Geology of Hong Kong

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The geology of Hong Kong is dominated by igneous rocks (including granitic rocks and volcanic rocks) formed during a major volcanic eruption period in the Mesozoic era. It made up 85% of Hong Kong's land surface and the remaining 15% are mostly sedimentary rocks located in the northeast New Territories. There are also a very small percentage (less than 1%) of metamorphic rocks in the New Territories, formed by deformation of pre-existing sedimentary rocks (metamorphism).[1]

The geological history of Hong Kong started as early as the Devonian period (~420 million years ago) which is marked by the discovery of Placoderm (a Devonian fish) fossils in northeast Hong Kong.[2][3] While the youngest rocks in Hong Kong are formed during the Paleogene period(~50 million years old). They are today exposed in Tung Ping Chau[4][5] in northeast Hong Kong.

Each of the three types of rocks: igneous, sedimentary, and metamorphic rocks formed spectacular geological features in Hong Kong. Igneous rocks formed the hexagonal columns in Sai Kung. Sedimentary rocks formed various erosion features such as wave-cut platforms and sea stacks in Tung Ping Chau.[4] Metamorphic rocks formed the iron ore deposits in Ma On Shan. Each of these will be introduced in later sections.

In terms of structural geology, faults in Hong Kong are mainly running from the northeast to the southwest. Deformation features such as sheared rocks, folds and faulted rocks can be found near major faults such as are the banks of the Tolo Channel. Past fault activities can be traced by some structures such as the Lantau dyke swarm and deformed caldera, etc.[6] Faulting have shaped the landscape of Hong Kong. (See more on "Faulting" section)

[Fig.1] Geological map of Hong Kong showing the distribution of faults and different rock types in Hong Kong. Modified from Civil Engineering Development Department, HKSAR.[7]
  1. ^ Sewell, R. J. (2000). The Pre-Quaternary Geology of Hong Kong (PDF). Geotechnical Engineering Office. Hong Kong: Hong Kong Geological Survey. ISBN 978-9620202995.[permanent dead link‍]
  2. ^ Lee, Cho Min (May 1983). "The Occurrence of a Devonian Placodermi Fish Fossil in Hong Kong" (PDF). Geological Society Hong Kong Newsletter. 1 (4): 5–6.
  3. ^ Lee, C. M.; Chen, J. H.; Atherton, M. J.; He, G. H.; Wu, S. Q.; Lai, K. W.; Nau, P. S. (June 1990). "Supplementary report on the discovery of lower and middle Devonian fossils in Hong Kong" (PDF). Geological Society Hong Kong Newsletter. 8 (2): 16–24.
  4. ^ a b Wang, Lulin (7 February 2015). "Discussion on the sedimentary structure, geochemical characteristics and sedimentary environment of Ping Chau formation at Tung Ping Chau, Hong Kong". Journal of Environmental Biology. 36: 777–788. PMID 26387352.
  5. ^ Lee, C. M.; Chen, J. H.; He, G. X; Atherton, M. J.; Lai, K. W. (March 1991). "On the age of the Ping Chau Formation" (PDF). Geological Society Hong Kong Newsletter. 9 (1): 34–49.
  6. ^ Lai, K. W.; Langford, R. L. (January 1996). "Spatial and temporal characteristics of major faults of Hong Kong". Geological Society of Hong Kong Bulletin. 5 – via Research Gate.
  7. ^ "The Geology of Hong Kong (Interactive On-line)". www.cedd.gov.hk. Retrieved 16 November 2018.