Geological History of India


The Geological History of India began with the geographical transformation of other parts of the earth, to be precise, 4.57 Ga (billion years back). India is famous for its varied geological features. Various parts of India are made up of rocks of all categories of several geologic periods. A few of the rocks are poorly malformed and metamorphosed. At the same time, other types of rocks are newly silted alluvial soils that are still to go through chemical and physical changes. Source of minerals of significant diversity is seen in the subcontinent area in substantial amount.

Even the fossil evidences are remarkable that contain invertebrates, stromatolites, plant and vertebrates fossils.

Geology of India: An Overview



The geological territories of India can be categorized into the following:
  • Deccan Trap
  • Vindhyan
  • Gondwana

To begin with, the Deccan Trap encompasses nearly the whole area of Maharashtra and parts of Karnataka , Gujarat, Andhra Pradesh, and Madhya Pradesh to some extent. It is assumed that the Deccan Trap was created as a consequence of sub aerial volcanic operations related to the tectonic shift in this portion of the earth in the Mesozoic period. This is the reason why rocks seen in this area are usually of igneous category.

At the time of its passage to the north following its separation from the remainder of Gondwana, the Indian tectonic plate went above a geologic hotspot, which is known as the Reunion hotspot. This resulted in widespread melting below the Indian craton. The melted materials penetrated the shell of the craton in a huge flood basalt occurrence, forming what is named as the Deccan Trap. It is also believed that Reunion Hotspot resulted in the partition of India and Madagascar.

The Vindhyan and Gondwana contain within its crease areas of Chhattisgarh, Madhya Pradesh, Bihar, Orissa, Andhra Pradesh, West Bengal, Jammu and Kashmir, Maharashtra , Himachal Pradesh, Punjab, Uttaranchal, and Rajasthan.

The Gondwana Supergroup creates an exclusive series of fluviatile stones deposited in Permo-Carboniferous period. Rajmahal hills and Sone and Damodar river basins in the eastern India are reservoirs of the Gondwana rocks.

History of the Deccan Traps



The Deccan Traps were created between 60 and 68 million years back, at the close of the Cretaceous era. The majority of the volcanic outbreak took place at the Western Ghats Range (close to Mumbai) around 66 million years back. This sequence of explosions may have survived for almost 30,000 years altogether.

The actual territory encompassed by lava flows is calculated to have been as big as 1.5 million km², which is about 50% of the dimension of contemporary India . The Deccan Traps area was diminished to its present volume as a result of tectonic movements and wearing away. Now, the existing zone of openly visible lava flows is approximately 197,684 sq miles or 512,000 km2.

Formation of Gondwana



The accumulation of Gondwana or Gondwanaland was a long-drawn-out procedure. Many geological processes resulted in its ultimate merger 550–500 million years back at the close of the Ediacaran era, and into the Cambrian era. These comprise the East African Orogeny, the Brasiliano Orogeny, the Kuunga Orogeny, and the Malagasy Orogeny. The last phases of Gondwana accumulation coincided with the unfolding of the Iapetus Ocean amid western Gondwana and Laurentia. Throughout this gap, the Cambrian Explosion took place.

Gondwana was created by these previous continents and microcontinents and others having a collision in these geological processes:

Azania: Majority of central Madagascar, areas of Yemen and Arabia and the Horn of Africa. The name of the place was given by Collins and Pisarevsky (2005): “Azania” was a Greek expression denoting the shoreline of East Africa.

Neoproterozoic India: India, the Seychelles, the Antongil Cluster in distant east Madagascar, and the Rayner and Napier Compounds in East Antarctica.

The Congo–Tanzania–Bangweulu cluster of Central Africa.

The Australia/Mawson continent: The western parts of Adelaide in Australia and a big stretch into Eastern Antarctica.

Other clusters which assisted to create Argentina and other neighboring areas, including a portion shifted from Laurentia when the western rim of Gondwana rubbed with southeastern Laurentia in the Ordovician era.This is the Famatinian cluster, and it previously carried on the row of the Appalachians to the south.

One of the important locations of Gondwana merger was the Orogen of East Africa (Stern, 1994), where these two important geological processes are overlaid on one other:

The Orogen of East Africa (as described afterward) at ~650–630 Ma influenced a significant portion of Arabia, East Africa, northeast Africa, and Madagascar. Windley and Collins in 2002 suggested that in this process, Azania bumped with the Congo–Tanzania–Bangweulu Cluster. The subsequent Malagasy process at 550–515 Ma influenced the eastern part of East Africa, Madagascar, and South India. In it Neoproterozoic India bumped with the already united Azania and Congo–Tanzania–Bangweulu Cluster.

