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== Geology of Hong Kong ==
== Geology of Hong Kong ==
'''Geology of Hong Kong''' is dominated by [[Igneous rock|igneous rocks]] formed during a major volcanic eruption period in [[Mesozoic]]. It made up 85% of Hong Kong's land surface. The remaining 15% are mostly [[Sedimentary rock|sedimentary rocks]] formed by deposition of sediments located in northeast [[New Territories]] of Hong Kong. There are also a very small percentage (less than 1%) of [[Metamorphic rock|metamorphic rocks]] found in New Territories. These are formed by deformation of pre-existing sedimentary rocks which changed the mineral assemblages in the rock ([[metamorphism]]).
'''Geology of Hong Kong''' is dominated by [[Igneous rock|igneous rocks]] formed during a major volcanic eruption period in [[Mesozoic]]. It made up 85% of Hong Kong's land surface. The remaining 15% are mostly [[Sedimentary rock|sedimentary rocks]] formed by deposition of sediments located in northeast [[New Territories]] of Hong Kong. There are also a very small percentage (less than 1%) of [[Metamorphic rock|metamorphic rocks]] found in New Territories. These are formed by deformation of pre-existing sedimentary rocks which changed the mineral assemblages in the rock ([[metamorphism]]).<ref name=":0">{{Cite book|title=The Pre-Quaternary Geology of Hong Kong.|last=Sewell|first=R. J.|publisher=Geotechnical Engineering Office. Hong Kong: Hong Kong Geological Survey|year=2000|isbn=9620202996|location=|pages=}}</ref>


Geological history of Hong Kong started as early as [[Devonian]] period (~420 million years old) which was determined by the discovery of [[Placodermi|Placoderm]] (a Devonian fish) fossils in northeast Hong Kong.<ref>{{Cite journal|last=Lee|first=Cho Min|date=May 1983|title=THE OCCURRENCE OF A DEVONIAN PLACODERMI FISH FOSSIL IN HONG KONG|url=http://geolsoc.org.hk/_newsletters/1983_May_Vol_1-4.pdf|journal=Geological Society Hong Kong Newsletter|volume=1|issue=4|pages=5-6|via=}}</ref><ref>{{Cite journal|last=Lee|first=C. M.|last2=Chen|first2=J. H.|last3=Atherton|first3=M. J.|last4=He|first4=G. H.|last5=Wu|first5=S. Q.|last6=Lai|first6=K. W.|last7=Nau|first7=P. S.|date=June 1990|title=Supplementary report on the discovery of lower and middle Devonian fossils in Hong Kong|url=http://www.geolsoc.org.hk/_newsletters/Newsletter%201990%20Vol.8%20No.2.pdf|journal=Geological Society Hong Kong Newsletter|volume=8|issue=2|pages=16-24|via=}}</ref> The youngest rock in Hong Kong from [[Paleogene]] (~50 million years old) is exposed in [[Tung Ping Chau]], an island in the northeastern corner of Hong Kong.<ref>{{Cite journal|last=Lee|first=C. M.|last2=Chen|first2=J. H.|last3=He|first3=G. X|last4=Atherton|first4=M. J.|last5=Lai|first5=K. W.|date=March 1991|title=On the age of the Ping Chau Formation|url=http://www.geolsoc.org.hk/_newsletters/Newsletter%201991%20Vol.9%20No.1.pdf|journal=Geological Society Hong Kong Newsletter|volume=9|issue=1|pages=34-49|via=}}</ref>
Geological history of Hong Kong started as early as [[Devonian]] period (~420 million years old) which was determined by the discovery of [[Placodermi|Placoderm]] (a Devonian fish) fossils in northeast Hong Kong.<ref name=":1">{{Cite journal|last=Lee|first=Cho Min|date=May 1983|title=THE OCCURRENCE OF A DEVONIAN PLACODERMI FISH FOSSIL IN HONG KONG|url=http://geolsoc.org.hk/_newsletters/1983_May_Vol_1-4.pdf|journal=Geological Society Hong Kong Newsletter|volume=1|issue=4|pages=5-6|via=}}</ref><ref>{{Cite journal|last=Lee|first=C. M.|last2=Chen|first2=J. H.|last3=Atherton|first3=M. J.|last4=He|first4=G. H.|last5=Wu|first5=S. Q.|last6=Lai|first6=K. W.|last7=Nau|first7=P. S.|date=June 1990|title=Supplementary report on the discovery of lower and middle Devonian fossils in Hong Kong|url=http://www.geolsoc.org.hk/_newsletters/Newsletter%201990%20Vol.8%20No.2.pdf|journal=Geological Society Hong Kong Newsletter|volume=8|issue=2|pages=16-24|via=}}</ref> The youngest rock in Hong Kong from [[Paleogene]] (~50 million years old) is exposed in [[Tung Ping Chau]]<ref name=":2">{{Cite journal|last=Wang|first=Lulin|date=7 February 2015|title=Discussion on the sedimentary structure, geochemical characteristics and sedimentary environment of Ping Chau formation at Tung Ping Chau, Hong Kong|url=https://www.ncbi.nlm.nih.gov/pubmed/26387352|journal=Journal of Environmental Biology|volume=36|pages=777-788|via=}}</ref><ref name=":3">{{Cite journal|last=Lee|first=C. M.|last2=Chen|first2=J. H.|last3=He|first3=G. X|last4=Atherton|first4=M. J.|last5=Lai|first5=K. W.|date=March 1991|title=On the age of the Ping Chau Formation|url=http://www.geolsoc.org.hk/_newsletters/Newsletter%201991%20Vol.9%20No.1.pdf|journal=Geological Society Hong Kong Newsletter|volume=9|issue=1|pages=34-49|via=}}</ref>, an island in the northeastern corner of Hong Kong.


