Karst in China

The distribution of carbonate rocks on the earth’s surface is uneven and irregular. Large areas of the world, like much of the shield of Africa have little or no carbonate deposits, but in China, carbonate rocks outcrop widely at the surface or exit at shallow depths below the surface, covering 1.3 million km² or one-seventh of the country’s territory. About one-quarter of the world’s total of terrestrial carbonate rocks occurs in China. China is an immense country; its area is almost 9.6 million km² and it comprises about 6.5% of the world’s total land area. About 10% of China’s rural population live in the karstified tropics of South China; 61% of the food supplies and 93% of the rice are produced there (Barbary et al. 1991). The major karst areas in China are located in densely populated and economically important regions, particularly in the northeast, south and southwest (Figs. 1 and 2). Moreover, the distribution of karstic rocks is so widespread that almost every geomorphological type of karst can be found in China (Ren Mei et al. 1982). If covered and buried karsts are included, in addition to surface karst, up to one-third of the country is involved. The management and development of the karst areas thus form important sectors of the economy. Almost one-quarter of the total water resources of China is of karstic origin (Yuan Daoxian et al. 1991), and a good proportion of the Chinese petroleum reserves occurs in karstic rocks. Limestones and karst in China thus permeate almost every aspect of its physical geography and no other country of comparable size (Russia, Brazil, USA or Australia for example) is so dominated in its modern geology and geography by karstic problems.

Ford and Williams (1989) have said that in Europe the “Mediterranean Basin is the cradle of Karstic Studies”. In China, karst studies in general developed separately from the West. The relatively late discovery by outsiders of the Chinese karstlands was partly due to civil unrest and difficulties of travel in China. The Sino-Japanese war, followed by the revolution and then the “Cultural Revolution”, meant that there were few opportunities for scientists to work in China. Travellers and archaeologists, like Sven Hedin and Aurel Stein, worked in what is now Chinese central Asia in the 19th and early 20th centuries (Hedin 1898; Stein 1912). The first geological reconnaissances in N China were made by von Richthofen from 1866–1872, paying particular attention to the loess landscapes (von Richthofen 1877–1912). However, little attention was given to South China. It was not until the 1920s and 1930s that Western scientists made any contribution to the study of the limestones in China. The first European description of the tower karst is believed to have been given by Handel-Mazetti, a botanist in 1926 and discussed by the geographer, O. Lehmann (Handel-Mazetti 1926; Lehmann 1926). In fact, the botanists and “plant-hunters” were some of the most important travellers in S and W China in the early years of this century (Sweinfurth and Sweinfurth-Marby 1975 on Kingdom Ward). Much significant work was done by French geologists, including the Jesuit, Teilhard de Chardin; de Chardin not only assisted in the excavation of the Peking Man site at Zhoukoudian, but also studied the Devonian limestone sequences of S China and made the first section across the tower karst limestones of the Guangxi basin near Guilin in the 1930s (Teilhard de Chardin et al. 1935). Bouillard also surveyed the caves of Yunshui in the Shangfang mountains near Peking in 1924; these caves are developed in siliceous dolomites of the Wumishan formation, middle Proterozoic (Bouillard 1924). The American geologist, Barbour (1930) discussed travertines in N China.

Before discussing the main karst types in China, some aspects of Chinese karst terminology should be described. In geomorphology, Chinese geographers and hydrogeologists are more concerned with groupings of landforms than with the origins of individual forms. Emphasis in China has been on the hills or positive forms of karst, whereas in Europe more attention has been given to the negative landforms — the closed depressions. Closed depressions interrupt or seem to replace the valley drainage networks, and were regarded by European geomorphologists as the main organizational units in the landscape. The main Chinese terms for different types of karst hills, for dry valleys and for closed depressions are given by Atkinson in Song Linhua (1986a) and to which reference will now be made. These terms are descriptive and do not in any way presume any particular mode or age of formation. There are also some variations in their use in different parts of China.

The name “Guilin” means “the forest of the sweet-scented osmanthus tree” (Osmunda sp., Osmanthus delaboyi) and the town is one of the historical cities designated by the Chinese government. The town goes back to the Qin Dynasty (221–206 B.C.) and was named Shian under the Han Dynasty (111 B.C.). As the political centre for the Guangxi region in the Tang Dynasty (618–907 A.D.), it has many stone inscriptions and statues of that age, and continued to be predominant under the Song Dynasty (960–1279 A.D.), becoming the provincial capital under the Ming and Qing Dynasties. During the Ming Dynasty in 1393, Prince Jing Jiang constructed a palace with pavilions, terraces, altars and temples. Although damaged in the Qing period, the palace was sufficiently repaired for Sun Yatsen to set up his headquarters there in 1921. It now houses the Guangxi Teachers’ University (Ru Jinwen et al. 1991). During the Sino-Japanse war, when much of China was occupied by the Japanese, many scientists, artists and writers fled to Guilin. Among these was J.S. Lee (Li Siguang), the famous geologist whose laboratory was at Yanshan, S of Guilin.

Guizhou province covers 176 000 km² of which 72% is karstic. The Guizhou plateau has an altitude of between 1000 m a.s.l. to over 3000 m, but is mostly between 1000–2000 m. The plateau extends into the neighbouring provinces of Yunnan, Hunan, Hebei and Sichuan (Fig. 2). It is part of the second great topographic step of China and falls to the E to neighbouring Guangxi. The plateau slopes generally from W to E. It is drained to the N by major tributaries of the Changjiang (Yangtse) and to the S to the Zhujiang (Pearl) river. The average annual rainfall is about 1100 mm, mostly coming in summer with considerable winter drizzle on the plateau. Guizhou has a cloudy climate, like that of Sichuan, as a result of the meeting of different air masses which arrive from the NE in winter and the S in summer. Average temperatures are 11–19 °C. Mountain ranges run generally NE-SW, except the Miao range which is E-W.

