House Features and geological significance of geological relics of Yuntaishan Geopark Tongchang Jiang, ZHENG YAO Faculty of Geographical Science, Beijing Normal University, Beijing, China, 100875 Abstract: Yuntaishan Geopark, one of the first Geological Parks in China, is of special scientific significance and aesthetic value and featured by geological relics and geo- logical landscape. There are many kinds of geological relics in this area, such as stratum relics, rock relics, tectonic relics, hydro-geological relics and geological-geo- morphologic relics, all of which have different features and important significance in geomorphology, stratigraphy, sedimentology, lithology and paleontology. Compared with other geological parks in Taihang Mountains, the landscape of canyons is not unique enough and the karst landform is less typical. Keywords: Yuntaishan Geopark; geological relics; geological value 1 Introduction Yuntaishan Geopark is one of the first Global Geoparks approved by the UNESCO. Located in the northern mountain area of Jiaozuo, Henan Province of China, the Park covers an area of 556 km2. The structure is located in the south of the North China plate, the south of Taihang Mountains. The geological relics in the Park are concen- trated and the strata are well distributed. Sandstone of Yunmengshan Formation of Mesoproterozoic Erathem in which stratigraphic sequence is preserved integrally is the main part of Yuntaishan Geopark as well as an important part of the strata in Tai- hang Mountains. The Park is featured by geological relics and geological landscapes which constitute Yuntai landform forming under the effects of rifting. The Yuntai landform is a typical relic of Neotectonism and a new type of Chinese landforms. In the North China craton, a relatively complete and typical platform sediment formed to keep the marine environment of Mesoproterozoic Era and Paleozoic Era, especially the sedimentary relics in the epicontinental sea environment. Therefore, the study on geological relics in Yuntaishan Geopark will help to understand the evolution process of sediment of shallow marine facies of the Proterozoic Era and change of geogra- phical environment in the North China. Author: Tongchang Jiang, Ph. D. Candidate, Faculty of Geographical Science, Beijing Normal University, Beijing, China, 100875 Email: [email protected] Zheng Yao, Post-doctor, Institute of Finance and Economics Research, Central University of Finance and Eco- nomics, Beijing 100081, China; Associate researcher, Development and Research Center, China Geo- logical Survey, Beijing 100037, [email protected] 44 INTERNATIONAL JOURNAL OF GEOHERITAGE 2 Location of study area Located in Jizuo, the north of Henan Province (E112°44′~113°26′, N35°11′~35°29′), (Figure 1) Yuntaishan Geopark composed of low mountains 6001308 m above the sea level is included in Taihang Mountains, among which Zhuyu Peak is the summit. Yuntai Mountain is a part of the second stair (the Loess Plateau) and the third stair (North China Plain) of Chinese mainland. The Geopark is a strip in the direction of northeast-southwest, crossing about 215 km in south-north and 63 km in east-west and covering an area of 556 km2. The studied area borders on Shanxi Province on the north, adjoins Jiyuan of Henan Province on the west and is contiguous to Xinxiang of Henan Province on the east. The Geopark is mainly characterized by canyons and waterscape, and also featured by natural ecological and human landscapes, which are of aesthetic and scientific value. Figure 1 Location of Yuntaishan Geopark 3 Geological background of study area Yuntaishan Geopark has experienced a long and complicated geological evolution. 2.5 billion years ago, that is in the late Archean Eron, the Embryonic Platform formed and then entered upon the phrase of platform development about 1.8 billion years ago. About 1.2 billion years ago, in the Jixian Period, the platform declined to accept the clastic sediments of littoral facies, then the tectosphere of platform overburden and unconformity between Yunmengshan Formation of Jixian System of Mesoproterozoic Erathem and the Archean Erathem (Fan, 2004). In the epicontinental sea environment of 543-490Ma Cambrian Period, the thick sediment mainly composed of carbonatite formed (Wang, 2005), constituting the parallel unconformity between the Cambrian System and Yunmengshan Formation; the epicontinental sea environment in the Cambrian Period remained to the Ordovician Epoch, in which the sediments were mainly composed of carbonatite. In late Mesozoic Era, the subduction of Pacific plate to the Eurasian plate led to the strong tectonism, and the early and medium phases of GeYu: Features and geological significance of geological relics of Yuntaishan Geopark 45 Indosinian-Yanshan movement led to orogenesis (Qi, 2002). In the late Early Creta- ceous Epoch-the beginning of Paleogene Period, it was the embryonic stage of rifting. The Paleogene Period was the prime of rifting and the Neogene Period was a depres- sion period of rifting. The characteristics of tectonic movement in the Neogene Period remained to the Quaternary Period and the well preserved geological relics in the Park are a record of the history and tectonic evolution of the earth. 