Geology of India

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Plates in the crust of the earth, according to the plate tectonics theory

The geology of India is diverse. Different regions of India contain

geologic periods, dating as far back as the Eoarchean Era. Some of the rocks are very deformed and altered. Other deposits include recently deposited alluvium that has yet to undergo diagenesis. Mineral deposits of great variety are found in the Indian subcontinent in huge quantities. Even India's fossil record is impressive in which stromatolites, invertebrates, vertebrates and plant fossils
are included. India's geographical land area can be classified into the
Vindhyan
.

The Deccan Traps covers almost all of Maharashtra, a part of Gujarat, Karnataka, Madhya Pradesh and Andhra Pradesh marginally. During its journey northward after breaking off from the rest of Gondwana, the Indian Plate passed over a geologic hotspot, the Réunion hotspot, which caused extensive melting underneath the Indian Craton. The melting broke through the surface of the craton in a massive flood basalt event, creating the Deccan Traps. It is also thought that the Reunion hotspot caused the separation of Madagascar and India.

The

Punjab, Himachal Pradesh, Rajasthan and Uttarakhand. The Gondwana sediments form a unique sequence of fluviatile rocks deposited in Permo-Carboniferous time. The Damodar and Sone river valleys and Rajmahal
hills in eastern India contain a record of the Gondwana rocks.

The

Plate tectonics

The Indian

Himalaya Mountains and the Tibetan Plateau in South Asia. The current orogenic event is causing parts of the Asian continent to deform westward and eastward on either side of the orogen. Concurrently with this collision, the Indian Plate sutured on to the adjacent Australian Plate, forming a new larger plate, the Indo-Australian Plate
.

Tectonic evolution

Due to continental drift, the India Plate split from Madagascar and collided with the Eurasian Plate resulting in the formation of the Himalayas.

The earliest phase of tectonic evolution was marked by the cooling and solidification of the upper

Indian Craton. The Aravalli Range
is the remnant of an early Proterozoic orogen called the Aravali-Delhi Orogen that joined the two older segments that make up the Indian Craton. It extends approximately 500 kilometres (311 mi) from its northern end to isolated hills and rocky ridges into Haryana, ending near Delhi.

Minor igneous intrusions, deformation (folding and faulting) and subsequent metamorphism of the Aravalli Mountains represent the main phase of orogenesis. The erosion of the mountains, and further deformation of the sediments of the Dharwarian group (Bijawars) marks the second phase. The volcanic activities and intrusions, associated with this second phase are recorded in the composition of these sediments.

Early to Late Proterozoic(2.5 to 0.54 billion years) calcareous and arenaceous deposits, which correspond to humid and semi-arid climatic regimes, were deposited the Cuddapah and Vindhyan basins. These basins which border or lie within the existing crystalline basement, were uplifted during the Cambrian (500 Ma (ICS 2004)). The sediments are generally undeformed and have in many places preserved their original horizontal stratification. The Vindhyans consist of a lower Supergroup that was deposited sometime between ~1800-1600 Ma. The lower Vindhyan rocks were slightly deformed (tilted) and the Upper Vindhyan sequence lies unconformably over the Lower Vindhyan. The age of Upper Vindhyan (Kaimur, Rewa and Bhander) sedimentation is contentious. Kaimur rocks were intruded by the 1073 Ma Majhgawan kimberlite (Gregory et al., 2006) and are therefore older than 1073 Ma. The Rewa contains diamondiferous conglomerates suggesting that they formed after the Kaimur. The Rewa is conformably overlain by the Bhander Group. Indirect evidence for the age of the Upper Vindhyan was discussed by Meert and Pandit (2015) who noted the similarity in paleomagnetic directions from the 1073 Ma Majhgawan kimberlite, the 1.1 Ga Mahoba dyke and sediments of the Bhander and Rewa Groups. In addition, multiple detrital zircon studies failed to isolate any ages younger than ~1000 Ma from Upper Vindhyan rocks. A recent claim of the iconic Ediacaran fossil "Dickinsonia" located in the Upper Bhander (Retallack et al., 2021) required an Ediacaran age for that Group; however, Meert et al. (2023) demonstrated that the fossil was misidentified and therefore the age of the Upper Vindhyan is still debated.

