China is one of the countries with the widest distribution of karst landforms in the world, covering almost all provinces, autonomous regions and municipalities directly under the central government (Table 3- 1). According to statistics, the distribution area of carbonate rocks in China is about 3.6 million km2, and the exposed area is about 6.5438+250 million km2. According to Lu Yaoru (1973), it is described as follows: ① Southwest and Central China. Including Yunnan, Guizhou, Sichuan, Chongqing, Guangxi, Hubei, Hunan and so on. , is a relatively concentrated carbonate rock in China, which can be connected into large areas. The exposed area of thick carbonate rocks is 540,000 km2, and the interlayer area of carbonate rocks is 739,700 km2, accounting for 4 1.86% of the total area in this area. It is the area with the best development of contiguous peak forest landform in the world, and there are others, such as large caves and giant caves. Travertine (turbidite), stone forest and other karst tourism products also appear in this area, which is the most typical karst landform development area in China and even the world, and also the most developed and promising karst tourism area. ② North China. Carbonate rocks are distributed in Taihang Mountain, Shanxi Plateau, Luliang Mountain and hilly areas in central and southern Shandong Province, which is a typical karst landform distribution area in the north. Large karst springs with a basin area of hundreds to thousands of square kilometers, such as Baotu Spring in Jinan, Jinci Spring in Taiyuan, Niangziguan Spring in Henan and Baiquan in Henan, are both typical karst springs and famous tourist attractions. There are also large-scale caves in this area, such as Shihua Cave in Beijing, Yinhu Cave in Xinzhou, Shanxi, Qinglong Cave in Shandong, Baiyun Cave in Hebei and Xuehua Cave in Henan, which are also famous scenic spots. In addition, the early Paleozoic limestone in Taihang Mountain and Xishan Mountain in Beijing also developed the northern bee forest landform. ③ Southeast region. Carbonate rocks are also exposed in Jiangsu, Zhejiang, Anhui, Jiangxi, Fujian, Guangdong and other provinces, but the distribution is sporadic. The main karst landscape is karst caves. For example, Shanjuan Cave in Jiangsu, Yaolin Cave in Zhejiang, Lingqi Cave in Anhui, Taiji Cave in Pengze, Jiangxi, Yuhua Cave in Jiangle, Fujian and Baoshuangyuan Cave in Zhaoqing, Guangdong are all famous. ④ Northeast China. The exposed area of carbonate rocks is small, which is distributed in the Taizihe River Basin of Liaoning Province, forming a karst landscape represented by Benxi Water Cave. There are early karst peaks and caves in Lin Xiaoxi area of Xiaoxing 'anling, and there are karst landscapes influenced by the ocean in Liaodong Peninsula. ⑤ Xinjiang and Inner Mongolia. Although there are many carbonate rocks in Altai Mountain, Tianshan Mountain, Kunlun Mountain, Qilian Mountain and Yinshan Mountain, the annual rainfall is only 100 ~ 300mm, and only 20 ~ 25mm in some areas. And the annual average temperature is only 8℃ ~ 10℃, and the karst landform is very undeveloped, with a few caves. ⑥ Qinghai-Tibet region. It is the highest karst landscape distribution area in the world. Mount Everest is composed of carbonate rocks, and there are low-peak forests and shafts in Mesozoic and Cenozoic limestone at an altitude of more than 5400 meters on its northern slope. Obviously, it was formed in the early warm climate. There is a large karst spring exposed at Nachitai, 3800m above sea level in Kunlun Mountain, and the flow can reach1.5 m3/s. The alpine karst on the Qinghai-Tibet Plateau is unique to China. ⑦ Taiwan Province Province, Hainan Island and South China Sea Islands. Marble is distributed in the mountains of central Taiwan Province Province, forming Taroko Grand Canyon, and there are coral reefs exposed in Kenting, including small caves. The carbonate rocks in Hainan Island have sharp karst landforms, which are obviously the wonders of tropical karst. Most of the islands in the South China Sea are formed by coral reefs, with small caves and niches formed by seawater erosion and dissolution.