4 Regional structure and stratum The crust of Yuntaishan Geopark has a structure of double-layer. The metamorphic schist and gneiss in the Archean Erathem constitute the base; the terrigenous clastic rocks in the Mesoproterozoic Erathem, carbonatite of shallow marine facies and shale in the Cambrian System and Ordovician System constitute the overburden. According to Mattner’s structural hierarchy, the base is the lower structural hierarchy mainly with the plastic deformation. The overburden is the upper structural hierarchy mainly with the brittle deformation and the brittle fractures in various directions in the Park. The fold structures are seldom seen in the Park and many brittle fractures have formed (Figure 2). Figures 2 Geological background of Yuntai Mountain The Yuntaishan Geopark with a complete range of strata of the Archean Eonothem, Proterozoic Eonothem, Paleozoic Erathem and Cenozoicis Erathem located in the south of the Taihang Mountains (Figure 3). A set of gneiss complex of the Archaeo- zoic Erathem is the most ancient base distributed sporadically in the Park. 5 Conclusions To analyze the geological value of Yuntai Mountain, publications and journal articles relating to Yuntaishan Geopark have been consulted and field investigation was car- 46 INTERNATIONAL JOURNAL OF GEOHERITAGE Figure 3 The exposed strata in Yuntai Mountain ried out. In addition, canyons in Yuntaishan Geopark were compared with canyons in other geological parks in Taihang Mountains, Yuntai landform was compared with karst landform, and Yuntaishan Geopark was compared with other world heritage sites. 5.1 Basic features of geological relics in Yuntaishan Geopark A geological relic is a geological phenomenon under the endogenic agent and exo- genic agent of the earth. With the diversity of geological processes, the geological relics are various. Geoparks are built on the basis of geological relics and for the purpose of displaying the scientific significance of geological relics. The classifica- tion and identification of geological relics require the recognition of international counterparts. Yuntaishan Geopark featured by geological relics and geological land- scapes is composed of a series of geological relics which can indicate the geological history and geological process of this area. The Yuntai landform under effects of rift- ing is a typical relic of Neotectonic movement. The North China craton and the unique hydrodynamic conditions lead to unique and diverse geological relics and geological landscapes in the Park. Geological relics of Yuntaishan Geopark include stratum relics, rock relics, tectonic relics, sedimentary relics, paleontological fossil relics, hydro-geological relics and geological- geomorphologic relics. 5.1.1 Stratum relics A stratum is a layer of sedimentary rock forming in an epoch in the geological history. Strata in Yuntaishan Geopark mainly include the profile of Yunmengshan Formation of Jixian System of the Mesoproterozoic Erathem in Wenpan Valley and the profile of Mantou Formation of the Cambrian System in Xiaozhai Valley. The former covers on the base, and as the earliest sedimentary formation preserved in this area and with diverse structures inside and outside the stratum, it reveals the first transgression GeYu: Features and geological significance of geological relics of Yuntaishan Geopark 47 process and has research value and ornamental value. Basal conglomerate formed in the base, and the aubergine quartz sandstones mainly constituted the lower and middle part (Sun, 2005). The rocks are rich in iron and tabular cross-bedding, herringbone cross-bedding and tidal complex-bedding have developed with polygonal cracks and ripple marks in different sizes and shapes commonly being seen. The upper part is aubergine and red pure quartz sandstone with nearly horizontal cross-bedding and small ripple marks-bedding developing. The profile of the latter is preserved inte- grally and as the representative in the North China, it reveals the first transgression process of the North China epicontinental sea. From the bottom to top, terrigenous clastic sediments of littoral tidal flat gradually