Simultaneously, in the Kuunga Orogeny Neoproterozoic era, India bumped with the Australia/Mawson continent.

Plate Tectonics



At one time, the Indian craton was a segment of the Pangaea supercontinent. During that period, it was linked with Southern Africa and Madagascar on the southwestern shore and Australia beside the eastern shore. During the Jurassic era, at approximately 160 Ma (ICS 2004), fissuring led Pangaea to split into two supercontinents i.e. Laurasia (in the north) and Gondwana (in the south). However, the Indian craton stayed linked to Gondwana till the supercontinent started to split into pieces approximately in the beginning phase of the Cretaceous era around 125 Ma (ICS 2004). The tectonic plate of India started moving to the north in the direction of the Eurasian plate, at a velocity which is the quickest shift by any recognized plate. It is normally assumed that Indian tectonic plate broke off from Madagascar approximately 90 Ma (ICS 2004). Nevertheless, some geographical and biogeographical proofs indicate that the link between Africa and Madagascar was held at the period when the Indian tectonic plate bumped into the Eurasian Plate at approximately 50 Ma (ICS 2004). This geological process, which is going on at present, is associated with the sealing of the Tethys Ocean. The Tethys Ocean’s sealing had resulted in formation of the Caucasian Mountain Range in West Asia and the Alps in Europe. It also formed the Tibetan highland in South Asia and the Himalayan Mountain Ranges. The present orogenic occurrence is creating segments of the Asian continent to bend to the east and west on both side of the process. In tandem with the impact, the Indian tectonic plate stitched up with the bordering Australian Plate, creating a new bigger plate, which is known as the Indo-Australian Plate.

Tectonic Evolution in India



The oldest stage of tectonic evolution was identified by the chilling and hardening of the outermost layer of the shell of the earth in the Archaean period (earlier than 2.5 billion years), which is characterized by the presence of granites and gneisses, particularly on the peninsular area. These rocks create the center of the Indian craton. The Aravalli Mountain Range is the remains of a prehistoric Proterozoic geological formation, known as the Aravalli-Delhi geologic formation, which coupled the two earlier parts that comprise the Indian craton. It stretches for about 311 miles or 500 km from its northernmost tip to remote hills and stony crests into Haryana, culminating close to Delhi.

Insignificant igneous infringements, bends (twisting and fissuring), and resultant metamorphism of the rocks of the Aravalli Mountain Ranges characterize the primary stage of orogenesis. The wearing away of the hills and additional distortion of the layers of the Dharwaian cluster (Bijawars) indicates the next stage. The volcanic events and disturbances related with the second stage are traced in formation of these layers.

Early to late Proterozoic period arenaceous and calcareous deposits, which characterize the moist and semi-dry climatic systems, were put down in the Vindhyan and Cuddapah valleys. These valleys that enclose or are positioned within the current crystalline foundation, were raised up at the Cambrian period 500 Ma (ICS 2004). The layers are usually undistorted and have in various areas maintained their original flat building up of layers. The Vindhyans are assumed to be deposited in the middle of ~1700 and 650 Ma (ICS 2004).

Early Paleozoic period rocks are seen in the Himalayan Mountain Ranges and they comprise layers originating from the south, worn down from the crystalline craton and put on the Indian territory.

During the late Paleozoic period, Permo-Carboniferous glaciations put down widespread glacio-fluvial silts throughout central India, in new valleys formed by common fissuring or wilting. These glacially originated layers and tillites represent the Gondwana sequence. The layers are superimposed by stones formed by a Permian oceanic lapse 270 Ma (ICS 2004).

The late Paleozoic period concurred with the distortion and shift of the Gondwana supercontinent. Towards this movement, the rise of the Vindhyan layers and the storage of side-line layers of the north in the Himalayan Sea can be accredited.

At the time of Jurassic era, when Pangaea started to break into pieces, big grabens were created in the central part of India, loaded with Lower Cretaceous and Upper Jurassic granites and puddingstones.