The three type of rocks: igneous, sedimentary, and metamorphic rocks all formed spectecular geological landscapes in Hong Kong. Igneous rocks formed the famous hexagonal columns in [[Sai Kung Peninsula|Sai Kung]] and most of the hills in Hong Kong. Sediementary rocks formed various erosional features such as [[Wave-cut platform|wave-cut platforms]] and [[Stack (geology)|sea stacks]] in Tung Ping Chau. Metamorphic rocks fromed the iron ore site in [[Ma On Shan (town)|Ma On Shan]] which was an active mining site. Each of these will be introduced in later sections.
The three type of rocks: igneous, sedimentary, and metamorphic rocks all formed spectecular geological landscapes in Hong Kong. Igneous rocks formed the famous hexagonal columns in [[Sai Kung Peninsula|Sai Kung]] and most of the hills in Hong Kong. Sediementary rocks formed various erosional features such as [[Wave-cut platform|wave-cut platforms]] and [[Stack (geology)|sea stacks]] in Tung Ping Chau.<ref name=":2" /> Metamorphic rocks fromed the iron ore site in [[Ma On Shan (town)|Ma On Shan]] which was an active mining site. Each of these will be introduced in later sections.


In terms of [[Structural geology|sturctural geology]], [[Fault (geology)|faults]] in Hong Kong are mainly running from the northeast to the southwest of Hong Kong. Deformation features such as sheared rocks, [[Fold (geology)|folds]] and faulted rocks can be found near the fault. These faults can be identified by some igneous features formed due to faulting such as the Lantau [[Dike swarm|dyke swarm]], defromed [[caldera]], etc.<ref>{{Cite journal|last=Lai|first=K. W.|last2=Langford|first2=R. L.|date=January 1996|title=Spatial and temporal characteristics of major faults of Hong Kong|url=https://www.researchgate.net/publication/279631416_Spatial_and_temporal_characteristics_of_major_faults_of_Hong_Kong|journal=Geological Society of Hong Kong Bulletin|volume=5|pages=|via=Research Gate}}</ref> (See more on "Structural Geology" section)
In terms of [[Structural geology|sturctural geology]], [[Fault (geology)|faults]] in Hong Kong are mainly running from the northeast to the southwest of Hong Kong. Deformation features such as sheared rocks, [[Fold (geology)|folds]] and faulted rocks can be found near the fault. These faults can be identified by some igneous features formed due to faulting such as the Lantau [[Dike swarm|dyke swarm]], defromed [[caldera]], etc.<ref>{{Cite journal|last=Lai|first=K. W.|last2=Langford|first2=R. L.|date=January 1996|title=Spatial and temporal characteristics of major faults of Hong Kong|url=https://www.researchgate.net/publication/279631416_Spatial_and_temporal_characteristics_of_major_faults_of_Hong_Kong|journal=Geological Society of Hong Kong Bulletin|volume=5|pages=|via=Research Gate}}</ref> (See more on "Structural Geology" section)