Yunnan is the most westerly province of S China and nearly 26% of the whole province of 97 000 km² is karstic. The easterly parts of Yunnan form the western sectors of the Yangtse platform with folds generally NE-SW and NNE-SSW. However, from Kunming, the capital of Yunnan, westwards, the structure lines are N-S or NNW-SSE (Figs. 3 and 4). Western Yunnan is the region where the eastern Himalayas and the mountains of Assam and Burma impinge on the South China paraplatform and where high ridges separate the deep valleys of the rivers which have risen in Tibet — the Mekong, Salween, and Irrawaddy and the Red river which flows to Hanoi. There are three main areas of karst in Yunnan: (1) in the west and south in the N-S ranges adjacent to the Burmese and Vietnam borders; (2) the graben or karst basins aligned N-S in the Kunming and Nanpan river areas; (3) the undulating plateau area in E Yunnan which is a continuation of the Guizhou plateau, but at a higher altitude where the famous “Stone forest” of Lunan is situated. The Indo-Sinian (or Neo-Cathaysian) folds affected the rocks in Yunnan as they did in Guizhou and Guangxi. However, the effects of the Cenozoic and later the Quaternary uplifts are much greater in Yunnan than in the more easterly provinces. The proximity of W Yunnan to SE Tibet is the most important aspect of the relief. Carbonate rocks of the Palaeozoic and the Triassic are predominant in E Yunnan; in W Yunnan, the carbonates are mainly Permian and Triassic, but in some areas, older metamorphic limestones (Ordovician) occur, as at Dali.

There are other areas of peak forest/peak cluster landscape in South China, which though not as famous as Guilin, have some fine karst. It will be seen from the map of karst types (Fig. 15) that the peak forest type stretches in a broad band from the Vietnam border, near Nanning in the SW, to near the Yangtse delta near Shanghai. Not all of this area was covered by limestones — because of magmatic activity associated with the Pacific plate or as in some areas the limestones have been removed by erosion and the underlying base ment is exposed. As indicated in Chapter 1, the present state of preservation of the soluble rocks depends upon the zones of uplift and subsidence, which have affected the eastern part of China. In the areas of Guangdong, Fujian and Zhejiang, which belong to the second uplift zone, the soluble rocks have been to some extent removed by denudation, or were never deposited and their real distribution covers only a small part of the region — usually in down-faulted basins. However, in the subsidence zone to the W in Guangxi, Hunan, Jiangxi and to the S (Anhui, Henan, Hebei and parts of Shandong and Liaoning in the N) 40–60% of the soluble rocks has been preserved, though often they are buried under a cover of newer rocks (see location map of S China, Fig. 45).

Much of China is mountainous or high plateau, as 65% of the country is over 1000 m. In areas where carbonate rocks are important, high altitude karst develops. These include high mountain or Alpine karst in West Sichuan on the eastern slopes of the Tibetan plateau and the karst on the Tibetan plateau.

These areas of mainly high-altitude karst occur in the western half of China, west of the Hengduan-Longmen-Luipan-Helan mountains line (see Sect. 1.1 and Figs. 4 and 61). It is almost half the total area of China. Limestones occur over much of this western tectonic megaregion, particularly in Tibet, where about one-fifth of the terrain is karstic (Fig. 1). All this vast area is arid, with an aridity index of one or more (Yuan Daoxian et al. 1991), and with an annual average rainfall of 100–400 mm and in parts like the Tarim basin (Tali-mu) only 20–25 mm. The average annual temperature is about 2–6 °C outside the basins and 8-10 °C inside them (Yuan Daoxian et al., 1991, p. 110), but the climate is still strongly seasonal. The area includes Xinjiang, Qinghai, Inner Mongolia, Gansu and Tibet and stretches from the Himalayas in the south to Lake Baikal in the north. It is a zone of north-south compressional deforma tion stretching from the Himalayas to Baikal (Molnar and Deng cited in Dewey et al. 1988). Within this zone of deformation are rigid regions such as the Tarim and Qaidam basins (Fig. 61). The tectonic evolution of the high Tibet plateau was discussed by Dewey et al. (1988). They argue that a thick underthrust of the Indian Shield does not underlie Tibet as often thought, and discuss alternative views. They contend that rapid lithospheric thinning by deformation or stoping would account for the very rapid and recent uplift of the Tibetan plateau, its widespread recent volcanism, its hot springs and E-W extension (Dewey, et al. 1988). “The Indian lithosphere may be thought of as an indenting buttress with a thinner Northern edge generated by Neotethyan Triassic/Jurassic rifting, which collapsed to form the Himalayan Zone of shortening” (Dewey et al. 1988).

Reference has been made several times in the discussions of the karst geomorphology to the springs and underground waters of the karst areas. This chapter gives a summary review of the karst hydrogeology and the characteristics of the karst waters, particularly in relation to the geomorphology. Both this and the concluding chapter review the contributions of Chinese karst to world karst geomorphology, and its position in general world karst studies.

As we have shown, karst studies in China developed separately from the West. Many of concepts are similar in both areas, but because of differences in geology, physiography, climate and in culture and land exploitation, Chinese karst is quite distinctive. It is difficult to compare karstification in different parts of the world since the geological, physiographic and climatic influences are never the same, but certain observations can be made.