By the late Cretaceous period, India had detached from Africa and Australia and was shifting to the north in the direction of Asia. During this period, before the Deccan volcanic explosions, uplift in South India led to deposition and layering in the neighboring emerging Indian ocean. Displays of these stones are found beside the shorelines in South India in Tamil Nadu and at Pondicherry.

At the culmination of the Mesozoic period, one of the biggest volcanic outbreaks in the history of the earth took place, which is known as the Deccan lava flows. Encompassing a zone of over 500,000 square kilometers (193,051 sq mi), these indicate the last rift from Gondwana.

During the early Tertiary period, the initial stage of the Himalayan geologic process, the Karakoram stage took place. The Himalayan geological process has sustained to the present day.

Important rock categories



Precambrian super-eon

A substantial territory of peninsular India, which is also known as the Indian Shield, comprises schists and Archean gneisses and these are the earliest forms of rocks seen in India. The Precambrian rocks of India are categorized into two systems and they are as follows:

The Archean System The Dharwar System The stones of the Dharwar System are mostly sedimentary rocks. They are typically found in Mysore and Bellary in Karnataka and Aravalli Mountain Range, Rajputana, Rajasthan. These rocks serve as sources of minerals like iron ore and manganese. Gold is found in the Kolar gold mines in Kolar, Karnataka. The Vaikrita System, located to the west and north of India, which exists in Kumaon, Hundes, and Spiti territories, the Shillong sequence in Assam and the Dailing sequence in Sikkim, are assumed to be of the equal age as the Dharwar system.

The gneisses or metamorphic stones can be further categorized into the Bundelkhand gneiss, the Bengal gneiss, and the Nilgiri gneiss. The Niligiri system is made up of Charnockites varying from granites to granular intrusive rocks.

Phanerozoic

Lower Paleozoic – Stones of the oldest Cambrian era are seen in Spiti in the central Himalayan ranges and the Salt range in Punjab. These areas comprise a dense series of fossilized layers. The Pseudomorph Area in the Salt Range is made up of sandstones and dolomites.

The sediments in Spiti are named as Haimanta system and they are made up of dolomitic limestones, micaceous quartzite, and slates. The Ordovician stones consist of limestones, flexible shales, quartzites, red quartzites, puddingstones, and sandstones.

Silurian stones which include distinctive Siluria fauna are also seen in the Vihi district in Kashmir.

Upper Paleozoic: Corals and Devonian fossils are seen in black-colored calciferous limestone in the Chitral region and grey-colored calciferous sedimentary rocks in the Central Himalayan Mountain Ranges. The Carboniferous consists of two separate series and they are - lower Carboniferous Lipak and upper Carboniferous Po. Trilobites and brachiopods fossils are seen in the calcareous and arenaceous stones of the Lipak sequence. In Kashmir, the Syringothyris limestone also is a part of the Lipak. The genus of limestones is broadly denoted as productus limestone. This limestone has its source in the ocean and can be categorized into the Late Permian Chideru (with high ammonite content), the Middle Permian Amb division, and the Late - Middle Permain Virgal.

Mesozoic

During the Triassic periods, the Ceratite stonebeds were formed, which derived their name from the ammonite ceratite. They comprise marls, calcareous sandstones, and sandy limestones. The Jurassic comprises two separate divisions – the upper Jurassic and the middle Jurassic. The Upper Jurassic is characterized by the black shales in Spiti and expanses from Sikkim to the Karakoram. Cretaceous stones encompass a huge territory in India.

In South India, the sedimentary rocks are categorized into four types; the Ariyalur, the Niniyur, the Utatur, and the Trichinopoly phases.

Cenozoic

Tertiary period – This is the era when the Himalayan geological process started and the volcanic activities related to the Deccan Traps went on. The rocks of this period have priceless deposits of coal and petroleum. Granites or sandstones are seen in Punjab. In Shimla, three types of stones are found – the Sabathu Series (Grey and red shales), the Kasauli Series (sandstones), and the Dagshai Series (bright red clays). You will see Nummulitic limestone in the Khasi hills to the east of Assam. Beside the foothills of the Himalayas, there are puddingstones, sandstones, and shales, collectively known as the Siwalik Molasse.

Quaternary Period – The alluvial soil seen in the Indo-Gangetic basin is of this period. The alluvial deposits are categorized into older alluvium and newer alluvium. The newer alluvial soil is known as Khaddar and the older alluvial soil is known as Bhangar. This soil is worn down from the Himalayas and is one of the productive soils in the country.

Last Updated on 02 February 2011