Geology of Taiwan
The
The island is active geologically, formed on a complex convergent boundary between the Yangtze Subplate of the Eurasian Plate to the west and north, the Okinawa Plate on the north-east, the Philippine Sea Plate on the east and south, and the Sunda Plate to the southwest. Subduction changes direction at Taiwan. The upper part of the crust on the island is primarily made up of a series of terranes, mostly old island arcs which have been forced together by the collision of the forerunners of the Eurasian Plate and the Philippine Sea Plate, which is moving to the northwest. These have been further uplifted as a result of the detachment of a portion of the Eurasian Plate as it was subducted beneath remnants of the Philippine Sea Plate, a process which left the crust under Taiwan more buoyant.[4]
South of Taiwan, the Sunda Plate is subducting under the Philippine Sea Plate, forming the
From the northeast of Taiwan and continuing eastwards in the
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Geology Map of Taiwan |
Terranes
The
The Eastern Central Range terrane can be divided into the Tailuko belt on the west with greenschist metamorphism and the Yuli belt on the east with blueschist metamorphism. The two metamorphic belts are possibly separated by a fault called Shoufeng fault, but this is unproven.[7]
Central Mountains
The oldest exposed rocks are heavily metamorphosed and found in the Central Mountains.
The Yuli Schist is
The Changchun Schist being mostly greenschist is found on the western side and forms thick beds. It is found along with smaller amounts of chert, and black schist. The rock is foliated dark green rock containing chlorite, epidote, quartz, calcite, biotite, albite and actinolite. They are derived from mafic volcanic rocks. These rocks can host copper sulfide ores.[10]
Siliceous schists are coloured grey, they are metamorphosed sandstone, rich in quartz. Quartzite and chert bands can be found, and they are commonly associated with the black schist.
The Chiuchu Formation or Tailuge Marble forms a band from Tailuko in the north to a point between Wulu and Kuanshan in the south. The limestone is mined in quarries south of Suao for cement manufacture. Although the colour is usually a shade of grey, there are also black or white limestone, which is chopped into blocks for building purposes. dolomite is also found along with the limestone particularly at Chingchangshan, Hopingchi, and Mukuashan.[10]
The Kainangan Gneiss or Kanagan Formation occurs in several elongated bodies. The gneiss derived from sedimentary rocks contains coarse grained quartz, biotite, and albitic plagioclase. There is also orthogneiss derived from granite. This is light grey and contains sodic plagioclase, quartz, biotite, and muscovite. Within the gneiss there are pegmatite dikes containing quartz, feldspar and mica.[10]
Other igneous rocks found in the old metamorphic belt are
Green serpentinite from near Yuli makes a good quality building stone. A band of ultramafic rocks extends for 25 km north of Litao, Taitung (離島).[10]
The area was subjected to the Nanao Orogeny around 85 Ma which involved the granite intrusion and regional metamorphism. Rifting that opened the South China Sea around 40 Ma may be connected with some dolerite intrusions. The Penglai Orogeny started about 10 Ma and continues at the present time.[11]
Eastern stratigraphic region
The most recently added part of the island is the
The Pinanshan conglomerate is found on Pinanshan Hill and along the Pinantachi stream north of Taitung (台東). The constituents are 5–15 cm cobbles erodes by freshwater from the Central Range. It formed somewhere from middle to late Pleistocene, and indicates the plate collision had taken place.[12]
The Milun Conglomerate is to the north of Hualien. This has also gone under the names of Beiron Conglomerate Formation and Milunpi Conglomerate. It is tilted at 30°. It is undated but is likely from Pleistocene.[12]
Central Mountains strata
Shibachongxi Formation is from the Eocene consisting of slate and then beds of metamorphosed sandstone. The total thickness is up to 1000 m.[8]
Dajian Formation consists of sandstone from the upper Eocene, up to 2700 meters thick.[8]
Xichun Formation slate and phyllite is from the lower Oligocene. The thickness is from 0.6 to 3 km.[8]
Siling Formation coarse sandstone in thick beds is from the Oligocene.[8]
Shuichungliu Formation form the Oligocene contains
Bilushan Formation contains slate and phyllite from the Eocene.[8]
Lushan Formation from the Miocene contains shale slate and sandstone.[8]
Aodi Formation contemporary
Sule Formation slate and sandstone from the later Miocene.
Western stratigraphic region
The west part of the island exposes deformed and metamorphosed Cenozoic sediments, overlaid by Quaternary piedmont region in the flat plains on the west coast.
Cretaceous, Paleocene and Eocene deposits are not exposed on the surface, but are buried. They have been discovered by drilling.