Early

Himalayas
and consist of southerly derived sediments eroded from the crystalline craton and deposited on the Indian platform.

In the Late Paleozoic,

glacio-fluvial deposits
across central India, in new basins created by sag/normal faulting. These tillites and glacially derived sediments are designated the Gondwanas series. The sediments are overlain by rocks resulting from a Permian marine transgression (270 Ma (ICS 2004)).

The late Paleozoic coincided with the deformation and drift of the Gondwana supercontinent. To this drift, the uplift of the Vindhyan sediments and the deposition of northern peripheral sediments in the Himalayan Sea, can be attributed.

During the Jurassic, as Pangea began to rift apart, large grabens formed in central India filling with Upper Jurassic and Lower Cretaceous sandstones and conglomerates.

By the Late Cretaceous India had separated from Australia and Africa and was moving northward towards Asia. At this time, prior to the Deccan eruptions, uplift in southern India resulted in sedimentation in the adjacent nascent Indian Ocean. Exposures of these rocks occur along the south Indian coast at Pondicherry and in Tamil Nadu.

At the close of the Mesozoic one of the greatest volcanic eruptions in earth's history occurred, the Deccan lava flows. Covering more than 500,000 square kilometres (193,051 sq mi) area, these mark the final break from Gondwana.

In the early Tertiary, the first phase of the Himalayan orogeny, the Karakoram phase occurred. The Himalayan orogeny has continued to the present day.

Greater India

Greater India or the Greater India Basin means the

plate tectonic theory,[6]
but the term has seen increased usage since the 1970s.

The

Indian plate and the Eurasian Plate have converged up to 3,600 km (2,200 mi) ± 35 km (22 mi). The upper crustal shortening is documented from the geological record of Asia and the Himalaya as up to approximately 2,350 km (1,460 mi) less. Much of the lost area was pushed under Asia to form the Tibetan highland.[7]

Major rock groups

Map of chronostratigraphic divisions of India
1911 Geological map of India

Precambrian super-eon

A considerable area of peninsular India, the

schists which are the oldest rocks found in India. The Precambrian rocks of India have been classified into two systems, namely the Dharwar system
and the Archaean system (gneiss and schists).

The Dharwar System

The rocks of the Dharwar system are mainly sedimentary in origin,

Kolar gold mines located in Kolar. In the north and west of India, the Vaikrita system, which occurs in Hundar, Kumaon and Spiti areas, the Dailing series in Sikkim and the Shillong series in Assam
are believed to be of the same age as the Dharwar system.

The metamorphic basement consists of gneisses which are further classified into the

gabbros
.

Phanerozoic

Palaeozoic

Lower Paleozoic

Rocks of the earliest part of the Cambrian Period are found in the Salt range in

fauna are also found in the Vihi district of Kashmir
.

Upper Paleozoic

productids are found in the limestones of the Permo-Triassic, which has led to these rocks being referred to as "productus limestone". This limestone is of marine origin and is divided into three distinct lithostratigraphic units based on the productus chronology: the Late Permian Chideru, which contains many ammonites, the Late — Middle Permian
Virgal, and the Middle Permian Amb unit.

Mesozoic

In the Triassic the Ceratite beds, named after the ammonite

phosphate nodules, which constitute an important source of phosphates in the country. In the central provinces, the well developed beds of Lameta contain fossil records which are helpful in estimating the age of the Deccan Traps. This sequence of basaltic rocks was formed near the end of the Cretaceous period due to volcanic activity. These lava flows occupy an area of 200,000 square miles (520,000 km2). These rocks are a source of high quality building stone and also provide a very fertile clayey loam
, particularly suited to cotton cultivation.

Cenozoic

Tertiary period

In this period the

hominoids
.

Quaternary period

The

flood plains
. This region has some of the most fertile soil found in the country as new silt is continually laid down by the rivers every year.