'''[add HK geological map]'''


== Geological Evolution ==
== Geological Evolution ==
Geological history of Hong Kong is mainly divided into three periods. From Devonian to early Jurassic is a pre-volcanic sedimentary period. Environments of Hong Kong mainly shiftes between river plains and marine environments.<ref>{{Cite journal|last=Lee|first=C. M.|last2=Chan|first2=K. W.|last3=Ho|first3=K. H.|date=August 2017|title=香港的地层序列" [Stratigraphic sequence of Hong Kong]|url=http://big5.oversea.cnki.net.eproxy.lib.hku.hk/kcms/detail/detail.aspx?QueryID=0&CurRec=1&DbCode=CJFD&dbname=CJFD9697&filename=DCXZ703.000&uid=WEEvREcwSlJHSldRa1Fhb09jSnU2c1hUMFpBZGhabkVkU2ZFNVJJai9Tcz0=$9A4hF_YAuvQ5obgVAqNKPCYcEjKensW4IQMovwHtwkF4VYPoHbKxJw!!|journal=Journal of Stratigraphy|volume=21|issue=3|pages=161-182|via=China Academic Journals Full-text Database}}</ref> Rocks of this period is characterised by a variety of fossils and deformation features formed in the volcanic period<ref name=":4">{{Cite journal|last=Yim|first=W. S.|last2=Nau|first2=P. S.|last3=Rosen|first3=B. R.|date=November 1981|title=Permian Corals in the Tolo Harbour Formation, Ma Shi Chau, Hong Kong|url=https://www.jstor.org/stable/1304558|journal=Journal of Paleontology|volume=55|issue=6|pages=1298-1300|via=JSTOR}}</ref>. Later, from middle Jurassic to early Cretaceous, it is a volcanic period. Hong Kong entered an active zone where Pacific oceanic plate was subducted beneath South China continental plate.<ref>{{Cite journal|last=Campbell|first=S. D.|last2=Sewell|first2=R. J|date=November 1997|title=Structural control and tectonic setting of Mesozoic volcanism in Hong Kong|url=https://www.researchgate.net/publication/249546895_Structure_control_and_tectonic_setting_of_Mesozoic_volcanism_in_Hong_Kong|journal=Journal of the Geological Society|volume=154|issue=6|pages=1039-1052|issn=0016-7649|via=Researchgate}}</ref> It is marked by the masive coverage of volcanic lava, ash, and granitic rocks around Hong Kong. From middle Cretaceous onward, it is a post-volcanic sedimentary period. It is represented by reddish terrestrial sedimentary rocks. The reddish colour indicates an arid tropical climate during the period.