Figure 3- 1 Schematic Diagram of Carbonate Distribution in China
Table 3- 1 List of Carbonate Rock Area in China (unit: km2)
1. carbonate stratigraphic age
Strata have been exposed in all ages in China, from Archean (before 2500Ma), Proterozoic (2500~542Ma), Paleozoic (542 ~ 25 1~65Ma), Mesozoic (25 1 ~ 65Ma) and Cenozoic (65Ma to the present). The carbonate strata closely related to karst landform are distributed as follows:
(1) Archean carbonate strata
The oldest carbonate rock in China was found in Archean Cao Zhuang Formation (3,600 ~ 3,200ma) in eastern Hebei, and its lithology is thin marble, which indicates that China has had oceans since Archean. There are thin marble in Sanggan complex in Middle Archean (3200～2800ma). There are gneiss mixed with marble, marble formation and thick marble in Wulashan Group in Yinshan area of Neoarchean (2800～2500ma). There are graphite diopside Dali strata in Jining group; Anshan group has marble interlayer; There are four groups of carbonate rocks in the seventh group of Fuping Group in Taihang Mountain, that is, there is a layer of dolomite marble in Suojiazhuang Group; Muchang Formation consists of diopside marble and feldspar marble. Sidaohe Formation consists of diopside marble, tremolite marble and phlogopite marble. Hongtupo Formation contains a layer of white phlogopite marble with a thickness of 10~40m ~ 40m. Marble is distributed in other Archean strata, such as Luliang Group, Wutai Group, Taihua Mountain Taihua Group, Shanxi Jiehekou Group, Sichuan Kangding Group, etc. From Archean to NeoArchean, carbonate strata gradually increased, but Archean carbonate rocks have all turned into marble, and karst landforms are not developed except for small caves in some areas.
(2) Proterozoic carbonate strata
Since Proterozoic, the distribution range and thickness of carbonate strata have greatly increased. For example, in the Paleoproterozoic (2500 ~ 1800 Ma) strata represented by Hutuo system (2300 ~ 1800 Ma) (with a total thickness of 970 1m), the thickness of carbonate strata is about half, especially the upper east branch group is mainly composed of In Mesoproterozoic (1800 ~ 1000 Ma), the carbonate-bearing strata represented by Great Wall System and Jixian System are, from bottom to top, Tuanshanzi Formation, which is mainly composed of iron-bearing dolomite and sandy microcrystalline dolomite. The thickness of 479m higher than that of Zhuang Formation is banded chert dolomite, manganese-bearing dolomite and argillaceous dolomite, with a total thickness of/. Wumishan Formation is composed of a set of thick dolomite and stromatolite with flint belt, with a total thickness of 3,340 meters, which is the main stratum of karst landform in northern China. Tieling Formation is mainly composed of tidal limestone and dolomitic limestone with a total thickness of 333m, which can form peak forests and caves. The Neoproterozoic (1000 ~ 542 Ma) is represented by Qingbaikou and Sinian. The Jingeryu Formation in the upper part of Qingbaikou system is mainly composed of thin-layer dolomitic micrite limestone mixed with mud, and the karst landform is not developed because of the thin and miscellaneous layers. In the Southern Sinian system represented by the Three Gorges area, carbonate rocks appear in the Dengying Formation at the top, with dolomite as the main lithology and siliceous and phosphorus in the upper part. The total thickness varies from 200m to1000m, and large caves are developed.
(3) Paleozoic carbonate strata
Paleozoic * * * includes six systems, including Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Due to the wide distribution of Paleozoic oceans, a large number of marine organisms appeared, and the calcareous skeletons of organisms were deposited on the seabed to form various biological limestone, while the magnesium in seawater was relatively reduced, and the dolomite formed was relatively less than that in Proterozoic. In this era, carbonate rocks are thick, with many extremely thick layers and they do not deteriorate, which is the most developed stratum in karst landform. The carbonate rocks in the scenic spot are divided into the following series: a. Cambrian (542 ~ 488 Ma) carbonate rocks are mainly composed of stable deposits of continental shallow sea facies, distributed in North China Block, Yangtze Block and Tarim Block. The karst landscape horizons of North China Block are Zhangxia Formation and Gangshan Formation of Middle Cambrian, Changshan Formation and Fengshan Formation of Upper Cambrian. Zhangxia Formation is composed of oolitic limestone and bioclastic limestone, and Gushan Formation is composed of argillaceous banded limestone with bamboo-like limestone and oolitic limestone, all of which are nearly 300 meters thick, forming hilly landforms and karst caves in eastern Shandong. Taihang Mountain area is composed of barrier valley, steep cliff and urn valley. Changshan Formation is bamboo-leaf limestone and argillaceous banded limestone, Fengshan Formation is medium-thick micrite limestone mixed with bamboo-leaf limestone and shale, with a total thickness exceeding 100 m, and karst caves are developed. In the Yangtze block area, the thickness of Cambrian carbonate rocks is above 1000 m, and the karst landscape horizon is also middle-upper series, such as Doupo Temple Formation, Xixiangchi Scenic Area Group, Sanyoudong Group and