Earthquakes

The Indian subcontinent has a history of devastating earthquakes. The Assam earthquake of 1950 registered a magnitude of 8.6; it is one of the most powerful earthquakes to have ever been recorded.[9] A similar earthquake in a densely populated area today would kill hundreds of thousands if not millions. This is why the Himalayan range is believed to be one of the most dangerous places to build large dams. The major reason for the high frequency and intensity of the earthquakes is that the Indian plate is driving into Asia at a rate of approximately 47 mm/year.[10] Geographical statistics of India show that almost 54% of the land is vulnerable to earthquakes. A World Bank & United Nations report shows estimates that around 200 million city dwellers in India will be exposed to storms and earthquakes by 2050.[11] National Disaster Management Authority says that 60% of Indian landmass is prone to earthquake and 8% susceptible to cyclone risks.

See also

References

  1. ^ "National Geological Monument, from Geological Survey of India website". Archived from the original on 12 July 2017. Retrieved 21 January 2019.
  2. ^ "Geo-Heritage Sites". pib.nic.in. Press Information Bureau. 9 March 2016. Retrieved 15 September 2018.
  3. ^ national geo-heritage of India Archived 11 January 2017 at the Wayback Machine, INTACH
  4. ^ Briggs, John C. (2003) The biogeographic and tectonic history of India. Journal of Biogeography 30:381–388
  5. .
  6. ^ Argand, E., 1924. La tectonique de l' Asie. Proc. 13th Int. Geol. Cong. 7 (1924), 171–372.
  7. ^ "The Greater India Basin hypothesis" (PDF). University of Oslo. Retrieved 20 December 2016.
  8. .
  9. .
  10. ^ "Earthquake Hazards and the Collision between India and Asia". Archived from the original on 19 September 2006. Retrieved 13 May 2006.
  11. ^ "Indian cities under threat of storms & earthquakes by 2050: World Bank & United Nations". The Times Of India. 9 December 2011.

Further reading

  • Gregory, L. C., Meert, J. G., Pradhan, V., Pandit, M. K., Tamrat, E., & Malone, S. J., 2006. A paleomagnetic and geochronologic study of the Majhgawan kimberlite, India: implications for the age of the Upper Vindhyan Supergroup. Precambrian Research, 149, 65-75.
  • Grout, Andrew. "Geology and India, 1775-1805: an episode in colonial science." South Asia Research 10.1 (1990): 1-18.
  • Jain, A.K., D.M. Banerjee, et al. eds. Tectonics of the Indian Subcontinent (Society of Earth Scientists Series) (2020). excerpt
  • Medlicott, Henry Benedict, and William Thomas Blanford. A Manual of the Geology of India: Chiefly Compiled from the Observations of the Geological Survey (2nd ed. 1892) reprinted by Cambridge University Press, 2011.
  • Meert, J.G. and Pandit, M.K., 2015. The Archaean and Proterozoic history of Peninsular India: tectonic framework for Precambrian sedimentary basins in India. Geological Society, London, Memoirs, 43, 29-54.
  • Meert, J.G., Pandit, M.K, Kwafo, S., Singha, A., 2023. Stinging News: ‘Dickinsonia’ discovered in the Upper Vindhyan of India not worth the buzz, Gondwana Research, doi:10.1016/j.gr.2023.01.003.
  • Raju, D. S. N. "Paleogene Stratigraphy of India: An Overview." The Indian Paleogene. (Springer, Cham, 2018). 1-89.
  • Ramakrishnan, Moni, and Rajagopala Vaidyanadhan. Geology of India (2 vol. GSI Publications 2.1 (2010).
  • Retallack, G.J., Matthews, N.A., Master, S., Khangar, R.G. and Khan, M., 2021. Dickinsonia discovered in India and late Ediacaran biogeography. Gondwana Research, 90, 165-170.
  • Saikia, Arupjyoti. "Earthquakes and the Environmental Transformation of a Floodplain Landscape: The Brahmaputra Valley and the Earthquakes of 1897 and 1950." Environment and History 26.1 (2020): 51-77.
  • Wadia, Darashaw Nosherwan. Geology of India (Macmillan, 1939).
  • Wadia, Darashaw Nosherwan. Geology of India: For Students (Macmillan, 1919) online.