Major stratigraphies of Hong Kong are shown in the table below.
{| class="wikitable"
{| class="wikitable"
|+
|+
Geological Stratigraphy of Hong Kong
!Period
!Period
!Formations
!Representative Formations
!Representative rock types
!Representative rock types
!Deposition environment
!Deposition environment
!Notes
!Notes
|-
|-
|Devonian
|Devonian (ca. 416 - 359 million years old)
(ca. 416 - 359 million years old)
|Bluff Head formation
|Bluff Head formation
|Brownish folded sandstone<ref name=":5">{{Cite journal|last=Jones|first=N.S.|last2=Fyfe|first2=J.A.|last3=Sewell|first3=R.J.|last4=Lai|first4=K.W.|last5=Lee|first5=C. M.|date=15 December 1997|title=Devonian fluviodeltaic sedimentation in Hong Kong|url=https://www.sciencedirect.com/science/article/pii/S0743954797000366|journal=Journal of Asian Earth Sciences|volume=15|issue=6|pages=533-545|via=Science Direct}}</ref>
|Brownish folded sandstone
|River channels
|River channels<ref name=":5" />
|the oldest rock in Hong Kong, age determined by Placoderm fossils<ref name=":1" />
|
|-
|-
| rowspan="2" |Carboniferous (ca. 359 - 299 million years old)
| rowspan="2" |Carboniferous (ca. 359 - 299 million years old)
Line 28: Line 33:
|white or greyish marble
|white or greyish marble
|marine
|marine
|metamorphosed in Mesozoic volcanic period
|metamorphosed in Mesozoic volcanic period, formed iron ore in Ma On Shan mine
|-
|-
|Lok Ma Chau formation
|Lok Ma Chau formation
|metasandstones and graphite beds
|metasandstones and siltstone graphite beds
|deltaic swamps
|metamorphosed in Mesozoic volcanic period
|metamorphosed in Mesozoic volcanic period
|
|-
|-
|Permian (ca. 299 - 252 million years old)
|Permian (ca. 299 - 252 million years old)
|Tolo Harbour formation
|Tolo Harbour formation
|siltstone, sandstone, conglomerate
⚫
|black mudstone, grey siltstone
|tidal shore
⚫
|shallow maine
|oldest ammonoid fossils in Hong Kong <ref name=":4" />
|
|-
|-
|Triassic (ca. 252 - 201 million years old)
|Triassic (ca. 252 - 201 million years old)
Line 49: Line 54:
| rowspan="5" |Jurassic (ca. 201 - 145 million years old)
| rowspan="5" |Jurassic (ca. 201 - 145 million years old)
|Tolo Channel formation
|Tolo Channel formation
⚫
|black mudstone, grey siltstone
|
⚫
|shallow marine
|
|
|
|-
|-
|Tai O formation
|Tai O formation
|light grey sandstone, siltstone
|
|river plain
|
|
|
|-
|-
|Tuen Mun formation
|Tuen Mun formation
|Andesitic lava and crystal tuff breccia<ref>{{Cite journal|last=Li|first=Yan Hei Martin|last2=Zhou|first2=Mei Fu|last3=Lai|first3=Kuen Wai|last4=Chan|first4=Lung Sang|last5=Chen|first5=Wei Terry|date=17 January 2014|title="Geochemical and geochronological constraints on Late Jurassic volcanic rocks at Tuen Mun, Hong Kong, with implications for the Palaeo-Pacific subduction|url=https://www.researchgate.net/publication/271747572_Geochemical_and_geochronological_constraints_on_Late_Jurassic_volcanic_rocks_at_Tuen_Mun_Hong_Kong_with_implications_for_the_Palaeo-Pacific_subduction|journal=International Geology Review|volume=56|issue=4|pages=408-429|eissn=0020-6814|via=Researchgate}}</ref>
|
|volcanic arc
|
|Volcanic period started here.
|
|-
|-
|Tsuen Wan Volcanic Group
|Tsuen Wan Volcanic Group
|coarse ash crystal tuff<ref name=":0" />
|
|back-arc volcano
|
|covered a large area in New Territories
|
|-
|-
|Lantau Volcanic Group
|Lantau Volcanic Group
|rhyolite with larger crystals (porphoritic)<ref name=":0" />
|
|back-arc volcano
|
|related to Lantau caldera and dyke swarm, covered most of Lantau island
|
|-
|-
| rowspan="6" |Cretaceous (ca. 145 - 66 million years old)
| rowspan="5" |Cretaceous (ca. 145 - 66 million years old)
|Mount Davis formation
|Mount Davis formation
|coarse ash crystal tuff<ref name=":0" />
|
|back-arc volcano
|
|related to Kowloon granite
|
|-
|-
|High Island formation
|High Island formation
|fine ash tuff<ref name=":0" />
|
|back-arc volcano
|
|formed hexagonal columns
|
|-
|-
|Kau Sai Chau Volcanic Group
|Kau Sai Chau Volcanic Group
|lapilli bearing tuff with rhyolitic bands<ref name=":0" />
|
|back-arc volcano
|
|Volcanic period ended here
|
|-
|-
|Pat Sin Leng formation
|Pat Sin Leng formation
|reddish conglomerate and ash bearing sandstone<ref name=":0" />
|
|river plain
|
|volcanic ashes mixed with depositions, the red colour showed an arid climate
|
|-
|-
|Port Island formation
|Port Island formation
|reddish conglomerate and sandstone<ref name=":0" />
|
|river plain
|
|
|-
|Kat O formation
|
|
|
|
|-
|-
|Paleogene (ca. 66 - 23 million years old)
|Paleogene (ca. 66 - 23 million years old)
|Ping Chau formation
|Ping Chau formation
|calcium carbonate bearing siltstones<ref name=":3" />
|
|lake
|
|Sea stacks and wave-cut platforms on Ping Chau formation
|
|}
|}
'''[Add HK geological map]'''