Loushanguan Group. Ordovician carbonate rocks (488 ~ 443 ma) are also stable continental shallow marine sediments. The middle and lower parts of North China block are carbonate rocks, and the lower parts are Yeli Formation, Liangjiashan Formation and Majiagou Formation. The lithology is leopard limestone, argillaceous banded limestone, dolomite and limestone, biolimestone, thick pure limestone and argillaceous dolomite. With a total thickness of 330 ~ 1 100 m, large caves and karst springs are mostly found in Majiagou limestone. The lower, middle and upper layers of the Yangtze block are all exposed, with a total thickness of 300 ~ 500m. The lower layers are Nanjinguan Formation, Fenxiang Formation and Honghuayuan Formation, and the lithology is black limestone, dolomite limestone mixed with shale and biolimestone. Zhongdawan Formation and Guniutan Formation are nodular limestone and shell limestone; The upper series is thin and characterized by fractured limestone in Baota Formation. Large-scale caves, canyons and sinkholes are developed, especially recently, the author found a beautiful new stone forest landform in the fractured limestone in Liang Long Township, Xingwen County, southern Sichuan, which further increased the tourism value of Ordovician carbonate rocks. In particular, Mount Everest is also composed of Ordovician limestone, which makes karst climb to the top of the world. C. Silurian (443 ~ 4 16Ma) is dominated by clastic strata, and carbonate strata are undeveloped, so this series has no valuable karst landscape. D Devonian system (4 16 ~ 359 Ma) is the first system of Upper Paleozoic. At this time, the paleogeographic features have changed greatly, and there is no sediment in North China. Marine stable carbonate deposits are mainly distributed in Guangxi, Guizhou, Chongqing, Sichuan, Yunnan, Guangdong and Jiangxi, and the middle and upper Devonian are well developed. For example, the Donggangling Formation in the upper part of the Middle Devonian is dolomitic foraminiferal limestone and bioclastic limestone mixed dolomite, and the upper Devonian Guilin Formation and Rongxian Formation are continuously deposited with a thickness of about 300m, while the Guilin Formation is thick micrite limestone, foraminiferal bioclastic limestone, sandy limestone, fine dolomite and thin limestone. , the thickness is 356 ~ 557 m; Rongxian Formation is composed of medium-thick pebble sand limestone, oolitic limestone and thin limestone. , thickness of several hundred meters, local more than 1000 meters. Devonian carbonate rocks are thick, pure and gentle, and are one of the most typical rock formations with peak forest and peak cluster landforms. "The river is a green belt and the mountain is like a jade hairpin" is the best compliment to the karst landform formed by Devonian carbonate rocks. E. Carboniferous (359 ~ 299 Ma) carbonate rocks are scattered and rarely connected into large blocks. In North China, only the upper part of Taiyuan Formation contains thin limestone; The lithology of Lower Carboniferous in South China is dominated by marl, micrite and nodular limestone, with local coal deposits. There is a set of 100-meter-thick pure calcium carbonate deposits at the junction of Yunnan, Guizhou and Guangxi, and the Shangmaping Formation is 100-meter-thick pure limestone and dolomite with caves. F the Permian (299 ~ 25 1ma) carbonate rocks are mainly middle Permian Qixia formation and maokou formation, and the lithology is mainly bioclastic limestone, dolomite, banded bioclastic micrite limestone containing flint, thick-thick amphibolite limestone and eyeball limestone, with a thickness of 300 ~ 600 m, and Yunnan Shilin is 297 ~ 365433.
(4) Mesozoic carbonate strata
In the Mesozoic era, China's oceans gradually retreated, showing the scene of the South China Sea and the northern land. During Triassic, there were thick carbonate deposits in the Southern Ocean, and there were no important marine carbonate deposits in Chinese mainland after Triassic. The main horizons (25 1 ~ 199 Ma) of Triassic carbonate rocks are lower Triassic Jialingjiang Formation, middle Triassic Anshun Formation, Guanling Formation and Gejiu Formation. Jialingjiang Formation in Sichuan is more than 500 meters thick, and its lithology is micrite limestone, micrite dolomite, oolitic banded limestone, bright oolitic limestone and hard-shell bright calcite. The Anshun Formation in central Guizhou is 350 ~ 637 m thick, and its lithology is dolomite, argillaceous dolomite, marl, bioclastic limestone and oolitic dolomite. The thickness of the Middle Triassic Guanling Formation in central Guizhou is1000 m ~ 920 m, and the bottom is a layer of yellow-green vitrinite tuff, which is covered with medium-thick fine-grained dolomite, thin to medium-thick limestone, wormlike gravel limestone and marl. The thickness in Anlong and Xingyi areas is more than 400 m, and it is composed of reef limestone, dolomite and dolomite limestone. Gejiu Formation is mainly composed of dolomite. Karst landforms developed in Triassic carbonate rocks, such as typical peak forest, peak cluster and canyon landforms in Xingyi and Anlong areas, and stone forest landforms in reef limestone, are another important karst landscape layer after Devonian peak forest and peak cluster landforms in Guilin area and stone forest landforms in Permian limestone in Yunnan.
