Origin and Physiography of the Peninsular India

In this article we will discuss Origin and Physiography of the Peninsular India

In this article, we will discuss Origin and Physiography of the Peninsular India. So, let’s get started.

Origin and Physiography of the Peninsular India

The origin of rocks of Peninsular India is more than 3600 million years old. Before the Carboniferous period, it was a part of the Gondwanaland. In the opinion of geologists, during the Archaean Period, the Indian Peninsula never subsided under the sea permanently. It was more rigid, stable and had remained almost unaffected by the mountain building forces. However, it experienced block faulting and displacement during the subsequent periods as evidenced by the Dharwar and Gondwana formations and the fault valleys of the Narmada, Tapi and Son rivers.

It was during the Carboniferous Period that coal was formed in the Damodar, Son Mahanadi,
and Godavari basins. During the Cretaceous Period, large scale vulcanicity produced the Deccan Trap (the Lava Plateau of India), comprising lava sheets of several thousand metres in depth. The Deccan Trap originated about 146 million years back when the magma flowed from the depth of about 40 km below the crust.

Major Geological Formations of the Peninsular India (about 3600 million years ago)

The plateau of Peninsular India exhibits a complex system of geological structures. It has some of the oldest rocks of the world from the Precambrian period (Archaean) and the youngest rocks of the Holocene epoch (Quatemary / recent period). The major rock systems found in the Peninsular India have been described briefly in the following section:

Cratonisation
It is the process by which the formation of crators takes place from the early rocks. A craton is an old but stable part of the continental crust that survived during the merging and the splitting of the continents. The first cratonic landmass was formed during the Archaean eon. They may be up to 2 million years old.
During this period, the Earth’s heat flow was about three times greater than the present time
and had increased tectonic and volcanic activities. The mantle was much more liquid and the crust was thinner. As a result the oceanic ridges at the crust and hot spots were rapidly formed. It is believed that the earth’s surface got broken into small plates with volcanic islands and arcs. Small cratons were melted and remelted by the hotspots and recycled in the subduction zones. The early Archaean period did not have large continents. The formation of cratons took place at the hotspots.
Cratons are composed of igneous rocks like granite and have a thick crust with deep roots that extend into the mantle to the depth of 200 km.

The Archaean Group
Ancient crystalline and highly metamorphosed gneisses of the Archaean System are found in the plateaux of Tamil Nadu, Nilgiris, Karnataka, Andhra Pradesh, Maharashtra, Chhotanagpur, West Bengal, Odisha, Jharkhand, Chhattisgarh, Madhya Pradesh, Meghalaya, Mikir, Bundelkhand (UP), and the Aravallis (Rajasthan). The Bengal gneiss known as ‘Khondolite’ is found in the Eastern Ghats. These rocks are rich in metallic and non-metallic minerals, precious stones, and building materials, and covered more than 2/3 part of peninsula.

The Dharwar System
These are the oldest metamorphosed-sedimentary rocks found in narrow geosynclines flanking the Archaean gneiss (Pre-Cambrian Age). They occur mainly in (i) Dharwar, Bellary and Hospet districts of Karnataka, (ii) the Chhotanagpur Plateau, (iii) the upper reaches of Godavari (Durg, Bastar, Dantewala, Chandrapur, etc.), and (iv) the Aravallis (Delhi, Rajasthan, and Gujarat). It is presumed that the majority of the Dharwar rocks had escaped folding completely and had deposited into the hollows and the corrugations of landmasses or were only mildly folded. These rocks are rich in iron ore, manganese, mica, copper, zinc, lead, silver, gold, slate, asbestos, marble, and limestone.

The Cuddapah System
The Cuddapah formation (Andhra Pradesh) occupy the deep basin of: (i) the lower valleys of Penganga and Godavari, (ii) the Talcher Series between Mahanadi and Brahmani (Odisha), the upper courses of the Narmada and Son rivers, and (iii) the west of Aravallis near Jodhpur. These rocks are rich in building material, shales, limestone, and sandstone. Some inferior quality of iron ore, manganese, copper, and asbestos are also found in these formations.

The Vindhyan System
The Central Indian Highlands known as the Vindhvan Mountains occupy a large basin extending from Chittorgarh (Rajasthan) in the west to Sasaram and Dehri-on Son (Bihar) in the east. One branch of it extends from Sasaram to Hoshingabad (Madhya Pradesh). It occupies a large contiguous area stretching over one lakh sq km from the Chambal to Son rivers. Several isolated exposures of sedimentary rocks occur in the Bastar area of Chhattisgarh. In some of the exposures of the Vindhyan system are found the diamond bearing conglomerates. The Panna District of Madhya Pradesh and the Kurnool District of Andhra Pradesh are well known for diamond production. Elsewhere in the south the upper Vindhyans are covered by the Deccan Traps. The Vindhyans are known for the good quality of building materials. They are rich in ornamental stones, precious stones diamonds and materials used in ceremics. The historical monuments of the Medieval Period and majestic religious places like Stupa of Sanchi, Agra Fort. Fatehpur Sikri, Red Fort, Jama Masjid, Birla Mandir, etc., have been constructed with the red sandstones obtained from the Vindhyan Ranges.

Gondvana System
The present coal belt of Peninsular India were developed during the Gondwana (Carboniferous)
period. The Talcher Series, the Damuda Series and the Panchet Series are the products of this period. The rocks of the Upper Carboniferous Period, Permian, Triassic, Jurassic, Cretaceous, Tertiary, etc.,are preserved in different parts of the Damodar, Mahanadi, Godavari, and Krishna river basins.

The Deccan Trap
The Cretaceous system is a very widely distributed system in the country. The Gondwanaland developed fissures and its broken parts started drifting from each other. There was large scale upheaval of lava (basalt) from the interior of the Earth to form the Deccan Trap. The eruption of lava was of the Hawaiian or fissure type. This period is marked by the transgression of the sea (Narmada valley and Coromandal coast), and outpouring of huge quantity of basalt so as to form the Deccan Trap. There had been intrusions of the plutonic rocks such as gabbro and granite. The basalt of the Deccan Trap is used for the construction of roads and buildings. Moreover, there are quartzites, agates, and carnelians in the lava formations of the Deccan Plateau.

The Tertiary System
The final fragmentation of the Gondwana took place during the Tertiary Period. There occurred
faulting of the Peninsula alongwith the subsidence of the broken blocks beneath the Arabian Sea and the Bay of Bengal. The Tertiary rocks are found in Kathiawar, Kachchh (Gujarat), Laki Series (Rajasthan), and along the Coromandal and Malabar coasts. In north-east, they are found in the Meghalaya Plateau; the Jaintia Series.

The Pleistocene Period
The Pleistocene deposits are found in the lower reaches and deltas of Mahanadi, Godavari, Krishna, and Kaveri and the western coastal plains of Gujarat, Konkan, and Malabar. These deposits are, however, more pronounced along the eastern coast of India.

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