== Igneous rocks ==
== Igneous rocks ==

Revision as of 15:56, 13 November 2018

Geology of Hong Kong

Geology of Hong Kong is dominated by igneous rocks formed during a major volcanic eruption period in Mesozoic. It made up 85% of Hong Kong's land surface. The remaining 15% are mostly sedimentary rocks formed by deposition of sediments located in northeast New Territories of Hong Kong. There are also a very small percentage (less than 1%) of metamorphic rocks found in New Territories. These are formed by deformation of pre-existing sedimentary rocks which changed the mineral assemblages in the rock (metamorphism).[1]

Geological history of Hong Kong started as early as Devonian period (~420 million years old) which was determined by the discovery of Placoderm (a Devonian fish) fossils in northeast Hong Kong.[2][3] The youngest rock in Hong Kong from Paleogene (~50 million years old) is exposed in Tung Ping Chau[4][5], an island in the northeastern corner of Hong Kong.

The three type of rocks: igneous, sedimentary, and metamorphic rocks all formed spectecular geological landscapes in Hong Kong. Igneous rocks formed the famous hexagonal columns in Sai Kung and most of the hills in Hong Kong. Sediementary rocks formed various erosional features such as wave-cut platforms and sea stacks in Tung Ping Chau.[4] Metamorphic rocks fromed the iron ore site in Ma On Shan which was an active mining site. Each of these will be introduced in later sections.

In terms of sturctural geology, faults in Hong Kong are mainly running from the northeast to the southwest of Hong Kong. Deformation features such as sheared rocks, folds and faulted rocks can be found near the fault. These faults can be identified by some igneous features formed due to faulting such as the Lantau dyke swarm, defromed caldera, etc.[6] (See more on "Structural Geology" section)

[add HK geological map]

Geological Evolution

Geological history of Hong Kong is mainly divided into three periods. From Devonian to early Jurassic is a pre-volcanic sedimentary period. Environments of Hong Kong mainly shiftes between river plains and marine environments.[7] Rocks of this period is characterised by a variety of fossils and deformation features formed in the volcanic period[8]. Later, from middle Jurassic to early Cretaceous, it is a volcanic period. Hong Kong entered an active zone where Pacific oceanic plate was subducted beneath South China continental plate.[9] It is marked by the masive coverage of volcanic lava, ash, and granitic rocks around Hong Kong. From middle Cretaceous onward, it is a post-volcanic sedimentary period. It is represented by reddish terrestrial sedimentary rocks. The reddish colour indicates an arid tropical climate during the period.

Major stratigraphies of Hong Kong are shown in the table below.

