Investigation into rock moisture and salinity regimes: implications of sandstone weathering in Yungang Grottoes, China
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Yungang Grottoes in north of China are the classical masterpieces of Chinese Buddhists, dating from the Northern Wei Dynasty 1,500 years ago. This rock art is threatened by weathering processes that has been accelerated due to coal mining. The dominant weathering processes occurring on the rock surface are collapse, flaking, and efflorescence. Salt crystal growth plays a major cause of these deteriorations, and it has a close relationship with water movement. The major salt on the rock surface are sulfates, with a primary composition of epsomite, thenardite, and gypsum. In addition, carbonate minerals are found, mostly calcite and nesquehonite. In this paper, three grottoes in the eastern part have been investigated via measuring the rock surface moisture and recording the surface temperature and humidity. These nondestructive techniques are used for the first time in China on cultural relics. The movement of moisture has been calculated and mapped, and then analyzed for its relationship with the weathering process. Three main sources of water transport in the sandstone are adopted to explain the moisture content patterns. The aim of this study is to help rock art conservation in Yungang Grottoes, thus to provide a better understanding regarding the driving processes of internal moisture transport, which results in significant weathering processes. The evidence shows that the natural character of sandstone, water transport mechanism, and continental semi-arid conditions are the major causes of rock deterioration. Meanwhile, air pollution due to coal mining is also an important factor in driving the weathering process.
KeywordsSandstone Weathering Salt Moisture Yungang
Financial support was provided by the Ministry of Science and Technology of The People’s Republic of China (2009BAK53B02). We would like to thank the reviewers who read the first draft of this paper for their constructive comments. Special thanks to Prof. Heather Viles from University of Oxford for her insightful comments on this manuscript, Mr. Yik Yu Au from Institute of Karst Geology, Prof. Zhao Yaqian from University College Dublin for their help to improve the language of the paper, and Hong Zhang from University of Oxford for her technical support and very helpful comments.
- Bryan K (1928) Niches and other cavities in sandstone at Chaco Canyon, New Mexico. Z Geomorphol 3:125–140Google Scholar
- Goudie A, Viles H (1997) Salt Weathering Hazards. Wiley, ChichesterGoogle Scholar
- Hall Ch, Hamilton An, Hoff WD, Viles HA, Eklund JA (2010) Moisture dynamics in walls: response to micro-environment and climate change. Proc R Soc 1–18Google Scholar
- Huang KZ (1984) Problems of sandstone sculpture weathering in Yungang Grottoes. Hydrogeol Eng Geol 3:32–35 (in Chinese)Google Scholar
- Huang JZ (2003) Study on geological character in Yungang Grottoes. Southeast Cult 5:91–93 (in Chinese)Google Scholar
- Meiklejohn KI (1997) The role of moisture in the weathering of the clarens formation in the KwaZulu/Natal Drakensberg: implications for the deterioration and preservation of indigenous rock art. S Afr Geogr J 79:199–206Google Scholar
- Paradise TR (2002) Sandstone weathering and aspect in Petra. Jordan Z Geomorphol 46:1–17Google Scholar
- Schaffer RJ (1932) The weathering of natural building stones. Garston (reprinted 1972)Google Scholar
- The Third Team of Hydrogeology and Engineering Geology, Bureau of Shanxi Geology and Mineral, 1990. Engineering geological investigation and experiment report on water seepage prevention on the top of Yungang GrottoesGoogle Scholar