The Yunlin Formation is from the Cretaceous and only known from boreholes. The rocks are siltstone, basalt, shale and limestone.
The Paleocene Wangong Formation consisting of
In the Eocene the Shuangji Formation formed mostly from volcanic particles in the form of tuff and tuffaceous sandstone. These beds are from 100 m to 3 km thick.
In the Oligocene the Wuzhishan Formation or Wuchihshan Formation (五指山組) formed thick beds of sandstone. The total thickness is 0.9 to 1.2 km.
The Yeliu Group from the Miocene is fine grained sandstone, with some beds of shale, basaltic tuff and three seams of coal.[13] Possibly including Wushan Formation, Piling Shale, Peiliao Formation, Talu shale, Shihti Formation, Kuanyiongshan sandstone.[14]
The Ruifang Group contains beds of sandstone, siltstone, shale and six thin coal beds. These beds are 0.8 to 1.6 km thick.
The Sangxia Group starts with medium grained sandstone, but in the upper layers increases shale. Eight thin coal seams are included. The total thickness of the deepest beds exceeds 5 km. This includes the Kueichulin Formation with the Yutengping Sandstone, Shihliufen Shale, Kuantaoshan Sandstone; the Nanchuang Formation including Shangfuchi Sandstone and Tungkeng Formation.[14]
The Jinshui Formation or Chinshui Formation from the Pliocene is mostly shale interbedded with some mudstone and sandstone is between 80 and 400 m thick.
The Zhuolan Formation or Cholan Formation (卓蘭層) starts in the Pliocene and extends into the first stage of the Pleistocene. It consists of fine grained sandstone. This is 1.5 to 2.5 km thick. At the same time on the southern tip of the island, the Kending Formation or Kenting Formation (墾丁組) was formed consisting of mudstone with ophiolite melange.[15] The ophiolite melange contains pebbles and blocks of Miocene age consisting of basic and ultrabasic rock from the ocean floor. The interpretation is that a wedge of seafloor was pushed above sea level, eroded and dropped fragments into the mud.[16]
The Toukoshan Formation (Toukeshan) (頭嵙山層) commenced with fine sandstone with thin beds of conglomerate, and continued into mainly conglomerate with sandstone beds. This was formed in stage 1 and 2 of the Pleistocene. It is from 0.4 to 3 km thick.
The Szekou Formation is a light bluish gray siltstone, with shale and fine grained sandstone. The Maanshan Formation is very similar. It is overlain by Hengchun Limestone and may interfinger.[15]
Western piedmont region
The Hengchun Limestone was formed after the Penglai movement in the third Pleistocene stage. Also at this time
Volcanic rocks
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Volcanic Distribution Map |
The
The Caolingshan Basalt consists of olivine and pyroxene, with crystals of biotite and plagioclase. This is rich in K, Rb, Mg, Sr, Cr, and Ni, but poor in Na, Al, and Fe. Rare earth elements are strongly enriched. The magma was derived by deep mantle melting of the underthrust sea plate behind the Ryukyu Volcanic Arc during the Pleistocene.[8]
The
Alkaline volcanic rocks from north west Taiwan are found at the
Volcanoes on the Coastal Range and
Pleistocene basalt and tholeiite is found in the
Structures
- Hengchun Valley syncline under the Hengchun Valley[15]
- Hengchun Fault on east side of Hengchun Valley. It extends along the Pintung Valley as the Chaochow fault and Laonungchi fault.[15]
- Kenting Park anticline is overturned and folds Miocene rocks of the Changlo Formation, Lushan Formation to the north. Loshui Formation is on the sides of the anticline.[15]
Tectonics
The Philippine Sea Plate is converging with the continent at 7 cm per year in the west north west direction. It has compressed Cenozoic sediments by around 200 km in the last 4 Ma. The piled up sediment is rising into mountains at the rate of 5 mm per year.[8]
The major seismic faults in Taiwan correspond to the various suture zones between the various terranes. As a result, Taiwan has numerous
Offshore
The offshore features include the Kaoping Slope extending off the southwest coast of Taiwan into the South China Sea. This is emerging from the sea over time to extend the island. [6]
The Hengchun Ridge extends south from the
The Taiwan Banks are a shallow part of the main continental shelf off mainland China lying to the south and south west of
The Okinawa Trough, the back-arc basin behind the Ryukyu Islands, shows up on the coastline as a bay between Dome Point north to Sanshokiaku (easternmost point of Taiwan) (24.6° to 25°N).[6]
Geophysics
Taiwan has a very strong, positive
Positive magnetic variations are found in narrow strips, west-southwest oriented of the west coast, and east-northeast off the northern coast, and south-north offshore from the Coastal Range heading south. These are of the order of 200 nT.[26]
The Crustal thickness is around 30 km, with over 2 km of thickening under the Central Range, and thinning off the east coast. Taiwan is on the edge of the continental shelf, so the thickness of the crust is constant through the Taiwan Strait to the mainland.[25]
Heat flow is greatest to west of the Longitudinal Valley at rates exceeding 240 mWm−2.