Geological Stratigraphy of Hong Kong
Period Representative Formations Representative rock types Deposition environment Notes
Devonian (ca. 416 - 359 million years old) Bluff Head formation Brownish folded sandstone[10] River channels[10] the oldest rock in Hong Kong, age determined by Placoderm fossils[2]
Carboniferous (ca. 359 - 299 million years old) Yuen Long formation white or greyish marble marine metamorphosed in Mesozoic volcanic period, formed iron ore in Ma On Shan mine
Lok Ma Chau formation metasandstones and siltstone graphite beds deltaic swamps metamorphosed in Mesozoic volcanic period
Permian (ca. 299 - 252 million years old) Tolo Harbour formation siltstone, sandstone, conglomerate tidal shore oldest ammonoid fossils in Hong Kong [8]
Triassic (ca. 252 - 201 million years old) missing N/A N/A
Jurassic (ca. 201 - 145 million years old) Tolo Channel formation black mudstone, grey siltstone shallow marine
Tai O formation light grey sandstone, siltstone river plain
Tuen Mun formation Andesitic lava and crystal tuff breccia[11] volcanic arc Volcanic period started here.
Tsuen Wan Volcanic Group coarse ash crystal tuff[1] back-arc volcano covered a large area in New Territories
Lantau Volcanic Group rhyolite with larger crystals (porphoritic)[1] back-arc volcano related to Lantau caldera and dyke swarm, covered most of Lantau island
Cretaceous (ca. 145 - 66 million years old) Mount Davis formation coarse ash crystal tuff[1] back-arc volcano related to Kowloon granite
High Island formation fine ash tuff[1] back-arc volcano formed hexagonal columns
Kau Sai Chau Volcanic Group lapilli bearing tuff with rhyolitic bands[1] back-arc volcano Volcanic period ended here
Pat Sin Leng formation reddish conglomerate and ash bearing sandstone[1] river plain volcanic ashes mixed with depositions, the red colour showed an arid climate
Port Island formation reddish conglomerate and sandstone[1] river plain
Paleogene (ca. 66 - 23 million years old) Ping Chau formation calcium carbonate bearing siltstones[5] lake Sea stacks and wave-cut platforms on Ping Chau formation

[Add HK geological map]

Igneous rocks

Volcanic rocks

Granitic rocks

Sedimentary rocks

Metamorphic rocks

Structural geology

Folds

Faults

References

  1. ^ a b c d e f g h Sewell, R. J. (2000). The Pre-Quaternary Geology of Hong Kong. Geotechnical Engineering Office. Hong Kong: Hong Kong Geological Survey. ISBN 9620202996.
  2. ^ a b 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.
  5. ^ a b 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. ^ Lee, C. M.; Chan, K. W.; Ho, K. H. (August 2017). "香港的地层序列" [Stratigraphic sequence of Hong Kong]". Journal of Stratigraphy. 21 (3): 161–182 – via China Academic Journals Full-text Database.
  8. ^ a b Yim, W. S.; Nau, P. S.; Rosen, B. R. (November 1981). "Permian Corals in the Tolo Harbour Formation, Ma Shi Chau, Hong Kong". Journal of Paleontology. 55 (6): 1298–1300 – via JSTOR.
  9. ^ Campbell, S. D.; Sewell, R. J (November 1997). "Structural control and tectonic setting of Mesozoic volcanism in Hong Kong". Journal of the Geological Society. 154 (6): 1039–1052. ISSN 0016-7649 – via Researchgate.
  10. ^ a b Jones, N.S.; Fyfe, J.A.; Sewell, R.J.; Lai, K.W.; Lee, C. M. (15 December 1997). "Devonian fluviodeltaic sedimentation in Hong Kong". Journal of Asian Earth Sciences. 15 (6): 533–545 – via Science Direct.
  11. ^ Li, Yan Hei Martin; Zhou, Mei Fu; Lai, Kuen Wai; Chan, Lung Sang; Chen, Wei Terry (17 January 2014). ""Geochemical and geochronological constraints on Late Jurassic volcanic rocks at Tuen Mun, Hong Kong, with implications for the Palaeo-Pacific subduction". International Geology Review. 56 (4): 408–429. eISSN 0020-6814 – via Researchgate.
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