Carbonate strata have appeared in China since Archean. From Mesoproterozoic to Mesozoic Triassic, carbonate rocks with a thickness of more than 10,000 meters were continuously deposited except Silurian, which laid a solid material foundation for the extensive development of karst landforms in China.
2. Structural conditions
Seen from the plate, Chinese mainland is located in the southeast of Eurasia plate, with Indian plate in the southwest and Pacific plate and Philippine Sea plate in the southeast. During Eocene-Oligocene, about 50Ma ago, the Indian plate collided with the Eurasian plate from south to north and was inserted under it, causing the Himalayas to rise from the ground and become the roof of the world. The tectonic event of collision between Indian plate and Eurasian plate is called Himalayan tectonic movement, also known as Himalayan orogeny. Himalayan movement not only created the overall landscape pattern of the four steps in Chinese mainland, but also was the internal dynamic geological condition for the formation of various micro-landforms (or sculptural landforms). Li Tingdong and others (1980) divided Himalayan orogeny into three acts. The first scene took place at the end of Eocene, showing the closure of the Tethys Sea (ancient Mediterranean); The second act took place in the middle and late Miocene (20 ~ 100 Ma), showing strong folds and fractures. The third act took place in Pliocene-Early Pleistocene, mainly manifested in the uplift and fault activities of the Qinghai-Tibet Plateau. Most of the karst landforms we see today are the products of the third act. Geodetic data show that the Indian plate is still advancing northward at a speed of about 5 cm/year, and the Qinghai-Tibet Plateau continues to rise at a speed of several millimeters to several centimeters per year. Most karst canyons, sinkholes, peak forests, peak clusters and stone forests in China were formed by dissolution and erosion during the uplift of Himalayan orogeny, and multi-layer caves were also formed by dissolution during the intermittent uplift of this movement. All kinds of karst landforms in Chinese mainland are controlled by Himalayan movement. When studying karst landforms, we must understand the geological structure background of China. What needs to be pointed out here is that Chinese mainland formed a unified plate at the end of Triassic and became a part of Eurasian plate, while Chinese mainland lithosphere was a composite continent composed of multiple landmasses before that. According to research, there were six ancient plates in China and its adjacent areas before Mesozoic, namely Siberia plate, Kazak plate, Tarim plate, North China plate, South China plate and South China Sea-Indochina Peninsula plate (Figure 3-2). Geological background (stratum, structure, igneous rock, etc.). ) is also different, and the resulting karst landforms are also obviously different. The most distinctive karst landforms in China are mostly concentrated in the South China Plate, which is a good example. It is still a brand-new subject to study the formation, evolution and distribution of karst landforms with plate structure theory.
3. Climatic conditions
Temperature and humidity are the main factors of climate and karst development. The karst landforms we see today were mainly formed at the end of Cenozoic, which depends on the climatic conditions in this period to some extent. At the beginning of Tertiary, the climate in Chinese mainland was dry. According to the research of Academician Liu Dongsheng, the climate of China in Eocene was controlled by the planetary wind system, thus an east-west arid zone was formed between18 ~ 35 N. At the end of Eocene, the arid zone continued to move northward. At the end of Oligocene, the southeast monsoon was initially formed, and the forest south of the Yellow River developed. In the middle Miocene, the southwest monsoon began to form. Due to the influence of southeast monsoon and southwest monsoon, the south of China becomes humid. At the end of Miocene, the climatic characteristics and geographical distribution of China arid zone were close to today's pattern. The rapid uplift of the Qinghai-Tibet Plateau from the end of Pliocene to the beginning of Pleistocene blocked the water vapor from the Indian Ocean, making the northern part of China drier and the southern part wetter. Especially in the Middle Pleistocene, the climate in South China and Central China was hot and humid, which was the main formation period of karst. At present, the climate in China is still dominated by monsoon, which is controlled by southeast monsoon (tropical and subtropical Pacific summer monsoon), southwest monsoon (Indian Ocean summer monsoon crossing the equator) and northwest monsoon (sub-Arctic winter monsoon). It is characterized by the transition from south to north and from east to west from hot and humid climate to dry and cold climate, and the development intensity of karst landforms is consistent with this climate trend.
Fig. 3-2 Schematic diagram of ancient plate distribution in Chinese mainland (according to Xia Yucheng, 2003)