Hydrology
Many of the rocks in Taiwan have low pore space and have little ground water.
There are several hot springs in Taiwan, with most around the northern volcanic region. The Chingshui geothermal region is named after the
Rivers in Taiwan transport a large amount of sediment to the sea. The south end of the Longitudonal Valley discharges the
Study
Mapping
The first
References
- ^ "The Geology of Taiwan". Department of Geology, National Taiwan Normal University. Archived from the original on 22 February 2008.
- ^ "Geology of Taiwan". Department of Geology, University of Arizona. Archived from the original on 2017-04-13. Retrieved 2012-05-06.
- ISBN 978-0-415-44723-2.
- ^ "Geology of Taiwan — University of Arizona". Geo.arizona.edu. Archived from the original on 13 April 2017. Retrieved 1 August 2010.
- ISBN 1-86239-147-5p84–86
- ^ a b c d e Megan Anderson (5 March 2001). "Introduction to Geologic Features". Taiwan: An Active Continental Subduction Zone. Archived from the original on 15 June 2017. Retrieved 20 March 2011.
- ^ "Metamorphc Belts". Archived from the original on 2010-12-15.
- ^ ISBN 978-7-116-02268-3.
- ^ "Eastern Central Range Introduction". Archived from the original on 2011-05-24.
- ^ a b c d e f "Eastern Central Range Occurrence and Lithology of Metamorphic Rocks". Archived from the original on 2010-12-15.
- ^ "Eastern Central Range Radiometric Ages". Archived from the original on 2010-12-15.
- ^ a b c Central Geological Survey MOEI. "Eastern Coastal Range Stratigraphy and Lithology". Archived from the original on 2011-09-27.
- ^ "Tertiary in Petroliferous Regions of China" (PDF).
- ^ ISBN 978-0-8137-2358-7.
- ^ a b c d e "Geology of the Hungchun Peninsula". Archived from the original on 2011-07-24.
- ^ Benjamin M. Page; Ching-Ying Lan (May 1983). "The Kenting Melange and its Record of Tectonic Events" (PDF). Memoir of the Geological Society of China (5): 227–248. Archived from the original (PDF) on 2016-03-05.
- ^ Song Zhi-chen; Huang Fei (February 2004). "Cretaceous and Tertiary Palynofloras in Taiwan Area and its Correlation with those in Neighbouring Coastal Regions of Mainland China". Journal of Tropical Oceanography.
- ^ "Geographic Setting". Geology of Taiwan. Central Geological Survey. Archived from the original on 24 May 2011.
- ^ "構造模型實驗室 盧佳遇老師 - Eastern Coastal Range". Archived from the original on 2011-07-24. Retrieved 2011-03-21.
- ^ Theodorou, Christine; Lee, Andrew (3 March 2010). "6.4-magnitude quake hits southern Taiwan". CNN.com. Archived from the original on 5 March 2010. Retrieved 4 March 2010.
- ^ "USGS seismic hazard map of Eastern Asia". Seismo.ethz.ch. Archived from the original on 2000-03-03. Retrieved 2011-05-30.
- S2CID 54689775.
- doi:10.3319/TAO.1998.9.3.453(TAICRUST). Archived from the original(PDF) on 2011-08-30.
- ^ "Magnitude 5.5 - TAIWAN REGION". Archived from the original on 2011-03-24. Retrieved 2017-08-28.
- ^ a b Geology of China page 62
- ^ Geology of China page 66
- ^ K. C. Fan; et al. (30 January 2006). "Evaluation of Natural Recharge of Chingshui Geothermal Reservoir in Taiwan" (PDF). Archived (PDF) from the original on 11 March 2016. Retrieved 31 March 2011.
- ^ "Home - Springer". Springerimages.com. Archived from the original on 13 March 2012. Retrieved 4 November 2018.
- ^ a b c d e f g "Earlier Geologic Maps Of Taiwan". Archived from the original on 2011-05-24.
External links
- Chao-Hsia Chen; Hsin-Chang HoKai-Shuan Shei; et al. (2000). "Geologic Map of Taiwan". Central Geological Survey, Ministry of Economic Affairs. Archived from the original on 2011-08-15. Retrieved 2011-03-29.